THE DEVITRIFICATION OF SODA-LIME-SILICA GLASSES1

The isotherms and boundary curves in that portion of the ternary system Na₂O-SiO₂–CaO.SiO₂–SiO₂ of direct application to glass technology, namely, from 64 to 78% SiO₂, 0 to 20% CaO, including the whole of the field of the compound Na₂O.3CaO.6SiO₂, and portions of the adjoining fields of Na₂O.2SiO₂, Na₂O.2CaO.3SiO₂, CaO.SiO₂, tridymite, and quartz, have been determined with greater precision than in a previous study² by greatly increasing the number of mixtures studied, and thereby decreasing the interpolation necessary in the interpretation. An extended discussion is given of the devitrification of glass, in which it is shown that the liquidus temperature is the only datum point which is solely a function of glass composition, and is unaffected by the past history of the glass or by fortuitous circumstances at the time devitrification is taking place. At the liquidus the first trace of crystalline phase is in equilibrium with the glass; above the liquidus the glass will dissolve any such crystals which may have been formed at some previous time, but new crystals cannot form; while only below the liquidus is there a tendency for crystals to separate. The driving force causing this reaction is derived from the difference in free energy between the unstable glass and the stable aggregation of crystalline phases, and this force is opposed by a resistance of the nature of a viscosity. The dissociation in the liquid phase of the compounds which separate on devitrification diminishes the rate at which the devitrification equilibrium is reached, and increasing the complexity of the glass will have a similar effect. The excess in surface energy at the interface glass-crystal may have an influence at the instant of formation of the first infinitesimal crystal, hut after the crystal has grown to a dimension appreciably greater than the sphere of molecular action the excess energy at this interface ceases to be of importance. The only surface tension measurements which have been made on glass refer to the interface glass-air, and the excess energy at this interface has no necessary correlation with the devitrification process.     

ON THE CAUSES OF THE SURFACE DEVITRIFICATION OF GLASSES1

The explanation on the causes of the surface devitrification of glasses upon heating, as heretofore considered, is imperfect. The modes of surface devitrification are greatly influenced by the surface conditions of the glasses. The author gives an interpretation on the causes of this phenomenon of surface devitrification, i.e., the surface contraction which is caused by the surface tension at the glass surface acts most seriously toward the surface devitrification.     

EFFECT OF ALUMINA ON DEVITRIFICATION OF SODIUM OXIDE-DOLOMITE LIME-SILICA GLASSES*

The effect of the substitution of A1₂O₃ for the oxides of sodium, silicon, calcium, and magnesium in the ratio in which they occur in dolomite on the liquidus temperatures and phase relations for glasses lying within the composition range, Na₂O 12 to 16%, CaO-MgO 0 to 20%, SiO₂ 63 to 78%, and A1₂O₃ 0 to 10%, has been determined. The results on 116 individual determinations are given. Devitrite is the primary phase in very few glasses. Several glasses were found which cannot be devitrified. A comparison of devitrification temperatures of calcite and dolomite-lime glasses is made.     

TiO2对凝胶法制备Li2O-Al2O3-SiO2系微晶玻璃析晶性能的影响

采用高分子网络凝胶法制得Li2O-Al2O3-SiO2系微晶玻璃粉体,加入TiO2以调节其析晶性能,采用TG-DTA、IR、XRD等手段来表征和分析烧结产物,研究掺杂TiO2对微晶玻璃晶化行为的影响。结果表明:TiO2的掺杂使析晶温度提前,降低了析晶活化能,引起了玻璃的整体析晶,促使β-石英固溶体向β-锂霞石固溶体的转变,掺杂还使晶粒细化。     

CaO—Al2O3-SiO2-F系统玻璃密度与结构关系研究

采用传统熔融冷却法制备了CaO-Al2O3-SiO2-AlF3(A系列)和CaO-Al2O3-SiO2-CaF2(C系列)系统玻璃,在其组成范围SiO245mol%、Ca/Al1(mol)、F/Al1(mol)内,利用Doweidar密度模型在CaO-Al2O3-SiO2-F系统玻璃A系列和C系列中分别得到AlO3F四面体的体积,其值可认为是一常数VAl-f=57.82×10-24cm-3,与引入氟的形式(CaF2或AlF3)和化学计量浓度的改变无关;AlO4四面体的体积大于AlO3F四面体体积(VAl-fVAl-o),分析认为这与质点间的键力发生改变有关(fAl-ffAl-0),键力越小,质点间的距离越大,使VAl-f变大。由此模型得到的CaO-Al2O3-SiO2-F玻璃理论计算密度值与实际测量密度值基本相符,误差小于0.03%。     

Al2O3对CaO-Al2O3-SiO2系微晶玻璃晶化和性能的影响

以CaO-Al2O3-SiO2三元系微晶玻璃为研究对象,从玻璃析晶动力学方面进行研究,通过DTA和SEM等分析方法,对微晶玻璃析晶行为进行研究,利用析晶活化能E和析晶参数n值来分析析晶机理;实验结果表明:析晶参数n=2,体系属于整体析晶。随着Al2O3含量的增加,析晶温度有升高的趋势,析晶活化能增大,有利于玻璃的烧结;试样密度增大,显微硬度增加。     

REFRACTIVE INDICES OF SOME GLASSES IN THE TERNARY SYSTEM K2O 4SiO2-Fe2O3-SiO2*

In the course of some phase-rule investigations of the ternary system K₂O-4SiO₂-Fe₂O₃-SiO₂ by the “quenching method” of Shepherd, Rankin, and Wright, the refractive indices of 30 glasses were measured by the usual petrographic immersion method. The refractivities varied from 1.438 for a K₂O-7SiO₂ glass to 1.621 for the most ferriferous glass which contained 32.3% Fe₂O₃. The maximum FeO content reached a value of 0.33 % in a glass originally containing 25 % Fe₂O₃. Along the sections K₂O 4SiO₂, K₂O-5SiO₂, K₂O-6SiO₂, and K₂O-7SiO₂, the relation between the Fe₂O₃ content of the glasses and the refractive index is apparently linear. The isofracts, however, in the ternary system are curved lines.     

Na2O对氧化物/MoSi2基复合材料的高温蠕变特性的影响

研究了脱Na工艺前后氧化物/MoSi2基发热元件材料对石英玻璃管失透性的影响及其高温蠕变特性.结果表明通过脱Na处理氧化物/MoSi2基复合材料对石英玻璃管的失透现象基本消失, 而且高温蠕变特性有了明显改善, 材料蠕变应力指数和活化能分别从原来的0.83, 281 kJ*mol-1变化到0.71, 292 kJ*mol-1.并且氧化物/MoSi2基复合材料的这种蠕变行为可以从晶界滑移理论得到很好的解释.     

ZnO对MgO-Al2O3-SiO2体系的结构和红外辐射性能的影响

采用固相反应法制备名义组成为Mg2 ( 1x) Zn2xAl4Si5O1 8(x =0～ 0 .6)的红外辐射材料 ,测试了样品的红外辐射性能 ,并用XRD ,IR ,2 9SiMASNMR等方法研究了体系的结构。研究结果表明 :x≤ 0 .2时样品主要为Zn2 固溶α堇青石结构 ,Zn2 的固溶使T1 (与 [MgO6 ]八面体一起在六元环之间起连接作用的四面体 )和T2 (组成六元环结构的四面体 )四面体上Al,Si分布的有序度提高 ,引起α堇青石晶格产生畸变 ,增强了晶格振动的非简谐效应和样品的红外辐射性能。x =0 .2时样品的红外辐射性能达到最佳 ,其法向全波段比辐射率达到 0 .89,在 8～ 2 5 μm内各波段的辐射率达到 0 .90～ 0 .93。x >0 .2时样品的红外辐射性能随x的增大而降低 ,x≥ 0 .4时样品中主要形成 (Mg1xZnx)Al2 O4尖晶石固溶体和方石英     

CaO对CaO-Al2O3-SiO2微晶玻璃晶化过程活化能的影响

CaO对CaO-Al2O3-SiO2系统微晶玻璃的烧结及析晶性能有较大影响,从而影响了微晶玻璃的结构及性能.本文运用DTA、烧结收缩率分别测定了CaO-A12O3-SiO2系统微晶玻璃的烧结活化能及析晶活化能,研究了这两者的变化趋势.     

P2O5含量对Al2O3-SiO2-P2O5系统玻璃结构和析晶性能的影响

采用高温熔融冷淬法制备Al2O3-SiO2-P2O(5ASP)系统玻璃,用原位晶化法获得了磷酸盐微晶玻璃;用IR、DSC、XRD、SEM等测试方法表征了玻璃结构及析晶性能,讨论了P2O5含量对ASP玻璃结构和析晶性能的影响。结果表明:P2O5含量在35～50%能形成稳定的ASP玻璃。在磷含量较低时,玻璃结构中的P5 主要以不含P=O双键的[PO4]四面体形式存在,P2O5含量较高时,结构中的P-O-键削弱,P=O双键加强,P5 部分以含P=O双键的[PO4]四面体形式存在。随着P2O5含量的增加,玻璃稳定性变差,析晶趋势增强;晶化后的玻璃以AlPO4为主晶相,同时含有少量的Al(PO)3晶相,当晶化温度由650℃升高到800℃时,晶相含量增加并出现YPO4晶相。     

Fe2O3对CaO-SiO2玻璃和微晶玻璃性能的影响

利用溶胶-凝胶法制得Fe2O3-CaO-SiO2系基础玻璃,研究不同含量的Fe2O3对CaO-SiO2玻璃和微晶玻璃性能的影响.经分析,不同组分的玻璃凝结时间不同,处于低共熔点的样品凝结时间最短,而离低共熔点最远的样品凝结时间最长.样品的密度并不随成分而变化.溶胶凝胶转变过程中,不同组分所得的凝胶玻璃有一定的耐酸碱性.而微晶玻璃的耐酸碱性比玻璃都略有增强.微晶玻璃的饱和磁化强度和磁铁矿在玻璃中所占的体积分数有关.随着玻璃中Fe2O3含量的增加,饱和磁化强度增大.     

Bi_2O_3-SiO_2系统玻璃非等温析晶动力学

利用高温熔体冷却法制备了Bi2O3-SiO2(BS)系统玻璃,通过差热分析和X射线衍射,并借助Kissinger方程和Augis-Bennett方程,研究了BS系统玻璃的非等温析晶动力学和玻璃相转变动力学行为。结果表明:在热处理过程中,BS系统基础玻璃依次产生了3种主晶相:Bi12SiO20,Bi2SiO5和Bi4Si3O12;对应的活化能Ep1=150.6kJ/mol,Ep2=474.9kJ/mol,Ep3=340.3kJ/mol;平均析晶指数m1=2.5,m2=2.1,m3=2.2,所产生晶相均为体积成核,一维空间生长;系统中产生的亚稳定相Bi2SiO5易于向稳定的Bi4Si3O12相转变,通过Kissinger方程计算出该相转变的活化能Eg为90.5kJ/mol。     

稀土掺杂对TiO2-SiO2薄膜晶相转变及性能的影响

采用溶胶-凝胶法在釉面砖上制备了均匀的稀土离子La3+掺杂和ce4+掺杂的TiO2-SiO2,光催化薄膜.应用X射线衍射(XRD)和紫外可见分光光度计研究了La3+掺杂和ce4+掺杂对TiO2-SiO2,薄膜晶相转变、光催化性能及亲水性能的影响,用紫外光照射亚甲基蓝的光催化降解实验比较了不同薄膜的光催化性能.结果表明:La3+掺杂后,抑制了TiO2-SiO2薄膜中的TiO2,从锐钛矿向金红石相的晶型转变,显著提高了TiO2-SiO2,薄膜的光催化性能,也提高了其亲水性能;ce4+掺杂后,则促进了TiO2-SiO2,薄膜中TiO2从锐钛矿向金红石相的晶型转变,同时降低了薄膜的光催化性能.     

ZnO对Li2O-Al2O3-SiO2系统低膨胀微晶玻璃性能的影响

利用DTA、X-射线衍射、SEM(电镜扫描)的测定分析及热膨胀系数的测定等实验手段,研究了ZnO对Li2O-Al2O3-SiO2系统低膨胀微晶玻璃的熔制性能、析晶性能及热膨胀性能的影响.     

ZnO和Na2O对CaO-B2O3-SiO2介电陶瓷结构与性能的影响

研究了烧结助剂ZnO和Na2 O对CaO -B2 O3 -SiO2 (CBS)系微波介质陶瓷介电性能、相组成及结构特性的影响。烧结助剂ZnO在烧结过程中与B2 O3 及SiO2 生成低熔点玻璃相 ,有效地降低了材料的致密化温度 ,烧结机理为液相烧结。碱金属氧化物Na2 O虽然能够有效降低材料的烧结温度 ,但会破坏硅灰石晶体结构 ,引起材料微波性能显著降低。通过实验 ,制备出了具有优良微波介电性能的陶瓷材料 ,适用于LTCC基板及滤波器等高频微波器件的生产     

显微Raman光谱法对Al2O3-SiO2-H2O系反应过程的探索表征

用显微Raman光谱法在Al2O3-SiO2-H2O体系不除去所含水分的情况下对样品进行了检测,避免了脱水处理过程对样品微结构的损伤.研究了反应产物和微结构随时间进展的变化情况,对同一样品进行了定点跟踪观察,Raman光谱检测结果和在显微镜下观测结果很好地对应.结果表明:对于配比为m(钾水玻璃):m(偏高岭土):m粉煤灰): m(硅灰)=10:9:1:1,石膏掺量为3.7%的实验样品,在搅拌后4 h之内,二水石膏溶解于体系,Ca2 浓度提高,[SiO4]4-聚合度下降,偏高岭土中的五配位铝逐渐消失;在搅拌后4h至1 d中,大量的含水凝胶物形成,材料也因此开始有强度,样品表面变得致密;在搅拌后1 d至7d中,结晶态K2SO4形成,样品表面致密程度大幅提高,材料的强度也随之提高.     

MELTING RATE OF SODA-LIME-SILICA GLASSES AS INFLUENCED BY COMPOSITION AND THE EFFECT OF MINOR CONSTITUENTS*

Using the disappearance of batch as a criterion of melting, a comparison of the rate of melting of twenty-six soda-lime-silica glass compositions has been made. With the composition, Na10 14%, CaO 12%. and SiOt (+R20.) 74%, as abase glass, theeffect of substituting small amounts of B.O., BaO, SOI, etc., on the rate of melting was studied. Theraw materials used were soda ash, calcite limestone. silica sand, dehydrated borax, barytes, salt cake, Chilean saltpeter, ammonium sulfate, fluorspar, and common salt.     

EQUILIBRIUM RELATIONSHIPS ON THE LIQUIDUS SURFACE IN PART OF THE MnO-Al2O3-SiO2 SYSTEM*

The minerals found to have a stability range on the liquidus surface in the system MnO-Al₂O₃-SiO₂ are cristobalite and tridymite, SiO₂; mullite, 3Al₂O₃. 2SiO₂; corundum, Al₂O₃; rhodonite, MnO.SiO₂; tephroite, 2MnO.SiO₂; galaxite, MnO.Al₂O₃; spessartite, 3MnO.Al₂O₃.3SiO₂; and a new compound, 2MnO.2Al₂O₃.5SiO₂. The quintuple points and boundary lines found in that part of the MnO.Al₂O₃.SiO₂ system bounded by the systems 3MnO.Al₂O₃.3SiO₂-SiO₂, 3MnO.Al₂O₃.3SiO₂-Al₂O₃, and Al₂O₃-SiO₂have been determined. Quintuple points and boundary lines involving the area inclosed by the systems 2MnO . SiO₂-3MnO . Al₂O₃ . 3SiO₂, 3MnO . Al₂O₃ . 3SiO₂-SiO₂, and 2MnO.-SiO₂-SiO₂ are indicated. Isotherms and isofracts (lines of equal refractive index) are given for the portion of the system investigated. X-ray data show that crystals of the compound 3MnO.Al₂O₃.3SiO₂ have the same structure as the garnet mineral spessartite (manganese garnet). The compound 2MnO. 2Al₂O₃ . 5SiO₂, which is shown by X-ray data to have a basic structure similar to cordierite, 2MgO.2Al₂O₃.5SiO₂, seldom crystallizes from the glass, but a third substance which has a high extinction angle crystallizes readily from the reheated glass. These high extinction angle crystals are replaced by 2MnO .2Al₂O₃.5SiO₂ when a proper heating cycle is employed, and they are not found again until the product is melted and crystallization is repeated.     

VISCOSITY STUDIES OF SYSTEM CaO-MgO-Al2O3-SiO2: II,CaO-Al2O3-SiO2*

Viscosity data are presented covering those compositions in the CaO-Al₂O₃-SiO₂ system which are liquid at 1500°C. The pattern of isokoms on the CaO-Al₂O₃-SiO₂ face of the compositional tetrahedron which represents the CaO-MgO-Al₂O₃-SiO₂ system is a system of lines which roughly parallel the lines along which the lime content is constant. There are, however, considerable deviations from this parallelism in regions of very low and very high alumina content.