B2O3-Al2O3-SiO2系微晶玻璃析晶动力学研究

采用差示扫描量热（DSC）分析法对B2O3-Al2O3-SiO2系统微晶玻璃的析晶动力学参数进行了测定，研究了该系统微晶玻璃的析晶动力学。结果表明：随着B2O3/SiO2比的降低，该系统玻璃的析晶活化能E呈先升高后降低的变化趋势，当B2O3/SiO2比为11：5时，析晶活化能最小，Emin=375．4kJ／mol，晶化指数n则先减小后增大，但均〉4，表明该系统玻璃可整体析晶。     

Crystal growth of tetragonal ZrO2 in the glass system ZrO2-SiO2 prepared by the sol-gel process from metal alkoxides

Glasses in the system ZrO₂-SiO₂ containing 40 to 60 mol % ZrO₂ were prepared by the sol-gel process from metal alkoxides. Tetragonal ZrO₂ was precipitated by heat treatment at 800 and 1200° C, and its crystal growth was measured by differential thermal and X-ray diffraction analyses. At 800 to 900° C, tetragonal ZrO₂ crystals grew three-dimensionally and the activation energy for growth was calculated as about 680 kJ mol⁻¹. On the other hand, the secondary growth of tetragonal ZrO₂ at 1000 to 1200° C followed the cube-root-of-time law. The activation energy for secondary growth was about 380 kJ mol⁻¹. It is suggested that the diffusion of Zr⁴⁺ ions is the rate-limiting process for the secondary crystal growth of tetragonal ZrO₂.     

B2O3-Al2O3-SiO2透明玻璃陶瓷研究

玻璃陶瓷属于一类多晶陶瓷材料.通过调整玻璃基质和晶相组成可以制备出具有良好的力学、热学、电学和光学性能的玻璃陶瓷材料.采用传统的熔融和退火技术制备出含B2O3-Al2O3-SiO2-Li2O-K2O组分的硼铝硅玻璃,并通过成核和长晶工艺最终制备出透明玻璃陶瓷.配合料在铂金坩埚中于1450℃下熔融2h,然后经两步热处理制度控制晶核的生成和晶粒的长大.采用差热分析技术确定成核和长晶温度.采用X射线衍射技术对不同热处理制度下的玻璃陶瓷样品进行分析,以确定最佳成核和长晶条件.采用扫描电子显微镜分析玻璃陶瓷形态,晶粒尺寸及其在残余玻璃相中的分布.采用UV-Vis-Nir分光光度计测定玻璃陶瓷样品的透过率.     

Luminescence of nanostructured SnO2-SiO2 glass-ceramics prepared by sol-gel method

Nanostructured silica based glass-ceramics samples of composition (100 - x)SiO2-xSnO2, with x from 1 to 10, have been synthesized by thermal treatment of precursor sol-gel glasses. The average size of the obtained SnO2 nanocrystals, calculated by using the X-ray diffraction, can be predetermined by using well-controlled concentration of tin precursor. The mean radius ranging from 1.6 to 5.5 nm, is comparable to the exciton Bohr radius, corresponding to wide band-gap semiconductor quantum-dots in an insulator SiO2 glass. A spectroscopy study in terms of optical absorption and photoluminescence spectra has been carried out as a function of SnO2 concentration. Size-dependent red-shifts of excitation and emission bands, with increasing of tin precursor concentration, point to the quantum confinement effect. The nanocrystal sizes have been obtained and compared by using the Brus and Scherrer equations. The band gap increase is in agreement with results, based on the effective mass model. The recombination of conduction band electron with oxygen vacancies is proposed to explain the luminescence red-shift.     

The infrared and Raman spectra of ZrO2-SiO2 glasses prepared by a sol-gel process

Infrared and Raman spectra were measured and interpreted on the basis of structure for various ZrO₂-SiO₂ glasses that were prepared by a sol-gel process involving zirconium nitrate. Interpretation of the spectra indicates the presence of both Zr-O-Si and Si-O-H linkages depending upon heat treatment conditions, and the evidence of zirconium atoms with eight fold coordination for glasses with high ZrO₂ contents. The crystalline products formed during glass devitrification were monitored by vibrational spectra. The formation and detection of tetragonal ZrO₂, zircon, monoclinic ZrO₂ and -cristobalite depended upon the conditions of devitrification.     

Transparency of LiTaO3-SiO2-Al2O3 glass-ceramics in relation to their microstructure

The glasses with various compositions in the LiTaO₃-SiO₂-Al₂O₃ system were heated from room temperature to temperatures ranging from 750° to 1050° C at a rate of 5° C min^–1. From the glasses in the LiTaO₃-SiO₂ system no transparent glass-ceramic was obtained even when their LiTaO₃/SiO₂ mole ratios were as high as 2.33. The diameter and number of the LiTaO₃ crystal grains precipitated in the glasses were 5–15 m and 10⁸–10¹⁰ grains cm^–3, respectively. On the contrary, transparent glass-ceramics were obtained from the glasses containing Al₂O₃; their compositions covered a fairly large area in the LiTaO₃-SiO₂ -Al₂O₃ system, which encompasses the compositions with the LiTaO₃/SiO₂+AlO_1.5 mole ratio as low as 0.25. The diameter and number of the LiTaO₃ crystal grains precipitated in the transparent glass-ceramics were as small as 10–20 nm and as many as 10¹⁶–10¹⁸ grains cm^–3, respectively. High nucleation rates of the LiTaO₃ crystals in the Al₂O₃-containing glasses were interpreted in terms of structural inflexibility induced in the glass-network by the addition of Al₂O₃ to the LiTaO₃-SiO₂ system.     

Hot isostatic pressing of tetragonal ZrO2 solid-solution powders prepared from acetylacetonates in the system ZrO2-Y2O3-Al2O3

In compositions having ZrO₂/Y₂O₃=(74.25–71.25)/(0.75–3.75) (mol% ratio) with 25 mol% Al₂O₃, metastable t-ZrO₂ solid solutions crystallize at 780° to 860°C from amorphous materials prepared by the simultaneous hydrolysis of zirconium, yttrium and aluminium acetylacetonates. Hot isostatic pressing has been performed for 1 h at 1130 and 1230°C under 196 MPa using their powders. Two kinds of material are fabricated: (i) perfect ZrO₂ solid-solution ceramics and (ii) composites of ZrO₂ solid solution and -Al₂O₃. Their mechanical properties are examined, in connection with microstructures and t/m ZrO₂ ratios. Composites with a homogeneous dispersed -Al₂O₃ derived from solid-solution ceramics result in a remarkable increase of strength.     

Sm3+:ZnO-B2O3-Al2O3-SiO2系透明玻璃陶瓷的制备和表征

采用熔融和晶化技术合成出含ZnAl2O4微晶的Sm3+:ZnO-B2O3-Al2O3-SiO2(ZBAS)玻璃陶瓷材料,并通过DSC、XRD、SEM和UV-Vis-Nir分光光度计和傅里叶变换荧光光谱仪等对样品进行了表征.结果表明,玻璃陶瓷主晶相为ZnAl2O4,晶相粒径为30nm;可见光透过率为最高可达70％,近红外透过率为70％～85％.该玻璃陶瓷能够受激发射出红光,且发光强度高于同组分的玻璃.     

Characterization of B2O3-SiO2 glasses prepared via sol-gel

B₂O₃-SiO₂ glasses were prepared by the sol-gel method from boron and silicon alkoxides. The gels were densified by several heat-treatments at temperatures above 800° C. The gel-glass transition was studied with the data obtained from differential thermal analysis, dilatometry and thermal evolution of density. The structural features of the glassy materials prepared were analysed by means of infrared (IR) and near-infrared (NIR) spectroscopy. The IR spectra indicated the existence of mixed Si-O-B bonds, preferential located at the outside of the material particles. The NIR spectra, recorded from gels heat-treated at low temperatures, demonstrated the existence of a great number of OH^– groups varying in nature, as well as their evolution and their positional changes on the silica particle surface as a function of the heat-treatment.     

Phase development and activation energy of the Y2O3-Al2O3 system by a modified sol-gel process

The phase development of Y₃Al₅O₁₂ (YAG), YAlO₃ (YAP), and Y₄Al₂O₉ (YAM) synthesized by a modified sol-gel method has been studied. A chelate agent (ethyl acetoacetate) is added to control the hydrolysis and to modify the sol-gel process. The sol-gel-derived powder is then heat-treated to induce crystallization. The X-ray diffraction method is employed to determine the crystalline phases of the resulting powders. The formation of YAG, YAP, and YAM is described. For both YAP and YAM compositions, there is a phase transformation from YAP polymorphism to perovskite YAP. The activation energies of YAG are estimated at about 69 kcal/mol by the isothermal process as fitted with the Johnson-Mehl-Avrami equation and about 222 ± 2 kcal/mol by the continuous heating method as fitted with Kissinger and Sotgiu plots. The difference of activation energies calculated from the two methods is mainly due to the complicated crystallization of YAG.     

Characterization and study of Na2O-B2O3-SiO2 glasses prepared by the sol-gel method

The sol-gel procedure has been used to prepare vitreous materials whose compositions are situated in the liquid-liquid immiscibility area of the Na₂O-B₂O₃ SiO₂ phase equilibrium diagram. Gels were prepared from different precursors and under different experimental conditions. After determining optimum conditions for gelling and heat-treatment, the gels were characterized with the aid of thermal analysis, X-ray diffraction, density and specific surface area measurements, as well as infrared and near-infrared spectroscopy. The textures of the samples and their microstructures were studied by means of scanning electron microscopy and transmission electron microscopy, respectively. The phase separation in the gels was compared to the same phenomenon in one of the glasses of identical composition, but prepared by conventional melting.     

CaO-Al2O3-SiO2系黑色装饰微晶玻璃的研究

为了研究制备黑色装饰微晶玻璃,使用Fe2O3、Ni2O3、Co2O3等着色剂,研究了其对微晶玻璃装饰板材的颜色、烧结和晶化性能的影响规律,确定合理的着色剂种类、含量以及热处理制度,并利用XRD与SEM等技术研究了黑色装饰微晶玻璃的结构.研究表明:以Fe2O3、Co2O3组合和Fe2O3、Co2O3、Ni2O3的组合都可制得黑色系列玻璃与花纹清晰的黑色微晶玻璃;100g玻璃配合料中,较合理的着色剂用量为:Fe2O33～5g,Co2O30.15～0.25 g,Ni2O30.2～0.4 g.     

Ultrafine particles of the ZrO2-SiO2 system prepared by the spray-ICP technique

Ultrafine powders of the ZrO₂-SiO₂ system prepared by spraying aqueous mixed solutions of ZrO(NO₃)₂·2H₂O and silicone oil into an ultrahigh temperature inductively coupled plasma (the spray-ICP technique) have been investigated in connection with particle growth and phase change caused by heat treatment. The prepared powders were composed of roundish ultrafine particles 10 to 20 nm in size, and their components were tetragonal ZrO₂ (t-ZrO₂) and amorphous SiO₂ (a-SiO₂).a-SiO₂ alone did not crystallize below 1400° C, though the particles grew above 900° C.t-ZrO₂ converted to monoclinic ZrO₂ (m-ZrO₂) above 400° C, also followed by particle growth. On the other hand composite powders oft-ZrO₂ anda-SiO₂ exhibited no particle growth below 1200° C. Above 1200° Ct-ZrO₂ converted tom-ZrO₂, and its amount decreased with an increase in SiO₂ content. At 1400° C particle growth occurred, and the round particles of ZrO₂ were dispersed in ana-SiO₂ glass medium. These results indicate that ZrO₂ and SiO₂ mutually block particle growth, and that SiO₂ contributes to the quenching oft-ZrO₂ by keeping the particles of ZrO₂ within the critical particle size oft-ZrO₂.     

溶胶凝胶法制备Er3+-Yb3+共掺纳米SiO2粉

利用溶胶-凝胶法合成了Er2O3-Yb2O3-SiO2纳米二氧化硅(SiO2)粉。Er3 和Yb3 直接加入有机酸催化的TEOS反应溶液中,凝胶后经过700~900℃,得到Er3 -Yb3 共掺纳米SiO2粉。样品经过红外光谱、XRD、TEM等分析,结果表明,纳米粉的粒径受有机酸比例和处理温度的影响。在室温PL谱上,样品可观察到较强的1530nm荧光,同时镱的引入对掺铒SiO2纳米粉在1.54μm的荧光发射有增强作用。