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Showing result 1 - 5 of 16 swedish dissertations matching the above criteria.

  2. 1. Investigation of Nuclear Materials with Positron Measurements

    Author : Petty Bernitt Cartemo; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; depth profiling; positron beam; nuclear materials; radiation damage; positron lifetime measurements;

    Abstract : Positron Annihilation Lifetime Spectroscopy can be used to characterize radia- tion-induced material defects to subsequently optimize nuclear materials with respect to radiation damage. Nuclear Systems of the future such as Generation IV and fusion concepts demand high performance from structural materials, comprising a material's stability in highly-radiative and hot environments. READ MORE

  4. 2. Free Volume Depth Profiling at Polymer Surfaces and Interfaces

    Author : John Algers; Centrum för analys och syntes; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; biopolymers; Polymerteknik; Polymer technology; polymer interfaces; polymer surfaces; positron lifetime; free volume;

    Abstract : Pulsed low energy positron beams provide a unique and non-destructive tool to depth probe the free volume of polymers at surfaces and interfaces. Since the employment of low energy positron beams in polymer research is an emerging technique, some focus in this thesis has been on extracting methods and equations needed to interpret the experimental data. READ MORE

  5. 3. Radiation Detection Techniques for the Enhancement of Nuclear Safety

    Author : Petty Bernitt Cartemo; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; MEDICIN OCH HÄLSOVETENSKAP; MEDICAL AND HEALTH SCIENCES; whole body counting; depth profiling; voxel phantom; nuclear safeguards; Monte Carlo; orphan sources; radiation-induced material damage; pulsed beam; positron lifetime;

    Abstract : The hazard originating from the use of nuclear materials in various areas of the society necessitates a number of experimental techniques for controlling and increasing the safety connected to radioactive substances.The following thesis is divided into two parts, representing different aspects to the detection of radiation effects. READ MORE

  6. 4. Free Volume Determination in Polymers and Polymer Blends

    Author : Camilla Wästlund; Chalmers tekniska högskola; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; positronium formation; crystallinity; polymer blends; inhibition; polymers; free volume; positron annihilation; phase separation; distribution;

    Abstract : The free volume of a polymer, which corresponds to the unoccupied regions accessible to segmental motions, is an important parameter for understanding and predicting many of its characteristic properties. The concept of free volume is the basis for understanding the molecular mobility in polymers. READ MORE

  7. 5. Free Volume and Mesopores in Polymer Nanocomposites

    Author : Petra Winberg; Centrum för analys och syntes; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; Chemical technology and engineering; Kompositmaterial; Composite materials; Macromolecular chemistry; permeability ; membrane ; positron annihilation ; fumed silica ; clay ; mesopores ; polymer nanocomposites ; free volume ; Kemiteknik och kemisk teknologi; Makromolekylär kemi;

    Abstract : The free volume in polymers is coupled to several important physical properties, such as density, viscosity and gas diffusivity. The physical properties of polymers close to a solid surface have been shown to be significantly perturbed as compared to their bulk state. READ MORE