• Issue front cover thumbnail

      Volume 30, Issue 3

      June 2007,   pages  197-299

    • Bulk magnetic properties of CdFe2O4 in nano-regime

      Rucha Desai R V Mehta R V Upadhyay Amita Gupta A Praneet K V Rao

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      Cadmium ferrite particles have been synthesized using co-precipitation technique followed by a low temperature (600°C) annealing in a time scale much shorter than reported in literature. Incorporation of sodium chloride during annealing helps to form a single phase spinel structure with a final particle size of around 50 nm. Even at such a short length scale we observe the overall magnetic properties to be similar to those of the bulk. The observed magnetic properties can be explained on the basis of an anti-ferromagnetic core with a shell containing ‘ferromagnetic-like’, but canted spin structure.

    • A comparative study of proton transport properties of zirconium phosphate and its metal exchanged phases

      Rakesh Thakkar Heemanshu Patel Uma Chudasama

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      A new phase of amorphous zirconium phosphate (ZrP), an inorganic ion exchanger of the class of tetravalent metal acid (TMA) salt, is synthesized by sol–gel method. The protons present in the structural hydroxyl groups indicate good potential for TMA salts to exhibit solid state proton conduction. Cu2+ and Li+ are exchanged onto ZrP to yield CuZrP and LiZrP exchanged phases. All these materials were characterized for elemental analysis (ICP–AES), thermal analysis (TGA, DSC), X-ray analysis and FTIR spectroscopy. The transport properties of these materials were explored and compared by measuring conductance at different temperatures using an impedance analyser. It is observed that conductivity decreases with increasing temperature in all cases and mechanism of transportation is proposed to be Grotthuss type. Conductivity performance of ZrP, CuZrP and LiZrP is discussed based on conductivity data and activation energy.

    • Influence of microgravity on Ce-doped Bi12SiO20 crystal defect

      Y F Zhou J Y Xu Y Liu L D Chen Y Y Huang W X Huang

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      Space grown BSO crystal doped with Ce was characterized by means of X-ray fluorescence spectra, X-ray topography, dislocation density etc. Influence of microgravity on Ce-doped BSO crystal defect was studied by comparing space grown BSO crystal with ground grown one. These results show that compositional homogeneity and structural perfection of crystal can be improved under microgravity conditions.

    • Thermal and IR studies on copper doped polyvinyl alcohol

      Ch Linga Raju J L Rao B C V Reddy K Veera Brahmam

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      5 mol% PVA : 𝑥 mol% Cu2+ polymer films were prepared by casting process. Thermal transitions and thermal degradation of samples with respect to copper concentration were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA), respectively. Increase in glass transition temperature as a function of copper concentration shows a strong branching and steric effects in copper doped PVA complexes. Thermal degradation of films to an extent of 4–5% was found with an increase in copper content. FTIR spectrum of PVA doped Cu2+ ions indicate the presence of O–H, C–H, C=C and C–O groups.

    • Effect of a new condensation product on electrodeposition of zinc from a non-cyanide bath

      Ganesha Achary H P Sachin Y Arthoba Naik T V Venkatesha

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      Zinc electrodeposition from sulphate chloride bath was carried out in presence of condensation product formed between chitosan and veratraldehyde. The bath constituents and operating parameters such as pH, temperature and current density were optimized through Hull cell experiments. Current efficiency and throwing power were measured. Polarization study revealed high shift of potential towards negative direction in the presence of addition agents. Corrosion resistance test revealed good protection of base metal by zinc coating obtained from developed electrolyte. SEM photomicrographs showed fine-grained deposit in the presence of condensation product. The IR spectrum of the deposit showed inclusion of the condensation product during electroplating. The consumption of brightener in the lab scale was 5 mLL-1 for 1000 amp-h.

    • Synthesis of CaTiO3 from calcium titanyl oxalate hexahydrate (CTO) as precursor employing microwave heating technique

      B M Patil R S Srinivasa S R Dharwadkar

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      Calcium titanate, CaTiO3, an important microwave dielectric material and one of major phases in synroc (synthetic rock), a titanate ceramic with potential application for fixation of high level nuclear waste was synthesized from calcium titanyl oxalate [CaTiO (C2O4)2.6H2O] (CTO) by employing microwave heating technique. CTO heated in microwave heating system in air at 500°C for 1 h gave a perovskite, CaTiO3. The product obtained by heating of CTO in the same system at 700°C for the same duration was however, much more crystalline. CaTiO3 obtained by the present method was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET surface area measurement.

    • Titania doped triaxial porcelain: Enhancement of strength by controlled heat treatment

      Sunipa Bhattacharyya Swapan Kumar Das Kausik Dana Nirendra Krishna Mitra

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      Titania doped vitrified triaxial porcelain samples were subjected to controlled heat treatment at different temperatures of 600, 800 and 1000°C with a specific heating schedule. The results revealed that flexural strength of 800°C heat treated sample was significantly enhanced to 60 MPa from its original value of 40 MPa. XRD pattern revealed the formation of mullite in the system both before and after heat treatment and the differences in their growth was ascertained through SEM analysis. The present heat treatment process may be useful to produce high strength porcelain body from a common triaxial system.

    • Instrumental characterization of clay by XRF, XRD and FTIR

      Preeti Sagar Nayak B K Singh

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      Instrumental characterizations of the clay were performed by different techniques such as XRF, XRD and FTIR. XRF shows the chemical compositions of the clay where Al-oxide and silica oxide are present in major quantity whereas XRD confirms the presence of these minerals in clay. FTIR studies show the presence of quartz, alumina, haematite and different mineral matters.

    • Magnesium oxychloride cement concrete

      A K Misra Renu Mathur

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      The scope of magnesium oxychloride (MOC) cement in concrete works has been evaluated. MOC cement concrete compositions of varying strengths having good placing and finishing characteristics were prepared and investigated for their compressive and flexural strengths, 𝐸-values, abrasion resistance etc. The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ratio of compressive to flexural strength varies between 6 and 8. The elastic moduli of the compositions studied are found to be 23–85 GPa and the abrasion losses between 0.11 and 0.20%. While alternate heating–cooling cycles have no adverse effect on MOC concrete, it can be made durable against freezing–thawing and the excessive exposure to water and salt attack by replacing 10% magnesium chloride solution by magnesium sulphate solution of the same concentration.

    • Structural and optical properties of ZnO films grown on silicon and their applications in MOS devices in conjunction with ZrO2 as a gate dielectric

      S K Nandi S Chakraborty M K Bera C K Maiti

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      Photoluminescence (PL) properties of undoped ZnO thin films grown by rf magnetron sputtering on silicon substrates have been investigated. ZnO/Si substrates are characterized by Rutherford backscattering (RBS), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). ZrO2 thin films have been deposited on ZnO using microwave plasma enhanced chemical vapour deposition at a low temperature (150°C). Using metal insulator semiconductor (MIS) capacitor structures, the reliability and the leakage current characteristics of ZrO2 films have been studied both at room and high temperatures. Schottky conduction mechanism is found to dominate the current conduction at a high temperature. Good electrical and reliability properties suggest the suitability of deposited ZrO2 thin films as an alternative as gate dielectric on ZnO/𝑛-Si heterostructure for future device applications.

    • Theoretical analysis of effect of temperature on threshold parameters and field intensity in GaN material based heterostructure

      S A Gaikwad E P Samuel D S Patil D K Gautam

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      Temperature dependent analysis to achieve better performance by reducing threshold current requirements and field intensity has been carried out for GaN/AlGaN heterostructure lasers. The mirror loss in the GaN cavity has been obtained as a function of temperature and cavity length. The quantum efficiency has been deduced for different values of cavity length. Dependence of recombination rate on band gap and temperature has been investigated. Threshold current density has been deduced for GaN lasers and effect of temperature on it has been investigated. The near field intensity analysis has been carried out at different temperatures for 10% aluminum mole fraction in GaN/AlGaN heterostructure lasers. Furthermore, the effective index and FWHM of near field has been investigated as a function of temperature. It has been deduced from our analysis that temperature has a dominant effect on the threshold conditions and near field intensity in the wide band gap GaN based lasers.

    • Nanocrystalline TiO2 by three different synthetic approaches: A comparison

      T V Anuradha S Ranganathan

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      A comparison of the efficiency of three different synthetic routes viz. sol–gel method involving templating, mechanochemical synthesis and combustion synthesis for the production of nanostructured TiO2, is reported. In the sol–gel method, nanocrystalline TiO2 is produced when titanium tetraisopropoxide is templated onto dodecylamine which forms the liquid crystalline hexagonal structure and the template is then extracted using 1 : 1 solution of ethanol–hydrochloric acid mixture. Mechanochemical synthesis of nanocrystalline TiO2 involved mechanical milling of stoichiometric amounts of titanium and cupric oxide in a planetary ball mill using stainless steel vial with wear resistant stainless steel balls. Nanocrystalline TiO2 is produced by the combustion reaction involving titanyl nitrate and fuels like glycine and citric acid. Nanostructured TiO2 with an average particle size of ∼ 14 nm is produced by the sol–gel method whereas the mechanochemical reaction between titanium and cupric oxide resulted in the formation of nanocrystalline TiO2 with an average particle size of ∼ 20 nm after 12 h of milling. On the other hand, combustion synthesis resulted in the formation of nanocrystalline TiO2 with an average particle size of less than ∼ 50 nm. The microstructures of nanocrystalline TiO2 produced by the above three methods are analysed.

    • Nanowires: properties, applications and synthesis via porous anodic aluminium oxide template

      Jaya Sarkar Gobinda Gopal Khan A Basumallick

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      Quasi one-dimensional nanowires possess unique electrical, electronic, thermoelectrical, optical, magnetic and chemical properties, which are different from that of their parent counterpart. The physical properties of nanowires are influenced by the morphology of the nanowires, diameter dependent band gap, carrier density of states etc. Nanowires hold lot of promises for different applications. Basic electronic devices like junction diodes, transistors, FETs and logic gates can be fabricated by using semiconductor and superlattice nanowires. Thermoelectric cooling system can be fabricated by using metallic nanowires. Semiconductor nanowire junctions can be used for different opto-electronic applications. Moreover, periodic arrays of magnetic nanowires hold high potential for recording media application. Nanowires are also potential candidates for sensor and bio-medical applications.

      In the present article, the physical and chemical properties of nanowires along with their probable applications in different fields have been reviewed in detail. The review also includes highlights of the synthesis of nanowires via porous anodic aluminium oxide template since the technique is simple, cost-effective and a low temperature technique.

    • Zinc nanoparticles in solution by laser ablation technique

      S C Singh R Gopal

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      Colloidal zinc metallic nanoparticles are synthesized using pulsed laser ablation of metal plate in an aqueous solution of suitable surfactant to prevent aggregation. UV-visible absorption, TEM, small angle X-ray diffraction and wide-angle X-ray diffraction are used for the characterization of colloidal zinc metallic nanoparticles. Colloidal nanoparticles are found highly stable for a long time.

    • Raman study on single-walled carbon nanotubes with different laser excitation energies

      S S Islam Khurshed Ahmad Shah H S Mavi A K Shaukla S Rath Harsh

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      The industrial use of carbon nanotubes is increasing day by day; therefore, it is very important to identify the nature of carbon nanotubes in a bundle. In this study, we have used the Raman spectroscopic analysis on vertically aligned single-walled carbon nanotubes (SWCNTs) grown by the chemical vapour deposition (CVD) technique. The grown sample is excited with two laser excitation wavelengths, 633 nm from He–Ne laser and 514.5 nm from Ar+ laser. Raman spectrum in the backscattering geometry provides the characteristic spectra of SWCNTs with its radial breathing mode (RBM), defect-induced disorder mode (D band), and highenergy modes (G and M bands). The Raman signal positions of the spectra in RBM, G and M bands confirm the grown sample to be of semiconducting type in nature.

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