The Science of Engineering Ceramics III

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Authors: Daniel G. Carillo, M.C. Curiel, Ho Sung Aum, Soo Wohn Lee
Abstract: Trauma related loading of hip prostheses has been reported as a cause of failure of implanted ceramic materials, ball and/or cup. In this study a computer simulated model is made to evaluate contact pressures and stresses in the stem/ball contact pair, as well as stress concentration regions in the ceramic cup. A 3D Non-Linear Finite Element Analysis was performed in a “proof test” scenario. A high peak trauma-like loading of 15 KN was used. 28mm ball heads (in diameter) were modeled and two sizes for taper lock were simulated to report their influence on the contact pressure over the critical areas of the ballhead. It was found that the ball head cone’s depth has a major incidence in the stress and contact pressure surrounding the stem when an impact load is applied. The best stress and pressure configurations were found for the case of the stem lying completely inside the ballhead.
Authors: Hyung Mi Lim, Ji Sook Jung, Bong Young Kim, Seung Ho Lee
Abstract: Zeolites with different sizes and structures were applied on the surface of cellulose fibers with organic and inorganic binders. The effects of zeolite structure and size and choice of binder on the deodorization rate have been studied. The smaller the particle size, the more effective the deodorization rate of both the zeolite coated cellulose fibers and the powder itself. The deodorization rate depends on both the type and amount of inorganic binder. A silica based inorganic binder revealed higher efficiency on deodorization than silicate based inorganic binder and also higher than organic binders.
Authors: Motoki Kaneno, Kiyoko Sakamoto, Shunro Yamaguchi, Katsuaki Suganuma
Abstract: β-tricalcium bis (orthophosphate) [Ca3(PO4)2] (β-TCP) was mechanochemically treated with mortar grinder. The ground β-TCP was hydrolyzed in an aqueous ammonium solution (pH=11.0) at 90 to give Ca-deficient HAp involving small amount of CO3 2- ions. With an increase in grinding time of β-TCP, it was hydrolyzed easily. Well-crystalline Ca-deficient HAp was obtained after grinding of β-TCP for 7 hours and the successive hydrolysis.
Authors: Masato Tamai, Koji Nishio, Toshiyuki Isshiki, Atsushi Nakahira
Abstract: In our previous study, we reported that a metastable phase with high Ca/P molar ratio appeared in the temperature range from 700 οC to 800οC The purpose of this study is to investigate the crystallographic relationship between the metastable phase and HAp matrix. Ca-def HAp was annealed at 500-1000' ο C in air. High-resolution transmission electron microscopic (HRTEM) observations were performed along the [010], [110] and [001] zone axes in order to investigate the structure of the metastable phase. From HRTEM images and results of the analysis of selected area electron diffraction patterns along [010], [110] and [001] zone axes, the lattice constants of the metastable phase were analyzed into a=2.86nm, b=0.94nm, and c=0.69nm of an orthorhombic crystals system.
Authors: Dong Seok Seo, Hwan Kim, Kyu Hong Hwang, Jong Kook Lee
Abstract: Dissolution of hydroxyapatite (HAp) in distilled water and related mechanical properties were investigated. The commercially obtained stoichiometric HAp powders were used as starting materials. After preparing powder compacts, the disks were sintered at 1200oC for 2 h in air with under moisture protection. The sintered specimens were then placed into 40 ml of 7.4 distilled water. After immersing for certain period of time at 37oC, weight loss, microstructure, and mechanical characteristics of the specimens were investigated. Fracture toughnesses were measured for both sintered and immersed HAp for comparison. Evidence for the surface damage was observed with appearance of micron-level of pitting and grain boundaries dissolved. The value for fracture toughness decreased due to dissolution of the materials.
Authors: Hyung Mi Lim, Seung Ho Lee, Jun Bo Park, Jin A Kwon, Yeon Su Yu
Abstract: Physical properties of various inorganic materials have been measured in terms of pore size distribution and porosity, BET surface area by nitrogen adsorption, pH, ion conductivity, and concentration of ions after elution test. The microbial survival rate and their stability have been monitored in every 10 days during 120 days by dilution plating method. The correlations between physical property of the inorganic carrier and microbial survival rate have been examined for the better preparation of microbial fertilizer. Average size of pore, and concentration of soluble ions were unequivocal factors affecting on microbial survival rate but BET surface area, average porosity, and ion conductivity revealed the equivocal correlation with microbial survival rate. Higher concentration of soluble ions gives lower survival rate and inorganic carriers with high microbial survival rate seemed to have preferred range of pore size.
Authors: Rong Jun Xie, Mamoru Mitomo, Naoto Hirosaki
Abstract: Rare-earth doped Ca-α-SiAlON phosphors, with the compositions of (Ca1-3/2xREx)m/2Si12-m-nAlm+nOnN16-n (RE = Ce, Sm, Eu, Tb, Yb and Dy, 0.5 ≤ m = 2n ≤ 3.0), were prepared by reaction at 1700oC for 2h under 10 atm N2. The concentration of rare earths varied from 3 to 30 at% with respect to Ca. The photoluminescence properties of the powders were investigated at room temperature. The results show that (i) strong visible emissions are observed in rare-earth doped Ca-α-SiAlONs; (ii) the emission properties can be optimized by tailoring the activator concentration and the composition of the α-SiAlON host crystal; and (iii) the yellow Eu2+-doped Ca-α-SiAlON phosphors can be used in warm white LEDs.
Authors: Chung Hsin Lu, V. Natarajan
Abstract: The emission of Sn2+ ion can vary from blue to red depending on its co-ordination number in the host lattice. Since Sn2+ ion has strong absorption in the ultra-violet region and can act as a reducing agent, it is of interest to examine the effects of co-doping Sn2+ ions on the luminescence properties of Eu3+ ions in different inorganic phosphor materials. In the present work, Eu3+ and Sn2+ ions co-doped strontium phosphate phosphors were synthesized via a solid-state reaction method in air, argon and reducing atmosphere. The prepared samples were characterized via X-ray diffraction. It was observed that the prepared Eu3+-doped strontium phosphate phosphor material had enhanced Eu3+ emission upon excitation with 395 nm light.
Authors: Chang Yeoul Kim, Jin Wook Choi, Tae Yeoung Lim, Duck Kyun Choi
Abstract: Electrochromic WO3 thin film was prepared by using tungsten metal solution in hydrogen peroxide as a starting solution and by sol-gel dip coating method. XRD pattern showed that tungsten oxide crystal phase formed at 400. In the view of electrochemical property, WO3 thin film which was heat-treated at 300 and was amorphous had better than that of the crystalline phase.
Authors: Hisashi Kaga, Ryoji Asahi
Abstract: Al-doped ZnO ceramics were fabricated by the electrical field-assist sintering method and their thermoelectric properties were examined. When the current density of 10A/cm2 was applied, the electrical conductivity was increased by about 30 % compared with that of a specimen set in the same furnace without any applied current. The Seebeck coefficient was also increased by approximately 10%. The power factor was thus improved about 60%, reaching 1.3x10-3 W/mK2 at 1053K, which is one of the best power factor in bulk oxides. Analyses of Hall measurement and thermal conductivity showed that longer mean free paths of both electrons and phonons were obtained by the electrical field-assist sintering method, suggesting promotion of the grain growth and/or reduction of barriers at the grain boundary in the direction of current.

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