压电陶瓷驱动球基微驱动器的动力学研究

研制出了尺寸为30 mm×30 mm×50 mm的压电陶瓷驱动的球基微驱动器样机,并对该微驱动器进行动力学分析以及微型轴孔装配的实验研究。建立了微驱动器金属球空间坐标关系,分析了球基微驱动器的动力学特征,并建立了其动力学模型。采用龙格-库塔法计算出了微驱动器的动力学参数,并利用MATLAB的SIMULINK模块搭建了微驱动器的仿真模型,并对其进行了动力学仿真分析。研制出了球基微驱动器样机,并在此基础上,集成微夹持器形成微操作器,对微驱动器性能进行了实验测试,并开展了Φ180 μm微型轴与Φ200 μm微型孔之间的精密微装配实验研究。最后,分析了微驱动器金属球质量、驱动信号频率、以及金属球与微驱动单元摩擦块接触表面摩擦系数对其性能的影响。实验结果表明:该球基微驱动器的转动分辨率为0.000 1°,转动定位精度为0.000 5°,微驱动器最大工作频率为1 200 Hz。实验结果验证了逆转振动模型的正确性,由该微驱动器所集成的微操作器,完全可以满足对微小元器件的微米级操作与装配等精密作业的要求。     

基于微型悬臂梁的发电机制探索

微机电系统(MEMS)微型化过程中,要求电源装置也必须向微型化发展.在现有微电源研究基础上,结合微型硅悬臂梁的力学分析以及压电晶体材料压电效应特性,提出一种新的压电陶瓷(PZT)微型硅悬臂梁发电装置.借助微型硅悬臂梁质量块的振动和PZT的正压电效应,实现振动机械能向电能转换.该装置结构简单、体积小、质量小,可以用MEMS集成加工工艺实现结构加工,因此与其他微型MEMS器件可以集成在一个基础上.     

新型集成三维微力检测微夹持器

提出了一种以压阻检测技术为基础,压电陶瓷为微驱动元件,具有两级位移放大且集成三维微力传感器的微夹持器。采用有限元软件对微操持器放大机构和传感器弹性体进行分析,并给出了传感器的标定方法。实验证明,该传感器具有无耦合、测量分辨率高、线性度好、标定简单的优点,满足了预计的设计要求,传感器最大量程为10 mN,X向与Y向的分辨率均为2.4 μN,Z向的分辨率为4.2 μN;同时也验证了所设计的微夹持器的合理性和实用性,当压电陶瓷驱动电压取200 V时,微夹持器的张合量达到最大值274 μm。     

激光干涉微轮廓测量仪

基于Michelson干涉仪测量原理研制的微轮廓测量仪,载物平台采用步进电机和压电陶瓷(PZT)两级闭环驱动与定位,步进电机用于快速粗定位和扩大测量范围,压电陶瓷用于精密定位,重复定位精度为10 nm;测量光路采用共干涉系统,对机械振动,温度漂移不敏感;测量范围20 mm×20 mm×0.4 mm,纵向分辨率为0.32 μm,横向分辨率为0.5μm.     

基于柔性铰链的二级放大微夹持器的研究

微夹持器是微装配系统的关键部件,设计了一种以柔性铰链为基础的二级位移放大机构的夹持器,该夹持器由压电陶瓷驱动。计算了夹持器的放大倍数和柔性铰链的节点应力,并对夹持器的最大张合量、放大倍数、夹持力和刚度进行有限元仿真分析。分析结果表明:夹持器的结构设计满足实际应用要求,对实现微小零件的自动装配有实际意义。     

基于MEMS机构装配的微夹持器研究

微夹持器作为末端执行装置,直接决定了微装配的效率。MEMS机构中包含许多微小的活动部件和功能元件,为实现这些微小器件的稳定夹取和自动装配,设计了一种采用压电陶瓷驱动、基于柔性铰链的二级放大微夹持器结构。对该微夹持器的节点应力、刚度及最大张合量等进行了分析计算,并对微夹持器进行了试制。实验与分析结果表明,该夹持器最大张合量是245μm,放大倍数约为12.3倍,满足MEMS机构的装配要求。在此基础上,重点对张合量与夹持力进行了系统测试,通过对测试数据的非线性回归,推导出99.99%可靠度的驱动电压计算公式,实现了微夹持的精确控制。     

用于微装配的二级放大微夹持器的设计与实验

微装配系统中的重要工具之一就是微夹持器,因此设计了利用压电陶瓷驱动的二级放大的微夹持器并利用Pro/E对其建模,计算了其放大倍数和节点应力,同时采用有限元方法对所设计的微夹持器进行张合量、放大倍数、应力、刚度及夹持力的分析计算,最后对微夹持器进行试制,实验测试,测试结果表明该微夹持器设计合理,基本符合要求。     

基于PZT薄膜的集成式微悬臂梁结构设计与制作

设计了基于PZT压电薄膜的双层和双片压电微悬臂梁结构,利用压电材料的正压电效应和逆压电效应,通过两个压电元件实现传感和执行功能的集成.悬臂梁结构采用体硅加工工艺制作,锆钛酸铅(Pb(Zr,Ti)O3,PZT)压电薄膜采用sol-gel方法在Pt/Ti/SiO2/Si衬底上制作,压电薄膜具有完整的钙钛矿结构和(111)择优取向.为了提高悬臂梁的性能和制作成品率,对制作微悬臂梁的关键工艺进行了优化.     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

面向MEMS微装配的夹持器的设计和实验研究

介绍了一种由PZT（压电陶瓷）驱动的用于MEMS微装配的微夹持器的设计，计算了夹持器本体的放大倍数和刚度,并用ANSYS仿真验证了数学计算的准确性,采用了基于视觉的标定方法，标定了微夹持器刚度、张合量、夹持力以及夹持力和张合量的关系。实验表明：夹持器张合量达280μm，夹持力达0．1N，可精确操作200～2000μm的微齿轮，实现了微行星齿轮减速器的装配。     

Frequency dependences of higher-order constants of piezoelectric ceramics

The properties of TBC-3 and PZT-23 piezoelectric ceramics have been studied by the method of loaded three-element complex oscillator. Changes in the higher-order (up to fifth) parameters are considered for large mechanical (0–120 MPa) and electric (0–600 kV/m) loads. Results of studying the longitudinal flexibility s ₁₁ ^E , piezoelectric modulus d ₃₁, and dielectric permittivity ε ₃₃ ^σ are presented within a frequency range of 20–200 kHz, where the frequency dispersion of dielectric as well as piezoelectric and elastic parameters is observed.     

Microstructure and electrical properties of NaNbO3-BaTiO3 lead-free piezoelectric ceramics

Lead-free piezoelectric ceramics (1 − x) NaNbO3-xBaTiO₃ have been fabricated by a traditional ceramic sintering technique. The effects of BaTiO₃ (BT) synthesized by hydrothermal method on crystal structure, density, dielectric, piezoelectric, and electromechanical properties were investigated. Results show that the phase structure transforms from the orthorhombic phase to the tetragonal phase with the increase of the content of BT, and the two phases co-exist when 0.08<×⩽0.10. However, the optimum composition for (1 − x)NaNbO₃-xBaTiO₃ ceramics is 0.90NaNbO₃-0.10BaTiO₃. The 0.90NaNbO₃-0.10BaTiO₃ ceramics sintered at 1250°C have higher properties: piezoelectric constant d ₃₃ of 120 pC/N, dielectric constant ε_τ of 718, planar electromechanical coupling factor k _p of 24%, planar frequency N _d of 3 MHz·mm, and the mechanical quality factor Q _m of 138, respectively. The results show that the (1−x)NaNbO₃-xBaTiO₃ ceramics is one of the promising lead-free materials for high-frequency applications.     

Tribological behavior of RH ceramics made from rice husk sliding against stainless steel,alumina, silicon carbide,and silicon nitride

The tribological behavior of rice husk (RH) ceramics, a hard, porous carbon material made from rice husk, sliding against stainless steel, alumina, silicon carbide, and silicon nitride (Si₃N₄) under dry conditions was investigated. High hardness of RH ceramics was obtained from the polymorphic crystallinity of silica. The friction coefficients for RH ceramics disks sliding against Si₃N₄ balls were extremely low (<0.1), irrespective of contact pressure or sliding velocity. Transfer films from RH ceramics formed on Si₃N₄ balls. Wear-mode maps indicated that the wear modes were powder formation under all tested conditions, resulting in low specific wear rates (<5×10⁻⁹ mm²/N).     

Development of a microgripping system for handling of microcomponents

This paper reports the development of a semi-automatic microgripping system that consists of a microgripper and an x, y, z positioning system. The microgripper has two 1DOF fingers fabricated by an amorphous, soft magnetic material and is actuated electromagnetically. The microgripper is embedded in the 3DOF positioning system with the help of a stainless steel holder under an angle, which is manually adjusted, in respect to the working field. The position of the microgripper is observed optically and by three digital indicators¹ from Mitutoyo, which offer easy reading and continuous position tracking. All axes are actuated by step motors which allow precise positioning of the microparticles under manipulation. The microgripping system was tested in pick and place cases, under an optical microscope in atmospheric conditions. Optical fibres (125 μm in diameter) and bonding wires (50 μm in diameter) were handled. The temperature on the actuator, on the microgripper fingers and on the microgripper tips during manipulation was measured using K type (Ni/CrNi) thermocouples. The gripping force was evaluated as well.     

多孔体坩埚生长氟化钙晶体

采用独特设计的多孔体坩埚和自行设计的晶体生长炉,在真空条件下,用Bridgman-Stockbarger法生长出了CaF₂光学晶体。在真空度低于3×10^-3 Pa,生长区中心轴温度梯度为1.8~2.5 ℃/mm,径向梯度＜0.5 ℃/mm,生长速率为3~4 mm/h,初退火降温速率控制在20 ℃/h以下的生长条件下,进行熔料、氟化去氧、均一化熔体、控速生长及初退火,一炉次生长了七根57 mm×190 mm的CaF₂光学晶体,并进行了性能分析。结果表明,生长出的晶体透带宽,从紫外190 nm到红外9 000 nm均有良好的透过率,190 nm处透过率可达81%,9 000 nm处透过率可达83%,单晶率可达80%,位错密度达30/mm²。使用本文提出的设备和工艺,提高了CaF₂晶体的单晶率,降低了使用损耗,可实现中小尺寸CaF₂晶体的规模化生产。     

Electrochemical machining analysis on grid cathode composed of square cells

During the electrochemical machining (ECM), the cathodes designed by the existing methods are mainly unitary cathodes, which can be only used to produce the workpieces with the same shapes. However, there are few researches on designing cathodes for machining the different workpieces with the different surfaces. This paper presents the grid cathode composed of the square cells to produce the workpieces with different shapes. Three types of the square cells, 2.5 mm′2.5 mm, 3 mm′3 mm, and 4 mm′4 mm, are utilized to construct the plane, the slant, and the blade cathode. The material of the cathode and the anode is CrNi 18 Ti 9 , and the ingredient of electrolyte is 15% NaCl and 15% NaNO 3 . The machining equilibrium machining current and time are acquired and analyzed, the machining process and the workpiece quality are compared between using the grid cathode and the unitary cathode. Moreover, the machining errors on the workpiece surface are measured and analyzed, and the error reasons are traced and discussed to obtain the better surface quality of the workpiece. The experiment and analysis results show that the grid cathode can be used to manufacture the workpieces with complex shapes in certain range of the error. The workpiece quality improves with the size of the square cell being reduced, and if the square element is small enough, the workpiece quality is almost equal to the one machined by the unitary cathode. The proposed research realizes a single cathode machining the different workpieces with the different surfaces.     

Computational parametric analysis and experimental investigations of a compact flexure-based microgripper

This paper presents a flexure-based piezoelectric actuated microgripper for high precision grasping/releasing tasks. The design of the microgripper consists of a three-stage amplification and transmission mechanism, and the parallel grasping technique. A bridge-type mechanism and two sequential lever-type mechanisms are symmetrically connected to amplify the output displacement of the embedded piezoelectric actuator. The parallelogram mechanisms assist in linearizing the output displacement of both jaws of the microgripper. The computational analysis is conducted to investigate the effect of the dimensional parameters on the characteristics of the microgripper. A computational parametric optimization methodology is established to achieve the required attributes of the microgripper. The design optimization resulted in a compact design, a high displacement amplification ratio, and a large output displacement of the microgripper. The experimental studies are conducted to investigate the key characteristics of the microgripper such as the displacement amplification ratio, the output displacement, tracking performance. Further, the parasitic motion, input-end and output-end motion resolution of the microgripper are identified. The experimental results indicate that the compact microgripper can achieve a high displacement amplification ratio and large output displacement with a high positioning accuracy.     

Friction–wear behavior and tribochemical reactions of different ceramics in HFC-134a gas

The friction and wear properties of the ionic ceramics Al₂O₃ and ZrO₂, and the covalent ceramics Si₃N₄ and SiC rubbing against an Al₂O₃ ball in vacuum (10⁻⁵ Pa) and in CF₃CH₂F (HFC-134a) gas at 10⁴ Pa were investigated using a ball-on-disk type tribometer. Without exposure to air, the surface composition and chemical state of the wear tracks and debris on the disks were determined with X-ray photoelectron spectroscopy (XPS). It is found that HFC-134a gas significantly reduces the friction and wear of all the ceramic couples, and that the ionic ceramic pairs show lower friction and wear. On the other hand, metal fluorides and/or fluorine-containing organic compounds are detected on the sliding surfaces. The differences in the friction–wear behavior of the ceramics rubbing in HFC-134a gas may be due to the products of tribochemical reactions, which are dependent on the bond type of the ceramics.     

An infrared interferometer for investigating subthermonuclear plasma in the GOL-3 multimirror trap

A simple Michelson CO₂ interferometer for measuring the high-temperature plasma density within one interference fringe (n _e l = 10¹⁶ cm^?2) at two points (0.8 and 9.0 m) of the long (L = 12 m) GOL-3 corrugated trap was used. A piezoelectric element that provides displacements of the mirror in the reference arm of the interferometer is used to calibrate the interferometer and perform remote control of the initial measurement phase. The interferometer is manufactured from dielectric materials, thus excluding a mechanical action of stray magnetic fields on its elements. The time resolution of the interferometer is determined by a HgCdTe diode and equals ??1 ns. The sensitivity of the interferometer is ??5 × 10^?4 of a fringe (n _e l = 2 × 10¹³ cm^?2).     

Metallurgical interactions at the contacts GaAs interface

Interface morphology, phase composition, and elemental diffusion of Pt/Ti/Ge/Pd ohmic contacts to both n and p⁺-GaAs have been investigated as a function of annealing temperature. Structural and chemical results were correlated with specific contact resistances (ρ_c) measured for each thermal treatment. Annealing at 450°C yielded the lowest ρ_c, ～6.4 × 10^?7Ω-cm². The interface was observed to be smooth and abrupt. Two interface phases were detected; a primary phase, PdGe, and a secondary, Ga-rich Pd-Ga-As ternary phase. The presence of this ternary phase was found to be critical to contact formation on n-GaAs. The Ti and Pt layers remained pristine. Annealing at 550°C resulted in a slightly higher ρ_c, ～2.1 × 10^?6Ω-cm². There was significant elemental diffusion within the contact metal and minor diffusion into the GaAs substrate. The interface possessed limited areas of spiking with uniform composition. Annealing at 600°C proved to have a detrimental effect on the ρ_c, ～10^?4Ω-cm². This electrical degradation was accompanied by strong chemical intermixing between the contact and substrate, resulting in a continuous nonplanar interface with deep multiphase protrusions.