快速电子辐照F-40的ESR和DSC研究

室温时空气中辐照F-40样品中残存有链侧和链端过氧化自由基,这些自由基在室温下衰变缓慢.DSC研究表明,F-40样品熔融温度T_m随辐照剂量的增加而下降,本文用聚合物片晶熔融的一般模型加以解释.     

γ辐照对掺Er硅酸盐玻璃吸收和发光特性的影响

用传统的高温熔融法熔制了一系列掺Er硅酸盐玻璃, 并测试了这些样品经5 kGy γ 射线辐照前后紫外至近红外的吸收和荧光光谱. 实验结果表明, 辐致暗化效应使得玻璃材料中形成了大量色心, 导致在400 nm附近出现强吸收带, 其尾端延伸至近红外区. 辐照产生的新能带增加了基质与Er³⁺ 特定能级(如²H_11/2, ⁴S_3/2及⁴F_9/2等) 之间的能量传递, 从而使辐照后的样品荧光寿命减小, 且在相同激发条件下荧光强度下降. 室温下辐照样品在荧光测试过程中出现了漂白现象.     

离子辐照对聚苯乙烯低温导电特性的影响

室温下用3MeV的硅离子对聚苯乙烯(PS)进行辐照,对辐照后的样品在室温至液氮温度范围的导电特性进行了测量.结果表明,当辐照剂量在1×1012cm-2附近,PS的室温电阻发生突变.随着温度的降低,PS电阻增大,在低辐照剂量下,电阻在155K附近急剧增加.对于高辐射剂量样品,在较高的温度下呈现热激活导电,在低温下电子通过隧穿传导.分析认为,PS电阻随温度的变化是由于不同剂量辐照离子在聚合物中形成的对电子传导有贡献的导电中心密度不同.通过拟合样品的渗流临界特性,分析了样品电阻随辐照剂量的变化 关键词： 聚苯乙烯 硅离子辐照 低温导电     

高能氩离子在聚苯乙烯中的电子能损效应研究

用1.4GeV氢离子对多层堆叠的厚约53m的聚苯乙烯薄膜在室温和真空条件下进行了辐照;对辐照后的样品进行了从红外到紫外的光吸收测量.测量结果显示,材料经高能红离子辐照后发生化学降解,降解过程强烈依赖于电子能损;在能量沉积密度很高的径迹芯中,分子主链和苯环均遭到破坏;在电子能损高于0.77keV/nm时有炔基产生.     

紫外光辐照镍系聚丁二烯的NMR研究

用¹H NMR谱,¹³C NMR谱,二维谱,X-射线衍射等方法研究了镍系高顺式聚丁二烯橡胶(NiBR) 在强紫外（UV）光辐照前后的微观结构变化和分子运动情况. 分析表明NiBR样品随着UV光辐照时间的增加,侧链乙烯基端基双键比主链端基双键更易发生氧化反应;并且随着NiBR样品的各基团的半峰宽值逐渐增加,表明NiBR在UV辐照过程中发生了部分交联反应. 样品的X-射线衍射谱图中结晶峰强度随UV光辐照时间的增加逐渐降低,表明样品的晶形无序程度增加了. 自旋-晶格弛豫时间（T₁）和自旋-自旋弛豫时间（T₂）值给出了有关NiBR辐照前后分子运动变化的信息.      

低温下质子辐照对Y-Ba-Cu—O和La-Sr-Cu-O性质的影响

使用外延YBa₂Cu₃O₇薄膜,测量了低温下(液氮或液氦温度)质子辐照对样品输运性质的影响。不仅观察到由低温辐照引起的样品超导转变温度T_c下降及电阻率P上升,还观察到dp/dT的上升和发生金属至非金属的相变。经室温热循环的样品显示出强烈室温退火效应。近60％由辐照引起的样品电阻升高和T_c下降可以得到恢复,并可伴随发生非金属至金属的相变,在La-Sr-Cu-O薄膜的低温辐照实验中观察到了类似的室温退 关键词：     

不锈钢辐射损伤随温度和剂量的变化(英文)

用重离子辐照模拟和正电子湮没寿命技术研究了改进型316L不锈钢在21 和33 dpa辐照剂量下的辐照损伤在室温到802 °C温度范围随辐照温度变化和室温下0—100 dpa剂量范围随辐照剂量变化. 在580 °C左右实验观察到辐照肿胀峰， 在21 和33 dpa辐照剂量下相应的空位团分别由14和19个空位组成， 尺度分别为0.68 和0.82 nm. 空位团尺寸随辐照剂量增加， 在100 dpa时空位团由8个空位组成， 尺度为0.55 nm. 实验结果表明， 在改进型316L不锈钢中辐照损伤随辐照温度变化更灵敏.     

Kr2+辐照导致的Ca8LnNa(PO4)6F2(Ln=La,Nd和Sm)磷灰石结构陶瓷材料的非晶转变

采用传统固相烧结法成功制备出磷灰石结构材料Ca₈LnNa（PO₄）₆F₂（Ln=La,Nd和Sm）,并通过常规X射线衍射（X-ray diffraction,XRD）进行表征确定三种样品都为单一相。在室温条件下用800 keVKr2+对三种样品进行辐照实验,辐照后的样品利用掠入射X射线衍射（grazing incidence X-ray diffraction,GIXRD）进行表征获取其表面辐照损伤层的结构信息。发现在实验辐照剂量范围内（1.0×1014~7.0×1014cm-2）三种样品都发生了从晶体结构到非晶结构的转变,不过三种样品的抗辐照非晶性能却有差异,抗辐照非晶能力大小关系是Ca₈LaNa（PO₄）₆F₂ > Ca₈NdNa（PO₄）₆F₂ > Ca₈SmNa（PO₄）₆F₂。这是由于在Ca₈LnNa（PO₄）₆F₂中,当镧系核素半径越小时,将有更大概率占据Ca（2）位置与F形成比Ca-F更弱的离子键。因此,镧系核素半径越小,辐照下将有更多的点缺陷保留下来,更容易发生非晶相变。     

电子束在VO_2薄膜中引起的价态、相结构和光学性能的改变

利用能量为 1 .7Me V,注量分别为 1 .2 5× 1 0 13 /cm2 ,1 .2 5× 1 0 14 /cm2 ,1 .2 5× 1 0 15/cm2 的电子束辐照 VO2 薄膜 ,采用 XPS,XRD等测试手段对电子辐照前后的样品进行分析 ,并研究了电子辐照对样品相变过程中光透射特性的影响。结果表明电子辐照引起 VO2 薄膜中 V离子出现价态变化现象 ,并使薄膜的 X射线衍射峰发生变化。电子辐照在样品中产生的这些变化显著改变了 VO2 薄膜的热致相变光学特性     

Nd2-xSrxNiO4多晶输运性质的研究

研究了Nd2-xSrxNiO4多晶的输运性质.0< x0.5样品低温下的电阻率很好地满足变程跳跃公式,0.8x1.1样品在室温以上呈现金属性行为,随着温度降低出现金属-绝缘体转变,x=1.4样品的金属性从室温开始一直保持到14K. 用变程跳跃机制很好地解释了x=0.33样品的热电势-温度关系曲线.     

Electron Spin Resonance study of gamma irradiated MA-AMPS copolymer

Electron Spin Resonance (ESR) spectra of gamma irradiated methylacrylamide-2-acrylamido-2-methyl-propanesulphonic acid (MA-AMPS) are recorded to identify the radical species formed during the irradiation of the copolymer. The ESR spectrum observed for irradiated MA-AMPS copolymer at liquid nitrogen temperature (LNT) (77 r K) is an asymmetric triplet; while the spectrum observed at room temperature (RT) is a quintet. The intensity distribution of both the spectra deviated appreciably from the expected theoretical values. Computer simulations are employed to analyze the ESR spectra observed at different temperatures. The triplet spectrum observed at LNT is simulated to be a superposition of component spectra arising from macroradicals of the type～CH 2 - \dot {\rm C} H-CH 2 ～ (I), radicals of the type \dot {\rm C} H 2 SO 3 H (II), and peroxy radicals (III). In contrast, the RT spectrum is simulated to be a superposition of component spectra arising due to radicals I, II, III together with the component quartet assigned to methyl radicals ( \dot {\rm C} H 3 ). The formation of such free radicals in irradiated copolymer is discussed.     

Characteristics of splat-cooled Sn- \hbox{Bi}_{5} - \hbox{Pb}_{\bi x} alloys

A Sn-5 \, wt.%Bi binary master alloy was prepared by melt spinning. Ternary alloys with different Pb contents ( x = 0 - 2.5\,\hbox{wt.}\% ) were prepared with the same technique. All the alloys were irradiated with 1.2\,\hbox{MGy} \gamma -radiation at room temperature. The internal friction, Q^{-1} , the thermal diffusivity D_{\rm th} and the Young's modulus Y obtained by applying the resonance technique were measured at room temperature before and after irradiation. DTA thermograms and X-ray diffraction patterns were obtained for the tested alloys. The results showed a remarkable dependence on both the amounts of the ternary addition and irradiation with \gamma -rays. The observed changes in the measured values were attributed to a composition inhomogeneity, caused by the distribution mode of the third element in the matrix and the defects induced by irradiation.     

TIME DECAY BEHAVIOR OF FULLERENE-C60 STUDIED BY TIME-RESOLVED PHOTOLUMINESCENCE

The time-resoved photoluminescence spectra of C₆₀ have been studied from toluence solution at room temperature and from thin film at both room temperature and 77K. A photoluminescence peak at about 730nm was detected from solution at room temperature and film at 77K, in which lifetimes waz determined to be 1.1 and 0.9ns, respectively. At room temperature, the photoluminescence peak of thin film shifted to 740 nm with fast decay behavior which was fitted well to a double-exponential lifetimes with τ₁ = 0.087ns, τ₂= 0.68 ns. Two relaxation mechanisms are given tentatively in explaining this phenomenon.     

Rectifying effect of heterojunctions between metals and doped conducting polymer nanostructure pellets

This paper reports that the Schottky junctions between low work function metals （e.g. Al and In） and doped semiconducting polymer pellets （e.g. polyaniline （PANI） microsphere pellet and polypyrrole （PPy） nanotube pellet） have been prepared and studied. Since Ag is a high work function metal which can make an ohmic contact with polymer, silver paste was used to fabricate the electrodes. The Al/PANI/Ag heterojunction shows an obvious rectifying effect as shown in I - V characteristic curves （rectifying ratio γ = 5 at ±6 V bias at room temperature）. As compared to the Al/PANI/Ag, the heterojunction between In and PANI （In/PANI/Ag） exhibits a lower rectifying ratio γ= 1.6 at ±2 V bias at room temperature. In addition, rectifying effect was also observed in the heterojunctions Al/PPy/Ag （γ = 3.2 at ±1.6 V bias） and In/PPy/Ag （γ = 1.2 at ±3.0 V bias）. The results were discussed in terms of thermoionic emission theory.     

Space-selective modification of the magnetic properties of transparent Fe3+-doped glass by femtosecond-laser irradiation

We have demonstrated spatially selective modification of the magnetic properties of transparent iron-oxide-doped glass by femtosecond- (fs-) laser irradiation and subsequent annealing. A near-infrared fs-laser beam with a wavelength of 775 nm was focused 1 mm below the surfaces of glass samples. This produces absorption peaks due to the formation of hole-trap centers in the irradiated region. Transparency was recovered after annealing at 450°C. A ferrimagnetic component was observed in the M–H curve even at room temperature, whereas the diamagnetic component dominated in the M–H curve of the as-prepared glass sample. This indicates that fs-laser irradiation enhanced the magnetization in the irradiated area. The irradiated and annealed glass sample also exhibited superparamagnetic blocking in the temperature dependence of the magnetization with a blocking temperature higher than room temperature. This change in magnetism is presumably due to local crystallization of ferrimagnetic nanoparticles, such as magnetite, induced by fs-laser irradiation and annealing. The magnetic and optical properties of glass that had been annealed but not irradiated by a fs-laser beam remained unchanged.     

Multi-frequency EPR study of radiation-induced radicals in tooth enamel

Human tooth enamel powders, unheated as well as heated prior to X -irradiation at room temperature, have been investigated by means of Q - and W -band Electron Paramagnetic Resonance (EPR). Upon irradiation of enamel, carbonate-derived radicals are generated. The simplest acquired EPR spectra in this study consist mainly of a group of three different \hbox{CO}_3^{3-} signals, with a very weak \hbox{CO}_2^{-} contribution. The characterisation of the paramagnetic species in enamel is quite important for the reliability of EPR applications ( e.g. , EPR retrospective dosimetry). The spectra from the heated samples reveal a striking resemblance with spectra from certain irradiated synthetic apatite powders. The spin Hamiltonian parameters obtained from the computer simulations of the Q - and W -band spectra are compared with those reported in the literature.     

2.1GeV?Kr离子在聚碳酸酯膜中引起的辐照效应研究

用傅立叶变换红外光(FTIR)谱仪和紫外/可见光(UV/VIS)谱仪研究了2.1GeVKr离子在聚碳酸酯(PC)膜中产生的效应.研究结果表明,在高能Kr离子辐照下,PC膜中发生了断键、断链和键的重组,炔基的出现是键的断裂和重组的结果.这些效应与辐照剂量和电子能损有关.辐照也使PC膜中发生了从氢化非晶态碳向非晶态碳的转变,在UV/VIS中,波长为380,450和500nm处的相对吸光度随能量沉积密度的增加近似按线性变化.     

Effect of 100 keV N+ ion irradiation on the organic single crystal of hippuric acid for nonlinear optical applications

The potential organic nonlinear optical material of hippuric acid (HA) single crystal has been grown by the slow evaporation solution growth technique using N, N-dimethylformamide as the solvent. Single crystals of pure HA were irradiated at room temperature with 100 keV Nitrogen (N⁺) ions at fluence 1×10¹⁶ and 5×10¹⁶ ions/cm². The pure and irradiated HA single crystals were characterized by different characterization technique. The photoluminescence and UV–visible absorption were performed at room temperature. The crystalline perfection of the pure and irradiated single crystals has been examined by high-resolution X-ray diffraction. Vickers microhardness technique was used to study the effect on the mechanical strength of the crystal at different ion fluences. The structural changes were analyzed by powder X-ray diffraction analysis. The functional groups of the synthesized compound have been identified by Fourier transform infrared spectroscopy. The dielectric constant and dielectric loss as a function of frequency were analyzed at room temperature.     

γ辐射引发淀粉目由基衰减的动力学研究

用ESR方法研究了红薯淀粉在γ射线预辐照下,产生的淀粉自由基特性及其室温下的自由基衰减动力学反应。结果表明在室温条件下,淀粉自由基的相对浓度随辐射剂量的增大而增加。自由基相对浓度的室温衰减用二级反应动力学处理,求得了衰减速率常数和淀粉自由基反应的半衰期。