Key Engineering Materials Vol. 807

Abstract: The AZO films deposited on quartz glass by magnetron sputtering with different deposition time various from 30min to 120min.All of the obtained samples had a (002) diffraction peak range from 34.31 to 34.52°, while the mean grain size increased from 30.1nm (30min) to 56.1nm (120min) respectively. The XPS survey indicated the photoelectron peaks of Zn ,O and C elements occured. The optimal transmittance of the films reduced obviously from about 92% to 78% near 550nm with deposition time increased from 30min to 120min. And the average transmittance of AZO films prepared at 30, 60 and 90min was about 85% in the visible light region.

Abstract: Through continuous experiments, scientists have found that nanomaterials have self-cleaning properties. Solar cells coated with nanometer film can keep their surface clean for a long time and maintain high photoelectric conversion efficiency. nanodiamond films were prepared on glass substrate by sol-gel method. nanosilicon carbide was also selected as the contrast material. Silicon carbide (SiC) has good chemical stability, corrosion resistance and other characteristics. nanosic films were prepared by sol-gel method on glass substrate. The production cost of sol-gel method was relatively low, the coating uniformity was suitable for mass production

Abstract: In this study, Si@C/Graphite composite anodes were synthesized through spray drying and pyrolysis using silica, artificial graphite, and two kinds of organics (phenolic resin or pitch). The Si@PR-C/Graphite exhibits enhanced electrochemical performance for lithium-ion batteries. The first charge-discharge specific capacity is 512.8mAh/g and 621.8mAh/g, respectively, the initial coulombic efficiency is 82.5% at 100mA/g, and its capacity retention rate reached as high as 85.4% with the capacity fade rate of less than 0.18% per cycle after 85 cycles. The Si@PI-C/Graphite also presents excellent discharge specific capacity of 702.8mAh/g with the capacity retention rate of 76.9% after 30 cycles. Mechanisms for high electrochemical performances of the Si@C/Graphite composite anode are discussed. It found that the enhanced electrochemical performance due to the formation of core/shell microstructure. These encouraging experimental results suggest that proper organic carbon source has great potential for improvement of electrochemical properties of pure silicon as anode. Key words:lithium-ion batteries; anode; Si@C/Graphite composite; electrochemical performance

Abstract: In this paper, nanodiamond films (NDF) were prepared on glass substrate by screen printing with nanodiamond. The NDF was printed with two layers and treated with different surface treatments.The field emission model of nanodiamond thin film was established. Field Emission of different Ratio was studyed. The mechanism by which the field emission characteristics of nanocrystalline diamond films are improved was analyzed.

Abstract: In-vitro experiment method was used to study biomineralization properties of carbonate apatite bulk and electrophoresis coating with different carbonate contents. The mineralization processes in SBF solution were investigated by means of XRD, SEM and so on. Research results show that the apatite with poor crystallization and small grain size induced by the carbonate substitution is beneficial to the sintering of the bulk and the formation of the bone-like hydroxyl-carbonate apatite (HCA) layer on the surface after soaking in the SBF. However, the carbonate substitution greatly reduces the pore size and porosity of coating, which is not conducive to the deposition and growth of the mineralized layer, thus weakens the biomineralization properties of the coating.

Abstract: The effects of the ratio of magnesium to phosphorus (Mg/P) on the compressive strength, bond strength, drying shrinkage and pH value of magnesium phosphate cement (MPC) were investigated. The results show that the consistent effect of the ratio of Mg/P on compressive strength and bond strength, as the ratio increases, the strengths are both first increased and then decreased, and the best ratio is 3:1. For setting time and drying shrinkage, the effects of the ratio of Mg/P are both obvious. Mainly manifested as the increase of the ratio, all of them show a decreasing trend. And the setting time can be shortened by 78%, furthermore, 28d the maximum drying shrinkage rate can be reduced by 29%. The effect of the ratio of Mg/P on pH value is mainly that when the ratio increases, the time of the inflection point of pH value is obviously advanced, and their final pH value is close.

Abstract: A novel red-emitting K₂SiF₆:Mn⁴⁺ phosphors with different Mn⁴⁺ doping mole fraction were synthesized by co-precipitation method. X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and fluorescence spectrometer were used to characterize the properties of K₂SiF₆:Mn⁴⁺ phosphors. As-prepared K₂SiF₆:Mn⁴⁺ phosphors have cubic crystal structure. Under excitation at 450 nm, an intense red emission peak around 632 nm corresponding to the ²E_g-⁴A₂ transition of Mn⁴⁺ was observed for 8.37 mol% K₂SiF₆:Mn⁴⁺ phosphors and was used as the optimum doping concentration. The excellent luminescent properties make the phosphor K₂SiF₆:Mn⁴⁺ a candidate for applications in InGaN-YAG:Ce³⁺ type LEDs for high color rendering. “A warm” white light LED with an efficiency of 147 lm/w and a color rendering index of 87.4 at a color temperature of 2864K has been obtained by fabricating YAG:Ce³⁺ with K₂SiF₆:Mn⁴⁺ on an InGaN chip.

Abstract: First-principles calculations are performed to study the electronic structures and optical properties of the As-doped ZnO under pressure up to 8 GPa. After doped, the electron density difference demonstrates the considerable electron charge density redistribution, which induces the effect of As-doped ZnO to increase the charge overlap between atoms. Moreover, as the pressure increases, the conduction and valence band shift to lower and higher energies, respectively. The shifts of the conduction and valence band result in a decreasing band gap. Additionally, the calculated optical constants of As-doped ZnO under pressure are also presented. Keywords: high pressure; As-doped ZnO; optical properties, Density functional theory.

Abstract: Based on the density functional theory (DFT), the first-principles approach is used to study the electronic band structure of B-doped wuritzite ZnO with different pressure. The pressure effects on the lattice parameters, electronic band structures, and partial density of states (PDOS) of crystalline B-doped ZnO are calculated up to 8 GPa. Moreover, the evolution of the dielectric function, absorption coefficient (), reflectivity (), and the real part of the refractive index () at high pressure are also presented. Keywords: high pressure; density functional theory; B-doped ZnO.

Abstract: Fe-based alloys were deposited on 1045 steel by plasma cladding technique and the specimens were annealed at different temperatures. Instrumented indentation technique was adopted to investigate the plastic properties of the coatings, especially the stress-strain relations, critical yield stress and the strain hardening exponent. The results show that the elastic recovery in nanoindentation is less than 20% for all coatings and proves an obvious existence of plastic deformation in the coatings. It is found in the stress-strain curves that the annealing process makes the distribution of elastic modulus among the whole coating more uniformly. With the penetration depth increasing, the initial plastic deformation value gradually decreased which is more obvious for coatings annealing at high temperatures. In addition, the strain hardening exponent of the as-cladding coating and coatings annealed at 500°C keeps steady around 0.15 while the corresponding values of coatings annealed at 600°C and 700°C increased sharply with the penetration depth increasing and the maximum value is up to 0.32.