Transparent ceramics are at the heart of modern magneto-optical materials providing promising opportunities for Faraday isolators.1.0 at%RE:Tb3Ga5O12(rare earth(RE)=Pr,Tm,Dy)transparent ceramics were successfully prep...Transparent ceramics are at the heart of modern magneto-optical materials providing promising opportunities for Faraday isolators.1.0 at%RE:Tb3Ga5O12(rare earth(RE)=Pr,Tm,Dy)transparent ceramics were successfully prepared by air sintering and sequential HIP technique using the coprecipitated powders as the raw material.All the powders have shown to be a pure cubic terbium gallium garnet(TGG)phase and exhibit good dispersion.Additionally,a change could not be observed in particle shape with the different doped ions.After the two-step sintering,all the obtained ceramics have good optical quality,and the in-line transmittances at 1070 nm are higher than 80%.Moreover,no secondary phase can be detected from the microstructures.However,the pores which remain entrapped in the ceramics can be noted.The Verdet constant of ceramic samples is optimized by RE doping,and the Verdet constant at 632.8 nm is about−143 rad·T^(−1)·m^(−1),which is about 5%higher than that of TGG ceramics.Finally,the thermo-optical properties of 1.0 at%RE:TGG transparent ceramics are compared.The annealed TGG ceramic showed the best thermo-optical properties,and the thermally induced depolarization of 1.0 at%Ce:TGG and 1.0 at%Tm:TGG was inferior to that of annealed TGG ceramic.展开更多
研究了碱激发矿渣(alkali active slag cement,AASC)胶凝材料的介电性能。结果表明:在100℃干燥4h可以消除胶凝材料硬化浆体中自由水对其介电性能的影响。介电频谱表明:在高频区域,胶凝材料的介电常数(εr)在6～8之间,介电损耗(tanδ)在...研究了碱激发矿渣(alkali active slag cement,AASC)胶凝材料的介电性能。结果表明:在100℃干燥4h可以消除胶凝材料硬化浆体中自由水对其介电性能的影响。介电频谱表明:在高频区域,胶凝材料的介电常数(εr)在6～8之间,介电损耗(tanδ)在0.02～0.04之间;但是,干燥样品放置在相对湿度约为40%的大气环境中与水汽接触时,胶凝材料表面的毛细孔吸附空气中的水汽,饱和吸附量的质量分数(下同)约为1.2%,导致胶凝硬化浆体的εr和tanδ急剧增大。因此,通过低温干燥处理不能改善胶凝硬化浆体的吸水性能。进一步的差热分析(differential thermal analysis,DTA)和热重分析(thermogravimetry analysis,TGA)可知:100℃干燥样品中仍有2%左右的化合水,这是干燥样品tanδ仍然高于陶瓷材料的主要原因。展开更多
The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct ...The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored.The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.展开更多
基金supported by the National Key R&D Program of China(Grant No.2017YFB0310500)the NSFC-RFBR Cooperative Research Project(Grant No.61911530135)+1 种基金the Key Research Project of the Frontier Science of the Chinese Academy of Sciences(No.QYZDB-SSW-JSC022)supported partially by the Ministry of High Education and Science of the Russian Federation and the State Task executed in the Institute of Applied Physics RAS(Project No.00352019-0015)。
文摘Transparent ceramics are at the heart of modern magneto-optical materials providing promising opportunities for Faraday isolators.1.0 at%RE:Tb3Ga5O12(rare earth(RE)=Pr,Tm,Dy)transparent ceramics were successfully prepared by air sintering and sequential HIP technique using the coprecipitated powders as the raw material.All the powders have shown to be a pure cubic terbium gallium garnet(TGG)phase and exhibit good dispersion.Additionally,a change could not be observed in particle shape with the different doped ions.After the two-step sintering,all the obtained ceramics have good optical quality,and the in-line transmittances at 1070 nm are higher than 80%.Moreover,no secondary phase can be detected from the microstructures.However,the pores which remain entrapped in the ceramics can be noted.The Verdet constant of ceramic samples is optimized by RE doping,and the Verdet constant at 632.8 nm is about−143 rad·T^(−1)·m^(−1),which is about 5%higher than that of TGG ceramics.Finally,the thermo-optical properties of 1.0 at%RE:TGG transparent ceramics are compared.The annealed TGG ceramic showed the best thermo-optical properties,and the thermally induced depolarization of 1.0 at%Ce:TGG and 1.0 at%Tm:TGG was inferior to that of annealed TGG ceramic.
基金supported by the National Natural Science Foundation of China (Grants 11372308, 11372307)the Fundamental Research Funds for the Central Universities (Grant WK2480000001)
文摘The seemingly contradictory understandings of the initial crush stress of cellular materials under dynamic loadings exist in the literature, and a comprehensive analysis of this issue is carried out with using direct information of local stress and strain. Local stress/strain calculation methods are applied to determine the initial crush stresses and the strain rates at initial crush from a cell-based finite element model of irregular honeycomb under dynamic loadings. The initial crush stress under constant-velocity compression is identical to the quasi-static one, but less than the one under direct impact, i.e. the initial crush stresses under different dynamic loadings could be very different even though there is no strain-rate effect of matrix material. A power-law relation between the initial crush stress and the strain rate is explored to describe the strain-rate effect on the initial crush stress of irregular honeycomb when the local strain rate exceeds a critical value, below which there is no strain-rate effect of irregular honeycomb. Deformation mechanisms of the initial crush behavior under dynamic loadings are also explored.The deformation modes of the initial crush region in the front of plastic compaction wave are different under different dynamic loadings.
