BiFeO3 films doped in the A or B sites: effects on the structural and morphological properties

Metal-Organic Chemical Vapor Deposition (MOCVD) has been applied to the fabrication of BiFeO3 films undoped and doped with Ba or Ti on SrTiO3 (100) and YSZ (100) substrates. The films have been deposited using a multi-metal source, consisting of the Bi(phenyl)3, Fe(tmhd)3 and Ba(hfa)2 tetraglyme or Ti(tmhd)2(O-iPr)2 (phenyl = -C6H5, H-tmhd = 2,2,6,6-tetramethyl-3,5-heptandione; O-iPr = iso-propoxide; H-hfa = 1,1,1,5,5,5-hexafluoro-2,4-pentanedione; tetraglyme = CH3O(CH2CH2O)4CH3) precursor mixture. The structural and morphological characterization of films has been carried out using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Chemical compositional studies have been performed by energy dispersive X-ray (EDX) analysis. Structural and morphological characterizations point to the formation of homogeneous and flat surfaces for both undoped and doped BiFeO3 films.     

Utilization of clays and zeolites for coagulation treatment of municipal wastewater

This study is to evaluate the role of clays and zeolites on the coagulation and ion exchange treatment of municipal wastewater. Clay minerals used included kaolinite, montmorillonite, halloysite, and bentonite. Zeolites used included mordenite, faujasite, silicalite, and synthetic zeolite‐A. Clays and zeolites proved to be rather ineffective in decreasing the turbidity. Clays and zeolites showed a limited succes in removing Na from the wastewater. Most zeolites appeared to be quite effective in removing Ca and Mg from the wastewater with about 100% removal efficiency for Ca at a dosage of 2.0 g/l. The TOC removal efficiency of primary effluent ranged from 14 to 34% at a dosage of 1.0 g/l. Bentonite and silicalite were most effective in removing organic carbon from primary effluent.     

A theoretical framework for determining the minimum number of bidders in construction bidding competitions

A theoretical framework is proposed for determining the minimum number of bidders in competition for projects in the construction industry. This is based on the neo-classical micro-economic theory for price determination in construction and the assumption of random contractor-selection. Empirical analysis of the Hong Kong data set not only illustrates the applicability of the framework, but also supports the relevance of the microeconomic model for construction price determination. The main implication for clients is that, in order to obtain the most competitive bids for projects in the most cost-efficient way, they should vary the minimum number of bidders in competition according to market conditions.     

Modeling the transport of metals with rate-limited EDTA-promoted extraction and dissolution during EDTA-flushing of copper-contaminated soils

EDTA-flushing of artificially contaminated soils enhanced Cu extraction but also induced mineral dissolution simultaneously. The mobilization and transport of these metal-EDTA complexes was investigated with column experiments. A quantitative transport model was proposed for simulating the experimental breakthrough curves of Cu, Fe, Al, and Ca. The rate-limited EDTA-promoted extraction and dissolution could be described by respective second-order kinetic terms, which were necessary for explaining the time-dependent depletion of extractable metals (sorbed and indigenous) in soils with continuous EDTA-flushing. Simultaneous simulation of extraction of sorbed Cu and dissolution of soil Fe, Al, and Ca is more conceptually accurate than individual modeling of each metal because the latter approach tends to overestimate the concentration of free EDTA during transport and thus underestimate the rate coefficients of EDTA-promoted dissolution. The fitted rate coefficients of Cu were about an order of magnitude larger than those of Fe and Al; these values probably reflect Cu extraction from weakly sorbed fractions and Fe and Al dissolution from amorphous oxides. The apparent retardation of Fe, Al, and Ca transport had to be taken into account by empirical determination, which was attributed to the metal lability in soils and thermodynamics of surface complexation.     

Feasibility of using Hericium erinaceus as the substrate for vinegar fermentation

In this study we investigated the production of vinegar using a Hericium erinaceus fermentation. After 9 days of alcoholic fermentation, the alcohol contents reached 16% with all concentrations (1.25%, 2.5% and 5.0%) of H. erinaceus powder investigated, whereas the sugar content decreased from 25 °Brix to 14 °Brix. Also, the broth pH decreased from 4 to 3.7 and the acidity increased from 0% to 0.3%. According to the sensory evaluation, the mushroom wine produced with 5.0% H. erinaceus powder was preferred by the panel, which was then chosen for subsequent acetic acid fermentation. During the acetic acid fermentation, there was little change in pH, even though the acidity increased from 2% to 4.09%. Besides the abundant acetic acid present in the H. erinaceus vinegar, malic acid and succinic acid were also detected after 9-day of fermentation. Moreover, the H. erinaceus vinegar showed antioxidant activity comparable to other vinegar products when assayed by DPPH and ABTS.     

Isothermal crystallization of polyethylene oxide/silver nanoplate composites

This research was accomplished to investigate the kinetics of isothermal crystallization of polyethylene oxide (PEO)/silver nanoplate composites. It was obtained that the spherulites increased in size and numbers with time for the composites with various particle loadings. Additionally, the spherulite growth rate of composites decreased with an increase in the crystallization temperature and increased with the addition of nanoplates. The spherulite growth rate was further analyzed by the theory developed by Lauritzen and Hoffman. The product of the lateral surface free energy (σ) and the end surface free energy (σ_e) decreased with an increase in the content of nanoplates. We proposed the possible crystallization mechanisms of these PEO/nanoplate composites according to the change of σ and σ_e with the presence of nanoplates. A controlled experiment showed a minor change in PEO crystallization with the presence of a surfactant C₁₆TAB. This implied that the unique size and shape of nanoplates plays a key role on hindering the primary nucleation of PEO and increasing the spherulite growth rate. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Tandem cationic and sol–gel photopolymerizations of a vinyl ether alkoxysilane

In the present study, a novel single hybrid monomer combining a vinylether and trimethoxysilane groups in the same molecule was synthesized by chemoselective hydrosilation and subjected to UV‐irradiation in the presence of a triarylsulfonium salt. Through the UV‐decomposition of this photoacid generator, two acid‐catalyzed processes occurred simultaneously: the cationic polymerization of the vinyl ether functions and the sol–gel polycondensation of the alkoxysilyl groups, leading to a type II polyvinyl‐polysilicate nanocomposite film. Both reaction kinetics were efficiently monitored by real‐time Fourier transform infrared spectroscopy, and the influence of different key experimental parameters was investigated (laminated conditions, UV irradiation equipment, and film thickness). A particular attention was also given to the complete characterization of the hybrid microstructure by associating ²⁹Si and ¹³C solid‐state NMR. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Production of Low-trans Fatty Acids Edible Oil by Electrochemical Hydrogenation in a Diaphragm Reactor Under Controlled Conditions

Electrochemical hydrogenation is a novel, alternative process for selective hydrogenation of vegetable oils, because of its high extent of hydrogenation and low trans-isomer formation. Electrochemical hydrogenation of soybean oil in a diaphragm reactor with a formate ion concentration of 0.4 mol/l at pH 5.0 under moderate temperature conditions using a current density of 10 mA/cm² was investigated to identify the critical conditions affecting the selective hydrogenation reaction and the resulting fatty acid profile. The optimum composition was an oil-to-formate solution ratio of 0.3 (w/w), 2?C3 g EDDAB in 100 g soybean oil, and 0.8% Pd?CC catalyst loading. The electrochemical hydrogenation reaction of soybean oil was described by first-order kinetics, and the kinetic rate constants and reaction selectivity were determined accordingly. Re-use of the Pd?CC catalyst up to five times was found to be acceptable. A comprehensive evaluation revealed that the most significant conditions affecting the extent of hydrogenation and the trans fatty acids content of final products were operating temperature, pH of the formate solution, and catalyst loading.     

Impact of Ni Concentration on the Performance of Ni Silicide/HfO2/TiN Resistive RAM (RRAM) Cells

We present a study of Ni silicide as the bottom electrode in HfO₂-based resistive random-access memory cells. Various silicidation conditions were used for each device, yielding different Ni concentrations within the electrode. A higher concentration of Ni in the bottom electrode was found to cause a parasitic SET operation during certain RESET operation cycles, being attributed to field-assisted Ni cation migration creating a Ni filament. As such, the RESET is affected unless an appropriate RESET voltage is used. Bottom electrodes with lower concentrations of Ni were able to switch at ultralow currents (RESET current <1 nA) by using a low compliance current (<500 nA). The low current is attributed to the tunneling barrier formed by the native SiO₂ at the Ni silicide/HfO₂ interface.