Synthesis and Characterization of Poly （L-lactide-co-glycolide）

Poly （ l- lactide- co-glycolide ） （ PLGA ） with different compositions was prepared using stannous octaoate as catalyst by bulk ring-opening copolymerization of l-lactide and glycolide. The structure and properties of the PLGA copolymers were cbaracterized by means of attenuated total reflectance-Fourier transform infrared （ATR-FTIR）, ^1H NMR, differential scanning calorimeter （ DSC and X-ray diffraction （XRD） methods, The experimented results indicate that the synthetic conditions and the composition of copolymers have art obvious influence on the structure of PLGA copolymers, The degradation rate of eopolymers increased with the increasing of the glycolide component in the copolymers.     

Mechanism and Microstructure of Electroless Ni-Fe-P Plating on CNTs

Electroless Ni-Fe-P alloy plating on the surface of CNTs was carded out with a bath using citrate salt and lactic acid as complex agents. We proposed a chemical reaction mechanism. The morphology, structure and chemical composition of the Ni-Fe-P/CNTs were studied with the aid of a scanning electronic microscope （SEM）, X-ray diffraction （XRD） and an energy-dispersive X-ray spectral analysis （EDS）. The results show that through a correct pre-treatment and electroless plating, Ni-Fe-P/CNTs composite particles can be obtained. The optimum electroless plating parameters of 35-42℃ and pH of 8.5-9.7 were achieved. The as-plated Ni-Fe-P alloy is amorphous. After a heat treatment at 500℃ for 90 min in H2, the coating is transformed into crystalloid Ni3E Fe2NiP and （Fe,Ni）3R The Ni-Fe-P alloy coating on the surface of CNTs is smooth and unique. The amount of Ni on the surface （mass fraction） of the Ni-Fe-P/CNTs composite particles is 29.13%, that of Fe 3.19% and that of P 2.28%.     

Surface films formed on SnO<Subscript>2</Subscript> anode in lithium secondary batteries by FTIR spectroscopy

The chemical composition of the passivating layer formed on nano SnO2 anodes in 1 M LiClO4＋ （ethylene carbonate）EC ＋ （dimethyl carbonate）DMC at different charge/discharge states in lithium secondary batteries was studied using extra reflectance FTIR spectra. Results show that solvent decomposition reaction that generally occurs on the surface of carbon and alkali metal electrodes also takes place on nano-SnO2 anode, and the major constituent of the passivating layer is Li2CO3 and ROCO2Li. Formation of the passivating layer would certainly lead to the irreversible capacity loss.     

Electrochemical performance of nano-scale β-Ni（OH） 2 prepared at different transformations of pH value

The influence of transforming pH values on the electrochemical performance of nano-scale Ni （OH）2 was analyzed. The measurement results of XRD indicate that the nano-scale Ni （OH） 2 prepared at different transformations of pH value is β （ Ⅱ ）-phase with different crystal lattice parameters. Cyclic voltammograms （CV） and electrochemical impedance spectroscopy（EIS） measurement results show that transformations of pH value affect the proton diffusion coefficient （D） and charge-transfer resistance （Re,） of the material. The simulation of.cell experiment shows that the sample prepared at a pH of 10. 1 exhibits the maximum specific capacity （327.8 mAh/g） and higher discharge platform, the discharge performance of electrodes depends on both D and Rct, so the kinetics characteristics that electrodes reaction is controlled by both mass-transfer step and charge- transfer step are put forward.     

Action time effect of lime on its depressive ability for pyrite

Two sample groups of bulk concentrates consisting mainly of pyrite and chalcopyrite from Daye and Chenghchao Mines in Hubei Province of China were used to investigate the effect of the action time of lime on its depressive ability for pyrite. The experimental results conducted with different samples and collectors showed that the action time between lime and pyrite markedly influences the depressive ability of lime. The depressive ability of lime increased with the action time increasing. It was also proved that the depressive results obtained at a large lime dosage after a shorter action time are similar to those obtained at a small lime dosage after a longer action time. The increase of depressive ability of lime after a longer action time is because that there are different mechanisms in different action time. The composition on the surface of pyrite acted for different time with lime was studied by using ESCA (Electron Spectroscopic Chemical Analysis). The results showed that iron hydroxide and calcium sulphate formed on the pyrite surface at the presence of lime in the pulp but the amounts of iron hydroxide and calcium sulphate were different at different action time. At the beginning action time the compound formed on the pyrite surface was mainly calcium sulphate and almost no iron hydroxide formed; but with the action time increasing, iron hydroxide formed. The longer the action time, the more iron hydroxide and the less calcium sulphate formed. It was considered that the stronger depressive ability of lime after a longer action time is because more iron hydroxide forms on the pyrite surface.     

Microstructural characterization and mechanical property of Fly Ash/Al-25Mg composites

Fly ash/Al-Mg composites are fabricated by powder metallurgical method. The morphology and structure of fly ash/A l-Mg composites are characterized by scanning electron microscope （SEM） and X-ray diffraction, respectively. The influences of different fly ash content on the friction and wear behavior of the composites are investigated at a constant sliding velocity of 400 r/min and the worn mechanism of composites is discussed. The results indicate that the friction coefficient is steadily lower than that of Al alloy matrix at the lower fly ash content and loads. For the fly ash/Al-Mg composites, the wear mechanism is characterized as abrasive wear and adhesive wear under small normal load and at low fly ash content, and it is characterized as delamination wear and abrasive wear transferred onto the counterpart under high normal load and at high fly ash content.     

Modeling and Optimization of Heat Dissipation Structure of EV Battery Pack

In order to solve the problems of high temperature and inconsistency in the operation of electric vehicle (EV) battery pack,computational fluid dynamics (CFD) simulation method is used to simulate and optimize the heat dissipation of battery pack.The heat generation rate at different discharge magnifications is identified by establishing the heat generation model of the battery.In the forced air cooling mode,the Fluent software is used to compare the effects of different inlet and out-let directions,inlet angles,outlet angles,outlet sizes and inlet air speeds on heat dissipation.The simulation results show that the heat dissipation effect of the structure with the inlet and outlet on the same side is better than that on the different sides;the appropriate inlet angle and outlet width can improve the uniformity of temperature field;the increase of the inlet speed can improve the heat dissipation effect significantly.Compared with the steady temperature field of the initial structure, the average temperature after structure optimization is reduced by 4.8益and the temperature difference is reduced by 15.8℃,so that the battery can work under reasonable temperature and temperature difference.     

Modeling and Optimization of Heat Dissipation Structure of EV Battery Pack

In order to solve the problems of high temperature and inconsistency in the operation of electric vehicle (EV) battery pack,computational fluid dynamics (CFD) simulation method is used to simulate and optimize the heat dissipation of battery pack.The heat generation rate at different discharge magnifications is identified by establishing the heat generation model of the battery.In the forced air cooling mode,the Fluent software is used to compare the effects of different inlet and outlet directions,inlet angles,outlet angles,outlet sizes and inlet air speeds on heat dissipation.The simulation results show that the heat dissipation effect of the structure with the inlet and outlet on the same side is better than that on the different sides;the appropriate inlet angle and outlet width can improve the uniformity of temperature field;the increase of the inlet speed can improve the heat dissipation effect significantly.Compared with the steady temperature field of the initial structure,the average temperature after structure optimization is reduced by 4.8℃ and the temperature difference is reduced by 15.8℃,so that the battery can work under reasonable temperature and temperature difference.     

Pore structure of ore granular media by computerized tomography image processing

The pore structure images of ore particles located at different heights of leaching column were scanned with X-ray computerized tomography （CT） scanner, the porosity and pore size distribution were calculated and the geometrical shape and connectivity of pores were analyzed based on image process method, and the three dimensional reconstruction of pore structure images was realized. The results show that the porosity of ore particles bed in leaching column is 42.92%, 41.72%, 39.34% at top, middle and bottom zone, respectively. Obviously it has spatial variability and decreases appreciably along the height of the column. The overall average porosity obtained by image processing is 41.33% while the porosity gotten from general measurement method in laboratory is 42.77% showing the results of both methods are consistent well. The pore structure of ore granular media is characterized as a dynamical space network composed of interconnected pore bodies and pore throats. The ratio of throats with equivalent diameter less than 1.91 mm to the total pores is 29.31%, and that of the large pores with equivalent diameter more than 5.73 mm is 2.90%.     

Effect of temperature on microstructure ofmolybdenum diffusion coating on titanium substrate

The halide-activated pack cementation process was used to form molybdenum diffusion coating on titanium substrate. The morphology, structure, elements diffusion distribution and microhardness of the coatings formed at different diffusion temperatures were studied. The results indicate that the coating is made up of deposition layer and diffusion layer, and the surface roughness of specimens is increased after diffusion. In the diffusion layer, the major phases are Mo and β-Ti phase with addition of α′-Ti phase and α″-Ti phase. And the phase composition of Mo →β→α″→α′ is formed for different Mo contents in the diffusion layer from outside to inside. The diffusion of Ti element is very obvious as well as Mo element. With increasing the diffusion temperature, the thickness of diffusion layer is increased rapidly, and the microhardness is changed more smoothly with diffusion depth, which shows the same distribution rules as the Mo content.     

Fabrication of Poly-Si Thin Film on Glass Substrate by Aluminum-induced Crystallization

Amorphous silicon （ a-Si ） thin films were deposited on glass substrate by PECVD, and polycrystalline silicon （ poly- Si ） thin films were prepared by aluminum- induced crystallization （ AlC ）. The effects of annealing temperature on the microstructure and morphology were investigated. The AlC poly-Si thin films were characterized by XRD, Raman and SEM. It is found that a-Si thin film has a amorphous structure after annealing at 400℃ for 20 min, a-Si films begin to crystallize after annealing at 450 ℃ for 20 min, and the crystallinity of a-Si thin films is enhanced obviously with the increment of annealing termperature.     

Precipitation behaviors of X70 acicular ferrite pipeline steel

The morphology, structure, and chemical composition of precipitates in the final microstructure of Nb-V-Ti microalloyed X70 acicular ferrite pipeline steel were investigated using transmission electron microscopy （TEM） and energy dispersive X-ray spectroscopy （EDS）. Precipitates observed by TEM can be classified into two groups. The large precipitates are complex compounds that comprise square-shaped TiN precipitate as core with fine Nb-containing precipitate nucleated on pre-existing TiN precipitate as caps on one or more faces at high temperature. In contrast, the fine and spherical Nb carbides and/or carbonitrides precipitate heterogeneously on dislocations and sub-boundaries at low temperature. From the analysis in terms of thermodynamics, EDS and chemical cornposition of the steel, NbC precipitation is considered to be the predominant precipitation behavior in the tested steel under the processing conditions of this research.     

Effect of Pre-oxidation on the Properties of Crushed Bituminous Coal and Activated Carbon Prepared Therefrom

The influence of a pre-oxidation process on the chemical properties of crushed bituminous coal and on adsorption properties of the subsequently formed char and activated carbon is discussed in this paper.Datong bituminous coal samples sized 6 mm were oxidized at different temperatures and for different times and then carbonized and activated by steam to obtain activated carbons.A Uniform Design method was used to arrange the experiments, IR and adsorption experiments were used to characterize these oxidized coals, chars and activated carbon samples.The results show that the carboxyl group disappeared and α-CH2 groups joined to alkenes decreased dramatically but the carbonyl group clearly increased in the coal sample oxidized at 543 K; The chemical composition of coal samples oxidized at lower temperature is different from that of coal oxidized at 543 K.Oxidizing coal samples at higher temperatures for a short time or at lower temperatures for a longer time resulted in activated carbon samples that tended toward the same adsorption properties Iodine number 1100 mg/g and Methylene blue value 252 mg/g.The yield of activated carbon obtained from the pre-oxidized coal is 10% higher than the yield from parent coal but the activated carbons have the same adsorption properties.     

Thermodynamic Behavior of Lead-Antimony Alloy in Vacuum Distillation

The distribution of metals in Pb-Sb ailoy during vacuum distillation was calculated.The composition curve of vapor-liquid phases determined by this work is different from those of. other researchers.The curve intersects the diagonal at C.The compositions of vapor and liquid at C are identical.The antimony content of vapor on the left of C is less than that of liquid,and the vapor on the right-side of C contains more antimony.These characteristics can be applied to the elimination of antimony from crude lead or the elimination of lead from crude antimony.The position of C moves rightwards with temperature increment.The discrepency among the compositions of C suggested by diffrent authors was explained.     

Structure and properties of TiB<Subscript>2</Subscript> thin films deposited at low temperatures using RF magnetron sputtering

The TiB2 thin films were deposited on steel substrates using RF magnetron sputtering technique with the low normalized substrate temperature （0.1〈Ts/Tm〈0.2）. Microstructure of these films was obtained by field emission scanning electron microscope （FESEM） and the grazing incidence X-ray diffraction （GIXRD） characterization, while the composition of films was obtained using Auger emission spectroscopy （AES） analysis. It was found that the TiB2 thin films were overstoichiometric with the B/Ti ratio at 2.33 and the diffusion of Ti and B atoms on the substrate surface was greatly improved at 350 ℃. Moreover, a new dense structure, named ＂equiaxed＂ grain structure was observed by FESEM at this substrate temperature, Combined with FESEM and AES analysis, it was suggested that the ＂equiaxed＂ grain structure was located in Zone 2 at the normalized substrate temperature as low as 0.18.     

Low-cost preparation of boron nitride ceramic powders

The amorphous boron nitride ceramic powders were prepared at 750-950 ℃ by the low-cost urea route, and the effects of preparation temperatures, molar ratios of the raw materials and oxidation treatment on the composition, structure and surface morphology of the products were investigated through FT-IR, XRD and SEM. The results show that the products ceramize and crystallize gradually with the increase of the temperature. When the molar ratio and reaction temperature are 3:2 and 850 ℃, respectively, the products have high purity, compact structure and nice shape. The oxidation treatment at 450 ℃ will not impair the composition and structure of boron nitride but effectively remove the impurities.     

Numerical Simulation on Explosion in Double-Layer Medium of Concrete and Soil

The numerical simulation on explosion in concrete and soil is performed by using the three-dimension finite element code LS-DYNA, into which a continuum damage model which can well describe the fracture of concrete is implemented. As a consequence, wave propagation and attenuation in concrete and on soil-concrete interface are obtained respectively. Moreover, the damage regions of concrete at different thicknesses of soil （TOS） and depths of charge （DOC） are procured. The existent soil reduces damage region of concrete. Numerical results provide reference for design of warhead and protective structure and blasting.     

Error Analysis of Three Degree-of-Freedom Changeable Parallel Measuring Mechanism

A three degree-of-freedom （DOF） planar changeable parallel mechanism is designed by means of control of different drive parameters. This mechanism possesses the characteristics of two kinds of parallel mechanism. Based on its topologic structure, a coordinate system for position analysis is set-up and the forward kinematic solutions are analyzed. It was found that the parallel mechanism is partially decoupled. The relationship between original errors and position-stance error of moving platform is built according to the complete differential-coefficient theory. Then we present a special example with theory values and errors to evaluate the error model, and numerical error solutions are gained. The investigations concentrating on mechanism errors and actuator errors show that the mechanism errors have more influences on the position-stance of the moving platform. It is demonstrated that improving manufacturing and assembly techniques can greatly reduce the moving platform error. The small change in position-stance error in different kinematic positions proves that the error-compensation of software can improve considerably the precision of parallel mechanism.     

Preparation and Characterization of Super Absorbent Resin from Natural Cellulose

The grafting polyacrylamide onto wood pulp cellulose (cell-g-PAM) was performed with cerous ammo-nium nitrate as the initiator and hydrolyzed to produce the super absorbent resin. The FTIR shows that the poly-acrylamide is grafted on the cellulose. After hydrolyzation, part of acrylamino groups are transformed into car-boxyl groups. The XRD analysis shows that the graft polymerization occurred at the amorphous section and the surface of the crystal section of cellulose. The SEM graph reveals that there is a layer of polymer on the surface of cellulose fiber and the fibril structure of the cellulose surface is covered. After hydrolyzation, the surface of the product is different from that of cell-g-PAM‘s and the surface is scraggy. The technical conditions to prepare high water absorbent resin were confirmed. Through the radical graft copolymerization, the high water absorbent resin can be produced from wood pulp cellulose.     

Photocatalytic activities of amorphous TiO<Subscript>2</Subscript>-Cr thin films prepared by magnetron sputtering

Chrome-doped titanium oxide films were prepared by reactive magnetron sputtering method. The films deposited on glass slides at room temperature were investigated by atom force microscope, X-ray diffractometer, X-ray photoelectron spectroscopy, UV-Vis spectrophotometer, the photoluminescence （PL） and ellipse polarization apparatus. The results indicate that TiO2-Cr film exists in the form of amorphous. The prepared films possess a band gap of less than 3.20 eV, and a new absorption peak. The films, irradiated for 5 h under UV light, exhibit excellent photocatalytic activities with the optimum decomposition rate at 98.5% for methylene blue. Consequently, the thickness threshold on these films is 114 nm, at which the rate of photodegradation is 95% in 5 h. When the thickness is over 114 nm, the rate of photodegradation becomes stable. This result is completely different from that of crystalloid TiO2 thin film.