2025-04-14 2012, Volume 27 Issue 6

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  • B. Munkhbayar , Nasan Bayaraa , Hafizur Rehman , Junhyo Kim , Hanshik Chung , Hyomin Jeong

    The synthesis of new materials containing multi-walled carbon nanotubes (MWCNTs) and the microstructure of alumina particles were investigated and characterized. The MWCNTs and alumina particles were ground under both the dry and wet conditions with various rotation speeds (200–400 r/min) in planetary ball milling machine, and their combination characteristics were described. The experimental results were examined by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and particle sizing analysis (PSA). SEM result revealed that the combination of MWCNTs — Alumina particles mixed quite well under both the dry and wet grinding with rotation speed of 400 r/min. XRD characterization indicated the better result could get in ground samples at a rotation speed of 400 r/min. PSA result showed the particle size decreased with increase the grinding speeds. From the overall results, we observed that the grinding method can be used to synthesize new material with high efficiency.

  • Tangchao Peng , Xiangheng Xiao , Feng Ren , Jinxia Xu , Xiaodong Zhou , Fei Mei , Changzhong Jiang

    TiO2 thin films were deposited on quartz substrates by DC reactive magnetron sputtering of a pure Ti target in Ar/O2 plasma at room temperature. The TiO2 films were annealed at different temperatures ranging from 300 to 800 °C in a tube furnace under flowing oxygen gas for half an hour each. The effect of annealing temperatures on the structure, optical properties, and morphologies were presented and discussed by using X-ray diffraction, optical absorption spectrum, and atomic force microscope. The films show the presence of diffraction peaks from the (101), (004), (200) and (105) lattice planes of the anatase TiO2 lattice. The direct band gap of the annealed films decreases with the increase of annealing temperature. While, the roughness of the films increases with the increases of annealing temperature, and some significant roughness changes of the TiO2 film surfaces were observed after the annealing temperature reached 800 °C. Moreover, the influences of annealing on the microstructures of the TiO2 film were investigated also by in situ observation in transmission electron microscope.

  • Xuekun Hong , Haihong Hou , Debao Zhang

    We investigated the effect of annealing process on microstructures and optical properties of the sol-gel derived Ba0.9Sr0.1TiO3 (BST) films. The BST films, fabricated by layer-by-layer high-temperature (⩾ 650 °C) annealing process, had laminated structures consisting of alternating dense and porous BST layers, and exhibited excellent optical performance as Bragg reflectors. The Bragg reflection characteristic can be enhanced with increasing annealing temperature. Those BST films fabricated at temperatures lower than 650°C displayed uniform cross-sectional morphologies even treated at a higher temperature. The difference in the microstructures of the BST thin films was also discussed.

  • Zhengtao Duan , Yanmei Li , Mingya Zhang , Minghan Shi , Fuxian Zhu , Shunhu Zhang

    The effects of direct quenching and tempering (DQ-T) process and conventional reheat quenching and tempering (RQ-T) processes on mechanical properties and microstructure of high strength steel were investigated. The DQ process was found to enhance the hardenability of steel effectively. The tensile strength and yield strength of DQ specimen was 975 MPa and 925 MPa respectively, which were higher than those of RQ specimen’s of 920 MPa and 871 MPa. In contrast, low temperature toughness (−40 °C, AKV) of DQ-T specimen (124 J) was generally inferior to that of RQ-T specimen (156 J). The direct quenching temperature was one of the potential process parameters to determine strength/toughness balance of steel manufactured by DQ process. The experimental results showed that excellent strength/toughness balance was obtained when the specimens was quenched at temperature in the range of 850–910 °C. The yield strength and impact energy (−40 °C) of DQ steel decreased significantly with increasing of quenching temperature, although the tensile strength was nearly stable.

  • Rong Zhu , Yanjun Wu , Wenqing Ji

    Magnesium alloy Mg-3%Al-1%Zn (AZ31) billets prepared from equal channel angular pressing (ECAP) were utilized in low-cycle fatigue tests in order to investigate their fatigue life. Fully reversed strain-controlled tension-compression fatigue tests were conducted at the frequency of 1 Hz in ambient air. The microstructures were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The hysteresis loops of the ECAP processed and conventionally extruded samples display obviously different shapes in the total strain amplitude range from 0.2% to 0.6%. Accordingly, the low cycle fatigue lives of ECAP processed samples are found to be longer than those of extruded samples, which can be attributed to the different in the hysteresis energy incorporating tensile strain energy.

  • Xuefeng Guo , Wenpeng Yang , Fang Ren

    RRE-Mg66 alloy with a composition of Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6Zr was prepared by combinatorial processes of rapid solidification, reciprocating extrusion and extrusion. Microstructure was evaluated on SEM and TEM. The average grain size of the alloy is 0.7 μm, the size of the second phase at grain boundary is 0.15 μm, and the size of the intragranular precipitates in round shape is less than 20 nm. Superplastic behavior of the material was investigated in a temperature range of 150 to 250 °C and initial strain rate range of 3.3×10−4 to 3.3×10−2 s−1 in air. The highest elongation of 270% was obtained at 250 °C and 3.3× 10−3 s−1. High-strain-rate superplasticity and low-temperature superplasticity were achieved. The superplasticity results from intragranular sliding (IGS) at temperatures from 170 to < 200 °C and grain boundaries sliding (GBS) at 250 °C. At 200 °C a combination of IGS and GBS contributes to the superplastic flow.

  • Huajun Yu , Yingmao Xie , Hong Shen

    A series of Ni-Fe-Ga alloys near the prototype Heusler composition (X2YZ) were prepared through arc-melting suction-casting method. The dependences of the transformation behavior on the alloy composition and annealing treatment were studied in detail by an optical microscope, X-ray diffraction, and differential scanning calorimeters methods. The experimental results show that the martensitic transformation temperatures increase almost linearly with increasing Ni content in all the NiFeGa alloys. Annealing the Ni55.5Fe18Ga26.5 alloy at 100–500 °C for 3 h and at 300 °C for 1–10 h shifts the martensitic transformation start temperature by almost 20 °C to high temperature. The variations in the martensitic transformation temperatures in these alloys are discussed in terms of structural differences resulting from alloy composition and annealing treatment.

  • Zeqin Cui , Hongwei Yang , Wenxian Wang , Hongliang Wu , Bingshe Xu

    To improve the wear resistance and corrosion resistance of magnesium alloys, a 5 kW continuous wave CO2 laser was used to investigate the laser surface cladding on AZ31B magnesium alloys with Al-Si/Al2O3 -TiO2 composite powders. A detailed microstructure, chemical composition, and phase analysis of the composite coatings were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The laser cladding shows good metallurgical bonding with the substrate. The composite coatings are composed of Mg17Al12, Al3Mg2, Mg2Si, Al2O3, and TiO2 phases. Compared to the average microhardness (50HV0.05) of the AZ31B substrate, that of the composite coatings (230HV0.05) is improved significantly. The wear resistances of the surface layers were evaluated in detail. The results demonstrate that the wear resistances of the laser surface-modified samples are considerably improved compared to the substrate. It also show that the composite coatings exhibit better corrosion resistance than that of the substrate in 3.5wt% NaCl solution.

  • Xincai Xiao , Cheng Lu

    Monodisperse microspheres (mean diameter 200–300 nm) with polystyrene cores and poly(acrylamide-co-butyl methacrylate) shells were prepared by using a free radical polymerization method. Moreover, the effect of mixed solvent on the preparation, morphology and monodispersity was investigated. The experimental results showed that solubility parameter of butyl methacrylate and solvent affected mainly the molding of monodisperse core-shell microspheres. When the microspheres were fabricated in a sequential synthesis process, addition of hydrophilic and organic solvent including butyl methacrylate led to spherical degree of the particles becoming worse, and the mean diameter of the microspheres decreased and the monodispersity became better with increasing the crosslinker methylenebisacrylamide dosage.

  • Xuan Cheng , Chengyan Li , Li Rao , Haihan Zhou , Tao Li , Yanwen Duan

    Platinum (Pt) implants coated with poly (3, 4-ethylenedioxythiophene)/carbon nanotube (PEDOT/CNT) composite films were implanted into the brain of rats, and the brain response was evaluated 6 weeks after the implantation. The surface morphology of Pt implants with and without the PEDOT/CNT coating was studied using scanning electron microscopy (SEM). After 6 weeks post-implantation, the expression of laminin (vascular endothelial marker) and neuronal nuclei (NeuN, neuronal marker) were evaluated by immnohistochemistry. It is revealed that the obvious improvements of the surface density of blood vessels and neurons aound the Pt implants with the coating, which were evidenced by laminin and NeuN staining in the zone within the distance of 150 μm to the implant interface. These results suggest the PEDOT/CNT composite films can improve the biocompatibility of the Pt electrodes while it is implanted in brain.

  • Qihuan Zhang , Xin Yan , Yuhua Yan , Honglian Dai , Xin Jiang , Shipu Li

    β-TCP ceramics drug carrier was first prepared and characterized. SEM showed that β-TCP carrier was in porous amorphous structure with diameters around 10 μm. The physical properties including apparent porosity, volume-weight, tensile strength and the permeability were measured and the results indicated those properties fit the clinical usage of β-TCP drug carrier. Furthermore, drug release experiment in vitro showed that the carrier could prolong drug release in simulated body fluid which provides basis for the clinical use of β-TCP ceramics as drug carrier.

  • Songquan Wu , Shaozhu Liu , Yuyan Liu , Qi Zhu , Huige Wei

    The thermal stability of latent resin systems, cycloaliphatic epoxy/4,4′-dihydroxydiphenylsulfone/aluminum complexes, was investigated by dynamic differential scanning calorimetry (DSC) analysis. Experiments were conducted under non-isothermal condition in a nitrogen atmosphere at the heating rate of 10, 20, 30 and 40 °C/min, respectively. TG curves showed that, in the temperature range of 25 to 600 °C, the stability of the resin systems could be enhanced by increasing the length of the aliphatic chain in the initiator. Both the Kissinger method and the Ozawa-Flynn-Wall method were employed to calculate activation energies of the decomposition reaction, and the values obtained from the two methods were compared. Moreover, the corresponding reaction mechanism was identified by the Achar differential method and the Coats-Redfern integral method. The experimental results showed that these four methods were reliable and effective to study the kinetics of the thermal decomposition reaction; and the most probable thermal decomposition mechanism of the resin systems we proposed was found to comply with Mampel power law (m=1).

  • Zhe Zhang , Ying Chang , Jian Xu , Zhancui Wu , Hengchang Ma , Ziqiang Lei

    Palygorskite (PGS) and vinyl tris-(2-methoxyethoxy) silane (KH-172) modified palygorskite (OPGS) were used to prepare acrylonitrile-butadiene-styrene (ABS)/clay composites. Thermal stability of the composites was evaluated by using thermogravimetric analysis (TGA). The morphology of the fractured surface and the degree of dispersion of the clay in the ABS matrix were observed by scanning electron microscopy (SEM). X-ray diffraction (XRD) analysis results showed the variation of the crystal structure. Measurements of the tensile properties of the ABS/clay composites proved that the ABS/OPGS composited material represented the most excellent tensile property, because of good compatibility and dispersion of ABS with OPGS.

  • Shihao Yu , Xueping Wei , Hui Zeng

    A wear-resistant material reinforced with VCp was manufactured by the in-mold melting process, in which the high-vanadium alloy-rods were melted by high temperature liquid steel and elements diffused into the liquid. Microstructure of the material was examined by OM, SEM, and XRD, and alloy elements in the diffusion layer were studied by EDS, and the hardness of the material was tested by HRS. The experimental results show that the material gradually changes hardness, which is due to the uniformly existents of carbide particles on martensite matrix and the gradient distribution of vanadium and carbide.

  • Yanqiao Jin , Yizhuan Zhang , Xiaoxiao Zhao , Xiansu Cheng

    Novel woodceramics were successfully fabricated by enzymatic hydrolysis lignin (EHL) modified phenol-formaldehyde resin and woodpowders. The microstructure of woodceramics was investigated by FT-IR, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of EHL-modified PF resin on the properties of woodceramics, such as the weight loss ratio, volume shrinkage ratio, open porosity, bending strength and compressive strength, were studied. The experimental results showed that EHL modified woodceramics had a uniform porous structure. EHL-modified PF resin played an important role in the properties of woodceramics. With the increase of EHL-modified PF resin content, the open porosity, weight loss ratio and volume shrinkage ratio of woodceramics increased, but the bending strength and compressive strength decreased.

  • Zhi Zhang , Changjin Li , Jiyin Zhang , Taihe Shi

    The corrosion behavior of C110 bushing at high temperature and high pressure with a high H2S/CO2 was studied, and a basis for the materials selection of sour gas well bushing was provided in H2S, CO2 and saline coexisting environment. Under acidic condiction, hydrogen atoms greatly entered into the material and caused the material properties changed. Weight loss method was used to study the corrosion rate of hydrogen charging samples and original untreated samples in simulated oil field environment. PAR2273 electrochemical workstation was used to examine the electrochemical performance of samples untreated, hydrogen charging after reacting in autoclave. The corrosion product film was observed through SEM. The experimental results show that sample with hydrogen charging has a much more obvious partial corrosion and pitting corrosion than the untreated blank sample even the downhole corrosion speed of bushing is increased after being used for a period of time. Polarization curve shows the corrosion tendency is the same between sample with or without hydrogen charging and corrosion tendency is reduced by corrosion product film. A layer of dense product film formed on the surface of samples provides a certain protective effect to the matrix, but cracked holes which will accelerate partial corrosion of the sample were also observed.

  • Xiaofang Zhang , Cuili Guo , Xiaoli Wang , Yuanyuan Wu

    Mesoporous silica with controllable bimodal pore size distribution was synthesized with cetyltrimethylammonium bromide (CTAB) as chemical template for small mesopores and silica gel as physical template for large mesopores. The structure of synthesized samples were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and N2 adsorption-desorption measurements. The experimental results show that bimodal mesoporous silica consists of small mesopores of about 3 nm and large mesopores of about 45 nm. The small mesopores which were formed on the external surface and pore walls of the silica gel had similar characters with those of MCM-41, while large mesopores were inherited from parent silica gel material. The pore size distribution of the synthesized silica can be adjusted by changing the relative content of TEOS and silica gel or the feeding sequence of silica gel and NH4OH.

  • Tie Li , Zhen Wang , Ninghui Wang

    The temperature field in MgO single crystal furnace is crucial to grow high-purity MgO single crystals with large sizes. In order to build proper temperature gradient, firstly finite element method (FEM) was used to study the temperature field distributions, and then a temperature controller with adaptive neurofuzzy inference system (ANFIS) was developed based on the result of FEM and practical experiences. When the temperature in MgO single crystal furnace was changed, the controller would regulate the positions of threephase electrodes and the voltage of the power simultaneously. The experimental results indicate that using the adaptive neuro-fuzzy control system can improve the quality and the quantity of the MgO single crystal production.

  • Xianyong Zhu

    Cuprous oxides with different morphologies were formed on F-doped tin oxide (FTO) covered glass substrates by potentiostatic deposition of cupric acetate. The effects of CTAB and Cl on the crystal morphologies of cuprous oxide were studied. Different crystal morphologies of cuprous oxides were obtained by the change of the concentrations of CTAB and Cl. The flowerlike and cubic morphologies of Cu2O crystals were obtained when using higher concentration of CTAB and KCl, respectively. Photoelectrochemical properties of the Cu2O thin films prepared in the system were also studied.

  • Wei Yan , Xiaoxi Hu , Gangshen Zhang , Min Deng , Changfeng Yi , Zushun Xu

    The emulsifier-free emulsion polymerization of N-hydroxymethyl acrylamide (NMA), methyl methacrylate (MMA) and styrene (St) was successfully carried out under microwave irradiation, and monodisperse polymeric microspheres were prepared. The experimental results show that the emulsifier-free emulsion polymerization under microwave irradiation has more rapid reaction rate, higher conversion and shorter induction time than the copolymerization with conventional heating. The apparent activation energies are 61.04 and 83.75 kJ/mol, respectively; the microspheres have spherical morphology, and the microspheres prepared by emulsifier-free emulsion polymerization under microwave irradiation are smaller, more uniform than those obtained with conventional heating.

  • Xiao Luo , Lei Bai , Kejian Za , Dongwen Li , Wei Han , Xiaolin Pu

    A comb-like acrylamide copolymer (HCJ-1) was synthesized by using aqueous free radical polymerization of acrylamide (AM) as main monomer and ether carboxylate as functional monomer. The copolymers were characterized with FT-IR and SEM. The SEM results show that the molecular structure of copolymer is extended in salt water. It is proved that the copolymer shows good salt resistance.The solution properties of HCJ-1 were studied and compared with those of partially hydrolyzed polyacrylamide (HPAM). The experimental results show that the obtained HCJ-1, compared with HPAM, exhibits a dramatic enhancement in the salt-resistant properties. The apparent viscosity retention rate of 1.5 g L HCJ-1 aqueous solution and salt solution after 180 days at 60 °C are 70.6% and 64.5%, respectively, exhibiting good thermal stability. In addition, HCJ-1 solution also displays the excellent shearing resistance. In a word, the experimental results show the HCJ-1 is a promising profiling agent for high salinity reservoir.

  • Wenhua Du , Cong Du , Huachang Wang , Hongfu Wang , Junyuan Wang

    To meet the performance requirements of hot forging die heat resistant layer, the Ni60-SiC coating, Ni60-Cr3C2 coating, and Ni60-WC coating were prepared using W6Mo5Cr4V2 as substrate material with 30%SiC, 10%Cr3C2, 30%WC powder by means of plasma spraying and plasma spray re-melting and plasma spray welding, respectively. Microstructure of each carbide coating was analyzed, micro-hardness was tested, and mainly thermal parameters of coating were detected. The experimental results show that using plasma spray welding, the performance of 70%Ni60/30%SiC powder is the best, and its micro-hardness can achieved 1100HV, showing good thermal-physical property.

  • Zhaoqian Xie , Qingqiang Zeng , Huayuan Huang , Zhihai Cai , Yuqiang Zhao

    In order to solve the problem of wear-out-failure of diesel engine cylinder, the laser-quenching and low temperature ion sulfurizing complex surface treatment technology was operated on the surface of 42MnCr52 steel. And the tribological properties of the complex layer were investigated. The experimental results indicated that the complex layer was composed of soft surface sulphide layer and sub-surface laserquenching harden layer, and showed excellent friction-reduction and wear-resistance performance at high temperature. The synergistic effect of the complex layer resulted in 20% increase in hardness, 10% reduction in friction coefficient and 50% reduction in wear weight loss, respectively, compared with those of the standard samples. The bench-test further demonstrated that this technology can improve the lubricating condition between cylinder and piston ring, and reduce both abnormity wear when the lubricating oil is deficiency at the time of start-up and sticking wear at high temperature during the operating period, and then prolong the service life of engine.

  • Junting Luo , Yan Sun , Chunxiang Zhang , Zhiyong Zhao

    Finite element simulations were conducted to study the mechanism of spark plasma sintering. The spark plasma sintering of SiC ceramics was simulated by the Marc software based on the load current curve and temperature-time curve deserved by SPS experiment. The concept of equivalent radiation coefficient was presented and applied during the simulation. The temperature distribution regularity of SiC ceramics sintered by SPS technology was got by thermal-electrical coupled finite element simulation. The experimental results show that by thermal-electrical coupled finite element analysis, the temperature rising and distribution regularity of nonconductive material can be preferable forecasted in the sintering process of SPS. In the initial stage of the heat preservation, the temperature of the central part of the sample has achieved sintering temperature, but now, the temperature of the sample is not uniform. The temperature for each part of the die is also quite different and the sample temperature in the center is higher than that in the edge. In the end of heat preservation, the central temperature of the sample is 50 °C higher than the required sintering temperature, and the temperature gap for each part of the die decreases gradually.

  • Bingbing Fan , Rui Zhang , Bing Sun , Xuqin Li , Chunguang Li

    Microwave sintering method was carried out to prepare porous mullite composite. An insulation structure based on hybrid heating mode was well designed with the wall of mullite and the aided heaters of SiC. The obtained samples were characterized by XRD analysis, apparent porosity detection, and bending strength measurement. SEM was used to observe the microstructure of the sample. It is found that the porous mullite composite could be prepared through the microwave sintering within 2 h at relatively low temperatures around 1000 °C. The lasted samples show comparatively superior properties to the products prepared by conventional processing.

  • Kun Li , Tiexiong Su

    A chromium layer about 100 μm thickness was plated on the 38CrMoAl cylinder liner and the chromium layer was mcro quilting milled by using quilting grinding machine. The tribological properties and wear comparison test were studied. The friction coefficient of the cylinder liner plated chromic layer and micro quilting milled is 15%–30% lower than the ordinary cylinder liner. The pits generated by micro quilting milling on the chromic layer surface had good effect of accommodating the abrasive grains and storaging lubricants, which improved the effect of the friction pair significantly. The single-cylinder machine run-in tests revealed that the cylinder liner with plated chromic layer and micro quilting milling had good wear durability, and was different wear mechanisms to ordinary cylinder liner.

  • Yonghong Gao , Xiaohui Gu , Tiansheng Liu

    In order to study the properties of high-temperature sintered tungsten-copper powder shaped charge liner, the tungsten powder and copper powder, whose particle size is below 20 μm, were chosen as the main material. The mixed powder were directly pressed into the desired shape of the charge liner by the top direct-pressure way. The microscopic morphology of the spinning shaped charge liner, and the particle properties of the copper and tungsten powder were studied with scanning electron microscopy. The experimental results showed that the irregular copper powder and regular tungsten powder both are effectively and hightemperature sintering, which can improve the compactness of the powder liner effectively. The wall thickness and density of the no sintered and sintered liner were tested, showing that sintering thinned down the wall thickness and improved the density. The penetration depth of no sintered powder liner, sintered powder liner and the spinning copper plate liner were respectively tested in different standoff, showing that the penetration properties of sintered powder liner are well.

  • Tianya Tan , Mitsuaki Tohno , Masakazu Matsumoto , Yoshiki Naoi , Shiro Sakai

    A 385 nm InGaN/GaN LED on the sapphire with the nano-pattern was fabricated and its electroluminescence property was investigated in a three-dimensional (3D) space. The experimental results showed that the luminescent intensity of the LED was obviously oriented based on the nano-pattern of the sapphire substrate. And the optical interference was used to explain the luminescence orientation of the LED on the nano-patterned substrate.

  • Peng Si , Xiuchen Qiao , Jianguo Yu

    The alumina recovery from low grade kaolin (K-JS) treated through thermal and mechanical methods was investigated. High grade kaolin (K-SX) was used as comparison. The optimum calcination temperatures for K-JS and K-SX were both 600 °C, which resulted in 89.34wt% of alumina extraction from K-JS and 83.37wt% from K-SX. With the increase in calcination temperature, the chemical reactivity of calcined K-JS and K-SX to acid decreased. Mechanical treatment was much more effective in increasing the alumina extraction from activated kaolin. Around 99wt% of alumina was extracted from K-JS ground for 10 hours and 95wt% of alumina was extracted from K-SX ground for 20 hours. The IR results showed that the substitute of Al for Si occurred in calcined K-SX, however, the impurities in K-JS decreased this substitute. More alumina could be extracted from low grade kaolin than that from high grade kaolin under identical thermal or mechanical conditions.

  • Jingfu Kang , Bo Zhang , Guangyu Li

    The abrasion resistance properties of rubberized concrete were comparatively studied by taking silica fume and crumb tire rubber as the additives. The abrasion tests were conducted in accordance with the Chinese standard test method DL/T 5150 — 2001, two recommended test methods: under water method and ring method, were used. The crumb tire rubbers with the sieve size of 8-mesh and 16-mesh were incorporated into the concrete by replacing same volume of sand and as an additive. The abrasion resistance of concrete was evaluated according to the abrasion resistance strength and the mass loss. Test results show that the addition of silica fume enhanced both compressive strength and abrasion resistance of concrete, and the addition of crumb rubber reduced the compressive strength but increased notably the abrasion resistance of the concrete. Silica fume concrete performed a better abrasion resistance than control concrete, and the rubberized concrete performed a much better abrasion resistance than silica fume concrete. The abrasion resistance of rubberized concrete increased with the increase of rubber content.

  • Chengwei Hao , Min Deng , Liwu Mo , Kaiwei Liu

    Surfaces of grade III fly ashes were modified through mixing with carbide slag and calcining at 850 °C for 1 h. Mineralogical compositions and surface morphology of fly ashes before and after modification were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. Effect of surface-modified fly ashes on compressive strength and autogenous shrinkage of blended cement pastes was investigated. Microstructures of cement pastes were examined by backscattered electron (BSE) imaging and mercury intrusion porosimetry (MIP). The experimental results showed that β-C2S was formed on the surfaces of fly ashes after modification. Hydration of β-C2S on the surface-modified fly ashes densified interface zone and enhanced bond strength between particles of fly ashes and hydrated clinkers. In addition, surface modification of fly ashes tended to decrease total porosity and 10–50 nm pores of cement pastes. Surface modification of fly ashes increased compressive strength and reduced autogenous shrinkage of cement pastes.

  • Hongqiang Chu , Linhua Jiang , Ning Xu , Chuansheng Xiong

    With the zinc salt and magnesium salt solutions, the influence of anion types on the electrodeposition healing effect of concrete cracks was investigated, four parameters such as rate of weight gain, surface coating, crack closure, and crack filling depth were measured, and the mineral composition and appearance of electrodeposits in the cracks were analyzed. The experimental results demonstrate that the electrodeposition healing effect is the best by adopting ZnSO4 and MgSO4 solutions. The mineral composition of electrodeposits in the cracks does not change with the anion types. The most particles of ZnO crystal appear as fusiform by using zinc salt solutions. If we selected MgSO4 solution, the Mg(OH)2 crystal was porous honeycomb. The electrodeposits present as flake structure while the other magnesium salt solutions were adopted.

  • Jiliang Wang , Kaimin Niu , Bo Tian , Liqun Sun

    The relation between the methylene blue (MB) value of MS and its limestone powder content and clay content was investigated. The effects of MB values ranging from 0.35 to 2.5 on the workability of fresh concrete, the mechanical properties, the resistance to freezing as well as the resistance to chlorine ion permeation of the hardened concrete were all investigated. The experimental results showed that the MB value had no correlation with the limestone powder content of MS, while it was directly related to the clay content. With an increase of MB value, concrete workability decreased, as did the flexural and 7-day compressive strengths, however, the 28-day compressive strength was not affected. Furthermore, influence of MB value on concretes of different strength levels was different. For low-strength concretes, an increase of MB value could improve its impermeability, but this was not the case for high-strength concretes. Instead, their resistance to chloride ion permeability decreased slightly. However, even a slight increase in MB value remarkably accelerated freeze-thaw damage of MS concrete. It was thus concluded that the critical MB value of 1.4 would not cause significant deterioration in the performance of MS concretes.

  • Caihui Wang , Wei Sun , Jinyang Jiang

    In order to study the chloride ion transport performance in fly ash addition mortar, a new method, in which the fatigue loading and chloride diffusion are undertaken simultaneously, was developed. This method realizes coupling the fatigue damage process and the process of chloride transporting of fly ash mortar. The transport performance of chloride in fly ash mortar specimens was studied under different stress levels. Moreover, the effect of fly ash content on transport performance of chloride ion in mortar was investigated. AE (Acoustic Emission) and SEM were used to acquire the damage distribution of mortar specimens under action of fatigue load. The results show that the diffusion coefficient of chloride in mortar specimens increases with stress level of fatigue loading. The addition of fly ash can mitigate the penetration of chloride ion. The results of microcrack 3D location acquired by AE, accompanied with crack characterizing from SEM, indicate that the damage degree of mortar specimen increases with stress level of fatigue loading. Furthermore, higher damage degree of mortar leads to more the chloride ion content in the sample.

  • Baoguo Ma , Lei Su , Shouwei Jian , Xuefeng Song

    The early stage hydration mechanism of cellulose ether modified thin layer cement pastes was studied, using brick as the matrix. Samples of 6 h, 24 h, and 3 d and 7 d hydration time were analyzed to study the hydration law on the surface of high water-absorbing matrix. Hydration products were qualitatively and semi-quantitatively analyzed using XRD, TG-DSC-DTG, FTIR and SEM. The experimental results show that there is no enough water for 2 mm thick cement pastes to hydrate, because of rapid water absorption of matrix. Trace amounts of Ca (OH)2 was detected after three days hydration. With the prolongation of hydration time, the category and concentration of hydration products do not change. Compared with 2 mm thick cement pastes, 6 mm thick cement pastes and 10 mm thick cement pastes have lower dehydration rate and water loss. The humidity field of the cement paste show different changes within the same time. 6 mm thick cement paste and 10 mm thick cement pastes have longer time and more water to hydrate. Ca(OH)2 and ettringite were detected after 6 hours hydration and the concentrations of hydration products increased from 24 hours to 7 days.

  • Huiyong Guo , Yu Zheng , Jianguan Tang , Xiaofu Li , Haihu Yu , Hongqiao Wen , Desheng Jiang

    One method based on the end-face reflection as a reference was used to measure weak grating reflectivity of 0.01%–1%. For measuring ultra-weak grating reflectivity, the grating group with an identical wavelength was used. By using anhydrous alcohol and deionized water as the reflecting medium, the singlepulse FBG reflectivity of a highly doped-Ge photosensitive fiber was calculated to be about 0.747% and 0.739%, respectively; and the single-pulse FBG reflectivity of ordinary SMF fiber was about 0.016% and 0.015%, respectively. The consistent results by the two different reflecting media showed that the end-face reflection method on the grating group was feasible.

  • Xian Zhong , Jingling Yuan , Haizheng Tao , Yonghua Liu , Chengkui Zu

    We investigated image processing algorithms of the original infrared glass flaw image. Using the Laplacian edge enhancement following LSD (Line Segment Detector) algorithm, we can get a good flaw image very consistent with the original one. This study is very helpful to further enhance the infrared glass flaw inspection technique.

  • Liping Yu , Qiqiang Zhu , Dayong Fan , Zili Lan

    Zinc oxide (ZnO) is a wide band-gap material of the II-VI group with excellent optical properties for optoelectronics applications, such as the flat panel displays and solar cells used in sports tournament. Despite its advantages, the application of ZnO is hampered by the lack of stable p-type doping. In this paper, the recent progress in this field was briefly reviewed, and a comprehensive summary of the research was carried out on ZnO fabrication methods and its electrical, optical, and magnetic properties were presented.

  • Yunlai Shi , Chao Chen , Chunsheng Zhao

    A transient response model for describing the starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor was presented. Based on the contact dynamic model, the kinetic equation of the motor was derived. The starting and stopping characteristics of the standing wave piezoelectric linear ultrasonic motor according to different loads, contact stiffness and inertia mass were described and analyzed, respectively. To validate the transient response model, a standing wave piezoelectric linear ultrasonic motor based on in-plane modes was used to carry out the simulation and experimental study. The corresponding results showed that the simulation of the motor performances based on the proposed model agreed well with the experimental results. This model will helpful to improve the stepping characteristics and the control flexibility of the standing wave piezoelectric linear ultrasonic motor.