Advanced Materials Research Vol. 904

Abstract: The different influencing regular of fly-ash fractiontype of fibre (steel fibre and polypropylene fibre) and fibre fraction on the mechanical property and fracture behavior of Reactive Powder Concrete (PRC) are studied. Fracture mechanical properties of RPC is researched in double-K fracture model and fracture energy release rate G . Test results show that the crack propagation of RPC with steel fibers is limited. Its fracture toughness and pre-critical crack length is largely enhanced. Double-K fracture model and fracture energy release rate G are consistent with describing the fracture behavior of RPC.

Abstract: In this paper, the diphenyl methane diisocyanate (MDI) was used to modify montmorillonoid (MMT) and got the organic montmorillonite (OMMT), which was used with the monomers of PET by in situ polymerization method to prepare PET/MMT nanocomposition. The OMMT was analyzed by the X ray diffraction (XRD) to test the change of the spacing layer. Dispersion of MMT in the PET/MMT nanocomposites were studied with XRD and SEM and by means of thermogravimetric analyzer (TGA) on the thermal stability of PET/MMT nanocomposites. The results showed that, MDI modified MMT successfully, and the compatibility of MMT and PET was increased .

Abstract: In this paper, the influence of catalytic on the extinguishing effect of inorganic salt fire extinguishant has been studied. Results of TG test and burning test indicated that catalytic synergist ammonium tungstate and sodium tungstate can effectively increase the fire extinguishing effect of the inorganic salt fire extinguishant, and sodium tungstate has a better catalytic synergistic effect than ammonium tungstate.

Abstract: The quality of the honeycomb radiator structure has a great impact on thermal performance of the LED lamp. In order to make honeycomb radiators structure more uniform and materials fluidity much better; we firstly take use of cold extrusion to form the honeycomb radiator, then it will be machined. In the honeycomb radiator deformation than the larger places where prone to stress concentration, that has a seriously affect on the effect of the radiator forming. Therefore, we optimized the extrusion die, including upper and lower mold prone to stress concentration places create fillet. The results show that an appropriate fillet of the mold can greatly improve the forming uniformity and reduce the force on the die.

Abstract: An inorganic salt complex which had a strong ability to generate lot of inert gases rapidly in a fire was prepared. Fire extinguishing agent added with sodium tungstate as a synergist had a great performance in gas release. Flammable gas and oxygen in fire could be diluted by Carbon dioxide and ammonium which released from the heating of inorganic salt complex.

Abstract: Transparent conducting gallium doped zinc oxide (GaZnO) films were prepared by magnetron sputtering technique. The influence of growth temperature on the microstructural and optical properties of the films were investigated by means of X-ray diffraction (XRD), spectrophotometer and optical characterization method, respectively. The results show that all the samples are polycrystalline in nature having a hexagonal wurtzite type crystal structure with a preferred grain orientation in the (002) direction. The growth temperature significantly affects the crystal structure and optical properties of the samples. The film deposited at the growth temperature of 670 K possesses the largest grain grain, the minimum dislocation density and the lowest microstrain. The average visible transmittance and optical energy gap of the samples increase gradually with the increment of growth temperature.

Abstract: Sapphire substrate was treated by SiH₄ under NH₃ atmosphere before GaN growth and nanosize islands SiN_x mask was formed on the substrate. Properties of GaN films were investigated by high resolution X-ray diffraction, photoluminescence and transmission electron microscopy. The results indicated that the SiH₄ flow rate is an important factor affecting the size and density of SiN_x mask besides SiH₄ treatment time.The GaN films grown on the SiN_x-patterned sapphire substrate revealed an epitaxial lateral overgrowth mode, which affected 3D to 2D growth time and the microstructures of GaN films. The lowest FWHM value of (102) rocking curve was 286 arcsec. as the SiH₄ flow rate of 0.5sccm, with the calcultated edge-type dislocations density of 4.28×10⁹cm^-2.

Abstract: A combustion synthesis method has been developed for synthesis of Eu²⁺ doped CaAlSiN₃:Eu²⁺ phosphor and its photoluminescence properties were investigated. Ca, Al, Si, and Eu₂O₃ powders were used as the Ca,Al,Si,and Eu sources. NaN₃ and NH₄Cl were found necessary to be added for the formation of the product phase and addition of Si₃N₄ was found to enhance the product yield. These powders were mixed and pressed into a compact which was then wrapped up with an igniting agent (Mg+Fe₃O₄). The reactant compact was ignited by electrical heating under a N₂ pressure of 0.8 MPa. The synthesized CaAlSiN₃:Eu²⁺ phosphor absorbs light in the region of 240-520 nm and shows a broad band emission in the region of 500-800 nm due to the 4f⁶5d¹4f⁷ transition of Eu²⁺.The synthesized phosphor thus has a potential application as a red phosphor for white LED lighting.

Abstract: The numerical simulation of equal channel angular extrusion (ECAE) with variable back pressure was researched by applying the commercial Deform-3D software, in which choosing the hard deformation materials of 7075 aluminum alloy, and comparing the traditional ECAE without back pressure process. The influence of back pressure on the mean stress and the effective strain rate in the shear deformation zone was studied. The results show that the extrusion force transformation laws were different in both load ways, with the increase of back pressure, extrusion force enhances increasingly, but the final load-time curves tended towards stability, but in ECAE without back pressure, the final load-time curves tended towards decreasing; thus the whole deformation process can be divided into different stages. In addition, the larger the absolute value of the hydrostatic stress at the corner, the more beneficial to refine grain and improve the plasticity. The back pressure makes the distribution of effective strain rate in plastic deformation area more uniform and improves the uniformity of deformation.