Advanced Materials Research Vols. 690-693

Abstract: This article reviews the synthesis of Si-B-C-N ceramics, and the characteristics and principle of fabricating Si-B-C-N ceramics by using different precursors. So far, there only have two reports on preparation of Si-B-C-N ceramics, which are precursor pyrolysis and mechanical alloying. Therefore, this paper mainly discusses precursor pyrolysis and mechanical alloying. In addition, this paper proposed some prospects on the development and applications of Si-B-C-N ceramics in material science.

Abstract: This paper reports the spectral variation of Sr3SiO5: Ce3+, Li+ phosphor. It was synthesized by the conventional solid state method. The effects of calcining temperature and codoption of Mg2+ and Ba2+ on phase composition, structure, photoluminescence and thermal stability were firstly investigated in detail. Under the near-UV excitation of 415 nm, Sr3SiO5: Ce3+, Li+ emits a bright greenish-yellow color centered at 532nm, which originates from 5d to 4f (2F7/2 and 2F5/2) transition of Ce3+. The PL spectra show the different emission color variation with substituting Sr2+ cations with smaller Mg2+ or larger Ba2+, which makes it be applied as a color-tunable phosphor for LED based on near-UV chip/phosphor technology. Simultaneously, the thermal stability of (Sr,Ba)3SiO5: Ce3+, Li+ phosphor is improved markedly.

Abstract: An investigation on structural stability of LuN under high pressure has been conducted using first-principles calculations. At elevated pressures LuN is predicted to undergo a phase transition from NaCl-type structure (B1) into CsCl-type structure (B2). The predicted transition pressure is 220 GPa. The phonon dispersion curves of B1 and B2 at 0 and 220 GPa are presented.

Abstract: We use S-Parameter Methodto extract device parameter of InAlN/GaN HEMT in this paper. We find thatparasitic capacitance and parasitic inductance can be extracted in traditionaltest structure method, but do nothing about parasitic resistor. Cold parameter methodcan extract parasitic resistor efficiently, but there is greater error inparasitic capacitance and parasitic inductance extraction. We propose a methodwhich combines test structure method and cold parameter method to extract parasitic parameteraccurately. We can acquire intrinsic parameters through getting rid ofparasitism parameters, and can fitting test outcome satisfactorily. It canreflect accurately the physical characteristics of GaN HEMT devices, and givesfeedback and guidance to device technology at the same time.

Abstract: The microstructure and electrical properties of ZnTe films were investigated by using thermal evaporation with emphasis on the effects of a deposition temperature. Microstructure, crystallinity, carrier concentration, resistivity, and mobility are shown to be dependent on the deposition temperature. The highest carrier concentration of 9.1×1014 cm-3, the lowest resistivity of 9.9 Ω-cm and the largest mobility of 667 cm2V-1S-1 are presented at a deposition temperature of 580oC, respectively. The ZnTe thin films using thermal evaporation can find applications in solar cell or light emitting diodes.

Abstract: A novel gadolinium triple-decker sandwich-type complex containing tetrabenzoporphyrin (TBP) ligands-Gd (TBP)₃ was prepared from porphyrin 1 and Gd (acac)₃.nH₂O in boiling 1, 2, 4-Tcb for 45~48 h under Ar. Its structure is characterized by Uv-Vis spectroscopy and HR-MS. The spectroscopic properties show that its longest-wavelength visible band (600-800 nm) is obviously red-shifted due to the extension of the π conjugated systems derived from the linear benzoannulation in the TBP ring. The magnetic studies also indicate that there is no magnetic interactions between two Gd (III) ions in the triple-deckers in the range from room temperature down to 20K and very weak antiferromagnetic coupling exists between two Gd (III) ions below 20K.

Abstract: This study would create a decision making model for new product development (NPD) in light-emitting diode (LED) plant lighting industry. At first literature reviews and expert interviews will be employed to list five perspectives and 19 criteria thereof. A fuzzy Delphi method (FDM) will be then used to screen factors for the criteria. An interpretive structural model (ISM) will be managed to get the relationships among the perspectives and among the criteria. A fuzzy analytic network process (FANP) will be finally manipulated to compute the weights of all criteria. Results of the study will provide an assessment model of NPD decision making for LED plant lighting industry.

Abstract: A twin-roll casting process was used to produce high strength non-oriented electrical steel casted strips. The typical character in chemical composition is the adding of Ni and Cr.The main role of Ni and Cr is solution strengthening. MEM, SEM, and TEM were used to observe microstructure, texture, and precipitate characteristics of a casted strip. The casted strip character under different secondary cooling process was compared. The results show that water-cooled as-cast strip is composed of the equiaxed grains, air-cooled as-cast strip is characterized by a mixture of the quiaxed and columnar grains. The texture of water-cooled as-cast strip is weaker and diffuser than air-cooled as-cast strip. Precipitates mostly are AlN and MnS, which mostly precipitate in the grain. The precipitates of Ni and Cr is not observed. The size distinction of MnS between two secondary cooling process is not remarkable. The size of AlN in water-cooled process is smaller than in air-cooled process.

Abstract: A series of chiral donor-acceptor helicenes have been designed using the molecular engineering of organic nonlinear optical materials. The geometries of donor-acceptor helicenes 1, 2, 3, 4, 5 are optimized using density functional theory (DFT-B3LYP) method at the 6-31g (d, p) basis set level. Based on the obtained stable molecular configuration, we adopt the TDHT/PM3 method and time-dependent density-functional theory (TD-DFT) to calculate the nonlinear optical (NLO) properties and electronic spectra of these molecules. Results show that molecule 4 has the largest static hyperpolarizability β_μ of 40.4×10^-30esu, which is enhanced by its two charge transfer orientations. In molecule 2, there exists two competitive charge transfers that weaken the second-order nonlinear optical effect of D-π-A structures greatly. The structural type of molecule 3, 4 and 5 are expected to be more efficient to achieve large β values.

Abstract: The structure, electronic and magnetic properties of full-Heusler alloy Co₂TiGa are investigated by means of the full potential linearized augmented plane-wave method. Our results show that the ground state of Co₂TiGa is of the nearly half-metallic ferromagnetism with a magnetic moment of 1.00218 μ_B per unit cell, which are contributed by the atoms Co and Ti. Meanwhile, the spin polarization around the Fermi level is up to 93.2%, almost 100%, which indicates that full-Heusler alloy Co₂TiGa with the well magnetism and spin polarization would be possibly applied to the field of the material engineering and information technology.