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Borides are considered advanced building materials due to their high melting temperature, hardness, wear/corrosion/oxidation resistance and excellent thermal and electrical properties. Among the many metal borides, chromium borides are known for their high electrical conductivity and high hardness. In this study, it is aimed to form CrxBx on powder metal pure Cr material and to examine its wear characteristics. For the production of samples, commercial purity Cr powders were mixed for 60 min and pressed under 850 MPa pressure to obtain raw samples. After pressing, the samples were boronized at 1000 ºC for 2, 4, 6 and 8 h, and a hard boride layer was formed on the outer surface. Hardness, abrasion tests and then then Field Emission Scanning Electron Microscopy, energy-dispersive x-ray spectroscopy and x-ray diffraction analyzes were applied to the samples obtained. It was determined that CrB, Cr2B, Cr2B3and Cr3B4 borides were formed on the surface with boronizing process and the hardness of these phases increased significantly. The wear resistance of P/M Cr specimens could also be improved by increasing the hardness. © 2022, ASM International.

Electroless nickel-based coatings are frequently used in the field of coatings to improve the surface properties of materials such as wear, hardness, and corrosion. In this study, Ni-W-P alloy and Ni-W-P/Al2O3 composites were coated on the aluminum substrate by electroless technique. Composite coatings were carried out after suspending process of alumina (Al2O3) particles at different concentrations in the electroless bath. The characterizations of the coatings were studied to be able to reach optimum particle concentration. Aluminum oxide particles (average particle size 300 nm) with different concentrations (5, 10, 15, 20 g/L) were added to the bath to determine the concentration effect. Scanning electron microscope (SEM) and field emission scanning electron microscopy (FESEM) analyses were performed to examine the microstructure images of the composite coatings. x-ray diffraction (XRD) analysis was performed to determine the coating layers' phase structures. The hardness of the coatings was determined by applying the hardness test on a microscopic scale. CSM tribometer was used to establish the wear and friction properties of the coatings. Galvanometer was used to determine corrosion resistance. After the studies, hardness values of coatings were successfully increased from 552 to 700 HV depending on the amount of particles in the coating layer. The friction coefficient was also improved by decreasing that from 0.45 to 0.1 µ grades with the contribution of Al2O3 particle reinforcement to Ni-W-P coating. The wear rate of the coatings decreased from 5.96 × 10 −5 to 3.16 × 10−5 mm3/Nm) with the increase of Al2O3 particles in the composite coating which indicates approximately two times improvement in the wear resistance. The corrosion resistance of composite coatings also increased, and an improvement in corrosion rate was achieved from 392 value to 063µm/year value with increasing particle concentration. © 2023, ASM International.

Crystal shape is a critical determinant of the physical and chemical properties of crystalline materials; hence, it is the challenge of controlling the crystal morphology in a wide range of scientific and technological applications. The morphology is related to the geometry of their exposed surfaces, which can be described by their surface energies. The surface properties of β-ZnMoO4 have not yet been well explored, either experimentally or theoretically. Thus, the first-principle calculation at the density functional theory level was carried out for different low-index surfaces of β-ZnMoO4, specifically (001), (010), (110), (011), (101), and (111), and the surface energy values (Esurf) were reported. The surface stability was found to be controlled by the undercoordinated [MoOn…yVxO] and [ZnOn…yVxO] (n = 4 and 5; y = 1 and 2) clusters, i.e., their local coordination of Mo and Zn cations at the exposed surfaces, respectively, with the (111) surface being the most stable. A complete map of investigated β-ZnMoO4 morphologies was obtained using the Wulff construction and changing the values of the calculated energy surfaces. The final geometries from this map were compared with field emission-scanning electron microscopy images showing excellent agreement, prevising rectangular and hexagonal plates. Our findings will promote the use of facet engineering and might provide strategies to produce β-ZnMoO4-based materials for achieving morphology-dependent technological applications.

In this article, the synthesis by means of the spray pyrolysis method, of the CaMoO4 and rare-earth cation (RE3+)-doped CaMoO4:xRE3+ (RE3+ = Eu3+, Tb3+, and Tm3+; and x = 1, 2, and 4% mol) compounds, is presented. The as-synthesized samples were characterized using X-ray diffraction, Rietveld refinement, field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and photoluminescence (PL) spectroscopy. To complement and rationalize the experimental results, first-principles calculations, at the density functional theory level, have been performed to analyze the band structure and density of states. In addition, a theoretical method based on the calculations of surface energies and Wulff construction was applied to obtain the morphology transformation of the CaMoO4 and CaMoO4:RE3+ microstructures. The experimental morphologies can be observed in the FE-SEM images. The PL behavior of the Co-doped samples exhibited well-defined bands in the visible region. The samples with 2 and 4% of RE3+ released white emission according to the chromaticity coordinates (0.34, 0.34) and (0.34, 0.33), respectively. The present results provide not only a deep understanding of the structure–property relationships of CaMoO4-based phosphor but also can be employed as a guideline for the design of the electronic structure of the materials and the fabrication of photofunctional materials with optimal properties, which allows for the modeling of new phosphors for applications in solid-state lighting.

In this paper, heavily C-doped GaN samples were deposited on glass and PET substrates by the thermionic vacuum arc (TVA) method, for the first time. Microstructure, surface and optical properties of the carbon-doped GaN samples were investigated by X-ray diffraction (XRD), field emission scanning electron microscopy, atomic force microscopy, and UV–Vis spectrophotometer. According to XRD pattern, fullerene (C60) structures were able to deposit in doped samples, for the first time. The fullerene structures were detected at heavily carbon-doped GaN. The obtained band gap changes of heavily carbon-doped GaN samples are determined. The band gap of CGaN on PET substrate decreased to a lower value, about 100 meV. The band gaps were shifted to the lowest wavelengths towards the edge of the UV region by heavily doped carbon. (002) and (004) peaks for GaN were also detected. © 2016 Elsevier Ltd

In this paper, copper oxide (CuO/Cu2O) nanocrystalline thin films were deposited by radio frequency (RF) magnetron sputtering system at 75 W and 100 W. The surface, optical, composition and structural properties of obtaining samples were characterized by using atomic force microscopy (AFM), UV–Vis spectrophotometer, field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The optical band gaps of produced films were calculated as 2.05 eV and 1.83 eV for 75 W and 100 W. The layer’s thicknesses were measured as 20 nm and 50 nm using a Filmetrics F20. FESEM images of the samples prove the AFM images change and also show homogeneity of thin films and variation relative to power change, thus revealed the surface of samples disturb in homogen mode. EDX results denote presence of Cu and O elements inside the deposited samples.

A major bottleneck in the fabrication of efficient bio-organic nanoelectronic devices resides in the strong charge recombination that is present at the different interfaces forming the complex system. An efficient way to overcome this bottleneck is to add a self-assembled monolayer (SAM) of molecules between the biological material and the electrode that promotes an efficient direct electron transfer whilst minimising wasteful processes of charge recombination. In this work, the presence of a pyrene-nitrilotriacetic acid layer carrying different metal centers as SAM physisorbed on graphene is fully described by mean of electrochemical analysis, field emission scanning electron microscopy, photoelectrochemical characterisation and theoretical calculations. Our multidisciplinary study reveals that the metal center holds the key role for the efficient electron transfer at the interface. While Ni2+ is responsible for an electron transfer from SAM to graphene, Co2+ and Cu2+ force an opposite transfer, from graphene to SAM. Moreover, since Cu2+ inhibits the electron transfer due to a strong charge recombination, Co2+ seems the transition metal of choice for the efficient electron transfer., Comment: 28 pages, 7 figures

Room-temperature ferromagnetism of GaN and doped GaN materials has been reported in nanostructured form. Especially, nanoparticles show ferromagnetic properties at room temperature. In this paper, Ti-doped effects on GaN were deposited on glass and Polyethylene terephthalate (PET) substrates by thermionic vacuum arc and their room temperature magnetic properties are presented for the first time. The structure of the Ti-doped GaN was crystallized in a novel form, nano honeycomb formation. Optical and surface properties of the nano honeycombs and honeycomb nanosheets were determined. GaN and TiN phases were detected in X-ray diffraction patterns. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) device were used for imaging of the crystal structure. According to FESEM images, hexagonal crystal formations were detected for all samples. Crystal formations are very good oriented on PET substrates materials according to glass samples. The band gap value of the sample is changed by crystallization dimension. It was found that increasing crystallizations and decreasing crystal dimensions were increased the band gap of the Ti-doped GaN approximately 50 meV. Fourier transform infrared spectra and a vibrating sample magnetometer results were presented. These results confirm the Ti doped GaN honeycomb nanosheets and nano honeycombs show the room temperature ferromagnetic properties. © 2017, © 2017 Taylor & Francis.

The present study demonstrates a solution-processed humidity sensor based on poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene]:polyvinylpyrrolidone (MEH-PPV:PVP) organic microstructured composite thin film. The capacitive type humidity sensor has been fabricated in the surface type geometry of Al/MEH-PPV:PVP/Al, wherein organic composite (MEH-PPV:PVP) has been deposited onto the aluminium electrodes by electrospinning technique. The structural and morphological properties of organic thin film have been characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM). The humidity sensing properties of the sensor have been investigated at ∼1 volt AC operational bias, by measuring the capacitance as a function of a broad range (20–90%) of relative humidity (RH). The temperature and operational frequency dependency of the capacitance of the sensor has also been analyzed in detail. The proposed sensor exhibits high sensitivity (114 fF/% RH @ 100 Hz), small hysteresis (∼2% RH) and fast response (18 s and 8 s for adsorption and desorption processes, respectively). Compared with traditional spin-coated and drop-casted organic humidity sensors, the microstructure composite based sensor has demonstrated significantly improved sensing parameters, highlighting the unique advantages of the electrospinning process for humidity sensor fabrication. The possible humidity sensing mechanism of the proposed capacitive sensor has also been elaborated. Authors are thankful to the Ministry of Education for the financial support under High Impact Research (HIR) grant UM.S/625/3/HIR/MOE/26 with account number UM.0000080/HIR.C3 and University Malaya Research Grant (UMRG) under grant number RP007A-13AFR. This project was also partially funded by the University Malaya postgraduate grant PG089-2012B. Scopus

In this paper, GaN thin film production was realized by thermionic vacuum arc (TVA), a plasma deposition technique, for the first time. We present a new deposition mechanism for GaN thin films with a very short production time. Microstructure properties of samples were analyzed by X-ray diffractometry. The peak at 2? = 72.88° corresponding to GaN (0004) was detected in XRD spectra. The surface morphology of the deposited GaN films was analyzed using field emission scanning electron microscopy and atomic force microscopy. The surface properties of the produced samples are quite different. The average roughness values were determined to be 0.48 nm for GaN/PET and 1.17 nm for GaN/glass. The optical properties (i.e., refractive index and reflection) were determined using an interferometer. Moreover, the obtained optical data were compared with bulk GaN materials. The refractive indexes were measured as 2.2, 3,0 and 2,5 for the GaN/glass, GaN/PET and bulk GaN, respectively. The transparencies of the different GaN-coated substrates are nearly the same. The obtained band gap values were measured in the energy range of 3.3-3.5 eV. TVA is a novel non-reactive plasma technique for the generation of metal organic thin films. The main advantage of this method is its fast deposition rate without any loss in the quality of the films. © 2015 Elsevier B.V.

Current research presents a new deposition method for GaN thin films that produces in a very short production time for GaN-based solid-state applications. A Mo doped GaN thin film on a glass substrate was produced by thermionic vacuum arc (TVA) technique. The TVA technique is a novel non-reactive plasma technique. The optical properties were determined by Filmetrics F20 interferometer and UV–Vis double beam spectrophotometer. The surface morphology was analyzed using field emission scanning electron microscopy and atomic force microscopy. The mean thickness value was measured as 100 nm by Filmetrics interferometer. The crystalline structure of the produced thin film has a Wurtzite crystal structure (004) as obtained by X-ray diffraction. Hardness value was determined as 14 GPa with the Oliver–Pharr method. The obtained properties are consistent with the values reported in related literature. The findings indicate that the TVA method provides advantages for optical and industrial applications. © 2015, Springer Science+Business Media New York.

Persuaded by the necessity of finding new sources of antibiotics, silver nanoparticles (Ag NPs) were synthesized by adopting a newly developed green synthesis technique and subsequently, their antibacterial activity against different pathogenic bacteria was evaluated. We have successfully synthesized bio-molecule capped ferromagnetic Ag NPs with an average crystallite size of 13 nm using AgNO3 solution as a precursor and Artocarpus heterophyllus leaf extract as a reducing and capping agent. The characterization of the synthesized Ag NPs was carried out using various techniques such as UV-visible (UV-Vis) spectroscopy, energy dispersive X-ray (EDX) spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetry (TG), and vibrating sample magnetometer (VSM) analyses. After exposing the synthesized Ag NPs to two Gram-positive bacteria-Staphylococcus aureus and Bacillus cereus and two Gram-negative bacteria-Escherichia coli and Salmonella typhimurium, the zones of inhibition were found to be 15, 16, 19, and 18 mm, respectively. These results imply that the Artocarpus heterophyllus leaf extract mediated green synthesized bio-molecules encapsulated Ag NPs can be considered as a potential antibiotic against human pathogens which is very encouraging. © The Royal Society of Chemistry.

Using a thermionic vacuum arc, single?crystal gallium arsenide (GaAs) layers of micron thickness were grown on PET and glass substrates in 2 min. We present a new deposition mechanism and parameters for GaAs thin films produced in a very short time. Crystal direction was found to be (111) plane for the GaAs/PET sample and (022) plane and (133) plane for the GaAs/glass sample, respectively. The average roughness values of the deposited thin films were determined to be approximately 30 nm for GaAs/PET and 60 nm for GaAs/glass. The structures can be seen clearly in field emission scanning electron microscopy and atomic force microscopy. The obtained optical band is nearly the same with literatures values of the GaAs. Although produced structures in different crystal formations, only aggregations dimensions and absorbance of the layers were changed. Obtained refractive index values are nearly same with database info. © 2015, Springer Science+Business Media New York.

Bio-molecule capped α-MnO2 nanoparticles have been successfully synthesized from the reduction of KMnO4 via a facile green synthesis route using an aqueous leaf extract of Bryophyllum pinnatum as a reducing and capping agent. The synthesized α-MnO2 nanoparticles were characterized by x-ray diffraction (XRD), Fourier transform—infrared (FT-IR), energy dispersive x-ray (EDX), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), thermogravimetric (TG) and differential scanning calorimetry (DSC) techniques. Experimental results clearly demonstrate the successful synthesis of bio-molecule capped crystalline tetragonal α-MnO2 nanoparticles with the size of 4–18 nm. The magnetic property of the product was evaluated using a vibrating sample magnetometer (VSM) and the result reveals that the presently synthesized bio-molecule capped α-MnO2 nanoparticles exhibit ferromagnetic property at room temperature.

Aluminium doped zinc oxide (AZO) nanostructures have been successfully synthesized on sapphire substrates by using nanoparticle assisted pulsed laser deposition (NAPLD) in Ar atmosphere without using any catalyst. The growth of the AZO nanowires has been investigated by varying the argon flow rates. The coatings have been characterized by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), Diffuse Reflectance Spectroscopy (DRS), Laser Raman spectroscopy and Photoluminescence spectroscopy. The results of XRD indicate that the deposited films are crystalline ZnO with hexagonal wurtzite structure with (0 0 2) preferred orientation. FESEM images also clearly reveal the hexagonal structure and the formation of nanowires with aspect ratios between 15 and 20. The surface roughness value of 9.19 nm was observed from AFM analysis. The optical properties of the sample showed that under excitation with ? = 325 nm, an emission band was observed in UV and visible region. The characteristic Raman peaks were detected at 328, 380, 420, 430 cm-1. � 2013 Elsevier B.V. All rights reserved.

Synthesis and characterization of Ga-doped ZnO nanodisk and the formation of nanodisk/nanorod hybrid morphologies on AlN/Si substrate by polymer assisted one-pot hydrothermal process have been studied. The low concentration of Ga-ZnO sol (0.2. M) and optimized concentration (0.5. M) of Zinc sol is used to vary the morphology and physico-chemical properties. Varying amounts of Ga (1%-3%) doped ZnO nanodisks have also been synthesized and characterized. The morphology and structural properties were determined by field emission scanning electron microscopy (FESEM) and X-ray diffraction techniques. Ga-ZnO nanodisk shows major intense X-ray diffraction peak at ZnO (101). X-ray photoelectron spectroscopy (XPS) confirms the effect of gallium doping and variation in their surface property after Ga doping in ZnO. FESEM images clearly confirm the pure nanodisk formation for Ga-ZnO (0.5) at optimized ZnO concentration and hybrid nanodisk/nanorod formation obtained for Ga-ZnO (0.2) at lower ZnO concentration. The pure Ga-ZnO (0.5) nanodisk on AlN/Si thin film substrate showed effective response and fast recovery time towards UV light sensing in dark condition compared to low concentration route prepared Ga-ZnO (0.2)/AlN/Si sample. � 2013 Elsevier B.V.

This study focuses on characterization and understanding of the substrate effect on Ge doped GaN thin films coated onto transparent substrates. The produced films were deposited onto unheated glass and unheated polyethylene terephthalate by using thermionic vacuum arc technique. Gallium nitride and germanium pellets were used in the thin film production. Reflectance, refractive index and thicknesses of Ge doped GaN thin films were measured by optical interferometer using Cauchy model for fitting. The transmittances were determined in the wavelength range between 200 and 1000 nm by using UV–Vis double beam spectrophotometer. The optical Tauc method was used to determine the band gap energies of produced thin films. Surface morphologies of produced thin films were characterized by atomic force microscopy and also field emission scanning electron microscopy. In conclusion, the substrate effect on the optical and morphological properties of the produced thin films was observed. © 2016, Springer Science+Business Media New York.

Oil contaminated water is one of the challenges in water resources management. It is crucial to remove the oil droplets from water in order to meet the discharge regulations set by the environmental authorities. Carbon nanotubes (CNTs) have generated a lot of attention as a new type of adsorbent due to their exceptionally high adsorption capacity for oil-water separation. The high hydrophobicity of CNTs makes them good candidates to enhance the de-oiling process from wastewater. In this study, we have reported the synthesis and evaluation of novel iron-oxide/CNTs nanocomposites for oil-water separation. The CNTs were doped with different loadings of iron oxide nanoparticles using a wet impregnation technique. The synthesized nanocomposite nanomaterials were characterized using field emission scanning electron microscopy (FE-SEM), high resolution transmission electron microscopy (TEM), Brunauer, Emmett and Teller (BET) technique, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). The effect of adsorption parameters, including, adsorbent dosage, contact time, and agitation speed on the oil removal efficiency were optimized using batch experiments. The sorption capacities of doped CNTs were found to be greater than 7 g/g for gasoline oil. The doped CNTs reached maximum sorption capacity after only 15 min providing one of the fastest minimum contact times reported of all oil sorbent materials. The loading of Fe2O3 nanoparticles on the negative surface of CNT decreases the negative sign and magnitude of the zeta potential by overcoming the repulsive effects of the electrical double layers to allow the finely sized oil droplets to form larger droplets through coalescence. Therefore increasing percentage of the Fe2O3 on the surface of CNT increased the removal of the emulsified oil from the water. 2016 Elsevier B.V. The authors are grateful to the Qatar Environment and Energy Research Institute (QEERI), Qatar Foundation for financial support under project WGC-4004. Also, the authors are grateful to Mr. Faraj Ahmed Abuilliw, General Science and Studies Unit, Hafr AlBatin Community College, Hafr AlBatin, King Fahad University of Petroleum & Minerals (KUFPM), Saudi Arabia for providing raw material for this study. Scopus

High-energy ball-milling of powder mixtures of zincite (ZnO) and iron (α-Fe) at different weight ratios was performed in air using a planetary ball mill with a stainless steel milling assembly. Structural and microstructural changes during the ball-milling (up to 30 h) were monitored using X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and UV-Vis diffuse reflectance spectroscopy. The mechanism of iron oxidation was determined from the results of Mossbauer spectroscopy. It was found that an early phase of ball-milling caused the oxidation of iron from Fe(0) to Fe(2+) followed by the formation of a solid solution structurally similar to wustite. The wustite-type phase rapidly disappeared upon prolonged milling, which was accompanied by further oxidation of iron from Fe(2+) to Fe(3+) and the formation of spinel-type ferrite structurally similar to franklinite (ZnFe2O4) in the products with a high zinc content, or magnetite (Fe3O4) in the products with a high iron content. Further milling or annealing had a low impact on the franklinite-type phase, but caused the transition of the magnetite-type phase to the phase structurally similar to hematite (α-Fe2O3). The results of energy dispersive X-ray spectrometry (EDS) showed a dramatic increase in the degree of contamination with the increase in the proportion of the starting iron (∼9 times higher contamination during the milling of pure iron compared with pure zincite). It was shown that the source of contamination (balls or vial) strongly depends on the type of milled sample. Ball-milling of relatively big and heavy grains (starting iron) caused preferential contamination from the vial whereas ball-milling of smaller and lighter grains (products obtained after prolonged milling) caused preferential contamination from the balls. After prolonged milling the contamination due to wear of the balls was dominant in all the products. An explanation for the observed impact of grain size on the source and the degree of contamination was proposed.

Deposition of IRMOF-8 thin films by atomic layer deposition was studied at 260–320 C. Zinc acetate and 2,6-naphthalenedicarboxylic acid were used as the precursors. The as-deposited amorphous films were crystallized in 70% relative humidity at room temperature resulting in an unknown phase with a large unit cell. An autoclave with dimethylformamide as the solvent was used to recrystallize the films into IRMOF-8 as confirmed by grazing incidence x-ray diffraction. The films were further characterized by high temperature x-ray diffraction (HTXRD), field emission scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), time-of-flight elastic recoil detection analysis (TOF-ERDA), nanoindentation, and energy-dispersive x-ray spectroscopy. HTXRD measurements revealed similar behavior to bulk IRMOF-8. According to TOFERDA and FTIR, composition of the films was similar to IRMOF-8. Through-porosity was confirmed by loading the films with palladium using Pd(thd)2 (thd ¼ 2,2,6,6-tetramethyl-3, 5-heptanedionato) as the precursor. peerReviewed

The purpose of this paper is to analyze surface properties of AlGaN thin film produced using thermionic vacuum arc technique. Thermionic vacuum arc is an alternative deposition technique for GaN thin films that produces in a very short production time for GaN-based solid-state applications. XRD results showed that AlGaN thin film with cubic crystal structure on a amorphous glass was grown. Conductivity type of AlGaN thin film is determined as p-type by hot-probe method which is a very simple method. The surface morphology was analyzed and discussed using field emission scanning electron microscopy (FESEM) and atomic force microscopy. The contact angles in four different testing liquid and surface free energy of the AlGaN thin film were investigated by optical tensiometer. © 2015 Elsevier B.V.

In the present work, we synthesized and systematically characterized two novel graphene-based nanomaterials, a chemically reduced graphene oxide (GO) sponge and a microwave-exfoliated GO. Textural properties were determined by N2 adsorption/desorption at 77 K, while additional characterization techniques were employed, such as Micro-Raman Spectroscopy, Field-Emission Scanning Electron Microscopy and High-Resolution Transmission Electron Microscopy, to elucidate further the structural and morphological features. Both nanomaterials were additionally evaluated for their H2 storage capacity and were critically compared to commercially available carbons (e.g. few-layer graphenes, carbon nanotubes) based on systematic H2 adsorption/desorption measurements at 77 K between 0 and 1 bar. Maximum H2 gravimetric capacities of ∼0.5 wt% and ∼0.7 wt% were recorded at 77 K and 1 bar for the reduced GO sponge and the microwave-exfoliated GO, respectively. © 2015 Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. 40 6844 6852 6844-6852

In this contribution, we present a simple electrochemical approach to obtain large-area free-standing TiO2 nanotube membranes, via a three-step anodic oxidation of pure Ti sheets in fluoride-containing ethylene glycol. The highly ordered vertically oriented TiO2 nanotubes were characterized by Field Emission Scanning Electron Microscopy (FE-SEM) and Glancing Angle X-Ray Diffraction (GA-XRD) analysis. In particular, we report some details related to the synthetic procedure by SEM images of the fundamental steps, evidencing the development of the morphology of the catalytic surface. The study was focused on the ability to control the nanotube morphology, length, pore size, wall thickness and packing degree, by varying some parameters during the synthesis (such as voltage, electrolyte, pH, time of anodization, water concentration, etc.). The 1D nanostructured films (well-ordered vertically aligned TiO2 nanotubes) can be used as electrodic materials for solar devices (dye-sensitized or photo-electrochemical solar cells). Results showed that smooth surface and high aspect ratio TiO2 nanotube arrays were fabricated, which may have wide applications in the development of micro-confined reactors for a sustainable production of energy.

A facile surfactant free laser ablation mediated synthesis (LAMS) of gold-graphene composite is reported here. The material was characterized using transmission electron microscopy, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, powdered X-ray diffraction, Raman spectroscopy, Zeta potential measurements and UV-Visible spectroscopic techniques. The as-synthesized gold-graphene composite was effectively utilized as catalyst for decolorization of 4 important textile and laser dyes. The integration of gold nanoparticles (AuNPs) with high surface area graphene has enhanced the catalytic activity of AuNPs. This enhanced activity is attributed to the synergistic interplay of pristine gold's electronic relay and ?-? stacking of graphene with the dyes. This is evident when the Rhodamine B (RB) reduction rate of the composite is nearly twice faster than that of commercial citrate capped AuNPs of similar size. In case of Methylene blue (MB) the rate of reduction is 17,000 times faster than uncatalyzed reaction. This synthetic method opens door to laser ablation based fabrication of metal catalysts on graphene for improved performance without the aid of linkers and surfactants.� 2014 Elsevier B.V. All rights reserved.

Chitosan films containing mesoporous SBA-15 supported silver nanoparticles (AgNPs) were prepared to be applied as a potential wound dressing material. First SBA-15-silver nanoparticle (SBA-15-Ag) composite materials were prepared by a controlled annealing process without the use of organic solvents and reagents. The SBA-15-AgNPs were characterized in detail by X-ray powder diffraction, field emission scanning electron microscopy and transmission electron microscopy which evidenced the presence of uniformly distributed silver nanostructures inside the silicate pores. UV-vis spectra of the sample showed a band at 430 nm characteristic of the surface plasmon resonance of silver nanoparticles with a diameter below 10 nm and X-ray photoemission spectra confirmed the formation of metal-nanoparticles on the silicate template. Then SBA-15-Ag was used to prepare chitosan films which were characterized in detail. In particular, they showed good hydration properties, water vapor transmission rate and mechanical properties. After hydration films exhibited good antimicrobial activity against both Gram-negative (Pseudomonas aeruginosa) and Gram-positive (Staphylococcus epidermidis and S. aureus) bacteria. This journal is © the Partner Organisations 2014.

The correlation between structural and electronic order–disorder effects in understanding the optical properties of flower-like ZnO nanocrystals synthesized by the microwave-assisted hydrothermal method at low temperatures and short times is discussed. Theoretical simulations were performed at the density functional theory level to gain a better understanding of the experimental data from X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), electron paramagnetic resonance (EPR), ultraviolet-visible diffuse reflectance (UV-vis) spectroscopy and photoluminescence (PL) measurement studies at different temperatures. The decrease in band gap values is due to the presence of intermediate states above the conduction band. These discrete levels are formed by structural and electronic disorder of tetrahedral [ZnO4] clusters which enhance the electron–hole pair.

The present work describes the synthesis of cobalt oxide nanoparticle decorated hydrogen exfoliated graphene (Co 3O 4/HEG) by exfoliating graphite oxide in hydrogen atmosphere followed by chemical reduction of cobalt salt using sodium borohydride. The synthesized material has been characterized by X-ray diffractometry, thermogravimetric analysis, field emission scanning electron microscopy and transmission electron microscopy. A flexible field emitter has been fabricated by spin coating this material on carbon cloth. Electron emission characteristics of Co 3O 4/HEG have been investigated using an in-house fabricated setup and analyzed using Fowler-Nordheim equation. Turn-on and threshold fields of 1.12 and 1.35 V ?m -1, respectively have been observed for this material. Moreover, the present field emitter shows a reasonably good stability and repeatability. � 2012 Elsevier B.V. All rights reserved.

Novel polymer nanocomposites comprising of MnO2 nanotubes (MNTs), functionalized multiwalled carbon nanotubes (f-MWCNTs), and polyvinylidene fluoride (PVDF) were synthesized. Homogeneous distribution of f-MWCNTs and MNTs in PVDF matrix were confirmed by field emission scanning electron microscopy. Electrical conductivity measurements were performed on these polymer composites using four probe technique. The addition of 2 wt.% of MNTs (2 wt.%, f-MWCNTs) to PVDF matrix results in an increase in the electrical conductivity from 10-16S/m to 4.5 × 10-5S/m (3.2 × 10-1S/m). Electromagnetic interference shielding effectiveness (EMI SE) was measured with vector network analyzer using waveguide sample holder in X-band frequency range. EMI SE of approximately 20 dB has been obtained with the addition of 5 wt.% MNTs-1 wt.% f-MWCNTs to PVDF in comparison with EMI SE of approximately 18 dB for 7 wt.% of f-MWCNTs indicating the potential use of the present MNT/f-MWCNT/PVDF composite as low-cost EMI shielding materials in X-band region.

Controllable fabrication of spontaneously ordered and varied geometry fullerene C 60 based molecular architecture was achieved upon hierarchical self-assembly of the fullerene-N,N-dimethylaminoazobenzene acceptor-donor hybrid (DPNME). Simple preparation techniques, such as Langmuir-Blodgett (LB), solution-cast, and immersion at the liquid-air and solid-air interfaces, were used without templates as a function of DPNME concentration, media pH, time, and supporting substrate characteristics. The resulting structures depending upon the preparation methods were investigated with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), and molecular modeling, which revealed a delicate role of intermolecular donor-acceptor, ?-?, and van der Waals interactions between the electron deficient fullerene core and the N,N-dimethylaminoazobenzene electron donor under neutral conditions. Upon protonation, the electrostatics associated with the charged DPNME moiety and the dominant intermolecular fullerene-fullerene interactions guided the self-assembly process. Increased time scales led the molecular subunits to grow by maximizing the most favored orientations and yielded one-dimensional (1D) and two-dimensional (2D) structures in neutral and acidic conditions, respectively, which upon solvent evaporation formed the final multipods or stacked squares upon oriented attachment. For the protonated DPNME, 2D lamellar sheets formed from the bilayers gained cohesive energy, forming ultimately rectangular sheets. Interestingly, the Si(100) supported multilayer DPNME Langmuir films as a function of surface pressure and pH yielded a uniform and directional structure pattern in comparison with the geometry obtained from drop casting methods. This controllable structure architecture of the fullerene-azobenzene hybrid opens up a new alley in fullerene C 60 based self-assembly. � 2011 American Chemical Society.

The present work investigates the structural stability, dispersion, viscosity, and convective heat transfer properties of nanofluids based on multiwalled carbon nanotubes (MWCNT). Oxidative acid refluxation on MWCNT was examined for different time periods in order to achieve good dispersibility and thermal enhancement. Structural stability and efficient chemical functionalization was investigated by thermogravimetric analysis. Fourier transform infrared spectroscopy was conducted to ascertain the formation of chemical functional groups on covalently modified MWCNT. Raman band study on oxidized MWCNT was analyzed by Raman scattering measurements. Dispersion of functionalized MWCNT was studied by ultraviolet-visible spectroscopy. Field emission scanning electron microscopy and transmission electron microscopy have been performed to ascertain the structural durableness of nanomaterials in fluids. Viscosity and thermal conductivity behavior of DI water and ethylene glycol based MWCNT nanofluids were studied with varied volume fractions and temperature (30-70 �C). Further, steady-state forced convective heat transfer experiments have been conducted to estimate the cooling capabilities of above-mentioned nanofluids. � 2011 American Chemical Society.

Three nano-porous NiO samples with high specific surface area were prepared by a simple hydrothermal method under homogeneous precipitation conditions using CTAB as a template and urea as the hydrolysis controlling agent. This study was done to determine the effect of different anions (acetate, nitrate and chloride) present in the precursor salts on the morphology and pseudocapacitance behavior of NiO. The samples were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Brunauer-Emmet-Teller (BET) isotherm and field emission scanning electron microscopy (FESEM). The final NiO samples showed different hierarchical surface morphologies and their effect on the electrochemical pseudocapacitance behavior was carefully studied by cyclic voltammetry, galvanostatic charge-discharge cycles (chronopotentiometry) and impedance spectroscopic techniques. The specific capacitance of NiO sample synthesized by NO3 - ion intercalation showed higher surface area, intermediate porosity and a novel pine-cone morphology with nano-wire surface attachments. This sample exhibits the highest pseudocapacitance of 279 F g -1 at a scan rate of 5 mV s-1, calculated from the cyclic voltammetry measurements. The sample synthesized by Cl- intercalation shows a nano-flower morphology with lower surface area, porosity and pseudocapacitance behaviour. The NiO sample prepared in the presence of CH 3COO- ions showed a honeycomb type surface morphology with an intermediate pseudocapacitance value but higher reversibility. The galvanostatic charge-discharge and impedance spectroscopic measurements on these NiO electrodes were consistent with CV results. The Coulombic efficiency of all the three NiO samples was found to be high (?85 to ?99%) after 100 galvanostatic charge-discharge cycles. This study shows that the surface morphology and porosity of NiO are strongly influenced by the anions in the precursor salts, and in turn affect significantly the pseudocapacitance behavior and the power performance of NiO powders. � 2011 The Royal Society of Chemistry.

A hybrid nanostructure consisting of 1D carbon nanotubes and 2D graphene was successfully synthesized. Nanofluids were made by dispersing the hybrid nanostructure in deionized (DI) water and ethylene glycol (EG) separately, without any surfactant. Later the thermal conductivity and heat transfer coefficient of the nanofluids were experimentally measured. Meanwhile, multiwalled carbon nanotubes (MWNT) were prepared by catalytic chemical vapor deposition (CCVD), and hydrogen exfoliated graphene (HEG) was synthesized by exfoliating graphite oxide in a hydrogen atmosphere. The hybrid nanostructure (f-MWNT+f-HEG) of functionalized MWNT (f-MWNT) and functionalized HEG (f-HEG) was prepared by a post mixing technique, and the sample was characterized by powder X-ray diffraction, Raman spectroscopy, field emission scanning electron microscopy and transmission electron microscopy. Thermal conductivity of the nanofluids was measured for different volume fractions of f-MWNT+f-HEG at different temperatures. The hybrid nanostructure dispersed in the DI water based nanofluid shows a thermal conductivity enhancement of 20% for a volume fraction of 0.05%. Similarly, for a Reynolds number of 15500, the enhancement of the heat transfer coefficient is about 289% for a 0.01% volume fraction of f-MWNT+f-HEG. � 2011 The Royal Society of Chemistry.

Un microscope ionique a champ fonctionnant par pompage ionique sous ultravide a ete realise. La temperature de l'echantillon peut atteindre 21 °K et l'image est obtenue par conversion des ions en electrons puis multiplication de ceux-ci par une galette de microcanaux.