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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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
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.
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.
Skutterudite-based compounds, Co4Sb12-x-yTe xSey (x=0.4, 0.5, 0.6 and y=0.0, 0.1), are synthesized by the solid state reaction and the spark plasma sintering methods, and their structure and the thermoelectric propert...
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Bismuth strontium titanate ceramics are rarely used for energy storage. In this paper, the energy storage characteristics of bismuth strontium titanate ceramics (1-(x/3))SrTiO 3 -(x/3)(Bi 2 O 3 ·3TiO 2 ) were sys...
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Bismuth strontium titanate ceramics are rarely used for energy storage. In this paper, the energy storage characteristics of bismuth strontium titanate ceramics (1-(x/3))SrTiO 3 -(x/3)(Bi 2 O 3 ·3TiO 2 ) were systematically researched. The traditional solid phase sintering method was employed for preparing bismuth strontium titanate ceramics. The frequency dependence of dielectric constant, the frequency dependence of the dielectric loss, and the DC electric field dependence of dielectric constant were measured. The energy storage density was obtained by integrating the area within the polarization axis and the discharge curve in the polarization-electric field (P-E) curve. Experimental results show that, when x=0.15, (1-(x/3))SrTiO 3 -(x/3)(Bi 2 O 3 ·3TiO 2 ) ceramic has high dielectric constant, fine frequency stability, high resistivity, low dielectric loss and weak DC electric field dependence of dielectric constant. And its energy storage density could achieve 1.63 J/cm 3 at 217.6 kV/cm electric field. Thus, it may possess the potential being used as a kind of energy storage dielectric material.
Laminated ZrB2-SiC ceramics with porous ZrB2 interlayers were successfully prepared by Spark plasma Sintering (SPS)/tape casting, laminating and Reactive Spark Plasma Sintering (RSPS). ZrB2-SiC plates were sintered by...
Laminated ZrB2-SiC ceramics with porous ZrB2 interlayers were successfully prepared by Spark plasma Sintering (SPS)/tape casting, laminating and Reactive Spark Plasma Sintering (RSPS). ZrB2-SiC plates were sintered by SPS. And ZrO2-B4C sheets were prepared by tape casting, which will undergo reducing reaction that produces porous ZrB2 interlayers during SSPS processing. The ZrB2-SiC plates and ZrO2-B4C sheets were laminated alternately and reactive sintered to laminated ceramics with porous ZrB2 interlayers. The porosity and thickness of the porous layers were controlled by the tape casting processing and sintering pressure. The microstructure of the laminated ZrB2-SiC ceramics was analysed and discussed in details.
Life is a typical chiral system,and chiral phenomena are ubiquitous in nature from macroscopic to molecular levels.1 For example,small natural biomolecules are mostly chiral molecules which show distinct chiral prefer...
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Life is a typical chiral system,and chiral phenomena are ubiquitous in nature from macroscopic to molecular levels.1 For example,small natural biomolecules are mostly chiral molecules which show distinct chiral preference,e.g.L-amino acids,D-sugars, L-phospholipids,etc..They integrate together via multiple chemical bonding or weak molecular interactions to form biomacromolecules with special steric confomiations and functions,which further assemble to form organelles,cells,tissues,and organs.
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