The structure and electric properties of (0.9-x)Bi(Mg1/2Ti 1/2)O3-xPbTiO3-0.1BaZrO3 (0.45 x 0.53) ceramics were investigated. The morphotropic phase boundary between tetragonal ferroelectric and pseudo-cubic relaxor p...
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In the paper, we used the LS-DYNA FE code to simulate the bullet penetration against the target plate with different ceramic-steel ratio of thickness. The main stages of the bullet penetration and damage contours of t...
In the paper, we used the LS-DYNA FE code to simulate the bullet penetration against the target plate with different ceramic-steel ratio of thickness. The main stages of the bullet penetration and damage contours of the target were studied by analyzing the residual velocity-time curves. We also studied energy absorption of the ceramic/metal target. Considering curves of residual velocity-time, we reckon the process of penetration contains four stages. Ceramic performed good resistance before the formation of damage cone of ceramic. But after the damage cone formed, the anti-penetration behavior kept declining. When the bullet started to penetrate the layer of metal, the anti-penetration behavior of target rose slightly. Compared with thickness ratio of 0.4 and 0.6, ceramic with 0.2 absorbed more energy and works longer. Of several different thicknesses, layers of ceramic and steel were studied. Steel per cm absorbed more energy than ceramic per cm.
In this article, mechanical properties of nanocrystalline Al+α-Al2O3 composites are investigated using molecular dynamics simulations. The configurations of matrix and volume fraction of α-Al2O3 may affect the mecha...
In this article, mechanical properties of nanocrystalline Al+α-Al2O3 composites are investigated using molecular dynamics simulations. The configurations of matrix and volume fraction of α-Al2O3 may affect the mechanical properties of the particle reinforced metal-matrix composites and are taken into account. The potentials for the Al+α-Al2O3 system developed by Xin Lai et al. are adopted to depict the interactions between Al and α-Al2O3. Monocrystal Al and Bicrystal Al based α-Al2O3 particle reinforced nanocomposites are modelled respectively. Results show that: (1) volume fraction of the particles has no explicit effects on the elastic modulus and ultimate strength in both monocrystal Al and bicrystal Al based matrix nanocomposites, (2) disappearance of valley in the stress-strain curve of bicrystal Al results from existence of dislocation in matrix of various orientations.
Ballistic performance of the gradient material is superior to laminated material, and gradient materials have different gradient types. Using ls-dyna to simulate the ballistic performance of ALN-AL gradient target pla...
Ballistic performance of the gradient material is superior to laminated material, and gradient materials have different gradient types. Using ls-dyna to simulate the ballistic performance of ALN-AL gradient target plates which contain three gradient index (b = 1, b = 0.5, b = 2). Through Hopkinson bar numerical simulation to the target plate materials, we obtained the reflection stress wave and transmission stress wave state of gradient material to get the best gradient index. The internal stress state of gradient material is simulated by amplification processing of the target plate model. When the gradient index b is equal to 1, the gradient target plate is best of all.
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...
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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.
Cu-12 wt.%Al(Cu-12Al) alloy fabricated by continuous unidirectional solidification(CUS) process has high elasticity,high strength,high conductivity,high plasticity and other good comprehensive properties,which has a p...
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ISBN:
(纸本)9783037856093;3037856092
Cu-12 wt.%Al(Cu-12Al) alloy fabricated by continuous unidirectional solidification(CUS) process has high elasticity,high strength,high conductivity,high plasticity and other good comprehensive properties,which has a potential to develop into a high-performance elastic material as the alternative to beryllium ***,the room temperature tensile elongation of the columnar-grained structure(CGS) Cu-12Al alloy with high <001>β orientation along the axial direction exceeded 20%,which is six times more than that of the ordinary polycrystalline structure(OPS) Cu-12Al alloy(ε=2-4%) fabricated by traditional *** CGS Cu-12Al alloy shows lower flow stress and work-hardening rate during plastic deformation,which determines a dramatic improvement of workability comparing with the OPS *** the present paper,both the effects of the rolling process and its parameters on the microstructure and properties of the CGS Cu-12Al alloy sheets were *** results showed that the CGS sheets(σb=310 MPa,ε=19%) have the maximum reduction of 80% and remain columnar-grained structure after the first rolling pass at 700℃.After deformation the tensile strength was 401 MPa and the tensile elongation approached to 14%.Then,the hot rolled sheets were rolled again through the second pass at 325℃ and 700℃,*** maximum reduction of CGS sheets at 325℃ warm rolling was 20%,the sheets remain columnar-grained structure and β1'→α1' martensitic phase transformation occured;The second pass hot-rolling at 700℃ showed that the maximum reduction exceeded 60%,and the recrystallization occured in the *** two passes of hot-rolling(total deformation was 92%),although the recrystallization occured,the CGS sheets remained columnar-grained structure(CGS) high tensile elongation(8.3%),which is two times more than that of the as-cast OPS sheets,and is five times as much as the OPS sheets with the same total deformation.
The ZrB2/SiC/Zr2Al4C5 multi-phase ceramics were fabricated by spark plasma sintering (SPS) at 1800 °C for 3 min under 20 MPa in an vacuum. Oxidation behavior of multi-phase ceramics were investigated using thermo...
The ZrB2/SiC/Zr2Al4C5 multi-phase ceramics were fabricated by spark plasma sintering (SPS) at 1800 °C for 3 min under 20 MPa in an vacuum. Oxidation behavior of multi-phase ceramics were investigated using thermo gravimetric analysis (TGA) from 20 °C to 1500 °C and muffle furnace in stagnant air at 1200 °C. Samples were analyzed after oxidation by X-ray diffraction (XRD), scanning electron microscopy (SEM) along with energy dispersive spectroscopy (EDS) to determine the reaction products and to observe the microstructure. The results showed that the aluminium borate and mullite crystallize on the surface in the samples oxidized. The effect of Zr2Al4C5 content on the oxidation resistance of the ZrB2 ceramics were discussed respectively, and oxidation mechanism was also analysised.
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