Papers by Keyword: Cubic

Abstract: Sublimation-grown 3C-SiC crystals were implanted with B ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 1.3×10¹⁷ atoms/cm² in order to form intermediate band (IB) in 3C-SiC. The samples were then annealed at 1400 °C for 60 min. An anomalous area in the center was observed in the PL emission pattern. The SIMS analysis indicated that the B concentration was the same both within and outside the anomalous area. The buried boron box-like concentration profile can reach ~3×10²¹ cm^-3 in the plateau region. In the anomalous area a broad emission band (possible IB) emerges at around ~1.7-1.8 eV, which may be associated with B-precipitates having a sufficiently high density.

Abstract: Sublimation-grown 3C-SiC crystals were implanted with 2 atomic percent of boron ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 8.5×10¹⁶ atoms/cm². The samples were then annealed at 1400, 1500 and 1600 °C for 1h at each temperature. The buried boron box-like concentration profile can reach ~2×10²¹ cm^-3 in the plateau region. The optical activity of the incorporated boron atoms was deduced from the evolution in absorption and emission spectra, indicating possible pathway for achieving an intermediate band behavior in boron doped 3C-SiC at sufficiently high dopant concentrations.

Abstract: The cubic WO₃ powder was prepared by sol-gel method with WCl₆ as the soure of tungsten and P₁₂₃ as the structure-directing agent. The crystalline phase and microstructure of the powder were characterized through TG-DSC, XRD and SEM techniques, respectively. It was found the powder annealed at 250°C for 4h mainly was cubic WO₃ with a little monoclinic phase. The SEM micrographs revealed the powder has a petal shape with about 200 nm mean particle diameter. The photocatalytic activity of the powder was evaluated by methyl orange as mode compound to photocatalytic degradation under UV light irradiation. The results show the cubic WO₃ powder has much higher photocatalytic activity than the monoclinic phase.

Abstract: Firstly, based on the Cox-de Boor recursive formula, random degree NURBS curve generation algorithm is given. Then, this article discusses knot vector, the weight factor's influence on NURBS and presents the determination method of knot vector and weight factor. Secondly, NURBS curve inverse algorithm is studied and the focus is on cubic NURBS curve inverse algorithm, which is widely applied in engineering. Finally, based on C++ Builder development environment, the paper completes algorithm simulation and gives the specific application examples. Examples verify the efficiency and reliability of the algorithms, which has a high practical value in the CAD/CAM.

Abstract: In this paper single crystal alloys [111] orientation on tensile stress creep performance testing and organization was observed, on the high temperature and low stress conditions, combining with the creep characteristics of SEM observation, organizational morphology constructed raft shape g in 3d space ordered phase mode of existence of; Study the single crystal alloys [111] orientation in high-temperature creep of tensile stress during directional coarsening regularity, and using the finite element method, this paper analyzes the monocrystal [111] orientation in ni-based alloy cubic / two-phase interface von Mises stress distribution and the lattice strain energy change rule, through the immune genetic algorithm analysis [111] orientation of single crystal alloy phase of evolution rule ordered .

Abstract: This paper describes Transmission Electron Microscopy studies of the structural changes of GaN1-xAsx alloys grown by Molecular Beam Epitaxy at low temperatures on Al2O3 substrate. We found that by lowering the growth temperature increasing amount of As can be incorporated in GaN1-xAsx forming a single phase alloy. For the low As content a columnar growth of wurtzite structure is observed but for increasing As in the range of 0.170.75 the layer becomes amorphous. Increase in Ga flux at low growth temperature (about 200°C) leads to columnar alloys with As content >75% with a cubic structure. In addition to the structural changes monotonic change of the band gap is also observed with the As content in the alloy. The amorphous alloy is stable up to annealing at temperatures not higher than 600°C. Annealing at higher temperature leads to phase separation of GaAs:N and GaN:As confirmed by Z-contrast electron microscopy.

Abstract: Numerical analysis of a wire drawing operation to compute the stress distribution along the blank cross-section is presented. The governing equation describing the wire drawing equation is weakened using the Bubnov-Galerkin finite element method to obtain the finite element model. The blank is descritized into a mesh of C⁰ quadratic isoparametric and C⁰ cubic finite elements. Stiffness matrices for all elements are obtained using the finite element model which were subsequently assembled by enforcing continuity of the nodal stress. Boundary conditions are applied and the resulting condensed system of equation solved for unknown nodal stresses using Gauss Seidel method. The relative performance of the C⁰ quadratic and C⁰ cubic elements are assessed. Parametric analysis is carried out to show the influence of drawing parameters on the stresses generated and drawing load. The analysis was carried out using a Visual Basic.Net program developed by the authors.The results are presented in both graphical and tabular forms.