刚玉莫来石复相陶瓷热震及蠕变性能的影响因素分析

采用正交设计方法研究了硅微粉、氧化铝微粉及烧成温度对刚玉莫来石复相陶瓷热震稳定性及蠕变性能的影响机制。结果表明:烧结温度对复相陶瓷热震稳定性及蠕变性的影响最大,氧化铝微粉次之,硅微粉最小。高温抗折强度损失率在烧成温度为1650℃时最低,随氧化铝的含量增加而减小,并随硅微粉含量增加而增大。蠕变率随烧成温度的提高而减少,氧化铝质量分数为7%时最低,并随硅微粉含量增加而增大。通过调节硅微粉、氧化铝微粉及烧结温度,可控制颗粒与基质、莫来石的结合状态,气孔及残留α-Al2O3,从而改善材料的抗热震性及蠕变性。     

硅溶胶对刚玉莫来石复相陶瓷的性能影响

采用溶胶-凝胶法在刚玉-莫来石质材料中引入活性硅溶胶(SiO2),分析了硅溶胶对刚玉-莫来石复相陶瓷性能的影响机制。研究结果表明,SiO2在主体材料中形成纳米包裹薄膜,SiO2的分布可控、掺入均匀,从而提高了复相陶瓷的抗热震性、高温强度及蠕变性。加入SiO2溶胶产生的莫来石反应化和微裂纹增韧是刚玉-莫来石质材料热震稳定性提高的主要原因。     

锆溶胶制备及其对刚玉莫来石复相陶瓷性能的影响

采用溶胶-凝胶法合成了锆溶胶,并在刚玉-莫来石质材料中引入ZrO2,分析了ZrO2溶胶对刚玉-莫来石复相陶瓷性能的影响特征。研究结果表明,ZrO2在主体材料中形成纳米包裹薄膜,ZrO2的分布可控和均匀掺入,不仅提高复相陶瓷的抗热震性、高温强度及蠕变性,而且还使微观结构可控、晶粒尺寸均匀。加入ZrO2溶胶产生氧化锆粒子的应力诱导相变增韧和微裂纹增韧是刚玉-莫来石质材料热震稳定性提高的主要原因。     

红柱石基刚玉-莫来石复相陶瓷的显微结构及性能

以红柱石颗粒为主要骨料,辅以莫来石颗粒和刚玉颗粒,硅微粉、铝微粉为基质料,经混合、困料及成型后,经不同温度下烧成4h,制得莫来石基刚玉-莫来石复相陶瓷,分析了烧成温度对复相陶瓷的物相组成、显微结构、烧成性能、力学性能及热学性能。结果表明:红柱石在高温下转化成针状和柱状莫来石改善复相陶瓷的烧成性能和抗热震性能;在1480℃烧成时,红柱石刚玉-莫来石复相陶瓷具有优越性能,其抗折强度为15.4MPa,耐压强度为91.6MPa,热膨胀系数为5.5×10-6/K,1100℃下水冷的抗热震次数达到99次。     

莫来石——钛酸铝复相陶瓷的强度与热膨胀性

本文介绍了莫来石－－钛酸铝复相陶瓷的室温强度和热膨胀－－冷却曲线等性能。重点分析了强度提高及冷却滞后现象的原因。     

莫来石—钛酸铝复相陶瓷研究

本文介绍了莫来石－钛酸铝复相陶瓷的制备工艺及其主要性能；重点讨论了该复相陶瓷的烧结性、增强机制、膨胀性能影响、高温分解、高温强度及抗热震性等方面的变化；简单介绍该材料的应用前景。     

刚玉–莫来石–镁铝尖晶石复合陶瓷的原位合成及热震行为

以α-Al2O3、苏州土、滑石和石英为主要原料,采用无压烧结制备了刚玉–莫来石–镁铝尖晶石多相复合陶瓷,研究了烧结温度对样品的体积密度、线性收缩率和吸水率等烧结性能以及机械性能的影响。通过X射线衍射和扫描电子显微镜分析了复相陶瓷热震前后的物相组成和显微结构。结果发现：经1480℃烧结的样品吸水率为0.19%,体积密度为3.06g/cm3,抗折强度达99.59MPa,复合材料有较好的热震性能,1100℃空冷热震损失率仅6.9%,可耐受17次热冲击。该复相陶瓷可作为潜在的太阳能热发电材料。     

刚玉—莫来石质泡沫陶瓷的研制

通过对泡沫陶瓷的研究,制备出了以刚玉－莫来石为主晶相,相对密度为０．３￣１、气孔率为８０％￣９０％的泡沫陶瓷。经过配方及工艺设计,基本掌握了该系材料具有良好的网络结构及强度,证实了添加ＭｇＯ－ＺｒＯ２对该系材料的增强作用。     

常压烧结莫来石／氧化锆／碳化硅复相陶瓷的研究

本文对莫来石／氧化锆／碳化硅复相陶瓷进行了Ｎ２气氛中常压烧结的研究。实验结果表明：ＳｉＣ粒子添加量≤２０ｖｏｌ％，材料均可致密烧结并可获得均匀的微观结构。ＳｉＣ粒子的加入使材料人力学性能较莫来石／氧化锆陶瓷有明显的提高，并在ＳｉＣ含量为１０ｖｏｌ％时达到峰值，室温强度和断裂韧性分别为６０１ＭＰａ和５．８ＭＰａ＾Ｃ２，接近热压材料。     

Preparation and Performance Study of Mullite/Al2O3 Composite Ceramics for Solar Thermal Transmission Pipeline

For lowering sintering temperature of mullite/Al₂O₃ composite ceramics for solar thermal transmission pipeline, kaolin, potassium feldspar, quartz, and γ‐Al₂O₃ were used as raw materials to in situ synthesize the composite ceramics with pressureless sintering method. Densification, mechanical properties, thermal expansion coefficient, thermal shock resistance, phase composition, and microstructure were investigated. The experiment results demonstrated that the introduction of potassium feldspar and quartz decreased the lowest sintering temperatures greatly to 1300°C. The optimum sample A3 sintered at 1340°C obtained the best performances. The water absorption, apparent porosity, bulk density, bending strength, and thermal expansion coefficient of A3 were 0.04%, 0.12%, 2.71 g/cm³, 94.82 MPa, and 5.83 × 10^?6/°C, respectively. After 30 thermal shock cycles (wind cooling from 1100°C to room temperature), no cracks were observed on the surfaces of the sample, and the bending strength increased by ?7.96%. XRD analysis indicated that the main phases of samples before and after 30 thermal shock cycles were consistently mullite, corundum, and α‐cristobalite, while the content of mullite increased after thermal shock. SEM micrographs illustrated that the mullite grains growth and micro‐cracks appeared after thermal shock endowed the composite ceramics with excellent thermal shock resistance.     

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。     

Thermal Shock Behavior of Duplex Ceramics

The thermal-stress fracture behavior of duplex ceramics is investigated by quenching in water and in oil. Comparison with the matrix materials shows that the critical quenching temperature difference, Δ T _c , is not or is only slightly reduced, even for duplex ceramics of significantly reduced strength. In sintered composites, thermal-stress-induced microcracking within pressure zones and crack initiation at pressure zone–matrix interfacial defects develop before Δ T _c is reached. The effects are accompanied by a gradual reduction in strength. At Δ T _c , critical crack propagation occurs. The retained strength after thermal shock of duplex ceramics is significantly improved compared with the respective matrix materials. This behavior can be related reasonably well with the K ^R -curve behavior.     

基质相对莫来石-刚玉窑具性能的影响

研究了基质相组成,对莫来石-刚玉窑具性能的影响.研究发现:基质相对窑具的性能影响较大,硅线石的加入可以提高窑具的常温强度和高温强度,莫来石生粉加入可以提高窑具的抗热震性.     

铝硅凝胶粉对刚玉莫来石气幕挡墙性能和显微结构的影响

以临界粒径为1 mm的板状刚玉为骨料,以白刚玉为细粉,以ρ-氧化铝和硅微粉为结合剂,添加不同量的铝硅凝胶粉,浇注成型制备了中间包用刚玉莫来石质气幕挡墙,研究了铝硅凝胶粉对材料物理性能和孔径分布的影响.结果表明:随着铝硅凝胶粉的加入,试样致密度提高,强度增大;在热处理过程中,凝胶粉反应生成莫来石,体积膨胀,促进致密化,降低气孔孔径;加入较多时,使得试样过烧结.在本实验条件下,铝硅凝胶粉加入4％时,刚玉莫来石气幕挡墙性能较好.     

莫来石基纳米复合陶瓷

纳米陶瓷是八十年代中期发展起来的一个新兴材料领域,纳米陶瓷的力学性能较同化学组成陶瓷相比有数量级的提高,并具有一些新的特性,为材料开拓了新的应用领域。本文介绍了莫来石基纳米陶瓷结构特点,主要制备方法,工艺要点及相关性能,并总结了纳米粒子在莫来石基体中的作用。     

High-Temperature Compressive Creep of Polycrystalline Mullite

Aluminosilicates of three compositions with mullite as the major phase were synthesized by a sol-gel process and characterized with bulk and microchemical analyses and microstructural observation. An apparatus for measuring the compressive creep up to 1900 K with a sensitivity of ±1 μm was constructed and used to measure the creep of singlephase mullite, mullite with second-phase glass, and mullite with second-phase corundum. Measurements in air at stresses of 15 to 100 MPa and temperatures of 1471 to 1724 K determined that samples with second-phase glass crept more rapidly than single-phase mullite or mullite with secondphase corundum. The apparent creep activation energies determined at 100 MPa were 742 kJ/mol for the mullite containing glass, 819 kJ/mol for the single-phase mullite, and 769 kJ/mol for the mullite with second-phase corundum. The stress exponents determined at 1724 K were 1.6 for the mullite plus glass, 1.5 for the single-phase mullite, and 1.2 for the mullite with α-Al₂O₃. The creep behavior of the aluminosilicates containing glass were consistent with rate control by the viscous flow of the glass and the measured creep rates were in good agreement with creep rates calculated from a model by Dryden. The creep behavior of the completely crystalline aluminosilicates was consistent with rate control by diffusional creep.