Effect of Silicon Addition on Microwave Synthesis of Al_(4)SiC_(4)

Al_(4)SiC_(4)was prepared using Al powder,silicon carbide powder,and graphite as raw materials,and silicon as the additive by microwave sintering.Effects of silicon additions(0,5%,10%and 15%,by mass)on the phase composition,microstructure,apparent porosity and bulk density of the Al_(4)SiC_(4)sample prepared with different aluminum additions(20%,25%,by mass)were researched.Then the developed Al_(4)SiC_(4)samples were applied to MgO-C bricks to investigate the effect on the oxidation resistance and mechanical properties of the MgO-C bricks.The results show that Al_(4)SiC_(4)can be synthesized at lower temperatures using the microwave sintering method.The sample with 20%aluminum addition has a lower Al_(4)SiC_(4)content than the one with 25%aluminum.When the silicon addition is 10%and the aluminum addition is 25%,the sample appears needlelike system,the porosity is only 28.69%,and the sample is dense.The developed Al_(4)SiC_(4)was added into MgO-C bricks as the antioxidant,which greatly increased the oxidation resistance and the mechanical properties of the MgO-C bricks.

Aluminum and Activated Alumina Powder Additions on Microwave Synthesis of Al_(4)SiC_(4)

Aiming at improving the properties of magnesia carbon materials,silicon aluminum carbide(Al_(4)SiC_(4))containing materials were prepared using industrial aluminum powder,silicon carbide powder,and graphite as raw materials,and activated alumina powder as an additive,mixing thoroughly,pressing into cylinders and then firing at 1200℃for 30 min in a carbon embedded atmosphere by the microwave method.The effects of the aluminum powder addition(20%and 24%,by mass)and activated alumina powder addition(0,3%,5%and 7%,by mass)on the microwave synthesis of Al_(4)SiC_(4) as well as the effect of the obtained Al_(4)SiC_(4) containing material on the properties of magnesia carbon bricks were studied.The results show that:compared with the samples with 20%aluminum powder,those with 24%aluminum powder generate more Al_(4)SiC_(4).With the activated alumina powder addition increasing from 0 to 7%,the amount of Al_(4)SiC_(4) generated increases first and then decreases.Compared with the sample without activated alumina powder,the samples with activated alumina powder show lower bulk density and higher apparent porosity.With the activated alumina powder addition increasing from 3%to 7%,the bulk density of the samples increases first and then decreases,while the apparent porosity of the samples shows an opposite trend.The optimal additions are 24%aluminum powder and 5%activated alumina powder,and Al_(4)SiC_(4) synthesized in this sample has a hexagonal plate structure.With the synthesized Al_(4)SiC_(4) containing material added,the magnesia carbon brick has slightly increased cold modulus of rupture,basically the same modulus of elasticity and improved oxidation resistance.

Microwave-assisted Synthesis of Al_(4)SiC_(4) and Its Effect on Properties of MgO-C Refractories

Al_(4)SiC_(4) was synthesized from Al powder, silicon carbide, and graphite by microwave sintering, and characterized by XRD and SEM. Then the synthesized material was added to the magnesia carbon refractory brick to study its effect on the oxidation resistance, apparent porosity, bulk density, elastic modulus, and modulus of rupture. It is found that Al_(4)SiC_(4) can be synthesized by microwave sintering at 1 300 ℃ and the addition of Al_(4)SiC_(4)-containing material as an antioxidant can enhance the oxidation resistance of the magnesia carbon refractory brick.