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ISSN 1005-0302
CN 21-1315/TG
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      28 November 2003, Volume 19 Issue 06 Previous Issue    Next Issue
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    Research Articles
    Equal Channel Angular Deformation (ECAD) of As-Cast AM60 Magnesium Alloy
    Peng LUO, Xiaolin WU, Kenong XIA
    J. Mater. Sci. Technol., 2003, 19 (06): 513-515. 
    Abstract   HTML   PDF (1452KB)
    As-cast AM60 magnesium alloy ingot with grains coarser than those of as-extruded AZ series is more liable to produce cracks under ECAD with severe shear strain. A feasible scheme of equal channel angular deformation (ECAD) for as-cast AM60 magnesium alloy ingot was proposed in this paper. The tests were conducted on Instron machine with hydraulic back-force machine. Through analysing load vs displacement curves, the effects of ECAD processing conditions on deformability and microstructure of as-cast magnesium AM60 billets were discussed. During testing, the back-force employment was helpful to keep ECAD processing more stable. And with back-force, it was observed that the number of ECAD passes in different routes could tremendously affect the deformability and microstructure of magnesium specimens. It was concluded that ECAD processing is entirely feasible for as-cast magnesium AM60 alloy under severe shear strain, and back-force employment, multi-passes deformation and lubrication of graphite paper are the factors primarily beneficial to improvement of deformability and refinement of grained structure. This work provides a way to produce magnesium alloy with fine-grained structure directly from casting ingot by ECAD technique.
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    Influence of Four Factors on Discharge Capacity and Self-Discharge Rate of Iron Electrode
    Dongfeng LIN, Shihai YE, Rong CAI, Deying SONG, Panwen SHEN
    J. Mater. Sci. Technol., 2003, 19 (06): 515-517. 
    Abstract   HTML   PDF (616KB)
    Ni-Fe rechargeable batteries possess the advantages of long cycle life, high theoretical specific energy, abundant raw material, low price and environmental friendship. It has a wide applied perspective. The advantages, disadvantages and preparation methods of iron electrodes were summarized. The influence of four factors on discharge capacity and self-discharge rate of iron electrode were discussed by means of orthogonal experiments, galvanostatic charges and discharges. The influences of graphite on the discharge capacity and self-discharge rate of iron electrode were the most remarkable, the most unapparent influences on the discharge capacity and self-discharge rate were HPMC (hydroxyl propoxy methoxy cellulose) and sodium sulphide, respectively. The aim of the present research was to study the effects of graphite, HPMC and iron powder added in the electrodes, sodium sulphide added in the electrolytes on the discharge capacity and self-discharge rate of iron electrodes. The largest discharge capacity of the iron electrodes was 488.5 mAh/g-Fe at 66.4 mA/g-Fe in the first ten cycles, and the average self-discharge rate was 0.367% per hour.
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    Laser-Heated Diamond-Anvil Cell (LHDAC) in Materials Science Research
    N.V.Ch, ra Shekar, P.Ch.Sahu, K.Govinda Rajan
    J. Mater. Sci. Technol., 2003, 19 (06): 518-525. 
    Abstract   HTML   PDF (1568KB)
    Laser-heated diamond-anvil cell (LHDAC) is emerging as the most suitable, economical and versatile tool for the measurement of a large spectrum of physical properties of materials under extreme pressure and temperature conditions. In this review, the recent developments in the instrumentation, pressure and temperature measurement techniques, results of experimental investigations from the literature were discussed. Also, the future scope of the technique in various avenues of science was explored.
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    Microstructure and Temperature Distribution in ZnAl2O4 Sintered Body by Pulse Electric Current
    Dongming ZHANG, Zhengyi FU, Jingkun GUO
    J. Mater. Sci. Technol., 2003, 19 (06): 526-528. 
    Abstract   HTML   PDF (1643KB)
    Microstructure of reaction sintering of ZnAl2O4 at 1500ºC by hot-pressing(HP) and pulse electric current was investigated. The results indicated that the existed cracks in sintered body were caused by structure mismatch. It is the evidence that periodical temperature field existed during pulse electric current sintering of nonconductive materials. The distance between high temperature areas was related to die diameter.
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    Prediction of Properties in Thermomechanically Treated Cu-Cr-Zr Alloy by an Artificial Neural Network
    Juanhua SU, Qiming DONG, Ping LIU, Hejun LI, Buxi KANG
    J. Mater. Sci. Technol., 2003, 19 (06): 529-532. 
    Abstract   HTML   PDF (4103KB)
    A supervised artificial neural network (ANN) to model the nonlinear relationship between parameters of thermomechanical treatment processes with respect to hardness and conductivity properties was proposed for Cu-Cr-Zr alloy. The improved model was developed by the Levenberg-Marquardt training algorithm. A basic repository on the domain knowledge of thermomechanical treatment processes is established via sufficient data acquisition by the network. The results showed that the ANN system is an effective way and can be successfully used to predict and analyze the properties of Cu-Cr-Zr alloy.
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    Solidification Simulation of Investment Castings of Single Crystal Hollow Turbine Blade
    Jiarong LI, Shizhong LIU, Hailong YUAN, Zhengang ZHONG
    J. Mater. Sci. Technol., 2003, 19 (06): 532-534. 
    Abstract   HTML   PDF (1843KB)
    The three-dimensional solidification simulation of the investment castings of single crystal hollow turbine blade at the withdrawal rates of 2 mm/min, 4.5 mm/min and 7mm/min has been performed with the finite element thermal analysis. The calculated results are in accordance with the experimental ones. The results show that with the increase of withdrawal rate the concave curvature of the liquidus isotherm is larger and larger, and the temperature gradients of the blades increase. No effects of withdrawal rate on the distribution of the temperature gradients of the starter and helical grain selector of the blades are observed at withdrawal rates of 2 mm/min, 4.5 mm/min and 7 mm/min. The relatively high temperature gradient between 500ºC/cm and 1000 ºC/cm in the starter and helical grain selector is obtained at three withdrawal rates.
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    Investigation of Surface Reaction and Degradation Mechanism of Kapton during Atomic Oxygen Exposure
    Shuwang DUO, Meishuan LI, Yanchun ZHOU, Jingyu TONG, Gang SUN
    J. Mater. Sci. Technol., 2003, 19 (06): 535-539. 
    Abstract   HTML   PDF (1249KB)
    The erosion behavior of Kapton when exposed to atomic oxygen (AO) environment in the ground-based simulation facility was studied. The chemical and physical changes of sample surfaces after exposed to AO fluxes were investigated by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results indicated that Kapton underwent dramatically degradation, including much mass loss and change of surface morphologies; vacuum outgassing effect of Kapton was the key factor for initial mass loss in the course of atomic oxygen beam exposures. XPS analysis showed that the carbonyl group in Kapton reacted with oxygen atoms to generate CO2, then CO2 desorbed from Kapton surface. In addition, PMDA in the polyimide structure degraded due to the reaction with atomic oxygen of 5 eV.
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    First-Principles Study of the Polar TiC/Ti Interface
    Limin LIU, Shaoqing WANG, Hengqiang YE
    J. Mater. Sci. Technol., 2003, 19 (06): 540-544. 
    Abstract   HTML   PDF (1078KB)
    The interface structure, work of adhesion, and bonding character of the polar TiC/Ti interface have been examined by the first-principles density functional plane-wave pseudopotential calculations. Both Ti- and C-terminated interfaces including six different interface structures were calculated, which present quite different features. For the Ti-terminated interface, the interfacial Ti-Ti bond has a strong metallic and weak covalent character; while for the C-terminated interface, the interfacial bond is a strong polar covalent interaction between the Ti-3d and C-2p orbital. The work of adhesion of C-terminated interface is nearly 9 J/m2 stronger than that of the Ti-terminated. It is found that each termination has relatively large work of adhesion, which is consistent with other polar interfaces.
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    Phase Stability, Kinetic Diagrams and Diffusion Path in High Temperature Oxidation of Binary Solid-Solution Alloys
    Yan NIU, F.Gesmundo
    J. Mater. Sci. Technol., 2003, 19 (06): 545-552. 
    Abstract   HTML   PDF (1790KB)
    The phase diagrams of ternary systems involving two metal components and one oxidant are considered first, the limitations to their use is discussed in relation to the high temperature oxidation of binary alloys. Kinetic diagrams, which are useful to predict the conditions for the stability of the two mutually insoluble oxides as the external scale, are then calculated on the basis of thermodynamic and kinetic data concerning both the alloys and the oxides, assuming the validity of the parabolic rate law. A combination of the two types of diagrams provides a more detail information about the oxidation behavior of binary alloys. The calculation of the diffusion paths, which relate the oxidant pressure to the composition of the system in terms of the alloy components both in the alloy and in the scale during an initial stage of the reaction in the presence of the parabolic rate law, is finally developed.
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    Microstructural Evolution of Rapidly Solidified Co-Mo and Ni-Mo Eutectic Alloys
    Xiujun HAN, Wenjing YAO, Bingbo WEI
    J. Mater. Sci. Technol., 2003, 19 (06): 553-556. 
    Abstract   HTML   PDF (1027KB)
    Droplets of Co-37.6 wt pct Mo and Ni-47.7 wt pct Mo eutectic alloys were rapidly solidified during containerless processing in a 3 m drop tube. A kind of anomalous eutectic appears in these two eutectic alloys when undercooling is beyond 56 and 61 K, respectively. The two eutectic phases in anomalous eutectic were observed to grow in dendrite manner. The formation of anomalous eutectic is ascribed to the cooperative dendrite growth of the two independently nucleated eutectic phases. Current dendrite and eutectic growth theories are applied to describe the observed processes.
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    Homogeneous Plastic Flow of Fully Amorphous and Partially Crystallized Zr41.2Ti13.8Cu12.5Ni10Be22.5 Bulk Metallic glass
    Q.WANG, J.J.Bl, in, M.Suery, B.Van de Moortele, J.M.Pelletier
    J. Mater. Sci. Technol., 2003, 19 (06): 557-560. 
    Abstract   HTML   PDF (1142KB)
    The homogeneous plastic flow of fully amorphous and partially crystallized Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass (Vit1) has been investigated by compression tests at high temperatures in supercooled liquid region. Experimental results show that at sufficiently low strain rates, the supercooled liquid of the fully amorphous alloy reveals Newtonian flow with a linear relationship between the flow stress and strain rate. As the strain rate is increased, a transition from linear Newtonian to nonlinear flow is detected, which can be explained by the transition state theory. Over the entire strain rate interval investigated, however, only nonlinear flow is present in the partially crystallized alloy, and the flow stress for each strain rate is much higher. It is found that the strain rate-stress relationship for the partially crystallized alloy at the given temperature of 646 K also obeys the sinh law derived from the transition state theory, similar to that of the initial homogeneous amorphous alloy. Thus, it is proposed that the flow behavior of the nanocrystalline/amorphous composite at 646 K is mainly controlled by the viscous flow of the remaining supercooled liquid.
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    Phase Development and Crystallization Kinetics of NiTi Prepared by Mechanical Alloying
    Xunyong JIANG, Xueping GAO, Deying SONG
    J. Mater. Sci. Technol., 2003, 19 (06): 560-562. 
    Abstract   HTML   PDF (1142KB)
    NiTi alloy is produced by mechanical alloying(MA). It becomes amorphous after milling for enough time, such as 100 h in this paper. DSC measurement shows that the crystallization temperature is 676 K for the amorphous powder. Activation energy of crystallization is 199.98 kJ/mol for MA powder, which is lower than that of amorphous prepared by magnetron sputtering. Avrami parameter of crystallization is 1.07.
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    Mechanical and Wear Properties of Nanostructured Surface Layer in Iron Induced by Surface Mechanical Attrition Treatment
    Nairong TAO, Weiping TONG, Zhenbo WANG, Wei WANG, Manling SUI, Jian LV, Ke LU
    J. Mater. Sci. Technol., 2003, 19 (06): 563-566. 
    Abstract   HTML   PDF (818KB)
    A porosity-free and contamination-free surface layer with grain sizes ranging from nanometer to micrometer in Fe samples was obtained by surface mechanical attrition treatment (SMAT) technique. Mechanical and wear properties of the surface layer in the SMATed and annealed Fe samples were measured by means of nanoindentation and nanoscratch tests, respectively. Experimental results showed that the hardness of the surface layer in the SMATed Fe sample increased evidently due to the grain refinement. The elastic moduli of the surface layers in the SMATed and annealed Fe samples were unchanged, independent of grain size in the present grain size regime. Compared with the original Fe sample, the wear resistance enhanced and the coefficient of friction decreased in the surface layer of the SMATed Fe sample.
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    Oxidation and Hot Corrosion Behavior of a Composite Coating System
    Dongbai XIE, Fuhui WANG
    J. Mater. Sci. Technol., 2003, 19 (06): 567-570. 
    Abstract   HTML   PDF (1061KB)
    The oxidation and hot corrosion behavior of Co-Ni-Cr-Al-Ta-Y coating produced by magnetron sputtering with and without enamel coating has been investigated in air at 900ºC and in molten 75 wt pct NaCl+25 wt pct Na2SO4 at 850ºC. The results show that the enamel coating possesses good hot corrosion resistance in the molten salts, in comparison with the sputtered Co-Ni-Cr-Al-Ta-Y coating. In the hot corrosion test, breakaway corrosion did not occur on the samples with enamel coating and the composition of enamel coating did not significantly change either. The oxidation resistance of the sputtered coating, which offers good adhesion, can be improved by the enamel coating.
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    Critical and Impeding Pressures of Al Evaporation during ISM Processing of NiAl
    Guizhong LIU, Jingjie GUO, Yanqing SU, Jingzhe GUO, Jun JIA, Hengzhi FU
    J. Mater. Sci. Technol., 2003, 19 (06): 571-575. 
    Abstract   HTML   PDF (1249KB)
    In this paper, the critical pressure pcrit and impeding pressure pimpe of the elemental evaporation were defined and studied based on the calculation of the relationship between the evaporation loss rate Nm and the chamber pressure p during melting of NiAl alloys. When the chamber pressure is lower than pcrit or higher than pimpe, Nm tends to be the maximum or minimum value and remains almost unchanged. However, declines sharply with the increase of the chamber pressure when pcrit References | Related Articles | Metrics
    Effects of Mg Doping on Photoconductivity of GaN Films
    Deheng ZHANG, Qingpu WANG, Yunyan LIU
    J. Mater. Sci. Technol., 2003, 19 (06): 575-577. 
    Abstract   HTML   PDF (1249KB)
    This paper presents the UV photoconductivity properties of GaN films doped with different Mg concentrations deposited by MOCVD. It was observed that for the undoped and weakly doped GaN films the UV photocurrent response was relatively large and the relax time was relatively short. With an increase in doped Mg content, the samples became p-type, the photocurrent response became weak and the relax time became longer.
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    Structure and Properties of Modified Unsaturated Polyester Resin by Nano-TiO2
    Ying XU, Mingli LI, Yan GUO, Fengji LU
    J. Mater. Sci. Technol., 2003, 19 (06): 578-580. 
    Abstract   HTML   PDF (1370KB)
    The nano-TiO2/unsaturated polyester resin (referred to as nano-TiO2/UPR hereafter) was prepared with the ``reaction method", by which a chemical bond generated between nano-TiO2 and UP was inserted in the UP long chain. The performance of the nano-TiO2/UPR was determined by such a new structure. The research results showed that the reactivity of nano-TiO2/UPR is higher than that of UPR. The impact strength and bending strength of nano-TiO2/UPR are greatly enhanced as compared with that of UPR. Thermal resistance and dielectric property of nano-TiO2/UPR are the same as that of UPR.
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    Effects of Carbon on the CG HAZ Toughness and Transformation of X80 Pipeline Steel
    Xiaohuai XUE, Luhai WU, Bainian QIAN, Jingli LI, Songnian LOU
    J. Mater. Sci. Technol., 2003, 19 (06): 580-582. 
    Abstract   HTML   PDF (1371KB)
    X80 pipeline steel produced by TMCP has high strength and high toughness with ultrafine grain microstructure. The microstructure coarsens and the toughness worsens at the coarse grained (CG) HAZ apparently after weld simulation. The experimental results indicated that the bainitic ferrite and the second phases formed at cooling are differently as the variation of carbon in base metal. In low carbon steels, the bainitic ferrite laths are long and narrow, the second phases are complex including residual austenite, martensite, the M-A constituent and the Fe3C carbide. The formation of Fe3C carbide is the main reason of the poor toughness in CG HAZ. The ultralow carbon in base metal, however, can improve the CG HAZ toughness through restraining the formation of carbides, decreasing the M-A constituent, increasing the residual austenite content, which are beneficial to the CG HAZ toughness.
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    Carbon-Coated-Nylon-Fiber-Reinforced Cement Composites as an Intrinsically Smart Concrete for Damage Assessment during Dynamic Loading
    Zhenjun ZHOU, Zhiguo XIAO, Wei PAN, Zhipeng XIE, Xixian LUO, Lei JIN
    J. Mater. Sci. Technol., 2003, 19 (06): 583-586. 
    Abstract   HTML   PDF (826KB)
    Concrete containing short carbon-coated-nylon fibers (0.4~2.0 vol. pct) exhibited quasi-ductile response by developing a large damage zone prior to fracture localization. In the damage zone, the material was microcracked but continued to local strain-harden. The carbon-coated-nylon-fiber-reinforced concrete composites (NFRC) were found to be an intrinsically smart concrete that could sense elastic and inelastic deformation, as well as fracture. The fibers served to bridge the cracks and the carbon coating gave the conduction path. The signal provided came from the change in electrical resistance, which was reversible for elastic deformation and irreversible for inelastic deformation and fracture. The resistance decrease was due to the reduction of surface touch resistance between fiber and matrix and the crack closure. The resistance irreversible increase resulted from the crack opening and breakage of the carbon coating on nylon fiber.
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    Influence of Processing Parameters on Granularity Distribution of Superalloy Powders during PREP
    Huanming CHEN, Benfu HU, Yiwen ZHANG, Huiying LI, Quanmao YU
    J. Mater. Sci. Technol., 2003, 19 (06): 587-590. 
    Abstract   HTML   PDF (1111KB)
    In order to investigate the influence of processing parameters on the granularity distribution of superalloy powders during the atomization of plasma rotating electrode processing (PREP), in this paper FGH95 superalloy powders is prepared under different processing conditions by PREP and the influence of PREP processing parameters on the granularity distribution of FGH95 superalloy powders is discussed based on fractal geometry theory. The results show that with the increase of rotating velocity of the self-consuming electrode, the fractal dimension of the granularity distribution increases linearly, which results in the increase of the proportion of smaller powders. The change of interval between plasma gun and the self-consuming electrode has a little effect on the granularity distribution, also the fractal dimension of the granularity distribution changed a little correspondingly.
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    Effect of Training on Two-way Shape Memory Effect and Its Stability in a Ti-Ni-Hf High Temperature Shape Memory Alloy
    Xianglong MENG, Wei CAI, K.T.LAU, L.M.ZHOU, Liancheng ZHAO
    J. Mater. Sci. Technol., 2003, 19 (06): 590-592. 
    Abstract   HTML   PDF (1111KB)
    The Effect of the thermal cycling training under constant strain on the two-way shape memory effect (TWSME) in a Ti36Ni49Hf15 high temperature shape memory alloy (SMA) has been investigated by bending tests. The results indicated that the training procedure is beneficial to get the better TWSME. The two-way shape memory strain increases with increasing the training strain. And it decreases with increasing the training temperature. The TWSME obtained in the present alloy shows poorer stability compared with that obtained in the TiNi alloys.
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    Energy of Grain Boundaries of Different Type in fcc Solid Solutions, Ordered Alloys and Intermetallics with L12 Superstructure
    O.B.Perevalova, E.V.Konovalova, N.A.Koneva, E.V.Kozlov
    J. Mater. Sci. Technol., 2003, 19 (06): 593-596. 
    Abstract   HTML   PDF (1193KB)
    The study of the triple junctions of the grain boundaries in some fcc solid solutions, ordered alloys and intermetallics with L12 has been carried out using the optical metallography and TEM methods. Two-types of the triple junctions were found in the alloys investigated (1), consisting of the boundaries of the random (RT), and (2), consisting of the RT boundary and the special boundaries (ST). The relative values of the RT and ST boundary energy were determined on the basis of the measurements of the angles between the grain boundary planes. It has been shown that the energy of ST boundaries increases with the increase of the stacking fault (SF) energy. The energy of the RT boundaries does not depend on the SF energy.
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    Characterization of Iron Oxide Generated in Ruthner Plant of Pickling Unit in Mobarakeh Steel Complex
    M.C.Amiri
    J. Mater. Sci. Technol., 2003, 19 (06): 596-598. 
    Abstract   HTML   PDF (1193KB)
    Reducing the chloride content in regenerated iron oxides (RIO) from steel-pickling acid waste economically treated by Ruthner process is the most critical issue for the development of RIO as a useful raw material resource. In this paper, the results of a new method for characterization and modification of RIO produced in Mobarakeh Steel Complex were reported.
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    Characterization of a Mineral Synthesized by Availing Silica from Plant Source
    M.Sharif Nizami
    J. Mater. Sci. Technol., 2003, 19 (06): 599-603. 
    Abstract   HTML   PDF (1897KB)
    Rice husk was used to prepare the silica of amorphous nature being several times more reactive than that obtained from the mineral kingdom. Number of rice husk batches were pyroprocessed under varying time-temperature parameters for this purpose. The ash resulting from a batch pyroprocessed at 500ºC for 8 h contained 92.01% silica. It was upgraded to 98.50% by applying physicochemical purification procedures. The mineral, wollastonite (CaSiO3), was synthesized from thus prepared silica and limestone containing 55.91% CaO. Solid state reaction, between CaO and SiO2 was attempted at different temperatures in the presence of a mineralizer. The sintering temperature, for affecting the said synthesis, was ranged between 900ºC to 1300ºC with the steps of 100ºC. Specific chemical analysis techniques were applied to determine the effectiveness of carried out reaction and promising batches were subsequently subjected to XRD investigations. The produced mineral was also characterized regarding its physical properties like: colour, hardness, melting point and specific gravity. Percent yield of the produced wollastonite was also estimated and compared with that of obtained by other researchers who synthesized it by using silica from mineral kingdom. Batches sintered at 1200ºC and 1300ºC for 1 h showed the overall best results.
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    Study on the Basic Mechanical Behaviors of High Density Polyethylene Electrofusion Welded Joints at Different Temperature
    Lixing HUO, Fangjuan QI, Yufeng ZHANG, Hongyang JING, Xinqi YANG
    J. Mater. Sci. Technol., 2003, 19 (06): 603-606. 
    Abstract   HTML   PDF (1897KB)
    The basic mechanical behaviors of high density polyethylene electrofusion welded joint at different temperatures were studied by using differently designed specimens in this paper. The results show that the strength of weld bonding plane is higher than that of the pipe and socket materials at room temperature. In order to get the shear strength of electrofusion welded joint, the effective bond lengths were reduced by cutting artificial groove through the socket. The effective bonding length of welded joint to get the shear strength is decreased with decreasing testing temperature. The shear strength and the sensibility to sharp notch of HDPE material increased with decreasing temperature.
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    Study on Enhancement in Gibbsite Precipitation of Bayer Process under 33 kHz Ultrasound
    Jihua ZHAO, Qiyuan CHEN
    J. Mater. Sci. Technol., 2003, 19 (06): 607-610. 
    Abstract   HTML   PDF (1498KB)
    The enhancement of gibbsite precipitation in Bayer process by 33 kHz ultrasound has been studied. From orthomethod experiment, the optimized operating parameters of treatment under 33 kHz ultrasonic cleaner have obtained. Compared with crystallization of Al(OH)3 without treatment of ultrasound, the precipitation time is reduced by 15 h when the precipitation ratio is 45%. From the results of grain size distribution and SEM photographs of gibbsite, it is found that secondary nucleation and agglomeration could be enhanced under 33 kHz ultrasound. The products are same from comparison of X-ray powder diffraction, but the Raman spectrum of sodium aluminate solution under 33kHz ultrasound is different from that without ultrasound.
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    Composition Distribution in the MnxCd(1-x)In2Te4 Ingot Grown by ACRT-B Method
    Yongqin CHANG, Wanqi JIE, Xiping GUO, Fuyi CHEN, Weijun AN
    J. Mater. Sci. Technol., 2003, 19 (06): 610-612. 
    Abstract   HTML   PDF (1498KB)
    MnxCd(1-x)In2Te4 (x=0.1) ingot was successfully grown by the modified Bridgman technique, which applied the accelerated crucible rotation technique (ACRT) in Bridgman process, or briefly ACRT-B. The growth interface profile shape and the composition distribution in the MnxCd(1-x)In2Te4 (x=0.1) ingot were analyzed. Even though the stoichiometric composition was synthesized in the original ingot, the composition has been redistributed during the ACRT-B growth process. Mn and Cd contents decrease while In increases along the longitudinal axis. The partition ratios of solutes Mn, Cd and In at the growth interface are evaluated by a mathematical method based on the experimental data, which are found to be 1.286, 1.926 and 0.729 in α phase growth process, and 1.120, 1.055 and 0.985 in β phase growth process, respectively. In the radial direction, Mn and Cd contents increase while In decreases with the distance from the centerline of the ingot.
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    Slurry Preparation and Rolling of Semi-solid 60Si2Mn Spring Steel
    Weimin MAO, Aimin ZHAO, Dong YUN, Leping ZHANG, Yonglin KANG
    J. Mater. Sci. Technol., 2003, 19 (06): 613-616. 
    Abstract   HTML   PDF (2086KB)
    The nondendritic semi-solid slurry preparation of 60Si2Mn spring steel has been studied in this paper. The experiments have shown that when stirred for 2 min on the test condition, the semi-solid slurry with 50%~60% fraction solid and spherical primary austenitic grains in the size of 100~300 μm can be obtained and is easy to be discharged from the bottom little hole of the stirring chamber. The nondendritic slurry of 60Si2Mn spring steel can be rolled into given plate form successfully, but the solid phase and liquid phase is easy to be separated in rolling process so that the solid primary austenite is concentrated in the center and the liquid is near the edge of the rolled plate. The rupture strength and elongation of the plate rolled only once with semi-solid slurry are lower than that of the traditionally repeated hot-rolled plate of 60Si2Mn spring steel.
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    Effect of Carbon on DA718 Alloy with P Addition
    Na LI, Shouren GUO, Dezhong LU, Wenru SUN, Yan XU, Zhuangqi HU
    J. Mater. Sci. Technol., 2003, 19 (06): 616-618. 
    Abstract   HTML   PDF (2086KB)
    Lower content of carbon can further improve the stress rupture life of p-modified DA 718 alloy up to more than 270%. Meanwhile, the ductility of the alloy decreased a little. More boron atoms dissociate due to decreasing carbon content and interact with phosphorus which brings the longer stress rupture life of the alloy. Less carbon may induce more phosphorus segregating in the grain boundary and result in brittleness.
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    Volatilization Kinetics of Sb2S3 in Steam Atmosphere
    Yixin HUA, Yong YANG, Fuliang ZHU
    J. Mater. Sci. Technol., 2003, 19 (06): 619-622. 
    Abstract   HTML   PDF (1233KB)
    The volatilization kinetics of antimony trisulfide in steam atmosphere was studied with thermogravimetry at temperatures from 923 to 1123 K. A theoretical model was developed to calculate the overall rate constant and the mass transfer coefficient in gas phases. The experimental results show that the volatilization rate is enhanced with increasing temperature and steam flow rate. The volatilization rate is mainly controlled by the mass transport in gas phases. The apparent activation energy for the process is found to be 59.93 kJ/mol. It is demonstrated that Sb2S3 is dominantly oxidized into Sb2O3 and H2S by water vapor in the volatilization process. Some antimony metal is formed. The reaction mechanism is discussed in accordance with experimental data.
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    Irreversible Colossal Magnetoresistance in La0.58Dy0.09Ca0.33MnO3
    Baoxin HUANG, Yihua LIU, Ruzhen ZHANG, Youyong DAI, Chengjian WANG, Xiaobo YUAN, Liangmo MEI
    J. Mater. Sci. Technol., 2003, 19 (06): 622-624. 
    Abstract   HTML   PDF (1233KB)
    The representative sample La0.58Dy0.09Ca0.33MnO3 of Dy doped La0.67Ca0.33MnO3 rare-earth manganites was investigated. The most important effect of Dy doping is to introduce the magnetoimpurity and form the spin clusters which induce dramatically large CMR in La0.58Dy0.09Ca0.33MnO3. The fitting results of field-induced resistivity decrease to the Brillouin function indicate that the CMR is caused by the spin dependent hopping between spin clusters. It is the magnetic field that reduces the size of spin clusters and induces a field-induced irreversible CMR behaviour.
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    Effect of Nb on the Interfacial Wettability in Al2O3/Medium Mn Steel
    Sirong YU, Yaohui LIU, Zhenming HE
    J. Mater. Sci. Technol., 2003, 19 (06): 625-627. 
    Abstract   HTML   PDF (559KB)
    To develop medium Mn steel (MMS) matrix composites reinforced by Al2O3 particles, the effect of Nb on the interfacial wettability of Al2O3/MMS and its mechanism were investigated in this paper. The results show that the wetting angle of the specimens with different Nb contents are bigger than that of the specimen without Nb at the first stage, and then decreases with time at 1450 ºC. At certain time, the wetting angle is lower than that of the specimen without Nb. At 1550 and 1600ºC, the wetting angle of the specimens containing Nb decreases quickly with time at first stage. After 10 min, the wetting angle reaches a steady state, and hardly changes with time. The mechanisms of Nb to improve the wettability can be attributed to the enrichment of Nb at the interface and Nb serves as surface active agent of MMS at T<1550ºC, and as catalyzer for the interfacial reaction of Al2O3/MMS at T≥1550ºC, and reduces the interfacial energies.
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    Influence of Ethylene Glycol on the Formation of Calcium Phosphate Nanocrystals
    Yi ZUO, Yubao LI, Jie WEI, Yonggang YAN
    J. Mater. Sci. Technol., 2003, 19 (06): 628-630. 
    Abstract   HTML   PDF (851KB)
    A synthesis route of using calcium hydroxide Ca(OH)2 with ethylene glycol solvent and orthophosphoric acid (H3PO4) as reagents is described. Three ratios of ethylene glycol to distilled water 1:0, 1:1 and 0:1 are used as diluting media for Ca(OH)2. Crystals of different morphology and composition are formed under weak alkaline circumstance at pH 7.0$\sim$8.0. Acicular calcium phosphate nanocrystals are prepared in pure ethylene glycol while rod-like calcium phosphate nanocrystals form in pure distilled water. The nanograde size of the former is smaller than that of the latter. Calcium-deficient apatite (CDAP) is obtained with a Ca/P molar ratio of 1.66. Therefore, it was deduced that the usage of ethylene glycol solvent could influence the formation of calcium phosphate crystal lattice.
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    Aging Behaviors of W-Ni-Fe Ternary Alloys with High Ni-to-Fe Ratios
    Ronghua LI, Jihua HUANG, Sheng YIN, Jun ZHAO
    J. Mater. Sci. Technol., 2003, 19 (06): 631-633. 
    Abstract   HTML   PDF (686KB)
    The hardness variation of two kinds of alloys with 36 wt pct W content and 7/3, 9/1 Ni-to-Fe ratios during strain aging at 800ºC was studied. The microstructures of the aged alloys were analyzed by X-ray diffraction and TEM. The results show that the strain aging hardness of W-Ni-Fe ternary alloy with 7/3 Ni-to-Fe ratio decreases monotonically with the increase of aging time. Under the same conditions, the hardness of 9/1 Ni-to-Fe ratio alloy decreases in the initial aging stage, but then increases as aging process goes on. X ray diffraction and TEM analysis show that there is not any precipitation depositing from the alloy with 7/3 Ni-to-Fe ratio during aging. The monotonic decrease in hardness of this alloy during aging process results from the recovery, recrystallization and solid solubility declining. In the alloy of 9/1 Ni-to-Fe ratio, the fine β phase precipitates dispersively during aging which hardens the alloy. The two different kinds of mechanisms (the softening one and the hardening one) decide the hardness variation of the alloy with 9/1 Ni-to-Fe ratio mentioned above.
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    Laser Direct Writing of Ag Films from Solution on Si Substrate
    Ke SUN, Caibei ZHANG, Yan ZHAO
    J. Mater. Sci. Technol., 2003, 19 (06): 634-636. 
    Abstract   HTML   PDF (1131KB)
    Pulsed Nd:YAG laser was used to irradiate Si substrate immersed in AgNO3 ethylene glycol solution to deposit Ag films along the lines scanned by laser on the substrate, which is a photo-thermal decomposing process. The decomposed Ag atoms congregate and form polycrystalline Ag particles. The Ag concentration changes greatly with the total laser energy absorbed by substrate. Transmission electron microscopy (TEM) observation shows the Ag particles are inlaid in the Si substrate. Auger electron spectrum (AES) shows that the Ag concentration decreases with the increase of the sputtering depth, and there is no oxygen element on the surface of the deposited Ag films.
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    Single-Wall Carbon Nanotube Growth from Graphite Layers-a Tight Binding Molecular Dynamics Simulation
    Yuntuan FANG, Min ZHU, Yongshun WANG
    J. Mater. Sci. Technol., 2003, 19 (06): 637-638. 
    Abstract   HTML   PDF (508KB)
    The growth of single-wall carbon nanotube from graphite layers is studied by tight binding molecular dynamics simulation. Given temperature of 2500 K or 3500 K and an interval of 0.25 nm for the two layers of graphite, a single-wall carbon nanotube with a zigzag shell will be produced. On the other conditions the carbon nanotube cannot grow or grows with too many defects. All carbon nanotube ends have pentagons which play an important role during the tube ends closing.
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CN: 21-1315/TG
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