ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, ...ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.展开更多
In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular s...In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.展开更多
Sintering kinetics have been found to be effective in judging the evolution of ceramics.By using magnesium oxide-partially stabilized zirconia(Mg-PSZ)powder prepared by co-precipitation as raw materials,the evolution ...Sintering kinetics have been found to be effective in judging the evolution of ceramics.By using magnesium oxide-partially stabilized zirconia(Mg-PSZ)powder prepared by co-precipitation as raw materials,the evolution of densification and grain growth for Mg-PSZ ceramics were investigated.The results indicated that the densification of samples was mainly controlled by grain boundary diffusion in intermediate sintering stage.During the sintering process,the grain growth mechanisms included normal grain growth,abnormal grain growth and solid solution drag-controlled grain growth.Interestingly,the apparent activation energy for grain growth of Mg-PSZ ceramics is lower than that of ZrO_(2)–Y_(2)O_(3)ceramics in the solid solution drag-controlled grain grow process,which will cause grain to grow easily.The sintering kinetics and microstructure of Mg-PSZ ceramics were studied,and the kinetic equation of grain growth at different temperatures was established.The results show that the strength difference between Mg-PSZ and yttrium oxide-stabilized zirconia is closely related to the easy grain growth of Mg-PSZ ceramics.展开更多
基金financially supported by National Natural Science Foundation of China(Grant No.51372193)Natural Science Basic Research Fund of Shaanxi Province(Grant No.2014JM6224)
文摘ZrO2 sizing nozzles with a basic Jormulation were prepared using 45% （by mass, the same hereinafter ） （ Mg, Y） - PSZ aggregate, 55% （ Mg, Y） - PSZ fines and 5% PVA binder. Al2O3 - ZrO2 composite powders （ 3%, 6%, 9% and 12% ） prepared by sol - gel method were added to replace the equal amount of （ Mg, Y） - PSZfines. Effects of Al2O3 - ZrO2 composite powders on physical properties, phase composition and microstructure of the ZrO2 sizing nozzles were studied. The results show that： the performances of the modified sizing nozzles with 3% Al2O3 - ZrO2 composite powder are better than those of the nobles without composite powder used in current production process, and the thermal shock resistance of the ,former nozzles is six times of that of the latter one.
基金financially supported by the Science Foundation for International Cooperation of Sichuan Province (2014HH0016)the Fundamental Research Funds for the Central Universities (SWJTU2014: A0920502051113-10000)National Magnetic Confinement Fusion Science Program (2011GB112001)
文摘In this study, finite element analysis （FEA） has been used to investigate the effects of different Laval nozzle throat sizes on supersonic molecular beam. The simulations indicate the Mach numbers of the molecular stream peak at different positions along the center axis of the beam, which correspond to local minimums of the molecular densities. With the increase of the throat diameter, the first peak of the Mach number increases first and then decreases, while that of the molecular number density increases gradually. Moreover, both first peaks shift progressively away from the throat. At the last part, we discuss the possible applications of our FEA approach to solve some crucial problems met in modern transportations.
基金The work has been supported by the National Key Research and Development Program of China(No.2017YFB0310401)National Natural Science Foundation of China(Nos.U1908227 and U20A20239).
文摘Sintering kinetics have been found to be effective in judging the evolution of ceramics.By using magnesium oxide-partially stabilized zirconia(Mg-PSZ)powder prepared by co-precipitation as raw materials,the evolution of densification and grain growth for Mg-PSZ ceramics were investigated.The results indicated that the densification of samples was mainly controlled by grain boundary diffusion in intermediate sintering stage.During the sintering process,the grain growth mechanisms included normal grain growth,abnormal grain growth and solid solution drag-controlled grain growth.Interestingly,the apparent activation energy for grain growth of Mg-PSZ ceramics is lower than that of ZrO_(2)–Y_(2)O_(3)ceramics in the solid solution drag-controlled grain grow process,which will cause grain to grow easily.The sintering kinetics and microstructure of Mg-PSZ ceramics were studied,and the kinetic equation of grain growth at different temperatures was established.The results show that the strength difference between Mg-PSZ and yttrium oxide-stabilized zirconia is closely related to the easy grain growth of Mg-PSZ ceramics.
