Papers by Keyword: Carbothermal Reduction

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Authors: Bing Qiang Liu, Chang Chun Wang, Ai Ling Sun, Chuan Zhen Huang
Abstract: A TiC whisker toughening Al2O3 composite ceramic tool material was developed by an in situ carbothermal reduction synthesis technology. The influence of different synthesis temperatures (1480°C and 1700°C) and holding times (90min, 60min and 30min) on the mechanical properties of the composite was investigated. The results showed that either the lower synthesis temperature (1480°C) or the higher synthesis temperature (1700°C) was necessary to the improvement on the fracture toughness of the composite. However, when an Al2O3-TiO2 eutectic system was formed during the higher temperature synthesis process, grain coarsening of the Al2O3 matrix became much serious, which resulted in obvious decrease in the flexure strength of the composite. Therefore, the carbothermal reduction synthesis process should be divided into two parts including the lower temperature synthesis process for increasing the yield of the TiC whisker and the subsequent higher temperature synthesis process for increasing the carbon content in the TiC whisker, and and the lower temperature synthesis process should be held for enough time (e.g. 60min) to avoid an incomplete carbothermal reduction of TiO2.
Authors: Yi Bing Cheng, Kun Wang, Huan Ting Wang
Abstract: Mesoporous silica-carbon nanocomposites (C-SiO2) were synthesized and used as a host carrier in carbothermal reduction to fabricate highly crystalline silicon carbide nanoparticles and nanofibers. SiC nuclei were introduced into the mesopores as seeds by infiltration of preceramic precursor polycarbosilane (PCS) prior to the heat-treatment of carbothermal reduction. X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption analysis were used to characterize C-SiO2 nanocomposites and SiC products. Crystalline SiC was not formed in the mesoporous C-SiO2 nanocomposites with a low carbon content (e.g. C/SiO2 ratio = 1.01) at 1450 °C. However, when a given amount of PCS was infiltrated into the mesoporous C-SiO2, SiC nanofibers and nanoparticles were produced at 1450 °C even in the low carbon content sample. The major morphology formed from the mesoporous C-SiO2 nanocomposites without PCS infiltration was nanoparticles, while nanofibers dominated in the products of the PCS infiltrated compositions. The results indicate that the conversion of PCS into SiC nuclei in mesopores prior to carbothermal reduction has facilitated the formation of SiC nanofibers. Therefore infiltration of seeds into mesopores of C-SiO2 precursors appears to be an effective means in accelerating the reaction and controlling of nanostructures of silicon carbide.
Authors: Bei Yue Ma, Bo Li, Yu Shi Ding, Chen Yan, Ying Li, Yao Shu
Abstract: The latest development on preparation of SiC-AlN, SiC-mullite and β-Sialon materials using fly ash via in-situ carbothermal reduction process was reviewed. The synthesis mechanisms of SiC based materials and β-Sialon were also discussed.
Authors: Elias Fagury-Neto, Ruth Herta Goldsmith Aliaga Kiminami
Authors: Hanizam Shah Saidin, S. Aishah Syed Salim, Norlia Baharun, S.A. Rezan, Hussin Hashim
Abstract: Statistical design analysis (factorial design) was utilized to verify the significance and the interaction between the studied factors include temperature, reduction time and catalyst amount. Carbothermal reduction of iron ore sample was carried out at temperature between 1000°C to 1200°C. The effects of operating parameters studied were extent of reduction (X), carbon consumed (Cconsumed ) and nitridation (XN). Temperature was the most influential parameter that showed strong interaction with the operating parameters, meanwhile, reduction time and catalyst have showed the contrary results and had a very low percentage of contribution. The results of the experimental design showed that the extent of reduction reached up to 93% at 1200°C using 10 wt. % catalysts after 180 minutes reduction. The use of 0-10 wt % catalyst at 1200°C for 180 min reduction significantly affect the X but did not for Cconsumed and XN.Keywords: Carbothermal Reduction, Factorial Design, Malaysian Ilmenite, Nitridation.
Authors: Qing Wang, Ya Hui Zhang
Abstract: Biomorphic silicon carbide (bioSiC) was prepared by high temperature pyrolysis and sol-gel and carbothermal reduction processing at 1600 oC. The morphology and microstructure of carbon-silica composites and purified bioSiC samples were characterized by scanning electron microscopy. The phase composition of the resulting sample was analyzed by X-ray diffraction. The results suggest that the bioSiC mainly consists of cubic ß-SiC, and principally replicates the shape and microstructure of the carbon template.
Authors: Xin Hai He, Jun Bo Wang, Xiao Lei Su, Chong Fu, Jie Xu, Minge Yang
Abstract: Biomorphic SnO2/C ceramic has been prepared by molding into a composite billet and carbothermal-reduction under vacuum from ramie fibers/Sn(OH)4 precursors. The phase composition and microstructure of the prepared samples were characterized. The effects of the carbonization temperature and the other factors on the crystal structure, morphology and ingredients of the prepared samples were discussed. The results showed that there is no peak corresponding to carbon. So, it is inferred that the carbon exists in amorphous form and the sintering temperature have significant effects on the microstructure of SnO2 in biomorphic SnO2/C ceramics. The prepared products at the sintering temperature between 480°C and 630°C are biomorphic SnO2/C ceramics.
Authors: Yong Jie Yan, Zheng Ren Huang, Shao Ming Dong, Dong Liang Jiang
Abstract: Ultra-fine titanium diboride (TiB2) powders have been prepared by carbothermal reduction reactions in TiO2-B2O3-C system using tetrabutyl titanate, boric acid and phenolic resin as the solution-derived precursors. The reactions were substantially completed at relatively lower temperature (<1400°C) and the resulting products had a smaller average crystallite size (< 200 nm). However, below 1100°C, titanium carbide was the predominant phase and the relative content decreased with the rise of temperature. The thermodynamic change in TiO2-B2O3-C system was mainly studied by TG-DTA and the mechanism of synthesis of TiB2 was discussed. The crystallite size and morphology of the synthesized powders were characterized by SEM and TEM.
Authors: Ding Peng, Hao Wang, Wei Min Wang, Yu Cheng Wang, Zheng Yi Fu
Abstract: In this paper, a carbothermal reduction and nitridation (CRN) synthesis for cubic aluminum oxynitride (γ-AlON) powders is reported. The CRN reaction was conducted via a two-step synthesis procedure at a heating rate of 100 °C/min. In the first step, the mixture of fine γ-Al2O3 and soluble starch was annealed at 1550~1580 °C for different duration. It is found that the mixture of α-Al2O3 and AlN with an appropriate ratio can be obtained by CRN reaction. The content of AlN in mixture is closely related with the reaction condition. In the second step, the as-received mixture of α-Al2O3 and AlN was heat-treated at 1700 °C for 10 min. The single phase γ-AlON powders with particle size less than 3 µm were obtained.
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