Started in 1985 Monthly
ISSN 1005-0302
CN 21-1315/TG
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      10 May 2019, Volume 35 Issue 5 Previous Issue    Next Issue
    Orginal Article
    Synthesis of ultra-narrow PbTe nanorods with extremely strong quantum confinement
    Han Lu, Fang Honghua, Du Chunmiao, Sun Jianxia, Li Youyong, Ma Wanli
    J. Mater. Sci. Technol.. 2019, 35 (5): 703-710.   DOI: 10.1016/j.jmst.2018.10.019
    Abstract   HTML   PDF (3244KB)

    Monodisperse, high-quality, ultra-narrow PbTe nanorods were synthesized for the first time in a one-pot, hot-injection reaction using trans-2-decenoic acid as the agents for lead precursors and tris(diethylamino)phosphine telluride together with free tris(diethylamino)phosphine as the telluride precursors. High monomer reactivity, rapid nucleation and fast growth rate derived from the new precursors led to the anisotropic growth of PbTe nanocrystals at low reaction temperatures (<150°C). In addition, the aspect ratio of PbTe nanorods could be largely adjusted from 4 to 15 by tuning the Pb to Te precursor molar ratio and reaction temperatures. Moreover, the synthesized ultra-narrow PbTe nanorods exhibited extremely strong quantum confinement and presented unique optical properties. We revealed that the diameter and length of PbTe nanorods could significantly affect their optical properties, which potentially offer them new opportunities in the application of optoelectronic and thermoelectric devices and make them desired subjects for multiple exciton generation and other fundamental physics studies.

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    Electrical characteristics and detailed interfacial structures of Ag/Ni metallization on polycrystalline thermoelectric SnSe
    Kim SnSeYeongseon, Jin Younghwan, Yoon Giwan, Chung In, Yoon Hana, Yoo Chung-Yul, Hyun Park Sang
    J. Mater. Sci. Technol.. 2019, 35 (5): 711-718.   DOI: 10.1016/j.jmst.2018.11.020
    Abstract   HTML   PDF (4960KB)

    SnSe is a promising thermoelectric material with a high figure of merit in single crystal form, which has stimulated continuous research on polycrystalline SnSe. In this study, we investigated a metallization techniques for polycrystalline SnSe to achieve highly efficient and practical SnSe thermoelectric modules. The Ag/Ni metallization layers were formed on pristine polycrystalline SnSe using various deposition technique: sputter coating Ni, powder Ni and foil Ni by spark plasma sintering. Structural analysis demonstrated that the microstructure and contact resistance could be different according to the metallization process, despite using the same metals. The Ag/Ni metallization layer using foil Ni acted as an effective diffusion barrier and minimized electrical contact resistance (2.3×10-4 Ω cm2). A power loss in the thermoelectric module of only 5% was demonstrated using finite element simulation.

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    Plasma spray of biofunctional (Mg, Sr)-substituted hydroxyapatite coatings for titanium alloy implants
    Cao Lei, Ullah Ihsan, Li Na, Niu Shiyu, Sun Rujie, Xia Dandan, Yang Rui, Zhang Xing
    J. Mater. Sci. Technol.. 2019, 35 (5): 719-726.   DOI: 10.1016/j.jmst.2018.10.020
    Abstract   HTML   PDF (3321KB)

    Plasma-sprayed hydroxyapatite (HA) coatings have been widely utilized in load-bearing titanium alloy implants. In this study, Mg, Sr co-substituted HA ((Mg, Sr)-HA) nano-scale powders have been synthesized, which are further used to prepare (Mg, Sr)-HA coatings on Ti-6Al-4V alloys in order to improve the biological functions. The average size of (Mg, Sr)-HA nano particles is 75nm. The average bonding strength for (Mg, Sr)-HA coating and samples after heat treatment at 500 °C or 600 °C for 3 h are 26.17 ± 2.11 MPa, 36.07 ± 4.48 MPa and 37.07±2.95 MPa, respectively. There is a significantly increase of bonding strength likely due to low residual stress after heated treatment. MC3T3-E1 cells show a high proliferation rate when cultured with (Mg, Sr)-HA coating extract compared to the normal culture medium, which also exhibit large extension and deposition of extracellular matrices when adhered on the coating surfaces. Thus, these (Mg, Sr)-HA coatings show high bonding strength and improved biological functions, which offer promising future applications in the fields of orthopedics and dentistry.

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    Controllable phase transformation and improved thermal stability of nickel on tungsten substrate by electrodeposition
    Xu Minjie, Hu Chao, Xiang Haiyan, Lu Haozi, Shihao Hu Travis, Hu Bonian, Liu Song, Yu Gang
    J. Mater. Sci. Technol.. 2019, 35 (5): 727-732.   DOI: 10.1016/j.jmst.2018.11.002
    Abstract   HTML   PDF (2729KB)

    Present study reports a controllable phase transformation of nickel (Ni) from amorphous to cubic crystal structures on tungsten (W) substrate by electrodeposition. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy were used to characterize the microstructure, micro-constituents and surface morphology of as-prepared Ni. The microstructure of Ni was strongly affected by the applied overpotential and deposition time. It is demonstrated that by controlling these two parameters either amorphous or cubic crystal structure of Ni on the W substrate could be obtained. The crystallization mechanism is discussed based on Gibbs crystal growth theory and Ostwald’s rule. It is concluded that W substrate, acting as a heat sink, can effectively promote the thermal stability of amorphous Ni, based on the data from differential scanning calorimetry and Kissinger’s model. This work contributes to the elucidation of the crystallization mechanism of Ni on W powder substrates, and proves that, better than alloying with other elements, incorporating powder substrates will significantly improve the crystallization temperature, hence the thermostability of amorphous Ni.

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    Friction stir spot welding of SPCC low carbon steel plates at extremely low welding temperature
    Sun Y.F., Fujii H., Sato Y., Morisada Y.
    J. Mater. Sci. Technol.. 2019, 35 (5): 733-741.   DOI: 10.1016/j.jmst.2018.11.011
    Abstract   HTML   PDF (4071KB)

    Friction stir spot welding (FSSW) was applied to 2.0 mm thick steel plate cold-rolled commercial (SPCC) low carbon steel plates at a very low rotation speed that ranged from 5 to 50 rpm, which was much lower than that generally used for the conventional FSSW technique. Due to the very low heat input, the welding processes could therefore be completed at a peak welding temperature below 160 °C. As a result, a significantly refined microstructure with an average grain size of about 0.41 μm was formed in the stir zone of the joints and the J1{0-11}<-211> and J2{1-10}<-1-12> shear textures were the dominant components, which are different from the D1{11-2}<111> and D2{-1-12}<111> shear textures formed in the conventional FSSW joints. In addition, no heat affected zone could be detected along the cross-sectional plane of the joints. Although a few void-like non-bonded areas were still observed along the interface between the upper and lower steel plates, the shear tensile loads of the joints increased to about 10.0 kN when welded at a condition of 8 t, 20 rpm and 30 s, and the joints fractured through the plug failure mode.

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    Three principles for preparing Al wire with high strength and high electrical conductivity
    Hou J.P., Li R., Wang Q., Yu H.Y., Zhang Z.J., Chen Q.Y., Ma H., Wu X.M., Li X.W., Zhang Z.F.
    J. Mater. Sci. Technol.. 2019, 35 (5): 742-751.   DOI: 10.1016/j.jmst.2018.11.013
    Abstract   HTML   PDF (3445KB)

    The trade-off relation between the strength and the electrical conductivity has been a long-standing dilemma in metallic materials. In the study, three key principles, i.e. elongated grains, sharp texture and nano-scale precipitates, were presented for preparing Al wire with high strength and high electrical conductivity based on the specially designed experiments for breaking the mutually exclusive relation between the strength and the electrical conductivity. The results show that the elongated grains could lead to a higher electrical conductivity in Al wire without sacrificing the strength; while, the <111> sharp texture can efficiently strengthen the Al wire without influencing the electrical conductivity. Furthermore, nano-scale precipitates with proper size can simultaneously improve the strength and electrical conductivity of Al alloy wire. Under the guidance of the above three key principles, Al wires with high strength and high conductivity were prepared.

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    Stress dependence of the creep behaviors and mechanisms of a third-generation Ni-based single crystal superalloy
    Yue Quanzhao, Liu Lin, Yang Wenchao, He Chuang, Sun Dejian, Huang Taiwen, Zhang Jun, Fu Hengzhi
    J. Mater. Sci. Technol.. 2019, 35 (5): 752-763.   DOI: 10.1016/j.jmst.2018.11.015
    Abstract   HTML   PDF (6574KB)

    Elevated temperature creep behaviors at 1100 °C over a wide stress regime of 120-174 MPa of a third-generation Ni-based single crystal superalloy were studied. With a reduced stress from 174 to 120 MPa, the creep life increased by a factor of 10.5, from 87 h to 907 h, presenting a strong stress dependence. A splitting phenomenon of the close- (about 100 nm) and sparse- (above 120 nm) spaced dislocation networks became more obvious with increasing stress. Simultaneously, a0<010> superdislocations with low mobilities were frequently observed under a lower stress to pass through γ′ precipitates by a combined slip and climb of two a0<110> superpartials or pure climb. However, a0<110> superdislocations with higher mobility were widely found under a higher stress, which directly sheared into γ′ precipitates. Based on the calculated critical resolved shear stresses for various creep mechanisms, the favorable creep mechanism was systematically analyzed. Furthermore, combined with the microstructural evolutions during different creep stages, the dominant creep mechanism changed from the dislocation climbing to Orowan looping and precipitates shearing under a stress regime of 137-174 MPa, while the dislocation climbing mechanism was operative throughout the whole creep stage under a stress of 120 MPa, resulting a superior creep performance.

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    Magnetic and magnetotransport properties of single-crystalline R2PdGe6 (R = Pr, Gd and Tb)
    Zhang Lei, Ren Weijun, Luo Xiaohua, Zhang Zhidong
    J. Mater. Sci. Technol.. 2019, 35 (5): 764-768.   DOI: 10.1016/j.jmst.2018.11.010
    Abstract   HTML   PDF (1748KB)

    Single crystals of R2PdGe6 (R = Pr, Gd and Tb) compounds were grown by the Bi-flux method. Pr2PdGe6 is an antiferromagnetic compound with Néel temperature TN = 15 K, in which a field-induced magnetic transition (spin flip) occurs when a magnetic field is applied along either a or b axis; a small magnetization and hysteresis loop were observed when a field is applied along c axis. Gd2PdGe6 is a collinear antiferromagnetic compound with TN = 37 K along b axis. Tb2PdGe6 is an antiferromagnetic compound with TN = 48 K and its hard magnetization direction is along b axis. The temperature dependences of the resistance of the entire three compounds present inflection points at the respective TN. A large resistance (as well as magnetoresistance) change can be found at the spin flip transition of Pr2PdGe6, but the change is not obvious at the spin flop transition of Gd2PdGe6.

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    Atomic-layer-deposited (ALD) Al2O3 passivation dependent interface chemistry, band alignment and electrical properties of HfYO/Si gate stacks
    Liang Shuang, He Gang, Wang Die, Qiao Fen
    J. Mater. Sci. Technol.. 2019, 35 (5): 769-776.   DOI: 10.1016/j.jmst.2018.11.003
    Abstract   HTML   PDF (3657KB)

    In this work, the effects of atomic-layer-deposited (ALD) Al2O3 passivation layers with different thicknesses on the interface chemistry and electrical properties of sputtering-derived HfYO gate dielectrics on Si substrates have been investigated. The results of electrical measurements and X-ray photoelectron sepectroscopy (XPS) showed that 1-nm-thick Al2O3 passivation layer is optimized to obtain excellent electrical and interfacial properties for HfYO/Si gate stack. Then, the metal-oxide-semiconductor capacitors with HfYO/1-nm Al2O3/Si/Al gate stack were fabricated and annealed at different temperatures in forming gas (95% N2+5% H2). Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics showed that the 250°C-annealed HYO high-k gate dielectric thin film demonstrated the lowest border trapped oxide charge density (-3.3×1010cm-2), smallest gate-leakage current (2.45×10-6 A/cm2 at 2V) compared with other samples. Moreover, the annealing temperature dependent leakage current conduction mechanism for Al/HfYO/Al2O3/Si/Al MOS capacitor has been investigated systematically. Detailed electrical measurements reveal that Poole-Frenkle emission is the main dominant emission in the region of low and medium electric fields while direct tunneling is dominant conduction mechanism at high electric fields.

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    Effect of grain refinement and crystallographic texture produced by friction stir processing on the biodegradation behavior of a Mg-Nd-Zn alloy
    Zhang Wen, Tan Lili, Ni Dingrui, Chen Junxiu, Zhao Ying-Chao, Liu Long, Shuai Cijun, Yang Ke, Atrens Andrej, Zhao Ming-Chun
    J. Mater. Sci. Technol.. 2019, 35 (5): 777-783.   DOI: 10.1016/j.jmst.2018.11.025
    Abstract   HTML   PDF (2611KB)

    The application of a single pass of friction stir processing (FSP) to Mg-Nd-Zn alloy resulted in grain refinement, texture evolution and redistribution of second phases, which improved corrosion resistance. In this work, an as-rolled Mg-Nd-Zn alloy was subjected to FSP. The microstructure in the processed zone of the FS-400 rpm alloy exhibited refined grains, a more homogenous grain size distribution, less second phases, and stronger basal plane texture. The corrosion behavior assessed using immersion tests and electrochemical tests in Hank’s solution indicated that the FS-400 rpm alloy had a lower corrosion rate, which was attributed to the increase of basal plane intensity and grain refinement. The hardness was lowered slightly and the elongation was increased, which might be attributed to the redistribution of the crushed second phases.

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    On the double-side probeless friction stir spot welding of AA2198 Al-Li alloy
    Chu Q., Li W.Y., Hou H.L., Yang X.W., Vairis A., Wang C., Wang W.B.
    J. Mater. Sci. Technol.. 2019, 35 (5): 784-789.   DOI: 10.1016/j.jmst.2018.10.027
    Abstract   HTML   PDF (2559KB)

    Double-side probeless friction stir spot welding (DP-FSSW) of AA2198 alloy was conducted to investigate the microstructure and mechanical properties. Compared with common single-side probeless friction stir spot welding (P-FSSW), the plastic strain during DP-FSSW is nearly symmetrical with respect to the bondline to suppress the extension of hook defect, which is detrimental to the joint mechanical strength. With DP-FSSW, a fully metallurgically bonded region has formed due to severe plastic deformation at high temperatures. Tensile/shear tests show that the joint strength could exceed 8kN, which is comparable to P-FSSW and refill FSSW, and all fractures happen in a shear failure mode as cracks extend along the interface of two sheets. The microhardness profile exhibits a uniform distribution along the thickness direction, in which the hook defect shows the lowest value.

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    Rolling texture and its effect on tensile property of a near-α titanium alloy Ti60 plate
    Li Wenyuan, Chen Zhiyong, Liu Jianrong, Zhu Shaoxiang, Sui Guoxin, Wang Qingjiang
    J. Mater. Sci. Technol.. 2019, 35 (5): 790-798.   DOI: 10.1016/j.jmst.2018.10.032
    Abstract   HTML   PDF (4189KB)

    Rolling texture and its effect on tensile properties of Ti60 alloy plates were investigated in the present study. The plates were β-rolled at 1070 °C and (α + β)-rolled at 980 °C, using uni-directionally rolling (UDR) and cross-directionally rolling (CDR) processes, respectively. β-rolled plates exhibited weak textures, which were attributed to the dispersive orientations of secondary α during the β → α phase transformation. Strong deformation textures formed in (α + β)-rolled plates as a result of slipping mechanisms: the strong T-type texture in UDR plate was related to {10 1ˉ0}[11 2ˉ0] slipping, while the B-type texture in CDR plate was relevant with {0001}[11 2ˉ0] slip. Strong T-type textures led to anisotropic tensile properties. B-type textures would decrease such an anisotropy. The (α + β)-CDR process was found to be a candidate process for reducing anisotropy of Ti60 alloy plates.

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    Influence of Sn and Mo on corrosion behavior of ferrite-pearlite steel in the simulated bottom plate environment of cargo oil tank
    Hao Xuehui, Dong Junhua, Mu Xin, Wei Jie, Wang Changgang, Ke Wei
    J. Mater. Sci. Technol.. 2019, 35 (5): 799-811.   DOI: 10.1016/j.jmst.2018.11.012
    Abstract   HTML   PDF (5317KB)

    This work investigated the influence of Sn and Mo on corrosion behavior of ferrite-pearlite steel in the simulated bottom plate environment of cargo oil tank. The results indicate that the corrosion rate of three ferrite-pearlite steels increased with extending the immersion time due to the continuous accumulation of the residual Fe3C. However, the addition of Sn or the combined addition of Sn and Mo could reduce the corrosion rate of Sn containing steel and Sn-Mo containing steel to 37.5% and 20% of that of carbon steel, respectively. Moreover, the cathodic reaction of Sn containing steel and Sn-Mo containing steel was always controlled by the charge transfer step during the whole immersion test, while that of carbon steel was gradually transformed into the diffusion-controlled process. These results were mainly related with the deposition of metallic Sn and Mo on the steel surface. The metallic Sn and Mo with uniform distribution restrained the galvanic effect through suppressing both the anodic dissolution of ferrite and cathodic hydrogen evolution reaction on the residual Fe3C.

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    Incipient plasticity and activation volume of dislocation nucleation for TiZrNbTaMo high-entropy alloys characterized by nanoindentation
    Wang Shao-Ping, Xu Jian
    J. Mater. Sci. Technol.. 2019, 35 (5): 812-816.   DOI: 10.1016/j.jmst.2018.11.014
    Abstract   HTML   PDF (1363KB)

    With instrumented nanoindentation, incipient plasticity of two as-cast BCC TiZrNbTa and TiZrNbTaMo high-entropy alloys (HEAs) are investigated in terms of pop-in events during loading, to characterize the dislocation behavior in these solid-solution alloys. It is shown that the maximum shear stress (τmax) required for dislocation nucleation is determined to be 1/16-1/12 and 1/18-1/14 of shear modulus for the TiZrNbTa and TiZrNbTaMo HEAs, respectively, which is nearly comparative to the theoretical shear stress of these alloys. The activation volumes of dislocation nucleation the TiZrNbTa and TiZrNbTaMo HEAs are determined to be 1.2b3 for and 1.3b3, respectively, which is substantially irrespective of alloying with Mo. Furthermore, activation volumes of these two HEAs are on the order of cubic burger’s vector and only one-third of the value for TiZrHfNb HEA, suggesting that a heterogeneous nucleation of dislocation took place in a way of direct atom-vacancy exchange, rather than of the cooperative motion of several atoms. These findings reveal the unique feature in deformation of BCC solid-solution complex alloys.

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    Surface energy-mediated fibronectin adsorption and osteoblast responses on nanostructured diamond
    Tian Yixing, Liu Huiling, W. Sheldon Brian, J. Webster Thomas, Yang Sichen, Yang Huilin, Yang Lei
    J. Mater. Sci. Technol.. 2019, 35 (5): 817-823.   DOI: 10.1016/j.jmst.2018.11.009
    Abstract   HTML   PDF (1941KB)

    Nanostructured diamond have potential applications in many biomedical related fields and demonstrated extraordinary capacity to influence cellular responses. Studying the surface property of nanodiamond and its influence to protein adsorption and subsequent cellular responses along with the mechanism behind such capacity becomes more important. Here the role of surface energy associated with nanostructured diamond in modulating fibronectin and osteoblast (OB, bone forming cells) responses was investigated. Nanocrystalline diamond (NCD) and submicron crystalline diamond (SMCD) films with controllable surface energy were prepared by microwave-enhanced plasma chemical vapor deposition (MPCVD) techniques. Fibronectin adsorption on the diamond films with varied surface energy values was measured via the enzyme-linked immunosorbent assay (ELISA) and the relationship between the surface energy and fibronectin adsorption was studied. The result indicated that fibronectin adsorption on nanostructured surfaces was closely related to both surface energy and material microstructures. The spreading and migration of OB aggregates (each containing 30-50 cells) on the NCD with varied surface energy values were also studied. The result indicates a correlation between the cell spreading and migration on nanodiamond and the surface energy of nanostructured surface.

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    Effects of welding speed on the multiscale residual stresses in friction stir welded metal matrix composites
    Zhang X.X., Wu L.H., Andrä H., Gan W.M., Hofmann M., Wang D., Ni D.R., Xiao B.L., Ma Z.Y.
    J. Mater. Sci. Technol.. 2019, 35 (5): 824-832.   DOI: 10.1016/j.jmst.2018.11.005
    Abstract   HTML   PDF (2676KB)

    The effects of welding speed on the macroscopic and microscopic residual stresses (RSes) in friction stir welded 17 vol.% SiCp/2009Al-T4 composite plates were studied via neutron diffraction and an improved decoupled hierarchical multiscale modeling methods. Measurements showed that the macroscopic and total RSes had the largest variations in the longitudinal direction (LD). Increasing the welding speed led to higher values of measured LD macroscopic and total RSes in the matrix. The welding speed also significantly influenced the distributions and magnitudes of the microscopic RSes. The RSes were predicted via an improved hierarchical multiscale model, which includes a constant coefficient of friction based thermal model. The RSes in the composite plates before friction stir welding (FSW) were computed and then set as the initial states of the FSW process during modeling. This improved decoupled multiscale model provided improved predictions of the temperature and RSes compared with our previous model.

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    Advances on strategies for searching for next generation thermal barrier coating materials
    Liu Bin, Liu Yuchen, Zhu Changhua, Xiang Huimin, Chen Hongfei, Sun Luchao, Gao Yanfeng, Zhou Yanchun
    J. Mater. Sci. Technol.. 2019, 35 (5): 833-851.   DOI: 10.1016/j.jmst.2018.11.016
    Abstract   HTML   PDF (8972KB)

    Thermal barrier coating (TBC) materials play important roles in gas turbine engines to protect the Ni-based super-alloys from the high temperature airflow damage. High melting point, ultra-low thermal conductivity, large thermal expansion coefficient, excellent damage tolerance and moderate mechanical properties are the main requirements of promising TBC materials. In order to improve the efficiency of jet and/or gas turbine engines, which is the key of improved thrust-to-weight ratios and the energy-saving, significant efforts have been made on searching for enhanced TBC materials. Theoretically, density functional theory has been successfully used in scanning the structure and properties of materials, and at the same time predicting the mechanical and thermal properties of promising TBC materials for high and ultrahigh temperature applications, which are validated by subsequent experiments. Experimentally, doping and/or alloying are also widely applied to further decrease their thermal conductivities. Now, the strategy through combining theoretical calculations and experiments on searching for next generation thermal insulator materials is widely adopted. In this review, the common used techniques and the recent advantages on searching for promising TBC materials in both theory and experiments are summarized.

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    Microstructure characterization and thermal properties of the waste-styrene-butadiene-rubber (WSBR)-modified petroleum-based mesophase asphalt
    Hu Jingbo, Fang Changqing, Zhou Shisheng, Cheng Youliang, Han Hanzhi
    J. Mater. Sci. Technol.. 2019, 35 (5): 852-857.   DOI: 10.1016/j.jmst.2018.09.027
    Abstract   HTML   PDF (1916KB)

    In this work, waste-styrene-butadiene-rubber (WSBR) -modified petroleum- based mesophase asphalt was prepared through a co-carbonization process. The influence of contents of WSBR and carbonization temperature on the properties of mesophase asphalt was investigated. The chemical constituents, microstructure and thermal property of the samples were characterized. The results show that using WSBR as modifier can significantly promote the formation of mesophase. When the temperature is constant, the addition of WSBR results in more optically anisotropic crystal structure in the samples, and a better thermal stability. When the content of WSBR is invariable, with increasing temperature, the content of anisotropic structure in mesophase asphalt becomes higher and more uniform. The thermal stability of the samples is the best when WSBR content is 10 wt%.

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    Understanding formation of Mg-depletion zones in Al-Mg alloys under high pressure torsion
    Xue Jing, Jin Shenbao, An Xianghai, Liao Xiaozhou, Li Jiehua, Sha Gang
    J. Mater. Sci. Technol.. 2019, 35 (5): 858-864.   DOI: 10.1016/j.jmst.2018.11.017
    Abstract   HTML   PDF (3715KB)

    Redistribution of elements may take place in alloys during severe plastic deformation, which significantly alters the mechanical properties of the alloys. Therefore, comprehensive knowledge about deformation-induced redistribution of elements has to be established. In the present paper, the distribution of Mg in an Al-Mg alloy processed by high pressure torsion was examined using atom probe tomography (APT). With crystallographic information extracted by APT data analysis, this research reveals that the movement of dislocations plays an important role in the formation of Mg-depletion zones in the deformed microstructure.

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    Differences in dry sliding wear behavior between HVAF-sprayed amorphous steel and crystalline stainless steel coatings
    Guo Hui, Zhang Suode, Sun Wenhai, Wang Jianqiang
    J. Mater. Sci. Technol.. 2019, 35 (5): 865-874.   DOI: 10.1016/j.jmst.2018.11.006
    Abstract   HTML   PDF (6241KB)

    Dry sliding wear behavior of amorphous steel coating (ASC) and crystalline stainless steel coating (SSC) manufactured by high-velocity-air-fuel-spraying was investigated. With increasing normal load, coefficient of friction (COF) of ASC decreases slightly from 0.78 to 0.69. COF of SSC presents a minor difference under various normal loads but increases with sliding time accompanied by relatively large fluctuation. Such a difference in friction behavior between such two coatings can be understood based upon the roles of shear stress and flash temperature. Wear rate of SSC is much higher than that of ASC, suggesting better wear resistance of ASC. The enhanced wear resistance is correlated with high hardness (H), reduced Young’s modulus (Er), and ratios of H/Er and H3/Er2. Detailed analyses on worn surfaces and sub-surfaces indicate that the wear mechanisms for ASC include delamination, abrasive and oxidation wear, whereas those for SSC are delamination and oxidation.

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    Preparation and CO2 adsorption properties of porous carbon by hydrothermal carbonization of tree leaves
    Yang Guangzhi, Song Shen, Li Jing, Tang Zhihong, Ye Jinyu, Yang Junhe
    J. Mater. Sci. Technol.. 2019, 35 (5): 875-884.   DOI: 10.1016/j.jmst.2018.11.019
    Abstract   HTML   PDF (4442KB)

    Porous carbon materials were prepared by hydrothermal carbonization (HTC) and KOH activation of camphor leaves and camellia leaves. The morphology, pore structure, chemical properties and CO2 capture ability of the porous carbon prepared from the two leaves were compared. The effect of HTC temperature on the structure and CO2 adsorption properties was especially investigated. It was found that HTC temperature had a major effect on the structure of the product and the ability to capture CO2. The porous carbon materials prepared from camellia leaves at the HTC temperature of 240 °C had the highest proportion of microporous structure, the largest specific surface area (up to 1823.77 m2/g) and the maximum CO2 adsorption capacity of 8.30 mmol/g at 25 °C under 0.4 MPa. For all prepared porous carbons, simulation results of isothermal adsorption model showed that Langmuir isotherm model described the adsorption equilibrium data better than Freundlich isotherm model. For porous carbons prepared from camphor leaves, pseudo-first order kinetic model was well fitted with the experimental data. However, for porous carbons prepared from camellia leaves, both pseudo-first and pseudo-second order kinetics model adsorption behaviors were present. The porous carbon materials prepared from tree leaves provided a feasible option for CO2 capture with low cost, environmental friendship and high capture capability.

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    Formation of a new intermediate phase and its evolution toward θ' during aging of pre-deformed Al-Cu alloys
    Ma Peipei, Liu Chunhui, Ma Ziyao, Zhan Lihua, Huang Minghui
    J. Mater. Sci. Technol.. 2019, 35 (5): 885-890.   DOI: 10.1016/j.jmst.2018.11.022
    Abstract   HTML   PDF (3032KB)

    The frequent occurrence of hitherto unknown phase Pre-θ'-2 and unusual 1.5 cθ' thick θ' precipitate was observed by atomic-resolution scanning transmission electron microscopy in the well-studied Al-Cu alloys. This phenomenon is associated with heterogeneous precipitate nucleation and growth on pre-existing dislocations introduced by slight deformation prior to aging. In this study, the precise structure details of Pre-θ'-2 was determined by atomic scale imaging, image simulation based on image forming theories and first principle calculations. Pre-θ'-2 has a well-defined ordered structure sandwiched between two 2aAl (~1.5cθ') spaced Cu layers on {200}Al planes. The strong structural similarities between Pre-θ'-2 and 1.5 cθ' thick θ' in terms of interfacial structure and thickness, coupled with energetic calculations and preliminary in-situ observations, lead us to propose a new precipitation path toward key strengthening phase θ'.

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    Improved corrosion resistance of Mg alloy AZ31B induced by selective evaporation of Mg using large pulsed electron beam irradiation
    Jin Lee Woo, Kim Jisoo, Wook Park Hyung
    J. Mater. Sci. Technol.. 2019, 35 (5): 891-901.   DOI: 10.1016/j.jmst.2018.12.004
    Abstract   HTML   PDF (4138KB)

    Large pulsed electron beam (LPEB) irradiation was employed as a surface treatment of magnesium (Mg) alloy AZ31B to enhance its corrosion and wear resistance. Selective evaporation of Mg induced by LPEB irradiation at an energy density of 5 J/cm2 for 40 cycles has led to the formation of an Al-enriched re-solidified layer with nano-grained structure consisting of Mg3.1Al0.9 metastable phase. The formation of such a re-solidified layer after LPEB irradiation has enabled a decrease in corrosion rate of Mg alloy AZ31B in 3.5% NaCl solution. Different equivalent electrical circuit models were proposed to account for the corrosion behavior of untreated Mg alloy AZ31B and those subjected to LPEB irradiation. A decrease in wear depth when compared to that of the untreated alloy suggests an increase in wear resistance of LPEB-irradiated Mg alloy AZ31B. Adhesive wear is the predominant mechanism of untreated Mg alloy AZ31B while abrasive wear mechanism dominates for LPEB-irradiated Mg alloy AZ31B.

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    The interaction and migration of deformation twin in an eutectic high-entropy alloy AlCoCrFeNi2.1
    Zhang Yaoli, Li Jinguo, Wang Xinguang, Lu Yiping, Zhou Yizhou, Sun Xiaofeng
    J. Mater. Sci. Technol.. 2019, 35 (5): 902-906.   DOI: 10.1016/j.jmst.2018.09.067
    Abstract   HTML   PDF (2498KB)

    An eutectic high-entropy alloy consisting Al, Co, Cr, Fe and Ni elements was prepared by vacuum directional solidification technology. The alloy exhibits excellent comprehensive mechanical performance during tension at temperature range of 600-700 °C. The microstructure reveals the intersection of twin-twin is the prevailing deformation mechanism and the twins play a dual role in strengthening and toughening the alloy in the thermomechanical process. The deformation twin variants I and Π were formed by the edge dislocation 112ˉ and the mixed dislocation 211ˉ on the {111} crystal planes, respectively. Besides, the dislocation jogs and kinks caused by twin intersection on the slip planes can strengthen the alloy, which may contribute to the high strength (the tensile strengths at the 600° and 700° tensile tests are respectively780 MPa and 630 MPa.). Moreover, the coherent twin boundary migration has the function of coordinating deformation and contributes to the high ductility of the alloy.

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    Modeling hot deformation behavior of low-cost Ti-2Al-9.2Mo-2Fe beta titanium alloy using a deep neural network
    Li Cheng-Lin, Narayana P.L., Reddy N.S., Choi Seong-Woo, Yeom Jong-Taek, Hong Jae-Keun, Hee Park Chan
    J. Mater. Sci. Technol.. 2019, 35 (5): 907-916.   DOI: 10.1016/j.jmst.2018.11.018
    Abstract   HTML   PDF (6671KB)

    Ti-2Al-9.2Mo-2Fe is a low-cost β titanium alloy with well-balanced strength and ductility, but hot working of this alloy is complex and unfamiliar. Understanding the nonlinear relationships among the strain, strain rate, temperature, and flow stress of this alloy is essential to optimize the hot working process. In this study, a deep neural network (DNN) model was developed to correlate flow stress with a wide range of strains (0.025-0.6), strain rates (0.01-10 s-1) and temperatures (750-1000 °C). The model, which was tested with 96 unseen datasets, showed better performance than existing models, with a correlation coefficient of 0.999. The processing map constructed using the DNN model was effective in predicting the microstructural evolution of the alloy. Moreover, it led to the optimization of hot-working conditions to avoid the formation of brittle precipitates (temperatures of 820-1000 °C and strain rates of 0.01-0.1 s-1).

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    Effects of temperature on the tribological behavior of Al0.25CoCrFeNi high-entropy alloy
    Du L.M., Lan L.W., Zhu S., Yang H.J., Shi X.H., Liaw P.K., Qiao J.W.
    J. Mater. Sci. Technol.. 2019, 35 (5): 917-925.   DOI: 10.1016/j.jmst.2018.11.023
    Abstract   HTML   PDF (3804KB)

    The tribological behavior of Al0.25CoCrFeNi high-entropy alloy (HEA) sliding against Si3N4 ball was investigated from room temperature to 600 ℃. The microstructure of the alloys was characterized by simple FCC phase with 260 HV. Below 300 ℃, with increasing temperature, the wear rate increased due to high temperature softening. The wear rate remained stabilized above 300 ℃ due to the anti-wear effect of the oxidation film on the contact interface. The dominant wear mechanism of HEA changed from abrasive wear at room temperature to delamination wear at 200 ℃, then delamination wear and oxidative wear at 300 ℃ and became oxidative above 300 ℃. Moreover, the adhesive wear existed concomitantly below 300 ℃.

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    Preparation and laser performances of Nd3+:GSGG ceramic powder raw materials
    Wang Shuming, Lin Xin, Ye Qing, Li Jiangshan, Zhang Xiaofang, Wang Ruiping, Wang Yanru
    J. Mater. Sci. Technol.. 2019, 35 (5): 926-929.   DOI: 10.1016/j.jmst.2018.11.021
    Abstract   HTML   PDF (1057KB)

    This paper explores a new laser working material: gallium scandium gadolinium (GSGG), which was successfully prepared by one step co-precipitation method, and the potential properties of this Nd3+ doped laser ceramic raw materials were proposed. The size of the prepared powder was uniform and mainly about 65 nm. The GSGG phase could be obtained after a heat-treatment of 1000?°C for 4 h, and the characterized fluorescence decay curves showed that about 1 at.% concentration of Nd3+ in Nd3+:GSGG precursor presented optimum fluorescence intensity at 1.06 μm waveband.

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    Formation of coherent, core-shelled nano-particles in dilute Al-Sc-Zr alloys from the first-principles
    Zhang Chaomin, Jiang Yong, Cao Fuhua, Hu Tao, Wang Yiren, Yin Dengfeng
    J. Mater. Sci. Technol.. 2019, 35 (5): 930-938.   DOI: 10.1016/j.jmst.2018.11.004
    Abstract   HTML   PDF (2122KB)

    We present a systematic first-principles based study on the formation of coherent L12-phase nano-particles in dilute Al-Sc-Zr alloys. Bulk structures and properties, solute substitution, interface formation energies, and interfacial coherent strains are all calculated. Nucleation modeling and relevant energetic calculations are performed on various possible structures of L12-phase nano-precipitates, i.e. individual L12-Al3Sc and L12-Al3Zr, homogeneous L12-Al3(ScxZr1-x) and the core-shelled L12-Al3Sc(Al3Zr) and L12-Al3Zr(Al3Sc). The following insights are obtained. Matrix-dissolved Sc or Zr strongly prefers to substitute the X sublattice sites in L12-Al3X (X = Zr or Sc), while the inter-substitution between L12-Al3Sc and Al3Zr is only weakly feasible. The cube-on-cube orientation with the (100)/(100) contacting facets is the most energy favored for the Al/Al3Sc(L12), Al/Al3Zr(L12) and Al3Sc (L12)/Al3Zr(L12) interfaces. All these interfaces are highly coherent, with fairly low formation energy. And particularly, the Al3Sc(L12)/Al3Zr(L12) interface has essentially zero formation energy. Ternary L12-Al3(ScxZr1-x) precipitates tend to form a Al3Sc-based core and Al3Zr-based shell structure, with a relatively sharp inner interface of Al3Sc(L12)/Al3Zr(L12). This core-shelled structure becomes energetically more favorable for the particle size R > 1-2 nm. The potential influence of the Sc/Zr ratio and temperature on the relative stabilities of L12-phases in Al is also evaluated and discussed.

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    Fabrication and characterization of novel meso-porous carbon/n-octadecane as form-stable phase change materials for enhancement of phase-change behavior
    Liu Yurong, Xia Yongpeng, An Kang, Huanga Chaowei, Cui Weiwei, Wei Sheng, Ji Rong, Xu Fen, Zhang Huanzhi, Sun Lixian
    J. Mater. Sci. Technol.. 2019, 35 (5): 939-945.   DOI: 10.1016/j.jmst.2018.11.001
    Abstract   HTML   PDF (2161KB)

    In this study, series of novel composite phase change materials (PCMs) were prepared through vacuum impregnation by using meso-porous carbon as a supporting matrix and n-octadcane as PCMs. The meso-porous carbon material was prepared through one-pot co-assembly method, using resorcinol and formaldehyde as carbon precursor, tetraethoxysilane as silica sources and triblock copolymer F127 as a template. And the phase behaviors of n-octadcane confined in the nano-porous structure of the meso-porous carbon were further investigated. Fourier transform-infrared spectroscopy spectra show that n-octadecane was effectively encapsulated in the porous structure of mesoporous carbon and the composite PCMs were successfully prepared. Differential scanning calorimetry results confirm that the composite PCMs possess a good phase change behavior, fast thermal-response rate and excellent thermal cycling stability. In addition, the composite PCMs possess expected heat storage and heat release properties. All these results demonstrate that the composite PCMs possess good comprehensive property so that they can be used widely in energy storage systems.

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