【作者】 徐瑜；

【导师】 吴建锋；

【作者基本信息】 武汉理工大学 ， 材料学， 2012， 硕士

【摘要】 能源的相对短缺、能源在开发与利用过程中的低效率及所造成的环境污染正成为我国经济与社会可持续发展的重要制约因素。目前就全国而言,急需发展低成本的、使用方便的可再生能源利用技术,以适应不同地区的需要。太阳能是一种取之不尽,用之不竭的新型可再生能源,而太阳能热发电是太阳能热利用的重要方向,也是最有可能引发能源革命的技术成果之一。目前,塔式太阳能热发电系统中热流的输送主要采用低合金耐热钢管,但合金材料在实际生产和应用过程中存在抗热冲击性差,使用寿命不长和制造成本偏高等一些问题,阻碍了太阳能热发电高效规模化发展。因此,研制一种耐高温的、抗热震性好的输热管道材料已成为重要的科学研究课题。本文针对这一课题,研制了红柱石基复相陶瓷输热管道材料及相应的连接剂。研究了不同的配方组成和烧结温度对红柱石基复相陶瓷材料的结构、性能的影响,探讨了提高红柱石陶瓷抗热震性,降低红柱石基陶瓷烧结温度和拓宽烧结范围的机理。结果表明,红柱石基复相陶瓷材料有望作为太阳能热发电用输热管道材料。以红柱石、微米级PSZ(5.2wt%Y203部分稳定的氧化锆)和苏州土为主要原料,采用烧结法制备了红柱石复相太阳能热发电陶瓷输热管。研究了配方组成和烧结温度对材料烧结性能和力学性能的影响。利用XRD、SEM以及万能试验机表征样品的物相组成、微观结构和力学性能。结果表明：经1490℃烧结A4(红柱石50wt%、微米级PSZ10wt%、苏州土25wt%、山铝钾长石10wt%、林州钠长石5wt%)样品性能优良,样品吸水率为0.41%,气孔率为1.10%,体积密度为2.69g/cm3,抗折强度达128.78MPa；经30次抗热震(在空气中气冷,室温-1100℃)测试后,样品无裂纹、不开裂,样品的抗折强度为142.55MPa,强度不仅没有损失,反而增加了。相组成分析表明,A4配方样品的晶相为莫来石、硅酸锆、单斜氧化锆和α-方石英。SEM研究结果表明,A4配方样品结构较致密,存在少量气孔,柱状莫来石晶体纵横交错排列,成柱状“互锁”,颗粒状的硅酸锆和氧化锆填充在柱状莫来石的晶粒间,阻止了微裂纹的扩展,提高了材料的强度。为了降低红柱石陶瓷的烧结温度,实验以红柱石、微米级PSZ、苏州土、滑石为主要原料,并添加白云石和锂辉石,制备了红柱石基复相陶瓷。研究了白云石和锂辉石的添加量对红柱石基复相陶瓷烧结性能和力学性能的影响。利用XRD、SEM以及万能试验机表征样品的物相组成、微观结构和力学性能。结果表明：经1400℃烧结的B5(红柱石50wt%、微米级PSZ10wt%、苏州土23wt%、滑石10wt%、锂辉石7wt%)样品性能优良,与A系列相比降低烧结温度90℃,样品吸水率为0.28%,气孔率为0.74%,体积密度为2.61g/cm3,抗折强度达96.08MPa,热震(室温-1100℃,气冷)30次无裂纹、不开裂,热震后抗折强度为117.61MPa,强度不仅没有损失,反而增加了。随着锂辉石添加量的增大,样品的体积密度增大。相组成分析表明,B5配方样品的主晶相为莫来石、硅酸锆和单斜氧化锆。显微结构研究结果表明,B5配方样品结构较致密,存在少量的气孔,其中以闭气孔居多。在高倍数图片中可观察到柱状的莫来石晶体相互交织在一起形成骨架,氧化锆以晶内型和晶间型均布在莫来石的基质中,提高了样品强度和韧性。降低烧结温度的机理是添加锂辉石使系统生成低熔点液相,在烧结前期产生液相,对粉料起到润湿、溶解作用,使晶粒表面得到活化,自由能升高,烧结机理从固相烧结变为液相烧结,增强了表面扩散,加速了晶粒生长过程,使材料烧结温度降低。同时,玻璃软化产生的表面张力使晶粒更加靠拢,促进红柱石基陶瓷可以在较低的温度下实现烧结。为了拓宽红柱石陶瓷的烧结温度范围,实验以红柱石、微米级PSZ、苏州土、滑石和锂辉石为主要原料,外加硼酸,制备了红柱石基复相陶瓷。研究了硼酸的添加量对红柱石基复相陶瓷烧结性能和力学性能的影响。利用XRD、SEM以及万能试验机表征样品的物相组成、微观结构和力学性能。结果表明：经1420℃烧结的C1(红柱石50wt%、微米级PSZ10wt%、苏州土23wt%、滑石10wt%、锂辉石7wt%、外加硼酸1wt%)样品性能最佳,与A系列相比拓宽烧结温度范围40℃,样品的吸水率、气孔率和体积密度分别为0.30%、0.71%和2.40g/cm3,抗折强度为85.73MPa,热震(室温-1100℃,气冷)30次无裂纹、不开裂,热震后抗折强度为73.08MPa,强度损失率为14.76%。相组成分析表明,Cl配方样品的主晶相为莫来石、硅酸锆、立方氧化锆和α-方石英。显微结构研究结果表明,C1配方样品样品中分布了较多气孔,其中以闭气孔居多。在放大10000倍图片中可看出,在材料内部有许多长柱状莫来石晶体,这些长柱状晶体纵横交错,无序排布在材料的内部,任意一个长柱状晶体都与周围长柱状晶体相连结,彼此相互制约和增强。在材料内部还可以看到存在大量氧化锆颗粒,它们钉扎裂纹,阻止裂纹的扩展,起到了缓冲热应力的作用。拓宽烧结温度范围的机理是添加的B203在熔体中可以形成具有三维空间连接作用的硼氧四面体[B04],减少熔体中非桥氧离子的数目,起着“补网”作用。硼的加入使熔体的网络结构紧密聚集,粘度提高,这时的熔体结构中除了原有的硅氧四面体网络和铝氧四面体网络外,还形成了硼氧四面体网络,硼硅氧四面体网络、硼铝氧四面体网络及其它的含硼四面体网络结构。B203的加入使熔体有较高的高温粘度,改善了瓷坯的抵抗高温变形的能力,而且当温高上升时,粘度的降低也是较为平缓的。因此,红柱石基陶瓷烧结温度范围得以拓宽。以管道坯粉最优配方C1为基础点,加入低温熔剂A制备了红柱石基陶瓷管道间连接用的连接剂,重点探讨了低温熔剂A的添加量、相组成和微观结构对连接剂性能的影响,利用XRD、SEM以及万能试验机表征连接剂的物相组成、微观结构和连接强度,并讨论了连接机理。结果表明：经1100℃烧成的E2配方连接剂(管道坯粉80wt%,低温熔剂A20wt%)的性能最佳,连接件的连接强度最大,为20.08MPa。热震(室温-1100℃,气冷)14次无裂纹,不开裂。相组成分析表明,E2配方连接剂的晶相为硅酸锆、硼酸铝、红柱石、单斜氧化锆。连接剂中的红柱石未发生莫来石化,硼酸脱水产生的B203与A1203发生反应,生成硼酸铝。SEM研究结果表明,从低倍数图片可以看出,连接剂较为密实,存在气孔,连接剂层存在微裂纹,连接剂/母材界面也存在较多缝隙。从高倍数图片可以看出,连接剂/母材基质的界面处存在大量液相,液相在毛细作用下,很容易的扩散到母材基体内部,并与母材基质粘合紧密。连接剂/母材界面粘合处的液相中,存在一些微裂纹。这是因为液相在冷却过程中产生收缩,液相与连接剂和母材的热膨胀系数不匹配,从而产生界面应力。当液相冷却为玻璃相时,界面应力导致微裂纹的产生。连接机理是低温熔剂A形成液相,润湿母材表面,并扩散入母材内部。连接件冷却后,液相形成玻璃相,与母材产生界面结合,形成液相扩散连接。抗热震机理研究表明：红柱石复相陶瓷材料固有强度较高,产生热震断裂所需热应力也较大,抗热震性好；通过引入微米级PSZ,利用颗粒钉扎裂纹,氧化锆相变增韧材料,从而提高材料的抗热震性。在材料内部有许多长柱状莫来石晶体,这些莫来石晶体纵横交错,无序排布在材料的内部,任意一个长柱状晶体都与周围长柱状晶体相连结,彼此相互制约和增强,改善了材料的抗热震损伤性能。另外,通过引入锂辉石降低材料的热膨胀系数,也大大改善了材料的抗热震性。更多还原

【Abstract】 Energy shortage, low efficiency of the development, and environment pollution caused by the development and the use of energy are becoming main factors which limit the persistent development of the economy and the society of our country. Currently as far as our whole country is concerned, the low-cost convenient renewable energy technology is needed urgently to meet the demands of different areas. Solar energy is an inexhaustible and environmentally—friendly renewable energy source. Solar thermal power generation is an important direction of solar thermal utilization, and it is most likely to lead to a revolution in energy technology. At present, alloy steel pipe is used to transport the heat flow in the tower solar thermal power generation system. However, the alloy steel pipe existed some shortage, such as poor thermal shock resistance, short service life and high manufacturing cost, hindering the development of the solar thermal power generation. Therefore, the development of a high temperature heat pipe material with good thermal shock resistance has become an important research topic. Andalutsite-matrix composite ceramic heat pipe materials were prepared in response to this topic, the effects of different formulations and sintering temperature on microstructure and properties of the andalusite-matrix composition were investigated, the key physical properties were analyzed, relevant mechanism of thermal shock resistance was discussed, The methods of reducing sintering temperature and broadening the sintering temperature range of andalusite-matrix composition were investigated. The results indicated that the andalusite-matrix composition could be used as high temperature heat pipe material in solar power generation.The andalusite composite ceramic was fabricated from andalusite, PSZ(partially stabilized zirconia) and Su Zhou clay as raw materials. The effects of composition of raw materials and the sintering temperature on the sintering character and mechanical properties of the samples were also analyzed. Moreover, the composition, microstructure and mechanical properties of the samples were characterized by SEM, XRD and universal testing machine, respectively. The results show that the water absorption is0.41%, porosity is1.10%, bulk density is2.69g/cm3, bending strength is128.78MPa, when the samples were sintered at1490℃for2h. After30times thermal shock cycles from1100℃to room temperature in air, the bending strength increased from128.78to142.55MPa. X-ray diffraction peaks suggested fully developed mullite, zircon phases by reaction sintering of andalusite and PSZ. Microstructure consisting in mullite as a continuous predominant phase in which zircon grain was homogeneously distributed improved almost all the mechanical and fracture properties.In order to reduce the sintering temperature of andalusite-matrix ceramics, composite materials have been fabricated by using starting materials such as andalusite, PSZ, Su Zhou clay, and talc with addition of dolomite and spodumene. The effect of dolomite and spodumene content on the microstructure and mechanical properties of the andalusite-matrix composition was also analyzed. Moreover, the composition, microstructure and mechanical properties of the samples were characterized by SEM, XRD and universal testing machine, respectively. The results show that the water absorption is0.28%, porosity is0.74%, bulk density is2.61g/cm3, bending strength is96.08MPa, when the samples were sintered at1400℃for2h, After30times thermal shock cycles from1100℃to room temperature in air, the bending strength increased from96.08to117.61MPa. The densification of sample was improved with the increase of spodumene content. XRD analysis showed that the main phase of B5were mullite, Zircon and m-ZrO2. SEM results showed that the structure of B5sample is very compact, there is a small amount of pores in the sample, which is mostly closed pores. The columnar mullite crystals are intertwined together to form the skeleton, PSZ occupies both an intergranular and intragranular position in the mullite matrix, which improved the strength and toughness of sample. Relevant mechanism of reducing sintering temperature was discussed. The system generates low-melting point liquid with addition of spodumene, it can wet and dissolve the powder, sintering mechanism changed from solid phase sintering to liquid phase sintering. The sintering temperature is reduced. At the same time, the surface tension of glass softening makes the grain move closer, andalusite-matrix ceramics become desity at a lower temperature.In order to broaden the sintering temperature range of andalusite-matrix ceramics, composite materials have been fabricated by using starting materials such as andalusite, PSZ, Su Zhou clay, talc and spodumene with addition of boric acid. The effect of boric acid content on the microstructure and mechanical properties of the andalusite-matrix composition was also analyzed. Moreover, the composition, microstructure and mechanical properties of the samples were characterized by SEM, XRD and universal testing machine, respectively. The results show that the water absorption is0.30%, porosity is0.71%, bulk density is2.40g/cm3, bending strength is85.73MPa, when the samples were sintered at1420℃for2h. After30times thermal shock cycles from1100℃to room temperature in air, the bending strength reduced from85.73to73.08MPa. XRD analysis showed that the main phase of C1were mullite, Zircon, c-ZrO2and a-cristobalite. SEM results showed that the structure of Cl sample is very compact, there is a small amount of pores in the sample, which is mostly closed pores. The columnar mullite crystals are intertwined together to form the skeleton, PSZ grain was homogeneously distributed in the mullite matrix, which prevented crack propagation. Relevant mechanism of broadening the sintering temperature range was discussed. Adding B2O3is to let the melt have high temperature viscosity and improve the ability of deformation resistance at high temperature for porcelain body, as well as the viscosity reduced relatively gently with the temperature increasing.The optimal adhesive was prepared by using starting materials such as andalusite, PSZ, Su Zhou clay, talc, spodumene and low temperature flux A. The effects of low temperature flux content, phase composition and the micro structure on the properties of adhesive were also analyzed. Moreover, the composition, microstructure and mechanical properties of adhesive were characterized by XRD, SEM and universal testing machine, respectively. The results show that the bending strength is20.08MPa, when the adhesive was fired at1100℃for1h. After14times thermal shock cycles from1100℃to room temperature in air, the sample without crack. XRD analysis showed that the main phase of E2were Zircon, aluminium borate, andalusite and m-ZrO2. SEM results showed that the structure of E2is compact, there is a small amount of pores in the interface. There are a lot of liquid at the interface of adhesive/parent material. Liquid phase under capillary action, it is easy to diffuse to the parent material, and adhesion closely with matrix. The research of Joining mechanism showed that the liquid produces by low temperature flux could wet and diffuse into the parent material to form interface bond and intergrate them.The research of thermal shock resistance mechanism showed that andalusite composite ceramic material has good thermal shock resistance for its high inherent bending strength. The thermal shock resistance of the sample was significantly improved by the addition of ZrO2. The columnar mullite crystals improve the performance of thermal shock resistance of material. In addition, with the introduction of spodumene reduce the thermal expansion coefficient of the material, also greatly improved the thermal shock resistance of the material.更多还原