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...
详细信息
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.
Multilayered TiO2/ATO thin films were prepared by the spin-coating method to evaluate the electronic interactions and the effect of the experimental conditions on optical transparency, electric resistivity and carrier...
Multilayered TiO2/ATO thin films were prepared by the spin-coating method to evaluate the electronic interactions and the effect of the experimental conditions on optical transparency, electric resistivity and carrier density. ATO chemical composition, number of layers and annealing temperature were modified to study their effect on the global properties of the TiO2/ATO system. TiO2/ATO films exhibited an optical transparency as high as 81 % in the visible wavelength and a strong absorption within the UV spectra. Electric resistivity as low as 3.4 × 10−1 Ωcm was measured for TiO2/ATO films. Optical properties were influenced mainly by the presence of upper TiO2 layer and ATO film thickness. The effect of ATO film thickness, composition and annealing temperature on TiO2/ATO transparency and resistivity are discussed.
Antimony-doped tin oxide (ATO) nanoparticles with controlled doping level were prepared by a nonaqueous solution route, using alcohol as the solvent, citric acid as an agent, tin (IV) tetrachloride as tin source and a...
详细信息
ISBN:
(纸本)9783037856079;3037856076
Antimony-doped tin oxide (ATO) nanoparticles with controlled doping level were prepared by a nonaqueous solution route, using alcohol as the solvent, citric acid as an agent, tin (IV) tetrachloride as tin source and antimony (III) chlorideas as antimony sources. As-synthesized samples were characterized by Thermogravimetric analysis (TGA), powder X-ray diffraction (XRD), transmission electron micrographs (TEM), N2 adsorption-desorption isotherms, and X-ray photoelectron spectroscopy (XPS). The results showed that the content of citric acid was the most important processing parameter which was largely governing the reaction course and the complete incorporation of Sb. When the citric acid to metal mol ratio was 2, the particles were the highly crystallized ATO nanoparticles of about 20nm and the Sb atoms were indeed incorporated into the SnO2 crystal structure (cassiterite SnO2 ).
SiC/Cu composites exhibit low density, low coefficient of thermal expansion and excellent mechanical properties. In this study, Zn of 2 wt. % was added as the sintering activator, and the high volume faction (60%) SiC...
详细信息
ISBN:
(纸本)9783037856079;3037856076
SiC/Cu composites exhibit low density, low coefficient of thermal expansion and excellent mechanical properties. In this study, Zn of 2 wt. % was added as the sintering activator, and the high volume faction (60%) SiC/Cu composites was fabricated by hot pressing sintering technology. The phase composition and morphology of as-prepare samples were characterized by X-ray diffraction (XRD) system and scanning electron microscopy (SEM) equipped with an energy-dispersive spectroscopy (EDS) system. The as-prepared SiC/Cu composites were dense and uniform as well as void free. The results show that SiC/Cu composites can reach excellent mechanical properties of SiC/Cu composites. With the increase of sintering temperature, Vickers hardness and the bending strength of the samples increased obviously and the as-prepared SiC/Cu composites achieved a maximum Vickers hardness and bending strength respectively of 195MPa and 140MPa.
The isothermal oxidation behaviors at 800-1000 ℃ for 20h in air of bulk Ti2 AlN and Ti2 AlN/TiN were investigated by TG,XRD and SEM coupled with *** oxidation behaviors generally follow the parabolic *** activation e...
详细信息
The isothermal oxidation behaviors at 800-1000 ℃ for 20h in air of bulk Ti2 AlN and Ti2 AlN/TiN were investigated by TG,XRD and SEM coupled with *** oxidation behaviors generally follow the parabolic *** activation energies of Ti2 AlN and Ti2 AlN/TiN composite are 614.93 KJ mol-1 and 541.35 KJ mol-1 *** antioxidation property of Ti2 AlN/TiN composite is better than Ti2 *** process of single-phase Ti2 AlN is composed by the outward diffusion of Al3+ and Ti4+,and inward diffusion of *** process of Ti2 AlN/TiN composite consists of two parts:firstly,the oxidation of TiN,the oxidation temperature is 500 ℃;the second step is the oxidation of Ti2 AlN,carried out mainly in the 800-1000 ℃.
In our present work, the effect of the Zn-vacancy concentration on the lattice thermal conductivity of β-Zn4Sb3 at room temperature is studied by using the nonequilibrium molecular dynamics approach. Along both the x...
In our present work, the effect of the Zn-vacancy concentration on the lattice thermal conductivity of β-Zn4Sb3 at room temperature is studied by using the nonequilibrium molecular dynamics approach. Along both the x- and z- axes, the heat flux and the temperature gradient exponentially decay and increase respectively. The lattice thermal conductivity of the single crystal bulk β-Zn4Sb3 rapidly decreases when there exists Zn atom vacancy, and then the lattice thermal conductivity slowly falls further with the growing Zn atom vacancy proportion, which suggests that the Zn atom vacancy (nv) to the lattice thermal conductivity (kvac) leads to a scaling law of kv ∼ nv−α This phenomenon is attributed to the fact that the existence of vacancy scattering can significantly decrease the mean free path. When the vacancy proportion of Zn atom reaches 10%, that is the vacancy model of β-Zn4Sb3, the lattice thermal conductivity of β-Zn4Sb3 is 1.32 W/mk and 1.62 W/mk along the x- and z- axes respectively, which drops by ∼ 90% than that of its full occupancy model.
With good electrical properties and an inherently complex crystal structure, Cu2-xSe is a potential ＂phonon glass electron crystal＂ thermoelectric material that has previously not attracted much interest. In this st...
详细信息
With good electrical properties and an inherently complex crystal structure, Cu2-xSe is a potential ＂phonon glass electron crystal＂ thermoelectric material that has previously not attracted much interest. In this study, Cu2-xSe （0 ≤ x ≤0.25） compounds were synthesized by a melting-quenching method, and then sintered by spark plasma sintering to obtain bulk material. The effect of Cu content on the phase transition and thermoelectric properties of Cu2-xSe were investigated in the temperature range of 300 K-750 K. The results of X-ray diffraction at room temperature show that Cu2-xSe compounds possess a cubic structure with a space group of Fm3m （#225） when 0.15 〈 x ≤ 0.25, whereas they adopt a composite of monoclinic and cubic phases when 0 ≤x ≤ 0.15. The thermoelectric property measurements show that with increasing Cu content, the electrical conductivity decreases, the Seebeck coefficient increases and the thermal conductivity decreases. Due to the relatively good power factor and low thermal conductivity, the nearly stoichiometric Cu2Se compound achieves the highest ZT of 0.38 at 750 K. It is expected that the thermoelectric performance can be further optimized by doping appropriate elements and/or via a nanostructuring approach.
暂无评论