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    • >Materials Science
    • Effect of annealing temperature on hydrogen storage properties of LaNi3.8Al1.0Mn0.2 alloy

      2016, 45(4):821-828.

      Abstract (1613) HTML (138) PDF 664.35 K (1612) Comment (0) Favorites

      Abstract:The LaNi3.8Al1.0Mn0.2 hydrogen storage alloy annealed at different temperatures (T=1173K, 1223K, 1273K, 1323K) was investigated to examine the effect of annealing temperature on the crystal structure, activation and hydrogen absorption/desorption performance. It was found that the non-CaCu5 phases became more tiny and dispersive after annealing. All the alloys consisted of the same matrix phase with CaCu5 type structure. Although it was harder to activate the annealed alloy than the as-cast alloy, the activation became easier with the increase of annealing temperature for the annealed alloy. The plateau pressure was decreased at first with the increase of annealing temperature when T≤1223K and then increased. Changes in both the lattice strain and the degree of Sf in the alloys showed the same trend with that of the annealing temperature, exhibiting a maximum at T=1223K. . It was also found that the absolute value of the enthalpy was increased with the increase of annealing temperature when T≤1223K and then decreased, showing the same change trend as that of the cell volume. Moreover, the pulverization resistance and kinetics of the alloy were improved by annealing. The pulverization resistance was weakened at first with the increase of annealing temperature when T≤1223K and then increased, but the kinetics of the alloy was almost not influenced by the annealing temperature.

    • Low Cycle Fatigue Behavior of SnAgCu Solder Joints

      2016, 45(4):829-835.

      Abstract (1848) HTML (149) PDF 0.00 Byte (1027) Comment (0) Favorites

      Abstract:Low cycle mechanical fatigue tests on 96.5Sn-3Ag-0.5Cu solder joints were carried out using micro-uniaxial fatigue testing system at 25℃ with different frequencies (1Hz~10Hz) and a wide range of strain (2%~8%). The results showed that the low cycle fatigue (LCF) life followed the Coffin-Manson equation in different strain ranges. Frequency-modified Coffin-Manson equation can describe the frequency effect well on the fatigue life of solder joints. The analysis of failure process showed that the fatigue cracks initiated at the interfaces between the solder and inter-metallic compound (IMC) around the edge of the joints, then the cracks propagated within the solder along the solder/IMC interfaces proximately. Fracture morphologies of solder joints with different frequencies were similar which mainly consisted of an initiated region, a propagation region and a final fracture region. The fracture mechanism of the final fracture region transformed from inter-granular fracture to trans-granular fracture with increasing frequency.

    • Analysis of the Multi-wedge Cross Wedge Rolling Process of 42CrMo4 Large and Long Hollow Shaft

      2016, 45(4):836-842.

      Abstract (1564) HTML (163) PDF 453.90 K (1321) Comment (0) Favorites

      Abstract:Large and long thick-walled hollow shafts are the key parts of industry equipments, which are formed by the multi-wedge cross wedge rolling (MCWR) in this paper. First, the deflection angle equations of side-wedges applied at the multi-wedge cross wedge rolling of hollow shafts were derived, which lay important foundation for designing the MCWR mold. Second, It is found that the spreading angle's impacts on single-wedge cross wedge rolling of thick-walled hollow shaft-part. And, compared to roll small diameter of hollow shaft, the ellipiticity of the large and long thick-walled hollow shaft could be controlled, the selection range could be extended. At the same time, it was also found that the ellipiticity was could also be controlled by empty top surface of the mold. At last, the FE model of double-wedge cross wedge rolling of large and long thick-walled hollow shaft was established. The forming process was simulated, and the ellipiticity of symmetrical cross-section was monitored. The ellipiticity of large and long thick-walled hollow shaft was controlled, the ellipiticity of symmetrical cross-section is 4.98%, the experimental ellipiticity is 5.56%. The research results indicate that it is feasible to produce large and long thick-walled hollow shafts with double-wedge Cross Wedge Rolling.

    • The Effect of Different Substrate Temperatures on the Microstructure and Residual Stress of Ti Film

      2016, 45(4):843-848.

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      Abstract:In this paper, the influence of different substrate temperatures of Ti film prepared by the direct current (DC) magnetron sputtering on the internal residual stress of Ti film was investigated experimentally by nanoindentation technique using Suresh model and Lee model. The comparison between the results of nanoindentation method and curvature method was performed. At the same time, the surface morphology and microstructure of Ti film are analyzed using atomic force microscope (AFM) and X-ray diffraction (XRD). The results showed that the residual stress value obtained using Suresh model was almost the same as that by the curvature method, so the Suresh model is more suitable for calculating the residual stress of Ti film. Together with the nanoindentation data and micro-structure analysis, it was found that with the substrate temperature rising, the grain size of Ti film first increased and then decreased; the residual stress of the Ti film changed from the compressive stress to tensile stress.

    • Effects of compressive stress on the magnetostrictive characteristics of Sm-Fe-B films

      2016, 45(4):849-852.

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      Abstract:In this study, a set of Sm-Fe-B film with different compressive stress were prepared on substrate of different prestrain by Ion Beam Spurting Deposition (IBSD). The influence of compressive stress on the magnetic anisotropy and the magnetostriction in sputter-deposited amorphous Sm-Fe-B films were investigated. Films affected by compressive stress showed in-plane anisotropy and easy axis along the direction of stress was induced in the film with the increase of compressive stress . Magnetostriction of Sm-Fe-B films affected by compressive stress was improved in low magnetic field while saturation of magnetostriction decreased slightly. At the same time, the magnetostriction rised rapidly in low field measured in a field parallel to the film plane at room temperature with the growth of compressive stress. It has also been found that the magnetic domain component which was perpendicular to the film plane increased on a small scale, though the magnetic domain or the magnetic domain component parallel to film plane still existed dominant.

    • Effect of Carbon Content on Morphology, Size and Phase of Submicron Tungsten Carbide Powders Prepared by Salt-assisted Combustion Synthesis

      2016, 45(4):853-857.

      Abstract (2073) HTML (156) PDF 482.97 K (1408) Comment (0) Favorites

      Abstract:The Diluent NaCl was introduced into the WO3-Mg-C-Na2CO3 system (WO3, C, Mg powders and Na2CO3) to prepare submicron tungsten carbide (WC) powders via salt-assisted combustion synthesis. The products were analyzed by SEM, EDS and XRD, and effect of C content on morphology, average particle size and phase composition of the products were studied. The Results show that on basis of the m = 0.125 (the number of moles of Na2CO3), when the number of moles of carbon in raw material increases from l=2 to 2.25 and 2.5, respectively, before leaching, the product was made up of a small number of large size particles and a large number of small size particles; After leaching, samples were composed of aggregates of submicron particles, the fusion sintering phenomenon between particles was very weak, indicating low degree of aggregation. Particle size distribution of leached product almost falls into the normal distribution, and the particle sizes range from 200 nm to 350 nm. Under the condition of l=2.25, a main target product is WC, and content of by-products W2C is extremely few. That is, k = 2.0 (the number of moles of NaCl), m = 0.125, and l=2.25 are the process conditions for single-phase WC synthesis.

    • Surface roughness and hydrophilicity of titanium after anodic oxidation

      2016, 45(4):858-862.

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      Abstract:Anodic oxidation was applied to produce nanostructured titanium (Ti) surface with different roughness and hydrophilicity. The morphology was characterized by scanning electron microscopy (SEM). The surface roughness was characterized by atomic force microscopy (AFM), and the hydrophilicity was assessed from the contact angle between the deionized water and sample surface at room temperature. The results showed that surface morphologies changed remarkably with the changing of applied voltage and oxidation time during anodic oxidation. Under optimized oxidation conditions, well-ordered nanotubes were fabricated. Roughness values increased with the oxidation time, ranging from several dozen to several hundred nanometers, while the influence of voltage on surface roughness was not obvious. The water contact angles initially increased with the oxidation time, but then decreased. The variation of surface morphology, roughness and hydrophilicity was correlated to the reactions occured during the anodic oxidation.

    • Facile Hydrothermal Synthesis of MnOOH Nanorods and Their Application

      2016, 45(4):863-868.

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      Abstract:Single crystal manganese oxyhydroxide (MnOOH) nanorods were successfully prepared without extra template or surfactant employing a simple hydrothermal route based on the redox between potassium permanganate (KMnO4) and N-methyl pyrrolidone (NMP). By adjusting the reaction temperature, reaction time, and the volume ratio of H2O/NMP, MnOOH nanorods with lengths up to 20 μm and square cross-sections with edge lengths in the range of 50-400 nm could be facilely prepared in high yield. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and Fourier transformed infrared spectroscopy (FTIR). The formation mechanism of MnOOH nanorods was preliminarily discussed based on the Ostwald's ripening process. Furthermore, Mn2O3 nanorods were obtained by calcination of MnOOH nanorods.

    • Microstructure and properties of Ag-SnO2 coating fabricated by plasma spraying

      2016, 45(4):869-873.

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      Abstract:Ag-SnO2 coating on copper substrate has been prepared by atmospheric plasma spraying method using the energy ball milled Ag-12wt.%SnO2 composite powders as the raw materials. The microstructures of Ag-SnO2 coating were characterized using XRD and SEM, respectively. The mechanical properties and arc erosion performance of as sprayed coating have been determined by tensile test, microhardness and arc erosion test, respectively. The results show that Ag-SnO2 coating presented the compact microstructure, and the nanosized SnO2 particles are uniformly dispersed in the Ag matrix of coating. The mechanical properties and arc erosion performance of Ag-SnO2 coating are close to that of bulk alloy. After arcing test, the surface of coating presents the dispersion of cathode spots and a little erosion, indicating that Ag-SnO2 coating has excellent arc-erosion resistance. Plasma spray technique is an effective approach to manufacture Ag-SnO2 contact coating with good mechanical properties and arc erosion resistance performance.

    • Prediction of Melting Temperature and Latent Heat for Low-melting Metal PCMs

      2016, 45(4):874-880.

      Abstract (1673) HTML (179) PDF 695.48 K (1390) Comment (0) Favorites

      Abstract:In this paper, models are presented for predicting the melting point and latent hear of low-melting alloys to facilitate the design of PCMs. Based on the characteristics of entropy and enthalpy during the transition of material phase, the prediction model of melting point and latent heat for eutectic binary system are established at first, and then the models are extended into multicomponent system. Calculated melting point and latent heat of 15 selected low-melting alloys are compared with measurement results using DSC, which shows a good agreement between the prediction and the experimental data. A criterion for preparation of metallic PCMs is also proposed that in order to obtain higher latent heat alloy, an element with higher latent heat should be selected as component of alloy, and the mole fraction of the element should be increased. The advantage of the models proposed is that the melting point and latent heat of certain PCM can be predicted mathematically, avoiding the many experiments needed in conventional ways.

    • Theoretical calculations on Electronic Structure and Optical Properties of Orthorhombic SrHfO3 in Cmcm Space Group

      2016, 45(4):881-884.

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      Abstract:Electronic structure and optical properties of Cmcm orthorhombic SrHfO3 were computed, using the plane-wave ultrasoft pseudopotential technique based on the first-principles density functional theory (DFT). The equilibrium lattice parameters of orthorhombic SrHfO3 are in good agreement with experimental values. The band structure, densities of states (DOS) and charge densities of Cmcm orthorhombic SrHfO3 have been obtained. The band structure shows that Cmcm orthorhombic SrHfO3 has direct band gap. The charge densities of Cmcm orthorhombic SrHfO3 indicate that bonding between Hf and O is mainly covalent whereas bonding between Sr and O is mainly ionic. The complex dielectric function, refractive index and absorption coefficient of Cmcm orthorhombic SrHfO3 have been predicted. The imaginary and real parts of the calculated complex dielectric function are close to the experimental measurements.

    • Synthesis and Thermal Stability of Nanocrystalline Nickel Coatings by Direct Current Electrodeposition

      2016, 45(4):885-888.

      Abstract (1625) HTML (163) PDF 736.43 K (1584) Comment (0) Favorites

      Abstract:The influence of current density and saccharin concentration on nanocrystalline nickel coatings synthesized by direct current electrodeposition was systematically analyzed. For current densities ranging from 0.5 A/dm2 to 1.5 A/dm2, nanocrystalline nickel with broad microhardness distribution ranging from 415 Hv to 603 Hv could be synthesized by adjusting saccharin concentration. The preferred orientation in the deposits existed at 0.5 A/dm2 and changed progressively from a (111), (200) double orientation texture to a (200) orientation texture as saccharin concentration increased. The internal stresses of the samples at 0.5 A/dm2 decreased to nearly 0 MPa as saccharin concentration increased to 1.2 g/L. The results of DSC curves show that the samples grew until 600 癈 and were stable near to bulk nickel when grain size ranged from 28 nm to 98 nm. However, when grain size was 10 nm, the samples initially grew abnormally at 317 癈. Moreover, thermal stability decreased sharply.

    • Thermoelectric Performance of Sb-doped Mg2-xZnxSi solid solutions

      2016, 45(4):889-892.

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      Abstract:Mg2-xZnxSi0.99Sb0.01(0 ≤ x ≤ 0.1) solid solutions were prepared by B2O3 flux method combined with spark plasma sintering (SPS) technique. The electrical conductivity, Seebeck coefficient and thermal conductivity have been measured as a function of temperature from 300 K to 780 K. The lattice thermal conductivity reduces upon Zn substitution, however, the electrical conductivity first decreases and then increases with Zn content increasing. The underlying mechanism was discussed. Among the samples, the maximum PF of 1.76 mWm-1K-2 at x=0.075 was obtained at 780 K, about 18% higher than that of Mg2Si0.99Sb0.01.The lowest lattice thermal conductivity of 2.86 Wm-1K-1 is obtained at 770 K for the x=0.1 sample. As a result, a maximum dimensionless figure of merit of 0.37 was obtained for Mg1.9Zn0.1Si0.99Sb0.01 at 780 K .

    • Characteristics of nano-alumina particles dispersion strengthened copper fabricated by reaction synthesis

      2016, 45(4):893-896.

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      Abstract:Alumina dispersion strengthened copper (ADSC) composite was prepared by reaction synthesis (RS) process. Studies show that nano-sized γ-Al2O3 particles of about 10 nm in diameter are homogeneously distributed in copper matrix. A coherent interface relationship with (002)Cu // γ-Al2O3,[110]Cu// [011]γ-Al2O3 characterizes along the explored interfaces of the composites. The composites obtain high tensile properties. Namely the tensile strength can reach to 570 MPa and the yield strength can reach to 475MPa at room temperature. Meanwhile, the softening temperature is higher than 1173 K. The electrical conductivity of sample is 85% IACS and the Rockwell hardness can reach to 86 HRB.

    • The Research of Titanium Nanometric Cutting Process Based on Molecular Dynamics

      2016, 45(4):897-900.

      Abstract (1638) HTML (163) PDF 420.85 K (1244) Comment (0) Favorites

      Abstract:Based on the molecular dynamics simulation (MDS) method, this article built up a molecular dynamics (MD) model of titanium nanometric cutting, chose representative cutting conditions, obtained the instantaneous image of atomic position through simulation and analyzed the material removal phenomenon, surface formation process, change rules of system potential energy and workpiece temperature in cutting process. It is found that the formation of the chips and the machined surface in cutting process are caused by the release of lattice energy and the lasting expansion of dislocation. The elastic recovery and lattice reconstruction of the machined surface and can slow down the increasing trend of total potential energy and temperature, and make them accompanied by slight fluctuations.

    • >Materials Technology
    • Kinetics of Ilmenite concentrate electrolysis process in molten salt

      2016, 45(4):907-912.

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      Abstract:Now using titanium-bearing material to product titanium and titanium alloy based on Fusedsaltelectrolysis method has become an important research direction at home and abroad. But less research has been done on the kinetics of Fusedsaltelectrolysis process. Electrolysis kinetics for different temperature was studied using an improved model, internal diffusion was considered as the restrictive link of electrolysis process of Ilmenite concentrate in molten salt. High reaction temperature and big porosity of cathode can be used to improve the internal diffusion speed, however, at this case, side reaction will increase, which affects the electrolysis speed at the same time.

    • The Phase Structure, Morphology and Luminescent Properties of ZnWO4 Powders by Hydrothermal Process

      2016, 45(4):913-917.

      Abstract (1975) HTML (166) PDF 965.89 K (1817) Comment (0) Favorites

      Abstract:Under various calcination temperatures and with different dosage of PEG-1000, a series of ZnWO4 phosphors were synthesized by hydrothermal process. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, Scanning electron microscope and Fluorescence spectrophotometer. The results show that as-synthesized blue-emitting phosphors ZnWO4 are pure wolframite structure. The particles of hydrothermal product are spheres in shape, and after calcination at 700 ℃, the morphology is changed from spheres to short rods. Under the condition of adding 0.5 g PEG-1000 and calcination at 700 ℃, the obtained particles are still short rods in shape, but the size is reduced significantly. The emission spectrum of ZnWO4 is composed of a broad band with the main peak at 465 nm. The crystallinity and luminescent property of the ZnWO4 powder synthesized by hydrothermal process can be improved by calcination, and the optimal calcination temperature is 700 ℃. Adding surfactant PEG-1000 can also increase the luminescent intensity of the phosphors, and the optimal dosage is 0.8 g.

    • Effects of Sodium Tetraborate in the Electrolyte Systems on Micro-arc Oxidation of Magnesium Alloy

      2016, 45(4):918-922.

      Abstract (1994) HTML (153) PDF 454.79 K (2416) Comment (0) Favorites

      Abstract:The microstructure and corrosion resistance of ceramic coatings formed by micro-arc oxidation on magnesium alloys in electrolyte systems with different Na2B4O7 concentrations was investigated by scanning electron microscopy and electrochemical workstation respectively. The function of sodium tetraborate in the formation and growth process of micro-arc oxidation coatings was analyzed. The results showed that a compound of (B4O7) 2- and Mg2 on the anode surface was formed the water-insoluble material of Mg(BO2)2 before the occurrence of micro-arc discharge. As the concentrations of Na2B4O7 increased from 3g/L to 15g/L, the morphology of deposited layer transited from granular to net structure gradually. The formation of Mg(BO2)2 layer with a high impedance characteristic set up a suitable electric field condition for MAO process. After micro-arc discharge happened, Mg(BO2)2 on the anode surface by raising the discharge voltage enhanced the strength of single pulse discharge under constant pulse width and peak current, and then speed up the growth of micro-arc oxidation coatings.

    • Study on Mechanical Behavior of near β-Type TLM Titanium Alloy Tube with Small Diameter and Thin Wall

      2016, 45(4):923-927.

      Abstract (1719) HTML (162) PDF 858.82 K (1761) Comment (0) Favorites

      Abstract:Near β-type TLM titanium alloy tubes with small diameter and thin wall were fabricated by a combination of cold rolling and intermidate anneal. The mechanical behaviors related to the phases and microstructures were studied using optical metallography (OM), X-ray diffraction (XRD), scanning electron microscope (SEM) and tensile tests. The results show that the cold-rolled microstrcutre composed of β phase and stress induced martensite (SIMα?) exhibits obvious non-linear elastic deformation behavior, while the annealed single β phase displays the “double-yielding” associated with stress-induced martensitic phase transformation. Present authors consider that the non-linear elasticity has certain dependence on both of SIMα? and complicated sub-structures induced by the cold deformation, but both of which make an unconspicuous contribution to the plasticity. Although the elongation decreases after the cold rolling, the cold rolled microstructure still shows the ductile fracture mode similar with that of annealed specimens, which indicates that wider plasticity range of present TLM alloy supplys a tremendous potential in its deep cold deformation.

    • Investigations on the preparation and lithium storage performance of activated carbon-CNT/PEG/sulfur composite cathode materi

      2016, 45(4):928-933.

      Abstract (1775) HTML (162) PDF 741.42 K (1847) Comment (0) Favorites

      Abstract:Activated carbon-CNT/sulfur composite cathode material for lithium-ion battery was prepared by melting method in a sealed FTPE reactor. Further, the composite was modified by PEG-coating, and the cathode composite material of C-CNT/S (PEG) was obtained. X-ray diffraction (XRD) analysis showed that the C-CNT/S (PEG) composite had an amorphous structure, and the sulfur was dispersed into the microspores of carbon material. Scanning electron microscopy (SEM) tests indicated that the CNT was uniformly dispersed in the composite, which formed a three-dimensional conductive structure. Discharge capacity tests showed the addition of CNT improve the discharge capacity of the composite. The first discharge capacity of PEG-coated composite (C-CNT/S (PEG)) was up to 1371.1mAh/g and the discharge capacity remained to be 662.8mAh/g after 50 cycles. The results demonstrated that the addition of CNT and PEG-coating can greatly improve the electrochemical performance of activated carbon/sulfur cathode materials.

    • Effect of DC magnetic field on solidified structure, crystal texture and mechanical properties of Mg97Y2Cu1 alloy

      2016, 45(4):934-939.

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      Abstract:Solidified structure, crystal texture and mechanical properties of Mg97Y2Cu1 alloy reinforced by long period ordered structure under DC magnetic field(0~1.2T) were studied. The results show that primary grain size and content of Y in matrix of the alloy decrease with DC magnetic field treatment. With the increase of magnetic field strength, the plane texture enhances firstly, then weakens, and the turning point is 0.9T, the plane texture enhances gradually. The strength and elongation of the alloy increase gradually in general. When the magnetic field strength is 0.9T, comprehensive mechanical properties of the alloy are the best. Tensile strength and elongation of the alloy are increased by up to 96.6% and 61.1%, respectively, compared with the sample without treatment.

    • Fabrication of W particle reinforced composite layer on copper substrate via mechanical alloying method

      2016, 45(4):940-945.

      Abstract (1622) HTML (151) PDF 380.67 K (1543) Comment (0) Favorites

      Abstract:High-energy planetary ball mill was applied to fabricate W particle reinforced composite layer in the surface of pure copper substrate. Scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and micro-hardness test technique were used to investigate the microstructure and mechanical properties of the coatings prepared at different milling time, and then the mechanism of the formation of the coatings were studied. The results showed that the thickness of the particle reinforced layer reached the maximum within a certain milling time at the selected milling parameters. However, the bongding between reinforcing particles and substrate could be enhanced through appropriate extension of milling duration, which would simultaneously facilitate the densification in the composite layer.

    • Study on Properties of IrO2-Ta2O5 Coated Titanium Anodes Modified with Graphene

      2016, 45(4):946-951.

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      Abstract:The IrO2-Ta2O5 coated titanium anodes (Ti/IrO2-Ta2O5-G) with different graphene contents were prepared by thermal decomposition method. The microstructure was analyzed by FESEM and EDX, and the electrochemical properties were investigated by electrochemical testing including cyclic voltammetry(CV), anode polarization curves, and electrochemical impedance spectroscopy(EIS). As compared with the traditional Ti/IrO2-Ta2O5 anode, the results indicate that the rugged surface morphology with tiny cracks of the Ti/IrO2-Ta2O5-G anodes offer more active center for oxygen evolution reaction and have larger electrochemically active surface area, better electrocatalytic activity for oxygen evolution. The Ti/IrO2-Ta2O5-G anode with 0.4 g稬-1 graphene contents presents the best electrochemical performance.

    • Research on Preparation and Property of Anti-Corrosion Film on Surface of Aluminum Alloy

      2016, 45(4):952-956.

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      Abstract:3-Triethoxysilylpropylamine(KH550) film and KH550/graphene oxide(GO) composite film were prepared on aluminum alloy by Self-Assembly Moleculars(SAM). Surface morphology and microstructure of the samples were characterized by SEM, Raman and FITR. Corrosion potential and current density of the samples was also tested by the electrochemical workstation. The results showed that a condensation reaction took place between amino groups(-NH2) of KH550 and carboxy groups(-COOH) of GO, which made success combination of KH550 and GO. The adhesion ability of film was enhanced for the chemical reaction between film and aluminum alloy which led to the generation of Si-O-Al linkage. Moreover, the corrosion resistance of aluminium alloy was effectively improved by the two kinds of films.

    • Wear resistance and corrosion resistance of Fe-based amorphous alloy coating

      2016, 45(4):957-962.

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      Abstract:Fe-based amorphous alloy is widely applied in the fields of petroleum, coal, steel and ship etc. because of its excellent wear and corrosion resistance. Fe-based amorphous alloy coatings are prepared by high velocity oxygen fuel thermal spraying on 316 stainless steel substrate in this paper. Fe-based amorphous alloy coatings’ grinding performance, the grinded surface’ wear resistance and corrosion resistance are explored separately. The results show that the grinding depth has the most impact on surface roughness and corrosion resistance of the coatings’ surface, feed speed takes the second place; the feed speed has the most impact on wear resistance of the coatings’ surface, grinding depth takes the second place; the grinding speeding has the least impact on surface roughness, wear resistance and corrosion resistance of the coatings’ surface. Finally, the best grinding parameters combinations are selected according to the different characteristics of coatings.

    • Study of microstructure evolution of DCP-derived W/ZrC cermets in ultra-high temperature

      2016, 45(4):963-967.

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      Abstract:W/ZrC cermets were fabricated by DCP method. The evolution laws of composition and microstructure of W/ZrC cermets in different ultra high temperature environment were investigated. Results show that the heat-treated microstructure of W/ZrC cermets is still comprised of metal tungsten and ceramic zirconium carbide. With an accretion of temperature, the weight loss first increases and then decreases, attaining a maximum 2.05 wt.% at 2200 ℃, and the open porosity increases constantly, reaching to 9.29 vol.% at 2600 ℃. On the materials surface, the residual Cu melt and volatilize firstly, and then residual Zr, a few ZrC vaporizing at 2600 ℃. While inside the materials, the WC phases disappear after heat treatment at 1800 ℃, also the residual Zr-Cu alloy phases and W2C phases at 2200 ℃, when heat treated at 2600 ℃, only W phases and ZrC phases reserve in W/ZrC cermets. Moreover, more W atoms diffuse into the ZrC phases along with the temperature increases, leading to lattice constants of ZrC decrease, and the orbicular W phases change to be ruleless long strip, also the quantity and volume fraction of W phases reduce, and lots of obturators form contrarily. The melting loss of remanent Zr-Cu alloy and diffusion of W atoms are important reasons for arosing composition and mircrostructure changes of W/ZrC cermets in ultra-high temperature.

    • The effects of excess Mg, Si on the properties of 6101 conducting wire and exploring the mechanism

      2016, 45(4):968-974.

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      Abstract:The effects of excess Mg, Si on the conductivity and mechanical properties of 6101 conducting wire were studied by the ways of conductivity measurement, tensile test, XRD and microstructure analysis .The results showed that, the alloys with more than 0.15% excess of Mg, after aging, one side, Mg would still exist in matrix and cause lattice distortion. On the other hand, the solubility of precipitates would be significantly reduced and easily turn to coarse phase causing by excess Mg. The changes in this two aspects restrict the improve of conductivity and mechanical properties; To the alloys with 0.13%, 0.05% excess of Si, after aging , the excess Si separate from the matrix, which decreases the degree of lattice distortion and promote the precipitation of β. In addition, excess Si reduces the bad effect of Fe by forming AlSiFe ternary phase. So excess Si does good for improving alloy’s conductivity and mechanical properties.

    • Primary carbide and its strengthening roles in K465 and K492 Superalloy

      2016, 45(4):975-978.

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      Abstract:The tensile, high cycles fatigue and DSC tests were made on K465 and K492 alloy. The morphology and distribution of primary carbide were investigated being used on SEM and TEM. MC-type carbide was formed as Chinese script morphology in K465 alloy. The tensile strength of as–cast K465 alloy was improved at room-temperature because of Chinese script MC-type carbide. Dispersed MC carbide was produced in as-cast K492 alloy. High-cycle fatigue strength was decreased when the size of carbide became large. High-cycle fatigue strength was increased when the size of carbide became small.

    • Study of evolution behaviors of secondary phase particles in 1235 ultra-thin double zero foil blank during rolling process

      2016, 45(4):979-981.

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      Abstract:The evolution behaviors ofAl-Fe-Si secondary phase particles in 1235 ultra-thin double zero foil blank during rolling process were observed by TEM. The results shown that bulk secondary phase particles were elongated under the shear stress during rolling process. Meanwhile many small spherical secondary phase particles were concentrated around the elongated bulk secondary phase particles. The major reason for secondary phase particles dissolution and spheroidizing was diffusion process, crystal defects such as high density dislocations and vacancies are the main channels of secondary phase particles dissolution.

    • Microstructure Evolution During Aging of Alloy 617B for 700 ℃ Ultra-Supercritical Boiler Pipe

      2016, 45(4):982-989.

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      Abstract:The microstructure stability during high temperature long-term aging of material for power plants is critical for the material choice and safety of power plants. In this paper the microstructure stability and mechanical properties of alloy 617B after 720 ℃/10000 h, 800 ℃/2000 h and 850 ℃/100 h aging and short term aging at different temperature are studied. The results show that the microstructure stability of alloy 617B after aging at 720 ℃ for 10,000 is relatively poor, γ? phase coarsens and harmful phase precipitates on grain boundary. Aging temperature has important influence on the microstructure stability of alloy 617B as γ? phase coarsened rapidly with the increasing of aging temperature and the intragranular precipitates transferred. The hardness of alloy 617B is mainly influenced by the precipitation rule of γ? phase. There are zipper-like precipitates in grain during 720 ℃ aging while the structure of phase needs further study.

    • Effects of Si and Nd co-addition on microstructures and mechanical properties of Mg-11Li-3Al alloy

      2016, 45(4):990-996.

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      Abstract:In this paper, Magnetic high frequency induction heating method is used to prepare the high quality magnesium-lithium alloys. The effects of Si-Nd co-addition on microstructures and mechanical properties of Mg-11Li-3Al alloy were studied. The results indicate that two main second phase Mg2Si and Al11Nd3 were formed in the alloys adding Si and Nd elements. The added Si element can promote the formation of a black precipitate morphology Chinese characters gathering area, and Nd can refine the rod-like black precipitates and reduce the grain size, clean tissue. When the addition amount of Nd was 1 wt%, the best refinement was obtained. The XRD and EDS analysis found that the rod-like black precipitates were combined phases of Mg2Si and Al11Nd3. The tensile strength of the as-cast alloys increase with the Si content and finally level off. The plasticity will not change monotonously with a certain or compound element. The Mg-11Li-3Al-1Si-1Nd alloy acquires the best comprehensive mechanical properties, its tensile strength and elongation reach 212.3 MPa and 46.2 %, respectively.

    • Effect of active element on interface wettability and microstructure of NiAl-modified C/C composites prepared by infiltration

      2016, 45(4):997-1002.

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      Abstract:Wetting behaviors of carbon, TiC, SiC or ZrC by molten NiAl intermetallic compound at 1800℃ were investigated by the sessile drop technique under vacuum. Active element and addition quantity were optimized by spreading and infiltrating experiment in the NiAl-modified C/C composite. NiAl-modified C/C composites were prepared by the vacuum molten infiltration. The microstructures and infiltration mechanism were analysed by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The results show that NiAl has lower wettability on carbon or SiC, while has higher wettability on TiC or ZrC. It is indicated that adding Ti can improve the wettability between C/C composites and NiAl intermetallic. NiAl with about 15%Ti (mass fraction) possesses good wettability on the surface of C/C composites. The death of NiAl permeable layer on C/C composite is about 0.8~0.9 mm. The molten NiAl intermetallic compound containing titanium infiltrates into the C/C composites preform, and TiC phase forms in the NiAl-modified C/C composites. The improvement of adding titanium for molten NiAl infiltration into the C/C composites preform results from the improvement of the chemical and physical adsorption characteristic of NiAl on the composites. The liquid NiAl infiltrates into the preform under the capillary pressure.

    • Mechanism of Rare Earth CeO2 on the Ni -Based Laser Cladding Layer of 6063 Al Surface

      2016, 45(4):1003-1007.

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      Abstract:Abstract: On the surface of 6063 aluminum alloys, using laser cladding technology prepared Ni60 alloy cladding layer with added rare earth CeO2, and by metallographic microscope, XRD, SEM and EDS equipment for the testing and analysis, researched the influence of CeO2 on the phase structure, compositions and other microstructures of 6063 aluminum surface laser cladding Ni-based cladding layer, to explore the effect and mechanism of rare earth oxide CeO2. The results showed that : Adding 5% CeO2 can effectively reduce the cracks and holes of Ni60 cladding layer, so that the cladding layer has a better structure morphology; The main phase structures of 5% CeO2 Ni60 cladding layer and Ni60 cladding layer both are β-NiAl (Cr) and a small amount of NiAl3, Ni3Al, Al, etc; After the addition of rare earth, the intensity of β-NiAl phase (110)、(200)、(211) diffraction peaks and Al peaks are significantly reduced, and there are clear peaks of NiAl3 phase; Compared with Ni60 cladding layer without adding rare earth CeO2, the Ni60 cladding layer added CeO2 have a uniform element distribution, a lower dilution rate; Adding 5% CeO2 can significantly reduce the porosity, refine the grain size and have more diffuse distribution grains at the surface of Ni60 cladding layer, but the effect is not obvious to the microstructure at the bottom of the cladding layer.

    • Preparation and Electrochemical Property of Combined Electrode of LaMg2Ni2.7Co2.1Mn2.7Cu1.5 Coated with TiO2

      2016, 45(4):1008-1011.

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      Abstract:LaMg2Ni2.7Co2.1Mn2.7Cu1.5 hydrogen storage alloy was synthesized by the method of co-precipitation and reduction diffusion, and TiO2 powder by hydrothermal method, then the alloy was coated with TiO2 powder to prepare composite electrode. The structures of the hydrogen storage alloy and TiO2 powder were characterized by X-ray diffraction. The electrochemical performances of composite electrode were tested by battery tester under two different conditions. In one condition, the electrode was kept in a dark box. In another condition, the electrode was kept under radiation of a ultraviolet lamp. The results show that in dark box the activation performance and maximum discharge capacity of composite electrode are not as good as that of original alloy electrode that is not coated with TiO2, but the cyclic stability becomes better. In light condition, the electrochemical performances of the composite electrode, including activation performance, maximum discharge capacity and cyclic stability, become better than that of original alloy electrode. For example, the maximum discharge capacity of composite electrode (coated with 20% TiO2) increases 25mA?h?g-1 compared with original alloy electrode. They are also better than that in dark box. The results of this paper illustrate that combination of LaMg2Ni2.7Co2.1Mn2.7Cu1.5 hydrogen storage alloy with TiO2 by surface coating method is effective to improve electrochemical performances of the alloy.

    • Design of WC Composite Powders and Coatings with Characteristic of in-situ Synthesis Al2O3

      2016, 45(4):1012-1017.

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      Abstract:Nanostructured WC-Co-Al powders with characteristic of in-situ synthesis Al2O3 were synthesized from submicron structured WC-12Co powder and Al powder using ball-milling method. XRD analysis showed that the average size of WC grains was 93.1nm, 39.0nm and 44.8nm after milling 10h, 30h and 50h, respectively. When sprayed by high velocity oxygen fuel (HVOF) thermal spraying, WC-Co-Al powders were more easily flattened than WC-12Co powder without ball-milling. The porosity of WC-Co-Al coating was only 0.57% which was much lower than that of WC-12Co coating with a value of 1.62%. During spraying Al reacted with oxygen, which effectively inhibited the decarburization of WC, and Al2O3 hard ceramic particles were in situ generated in coatings. The microhardness of WC-Co-Al coating was 1298?3HV0.1, higher about 36% than that of WC-12Co coating, which mainly benefitted by the enhancement effect of Al2O3 particles, nanocrystallization of WC phase and lower porosity.

    • Morphology and microstructure of gas-atomized hypereutectic Al-Si alloy powders

      2016, 45(4):1018-1023.

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      Abstract:The morphology and microstructure of hypereutectic Al-Si alloy powder were analysized as a function of particle size using scanning electron microscope, differential scanning calorimetry and X-ray diffraction. The cooling rate and undercooling of powder was calculated. The results show that the homogeneousity of distribution of Si phases decreases with the decrease of particle size. Size of primary Si phase decreases with the decrease of particle size and the morphology of primary Si phase becomes regular. The morphology of eutectic Si changes into a network structure. X-ray diffraction line becomes boarded and shifts with the decrease of particle size. The DSC curve features of powders with different sizes deviate at the same time. The calculated results indicate that cooling rate and undercooling increases with the decrease of particle size, which leads to the deviation of microstructure.

    • Effect of Zr addition on the spinodal decomposition and discontinuous precipitation of Cu-4Ti alloy

      2016, 45(4):1024-1029.

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      Abstract:The Cu-Ti series alloys, strengthen by the spinodal decomposition during the heat treatment, are easy of losing strength and hardness after over aging, which need to add elements to optimize them. The effect of 0.1wt% zirconium addition on the spinodal decomposition and discontinuous precipitation of Cu-4Ti alloy has been studied. Microstructure was investigated by Optical Microscope (OM) and Transmission Electron Microscope (TEM). Mechanical properties and electrical conductivity (EC) were tested to show the properties of these alloys. The results show that spinodal decomposition process was retarded and discontinuous precipitation was suppressed by 0.1 wt% zirconium added to Cu-4Ti alloys, because of the hindering of zirconium to titanium’s diffusion. Zirconium elevated the properties of this alloy on peak aging at 450℃ for 7h. The zirconium has little influence on electrical conductivity of the Cu-4Ti-0.1Zr alloy. The tensile strength was 1155 MPa, microhardness was 330 and the electrical conductivity was 15.4%IACS.

    • Preparation and Luminescence Properties of Red Phosphors Ca3Y2Si3O12:Eu3

      2016, 45(4):1030-1034.

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      Abstract:The red phosphor Ca3Y2Si3O12:Eu3 was synthesized by the high temperature solid-state method. The Eu3 ion doping concentration, flux and Gd3 co-doping on the luminescence properties were studied. XRD analysis showed that the principal crystalline phase was Ca3Y2Si3O12, attributed to monoclinic system. Fluorescence spectroscopy showed that the emission spectrum of silicate phosphor Ca3Y2Si3O12:Eu3 consisted of two main emission peaks, located at 590nm(5D0 → 7F1) and 614nm(5D0 → 7F2). Monitored with the strongest peak of 614nm, excitation spectrum was obtained which ranged from 200 to 500nm. The results showed that the emission intensity of the phosphors firstly increased and then decreased with the increasing of the doping concentration of Eu3 ion. It is found that the optimum doping concentration of Eu3 ion was 20mol%. The influence of several kinds of fluxes was discussed that The influence of several kinds of fluxes was discussed that the phosphor emission intensity decreased by adding a certain amount H3BO3, but increased significantly by adding NH4F. There is little effect to the phosphor emission intensity by adding NaCl or CaF2. Gd3 ion could be acted as a good co-activator, improving the emission intensity of Eu3 ion.

    • The Effect of Microstructure on Fatigue Crack Propagation of Er-containing Aluminum Alloy

      2016, 45(4):1035-1039.

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      Abstract:The Er-containing Al-Mg alloy plates were processed by different heating treatments. The effects of microstructure on fatigue crack propagation of the plates were analyzed. The results show that, the more slender of the grain, the faster of fatigue crack propagation rate; with the reduction of fatigue crack propagation rate, the crack width increase and crack path twists and turns. Due to the addition of rare earth element Er, formed Al3 (Er, Zr) peticipate particles in the alloy, the Al3 (Er, Zr) pin the dislocation, strongly hinder dislocation motion, in order to reduce the stress concentration in the grain boundary produced by the dislocation pile-up, and then reduce the fatigue crack growth rate.

    • Effect of solution temperature on the properties and microstructure of a Al-11.7Zn-2.2Mg-2.0Cu-0.12Zr aluminum alloy

      2016, 45(4):1040-1044.

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      Abstract:Effect of solution temperature on solid solubility, tensile properties, microstructure and fractography of a new Al-Zn-Mg-Cu-Zr aluminum alloy were studied by tensile testing, optical microscopy, XRD, SEM and EPMA. The results indicated that the solid solubility of matrix increase with the increasing temperature, and when it reach stable state at 474℃, about 99 wt.%Zn, Mg and 75 wt.%Cu enter matrix, the residual elements enrichment in the second phase particles(T phase)located on grain boundary. The optimal solution temperature is 474℃, the tensile strength of forge can get up to 688MPa, and elongation is 8%. At 476℃, the slight over-burned in local region is observed, which lead to the decrease of elongation rapidly. It is found that the tensile fractography was affected by the volume fraction of residual particles and the recrystallization level of deformed grains. With the temperature increasing, the fractography transform from intergranular cracking mixed dimple-type transgranular cracking to intergranular cracking.

    • Study on Structural Stabilities and electronic structure of Mg17Al12、Al2Ca、Al2Nd、Al2Er intermetallic compounds by first principles

      2016, 45(4):1045-1050.

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      Abstract:The structural stabilities and electronic structures of Mg17Al12, Al2Ca, Al2Nd and Al2Er intermetallic compounds have been investigated by Castep module based on the density functional theory. The heats of formation, cohesive energies and densities of states (DOS) of these compounds are calculated and the crystal structures are optimized. Results show that the heats of formation and cohesive energies are all negative. The Al2Er has the strongest alloying ability and structural stability, then Al2Nd, thirdly Al2Ca and finally Mg17Al12. The calculated DOS of all the compounds in this study shows that Al2Er and Al2Nd exhibit the stronger structural stabilities and the reason can be deduced as follows: (1) The valence electrons between Al (3p) and Er (4f), Al (3p) and Er (5d), Al (3p) and Nd (4f), Al (3p) and Nd (5d) orbits hybrid seriously in the lower energy region below Fermi level. (2) The bonding electron numbers of Al2Nd and Al2Er are more than Al2Ca and Mg17Al12. (3) The bonding abilities of Al2Nd and Al2Er are stronger. Moreover, the calculations of density of charge indicate that all of these compounds contain metallic, ionic and covalent bonds. In these compounds, Al2Er and Al2Nd have the stronger covalent bonds than Al2Ca and Mg17Al12, while the Al2Ca has the strongest ionic bonds and the Mg17Al12 is dominated by the metallic bond.

    • A Study of hot deformation behavior for a New type of Nb-based alloy

      2016, 45(4):1051-1054.

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      Abstract:In order to investigation the forging permormance of a New type Nb-based alloys, the deformation behavior of this alloy is researched at temperature range 1000-1200℃ and strain rate range10-1-10s-1 with a Gleeble-3500 machine by hot compression. The results show that the flow stress is controlled by both strain rate and deformation temperature,the flow stress decreases with the increase of temperature,while increases with the increase of strain rate.The high-temperature deformation obeys a power-law type equation. The stress exponent n is evaluated to be 12.03 and the apparent activation energy is 577.06 kJ/mol, and the constitutive equation that reflects how the thermal mechanical parameters influence the forming of material is regressed.

    • The microstructure and mechanical properties of Mg-6Al-5Zn-xCa(x=4,5,6,7)-5Gd alloys.

      2016, 45(4):1055-1060.

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      Abstract:The effects of different high content of Ca and heat treatment on microstructure and mechanical properties of the as-cast Mg-6Al-5Zn-xCa-5Gd alloys were investigated in this paper. The results indicate that with the addition of Ca content in as-cast condition, the β-Mg25(Al, Zn)37.5 phase which continuously distributes in grain boundary becomes finer. The granular Al2Gd and the block CaZn5 phase gradually dissolve in the matrix more uniformly. Hence the tensile strength and yield strength increases firstly, then decreases, and the elongation decreases all the way. After the solid solution treatment, the most of β-Mg25(Al, Zn)37.5 phase is dissolved in the matrix, and the strength and the elongation increases obviously. With the increase of Ca content, much more granular and lump phase distribute in the surface. And the ultimate tensile strength and yield strength increases firstly, then decreases, but little change has happened with the elongation. After solid solution treatment and aging treatment, the age-hardening of alloys reachs the peak at 12h. Then the hardness tends towards stability after slightly lowering, which shows that the alloy has significant thermal stability. Fracture analysis shows that with the increase of calcium and the different heat treatment, fracture mechanism of the alloys transforms from brittle to ductile. With the content of Ca increasing to 6wt%, dimples can be observed obviously. After the heat treatment, the dimples are increasing and the size of which are uniform. The mechanical properties of the alloy of Mg-6Al-5Zn-6Ca-5Gd by solid solution treatment at 390℃/8h and aging treatment at 200℃/12h get optimal performance.

    • Study on Microstrcture Evolution and Mechanical Properties of Ti-35Nb-7Zr-10CPP Biocomposites

      2016, 45(4):1061-1066.

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      Abstract:Ti-35Nb-7Zr-10 Calcium pyrophosphate (CPP) composites were prepared by spark plasma sintering (SPS) technology varied from 950 ℃ to 1150 ℃. The effects of the sintering temperature on the relative density, microstructure evolution, and mechanical properties of the composites were investigated. The results showed that the composites were consisted of a β-Ti phase matrix, a little residual α-Ti phase and metal - ceramic phases (Ti2O, CaO, CaTiO3, CaZrO3 and TixPy). With the sintering temperature increasing, the residual α-Ti phase decreased, while the metal - ceramic phase gradually increased. The elastic modulus and compressive strength of composites appeared a tendency of increase with the sintering temperature rising. However, when the sintering temperature was over 1050 ℃, metal - ceramic phases rapidly increased due to the violent reaction between metal and ceramic, which led to the elastic modulus increasing drastically. Thus, when the sintering temperature were in the range of 1000 - 1050 ℃, The elastic modulus and compressive strength of composites were in the range of 42 - 45 GPa and 1240 - 1330 MPa, respectively, revealing better overall mechanical properties. At the same time, the surface of the composite after soaking in SBF for 7 days formed a dense bone-like apatite layer, which showed a good bioactivity.

    • Au@SiO2 Nanoparticle with Different Shell Thickness for Surface Enhanced Raman Scattering

      2016, 45(4):1067-1071.

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      Abstract:In this work, well-crystallized Au nanoparticles with avarage sizes of 30 ~35 nm were obtained through Galvanic replacement, and subsequently the Au@SiO2 composite particles with different silica shell thicknesses were successfully synthesized. The microstructures and morphologies of the Au@SiO2 nanoparticles were also characterized using UV-Vis, TEM and HRTEM. The Rhodamine 6G (R6G) dye was selected as probe molecules to evaluate the SERS effects of Au@SiO2 nanoparticles with various shell thicknesses. The results show that SRES signal intensity and quality of the R6G molecules are obviously improved as compared with Au NPs synthesized using the same method. Furthermore, the SiO2 shell thickness has a significant influence on the SERS acitivity. The highest SERS effect is abtained using Au@SiO2 nanoparticles with shell thickness of 2nm with an extremely low detection limit of 10-7 mol/L.

    • Preparation and analysis of molybdenum coating on the surface of silicon carbide

      2016, 45(4):1072-1077.

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      Abstract:The molybdenum coating was successfully deposited on the surface of silicon carbide by magnetron sputtering method, its surface morphology and chemical composition were analyzed. In order to ameliorate the surface morphology and the state of molybdenum coating, different kinds of crystallized heat-treatment were carried out. The evolution of the surface morphology and chemical composition of the molybdenum coating were investigated in detail and the results are as follows: The molybdenum coating can be successfully deposited on the surface of silicon carbide by magnetron sputtering method, with the sputter time postponed the roughness and the thickness of the coating was enhanced, and furthermore the molybdenum on the surface was in amorphous state. During the crystallized heat-treatment process, the morphology evolution of the molybdenum coating was as follows: the primary densification phase, the compactly crystallization of molybdenum atoms, the dispersive accumulation of molybdenum coating, the reaction between molybdenum and silicon carbide. The state evolution of molybdenum atoms was as follows: amorphous molybdenum, crystalline molybdenum, molybdenum compound (Mo2C and MoSi2). And the best heat treated temperature range is about 800℃-900℃. It is believed that the uniform and compactly Mo coating will broaden the application filed of SiC particles as the reinforcement in metal matrix composites especially have advantaged in control the interfacial reaction and improve interface bonding force in metal matrix composite.

    • On the formation cause of stress collapse in TC6 alloy under dynamic compression

      2016, 45(4):1078-1081.

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      Abstract:Using the technology of split Hopkinson bar and a new method that can be used to interrupt test and obtain different amount of strain, dynamic compression test has been done on TC6 titanium alloy. By associating microstructure of shear band under different amount of strain with mechanical response of material, the formation cause of stress collapse in TC6 alloy under dynamic compression has been studied. It is shown that formation of adiabatic shear band of materials under high strain rate is a process composed of initiation, expansion and full development, and that stress collapse in stress-strain curvy is not resulted from the initiation and growing of adiabatic shear band, even involving cracks with its size not larger than certain critical size. Real reason of stress collapse in curvy is due to size of cracks has exceeded certain size within the adiabatic shear band.

    • Study on Microstructure and Formation Mechanism of Al Matrix Composite Reinforced with In-Situ TiAl3 Intermetallic particles

      2016, 45(4):1082-1087.

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      Abstract:The Ti-80Al (wt. %) composite was deposited by cold spraying of Ti/Al mixture powder and a Al matrix composite reinforced with in-situ TiAl3 intertermtallic particles was prepared through annealing treatment of the above-mentioned cold-sprayed Ti/Al deposit. The microstructural evolution of TiAl3/Al composite during annealing treatment were investigated by Scan electrom microscopy (SEM), Engergy disperse spectroscopy (EDS) and X-ray diffraction instrumentor. The solid diffusion reaction between Ti particles and Al particles in the annealed Ti/Al deposit was studied and the in-situ formation mechanism of TiAl3 intermetallics was investigated. Results found that the as-sprayed Ti/Al deposit exhibited dense microstucture and had the same phase constitutes with that of the feedsock powder. The solid diffusion reaction between Ti particles and Al particles occurred in the local area of Ti/Al deposit when annealed at a temperature of 450oC and consenquently formed in-situ TiAl3 intermetallics. With increasing annealing temperature, content of TiAl3 intermetallics continuously increased. After annealing at 600oC, all Ti particles in the Ti/Al deposit had completely transformed into TiAl3 intermetallics, as a result, the Al matrix composite reinforced with in-situ TiAl3 intermetallics partices was prepared.

    • >Reviews
    • Research Progress of AlMgB14 Super-hard Materials

      2016, 45(4):1088-1092.

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      Abstract:AlMgB14 is of great interest due to its extreme hardness, low density, high thermal stability and desirable thermoelectric properties. AlMgB14 is a very promising candidate as wear-resistant, self-lubricating and protective coatings for cutting tools and protective coatings for micro devices and micro electromechanical components. Some methods for preparing AlMgB14 super-hard materials were introduced, especially a two-step heat treatment method. AlMgB14 disks were synthesized at ambient pressure through a two-step heat treatment. In the first step, MgB2 disks doped with Al and Ti were fabricated through composition of uniformly mixed Mg, B, Al powders and different contents Ti powder in the form of pressed disks heated at 850 ℃ for 2 hours in closed argon atmosphere. And in the second step, target AlMgB14-TiB2 disks were obtained after sintering the MgB2 disks at 1050 ℃ for 0.5 hours in vacuum. The phase, microstructure and superconductivity were characterized by means of X-ray diffraction (XRD), Scanning electron microscope (SEM) and superconducting quantum interference device (SQUID). The grain size of AlMgB14 is fine and the nano-scale TiB2 particles as the second phase induced by Ti doping are uniformly distributed in the sample matrix. The research status on bulk and film of AlMgB14 and the future researching scope of AlMgB14 were introduced.

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