Advanced Materials Research Vol. 1053

Abstract: A variety of different magnetic structure models of cobalt doped zinc oxide have been calculated by density functional theory (DFT) of first-principle method. Crystal structure parameters and the total energy of the models are obtained through the computational simulation. Through contrasting and analyzing the total energy of each of the structure models, it is found that the cobalt doped zinc oxide crystal material with anti-ferromagnetic state is more stable than the one with ferromagnetic state. The electronic structure of the models with anti-ferromagnetic is investigated and the results show that the cobalt 3d electrons have a great impact on the characteristics of the electronic structure of the zinc oxide.

Abstract: This paper studied the structural and optical properties of Dy³⁺-doped CaBi₄Ti₄O₁₅ phosphors synthesized by a traditional solid state method. The phosphors have been characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and fluorescence measurements. Upon 450 nm blue light excitation, the phosphors show yellow emission centered at 574 nm with the color coordination of (x=0.44, y=0.54). And the phosphors exhibit a tunable white color emission under the near ultraviolet source by adjusting the ratio of Dy³⁺ appropriately. The optimal composition of Ca_0.93Bi₄Ti₄O₁₅:0.07Dy³⁺ generates white light with the color chromaticity of (x=0.31, y=0.36), indicating that CaBi₄Ti₄O₁₅:Dy³⁺ phosphor would be a potential candidate for white light emitting diodes (LEDs) applications.

Abstract: The micron-sized flake-shaped carbonyl iron powder (FS-CIP) was prepared by wet ball milling method with ethanol as process control agent (PCA). Influence of the ratio of ball to powder on the microstructure, microwave electromagnetic parameter and reflectivity of the FS-CIP were studied. The results show that, with the increasing of the ratio of ball to powder, grain size of FS-CIP gradually decreases and the aspect ratio increased significantly. Beneficial the anisotropy of the FS-CIP, the magnetic loss and dielectric loss performance were enhanced dramatically. Epoxy resin was applied as binder. The single-layer microwave absorbing coatings with 1.0 mm in thickness and the FS-CIP volume fraction is 30% were prepared. The lightest coating weights 2.96 kg/m², when it meets the request of band width more than 10 GHz with in which the reflectivity less than-7.5 dB at the frequency range of 8~18 GHz.

Abstract: The effects of micro-arc oxidation (MAO) voltage (370V, 400V, 420V) on the surface morphology, adhesion of film/substrate, corrosion resistance and fretting friction and wear properties after micro-arc oxidation and heat-treatment for 48h of TiNi alloy were investigated. The results show that, as the voltage gradually increases: (1) micro-arc oxidation coatings form, when the voltage increase to 420V, the coating shows a significant micro-arc oxidized porous characteristics; (2) the Ca/P ratio in the coatings also increases, so the Ca/P ratio can be controlled by adjusting the voltage of micro-arc oxidation; (3) the corrosion resistance of MAO coatings can be significantly improved by increasing the output voltage, the corrosion rate and the corrosion potential of 420V are smaller two magnitude than 370V’s; (4) the coating of 420V shows lower friction coefficient with higher resistance, narrower wear scar width; (5) the MAO coatings have formed different types of hydroxyapatite crystals (HA) after immersed in high temperature and pressure reactor for 48h, and the phase composition of the coating are mainly apatite.

Abstract: LaCo_0.6Ni_0.4O_3-δ (LCN) as cathode contact material (CCM) for application in solid oxide fuel cell (SOFC) is studied in this paper. LCN is prepared through the polymeric steric entrapment precursor route with polyvinyl alcohol (PVA) as the entrapment agent and then calcined at 800 °C and 1100 °C for 3 h respectively. Polished SUS430 pellets heated at 800 °C for 6 days as well as the untreated ones are used as interconnect. The assembly of LCN calcined at 800 °C with pretreated SUS430 at 800 °C for 6 days exhibit the best performance of a low and stable ASR value about 112 mΩ cm² at the end of the 200 h test. The calcination temperature and the pretreatment of interconnect are considered to be crucial factors affecting the ASR property of LCN CCM for application in stack.

Abstract: In this paper, the magnetic phase transition and magnetocaloric effect have been investigated in the Fe₂P-type MnFeP_0.63Ge_0.12Si_0.25 compound. The X-ray diffraction patterns measured at different temperatures indicate that the crystal structure remains and the lattice parameters change sharply near the transition temperature when a phase transition takes place. The isofield magnetization curves on heating and cooling and the Arrott plots reveal that the nature of the transition is first order. The characteristic of giant magnetocaloric effect results from the field-induced first-order metamagnetic phase transition, which makes the compound having potential applications in magnetic refrigeration.

Abstract: An Ni-Fe alloy on the surface of nickel foam was prepared by electro deposition. The effects of technological parameters including current density, pH value, temperature and the ratio of [Ni²⁺] to [Fe²⁺] of planting solution on the thickness and iron content of the alloy coating were studied. The cross-section microstructure and surface morphologies were observed by optical microscopy and scanning electron microscope, and the compositions of the alloy coating were analyzed by energy dispersive spectrometer and ICP-AES. Experiment results show that the thickness of the alloy coating is increased with increasing current density, temperature, pH value and the ratio of [Ni²⁺] to [Fe²⁺] of the planting solution. The Fe contents of the alloy coating is increased with increasing current density and pH value of the planting solution, and decreased with increasing temperature and the ratio of [Ni²⁺] to [Fe²⁺] of the planting solution. A 36.2 μm thick alloy layer of uniform and dense coating with the Fe content of 60.5 wt% is obtained under the parameters of n(Ni²⁺)/ n(Fe²⁺)= 4, current density = 10 A/dm² and pH = 4.2 at 50 °C for one hour.

Abstract: The preparation of aluminium sulfate adopting the sulfuric acid heating method with Al (OH)₃ as raw material, and join the β complexing agent in aluminium sulfate solution to remove impurities; ammonium aluminum sulfat is prepared by the reaction of the ammonium solution and aluminum sulfate, and purify ammonium aluminum sulfate to get high purity ammonium aluminum sulfate crystals containing crystal water. Purify the crystallization of ammonium aluminum sulfate with containing water treated at 1250 °C for 3 h. Then the high purity alumina was prepared. Break the high purity alumina to press, and then again process in 3 h under 1650 °C, get Al₂0₃ which is craw materials of sapphire crystal LED. The samples were characterized by atomic absorption spectrum (AAS), differential thermal analysis (TG/DTA), scanning electron microscopy, XRD and chemical analysis. The purity of high purity alumina is 99.991%, which will be applied to the LED manufacturers on sapphire artificial sapphire growth test.

Abstract: The electropolishing behavior of high-purity aluminum in perchloric acid ethanol electrolytes is studied by the electrochemical methods. The morphologies of electropolished surface are examined by SEM. The results of anodic polarization shows that the limiting current density was decreased with the 1,2-propylene glycol and perchloric acid volume ratio increasing and the temperature decreasing. The results of SEM show that A salt film with porous pores on the electropolishing surface was formed on high-purity aluminum in the mixed solution of 1, 2 propylene glycol and perchloric acid at the volume ratio of 4:1 and 6:1, porosity of film increases from 12.3 % to18.4%, and the pore diameter of film increases from 19 nm to 23 nm with the current density increased from 120 mAcm^-2 to 140 mAcm^-2.