This work quantifies the influence of nonlinear elasticity on the accuracy of the thermal shock damage evaluation of highalumina refractory castables based on dynamic Young's modulus and damping characterization d...
详细信息
This work quantifies the influence of nonlinear elasticity on the accuracy of the thermal shock damage evaluation of highalumina refractory castables based on dynamic Young's modulus and damping characterization data obtained via the impulse excitation technique (IET).The nonlinear elasticity leads to shifts in the Young's modulus and damping values in dependence of the impulse intensity. An IET apparatus was employed according to the ASTM E1876-07 standard;the method was improved by nonlinear analysis based on the excitation control. Two arbitrary coefficients were defined to evaluate the nonlinearity with respect to the impulse intensity. Three high-alumina refractory castables were submitted to progressive thermal shock damage and evaluated. The results show that the influence of nonlinear elasticity on the Young's modulus is significant and that nonlinear elasticity is a determining factor for the accuracy of the damping characterization (up to -0.93 % and +114 %, respectively, depending on the damage level).
作者：
Seong Yoon LimJunhyoung AhnJoon Seok LeeMin-Gon KimChan Beum ParkDepartment of Materials Science and Engineering
Korea Advanced Institute of Science and Technology (KAIST) 335 Science Road Daejeon 305-701 Korea Biomonitoring Research Center
Korea Research Institute of Bioscience and Biotechnology (KRIBB) 125 Science Road Daejeon 305-806 Korea Advanced Photonics Research Institute
Graduate Program of Photonics and Applied Physics Gwangju Institute of Science and Technology Gwangju 500-712 Korea Chan Beum Park
Department of Materials Science and Engineering Korea Advanced Institute of Science and Technology (KAIST) 335 Science Road Daejeon 305-701 Korea. Min-Gon Kim
Advanced Photonics Research Institute Graduate Program of Photonics and Applied Physics Gwangju Institute of Science and Technology Gwangju 500-712 Korea
A numerical model of an experimental gallium nitride horizontal vapor phase epitaxy reactor is presented. The model predicts the flow, concentration profiles, and growth rates. The effects of flowrate variation and ge...
A numerical model of an experimental gallium nitride horizontal vapor phase epitaxy reactor is presented. The model predicts the flow, concentration profiles, and growth rates. The effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated. Numerical model predictions are compared to experimentally observed values. Parasitic gas phase reactions between group III and group V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and inferior crystal quality. A low ammonia concentration is correlated to deposition of polycrystalline films. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize parasitic reactions and wall deposition while providing a uniform reactant distribution across the substrate.
We present here an overview of recent studies of the influence of oxygen doping on the electrical and structural properties of semiconductors grown through the metal organic vapor phase epitaxy (MOVPE) technique. In p...
We present here an overview of recent studies of the influence of oxygen doping on the electrical and structural properties of semiconductors grown through the metal organic vapor phase epitaxy (MOVPE) technique. In particular, we have measured the impact of oxygen introduction on several of the principal aspects of the growth process: incorporation, activation, and influence on the growing surface structure. The gas phase chemistry and dopant incorporation was investigated for two different precursors: dimethyl aluminum methoxide and diethyl aluminum ethoxide. The simple change in the structure of the oxygen source leads to significant changes in the oxygen incorporation behavior. Complementary studies of the gas phase decomposition of these oxygen sources have indicated that the decomposition mechanism is substantially different for these two sources leading to the change in incorporation behavior. The impact of the selective incorporation of oxygen at heterointerfaces has been studied here through the growth of superlattice structures. Glancing angle X-ray diffraction and atomic force microscopy measurements have shown that the incorporation of oxygen at the GaAs-to-AlxGa1−x As interface leads to modest increases in the average roughness of the heterointerface with more significant changes in the interfacial structure. The structure of this interfacial roughness was also studied through measurements of the diffuse X-ray scattering about a Bragg peak. Measurements of the component of the roughness which is correlated between the superlattice layers show significant changes with oxygen addition.
The effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated in a horizontal Gallium Nitride vapor phase epitaxy reactor. To better understand the effects ...
The effects of flowrate variation and geometry on the growth rate, growth uniformity and crystal quality were investigated in a horizontal Gallium Nitride vapor phase epitaxy reactor. To better understand the effects of these parameters, numerical model predictions are compared to experimentally observed values. Parasitic gas phase reactions between group III and group V sources and deposition of material on the wall are shown to lead to reduced overall growth rates and may be responsible for inferior crystal quality. A low ammonia concentration is correlated with the deposition of polycrystalline films. A low V/III ratio and an ammonia concentration lead to poor crystalline quality and increased yellow luminescence. An optimum HVPE growth process requires selection of reactor geometry and operating conditions to minimize these parasitic reactions and wall deposition while providing a uniform reactant distribution across the substrate.
We present results from a study of the vibrational, structural, and electronic properties of C60 powder and thin films. Raman spectroscopy and diamond anvil cell have been used to study pressure dependence of the Rama...
We present results from a study of the vibrational, structural, and electronic properties of C60 powder and thin films. Raman spectroscopy and diamond anvil cell have been used to study pressure dependence of the Raman active modes of C60 powder. The material undergoes structural phase transition between 9 and 15 GPa. Some of the Raman modes soften, while others harden with increasing pressure. Thin films of C60 and La-doped C60 have also been studied by using Raman scattering, x-ray diffraction, x-ray photoelectron spectroscopy and uv photoemission spectroscopy. Whereas the powder and La-doped C60 films exhibit fcc crystalline structure, the C60 film appears disordered. Further, we observe a significant difference in the electronic valence bands of the doped and undoped films.
暂无评论