Software piracy has been a very perilous adversary of the software based industry, from the very beginning of the development of the latter into a significant business. There has been no developed ...foolproof system that has been developed to appropriately tackle this vile issue. We have in our scheme tried to develop a way to embark upon this problem using a very recently developed technology of RFID.
Dense spinel products for refractory applications are difficult to manufacture directly from mixtures of Al2O3 and MgO powders via a solid-state route using conventional pressureless sintering, due ...to the volume expansion during spinel formation. The reaction sintering of alumina-rich (90% Al2O3) spinel was studied. This method enables dense spinel aggregates to be produced in a single firing process, thus decreasing the number of firings, which helps keep costs down. The effect of alumina reactivity on reaction sintering was also studied. Product properties (density, strength) and microstructure were characterised. Maximum densification was achieved when the starting Al2O3 (calcined at 1200 C) has a surface area of 2 m2/g. Batches containing highly reactive alumina are subject to more expansion during spinel formation than those containing alumina calcined at high temperatures. 13 refs.
The use of SiO2 sol as a binder for castables has brought about significant changes in castable refractory technology. A gel-bonded castable is basically a cement-free castable that develops initial ...strength through gelation of the sol. It forms the final fired matrix through reaction between gel particles and reactive/finer components of the castable during firing. Cement-free Al2O3-SiC-C castables with a SiO2 sol binder were developed for the working lining of blast furnace troughs. The absence of an RO (CaO, MgO or FeO) group allows a better ceramic bond in the castable without the formation of low-melting phases. At high temperatures, mullite is formed, providing a ceramic bond and hot strength in the products, and imparting better thermal shock resistance. Addition of organic fibre improved the densification, strength, corrosion and slag penetration in the dried and fired state. 5 refs.
Quartz is the highest-melting-temperature component in whiteware compositions, and attempts have been made to replace it by other silica sources in order to decrease the firing temperature. Some of ...these studies are noted. A comparative study of the use of waste silica, produced in large amounts in the aluminium fluoride industry, as a complete replacement for quartz in normal porcelain compositions is described. The other components remain the same. The effects of this waste silica on the fired characteristics were studied. Physical, mechanical, and thermal properties, phase content and microstructure were compared. Waste silica was found to improve flexural strength and increase the mullite content of bodies, and decrease the vitrification temperature, without affecting other properties. 8 refs.
Sintered zirconia mullite composites were developed from zircon sand and calcined alumina. The effect of La2O3 as additive at various amounts on the properties of the composite was studied. ...Densification was found to improve in the presence of the additive, but a certain amount of closed porosity occurred in the sintered product. Hot strength of the composites was improved up to 3 mol% of the additive. Retainment of tetragonal phase of the composites also was found to be increasingly improved with increasing amount of additive. Microstructural features reveal liquid phase sintering of the composite in the presence of the additive, which is the reason for deterioration of the hot properties at higher amounts of the additive.
Clay & Traditional Ceramics Div., Central Glass-Ceramic Research Institute, Kolkata, India Synthetic mullite-gel aggregates prepared using a hydroxyl-hydro gel method were used in clay-based ...solbonded castables which then were tested for glass corrosion using normal soda-lime-silica and high-lead-bearing glasses. Glass corrosion tests for all compositions showed almost no corrosion or penetration of the glass into the castable for the normal soda-lime-silica glass and highly corrosive leadcontaining glass. SEM photographs of the glass-containing cups showed no damage to the glass-containing bottoms and the three-phase (glass-refractory-air) zones of all the compositions. The castables were found to be resistant to these two glass compositions.
PDF
