Key Engineering Materials Vols. 317-318

Abstract: Uniformly nano-sized macroporous silica consisting of well-defined pore sizes were successfully fabricated. A modified sol-gel process, using mono-dispersed polystyrene(PS) spheres as templates, was employed for configuring three-dimensionally ordered macroporous structure. The nano-sized macroporous silica structure was formed when the templates were removed by the calcination at high temperature. The pH value affected uniformly stacked order in the PS/silica matrix due to the PS being uniformly coated by silica film at appropriate pH value. Also this pH value affected the iso-electrics points between the PS and silica particles surface charges. The heating temperatures and the reaction times were considered to conform the microstructural morphology, the thermal deposition of organic components, the matrix wall thickness and densification behavior. Three-dimensionally assembled porous silica consists of uniform-sized pores of 200nm and high specific surface area of 163 m2/g.

Abstract: Thermoset molding in wet and dry state was successfully employed to fabricate high strength reaction bonded silicon carbide (RBSC) ceramics. Granule transfer molding (GCM) was developed to prevent segregation of component particles and binder phase in wet state, while granule compression molding was applied in dry state to fabricate green compact with significant variation of compaction ratio. Low-fill density granules with mixing homogeneity were critical for promoting lateral deformation of granules during consolidation. In addition, anodic performance of Ni-YSZ anode was significantly enhanced by replacing solid fugitive phase with viscoelastic fugitive phase used as binder in thermoset molding.

Abstract: There are several TiO2-containing minerals, such as rutile (TiO2-based, typically 90-98%), leucoxene (FeTiO3-TiO2 based, typically 60-92%) and ilmenite (FeTiO3-based, 35-65% TiO2), and most of them are mined in Australia and South Africa. The 2003 world production of mineral rutile (containing highest amount of TiO2 among aforementioned TiO2-related minerals) was 346,000 tons. Although the price of TiO2-related ores have not fluctuated so much for these three years, that of high-purity TiO2 (Produced from these raw ores) tends to increase due to its activated demand. The world demand of TiO2 in FY2004 is estimated to be 4,267 kt, and will be increased by 5-7% (in price) compared with 2003 (about $7.8 billion). Currently, a large portion of TiO2 is used in pigment, however, other value-added uses such as photocatalysts have been extensively studied. The demand for value-added products with reduced cost is desired. In this report, current status of Australian mines, natural rutile production, price and quality trend, and our recent nanomaterial development are demonstrated.

Abstract: Industrial wastes have exerted high loads on environment in view of the difficulties to reserve landfill space and the risk of air pollution. In this study we proposed a method of simultaneous disposing of inorganic waste and common organic waste, in light of cascade recycling concept. Zeolite-carbon composite was synthesized by a combination of calcinations and hydrothermal treatment of coal fly ash and sawdust mixtures. The microstructure, phase compositions and electromagnetic wave absorption properties of the composite were evaluated. The results showed that the low cost composite has the potential to be used as high value-added humidity-controlling building material with the ability to absorb electromagnetic wave.

Abstract: In order to develop low-energy ceramic processing, we evaluated the energy consumption of total fabrication processes of alumina ceramics with various particle sizes. It is demonstrated that the optimum particle size is several tens of nanometers for energy-saving, and decreasing particle size from 400 to 40 nm enables the 40 % energy reduction in this assessment.

Abstract: We have developed a new environmentally friendly fabrication process for alumina ceramics using hydraulic alumina (HA) and water. Without the addition of an organic binder, alumina green bodies retained their original shapes by the hydration of HA in the green bodies. In the case of α-Al2O3-HA-H2O system, alumina ceramics with 97.8% theoretical density were obtained. Added water acted as a fugitive material in the hardened green body. In the case of HA-H2O system, porous alumina ceramics with a wide range of open porosity (56.6–69.1%) and narrow pore size distributions were fabricated without the use of organic fugitive materials. The results of evolved gas analysis-mass spectrometry measurements showed that the new fabrication process for alumina ceramics was confirmed to be eco-friendly.

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 are investigated with the firing temperature and glass content. The properties are improved with increasing both the firing temperature and glass content. These properties, except the compressive strength, tend to be saturated from the glass contents of 70 wt % in the case of 1050
. The compressive strength shows the maximum values at the glass contents of 70 wt% and then which are decreased with increasing the glass contents. The optimal properties obtained in the tiles are 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% is fired at 1050
. These results are better than the properties of commercial clay tiles, due to easy melting and densification of glassy phase in the tiles.

Abstract: The extruded honeycomb supports, porous filters and catalyst monoliths are innovative ceramic products used in environmental protection. The development and applications of these novel materials and products are mainly driven by the environmental legislation in the region, the availability of technology, the mass manufacturing facilities and the cost effectiveness. This paper highlights some of the recent innovations and challenges in ceramic materials and design, and our findings in systematic understanding and applications of the principle of fabrication of honeycomb ceramics for various air pollution control systems in India. The use of locally available platy kaolin and advanced extrusion process control using rheological parameters of the paste are advantageously adopted for production of thin walled and high thermal shock resistant cordierite honeycomb supports for catalytic converters. The low cost design of diesel particulate filter (DPF) with off board electric regeneration system is found to be very effective in reducing the particulate emission in urban transport buses and proven for more than 100,000 km on Indian roads. The Ti-WV based SCR catalyst extruded in the form of honeycomb using high surface area TiO2 has shown high NOX reduction in coal fired boiler exhaust. The preparation of high surface area honeycombs from activated carbon and zeolites with adequate mechanical strength opens up new application areas. Some of the case studies on the above products and applications are presented in this paper.

Abstract: In this study, porous hydroxyapatite (HAp) bodies were prepared by the simple process. We fabricated porous fibers consisting of polyacrylonitrile (PAN) and HAp by an extrusion method of the mixture of PAN and HAp in dimethylformamide (DMF) solution. Fibers obtained by this extrusion method were chopped and molded. Subsequently, these compactions from chopped fibers consisting of HAp and PAN were sintered at various temperatures in air atmosphere. The sintered HAp bodies had high porosity and a number of pores with diameter some hundreds μm. These porous HAp bodies can be used as a scaffold in the body.

Abstract: Calcium phosphate-AMP layered material was synthesized by the hydrolysis of α−TCP in the presence of AMP at pH=6.2. The resulting composite was a mixture of DCPD and calcium phosphate-AMP layered material. The composition and structures of the calcium phosphate-AMP layered material were estimated based on elemental analysis, thermal analysis, and spectroscopic analyses. About 30 wt% of the composite comprises AMP, which is oriented in alternately layered structure of AMP and calcium phosphate layers. Furthermore, the composite showed better cell adhesion than DCPD.