Papers by Keyword: Positron

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Authors: M. Borrell, R.I. Grynszpan, N. Ji
Authors: D.M. Hunter, R.I. Grynszpan
Authors: Morten M. Eldrup, G.M. Hood, N.J. Pedersen, R.J. Schultz
Authors: S.G. Usmar, R.N. Wright
Authors: Zhe Jie Zhu, Wei Yang, Jian Jian Shi, Tong Guang Zhai, Yi Chu Wu
Abstract: The oxidized Mo-50Re alloys in air at 573 K and 873 K for various times were investigated by X-Ray diffraction and positron annihilation lifetime spectroscopy. The results indicated that main orthogonal phase MoO3 together with small amount of monoclinic phase Mo8O23 were formed on on the surface of the specimens, and the oxide film of specimens oxidized at 873 K were much thicker than that of specimens oxidized at 573 K. Meanwhile, when Mo-50Re specimens oxidized in air at 873K, the defect’s size within interface layer of the specimens was larger, and the oxide film on the surface of the specimens contained much more defects. Faster oxidation process were observed occured at 873K, which was likely due to the formation of larger-size interfacial defects.
Authors: Xiao Wu Huang, Jia Hua Han, Yi Wang, Yan Li, Yijin Du
Authors: Carlos Pascual-Izarra, Aurelia W. Dong, Steven J. Pas, Ben J. Boyd, C.J. Drummond, Anita J. Hill
Abstract: Self-assembled amphiphile systems are utilized in a wide variety of applications including drug delivery and energy storage. Nano-scale physical and chemical interactions govern the packing of self-assembled amphiphilic molecules, resulting in thermodynamically stable phases of defined geometries. Possible phases include micellar, hexagonal, cubic, lamellar and sponge phases. The internal nano-structure of the amphiphile self-assembly materials plays an important role in the properties of these systems and their application. To date small angle x-ray scattering (SAXS) has been the most common technique used to characterise their structure. We explore positron annihilation lifetime spectroscopy (PALS) as an alternative and/or complementary technique for this purpose, using the phytantriol/water system. While PALS is a well established technique for characterising many materials, the coexistence of aqueous and hydrophobic regions in a soft self-assembled amphiphile material poses a challenge to the analysis and interpretation of the results. In order to alleviate these difficulties we developed a computer program for general-purpose PALS data analysis called PAScual. Amongst the most salient features of this new code are the possibility to perform bounded fits and the option of using advanced algorithms to provide a more robust and unbiased fit: on the one hand, it incorporates a global nonlinear optimisation routine based on the Simulated Annealing algorithm and, on the other hand it gives information on the reliability of the results by means of a Markov Chain Monte-Carlo Bayesian Inference method. In this work we present the newly developed PALS data analysis techniques as well as the results for the phytantriol/water system, comparing them with additional data obtained from complementary techniques.
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