共查询到20条相似文献,搜索用时 31 毫秒
1.
Koushik Majhi Kalidhindi B. R. Varma 《International Journal of Applied Ceramic Technology》2010,7(Z1):E89-E97
Glasses in the system CaO–Bi2O3–B2O3 (in molar ratio) have been prepared using melt-quenching route. Ion transport characteristics were investigated for this glass using electric modulus, ac conductivity and impedance measurements. The ac conductivity was rationalized using Almond–West power law. Dielectric relaxation has been analyzed based on the behavior of electric modulus behavior. The activation energy associated with the electrical relaxation determined from the electric modulus spectra was found to be 1.76 eV, close to that the activation energy for dc conductivity (1.71 eV) indicating that the same species took part in both the processes. The stretched exponent β (0.5–0.6) is invariant with temperature for the present glasses. 相似文献
2.
《Journal of the European Ceramic Society》2004,24(7):2103-2111
Neodymium aluminosilicate (Nd2O3–Al2O3–SiO2; NdAS) glasses have been investigated for the effect of concentration of TiO2 on the crystallization mechanism and for the effect of surface condition on crystal growth. NdAS glasses with 0–10 wt.% TiO2 were heat-treated for nucleation and crystal growth and were examined for phase separation and morphology of surface crystals as well as for crystal growth rate. All the glasses exhibit surface crystallization, however, the glass having 8 wt.% TiO2 also exhibits internal crystallization after a two-stage heat treatment. Surface crystallization was dependent on the condition of the glass surface and the amount of TiO2. The crystal growth on the cut surface was faster than on the fractured surface and the growth rate in surface increased with increasing TiO2. The phase separation found in NdAS glasses containing above 8 wt.% TiO2, was confirmed to be an important factor controlling the internal crystallization process in Nd2O3–Al2O3–SiO2–TiO2 glasses. 相似文献
3.
《Journal of the European Ceramic Society》2000,20(2):195-199
We investigated the sintering behavior of Cr2O3–Al2O3 ceramic materials. In our observation of the isothermal shrinkage behavior of Cr2O3–Al2O3 ceramic, the activation energy of sintering reaction was measured to be 102 kJ/mol, that is, the near value of the activation energy of diffusion of Al ions in Al2O3 single crystal. Therefore the diffusion of cations is believed to control the sintering behavior of this material. With the addition of TiO2, (the compound chosen to accelerate the diffusion of cations) to Cr2O3–Al2O3, the sintering behavior was accelerated. 相似文献
4.
《Ceramics International》2017,43(14):11132-11141
Dy3+ doped calcium bismuth borate glasses were synthesized in the composition range of xLiCl-(30 − x)CaO-20Bi2O3-50B2O3 + 1 mol% Dy2O3 (x = 0, 2, 5, 7, 10 and 15 mol%, LC0, LC2, LC5, LC7, LC10 and LC15 respectively) using conventional melt-quench technique. Broad XRD profiles confirmed non-crystalline nature of synthesized compositions. The compositional dependencies of structural changes (using FTIR spectra), thermal behavior (using DSC thermographs) and optical band gap (using UV–Vis–NIR spectra) were discussed. Photoluminescence (PL) excitation spectra recorded at 577 nm yielded six different excitation peaks belonging to Dy3+ ions. The PL emission spectra recorded at 451 nm were analyzed to extract different light emission parameters viz. Y/B ratio, color coordinates, correlated color temperature (CCT) following CIE 1931 chromaticity diagram. The emission colors were found to lie in white light region and lies very close to standard white light emission. The CCT of sample LC10 (5335 K) is closest to CCT of standard white light (5615 K) which depicted the optimized concentration of LiCl for application of these glasses in WLED application. 相似文献
5.
Alzahrani Jamila S. Alrowaili Z. A. Saleh H. H. Al-Baradi Ateyyah M. Alothman Miysoon A. Al-Buriahi M. S. 《Journal of Inorganic and Organometallic Polymers and Materials》2021,31(11):4300-4312
Journal of Inorganic and Organometallic Polymers and Materials - This research article focuses on the significant role of Tb2O3 content on the optical properties and radiation shielding performance... 相似文献
6.
To support commercialization of the MgO–Al2O3–B2O–SiO2-based low-dielectric glass fibers, crystallization characteristics of the relevant glasses was investigated under various heat-treatment conditions. The study focused on the effects of iron on the related thermal properties and crystallization kinetics. Both air-cooled and nucleation-treated samples were characterized by using the differential thermal analysis/differential scanning calorimeter method between room temperature and 1200°C. A collected set of properties covers glass transition temperature (Tg), maximum crystallization temperature (Tp), specific heat (ΔCp), enthalpy of crystallization (ΔHcryst), and thermal stability (ΔT=Tp—Tg). Using the Kinssiger method, the activation energy of crystallization was determined. Crystalline phases in the samples having various thermal histories were determined using powder X-ray diffraction (XRD) and/or in situ high-temperature XRD method. Selective scanning electron microscope/energy-dispersive spectroscopy analysis provided evidence that crystal density in the glass is affected by the iron concentration. Glass network structures, for air-cooled and heat-treated samples, were examined using a midinfrared spectroscopic method. Combining all of the results from our study, iron in glass is believed to function as a nucleation agent enhancing crystal population density in the melt without altering a primary phase field. By comparing the XRD data of the glasses in two forms (bulk versus powder), the following conclusions can be reached. The low-dielectric glass melt in commercial operation should be resistant to crystallization above 1100°C. Microscopic amorphous phase separation, possibly a borate-enriched phase separating from the silicate-enriched continuous phase can occur only if the melt is held at temperatures below 1100°C, that is, below the glass immiscibility temperature. The study concludes that neither crystallization nor amorphous phase separation will be expected for drawing fibers between 1200°C and 1300°C in a commercial operation. 相似文献
7.
Barbara Lothenbach Laure Pelletier-Chaignat Frank Winnefeld 《Cement and Concrete Research》2012,42(12):1621-1634
The solubility of AH3, CAH10, C2AH7.5, and C3AH6 was determined experimentally at 7 to 40 °C and up to 570 days. During the reaction of CA, at 20 °C and above initially C2AH7.5 formed which was unstable in the long-term. The solubility products calculated indicate that the solubilities of CAH10, C2AH7.5 and C4AH19 increase with temperature while the solubility of C3AH6 decreases. Thus at temperatures above 20 °C, C3AH6 is stable, while at lower temperature also CAH10 and C4AH19 are stable, depending on the C/A ratio.At early hydration times, CAH10 can be stable initially at 30 °C and above, as the formation of amorphous AH3 stabilises CAH10 with respect to C3AH6 + 2AH3. With time, as the solubility AH3 decreases due to the formation of microcrystalline AH3, CAH10 becomes unstable at 20 °C and above. 相似文献
8.
The glass structure, wetting behavior and crystallization of BaO–Al2O3–B2O3–SiO2 system glass containing 2–10 mol% Al2O3 were investigated. The introduction of Al2O3 caused the conversion of [BO3] units and [BO4] units to each other and it played as glass network former when the content was up to 10 mol%, accompanied by [BO4] → [BO3]. The stability of the glass improved first and then decreased as Al2O3 increased from 2 to 10 mol%, the glass with 5 mol% Al2O3 being the most stable one. The wetting behavior of the glasses indicates that excess Al2O3 leads to high sealing temperature. The glass containing 5 mol% Al2O3 characterized by a lower sealing temperature is suitable for SOFC sealing. Al2O3 improves the crystallization temperature of the glass. The crystal phases in the reheated glasses are mainly composed of Ba2Si3O8, BaSiO3, BaB2O4 and BaAl2Si2O8. Al2O3 helps the crystallization of BaSiO3 and BaAl2Si2O8. 相似文献
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10.
《Journal of the European Ceramic Society》2014,34(16):4383-4388
Homogeneous transparent optical glass–ceramics precipitated with unique nonlinear crystals are promising materials for photonic applications. We have utilized heat treatment method to prepare transparent ZnO–Bi2O3–B2O3 glass–ceramic containing Bi2ZnB2O7 nonlinear nanocrystals. A large third-order nonlinear susceptibility χ(3) of glass–ceramic is measured by Z-scan technique, which mainly attributed to unique [BiO6] and [B2O5] units in Bi2ZnB2O7 crystal structure and the quantum size effect of nanoparticles. The discovery is of great potential in the application of nonlinear optical integrated devices. 相似文献
11.
Sergey Sirotkin Robert Meszaros Lothar Wondraczek 《International Journal of Applied Glass Science》2012,3(1):44-52
We report on chemical stability and corrosion behavior of highly depolymerized sulfophosphate glasses from the system ZnO–Na2O–SO3–P2O5 in aqueous solution, providing data on weight loss, ion release rates, and modifications of surface topology as a function of time, temperature and pH value. Observations seem consistent with the previously developed structural model of chemical heterogeneity, where cations Na+ and Zn2+ cluster selectively in the vicinity of sulfate and phosphate anions, respectively. 相似文献
12.
Gurpreet Singh Sandeep Kumar Sumeet K. Sharma Moolchand Sharma Vinay P. Singh Rahul Vaish 《Journal of the American Ceramic Society》2019,102(6):3378-3390
Transparent TiO2 crystallized 5CaO–10BaO–65B2O3–Al2O3–20TiO2–10ZnO (CBBATZ) glass nanocomposites were fabricated using melt-quenching technique followed by specific heat treatments. As-quenched glass samples were provided three different heat treatments at 630°C for 3, 5, and 10 hours in order to obtain different amounts of TiO2 nanocrystals in the glass. The presence of rutile phase of TiO2 nanocrystals in glass was confirmed by X-ray diffraction. The glass nanocomposite heat treated for 10 hours showed a hydrophobic nature with contact angle of 90.90°. Contact angle decreased from 90.90 to 22.20°, when irradiated under ultraviolet (UV) radiation for 45 minutes. This photoinduced hydrophilicity showed a photocatalytic and self-cleaning properties of glass nanocomposite. During photocatalytic ink test, the maximum change in color of Resurin (Rz) ink and 60% degradation in absorbance of ink within 150 minutes under UV radiation were found for glass nanocomposite heat treated at 10 hours. Also, 78% degradation in absorbance of methylene blue dye (pollutant) within 180 minutes under UV irradiation was found for glass naocomposite heat-treated at 10 hours. Antibacterial performance of transparent glass nanocomposite against Escherichia coli was evaluated as well. More than 95% of the bacterial cells were degraded with glass nanocomposite heat-treated at 10 hours. CBBATZ glass nanocomposite found to impart the antibacterial effect through generation of reactive oxygen species (ROS) in aqueous medium. ROS species which was confirmed in the bacterial cell through intracellular ROS generation kit. During evaluation of mechanical properties using nanoindentation technique, the values of hardness and reduced modulus increased by ~26% and 10%, respectively, for glass nanocomposite heat-treated at 10 hours as compared to as-quenched glass. 相似文献
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14.
采用体积电阻率法、红外光谱、X射线衍射研究了V2O5–P2O5–Sb2O3–Bi2O3体系玻璃的电性能、结构和析晶状况。结果表明:随着Sb2O3取代部分V2O5,玻璃的体积电阻率显著升高,电子分别以V4+和V5+为中心不停地进行电子跃迁的电子导电特征得到明显抑制,15%Sb2O3、20%Sb2O3玻璃的体积电阻率可以达到实用水平。当Sb2O3取代V2O5进入钒酸盐玻璃中,玻璃结构得到增强,析晶状况得到改善,削弱了玻璃的导电能力。 相似文献
15.
《Ceramics International》2016,42(9):11003-11009
A low temperature sintering method was used to avoid the relatively high sintering temperatures typically required to prepare 0.67CaTiO3–0.33LaAlO3 (CTLA) ceramics. Additionally, CeO2 was introduced into the CTLA ceramics as an oxygen-storage material to improve their microwave dielectric properties. 0.67CaTiO3–0.33LaAlO3 ceramics co-doped with B2O3–Li2O–Al2O3 and CeO2 were prepared by a conventional two-step solid-state reaction process. The sintering behavior, crystal structure, surface morphology, and microwave dielectric proprieties of the prepared ceramic samples were studied, and the reaction mechanism of CeO2 was elucidated. CTLA+0.05 wt% BLA+3 wt% CeO2 ceramics sintered at 1360 °C for 4 h exhibited the optimal microwave dielectric properties: dielectric constant (εr)=45.02, quality factor (Q×f)=43102 GHz, and temperature coefficient of resonant frequency (τf)=2.1 ppm/°C. The successful preparation of high-performance microwave dielectric ceramics provides a direction for the future development and commercialization of CTLA ceramics. 相似文献
16.
《Ceramics International》2015,41(8):9239-9243
BaO–CaO–Al2O3–B2O3–SiO2 (BCAS) glass–ceramics can be used as sealant for large size planar anode-supported solid oxide fuel cells (SOFCs). BCAS glass–ceramics after heat treatment for different times were characterized by means of thermal dilatometer, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show that the coefficients of thermal expansion (CTE) of BCAS glass–ceramics are 11.4×10−6 K−1, 11.3×10−6 K−1 and 11.2×10−6 K−1 after heated at 750 °C for 0 h, 50 h, and 100 h, respectively. The CTE of BCAS matches that of YSZ, Ni–YSZ and the interconnection of SOFC. Needle-like barium silicate, barium calcium silicate and hexacelsian are crystallized in the BCAS glass after heat-treatment for above 50 h at 750 °C. The glass–ceramics green tape prepared by aqueous tape casting can be directly applied in sealing the cell of SOFCs with 10 cm×10 cm. The open circuit voltage (OCV) of the cell keeps 1.19 V after running for 280 h at 750 °C and thermal cycling 10 times from 750 °C to room temperature. The maximum power density is 0.42 W/cm2 using pure H2 as fuel and air as oxidation gas. SEM images show no cracks or pores exist in the interface of BCAS glass–ceramics and the cell. 相似文献
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18.
《Journal of the European Ceramic Society》2000,20(8):1091-1098
Compounds in the system Y2O3-Al2O3 are promising materials for optical, electronic and structural applications. In this study, a melt extraction process with a new approach to making ceramic fibers was used to produce amorphous fibers in the Y2O3–Al2O3 system within the 20–30-micron size range. Smooth and uniform cross section fibers with relatively high tensile strength were obtained depending on the wheel velocity. X-ray diffraction of as-extracted fibers revealed the non-crystalline nature of the yttria-alumina compositions. The crystallization and glass transition temperatures of non-crystalline fibers were determined using differential thermal analysis (DTA). Crystalline phases were identified by X-ray diffraction in the fibers after heat treatment. 相似文献
19.
《Journal of the European Ceramic Society》1999,19(1):139-142
Dielectric ceramics in the BaO–Nd2O3–TiO2–Ta2O5 system were prepared and characterized. The ceramics with tungsten–bronze structure based on the compositions Ba2NdTi2Ta3O15 and Ba5NdTi3Ta7O30 had a high dielectric constant (>100) with a lower frequency-dependency when complete densification was achieved; a low dielectric loss was obtained in the former. 相似文献
20.
AbstractVariation in the viscous flow behaviour, nature and extent of glass fluidity in glass/filler composites are addressed with respect to various factors such as filler type, content, size, density and migration distance. The characterisation of a glass (Bi2O3–B2O3–ZnO) composite consisting of two different fillers (cordierite and willemite) was determined using hot stage microscopy, a differential scanning calorimeter and a flow button test. The microstructure was analysed using a scanning electron microscope. The apparent viscosity of the glass composites increased on increasing concentration and density of the filler. The variation in the viscosity is due to the diffusion of the glass matrix through channels in the cordierite filler of the composite. Based on the calculated migration distance of the filler in the glass matrix, the present work suggests that the interfacial behaviour and the density of the filler play a significant role in determining the viscous flow of the glass composites. 相似文献