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Ceramics, Volume 5, Issue 3 (September 2022) – 14 articles

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Article
Kinetics of the Synthesis of Aluminum Boride by the Self-Propagating High-Temperature Synthesis Method
Ceramics 2022, 5(3), 435-446; https://doi.org/10.3390/ceramics5030033 (registering DOI) - 15 Aug 2022
Abstract
The influence of certain factors on the kinetics of the process of obtaining aluminum borides (burning rate, ingot formation, and phase separation) was investigated. In this study, we report the registration of diboride using the SHS protocol. The synthesis of aluminum diboride from [...] Read more.
The influence of certain factors on the kinetics of the process of obtaining aluminum borides (burning rate, ingot formation, and phase separation) was investigated. In this study, we report the registration of diboride using the SHS protocol. The synthesis of aluminum diboride from boric anhydride occurred by the aluminothermic method. The initial components were boron trioxide and aluminum in the form of powders. Researchers paid special attention to the degree of grinding of the charge fluxing substances. The influence this had on the rate of development of the degree of charge concentration was studied. To calculate the degree of charge, a composition was chosen according to the speed obtained from a number of experiments where melting was carried out with the following charge densities in g/cm3: 0.80; 1.08; 1.18; 1.74. The method of melting was ignition from above. The experimental results allowed us to conclude that the nature of the change in the combustion rate of the system, where there was an excess of the reducing agent in the charge, is the same. An increase in the combustion rate, where there was an excess of aluminum of up to 20%, was likely due to the fact that the reaction area of the charge components increased. In addition, an increase in speed can be explained by a decrease in heat losses due to a reduction in the melting time. With an increase in excess aluminum above 20% of the stoichiometry, the observed decrease in the combustion rate can be explained by a decrease in the specific heat of the process due to the melting of the excess aluminum, which played the role of a ballast. Full article
(This article belongs to the Special Issue Geopolymers and Ceramics)
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Article
Powders Based on Ca2P2O7-CaCO3-H2O System as Model Objects for the Development of Bioceramics
Ceramics 2022, 5(3), 423-434; https://doi.org/10.3390/ceramics5030032 - 13 Aug 2022
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Abstract
Nanoscale powders of hydrated Ca2P2O7, CaCO3, and a product of mixed-anionic composition containing P2O74− and CO32− anions were synthesized from aqueous solutions of Ca(CH3COO)2, pyrophosphoric [...] Read more.
Nanoscale powders of hydrated Ca2P2O7, CaCO3, and a product of mixed-anionic composition containing P2O74− and CO32− anions were synthesized from aqueous solutions of Ca(CH3COO)2, pyrophosphoric acid (H4P2O7), and/or (NH4)2CO3. Pyrophosphoric acid was previously obtained on the basis of the ion exchange process from Na4P2O7 solution and H+-cationite resin for further introduction into the reactions as an anionic precursor. The phase composition of powders after the syntheses was represented by bioresorbable phases of X-ray amorphous Ca2P2O7 phase, calcite and vaterite polymorphs of CaCO3. Based on synthesized powders, simple cylindrical constructions were prepared via mechanical pressing and fired in the temperature range of 600–800 °C. Surface morphology observation showed the presence of bimodal porosity with pore sizes up to 200 nm and 2 μm, which is likely to ensure tight particle packing and roughness of the sample surface required for the differentiation of osteogenic cells. Thus, the prepared ceramic samples can be further examined as model objects for bone tissue repair. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
Article
Possibilities of Mechanochemical Synthesis of Apatites with Different Ca/P Ratios
Ceramics 2022, 5(3), 404-422; https://doi.org/10.3390/ceramics5030031 - 03 Aug 2022
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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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Article
Oxidation Resistance of γ-TiAl Based Alloys Modified by C, Si and Y2O3 Microdopants
Ceramics 2022, 5(3), 389-403; https://doi.org/10.3390/ceramics5030030 - 02 Aug 2022
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Abstract
This work aimed to study the oxidation resistance of γ-TiAl based alloy, doped with small concentrations of carbon, silicon, and yttrium oxide in air at 800 and 1100 °C for 30 h. The TNM-B1 alloy samples were produced via high-energy ball milling, self-propagating [...] Read more.
This work aimed to study the oxidation resistance of γ-TiAl based alloy, doped with small concentrations of carbon, silicon, and yttrium oxide in air at 800 and 1100 °C for 30 h. The TNM-B1 alloy samples were produced via high-energy ball milling, self-propagating high-temperature synthesis, and hot isostatic pressing techniques. The microstructure, oxidation kinetics at 800–1100 °C, scale structure, and oxidation mechanism were studied. The oxidation of alloys modified with carbon and silicon at 1100 °C was characterized by the formation of a three-layer coating. The Y2O3 modified alloy performed the greatest oxidation resistance at 1100 °C and promoted the formation of a dense Al2O3 interlayer. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Ti/Cu/Kovar Multilayer Interlayer PTLP Diffusion Bonding Si3N4/Ht250
Ceramics 2022, 5(3), 372-388; https://doi.org/10.3390/ceramics5030029 - 31 Jul 2022
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Abstract
In this paper, partial transient liquid phase (PTLP) diffusion bonding between Si3N4 ceramics and Ht250 cast iron was carried out by using an Ti/Cu/Kovar/Cu/Ti interlayer. The effects of the heating temperature and holding time on the microstructure, formation mechanism, and [...] Read more.
In this paper, partial transient liquid phase (PTLP) diffusion bonding between Si3N4 ceramics and Ht250 cast iron was carried out by using an Ti/Cu/Kovar/Cu/Ti interlayer. The effects of the heating temperature and holding time on the microstructure, formation mechanism, and mechanical properties of Si3N4/Ht250 cast iron joints were studied. The results show that the maximum shear strength of the joint is 112 MPa when the welding temperature is 1000 °C and the holding time is 1 h. In addition, the problems of Ti/Cu/Ti intermetallic compound formation and Cu/Si3N4 ceramic residual thermal stress in the joint can be effectively alleviated. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Synthesis and Thermal Behaviour of Calcium Alkyl Phosphates as Bioceramic Precursors
Ceramics 2022, 5(3), 362-371; https://doi.org/10.3390/ceramics5030028 - 29 Jul 2022
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Abstract
Powders of alkyl phosphoric acids and calcium alkyl phosphates with various alkyl chains (butyl, octyl, and dodecyl) have been synthesized. The resulting powders were characterized by X-ray phase analysis, electron microscopy, and thermal analysis. It was shown that the calcium alkyl phosphates correspond [...] Read more.
Powders of alkyl phosphoric acids and calcium alkyl phosphates with various alkyl chains (butyl, octyl, and dodecyl) have been synthesized. The resulting powders were characterized by X-ray phase analysis, electron microscopy, and thermal analysis. It was shown that the calcium alkyl phosphates correspond to the composition of acid salts of calcium alkyl phosphates Ca(RPO4H)2, data on which are not presented in the literature. The thermal behaviour of calcium alkyl phosphates can be described as a complex phase transformation into biphasic calcium phosphate mixture (of Ca2P2O7 and Ca3(PO4)2) with the increase of the Ca to P ratio in comparison to initial materials. The powders thermally treated in the range of 400–600 °C could be recommended as single precursors of biphasic bioceramics. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Photonic Sintering of Oxide Ceramic Films: Effect of Colored FexOy Nanoparticle Pigments
Ceramics 2022, 5(3), 351-361; https://doi.org/10.3390/ceramics5030027 - 28 Jul 2022
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Abstract
Alumina and zirconia thin films modified with colored nano-FexOy pigments were sintered by the flash-lamp-annealing method. We selected a nano α-Al2O3 and micron α-Al2O3 bimodal mixture as the base precursor material, and we doped [...] Read more.
Alumina and zirconia thin films modified with colored nano-FexOy pigments were sintered by the flash-lamp-annealing method. We selected a nano α-Al2O3 and micron α-Al2O3 bimodal mixture as the base precursor material, and we doped it with 5 vol% of FexOy red/brown/black/yellow pigments. The coatings were deposited from nanoparticle dispersions both on glass and on flexible metal foil. The characteristics of the thin films obtained with the use of various additives were compared, including the surface morphologies, optical properties, crystallinities, and structures. Flash lamp annealing was applied with the maximum total energy density of 130 J/cm2 and an overall annealing time of 7 s. Based on the simulated temperature profiles and electron-microscopy results, a maximum annealing temperature of 1850 °C was reached for the red Al2O3: Fe2O3 ceramic film. The results show that red α-Fe2O3 pigments allow for the achievement of maximum layer absorption, which is effective for flash lamp sintering. It was also possible to use the selected red α-Fe2O3 particles for the flash-lamp-assisted sintering of ZrO2 on a 30 µm-thin flexible stainless-steel substrate. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Chemically Bound Resorbable Ceramics as an Antibiotic Delivery System in the Treatment of Purulent–Septic Inflammation of Bone Tissue
Ceramics 2022, 5(3), 330-350; https://doi.org/10.3390/ceramics5030026 - 27 Jul 2022
Viewed by 258
Abstract
Local drug delivery systems are an effective approach in the treatment of purulent–septic inflammation of bone tissue. Chemically bonded multiphase ceramics based on calcium-deficient carbonate-substituted hydroxyapatite combine resorbability, osteoconductivity, and the possibility of volumetric incorporation of antibiotics. Macroporosity is regulated by the concentration [...] Read more.
Local drug delivery systems are an effective approach in the treatment of purulent–septic inflammation of bone tissue. Chemically bonded multiphase ceramics based on calcium-deficient carbonate-substituted hydroxyapatite combine resorbability, osteoconductivity, and the possibility of volumetric incorporation of antibiotics. Macroporosity is regulated by the concentration of polyethylene glycol granules introduced into the initial powder composition, followed by their extraction. The selected conditions for the consolidation of the ceramic matrix and the extraction of PEG granules retain the activity of vancomycin, which is confirmed by the results of microbiological studies. The concentration of vancomycin and the porosity affect the local concentration and release of the antibiotic. The incorporation method provides a prolonged release of the antibiotic for up to 31 days. In vivo experiments with bone implantation have shown that chemically bound macroporous ceramics with incorporated vancomycin are a therapeutically effective carrier of the substance during the healing of bone defects in conditions of surrounding purulent–septic inflammation, and can be considered as a carrier for local antibacterial therapy, at the site of implantation. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Incorporation of Manganese (II) in Beta-Tricalcium Phosphate from EPR and ENDOR Measurements for Powders
Ceramics 2022, 5(3), 318-329; https://doi.org/10.3390/ceramics5030025 - 26 Jul 2022
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Abstract
Powders of β-tricalcium phosphate (β-TCP, Ca3PO4) doped with manganese (Mn2+) are comprehensively analyzed with electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques. The modeling of the spectra permitted to calculate the values of zero-field splitting [...] Read more.
Powders of β-tricalcium phosphate (β-TCP, Ca3PO4) doped with manganese (Mn2+) are comprehensively analyzed with electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) techniques. The modeling of the spectra permitted to calculate the values of zero-field splitting (B20 = −904 MHz; B40 = −1.41 MHz and B43 = 195.2 MHz) and explain the origin of the low-field hyperfine structures as the allowed spin transitions of fine structure. Three structurally inequivalent positions for Mn2+ in the β-TCP crystal lattice are identified and their g-factors and hyperfine constants are quantified. The obtained results can serve as fundamental background to the study of structurally disordered matrices with high spin (S ≥ 1) impurities which are important for catalytic systems. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Calcium Silicate Hydrate Cation-Exchanger from Paper Recycling Ash and Waste Container Glass
Ceramics 2022, 5(3), 301-317; https://doi.org/10.3390/ceramics5030024 - 22 Jul 2022
Viewed by 340
Abstract
Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich [...] Read more.
Synthetic 11 Å tobermorite (Ca5Si6O16(OH)2.4H2O) and its Al-substituted analogue are layer-lattice ion-exchangers with potential applications in nuclear and hazardous wastewater treatment. The present study reports the facile one-pot hydrothermal synthesis of an Al-tobermorite-rich cation-exchanger from a combination of paper recycling ash, post-consumer container glass, and lime, with compositional ratios of [Ca]/[Si + Al] = 0.81 and [Al]/[Si + Al] = 0.18. The reaction products were characterized by powder X-ray diffraction analysis, 29Si magic angle spinning nuclear magnetic resonance spectroscopy, and scanning electron microscopy. Hydrothermal processing in 4 M NaOH(aq) at 100 °C for 7 days yielded an Al-tobermorite-rich product that also contained katoite (Ca3Al2SiO12H8), portlandite (Ca(OH)2), calcite (CaCO3), and amorphous silicate gel. The hydrothermal product was found to have a Cs+ cation exchange capacity of 59 ± 4 meq 100 g−1 and selective Cs+ distribution coefficients (Kd) of 574 ± 13 and 658 ± 34 cm3 g−1 from solutions with molar ratios [Cs+]:[Na+] and [Cs+]:[Ca2+] of 1:100. In a batch sorption study at 20 °C, the uptakes of Pb2+, Cd2+, and Cs+ were determined to be 1.78 ± 0.04, 0.65 ± 0.06, and 0.36 ± 0.03 mmol g−1, respectively. The kinetics of Pb2+, Cd2+, and Cs+ removal were described by the pseudo-second-order rate model, which gave respective rate constants (k2) of 0.010, 0.027, and 1.635 g mmol−1 min−1, and corresponding correlation coefficients (R2) of 0.997, 0.996, and 0.999. The metal ion sorption properties of the tobermorite-rich product compared favorably with those of other waste-derived tobermorites reported in the literature. Potential strategies to improve the yield, crystallinity, and sorption characteristics of the product are discussed. Full article
(This article belongs to the Special Issue Geopolymers and Ceramics)
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Article
FIB and Wedge Polishing Sample Preparation for TEM Analysis of Sol-Gel Derived Perovskite Thin Films
Ceramics 2022, 5(3), 288-300; https://doi.org/10.3390/ceramics5030023 - 20 Jul 2022
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Abstract
In ceramic thin films, choosing an appropriate sample preparation method for transmission electron microscopy (TEM) analyses is of paramount importance to avoid preparation-induced damage and retain nanoscale features that require investigation. Here we compare two methods of TEM thin film sample preparation, namely [...] Read more.
In ceramic thin films, choosing an appropriate sample preparation method for transmission electron microscopy (TEM) analyses is of paramount importance to avoid preparation-induced damage and retain nanoscale features that require investigation. Here we compare two methods of TEM thin film sample preparation, namely conventional wedge polishing and focused ion beam (FIB) based lift out preparation applied to ferroelectric barium titanate (BaTiO3, BT) thin films made by chemical solution deposition (CSD). The aim of the work is to determine the pros and cons of each method considering not only the quality of the TEM specimen, but also aspects such as availability, ease of use, and affordability. Besides some limitations on the selection of visualized area due to thickness constraints on the FIB-made sample, both methods offer the capability to prepare samples with very comparable quality, as indicated by achieving the same thickness, a largely agreeing microstructure, no secondary phases on the diffraction pattern, and good atomic resolution. This last observation is especially important in the current context of material science, where more nanoscale phenomena are becoming the subject of study. The wedge polishing method, however, is deemed more affordable in terms of instrumentation, as it only requires a tripod polisher, a polishing wheel, and a precision ion polishing system, whereas the lift out method requires a scanning electron microscope (SEM) equipped with an FIB system. We believe that this work serves groups working on ferroelectric thin films in preparing TEM samples in a more effective and uncomplicated manner, facilitating progress in understanding this fascinating class of materials. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Thermoelectric Properties of Si-Doped In2Se3 Polycrystalline Alloys
Ceramics 2022, 5(3), 281-287; https://doi.org/10.3390/ceramics5030022 - 09 Jul 2022
Viewed by 352
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 (In2−xSixSe3, 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 (In1.985Si0.015Se3) 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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Article
Investigation of Targeted Process Control for Adjusting the Macrostructure of Freeze Foams Using In Situ Computed Tomography
Ceramics 2022, 5(3), 269-280; https://doi.org/10.3390/ceramics5030021 - 07 Jul 2022
Viewed by 398
Abstract
Freeze foams are novel and innovative cellular structures that are based on a direct foaming process and that can be manufactured using any material that can be processed by powder technology. The foam formation process is characterized by the highly complex interaction of [...] Read more.
Freeze foams are novel and innovative cellular structures that are based on a direct foaming process and that can be manufactured using any material that can be processed by powder technology. The foam formation process is characterized by the highly complex interaction of various process and material parameters that were chosen empirically and that have so far been difficult to reproduce. To allow properties to be specifically tailored towards certain applications, it is necessary to examine the phenomena observed during foam formation as well as the impact of the process and material parameters on the structural constitution to deduce guidelines for manufacturing and quality assessment (e.g., mechanical strength, cell and pore sizes, pore size distribution). The variety of possible applications are a result of the wide spectrum of initial suspensions and especially the foam structure properties derived from process parameters such as the cell geometry, pore size distribution, fraction of open and closed porosity, and the textures of the cell struts. Due to earlier findings, the focus of this paper focuses on adjusting and tailoring the macrostructure (homogenization of the pore sizes and their distribution inside foam cells) to create load- and application-adapted ceramic foams. To this end, an experiment was designed using previously identified pore and characteristic influencers (air and water content, temperature of the suspension, pressure reduction rate) as influencing parameters. Their interconnected impacts on selected target values were examined during the freeze foaming process using an in situ freeze foaming device inside an X-ray. Full article
(This article belongs to the Special Issue Ceramic Processing and Sintering)
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Article
Smart Self-Sensing Piezoresistive Composite Materials for Structural Health Monitoring
Ceramics 2022, 5(3), 253-268; https://doi.org/10.3390/ceramics5030020 - 21 Jun 2022
Viewed by 493
Abstract
The use of fiber-reinforced composite materials has widely spread in various sectors, including aerospace, defense, and civil industry. The assessment of these heterogeneous material systems is important for safer and risk-free applications and has contributed to the need for self-sensing composites. This work [...] Read more.
The use of fiber-reinforced composite materials has widely spread in various sectors, including aerospace, defense, and civil industry. The assessment of these heterogeneous material systems is important for safer and risk-free applications and has contributed to the need for self-sensing composites. This work is focused on the development of piezoresistive composites, the prediction of their performance and structural health monitoring (SHM). Additionally, this work unpacks the complexity of carbon nanotubes (CNTs) micro-fabrication and the development of piezoresistive and electromagnetic (EM) waves detection electrodes. Scanning electron microscopy (SEM) was used to characterize the CNTs structure and morphologies. The manufactured CNTs were incorporated in epoxy systems to fabricate glass fiber reinforced polymer (GFRP)-CNTs smart composites with piezoresistive properties. The detection of micro-damage onset and its progression was carried out in mode I, to evaluate the sensitivity of the smart composites to damage development. The change in electrical conductivity of the nanotubes-reinforced composite systems due to localized mechanical strains enabled crack propagation detection. The relationship between crack propagation, fracture toughness, and electrical resistivity of the smart composite was analyzed. Full article
(This article belongs to the Special Issue Innovative Processing Routes for Electroactive Materials)
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