The samples were attained through altering the cooling system of producing glass-ceramics. The X-ray diffraction was used to test the stress value of different samples. The relation of the cooling system and internal ...The samples were attained through altering the cooling system of producing glass-ceramics. The X-ray diffraction was used to test the stress value of different samples. The relation of the cooling system and internal stress were also investigated. The experimental results show that the stress of glass-ceramic had a close relation with starting cool temperature. Above 800 ~C, glass-ceramic could be accelerated cooling and did not bring stress. Temperature between 500 ℃ and 800℃ was an important temperature range of the formation of stress in glass-ceramic, in which the glass-ceramic stress would change obviously. Cool system was the key on how to control and eliminate internal stress in order to reduce the destroy of materials crated by internal stress. In addition, glass particles size increase, glass-ceramic stress increase in consequent.展开更多
The crystallization behavior and mechanical properties of CaO-Al2O3-SiO2 (CAS) system glass-ceramics with addition of Y2O3 were investigated. The optimal sintering temperatures of all heat-treated glasses were altered...The crystallization behavior and mechanical properties of CaO-Al2O3-SiO2 (CAS) system glass-ceramics with addition of Y2O3 were investigated. The optimal sintering temperatures of all heat-treated glasses were altered and the crystallization was accelerated with Y2O3 addition, and only wollastonite as a main crystalline phase was precipitated. The volume fraction of crystalline phase and density were increased with Y2O3 addition. The results suggest that the CAS glass-ceramics would get the lowest sintering temperature and optimal microstructure with the addition of Y2O3 by 3.25 %. The bending strength has a maximum due to the oriented and interlocked wollastonite crystal, which causes crack divert or blunts to limit the further development of the flaw size and increases the surface energy of fracture.展开更多
In order to study the relationship between thickness and residual stress in CaO-Al2O3-SiO2 glass-ceramics.The residual stress was measured in CaO-Al2O3-SiO2 system glass-ceramic with different thickness,and the format...In order to study the relationship between thickness and residual stress in CaO-Al2O3-SiO2 glass-ceramics.The residual stress was measured in CaO-Al2O3-SiO2 system glass-ceramic with different thickness,and the formation mechanism and characterization of residual stress in CAS system Glass-ceramic were analyzed by the X-ray diffraction analysis.The experimental results show the compressive residual stress increass with thickness of glass-ceramic increasing.展开更多
The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from tha...The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from that with Sr substitution, which indicates the existence of orthorhombic phase in the latter ones. TEM bright field observation shows nanosized microstructures, while for samples with Sr, typical eutectic microstrncture with separated crystallized bands is found in the glass matrix. Dielectric properties measurement of the samples indicates an obvious improvement of dielectric constant, dielectric loss, DC field and temperature dependence of dielectric constant when the molar ratio of Sr to Pb is 4：6.展开更多
Na2O-Al2O3-SiO2 glass-ceramics doped with Er^3＋ ions were synthesized by the conventional melt quenching technique at a low melting temperature.The samples were characterized by differential scanning calorimetry（DSC...Na2O-Al2O3-SiO2 glass-ceramics doped with Er^3＋ ions were synthesized by the conventional melt quenching technique at a low melting temperature.The samples were characterized by differential scanning calorimetry（DSC）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,UV-vis-NIR scanning spectrophotometry,and fluorescence spectrometry.The results show that the main crystalline phase of glass-ceramics is nepheline.The best heat-treatment process is at 520 ℃ for 2 h.Because the up-conversion luminescence and near infrared luminescence properties of glass doped with Eu^3＋ are studied in detail.展开更多
ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient t...ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient temperature furnace, DTA and XRD. Then, sintering process of the glass-ceramics was investigated by testing sintering shrinkage, dielectric constant and loss. The experimental results shows that the glass-ceramics doped with nucleating additives represents higher crystallization, with ZrO2 as an exceptional effective dopant to promote the precipitation of wollastonite crystal. Finally, ZrO2 containing glass-ceramics was chosen to study the influence of sintering temperature and soaking time with the help of X-ray diffraction analysis and density measurement. The glass-ceramics can be well consolidated at 850 ℃ for 10 min, with low dielectric constant （5.87） and loss （3.21×10^-4）, which is desirable for LTCC application.展开更多
X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of differ...X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.展开更多
基金National Natural Science Foundation of China(50272043)Natural Science Foundation of Hubei Province(2002AB077)+1 种基金Natural Science Foundation of Wuhan University of Technology(2003XJJ013)Natural Science Foundation of Key Laboratory of Silicate Materials Science and Engineering of Ministry of Education,Wuhan University of Technology
文摘The samples were attained through altering the cooling system of producing glass-ceramics. The X-ray diffraction was used to test the stress value of different samples. The relation of the cooling system and internal stress were also investigated. The experimental results show that the stress of glass-ceramic had a close relation with starting cool temperature. Above 800 ~C, glass-ceramic could be accelerated cooling and did not bring stress. Temperature between 500 ℃ and 800℃ was an important temperature range of the formation of stress in glass-ceramic, in which the glass-ceramic stress would change obviously. Cool system was the key on how to control and eliminate internal stress in order to reduce the destroy of materials crated by internal stress. In addition, glass particles size increase, glass-ceramic stress increase in consequent.
文摘The crystallization behavior and mechanical properties of CaO-Al2O3-SiO2 (CAS) system glass-ceramics with addition of Y2O3 were investigated. The optimal sintering temperatures of all heat-treated glasses were altered and the crystallization was accelerated with Y2O3 addition, and only wollastonite as a main crystalline phase was precipitated. The volume fraction of crystalline phase and density were increased with Y2O3 addition. The results suggest that the CAS glass-ceramics would get the lowest sintering temperature and optimal microstructure with the addition of Y2O3 by 3.25 %. The bending strength has a maximum due to the oriented and interlocked wollastonite crystal, which causes crack divert or blunts to limit the further development of the flaw size and increases the surface energy of fracture.
文摘In order to study the relationship between thickness and residual stress in CaO-Al2O3-SiO2 glass-ceramics.The residual stress was measured in CaO-Al2O3-SiO2 system glass-ceramic with different thickness,and the formation mechanism and characterization of residual stress in CAS system Glass-ceramic were analyzed by the X-ray diffraction analysis.The experimental results show the compressive residual stress increass with thickness of glass-ceramic increasing.
文摘The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from that with Sr substitution, which indicates the existence of orthorhombic phase in the latter ones. TEM bright field observation shows nanosized microstructures, while for samples with Sr, typical eutectic microstrncture with separated crystallized bands is found in the glass matrix. Dielectric properties measurement of the samples indicates an obvious improvement of dielectric constant, dielectric loss, DC field and temperature dependence of dielectric constant when the molar ratio of Sr to Pb is 4：6.
基金Funded by the National High Technology Research and Development Program of China(No.2011AA030204)Key Research Project of Jilin Provincial Science and Technology Department(No.20150204051GX)
文摘Na2O-Al2O3-SiO2 glass-ceramics doped with Er^3＋ ions were synthesized by the conventional melt quenching technique at a low melting temperature.The samples were characterized by differential scanning calorimetry（DSC）,X-ray diffraction（XRD）,scanning electron microscopy（SEM）,UV-vis-NIR scanning spectrophotometry,and fluorescence spectrometry.The results show that the main crystalline phase of glass-ceramics is nepheline.The best heat-treatment process is at 520 ℃ for 2 h.Because the up-conversion luminescence and near infrared luminescence properties of glass doped with Eu^3＋ are studied in detail.
基金Funded by the Shanghai Leading Academic Discipline Project (B502)Shanghai Key Laboratory Project (08DZ2230500)
文摘ZrO2, TiO2 and P2O5 were doped in CaO-B2O3-SiO2 glass-ceramics as nucleating additives. Effects of different nucleating additives on the phase separation and crystalline behaviors were investigated by using gradient temperature furnace, DTA and XRD. Then, sintering process of the glass-ceramics was investigated by testing sintering shrinkage, dielectric constant and loss. The experimental results shows that the glass-ceramics doped with nucleating additives represents higher crystallization, with ZrO2 as an exceptional effective dopant to promote the precipitation of wollastonite crystal. Finally, ZrO2 containing glass-ceramics was chosen to study the influence of sintering temperature and soaking time with the help of X-ray diffraction analysis and density measurement. The glass-ceramics can be well consolidated at 850 ℃ for 10 min, with low dielectric constant （5.87） and loss （3.21×10^-4）, which is desirable for LTCC application.
文摘X-ray powder diffraction and Fourier transform infrared spectroscopy were applied for characterization of Li2O-Al2O3-SiO2 glass-ceramic powders doped with Eu2O3,Gd2O3 and Er2O3,respectively,in the conditions of different heat-treatment temperatures and with various amounts.The powders were derived from the polyacrylamide gel method.The results show that,the wet gels prepared by polyacrylamide perform a unique crystallization behavior in the process of drying,comparing with some customary preparation such as melt processing.The main crystal phase and crystallization sequence of Li2O-Al2O3-SiO2 micro-powders have no distinct with addition of Eu2O3,Gd2O3 or Er2O3,while the crystallization temperature of the β-spodumene decreased and the amount of the β-spodumene increased.
