III-V semiconductor nanowire for solid oxide fuel cells

Solid oxide fuel cells (SOFC) have much promise as efficient devices for the direct conversion of the energy stored in chemical fuels into electricity. The development of highly robust SOFC that can operate on a range of fuels, however, requires improvement in the electrodes, especially the anode, where nanoscale engineering of the structure is required in order to maximize the number of sites where the electrochemical reactions take place. In this article, we briefly explained the growth of III-V semiconductor nanowire layer on GaAs substrate as an anode electrodes using metal organic chemical organic vapor deposition (MOCVD). Field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and conductivity atomic force microscopy (CAFM) analysis were carried out to investigate the structural properties and current-voltage changes in the wires. Results show that the III-V nanowires grow with less defect structure, uniform in composition and diameters with optimal growth parameters. The current-voltage measurement showed similar to that of a p-n junction characteristic which is suitable in the SOFC application

Cu2+ and Al3+ co-substituted cobalt ferrite: structural analysis, morphology and magnetic properties

Cu-Al substituted Co ferrite nanopowders, Co1-xCux Fe2-x Alx O4 (0.0 ≤ x ≤ 0.8) were synthesized by the co-precipitation method. The effect of Cu-Al substitution on the structural and magnetic properties have been investigated. X-ray diffraction (XRD) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, field emission scanning electron microscopy (FESEM) and vibrating sample magnetometer (VSM) are used for studying the effect of variation in the Cu-Al substitution and its impact on particle size, magnetic properties such as Ms and Hc. Cu-Al substitution occurs and produce a secondary phase, α-Fe2O3. The crystallite size of the powder calcined at 800°C was in the range of 19-26 nm. The lattice parameter decreases with increasing Cu-Al content. The nanostructural features were examined by FESEM images. Infrared absorption (IR) spectra shows two vibrational bands; at around 600 (v1) and 400 cm-1 (v2). They are attributed to the tetrahedral and octahedral group complexes of the spinel lattice, respectively. It was found that the physical and magnetic properties have changed with Cu-Al contents. The saturation magnetization decreases with the increase in Cu-Al substitution. The reduction of coercive force, saturation magnetization and magnetic moments are may be due to dilution of the magnetic interaction

Alsolation and characterization of a heavy metalreducing enterobacteriaceae bacterium strain DRY 7 with the ability to assimilate phenol and diesel

Background/Objectives: Molybdenum, phenol and diesel are toxic to organism, and are part of global pollution. Their removal using microorganisms with multiple detoxification ability is being intensely sought as a cleaner and economic approach. Methods/Statistical analysis: A soil suspension was spread plated on a minimal salts media supplemented with molybdenum. Blue colonies, indicating molybdenum reduction was then screened for phenol and diesel degradation capabilities. Findings: A molybdenum-reducing bacterium locally isolated showed the ability to grow on phenol and diesel. The bacterium required pHs of between 5.8 and 6.3 and temperatures of between 30 and 40oC for optimal reduction. Among the carbon sources tested for supporting reduction, glucose was the best. A critical concentration of phosphate at just 5 mM was required, while molybdenum (sodium molybdate) was required between 15 and 25 mM. The absorption spectrum of the Mo-blue produced showed a characteristic maximum peak at 865 nm. The reduction of molybdenum was inhibited by the ions mercury, copper, chromium, lead and silver by 78.9, 78.4, 77.4, 53.5 and 36.8%, respectively. Analysis using phylogenetic analysis identifies the bacterium as Enterobacteriaceae bacterium strain DRY7. Growth on phenol and diesel as carbon sources showed that the optimal concentrations supporting growth was between 300 and 400 mg/L and between 300 and 500 mg/L, respectively. Application/Improvements: The capacity of this bacterium to detoxify a number of toxicants is an important property or bioremediation of soils contaminated with multiple toxicants

The influence of tertiary butyl hydrazine as a co-reactant on the atomic layer deposition of silver

Ultra-thin conformal silver films are the focus of development for applications such as anti-microbial surfaces, optical components and electronic devices. In this study, metallic silver films have been deposited using direct liquid injection thermal atomic layer deposition (ALD) using (hfac)Ag(1,5-COD) ((hexafluoroacetylacetonato)silver(I)(1,5-cyclooctadiene)) as the metal source and tertiary butyl hydrazine (TBH) as a co-reactant. The process provides a 23 °C wide ‘self-limiting’ ALD temperature window between 105 and 128 °C, which is significantly wider than is achievable using alcohol as a co-reactant. A mass deposition rate of ∼20 ng/cm2/cycle (∼0.18 Å/cycle) is observed under self-limiting growth conditions. The resulting films are crystalline metallic silver with a near planar film-like morphology which are electrically conductive. By extending the temperature range of the ALD window by the use of TBH as a co-reactant, it is envisaged that the process will be exploitable in a range of new low temperature applications

Morphology and chemical composition of inxGa1-xAs NWs Au-assisted grown at low growth temperature using MOCVD

Cylindrical InxGa1-xAs NWs have been successfully grown at low growth temperature using MOCVD. Field Emission-Scanning Electron Microscopy (FE-SEM) characterization and Energy Dispersive X-ray (EDX) analysis have been used to investigate the morphology and chemical composition of NWs, respectively. Both characterization results consistently reinforce that the NWs growth were via direct impinging mechanism and NW have relatively uniform chemical composition

Effects of silica composition on gas permeability of ENR/PVC membrane

This paper studied the potential of a hybrid organic-inorganic membrane, ENR/PVC/SiO2 membrane for separation purposes. The ENR/PVC/SiO2 membranes were prepared usingspontaneous solvent exchange and evaporation techniques. The amount of SiO2 added was  varied at 1, 3, 5 and 8 wt%. The SEM micrographs showed that pores were developed upon addition of SiO2. The tensile strength and modulus were also enhanced with increasing amount of SiO2 up to 5 wt%. At higher SiO2 loadings, the mechanical strength of the membrane decreased due to the agglomeration of SiO2 particles. Gas permeation test was done on ENR/PVC/SiO2 membranes using NO2 gas and CO2 gas. The permeability of both gasses increased with the amount of SiO2 added to the membrane, which attributed to the increase in nanopores. The membranes with SiO2 had a higher permeability to CO2 than NO2Keywords: epoxidised natural rubber; polyvinyl chloride; membrane; silica; gas separation

The effect of V/III ratio on the crystal structure of gallium arsenide nanowires

Gallium arsenide (GaAs) nanowires were grown vertically on GaAs (111)B substrate by gold particle-assisted using metal-organic chemical vapour deposition. Transmission electron microscopy and X-Ray diffraction analysis were carried out to investigate the effects of V/III ratio and nanowire diameter on structural properties and crystallinity changes. Results show that GaAs nanowires grow preferably in the wurtzite crystal structure than zinc blende structure with increasing V/III ratio. Additionally, XRD studies have revealed that wurtzite nanowires show prominent peaks especially at (222) orientation. The optimum V/III ratio was found to be 166 with less defect structure, uniform diameter and peak prominence. The nanowires with high quality are needed in solar cells technology for energy trapping with maximum capacity.Keywords : Nanowire; crystal structure; Gallium arsenide; Vapor Liquid Soli

Germanium nanoislands grown by radio frequency magnetron sputtering grown germanium nanoislands: annealing time dependent surface morphology and photoluminescence

Structural and optical properties of ~ 20 nm Ge nanoislands grown on Si(100) by radio frequency (rf) magnetron sputtering under varying annealing conditions are reported. Rapid thermal annealing at a temperature of 600°C for 30 s, 90 s, and 120 s are performed to examine the influence of annealing time on the surface morphology and photoluminescence properties. X-ray diffraction spectra reveal prominent Ge and GeO2 peaks highly sensitive to the annealing time. Atomic force microscope micrographs of the as-grown sample show pyramidal nanoislands with relatively high-density 1011 cm-2)). The nanoislands become dome-shaped upon annealing through a coarsening process mediated by Oswald ripening. The room temperature photoluminescence peaks for both as-grown 3.29 eV) and annealed 3.19 eV) samples consist of high intensity and broad emission, attributed to the effect of quantum confinement. The red shift (~0.10 eV) of the emission peak is attributed to the change in the size of the Ge nanoislands caused by annealing. Our easy fabrication method may contribute to the development of Ge nanostructure-based optoelectronics

Modified fibrous silica for enhanced carbon dioxide adsorption: Role of metal oxides on physicochemical properties and adsorption performance

This work investigates the effectiveness of FS loaded with CaO, MgO, and CeO2 for CO2 adsorption. Different techniques such as XRD, ATR–FTIR, Raman, CO2–TPD, in situ FTIR, FESEM, and TEM were employed. Upon the metal oxides loading, the alteration of textural properties, increases in the weak and moderate basic strength and quantity of basic active sites as well as disappearance of the dendritic structures in CaO/FS were observed. The in situ FTIR studies confirmed the formation of different carbonates species upon the interaction with CO2. The greatest CO2 physisorption capacity was demonstrated by CaO-FS (0.76 ​mmol/g), while the highest CO2 chemisorption uptake was shown by MgO-FS (9.77 ​mmol/g). The CO2 physisorption activity depends mainly on the porosity and basic strength of the adsorbents. On the contrary, the CO2 chemisorption performance is determined by the basic strength and basic sites as well as CO2 affinity of the adsorbents