Through measuring the coefficient of linear expansion, the structure and properties of the Li2O-Al2O3-SiO2 low expansion glass ceramics containing B2O3 are studied by JR and XRD. It is shoutn that the IR method is eff...Through measuring the coefficient of linear expansion, the structure and properties of the Li2O-Al2O3-SiO2 low expansion glass ceramics containing B2O3 are studied by JR and XRD. It is shoutn that the IR method is efficient in the study of the glass-ceramics structure. There is a " Boron abnormality" in the system which has an important influence on the properties of the glass-ceramics.展开更多
CaO-B203-SiO2 （CBS） glass powders are prepared by conventional glass melting method at different melting temperatures whose properties and microstructures are characterized by X-ray diffraction （XRD） and scanning ...CaO-B203-SiO2 （CBS） glass powders are prepared by conventional glass melting method at different melting temperatures whose properties and microstructures are characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. It is found that there are SiO2 and some unknown phases in CBS glass melting liquid from 1 300 ℃ to 1 500 ℃ and the amount of these phases decreases with the increase of the melting temperature. The CBS glass melted at 1 450 ℃ could be sintered from 830 ℃ to 930 ℃ and the bulk densities of the samples are all higher than 2.4 g/cm^3. From the points of the properties and energy conservation, the melting temperature of 1 450 ℃ is the optimal melting temperature. The glass ceramic sintered at 850 ℃ exhibits better dielectric properties： er=6.33, tan6=2.2×10^-3 at 10 GHz, and the major phases of the samples are CaSiO3, CaB2O4 and SiO2.展开更多
The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B203-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope （FTIR）, differential ther...The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B203-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope （FTIR）, differential thermal analysis （DTA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that with the increase of Al2O3 content the bands assigned to [SiO4] nearly disappear. Aluminum replaces silicon in the glass network, which is helpful for the formation of boron-oxygen rings. The increase of the transition temperature Tg and softening temperature Tf of PbO-B2O3-SiO2 glass ceramics leads to the increase of liquid phase precipitation temperature and promotes the structure stability in the glasses, and consequently contributes to the decreasing trend of crystallization. Densification and dielectric constants increase with the increase of Al2O3 content, but the dielectric loss is worsened. By contrast, the 3% （mass fraction） Al2O3-doped glass ceramics sintered at 725℃ have better properties of density p=2.72 g/cm3, dielectric constant Er=6.78, dielectric loss tan8=2.6×10^-3 （measured at 9.8 GHz）, which suggest that the glass ceramics can be applied in multilayer microwave devices requiring low sintering temperatures.展开更多
Li2O-Al2O3-SiO2 glass prepared from traditional melting and cooling process was investigated.The surface characteristic of LAS glass was studied by simulating tin bath with different temperature and time,and the effec...Li2O-Al2O3-SiO2 glass prepared from traditional melting and cooling process was investigated.The surface characteristic of LAS glass was studied by simulating tin bath with different temperature and time,and the effect of surface tension/viscosity ratio on flatting time was analyzed.The results demonstrated that LAS glass can polish effectively when polishing at 1 300 ℃ for 8 min,and the optimum flatting and polishing temperature was 1 250-1 300 ℃.展开更多
文摘Through measuring the coefficient of linear expansion, the structure and properties of the Li2O-Al2O3-SiO2 low expansion glass ceramics containing B2O3 are studied by JR and XRD. It is shoutn that the IR method is efficient in the study of the glass-ceramics structure. There is a " Boron abnormality" in the system which has an important influence on the properties of the glass-ceramics.
基金Project(2007AA03Z0455) supported by the National High Technology Research and Development Program of ChinaProject(BE2010194) supported by Science&Technology Pillar Program of Jiangsu Province, China+1 种基金Project(KF201103) supported by the State Key Laboratory of New Ceramic and Fine Processing, Tsinghua University, ChinaProject supported by the Priority Academic Development of Jiangsu Higher Education Institutions, China
文摘CaO-B203-SiO2 （CBS） glass powders are prepared by conventional glass melting method at different melting temperatures whose properties and microstructures are characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. It is found that there are SiO2 and some unknown phases in CBS glass melting liquid from 1 300 ℃ to 1 500 ℃ and the amount of these phases decreases with the increase of the melting temperature. The CBS glass melted at 1 450 ℃ could be sintered from 830 ℃ to 930 ℃ and the bulk densities of the samples are all higher than 2.4 g/cm^3. From the points of the properties and energy conservation, the melting temperature of 1 450 ℃ is the optimal melting temperature. The glass ceramic sintered at 850 ℃ exhibits better dielectric properties： er=6.33, tan6=2.2×10^-3 at 10 GHz, and the major phases of the samples are CaSiO3, CaB2O4 and SiO2.
基金Project(2007AA03Z0455) supported by the National High Technology Research and Development Program of ChinaProject supported by the Priority Academic Program Development of Jiangsu Higher Education Institution, China
文摘The effects of Al2O3 addition on both the sintering behavior and microwave dielectric properties of PbO-B203-SiO2 glass ceramics were investigated by Fourier transform infrared spectroscope （FTIR）, differential thermal analysis （DTA）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The results show that with the increase of Al2O3 content the bands assigned to [SiO4] nearly disappear. Aluminum replaces silicon in the glass network, which is helpful for the formation of boron-oxygen rings. The increase of the transition temperature Tg and softening temperature Tf of PbO-B2O3-SiO2 glass ceramics leads to the increase of liquid phase precipitation temperature and promotes the structure stability in the glasses, and consequently contributes to the decreasing trend of crystallization. Densification and dielectric constants increase with the increase of Al2O3 content, but the dielectric loss is worsened. By contrast, the 3% （mass fraction） Al2O3-doped glass ceramics sintered at 725℃ have better properties of density p=2.72 g/cm3, dielectric constant Er=6.78, dielectric loss tan8=2.6×10^-3 （measured at 9.8 GHz）, which suggest that the glass ceramics can be applied in multilayer microwave devices requiring low sintering temperatures.
基金Funded partly by the National Key Technology R&D Program in the 11th Five Year Plan of China(No. 2006BAJ02B00)Natural Science Foundation of Hubei Province (No.2008CDA037)
文摘Li2O-Al2O3-SiO2 glass prepared from traditional melting and cooling process was investigated.The surface characteristic of LAS glass was studied by simulating tin bath with different temperature and time,and the effect of surface tension/viscosity ratio on flatting time was analyzed.The results demonstrated that LAS glass can polish effectively when polishing at 1 300 ℃ for 8 min,and the optimum flatting and polishing temperature was 1 250-1 300 ℃.
