Fabrication And Superplasticity Of Nano-Sized AlN Ceramics

Superplastic property was thought to be a effective method to solve the problem of the unworkability for ceramic material. AlN ceramic is a kind of excellent electronic packaging material, and has extensive application. The application of complex shaped AlN ceramic is more and more widespread, but, at present, there is no reporting for the preparation of nano-sized AlN ceramic with superplasticity. In this paper, the AlN ceramic was prepared by hot pressed sintering(HPS), with MoSi₂ as the sintering additives. The mechanical properties and superplasticity were investigated.MoSi₂ powder was prepared with Si and Mo by mechanical alloying(MA) under 510rpm miled for 96h, 144h and 192h. These three kinds of MoSi₂ powder were studied by X-ray diffraction(XRD), transmission electron microscope(TEM), differential thermal analysis(DTA)and energy dispersive spetrum(EDS). The analysis results indicated that MoSi₂ powder miled for 144h was considered to own the minimum grain size(only 12.68nm)and the most uniform organization.Prepared nano-sized AlN ceramic by hot pressed sintering(HPS)under 1500℃, 1600℃and 1700℃, with MoSi₂ powder miled for 144h as the sintering additives. For comparision, prepared pure AlN ceramics by HPS at the same temperatures. Six kinds of ceramic blocks were studied by XRD, TEM, DTA and mechanical analysis such as Young′s modulus, Vickers hardness and fracture toughness property. The analysis results indicated that nano-sized AlN ceramic own higher density of 99.1% and excellent plasticity.The compression and extrusion experimets were proceeded for nano-sized AlN ceramic. The compression ratio is 71% at strain rates of 4.0×10^-3s^-1 and low temperature of 1600℃, this result indicates that nano-sized AlN ceramic owns excellent superplasticity. Shapped ceramic annular samples by the method of combined extrusion at 1600℃. Based on SuperForm, simulate the combined extrusion of nano-sized AlN ceramic. Compare the analog results and the exprimental results to obtain the the rule of the superplastic deformation.