Effects of thermal treatment on the characteristics of boron and tantalum-doped ZnO thin films deposited by the electrospraying method at atmospheric pressure

Metal-doped (B and Ta) ZnO thin films were deposited by the electrospraying method onto a heated glass substrate. The structural, electrical and optical properties of the films were investigated as a function of dopant concentration in the solution and also as a function of annealing temperature. The results show that all the prepared metal-doped ZnO films were polycrystalline in nature with a (0 0 2) preferred orientation. As the amounts of dopant were increased in the starting solution, the crystallinity and transmittance decreased. On the other hand, heat treatment of the films enhanced the transmittance, Hall mobility, carrier concentration and crystallinity. It was also observed that 2 at.% is the optimal doping amount in order to achieve the minimum resistivity and maximum optical transmittance. As-deposited films have high resistivity and low optical transmittance. The annealing of the as-deposited thin films in air resulted in the reduction of resistivity. Depending on the characteristics of dopant, mainly ionic radius, the effects of dopant were studied on the properties of ZnO thin films. Boron and tantalum have been considered as dopants, tantalum being the superior of the two, since it showed the lower resistivity and higher carrier concentration as well as higher mobility. The minimum value of resistivity was 1.95 × 10^− 4 Ω cm (15 Ω/□) with an optical transmittance more than 93% in the visible region and minimum resistivity of 2.16 × 10^− 4 Ω cm (18 Ω/□) with an optical transmittance greater than 96% for 2 at. % tantalum- and boron-doped ZnO films respectively. The present values of resistivities were closer to the indium tin oxide (ITO) resistivity and also closest to the lowest resistivity values among the ZnO films that were previously reported. The prepared films exhibit the good crystalline structure, homogenous surface, high optical transmittance and low resistivity that are preferable for optical devices.     

Assessing the Impact of Front Grid Metallization Pattern on the Performance of BSF Silicon Solar Cells

Silicon - The aim of this research work was to assess the impact of front and rear grid metallization pattern on the performance of silicon solar cells. We have investigated the effect of front...     

Synthesis of nano‐sized ZnO and polyaniline‐zinc oxide composite: Characterization,stability in terms of DC electrical conductivity retention and application in ammonia vapor detection

Nano‐sized particles of Zinc oxide (ZnO) were synthesized using a new chemical rout. The chemical oxidative polymerization of aniline in the presence of nano ZnO was employed to synthesize a polyaniline‐zinc oxide (PANI‐ZnO) nanocomposite. The material was characterized by using transmission electron microscopy, XRD, scanning electron microscopy (SEM), fourier transform infrared spectroscopy (FTIR), and Thermogravimetric analysis (TGA). The conductivity measurements showed the resulting composites possessed higher conductivity as compared to pure polyaniline (PANI). The nanocomposite exhibited fairly sensitive towards solution of aqueous ammonia (NH₃), when it was exposed to various concentrations of NH₃ in an ambient room temperature. The results show that the sensor has good sensitivity and good repeatability upon repeated exposure to NH₃. PANI‐ZnO nanocomposite was also used to study electrical conductivity under isothermal conditions in the temperature range 50–130°C. The composite was found stable under ambient conditions below 90°C in terms of DC electrical conductivity retention. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effects of Calcination on Structural, Photocatalytic Properties of TiO2 Nanopowders Via TiCl4 Hydrolysis

Photocatalytic degradation of methyl orange (MO) in water was examined using TiO₂ nanopowders under solar irradiation. These photocatalysts were successfully synthesized by hydrolysis of titanium tetra chloride (TiCl₄) in the temperature range of 70-95 °C and calcined at higher temperatures of between 400 and 900 °C. The samples prepared were characterized using x-ray powder diffraction, scanning electron microscope (SEM) and Fourier transform infrared spectrophotometer (FTIR). UV-Vis spectrometer was used for analyzing the concentration of MO in solution at different time intervals during the photodegradation experiment. Parameters affecting the photodegradation rate such as catalyst crystallinity, concentration of the catalyst, MO concentration, and pH of the solution have been investigated. The results indicate that TiO₂ nanopowder was antase at low calcination temperatures in the range of 400-500 °C. The sample calcined at 600 °C is composed of both anatase and rutile phase. Further increase in the temperature enhanced the intensities of diffraction peaks of the rutile phase. The size of the crystallites for all the samples prepared were found to be in the 6-13 nm range and from SEM micrographs it was in the range of 19-43 nm. The mixture of both phases exhibited a higher photoactivity in comparison with pure anatase or rutile catalysts.     

Synthesis and properties of aqueous polyurethane dispersions: Influence of molecular weight of polyethylene glycol

Aqueous polyurethane dispersions (PUDs) have recently emerged as important alternatives to their solvent-based counterparts for various applications due to increasing health and environmental awareness. A series of aqueous polyurethane dispersions containing carboxylate anion as hydrophilic pendant groups were synthesized through step growth polymerization reaction using hexamethylene diisocyanate (HDI), 1,4-butanediol (1,4-BDO), dimethylol propionic acid (DMPA) and polyethylene glycol (PEG) of different molecular weight. Effect of PEG molecular weight was investigated on molecular structure, contact angle measurement, and physical and adhesive properties of PU emulsions. Fourier transform infrared spectroscopy (FT-IR) was used to check the completion of polymerization reaction. Contact angle measurement indicated that the hydrophilicity of polymer increases by increasing molecular weight of PEG with a corresponding decrease in contact angle. Results of T-peel test showed a decrease in peel strength by increasing molecular weight of PEG. Moreover, solid contents%, drying time and storage stability suggested fast drying properties and greater stability of aqueous PU dispersions.     

Synthesis, Characterization, Biodegradation and Evaluation of the Surface Active Properties of Nonionic Surfactants Derived from Jatropha Oil

Four nonionic surface active agents were synthesized using the fatty acids obtained from the hydrolysis of Jatropha oil. The fatty acids obtained contained different fatty acids including: palmitic, stearic, oleic, linoleic and linolenic acids in different proportions. The chemical structures of the obtained surfactants were characterized using elemental analysis and FTIR spectroscopy. The surface activities of the different surfactants were determined using surface and interfacial tension measurements. The surfactants showed good surface and interfacial activities, which are dependent on their chemical structures. Thermodynamic parameters of adsorption and micellization confirmed these results. The biodegradation tests in river water showed that the surfactants are readily biodegradable, and reached the European standards after 24 days. Surfactants containing longer nonionic chains formed stable emulsions with paraffin oil, while shorter chains exhibit a lower emulsion stability performance.     

Structural,optical and photocatalytic properties of hafnium doped zinc oxide nanophotocatalyst

A series of novel hafnium (Hf) doped ZnO nanophotocatalyst were synthesized using a simple sol–gel method with a doping content of up to 6 mol%. The structure, morphology and optical characteristics of the photocatalysts were characterized by XRD, SEM, TEM, FTIR, XPS, DRS and PL spectroscopy. The successful synthesis and chemical composition of pure and doped ZnO photocatalysts were confirmed by XRD and XPS. DRS confirmed that the spectral responses of the photocatalysts were shifted towards the visible light region and showed a reduction in band gap energy from 3.26 to 3.17 eV. Fluorescence emission spectra indicated that doped ZnO samples possess better charge separation capability than pure ZnO. The photocatalytic activity of Hf-doped ZnO was evaluated by the methylene blue (MB) degradation in aqueous solution under sunlight irradiation. Parameters such as irradiation time and doping content were found effective on the photoactivity of pure ZnO and Hf-doped ZnO. The photocatalysis experiments demonstrated that 2 mol% Hf-ZnO exhibited higher photocatalytic activity as compared to ZnO, ZnO commercial and other hafnium doped ZnO photocatalysts and also revealed that MB was effectively degraded by more than 85% within 120 min. The enhanced photoactivity might be attributed to effective charge separation and enhanced visible light absorption. It was concluded that the presence of hafnium within ZnO lattice could enhance the photocatalytic oxidation over pure ZnO.     

Modulation of Gut Microbial Diversity through Non-Pharmaceutical Approaches to Treat Schizophrenia

Schizophrenia (SCZ) is a psychotic syndrome with well-defined signs and symptoms but indecisive causes and effective treatment. Unknown underpinning reasons and no cure of the disease profoundly elevate the risk of illness. Gut microbial dysbiosis related metabolic dysfunction is providing a new angle to look at the potential causes and treatment options for schizophrenia. Because of the number of side effects, including gut dysbiosis, of traditional antipsychotic drugs, new alternative therapeutic options are under consideration. We propose that non-pharmacotherapy using biotherapeutic products could be a potent treatment to improve cognitive impairment and other symptoms of schizophrenia. Use of live microorganisms (probiotics), fibers (prebiotics), and polyphenols alone or in a mixture can maintain gut microbial diversity and improve the two-way relationship of the gut microbiota and the central nervous system. Fiber and polyphenol induced management of gut microbiota may positively influence the gut–brain axis by increasing the level of brain-derived neurotrophic factors involved in schizophrenia. Furthermore, we endorse the need for comprehensive clinical assessment and follow-up of psychobiotic (pro and prebiotics) treatment in mental illness to estimate the level of target recovery and disability reduction in schizophrenia.     

In situ Polymerization of Multi-Walled Carbon Nanotube/Nylon-6 Nanocomposites and Their Electrospun Nanofibers

Multiwalled carbon nanotube/nylon-6 nanocomposites (MWNT/nylon-6) were prepared by in situ polymerization, whereby functionalized MWNTs (F-MWNTs) and pristine MWNTs (P-MWNTs) were used as reinforcing materials. The F-MWNTs were functionalized by Friedel-Crafts acylation, which introduced aromatic amine (COC₆H₄-NH₂) groups onto the side wall. Scanning electron microscopy (SEM) images obtained from the fractured surfaces of the nanocomposites showed that the F-MWNTs in the nylon-6 matrix were well dispersed as compared to those of the P-MWNTs. Both nanocomposites could be electrospun into nanofibers in which the MWNTs were embedded and oriented along the nanofiber axis, as confirmed by transmission electron microscopy. The specific strength and modulus of the MWNTs-reinforced nanofibers increased as compared to those of the neat nylon-6 nanofibers. The crystal structure of the nylon-6 in the MWNT/nylon-6 nanofibers was mostly γ-phase, although that of the MWNT/nylon-6 films, which were prepared by hot-pressing the pellets between two aluminum plates and then quenching them in icy water, was mostly α-phase, indicating that the shear force during electrospinning might favor the γ-phase, similarly to the conventional fiber spinning.     

Effect of Copper and Zirconium Addition on Properties of Fe-Co-Si-B-Nb Bulk Metallic Glasses

In this research work, iron-based bulk metallic glasses (BMGs) have been fabricated, characterized and compared with Fe-Si alloy. BMG alloys of composition ((Fe_0.6Co_0.4)_0.75B_0.20Si_0.05)₉₆Nb₄) were synthesized by suction casting technique using chilled copper die. Effect of copper and zirconium addition on magnetic, mechanical, thermal and electrochemical behavior of ((Fe_0.6Co_0.4)_0.75B_0.20Si_0.05)₉₆Nb₄ BMGs was investigated. Furthermore, effect of annealing on nano-crystallization and subsequently on magnetic and mechanical behavior was also analyzed. Amorphousness of structure was evidenced by XRD analysis and microscopic visualization, whereas nano-crystallization behavior was identified by peak broadening of XRD patterns. Magnetic properties, measured by vibrating sample magnetometer, were found to be improved for as-cast BMG alloys by copper addition and further enhanced by nano-crystallization after annealing. Mechanical properties were observed to be increased by zirconium addition while slightly declined by copper addition. Potentiodynamic polarization analysis manifested the positive role of zirconium in enhancing corrosion resistance of BMGs in acidic, basic and brine mediums. Moreover, mechanical properties and corrosion analysis results affirmed the superiority of BMG alloys over Fe-Si alloy.