Structural, thermal and electrical characterization of NdLiMo2O8 electroceramics, using impedance spectroscopy

We report electrical property of a polycrystalline NdLiMo2O8 ceramics using complex impedance analysis. The material shows temperature dependent electrical relaxation phenomena. The d.c. conductivity shows typical Arrhenius behavior, when observed as a function of temperature. The a.c. conductivity is found to obey Jonscher's universal power law. The material was prepared in powder form by a standard solid-state reaction technique. Material formation and crystallinity have been confirmed by X-ray diffraction studies. Impedance measurements have been performed over a range of temperatures and frequencies. The results have been analyzed in the complex plane formalism and suitable equivalent circuits have been proposed in different regions. The role of bulk and grain boundary effect in the overall electrical conduction process is discussed with proper justification. (C) 2011 Elsevier Ltd. All rights reserved.

Structural, dielectric relaxation and piezoelectric characterization of Sr2+ substituted modified PMS-PZT ceramic

Pyrochlore phase free [Pb0.94Sr0.06] [(Mn1/3Sb2/3)(0.05)(Zr0.53Ti0.47)(0.95)] O-3 ceramics has been synthesized with pure Perovskite phase by semi-wet route using the columbite precursor method. The field dependences of the dielectric response and the conductivity have been measured in a frequency range from 50 Hz to 1 MHz and in a temperature range from 303 K to 773 K. An analysis of the real and imaginary parts of the dielectric permittivity with frequency has been performed, assuming a distribution of relaxation times. The scaling behavior of the dielectric loss spectra suggests that the distribution of the relaxation times is temperature independent. The SEM photographs of the sintered specimens present the homogenous structures and well-grown grains with a sharp grain boundary. The material exhibits tetragonal structure. When measured at frequency (100 Hz), the polarization shows a strong field dependence. Different piezoelectric figures of merit (k(p), d(33) and Q(m)) of the material have also been measured obtaining their values as 0.53, 271 pC/N and 1115, respectively, which are even higher than those of pure PZT with morphotropic phase boundary (MPB) composition. Thus the present ceramics have the optimal overall performance and are promising candidates for the various high power piezoelectric applications. (C) 2011 Elsevier B.V. All rights reserved.

Synthesis, Spectral Characterization, Crystal Structure and Thermal Behavior of Tert-butyl 2,2-bis(2,4-dinitrophenyl)ethanoate

Tert-butyl 2,2-bis(2,4-dinitrophenyl)ethanoate was prepared from the ethanolic solution of 1-chloro-2,4-dinitrobenzene, tert-butyl 3-oxobutanoate and triethylamine. Acetyl group in tert-butyl 3-oxobutanoate has cleaved off during the formation of the title molecule. UV-VIS, IR, 1H NMR, 13C NMR, Proton-Proton COSY data and single crystal XRD results support the proposed structure. Flammability test, impact sensitivity test and TG/DTA studies at different heating rates on the synthesized molecule imply that it is an insensitive high energy density material.

Characterization and iodide adsorption behaviour of HDPY+ modified bentonite

Owing to its favourable physical, chemical and rheological properties, densely compacted bentonite or bentonite-sand mix is considered as a suitable buffer material in deep geological repositories to store high level nuclear waste. Iodine-129 is one of the significant nuclides in the high level waste owing to its long half life and poor sorption onto most geologic media. Bentonite by virtue of negatively charged surface has negligible affinity to retain iodide ions. As organo-bentonites are known to retain iodide ions, the present study characterizes hexadecylpyridinium chloride (HDPyCl.H2O) treated bentonite from Barmer India (referred as HDPy+B) for physico-chemical properties, engineering properties and the iodide adsorption behavior of the organo clay. Batch experiments revealed that HDPy+ ions are largely retained (94 % retention) via cation exchange; the ion-exchange process neutralizes the negative surface charge and bridges clay particles leading to reduction in Atterberg limits, clay content and sediment volume. The organo clay retains iodide by Coulombic attraction (at primary sites) and anion exchange (at secondary sites). The free-energy change (Delta G (o) = -25.5 kJ/mol) value indicated that iodide retention by organo clay is favored physical adsorption process. Iodide adsorption capacity of organo clay decreased significantly (85-100 %) on dilution with 50-80 % bentonite. On the other hand, dilution of bentonite with 50 % organo clay caused 58 % reduction in swell potential and 21 % reduction in swell pressure.

Synthesis and characterization of nickel/barium hexa-aluminate composite coatings

Electrodeposition of nickel/barium hexa-aluminate (Ni/BHA) composite coatings has been carried out from a Watt's bath on mild steel substrate. BHA powders with plate habit were synthesized by solution combustion synthesis followed by heat treatment to ensure complete conversion to the hexa-aluminate phase. Heat treated material was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) combined with X-ray analysis. The dispersion behaviour and stability of BHA suspensions with cationic and anionic surfactants at room temperature were studied by dynamic light scattering under different pH. The influence of BHA concentration in the electrolytic bath, deposition temperature, pH, current density and duty cycle on particle incorporation in the coatings were studied and conditions for maximum particle incorporation were established. Coatings with a roughness of about 0 center dot 4 mu m were produced by using this technique. Effect of BHA content on microhardness was also investigated. A reasonably good thickness of the coatings was achieved in a given set of conditions.

Thermal oxidation strategy for the synthesis of phase-controlled GeO2 and photoluminescence characterization

We report the synthesis of trigonal and tetragonal phase GeO2 films/microrods from a Ge wafer/powder by thermal oxidation. Both trigonal and tetragonal GeO2 exhibit excitation-dependent luminescence. Trigonal GeO2 exhibits strong green luminescence while tetragonal GeO2 exhibits strong blue luminescence when excited with ultra-violet light. Yellow-red luminescence is observed when both the phases are excited with green light. The emission wavelength varies almost linearly with the excitation wavelength both for trigonal and tetragonal GeO2. The variation is significant in the case of tetragonal GeO2, indicating a potential wavelength converter material.

Hydro-mechanical characterization of Barmer 1 bentonite from Rajasthan, India

The conceptual model for deep geological disposal of high level nuclear waste (HLW) is based on multiple barrier system consisting of natural and engineered barriers. Buffer/backfill material is regarded as the most important engineered barrier in HLW repositories. Due to large swelling ability, cation adsorption capacity, and low permeability bentonite is considered as suitable buffer material in HLW repositories. Japan has identified Kunigel VI bentonite, South Korea - Kyungju bentonite, China - GMZ bentonite, Belgium - FoCa clay, Sweden - MX-80 bentonite, Spain - FEBEX bentonite and Canada - Avonseal bentonite as candidate bentonite buffer for deep geological repository program. An earlier study on Indian bentonites by one of the authors suggested that bentonite from Barmer district of Rajasthan (termed Barmer 1 bentonite), India is suited for use as buffer material in deep geological repositories. However, the hydro-mechanical properties of the Barmer 1 bentonite are unavailable. This paper characterizes Barmer 1 bentonite for hydro-mechanical properties, such as, swell pressure, saturated permeability, soil water characteristic curve (SWCC) and unconfined compression strength at different dry densities. The properties of Barmer 1 bentonite were compared with bentonite buffers reported in literature and equations for designing swell pressure and saturated permeability coefficient of bentonite buffers were arrived at. (C) 2013 Elsevier B.V. All rights reserved.

Synthesis and Characterization of Fly Ash Geopolymer Sand

Geopolymers are an alternative binder to portland cement in the manufacture of mortars and concrete, as its three-dimensional aluminosilicate network imparts excellent mechanical properties. Use of geopolymers in place of ordinary portland cement is favored owing to the possible energy and carbon dioxide savings. River sand is another construction industry material that needs development of a sustainable alternate in India. Geopolymerization of fly ash amorphous silica mixtures is employed to produce fine aggregates as a possible replacement to river sand. Geopolymerization of fly ash amorphous silica mixtures in 10M NaOH solution at 100 degrees C for 7days produced fine aggregates termed fly ash geopolymer sand (FAPS)] that had comparable grain size distribution, specific gravity, and improved frictional resistance with river sand. The FAPS particles exhibited more alkaline pH (12.5) and higher total dissolved solids (TDS) concentration (TDS=747 mg/L) in comparison to the river sand specimen (pH=7.9 and TDS=32.5 mg/L). However, when used as fine aggregate in mortar, FAPS-mortar specimens develop similar pH, lower TDS, similar compressive strength, and modulus in relation to river sand-mortar specimens. The experimental results suggest that FAPS particles have the potential to replace river sand in the manufacture of mortar and concrete.

Rapid, microwave-assisted synthesis of Gd2O3 and Eu:Gd2O3 nanocrystals: characterization, magnetic, optical and biological studies

Ultra-small crystals of undoped and Eu-doped gadolinium oxide (Gd2O3) were synthesised by a simple, rapid microwave-assisted route, using benzyl alcohol as the reaction solvent. XRD, XPS and TEM analysis reveal that the as-prepared powder material consists of nearly monodisperse Gd2O3 nanocrystals with an average diameter of 5.2 nm. The nanocrystals show good magnetic behaviour and exhibit a larger reduction in relaxation time of water protons than the standard Gd-DTPA complex currently used in MRI imaging. Cytotoxicity studies (both concentration- and time-dependent) of the Gd2O3 nanocrystals show no adverse effect on cell viability, evidencing their high biological compatibility. Finally, Eu:Gd2O3 nanocrystals were prepared by a similar route and the red luminescence of Eu3+ activator ions was used to study the cell permeability of the nanocrystals. Red fluorescence from Eu3+ ions observed by fluorescence microscopy shows that the nanocrystals (Gd2O3 and Eu:Gd2O3) can permeate not only the cell membrane but can also enter the cell nucleus, rendering them candidate materials not only for MRI imaging but also for drug delivery when tagged or functionalized with specific drug molecules.

Extremely High Near Field Enhancement in a Novel Plasmonic Nano Material used for Photovoltage Generation

Enhancement of localized electric field near metal (plasmonic) nanostructures can have various interesting applications in sensing, imaging, photovoltage generation etc., for which significant efforts are aimed towards developing plasmonic systems with well designed and large electromagnetic response. In this paper, we discuss the wafer scale fabrication and optical characterization of a unique three dimensional plasmonic material. The near field enhancement in the visible range of the electromagnetic spectrum obtained in these structures (order of 106), is close to the fundamental limit that can be obtained in this and similar EM field enhancement schemes. The large near field enhancement has been reflected in a huge Raman signal of graphene layer in close proximity to the plasmonic system, which has been validated with FEM simulations. We have integrated graphene photodetectors with this material to obtain record photovoltage generation, with responsivity as high as A/W. As far as we know, this is the highest sensitivity obtained in any plasmonic-graphene hybrid photodetection system till date.

Solution processible Cu2SnS3 thin films for cost effective photovoltaics: Characterization

Thin films of Cu2SnS3 (CTS) were deposited by the facile solution processed sol-gel route followed by a low-temperature annealing. The Cu-Sn-thiourea complex formation was analysed using Fourier Transform Infrared spectrophotometer (FTIR). The various phase transformations and the deposition temperature range for the initial precursor solution was determined using Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC). X-Ray Diffraction (XRD) studies revealed the tetragonal phase formation of the CTS annealed films. Raman spectroscopy studies further confirmed the tetragonal phase formation and the absence of any deterioratory secondary phases. The morphological investigations and compositional analysis of the films were determined using Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) respectively. Atomic Force Microscopy (AFM) was used to estimate the surface roughness of 1.3 nm. The absorption coefficient was found to be 10(4) cm(-1) and bandgap 1.3 eV which qualifies CTS to be a potential candidate for photovoltaic applications. The refractive index, extinction coefficient and relative permittivity of the film were measured by Spectroscopic ellipsometry. Hall effect measurements, indicated the p type nature of the films with a hole concentration of 2 x 10(18) cm(-3), electrical conductivity of 9 S/cm and a hole mobility of 29 cm(2)/V. The properties of CTS as deduced from the current study, present CTS as a potential absorber layer material for thin film solar cells. (C) 2015 Elsevier B.V. All rights reserved.

Flower-like porous cobalt(II) monoxide nanostructures as anode material for Li-ion batteries

In the present study, a microwave-assisted, solution-based route has been employed to obtain porous CoO nano structures. Detailed characterization reveals that the flower-like nanostructures comprise petal-like sheets, each of which is made of an ordered, porous arrangement of crystallites of CoO measuring about 6 nm. TEM analysis shows that each ``petal'' is an oriented aggregate of CoO nanocrystals, such aggregation promoted by the hydroxyl moieties derived from the solution. The structure provides a large specific area as well as the porosity desirable in electrodes in Li-ion batteries. Electrochemical measurements carried out on electrodes made of nanostructured CoO show excellent Li ion-storing capability. A specific capacitance of 779 mAh g(-1) has been measured at a specific current of 100 mA g(-1). Measurements show also excellent cyclability and coulombic efficiency. Impedance spectroscopy provides evidence for charge transfer occurring in the porous networks. (C) 2015 Elsevier B.V. All rights reserved.

Characterization of silver-kaolinite (AgK): an adsorbent for long-lived I-129 species

Bentonite is a preferred buffer and backfill material for deep geological disposal of high-level nuclear waste (HLW). Bentonite does not retain anions by virtue of its negatively charged basal surface. Imparting anion retention ability to bentonite is important to enable the expansive clay to retain long-lived I-129 (iodine-129; half-life = 16 million years) species that may escape from the HLW geological repository. Silver-kaolinite (AgK) material is prepared as an additive to improve the iodide retention capacity of bentonite. The AgK is prepared by heating kaolinite-silver nitrate mix at 400 degrees C to study the kaolinite influence on the transition metal ion when reacting at its dehydroxylation temperature. Thermo gravimetric-Evolved Gas Detection analysis, X-ray diffraction analysis, X-ray photo electron spectroscopy and electron probe micro analysis indicated that silver occurs as AgO/Ag2O surface coating on thermally reacting kaolinite with silver nitrate at 400 degrees C.

Microstructural characterization of ultrafine-grain interstitial-free steel by X-ray diffraction line profile analysis

This paper highlights the microstructural features of commercially available interstitial free (IF) steel specimens deformed by equal channel angular pressing (ECAP) up to four passes following the route A. The microstructure of the samples was studied by different techniques of X-ray diffraction peak profile analysis as a function of strain (epsilon). It was found that the crystallite size is reduced substantially already at epsilon=2.3 and it does not change significantly during further deformation. At the same time, the dislocation density increases gradually up to epsilon=4.6. The dislocation densities estimated from X-ray diffraction study are found to correlate very well with the experimentally obtained yield strength of the samples.

Expression, Purification and Characterization of Peanut (Arachis hypogaea) Agglutinin (PNA) from Baculovirus Infected Insect Cells

Peanut (Arachis hypogaea) seed lectin, PNA is widely used to identify tumor specific antigen (T-antigen), Gal beta 1-3GalNAc on the eukaryotic cell surface. The functional amino acid coding region of a cDNA clone, pBSH-PN was PCR amplified and cloned downstream of the polyhedrin promoter in the Autographa californica nucleopolyhedrovirus (AcNPV) based transfer vector pVL1393. Co-transfection of Spodoptera frugiperda cells (Sf9) with the transfer vector, pAcPNA and AcRP6 (a recombinant AcNPV having B-gal downstream of the polyhedrin promoter) DNAs produced a recombinant virus, AcPNA which expresses PNA. Infection of suspension culture of Sf9 cells with plaque purified AcPNA produced as much as 9.8 mg PNA per liter (2.0 x 10(6) cells/ml) of serum-free medium. Intracellularly expressed protein (re-PNA) was purified to apparent homogeneity by affinity chromatography using ECD-Sepharose. Polyclonal antibodies against natural PNA (n-PNA) crossreacted with re-PNA. The subunit molecular weight (30 kDa), hemagglutination activity, and carbohydrate specificity of re-PNA were found to be identical to that of n-PNA, thus confirming the abundant production of a functionally active protein in the baculovirus expression system.