Thu, 21 Aug 2008 07:12:19 BST CiteULike: zhaoxuanhe research http://www.citeulike.org/user/zhaoxuanhe/tag/research CiteULike.org en-gb Copyright © 2004-2008 citeulike.org http://www.citeulike.org/user/zhaoxuanhe/article/758538 <i>Nature, Vol. 428, No. 6986. (29 April 2004), pp. 911-918.</i> The path to ubiquitous and low-cost organic electronic appliances on plastic Stephen Forrest doi:10.1038/nature02498 Nature, Vol. 428, No. 6986. (29 April 2004), pp. 911-918. 2006-07-14T01:55:12-00:00 2004 Nature 428 6986 911 918 research http://www.citeulike.org/user/zhaoxuanhe/article/790907 <i>Vol. 5, No. 8. (August 2006), pp. 660-664.</i><br /><br />Dendritic crystal growth patterns have fascinated scientists for several centuries. Much of the aesthetic appeal of these patterns stems from the hierarchical structure of primary-, secondary-, and higher-order branches, which typically grow along principal crystallographic axes. Atypical growth directions have also been observed. Here, we demonstrate both computationally and experimentally that the range of possible dendrite growth directions, and hence the morphological diversity of the resulting dendritic structures, is much richer than previously anticipated. In particular, we show that primary dendrite growth directions can vary continuously between different crystallographic directions as a function of the composition-dependent anisotropy parameters. The study combines phase-field simulations of equiaxed dendritic growth and directional freezing of Al–Zn alloys. Both simulations and experiments exhibit continuous changes of direction from 100 to 110 for an underlying cubic symmetry. These results have important implications for controlling the microstructure of a wide range of cast alloys that solidify dendritically. Orientation selection in dendritic evolution Tomorr Haxhimali Alain Karma Frédéric Gonzales Michel Rappaz Vol. 5, No. 8. (August 2006), pp. 660-664. 2006-08-09T12:50:59-00:00 2006 5 8 660 664 research http://www.citeulike.org/user/zhaoxuanhe/article/790904 <i>Nature Materials, Vol. 5, No. 8. (August 2006), pp. 619-622.</i><br /><br />The distribution of elastic strains (and thus stresses) at the submicrometre length scale within deformed metal single crystals has remarkably broad implications for our understanding of important physical phenomena. These include the evolution of the complex dislocation structures that govern mechanical behaviour within individual grains1-3, the transport of dislocations through such structures4-6, changes in mechanical properties that occur during reverse loading7-9 (for example, sheet-metal forming and fatigue), and the analyses of diffraction line profiles for microstructural studies of these phenomena10-15. We present the first direct, spatially resolved measurements of the elastic strains within individual dislocation cells in copper single crystals deformed in tension and compression along 001 axes. Broad distributions of elastic strains are found, with important implications for theories of dislocation structure evolution3, 16-20, dislocation transport4-6, and the extraction of dislocation parameters from X-ray line profiles10-15, 21-24. X-ray microbeam measurements of individual dislocation cell elastic strains in deformed single-crystal copper Lyle Levine1 Bennett Larson Wenge Yang Michael Kassner Jonathan Tischler Michael Delos-Reyes Richard Fields Wenjun Liu Nature Materials, Vol. 5, No. 8. (August 2006), pp. 619-622. 2006-08-09T12:38:44-00:00 2006 Nature Materials 5 8 619 622 research