用于衬底隔离的选择性氧化多孔硅厚膜的制备

对N+型硅衬底上用于衬底隔离的选择性氧化多孔硅厚膜的制备进行了研究.实验过程中通过控制阳极氧化反应中HF溶液的浓度、电流密度和反应时间形成了不同厚度和孔隙度的多孔硅厚膜,并采用两步氧化的方法得到氧化多孔硅厚膜.实验得到的平整的氧化多孔硅厚膜最大厚度为60μm.对氧化多孔硅作为衬底隔离材料应用于硅基射频集成电路进行了初步的探索.     

高阻硅衬底上多孔硅牺牲层工艺的研究

采用离子注入的方法在高电阻率的硅衬底上选择性地形成低阻区,制备了多孔硅牺牲层,研究用"先做微结构后形成多孔硅"的多孔硅牺牲层工艺制作微悬空结构.     

电化学方法制备Cu_2O微晶及其形貌控制

以简单的电化学方法在碱性NaCl溶液中以金属铜片为阳极,石墨片为阴极,Na_2Cr_2O_2为添加剂制备Cu_2O微晶,对制备的产品用X射线衍射(XRD)、扫描电子显微镜(FESEM)、透射电子显微镜(TEM)、选区电子衍射(SAED)和紫外吸收光谱(UV-vis)进行表征。结果表明除Cu_2O本身的属性以外,溶液的pH值对它的形貌也产生很大的影响,并讨论Cu_2O微晶的形成机理。     

电化学光整加工对表面微观几何形貌的影响

通过对电化学光整加工过程中所得到的工件阳极表面微观几何形貌变化的分析，指出电化学光整加工过程是表面微观几何形貌的“圆角化”过程；结合表面微观几何形貌电化学溶解过程所建立的数学模型，提出“尖峰”形表面微观几何形貌的存在有利于改善电化学光整加工质量的观点，并在此基础上借助强化机械作用的手段，实现了大型反应釜内表面的光整加工处理，其表面粗糙度R“值可在短时间内降至0．04μm以下。     

多孔硅微机械加工温敏传感器的研究

本文在对阳极氧化反应形成多孔硅及艰多孔硅选择性生长机理、刻蚀研究的基础上做出到衬底距离大于５０μｍ的微桥结构。然后在微桥上溅射－铬电阻薄膜,形成温敏传感器微结构,并对其温度电阻特性,热响应时间进行了测量。利用该本文还设计出一种新型的温敏、气敏多功能传感结构。     

电化学修形对齿轮表面微观几何形貌的影响

对电化学修形前后齿面微观不平度高度特征参数和形状特征参数进行了测量和统计计算,研究了电化学加工表面平滑化对齿面摩擦、齿面闪温及润滑状态的影响。     

电化学机械光整加工表面形貌研究

提出了用于圆柱表面精密光整的夹心式电化学机械加工装置核心部件设计方案,探讨了主要工艺参数对表面质量影响规律。对采用这种新型加工方法所产生表面的轮廓高度特性、间距特性、形状特性、轮廓峰分布及表面波纹度进行了试验研究,结果表明电化学机械光整表面轮廓以高频小振幅波度为主要成分。     

分散工艺对酸沥滤法制备高硅氧微纤维的影响

以无碱玻璃纤维为原料,采用酸沥滤工艺制备了高硅氧微纤维,研究了不同的搅拌形式和搅拌速度对纤维中SiO2含量和纤维宏观形貌的影响。结果表明:适当提高搅拌速度可以加速分散,但过高的搅拌速度不仅会造成SiO2含量的降低,而且会严重影响纤维的长度;采用双向搅拌,且搅拌转速在75r.min-1时,可以获得SiO2质量分数为97.38%的高硅氧微纤维,其比表面积为364.59m2.g-1,平均孔径为0.73nm。     

硅对锌铝合金凝固组织的影响

研究了硅对ＺＡ－２７、ＺＡ－４０、ＺＡ－６０及ＺＡ－８０等合金铸态凝固组织的影响规律及硅相形貌的变化。     

硅渣和玻璃粉直接烧结制备多孔材料的气孔结构与力学性能

以硅渣和玻璃粉为原料,采用粉体直接烧结法制备多孔材料,研究了烧结温度(700~900℃)、烧结时间(15~120min)和升温速率(10~100℃·min^-1)对多孔材料表观密度、气孔率、物相组成、抗压强度的影响。结果表明:气孔结构均匀性随烧结温度的升高而降低;表观密度随烧结温度的升高先减小后增大,随保温时间的延长而增大,随升温速率的增大而减小,气孔率的变化趋势与表观密度的相反;多孔材料的主要物相为玻璃相和硅、SiC、SiO2、Ca2Al2SiO7等结晶相,且结晶度随烧结温度的升高而降低;抗压强度随烧结温度的升高呈先增大后减小的趋势;当烧结温度为750℃,升温速率为30℃·min^-1,烧结时间为30 min时,多孔材料的主晶相为硅和Ca2Al2SiO7,抗压强度最大(1.60MPa),表观密度为0.43g·cm^-3,气孔率为80%。     

The effect of silicon content and morphology on the wear of aluminium-silicon alloys under dry and lubricated sliding conditions

Improvement in the efficiency of the internal combustion engine has resulted in the increased usage of aluminium alloys and, in particular, aluminium-silicon as a substitute for cast iron. Despite the wide use of such materials in tribological environments little knowledge is available on the wear resistance of aluminium-silicon alloys. This paper investigates the wear performance of a range of binary aluminium-silicon alloys produced by a novel melt-spray technique. In addition, samples of the 11wt% silicon alloy were produced by conventional casting methods to elucidate the influence of silicon morphology on wear resistance. Pin-on-ring wear tests were carried out under dry and boundary-lubricated conditions. Surface analysis showed a similar wear mechanism under both conditions, these being: (1) oxidative and (2) metallic wear. Under boundary-lubricated conditions the load at which the transition to metallic wear occurred was increased. Raising the silicon content of the alloy was reflected in an increase in both wear resistance and transition load. Under dry sliding conditions the wear rate of the 11wt% alloy increased with a reduction in the silicon particle size, whereas under boundary-lubricated conditions the reverse was observed and the sand-cast alloy exhibited superior performance.     

复合湿法腐蚀工艺制备硅基三维曲面

提出了将各向异性湿法腐蚀与各向同性湿法腐蚀相结合的复合工艺,通过控制刻蚀工艺参数进行体硅加工,成功刻蚀了硅基材料三维曲面回转体结构.在各向同性腐蚀过程中,由各向异性刻蚀得到的多面体结构的表面垂直腐蚀速率与刻蚀液浓度呈指数关系,而搅拌使得多面体结构表面峰值与谷底的刻蚀液存在流速差,基于此原理可得到光滑的三维曲面.刻蚀过程中,通过各向异性湿法腐蚀控制结构深度,通过各向同性湿法腐蚀"抛光"结构曲面.最后,采用实验优化湿法腐蚀过程的工艺参数,基于直径为600～1 000 μm的圆形掩模板,在硅材料表面制备得到了高度为100～200μm的三维曲面回转结构.提出的工艺简单、有效且便于操作,有望用于制作不同曲面形状的三维硅结构及聚合物光学器件模具.     

AZO薄膜理想表面形貌的制备与加工工艺优化

非晶硅薄膜太阳能电池主要采用掺氟氧化锡(FTO)导电玻璃作为基板,但FTO薄膜雾度较低、表面形貌无法优化,导致无法得到较优的陷光结构,从而限制了太阳能电池的转换效率。为了进一步提升太阳能电池的转换效率,探讨了替代型的掺铝氧化锌(AZO)薄膜,通过优化前段磁控溅射镀膜工艺和后段湿化学蚀刻工艺,用以平衡AZO薄膜的光电性能和雾度,从而获得具有理想表面形貌的AZO导电玻璃,使其成为理想的非晶硅薄膜太阳能电池的基板材料。实验表明,经工艺优化后制作的AZO导电玻璃可提升光电转换效率。     

单晶硅各向异性湿法刻蚀的形貌控制

针对摆式微加速度计的制作,对利用两种添加剂共同修饰的TMAH刻蚀液的单晶硅湿法刻蚀技术及其相关刻蚀特性进行了研究。分析了两种添加剂之间的作用机理及对单晶硅湿法刻蚀的影响,选择合适的添加剂刻蚀液配比,实现了稳定的刻蚀形貌控制。通过两种添加剂的共同作用,获得了具有光滑刻蚀表面(粗糙度约为1nm)和良好凸角保护(凸角侧蚀比率小于0.8)的刻蚀形貌。实验结果表明,在三重溶液(TMAH+Triton-X-100+IPA)下的刻蚀形貌具有明显优势。最后,基于添加剂对疏水性单晶硅材料的作用机理及表面张力调节,表面活性剂和酒精类添加剂之间的相互作用分析了刻蚀形貌发生变化的原因。以典型悬臂梁-质量块的制作为例,验证了采用该单晶硅刻蚀形貌控制方法可以获得微加速度计光滑的悬臂梁表面和无需凸角补偿的完整质量块。相比于其它制作工艺,该方法简单、易操作,有利于提高微机电器件的性能。     

Ultraprecision surface flattening of porous silicon by diamond turning

Porous silicon is receiving increasing interest from a wide range of scientific and technological fields due to its excellent material properties. In this study, we attempted ultraprecision surface flattening of porous silicon by diamond turning and investigated the fundamental material removal mechanism. Scanning electron microscopy and laser Raman spectroscopy of the machined surface showed that the mechanisms of material deformation and phase transformation around the pores were greatly different from those of bulk single-crystal silicon. The mechanism of cutting was strongly dependent on the direction of cutting with respect to pore edge orientation. Crack propagation was dominant near specific pore edges due to the release of hydrostatic pressure that was essential for ductile machining. Wax was used as an infiltrant to coat the workpiece before machining, and it was found that the wax not only prevented chips from entering the pores, but also contributed to suppress brittle fractures around the pores. The machined surface showed a nanometric surface flatness with open pores, demonstrating the possibility of fabricating high-precision porous silicon components by diamond turning.     

蒸发诱导自组装法制备多孔二氧化硅光学薄膜

报道采用溶胶—凝胶技术、蒸发诱导自组装法,通过酸/酸二步法控制实验条件,实验中采用表面活性剂十六烷基三甲基溴化氨(CTAB)为模板剂,正硅酸乙酯为硅源,以及二次去离子水,盐酸为催化剂等原料制备前驱体溶胶。加入不同量的1,3,5-三甲基苯(TMB)辅助剂来调整膜的孔径。简单提拉迅速蒸发溶剂制备多孔二氧化硅光学薄膜,利用红外光谱对样品进行结构分析,采用UV-VIS-NIR分光光度计测量了薄膜的透过光谱,原子力显微镜(AFM)观察发现多孔薄膜的表面形貌具有明显的多孔结构、表面光滑、均匀;结果表明所制备的薄膜有好的光学性能、机械性能。     

Fabrication of WC micro-shaft by using electrochemical etching

Tungsten carbide (WC) micro-shaft can be used as various micro-tools for MEMS because of its high rigidity and toughness. In this study, we performed fabrication experiments of the WC micro-shaft using electrochemical etching. H₂SO₄ solution was used as the electrolyte because it can dissolve tungsten and cobalt simultaneously. Optimal electrolyte concentration and applied voltage resulting in uniform shape, good surface quality, and high material removal rate (MRR) of a workpiece were experimentally selected. A straight micro-shaft with 5 μm diameter and 3 mm length was obtained by controlling the various machining parameters. Using the fabricated micro-shafts as tools, we machined a high quality micro-hole with 8 μm diameter and a micro-groove with 9 μm width in stainless steel 304 (304 SS).     

Effect of platinum on sintering morphology of porous YSZ ceramics

Platinum/yttria‐stabilized zirconia (Pt/YSZ) porous ceramics were prepared by sintering of the Pt/PMMA/YSZ stripe‐like membrane with a porogen of spherical polymethyl methacrylate (PMMA) and a precursor of platinum (Pt) of chloroplatinic acid. The microstructure of raw and processed material and Pt/ZrO₂ calcination process at different sintering temperatures were investigated. The results showed that the spherically porous structure of Pt/YSZ was observed at a sintering temperature below 400 °C due to the thermal decomposition of PMMA. However, the pores were shrunk about 35% in diameter when YSZ compacts were sintered at the temperature of 1,450 °C. In addition, the spherical pores can be retained in the compacts when the content of Pt <5% and then gradually merged into changing when the content of Pt increased to 50%. The relative density was increased from 42% to 90% and the open porosity was decreased from 60% to 10% when Pt was added with content from 5% to 80%. The change of microstructure for Pt/YSZ is due to the migration of Pt and YSZ in the composites. The preferential migration and coalescence proceeded for Pt in Pt/YSZ is about 500 °C and YSZ clusters can keep stable until up to 900 °C. However, the growth of YSZ particle in the sintering process was hindered by the scattering of Pt phase.