CaZrO3 powder was prepared using CaO,CaCO3 and Ca(OH)2 as calcium source,nano m-ZrO2 powder,micron m-ZrO2 powder,micron CaO partially stabilized ZrO2(Ca-PSZ)powder as zircon source,through high temperature solid react...CaZrO3 powder was prepared using CaO,CaCO3 and Ca(OH)2 as calcium source,nano m-ZrO2 powder,micron m-ZrO2 powder,micron CaO partially stabilized ZrO2(Ca-PSZ)powder as zircon source,through high temperature solid reaction.Effect of the calcination temperature(800,900,1000,1100,1200,1300,1400,1500,and 1600℃)and the holding time(3,4,and 5 h)on the phase composition change was studied to research the synthesis mechanism.The synthesized CaZrO3 powder was mixed with CaO,MgO,Al2O3,Cr2O3,SiO2,and ZrO2 powder separately and fired at 1500℃for 3 h to prepare specimens to research the high temperature chemical stability of CaZrO3 with different reaction mediums.The results show that during the synthesis process,the CaZrO3 content does not always increase with the increasing calcination temperature or the prolonging holding time,CaZrO3 decomposes resulting from the diffusion of Ca2+and O2-in CaZrO3 to m-ZrO2 or c-ZrO2.At high temperatures,when CaZrO3 is in alkaline environment(such as environment containing CaO or MgO),the high temperature chemical stability is high,but when CaZrO3 is not in alkaline environment(such as environment containing Al2O3,Cr2O3,SiO2 or ZrO2),the high temperature chemical stability is low.展开更多
The sintering temperature decreases theoretically with the grain size of the ceramic powders,but it is not always right for fine grain sized nanopowders due to the inevitable agglomerations,and thus pores are hard to ...The sintering temperature decreases theoretically with the grain size of the ceramic powders,but it is not always right for fine grain sized nanopowders due to the inevitable agglomerations,and thus pores are hard to eliminate thoroughly during sintering.To overcome this difficulty,a new approach is designed to sintering ceramics at low temperature from nanoparticles.In this scheme,excessive dopants,such as ZnO,are synthesized into the nanoparticles,and they would be liberated again on the surfaces of the grains at high temperature as sintering aids homogenously to promote densification.Here,we compared the ceramic sintering of ZnO-doped barium zirconate titanate (BaZrxTil-xO3,BZT) nanoparticles with BZT nanoparticles using ZnO as additive at 1150 ℃.Both kinds of nanoparticles were directly synthesized by the same process at room temperature and yielded the same initial grain size of～10 nm.The dense BZT ceramic with relative density of 99％ was fabricated from the 2 mol％ ZnO-doped nanoparticles.On the other hand,the porous BZT ceramic with density of 78％ was obtained from nanoparticles with 2 mol％ ZnO as additive.Therefore,our strategy to ceramic sintering at low temperature from nanoparticles was confirmed.展开更多
基金supported by Hebei Iron and Steel Joint Fund, China (No.E2014209273)
文摘CaZrO3 powder was prepared using CaO,CaCO3 and Ca(OH)2 as calcium source,nano m-ZrO2 powder,micron m-ZrO2 powder,micron CaO partially stabilized ZrO2(Ca-PSZ)powder as zircon source,through high temperature solid reaction.Effect of the calcination temperature(800,900,1000,1100,1200,1300,1400,1500,and 1600℃)and the holding time(3,4,and 5 h)on the phase composition change was studied to research the synthesis mechanism.The synthesized CaZrO3 powder was mixed with CaO,MgO,Al2O3,Cr2O3,SiO2,and ZrO2 powder separately and fired at 1500℃for 3 h to prepare specimens to research the high temperature chemical stability of CaZrO3 with different reaction mediums.The results show that during the synthesis process,the CaZrO3 content does not always increase with the increasing calcination temperature or the prolonging holding time,CaZrO3 decomposes resulting from the diffusion of Ca2+and O2-in CaZrO3 to m-ZrO2 or c-ZrO2.At high temperatures,when CaZrO3 is in alkaline environment(such as environment containing CaO or MgO),the high temperature chemical stability is high,but when CaZrO3 is not in alkaline environment(such as environment containing Al2O3,Cr2O3,SiO2 or ZrO2),the high temperature chemical stability is low.
文摘The sintering temperature decreases theoretically with the grain size of the ceramic powders,but it is not always right for fine grain sized nanopowders due to the inevitable agglomerations,and thus pores are hard to eliminate thoroughly during sintering.To overcome this difficulty,a new approach is designed to sintering ceramics at low temperature from nanoparticles.In this scheme,excessive dopants,such as ZnO,are synthesized into the nanoparticles,and they would be liberated again on the surfaces of the grains at high temperature as sintering aids homogenously to promote densification.Here,we compared the ceramic sintering of ZnO-doped barium zirconate titanate (BaZrxTil-xO3,BZT) nanoparticles with BZT nanoparticles using ZnO as additive at 1150 ℃.Both kinds of nanoparticles were directly synthesized by the same process at room temperature and yielded the same initial grain size of～10 nm.The dense BZT ceramic with relative density of 99％ was fabricated from the 2 mol％ ZnO-doped nanoparticles.On the other hand,the porous BZT ceramic with density of 78％ was obtained from nanoparticles with 2 mol％ ZnO as additive.Therefore,our strategy to ceramic sintering at low temperature from nanoparticles was confirmed.
