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  • Composite coatings formed using plasma electrolytic oxidation and fluoroparaffin materials
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    D.V. Mashtalyar, S.V. Gnedenkov, S.L. Sinebryukhov, I.M. Imshinetskiy, A.S. Gnedenkov, V.M. Bouznik

    The morphology, electrochemical and mechanical properties of the protective composite coatings, formed on the magnesium alloy surface by means of plasma electrolytic oxidation (PEO) and fluorocarbon materials have been established. After the treatment of the PEO-coating by fluoroparaffins the impedance modulus and polarization resistance have increased by two orders of magnitude and wear resistance in more than 10 times as compared to the base PEO-layer. Hydrophobic properties of the composite coatings have been established: values of the contact angle changed in the range from 122° up to 137°, depending on the flouroparaffin type.

    更新日期:2018-07-12
  • Low energy ion irradiation induced SPR of Cu-Fullerene C70 nanocomposite thin films
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Rahul Singhal, Jyotsna Bhardwaj, Ritu Vishnoi, S. Aggarwal, Amit Kumar Sharma, G.D. Sharma

    Metal-matrix composites have a diverse range of applications by virtue of their improved properties. However, further improvements in the characteristics of the composites can be made if we are able to tune the properties of a single constituent of the composite. In the present work, Cu-C70 thin films were grown on glass substrate with thermal co-evaporation technique. In order to induce the surface plasmon resonance (SPR) band, the nanocomposite thin films are irradiated with 120 keV N+ ion beam at the fluence ranging from 1 × 1014 to 3 × 1016 ions/cm2. The Rutherford backscattering is used to know the thickness and concentration of the components present in the nanocomposite thin film. TEM is used to show the increase in particle size of Cu nanoparticles with the increase in the irradiation fluence. The surface analysis shows a decrease in the roughness of the film upto a fluence of 3 × 1014 ions/cm2 and then the roughness increases with the increase in fluence. The UV–vis. spectrum shows the formation of SPR band at ∼630 nm at the highest fluence of 3 × 1016 ions/cm2 ascribed to the increase in the size of the Cu nanoparticles. The FTIR spectrum shows various bonds of copper and fullerene in pristine film. Raman spectroscopic investigations show the transformation of fullerene C70 matrix of Cu-C70 thin film into amorphous carbon matrix at higher fluences. XPS is also performed to show the elemental state of composite material.

    更新日期:2018-07-12
  • Plasma sprayed diamond reinforced molybdenum coatings
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Purnendu Das, Soumitra Paul, P.P. Bandyopadhyay

    The present investigation deals with the fabrication of a novel thermally sprayed coating using a diamond reinforced molybdenum feedstock. Molybdenum powders were ball-milled with 10 wt% mono-crystalline diamond particles to produce a powder feedstock. Both milled and as-received powders were deposited on steel substrates using air plasma spraying to produce coatings with a thickness in the range of 250–280 μm. Characterisation of the coatings was performed in terms of micro-structure, phases, hardness, elastic modulus and residual stress. Retention of diamond in the composite coating was confirmed using Raman imaging. Micro-hardness and elastic modulus of coatings improved with diamond reinforcements.

    更新日期:2018-07-12
  • An efficient sodium-ion battery consisting of reduced graphene oxide bonded Na3V2(PO4)3 in a composite carbon network
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Erlong Gu, Shuhu Liu, Zhuangzhuang Zhang, Yuyan Fang, Xiaosi Zhou, Jianchun Bao

    Sodium-ion batteries have been considered as the most promising candidate for large-scale energy storage applications. However, the poor cycling stability and inferior rate capability of existing cathode materials for sodium-ion batteries restrict future developments. Herein, we report a chemically bonded cathode material for sodium-ion batteries that is synthesized by freeze-drying and subsequent annealing to generate Na3V2(PO4)3/reduced graphene oxide−carbon nanotubes (NGC) composite. The NGC composite with 79 wt % Na3V2(PO4)3 shows a high initial Coulombic efficiency (>93%) and high specific capacity with superior cycling stability (∼105 mAh g−1 after 500 cycles at 1 C based on the mass of Na3V2(PO4)3). More importantly, in situ electrochemical impedance spectroscopy and ex situ X-ray diffraction, X-ray photoelectron spectroscopy, X-ray absorption near edge structure spectroscopy, and transmission electronic microscopy are employed to reveal the robust V−O−N bonding and excellent sodium storage performance of the NGC composite.

    更新日期:2018-07-12
  • Uniform NiCo2O4/NiFe2O4 hollow nanospheres with excellent properties for Li-ion batteries and supercapacitors
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Yanan Duan, Yuqiu Huo, Yun Qi, Lu Li, Qingyin Wu, Chungang Wang, Zhongmin Su

    Designing mixed metal oxides with uniform nanostructures as a significant electrode material in energy storage devices is a vital concern for the whole world. But achieving this goal is plagued by many problems such as tedious procedures, hard morphology control and poor conductivities. The NiCo2O4/NiFe2O4 hollow nanospheres (NSs) are prepared for the first time through a novel one-pot approach. The introduced NiFe2O4 has amazingly improved the electrochemical performance of NiCo2O4 hollow NSs in both Li-ion batteries (LIBs) and supercapacitors (SCs). And the ratio of Fe to Ni plays an important role for the improvement of electrochemical performance. The NiCo2O4/NiFe2O4 hollow NSs exhibit superior capacity/capacitance values (3795 F g−1 at a current density of 1 A g−1) and fine cycling performances (11.0% specific capacitance decay after 6000 cycles) which can be attributed to the larger specific surface area of hollow NSs and the synergistic effect of two components. This provides a feasible preview of their practical applications.

    更新日期:2018-07-12
  • Ti(OBu)4 and cobalt iron oxide co-modified hematite nanoparticles synthesized by a facile anodic electrodeposition for highly efficient water oxidation
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Longzhu Li, Honglei Zhang, Changhai Liu, Penghua Liang, Naotoshi Mitsuzaki, Zhidong Chen

    Based on the bare hematite prepared by a facile anodic electrodeposition, Ti(OBu)4 modified hematite through FeOOH film surface is a better method for obtaining more excellent photoelectrochemical perfomance. This is due to the significantly increased bulk charge separation efficiency caused by the refined grain, preferred orientation of (110) plane and higher donor density. Coupled with Cobalt Iron Oxide (CIO) nanoparticles, Ti(OBu)4 modified hematite photoanode has a 3 times enhanced photocurrent density of 1.02 mA cm−2 and a negative shift of onset potential about 40 mV compared with bare hematite photoanode. In which, Ti(OBu)4 can increase the electron-hole separation and passivate the surface trap states simultaneously. The CIO nanoparticles coated on the surface of Ti/FeOOH sample not only act as a catalyst for promoting the surface hole injection for water oxidation, but also boost the charge separation with passivating the surface states. This work provides an indepth understanding of the effect of Ti(OBu)4 and CIO nanoparticles on morphology, crystalline structure and photoelectrochemical performance of anodic electrodeposited hematite photoanode via systematical characterization with scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-vis spectra, X-ray diffractometry (XRD), X-ray photoelectron spectra (XPS), and photoelectrical measurements.

    更新日期:2018-07-12
  • An insight to origin of ferromagnetism in ZnO and N implanted ZnO thin films: Experimental and DFT approach
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Parmod Kumar, Hitendra K. Malik, Anima Ghosh, R. Thangavel, K. Asokan

    In the present study, we have elucidated an effective way to simultaneously tune the optical bandgap and magnetic properties of zinc oxide (ZnO). This can be achieved by the incorporation of nitrogen ions via any means in the host matrix. On a broader way, we have systematically investigated the influence of N ions in ZnO thin films through experimental techniques and density functional theory (DFT) calculations to understand the physical mechanism governing the observed magnetic behaviour and variation in bandgap. For this, RF sputtered ZnO thin films deposited over Si substrates were implanted with N ions by varying the fluences and studied for their optical and magnetic properties. The pristine ZnO films is having saturation magnetization of ∼2.45 emu/cm3 which becomes almost twice compared for the fluence of 1 × 1017 ions/cm2. Furthermore, the optical bandgap is tuned from 3.27 eV to 3.04 eV with N ion fluences. Our work signifies the new insight to understand the basis of ferromagnetism in non-magnetic ions doped ZnO system.

    更新日期:2018-07-12
  • Nano-multilayered coatings of (TiAlSiY)N/MeN (Me=Mo, Cr and Zr): Influence of composition of the alternating layer on their structural and mechanical properties
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    YaO. Kravchenko, L.E. Coy, B. Peplińska, I. Iatsunskyi, K. Załęski, M. Kempiǹski, V.M. Beresnev, P. Kanarski, S. Jurga, A.D. Pogrebnjak

    Multilayered design showed itself to advantage for improvement of functional nitride coatings, which are widely required in various industries. This article reports on deposition and detailed characterization series of combined nano-multilayered coatings based on (TiAlSiY)N with changes in components of alternating binary layers. Vacuum-arc deposited (TiAlSiY)N/MoN, (TiAlSiY)N/CrN and (TiAlSiY)N/ZrN coatings were analyzed by means of extensive set of investigation methods as SEM with EDS, XRD and GIXRD, SIMS, XPS and Raman spectroscopy. Microstructure of (TiAlSiY)N/MoN coating was characterized by creation of fine-grained fcc-AlTiN phase of (200) plane with congruent growth of γ-Mo2N (200) due to high isostruturality of lattices of alternating layers. The formation of fcc-AlYTiN phase of (111) plane and fcc-TiCrN phase of (200) plane were observed in multilayered (TiAlSiY)N/CrN coating and referred to the loss of clear interfaces and the formation of transition layers due to the diffusion of Ti atoms. Nano-multilayered (TiAlSiY)N/ZrN system showed the formation of stoichiometric fcc compounds of TiN with (200) plane and ZrN with (111) plane, respectively. The evaluation of mechanical properties by nanohardness, reduced elastic modulus, elastic strain prior to failure, and resistance to plastic deformation measurements was performed. The presented results showed important information about the physical and mechanical properties of new nano-multilayered systems for their subsequent application, as well as improvement of existing achievements.

    更新日期:2018-07-12
  • Facile constructing novel 3D porous g-C3N4/BiOBr0.2I0.8 hybrids: Efficient charge separation for visible-light photocatalysis
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Yibing Feng, Yi Du, Minxing Du, Zhongfu Li, Zuoli He, Kai Yang, Xingjie Lv, Nan Jiang, Yang Liu

    In this work, we reported a novel three-dimensional (3D) visible-light-driven hybrid photocatalyst synthesized via a facile hydrothermal process, which consists of two different 2D materials: g-C3N4 and BiOBr0.2I0.8. The physicochemical properties of the as-synthesized 3D hybrid photocatalyst were fully characterized using Electron spin resonance, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy and UV–Vis diffuse reflectance spectrometry. The 10CN/BiOBr0.2I0.8 composite exhibits the best performance in visible-light-driven photocatalytic degradation of RhB among prepared samples. In such hybrid systems, electrons generated in g-C3N4 transfer to BiOBr0.2I0.8, while photo-generated holes on BiOBr0.2I0.8 transfer to g-C3N4, which enhances the charge separation through the heterojunction interface. The hole left on the valence band of g-C3N4 is the most efficient active species in the degradation process of RhB, therefore, heterojuncted BiOBr0.2I0.8 need better control for keeping some active sites on g-C3N4. In addition, the photodegradation efficiency of RhB still remains over 98% after six consecutive cycles, which indicates the good stability of such 3D g-C3N4/BiOBr0.2I0.8 hybrid photocatalysts.

    更新日期:2018-07-12
  • 15-mode piezoelectric composite and its application in a magnetoelectric laminate structure
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Il-Ryeol Yoo, Cheol-Woo Ahn, Kyung-Hoon Cho

    Magnetoelectric composites have recently been attracting attention owing to their possible application in various advanced electronics. The piezoelectric material used in a magnetoelectric composite is an important determinant of the electrical performance of the device. In this study, we report on the fundamental characteristics and magnetoelectric application of a 15-mode piezoelectric composite. The centimeter-scale 15-mode piezoelectric composite implemented by a novel fabrication process exhibits successful 15-mode operation along with excellent piezoelectric properties d15 = 793 × 10−12 C N−1, g15 = 32 × 10−3 V m N−1, k15 = 0.62, and d15·g15 = 25376 × 10−15 m2 N−1. Magnetostrictive-piezoelectric laminate structures designed to generate shear stress were fabricated using the 15-mode piezoelectric composites, and their magnetoelectric characteristics were investigated systematically. A giant magnetoelectric voltage coefficient of 18.4 V cm−1 Oe−1 was obtained at a low frequency of 660 Hz from the laminate, indicating the potential of the 15-mode piezoelectric composite for application in high-performance magnetoelectric devices.

    更新日期:2018-07-12
  • Improved structural homogeneity and mechanical properties of nanoparticles reinforced Al composites after orthogonal thermomechanical processes
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Jun Liu, Zhe Chen, Fengguo Zhang, Gang Ji, Yu Ma, Mingliang Wang, Shengyi Zhong, Jian Li, Hong Wang, Haowei Wang

    Orthogonal thermomechanical processes consisting of a hot extrusion and the subsequent orthogonal rolling are proposed to disperse the nanoparticle clusters and optimize the grain structures of matrices in in-situ synthesized TiB2 particles reinforced Al-Zn-Mg-Cu composites. The particle distributions and grain structures of composites are investigated by scanning electron microscopy, electron backscatter diffraction and neutron diffraction techniques. Compared with the hot extruded counterparts, the composites fabricated by the new process exhibit uniform particle distributions, less elongated grains and weak textures, owing to the strain path change and enhanced recrystallizations. Both high strength (669 MPa and 606 MPa) and good ductility (11.1% and 14.2%), are achieved in the resultant composites along the longitudinal and transverse direction respectively. The underlying mechanisms for modified mechanical properties are discussed in detail from the perspectives of the uniform TiB2 particles and improved structural homogeneity.

    更新日期:2018-07-12
  • An atomic mechanism for the formation of nanotwins in high carbon martensite
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Yulin Chen, Dehai Ping, Yunzhi Wang, Xinqing Zhao

    High carbon martensite possesses outstanding hardness and strength but poor ductility, even though it consists of numerous twins which have been regarded as the favorable structure for deformation in metals and alloys. So far, the role of high density of twins in the conflict, fully twined structure and poor ductility, in high carbon martensite is not clear. In this letter, we proposed an atomic mechanism for the formation of nanotwins to reveal the nature of poor ductility of high carbon martensite. This mechanism suggests that interstitial carbon atoms stabilize ω phase which facilitates the nucleation and termination of {112} 〈<111〉> type nanotwins in high carbon martensite. The nanoscale ω particles embedded in boundaries of nanotwins pins naonotwins, impeding the motion of twins in the martensite. This mechanism constructs a correlation between the nanotwins and poor ductility of martensite in high carbon steels.

    更新日期:2018-07-12
  • Enhanced electromagnetic properties of carbon nanotubes and SiO2-coated carbonyl iron microwave absorber
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-10
    Chaoqun Ge, Liuying Wang, Gu Liu, Tao Wang

    The carbon nanotubes/SiO2-coated carbonyl iron (CNTs/CI@SiO2) composites were fabricated as microwave absorption materials (MAMs) by a simple mechanical mixing method for the purpose of the MAMs with lightweight, thin thickness, broad bandwidth and high oxidation resistance. The effects of different concentration of CNTs on the electromagnetic properties of the CNTs/CI@SiO2 composites were investigated. The results indicate that the complex permeability does not change obviously with the increasing concentration of CNTs because of the constant concentration of CI@SiO2 in the composites. While the complex permittivity and attenuation constant increase with the increasing concentration of CNTs, and the impedance matching ratio decreases with the increasing concentration of CNTs. The reflection loss (RL) calculation results show that 2 wt% CNTs mixed with 65 wt% CI@SiO2 has the optimum microwave absorption properties. The minimum RL is −51.54 dB at 15.44 GHz with a matching thickness of 1.41 mm. The bandwidth corresponding to the RL below −10 dB is more than 6.08 GHz with a thickness of 1.5 mm. The enhanced microwave attenuation ability, improved impedance matching in air-absorber interface and the quarter-wavelength cancellation are believed to contribute the excellent microwave absorption properties of the CNTs/CI@SiO2 composites.

    更新日期:2018-07-12
  • Ultrathin ReS2 nanosheets growing on ordered microporous carbon for high capacity lithium ion batteries
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Huijun Wang, Xia Yang, Yaqin Chai, Sheng Liu, Ruo Yuan

    To improve the Li storage capability of rhenium disulfide (ReS2) as anode materials for lithium ion batteries (LIBs), the ReS2@CMK-3 composites were designed and prepared by using CMK-3 as a nanoreactor. The ReS2@CMK-3 composites possessed a special nanosheets-on-channel architecture that the ultrathin ReS2 nanosheets grown on the channel of CMK-3. Owing to the large surface area, ordered mesoporous structure and excellent electronic conductivity, the ReS2@CMK-3 composites exhibited larger discharge capacity, superior cycling performance and higher rate performance compared with pristine ReS2 when they were applied as anode materials for LIBs. As a result, the ReS2@CMK-3 composites delivered a reversible capacity of 620 mAh g−1 after 200 cycles at 0.5 A g−1, indicating their potential as promising anode materials for LIBs.

    更新日期:2018-07-12
  • Structure and spectroscopic properties of Tb3+/Sm3+ co-doped oxyfluoride glass ceramics containing LiYF4 nanocrystals
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Bin Zheng, Hui Cao, Jianxu Hu, Zhaofeng Gu, Yuepin Zhang

    In this paper, transparent oxyfluoride glass ceramics containing LiYF4 nanocrystals were successfully synthesized by appropriate heat-treatment on the SiO2-Al2O3-YF3-LiF precursor glass. The average diameter of the LiYF4 nanocrystals is about 16 nm, which has been confirmed by XRD and TEM characterization. Compared with RE3+ (RE = Tb, Sm)-doped glasses, glass ceramics have shown stronger emission intensities due to most rare earth ions have entered LiYF4 nanocrystals with lower phonon energy. A combination of blue, green and orange-red emissions has emerged in Tb3+/Sm3+ co-doped glass ceramics, and white light emission could be realized by varying the proportions of Tb3+ and Sm3+ under UV light excitation. Furthermore, the concentration quenching effect and the Tb3+→Sm3+ energy transfer process were investigated in this paper. Our results indicate that the Tb3+/Sm3+ co-doped oxyfluoride glass-ceramics containing LiYF4 nanocrystals show great potential to achieve a white light emission.

    更新日期:2018-07-12
  • Tunable emission with excellent thermal stability in single-phased SrY2O4:Bi3+,Eu3+ phosphors for UV-LEDs
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Rongfei Wei, Zhigang Zheng, Yafei Shi, Xiusha Peng, Hui Wang, Xiangling Tian, Fangfang Hu, Hai Guo

    Novel single-phased phosphors SrY2O4:Bi3+,Eu3+ (SYO:Bi3+,Eu3+) with tunable emitting were successfully synthesized by the conventional solid-state method. X-ray diffraction, excitation and emission spectra, decay curves as well as temperature-dependent luminescence were applied to characterize the as-obtained phosphors. Under ultraviolet (UV) excitation, blue luminescence centered at 410 nm was found in SYO:Bi3+. By introducing Eu3+ into SYO:Bi3+, highly efficient energy transfer (ET) process with ET efficiency of 92.65% from Bi3+ to Eu3+ was obtained before concentration quenching. The possible ET mechanism from Bi3+ to Eu3+ were investigated systematically. By altering Eu3+ content, tunable emission from blue to red was realized. More importantly, investigation of the thermal stability showed that over 98% of the room-temperature emission intensity was still preserved at 155 °C, which is superior to that of most recently reported Bi3+,Eu3+ co-doped phosphors. These results indicate that this kind of easy fabrication, low-cost and highly stable SYO:Bi3+,Eu3+ are potential candidates for blue-red phosphors for application in UV chip based w-LEDs.

    更新日期:2018-07-12
  • Martensitic transformation in ordering-treated Fe74Ga26 alloy
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Xiaolian Liu, Junming Gou, Changsheng Zhang, Baixing Peng, Tianyu Ma, Xiaobing Ren

    Peak magnetostriction of Fe100-xGax with x around 27 has been attributed to shear modulus softening, analogues to the scenario for a martensitic transformation. Recently, stress-induced local six-layer modulated monoclinic (6 M) martensites have been investigated in Fe-Ga alloy. To identify the spontaneous martensitic transformation behavior, here we performed a comparative study of a Fe74Ga26 alloy with lower D03 ordering degree at the quenched state and with higher D03 ordering degree after subsequent long-term aging. In comparison with the quenched state that bears no martensites, the aged one undergoes spontaneous martensitic transformation upon cooling, and local 6 M martensites are observed after heating from liquid nitrogen temperature to room temperature. It is found that both the ordering degree and the structural stability of D03 phase are significantly improved after long-term aging, which makes the temperature-induced martensites visible. The present finding verifies that martensitic transformation is a universal phenomenon in the magnetostrictive Fe-Ga alloy.

    更新日期:2018-07-12
  • The best addition of graphene to LiMn0.7Fe0.3PO4/C cathode material synthesized by wet ball milling combined with spray drying method
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Liwei An, Hao Liu, Yuanyuan Liu, Zhenfei Li, Xin Ren, Liang Guangchuan

    LiMnxFe1-xPO4 with high electronic conductivity is synthesized by a combination of wet ball milling, spray drying, carbon thermal reduction technology and using graphene oxide (denoted as GO) as the carbon additive. The effect of graphene content on morphology and structure of LiMn0.7Fe0.3PO4/C cathode material is systematically investigated. The graphene-LiMn0.7Fe0.3PO4 composite has ordered olivine structure and micro-spherical morphology assembles with nanosized primary particles. SEM and TEM images indicate that the particle size of LiMn0.7Fe0.3PO4-G2 is about 800 nm in diameter. The initial discharge capacity of LiMn0.7Fe0.3PO4-G2 nanoparticles is 153 mAh·g−1. It shows that graphene oxide can restrict the growth of LiMn0.7Fe0.3PO4 and improve the electrical conductivity. Through adding different amount of graphene, we get the best addition of graphene. The LiMn0.7Fe0.3PO4-G2 sample has a core-shell structure, not only does the surface of nanoparticles have a homogeneous and complete carbon coating but also exhibits a microspherical morphology. What ’s more the surface of microspheres is fully covered with GO sheets, which enhances electronic conductivity. All above mention factors lead to its excellent electrochemical performance at room temperature and low temperature.

    更新日期:2018-07-12
  • Three-dimensional microflowers assembled by carbon-encapsulated-SnS nanosheets for superior Li-ion storage performance
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Jian-Gan Wang, Huanhuan Sun, Rui Zhao, Xiaozhi Zhang, Huanyan Liu, Chunguang Wei

    SnS-based materials show great potential as high-capacity anode candidates of Li-ion batteries owing to their dual-mechanisms of conversion and alloying reactions. However, the practical application is substantially hampered by its poor electrochemical utilization and stability. Herein, we demonstrate three-dimensional SnS/C microflowers prepared by a controllable self-polymerization and carbonization of polydopamine-coated SnS2 precursors. The building nanosheet consists of uniform encapsulation of ultrafine SnS nanoparticles into the conductive carbon framework. Benefiting from the nanoscaled building blocks and the porous three-dimensional architecture, the carbon-encapsulated nano-SnS microflowers show a significant enhancement in the electrochemical reaction kinetics and durability. As a result, the hybrid exhibits a high specific capacity of ∼1000 mAh g−1 at 0.1 A g−1 with a high initial Coulombic efficiency of 84.2%, good rate capability, and stable cyclability. The present work provides a reliable strategy for the rational fabrication of carbon-encapsulated SnS composites for high-performance Li-ion batteries.

    更新日期:2018-07-12
  • Role of Gd-doping in conduction mechanism of BFO-PZO nanocrystalline composites: Experimental and first-principles studies
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Ambika Ray, Tanmoy Basu, Banarji Behera, Mathan Kumar, Ranjit Thapa, Pratibindhya Nayak

    In this paper, in the conduction behaviour of Gd-doped 0.4BiGdxFe(1-x)O3–0.6PbZrO3 (BFO-PZO) with x = 0.0, 0.05, 0.10, 0.15, 0.20 composites, synthesized by solid-state reaction (mixed oxide) technique, was investigated. X-ray diffraction study with Rietveld refinement method revealed the formation of rhombohedral (R3c) phase. Dielectric constant and dielectric loss studies as a function of frequency reveal dispersion due to Maxwell-Wagner type of interfacial polarization while weak ferroelectric hysteresis loops have been recorded for all the samples. Complex impedance spectroscopy technique-based impedance, electrical modulus, and electrical conductivity of the composites revealed non-Debye type relaxation mechanism. Correlated barrier hopping (CBH) mechanism dominates in all the composites exhibiting high value of density of states (1023 eV−1 cm−1) which increased further after doping with Gd. It was seen that doping of Gd affects the activation energy of these composites which was complemented by performing density functional theory calculations. Bader charge calculation was performed to understand the chemical environment and charge transfer upon doping. In addition, a small change in the bandgap was found which may cause the change in activation energy.

    更新日期:2018-07-12
  • Enhanced performance of LiFePO4 originating from the synergistic effect of graphene modification and carbon coating
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Guodong Jiang, Zhihai Hu, Jian Xiong, Xing Zhu, Songdong Yuan

    LiFePO4@Carbon/reduced graphene oxide (LFP@C/rGO) composites as cathode materials for lithium-ion batteries were prepared by a simple solvothermal method followed with a carbon coating. The characterizations indicated that LiFePO4 particles with pure orthorhombic olivine phase were attached to graphene oxide, which could be reduced in the synthesis of LiFePO4 and constructed a conductive network in the composite. After a post carbon encapsulation, a uniform and thin carbon layer on LiFePO4 was formed and could quickly collect electrons via a shorter pathway around LiFePO4 nanoparticles during the charge/discharge. The results showed LFP@C/rGO composites delivered a discharge specific capacity of 148.3 mAh/g at the rate of 1 C, higher than LiFePO4 only modified with graphene or coated with carbon layers. The discharge capacity of 129 mAh/g can still be maintained when the current density increased to 20 C. Furthermore, LFP@C/rGO manifested a satisfactory lifespan and no capacity fading was observed after 200 cycles at the rate of 10 C. Compared with synthesized LiFePO4@C, LFP@C/rGO composites also exhibited a high capacity of 108 mAh/g at −20 °C at a rate of 1 C. Even after 500 charge/discharge cycles, capacity fading was scarcely seen. Electrochemical tests suggested the unique architecture resulted in a synergistic effect between 3D reduced graphene oxide (rGO) conductive network and carbon coating, which remarkably improved the conductivity of electrode and electrochemical kinetics, contributing to outstanding rate performance and cycle life.

    更新日期:2018-07-12
  • Analysis of flow softening during hot deformation of Ti-17 alloy with the lamellar structure
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Jianwei Xu, Weidong Zeng, Dadi Zhou, Haoyuan Ma, Shengtong He, Wei Chen

    Flow softening of Ti-17 alloy with the lamellar structure during hot deformation is investigated in this work. For this purpose, hot compression tests are conducted with strain rate of 0.001–10 s−1 at 780–860 °C. The experimental results are analyzed through theoretical calculation and microstructure observation (SEM, TEM and EBSD). Flow softening extent of Ti-17 alloy increases with the decreasing temperature and increasing strain rate. The softening behavior can be explained by the two aspects: deformation heating and microstructure changes. Deformation heating effect is caused by temperature rise, which is more serious at higher strain rate. Microstructure changes include the bending, kinking, rotation and separation of the lamellar alpha, which can be defined as the pan-globularization of alpha phase. In addition, the EBSD observations indicate that the continuous dynamic recrystallization occurs in beta phase. Microstructure changes of alpha and beta phases influence together flow softening behavior. Specifically, the pan-globularization of alpha phase and continuous dynamic recrystallization of beta phase result in flow softening of Ti-17 alloy.

    更新日期:2018-07-12
  • Pyranine functionalized Fe3O4 nanoparticles for the sensitive fluorescence detection of Cu2+ ions
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Muhammad Tariq Shah, Esra Alveroglu, Aamna Balouch

    In this study, a sensitive fluorescence sensor was synthesized for the detection of Cu2+ ions based on the quenching of fluorophore. The sensor is composed of pyranine functionalized amino silane shell modified magnetite (Fe3O4) core nanostructures. The synthesized nanomaterials were characterized by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Powder Diffraction (XRD), Vibrating Sample Magnetometer (VSM) and Transmission Electron Microscopy (TEM). The fluorescent magnetic nanoparticles were analyzed by fluorescence spectroscopy. The characterization data showed that the magnetic core was highly superparamagnetic with an average particles diameter up to 10 nm. The fluorescence response of Fe3O4@-SiO2-NH2-Pyr nanosensor towards Cu2+ ions showed an enhanced and selective fluorescence quenching. Pyranine functionalized magnetic nanoparticles were found to be highly selective for Cu2+ ions without giving any response to other interfering cations and biomolecules. The nanosensor not only provided a sensitive (LOD = 6 nM), fast and selective detection of Cu2+ ions but a new fluorescent and biocompatible material with potential uses in biological and environmental fields.

    更新日期:2018-07-12
  • Non-isothermal oxide bond phase formation kinetics of SiC powder coated with yttrium aluminum garnet (YAG) sol
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Sanchita Baitalik, Atiar Rahaman Molla, Nijhuma Kayal

    SiC powders (d50 = 6.25 μm) were coated with YAG by co-precipitation method and the coated powders were characterized by surface area, surface potential measurement, FTIR spectroscopy, XRD and thermal analysis. Non-isothermal kinetic data of two exothermic peaks in the temperature range 1200–1450 °C were evaluated by isoconversional methods using Netzsch Thermokinetics software module. The best fitting was obtained with second order reaction (F2) model for the peak I (1207–1359 °C) and Avrami-Erofeev (An) nucleation model for the peak-II (1324–1450 °C). The activation energy was determined as 605.57 kJ/mol and 1041 kJ/mol for peaks I and II respectively. Oxide bonded porous SiC ceramics fabricated at 1450 °C using YAG coated SiC powders exhibited flexural strength of ∼26.1 MPa at porosity level of ∼38.6 vol %. The corrosion results of ceramic sample after 10 days in strong acid solution revealed 6.5 wt % mass loss and 80% reduction of flexural strength.

    更新日期:2018-07-12
  • Corrosion behavior of extremely hard Al-Cu/Mg-SiC light metal alloy composites
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Sivakumar S, Sravan Kumar Thimmappa, Brahma Raju Golla

    In this study, hot-pressing technique was used to produce Al-5wt.% Cu-20 vol.% SiC and Al-5wt.% Mg-20 vol.% SiC particulate metal matrix composites. The powders were ball milled and the powder mixtures were hot pressed uniaxially under a pressure of 550 MPa at a temperature of 450 °C in vacuum atmosphere for different holding times of 30, 60 and 120 min. A common observation was that the density of Al composites decreased slightly with increasing hot press sintering time. The Al-5wt.% Cu-20 vol.% SiC samples exhibited maximum density of ∼95.7% ρth (theoretical density) and Al-5wt.% Mg-20 vol.% SiC composite was measured with maximum density of ∼97.8 ρth after hot pressing for 30 min. The XRD and SEM characterization confirms presence of Al, SiC and CuAl2 phases for Al-Cu-SiC. Whereas the microstructure of Al-Mg-SiC composite consists of Al0.95Mg0.05 solid solution phase along with SiC phase. Among all the compositions, a maximum hardness of 3.2 GPa was noted for the Al composites, which were hot pressed at 60 min. A comparison with the existing literature reveals the presently developed Al alloy composites exhibited superior hardness. Corrosion tests were carried out using potentiodynamic polarization and electrochemical impedance spectroscopy to study the corrosion behavior of both these hard composites in marine environment (3.5wt.% NaCl) at room temperature. The corrosion rate of the samples varied between 1.8 and 2.7 mpy (mils per year), particularly, Al-5wt.% Cu-20 vol.% SiC composite showed better corrosion resistance. Further impedance spectroscopy analysis revealed that Al-Cu-SiC has relatively larger semi-circular diameter when compared to Al-Mg-SiC. These observations indicate that Al-Cu-SiC exhibits high polarization resistance than Al-Mg-SiC composite.

    更新日期:2018-07-12
  • The effect of manganese additions on the high temperature oxidation behavior of the high-vanadium cast iron
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Pinghu Chen, Zhilin Liu, Ruiqing Li, Xiaoqian Li

    Manganese (Mn) addition was found to remarkably relieve the weight gain of the wear-resistant high vanadium cast iron during oxidation at 950 °C. The mechanism of such oxidation behaviour in the associated cast iron was investigated through adding different Mn contents. During oxidation process, the decrease in weight gain was sensitive to Mn addition, where the smallest weight gain corresponded to an optimal content of 3.0 wt.% Mn. Meanwhile, the degree of macrocracks was closely dependent on Mn contents. Using FIB-TEM site-specific sample preparation technique, an initial Cr2O3 layer with a thickness of 50–200 nm was identified between the matrix cast iron and the post layer of other oxidation products. In addition, Mn additions promoted to refine the precipitating V4C3 particles that uniformly distributed in the matrix cast iron. The relationship between Mn and cracking was then analysed subsequently. Based on oxidation tests and microstructural characterization, the kinetic mechanism of oxidation behaviour of the high-vanadium cast iron at high temperature was then proposed.

    更新日期:2018-07-12
  • Lysine assisted hydrothermal synthesis and formation process of MoO3:Sm3+ phosphors with hierarchical structures and its electron trapping luminescence properties
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    H.S. Yogananda, R.B. Basavaraj, Ramachandra Naik, G.P. Darshan, S.C. Sharma, Daruka Prasad, H. Nagabhushana

    We report the synthesis of Sm3+ doped MoO3 nanostructures (NSs) effectively by hydrothermal route using lysine as surfactant. The hexagonal and orthorhombic phases were confirmed by means of Powder X-ray diffraction (PXRD) results. The effect of hydrothermal reactions, such as reaction temperature, surfactant concentration, pH value on the morphology was studied in detail by utilizing scanning electron microscopy (SEM) results. Optical properties of the Sm3+ (1–9 mol %) doped MoO3 were studied by means of diffuse reflectance spectroscopy (DRS). The 4f-4f emission bands of Sm3+ ions were observed at 563, 610, 647 and 698 nm attributed to 4G5/2–6HJ (J = 5/2, 7/2, 9/2, 11/2) of Sm3+ respectively under 405 nm (6H5/2 → 4F5/2 + 4M7/2) excitation. Judd–Ofelt theory was utilized to calculate the, transition probabilities (AT), radiative lifetime (τrad), branching ratio (β), and asymmetric ratio (A21) by using the intensity parameters. The average quantum efficiency and color purity values of the prepared samples were found to be ∼79.61% and 97% respectively. The CIE color coordinates confirmed that the phosphor emits orange-red light, which were quite useful for the fabrication of white light emitting diodes.

    更新日期:2018-07-12
  • Hierarchical mesoporous Li2FeSiO4/C sheaf-rods as a high-performance lithium-ion battery cathode
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Qingtang Zhang, Chao Yan, Yan Meng, Xiaomei Wang

    Hierarchical mesoporous Li2FeSiO4/C sheaf-rods (HMLFS-SRs) were fabricated using a hard template method with SBA-15 as a silicon source. For comparsion, Li2FeSiO4/C nanocomposites (LFS) were prepared using nano-SiO2 under the same conditions. XRD results prove that both the HMLFS-SRs and LFS contain crystalline Li2FeSiO4 and trace amounts of Fe3O4 impurities. The SEM and TEM images indicate that the HMLFS-SRs are hierarchical sheaf rods composed of nanoparticles. EDS data prove that elemental Fe, Si, O and C are uniformly distributed throughout the whole Li2FeSiO4/C sheaf rod. Nitrogen adsorption/desorption analyses further indicate that the HMLFS-SRs are typical mesoporous materials with an external surface area of 47 m2 g−1, which is higher than that of the LFS (31 m2 g−1). These unique structures enable the HMLFS-SRs to exhibit much better electrochemical performance than the LFS. The HMLFS-SRs deliver a high discharge capacity of 206.6 mAh g−1 at 0.1 C. In addition, the HMLFS-SRs also have good cycling performance, satisfactory rate performance, a low charge transfer resistance and a large lithium-ion diffusion coefficient.

    更新日期:2018-07-12
  • Crystal structure of as-cast and heat-treated Ti0.5Zr0.5(Mn1-xFex)Cr1, x=0, 0.2, 0.4
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Sakine Khajavi, Mohammad Rajabi, Jacques Huot

    The crystal structure of AB2 metal hydride alloys of composition Ti0.5Zr0.5(Mn1-xFex)Cr1, x = 0, 0.2, 0.4 in the as-cast state and after heat treatment has been investigated. Based on SEM and X-ray diffraction results, all alloys were found to be multiphase. The best fitting of Rietveld refinement shows that the two main phases of each alloy have the same hexagonal structure with closely related lattice parameters and chemical composition. There is also some evidence that the microstrain values determined by Rietveld refinements are in fact an expression of composition variation within the phase and not a pure microstrain.

    更新日期:2018-07-12
  • Superparamagnetism in CoFe2O4 nanoparticles: An example of a collective magnetic behavior dependent on the medium
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    M. Virumbrales, V. Blanco-Gutierrez, A. Delgado-Cabello, R. Sáez-Puche, M.J. Torralvo

    Cobalt ferrite particles with homogeneous microstructure have been prepared encased in MCM (Mobil Composition Matter) and SBA (Santa Barbara Amorphous) silica mesoporous structures. In addition, it was possible to obtain ferrite nanowires once the silica matrix was dissolved. The variety of samples prepared has allowed to deeply analyze the matrix effect in the magnetic behavior of these particles that behave as superparamagnetic at room temperature. It was found at 5 K, a drastic magnetic hardening of the encased ferrite particles due to the employment of such matrices, while no matrix effect was observed at 250 K.

    更新日期:2018-07-12
  • Magnetic and Mössbauer investigations of soft Co2Z-type hexa nanoferrites
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Anita Manhas, Khalid M. Batoo, M. Singh

    Co2Z-type hexa nanoferrites of the series Ba3-XSrXCo2Fe24O41 (where x = 0, 0.5, 1.0, 1.5 and 2.0) are synthesized by sol-gel auto combustion method. The effects of Sr2+ substitution for Ba2+ and optimized synthesis conditions are reported using the structural, magnetic and Mössbauer study. The X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM) along with the selected area electron diffraction (SAED) clearly indicate the formation of a single-phased Z-type hexagonal nanoferrites with P63/mmc space group. The hysteresis curves obtained by vibrating sample magnetometer (VSM) at room temperature displayed the typical characteristics of magnetically soft materials indicating the decrease in coercivity with the increase in Sr2+ concentration in synthesized hexa nanoferrites, which are validated by the room temperature Mössbauer spectra with least-squares fit sextets of six distinguishable sites (A: 4fIV, B: 4fIV*, C: 12kVI*, D: 4fVI* + 4eIV, E: 12kVI and F: 2dV + 2aVI + 4fVI + 4eVI). Selection of Sr2+ dopant and sol-gel auto combustion soft chemical route are the leading ways to control the coercivity of Co2Z-type hexa nanoferrites.

    更新日期:2018-07-12
  • Synthesis and properties of 1D manganese-doped hematite particles
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-11
    Mira Ristić, Ernö Kuzmann, Zoltán Homonnay, Svetozar Musić

    The properties of Mn-doped hematites and their Mn-doped precursors were investigated using the 57Fe Mössbauer spectroscopy, XRD, FT-IR, UV/Vis/NIR and FE SEM. Mn-doped goethite precursors were synthesized in a high alkaline pH medium starting with iron choline citrate. The XRD analysis of all Mn-doped goethites and Mn-doped hematites showed only the presence of a goethite or hematite crystal structure. The RT Mössbauer spectrum of reference goethite showed typical features of precipitated goethite. With increased Mn-doping the spectral lines of the goethite precursor were broadening, the hyperfine magnetic field decreased and the relative intensity of central quadrupole doublets increased. The RT Mössbauer spectra of Mn-doped hematite showed features of the hematite phase and increased relative intensity of a central quadrupole doublet which disappeared in the spectra recorded at liquid N2 temperature. The presence of this superparamagnetic component in the RT Mössbauer spectra is a direct consequence of Mn-doping. In the FT-IR spectra the characteristic IR bands sensitive to Mn-doping were identified. The UV/Vis/NIR spectra showed shifts of optical absorption bands and a strong absorption increase in the visible part of the spectrum. FE SEM images of Mn-doped goethite precursor showed a change in shape from rod to star-like particles. Upon heating at 300 °C for 4 h in air, the obtained Mn-doped hematite particles preserved the original morphologies of Mn-doped goethite precursors. Taking into account the superparamagnetic spectra (RT and liquid N2 temperature), XRD and the corresponding FE SEM images of Mn-doped hematite particles it can be concluded that these particles contained substructure. In this substructure of Mn-doped hematites the fraction of superparamagnetic crystallites (domains) is given by calculated value for the superparamagnetic doublet present.

    更新日期:2018-07-12
  • Colossal permittivity and defect-dipoles contribution for Ho0.02Sr0.97TiO3 ceramics
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Xiaohua Zhang, Jie Zhang, Yuanyuan Zhou, Zhenxing Yue, Longtu Li

    High-performance dielectric materials arouse persistently considerable attention due to their potential in the field of solid state capacitors. Ho-doped SrTiO3 ceramics with the composition of Ho0.02Sr0.97TiO3 were prepared by the solid state reaction technique. Structure, colossal dielectric behavior and relaxation mechanism of Ho0.02Sr0.97TiO3 ceramics were investigated in detail. The results indicated that Ho substitution of 0.02 content into the host materials maintain a single cubic perovskite structure. The Ho0.02Sr0.97TiO3 ceramics sintered at high temperature (1350 °C) show colossal permittivity (up to 4908 at 10 kHz) with low dielectric loss (about 0.03) at room temperature, and good dielectric stability over a broad frequency range of 100 Hz - 100 kHz as well. Four kinds of dielectric relaxations are present in a broad temperature range from -140 to +350 °C. Thermally stimulated depolarization current (TSDC) measurements were performed to explore the defects associated relaxation process. Four polarization relaxation peaks were detected in Ho0.02Sr0.97TiO3 ceramics, and three of them were assigned to defect dipole relaxations. There seems a possibility to form some defect dipoles because of the interactions among the defects available such as Sr vacancies, Ti3+, (HoSr)•, ionized oxygen vacancies and localized electrons. These defect clusters would give rise to relaxation behaviors and thus contribute to the colossal dielectric characteristics.

    更新日期:2018-07-12
  • Thermal-stable void-free interface morphology and bonding mechanism of low-temperature Cu-Cu bonding using Ag nanostructure as intermediate
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Ziyu Liu, Jian Cai, Qian Wang, Zheyao Wang, Lei Liu, Guisheng Zou

    To lower the bonding temperature and save the time of the Cu-Cu bonding technique applied for 3D integration, Ag nanostructure was deposited on the Cu pads as intermediate by femtosecond pulsed laser deposition (PLD). The interface morphology after bonding including oxidation detection and microstructure evolution during high-temperature storage was investigated. The underlying bonding mechanisms were then analyzed and concluded. The element distribution of Ag nanostructures after PLD deposition is detected using the scanning transmission electron microscope equipped with energy dispersive X-ray spectroscopy mapping, and no oxygen is found inside the nanostructures. The electron energy loss spectroscopy shows that no oxidation happens across the Cu-Ag-Cu bonding interfaces during the bonding process by observing the same chemical state of Ag and Cu as the pure metal atom. The as-bonded Cu-Ag-Cu samples were stored at the temperature of 200 °C for 500 h and the microstructure at the bonding interface were observed. Based on the interface microstructure and crystal structure, the physical mechanisms of Cu-Cu bonding using Ag nanostructure as intermediate was explored and summarized in detail. The mechanical interlock between Ag nanostructures, large plastic deformation, surface melting and bulk diffusion are found to simultaneously contribute to the bonding.

    更新日期:2018-07-12
  • Self-powered ultraviolet photodetection realized by GaN/Si nanoheterostructure based on silicon nanoporous pillar array
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Xue-Xia Chen, Xu-Hua Xiao, Zhi-Feng Shi, Rui Du, Xin-Jian Li

    Using silicon nanoporous pillar array (Si-NPA) as substrate, a kind of GaN/Si nanoheterostructure (GaN/Si-NPA) is prepared by depositing GaN nanocrystallites on Si-NPA with chemical vapor deposition method. The morphology characteristics and optical properties of GaN/Si-NPA are investigated systematacially. Based on GaN/Si-NPA, a self-powered ultraviolet (UV) photodetector (PD) with device structure of ITO/GaN/Si-NPA/sc-Si/Ag is constructed by depositing ITO on GaN layer and silver on single crystal silicon, respectively. At zero bias voltage without an external power supply, GaN/Si-NPA exhibits a responsivity of 0.072 mA/W, a high current on/off ratio of ∼104 (16 μW/cm2) and fast response speeds of 39.98/40.10 ms under an UV light irradiation at 305 nm. The high performance of GaN/Si-NPA is attributed to the built-in electric field in the heterojunction, which is interpreted via building the energy-band diagrams. The results illustrate that GaN/Si-NPA might be a suitable material system for self-powered UV PDs.

    更新日期:2018-07-12
  • Manufacturing of high strength aluminium composites reinforced with nano tungsten particles for electrical application and investigation on in-situ reaction during processing
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Saurabh Dixit, Sanjay Kashyap, Satish V. Kailas, K. Chattopadyay

    The improvement of strength without compromising the conductivity remains a major issue in developing superior aluminium conductors. This could be addressed by dispersion of nano-sized high melting point elements such as tungsten which has limited solid-solubility in the aluminium matrix. The composites fabricated in this study shows 1.3 times improvement in yield strength, and 2 times increase in UTS. The composites also exhibit superior electrical conductivity compared to other aluminium alloys. Solid-state processing technique was adopted for composite fabrication to avoid thermally activated reaction, between matrix and particles. An unexpected result was the observation of mechanical energy induced interface reaction between aluminum and tungsten during the processing which was not expected at the low processing temperatures. This was confirmed by detailed TEM examination that probed the formation and structure of this new phase. These findings open up newer possibilities toward efficient and scalable manufacturing of high conductive composites with improved strength.

    更新日期:2018-07-12
  • Improved structural stability, electron transport and defect formation in PrBaCo2–xAlxO6–δ
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    S.N. Marshenya, B.V. Politov, A. Yu Suntsov, I.A. Leonidov, S.A. Petrova, M.V. Patrakeev, V.L. Kozhevnikov

    The double perovskite-like solid solutions PrBaCo2–xAlxO6–δ are obtained via combustion of glycerol-nitrate organo-metallic precursors. The aluminum doping occurs favorable for mitigation of thermal expansion and stabilization of the tetragonal structure in a wide range of temperature changes. The variations of equilibrium oxygen content in PrBaCo1.9Al0.1O6–δ are measured with a coulometric titration technique, and analyzed in terms of defect chemistry. It is shown that aluminum incorporation is accompanied by formation of rigid AlO6 octahedra in the crystal structure and enhanced disproportionation of Co3+ cations. The developed defect model is successfully applied in order to explain the data for conductivity and thermopower. The structural stability, moderate thermal expansion and high conductivity represent an advantageous properties combination for the using of PrBaCo1.9Al0.1O6–δ cobaltite in various high-temperature solid state electrochemical devices.

    更新日期:2018-07-12
  • Effect of solution heat treatment on the microstructure and mechanical properties of Inconel 625 superalloy fabricated by laser solid forming
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Y.L. Hu, X. Lin, S.Y. Zhang, Y.M. Jiang, X.F. Lu, H.O. Yang, W.D. Huang

    In this study, the effect of solution heat treatments on the microstructure and mechanical properties of Inconel 625 superalloy fabricated by laser solid forming was investigated. The microstructure of deposit was mainly composed of columnar grains, which didn't change until the solution temperature reached 1200 °C after solution heat treatment. Due to the large size Laves phase which can pin grain boundary and obstruct grain boundary migration, the recrystallization fully occurred when the solution temperature exceeded 1200 °C. With the increment of the solution temperature, the average diffusion coefficient of solute elements and the dissolution velocity increased obviously. Besides, the volume fraction and size of Laves phase decreased, and the dislocation density decreased apparently. As a result, the microhardness and yield strength decreased with the increment of the solution temperature, but the tensile strength didn't change much after solution heat treatment, and the elongation increased significiantly with the solution temperature improving. The room-temperature tensile properties in different states of Inconel 625 fabricated by laser solid forming were higher than those of Inconel 625 fabricated by casting.

    更新日期:2018-07-12
  • Thermodynamic assessment of the Fe-Te system. Part II: Thermodynamic modelling
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    C.-M. Arvhult, C. Guéneau, S. Gossé, M. Selleby

    A thermodynamic description of the Fe-Te system modeled via the Calphad method is proposed, based on data published in a preceding publication Part I: Experimental study, and that available in literature. End-member formation energies for the phases β , β ' , δ , δ ' and ε , as well as lattice stabilities of FCC and BCC tellurium, have been evaluated via DFT and used in the numerical optimization. The final Gibbs energy models fit thermodynamic and phase diagram data well, and inconsistencies are discussed. The thermodynamic description is then used to evaluate Gibbs energy of formation for selected Fe-Te compounds of interest for the modeling of internal corrosion of stainless steel fuel pin cladding during operation of Liquid Metal-cooled Fast Reactors (LMFR).

    更新日期:2018-07-12
  • Structural and photoelectrochemical characterization of Cu2SnSe3 thin films fabricated by electrochemical co-deposition and selenization
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Remigijus Juškėnas, Zenius Mockus, Raimondas Giraitis, Algirdas Selskis, Giedrius Stalnionis, Stasė Kanapeckaitė, Audrius Drabavičius, Putinas Kalinauskas, Gediminas Niaura

    The Cu-Sn alloy as a precursor for Cu2SnSe3 (CTSe) thin films was electrochemically co-deposited from a modified electrolyte solution using magnetic steering. The Cu-Sn film on the Mo/glass substrate was continuous, smooth and contained no organic contaminants according to Raman spectroscopy. The current efficiency of Cu-Sn electrodeposition in the solution was about 90%, i.e. significantly higher than that previously reported. The Cu-Sn films with the Cu/Sn ratio in the range of 1.6–2.3 were selenized at temperatures of 350, 400, 450, 500 and 560 °C. The synthesized CTSe films were characterized by XRD, SEM, EDX and Raman spectroscopy. The photo-activity of the films was assessed by photoelectrochemical measurements in a 0.2 M Eu(NO3)3 aqueous solution. The conducted investigations revealed that the Cu2SnSe3 film with Cu/Sn = 1.9 selenized at a temperature of 500 °C demonstrated the best photoelectrochemical response and presented p type doping. The photo-activity of the film increased after additional annealing in air at a temperature of 200 °C. Raman spectroscopy studies of Cu2SnSe3 thin films revealed a rather insignificant difference between the spectra of cubic and monoclinic polymorphs, however, one of the bands in the low energy region could be treated as a marker of the monoclinic phase. The Raman spectra evidenced that nearly all of the studied Cu2SnSe3 films contained SnSe2 the presence of which is detrimental for the photovoltaic characteristics of both Cu2SnSe3 and Cu2ZnSnSe4.

    更新日期:2018-07-12
  • Crystal-site engineering for developing tunable green light emitting Ba9Lu2Si6O24:Eu2+ phosphors for efficient white LEDs
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Sayed Ali Khan, Zhong Hao, Wei Wei Ji, Noor Zamin Khan, Hamidreza Abadikhah, Luyuan Hao, Xin Xu, Simeon Agathopoulos, Qiaoliang Bao

    Phosphors with tuning capabilities in their excitation and emission spectra are in high demand in the field of advanced optical technology. In this article, Eu2+ doped Ba9Lu2Si6O24 (BLSO: Eu2+) phosphors, which emit an intense light hat can be tuned from dark blue (463 nm) to efficient green (514 nm), were produced, simply by increasing the Eu2+ concentration in the BLSO host lattice. This tuning capability suggests that there are multiple and distinguishable crystallographic sites in the host lattice of the BLSO phosphors. The Eu2+ activators exhibit preferable site distributions in the BLSO host lattice, depending on the Eu2+ concentration. This offers the possibility for engineering the appropriate site surroundings, available for the Eu2+ activators. The Ba8.4Eu0.6Lu2Si6O24 phosphor displays a prominent yellowish-green emission under blue light (440 nm) excitation, compared to the dark blue emission of BLSO: 0.1Eu2+ phosphors. The green emission from the BLSO: xEu2+ phosphor is closely associated with the specific coordinating environment of the Eu2+ activator in various crystallographic Ba sites. However, concentration quenching phenomena results in intensity decrease, a problem which is then solved by introducing Sr2+.

    更新日期:2018-07-12
  • Achieving high oligocrystalline degree via strut architecture tailoring to increase the damping and mechanical properties of spherical porous CuAlMn SMAs
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    Hua Li, Bin Yuan, Yan Gao

    Spherical and uniform CuAlMn shape memory foams (SMFs) with quasi-oligocrystalline microstructure and various foam structures were manufactured by the silica-gel beads infiltration method. The strut architecture was quantitatively characterized by strut node size N, strut length L and L/N, and the oligocrystalline degree of foams was characterized by grain size d over N (d/N) for the first time. d/N is found to increase linearly with L/N due to the constricted effect of complex strut architecture on two-dimensional grain growth. The coupling effect of strut sizes and oligocrystalline degree on properties of the SMFs was explored. Too thin struts (smaller N) result in higher quenching rate and consequently more quenched-in vacancies, hindering the thermal-induced martensitic transformation and low-amplitude martensite damping. The peak damping becomes more dependent on d/N and tends to increase with increasing d/N, while the high-amplitude martensite damping improves linearly with d/N. The compression recovery strain also increases linearly with d/N under certain porosity, although higher porosity tends to compromise the favorable effect of higher d/N. The results demonstrate that higher d/N, which corresponds to higher oligocrystalline degree and lower grain constraints, favors the boundary mobility and martensite accommodation and thus improves the damping and compression recovery properties of Cu-based SMFs.

    更新日期:2018-07-12
  • High dielectric constant and relaxor behavior in La0.7Sr0.25Na0.05Mn0.8 Ti0.2O3 manganite
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-12
    S.E.L. Kossi, Ch. Rayssi, A.H. Dhahri, J. Dhahri, K. Khirouni

    The dielectric properties of La0.7Sr0.25Na0.05Mn0.8Ti0.2O3 (LSNMTi0.2) were investigated as a function of temperature and frequency. Compared with the dielectric constants of most ferroelectric and relaxor materials, in this compound we have found a colossal dielectric constant phenomenon consisting in a low frequency dielectric constant ε ″ over 106 around room temperature. However, Frequency and temperature dependent ac conductivity and complex impedance studies were linked to semiconducting grains and insulating grain boundaries, which support the non-Debye type of relaxation in the polycrystalline sample. Furthermore, decrease in the resistive properties with an increase in temperature, explained in terms of the mobility of the charge carriers, signaled the semi-conductor behavior with negative temperature coefficient of resistance (NTCR). The scaling behavior of the Modulus spectra M″ versus frequency allowed us to understand whether the short-range or the long-range movement of charge carriers is the dominant in relaxation process, confirming the non-Debye type of multiple relaxations in the system. The variation in the dielectric permittivity, explained in terms of the space charge polarization according to the Maxwell–Wagner model and the Koop's phenomenological theory and the large dielectric response, was induced by the barrier layers in the grain boundaries and the mixed-valent structures of Mn3+/Mn4+ and Ti4+/Ti3+.

    更新日期:2018-07-12
  • Mn3O4 nanoparticles grown on surface activated graphite paper for aqueous asymmetric supercapacitors
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    R. Aswathy, M. Ulaganathan, P. Ragupathy

    Mn3O4 nanoparticles were anchored on the surface of oxidised graphite paper via template-free hydrothermal method. Synthesized samples were characterized using different techniques such as X-ray diffraction (XRD), Raman spectroscopy, Field Emission Scanning Electron Microscopy (FE-SEM), High Resolution Transmission Electron Microscopy (HRTEM) and X-ray Photoelectron Spectroscopy (XPS). Electrochemical capacitor behaviour was evaluated using cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The binder free material was found to exhibit a specific capacitance of 471 F g−1 at a current density of 1 mA cm−2 in 1 M Na2SO4. Conductive additive free, Mn3O4 anchored electrode was used as positive electrode in the asymmetric cell fabrication; the asymmetric cell was tested at a potential window of 1.6 V and its performance characteristics were evaluated. The asymmetric cell delivered a maximum specific energy of 47 Wh kg−1 at a power density of 2024 W kg−1 which evidenced the superior performance of the synthesized electrode material. Here in the present work, the surface oxidised graphite paper was used as an excellent current collector and active sites for anchoring Mn3O4 due to its desirable properties.

    更新日期:2018-07-10
  • Tensile properties and strengthening effects of 6061Al/12wt.%B4C composites reinforced with nano-Al2O3 particles
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Xiaoxuan Pang, Yajiang Xian, Wei Wang, Pengcheng Zhang

    Aluminum matrix Boron carbide composites is an important thermal neutron shielding material. In order to prepare 12 wt% B4C/6061Al composite with higher mechanical properties by powder metallurgy method, the new composite reinforced by Nano-Al2O3 particles was fabricated by hot isostatic pressing in the semi-solid temperature range. The tensile properties and strengthening effects of the composite were investigated in this research. The tensile stress-strain curve of the composites was tested by material testing machine, and the microstructure and tensile fracture morphology of composites were analyzed by scanning electron microscopy (SEM) and transmission electron microscopes (TEM). The results indicated that the tensile strength of the composite was greatly improved by the addition of Nano-Al2O3, but the elongation decreased obviously. Nano-Al2O3 particles had seriously affected the microstructure and fracture morphology of the composite and lead to the more obvious brittle fracture characteristics. Strengthening mechanisms of Nano-Al2O3 particles reinforced 6061Al/B4C composite have been discussed, which reveals that grain boundary strengthening mainly plays the most important role.

    更新日期:2018-07-10
  • Mo-doping for improving the ZrF4 coated-Li[Li0.20Mn0.54Ni0.13Co0.13]O2 as high performance cathode materials in lithium-ion batteries
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Yi Lu, Shiliang Shi, Fan Yang, Tianyu Zhang, Huiyong Niu, Tao Wang

    The different amounts of Mo6+ and the 2 wt% ZrF4 coating layer have been co-modified the Li[Li0.20Mn0.54Ni0.13Co0.13]O2 cathode material via using the carbonate co-precipitation method and wet coating process. And the influences of Mo6+ doping and ZrF4 surface coating on the cathode crystal structure, morphology and electrochemical properties were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), Transmission Electron Microscope (TEM) and galvanostatic charge–discharge tests. The 2 wt% ZrF4 coated-Li[Li0.20Mn0.52Ni0.13Co0.13Mo0.02]O2 demonstrated the lower cation mixing and a thickness of 15–35 nm film coated on the surface of cathode particles. Compared with the pristine cathode, the samples after ZrF4 coating and Mo6+ doping exhibited the less irreversible capacity loss, better high rate capability and superior cyclic performance owing to the lower impedance for Li+ migration across the SEI film and the faster Li+ migration speed in the cathode bulk. Among all samples, the 2 wt% ZrF4 coated-Li[Li0.20Mn0.52Ni0.13Co0.13Mo0.02]O2 showed the optimum electrochemical properties, with a high capacity retention of 88.7% after 100 cycles at 55 °C, much higher than that (82.9%) of the pristine cathode. Besides, when the electric current increased to 5C high rate, the pristine Li[Li0.20Mn0.54Ni0.13Co0.13]O2 delivered a discharge capacity of 21.9 mAh g−1 lower than that of 2 wt% ZrF4 coated-Li[Li0.20Mn0.52Ni0.13Co0.13Mo0.02]O2.

    更新日期:2018-07-10
  • Effects of temperature on microstructure and mechanical properties of IN718 reinforced by reduced graphene oxide through spark plasma sintering
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Shuan Ma, Yanjie Yang, Ang Li, Shiqi Zhou, Lan Shi, Shaolan Wang, Mabao Liu

    The research of Nickel-based superalloys with excellent mechanical properties is of significance for aerospace. Here we report the effect of sintering temperature of 850 °C, 900 °C and 950 °C with the heating rate of 100 °C/min via spark plasma sintering (SPS) on Inconel 718 (IN718) superalloy reinforced with 0.25 wt. % reduced oxide graphene (RGO). The microstructures and mechanical properties of IN718-RGO composite were investigated by scanning electron microscopy (SEM) and MTS servo hydraulic testing machine, respectively. SEM results demonstrate that the RGO is almost uniformly distributed into the IN718 powders after 3D rock-milling for 8h. The mechanical properties of the composite increase with increasing the sintering temperature. When the sintering temperature is 950 °C, a relative density of 92.5%, a microhardness of 375 Hv and an ultimate compressive strength of 1748.20 MPa after aging heat treatment was obtained for the IN718–0.25 wt. % RGO, respectively. The fracture mechanism of the composite changes from intergranular fracture to transgranular fracture with the sintering temperature increasing.

    更新日期:2018-07-10
  • The multiple orientation relationships and morphology of β' phase in Al-Mg-Si-Cu alloy
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Yaoyao Weng, Zhihong Jia, Lipeng Ding, Shinji Muraishi, Xiaozhi Wu, Qing Liu

    The orientation relationships (ORs), segregation behavior and morphologies of β' precipitate in an over-aged Al-Mg-Si-Cu alloy are systematically characterized by atomic resolution high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Six different ORs and two morphologies, i.e. rod- and lath-like are revealed for β' precipitates, and Cu segregation at the β′/α-Al interface is observed in all these precipitates. The rod-like β' precipitate has multiple β'-angles ranging from 6.1° to 14.1° and non-uniform Cu segregation at the β′/α-Al interface, while the lath-like β' precipitate has a constant β'-angle of 0° and a periodic Cu segregation. These different ORs are explained to be attributable to the rotation of QP lattice, a near-hexagonal network of Si columns formed within β' precipitates, which causes different lattice matching of β′ with α-Al lattice. These findings provide new insights in controlling the precipitation hardening and mechanical properties of this type of alloys.

    更新日期:2018-07-10
  • Fabrication of hierarchical NiCo2O4@NiCo2S4 core/shell nanowire arrays by an ion-exchange route and application to asymmetric supercapacitors
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Xiuhua Wang, Bo Shi, Feifei Huang, Yao Fang, Fang Rong, Ronghui Que

    Although supercapacitors have been extensively investigated due to the good electrochemical performance, the awful energy density, poor cycle stability and low rate performance still remain challenges in applications. In this article, we successfully design and synthesize the hierarchical NiCo2O4@NiCo2S4 core/shell nanowire arrays on Ni foam by a special interface ion-exchange process. As supercapacitor material, it exhibits a high specific capacitance of 3176 F g−1 at a current density of 2 A g−1 and can retain 86.52% at a high current density of 10 A g−1, indicating excellent rate capability. In addition, an asymmetric supercapacitor is assembled with NiCo2O4@NiCo2S4 as the cathode electrode and porous carbon as the anode electrode and KOH solution as the electrolyte, showing a super energy density of 196.8 Wh kg−1 at 752.33 W kg−1 and a high power density of 5625.12 W kg−1 at 162.45 Wh kg−1. After 15000 cyclic voltammetry cycles at a scan rate of 60 mV s−1, 137% of initial capacitance is maintained. Theoretical analysis reveals that the diffusion-controlled reaction is dominant in the total capacitance of NiCo2O4@NiCo2S4 electrode, which may be the reason for the high specific capacitance and excellent rate capability. Thereby, these electrochemical performances demonstrate that the as-fabricated NiCo2O4@NiCo2S4 core/shell nanowire arrays are the promising candidates for high-performance supercapacitors.

    更新日期:2018-07-10
  • Unified modeling of work hardening and flow softening in two-phase titanium alloys considering microstructure evolution in thermomechanical processes
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    J. Guo, M. Zhan, Y.Y. Wang, P.F. Gao

    One of the most critical aspects in understanding the deformation behavior of two-phase titanium alloys subjected to thermomechanical processes (TMPs) lies in being able to describe the flow stress accurately. To this end, in this study, initially, hot tension tests were conducted on a two-phase Ti-6Al-2Zr-1Mo-1V alloy. It was observed that the flow stress at a given temperature and strain rate exhibits work hardening, followed by flow softening. Flow softening occurs at the peak strain, where the maximum stress is observed; peak strain decreases with increasing temperature and decreasing strain rate. Variations in peak strain are more obvious at low temperatures and high strain rates. Later, the microstructure of the alloy was analyzed and the results show that work hardening and flow softening are caused by dynamic recrystallization (DRX). The DRX volume fraction was found to exhibit an increasing trend and discontinuous dynamic recrystallization (DDRX) was observed at increasing temperature and decreasing strain rate. With respect to microstructure evolution, a unified model consisting of a thermally activated stress component and an athermal stress component was developed. In the athermal stress term, dislocation density and the Hall-Petch effect were used to describe the work-hardening and flow-softening behavior. In the case of the dislocation term, the DRX effects were modeled considering the critical strain for DRX initiation and the DRX rate, which are both temperature-and strain rate-dependent. In the Hall-Petch effect term, the dependence of the Hall-Petch coefficient on the processing conditions was considered and the loss of Hall-Petch strengthening with deformation was modeled. Using the proposed model, the work-hardening and flow-softening behavior and microstructure evolution in Ti-6Al-2Zr-1Mo-1V alloys subjected to TMP were predicted. A good agreement could be observed between the experimental and predicted results. This study provides a solution for modeling work-hardening and flow-softening behavior and helps us understand the deformation behavior of two-phase titanium alloys subjected to TMP.

    更新日期:2018-07-10
  • Influence of upconversion luminescence modification on near infrared luminescence and cooperative energy transfer in the YbPO4:Er3+, Nb3+/Er3+inverse opals excited at 980 or 808 nm
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Zhuangzhuang Chai, Zhengwen Yang, Anjun Huang, Chengye Yu, Jianbei Qiu, Zhiguo Song

    The photoluminescence modification of rare earth ions base on the photonic band gap engineering was extensively reported. In this work, the effect of up-converting luminescence suppression of Er3+ on the near infrared luminescence and cooperative energy transfer from Er3+ to Yb3+ was investigated in the YbPO4 inverse opals single-doped with Er3+ and co-doped with Nd3+ and Er3+. For the YbPO4:Er3+ inverse opals, when the photonic band gap is overlapped with the green or red up-converting luminescence of Er3+, the green or red up-converting luminescence of Er3+ was suppressed in the YbPO4:Er3+ inverse opals upon the 980 nm excitation, respectively. It is significative that the enhancement of near infrared luminescence of Er3+ was observed, which is attributed to the electron redistribution in the excited energy levels caused by the upconversion luminescence suppression in the YbPO4:Er3+ inverse opals. For the YbPO4:Nd3+,Er3+ inverse opals, the green upconversion and near infrared luminescence of Er3+ and the near infrared luminescence of Yb3+ were observed excited at 808 nm. The near infrared luminescence enhancement of Yb3+ was obtained due to the cooperative energy transfer enhancement from Er3+ to Yb3+ caused by the green upconversion luminescence suppression. The result is helpful to learn the relationship between upconversion and infrared luminescence in rare earth ions doped materials.

    更新日期:2018-07-10
  • Improved performance of thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering: Prediction and experimental verification
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    D. Kolenaty, J. Houska, J. Vlcek

    The paper deals with thermochromic VO2/SiO2 coatings prepared by low-temperature pulsed reactive magnetron sputtering on conventional soda-lime glass substrates without any substrate bias and without any interlayer. Thermochromic VO2 layers were deposited using reactive high-power impulse magnetron sputtering with a pulsed O2 flow control at a substrate surface temperature of 300 °C. Antireflection SiO2 layers were deposited using mid-frequency bipolar dual magnetron sputtering onto the top of VO2 layers at a surface temperature below 35 °C in order to improve the optical and mechanical performance. We focus on the dependence of the luminous transmittance (Tlum) and the modulation of the solar transmittance (ΔTsol) on the SiO2 layer thickness. The measured dependencies are in good agreement with those predicted using properties of pure VO2 layers measured by spectroscopic ellipsometry. Two different VO2 layer thicknesses (30 and 88 nm) have been used to demonstrate the tradeoff between Tlum and ΔTsol. We show an improvement due to the SiO2 overlayer of up to 16% (from 40.3% to 56.3%) for Tlum measured ar 25 °C and up to 2.6% (from 7.7% to 10.3%) for ΔTsol. The results are important for the design and low-temperature fabrication of high-performance durable thermochromic VO2-based coatings for smart window applications.

    更新日期:2018-07-10
  • Colour- and structure-stable CsPbBr3-CsPb2Br5 compounded quantum dots with tuneable blue and green light emission
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Pengjie Song, Bo Qiao, Dandan Song, Zhiqin Liang, Di Gao, Jingyue Cao, Zhaohui Shen, Zheng Xu, Suling Zhao

    Even though all-inorganic lead halide perovskite (CsPbX3; X = Cl, Br, I) quantum dots (QDs) with great optoelectronic properties such as high fluorescence quantum yield, facile colour tunability, and high colour purity have been under the spotlight in recent years, their poor stability makes their application in LEDs difficult. In comparison to CsPbBr3 QDs that display green emission, CsPbCl3 QDs with blue light emission contain more defects in the material and exhibit lower fluorescence quantum yield and device service time, which is the bottleneck in realizing blue, green, and red three-base coloured perovskite QD-based LEDs. It is therefore a pressing issue to develop other techniques instead of anion exchange to adjust the light emission of CsPbX3 and simultaneously enhance the stability of the nanocrystals, especially for blue emission. In this work, CsPbBr3 QDs compounded with CsPb2Br5 (CsPbBr3-CsPb2Br5 QDs) with stable blue and green emissions are obtained using improved one-step solution-phase method. CsPb2Br5 can enhance the luminescent colour and structural stability of CsPbBr3 QDs. CsPbBr3-CsPb2Br5 QDs showed greater stability than pure CsPbBr3 QDs in various environments. Moreover, CsPbBr3-CsPb2Br5 QDs are smaller than CsPbBr3 QDs synthesized at the same temperature, which results in blue-shift of the photoluminescence spectra. Owing to the strong stability, their photoluminescence emission peak can be simply and reliably tuned continuously between 480 nm and 520 nm through the reaction temperature.

    更新日期:2018-07-09
  • Enhanced mechanical properties of hypoeutectic Al-10Mg2Si cast alloys by Bi addition
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Xiao-Feng Wu, Yu Wang, Ke-Yan Wang, Rong-Da Zhao, Fu-Fa Wu

    In the present work, the influence of Bi on the microstructures, tensile properties, and fracture behavior of the cast Al-10Mg2Si alloys has been systematically investigated. It was found that Bi addition caused a significant modification and refinement efficiency on the eutectic Mg2Si in the cast Al-10Mg2Si alloys. The morphology of the eutectic Mg2Si in the cast alloys transformed from plate-like structure to a thin coral-like and fibrous one, and the mean size and aspect ratio sharply decreased with the increase of Bi content. Bi addition changed the mode of fracture from brittle to ductile due to the presence of a large number of deep and well-distributed dimples, and fine Mg2Si particles embedded in the Al-matrix, resulting to the significant improvement of the tensile properties of the cast Al-10Mg2Si alloys.

    更新日期:2018-07-09
  • Correlation between crystallographic and microstructural features and low hysteresis behavior in Ni50.0Mn35.25In14.75 melt-spun ribbons
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Haile Yan, C.F. Sánchez-Valdés, Yudong Zhang, J.L. Sánchez Llamazares, Zongbin Li, Bo Yang, Claude Esling, Xiang Zhao, Liang Zuo

    In this work, crystallographic, microstructural and magnetocaloric investigations were performed on textured Ni50Mn35.25In14.75 melt-spun ribbons with low thermal (6 K) and magnetic-field induced hysteresis (–0.73 J kg−1 at 2 T) and moderate maximum magnetic entropy change ΔSMmax (11 J kg−1 K−1 at 5T) at room temperature (302 K). The austenite in the ribbons crystallizes into a L21 structure, whereas martensite has a monoclinic incommensurate 6M modulated structure as determined with the superspace theory. By means of electron backscatter diffraction technique, the morphological and crystallographic features of microstructure were systematically characterized. Ribbons possess a fine microstructure with an average grain size (initial austenite phase) of around 10 μm, whereas the 6M martensite has a self-accommodated microstructure with 4 kinds of twin-related martensite variants. During inverse martensitic transformation, the austenite prefers to nucleate at the grain boundaries of initial austenite. By means of cofactor conditions and crystallographic orientation analyses, the good geometrical compatibility between austenite and martensite was confirmed. Based on the crystal structure and microstructure information obtained, the reason of the low thermal hysteresis was discussed.

    更新日期:2018-07-09
  • Sea urchin-like Li4Ti5O12 nanostructure as a Li-Ion battery anode with high energy density and improved ionic transport
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-09
    Min-Cheol Kim, Sang-Hyun Moon, Sang-Beom Han, Da-Hee Kwak, Ji-Eun Lee, Eun-Soo Kim, Sojeong Choi, Yeon-Kyung Shin, Kyung-Won Park

    Li4Ti5O12 (LTO) with a spinel structure is attractive as a promising anode for lithium-ion batteries due to a high charge/discharge voltage versus Li/Li+ and almost no volumetric expansion with improved cycle performance. In this study, a sea urchin-like nanostructured LTO (F-LTO) was prepared in the presence of F-127 as a surfactant. The morphology and structure of the samples were confirmed using field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) method. To investigate the electrochemical properties of the samples, charging/discharging analysis was performed for 1000 cycles at a high current density. F-LTO showed an improved capacity retention rate and a high average capacity compared to the LTO sample prepared in the absence of F-127. It was found that, when using the high-rate performance analysis at different charging/discharging current densities, the intercalation of Li+ ion to an electrode might be a crucial factor to reduce capacity and energy density. Due to its porous nanostructure with high specific area, F-LTO showed low polarization and improved kinetic properties, resulting in enhanced LIB performance including high energy density and cycling properties.

    更新日期:2018-07-09
  • Analysing single twinning events in Mg-6Zn using nanoindentation
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-05
    Tingting Guo, Qi Chao, Filip Siska, Jun Cheng, Rameshkumar Ramkaran Varma, Matthew R. Barnett

    The present work addresses the challenge of estimating the twin thickening stresses. Single twinning events were captured in solution treated and peak-aged Mg-6Zn alloy subjected to {101¯0} nanoindentation. Markedly different responses of twinning to aging are seen compared to slip. 3D EBSD and high resolution EBSD are combined with crystal plasticity finite element modelling to fully characterize the twinning event. A model is then derived to allow us to estimate the influence of alloying with Zn and peak aging on the stresses required for twin thickening using the depth of the pop-in and the nanoindentation hardness before twinning. The stress for twin thickening increases from 6 MPa to 26 MPa and 74 MPa with an error of ± 10% due to the addition of solute Zn and the presence of particles formed during peak aging respectively.

    更新日期:2018-07-08
  • Fast chemical vapor-solid reaction for synthesizing organometal halide perovskite array thin films for photodetector applications
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-05
    Yan Lei, Longyan Gu, Xiaogang Yang, Leilei Zhang, Yuanhao Gao, Jianxi Li, Zhi Zheng

    Preparing organometal halide perovskite array thin films from solution is a big challenge due to its soluble nature. In this work, we provide a fast chemical vapor-solid reaction (FCVR) for fabricating perovskite array thin films. An elemental Pb array thin film was firstly prepared by magnetron sputtering using a shadow mask, which then converted to CH3NH3PbI3 arrays by reacting with CH3NH3I. The related photoelectric chracteristics were investigated by Uv-Vis spectroscopy, photoluminescence spectroscopy, and transient photovoltage analysis. The photodetector devices were assembled using these resultant perovskite thin films, which showed a fast response with 3 ms rise time and 3 ms decay time both under 405 nm and 660 nm light illumination. The response was faster than the commercial photodetector. This FCVR method not only provides a high quality perovskite array thin film, but also a novel synthesis strategy for new organic-inorganic hybrid perovskite photoelectric materials.

    更新日期:2018-07-08
  • Supersonically spray-coated zinc ferrite/graphitic-carbon nitride composite as a stable high-capacity anode material for lithium-ion batteries
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-05
    Bhavana Joshi, Edmund Samuel, Tae-Gun Kim, Chan-Woo Park, Yong-Il Kim, Mark T. Swihart, Woo Young Yoon, Sam S. Yoon

    This manuscript reports the preparation, characterization, and testing of stable high-capacity lithium-ion battery anodes based on graphitic carbon nitride (g-CN) nanosheets hosting ZnFe2O4 nanoparticles (ZFCN). The ZFCN is prepared by a one-pot thermal process, then supersonic cold spraying is used to rapidly deposit films with a lamellar morphology that allows enhanced capacity retention by preventing particle agglomeration. The presence of g-CN nanosheets minimizes degradation of ZnFe2O4 by providing a buffering space during the lithiation/delithiation process. The ZFCN composite anodes exhibit first reversible capacities of 1550 mAh·g−1 at 50 mA·g−1 and up to 934 mAh·g−1 at 1000 mA·g−1 after 20 cycles. The superior electrochemical performance and capacity retention (88% after 160 cycles at 100 mA·g−1 relative to the first reversible capacity) are attributed to highly reversible alloying/conversion mechanisms. The combination of high performance and stability with the use of low-cost earth-abundant elements and scalable processing approaches gives this ZFCN composite immense potential for use as a stable high-performance anode material for lithium-ion batteries.

    更新日期:2018-07-08
  • Tribological behaviors of a Ni-free Ti-based bulk metallic glass in air and a simulated physiological environment
    J. Alloys Compd. (IF 3.779) Pub Date : 2018-07-05
    Ying Liu, Shujie Pang, Wei Yang, Nengbing Hua, Peter K. Liaw, Tao Zhang

    Ni-free Ti-based bulk metallic glasses (BMGs) with good mechanical properties, high corrosion resistance, and good biocompatibility are potential biomaterials. For the applications as load-bearing orthopedic implant materials, excellent wear resistance is required. In the present study, tribological behaviors of the Ni-free Ti47Cu38Zr7.5Fe2.5Sn2Si1Ag2 BMG in air and a phosphate buffer saline (PBS) solution were investigated and compared with Ti−6Al−4V and Co−28Cr−6Mo alloys. It was found that the wear resistance of the Ti-based BMG in air was superior to that of the Ti−6Al−4V alloy and paralleled with that of the Co−28Cr−6Mo alloy, mainly attributing to the high hardness of the Ti-based BMG. Under the dry-sliding condition, the predominant wear mechanism of the Ti-based BMG was characterized as the oxidation and abrasive wear. Under the PBS-solution condition, although the Ti-based BMG suffered from tribocorrosion that is controlled by the combined effects of abrasive and corrosive wear, the wear resistance of the Ti-based BMG was three times lower than that of the Ti−6Al−4V alloy and slightly inferior to that of the Co−28Cr−6Mo alloy. The effect of corrosion behavior on wear resistance of the Ti-based BMG in the PBS solution is discussed.

    更新日期:2018-07-08
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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