Papers by Author: Hong Gao

Abstract: Microtopography of fiber of Discorea nipponica Makino before and after mechanical activated by AGO-2 planetary mill was observed by SEM, and they changed the thick floccules to fine particles (D50 particle sizes were 10.18μm). Discorea fiber powder after mechanical activation had a narrow size distribution. According to XRD, the granularity and structures of discorea fiber with and without mechanical activation significantly differed, and the crystalline of discorea fiber was significantly converted into amorphous state after mechanical activation. On the basis of TG–DSC analysis, the activity of discorea fiber was enhanced, and certain internal energy were stored, and complete decomposition in advance. According to FT-IR, none of the functional groups of the mechanically activated discorea fiber disappeared, and no new functional groups appeared, which indicate that mechanical activation does not induce a chemical transformation of discorea fiber. According to the activation energy analysis, the thermal activation energy of dioscorea fiber after mechanical activation was18.49 kJ•mol, and the mechanical transfer activation energy was 56.06 kJ•mol, indicating that about 1/3 of the mechanical transfer activation energy was stored in the activated dioscorea fiber fine powder in the form of surface energy and internal energy.

Abstract: The activation effect of ball-to-powder ratio and activation time on phosphorite ore that takes place in mechanochemical activation has been investigated in present paper, which is carried out in a planetary mill AGO-II. The results show that, particle sizes decreased after activation; the leaching rate of water-soluble P₂O₅ increased 4.6 percentage as ball-to-powder ratio rose from 8:1 to 40:1; the activated particle of samples has been highly dispersed, while the leaching rate of water-soluble P₂O₅ reached 10.1% after milling 15 minutes during activation, which was 4 times as high as the un-activated samples. The results show a potential utilization of low-medium grade phosphorite ore with mechanochemical activation directly.

Abstract: Superfine, high-purity and well-distributed magnesium aluminate spinel powders were fabricated by controlling alkoxides hydrolysis process. Magnesium aluminate alkoxides were prepared by sol-gel with magnesium, aluminum and n-butyl alcohol as starting materials. Magnesium aluminate spinel powders were fabricated by double alkoxides sintering at 1200 °C for 1h. Controlling hydrolyzing process could obtain the optimum gel time and spinel powders were analyzed by OMEC LS-800 type Laser Particle Size Analyzer. Integrated gel time and particle size, the optimum hydrolyzing parameters are obtained for double metal alkoxides: the concentration of the double metal alkoxides is below 0.3 mol/L, hydrolysis temperature is 20 °C, the molar rate of alkoxides and water is 1: 10 and the mechanism of the hydrolysis is investigated. Nicolet Avatar 360 type FTIR spectrometer shows that acetylacetone and alkoxides can form a stable hexatomic ring which restrains hydrolysis reaction and controls particle size.

Abstract: AlCl₃ was used as catalyst in the reaction. The reaction kinetics of aluminum and isopropanol was investigated in this paper. Metallograph showed that the surface of the aluminum bar had corrosive pitting. The reaction was zero order reaction when aluminum was overdosed. Reaction order was 0.75 when isopropanol was overdosed. Finally, catalytic mechanism of AlCl₃ was investigated and the reaction of corrosive pitting was the same as that in microbattery.

Abstract: The as-cast and semi-solid microstructures of quasicrystal reinforced AZ91 alloys were investigated. The results show that the main phases of as-cast AZ91ZY1 and AZ91ZY2 alloys are all α-Mg, I-phase, Mg17Al12 and Al2Y phase. The grain boundary phases contents increase with increasing Y and Zn contents. The better semi-solid processing technological parameters of AZ91ZY1 and AZ91ZY2 alloys are 580 °C, 30 min and 560 °C, 30 min respectively. The better semi-solid processing temperature of AZ91ZY2 alloy is lower than the one of AZ91ZY1 alloy is mainly attributed to the higher contents of the grain boundary phases in the AZ91ZY2 alloy.

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 coal gangue was activated by calcine activation, calcine activation + mechanical activation (MA) complex activation. From the results of O₂-TPO-MS and Ar-TPR-MS, we can speculate the reactions occurred during the coal gangue calcine activation processing. Effects of calcine temperature, calcine activation + MA complex activation, kinds of acid on the extraction percent of Al were investigated. The results of the extraction percent of Al and particle size analysis show that calcine (400~600 oC) activation and calcine (400~600 oC) + MA complex activation can enhance the extraction percent of Al and decrease the particle size. Much higher extraction percent of Al can be obtained with H₂SO₄ as acid medium than with HCl as acid medium for the coal gangue activated with the same condition.

Abstract: Liquid electrolyte for dye-sensitized solar cells (DSSCs) was prepared by using the mixture of sulfolane and 3-methoxypropionitrile as a solvent, 4-tert-butylpyridine as an additive. The influences of sulfolane on electrolyte conductivity, photoelectric performances and the DSSCs stability were investigated. The results indicated that when the ratio of 3-methoxypropionitrile to sulfolane achieves 3:2, the cell showed the optimal photoelectric properties and stability, and the short-circuit current and photoelectric conversion efficiency achieved 7.58mA/cm2 and 2.79%, respectively.

Abstract: The microstructures and mechenical properties were studied of the reinforced cast aluminum bronze by modified nano-SiC powders have been invastigated in this paper. The results show that the structures and fractograph of the samples are obviously refined, and the β phase was obviously reduced, while the strength and toughness are significantly increased by 14% and 51% simultaneously.

Abstract: The microstructures and mechanical properties of quasicrystal reinforced Mg-Al-Zn-Y alloys with different Y and Zn contents were investigated. The results show that I-phases and Mg₁₇Al₁₂ phases form in all alloys. When Y content exceeds 1.0 at.%, the blocky Al2Y particles form, and it is disadvantageous to improve tensile strength and elongation rate. The tensile failure modes of Mg-Al-Zn-Y alloys are quasi-cleavage fracture. The tensile strength and elongation rate increase firstly and then decrease with increasing Y and Zn contents. When Y content reaches 1.0 at.%, the tensile strength and elongation rate achieve the highest values.