Preparation and characterization of epoxy/γ-aluminum oxide nanocomposites

Epoxy/γ-Al₂O₃ nanocomposites were prepared with a homogenizer and followed by a stepwise thermal curing process in this study. The dispersion of γ-Al₂O₃ nanoparticles was examined with a transmission electron microscopy (TEM). Meanwhile, the effects of γ-Al₂O₃ nanoparticles on thermal, dynamic mechanical and tensile properties of epoxy/γ-Al₂O₃ nanocomposites were also investigated and discussed. When the γ-Al₂O₃ content was increased from 1phr to 5phr, results revealed that γ-Al₂O₃ nanoparticles were effective to enhance both the stiffness and toughness of epoxy resin. Meanwhile, the maximum properties of glass transition temperature (T_g), T_d5%, storage modulus, tensile modulus, and elongation at break were observed in the epoxy/5phr γ-Al₂O₃ nanocomposite.     

Synthesis and electrical properties of graphene–manganese oxide hybrid nanostructures

Journal of Materials Science: Materials in Electronics - In the present contribution, grapheme–manganese oxide hybrid nanostructures (G/MnO2) were synthesized via rapid and facile microwave...     

Preparation and properties of electroless Ni–Zn–P alloy films

Electroless deposition of Ni–Zn–P layers was studied on steel electrodes by varying the bath temperature (40–90°C), pH and chemical composition. The deposition parameters were optimized. Alloys containing 70–86 wt % Ni, 6–20 wt % Zn and 6–10 wt % P are obtained at 20 m h^–1 and 85°C. Corrosion measurements were performed in aerated 5% sodium chloride solution, the corrosion potential and current density are, respectively, –0.49 V/SCE and 2.6 A cm^–2.     

Structure and optical properties of ordered mesoporous copper oxide–silica composite films

In this study, ordered mesoporous copper oxide–silica (CuO–SiO₂) composite films with CuO/SiO₂ molar ratio ≤6% have been prepared. Small-angle X-ray diffraction and transmission electron microscopy investigations show that the mesoporous CuO–SiO₂ composite films have a hexagonally ordered pore array nanostructure. Wide-angle X-ray diffraction analysis reveals that the copper oxide and silica in the composite films are non-crystalline. The non-crystalline CuO in the mesoporous composite films has an obvious blue-shift phenomenon of the absorption edge. The calculated band gap energy for CuO is 3.2?eV, which is much higher than its bulk counterparts (1.21–1.5?eV).     

Physical and electrical properties of polyimide/ceramic hybrid films prepared via non-hydrolytic sol–gel process

In this study, TiO₂ and SiO₂ were chosen as ceramic fillers in the 3,3′,4,4′-benzophenone tetracarboxylic dianhydride–4,4′-oxydianiline (BTDA–ODA) polyimide matrix. Physical properties of hybrids with up to 30 wt% SiO₂ and 7 wt% TiO₂ were evaluated and discussed. Nano-size ceramic particles were prepared by non-hydrolytic sol–gel (NHSG) process. SEM micrographs show that both films have nano-sized ceramic particles with a narrow size distribution. Thermal conductivities of the hybrids increase from 0.12 to 0.21 W/m-K, as the SiO₂ and TiO₂ in the hybrid increases from 0 to 30 and 7 wt%, respectively. Electrical surface resistivity slightly decreases with increasing ceramic filler content. Dielectric constant of the hybrid increases from 2.45 to 2.72 with the incorporation of the 7 wt% (5.4 vol%) TiO₂. Water absorption decreases considerably with increasing filler content. With 30 wt% (20.2 vol%) SiO₂ addition, the water absorption of the hybrid film reduces by 85% from that of pure polyimide.     

The influence of zinc oxide–cerium oxide nanoparticles on the structural characteristics and electrical properties of polyvinyl alcohol films

With the objective to investigate the influence of zinc oxide–cerium oxide (ZnO–Ce₂O₃) nanoparticles on the electrical properties of polyvinyl alcohol (PVA), PVA/ZnO–Ce₂O₃ nanocomposite films were prepared by solution intercalation method with different weight percentage viz., 0.5, 1.0, and 2.0?wt% of ZnO–Ce₂O₃ nanoparticles. The fabricated nanocomposites were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). The effect of ZnO–Ce₂O₃ nanoparticles on the dielectric constant (ε′), dielectric loss (ε″), electric modulus (M′ and M″), ac conductivity (σ _ac), and dielectric loss tangent (tan δ) over a range of frequencies at room temperature of PVA nanocomposites have been studied. FT-IR, XRD, and DSC analysis indicates the nature of ZnO–Ce₂O₃ nanoparticles interaction with the PVA matrix. The morphological behavior of the nanocomposites has been performed using scanning electron microscopy (SEM). The dielectric behaviors such as dielectric constant (ε′) and dielectric loss (ε″) increases with increase in nanoparticle concentration, but decreases with increase in frequency. But, the electric modulus (M′) increases with increase in frequency. Dielectric loss tangent (tan δ) decreases with increase in filler content at lower frequency, but at higher frequencies the tan δ increases with increase in nanoparticles content. AC conductivity (σ _ac) of PVA/ZnO–Ce₂O₃ nanocomposites increases with increasing frequency following the universal dielectric response law.     

Preparation and properties of an organic–inorganic hybrid materials based on fluorinated block copolymer

The block copolymers of poly 2,2,3,4,4,4-hexafluorobutyl methacrylate-block-poly[3-(trimethyoxysilyl)propyl methacrylate] (PHFMA-b-PTMSPMA) were synthesized via atom transfer radical polymerization and used for the preparation of organic/inorganic hybrid materials by the sol–gel approach. The polymers were characterized by gel permeation chromatography, Fourier transform infrared and ¹H nuclear magnetic resonance. The properties of the hybrid materials were investigated by Scanning electronic microscopy, contact angle, Scotch tape test, transmittances measurement, differential scanning calorimetry, and thermogravimetric analysis. The results were as follows: First, the hybrid materials had surface roughness, good hydrophobicity (>95° in contact angle with water), and could improve the contact angle of glass from 65.2° to 99.9° (the content of TMSPMA was 4.9 wt% in its polymer). Second, the adhesion of the hybrid materials to glass were enhanced by incorporating TMSPMA. Third, light transmittances of all the hybrid materials were above 90% in the visible range. Finally, the thermal stability of the hybrid materials were enhanced by incorporating silica moiety.     

Preparation and luminescent properties of Eu-doped BaTiO3 thin films by sol–gel process

Eu-doped BaTiO₃ thin films with a pseudo-cubic perovskite structure were successfully fabricated on magnesia substrates at low temperature by using a high-concentration sol–gel process, in which the newly developed gel-aging process on substrate was employed. Film microstructure, crystallinity, sintering properties and photoluminescence (PL) were investigated. The xerogel thin films exhibited strong PL associated with Eu³⁺ ions under ultraviolet excitation at room temperature; the PL was visible to naked eyes. The intensity maximum of PL was reached with doping concentration of about 8 mol%. Sintering above 600 °C caused reduction of europium, resulting in a rapid quenching of Eu³⁺ emission and enhancement of Eu²⁺ emission.     

Electrical and optical properties of µc-SiH films

Microcrystalline silicon films have been found quite useful in amorphous silicon solar cells as a contact material in n-i-p cells. Microcrystalline silicon films are obtained when amorphous silicon films are prepared by R.F. glow discharge of SiH₄ + H₂ at higher power ratings. These films possess higher conductivity as well as high transmission than amorphous silicon films. The present paper reports the preparation technique ofμc-SiH films using R.F. capacitive glow discharge of hydrogen-diluted silane. X-ray studies andtem studies of the films indicate microcrystallinity of the films. The electrical and optical properties are also reported.     

Preparation and stability of iodine/α-cyclodextrin inclusion complex

Abstract

Inclusion complexes of iodine and α-cyclodextrin were prepared using the coprecipitation method. The complexes obtained were characterized in their solid state using differential scanning calorimetry and in their liquid phase using spectrophotometry, titrimetry and electrochemistry assays. The inclusion and preparation yields were determined. The 1:1 stoichiometry ratio of the inclusion compound was estimated on the basis of the inclusion yield. After optimization of the parameters of the laboratory assays, a scale-up experiment for the complex preparation was carried out. Stability studies showed that, after 16 months preservation, the inclusion complex remained quite stable and suitable for industrial scale-up according to a number of conditions.     

Carbon/ceramics composites — Preparation and properties

Fabrication methods for carbon/ceramics composites were established by using two different processes of hot-pressing and pressureless sintering without any binder phase. In the hot pressing method, some boron compounds were found to be an effective aid for sintering and graphitization of coke powder above 2000°C under some pressure. When the content of boron compound such as B₄C was high, graphite/B₄C composites could be fabricated. If some other ceramic powder such as NbC, TiC or TaC was mixed in addition to the B₄C, three component composites with graphite matrix could be obtained. In pressureless sintering method, raw coke carbon powder was ground for a long time to be transformed in to a sinterable and non-graphitizing-type carbon powder. From a mix of ceramic powders such as SiC or B₄C with the ground coke powder, the composites of carbon/SiC or carbon/SiC/B₄C systems could be fabricated by heat-treatment under normal pressure.Some properties of the graphite samples and carbon/ceramic composites were investigated. It was found that their mechanical properties were much better than those of conventional graphite samples and the resistance to oxidation and corrosion was also excellent. It is suggested that the composites could be applied as bearing or mechanical seals both for use in high temperature environments and as machine parts in contact with some molten metals.     

Thermal stability and electrical properties of Ag–Ti films and Ti/Ag/Ti films prepared by sputtering

Ag–Ti (100 nm) alloy film, and Ti/Ag (100 nm) double-layer and Ti/Ag (100 nm)/Ti triple-layer films were prepared by rf sputtering to investigate the effect of Ti on suppression of agglomeration of the Ag thin film caused by thermal treatment. Scanning electron microscopy revealed that the Ag–Ti and Ti/Ag/Ti films had high thermal stability. X-ray photoelectron spectroscopy analysis showed that the surfaces of both kinds of films were covered with a TiO₂ layer after annealing, which was considered to be the key factor for improvement of the thermal stability of the films. In addition, scratch tests indicated improvement of the adhesive strength of the Ti/Ag/Ti film to the SiO₂ substrate due to the underlying Ti film layer, which effectively promoted suppression of Ag agglomeration. However, the resistivity of the Ag–Ti films increased abruptly with increasing Ti content due to the impurity scattering effect, and minimum usage of the alloying element was required to achieve low resistivity. In contrast, the Ti/Ag/Ti film exhibited both low resistivity and high thermal stability.     

The influence of cobalt oxide–graphene hybrids on thermal degradation,fire hazards and mechanical properties of thermoplastic polyurethane composites

In this work, cobalt oxide nanoparticles decorated on graphene nanosheets was firstly synthesized by a facile hydrothermal method. The structure and morphology of the synthesized hybrids were characterized by X-ray diffraction, Raman spectrum and Transmission electron microscopy measurements. Subsequently, the hybrids were introduced into thermoplastic polyurethane matrix for acting as reinforcements. The hybrids were well dispersed in thermoplastic polyurethane and no obvious aggregation of graphene nanosheets was observed. The obtained nanocomposites exhibited significant improvements in thermal stability, flame retardancy, mechanical properties and reduced the fire toxicity effectively, compared with those of neat polyurethane. The obvious improvements of these properties were mainly attributed to the ‘‘tortuous path’’ effect of graphene nanosheets, catalytic char formation function of cobalt oxide–graphene hybrids and the synergism between the catalysis effect of cobalt oxide nanoparticles and the adsorption effect of graphene nanosheets.     

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.     

Preparation and conductivity of dithiolene complex Langmuir–Blodgett films

The d.c. electrical property of the dithiolene complex, or bis(4-diethyannodithiobenzil)nickel (BDN) and stearyl alcohol (SA) mixed Langmuir–Blodgett films was investigated. The conductivity of the LB films as a function of the thickness of the films and the ratio of BDN:SA as well as the current versus voltage (I–V) characteristics have been measured. The conductivity of the LB films is about 3.5 x 10^-10 S cm^-1 which is less than the bulk conductivity of BDN, and the conductivity of the LB films is strongly influenced by BDN concentration. The I–V property of Al-LB films is governed by the thickness of oxide layers at the LB films with Al electrodes after Auger depth profiling analysis.     

Preparation of water dispersible,fluorescent Ag–PAA–PVP hybrid nanogels and their optical properties

A simple method of synthesizing hybrid silver–polyacrylic acid–poly(N-vinylpyrrolidone) (Ag–PAA–PVP) nanogels was demonstrated through in situ reducing Ag⁺ inside PAA–PVP nanogels, which were formed by polymerization of acrylic acid in the PVP solution. Due to the ion exchange between Ag⁺ and acid protons of PAA, stable Ag⁺ clusters were formed inside the PAA–PVP nanogels, and hybrid nanogels were obtained by reducing Ag⁺ by ascorbic acid. Transmission electronic microscopic (TEM) images clearly showed the existence of silver nanoparticles inside the Ag–PAA–PVP nanogels. These hybrid nanogels showed typical surface plasma resonance absorption peak around 420 nm, and the size of the silver nanoparticles inside the Ag–PAA–PVP nanogels could be controlled from 9.5 ± 1.6 nm to 1.9 ± 0.4 nm by increasing the feeding amount of Ag⁺. In addition, these hybrid nanogels showed photoluminescent properties in fluorescent spectra. Considering the pH sensitive property of these hybrid nanogels, they will have potential application in drug delivery and biomedical imaging systems.     

Preparation and properties of WC–Co textured components

Abstract

WC–Co components having one {0001} textured surface have been produced and tested. The textured surface has beenfound to be harder and more resistant to fracture and abrasive wear than standard surfaces. A method is proposed to produce WC–Co components having a bulk {0001} texture.

MST/1337