Chengji Deng

The Influence of TiO2 Addition on the Modulus of Rupture of Alumina-Magnesia Refractory Castables

The addition of TiO2 to alumina-magnesia refractory castables could accelerate the in situ spinel and calcium hexa-aluminate (CA6) formation and change the phase evolution, which will have direct effect on the overall modulus of rupture values. The cold (CMOR) and hot (HMOR) modulus of rupture, thermal expansion, and elastic modulus of alumina-magnesia refractory castables with different amounts of TiO2 were measured. The correlation of CMOR, theoretical strength, fracture toughness, and the fractal dimension of the fracture surface for these compositions were investigated. HMOR data were described using the model based on Varshni approach and Adam-Gibbs theory. The influence of TiO2 addition on the modulus of rupture of alumina-magnesia refractory castables was related to microcracks derived from expansive phase formation and pore filling or viscous bridging due to the presence of liquid phase at high temperature. The contribution of the above factors to the modulus of rupture for castables varied with the temperature.

In-Situ Reactions and Properties of Alumina-Magnesia Refractory Castables with Addition of TiO2

In the present work, the phase composition, apparent porosity, permanent linear change and microstructure were examined in castables containing 0–2 mass-% of TiO2 with and without magnesia to investigate the effect of TiO2 on in-situ reactions and properties in alumina-magnesia refractory castables after calcination at 1450°C/5 h. The results show that the addition of TiO2 can modify in-situ reactions and sintering processes. The amounts of spinel and calcium hexaaluminate (CA6) formed in overall castables increased with TiO2 addition, and the grain size of CA6 decreased gradually. The difference of the phase composition in overall and the matrix of castables indicated that the aggregates were involved in the CA6 formation. The permanent linear change and cold modulus of rupture of castables were dependent on TiO2 addition. For design of alumina-magnesia refractory castables, TiO2 could be used as an alternative to achieve good strength and certain expansion.

Preparation of Non-Aqueous Mg Green Tapes by Tape Casting

Mg green tapes by tape casting were prepared. The effects of different powder size and shape, solid loading, the content of binder, and the binder to plasticizer ratio on non-aqueous Mg slurry for tape casting and green tapes were investigated. The rheological behavior of Mg slurry and microstructure of green tapes obtained in different conditions were analyzed. The results demonstrated that Mg powders, with smaller size 27.32 μm, sphericity, were suitable for preparation of slurry with low viscosity and green tapes with higher density. The optimum solid loading, binder content, and binder to plasticizer ratio for Mg slurry and compact green tape were respectively 55 wt%, 3.2 wt%, and 3.75. Mg slurry belonged to Bingham plastic flow and were suitable for tape casting.

The Influence of SnO2 Addition on the Properties of Spinel-based Castables

The development of eco-friendly chromium-free refractory products has been attracting more and more attention for environmental protection reasons. Refractories from the MgO-Al2O3-SnO2 system were selected as chrome-free alternatives. Novel spinel-based castables with SnO2 have the potential to be used in copper smelting. The effect of SnO2 addition up to 10 mass-% on the properties of spinel-based castables was investigated. Phase composition, microstructure, physical and mechanical properties as well as corrosion resistance of the refractories were characterized. The results showed that spinel-based castables with 10 mass-% SnO2 after firing at 1350 °C presented the best comprehensive performance due to lower porosity and higher strength.

Molten Salt Synthesis of Forsterite Heat Insulation Material

The forsterite thermal insulation materials were prepared by the molten salt method and using natural forsterite and NaCl-Na2CO3 molten salt as raw materials. The influences of different mass ratios and reaction temperatures on thermal insulation materials were investigated. Apparent porosity, bulk density and compressive strength of the samples were characterized. And the pore size distribution and microstructure were analyzed by mercury injection apparatus and scanning electron microscopy. The results demonstrated that when the sample was sintered at 1100 °C, and the content of molten salt was 40 wt%, the forsterite thermal insulation materials were better with high apparent porosity and certain compressive strength. The distribution of the pore size was very uniform. Molten NaCl provided liquid environment promoted the sintered of forsterite, the pore was received after the NaCl was removed and the decomposition of Na2CO3.

Preparation of Al8B4C7 composite materials by using oxide raw materials

Al8B4C7 composites materials were prepared by using Al, B2O3 and C as raw materials. The effect of sintering temperature and different additives (Al and C) on Al8B4C7 composites materials were investigated. The Al8B4C7 composites materials were characterized from microstructure, apparent porosity, bulk density and compressive strength. The results demonstrated that the increasing of sintering temperatures could make the samples denser and improve compressive strength. The optimal sintering temperature was 1700 °C, and the main phase composition of Al8B4C7 composites materials were Al8B4C7 and Al2O3. Al additive could improve the properties while C additive played an harmful role. The Al8B4C7 grains were irregular flake and the size was 2~4 μm.