tailieunhanh - Heat Analysis and Thermodynamic Effects Part 12

Tham khảo tài liệu 'heat analysis and thermodynamic effects part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Synthesis of Novel Materials by Laser Rapid Solidification 319 relative orderly arranged and densely packed blocks while that prepared by solid state reactions consists of densely packed irregular shaped globose grains. The unique microstructures of the samples produced in the laser synthetic route are attributed to the relatively oriented crystalline growth governed by heat transfer directions. Although both samples have similar density by LRS and by SSR the sample prepared by LRS exhibits much superior conductivities and Scm-1 obtained at 600 700 and 800 C to the sample prepared by solid state reactions and Scm-1 Zhang et al. 2010 . Both XRD analysis and Raman spectroscopic study suggest that the sample prepared by LRS crystallized in an orthorhombic and that by solid state reactions in a monoclinic phase. The samples with high purity were also prepared by LRS. It is shown that that Co-doped LSGMs exhibit unique spear-like or leaf-like microstructures not shown here and superior oxide ion conductivity. The electrical conductivities of are measured to be and Scm-1 at 600 700 and 800 C respectively being much higher than those of the same composition by solid state reactions Scm-1 . The unique microstructures of the samples prepared by LRS should account mainly for their superior electrical properties to those of the samples prepared by solid state reactions. The relatively oriented and densely packed ridge-like for LSGM or leave-like Co-doped LSGM grains with large and regular sizes in the samples by LRS greatly reduce the scattering probabilities and thus increase the mean free path or the mean free time of charge carriers during the drift motion. It can be speculated from the appearances and SEM images that the starting materials were sufficiently molten in the molten pool. Since the melting points of the raw .