MgAlON ceramics were prepared by spark plasma sintering (SPS) and hot pressing (HP), respectively. It was found that SPSed MgAlON samples had a single MgAlON phase with almost no open pore while HPed MgAlON had a minor AlN phase. The strength of SPSed samples is higher than 500MP, being much higher than that of the HPed samples. The experimental results revealed that that SPS was a rapid and reliable process for the further development of MgAlON.
Slide gates are installed at the bottom of a ladle or tundish to control the flow of molten steel. It plays an important role in ladle refining process and continuous casting. Al2O3-ZrO2-C refractories are widely used as slide gate materials due to its excellent corrosion and thermal shock resistance. At the start of casting, molten steel almost 1600°C passes through the bore of slide gate, the plate is rapidly heated up, the temperature difference between the bore and edge part, the slide gates are subject to large thermal gradients, so there is large thermal stress in the plate. This paper will show the results of our improved slide gates with good thermal shock resistance.
In this paper, the MgAlON ceramic was fabricated by Spark Plasma Sintering (SPS) and hot press sintering respectively. The results showed that highly pure and single-phase MgAlON could be fabricated at lower sintering temperature in a short period through SPS process, compared with the conventional Hot Press sintering (HP) process. The bending strength of MgAlON specimens prepared by SPS process was higher than 500MPa while bending strength of HP specimens was much lower. The open porosity was almost eliminated in SPS MgAlON specimens. Spark Plasma Sintered MgAlON had a single phase of MgAlON while Hot Press Sintered MgAlON had major MgAlON and minor AlN and Al2O3.
The isothermal oxidation behaviors of MgAlON/Si3N4 composite which was synthesized by pressureless nitridation reaction sintering have been investigated in flowing air at 1100°C, 1200°C and 1300°C respectively. The results show that the composite represents excellent self-healing property of oxidation at 1300°C, which might be attributed to the formation of protective silicate film with reasonable viscosity, good spreading power and very low oxygen diffusion coefficient, and to the formation of compact surface resulted from the expansion effect of forming mullite from SiO2 and Al2O3. However, the self-healing property of it is relatively poor at 1100°C and 1200°C as compared to 1300°C.
The thin-film of silicon deposited by RTCVD on pressureless sintered SiC substrate with the size of 30mm×20mm, which is cleaned by ultrasonic method and chemical treatment. The crystal size of silicon columnar grain can reach 190 µm and its preferred orientation is [111] after ZMR process.
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