Applied Mechanics and Materials Vol. 692

Abstract: The components of a fermentation medium were optimized to produce cellulose from HDZK-BYTF620 (Aureobasidium pullulans) which is from the gut of termites and can produce cellulose under liquid state fermentation conditions by response surface methodology. By Plackett-Burman design screened out three major factors of strains HDZK-BYTF620 which affected production of the activity cellulose, immediately, CaCl₂, MgSO₄ and CMC-Na. The fermentation conditions were optimized with Box-Behnken experiment and the largest regional of the activity of cellulase was approach with the steepest ascent experiment. The optimum composition of medium addition of CaCl₂, MgSO₄ and CMC-Na was 0.77 g/L, 0.41 g/L and 21.88 g/L, respectively. Under the optimum fermentation medium conditions, the activity of cellulase was (598.00±2.56)×10^-3 IU/mL, increased 5.0 % to that of using initial medium.

Abstract: In this study, the soil column experiment was adopted to investigated the release characteristic of P from soil by citric acid leaching. The results showed that the P release characteristics were different from each other under various citrate concentrations. At high concentration (50 mM) treatment, P concentration of effluents increased rapidly with effluent volume at the beginning, reached the maximum value after approximately 150 ml solution had passed through the columns. For the column treated with 5 mM of citric acid, the P in leachates was increased gradually to the maximum concentration, and then approached a relatively stable level during the 1000-3050 ml effluent volume. For low concentration (0.5 mM) treatment, the level of P in the effluents has always been very low, though a small peak was observed during the leaching.

Abstract: Dynamic mechanical properties and microstructures of pure iron and Fe-30Mn-3Si-4Al TWIP (TWinning Induced Plasticity) steel were conducted by SHPB (Split-Hopkinson Pressure Bar), OM (Optical Microscopy) and TEM (Transmission Electron Microscope), at the strain rate ranging from 10² to 10⁵ s^-1 and at room temperature. The effect of high strain rate on the mechanical responses of pure iron and Fe-30Mn-3Si-4Al TWIP steel belonging to BCC (Body Centered Cubic) and FCC (Face Centered Cubic) structures respectively was evaluated. The comparison of deformation mechanism was analyzed between them and it concluded that dislocation gliding is a major deformation mechanism in pure iron with BCC structure and deformation twinning plays a significant role in Fe-30Mn-3Si-4Al TWIP steel with FCC structure.

Abstract: Time-resolved photoluminescence spectra of vertical cavity surface emitting laser (VCSEL) structures under different excitation intensity are investigated. The effect of the distributed Bragg reflectors (DBR) on the laser emission and the mechanism of multi-longitudinal-mode are analysed. A broad peak around 2.80eV is observed from the structure without DBR cavity when pumped under low excitation intensity. At higher excitation density up to 21.4kW/cm², a lasing peak appears at 2.86eV, and exhibits a rapid growth and red shift with the increase of the excitation density. The decay time of the peak is about 66ps. When the spectrum is measured after the deposition of DBR on the top side of the grown nitride structure, the number of peaks increases to 7, and the free spectral range 0.21×10¹⁴ Hz is close to the value that calculated by the Fabry-Perot cavity length. After depositing the second DBR, multi PL peaks around 2.87eV are observed. The relationship of laser emission intensity and angle of the polarizer shows nearly a cosine square variation. However, the polarization characteristics of the four main peaks are different, which indicates that these peaks occurr by the oscillation of different optical cavities.

Abstract: This study used ceramic membrane technology to concentrate tungsten fine particles for its inefficient recycling issue. Factors affecting the membrane concentration test were discussed, and the results show that: under the feed flow of 7000 mL/min, concentration time of 3 hours, and concentration liquid flow of 500 mL/min, it is the optimal effect of ceramic membrane concentration tungsten fine particle, which the interception rate reaches more than 99%, the membrane permeation flux can be nearly reach 470mL/(min×1099cm²) above, and concentrate concentration can be basically stable at around 29% . Ceramic membrane flux recovery rate can be as high as 93% by 7 minutes backwashing firstly and then 2 minutes forward cleaning.

Abstract: This paper makes the experimental experiment on adding rare earth elements cerium doped in diamond matrix composites. Based on the doping of rare earth in metal powders including tungsten carbide, iron and nickel, the cobalt in diamond matrix is entirely with iron and the process route of rare earth doping is indicated. The performance of matrix composites with rare earth elements and free of rare earth elements is measured and the results obtained show that the flexural strength, the hardness and the impact ductility of matrix composites with rare earth elements are improved and the flexural strength increases by 10~62% over that of the composites free of rare earth elements, and the impact ductility by about 5% correspondently. We have successfully studied out the rare-earth diamond tool matrix composites replacing Co with Fe, bearing good practical service performance and low price, and have made corresponding diamond bit.

Abstract: Single-crystal hematite (α-Fe₂O₃) nanoeggs are firstly synthesized using an anion-assisted hydrothermal method. By adjusting the ratios of phosphate to ferric ions, we are able to produce an egg-like nanostructure. And then α-Fe₂O₃ nanoeggs are converted to magnetite (Fe₃O₄) by a chemical reduction while preserving the same morphology. The characterizations of Fe₃O₄ nanoeggs indicate Fe₃O₄ nanoeggs with uniform size and shape are successful synthesized. Our results provide an easily scaled-up method for preparing tailor-made large-sized iron oxide nanoeggs that could meet the demands of a variety of applications.

Abstract: From the previous researches, the author of this paper finds that the steel tube with the hexagonal section under the lateral compression has a good energy absorption property. In order to further enhance the energy absorption of the steel tube with the hexagonal section, this paper develops the polyurethane foam filled hexagonal steel tube, and through experiment, studies its characteristics of lateral compression energy absorption, and makes the comparative analysis against the hollow hexagonal steel tube. The results show that the hexagonal section steel tube filled with polyurethane foam has substantially growth in both the loads of the yield platform and the energy absorption capability.

Abstract: Al₂O₃ composite ceramics materials used for heat transmission pipeline were prepared by pressureless sintering in air. Calcined bauxite, talc and commercial alumina powder were used as the main raw materials, partially stabilized zirconia was also added to improve the thermal shock resistance of the samples. The effects of composition and sintering temperature on density, phase composition, microstructure and thermal shock behavior of samples were evaluated. It shows that the B2 sample which was sintered at 1400 °C for 2 h has optimal properties with porosity 0.4%, bulk density 3.2 g•cm^-3.The bending strength increases 19.46 MPa after 30 times thermal shock cycles from 1100 °C to room temperature. The main phases of B2 are corundum and spinel, meanwhile, a small amount of monoclinic zirconia and α-quartz are also detected according to XRD pattern. Microstructure analysis reveals that spinel crystals are interlocked by prismatic corundum crystals, bright white beaded monoclinic zirconia particles are distributed uniformly, and it is beneficial to improve the thermal shock resistance of sample.

Abstract: The effect of phase composition and microstructure of Al₄SiC₄-Al₄O₄C composite refractories after sintered and immersion in the slag on its slag resistance was preliminary investigated. The penetration layer in refractories synthesized at 1700 °C resulted from loose microstructure led to worse slag resistance. While the refractories synthesized at 1800 °C presented better slag resistance because the dense microstructure and higher Al₄SiC₄ content inhibited the slag penetration and corrosion.