Editorial

2 pages, 175 KiB

Open AccessEditorial

Special Issue: Carbon–Refractory Metal Nanostructures: Synthesis, Characterization and Applications

by Rodica Vladoiu

Materials 2021, 14(4), 831; https://doi.org/10.3390/ma14040831 - 09 Feb 2021

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There is a great demand for joining carbon, as well as titanium, with other elements, which ensures high resistance against chemical and corrosive environment attacks, as well as, importantly, better adherence of the carbon and titanium to coated substrates [...] Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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12 pages, 3340 KiB

Open AccessArticle

Diamond-Coated Plasma Probes for Hot and Hazardous Plasmas

by Codrina Ionita, Roman Schrittwieser, Guosheng Xu, Ning Yan, Huiqian Wang, Volker Naulin, Jens Juul Rasmussen and Doris Steinmüller-Nethl

Materials 2020, 13(20), 4524; https://doi.org/10.3390/ma13204524 - 13 Oct 2020

Cited by 2 | Viewed by 1791

Abstract

Plasma probes are simple and inexpensive diagnostic tools for fast measurements of relevant plasma parameters. While in earlier times being employed mainly in relatively cold laboratory plasmas, plasma probes are now routinely used even in toroidal magnetic fusion experiments, albeit only in the [...] Read more.

Plasma probes are simple and inexpensive diagnostic tools for fast measurements of relevant plasma parameters. While in earlier times being employed mainly in relatively cold laboratory plasmas, plasma probes are now routinely used even in toroidal magnetic fusion experiments, albeit only in the edge region, i.e., the so-called scrape-off layer (SOL), where temperature and density of the plasma are lower. To further avoid overheating and other damages, in medium-size tokamak (MST) probes are inserted only momentarily by probe manipulators, with usually no more than a 0.1 s per insertion during an average MST discharge of a few seconds. However, in such hot and high-density plasmas, their usage is limited due to the strong particle fluxes onto the probes and their casing which can damage the probes by sputtering and heating and by possible chemical reactions between plasma particles and the probe material. In an attempt to make probes more resilient against these detrimental effects, we tested two graphite probe heads (i.e., probe casings with probes inserted) coated with a layer of electrically isolating ultra-nano-crystalline diamond (UNCD) in the edge plasma region of the Experimental Advanced Superconducting Tokamak (EAST) in Hefei, People’s Republic of China. The probe heads, equipped with various graphite probe pins, were inserted frequently even into the deep SOL up to a distance of 15 mm inside the last closed flux surface (LCFS) in low- and high-confinement regimes (L-mode and H-mode). Here, we concentrate on results most relevant for the ability to protect the graphite probe casings by UNCD against harmful effects from the plasma. We found that the UNCD coating also prevented almost completely the sputtering of graphite from the probe casings and thereby the subsequent risk of re-deposition on the boron nitride isolations between probe pins and probe casings by a layer of conductive graphite. After numerous insertions into the SOL, first signs of detachment of the UNCD layer were noticed. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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10 pages, 4914 KiB

Open AccessArticle

Iron Oxide and Iron Sulfide Films Prepared for Dye-Sensitized Solar Cells

by Kostyantyn Tuharin, Zdeněk Turek, Michal Zanáška, Pavel Kudrna and Milan Tichý

Materials 2020, 13(8), 1797; https://doi.org/10.3390/ma13081797 - 11 Apr 2020

Cited by 12 | Viewed by 2776

Abstract

In this paper, the prospects of iron oxide films and their sulfidation for dye-sensitized solar cells (DSSC) are reviewed. Iron oxide thin films were prepared by hollow cathode plasma jet (HCPJ) sputtering, with an admixture of oxygen in the argon working gas and [...] Read more.

In this paper, the prospects of iron oxide films and their sulfidation for dye-sensitized solar cells (DSSC) are reviewed. Iron oxide thin films were prepared by hollow cathode plasma jet (HCPJ) sputtering, with an admixture of oxygen in the argon working gas and with an iron nozzle as the sputtering target. The discharge was powered by a constant current source in continuous mode and by a constant voltage source in pulsed mode. Plasma composition was measured by an energy-resolved mass spectrometer. Moreover, secondary electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), absorption and Raman spectra of the films are presented. Strong correlation between the color of the iron oxide film and its phase composition was revealed. Iron oxide films were sulfided at 350 °C. A relatively clean pyrite phase was obtained from the magnetite, while the marcasite with admixture of the pyrite phase was obtained from the hematite. Low influence of sulfidation on the films’ microstructure was demonstrated. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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13 pages, 5179 KiB

Open AccessArticle

Characterization of Platinum-Based Thin Films Deposited by Thermionic Vacuum Arc (TVA) Method

by Sebastian Cozma, Rodica Vlǎdoiu, Aurelia Mandes, Virginia Dinca, Gabriel Prodan and Vilma Buršíková

Materials 2020, 13(7), 1796; https://doi.org/10.3390/ma13071796 - 10 Apr 2020

Cited by 4 | Viewed by 2978

Abstract

The current work aimed to characterize the morphology, chemical, and mechanical properties of Pt and PtTi thin films deposited via thermionic vacuum arc (TVA) method on glass and silicon substrates. The deposited thin films were characterized by means of a scanning electron microscope [...] Read more.

The current work aimed to characterize the morphology, chemical, and mechanical properties of Pt and PtTi thin films deposited via thermionic vacuum arc (TVA) method on glass and silicon substrates. The deposited thin films were characterized by means of a scanning electron microscope technique (SEM). The quantitative elemental microanalysis was done using energy-dispersive X-ray spectroscopy (EDS). The tribological properties were studied by a ball-on-disc tribometer, and the mechanical properties were measured using nanoindentation tests. The roughness, as well as the micro and nanoscale features, were characterized using atomic force microscopy (AFM) and transmission electron microscopy (TEM). The wettability of the deposited Pt and PtTi thin films was investigated by the surface free energy evaluation (SFE) method. The purpose of our study was to prove the potential applications of Pt-based thin films in fields, such as nanoelectronics, fuel cells, medicine, and materials science. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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14 pages, 2934 KiB

Open AccessArticle

Detailed Molecular and Structural Analysis of Dual Emitter IrQ(ppy)₂ Complex

by Iulia Corina Ciobotaru, Daniel Nicolae Crisan, Primoz Šket, Constantin Claudiu Ciobotaru and Silviu Polosan

Materials 2020, 13(7), 1617; https://doi.org/10.3390/ma13071617 - 01 Apr 2020

Cited by 3 | Viewed by 2227

Abstract

The molecular structure of the 8-hydroxyquinoline–bis (2-phenylpyridyl) iridium (IrQ(ppy)₂) dual emitter organometallic compound is determined based on detailed 1D and 2D nuclear magnetic resonance (NMR), to identify metal-ligands coordination, isomerization and chemical yield of the desired compound. Meanwhile, the extended X-ray [...] Read more.

The molecular structure of the 8-hydroxyquinoline–bis (2-phenylpyridyl) iridium (IrQ(ppy)₂) dual emitter organometallic compound is determined based on detailed 1D and 2D nuclear magnetic resonance (NMR), to identify metal-ligands coordination, isomerization and chemical yield of the desired compound. Meanwhile, the extended X-ray absorption fine structure (EXAFS) was used to determine the interatomic distances around the iridium ion. From the NMR results, this compound IrQ(ppy)₂ exhibits a trans isomerization with a distribution of coordinated N-atoms in a similar way to facial Ir(ppy)₃. The EXAFS measurements confirm the structural model of the IrQ(ppy)₂ compound where the oxygen atoms from the quinoline ligands induce the splitting of the next-nearest neighboring C in the second shell of the Ir³⁺ ions. The high-performance liquid chromatography (HPLC), as a part of the detailed molecular analysis, confirms the purity of the desired IrQ(ppy)₂ organometallic compound as being more than 95%, together with the progress of the chemical reactions towards the final compound. The theoretical model of the IrQ(ppy)₂, concerning the expected bond lengths, is compared with the structural model from the EXAFS and XRD measurements. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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11 pages, 2774 KiB

Open AccessArticle

Synthesis and Characterization of Complex Nanostructured Thin Films Based on Titanium for Industrial Applications

by Rodica Vladoiu, Aurelia Mandes, Virginia Dinca, Maria Balasoiu, Dmytro Soloviov and Vitalii Turchenko

Materials 2020, 13(2), 399; https://doi.org/10.3390/ma13020399 - 15 Jan 2020

Cited by 7 | Viewed by 2135

Abstract

Titanium-based composites—titanium and silver (TiAg) and titanium and carbon (TiC)—were synthesized by the Thermionic Vacuum Arc (TVA) method on substrates especially for gear wheels and camshaft coating as mechanical components of irrigation pumps. The films were characterized by surface morphology, microstructure, and roughness [...] Read more.

Titanium-based composites—titanium and silver (TiAg) and titanium and carbon (TiC)—were synthesized by the Thermionic Vacuum Arc (TVA) method on substrates especially for gear wheels and camshaft coating as mechanical components of irrigation pumps. The films were characterized by surface morphology, microstructure, and roughness through X-ray Diffraction (XRD), Atomic Force Microscopy (AFM), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and Small-Angle Neutron Scattering (SANS). The silver (Ag) films crystallized into a cubic system with lattice a = 4.0833 Å at room temperature, indexed as cubic Ag group Fm3m. The crystallites were oriented in the [111] direction, and mean grain size was <D>₁₁₁ = 265 Å. The TiC structure revealed a predominant cubic TiC phase, with a = 0.4098 as a lattice parameter determined by Cohen’s method. Average roughness (Ra) was 8 nm for the as-grown 170 nm thick TiAg film, and 1.8 nm for the as-grown 120 nm thick TiC film. Characteristic SANS contribution was detected from the TiAg layer deposited on a substrate of high-quality stainless steel with 0.45% carbon (OLC45) in the range of 0.015 Å⁻¹ ≤ Q ≤ 0.4 Å⁻¹, revealing the presence of sharp surfaces and an averaged triaxial ellipsoidal core-shell object. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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17 pages, 6974 KiB

Open AccessArticle

Structural, Compositional, and Mechanical Characterization of W_xCr_yFe_1−x−y Layers Relevant to Nuclear Fusion, Obtained with TVA Technology

by Mihail Lungu, Ioana Porosnicu, Paul Dinca, Alin Velea, Flaviu Baiasu, Bogdan Butoi, Oana Gloria Pompilian, Cornel Staicu, Parau Anca Constantina, Corneliu Porosnicu, Cristian Lungu and Ion Tiseanu

Materials 2019, 12(24), 4072; https://doi.org/10.3390/ma12244072 - 06 Dec 2019

Cited by 2 | Viewed by 1874

Abstract

Reduced activation ferritic and martensitic steel like EUROFER (9Cr-1W) are considered as potential structural materials for the first wall of the future next-generation DEMOnstration Power Station (DEMO) fusion reactor and as a reference material for the International Thermonuclear Experimental Reactor (ITER) test blanket [...] Read more.

Reduced activation ferritic and martensitic steel like EUROFER (9Cr-1W) are considered as potential structural materials for the first wall of the future next-generation DEMOnstration Power Station (DEMO) fusion reactor and as a reference material for the International Thermonuclear Experimental Reactor (ITER) test blanket module. The primary motivation of this work is to study the re-deposition of the main constituent materials of EUROFER, namely tungsten (W), iron (Fe), and chromium (Cr), in a DEMO type reactor by producing and analyzing complex W_xCr_yFe_1−x−y layers. The composite layers were produced in laboratory using the thermionic vacuum arc (TVA) method, and the morphology, crystalline structure, elemental composition, and mechanical properties were studied using scanning electron microscopy (SEM), X-ray diffraction (XRD), micro-X-ray fluorescence (micro-XRF), and glow discharge optical emission spectrometry (GDOES), as well as nanoindentation and tribology measurements. The results show that the layer morphology is textured and is highly dependent on sample positioning during the deposition process. The formation of polycrystalline W_xCr_yFe_1−x−y was observed for all samples with the exception of the sample positioned closer to Fe anode during deposition. The crystalline grain size dimension varied between 10 and 20 nm. The composition and thickness of the layers were strongly influenced by the in-situ coating position, and the elemental depth profiles show a non-uniform distribution of Fe and Cr in the layers. The highest hardness was measured for the sample positioned near the Cr anode, 6.84 GPa, and the lowest was 4.84 GPa, measured for the sample positioned near the W anode. The tribology measurements showed an abrasive sliding wear behavior for most of the samples with a reduction of the friction coefficient with the increase of the normal load. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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10 pages, 9012 KiB

Open AccessArticle

Hydration Resistance of CaO Material Prepared by Ca(OH)₂ Calcination with Chelating Compound

by Jinhu Wang, Yaowu Wei, Nan Li and Junfeng Chen

Materials 2019, 12(14), 2325; https://doi.org/10.3390/ma12142325 - 22 Jul 2019

Cited by 16 | Viewed by 3296

Abstract

The hydration resistance of CaO materials prepared by Ca(OH)₂ calcination with chelating compounds are investigated in this paper. The crystalline phases and microstructure characteristics of sintered specimens were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and energy [...] Read more.

The hydration resistance of CaO materials prepared by Ca(OH)₂ calcination with chelating compounds are investigated in this paper. The crystalline phases and microstructure characteristics of sintered specimens were studied by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy and energy dispersive spectrometer (SEM, EDS). The bulk density, apparent porosity, and hydration resistance of samples were also tested. The results showed that chelating compounds improved the hydration resistance of the treated CaO specimens significantly. The surface-pretreated specimens showed an increase in bulk density and a decrease in apparent porosity after heating. The surface pretreatment of the Ti chelating compound promoted the solid phase sintering and grain growth of CaO specimens, which increased the density of the heated CaO sample. The Al chelating compound promoted the liquid-phase sintering of CaO specimens, which led to the grain growth and increased density of the sample. CaO grains were bonded by the formed tricalcium aluminate (C₃A) and the apparent porosity of the sample was reduced, reducing the contact area of CaO with water vapor. The Al chelating compound was more effective in improving the hydration resistance of the CaO material in the situation of this study. Full article

(This article belongs to the Special Issue Carbon-Refractory Metals Nanostructures: Synthesis, Characterization and Applications)

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