Presence Of Additional Phase Research Articles

Facile synthesis of silver chloride-polyaniline nanocomposites and its photocatalytic activity for the degradation of methylene blue

Herein, we report a green and an effective strategy for the synthesis of polyaniline-silver chloride (AgCl@PANI) nanocomposites by using facile in-situ chemical oxidative polymerization method in the presence of as-synthesized silver nanoparticles (Ag NPs) for the study of their photocatalytic activity towards the photodegradation of methylene blue (MB) under UV irradiation. The contents of Ag NPs varied from 2% to 6% during polymerization reaction to get AgCl@PANI nanocomposites. These synthesized polymer nanocomposites were characterized for their structural and optical properties, thermal stability, dc conductivity and photocatalytic activity by FT-IR spectroscopy, XRD, UV–Vis spectroscopy, TGA, SEM, standard four probe method and the photodegradation activity of MB, respectively. XRD analysis confirm the successful formation of AgCl@PANI nanocomposites without the presence of additional phases. TGA shows that AgCl@PANI nanocomposites have excellent thermal stability due to the barrier effect of AgCl moieties bounded with in the polymer chain and the strong physiochemical interactions between PANI and AgCl as inferred from FT-IR and UV–vis analysis. Under UV irradiation, the AgCl@PANI nanocomposite, with 4 wt% of Ag NPs (AgCl@PANI-4%), demonstrated excellent photocatalytic activity for MB degradation with the photodegradation percentage of ∼ 99 % in 20 min. The experimental findings illustrate that the superior photocatalytic activity of AgCl@PANI nanocomposites is owing to incorporation of AgCl moieties in the polymer structure, less needed energy for the formation of electron-hole pairs in the quinoid ring of PANI in the UV-region, enhanced light absorption owing to smaller grain size morphology, high surface area of the nanocomposite and high electrical conductivity (128 mS.cm−2). These results suggest the potential of these synthesized conjugated polymer-based nanocomposites as a photocatalyst for cost-effective and efficient wastewater treatment for the industrial applications.

Fingerprinting stealth metasomatism in ophiolitic peridotites

Mantle wedge peridotites are characterized by extraordinarily depleted compositions and their genesis is still controversial. In this study, we present microstructural observations and mineral chemical analyses of mantle harzburgites in the Lycian ophiolite of SW Turkey that reveal their formation in a suprasubduction zone mantle wedge. The textures of clinopyroxene in the harzburgites, particularly chromite-clinopyroxene symplectites and grains containing mineral inclusions, do not support a partial melting origin. Zoning textures and the presence of additional phases within the orthopyroxene porphyroclasts indicate that they underwent melt/fluid infiltration. Olivine crystals and interstitial grains are enclosed in orthopyroxene porphyroclasts, implying that the orthopyroxene grains crystallized by consuming olivine. Chromite grains in the harzburgites not only have zoned, but also contain a variety of mineral inclusions. Amphibole grains in some of the harzburgites also have compositions similar to those in the chromitites. Therefore, all mineral phases in the Lycian harzburgites have well-preserved metasomatic signatures that overprinted their partial melting features. The enrichment of fluid-mobile elements, such as Cs, Rb, U, and Pb in clinopyroxene and amphibole, coupled with their high Mg# values (92.8–95.6 and 93.7–96.4, respectively), suggest formation by Cr- and Mg-rich, hydrous metasomatic melts/fluids. The consistent compositions of clinopyroxene and chromite in the harzburgites and chromitites, together with the decreasing intensity of alteration and crystallization temperature of amphibole in the chromitite pods through dunites to harzburgites, imply that the hydrous melts/fluids were partially released from chromite surfaces during chromitite formation and/or from dehydration of the metamorphic sole, which likely attributed to metasomatism at different depths. Moreover, chromite-hosted inclusions in the harzburgites may reflect the reaction before solidification of an inclusion-rich zone possibly signifying a rapid increase of chromite-oversaturated melt. Positive correlations between Cr and Al in pyroxenes of ophiolites are widely preserved in metasomatic mantle peridotites from different tectonic settings and thus they provide a robust chemical proxy for the metasomatism. • Direct evidence of stealth metasomatism for harzburgites in the mantle section of the Lycian ophiolite; • The depleted Cr and Mg-rich hydrous melts/fluids are released from chromite surfaces or heating dehydration of the metamorphic sole; • The positive Cr and Al correlation of pyroxene suggest that metasomatism in the lithospheric mantle is widespread

Temperature effect in physicochemical and bioactive behavior of biogenic hydroxyapatite obtained from porcine bones

Biogenic hydroxyapatite (BHAp) is a widely used material in the biomedical area due to its similarities with the bone tissue mineral phase. Several works have been spotlighted on the thermal behavior of bone. However, little research has focused on determining the influence of calcination temperature in the physicochemical and bioactive properties of BHAp. In this work, a study of the physicochemical properties’ changes and bioactive response of BHAp produced from porcine femur bones using calcination temperatures between 900 to 1200 °C was conducted. The samples’ structural, morphological, and compositional changes were determined using XRD, SEM, and FTIR techniques. XRD results identified three temperature ranges, in which there are structural changes in BHAp samples and the presence of additional phases. Moreover, FTIR results corroborated that B-type substitution is promoted by increasing the heat treatment temperature. Likewise, samples were immersed in a simulated biological fluid (SBF), following the methodology described by Kokubo and using ISO 23317:2014 standard, for 3 and 7 days. FTIR and SEM results determined that the highest reaction velocity was reached for samples above 1000 °C, due to intensity increasing of phosphate and carbonate bands and bone-like apatite morphologies, compared to other temperatures evaluated.

Reactivity of solid BaCe0.9Y0.1O3 towards liquid V2O5

In this work the reactivity in solid BaCe0.9Y0.1O3-δ - liquid V2O5 system was investigated in order to evaluate the possibility of composite formation in this system. Impregnation of melted vanadium(V) oxide into solid Y-doped BaCeO3 was performed in various temperature and time conditions. Due to the relatively high reactivity of components in this system an analysis of the synthesized materials was divided into discussion of the properties of the reactive layer and the inner part. As was shown, decomposition of Y-doped BaCeO3 in contact with melted vanadium(V) oxide occurs already at temperature 700 °C and results in formation of CeVO4 as one of the main phases. Moreover, the presence of Ba8V7O22 as the intermediate phase was observed. The extension of reaction time and increase of temperature resulted in significant changes in the microstructure and chemical composition of the reactive layer. The incorporation of vanadium into yttrium doped BaCeO3 structure for inner parts of the synthesized materials was postulated based on the modification of the materials electrical properties and chemical stability towards CO2 and H2O. Also, the presence of additional phase in the intergranular voids of doped-BaCeO3 was suggested.

Investigation of Pristine Li1.2Ni0.13Mn0.56Co0.13O2 By Advanced TEM

Layered Li-transition metal (TM) oxides are very promising materials for new Li ion battery cathodes. Compounds with an increased content of Li and Mn are particularly interesting because they exhibit a high capacity of 200-300 mAhg-1 even after an initial drop in capacity during the first charging cycle.[1] The structure of such compounds and their capacity degradation over multiple cycles is not fully understood due to the complexity of the crystallographic phases, the ambiguities in the diffraction data and the presence of additional phases. The investigated compound Li1.2Ni0.13Mn0.56Co0.13O2 is derived from LiNi0.33Mn0.33Co0.33O2, (NMC). Due to the higher capacity of the Li-rich compound, it will be referred to as high energy NMC (HENMC).[2] The chemical formula of HENMC can be rewritten as Li2MnO3 · LiNi0.33Mn0.33Co0.33O2 which implies that this compound is a mixture of trigonal NMC and monoclinic Li2MnO3. In NMC, there are two different cation layers which are exclusively occupied by Li and TM respectively. In Li2MnO3 one third of the TM sites are occupied by Li. HENMC must be either a phase mixture with distinct domains of the two oxides or a solid solution of the two, with “Li rich” positions in the TM layers and an overall reduced, monoclinic symmetry (Figure 1).[3] The exact nature of HENMC and similar materials is crucial to understand the de-lithiation processes during charging cycles. The layered structure and its relation to other phases was investigated with a combination of electron diffraction in bright-field and scanning modes with high resolution transmission electron microscopy (HRTEM) and high-angle annular dark-field scanning TEM (HAADF-STEM) imaging. Due to the high structural similarity of NMC and Li2MnO3, all lattice distances which can be found for NMC can also be found for Li2MnO3; as seen in the respective electron diffraction patterns (Figure 2). HAADF-STEM imaging reveals the presence of Li-rich positions in the TM layers as indicated by a lower intensity of the related atom columns (Figure 3). Due to the stacking faults of the TM layers, the interpretation of contrast in any other orientation becomes by far less intuitive as we will demonstrate. A LiTM2O4 spinel phase is found on the surface quite frequently. Its relation to the bulk phase was derived from high resolution images. STEM-EELS revealed the presence of surface reduction due to oxygen depletion in HENMC. This work thus provides structural information about the synthesized material in its pristine state to facilitate understanding the changes the material undergoes during the (de-)lithiation segments of electrochemical cycling. Further investigations on such effects are currently being carried out and will be discussed. [1] B. L. Ellis, K. T. Lee, L. F. Nazar, Chem. Mater. 2010, 22, 691-714. [2] C. S. Johnson, N. Li, C. Lefief, J. T. Vaughey, M. M. Thackeray, Chem. Mater. 2008, 20, 6095-6106. [3] H. Yu, H. Zhou, J. Phys. Chem. Lett. 2013, 4, 1268−1280. Figure 1

Photocatalytic activity of V doped ZnO nanoparticles thin films for the removal of 2- chlorophenol from the aquatic environment under natural sunlight exposure

Vanadium doped ZnO powders were used as precursors to deposit thin films of V5+ incorporated ZnO nanoparticles on glass substrates by the pulsed laser deposition technique. The observed variations in Raman signals, visible region shift in the diffuse reflectance spectra along with a small shift in the (101) reflections of the X-ray diffraction (XRD) confirmed the insertion of V5+ ions in ZnO lattice. No other additional reflection in the XRD results other than ZnO further endorsed the occupation of lattice positions by V entities rather than independent oxide formation. The asymmetric XPS peaks of Zn2p and V2p core levels confirmed the existence of both in the vicinity. The existence of minimal proportion of V3+ along with V5+ states varied the alteration of the oxidation states V in the synthetic route. The SEM images at various resolutions displayed the uniform distribution identical nanoparticles without the presence of additional phases in the deposited films. The SEM cross-section measurements revealed the uniform thickness of ∼90 nm of each film, whereas the surface studies of the films were performed by AFM. The as-synthesized films were tested for photocatalytic activity in sunlight illumination for the removal of 2-chlorophenol. The unique feature of the study was the estimation of the photocatalytic activity 20 ppm of 2-chlorophenol by exposing the low exposed area. The degradation of the substrate was measured by liquid phase UV–vis spectroscopy, whereas total organic carbon measurement revealed the mineralization of the substrate. The released Cl− ions were also measured by ion chromatography. The estimated flatband potentials and pHzpc values of the V doped materials, by Mott-Schottky analysis and zeta potential measurements respectively, were correlated with the photocatalytic activity. The kinetics of the photocatalytic degradation/mineralization process was estimated and results were correlated with the plausible mechanism.

Effect of Tungsten and Molybdenum on the Crystallization, Microstructure and Properties of Silumin 226

Abstract The work presents the results of the examinations of silumin 226 as well as a silumin produced on its basis containing a W and Mo addition introduced in the amount of 0.1; 0.2; 0.3 and 0.4% of both elements simultaneously. Investigations of the crystallization process of the silumins by the TDA method were conducted. Also, a microscopic analysis of their microstructure was performed and their basic mechanical properties were determined. Microstructure tests were made on casts produced in an TDA sampler as well as by the pressure method. The investigations exhibited a change in the course of crystallization of the silumin containing 0.3 and 0.4% W and Mo with respect to silumin 226 and the silumin with the addition of 0.1 and 0.2%. The presence of additional phases which did not occur in the case of lower addition contents was established in the silumin containing 0.3-0.4% W and Mo, regardless of the applied casting technology. The tests showed the possibility of increasing the tensile strength Rm, the proof stress Rp0,2 and the unit elongation A of the silumin as a result of a simultaneous introduction of the W and Mo addition. The highest values of Rm, Rp0,2 and A were obtained in the silumins with the additions of these elements within the range of 0.1-0.2% each.

Local Structure and Bonding of Transition Metal Dopants in Bi2Se3 Topological Insulator Thin Films

Transition metal (TM) doped topological insulators have been the focus of many recent studies since they exhibit exotic quantum and magneto-electric effects, and offer the prospect of potential applications in spintronic devices. Here we report a systematic study of the local electronic and structural environment using X-ray absorption fine structure (XAFS) in TM (=Cr, Mn, and Fe) doped Bi2Se3 thin films grown by molecular beam epitaxy. Analysis of the TM K-edge XAFS reveals a divalent character for Cr, Mn, and Fe when substituting Bi in the films, despite the trivalent character of the Bi. All dopants occupy octahedral sites in the Bi2Se3 lattice, which agrees with substitutional incorporation onto the Bi sites. With the incorporation of TM dopants a local structural relaxation of the Bi2Se3 lattice is observed, which strengthens the covalent character of the TM–Se bond. The presence of additional phases and interstitial incorporation for the Mn and Fe dopants is also observed, even at low concentrations.

Influence of Substrate on Hafnium Silicate Metal-Insulator-Metal Capacitors Grown by Atomic Layer Deposition

Metal insulator metal (MIM) capacitors are fundamental components of the electronic circuitry commonly found in many devices in areas such as analogue to digital conversion, micro-electromechanical systems, medical, automotive and memory applications [1-4]. Current MIMCAPS generally employ optimised low dielectric constant (k) materials (k~3.9 - 7) to attain the target electrical properties of high breakdown field and low current leakage. However, device scaling is limited due to the low k value of these materials and this presents a significant challenge to the future development of these technologies [5]. Many high k materials are under investigation to replace these lower k dielectrics to substantially increase the maximum capacitance density and reduce the area associated with the integration of MIM structures. In this work we investigate the growth of hafnium silicate films by plasma assisted atomic layer deposition on a metal electrode. The hafnium silicate film was deposited using Tetrakis(dimethylamino)hafnium (TDMAHf) and Tetrakis(dimethylamino)silane (TDMASi) precursors at 250oC with a remote oxygen plasma (300 W). From HR-TEM analysis and Raman spectroscopy it has been observed that the main crystalline phase is monoclinic HfO2. This crystallographic phase appears to be templated by the underlying titanium adhesion (10 nm) layer through the platinum electrode (200 nm). The HR TEM analysis also reveals the presence of nanoparticles, located primarily towards the lower platinum metal layer. Based on electron energy loss spectroscopy (EELS) analysis the nanoparticles are consistent with silicon oxide inclusions, located at HfO2 grain boundaries. In addition, the presence of additional phases was detected; these included a super-cell structure within the bulk and an amorphous phase. No hysteresis was observed in the capacitance voltage measurements and the material was observed to exhibit a k value of ~18.

Effect of temperature on structural, optical and photoluminescence properties of polycrystalline CuInS2 thin films prepared by spray pyrolysis

Copper indium disulphide (CuInS2), is a good absorber material for photovoltaic applications. In this work, CuInS2 is deposited by chemical spray pyrolysis on heated glass substrates. It is observed that the film growth temperature and the ion ratio Cu/In affects the structural and optical properties of CuInS2 thin films. This paper presents the effect of temperature on the growth (for the ion ratio Cu/In=1.25), optical and photoluminescence properties of sprayed CuInS2 films. The XRD patterns confirm the well defined single phase composition of CuInS2 films grown from 300 to 350 °C (at Cu/In=1.25) as optimum temperature for depositing well defined crystallites along (1 1 2) oriented CuInS2 thin films with chalcopyrite structure. D2d point symmetry group is associated with the CuInS2 crystallites with energy gap of 1.53 eV at room temperature. The chemical nature and the presence of additional phases are discussed based on the EDAX measurements. The absorption coefficient of sprayed CuInS2 films is found to be in the order of 105–106 cm−1 in the UV–visible region and the optical band gap decreases with increase in temperature. Defects-related photoluminescence properties are also discussed. CuInS2 polycrystalline films are prepared by the cost effective method of spray pyrolysis from the aqueous solutions of copper (II) chloride, indium (III) chloride and thiourea for synthesis on heated glass substrates.

Photoluminescent BaMoO 4 nanopowders prepared by complex polymerization method (CPM)

The BaMoO 4 nanopowders were prepared by the Complex Polymerization Method (CPM). The structure properties of the BaMoO 4 powders were characterized by FTIR transmittance spectra, X-ray diffraction (XRD), Raman spectra, photoluminescence spectra (PL) and high-resolution scanning electron microscopy (HR-SEM). The XRD, FTIR and Raman data showed that BaMoO 4 at 300 °C was disordered. At 400 °C and higher temperature, BaMoO 4 crystalline scheelite-type phases could be identified, without the presence of additional phases, according to the XRD, FTIR and Raman data. The calculated average crystallite sizes, calculated by XRD, around 40 nm, showed the tendency to increase with the temperature. The crystallite sizes, obtained by HR-SEM, were around of 40–50 nm. The sample that presented the highest intensity of the red emission band was the one heat treated at 400 °C for 2 h, and the sample that displayed the highest intensity of the green emission band was the one heat treated at 700 °C for 2 h. The CPM was shown to be a low cost route for the production of BaMoO 4 nanopowders, with the advantages of lower temperature, smaller time and reduced cost. The optical properties observed for BaMoO 4 nanopowders suggested that this material is a highly promising candidate for photoluminescent applications.

Optical and conductive properties of AlSi-alloy/SiC p composites: application in modelling CO 2 laser processing of composites

The optical properties—reflectivity, real part of the refractive index, absorption coefficient as well as the thermal and electrical conductivity of AlSi-alloy/SiC p composite were measured. The optical parameters and both conductivities decreased with the increase of SiC p particles volume in AlSi-alloy matrix. This decrease was almost linear for the volume fraction of SiC p particle up to 10 vol% of the total mass of the composite. For the 15 vol% of SiC p particles, the departure from linearity is connected with the presence of additional phases in AlSi-alloy/SiC p composite materials. The measured temperature dependencies of optical reflectivity and electrical conductivity for AlSi-alloy/SiC p 15 vol% are of metallic character. Modelling of the interaction of the CO 2 laser radiation with AlSi-alloy/SiC p 15 vol% composite should allow to estimate the initiation time at which the surface composite reaches melting temperature.

EXELFS as a tool for quantifying phase distributions in materials

A method has been developed to quantify phase distributions in multiphase materials by using the information contained in the EXtended Energy Loss Fine Structure (EXELFS) of a probe atom in an Electron Energy Loss Spectroscopy (EELS) spectrum. The EELS and EXELFS determine, in addition to the atomic composition, the near-neighbor atomic environment about each atom type separately. The method is applicable to electron-transparent foils observed in a Transmission Electron Microscope (TEM) equipped with a parallel-detection electron energy loss spectrometer. The relative amounts of phases that have a common element can be determined even in the presence of additional phases which do not share that common element. The method is particularly applicable to layered materials and can be used, for example, to determine the local relative thickness of a metal and its oxide layer. The Mg MgO system was used to demonstrate the method, and it was found that the accuracy in relative thickness determination is about 5%. The near-edge fine structure information was consistent with the results of the EXELFS analysis.

Structure and morphology of the 60/40 poly(p‐oxybenzoate‐co‐ethylene terephthalate) copolymer

AbstractThe copolyester composed of 60 mol% p‐hydroxybenzoic acid and 40 mol% ethylene terephthalate has been studied extensively by earlier workers. However, some confusion exists particularly with respect to the nature of the thermal transitions and the possible presence of additional phases. In the present study we have examined this copolyester and found that it is possible to separate the material into soluble and insoluble fractions with significantly different ratios of p‐hydroxybenzoic acid to ethylene terephthalate. In fact, the soluble PET‐rich fraction is blocky in nature, while the PHBA‐rich fraction is more random. The multiple thermal transitions can now be readily interpreted in terms of a heterogeneous composition which tends to segregate and phase separate.

Review of Oxygen Activities and Phase Boundaries in Wustite as Determined by Electromotive‐Force and Gravimetric Methods

All data available in the literature regarding oxygen activities and composition limits for the wustite phase were analyzed critically. The most reliable activity data were collected into a composite in which (1) the partial molal free energy of oxygen varied linearly with composition and reciprocal temperature and (2) the partial molal enthalpy and entropy of oxygen varied linearly with composition and were independent of temperature. These linear variations of the thermodynamic properties are inconsistent with the presence of additional phases which have been reported within the wustite phase field. The composition limits of the wustite phase, which were computed from the composite, were in excellent agreement with Darken and Gurry's original phase diagram.