The objective of the present work was to study the preparation a fully dense MgO+C dopped alumina. The sintered materials was characterized by their microstructure and the microstructure variation during the different thermal treatment. The atmosphere is suggested to play an important role during the annealing of MgO+C dopped Al2O3. From the results it can be seen that MgO+C increased the densification rate of Al2O3 and the density is arrived very near the theoritical density. The Vaccum secondary and the absence eventually gas in the pores have been played in the densification rate. The other role of MgO+C in powder is to lower the boundary mobility which helps to keep the pores attached to the moving boundary even though the pores are controlling grain growth and not to change the grain size/density significantly. That is to say, the pesence of carbon or MgO in powder is to inhibit grain growth and to promote the development of more uniform grain structure by formation the precipitate and segregation. Because of the above roles of MgO+C in Al2O3, it is possible to arrive the theoritical density without the abnormal grain.

Dense Silicon nitride was investigated to determine the effect of its microstructural parameters and densification on thermo-mechanical properties and thermal stress resistance to fracture initiation during a hot or cold mechanical and thermal shock testing. The different materials and microstructures were obtained by changing the parameters such as the type of the powder, additive, forming process and sintering condition. Maximum crack growth and thermal shock resistance of dense Si3N4 are achieved after complete conversion of the a®b transformation, and after the change in grain morphology towards elongated grain and the relative crystallization of the second phases have been obtained. The characteristics are obtained by a high a phase content of the starting powder, high Y2O3 and sintering condition of higher temperature (2000o C), longer soaking times (1h) and load application at the beginning of the thermal cycle.

Induced current and subsequent maximum heat generation in MF furnace occurs in liquid metal near to the contact surface with the refractory wall. In addition, due to non-uniformity of healing the cracks, corrosion of the refractory lining may become severe if appropriate precautions are not considered.In the present paper particle size distribution (PSD), cold crushing strength (CCS), and free iron content of two silica mixes, i.e. Iranian and imported ones, which are currently used in service, were studied. Results from postmortem analysis of both silica ramming mixes after 5 working days showed that the probable reason for the short life of the refractory lining can be attributed to non-uniformity of ramming and sintering as well as the healing profile and the amount of acid boric in the refractory silica mixes. The effects of each mentioned parameters have been discussed in this article.

Silicium-Based Ceramics were investigated to determine the effect of microstructural parameters and densification on thermal stress resistance to fracture initiation during thermal shock testing. The different materials and microstructures were obtained by changing parameters such as the type of powder, additive, forming process and sintering condition. Critical temperature differences (DTc), after water quenching, are discussed in relation to change in Young's module of elasticity, a variable affecting thermal shock. The maximum thermal shock resistance of dense Si3N4 has been achieved after completing conversiona®b, the changes in grain morphology toward elongated grain and the relative crystallization of the second phase. These characteristics are produced by a higher percentage of the powder in the  a-phase, high Y2O3, and the sintering condition at a higher temperature (2000°C), longer soaking times (1h) and load application at the beginning of thermal cycle.

Electrophoretic deposition has been used by establishing an electric field in a stable suspension, a perfectly smooth and uniform surface is obtained. In this study a coating is applied on a Inconel substrate by the ionizations of alumina single crystals in a suspension and in an electric field. Then, with sintering treatment, a dense coating is obtained. The effect of time, applied voltage, processing, sintering temperature, and the pH of the solution on the thickness of deposited layer are also investigated. To determine the thickness and analysis of coating layer, scanning electron microscopy was used.It was found that by increasing voltage, applied current, sintering temperature and also applying optimum processing of sintering treatment and increasing pH, the thickness of deposited layer was increased. Each of the mentioned factors had different effects on the thickness of coating layer. With due attention to the effective factors on the thickness of the deposited layer, optimum conditions for applying coating was achieved.