• Issue front cover thumbnail

      Volume 32, Issue 2

      April 2009,   pages  117-214

    • Microstructural characteristics and mechanical properties of magnetron sputtered nanocrystalline TiN films on glass substrate

      Vipin Chawla R Jayaganthan Ramesh Chandra

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      Nanocrystalline TiN thin films were deposited on glass substrate by d.c. magnetron sputtering. The microstructural characteristics of the thin films were characterized by XRD, FE-SEM and AFM. XRD analysis of the thin films, with increasing thickness, showed the (200) preferred orientation up to 1.26 𝜇m thickness and then it transformed into (220) and (200) peaks with further increase in thickness up to 2.83 𝜇m. The variation in preferred orientation was due to the competition between surface energy and strain energy during film growth. The deposited films were found to be very dense nanocrystalline film with less porosity as evident from their FE-SEM and AFM images. The surface roughness of the TiN films has increased slightly with the film thickness as observed from its AFM images. The mechanical properties of TiN films such as hardness and modulus of elasticity (𝐸) were investigated by nanoindentation technique. The hardness of TiN thin film was found to be thickness dependent. The highest hardness value (24 GPa) was observed for the TiN thin films with less positive micro strain.

    • Structural and optical properties of chemically deposited Cd(S–Se) : CdCl2, Sm films

      R S Singh S Bhushan

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      Results of SEM and XRD studies, optical absorption and photoluminescence (PL) emission spectra and photoconductivity (PC), rise and decay studies are reported for Cd(S–Se) : CdCl2, Sm films prepared by chemical deposition method on glass substrates at 60°C in a water bath. SEM studies show ball-type structures along with voids which are related to layered growth. XRD studies show prominent diffraction lines of CdS and CdSe along with some peaks of CdCl2 and impurity Sm. The values of strain (𝜀), grain size (𝐷) and dislocation density (𝛿) are evaluated from XRD studies and the nature of crystallinity of the films are discussed. Optical absorption spectra also show the presence of Sm in the lattice. From the results of optical absorption spectra, the band gaps are determined. PL emission spectra of Cd(S–Se) consist of two peaks which are related to the edge emission of CdS and CdSe involving excitons. In Sm-doped emissions corresponding to transitions ${}^{4}G_{5/2}$ to ${}^{6}H_{5/2}$, ${}^{6}H_{7/2}$ and ${}^{6}H_{9/2}$ are observed. Sufficiently high photo current (𝐼pc) to dark current (𝐼dc) ratios with a maximum value of the order of 106 are also obtained in some special cases. This high photosensitization is related to increase in mobility and life time of carriers due to photo excitation.

    • Carbon nanotube synthesis from propane decomposition on a pre-treated Ni overlayer

      J Sengupta S K Panda C Jacob

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      Growth of carbon nanotubes (CNTs) was performed by atmospheric pressure chemical vapour deposition (APCVD) of propane on Si(111) with a pre-treated Ni overlayer acting as a catalyst. Prior to the growth of CNTs, a thin film of Ni was deposited on Si(111) substrate by evaporation and heat treated at 900°C. The growth of nanotubes was carried out at 850°C using propane as a source of carbon. Distribution of the catalyst particles over the Si substrate was analysed before and after heat treatment by atomic force microscopy (AFM). The X-ray diffraction (XRD) pattern of the grown material revealed that they are graphitic in nature. Field emission scanning electron microscopy (FESEM) was used to investigate the growth process and it was found that a catalytic particle was always situated at the tip of the tube thus implying a tip growth mechanism. Evidence for the presence of radial breathing mode from multi-wall nanotubes (MWNTs) in the grown sample was obtained from micro-Raman analysis. Finally, high-resolution transmission electron microscopic (HRTEM) analysis confirmed that the graphene layers of the CNTs are well ordered with typical 0.34 nm spacing.

    • Low temperature synthesis of nanosized Mn1–𝑥Zn𝑥Fe2O4 ferrites and their characterizations

      Rajesh Iyer Rucha Desai R V Upadhyay

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      Nanosized Mn1–𝑥Zn𝑥Fe2O4 (𝑥 = 0, 0.1, 0.3, 0.5, 0.6, 0.7, 0.9) mixed ferrite samples of particle size < 12 nm were prepared using the co-precipitation technique by doping the Zn2+ ion impurities. Autoclave was employed to maintain constant temperature of 80°C and a constant pressure. The X-ray analysis and the IR spectrum analysis were carried out to confirm the spinel phase formation as well as to ascertain the cation distribution in the ferrite samples. This clearly points to the fact that the Zn2+ ion’s presence is not restricted to A-site alone for some of the Mn–Zn ferrite series. The real part of a.c. susceptibility measurements clearly indicated the superparamagnetic behaviour of the ferrite samples. There is a systematic decrease in the particle size, Curie temperature and magnetization with the increase in the Zn2+ ion doping, measured using magneto thermal gravimetric analysis (MTGA) and vibrating sample magnetometer (VSM), respectively. The lattice constant is found to be constantly decreasing till 𝑥 = 0.6 and beyond this an unusual slight increase in the lattice constant is found.

    • Synthesis and characterization of nano-sized Ba𝑥Sr1–𝑥SO4 (0 ≤ 𝑥 ≤ 1) solid solution by a simple surfactant-free aqueous solution route

      Yu-Feng Li Jia-Hu Ouyang Yu Zhou Xue-Song Liang Ji-Yong Zhong

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      A facile aqueous solution route has been employed to synthesize Ba𝑥Sr1–𝑥SO4 (0 4 𝑥 ≤ 1) solid solution nanocrystals at room temperature without using any surfactants or templates. The as-synthesized products were characterized by means of X-ray diffraction (XRD), X-ray fluorescence spectrometer (XRF), scanning electron microscopy (SEM), and differential scanning calorimetry–thermogravimetry (DSC–TG). The Ba𝑥Sr1–𝑥SO4 solid solution nanocrystals exhibit an orthorhombic structure and an ellipsoidal-shaped morphology with an average size of 80–100 nm. The lattice parameters of Ba𝑥Sr1–𝑥SO4 solid solution crystals increase with increasing x value. However, they are not strictly coincident with the Vegard’s law, which indicates that the as-obtained products are non-ideal solid solutions. The Ba𝑥Sr1–𝑥SO4 solid solution nanocrystals have an excellent thermal stability from ambient temperature to 1300°C with a structural transition from orthorhombic to cubic phase at about 1111°C.

    • Syntheses of Fe–TiC nanocomposite from ilmenite concentrate via microwave heating

      Mansour Razavi Mohammad Reza Rahimipour Tooraj Ebadzadeh Seyed Salman Razavi Tousi

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      In this paper, the possibility of production of Fe–TiC nanocomposite as a useful ceramic, from ilmenite concentrate, aluminum powder and carbon black has been investigated. Different amounts of FeTiO3, carbon black and Al powder were activated by a high-energy ball mill. Then the mixtures were synthesized by microwave heating at various times. The results of XRD investigation indicated that TiC has been synthesized within 5–10 min treatment microwave time. Moreover, it was found that by increasing the aluminum content, the Fe2O3 phase was replaced by SiC and Al2O3. In addition, from the broadening of the diffraction lines in the XRD patterns analysis, it was concluded that the TiC crystallites are nano-sized. Also, it was found that the existence of Al lead to increased grain size and decrease of the strain in the process.

    • Bicomponent AgCl/PVP nanofibre fabricated by electrospinning with gel–sol method

      Jie Bai Yaoxian Li Lei Sun Chaoqun Zhang Qingbiao Yang

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      A new series of poly(vinyl pyrrolidone) (PVP) and silver chloride nanoparticles (AgCl) composite fibres have been synthesized by electrospinning and gel–sol technology. We used sol–gel process to prepare AgCl nanoparticles in the PVP solution, and then the solutions were electrospun to obtain AgCl/PVP composite nanofibres. The final products were thoroughly characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscopy (FESEM), which showed the formation of AgCl nanoparticles/PVP composite nanofibres.

    • Synthesis and optical characteristics of ZnO nanocrystals

      D Sridevi K V Rajendran

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      Zinc oxide nanomaterials with an average particle size of 20–30 nm are readily synthesized by the reaction of zinc acetate and oxalic acid under hydrothermal conditions. The samples are characterized by XRD, SEM, TEM, UV and photoluminescence (PL) studies. The average crystal size of the as prepared ZnO nanopowder is determined by XRD and the values are in good agreement with the TEM analysis. UV absorption spectra revealed the absorption at wavelength < 370 nm indicating the smaller size of ZnO nanoparticles. The quality and purity of ZnO nanomaterial crystalline samples are confirmed by photoluminescence spectra

    • Sintering behaviour of spinel–alumina composites

      Soumen Pal A K Bandyopadhyay P G Pal S Mukherjee B N Samaddar

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      Study of alumina–magnesia binary phase diagram reveals that around 40–50 wt% alumina dissolves in spinel (MgAl2O4) at 1600°C. Solid solubility of alumina in spinel decreases rapidly with decreasing temperature, which causes exsolution of alumina from spinel phase. Previous work of one of the authors revealed that the exsolution of alumina makes some interlocking structures in between alumina and spinel phases. In the present investigation, refractory grade calcined alumina and spinel powder were used to make different batch compositions. Green pellets, formed at a pressure of 1550 kg cm-2 were fired at different temperatures of 1500°, 1550° and 1600°C for 2 h soaking time. Bulk density, percent apparent porosity, firing shrinkage etc were measured at each temperature. Sintering results were analysed to understand the mechanism of spinel–alumina interactions. SEM study of present samples does not reveal the distinct precipitation of needle shaped 𝛼-alumina from spinel, but has some effect on densification process of spinel–alumina composites. Microstructural differences between present and previous work suggest an ample scope of further work in spinel–alumina composites.

    • Effects of talc and clay addition on pressureless sintering of porous Si3N4 ceramics

      Yu Fangli Yang Jianfeng Xue Yaohui Du Jun Lu Yuan Gao Jiqiang

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      Porous Si3N4 ceramics were successfully synthesized using cheaper talc and clay as sintering additives by pressureless sintering technology and the microstructure and mechanical properties of the ceramics were also investigated. The results indicated that the ceramics consisted of elongated 𝛽-Si3N4 and small Si2N2O grains. Fibrous 𝛽-Si3N4 grains developed in the porous microstructure, and the grain morphology and size were affected by different sintering conditions. Adding 20% talc and clay sintered at 1700°C for 2 h, the porous Si3N4 ceramics were obtained with excellent properties. The final mechanical properties of the Si3N4 ceramics were as follows: porosity, 𝑃0 = 45.39%; density, ρ = 1.663.g.cm-3; flexural strength, 𝜎b (average) = 131.59 MPa; Weibull modulus, 𝑚 = 16.20.

    • Growth of Nd3+ doped LiNbO3 crystals using Bridgman method and its spectral properties

      Jinhao Wang Yueping Zhang Haiping Xia Jiawei Sheng

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      The growth of Nd3+ doped lithium niobate crystals using Bridgman method has been reported in this paper. By means of the optimum conditions such as proper feed materials, sealed platinum crucibles, growth rate of 1–1.5 mm/h and temperature gradient of 30–35°C/cm across the solid–liquid interface under the furnace temperature of 1300°C, single crystals containing Nd3+ ion with 0.54 mol% concentration were obtained. X-ray diffraction and ICP–AES were used to characterize the crystals and its composition. The absorption, emission and fluorescence lifetime are also measured. Based on the Judd–Ofelt theory, we obtained the optical parameters of the crystal such as the luminescent quantum efficiency, the radioactive lifetimes, the branching ratios and the emission cross-section.

    • Study of gel grown mixed crystals of Ba𝑥Ca(1–𝑥)(IO3)4

      S L Garud N K Mahajan K B Saraf

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      The growth of mixed crystals of Ba𝑥Ca1–𝑥(IO3)4 were carried out with simple gel method. The effect of various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants on the growth was studied. Crystals having different morphologies and habits were obtained. The grown crystals were characterized by XRD, FT–IR, EDAX, TGA, DTA and DSC.

    • Hydrothermal synthesis of Pb(Zr0.52Ti0.48)O3 powders at low temperature and low alkaline concentration

      Zhong-Cheng Qiu Jian-Ping Zhou Gangqiang Zhu Peng Liu Xiao-Bing Bian

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      Pb(Zr0.52Ti0.48)O3 (PZT) powders were prepared by hydrothermal method. The effects of experimental parameters, including Pb/(Zr, Ti) ratio, alkaline concentration, reaction temperature and time on the product powders were studied in detail. Pure PZT powders were synthesized at suitable experimental conditions and Raman spectra confirmed the PZT with a perovskite-type structure. The homogeneous PZT powders with cubic-shaped morphology were formed at alkaline concentration of 1.2 M after reacting at 230°C for 2 h. The pure PZT powders obtained at low temperature and low alkaline concentration were attributed to precursors, TiCl4, with high activity and mineralizer NaOH with small cation radius.

    • Studies on blends of cycloaliphatic epoxy resin with varying concentrations of carboxyl terminated butadiene acrylonitrile copolymer I: Thermal and morphological properties

      Garima Tripathi Deepak Srivastava

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      Differential scanning calorimetric (DSC), thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA) of the blends of cycloaliphatic epoxy (CAE) resin toughened with liquid elastomer such as carboxyl terminated butadiene acrylonitrile copolymer (CTBN) have been carried out. Exothermal heat of reaction due to cross linking of the resin in the presence of diamino diphenyl sulphone (DDS, an amine hardener) showed a decreasing trend with increasing rubber concentration. Enhancement of thermal stability as well as lower mass loss of the epoxy–rubber blends with increasing rubber concentration have been observed in thermogravimetric analysis (TGA). Dynamic mechanical properties reflected a monotonic decrease in the storage modulus (𝐸′) with increasing rubber concentration. The loss modulus (𝐸″) and the loss tangent (tan 𝛿) values, however, showed an increasing trend with rise of temperature up to a maximum (peak) followed by a gradual fall in both cases.

    • Spectroscopic, thermal and biological studies of coordination compounds of sulfasalazine drug: Mn(II), Hg(II), Cr(III), ZrO(II), VO(II) and Y(III) transition metal complexes

      M G Abd El-Wahed M S Refat S M El-Megharbel

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      The complexations of sulfasalazine (H3Suz) with some of transition metals have been investigated. Three types of complexes, [Mn(HSuz)-2(H2O)4].2H2O, [M(HSuz)-2(H2O)2].𝑥H2O (M = Hg(II), ZrO(II) and VO(II), 𝑥 = 4, 8 and 6, respectively) and [M(HSuz)-2(Cl)(H2O)3].𝑥H2O (M = Cr(III) and Y(III), 𝑥 = 5 and 6, respectively) were obtained and characterized by physicochemical and spectroscopic methods. The IR spectra of the complexes suggest that the sulfasalazine behaves as a monoanionic bidentate ligand. The thermal decomposition of the complexes as well as thermodynamic parameters (𝛥 𝐸*}, 𝛥 𝐻*, 𝛥 𝑆* and 𝛥 𝐺*) were estimated using Coats–Redfern and Horowitz–Metzger equations. In vitro antimicrobial activities of the H3Suz and the complexes were tested.

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