晶化温度对Li2O-ZnO-SiO2玻璃陶瓷显微结构和性能的影响

采用差热分析方法研究了LZS系玻璃陶瓷的析晶动力学和析晶过程,讨论了晶化温度对玻璃陶瓷的晶相、显微结构及热膨胀系数的影响.结果表明该LZS系玻璃陶瓷析晶活化能为173.28KJ/mol,晶化指数为2.76,体积析晶趋势较大;晶化温度在775℃以下时,主晶相为硅酸锂锌,次晶相为Li2ZnSiO4并有极少量方石英,为枝状晶体;在此温度上主晶相为方石英,次晶相为硅酸锂锌和Li2ZnSiO4,为粒状晶体,晶粒大小在0.1 5～0.4μm之间.制得的玻璃陶瓷的热膨胀系数在103～137×10-7℃-1之间,大小依赖于晶相与其含量;不同晶化温度下主晶相的热膨胀系数是玻璃陶瓷热膨胀系数的决定性因素.     

硅锂比对二硅酸锂玻璃陶瓷的结构与性能的影响

研究了硅锂摩尔比对二硅酸锂体系玻璃的结构与性能的影响,并在具有最佳性能的组分基础上,探究成核处理对玻璃的结构与力学性能的影响规律。结果表明:硅锂摩尔比n(SiO_2):n(Li_2O)从2.0增加到2.4,玻璃的结构和热性能及力学性能发生显著变化。其中,n(SiO_2):n(Li_2O)为2.2的组分最易析晶,具有最佳的力学性能[玻璃陶瓷三点弯曲强度(404±30) MPa]。同时研究了成核温度、时间对玻璃结构与力学性能的影响规律。n(SiO_2):n(Li_2O)为2.2的组分经优化晶化工艺处理后,一次热处理的主晶相为偏硅酸锂,二次热处理的主晶相为二硅酸锂,断裂韧性为3.58 MPa·m~(–1/2)。     

可加工氟云母玻璃陶瓷研究进展

可加工氟云母玻璃陶瓷是一种新型的结构材料,可用普通的金属刀具进行机械加工,自问世以来一直是陶瓷材料领域的一个研究热点.传统的可加工氟云母玻璃陶瓷中的主晶相是氟金云母和四硅氟云母,近年来又开发出钡云母、钙云母、锂云母和复相氟云母等新型的氟云母玻璃陶瓷,本文综述了近年来国内外在这方面的研究进展.     

基于正交试验的钡硼硅酸盐玻璃陶瓷的热处理制度研究

热处理是使玻璃陶瓷获得预定结晶相的关键工序.采用正交试验法研究了热处理制度(核化温度、晶化温度、保温时间)对钡硼硅酸盐玻璃陶瓷晶相结构和显微结构的影响.结果表明:采用一步法(核化、晶化同时进行)和二步法(核化、晶化分开进行)热处理时,样品的主晶相均为CaZrTi2O7-2M,还含有少量ZrO2相.对于两步法,在720℃核化2h、850℃晶化3h的条件下,钙钛锆石的晶相含量较高,晶粒为长条状,长约20～30 μm.当晶化温度较高(900～950℃)或晶化时间较长(2～3 h)时,都会出现CaTiSiO5晶相.各参数对玻璃陶瓷中晶相含量的影响顺序为:晶化温度＞核化温度＞晶化时间＞核化时间.一步法热处理温度变化对样品的晶相组成和显微结构变化较小.     

晶化温度对钢渣玻璃陶瓷显微结构的影响

本文以钢渣为主要原料制备玻璃陶瓷。用DTA、XRD和SEM研究晶化温度范围并鉴定玻璃陶瓷主晶相与显微结构。探讨了不同晶化温度时玻璃陶瓷显微结构的影响。研究表明：钢渣玻璃陶瓷主晶相为透辉石，晶化温度提高导致晶体长大并增多，抗弯强度、晶相含量也随之增大。     

烧结粉煤灰微晶玻璃装饰板的研究

以粉煤灰为主要原料,采用烧结法制备粉煤灰微晶玻璃装饰板,并借助Ｘ射线衍射法鉴定材料的主晶相。测定了微晶玻璃的主要性能,研究了基础玻璃成分、热处理制度对烧结、晶化过程及样品外观的影响,确定了合理的玻璃成分范围和工艺制度。     

复合废渣微晶玻璃热处理制度的确定与显微结构分析

介绍了以钢渣、粉煤灰、铜尾矿及砂岩为主要原料制备微晶玻璃的方法.利用DTA、XRD、SEM及EDS等方法研究了微晶玻璃的热处理制度;确定其主晶相为透辉石及其晶相组成成分;晶粒形貌为颗粒状,晶粒的尺寸约为0.5μm.实验结果表明:当废渣及工业砂岩引入为90%时,主晶相为透辉石,材料结构均匀致密、性能良好.实验热处理制度工艺参数为:退火温度:550℃,保温1h;晶化温度900℃,保温2h.     

钢铁工业废渣制备玻璃陶瓷的研究

以CaO-Al2O3-SiO2系统为基础玻璃成分，钢铁工业废渣为主要原料，CaF2，Fe2O3，Cr2O3，ZrO2作为复合晶核剂，采用熔融法制备了钢铁工业矿渣玻璃陶瓷，运用DTA，XRD和SEM等测试方法对材料工艺制度和晶相进行了分析和观察，测定了材料的主要物理和化学性能，并对晶核剂的作用机理、材料性能以及工艺制度进行了分析和研究。实验表明：所制玻璃陶瓷的主晶相为普通辉石[Ca(Mg，Fe，Al)(Si，Al)2O6]和透辉石[CaMg(SiO3)2]，其化学稳定性较好，密度达到3.02g／cm^3，吸水率低于0.04％，抗弯强度达250MPa。     

掺杂玻璃助剂的Ba5Nb4O15陶瓷烧结特性及介电性能

引入玻璃烧结助剂,采用液相烧结手段制备了低温烧结Ba5Nb4O15微波介质陶瓷.采用X射线衍射和扫描电子显微技术分析了陶瓷的物相组成和微观形貌.研究表明:陶瓷主晶相为Ba5Nb4O15,铋硅酸盐玻璃在陶瓷中以液相形式存在,促使陶瓷烧结温度从1300℃降至1100℃.添加4wt.％铋硅酸盐玻璃的Ba5Nb4O15陶瓷在1100℃烧结,具有良好的微波性能:相对介电常数εr=39.01,品质因子Q × f=12214GHz.     

锂云母对铝矾土尾矿低温烧结制备莫来石–刚玉复相陶瓷力学性能的影响

铝矾土尾矿是一种具有挑战性的固体废弃物，利用前景相对较小，大量堆存破坏生态环境，是铝土矿实现可持续开发利用过程中亟需解决的问题。以铝矾土尾矿为主要原料，添加铝矾土熟料、锂瓷石制备了莫来石–刚玉质复相陶瓷，通过添加了不同含量的锂云母，探究了其对莫来石–刚玉质复相陶瓷的性能影响。利用X射线衍射仪、扫描电子显微镜对陶瓷的物相组成和形貌进行分析，研究锂云母的含量、烧结温度等对陶瓷力学性能的影响。结果表明：锂云母的加入可降低陶瓷烧结温度，提高其力学性能，当添加质量分数为10%的锂云母、烧结温度为950℃，制得莫来石–刚玉质复相陶瓷的力学性能较好，满足建筑陶瓷材料应用领域及建筑砖使用要求，其物相组成为刚玉、莫来石、石英、赤铁矿、金红石及玻璃相，体积密度为1.75 g/cm³，导热系数为0.447 W/(m·K)，收缩率为5.47%，常温抗压强度为74.87 MPa，在建筑陶瓷材料等领域具有广泛的应用前景。     

IR Spectroscopy Study of Pre-Crystallization and Its Effect on the Phase Composition of Lithium Aluminosilicate Glass and Glass Ceramic

The effect of pre-heating on the phase composition of lithium aluminosilicate glass and glass ceramic is studied by the IR spectroscopy method. The results obtained provide a deeper insight into the kinetics of phase transformation in heat-treated materials and the temperature regime of crystal nucleation.     

High-Temperature Dynamic Mechanical Thermal Analysis of a Lithium Zinc Silicate Glass-Ceramic

High-temperature dynamic mechanical thermal analysis (DMTA) has been used to study a lithium zinc silicate glassceramic. The DMTA technique was capable of measuring the glass transition temperature of the original starting glass composition, as well as being able to follow crystallization and structural changes within the glass. The greater sensitivity of DMTA compared to differential thermal analysis, or differential scanning calorimetry, enabled the detection and measurement of the glass transition temperature of the residual glass phase in a largely crystalline glassceramic. An activation energy of 542 kJ·mol^-1 for this glass transition was obtained from a multifrequency experiment. A second transition was found in the crystallized glassceramics, and this is thought to be due to a crystal phase transition. Some evidence was also found supporting the view that in these glasses nucleation occurs by an amorphous phase separation mechanism.     

Effect of CuO addition on crystallization and thermal expansion properties of Li2O–ZnO–SiO2 glass-ceramics

A Li₂O-ZnO-SiO₂ (LZS) glass system was modified with CuO, and its phase development, microstructure evolution, crystallization kinetics and thermal expansion properties were investigated as a function of heat treatment temperature. As a result of the X-ray diffraction study and microstructure observation, lithium zinc silicate formed as the first crystalline phase with increasing heat treatment temperature. Silica polymorph developed as minor crystalline phase at higher temperatures. From the X-ray diffraction patterns, CuO addition led to a decrease in both the crystallization temperature of lithium zinc silicate phase and the volume fraction of quartz phase. According to the crystallization kinetics, the crystallization activation energy for lithium zinc silicates is almost equal to the diffusion activation energy of Zn²⁺ in glass, it suggests that the diffusion of network modifier Zn²⁺ dominates the crystallization of lithium zinc silicates. Additionally, CuO addition caused the transition of Zn²⁺ from network modifiers to network formers. From the thermal expansion coefficient measurements, two abrupt changes in slope of the thermal expansion curves were observed and attributed to the phase transitions of cristobalite and lithium zinc silicate, respectively. Comparison of the thermal expansion coefficient of two types of glass-ceramics revealed that CuO addition in the LZS system can partly inhibit the formation of cristobalite at high temperatures.     

Crystallization and thermal expansion behavior of lithium zinc silicate sealing glass

Effect of heat treatment schedule on the crystallization and thermal expansion behavior of a lithium zinc silicate glass system was investigated by differential scanning calorimeter (DSC), X-ray diffraction, and linear thermal expansion test. Two well-defined crystallization exothermic peaks were observed from the DSC trace. According to the apparent activation energies and avrami parameter values calculated from the two crystallization exothermal peaks, the first crystallization exothermal peak was attributed to a combining surface and internal crystallization behavior, while the second one was found to be internal crystallization. Additionally, the phase evolution and the thermal expansion behavior with increasing heat treatment temperature were found to be closely related. Interestingly, it was found in comparison with previous reports that addition of CaO varies the phase composition of the resulting glass–ceramic in an opposite way to K₂O and the deep rooted reason has been discussed which may cast light on the modulation of properties of glass–ceramic involved crystalline phase of quartz or cristobalite. At last, average thermal expansion coefficient of 7.99–15.38×10⁻⁶ K⁻¹ in the temperature range of 25–400 °C has been obtained with different heat treatment schedules.     

Influence of heat treatment temperature on the properties of the lithium disilicate-fluorcanasite glass-ceramics

This study aims to investigate the influence of heat treatment temperatures on the mechanical properties and chemical solubility (CS) of lithium disilicate-fluorcanasite glass-ceramics and to develop new dental materials. The glasses and glass-ceramics were prepared using CaF₂-SiO₂-CaO-K₂O-Na₂O-Li₂O-Al₂O₃-P₂O₅-based glass system using a conventional melt quenching method followed by a two-stage crystallization process. This two-stage method involves two heating temperature steps: first at a constant temperature (T_S1) of 600°C and second step at varying temperatures (T_S2) of 650, 700, 750, and 800°C. The crystallization behavior, phase formation, microstructure, translucency characteristic, density, hardness, fracture strength, and CS were investigated. It was found that the lithium disilicate crystal acted as the main crystalline phase, and the crystalline phase of fluorcanasite occurred at the heat treatment temperatures of 750 and 800°C. In addition, it was found that density, hardness, fracture strength, and CS increased while the translucency values decreased with increasing heat treatment temperatures. Furthermore, the CS increased dramatically when the fluorcanasite phases occurred in the glass-ceramic samples. The maximum density values, Vickers hardness, fracture toughness, and flexural strength are 2.56 g/cm³, 6.73 GPa, 3.38 MPa.m^1/2, and 259 MPa, respectively. These results may offer a possibility to design a new material for dental applications based on lithium disilicate-fluorcanasite glass-ceramics.     

Li2S-P2S5玻璃陶瓷固体电解质的制备研究

利用高能球磨及随后热处理的方法制备了具有高锂离子导电性的80Li2S-20P2S5（mol%）玻璃陶瓷固体电解质。通过X射线衍射分析、扫描电镜及交流阻抗法分别研究了固体电解质的物相种类、形貌及离子电导率。研究发现,球磨时间对玻璃态的形成具有直接影响,高能球磨得到的玻璃态中间体经过热处理形成了玻璃陶瓷电解质,其中含有Li7PS6、Li3PS4以及thioLISICON类似物等晶体,晶粒之间接触十分紧密,其室温锂离子电导率较玻璃态有明显提高。     

Influence of Al2O3 and B2O3 on Sintering and Crystallization of Lithium Silicate Glass System

This article reports on the effect of Al₂O₃ and B₂O₃ added as dopants on the preparation of glass‐ceramics (GCs) belonging to the lithium silicate glass system. The GCs are prepared by sintering route using glass powders. The reasons for the crystallization of the metastable crystalline phase lithium metasilicate (LS) are discussed and the impact of the dopants on the thermodynamics and kinetics of crystallization is investigated. The addition of dopants modifies the thermodynamic equilibrium of the system and this change is mainly entropy driven and also slowdown the kinetics of crystallization. Differential thermal analysis and hot‐stage microscopy are employed to investigate the glass‐forming ability, sintering, and crystallization behavior of the studied glasses. The crystalline phase assemblage studied under nonisothermal heating conditions in the temperature range of 800°C–900°C in air. Well sintered and dense glass‐ceramics are obtained after sintering of glass powders at 850°C–900°C for 1 h featuring crystalline phase assemblage dominated by lithium disilicate (LS₂).     

Effect of Temperature on the Structuring and Properties of Glass and Glass Ceramic of Lithium Aluminosilicate Composition

Results of a study of sintering and crystallization of lithium aluminosilicate-based glass ceramic prepared by casting aqueous high-density slips into porous molds are reported. Optimum conditions for the formation of structure and phase composition of the glass ceramic and the development of required properties are established.     

Insights on Ceramics as Dental Materials. Part I: Ceramic Material Types in Dentistry

Ceramics are widely used biomaterials in prosthetic dentistry due to their attractive clinical properties. They are aesthetically pleasing with their color, shade and luster, and they are chemically stable. The main constituents of dental ceramic are Si-based inorganic materials, such as feldspar, quartz, and silica. Traditional feldspar-based ceramics are also referred to as “Porcelain”. The crucial difference between a regular ceramic and a dental ceramic is the proportion of feldspar, quartz, and silica contained in the ceramic. A dental ceramic is a multiphase system, i.e. it contains a dispersed crystalline phase surrounded by a continuous amorphous phase (a glassy phase). Modern dental ceramics contain a higher proportion of the crystalline phase that significantly improves the biomechanical properties of ceramics. Examples of these high crystalline ceramics include lithium disilicate and zirconia.     

Phase separation and crystallization in glasses of the lithium silicate system xLi2O · (100 ? x)SiO2 (x = 23.4, 26.0, 33.5)

The phase separation in ultimately homogenized glasses of the lithium silicate system xLi₂O · (100 − x)SiO₂ (where x = 23.4, 26.0, and 33.5 mol % Li₂O) has been investigated. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which provide the maximum dehydration and the removal of bubbles from the glass melt. The parameters of nucleation and growth of phase_separated inhomogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates I _st of lithium disilicate crystals in the 23.4Li₂O · 76.6SiO₂ and 26Li₂O · 74SiO₂ glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates I _st for the glass of the stoichiometric lithium disilicate composition. It has been established that the crystal growth rate have a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low-temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li₂O-SiO₂ system is compared with that in the glass of the stoichiometric lithium disilicate composition. The inference has been made that the phase separation weakly affects the nucleation parameters of lithium disilicate and has a strong effect on the crystal growth.