稀土硅酸盐热防护连接件材料的制备与表征(硕士)

稀土硅酸盐热防护连接件材料的制备与表征(硕士)(论文40000字)
摘要
传统的热防护系统连接件多为金属材质，因金属材料存在热导率过高和与热防护系统材料热膨胀系数不匹配等缺点，容易出现热短路和损伤热防护系统等问题。因而，对于综合性能优良的热防护连接件材料的需求日益突出。为了开发新型热防护连接件材料，本文选择热导率较低和高温性能较稳定的Y2SiO5作为基础材料，通过添加增强相和对材料本身的结构设计，制备出了高强度、低热导热防护连接件材料。
本文研究的主要内容为以粉末固相反应法制备出的较高纯度的Y2SiO5粉体为原料，根据第二相增强的原理，选择ZrO2纤维和Ni作为增强相，采用干压结合冷等静压的生坯成型方法，结合无压烧结技术，成功制备出ZrO2纤维增强Y2SiO5陶瓷基复合材料和Ni增强Y2SiO5陶瓷基复合材料，并研究了增强相含量和烧结温度对材料性能的影响。结果显示，1450℃制备出的20vt%ZrO2(f)/Y2SiO5复合材料和1400℃制备出的Ni/Y2SiO5复合材料有最佳的力学性能，两种材料的弯曲强度分别为124.71MPa和78.00MPa，较Y2SiO5陶瓷性能提升了29.41%和47.09%；剪切强度分别为86.10MPa和76.51MPa，较Y2SiO5陶瓷性能提升了65.20%和69.65%；拉伸强度分别为53.52MPa和47.67MPa，较Y2SiO5陶瓷性能提升了57.27%和64.38%。同时兼具较好的优良热学性能，热导率分别为0.542W/(m•K)和0.456W/(m•K)。
以之前的研究成果为基础，通过选择不同增强相含量的ZrO2(f)/Y2SiO5物料和Ni/Y2SiO5物料，调整梯度层间配料的体积之间合理的搭配，设计并制备出多层梯度ZrO2(f)/Y2SiO5和Ni/Y2SiO5复合材料，研究了多层梯度复合材料的同步烧结问题和相邻层梯度差变化对材料弯曲、剪切和拉伸性能的影响。结果显示，所构建的多层梯度结构材料中层间物料种类和体积的选择搭配在合理范围内，没有出现分层开裂现象，实现了各梯度层的同步烧结。且通过对非梯度试样与相对应的梯度多层梯度试样径向收缩率比较后得出，多层梯度这种特殊的结构形式，对于多层梯度ZrO2(f)/Y2SiO5复合材料，有利于促进复合材料端部的致密化，同时可以提高材料中部的气孔率；对于多层梯度Ni/Y2SiO5复合材料，则有利于促进材料整体的致密化。多层梯度ZrO2(f)/Y2SiO5系列复合材料的力学性能，较Y2SiO5陶瓷出现了不同程度的下降，弯曲强度下降幅度最大为74.63%；剪切强度下降幅度最大为39.75%；拉伸强度下降幅度最大为59.51%。多层梯度Ni/Y2SiO5系列复合材料的弯曲强度，较Y2SiO5陶瓷出现了不同程度的上升，上升幅度最大为46.73%；剪切和拉伸强度则均出现了不同程度的下降，剪切强度下降幅度最大为28.29%；拉伸强度下降幅度最大为36.48%。
以制备出的热力学性能较为优异的单相20vt%ZrO2(f)/Y2SiO5复合材料和单相20vt%Ni/Y2SiO5复合材料外加做参照的Y2SiO5陶瓷为原料，使用金刚石刀具对其进行机械加工，制备出了三种不同材质的螺栓连接件，并研究了增强相对复合材料可加工性能和螺栓的拉伸性能的影响。结果表明，ZrO2纤维的加入降低Y2SiO5陶瓷的可加工性，Ni的加入提高了Y2SiO5陶瓷的可加工性。机械加工对材料的力学性能有损伤，加工出的Y2SiO5陶瓷螺栓和20vt%Ni/Y2SiO5复合材料螺栓的拉伸强度较原材料的拉伸强度分别下降了67.21%和72.73%。另外还研究了多层梯度ZrO2(f)/Y2SiO5复合材料和多层梯度Ni/Y2SiO5复合材料制备出的螺栓连接件的根部剪切强度的变化情况。多层梯度ZrO2(f)/Y2SiO5复合材料螺栓的最大根部剪切强度为36.53MPa，多层梯度Ni/Y2SiO5复合材料螺栓的最大根部剪切强度为16.35MPa。
关键词：Y2SiO5；ZrO2纤维；Ni；干压；冷等静压；热导率；微观结构；弯曲强度；剪切强度；拉伸强度；
 
ABSTRACT
Traditional connectors of thermal protection system are mostly made of metal materials. Due to the higher thermal conductivity of metal materials and thermal expansion coefficient mismatch between thermal protection system materials and connectors, it’s easy to generate thermal short circuit and damage to thermal protection systems.Therefore, there is an increasing demand for the comprehensive performance of the thermal protection connector material. In order to developing a new thermal protection connector material to match with the requirement, we choice Y2SiO5 ceramicswhich has low thermal conductivity and high temperature performance as the basic material.By adding reinforcing phase and designing structure of the material itself, the connector material with high strength and low thermal conductivity succeed to be prepared.
In this paper, the highly pure Y2SiO5 powder,as raw material, was obtained by the powder solid reaction. According to the principle of the second phase enhancement, ZrO2 fiber and Ni are selected as reinforced phase in this study. Dry-pressure and cold isostatic pressing technologies are used in the preparation of green body, combining with pressureless sintering process, and we successfully prepared ZrO2 fiber reinforced Y2SiO5 ceramic matrix composites and Ni enhanced Y2SiO5 ceramic matrix composites. The influence of the enhanced phase content and the sintering temperature on the properties of the composites is also studied. Results showed that 20vt%ZrO2(f)/Y2SiO5 composites sintering at 1450℃ and 20vt%Ni/ Y2SiO5 composites at 1400℃have the best mechanical properties, the flexural strength of the two kinds of composites are 124.71MPa and 78.00MPa respectively, improved 29.41% and 47.09% than that of Y2SiO5 ceramic;the shearing strength is 86.10MPa and 76.51MPa respectively, to enhance the 65.20% and 69.65% compared with the properties of Y2SiO5 ceramics; the tensile strength is 53.52MPa and 47.67MPa respectively, increased by 57.27% and 64.38% compared with the properties of Y2SiO5 ceramics. At the same time, those have good thermal properties, and the thermal conductivity are 0.542W/(m•K) and 0.456W/(m•K) respectively.
Based on the previous research results, by adjusting the mix of composition and volume between layers, the gradient ZrO2(f)/Y2SiO5 and Ni/Y2SiO5 composites were successfully prepared. In the study for gradient composites, we researched what happened of gradient compositesduring thesintering process, and how the change of the gap between layers’ enhanced phase contenteffected the bending strength, shearing strength and tensile strength of gradient composites. The results show that there are nodemixing and craze in the gradient compositesprepared. So the choice of material type and volume for layers is reasonable. After comparing the radial shrinkage ratio between non-gradient and gradient composites, we can find that this special structure of compositescan be conducive to the densification of the end of the ZrO2(f)/Y2SiO5 composites and meanwhile increase the porosity of the middle part of the composites. For the gradient Ni/Y2SiO5 composites, it is beneficial to promote the densification of the whole composites. Compared with Y2SiO5 ceramic, the mechanical properties of gradient ZrO2(f)/ Y2SiO5 series composites appeared different degrees of decline, the bending strength loses 74.63%, the shearing strength loses 39.75%, the tensile strength loses 59.51%. The flexural strength of gradient Ni/Y2SiO5 series composites is higher than that of Y2SiO5 ceramic, with the maximum increase of 46.73%. The shearing and tensile strengths of the composites suffer different degrees of decline.The shearing strength loses 28.29%; the tensile strength loses 36.48%.
Three materials, the single 20vt%ZrO2(f)/Y2SiO5 composite, 20vt%Ni/Y2SiO5 composite with better thermal and mechanical properties compared with other composites and Y2SiO5 ceramic as reference, were machined with a diamond cutter to prepare three different types of bolts. What the enhanced phase influence the machinability of the composite and the tensile strength of the bolts were studied.The results show that the addition of ZrO2 fiber reduces the machinability of Y2SiO5 ceramics, and the addition of Ni improves the machinability of Y2SiO5 ceramics. Mechanical processing has damage to the mechanical properties of composites. The tensile strength of bolt made of Y2SiO5 ceramic and 20vt%Ni/Y2SiO5 composite is decreased by 67.21% and 72.73% compared with that of raw material respectively. In addition, the shearing strengths of the bolts’ roots, the bolts prepared by the two series of gradient composites, was also studied. The maximum root shearing strength of bolts made by gradient ZrO2(f)/Y2SiO5 composites is 36.53MPa, and the maximum root shearing strength of gradient Ni/Y2SiO5 composites bolts is 16.35MPa.
Key words: Y2SiO5; ZrO2 fiber; metal Ni; dry pressing; cold isostatic pressure; thermal conductivity; microstructure; bending strength; shear strength; tensile strength;

目录
摘要    ii
ABSTRACT    iv
1.绪论    1
1.1选题的背景与意义    1
1.2连接件体系研究现状    1
1.3多孔材料的制备方法    3
1.3.1添加造孔剂法    3
1.3.2发泡法    4
1.3.3溶胶-凝胶法    5
1.3.4冷冻干燥法    6
1.4 Y2SiO5陶瓷的性能介绍    7
1.4.1力学性能    7
1.4.2热学性能    8
1.5提高陶瓷材料力学性能的方法    8
1.5.1相变增韧    9
1.5.2原位增韧    9
1.5.3纤维增韧    10
1.5.4金属颗粒增韧    11
1.6本文的研究内容    11
2.制备工艺与表征方法    13
2.1实验原材料与试剂    13
2.2实验设备    13
2.3工艺过程    13
2.3.1引言    14
2.3.2 Y2SiO5粉体的制备    14
2.3.3 Y2SiO5基复合材料的制备    15
2.3.4性能表征试样的制备    16
2.4表征手段    17
2.4.1密度    17
2.4.2热导率    17
2.4.3力学性能    17
2.4.4微观结构    19
3.ZrO2(f)/Y2SiO5和Ni/Y2SiO5复合材料的性能研究    23
3.1引言    23
3.2 ZrO2(f)/Y2SiO5复合材料的性能研究    23
3.2.1ZrO2纤维含量对复合材料性能的影响    23
3.2.2 烧结温度对复合材料性能的影响    27
3.3 Ni/Y2SiO5复合材料的性能研究    29
3.3.1 Ni含量对复合材料性能的影响    29
3.3.2烧结温度对复合材料性能的影响    31
3.4不同增强相Y2SiO5基复合材料的性能对比    32
3.5本章小结    33
4.多层梯度ZrO2(f)/Y2SiO5和Ni/Y2SiO5复合材料的性能研究    39
4.1引言    39
4.2多层梯度复合材料的结构设计与实现    39
4.3多层梯度结构变化对复合材料烧结性能的影响    42
4.4多层梯度结构变化对复合材料力学性能的影响    45
4.5本章小结    47
5.ZrO2(f)/Y2SiO5和Ni/Y2SiO5复合材料螺栓连接件性能研究    49
5.1引言    49
5.2复合材料的加工性能比较    49
5.3性能测试及表征    51
5.3.1螺栓拉伸性能测试分析    51
5.3.2螺栓剪切性能测试分析    52
5.4本章小结    54
6.总结与展望    55
6.1总结    55
6.2展望    57
参考文献    59