Wetting of gold by Bi2O3-B2O3 melts

The wetting of gold by Bi₂O₃-B₂O₃ melts has been studied by the sessile drop method, with the sample and substrate heated separately before being brought into contact. Only the melts containing 18.5 and 33.3 mol % B₂O₃ were found to have steady-state contact angles.     

Phase formation kinetics in SrO-Al2O3-SiO2-B2O3 glass

Phase formation in Sr-celsian glass, containing 3 wt% B₂O₃ (SA2SB), was investigated by using non-isothermal and isothermal kinetic analyses. While stoichiometric celsian (SA2S) glass showed two-stage crystallization of glass, from glassy state to hexacelsian and from hexacelsian to monocelsian, SA2SB glass showed direct crystallization of glass to monocelsian, resulting in considerable decrease in the temperature of monocelsian formation. The activation energy for monocelsian formation in SA2SB glass was 390 kJ/mol, which is lower than those for hexacelsian and monocelsian formation respectively in SA2S glass. The Avrami exponent of SA2SB glass was 2.0, indicating two-dimensional crystal growth with interface-controlled mechanism at a zero nucleation rate.     

D.c. conductivity and hopping mechanism in Bi2O3-B2O3 glasses

The physical and transport properties of semiconducting glasses are highly interesting, providing useful information regarding the structure and conduction mechanism, respectively. The physical and transport properties such as density, number of ions per unit volume, hopping distance, polaron radius, d,c. conductivity and activation energy are reported. Similarly the hopping conduction mechanism is examined. The physical property (density) is used to determine the probable structure of the glass sample. The small polaron hopping model is applied to the glass system. The methods of examining the hopping conduction mechanism are discussed in the light of the small polaron model. The methods suggested by Holstein and by Sayer and Mansingh are applied to the determination of adiabatic or non-adiabatic hopping conduction. It was observed that in this system adiabatic hopping conduction is present.     

Structural studies of some V2O5-P2O5-B2O3-Fe2O3 glass systems

X-ray diffraction and infrared measurements were performed on vanadium borophosphate glass containing different amounts of iron ranging from 0–7.5 mol % and heat treated at 300 °C for various times. The structure and phase separation could be determined for each glass composition. V₂O₅ was the main precipitated phase in all heat-treated samples, and its amount was dependent on the heat-treatment time and Fe₂O₃ content. Also FeP was detected in samples heat treated for 24 h. The infrared measurements showed the presence of both V⁴⁺ and V⁵⁺. The symmetry of V₂O ₇ ⁴⁻ and VO ₄ ³⁻ groups was found to increase with increasing Fe₂O₃ content. It was also found that some PO₄ changed to BO₃, forming a non-bridging oxygen.     

热处理温度对溶胶凝胶Bi2O3-SiO2-B2O3系玻璃粉体结构的影响

采用溶胶-凝胶法制备了一种Bi2O3-SiO2-B2O3系玻璃粉体,在200~800℃温度范围内对凝胶玻璃进行热处理,通过多种表征手段研究了热处理温度对玻璃粉体网络结构的影响。结果显示,在试验温度范围内,粉体始终呈现玻璃态结构;随热处理温度升高,Bi3+逐渐进入玻璃网络中,[BiO6]八面体和[BiO3]三角体、[BO4]四面体和[BO3]三角体分别与[SiO4]四面体以顶角相连的方式构建玻璃网络结构;O1s可分为桥氧和非桥氧,O1s和Bi4f的电子结合能逐渐增大,B1s的电子结合能减小,玻璃网络结构稳定性增强。     

阳极支撑型ITSOFC密封材料SrO-La2O3-Al2O3-B2O3-SiO2微晶玻璃的研究

研究了应用于阳极支撑型的中温固体氧化物燃料电池(ITSOFC)密封的SrO-La2O3-Al2O3-B2O3-SiO2体系微晶玻璃不同组分的线膨胀率,结果表明当微晶玻璃粉组成SrCO3 28.14%(摩尔分数),La2O3 21.17%(摩尔分数),Al2O3 7.22%(摩尔分数),H2BO3 41.72%(摩尔分数),SiO2 1.76%(摩尔分数)(SLABS3) 时,最符合ITSOFC密封要求.差热分析结果表明SLABS3的玻璃转变温度在670℃～760℃之间,结晶温度在813～840℃之间,玻璃软化点约在900℃,XRD测试表明微晶玻璃与Ni-La0.3Ce0.7O1.85(Ni-LDC)阳极化学相容性好,将微晶玻璃和Ni-LDC在850℃烧结100h后,SEM观察界面粘附性好,EPMA测试界面的元素含量结果表明,虽然阳极的Ce会向微晶玻璃扩散10μm的深度,但观察不到微晶玻璃的元素向Ni-LDC扩散现象.用SLABS3密封模拟电池,测试开路电压结果表明SLABS3的密封效果和稳定性良好.     

Preparation of magnetic glass-ceramics through glass crystallization in the Na2O-SrO-Fe2O3-B2O3 system

Glasses with the nominal compositions SrFe₁₂O₁₉ + nNa₂Sr₂B₄O₉ (n = 4, 6, 8, 10) and SrFe₁₂O₁₉ + 6Na₂Sr₃B₄O₁₀ were prepared via rapid quenching of oxide melts and were then heat-treated between 500 and 800°C in order to produce glass-ceramics containing fine SrFe₁₂O₁₉ particles. The materials were characterized by x-ray diffraction, differential thermal analysis, electron microscopy, and magnetic measurements. The crystallization behavior of the glasses was investigated. The coercivity of the glass-ceramics was shown to increase with heat-treatment temperature, up to 486 kA/m. By dissolving the nonmagnetic matrix of the glass-ceramics with the nominal compositions SrFe₁₂O₁₉ + 6Na₂Sr₃B₄O₁₀ and SrFe₁₂O₁₉ + 4Na₂Sr₂B₄O₉, submicron-sized strontium hexaferrite particles were obtained.     

Effect of phase separation on the fracture toughness of SiO2-B2O3-Na2O glass

Fracture toughness of glass is usually poor, due to the absence of grain boundaries and discontinuities. The compositions of the glass studied are in the phase separated region of SiO₂-B₂O₃-Na₂O system. The interface between the glass in glass separation enhances the fracture toughness. The increase in the connectivity of phase separated regions causes increase of fracture toughness from 0.98 through 1.43 to 1. 54 MPam1/2.     

Unusual thermal expansion behaviour of PbO-rich PbO-B2O3 glasses

An unusual discontinuity in the thermal expansion behaviour of a 36 PbO-64 B₂O₃ wt % phase-separated glass was examined. Expansion tests combined with other experimental techniques established a correlation with a structural rearrangement in the cracked particles of the dispersed phase.     

Dielectric behaviour of glasses and glass ceramics in the system BaO-PbO-TiO2-B2O3-SiO2

Glasses with varying molar ratios of PbO/BaO in the system BaO-PbO-TiO₂-B₂O₃-SiO₂ were prepared keeping (BaO + PbO)/TiO₂ ratio equal to one. The glasses were ceramized by two-stage heat treatment. X-ray diffraction indicates that PbTiO₃ crystallizes in lead-rich glasses while BaTiO₃ precipitates in barium-rich compositions. Solid solution (Ba, Pb)TiO₃ does not seem to crystallize over the entire range of compositions. Simultaneous presence of PbO and BaO in the initial glass composition reduces the yield of ferroelectric phase. Dielectric properties have been interpreted in terms of microstructural features.     

Microstructural and dielectric behaviour of glass ceramics in the system PbO-BaO-TiO2-B2O3-SiO2

Glasses in the system PbO-BaO-TiO₂-B₂O₃-SiO₂ with and without P₂O₅ as nucleant have been prepared. The glass samples were ceramized based ondta studies. The ferroelectric phase crystallizing out has been found to be BaTiO₃ fromxrd. The optical and scanning electron micrographs show the presence of BaTiO₃ as major phase. In these glass ceramic samples, dielectric constant and dissipation factor are approximately constant with temperature and frequency upto the glass transition temperatureT _g and thereafter increase sharply with temperature and finally level off. The addition of P₂O₅ as nucleant and molar ratio of (PbO + BaO) to TiO₂ has marked influence on the dielectric behaviour and composition of ferroelectric phase crystallizing out.     

Transformation of Na2O-CeO2-B2O3 glass into a material with interconnected pores

Substitution of SiO₂ with CeO₂ in the ternary sodium borosilicate system was found to produce phase-separable glasses. Heat treatment of these glasses resulted in separation into two different phases. The one phase enriched in sodium borate was then leached out leaving a CeO₂-rich framework. The structure of the leached material was crystalline (Pt/Rh crucible melt) which changed to a rather net-like appearance if Al₂O₃ resulting from erosion of alumina crucibles was added. B₂O₃ remained partially in the insoluble CeO₂-skeleton. X-ray diffraction analysis of leached material proved the presence of crystalline cubic CeO₂ and cerium borate (metaborate of the aragonite type) in Pt/Rh crucible melts, whereas cubic CeO₂, 2Al₂O₃ · B₂O₃ and traces of sodium borate were detected in Al₂O₃ containing melts. The specific surface areas of the leached materials ranged between 25 and 120m²g^–1 while the main radii of interconnected pores were calculated to be between 0.5 and 17nm. A sintering temperature of about 1500° C was estimated from void volume and bulk density measurements.     

Transformation of Na2O-HfO2-B2O3 glass into a material having interconnected pores

Substitution of SiO₂ in the ternary sodium borosilicate system with HfO₂ was found to produce glasses, which after heat treatment decomposed into immiscible microphases, one of which was water soluble. The structure of the leached material after heat treatment was either glassy (mainly in the presence of Al₂O₃) or crystalline. Crystalline forms found during X-ray diffraction analysis of heat treated and leached material (melted in Pt/Rh crucibles) were monoclinic HfO₂. Monoclinic HfO₂ was also found in heat treated, leached and then fired materials melted in Pt/Rh or Al₂O₃ crucibles, in the latter an additional 9Al₂O₃ · 2B₂O₃ phase was detected. The higher solubility of HfO₂ in a Na₂O-B₂O₃ matrix than that of ZrO₂ (30 wt% against 15 wt%) resulting in clear glasses is of interest. The specific surface areas of the leached materials ranged between 41.3 and 290 m²g^–1, while the mean radii of interconnected pores were calculated to be 1.2 and 15.2nm. A firing temperature between 1450 and 1500° C is estimated from void volume and bulk density measurements.     

Optical absorption of the Gd3Ga5O12 epitaxial films grown from Bi2O3-B2O3-CaO solution melt system

Single-crystalline garnet films with a stoichiometric composition of Gd₃Ga₅O₁₂ were grown for the first time by liquid phase epitaxy from a supercooled melt of the Bi₂O₃-B₂O₃-CaO solid solution system. The films exhibit no absorption bands in the visible spectral range.