CaO含量对镧硼硅酸盐玻璃陶瓷晶相和化学稳定性的影响

采用熔融冷却法制备了Na₂O-CaO-La₂O₃-B₂O₃-SiO₂玻璃,经热处理获得了硅酸盐氧基磷灰石硼硅酸盐玻璃陶瓷,并采用X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)、差示扫描量热法(DSC)、产品一致性试验(PCT)法等方法探究了CaO取代SiO₂对该硼硅酸盐玻璃陶瓷物相、微观结构和化学稳定性的影响规律。结果显示:随着CaO含量增加,硅酸盐氧基磷灰石晶相衍射峰增强,其他晶相的衍射峰减弱直至消失,当CaO摩尔分数为15%时获得只含CaLa₄(SiO₄)₃O晶相的玻璃陶瓷样品;CaO含量会对玻璃陶瓷的晶相种类和晶体形状、大小、分布产生影响,CaO含量变化会造成陶瓷相晶体发生团簇和长大;采用PCT法浸泡28 d后,所有样品关于Si、Ca、La三种元素的归一化浸出率(g·m^-2·d^-1)均保持在10^-3数量级以下,表明其具有优异的化学稳定性,且CaO摩尔分数为15%的玻璃陶瓷样品化学稳定性最优异。研究结果表明,硅酸盐氧基磷灰石硼硅酸盐玻璃陶瓷是固化富La和某些锕系元素高放废物的潜在基材。     

硼硅酸盐玻璃固化体蚀变层结构及浸出行为研究

采用挂片静态浸泡法评价了硼硅酸盐玻璃固化体经模拟地下水侵蚀长达364 d的浸出行为,用X射线衍射仪(XRD)和扫描电子显微镜-X射线能谱仪(BSE-EDS)等手段分析了蚀变层物相、形貌及成分随时间的变化情况.结果表明,浸泡56 d后玻璃固化体表面出现了蜂窝状的页硅酸盐,其结构疏松且孔隙较大,使得Si、B的浸出速率略有升高;91 d后由蜂窝状转变为短棒状形貌并出现了棱柱状CaCO3和片状BaSO4晶体,随着时间进一步延长其结构变得更加致密,Si、B的浸出速率因此逐渐下降且Si的浸出比B低一个数量级;蚀变层主要由富Mg硅酸盐二次相和凝胶层构成,其厚度随着浸泡时间的延长而增加,二次相厚度在182d后基本保持不变;Cs在7 d内快速浸出后逐渐下降,U的浸出速率总体呈下降趋势.     

拉曼光谱强度可控的硼硅锌光学玻璃制备

本文采用高温固相法制备了拉曼光谱强度可控的硼硅锌(ZnO-B2O3-SiO2)玻璃。分别采用X射线衍射仪(XRD)、荧光光谱(RF)和拉曼光谱(Raman)表征了样品的结构和光学性能。结果表明,ZnO-B2O3-SiO2玻璃基质中掺杂微量BaCO3、TiO2,制备出拉曼光谱强度可控的硼硅锌玻璃。硼硅锌玻璃样品配方中SiO2和B2O3含量对玻璃拉曼光谱强度有重要影响,随着SiO2含量的增加和B2O3含量的减少,玻璃样品拉曼光谱强度逐渐降低。当SiO2含量为40%,B2O3含量为36.2%时,在514 nm波长下激发,玻璃样品与参考玻璃的荧光激发光谱最为接近。     

温度对模拟高放玻璃固化体显微结构和抗浸出性能的影响

以模拟北山地下水为浸泡剂,采用静态浸出试验法(MCC-1),研究了温度(40～150℃)对模拟高放废液硼硅酸盐玻璃固化体显微结构和抗浸出性能的影响.结果表明:玻璃固化体浸泡42 d后,在90℃及以上温度出现了蜂窝状的页硅酸盐和铝硅酸盐矿物,在150℃还新生成了白色板状BaSO4晶体;Si、B、Cs和U元素的归一化浸出率(LR)在28 d后趋于平稳,且随着温度升高浸出率逐渐升高;基于B元素浸出速率的表观活化能约为27.8 kJ/mol;玻璃固化体在90℃模拟地下水浸泡28 d后的LRSi、LRB、LRCs、LRU分别为1.45×10-1、1.39×10-1、2.48×10-1、1.3×10-1g/(m2·d).     

磷钼杂多酸盐含量对硼硅酸盐玻璃固化体结构和抗浸出性能的影响

我国现存高放泥浆主要成分为磷钼杂多酸盐(PM),磷和钼在硼硅酸盐玻璃中溶解度较低,超过一定溶解度后会在玻璃表面产生分相从而影响玻璃化的效率和安全。本文主要研究了PM含量对硼硅酸盐玻璃固化体物相组成、微观结构和抗浸出性能的影响。结果表明,当PM掺量为0%～4%(质量分数,下同)时,样品为透明玻璃,而PM掺量高于5%时,样品为含钼酸钙和钼酸钡晶相的玻璃陶瓷。随着PM掺量从0%增加至6%,玻璃网络结构中的[SiO₄]结构逐渐解聚,[MoO₄]^2-结构逐渐增加,且[BO₄]、Q³和Q⁴结构单元含量逐渐降低,玻璃网络结构的致密程度也逐渐降低。随着PM掺量增加,Si、B和Na元素28 d归一化浸出率先降低后升高,Mo元素28 d归一化浸出率先升高后降低。     

煤及其热解过程中微观结构的光谱学研究进展

介绍了利用现代仪器光谱学技术对煤微观结构研究的方法,综述了利用X射线衍射(XRD)、红外光谱(FTIR)、拉曼光谱(Raman)等现代仪器光谱技术在煤微观结构的分析、煤的热解过程及其热解后产物的微观结构分析的研究现状,分析了煤微观结构的变化对煤的性质及其热解过程中性质变化的影响,展望了现代分析仪器在煤化工领域的应用前景。     

用于硅酸盐熔体微结构研究的高温Ramam光谱技术

硅酸盐熔体微结构通常在熔态下进行实验研究，而不是采用淬冷物质或玻璃样品的间接研究方法。为此比较了当前若干微结构测试方法用于高温的可能性，方法的特点，适用范围和缺陷。此处介绍一种高温Raman光谱技术，它配备了显微热台，实现了高温达1623K的共焦显微Raman；并采用了光谱信号的时间分辨检测技术，实现了可达2023K温度下的宏观Raman，拓展了Raman光谱研究高温物质结构的应用。通过对硅酸盐等熔体的Raman光谱测定和相关淬冷玻璃光谱的比较研究，表明高温Raman光谱是实时和原位研究熔体微结构的有效实验方法，同时探讨了将电荷耦合探测技术引入高温Raman光谱技术的可行性。     

硼硅酸盐泡沫玻璃研究

以C和Sb2O3组合作为发泡剂,通过粉末烧结发泡工艺制备了硼硅酸盐泡沫玻璃,采用SEM观察了试样的微观结构形貌,并研究了试样的耐酸腐蚀性能.结果表明:当发泡剂C的质量分数为0.9%、Sb2O3的质量分数为8.1%时,在1200 ℃、保温30 min条件下,可以制备出平均孔径为0.2～1.0 mm、气孔分布较均匀的硼硅酸盐泡沫玻璃.试样中气孔结构主要与气泡内的气体压力、玻璃的表面张力和粘度有关.将试样浸泡在0.1 mol/L的稀硫酸中做耐酸腐蚀性实验,60 d内试样的质量先有微量增加后保持不变,这主要是由于稀硫酸进入试样的气孔结构中后形成了一层保护膜,从而阻碍了进一步的侵蚀.     

硼硅酸盐微晶泡沫玻璃耐酸性研究

以废玻璃粉为主要原料,掺入适量的脱镁硼泥,以C和MnO2为复合发泡剂,以ZrO2、TiO2为晶核剂,引入适量的添加剂,采用粉末烧成法工艺制备硼硅酸盐微晶泡沫玻璃。运用DSC-TG、XRD、SEM等微观测试方法,确定试样的核化和晶化温度、晶相种类以及在酸中浸泡前后的微观形貌,研究试样的耐酸腐蚀性。研究结果表明:当废玻璃粉和脱镁硼泥的质量比为8∶2,添加3%TiO2晶核剂,在1150℃保温30min,制备出硼硅酸盐微晶泡沫玻璃试样。把试样浸泡在0.1mol/L的稀硫酸中,浸泡14d后质量仅增加了0.02%,而浸泡35d-42d试样质量基本不变,说明硼硅酸盐微晶泡沫玻璃具有较强的耐酸性。     

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.     

Leached Layer Formation on Float Glass Surfaces in the Presence of Acid Interleave Coatings

Acid interleave coatings are routinely used in the float glass industry to inhibit corrosion during transport and storage in hot, humid environments. It is well recognized that acid interleave coatings neutralize surface alkalinity, and thereby delay the onset of etching, dissolution, and permanent staining (so-called Stage II corrosion). However, the effect of acid interleave coatings on leached layer formation (so-called Stage I corrosion) has not been reported. For many applications of float glass, the presence of a shallow leached layer may be of little consequence, but in other applications, there can be nanoscale effects on scratch resistance, optical properties, adsorption, adhesion, and interface stability. In this study, complementary techniques of X-ray photoelectron spectroscopy (XPS) sputter depth profiling and infrared reflection spectroscopy were used to evaluate the thickness of leached layers in float glass samples weathered in a controlled manner, both with and without acid interleave coatings applied. The results reveal that acid interleave coatings do, in fact, enhance leaching during both cyclic and static weathering. This confirms that the acid not only neutralizes the alkaline reaction products of weathering but also reacts with the glass itself by ion exchange. The concentration of acid in the coating influences the thickness of the resultant leached layer, but this effect depends on the weathering conditions (cyclic versus static) and the duration of the exposure; boric acid and adipic acid coatings performed similarly. An excellent correlation was found between the more direct method of XPS depth profiling of the sodium leaching profile and the less direct, but perhaps more convenient, method of infrared reflection spectroscopy.     

Chemical durability of borosilicate pharmaceutical glasses: Mixed alkaline earth effect with varying [MgO]/[CaO] ratio

Glass for pharmaceutical packaging requires high chemical durability for the safe storage and distribution of newly developed medicines. In borosilicate pharmaceutical glasses which typically contain a mixture of different modifier ions (alkali or alkaline earth), the dependence of the chemical durability on alkaline earth oxide concentrations is not well understood. Here, we have designed a series of borosilicate glasses with systematic substitutions of CaO with MgO while keeping their total concentrations at 13 mol% and a fixed Na₂O concentration of 12.7 mol%. We used these glasses to investigate the influence of R = [MgO]/([MgO] + [CaO]) on the resistance to aqueous corrosion at 80°C for 40 days. It was found that this type of borosilicate glass undergoes both leaching of modifier ions through an ion exchange process and etching of the glass network, leading to dissolution of the glass surface. Based on the concentration analysis of the Si and B species dissolved into the solution phase, the dissolved layer thickness was found to increase from ~100 to ~170 nm as R increases from 0 to 1. The depth profiling analysis of the glasses retrieved from the solution showed that the concentration of modifier ions (Na⁺, Ca²⁺, and Mg²⁺) at the interface between the solution and the corroded glass surface decreased to around 40%–60% of the corresponding bulk concentrations, regardless of R and the leaching of modifier cations resulted in a silica-rich layer in the surface. The leaching of Ca²⁺ and Mg²⁺ ions occurred within ~50 and <25 nm, respectively, from the glass surface and this thickness was not a strong function of R. The leaching of Na⁺ ions varied monotonically; the thickness of the Na⁺ depletion layer increased from ~100 nm at R = 0 to ~200 nm at R = 1. Vibrational spectroscopy analysis suggested that the partial depletion of the ions may have caused some degree of the network re-arrangement or re-polymerization in the corroded layer. Overall, these results suggested that for the borosilicate glass, replacing [CaO] with [MgO] deteriorates the chemical durability in aqueous solution.     

The dissolution behavior in alkaline solutions of a borosilicate glass with and without P2O5

There are a variety of applications for glasses in alkaline environments, including glass fibers and glass‐coated steel to reinforce concrete structures. To understand how a simple glass reacts in such environments, the dissolution behavior of a 25Na₂O–25B₂O₃–50SiO₂ (mol%) glass, doped with and without 3 mol% P₂O₅, in pH 12 KOH and pH 12 KOH saturated with Ca²⁺ ions was studied. Ca²⁺ ions in the solution significantly reduce the glass dissolution rate by forming a passivating calcium silicate hydrate (C–S–H) gel layer on the glass surface. When these corroded glasses were then exposed to Ca‐free KOH, the C–S–H layer redissolves into the undersaturated solution and the glass dissolution rate increases. For phosphate‐doped borosilicate glass, PO₄^3? units released from the dissolving glass react with Ca²⁺ ions in saturated solutions to form crystalline hydroxylapatite on the glass surface, but this layer does not protect the glass from corrosion as well as the C–S–H does. The nature of the C–S–H layer was characterized by Raman spectroscopy, which reveals a gel layer constituted mainly of silicate anions.     

Corrosion of Borosilicate Sealing Glasses for Molten Carbonate Fuel Cells

The development of a new sealant for molten carbonate fuel cells (MCFC) requires a study of the attack of molten carbonates on selected materials. Silica and Pyrex® glasses have better corrosion resistance against molten carbonates than other glasses, but they have unsuitable thermal expansion coefficients. Comparisons have also been made between borosilicate glasses of suitable thermal expansion for sealants for MCFC and silica and Pyrex® glasses. The corrosion kinetics in molten carbonates follows two limiting relations and involves two corrosion mechanisms. The weight loss varied linearly with time, indicating a dissolution of the glass network at short times. Longer times show corrosion, depending on the square root of time, typical of a diffusion mechanism and indicating formation of a protective layer on the surface of the glass. The main crystalline corrosion product is lithium methasilicate. The glass-corrosion rate follows the well-known Arrhenius law. These studies used scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and chemical analysis. A general corrosion mechanism of borosilicate glasses in molten carbonates is proposed.     

Experimental investigation on thermal healing of subsurface damage in borosilicate glass

Subsurface damage (SSD) is the fracture and deformation near the surface of brittle optical materials, caused by surface lapping or grinding. The existence of SSD dramatically influences the performance of optical glass and reduces the laser-induced damage threshold. Subsurface cracks of borosilicate glass can be spontaneously healed when heated under appropriate conditions. In this paper, thermal healing experiments of borosilicate glass (BK7) subsurface cracks are conducted on typical cracks induced by an indentation process, and the effects of the Beilby layer, temperature, crack depth, and water vapor pressure are studied. A semi-empirical relation is obtained through the regression of experimental results to describe the variation of subsurface crack length. Finally, a healing experiment is performed on the subsurface damage formed by grinding. The detection results show both the damage density and maximum damage depth have been reduced after heat treatment, demonstrating the effectiveness of the thermal healing method on eliminating glass subsurface damage.     

氧化镧对钒磷二元玻璃结构的影响

采用红外吸收光谱、Raman光谱和51V静态固体核磁共振研究了La2O3对钒磷二元玻璃结构变化的影响.结果表明:钒作为主要的玻璃形成体构成基本网络,磷以孤立的磷氧四面体分散存在于钒为主体的玻璃网络中.磷氧四面体只与钒连接作用,钒在玻璃中主要以(VO3)n单链、(V2O8n锯齿状链、VO4分枝和V2O4-7基团等形式存在,其中前两种基团占支配地位,对玻璃的性质起决定性影响,La2O3的引入破坏了网络平衡中间态的结构,(V2O8)n锯齿状链结构逐渐转化为(VO3)n单链,使玻璃的结构更加疏松.     

Some Features of Leaching of Two-Phase Alkali Borosilicate Glass Containing PbO

The paper reports the results of a comparative investigation into the leaching kinetics of two-phase alkali borosilicate glasses containing lead oxide in 3 M HCl solution at 100°C and the glasses free from lead oxide. It is revealed that the mechanisms of leaching of the studied glasses exhibit a common feature which resides in the fact that the temporary precipitation of the products of dissolution of the glass components within the leached layer occurs as an intermediate stage of the glass leaching. Unlike glasses free from PbO, the precipitation within the porous layer of a leached lead-containing glass is observed visually, and the presence of crystalline boron-containing precipitates in this layer is confirmed by X-ray powder diffraction analysis. Compared to glasses prepared from two-phase alkali borosilicate glasses free from PbO, the porous glasses produced from two-phase glasses containing PbO are characterized by considerably smaller sizes of micropores and their larger specific surface at the same total porosity.     

Preparation and Characterization of Immobilizing Radioactive Waste Glass From Industrial Wastes

The borosilicate glass is the most common industrial solution host barrier used for the immobilization of low-level wastes for its excellent chemical durability and mechanical properties. The borosilicate glass samples were prepared in a muffle furnace at a temperature 1300 °C, glass samples were then annealed in a furnace at 400 °C. In this study, density, microhardness, pH and the durability of borosilicate glass were tested. Many leaching solutions such as HCl, NaOH and ground water were used. The results show that the prepared glass has good microhardness. The glass composition containing 37.5 % slag ?37.5 % cement dust – 25 % B₂O₃ is the most durable glass in acidic solution and the borosilicate glass of the composition 37.5 % cullet – 37.5 % cement dust – 25 % B₂O₃ is the most corroded glass in acidic solution. The durability was also studied after subjecting the glass samples to different irradiation doses of γ- rays. Infrared absorption results were interpreted in the light of the effect of corrosion and irradiation on the vibrational bands.     

Atomic and micro-structure features of nanoporous aluminosilicate glasses from reactive molecular dynamics simulations

Long-term chemical durability of borosilicate glasses that makes them a widely accepted form of nuclear waste disposal is achieved through the formation of a porous aluminosilicate gel layer that provides passivity and limits the transport of water to the reaction front. Detailed understanding of the porous silicate gel layer is thus critical in elucidating the corrosion mechanism of these glasses and to design of new glass composition for waste immobilization and other applications. In this paper, we use the diffuse charge reactive potential to generate porous aluminosilicate glass structures with compositions equivalent to the gel layers formed at the glass-water interface with an aim to understand the processing condition on the microstructure and atomic structure of these systems. We demonstrate the use of the charge scaling techniques is an effective approach to generate these porous structures with controllable pore mophologies. After initial validation of the potentials and calcium aluminosilicate glass structures using neutron diffraction, we created gel structures with compositions similar to well-known model nuclear waste borosilicate glasses. The porosities and the pore size distribution bear a strong correlation to the processing temperature, as well as to the local atomic structure. Thus, by controlling the processing parameters, the generated porous structures can be customized to closely resemble gel structures due to borosilicate glass corrosion. These results provide insights of the micro- and atomic structure features of the porous aluminosilicate glasses and on the optimal procedure to generate porous structures that can be comparable to experimentally observed gel layer structures thus to elaborate on the correlations between the structure and phenomena in glass-water interactions.