铝硼硅酸盐玻璃纤维结构与耐水动力学

采用红外光谱、示差扫描量热分析等手段研究了氧化硼对铝硼硅酸盐玻璃结构及转变温度的影响，并用粉末法测试了玻璃的耐水性。结果发现，随着氧化硼含量增加，玻璃转变温度先降低后升高。玻璃与水反应初期受硼酸盐的水解动力学控制，后期主要为水分子对硅氧骨架的侵蚀和Ca^2＋与H^＋离子的离子交换过程。分析认为，引入少量的B2O3主要与碱性的CaO结合，生成含有非桥氧的端氧键B-O-Ca，破坏了玻璃网络结构，B2O3过量时，更多的硼酸盐基团与硅酸盐基团结合，生成桥氧键B-O-Si键，增强了玻璃结构。     

Al2O3对硼硅酸盐玻璃热膨胀和分相的影响

通过红外光谱分析了Al2O3取代SiO2后硼硅酸盐玻璃结构的变化,测试了玻璃的热膨胀系数和膨胀软化温度,通过扫描电子显微镜分析硼硅酸盐玻璃的分相,并结合X射线能谱分析了富硅相的组成.结果表明:硼硅酸盐玻璃中引入Al2O3后,随着Al2O3取代量的增加,玻璃结构中[BO3]增多,[BO4]减少;玻璃的热膨胀系数增大,转变温度和软化温度提高;硼硅酸盐玻璃中引入Al2O3后对玻璃的分相没有明显的改善作用.     

(Na2O-Al2O3)/B2O3对高硼硅酸盐玻璃粘度和热学性能的影响

采用熔融冷却法制备了不同R’系数的高硼硅酸盐玻璃,其中R’=(Na2O-Al2O3)/B2O3.利用红外光谱、高温旋转粘度计和热膨胀仪等对玻璃的结构和性能进行表征.结果表明:高温段粘度-温度关系符合阿伦尼乌斯定律;R’值的增大导致非桥氧的增加,高温粘度和熔制温度呈显著降低.当R’＞0.5时,热膨胀系数近似线性增大,玻璃化转变温度增大至590℃基本维持不变.R’值影响结构中的[BO3]与[BO4]的比例及硅氧网络的完整程度,从而决定高硼硅酸盐玻璃的性能.     

添加剂对铅硅酸盐低熔点玻璃热性能的影响

采用常规玻璃熔融退火工艺制备了两组铅硅酸盐玻璃试样,玻璃组成为(物质的量含量,下同):(55-x)PbO-(10+x)B2O3-30SiO2-5ZnO(x=0,5,10,15)和(55-x)PbO-10B2O3-30SiO2-5ZnO-xSB2O3(x=5,10,15),以及与两组参照的传统铅硅酸盐玻璃55PbO-5Al2O3-10B2O3-30SiO2.利用热膨胀仪观察氧化物添加剂对玻璃转变温度范围△T(T1-Tg)的影响.实验结果表明,随着氧化硼加入量的不断提高,玻璃的转变温度(Tg)与软化温度(Tf)随之提高,而△T先减小后增大,即出现所谓的硼反常现象.当添加的氧化锑量在5%～10%(物质的量含量,下同)范围时,与参照样品相比,玻璃的软化温度(Tf)基本保持不变而转变温度(Tg)则提高10℃以上.当添加的氧化锑量达到15%时,玻璃的转变温度(Tg)与软化温度(Tf)均显著下降,但△T基本保持不变.     

n(B2O3)/n(SiO2)对硼硅酸盐玻璃结构和性能的影响

采用热膨胀仪、扫描电镜和红外光谱仪研究了硼硅酸盐玻璃的结构与性能随n(B2O3)/n(SiO2)和n(B2O3)/n(Na2O)的变化规律,深入探讨了结构对分相、热膨胀系数和膨胀软化温度的影响规律。结果表明:热膨胀系数取决于玻璃中[BO3]、[BO4]和[SiO4]的数量变化;玻璃的转变温度和软化温度主要由SiO2决定;[BO3]对玻璃的分相有着重要的影响;不论n(B2O3)/n(Na2O)比值多少,玻璃结构中均存在[BO3]和被破坏的[SiO4]。     

Al2 O3对硼硅酸盐玻璃结构和性能的影响

硼硅酸盐玻璃具有优良的抗热冲击性能和优异的光学性能。主要探讨了Al2 O3对硼硅酸盐玻璃的结构和性能的影响。通过红外光谱测试分析了Al2 O3含量不同时玻璃的结构变化,测试了玻璃的热膨胀系数,转变温度、膨胀软化温度、粘度和化学稳定性。研究结果表明：Al2 O3的加入使得玻璃结构中[ BO4]减少,[ BO3]相应增加,从而使得玻璃结构疏松。玻璃的热膨胀系数增大,Tg 和膨胀软化点Td 降低,化学稳定性减弱;但玻璃的软化点Tf 在Al2 O3含量小于3%时,随Al2 O3含量增加有降低趋势,大于3%时随Al2 O3含量增加有增大的趋势。玻璃的高温粘度随Al2 O3的加入增大,但低温粘度减小。     

Bi_2O_3–ZnO–B_2O_3三元系统玻璃结构与性能

采用X射线吸收精细结构和红外吸收光谱分别对铋锌硼玻璃中铋离子邻近结构和硼氧网络结构进行研究,分析其结构变化对玻璃转变温度Tg和热膨胀系数α的影响。结果表明:1)铋离子以三配位([BiO3])和六配位([BiO6])两种配位状态存在;随Bi2O3含量增加,三配位铋离子的配位数上升,六配位铋离子配位数下降,同时铋离子总配位数上升。2)随Bi2O3含量增加,硼氧网络中硼氧四面体含量下降,硼氧三角体含量上升,硼氧四面体网络解聚形成硼氧三角体网络。3)上述结构因素是造成玻璃转变温度Tg下降和热膨胀系数α上升的主要原因。     

Si-B4C复合抗氧化剂对MgAlON材料高温氧化行为的影响

研究了Si-B4C复合抗氧化剂对MgAlON材料高温氧化行为的影响.通过对氧化后试样脱色层的厚度、相组成、氧化产物中尖晶石相的晶格常数及显微结构的研究发现,该复合抗氧化剂能显著改善MgAlON材料的高温抗氧化性能.抗氧化机理在于在相对较低的温度(1100℃以下)下,SiO2和B2O3作用形成低粘度、低挥发性、低氧扩散系数的硼硅酸盐玻璃而有效地封闭气孔和裂纹;在较高温度下,硼硅酸盐玻璃中的SiO2和B2O3又能和MgAlON氧化产物中的α-Al2O3作用,形成由莫来石和Al18B4O33构成的致密氧化物层,有效阻挡外界的氧向试样内部扩散.     

铝硼硅酸盐硼挥发抑制的初步研究

通过热分析手段研究氧化镧对铝硼硅酸盐玻璃熔制过程中硼挥发量的影响。TG测试结果表明,随着玻璃配合料中氧化镧质量分数的增加,硼挥发量逐渐降低。当La2O3与B2O3摩尔比超过0.2时,这种趋势变化不明显。同时通过XRD分析出了不同热处理机制下,氧化镧和硼酸的混合物的产物在650,℃时,除了La2O3和H3BO3之外,还有新相LaBO3生成;800,℃时,产物为La（BO2）3。与碱土金属硼酸盐相比,La（BO2）3和LaBO3具有更低的饱和蒸汽压,这是硼的挥发量降低的根本原因。     

Cf/SiBON-ZrB2陶瓷基复合材料抗氧化性能的研究

主要研究炭纤维增强SiBON-ZrB2陶瓷基复合材料在1700℃下的氧化行为.通过对氧化层表面以及对氧化截面的SEM以及XRD分析,发现ZrB2氧化生成ZrO2氧化膜和B2O3,其中B2O3能够与材料自反应生成的SiC氧化后的产物SiO2结合形成硅硼酸盐玻璃相,从而避免B2O3的挥发,而硅硼酸盐玻璃相能够填补炭纤维氧化...     

Multiple-Quantum Magic-Angle Spinning 17O NMR Studies of Borate, Borosilicate, and Boroaluminate Glasses

Multiple-quantum magic-angle spinning (MQMAS) ¹⁷O NMR spectroscopy has been applied to study boron oxide, sodium borate, sodium potassium borosilicate, and sodium boroaluminate glasses. Up to eight distinct oxygen sites are identified, with the chemical shift and quadrupolar coupling parameters determined for each. Previous assignment of the B-O-B and Si-O-B resonances has been found to be incorrect. In contrast to standard models of glass structure, three-coordinated boron mixes with the silicon oxide network to a great extent. Sodium borosilicate glasses with low-sodium content are likely to be phase-separated on the nanoscale. Those with intermediate sodium content form homogeneous glasses with boron atoms distributed evenly in the SiO₂ network. A boron avoidance rule analogous to the aluminum avoidance rule may apply in this region, when BO₄ groups are abundant. Adding excess sodium cations to the system may again lead to compositional heterogeneity. The existence of diborate group as the basic building unit in glasses with appropriate sodium content is not well supported. The network-forming cations in sodium boroaluminate glasses are well mixed, with no Al-O-Al resonance observed by MQMAS. The effect of cation type and thermal history on glass structures is also discussed.     

Development of boron oxide potentials for computer simulations of multicomponent oxide glasses

Molecular dynamics and related atomistic computer simulations are effective ways in studying the structures and structure–property relations of glass materials. However, simulations of boron oxide (B₂O₃)-containing oxide glasses pose a challenge due to the lack of reliable empirical potentials. This paper reports development of a set of partial charge pairwise composition-dependent potentials for boron-related interactions that enable simulations of multicomponent borosilicate glasses, together with some of the existing parameters. This set of potentials was tested in sodium borate glasses and sodium borosilicate glasses and it is shown capable to describe boron coordination change with glass composition in wide composition ranges. Structure features such as boron N₄ value, density, Q_n species distribution, fraction of non-bridging oxygen around boron and silicon, total correlation function, and bond angle distribution function were calculated and compared with available experimental data. Mechanical properties of the simulated glasses calculated with the new potential also show good agreement with experiments. Therefore, this new set of potential can be used to simulate boron oxide-containing multicomponent glasses including those with wide industrial and technology applications.     

Li2S—SiS2—LiBO2—LiCl体系玻璃的XPS表征

本文采用光电子能谱分析方法,首次研究Li_2S-SiS_2-LiBO_2-LiCl体系硫氧化物玻璃锂离子导体的组成、结构和状态。指出在该玻璃体系中,除与硅(硼)相键合的桥硫存在外,还有不与硅(硼)相键合的非桥硫存在;玻璃中的硫取代了氧的位置,进入玻璃网络中使结构紧密交联。对网络中的元素状态,成键及性能进行了讨论。     

Vibrational Spectra of Vitreous B2O3.xH2O

The infrared absorption spectra of boron oxide glasses of low and high water content have been obtained in the 400- to 4000-cm.⁻¹ region using thin films or fine powders dispersed in a liquid. A structural interpretation of the glass spectra has been made with the aid of the spectra of the closely related materials boric acid, orthorhombic metaboric acid, and partly deuterated boron oxide glass of high water content. It has been shown that the glass spectra are consistent with a random-network structure in which each boron is triangularly coordinated by three oxygens and that the presence of water leads to weak hydrogen bonding between oxygen atoms. No evidence for a substantial amount of tetrahedral coordination of boron by oxygen has been found in glasses of either low or high water content.     

A quantum-chemical study of the mechanism of ionic conductivity in alkali borate glasses

The incorporation of alkali metal oxide molecules into a continuous random network of vitreous boron oxide is considered within the cluster approximation at a semiempirical MNDO level. It is found that the oxygen atom of the Li₂O molecule easily forms an additional bond with the threefold-coordinated boron atom with the formation of the BO₄ tetrahedron. Different types of metal cation motion in alkali borate glasses are treated. It is revealed that the M⁺ cation in neutral systems is predominantly located near the edges of a BO ₄ ^- tetrahedron on the outside of the B-O-B corner fragments and can readily change its position. The M⁺ cation in the neighborhood of the pentaborate grouping makes a complete turn without considerable expenditure of energy. The vibrations with a change in the rotation angle from 180° to 270° are possible in tetraborates, and, only in the neighborhood of triborate, one position is substantially more stable than the other positions. The cation can migrate from center to center along chains of a continuous glass network on the outside of the B-O-B corner fragments. In the pentaborate and tetraborate centers, the cation can migrate into another chain and change its direction of motion. From the materials of the paper reported at the International Conference “Glasses and Solid Electrolytes” (St. Petersburg, 1999, May 17–19).     

A quantum-chemical study of the mechanism of ionic conductivity in alkali borate glasses

The incorporation of alkali metal oxide molecules into a continuous random network of vitreous boron oxide is considered within the cluster approximation at a semiempirical MNDO level. It is found that the oxygen atom of the Li₂O molecule easily forms an additional bond with the threefold-coordinated boron atom with the formation of the BO₄ tetrahedron. Different types of metal cation motion in alkali borate glasses are treated. It is revealed that the M⁺ cation in neutral systems is predominantly located near the edges of a BO ₄ ^- tetrahedron on the outside of the B-O-B corner fragments and can readily change its position. The M⁺ cation in the neighborhood of the pentaborate grouping makes a complete turn without considerable expenditure of energy. The vibrations with a change in the rotation angle from 180° to 270° are possible in tetraborates, and, only in the neighborhood of triborate, one position is substantially more stable than the other positions. The cation can migrate from center to center along chains of a continuous glass network on the outside of the B-O-B corner fragments. In the pentaborate and tetraborate centers, the cation can migrate into another chain and change its direction of motion. From the materials of the paper reported at the International Conference “Glasses and Solid Electrolytes” (St. Petersburg, 1999, May 17–19).     

The Rigidity of Vitreous Networks: An Alternative Viewpoint

An alternative, and much more intuitive, approach is proposed to the rigidity of (relatively) strain-free oxide glass networks, based on effectively rigid basic structural units and the true degrees of freedom that allow the formation of such networks; viz. bond torsion angles plus the bond angle at the bridging oxygen atoms. These ideas are extended to borate networks that include rigid superstructural units with no internal degrees of freedom in the form of variable bond and torsion angles, and it is shown that, for an isostatic network, the average (super)structural unit connectivity is equal to 4. The role of network rigidity in determining glass formation is discussed, together with the effects of steric hindrance, and a comparison with conventional constraints theory is presented for vitreous SiO₂ and B₂O₃. Finally, it is argued that the so-called intermediate phase is merely an extended rigidity transition range, due to the chemical nano-heterogeneity that characterizes the structure of glasses having more than one component, and that, in the case of Ge-Se glasses, the bonding in the interfacial regions between the Se and GeSe₂ regions exhibits significant metalloid character.     

Structural Interpretation of Immiscibility in Oxide Systems: IV, Occurrence, Extent, and Temperature of the Monotectic

Liquid immiscibility data in known binary oxide systems are analyzed in relation to three fundamental aspects. Immiscibility in glassforming systems is related to differences in ionic field strengths or electrostatic bond strengths between the network cation with oxygen and the modifier cation with oxygen. If this difference is too small or too large, immiscibility is not present. Analysis also indicates that immiscibility is not to be expected in binary phosphate and vanadia systems. Factors governing the extent of immiscibility are essentially unrelated to its occurrence; in borate and silicate systems, immiscibility is inversely correlated with the number of oxygens per modifier cation in the modifier-rich liquid. Temperature of the monotectic almost always lies between the melting point of the glass former and the first compound beyond the immiscibility gap. Properties of the monotectic, such as the primary phase under the two liquids and location of the eutectic, are fixed according to whether the monotectic temperature is above or below the melting point of the glass former. Principles of immiscibility are summarized.     

IR spectroscopic study of water in the structure of binary alkali borate glasses

The influence of the synthesis conditions and composition of binary sodium and potassium borate glasses on the spectral absorption in the wavelength range 2.5–4 µm due to the presence of structurally bound water is investigated. It is demonstrated that water in the structure of alkali borate glasses, as in the structure of alkali silicate glasses, can exist in the form of so-called free and bound hydroxyl groups that are incorporated into the glass network in different ways. The ratio between the numbers of these forms of structural water in borate glasses is determined by the synthesis conditions and composition of the glass. The synthesis under different conditions makes it possible to prepare glasses not only with different water contents but also with different ratios between the numbers of free and bound hydroxyl groups.Original Russian Text Copyright © 2005 by Fizika i Khimiya Stekla, Golubeva, Pavinich.     

Mixed alkali effects in Er3+-doped borate glasses: Influence on physical,mechanical, and photoluminescence properties

Engineering borate glass structure by simple compositional modification is essential to meet the particular demands from both industrial and photonic research communities. In this article, we demonstrate how the mixing of Li₂O with Na₂O, K₂O, or Cs₂O influences the relative abundance of 3- and 4-coordinated borons in the glass network, as exhibited by nuclear magnetic resonance (NMR) and Raman spectra. A systematic study is given of the alkali mixing effect on the glass properties including: glass transition temperature, microhardness, density, refractive index, and particularly the near-infrared photoluminescence properties (eg, bandwidth and lifetime) of Er³⁺ which has been barely studied in mixed alkali borate glasses. It is interesting to note that the glass transition temperature, refractive index and emission lifetime of Er³⁺ manifest mixed alkali effect, in sharp contrast with microhardness, density, and emission bandwidth which vary monotonically upon the alkali mixing. The possible causes for the differences are discussed in the light of the compositional dependence of boron species and nonbridging oxygen upon alkali mixing.