The iron/electrolyte interface at extremely large current densities

Electrochemical Machining (ECM) is a technique to shape metal parts by anodic dissolution in neutral solutions (e.g. aqueous NaNO₃) at extremely large current densities of about 100 A cm⁻². We developed a capillary based microcell to simulate this process in the laboratory and to simultaneously analyze the products by UV-Vis spectroscopy. In addition, a brief overview of electrochemical micro techniques is given.     

光学非球曲面器件的超精密磨削加工技术研究

为磨削加工出高精度、高质量的光学非球曲面器件。详尽分析了砂轮的安装及半径等误差对零件加工精度的影响。设计研制出了一套非球曲面磨削系统 ,并用它进行了实验研究。实验结果表明 :要获得高精度的非球曲面器件 ,只有当金刚石砂轮的平均磨粒尺寸低于 10 μm ,并在采用较高的砂轮线速度和较小的进给量的情况下 ,才能实现光学非球曲面的超精密磨削加工 ,经过各种磨削参数的优化选择 ,其非球曲面最终的零件轮廓精度为 0 4 μm ,表面粗糙度Ra优于 0 0 1μm。     

基于纳米压痕测试的激光晶体光学加工性能研究

针对高功率固体激光器中使用的四类重要激光晶体(YAG、LBO、YCOB、KDP)元件,开展了晶体材料的光学加工性能研究.基于纳米压痕测试实验,研究了几种激光晶体材料在激光器实际使用晶向角度下的的表面力学特性差异,获得了载荷、弹性模量、压痕硬度等参数与压痕深度之间的变化规律;利用超景深显微镜及场发射扫描电镜观察了激光晶体表面的纳米压痕形貌,揭示了裂纹形貌随压力载荷的演变规律以及晶体材料力学各向异性现象.以熔石英材料为参照,从力学特性角度横向对比了几种激光晶体材料获得超光滑表面的光学加工难易程度.     

飞秒超短脉冲激光加热金属平面靶

从能流分析出发,对飞秒超短脉冲激光与金属平面靶相互作用的机制进行了理论研究,对其中主要物理过程的能流损耗作了详尽的分析,并根据一维,双温热扩散模型推导了自由电子温度随时间变化的函数关系.并从理论上推导了超短脉冲近似假设成立的脉宽范围和在此条件下自由电子所能达到的最高温度表达式.     

基于飞秒激光加工的微纳高温光纤振动传感器

报道了一种基于飞秒激光加工的微纳高温振动传感器。通过熔接形成单模光纤-空芯光纤-单模光纤的结构,利用单模光纤和空芯光纤在熔接面形成的菲涅尔反射,构成外腔式法布里-珀罗干涉仪(EFPI)。用飞秒激光烧蚀空芯光纤,形成悬臂梁结构。末端的单模光纤作为质量块,在受到振动时带动悬臂梁振动,使悬臂梁产生微弯,进而使EFPI腔长发生变化。实验结果表明,传感器的工作区域为20~300Hz,在100Hz时,0~3.01g范围内测得加速度分辨率为5×10-4 g,加速度响应灵敏度为129.6nm/g。传感器受温度影响小,腔长的温度交叉响应仅为0.225nm/℃,传感器可耐950℃高温冲击。     

位错型微机械可变光衰减器的研究

介绍了一种基于微机械技术实现的可变光衰减器,通过微电磁驱动器改变输入输出光纤之间的径向偏移量来调整衰减量。基于波导传输理论分析确定了器件的结构参量,并通过集成电路微细加工工艺实现了器件的制作和封装。测试结果表明,该可变光衰减器的插入损耗小于1dB,动态范围约35dB,工作电压小于5V,偏振相关损耗小于0.1dB,体积为20mm×15mm×8mm,有望为全光网提供一种低成本,高性能的光通信器件。     

Estimating the tensile strength of super hard brittle materials using truncated spheroidal specimens

New approaches need to be introduced to measure the tensile capacity of super hard materials since the standard methods are not effective. To pursue this objective, a series of laboratory tests were constructed to replicate the fracture mechanism of diamond-based materials. Experiments indicate that under a certain compressive test condition, stresses normal to the axisymmetric line in truncated spheroidal specimens (bullet-shaped specimens) are in tension contributing to the tensile fracture of the material. From experimental and numerical studies, it is concluded that semi-prolate spheroidal specimens can be used to determine precisely the tensile strength of brittle stiff diamond-like composites.     

Laser milling of martensitic stainless steels using spiral trajectories

A laser beam with sub-picosecond pulse duration was driven in spiral trajectories to perform micro-milling of martensitic stainless steel. The geometry of the machined micro-grooves channels was investigated by a specifically conceived Scanning Probe Microscopy instrument and linked to laser parameters by using an experimental approach combining the beam energy distribution profile and the absorption phenomena in the material. Preliminary analysis shows that, despite the numerous parameters involved in the process, layer removal obtained by spiral trajectories, varying the radial overlap, allows for a controllable depth of cut combined to a flattening effect of surface roughness. Combining the developed machining strategy to a feed motion of the work stage, could represent a method to obtain three-dimensional structures with a resolution of few microns, with an areal roughness S_a below 100 nm.     

Surface-plasmon wave at the planar interface of a metal film and a structurally chiral medium

The solution of a boundary-value problem formulated for a modified Kretschmann configuration shows that a surface-plasmon wave can be excited at the planar interface of a sufficiently thin metal film and a nondissipative structurally chiral medium, provided the exciting plane wave is p-polarized. An estimate of the wavenumber of the surface-plasmon wave also emerges thereby.     

Planewave remittances of an axially excited chiral sculptured thin film with gain

Reflectances and transmittances of chiral sculptured thin films (STFs) with gain qualitatively differ from those of lossless and lossy chiral STFs, chiefly at the edges of the Bragg regime, for normally incident plane waves. The difference is explained in terms of the photonic density of states. A chiral STF with a central twist defect exhibits a reflection hole if there is no gain and emits narrowband radiation if there is gain, provided the thickness is not large. This narrowband feature diminishes as the thickness increases, and is replaced by an ultranarrowband transmission hole only if the chiral STF has neither gain nor loss.