氟硅酸盐微晶玻璃的热膨胀性能研究

氟硅酸盐微晶玻璃的热膨胀性能主要取决于微晶玻璃的晶相组成及其相对含量．透辉石结晶相的含量增加使微晶玻璃的热膨胀系数降低,与此相反碱镁闪石结晶相的含量增加却使微晶玻璃的膨胀系数增加．K2O－MgO－SiO2－CaF2系统氟硅酸盐微晶玻璃的最小热膨胀系数为：78．4×10－7（20～300℃）;最大热膨胀系数为：85．6×107（20～300℃）．     

β-锂霞石负膨胀微晶玻璃的制备技术及结构特征

研究了β锂霞石微晶玻璃的制备技术、结构特征及其负膨胀特征。首先采用玻璃结晶法制备β锂霞石负膨胀微晶玻璃材料,然后通过XRD、SEM等测试手段,表征了β锂霞石微晶玻璃材料的结构特征。并讨论β锂霞石负膨胀微晶玻璃的膨胀系数及其与晶相组成和晶化温度及时间的依从关系,使其负膨胀系数在一定范围内连续可调。研究并制备出热膨胀系数可达到为-1.037×10-5/℃的β锂霞石微晶玻璃。     

纤维补强微晶玻璃复合材料性能设计

在 Li_2O-Al_2O_3-SiO_2和 Li_2O-MgO-CaO-Al_2O_3-SiO_2系统中,对具有不同热膨胀系数(α)的烧结微晶玻璃基体作了研究。一些微晶玻璃基体能够同补强纤维结合得很好,适用于制备成碳纤维或 SiC纤维补强微晶玻璃复合材料。当微晶玻璃基体的α调节到比加入纤维的α稍低的范围内,复合材料的抗折强度和断裂韧性可达到满意的水平,F_b 为584MPa,K_(1c)为16.5MPa·m~(1/2)。实验结果作为纤维补强微晶玻璃复合材料性能设计原则,在上述系统中得到了验证。文中对微晶玻璃这类多相复合体热膨胀系数设计的理论依据作了讨论。     

添加铅硅玻璃对烧结堇青石基微晶玻璃性能的影响

研究了铅硅玻璃在堇青石基微晶玻璃烧结中的作用及其添加量对微晶玻璃性能的影响．结果表明：铅硅玻璃的加入可以促进微晶玻璃的烧结致密化;随着铅硅玻璃加入量的增加,烧结样品的介电常数亦增加,且与密度变化曲线相似;微晶玻璃烧结样品的热膨胀系数符合加和性规律．     

氧化锆对锌硼硅玻璃热震稳定性的影响

在锌硼硅玻璃中添加0％～10％（质量分数）的部分稳定氧化锆粉体，在一定温度下烧结后制备成氧化锆／锌硼硅微晶玻璃。采用半圆涂敷法测试微晶玻璃的耐冷热激变炸裂的性能；利用万能试验机测量微晶玻璃遭受热冲击后的残留抗压强度；采用402ES．3电子热膨胀仪和TC-100常温接触式导热系数测定仪测试氧化锆，锌硼硅微晶玻璃的热膨胀系数和导热系数。结果表明，氧化锆可以明显增加微晶玻璃受冷热冲击而炸裂的次数，使微晶玻璃热冲击后残留抗压强度下降的程度大大减小。氧化锆／锌硼硅微晶玻璃的热膨胀系数与导热系数随着氧化锆含量的增加而下降。由此可见，氧化锆可以明显改善锌硼硅微晶玻璃的热震稳定性，从而提高其使用可靠性。     

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.     

低介低损耗微晶玻璃中晶相与热膨胀性能关系的研究

本文以堇青石微晶玻璃为研究对象, 首次研制得到了一种低介（ ε＝ ５１） 、低损耗（ｔｇδ＜１０ － ３） 、热膨胀系数（４６ ～４８ ×１０ － ７‘ Ｃ） 能与其它器件相匹配的新型微晶玻璃介质材料通过 Ｘ射线衍射分析, 扫描电镜观察等测试手段, 研究了该材料的晶化过程和热膨胀系数的变化规律发现样品的热膨胀系数随温度的变化行为是与样品中析出的晶相种类及析出量随温度的变化规律相对应的     

SiC纤维／LCMAS微晶玻璃基复合材料的界面结合和力学性能

本工作通过在母体玻璃中引入ＭｇＯ后进行热处理得到一系列具有不同热膨胀系数的微晶玻璃．ＳｉＣ纤维／ＬＣＭＡＳ微晶玻璃基复合材料在烧结条件下，在纤维和基体间形成一厚度约为２μｍ的界面层．纤维、基体间的界面剪切应力通过单根纤维压出法测试，发现纤维、基体间的界面剪切强度对复合材料的力学性能有严重的影响，并且ＳｉＣ纤维／ＬＣＭＡＳ系微晶玻璃基复合材料具有较高的界面剪切强度，通过降低基体的热膨胀系数减弱界面剪切强度，可使复合材料的强度和断裂韧性都得到明显的改善．     

透明LAS微晶玻璃的显微结构和热性能研究

用熔融法制备LAS透明微晶玻璃;采用DSC,XRD,SEM等测试方法,研究了透明LAS微晶玻璃的晶相组成、显微结构及热性能。结果表明:720℃核化2 h,780~900℃晶化2 h均得到β-石英固溶体微晶玻璃,晶粒尺寸在10~30 nm之间,具有优良的透明性,30~700℃的热膨胀系数在(3.50~5.92)×10-7/℃之间变化;720℃核化2 h,860℃晶化2 h得到的微晶玻璃在900℃保温10 h后透明性优良,30~700℃的热膨胀系数为3.64×10-7/℃。     

白榴石增强的牙科饰面瓷研究现状

回顾了白榴石微晶玻璃在制备方法、热稳定性和力学性能3个方面的研究进展。与传统的玻璃析晶法相比,先制备白榴石晶体,然后将其与低软化点玻璃混合烧结,这种方法在控制白榴石晶体尺寸方面更具优势。烤瓷温度和时间会影响微晶玻璃中白榴石晶体的含量,进而影响微晶玻璃的热膨胀系数,因此需要严格控制。微晶玻璃中白榴石晶体的直径应该小于4μm,这样可以将微晶玻璃中微裂纹的影响减少到最小。作者制备的一种白榴石微晶玻璃在950℃保温60 min后析晶完成,并且白榴石晶体的尺寸在1μm左右。     

陶瓷薄基板材料裂纹预制与断裂韧性评价

预制长度可控的裂纹以及原位观察裂纹扩展是研究陶瓷薄基板抗断裂行为的两大重点。本研究提出应变诱导法, 通过将基板与黄铜梁粘结形成复合体, 利用黄铜梁弯曲变形带动侧面陶瓷薄板受拉侧拉伸变形产生可控裂纹。在工具显微镜下对复合体进行四点弯曲, 原位观察样品的裂纹扩展情况, 通过调节黄铜梁宽度来控制初始裂纹长度, 在初始裂纹萌发后继续加载, 使裂纹达到测试断裂韧性的标准长度。将这种测试方法与块体材料断裂韧性的测试标准进行了对比, 结果表明: 采用该方法预制裂纹后测试断裂韧性具有简易性和可靠性。应变诱导法预制裂纹成功率高, 裂纹萌发位置及长度可控, 且操作方便, 可推广应用于超薄玻璃等其他超薄脆性材料的断裂韧性评价和分析裂纹扩展阻力。     

低熔可切削生物活性微晶玻璃的研究

选择一种出SiO₂-MgO-Al₂O₃-K₂O-CaO-P₂O₅-F基础玻璃体系,并添加不同量的ZnO,制备出性能良好的可切削生物微晶玻璃.结果表明,由于ZnO的添加,可使母玻璃的熔化温度由1450℃降至1300℃,可切削生物活性微晶玻璃的母玻璃能够在较低的温度熔化制备.母玻璃晶化后析出相主要为云母相和氟磷灰石相;各种晶相的组合形貌为花瓣形态,其断口呈现穿晶断裂的特征,并有晶体拔出,使材料具备了较高的强度;由于析出了较多的云母相,该微晶玻璃兼具良好的可切削性能.     

An investigation on failure mechanisms of ceramic/metal armour subjected to the impact of tungsten projectile

The failure mechanism of AD95 ceramic/4340 steel armour subjected to the penetration of the tungsten projectile was investigated at the nominal velocity of 820 m/s. Typical failure modes of the targets with various boundary conditions were presented. The effect of cover plate and confinement on failure mechanisms of the target was analyzed. The results showed that the cover plate can effectively reduce the damage of the target due to it can force the ejected ceramic fragments to decelerate the projectile, and a ceramic powders column was formed beneath the eroded projectile in the confined ceramic sandwiched between cover and support plate during penetration. Compared to the confinement, cover plate is more effective to reduce the damage of the support plate. Based on the experimental results, the failure mechanisms and penetration process of different target configuration have been discussed.     

Development of calcium phosphate based bioceramics

Two bioceramics (Ca-P-O glass and A-W glass ceramic) were produced using conventional methods of ceramic technology. X-ray powder diffraction patterns were used for identifying the phases and 3-point bend test was carried out for the determination of fracture strength of the bioceramics. Biocompatibility of both ceramics was evaluated using animal model experiments. Histological studies showed that A-W glass ceramic implanted in the tibia of rat formed an intimate contact with newly grown bone and provided enough strength to the bone to bear the animal weight. Implants made of Ca-P-O glass was almost fully resorbed and was replaced by new bone. The implants made of both the bioceramics were biocompatible and did not exhibit any kind of adverse effect to the surrounding tissues.     

Densification, phase composition, and properties of borosilicate glass composites containing nano-alumina and titania

Five samples of glass/ceramic composites were prepared from borosilicate glasses and both nano-aluminum oxide and nano-titanium oxide. The glass composite samples contain 10, 20, 30, 40, 50 wt.% of alumina and titania mixture. The ratio of Al₂O₃:TiO₂ in the mixture was 1:1. The formation of cristobalite in the glass matrix of low firing glass/ceramic composite substrates limits the efficiency of the ceramic substrate when it is used in circuit boards. In the present study, addition of both alumina and titania to a borosilicate glass as a ceramic filler caused the diffusion of alumina and titania phases (anatase and rutile) constituents into the glass matrix and prevented the formation of a cristobalite. Addition of both the ceramics suppresses cristobalite formation more effectively than one of them used alone and results in lower dielectric constant and thermal expansion coefficients.     

止裂层对陶瓷复合防弹插板冲击损伤行为研究

目的 研究冲击载荷下迎弹面覆盖止裂层的复合防弹插板陶瓷面板碎裂机理和抗侵彻性能。方法 对所设计的复合防弹插板进行空气炮打靶试验,构建冲击仿真有限元计算模型。结合试验和数值模拟,研究覆盖环氧树脂、凯夫拉平纹织物止裂层及无止裂层复合防弹插板的抗侵彻性能,分析不同冲击速度下复合防弹插板陶瓷损伤失效过程。采用内聚力单元对止裂层和陶瓷之间的黏结区域进行建模,分析黏结程度对陶瓷损伤和失效的影响。结果 止裂层表面约束的陶瓷在冲击过程中产生的径向裂纹随着撞击点附近的环向拉应力波的传播而延伸。止裂层黏结作用增强时,陶瓷的冲击缺口面积增大,但质量损失基本不变;迎弹面止裂层未对侵彻过程中子弹动能和复合防弹插板背凸情况产生显著影响。结论 止裂层在一定程度上能减少陶瓷质量损失,但也会造成更多的损伤,这种现象在高速情况下较为明显,且凯夫拉平纹织物止裂层所造成的损伤更多。相关研究工作可为陶瓷复合防弹板的设计提供参考。     

基于单向拉伸的glare板力学性能测试

目的 研究使用新方法制造小型大曲率glare板零件的可能性。方法 通过使用传统的模具来充液成形/普通拉深成形含有半固化玻璃纤维预浸料的glare板,成形后再进行固化。在室温下,使用单向拉伸方法分别对金属、含半固化玻璃纤维预浸料的glare板和固化之后的glare板进行力学性能测试。结果 含半固化玻璃纤维预浸料的glare板主要失效形式为金属板断裂,固化之后的glare板的主要失效形式为玻璃纤维断裂;含半固化玻璃纤维预浸料的glare板有着和金属相近的断后伸长率,具有较好的塑性,固化之后的glare板的断后伸长率远小于金属的断后伸长率,塑性极差。结论 通过使用传统的模具来充液成形/普通拉深成形含有半固化玻璃纤维预浸料的glare板,成形后再固化的方法来制造小型大曲率glare板零件是有可能的。     

陶瓷复合装甲优化设计及弹击后剩余弯曲强度

根据防护要求和防护机制,设计了一种C/C-SiC陶瓷/铝基复合泡沫复合装甲。在确保复合装甲面密度为44 kg/m²的前提下,以弹击后剩余弯曲强度为评价标准,以陶瓷板布置位置、各组成层厚度、泡沫金属中泡沫孔径尺寸为研究因素,设计了三因素三水平的正交模拟优化方案,利用有限元软件ABAQUS模拟了子弹侵彻陶瓷靶板的过程及弹击损伤后复合装甲的弯曲实验过程,预测了剩余弯曲强度,并进行了结构优化。根据数值模拟结果制备陶瓷复合装甲试样,进行实弹打靶和弯曲实验以验证复合装甲试样剩余弯曲强度。结果表明,以MIL-A-46103E Ⅲ类2A级为防护标准,剩余弯曲强度最高的陶瓷复合装甲最优化结构形式为：陶瓷板厚度12 mm、陶瓷板做防弹面板、Al基复合泡沫孔径为4 mm+10 mm的混合;对剩余弯曲强度的主次影响因素排序为：陶瓷板厚度>陶瓷板布置位置>Al基复合泡沫孔径。     

Multi-photon luminescence in Er/Yb:SrO⋅TiO2 glass ceramic

Er³⁺/Yb³⁺ doped strontium titanate borosilicate glass was prepared. Glass ceramic was prepared by controlled heat treatment (at 955 °C) of glass. Ti₁₀O₁₉ and Sr₃Ti₂O₇ were found as major crystalline phases. The emission spectra of glass and glass ceramic samples were investigated under 976 nm laser excitation. In glass ceramic, the intensity of the emitted radiation was much higher (≈50 times for green and ≈10 times for red emission) than in the glass. A new three photon process was found to be responsible for emission at low power which is not yet observed in Er³⁺/Yb³⁺:SrO⋅TiO₂ glass ceramic system to the best of our knowledge. The details of upconversion mechanisms e.g. Energy Transfer (ET) and Excited State Absorption (ESA) were studied by power-intensity log dependence. It is expected that Er³⁺/Yb³⁺ doped nanocrystalline (?10 nm) Sr₃Ti₂O₇ phase was responsible for the observed upconversion phenomenon in glass ceramic.     

Sintered glass ceramic composites from vitrified municipal solid waste bottom ashes

A glass ceramic composite was obtained by sinter-crystallisation of vitrified municipal solid waste bottom ashes with the addition of various percentages of alumina waste. The sintering was investigated by differential dilatometry and the crystallisation of the glass particles by differential thermal analysis. The crystalline phases produced by the thermal treatment were identified by X-ray diffraction analysis. The sintering process was found to be affected by the alumina addition and inhibited by the beginning of the crystal-phase precipitation. Scanning electron microscopy was performed on the fractured sintered samples to observe the effect of the sintering. Young's modulus and the mechanical strength of the sintered glass ceramic and composites were determined at different heating rates. The application of high heating rate and the addition of alumina powder improved the mechanical properties. Compared to the sintered glass ceramic without additives, the bending strength and the Young's modulus obtained at 20 degrees C/min, increased by about 20% and 30%, respectively.