Materials Science Forum Vol. 761

Abstract: Electromagnetic wave absorbing properties in GHz region were investigated for magnetite prepared by hydrogen reduction of hematite, which was synthesized via drip thermal oxidation using a fluidized bed. The magnetite powder product showed better absorption ability when the precursor hematite was prepared at a higher bed temperature, which also induced an improvement in morphology. This morphological enhancement is believed to result from the rapid thermal oxidation treatment of the hematite powder in the bed along with an accelerated evaporation of aqueous FeCl₂ solution.

Abstract: A new and simple method is proposed to fabricate fully dense and single fcc phase of substoichiometric titanium nitride (TiNx). Powders mixture composed of titanium hydride (TiH2) and titanium nitride (TiN) was consolidated by using pulsed electric current sintering. All samples showed relative density values higher than 98% with larger grain size at lower nitrogen concentration. Lattice parameter increased linearly with increasing [N]/[Ti] ratio. In addition, TiNx with substoichiometric compositions was more easily densified than stoichiometric TiN. The addition of TiH2 improves the sinterability of the samples preserving the fcc phase characteristic of TiN.

Abstract: Calcium silicate phosphors, Ca2-xSiO4(CS):Eu3+x, CS:Eu2+x and Ca2-y-zMgSi2O7 (CMS):Eu2+y,Dy3+z were prepared by the solid state reaction. The phases in CS:Eu3+ system were β- and αL’ -types. The fluorescent color under a black-light irradiation was red and the emission spectrum consisted of 590nm(αL’), 615nm(β) and 625nm(αL’) peaks. The emission intensity took a maximum value at x=0.2. The addition of B3+ accelerated the solid solution of Eu3+. The phase in CS:Eu2+ system was β-type only. The fluorescent color was yellow-green(520nm). The emission intensity took a maximum value at x=0.01. The CMS product showed the akermanite phase. The lattice constants of CMS:Eu2+ increased with increasing Eu content, but those became constant at y>0.05. The fluorescent color of CMS:Eu2+ was yellow-green and the emission intensity took a maximum value at y=0.03. In the case of CMS:Eu2+0.03,Dy3+z, the fluorescent color and the afterglow color were same, yellow-green. The emission intensity took a maximum value at z=0.06. The longest afterglow time, 23min., was obtained at z=0.09. The trap depth were 0.64-0.69 eV.

Abstract: In an environmental and economic point of view, recycling of silicon wafer sludge is important. The aim of this work is to investigate the recycling method of silicon wafer sludge. Therefore, drying rate of silicon wafer sludge has been studied for separation of liquid and solid from sludge. Silicon and silicon carbide powder obtained from silicon wafer sludge were analyzed by SEM, XFR, XRD and particle size analyzer. The recovered oil was also characterized using GC-MS. From this work, it can be seen that the falling drying rate of silicon wafer sludge is linear equation. Various metal components have been found in recovered solid powder caused by wire sawing processing.

Abstract: Characterization of silicon kerf from photovoltaic silicon-wafer production was carried out. Also, SiC powder was synthesized using high purity silicon kerf by varying grinding conditions. With increase of grinding time, surface of the silicon was oxidized to form silicon oxide. Also, it was observed that the unreacted silicon oxide and free silicon amount in the SiC powder increases with an increasing grinding times, even though silicon particle size of the starting material is decreased.

Abstract: This paper proposes a model for estimating stress history during sintering of ceramic laminates. A symmetrical 3-layered laminate is assumed, and one-dimensional elastic calculation gives the stress change of each layer during heating, keeping at the sintering temperature, and cooling, respectively. How to get the stress history is actually shown by incorporating data of mechanical and thermal expansion properties of calcined monolayers. The validity of this model is discussed with a preliminary experiment on dense alumina / porous alumina laminates.

Abstract: In this research, in order to optimize casting design of an automobile part (Gear Box), Computer Aided Engineering (CAE) was performed by using the simulation software (Z-Cast). The simulation results were analyzed and compared with experimental results. During the filling process, internal porosities caused by air entrap were predicted and reduced remarkably by the modification of the gate system and the configuration of overflow. With the solidification analysis, internal porosities caused by the solidification shrinkage were predicted and reduced by the modification of the gate system. For making better permanent High Pressure Die Casting (HPDC) mold, cooling systems on several thick areas are proposed in order to reduce internal porosities caused by the solidification shrinkage.

Abstract: Effects of carbon nanotubes (CNT) addition on mechanical properties, electric conductivity and oxidation resistance of CNT/Al₂O3-TiC composite were investigated. It was found that flexural strength, Young’s modulus and fracture toughness of the composites were improved by addition of more than 2 vol%-CNT. In the composites with more than 3 vol%-CNT, the oxidation resistance of the composite was degraded. In comparison with Al₂O3-26vol%TiC sample as TiC particle-percolated sample, the Al₂O3-12vol%TiC-3vol%CNT sample, which is not TiC particle-percolated sample, shows almost the same mechanical properties and electric conductivity, and also shows thinner oxidized region after oxidation at 1200°C due to less TiC in the composite.

Abstract: Eco (Ecology & Economy)-fabrication is important in the future manufacturing. There are some elements to achieve this synthesis. When synthesizing, neither waste nor the air pollutant are not generated, and it is safe material is preferable with cheap fabrication device. We developed a new metal nanoparticle related materials synthesis method that achieved in these viewpoints. This new synthesis method is with microwave as non-equilibrium reactor and the metal oxide and alcohol based solvent are used for the raw material. Moreover, the oxide and alcohol generally are cheap without toxicity. We synthesized metal nanoparticle related materials by microwave in liquid-solid (alcohol - metal oxide) slurry and controlled morphology of products. Microwave irradiation in liquid-solid process can be expected as chemical non-equilibrium and nonlinear reactors for metal nanoparticle related materials synthesis. The alcohol based solvent and the metal oxide powder are put in the beaker and only irradiated by ultrasound or microwave. The metal oxide simply was reduced into metal and morphology of metal nanoparticles was changed by various conditions. Various metal nanoparticle related materials were fabricated by microwave irradiation as non-equilibrium reaction field.

Abstract: Zeolite is a microporous aluminosilicate material with uniform pore size of less than 2 nm and chemical, mechanical, and thermal stability. In general zeolite is synthesized from silica, alumina, mineralizer (alkali metal hydroxide and fluoride) and water. Recently it has been reported that various zeolites is synthesized from soda-lime glass, slag and coal fly ash as silica and alumina source. On the other hand, the production volume of various kinds of high-quality glass which are utilized for high-tech products such as liquid crystal displays and plasma displays is rapidly increasing. The purpose in this study is to synthesize a zeolite from crushed aluminoborosilicate glasses which is used as LCD panels glass substrate. According to the XRD analysis, it was found that the synthesized sample had zeolite related structure. And the results of SEM observation of the products suggest that the zeolite structure was obtained as well as XRD results. It was thought that zeolite was successfully synthesized from the glass by this synthetic processing.