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.     

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).     

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.     

Influence of foaming process on the structure–properties relationship of foamed LDPE/silica nanocomposites

In this paper LDPE/silica nanocomposites are foamed by two different processes. First one is the pressure quench method which is based on the use of a physical blowing agent and second one is the improved compression moulding technique. As the latter process uses a chemical blowing agent, both types of foamed nanocomposites will provide very useful information about the relationship between foaming process-microstructure and macroscopic properties. Results have revealed how silica nanoparticles are able to act as nucleating sites during foaming step in both processes; however, the optimum amount of particles strongly depends on the foaming route. Thermal and mechanical properties of solid and foamed nanocomposites have been analyzed by means of thermogravimetric analysis and compression tests. Results have revealed that nanosilica particles act as effective nucleating agents, not only reducing cell size and increasing cell density but also achieving more homogeneous cellular structures. Thermal and mechanical properties are improved due to the presence of silica nanoparticles. It has been found that the improvement degree reached for samples produced using chemical blowing agents is greater than that achieved for samples produced using physical blowing agents.     

Preparation and properties of antibacterial TiO2@C/Ag core–shell composite

Abstract

An environment-friendly hydrothermal method was used to prepare TiO₂@C core–shell composite using TiO₂ as core and sucrose as carbon source. TiO₂@C served as a support for the immobilization of Ag by impregnation in silver nitrate aqueous solution. The chemical structures and morphologies of TiO₂@C and TiO₂@C/Ag composite were characterized by x-ray diffraction, transmission electron microscopy, Fourier transform infrared spectroscopy, energy dispersive x-ray spectroscopy and Brunauer–Emmett–Teller (BET) analysis. The antibacterial properties of the TiO₂@C/Ag core–shell composite against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were examined by the viable cell counting method. The results indicate that silver supported on the surface of TiO₂@C shows excellent antibacterial activity.     

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 electromagnetic-wave-absorption properties of a nitrogen-doped carbon–supported iron(II,III) oxide composite

Journal of Materials Science: Materials in Electronics - A single material with dielectric or magnetic loss behavior cannot optimally absorb electromagnetic waves because such waves are composed of...     

Fabrication and optical features of the sol–gel derived silica glasses doped with copper oxide nanoparticles and europium

Novel sol–gel derived silica glasses doped with copper oxide nanoparticles and europium ions have been fabricated in order to design a multicomponent luminescent material. The photoluminescence studies indicated the significant effect of copper oxide upon the light emission due to europium ions while the emission from copper oxide is similar with that due to Cu⁺. The emission of europium ions in the Cu₂O:Eu³⁺-codoped glasses can be done through excitation of copper oxide.     

Preparation of non-spherical silica composite abrasives by lanthanum ion-induced effect and its chemical–mechanical polishing properties on sapphire substrates

Chemical–mechanical polishing is the only technology that can provide a global planarization, and has become widely accepted. Abrasives are one of the important factors influencing chemical–mechanical polishing. In order to improve surface planarization and increase material removal rate of sapphire substrates, non-spherical silica composite abrasives were synthesized by lanthanum ion-induced effect-assisted growth method. Scanning electron microscopy showed the morphologies of non-spherical silica composite abrasives were peanut-shaped, chemical–mechanical polishing tests displayed the material removal rate of the non-spherical silica composite abrasives increased by 32.6% compared with spherical silica composite abrasives, Ambios Xi-100 surface profiler indicated the best surface roughness of sapphire substrate was 1.540 nm, and the element compositions of solids after polishing were analyzed by X-ray photoelectron spectroscopy, which investigated the interactions between abrasives and sapphire substrates. Non-spherical silica composite abrasives may lead to more solid-chemical reactions with sapphire substrates, and higher material removal rate may be also attributed to the mechanical grinding effect enhanced owing to the unique shape to achieve the purpose of material removal.     

Preparation and properties of TaC/C/TaC∼TaC composite micro-tubes by vapor phase tantalizing of the regular carbon micro-coils/micro-tubes

TaC/C/TaCTaC composite micro-tubes were prepared by the vapor phase tantalizing of the regular carbon micro-coils/micro-tubes, and the preparation conditions and some properties were examined. The carbon micro-coils with a tube-like morphology were tantalized from the surface to the core of the carbon fibers with full preservation of the tube-like morphology to form TaC/C/TaCTaC composite micro-tubes. The bulk electrical resistivity and specific surface area of the TaC/C/TaCTaC composite micro-tubes were 4 × 10^–3 to 5 × 10^–4 ·m and 5 × 10³ to 2 × 10⁴ m²/kg, respectively, depending on the tantalized ratio and the bulk density.     

Preparation, characterization, and fluorescence properties of well-dispersed core–shell CdS/carbon nanoparticles

The core–shell CdS-carbon (CdS/C) nanoparticles were synthesized for the first time via a facile pyrolysis approach of bis(β-mercaptoethanol)-cadmium(II) as a single-source precursor. After using acid treatment method, well-dispersed and homogeneous core–shell CdS/C nanoparticles were obtained. The morphology, structure, and properties of CdS/C nanoparticles were investigated by X-ray diffraction (XRD), Raman spectra, transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), and fluorescence spectroscopy. Most of the prepared nanoparticles presented core–shell structures with core diameter of ~10 nm and shell thickness of ~4 nm. The CdS core belonged to hexagonal crystal system. The carbon shell was employed as a good dispersion medium to form well-dispersed small sized CdS particles. XRD and XPS results revealed that there is an interaction between CdS core and carbon shell. Fluorescence measurement showed that the monodispersed CdS-carbon nanoparticles exhibit remarkable fluorescence enhancement effect compared with that of the pristine CdS nanoparticles, which indicates the prepared nanoparticles are a promising photoresponsive material.     

Thermo-viscoelastic modelling of organic matrix composite behaviour – Application to T700GC/M21

The purpose of this study is to propose a thermo-viscoelastic model able to describe the strain rate dependency, from creep to dynamic tests, and temperature dependency, from −100 °C to room temperature, of organic matrix composite materials. A bi-spectral viscoelastic model, proved to be representative of the T700GC/M21 behaviour on a large range of strain rates, is used and improved in this study for temperature dependency. First, thermal residual stresses are introduced and proved not to be sufficient to describe the temperature dependency of the laminate. Subsequently, further to the analysis of the time–temperature superposition principle on DMA tests, the viscoelastic model is improved with the introduction of an Arrhenius like shift factor. The proposed model is proved to be representative and predictive of the strain rate and temperature dependencies of the T700GC/M21 composite material.     

Preparation and properties of coke powder activated carbon/α-Co(OH)2 composite electrode materials

Coke powder activated carbon (CPAC) was prepared by dipping-calcined KOH activation method. Using CPAC as the raw material a series of composite electrode materials of CPAC/α-Co(OH)₂ with different mass fractions of cobalt were synthesized by the Sol–gel method. The physical properties of the resulting samples were characterized by the field emission scanning electron microscopy and the X-ray diffraction. The results show that composite materials, CPAC/α-Co(OH)₂, have a flower-like structure. The results of electrochemical performances show that the composite material has a good electrochemical capacity of 472.3 F g^?1 with a cobalt doping amount of 30 wt %. By the cyclic voltammetry testing, we found that the anodic peak potential of the redox peaks in composite electrode materials shifted positively when the scan rate increased, while the cathodic peak potential shifted negatively, and that would cause a gradual increase of the peak potential difference of redox peaks. In contrast, the lower of the scan rate, the smaller of the peak potential difference and the better of the reversibility of composite material. The results of impedance testing show that CPAC/α-Co(OH)₂ has a lower electrochemical impedance than that of CPAC.     

Effect of the content of hydroxyapatite nanoparticles on the properties and bioactivity of poly(l-lactide) – Hybrid membranes

Poly(l-lactide)/hydroxyapatite, PLLA/HA, composite membranes for bone regeneration with different concentrations of nanoparticles have been prepared and their physicochemical properties and bioactivity have been determined. Hydroxyapatite nanoparticles act as nucleating agent of the poly(l-lactide) crystals, as detected by DSC, and as reinforcing filler, as proven by the monotonous increase of the elastic modulus of the microporous membranes with increasing nano-filler content. The bioactivity, which regards to the use of these materials in bone regeneration, was tested by immersing the samples in a simulated body fluid, SBF. A faster deposition of a biomimetic apatite layer was observed as increases the content of hydroxyapatite nanoparticles, thus membranes with a 15% (w/w) of hydroxyapatite particles (relative to PLLA weight) present a homogeneous layer of hydroxyapatite on the surface of their pores after 7 days of immersion in SBF. An especial emphasis has been made on the influence of a plasma treatment on the bioactivity of the membranes. With this aim, the membranes were submitted to a plasma treatment previously to their immersion in a simulated body fluid. It has been observed that the surface of a PLLA membrane after 21 days of immersion in SBF is still not completely covered by hydroxyapatite whereas the same sample treated with plasma show a smooth layer of biomimetic hydroxyapatite. The increase of bioactivity achieved with this treatment was less important in high hydroxyapatite content composites.     

Preparation,optical and thermal properties of CdSe–ZnS/poly(lactic acid) (PLA) nanocomposites

In this study, CdSe–ZnS/poly(lactic acid) (PLA) nanocomposite films, containing different concentrations of surface-modified CdSe–ZnS quantum dots (QDs), were prepared via a solution casting method. The optical microstructural and thermal properties of the as-prepared QDs/PLA films were investigated. The QDs/PLA films exhibited strong and stable photoluminescence (PL) intensity with concentration dependent amplitudes. The transmission electron microscopy (TEM) pictures revealed that QDs of ∼5 nm diameter were uniformly dispersed in the PLA matrix. According to the results of thermogravimetric analysis, the weight-loss onset temperature of PLA clearly decreased with the QD content. A combination of Fourier transform infrared (FT-IR) spectroscopy, X-ray diffractometry (XRD) and differential scanning calorimetry (DSC) results suggested that the QDs exhibit obvious nucleation activity on the crystallization behavior of the PLA matrix. This research provides useful information to the foundations of practical applications of QDs/PLA nanocomposites as fluorescent and biodegradable functionalized materials.     

Morphology,rheology and mechanical properties of polypropylene/ethylene–octene copolymer/clay nanocomposites: Effects of the compatibilizer

The objective of this study was to investigate the effects of two compatibilizers, namely maleated polypropylene (PP-g-MA) and maleic anhydride grafted poly (ethylene-co-octene) (EOC-g-MA), on the morphology and thus properties of ternary nanocomposites of polypropylene (PP)/ethylene–octene copolymer (EOC)/clay nanocomposite. In this regard the nanocomposites and their neat polymer blend counterparts were processed twice using a twin screw extruder. X-ray diffraction, transmission electron microscopy, Energy dispersive X-ray spectroscopy, and scanning electron microscopy were utilized to characterize nanostructure and microstructure besides mechanical and rheological behaviors of the nanocomposites. Clay with intercalated structure was observed in EOC phase of the PP/EOC/clay nanocomposite. Better dispersion state of the intercalated clay in EOC phase was observed by adding EOC-g-MA as a compatibilizer. On the other hand, adding PP-g-MA resulted in migration of the intercalated clay from the EOC to the PP and to the interface regions. It was also demonstrated that the elastomer particles became smaller in size where clay was present. The finest and the most uniform morphology was found in the PP/EOC/clay nanocomposite. In addition, the rheological results illustrated a higher complex viscosity and storage modulus for PP/EOC/PP-g-MA/clay nanocomposite in which clay particles were present in the matrix. Mechanical assessments showed improvements in the toughness of the nanocomposites with respect to their neat blends, without significant change in stiffness and tensile strength values. These results highlight a toughening role of clay in the polymer blend nanocomposites studied.     

Bone response to surface modified titanium implants – studies on the tissue response after 1 year to machined and electropolished implants with different oxide thicknesses

The bone formation around titanium implants with varied surface properties was investigated after 1 year in rabbits. Machined and electropolished samples with and without thick, anodically formed surface oxides were prepared, surface characterized and inserted in the cortical bone of rabbits. Scanning electron microscopy, scanning Auger electron spectroscopy and atomic force microscopy revealed marked differences in oxide thickness, surface topography and roughness, but no significant differences in surface chemical composition between the different groups of implants. Light microscopic morphology and morphometry showed that all implants were in contact with bone and had a large proportion of bone within the threads. There were no significant differences between the differently prepared implant groups. Our study shows that a high degree of bone contact and bone formation is achieved after 1 year with titanium implants which are modified with respect to oxide thickness and surface topography. There is no indication that a reduction of surface roughness, which in the initial phase decreases the rate of bone formation, had any influence on the amount of bone after 1 year in rabbit cortical bone.     

Preparation of magnetic photocatalyst nanoparticles—TiO2/SiO2/Mn–Zn ferrite—and its photocatalytic activity influenced by silica interlayer

A magnetic photocatalyst, TiO₂/SiO₂/Mn–Zn ferrite, was prepared by stepwise synthesis involving the co-precipitation of Mn–Zn ferrite as a magnetic core, followed by a coating of silica as the interlayer, and titania as the top layer. The particle size and distribution of magnetic nanoparticles were found to depend on the addition rate of reagent and dispersing rate of reaction. The X-ray diffractometer and transmission electron microscope were used to examine the crystal structures and the morphologies of the prepared composites. Vibrating sample magnetometer was also used to reveal their superparamagnetic property. The UV–Vis spectrophotometer was employed to monitor the decomposition of methylene blue in the photocatalytic efficient study. It was found that at least a minimum thickness of the silica interlayer around 20 nm was necessary for the inhibition of electron transference initiated by TiO₂ and Mn–Zn ferrite.