A simple microwave approach for synthesis and characterization of Ag2S–AgInS2 nanocomposites

Ag₂S–AgInS₂ nanocomposites, with the aid of [Ag(HSal)] and InCl₃ as starting reagents, have been successfully synthesized by a microwave process from propylene glycol solution. Besides, the effects of preparation parameters such as irradiation time, solvents and sulfur source on the morphology and particle size of products were studied by SEM images. The synthesis procedure is novel, simple and uses less toxic reagents. The prepared Ag₂S–AgInS₂ nanostructures were characterized extensively by means of X-ray diffraction (XRD), energy-dispersive X-ray analysis (EDX), scanning electron microscopy (SEM), transmission electron microscopy (TEM), infrared (IR) spectrum, photoluminescence (PL) spectroscopy. The fill factor (FF), open circuit voltage (V_oc), and short circuit current (I_sc) were obtained by I–V characterization.     

Novel and simple route for the synthesis of core–shell chitosan–gold nanocomposites

This work presents a novel and simple route for the synthesis of water-soluble core–shell chitosan–gold nanocomposites. The experimental procedure can be summarized by the following steps: (i) chitosan deacetylation, (ii) chitosan depolymerization, (iii) chitosan nanoparticles’ formation and (iv) chitosan–gold nanocomposite formation. FT-IR spectroscopic results indicate that the formation of chitosan nanoparticles (ChtNPs) occurs via NH₃⁺ and PO⁻ groups electrostatic interactions, while UV–vis spectra points to a possible embedding of gold nanoparticles into the ChtNPs. This feature was confirmed by electronic transmission microscopy measurements. Chitosan and gold are biocompatible materials. Added to this, the obtained chitosan–gold nanocomposites presented thermal and absorbance properties which strongly point to their potential use in phototherapeutic processes.     

Microstructure,mechanical and wear properties of Cu–ZrO2 nanocomposites

Cu–ZrO₂ nanocomposites were produced by the thermochemical process followed by powder metallurgy technique. Microstructure development during fabrication process was investigated by X-ray diffraction, field emission scanning electron microscope and transmission electron microscope. The results show an improved distribution of zirconium dioxide (ZrO₂) nanoparticles (45?nm) in the copper matrix, which resulted in the improvement of mechanical properties of Cu–ZrO₂ composites. The nanocomposite with 9 wt-% ZrO₂ possesses the highest hardness (136.5 HV) and the superior compressive strength (413.5?MPa), resulting in an overall increase by 52 and 25%, respectively. The wear rate of the nanocomposites increased with increasing applied loads or sliding velocity.     

Synthesis and characterization of barium ferrite–silica nanocomposites

In this work, we prepared barium ferrite-silica (BaM-SiO₂) nanocomposites of different molar ratios by high-energy ball milling, followed by heat-treatment at different temperatures. The microstructure, morphology and magnetic properties were characterized for different synthesis conditions by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometry (VSM). The results indicate that 15 h of milling was enough to avoid the generation of hematite phase and to get a good dispersion of barium ferrite particles in the ceramic matrix. For milling periods beyond 15 h and heat treatment above 900 °C, the XRD patterns showed the presence of hematite phase caused by the decomposition of BaM. The agglomerate size observed through SEM analysis was around 150 nm with a good BaM dispersion into the SiO₂ matrix. The highest saturation magnetization (Ms) value obtained was 43 emu/g and the corresponding coercivity (Hc) value of 3.4 kOe for the composition 60BaM-40SiO₂ milled for 15 h and heat treated at 900 °C. This coercivity value is acceptable for the application in magnetic recording media.     

Preparation and characterization of ZrO2 and SO42−-promoted ZrO2

The acid-base and oxidizing properties and the structures of ZrOn prepared with ammonia or urea and ZrO₂ treated with sulfuric acid or ammonium sulfate have been investigated. The treatment of ZrO₂ with so₄²⁻ caused the remarkable increases in the phase transition temperature to monoclinic form, the surface area and the acid strength and the appearance of the oxidizing property. The acid strength was higher for ZrO₂ treated with H₂SO₄ than for ZrO₂ treated with (NH₄)₂SO₄, though the surface area was the reverse. The difference between ammonia and urea as precipitating reagents caused no difference in crystallography and acid strength, but the surface areas of ZrO₂-A and ZrO₂-A-H₂SO₄ prepared with ammonia were higher than those of ZrO₂-U and ZrO₂-U-H₂SO₄ prepared with urea, respectively.     

Preparation and characterization of PAN–KI complexed gel polymer electrolytes for solid-state battery applications

The free standing and dimensionally stable gel polymer electrolyte films of polyacrylonitrile (PAN): potassium iodide (KI) of different compositions, using ethylene carbonate as a plasticizer and dimethyl formamide as solvent, are prepared by adopting ‘solution casting technique’ and these films are examined for their conductivities. The structural, miscibility and the chemical rapport between PAN and KI are investigated using X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry methods. The conductivity is enhanced with the increase in KI concentration and temperature. The maximum conductivity at 30°C is found to be 2.089 × 10^?5 S cm^?1 for PAN:KI (70:30) wt%, which is nine orders greater than that of pure PAN (< 10^?14 S cm^?1). The conductivity-temperature dependence of these polymer electrolyte films obeys Arrhenius behaviour with activation energy ranging from 0.358 to 0.478 eV. The conducting carriers of charge transport in these polymer electrolyte films are identified by Wagner’s polarization technique and it is found that the charge transport is predominantly due to ions. The better conducting sample is used to fabricate the battery with configuration K/PAN + KI/I₂+ C + electrolyte and good discharge characteristics of battery are observed.     

Preparation and characterization of self-assembled percolative BaTiO3–CoFe2O4 nanocomposites via magnetron co-sputtering

BaTiO₃–CoFe₂O₄ composite films were prepared on (100) SrTiO₃ substrates by using a radio-frequency magnetron co-sputtering method at 750 °C. These films contained highly (001)-oriented crystalline phases of perovskite BaTiO₃ and spinel CoFe₂O₄, which can form a self-assembled nanostructure with BaTiO₃ well-dispersed into CoFe₂O₄ under optimized sputtering conditions. A prominent dielectric percolation behavior was observed in the self-assembled nanocomposite. Compared with pure BaTiO₃ films sputtered under similar conditions, the nanocomposite film showed higher dielectric constants and lower dielectric losses together with a dramatically suppressed frequency dispersion. This dielectric percolation phenomenon can be explained by the ‘micro-capacitor’ model, which was supported by measurement results of the electric polarization and leakage current.     

Synthesis and characterization of polymetalate based photochromic inorganic–organic nanocomposites

A novel reversible photochromic nanocomposite film based on a hybrid inorganic–organic matrix in which heteropolyacid H₃PW₁₂O₄₀ (PWA) was entrapped was prepared. The structure, photochromic behaviors and mechanism of the film were investigated by means of infrared (IR) spectroscopy, UV-Vis absorption spectra and electron spin resonance (ESR). The results showed that heteropolyanion, i.e. PW₁₂O₄₀³⁻ (PW₁₂), maintained a Keggin structure in the film and there was a strong interaction between anion PW₁₂ and cation R–NH₃⁺ (R=link of hybrid composite). The photochromic properties of the composite film originated from the reversible charge transfer between the anions and cations. Under ultraviolet (UV) irradiation, the anion would be reduced via one-electron step with simultaneous oxidation of the cation, accompanied by a color change from colorless to blue. Then the bleaching could occur when the film was in contact with ambient air or O₂ in the dark.     

Fabrication of CdO–Bi2O3 Ceramics

The phase formation in the CdO-rich part (10 wt % Bi₂O₃) of the CdO–Bi₂O₃ system was studied by x-ray diffraction, IR spectroscopy, electron microscopy, and other techniques. The results indicate that the grinding of the starting powder mixtures in a planetary mill leads to an inhomogeneous Bi₂O₃ distribution and a high defect density in the CdO and Bi₂O₃ particles. Sintering in the range 910–990 K gives rise to the formation of the _h phase, whose content depends strongly on the mixture composition and sintering conditions. At sintering temperatures above its melting point, the _h phase acts as a binder of CdO grains.     

Controllable synthesis and characterization of Ag@AgBr core–shell nanowires

Ag@AgBr core–shell nanowires have been synthesized in large quantities via a redox reaction between Ag nanowires and FeBr₃ in solution at room temperature. The effect of the molar ratio of Fe:Ag on the formation and optical absorption of the Ag@AgBr core–shell nanowires was systematically studied. The results showed that Ag nanowires were converted into Ag@AgBr core–shell nanowires and finally into AgBr nanorods with the increase of the molar ratio of Fe:Ag. At the same time, the optical absorption of Ag nanowires decreased gradually and disappeared finally. In addition, the growth mechanism of the Ag@AgBr core–shell nanowires was also discussed in detail.     

Sol–gel synthesis and characterization of mesoporous manganese oxide

Mesoporous manganese oxide (MPMO) from reduction of KMnO₄ with maleic acid, was obtained and characterized in detail. The characterization of the material was confirmed by high-resolution transmission electron microscopy (HRTEM), X-ray powder diffractometry (XRD) and N₂ sorptometry. The results showed that MPMO is a pseudo-crystalline material with complex network pore structure, of which BET specific surface area is 297 m²/g and pore size distribution is approximately in the range of 0.7–6.0 nm. The MPMO material turns to cryptomelane when the calcinating temperature rises to 400 °C. The optimum sol–gel reaction conditions are KMnO₄/C₄H₄O₄ molar ratio=3, pH=7 and gelation time>6 h.     

Microwave assisted hydrothermal synthesis of well-dispersed and thermally stable Ag@SnO2 core–shell nanocomposites for propane sensing applications

A simple microwave assisted hydrothermal precipitation (M–H) technique for the synthesis of Ag@SnO₂ core–shell structure nanoparticles (NPs) is reported. Ag NPs were synthesized via chemical reduction of metal salt followed by M–H deposition of tin dioxide shell for fabrication of monodispersed core–shell particles. The phase and morphology has been investigated by X-ray diffraction technique (XRD) and transmission electron microscopy (TEM) respectively. Ag@SnO₂ core–shell nanocomposites have shown distinct surface Plasmon spectrum in the range of 407–440 nm. The core–shell morphology is confirmed from the TEM images. XRD patterns have suggested the formation of silver and tin dioxide in the face-centered cubic and Cassiterite form respectively. Our investigations suggested that the formation of core–shell structure results in the enhanced thermal stability of the system. Synthesized material is used for the detection of propane gas. To understand the multi gas sensing ability and selectivity for detection of propane gas by Ag@SnO₂ core–shell materials based devices, Sinha–Tripathy soft-sensor model has been proposed.     

Synthesis and characterization of chitosan–multiwalled carbon nanotubes/hydroxyapatite nanocomposites for bone tissue engineering

Chitosan–multiwalled carbon nanotubes/hydroxyapatite nanocomposites were synthesized by a novel in situ precipitation method. The electrostatic adsorption between multiwalled carbon nanotubes and chitosan was investigated and explained by Fourier transform infrared spectroscopy analysis. Morphology studies showed that uniform distribution of hydroxyapatite particles and multiwalled carbon nanotubes in the polymer matrix was observed. In chitosan–multiwalled carbon nanotubes/hydroxyapatite nanocomposites, the diameters of multiwalled carbon nanotubes were about 10 nm. The mechanical properties of the composites were evaluated by measuring their compressive strength and elastic modulus. The elastic modulus and compressive strength increased sharply from 509.9 to 1089.1 MPa and from 33.2 to 105.5 MPa with an increase of multiwalled carbon/chitosan weight ratios from 0 to 5 %, respectively. Finally, the cell biocompatibility of the composites was tested in vitro, which showed that they have good biocompatibility. These results suggest that the chitosan–multiwalled carbon nanotubes/hydroxyapatite nanocomposites are promising biomaterials for bone tissue engineering.     

Fabrication and characterization of ZrO2–CaO–P2O5–Na2O–SiO2 bioactive glass ceramics

SiO₂–CaO–Na₂O–P₂O₅–ZrO₂ based bioactive glasses with different compositions of SiO₂ and yttrium stabilized ZrO₂ were prepared by the conventional melt quenching technique. The effects on the chemical–mechanical properties of bioactive glasses due to the addition of ZrO₂ by replacing SiO₂ were investigated. Microstructure and phase behavior were studied by scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis. Compressive strength, porosity, Vickers hardness, and Young’s modulus were measured as mechanical properties. Bioactivity and cell viability were investigated by immersion in simulated body fluid and MTT assay analysis. Osteosarcoma cell proliferation on the specimen surfaces was examined by confocal laser scanning microscopy. The results showed that replacing SiO₂ with ZrO₂ helps the bioactive glass to be completely vitrified at comparatively lower sintering temperature than conventional Bioglass^®. The mechanical properties were also improved without compromising biocompatibility. Bioactive glass containing 10 wt% ZrO₂ and 35 wt% SiO₂ showed compressive strength of 399.71 MPa, Young's modulus of 22.3 GPa, Vicker’s hardness of 502.54 HV, and porosity of 26 vol%.     

Combustion synthesis and structural characterization of Li–Ti mixed nanoferrites

Polycrystalline samples of the mixed nanoferrites, Li_{0·5 + 0·5x} Ti _x Fe_{2·5 − 1·5x} O₄ (0·02 ≤ x ≤ 0·1), were prepared by combustion method at lower temperatures compared to the conventional high temperature sintering for the first time at low temperatures, using PEG which acts as a new fuel and oxidant. XRD patterns reveal a single-phase cubic spinel structure. The as synthesized Li–Ti ferrites are in nanocrystalline phase. The crystallite size was found to be in the range 16–27 nm. SEM images reveal rod-like morphology in all the samples with a discontinuous grain growth. The B–H loops have been traced using VSM technique, for all the compositions, at room temperature and the hysteresis parameters are calculated. Saturation magnetization decreases with increase in Ti content due to the fact that the Ti^4 + ion, which is a non-magnetic ion, replaces a magnetic Fe^3 + ion. The hysteresis loops show clear saturation at an applied field of ±10 kOe and the loops are highly symmetric in nature. The cation distribution is known indirectly by using saturation magnetization values.     

Microwave assisted hydrothermal synthesis and characterization of ZnO–TNT composites

TiO₂ nanotubes with different contents of ZnO (3–40 wt.% ZnO) have been successfully synthesized by microwave assisted hydrothermal process by using commercial TiO₂-P25 as a precursor. The phase and crystallinity of the obtained ZnO–TNT were analyzed by X-ray Diffraction (XRD). The surface area of the ZnO–TNT was determined by BET method. The effect of the different contents of ZnO on morphology of TiO₂ nanotubes was investigated by SEM and TEM. Optical properties and band gap energy of ZnO–TNT were calculated by using UV–vis DRS spectroscopy and modified Kubelka–Munk equation. Photocatalytic performance of ZnO–TNT was investigated by degradation of rhodamine B (RhB) dye under UV and visible light irradiation. Increasing ZnO content in TNT gradually decreased the diameter and length of nanotubes. Furthermore, addition of 40 wt.% ZnO into the TNT exceeded the saturation limit of ion exchangeability of Zn²⁺ and Na⁺ ions and aggregation of finely dispersed ZnO particles on the surface of TNT were observed. The ZnO–TNT has shown relatively larger band gap energies than that of TiO₂-P25. However, ZnO–TNT has shown considerable increase in photo-activity for degradation of RhB dye in visible light as compared to UV light irradiation.