离子束在材料改性中的应用

引言离子束固体材料改性是核技术应用的一个重要方面。它是利用小型加速器将所需的离子加速并注入到材料的近表层,从而改变材料表层的物理、化学和机械性质的一种新技术,通常称为离子注入技术。国外在六十年代初,离子注入材料改性的研究是从半导体开始的。     

离子注入在陶瓷材料中的应用

随着科学技术的发展,离子注入的应用范围在不断扩大.它除了广泛应用于半导体、金属材料的表面改性外,在加工绝缘材料(如玻璃、陶瓷和高分子聚合物等)方面也表现出有一定的发展潜力,有可能在光的波导、磁泡储存,铁电陶瓷、光敏陶瓷、高温陶瓷、表面导电聚合物和表面催化等方面发挥作用.本文对离子注入在陶瓷材料中的一些应用及最近取得的一些成果作一综述.主要包括离子注入陶瓷材料的表面改性、离子注入合成陶瓷材料和离子轰击加强金属(陶瓷)/陶瓷界面的“缝合”三个方面. 一、离子注入陶瓷材料的表面改性 陶瓷泛指整个硅酸盐材料,是无机非金…     

离子注入强化金属表面的作用机制

离子注入技术是将高能束流的离子(一般为几十一几百keV)注入到固体材料的表面,从而改变材料表层的物理、化学和机械性能的一种新方法.早期,离子注入技术用于半导体器件的掺杂,大大促进了微电子学的发展.近年来,离子注入技术迅速地扩大应用到固体物理和材料科学的许多领域,如非晶态、超导、磁泡材料、集成光学材料等,成为一种重要的研究手段,并获得日益广泛的应用. 离子注入技术作为金属表面处理的一种新方法,可直接用于改善工程材料表层的耐磨损和耐腐蚀能力.与通常的离子氮化、离子镀膜和溅射镀膜不同,注入层与基体金属没有明显的分界面,…     

金属与陶瓷的离子束表面改性

近年来,用荷能离子束对金属和陶瓷材料的近表面区进行改性的研究工作得到很大的发展.离子束注入和离子束混合使材料的近表区结构、组成均发生变化,还因离子辐照引起碰撞级联造成缺陷,这些作用最终影响到材料的性能。离子注入固体或薄膜的表面,不仅是使其改性的重要手段,而且也是材料基础研究的一种理想的工具。本文综述了(i)离子注入金属与陶瓷引起的近表面区的各种变化;(ii)由此而导致的性能改变;(iii)离子束混合效应。     

等离子体源离子注入——一种材料表面改性的新技术

本文介绍了近几年发展起来的一种新型离子注入技术——等离子体源离子注入（Ｐｌａｓｍａ Ｓｏｕｒｃｅｌｏｎ　ｌｍｐｌａｎｔａｔｉｏｎ，简称 ＰＳＩＩ）——的原理、装置和应用．除可应用于半导体外，这一技术应可满足金属或非金属材料表面改性的需要．实践证明它是一种极有开拓前景的离子注入技术．     

阴极真空弧离子源的研制

为发展金属离子束材料表面改性技术的工业应用，北师大低能核物理所研制成阴极真空弧离子源和离子注入装置．简要介绍该设备的结构、原理和性能． The cathode vacuum arc ion source and ion implantation facility have been developed in our institute for industrial application of surface modification of materials. In this paper the principle structure and performance of these facilities were described.     

等离子体源离子注入（I）──原理和技术

等离子体源离子注入（ＰＳＩＩ）是用于材料表面改性的一种新的、廉价的、非视线技术，它消除了一般束线离子注入（ＩＢＩＩ）所固有的视线限制，克服了保持剂量问题，使注入装置变得简单和价廉。介绍了ＰＳＩＩ过程、装置和基本物理与技术问题，也介绍了在美国威斯康辛大学和哈尔滨工业大学ＰＳＩＩ研究室中进行的ＰＳＩＩ技术研究及其工业应用的初步结果。     

等离子体源离子注入（Ⅰ）—原理和技术

等离子体源离子注入（ＰＳＩＩ）是用于材料表面改性的一种新的、廉价的、非视线技术。它消除了一般束线离子注入（ＩＢＩＩ）所固有的视线限制，克服了保持剂量问题，使注入装置变得简单和价廉。介绍了ＰＳＩＩ过程、装置和基本物理与技术问题，也介绍了在美国威斯康辛大学和哈尔滨工业大学ＰＳＩＩ研究室中进行的ＰＳＩＩ技术研究及其工业应用的初步结果。     

低温等离子体对氟橡胶表面改性

低温等离子体技术(Low Temperature Plasma technique，LTP)是近年来发展较快的一门材料表面改性技术，本研究采用LTP技术对氟橡胶进行表面改性，考察了改性后的氟橡胶应用于三氨基三硝基苯炸药(TATB)为基的PBX体系中(TATB-PBX)对PBX力学性能的影响，结果表明将LTP技术运用到PBX中，对提高PBX的综合性能是行之有效的。     

MEVVA源离子注入金属表面优化应用

针对几种钢部件的磨损、耗能问题，本课题组应用ＭＥＶＶＡ源离子注入技术，对Ｈ１３、Ｔ１０Ａ、ＨＳＳ、Ｃｒ１７等钢材料进行了离子注入表面改性研究，得出了提高钢耐磨性和改善其固体自润滑的一套有用的离子注入工艺． Ion implantation with MEVVA source has been investigated on several types of steel such as H12,T10,HSS,Cr17 and so on,and the real industrial parts have been tested too...     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.     

A novel methodology for photometric compensation of projection display on patterned screen

We propose a novel methodology based on the projector-camera (ProCam) system to address the photometric compensation issue for the projection display on the patterned screen.The patterned screen is treated as the combination of a perfect white screen and a color modulator.The perfect white screen is used to automatically and accurately characterize the ProCam system offline using the polynomial model,and the parameters of the color modulator can be efficiently recovered by employing only two gray images based on the linear reflectance model.The experimental results show that the color artifacts of the display image can be greatly improved with this methodology,which demonstrates its feasibility and validity in the photometric compensation.     

Direction-of-arrival estimation using matrix spatial prefiltering approach

An approach to direction-of-arrival （DOA） estimation for multiple narrowband farfield signals is proposed. The technique uses a novel matrix spatial prefiltering approach. Specifically, a matrix filter is designed to spatially filter the incoming data snapshots. The un-wanted components arriving from the stopband angular sectors are attenuated and the desired components from the angular sector of interest pass with minimal distortion. The matrix filter spatially filters the element-space data and the output reserves the element-space data property, which makes it very useful by passing sensor data through a spatial prefilter prior to applying many other array processors to attenuate interferences and improve system performance. Several examples of DOA estimation problem are presented to illustrate the performance of the proposed spatial prefiltering approach. Results of simulation and real data show that the pre-filter can efficiently attenuate the spatial interferences and significantly improve the estimation and resolution capability of DOA estimators at low signal-to-noise ratios for the sources located inside the passband sector. In addition, the use of spatial prefilter makes it possible to estimate DOAs for multiple sources more than the number of the elements of an array.     

Quantum efficiency calibration of opto-electronic detector by means of correlated photons method

A new calibration method of detectors can be realized by using correlated photons generated in spontaneous parametric down-conversion (SPDC) effect of nonlinear crystal.An absolute calibration system of detector quantum efficiency is performed.And its principle and experimental setup are introduced.A continuouswave (CW) ultraviolet (351 nm),diode-pumped,frequency-doubled,and solid-state laser is used to pump BBO crystal.The quantum efficiencies of the photomultiplier at 633,702,and 789 nm are measured respectively.The coincidence peaks are observed using coincidence circuit.Some measurement factors including the filter bandwidth of trigger channel,the detector position alignment and polarization of the pump light are analyzed.The uncertainties of this calibration method are also analyzed,and the relative uncertainties of total calibration are less than 5.8%.The accuracy of this method could be improved in the future.