Amodel was preseted for calcultaing the thermal impedance of the insulation and refractory linings of rectangular microwave ovens,of which the oven cavity's dimensions are relatively small,while the linings re rel...Amodel was preseted for calcultaing the thermal impedance of the insulation and refractory linings of rectangular microwave ovens,of which the oven cavity's dimensions are relatively small,while the linings re relatively thick.展开更多
Effectiveness of microwave sintering process through investigation of microstructural characteristics and electrical properties of x(0.94PbZn_ 1/3Nb_ 2/3O_3 + 0.06BaTiO_3)+(1-x)PbZr_yTi_ 1-yO_3(PBZNZT)ceramics with x=...Effectiveness of microwave sintering process through investigation of microstructural characteristics and electrical properties of x(0.94PbZn_ 1/3Nb_ 2/3O_3 + 0.06BaTiO_3)+(1-x)PbZr_yTi_ 1-yO_3(PBZNZT)ceramics with x=0.6 and y=0.52 was evaluated.The relative density of 95% was achieved with sintering at 800℃ for 2 h.The small grain growth exponents indicate how easy the grain growth in these materials sintered using microwave radiation.Grain growth rate increases abruptly and is higher than that of conventional sintering at a temperature higher than 1050℃.This is attributed to the lower activation energy and higher grain boundary mobility.The activation energy required for the grain growth is found to be 132kJ/mol.Higher remanent polarization(Pr=50.1μC/cm2)and increase in remanent polarization with sintering temperature are observed in microwave sintering process when compared to that of conventional sintering process,due to fast increase in grain growth rate and homogeneity in the specimen.The results indicate lower sintering energy and reduction of PbO pollution in the working environment by microwave sintering process.展开更多
Si3N4 powder and hot-pressed Si3N4 ceramics added with Al2O3 are used for investigate their oxidation behvior in air and nitrogen atmosphere(with oxygen partial pressure PO2=1-10Pa),The oxidation products of Si3N4 are...Si3N4 powder and hot-pressed Si3N4 ceramics added with Al2O3 are used for investigate their oxidation behvior in air and nitrogen atmosphere(with oxygen partial pressure PO2=1-10Pa),The oxidation products of Si3N4 are examined by chemical analysi,X-ray diffraction (XRD) and XPS method,Also, thermodynamic calculation is made to analyze oxidation behavior of Si3N4.The results show that only passive oxidation will occur when Si3N4 is oxidized in air at high temperature,whereas in N2 at high temperature,the active oxidation is dominant in spite of the existence of a little passive oxidation.展开更多
Spherical zirconia particles formed by coagulation of colloidal particles in zirconia aqueous sol followed by calcination.The zirconia sol was prepared from zirconium oxychloride aqueous solution by adjusting its pH v...Spherical zirconia particles formed by coagulation of colloidal particles in zirconia aqueous sol followed by calcination.The zirconia sol was prepared from zirconium oxychloride aqueous solution by adjusting its pH value.The coag-ulation resulted from addition of preopanol in the sol the coagulation mechanism was discussed based on collicd theory.展开更多
文摘Amodel was preseted for calcultaing the thermal impedance of the insulation and refractory linings of rectangular microwave ovens,of which the oven cavity's dimensions are relatively small,while the linings re relatively thick.
文摘Effectiveness of microwave sintering process through investigation of microstructural characteristics and electrical properties of x(0.94PbZn_ 1/3Nb_ 2/3O_3 + 0.06BaTiO_3)+(1-x)PbZr_yTi_ 1-yO_3(PBZNZT)ceramics with x=0.6 and y=0.52 was evaluated.The relative density of 95% was achieved with sintering at 800℃ for 2 h.The small grain growth exponents indicate how easy the grain growth in these materials sintered using microwave radiation.Grain growth rate increases abruptly and is higher than that of conventional sintering at a temperature higher than 1050℃.This is attributed to the lower activation energy and higher grain boundary mobility.The activation energy required for the grain growth is found to be 132kJ/mol.Higher remanent polarization(Pr=50.1μC/cm2)and increase in remanent polarization with sintering temperature are observed in microwave sintering process when compared to that of conventional sintering process,due to fast increase in grain growth rate and homogeneity in the specimen.The results indicate lower sintering energy and reduction of PbO pollution in the working environment by microwave sintering process.
文摘Si3N4 powder and hot-pressed Si3N4 ceramics added with Al2O3 are used for investigate their oxidation behvior in air and nitrogen atmosphere(with oxygen partial pressure PO2=1-10Pa),The oxidation products of Si3N4 are examined by chemical analysi,X-ray diffraction (XRD) and XPS method,Also, thermodynamic calculation is made to analyze oxidation behavior of Si3N4.The results show that only passive oxidation will occur when Si3N4 is oxidized in air at high temperature,whereas in N2 at high temperature,the active oxidation is dominant in spite of the existence of a little passive oxidation.
文摘Spherical zirconia particles formed by coagulation of colloidal particles in zirconia aqueous sol followed by calcination.The zirconia sol was prepared from zirconium oxychloride aqueous solution by adjusting its pH value.The coag-ulation resulted from addition of preopanol in the sol the coagulation mechanism was discussed based on collicd theory.
