氧化锆对锂铝硅酸盐玻璃化学强化性能的影响

采用熔融淬冷法制备了含不同摩尔分数Zr O₂的锂铝硅酸盐玻璃,通过两步化学强化法对玻璃样片进行了化学强化,研究了Zr O₂对玻璃的稳定性、硬度和化学强化效果的影响。结果表明:随着Zr O₂的摩尔分数从0增加至5%,玻璃化转变温度随之升高,玻璃稳定无析晶现象。引入适量的Zr O₂会促进Li⁺-Na⁺离子交换,提高应力层深度,表面压应力随着Zr O₂浓度的增加而增加,并在摩尔分数为4%时达到最大值,为1 055.6 MPa。中心张应力随着Zr O₂浓度的增加先增加后缓慢减小,表明该系列样品具有较好的抗冲击能力。Zr O₂的浓度变化对强化后玻璃的硬度影响较小,在引入Zr O₂后其抗裂性有所降低,但仍具有较好的抗裂能力。     

化学强化玻璃的发展现状及研究展望

化学强化玻璃因其表面压应力层使玻璃的机械强度提高,被广泛用于电子产品显示屏领域。本文对钠钙玻璃、铝硅玻璃、磷铝硅玻璃、锂铝硅玻璃等的化学强化进行了综述,对进一步通过优化骨干网络结构来提高玻璃本征强度获得更高机械强度的玻璃做出了可行性探索。总结了目前化学强化玻璃面临的问题及发展方向,为相关科学研究和工业生产提供参考。     

Crack Initiation Tendency of Chemically Strengthened Glasses

The relationship between crack initiation tendency before chemical strengthening and fracture strength of chemically strengthened glass was investigated. Four kinds of glass compositions were used in this study: soda-lime silicate (SLS), aluminosilicate (ALS-1, ALS-2), and aluminoborosilicate (ALBS) glasses. The fracture strength of sheet glass was measured by the four-point bending test, the ring-on-ring test, the ball drop test, and the predamaged four-point bending test. ALBS glass, which has the lowest crack formation probability before chemical strengthening, is more damage tolerant than other glasses, and one of the best candidates for chemical strengthening.     

离子交换温度对化学钢化玻璃结构和性能的影响

离子交换法制备钠铝硅系化学钢化玻璃,分析测试玻璃表面K+和Na+的分布情况、玻璃的表面应力及应力层深度、弯曲强度、Weibull模量和显微硬度,研究离子交换温度对化学钢化玻璃在结构和性能上的影响.结果表明:经过离子交换后,玻璃的表面应力、弯曲强度、Weibull模量和显微硬度均显著提高.提高离子交换温度,玻璃表面应力、弯曲强度和显微硬度逐渐下降,应力层深度逐渐加厚.温度350℃时,玻璃表面离子交换层具有全K+层、K+-Na+层和富K+层三层结构.温度升高,全K+层消失和富K+层,K+-Na+层加厚并出现贫Na+层.温度410℃时玻璃的强度分散性最小,可靠性最高.     

铜渣胶凝材料高温力学性能的实验研究

利用工业固体废弃物铜渣制备无机胶凝材料,并对其胶砂试件的高温力学性能进行了实验研究.分别制备了普通硅酸盐水泥-铜渣复合胶凝体系(CSC-x)和碱激发铜渣胶凝体系(CSA-x),测试了常温及100℃、200℃、400℃、600℃、800℃、1000℃、1200℃高温作用后的质量损失、残余抗折强度和残余抗压强度.结果表明:200℃后,CSA-x体系的质量损失率低于CSC-x体系;CSA-x体系表现出较好的耐高温性能,1200℃高温作用后CSA-x体系的残余抗压强度为常温时的3～4倍.     

A Methodology for Estimating the Mechanical Properties of Oxides at High Temperatures

There are few data regarding the temperature dependence of elastic and related properties of materials. This paper describes a semiquantitative basis for estimating such properties in oxide materials to temperatures even approaching their melting points. The various elastic constants are shown to correlate with the field strength of the cationic species, and on V _o, the apparent atomic volume of oxygen. The value of V _o is readily determined from crystallographic data. High-temperature diamond pyramid hardness measurements are shown to correlate with V _o and to provide additional information regarding the structural stability of materials at high temperature. The various refractory oxides are analyzed using these approaches, allowing identification of oxides that appear to be exceptionally strong, stiff, and creep resistant at high temperature.     

Change in the Mechanical Properties of Liquid-Crystalline Thermoplastic Polymers at High Temperatures

The change in the modulus of elasticity and tensile strength of initial and heat-treated liquid-crystalline polyester fibres after annealing at a temperature 20-40°C higher than the melting point of the crystallites in the polymers was investigated. It was shown that from 50 to 90% of the initial values of the strength characteristics were preserved. In heating above the melting point of the crystallites, LC polyester fibres can melt into a monolith with preservation of elevated mechanical properties, which permits production of self-reinforced composites. The fibres melt as a result of cooperative molecular movement, and preservation of the strength indexes is ensured by the cross-links formed at high temperatures. Selection of the temperature—time conditions of heat treatment and molding is especially important for production of high-strength self-reinforced composites by melting of LC polyester fibres into a monolith.     

Study of the Physical Properties of Metallic Glasses at Cryogenic Temperatures

The problems of using metallic glasses for fabricating magnetic cores of cryogenic and superconducting electrotechnical devices, operating at low temperatures of 77 K, are considered. The experience of creating a number of devices, including electric generators, motors and transformers with HTSC windings, is analyzed. The advantages and disadvantages of magnetic cores from annealed tapes are considered. The results of the study of losses and magnetic characteristics of domestic amorphous and nanocrystalline alloys before and after high-temperature annealing are presented.     

Formation of Radiation-Induced Defects in Silica Glasses at High Irradiation Temperatures

The mechanisms of formation of radiation-induced defects in silica glasses are investigated under both simultaneous and sequential exposure to -radiation and high temperatures. It is demonstrated that silica glasses contain E"(T) centers (T = Si and Al) in impurity-free regions andE"_M (T) centers in the vicinity of alkali metal impurities. These centers can undergo transformations. The origin of a new center responsible for the absorption band at 360 nm is elucidated. This center is identified as a twofold-coordinated aluminum atom with a trapped electron.     

Mechanical Behavior of Magnesium Oxide at High Temperatures

Magnesium oxide crystals show a wide variety of deformation and fracture modes under tension. These modes are determined by the number of slip systems operating concurrently in a given volume. (1) At low temperatures, slip is confined to a single (110) (110) system and plasticity is limited by stress concentrations which develop where slip switches from one plane to another. (2) At intermediate temperatures, (110) (110) slip systems at 90° can interpenetrate but those at 60° cannot. Mechanical properties then depend on the initial slip distribution. When slip is confined to 90° systems there is little work hardening and crystals neck down to a knife-edge ductile fracture. When slip is confined to 60° systems, crystals work harden and fracture by cleavage. (3) At high temperatures, dislocations can interpenetrate on all systems and polygonization can occur. After easy glide the crystals work harden and elongate over 100% before fracturing in a completely ductile manner. The transition temperature from one mode to another depends on strain rate.     

Mechanical Behavior of Lithium Fluoride at High Temperatures

Single crystals of lithium fluoride were pulled in tension at high temperatures; the results of these tests are compared with data for magnesium oxide. Interpenetration of {110}〈110〉 slip systems does not occur in LiF as readily as in MgO. Because of this lack of interpenetrability, plastic instability and completely ductile fracture do not occur in LiF below 700°C (0.87 T _mp); the high-temperature tensile strength of LiF decreased very little from 300° to 700°C. This lack of interpenetrability of slip systems in LiF at high temperatures also had a profound effect on the deformation processes, the development of substructure, and the strain-hardening and fracture characteristics of the material. This work emphasizes the importance of interpenetration of slip not only in the high-temperature ductility and strain-hardening processes but also in the maximum tensile strength which ionic crystals develop before fracture.     

Dielectric Properties of Alumina at High Temperatures

The dielectric constant and dissipation factor of both single-crystal and polycrystalline alumina were measured in air over the frequency range lo² to 3 × 10⁵ cycles per second, in the temperature interval 900° to 1300° C. The three-electrode guard-ring method was used. The observed dielectric losses were due predominately to free-electron conduction mechanisms. The volume conductivity of single-crystal and polycrystalline alumina was calculated from the high-frequency data. The temperature dependences of the volume conductivity for two single crystals of different thicknesses were similar. The large thermal activation energy indicated intrinsic conductivity; the energy band gap of alumina was calculated to be approximately 7.3 electron volts. The bulk conductivities of the polycrystalline alumina were considerably higher than the single-crystal values, presumably because of impurities in the polycrystalline material. The results were compared with values previously reported in the literature.     

Mechanical Behavior of Polycrystalline Magnesium Oxide at High Temperatures

High-temperature tensile deformation of paolycrystalline magnesia prepared by ( a ) single-crystal recrystallization and ( b ) hot-pressing, is described. Recrystallized polycrystalline magnesia goes through a brittle-ductile transition at 1700°C (strain rate 10⁻⁴ sec⁻¹). The brittleness below 1700°C is due to a lack of slip systems and grain boundary sliding. At 1700°C grain boundary migration produces corrugations in the interface which interfere with sliding. Above 1700°C the matrix becomes sufficiently plastic through multiple slip and polygonization to accommodate any distortion. Polycrystalline specimens then neck down for completely ductile fracture. Hot-pressed magnesia starts through a transition at 2200°C, i.e. 500°C higher. The increase is attributed to pores and impurity. Porosity is considered to promote grain boundary sliding by ( a ) providing the source for intergranular sliding, ( b ) decreasing the interfacial contact area, and ( c ) preventing grain boundary migration and corrugation. These observations confirm that high-temperature deformation occurs by dislocation glide and climb and by grain boundary sliding and migration.     

The Mechanical Properties of Polymer Glasses

Polymer glasses are widely used in the container, appliance, construction, aerospace, and automobile industries in the form of compression or injection molded parts, solvent cast films, extruded films, coatings, adhesives, and composites. The increasing use of polymeric glasses in extreme service environments, particularly in the aerospace industry, requires a knowledge of their lifetime in such environments. To predict the lifetime of polymeric glasses in a service environment requires knowledge of: (1) details of the particular environment, (2) the nature of the failure processes, (3) the effect of the failure processes on the mechanical properties, (4) the structural parameters affecting the failure processes, and (5) how these structural parameters are modified by fabrication procedures and the service environment.     

Chemically Strengthened Low Crystallinity Black Glass-Ceramics with High Liquidus Viscosities

Strong, black materials are needed for electronic device backs and appliance facings. While glass-ceramics have good strength and toughness, their liquidus viscosity is too low to enable economical forming of these devices by the fusion or slot draw methods. Thus, we invented a new class of low crystallinity glass-ceramics with 10–20 nm crystallites in the Fe₂O₃-TiO₂-MgO system. These materials were formed into transparent glasses and then heat treated to make black opaque glass-ceramics containing magnetite, pseudobrookite, and/or ε-Fe₂O₃. The ε-Fe₂O₃ phase exhibited extensive solid solution (ss) between Fe₂O₃ and MgTiO₃. The blackness and opacity of the ε-Fe₂O₃ glass-ceramics peaked at a ceram temperature of 750°C where the Fe²⁺ in the crystallites was maximized, resulting in peak Fe²⁺-Ti⁴⁺ charge transfer absorption. The liquidus viscosity was increased to more than 100 kPa*s by optimizing the base glass composition and minimizing the amount of crystallinity, thereby enabling fusion formability. These fusion formable glass-ceramics had strengths exceeding the best commercially available glasses after ion exchange. This work provides a new class of low crystallinity fusion formable glass-ceramics with high strength.     

氢化丁腈橡胶高温力学性能研究

研究高温下不同炭黑用量的氢化丁腈橡胶(HNBR)的回弹值、邵尔A型硬度、拉伸强度、拉伸应力松弛性能和动态力学性能等,分析温度对橡胶分子链段和物理交联网络等微观运动和微观结构的影响。结果表明:随着温度从25℃升高至150℃,不同炭黑用量的HNBR硫化胶的邵尔A型硬度和拉伸强度逐渐减小,回弹值先增大后减小,应力松弛速率增大,应变扫描前后储能模量之差减小;炭黑用量越大,高温下HNBR硫化胶的拉伸强度保持率越大,应力松弛的平衡应力占比越小;温度升高会破坏炭黑补强HNBR硫化胶的填料网络结构,导致结合胶含量减少,HNBR硫化胶高温下的力学性能下降。     

碱性助剂对玻璃化学钢化性能的影响研究

本文以普通薄玻璃和KNO3为原料,采用低温离子交换法研究了KOH和K2 CO3对玻璃化学钢化效果的影响.利用X射线荧光光谱仪、维氏硬度计和扫描探针显微镜,观察了玻璃的成分变化、硬度变化和表面形貌.结果表明,在KNO3熔盐中添加KOH,破坏了玻璃的表面结构,降低了玻璃的硬度;在KNO3中添加质量比为9％的K2CO3,保温4h,维氏硬度达到672 HV.相比于纯KNO3熔剂,它可缩短2/3的钢化时间,起到了助剂作用.     

Preparation and Mechanical Properties of Mg-Al-Si-O-N Glasses

A three-component glass system (Mg–Al–Si) was nitrided by adding amorphous and crystalline Si₃N₄. Glasses with varying amounts of nitrogen were melted, and their mechanical properties were measured. Density, hardness, Young's elastic modulus, and fracture toughness increased with increasing nitrogen content.     

Electrical Properties of Single-Crystal and Polycrystalline Alumina at High Temperatures

The electrical conductivity of single-crystal and polycrystalline aluminum oxide has been measured over the temperature range 1300° to 1750°C. and at oxygen partial pressures of 10° to 10⁻¹⁰ atmospheres. Alumina exhibits p- type conductivity at high oxygen pressures and n -type conductivity at low oxygen pressures. The variation of conductivity with temperature depends on the specimen purity, oxygen pressure, and temperature level. Activation energies varying between 2.6 and 5.8 e.v. were found. The conductivity of alumina does not result from any single simple process over wide ranges of temperature and oxygen partial pressure. Apparently intrinsic conduction is found for single crystals at temperatures above 1600°C.     

水泥熟料的高温力学性能

为了解水泥熟料破碎阻力随温度的变化,在实验室制各熟料样品,并在熟料冷却阶段的不同温度点进行力学实验.分析了水泥熟料样品载荷-位移曲线、抗压强度、弹性模量等随温度的变化情况.结果表明:随温度的降低水泥熟料表现出明显的硬化特征,加载峰之后,水泥熟料的特性宏观上表现出塑性向脆性的渐次转变.在冷却阶段,水泥熟料的弹性模量和抗压...