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13 pages, 4288 KiB

Open AccessArticle

Drying Behaviour of Al₂O₃ Inks Containing Carboxymethylcellulose (CMC) for Use in Colloidal Processing

by Bruno Medeiros da Silva, Ésoly Madeleine Bento dos Santos, Vinícius Zancanelli Bôsco de Souza, Manuel Fellipe Rodrigues Pais Alves, Carlos Maurício Vieira and Claudinei dos Santos

Ceramics 2023, 6(2), 935-947; https://doi.org/10.3390/ceramics6020055 - 6 Apr 2023

Viewed by 1894

Abstract

One of the most important steps in the extrusion processing of ceramic inks is the initial drying of the ceramic parts. This study aimed to investigate the drying behaviour of an Al₂O₃-based ceramic ink optimised to be processed by [...] Read more.

One of the most important steps in the extrusion processing of ceramic inks is the initial drying of the ceramic parts. This study aimed to investigate the drying behaviour of an Al₂O₃-based ceramic ink optimised to be processed by extrusion processing methods, e.g., direct ink writing. Carboxymethylcellulose (CMC) was singly added to a suspension of deionised water and Al₂O₃ (50:50 wt.%) to perform as a dispersing and plasticising agent. To assess moisture loss as a function of time, the ceramic inks were extruded into two types of polymeric moulds: one with a completely closed profile producing cylindrical samples (disks) and one with an open profile producing ceramic bars. After the injection of the inks, the moulds were exposed to different controlled temperatures (20 and 40 °C) for up to 180 h; moisture loss and warpage were periodically measured, and exponential mathematical expressions (moisture loss × drying time) were obtained. The Al₂O₃-bars dried for 24 h in open moulds at 20 and 40 °C presented longitudinal warpages of 4.5% and 9%, respectively, while the Al₂O₃ disks dried in closed moulds presented warpages of 3.5% and 7% in these same temperatures (20 and 40 °C, respectively). The samples were sintered at 1610 °C for 4 h and characterised by scanning electron microscopy (SEM), relative density (Archimedes principle), and X-ray diffraction (XRD), presenting a relative density of 92.3 ± 0.5%, α-Al₂O₃ as crystalline phase and grain with equiaxed morphology varying between 1 and 5 μm. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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17 pages, 1116 KiB

Open AccessArticle

Affect of the Scattering Asymmetry by Structural Element of Thermal- or Environmental-Barrier Ceramics on Subsurface Radiant Overheating

by Vladimir Merzlikin, Evgeny Safonov, Andrey Kostyukov, Svetlana Parshina and Anna Dokukina

Ceramics 2023, 6(1), 717-733; https://doi.org/10.3390/ceramics6010044 - 13 Mar 2023

Cited by 1 | Viewed by 1722

Abstract

The problem of the formation and estimation of a thermoradiant and temperature field in ceramics Thermal- Environmental-Barrier Coatings (TBC/EBC) has been considered with complex heat transfer but under the influence of the penetrating intense radiant component. The authors proposed to analyze not only [...] Read more.

The problem of the formation and estimation of a thermoradiant and temperature field in ceramics Thermal- Environmental-Barrier Coatings (TBC/EBC) has been considered with complex heat transfer but under the influence of the penetrating intense radiant component. The authors proposed to analyze not only TBC but also EBC from the point of view of the optics of semitransparent scattering and absorbing media in the range of ~0.4–4 μm of external radiant action. This paradigm allows us to continue the study of ceramic fibers embedded in ceramic matrix CMCs (C/C, C/SiC, SiC/SiC) as a traditional class of opaque materials. However, at the same time, mullites, Al₂O₃/Al₂O₃ have been reviewed as a class of semitransparent elements for designing CMCs. The relevance of studying the effect of oriented fibers on the formation of thermoradiation and temperature fields in a semitransparent material was noted. Modeling the scattering asymmetry coefficient influence (scattering phase function) on the generation of the subsurface thermal radiation source was carried out. The methodology for calculating the thermoradiative field in a semitransparent medium (with relative absorption, scattering indexes, and scattering asymmetry coefficient) was used under a one-dimensional two-flux model as the first approximation for solving the radiative heat transfer equation. Calculations of temperature profiles in opaque and semitransparent ceramics were presented under heat load typical for the combustion chambers operating regime of diesel and gas turbine engines. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 3828 KiB

Open AccessArticle

Synthesis and Dielectric Relaxation Studies of K_xFe_yTi_8-yO₁₆ (x = 1.4–1.8 and y = 1.4–1.6) Ceramics with Hollandite Structure

by Alexey Tsyganov, Denis Artyukhov, Maria Vikulova, Natalia Morozova, Ilya Zotov, Sergey Brudnik, Aleksandra Asmolova, Denis Zheleznov, Alexander Gorokhovsky and Nikolay Gorshkov

Ceramics 2023, 6(1), 619-629; https://doi.org/10.3390/ceramics6010037 - 1 Mar 2023

Cited by 2 | Viewed by 2135

Abstract

Some solid solutions with the chemical composition K_xFe_yTi_8-yO₁₆ (KFTO) and a hollandite-like structure were successfully synthesized by modified sol–gel method. The obtained powders were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The ceramic [...] Read more.

Some solid solutions with the chemical composition K_xFe_yTi_8-yO₁₆ (KFTO) and a hollandite-like structure were successfully synthesized by modified sol–gel method. The obtained powders were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The ceramic pellets based on KFTO powders were obtained by compressing and sintering at 1080 °C for 4 h. The sinters were characterized by X-ray and impedance spectroscopy. XRD results show that KFTO powders have a mono-phase tetragonal structure at x = 1.4–1.8 and y = 1.4–1.6. However, it was recognized that the hollandite-like phase could be broken during sintering to form TiO₂ and Fe₂TiO₅ crystals distributed throughout the volume of the ceramics. A frequency dependency of dielectric properties for the sinters was studied by impedance spectroscopy. It was found that an increase in the TiO₂ (rutile) phase during the sintering contributes to a decrease in dielectric losses. At the same time, the KFTO ceramics with reduced content of potassium had increased permittivity. The contribution of electron-pinned defect dipoles (EPDD) and internal barrier layer capacitance (IBLC) in the permittivity of the obtained ceramics was estimated using the Havriliak–Negami equation. It is shown that the KFTO ceramics have the polydisperse characteristic of dielectric relaxation. The observed grain and grain boundary dipole relaxation times were 1.03 × 10⁻⁶ to 5.51 × 10⁻⁶ s and 0.197 to 0.687 s, respectively. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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19 pages, 6081 KiB

Open AccessArticle

Ceramic Materials in Na₂O-CaO-P₂O₅ System, Obtained via Heat Treatment of Cement-Salt Stone Based on Powder Mixture of Ca₃(C₆H₅O₇)₂∙4H₂O, Ca(H₂PO₄)₂∙H₂O and NaH₂PO₄

by Otabek U. Toshev, Tatiana V. Safronova, Tatiana B. Shatalova and Yulia S. Lukina

Ceramics 2023, 6(1), 600-618; https://doi.org/10.3390/ceramics6010036 - 26 Feb 2023

Cited by 2 | Viewed by 2243

Abstract

Ceramic materials in Na₂O-CaO-P₂O₅ system were obtained by firing cement-salt stone made from pastes based on powder mixtures including calcium citrate tetrahydrate Ca₃(C₆H₅O₇)₂∙4H₂O, monocalcium phosphate monohydrate [...] Read more.

Ceramic materials in Na₂O-CaO-P₂O₅ system were obtained by firing cement-salt stone made from pastes based on powder mixtures including calcium citrate tetrahydrate Ca₃(C₆H₅O₇)₂∙4H₂O, monocalcium phosphate monohydrate (MCPM) Ca(H₂PO₄)₂∙H₂O and/or sodium dihydrogen phosphate NaH₂PO₄. The phase composition of the obtained samples of cement-salt stone after adding water, hardening and drying included brushite CaHPO₄∙2H₂O, monetite CaHPO₄ and also unreacted Ca₃(C₆H₅O₇)₂∙4H₂O, Ca(H₂PO₄)₂∙H₂O and/or NaH₂PO₄. The phase composition of ceramics in Na₂O-CaO-P₂O₅ system obtained by firing cement-salt stone was formed due to thermal conversion of hydrated salt and heterophase reactions between components presented in samples during firing. The phase composition of ceramic samples based on powder mixture of Ca₃(C₆H₅O₇)₂∙4H₂O and Ca(H₂PO₄)₂∙H₂O after firing at 900 °C included β-calcium pyrophosphate (CPP) β-Ca₂P₂O₇. The phase composition of ceramic samples based on powder mixture of Ca₃(C₆H₅O₇)₂∙4H₂O, and NaH₂PO₄ after firing at 900 °C included β-sodium rhenanite β-CaNaPO_4. The phase composition of ceramic samples based on powder mixture of Ca₃(C₆H₅O₇)₂∙4H₂O, Ca(H₂PO₄)₂∙H₂O and NaH₂PO₄ after firing at 900 °C included β-Ca₂P₂O₇, β-CaNaPO_4, double calcium-sodium pyrophosphate Na₂CaP₂O₇, and Na-substituted tricalcium phosphate Сa₁₀Na(PO₄)₇. Obtained ceramic materials in Na₂O-CaO-P₂O₅ system including biocompatible and biodegradable phases could be important for treatments of bone tissue defects by means of approaches of regenerative medicine. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 3719 KiB

Open AccessArticle

Effect of Calcium Silicate and β-Tricalcium Phosphate Reinforcement on the Mechanical–Biological Properties of Freeze-Dried Collagen Composite Scaffolds for Bone Tissue Engineering Applications

by Temesgen Yiber Animut, Henni Setia Ningsih, Hsueh-Huan Shih, Meng-Huang Wu and Shao-Ju Shih

Ceramics 2023, 6(1), 548-560; https://doi.org/10.3390/ceramics6010033 - 18 Feb 2023

Cited by 6 | Viewed by 2825

Abstract

The development of a collagen-based composite scaffold to repair damaged bone is one of many important issues in tissue engineering. In this study, pure collagen, collagen/β-tricalcium phosphate (β-TCP), collagen/calcium silicate (CS), and collagen/β-TCP/CS scaffolds were fabricated using the freeze-drying method. The phase compositions, [...] Read more.

The development of a collagen-based composite scaffold to repair damaged bone is one of many important issues in tissue engineering. In this study, pure collagen, collagen/β-tricalcium phosphate (β-TCP), collagen/calcium silicate (CS), and collagen/β-TCP/CS scaffolds were fabricated using the freeze-drying method. The phase compositions, microstructures, and mechanical properties were characterized using X-ray diffraction, scanning electron microscopy, and a universal testing machine, respectively. In addition, cell viability was evaluated using an MTT assay. Finally, the correlations between the density, mechanical properties, and biodegradation behaviors of pore size distributions were discussed. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 3805 KiB

Open AccessArticle

High-Strength Optical Coatings for Single-Crystal ZnGeP₂ by the IBS Method Using Selenide and Oxide Materials

by Mikhail Zinovev, Nikolay N. Yudin, Vladimir Kuznetsov, Sergey Podzyvalov, Andrey Kalsin, Elena Slyunko, Alexey Lysenko, Denis Vlasov and Houssain Baalbaki

Ceramics 2023, 6(1), 514-524; https://doi.org/10.3390/ceramics6010030 - 13 Feb 2023

Cited by 2 | Viewed by 1884

Abstract

The paper presents the results on the development of an optical coating for a single-crystal ZnGeP₂ substrate based on a selenide-oxide pair of materials (ZnSe/Al₂O₃). The obtained coating ensures the operation of OPO in the mid-IR range up [...] Read more.

The paper presents the results on the development of an optical coating for a single-crystal ZnGeP₂ substrate based on a selenide-oxide pair of materials (ZnSe/Al₂O₃). The obtained coating ensures the operation of OPO in the mid-IR range up to 5 μm wavelengths. The possibility of ZnSe sputtering by the IBS method is shown. The obtained optical coating has a high laser-induced damage threshold (LIDT) value at a 2097 µm wavelength:

W_{o}^{E} = 3.51

J/cm² in energy density and

W_{o}^{P}

= 101 W/cm² in power density at a 10 KHz pulse repetition frequency and a pulse duration of 35 ns. Thus, it is shown for the first time that the pair of materials ZnSe/Al₂O₃ can be used for the deposition of optical coatings by the IBS method with high LIDT values for ZnGeP₂ optical elements operating in the mid-IR range. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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16 pages, 3364 KiB

Open AccessArticle

CerAMfacturing of Aluminum Nitride with High Thermal Conductivity via Lithography-Based Ceramic Vat Photopolymerization (CerAM VPP)

by Eric Schwarzer-Fischer, Uwe Scheithauer and Alexander Michaelis

Ceramics 2023, 6(1), 416-431; https://doi.org/10.3390/ceramics6010024 - 2 Feb 2023

Cited by 9 | Viewed by 3308

Abstract

Aluminum nitride (AlN) is an excellent material for heat sinks and is used, for example, in high-performance electronics, high-power LEDs and photovoltaics. In order to meet the constantly increasing demands on substrate materials and heat sinks resulting from the permanent increase in power [...] Read more.

Aluminum nitride (AlN) is an excellent material for heat sinks and is used, for example, in high-performance electronics, high-power LEDs and photovoltaics. In order to meet the constantly increasing demands on substrate materials and heat sinks resulting from the permanent increase in power density and resulting heat in electronic components, new types of components made of high-performance materials with highly complex geometries are required. In this work, AlN based on a commercial powder (“TOYALNITE^®”-JCGA-BLY5 by Toyal Europe), was successfully qualified for an AM technology through suspension and process development for CerAM VPP—a DLP-based vat photo polymerization technology. The properties of the components were characterized along the entire process chain, achieving densities of 3.33 g/cm³ (>99% Th.D.) and excellent thermal conductivities of more than 180 W/mK, which are comparable to state-of-the-art for conventionally manufactured AlN components. Homogeneous microstructures of good quality confirm the measured density and thermal conductivity. A complex-shaped component usable for an exemplary heating–cooling application demonstrates the potential of this development. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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12 pages, 4296 KiB

Open AccessArticle

Combining Pultrusion with Carbonization: Process Analysis and Material Properties of CFRP and C/C

by Jonas H. M. Stiller, Kristina Roder, David Löpitz, Marcus Knobloch, Daisy Nestler, Welf-Guntram Drossel and Lothar Kroll

Ceramics 2023, 6(1), 330-341; https://doi.org/10.3390/ceramics6010020 - 1 Feb 2023

Cited by 2 | Viewed by 2694

Abstract

Composites made of carbon-fiber-reinforced carbon (C/C or CFC) are high-performance materials with a wide range of properties, making them especially suitable for the design of thermally and mechanically highly stressed components. As the production process of these high-performance materials is currently still very [...] Read more.

Composites made of carbon-fiber-reinforced carbon (C/C or CFC) are high-performance materials with a wide range of properties, making them especially suitable for the design of thermally and mechanically highly stressed components. As the production process of these high-performance materials is currently still very expensive, new concepts for an economical manufacturing process are required. This paper focusses on an innovative approach that uses the polymer-based pultrusion process for shaping with a subsequent carbonization step to C/C. In this process, carbon fibers (CF) and a phenolic resin were used to manufacture a semi-finished product made of unidirectional (UD) carbon-fiber-reinforced plastic (CFRP) with a fiber volume content of 66%. The C/C composite shows dimensional stability and has a flexural strength of approx. 240 MPa and a flexural modulus of approx. of 135 GPa with an elongation of 1.8%. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 3218 KiB

Open AccessArticle

Indium Oxide Powder Synthesis in a Low-Current Discharge Plasma at Atmospheric Pressure

by Konstantin Savkin, Dmitry Sorokin, Dmitry Beloplotov, Marina Ostapenko, Viktor Semin and Efim Oks

Ceramics 2023, 6(1), 265-277; https://doi.org/10.3390/ceramics6010016 - 13 Jan 2023

Cited by 1 | Viewed by 2026

Abstract

The results of a study of the processes involved in the production of indium oxide In₂O₃ powder, which is widely used to create transparent and electrically conducting ceramics, are described. The powder was produced in a flow of rare gas [...] Read more.

The results of a study of the processes involved in the production of indium oxide In₂O₃ powder, which is widely used to create transparent and electrically conducting ceramics, are described. The powder was produced in a flow of rare gas (argon or helium) at atmospheric pressure under conditions for the formation of metal-containing plasma in a non-arc discharge mode. The discharge operated in pulsed mode with a pulse repetition rate of 70 kHz and pulse duration of 12 μs. The discharge current was 670 mA and discharge voltages were 180 V and 250 V when the working gases were argon and helium, respectively. These parameters ensure a mode in which the indium cap of a molybdenum cathode suffers thermal erosion. The morphology and elemental and phase composition of the erosion products were studied using transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) analysis. It was shown that the structure of the synthesized powder particles corresponded to a phase of indium oxide (III) with a body-centered cubic (bcc) lattice with lattice parameter a = 1.013 nm. The powder particles, regardless of the working gas (Ar or He), consisted of non-stoichiometric indium oxide In₂O₃ with a nanocrystalline structure. The average particle diameter was <d> = 13–16 nm. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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14 pages, 5866 KiB

Open AccessArticle

Influence of the Feedstock Preparation on the Properties of Highly Filled Alumina Green-Body and Sintered Parts Produced by Fused Deposition of Ceramic

by Thomas Heim and Frank Kern

Ceramics 2023, 6(1), 241-254; https://doi.org/10.3390/ceramics6010014 - 11 Jan 2023

Cited by 4 | Viewed by 3133

Abstract

This paper investigates new approaches for the blending and plastification of ceramic powder with a binder to form fused deposition of ceramic (FDC) feedstock. The fabrication of highly filled ceramic filaments was accomplished using the granulation by agitation technique, followed by twin-screw extruder [...] Read more.

This paper investigates new approaches for the blending and plastification of ceramic powder with a binder to form fused deposition of ceramic (FDC) feedstock. The fabrication of highly filled ceramic filaments was accomplished using the granulation by agitation technique, followed by twin-screw extruder homogenization and single-screw extruder filament extrusion. The feedstocks are based on alumina (Al₂O₃) powders, which were prepared with an industrial binder through three different routes: wet granulation, melt granulation and melt granulation with a suspension. After printing cubic samples and tensile test specimens on a commercial fused deposition modelling (FDM) printer, the properties of the resulting green-body and sintered parts were investigated. The green-body mechanical values are compared with results from commercially available filaments. Mixing the binder with the alumina powder and surfactant in a suspension produces the lowest viscosity and the best elongation at break. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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27 pages, 43194 KiB

Open AccessArticle

Low-Temperature Magnesium Calcium Phosphate Ceramics with Adjustable Resorption Rate

by Yulia Lukina, Sergey Kotov, Leonid Bionyshev-Abramov, Natalya Serejnikova, Rostislav Chelmodeev, Roman Fadeev, Otabek Toshev, Alexander Tavtorkin, Maria Ryndyk, Dmitriiy Smolentsev, Nikolay Gavryushenko and Sergey Sivkov

Ceramics 2023, 6(1), 168-194; https://doi.org/10.3390/ceramics6010011 - 10 Jan 2023

Cited by 6 | Viewed by 2917

Abstract

Low-temperature ceramics based on magnesium calcium phosphate cement are a promising resorbable material for bone tissue restoration with the possibility of functionalization. The replacement of the magnesium Mg²⁺ ion with a calcium Ca²⁺ ion at the stage of preparation of the [...] Read more.

Low-temperature ceramics based on magnesium calcium phosphate cement are a promising resorbable material for bone tissue restoration with the possibility of functionalization. The replacement of the magnesium Mg²⁺ ion with a calcium Ca²⁺ ion at the stage of preparation of the precursor leads to the production of multiphase ceramics containing phases of brushite, monetite, and newberyite, with different dissolution rates. Multiphase ceramics leads to volumetric resorption with preservation of their geometric shape, which was confirmed by the results of an evaluation of the output of magnesium Mg²⁺ and calcium Ca²⁺ ions into the contact solution of the ceramics and the X-ray density of ceramic samples during subcutaneous implantation. The combined introduction of sodium pyrophosphate decahydrate and citric acid monohydrate as setting inhibitors neutralizes their insignificant negative effect on the physico-chemical properties of ceramics (strength, pH, porosity), determining the optimal composition. In vivo experiments with setting inhibitors in the composition of ceramics showed a different biological response, affecting the rate of resorption on par with magnesium ions. Preliminary data on biocompatibility and solubility determined magnesium-calcium phosphate ceramics containing additives that regulate setting to be a potential material for bone tissue restoration and a vector for further research, including in orthotopic implantation models. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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30 pages, 16798 KiB

Open AccessArticle

Digital Image Correlation Characterization of Deformation Behavior and Cracking of Porous Segmented Alumina under Uniaxial Compression

by Vladimir Kibitkin, Nickolai Savchenko, Mikhail Grigoriev, Andrey Solodushkin, Alexander Burlachenko, Ales Buyakov, Anna Zykova, Valery Rubtsov and Sergei Tarasov

Ceramics 2023, 6(1), 102-131; https://doi.org/10.3390/ceramics6010008 - 9 Jan 2023

Cited by 3 | Viewed by 2048

Abstract

In this study, the two-dimensional digital image correlation (DIC) technique has been applied to sequences of images taken from the surfaces of porous, segmented alumina samples during uniaxial compression tests. The sintered alumina was structurally composed of polycrystalline alumina grains with interior ~3–5-μm [...] Read more.

In this study, the two-dimensional digital image correlation (DIC) technique has been applied to sequences of images taken from the surfaces of porous, segmented alumina samples during uniaxial compression tests. The sintered alumina was structurally composed of polycrystalline alumina grains with interior ~3–5-μm pores, a network of discontinuities that subdivided the sample into ~230 μm segments, and ~110 μm pores located at the discontinuity network nodes. Bimodal pore structure and the segment boundaries were the results of the evaporation and the outgassing of the paraffin and ultra-high-molecular-weight polyethylene admixed with alumina powder via slip casting. Only partial bonding bridges between the segments were formed during a low-temperature sintering at 1300 °C for 1 h. A special technological approach made it possible to change the strength of the partial bonding bridges between the segments, which significantly affected the deformation behavior ceramics during compression. The subpixel accuracy of the DIC results was achieved using an interpolation scheme for the identification functional. The vector fields obtained in the experiment made it possible to characterize the processes of deformation and destruction of a porous, segmented alumina using the strain localization in situ maps, cardinal plastic shear, and circulation of vector fields. The use of these characteristics made it possible to reveal new details in the mechanisms of deformation and destruction of segmented ceramics. The localizations of damage were identified and related to the characteristic structural heterogeneities of the tested porous segmented ceramics. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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16 pages, 16237 KiB

Open AccessArticle

Influence of Reinforcing Efficiency of Clay on the Mechanical Properties of Poly(butylene terephthalate) Nanocomposite

by Maria A. S. Colombo, Francisco R. V. Díaz, Deepa Kodali, Vijaya Rangari, Olgun Güven and Esperidiana A. B. Moura

Ceramics 2023, 6(1), 58-73; https://doi.org/10.3390/ceramics6010005 - 8 Jan 2023

Cited by 5 | Viewed by 2221

Abstract

In contrast to traditional fillers, clay, in particular, natural smectite clay, represents an environmentally significant alternative to improve the properties of polymers. Compared to conventional nanofillers, smectite clay can effectively enhance the physical and mechanical properties of polymer nanocomposites with a relatively small [...] Read more.

In contrast to traditional fillers, clay, in particular, natural smectite clay, represents an environmentally significant alternative to improve the properties of polymers. Compared to conventional nanofillers, smectite clay can effectively enhance the physical and mechanical properties of polymer nanocomposites with a relatively small amount of addition (<5 wt%). The present study focuses on investigating the reinforcing efficiency of different amounts (up to 5 wt%) of a natural Brazilian smectite clay modified (MBClay) on the mechanical properties of poly(butylene terephthalate) (PBT) nanocomposites and also evaluates the correlation between MBClay addition and the mechanical and thermal behaviors of the PBT/MBClay nanocomposites. Natural Brazilian clay modified by the addition of quaternary salt and sodium carbonate (MBClay) was infused into the PBT polymer by melt extrusion using a twin-screw extruder. It was found that the best properties for PBT were obtained at 3.7 wt% of modified BClay. Tensile strength at break exhibited increased by about 60%, flexural strength increased by 24%, and flexural modulus increased by 17%. In addition, an increase in the crystallinity percentage of PBT/BClay nanocomposite was confirmed by DSC and XRD analysis, and a gain of about 45% in HDT was successfully achieved due to the incorporation of 3.7 wt% of MBClay. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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15 pages, 5802 KiB

Open AccessArticle

Influence of Luminescent Properties of Powders on the Fabrication of Scintillation Ceramics by Stereolithography 3D Printing

by Lydia V. Ermakova, Valery V. Dubov, Rasim R. Saifutyarov, Daria E. Kuznetsova, Maria S. Malozovskaya, Petr V. Karpyuk, Georgy A. Dosovitskiy and Petr S. Sokolov

Ceramics 2023, 6(1), 43-57; https://doi.org/10.3390/ceramics6010004 - 7 Jan 2023

Cited by 10 | Viewed by 2899

Abstract

Luminescent and scintillation ceramic materials with complex shapes, which can be created by stereolithography 3D printing, are of interest for special phosphor and detector applications. Starting powders for such ceramics may possess UV absorption bands; therefore, it is important to study the possible [...] Read more.

Luminescent and scintillation ceramic materials with complex shapes, which can be created by stereolithography 3D printing, are of interest for special phosphor and detector applications. Starting powders for such ceramics may possess UV absorption bands; therefore, it is important to study the possible influence of the powders’ luminescent properties on the printing process. This paper deals with complex garnet oxides, Y₃Al₅O₁₂ and Gd₃Al₂Ga₃O₁₂—well-known hosts for luminescent materials. The photopolymerization rates of slurries based on the luminescent powders produced by various chemical routes are studied, as well as available printing regimes. The slurries containing Ce-doped powders with a broad absorption band in UV have significantly lower photopolymerization rates compared to the undoped ones; a high Ce doping virtually hinders printing with layers thicker than 25–50 μm. Furthermore, the choice of powder synthesis method is shown to influence the printing process. Slurries with Tb-doped powder, with absorption lines at shorter wavelengths, have good photopolymerization activity, close to that of the undoped powder, and can be printed with layer thicknesses of 25–100 μm. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 3589 KiB

Open AccessArticle

Utilization of Recycled Material for Producing Magnesia–Carbon Refractories

by Kirsten Moritz, Nora Brachhold, Jana Hubálková, Gert Schmidt and Christos G. Aneziris

Ceramics 2023, 6(1), 30-42; https://doi.org/10.3390/ceramics6010003 - 6 Jan 2023

Cited by 8 | Viewed by 2465

Abstract

The partial replacement of primary raw materials for the production of refractories with recycled ones gains in importance, as it contributes to the conservation of natural resources, energy saving, and reduction in greenhouse gas emissions. In this work, the use of a magnesia–carbon [...] Read more.

The partial replacement of primary raw materials for the production of refractories with recycled ones gains in importance, as it contributes to the conservation of natural resources, energy saving, and reduction in greenhouse gas emissions. In this work, the use of a magnesia–carbon (MgO-C) recyclate in the fractions 3–6, 1–3, and 0–1 mm as a raw material for MgO-C refractories was investigated. The recyclate was examined via optical and scanning electron microscopy. Using mixtures with different recyclate contents up to 82 wt%, MgO-C specimens were prepared to study the influence of the recyclate on their chemical composition, structure, and properties. The substitution of primary raw materials with the recyclate did not cause a decrease in the MgO content analyzed after carbon burnout, but the contents of the individual impurities changed. A comparison of the MgO-C that contains 82 wt% recyclate with the recyclate-free material through computed tomography indicated a change in the size distribution of the MgO grains. The porosity increased, and the cold modulus of rupture decreased with increasing recyclate content, whereas the thermal shock resistance improved. At a recyclate content of 40 wt%, the refractoriness under load was only slightly lower than that of the recyclate-free material. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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14 pages, 5685 KiB

Open AccessArticle

Synthesis of Nanocrystalline Yttrium Oxide and Evolution of Morphology and Microstructure during Thermal Decomposition of Y₂(C₂O₄)₃·10H₂O

by Pavel A. Gribov, Anatoly A. Sidelnikov, Rodion V. Belosludov and Alexander A. Matvienko

Ceramics 2023, 6(1), 16-29; https://doi.org/10.3390/ceramics6010002 - 6 Jan 2023

Viewed by 1850

Abstract

A study of the morphology and evolution of the microstructure during thermal decomposition of Y₂(C₂O₄)₃·10H₂O was conducted, and the stages and factors having the greatest impact on particle size and specific surface area [...] Read more.

A study of the morphology and evolution of the microstructure during thermal decomposition of Y₂(C₂O₄)₃·10H₂O was conducted, and the stages and factors having the greatest impact on particle size and specific surface area were identified. The effect of the yttrium oxalate hexahydrate phases on the course of decomposition was also investigated. The evolution of the morphology and microstructure of decomposition products was explained from the analysis of volume shrinkage at various stages of the reaction. The formation of oxycarbonate is accompanied by the largest shrinkage during the reaction. At this stage, there is a significant increase in the specific surface area to 60–90 m²/g. Conversely, the morphology and microstructure of the particles during the transformation of oxycarbonate into yttrium oxide change insignificantly. Yttrium oxide powders obtained from the monoclinic and triclinic hexahydrate phases have the same specific surface area, but different morphology and bulk density due to pseudomorph formation. The carbon formed during thermolysis was shown to affect the specific surface area of the decomposition product. Two methods for producing yttrium oxide with high specific surface area have been proposed, and nanocrystalline yttrium oxide with a specific surface area of 65 m²/g was obtained. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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15 pages, 6517 KiB

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Sr₂TiSi₂O₈ (STS) Polar Glass-Ceramics: Effect of Na₂O and CaO Additions in the Parent Glass on the Crystallization Mechanism and on the Piezoelectric Properties

by Maurice Gonon, Soufyane Satha, Thomas Zanin, Hamid Satha and Sandra Abdelouhab

Ceramics 2023, 6(1), 1-15; https://doi.org/10.3390/ceramics6010001 - 6 Jan 2023

Cited by 3 | Viewed by 1897

Abstract

Glass-ceramics containing pyroelectric Sr₂TiSi₂O₈ (STS) crystals are produced from parent glasses of compositions STS + 0.8 SiO₂ + (0.2 − x) Na₂O + x CaO, with x = 0; 0.05; 0.10; and 0.15. The aim [...] Read more.

Glass-ceramics containing pyroelectric Sr₂TiSi₂O₈ (STS) crystals are produced from parent glasses of compositions STS + 0.8 SiO₂ + (0.2 − x) Na₂O + x CaO, with x = 0; 0.05; 0.10; and 0.15. The aim of this work is to investigate the effect of the additions to the stoichiometric STS composition on the crystallization mechanisms and on the piezoelectric properties of the glass-ceramic. The DSC analyses evidence that the glass transition temperatures T_g, the onset temperature of the crystallization peak T_o and the temperature T_c of the maximum of this peak increase with the CaO/Na₂O ratio. On the basis of the DSC data, the crystallization of the parent glass samples was operated by thermal treatment. The observation of the cross-sections of the heat-treated samples highlights that the competition between the surface and volume crystallization mechanisms is influenced by the CaO/Na₂O ratio and the temperature. For all the samples, the XRD analyses performed on the surfaces as obtained after the crystallization treatment evidenced a preferential orientation of the STS crystals with the plans (00l) parallel to the surface. The XRD analyses performed after grinding the surface show that only the surface crystallized layers are preferentially oriented. Moreover, changes in preferential orientation to plans (202) or (201) are observed over the depth, depending on the composition and the temperature of the thermal treatment. These changes influence the polarization of the surface crystallized layer and, consequently, its piezoelectric charge coefficient d₃₃. The highest values of d₃₃ were measured on the glass-ceramic samples exhibiting mainly a (202) preferential orientation over their thickness. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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14 pages, 2252 KiB

Open AccessArticle

Optimization of Aluminum Boride Synthesis in the Self-Propagating High-Temperature Synthesis Mode to Create Waste-Free Technology

by Sestager Khusainovich Aknazarov, Alibek Zhumabekovich Mutushev, Juan Maria Gonzalez-Leal, Olga Stepanovna Bairakova, Olga Yuryevna Golovchenko, Natalia Yuryevna Golovchenko and Elena Alexandrovna Ponomareva

Ceramics 2022, 5(4), 1286-1299; https://doi.org/10.3390/ceramics5040091 - 14 Dec 2022

Cited by 1 | Viewed by 1924

Abstract

This paper is the continuation of our previous paper. In this work, we optimized the synthesis of aluminum borides by the SHS method. The purpose of the research was to develop the foundations of waste-free technology. The initial components were powders of boric [...] Read more.

This paper is the continuation of our previous paper. In this work, we optimized the synthesis of aluminum borides by the SHS method. The purpose of the research was to develop the foundations of waste-free technology. The initial components were powders of boric anhydride (B₂O₃), aluminum (Al), the oxide-heating additive (KNO₃), various fluxing additives, including mixed ones. The optimal ratios of the initial components for increasing the yield of aluminum boride with a high boron content and obtaining slag suitable for the production of high-alumina clinkers were determined. Studies have shown that the development of a waste-free technology for producing aluminum borides by the method of self-propagating high-temperature synthesis (SHS) is possible and yields target (alloy) and by-product (slag) products that meet the requirements for chemical and phase composition. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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17 pages, 11725 KiB

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Reducing the Distortion in Particle Filled Material Extrusion (MEX)-Based Additive Manufacturing (AM) by Means of Modifying the Printing Strategy

by Johannes Abel, Siddharth Tiwari, Milán Kardos, Maria Reichel and Uwe Scheithauer

Ceramics 2022, 5(4), 1225-1241; https://doi.org/10.3390/ceramics5040087 - 8 Dec 2022

Cited by 4 | Viewed by 2973

Abstract

This study addresses a ubiquitous challenge in powder metallurgy: sintering distortion. Sintering distortion can have various causes. On one hand, external factors such as friction with the sintering support during sintering or temperature gradients in the furnace, and, on the other hand, internal [...] Read more.

This study addresses a ubiquitous challenge in powder metallurgy: sintering distortion. Sintering distortion can have various causes. On one hand, external factors such as friction with the sintering support during sintering or temperature gradients in the furnace, and, on the other hand, internal factors such as anisotropic shrinkage due to directional layer build-up or residual stresses during production, can cause deformation by relieving mechanical stress. This paper presents an approach to reducing residual stresses in components produced by ceramic Fused Filament Fabrication (CerAM FFF) by changing the printing strategy using thermoplastic porcelain filaments with a solid loading of 57% vol. The starting point of the investigation was the torsion of standard sliced porcelain fragments after solvent debinding, which led to the idea to change the printing direction to prevent the distortion. Therefore, a Python™-based post-processor was developed to control the printing direction. It has been shown that this approach can even prevent warpage both for printed ceramic and also for the metal components for technical applications. This simple observation will help all powder metallurgical manufacturers using Material Extrusion (MEX)-based Additive Manufacturing (AM). Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 3710 KiB

Open AccessArticle

Microwave Plasma Assisted Aerosol Deposition (μ-PAD) for Ceramic Coating Applications

by Soo Ouk Jang, Changhyun Cho, Ji Hun Kim, In Je Kang, Hyonu Chang, Hyunjae Park, Kyungmin Lee, Dae Gun Kim and Hye Won Seok

Ceramics 2022, 5(4), 1174-1184; https://doi.org/10.3390/ceramics5040083 - 2 Dec 2022

Viewed by 2371

Abstract

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or [...] Read more.

To improve plasma and chemical resistance on various vacuum components used for semiconductor manufacturing equipment, various ceramic coating techniques have been applied. Among these methods for ceramic coating, the well-known atmospheric plasma spray (APS) is advantageous for providing thick film (100 µm or more) deposition. However, there are problems associated with the phase transition of the coating film and poor film quality due to formation of voids. To solve these problems, the aerosol deposition (AD) method has been developed. This method provides nice ceramic film quality. However, the coating rate is quite slow and has difficulty producing thick films (>30 µm). To overcome these limitations, microwave plasma-assisted aerosol deposition (μ-PAD) is applied at low vacuum conditions without the AD nozzle. This method uses a microwave plasma source during the AD process. After enduring a long-term durability test, as a trial run, μ-PAD has been applied on the actual process site. With the Al₂O₃ powder, μ-PAD shows a coating rate that is 12 times higher than the AD method. In addition, the formation of a thicker film (96 µm) deposition has been demonstrated. On the other hand, the coating film hardness, porosity, adhesion, and withstand voltage characteristics were confirmed to be less than the AD method. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 4599 KiB

Open AccessArticle

Fabrication of NiO/YSZ-Based Anodes for Solid Oxide Fuel Cells by Hybrid 3D Inkjet Printing and Laser Treatment

by Inna Malbakhova, Artem Bagishev, Alexander Vorobyev, Tatiana Borisenko, Olga Logutenko and Alexander Titkov

Ceramics 2022, 5(4), 1115-1127; https://doi.org/10.3390/ceramics5040079 - 1 Dec 2022

Cited by 5 | Viewed by 3203

Abstract

An anode for solid oxide fuel cells (SOFCs) was fabricated using 3D inkjet printing and layer-by-layer laser treatment of compositions based on the NiO/YSZ system followed by thermal sintering. The samples were characterized by scanning electron microscopy and X-ray phase analysis. The study [...] Read more.

An anode for solid oxide fuel cells (SOFCs) was fabricated using 3D inkjet printing and layer-by-layer laser treatment of compositions based on the NiO/YSZ system followed by thermal sintering. The samples were characterized by scanning electron microscopy and X-ray phase analysis. The study of the morphology of the as-prepared samples revealed the presence of both interlayer macroporosity and intralayer microporosity, which depends on the laser exposure during laser treatment. The use of graphite directly added to the printing composition as the pore former increased the intralayer porosity. The morphology and size of the pores were shown to be similar to those of the pore former. The microstructure and porosity of the anode support can be controlled by varying the laser exposure values and the graphite content of the ceramic composite, which in turn opens up great prospects for using these paste compositions and printing techniques for the manufacture of SOFC anode supports. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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18 pages, 5678 KiB

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Silicon Carbide Precursor: Structure Analysis and Thermal Behavior from Polymer Cross-Linking to Pyrolyzed Ceramics

by Sébastien Vry, Marilyne Roumanie, Pierre-Alain Bayle, Sébastien Rolère and Guillaume Bernard-Granger

Ceramics 2022, 5(4), 1066-1083; https://doi.org/10.3390/ceramics5040076 - 23 Nov 2022

Cited by 2 | Viewed by 3021

Abstract

The Silres H62C methyl-phenyl-vinyl-hydrogen polysiloxane is a promising candidate as a SiC precursor for 3D printing based on photopolymerization reaction. An in-depth nuclear magnetic resonance spectroscopy analysis allowed us to determine its structure and quantify its functional groups. The polysiloxane was found to [...] Read more.

The Silres H62C methyl-phenyl-vinyl-hydrogen polysiloxane is a promising candidate as a SiC precursor for 3D printing based on photopolymerization reaction. An in-depth nuclear magnetic resonance spectroscopy analysis allowed us to determine its structure and quantify its functional groups. The polysiloxane was found to have a highly branched ladder-like structure, with 21.9, 31.4 and 46.7% of mono-, di- and tri-functional silicon atoms. The polysiloxane cross-links from 180 °C using hydrosilylation between silyl groups (8.4% of the total functional groups) and vinyl groups (12.0%) and contains a non-negligible ethoxy content (2.4%), allowing cross-linking through a hydrolyze/condensation mechanism. After converting the polymer into ceramic and thus releasing mainly hydrogen and methane, the ceramic yield was 72.5%. An X-ray diffraction analysis on the cross-linked and pyrolyzed polysiloxane showed that the ceramic is amorphous at temperatures up to 1200 °C and starts to crystallize from 1200 °C, leading into 3C-SiC carbon-rich ceramic at 1700 °C in an argon atmosphere. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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15 pages, 4275 KiB

Open AccessArticle

Analysis of the Formed Protective Layer Inhibiting Alkali Corrosion in Aluminosilicate Refractory Castables

by Valentin Antonovič, Rimvydas Stonys, Povilas Zdanevičius, Romualdas Mačiulaitis, Renata Boris and Jurgita Malaiškienė

Ceramics 2022, 5(4), 1051-1065; https://doi.org/10.3390/ceramics5040075 - 19 Nov 2022

Cited by 3 | Viewed by 2297

Abstract

This article analyzes the mechanism of the protective layer formation under the action of alkali in a refractory castable when ground quartz sand (GQS) is used as an admixture to produce refractory conventional castables (CC) and medium cement castables (MCC). It was found [...] Read more.

This article analyzes the mechanism of the protective layer formation under the action of alkali in a refractory castable when ground quartz sand (GQS) is used as an admixture to produce refractory conventional castables (CC) and medium cement castables (MCC). It was found that, independently of the castable composition, the addition of GQS (2.5%) reduces the degree of K₂CO₃ dissolution at high temperature, and the released potassium reacts with the silica and forms a viscous potassium silicate glass, which reduces the mobility of alkali. The liquid phase formed filled some of the open pores and hindered the penetration of potassium into the deeper layers of the refractory castable. The thickness of the formed protective layer, after three cycles of the alkaline corrosion test, varies from 700 µm up to 1300 µm, depending on the castable composition. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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16 pages, 5129 KiB

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Complex Oxide Nanoparticle Synthesis: Where to Begin to Do It Right?

by Elizabeth Gager, William Halbert and Juan C. Nino

Ceramics 2022, 5(4), 1019-1034; https://doi.org/10.3390/ceramics5040073 - 19 Nov 2022

Cited by 4 | Viewed by 2598

Abstract

Synthesis of advanced ceramics requires a high degree of control over the particle size and stoichiometry of the material. When choosing a synthesis method for complex oxides it is important to begin with the correct precursors and solvents to achieve high purity nanoparticles. [...] Read more.

Synthesis of advanced ceramics requires a high degree of control over the particle size and stoichiometry of the material. When choosing a synthesis method for complex oxides it is important to begin with the correct precursors and solvents to achieve high purity nanoparticles. Here, we detail the selection process for precursors and solvents for liquid-phase precipitation synthesis. Data for metal nitrate, chloride, acetate, and oxalate precursors has been compiled to assist future synthesis. The role of hydration within the precursors is discussed as it affects the final stoichiometry of the material. Melting temperatures are also compiled for these compounds to assist in material selection. The solubility of the precursors in different solvents is examined to determine the correct solvent during synthesis. As an example, using the methodology presented here, two different materials are synthesized based on commonly available precursors. A catalyst based on a quaternary perovskite and an advanced ionic conductor based on a high entropy fluorite oxide are synthesized using precipitation methods and their characterization is detailed. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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14 pages, 7927 KiB

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Forming of Additively Manufactured Ceramics by Magnetic Fields

by Christina Klug, Simone Herzog, Anke Kaletsch, Christoph Broeckmann and Thomas H. Schmitz

Ceramics 2022, 5(4), 947-960; https://doi.org/10.3390/ceramics5040068 - 3 Nov 2022

Cited by 1 | Viewed by 2184

Abstract

The application of additive manufacturing using liquid material extrusion is inherently linked to material-related deformations and limitations in the choice of component geometry. This empirical study addresses the question of how the plasticity of a ceramic composite material can be utilized for a [...] Read more.

The application of additive manufacturing using liquid material extrusion is inherently linked to material-related deformations and limitations in the choice of component geometry. This empirical study addresses the question of how the plasticity of a ceramic composite material can be utilized for a new integrated design and manufacturing process. In the exploratory approach, the liquid material is not limited in its soft plastic state, but its malleability is harnessed for a design-oriented approach. For this purpose, soft magnetic particles are added to a liquid clay mass. The developed composite material can be controlled, stabilized, and shaped by magnetic fields directly in the additive manufacturing process using modified equipment. In this study a permanent magnet and an electromagnet were compared while the distance between the printed part and the magnet was controlled by an optical sensor. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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19 pages, 16805 KiB

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The Solution Combustion Synthesis of ZnO Powder for the Photodegradation of Phenol

by Aleksandr P. Amosov, Vladislav A. Novikov, Egor M. Kachkin, Nikita A. Kryukov, Alexander A. Titov, Ilya M. Sosnin and Dmitry L. Merson

Ceramics 2022, 5(4), 928-946; https://doi.org/10.3390/ceramics5040067 - 3 Nov 2022

Cited by 6 | Viewed by 2807

Abstract

Nanoscale and submicron powder of zinc oxide (ZnO) is known as a highly efficient photocatalyst that is promising for solving the problem of wastewater treatment from toxic organic pollutants including phenol and its derivatives. The results of laboratory studies of ZnO preparation by [...] Read more.

Nanoscale and submicron powder of zinc oxide (ZnO) is known as a highly efficient photocatalyst that is promising for solving the problem of wastewater treatment from toxic organic pollutants including phenol and its derivatives. The results of laboratory studies of ZnO preparation by a simple, energy-saving, and highly productive method of solution–combustion synthesis from a mixture of solutions of zinc nitrate and glycine, as well as the use of the ZnO powder synthesized by combustion for the photocatalytic decomposition of phenol, are presented. The modes and characteristics of combustion, phase composition, chemical composition, and structure of the combustion product at different ratios of glycine with zinc nitrate were determined. It is shown that calcination at 650 °C reduces the content of carbon impurity in the combustion product to ~1 wt.% and leads to obtaining ZnO powder in the form of porous agglomerates up to 100 μm in size sintered from crystalline nanoscale and submicron ZnO particles with an average crystallite size of 44 nm. The ZnO powder exhibits high photocatalytic activity, leading to the almost complete degradation of phenol in an aqueous solution under the action of ultraviolet irradiation in less than 4 h. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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20 pages, 2358 KiB

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Micro-Analytical Study of a Zeolites/Geo-Polymers/Quartz Composite, Dielectric Behaviour and Contribution to Brønsted Sites Affinity

by Abdel Boughriet, Oscar Allahdin, Nicole Poumaye, Gregory Tricot, Bertrand Revel, Ludovic Lesven and Michel Wartel

Ceramics 2022, 5(4), 908-927; https://doi.org/10.3390/ceramics5040066 - 2 Nov 2022

Cited by 3 | Viewed by 2125

Abstract

The chemical and mineralogical surface properties of a brick-derived composite were examined by using an environmental scanning electron microscopy (ESEM) equipped with an energy dispersive X-ray spectrometer (EDS). Investigations revealed that the material could be assimilated to an adsorptive membrane having zeolites deposited [...] Read more.

The chemical and mineralogical surface properties of a brick-derived composite were examined by using an environmental scanning electron microscopy (ESEM) equipped with an energy dispersive X-ray spectrometer (EDS). Investigations revealed that the material could be assimilated to an adsorptive membrane having zeolites deposited onto quartz matrix. In our calculation, the membrane was considered as a diphase composite and its dielectric constant was evaluated from theoretical models developed in the literature. Electro-kinetic analysis showed that composite surfaces were hydroxylated with the formation of hydroxyl groups which behaved amphoterically. A theory-based approach was used for calculating thermodynamic constants relative to surface-protonation equilibriums. In the H-form of the composite, the occurrence of bridging Si–(OH)–Al sites were evidenced by mathematical calculations utilizing equations in direct relation to mineralogical, crystallographic and dielectric surface characteristics. ¹H MAS NMR spectroscopy confirmed the existence of bridging Brønsted acid sites at acidified composite surfaces interacting with ammonium (as probe ions). Owing to advancements in brick-based composites research, this should lead more to the development of “ceramic” adsorptive membranes with natural clay materials. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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18 pages, 6304 KiB

Open AccessArticle

Deliberate Surface Treatment of Zirconium Dioxide with Abrasive Brushing Tools

by Anton Hoyer and Eckart Uhlmann

Ceramics 2022, 5(4), 883-900; https://doi.org/10.3390/ceramics5040064 - 1 Nov 2022

Cited by 1 | Viewed by 1891

Abstract

Brushing with bonded abrasives is a flexible finishing process used to reduce the roughness of technical surfaces. Although industrially widespread, especially for the finishing of metallic surfaces, insufficient knowledge of the motion, the material removal, and the wear behavior of the abrasive filaments [...] Read more.

Brushing with bonded abrasives is a flexible finishing process used to reduce the roughness of technical surfaces. Although industrially widespread, especially for the finishing of metallic surfaces, insufficient knowledge of the motion, the material removal, and the wear behavior of the abrasive filaments complicates predictions of the work result. In particular, the reliable finishing of ceramics with bonded diamond grains proves difficult due to increased material removal rates, quickly leading to undesirable changes in the workpiece geometry. Based on technological investigations with abrasive brushing tools, this article provides insights into the surface finishing of zirconium dioxide with a focus on finding compromises between reduction in the surface roughness and alteration of the workpiece shape. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 5234 KiB

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Synthesis of Boron Carbide Powder via Rapid Carbothermal Reduction Using Boric Acid and Carbonizing Binder

by Bing Feng, Hans-Peter Martin and Alexander Michaelis

Ceramics 2022, 5(4), 837-847; https://doi.org/10.3390/ceramics5040061 - 21 Oct 2022

Viewed by 3905

Abstract

Raw material is one of the most decisive factors for the quality of sintered boron carbide (B₄C) products, in the past, there were relatively successful efforts for the synthesis of B₄C powders via carbothermal reduction approaches. To prepare high-quality [...] Read more.

Raw material is one of the most decisive factors for the quality of sintered boron carbide (B₄C) products, in the past, there were relatively successful efforts for the synthesis of B₄C powders via carbothermal reduction approaches. To prepare high-quality powder, a deeper understanding of the relationship between technological manufacturing parameters and resulting powder properties is required. In this paper, pure B₄C powders were synthesized by rapid carbothermal reduction (RCR) under B₂O₃ excess conditions using boric acid and a carbonizing binder as B₂O₃ and carbon source, respectively. The molar ratio of B₂O₃/C of starting mixtures was varied from 0.75:1 to 4:1. The effects of heat-treating temperature and starting composition on phase constitution, morphology as well as stoichiometry of the prepared powders were investigated. The studies show that the starting composition has no effect on the stoichiometry of the powders, all boron carbides synthesized at 1900 °C have a stoichiometric composition of B₄C. With increasing heating temperature and B₂O₃ content in the starting composition, the particle size of B₄C was reduced. Uniform B₄C powders with an average grain size of 300 nm were synthesized at 1900 °C from a starting powder mixture with a molar ratio of B₂O₃/C = 4. A formation mechanism is proposed under large B₂O₃ excess conditions. For the starting powder mixtures with a molar ratio of B₂O₃/C < 2, the formation of boron carbide occurs through both liquid–solid reaction and gas–solid reaction. Accordingly, the synthesized powders exhibit a morphology with mixed elongated platelets and small polyhedral particles. For the starting powder mixtures with a molar ratio of B₂O₃/C ≥ 2, fine-sized B₄C particles were formed by a liquid–solid reaction. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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9 pages, 3964 KiB

Open AccessArticle

Fabrication of Basalt Matrix Composite Material by Pressureless Aluminum Melt Infiltration in Air Atmosphere

by Roman A. Shishkin, Yuliy V. Yuferov and Dmitriy O. Polyvoda

Ceramics 2022, 5(4), 780-788; https://doi.org/10.3390/ceramics5040056 - 15 Oct 2022

Viewed by 1894

Abstract

The microstructure of Basalt matrix composite materials produced by pressureless aluminum melt infiltration at 950 °C was investigated. It is established that uniform elements distribution is observed within the whole sample depth. Interestingly, aluminum content variation considerably matches the hardness of the sample [...] Read more.

The microstructure of Basalt matrix composite materials produced by pressureless aluminum melt infiltration at 950 °C was investigated. It is established that uniform elements distribution is observed within the whole sample depth. Interestingly, aluminum content variation considerably matches the hardness of the sample profile that is connected with alumina phase presence. Sample color changes during temperature treatment due to phase transitions were observed. The appearance of the hematite (Fe₂O₃) phase makes the initial preform red. After infiltration by molten aluminum, oxygen-deficient alumosilicate phases turn the color black. The infiltration process decreases the porosity insufficiently due to a partial reduction of alumosilicates by molten Al and the hardness of infiltrated samples was only 2.2 GPa. Nevertheless, a huge thermal conductivity rise from 1.45 to 4.53 W/(m·K), along with a fracture toughness increase, makes the produced composite a prospective wear-resistant material. Moreover, the developed low-temperature production technology allows for obtaining a very cost-effective material. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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17 pages, 6362 KiB

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A “Red-and-Green Porcelain” Figurine from a Jin Period Archaeological Site in the Primor’ye Region, Southern Russian Far East

by Irina S. Zhushchikhovskaya and Igor Yu Buravlev

Ceramics 2022, 5(4), 673-689; https://doi.org/10.3390/ceramics5040049 - 30 Sep 2022

Cited by 1 | Viewed by 1874

Abstract

This paper considers the results of an examination of a polychrome glazed anthropomorphic ceramic figurine from the Prmor’ye region (southern Russian Far East) discovered at one of the Jin period (1115–1234 CE) archaeological sites. The study attests to the hypothesis about the attribution [...] Read more.

This paper considers the results of an examination of a polychrome glazed anthropomorphic ceramic figurine from the Prmor’ye region (southern Russian Far East) discovered at one of the Jin period (1115–1234 CE) archaeological sites. The study attests to the hypothesis about the attribution of this unique art object to the “red-and-green porcelain” produced in Northern China since the mid-Jin period. At present “the red-and-green porcelain” is the object of certain research interest as an important stage of Chinese ceramics history preceding the invention of famous porcelains with overglazed enamel decoration. The main technological features and material properties of the studied object were determined using analytical methods of optical and electron (SEM) microscopy with the use of X-ray elemental composition analysis (EDS, pXRF). The main result of the study presented in the paper includes evidence that the polychrome ceramic figurine found at the Anan’evka walled town in Primor’ey in the south of the Russian Far East belongs to the category of “red-and-green porcelain”, or “red-green ware”. As supposed, the figurine portrays Zen monk Budai—a person popular in Chinese arts and spiritual culture of the Song and Jin periods. Therefore, the polychrome ceramics figurine from the Primor’ye region may be considered today as the most northeastern case of “red-and-green porcelain” discovered in an archaeological context. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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18 pages, 5099 KiB

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X-ray Diffraction, Micro-Raman and X-ray Photoemission Spectroscopic Investigations for Hydrothermally Obtained Hybrid Compounds of Delafossite CuGaO₂ and Wurtzite ZnO

by Minuk Choi, Christoph Brabec and Tomokatsu Hayakawa

Ceramics 2022, 5(4), 655-672; https://doi.org/10.3390/ceramics5040048 - 22 Sep 2022

Cited by 6 | Viewed by 2548

Abstract

P-type delafossite CuGaO₂ is a wide-bandgap semiconductor for optoelectronic applications, and its lattice parameters are very similar to those of n-type semiconductor wurtzite ZnO. Accordingly, the investigation of crystalline heterostructures of CuGaO₂ and ZnO has attracted significant attention. In this study, [...] Read more.

P-type delafossite CuGaO₂ is a wide-bandgap semiconductor for optoelectronic applications, and its lattice parameters are very similar to those of n-type semiconductor wurtzite ZnO. Accordingly, the investigation of crystalline heterostructures of CuGaO₂ and ZnO has attracted significant attention. In this study, interfacial CuGaO₂/ZnO hetero-compounds were examined through X-ray diffraction (XRD) analysis, confocal micro-Raman spectroscopy, and X-ray photo-electron spectroscopy (XPS). XRD and Raman analysis revealed that the hydrothermal deposition of ZnO on hexagonal platelet CuGaO₂ base crystals was successful, and the subsequent reduction process could induce a unique, unprecedented reaction between CuGaO₂ and ZnO, depending on the deposition parameters. XPS allowed the comparison of the binding energies (peak position and width) of the core level electrons of the constituents (Cu, Ga, Zn, and O) of the pristine CuGaO₂ single crystallites and interfacial CuGaO₂/ZnO hybrids. The presences of Cu²⁺ ions and strained GaO₆ octahedra were the main characteristics of the CuGaO₂/ZnO hybrid interface. The XPS and modified Auger parameter analysis gave an insight into a specific polarization of the interface, promising for further development of CuGaO₂/ZnO hybrids. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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28 pages, 8884 KiB

Open AccessArticle

Ecofriendly High NIR Reflectance Ceramic Pigments Based on Rare Earths Compared with Classical Chromophores Prepared by DPC Method

by Guillermo Monrós, José A. Badenes and Mario Llusar

Ceramics 2022, 5(4), 614-641; https://doi.org/10.3390/ceramics5040046 - 20 Sep 2022

Cited by 8 | Viewed by 2757

Abstract

A high NIR reflectance ceramic pigments palette based on rare earths except black (La,Li-SrCuSi₄O₁₀ blue wesselsite, Pr-CeO₂ red-brown cerianite, Mo-Y₂Ce₂O₇ yellow cerate, Sr₄Mn₂CuO₉ black hexagonal perovskite) was compared with [...] Read more.

A high NIR reflectance ceramic pigments palette based on rare earths except black (La,Li-SrCuSi₄O₁₀ blue wesselsite, Pr-CeO₂ red-brown cerianite, Mo-Y₂Ce₂O₇ yellow cerate, Sr₄Mn₂CuO₉ black hexagonal perovskite) was compared with the coolest traditional pigments palette prepared by dry powder coating (DPC) to obtain “core-shell” pigments (Co-willemite blue, Cr-franklinite brown, Ni,Sb-rutile yellow, Co,Cr-spinel black). Adding CaCO₃ as a binder, normalized NIR reflectance at L* = 85, 55 and 30 was compared for yellow, brown and blue-black powders, respectively. Rare earths lack intense absorption bands in the NIR range and therefore its pigments show higher NIR reflectance, but normalized measurements show smaller differences and even have an inverse result for blue pigments. The pigmenting capacity and stability study in different media show that the stability of cool rare earth pigments is lower than that of DPC classical pigments, except in the case of the red-brown Pr-cerianite pigment. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 2772 KiB

Open AccessArticle

Electrical Conductivity of Thin Film SrTi_0.8Fe_0.2O_3−δ-Supported Sr_0.98Zr_0.95Y_0.05O_3−δ Electrolyte

by Adelya Khaliullina, Aleksander Pankratov and Liliya Dunyushkina

Ceramics 2022, 5(3), 601-613; https://doi.org/10.3390/ceramics5030045 - 17 Sep 2022

Viewed by 2448

Abstract

Thin films of Sr_0.98Zr_0.95Y_0.05O_3−δ (SZY) electrolyte were grown on porous supporting SrTi_0.8Fe_0.2O_3−δ electrodes by the chemical solution deposition method from a low-viscous solution of inorganic salts. The films were characterized by [...] Read more.

Thin films of Sr_0.98Zr_0.95Y_0.05O_3−δ (SZY) electrolyte were grown on porous supporting SrTi_0.8Fe_0.2O_3−δ electrodes by the chemical solution deposition method from a low-viscous solution of inorganic salts. The films were characterized by X-ray diffraction and scanning electron microscopy. The gas-tightness of the films was evaluated using the differential-pressure method. The across-plane electrical conductivity of 1 mm thick SZY film was measured by impedance spectroscopy and compared to that of a massive ceramic sample. The revealed difference in electrical properties of the film and massive SZY samples indicates that diffusional interaction between the film and the substrate influences the performance of the supported electrolyte. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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8 pages, 1283 KiB

Open AccessArticle

Modelling the Mechanical Properties of Hydroxyapatite Scaffolds Produced by Digital Light Processing-Based Vat Photopolymerization

by Francesco Baino, Martin Schwentenwein and Enrica Verné

Ceramics 2022, 5(3), 593-600; https://doi.org/10.3390/ceramics5030044 - 16 Sep 2022

Cited by 10 | Viewed by 2852

Abstract

Porosity is a key feature in dictating the overall performance of biomedical scaffolds, with special relevance to mechanical properties. Usually, compressive strength and elastic modulus are the main parameters used to determine the potential mechanical suitability of porous scaffolds for bone repair. However, [...] Read more.

Porosity is a key feature in dictating the overall performance of biomedical scaffolds, with special relevance to mechanical properties. Usually, compressive strength and elastic modulus are the main parameters used to determine the potential mechanical suitability of porous scaffolds for bone repair. However, their assessment may not be so easy from an experimental viewpoint and, especially if the porosity is high, so reliable for brittle bioceramic foams. Hence, assessing the relationship between porosity and mechanical properties based only on the constitutive parameters of the solid material is a challenging and important task to predict the scaffold performance for optimization during design. In this work, a set of equations was used to predict the compressive strength and elastic modulus of bone-like hydroxyapatite scaffolds produced by digital light processing-based vat photopolymerization (total porosity about 80 vol.%). The compressive strength was found to depend on total porosity, following a power-law approximation. The relationship between porosity and elastic modulus was well fitted by second-order power law, with relative density and computational models obtained by numerical simulations. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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18 pages, 4290 KiB

Open AccessArticle

Sol–Gel Synthesis of Iron-Doped Sepiolite as a Novel Humidity-Sensing Material

by Ahmed Sabry Afify, Mehran Dadkhah and Jean-Marc Tulliani

Ceramics 2022, 5(3), 575-592; https://doi.org/10.3390/ceramics5030043 - 15 Sep 2022

Cited by 4 | Viewed by 1942

Abstract

Nowadays, humidity sensors are attracting a great deal of attention, and there are many studies focusing on enhancing their performances. Nevertheless, their fabrication through facile methods at reasonable cost is a significant factor. In this article, a new magnesium silicate nanopowder was successfully [...] Read more.

Nowadays, humidity sensors are attracting a great deal of attention, and there are many studies focusing on enhancing their performances. Nevertheless, their fabrication through facile methods at reasonable cost is a significant factor. In this article, a new magnesium silicate nanopowder was successfully synthesized using a simple and low-cost sol–gel method. Subsequently, modified sepiolite was achieved by the substitution of iron ions in the synthesized nanopowders. The specimens were then characterized by X-ray diffraction, field emission–scanning electron microscopy, X-ray photoelectron spectroscopy, thermogravimetric–differential thermal analysis, infrared spectroscopy, and nitrogen adsorption. Furthermore, humidity sensors were manufactured by screen printing the prepared powders on alumina substrates with interdigitated Pt electrodes. The results showed that the fabricated sensors with modified sepiolite exhibited interesting characteristics for humidity detection. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 35314 KiB

Open AccessArticle

Fabrication of Complex Three-Dimensional Structures of Mica through Digital Light Processing-Based Additive Manufacturing

by Sinuo Zhang, Imam Akbar Sutejo, Jeehwan Kim, Yeong-Jin Choi, Chang Woo Gal and Hui-suk Yun

Ceramics 2022, 5(3), 562-574; https://doi.org/10.3390/ceramics5030042 - 8 Sep 2022

Cited by 8 | Viewed by 3102

Abstract

Mica is a group of clay minerals that are frequently used to fabricate electrical and thermal insulators and as adsorbents for the treatment of cationic pollutants. However, conventional subtractive manufacturing has the drawback of poor three-dimensional (3D) shape control, which limits its application. [...] Read more.

Mica is a group of clay minerals that are frequently used to fabricate electrical and thermal insulators and as adsorbents for the treatment of cationic pollutants. However, conventional subtractive manufacturing has the drawback of poor three-dimensional (3D) shape control, which limits its application. In this study, we propose digital light processing (DLP)-based additive manufacturing (AM) as one of the most effective ways to address this drawback. Two major challenges for the ceramic DLP process are the production of a homogeneous and stable slurry with the required rheological properties and the maintenance of printing precision. The mica green body was fabricated using a 53 vol.% solid loading slurry through DLP, which exhibited good dimensional resolution under an exposure energy dose of 10 mJ/cm². The precise, complex 3D structure was maintained without any defects after debinding and sintering at 1000 °C. The use of ceramic AM to overcome the shape-control limitations of mica demonstrated in this study offers great potential for expanding the applications of mica. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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17 pages, 3809 KiB

Open AccessArticle

Influence of Porosity on R-Curve Behaviour of Tetragonal Stabilized Zirconia

by Dino N. Boccaccini, Vanesa Gil, Jonas Gurauskis, Rosa I. Merino, Andrea Pellacani, Cecilia Mortalò, Stefano Soprani, Marcello Romagnoli and Maria Cannio

Ceramics 2022, 5(3), 533-549; https://doi.org/10.3390/ceramics5030040 - 5 Sep 2022

Viewed by 2213

Abstract

Y₂O₃ at 3% mol partially stabilized Zr₂O₃ (3YSZ) porous specimens with variable open porosity, from fully dense up to ~47%, and their potential use as anode supports for new solid oxide cell designs were fabricated by tape [...] Read more.

Y₂O₃ at 3% mol partially stabilized Zr₂O₃ (3YSZ) porous specimens with variable open porosity, from fully dense up to ~47%, and their potential use as anode supports for new solid oxide cell designs were fabricated by tape casting. The stiffness, strength and fracture properties were measured to investigate the influence of porosity on mechanical properties. The evolution of Young’s modulus and characteristic strength was evaluated by ball-on-ring tests. The variation of critical plane stress Mode I stress intensity factor with porosity has also been investigated and modelled from the results obtained from fracture mechanics testing. R-curve behaviour was observed in dense 3YSZ specimens and in porous 3YSZ compositions. The width of the transformation zone after fracture mechanics testing and the variation with porosity were investigated. The phases existing in the fracture zone were determined and quantified by Raman spectroscopy. It was found that the width of the transformation zone increased with increasing porosity. A new general R-curve model for 3YSZ based on the McMeeking–Evans equation is presented, which can be used to predict the behaviour of the R-curve as a function of porosity, simply by knowing the properties of the dense material and introducing in this equation porosity-dependent laws on the key properties that affect fracture toughness. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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17 pages, 3383 KiB

Open AccessArticle

Synthesis and Optical Characteristics of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ Ceramic Solid Solutions Prepared under Different Temperature Conditions

by Mikhail Palatnikov, Olga Shcherbina, Maxim Smirnov, Sofja Masloboeva, Vadim Efremov and Konstantin Andryushin

Ceramics 2022, 5(3), 499-515; https://doi.org/10.3390/ceramics5030038 - 26 Aug 2022

Cited by 1 | Viewed by 1933

Abstract

Fine powders of mixed gadolinium tantalum niobates doped with Eu, Sm, Tb, and Er were synthesized. Ceramic samples of polycomponent solid solutions of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ were obtained from synthesized [...] Read more.

Fine powders of mixed gadolinium tantalum niobates doped with Eu, Sm, Tb, and Er were synthesized. Ceramic samples of polycomponent solid solutions of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ were obtained from synthesized powders using conventional sintering technology. The phase composition and phase structure characteristics of the Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ ceramic phases were determined by XRD. The effect of ceramic sintering temperature on the physical characteristics of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ solid solutions is shown. The morphological features of the microstructure of the Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ ceramics were studied in relation to its mechanical characteristics. At the same time, the strength characteristics (Young’s modulus, microhardness) and the critical stress intensity factor for mode I K_IC were evaluated for the first time for the synthesized compounds. Photoluminescence and cathodoluminescence were studied in the visible region. The study confirms the potential application of Gd_0.96Eu_0.01Sm_0.01Tb_0.01Er_0.01Nb_0.9Ta_0.1O₄ ceramic solid solutions as scintillators and radioluminescent light sources. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 3355 KiB

Open AccessArticle

Effects of the Processing Technology of CVD-ZnSe, Cr²⁺:ZnSe, and Fe²⁺:ZnSe Polycrystalline Optical Elements on the Damage Threshold Induced by a Repetitively Pulsed Laser at 2.1 µm

by Nikolay Yudin, Oleg Antipov, Stanislav Balabanov, Ilya Eranov, Yuri Getmanovskiy and Elena Slyunko

Ceramics 2022, 5(3), 459-471; https://doi.org/10.3390/ceramics5030035 - 20 Aug 2022

Cited by 7 | Viewed by 2657

Abstract

Polycrystalline zinc selenide (ZnSe) and Cr²⁺ or Fe²⁺ doped ZnSe are key optical elements in mid-infrared laser systems. The laser-induced damage of the optical elements is the limiting factor for increasing the power and pulse energy of the lasers. In the [...] Read more.

Polycrystalline zinc selenide (ZnSe) and Cr²⁺ or Fe²⁺ doped ZnSe are key optical elements in mid-infrared laser systems. The laser-induced damage of the optical elements is the limiting factor for increasing the power and pulse energy of the lasers. In the present work, the optical damage of the ZnSe, Cr²⁺:ZnSe, and Fe²⁺:ZnSe samples induced by a repetitively pulsed Ho³⁺:YAG laser at 2091 nm was studied. The probability of the optical damage and the laser-induced damage threshold (LIDT) were determined for the samples manufactured using different processing techniques. The highest LIDT was found in ZnSe samples annealed in an argon atmosphere. It was also found that the samples annealed in a zinc atmosphere or with hot isostatic pressing resulted in a decrease in the LIDT. The Cr²⁺-doped ZnSe had the lowest LIDT at 2.1 µm compared to Fe²⁺-doped or undoped ZnSe. The LIDT fluence of all tested ZnSe samples decreased with the increase in the pulse repetition rate and the exposure duration. The results obtained may be used to improve the treatment procedures of ZnSe, Cr²⁺:ZnSe, and Fe²⁺:ZnSe polycrystals to further increase their LIDT. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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19 pages, 8347 KiB

Open AccessArticle

Possibilities of Mechanochemical Synthesis of Apatites with Different Ca/P Ratios

by Marina V. Chaikina, Natalia V. Bulina, Olga B. Vinokurova, Konstantin B. Gerasimov, Igor Yu. Prosanov, Nikolay B. Kompankov, Olga B. Lapina, Evgeniy S. Papulovskiy, Arcady V. Ishchenko and Svetlana V. Makarova

Ceramics 2022, 5(3), 404-422; https://doi.org/10.3390/ceramics5030031 - 3 Aug 2022

Cited by 21 | Viewed by 3046

Abstract

Apatite is widely used in medicine as a biomaterial for bone tissue restoration. Properties of apatite depend on its composition, including the Ca/P ratio. This paper shows what range of Ca/P ratio can be attained in apatite by the mechanochemical method of synthesis, [...] Read more.

Apatite is widely used in medicine as a biomaterial for bone tissue restoration. Properties of apatite depend on its composition, including the Ca/P ratio. This paper shows what range of Ca/P ratio can be attained in apatite by the mechanochemical method of synthesis, providing fast formation of a single-phase product. The synthesis was carried out from a reaction mixture of CaHPO₄ and CaO at different Ca/P ratios in the range of 1.17–2.10. The products were studied by PXRD, FTIR and NMR spectroscopy, HRTEM, and STA. In mixtures with a low initial Ca/P ratio (1.17–1.48), directly in the mill, the formation of calcium orthophosphate with whitlockite structure containing an HPO₄²⁻ group and structural water is shown for the first time. This phosphate has structure similar to that of whitlockites of hydrothermal origin and differs from high-temperature β-tricalcium phosphate that has composition Ca₃(PO₄)₃. A series of samples of apatite was obtained with varied composition, which depends on the initial Ca/P ratio. At Ca/P < 1.67, the formation of two types of calcium-deficient apatite was documented. At Ca/P > 1.67, the existence of two types of calcium-rich apatite is confirmed. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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7 pages, 2769 KiB

Open AccessArticle

Thermoelectric Properties of Si-Doped In₂Se₃ Polycrystalline Alloys

by Okmin Park, Se Woong Lee and Sang-il Kim

Ceramics 2022, 5(3), 281-287; https://doi.org/10.3390/ceramics5030022 - 9 Jul 2022

Cited by 4 | Viewed by 2386

Abstract

Post-metal chalcogenides, including InSe, In₂Se₃, and In₄Se₃, have attracted considerable attention as potential thermoelectric materials because of their intrinsically low thermal conductivity, which is attributed to their layered structure with weak van der Waals bonds. [...] Read more.

Post-metal chalcogenides, including InSe, In₂Se₃, and In₄Se₃, have attracted considerable attention as potential thermoelectric materials because of their intrinsically low thermal conductivity, which is attributed to their layered structure with weak van der Waals bonds. In this study, we examined the electrical and thermoelectric properties of Si-doped In₂Se₃ (In_2−xSi_xSe₃, x = 0, 0.005, 0.01, 0.015, and 0.02) polycrystalline samples. Hexagonal α(2H)-In₂Se₃ phase was synthesized without any impurity, and gradual changes in the lattice parameters were observed with Si doping. Drastic changes were observed for the measured electrical and thermal transport properties at 450–500 K, due to the phase transition from α to β at 473 K. The highest power factors were achieved by the sample with x = 0.015 for both α and β phases, exhibiting the values of 0.137 and 0.0884 mW/mK² at 450 and 750 K, respectively. The total thermal conductivities of the α phase samples decreased gradually with increasing Si doping content, which is attributed to the point defect phonon scattering by Si doping. The total thermal conductivities of the β phase samples significantly decreased compared to those of the α phase samples. Therefore, the sample with x = 0.015 (In_1.985Si_0.015Se₃) showed the maximum thermoelectric figure of merit values of 0.100 and 0.154 at 450 and 750 K, which are enhanced by 152 and 48% compared with those of the undoped α- and β-In₂Se₃ samples, respectively. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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19 pages, 8110 KiB

Open AccessArticle

Highlighting of LaF₃ Reactivity with SiO₂ and GeO₂ at High Temperature

by Hussein Fneich, Manuel Vermillac, Daniel R. Neuville, Wilfried Blanc and Ahmad Mehdi

Ceramics 2022, 5(2), 182-200; https://doi.org/10.3390/ceramics5020016 - 6 May 2022

Cited by 8 | Viewed by 3002

Abstract

LaF₃ is commonly added to oxide glass, in particular to silica, to form oxyfluoride glass. After appropriate thermal treatment at a temperature lower than 800 °C, usually, glass ceramics are obtained. Recently, LaF₃ nanoparticles have been used as precursors to obtain [...] Read more.

LaF₃ is commonly added to oxide glass, in particular to silica, to form oxyfluoride glass. After appropriate thermal treatment at a temperature lower than 800 °C, usually, glass ceramics are obtained. Recently, LaF₃ nanoparticles have been used as precursors to obtain amorphous nanoparticles of undefined composition in optical fiber. However, fiber fabrication necessitates temperature much higher (typically up to 2000 °C) than the one required for bulk glass. In this article, we report on the reactivity of fluoride ions in LaF₃ with SiO₂ and GeO₂ (a common dopant used to dope optical fiber) powders at high temperature. TGA, EDX-SEM, XRD and Raman analyses were performed. Above 1000 °C, LaF₃ starts to react, preferentially with SiO₂, to form SiF₄ gaseous species. The remaining lanthanum ions form La₂Si₂O₇ and La₂Ge₂O₇ phases. These results could contribute to improve material development for the fiber optics community. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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9 pages, 4478 KiB

Open AccessArticle

Microstructure, Thermal and Mechanical Properties of Refractory Linings Modified with Polymer Fibers

by Marcin Prochwicz, Paweł Czaja, Jerzy Morgiel, Tomasz Czeppe and Anna Góral

Ceramics 2022, 5(2), 173-181; https://doi.org/10.3390/ceramics5020015 - 8 Apr 2022

Cited by 1 | Viewed by 3223

Abstract

The reduction in the inherent brittleness of coatings applied on parts of ceramic shielding used for continuous steel casting (CSC) processes is highly desired, since it can significantly diminish losses occurring during post-application handling and mounting. One of such coatings, prepared mostly from [...] Read more.

The reduction in the inherent brittleness of coatings applied on parts of ceramic shielding used for continuous steel casting (CSC) processes is highly desired, since it can significantly diminish losses occurring during post-application handling and mounting. One of such coatings, prepared mostly from fused silica, ludox, tabular alumina, chamotte, cenospheres, dextrine and aluminum powder, is known commercially as Thermacoat™. The present experiment is focused on the effect of the modification of its composition by rising the content of the cenospheres (max. 2.5 wt.%) or by introducing up to 1.5 wt.% of polymer Belmix™ fibers (~34 μm diameter/12 mm length) on the microstructure and mechanical properties. The maximum amount of introduced additions was limited by the accompanying loss of mass viscosity, which must allow for deposition through immersion. Next, the differential scanning calorimetry and differential thermogravimetric analysis techniques were employed to evaluate the extent of the weight change and heat response of the mass during the drying and annealing stages. The dried materials’ microstructure was investigated with light and scanning electron microscopy, while the chemical composition was studied by energy dispersive spectroscopy. Finally, a three-point flexural bending method was used to determine changes in the material mechanical properties. The performed experiments proved that the small addition (~1 wt.%) of polymer fibers is sufficient for the significant improvement of the Thermacoat™ green mechanical strength at ambient temperature, presenting a reproducible ultimate flexural strength of ~0.2 MPa. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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13 pages, 5207 KiB

Open AccessArticle

Reinforcement of the Ceramic Matrix of CaO-ZrO₂-MgO with Al₂O₃ Coarse Particles

by João Mamede, Duarte Felix Macedo, Alberto Maceiras and Abílio P. Silva

Ceramics 2022, 5(1), 148-160; https://doi.org/10.3390/ceramics5010013 - 4 Mar 2022

Cited by 3 | Viewed by 3288

Abstract

A thermal protection system is subject to high forces, in particular compression, bending and wear, to aggressive environments of high temperatures, high velocity gases and particle shock. Typically, ceramic materials appear as a first barrier or outer shield over a metallic substrate responsible [...] Read more.

A thermal protection system is subject to high forces, in particular compression, bending and wear, to aggressive environments of high temperatures, high velocity gases and particle shock. Typically, ceramic materials appear as a first barrier or outer shield over a metallic substrate responsible for the structure. When it comes to a coating due to the small thickness, the particles of the raw material are sub-micron scale, but when a shield with a few centimeters is built its structural and economic viability requires the use of wider particle size distributions. In this work, a ceramic fine-grained matrix of CaO-ZrO₂-MgO was reinforced with commercial coarse Al₂O₃ particles. The results show that for larger size distributions, CZM-4A, replacing 63% of fine-grained matrix by coarse Al₂O₃ particles, the dimensional stability is obtained (ΔL = 5%) and the good mechanical properties such as flexural strength of 154 MPa, elastic modulus of 286 GPa, and hardness of 8.5 GPa, which allows to propose this ceramic composite for a structural application. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 2702 KiB

Open AccessArticle

Foam-Replicated Diopside/Fluorapatite/Wollastonite-Based Glass–Ceramic Scaffolds

by Francesco Baino, Dilshat U. Tulyaganov, Ziyodilla Kahharov, Abbas Rahdar and Enrica Verné

Ceramics 2022, 5(1), 120-130; https://doi.org/10.3390/ceramics5010011 - 21 Feb 2022

Cited by 11 | Viewed by 3473

Abstract

Implantation of three-dimensional (3D) bioactive glass-derived porous scaffolds is an effective strategy for promoting bone repair and regeneration in large osseous defect sites. The present study intends to expand the potential of a SiO₂–P₂O₅–CaO–MgO–Na₂O–CaF₂ [...] Read more.

Implantation of three-dimensional (3D) bioactive glass-derived porous scaffolds is an effective strategy for promoting bone repair and regeneration in large osseous defect sites. The present study intends to expand the potential of a SiO₂–P₂O₅–CaO–MgO–Na₂O–CaF₂ glass composition, which has already proven to be successful in regenerating bone in both animals and human patients. Specifically, this research work reports the fabrication of macroporous glass–ceramic scaffolds by the foam replica method, using the abovementioned bioactive glass powders as a parent material. The sinter-crystallization of the glass powder was investigated by hot-stage microscopy, differential thermal analysis, and X-ray diffraction. Scanning electron microscopy was used to investigate the pore–strut architecture of the resultant glass–ceramic scaffolds in which diopside, fluorapatite, and wollastonite crystallized during thermal treatment. Immersion studies in simulated body fluids revealed that the scaffolds have bioactive behavior in vitro; the mechanical properties were also potentially suitable to suggest use in load-bearing bone applications. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 4942 KiB

Open AccessArticle

Interfacial Reactions between Si and SiO₂ with Ceramic Additives

by Yu-Hsiang Chen, Kun-Lin Lin and Chien-Cheng Lin

Ceramics 2022, 5(1), 44-54; https://doi.org/10.3390/ceramics5010005 - 28 Jan 2022

Cited by 1 | Viewed by 3586

Abstract

In this study, 10 wt.% ceramics—Al₂O₃, La₂O₃, Y₂O₃, MgO, and TiO₂—were employed as additives for amorphous SiO₂ after pressing and annealing at 1300 °C. The amorphous SiO₂ [...] Read more.

In this study, 10 wt.% ceramics—Al₂O₃, La₂O₃, Y₂O₃, MgO, and TiO₂—were employed as additives for amorphous SiO₂ after pressing and annealing at 1300 °C. The amorphous SiO₂ changed to cristobalite SiO₂. Through X-ray diffraction, scanning electron microscopy, and transmission electron microscopy with energy-dispersive spectrometry, the reaction phases of La₂Si₂O₇, Y₂Si₂O₇, and MgSiO₃ (Mg₂SiO₄) were found in the SiO₂ with 10 wt.% La₂O₃, Y₂O₃, and MgO additives. Cracks formed in the Si and SiO₂–ceramic additive sites because of the difference in the coefficients of thermal expansion among the Si, SiO₂, ceramic additives, and reaction phases. After Si came into contact with the SiO₂–ceramics, two types of microstructures were found: those with and those without an amorphous SiO₂ reaction layer at the interface. Amorphous SiO₂ layer formation is due to the replacement of the Si position in SiO₂ by Al³⁺ and Ti⁴⁺ impurities, which can break the bonds between Si atoms. The O content in the Si decreased from 6–9 × 10¹⁷ atoms/cm³ for SiO₂ to less than ~10¹⁶ for SiO₂–Al₂O₃ and SiO₂–MgO. The average resistivity of the Si was 3 Ω·cm for SiO₂ and decreased to 0.12–0.36 Ω·cm for the SiO₂ with ceramic additives. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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10 pages, 3075 KiB

Open AccessArticle

Three-Dimensional Finite Element Analysis of Different Connector Designs for All-Ceramic Implant-Supported Fixed Dental Prostheses

by Laura H. J. Alberto, Lohitha Kalluri, Josephine F. Esquivel-Upshaw and Yuanyuan Duan

Ceramics 2022, 5(1), 34-43; https://doi.org/10.3390/ceramics5010004 - 5 Jan 2022

Cited by 6 | Viewed by 4194

Abstract

All-ceramic fixed dental prostheses (FDPs) tend to fracture at the connector regions due to high stress concentration at these areas influenced by their design. This study was performed as an adjunct to an existing clinical study to evaluate the influence of the different [...] Read more.

All-ceramic fixed dental prostheses (FDPs) tend to fracture at the connector regions due to high stress concentration at these areas influenced by their design. This study was performed as an adjunct to an existing clinical study to evaluate the influence of the different radii of curvature of gingival embrasure on the stress distribution of a three-unit all-ceramic implanted supported FDP. Three three-dimensional (3D) models were created by scanning two titanium dental implants, their suitable zirconia abutments, and a patient-retrieved dental prosthesis using a micro-CT scanner. The radius of curvature of the gingival embrasure for the distal connector of the FDP was altered to measure 0.25 mm, 0.50 mm, and 0.75 mm. A finite element analysis (FEA) software (ABAQUS) was used to evaluate the impact of different connector designs on the distribution of stresses. Maximum Principal Stress data was collected from the individual components (veneer, framework, and abutments). The radius of curvature of gingival embrasure had a significant influence on the stress distribution at the assessed components. The tensile peak stresses at all structures were highest in the 0.25 mm model, while the 0.50 mm and 0.75 mm models presented similar values and more uniform stress distribution. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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11 pages, 2915 KiB

Open AccessArticle

Study of Radiation Embitterment and Degradation Processes of Li₂ZrO₃ Ceramic under Irradiation with Swift Heavy Ions

by Baurzhan Abyshev, Artem L. Kozlovskiy, Kassym Sh Zhumadilov and Alex V. Trukhanov

Ceramics 2022, 5(1), 13-23; https://doi.org/10.3390/ceramics5010002 - 24 Dec 2021

Cited by 5 | Viewed by 3440

Abstract

The work is devoted to the study of radiation damage and subsequent swelling processes of the surface layer of Li₂ZrO₃ ceramics under irradiation with heavy Xe²²⁺ ions, depending on the accumulation of the radiation dose. The samples under study [...] Read more.

The work is devoted to the study of radiation damage and subsequent swelling processes of the surface layer of Li₂ZrO₃ ceramics under irradiation with heavy Xe²²⁺ ions, depending on the accumulation of the radiation dose. The samples under study were obtained using a mechanochemical synthesis method. The samples were irradiated with heavy Xe²²⁺ ions with an energy of 230 MeV at irradiation fluences of 10¹¹–10¹⁶ ion/cm². The choice of ion types is due to the possibility of simulating the radiation damage accumulation processes as a result of the implantation of Xe²²⁺ ions and subsequent atomic displacements. It was found that, at irradiation doses above 5 × 10¹⁴ ion/cm², point defects accumulate, which leads to a disordering of the surface layer and a subsequent decrease in the strength and hardness of ceramics. At the same time, the main process influencing the decrease in resistance to radiation damage is the crystal structure swelling as a result of the accumulation of defects and disordering of the crystal lattice. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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Open AccessArticle

Porous Functional Graded Bioceramics with Integrated Interface Textures

by Jonas Biggemann, David Köllner, Swantje Simon, Paula Heik, Patrizia Hoffmann and Tobias Fey

Ceramics 2021, 4(4), 681-695; https://doi.org/10.3390/ceramics4040048 - 9 Dec 2021

Cited by 4 | Viewed by 3658

Abstract

Porous functional graded ceramics (porous FGCs) offer immense potential to overcome the low mechanical strengths of homogeneously porous bioceramics used as bone grafts. The tailored manipulation of the graded pore structure including the interfaces in these materials is of particular interest to locally [...] Read more.

Porous functional graded ceramics (porous FGCs) offer immense potential to overcome the low mechanical strengths of homogeneously porous bioceramics used as bone grafts. The tailored manipulation of the graded pore structure including the interfaces in these materials is of particular interest to locally control the microstructural and mechanical properties, as well as the biological response of the potential implant. In this work, porous FGCs with integrated interface textures were fabricated by a novel two-step transfer micro-molding technique using alumina and hydroxyapatite feedstocks with varied amounts of spherical pore formers (0–40 Vol%) to generate well-defined porosities. Defect-free interfaces could be realized for various porosity pairings, leading to porous FGCs with continuous and discontinuous transition of porosity. The microstructure of three different periodic interface patterns (planar, 2D-linear waves and 3D-Gaussian hills) was investigated by SEM and µCT and showed a shape accurate replication of the CAD-designed model in the ceramic sample. The Young’s modulus and flexural strength of bi-layered bending bars with 0 and 30 Vol% of pore formers were determined and compared to homogeneous porous alumina and hydroxyapaite containing 0–40 Vol% of pore formers. A significant reduction of the Young’s modulus was observed for the porous FGCs, attributed to damping effects at the interface. Flexural 4-point-testing revealed that the failure did not occur at the interface, but rather in the porous 30 Vol% layer, proving that the interface does not represent a source of weakness in the microstructure. Full article

(This article belongs to the Special Issue Advances in Ceramics)

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