Issue No. 1

Abstract

This paper reports an investigation carried out on the deskulling problem of tundishes at the Mobarakeh Steel Plant in Iran. Bad deskulling of tundishes is a major problem in continuous casting of steel, and can occur due to the chemical reactions between the refractory lining and the slag carry over from ladle to tundish. Post-mortem analysis of the slag/commercial magnesia-olivine mix refractory interface by XRF, XRD, OM, TEM, SEM and EDS techniques showed that the volume of slag carry over from ladle to tundish has a direct effect on refractory wear in the tundish. The percentage of tundishes where the skull was locked into the safety lining was dependent on the slag basicity and amount of Al₂O₃ in the slag inside the tundish. It has been shown that a direct corrosion mechanism occurs in basic slag and also in acidic slag containing low alumina, but an indirect corrosion mechanism occurs in acidic slag containing high alumina.

Abstract

Spinel formation was studied by phase analysis and dilatomeric experiment using commercially available caustic magnesia and technical alumina in the temperature range of 1000 °C to 1400 °C. AlF₃ as mineralizer was added up to 3 wt%. AlF₃ was found to reduce the spinel formation temperature significantly, but also reduces the reactivity of the calcined products, measured by specific surface area.

Abstract

Five sample mixtures of Ugandan kaolin, ball clay, feldspar and flint were formulated and porcelain samples fabricated by extrusion through a vacuum pugmill. Samples were evaluated for formability. The degree of densification of sintered specimens fired at 1200 to 1350 °C was evaluated by measuring the firing shrinkage, bulk density, water absorption and bending strength. Crystalline phases and mullite morphology were studied using XRD and SEM respectively. Dielectric strength measurements were carried out on disc specimens. Dielectric and bending strength properties deteriorated at high temperatures because of pore formation and decreasing amount of undissolved quartz in the crystalline phase. An optimum composition of 30% kaolin, 15% ball clay, 30% feldspar and 25% quartz yielded an unglazed body with highest bending strength of 72MPa and dielectric strength of 19MVm-1 after firing at 1250 °C. The body consisted of small, closely packed mullite needles and undissolved quartz crystals embedded in a glass matrix.

Abstract

A l₂O₃/(W,Ti)C ceramic composites were prepared for use as nozzles in coal-waterslurry (CWS) industrial boilers. Effects of nozzle length, nozzle inlet angle, nozzle exit structure, atomizing air pressure and experimental temperature on the erosive wear of these ceramic nozzles have been investigated. Results showed that reasonable nozzle structure is beneficial to decrease nozzle wear. Lower atomizing air pressure can help to increase nozzle life. Thermal shock damage such as cracking and chipping was considered as the dominant reason for the failure of ceramic nozzles.

Abstract

A brief review of the current knowledge on nanostructured ceramic materials is given. The attention played by scientists and economists for this new class of material is continuously growing, due to their unique and improved properties, compared with the corresponding microcrystalline materials. After a short discussion on nanotechnology and nanomaterials in general, the key concepts, correlated to nanostructured ceramics (applications, types, synthesis and properties), are given.

Abstract

In the article it has been emphasized that superconductivity is only the enabling technology for Super-MAGLEV and the superconducting transmission lines, because all the cost is in cryogenic engineering, electrotechnology and general engineering infrastructure. So if in the long term the hydrogen economy can be combined with superconducting cables and ultra fast trains running in the same vacuum tunnels network it will be the forerunner to a transportation and energy transfer revolution called SuperTransGrid. In such system hydrogen fuel could be provided for energy storage and transfer, very effectively cooling high power superconducting cables but would also feed low pollution Cryoplanes and fuel-cell powered cars transporting train passengers at speed ~2000
miles/hour.

Abstract

The effect of heat treatment on phase composition, microstructure, as well as densification and microwave dielectric properties of ceramic bodies sintered at 1300 °C with different soaking times (3 - 6h ) was studied. X-ray diffraction results show the presence of many satellite crystalline phases association with Ba₂Ti₉O₂₀ phase. The presence of Ba₂Ti₁₃O₂₂, Ba_1.15Ti₈O₁₆, Ti₄O₇ , Ba₂TiO₄ and Ba_1.12Ti₈O₁₆ in sintered ceramics bodies, depends on the soaking time. The results also reveal that the formation of these additional crystalline phases except Ba₂Ti₁₃O₂₂ is beneficial to improve microwave dielectric properties displaying dielectric constant of ~21 and quality factor (Q x ƒ) = 113.400 -116.300 GHz at ~11GHz.