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Guo-jun Zhang - One of the best experts on this subject based on the ideXlab platform.
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a thermoset hybrid sol for the syntheses of Zirconium Carbide silicon Carbide foam via replica method
Journal of Porous Materials, 2019Co-Authors: Weichao Bao, Xiao Huang, Guo-jun ZhangAbstract:Zirconium Carbide–silicon Carbide (ZrC–SiC) ceramics are amongst the promising candidate materials for thermal protection structures in hypersonic re-entry space vehicles. A thermoset hybrid sol for the syntheses of monolithic ZrC–SiC composites was prepared by a simple sol–gel method. Furfuryl alcohol, polyzirconoxane and tetraethyl orthosilicate were used as raw materials. The as-synthesized sol can be cured at 85 °C for 24 h to obtain a bulk gel. The cured gel is converted into porous ZrC–SiC monolith with porosity of 44.1% after pyrolysis at 1500 °C for 1 h in vacuum. The ZrC–SiC monolith is composed of well distributed nano-sized ZrC and SiC particles. Highly porous ZrC–SiC ceramic foam with density of 0.34 g/cm3 and porosity of 78.1% is prepared by replica method using the hybrid sol as precursor and melamine foam as templates. The hybrid sol and ZrC–SiC composites are characterized by FT-IR, TG–DTA, XRD, SEM, EDS and TEM.
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one pot syntheses and characterization of Zirconium Carbide microspheres by carbon microencapsulation
Ceramics International, 2015Co-Authors: Xiao Huang, Guo-jun Zhang, Zhuang Kang, Hongjie LuoAbstract:Abstract Due to the extremely harsh reaction conditions, it is very difficult to control the particle morphology during the synthesis of ZrC, a well-known ultra high temperature ceramic material. In this paper, carbon encapsulated zirconia microspheres (ZrO 2 @C) are synthesized via two consecutive hydrothermal reactions in one pot. After carbothermal reduction, ZrC particles with controlled spherical morphology can be prepared. The spherical morphology suggests that carbon diffuses into zirconia during carbothermal reduction. The influences of reactant concentrations, reaction time and temperature on the microencapsulation process are also investigated. Meanwhile, as a comparison, zirconia coated carbon microspheres (C@ZrO 2 ) are also prepared, which results in ZrC particles with layered structure.
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preparation of Zirconium Carbide foam by direct foaming method
Journal of The European Ceramic Society, 2014Co-Authors: Zhuang Kang, Xiao Huang, Xingang Wang, Guo-jun ZhangAbstract:Abstract Ultra light, highly porous, closed-cell structured ZrC foam can be produced in two steps. First, pre-ceramic foam is prepared by direct foaming of zirconia sol and phenolic resin. In the next step, the foamed green body is converted into ZrC foam after carbothermal reduction at 1600 °C under argon atmosphere. The obtained ZrC foam has porosity of 85% and possesses uniform cells with an average size of about 40 μm. The foam also displays excellent thermal stability up to 2400 °C. Its compressive strength and thermal conductivity at room temperature are 0.4 MPa and 0.94 W/(m K), respectively.
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fabrication of Zirconium Carbide nanofibers by electrospinning
Ceramics International, 2014Co-Authors: Zhuang Kang, Xiao Huang, Guo-jun ZhangAbstract:Abstract In this work, we present an easy approach to prepare Zirconium Carbide (ZrC) nanofibers by electrospinning technique. Polyzirconoxane (PZO) is used as the Zirconium source. Polyacrylonitrile (PAN) is used as the spinning aid and primary carbon source while sucrose is used as the additional carbon source. The as-spun green fibers are converted to ZrC nanofibers after carbothermal reduction at 1400 °C. Core–shell structured nanofibers are obtained when using PAN only as the carbon source, while more homogeneous nanofibers which are composed of uniformly nano-sized ZrC crystals are obtained when using PAN and sucrose as the carbon source. The carbon source has a strong influence on the fiber morphology by affecting the kinetics of the carbothermal reduction reaction. The obtained ZrC fibers are characterized by XRD, SEM and TEM.
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reactive spark plasma sintering of zrc and hfc ceramics with fine microstructures
Scripta Materialia, 2013Co-Authors: Guo-jun Zhang, Wenwen Wu, Tohru S Suzuki, Yoshio SakkaAbstract:Abstract Zirconium Carbide and hafnium Carbide ceramics were prepared by reactive spark plasma sintering, using oxides and carbon black as the raw materials. The phase and microstructure evolution during the sintering process was investigated. It was found that ZrC and HfC powder intermediates were formed at 1750 and 1800 °C, respectively. Due to the high sinterability of the in situ formed Carbide particles, samples with a fine microstructure could be densified at a relatively low temperature.
W E Lee - One of the best experts on this subject based on the ideXlab platform.
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Zirconium Carbide oxidation maltese cross formation and interface characterization
Oxidation of Metals, 2017Co-Authors: Claudia Gasparrini, Denis Horlait, Renaud Podor, Richard J Chater, W E LeeAbstract:Oxidation of dense hot-pressed ZrC specimens from 1073 to 1473 K was investigated using an in situ technique: HT-ESEM. Cuboid specimens were monitored on the surface and on edges and corners during oxidation in order to understand the influence of crack formation and propagation on the Maltese cross shape development of the oxide. The oxidation mechanism comprised three steps: (1) delamination of sample edges, (2) crack formation at corners and (3) crack propagation towards the inner core and formation of microcracks parallel to the interface that increase the accessible surface area followed by a drastic volume expansion. The microcrack pattern is found to be repetitive as if a cyclic debonding of the interface occurred. Characterization of the interface by TEM and HRTEM revealed the interface between ZrC and ZrO2 to comprise a 2 µm thick amorphous carbon matrix with ZrO2 nanocrystals embedded in it.
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synthesis of biopolymer derived Zirconium Carbide powder by facile one pot reaction
Journal of the American Ceramic Society, 2015Co-Authors: Niranjan Patra, Daniel Doni Jayaseelan, W E LeeAbstract:Zirconium Carbide (ZrC) was synthesized by polycondensation and carbothermal reduction reactions from an organic–inorganic hybrid complex. A natural biopolymer Gum Karaya (GK) and zirconyl oxychloride octahydrate (ZOO) were used as the sources of carbon and Zirconium, respectively. FTIR of as-synthesized dried complexes revealed formation of Zr–O. Pyrolysis of the complexes at 1200°C/1 h under argon resulted in tetragonal and monoclinic zirconia which after heat treatment at 1400°C–1550°C transformed to Zirconium Carbide. Thermal analysis shows that the GK–ZOO complexes lost less mass than the pristine GK to 600°C. The intensity of exothermic decomposition decreases and shifted to higher temperature for the hybrid complexes indicating that zirconia induced thermal stability. A maximum ZrC yield of ~60 wt% is obtained for the intermediate GK–ZOO ratio of 1:2. Particles pyrolyzed for 1 h at 1550°C were coarser (5–10 μm) with flakes for lower GK–ZOO weight ratio, but were spheroidal with narrow size distribution (~1 μm) with increasing GK–ZOO weight ratio.
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the zrc c eutectic structure and melting behaviour a high temperature radiance spectroscopy study
Journal of The European Ceramic Society, 2013Co-Authors: D Manara, Heather F Jackson, C Perinetticasoni, K Boboridis, M J Welland, L Luzzi, P M Ossi, W E LeeAbstract:Abstract A fast spectro-pyrometer has been employed for radiance measurements of Zirconium Carbide samples laser-heated to very high temperature, for compositions 0.7 ≤ C/Zr ≤ 2.61 and in a spectral range 0.550 μm ≤ λ ≤ 0.900 μm. The ZrC–C eutectic temperature has been taken as the radiance reference. The measured normal spectral emissivity (NSE) ɛ λ of solid Zirconium Carbide is close to 0.6 at 0.650 μm, in agreement with previous literature. Its high-temperature behaviour, value in the liquid, carbon-content and wavelength dependences in the visible-near infrared range have been determined here for the first time. Liquid Zirconium Carbide seems to interact with electromagnetic radiation in a more metallic way than the solid. A considerable NSE increase has been observed at increasing carbon content, which can be interpreted on the basis of preferential growth along the “c” plane of the carbon lamellae in the eutectic structure.
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laser melting of Zirconium Carbide determination of phase transitions in refractory ceramic systems
Journal of the American Ceramic Society, 2011Co-Authors: Heather Jackson, D Manara, Daniel Doni Jayaseelan, Carlo Perinetti Casoni, W E LeeAbstract:Pulsed laser heating and optical pyrometry were used to generate time–temperature thermogram data suitable for the determination of extremely high-temperature (>3000 K) solidus, liquidus, and eutectic transitions for ceramics in the Zr–C system. Transition temperatures correlated well with phase boundaries and individual measurements published previously. Microstructural and diffraction analysis of melted specimens confirmed that ZrC existed in the liquid phase and resolidified to ZrC or a ZrC+graphite eutectic. Transition temperatures were insensitive to laser pulse timescale and repeated melting, and microstructures of melted surfaces were consistent with the phase diagram, indicating the local attainment of thermodynamic equilibrium. Subsurface nonequilibrium microstructures were attributed to thermal gradients with depth and solute partitioning during freezing. The present work indicates that pulsed laser heating is a viable technique for producing equilibrium microstructures in ZrC as a prerequisite for precision measurement of phase transition temperatures. The main source of uncertainty in reported temperatures was the estimation of ZrC emittance. A consistently observed discontinuous temperature decrease upon the solid–liquid phase transition indicated a decrease in the emittance of liquid ZrC with respect to solid ZrC. Based on an estimated emittance of solid ZrC of 0.6, emittance of liquid ZrC was estimated at 0.44–0.58.
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laser melting of spark plasma sintered Zirconium Carbide thermophysical properties of a generation iv very high temperature reactor material
International Journal of Applied Ceramic Technology, 2010Co-Authors: Heather F Jackson, D Manara, W E Lee, Doni D Jayaseelan, Michael J Reece, Fawad Inam, Carlo Perinetti Casoni, Franck De Bruycker, K BoboridisAbstract:Commercial ZrC(0.96) powder (ABCR, Karlsruhe, Germany) was densified by spark plasma sintering to greater than 96% relative density at temperatures of 1900-2180 degrees C, applied pressures of 40-100 MPa, and soak time of 6-30 min. Effects of process parameters on microstructure were assessed by ceramography. High temperature (>2000 degrees C) was more instrumental in full densification than was high pressure, and excessive ramp rate resulted in high residual porosity. Grain coarsening was promoted by prolonging the isothermal dwell. Laser heating was used to melt sintered ceramics, as part of a novel thermal analysis technique for probing extremely high temperature phase transformations. Temperatures well in excess of the expected melting temperature of ZrC and up to 4000 K were achieved. The feasibility of the technique for detecting melting transitions in Zirconium Carbide was demonstrated, and solidus and liquidus temperatures within 50-80 K of predicted values were measured. Post-melting analysis of laser-melted specimens revealed dendritic microstructure and composition consistent with single phase ZrC.
William G Fahrenholtz - One of the best experts on this subject based on the ideXlab platform.
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mechanical properties and grain orientation evolution of Zirconium diboride Zirconium Carbide ceramics
Journal of The European Ceramic Society, 2018Co-Authors: Andrea Dangio, Ji Zou, Jon G P Binner, Gregory E Hilmas, William G FahrenholtzAbstract:Abstract The effect of ZrC on the mechanical response of ZrB 2 ceramics has been evaluated from room temperature to 2000 °C. Zirconium diboride ceramics containing 10 vol% ZrC had higher strengths at all temperatures compared to previous reports for nominally pure ZrB 2 . The addition of ZrC also increased fracture toughness from ∼ 3 .5 MPa m for nominally pure ZrB 2 to ∼ 4 .3 MPa m due to residual thermal stresses. The toughness was comparable with ZrB 2 up to 1600 °C, but increased to 4 .6 MPa m at 1800 °C and 2000 °C. The increased toughness above 1600 °C was attributed to plasticity in the ZrC at elevated temperatures. Electron back-scattered diffraction analysis showed strong orientation of the ZrC grains along the [001] direction in the tensile region of specimens tested at 2000 °C, a phenomenon that has not been observed previously for fast fracture (crosshead displacement rate = 4.0 mm min −1 ) in four point bending. It is believed that microstructural changes and plasticity at elevated temperature were the mechanisms behind the ultrafast reorientation of ZrC.
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Zirconium Carbide tungsten cermets prepared by in situ reaction sintering
Journal of the American Ceramic Society, 2007Co-Authors: Shi C Zhang, Gregory E Hilmas, William G FahrenholtzAbstract:Zirconium Carbide–tungsten (ZrC–W) cermets were prepared by a novel in situ reaction sintering process. Compacted stoichiometric Zirconium oxide (ZrO2) and tungsten Carbide (WC) powders were heated to 2100°C, which produced cermets with 35 vol% ZrC and 65 vol% W consisting of an interpenetrating-type microstructure with a relative density of ∼95%. The cermets had an elastic modulus of 274 GPa, a fracture toughness of 8.3 MPa·m1/2, and a flexural strength of 402 MPa. The ZrC content could be increased by adding excess ZrC or ZrO2 and carbon to the precursors, which increased the density to >98%. The solid-state reaction between WC and ZrO2 and W–ZrC solid solution were also studied thermodynamically and experimentally.
D Manara - One of the best experts on this subject based on the ideXlab platform.
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the zrc c eutectic structure and melting behaviour a high temperature radiance spectroscopy study
Journal of The European Ceramic Society, 2013Co-Authors: D Manara, Heather F Jackson, C Perinetticasoni, K Boboridis, M J Welland, L Luzzi, P M OssiAbstract:Abstract A fast spectro-pyrometer has been employed for radiance measurements of Zirconium Carbide samples laser-heated to very high temperature, for compositions 0.7 ≤ C/Zr ≤ 2.61 and in a spectral range 0.550 μm ≤ λ ≤ 0.900 μm. The ZrC–C eutectic temperature has been taken as the radiance reference. The measured normal spectral emissivity (NSE) ɛ λ of solid Zirconium Carbide is close to 0.6 at 0.650 μm, in agreement with previous literature. Its high-temperature behaviour, value in the liquid, carbon-content and wavelength dependences in the visible-near infrared range have been determined here for the first time. Liquid Zirconium Carbide seems to interact with electromagnetic radiation in a more metallic way than the solid. A considerable NSE increase has been observed at increasing carbon content, which can be interpreted on the basis of preferential growth along the “c” plane of the carbon lamellae in the eutectic structure.
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the zrc c eutectic structure and melting behaviour a high temperature radiance spectroscopy study
Journal of The European Ceramic Society, 2013Co-Authors: D Manara, Heather F Jackson, C Perinetticasoni, K Boboridis, M J Welland, L Luzzi, P M Ossi, W E LeeAbstract:Abstract A fast spectro-pyrometer has been employed for radiance measurements of Zirconium Carbide samples laser-heated to very high temperature, for compositions 0.7 ≤ C/Zr ≤ 2.61 and in a spectral range 0.550 μm ≤ λ ≤ 0.900 μm. The ZrC–C eutectic temperature has been taken as the radiance reference. The measured normal spectral emissivity (NSE) ɛ λ of solid Zirconium Carbide is close to 0.6 at 0.650 μm, in agreement with previous literature. Its high-temperature behaviour, value in the liquid, carbon-content and wavelength dependences in the visible-near infrared range have been determined here for the first time. Liquid Zirconium Carbide seems to interact with electromagnetic radiation in a more metallic way than the solid. A considerable NSE increase has been observed at increasing carbon content, which can be interpreted on the basis of preferential growth along the “c” plane of the carbon lamellae in the eutectic structure.
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laser melting of Zirconium Carbide determination of phase transitions in refractory ceramic systems
Journal of the American Ceramic Society, 2011Co-Authors: Heather Jackson, D Manara, Daniel Doni Jayaseelan, Carlo Perinetti Casoni, W E LeeAbstract:Pulsed laser heating and optical pyrometry were used to generate time–temperature thermogram data suitable for the determination of extremely high-temperature (>3000 K) solidus, liquidus, and eutectic transitions for ceramics in the Zr–C system. Transition temperatures correlated well with phase boundaries and individual measurements published previously. Microstructural and diffraction analysis of melted specimens confirmed that ZrC existed in the liquid phase and resolidified to ZrC or a ZrC+graphite eutectic. Transition temperatures were insensitive to laser pulse timescale and repeated melting, and microstructures of melted surfaces were consistent with the phase diagram, indicating the local attainment of thermodynamic equilibrium. Subsurface nonequilibrium microstructures were attributed to thermal gradients with depth and solute partitioning during freezing. The present work indicates that pulsed laser heating is a viable technique for producing equilibrium microstructures in ZrC as a prerequisite for precision measurement of phase transition temperatures. The main source of uncertainty in reported temperatures was the estimation of ZrC emittance. A consistently observed discontinuous temperature decrease upon the solid–liquid phase transition indicated a decrease in the emittance of liquid ZrC with respect to solid ZrC. Based on an estimated emittance of solid ZrC of 0.6, emittance of liquid ZrC was estimated at 0.44–0.58.
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laser melting of spark plasma sintered Zirconium Carbide thermophysical properties of a generation iv very high temperature reactor material
International Journal of Applied Ceramic Technology, 2010Co-Authors: Heather F Jackson, D Manara, W E Lee, Doni D Jayaseelan, Michael J Reece, Fawad Inam, Carlo Perinetti Casoni, Franck De Bruycker, K BoboridisAbstract:Commercial ZrC(0.96) powder (ABCR, Karlsruhe, Germany) was densified by spark plasma sintering to greater than 96% relative density at temperatures of 1900-2180 degrees C, applied pressures of 40-100 MPa, and soak time of 6-30 min. Effects of process parameters on microstructure were assessed by ceramography. High temperature (>2000 degrees C) was more instrumental in full densification than was high pressure, and excessive ramp rate resulted in high residual porosity. Grain coarsening was promoted by prolonging the isothermal dwell. Laser heating was used to melt sintered ceramics, as part of a novel thermal analysis technique for probing extremely high temperature phase transformations. Temperatures well in excess of the expected melting temperature of ZrC and up to 4000 K were achieved. The feasibility of the technique for detecting melting transitions in Zirconium Carbide was demonstrated, and solidus and liquidus temperatures within 50-80 K of predicted values were measured. Post-melting analysis of laser-melted specimens revealed dendritic microstructure and composition consistent with single phase ZrC.
Yibing Cheng - One of the best experts on this subject based on the ideXlab platform.
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synthesis and evolution of Zirconium Carbide via sol gel route features of nanoparticle oxide carbon reactions
Journal of the American Ceramic Society, 2013Co-Authors: Caen Khim Ang, Tim Williams, Aaron Seeber, Huanting Wang, Yibing ChengAbstract:A sol–gel route was used to synthesize nanocrystalline Zirconium Carbide (ZrC). The starting materials were Zirconium propoxide, with carbon introduced by furfuryl alcohol (FA). A block copolymer surfactant was used to homogenize the oxide and carbon components. ZrC was produced at a low temperature of 1250°C and complete conversion achieved at 1450°C. The powder was nanocrystalline size less than 100 nm. Phase changes were studied using X-ray diffraction and Raman spectroscopy. Rietveld analysis followed the changes in crystallite size and lattice parameters of the phases during carbothermal reduction. Morphology changes were observed using nitrogen gas sorption. High-resolution TEM and EDS were used to image the Carbide lattice, surface oxides, and graphene-like carbons. The results indicate that nanoparticle carbothermal synthesis involves agglomeration and necking as the most viable mode of mass transport to complete the carbothermal reduction.
