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1.
The temperature–concentration dependence of the electrical conductivity of glasses in the NaPO3–NaF system has been investigated. The regularities revealed are interpreted from the standpoint of the structural microinhomogeneity of glasses, which is due to the formation of polar structural units of the Na+[O–POO2/2], Na2
+[O–
2POO1/2], Na+[F–POO2/2], and Na+F– types. It is shown that the concentration dependence of the electrical conductivity is governed by the ratio between the concentrations of these structural units. 相似文献
2.
Effect of Tungsten Oxide on the Crystallization Properties of Glasses of the B2O3–La2O3–Nb2O5 System
Glass Physics and Chemistry - The effect of tungsten oxide on the crystallization properties of glasses of the 37.5B2O3 22.5La2O3 (40 – x)Nb2O5 xWO3 (where x = 10, 15, 20, 30, 40 mol %)... 相似文献
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P2O5-B2O3-V2O5无铅低熔玻璃形成能力和结构 总被引:1,自引:0,他引:1
以取代用作封接玻璃和电子浆料粘接相含铅低熔玻璃为目的,实验研究了P2O5-B2O3-V2O5体系玻璃的形成能力,结构和低熔性能.P2O5-B2O3-V2O5体系中,组成在B2O35%~30%、V2O50%~45%、P2O35%~50%(物质的量浓度,下同)区域内的玻璃具有较强的玻璃形成能力,较低的转变温度、良好的重熔流动性和抗析晶性能.优选玻璃组成为:15P2O5-35V2O5-25B2O3-3SiO2-2Al2O3-10ZnO-5SnO-7BaO-3Bi2O3,玻璃转变温度为308℃,在450℃玻璃细粉重熔熔体流动性好,适合用作在450~500℃烧结的封接玻璃和电子浆料的粘接相.红外光谱分析表明:玻璃结构是由大量孤立的[PO4]、[BO3]、[VO2]和[VO3]基团形成的层状结构,在层与层之间有少量的诸如B-O-B、P-O-P、P-O-V、P-O-B等桥氧键连接. 相似文献
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Maria S. Avila Charito I. Vignatti Carlos R. Apesteguía V. Venkat Rao Komandur Chary Teresita F. Garetto 《Catalysis Letters》2010,134(1-2):118-123
Propane combustion was studied on Pt(0.4%)/V2O5–Al2O3 catalysts containing up to 20% V2O5. The density, strength and nature of surface acid sites were determined by TPD of NH3 and FTIR spectra of adsorbed pyridine. The sample acidity increased with the vanadium content, essentially because the addition of vanadium oxide generated Brønsted acid sites. The Pt dispersion as determined by H2 chemisorption increased with increasing V2O5 loading. The sample activity for propane combustion was evaluated through both conversion versus temperature (light-off curves) and kinetically-controlled conversion versus time catalytic tests. The propane combustion turnover rate on Pt/V2O5–Al2O3 increased with the amount of vanadium, probably because the intrinsic Pt oxidation activity increases with the sample acidity. 相似文献
6.
《应用陶瓷进展》2013,112(6):352-357
AbstractMgO–Al2O3–SiO2 (MAS) cordierite based glass ceramics were prepared by volume crystallisation. X-ray diffraction, Scanning electron microscopy and Energy diffraction scanning were used to investigate crystallisation behaviour and the influence of P2O5 on microstructure MAS based glass ceramics. The results showed that P5+ could promote the phase separation of MAS glass and that the glass was divided into two areas, such as Mg4Al2Ti9O25 and the containing P5+ area at <900°C. Mg4Al2Ti9O25 and Mg3(PO4)2 in the area were both advantageous to the precipitation of μ cordierite, which further transformed to α cordierite due to P5+ in the residual glassy phase. However, P5+ inhibited the presence of cordierite when the heat treatment temperature was >900°C. 相似文献
7.
Sb2O5和Bi2O3添加剂对Ag(Nb1-xTax)O3陶瓷结构、形貌和性能的影响 总被引:1,自引:0,他引:1
研究了Sb2O5和Bi2O3添加剂对Ag(Nb1-xTax)O3陶瓷材料的结构、形貌和介电性能的影响.结果表明:当Sb2O5和Bi2O3的质量分数较少(<2.5%)时,不会影响Ag(Nb1-xTax)O3的钙钛矿结构,但能促进其烧结,使所得陶瓷样品更均匀致密.添加适量的Sb2O5和Bi2O3均可使Ag(Nb1-xTax)O3的介电常数(ε)增大,介电损耗(tgδ)减小,介电性能的温度稳定性得到改善.Bi2O3较Sb2O5对降低Ag(Nb1-xTax)O3陶瓷损耗及改善温度稳定性的效果更佳. 相似文献
8.
《Ceramics International》2016,42(13):14350-14354
ZnO–Bi2O3–MnO2 (ZBM)-based varistors were fabricated via doping a novel synthetic multi-phase (SMP) additive produced by calcining the mixture of 18Bi2O3·Cr2O3 at a given temperature. The effects of the SMP on the microstructural and electrical properties of ZBM varistors were investigated. It was found that the SMP dopant was a compound crystalline phases including Bi–Cr–O phases (Bi7.38Cr0.62O12+x and CrBi18O30) and small amounts of Bi2O3 rather than a synthesized polycrystal. The Bi–Cr–O phases were not emerged for samples with x=1, indicating that the amount of it is tiny and the small Bi2O3 may accelerate ZnO grain growth. With more SMP doping (x>1) in the ZBM ceramics, it acted as a barrier inhibiting grain growth. For samples with x=5, excellent electrical properties were obtained: the nonlinear coefficient α increased up to 50.19 corresponding to the highly barrier height of 2.62 eV; the leakage current IL reduced to 0.3 μA. The dielectric constant εa is proportional to the ratio of the grain size d to the thickness of the depletion layer width t, which explained the εa increased at f=1 kHz for the samples with x=1 and 5. The improvement of the electrical properties can be explained by the oxygen absorption mechanism. 相似文献
9.
Hong Li Haotian Yu Peng Chen Yi Yue Xin Cao Lifen Shi Changqing Li Dehua Xiong 《Journal of the American Ceramic Society》2021,104(10):5050-5066
As a new kind of energy-saving glass, vacuum glazing has excellent thermal and sound insulation properties and is widely used in building, household appliances and solar photovoltaic. The edge sealing material, along with sealing method, is key to the fabrication of vacuum glazing. Low transition temperature (Tg) and good fluidity at sealing temperature (Ts) make low-melting glass of V2O5–TeO2–Bi2O3 (VTB) system perfect to be the edge sealing material for vacuum glazing. The glass forming region of VTB ternary system was mapped for the first time in this work. Low-melting VTB glass of 40V2O5–50TeO2–5Bi2O3–3ZnO–2Na2O (wt%) was optimized to be the sealing material. Glass powder of this composition could be used to seal the edges of vacuum glazing at an extremely low temperature of 360°C. With the assistance of anodic-bonding method, the bonding strength of vacuum glazing was dramatically enhanced. Vacuum glazing fabricated under the optimized process parameters of 420°C, 600 V, and 60 min possesses a highest bonding strength of 4.31 MPa. Furthermore, anodic-bonding mechanism of low-melting VTB glass applied in vacuum glazing sealing has been thoroughly researched. 相似文献
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《Ceramics International》2023,49(8):12499-12507
MgO–Al2O3–SiO2 glass-ceramics have been widely used in military, industrial, and construction applications. The nucleating agent is one of the most important factors in the production of glass-ceramics as it can control the crystallization temperature or the grain size. In this study, we investigated the effect of replacing P2O5 with different amounts of TiO2 on the crystallization, structure, and mechanical properties of an MgO–Al2O3–SiO2 system. The crystallization and microstructure were investigated by differential scanning calorimetry, Raman spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The mechanical properties were investigated by measuring the Vickers hardness, Young's modulus, and fracture toughness. The results showed that adding TiO2 favored the precipitation of fine grains and significantly increased the Vickers hardness, Young's modulus, and fracture toughness of the glasses. Introducing an appropriate amount of TiO2 can make a glass structure more compact, promote crystallization, and improve the mechanical properties of MgO–Al2O3–SiO2 glass-ceramics. 相似文献
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The ignition temperature of the Al–CuO thermite was measured using DTA at a scan rate of 50 °C min?1 in a nitrogen atmosphere. Thermite reactions are difficult to start as they require very high temperatures for ignition, e.g. for Al–CuO thermite comprising micron particles it is ca. 940 °C. It was found that the ignition temperature is significantly reduced when the binary Si–Bi2O3 system is added as sensitizer. Further improvement is achieved when the reagents are nano-sized powders. For the composition Al + CuO + Si + Bi2O3 (65.3:14.7:16:4 wt.%), with all components nano-sized, the observed ignition temperature is ca. 613 °C and a thermal runaway reaction is observed in the DTA. 相似文献
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采用传统的熔融冷却的方法制备了(40-x)Bi2O3-30B2O3-30ZnO-xP2O5(0≤x≤15mo1%)体系玻璃.使用红外光谱、拉曼光谱、DSC和热膨胀仪研究了封接玻璃的结构和热性能.红外光谱及拉曼光谱结果表明,P2O5作为网络形成体,以[PO4]进入到玻璃的网络结构中,玻璃的网络结构性增强.玻璃结构中[BO3]三角体结构单元相对含量有增多趋势,[BO4]四面体、[BiO3]三角体、[BiO6]八面体结构单元相对含量减少.随着P2 O5含量的增加,玻璃化转变温度和玻璃的初始析晶温度升高;玻璃的密度减小.Bi2O3-B2O3-ZnO-P2O5体系封接玻璃热膨胀系数减小,从8.289×10-6℃-1减小到6.354×10-6℃-1.玻璃的软化点逐渐增大,从416℃升高到524℃. 相似文献
16.
Jingqi Guan Hongsu Wang Ying Yang Bo Liu Xiaofang Yu Yuanyuan Ma Qiubin Kan 《Catalysis Letters》2009,131(3-4):512-516
Mo–V–Te–P mixed oxide catalysts, prepared by a dry-up method at various pHs (in the range of about 1.0–9.0), have been tested in the partial oxidation of isobutane. The best catalytic performance was achieved over a catalyst prepared at a pH about 7.0. In this case, high selectivity to methacrolein (37.0%) at an isobutane conversion of 12.7% has been obtained at 380 °C. The surface V4+/V5+ ratios of the calcined samples were strongly influenced by the pH in the synthesized solution, which is one of the key factors in the catalytic performance for selective oxidation of isobutane. 相似文献
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《Ceramics International》2023,49(20):33188-33196
Nowadays, Y2O3–Al2O3–SiO2 (YAS) glass joining is considered to be a promising scheme for nuclear-grade continuous silicon carbide (SiC) fiber reinforced SiC matrix composites (SiC/SiC). CaO has great potential for nuclear applications since it has low reactivity and low decay rate under nuclear irradiation. In this paper, the effect of CaO doping on the structure, thermophysical properties, and crystallization behavior of YAS glass was systematically studied. As the CaO doping content increased, the number of bridge oxygens and the viscosity at high temperatures reduced gradually. After heat treatment at 1400 °C, the main phases in YAS glass were β-Y2Si2O7, mullite, and SiO2 (coexistence of crystalline and glass phases), while that with 3.0% CaO doping turned into a single glassy phase under the same treatment conditions. Moreover, a structural model and the modification mechanism were proposed, which provided a theoretical basis for the subsequent component design and optimization. 相似文献
18.
《Ceramics International》2016,42(12):13976-13982
Phase equilibria in the La2O3-Fe2O3–Sb2O5 system have been studied. The isothermal section was constructed at T=900 °С. The existence of the ternary oxide LaFe0.5Sb1.5O6 was confirmed. The structure of this compound was solved using Rietveld refinement of synchrotron radiation-based powder XRD data. LaFe0.5Sb1.5O6 crystallizes in a trigonal layered structure relating to PbSb2O6 type (space group P-31m, a=b=5.2446(3) Å, c=5.1930(3) Å, Z=1). The fine powder of LaFe0.5Sb1.5O6 was prepared by molten salt synthesis. The compound was characterized by diffuse reflection and Mossbauer spectroscopy, magnetic measurements, scanning electron microscopy and photocatalytic tests. The magnetic behavior of LaFe0.5Sb1.5O6 in the applied magnetic field H=5000 Oe is entirely paramagnetic. By contrast, in the small magnetic field H=100 Oe the magnetic data of LaFe0.5Sb1.5O6 indicates an unusual critical behavior near phase transition at T<2 K. 相似文献
19.
Phase composition, microstructure and electrical conductivity of glass ceramics in the VO2–V2O5–P2O5–SnO2 and VO2–V2O5–P2O5–Cu2O–SnO2 systems have been studied. Only crystalline phases VO2, SnO2 and vanadium phosphate glass of the V2O5–P2O5 system have been found in glass ceramic compositions in the VO2–V2O5–P2O5–SnO2 system. Besides the above-mentioned phases, probably the X-ray lines of V3O5, V4O7, V5O9, V6O11, V7O13, V4O9, V6O13, V2O5, SnO2, SnO, Sn2O3, Sn3O4 and CuO phases are observed in the X-ray spectra of glass ceramics in the VO2–V2O5–P2O5–Cu2O–SnO2 system. According to SEM/EDS data, these phases were observed as submicrometer fine-crystalline inclusions in glass on the surface of VO2 crystallites and between them. The formation of these phases was caused by the redox processes in the liquid phase during glass ceramics synthesis. The important role of tin oxides possessing high electrical conductivity and vanadium oxides exhibiting a low temperature of metal–semiconductor phase transition in the stabilization of glass ceramics electrical properties related to the phase transition in VO2 has been established. 相似文献
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