γ辐照接枝聚四氟乙烯特性和自由体积的关系

用正电子湮没技术研究在聚四氟乙烯照接技过程中的自由体积与正电子湮没寿命谱的关系。吸收剂量,吸收剂量率以及辐照环境等对接枝率有明显影响。而正电子湮没寿命可十分敏感地反映接枝率的变化。接技率的变化规律可用自由体积模型解释。用扫描电子显微镜对样品进行了观察比较。     

环氧树脂/贝壳粉复合材料的自由体积特性的正电子湮没研究

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.     

聚氯乙烯共混改性的正电子湮没研究

采用正电子湮没对添加聚丙烯酯类增韧粒子的聚氯乙烯共混材料进行了研究。结果表明,随ＡＣＲ比例的上升,ＰＶＣ结构中氯原子的强电负性受到削弱,ＰＶＣ主链区和结构改性剂中自由体积缺陷尺寸及数量增加。     

正电子湮没对研究热平衡点缺陷的应用

根据有关理论,在热平衡下单、双空位浓度C_(1v)、C_(2v)之间的关系为C_(2v)=1/2+Zexp(ΔS_(2v)K)exp(H_v~B/KT)(C_(1v))~2ΔS_(2v)是双空位间的组合熵。若不考虑三空位和更多空位的成团,则晶体内总空位浓度为C_v′=C_(1v)+2C_(2v)。假定晶体内还存在点缺陷(如某种间隙),由推导可得     

界面极化和自由体积尺寸对正电子素形成的影响

测量了高冲聚苯乙烯、高密度聚乙烯、低密度聚乙烯、聚丙烯和高冲聚苯乙烯分别与其它3种材料的共混物随时间测量的正电子湮没寿命谱。结果显示,所有测量样品的长寿命组分τ3值不随时间变化,而且大部分样品相应的长寿命强度I3也保持不变,仅有几种聚合物随时间呈现减小。I3的减小被认为是在测量过程中聚合物表面电场形成的结果,I3保持不变则与聚合物体内的自由体积尺寸和在测量过程中形成的界面极化密切相关。     

端羟基液体丁腈增韧环氧树脂体系的正电子谱学研究

采用正电子湮没技术研究了端羟基液体丁腈(HTBN)增韧环氧树脂(EP)体系的自由体积特性,证实了HTBN橡胶相与EP基体相界面过渡区域自由体积尺寸的大小和浓度与增韧效果相关.当HTBN的浓度为5%时,增韧效果最佳,相尺寸小,相界面过渡区域自由体积空穴尺寸与EP自身分子间自由体积空穴尺寸相当,增韧效果好;当HTBN的含量继续增加,分散相尺寸增大,过渡区域自由体积尺寸增加较快,增韧效果弱化.     

高冲聚苯乙烯-低密度聚乙烯的自由体积特征与其相溶性的关系

不同组成的高冲聚苯乙烯(HIPS)和低密度聚乙烯(LDPE)共混物的正电子湮没寿命谱被测量，结果表明HIPS和LDPE是不相溶共混物。在界面处，二组分的不相溶主要归因与一个组分没有足够大的自由体积孔穴尺寸容纳另一组分的侧基和分子链端基。另外，测量的自由体积分数产生的负偏差被认为主要由最长寿命强度I3所引起。     

5.0MeV和9.5MeV快中子辐照在GaAs中产生的辐射损伤的正电子湮没研究

采用正电子湮没寿命测量方法研究了５．０ＭｅＶ和９．５ＭｅＶ快中子辐照在ＧａＡｓ中产生的辐射损伤，实验结果表明１０＾１１－１０＾１２ｎ／ｃｍ＾２注量的中子辐照只产生单空位缺陷１０＾１３ｎ／ｃｍ＾３注量的中子辐照产生单空位和双空位缺陷，１０＾１２ｎ／ｃｍ＾２注量的９．５ＭｅＶ中子辐照的ＧａＡｓ经４５０－６２０℃退火产生三空位缺陷，产生的缺陷浓度随中子能量和注量的增大而增大，但缺陷产生率对中子注量更灵敏     

等离子体表面处理的正电子湮没研究

本文将正电子湮没技术用于等离子体喷涂的研究。测量了等离子体喷涂合金的缺陷以及缺陷的退火效应，观察到了正电子寿命的一些异常现象。     

Effect of curing agent polarity on water absorption and free volume in epoxy resin studied by PALS

Microstructure and water absorption were systematically studied by positron annihilation lifetime spectroscopy (PALS), gravimetric measurements and Differential Scanning Calorimetry (DSC) for epoxy resins DER331 (E51) cured with three different kinds of amine curing agents DDS, DDM and MOCA. Experimental results indicated that the water absorption as a function of immersed time could be well fitted to Fick’s second law. Based on the gravimetric measurement, we found that the equilibrium water sorption M_∞ and the diffusion coefficients D of the epoxy resins have an order: E51-DDS > E51-DDM > E51-MOCA, which indicated that the curing agent plays an important role in determining the content of the water absorbed. Positron experimental results showed that the o-Ps lifetime dramatically decreased with the immersed time from 0 to 6 h, which suggested that water molecules were filled into free-volume holes and the interaction between the water-polymer decreased the mobility of molecular chains. In order to deeply discern the influence of water absorption upon the free volume, the continuous lifetime analysis, i.e. the maximum entropy lifetime method (MELT) was employed to obtain the distributions of the ortho-positronium (o-Ps) lifetime and the of the free-volume holes. From MELT analyses, we found the existences of two the long-lived components (τ₃ and τ₄), which indicated that two kinds of different o-Ps states exist. The shorter long-lived component (τ₃) is related to the segmental packing density in local ordered region. Compared to dry sample, two peaks of the o-Ps lifetime and the free-volume hole in the wet samples all drift to low values, especially, this drifts is more marked for the water sorption occurring at higher temperature 75 °C. This fact suggested that when the epoxy resin is in the glassy state, the interaction between the water and matrix restricts the motion of segmental chains and prevents from the free-volume hole swelling.     

非晶态FeCuNbSiB系合金结构缺陷的正电子湮没研究

通过测量不同温度下退火的非晶合金Ｆｅ７３．５Ｃｕ１Ｎｂ３Ｓｉ１３．５Ｂ９和Ｆｅ７３．５Ｃｕ１Ｎｂ１．５Ｍｏ１．５Ｓｉ１３．５Ｂ９的正电子湮没有寿命谱，配合Ｘ射线衍射分析，研究了非晶合金结构缺陷随退火温度的变化。结果表明，非晶合金中存在两种类型的自由体积。正电子湮没有寿命随样品退火温度的变化曲线对应着结构弛豫，局域晶化和完全晶化阶段。     

超高分子量聚苯乙烯中的正电子寿命谱

以２，３－二氰基－２，３－二（ｐ－Ｘ取代苯基）丁二酸二乙酯（Ｘ＝Ｈ，ＣＨ３，Ｃｌ）为引发剂，用本体法合超高分子量聚苯乙烯，研究了不同引发剂对苯乙烯聚合物正电子湮没寿命谱的影响。通过比较聚合物的分子量和自由体积，表明引发剂的分解速率对自由体积有较大的影响，而浓度对自由体积的影响不大。     

D2钢电子束表面改性抗微动磨损性能研究

利用强流脉冲电子束（HCPEB）技术对D2钢进行了表面改性处理。结果表明，电子束聂击试样近表层组织结构发生了很大变化，且亚表层显微硬度明显增加。微动磨损结果显示，电子束处理可以改善D2钢抗微动磨损性能，预涂覆TiN和Cr层效果更明显。磨痕SEM分析表明，涂覆Cr层的样品微动磨损主要机制是粘着和氧化，而TiN涂层及电子束直接处理试样主要磨损机制则是表面疲劳微裂纹的扩展和断裂产生的剥落颗粒，在摩擦面造成磨粒磨损，同时也伴随轻微的粘着和氧化，其磨损机制相对比较复杂。     

Effect of electron beam radiation on the polypropylene/polyethylene blends: Radiation stabilization of polypropylene

The effect of incorporation of polyethylene in the polypropylene matrix, on the radiation sensitivity of polypropylene, has been investigated. The changes in the properties such as tensile strength, elongation at break, Shore D hardness, density and melt flow index were monitored as function of polyethylene content and electron beam radiation dose. A correlation between the mechanical properties and morphology of the irradiated polymeric blends has been observed, which has been explained on the basis of Fourier-transform infrared spectroscopy, scanning electron microscope and X-ray diffraction studies. Improvement in the mechanical properties of the polypropylene, irradiated to an optimum electron beam dose, could be achieved by blending it with polyethylene >20%. The optimum radiation dose was found to be dependent on blend composition and morphology, however, an absorbed dose of 250 kGy found to be effective enough to ensure good mechanical properties of the polypropylene/polyethylene blends.