| The enamel tooth is the best dental restoration materials at present. Ceramics materials used in dental clinic mainly is main current in the way of the ceramics materials and consists of the feldspar porcelain, alumina porcelain and glass ceramics, the feldspar porcelain is most constantly adopted. The dental ceramics pertains to the brittle materials, and it is feeble to disperse the part stress capability , and possesses low interfacial tension to meet an emergency , and the book snaps that the preceding deformation be able to stand is 0.1% around .To improve strength of dental ceramics materials is always the target that is pursued by dental physicians and material scientists. There are some problems of the porcelain in the research at present as follows:(l)The basic theory is researched insufficiently : Controlling the formation of leucite is based on experience; The interface feature between metal and the porcelain is not clear.The sort and guantification of interface adhesion, sintering performance are lacking in deep research; The properties of interface, sintering and osmosis diffusing for the porcelain such as opaque, body and incisal are little researched. The investigation on rheological properties including rheological model, distribution and morphology of powder particles has not been reported in literature. Since it is lacking in theory direction, porcelain tooth technicians work merely according to their experience. Thus the strength and color effect of dental restoration is difficult to guarantee, the yield of products is low.(2)Preparing process is aging: The manufacture of porcelain powder nearly is used by tradition heating technology to attain to melt, and crystallize; moreover theblending means of powder falls behind. The crystallizing amount, grain size distribution and morphology of leucite particles are difficult to the idealize, it results in crumbling prosthesis and cracking porcelain usually.(3)The treating technique of crown surface falls behind: The treating techniqueof metal crown surface fall behind , for instance, controlling the oxidizing thickness of metal crown according to experience merely ,it is difficult to attain good adhesive strength between metal and porcelain.(4) Controlling the the color on porcelain layer according to experience: Technicians can merely be able to lean against the experience to measure system porcelain layer color, the man-made factor effects the beautiful effect.Aim at above statement, the studies on increase in properties of porcelain will be mainly carried out in the following six aspects in the present thesis:(l)Study on the new process of preparing leucite crystallite using there step heat treatment:Expansion coefficient of leucite reaches 27 X 10-6 , it can increase in expansion coefficient of porcelain glaze. In order to prepare the porcelain powder having high adhesive strength, the high quality potassium feldspar is used as the raw materials, by heat treatment, the study on effects of K2O and Al2O3 amounts on properties of powders is carried out. By means of XRD diffraction and microstructure analysis, the optimal processing parameters such as melt temperature, nucleation temperature and crystalline temperature of preparing leucite crystallite have been obtained. The melt temperature is 1250 , nucleation temperature is 900 , the crystalline temperature is 1000 . By using this new process, the obtained amounts of the leucite crystalline over 40%, the size of crystalline grain is 0.8 -1.0 m. The morphology of crystalline grain on the fracture of leucite micro-crystalline glass presents tiering shape.(2) Process of preparing the porcelain powder: the leucite micro- crystalline glass is mixed into raw materials by proper proportion to obtain porcelain powder. It has been shown that the larger size of opaque porcelain is, the better the transparency, the lower the intensity and the strengthis. The grain size distribution is met the need for 0 |
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