• Volume 31, Issue 4

August 2008,   pages  585-711

• Studies on nanocrystalline zinc coating

Nano zinc coatings were deposited on mild steel by electrodeposition. The effect of additive on the morphology of crystal size on zinc deposit surface and corrosion properties were investigated. Corrosion tests were performed for dull zinc deposits and bright zinc deposits in aqueous NaCl solution (3.5 wt.%) using electrochemical measurements. The results showed that addition of additive in the deposition process of zinc significantly increased the corrosion resistance. The surface morphology of the zinc deposits was studied by scanning electron microscopy (SEM). The preferred orientation and average size of the zinc electrodeposited particles were obtained by X-ray diffraction analysis. The particles size was also characterized by TEM analysis.

• Preparation and characterization of Co9S8 nanocrystalline and nanorods

Hexagonal Co9S8 nanocrystal and nanorods were synthesized using cobalt chloride (CoCl2.6H2O), dimethyl sulfoxide (DMSO) and non-aqueous alcohol as the starting materials, and taking dimethyl sulfoxide as both sulfur source and strong infiltrator in nanorods preparation. The Co9S8 samples were characterized by X-ray diffraction (XRD), scanning tunneling microscope (SEM), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and laser Raman spectrometer. The results show that the as-prepared Co9S8 nanocrystal with a size of 6 nm take on weak paramagnetism at room temperature. The lengths and diameters of the nanorods were about 4 𝜇m and 200 nm, respectively. The reason for the relative lower synthesis temperature of nanorods was discussed and a ‘micro-autoclave reactor’ model was suggested as well.

• ZnO nanostructured microspheres and grown structures by thermal treatment

Synthesis of flower-shaped ZnO nanostructures composed of ZnO nanosticks was achieved by the solution process using zinc acetate dihydrate, sodium hydroxide and polyethylene glycol-20000 (PEG-20000) at 180°C for 4 h. The diameter of individual nanosticks was about 100 nm. Detailed structure characterizations demonstrate that the synthesized products are wurtzite hexagonal phase, grown along the [001] direction. The infrared (IR) spectrum shows the standard peak of zinc oxide at 571 cm-1. Raman scattering exhibits a sharp and strong 𝐸2 mode at 441 cm-1 which further confirms the good crystal and wurtzite hexagonal phase of the grown nanostructures.

• Synthesis of SrCrO4 nanostructures by onion inner-coat template and their optical properties

This paper describes a bio-template method of the squama inner coat of onion for preparing the SrCrO4 nanostructures including nanospheres, nanorods and dumbbell-shaped superstructure. The method is able to make SrCrO4 nanoparticles with average diameters in the range of 90–170 nm, SrCrO4 nanorods with length in the range 0.70–2 𝜇m, width in the range of 80–180 nm, and SrCrO4 dumbbell-shaped superstructure with length in the range 10–14 𝜇m. The dumbbell-shaped superstructures are assembled by many SrCrO4 nanowires with length in the range 10–14 𝜇m and width in the range 30–50 nm. The products were characterized by transmission electron microscope, powder X-ray diffraction, UV-Vis spectroscopy and luminescence spectrophotometer. A possible formation mechanism was also proposed. In the preparation, the SrCrO4 nanostructures were synthesized at room temperature without any surfactants. This new bio-template method will have potential applications in preparation of the nanoscale materials with different morphologies.

• Synthesis of single wall carbon nanotubes from a lamellar type aluminophosphate (AlPO4-L)

Single wall carbon nanotubes are synthesized from a lamellar type aluminophosphate, AlPO4-L. The lamellar aluminophosphate was synthesized from hexamethyleneimine template. The latter was calcined at argon atmosphere for 12 h at 600°C. The resulting carbonaceous material was treated with 1 N H2SO4 to remove the aluminophosphate skeleton. Characterization of the resulting carbon revealed to contain single walled nanotubes. These nanotubes are applicable to store more hydrogen.

• Synthesis and characterization of tin(IV) phenyl phosphonate in nano form

An inorgano–organic ion exchanger, Sn(IV) phenyl phosphonate, has been synthesized in amorphous form. Further, an attempt has been made to synthesize Sn(IV) phenyl phosphonate in the nano form. The materials have been characterized for elemental analysis (ICP–AES), thermal analysis (TGA), X-ray analysis and FTIR spectroscopy. Chemical resistivity of these materials has been accessed in acidic, basic and organic solvent media. Catalytic activity has been studied and compared by using esterification of ethylene glycol as a model reaction wherein glycoldiacetate has been prepared. The transport properties of these materials have been explored by measuring specific proton conduction at different temperatures using SOLARTRON DATASET impedance analyser over a frequency range 1 Hz–1 MHz. It has been observed that Sn(IV) phenyl phosphate in the nano form behaves as a better Bronsted catalyst and proton conductor as compared to the amorphous form.

• Influence of synthesis conditions on particle morphology of nanosized Cu/ZnO powder by polyol method

Cu/ZnO in nanosizes have been synthesized using ethylene glycol at various conditions. The effects of reaction temperature, extent of reduction, various precursors such as CuX$_{2}.n$H2O, ZnX$_{2}.n$H2O (X = Cl, NO$^{–}_{3}$, CH3CO$^{–}_{2}$), the addition of water and the removal of volatile compounds including water were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), and dynamic light scattering (DLS). Cu/ZnO powders with an average diameter of as low as 50 nm was obtained with a very low polydispersity in the absence of a protective polymer. Ethylene glycol oxidation products were also identified by Fourier transform infrared (FTIR) spectroscopy. The morphology of Cu/ZnO powders and the yield of powders are found to be strongly dependent on the synthesis conditions.

• Effects of pH and concentration on ability of Cl and NO$^{–}_{3}$ to intercalate into a hydrotalcite-like compound during its synthesis

In this study, we confirmed that the characteristics of anion intercalation into the interlayer of a hydrotalcite-like compound (HT) during synthesis are similar to those of the anion-exchange reaction of HTs as well as the reconstruction reaction of HTs from Mg–Al oxide. We demonstrated that

1. Cl, which has a higher charge density than NO$^{–}_{3}$, more easily reacted with Mg and Al species to form HT structure, resulting in greater intercalation of Cl into the HT interlayer; and

2. for HTs with lower Mg : Al molar ratios, OH, which has a higher charge density than Cl and NO$^{–}_{3}$, was more likely to interact with Mg and Al species to form HT structure, blocking the intercalation of Cl and NO$^{–}_{3}$.

Furthermore, we showed that high concentrations of Cl and NO$^{–}_{3}$ in solution regulated their intercalation into the HT interlayer. The high activity of Cl and NO$^{–}_{3}$ in solution would facilitate the anions’ reactions with Mg and Al species to form HTs, resulting in a high degree of anion intercalation into the interlayer of HTs.

• Synthesis and structural studies of Na2O–ZnO–ZnF2–B2O3 oxyfluoride glasses

This paper describes the synthesis and spectroscopic studies of the glass system, 20Na2O–(20–𝑥) ZnO–𝑥ZnF2–60B2O3 (𝑥 = 0, 5, 10, 15, 20), prepared by melt quenching method. The analyses of DSC and XRD did not show the crystallinity of the glass sample. 11B MAS–NMR shows the presence of sharp peak around –14 ppm. From the IR studies, the broadening of the peak around 1200–1400 and 800–1100 cm-1 shows the presence of mixed linkages like B–O–B, B–O–Zn in the network.

• Dielectrical and structural characterization of iron oxide added to hydroxyapatite

In this work we report preparation, structural and dielectric analyses of iron oxide added in hydroxyapatite bioceramic (Ca10(PO4)6(OH)2 – HAP). Hydroxyapatite is the main mineral constituent of teeth and bones with excellent biocompatibility with hard and muscle tissues. The samples were prepared through a calcination procedure associated with dry high-energy ball milling process with different iron concentrations (1, 2.5 and 5 wt%). The dielectric analyses were made measuring the sample impedance in the frequency range 1 kHz–10 MHz, at room temperature. The relative permittivity of the ceramics, at 10 MHz, are between 7.13 ± 0.07 (1 wt%) and 6.20 ± 0.11 (5 wt%) while e″ are between 0.0795 ± 0.008 (1 wt%) and 0.067 ± 0.012 (5 wt%). These characteristics were related to the sample microstructures studied by X-ray diffraction and SEM.

• Growth and study of mixed crystals of Ca–Cd iodate

Mixed crystals of calcium–cadmium iodate were grown by a simple gel technique using diffusion method. The optimum conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants etc. Crystals having different morphologies and habits were obtained. Prismatic, dendritic crystals of calcium–cadmium iodate and prismatic needle shaped, hopper crystals of mixed iodate were obtained. Some of them were transparent, some transluscent and a few others were opaque. The crystals were characterized using FT–IR, EDAX, XRD, TGA and DTA.

• Crystal growth and structural analysis of zirconium sulphoselenide single crystals

A series of zirconium sulphoselenide (ZrS𝑥Se3–𝑥, where 𝑥 = 0, 0.5, 1, 1.5, 2, 2.5, 3) single crystals have been grown by chemical vapour transport technique using iodine as a transporting agent. The optimum condition for the growth of these crystals is given. The stoichiometry of the grown crystals were confirmed on the basis of energy dispersive analysis by X-ray (EDAX) and the structural characterization was accomplished by X-ray diffraction (XRD) studies. The crystals are found to possess monoclinic structure. The lattice parameters, volume, particle size and X-ray density have been carried out for these crystals. The effect of sulphur proportion on the lattice parameter, unit cell volume and X-ray density in the series of ZrS𝑥Se3–𝑥 single crystals have been studied and found to decrease in all these parameters with rise in sulphur proportion. The grown crystals were examined under optical zoom microscope for their surface topography study. Hall effect measurements were carried out on grown crystals at room temperature. The negative value of Hall coefficient implies that these crystals are 𝑛-type in nature. The conductivity is found to decrease with increase of sulphur content in the ZrS𝑥Se3–𝑥 series. The electrical resistivity parallel to c-axis as well as perpendicular to 𝑐-axis have been carried out in the temperature range 303–423 K. The results obtained are discussed in detail.

• Microwave processing: A potential technique for preparing NiO–YSZ composite and Ni–YSZ cermet

In the present study, microwave energy (2.45 GHz) has been used to prepare nickel oxide–yttria stabilized zirconia (NiO–YSZ) composites of composition, 𝑚NiO–(1 – 𝑚) Zr0.9Y0.1O1.95 (𝑚 = 0.2, 0.3, 0.4, 0.5 and 0.6), from a precursor obtained by mixing NiO, Y2O3 and monoclinic ZrO2 in their stoichiometric ratio. The composites have been prepared by conventional processing also to compare the products with those of microwave processed products. During comparison, it was observed that NiO–YSZ composites of each composition obtained by microwave processing had cubic phase of YSZ while in the conventionally prepared composites of compositions, 𝑚 = 0.2 and 0.3, monoclinic, tetragonal and cubic phases of zirconia existed instead of its pure cubic phase. The composites were reduced to yield Ni–YSZ.

• Investigations on d.c. conductivity behaviour of milled carbon fibre reinforced epoxy graded composites

This paper reports the d.c. conductivity behaviour of milled carbon fibre reinforced polysulphide modified epoxy gradient composites. Milled carbon fibre reinforced composites having 3 vol. % of milled carbon fibre and poly sulphide modified epoxy resin have been developed. D.C. conductivity measurements are conducted on the graded composites by using an Electrometer in the temperature range from 26°C to 150°C. D.C. conductivity increases with the increase of distance in the direction of centrifugal force, which shows the formation of graded structure with the composites. D.C. conductivity increases on increase of milled carbon fibre content from 0.45 to 1.66 vol.%. At 50°C, d.c. conductivity values were 1.85 × 10-11, 1.08 × 10-11 and 2.16 × 10-12 for samples 1, 2 and 3, respectively. The activation energy values for different composite samples 1, 2 and 3 are 0.489, 0.565 and 0.654 eV, respectively which shows decrease in activation energy with increase of fibre content.

• Thermally stimulated luminescence studies in combustion synthesized polycrystalline aluminum oxide

Synthesis of materials by combustion technique results in homogeneous and fine crystalline product. Further, the technique became more popular since it not only saved time and energy but also was easy to process. Aluminum oxide phosphor was synthesized by using urea as fuel in combustion reaction. Photoluminescence (PL) and thermally stimulated luminescence (TSL) characteristics of 𝛾-irradiated aluminum oxide samples were studied. A broad PL emission with a peak at ∼ 465 nm and a pair of strong and sharp emissions with peaks at 679 and 695 nm were observed in 𝛾-rayed samples. The PL intensity was observed to increase with increase in 𝛾-ray dose. Two prominent and well resolved TSL glows with peaks at 210°C and 365°C were observed in all 𝛾-irradiated Al2O3 samples. The TSL intensity was also found to increase with increase in 𝛾-ray dose. The TSL glow curves indicated second order kinetics.

• Antireflection coatings on plastics deposited by plasma polymerization process

Antireflection coatings (ARCs) are deposited on the surfaces of optical elements like spectacle lenses to increase light transmission and improve their performance. In the ophthalmic industry, plastic lenses are rapidly displacing glass lenses due to several advantageous features. However, the deposition of ARCs on plastic lenses is a challenging task, because the plastic surface needs treatment for adhesion improvement and surface hardening before depositing the ARC. This surface treatment is usually done in a multi-stage process—exposure to energetic radiations, followed by deposition of a carbonyl hard coating by spin or dip coating processes, UV curing, etc. However, this treatment can also be done by plasma processes. Moreover, the plasma polymerization process allows deposition of optical films at room temperature, essential for plastics. The energetic ions in plasma processes provide similar effects as in ion assisted physical deposition processes to produce hard coatings, without requiring sophisticated ion sources. The plasma polymerization process is more economical than ion-assisted physical vapour deposition processes as regards equipment and source materials and is more cost-effective, enabling the surface treatment and deposition of the ARC in the same deposition system in a single run by varying the system parameters at each step. Since published results of the plasma polymerization processes developed abroad are rather sketchy and the techniques are mostly veiled in commercial secrecy, innovative and indigenous plasma-based techniques have been developed in this work for depositing the complete ARCs on plastic substrates.

• Influence of radio frequency power on structure and ionic conductivity of LiPON thin films

Lithium phosphorus oxynitride (LiPON) thin films as solid electrolytes were prepared by radio frequency magnetron sputtering of a Li3PO4 target in ambient nitrogen atmosphere. The influence of radio frequency (rf) power on the structure and the ionic conductivity of LiPON thin films has been investigated. The morphology, composition, structure and ionic conductivity of thin films were characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy and a.c. impedance measurement. It was found that ionic conductivity of LiPON thin films increases with N content in thin films. XPS measurements reveal that ionic conductivity also keeps relativity with the structure of thin films. Higher the 𝑁t/𝑁d ratio, higher will be the ionic conductivity of LiPON thin films. And both of them can be improved by increasing rf power from 1.5 W/cm2 to 5.5 W/cm2.

• Surface hardness behaviour of Ti–Al–Mo alloys

The microhardness characteristics of various micro-constituents formed in the Ti–Al–Mo alloys have been investigated. Four alloys having compositions, Ti–40Al–2Mo, Ti–42Al–2Mo, Ti–40Al–6Mo and Ti–42Al–6Mo, have been chosen for this purpose. All of these were heat treated at 1300°C and 1400°C for 1 h and water quenched. All the specimens after above heat treatments have displayed load independent Vickers hardness values (VHN) around 300 g of applied load. The average surface hardness characteristic of the alloys is largely found to be dictated by the phases that are present. The microstructural specific VHN values vary between 600 and 750. The indentation behaviour, however, is governed by the morphologies and length scales of microstructures. The most remarkable finding of the present study pertains to the formation of shear bands around the periphery of the indenter for a finer basket weave microstructure in the Ti–40Al–2Mo. The cluster of finely located slip steps was clearly seen. Such a report is lacking in literature in this class of alloys.

• Effect of surface morphology on atmospheric corrosion behaviour of Fe-based metallic glass, Fe67Co18Si14B1

The nature of atmospheric corrosion behaviour of an as-cast metallic glass, Fe67Co18Si1B14 ribbon, was evaluated. The wheel side surface of the ribbon was more corroded than the air side surface, due to the higher density of air pockets present. The phases present in atmospheric rust were analysed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) to be goethite, lepidocrocite, magnetite, cobalt oxide and cobalt hydroxide phases. Goethite and lepidocrocite were in amorphous form. The nature of rusting was understood by scanning electron microscopy (SEM). Nucleation of rust started at preferred locations on the surface and grew along the surface in certain directions.

• Inhibition of corrosion of mild steel in acid media by N′-benzylidene-3-(quinolin-4-ylthio)propanohydrazide

In the present investigation a new corrosion inhibitor, N′-(3,4-dihydroxybenzylidene)-3-{[8-(trifluoromethyl) quinolin-4-yl]thio}propanohydrazide(DHBTPH) was synthesized, characterized and tested as a corrosion inhibitor for mild steel in HCl (1 M, 2 M) and H2SO4 (0.5 M, 1 M) solutions using weight-loss method, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization methods. The corrosion inhibition efficiency measured by all the above three techniques were in good agreement with each other. The results showed that DHBTPH is a very good inhibitor for mild steel in acidic media. The inhibition efficiency in different acid media was found to be in the decreasing order 0.5 M H2SO4 &gt; 1 M HCl &gt; 1 M H2SO4 &gt; 2 M HCl. The inhibition efficiency increases with increasing inhibitor concentration and with increasing temperature. It acts as an anodic inhibitor. Thermodynamic and activation parameters are discussed. Adsorption of DHBTPH was found to follow the Langmuir’s adsorption isotherm. Chemisorption mechanism is proposed. The mild steel samples were also analysed by scanning electron microscopy (SEM).

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• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019