The downgraded and upgraded BaZrxTi2−xO5 (x=0, 0.01, 0.02, 0.03 and 0.04) films normal to Pt/Ti/SiO2/Si substrates were prepared by sol-gel method. The microstructure and dielectric properties of the compositionally g...
The downgraded and upgraded BaZrxTi2−xO5 (x=0, 0.01, 0.02, 0.03 and 0.04) films normal to Pt/Ti/SiO2/Si substrates were prepared by sol-gel method. The microstructure and dielectric properties of the compositionally graded BaZrxTi2−xO5 films were investigated. The single-phase downgraded and upgraded films were obtained as the films were annealed at 900 °C for 30 min. The downgraded BaZrxTi2−xO5 film had dense surface, while there were pores in the surface of the upgraded BaZrxTi2−xO5 film. The thicknesses of both upgraded and downgraded BaZrxTi2−xO5 films were about 500 nm. The values of permittivity (r) for the downgraded and upgraded BaZrxTi2−xO5 films were 84 and 100, respectively, at 1 MHz.
Supercritical carbon dioxide (ScCO2) foaming which is inexpensive and environmental friendly has been widely used to prepare polymer-based microporous materials. In this paper, PMMA graded microporous materials were f...
Supercritical carbon dioxide (ScCO2) foaming which is inexpensive and environmental friendly has been widely used to prepare polymer-based microporous materials. In this paper, PMMA graded microporous materials were foamed by PMMA matrix after an unstable saturation process which was done under supercritical condition of 28MPa and 50 °C. The scanning electron microscopy (SEM) was utilized to observe the morphology of the graded foam. A gas adsorption model was proposed to predict the graded gas concentration in the different region of the polymer matrix. The SEM results showed that the solid and foam region of the graded foam can be connected without laminated layers. With the increasing thickness position of the graded microporous foam, the cell size increased from 3.4 to 27.5 μm, while the cell density decreased from 1.04 × 109 to 1.96 × 107 cells/cm3. It also found that the gradient microporous structure of the foam came from graded gas concentration which was obtained in the initial saturation process.
The microstructure deformation and fracture mechanisms of particulate-filled polymer composites were studied based on microstructure observations in this paper. By using in-situ tensile test system under scanning elec...
The microstructure deformation and fracture mechanisms of particulate-filled polymer composites were studied based on microstructure observations in this paper. By using in-situ tensile test system under scanning electron microscopy, three different composites composed of polymer binder filled by three different types of particles, namely Al particles, AP particles and HMX particles, with the same total filler content were tested. The roles of initial microstructure damage and particle type on the microstructure deformation and damage are highlighted. The results show that microstructure damage starts with the growth of the initial microvoids within the binders or along the binder/particle interfaces. With the increase of strain, the microstructure damages including debonding at the particle/binder interface and tearing of the binder lead to microvoid coalescence, and finally cause an abrupt fracture of the samples. Coarse particles lead to an increase of debonding at the particle/binder interface both in the initial state and during the loading process, and angular particles promote interface debonding during the loading process.
The fabrication of polymeric foams with gradient density is a key to investigate the response of materials in quasi-isentropic loading. In this work, a non-traditional approach was proposed to fabricate the polymeric ...
The fabrication of polymeric foams with gradient density is a key to investigate the response of materials in quasi-isentropic loading. In this work, a non-traditional approach was proposed to fabricate the polymeric foam monolayer with designed density in a fixed volume by using the pre-mixture of expandable and expanded polymeric microballoons. After heating, the expandable microballoons expanded and bonded together to be integrated block with the final density from 0.1 g/cm3 to 0.5 g/cm3. The gradient density foams were fabricated by bonding with different monolayer. The microstructure and mechanical properties of each layer were investigated by SEM and compression strength tests. The results showed that the density of polymeric foams was matched with the design value very well by controlling the ratio of expandable and expanded polymeric microballoons. The uniform closed-cell structure with good bonding interface was shown from the SEM picture. And the mean cell size is less than 35μm. The polymeric foams exhibited ideal compressive behavior with the compressive strength as high as 9MPa. The Young's modulus and compressive strength nearly linear increased with the increasing of density. The extremely wide range of accessible densities should make this technology for broad application prospects.
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.
Ti/Al2O3 composite of different components were prepared by Spark Plasma Sintering technique, mechanical and acoustical properties of Ti/Al2O3 composite were analyzed, weldability of Ti/Al2O3 composite with Mo and Al ...
Ti/Al2O3 composite of different components were prepared by Spark Plasma Sintering technique, mechanical and acoustical properties of Ti/Al2O3 composite were analyzed, weldability of Ti/Al2O3 composite with Mo and Al was also studied. The results indicate that 38.5vol%Ti/Al2O3 composite has good mechanical performance with relative density >99.20%, bending strength 897MPa, fracture toughness 17.38 MPam1/2 and micro-hardness 17.13GPa. The wave impedance of the composite was between which of Mo and Al, and the 38.5vol% Ti/Al2O3 welded well with Mo and Ti. These demonstrate that 38.5vol%Ti/Al2O3 composite could serve as one of interlayer materials in W-Mo-Al system graded flier-plate.
The influence of Zn vacancy on lattice thermal conductivity of β-Zn4Sb3 is studied by non-equilibrium molecular dynamics approach. The lattice thermal conductivity of single-crystal bulk β-Zn4Sb3 decreases rapidly w...
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The leakage current, dielectric and loss properties of the integrated Pt/PbTiO3/PbZr0.3Ti0.7O3/PbTiO 3/Pt capacitors have been investigated. The capacitor has a same leakage mechanism as the film, in the low field reg...
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Well-ordered large-area two-dimensionally (2D) periodic and individually addressable metal-ferroelectric-metal (M/F/M) nanocapacitor arrays were fabricated by focused ion beam (FIB) milling with synchronal and serial ...
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