Materials Science Forum Vols. 544-545

Abstract: A process for the recovery of nanoporous silica and sodium fluoride from hexafluorosilicic acid and sodium silicate under the different molar ratios was studied. In order to prepare the appropriate solutions of initial compounds 25% of hexafluorosilicic acid and the 18% of sodium silicate were used. Obtained nanoporous silica and sodium fluoride have been characterized by XRD, BET, TGA, EDX and SEM.

Abstract: Homogeneous precipitated calcium carbonate(PCC) was synthesized by calcinations, hydration and carbonation of limestone which has been deposited in Danyang, Korea. In the reaction process, shapes(scalenohedral and cubic) and sizes(0.2~0.3μm and 2.0μm) of the powder were controlled by reaction temperature. Synthesized PCC was applied to hand-made paper as filler and coated paper. For the prepared papers, physical/optical properties(brightness, whiteness, opacity, roughness, gloss, tensile strength, internal tearing strength, stiffness, bursting strength) and printability(ink gloss, ink set-off, dry pick, wet pick) were characterized

Abstract: This paper presents a numerical simulation of Automobile Shredder Residue (ASR) chips motion and combustion in a cement works precalciner. The work was done using the commercial computational fluid dynamic (CFD) code FLUENT. The aim of this work is to develop an understanding of the processes within the percalciner to aid in the prediction of ASR chip aerodynamic and combustion behaviors for its use as an alternative fuel. The effects of the mutual interactions between ASR chips were simulated by discrete phase modeling approach, while ASR combustion was simulated by the finite rate devolatilization models. A useful approach to simulate the characteristics of turbulent gas-particle flow, heat transfer and ASR combustion process in a precalciner has been demonstrated.

Abstract: Chemical composition and uniaxial compressive stress are varied to observe their effect on the current-voltage behaviors of ZnO based ceramics. Chemical composition variation produces two kinds of ceramics showing ohmic and nonohmic current-voltage behaviors. The current at a fixed voltage is increased with the increase of the compressive stress for both ceramics. Ceramics with nonohmic behavior shows better reversible return of current-voltage curve when the applied compressive stress is removed from the ceramic than those with ohmic behavior do. We found out an appropriate chemical composition showing linear relation between current and stress at a fixed voltage as a potential application of the ceramic material to pressure sensor.

Abstract: Freeze casting is a useful forming technique to produce complex-shaped ceramic parts. In order to optimize freeze casting slurries, several processing additives are usually employed. Therefore, the relationships between additives and suspension characteristic should be understood. The effects of incorporating processing additives on dispersion and viscosity functions of aqueous alumina/zirconia and mullite/zirconia suspensions have been investigated.

Abstract: We report on a process in which CuO nanopowder was produced in a high yield by adopting ultrasonic in aqueous solution. In our experiment, CuCl2 solution was reacted with NaOH solution and NaNO2, at ambient conditions applying ultrasonic for 5 min. Precipitation was performed by varying the molar ratios of NaOH/CuCl2 and NaNO2/CuCl2. CuO nanoparticles of ~ 5 nm and spherical shape were obtained at the NaOH/CuCl2 of 2.0 and the NaNO2/CuCl2 of 0.097. Without ultrasonication, an amorphous phase was formed at these conditions. This indicates that sonochemical reaction facilitates direct formation of the nanosized CuO particles. In addition, the particle morphology varied from sphere through ellipsoid to needle forms depending on pH. In thick films prepared with the CuO powder for gas sensing, the maximum CO gas sensitivity reached 93 % at the temperature of 250 °C and depended linearly on CO concentration in log scale over the range of 10 ~ 104 ppm.

Abstract: In this study, FLEC testing skill is tested and examined to validate its applicability to the emission tests for IAQ. FLEC system has advantages to adapt to in-situ conditions for sampling, which eases the potential error caused by the distorted test conditions in the lab. The test results from chamber test and FLEC test are also reviewed in this study and the proper guideline to correlate the FLECT test result to the chamber test result will be also produced.

Abstract: Thermal conductivity and microstructure of 3YSZ/monazite-type LaPO4 composites were investigated. Powders were prepared by two kinds of preparation methods such as conventional ball-milled and chemical precipitation of LaPO4 on the zirconia powder surface. Thermal conductivity of 3YSZ/monazite-type LaPO4 composites was lower than that of 3YSZ. That of 3YSZ/monazite-type LaPO4 composites was influenced on the powder preparation methods and as a function of measured temperature. Microstructure of 3YSZ/monazite-type LaPO4 composites was not much affected by the amount of dispersed LaPO4 particles. 3YSZ/monazite-type LaPO4 composites were observed to pores after thermal etched. The pore of synthesized specimens was observed remarkably in compared with conventional ball-milled specimens.

Abstract: The creation of large impervious surface in urban and urbanizing areas have led to significant impacts on local climate, which is commonly known as urban heat island (UHI). In this study, porous pavements made of recycled sludge were examined as a way to control UHI by lowering the surface temperature. A novel image analysis technique was applied to quantify cooling effect of porous pavement materials without and with water. Although the porous pavement itself has smaller heat capacity than the natural soil, supplying water to the pavement decreased its surface temperature. At its highest point, the difference in surface temperatures without and with water was more than 10 oC. The water was supplied either from the top of the pavement or from the bottom of the pavement using the capillary effects. In both cases, pavement temperature was effectively lowered. The cooling effect of pavement by surface coating using epoxy-based polymers was negligible because surface pores were blocked. Field tests also confirmed the cooling potential of porous pavements.