Comparison of Methods to Determine the Fracture Toughness of Three Glass-Ceramics at Elevated Temperatures

Two standardized methods for measuring k _Ic in ceramics are compared for use at high temperatures (precracked beam and surface crack in flexure). Results from a third technique involving the measurement of cracks around Vickers indentations are also presented. Three dental glass-ceramics, differing primarily in microstructure, were used as model materials in this study. They emphasized the importance of microstructure in determining high-temperature k _Ic values and the challenges in measuring them. The measured fracture toughnesses decreased with temperature and increased with imbedded grain size for all three methods.     

钛酸铅微晶玻璃介电性能研究

主要对钛酸铅系铁电性微晶玻璃的介电性能做了研究,研制的微晶玻璃初始组成由形成主晶相的氧化物和形成玻璃相的氧化物构成,经过熔融、热处理可以得到以钛酸铅为主晶相的微晶玻璃,分析了不同组成情况下微晶玻璃的介电性能.     

玻璃陶瓷材料发展的回顾与展望

本文回顾了玻璃陶瓷材料的发展过程,特别对近几年来玻璃陶瓷材料的研究进展进行了概述和分析,在此基础上,对玻璃陶瓷的发展趋势进行了探讨。     

Effect of Heat-Treatment Temperature on the Properties of a Lithium Aluminosilicate Glass

The effects of isochronal heat treatments on the properties of a lithium aluminosilicate glass have been measured. Heat treatment of the base glass at temperatures between 700° and 1100°C initially results in phase separation of the glass, followed by the formation of β-quartz solid solution ( ss ) at about 850°C. The β-quartz( ss ) converts to β-spodumene in the temperature range between 950°C and 1000°C. The dependence of the properties of the material on the heat-treatment temperature is controlled by phase separation below 850°C, by the rapid crystallization of β-quartz( ss ) between 850°C and 900°C, and by the lack of change in morphology with heat treatment above 900°C. The effects of heat treatment on the properties of this material are explained on the basis of the changes in the composition and morphology of the residual amorphous and crystalline phases.     

ZrO_2增韧Al_2O_3－硼化物陶瓷性能研究

本文对原料配方研制的ＺｒＯ_２增韧Ａｌ_２Ｏ_３－硼化物陶瓷进行性能测试，并进行分析研究，得出了该陶瓷所具有的性能结论。     

压力容器封头韧性劣化原因分析及处理

本文通过压力容器封头制造中材料韧性出现劣化的案例,分析了其中原因,并做了相应处理。为压力容器外协、外购件的制造和加工提供借鉴。     

玻璃及微晶玻璃的脆性表征

脆性是玻璃和陶瓷等材料的一个重要力学性能,但是目前对于脆性材料的脆性表征,没有统一的明确的表征方法.简述了玻璃及微晶玻璃的脆性断裂机理,对文献中可见的各种脆性表征手段进行了综述和比较,认为压痕法是一种方便、快捷、高效和低成本的实验方法.进一步,本文用压痕法对不同的微晶玻璃的脆性进行了测试,并和抗冲击法进行了对比,结果表明,压痕法对样品脆性的区分能力可以满足对微晶玻璃进行脆性评价的需求,可用于玻璃与微晶玻璃的脆性评判.     

Effect of Ribbon Orientation on the Fracture Toughness of a Metallic-Glass-Ribbon-Reinforced Glass-Ceramic Matrix Composite

A commercially available amorphous metal ribbon incorporated into a glass-ceramic matrix was assessed from the standpoint of fracture toughness. The ribbon orientation (with respect to the long and short transverse sides) relative to the opening crack significantly affected the fracture toughness of such composites. The strong dependence of the fracture toughness on the ribbon orientation was correlated with the differences in the bending contributions of the ribbons in the different orientations. The effect of the ribbon orientation on the crack growth rate in the matrix was also investigated.     

利用生活垃圾灰渣制备低硅含量玻璃及微晶玻璃

利用无机废弃资源制备高附加值玻璃及微晶玻璃制品,具有重要的社会及实际应用价值。通过低氧化硅含量的玻璃组成设计及微晶化处理,在生活垃圾焚烧灰渣利用率在90%的情况下,制备获得成型性能、机械性能与化学稳定性良好的微晶玻璃材料,并探讨了玻璃化学组成及热处理工艺对化学稳定性的影响。     

Viscoelastic Effect of Heat Treatment on the Fracture Toughness of Metal-Particulate/Glass-Matrix Composites

The fracture toughness ( K _Ic) of a 90/10 glass-matrix/metal-particulate composite was measured as a function of treatment temperature and hold time. The toughness was 20% higher at a heat-treatment temperature 15°C below T _g than at the other four treatment temperatures examined. K _Ic also varied as a function of time at temperature. The volume fraction of exposed particulate phase on the fracture surface was proportional to the increase in the fracture toughness.     

Fracture Toughness of Amorphous Precursor-Derived Ceramics in the Silicon-Carbon-Nitrogen System

The toughness of amorphous precursor-derived ceramics in the Si-C-N system is investigated. Crack-growth data are obtained from DCB specimens, whereas the crack-tip toughness is determined from the crack-tip profile of indentation cracks. For amorphous Si-C-N ceramics that have been fabricated via the powder route, an R -curve effect is observed. The initial values of the rising R -curve are consistent with the estimated crack-tip toughness.     

Li2O-ZnO-SiO2系高膨胀微晶玻璃的制备和研究

利用传统熔体冷却方法制得了以P2O5为晶核剂的Li2O-ZnO-SiO2系统玻璃,并探索了该系统微晶玻璃的制备工艺。同时借助X射线衍射仪和和膨胀系数测定仪确定了试样的晶相种类、基玻璃的转化和软化温度以及玻璃的热膨胀系数,探讨了热处理时间对微晶玻璃膨胀系数的影响,从而对该系统玻璃焊料与金属封接的应用前景作了分析。     

钢渣玻璃陶瓷的研制与显微结构

介绍了以宝钢钢渣为主要原料制备玻璃陶瓷的方法.用DTA、XRD、SEM等方法研究了玻璃陶瓷的核化、晶化制度,确定其主晶相为透辉石,晶粒形貌为颗粒状,晶粒的尺寸约为1μm.用钢渣生产玻璃陶瓷是钢渣开发利用的有效新途径.     

核化温度对钢渣玻璃陶瓷性能的影响

以钢渣为主要原料制备玻璃陶瓷。测定了在不同核化温度下试样的抗弯强度,用DTA、XRD和SEM研究核化温度范围并鉴定玻璃陶瓷主晶相。探讨了核化温度与抗弯强度之间的关系。研究表明:抗弯强度、晶相含量随温度的升高先提高然后有所下降。用钢渣生产玻璃陶瓷是钢渣开发利用的一条有效新途径。     

陶瓷材料断裂韧性测试技术在中国的研究进展

本文对近十年来中国学者在陶瓷材料断裂韧性测试技术方面所取得的进展作了简要介绍，并着重评述了这些进展与国际先进水平相比所具有的特色及存在的问题。     

高掺量煤矸石固废微晶玻璃结构与性能研究

本文通过XRD、SEM、TG-DSC、耐腐蚀性、密度、硬度、断裂韧性等测试,研究不同热处理制度和煤矸石掺量对微晶玻璃晶体结构、微观形貌、物化性能的影响。结果表明,该体系煤矸石微晶玻璃析出的主晶相为钙长石相(CaAl₂Si₂O₈),随着热处理晶化温度的升高,析出的主晶相数量变多,尺寸变大,但主晶相种类并未改变。当热处理制度为核化温度750 ℃保温1 h、晶化温度1 000 ℃保温1 h时,主晶相晶体尺寸大小约300~400 nm。在优化热处理制度下,当煤矸石掺量从44%(质量分数)增加到70%时,4种不同煤矸石掺量微晶玻璃的物化性能相差不大。综合考虑煤矸石固废利用率和样品的物化性能指标,煤矸石掺量为70%的样品综合性能最佳。本文设计的煤矸石微晶玻璃体系,对煤矸石固废的包容性好,消纳性强,可实现煤矸石固废的大掺量高值化利用,为解决煤矸石固废堆积、环境污染等问题提供了理论基础和实验依据。     

Effect of Nonstoichiometry on Fracture Toughness and Hardness of Yttrium Oxide Ceramics

This work deals with the changes in mechanical properties of yttrium oxide ceramics induced by nonstoichiometry. The maximum fracture toughness, K_lc, is observed at the stoichiometric composition. For an oxygendeficient ceramic, a decrease of K_lc is observed from 3.5 to 2.3 MPa.m^1/2. On the other hand, the Vickers hardness seems to be less dependent on stoichiometry. These results are discussed in the frame of the evolution of the Y-O bond with the stoichiometry. They set in particular the problem of the role of electrostatic energy stored in a brittle material containing charged defects in the energy balance controlling crack propagation.     

刚玉瓷成形工艺与断裂韧性K_(IC)的关系

用不同的成形工艺制备氧化铝陶瓷,测量其抗弯强度、断裂韧性等主要力学性能;并讨论了不同的成形工艺与其主要力学性能尤其是断裂韧性K_(IC)的关系。