| Ceramic is praised as "future material" for its unique properties, especially is considered to be the best choice as prosthetics materials because of its excellent biocompatibility,corrosion and abrasive resistance ,nature aesthetic traits. Now the porcelain-fused-to-metal ( PFM ) restoration has become the most commonly clinical restorative way since the matching problem between ceram and metal material was resolved in the 60s'last century.But the metal substructures exist many shortcomings such as the poor biocompatibility and poor aesthetics caused by the deposition of metal ions, the absence of nature vigour because of the poor transparence,et al. To overcome the disadvantages, all - ceram restoration which substitute the ceramic core crown for metal substructure has become the developping trend and researching focus. But the inherent brittleness and lower strength limit the all-ceram materials'application.researchers are attemping to overcome the brittleness ,enhance its fracture strength and toughness. With the developping of nanotechnology,nano-ceramic was considered to be the statistic way to resolve ceramic's brittleness. So The key idea in this study was to bring nano-materials into dental material research, combine the toughening effect of phase transformation of Zirconia and nano-particles to develop new type of Zirconia nano-ceramic composites,which have better mechanical properties and can meet the demand of prosthetics material.In addition,we try to use advanced S P S technology to develop Zirconia nano-ceramic composites for dental application,and get some benefit results. The study including:1,The preparation of ZrO2 (3Y ) nanopowder by co-precipitation under ultra-sonic radiation.In this experiment we prepared ZrO2(3Y) nanopowder which average granule diameter was D101 =15.58nm using ZrOCl 2·8H 2O and Y2 O3 as raw materials,ethanol which had low surface tension as reaction solvent under low-frequent ultro-sonic radiation; 2,The preparation of Al2O3 nanopowder by chemical-precipitation under ultra-sonic radiation.In this experiment we preparedα- Al2O3 nanopowder which average granule diameter was D202=31.44nm under the same reactive conditions above.3,The preparation of Zirconia nano-ceramic composites; Different volume percentage of ZrO2 ( 3Y ) and α- Al2O3 nanopowder was added into micronmetric ZrO2 ( 3Y ) granulated powder respectively , different test ways, including X-ray diffraction (XRD),scanning electron microscopy (SEM) ,and mechanical tests were used in this study ;4,The preparation of Zirconia nano-ceramic and nano-ceramic composites by Spark plasma sintering (SPS) method. In this experiment we prepared ZrO2(3Y) nano-ceramic and Al2O3- ZrO2(3Y) nano-ceramic composites by advanced SPS technology and tested their properties respectively.The results showed:1,We can get uniform dispersed nano-sized ZrO2 ( 3Y )andα- Al2O3 powder by chemical precipitation method under ultrasonic radiation;2,Low frequency of ultrasonic could have effective anti-agglemeration action during the preparation of nano-powder;3,Nano-powder as the additive has a well proportion,the samples mingled with 10vol % ZrO2 ( 3Y ) nano-powder and 5vol %α- Al2O3 nano-powder has the best mechanical properties in their group respectively ,the strength of three point bend and fracture toughness of the nano-ceramic composites mingled with 10vol % ZrO2 ( 3Y ) and 5vol%α- Al2O3 nano-powder were 673.17±47.19Mpa and 9.01±0.82Mpa·m1/2,659.17±46.54 Mpa and 8.55±0.89 Mpa·m1/2 respectively. Too much nano-powder worsened the mechanical properties on the contrary;4,The Zirconia ceramic sintered by SPS needed subsequence oxidation because of the deoxidation of the stabilizer ;5,Al2O3- ZrO2 (3Y) nano-ceramic composites undergone subsequence oxidation had better mechanical properties which could satisfied the demands to be dental ceramic material, the strength of three point bend and fracture toughness of the samples were633.50±51.70 Mpa and 8.25?...
|
PDF Full Text Request