Advanced Materials Research Vols. 415-417

Abstract: The grain size and the distribution of crystal orientation have an important effect on the mechanical properties of wrought AZ31B magnesium alloy sheets. Because the AZ31B magnesium alloy sheets rolled by conventional rolling have a poor formability at room temperature, a new rolling technology of differential speed rolling is used to improve the mechanical properties of AZ31B magnesium alloy. The research shows that the number of twinning crystal decreases, the number of the core of dynamically recrystallized grain increases, and the grain size become fine and isotropy by differential speed rolling with the increase of the reduction and the improving of the rolling temperature to some extent. The differential speed rolling not only improves the isotropy of the basal texture and also improves the microstructure and mechanical properties.

Abstract: In order to confirm the surface fractal dimension of the internal pore of complex porous materials by means of the FHH model and nitrogen adsorption method. Study the change rule on fractal characteristics of the pore of cement based materials further. The results shows that, surface area of the complex internal structure of cement based materials has the fractal characteristics observably. Testing and evaluating the fractal characteristics on surface area of the pore of cement-based materials is effective by nitrogen adsorption method. It is good for analyzing surface characteristics of pore structure further. Surface fractal dimension of pore structure and surface area have not good correlation. The characteristics and conclusion that quality fractal dimension of powder and surface area evaluating fineness of powder have not very good correlation is consistent.

Abstract: The dissertation introduced first simple uniaxial compression test of concrete, and in the specimen under uniaxial compression of the breakage mode reinforced and improved. For tensile destruction and shear failure damage model, bring forward the corresponding calculation model and some model set up compressive strength and tensile strength of the interrelations with each other, analysis of compressive strength and much higher than the tensile strength.In addition, from different model, drew diagrams with Matlab software，analysis of the compressive strength and tensile strength of the intrinsic value of relations.Finally, model for the primary split breakage and that shear failure can be ignored, used the buckling theory and the theory of mutation analysis, and calculated the corresponding critical stress.

Abstract: The protein content of Rhodotorula rubra 2.1817,Candida tropicalis 2.1775 and Geotrichum candidum 2.1175 were assayed by Coomassie brilliant blue methods. Screening the high-yield SCP strains.Then,the cultur condition of the strains were optimizated by single-factor test.It is shown that the high-yield SCP strains was Candida tropicalis 2.1775,the protein content was 32.46%.The optimal factors: inoculum size 10% (V/V),temperature 30°C,shaking 200 rpm,culture time 5 days.

Abstract: In this paper, melt-spinning technology was used for preparing Mg₂₀Ni_10-xCo_x (x = 0, 1, 2, 3, 4) hydrogen storage alloys. The influences of both the Co substitution and the melt spinning on the the physical and electrochemical hydrogen storage kinetics of the alloys were investigated. The XRD, SEM and TEM characterization exhibits that the as-spun Co-free alloy holds a typical nanocrystalline structure, whereas the as-spun alloys substituted by Co display a nanocrystalline and amorphous structure, confirming that the substitution of Co for Ni facilitates the glass formation in the Mg₂Ni-type alloy. The Co substitution gives rise to forming secondary phase MgCo₂ without altering the Mg₂Ni major phase of the alloys. The measurement of the physical and electrochemical hydrogen storage kinetics of the alloys shows that both the melt spinning and the substitution of Co for Ni markedly improve the physical hydriding and dehydriding kinetics and the electrochmeical kinetics (HRD) of the alloys.

Abstract: Disordered carbons prepared by the pyrolysis of peanut shells with and without a porogen were investigated. The first-cycle lithium insertion capacity of the porogen-treated carbon was 3504 mAh/g, and was related to the high surface area (2099 m²/g) of the carbon. It was concluded from x-ray diffraction studies that the extra lithium was stored in the microporous voids in the carbon. The large irreversible capacity for this carbon is believed to be associated with the loss of lithium through its reaction with surface groups as well as with lithium plating and subsequent passive film formation. The impedance profiles of the carbons at various potentials were analyzed and modeled with suitable equivalent circuits. Charge-discharge studies with the porogen-treated carbon, pre-charged and discharged prior to use in coin cells, indicated that the first-cycle reversible capacity was the greatest when the charge-discharge rate was 0.4 C. The carbon maintained capacities of about 325 mAh/g for 20 cycles, and then stabilized around 380 mAh/g for over 70 cycles.

Abstract: A series of copolymers P(VP-HEMA) composed of hydroxyl ethyl methacrylate (HEMA) and 4-vinyl pyridine (VP) were prepared by a solution copolymerization technique. Based on the copolymer P(VP-HEMA) prepared by the content of VP 50%, the amount of AIBN 3% and the optimized liquid electrolyte, a polymer solution electrolyte with concentration of 9.0% was formed. By addition of 1,4-dibromobutane into the solution, the copolymer gel electrolyte with higher conductivity 6.14mS/cm was prepared. Gelation is caused by the quaterisation between the group of pyridine in P(HEMA-VP) and 1,4-dibromobutane. Based on the copolymer gel electrolyte, a dye-sensitized solar cell was fabricated with short-circuit current of 13.62mA/cm²,open circuit voltage of 0.72V, fill factor of 0.5465 and an overall conversion efficiency of 5.24% under irradiation 100mW/cm² (AM1.5).

Abstract: Some conditional experiments for the preparation of Poly Silicate Aluminium Ferric Boron (PSAFB) composite flocculant and its coagulation and flocculation for the removal of COD_Cr were conducted and discussed．Preliminary results show the optimum synthesis condition as follows: Si/Al( mole ratio) =2/1, Si/Fe( mole ratio)=1/1,Si/B( mole ratio)=10/1. Under optimal operating conditions，PSAFB can remove 69.3％ of COD_Cr from the printing and dyeing wastewater.

Abstract: Spinel MCr₂O₄(M = Cu, Ni) nanopowders were synthesized by co-precipitation technique from alcohol-aqueous system and the performance of MCr₂O₄/TiO₂ composite film electrodes was studied. The synthesized MCr₂O₄ nanopowders were characterized by X-ray diffraction (XRD) and UV-vis diffuse reflectance spectrum (UV-vis). The MCr₂O₄ nanopowders were doped into nanocrystalline semiconductor oxide film electrode of DSSCs and the influence of doping content was investigated. Compared with the pure TiO₂ film electrode, the absorbance of different MCr₂O₄/TiO₂ composite film electrode increased significantly. Furthermore, the light respondence of CuCr₂O₄/TiO₂ composite electrode was better than NiCr₂O₄/TiO₂ composite electrode. When the content of CuCr₂O₄ 2%, the photoelectric conversion efficiency increased by 54%, and doping 1% NiCr₂O₄ nanopowders, the photoelectric conversion efficiency was improved 30%.

Abstract: The adsorption of phenol onto activated carbon fiber (ACF) from aqueous solutions were studied. The adsorption isotherms of phenol onto ACF at 298.15 K,303.15 K and 308.15K follow the Freundlich and Langmuir isotherm equation. The Freundlich model was verified to be the best to describe the adsorption data.Values of ∆G⁰ for phenol adsorption onto ACF are-8.549、-7.899 and -7.516 kJ•mol-1 at 298.15,303.15and 308.15K , respectively. The values of ∆H⁰ and ∆S⁰ are -39.30 kJ•mol-1 and -103.3 J.mol-1.k-1, respectively. The adsorption process is spontaneous and exothermic. Negative △S⁰ values suggested the randomness of phenol molecules at solid-liquid interface and an decrease in the degree of freedom of the adsorbed species.