Papers by Keyword: CaTiO3

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Authors: Jin Gang Jia, Bao Qiang Xu, Bin Yang, Dong Sheng Wang, Heng Xiong, Da Chun Liu
Abstract: Preparing titanium powders by calcium vapor reduction of titanium oxide directly is a new way with short flow sheet and CaTiO3 is the very important intermediate compound in this process. In this paper, the behavior of intermediate CaTiO3 in the reduction process of TiO2 was investigated. The thermodynamic calculation indicated that the Gibbs free energy change of the reaction to produce CaTiO3 by CaO and TiO2 was always negative below 1000 °C; The reaction Gibbs free energy change of the calciothermic reduction of CaTiO3 was lower than that of TiO, which would be the most predominant step from TiO2 to Ti. The experimental results showed that CaTiO3 phase derived from the reaction between TiO2 and the reduction by-product CaO, and the reaction between TiO2 and the decomposition product CaO from the additive of CaCl2 with crystal water as well in the calcium vapor reduction process of titanium oxide. But CaTiO3 could be reduced to Ti much easier than that of TiO2 by calcium vapor.
Authors: Maria Preda, Monica Caldararu, Mirela-Anca Dragan
Authors: Koichi Banno, Tomomi Koga, Toshikazu Takeda, Harunobu Sano, Tadashi Morimoto, Hiroshi Takagi
Abstract: A conventional solid phase reaction method was followed to prepare (1−x)BaTiO3-xCaTiO3 based ceramics with content fractions ranging from x = 0.00 to 1.00. Phase segregation was observed when x exceeded 0.10. DC breakdown voltage (DC-BDV) abruptly changed at x = 0.30 and 0.85. Furthermore, the DC-BDV values of insoluble compositions (x = 0.30−0.85) were much higher than those of solubility limit (x = 0.20 and 0.90). Results obtained by investigation of the amount of absorbed current and the dependence of the rate of voltage increase for DC-BDV and AC-BDV confirmed the formation of space charge in insoluble compositions. This suggests that the dependence of the DC-BDV value for (1−x)BaTiO3-xCaTiO3 based ceramics was affected by the formation of space charge.
Authors: Danyang Ying, L.X. Luo, B. Young, A.F. Julian
Abstract: An in vivo biocompatibility test of a novel biocomposite, with major phases of CaTiO3 and Ti2O, and minor phases of AlTi3, TiO, CaO and Al2O3, was conducted on rats using subcutaneous implantation. The biocomposite and titanium alloy control specimens were removed at 6 and 14 weeks post-implantation. Histological examination revealed no significant adverse reaction of the surrounding tissue to the either the biocomposite or the control material. We conclude that the composite is well tolerated in a physiological environment.
Authors: Xiao Chuan Lang, Hong Wei Xie, Xiang Yu Zou, Pyong Hun Kim, Yu Chun Zhai
Abstract: The CaTiO3 compounds were prepared by sintering the mixtures of the TiO2 and CaO in air. The compounds were used as cathode, the graphite as anode and the molten CaCl2-NaCl as electrolyte. Electrolysis was performed at 800°C and constant-voltage 3.2V in dry argon atmosphere. The results showed that the electrolytic rate could be significantly enhanced because of the additive CaO. The electrolysis time was shortened efficiently than that of direct electrochemical reduction of solid TiO2.
Authors: V.M. Vukotić, N. Radojević, Ljiljana Živković, Z. Vuković, B.D. Stojanović
Abstract: Crystalline calcium titanate was synthesized by mechanical activation of a mixture of CaO, obtained by thermal treatment of CaCO3, and TiO2 in anatase or rutile form, in a planetary ball mill for 30, 60, 120 and 240 min.. The effect of milling on the solid-state reaction was followed by X-ray diffraction. Changes in powder size and morphology due to milling were determinate by SEM, while BET analysis was made to determine the specific surface area of powders. It was pointed out that the formation of calcium titanate was more easily achieved by mechanical activation synthesis of the mixture of calcium oxide and anatase modification of titanium oxide compared to the rutile form.
Authors: V.M. Vukotić, Tatjana Srećković, Z. Marinković, G. Brankovic, M. Cilense, D. Arandjelović
Authors: Bo Li, Xiao Hua Zhou, Shu Ren Zhang, Long Cheng Xiang
Abstract: The microwave properties and microstructures of (ZnMg)TiO3-based dielectric prepared by conventional solid-state method were investigated as functions of CaTiO3 and CaO-B2O3-SiO2 additions. The effects of CaTiO3 on the crystal phase and the evolution of microstructure of (Zn0.65Mg0.35)TiO3 were studied. The result indicated that CaTiO3 secondary phase coexists with (ZnMg)TiO3 main phase in the ZMT-CT ceramics, which confirmed by EDS analysis. Because of CaTiO3 with large τf value (τf = 800 ppm/°C), the temperature coefficient of resonant frequency (τf) of ZMT-CT with biphasic structure was adjusted to near zero value. The microwave properties of (Zn0.65Mg0.35)TiO3 ceramics doped with 5wt% CaTiO3 sintered at 1150°C were ε ≈ 24, τf ≈ ±10 ppm/°C, Q×f > 45,000 GHz. Further, it was found that the CaO-B2O3-SiO2 additive could successfully reduce the sintering temperature of (Zn0.65Mg0.35)TiO3–CaTiO3 ceramics from 1150 to 950°C, and significantly improve the densification of this system, which were densified below 1000°C. This was due to the formation of liquid phases during the sintering observed by SEM. The (Zn0.65Mg0.35)TiO3–0.05CaTiO3 dielectrics with 1 wt% CaO-B2O3-SiO2 sintered at 950~1000°C exhibited the optimum microwave properties: ε ≈ 22, Q×f ≈ 20,000 GHz and τf ≈ ±10 ppm/°C.
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