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CN 21-1315/TG
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      15 December 2020, Volume 59 Issue 0 Previous Issue   
    Research Article
    Analysis of crystallographic orientation and morphology of microstructure during hot working for an alpha/beta titanium alloy
    panelJianwei Xu, Weidong Zeng, Dadi Zhou, Wei Chen, Shengtong He, Xiaoyong Zhang
    J. Mater. Sci. Technol.. 2020, 59 (0): 1-13.   DOI: 10.1016/j.jmst.2020.06.002
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    This work focuses on analysis of microstructure morphology and crystallographic orientation for Ti-17 alloy during hot working. The results show that alpha phase and beta phase influence each other and there is a coordinate deformation between them. The non-uniform deformation is observed under small deformation conditions. The observing area can be divided into small deformation zone (area L) and large deformation zone (area H). Both alpha and beta phases remain the initial morphology, and they have better capability of coordinate deformation in area L, while coordinate capability is weak in area H in which alpha phase is globularized. Correspondingly, the Burgers orientation relations are well preserved in area L, but the orientation relations are more or less destroyed in area H. Dynamic recovery is the main mechanism of beta phase evolution when height reduction is lower. By contrast, the continuous dynamic recrystallization (CDRX) of beta phase gradually dominates the deformation pattern as the deformation increases. An uniformly globularized alpha structure is obtained under large deformation condition. The unsynchronized rotation of alpha phase around <11-20> pole occurs during deformation, which leads to the uniform crystal structure inside the same alpha lamellae. This process is an important step of globularization of the lamellar structure.

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    Electrostatic assembly functionalization of poly (γ-glutamic acid) for biomedical antibacterial applications
    Xiaodan Wang, Hengchong Shi, Haoyu Tang, Huan Yu, Qiuyan Yan, Huawei Yang, Xu Zhang, Shifang Luan
    J. Mater. Sci. Technol.. 2020, 59 (0): 14-25.   DOI: 10.1016/j.jmst.2020.05.017
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    Poly (γ-glutamic acid) (γ-PGA) has been found widespread applications in biomedical field because of its excellent water solubility, biocompatibility, and bioactivity. Herein, a water-insoluble γ-PGA antibacterial compound is facilely fabricated via one-pot electrostatic assembly of γ-PGA with cationic ethyl lauroyl arginate (ELA). The functionalized γ-PGA compound (γ-PGA-ELA) ethanol solution can facilely produce colorless and transparent coatings on various inorganic, metal, and polymeric substrates, especially for the lumen of slender catheters (length up to 2 m, and inner diameter down to 1 mm). The functionalized γ-PGA coating presents remarkable antibacterial efficacy in vitro and in vivo. In addition, the γ-PGA compound is used as antibacterial additives of polyolefin via melting extrusion, and the as-prepared antibacterial polyolefin demonstrates advantageous antibacterial efficacy. More importantly, the functionalized γ-PGA coating exhibit good hemocompatibility, low cytotoxicity, and satisfactory histocompatibility. The as-proposed γ-PGA compound has a great potential to serve as a safe and multifunctional antibacterial candidate to combat biomedical devices-related infections.

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    Processing soft ferromagnetic metallic glasses: on novel cooling strategies in gas atomization, hydrogen enhancement, and consolidation
    N. Ciftci, N. Yodoshi, S. Armstrong, L. Mädler, V. Uhlenwinkel
    J. Mater. Sci. Technol.. 2020, 59 (0): 26-36.   DOI: 10.1016/j.jmst.2020.03.077
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    Processing soft ferromagnetic glass-forming alloys through gas atomization and consolidation is the most effective technique to produce bulk samples. The commercial viability of these materials depends on commercial purity feedstock. However, crystallization in commercial purity feedstock is several orders of magnitude faster than in high purity materials. The production of amorphous powders with commercial purity requires high cooling rates, which can only be achieved by extending the common process window in conventional gas atomization. The development of novel cooling strategies during molten metal gas atomization on two model alloys ({(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 and Fe76B10Si9P5) is reported. Hydrogen inducement during liquid quenching significantly improved the glass-forming ability and soft magnetic properties of {(Fe0.6Co0.4)0.75B0.2Si0.05}96Nb4 powders. Spark plasma sintering experiments verified that amorphous rings could be produced regardless of the cooling strategies used. While the saturation magnetization was almost unaffected by consolidation, the coercivity increased slightly and permeability decreased significantly. The magnetic properties of the final bulk samples were independent of feedstock quality. The developed cooling strategies provide a great opportunity for the commercialization of soft ferromagnetic glass-forming alloys with commercial purity.

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    A new guide for improving mechanical properties of non-equiatomic FeCoCrMnNi medium- and high-entropy alloys with ultrasonic nanocrystal surface modification process
    Timothy Alexander Listyawan, Hyunjong Lee, Nokeun Park
    J. Mater. Sci. Technol.. 2020, 59 (0): 37-43.   DOI: 10.1016/j.jmst.2020.04.039
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    Ultrasonic nanocrystal surface modification (UNSM) treatment on non-equiatomic medium- and high-entropy alloy (HEA) of Fex(CoCrMnNi)100-x is firstly introduced and its impact on microstructure and mechanical properties are revealed. By UNSM, severe plastic deformation-induced dislocation and deformation twins (DTs) arise at the topmost surface. Especially, Fe60(CoCrMnNi)40 (Fe60), which is classified as a medium-entropy alloy (MEA), exhibits ε-martensitic transformation. In the room temperature tensile test, a high strength of ~600 MPa and ductility of ~65 % elongation (strain to failure) is accomplished in Fe60. Initially formed DTs and ε-martensitic transformation by UNSM treatment plays a key role in retardation of necking point via both twinning-induced plasticity and transformation-induced plasticity. However, Fe20(CoCrMnNi)80 (Fe20) comparatively shows low strength of ~550 MPa and ~40 % elongation, owing to the low accommodation of DTs than Fe60. Our research will provide new guidelines for enhancing the mechanical properties of MEA and HEA.

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    Microstructure and texture optimization by static recrystallization originating from {10-12} extension twins in a Mg-Gd-Y alloy
    S.H. Lu, D. Wu, R.S. Chen, En-hou Han
    J. Mater. Sci. Technol.. 2020, 59 (0): 44-60.   DOI: 10.1016/j.jmst.2020.04.040
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    During the deformation of Mg alloys, {10-12} extension twin often contributes to the formation of basal texture but rarely assists the nucleation of recrystallization, i.e., effective grain refinement, therefore it seems to make against the improvement of formability and mechanical properties. In this work, {10-12} extension twin has been creatively utilized as a preference nucleation site for static recrystallization (SRX), achieving grain refinement and orientation randomization in a Mg-Gd-Y alloy using multi-directional impact forging (MDIF) and subsequent annealing treatment. Effect of {10-12} extension twin on SRX behavior has been investigated by annealing treatment at 450 °C using quasi-in-situ optical microscopy (OM) and quasi-in-situ electron back-scattering diffraction (EBSD). The microstructural evolution during annealing shows that several SRX gains can nucleate from the grain boundary of untwinned grains, but they only have few influences on the final microstructure due to their limited volume faction and sluggish growth. In contrast, a large number of SRX gains can initiate from {10-12} extension twin and grow up without the confine of twin boundaries. Finally, they consume their parent grains and make the main contribution to grain refinement. This should be attributed to those pinned {10-12} twin boundary, by interacting with various dislocation slips during the MDIF process, which can operate like grain boundary, store enough strain energy, and promote the nucleation of SRX during annealing. On the other hand, SRX grains usually keep initial random orientation and further randomize the forging texture during annealing treatment.

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    Improving toughness of a Mg2Ca-containing Mg-Al-Ca-Mn alloy via refinement and uniform dispersion of Mg2Ca particles
    Huan Liu, Chao Sun, Ce Wang, Yuhua Li, Jing Bai, Feng Xue, Aibin Ma, Jinghua Jiang
    J. Mater. Sci. Technol.. 2020, 59 (0): 61-71.   DOI: 10.1016/j.jmst.2020.02.092
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    In this work, two wrought Mg-3.66Al-4.25Ca-0.43 Mn (wt%) alloys with different morphology and distribution of Mg2Ca particles were fabricated by hot extrusion and multi-pass (32) equal channel angular pressing (ECAP). The as-extruded alloy exhibits a banded microstructure with alternately arranged Mg2Ca particle bands, fine α-Mg dynamically recrystallized (DRX) grain bands, and coarse α-Mg deformed grain bands. The Mg2Ca bands are composed of broken Mg2Ca particles which are aggregated and aligned along extrusion direction. The microstructure of ECAP alloy contains complete α-Mg DRX grains and refined Mg2Ca particles which are dispersedly distributed at grain boundaries. Tensile test results show that the as-extruded alloy possesses high ultimate tensile strength (UTS) of 420 MPa and poor fracture elongation of 7 %, while the ECAP alloy exhibits improved toughness with UTS of 347 MPa and fraction elongation of 16 %. The higher strength of as-extruded alloy is mainly ascribed to the contribution of coarse deformed grains with strong texture, and its poor toughness is resulted from the formation of Mg2Ca bands within which microcracks could form and extend rapidly. On the contrary, the refined and dispersedly distributed Mg2Ca particles are effective to retard crack initiation and impede crack propagation, thereby enhancing the toughness of ECAP alloy significantly.

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    A new model to describe composition and temperature dependence of thermal conductivity for solution phases in binary alloys
    Shiyi Wen, Yuling Liu, George Kaptay, Yong Du
    J. Mater. Sci. Technol.. 2020, 59 (0): 72-82.   DOI: 10.1016/j.jmst.2020.04.045
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    Modelling temperature- and composition-dependent thermal conductivity in alloys is challengeable and is seldom studied systematically. In the present work, a new model is developed to describe the temperature and concentration dependence of thermal conductivity for binary alloys. In this new model, firstly thermal conductivity of pure metals was modelled as the function of temperature for each phase and each magnetic state by the corresponding physically sound model. Secondly, in order to describe the composition and temperature dependence of thermal conductivity for solid phases, the combination of the theories of Nordheim and Mott for electric conductivity of alloys with the Wiedemann-Franz law was performed. Thirdly, the reliability of the new model was verified by presently measured thermal conductivities for pure Co, Ni and Co-Ni alloys at 300, 600, 900 and 1100 K as well as for binary Al-Zn, Mg-Zn and U-Zr systems using the data taken from the literature. The calculated thermal conductivities can well reproduce the measured ones in one-phase regions of a series of Co-Ni alloys. The thermal conductivity in a two-phase region of the Co-Ni system is reasonably predicted as well. It is demonstrated that the new model can be utilized to evaluate the thermal conductivity over the whole investigated composition and temperature ranges for the first time and is expected to be extended to ternary and multicomponent systems by CALPHAD method, which contributes significantly to the development of computational design of materials.

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    Improved distortion prediction in additive manufacturing using an experimental-based stress relaxation model
    Ruishan Xie, Qingyu Shi, Gaoqiang Chen
    J. Mater. Sci. Technol.. 2020, 59 (0): 83-91.   DOI: 10.1016/j.jmst.2020.04.056
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    In additive manufacturing (AM), numerous thermal cycles make stress relaxation a significant factor in affecting the material mechanical response. However, the traditional material constitutive model cannot describe repeated annealing behavior. Here, we propose an improved constitutive model based on a serial of stress relaxation experiments, which can descript the temperature and time-dependent stress relaxation behavior during AM. By using the proposed relaxation model, the prediction accuracy is significantly improved due to the recovery of inelastic strain during multilayer deposition. The results are validated by both in-situ and final distortion measurements. The influence mechanism of the relaxation behavior on material mechanical response is explained by the three-bar model in thermo-elastic-plastic theory. The relaxation behavior during the whole AM process is clarified. The stress behavior is found to have a limited effect when merely depositing several layers; nevertheless, it becomes a prominent impact when depositing multiple layers. The proposed model can enhance modeling accuracy both in AM and in multilayer welding.

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    Waste cotton fabric derived porous carbon containing Fe3O4/NiS nanoparticles for electrocatalytic oxygen evolution
    Shan Jiang, Hao Shao, Genyang Cao, Han Li, Weilin Xu, Jingliang Li, Jian Fang, Xungai Wang
    J. Mater. Sci. Technol.. 2020, 59 (0): 92-99.   DOI: 10.1016/j.jmst.2020.04.055
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    Developing low-cost, active and durable electrocatalysts for oxygen evolution reaction (OER) is an urgent task for the applications such as water splitting and rechargeable metal-air battery. Herein, this work reports the fabrication of a metal and hetero atom co-doped fibrous carbon structure derived from cotton textile wastes and its use as an efficient OER catalyst. The free-standing fibrous carbon structure, fabricated with a simple two-step carbonization process, has a high specific surface area of 1796 m2/g and a uniform distribution of Fe3O4/NiS nanoparticles (Fe3O4/NiS@CC). The composite exhibits excellent OER performance with an onset potential of 1.44 V and a low overpotential of 310 mV at the current density of 10 mA/cm2 in a 1.0 M KOH solution, which even surpass commercial RuO2 catalyst. Additionally, this ternary catalyst shows remarkable long-term stability without current density loss after continuous operation for 26 h. It can be believed that the outstanding OER performance is attributed to the synergistic effect between the iron oxides and nickel sulphides, as well as the micro-meso porous carbon structure. This study demonstrates a new strategy to use conventional textile materials to prepare highly efficient electrocatalysts; it also provides a simple approach to turn textile waste into valuable products.

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    Thermal stress relaxation in shot peened and laser peened nickel-based superalloy
    K.S. Chin, S. Idapalapati, D.T. Ardi
    J. Mater. Sci. Technol.. 2020, 59 (0): 100-106.   DOI: 10.1016/j.jmst.2020.03.059
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    The effects of cold work produced by peening processes in residual stress relaxation under elevated temperatures were investigated. Two types of peening processes namely shot peening and laser peening were used to generate different amount of cold work and residual stresses in the study. Characterisation of residual stress induced by cold working were carried out using X-ray diffraction coupled with electrochemical polishing method to measure the variation of residual stress with depth. Residual stresses in shot peened samples were observed to relax more rapidly than that of laser peened ones when subjected to thermal exposure. The data collected from the experimental investigation was then used to build a correlation function to model the effects of cold work on residual stress relaxation. A parameter describing cold work’s contribution to stress relaxation is introduced into the well-known Zener-Wert-Avrami (ZWA) model. The model was validated against experimental measurements and showed good agreement in both shot peened and laser peened samples.

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    Corrosion performance, corrosion fatigue behavior and mechanical integrity of an extruded Mg4Zn0.2Sn alloy
    Pingli Jiang, Carsten Blawert, Jan Bohlen, Mikhail L. Zheludkevich
    J. Mater. Sci. Technol.. 2020, 59 (0): 107-116.   DOI: 10.1016/j.jmst.2020.04.042
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    Magnesium alloys are promising as load bearing components. They are inevitably exposed to cyclic loading and corrosive environment in actual service, which can consequently result in corrosion fatigue failure and loss of mechanical integrity of the material. Therefore, in the present study, the corrosion behavior, corrosion fatigue performance and mechanical integrity of an extruded Mg4Zn0.2Sn (wt.%) alloy were thoroughly studied in two corrosive electrolytes. Strong localized corrosion occurred when the alloy was immersed in deionized water based sodium chloride (NaCl) solution. The poor corrosion resistance of the alloy resulted in a fast deterioration of the tensile properties after pre-exposure to salt spray and a poor fatigue resistance in deionized water based NaCl solution. In comparison, the active dissolution of the substrate was sufficiently suppressed in artificial tap water based NaCl solution due to the formation of highly protective corrosion product layers. This consequently conferred longer fatigue life on the alloy in the electrolyte. Our results emphasized the influence of corrosion on the fatigue behavior and tensile properties of magnesium alloys.

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    Electrochemical characterization and microstructure of cold sprayed AA5083/Al2O3 composite coatings
    Xiawei Yang, Wenya Li, Siqi Yu, Yaxin Xu, Kaiwei Hu, Yaobang Zhao
    J. Mater. Sci. Technol.. 2020, 59 (0): 117-128.   DOI: 10.1016/j.jmst.2020.04.041
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    This work focused on the role of Al2O3 particles in the corrosion behavior of cold sprayed AA5083 aluminum alloy matrix composite (Al-MMC) coatings. The electrochemical characterization of the coatings was investigated in a 3.5 wt.% NaCl solution as a function of time. The results show that fragmentation of Al2O3 particles is not clearly observed in the case of AA5083/20 vol.% Al2O3 coating, while the broken Al2O3 particles can be seen clearly in AA5083/40 vol.% Al2O3 and AA5083/60 vol.% Al2O3 coatings. The addition of 20 vol.% Al2O3 particles yield the coating with the lowest porosity, and different volume fractions of Al2O3 in the feedstock have important effects on the electrochemical behavior of composite coatings. The Al-MMC coating reinforced with 20 vol.% Al2O3 particles exhibits the highest Ecorr and the lowest icorr compared with the other conditions. The order of current density is as follows: AA5083/20 vol.% Al2O3 < AA5083 < AA5083/40 vol.% Al2O3 < AA5083/60 vol.% Al2O3.

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    A novel hole cold-expansion method and its effect on surface integrity of nickel-based superalloy
    XianCao Ping, ZhangShuang Liu, Xue-Lin Lei, Run-Zi Wang, Xian-Cheng Zhang, Shan-Tung Tu
    J. Mater. Sci. Technol.. 2020, 59 (0): 129-137.   DOI: 10.1016/j.jmst.2020.05.022
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    Preferred surface integrity around the hole wall is one of the key parameters to ensure the optimized performance of hole components for nickel-based superalloy. The novel hole cold expansion technique introduced in this work involves the laser texturing process (LTP) followed by the Hertz contact rotary expansion process (HCREP), where the cylindrical sleeve is the critical component connecting the above-mentioned two processes. The purpose of LTP is to obtain the most optimized strengthened cylindrical sleeve surface, preparing for the following HCREP. Hereafter, the HCREP acts on the nickel-based hole components by the rotary extruding movements of the strengthened sleeve and conical mandrel tools. As compared to the as-received GH4169 material, the surface integrity characterization for the strengthened hole shows that a plastic deformation layer with finer grains, higher micro-hardness, deeper compressive residual stress (CRS) distribution and lower surface roughness is formed at the hole wall. In addition, transmission electron microscope (TEM) observations reveal the microstructure evolution mechanism in the strengthened hole. Grain refinement near the hole wall is regarded as the fundamental reason for improving the surface integrity, where the aggregated dislocations and recombined dislocation walls can be clearly observed.

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    Multi-scale crystal plasticity finite element simulations of the microstructural evolution and formation mechanism of adiabatic shear bands in dual-phase Ti20C alloy under complex dynamic loading
    Yu Zhou, Qunbo Fan, Xin Liu, Duoduo Wang, Xinjie Zhu, Kai Chen
    J. Mater. Sci. Technol.. 2020, 59 (0): 138-148.   DOI: 10.1016/j.jmst.2020.03.079
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    A dynamic compression test was performed on α + β dual-phase titanium alloy Ti20C using a split Hopkinson pressure bar. The formation of adiabatic shear bands generated during the compression process was studied by combining the proposed multi-scale crystal plasticity finite element method with experimental measurements. The complex local micro region load was progressively extracted from the simulation results of a macro model and applied to an established three-dimensional multi-grain microstructure model. Subsequently, the evolution histories of the grain shape, size, and orientation inside the adiabatic shear band were quantitatively simulated. The results corresponded closely to the experimental results obtained via transmission electron microscopy and precession electron diffraction. Furthermore, by calculating the grain rotation and temperature rise inside the adiabatic shear band, the microstructural softening and thermal softening effects of typical heavily-deformed α grains were successfully decoupled. The results revealed that the microstructural softening stress was triggered and then stabilized (in general) at a relatively high value. This indicated that the mechanical strength was lowered mainly by the grain orientation evolution or dynamic recrystallization occurring during early plastic deformation. Subsequently, thermal softening increased linearly and became the main softening mechanism. Noticeably, in the final stage, the thermal softening stress accounted for 78.4 % of the total softening stress due to the sharp temperature increase, which inevitably leads to the stress collapse and potential failure of the alloy.

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    Multi-scale characterization and simulation of impact welding between immiscible Mg/steel alloys
    Jiahao Cheng, Xiaohua Hu, Xin Sun, Anupam Vivek, Glenn Daehn, David Cullen
    J. Mater. Sci. Technol.. 2020, 59 (0): 149-163.   DOI: 10.1016/j.jmst.2020.04.049
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    Vaporizing foil actuator spot welding method is used in this paper to join magnesium alloy AZ31 and uncoated high-strength steel DP590, which are typically considered as un-weldable due to their high physical property disparities, low mutual solubility, and the lack of any intermetallic phases. Characterization results from scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM) of the weld interface indicate that the impact creates an Mg nanocrystalline interlayer with abundant Fe particles. The interlayer exhibits intact bonding with both DP590 and AZ31 substrates. To investigate the fundamental bond formation mechanisms at the interface, a finite element (FE)-based process simulation is first performed to calculate the local temperature and deformation at the interface under the given macroscopic experimental condition. Taking the FE results at the interface as inputs, molecular dynamics (MD) simulations are conducted to study the interlayer formation at the Mg/Fe interface during the impact and cooling. The results found a high velocity shearing-induced mechanical mixing mechanism that mixes Mg/Fe atoms at the interface and creates the interlayer, leading to the metallurgical bond between Mg/steel alloys.

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    Controllable synthesis of mesoporous carbon hollow microsphere twined by CNT for enhanced microwave absorption performance
    Minghang Li, Xiaomeng Fan, Hailong Xu, Fang Ye, Jimei Xue, Xiaoqiang Li, Laifei Cheng
    J. Mater. Sci. Technol.. 2020, 59 (0): 164-172.   DOI: 10.1016/j.jmst.2020.04.048
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    The low dielectric loss of mesoporous carbon hollow microsphere (PCHM) requires high filler loading (higher than 20 wt%) when it is used as microwave absorbers. In order to decrease the filler loading of PCHM, a new strategy for synergistic increase of polarization and conductive loss was developed by twining PCHM with carbon nanotube (CNT) according to theoretic calculation. By the optimization of CNT content, the minimum reflection coefficient was -34.6 dB with a filler loading of only 10 wt%, which was much lower than -2.1 dB of PCHM. In addition, the effective absorption bandwidth was 3.6 GHz at X band with a thickness of 2.8 mm. The enhanced microwave absorption performance can be ascribed to the unique combination of hollow PCHM and one-dimensional CNT with higher graphitization degree, leading to increase of conductivity and heterogeneous interfaces. As a result, the conductive loss increased from 0.12 to 2.27 and polarization loss increased from 0.15 to 0.67, achieving the balance between attenuation ability and impedance match.

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    Mechanisms of eutectic lamellar destabilization upon rapid solidification of an undercooled Ag-39.9 at.% Cu eutectic alloy
    H. Dong, Y.Z. Chen, Z.R. Zhang, G.B. Shan, W.X. Zhang, F. Liu
    J. Mater. Sci. Technol.. 2020, 59 (0): 173-179.   DOI: 10.1016/j.jmst.2020.05.019
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    The eutectic Ag-Cu alloys exhibiting fine Ag-Cu lamellar eutectic structure formed upon rapid solidification have great potentials being used in various engineering fields. However, the desired fine primary lamellar eutectic structure (PLES) is usually replaced by a coarse anomalous eutectic structure (AES) when the undercooling prior to solidification exceeds a certain value. The forming mechanism of AES in the undercooled eutectic Ag-Cu alloy has been a controversial issue. In this work, the undercooled Ag-39.9 at.% Cu eutectic alloy is solidified under different cooling conditions by using techniques of melt fluxing and copper mold casting. The results show that the coupled eutectic growth of this alloy undergoes a transition from a slow eutectic-cellular growth (ECG) to a rapid eutectic-dendritic growth (EDG) above a undercooling of 72 K, accompanying with an abrupt change of the distribution and amount of AES in as-solidified microstructures. Two kinds of primary lamellar eutectic structures are formed by ECG and EDG during recalescence, respectively. The destabilization of PLES that causes the formation of AES is ascribed to two different mechanisms based on the microstructural examination and theoretical calculations. Below 72 K, the destabilization of PLES formed by slow ECG is caused by the mechanism of “termination migration” driven by interfacial energy. While above 72 K, the destabilization of PLES formed by rapid EDG is attributed to the unstable perturbation of interface driven by interfacial energy and solute supersaturation.

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    Multi-3D hierarchical biomass-based carbon particles absorber for solar desalination and thermoelectric power generator
    Hao Jiang, Xuemin Geng, Simin Li, Hongyu Tu, Jiliang Wang, Lixia Bao, Peng Yang, Yanfen Wan
    J. Mater. Sci. Technol.. 2020, 59 (0): 180-188.   DOI: 10.1016/j.jmst.2020.05.023
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    To meet challenges of the global energy crisis and the freshwater resources shortage, the interfacial solar-to-steam conversion (ISSC) system was developed quickly in recent years. The photothermal materials play an important role in the ISSC system. We are devoted to developing a unique photothermal material integrating multiple 3D design philosophy both at macroscopic and microscopic levels by employing the cost-effective and widespread resources like straw, rose and coffee grounds, for carbonization as solar absorbers. The biomass-based carbonized particles (CPs) possess three major advantages: (1) wide size-distribution is accessible to form 3D porous rough surface of absorber layer to enhance ability of light absorption; (2) the pristine hierarchical microstructure could absorb nearly all the incident light; (3) the intrinsic vascular bundles with pores on their lumen walls provide a rapid and omnidirectional transport for water and steam escape. A high-efficient solar steam device was fabricated based on the absorber material with its internal 3D micro textures and external 3D architectures. Under the illumination of 1 sun, the photothermal conversion efficiency of straw, rose and coffee CPs can reach 93.4 %, 92.8 % and 76 %, respectively. Simultaneously, a high-efficient solar thermoelectric generator (STEG) is made by coating CPs on a commercial thermoelectric generator and the maximum power of STEG can reach 538.0 μW. Such scalable biomass-based photothermal materials and high-grade thermoelectric conversion capability could be applied to the water purification and the electricity production.

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    Enhanced thermoelectric properties of Zintl phase YbMg2Bi1.98 through Bi site substitution with Sb
    Jing Wang, Muchun Guo, Jianbo Zhu, Dandan Qin, Fengkai Guo, Qian Zhang, Wei Cai, Jiehe Sui
    J. Mater. Sci. Technol.. 2020, 59 (0): 189-194.   DOI: 10.1016/j.jmst.2020.04.052
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    Benefiting from the unique “Phonon-Glass, Electron-Crystal” (PGEC) characteristic, Zintl phases have been considered as a kind of promising thermoelectric materials. For the typical AM2X2 compounds with the CaAl2Si2-type structure, YbMg2Bi2 has shown competitive thermoelectric performance recently. Nevertheless, the optimization of YbMg2Bi2 compounds is primarily focused on the substitution on Yb or Mg site. Herein, the Bi site is substituted by isoelectric Sb and the effect on the thermoelectric transport behavior is investigated. The partial substitution reduces the carrier concentration and induces the lattice deformation caused by the different atomic radius and mass between Bi and Sb, further leading to the decreased power factor and thermal conductivity. Fortunately, the reduction extent of the thermal conductivity outperforms that of power factor. Finally, the Sb substitution successfully results in a better thermoelectric performance compared with that of the pristine YbMg2Bi1.98. Especially, the calculated energy conversion efficiency (η) of YbMg2Bi1.88Sb0.1 which also possesses a relatively high output power density reaches the maximum value of 9.8 % when Th = 873 K, and Tc = 300 K, respectively. This work demonstrates that the idea of substitution on anionic site should be a new strategy to achieve better ZT values for AM2X2 compounds.

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    Influence of a UV-ozone treatment on amorphous SnO2 electron selective layers for highly efficient planar MAPbI3 perovskite solar cells
    Kyungeun Jung, Du Hyeon Kim, Jaemin Kim, Sunglim Ko, Jae Won Choi, Ki Chul Kim, Sang-Geul Lee, Man-Jong Lee
    J. Mater. Sci. Technol.. 2020, 59 (0): 195-202.   DOI: 10.1016/j.jmst.2020.04.054
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    The effect of ultraviolet-ozone (UVO) irradiation on amorphous (am) SnO2 and its impact on the photoconversion efficiency of MAPbI3-based perovskite solar cells were investigated in detail. UVO treatment was found to increase the amount of chemisorbed oxygen on the am-SnO2 surface, reducing the surface energy and contact angle. Physicochemical changes in the am-SnO2 surface lowered the Gibbs free energy for the densification of perovskite films and facilitated the formation of homogeneous perovskite grains. In addition, the Fermi energy of the UVO-treated am-SnO2 shifted upwards to achieve an ideal band offset for MAPbI3, which was verified by theoretical calculations based on the density functional theory. We achieved a champion efficiency of 19.01 % with a statistical reproducibility of 17.01 ± 1.34 % owing to improved perovskite film densification and enhanced charge transport/extraction, which is considerably higher than the 13.78 ± 2.15 % of the counterpart. Furthermore, UVO-treated, am-SnO2-based devices showed improved stability and less hysteresis, which is encouraging for the future application of up-scaled perovskite solar cells.

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    Integration of machine learning with phase field method to model the electromigration induced Cu6Sn5 IMC growth at anode side Cu/Sn interface
    Anil Kunwar, Yuri Amorim Coutinho, Johan Hektor, Haitao Ma, Nele Moelans
    J. Mater. Sci. Technol.. 2020, 59 (0): 203-219.   DOI: 10.1016/j.jmst.2020.04.046
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    Currently, in the era of big data and 5G communication technology, electromigration has become a serious reliability issue for the miniaturized solder joints used in microelectronic devices. Since the effective charge number (Z*) is considered as the driving force for electromigration, the lack of accurate experimental values for Z* poses severe challenges for the simulation-aided design of electronic materials. In this work, a data-driven framework is developed to predict the Z* values of Cu and Sn species at the anode based LIQUID, Cu6Sn5 intermetallic compound (IMC) and FCC phases for the binary Cu-Sn system undergoing electromigration at 523.15 K. The growth rate constants (kem) of the anode IMC at several magnitudes of applied low current density (j = 1 × 106 to 10 × 106 A/m2) are extracted from simulations based on a 1D multi-phase field model. A neural network employing Z* and j as input features, whereas utilizing these computed kem data as the expected output is trained. The results of the neural network analysis are optimized with experimental growth rate constants to estimate the effective charge numbers. For a negligible increase in temperature at low j values, effective charge numbers of all phases are found to increase with current density and the increase is much more pronounced for the IMC phase. The predicted values of effective charge numbers Z* are then utilized in a 2D simulation to observe the anode IMC grain growth and electrical resistance changes in the multi-phase system. As the work consists of the aspects of experiments, theory, computation, and machine learning, it can be called the four paradigms approach for the study of electromigration in Pb-free solder. Such a combination of multiple paradigms of materials design can be problem-solving for any future research scenario that is marked by uncertainties regarding the determination of material properties.

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    Breaking or following the membrane-targeting mechanism: Exploring the antibacterial mechanism of host defense peptide mimicking poly(2-oxazoline)s
    Chengzhi Dai, Min Zhou, Weinan Jiang, Ximian Xiao, Jingcheng Zou, Yuxin Qian, Zihao Cong, Zhemin Ji, Longqiang Liu, Jiayang Xie, Zhongqian Qiao, Runhui Liu
    J. Mater. Sci. Technol.. 2020, 59 (0): 220-226.   DOI: 10.1016/j.jmst.2020.06.006
    Abstract   HTML   PDF

    Peptides exert important biological functions but their application is hindered by their susceptibility to proteolysis and poor stability in vivo. Thus, functional peptide mimics have drawn a great deal of attention to address this challenge. Poly(2-oxazoline)s, a class of biocompatible and proteolysis-resistant polymer, can work as host defense peptide mimics without following the general membrane-targeting mechanism as shown in our previous work. This observation encouraged us to figure out if poly(2-oxazoline)s are special and break the general membrane-targeting mechanism of host defense peptides and their mimics. In this study, we aimed at the connection between structure and antibacterial mechanism of poly(2-oxazoline)s. A new γ-aminobutyric acid (GABA)-pendent poly(2-oxazoline) was synthesized and investigated to compare with glycine-pendent poly(2-oxazoline) in our previous study, with the former polymer has two extra CH2 groups in the sidechain to increase the hydrophobicity and amphiphilicity. Membrane depolarization assay suggested that incorporating two more CH2 groups into the sidechain of poly(2-oxazoline) resulted in a mechanism switch from DNA-targeting to membrane-targeting, which was supported by the slow time-kill kinetics and slightly distorted and sunken membrane morphology. Besides, GABA-pendent poly(2-oxazoline) showed potent activity against methicillin-resistant S. aureus and low hemolysis on human red blood cells. Moreover, repeated use of the antimicrobial poly(2-oxazoline) did not stimulate bacteria to obtain resistance, which was an obvious advantage of membrane-targeting antimicrobial agents.

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    Prospective
    Mechano-active biomaterials for tissue repair and regeneration
    Xiao Lin, Yanjie Bai, Huan Zhou, Lei Yang
    J. Mater. Sci. Technol.. 2020, 59 (0): 227-233.   DOI: 10.1016/j.jmst.2020.03.074
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    There is a lack of effective tissue repair and regeneration strategies in current clinical practices. Numerous studies have suggested that smart or responsive biomaterials possessing the ability to respond to endogenous stimuli in vivo may positively mediate the tissue micro-environment towards a tissue repair or regeneration. Mechanical stimuli, which constantly exist in a wide range of biological systems and are involved in almost all the physiological processes, belong to such stimuli to which responsive biomaterials can respond. In recent studies, a new type of smart biomaterials, which can dynamically adapt to the mechanical stimuli in vivo and thus has specific functionality consistently mediated by such mechanical stimuli, has emerged. In contrast to common biomaterials that passively react to the mechanical environment of an implantation site, such mechano-active biomaterials have enabled various active or automatic strategies for tissue repair or regeneration, such as providing precise spatial-temporal controls on delivery of drugs or cells in the organs of the musculoskeletal and the circulatory systems; in situ reconstructing the original or a favorable mechanical environment at a lesion site; and accelerating the tissue remodeling or healing process via a mechanobiological effect. This article elucidates a perspective of perfecting tissue repair or regeneration using mechano-active biomaterials, especially highlighting the rationale behind the concept of mechano-active biomaterials and their potential in the repair or regeneration of musculoskeletal and cardiovascular tissues. Albeit outstanding challenges and unknowns, the emergence of mechano-active biomaterials has become a new avenue for tissue engineering and regenerative medicine.

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    Research Article
    Highly sensitive detection of phosphopeptides with superparamagnetic Fe3O4@mZrO2 core-shell microspheres-assisted mass spectrometry
    Ruifang Gao, Jin Li, Rui Shi, Yang Zhang, Fuzhou Ouyang, Ting Zhang, Lihua Hu, Guoqiang Xu, Jian Liu
    J. Mater. Sci. Technol.. 2020, 59 (0): 234-242.   DOI: 10.1016/j.jmst.2020.02.091
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    Protein phosphorylation is one of the most important post-translational modifications. It is an active research area to study phosphoproteomics for discovery of disease biomarkers and druggable targets. Here we report the development of superparamagnetic Fe3O4@mZrO2 core-shell microspheres with mesoporous structures for highly efficient enrichment of phosphopeptides. We have demonstrated that the mesoporous ZrO2 layer dramatically improves the selective enrichment of phosphopeptides. Our approach allows for in-situ elution and sensitive identification of both mono-phosphorylated and multi-phosphorylated peptides in MALDI-TOF mass spectrometry, with the detection limit of down to the femtomole range. The target phosphopeptides can reliably be enriched for MS analysis from various complex samples including the spiked protein digests and tumor cell lysates. The Fe3O4@mZrO2 core-shell microspheres promise a useful tool for phosphoproteomics by allowing for highly efficient and selective enrichment of the crucial signaling regulators in a low abundance.

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    Invited Review
    Electrospinning nanofiber scaffolds for soft and hard tissue regeneration
    Xianrui Xie, Yujie Chen, Xiaoyu Wang, Xiaoqing Xu, Yihong Shen, Atta ur Rehman Khan, Ali Aldalbahi, Allison E. Fetz, Gary L. Bowlin, Mohamed El-Newehy, Xiumei Mo
    J. Mater. Sci. Technol.. 2020, 59 (0): 243-261.   DOI: 10.1016/j.jmst.2020.04.037
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    Tissue engineering is an interdisciplinary field that integrates medical, biological, and engineering expertise to restore or regenerate the functionality of healthy tissues and organs. The three fundamental pillars of tissue engineering are scaffolds, cells, and biomolecules. Electrospun nanofibers have been successfully used as scaffolds for a variety of tissue engineering applications because they are biomimetic of the natural, fibrous extracellular matrix (ECM) and contain a three-dimensional (3D) network of interconnected pores. In this review, we provide an overview of the electrospinning process, its principles, and the application of the resultant electrospun nanofibers for tissue engineering. We first briefly introduce the electrospinning process and then cover its principles and standard equipment for biomaterial fabrication. Next, we highlight the most important and recent advances related to the applications of electrospun nanofibers in tissue engineering, including skin, blood vessels, nerves, bone, cartilage, and tendon/ligament applications. Finally, we conclude with current advancements in the fabrication of electrospun nanofiber scaffolds and their biomedical applications in emerging areas.

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