【作者】 陈洪波；

【导师】 张联盟；

【作者基本信息】 武汉理工大学 ， 复合材料， 2007， 硕士

【摘要】 高强气体放电灯具有光效高、寿命长、光色好的优点，应用前景十分广阔。高强气体放电灯对封接的要求很高：耐高温、耐腐蚀、耐高压、高气密性。常用的封接为金属Mo与石英玻璃的直接封接。Mo和石英的热膨胀系数相差很大，导致过大的残余热应力。现有的技术尚难以对封接残余应力有效控制，从而影响高强气体放电灯的寿命。本工作提出用梯度材料来有效缓解热应力，制备出封接用的Mo／SiO₂系梯度材料。首先通过热力学计算并通过实验实测了其析晶温度，在短时间内其析晶温度在1150℃以上。为避免由熔融石英中析出晶体，研究了放电等离子（SPS）烧结熔融石英粉的烧结机理，实现了熔融石英粉的低温致密化。结果表明，SPS烧结熔融石英粉是一种表层熔融烧结机制，模具大小和压力对烧结致密化有很大影响。熔融石英粉适宜的烧结工艺参数为：1150℃～1200℃、20MPa、5min。样品的致密度为95.8％～99.7％（与模具大小有关）。研究了用SPS烧结时纯Mo的烧结行为和烧结助剂Ni、Cu对Mo致密化的影响。结果表明，纯Mo粉在1200℃SPS烧结时无法实现致密化，致密度仅为80.1％。添加Ni、Cu有助于Mo的致密化。在致密化过程中，Cu主要起溶解Ni的作用，Ni溶解Mo来实现致密化。Ni、Cu适宜的添加量分别为3％和2％，此时在1200℃烧结的Mo的致密度可达到99.1％。在1200℃-20MPa-5min的SPS烧结条件下，制备出了不同组分的Mo／SiO₂复合材料，测定了复合材料的致密度、电性能、力学性能、热性能和微观结构。Mo颗粒填充在熔融石英基体的孔隙，从而提高了复合材料的致密度。Mo在低含量时弥散分布在石英基体中，随着含量的增加，形成渗流结构，使Mo／SiO₂复合材料由绝缘体变成导体。其临界含量与Mo颗粒大小有关。d₅₀=5μm的Mo的颗粒，其临界含量为35wt％～40wt％，d₅₀=10μm的Mo的颗粒，其临界含量为40wt％～45wt％。利用有限元法对梯度材料的残余热应力缓和与结构设计，结果表明梯度复合材料可以有效地缓和梯度材料制备过程中产生的残余热应力。当50％Mo-SiO₂／SiO₂梯度材料层数为6层时，应力缓和效果达60％。采用SPS技术，通过粉末铺填成功制备出了层数为6层的50％Mo-SiO₂／SiO₂梯度材料。更多还原

【Abstract】 High-pressure gas discharge lamp （HGDL） has promising market due to highluminous efficiency, long life and good colorimetric characteristic. The part of sealing isimportant for HGDL and needs high temperature resistant, corrosion-resistant, highpressure-resistant and high airtight. The conventional sealing of HGDL is usually of thesandwich type between a thin Mo foil and a fused silica envelope. Due to the difference inthermal expansion between Mo and silica, high residual stress develops during sealingand operation, which often results in crack and delamination. In this study, the Mo/SiO₂FGM is fabricated to apply into sealing for relaxing residual stress.The dense samples were obtained by spark plasma sintering（SPS）. The mechanismof sintering fused quartz powder was studied. The result indicates that fused quartz issintered by exterior fused. The size of mould and pressure of sintering affect thesintering behavior. The appropriate sintering condition is as below:1150℃～1200℃、20MPa、5min. The relative density of the obtained fused quartz reaches 95.8%～99.7% （relates to the size of mould）.The sintering behavior of pure Mo and additive Ni, Cu in Mo alloy sintered bySPS was studied. The experimental results illustrate that the relative density of pureMo sintered at 1200℃is only 80.1%. The powders Ni and Cu can promote thedensity of sintered Mo. In the processing of sintering, Cu powder melts and Ni,dissolves in liquid Cu. The relative density of Mo alloy is 99.1% when the content ofadditive Ni is 3% and Cu is 2%.The Mo/SiO₂ composites with different Mo content were fabricated by SPS at thecondition of 1200℃-20MPa-5min. The relative density, electrical property,mechanical property and thermal property were measured and the microstructure wasobserved. The relative density is promoted because Mo particles fill into the holes offused quartz. With the increasing Mo content, the Mo powders disperse into the fusedquartz to form percolation structure, which leads to the conducting of the composite.The critical mass fraction for the Mo powder with a size of d₅₀=5μm and d₅₀=10μmis 35%～40% and 40%～45%, respectively.The finite element method is employed to calculate residual thermal stress and designthe structure. The result indicates that graded composites can effectively reduce theresidual thermal stress. The relaxation effect is up to 60% when the amount of layers between 50%Mo-SiO₂/SiO₂ is four. With the design and optimization, the50%Mo-SiO₂/SiO₂ FGM （six layers） was fabricated with the powder stacking-method bySPS.更多还原