复合式MEMS微夹持器的研制

为实现对亚毫米微小构件稳定夹取及可靠释放等操作,研制了一种复合式微夹持器.采用有限元软件分析了微夹持器的机构及动力特性.应用MEMS体硅工艺将静电梳齿驱动与气动吸放集成构成复合式驱动,气动吸放的引入改善了微夹持器的操作性能,S形柔性梁结构的设计将梳齿驱动的直线运动转化成末端夹爪的转动实现了夹持操作.两种不同尺寸的微夹持器,有效扩展了微夹持器的夹持范围.根据微夹持器的操作控制需求,设计了微夹持器静电驱动控制系统以及气压控制系统.在80 V的驱动电压下,微夹持器末端夹爪位移可达25 μm.针对100～200 μm的小球进行了微操作实验,实验结果表明,静电梳齿驱动结合真空吸附能够使夹取操作更加稳定,基于闭环控制的气路正压力能有效克服小球与夹爪之间的粘附力,实现可靠的释放操作.微夹持器基本满足100～200 μm微小构件的操作需求.     

无掩膜流动刻蚀技术研究

为了实现玻璃材料高深宽比微结构的加工,提出了一种基于微尺度下流体分层流动现象的微流道内无掩膜流动刻蚀方法。通过对玻璃基体材料进行大量的工艺实验,明确了流动参数对于刻蚀成型微结构深宽比、侧壁形状、刻蚀速率的影响。证明了可以通过改变刻蚀剂与隔离剂的流动参数实现对成型微结构形貌的控制。实验结果表明约束流动刻蚀工艺可以在玻璃基体材料上加工出形态复杂、大深宽比的微结构,微结构的形貌取决于微流道中流体的流速。本实验的结果对于微尺度下分层流动的特性研究有一定的参考价值,并可为解决各向同性材料的微结构加工难题提供有效的解决方案。     

微孔气流加压对ITO玻璃激光刻蚀平面度的影响

针对ITO玻璃表面线路激光刻蚀中因定位问题玻璃工件产生的微变形,采用微孔陶瓷对工件进行微气流阵列加压,确保高精度的激光刻蚀加工。分析不同加工工艺下的微气流压力分布,探究气流压力和刻蚀间隙对ITO玻璃刻蚀表面平面度的作用机制。结果表明：经微孔气流加压后,工件在气体流动的区域受到正压力,加工区域的压力分布较为均匀。由此可知,工件表面受到均布气压有利于刻蚀表面的定位,但过大的压力会导致工件微变形。实验结果显示：在合适的压力下,微孔气流加压可使得平面度低至8μm,当压力在0.16～0.2 kPa,刻蚀间隙在1.8～1.9 mm时,工件表面压力为13.2～14.4 Pa,此时平面度最好,微米尺度的刻蚀线路清晰,不产生破损。最后,对微孔气流加压的ITO玻璃进行激光刻蚀加工,可得到8μm以及25μm的表面微细线路,解决了通常无微孔气流加压的刻蚀工艺导致局部断点或变形线路引起产品短路或开路等问题。     

应用双埋层SOI工艺制备低g值微惯性开关

采用双埋层SOI( Silicon-On- Insulator)材料,结合KOH腐蚀工艺、电感耦合等离子体(ICP)刻蚀工艺、阳极键合以及喷雾式涂胶工艺,研制了一种基于平面矩形螺旋梁的低g值微惯性开关.利用二氧化硅KOH腐蚀/ICP刻蚀自停止的特点,平面矩形螺旋梁厚度的精度为±0.46 μm.分析了双埋层SO1材料的电学特性,采用等电位技术,实现了双埋层SOI与上下两层硼硅玻璃的阳极键合.采用玻璃无掩模湿法腐蚀技术,在玻璃封盖底部设计制作了大小为200 μm×200μm的防粘连凸台,解决了芯片在清洗干燥过程中的粘连问题.采用ICP刻蚀用硅衬片方法,解决了ICP刻蚀工艺中高温导致的金硅共晶合金问题.实验验证显示,提出的方法效果较好,芯片成品率得到较大提高,为大批量地研制低g值微惯性开关提供了可靠的工艺基础.     

等离子体脱硫反应装置的设计

等离子体脱硫装置的设计主要包括等离子体反应器的结构设计和电参数设计两个方面.通过改进介质阻挡放电的电介质材料、加工工艺以及放电间隙结构优化等离子体反应器设计,实现强电离放电,提高脱硫效率.     

六相交流电弧放电装置电源系统设计及性能测试

为了解决单相交流电弧放电不稳定和射流短的问题,设计了一个六相交流电弧放电装置。六相交流电弧放电相比于单相交流电弧放电更稳定,可以产生更大功率的等离子体。主要介绍六相交流电弧放电装置的电源系统电路设计,并给出了六相交流电源驱动的电弧等离子体放电的伏安特性曲线以及不同弧电流对等离子体射流特性的影响规律。     

菲涅耳微透镜芯模表面形貌的检测及加工误差分析

采用扫描白光干涉法对菲涅耳微透镜芯模表面浮雕结构进行了检测,并对元件表面微观形貌进行了三维重建.根据其表面形貌数据,引入幅度参数表征法,分别计算出横向线宽误差以及样品的系统刻蚀深度误差和随机刻蚀深度误差等纵向加工偏差.通过表面高度分布的偏斜度、表面高度分布的峭度等参数获得了有关微芯模表面误差和缺陷的量化信息.实验研究表明,扫描白光干涉法能精确定量化表征微芯模表面形貌特征,这对探索适用于新型微光学器件表面三维形貌误差的无损检测评价方法具有实际意义.     

平行微带谐振结构器件微尺度效应研究

研究了微尺度条件下射频微机械系统中平行微带谐振器件的相关效应.对该谐振器的表面粗糙度、导热率、电学尺度等因数引起的微尺度效应进行了分析,得出该结构相关微尺度条件下相关物理量的微尺度规律.在微尺度表面粗糙度条件下,对平行微机械微带结构谐振/滤波器的性能做出了分析,得出该器件在电磁、机械、几何等微尺度量影响下的一些性能指标,为射频微机电系统相关微尺度效应研究提供了理论参考.     

电熔爆等离子体电弧的多场耦合仿真与试验分析

针对电熔爆加工过程中等离子体电弧分布研究量化程度不足的现状,运用磁流体动力学理论,建立了包含阴极-等离子体电弧-阳极表面的二维数学模型,采用Comsol有限元仿真软件求解出不同加工电流等离子体电弧温度场、压力场、电势场及阳极表面电流密度分布特性,并根据电熔爆等离子体电弧的加工需求搭建了试验系统,对仿真结果进行验证。研究结果表明:增大加工电流可提高电弧最高温度,使电熔爆放电通道内温度和压力梯度增大,造成放电通道不稳定;增大电流使电弧受到指向电弧中心的电磁力增加,导致电弧收缩明显,加工能量过于集中,使加工表面质量降低;在电流100～175 A之间,加工后表面粗糙度可控制在Ra 6.3μm以下,试验结果与仿真结论具有较好的一致性。     

微通道结构带状电极电火花加工方法研究

针对大厚度、高深宽比金属微通道结构加工的难题,提出一种带状电极电火花加工方法,利用厚度30～100 μm的带状电极,在金属基体上高效制造微通道结构。研究了带状电极电火花加工机理,建立了带状电极在加工间隙中的运动模型,分析了影响带状电极运动的主要因素,搭建了带状电极电火花加工装置,开展了微通道结构带状电极加工实验研究,获得了带状电极电火花加工基础工艺规律。利用带状电极电火花加工方法成功加工出的具有200条微通道的反应器结构和44×45微换热器阵列结构,表明带状电极电火花加工可以实现窄宽度(100 μm以下)、大厚度(35 mm以上)、高深宽比(10以上)和高精度(缝宽标准差3 μm以内)的大批量微通道结构的高效加工,相关方法和技术有望在微模具、微散热器、微反应器等领域获得推广和应用。     

Non-thermal plasma for exhaust gases treatment

This article describes a study on a non-thermal plasma device to treat exhaust gases in an internal combustion engine. Several tests using a plasma device to treat exhaust gases are conducted on a Honda GX200-196 cm³ engine at different rotational speeds. A plasma reactor could be efficient in degrading nitrogen oxides and particulate matter. Monoxide and carbon dioxide treatment is minimal. However, achieving 1%–3% degradation may be interesting to reduce the emission of greenhouse gases.     

Safe fabrication of sharp gold tips for light emission in scanning tunnelling microscopy

Gold is the optimal tip metal for light emission in scanning tunnelling microscopy (LESTM) under ambient conditions. Sharp Au-tips of 10 nm radius were produced reliably using a safe, two-step etching method in 20% (w/w) CaCl₂ solution. Previous CaCl₂-based methods have tended to produce blunter tips, while other etching techniques that do produce sharp Au-tips, do so with the use of toxic or hazardous electrolytes. The tips are characterised using scanning electron microscopy and their efficacy in LESTM is evidenced by high-resolution, simultaneous topographic and photon mapping of Au(1 1 1)- and polycrystalline Au-surfaces. Spectra of the optical emission exhibit only one or two peaks with etched tips in contrast to the more complex spectra typical of cut tips; this feature, together with the highly symmetric geometry of the tips, facilitates a definitive analysis of the light emission process.     

High strain rate compression of titanium and some titanium alloys

A modified Hopkinson bar was used to compress specimens of commercially-pure titanium, IMI 125 and titanium alloys, AMS 4911B and AMS 4916B, at natural strain rates of between 3 × 10³ s⁻¹ and 3 × 10⁴ s⁻¹. All three materials deformed in a viscous manner with a linear increase of flow stress with strain rate and a macroscopic viscosity of 4·5 kPa s, 5·7 kPa s and 9·2 kPa s, respectively. At strain rates above about 1 × 10⁴ s⁻¹ there was a decrease in macroscopic viscosities to 0·9 kPa s and 2·5 kPa s for the titanium and 4911B alloy respectively, which is attributed to changes in the dislocation drag mechanisms. The results for the 4916B alloy at the higher strain rates were too scattered to give a definite trend. It is suggested that the increase in the macroscopic viscosity with alloying is due to an increase in the dislocation drag coefficient by solution hardening and to a reduction in the density of mobile dislocations by dislocation pinning.

It is also proposed that the susceptibility of these materials to catastrophic shear failure which occurs without prior linear work-softening is due to the higher propensity for titanium and titanium alloys to shear failure as a consequence of their thermo-mechanical properties. The decrease of strain at which shear occurred with increasing strength is in accord with this suggestion.     

The high strain rate compression of 1023 and 4130 steels

Steel specimens of type 1023 and heat treated 4130 steel of hardnesses, between 257 and 450 HV10, were compressed at strain rates between 3 × 10³ and 3 × 10⁴ s⁻¹ using a modified Hopkinson bar. Both steels showed viscous type flow behaviour with a linear increase in flow stress with strain rate. For the 1023 steel there were two linear regions, one from 3 to 12 × 10³ s⁻¹ with a macroscopic viscosity of 4·7 kPa s and two from 14 to 27 × 10³ s⁻¹ with a viscosity of 0·7 kPa s. These results indicate some change in the controlling mechanism. For the 4130 steel the macroscopic viscosity decreased linearly with increasing hardness from 7·4 kPa s at 257 HV 10 to 2·2 kPa s at 450 HV 10. This was probably due to a decrease in the density of mobile dislocations with increased tempering temperatures. At lower hardness values (257 and 300 HV 10) and higher strain rates, a levelling off of the flow stress occurred but the data were too scattered to give a definite trend. The heat generated due to deformation of the 1023 steel was sufficient to produce steady state flow at strains above about 0·3. In the 4130 steel the thermo-mechanical properties were such that linear work softening was observed at a rate inversely proportional to the square root of the strain rate and independent of the hardness. This suggests that the work softening was a function of properties of the common ferrite matrix. The strain at which the work softening commenced decreased with increasing hardness, because of the more rapid heat generation at higher flow stresses. At higher hardness and higher strain rates 4130 steel failed by shear. Shear failure occurred at lower strain rates with increasing hardness and, for a given hardness, at lower strains with increasing strain rate. This behaviour was consistent with Recht's analysis of catastrophic shear failure.     

Plasma characterization of dry ��-EDM

An attempt was made to characterize the dry microelectric discharge machining (??-EDM) plasma systematically by using optical emission spectroscopy. In order to characterize the plasma and its parameters such as plasma temperature, electron density, Debye length, and gamma parameter, the optical spectra were recorded for different energies and with different diameters of tool electrode. From the recorded spectra, using line pair method and modified Saha equation, plasma temperature and electron density, respectively were calculated. From these two, Debye length and plasma parameter were also calculated. These studies indicate that the plasma produced in dry ??-EDM is ideal. In addition to this, we found that the dry ??-EDM region is below the conventional EDM region in log electron density and log temperature plot. Morphological analysis was carried out on crater produced by different energies on the workpiece using a scanning electron microscope. The crater shape may dependent on the geometry of the tool tip, number of discharges, and energy of discharge.     

锶原子光钟钟跃迁谱线探测中的程序控制

为了实现中国科学院国家授时中心研制的锶原子光晶格钟钟跃迁的自动化探测,设计了完整的自动控制系统。该系统主要由延迟精度与同步精度在μs量级的时序控制系统和满足要求的激光频率扫描系统组成。两个控制系统均通过LabVIEW软件编程及虚拟仪器控制光场和磁场。完成了锶原子的两级冷却和光晶格囚禁,最终得到了高信噪比载波线宽为180Hz的锶原子1S0-3P0钟跃迁谱线。谱线展现了高信噪比和窄线宽的特点,表明整个锶原子光钟系统的运行较为稳健,整个控制系统满足实验对于控制精度的需求,实现了锶原子光钟系统的自动化操作与控制。该控制系统具有一定普适性,也可拓展至需要对光场及磁场进行控制的其他系统中。     

Microsecond time-resolved Fourier transform infrared analytics in a low pressure glow discharge reactor

A low pressure glow discharge reactor has been designed to allow time-resolved infrared spectroscopic investigation of the discharge zone in practical conditions. The benefits of such reactor are demonstrated through the study of the evolution in the infrared spectra of air/CO(2) gas mixture at the microsecond time-scale. It has been shown that the spectra are greatly affected by the electrical discharge in the 2400-2200?cm(-1) region, where the asymmetric stretch mode of CO(2) falls. The CO(2) molecules are excited through a collision with excited N(2) molecules, where the transfer of energy occurs by a resonant effect. The mechanisms involved are reversible and following plasma pulses.     

Preliminary considerations in the use of industrial sonic nozzles

Preliminary considerations applying to the necessary instrumentation for the use of sonic nozzles is reviewed. A way to make sonic nozzles for industry, together with a method to determine the discharge coefficient of a convergent nozzle operating in the sonic regime in conditions of ideal flow is suggested. The results obtained for the behaviour of the discharge coefficient of sonic nozzles, in the range from 4×10⁴ to 2×10⁵ are compared with the standard ISO 9300 (Standard ISO 9300. Measurement of gas flow by means critical flow Venturi nozzles, 1990) and the curve proposed by Ishibashi et al. (M. Ishibashi, M. Takamoto, N. Wanatabe, Y. Nakao. Precise calibration of critical nozzles of various shapes at the Reynolds number of 0.2–2, 5×10⁵. Proceedings of FLOMEKO 94).     

Image sensor as a three-channel spectrometer with application to in situ monitoring of wet etching

A three-channel spectrometer is constructed with a 460 nm high brightness light-emitting diode (LED) source (250 mW peak optical power output, 1 mm sq, 150 μm thick) and a red-green-blue (RGB) image sensor (3 × 4 mm, 1 mm thick) for purposes of a small form factor spectrometer to monitor reflectance/emission spectra from chemical wet etching experiments. The linearity and spectral response of the RGB image sensor is characterized and a three-channel spectral model is fitted to the extracted spectral response. We use this information to quantify time developments of the RGB image sensor outputs for in situ copper and aluminum etching experiments in terms of three defined spectral bands.     

同步辐射光电离质谱检测氟原子在二氧化硅表面反应产物

采用微波放电等离子体源产生高密度F原子,结合同步辐射真空紫外光电离质谱全面检测F原子在二氧化硅表面刻蚀反应的产物,并探究其反应机理。通过扫描同步辐射光子能量,获得具有特定质量选择的离子光电离效率谱,测量了反应产物的电离能及碎片离子的出现势等基本参数;同时结合量子化学理论计算质谱中离子的来源,即对光电离和光解离过程进行了区分。结果表明,F原子在二氧化硅表面会反应生成一系列的氟氧硅化合物 (Si_xO_yF_z),主要包括SiF₄、SiF₃OSiF₃和SiFOSiF₂OF等,质谱中观察到的SiF₃⁺、SiF₃OSiF₂⁺等离子信号来源于其对应母体离子的解离碎片。实验测得SiF₄的电离能为15.85 eV,SiF₃⁺和SiF₃OSiF₂⁺碎片离子的出现势分别为16.20、16.40 eV。该方法实现了高效检测F原子刻蚀反应的产物,由于F原子具有较高的化学反应活性,该实验装置也可用于开展气相自由基反应研究,模拟大气化学和燃烧火焰等体系中的化学反应过程。