Key Engineering Materials Vol. 633

Abstract: Powder flowability is one of the most important properties affecting the filling and delivering processes of dry powder inhalations. When the powder is exposed to different environmental (temperature, relative humidity (RH)) conditions, the interaction between particulates would influence the flowability of powders. Blends of 83% coarse lactose (D₅₀ =126μm) and 17% fine lactose (D₅₀ = 7μm) were prepared at three different mixing environments and the effects of temperature and humidity on powder flowability were investigated. Results indicated that mixing under relatively higher temperature and lower RH environmental conditions improved the flowability of lactose blends.

Abstract: Extracting aluminum oxide from high-alumina coal fly ash are significant to make up for the inadequacy of bauxite resource in China. How to comprehensively utilize silica components in coal fly ash is a key technical question in industrialization for extracting of alumina from coal fly ash. Desilication of coal fly ash (CFA) and preparation of xonotlite were studied using the silica-rich solution from the CFA as silica source and calcium oxide as calcium source respectively. The CFA is from a power plant at Shizuishan city in Ningxia, China. Xonotlite was successfully prepared by a series processes including predesilication, hydro-thermal synthesis. The experimental results indicated that SiO₂ in the coal fly ash changed into NaSiO₃ after the coal fly ash was treated by desilication using NaOH solution. Hydrated calcium silicate was obtained from the reaction of the solutions produced by desilication and Ca (OH)₂ at the condition of Ca/Si (mol)=1, T=160°Cand t=1h. Xonotlite was synthesized by the hydrated calcium silicate using the hydrothermal temperature of 260°C for 2 hours. Keywords: Coal Fly Ash, Pre-desilication, alkali Hydrothermally-treated, Xonotlite nanofibres

Abstract: During the synthesis of γ-Fe₂O₃ nanoparticles using a chemically-induced transition in a FeCl₂ solution, Co-surface modification was attempted by adding Co (NO₃)₂ and NaOH to the solution. The magnetization behaviors, morphologies, crystal structure, and chemical compositions of the as-prepared samples were characterized using vibrating sample magnetometry, transmission electron microscopy, X-ray diffractometry, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The as-prepared particles consisted of γ-Fe₂O₃/CoFe₂O₄ composite crystallite and a CoCl₂·6H₂O coating. The molar, mass and volume ratios of the phases were estimated from the characterization results for each sample. The Co-modified γ-Fe₂O₃ nanoparticles’ anisotropic constant is approximately 1.48×10^-1 J/cm³. Their coercivity depends on the size of composite crystallites, which is based on the γ-Fe₂O₃/CoFe₂O₄ content rather than the Co content.

Abstract: In this paper, spherical nanohydroxyapatite was synthesized by hydrothermal method. During the synthesizing process, different amount of L-lysine template was added with the hydrothermal temperature 185 °C and the time 25 h. The products were characterized by using FTIR, XRD and TEM. Results showed that the rod-like nanohydroxyapatite changed its granule morphology into spherical obviously after adding L-lysine. Spherical nanohydroxyapatite was synthesized with mean particle size about 25 nm.

Abstract: In the experiment, the tetrabutyl titanate and samarium trinitrate were used as raw material, samarium doped TiO₂ powder was prepared by sol-gel method. Main factors that affect the TiO₂ nanoparticles, such as catalyst, ratio of raw materials, and calcination temperature of the preparation process were studied. TiO₂ powder was characterized by using XRD, UV-vis, IR to determine the crystal structure, grain size and spectral properties. The results show that, the amount of catalyst is 50mg, the calcination temperature is 500 °C, samarium doping ratio is 0.4%, and the visible light photocatalytic degradation time at 60min, the degradation of methyl orange solution rate of 20mg/L can reach 42.8%. Samples with anatase as the main, in the catalyst preparation process, due to the synergistic effects of samarium doping, the modified TiO₂ absorption band of different redshift, enhanced the catalytic activity of TiO₂ visible light.

Abstract: A simple template assembled sol-gel method is used to prepare the wire-liked NiFe₂O₄ nano-particles with high specific surface area and excellent magnetic. Influence of template and calcined temperatures on the composition, microstructure, BET, magnetic properties as well as radio frequency(RF) heating rate are studied through XRD, TEM, BET, VSM and RF heat test. Results show that the template-assembled sol-gel method is a successful and easy method to obtain randomly oriented wire-liked NiFe₂O₄ nano-particles. The spinel NiFe₂O₄ was the main phase, impurity rhombohedral Fe₂O₃ phase is also detected in all samples. An increase in grain size is observed with the increased calcined temperatures as well as the concentration of sol, while the specific surface area decreases from 50.3 to 13.2 m²/g. As the sintering temperature equals to 700°C, the nano-particles can be observed with a diameter approximately 50 nm and a length approximately 700 nm. M_s increases with the increase of sintering temperature and slightly waves with the increase of sol concentrations, C-1-1000 exhibits higher M_s (73.0 emu/g) and lower M_r and H_c values (13.5 emu/g, 79.3Oe ), respectively. The calculated hysteresis loss and the measured RF heating rate exhibits good agreement. The sample C-1-800 has the highest heating rate of 1.72 °C/s.

Abstract: Zirconium diboride (ZrB2) ceramics were synthesized by Aqueous gelcasting method sintering effects of the additives were examined. The dispersion and rheological properties behavior of water-based gelcasting ZrB2-4wt.%B4C suspensions were characterized by zeta potential and viscosity measurements, respectively. A 50 vol.% ZrB2-4wt.%B4C suspension with a relative low viscosity was prepared with 3wt.% A70 and 4wt.% AM at pH = 11. Using the liquid desiccant drying method, the weight loss was 7.7 % after drying for 24 h, which is higher than the drying at RT (7.2 %).

Abstract: In this paper, wollastonite nanopowder were successfully synthesized by the surfactants modified-calcined method using calcium silicate residue of potassium feldspar after extraction of potassium and alumina. The effects of modifier and calcined temperature on the phase composition, morphology and microstructure were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that the phase of samples with different modifier processing is wollastonite-2M, while CTAB as modifier can avoid preferred orientation growth. The obtained wollastonite powder is spherical in morphology and well dispersed with the particle size of approximately 150nm.

Abstract: In this work, highly-ordered TiO₂ nanotubes arrays were fabricated by two-step anodic oxidation method to serve as photoanodes for dye-sensitized solar cells. We investigated the effect of TiCl₄ treatment on the microstructure and morphologies of TiO₂ nanotubes arrays. It is found that the TiCl₄ treatment can generally introduce 10-15 nm TiO₂ nanoparticles into the TiO₂ nanotube arrays. The photovoltaic performance of dye-sensitized solar cells is related to the concentration and treated-time of TiCl₄ treatment. A power conversion efficiency of 7.63% was achieved for dye-sensitized solar cell with photoanode treated by 0.04 M TiCl₄ for 60min. The improved power conversion efficiency can be attributed to the increased available surface for dye adsorption in photoanodes.