Papers by Keyword: Layered Structure

Abstract: In multi-layer structures impurity scattering is effectively reduced by the modulation doping in order to achieve high charge carrier mobility and, as a consequence, better device performance. In this paper, the thermoelectric properties of superlattices when electrons are scattered by strongly screened ionized impurities are discussed. In low-temperature and strong screening circumstances, dependence of the thermopower, power factor, and figure of merit on the superlattice period, miniband width, and screening radius is found. For the specified superlattice parameters and ionized impurity concentration, the figure of merit reaches the value of 2.6. The thermopower of the superlattices five times exceeds that of bulk samples.

Abstract: We applied the dielectric function method to solve analytically L-NL-L structure problems with negative Kerr nonlinearity. A damped wave in linear and a periodic standing wave in non-linear media had to be matched at boundaries. We gave a formulation of boundary conditions that did not explicitly include a film thickness. The boundary-value of a dielectric function can be expressed through the constant of non-trivial integral of motion. Using it, one generates a family of matched solutions satisfying boundary conditions. Then arbitrary film thickness can be checked against this family of solutions in search of matches. As a result, all fitted solutions are determined straightforwardly.

Abstract: To study the damage effect of different projectile structures and jacket materials of PELE upon perforation of multi-layered plates, an experiment of three different kinds of projectiles impacting on multi-layered plates was conducted. The experimental results show that the layered PELE can change the characteristics of fragments broken by jacket which include quantity, mass and the area of distribution. The jacket of layered structure PELE can generate more number of fragments of uniform quality and centralized distribution than common PELE. So it results in the occurrence of cumulative damage effects on target plate. Using the W fiber /Zr-based amorphous matrix composites as the jacket material of PELE, the jacket can be broken into lots of single W fibers and W fiber bundle fragments, and the fragments distribute centrally. The impulse of the fragments loads on the plate intensively, which reduces the plate resistance and improves the opening size substantially.

Abstract: We examined the relation between the cutting force and the cutting characteristics of CFRP in diamond saw cutting. When a larger cutting force was applied, the cutting had been propagated with a mixed mechanism of the cutting by cutting edges and the cleaving of carbon fiber by shear force. While a good cutting surface was formed in the case of cutting with less than 23 N of cutting force. In this condition, the cutting had been propagated only by the cutting with cutting edges.

Abstract: The layered LiNi_1/3Mn_1/3Co_1/3O_{2 ­­} that formed with the α-NaFeO₂ structure were synthesised by conventional solid state method. Rietveld refinement results indicated that the amount of cation disorder (or known as interlayer mixing) affected by temperature. The samples that prepared at 950°C in oxygen possessed slightly lower amount of interlayer mixing and excellent cycling performance compared to samples that prepared at 900°C. The initial charge-discharge capacity delivered was ~204 mAh/g and ~140 mAh/g, respectively. Furthermore, the structural and electrochemical properties were quite comparable to reported in literatures.

Abstract: The interlayer mixing of layered rock salt cathode materials LiNi_0.7Mn_0.1Co_0.2O₂ that prepared by mixed hydroxide method at various temperatures (750-950°C) has been studied. X-ray Diffraction (XRD) was used to determine a suitable temperature range to obtain the fully reacted sample. Phase of pure sample was obtained at high temperature above 850°C. The results of XRD show that the LiNi_0.7Mn_0.1Co_0.2O₂ samples are iso-structural with α-NaFeO₂ with space group of R-3m.The sample that heated at 900°C exhibits a well-ordered and lower cation mixed layered structure than others. Rietveld refinement using XRD data was used to determine the amount of interlayer mixing vary as a function of temperature. Refinements data showed that the interlayer mixing varies depend upon the synthesis temperature and the optimum temperature to prepare LiNi_0.7Mn_0.1Co_0.2O₂ with the lowest amount of interlayer mixing was 900°C.

Abstract: The layered rock salt LiNi_0.7Mn_0.3O₂ was prepared by conventional solid-state synthesis route. The prepared samples were analysed using X-ray diffraction (XRD) to determine purity of samples. Then, structural analysis and crystallographic properties of samples were analysed using Rietveld refinement. Rietveld refinement results indicated that the amount of cation disorder in the layered rock salt structure highly influenced by temperature and synthesis conditions. The most optimum temperature to obtain the highest degree of cation ordering is between 850^oC and 900^oC in air.

Abstract: Acetylene (C₂H₂) was used as carbon source gas, nitrogen (N₂) as dilution gas. The electric properties of carbon fibers was briefly discussed by energizing the carbon fibers in vacuum condition which were applied for the preparation of carbon/carbon composites by the method of chemical vapor deposition. The deposition mechanism and microstructure of pyrolytic carbons in carbon fibers under different deposition crafts were also discussed. Results indicate that the greater the initial voltage, the higher the temperature, we can change the deposition temperature by changing the initial voltage according to the relationship between the brightness and the surface temperature of carbon fibers. The surface of carbon fibers will be etched in the process of electrifying which would make the pyrolytic carbons preferred deposition on the etching point which became the growth center in the early deposition process. The pyrolytic carbons deposited with a spherical microcrystalline structure under the gas flow of C₃H₆/N₂=2:3, When the rate of gas flow is C₃H₆/N₂=1:2, The pyrolytic carbons deposited with a spherical microcrystalline structure after deposited for 0.5h, but after deposited for 1h, the deposition of large patches of molecular is dominant which lead to that: from a macro perspective, the pyrolytic carbons were a layered structure, From a microscopic perspective, they were a spherical microcrystalline structure with different size.

Abstract: Spectral dependences of the polar Kerr effect in Co/TiO₂ multilayer films in the spectral range 400--1000 nm have been studied. It is shown that the sign, value, and shape of the magneto-optical spectrum depend on the thickness of a dielectric spacer and the number of layers in the structure. It has been established that the magneto-optical rotation in the Co/TiO₂ films considerably exceeds that in homogeneous Co films. The magneto-optical rotation attains the record value 2θ_k = 7.3 deg in the Co (5 nm)/ TiO₂ (17 nm) layered structure with the number of layer pairs n = 8 at a wavelength of 560 nm.

Abstract: Based on the vascular membrane stress model and the pseudo-elastic vessel model, the combination constitutive model with a layered structure in microvessel is presented in this paper. By using obtained constitutive equations of the current model, the circumferential stress of the membrane intimal (inner) layer and the three-dimensional stress distribution of the structural outer layer are analyzed. Under the initial blood pressure state, the vascular static stress changes with the inner stiffness increase are also discussed. The results show that with inner stiffness increasing, the stress of outer layer is less affected but the circumferential stress of the intimal layer is increased significantly, which may be one potential risk factor for the vascular injury. These analysis methods and its conclusions have some theoretical significance for studying the problems of arteriosclerosis and other diseases, and preventing the occurrence of related diseases.