Preparation Of “siCw Strengthen ZTA” Ceramic Brackets By Pseudo-boehmite Gel Method

Objectives The silicon carbide whiskers strengthen zirconia toughened alumina ceramic brackets are fabricated by pseudo-boehmite gel method. This new ceramic brackets has been added silicon carbide whiskers（SiCw） into zirconia toughened alumina（ZTA） ceramics. This study is to explore the influence of the new gel method molding process, pseudo-boehmite, silicon carbide whisker（SiCw） and zirconium dioxide（Zr O₂） on the mechanical behavior of the ceramic brackets respectively,through the brending test of the ceramic metarial, water absorption, phase composition and micro topography. It provides an important experimental basis for toughen and clinical use of the ceramic brackets.Methods Zirconia toughened alumina ceramics are formed after gelling using pseudoboehmite as binder. Pseudo-boehmite has a character which can be gelling with nitric acid. Put the ceramic particle of Zr O₂ and Al2O3 in the double shells, which formed of pseudoboehmite, can be preparing a homogeneous and stable ceramic slurry. Heat insulation for 12 hours at 35℃,and then heat up to 60℃ heat insulation for 24 hours, make it dry into ceramic body. On the basis of the preparation process, development of the four factors and three levels table, which throng the solids content, sintering temperature, sintering holding time and the amount of Zr O₂ as a result of the impact and each factor is divided into three levels. According flexural strength to reference index,can be confirm the best preparation process. Then according to the fixed proportion as 3%, 5%, 7%, 10% and 15% SiCw into ceramic powder. By measuring the bending strength, water absorption, and microscopy morphology, the influences of SiCw cotent on the materials performance were discusses. Based on the microstructure observation, the principle of increasing toughness were studied..Results 1 It needs three hours from sol to gelatination, when the p H value is between 3 to 4. The advantage of using pseudo-boehmite to prepared ceramics is it not only enable to make the ceramic particles firmly fitted in the electric double layer, but also ensure there is enough operation time to mix ceramic particles mixed uniformly and pour them into the culture dish before gel slurry. 2 The result of orthogonal test shows the four factors of influence degree during the preparation of the ceramic is: Zr O₂ content> sintering temperature> holding time> solid content. Finally, ZTA ceramic brackets can be preparated by 45% solids, 30% Zr O₂ particles added by 1570℃, sintering environment incubated 5h, which is the optimum preparation, the bending strength is 304.7142 MPa and the water absorption is 0.049%. 3 On the basis of preliminary experiments, the different proportions of SiCw added to the ceramic powder, preparation of SiCw ZTA ceramic brackets materials, measurement results. Compared with the ZTA ceramic material toughening effect, when the proportion of the SiCw added to 5%, the bending strength of the ceramic material prepared most was the best, reached 354.9875 MPa.Conclusions 1 Using the pseudo-boehmite gel method is able to make ceramic brackets material of "SiCw Strengthen ZTA" successfully. 2 The addition of SiCw has many advantages, such as it improves the compressive strength of ceramic brackets ceramic brackets to 354.99 MPa, reduces the brittleness and has important clinical application value. 3 Therefore, this preparation of ceramic material in the process of forming the ceramic brackets, not only simple, inexpensive, but also the use of pseudo-boehmite gel plays better toughened of Zr O₂ and SiCw, to increase and improve the density of the ceramic body as well as the bending strength of ceramic brackets.