Investigation of SPPO Membranes by Positron Annihilation Lifetime Spectroscopy

Positron annihilation lifetime spectroscopy （PALS） is a powerful technique to study the free volume in polymers. The lifetime of ortho-positronium （o-Ps）, a bound state of an electron and a positron, can be used to assess the pore size while the intensity can be used to characterize the number of pores. On the basis of the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes in the sulfonated poly （2,6-dimethyl-1,4- phenyleneoxide） （SPPO） membranes with different amounts of LiCl were calculated. It was found that, with the increasing amount of LiCl, the free volume radius and the fractional free volume firstly increased and then decreased. After immersing the membranes in distilled water, the free volume radius and the fractional free volume changed with different water concentrations in the membrane.     

Sulfonated polyetherketone （SPEK-C） films investigated by positron annihilation lifetime spectroscopy and atomic force microscopy

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.     

Comparison of the Free Volume of LiCl-Added SPPO Membrane and SPPO-PES Blend Membrane by Positron Annihilation Method

Positron annihilation lifetime spectroscopy （PALS） is a powerful technique for the study of free volume in polymers. The lifetime of ortho-positronium （o-Ps）, a bound state of an electron and a positron, can be used to assess the pore size, while the intensity can be used to characterize the number of pores. Based on the values of the long-lived o-Ps components in the lifetime spectra, the radii and fractional free volumes of sulfonated poly （2,6-dimethyl-1,4- phenyleneoxide） （SPPO） membranes with added LiCl and SPPO-PES （Polyethersulfone） blend were compared. Free volume radii in both kinds of membranes are discussed.     

POSITRON LIFETIME STUDIES ON SYSTEMS OF PALLADIUM FILLED GALVANOSTATICALLY WITH HYDROGEN OR DEUTERIUM

The positron lifetime spectroscopy was used to investigate the electron structures of crystal lattice and its defects in palladium samples filled galvanostatically with hydrogen and deuterium, respectively. The results have indicated that the positron lifetime were all the same between hydrogen and deuterium filled samples in which the positron lifetime τ(?) increased about 10%, corresponding to the volume expansibility after the formation of hydrides PdH or PdD phases during electrolyzing commom water or heavy water with Pd cathode; and Will not change with time in 3 weeks after stopping electrolysis; but could be recovered to 116±1ps, the value in polycrystalline pure palladium, after annealing at high temperature.     

Positron annihilation study of effect of aluminum on iron－based amorphous alloys

Seven Fe-based amorphous alloys have been studied by Doppler broadening and lifetime techniques of the positron annihilation.It is shown that the parameters of positron annihilation in the Fe-based amorphous alloys containing more aluminum are larger than those in the alloys with less aluminum,which means that the existence of element Al in Fe-based amorphous alloys results in more vacancy-like defects.     

Positorn annihilation study on point defects in lead tungstate

A study on point defects in leas tungstate(PbWO4) by using positron annihilation lifetime method is presented,The measurement was carried out for the cases of untreated,vacuum-annealed,oxygen-annealed and La-doped PbWO4 crystals,It was found that the components T2,which reflect the positron annihilation in point defects ,are different from each other for each case,Some tentative models for the defects are dicussed.     

Microstructure of N—Picolylpolyurethane Transition Metal Complexes

Spectroscopic methods are used to investigate coordination structure of N-picolylpolyurethane transition metal complexes(PUPYM,M=Co^2 and Ni^2 ) .Geometrical arrangement of ligands in first-shell coordination sphere of metal ions is postulated to be tetrahedral CoL2Cl2 and octahedral NiL2-Cl2Z2.where L is the picolyl group and Z is a hydrate.From extended X-ray absorption fine structure (EXAFS) analysis,bond lengths for metal-chlorine and metal-ligand of PUPYM are similar to those of small molecular weight transition metal complexes.A two-phase model of PUPYM which best describes the experimental data of DMTA and SAXS.is proposed.One microphase is the hard domain of self segregated haed segments brought about by metal-ligand interaction.and the other phase is the matrix of soft segments.Transition metal ion-ligand moieties and their interactions dominate the macroscopic thermal behavior of PUPYM.The ligand field stabilization energy difference(ΔLFSE) between mteal d-electrons in complexes with two picolyl ligands in the coordination sphere of metal ions and complexes maintaining one picolyl ligand as coordination pendent group is calculated on the basis of observed coordination structure,and it represents the energy supplied to split coordination cross-links.ΔLFSE of polyurethane nickel(II) complex is larger than that of the cobalt(II) complex,Since the mobility of hard segments is in inverse proportion to the strength of coordination cross-links.a higher α-transition temperature of PUPYNi^2 with respect to PUPYCo^2 is found as expected.     

Radiation—induced plasmons in Si—SiO2

The first level plasmons of Si in pure Si state(corresponding to bonding energy(BE) of 116.95eV) and in the SiO2 state (corresponding to BE of 122.0 eV) of Si-SiO2 prepared by irradiationn hard and soft processing were studied with XPS before and after ^60Co radiation.The experimental results indicate that there was an interface consisting of the two plasmons,this interface was extended by ^60Co radiation,the fractions of the plasmon for Si in the Si-SiO2 were changed with the variation of radiation dosage,the difference of the change in fraction of plasmons for the two kinds of samples was that the soft varied faster than hard,the change of concentrations in plasmons for both hard and soft Si-SiO2 irradiated in positive bias field were greater than that in bias-free field.The experimental results are explained from the view point of energy absorbed in form of quantization.     

Variation of Radiation Damage with Irradiation Temperature and Dose in CLAM Steel

The dependences of radiation induced defects on irradiation temperature up to 700℃ at 15 dpa and on irradiation dose up to 85 dpa at room temperature have been inves-tigated by the heavy ion irradiation and the positron annihilation lifetime spectroscopy for the CLAM.A void size peak is observed at ～500℃ where the vacancy cluster contains 9 vacancies and has an average diameter of 0.59 nm.The size of the vacancy clusters increases with the increase of irradiation dose at room temperature,and the vacancy cluster at 85 dpa consists of 9 vacancies and reaches a size of 0.60 nm in diameter.The absolute values of the void size at the peak and the increase of void size with dose in the CLAM steel are negligible compared to those of the normal stainless steels,indicating that the CLAM steel has good radiation resistant property.     

XPS STUDIES OF IRRADIATED HARD AND SOFT Si—SiO_2

The interracial structure of hard and soft oxides grown by dry oxidation on<100> n-type silicon substrates is examined using high resolution mild X-ray photoelectron spectroscopy (XPS) before and after irradiation. Substantial differences in silicon of silica state (B.E. 103.4 eV), silicon of transitional state (B.E. 101.5 eV), surplus oxygen (B.E. 529.6 eV) and negative two-valence oxygen (B.E. 531.4 eV) are observed between the two kinds of samples. The XPS spectra strongly depend on the conditions of irradiation for soft samples, but do not as remarkablely as soft samples for hard samples. The effects of irradiation doses on XPS are greater than that of irradiation bias fields. Some viewpoints of irradiation induced hole electron pair are proposed to explain the results.     

用PAT研究多嵌段聚醚氨酯脲的微畴结构

本文用正电子湮没、小角X射线散射和差示扫描量热等方法研究多嵌段聚醚氨酯脲的微畴结构。实验结果表明,硬段含量的增加引起微畴体积和自由体积减小,而软段分子量增加引起微畴体积和自由体积增大。     

金属中空位及空位团的正电子寿命谱

本文从理论上讨论了金属中正电子湮没寿命和金属的空位、空位团的体积的关系,利用密度泛函和交换关联能的局域密度近似,系统地计算了一系列金属中不同空位团的正电子寿命值。可以看出,正电子湮没技术是研究金属微观缺陷结构的有力手段。     

正电子湮没技术与沸石分子筛

测量了３Ａ型及１３Ｘ型沸石分子筛在不同压强空气中的正电子寿命谱，并测量了１０Ｘ型分子筛在不同温度下焙烧后的寿命谱。测量表明：分子筛所吸附的气体对在其体内湮没的正电子有显著的影响．同时，沸石笼内水的存在也对其湮没参数有影响。研究表明，随着水的逐步脱除；笼内自由体积逐步增大；当脱水至一定程度后．笼内开始出现活性中心－质子酸。     

Study of PRIMAVERA steel samples by positron annihilation spectroscopy technique II – Lifetime measurements

In the present article, a positron annihilation lifetime technique was used for the study of VVER-440/230 weld materials, manufactured in the frame of the international PRIMAVERA project on microstructural investigation of the irradiated WWER-440 reactor pressure vessel steel. The present results complement our previous report of positron angular correlation experiments and provide in-depth characterization of vacancy type defects behavior under irradiation and thermal treatment. The results give new insight into the previously published atom probe tomography and angular correlation of annihilation radiation studies. The measurements do not show any association of phosphorus or its segregation to the open volume defects investigated by positron annihilation spectroscopy. The embrittlement effects related to the phosphorus seem to be effectively annealed-out during 475 °C thermal treatment and the post annealing microstructure and mechanical properties of the material are consequently affected mostly by agglomerations of vacancy clusters coarsened during thermal treatment.     

辐照接枝氟塑料的正电子寿命谱研究

用正电子湮没寿命谱研究了对聚四氟乙烯和聚合氟乙丙烯进入γ辐照接枝的反应机理。结果表明：γ辐照和辐照接枝使聚合物的凝聚态结构发生了变化。随着辐剂量的增加,接枝率不断提高,而正电子湮没长寿命产生明显改变。说明了辐照接枝主要发生在非晶区以及非晶区和晶区的交界处,将实验结果与红外光谱进行了比较。     

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。     

Investigation on the porosity of zeolite NU-88 by means of positron annihilation lifetime spectroscopy

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.     

Positron affinity for precipitates in reactor pressure vessel steels

The sensitivity of positron annihilation spectroscopy to irradiation-induced precipitates in reactor pressure vessel steels is discussed in the light of recent positron affinity and lifetime calculations. Carbide and nitride precipitates are found to trap positrons only if they contain metal vacancies. Copper precipitates are also attractive to positrons but they are probably detected through annihilation at the precipitate-matrix interface. These findings are related to available experimental data.     

微动摩擦对聚合物自由体积的影响

采用正电子湮没方法对聚四氟乙烯,尼龙以及聚对苯二甲酸丁二醇酯材料微动摩擦后自由体积缺陷的变经规律进行了研究,结果表明,微动摩擦造成了材料内部平均自由体积尺寸增大,导致了材料的磨损及失效。