高强气体放电灯管封接用功能梯度材料的设计与制备
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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／SiO_2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／SiO_2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／SiO_2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。d_(50)=5μm的Mo的颗粒，其临界含量为35wt％～40wt％，d_(50)=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-SiO_2／SiO_2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-SiO_2／SiO_2梯度材料。
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/SiO_2FGM 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/SiO_2 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 d_(50)=5μm and d_(50)=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-SiO_2/SiO_2 is four. With the design and optimization, the50%Mo-SiO_2/SiO_2 FGM (six layers) was fabricated with the powder stacking-method bySPS.
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／SiO_2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／SiO_2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。d_(50)=5μm的Mo的颗粒，其临界含量为35wt％～40wt％，d_(50)=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-SiO_2／SiO_2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-SiO_2／SiO_2梯度材料。
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/SiO_2FGM 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/SiO_2 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 d_(50)=5μm and d_(50)=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-SiO_2/SiO_2 is four. With the design and optimization, the50%Mo-SiO_2/SiO_2 FGM (six layers) was fabricated with the powder stacking-method bySPS.
引文
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[3] 朱绍龙．高强度气体放电灯的钼片—石英玻璃封接．灯与照明，第26卷第6期。
[4] G.Leichtfried, G.Thumer, R.weiraher Molybdenum alloys for glass-to-metal seals International Journal of Refractory Metals & hard materials 16 (1998) 13-22
[5] 马英仁．封接玻璃(十)—与金属封接的微晶玻璃．玻璃与搪瓷，第22卷2期。
[6] 邵力为．耐超高气压钨杆与石英的封接技术．中国照明电器，1997年第5期。
[7] 新野正之，斜机能材料．粉体粉末冶金．1990，37(2)：61～642
[8] 吴人洁 复合材料天津：天津大学出版社，2000
[9] 朱景川，来忠红，尹钟大，李明伟．ZrO_2-Ni功能梯度材料的热冲击与热疲劳行为．材料科学与工艺，第9卷第4期。
[10] Kenta Takagi et al. Fabrication and evaluation of PZT/Pt piezoelectric composites and functionally graded actuators. J. Euro. Ceram. Soc, Volume 23, Issue 10, September 2003, Pages 1577-1583
[11] 夏军．梯度功能材料的制备技术与应用前景．化工新型材料，29卷6期。
[12] 沈强，王文涛，张联盟．Ni／Ni3Al-TiC系梯度功能材料的热应力缓和特性设计，硅酸盐通报，1997，[2]：34-36．
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[14] S.Seifried. Nanoscaled gradient materials by chemical vapor synthesis. Functionally Graded Materials; 1998,277.
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[17] Khor, K.A.Gu,Y.W. Effects of residual stress on the performance of plasma sprayed functionally graded ZrO_2/NiCoCrAlY coating. Materials Science and Engineering A: Structure Materials: properties, microstructure and processing,2000,277:64.
[18] M.Izaki. Preparation of functionally graded ZnO film by electrochemical reaction from an aqueous solution. Functionally Graded Materials 1998,290-294
[19] Teng L.D., Wang F.M., Li W.C., et al. Preparation and microstructure of Ti-ZrO_2 gradient materials. Journal of the Chinese Ceramic Society,2000.28(5):422
[20] Maarten Biesheuvel, EVerweij,Henk. Calculation of the composition profile of a functionally graded material produced by centrifugal casting. Joumal of the American Ceramic Society, 2000,83:743.
[21] L.M.Zhang,C.B.Wang,Q.Shen,J.G.Li. Generating quasi-isentropic compression waves via layered flier-plate materials. Ceramic Transactions,2001,114:667.
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[23] 李玉书 熔融石英的石英陶瓷研究 中国陶瓷 1994年1期
[24] 陈肇友 耐火材料 1993(3)：1～5
[25] 郑士远 罗永明 李荣缇 氮化硅对石英陶瓷性能的影响．佛山陶瓷，总39期 9～10
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[29] 罗锡裕．放电等离子烧结材料的最新进展．粉末冶金工业，第11卷，第6期，2001年12月。
[30] 彭金辉，张利波，张世敏．等离子体活化烧结技术新进展．第9卷第3期2000年6月。
[31] 冯海波，周玉，贾德昌．放电等离子烧结技术的原理及应用．第11卷，第3期，2003年9月
[32] 张久兴，刘科高，周美玲．放电等离子烧结技术的发展和应用．粉末冶金技术，第20卷第3期，2002年6月。
[33] 张东明，傅正义．放电等离子加压烧结(SPS)技术特点及应用．武汉工业大学学报，第21卷，第6期，1999年12月。
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[2] 严增濯 石英玻璃与金属的封接技术进展 光源与照明 2005年第4期
[3] 朱绍龙．高强度气体放电灯的钼片—石英玻璃封接．灯与照明，第26卷第6期。
[4] G.Leichtfried, G.Thumer, R.weiraher Molybdenum alloys for glass-to-metal seals International Journal of Refractory Metals & hard materials 16 (1998) 13-22
[5] 马英仁．封接玻璃(十)—与金属封接的微晶玻璃．玻璃与搪瓷，第22卷2期。
[6] 邵力为．耐超高气压钨杆与石英的封接技术．中国照明电器，1997年第5期。
[7] 新野正之，斜机能材料．粉体粉末冶金．1990，37(2)：61～642
[8] 吴人洁 复合材料天津：天津大学出版社，2000
[9] 朱景川，来忠红，尹钟大，李明伟．ZrO_2-Ni功能梯度材料的热冲击与热疲劳行为．材料科学与工艺，第9卷第4期。
[10] Kenta Takagi et al. Fabrication and evaluation of PZT/Pt piezoelectric composites and functionally graded actuators. J. Euro. Ceram. Soc, Volume 23, Issue 10, September 2003, Pages 1577-1583
[11] 夏军．梯度功能材料的制备技术与应用前景．化工新型材料，29卷6期。
[12] 沈强，王文涛，张联盟．Ni／Ni3Al-TiC系梯度功能材料的热应力缓和特性设计，硅酸盐通报，1997，[2]：34-36．
[13] 许杨健，赵志岗，涂代惠．梯度功能材料热弹性应力的研究进展材料导报，1998年2月12卷第1期：10-12
[14] S.Seifried. Nanoscaled gradient materials by chemical vapor synthesis. Functionally Graded Materials; 1998,277.
[15] Y.Miyamoto. Functionally graded materials:design, processing and Application: 199
[16] Khor, K.A.Dong,Z.L.Gu, et al. Influence of oxide mixtures on mechanical properties of plasma sprayed functionally graded coating. Thin Solid Films,2000,386:86
[17] Khor, K.A.Gu,Y.W. Effects of residual stress on the performance of plasma sprayed functionally graded ZrO_2/NiCoCrAlY coating. Materials Science and Engineering A: Structure Materials: properties, microstructure and processing,2000,277:64.
[18] M.Izaki. Preparation of functionally graded ZnO film by electrochemical reaction from an aqueous solution. Functionally Graded Materials 1998,290-294
[19] Teng L.D., Wang F.M., Li W.C., et al. Preparation and microstructure of Ti-ZrO_2 gradient materials. Journal of the Chinese Ceramic Society,2000.28(5):422
[20] Maarten Biesheuvel, EVerweij,Henk. Calculation of the composition profile of a functionally graded material produced by centrifugal casting. Joumal of the American Ceramic Society, 2000,83:743.
[21] L.M.Zhang,C.B.Wang,Q.Shen,J.G.Li. Generating quasi-isentropic compression waves via layered flier-plate materials. Ceramic Transactions,2001,114:667.
[22] H.ISHIBASHI, H.TOBIMATSU et al, Characterization of Mo-SiO2 Functionally Graded Materials. Metallurgical and Materials; Jan 2000;31A, 1.
[23] 李玉书 熔融石英的石英陶瓷研究 中国陶瓷 1994年1期
[24] 陈肇友 耐火材料 1993(3)：1～5
[25] 郑士远 罗永明 李荣缇 氮化硅对石英陶瓷性能的影响．佛山陶瓷，总39期 9～10
[26] 杨德安 沈继耀 朱海强 加入物对石英陶瓷烧结和析晶的影响 耐火材料 1994年第28卷第4期
[27] 李友胜 韩志强 李楠 外加剂对熔融石英陶瓷烧结性能的影响 耐火材料 2004，38(5)334～335，346
[28] 高濂，宫本大树．放电等离子烧结技术．无机材料学报，第12卷第2期，1997年4月。
[29] 罗锡裕．放电等离子烧结材料的最新进展．粉末冶金工业，第11卷，第6期，2001年12月。
[30] 彭金辉，张利波，张世敏．等离子体活化烧结技术新进展．第9卷第3期2000年6月。
[31] 冯海波，周玉，贾德昌．放电等离子烧结技术的原理及应用．第11卷，第3期，2003年9月
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