Chalk River Laboratories

About: Chalk River Laboratories is a based out in . It is known for research contribution in the topics: Neutron diffraction & Neutron scattering. The organization has 2297 authors who have published 2700 publications receiving 73287 citations.

Atomic structure holography using thermal neutrons

Abstract: The idea of atomic-resolution holography has its roots in the X-ray work of Bragg1 and in Gabor's electron interference microscope2. Gabor's lensless microscope was not realized in his time, but over the past twelve years there has been a steady increase in the number of reports on atomic-resolution holography. All of this work involves the use of electrons3,4,5,6 or hard X-rays7,8,9,10,11 to produce the hologram. Neutrons are often unique among scattering probes in their interaction with materials: for example, the relative visibility of hydrogen and its isotopes is a great advantage in the study of polymers and biologically relevant materials. Recent work12 proposed that atomic-resolution holography could be achieved with thermal neutrons. Here we use monochromatic thermal neutrons, adopting the inside-source concept of Szoke13, to image planes of oxygen atoms located above and below a single hydrogen atom in the oxide mineral simpsonite14.

Direct observation of the near-surface layer in Pb ( Mg 1 ∕ 3 Nb 2 ∕ 3 ) O 3 using neutron diffraction

Abstract: Spatially resolved neutron diffraction as a function of crystal depth in $\mathrm{Pb}({\mathrm{Mg}}_{1∕3}{\mathrm{Nb}}_{2∕3}){\mathrm{O}}_{3}$ reveals the presence of a distinct near-surface region where a strong distortion in the lattice exists A dramatic change in both the lattice constant and the Bragg peak intensity as a function of crystal depth is observed to occur in this region over a length scale $\ensuremath{\sim}100\phantom{\rule{03em}{0ex}}\ensuremath{\mu}\mathrm{m}$ This confirms a previous assertion, based on a comparison between high-energy x rays and neutrons, that such a near surface region exists in the relaxors Consequences to both single crystal and powder diffraction measurements and previous bulk neutron diffraction measurements on large single crystals are discussed

A dislocation-based model for variant selection during the γ-to-α′ transformation

Abstract: A phase transformation model is described for variant selection during the austenite-to-martensite transformation. The model depends entirely on the presence of glide dislocations in the deformed austenite. The direct correlation between the 24 slip systems of the Bishop and Hill (B-H) crystal plasticity model and the 24 〈112〉 rotation axes of the Kurdjumov-Sachs (K-S) orientation relationship is employed. Two selection criteria, based on slip activity and permissible dislocation reactions, govern the variants that are chosen to represent the final transformation texture. The development of the model via analysis of the experimental results of Liu and Bunge is described. The model is applied to the four distinct strain paths: (1) plane strain rolling, (2) axisymmetric extension, (3) axisymmetric compression, and (4) simple shear. Experimental deformation and transformation textures were produced for comparison purposes via appropriate deformation and quenching procedures. In each case, the transformation texture predicted using the dislocation reaction model is in excellent agreement with the experimental findings.