共查询到19条相似文献,搜索用时 46 毫秒
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应用正电子湮没寿命谱(Positron annihilation lifetime spectroscopy,PALS)和正电子湮没符合多普勒展宽能谱(Coincidence Doppler broadening energy spectroscopy,CDBES)等正电子湮没谱学技术能从微观尺度上对聚合物-金属有机骨架材料杂化膜的微观结构进行表征。结果表明,随着金属有机骨架(Metal-Organic Frameworks,MOFs)添加量的增大,杂化膜中较小的和较大的自由体积的尺寸都减小了;杂化膜的正电子湮没符合多普勒展宽能谱显示,MIL-101(Material Institute Lavoisier-101)亚纳米粒子的加入使得正电子在聚二甲基硅氧烷(Poly(dimethyl siloxane),PDMS)氧原子上的偏向湮没效应减弱,部分正电子与来自MIL-101亚纳米粒子中金属原子的电子发生湮没,表明MOFs加入改变了聚合物基体自由体积周围的化学环境。 相似文献
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采用气流磨粉碎的方法制备了平均粒径在微米尺寸的三角蚌贝壳粉,将此贝壳粉与环氧树脂进行熔融共混得到一系列不同配比的复合材料.贝壳粉的有机质有助于提高两相间的相互作用,适量微米级贝壳粉的引入,在环氧基体和粒子相之间形成了一定数量的界面层,两相间有较强的界面亲和力,体系的自由体积尺寸与强度略有下降,中间寿命分量强度升高,这种较好的界面效应使得复合材料在受到外力作用时,断裂能和应力能够很好地通过界面传递到贝壳粒子上,从而使复合材料的性能提高. 相似文献
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用^22Na的正电子测量固体表面膜的寿命谱学技术 总被引:1,自引:0,他引:1
以薄金属膜为例,全面地阐述在等温和金属原子所占空间体积不变的条件下,用^22Na的正电子测量固体表面膜的寿命谱学法的原理和实用技术。 相似文献
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用1.15GeV的氩离子在室温下对二氧化硅玻璃样品进行了辐照,并通过正电子寿命测量技术研究了辐照后材料微观结构的变化。结果表明,在未辐照二氧化硅玻璃中有近81%的正电子是以正电子不的形式湮灭的;根据o-Ps的撞击湮灭寿命确定出未辐照样品的自由体积分布在0.02-0.13nm^3的区域里,平均自由体积半径为2.5nm。辐照后材料的自由体积分布函数变窄,峰位下降,显示样品经辐照后有密度增大的现象。随着剂量的增大,第二正电子寿命成分的强度逐渐增加,而相应于o-Ps的寿命成分的强度逐渐减小,这被认为是由于辐照产生的电离电子在自由体积中漫游,使正电子与这些漫游电子发生湮灭的几率增大,从而减小了正电子素的形成几率。 相似文献
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对LiF(F_2~+)和LiF:(OH)~-(F_2~+)色心晶体经液氮温度电子束辐照后,在室温下放置不同时刻的正电子湮没谱进行了研究,发现寿命谱中第一、第二成分的相对强度I_1、I_2及Doppler展宽谱中S参数随着F_2~+心的衰减呈有规律的变化,且与辐照剂量有一定关系。 相似文献
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聚乙烯基炭黑复合PTC材料的研究 总被引:1,自引:0,他引:1
研究了以两种不同的高密度聚乙烯为基体炭黑复合材料的电阻正温度系数(PTC)特性与填料浓度、加工工艺及后处理条件的关系,给出了最优化工艺条件。实验结果表明,两种聚乙烯/炭黑复合材料在材料的混炼和后处理工艺、以及室温电阻R0和PTC特性等方面都表现出较大的差异。具有高熔融指数的聚乙烯/炭黑复合体系(PE20/CB)具有良好的易混炼性和材料的均匀性,并且当炭黑含量在18%-26%范围内变化时,材料具有较理想的R0和PTC性能。低熔融指数聚乙烯/炭黑复合体系(PE2/CB)则在材料的稳定性和NTC现象的消除方面胜出一筹。 相似文献
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用正电子湮没技术研究了甲基丙烯酸甲酯-甲基丙烯酸共聚物(P(MMA-MAA))/梯形聚苯基硅倍半氧烷(PPSQ)原位共混体系的自由体积孔穴尺寸及浓度与其组成的关系。具有两种不同配比的该共混物的正电子寿命温度谱表明:该共混物有两种结构转变,即:Tb、Tg,因含5%PPSQ的共混试样C5中的自由体积分数较大,其Tp、T均小于含1%PPSQ的共混试样.C1。研究了热历史对P(MMA-MAA)/梯形PPSQ共混物结构的影响。还发现正电子平均寿命与自由体积分数有着类似的随温度变化的规律 相似文献
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用正电子湮没寿命研究了多掺杂和单掺杂Sn的InP在不同载流子浓度、电导率和位错密度下空位浓度的变化。 相似文献
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G. Consolati M. Mariani F. Quasso 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2009,267(15):2550-2553
Seven well characterized zeolites were investigated by positron annihilation lifetime spectroscopy. The lifetime spectra were analysed in four discrete components. The third one was associated with ortho-positronium annihilation in the channels, framed in terms of infinite cylinders. Differences between the radii determined from the positron annihilation technique and X-ray diffraction data were found and explained in terms of the physical structure of the channel. An analogous study on a high-silica NU-88 zeolite gave a value of 0.33 nm for the corresponding radius, in agreement with Ar and N2 adsorption data as well as with the catalytic behaviour of this zeolite in several acid catalyzed reactions. The longest lifetime component in NU-88 reveals the existence of mesopores, with average radius of about 1.8 nm, which could explain the importance of hydrogen transfer reactions in this zeolite. 相似文献
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正电子湮没寿命的多寿命成分分析结果通常给出了各成份的寿命τi及其零时相对湮没强度Ii(0),指出用零时相对或绝对湮没强度讨论分析结果不合理,只有正电子在各湮状态上的零时相对占有Ni(0)=τiIi(0)或占有率ni(0)=Ni(0)/∑Ni(0)才能明确的物理意义,因为正电子在态上的几率密度ni(0)与正电子湮没环境介质的结构特性密切相关,并以二态捕获模型为例对上述论点作了证明。 相似文献
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YIN Ze-Jie TANG Shi-Biao HUANG Huan ZHU Da-Ming 《核技术(英文版)》2005,16(6):341-346
The characterization of sulfonated polyetherketone (SPEK-C) films was investigated by using positron annihilation lifetime spectroscopy (PALS) and atomic force microscopy (AFM). It was found that free volume radius and intensity depend on the variation of sulfonation degree and solvent evaporation time of the films. Pore size and distribution determined from PALS and AFM measurements showed reasonable agreement. 相似文献
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In the present article, a positron annihilation spectroscopy investigation of VVER-440/230 weld materials is discussed. Important characteristics of metals such as Fermi energy, concentration of electrons in the conduction band, size and concentration of defects were experimentally determined for three model materials with higher level of copper (0.16 wt.%) and phosphorus (0.027-0.038 wt.%). The impact of neutron irradiation and subsequent annealing on crystal lattice parameters was investigated. The experiments with the angular correlation of positron annihilation radiation (ACAR) complement the published positron annihilation spectroscopy (PAS) studies of the radiation treated VVER materials as well as previous experiments on PRIMAVERA materials. The availability of the experimental reactor to prepare strong 64Cu positron sources provided for unique experimental conditions, such as good resolution of spectra (0.4 mrad) and reasonable short time of measurement (36 h). The present paper aims to contribute to further understanding of RPV (reactor pressure vessel) steels behaviour under irradiation conditions as well as annealing recovery procedures, which have already been applied at several VVER NPP units in Europe. 相似文献
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BaF2正电子寿命谱仪时间分辨率的改进 总被引:2,自引:1,他引:1
介绍了不同材料,不同形状的封装对BaF2晶体光收集的影响。使用聚四氟乙烯薄膜对BaF2晶体作伞状封装,光收集效果较好,在此条件下,常规正电子湮灭寿命谱仪的时间分辨率在^22Na能窗下达到180ps。 相似文献
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M. Eldrup Meimei Li L.L. Snead 《Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms》2008,266(16):3602-3606
Positron annihilation lifetime spectroscopy measurements were performed on neutron-irradiated low carbon arc cast Mo. Irradiation took place in the high flux isotope reactor, Oak Ridge National Laboratory, at a temperature of 80 ± 10 °C. Neutron fluences ranged from 2 × 1021 to 8 × 1024 n/m2 (E > 0.1 MeV), corresponding to displacement damage levels in the range from 7.2 × 10−5 to 2.8 × 10−1 displacements per atom (dpa). A high density of submicroscopic cavities was observed in the neutron-irradiated Mo and their size distributions were estimated. Cavities were detected even at a very low-dose of ∼10−4 dpa. The average size of the cavities did not change significantly with dose, in contrast to neutron-irradiated bcc Fe where cavity sizes increased with increasing dose. It is suggested that the in-cascade vacancy clustering may be significant in neutron-irradiated Mo, as predicted by molecular dynamics simulations. 相似文献