• Volume 34, Issue 3

June 2011,   pages  417-594

• Gold nanoparticle-coated biomaterial as SERS micro-probes

We report for the first time, on the utility of plant-based biomaterial as enhanced-Raman scattering probes. The bio-substrate used in this study are commonly found in plant extracts, and are cost-effective, mechanically robust, flexible and easily transportable. The probe was fabricated by coating the plant extract with gold nanoparticles and characterized. By employing a ‘single-touch contact’ method, we reveal the ability of these probes to detect routinely used Raman markers such as 2-napthalenethiol and rhodamine B, at nano-molar concentrations, in dry and liquid forms, respectively. Reproducibility of the signals with variation &lt;5%, and the ability to detect biomolecules are demonstrated herein. We envision these bio-probes as potential candidates for enhanced Raman sensing in chemical, environmental, and archaeological applications. By further engineering the shape, morphology, and surface chemistry of these micro-probes, we foresee their utility as miniaturized, natural SERS substrates.

• Effect of process parameters on growth rate and diameter of nano-porous alumina templates

Anodic aluminium oxide (AAO) template with hexagonal shaped nano-pores with high aspect ratio was fabricated by two-step anodization processes from high purity aluminium foil. It was observed that pore dimensions were affected by anodizing voltage, electrolyte temperature and the duration of anodization time. The vertical growth rate of the pores (10–250 nm/min) was found to vary exponentially with anodizing voltage; however, it exhibits linear increment with the electrolyte temperature. The measured pore diameter (50–130 nm) shows a linear variation with anodizing voltage. The bottom barrier oxide layer was etched out by pore widening treatment to obtain through holes.

• Synthesis and characterization of pyrochlore-type yttrium titanate nanoparticles by modified sol–gel method

Pyrochlore-type yttrium titanate (Y2Ti2O7) nanoparticles were successfully synthesized by a simple soft-chemistry technique viz. citric acid sol–gel method (CAM). The preparation process was monitored by X-ray diffraction, thermogravimetric–differential thermal analysis and Fourier transform–infrared experiments and the microstructures and average size of as-prepared products were characterized by transmission electron microscopy and high resolution transmission electron microscopy images. It was found that compared with traditional solid state reaction (SSR), Y2Ti2O7 nanopowders were synthesized at a relatively low temperature (750°C) for shortened reaction time. Detailed analysis showed that the as-prepared Y2Ti2O7 with good dispersibility and narrow size distribution were quasi-spherical; the average size was about 20–30 nm, also, the obtained products had higher BET surface area (50 m2/g). These properties are very helpful for a photocatalyst to achieve excellent activity and may result in better behaviour in hydrogen storage.

• Formation of nanoscale tungsten oxide structures and colouration characteristics

In this work, pH dependent evolution of tungsten oxide (WO3) nanostructures is being reported along with physical characteristics. The synthesis was carried out via an inexpensive solvothermal cum chemical reduction route, with sodium tungstate (Na2WO4) and cetyl trimethyl ammonium bromide (C19H42NBr) as main reactants. The X-ray diffraction, together with transmission electron microscopic studies have revealed formation of regular polyhedral nanocrystalline structures and fractals as one goes from higher pH (= 5.5) to lower pH (= 2) values. The average crystallite size, as calculated throughWilliamson–Hall plots, was varied within 2.8–6.8 nm for different pH samples. Fourier transform infrared spectroscopy reveals in-plane bending vibration 𝛿 (W–OH), observable at ∼1630 cm-1 and strong stretching 𝜈 (W–O–W) located at ∼814 cm-1. Raman spectroscopy has divulged WO3 Raman active optical phonon modes positioned at ∼717 and 805 cm-1. The thermochromic and photochromic properties of the nanoscale WO3 sample prepared at pH = 5.5, are also highlighted.

• Structural and electrical properties of Ta2O5 thin films prepared by photo-induced CVD

Tantalum oxide (Ta2O5) films and Al/Ta2O5/Si MOS capacitors were prepared at various powers by ultraviolet photo-inducing hot filament chemical vapour deposition (HFCVD). Effects of ultraviolet light powers on the structure and electrical properties of Ta2O5 thin films were studied using X-ray diffraction (XRD) and atomic forcemicroscopy (AFM). The dielectric constant, leakage current density and breakdown electric field of the samples were studied by the capacitance–voltage (C–V) and current–voltage (𝐼–𝑉) measurements of the Al/Ta2O5/Si MOS capacitors. Results show that the Ta2O5 thin films grown without inducement of UV light belong to amorphous phase, whereas the samples grown with inducement of UV-light belong to 𝛿-Ta2O5 phase. The dielectric constant and leakage current density of the Ta2O5 thin films increase with increasing powers of the UV- lamps. Effects of UVlamp powers on the structural and electrical properties were discussed.

• An investigation in InGaO3(ZnO)m pellets as cause of variability in thin film transistor characteristics

Indium–gallium–zinc oxide (IGZO) is a novel amorphous oxide semiconductor, which recently has received much attention for thin film transistors (TFTs) in flat panel displays. Published literature reports significant variations in the properties of thin films and TFTs prepared from IGZO even though the reported process conditions are similar.We demonstrate that these differences could arise from the method for preparation of targets from which the films are made. Accordingly, we also propose simple and appropriate conditions, specifically using much lower sintering temperatures and thus avoiding use of sealed Pt tubes for preparation of IGZO targets in composition range, InGaO3(ZnO)m, with 1 ≤ m ≤ 5. These target materials are suitable in physical vapour deposition processes such as pulsed laser deposition and sputtering. In developing the process for sintering, the phase analysis of the target pellets was carried out using X-ray diffraction (XRD). The chemical compositions of the phases are also confirmed with inductively coupled plasma optical emission spectrometry (ICP-OES) and energy dispersive X-ray (EDX) techniques. We also demonstrate successful deposition of amorphous IGZO thin films by pulse laser deposition using the targets prepared by the proposed sintering process. Finally, we demonstrate that unmonitored method of making pellets for films deposition is a cause of variability associated in published literature on IGZO TFTs.

• Dielectric relaxation in double perovskite oxide, Ho2CdTiO6

A new double perovskite oxide holmium cadmium titanate, Ho2CdTiO6 (HCT), prepared by solid state reaction technique is investigated by impedance spectroscopy in a temperature range 50–400°C and a frequency range 75 Hz–1 MHz. The crystal structure has been determined by powder X-ray diffraction which shows monoclinic phase at room temperature. An analysis of complex permittivity with frequency was carried out assuming a distribution of relaxation times as confirmed by Cole–Cole plot. The frequency dependent electrical data are analysed in the framework of conductivity and electric modulus formalisms. The frequencies corresponding to themaxima of the imaginary electric modulus at various temperatures are found to obey an Arrhenius law with an activation energy of 0.13 eV. The scaling behaviour of imaginary part of electric modulus suggests that the relaxation describes the same mechanism at various temperatures. Nyquist plots are drawn to identify an equivalent circuit and to know the bulk and interface contributions.

• Magnetic and microwave-absorbing properties of SrAl4Fe8O19 powders synthesized by coprecipitation and citriccombustion methods

Al-substituted 𝑀-type hexaferrite is a highly anisotropic ferromagnetic material. In the present study, the coprecipitation and the citric-combustion methods of synthesis for SrAl4Fe8O19 powders were explored and their microstructure, magnetic properties, and microwave absorptivity examined. X-ray diffraction (XRD), scanning electron microscopy (SEM), a vibrating sample magnetometer, and a vector network analyser were used to characterize the powders. The XRD analyses indicated that the pure SrAl4Fe8O19 powder was synthesized at 900°C and 1000°C for 3 h by coprecipitation, but only at 1000°C for the citric-combustion processes. The SEM analysis revealed that the coprecipitation process yielded a powder with a smaller particle size, near single-domain structure, uniform grain morphology, and smaller shape anisotropy than the citric-combustion process. The synthesis technique also significantly affected the magnetic properties and microwave-absorptivity. Conversely, calcining temperature and calcining time had less of an effect. The grain size was found to be a key factor affecting the property of the powder. The powders synthesized by coprecipitation method at calcining temperature of 900°C exhibited the largest magnetization, largest coercivity, and best microwave absorptivity.

• Synthesis, growth, optical, mechanical and electrical properties of 𝐿-lysine 𝐿-lysinium dichloride nitrate (𝐿-LLDN) single crystal

Semi-organic nonlinear optical material, 𝐿-lysine 𝐿-lysinium dichloride nitrate (2C6H15N2O$^{+}_{2}$.H+.NO$^{-}_{3}$.2Cl-) was synthesized at room temperature. Single crystals of 𝐿-LLDN were grown by slow cooling solution growth technique. The grown crystal was confirmed by powder X-ray diffraction analysis. The crystalline perfection of the grown single crystal was characterized by high-resolution X-ray diffraction (HRXRD) studies. The cut-off wavelength was determined by UV-vis transmission spectral analysis. The frequency doubling of the grown crystal was confirmed by powder second harmonic generation (SHG) measurement. The refractive index and birefringence of the crystal were determined using He–Ne laser source. Mechanical property of the crystal was determined by Vickers hardness tester. The frequency and temperature dependence of dielectric constant (𝜀r), dielectric loss (tan 𝛿) and a.c. conductivity (𝜎ac) were also measured.

• Preparation and characterization of solid-state sintered aluminum-doped zinc oxide with different alumina contents

Aluminum-doped zinc oxide (AZO) ceramics with 0−2.5 wt.% alumina (Al2O3) content were prepared using a solid-state reaction technique. It was found that AZO grains became finer in size and more irregular in shape than undoped ZnO as the Al2O3 content increased. Addition of Al2O3 dopant caused the formation of phase transformation stacking faults in ZnO grains. The second phase, ZnAl2O4 spinel, was observed at the grain boundaries and triple junctions, and inside the grains. In this study, a 3-inch circular Al2O3 (2 wt.%)-doped ZnO ceramic target sintered at 1500°C for 6 h has a relative density of 99.8% with a resistivity of 1.8 × 10-3 𝛺-cm. The AZO film exhibits optical transparency of 90.3% in the visible region and shows an electrical resistivity of 2.5 × 10-3 𝛺 -cm.

• Structural characteristics of titanium coating on copper substrates

The growth characteristics of titanium films deposited on glass, silicon (100) and oxygen free high purity copper substrate using magnetron sputtering have been investigated using X-ray diffraction, electron microscopy and scratch indentation techniques. The study of interface between the titanium film and the substrate was carried out to determine coating thickness, as well as intermixing of the elements at the interface. Studies revealed that the interface is free from voids and intermixing of the film and the substrate. Microstructural and diffraction analysis showed that the Ti coating was polycrystalline and exhibited columnar growth. The Ti crystallite size varied between 24 and 58 nmdepending on the substrate. The thickness of the films were typically about 4 𝜇m. Scratch test indicated that the films are adherent and the first critical load to failure was observed to be 4.5 N ± 2 N.

• Electrical properties and scaling behaviour of Sm3+ doped CaF2-bismuth borate glasses

The electrical properties for 20Bi2O3–60B2O3 (20−𝑥)–CaF2–𝑥Sm2O3 glasses (0 ≤ 𝑥 ≤ 2) were measured in the temperature range 297 K up to 629 K and in the frequency range 0.1–100 kHz. The d.c. and a.c. conductivity values and the dielectric loss (tan 𝛿) values were found to increase with increasing Sm2O3 content, whereas the activation energy of conductivities and the dielectric constant decreased. These results were attributed to the introduction of the rare earth ions; promote the formation of a high number of non-bridging oxygen atoms, which facilitate the mobility of charge carriers. The frequency dependence of the a.c. conductivity follows the power law 𝜎ac(𝜔) =A𝜔s . The frequency exponent (𝑠) values (0.64 &lt; 𝑠 &lt; 0.8) decrease with increasing temperature. This suggested that the a.c. conduction mechanism follows the correlated barrier hopping model (CBH). The dielectric constant (𝜀') and dielectric loss (tan 𝛿 values) were found to increase with increasing temperature and increasing Sm2O3 concentration in the glass. The a.c. conductivities as a function of frequency at different temperatures of a given glass superimposed onto a master curve (Roling scaling model). Furthermore, we have performed to scale the data as a function of composition. Two master curves were obtained, which suggested that there are differences in dominant charge carriers between glasses having Sm2O3 concentration ≥1 and glass of Sm2O3 concentration &lt;1.

• Electronic properties and charge density of Be𝑥Zn1−𝑥Te alloys

Electronic band structure calculations are performed for the Be𝑥Zn1−𝑥Te (0 ≤ 𝑥 ≤ 1 in steps of 0.2) alloys following the empirical pseudopotential method. The alloying effects are modelled through the modified virtual crystal approximation. Throughout the composition, valence band maximum resides at the 𝛤 point. The conduction band minimum, however, shifts from 𝛤 to 𝑋 point of symmetry when 𝑥 = 0.27. The observed crossover from direct to indirect bandgap is well in accordance with the experimental observations. Effect of alloying on the density of states is also discussed. The charge density distribution along a few major planes is computed and discussed. The electronic band structure related parameters like bandwidths, bandgaps and ionicity are reported and compared with experimental data wherever available. We also give estimates of cohesive energy and bulk modulus for the alloys.

• Post irradiated microstructural characterization of Zr–1Nb alloy by X-ray diffraction technique and positron annihilation spectroscopy

Zr–1Nb samples were irradiated with 116 MeV O5+ ions at different doses ranging from 5 × 1017 to 8 × 1018 O5+/m2. X-ray diffraction line profile analysis was performed to characterize the microstructural parameters of these samples. Average domain size, microstrain and dislocation density were estimated as a function of dose. An anomaly was observed in the values of these parameters at a dose of 2 × 1018 O5+/m2. Positron annihilation spectroscopy was used to determine the existence and nature of vacancy clusters in the samples. Isochronal annealing was carried out for a sample to study the evolution of defect clusters.

• Numerical simulation for determination of limit strains of a cold rolled and solution treated Nimonic C-263 alloy sheet

Nimonic alloys are Ni-base superalloys used for several high temperature applications, notable among them are the components in space vehicles, rocket engines, submarines, nuclear reactors, chemical processing vessels and heat exchange tubing as they exhibit excellent mechanical strength and creep resistance at high temperatures. Hence, evaluation of their formability characteristics is of utmost importance to make them into several useful components. Limit strains or forming limit curve is one of the parameters that indicates the formability, especially the drawability of sheet metal for deep drawing applications. In this paper, the limit strains of Nimonic C-263 alloy is investigated and presented using an explicit finite element code LSDYNA 3D. The material properties and the material model are evaluated by conducting tensile tests. The limit strains obtained from the simulation are verified by the analytical equations developed using vertex theory. The results tally within ±10% error.

• Processing maps for Fe–24Ni–11Cr–3Ti–1Mo superalloy

Hot deformation characteristics of a Fe-base superalloy were studied at various temperatures from 1000–1200°C under strain rates from 0.001–1 s-1 using hot compression tests. Processing maps for hot working are developed on the basis of the variations of efficiency of power dissipation with temperature and strain rate and interpreted by a dynamic materials model. Hot deformation equation was given to characterize the dependence of peak stress on deformation temperature and strain rate. Hot deformation apparent activation energy of the Fe–24Ni–11Cr–1Mo–3Ti superalloy was determined to be about 499 kJ/mol. The processing maps obtained in a strain range of 0.1–0.7 were essentially similar, indicating that strain has no significant influence on it. The processing maps exhibited a clear domain with a maximum of about 40–48% at about 1150°C and 0.001 s-1.

• Preparation of ultrafine poly(sodium 4-styrenesulfonate) fibres via electrospinning

The ultrafine poly (sodium 4-styrenesulfonate) (NaPSS) fibres have been prepared for the first time by electrospinning. The spinning solutions (NaPSS aqueous solutions) in varied concentrations were studied for electrospinning into ultrafine fibres. The results indicated that the smooth fibre could be formed when the concentration of NaPSS was above 40 wt.%. The morphology of the fibres was shown by scanning electron microscope (SEM). The Fourier transform infrared spectroscopy (FTIR) indicated that the structure of NaPSS did not change after electrospinning.

• Effect of poly(ethylene glycol) surfactant on carbon-doped MoO3 nanocomposite materials and its photocatalytic activity

Carbon-doped MoO3 samples were prepared by impregnation method. The effect of addition of polyethylene glycol-400 (PEG-400) and carbon (0, 1, 2 and 3 wt. %) as substrates, were investigated systematically to get the desired phase of carbon-doped MoO3 material. The carbon used was prepared from the natural sources such as Acacia arabika plant wood. The resulting samples were calcined at 500°C. The effect of PEG-400 and carbon composite on the structure, particle size and morphology of MoO3 was investigated. The samples thus prepared gave better control of particle size and porosity. The prepared samples were characterized using XRD, SEM–EDS and FT–IR techniques. Photocatalytic activities of the samples were studied with degradation of methylene blue. The 3 wt.% carbon-doped MoO3 modified by PEG-400 (CMP3) sample showed enhanced photocatalytic activity in comparison with the undoped samples.

• Visible light photocatalytic properties of novel molybdenum treated carbon nanotube/titania composites

Two types of molybdenum–carbon nanotubes and molybdenum treated carbon nanotubes/titania composites were prepared using a sol–gel method. These composites were characterized comprehensively by the Brauer–Emett–Teller (BET) surface area, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. It was found that the photocatalytic degradation of a methylene blue solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, and the enhancement of molybdenum. The proposed redox mechanism of the photodegradation of methylene blue on Mo-CNT/TiO2 composites is suggested.

• Photocatalytic degradation of reactive black-5 dye using TiO2 impregnated ZSM-5

In the present study, photocatalytic degradation of reactive black-5 (RB-5) dye was investigated using supported TiO2 photocatalyst based adsorbent as a semiconductor photocatalyst in a batch reactor. The synthesized photocatalyst composition was developed using TiO2 as photoactive component and zeolite (ZSM-5) as the adsorbents. Attempts were also made to optimize the composition of the supported catalyst and to study the reliability of prepared catalyst. The optimum formulation of supported catalyst was found to be (TiO2: ZSM-5 = 0.15:1) which gave the highest efficiency with 98% degradation of 50 mg/L RB-5 solution in 90 min. Effect of different parameters such as initial concentration of dye solution, catalyst amount on the rate of photodegradation was also studied. The reduction in the chemical oxygen demand (COD, 88%) proves the mineralization of the RB-5 dye along with the colour removal. The supported TiO2 was found to be stable for repeated use.

• Combustion synthesis of Eu2+ and Dy3+ activated Sr3(VO4)2 phosphor for LEDs

Combustion synthesis and photoluminescence (PL) characterization of Sr3(VO4)2:Eu,Dy phosphors are presented in this paper. PL emission of Sr3(VO4)2:Eu phosphor shows green broad emission band centring at 511 nm and a red sharp band at 614 nm by excitation wavelength of 342 nm. The PL emission spectrum of Sr3(VO4)2:Dy phosphor exhibits an intense blue emission peak at 479 nm, yellow broad band centring at 573 nm and red band at 644 nm by the excitation wavelength of 426 nm in near visible blue region. The excitation wavelength of Eu (342 nm) and Dy (426 nm) activated Sr3(VO4)2 phosphor are well matched with the excitation of near UV excited solid state lighting and blue chip excitation of light emitting diodes, respectively. The effect of Eu2+ and Eu3+ ions concentration on the emission intensity of Sr3(VO4)2 was also investigated. The Sr3(VO4)2:Eu is a potential green and red emitting phosphor as well as Sr3(VO4)2:Dy is blue and yellow emitting phosphor for solid state lighting i.e. white LEDs. The XRD and SEM characteristics of Sr3(VO4)2 materials was also reported in this paper.

• Pitting corrosion protection of low nickel stainless steel by electropolymerized conducting polymer coating in 0.5 M NaCl solution

Conducting polymers of polyaniline (PANi) and poly(o-phenylenediamine) (PoPD) were electropolymerized by cyclic voltammetric technique on low nickel stainless steel (LN SS) in H2SO4 solution containing aniline and 𝑜-phenylenediamine monomers. The coatings were characterized by Fourier transform infrared spectroscopy, UV-visible and scanning electron microscopic techniques and the results are discussed. The corrosion protective properties of PANi and PoPD coatings on LN SS in 0.5 M NaCl were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopic (EIS) techniques. The potentiodynamic polarization and electrochemical impedance spectroscopic results indicate that the PoPD coating inhibits the corrosion of LN SS in 0.5 M NaCl solution more effectively than PANi.

• Inhibition effects of acetyl coumarines and thiazole derivatives on corrosion of zinc in acidic medium

The corrosion inhibition characteristics of acetyl coumarine (AC), bromo acetyl coumarine (BAC) and thiazole derivatives (BTMQ and BTCQ) on the corrosion of zinc in 0.1 M HCl solution were investigated by weight loss, potentiodynamic polarization and impedance techniques. The inhibition efficiency increased with increase in inhibitor concentration upto 5 × 10-4 M, then gave almost same inhibition efficiency. The polarizationmeasurements indicated the mixed nature of inhibitors. The adsorption of compounds obeyed Langmuir’s adsorption isotherm. The thermodynamic functions for adsorption processes were evaluated.

• Microwave-assisted synthesis of high-loading, highly dispersed Pt/carbon aerogel catalyst for direct methanol fuel cell

A Pt supported on carbon aerogel catalyst has been synthesized by the microwave-assisted polyol process. The Pt supported on carbon aerogel catalyst was characterized by high resolution transmission electron microscopy and X-ray diffraction. The results show a uniform dispersion of spherical Pt nanoparticles 2.5–3.0 nm in diameter. Cyclic voltammetry and chronoamperometry were used to evaluate the electrocatalytic activity of the Pt/carbon aerogel catalyst for methanol oxidation at room temperature. The Pt/carbon aerogel catalyst shows higher electrochemical catalytic activity and stability for methanol oxidation than a commercial Pt/C catalyst of the same Pt loading.

• Tribological characteristics of self-assembled nanometer film deposited on phosphorylated 3-aminopropyltriethoxysilane

Thin films deposited on the phosphonate 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM) were prepared on the hydroxylated silicon substrate by a self-assembling process from specially formulated solution. Chemical compositions of the films and chemical state of the elements were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies and nanotribological properties of the samples were analyzed by means of atomic force microscopy (AFM). As the results, the target film was obtained and reaction might have taken place between the thin films and the silicon substrate. It was also found that the thin films showed the lowest friction and adhesion followed by APTESSAM and phosphorylated APTES-SAM, whereas silicon substrate showed high friction and adhesion. Microscale scratch/wear studies clearly showed that thin films were much more scratch/wear-resistant than the other samples. The superior friction reduction and scratch/wear resistance of thin films may be attributed to low work of adhesion of nonpolar terminal groups and the strong bonding strength between the films and the substrate.

• In vitro study on biomineralization of biphasic calcium phosphate biocomposite crosslinked with hydrolysable tannins of Terminalia chebula

In this study, we report the preparation of a bone graft material, having cylindrical shape, containing biphasic calcium phosphate (BCP), gelatin (G), chitosan (C) and Terminalia chebula (TC) extract. TC extract was used as a crosslinker that gives stability to bone graft when it is placed in SBF. The graft was stable in the SBF solution for 21 days and FTIR, SEM, EDX and thermogravimetric studies revealed the ossification of the implant.

• # Bulletin of Materials Science

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December 2019

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019