铋锗酸盐玻璃中锗原子近邻结构的EXAFS研究

测量了GeO_2-Bi_2O_3元系玻璃的EXAFS~(***)谱,以晶态α石英型GeO_2作为标准样品,求得了玻璃中Ge—O、Ge—Ge键长及相应的配位数。所得结果表明,铋锗酸盐玻璃中锗原子以[GeO_4]四面体的形式存在,Bi_2O_3对[GeO_4]构成的三维网络有解聚作用。     

氟锆酸盐玻璃中锌原子近邻结构的EXAFS研究

氟锆酸盐玻璃由于具有从近紫外到中红外的较宽透光范围、较高的氟离子电导率和较好的稀土荧光特性,因而作为一类新颖的光导材料和电子材料已引起人们的关注。另外,氟锆酸盐玻璃的结构很显然地有别于其它已知玻璃的结构,这也激发了人们对它的结构进行探究的兴趣。 二元BaF_2-ZrF_4系统的玻璃形成范围为含50—75mol％ZrF_4,该系统玻璃由于难以制成大尺寸,因而缺乏实际应用价值。而在BaF_2-ZrF_4基玻璃中掺入一系列金属氟化物     

EXAFS在玻璃结构研究中的应用

一、引 言 X射线、电子和中子衍射的径向分布函数方法是了解玻璃中原子排列的基本手段,应用于元素固体能得到可靠的原子间距和配位数。但是对于多原子材料,此法有两个不足之处:(1)对于低浓度组份的配位情况不能提供信息,然而这些组份常常对物理或化学性质起着重要的作用;(2)得到的是不易确定的结构信息,因为对测得的径向分布函数可以作多种结构解释。近年来发展起来的连续X射线吸收光谱的精细结构(Extended X-Ray     

Li_2O-Al_2O_3-SiO_2系统微晶玻璃晶相的研究

本文研究了Li_2O-Al_2O_3-SiO_2系统微晶玻璃的晶相,借以获得新型微晶材料。取自鳞石英、偏硅酸锂、二硅酸锂和锂辉石4个相区的玻璃成分,经过熔制、析晶,并用X-射线衍射方法鉴定了析出的晶相。由于相图中的原始相往往在微晶玻璃中并不出现,因此作者探讨了析晶过程中晶相转变情况,试图找出析晶介质和晶相结构间的联系。最后作者提出了微不均区域的模型,描述了本系统微晶玻璃在晶化以前的结构。     

制造化工设备用的Li_2O-MgO-Al_2O_3-SiO_2系微晶玻璃

研制成一种以β-锂辉石为主晶相的Li_2O-MgO-Al_2O_3-SiO_2系热敏微晶玻璃,具有优良的机械性能、耐热冲击性能和化学稳定性,适合于制造化工耐蚀设备。探讨了这种玻璃的化学组成、晶化过程和制造工艺。     

Y_2O_3稳定ZrO_2结构的EXAFS研究

采用EXAFS分析方法研究了较大组成范围内Y_2O_3稳定ZrO_2多晶粉末中Zr~(4+)、Y~(3+)两种离子的近邻结构,得到了Zr-O、Y-O平均间距。进一步确证,Y_2O_3-ZrO_2体系完全稳定的立方相中,Y~(3+)置换了Zr~(4+)并伴随氧空位的产生。发现亚稳定的四方相中,Zr~(4+)、Y~(3+)两种离子的近邻结构与其在单斜相及立方相中有很大差别。     

Li_2O-BaO—P_2O_5系统玻璃的喇曼和红外光谱研究

用喇曼和红外光谱研究了Li_2O-P_2O_5系统玻璃中引入Ba~(2+)离子取代Li~+离子对玻璃结构的影响。喇曼和红外光谱测试表明,含钡锂磷酸盐玻璃的主要结构是以[PO_4]四面体为单元的链状网络结构。键角ф_(o-p-o)。和力常数F_(m-O)的错综变化,在喇曼光谱上表现为:玻璃主要结构特征峰的波数和强度发生微小的变化。玻璃中Ba~(2+)离子的存在,使连结非桥氧的方向键有所加强,将影响磷酸盐链之间离子键的强度,从而导致玻璃的一些物理性质的变化。     

Li_2O-ZnO-Al_2O_3-SiO_2微晶玻璃热处理制度的研究

通过两步法制备Li2O-Zn O-Al2O3-Si O2(LZAS)系微晶玻璃,并通过正交实验探究不同热处理工艺参数对微晶玻璃致密化的影响,使用P2O5作为晶核剂。结果表明;玻璃转化温度为492℃,析晶温度为560℃和714℃,材料软化点为685℃。各参数对微晶玻璃致密化的影响顺序为晶化温度晶化时间核化温度核化时间;析晶量主要受晶化温度和晶化时间影响;当温度为560℃时,开始有少量晶体析出,当温度超过580℃,主晶相为锂辉石,并且还有少量锂霞石;锂辉石的增多导致材料致密度下降。     

Structure of Sodium Aluminosilicate Glasses

A series of sodium aluminosilicate glasses composed of varying ratios ( R ) of Al₂O₃/Na₂O (0.25 R 2.0) has been simulated with the molecular dynamics technique using a tetrahedral form of a three-body interaction potential. Extrema in the activation energies for sodium diffusion and in the diffusion constants for all of the atomic species were observed for glasses with equal concentrations of Al₂O₃ and Na₂O ( R = 1.0). These changes corresponded to the minimum observed experimentally in the activation energy for electrical conductivity and to the maximum observed in the viscosity for glasses with compositions of R = 1.0. The coordination of aluminum remained 4 over the entire compositional range, negating the need to invoke a coordination change of aluminum to explain the changes in the physical properties. The changes to the simulated physical properties as R passed through the equivalence point were attributed to the elimination of nonbridging oxygen, to the introduction of oxygen triclusters, and to changes in the distribution of ring structures within the glass networks.     

Formation of Mixed Bond‐Angle Linkages in Zinc Boromolybdate Glasses

The short and medium range structure of glassy MoO₃–ZnO–B₂O₃ has been studied by neutron diffraction and reverse Monte Carlo simulation. The partial atomic pair correlation functions and coordination numbers are presented that are not yet reported for this system. We have established that the first neighbor distances do not depend on concentration within limit of error, the actual values are r_B‐O = 1.38 Å, r_Mo‐O = 1.72 Å, and r_Zn‐O = 1.97 Å. It is found that ZnO takes part in the glassy structure as network former, as ZnO₄ tetrahedral are linked both to MoO₄ and to BO₃ and BO₄ groups. It is revealed that BO₄/BO₃ increases with increasing B₂O₃ content. We have found that only small amount of boroxol ring is present, BO₃ and BO₄ groups are organized into superstructure units, and a small part is in isolated BO₃ triangles. The BO₃ and BO₄ units are linked to MoO₄ or ZnO₄ forming mixed ^[4]Mo‐O‐^[3]B, ^[4]Mo‐O‐^[4]B, ^[4]Mo‐O‐^[4]Zn, ^[3]B‐O‐^[4]Zn, ^[4]B‐O‐^[4]Zn bond linkages.     

Na_2O—CaO—B_2O_3—A1_2O_3—SiO_2玻璃的Raman光谱

微孔玻璃是基于分相原理得到的。人们发现,由于Na_2O-B_2O_3-SiO_2系统中同时存在两种形成玻璃网络的氧化物B_2O_3及SiO_2,电价不平衡的[BO_4]四面体趋于获得Na_2O中的游离氧而形成含富Na_2O-Ba_2O_3的相,从而与含富XiO_2相分开,当这种分相玻璃浸于稀盐     

Extended X-ray Absorption Fine Structure (EXAFS) Study on the local Environment around Copper in Low Thermal Expansion Copper Aluminosilicate Glasses

The local environment around copper in the Cu₂O·Al₂O₃·4SiO₃ and CuO·Al₂O₃·4SiO₂ glasses was investigated using the extended X-ray absorption fine structure (EXAFS) technique. It has been found that each Cu(I) in the former glass is coordinated to two oxygens through covalent Cu(I)-O bonds. This is the primary reason for its low thermal expansion coefficient (∼10 × 10⁻⁷ K⁻¹). In the latter glass, which was made by heating the former glass at 600°C in air, each Cu(II) is coordinated to four oxygens and the bonds are ionic in character, contributing to the increase in the thermal expansion coefficient to ∼30 × 10⁻⁷ K⁻¹.     

Spectroscopic Analysis of the Structure and Properties of Alkali Tellurite Glasses

Structural development of tellurite glasses with the addition of Li₂O and Na₂O has been studied using infrared, Raman, and X-ray photoelectron spectroscopies. The increase in intensity of the peak at 755 cm⁻¹ in the infrared spectra as compared to the peak at 620 cm ⁻¹ suggests the transformation of TeO₄ building units to TeO₃ pyramids with the addition of alkali oxide. Proposed structural change is further supported by the strong compositional dependence of the 755-cm⁻¹ peak in the Raman spectra as well as by the formation of a shoulder in the O 1 s peak of X-ray photoelectron spectra. In contrast to alkali silicate glasses, formation of nonbridging oxygens with the addition of alkali oxide is not observed.     

ZnO-B_2O_3-Bi_2O_3玻璃的结构性能研究

用传统熔融冷却法制备ZnO-B_2O_3-Bi_2O_3,系统玻璃,采用X射线衍射法和差热分析法研究了玻璃的结构和玻璃的特征温度T_g和T_f,测试了玻璃的密度、热膨胀系数和介电常数等性能。结果表明,在ZnO-B_2O_3-Bi_2O_3系统玻璃中,当用B_2O_3逐步取代Bi_2O_3时,玻璃的特征温度T_g和T_f呈现逐渐升高的趋势,玻璃热膨胀系数由11.13×10~(-6)/℃减小至6.22×10~(-6)/℃,玻璃的密度由5.920 g/cm~3减小至4.114 g/cm~3,同时,玻璃的介电常数也有一定程度的下降。     

P2O5对Bi2O3-B2O3-ZnO体系玻璃结构及热性能的影响

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℃.     

Corrosion of Borosilicate Glasses Subjected to Aggressive Test Conditions: Structural Investigations

Sodium borosilicate (NBS) and barium sodium borosilicate (BBS) glasses, used for immobilization of high‐level nuclear waste with compositions (SiO₂)_0.477(B₂O₃)_0.239(Na₂O)_0.170(TiO₂)_0.023(CaO)_0.068(Al₂O₃)_0.023 and (SiO₂)_0.482(B₂O₃)_0.244(Na₂O)_0.220(BaO)_0.054 were subjected leaching experiments under hydrothermal conditions in an autoclave at 200°C for different time durations. Morphological and structural transformations associated with leaching, have been monitored with techniques like XRD, SEM, solid‐state nuclear magnetic resonance. XRD and SEM along with NMR studies have confirmed that, upon leaching, formation of an aluminosilicate phase, Zeolite‐P (Na₆Al₆Si₁₀O₃₂·12H₂O), occurs with NBS glass. BBS glass upon subjecting to the same conditions leads to formation of multiple amorphous phases having Q⁴ (silica rich phase) and Q³ structural units of Silicon along with structurally modified residual glass. Upon leaching BO₃ structural units preferentially get released from BBS glass. Comparison of results with international simple glass confirmed that, for the latter, mass loss rates are one order of magnitude lower.