含F-锂镁铝硅微晶玻璃的制备及晶化行为的研究

采用熔融烧结法,引入一定量的MgF2,制备出LMASF系微晶玻璃,采用DTA、XRD对该微晶玻璃的析晶温度和物相组成进行了分析,并采用SEM观察了微晶玻璃的断面形貌.讨论了热处理对微晶玻璃析晶的影响,并对其晶化行为和微观形貌进行了研究.实验结果表明,该微晶玻璃首先析出LixAlx Si1-xO2晶体,后随着温度的升高析出β-锂辉石晶体;最佳晶化温度为786℃,在该温度下保温2h,析出棒状β-锂辉石晶体,晶体长度为2～5μm,长径比较大.     

红外玻璃陶瓷的力学性能

在一定的温度和时间下对GeS2-Sb2S3-CsCl系红外玻璃进行微晶化处理,制备了新型的红外透明玻璃陶瓷.测定了微晶玻璃的力学性能和光学性能,研究了微晶化处理条件对微晶玻璃的力学性能和光学性能的影响.研究结果表明,玻璃基体中析出微晶晶体,使材料的断裂韧性和裂纹初始应力显著增大,但这种增大效应取决于析晶相的种类和晶体尺寸.为了保持微晶玻璃的红外透明性,析出的晶体尺寸应小于100nm.     

热处理时间对透辉石系尾矿微晶玻璃析晶及其性能的影响

使用金尾矿和铁尾矿为主要原料,采用熔融法和一步法析晶热处理制备了透辉石系尾矿微晶玻璃。将其分别在低温段720℃和高温段820℃保温,使用DSC、XRD、Raman光谱、SEM和综合力学性能仪等手段研究了保温时间对透辉石系尾矿微晶玻璃析晶过程及性能的影响。结果表明：该系微晶玻璃的主晶相为单斜结构的透辉石晶体(Mg_0.6Fe_0.2Al_0.2)Ca(Si_1.5A_l0.5)O₆(JCPDS 72-1379),晶体的生长过程包括玻璃的分相、成核和晶体生长过程。热处理温度为低温段720℃时透辉石晶体的成核温度为720℃,随着保温时间的延长透辉石晶体逐渐长大且由球状晶向枝状晶演变,透灰石晶体的析出量逐渐增加;热处理温度为高温段820℃时透辉石晶体的形貌均为尺寸较大的枝状晶,但是随着保温时间的延长透辉石晶体的形貌和尺寸变化不大。综合性能最优的热处理制度为在820℃保温45 min,制备出的微晶玻璃密度为2.97 g/cm³,抗折强度为211.0 MPa,硬度为789.0 MPa,耐酸性99.3%,耐碱性99.1%。     

CaO/SiO2质量比对不锈钢渣微晶玻璃析晶及性能的影响

以不锈钢渣、废玻璃为原料,采用熔融法制备了主晶相为硅灰石相的微晶玻璃.利用DSC、XRD、SEM等测试分析手段研究了CaO/SiO2质量比对微晶玻璃物相组成、显微结构及理化性能的影响.结果表明:随CaO/SiO2质量比增加,玻璃转变温度和析晶放热峰温度逐渐降低,且析晶放热峰变尖锐;硅灰石相XRD衍射峰强度先增强后减弱;显微结构由表面析晶向整体析晶过渡,晶粒形状由球形颗粒变为针叶状晶,最后发育成片状晶,晶体尺寸先增加后减小;当CaO/SiO2质量比为0.72时微晶玻璃性能达到较优,显微硬度为6.49 GPa,密度为3.11 g/cm3,吸水率为0.11％,耐酸性96.51％,耐碱性99.92％.制备出的微晶玻璃有望应用在建筑装饰材料领域.     

低温烧结法制备LZS系微晶玻璃及其性能

采用烧结法制备出LZS系微晶玻璃.使用DTA分析了玻璃的析晶过程,运用XRD、SEM等对晶相和晶粒大小进行了观察和分析,讨论了温度对烧结程度、主晶相、晶体微观形貌及热膨胀系数的影响.结果表明:当晶化温度低于725℃时,主晶相为硅酸锂锌,次晶相为Li2ZnSiO4并有少量石英;温度高于725℃时,主晶相转变为石英,次晶相为硅酸锂锌和Li2ZnSiO4,为长度在1.5μm左右的棒状晶体.在700～725℃之间烧结接近完成.最佳烧结温度为725℃.微晶玻璃热膨胀系数与烧结程度、晶相含量和主晶相的热膨胀系数有关.     

SiO2-Al2O3-MgO-F系微晶玻璃的形变析晶

采用高温熔融法制备了SiO2 -Al2O3 -MgO-F系玻璃样品,应用X射线衍射(XRD)、扫描电子显微镜(SEM)研究了该微晶玻璃在自由形变时的析晶特征,得到了微晶玻璃自由形变析晶的规律.结果表明:在热处理过程中随着温度的升高,基础玻璃的黏度逐渐降低,可以在析晶前施加压力使之发生变形.在自由形变的前提下,微晶玻璃析出的晶体在垂直压力和平行压力方向上没有出现定向析晶.显微硬度测试结果也表明在微晶玻璃中没有明显的各向异性特征,不会带来材料性能在不同方向上的差异,为形状复杂、均质同性微晶陶瓷的制备提供了一个有效途径.     

裂纹玻璃晶化法制备建筑装饰用微晶玻璃

制备建筑装饰用微晶玻璃的现役工艺主要有烧结法和压延法两种,前者容易出现气孔缺陷,后者不能生成纹理.为克服现役工艺的不足,本文提出裂纹玻璃晶化法工艺,即以裂纹玻璃作为母玻璃,通过烧结、晶化二步热处理而制备出微晶玻璃.XRD测得裂纹玻璃晶化法微晶玻璃样品的主晶相为β-硅灰石;ESEM观察到样品的微观结构由不均匀分布的粒径在0.2~0.5μm的晶体组成;利用比重仪测得样品的气孔率低于现役烧结法样品.实验表明,裂纹玻璃晶化法能克服现役工艺的不足,制备出气孔率低、具有类似古生物残骸纹理的微晶玻璃,装饰效果更佳.     

氟化物对CaO-Al_2O_3-SiO_2系玻璃析晶行为的影响

采用DTA、XRD、SEM等现代测试分析手段研究了晶核剂CaF2 对CaO Al2 O3 SiO2 系玻璃析晶行为的影响。结果表明 ,晶核剂CaF2 能有效地促进玻璃的整体析晶 ,在一定热处理制度下 ,可制备出晶粒尺寸为0 .1～ 0 .2 μm的白色微晶陶瓷 ,主晶相为透辉石和硅灰石。随着CaF2 含量的增加 ,透辉石型晶相增多 ,硅灰石型晶相减少。     

CaF2对CAMS系矿渣微晶玻璃析晶特性及抗腐蚀性能的影响

以白云鄂博二次选后尾矿、高炉渣和粉煤灰为主要原料,采用熔融法制得不同CaF_2含量的CaOAl_2O_3-MgO-SiO_2(CAMS)系微晶玻璃,利用DSC、XRD、SEM、EDS等测试手段,研究了CaF_2对微晶玻璃析晶行为、显微结构及抗盐酸腐蚀性能的影响。结果表明:氟化钙添加量由2%增加至8%(质量分数),基础玻璃的析晶温度降低,析晶活化能由416.28kJ/mol降为309.02kJ/mol,但微晶玻璃的主晶相仍为透辉石相。氟化钙的添加在一定程度上降低了微晶玻璃的抗盐酸腐蚀性能,当氟化钙添加量为2%时,微晶玻璃经盐酸溶液浸泡21d,腐蚀层厚度为240μm;随着CaF_2添加量继续增大,微晶玻璃抗盐酸腐蚀性能急剧下降,当氟化钙添加量为8%时,盐酸腐蚀21d后,腐蚀层厚度为743μm。     

碳酸钙对缓冷高钛高炉渣制备泡沫微晶玻璃的影响

利用缓冷高钛高炉渣和废玻璃为主要原料,通过发泡和析晶同时进行的"一步法"在980℃烧结制备泡沫微晶玻璃。研究了CaCO_3对制备泡沫微晶玻璃的影响。结果表明,CaCO_3对发泡和析晶过程都有影响。在不同的CaCO_3添加量(1%~5%,质量分数)下,泡沫微晶玻璃的主要晶相类型无明显差异,都以透辉石Ca(Mg,Al)(Si,Al)_2O_6和普通辉石Ca(Mg,Fe,Al)(Si,Al)_2O_6为主晶相,以硅辉石CaSiO_3为次晶相;CaCO_3添加量由1%增至3%时晶相含量明显增加,而在3%~5%范围内晶相含量增加不大。随着CaCO_3含量增加,泡沫微晶玻璃晶体由不规则颗粒状变成针状和短柱状,泡孔孔径减小,气孔率和吸水率减小,体积密度和抗压强度增大,其中当CaCO_3含量为3%时泡沫微晶玻璃的综合性能最佳。     

The effect of microstructural features on the biaxial flexural strength of leucite reinforced glass-ceramics

In this study the effect of size and distribution of leucite crystals on the biaxial flexural strength of five leucite reinforced glass-ceramics used in dentistry for the construction of veneers was investigated. Three of these were found to have a non-uniform distribution of leucite crystals, which were associated with a considerable degree of microcracking in the glassy matrix around the leucite crystals. The mean values of biaxial flexural strength of these ceramics ranged from 56 to 70 MPa. The other two ceramics exhibited a more uniform distribution in their leucite crystals, which were also finer in size. The latter ceramics had a significantly higher biaxial flexural strength which ranged from 120 to 137 MPa. When the particle size of the starting powders of the three low strength ceramics was reduced, a more uniform microstructure with less evidence of microcracking was produced in the fired ceramics and the biaxial flexural strength values were significantly increased. We conclude that uniformity of microstructure and leucite crystal size are major factors in determining the biaxial flexural strength of leucite reinforced glass-ceramics.     

K_2O对白榴石生成的影响

以钾长石、碳酸钾为主要原料,设计高、中、低3种不同钾含量的配方固相合成白榴石晶体,探讨K2O的含量对白榴石生成的影响。通过实验发现,适当地提高配方中K2O的含量对白榴石生成是有利的,但当配方中K2O远高于其在白榴石中的理论含量时,其在高温下完全熔融成玻璃熔态物质,没有白榴石晶体的生成;当K2O的含量为25.4%,在1250℃熔融保温60min,其热膨胀系数为20.74×10-6℃-1(30～700℃),平均晶粒尺寸为3μm。     

Characterization of glass-ceramic to metal bonds

Glass-ceramic thick films were deposited on copper and copper/invar/copper substrates by screen printing and subsequent firing in a belt furnace. One lithium-zinc silicate glass and two lithium-aluminosilicate glasses were deposited. Microstructures of the coatings and the coating/substrate interfaces were studied using optical and electron optical techniques. SEM was used to investigate the glass-ceramic microstructure and EPMA to characterize chemical composition across the interface. Crystalline phases were identified using X-ray and electron diffraction. The lithium-aluminosilicate glass-ceramics were composed of lithium disilicate, -spodumene and quartz crystals in residual glass. Lithium disilicate and quartz were the only crystals identified in the lithium-zinc silicate glass-ceramic. In all the samples copper diffused extensively through the glass-ceramic during firing and formed Cu₂O precipitates in the glass-ceramics adjacent to the interface. Strong adhesion between the glass-ceramic and the substrates is promoted by copper diffusion and oxide development at the glass-ceramic/substrate interface. The strongest bonds develop when the Cu₂O forms as discrete particles rather than a continuous layer at the interface. Interfacial residual stress also influences the measured adhesion strength.Now at Department of Materials Engineering, University of Wollongong, Australia.     

Needle-like apatite-leucite glass-ceramic as a base material for the veneering of metal restorations in dentistry

A needle-like apatite-leucite glass-ceramic was prepared in the SiO₂-Al₂O₃-Na₂O-K₂O-P₂O₅-F system. Nucleation and crystallization processes were studied in bulk and powdered samples. The crystallization of leucite follows the mechanism of surface crystallization. After the precipitation of NaCaPO₄ crystals and another unknown crystal phase, the formation of needle-like apatite is based on a volume nucleation and crystallization process. The mechanism of the formation of needle-like apatite differs to those of apatite precipitation in glass-ceramics. The morphology of needle-like apatite is comparable to that of apatite in natural teeth.The properties of the glass-ceramic, especially the good chemical durability, the optical properties, as well as mechanical and thermal properties allow glass-ceramic to be used as a main component in a bio-material for the veneering of metal restorations in dentistry.     

Devitrification and microstructural coarsening of a fluoride-containing barium aluminosilicate glass

Barium aluminosilicate (BAS) glass-ceramics have the potential to be used in the production of cast prostheses for biomedical applications because of their radiopacity and increased strength compared with traditional feldspathic porcelains. It is essential to understand the crystallization kinetics of these materials in order to fabricate products with increased fracture resistance rapidly. It was hypothesized that the addition of fluoride (F) to the composition of BAS glass would reduce the necessary processing time and temperatures by obviating the need for a separate crystal nucleation treatment. BASF glass was subjected to both linear non-isothermal and one-stage isothermal crystallization treatments, and the resulting glass-ceramics were characterized using x-ray diffraction, differential thermal analysis, and stereology. BASF glass had a low energy barrier to crystallization (397 kJ/mol) and transformed to 76 ± 2% crystallinity within 30 min at 975°C. A fine-grained microstructure was produced by bulk crystallization without the need for a separate crystal nucleation stage. After the initial crystal precipitation, the mean crystal size and mean free path between crystals increased over time at elevated temperature by a diffusion rate-limited coarsening mechanism.     

Synthesis and characterization of coprecipitation-derived ferrimagnetic glass-ceramic

Ferrimagnetic glass-ceramics could be used for magnetic induction hyperthermia. This technique is utilised for the destruction of solid neoplastic diseases by application of an alternating magnetic field. Biocompatible ferrimagnetic materials could be easily incorporated into a tumour and could generate heat mainly by hysteresis loss. A ferrimagnetic glass-ceramic in the system SiO₂–Na₂O–CaO–P₂O₅–FeO–Fe₂O₃ has been prepared by melting of the coprecipitation-derived raw materials. This glass-ceramic contains a unique crystalline phase, magnetite, embedded in an amorphous matrix. Magnetite crystals precipitate during cooling from melting temperature. This glass-ceramic would no longer require any nucleation and growth thermal treatment, since the maximal quantity of magnetite crystals was produced during cooling. The average unit-cell parameter, crystallite size of magnetite, and the quantitative ratio of the crystallographic phases in the glass-ceramic samples were evaluated using two different methods. Similar results were obtained with both methods. The magnetite crystals are about 50 nm in dimensions. The samples contain 45 wt% of magnetite, homogeneously distributed in the amorphous residual matrix. The as prepared glass-ceramic has a saturation magnetisation of 34 A·m²/kg and a coercive force of 6.7 kA/m. The estimated magnetic loss/cycle under the magnetic field up to 796 kA/m is around 1.45 mJ/g. The specific power loss of this glass-ceramic under a magnetic field of 40 kA/m and a frequency of 440 kHz is 25 W/g. This material showed a bioactive behaviour, as after 2 weeks of soaking in a simulated body fluid the formation of a hydroxylapatite layer on their surface was observed. This feature makes it also suitable for bone cancer.     

K2O对LZAS微晶玻璃微观结构及热膨胀性能的影响

采用DTA、XRD、SEM、TEC(热膨胀系数)等分析手段研究了加入K2O前后LZAS系统微晶玻璃的微观结构和热膨胀性能.结果表明,650℃晶化时,试样析出γⅡ-LZS和方石英晶体;725℃时,γⅡ-LZS逐渐转变为γ0-LZS晶体,并且出现β-石英固溶体;800℃时,β-石英固溶体转变为β-锂辉石固溶体,晶粒尺寸逐渐长大.制得微晶玻璃的热膨胀系数在(50～130)×10-7℃-1(20～500℃)之间,其大小取决于晶相的种类和含量.并且K2O的加入降低了玻璃的转变温度、粘度,抑制了玻璃的析晶倾向,增大了微晶玻璃的热膨胀系数.     

Low temperature sintering and crystallisation behaviour of low loss anorthite-based glass-ceramics

Anorthite-based glass-ceramics including TiO₂ as nucleating agent were melted and quenched in this study. The effect of particle size on the sintering behaviour of glass powders was investigated in order to obtain low-temperature sintered glass-ceramics. Anorthite glass-ceramic starts to densify at the transition temperature of glass (T _g = 770°C) and is fully sintered before the crystallisation occurrence (880°C). Therefore, a dense and low-loss glass-ceramic with predominant crystal phase of anorthite is achieved by using fine glass powders (D ₅₀ = 0.45 m) fired at 900°C. The as-sintered density approaches 99% theoretical density and the apparent porosity is as low as 0.05 Vol%. The dense and crystallized anorthite-based glass-ceramic exhibits a fairly low dielectric loss of 4 × 10^–4 at 1 MHz and a thermal expansion coefficient of 4.5 × 10^–6°C^–1. Furthermore, the microwave characteristics were measured at 10 GHz with the results of K = 9.8, Q _f = 2250, and temperature coefficient of resonant frequency _f = –30 ppm/°C.     

Synthesis and characterisation of large chlorapatite single-crystals with controlled morphology and surface roughness

This work describes the synthesis of chlorapatite single crystals using the molten salt method with CaCl₂ as a flux. By manipulating the processing conditions (amount of flux, firing time and temperature, and cooling rates) it is possible to manipulate the crystal morphology from microscopic fibres to large crystals (up to few millimetre long and ~100?μm thick). The crystal roughness can be controlled to achieve very flat surfaces by changing the melt composition “in situ” at high temperature. The Young modulus and hardness of the crystals are 110?±?15 and 6.6?±?1.5?GPa respectively as measured by nanoindentation. Crystal dissolution in Hanks solution starts around the defects. Several in vitro assays were performed; ClAp crystals with different size and shape are biocompatible. Cell apoptosis was very low at 5, 10, and 15?days (Caspase-3) for all the samples. Proliferation (MTT) showed to be influenced by surface roughness and size of the crystals.