Study On Fabrication Of Ceramics At Room Temperture

Room ceramics bonded the ceramic powders by adhesives instead of the grain boundary formed during the sintering process, have a series of advantage, such as energy conservation, forming conveniency, machinable and economy, expected to application in domestic ceramic, composite, biomedical materials and so on.High-purity and homogeneous dispersed powders of tricalcium aluminate (C3A) with the small particle size were prepared by rapid ssynthesis method (SPS) and subsequent milling,which can meet the requirement of hydration.The the synthesis temperature and holding time on the purity and grain size of synthesized powders was investigated.The results showed that the C3A powder, which was prepared at 1350℃, holding for 20min, has good stability and the content of free calcium oxide is as low as 1.6%.C3A-Al2O3 ceramic was prepared at room temperature used the C3A synthesized by SPS as adhesives.The shaping method, curing method and the content of C3A were discussed by the investigating the porosity, pore size distribution, microstructure, hydrated products and mechanical properties. The results showed that cold isostatic press and high temperature reactor curing are the appropriate method compared the molding press and the standard curing and the optimized process parameter is cold isostatic press, high temperature reactor curing at 120℃and the content of adhesives is 40wt%. The 3 days compressive strength of the samples obtained in this process is 298Mpa.Cement-Al2O3 ceramic was prepared at room temperature used the Ordinary Portland Cement (OPC) milled by Planetary Ball Mill for 18h at speed of 250 rpm which has average size of 700nm.The water/cement ratio(w/c) and the content of cement were analysed.The experimental results show that the porosity and hydrated degree were increased as the as the w/c kept up(0.15～0.30), however the compressive strength increased to a maximum and then decreased. Both the porosity and hydrated degree are important factor to the compressive strength. In the low w/c, the hydrated degree plays a dominant role, but in the high w/c, the effect of porosity is significant. The most appropriate content of cement is 42wt%; When the w/c is 0.21 and the content of cement is 42wt%, the compressive strength of 3 days reaches maximum, up to 328MPa. Furthermore, in order to reduce the porosity and improve the performance, nano-SiO2 was added to the samples. The effects of SiO2 and its content were discussed. It's demostrated that proper SiO2 play a major role in reducing the porosity, improving the microstructure and increase the performance due to its filling effect, pozzolanic effect, interfacial effect. The compressive strength of 3days rise to 408MPa, the rate of which is up to 26.58% when the content of SiO2 is 5wt%.