Started in 1985 Semimonthly
ISSN 1005-0302
CN 21-1315/TG
Impact factor:6.155

The journal has been awarded the excellent periodical in China, and its articles are covered by SCI, EI, CA, SA, JST, RJ, CSA, MA, EMA, AIA etc., PASCAL web. ISI web of Science,SCOPUS.

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      28 July 2009, Volume 25 Issue 04 Previous Issue    Next Issue
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    Articles
    Aluminizing Low Carbon Steel at Lower Temperatures
    Xiao Si,Bining Lu,Zhenbo Wang
    J. Mater. Sci. Technol., 2009, 25 (04): 433-436. 
    Abstract   HTML   PDF (1312KB)

    This study reports the significantly enhanced aluminizing behaviors of a low carbon steel at temperatures far below the austenitizing temperature, with a nanostructured surface layer produced by surface mechanical attrition treatment (SMAT). A much thicker iron aluminide compound layer with a much enhanced growth kinetics of η-Fe2Al5 in the SMAT sample has been observed relative to the coarse-grained steel sample. Compared to the coarse-grained sample, a weakened texture is formed in the aluminide layer in the SMAT sample. The aluminizing kinetics is analyzed in terms of promoted diffusivity and nucleation frequency in the nanostructured surface layer.

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    Eutectic Solidification in Al-13.0%Si Alloys with Combined Addition of Strontium and Boron
    Hengcheng Liao,Ke Ding,Juanjuan Bi,Min Zhang,Huipin Wang Lei Zhao
    J. Mater. Sci. Technol., 2009, 25 (04): 437-440. 
    Abstract   HTML   PDF (808KB)

    The influence of addition of boron (B) on eutectic solidification in a near-eutectic Al-13.0%Si alloy modified with strontium (Sr) was investigated using thermal analysis and macro/microstructure observation. Addition of B in the Sr-modified alloy leads to a considerable increase in nucleation temperature (TN, the minimum temperature prior to recalescence (TM) and growth temperature (TG). In the Sr-modified alloy, nucleation of eutectic might originate at the heterogeneous sites on the mold wall or in the melt near the wall, and eutectic solidification proceeds gradually towards the center, controlled by undercooling of melt. However, with addition of B in the Sr-modified alloy, undercooling required for eutectic nucleation became small, and hence eutectic solidification might occur almost simultaneously within whole casting, controlled by amount of heterogeneous sites. With excessive addition of B in the Sr-modified alloy, nucleation of eutectic grains was explosive within the whole casting and the power of Sr on eutectic solidification was completely poisoned.

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    Serrated Flow Behavior during Compression at Elevated Temperatures in Mg-3Al-1Zn-0.1RE Alloy
    Wei Qiu,Enhou Han,Lu Liu
    J. Mater. Sci. Technol., 2009, 25 (04): 441-444. 
    Abstract   HTML   PDF (2361KB)

    The deformation behaviour of an AZE (Mg-3Al-1Zn-0.1RE) alloy at temperature between 393 and 453 K was investigated by uniaxial compression tests carried out at initial strain rate values of 1×10-4, 5×10-4 and 1×10-3 s-1 in air. The results show that serrated flow occurs at the strain rate of 10-4 s-1 under all test temperatures and 5×10-4 s-1 at 453 K. The mechanism of serrated °ow was proposed, which is mainly attributed to the interaction of dislocations to the precipitates.

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    Microstructures and Morphology Evolution of Icosahedral Phase of As-cast Mg 67.4 Zn 28.9Y3.7 Ternary Alloy Subjected to the Pouring Temperature
    Man Zhu,Gencang Yang,Diqing Wan,Suling Cheng,Yaohe Zhou
    J. Mater. Sci. Technol., 2009, 25 (04): 445-448. 
    Abstract   HTML   PDF (2176KB)

    The microstructure, chemical composition and morphology evolution of icosahedral quasicrystalline phase of Mg67.4Zn28.9Y3.7 ternary alloy were investigated in detail at different pouring temperatures by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectrum (EDS). Low interfacial energy favors the formation of I-phase. The experimental results show that the primary I-phase reveals petal-shaped with five and six branches, where each branch has facetted growth morphology with the size ranging from 50 to 100 μm. As the temperature decreases, the polygon-shaped I-phase forms, attributed to the decomposition of branch of petal-shaped I-phase, and then it grows bigger and some of the fine polygons join together to form large polygons. Besides these, (α-Mg+I-phase) eutectic structures disappear and the relative amount of Mg7Zn3 phase increases as the pouring temperature decreases. The chemical composition and morphology evolution of I-phase were also discussed.

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    Characteristics study on Bi-Pb Based Alloys Quenched from Melt
    Rizk Mostafa Shalaby
    J. Mater. Sci. Technol., 2009, 25 (04): 449-453. 
    Abstract   HTML   PDF (1299KB)

    Three different bismuth-lead systems namely, Wood's alloy (Bi50Pb25Sn12:5Cd12:5), Newton's alloy (Bi50Pb31:2Sn18:8) and Rose's alloy (Bi50Pb28Sn22), with one used as fusible alloys were quenched from melt by melt spinning technique. Thermal analysis, structure and mechanical properties of all alloys have been studied and analyzed. From X-ray diffraction analysis, an intermetallic compound phase, designated Pb7Bi3 is detected. The formation of an intermetallic compound phase causes a pronounced increase in the electrical resistivity. The Wood's alloy containing-cadmium exhibits mechanical properties superior to both the Newton's and Rose's alloys. The presence of cadmium in Wood's alloy decreases its melting point. Wood's alloy has better properties, which make it useful in various applications such as in  rotection shields for radiotherapy, locking of mechanical devices and welding at low temperature.

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    A New Aging Treatment Way for Near α High Temperature Titanium Alloys
    Na Peng,Qingjiang Wang,Xinan Wang
    J. Mater. Sci. Technol., 2009, 25 (04): 454-458. 
    Abstract   HTML   PDF (695KB)

    Two near α titanium alloys Ti-5.6Al-4.8Sn-2.0Zr-1Mo-0.35Si (1#) and Ti-6.0Al-4.8Sn-2.0Zr-1Mo-0.35Si (2#) were solution-treated in the upper α+β phase fields and the duplex mixture microstructures consisting of the less volume fraction primary phase ( αp) and the transformed phase (βt) were obtained. The aging treatments were carried out at 700℃ for 1# alloy and 760℃ for 2# alloy under varied terms, respectively. It guaranteed 2 ordered phase to precipitate only in p but not in t for the two alloys. The slower precipitation and growth of the α2 ordered phase and silicide was observed in 1# alloy in comparison with that in 2# alloy. The mechanical properties including tensile strength and ductility, the creep and lasting properties at the temperature of 600℃ were investigated. Prolonging aging time did not predominantly change the tensile strength and ductility for the two alloys. The 600℃/100h thermal exposure caused a notable decrease of tensile ductility in 2# alloy though no distinct decrease could be observed in 1# alloy after the thermal exposure. The lasting property of 1# alloy was increased with prolonging aging time and finally equal to or even better than that of 2# alloy. Nevertheless, No evident increase emerged in 2# alloy with prolonging aging time. Similarly, the creep property of 1 # alloy monotonously increased with increasing aging time and finally equal to or even better than that of 2# alloy. No evident increase could be observed for 2# alloy. It can be deduced that the overgrowth of α2 ordered phase and silicide is unable to enhance hot strength properties but causes an unacceptable damage to tensile ductility. The optimum equilibrium of the comprehensive properties depending on the proper control of α2 ordered phase and silicide can be achieved by selecting aging temperature and time.

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    Al Preparation from Solid Al2O3 by Direct Electrochemical Deoxidation in Molten CaCl2-NaCl at 550°C
    Hongwei Xie,He Zhang,Yuchun Zhai,Jinxia Wang,Chengde Li
    J. Mater. Sci. Technol., 2009, 25 (04): 459-461. 
    Abstract   HTML   PDF (570KB)

    Al was prepared by a new method in molten salt at low temperature. Sintered alumina pellets were used as cathode; graphite rod was employed as anode; and the molten CaCl2-NaCl was the electrolyte. A constant 3.2 V voltage was applied in this experiment, and oxygen in solid alumina cathode was reduced by direct electrochemical deoxidation at 550°C. In this process, the current gradually decreased with increasing time and the alumina pellets became grey and porous. The metallic particles were obtained and characterized by XRD (X-ray diffraction) and SEM (scanning electron microscopy).

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    Effect of Sulfur Precursor on Dimensions of One-dimensional CdS Nanocrystals
    M. Maleki,Sh. Mirdamadi,R. Ghasemzadeh,M. Sasani Ghamsari
    J. Mater. Sci. Technol., 2009, 25 (04): 462-464. 
    Abstract   HTML   PDF (429KB)

    One-dimensional CdS nanocrystals have been prepared by solvothermal method using cadmium acetate as a cadmium precursor, elemental sulfur and Na2S, as a sulfur precursor, and ethylenediamine as a solvent at 150°C for 5 h. The nanocrystals were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV-Vis absorption spectroscopy. XRD patterns indicate that both Na2S and elemental sulfur as the sulfur precursor result in CdS nanorods with wurtzite phase (hexagonal structure). SEM and TEM images show that diameter of CdS nanorods can be decreased using Na2S instead of elemental sulfur. For the growth of CdS nanorods, a mechanism has been proposed. Uv-Vis absorption of CdS nanorods (sulfur precursor: Na2S) was shown blue shift to 485 nm due to the quantum size effect.

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    Synthesis of Nanocrystalline Barium Ferrite in Ethanol/Water Media
    M. Montazeri-Pour,A. Ataie
    J. Mater. Sci. Technol., 2009, 25 (04): 465-469. 
    Abstract   HTML   PDF (2524KB)

    Nanocrystalline particles of barium ferrite magnetic material have been prepared by co-precipitation route using aqueous and non-aqueous solutions of iron and barium chlorides with a Fe/Ba molar ratio of 11 and subsequent drying-annealing treatment. Water and ethanol/water mixture with volume ratio of 3:1 were used as solvents in the process. Coprecipitated powders were annealed at various temperatures for 1 h. FTIR (Fourier transform infrared spectroscopy), XRD (X-ray diffraction), DTA/TGA (differential thermal analy-sis/thermogravimetric analysis) and SEM (scanning electron microscopy) techniques were used to evaluate powder particle characteristics. DTA/TGA results confirmed by those obtained from XRD indicated that the formation of barium ferrite occurs in sample synthesized in ethanol/water solution at a relatively low temperature of 631°C. Nano-size particles of barium ferrite with mean particle size of almost 75 and 100 nm were observed in the SEM micrographs of the samples synthesized in ethanol/water solution after annealing at 700 and 800°C for 1 h, respectively.

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    New Conditions for Intercalation of Organic Compounds into Semiconductor Nanomaterial
    A.A. El-Meligi
    J. Mater. Sci. Technol., 2009, 25 (04): 470-474. 
    Abstract   HTML   PDF (1822KB)

    The intercalation of organic guests, 2-methyl pyridine (2-picoline) and 3-methyl pyridine (3-picoline) into semiconductor layered nanomaterial (MnPS3) was investigated. New conditions were applied. New phases appeared and lattice expansions were 0.36 nm for 2-picoline intercalation and 0.728 nm for 3-picoline inter-calation. The XRD (X-ray diffraction) patterns exhibit sharp hkl rflections confirming that the material is highly crystalline. The interlayer gap (0.64 nm) of the host plays a role for the  rrangement of the guest in the interlayer region. The crystal structure of the MnPS3 was indexed in the monoclinic system before inter-calation. After intercalation, the crystal system was indexed in the trigonal unit cell. The lattice parameters were obtained and c-axis value was related to the (001) reflections.

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    Thermodynamic Properties of Nanograin Boundary and Thermal Stability of Nanograin Structure
    Jun Wei,Xiaoyan Song,Qingchao Han,Lingmei Li
    J. Mater. Sci. Technol., 2009, 25 (04): 475-478. 
    Abstract   HTML   PDF (312KB)

    The thermal features of the nanograin boundary were described by a developed thermodynamic model. Using the nanocrystalline Cu as an example, the pressure, the bulk modulus, and the volume thermal expansion coefficient were calculated to characterize the thermodynamic properties of the grain boundaries on the nanoscale. Based on the parabola-type relationship between the excess free energy and the excess volume of the nanograin boundary, the thermal stability, as well as its evolution characteristics, was analyzed. The experimental results of the temperature-varying grain growth in the nanocrystalline Cu, which exhibited the discontinuous nanograin growth behavior, verified the thermodynamic predictions. In addition, the quantitative relationships correlating the excess volume and the lattice expansion with the nanograin size were discussed.

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    Identification of Iron Oxides Qualitatively/Quantitatively Formed during the High Temperature Oxidation of Superalloys in Air and Steam Environments
    M. Siddique,N. Hussain,M. Shafi
    J. Mater. Sci. Technol., 2009, 25 (04): 479-482. 
    Abstract   HTML   PDF (377KB)

    Mossbauer spectroscopy has been used to study the morphology of iron oxides formed during the oxidation of superalloys, such as SS-304L (1.4306S), Incoloy-800H, Incoloy-825, UBHA-25L, Sanicro-28 and Inconel-690, at 1200°C exposed in air and steam environments for 400 h. The basic aim was to identify and compare the iron oxides qualitatively and quantitatively, formed during the oxidation of these alloys in two environments. The behaviour of alloy UBHA-25L in high temperature oxidation in both environments indicates that it has good oxidation resistance especially in steam, whereas Sanicro-28 has excellent corrosion resistance in steam environment. In air oxidation of Inconel-690 no iron oxide, with established MÄossbauer parameters, was detected.

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    Effects of Vacuum Ultraviolet Radiation on Atomic Oxygen Erosion of Polysiloxane/SiO2 Hybrid Coatings
    Longfei Hu,Meishuan Li,Yanchun Zhou
    J. Mater. Sci. Technol., 2009, 25 (04): 483-488. 
    Abstract   HTML   PDF (1230KB)

    Polysiloxane/SiO2 hybrid coatings have been prepared on Kapton films by a sol-gel process. The erosion resistance of polysiloxane/SiO2 (20 wt pct) coating was evaluated by exposure tests of vacuum ultraviolet radiation (VUV) and atomic oxygen beam (AO) in a ground-based simulation facility. The experimental results indicate that this coating exhibits better AO resistance than pure polysiloxane coating. The erosion yield (Ey) of the polysiloxane/SiO2 (20 wt pct) hybrid coating is about 10¡27 cm3/atom, being one or two orders of magnitude lower than that of polysiloxane. VUV radiation can affect the erosion process greatly. Under simultaneous AO and VUV exposure, the value of Ey of the polysiloxane/SiO2 (20 wt pct) hybrid coating increases by 39% compared with that under single AO exposure.

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    Effects of Substrate Temperature on the Growth of Polycrystalline Si Films Deposited with SiH4+Ar
    Hua Cheng,Aimin Wu,Jinquan Xiao,Nanlin Shi,Lishi Wen
    J. Mater. Sci. Technol., 2009, 25 (04): 489-491. 
    Abstract   HTML   PDF (281KB)

    Polycrystalline silicon (poly-Si) films were deposited using Ar diluted SiH4 gaseous mixture by electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD). The effects of the substrate temperature on deposition rate, crystallinity, grain size and the configuration of H existing in poly-Si film were investigated. The results show that, comparing with H2 dilution, Ar dilution could significantly decrease the concentration of H on the growing surface. When the substrate temperature increased, the deposition rate increased and the concentration of H decreased monotonously, but the crystallinity and the grain size of poly-Si films exhibited sophisticated trends. It is proposed that the crystallinity of the films is determined by a competing balance of the self-diffusion activity of Si atoms and the deposition rate. At substrate temperature of 200°C, the deposited film exhibits the maximum poly-Si volume fraction of 79%. Based on these results, higher substrate temperature is suggested to prepare the poly-Si films with advanced stability and compromised crystallinity at high deposition rate.

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    Microstructure of Cu-based Amorphous Composite Coatings on AZ91D Magnesium Alloy by Laser Cladding
    Kaijin Huang,Changsheng Xie,T.M. Yue
    J. Mater. Sci. Technol., 2009, 25 (04): 492-498. 
    Abstract   HTML   PDF (1529KB)

    To improve the sliding wear resistance of AZ91D magnesium alloy, Cu-based amorphous composite coatings made of Cu47Ti34Zr11Ni8 and Cu47Ti34Zr11Ni8+20 wt pct SiC powders were fabricated on AZ91D magnesium alloy by laser cladding, respectively. SEM (scanning electron microscopy), EDS (energy dispersive X-ray spectroscopy), XRD (X-ray diffraction) and TEM (transmission electron microscopy) techniques were employed to study the phases of the coatings. The results show that the coatings mainly consist of amorphous phase and different intermetallic compounds. The reason of formation of amorphous phase and the function of SiC particles were explained in details.

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    Influence of the Thermal Barrier Coatings Design on the Oxidation Behavior
    B. Saeedi,A. Sabour,A. Ebadi,A.M. Khoddami
    J. Mater. Sci. Technol., 2009, 25 (04): 499-507. 
    Abstract   HTML   PDF (4157KB)

    The properties of two different types of thermal barrier coatings (TBCs) were compared to improve the surface characteristics on high temperature components. These TBCs consisted of a duplex TBC and a five-layered functionally graded TBC. NiCrAlY bond coats were deposited on a number of Inconel-738LC specimens using high velocity oxy-fuel spraying (HVOF) technique. For duplex coating, a group of these specimens were coated with yttria stabilized zirconia (YSZ) using plasma spray technique. Functionally graded NiCrAlY/YSZ coatings were fabricated by plasma spray using co-injection of the two different powders in a single plasma torch. The amount of zirconia in functionally graded coatings were gradually increased from 30 to 100 vol. pct. Microstructural changes, thermally grown oxide (TGO) layer growth and damage initiation of the coatings were investigated as a function of isothermal oxidation test at 970°C. As a complementary test, the performance of the fabricated coatings by the optimum processing conditions was evaluated as a function of intense thermal cycling test at 1100°C. Also the strength of the adhesive coatings of the substrate was also measured. Microstructural characterization was analyzed by scanning electron microscopy (SEM) and optical microscopy whereas phase analysis and chemical composition changes of the coatings and oxides formed during the tests were studied by XRD (X-ray diffraction) and EDS (energy dispersive spectrometer). The results showed that microstructure and compositions gradually varied in the functionally graded coatings. By comparison of duplex and functionally graded TBCs oxidation behavior (duplex failure after 1700 h and funcitionally graded TECs failure after 2000 h), thermal shock test and adhesion strength of the coatings, the functionally graded TBC had better performance and more durability.

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    Mechanical and Abrasive Wear Properties of Anodic Oxide Layers Formed on Aluminium
    W. Bensalah,K. Elleuch,M. Feki,M. Wery,H.F. Ayedi
    J. Mater. Sci. Technol., 2009, 25 (04): 508-512. 
    Abstract   HTML   PDF (1297KB)

    Aluminium oxide coatings were formed on aluminium substrates in oxalic acid-sulphuric acid bath. Abrasion tests of the obtained anodic layers were carried out on a pin-on-disc machine in accordance with the ISO/DP 825 specifications. The Vickers microhardness, D (HV0:2), and the abrasion weight loss, Wa (mg) were measured. Influence of oxalic acid concentration (Cox), bath temperature (T) and anodic current density (J) on D and Wa has been examined, and the sulphuric acid concentration (Csul) was maintained at 160 g?L-1. It was found that high microhardness and abrasive wear resistance of oxide layers were produced under low temperatures and high current densities with the addition of oxalic acid. The morphology and the composition of the anodic oxide layer were examined by scanning electron microscopy (SEM), atomic force microscopy (AFM), optical microscopy and glow-discharge optical emission spectroscopy (GDOES). It was found that the chemistry of the anodizing electrolyte, temperature, and current density are the controlling factors of the mechanical properties of the anodic oxide layer.

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    Improved Fatigue Behavior of Pipeline Steel Welded Joint by Surface Mechanical Attrition Treatment (SMAT)
    Yu Wang,Min Huang,Lei Zhou,Zhixin Cong,Huilin Gao
    J. Mater. Sci. Technol., 2009, 25 (04): 513-515. 
    Abstract   HTML   PDF (406KB)

    A pipeline steel X80 with welded joint was subjected to surface mechanical attrition treatment (SMAT). After SMAT, a nanostructure surface layer with an average grain size of about 10 nm was formed in the treated sample, and the fatigue limit of the welded joint was elevated by about 13% relative to the untreated joints. In the low and the high amplitude stress regimes, both fatigue strength and fatigue life were enhanced. Formation of the nanostructured surface layer played more important role in the enhanced fatigue behavior than that of residual stress induced by the SMAT.

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    Cold Cracking of Flux Cored Arc Welded Armour Grade High Strength Steel Weldments
    G. Magudeeswaran,V. Balasubramanian,G. Madhusudhan Reddy
    J. Mater. Sci. Technol., 2009, 25 (04): 516-526. 
    Abstract   HTML   PDF (4089KB)

    In this investigation, an attempt has been made to study the influence of welding consumables on the factors that influence cold cracking of armour grade quenched and tempered (Q&T) steel welds. Flux cored arc welding (FCAW) process were used making welds using austenitic stainless steel (ASS) and low hydrogen ferritic steel (LHF) consumables. The diffusible hydrogen levels in the weld metal of the ASS and LHF consumables were determined by mercury method. Residual stresses were evaluated using X-ray stress analyzer and implant test was carried out to study the cold cracking of the welds. Results indicate that ASS welds offer a greater resistance to cold cracking of armour grade Q&T steel welds.

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    Interfacial Microstructure of Diffusion Bonded Inconel 738 and Ferritic Stainless Steel Couple
    Bulent Kurt,Mustafa Ulutan
    J. Mater. Sci. Technol., 2009, 25 (04): 527-530. 
    Abstract   HTML   PDF (2908KB)

    In this study, Inconel 738 alloy was diffusion bonded to a ferritic stainless steel. The effect of bonding temperature on the microstructural development across the joint region was investigated. Following the diffusion bonding, conventional characterization techniques such as scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and microhardness were used to examine the interfacial microstructure. It was seen that bonding temperature was effective on the diffusion of Ni from Inconel 738 to ferritic stainless steel that affected the microstructure of the interface. Austenite phase was formed at the interface as a result of Ni diffusion from the Inconel 738 to the interface.

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    Electron Paramagnetic Resonance and Optical Absorption Studies on Copper Ions in Mixed Alkali Cadmium Phosphate Glasses
    G. Giridhar,M. Rangacharyulu,R.V.S.S.N. Ravikumar,P. Sambasiva Rao
    J. Mater. Sci. Technol., 2009, 25 (04): 531-534. 
    Abstract   HTML   PDF (455KB)

    Electron paramagnetic resonance (EPR) and optical absorption studies were carried out at room temperature on copper doped mixed alkali cadmium phosphate (LiNaCdP) glasses to understand the nature and symmetry of dopant. Three samples with varying concentrations of alkali ions have been prepared. The spin Hamiltonian parameters obtained from room temperature EPR spectra are: g||=2.437, g=2.096, A||=117×10-4 cm-1, A=26×10-4 cm-1 for LiNaCdP1, g||=2.441, g=2.088, A||=121×10-4 cm-1, A=25×10-4 cm-1 for LiNaCdP2 and g||=2.433, g=2.096, A||=125×10-4 cm-1, A=32×10-4 cm-1 for LiNaCdP3. These EPR results indicate that the dopant Cu2+ ion enters the glass matrix into a tetragonally elongated octahedral site. The bonding parameters evaluated by correlating optical and EPR data suggest that bonding between the central metal ion and ligands is partially covalent. The mixed alkali effect in cadmium phosphate glasses was reported.

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    High-temperature Electric Properties of Polycrystalline La-doped CaMnO3 Ceramics
    Jinle Lan,Yuanhua Lin,Ao Mei,Cewen Nan,Yong Liu,Boping Zhang
    J. Mater. Sci. Technol., 2009, 25 (04): 535-538. 
    Abstract   HTML   PDF (840KB)

    Polycrystalline La-doped CaMnO3 ceramics have been prepared by a solid-state sintering method. Analysis of microstructure and phase composition indicates that the addition of La can prohibit the further growth of grain, and no impurity phase appears. The results revealed that the La doping can lead to a large change of the activation energy (from 0.22 to 0.02 eV), and thus result in a marked increase in electric conductivity of 2-4 orders of magnitude. The power factor can reach about 1.5×10-4 W?m-1?K-2 in a wide temperature range, which potentially make them attractive for n-type high-temperature thermoelectric materials.

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    Morphology Change of Metastable Regrown Graphite with Boron Additive under HPHT
    Chuanyi Zang,Xiaozhou Chen,Qiang Hu,Wei Guo,Guofeng Huang
    J. Mater. Sci. Technol., 2009, 25 (04): 539-542. 
    Abstract   HTML   PDF (868KB)

    By temperature gradient method under high pressure and high temperature (HPHT), with NiMnCo alloy as the solvent metal, at diamond-stable region of about 5.4 GPa and 1500 K, metastable regrown graphite crystals of different morphology were synthesized. With B as an additive incorporated into the NiMnCo-C system, metastable regrown graphite crystals of sphere-like shape were firstly obtained under HPHT. If the growth system does not contain B, sheet-like regrown graphite crystals, most with regular hexagonal morphology, are grown upwards and standing vertically in the metal solvent. When B additive of 1.0 wt pct was added into carbon source (graphite powder), all metastable regrown graphite crystals took on the habit of regular sphere-like morphology, and were grown by a spiral layer growth mechanism.

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    Damping and Mechanical Properties of Cocured Composite Laminates with Embedded Perforate Viscoelastic Layer
    Lijian Pan,Boming Zhang
    J. Mater. Sci. Technol., 2009, 25 (04): 543-546. 
    Abstract   HTML   PDF (440KB)

    The composite laminates with embedded acrylonitrile butadiene rubber (NBR) layer were fabricated by cocuring process. The embedded layers were perforated with a series of small holes to allow resin to flow through the damping layer and completely couple the structure to improve bending stiffness and interlaminar shearing strength of these cocured composite laminates. The damping, bending stiffness and shearing strength of these composite laminates with different perforation diameters were investigated. The experimental results show that increasing the perforation diameter leads to significant decreases in damping and significant increase in bending stiffness up to an area ratio of 7.065%. The area ratio here is defined as the ratio of perforation area to the total damping area. Beyond the area ratio of 7.065%, increasing the diameter to an area ratio of 50.24% results in only a slight variation in damping and bending stiffness. Moreover, increasing the perforation diameter does not always increase the shearing strength of the embedded viscoelastic layer. The shearing strength of embedded viscoelastic layer increases only when the area ratio is greater than 19.625%; instead, it will decrease.

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    Fabrication and Testing of Carbon Fiber Reinforced Truss Core Sandwich Panels
    Bing Wang,Linzhi Wu,Li Ma,Qiang Wang,Shanyi Du
    J. Mater. Sci. Technol., 2009, 25 (04): 547-550. 
    Abstract   HTML   PDF (561KB)

    Truss core sandwich panels reinforced by carbon fibers were assembled with bonded laminate facesheets and carbon fiber reinforced truss cores. The top and bottom facesheets were interconnected with truss cores. Both ends of the truss cores were embedded into four layers of top and bottom facesheets. The mechanical properties of truss core sandwich panels were then investigated under out-of-plane and in-plane compression loadings to reveal the failure mechanisms of sandwich panels. Experimental results indicated that the mechanical behavior of sandwich structure under in-plane loading is dominated by the buckling and debonding of facesheets.

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    Synthesis of Chitosan-Hydroxyapatite Composites and Its Effect on the Properties of Bioglass Bone Cement
    Jingxiao Liu,Fei Shi,Ling Yu,Liting Niu,Shanshan Gao
    J. Mater. Sci. Technol., 2009, 25 (04): 551-555. 
    Abstract   HTML   PDF (573KB)

    Chitosan-hydroxyapatite (CS-HA) composite powders were synthesized via in situ co-precipitation method, through the reaction of Ca(NO3)2 and H3PO4 in the simulated body fluid (SBF) containing appropriate amount of chitosan. The thermal evolution, microstructure and morphology were studied by TG-DTA (thermogravimetry-differential thermal analysis), XRD (X-ray diffraction), FTIR (Fourier transform infrared spectroscopy) and TEM (transmission electron microscopy). The in vitro bioactivity test showed that the obtained CS-HA composites had higher capability of inducing calcium ions deposition. Effects of CS-HA composites on the bioactivity and compressive strength of bioglass bone cement were investigated. The results indicated that the bioactivity of bioglass bone cement could be improved further when CS-HA composite powders were added into the cement, and appropriate amount of CS-HA additive was favorable for compressive strength improvement of bioglass bone cement.

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    An in vivo Evaluation of Ultra-fine Grained Titanium Implants
    S. Bindu,K.P. Sanosh,K. Smetana,A. Balakrishnan,T.N. Kim
    J. Mater. Sci. Technol., 2009, 25 (04): 556-560. 
    Abstract   HTML   PDF (676KB)

    The present work focuses mainly on an in vivo evaluation of ultra fine grained titanium (UFG-Ti) obtained by severe plastic deformation (SPD). The SPD on commercially produced Grade 2 titanium (Cp-Ti) resulted in the refinement of the grain size by several orders of magnitude. Polished surfaces having similar roughness from both UFG-Ti and Cp-Ti were prepared. In vitro test revealed the presence of fibronectin, which was involved in the attachment of the cells to the substrate. Phase contrast micrographs showed the highest signal of fibronectin in UFG-Ti, indicating that it is more cytocompatible than Cp-Ti. In vivo tests, by subcutaneous implantation of the metals in the rats showed the better biocompatibility of UFG-Ti over Cp-Ti. The improved biocompatibility of UFG-Ti was attributed to the presence of surface discontinuities (in the form of nano-defects), surface energy, higher wettability, surface stress and stable TiO2 films, which increased the protein adsorption on the surface.

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    Numerical Simulation of Macrosegregation for an Fe-0.8 wt pct C Alloy
    Dongrong Liu,Dianzhong Li,aoguang Sang
    J. Mater. Sci. Technol., 2009, 25 (04): 561-568. 
    Abstract   HTML   PDF (6883KB)

    Macrosegregation in Fe-0.8 wt pct C alloy solidifying with equiaxed morphology was numerically simulated. Based on a two-phase volumetric averaging approach, heat transfer, melt convection, composition distribution, nucleation and grain evolution on the system scale were described. A weak-coupling numerical procedure was designed to solve conservation equations. Simulations were conducted to study the effects of cooling rate and nuclei density on the macrosegregation pattern. The relative influence of thermal buoyancy- and solutal buoyancy-induced flows on macrosegregation was identified. Calculated results indicate that a higher cooling rate establishes a more homogeneous composition. More uniform solute distributions are formed with increasing nuclei density. In addition, it is noted that the direction of channel segregates depends on the relative strength of thermal and solutal buoyancy forces.

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    Initial Oxidation of γ-TiAl(111) Surface: Density-functional Theory Study
    Hong Li,Shaoqing Wang,Hengqiang Ye
    J. Mater. Sci. Technol., 2009, 25 (04): 569-576. 
    Abstract   HTML   PDF (2587KB)

    In this paper, we reported a first-principles investigation on the structural and electronic properties of O adsorption on the γ-TiAl(111) surface, to illustrate the oxidation process. It has been found that: (1) rather than stopping with one full monolayer of coverage, oxygen adsorption continues till two monolayer coverage, rendering an oxide-like structure; (2) full structural relaxation makes the surface oxide layer denser and more stable, which hinders the subsequent O adsorption (oxidation) process. In addition, the transformation from metal to oxide surface was identified by analyzing the local density of states through the oxidation steps, which was in good agreement with experimental results.

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ISSN: 1005-0302
CN: 21-1315/TG
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