High-Performance Ceramics III

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Authors: Wei Pan, Qiang Xu, Long Hao Qi, Jing Dong Wang, He Zhuo Miao, Kazutaka Mori, Taiji Torigoe
Abstract: The increase of the efficiency for gas turbines leads to the increasing combustion-chambertemperatures. Rapid degradation of the conventional yttria-stabilized zirconia coatings does not fulfill therequirements at these temperatures for a reliable thermal barrier coatings (TBCs) due to the phasetransformation of zirconia and the sintering behaviour. Therefore, it is very important to develop novelceramic materials for TBCs with low thermal conductivity and long-term stability at high temperatures.In this paper, the developments of potential novel ceramic materials for TBCs with low thermalconductivity are reviewed.
1497
Authors: Cai-Lin Wang, Wei Pan, Qiu Xu, C.J. Jiang, Kazutaka Mori, Taiji Torigoe
Abstract: The increase of the efficiency for gas turbines leads to the increasing combustion-chambertemperatures. Rapid degradation of the conventional yttria-stabilized zirconia coatings does not fulfill therequirements at these temperatures for a reliable thermal barrier coatings (TBCs) due to the phasetransformation of zirconia and the sintering behaviour. Therefore, it is very important to develop novel ceramic materials for TBCs with low thermal conductivity and long-term stability at high temperatures.In this paper, the developments of potential novel ceramic materials for TBCs with low thermalconductivity are reviewed.
1501
Authors: Jing Dong Wang, Wei Pan, Qiang Xu, Kazutaka Mori, Taiji Torigoe
Abstract: Rare-earth zirconate ceramics (Gd2Zr2O7, Sm2Zr2O7, Nd2Zr2O7, Dy2Zr2O7, Er2Zr2O7 and Yb2Zr2O7) were successfully prepared by pressureless sintering at 1550oC for 10 hours. The thermal conductivities of these ceramics were measured and the results indicated that the thermal conductivities of rare-earth zirconates were much lower than that of YSZ in the temperature range 20-800oC.
1503
Authors: Qiang Xu, Wei Pan, Jing Dong Wang, Long Hao Qi, He Zhuo Miao, Kazutaka Mori, Taiji Torigoe
Abstract: Rare earth Gd2Zr2O7 ceramic was prepared by spark plasma sintering from Gd2O3 and ZrO2 powders. The powders were sintered at 1400°C for 10min. The synthesized ceramic was annealed at 800°C for 2h under air atmosphere. XRD structural and SEM microstructural characterization showed the formation of a single phase material with pyrochlore crystal structure. The relative density of Gd2Zr2O7 ceramic was measured by the Archimedes method with an immersion medium of water and the results revealed that the relative density of the ceramic was 92%. The thermal conductivity of the ceramic was tested by laser flash method from room temperature to 700°C. The result shows the thermal conductivity of Gd2Zr2O7 ceramic is lower than that of 7YSZ.
1507
Authors: Young Min Park, Tae Young Yang, Seog Young Yoon, Ron Stevens, Hong Chae Park
Abstract: Calcium deficient (Ca/P = 1.53-1.61, molar ratio) whisker shaped hydroxyapatite (HAp) with a high aspect ratio ~26 (diameter: 0.2-0.3 µm) has been prepared by the hydrolysis of a-Ca3(PO4)2 (a-TCP) in an aqueous solvent system under controlled conditions. The influence of processing variables on the conversion of a-TCP to HAp, and the microstructure and composition of the HAp was characterized by means of XRD, SEM, TEM and ICP instruments.
1511
Authors: Hu Chen, Ying Jun Wang, Jian Wang, Kai Hui Nan
Abstract: The processing and properties of porous b-TCP ceramics were investigated. Naphthalene powders used as a pore-making agent. The b-TCP ceramics with a porosity of 75%, a bending strength of 5.3 MPa and pore sizes ranging from 200 ~ 500 µm were obtained. The results showed that the porosity of the ceramics decreased with increasing temperature, while the bending strength increased with increasing temperature. In addition, the phase composition and microstructures of the porous ceramics were examined by x-ray diffraction and scatting electronic microscopy, respectively.
1515
Authors: Jin Gou Ji, Jun Guo Ran, Li Gou, Fang Hu Wang, Lu Wei Sun
Abstract: Porous HA/β-TCP biphasic calcium phosphate (BCP) bioceramics were prepared by microwave plasma in order to solve the problems on sintering of Ca-P bioceramics by a conventional furnace. The plasma-sintered samples exhibit a higher densification rate, smaller grain size and higher compressive strength compared to those of conventional sintered samples. The [Ca2+] concentration and the dissolution rate are also higher than those of conventional sintered samples in physiological saline. After immersed in simulated body fluid (SBF) and simulated inflammation body fluid, the amount of bone-like apatite formed on plasma-sintered samples is more than that formed on conventional sintered samples. The results indicate that plasma sintered porous BCP bioceramics have better mechanical properties and may also have better biological properties. On the other hand, the surface of samples that underwent a simulated inflammation procedure is smoother and the amount of bone-like apatite formed on them is less than that formed on the samples immersed in normal SBF all the time, which may indicate that the light acid in an inflammation response would affect the bone reconstruction when Ca-P bioceramics implanted in living body.
1519
Authors: Xiang Cai Meng, Xing Yi Li, Tao Wang
Abstract: The paper deals with a kind of new method of the electro-deposition on titanium by a cathode revolves. The depositing characteristic and mechanic were studied by scanning electron microscopy and X-ray diffraction. The experimental results show that the more fine uniformity and compact calcium phosphate bioactive coatings could be produced, compared with the conventional methods. The gradient Coating, which is fine inside and porous outside, could be obtained by controlling revolving velocity. The coating would transform to the hydroxyapatite after heat-treatment. After soaking in a simulated body fluid (SBF), nano-depositions were formed on the surface of the coating, then those particles would grow up needle-like, net-like, and an apatite-like layer could be observed finally. The gradient porosity coatings produced by cathode revolving electrochemical deposition would have high anti-dissolution and bioactive.
1525
Authors: C.L. Shi, I. Ren, Zhao Xian Xiong
Abstract: A method of the preparation of an antibacterial ceramic powder is introduced in this paper. Hydroxyapatite is selected to absorb tightly and retain silver for antibacterial ceramic powder. The effect of antibacterial properties against bacterium of S.aureus and E.coli are tested. This antibacterial ceramic has sufficient antibacterial power. The antibacterial effectiveness of this antibacterial powder can reach almost 100%.
1529
Authors: Wei Min Gao, Qun Yan Li, Cheng Xiang Ruan, Yun Fa Chen
Abstract: Hydroxyapatite (HAp) was synthesized in the presence of a variety of amino acids in order to investigate the effect of amino acid on the morphology of HAp obtained by homogeneous precipitation and hydrothermal treating. In the results of X-ray diffraction analysis, HAp synthesized in the presence of some amino acids showed different crystallinity compared with HAp synthesized in the absence of amino acid. The results of Fourier transform infrared spectroscopy suggested the adsorption of these amino acids on HAp. Microphotographs of transmission electron microscope showed that the size and morphology of HAp adsorbed amino acids changed significantly. Collectively, this study suggests that the morphology and the crystallinity of synthesized HAp are different owing to the variation of amino acids in the synthesizing condition.
1533

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