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41.
In this work a treatment for surface preparation to improve mechanical resistance in adhesive bonding of plastic composites reinforced with fibres and metallic material, has been performed using an excimer laser. The following couplings have been selected to reproduce joints commonly used in the aerospace and automotive industry: CFC (carbon fibre composite) with CFC, CFC with Al 2024T3, Al 99% with Al 99%, GFC (glass fibre composite) with zinc-coated sheet in low carbon steel FeP01. The surfaces have been prepared using an excimer laser, adopting several values of laser parameters. The obtained surfaces have been examined by optical and scanning electron microscope: comparative measures of wetting and roughness have been performed to obtain an accurate characterisation and to select the proper finishes suitable to improve the mechanical resistance of the joints. The results obtained show that laser treatment always improves the final resistance of the joint; notable increases, and no significant surface damages have been highlighted. Better results have been obtained with the Al 99% with Al 99% joints which, with a low number of pulses treatment, have shown an increase of mechanical resistance up to the 70%. 相似文献
42.
CAO JunCheng 《中国科学:信息科学(英文版)》2012,(1):16-26
The terahertz(THz)quantum cascade laser(QCL)is a coherent THz source based on intersubband transitions of unipolar carriers.As semiconductor lasers,THz QCLs are solid-state,electrically pumped,tunable,and can be easily integrated.This paper reviews the state of the art for the design,operation temperature,and output power of THz QCLs.Their applications in THz communication and imaging are also discussed. 相似文献
43.
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45.
随着国内厚板产量的增加,其市场竞争日趋激烈。为了更好的谋求发展,莱钢宽厚板厂在降低生产成本的同时,通过技术改造极大地提高产品的质量。因为板坯成材规格需要精确的长度数据,所以宽厚板板坯长度的精确测量就显得非常重要。本文主要介绍激光测速仪在轧机后测长系统中的应用。 相似文献
46.
以TI公司的MSP430F5438单片机为控制核心,结合步进电机和精密电位器WDD35D-4,实现了基于自由摆的平板控制与激光追踪系统。当摆杆摆角为45°~60°时,平板可以承载8枚一元硬币,并在5个摆动周期内维持稳定;当摆杆摆角为30°~60°时,固定在摆杆平板上的激光笔可以在15s内找到并跟踪1.5m远处的靶心。 相似文献
47.
Usha Varshney R. J. Churchill H. P. Groger A. I. Kingon 《Journal of Superconductivity》1989,2(2):293-304
Recent advances in the fabrication of high-T
c
superconducting thick films demand processing techniques which can eliminate film/substrate interdifiusion that occurs during subsequent post-annealing heat treatment after the film is deposited, thereby limiting the application of the thick films for devices. The present study evaluates laser annealing techniques for plasma-deposited Y-Ba-Cu-O thick films using a high-energy CO2 laser (10.6m) in a continuous wave mode. The results are compared with those obtained by conventional furnace annealing techniques necessary for post-heat treatment of as-deposited superconducting thick films. The high-T
c
superconducting phase is recovered by cationic diffusion during subsequent post-annealing heat treatment. Crystallographic phases and microstructural characterization have been performed using XRD, SEM, and EPMA analytical techniques. The significance of the technology lies in the elimination of film/substrate interdiffusion problems, thereby resulting in high-quality superconducting thick films. The technology will significantly reduce the post-annealing times usually required by conventional furnace annealing techniques. 相似文献
48.
lpcvd polycrystalline silicon films were deposited on thermally oxidized silicon as well as onlpcvd silicon nitride deposited on silicon. Acw argon ion laser was used to recrystallize the polysilicon film into large grains (grain size from 5μm to 40μm). Boron was then implanted and standard N-channel silicon gate process and N-channel metal gate process were carried out
to realisemosfets on this material. Channel mobilities upto 450 cm2/V-sec for electrons have been measured. This thin filmmosfet has a four-terminal structure with a top and a bottom gate and the influence of one gate on the drain current due to the
other gate has been investigated. Comparison of theI
D
v-V
D
curves of the devices with physical models was found in good agreement. 相似文献
49.
H. Dodiuk A. Buchman S. Kenig M. Rotel J. Zahavi T. J. Reinhart 《The Journal of Adhesion》1993,41(1):93-112
An excimer laser may be used for preadhesion treatment of aluminum alloys. This method presents an alternative to the use of ecologically unfriendly chemicals involved in conventional anodizing pretreatments.
Experimental results indicate that preadhesion laser surface treatment significantly improved the shear strength of modified-epoxy bonded aluminum specimens compared with untreated and anodized substrates. The best results were obtained with laser energy of about 0.2 J/Pulse/cm2 where single lap shear strength was improved by 600-700% compared with that of untreated Al alloy, and by 40% compared with chromic acid anodizing pretreatment.
The mode of failure changed from adhesive to cohesive as the number of laser pulses increased during treatment. The latter phenomenon has been correlated with morphology changes as revealed by electron microscopy, and chemical modification as indicated by Auger and infrared spectroscopy.
It can be concluded that the excimer laser has potential as a precise, clean and simple preadhesion treatment of Al alloys. 相似文献
Experimental results indicate that preadhesion laser surface treatment significantly improved the shear strength of modified-epoxy bonded aluminum specimens compared with untreated and anodized substrates. The best results were obtained with laser energy of about 0.2 J/Pulse/cm2 where single lap shear strength was improved by 600-700% compared with that of untreated Al alloy, and by 40% compared with chromic acid anodizing pretreatment.
The mode of failure changed from adhesive to cohesive as the number of laser pulses increased during treatment. The latter phenomenon has been correlated with morphology changes as revealed by electron microscopy, and chemical modification as indicated by Auger and infrared spectroscopy.
It can be concluded that the excimer laser has potential as a precise, clean and simple preadhesion treatment of Al alloys. 相似文献
50.
为了减少CO爆炸给国民经济造成的巨大损伤,提出了一种能够快速地监测环境空气中痕量CO的气体传感器。由于CO分子基频吸收谱带的吸收线强要比泛频带和组合频带的吸收线强高出2~3个数量级,选择激射中心波长为4.65μm中红外量子级联激光器(QCL)作为光源,同时再配合长光程Herriott气室提高了CO体积分数检测下限。同时,该传感器采用单光源双探测器差分光学结构,消除了电调制光源所带来的不稳定性。实验表明:该传感器CO体积分数检测下限为2×10-6,并且操作人员可以通过替换在不同波长下运行的中红外QCL来测量其它气体。 相似文献