Catalysts consisting of Zeolite imidazolyl ester skeleton-67(ZIF-67)and graphene oxide(GO)were fabricated through a solvothermal method,followed by etching ZIF-67 with oxygen-rich functional groups on GO in a reductio...
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Catalysts consisting of Zeolite imidazolyl ester skeleton-67(ZIF-67)and graphene oxide(GO)were fabricated through a solvothermal method,followed by etching ZIF-67 with oxygen-rich functional groups on GO in a reduction atmosphere at 400℃.During this process,an open type of cobalt metal center was formed by the partial vaporization and oxidation of ZIF-67,further reducing to Co and partially combining with oxygen species to amorphous *** from the rich functional N,and metal/oxides active centers derived from the calcination process,the synthesized Co/CoOx@NSG-400 showed a low OER overpotential of 10 mA·cm^(-2) at 298 mV,and an ORR half-wave potential of 0.8 V,which demonstrated its excellent bifunctional catalytic *** a controllable calcination strategy with high yields could be expected to pave the way for synthesizing low-cost and efficient bifunctional electrocatalysts.
Polyacrylic acid(PAA)hydrogel composites with different hexagonal boron nitride(h-BN)fillers were synthesized and successfully 3D-printed while their thermal conductivity was systematically *** the content of h-BN inc...
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Polyacrylic acid(PAA)hydrogel composites with different hexagonal boron nitride(h-BN)fillers were synthesized and successfully 3D-printed while their thermal conductivity was systematically *** the content of h-BN increasing from 0.1 wt%to 0.3 wt%,the thermal conductivity of the 3D-printed composites has been ***,through the shear force given by the 3D printer,a complete thermal conductivity path is obtained inside the hydrogel,which significantly improves the thermal conductivity of the h-BN hydrogel *** maximum thermal conductivity is 0.8808 W/(m·K),leading to a thermal conductive enhancement of 1000%,compared with the thermal conductivity of pure PAA *** study shows that using h-BN fillers can effectively and significantly improve the thermal conductivity of hydrogelbased materials while its 3D-printable ability has been maintained.
This paper studied the thermal stresses of ceramicl metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating (TBC) and functionally gradient material (FGM). Thermal ...
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This paper studied the thermal stresses of ceramicl metal gradient thermal barrier coating which combines the conceptions of ceramic thermal barrier coating (TBC) and functionally gradient material (FGM). Thermal stresses and residual thermal stresses were calculated by an ANSYS finite element analysis software. Negative thermal expansion coefficient method was proposed and element birth and death method was applied to analyze the residual thermal stresses which have non-uniform initial temperature field. The numerical results show a good agreement with the analytical results and the experimental results.
The p-type Ge doped Fe0.4Co3.6Sb12-xGex skutterudites with multi-scaled impurity dots(500 nm-2 mm) were successfully prepared by using melt-quenching(MQ) and subsequent spark plasma sintering(SPS) technique. Com...
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The p-type Ge doped Fe0.4Co3.6Sb12-xGex skutterudites with multi-scaled impurity dots(500 nm-2 mm) were successfully prepared by using melt-quenching(MQ) and subsequent spark plasma sintering(SPS) technique. Compared with traditional method, the new technology significantly shortened the processing time from several days to less than 24 hours. The phase of impurity dots was demonstrated to be CoSb through analysis of X-ray diffraction(XRD) and energy-dispersive spectrum(EDS). Impurity dots were induced by Ge substitution of Sb in the non-equilibrium synthesized process. Due to the abandonment of the long reaction of annealing crystallization, a few of Ge atoms would fail to substitute Sb site of skutterudite in this non-equilibrium synthesized process, leading to that the multi-scaled impurity dots randomly distributed in the matrix of skutterudite Fe0.4Co3.6Sb12-xGex. The combination of multi-scaled impurity dots scattering long wavelength heat-carrying phonons and the point defect scattering short and middle wavelength heat-carrying phonons dramatically made the 22.2% reduction of lattice thermal conductivity. As a result, compared with unsubstituted sample of Fe0.4Co3.6Sb12, the maximum ZT value was increased by 30.5%. Thus, the two marked features of this new synthesis process, the shortened preparation time and the enhanced thermoelectric performance, would make a promising commercial application in the future.
The thermal reduction of graphene oxide(GO)was performed by a tube furnace at different temperatures,and its structure evolution was investigated in *** results showed that the oxygen-containing functional groups on t...
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The thermal reduction of graphene oxide(GO)was performed by a tube furnace at different temperatures,and its structure evolution was investigated in *** results showed that the oxygen-containing functional groups on the carbon plane surface of GO gradually decomposed as the temperature increase,and the reduced graphene oxide(rGO)powder was obtained at 800℃.Then,rGO powder was sintered under 30 MPa at 1800℃using spark plasma sintering(SPS)and hot-pressing(HP)to evaluate its structural stability at high *** defect densities of rGO were reduced after high-temperature *** edge flatness and sp^(2) hybrid carbon plane structure were reconstructed *** results demonstrate that the lamellar structure of rGO maintains the structural integrity during high-temperature sintering without obvious deterioration,which provides experimental and theoretical supports for GO reinforced ceramics.
Here, we introduce a Terahertz (THz) dual-band coding reflective metasurface based on the Pancharatnam-Berry (PB) phase theory. The coding metasurface is consisted of a metal layer with hollow opening resonant ring on...
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High infrared emissivity and excellent thermal conduction capability are crucial for the heat dissipation performance of heat dissipation coatings, which are applicable in the thermal management of modern electronic c...
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A novel in-situ reactive approach based on the reactions among TiN,aluminum and boron has been developed to synthesize TiB_(2)-based composites including TiB_(2)-h BN(TB)and TiB_(2)-h BN-AlN(TBA).Fully dense ceramics ...
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A novel in-situ reactive approach based on the reactions among TiN,aluminum and boron has been developed to synthesize TiB_(2)-based composites including TiB_(2)-h BN(TB)and TiB_(2)-h BN-AlN(TBA).Fully dense ceramics with fine-grained microstructure were successfully obtained via spark plasma sintering at 1850℃/60 MPa/5 *** analysis suggests h BN flakes were homogenously distributed in the TiB_(2)*** AlN,however,they were elongated into plate-like grains during sintering,in which lots of defects in terms of stacking faults and twinning structures were *** mechanical and thermophysical properties of as-sintered ceramics were comprehensively investigated and ***-corporating AlN significantly improved the flexure strength,hardness,fracture toughness and thermal conductivity of TiB_(2)-h BN *** electrical conductivity of TB(3.06×10^(6)S/m)is larger than that of TBA(2.35×10^(6)S/m)at room temperature,but the value(6×10^(5)S/m)was lower than that of TBA(6.9×10^(5)S/m)at 1173 *** on the measurement of electrical and thermal conductivity,electron and phonon contributions to thermal conductivities of TB and TBA were calculated and their temperature dependences were illustrated.
According to a space-charge theory analysis, the space-charge potential of YSZ is negative, which corresponds to a V-0(..) depletion in the space-charge layer. An extremely low grain-boundary conductivity of the high-...
According to a space-charge theory analysis, the space-charge potential of YSZ is negative, which corresponds to a V-0(..) depletion in the space-charge layer. An extremely low grain-boundary conductivity of the high-purity YSZ is thus explained. Under the condition that the bulk property is ensured by the optimal dopant additions, an idea of increasing the grain-boundary conductivity by the segregations of solutes with positive effective charge is put forward. The most likely driving force for the segregations is the elastic strain energy. And the feasibility of this idea has been proved by some experimental and theoretical results.
Hexagonal BN-coated powders have been widely used in various engineering sectors,however,their pro-ductions are restricted by the complexity of gas-solid *** this study,guided by thermodynamics,a novel approach to syn...
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Hexagonal BN-coated powders have been widely used in various engineering sectors,however,their pro-ductions are restricted by the complexity of gas-solid *** this study,guided by thermodynamics,a novel approach to synthesize Layer-structured hexagonal BN(hBN)-coated high entropy diboride pow-ders in vacuum was developed,using metal salt Zr(NO_(3))4·5H_(2)O,HfCl_(4),NbC_(15),TaC_(15),C_(16)H_(36)O_(4)Ti,boric acid,and sucrose as raw *** adjusting the ratio of carbon to metal source(C/M),powders only consisting of two boride solid solutions and hBN were finally obtained,under an optimal process-ing condition of C/M=5.5 and synthesis temperature of 1400 ℃.Parts of hBN were found to coat on high-entropy metal diborides ceramic(HEB)particles,corresponding formation mechanism for core-shell structured powders was investigated,together with the liquid precursor assisted boro/carbothermal re-duction *** from as-synthesized core-shell powders,(Ti_(0.2)Zr_(0.2)Hf_(0.2)Nb_(0.2)Ta_(0.2))B2-11 vol%hBN ceramics were densified at 1900 ℃ under 50 MPa without holding,with a high relative density of 97.3%.
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