Abstract: Both the Al-5wt%Mg powder mixture and Al-5wt%Mg/SiCp composite mixture were
separately ball-milled for 50h, followed by compaction under a pressure of 350MPa. To obtain the bi-materials, the compacted Al-5wt%Mg and Al-5wt%Mg/SiCp composites were bonded by sintering at 873K-1173K for 1-3h. At a relatively low temperature, 873K, the sound bi-materials could not be obtained. However, the bi-materials with the macroscopically bonded interface between Al-Mg and its composite were obtained at temperatures higher than 873K. The length of a well-bonded interface became longer with increasing temperature and time, indicating the improved contact in the bonded interface. The relative density in the bi-materials increased as the sintering temperature and time increased, and the bi-materials sintered at 1173K for 5h showed the highest density.
Abstract: Y-TZP/TiNi composites were successfully fabricated by reductive sintering process. Mechanical properties of Y-TZP / TiNi composites were much higher than those of Y-TZP monolith. XRD analysis revealed that TiNi-base intermetallic compounds such as Ni4Ti3, NiTi, Ni3Ti had been formed. Moreover, the electrical resistivity characteristics indicated that Y-TZP/TiNi composites
were a good conductor of the electricity.
Abstract: Porous ceramic fiber composites were coated with pyrolytic carbon by the decomposition of propane in a nitrogen atmosphere at 900°C. The amount of carbon coating was varied through adjusting deposition time to tailor the electrical conductivity of the carbon-coated composites. The electrical and thermal conductivity of the composites were measured at room temperature using a
two-point method and a hot-wire method, respectively. Up to 7 wt% pyrolytic carbon, the electrical conductivity σ is linearly increased to 0.02 S/cm and well fitted by the effective conductivity according to the parallel rule of a mixture σ eff = Σ Χ i ·σ i with a conductivity of pyrolytic carbon σ c= 20 S/cm .The thermal conductivity of the uncoated and coated composites is in the range 0.065-0.075 W/mK and little affected by carbon coating presumably owing to the small amount of coated carbon in this work.
Abstract: Co-base superalloys have been applied in the stationary compoents of gas turbine owing to their excellent high temperaure properties. The stationary Co-base alloy components are generally manufactured by casting. Solidification behavior of the alloy is an important factor in the selection of casting parameters. In the present study, solidification microstructure and carbide formation behaviors were studied by directional solidification. Directional solidification experiments were carried out at the solidification rates of 0.5 ~ 150µm/s with the Co-base superalloy ECY768. Between
the dendrites just below the final freezing temperature, MC carbide and M23C6 carbide were found. It was identified that the script or blocky carbides were Ta or W-rich MC carbide, and the lamellar carbides were Cr-rich M23C6 eutectic carbides. The solid/liquid interface morphology clearly showed that freezing of the Cr-rich eutectic carbide occurred just after the script type MC carbide.
Abstract: The synthesis and the sintering of SiC from coal gangue by carbothermal synthesized in N2 atmosphere are studied. The material, 5 percent carbon black added and sintered at 1400°C for 2 hours, had good properties and a bending strength of 137.8MPa. Too high temperature or too long holding time made the properties of the material to decrease. β-SiC found by observing the
microstructure is a major crystal phase in the synthesized ceramics, which would lead to fine mechanical properties.
Abstract: Stabilizing characteristics of heavy metals in the silicate glass (SD) and lead silicate glass(PD) containing Electric Arc Furnace(EAF) dust was studied by the toxic characterization leaching procedure(TCLP) test. Dependence of the amount of EAF dust upon structural changes of SD and PD glasses and TCLP results was also investigated by FT-IR spectroscopy. In the TCLP test,
the concentration of heavy metals leached from a glass increased with the amount of EAF dust added. The SD series specimens showed heavy metal leaching lower than the PD series specimens, but the Pb leaching from the PD series specimens was the highest owing to the high Pb content in the PD glass composition. The value R(oxygen/network former ion ratio) was used to compare the leaching
characteristics of glasses, and the SD had a higer R than PD series specimens to show a better chemical durability. Adding the EAF dust to the SD mother glass decreased the Si-O-Si symmetry and increased the non-bridging oxygen, which weakened the structure and decreased the chemical durability of glasses. It is concluded that SD is more effective in stabilizing the heavy metals of EAF
dust than PD series glass.
Abstract: Nutrient removal and recovery from wastewater is being challenged to avoid
eutrophication problems, and the discharge standards have also been tightened by water regulations. Therefore, this study was undertaken to recover the nutrients from both synthetic wastewater and swine wastewater in a fluidized bed reactor (FBR). The operational parameters were changed to find out the optimum conditions for struvite formation. The most suitable pH was identified around pH 9. When the molar ratio of magnesium as Mg: P was 2:1 in the FBR, the removal efficiency of NH4-N and PO4-P was 79 and 90 %, respectively. The seed material was effective to form struvite in the condition of 30 g dosage. Struvite crystallization in reaction was completed in 20 minutes. The growth of struvite crystals was confirmed by the analysis of XRD, FT-IR and TG-DTA. In addition, the struvite was successfully recovered when the optimum conditions were applied to the swine wastewater.
Abstract: Sodium silicate has been widely used as starting materials of chemical grout owing to its feasibility and short setting time with reasonable strength. Elution of sodium has been pointed out as the main reason of weak durability of homogel prepared with sodium silicate-cement grout. There are well known series of additives for controlling its setting time, fluidity, and compressive strength. We
studied the structural change on the sodium silicate with additive of sodium tripolyphosphate (STPP) by 29Si nuclear magnetic resonance spectrum and viscosity. The homogel was prepared by mixing cement/water suspension and diluted sodium silicate/STPP mixtures, and aged in the water. The development of compressive strength and its structural change were observed using a universal test machine, X-ray diffraction, and scanning electron microscope. The additive changed the distribution of Si and rheological property of liquid sodium silicate, which caused more uniform distribution of Ca and Si in the homogel to lead to high initial strength and durability.
Abstract: Wall and floor tiles were fabricated by a dry pressing method using waste glass and clay. The properties of the tiles such as absorption, bulk density, porosity, compressive strength, and abrasion loss were investigated with the firing temperature and glass contents. The properties were improved by increasing the firing temperature and glass contents. These properties, except the compressive strength, tended to be saturated from the glass contents of 70 wt % in the case of 1050 °C. The compressive strength showed the maximum values at the glass contents of 70 wt% and then decreased with increasing glass contents. The optimal properties obtained in the tiles were the water absorption of about 0.9 %, the bulk density of about 2.3 g/cm3, the apparent porosity of about 2.1 %,
the compressive strength of about 210 MPa, and the abrasion loss of about 0.022 g, when the composition containing the glass of 70 wt% was fired at 1050°C. These results are better than the properties of commercial clay tiles for easy melting and densification of glassy phase in the tiles.
Abstract: The reutilization of waste plastics as a fuel in the cement kiln precalciner process was investigated. For uniform feeding into the fluidized bed calciner, waste plastics were prepared to form of pellet type by shredding, melting, pressing, cutting and screening. We examine the property of combustion for different pellet size using the Computational Fluid Dynamic analysis program to minimize a risk and to optimize condition of an actual proof plant. Based on the results from the computational fluid dynamic analysis, the waste plastic for the industrial scale experiment were
used as 20mm, 50mm and 100mm in size. The experimental result of an actual proof plant showed comparatively good correlation with the computational fluid dynamic analysis.