Nai Peng

Effect of Briquetting Pressure on the Performance of In Situ Formed Sialon in Al2O3-C Refractory Bricks

In this paper, the effects of briquetting pressure on the performance of in-situ formed Sialon in Al2O3-C refractory bricks are investigated. The phase compositions and microstructure of the Al2O3-C refractory were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM).The results show the briquetting pressure hardly has effect on the phase of the sintered specimens, two new phases of Sialon with a Z value of 2 and SiC formed. The micrographs of Sialon crystals have the shape of both column and tabular column, but with a cone tip in the specimens sintered at 200MPa and 300MPa and smooth tip in specimens sintered at 400MPa and 500MPa.

Study on the Oxidation Kinetics of In Situ β-Sialon Bonded Al2O3-C Refractories

The oxidation behaviors and kinetics of in-situ β-Sialon bonded Al2O3-C refractories were investigated by TGA techniques via isothermal oxidation experiments at different temperatures. The results show that the oxidation process of in-situ β-Sialon bonded Al2O3-C refractories can be divided into three stages: oxidation reaction rate controlling stage, reaction and diffusion controlling stage, and diffusion controlling stage. The oxidation rate controlled by the reaction rate has no obvious changes as the temperature increases. The oxidation rate controlled by the reaction rate and the diffusion rate together has a trend of decline, so is the oxidation rate controlled by the diffusion rate.

Nitridation Isothermal Kinetics of In Situ β-Sialon Bonded Al2O3-C Refractories

The kinetics of in-situ β- Sialon bonded Al2O3-C (SAC) refractories were investigated by TGA techniques via isothermal nitridation experiments at different temperatures. The result show that the nitridation process of in-situ β-Sialon bonded Al2O3-C refractories can be divided into two stages: the nitridation reaction rate controlling stage in the first 10 min, and the apparent activation energy of nitridation reaction is 370 kJ/mol ; then the reaction is controlled by both chemical reaction and diffusion rate in the following 110 min, the apparent activation energy of nitridation reaction is 410 kJ/mol.

Effect of Soaking Time on the Properties of Al2O3-C Refractory

Al2O3-C refractory has many advantages, high strength, good corrosion resistance and good thermal shock resistance, so Al2O3-C refractory is widely used in the steel-making process. In this paper, the effect of different soaking time on the properties of Al2O3-C refractory at 1450°Cin nitrogen atmosphere was studied. The phase composition of the sintered sample has little change when the soaking time was from 2h to 5h. Cylindrical sialon appeared as the soaking time being 3h, and its grain size increased and became uniform, about 2.5um when the soaking time being 4~5h. In the general performance, with the soaking time changing from 2h to 5h, the samples increment percentage in weight decreased gradually, and the compressive strength of the sintered was first increased, and then decreased, reaching the maximum when the soaking time is 4h. Both the apparent porosity and bulk density of the samples had little different changing.

Investigate of Phase Compositions and Microstructure of MgO-C through In Situ Nitride

In this paper, the phase compositions and microstructure of MgO-C samples containing Si powder in N2 sintered at 1350-1500°C were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The α-Si3N4, β-Si3N4, MgSiN2 and SiC phases have formed together with MgO and C phases in the sintered samples. The morphologies of β-Si3N4 crystals were almost in the shape of rod-like through the α-β phase transformation of Si3N4 by Mg-Si-O-N and silicon liquid. The morphologies of α-Si3N4 crystals were in the shape of equiaxed. The morphology of MgSiN2 crystals was in the shape of polyhedron with the size of 5 μm.

Effect of Additive on Phase Composition and Microstructure of Silica Brick Matrix

The silica matrix specimens were prepared by adding microsilica and MoSi2 powder. The mixture were pressed to cylinder and then sintered at 1200oC, 1250oC, 1300oC and 1400oC for 8h respectively. The phase compositions of specimens were analyzed by X-ray diffusion and the tridymite crystal morphology and grain sizes were observed by SEM. The results show that with the addition amount of MoSi2 powders increase, the intensity of tridymite diffraction peaks first strengthen slightly and then decrease, becoming more and more amorphous process, while the diffraction peaks of residual quartz phase enhance. When adding 2.5% MoSi2, the precipitation of CaMoO4 phase reduces the O/Si ratio in the liquid phase, and promotes the generation of tridymite, so the number of tridymite increase, but the crystal size decreases. With the sintering temperature increase, the intensity of tridymite diffraction peaks increase, the residual quartzite amount reduces.

Effects of Sintering Temperature on Microstructure and Phase Formation of Nitrides Bonded MgAl2O4-Crefractory

The microstructure and phase analysis of in situ nitrides formation in MgAl2O4-C refractory were investigated with different temperature. The phase compositions and microstructure of the MgAl2O4-C refractory were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that sintering temperature has a significant influence on the microstructure and phase analysis of MgAl2O4 refractory. As the sintering temperatures are 1450°C and 1500°C, nitride that formed in samples is β-Sialon and the crystal morphology is columnar with short size. With the temperature rise to 1550°C and 1600°C, nitride formed in sample is AlON with the crystal morphology is tabular polymorph with large size.