蜂窝陶瓷蓄热材料的研究现状

蜂窝陶瓷蓄热材料应该具有热膨胀系数低、比热容大、比表面积大、导热性能好、抗热震性好等特性。本文详细介绍了几种多孔陶瓷材料的优缺点,指出堇青石质复相材料是目前研究最广泛的蜂窝陶瓷材料。堇青石与多种催化剂匹配性好,比表面积大、热膨胀系数小,但耐热性稍差,于是通过添加一些添加剂来提高堇青石作为蜂窝陶瓷蓄热体的性能。这些添加剂与堇青石结合形成复相材料,可以降低热膨胀系数、提高抗热震性等。     

Bi2O3对堇青石陶瓷的相组成、微观结构和性能的影响

采用X射线衍射、扫描电镜、差热分析和热膨胀仪等手段研究了由氧化物粉末(MgO，Ai2O3和SiO2)制备堇青石陶瓷时，添加Bi2O3对堇青石陶瓷相变、相组成和性能的影响，Bi2O3在烧结过程中的作用机理是低温产生液相促进烧结。试验表明，在1350℃烧结3h，该陶瓷由堇青石和孤立分布的玻璃相组成。随Bi2O3含量增加，陶瓷的致密度、弯曲强度和热膨胀系数逐渐升高。Bi2O3的添加量(质量分数)大于4％时，原料相石英消失。硅氧网络骨架结合力减小和一定量的玻璃相是引起堇青石陶瓷热膨胀系数升高的主要原因。     

原位生成堇青石结合红柱石太阳能热发电储热陶瓷的抗热震性能

为提高储热陶瓷材料的抗热震性能,采用原位生成堇青石增强技术,以红柱石为主要原料,通过半干压成型,无压烧结研制了用于太阳能高温热发电红柱石储热陶瓷材料样品。研究了配方组成、烧成温度、相组成、微观结构对样品抗热震性能的影响。结果表明：红柱石添加量为 70%,经1 400 ℃烧成的样品抗热震性能最佳：30 次热震实验（热震条件：1 100 ℃～室温,风冷）的强度不仅没有损失,反而增加了 26.20%。相组成和微观结构分析表明样品的晶相为堇青石、莫来石、硅线石、α-方石英、α-石英等,原位生成的堇青石晶体均匀分布在由红柱石转化的莫来石晶体之间,赋予样品较好的抗热震性能     

堇青石质多孔陶瓷高温过滤材料的研究

主要介绍了堇青石多孔陶瓷高温过滤材料的制备工艺及其性能检测，同时对影响材料性能的各种因素进行了分析和探讨。     

采用陶瓷过滤器的高温烟气处理技术

介绍了堇青石质、碳化硅质陶瓷过滤器的开发、生产及在处理高温烟气方面的应用。     

Fe2O3—堇青石系红外辐射陶瓷的结构与性能研究

用常规固相反应烧法制备出Ｆｅ２Ｏ３－堇青石系高效常温红外辐射陶瓷材料。研究了材料的微观结构,发现：在Ｆｅ２Ｏ３中掺杂ＭｎＯ２经还原气氛高温处理后生成的ＭｎＦｅ２Ｏ４与堇青石形成了转换型固溶体。Ｍｎ＾２＋的结构位置。同时,随着Ｆｅ２Ｏ３含量的增加,堇青石的结构从有序结构向无序结构过渡。这些结构上的变化,导致了辐射性能在常温下较单相有了很大改善。     

堇青石/碳化硅复相陶瓷窑具抗氧化性能研究

本文对碳化硅、堇青石的优点整合制备碳化硅/堇青石复相陶瓷窑具,以力学性能变化为基础通过研究偏钒酸铵含量、金属硅粉含量、烧成温度等3个方面对堇青石/碳化硅复相窑具材料抗氧化性能进行研究分析,并通过X-射线衍射(XRD)分析,复相陶瓷窑具中并未有明显的氧化物如SiO2等杂质相出现。     

堇青石蜂窝陶瓷热膨胀特性的研究

汽车尾气净化器用蜂窝陶瓷载体对材料的抗热冲击性能要求很高,要求材料具有特别低的热膨胀系数。本文通过对堇青石陶瓷的平均热膨胀系数及微观热膨胀系数的分析,研究了堇青石蜂窝陶瓷的热膨胀特性。     

堇青石陶瓷的研究现状

介绍了堇青石陶瓷的应用情况和基本结构特点,重点分析了堇青石陶瓷的研究现状和合成中存在的问题,并提出了相应的解决方法.     

Evaluation of Slow Crack Growth Resistance in Ceramics for High-Temperature Applications

The slow (subcritical) crack growth (SCG) resistance of Si₃N₄ and SiC ceramics has been evaluated by a stepwise loading test on bending bars precracked by Vickers indentation. Three highly refractory materials were selected for the evaluation: i.e., (1) high-purity Si₃N₄ sintered by hot isostatic pressing (HIP) without additives and (2,3) α - and β - SiC pressureless sintered with B and C addition. Under the hypothesis of linear elastic behavior at high temperature, which was found satisfied in the present materials, the SCG resistance was expressed in terms of initial stress intensity factor critical for SCG failure within a predetermined lifetime. The present method was found useful in shortening the testing time and consistent with other traditional fatigue tests (e.g., static-fatigue test): It is recommended as a screening test for materials under research and development. Among the materials tested in the present study, the highest SCG resistance up to 1440°C was found in the high-purity Si₃N₄ without additives.     

太阳能吸热器用莫来石--碳化硅陶瓷的原位合成(英文)

采用半干压成型和无压烧成技术,原位合成了用于太阳能热发电吸热器的莫来石结合碳化硅(SiC)吸热陶瓷。研究结果表明:经1 520℃烧成的样品B2(粒径≤61μm SiC 72%,粒径≤20μm SiC 18%,工业氧化铝4.64%,苏州高岭土5.36%)的综合性能最佳,其显气孔率、吸水率、体积密度和抗折强度分别为28.40%、13.35%、2.13g/cm3和44.20MPa;热震试验30次(1 100℃~室温,风冷),样品无裂纹,强度增加率达52.30%;在1 300℃氧化100h后,样品的氧化增重为25.43mg/cm2,氧化动力学常数为1.80×10--7kg2/(m4·s)。物相分析表明,样品的相组成为碳化硅、莫来石、石英和刚玉。显微结构分析表明,原位合成的莫来石结合于碳化硅颗粒间,赋予样品较好的抗折强度。热震试验30次后,可在样品中观察到更加致密的结构,碳化硅晶粒被树枝状微晶紧密联接,改善了样品的抗热震性。莫来石--碳化硅复相陶瓷可作为塔式太阳能热发电吸热器的潜在应用材料。     

蓄热技术在油田余热利用中的应用分析

针对油田应用广泛的低温余热资源和峰谷电价政策,建立了基于逐时负荷分析和内部收益率法的蓄热优化算法模型和自编程序求解。以实际项目为例,实现最佳蓄热规模求解,经济界限分析,并输出蓄热系统运行策略。     

太阳能热发电用氧化铝-碳化硅-氧化锆储热陶瓷的制备及表征

以α-Al2O3、部分稳定氧化锆(5.2%Y2O3,质量分数)和碳化硅为原料,采用无压烧成技术制备了太阳能热发电用 Al2O3–SiC–ZrO2(ASZ)储热陶瓷,研究了碳化硅和氧化锆添加量对 ASZ 储热陶瓷样品结构与性能的影响。结果表明：随着碳化硅添加量的增加,样品的力学性能、抗热震性和热物理性能均有提高;添加氧化锆可提高样品的力学性能和抗热震性能;经1280℃烧成的碳化硅添加量为50%、部分稳定氧化锆添加量为5%的样品的显气孔率、吸水率、体积密度和抗折强度分别为24.88%、10.44%、2.38 g/cm3和66.20 MPa;样品的比热容、导热系数和储热密度(600℃时)分别为1.05 kJ/(kg·K),2.26 W/(m·K)和916.91 kJ/kg。热震试验30次(室温～800℃)样品无裂纹,强度增长率为27.89%。     

Effect of β-to-α Phase Transformation on the Microstructural Development and Mechanical Properties of Fine-Grained Silicon Carbide Ceramics

Ultrafine β-SiC powders mixed with 7 wt% Al₂O_3, 2 wt% Y₂O₃, and 1.785 wt% CaCO₃ were hot-pressed and subsequently annealed in either the absence or the presence of applied pressure. Because the β-SiC to α-SiC phase transformation is dependent on annealing conditions, the novel processing technique of annealing under pressure can control this phase transformation, and, hence, the microstructures and mechanical properties of fine-grained liquid-phase-sintered SiC ceramics. In comparison to annealing without pressure, the application of pressure during annealing greatly suppressed the phase transformation from β-SiC to α-SiC. Materials annealed with pressure exhibited a fine microstructure with equiaxed grains when the phase transformation from β-SiC to α-SiC was <30 vol%, whereas materials annealed without pressure developed microstructures with elongated grains when phase transformation was >30 vol%. These results suggested that the precise control of phase transformation in SiC ceramics and their mechanical properties could be achieved through annealing with or without pressure.     

Electrochemical Techniques for Corrosion Rate Determination in Ceramics

Standard electrochemical test procedures have been successfully applied to determine the corrosion rates of SiC-based ceramics in aqueous reagents. Direct-current polarization measurements in HCI solutions indicate that the corrosion rate of α-SiC is 0.0050 ± 0.0002 mil/yr and is fairly independent of HCI concentration. The corrosion rates of α-SiC are significantly lower than those for reaction-sintered SiC in all of the electrolytes used including HCI, HNO₃, H₃, H₃PO₄, and aqua regia. It is believed that the free Si contained in the reaction-sintered SiC is responsible for the higher corrosion rates. It has been shown that electrochemical techniques are reproducible and eminently suitable for determining very low corrosion rates encountered in ceramics.     

换热设备在干燥行业尾气余热回收中应用的趋势

换热设备在大量使用热风的干燥行业尾气余热回收中具有重要的作用,本文介绍了双波全焊接板式换热器,相变能换热器等新型高效换热设备,这些对提高干燥行业尾气余热利用,提高能量利用率提供了新的选择。     

复合蓄热材料的研制与应用

以KAl(SO4)2·12H2O为相变材料,以多孔陶瓷为基体,采用熔融浸渍法制备了复合相变蓄热材料。此复合相变材料结合了潜热蓄热材料与显热蓄热材料的优点,并克服了无机盐相变材料相变过程无定型的缺点及陶瓷蓄热显热小的缺点。将自制的复合蓄热材料实际应用于咖啡壶加热设备中,实验结果表明加入复合蓄热材料后的咖啡壶每小时节能率达38.8%。     

相变储能材料在温室大棚中应用研究进展

采用相变储热材料(PCMs)潜热储蓄技术是最有效热能贮存方式之一,将其应用于温室节能有重要意义.本文综述了低温相变储热材料在温室大棚中的应用条件及类型,国内外低温相变储热材料的研究现状.分析了温室储热材料的性能与存在问题,展望了低温相变储能材料的发展方向和应用前景.