Papers by Keyword: Colloidal Process

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Authors: Li Hua Xu, Zhi Fei Cheng, Fang Lian, Ti Zhuang Wang, Yun Yao
Abstract: Carbon-containing refractories are widely used in metallurgical industry due to their excellent thermal property and resistance to corrosion by molten iron. In the present work, slip casting colloidal process, which is used to fabricate high performance structural ceramics, has been introduced into the preparation for magnesia-carbon refractory with selection of suitable dispersant. The results indicated that the curve of zeta-potential of magnesia was similar with that of carbon just containing dispersant and the homogenized mixtures were attained under a controlling of low pH value. Three kinds of preparing routes for green bodies were designed, and all of the final densities and the resultant hardness of sintered bodies using colloidal process were superior to these of the specimen using conventional dry pressing, whereas its high green density can be plausibly observed in dry pressing body because of high compaction pressure used.
Authors: Roxana Chotard-Ghodsnia, Sandrine Lucas, Cecile Pagnoux, Eric Champion, Marylène Viana, Dominique Chulia, Karine Anselme, Thierry Chartier
Abstract: The purpose of this study was to develop bioceramics with a well-defined porous structure in order to control drug loading and release over time. Porous structures were obtained through colloidal processing, using polymethyl methacrylate (PMMA) microspheres as templates (core) and hydroxyapatite (HA) nanoparticles as inorganic building blocks (shell). Dispersed HA suspensions were prepared and their electrokinetic properties were studied to determine a dispersant giving a high positive zeta potential (opposite to the negative zeta potential of PMMA). Upon mixture of well-dispersed HA and PMMA suspensions of opposite charge, core-shell structures were formed via heterocoagulation. After consolidation, polymers were removed by calcination, resulting in a porous structure of controlled size and distribution.
Authors: Wathun Boonsorn, Sukasem Watcharamaisakul, Boris Golman
Abstract: Al2O3/ZrO2 composites have been investigated as the bio-inert material. In the present work Al2O3/ZrO2 Micro/Nano composites were prepared by colloidal method. The effects of the concentration of zirconium propoxide and the sintering temperature were studied on the distribution of ZrO2 nano-grains in Al2O3 matrix and mechanical properties of composites. XRD patterns for all compositions showed a single phase of a-Al2O3, and the tetragonal and monoclinic ZrO2 phases. Samples sintered at 1650°C demonstrated the high bulk density with value of 86-92% of theoretical density. ZrO2 nano-grains were dispersed within Al2O3 grain and the grain boundary. The sample of the highest flexural strength of 710 MPa was synthesized using 100% Zr propoxide solution and sintered at 1650o C. The flexural strength was found to increase with increasing the concentration of Zr propoxide and sintering temperature.
Authors: Ming Tsung Weng, Wen Cheng J. Wei, Chi Yuen Huang
Abstract: Al2O3 composites with different volume fractions of 3Y-TZP (3 mol% yttria-doped tetragonal zirconia polycrystalline) were prepared by using a colloidal process and pressure-casting into green specimens, then were pressureless sintered to full density at 1550oC. The resulted two-phase microstructure contained uniformly distributed and submicro- meter-sized grains. The addition of 15 vol% ZrO2 resulted in an increase in bending strength (average 656 MPa by 4 pt. test). Appreciate amount of m-ZrO2 phase was detected after fracture. The enhanced transformability results in an increase in flexural strength and toughness. The addition of 30 vol% ZrO2 resulted in best toughness (5.4 MPam0.5) and outstanding wear resistance (7.2×10-8 cm3/Nm).
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