一步合成核壳结构C-TiO_2复合材料及UV-Vis光催化降解染料

以二(乙酰丙酮基)钛酸二异丙酯,异丙醇和尿素为原料,通过简单的一步无模板溶剂热法合成了核壳结构C-TiO_2复合材料前驱体,随后在氩气条件下不同温度煅烧得到高晶相CTiO_2复合材料。运用SEM、TEM、XRD、XPS、Raman、TG、N_2吸附-脱附、UV-Vis漫反射等技术对样品进行表征、并在UV-Vis光照射下分别对Rh B、MB、CR 3种染料溶液进行了催化降解测试。结果表明:550℃煅烧的样品的催化性能最佳,其为高晶相的锐钛矿相TiO_2材料,并包含少量的碳,而且550℃煅烧的样品依然保持了核壳结构。比表面积能够达到85.69 m^2/g、孔直径为16.4 nm、孔体积为0.423 m^3/g。其优越的催化性能可归于较大的比表面积能够提供吸附更多的染料分子;核壳结构更有利于捕获更多的光量子;高晶相更有利于催化过程中电子-空穴对的分离。

Effect of ruthenium on γ' precipitation behavior and evolution in single crystal superalloys

The effect of Ru on γ＇ precipitation behavior and evolution in single crystal superalloys with different Ru contents were investigated by scanning electron microscopy with energy dispersive spectroscopy,3D atomic probing,differential scanning calorimetry.The results show that the solvus of the γ＇ phase decreases gradually with increasing Ru content in the alloys by casting or by the same solution and aging treatments,the alloy with a larger Ru content yields a smaller γ＇ phase.The addition of Ru increases the growth rate and coarsening rate of the γ＇ phase.Ru mainly distributes in the γ phase,which causes more Re and Mo partition into the γ＇ phase,increasing the absolute value of mismatch and the rafting rate of the γ＇ phase.

Microstructure evolution of Zn-8Cu-0.3Ti alloy during hot deformation

The hot deformation behavior of homogenized zinc alloy was investigated through uniaxial compression test on a Gleeble-1500 thermal-mechanical simulator within a temperature range of 230-380°C and a strain rate range of 0.01-10 s -1 ,the corresponding flow curves and their characters were determined and analyzed,and microstructures were studied by optical,SEM and TEM microscopy.The results indicated that the microstructure evolution of zinc alloy during hot deformation involves the spheroidization of the phase of TiZn15,coarsening of the precipitated phase and dynamic recrystallization（DRX）of the phase of matrix,leading to the formation of the polyphase（η＋ε＋TiZn15）structure.The spheroidization of the phase of TiZn15 during hot deformation was beneficial to the particle nucleation stimulated and then promoted to DRX of matrix.The dynamic recrystallization grain size of the matrix phase decreased firstly and then increased with elevating the temperature,and the degree of DRX became more complete when the strain rate and strain became larger.Hot deformation accelerated the diffusion of Cu atom,which resulted in the coarsening of the precipitated phase.Thus,the microstructure was refined owing to the pinning effect of the precipitated phase.

Morphology and chemical composition of γ/γ' phases in Re-containing Ni-based single crystal superalloy during two-step aging

The γ/γ＇ microstructure of a Re-containing Ni-based single crystal super alloy after a two-step aging was studied using scanning electron microscopy （SEM）,transmission electron microscopy （TEM） and scanning transmission electron microscopy （STEM）.The crystals were grown by the floating zone （FZ） method.Both cuboidal and spherical γ＇ precipitates were formed after a two-step aging.The size of the cuboidal γ＇ phases first increased and then decreased with the extension of the second-step aging time.Re,Co and Cr strongly concentrated in the γ phase whereas Ni and Al enriched in the γ＇ phase.Thermodynamic calculation by JMatPro was performed to explain the experimental observations.

SYNTHESIS AND CHARAOTERIZATION OF NOVEL THERMOTROPIO LIQUID ORYSTALLINE POLYESTERS BEARING NONLINEAR OPTICAL AZOBENZENE SIDE GROUP

A series of novel thermotropic liquid crystalline polyesters bearing nonlinear optical azobenzene side group were synthesized by high temperature solution polycondensation and their structures,thermal stability, phase transition behavior and crystallinity were characterized by IR,elemental analysis, TG-DTA, polarizing optical microscope (POM) equipped with a hot stage and X-ray diffraction techniques. The results demonstrate that all the synthesized polyesters exhibit nematic liquid crystalline phases and show relatively high glass transition temperatures and good thermal stability.

Kinetics and microstructural evolution during recrystallization of a Ni_3Al-based single crystal superalloy

The recrystallization kinetics and microstructural evolution of a Ni3Al-based single crystal superalloy were presented, especially the different recrystallization behaviors between the dendrite arm and the interdendritic region. The single crystal alloy was deformed by grit blasting. A succeeding annealing under inert atmosphere at 1280 ℃ for different time led to the formation of recrystallized grains close to the grit blasting surface. It was found that the recrystallization depth and velocity in the dendrite arm were respectively deeper and faster than those in the interdendritic region where the Y-NiMo phase existed. The recrystallization process in the interdendritic region was significantly inhibited by the Y-NiMo precipitates. However, the pinning effect gradually weakened with the annealing time due to the dissolution of the Y-NiMo phase, and the recrystallization depth in the dendrite arm was deeper than that in the interdendritic region.

Structure of High Temperature Phase α-Ba_3Y(BO_3)_3 Crystal

The high temperature phase a-Ba3Y(BO3)3 was synthesized by Czochralski method, and its crystal structure has been determined by single-crystal X-ray diffraction. It crystallizes in the trigonal system, space group 3R with a = 13.028(2), c = 9.4992(2) ? V = 1396.1(5) ?, Ba3YB3O9, Mr = 677.36, Z = 6, Dc = 4.834 g/cm3, l(MoKa) = 0.71073 ? m = 18.721 mm-1, F(000) = 1764, the final R = 0.0718 and wR = 0.1640 for 1199 observed reflections with I > 2s(I). In this structure two alternate nonequivalent Y atoms form one-dimensional chains bridged by the Ba atoms with BO3 triangles which link Y(1) and Y(2), respectively. The Ba atom is surrounded by nine O atoms belonging to six BO3 triangles.

HBT's High Frequency Noise Modeling and Analysis

A T equivalent high frequency heterojunction bipolar transistor (HBT) noise model is reported.This model is derived from Hawkins noise model commonly used in Si BJT.The main modifications include the influence of the ideality factor,emitter resistance,intrinsic base collector capacitance,extrinsic base collector capacitance and other parasitic elements of HBT represented in equivalent circuit topology.In order to calculate accurate noise parameters from the equivalent circuit,the noise correlation matrix method is used to avoid any simplifications generated in circuit transformations and complex noise measurements.The analysis of the influence of the equivalent circuit elements on the minimum noise figure is reported,the results of analysis agree well with the physics explanations.By means of the formulae derived from device physics of HBT,the influence of device parameters on the minimum noise figure is also represented.

Critical Behavior of Gaussian Model on X Fractal Lattices in External Magnetic Fields

Using the renormalization group method, the critical behavior of Gaussian model is studied in external magnetic fields on X fractal lattices embedded in two-dimensional and -dimensional Euclidean spaces, respectively. Critical points and exponents are calculated. It is found that there is long-range order at finite temperature for this model, and that the critical points do not change with the space dimensionality (or the fractal dimensionality ). It is also found that the critical exponents are very different from results of Ising model on the same lattices, and that the exponents on X lattices are different from the exact results on translationally symmetric lattices.

Low phase noise millimeter wave monolithic integrated phase locked-loop

A Monolithic integrated phase locked-loop （PLL） with a low phase noise is proposed in this paper. Several techniques are utilized to improve the performance of the PLL which works at the milli- meter-wave band. The on-chip high-Q eoplanar waveguides （CPWs） are utilized in the resonant tank and the differential current amplifier with a resonator is used to realize the VCO. In the output buffer circuit, several stages of cascaded source-followers connect and differential amplifiers are adopted to improve the driving capability of the PLL＇ s output signals. An improved analog multiplier topology is also used in the PD circuit to improve the gain of the PD. The proposed PLL is realized with a 0.2p, m GaAs pseudomorphie high electron mobility transistor （PHEMT） process. At 10 kHz offset from the center frequency, the measured output phase noise of the PLL output is only -88.83dBc/Hz. The circuit exhibits a low root mean sauare （RMS） litter of 1.68Ds.

Effect of Precipitate Phases and Grain Size on Mechanical Properties of Inconel 718 Superalloy After Various Heat Treatments

Various heat treatments were conducted on Inconel 718 superalloy,and the resultant microstructures and properties were investigated to analyze the mechanisms of heat treatments.Results show that the type and quantity of precipitate phases and the grain size have different effects on the properties of Inconel 718 superalloy after various heat treatments.Theγ"andγ'phases as well as grain size mainly influence the strength,and theδphase mainly influences the plasticity.Besides,the precipitation ofγ"andγ'strengthening phases can improve the yield strength.The alloy strength is inversely proportional to mean grain size when theγ"andγ'phases have similar contents.The plasticity is susceptible to the content and shape ofδphase.A proper amount ofδphase is beneficial to the plasticity,but excessiveδphase degrades plasticity.

A Li-rich layered-spinel cathode material for high capacity and high rate lithium-ion batteries fabricated via a gas-solid reaction

Lithium-rich layered oxide(LLO)cathode materials have drawn extensive attention due to their ultrahigh specific capacity and energy density.However,their commercialization is still restricted by their low initial coulombic efficiency,slow intrinsic kinetics and structural instability.Herein,a facile surface treatment strategy via gaseous phosphine was designed to improve the rate performance and capacity stability of LLOs.During the solid-gas reaction,phosphine reacted with active oxygen at the surface of LLOs due to its reductivity,forming oxygen vacancies and spinel phase at the surface region.As a result,Li ion conductivity and structural stability were greatly enhanced.The phosphinetreated LLOs(LLO@P)showed a layered-spinel hybrid structure and delivered an outstanding rate performance of156.7 mA h g^-1 at 10 C and a high capacity retention of 74%after 300 cycles at 5 C.

The first-principle study on the equation of state of HMX under high pressure

The equation of states （EOS） of high energy explosive HMX （octahydro-l,3,5,7-tetranitro-1,3,5,7-tetrazocine） has been studied by using the first principle method. Our results include the lattice constants, elastic constants, and the dependence of total en- ergy and pressure on volume for β- and 5-HMX. The calculated elastic constants and the pressure-volume relationship of ^-HMX are also compared with the experimental values. The theoretical tensile experiments are implemented on the 13-HMX. The atomic-scale analysis displays that the fracture originates from the intermolecule of HMX and is possibly due to the weak interaction of intermolecules.

The polarization-dependent supercontinuum generation in photonic crystal fibers with high birefringence and two-zero dispersion

A polarization-dependent supercontinuum spectrum source of light from the UV to infrared region has been generated in our photonic crystal fiber with birefringence B=2.23×10 3.By tuning the polarization direction of the input pulse,it is found that the width of the supercontinuum spectrum changes dramatically with the input polarization directions.At the same time,we qualitatively explain the blue-shift peak and the red-shift peak in the experimental spectrum using phase matching conditions on dispersive waves,stoke waves and the pump wave.In addition,we also found that supercontinuum spectrum generation,to some extent,is dependent on the pump wavelength and average power of the pump.The spectrum is broadened with the increase of average power,but unchanged after average power reaches a certain value;when the pump wavelength is located in the anomalous dispersion and further away from the zero-dispersion wavelength,the spectrum of the supercontinuum is wider.