Advanced Materials Research Vol. 900

Abstract: The radiation shielding abilities of functional particles (Sm₂O₃, Er₂O₃, WO₃ and Bi₂O₃) were simulated and proved to have a stronger absorption region and a weaker absorption region respectively. Four kinds of functional particles/epoxy radiation shielding composites used for low energy γ/Xray were designed based on the edge absorption and synergistic absorption. By optimizing the proportion of functional particles in epoxy composites, the radiation shielding abilities bad been further improved. According to the results of optimal design, a kind of Sm₂O₃/Er₂O₃/WO₃/Bi₂O₃/Epoxy composite was prepared and proved to be very efficient to shield low energy γ/X radiation.

Abstract: PbSe quantum dots have a relavively narrow absorption spectrum and they can radiate quasi monochromatic light after absorbing sunlight. Also, the emission peak can be located in the range of the strongest spectral response of monocrystal silicon solar cell by adjusting particles sizes. In this paper we apply PbSe quantum dots into luminescent solar concentrator, analyse its physical process, establish mathematical model and optimize its size with C++. The simulation results show that its photoelectric conversion efficiency is size depended, when the length and width are 200cm and 150cm, respectively, its photoelectric transformation efficiency can reach 6.1%.

Abstract: A detailed theoretical study of electronic structure and optical properties of GaN under pressure was performed by the first-principles calculations of plane wave ultra-soft pseudo-potential method based on the density functional theory (DFT). The results indicate that Ga-N bond length becomes shorter and the valence bonds shift towards the low energy while the conduction bands towards high energy, the band gap becomes wider with the pressure increasing, and theoretical studies explained the relationship between the band edges, energy gap of GaN and pressure. In addition, the peak in band was cracked slightly, and the Ga 3d-N 2p hybridization was enhanced.

Abstract: We propose a photonic crystal power splitter that allows the electromagnetic waves with a phase shift of 180⁰ between output signals. The splitter consists of two parallel coupled-cavity waveguides placed in proximity. On the basis of the guided mode propagation analysis method, the self-imaging effect is discussed for the case of symmetric incidence. The finite-difference time-domain method is used to simulate the propagation of the beam and experimentally demonstrated. The results show that both output paths have the same physical length, the two output signals are synchronized. The splitter is very attractive for splitting high-speed optical signals in integrated optical circuits.

Abstract: Coal additives can promote coal burning and improve the utilization of coal, thus effectively saving coal resources. Coal additive was found to improve coal calorific value obviously by the tests of coal calorific value with two kinds additives, the maximum of calorific value could be increased by 19% , which indicated that the additives promoted coal combustion . By comparing the experimental data , when added directly , it was the most efficient to improve combustion heat for the dose group of 1% coal formulations. while immersed added, it was 0.5% dose formulations to improve coal combustion heat the most efficiently. The effect of immersed added was better than that of added directly. Through SEM micrographs analysis of coal sample experiments, surface roughness and angle were outstanding for not added coal additives. There are similar in shape of pulverized coal comparing the direct added additive with not added additive. The morphology of coal samples changed while dipping additives on them, coal was partially eroded , spherical trend , which increased the surface area, it was helpful for burning.

Abstract: In this paper, Microencapsulated paraffin/polyurea (PU) phase change materials were prepared through an interfacial polymerization method using composite paraffin with solid/liquid mass ratio 3:7 as core materials, 2,4 toluene diisocyanate and ethylenediamine as monomers, NP-10 as an emulsifier. It was investigated the effects of emulsion speed, the amount of emulsifier and polymerization temperature on the particle size and coating efficiency and storage-energy performance of microencapsulated paraffin / PU phase change materials. The results showed when the emulsion speed is 2000r/min and the amount of emulsifier to core material is 6% and the polymerization temperature is 70°C, Microencapsulated paraffin / PU phase change materials have better performance: the melting point of 28.1°C, the enthalpy of 58.4KJ/Kg, coating efficiency of 87.5%, the average particle size of 3~4μm, and the uniform particle size distribution.

Abstract: Using a self-developed triaxial seepage device, tests of coal samples from Liu Panshui coal mine were carried out to explore the relationship between permeability and pore pressure when effective stress and temperature conditions keep constant as well as the impact of pore pressure on gas seepage. The research results show that: Permeability decreases with the increase of pressure difference between inlet and outlet Δp when effective stress and temperature keep constant; permeability declines in a nonlinear tread with increase of pore pressure and they all have a exponential relationship; when pore pressure is low, permeability decreases faster with changes in pressure difference between inlet and outlet Δp. When gas pressure is low, with pore pressure increasing the gas flow pore narrowed.

Abstract: LiFePO₄/graphene composites were prepared via a simple hydrothermal method. The as-prepared LiFePO₄/graphene composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), galvanostatic charge-discharge test, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) tests. The lithium-ion batteries using LiFePO₄/graphene composites as cathode material exhibited a discharge capacity of 165 mAh/g, which was 97% of the theoretical capacity of 170 mAh/g.

Abstract: Vacuum insulation panels (VIPs) are regarded as one of the most promising high-performance thermal insulation solutions on the market today. In this paper, a novel structure, i.e., honeycomb glassfiber mat was proposed as the core material of VIP. The honeycomb glassfiber mat was composed of glass wool mat and glassfiber chopped strand mat. Among them, 70% centrifugal glass wool and 30% flame attenuated glass wool were mixed together to form the 0.5mm-thickness glass wool mat, while thirteen holes with diameter of 10mm were opened uniformly on the surface of glassfiber chopped strand mat. Glassfiber VIPs possessed honeycomb core material have superior thermal conductivity of 1.52mW/(m•K). In order to obtain better thermal insulation performance, ultrafine and stiff fibers with three-dimensional overlapping structure is preferable. Meanwhile, hollow fibers with bifurcated structure are the guarantee of high-strength core material.

Abstract: Cocrystal explosive can effectively improve the physical and chemical properties of explosive and contributed to new unique properties of cocrystal explosive. Based on cocrystal principle, a few recrystallization explosives of LLM-105 were prepared using solvent/non-solvent technique. The prepared samples were analyzed by IR spectroscopy. The results showed that cocrystals such as LLM-105/ HNIW, LLM-105/HMX and LLM-105/RDX can be prepared. Melting point and density of the cocrytals above changed little. It can be inferred the cocrystal explosive will have better energy and their application performances will not reduce obviously.