Academic literature on the topic 'Chromium doping'
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Journal articles on the topic "Chromium doping"
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Asmaa Mohammed Raoof. "Influence of Chromium Doping on the Structural and Optical Properties of Zinc Sulfide Thin Films Prepared via Spray Pyrolysis." International Journal of Scientific Research in Science, Engineering and Technology 12, no. 2 (2025): 01–07. https://doi.org/10.32628/ijsrset2512119.
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In this study, doping impact of Chromium (Cr) on the actual properties of Zinc Sulphide (ZnS) at different content of (0, 2, and 4 wt % Cr) was discussed. The considered examples were readied utilizing Spraying Technique. Other published papers matched structural, topographical, and optical characterization in similar writings. X-ray diffraction reveals the high peak matched (008) plane; grain size is set to increase from 12.23 to 13.44 nm with Chromium doping. In contrast, the dislocation density decreases from 66.85 to 55.36, while strain decreases from 28.33 to 25.79. AFM images indicate that average particle size was 63.3 nm to 31.89 nm with Undoped ZnS and ZnS: Cr with 0% and 4% concentrations, respectively. Transmittance offers good transparency, in the visible area between 68 and 63, for undoped ZnS and 4% Cr content. The absorption coefficient indices increased via increasing Chromium doping. The optical bandgap of undoped ZnS and ZnS:Cr films decreases from 3.47 eV to 3.37 eV as the chromium concentration increases from 0% to 4%. The extinction coefficient and refractive index decrease via increasing Chromium doping.
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Bhat, Vighneshwar S., T. S. Tilakraj, Mallikarjun K. Patil, Vikram Pujari, and Sanjeev R. Inamdar. "One-Pot Synthesis of Biocompatible Glycine Protected Chromium Doped ZnS Nanoparticles and their Optical Properties." IOP Conference Series: Materials Science and Engineering 1221, no. 1 (2022): 012029. http://dx.doi.org/10.1088/1757-899x/1221/1/012029.
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Abstract Here in, we report the synthesis and characterization of Chromium doped Zinc Sulfide nanoparticles (ZnS NPs). Initially, ZnS NPs are synthesized by bio-compatible glycine cap using simple one-pot co-precipitate method, and further it is doped by Chromium. The structure and morphology of these ZnS NPs was confirmed by X-Ray Diffractometry (XRD) and Scanning Electron Microscope with Elementary Dispersive Spectrum (SEM with EDS) techniques. The optical characterization techniques reveal that the Chromium doping affected the absorption and photoluminescence properties of the NPs. Photoluminescence of these NPs shifts from 384 nm to 428 nm upon Chromium doping. By using Tauc plot we obtained the energy band gap of 4.7 eV and it reduces to 3.9 eV for Chromium dope. The resultant ZnS NPs have size of 2.17nm and 1.86nm (with Chromium doping), also it gives Cubic Zinc blend phase as proved by XRD. The instrumentation techniques SEM with EDS, XRD, FTIR confirms that high purity Chromium doped ZnS NPs can be obtained by the proposed simple, low cost and highly effective method.
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Wang, Leini, Fei Lu, and Fanming Meng. "Synthesis and Photocatalytic Activity of TiOXPowders with Different Oxygen Defects." International Journal of Photoenergy 2012 (2012): 1–7. http://dx.doi.org/10.1155/2012/208987.
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The novel carbon- or chromium-doped TiOXphotocatalysts with different oxygen defects were synthesized by mechanochemical technique and heating process. The samples were characterized by X-ray diffraction, UV-vis spectrophotometer, and fluorescence spectrometer. Carbon and chromium species were incorporated into TiOXcrystal matrix. The mass fraction of Ti7O13in TiOXphotocatalysts could be tunable through carbon or chromium doping. The mass fraction of Ti7O13could be an indication of the degree of oxygen defects (the concentration of Ti3+) in the TiOX. The degree of oxygen defects increased for carbon doping, while the degree of oxygen defects decreased for chromium doping. The photocatalytic activity measurement results showed that photodegradation rate of methyl orange reached the maximum value with mass fraction of Ti7O13of about 66.93%, but the photodegradation rate decreased when mass fraction of Ti7O13is raised further. In addition, the origin of absorption in the visible spectral range for carbon-doped TiOXas well as the effect of band gap on photocatalytic activity has also been discussed in this paper.
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Santhosh, M., S. Satheeskumar, C. Shanthi, and B. V. Bhuvaneswari. "Influence of Cu substitution on structural, morphological and optical properties of Cr/ZnO nanopowders." Journal of Ovonic Research 18, no. 2 (2022): 113–20. http://dx.doi.org/10.15251/jor.2022.182.113.
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Chromium doped Zinc oxide (Zn0.96Cr0.04O), Chromium and Copper co-doped ZnO nanoparticles (Zn0.96Cr0.04Cu0.02O & Zn0.96Cr0.04Cu0.04O) successfully synthesized by chemical precipitation method at 5000C. The crystalline structure, surface morphology and optical properties of the prepared Cr/ZnO and Cr/Cu/ZnO nanoparticles were examined as a function of doping substance and the prepared samples were characterized using XRD, SEM, EDS and UV-Vis spectroscopy analysis. The synthesized nanoparticles show hexagonal wurtzite structure, and the phase segregation takes place for Cu doping. Optical studies revealed that Cr doping increases the energy band gap while Cu incorporation results in decrease of the band gap.
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Wang, Li Wei, and Terry A. Egerton. "The Effect of Chromium on the Optical Properties and Photoactivity of Nano-Particulate Rutile." Advanced Materials Research 554-556 (July 2012): 502–6. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.502.
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Chromium doped rutile TiO2was synthesized by either co-precipitation or impregnation (surface-doping) and characterized by XRD and reflectance spectroscopy. Chromium addition did not change the TiO2structure nor did the structure of the co-precipitated products differ from that of the impregnated samples. However, chromium doping moved the absorption of both sets of products into the visible and significantly affected the TiO2photocatalytic activity for isopropanol (IPA) oxidation. At high chromium concentrations the photoactivity of the co-precipitated samples was reduced by a larger amount than that of the impregnated samples; this was attributed to a higher concentration of Cr3+ions in the rutile lattice. Unexpectedly, increased photoactivity was measured for low Cr levels of surface-doped rutile. This may be caused by increased electron-trapping, at surface Cr6+ions, and correspondingly reduced, electron-hole recombination.
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Starchikov, S. S., I. S. Lyubutin, Chun-Rong Lin, et al. "Synthesis and magnetic properties of the chromium-doped iron sulfide Fe1−xCrxS single crystalline nanoplates with a NiAs crystal structure." Physical Chemistry Chemical Physics 17, no. 24 (2015): 15829–36. http://dx.doi.org/10.1039/c5cp01846c.
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Chromium-doped pyrrhotite Fe<sub>1−x</sub>Cr<sub>x</sub>S nanoparticles have been synthesized. The specific magnetic properties important for applications in technical devices can be tuned by chromium doping.
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Pedraza-Avella, J. A., R. López, F. Martínez-Ortega, E. A. Páez-Mozo, and Ricardo Gómez. "Effect of Chromium Doping on Visible Light Absorption of Nanosized Titania Sol-Gel." Journal of Nano Research 5 (February 2009): 95–104. http://dx.doi.org/10.4028/www.scientific.net/jnanor.5.95.
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Visible light absorption of TiO2 can be induced by the addition of transition metal impurities. However, many dissimilar results have been reported about this subject and there are various interpretations about the origin of these absorption features. In this work, samples of chromium-doped titania (TiO2-Cr) with different dopant contents (0.1, 0.5, 1.0 and 5.0 wt. %) were prepared by a sol-gel method. Their particle size was determined by dynamic light scattering and it was on the nanometer scale (18 nm). X-ray powder diffraction and Raman spectroscopy showed only the presence of anatase phase in all samples. X-ray photoelectron spectroscopy reveals that the oxidation state of chromium in the prepared materials is different than in the dopant precursor. This change can be associated to the oxidative gelling conditions used in the materials preparation. UV VIS diffuse reflectance spectroscopy showed that the chromium doping, until 1.0 wt. %, did not effectively narrow the TiO2 band-gap but it induces the visible light absorption probably through the formation of color centers.
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Setera, Brett, Ching-Hua Su, Bradley Arnold, et al. "Comparative Study of Bulk and Nanoengineered Doped ZnSe." Crystals 12, no. 1 (2022): 71. http://dx.doi.org/10.3390/cryst12010071.
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Chromium- and cobalt-doped zinc selenide nanoparticles were synthesized using a low-temperature reactive solution growth method. The morphological and optical characteristics were compared to those of doped zinc selenide (ZnSe) bulk crystals grown by the physical vapor transport (PVT) method. We observed agglomeration of particles; however, the thioglycerol capping agent has been shown to limit particle grain growth and agglomeration. This process enables doping by addition of chromium and cobalt salts in the solution. A slightly longer refluxing time was required to achieve cobalt doping as compared with chromium doping due to lower refluxing temperature. The nanoparticle growth process showed an average particle size of approximately 300 nm for both Cr- and Co-doped zinc selenide. The optical characterization of Co:ZnSe is ongoing; however, preliminary results showed a very high bandgap compared to that of pure ZnSe bulk crystal. Additionally, Co:ZnSe has an order of magnitude higher fluorescence intensity compared to bulk Cr:ZnSe samples.
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Lin, Jinpei, Jiaqi Zhang, Hao Sun, et al. "Structural and Magnetic Property of Cr3+ Substituted Cobalt Ferrite Nanomaterials Prepared by the Sol-Gel Method." Materials 11, no. 11 (2018): 2095. http://dx.doi.org/10.3390/ma11112095.
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Cobalt-chromium ferrite, CoCrxFe2−xO4 (x = 0–1.2), has been synthesized by the sol-gel auto-combustion method. X-ray diffraction (XRD) indicates that samples calcined at 800 °C for 3 h were a single-cubic phase. The lattice parameter decreased with increasing Cr concentration. Scanning electron microscopy (SEM) confirmed that the sample powders were nanoparticles. It was confirmed from the room temperature Mössbauer spectra that transition from the ferrimagnetic state to the superparamagnetic state occurred with the doping of chromium. Both the saturation magnetization and the coercivity decreased with the chromium doping. With a higher annealing temperature, the saturation magnetization increased and the coercivity increased initially and then decreased for CoCr0.2Fe1.8O4.
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Kushwaha, S. K., K. K. Maurya, D. Haranath, and G. Bhagavannarayana. "The effect of Cr3+doping on the crystalline perfection and optical properties of zinc tris(thiourea)sulfate, a nonlinear optical material." Journal of Applied Crystallography 44, no. 5 (2011): 1054–61. http://dx.doi.org/10.1107/s002188981102944x.
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A study of the effect of Cr3+doping in zinc tris(thiourea)sulfate (ZTS, a well known nonlinear optical material) single crystals on crystalline perfection and optical properties was carried out. Pure and chromium-doped (1 and 2 mol%) ZTS single crystals were grown by the slow evaporation solution technique. The actual concentration of chromium incorporated into the crystal lattice was found to be different, as evaluated by flame atomic absorption spectroscopy. High-resolution X-ray diffraction (HRXRD) analysis revealed that chromium doping led to the creation of vacancies in the grown single crystals. The photoluminescence emission spectra of pure and doped crystals supported the HRXRD findings. The optical band gap of the single crystals increased as a result of the Cr3+doping, but their transparency in the visible region decreased. The doped crystals exhibited higher linear refractive indices than the pure crystals. The optical dielectric constant (∊), the extinction coefficient (k), the average single-oscillator energy for electronic transitions (Eo) and the oscillator strength (Ed) were evaluated for ZTS single crystals and significant changes were observed in these parameters due to the Cr3+doping.
Dissertations / Theses on the topic "Chromium doping"
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Tásler, Jan. "Příprava a vlastnosti transparentních polykrystalických keramických materiálů." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-416665.
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The presented diploma thesis is focused on the preparation and properties of transparent polycrystalline ceramic materials based on Al2O3. Theoretically, the most important technological aspects of the processing of these materials are presented. Detailed attention is given to transparent Al2O3 polycrystalline ceramics doped with rare earth elements. The influence of microstructural parameters on the optical properties (represented by RIT) is investigated on Al2O3 samples doped and codoped with dysprosium, terbium and chromium. A significant effect of the average grain size on the light transmittance of all samples is observed. The highest RIT = 55 % (measured by a laser beam with a wavelength of 632,8 nm) was achieved by an optimized preparation process for a sample doped with 0,05 at. % of dysprosium. For all samples photoluminescent properties are also analysed. The photoluminescent emission spectra correspond to the activation of doping elements. In case of the terbium and chromium codoped samples, the differences in the activation of individual dopants depending on different excitation wavelengths were demonstrated, resulting in different colour emissions for different excitation wavelengths.
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Thomas, Régis. "MOX dopé chrome : optimisation du dopage et de l’atmosphère de frittage." Thesis, Bordeaux 1, 2013. http://www.theses.fr/2013BOR14832/document.
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Dans un contexte d’accroissement des marges de sûreté des réacteurs de générations II et III vis-à-vis des scénarios accidentels, des efforts importants de recherche sont consacrés à l’amélioration de la microstructure du combustible MOX à l’issue de son procédé de fabrication. Les deux caractéristiques microstructurales recherchées sont l’accroissement de l’homogénéité de répartition du plutonium et l’augmentation de la taille de grain. Dans cette optique, une solution envisagée est l’ajout lors du procédé de fabrication et sans modification de celui-ci, de sesquioxyde de chrome Cr2O3. Une précédente thèse sur le sujet a permis de proposer un modèle d’homogénéisation de la répartition du plutonium suite à l’ajout de Cr2O3. L’auteur a souligné l’importance de la formation du précipité PuCrO3 aux joints de grains lorsque la solubilité du chrome dans la matrice (U,Pu)O2 est atteinte. Cependant, les mécanismes d’action du chrome n’ont été étudiés que pour une atmosphère de frittage unique. Plusieurs points restent également à approfondir, notamment la solubilité du chrome et les conditions optimales de formation du précipité PuCrO3. Dans un premier temps, une étude de la spéciation du chrome solubilisé et précipité dans l’oxyde mixte (U,Pu)O2 a été réalisée. Les techniques ayant permis d’analyser directement le chrome sont la microsonde électronique et la spectroscopie d’absorption des rayons X. Il a été montré que le degré d’oxydation et l’environnement du chrome solubilisé sont indépendants de la pression partielle d’oxygène imposée lors du frittage et de la teneur en plutonium de l’oxyde mixte. La nature des précipités et la solubilité du chrome dépendent, quant à eux, de la variable thermodynamique et de la teneur en Pu. Sur la base de ces résultats, un modèle de solubilité du chrome dans l’oxyde mixte (U,Pu)O2-x a été construit. Ce modèle a été réalisé en fonction de la teneur en plutonium y de la solution solide (U1-yPuy)O2-x (y = 0,11 ; 0,275 et 1) et sur la gamme de potentiel d’oxygène d’intérêt pour le frittage du combustible (-445 kJ.mol -1< µO2 < -360 kJ.mol -1). Outre l’optimisation du dopage, ce modèle permet de définir les conditions optimales de formation du précipité PuCrO3 en fonction de la teneur en plutonium et de l’atmosphère de frittage. Dans un second temps, nous avons regardé si les conditions d’obtention du précipité PuCrO3 correspondaient à un accroissement de l’homogénéité de répartition du plutonium et une taille de grains maximale. Pour ce faire, des échantillons fabriqués avec ou sans présence de chrome et frittés sous différentes atmosphères ont été étudiés. Il a été mis en évidence que la cinétique d’interdiffusion U-Pu est complètement modifiée en présence de chrome. De plus, suite à l’ajout de chrome, les conditions permettant d’accroître la cinétique d’interdiffusion U-Pu ne sont pas forcément associées à une taille de grain maximale.A partir de ces résultats, des préconisations pour la mise en œuvre industrielle sont proposées. Elles concernent le choix de l’atmosphère de frittage et la teneur en chrome nécessaire à l’optimisation de la microstructure<br>Optimal use of the Mixed Oxide (U,Pu)O2 nuclear fuel in pressurized water reactors is mainly limited by the behavior of gaseous fission produced during irradiation. Within the MOX microstructure, the probability of fission gas release is increased by the presence of rich localized plutonium areas exhibiting a higher local burn-up. A solution consists in optimizing plutonium distribution within the industrial product and promoting the crystalline growth of the fuel grains. For this purpose, addition of chromium sesquioxide during the manufacturing process is currently considered. A previous thesis has shown that the best results are obtained for a Cr addition slightly greater than the solubility limit of Cr in (U,Pu)O2. In order to explain the enhanced plutonium homogeneity, the author highlighted the formation of PuCrO3 precipitates at grain boundaries. A sintering model under reducing atmosphere, with chromium addition, was proposed. However, several points have to be more thoroughly investigated, especially regarding the solubility limit of chromium, as well as the optimal conditions of PuCrO3 precipitates formation. In a first part, speciation of solubilized and precipitated chromium in the mixed oxide (U,Pu)O2 is studied using electron probe microanalysis (EPMA) and X-ray absorption spectroscopy (XAS). It was shown that the oxidation state and the environment of soluble chromium within the (U,Pu)O2 matrix do not depend on the oxygen partial pressure during sintering, neither on the plutonium content of the mixed oxide. However, both chemical nature of the precipitates and chromium solubility depend on the thermodynamic variable and on the plutonium content.Based on these results, a chromium solubility model in the mixed oxide (U,Pu)O2-x was built using the law of mass action governing solubility equilibrium. This model is described as a function of the plutonium content (y) of the solid solution (U1-yPuy)O2-x (y = 0,11 ; 0,275 et 1) and in the oxygen potential range of interest for MOX fuel sintering (-445 kJ/mol < µO2 < -360 kJ/mol). This thermodynamic model contributes to the optimization of the doping stage of fabrication and defines the optimal conditions of PuCrO3 precipitates formation.The aim of the second part is to verify if the thermodynamic conditions of PuCrO3 formation correspond to an optimal plutonium distribution and grain growth of the mixed oxide. Samples manufactured with and without Cr2O3 addition and sintered under various atmospheres were analyzed. It was shown that the U-Pu interdiffusion kinetics is completely modified with chromium addition. Morover, with chromium addition, sintering conditions which increase the U-Pu interdiffusion kinetics, don’t necessarily correspond to optimal grain growth. Based on these results, recommendations for the industrial manufacturing process are proposed. They deal with the choice of the sintering atmosphere and doping concentration to obtain an optimized microstructure
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Rosell-Laclau, Eliette. "Addition d'éléments de transition dans les alliages Al-Ni précurseurs des catalyseurs de nickel de Ranay." Grenoble INPG, 1994. http://www.theses.fr/1994INPG0071.
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Cette etude concerne l'influence d'elements d'addition (titane, fer et chrome) dans les alliages precurseurs al-ni, des catalyseurs de nickel de raney. Deux aspects principaux ont ete developpes lors de ce travail. La premiere partie traite de l'effet du dopant sur la reactivite des phases al#3ni et al#3ni#2 vis-a-vis de l'extraction d'aluminium par attaque alcaline. L'attaque de al#3ni par propagation d'un front plan, a permis de mettre en evidence un processus d'attaque identique que ce soit sans dopant ou en presence de titane ou de chrome. Une energie d'activation de 60 kj/mol a ete determinee pour ce phenomene. Par contre, la presence de fer semble modifier ce processus d'extraction, puisqu'il apparait deux regimes d'attaque differents, a basse et a haute temperature. Dans une deuxieme partie, la localisation du dopant a differentes etapes de la vie du catalyseur a ete etudiee. Pour cela, les compositions d'alliages eutectiques modeles ont ete optimisees. Les catalyseurs issus de ces alliages ont par la suite, ete testes dans une reaction d'hydrogenation. Le mecanisme d'extraction du dopant a ainsi ete mis en evidence. Le dopant, quelle que soit sa localisation initiale, s'extrait simultanement a l'aluminium, puis apres passage en solution, se redepose sous forme oxydee, sur la cristallite de nickel. Ce travail sur des alliages modeles a egalement conduit a une determination experimentale du systeme al-ni-cr du cote aluminium. En particulier, une transformation eutectique ternaire et deux phases ternaires ont ete mises en evidence. Ces investigations ont permis de proposer la premiere ebauche de la projection de la surface liquidus de la sous-section al-cr-alni
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Yang, Jing. "Synthesis and characterisation of metal oxyhydroxide and oxide nanomaterials." Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/45712/1/Jing_Yang_Thesis.pdf.
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In this work, a range of nanomaterials have been synthesised based on metal oxyhydroxides MO(OH), where M=Al, Co, Cr, etc. Through a self-assembly hydrothermal route, metal oxyhydroxide nanomaterials with various morphologies were successfully synthesised: one dimensional boehmite (AlO(OH)) nanofibres, zero dimensional indium hydroxide (In(OH)3) nanocubes and chromium oxyhydroxide (CrO(OH)) nanoparticles, as well as two dimensional cobalt hydroxide and oxyhydroxide (Co(OH)2 & CoO(OH)) nanodiscs. In order to control the synthetic nanomaterial morphology and growth, several factors were investigated including cation concentration, temperature, hydrothermal treatment time, and pH. Metal ion doping is a promising technique to modify and control the properties of materials by intentionally introducing impurities or defects into the material. Chromium was successfully applied as a dopant for fabricating doped boehmite nanofibres. The thermal stability of the boehmite nanofibres was enhanced by chromium doping, and the photoluminescence property was introduced to the chromium doped alumina nanofibres. Doping proved to be an efficient method to modify and functionalize nanomaterials. The synthesised nanomaterials were fully characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM) combined with selected area electron diffraction (SAED), scanning electron microscopy (SEM), BET specific surface area analysis, X-ray photoelectron spectroscopy (XPS) and thermo gravimetric analysis (TGA). Hot-stage Raman and infrared emission spectroscopy were applied to study the chemical reactions during dehydration and dehydroxylation. The advantage of these techniques is that the changes in molecular structure can be followed in situ and at the elevated temperatures.
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Mieszczynski, Cyprian. "Atomic scale structural modifications in irradiated nuclear fuels." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01057120.
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This thesis work reports in depth analyses of measured µ-XRD and µ-XAS data from standard UO2, chromia (Cr2O3) doped UO2 and MOX fuels, and interpretation of the results considering the role of chromium as a dopant as well as several fission product elements. The lattice parameters of UO2 in fresh and irradiated samples and elastic strain energy densities in the irradiated UO2 samples have been measured and quantified. The µ-XRD patterns have further allowed the evaluation of the crystalline domain size and sub-grain formation at different locations of the irradiated fuel pellets. Attempts have been made to determine lattice parameter and next neighbor atomic environment in chromia-precipitates found in fresh chromia-doped fuel pellets. The local structure around Cr in as-fabricated chromia-doped UO2 matrix and the influence of irradiation on the state of chromium in irradiated fuel matrix have been addressed. Finally, for a comparative understanding of fission gases behavior and irradiation induced re-solution phenomenon in standard and chromia-doped UO2, the last part of the present work tries to clarify the fission gas Kr atomic environment in these irradiated fuels. The work performed on Kr, by micro-beam XAS, comprises the determination of Kr next neighbor distances, an estimation of gas atom densities in the aggregates, and apparent internal pressures in the gas bubbles.
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Tsai, Sian-jhih, and 蔡賢治. "Tribological performance of chromium films with aluminum doping after high temperature oxidation treatment." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/32142887320962001312.
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碩士<br>國立成功大學<br>機械工程學系碩博士班<br>96<br>In this study, Cr-Al coatings were deposited on JIS SKH51 disks, Si (100) wafers, micro-drills and indexable inserts from one aluminum and tree chromium targets using Closed Field Unbalanced Magnetron (CFUBM) sputtering system. The main purpose of this study is to research the mechanical and tribological properties and cutting performance of the Cr-Al coatings before and after high temperature oxidation. The experiment was divided into three stages. In the first two stages, the ratio of chromium and aluminum contents (Al/Cr) and the effect of one hour oxidation treatment at 600 ℃ on the mechanical and tribological properties of the Cr-Al coatings was investigated, respectively. In the third stage, the effect of oxidation treatment at different temperature on the mechanical and tribological properties of Cr-Al coatings was investigated. Finally, the actual cutting performances of the optimal coatings were understood in the turning and micro-drilling tests.
The results reveal that the better hardness of HK25g 1274 and the best resistance were performed by the Cr-Al (Al/Cr=0.3) coatings. The hardness of Cr-Al(Al/Cr=0.3) coatings after 600℃ and one hour oxidation treatment increased to HK25g 1355. The wear resistance and adhesion performance of the Cr-Al coatings improve apparently after oxidation. It could be attributed to the forming of Cr2O3 and Al2O3 at the surface.
In actually turning and micro-drilling tests, the flank wear of inserts, and flank wear, corner wear, and diameter wear of the drillings on Cr-Al(Al/Cr=0.3) coated onces with 600℃ and one hour oxidation treatment can be reduced about 71 % , 53％, 71％, and 81％, respectively.
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Hsieh, Yi-Huan, and 謝宜寰. "Tribological performance of chromium films with tungsten doping after high temperature oxidation treatment." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/44315789083116035157.
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碩士<br>國立成功大學<br>機械工程學系碩博士班<br>95<br>In this study, Cr-W coatings were deposited on JIS SKH51 disks, silicon wafers, micro-drills and indexable inserts by closed field unbalanced magnetron system. The main purpose of this study is to research the mechanical and tribological properties and cutting performance of the Cr-W coatings before and after high temperature oxidation. The experiment is divided into three stages. In first stage, the effect of tungsten content on the mechanical properties of the Cr-W coatings was investigated. In second stage, the effect of one hour oxidation treatment at 600 ℃ on the mechanical properties of the Cr-W coatings was investigated. In third stage, the effect of oxidation treatment at different temperature and duration on the mechanical properties of Cr-W coatings was investigated. Finally, the actual cutting performances of the optimal coatings were understood in the turning and micro-drilling tests.
The results reveal that the highest hardness of HK25g 1650 and the best wear resistance were performed by the Cr-W coatings with the tungsten target current of 2.0 A. The hardness of Cr-W(2.0 A) coatings after 600 ℃ and one hour oxidation treatment increased to HK25g 1820. The wear resistance and adhesion performance of the Cr-W coatings improve apparently after oxidation. The coefficient of friction of Cr-W coatings after oxidation declines obviously. The best wear resistance and adhesion were performed for Cr-W(2.0 A) coatings after 600 ℃ and two hours oxidation treatment.
In actually turning and micro-drilling tests, the wear on Cr-W(2.0 A) coatings deposited on inserts and drills with high temperature oxidation treatment can be reduced about 71 % and 63 %, respectively.
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Roro, Kittessa Tolessa. "Influence of V and Mn doping on the electrical transport properties of A Cr +1.2 at.% Ga alloy." Thesis, 2008. http://hdl.handle.net/10210/1360.
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M.Sc.<br>Impurity resonance scattering effects are investigated in the Cr-Ga alloy system. This system has a triple point on its magnetic phase diagram where the paramagnetic (P), incommensurate (I) and commensurate (C) spin-density-wave (SDW) states co-exist. Alloying Cr with the nonmagnetic nontransitional element Ga affects the magnetic properties of Cr in a very unique way. In order to investigate the presence of resonant impurity scattering effects in binary Cr-Ga alloys, electrical resistivity measurements were carried out in the temperature range between 6 K and 85 K. The results of the investigation show: • A nonmonotonic increase in the residual resistivity of the Cr-Ga system with an increase in the Ga content, due to the presence of resonant impurity scattering of conduction electrons. • A low-temperature resistivity minimum observed in some of the Cr-Ga alloys, taken as further evidence for the presence of resonant impurity scattering effects on the conduction electrons. The impurity resonance scattering effects on the electrical resistivity of a Cr + 1.2 at.% Ga alloy, doped with V and Mn to tune the Fermi level through the impurity level, are also investigated. The investigation was complemented by thermal expansion and velocity of sound measurements in the temperature range 77 K to 450 K for the Cr + 1.2 at.% Ga alloy only. This specific Ga concentration was chosen to allow for studying resonant scattering effects in both the ISDW and CSDW phases of the system. This is possible because concentration of 1.2 at.% Ga is just above the triple point concentration. Doping with Mn to increase the electron concentration (eA) drives the alloy deeper into the CSDW phase region of the phase diagram, while doping with V, on the other hand, will drive the alloy towards the ISDW phase region. The results of the study are summarized as follows: • Two relatively sharp peaks, attributed to resonant impurity scattering effects, are observed in the curve of the residual resisitivity as a function of dopant concentration in the ISDW phase of the ternary (Cr0.988Ga0.012)1-xVx and (Cr0.988Ga0.012)1-yMny alloy systems. v • At 0 K the (Cr0.988Ga0.012)1-yMny alloy system transforms from the ISDW to the CSDW phase at y ≅ 0.0032, giving a CSDW phase for y > 0.0032. A peak is observed in the residual resistivity at about this Mn content. This peak can then either be ascribed to a jump occurring in the residual resistivity when the CSDW phase is entered from the ISDW phase or to resonant scattering effects. The conclusion is that the peak is rather related to the latter effect. • The resistivity as a function of temperature of the above two ternary alloy series show well-developed or weak minima at low temperatures for some of the samples. This is taken as further evidence of the influence of impurity resonant scattering effects on the resistivity of these alloys. • The resistivity and thermal expansion coefficient of the polycrystalline Cr0.988Ga0.012 alloy of the present study behaves anomalously close to the ISDW-CSDW phase transition temperature and warrant further investigation. The concentration-temperature magnetic phase diagram of the (Cr0.988Ga0.012)(Mn,V) alloy system was constructed from the magnetic transition temperatures obtained from electrical resistivity measurements. Theoretical analysis of the phase diagram was done using the two-band imperfect nesting model of Machida and Fujita. The results show: • A triple point at (0.21 at.% V, 225 K) where the ISDW, CSDW and P phases coexist on the magnetic phase diagram. • The curvature of all three theoretically calculated phase transition lines in the region of the triple point is of the same sign as that observed experimentally. • The theoretical fit is very good for the ISDW-P and ISDW-CSDW phase transition boundaries, while there is some discrepancy for the CSDW-P phase transition line. This may be attributed to the fact that the theory is one dimensional and that it does not include electron-hole pair breaking effects due to impurity scattering and also not effects of changes in the density of states due to alloying.<br>Dr. A.R.E Prinsloo Prof. H.L. Alberts
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Che-WeiLiu and 劉哲維. "Effect of lanthanum and chromium co-doping on the dielectric properties of bismuth ferrite." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/54149721425120860296.
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碩士<br>國立成功大學<br>材料科學及工程學系碩博士班<br>101<br>BiFeO3(BFO),which is one of the most potential multiferroics ,has high Curie temperature TC(~1123 K) and high Néel temperature TN(~643 K) resulting to the coexistence of ferroelectricity and ferromagnetism at room temperature.This study mainly reported the influence and change by the co-doping of lanthanum and different content of chromium.Bi3+ ions have close size as La3+ ions, and Fe3+ ions have close size as Cr3+ ions, so we hope to improve the ferroelectric properties with the substitution of La3+ ions for Bi3+ ions and Cr3+ ions for Fe3+ ions in the perovskite BiFeO3 structure. Bulks of BiFeO¬3 and BiFeO3 co-doping with La3+ and Cr3+ were prepared by the usual solid state reaction method. X-ray diffraction(XRD), Scanning electron microscopy(SEM), ferroelectric hysteresis measurements, leakage current measurements and dielectric measurement are used for understanding the effect of codoping. We found that second phases appeared when the doping amount of Cr were more than 5%, indicating that there was a limit for Cr doping in BFO.With the XPS analysis,La doping and the increased doping amount of Cr make more Fe ions change from Fe3+ to Fe2+,which resulting to higher conductivity by transfer of electrons between the neighboring Fe2+ and Fe3+ ions. Because of more Fe2+ ions, the conductive mechanism changes from ohmic conduction to space charge limit conduction by fitting the IV curve. The dielectric measurement can find out that the space charge is the main polarization mechanism.
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HUANG, YUNG-TING, and 黃詠廷. "Effect of Tungsten-doping in Chromium Nitride Based Films on Oxidation Resistance and Thermal Electricity Deposited on Ferritic Stainless Steel." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/m5a27e.
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碩士<br>國立高雄大學<br>化學工程及材料工程學系碩士班<br>105<br>Bipolar plates materials were used for solid oxide fuel cell accounted for 80% of weight and 45% of cost overall, which must have a good formability and low cost. Therefore ferritic stainless steel has been chosen. Considering the influence of working environment, bipolar plate also must have good high temperature oxidation resistance and high electrical conductivity. Fe-Cr-Mn alloy can form spinel structure which has good electrical conductivity in the surface of oxide scale, and protects inner layer chromia from rapid oxidation.
In this experiment, Fe-22Cr-0.5Mn stainless steel was used as the bipolar plate substrate, and the cold cathodic arc plasma deposition was used to dope CrN, CrWN, Cr2N and (Cr,W)2N films on the surface. Fe-22Cr-0.5Mn specimens undergoing 800 °C oxidation for sarious time period were observed the scale growth and phase transformation of films. Besides, CrN/Fe-22Cr-0.5Mn, CrWN/Fe-22Cr-0.5Mn, Cr2N/Fe-22Cr-0.5Mn and (Cr,W)2N/Fe-22Cr-0.5Mn also undergo ASR measurement during long-term oxidation at 800 °C to observe the electric behavior.
From the analysis of XRD, CrN and CrWN are composed of CrN main structure. The diffraction peaks are (111), (200), (220) and (311). Diffraction angles of CrWN are slightly lower because W solid solution in CrN cause D-spacing increasing. Cr2N and (Cr,W)2N films are mainly composed of Cr2N structure. The diffraction peaks are (110), (111), (300), and Cr2N film also has part of CrN structure which shows diffraction peak at (200). In addition, W in (Cr,W)2N film shown as W2N tissue appeared in the Cr2N structure. The average grain size of CrN, CrWN, Cr2N, (Cr,W)2N film were 16.29 nm, 16.05 nm, 12.82 nm and 8.01 nm, respectively. And the grain size of W2N in (Cr,W)2N was 3.01 nm. The total thickness of film were CrN：1.91 ± 0.06 µm, CrWN：3.57 ± 0.15 µm, Cr2N：1.71±0.07 µm, (Cr,W)2N：1.71±0.07 µm, respectively.
After the oxidation experiment at 800 °C, it was found that the oxide layers of all the specimens were divided into two layers: the (Mn, Cr)3O4 spinel with structure as the outer layer and the Cr2O3 as inner layer. In terms of oxidation kinetics, it is found that the oxidation rate cinstants are in the order of CrN:0.0236> Cr2N: 0.0173> CrWN: 0.0152> (Cr,W)2N: 0.0174 with R-square value are higher than 0.97 showing that the thickness of the oxide layer conforms to the parabolic law.
After 800°C oxidation the composition of oxide layers of CrN, CrWN, Cr2N, (Cr,W)2N didn’t show significantly dirrerent, keeping are the outer spinel layer and the inner chromia layer structure. Noted that the time that keeping spinel structure appear the same for all the films. The content of manganese in the surface of the scale increases with the increase of oxidation time, and there is no significant difference between different films at first 100 h. It is CrWN and Cr2N higher than CrN and (Cr,W)2N in the beginning. As the oxidation time comes to 1000 h, the manganese content of (Cr,W)2N is up to 15.52 at%; CrWN is 13.34 at% and Cr2N is 13.54 a.t.% ; CrN is the lowest 11.59 at%. As for the effect of the chromium nitride-based film and Fe-22Cr-0.5Mn on the oxidation of the CrN and CrWN systems, the CrN original film was found to be transformed into the Cr2N structure at 800 °C. That is, from the inner layer takes began to grow into Cr2N, and the excess N through the grain boundary quickly inward diffusion, where the internal Cr in Fe-22Cr-0.5Mn alloy diffused along in the grain boundary to form Cr2N, thus slowing down the outward diffusion capacity of alloy. The diffraction peak of the element W with good conductivity shown in the XRD diffraction diagram of (Cr,W)2N after 10 h oxidation and that W associated with Fr and Cr formed as CrWN were oberved. Such Fe-Cr-W intermetallic phase precipitates on grain boundaries of the films in the form of χ-phase, and have a very significant contribution to the barrier propagation of the cation through the thin film.
CrN/Fe-22Cr-0.5Mn, CrWN/Fe-22Cr-0.5Mn, Cr2N/Fe-22Cr-0.5Mn, (Cr,W)2N/Fe-22Cr-0.5Mn at 800 ° C for 1000 h. ASR value magnitude were (Cr,W)2N> Cr2N> CrWN> CrN, respectively. The ASR value is in the order of 0.11300, 0.00860, 0.00544 and 0.00399 Ω*cm2.
Keywords: Ferrite stainless steel, CrN CrWN, Cr2N, (Cr,W)2N, cathodic arc plasma deposition
Book chapters on the topic "Chromium doping"
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Low, I. M., H. Albetran, V. De La Prida, P. Manurung, and M. Ionescu. "Effect of Chromium-Doping on the Crystallization and Phase Stability in Anodized TiO2Nanotubes." In Developments in Strategic Materials and Computational Design III. John Wiley & Sons, Inc., 2012. http://dx.doi.org/10.1002/9781118217542.ch14.
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Krumpolc, M., D. Hill, and H. B. Stuhrmann. "Progress in the Chemistry of Chromium(V) Doping Agents Used in Polarized Target Materials." In High Energy Spin Physics. Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-642-76661-9_65.
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Liu, Yingjia, Kangli Wang, and Jeffrey W. Fergus. "Effect of Chromium Doping on the Crystal Structure, Electrical Conductivity and Thermal Expansion of Manganese Cobalt Spinel Oxides." In Ceramic Engineering and Science Proceedings. John Wiley & Sons, Inc., 2011. http://dx.doi.org/10.1002/9781118095249.ch11.
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C.A. Silva, Anielle, Jerusa M. de Oliveira, Luciana R.S. Floresta, et al. "Transition Metals Doped Nanocrystals: Synthesis, Characterization, and Applications." In Transition Metal Compounds - Synthesis, Properties, and Application. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97326.
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Doping is a technique that makes it possible to incorporate substitutional ions into the crystalline structure of materials, generating exciting properties. This book chapter will comment on the transition metals (TM) doped nanocrystals (NCs) and how doping and concentration influence applications and biocompatibility. In the NCs doped with TM, there is a strong interaction of sp-d exchange between the NCs’ charge carriers and the unpaired electrons of the MT, generating new and exciting properties. These doped NCs can be nanopowders or be embedded in glass matrices, depending on the application of interest. Therefore, we show the group results of synthesis, characterization, and applications of iron or copper-doped ZnO nanopowders and chromium-doped Bi2S3, nickel-doped ZnTe, and manganese-doped CdTe quantum dots in the glass matrices.
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Sridhar, Rapolu, D. Ravinder, J. Laxman Naik, K. Vijaya Kumar, N. Maramu, and S. Katlakunta. "Investigation of Structural, Magnetic and Electrical Properties of Chromium Substituted Nickel Ceramic Nanopowders." In Advanced Ceramic Materials. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.94941.
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Nano-ceramic of NiCrxFe2-xO4 (0.1 ≤ x ≤ 1.0) ferrites were synthesized by citrate-gel auto combustion method. The structural parameter such as lattice parameter, X-ray density, bulk density and porosity variations with Cr doping were studied. The average crystallite size is in the range 8.5–10.5 nm. The surface morphology and elemental analysis was studied with SEM (EDAX) spectrum and the structural information analyzed with FTIR spectra. Magnetic properties were discussed with Cr3+ion concentration. Electrical parameters like dc resistivity and drift mobility were reported with function of temperature and dopent concentration from room temperature to well beyond Curie temperature and explained with hopping mechanism between Fe2+↔Fe3+ ions. The activation energies in ferri and para magnetic regions were investigated. Dielectric parameters like dielectric constant, dielectric loss and ac conductivity were investigated variation with frequency and composition.
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Henderson, B., and G. F. Imbusch. "Spectroscopy at high dopant concentrations." In Optical Spectroscopy of Inorganic Solids. Oxford University PressOxford, 2006. http://dx.doi.org/10.1093/oso/9780199298624.003.0010.
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Abstract So far this treatment of the spectroscopy of optically active centres in solids has assumed these centres to be isolated from each other. When the concentration of centres is increased, or when a second type of optically active centre is also introduced, allowance must be made for the possibility that two centres are sufficiently close to each other to interact. This interaction may be too weak to have a detectable effect on the energy levels so that the centres retain their individual identities but may yet be sufficiently strong to enable excitation to be transferred from one to another. The occurrence of energy transfer between centres can significantly affect the luminescence properties of a material. In some cases two or more centres may be near enough to interact strongly, so forming a new spectroscopic centre. In fully concentrated crystals such as manganese fluoride, chromic oxide, or praseodymium trifluoride the inter-ion coupling is so strong that the excitation must be interpreted as shared by all the ions acting collectively.
Conference papers on the topic "Chromium doping"
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Modi, Anchit, Rajesh K. Thakur, Rasna Thakur, G. S. Okram, and N. K. Gaur. "Effect of chromium doping on the resistivity behavior of gadolinium manganite." In SOLID STATE PHYSICS: PROCEEDINGS OF THE 57TH DAE SOLID STATE PHYSICS SYMPOSIUM 2012. AIP, 2013. http://dx.doi.org/10.1063/1.4791527.
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Yadav, A., Mashkoor A. Dar, P. Choudhary, P. Shah, and Dinesh Varshney. "Chromium doping effects on structural and dielectric properties of Mn-Zn cobaltites." In INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC 2015): Proceeding of International Conference on Condensed Matter and Applied Physics. Author(s), 2016. http://dx.doi.org/10.1063/1.4946352.
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Saleem, M., and Dinesh Varshney. "Effect of chromium doping on the structural and vibrational properties of Mn-Zn ferrites." In 2ND INTERNATIONAL CONFERENCE ON CONDENSED MATTER AND APPLIED PHYSICS (ICC 2017). Author(s), 2018. http://dx.doi.org/10.1063/1.5032428.
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Stanoi, Carmen-Daniela, Gabriel Socol, Carmen Ristoscu, et al. "Pulsed laser deposition of chromium oxides thin films: chemical stabilizations by capping and doping." In SPIE Proceedings, edited by Valentin I. Vlad. SPIE, 2004. http://dx.doi.org/10.1117/12.582915.
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Ivleva, L. I., P. G. Zverev, I. S. Voronina, E. E. Dunaeva, and A. V. Nekhoroshikh. "Influence of chromium and niobium Co-doping on laser damage threshold of Raman active crystals." In 2013 Conference on Lasers & Electro-Optics Europe & International Quantum Electronics Conference CLEO EUROPE/IQEC. IEEE, 2013. http://dx.doi.org/10.1109/cleoe-iqec.2013.6801013.
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Perevalova, Olga, Elena Konovalova, Nina Koneva, and Eduard Kozlov. "The chromium doping of Ni3Fe alloy and restructuring of grain boundary ensemble at the phase transition A1→L12." In ADVANCED MATERIALS IN TECHNOLOGY AND CONSTRUCTION (AMTC-2015): Proceedings of the II All-Russian Scientific Conference of Young Scientists “Advanced Materials in Technology and Construction”. AIP Publishing LLC, 2016. http://dx.doi.org/10.1063/1.4937825.
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Pimentel, Joao Vitor, Manuel Evaristo, Tomas Polcar, and Albano Cavaleiro. "Self-lubricating W-S-C-Cr tribological coatings deposited by r.f. magnetron sputtering." In 13th International Conference on Plasma Surface Engineering September 10 - 14, 2012, in Garmisch-Partenkirchen, Germany. Linköping University Electronic Press, 2013. http://dx.doi.org/10.3384/wcc2.283-286.
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Tribological coatings composed of transition metal dichalcogenides (TMD) have long been studied for their excellent self-lubricant properties. However, they exhibit low load-bearing capacity, and their performance tends to deteriorate significantly in the presence of humidity. In previous works, doping disulfides and diselenides of tungsten and molybdenum has proven to be a way of greatly improving the tribological performance of this class of films in different environments. In this work, thin films were deposited by r.f. magnetron sputtering on silicon and steel samples, using two targets (carbon and chromium) and tungsten disulfide pellets. The final composition was controlled by the number of WS2 pellets and the ratio of the power applied to the targets. The carbon content was fixed at approximately 40 at.% in all depositions. The chromium content in the coatings was varied in the range 0 – 13.5 at.% and the S/W ratio was approximately 1.25 in all compositions in the series. The coatings were characterized in regard to their hardness, adhesion, chemical composition and bonding, microstructure and morphology, as well as their tribological behaviour.
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Lee, Byeonghee, Kyeongtae Kim, Seungkoo Lee, et al. "Design and Batch-Fabrication of Diamond Thermocouple Probes for the Quantitative Thermopower Profiling of Silicon IC Devices." In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-23347.
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We developed a measurement technique that can quantitatively map out the dopant density profile of a silicon integrated-circuit device. This method obtains the quantitative doping density profile by simultaneously carrying out local heating, temperature sensing, and thermoelectric voltage measurement at the tip of a diamond thermocouple probe. This probe, which is the key component of the proposed scheme, is fabricated through a nano-fabrication technique that makes use of boron-doped diamond film that can resist stress up to 10 Gpa, which is necessary for stable electric contact with silicon samples. The tip and cantilever of the probe are made of B-doped diamond by means of the silicon lost-mold technique that guarantees a sharper tip apex than that of a diamond-coated probe. A gold-chromium thermocouple junction is integrated at the tip apex for simultaneous heating and sensing. The size of the thermocouple is about 500 nm and the radius of the tip apex is less than 50 nm. The measurement technique is demonstrated by measuring the thermopower distribution across a silicon p-n junction and the result is compared with the theoretical values.
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Chai, Bruce H. T., Patrick LiKamWa, Hai-Sheng Wang, and Alan Miller. "Generation of 150 femtosecond tunable pulses in Cr:LiSrAlF6 and Cr:LiSrCaAlF6." In OSA Annual Meeting. Optica Publishing Group, 1991. http://dx.doi.org/10.1364/oam.1991.pd30.
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In this talk, we present the first demonstration of cw mode-locked operation of wavelength tunable Cr3+ doped LiSrAlF6 (Cr:LiSAF) and LiSr0.8Ca0.2AlF6 (Cr:LiSCAF). The Czochralski grown crystals, with a nominal chromium concentration of 2% in the melt, were Brewster cut and polished to 15mm lengths and mounted in a four mirror X-fold cavity. Cr:LiSAF1 and Cr:LiSCAF2 crystals showed similar cw and mode-locked performance. Pumping with a cw krypton laser (Laser Ionics) gave a threshold power of 210mW using the red doublet. The output power peaked at around 300mW with 1.5W input. The tuning range was 800 to 900nm using a birefringent filter, limited by the mirror bandwidths. To achieve mode-locked operation, a NEOS high-Q, acousto-optic modulator with broadband anti-reflection coatings centered at 800nm was used. An intracavity two prism sequence was inserted to compensate for group velocity dispersion. A stable, 82MHz mode- locked train was achieved with 1W of krypton pump. When fully optimized, intensity and interferometric autocorrelation and pulse bandwidth measurements confirmed chirp-free pulses of 150fsec duration. Tuning across the 800 to 900nm range was achieved using an intracavity slit. It is likely that self-phase modulation assists the spectral broadening and pulse shortening. The pump wavelength, lack of concentration quenching for the chromium doping and the low threshold makes these crystals good candidates for diode and flashlamp pumped ultrashort pulse sources.
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Yarrison-Rice, Jan M., Robert Klank, Mike Kwiatkowski, et al. "Two-beam coupling- and response-time measurements in strontium barium niobate crystals doped with different concentrations of chromium." In OSA Annual Meeting. Optica Publishing Group, 1993. http://dx.doi.org/10.1364/oam.1993.thdd.40.
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The role of chromium dopant concentration in photorefractive strontium barium niobate is investigated in two 5 mm cubed crystals doped with 0.011% and 0.06% chromium and one 0.5 mm thick (0.06% chromium). Two-beam coupling, grating formation and erasure times, and beam fanning are utilized to extrapolate several material parameters from these crystals.