Microwave sintering is being developed as a novel technique for the preparation of dense structural ceramics,but the mature theory has not been established due to the technical difficulties.The synchrotron radiation X...Microwave sintering is being developed as a novel technique for the preparation of dense structural ceramics,but the mature theory has not been established due to the technical difficulties.The synchrotron radiation X-ray computed tomography(SR-CT) technique was introduced for the first time into the study of microwave sintering to in-situ observe the microstructure evolution of silicon carbide(SiC) material in this paper.By applying the SR-CT technique,the reconstructed 2D and 3D images of the specimen were obtained and the double logarithm curve of mean neck size and time(Ln(x)-Ln(t)) were obtained from these reconstructed images.Various sintering phenomena including sintering neck growth during microwave treatment were observed from the reconstructed images.Furthermore,the differences in microstructure evolution and sintering kinetics between microwave and conventional sintering were analyzed based on the reconstructed images and the Ln(x)-Ln(t) curve.1) The sharp surface of grains near the contact region distinctly grew blunt and the sintering neck growth between these grains were obviously observed at the early stage.Besides,the larger particles grew faster than smaller ones.The main reason for these phenomena may be the micro-focusing effect of electric fields.2) During each of the three sintering stages,the sintering kinetics curve of double logarithm relationship between mean neck size and time shows a good linear relationship,but at the middle stage the slope of the curve increases dramatically,which is quite larger than conventional sintering.The preliminary interpretation for these extraordinary phenomena has been discussed in details.展开更多
外伤、肿瘤、先天畸形、重度牙周病导致的严重牙槽骨及牙列缺损,不仅可影响患者的面型和咀嚼、发音等生理功能,还可造成患者心理障碍。因此,较完善地修复颌骨软硬组织缺损并重建咬合功能十分必要。活动义齿修复重度颌骨缺损的效果较差,...外伤、肿瘤、先天畸形、重度牙周病导致的严重牙槽骨及牙列缺损,不仅可影响患者的面型和咀嚼、发音等生理功能,还可造成患者心理障碍。因此,较完善地修复颌骨软硬组织缺损并重建咬合功能十分必要。活动义齿修复重度颌骨缺损的效果较差,且连续缺牙伴重度骨缺损患者亦不是固定桥修复的适应证。种植修复由于能最大限度恢复患者口腔功能并获得理想的美学效果,目前已成为修复牙列缺损和缺失的首要方法,但当患者伴较严重的牙槽骨缺损时,需通过合适的骨增量技术重建缺牙区骨组织,这是保证治疗成功的重要前提[1]。本课题组联合应用牵张成骨、块状骨移植、引导骨再生(guided bone regeneration,GBR)等骨增量技术并复合浓缩生长因子(concentrated growth factor,CGF)及软组织移植技术,治疗外伤后前牙区牙列缺损伴上下颌软硬组织缺损患者一例,患者面部外形和咀嚼功能恢复均取得较满意的效果,现报道如下。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos 10902108, 10732080, 10872190)the National Basic Research Program of China ("973" Project) (Grant No 2007CB936800)
文摘Microwave sintering is being developed as a novel technique for the preparation of dense structural ceramics,but the mature theory has not been established due to the technical difficulties.The synchrotron radiation X-ray computed tomography(SR-CT) technique was introduced for the first time into the study of microwave sintering to in-situ observe the microstructure evolution of silicon carbide(SiC) material in this paper.By applying the SR-CT technique,the reconstructed 2D and 3D images of the specimen were obtained and the double logarithm curve of mean neck size and time(Ln(x)-Ln(t)) were obtained from these reconstructed images.Various sintering phenomena including sintering neck growth during microwave treatment were observed from the reconstructed images.Furthermore,the differences in microstructure evolution and sintering kinetics between microwave and conventional sintering were analyzed based on the reconstructed images and the Ln(x)-Ln(t) curve.1) The sharp surface of grains near the contact region distinctly grew blunt and the sintering neck growth between these grains were obviously observed at the early stage.Besides,the larger particles grew faster than smaller ones.The main reason for these phenomena may be the micro-focusing effect of electric fields.2) During each of the three sintering stages,the sintering kinetics curve of double logarithm relationship between mean neck size and time shows a good linear relationship,but at the middle stage the slope of the curve increases dramatically,which is quite larger than conventional sintering.The preliminary interpretation for these extraordinary phenomena has been discussed in details.
文摘外伤、肿瘤、先天畸形、重度牙周病导致的严重牙槽骨及牙列缺损,不仅可影响患者的面型和咀嚼、发音等生理功能,还可造成患者心理障碍。因此,较完善地修复颌骨软硬组织缺损并重建咬合功能十分必要。活动义齿修复重度颌骨缺损的效果较差,且连续缺牙伴重度骨缺损患者亦不是固定桥修复的适应证。种植修复由于能最大限度恢复患者口腔功能并获得理想的美学效果,目前已成为修复牙列缺损和缺失的首要方法,但当患者伴较严重的牙槽骨缺损时,需通过合适的骨增量技术重建缺牙区骨组织,这是保证治疗成功的重要前提[1]。本课题组联合应用牵张成骨、块状骨移植、引导骨再生(guided bone regeneration,GBR)等骨增量技术并复合浓缩生长因子(concentrated growth factor,CGF)及软组织移植技术,治疗外伤后前牙区牙列缺损伴上下颌软硬组织缺损患者一例,患者面部外形和咀嚼功能恢复均取得较满意的效果,现报道如下。
