New surface forces apparatus using two-beam interferometry

We designed a new surface forces apparatus for measuring the interactions between two nontransparent substrates and/or in nontransparent liquids. The small displacement of a surface, the bottom one in this study, was measured by the two-beam (twin path) interferometry technique using the phase difference between the laser light reflected by the fixed mirror and that by the mirror on the back of the bottom surface unit. It is possible to determine the distance with a resolution of 1 nm in the working range of 5 microm. This apparatus was successfully applied to measure the forces between mica surfaces in pure water and aqueous KBr solutions.     

Effect of laser processing on the cavitation erosion of Cr-Mo-Cu alloy cast iron

The cavitation behaviour of Cr-Mo-Cu alloy cast iron (cylinder liner material of diesel engines) samples processed by a continuous wave CO₂ laser was investigated with a magnetostriction apparatus. Untreated samples manifested the lowest resistance to cavitation erosion. Laser surface-fused and phase transformation hardened samples came next, but the improvement was very small. Samples clad with a Co 50 alloy by means of a laser exhibited excellent cavitation resistance, so much so that no erosion hole was created on the surface of the alloy layer after a 600 min cavitation test. The main mechanism in the cavitation erosion process for each microstructure is described and discussed.     

Full characterization and optimization of a femtosecond ultraviolet laser source for time and angle-resolved photoemission on solid surfaces

A novel experimental apparatus for time and angle-resolved photoemission on solid surfaces is presented. A 6.28 eV laser source operating at 250 kHz repetition rate is obtained by frequency mixing in nonlinear beta barium borate crystals. This UV light source has a high photon flux of 10(13) photons/s with relatively low number of photons/pulse so that Fermi surface mapping over a wide region of the Brillouin zone is possible while mitigating space charge effects. The UV source has been fully characterized spatially, spectrally, and temporally. Its potential for time and angle-resolved photoemission is demonstrated through Fermi surface mapping and photoexcited electron dynamics in Bismuth. True femtosecond time resolution <65 fs is obtained while the energy resolution of 70 meV appears to be mainly limited by the laser bandwidth.     

A high-pressure atomic force microscope for imaging in supercritical carbon dioxide

A high-pressure atomic force microscope (AFM) that enables in situ, atomic scale measurements of topography of solid surfaces in contact with supercritical CO(2) (scCO(2)) fluids has been developed. This apparatus overcomes the pressure limitations of the hydrothermal AFM and is designed to handle pressures up to 100 atm at temperatures up to ～350 K. A standard optically-based cantilever deflection detection system was chosen. When imaging in compressible supercritical fluids such as scCO(2), precise control of pressure and temperature in the fluid cell is the primary technical challenge. Noise levels and imaging resolution depend on minimization of fluid density fluctuations that change the fluid refractive index and hence the laser path. We demonstrate with our apparatus in situ atomic scale imaging of a calcite (CaCO(3)) mineral surface in scCO(2); both single, monatomic steps and dynamic processes occurring on the (1014) surface are presented. This new AFM provides unprecedented in situ access to interfacial phenomena at solid-fluid interfaces under pressure.     

The Effect of Laser Texturing of Steel Surfaces and Speed-Load Parameters on the Transition of Lubrication Regime from Boundary to Hydrodynamic

Laser surface texturing (LST) is an emerging, effective method for improving the tribological performance of friction units lubricated with oil. In LST technology, a pulsating laser beam is used to create thousands of arranged microdimples on a surface by a material ablation process. These dimples generate hydrodynamic pressure between oil-lubricated parallel sliding surfaces. The impact of LST on lubricating-regime transitions was investigated in this study. Tribological experiments were carried out on pin-on-disk test apparatus at sliding speeds that ranged from 0.15 to 0.75 m/s and nominal contact pressures that ranged from 0.16 to 1.6 MPa. Two types of oil with different viscosities (54.8 cSt and 124.7 cSt at 40°C) were evaluated as lubricants. Electrical resistance between flat-pin and laser-textured disks was used to determine the operating lubrication regime. The test results showed that laser texturing expanded the range of speed-load parameters for hydrodynamic lubrication. LST also reduced the measured friction coefficients of contacts that operated under the hydrodynamic regime. The beneficial effects of laser surface texturing are more pronounced at higher speeds and loads and with higher viscosity oil.     

Imaging the substructure of antibodies with tapping-mode AFM in air: the importance of a water layer on mica

Monoclonal antibodies (immunoglobulin G; IgG) against the N-terminal domain of the A subunit of DNA gyrase have been imaged using tapping-mode atomic force microscopy under ambient conditions on hydrophilic mica surfaces. The familiar tri-nodal submolecular resolution of IgG (i.e. 50-kDa resolution) has been achieved when operating the microscope with the tip predominantly in the attractive force regime. Under common laboratory conditions of about 40% relative humidity, the resolution of this substructure was not achieved owing to motion of the antibodies on the surface and/or image distortion from tip–sample instabilities. Reproducible imaging of the tri-nodal antibody substructure was achieved by desiccating the samples for extended periods of time (1 week or more) before imaging. This effect is attributed to the presence of a humidity-dependent thin water layer (a few molecules or nanometres thick), which has been observed previously using the surface force apparatus and scanning polarization force microscopy. Desiccation of the mica surfaces allowed enough water to be removed from the mica surface to prevent this effect. Degradation in the image quality over the imaging period of an hour or two was observed, owing to re-adsorption of water under the ambient laboratory conditions.     

Weak absorption test and defect analysis of optical coatings

1Introduction Inmodernoptics,especiallylasertechnolo gy,absorptionisoneofthemostimportant characterswhichmustbeconsidered,notonly foropticalproperties,butalsoforlaser induced damagethreshold(LIDT).Forexample,ab sorptiondefecthasplayedagreatroleinfluen cinglaserinduceddamagebehaviorsofthedie lectricopticalcoatings.Inmanyapplications,veryweakabsorption,1×10-6orless,should bemeasuredandcontrolled.However,thesensitivityofthebestregular spectrometerisonlylowto0.1%.Solutionshad beenfoundtoresolve…     

高灵敏度的全自动低值磁通测量系统

介绍了一种高灵敏度的全自动低值磁通测量方法，对于从测量线圈得到的感应电动势信号利用了高灵敏度的纳伏计作为前置放大器进行放大，因而测量低值磁通的分辨率达到了1nWb，比国外同类仪器高出了10倍，同时还研制了V／F变换器及数字积分器作为后续的积分系统。消除了常用的RC积分放大器法无法避免的回复误差，包括激励电源在内的测量仪器构成了一个基于计算的全自动测量系统，使用十分方便。这样的低值磁通测量系统配上一个探测线圈时可探测很微弱的磁场。当探测线圈的磁面积为0.2m^2（直径1cm，匝数约为4000）时，探测弱磁场的分辨率可达高5nT.     

PHOEBE,a prototype scanning laser-feedback microscope for imaging biological cells in aqueous media

Based on the principle of laser-feedback interferometry (LFI), a laser-feedback microscope (LFM) has been constructed capable of providing an axial (z) resolution of a target surface topography of ～ 1 nm and a lateral (x, y) resolution of ～ 200 nm when used with a high-numerical-aperture oil-immersion microscope objective. LFI is a form of interferometry in which a laser's intensity is modulated by light re-entering the illuminating laser. Interfering with the light circulating in the laser resonant cavity, this back-reflected light gives information about an object's position and reflectivity. Using a 1-mW He–Ne (λ = 632·8 nm) laser, this microscope (PHOEBE) is capable of obtaining 256 × 256-pixel images over fields from (10 μm × 10 μm) to (120 μm × 120 μm) in ～ 30 s. An electromechanical feedback circuit holds the optical pathlength between the laser output mirror and a point on the scanned object constant; this allows two types of images (surface topography and surface reflectivity) to be obtained simultaneously. For biological cells, imaging can be accomplished using back-reflected light originating from small refractive-index changes (> 0·02) at cell membrane/water interfaces; alternatively, the optical pathlength through the cell interior can be measured point-by-point by growing or placing a cell suspension on a higher-reflecting substrate (glass or a silicon wafer). Advantages of the laser-feedback microscope in comparison to other confocal optical microscopes include: the simplicity of the single-axis interferometric design; the confocal property of the laser-feedback microscope (a virtual pinhole), which is achieved by the requirement that only light that re-enters the laser meeting the stringent frequency, spatial (TEM₀₀), and coherence requirements of the laser cavity resonator mode modulate the laser intensity; and the improved axial resolution, which is based on interferometric measurement of optical amplitude and phase rather than by use of a pinhole as in other types of confocal microscopes.     

The Effect of Pulsed Laser Annealing on Wear and Corrosion Properties of Electroless Ni-P Plating

Electroless nickel-phosphorous alloy was plated onto quenched and hardened stainless steel. Laser surface treatments by YAG laser beams were carried out with the objective of improving -both the wear and the corrosion resistance of the platings. The friction and wear properties of the laser-treated platings were compared to unplated, untreated plated, and 400°C heat-treated plated substrates in pin-on-disc tests under unlubricated conditions. It was shown that laser treatments gave about a ten percent reduction in the friction coefficient compared with unplated substrates, and that controlled laser-treated plating improved the wear resistance of untreated plating to a level equivalent to 400°C heat-treated plating. It was found that the salt-spray corrosion resistance of the laser-treated platings was much greater than the unplated material and the 400°C heat-treated plating. The laser treatment is capable of improving both wear and corrosion resistance; and the wear resistance is externally governed by the hardness of the plating, and the corrosion resistance is governed by the crystal structure, especially the amount of amorphous nickel.     

基于USB的表面粗糙度虚拟测量仪的设计

设计了一种基于USB的表面粗糙度虚拟测量仪。该仪器利用激光三角法测量原理,借助Lab—VIEW软件开发平台,运用模块化设计,可实现对精密检测平面无损伤、快速、高精度的表面粗糙度测量。与同类产品相比,具有结构简单、实时处理能力强、测试精度高、显示结果直观、操作简便等优点。     

Measurement of large internal diameters with a compact apparatus based on dual-wavelength heterodyne interferometer

This paper presents a new method for measuring large internal diameters of 3∼20 m with submillimeter resolution. The method is based on a novel dual-wavelength heterodyne interferometer for absolute distance measurement and a new positioning method for aligning the laser beams with the diameter of the bore to be measured. The compact apparatus and convenience of operation in situ are the distinguishing features of this method. Preliminary experimental results of the prototype of the apparatus proved the feasibility of this method.     

机械零件三维表面形貌测量与评定的研究

介绍了机械零件三维表面形貌的测量与评定,分析了激光干涉式位移传感器的光学原理和干涉条纹信号的细分方法.激光干涉式位移传感器的精度达到了5nm左右.另外,带计量系统的二维工作台也是整个测量系统的关键部分.因为采用了光栅尺作为二维工作台的计量系统,所以在表面形貌的测量过程中二维工作台在X和Y两个水平方向上都能获得精确的定位.     

Ion optical design of a collinear laser-negative ion beam apparatus

An apparatus for photodetachment studies on atomic and molecular negative ions of medium up to heavy mass (M ? 500) has been designed and constructed. Laser and ion beams are merged in the apparatus in a collinear geometry and atoms, neutral molecules and negative ions are detected in the forward direction. The ion optical design and the components used to optimize the mass resolution and the transmission through the extended field-free interaction region are described. A 90° sector field magnet with 50 cm bending radius in combination with two slits is used for mass dispersion providing a resolution of M∕ΔM?800 for molecular ions and M∕ΔM?400 for atomic ions. The difference in mass resolution for atomic and molecular ions is attributed to different energy distributions of the sputtered ions. With 1 mm slits, transmission from the source through the interaction region to the final ion detector was determined to be about 0.14%.     

激光预处理提升DKDP晶体加工表面的抗损伤能力

针对晶体表面的损伤特性,采用小光斑扫描激光预处理技术预辐照DKDP晶体元件,并采用表面损伤自动探测系统实时分析每个脉冲辐照后晶体表面的损伤情况,比较预处理和未预处理区域的损伤点密度确定表面预处理效果,并进一步模拟分析表面各类缺陷在纳秒强激光辐照下的动态过程,解释激光预处理对精抛表面提升作用的微观机制并分析它对粗抛表面提升不明显的原因。实验结果表明,激光预处理技术对粗抛表面的提升作用并不明显,但是可以大幅度抑制精抛表面的损伤点密度。在本文的实验条件下,晶体表面的抗激光损伤能力可以提升约60%。比较体材料和精抛表面的预处理效果发现:当体材料的抗破坏能力通过预处理提升后,精抛表面的抗激光损伤能力也会提升,由此可见精抛表面的激光预处理效果与体材料性能相关。     

Atomic force microscopy observations of in situ deformed materials: application to single crystals and thin films on substrates

An experimental apparatus which consists of a compression machine interfaced with an atomic force microscope has been realized and allows the in situ observation of a sample surface under compressive stress. Taking advantage of the high resolution offered by this microscopy, the equipment is particularly suited both to analysing the fine slip line structure of deformed single crystals, providing interesting complementary information about plastic mechanisms taking place in the bulk, and to characterizing the mechanical behaviour of thin films on substrates with the investigation of the buckling phenomenon.     

Boundary Lubrication Properties of Surface Modified Material Produced by Laser and Electron Beam Surface Alloying

The surface-modified material can be produced by laser and electron beam surface alloying of a plasma-sprayed molybdenum layer on Cr-Mo steel. The boundary lubrication properties and the metal structure of the surface alloy have been investigated. The main points of this study are as follows. 1. The surface alloy is thick, about 5 mm, and of uniform composition.

2. The surface alloy shows good wear resistance and good seizure resistance, in the same level as electroplated chromium and plasma-sprayed molybdenum layers.

3. Good wear resistance is attributable to the metal structure which is composed of hard M₆C phase and soft α?Fe phase.

     

一种基于磁调制式电流比较仪的超导线接头电阻测试装置

本文介绍了一种超导线接头电阻的电流衰减法测试装置。本装置使用基于磁调制原理制成的电流比较仪对超导接头电流环中电流衰减过程进行测量,计算得到接头电阻。磁调制式电流比较仪为反馈控制系统,由磁调制器和控制电路组成。文中测试了电流比较仪性能,其分辨率优于1mA,40000秒内零点漂移小于0.2mA。最后对一个超导线接头样品进行了测量,其电阻小于3×10-14欧姆。     

激光强化40Cr合金钢表面磨损特性研究

采用CO2激光器及不同的激光强化参数对40Cr钢进行表面强化，并将其与热轧Q235钢组成摩擦副，在干摩擦条件下进行摩擦磨损试验，旨在确定合理的激光强化参数，为提高矫直辊耐磨性提供试验依据。通过对试验结果的定量分析得出，激光强化可以提高40Cr钢的耐磨性。采用扫描电镜对激光强化后的40Cr钢表面和磨损表面进行分析，发现激光强化后40Cr钢的金相组织主要是致密的马氏体，而且磨损表面比正常淬火的40Cr钢的表面光滑，仅产生一些微裂纹。     

NAK80模具钢表面激光熔覆钴基合金涂层的组织和摩擦磨损性能

采用激光熔覆方法在NAK80模具钢表面制备钴基合金熔覆层,用扫描电镜、X射线衍射仪分析了熔覆层的显微组织,通过干滑动摩擦试验研究了熔覆层的摩擦磨损性能,分析了其磨损机制,并用三维表面形貌仪观察磨损试样的表面形貌。结果表明:熔覆层的主要组成相为Cr23C6、Co3Mo2Si、MoC、FeCr和γ-Co;熔覆层由涂层与基体界面处的平面晶区、涂层中部的胞状树枝晶区和表层的网状等轴晶粒区组成;经激光熔覆处理后的NAK80模具钢表面硬度和耐磨性得到了显著改善,与NAK80模具钢相比,熔覆层表面的平均摩擦因数降低了约34%,比磨损率下降了约91.3%;熔覆层的磨损机制为粘着磨损和轻微的显微切削。