Papers by Author: Han Ning Xiao

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Authors: Han Ning Xiao, Tao Sun, Hua Bin Liu, Yin Cheng
Abstract: The influences of B2O3/SiO2 ratio and different alkali earth metal oxides MO (M= Ba, Mg, Ca) on the crystallization behavior of B2O3-Al2O3-SiO2 (BAS) glass were investigated by means of DSC, XRD and SEM. With the reduction of B2O3/SiO2 ratio, the crystallization activation energy increases at first and then decreases, reaching the minimum value of 375.4 kJ·mol-1 when the B2O3/SiO2 ratio is 2.2. The crystalline indices (n) are all more than 4, which indicates that the glass is in bulk crystallization. When the glass was heated to 800°C, the primary precipitated crystalline phase was Al4B2O9. With the increase of temperature up to 1100°C, Al18B4O33 and Al5BO9 appeared and became the major crystalline phases in BAS glass-ceramics.
149
Authors: Jian Qing Gong, Han Ning Xiao, Zheng Yu Huang, Jiu Su Li, Rong Kui Cao, Dan Mao
Abstract: This study was performed to evaluate the effects of micropowders content on the compressive strength of cement-based composite pastes. Granular ground blast slag (GGBS), grade I fly ash (FAI), ultra fine fly ash (UFA) and silica fume (SF) were selected as the micropowders. The compressive strength was tested after 3d, 7d and 28d curing. Results show that the paste containing both UFA and SF has the highest packing density and corresponding excellent compressive strength. The higher the packing density is, the better the compacting and filling effect of micropowders will be, which contributes to developing higher compressive strength of cement-based pastes.
1394
Authors: Jian Qing Gong, Han Ning Xiao, Zheng Yu Huang, Jiu Su Li, Jing Nie, Dan Mao
Abstract: The rheological parameters of cement pastes were investigated by varying the type and content of micropowders and the ratio of water to binder. Compressible packing model was used to calculate the packing density and to evaluate the influence of micropowders gradation on the rheological properties of fresh cement pastes. Results indicate that the higher the packing density is, the lower the yielding shear stress and plastic viscosity will be. When the ratio of water to binder is less than 0.20, the cement paste with 15% UFA and 15% SF has highest packing density and lowest yielding shear stress and plastic viscosity, which is beneficial to the workability of ultra-high performance concrete.
1398
Authors: Li Ping Yu, Han Ning Xiao, Yin Cheng
Abstract: Effects of mullite on the structure, microhardness and machinability of fluorphlogopitemullite glass-ceramics were investigated by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and microhardness tester. Results show that the microhardness and machinability are related closely to its microstructure. The microhardness decreases remarkably with the increase of crystallization and the formation of interlocking structure. The addition of mullite can decrease the size of mica crystals, which results in the spoil of interlocking structure. The microhardness of the glass-ceramics is slightly increased and then decreased with the addition of mullite. When the content of mullite is 15wt%, the glass-ceramics shows good machinability after reheated at 1200°C for 2h.
1576
Authors: Hua Bin Liu, Han Ning Xiao, Yao Ju Luo, Hong Wei Liao, Hai Bo Chen
Abstract: The effect of alkali earth metal oxides MO (M=Mg, Ca, Ba) on the crystallizing behavior and the microstructure of B2O3-Al2O3-SiO2 system (BAS) were studied. DSC, XRD and SEM were used to analyze the crystallization kinetics and to characterize the crystal phases and microstructures of the glass-ceramics. MO can effectively facilitate the formation of BAS glass, and the crystallinity of the glass increases in the order of MgO < BaO < CaO. For one given MO, the crystallinity of the glass is dependent on B2O3/SiO2 ratio: the lower the ratio is, the weaker the crystallinity of the glass will be. It was found that the early crystallization is aluminum metaborate (Al4B2O9) when the glass is heated at 800 °C, and it would transfer into aluminum borate(Al18B4O33) at temperatures over 1000 °C. The activation energy and the Avrami exponent of Al4B2O9 were calculated by Ozawa formulation.
1415
Authors: Yang Feng Huang, Han Ning Xiao, Shu Guang Chen
Abstract: ZnO nanorods were prepared by a hydrothermal reaction in the presence or absence of PVP (polyvinyl pyrrolidone). The obtained products were characterized by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared, UV-Vis absorption (UV) spectroscopy and photoluminescence (PL) spectroscopy. The results suggest that PVP plays an important role in the preparation of ZnO nanorods. The UV absorption spectrum showed PVP increases the UV-shielding ability but doesn’t influence the transparency in the visible light region. A weak UV emission at 353 nm of PL spectra exhibit the surface of ZnO nanorods is passivated and oxygen-related defects is supplied by PVP.
329
Authors: Ming Jian Wu, Peng Zhao Gao, Yan Li Liu, Han Ning Xiao
Abstract: A biomorphic porous carbon coated with gradient SiC coating (SiC/BPC) was prepared by controlled carbonizing native pine under Ar atmosphere and then processed with precursor infiltration-pyrolysis (PIP) of organosilan. Microstructure and component of SiC/BPC were performed by SEM, EDS (attached with line scanning program) and XRD. The non-isothermal oxidation properties and mechanism of SiC/BPC were studied by TGA. The kinetic parameters were calculated through model-functions methods. Experimental results showed that SiC/BPC has a topologically uniform interconnected porous network microstructure, the SiC coating was amorphous and combines well with the carbon surface, which improved the oxidation resistance of BPC material about 150K. The non-isothermal oxidation reaction of SiC/BPC exhibited the characteristic of self-catalytic, the oxidation mechanism of SiC/BPC was 2-D diffusion, decelerator -t curve, the kinetic parameters are lgA/min-1= 15.483;E/kJ•mol-1 = 287.49.
211
Authors: Hai Qiu Zhou, Han Ning Xiao, Xue Yan Hu
Abstract: A series of physical and chemical changes, including the shrinkage and the phase transformation, will continuously take place during the sintering process of ceramic green body, which is important for designing a scientific and economic sintering schedule. The sintering behavior of two electrical porcelains and a structural tile were investigated using thermal analysis techniques. The dehydration, phase changes and densification of ceramic green body during sintering process were characterized by DSC-TG and thermal expansion curves. The sintering temperature range of ceramic green body was measured by thermal dilatometer with different heating rates. The sintering temperature Ts is linear to the logarithm of heating rate V. The results were compared with that measured by conventional refractoriness tester. The Ts is much more accurate to evaluate the sintering behavior of ceramic green body from the thermal analysis technique than that from the traditional method. The projected sintering schedule is very concordant to the experimental sintering results.
226
Authors: Han Ning Xiao, Ji Xiang Yin, Tetsuya Senda
Abstract: Friction and wear tests of TiB2 sliding against SiC were conducted without lubricant from room temperature to 1200°C in air and in vacuum. The friction coefficient of the couple of TiB2/SiC is affected obviously by the oxidation of TiB2. It increases with the increase of temperature and reaches a maximum at some temperature in air, then decreases remarkably. The friction coefficient of TiB2/SiC in vacuum exhibites almost a constant and keeps smaller value than that in air. Transition of TiB2 onto the sliding surface of SiC was observed, which improved the wear resistance of SiC at high temperatures.
1580
Authors: Han Ning Xiao, Ji Xiang Yin, Tetsuya Senda
Abstract: Friction and wear tests of Al2O3 and SiC were conducted from room temperature to 1200°C both in air and in vacuum. Results show that the wear mechanism of Al2O3 is dominated by micro fracture, debris abrasive and delamination at temperatures below 600 °C, while is controlled by plastic deformation and recrystallization among 600~1200 °C, resulting in an obvious decrease of wear loss. The wear rate and surface microstructure of SiC are closely depending on the testing temperature, atmosphere and contact pressure. Oxidation of SiC at elevated temperatures plays important role on the wear rate. Self lubrication of both Al2O3 and SiC at high temperatures was observed, which is mainly depending on the formation of a specific surface layer composed of nano-particles or very thin glassy film.
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