Preparation and tribological properties of polyurethane/α-aluminum oxide hybrid films

This study focused on the preparation and tribological properties of polyurethane/α-aluminum oxide (PU/α-Al₂O₃) hybrid films. PU/α-Al₂O₃ hybrid films containing various nanoscaled α-Al₂O₃ contents were prepared by an effectively mechanical stirring method. The tribological properties of PU/α-Al₂O₃ hybrid films were investigated by a TABER type abrasion tester after 2000 cycles. The results of abrasion tests showed the abrasion resistance of the PU/α-Al₂O₃ hybrid film was increased as the α-Al₂O₃ content was increased. The abrasion resistance of the PU/α-Al₂O₃ hybrid film was significantly improved up to 27.4% by adding 2 wt.% nanoscaled α-Al₂O₃ particles. The surface morphologies of PU/α-Al₂O₃ hybrid films, before and after abrasion tests, were examined by scanning electron microscopy (SEM). For the loading of 2 wt.% α-Al₂O₃ particles, the SEM image of the worn surface of the PU/α-Al₂O₃ hybrid film showed much smoother than those of pure PU film and other PU/α-Al₂O₃ hybrid films.     

Mechanical and dielectric properties of epoxy–clay nanocomposites

Epoxy–clay nanocomposites were prepared using two types of surface-treated montmorillonite (Closite 30B and Nanomer I28E). Wide angle X-ray scattering showed that all the nanocomposites had an intercalated structure. Improvements in tensile and fracture properties were found. The pure epoxy polymer was very brittle with a fracture energy, G _c, of 131 J m^?2. The addition of the nanoclays significantly increased the value of G _c, up to 240 J m^?2 for 5 wt% C30B. The toughening mechanisms acting in the nanocomposites were identified using scanning electron microscopy as crack deflection and plastic deformation of the epoxy matrix around the clay platelets following debonding. From electrical testing, the permittivity and loss angle of the nanocomposites decreased, and their breakdown strength increased as desired for insulation applications. The breakdown strength of the pure epoxy was found to be 11.7 kV mm^?1, while for a 2 wt% C30B nanocomposite, it increased to 14.7 kV mm^?1. It was concluded that the restriction of chain mobility inhibited electrical polarisation and thus decreased the permittivity and loss angle. The electrical damage zone was analysed using scanning electron microscopy. It was found that the higher resistance-to-surface degradation by partial discharges and the creation of a tortuous electrical path, which delayed the propagation of the electrical tree, were the main factors which improved the breakdown strengths of the nanocomposites.     

Preparation and characterization of hydroxyapatite/polycaprolactone–chitosan composites

Hydroxyapatite (HA)/polycaprolactone (PCL)–chitosan (CS) composites were prepared by melt-blending. For the composites, the amount of HA was varied from 0% to 30% by weight. The morphology, structure and component of the composites were evaluated using environmental scanning electron microscope, X-ray diffraction and Fourier transform infrared spectroscope. The tensile properties were evaluated by tensile test. The bioactivity and degradation property were investigated after immersing in simulated body fluid (SBF) and physiological saline, respectively. The results show that the addition of HA to PCL–CS matrix tends to suppress the crystallization of PCL but improves the hydrophilicity. Adding HA to the composites decreases the tensile strength and elongation at break but increases the tensile modulus. After immersing in SBF for 14 days, the surface of HA/PCL–CS composites are covered by a coating of carbonated hydroxyapatite with low crystallinity, indicating the excellent bioactivity of the composites. Soaking in the physiological saline for 28 days, the molecular weight of PCL decreases while the mass loss of the composites and pH of physiological saline increase to 5.86% and 9.54, respectively, implying a good degradation property of the composites.     

Preparation and characterization of β-elemene-loaded microemulsion

Intravenously injectable emulsion of β-elemene was studied in detail. Both blank and β-elemene-loaded microemulsions were prepared using a simple water titration method. The pseudoternary phase diagram was constructed for the optimization of microemulsion. The loading capacity test, dilutability test, and especially the influence of antioxidants were conducted for further optimization of β-elemene-loaded microemulsion. Transmission electron microscope showed intact and spherical microemulsion droplets. Conductivity and viscosity measurements were used to study the phase behaviors of β-elemene-loaded microemulsions, providing convincing explanation. In vitro release study showed that β-elemene was steadily released until 12?h, which most fitted the first order.     

Preparation and characterization of β-elemene-loaded microemulsion

Intravenously injectable emulsion of β-elemene was studied in detail. Both blank and β-elemene-loaded microemulsions were prepared using a simple water titration method. The pseudoternary phase diagram was constructed for the optimization of microemulsion. The loading capacity test, dilutability test, and especially the influence of antioxidants were conducted for further optimization of β-elemene-loaded microemulsion. Transmission electron microscope showed intact and spherical microemulsion droplets. Conductivity and viscosity measurements were used to study the phase behaviors of β-elemene-loaded microemulsions, providing convincing explanation. In vitro release study showed that β-elemene was steadily released until 12?h, which most fitted the first order.     

Preparation and electrochemical characterization of lithium cobalt oxide nanoparticles by modified sol–gel method

Uniformly distributed nanoparticles of LiCoO₂ have been synthesized through the simple sol–gel method in presence of neutral surfactant (Tween-80). The powders were characterized by X-ray diffractometry, transmission electron microscopy and electrochemical method including charge–discharge cycling performance. The powder calcined at a temperature of 900 °C for 5 h shows pure phase layered LiCoO₂. The results show that the particle size is reduced in presence of surfactant as compared to normal sol–gel method. Also, the sample prepared in presence of surfactant and calcined at 900 °C for 5 h shows the highest initial discharge capacity (106 mAh g^?1) with good cycling stability as compared to the sample prepared without surfactant which shows the specific discharge capacity of 50 mAh g^?1.     

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 theophylline loaded chitosan/β-cyclodextrin microspheres

The purpose of this project was to develop sustained release chitosan/β-cyclodextrin microspheres of theophylline (TH) prepared by spray drying method. The effect of several formulation variables on the characteristics of microspheres was studied. The B microspheres had a narrower particle size distribution with the diameter between l and 10 μm. SEM showed spherical microspheres with smooth or slightly wrinkled surfaces. FT-IR spectroscopy revealed that hydrogen bonds were formed between TH and chitosan or β-cyclodextrin. The drug entrapments significantly increased from 13.33 to 35.70% with an increase of the ratio of drug/polymer. The encapsulation efficiencies were from 85.16 to 91.40%. The in vitro release of TH from microspheres was related to the pH of the medium, swelling ability, especially in the ratio of drug/polymer. The B microspheres had a prolonged release pattern with the release rate of 60.20% (pH 6.8) within 8 h.     

Fabrication and characterization of superparamagnetic nanocomposites based on epoxy resin and surface-modified γ-Fe2O3 by epoxide functionalization

In this study, the effect of modified epoxide-terminated γ-Fe₂O₃ on the magnetic, mechanical, and thermal properties of epoxy nanocomposite was investigated. The γ-Fe₂O₃ nanoparticles were prepared via a wet chemical approach, surface modified with 3-glycidoxypropyltrimethoxysilane (GPTMS), and characterized by particle size analyzer, XRD, FT-IR, and TGA techniques. The catalytic effect of γ-Fe₂O₃ on the cure reaction temperature of epoxy/triethylenetetramine (TETA) was determined by differential scanning calorimeter (DSC). The glass transition temperature (T _g) of nanocomposite containing 5 wt% modified γ-Fe₂O₃ increased slightly (12 °C), while the initial decomposition temperature (T _ID) did not show improvement. Transmission electron microscopy (TEM) showed improvement in dispersion of surface-modified γ-Fe₂O₃ nanoparticles in the resin matrix. The effect of interfacial bonding between modified γ-Fe₂O₃ and epoxy resin, via crosslink reactions, on the mechanical properties of nanocomposite such as flexural and tensile strength was studied, and the fractured surface of samples was investigated by scanning electron microscopy (SEM). Comparing with the mechanical properties of neat epoxy resin, tensile, and flexural strength of 10 wt% modified γ-Fe₂O₃/epoxy nanocomposite increased 20 and 19 %, respectively, while tensile and flexural strength of 10 wt% unmodified/epoxy nanocomposite decreased slightly. The saturation magnetization (M _s) of 5 wt% modified γ-Fe₂O₃/epoxy nanocomposites with superparamagnetic property was approximately 80 % greater than that of unmodified γ-Fe₂O₃/epoxy nanocomposites.     

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.     

Preparation and characterization of vanadia–titania mixed oxide for immobilization of Serratia rubidaea CCT 5732 and Klebsiella marcescens bacteria

Vanadia–titania mixed oxide was synthesized by sol–gel method and characterized by several techniques. Texturally, it is formed by mesopores and presents high-specific surface area and controlled porosity. Scanning electron microscopy revealed that vanadium is homogeneously distributed in the material. Structurally, it was possible to identify characteristic VO stretching bands by IR. The analysis of X-ray diffraction showed that the material, particularly vanadium, is highly dispersed. Application experiments were carried out through the immobilization of Serratia rubidae CCT 5732 and Klebsiella marcescens bacteria by adsorption on the surface of mixed oxide. The micrographies revealed that the bacteria were adsorbed on the entire support, with average surface densities of 8.55 × 10¹¹ cells/m² (Serratia rubidae CCT 5732) and 3.40 × 10¹¹ cells/m² (K. marcescens).     

Hybridization of kaolinite by consecutive intercalation: Preparation and characterization of hyperbranched poly(amidoamine)–kaolinite nanocomposites

Different nanocomposites based on virgin as well as treated kaolinites, as dispersed phases, and hyperbranched poly(amidoamine) (PAMAM) as a continuous phase were formulated using aqueous dispersion method. The interactive forces between the phases were evidenced using different techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), transmission electron microscope (TEM), thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that intercalation of PAMAM took place in pre-expanded kaolinite to give exfoliated nanocomposite. However, virgin kaolinite was successfully intercalated with PAMAM without pretreatment to give a nanocomposite of intercalated type with a basal space of about 47 Å. All samples exhibited lower Tg values along with worsened thermal stability compared to the parent polymer.     

Preparation and characterization of α-chitin from cicada sloughs

In this study, a new source of insect chitin was proposed. Insect chitin was extracted from cicada sloughs by 1 M HCl and 1 M NaOH treatment for demineralization and deproteinization, respectively. The brown color of this chitin from cicada sloughs was removed using 6% sodium hypochlorite as an oxidizing agent. It was found that the insect chitin extracted from the cicada sloughs has a higher percent recovery than the chitin from rice-field crab shells. The chemical structure and physicochemical properties of α-chitin from cicada sloughs were characterized using elemental analysis (EA), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), proton nuclear magnetic resonance spectroscopy (¹H NMR), solid-state ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance (CP/MAS) NMR spectroscopy, X-ray diffractometry (XRD), and thermogravimetry (TG). The degree of acetylation (DA) was determined by EA, ¹H NMR, and ¹³C CP/MAS NMR techniques. The DA values of chitin from cicada sloughs were in the range of 97% to 102% depending on each technique. Furthermore, it was found that the DA increased with an increasing thermal property and crystallinity.     

Preparation and supercapacitive performance of manganese‐cobalt sulfide/silver nanowires/graphene ternary nanocomposites

Journal of Materials Science: Materials in Electronics - Bimetallic sulfides are potential and attractive electrode materials for high-performance supercapacitors. In this study, the...     

Preparation and characterization of fenofibrate-loaded PLA–PEG microspheres

A series of biodegradable block copolymer of poly(lactide)(PLA)/poly(ethylene glycol) (PEG) were prepared by Ring-Opening polymerization of D, L-lactide, using stannous octoate as a catalyst. By nanoprecipitation method, the PLA-PEG can be made into microspheres containing fenofibrate, which is a kind of important cholesterol-lowering drugs. The purpose of this study is to investigate the effect of the copolymer composition on the size, the entrapment and the release behavior of the fenofibrate loaded microspheres. The microspheres can be achieved with small size below 100 nm, better encapsulation efficiencies of more than 55.3% and slower release rates. The release of fenofibrate from microsphere would reach the balance first, when the microsphere prepared by high proportion of hydrophilic PEG block. And the release property of fenofibrate/PLA-PEG microsphere was better than Lipanthyl (a commercial capsule of fenofibrate). It was observed that the composition of PLA-PEG copolymer played a major role in encapsulation efficiency of microspheres and release rates.     

Preparation and properties of fluorinated aliphatic alcohols/silica nanocomposites – Application to the encapsulation of anatase titanium oxide nanoparticles into these composite cores

A variety of fluorinated aliphatic alcohols [R_F-CH₂CH₂OH; R_F = CF₃(CF₂)₃CH₂(CF₂)₅, CF₃(CF₂)_n; n = 3, 5, 7] were applied to the preparation of the corresponding fluorinated alcohols/silica nanocomposites [R_F-CH₂CH₂OH/SiO₂] through the sol–gel reactions with tetraethoxysilane (TEOS) and silica nanoparticles under alkaline conditions. R_F-CH₂CH₂OH/SiO₂ nanocomposites thus obtained have a good dispersibility and stability in not only water but also traditional organic solvents such as methanol, ethanol, 1,2-dichloroethane and tetrahydrofuran. FE–SEM (field emission scanning electron microscopy) and dynamic light scattering (DLS) measurements show that these composites are nanometer size-controlled fine particles in methanol. These fluorinated nanocomposites were also applied to the surface modification of glass to exhibit a superhydrophilic characteristic with a superoleophobicity on the modified surface. Interestingly, R_F-CH₂CH₂OH/SiO₂ nanocomposites were found to exhibit no weight loss behavior corresponding to the contents of the alcohols in the composites even after calcination at 800 °C. In addition, anatase TiO₂ nanoparticles (an-TiO₂) were effectively encapsulated into R_F-CH₂CH₂OH/SiO₂ nanocomposite cores under the similar sol–gel reactions to give the corresponding fluorinated alcohol/SiO₂/an-TiO₂ nanocomposites. These obtained nanocomposites can give a higher photocatalytic activity even after calcination at 1000 °C for the decolorization of methylene blue under UV light irradiation than that of the an-TiO₂ nanoparticles under the similar conditions, although the parent TiO₂ nanoparticles after calcination were unable to give a photocatalytic activity.     

Preparation of tin ferrite–tin oxide by hydrothermal,precipitation and auto-combustion: photo-catalyst and magnetic nanocomposites for degradation of toxic azo-dyes

In this work, tin ferrite nanoparticles were first synthesized by simple chemical procedures such as co precipitation, sol–gel auto combustion and hydrothermal methods. In general, all three methods were compared in the synthesis of nanoparticles. Then tin ferrite–tin oxide (50%:50%) nanocomposites were prepared using co precipitation method. Crystal structures of nanoparticles and nanocomposite were studied using X-ray diffraction pattern. The particle size was determined by Scanning Electron Microscopy. Vibrating sample magnetometer was used to study the magnetic property of the products. And also, by applying Fourier transform infrared spectrometer, the purity of the material was determined. Photocatalytic activity of nanoparticles and nanocomposites was investigated under ultra-violet and visible spectroscopy (UV–Vis). The results show that prepared nanocomposites are applicable for magnetic and photocatalytic performance and they were able to degrade azo dyes (organic dyes) under UV–Vis radiation.     

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.     

Preparation and structural characterization of Zn1?xMnxSe thin films

Undoped and Mn doped ZnSe nanoparticles thin films of thickness ranging from 20 to 120 nm have been successfully synthesized via inert gas condensation (IGC) technique with constant Argon gas flow rate and deposition temperature 300 K. The energy dispersive X-ray analysis (EDX) for freshly deposited Zn_1−xMn_xSe thin films were carried out and revealed that Mn contents (x) were 0, 0.05, 0.16 and 0.25. The as-prepared deposited thin films of different thickness were examined using transmission electron microscope (TEM) and showed that all films were nanocrystalline with particle size ranging from 4.1 to 6.6 nm. The grazing incident in-plane X-ray diffraction (GIIXD) patterns verified nanocrystalline single phase zinc blende structure for 80 nm film thickness for all examined Zn_1−xMn_xSe compound films. A broadening of main characteristic lines (111), (220) and (311) of cubic phase was observed and was attributed to the lower particle size in nanocrystalline examined Zn_1−xMn_xSe compound films.