基础成分配比对白云鄂博尾矿微晶玻璃结构及性能的影响

以白云鄂博二次选后尾矿和粉煤灰为主要原料,采用熔融法制备得到了CaO-MgO-Al2O3-SiO2系尾矿微晶玻璃.制备流程包括熔融、退火、核化及晶化过程.其中玻璃熔融温度为1450℃,核化温度为720℃,晶化温度为850℃.利用XRD研究了基础玻璃成分配比对微晶玻璃结构的影响.结果表明基础玻璃成分配比直接决定微晶玻璃的主晶相形成.随着基础玻璃成分配比的变化,微晶玻璃可能形成辉石相、钙长石相、镁铁尖晶石相或磁铁矿相.当其他元素固定,CaO/MgO和CaO/Al2O3比值的减小会导致微晶玻璃由辉石相转变为镁铁尖晶石相和钙长石相.而当SiO2/CaO比值大于2时,主晶相则由辉石相转变为磁铁矿相.DTA测试结果表明CaO有利于析晶温度的降低,而MgO、Al2O3和SiO2相对提高了析晶温度.力学性能测试表明抗折强度、密度、耐酸碱度与微晶玻璃主晶相有直接关系.主晶相为辉石相的微晶玻璃具有更高的抗折强度、密度和耐酸性.     

Fe2O3对CaO-Al2O3-MgO-SiO2系微晶玻璃析晶及断裂特性的影响

采用熔融法,利用纯化学试剂制备了CaO-A12O3-MgO-SiO2 (CAMS)系微晶玻璃,利用DTA、XRD、拉曼光谱仪等研究了Fe2O3对微晶玻璃析晶特性的影响规律,微晶玻璃的物化性能由抗折强度、杨氏模量、剪切模量、泊松比、维氏硬度等进行评价.结果表明,微晶玻璃的析晶特性随着Fe2 O3含量的增加而增强,对应母体玻璃中首先出现富铁相,进而促进辉石主晶相的析出.微晶玻璃的断裂特性及裂纹扩展方式均随析晶度的提高得到明显改善.但过量的Fe2O3添加则对微晶玻璃的析晶特性无明显影响,反而降低了玻璃相的致密性.微晶玻璃的耐酸性、抗折强度、杨氏模量及剪切模量均呈现先增加后降低的趋势,微晶玻璃的Fe2 O3含量为6.6wt;时综合性能最优.     

透辉石微晶玻璃的低温烧结制备及性能表征

以废弃建筑玻璃为主体原料,将废玻璃粉、高岭土和氧化镁进行球磨混和,压制成型后直接烧结,在低温下成功制备出具有单一透辉石晶相结构的微晶玻璃.采用X射线衍射、场发射扫描电子显微镜等测试手段,研究了MgO加入量和烧结温度对微晶玻璃样品的晶相组成、显微结构及性能等的影响.结果表明:随着MgO加入量的增多以及烧结温度的升高,微晶玻璃的体积密度和抗弯强度均呈现先增大后减小的趋势.MgO加入量和烧结温度的提高可以有效促进透辉石晶相的析出.当MgO加入量为4;、975℃烧结2 h时所制备得到的透辉石微晶玻璃性能最好,其体积密度为2.395 g·cm-3,抗折强度102.1 MPa.     

熔融法转炉钢渣微晶玻璃的结构与性能研究

利用转炉钢渣制备出高性能的微晶玻璃,可有效提高其附加值,同时具有环保效益.本文以转炉钢渣为主要原料,通过组分设计,改变其掺人量,制备出了相应的基础玻璃与微晶玻璃.并通过XRD、DSC、FTIR、SEM以及抗折强度、密度、表面硬度等进行表征,获得了如下结果:转炉钢渣的掺量在45wt; ～ 55wt;之间变化时,均可以制备出微晶玻璃.随着CaO/SiO2的增加,有利于促进玻璃析晶,与此同时,会促进在架状结构的霞石晶相中析出聚粒状的二次晶相普通辉石.普通辉石晶相的析出不利于抗折强度的增长,但对密度和硬度均有所提高.当钢渣掺量为50wt;时,微晶玻璃的最高抗折强度为198.89 MPa,显微硬度为772 MPa,密度为2.86 g/cm3.     

微波法热处理制备CaO-MgO-Al2O3-SiO2系微晶玻璃的研究

以二氧化硅,三氧化二铝,氧化钙和氧化镁为主要原料,分别采用微波辐射和传统电加热制备了一系列CaO-MgO-Al2O3-SiO2 (CMAS)系微晶玻璃材料,对比两种方法的热处理制度对微晶玻璃结构与性能的影响,并进一步讨论了微波非热效应的影响.利用DTA、XRD、SEM和综合力学性能仪等手段,研究了两种对该系微晶玻璃显微结构及性能的影响.实验结果表明,两种方法制备的微晶玻璃主晶相均为辉石相,力学性能也基本相当.与传统热处理方法相比,微波法可在更短时间内制备出性能较好的微晶玻璃材料,微波非热效应有助于降低其晶化温度.     

不同冷却方式黄磷炉渣微晶玻璃析晶动力学研究

以水淬黄磷炉渣和自然冷却态黄磷炉渣为研究对象,采用熔融法制备CaO-Al2O3-SiO2系微晶玻璃.通过差热分析、X射线衍射和扫描电镜,并利用修正后的Johnson-Mehl-Avrami (JMA)方程和Augis-Bennett方程,分析了不同冷却方式下黄磷炉渣制备微晶玻璃的析晶规律.结果表明:不同冷却方式对微晶玻璃的析晶行为有所不同,水淬黄磷炉渣微晶玻璃的析晶活化能E为352.609 kJ/mol,自然冷却黄磷炉渣微晶玻璃的析晶活化能E为405.685kJ/mol;两种不同冷却方式的黄磷炉渣微晶玻璃的晶化机制均为三维体积晶化.水淬黄磷炉渣微晶玻璃中主晶相为硅灰石(CaSiO3)并含有少量的石英矿物;自然冷却黄磷炉渣微晶玻璃中主晶相为钙蔷薇辉石类(Ca(Mn2,Ca)Si2O6)和含铁硅灰石类固溶体((Ca,Fe) SiO3).以自然冷却渣制备的微晶玻璃性能优于水淬渣制备出的微晶玻璃.     

高性能铁磁性微晶玻璃析晶机理及磁性研究

以白云鄂博东尾矿及粉煤灰等固体废弃物为主要原料制备得到了性能优异的微晶玻璃.利用X射线衍射仪(XRD)及高分辨率透射电镜(HRTEM)等测试手段揭示了微晶玻璃的形核及析晶过程.结果表明,热处理过程中磁铁矿晶核首先析出,主晶相辉石相可在磁铁矿晶核上生长.通过调整氧化铁含量可改变微晶玻璃的析晶、物化及磁学特性.随氧化铁含量的增加,微晶玻璃的析晶特性及物化性能均有所降低,但磁学特性有所提高.在高氧化铁含量的微晶玻璃中,磁铁矿相与辉石相可以同时存在,微晶玻璃的磁性主要来源于磁铁矿相.     

铁含量及价态对白云鄂博尾矿微晶玻璃析晶特性及性能的影响

以白云鄂博尾矿及粉煤灰等固体废弃物为主要原料,采用熔融法、经退火、核化及晶化热处理制备得到了以辉石为主晶相的CaO-MgO-Al2O3-SiO2 (CMAS)系尾矿微晶玻璃.利用化学分析方法测定了不同氧化铁及碳含量对微晶玻璃中Fe3+/Fe2+的影响;利用XRD、DTA、SEM等研究了不同氧化铁及碳含量对微晶玻璃结构及析晶特性的影响.结果表明,不同氧化铁添加量对微晶玻璃中Fe3+/Fe2影响很小,因此对微晶玻璃的析晶特性无本质影响.而随着还原碳粉的加入,Fe3+/Fe2与未加碳粉相比减小明显,微晶玻璃中FeO质量分数的增加极大地提高了微晶玻璃的析晶特性.但过量的碳粉加入导致单质铁的析出,反而降低了微晶玻璃的析晶能力.上述析晶特性的变化直接影响到微晶玻璃的耐酸度及抗折强度.     

Cr2O3对白云鄂博西尾矿微晶玻璃显微结构及性能的影响

以白云鄂博西尾矿和粉煤灰为主要原料,采用熔融法制备了添加0～2.0wt; Cr2O3的CaO-MgO-SiO2-Al2O3系微晶玻璃,利用DTA、XRD、FESEM、EDS和综合力学性能仪等测试手段,研究了Cr2O3含量对该体系微晶玻璃显微结构及性能的影响.实验结果表明:少量Cr2O3 (0.5wt;)可有效降低样品的晶化温度,促进主晶相辉石相(Ca(Mg,Fe,Al) (Si,Al)2O6)的形成,同时细化其显微组织,从而提高样品的密度、抗折强度和耐酸碱性;当Cr2O3含量大于等于1.5wt;时,析晶峰温度由804℃提高到816℃,同时微晶玻璃中形成不规则块状结构的镁铁铬尖晶石(MgFeo.9 Cr1.1O4)第二相,并进而引起周围辉石相晶粒异常长大,降低其抗折强度.     

Fe2O3对纳米晶尾矿微晶玻璃结构及性能的影响

以铁尾矿和金尾矿为主要原料,采用熔融法制备了添加0 ～ 20wt; Fe2O3的CaO-MgO-Al2O3-SiO2(CMAS)系纳米晶尾矿微晶玻璃,利用差示扫描量热分析(DSC)、X射线衍射分析(XRD)、红外光谱(IR)、扫描电镜(SEM)和综合力学性能仪等测试手段,研究了Fe2O3含量对该体系微晶玻璃显微结构及性能的影响.实验结果表明:随着Fe2O3含量的增加,样品的晶化温度和玻璃化转变温度逐渐降低;且Fe2O3可促进主晶相透辉石相(Mg0.6Fe0.2Al0.2) Ca(Si1.5Al1.5)O6的形成;同时Fe2O3能够有效减小透辉石相平均晶粒尺寸;另外,微晶玻璃的密度、显微硬度和耐碱性随晶粒尺寸的减小而增加,而抗折强度和耐酸性随晶粒尺寸的减小而降低.     

高炉熔渣微晶玻璃的结构与性能研究

高温熔渣具有大量显热与渣体.采用熔融法制备微晶玻璃可以更好地利用其热和渣,达到高效利用的目的.通过高温条件下混熔的方式制备性能稳定的基础玻璃.利用差示扫描量热仪(DSC)确定基础玻璃的热处理工艺制度.结合高分辨透射电子显微镜(TEM)、X射线衍射分析(XRD)、场发射扫描式电子显微镜(FE-SEM)对微晶玻璃的结构进行了研究.研究表明:基础玻璃中氟含量的增加,有利于促进微晶玻璃成核和晶体长大,降低微晶玻璃的形核结晶温度.在低温热处理得到微晶玻璃的主晶相为萤石,高温热处理得到的微晶玻璃析出了霞石和萤石两个微晶相.高炉渣微晶玻璃中,微晶相的出现可有效提高微晶玻璃的力学性能,试样的显微硬度最高可达585.68 MPa,抗折强度最高可达126.21 MPa.     

微波加热制备含稀土(La2O3)矿渣微晶玻璃研究

利用矿渣制备微晶玻璃是提高矿产资源利用率的主要形式之一。本文以白云鄂博尾矿为原料,采用微波一步法制备了CaO-MgO-Al₂O₃-SiO₂(CMAS)系辉石相矿渣微晶玻璃。选择835 ℃作为晶化温度,研究了微波加热对微晶玻璃析晶行为和微观组织的影响。以La₂O₃作为研究变量探讨了La₂O₃添加对矿渣微晶玻璃析晶行为的作用。与传统的热处理制度相比,微波加热可以在较短的时间内达到较高的析晶效果。同时La₂O₃的添加促进了晶粒细化。由拉曼光谱分析,La离子添加会导致玻璃网络中桥氧的增多,促进了辉石相析晶。在La的添加量为4%(质量分数)时硬度最高,达到了829.22 MPa。     

Effect of crystal content on the properties of willemite glass-ceramics

Helium permeability, thermal expansion properties, and density have been measured for a series of glass-ceramics based on willemite as a lone crystalline phase. These glass-ceramics were prepared such that the compositions of both the glassy and crystalline phases were fixed, and only the relative concentrations of glass and crystal varied. Results of this study demonstrate that the helium permeability and glass transformation temperature of glass-ceramics are controlled by the glassy phase composition, whereas the density, thermal expansion coefficient, and dilatometric softening temperature are a function of both phases. All of these conclusions can be explained readily by simple continuity and mixing arguments.     

晶核剂P2O5对CaO-Al2O3-SiO2系黄磷炉渣微晶玻璃析晶的影响

采用熔融法以自然冷却黄磷炉渣为主要原料,P2O5为晶核剂,制备了黄磷炉渣微晶玻璃.利用X射线衍射仪(XRD)、差热分析(DTA)和扫描电子显微镜(SEM)等分析技术手段,探究了晶核剂P2O5(以KH2PO4的形式引入)对黄磷炉渣微晶玻璃晶化行为及物化性能的影响规律.结果表明:黄磷炉渣基础玻璃的析晶峰温度Tp及析晶活化能E随着P2O5晶核剂的增加呈现先减小后增大的趋势;当晶核剂P2O5加入量达到4wt;时,黄磷炉渣基础玻璃的析晶峰温度Tp及析晶活化能E最小,析晶效果最优,物化性能最优;主晶相硅灰石(CaSiO3)并不随着晶核剂P2O5加入量的增大而发生改变,同时能够促进晶相氟磷灰石(Ca5(PQ)3F)生成.     

Effect of heat-treatment condition on crystallization behavior and thermal expansion coefficient of Li2O-ZnO-Al2O3-SiO2-P2O5 glass-ceramics

Utilizing P₂O₅ as nucleation agent, a Li₂O-ZnO-Al₂O₃-SiO₂ glass was prepared by conventional melt quenching technique and subsequently converted to glass-ceramics with different crystal phases. During the processing, two-step heat-treatments including nucleation and crystallization were adopted. The effects of heat-treatment on the crystal type, the microstructure and the thermal expansion behavior of the glass-ceramics were studied by means of differential scanning calorimetry, X-ray powder diffraction analysis, scanning electron microscopy and thermal expansion coefficient tests. It was shown that the crystallization of occurred after the glass was treated at 580 °C. As the temperature increased from 580 °C to 630 °C, cristobalite and were identified as main and second crystal phases, respectively, in the glass-ceramic. An increase in the temperature to 700 °C, the β-quartz solid solution in the glass-ceramic accompanied by a decrease in cristobalite content. The transformation from to γ₀-Li₂ZnSiO₄ took place from 700 °C to 750 °C. The resulting crystallization phases in the glass-ceramics obtained at the temperature higher than 750 °C were β-quartz solid solution and γ₀-Li₂ZnSiO₄. The glass-ceramics containing or β-quartz solid solution crystal phase possessed a microstructure formed by the development of dendritic crystals. The thermal expansion coefficient of the glass-ceramics varied from 36.7 to 123.8 × 10⁻⁷ °C⁻¹ in the temperature range of 20-400 °C, this precise value is dependent on the type and the proportion of the crystalline phases presented.     

Internal residual stresses in glass-ceramics: A review

Internal residual stresses arise in glass-ceramics upon cooling down from the crystallization temperature. These stresses are due to the thermal expansion and the elastic mismatch between the crystalline and glassy phases. Therefore, the mechanical properties of glass-ceramics are likely to depend not only on their composition and microstructure but also on the type (tension or compression) and magnitude of these residual stresses. In this work, we critically review the most commonly used theoretical models concerning residual stresses in glass-ceramics and glass-matrix composites, taking into consideration the effects of crystallized volume fraction, crystal shape and thermal expansion anisotropy. We also discuss most of the reported measurements of residual stresses in these dual-phase materials using different techniques, such as X-ray diffraction, nuclear magnetic resonance, Raman and fluorescence spectroscopy, and indentation. The available models and experimental results regarding spontaneous microcracking due to residual stresses are also discussed. Finally, guidelines for future work are suggested.     

复合晶核剂对黄磷炉渣微晶玻璃析晶的影响

以黄磷炉渣为主要原料,通过添加不同种类的复合晶核剂,采用熔融法制备了黄磷炉渣微晶玻璃.借助化学热力学软件FactSage 6.4模拟计算晶相类型,借助Kissinger方程分析析晶能力,利用X射线衍射仪(XRD)和扫描电子显微镜(SEM)进行验证.结果表明:相比添加单一晶核剂TiO2,复合晶核剂TiO2+CaF2或复合晶核剂TiO2+P2O5均能够降低黄磷炉渣基础玻璃的析晶活化能E,促进其析晶,复合晶核剂TiO2+Cr2O3能够提高黄磷炉渣基础玻璃的析晶活化能E,抑制其析晶;无论添加单一晶核剂TiO2,还是添加复合晶核剂TiO2+CaF2、复合晶核剂TiO2+P2O5或复合晶核剂TiO2+Cr2O3,黄磷炉渣微晶玻璃晶相类型相同,主晶相为硅灰石(CaSiO3),副晶相为铝透辉石(Ca(Mg,Al)(Si,Al)2O6)和氟磷灰石(Ca5(PO4)3F),这与化学热力学软件FactSage 6.4模拟计算结果基本一致.     

A new class of infrared transmitting glass-ceramics based on controlled nucleation and growth of alkali halide in a sulphide based glass matrix

Oxides-based glass-ceramics have been intensively studied and while they exhibit exceptional thermo-mechanical properties, their transparency in the infrared is limited to the 3 μm region. In this paper we describe a new type of glass-ceramics which are transparent up to 11 μm and based on the controlled nucleation and crystallization of cesium chloride sub-micron particles inside a Ge-Sb-S glass matrix. The evolution of the optical transmission versus annealing time and temperature has been investigated. Observations under scanning electronic microscopy as well as X-ray diffraction indicate that the crystalline phase is a primitive cubic cell with a parameter slightly inferior to that of pure CsCl and that the grain sizes are about 100 nm. A preliminary test on fracture propagation shows a much better resistance of glass-ceramics to cracks than the corresponding pure glass matrix.     

Sol-gel synthesis of erbium-doped yttrium silicate glass-ceramics

Yttrium silicate glasses and glass-ceramics were prepared by the sol-gel process. Yttrium nitrate was added to tetraethyl orthosilicate in amounts representing between 0.2 and 20 mol%, as well as amounts corresponding to the disilicate composition. Some samples were doped with erbium acetate. The solutions underwent gellation in 2-7 days and were dried for 2 weeks. Differential thermal analysis was used to design a multi-step heat treatment to 1000 °C to densify samples to transparent or translucent monoliths. Above 1000 °C, samples crystallized to yttrium disilicate and cristobalite. Phase separation before crystallization influenced the formation of the crystal phases.     

Observation of nucleation effect on crystallization in lithium aluminosilicate glass by viscosity measurement

The crystal nucleation effect in lithium aluminosilicate glasses was investigated by the viscosity measurement with aid of the fiber elongation method. The abrupt increase of viscosity due to the crystallization of glass was observed in viscosity-temperature curve but the minimum viscosity temperature (T_η) related with crystallization showed a strong dependence on the nucleation state such as nucleation temperature, nucleation time and heating rate. The results by viscosity agreed well with those of DTA. The nucleation effect on the microstructure of glass-ceramics was also discussed. Finally, the nucleation effect on the crystallization kinetics was approached quantitatively by calculating the crystal volume from viscosity value.