Advanced Materials Research Vols. 512-515

Abstract: The relations between electronic structure, chemical bond and thermoelectric property of misfit layered cobaltite of Ca₃Co₄O₉ and 3d transitional metal (Ti, Cr, Mn, Fe and Cu) doped series are studied using density function and discrete variation method (DFT-DVM). Ca₃Co₄O₉ consists of two layers of CoO₂ and Ca₂CoO₃. The highest valence band (HVB) and the lowest conduction band (LCB) near Fermi level are only mainly from O 2p and Co 3d in Ca₂CoO₃ layer. Therefore, the semiconductor, or thermoelectric property of Ca₃Co₄O₉ should be mainly from Ca₂CoO₃ layer, but it seems to have no direct relation to the CoO₂ layer, which is consistent with that binary oxides hardly have thermoelectric property, but trinary oxide compounds have quite good thermoelectric property. The variation of electronic structure, chemical bond strength and thermoelectric property of doping series is discussed. The improvement of thermoelectric property of Cu-doped Ca₃Co₄O₉ is the most obvious.

Abstract: Effects of mole rate of methanol/oil, reaction time and technology on the free fatty acid ( FFA) level decrease of Zanthoxylum bungeanum seed oil with sulfuric acid as catalyst was investigated. Results show that, the acid level decreases with the mole rate of methanol/oil increases when the sulfuric acid is 2% based on the weight of Zanthoxylum bungeanum seed oil and reacting at 60°C for 2h. When the mole rate is 20~35∶1, the final acid value is less than 2mgKOH/g which meets the requirement for biodiesel production. When the mole rate is 25∶1, with sulfuric acid dosage 2% and reacting at 60°C, the acid value decreases fast at the beginning of the acid esterification. The acid value of ZSO was reduced to 1.56 mg KOH/g from 78.91 mg KOH/g by only one-step acid-catalyzed esterification with methanol-to-oil molar ratio 30:1, H2SO4 2%, temperature 60°C and reaction time 60 min, which was selected as optimum for the acid-catalyzed esterification.

Abstract: This work explores the use of metal-air electrochemical system to evaluate porous electrode properties i.e. specific surface area and pore volume density. Porous zinc electrodes are prepared from an acidic, chloride electrolytic bath of varying supporting electrolyte (NH₄Cl) formulation to produce electrodeposits of distinctive properties. Nitrogen physisorption at 77 K is utilized to evaluate the specific surface area and pore volume density of the electrodes. The zinc electrodeposits prepared from all electrolytic bath formulations are then assembled into zinc-air cells as the anodic electrode and characterized according to their limiting current density and discharge capacity. It is found that the variation in limiting current density matches that of BET surface area and the trend for discharge capacity follows that of pore volume density.

Abstract: Three rare-earth metal oxide nanopowders (CeO₂, PrO₂, and TbO₂) were synthesized using a facile hydrothermal method in a Teflon-lined autoclave. The rare-earth metal oxide nanocrystals with variable morphology were prepared by controlling the synthesis conditions with temperatures in the range of 70−220 °C. X-ray diffraction (XRD), thermal gravimetric analysis (TGA), and temperature programmed reduction (TPR) were used to characterize the average structures and redox properties of these materials. Transmission electron microscopy (TEM) was used to investigate the morphology, particle size, and formation and growth mechanisms of the rare-earth metal oxide nanoparticles in solution-based environment.

Abstract: A molecularly imprinted membrane was prepared in aqueous media using CS as functional monomer, EGCG as template molecules. The morphologies of molecularly imprinted membrane before and after modification with porogen (PEG) were observed by SEM. The imprinted membrane showed an excellent performance after several times adsorption and desorption. According to Scatchard analysis, the result showed that the imprinted membrane had a binding site for EGCG, the max adsorption capacity of imprinted membrane and equilibrium binding constant arrived at 49.52 mg/g, 4.046, respectively

Abstract: The poor electrochemical cycle stability of RE–Mg–Ni system A₂B₇-type electrode alloys have limited their practical application as the negative electrode materials of Ni–MH battery. In order to improve the electrochemical cycle stability of the La–Mg–Ni system A₂B₇-type electrode alloys, the partial substitution of Pr for La has been performed. The La_0.75−xPrxMg_0.25Ni_3.2Co_0.2Al_0.1 (x = 0–0.4) electrode alloys were fabricated by casting and melt-spinning. The microstructures and electrochemical cycle stability of the as-cast and spun alloys were investigated by XRD, SEM and HRTEM. The results show that the as-cast and spun alloys have a multiphase structure, consisting of two main phases (La, Mg)₂Ni₇ and LaNi₅ as well as a residual phase LaNi₂. The substitution of Pr for La brings on a notable grain refinement of the as-cast alloys instead of altering the phase structure of the alloys. The electrochemical measurement indicates that the cycle stability of the alloy remarkably grows with increasing both Pr content and spinning rate. The substitution of Pr for La and the melt spinning significantly ameliorate electrochemical cycle stability of the alloys. The capacity retaining rate (S₁₀₀) of the as-spun (15 m/s) alloys at 100th charging/discharging cycle is enhanced from 72.38% to 90.33% by increasing Pr content from 0 to 0.4. And that of the Pr0.3 alloy is increased from 78.11% to 92.32% by growing spinning rate from 0 (as-cast was defined as the spinning rate of 0 m/s) to 20 m/s.

Abstract: In this article, the properties of carbon particle modified silicon carbide (C_p/SiC) composites was studied. The mixture powder of nano carbon black and submicro-SiC was prepared through soft mechanochemical method. Then C_p/SiC composites was pressureless sintered.The result shows that appropriate content of carbon is 25 percent in this condition the machinability of C_p/SiC is better than that of SiC ceramic. At the same time, the oxidation resistence, wear resistence, and flexure strength of C_p/SiC meet the challenge for special fire resistant material.

Abstract: Ti-based PbO₂ electrodes with Sb-SnO₂ interlayers were prepared by thermal decomposition. The effects of calcination temperature and Sb content of the Sb-SnO₂ interlayer on the service life and microstructural characteristics of the Ti/Sb-SnO₂/PbO₂ anodes were investigated. The results show that the Ti-based PbO₂ electrodes without the Sb-SnO₂ interlayer, Ti/PbO₂ electrodes, are rapidly deactivated at the experiment conditions, while the service life of the Ti/Sb-SnO₂/PbO₂ electrodes increases remarkably. Calcination temperature and Sb content for preparing the Sb-SnO₂ interlayer exhibit remarkable effects on the service life of the Ti/Sb-SnO₂/PbO₂ anodes.

Abstract: Three kinds of mesoporous manganese oxides were prepared successfully via a simple hydrothermal method, using dodecyltrimethylammonium bromide (DTAB), cetyltrimethyl- ammonium bromide(CTAB) and octadecyltrimethyl ammonium bromide(OTAB) as structure directing agents, respectively. The as-synthesized samples were characterized by X-ray diffraction(XRD) and Brunauer -Emmett-Teller(BET)．The experimental results show that the carbon-chain length of surfactants have influences on not only crystal structure and metal valence, but also specific surface area and pore size of the as-prepared materials. The specific surface areas are 60 m²•g^-1, 25 m²•g^-1, 7 m²•g^-1，and the pore sizes are 4 nm，7 nm, 13 nm for the three kinds of mesoporous materials prepared using structure directing agents DTAB, CTAB, and OTAB, respectively.

Abstract: Lanthanum-doped anatase TiO₂ coatings, which are composed of assemble crystalline of 50 nm diameter particles, when the percentage of dopant is 0.5 wt%, have been successfully fabricated by sol–gel dip-coating process on light leakage silica fiber (LSF) which length is 15cm and diameter is 125μm. This was achieved by adjustment of the lanthanum-doped sol–gel parameters such as molar ratio of precursors in lanthanum-doped TiO₂-sols, the ratio of titanium tetrabutoxide to polyvinyl alcohol, dip-coating velocity, drying duration in air, thermal treatment and number of cyclical time of the process. Titania nano crystals were prepared at ambient temperature in a liquid media using titanium tetrabutoxide as precursor, and the crystallization of amorphous precursor was preceded by peptizing with acid and then refluxing for a periodic time in homothermal water-bath. The photocatalytic properties of the La-TiO₂ films had been testified by the photo degradation of methyl orange. The lanthanum-doped anatase TiO₂ thin films were characterized by XRD and TEM. The products show much improved photocatalytic activity that will be useful in the design of a novel antibacterial, deodorant and antipollution photo reactor.