The plastic slip process in crystals is described by a continuum mechanics technique using models for the behaviour of dislocations. Some new models are established for the mean glide path distance of dislocations during single slip and multiple slips and comparisons are made for the strain-hardening characteristics accompanying those models. The spontaneous transition in the deformation curve of single crystals from stage I to stage II is naturally introduced through models of the mean glide path distance.

Numerical modelling of plastic multislip in metal crystals of f.c.c. type

A new mechanism for relaxation of misfit stresses in composite nanowires (quantum wires) is suggested and theoretically examined, namely the formation of misfit dislocation loops. The stress field of a prismatic dislocation loop in a cylinder (nanowire) is calculated. The parameters of two-phase composite nanowires at which the formation of misfit dislocation loops is energetically favourable are estimated. The effect of stress fields of dislocation loops on the formation of compositionally modulated nanowires is discussed.

http://www.ipme.nw.ru/ipme/labs/ltdm/PhilMag_2004_Ovidko_Sheinerman.pdf

Misfit dislocation loops in composite nanowires

Molecular glasses prepared by vapor deposition have been revealed in recent years to have properties which the glasses prepared by ordinary liquid-quenching methods do not have. Thus the vapor-deposition method of material preparation has attracted increasing attention in the context of its possible application in manufacturing functional organic devices. The remarkable nature of vapor-deposited molecular glasses is that their properties depend very much on the deposition temperature and deposition rate. This suggests that the microscopic structure formed at the sample surface in the vapor deposition plays an important role in determining the sample properties. However, little of the structure of vapor-deposited molecular glasses has been clarified yet. In this article, we summarize first the research history of vapor-deposited molecular glasses, the concepts of amorphous solid and glass, and the methods for studying molecular glasses. We then summarize the research results reported to date for molecular glasses and related supercooled liquids. We also include in this article our recent research results in this field, and mention our present view on vapor-deposited molecular glasses.

Structural relaxation of vapor-deposited molecular glasses and supercooled liquids

This study presented a simple and environmentally friendly method of in situ synthesis of silver nanoparticles (AgNPs) on cotton fabrics for durable ultraviolet (UV) protection and antibacterial ac...

A green in situ synthesis of silver nanoparticles on cotton fabrics using Aloe vera leaf extraction for durable ultraviolet protection and antibacterial activity

A method for enhancing the brightness of an intense slow positron beam produced by an electron linear accelerator (LINAC) in order to obtain an intense positron microbeam was developed. The developed brightness enhancement system is simple and consists only of a few beam optics and a transmission remoderator. The slow positron beam produced by the LINAC is magnetically guided from the positron source to an experimental room. The beam is extracted from the magnetic field and is focused by a lens on the remoderator to enhance its brightness. The brightness-enhanced beam is extracted from the remoderator and focused on a sample by a lens. The beam size at the sample was 90 μm, which was two orders of magnitude smaller than that in the magnetic transport system that was about 10 mm. The efficiency of the transmission remoderator was about 5%. Adiabatic rules in the magnetic transport and the paraxial-ray equation were used to estimate the beam size that could be produced using this method.

A.L. Denison

Papers

Introduction; Success of the Technique

Development of positron diffraction and holography at LLNL

Technology of Positron Analysis

Monoenergetic Positron Beam Facilities and Proposals

New Developments in the Application of Positron Spectroscopy to Studies of Materials