红柱石骨料粒度对莫来石-刚玉材料抗热震性的影响

分别用20%(w)不同粒度(5～3、3～1、≤1 mm)的红柱石骨料等量替代莫来石-刚玉材料中同粒度的莫来石骨料,经1 450℃保温3 h烧成制备莫来石-刚玉材料,并着重研究红柱石骨料粒度对其抗热震性的影响。结果表明:随着红柱石骨料粒度的增大,烧成试样的抗折强度和弹性模量逐渐降低,但抗热震性逐渐提高。这是由于在试样烧结降温过程中,红柱石骨料与基质热膨胀系数失配产生了微裂纹,且微裂纹的尺寸随着红柱石骨料粒度的增大而增大;而微裂纹在热震过程中能够阻止新裂纹的产生和裂纹扩张,提高试样的抗热震性。     

红柱石粗颗粒预烧温度对莫来石-刚玉材料抗热震性的影响

为了研究经过预烧的红柱石粗颗粒对莫来石-刚玉耐火材料抗热震性的影响,将20%(w)的未经预烧或分别经1 300、1 400、1 500、1 600℃保温3 h预烧的南非红柱石粗颗粒(5～3 mm)分别与莫来石颗粒(3～1和≤1 mm)以及板状刚玉粉、活性氧化铝粉和SiO_2微粉配料,制样,于1 450℃保温3 h烧后制成莫来石-刚玉试样,检测其烧后线变化率、弹性模量、抗热震性,并进行显微结构分析。结果表明:随着红柱石粗颗粒预烧温度的提高,试样的常温抗折强度逐渐提高,但抗热震性能变差。这是由于随着红柱石粗颗粒预烧温度的提高,红柱石粗颗粒与基质的热膨胀系数差值变小,产生的微裂纹尺寸逐渐减小,且在热震过程中能够阻止新裂纹产生和裂纹扩张的微裂纹减少。     

热风炉管道用Al_2O_3-SiO_2浇注料性能的影响因素

为了提高热风炉管道用浇注料的使用寿命,以矾土均化料、红柱石颗粒和细粉、白刚玉细粉、纯铝酸钙水泥、SiO2微粉、α-Al2O3微粉、硅溶胶等为原料制备了热风炉管道用Al2O3-Si O2浇注料,并研究了SiO2微粉加入量、骨料类型、水泥加入量以及用硅溶胶作结合剂对浇注料性能的影响。结果表明:1)随着SiO2微粉加入量的增加,热处理后试样的常温抗折强度和常温耐压强度逐步增加,烧后收缩增大,体积密度先增加后降低,综合考虑,SiO2微粉的适宜加入量为4%(w);2)以矾土为骨料的试样具有较高的常温强度和较好的体积稳定性,但以红柱石为骨料时的抗热震性更好;3)结合系统含硅溶胶时,加入纯铝酸钙水泥能降低浇注料的烧后线变化,稍微提高常温强度和抗热震性,而加入柠檬酸则降低试样的抗热震性。     

红柱石对莫来石-高硅氧玻璃材料性能的影响

以莫来石M40(3~1 mm、≤1 mm和≤0.088 mm)和红柱石(1~0.5 mm、≤1 mm和≤0.074 mm)为原料,固定骨料和基质质量分数分别为70%和30%,调整红柱石的加入量(≤0.088 mm的加入量分别为0、5%、10%、15%、20%)和粒度(3种粒度分别添加10%),外加5%的硅溶胶结合剂,经混合、成型和烘干后,于1 200~1 600℃的空气气氛中保温3 h煅烧,测定烧后试样的线变化率、显气孔率、体积密度、耐压强度、荷重软化温度和抗热震性,并用SEM观察热震前后试样的显微结构。结果表明:(1)在相同煅烧温度下,随红柱石粉(≤0.088 mm)含量的增加,试样的线收缩率减小,显气孔率增大,体积密度下降或基本保持不变,耐压强度总体上逐渐增大;(2)在红柱石粉添加量相同的情况下,随煅烧温度的提高,试样线收缩率增大,显气孔率下降,体积密度增大,耐压强度升高;(3)加入不同粒度的红柱石均有利于提高材料的荷重软化温度,且采用1~0.5 mm的红柱石和提高烧成温度更加有效;加入不同粒度红柱石的试样,抗热震性均不是很好,其中以加入≤1 mm红柱石的试样抗热震性最好,加入1~0.5 mm的次之,加入≤0.074 mm的最差。     

引入不同粒度红柱石对Al_2O_3-SiC-C浇注料性能的影响

为了提高Al_2O_3-SiC-C铁沟浇注料的性能,在其配料中分别引入8～5、5～3、3～1和≤1 mm的红柱石,经成型、养护、干燥后,于1 450℃保温3 h热处理,然后检测试样的显气孔率、体积密度、烧后线变化率、常温抗折强度、弹性模量、抗热震性和抗渣性。结果表明:1)引入红柱石试样的显气孔率和体积密度均比未引入红柱石的小,烧后线膨胀率均比未引入红柱石的大。随着红柱石粒度的减小,显气孔率逐渐减小;体积密度呈先减小后增大的变化趋势,以引入5～3 mm红柱石试样的为最小;烧后线膨胀率呈先增大后减小的变化趋势,以引入5～3 mm红柱石试样的为最大。2)引入8～5 mm红柱石试样的常温抗折强度和弹性模量比未引入红柱石的小,其他试样的基本上比未引入红柱石的大;随着红柱石粒度的减小,试样的常温抗折强度和弹性模量逐渐增大。3)引入红柱石试样的抗热震性均比未引入红柱石的高;随着红柱石粒度的减小,抗热震性逐渐降低。4)各试样仅在渣-样交界处有轻微的侵蚀,引入不同粒度红柱石试样的抗渣性没有明显差别。     

骨料对KR脱硫搅拌头外衬浇注料性能的影响

针对KR脱硫搅拌头的使用要求,研究了骨料种类和粒度组成对其外衬浇注料性能的影响.结果表明:以莫来石为骨料的浇注料110 ℃干燥和1300 ℃烧后基本性能以及1100 ℃水冷3次后残余抗折强度均优于以刚玉、矾土或焦宝石为骨料的浇注料;临界粒度增大,浇注料干燥后和烧后冷态性能均有所提高;临界粒度不同浇注料试样达到最佳冷态性能时对应的粒度分布系数q是不同的,且该q值下的浇注料达到了较好的耐磨性和热震稳定性.     

MgAlON系复合材料的热震稳定性分析

研究了不同骨料、不同基质及不同热震冷却方法对MgAlON系复合材料热震稳定性的影响.实验原料为骨料、基质料、结合剂(糊精),压制成型后1500℃高温氮化烧成.先测定烧成后试样的抗折强度;然后将试样1000℃埋碳处理后降至室温风冷循环三次,测其抗折强度;再将试件加热保温到设定温度后立即取出,放入循环水中进行水冷后测定其抗折强度σf;并计算热震前后试样残余强度保持率;利用SEM观察试样热震后的显微结构特征.实验研究表明:MgO-MgAl2 O4-MgAlON系复合材料的临界热震温差ΔTC为400℃;热震后MgAl2 O4-MgAlON复合材料的残余强度保持率较高,MgAlON弥散于基质材料中,起到了原位自补强作用;同种骨料的试样相比,氧化铝基试样热震后的残余强度保持率相对较高.     

红柱石添加量对致密电熔刚玉浇注料高温性能的影响

本文以致密电熔刚玉、红柱石颗粒、红柱石细粉、活性α-Al2O3微粉、硅微粉为原料,纯铝酸钙水泥为结合剂,三聚磷酸钠为减水剂,制备了电熔刚玉浇注料,并研究红柱石颗粒及细粉加入量对致密电熔刚玉浇注料高温性能的影响.结果表明,红柱石反应生成的莫来石和二氧化硅玻璃相可以显著提高致密电熔刚玉浇注料的热震稳定性,红柱石添加量达到25％后,添加量的增加对试样热震稳定性的提高效果不明显.加入红柱石的致密电熔刚玉浇注料可以作为化铜感应炉的炉衬原料来提高炉子的使用寿命.     

热震条件下Al2O3-O’-SiAlON-SiC复合材料氧化行为研究

以板状刚玉(骨料和细粉)、α-Al₂O₃微粉和硅粉等为原料,在1 500 ℃下埋炭保温3 h烧结制备了Al₂O₃-O’-SiAlON-SiC复合材料。研究了热震及不同热震次数对复合材料氧化行为的影响。研究结果表明:在无热震和热震条件下,试样氧化增重率在900~1 300 ℃均随温度升高而增加;热震氧化条件下的增重率大于无热震条件,且随热震次数增加,氧化增重率略有增加。无热震条件下,试样恒温氧化曲线类似于抛物线型,而热震条件下,试样氧化曲线接近直线型。因此,热震明显促进了复合材料的氧化,其原因在于热震使试样表面的氧化保护膜破裂,试样产生微裂纹,为氧气进入试样内部提供通道,进而加速材料氧化。     

ZrO2和TiO2对刚玉质陶瓷蓄热体热震稳定性的影响

采用板状刚玉(＜0.044 mm)、活性氧化铝(d50=1.7 μm)为主要原料,CMC为结合剂,分别制备了无添加剂、添加TiO2、添加ZrO2以及复合添加ZrO2和TiO2 4种刚玉质陶瓷蓄热体试样;试样经1550℃保温2 h热处理后,检测了其热震稳定性、显气孔率和热膨胀系数.结果表明:与无添加剂和单独添加TiO2、单独添加ZrO2的刚玉质陶瓷蓄热体试样相比,复合添加ZrO2和TiO2的刚玉质陶瓷蓄热体试样的热震稳定性显著提高,其原因是:ZrO2的马氏体相变产生微裂纹增韧、钛酸铝(AT)与刚玉的线膨胀系数差形成微裂纹增韧及AT的线膨胀系数低三者协同增韧的机制显著提高了刚玉质陶瓷蓄热体试样的热震稳定性.     

Influence of Yb Substitution for La on Thermophysical Property of La2AlTaO7 Ceramics

The (La_1−xYb_x)₂AlTaO₇ ceramics were synthesized by pressureless sintering process at 1600 °C for 10 h in air. The crystal phase, microstructure and thermophysical properties were investigated. Results show that pure (La_1−xYb_x)₂AlTaO₇ cermics with single weberite structure are prepared successfully. Owing to the reduction of crystal-lattice tolerance-factor, the thermal conductivity of (La_1−xYb_x)₂AlTaO₇ (x>0) ceramics increases with increasing Yb₂O₃ fraction at identical temperatures, which is lower than that of La₂AlTaO₇. Due to the relatively high electro-negativity of Yb element, the addition of Yb₂O₃ increases the thermal expansion coefficient of (La_1−xYb_x)₂AlTaO₇ ceramics.     

绝缘导热高分子复合材料研究

介绍了导热绝缘高分子复合材料的导热性能、导热机理,综述了各类导热绝缘高分子如复合型导热塑料、橡胶、胶粘剂、涂层等的研究,并展望了其应用前景及未来发展方向.     

PPS导热绝缘塑料的制备及性能研究

通过聚苯硫醚(PPS)与大颗粒氧化镁(40~325目)混合经双螺杆挤出机挤出造粒制备了导热绝缘塑料。研究了导热性能与氧化镁填充量的关系。实验发现:热扩散系数和热导率随氧化镁的填充量的增加而增加;最高热导率达到3·4W/(m·K),此样品仍然可注射成型,且具有良好的机械性能。热失重分析表明失重率随氧化镁填充量的增加而成比例降低,氧化镁对PPS热分解温度没有明显影响,氧化镁的增加使处于高温降解阶段的PPS加速分解。     

Sm_2YbTaO_7和La_2AlTaO_7的热物理性能

采用固相反应法制备了Sm_2YbTaO_7和La_2AlTaO_7氧化物,并研究了其热物理性能。Sm_2YbTaO_7和La_2AlTaO_7氧化物在20℃~1200℃范围内的平均热导率分别是0.45 W/(m·K)和1.71 W/(m·K),明显低于现役的氧化钇部分稳定氧化锆陶瓷(YSZ)。与La_2AlTaO_7相比,Sm_2YbTaO_7较低的热导率可以归因于其取代原子与基质原子之间较高的原子质量差别,Sm_2YbTaO_7较高的热膨胀系数则可归因于其A位与B位离子之间较低的电负性差别。Sm_2YbTaO_7和La_2AlTaO_7的热导率和热膨胀系数均满足热障涂层的要求,具有做为新型热障涂层表面陶瓷层材料使用的潜力。     

绝热(保温)在精细化工中的应用探析

介绍二元酚项目中保温方案的选择;保温工程的施工与验收;保温效果的测试与评价。具有推广意义。     

Effects of zirconium carbide content on thermal stability and ablation properties of carbon/phenolic composites

Ceramic particles were utilized to improve thermal stability and ablation properties of carbon/phenolic (C/Ph) composites. In this study, zirconium carbide (ZrC) modified C/Ph composites were fabricated by vacuum impregnation method, and effects of ZrC content on thermal stability and ablation properties were investigated by thermogravimetry analysis and plasma wind tunnel test. Moreover, morphological characterization was carried out using X-ray diffraction, scanning electron microscopy and energy dispersive X-ray spectroscopy. Experimental results showed that increasing ZrC content could lead to an evident increase in char yield, but an observable reduction in linear ablation rates and back-face temperatures because of the formation of ZrO₂ layer on the ablation surface. The work provided an effective way to improve thermal stability and ablation properties of C/Ph composites.     

Preparation and thermophysical properties of Sm2YbTaO7 and Sm2YTaO7

Sm₂YbTaO₇ and Sm₂YTaO₇ ceramics were synthesized by solid reaction method at 1600 °C for 10 h. Crystal phases have been identified by X-ray diffraction, and their thermal conductivities and thermal expansion coefficients were measured using a laser flash method and the pushing-rod technology, respectively. Results indicate that Sm₂YbTaO7 and Sm₂YTaO₇ exhibit a typical defect fluorite-type crystal structure. Compared to Sm₂YTaO₇, Sm₂YbTaO₇ has lower thermal conductivity due to the higher atomic weight difference between the substituted and substituting atoms. The thermal expansion coefficient of Sm₂YbTaO₇ is greater than that of Sm₂YTaO₇ due to its elongated average interionic distance. Their thermal conductivities are much lower than that of YSZ, and their thermal expansion coefficients are very close to that of YSZ. The synthesized ceramics also exhibit excellent phase stability in the temperature range from ambient to 1200 °C.     

A new class of high-entropy fluorite oxides with tunable expansion coefficients,low thermal conductivity and exceptional sintering resistance

High-temperature thermal barrier coating (TBC) materials are desired for the development of high-efficient gas turbines and diesel engines. Herein, to meet up with this requirement, a new class of high-entropy fluorite-type oxides (HEFOs) has been synthesized via a solid-state reaction method. Comparing to La₂Ce₂O₇, a promising TBC material, the HEFOs exhibit similar high thermal expansion coefficients (TECs) of 11.92×10⁻⁶∼12.11×10⁻⁶ K^-1 at temperatures above 673 K but a better TEC matching performance at the temperature range of 473–673 K. It is also found that through tuning the average A-site cation radius, the TEC of the HEFOs could be tailored efficiently. The HEFOs also possess low thermal conductivities of 1.52-1.55 W∙m^-1∙K^-1 at room temperature, which is much lower than that of La₂Ce₂O₇ and comparable to pyrochlores as Gd₂Zr₂O₇. Moreover, the HEFOs display good sintering resistance and phase stability even at temperatures as high as 1873 K. The combination of these fascinating properties makes the HEFOs good candidates for thermal barrier coating and thermal insulating materials.     

Effect of TGO thickness on the thermal barrier coatings life under thermal shock and thermal cycle loading

Effect of thermally grown oxide (TGO) thickness on thermal shock resistance of thermal barrier coatings (TBCs) and also their behavior under a cyclic loading (including aging at maximum temperature) was evaluated experimentally. In order to form different thicknesses of TGO, coated samples experience isothermal loading at 1070?°C for various periods of times. Heat-treated samples were heated to 1000?°C and cooled down rapidly in water from the substrate side using a mechanical fixture. The life of samples was investigated as a function of TGO thickness. Furthermore, by performing an experiment the simultaneous effect of the TGO growth and thermal expansion mismatch– on the failure of thermal barrier coatings was evaluated. The results demonstrated that the presence of TGO with a thickness of 2–3?µm has a positive effect on the resistance against thermal shock.     

填充型导热塑料的热导率分析

运用等效热导率法则，对填充型导热塑料中的一个导热单元进行分析，根据热量传递的串并联原理及傅立叶定律，建立导热塑料中热量传递的理论模型，推导出预测其热导率的理论公式。经检验，建立的理论模型与实验测试结果能较好的吻合，从而证明该模型是合理的。