Tungsten Copper-based metals (W/Cu) were extensively used as electrical contact materials in switching systems for the electric power industry. In this paper, a novel investigation to prepare Tungsten Copper-based met...
Tungsten Copper-based metals (W/Cu) were extensively used as electrical contact materials in switching systems for the electric power industry. In this paper, a novel investigation to prepare Tungsten Copper-based metal composite materials according to functionally graded material (FGM) concept and the method of tape casting was reported. Cu-coated W powders with different Cu weight fraction were synthesized via electricless plain in methanol-water solvent. The green tapes with different composition and thickness were laminated and then sintered to prepare W-Cu functionally graded materials. XRD, EDS, SEM and metallographic analyses were used to characterize the material microstructure and combination between different layers. The results showed that the Cu-coated W powders had grate compressibility leading to wettability of powders. The parallelism and flatness of intermediate layer were good and the combination was tight.
Microstructure evolution during ART-annealing （austenite reverted transformation annealing） of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM, TEM and XRD. It was demonstrate...
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Microstructure evolution during ART-annealing （austenite reverted transformation annealing） of 0.2C-5Mn steel processed by austenitation at different temperatures was examined by SEM, TEM and XRD. It was demonstrated that the initial mi- crostructures resulted from austenization at different temperatures strongly affect the microstructure evolution during followed ART-annealing, even the ultrafine grained ferrite/austenite duplex structure with about 30% austenite could be obtained af- ter long time ART-annealing in all cases. Austenization in the intercritical region （between Ad and At3） gave a duplex structure after quenching, which was nearly not affected by followed annealing process. However, high temperature austenization （above A^3） resulted in a full martensite structure after quenching, which gradually transformed into a ferrite/austenite duplex structure during the following anneal- ing process. Based on the analysis of austenite fraction and carbon concentrate, it was found that not only carbon partitioning but also manganese paxtitioning in the austenite affected the stability of austenite and even dominated the development of lamellar ferrite and austenite duplex structure during intercritical annealing with different times. At last an austenite lath nucleation and thickening model was pro- posed to describe the microstructure evolution of medium mangenese steel during ART-annealing.
Cubic boron nitride/Tungsten carbide-cobalt (cBN/WC-Co) composites were fabricated at low temperature by pulse electric current sintering (PECS) using Ni-P as sintering additives to promote low temperature densificati...
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In the present study, silicon nitride (Si3N4) electromagnetic wave transparent ceramics with high porosity and porous gradient structure are prepared by cold spray and pressureless sintering technique. Zirconium phosp...
In the present study, silicon nitride (Si3N4) electromagnetic wave transparent ceramics with high porosity and porous gradient structure are prepared by cold spray and pressureless sintering technique. Zirconium phosphate solution is used as a binder material instead of the traditional organic materials, in order to prevent the residual carbon which is severe to the dielectric properties of the Si3N4 porous ceramics. Firstly, Si3N4 ceramic slurries with different phosphorus acid and pore-forming agent contents are prepared. Then the Si3N4 slurries are cold sprayed layer by layer to achieve a porous gradient structure, and finally the samples are presurelessly sintered at 1000 °C in a nitrogen atmosphere. The results show that the porosity of the obtained Si3N4 ceramics is 20~70 % and the Si3N4 ceramics exhibits a good porous graded structure from high to low porosity.
Ceramic materials are frequently used in protective armor applications for its low-density, high elastic modulus and high strength. It may be subject to different ballistic impacts in many situations, thus many studie...
Ceramic materials are frequently used in protective armor applications for its low-density, high elastic modulus and high strength. It may be subject to different ballistic impacts in many situations, thus many studies have been carried out to explore the approach to improve the mechanical properties of the ceramic material. However, the materials manufactured in real world are full of defects, which would involve in variable fractures or damage. Therefore, the defects should be taken into account while the simulations are performed. In this paper, the dynamic properties of ceramic materials (Al2O3) affected by different strain rate (500–5000) and porosity (below 5%) are investigated. Foremost, the effect of strain rate was studied by using different load velocities. Then, compression simulations are performed by setting different porosities and random distribution of pores size and location in ceramic materials. Crack extensions and failure modes are observed to describe the dynamic mechanical behavior.
The effect of cooling rate on plastic deformation of Zr-based bulk metallic glasses has been *** specimens with the diameters of 3 mm,4 mm and 6 mm cut from the same ladder-shaped Zr 55 Al 10 Ni 5 Cu 30 BMG rod were u...
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The effect of cooling rate on plastic deformation of Zr-based bulk metallic glasses has been *** specimens with the diameters of 3 mm,4 mm and 6 mm cut from the same ladder-shaped Zr 55 Al 10 Ni 5 Cu 30 BMG rod were used in the present *** experimental results indicated that the different plastic strains were induced for the three type compression *** compressive plastic strain increased with the decreasing diameter for the as-cast specimens,which means that the compressive plastic strain increased with the increasing cooling *** reason of the difference is attributed to the free volume existed in the BMGs during the rapid solidification,and the larger free volume was contained in the specimen fabricated with the higher cooling *** has been found that the prominent serrations and multiple shear bands appeared during the compressive deformation tests of the specimen with smaller diameter of 3 mm,indicating that the specimen with smaller diameter exhibits better plasticity due to more free volume content.
Skutterudite-based compounds, Co4Sb12-x-yTexSey (x = 0.4, 0.5, 0.6 and y = 0.0, 0.1), are synthesized by the solid state reaction and spark plasma sintering methods, and their structure and the thermoelectric properti...
Skutterudite-based compounds, Co4Sb12-x-yTexSey (x = 0.4, 0.5, 0.6 and y = 0.0, 0.1), are synthesized by the solid state reaction and spark plasma sintering methods, and their structure and the thermoelectric properties have been investigated systematically. It is found that the doping of Se resulted in a decrease of the lattice parameter and a refinement in the grain size compared with that of Te alone doped samples. The samples doping of Se do not yield a certain increase in the power factor due to the reduced electrical conductivity, but it shows a significant depression in the lattice thermal conductivity because of the enhanced point-defect scattering owing to the larger mass fluctuations and strain field fluctuations. Besides, the effect of the reduced grain size and the nano-precipitates on the lattice thermal conductivity should not be neglected. The highest dimensionless figure of merit ZT = 1.09 is achieved at 800 K in the Co4Sb11.3Te0.6Se0.1 compound, which is improved by 15% as compared with that of Te-alone-doped Co4Sb11.4Te0.6 compound at the corresponding temperature.
In the study of artificial biomaterials,a fundamental scientific issue is the interaction between biological systems and artificial materials at the *** a view of materials science,this
In the study of artificial biomaterials,a fundamental scientific issue is the interaction between biological systems and artificial materials at the *** a view of materials science,this
β-Zn4Sb3 is a promising candidate thermoelectric material with extraordinary low lattice thermal conductivity and high dimensionless figure of merit. In the paper, X-ray diffraction (XRD) patterns and X-ray photoelec...
β-Zn4Sb3 is a promising candidate thermoelectric material with extraordinary low lattice thermal conductivity and high dimensionless figure of merit. In the paper, X-ray diffraction (XRD) patterns and X-ray photoelectron spectra (XPS) of In-doped β-Zn4Sb3 compounds with nominal composition Zn4Sb3-mInm (0≤m≤0.18) were investigated to reveal the effect of indium doping on crystal structure and binding characteristics. The Rietveld refinement based on the XRD data indicates that the indium impurity preferentially occupies the 12c Sb(2) site in Zn4Sb3-mInm. The lattice parameter a increases and c decreases with the increasing m, accompanying with the lattice distortion and the bond length and angle modification. Indium doping enhances the occupancies of Zn atoms at the 36f Zn(1) and interstitial Zn sites, whereas the total occupancy of Sb and In atoms maintains constant. XPS analysis shows that the valence of Sb decreases and that of Zn increases with increasing the indium doping in Zn4Sb3-mInm. This implies that the negative charge might transfer from In and Zn to Sb atoms. Curve-fittings of Sb 3d photoelectron peaks prove that only the Sb atom at the 12c Sb(2) site is charged to more negative with the increasing m. Thus more Zn2+ ions near the 12c Sb(2) site are needed to maintain the charge balance, which is why the occupancy of electropositive Zn increases in the compound. The asymmetric Sb-In ionic bond forms by the In substituting Sb at the 12c Sb(2) site, which changes the vibration behavior of Sb-Sb dimer and leads to more dynamical disorders of the localized dumbbell vibrations in β-Zn4Sb3. These new lattice disorders in β-Zn4Sb3, introduced by the substitution of In for Sb, result in a much low lattice thermal conductivity of 0.49 W·m−1·K−1 of Zn4Sb2.96In0.04.
Dense graded material as a type of functionally graded material (FGM) changes its wave impedance gradually along the thickness direction. In this investigation, Al-W functionally graded material was fabricated via vac...
Dense graded material as a type of functionally graded material (FGM) changes its wave impedance gradually along the thickness direction. In this investigation, Al-W functionally graded material was fabricated via vacuum hot-pressing sintering method (VHPS). The results showed that densified Al-W composite was fabricated at 550°C-300MPa-120min which the relative density was higher than 98.5% without intermetallic compounds. The density graded material of Al-W FGM was attained at the optimized parameters which the component of Al was from 10% to 100%. The micro structure of Al-W FGM composite indicated that W particles in single-layer composite were distributed homogeneously. The density of each layer in Al-W FGM composite was consistent with the design value.
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