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In this work, we report the synthesis of sol-gel-derived lead iron niobate [Pb1.10(Fe0.5Nb0.5)O3] (PFN) powders and sintered ceramics. The PFN powders were calcined at (Ta), 973, 1073, 1173, 1273, and 1373 K for 3 h in air. As envisaged from x-ray-diffraction analyses, PFN powder calcined at 1173 K was crystallized into pure monoclinic perovskite phase whereas powders calcined at all other temperatures had varied amounts of retained pyrochlore (Pb3Nb4O13) phase coexisted with dominant monoclinic perovskite phase. The PFN pellet (prepared using the phase pure powder calcined at 1173 K) sintered at 1373 K for 4 h in air also had a minute quantity of retained pyrochlore phase coexisting with desired perovskite phase. From the temperature dependence of measured capacitance and loss tangent at different frequencies, the ferroelectric to paraelectric phase-transition temperature of PFN ceramics was observed at Tc≈370 K. The diffused nature of this transition and high dielectric constant of PFN is related to the cation disorder at the B site of A(BI+3BII+5)O3 lattice. For PFN powders, calcined at different temperatures, the temperature dependence of the magnetic susceptibility (χ) was measured in a temperature range of 2–360 K, whereas the magnetic hysteresis loops and electron magnetic resonance (EMR) spectra were measured at room temperature. Room-temperature ferromagnetism is observed in all the calcined powder samples and it was found that the magnetization increases with the increase in calcination temperature (Ta). The symmetric EMR line shape with g≈2.01 observed in all calcined samples was identified to be due to Fe3+ ions. It is suggested that the observed weak ferromagnetism, which increases with an increase in Ta, may be due to canting of the Fe3+ spins. These observations suggest PFN to be a very attractive single-phase ferroelectric/ferromagnetic material for room-temperature applications. [ABSTRACT FROM AUTHOR]

X-ray diffraction data from water-supported monolayers of fatty acids with chain lengths from 19 to 22 is presented. The structures of the tilted mesophases L2’, L2, and Ov are characterized in detail. The contributions to the unit cell distortion from the tilt and the ordering of the backbone planes of the molecules are separated. It is shown that at the swiveling transition L2’–L2, not only the tilt azimuth but also the packing of the backbone planes change discontinuously. We demonstrate that the tilting transition LS–L2 is accompanied by the ordering of the backbone planes and may be discontinuous. Evidence is presented for a herringbone ordering transition within the L2 region. The distortions are related to symmetry of the phases and described by the order parameters responsible for tilt and herringbone ordering of the backbone planes of the molecules. © 1995 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We have studied Langmuir monolayers of CH3(CH2)20OH (heneicosanol) using x-ray diffraction. Over the temperature range 7–55 °C, the monolayer isotherms show only one discontinuity, which may be either a ‘‘flat section’’ or a ‘‘kink;’’ we find that these are transitions between tilted and untilted phases. There are several untilted phases, with hexagonal and distorted-hexagonal structures, as in monolayers of the corresponding (heneicosanoic) acid. However, in contrast to the acid, when the pressure is lowered the molecules tilt only towards a next-nearest neighbor. The dependence of the lattice spacings on pressure and temperature indicate that the monolayer does not form a ‘‘tilted hexagonal’’ phase, even at temperatures where the untilted phase is hexagonal (rotator-II). [ABSTRACT FROM AUTHOR]

We have studied the structure of a monolayer of C21H43OH on water, in the region near close packing, by grazing incidence in-plane x-ray diffraction. For all temperatures studied the isotherms in the πa plane show a kink, signaling a phase transition. Along an isotherm, and for pressures above the kink, we observe that the transverse structure factor has one peak which has constant position, width, and intensity; below the kink the diffraction peak shifts to smaller scattering vector (larger separation) and the amplitude decays as the surface pressure decreases, but the width of the peak remains constant. We rationalize these observations in terms of the influence on the transverse structure factor of gauche configurations in the amphiphile tails, with the kink representing the point at which the last of the gauche configurations is squeezed out of the chain. Along an isobar which is at higher pressure than the kink pressures of all isotherms crossed, the transverse structure factor has a single peak above a transition temperature and two peaks below that temperature; for π=30 dyn/cm the transition temperature is in the range 16.3

Deals with a study which examined in situ x-ray diffraction studies of the growth of thin films using a synchrotron light source. Information on an off-axis faced magnetron sputtering chamber; Methodology of the study; Results and discussion.

Magnetic properties of oleic acid/oleylamine coated magnetite nanoparticles of average diameter D=4, 6, 8, 10, and 12 nm are reported. The samples were characterized by transmission electron microscopy and x-ray diffraction (XRD) with XRD showing increasing disorder with decreasing D. Magnetization M vs temperature T data show the blocking temperature TB decreasing with decreasing D from TB=38 K for 12 nm to TB=6.5 K for D=4 nm. The saturation magnetization Ms at 2 K also decreases from Ms=62 emu/g for 12 nm to Ms=17 emu/g for 4 nm but the coercivity at 2 K increases with a decrease in D. It is shown that Ms fits Ms=92(1-2d/D)3 with d=0.68 nm for D>4 nm and d=0.86 for D=4 nm. This equation is derived assuming a core-shell model with shell of thickness d consisting of disordered spins not contributing to Ms. [ABSTRACT FROM AUTHOR]

Adsorptive removal of Cr(VI) by N -3-trimethoxysilylpropylethylenediamine (AEAPTMS) functionalised MCM-48 prepared via grafting method was investigated with respect to contact time, adsorbent dose, initial metal ion concentration, pH, amine loading and temperature. The synthesized samples were characterized by X-ray diffraction (XRD), fourier transform infrared (FTIR) spectrocopy, scanning electron microscopy (SEM), N 2 adsorption-desorption isotherm and thermogravimetric analysis (TGA). 1.5 mmol AEAPTMS functionalised MCM-48 sample showed highest adsorption among the modified samples under similar conditions. Adsorption kinetics was successfully fitted by pseudo second-order kinetic model. The experimental data fitted well to the Langmuir adsorption isotherm model with a calculated maximum adsorption capacity of 166.67 mg/g. The overall adsorption was a spontaneous and endothermic process as signified by the thermodynamic parameters. Another aspect of the work was the high catalytic efficiency of chromium containing spent adsorbent obtained by adsorption of Cr(VI) from the aqueous solution. The catalytic activity of the obtained catalyst was found to depend on the amount of adsorbed chromium. The spent adsorbents behaved as efficient catalysts for oxidation of cyclohexene (81.0% conversion) and ethylbenzene (94.6% conversion) with 96.7% and 100% selectivity towards desired product when 70% tert-Butyl hydroperoxide (TBHP) was used as oxidant. [ABSTRACT FROM AUTHOR]

Chitin-glucan complex (ChGC) was extracted from Agaricus bisporus (White Button Mushroom) biomass using a hot alkaline treatment for several times and washed with distilled water. The prepared material was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), Scanning Electron Microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX) and biological activity of ChGC was tested against Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis, Escherichia coli. ChGC shows better antibacterial activity in comparison to native chitin. Hence, antibacterial study of ChGC may find better application opportunity in cosmetics, food packaging and medicinal fields. [ABSTRACT FROM AUTHOR]

In our present investigation we have used chitosan-stearic acid derivative for both antibacterial screening and drug delivery applications. Stearic acid being the fatty acid with aliphatic chain homologue -CH2 - (n=16) enhanced the chemical properties of chitosan which becomes beneficial for antibacterial activity and drug delivery applications. Ciprofloxacin antibiotic was taken as a model drug for the release study. Stearic acid readily improved the permeability of incorporated ciprofloxacin drug. The prepared chitosan-stearic derivative was characterized using FTIR, XRD and DSC techniques while drug release screening was performed using UV spectrophotometer. The prepared chitosan-stearic acid derivative showed good antibacterial activity against S. aureus and E. coli bacterial strains. The drug release screening results indicated a brust release at first hour; nearly 17% in case of non crosslinked film whereas neary 19% release in stearic acid crosslinked conjugate. At later stage, the drug release becomes steady and slow in both the cases. Nearly 88% of the total drug loaded released within 48 h and later on it do not show more release probably due to interaction with chitosan and stearic acid. [ABSTRACT FROM AUTHOR]

In the present work, the photocatalytic potential of zinc oxide nanoparticles, prepared using extracts of Ulva lactuca (U. lactuca) and Stoechospermum marginatum (S. marginatum), has been evaluated. The effect of catalyst dosage, pH of the solution, and initial dye concentration on the degradation of methyl red under sunlight has been studied. After 180 min of solar irradiation, the S. marginatum based zinc oxide nanoparticles (Sm-ZnO) exhibited the highest degradation efficiency, 92%, at pH 7, 5 mg/L dye concentration, and 2.5 mg/mL catalyst load. Under the same conditions, U. lactuca based ZnO NP (Ul-ZnO) recorded 90% degradation. The zinc oxide nanoparticles displayed notable performance during the three degradation cycles, and the stability of the catalyst is confirmed by X-ray diffraction analysis. The dye degradation reaction followed pseudo-first-order kinetics with a rate constant of 0.0167 min−1 for Sm-ZnO NPs and 0.0155 min−1 for Ul-ZnO NPs. The treated dye solution at pH 7, 2.5 mg/mL catalyst, and 10 mg/L dye concentration has been further utilized for watering green gram plants, and the growth parameters were, with a maximum shoot and root lengths of 13.5 cm and 1.8 cm, respectively. The total chlorophyll content was 72.9 μg/mL, protein content was 62 mg/g and the carbohydrate content 446 mg/g. • Zinc oxide nano photocatalysts fabricated using two different seaweeds, Stoechospermum marginatum and Ulva lactuca were used to degrade methyl red dye under sunlight. • Stoechospermum marginatum based ZnO nano catalyst exhibited better efficacy than Ulva lactuca based ZnO nanoparticles for degradation of methyl red dye under sunlight. • The feasibility of treated dye solution for irrigation purposes has been studied by analyzing the growth of green gram plants. • The parameters such as chlorophyll content, protein and carbohydrate content of the leaves of green gram plants have been evaluated as a measure of quality of treated water. [ABSTRACT FROM AUTHOR]

The structural characterization of fused thiazolopyrimidine 1 (CHNOS) is performed using the single crystal X-ray study, the DFT calculation, and the Hirshfeld surface analysis. The molecular packing of the crystal is mainly stabilized by C-H...O and C-H...π interactions. A DFT calculated HOMO-LUMO energy gap of 3.90 eV indicates a high kinetic stability of the compound. The 3D Hirshfeld surfaces and the associated 2D fingerprint plots are investigated for short contact interactions. The relative contribution of different interactions to the Hirshfeld surface indicates that the H...H, C...H, and O...H contacts account for about 83.4% of the total Hirshfeld surface area. [ABSTRACT FROM AUTHOR]

A novel chitosan derivative with ofloxacin (OFX) has been successfully prepared. The IR and 1H-NMR results revealed that the chitosan/ofloxacin (CH-OFX) complex exhibited an electrostatic interaction. The crystalline and surface morphology were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The antimicrobial activity of the complexes against various micro-organisms viz. Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus was tested. It was established that their antibacterial activity is up to four times greater than that of free quinolone drug and chitosan, probably due to the conjunction of favorable pharmacokinetics, excellent bacterial susceptibility and good stability towards metabolic degradation. [ABSTRACT FROM AUTHOR]

The effect of Cu doping (0.08-4%) on the structural, electrical, optical, and optoelectronic properties of sol-gel ZnO thin films deposited on glass substrates have been investigated. X-ray diffraction studies show that the doped films are single-phase wurizite structure with random orientations. A decreasing trend in the c-axis parameter up to 0.5% is observed followed by an increasing trend above that. Field-emission scanning electron microscopy shows a grain texture. The energy dispersive spectroscopy as well as the film color confirms the Cu doping. Optical transmittance measurements show 80% transparency in the visible region for the films up to 0.3% Cu content. The doped films become very resistive as indicated by the four probe electrical resistivity and current-voltage measurements. The photoluminescence spectra reveal with Cu doping, a green emission at 515 nm appeared and the UV peak intensity at 376 nm is drastically lowered. However, no green emission is observed as the doping is increased beyond 0.5%. The changes in the structural, electrical, and optical properties are correlated to interstitials defects. The photoconductivity studies show that the UV sensitivity of the films is enhanced up to 0.1%, which indicates that the films can be used as UV sensors. [ABSTRACT FROM AUTHOR]

Abstract: This study covers the performance of three cobalt-based catalytic systems (high surface area 15% Co/SiO2, low surface area 15% Co/SiO2, and 15% Co/Al2O3) of different characteristics in Fischer–Tropsch synthesis (FTS) in both conventional gas-phase and supercritical hexane (SCH) phase. The reaction was conducted in a high-pressure FTS reactor setup at reaction temperature of 240°C, syngas (H2/CO ratio of 2) flow rate of 50sccm/gcat, and total pressures from 20 to 65bar. The surface characteristics of these catalysts were measured by N2 physisorption using a TriStar 3000 gas adsorption analyzer. Room temperature X-ray diffraction (XRD), temperature and magnetic field (H) variation of the magnetization (M), and low-temperature (5K) electron magnetic resonance were used for determining the electronic states (Co0, CoO, Co3O4, Co2+) of cobalt for the calcined, reduced (before the reaction), and used samples (after the reaction). Correlations of the catalyst activity and selectivity with the catalysts surface characteristics reveal that pore radius of the catalyst has an influence on both syngas and CO conversions in gas-phase FTS. However, no such correlation was observed in the case of SCH-FTS, indicating an alleviation of that mass transfer limitations typically controlled by interparticle characteristics of the catalyst. This is attributed to the higher solubility of heavy products in the SCH medium that inhibits the condensation of those products inside the catalyst pores and enhances their in situ extraction. The XRD and magnetic characterizations of the used catalysts reveal that in situ reducibility of the Co3O4 to hcp-Co0 or fcc-Co0 is taking place during the FTS reaction. However, minimal in situ reduction was observed in the case of gas-phase FTS, whereby significant changes in the reduced cobalt electronic state and support (alumina, and silica) phase were detected under SCH-FTS conditions. As a result, both the activity and selectivity of the cobalt catalyst was found to be very stable and recoverable during SCH-FTS for relatively long time-on-stream (15 days). [Copyright &y& Elsevier]

Results of the characterization of six Co-based Fischer–Tropsch (FT) catalysts, with 15% Co loading and supported on SiO2 and Al2O3, are presented. Room temperature X-ray diffraction (XRD), temperature and magnetic field (H) variation of the magnetization (M), and low-temperature (5 K) electron magnetic resonance (EMR) are used for determining the electronic states (Co0, CoO, Co3O4, Co2+) of cobalt. Performance of these catalysts for FT synthesis is tested at reaction temperature of 240 °C and pressure of 20 bars. Under these conditions, 15% Co/SiO2 catalysts yield higher CO and syngas conversions with higher methane selectivity than 15% Co/Al2O3 catalysts. Conversely the Al2O3 supported catalysts gave much higher selectivity towards olefins than Co/SiO2. These results yield the correlation that the presence of Co3O4 yield higher methane selectivity whereas the presence of Co2+ species yields lower methane selectivity but higher olefin selectivity. The activities and selectivities are found to be stable for 55 h on-stream. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the influence of thickness and post deposition annealing temperature on thermally evaporated molybdenum oxide films has been studied. The X-ray diffraction (XRD) and Scanning Electron Microscope (SEM) are used for crystal structural and surface morphological characterization of the films, respectively. The XRD analysis showed that the presence of α-MoO 3 and MoO 2 crystalline phase of the films annealed at elevated temperature ~ 250 °C after deposition. The optical constants are determined from UV–Vis transmission spectra. The optical band gap and Urbach energy is found to be temperature dependent. The refractive index of the films is estimated by the optical method as well as cross-sectional SEM image analysis. It is found that the refractive index of the films increases from ~ 1.70 to 2.03 with the decrease in film thickness from ~ 2.9 to 1.7 µm. It is also observed that the refractive index decreased from ~ 2.03 to 1.61 with the increase in post deposition annealing temperature from room temperature (RT) to ~ 250 °C. Moreover, extinction coefficient, optical conductivity, porosity, and film density are investigated as a function of source-substrate distance and post deposition annealing temperature. The Photoluminescence (PL) properties of the films are also investigated by recording spectra under the excitation wavelength at 250 nm. Graphical abstract fx1 [ABSTRACT FROM AUTHOR]

Nanocrystalline bismuth telluride, Bi2Te3 has been synthesized by mechanical alloying (MA) the powder mixture composed of Bi and Te in the inert gas atmosphere within a short duration of 15 min. Microstructure characterization of the prepared powder has been investigated adopting the Rietveld’s method using X-Ray diffraction (XRD) data and analyzing high-resolution transmission electron microscopy (HRTEM) images. The XRD pattern of 15 min milled powder is composed of reflections of major Bi2Te3 phase with other two minor phases. Detailed structural information of these minor phases has been reported here which was not explored in any previous works. XRD analysis reveals that the stoichiometric Bi2Te3 phase has been formed after 1h of milling and there is no phase transition up to 10h of milling. HRTEM study also reveals the formation of single phase nanostructured Bi2Te3 phase. The DC (direct current) conductivities of 15min, 30min and 10h ball milled powders are measured within the temperature range of 359 to 633K. The electrical conductivity (σ) of Bi2Te3 indicates the semiconducting nature of the sample. There is no significant change of electrical conductivity of Bi2Te3 phase since its formation after 15min to 10h of milling, as there is no noticeable change in crystallite size.

Abstract: X-ray diffraction studies performed during the nucleation of hydrocerussite (PbCO3 ·Pb(OH)2) from a supersaturated aqueous solution, at a floating fatty acid monolayer template, reveal (√7×√7)-R19.1° reconstruction at the (001) surface of hydrocerussite. Reordering of surface atoms into epitaxial superstructures is thought to require extremely clean surfaces (cleaned electrochemically or under UHV). At this organic–inorganic interface, the organic monolayer relaxes to form an epitaxial match with the reconstructed lattice just below it. We speculate that this lattice match, along with the ion-specific interactions of the monolayer, provide the clean nucleation environment. [Copyright &y& Elsevier]