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CN 21-1315/TG
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Current Issue
 01 March 2020, Volume 40 Issue 0 Previous Issue    Next Issue
 Select Microstructure and stress corrosion cracking of a SA508-309L/308L-316L dissimilar metal weld joint in primary pressurized water reactor environment Lijin Dong, Cheng Ma, Qunjia Peng, En-Hou Han, Wei Ke J. Mater. Sci. Technol., 2020, 40 (0): 1-14.  DOI: 10.1016/j.jmst.2019.08.035 Stress corrosion cracking (SCC) of an SA508-309 L/308 L-316 L dissimilar metal weld joint in primary pressurized water reactor environment was investigated by the interrupted slow strain rate tension tests following a microstructure characterization. The 308 L weld metal shows a higher content of δ ferrite than the 309 L weld metal. In addition, no obvious Cr-depletion but carbides precipitation at γ/δ phase boundaries was observed in both 308 L and 309 L weld metals. The slow strain rate tension tests showed that the SCC susceptibility of the base and weld metals of the dissimilar metal weld joint follows the order of SA508 < 308 L weld metal < the heat affected zone of 316 L base metal < 309 L weld metal. The higher SCC susceptibility of 309 L weld metal than that of 308 L weld metal is likely due to the lower content of δ ferrite. In addition, a preferential SCC initiation in the 309 L weld metal adjacent to 308 L weld metal is attributed to few carbides in this region.
 Select Wettability and joining of SiC by Sn-Ti: Microstructure and mechanical properties Wei Fu, Xiaoguo Song, Ruichen Tian, Yuzhen Lei, Weimin Long, Sujuan Zhong, Jicai Feng J. Mater. Sci. Technol., 2020, 40 (0): 15-23.  DOI: 10.1016/j.jmst.2019.08.040 Reliable SiC/Sn-Ti/SiC joints were obtained by brazing (950 °C/10 min) and soldering (250 °C/2 min) following premetallization depend on the wettability of Sn-Ti on SiC. The microstructures of Sn-Ti/SiC interface were characterized by scanning electron microscopy, X-ray diffraction and transmission electron microscopy, and the mechanical properties of joints were evaluated by shear tests. Active Ti enhanced the wettability of Sn on SiC with the decrease of contact angle from 150° to 20°. Ti direct reacted with SiC to produce TiC and combines with released Si forming Ti5Si3. Much lower Ti concentration per contacting area in brazing and metallization, compared to wetting, resulted in defective bonding of Sn-Ti/SiC and few amounts of interfacial products (thin TiC layer or partial covered TiC layer with Ti5Si3). All of the SiC/SiC joints possess a similar shear strength of 27-32 MPa and rupture through β-Sn matrix in ductile fracture.
 Select An effective and green H2O2/H2O/O3 oxidation method for carbon nanotube to reinforce epoxy resin Qi Wang, Wen Shi, Bo Zhu, Dang Sheng Su J. Mater. Sci. Technol., 2020, 40 (0): 24-30.  DOI: 10.1016/j.jmst.2019.08.038 Facile green oxidation methods are always desired to functionalize carbon nanotubes (CNTs) in the production of advanced CNT/epoxy composites. In the present work, an optimized H2O2/H2O/O3 oxidation method was developed, and performances of the H2O2/H2O/O3 oxidized CNT in epoxy matrix were tested and compared with that of the H2O/O3 oxidized CNT and the most commonly used concentrated HNO3 oxidized CNT. The physical and chemical characteristics of the obtained oxidized CNTs were systematically characterized via transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and Raman. Mechanical performances of the obtained composites were explored by tensile tests, impact tests, dynamic mechanical analysis (DMA) and fracture toughness tests. It was found that the H2O2/H2O/O3 oxidized CNT exhibited all-around overwhelming advantages over the concentrated HNO3 oxidized CNT on reinforcing the epoxy matrix, while the H2O/O3 oxidized CNT only improved the material strength. Reinforcing mechanisms for the different methods oxidized CNTs were studied and compared. The optimized H2O2/H2O/O3 oxidation method makes scaled production possible, avoids environment pollutions, and holds great potentials to replace the most commonly used concentrated HNO3 oxidation method to oxidize CNT during the preparation of the advanced CNT/epoxy composite.
 Select Atomic-scale investigation of spinel LiFe5O8 thin films on SrTiO3 (001) substrates Kun Liu, Ruyi Zhang, Lu Lu, Shaobo Mi, Ming Liu, Hong Wang, Shengqiang Wu, Chunlin Jia J. Mater. Sci. Technol., 2020, 40 (0): 31-38.  DOI: 10.1016/j.jmst.2019.08.039 Microstructural properties of spinel LiFe5O8 (LFO) films grown on (001)-oriented SrTiO3 (STO) substrates have been investigated at the atomic-scale by advanced electron microscopy techniques. Two types of orientation relationship (OR) between the LFO films and the STO substrates have been determined, cube-on-cube and (111)[$\bar{1}$ 10]LFO//(111)[1 $\bar{1}$ 0]STO. Antiphase boundaries (APBs) and three types of twin boundaries (TBs) form within the LFO films, and the propagation of TBs and APBs results in their complex interactions. In most cases, interactions between TBs and APBs change the type of TBs and terminate the propagation of APBs since the APBs introduce a displacement vector of (a/4)〈110〉 into the TBs. In addition, the interactions between two coherent TBs are observed to generate the incoherent TB. The epitaxial strain of the LFO/STO (001) heterosystem can be released by the formation of TBs and APBs in the films and misfit dislocations at the interface. Considering that the magnetic coupling across the APBs and TBs can lead to novel physical properties, the appearance of APBs and TBs with a high density in the LFO films would affect the magnetic properties of the films.
 Select Engineering the epitaxial interface of Pt-CeO2 by surface redox reaction guided nucleation for low temperature CO oxidation Changjin Xu, Yutong Wu, Song Li, Jun Zhou, Jing Chen, Min Jiang, Hongda Zhao, Gaowu Qin J. Mater. Sci. Technol., 2020, 40 (0): 39-46.  DOI: 10.1016/j.jmst.2019.08.036 The interface between metal nanoparticles (NPs) and support plays a vital role in catalysis because both electron and atom exchanges occur across the metal-support interface. However, the rational design of interfacial structure facilitating the charge transfer between the neighboring parts remains a challenge. Herein, a guided nucleation strategy based on redox reaction between noble metal precursor and support-surface is introduced to construct epitaxial interfaces between Pt NPs and CeO2 support. The Pt/CeO2 catalyst exhibits near room temperature catalytic activity for CO oxidation that is benefited from the well-defined interface structure facilitating charge transfer from CeO2 support to Pt NPs. Meanwhile, this general approach based on support-surface-induced-nucleation was successfully extended to synthesize Pd and Cu nanocatalysts on CeO2, demonstrating its universal and feasible characteristics. This work is an important step towards developing highly active supported metal catalysts by engineering their interfaces.
 Select Primary dendrite growth kinetics and rapid solidification mechanism of highly undercooled Ti-Al alloys Z.C. Luo, H.P. Wang J. Mater. Sci. Technol., 2020, 40 (0): 47-53.  DOI: 10.1016/j.jmst.2019.08.034 The rapid solidification processes of undercooled Ti-(47, 50, 54) at.% Al alloys were investigated by electromagnetic levitation (EML) method combined with a high-speed photoelectric detector. The maximum undercoolings of the three liquid alloys were 376 K, 352 K and 316 K, respectively. Recalescence processes corresponding to the primary dendrite growth and subsequent phase transition were recorded at various undercoolings. The primary dendrite growth velocity V meets a double exponential relationship with the undercooling ΔT. Besides, a novel formula with physical meaning is proposed to explain that the more ordered liquid metal atoms accelerate the primary dendrite growth. Three recalescences are found at all undercoolings for Ti-47 at.% Al alloy and at high undercoolings for Ti-50 at.% Al alloy. The microstructures of solidified Ti-47 at.% Al alloys successively appear as coarse lamellar dendrites and finally evolve to refined parallel lamellar dendrites with the increasing undercooling. When ΔT rises, the microstructures of solidified Ti-50 at.% Al alloys appear from coarse primary dendrites and interdendritic dendrites to refined lamellar dendrites. In the process from low undercooling to high undercooling, the primary phase of undercooled Ti-54 at.% Al alloys changes from α-Ti (α) to γ-TiAl (γ) and the microstructures of solidified alloys evolve from spherical primary dendrites and matrix phases to cellular dendrite phases. Meanwhile, for the Ti-(47, 50) at.% Al, the transformation temperature of metastable intermediate α phase decreases with the increase of undercooling. Moreover, the microhardness of the three solidified alloys reaches the maximum when the undercoolings are 185 K, 270 K and 316 K, respectively.
 Select Effect of strain rate on plastic deformation bonding behavior of Ni-based superalloys Jian Yang Zhang, Bin Xu, Naeem ul Haq Tariq, Ming Yue Sun, Dian Zhong Li, Yi Yi Li J. Mater. Sci. Technol., 2020, 40 (0): 54-63.  DOI: 10.1016/j.jmst.2019.08.044 Plastic deformation bonding (PDB) has emerged as a promising solid state bonding technique with limited risk of phase transformations and residual thermal stresses in the joint. In this study, the PDB behavior of IN718 superalloy was systematically investigated by performing a series of isothermal compression tests at various processing conditions. It was revealed that, with increasing PDB strain rate at 1000 °C, different extents of dynamic recrystallization (DRX) occur in the bonding area of IN718 joints. The extent of DRX, average size of DRXed grains, and a newly proposed “interfacial bonding ratio (ΨBonding)” parameter (to quantify the bond quality) were initially reduced with increase in the strain rate up to 0.1 s-1 and later increased at further higher strain rates. Electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM) based interfacial microstructure analyses indicated that the quality of the bonded joints is closely related with the development of fine DRXed grains at the bonding interface with the increasing strain, which promotes adiabatic temperature rise. It was revealed that the initial bulging and subsequent migration of the original interfacial grain boundary (IGB) were the main mechanisms promoting DRX in the well bonded IN718 superalloy joints. Moreover, the mechanical properties of the bonded joints were not only controlled by the recrystallized microstructure but also depended upon the Bonding parameter of the joints.
 Select Anti-perovskite carbides and nitrides A3BX: A new family of damage tolerant ceramics Wei Zhang, Yuchen Liu, Yanchun Zhou, Wai-Yim Ching, Qian Li, Wenxian Li, Jiong Yang, Bin Liu J. Mater. Sci. Technol., 2020, 40 (0): 64-71.  DOI: 10.1016/j.jmst.2019.08.043 Synergy effect of high stiffness and good damage tolerance is always the focus of the development of novel structural materials. Herein, a new strategy on the future damage tolerant material design is proposed to merge the strong covalent bonds into the easy shear deformed A3B metallic box. This goal is realized by studying 126 A3BX phases and establishing a database on their mechanical properties through high-throughput first principles calculations. The combination strategies of A3B metallic box and XA3 octahedra show intensive influences on the expected mechanical properties. The family includes 49 quasi-ductile compounds. Among them, four compounds (Ti3AlN, Mn3CuN, Ti3TlN and Ni3SnN) exhibit excellent damage tolerance and the other six compounds (Mn3NiN, Mn3GaC, Mn3GaN, Mn3SnC, Cr3SnN, Co3AlC) show both damage tolerance and high stiffness. Their competitive high temperature properties are demonstrated through the detailed investigation on the typical cases of Co3AlC and Ti3TlN. This study leads a novel direction for the design of the future quasi-ductile and high stiffness ceramics.
 Select Electrochemically metal-doped reduced graphene oxide films: Properties and applications Myung-Sic Chae, Tae Ho Lee, Kyung Rock Son, Tae Hoon Park, Kyo Seon Hwang, Tae Geun Kim J. Mater. Sci. Technol., 2020, 40 (0): 72-80.  DOI: 10.1016/j.jmst.2019.09.014 The fine control of doping levels in graphene materials such as reduced graphene oxide (RGO) is important to properly manipulate their ambipolar transport characteristics for various device applications. However, conventional doping methods involve complex chemical reactions, large-scale doping processes, and poor stability. Herein, a simple and controllable electrochemical doping treatment (EDT), performed via the conductive channels created at the RGO surface by the application of an electric field, is introduced to tailor the electrical properties of RGO films. X-ray photoelectron spectroscopy and Raman spectroscopy measurements are performed to detect the presence of Ni atoms in RGO films after the EDT (EDT-RGO). Then, EDT-RGO field-effect transistors (FETs) are fabricated with different doping areas (0 to 100% fractional area) on the RGO active channel to investigate the effect and selective-area doping capability of the EDT. Owing to p-type doping compensation by the intercalated Ni atoms, the electron mobility of the EDT-RGO FET decreases from 1.40 to 0.12 cm2 V-1 s-1 compared with that of the undoped RGO-FET, leading to the conversion from ambipolar to unipolar p-type transfer characteristics.
 Select Improved multi-orientation dispersion of short carbon fibers in aluminum matrix composites prepared with square crucible by mechanical stirring Guanglong Li, Yingdong Qu, Yaohua Yang, Qiwen Zhou, Xishi Liu, Rongde Li J. Mater. Sci. Technol., 2020, 40 (0): 81-87.  DOI: 10.1016/j.jmst.2019.09.009 In order to improve the strength of short carbon fibers reinforced aluminum matrix (Csf/Al) composite, the dispersion of short carbon fibers with multi-orientation was controlled with a square crucible by mechanical stirring. The three-dimensional flow field models of liquid aluminum melt in the square/round crucibles were established and calculated, and the results were compared. The calculated results show that turbulent flow could be induced both in the square and round crucible, while the non-axisymmetric structure of the square crucible results in higher turbulent kinetic energy in the melt. Therefore, the uniformity and multi-orientation dispersion of the short fibers can be improved by the intensive turbulent flow in the square crucible, which will be increased by increasing the rotational velocity. The distribution of the short carbon fibers in the aluminum matrix prepared under different rotation velocities in square crucible was experimentally investigated. With the increase of stirring velocity, the multi-orientation dispersion of the short fibers in the composites increased gradually. The experimental results are consistent with the calculation results. The tensile testing results show that the strength of the Csf/Al composite can reach 172 MPa when the rotational velocity is 1000 rpm, and it is 48.3% higher than that prepared by the round crucible under the same conditions, which results from the improved multi-orientation dispersion of short carbon fibers in aluminum matrix.
 Select Mechanical and corrosion fatigue behaviors of gradient structured 7B50-T7751 aluminum alloy processed via ultrasonic surface rolling Xingchen Xu, Daoxin Liu, Xiaohua Zhang, Chengsong Liu, Dan Liu J. Mater. Sci. Technol., 2020, 40 (0): 88-98.  DOI: 10.1016/j.jmst.2019.08.030 In this work, ultrasonic surface rolling process (USRP) was utilized to produce a gradient structured layer on 7B50-T7751 aluminum alloy, and the mechanical properties and corrosion fatigue behavior of treated samples were studied. These results reveal that underwent USRP, a 425 μm thick gradient structure and a 700 μm deep compressive residual stress field are created, aluminum grain size become fine(~ 67 nm), and the corrosion rate of treated surface reduces by 60.08% owing to the combined effect of compressive residual stress and surface nanocrystallization. The corrosion fatigue strength is enhanced to 117% of that of 7B50 Al alloys by means of USRP due to the introduced compressive residual stress, which is considered as the major favorable factor in suppressing the initiation and early propagation of corrosion fatigue cracks. Besides, the gradient structure is an important factor in providing a significant synergistic contribution to the improvement of corrosion fatigue performance.
 Select Strong, lightweight, and highly conductive CNT/Au/Cu wires from sputtering and electroplating methods Thang Q. Tran, Jeremy Kong Yoong Lee, Amutha Chinnappan, W.A.D.M. Jayathilaka, Dongxiao Ji, Vishnu Vijay Kumar, Seeram Ramakrishna J. Mater. Sci. Technol., 2020, 40 (0): 99-106.  DOI: 10.1016/j.jmst.2019.08.033 In this study, we present a 2-step deposition method via sputtering and electroplating that uses carbon nanotube (CNT) wires synthesized from a wet-spinning technique to produce high-performance CNT/Au/Cu composite wires. After the Au sputtering pre-treatment, the deposition of Cu on the CNT wires was found to be much more homogeneous due to improved wettability and reactivity of the wire surface. At different electrodeposition time, the mechanical strength of the CNT/Au/Cu composite wires could be as high as 0.74 GPa (~ 2 times stronger than metal wires) while their electrical conductivity could reach 4.65 × 105 S/cm (~ 80% of that for copper). More importantly, the CNT/Au/Cu composite wires with high CNT volume fraction are expected to be lightweight (up to 42% lower than Cu mass density), suggesting that our high-performance composite wires are a promising candidate to substitute conventional heavy metal wires in the future applications.
 Select Enhancing the bake-hardening responses of a pre-aged Al-Mg-Si alloy by trace Sn additions Gang Lu, Shuai Nie, Jianjun Wang, Ying Zhang, Tianhai Wu, Yujie Liu, Chunming Liu J. Mater. Sci. Technol., 2020, 40 (0): 107-112.  DOI: 10.1016/j.jmst.2019.08.045 Effects of additions of trace Sn on the bake-hardening responses of a pre-aged Al-0.85Mg-0.85Si (in wt%) alloy were investigated through mechanical tests, differential scanning calorimetry, electrical resistivity and transmission electron microscopy. Results indicate that trace Sn additions reduced the number density of pre-aging clusters by inhibiting the formation of unstable counterpart during pre-aging treatment, leading to low strength and high supersaturation of solute atoms. In a subsequent paint-bake treatment, the presence of highly supersaturated solute atoms and high concentrated free vacancies moderated the activation energy barrier of βʺ phase and thus kinetically accelerated the formation of βʺ. Consequently, the trace Sn additions enhanced the bake-hardening responses of the pre-aged alloys significantly. The Sn-containing pre-aged Al-Mg-Si alloys with low strength and great bake-hardening responses hold promising potential for automotive body skin applications.
 Select Low contact resistivity and long-term thermal stability of Nb0.8Ti0.2FeSb/Ti thermoelectric junction Zhijie Huang, Li Yin, Chaoliang Hu, Jiajun Shen, Tiejun Zhu, Qian Zhang, Kaiyang Xia, Jiazhan Xin, Xinbing Zhao J. Mater. Sci. Technol., 2020, 40 (0): 113-118.  DOI: 10.1016/j.jmst.2019.08.046 Although half-Heusler compounds are quite promising for thermoelectric power generation, there is only limited research on the interfacial structure between metal electrode and half-Heusler compounds for device applications. This work reports on the characteristics of Nb0.8Ti0.2FeSb/Ti junction and its evolution behavior during 973 K. The Nb0.8Ti0.2FeSb/Ti interface consists of one Ti0.9Fe0.1 layer and one Fe-poor layer. There is an Ohmic contact and a low contact resistivity (0.15 μΩ cm-2) in this junction, on account of the matching of working functions between Nb0.8Ti0.2FeSb and Ti0.9Fe0.1 interlayer. The high doping of Ti high carrier concentration in NbFeSb matrix leads to a high carrier concentration, which results in inducing a large tunneling current at this interface. After aging treatment at 973 K, the Fe-poor layer and the Ti0.9Fe0.1 layer continues to expand, resulting in the increase of the thickness of the interfacial layer and the contact resistivity. The interfacial electrical is only 1.9 μΩ cm-2 after 25 days’ aging. The thickness of the interface layer has a good linear relation with the square root of aging time, which firmly indicates that the growth of the layer is determined by mutual diffusion of Fe and Ti atoms across the interface. The low contract resistivity and long-time thermal stability demonstrate the great potential of Nb0.8Ti0.2FeSb/Ti thermoelectric junction in high efficiency half-Heusler TE devices.
 Select MXenes induce epitaxial growth of size-controlled noble nanometals: A case study for surface enhanced Raman scattering (SERS) Renfei Cheng, Tao Hu, Minmin Hu, Changji Li, Yan Liang, Zuohua Wang, Hui Zhang, Muchan Li, Hailong Wang, Hongxia Lu, Yunyi Fu, Hongwang Zhang, Quan-Hong Yang, Xiaohui Wang J. Mater. Sci. Technol., 2020, 40 (0): 119-127.  DOI: 10.1016/j.jmst.2019.09.013 Noble nanometals are of significance in both scientific interest and technological applications, which are usually obtained by conventional wet-chemical synthesis. Organic surfactants are always used in the synthesis to prevent unexpected overgrowth and aggregation of noble nanometals. However, the surfactants are hard to remove and may interfere with plasmonic and catalytic studies, remaining surfactant-free synthesis of noble nanometals a challenge. Herein, we report an approach to epitaxial growth of size-controlled noble nanometals on MXenes. As piloted by density functional theory calculations, along with work function experimental determination, kinetic and spectroscopic studies, epitaxial growth of noble nanometals is initiated via a mechanism that involves an in situ redox reaction. In the redox, MXenes as two-dimensional solid reductants whose work functions are compatible with the reduction potentials of noble metal cations, enable spontaneous donation of electrons from the MXenes to noble metal cations and reduce the cations into nanoscale metallic metals on the outmost surface of MXenes. Neither surfactants nor external reductants are used during the whole synthesis process, which addresses a long-standing interference issue of surfactant and external reductant in the conventional wet-chemical synthesis. Moreover, the MXenes induced noble nanometals are size-controlled. Impressively, noble nanometals firmly anchored on MXenes exhibit excellent performance towards surface enhanced Raman scattering. Our developed strategy will promote the nanostructure-controlled synthesis of noble nanometals, offering new opportunities to further improve advanced functional properties towards practical applications.
 Select Effect of atomic structure on preferential oxidation of alloys: amorphous versus crystalline Cu-Zr Yifei Xu, Lars P.H. Jeurgens, Peter Schützendübe, Shengli Zhu, Yuan Huang, Yongchang Liu, Zumin Wang J. Mater. Sci. Technol., 2020, 40 (0): 128-134.  DOI: 10.1016/j.jmst.2019.10.001 The effect of structural order in the parent alloy substrate on the oxidation kinetics and oxide phase evolution was investigated for the thermal oxidation of amorphous Cu33at.%Zr67at.% and crystalline CuZr2 alloys of identical compositions in the temperature range of 200-250 °C. It was found that, besides the strong preferential oxidation of Zr in both alloys, the lack of structural order in the amorphous Cu33at.%Zr67at.% alloy results in much slower oxidation kinetics, as well as in distinctly different microstructures of the oxide overgrowth and its Zr-depletion zone in the wake of the ZrO2 overlayer growth front. The experimental findings can be rationalized on the basis of the strikingly different atomic mobilities of Cu, Zr and dissolved O in the amorphous and crystalline alloys, which also results in different nucleation barriers for crystalline oxide nucleation. The thus obtained knowledge on the underlying oxidation mechanisms provides new and profound insights into the surface engineering of metallic alloys.
 Select Hot-pressed graphene nanoplatelets or/and zirconia reinforced hybrid alumina nanocomposites with improved toughness and mechanical characteristics Iftikhar Ahmad, Mohammad Islam, Nuha Al Habis, Shahid Parvez J. Mater. Sci. Technol., 2020, 40 (0): 135-145.  DOI: 10.1016/j.jmst.2019.08.048 This work explains the synergistic contribution of graphene nanoplatelets (GNP) and zirconia ceramic nanoparticles (ZrO2) on the microstructure, mechanical performance and ballistic properties of the alumina (Al2O3) ceramic hybrid nanocomposites. Over the benchmarked monolithic alumina, the hot-pressed hybrid nanocomposite microstructure demonstrated 68% lower grain size due to grain pinning phenomenon by the homogenously distributed reinforcing GNP (0.5 wt%) and zirconia (4 wt%) inclusions. Moreover, the hybrid nanocomposite manifested 155% better fracture toughness (KIC) and 17% higher microhardness as well as 88% superior ballistic trait over the monolithic alumina, respectively. The superior mechanical and ballistic performance of the hybrid nanocomposites was attributed to the combined role of zirconia nanoparticles and GNP nanomaterial in refining the microstructure and inducing idiosyncratic strengthening/toughening mechanisms. Extensive combined electron microscopy revealed complicated physical interlocking of the GNP into the microstructure as well as excellent bonding of the GNP with alumina at their interface in the hybrid nanocomposites. We also probed the efficiency of the pull-out and crack-bridging toughening mechanisms through proven quantitative methods. Based on the information extracted from the in-depth SEM/TEM investigation, we outlined schematic models for understating the reinforcing ability as well as toughening mechanisms in the hybrid nanocomposites and meticulously discussed. The hot-pressed hybrid nanocomposites owning high toughness and hardness may have applications in advanced armor technology.
 Select Plastic deformation behavior of a nickel-based superalloy on the mesoscopic scale Qiang Zhu, Chuanjie Wang, Kai Yang, Gang Chen, Heyong Qin, Peng Zhang J. Mater. Sci. Technol., 2020, 40 (0): 146-157.  DOI: 10.1016/j.jmst.2019.09.020 Nickel-based superalloys have become the key materials of micro-parts depending on excellent mechanical properties at high temperatures. The plastic deformation behavior is difficult to predict due to the occurrence of size effect on the mesoscopic scale. In this paper, the effect of specimen diameter to grain size ratio (D/d) on the flow stress and inhomogeneous plastic deformation behavior in compression of nickel-based superalloy cylindrical specimens was investigated on the mesoscopic scale. The results showed that when D/d is less than 9.7, the flow stress increases with the grain size. Aiming at this phenomenon, a flow stress size effect model considering compressive strain partitioning was established. The calculated flow stress values agree well with the experimental values, thus revealing the effect of D/d on the flow stress in compression of nickel-base superalloy on the mesoscopic scale. The inhomogeneous plastic deformation during compression deformation increases with the grain size. The end surface profiles evolve from a regular circular shape to an irregular shape with the grain size. The surface folding phenomenon occurs only in partially compressed specimen with a few grains across the diameter. Crystal plasticity finite-element (CPFE) simulation of compression deformation on the mesoscopic scale real-time displayed the evolution of microstructure. The study of this paper has important guiding significance for understanding the influence of D/d on the compression deformation behavior of nickel-based superalloy on the mesoscopic scale.
 Select Novel insight into dry sliding behavior of Cu-Pb-Sn in-situ composite with secondary phase in different morphology B.W. Dong, S.H. Wang, Z.Z. Dong, J.C. Jie, T.M. Wang, T.J. Li J. Mater. Sci. Technol., 2020, 40 (0): 158-167.  DOI: 10.1016/j.jmst.2019.09.025 The Cu-24Pb-xSn (wt%) (x = 0, 2, 4, 6) alloys with Pb-rich second-phase particles (SPPs) in different shapes show obviously differently mechanical and self-lubricating properties. The influence of the SPPs’ shape difference on the alloys’ mechanical and self-lubricating properties was revealed. Cu-24Pb alloy with continuously netty SPPs shows much more intensive stick-slip phenomenon during dry sliding than the other three alloys with independently rodlike SPPs. That is mainly due to insufficient lubrication resulted by the netty SPPs’ splitting matrix. With the SPPs transforming from netty to rodlike shape under the addition of Sn, the stick-slip phenomenon was notably weakened, which was proven to be related to the higher self-lubricating property of alloys with rodlike SPPs. Simultaneously, the simultaneous increase of ductility and tensile strength was observed in the Cu-24Pb-xSn alloys with increasing Sn content, which is because the netty SPPs’ splitting behavior will be weakened with them replaced by the rodlike SPPs.
 Select Visible-light-activated N-doped CQDs/g-C3N4/Bi2WO6 nanocomposites with different component arrangements for the promoted degradation of hazardous vapors Mi Gyeong Kim, Wan-Kuen Jo J. Mater. Sci. Technol., 2020, 40 (0): 168-175.  DOI: 10.1016/j.jmst.2019.09.026 To investigate whether the arrangement of componentsin multi-composite photocatalysts may affect their photocatalytic properties, due to different charge-transfer routes, two ternary-nanocomposite photocatalysts with different component arrangements, comprising N-doped carbon quantum dots (NCQDs), g-C3N4 (CN), and Bi2WO6 (BWO) (hereafter referred to as NCQDs/CN/BWO), were developed, and the photocatalytic degradation of model hazardous vapors under visible-light illumination was investigated. Type I NCQDs/CN/BWO, which was developed by the combination of NCQDs/BWO and CN, exhibited photocatalytic ability superior to that of type II NCQDs/CN/BWO, which was developed by the combination of CN/BWO and NCQDs; the superior photocatalytic ability corresponded to the dual properties of NCQDs: charge mediation and upconversion photoluminescence. Moreover, the photocatalytic ability of NCQDs/CN/BWO was greater than those of the reference catalysts; in addition, this photocatalyst exhibited outstanding photochemical stability. Additionally, the effects of CN/(BWO + CN) weight ratio of the CN/BWO dual nanocomposites and the NCQDs/(BWO + CN + NCQDs) weight percentage of NCQDs/CN/BWO ternary nanocomposites on the pollutant removal efficiency were investigated. The plausible mechanisms over the two NCQDs/CN/BWO photocatalysts for the degradation of hazardous vapors were discussed. The component arrangement approach proposed herein afforded a technique toward the perceptive development of novel multi-component heterostructures for the photocatalytic degradation of hazardous vapors.
 Select Uniform assembly of gold nanoparticles on S-doped g-C3N4 nanocomposite for effective conversion of 4-nitrophenol by catalytic reduction Vellaichamy Balakumar, Hyungjoo Kim, Ji Won Ryu, Ramalingam Manivannan, Young-A Son J. Mater. Sci. Technol., 2020, 40 (0): 176-184.  DOI: 10.1016/j.jmst.2019.08.031 In this work, a simple synthesis of sulfur doped graphitic carbon nitride (S-g-C3N4) act as a support cum stabilizers for gold nanoparticles (Au) and its was characterized by UV-vis and XRD to measure the absorbance and crystallinity, respectively. The functional group and morphology of the samples were identified using FT-IR and TEM. Finally, the Au@S-g-C3N4 nanocatalyst exhibits good catalytic performance and stability in the reduction of hazardous 4-nitrophenol (NP) compared to S-g-C3N4 using NaBH4. Moreover, the Au@S-g-C3N4 nanocomposite holds a good catalytic efficiency (near 100%) achieved by within 5 min. The highest catalytic reduction of NP is due to the synergistic effect of Au nanoparticles decorated on S-g-C3N4. The fast electron transfer reduction mechanism was elucidated and discussed. Excellent reusability and stability of the developed nanocomposites were also observed in consecutive reduction experiments. The filtering and catalyzing device was used for the direct conversion of NP polluted water. This method can open a new avenue for the metal nanoparticles based carbon materials heterogeneous catalyst and its reduction of toxic contaminants.
 Select Correlating particle impact condition with microstructure and properties of the cold-sprayed metallic deposits Yujuan Li, Yingkang Wei, Xiaotao Luo, Changjiu Li, Ninshu Ma J. Mater. Sci. Technol., 2020, 40 (0): 185-195.  DOI: 10.1016/j.jmst.2019.09.023 Inter-particle bonding is an important factor affecting the property of cold sprayed metallic deposit. Because the interface bonding between particles in deposit is directly determined by plastic strain of particles during spraying, Cu deposits were made at series of impact velocities of 578 m s-1 to 745 m s-1 and 807 m s-1 to correlate particle impact condition with microstructure and properties of the deposits. Results show that as the average particle impact velocity increases from 578 m s-1 to 745 m s-1 and 807 m s-1, the deposition efficiency of feedstock powder increases from 58% to 84% and even to 95%. Although all three deposits reveal dense microstructure due to the high ductility of Cu, the deformation degree of the deposited particles remarkably increases with increasing impact velocity. The enhanced plastic deformation of the deposited particles leads to more dispersed oxide scale and thereby stronger inter-particle bonding with the strength of the deposit along the deposition direction increasing from 25.8 MPa to 148.5 MPa. The electrical and thermal conductivities at through-thickness direction of the deposit at particle impact velocity of 807 m s-1 are 78 % IACS, 295 W m-1 K-1, respectively.
 Select Ultra-small amorphous MoS2 decorated reduced graphene oxide for supercapacitor application Poulami Hota, Milon Miah, Saptasree Bose, Diptiman Dinda, Uttam K. Ghorai, Yan-Kuin Su, Shyamal K. Saha J. Mater. Sci. Technol., 2020, 40 (0): 196-203.  DOI: 10.1016/j.jmst.2019.08.032 Amorphous materials have recently gained much attention as electrode materials in supercapacitor application due to the presence of larger amount active sites which can efficiently increase the storage capacity of the materials. Nano engineering is an elegant approach to fully utilize the advantages of the amorphous structure. Moreover, large surface area and high conductivity of reduced graphene oxide (RGO) can efficiently increase the storage capacity of the system. Exploiting this idea, in the present work, we have successfully synthesized amorphous MoS2 of two different sizes on reduced graphene oxide and thoroughly investigated the supercapacitor behavior of the system. The specific capacitance of the composite structures has been found to be largely increased with decreasing size of the amorphous nano particle. The specific capacitance of amorphous MoS2-RGO composite containing nearly 50 nm of MoS2 found to be 270 F/g whereas when the particle size is reduced to 5-7 nm, value of specific capacitance increases to 460 F/g. The large increase in specific capacitance with the tuning of the size of amorphous nano particle has been explained by the presence of a large number of active sulfur edges of ultra-small MoS2 nano structure along with the better charge transport which can effectively increase the storage capacity of the overall system. The retention in the capacitance of the material has been found to be 90 % after 5000 cycles.
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