U(DBM)_4,U(TFBA)_4和渗杂U(Ⅳ)的Th(DBM)_4,Th(TFBA)_4单晶中U(Ⅳ)的光谱研究

本工作成功地制备了U(DBM)_4,U(TFBA)_4单晶和渗杂U(Ⅳ)的Th(DBM)_4,Th(TFBA)_4单晶(DBM为二苯酰甲烷,TFBA为4,4,4三氟-1-苯基-1,3丁二酮)。其DBM单晶是平行六面体,极不稳定,在光和热的作用下很易氧化和分解。结晶学研究表明,单晶中含有苯分子,是一种“溶剂化物”。其TFBA单晶是轻度畸变的反四棱锥体,性能稳定,位置对称是S_4。     

金单晶膜靶的制备

为了用单晶体中的阻塞效应来研究~(197)Au(~(12)C,f)反应产生的复合核~(209)At的寿命,需要很薄(≤1mg/cm~2)、厚度均匀、无针孔、表面平整如镜的单晶金靶。采用机械抛光、电解抛光或化学腐蚀抛光等减薄法都不行。为此我们以云母为底晶,真空蒸发银-金复膜的方法来制备符合这种要求的单晶膜。     

细颗粒电子灵敏乳胶的制备方法和性能

本文介绍了适用于电子显微镜放射自显影的HW-4型与HW-3型电子灵敏细颗粒乳胶的制备方法及其主要性能,并与英国依尔福(Ilford)L4型乳胶作了比较。HW-4型乳胶的溴化银颗粒分布及其主要性能与L4型乳胶相似,HW-3型乳胶溴化银颗粒则更小。     

用正电子湮没技术研究SrTiO_3的氧缺位

钛酸锶(SrTiO_3)单晶可作为红外光学材料和人工宝石,还可作为电极材料,在光的作用下分解水产生氢气,是开发太阳能源的研究途径之一。本工作测定了SrTiO_3单晶在具有不同氧缺位浓度下的正电子湮没寿命谱和多普勒增宽谱。     

无依托单晶金膜

我校束箔光谱组在研究束箔相互作用引起的原子和原子核极化机制的工作中,需要厚度仅500A的无依托单晶金靶,而且要求其表面平整、连续性好。我们采用异质外延法。首先在云母基板上外延制备单晶银膜,继而以单晶银膜为衬底,蒸发黄金,制备单晶金膜。最后,用酸蚀法使银腐蚀掉,获得无依托单晶金膜。     

化合物半导体GaAs CdTe核辐射探测器

叙述了半绝缘砷化镓体单晶表面势垒探测器和碲化镉单晶表面势垒探测器的制备工艺、特性以及它们对低能γ射线~(125)I,~(241)Am,~(57)Co在室温下工作时的能谱响应。着重讨论了欧姆接触所引起的正向电阻的大小对探测器性能的影响。讨论了制备工艺中表面纯化和老     

CdZnTe像素探测器的制备与表征

本文采用CdZnTe单晶制成像素探测器,并对其能谱响应特性及均匀性进行了系统表征。通过I-V和能谱响应测试,测定了晶体的电阻率和载流子迁移率与寿命的积,并用红外透过显微成像观察了晶体内Te夹杂的分布特性。采用光刻、剥离和真空蒸镀技术,在CdZnTe晶片上制备了8×8的像素电极,用丝网印刷和贴片技术通过导电银胶实现像素电极与读出电路的准确连接,制备出CdZnTe像素探测器。对像素探测器的测试表明,-300V下单像素最大漏电流小于0.7nA,对241 Am 59.5keV的能量分辨率可达5.6%,优于平面探测器。进一步分析了晶体内Te夹杂等缺陷对探测器漏电流和能谱响应特性的影响规律,结果表明,Te夹杂的聚集会显著增加漏电流,并降低探测器的能量分辨率。     

红外光谱法在选择锗(锂)半导体探测材料方面的应用

本工作用红外光谱法,在4000—200 cm~(-1)区域内,对一百多块单晶材料进行了测试。通过对影响单晶透过率变化因素的研究,总结出一些规律性,作为研制高分辨锗(锂)探测器的依据。井给出用红外光谱法选择后的单晶制得的锗(锂)探测器能量分辨率的实验结果。     

中子应力谱仪常用聚焦单色器的模拟与比较

用蒙特卡罗中子射线追踪程序McStas对中子衍射应力谱仪单色器部件进行模拟优化:以Cu(220)比较了单色器起飞角和准直系统对样品处中子注量率、分辨率的影响;计算得到给定条件下单色器最佳单晶条数和镶嵌度;单晶条倾角精度建议好于0.1°;计算了Cu(222)、(220)和(002)在不同起飞角情况下获得的中子注量率;相同条件下,Cu和Ge常用晶体单色器中以Cu(220)获得的中子注量率最大,而Cu(222)获得的波长分辨率最佳。     

化合物半导体GaAs CdTe核辐射探测器(英文)

叙述了半绝缘砷化镓体单晶表面势垒探测器和碲化镉单晶表面势垒探测器的制备工艺、特性以及它们对低能γ射线~(125)I,~(241)Am,~(57)Co在室温下工作时的能谱响应。着重讨论了欧姆接触所引起的正向电阻的大小对探测器性能的影响。讨论了制备工艺中表面纯化和老化对表面势垒探测器性能的影响,同时研究了欧姆接触制备工艺和所选用来制备欧姆接触的材料如Ni-Ge-Au,In-Ge-Ag等对探测器性能的影响。     

The electrical conductivity of carbon nanotube sheets by ion beam irradiation

A method for improving the electrical conductivity of carbon nanotube (CNT) sheets by ion beam irradiation is reported. CNT sheets prepared by a vacuum filtration method were irradiated by Ar and H ion beams at different temperatures. The electrical conductivity of the irradiated CNT sheets at a temperature of 800 K can be improved. The conductivity improvement can be ascribed to the formation of covalent bond crosslinks between CNTs induced by the ion beam irradiation at the elevated temperature.     

Critical strains and necking phenomena for different steel sheet specimens under uniaxial loading

When defining ultimate loads or failure criteria for shells, vessels and containment liners, for instance, reference will be made to critical strains of the material under consideration.In general the critical strains are derived from uniaxial tensile test results obtained with rods.The actual deformation behaviour of sheets (plate and shell type structures), however, differs considerably from the uniaxial rod behaviour.From various tests - along with theoretical investigations - it was found that for membrane or even bending stressed sheets higher ultimate strains are reached.The typical strain behaviour caused by increasing load starts with uniform strain distribution over the specimen length and finally ends with localized necking.As “critical strains” the well known uniform elongation strain and the ultimate strain are defined.For sheets in addition the quasi uniform elongation strain has been introduced in this paper.Whereas for rods under tension localized necking is directly following the uniform straining, tests with sheets show a so-called diffuse necking behaviour before localized necking starts.As a consequence the deformation capacity of steel sheets turns out to be significantly higher than relying on the data from standard tension tests with rods.     

聚乙烯的共混－辐射改性

采用共混，辐射，化学后处理的方法，对低密度聚乙烯（ＬＤＰＥ）进行表面改性，并对改性后ＬＤＰＥ片材的表面润湿性（接触角）进行了测量和分析。当ＬＤＰＥ中共混乙烯－乙酸乙烯共聚物（ＥＶＡ）及衣康酸（ＩＡ）时，辐射后用醇碱处理，改性效果较好。     

接枝型耐紫外线老化乙烯-乙酸乙烯酯共聚物的制备及其性能研究

摘要将4-丙烯氧基,2-羟基二苯甲酮（AHB）作为紫外光吸收剂与乙烯-乙酸乙烯酯共聚物（EVA）以不同比例共混后通过平板硫化机压成1mIn厚的的片材,空气氛围中,以4．4×10^5kGy·h^-1的剂量率对其进行辐照,将AHB以化学键方式接枝固定在EVA中。采用GB／T1040．2006方法考察共混片材的机械性能,FT-IR光谱表征共混膜中AHB的存在,紫外光谱考察紫外线吸收性能,光学显微镜观察片材拉断后的截面形貌。结果表明,随AHB的含量从0phr增加至2phr,材料的断裂伸长率从586％上升至772％;同时抗张强度从32．1MPa下降至22．4MPa;添加1份（每100份聚合物）紫外吸收剂的EVA抗紫外老化性能显著优于未添加的样品。     

A novel approach of deposition for uniform diamond films on circular saw blades

Uniform diamond films are highly desirable for cutting industries,due to their high performance and long lifetime used on cutting tools.Nevertheless,they are difficult to obtain on cutting tools with complicated shapes,greatly limiting the applications of diamond films.In this study,a novel approach of deposition for uniform diamond films is proposed,on circular saw blades made of cemented carbide using reflectors of brass sheets.Diamond films are deposited using hot filament chemical vapor deposition (HFCVD).A novel concave structure of brass sheets is designed and fabricated,improving the distribution of temperature field,and overcoming the disadvantages of the conventional HFCVD systems.This increases the energy efficiency of use without changing the structure and increasing the cost of HFCVD.The grains are refined and the intensities of diamond peaks are strengthened obviously,which is confirmed by scanning electron microscopy and Raman spectra respectively.     

Effects of Grain Morphology and Texture on High Temperature Deformation in Oxide Dispersion Strengthened Ferritic Steels

Oxide Dispersion Strengthened (ODs) ferritic steel is the promising candidate alloy for long-life core materials of fast reactor. A series of experiments, such as tensile tests, creep rupture tests, texture measurements and microstructure observations, are performed for the fabricated sheets of ODs ferritic steel with simulating type of morphology and also for the cladding tube in order to clarify the origin of the peculiar strength anisotropy of the cladding tube: degraded creep rupture strength in hoop direction. From these experiments, effects of grain morphology and texture on deformation of ODs ferritic steels are evaluated.

The sheets and the cladding tube have strong texture of {001}?110? and {111}?110?, respectively. In longitudinal and transverse directions of the sheets, strength level is significantly different from each other, but crystallographic orientation is almost equivalent. From that finding, it is considered that strength anisotropy of the cladding tubes is not attributed to the texture. From the results of micro structure analysis, it is concluded that origin of the degraded creep rupture strength in transverse hoop direction of the cladding tube comes from the grain boundary sliding at the large tilt angles.     

Numerical simulation of carbon arc discharge for graphene synthesis without catalyst

In this study, graphene sheets are prepared under a hydrogen atmosphere without a catalyst, and the growth mechanism of graphene by direct current arc discharge is investigated experimentally and numerically. The size and layer numbers of graphene sheets increase with the arc current.Distributions of temperature, velocity, and mass fraction of carbon are obtained through numerical simulations. A high current corresponds to a high saturation temperature, evaporation rate, and mass density of carbon clusters. When the carbon vapor is saturated, the saturation temperatures are 3274.9, 3313.9, and 3363.6 K, and the mass densities are 6.4×10~(22),8.42×10~(22), and 1.23×10~(23) m~(-3) under currents of 150, 200, and 250 A, respectively. A hydrogen-induced marginal growth model is used to explain the growth mechanism. Under a high current, the condensation coefficient and van der Waals force increase owing to the higher saturation temperature and mass density of carbon clusters, which is consistent with experimental results.     

Conversion of coalbed methane surrogate into hydrogen and graphene sheets using rotating gliding arc plasma

The use of atmospheric rotating gliding arc(RGA) plasma is proposed as a facile, scalable and catalyst-free approach to synthesizing hydrogen(H_2) and graphene sheets from coalbed methane(CBM). CH_4 is used as a CBM surrogate. Based on a previous investigation of discharge properties, product distribution and energy efficiency, the operating parameters such as CH_4 concentration, applied voltage and gas flow rate can effectively affect the CH_4 conversion rate,the selectivity of H_2 and the properties of solid generated carbon. Nevertheless, the basic properties of RGA plasma and its role in CH_4 conversion are scarcely mentioned. In the present work, a 3D RGA model, with a detailed nonequilibrium CH_4/Ar plasma chemistry, is developed to validate the previous experiments on CBM conversion, aiming in particular at the distribution of H_2 and other gas products. Our results demonstrate that the dynamics of RGA is derived from the joint effects of electron convection, electron migration and electron diffusion, and is prominently determined by the variation of the gas flow rate and applied voltage. Subsequently,a combined experimental and chemical kinetical simulation is performed to analyze the selectivity of gas products in an RGA reaction, taking into consideration the formation and loss pathways of crucial targeted substances(such as CH_4, C_2H_2, H_2 and H radicals) and corresponding contribution rates. Additionally, the effects of operating conditions on the properties of solid products are investigated by scanning electron microscopy(SEM) and Raman spectroscopy. The results show that increasing the applied voltage and decreasing CH_4 concentration will change the solid carbon from its initial spherical structure into folded multilayer graphene sheets, while the size of the graphene sheets is slightly affected by the change in gas flow rate.     

Measuremeints on Current Sheets in Plasmas

The acceleration of a gas undergoing ionization in a crossed electric-magnetic field leads to the formation of current sheets similar to those observed in coaxial plasma guns. The dynamics of such sheets is of great interest to workers in plasma physics in view of their application to controlled thermonuclear fusion experiments and to space propulsion. In the present paper a detailed mapping of the magnetic field in the vicinity of a current sheet is described. Conventional small search coils are used for the detection of this field. From the configuration of this field an attempt is made to understand the processes taking place in the sheet. All of the experiments described in the paper are performed on a plasma coaxial gun of mall aspect ratio.     

X-ray microtomography analysis and Molecular Dynamics calculations to understand the dynamic damage process in metals

Dynamic ductile damage has been created by a laser driven shock. The study of these processes consists of predicting it and analysing spatial distributions of pores observed in the target. The challenge is to use the Molecular Dynamics to calculate the propagation of shock waves in ultra thin sheets of metal as well as to compare results with ESRF’s X-ray microtomography.