Laner Wu

Performances of Multiphase Ceramics of SiC and Praseodymium Aluminates

Multiphase ceramics of SiC based composites were prepared by hot pressed (HP) and pressureless sintering with Al2O3 and Pr2O3 as sintering additives. The compositions were designed according to the two binary compounds of PrAlO3(PrAP) and PrAl11O18[β(Pr)] formed in Al2O3–Pr2O3 system. And the performances of the multiphase ceramics with different content of the second phases were investigated. The results showed that the weight loss, linear shrinkage and relative density of the samples in the group 1/B (SiC–PrAl11O18) containing more Al2O3 were higher than those of the samples in the group 1/1(SiC–PrAlO3) by pressureless sintering, and its supreme relative density was 91.5%. By hot pressed sintering, the relative density of the densest sample in group 1/1 and group 1/B reached 94.8 and 95%, respectively. In group 1/1, sample with 10wt% of additives possessed the greatest hardness of 21.1 GPa, and the maximal flexure strength of 494.9 MPa was achieved when additives content increased to 15 wt%. The sample containing 10wt% of additives in group 1/B had the best fracture toughness of 7.4 MPa m1/2.

Influence of sintering additives and TiC on properties of TiC/Si3N4 ceramics

The properties of TiC/Si3N4 ceramics were investigated. TiC acts as electrically conductive additive. The sintering additives are mainly Y2O3-MgO, by adding Al2O3 or AlN separately, forming system Al2O3-Y2O3-MgO and system AlN-Y2O3-MgO. The contents of TiC and sintering additives play an important role in sintering behavior, mechanical properties and conductive properties of the TiC/Si3N4 composite material. The experimental results show that: in the condition of the experiments, the densities of sintered TiC/Si3N4 composite are not high. Bending strength of the material is a little lower than that of common Si3N4 ceramics. Part of the samples has conductive property (TiC more than 30%). The best conductivity of the samples is 2.3×10−2s/cm. It does not satisfy the demand of electrical discharge machining. Further research is needed to be done. The conductivity of the AlN-Y2O3-MgO sintered samples is better than that of Al2O3-Y2O3-MgO system.

Dusting control of magnesium slag produced by Pidgeon process

Magnesium production by Pidgeon process has been developed very fast in China since 1990’s. The waste slag from magnesium production has attracted broad attention because the huge amounts of the slag. For each ton of magnesium produced, there will be 6-8 tons of the slag generated. A big part of the Mg slag exists as fine dust with particle size of D95 < 0.1mm, which may pollute air, soil and water surrounding the Mg industry. The fine particles are generated by phase transformations of dicalcium silicate C2S (2CaO⋅SiO2) during the slag cooling. There is a volume expansion of more than 10% with the transformation of β-C2S to γ-C2S phase, causing a disintegration or dusting of the Mg slag. In the present study, several chemical stabilizers were used to treat the dusting Mg slag at 1200°C, including borates, phosphates and rare earth oxides, in order to obtain volume stable slag aggregates for environmental protection and recycling of the Mg slag. The volume expanding rates of the samples were measured. XRD...

Preparation of γ-AlON transparent ceramics by one-step method with high-activity Al2O3 powders

In this paper, γ-AlON transparent ceramics are fabricated by one-step method—reactived hot-pressuring sintering technology by using as-prepared γ-Al2O3 powder as raw material. And the sintering process is also improved from two aspects: adjusting sintered technique parameters and improving the sintering agents. XRD, SEM, ICP-AES analysis results show that as-prepared γ-Al2O3 powders have advantages of super-fine, high-purity and high-activity so that can meet the requirements of starting material. By adding 1wt% Y2O3 as sintering agent, single-phase γ-AlON transparent ceramic can be fabricated under the optimum technological condition: hot-pressure sintering at 1950°C for 6h, under nitrogen atmosphere. The results from XRD and SEM indicate that the γ-AlON ceramic has high density and fine microstructures with relative density of 99.22%. The test result of IR spectrum show that the ceramic yield the best transmittance of 18.42% at 2.5μm and its transmitting wavelength range extend from 1.5 to 4.5μm.