Fabrication and characterization of dual sputtered Pd–Cu alloy films for hydrogen separation membranes

In this paper, submicron thin Pd–Cu alloy films are deposited using a dual sputtering technique, which allows a high composition control of the layer. The composition, surface morphology and phase structure of the sputtered layers are investigated by energy-dispersive spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffractiometry (XRD). For example, the XRD data prove that the Pd–Cu layers are an alloy of Pd and Cu. Subsequently, the characterized Pd–Cu alloy layers are deposited on a silicon support structure to create a 750-nm thin Pd–Cu membrane for hydrogen separation. The reported membrane obtained a high flux of 1.6 mol H₂/m² s at a temperature of 725 K, while the selectivity is at least 500 for H₂/He.     

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...     

Enhanced compressive response of hybrid Mg–CNT nano-composites

Uniaxial compressive properties of hybrid Mg/Al–CNT nano-composites are studied in the present paper. Hybrid nano-composites were fabricated using powder metallurgy route followed by microwave assisted rapid sintering technique and hot extrusion. The hybrid Mg/Al–CNT nano-composites exhibited slightly smaller grain sizes compared to monolithic Mg and reasonable hybrid Al–CNT nano-particle distribution up to Al content of 1.00 wt%. Compared to pure Mg, the Mg/Al–CNT nano-composites exhibited higher compressive yield strength (0.2% CYS), ultimate compressive strength (UCS) and work of fracture (WOF) (up to +36%, +76%, +36%) compared to pure Mg but failure strain was compromised. Inclusive of crystallographic texture changes, the effect of hybrid Al–CNT nano-particle integration on the enhancement of compressive properties of Mg is investigated in this paper.     

Strengthening in and fracture behaviour of CNT and carbon-fibre-reinforced epoxy–matrix hybrid composite

Advanced materials such as continuous fibre-reinforced polymer matrix composites offer significant enhancements in strength and fracture resistance properties as compared with their bulk, monolithic counterparts. In the present work, mode-I (tensile) fracture behaviour of the neat epoxy (without nano- or hybrid reinforcements), nanocomposite (with amino-functionalized multi-walled carbon nanotube (MWCNT) reinforcement to neat epoxy) and hybrid composite (with amino MWCNT and carbon fibre reinforcements to neat epoxy) along with their flexural strength and interlaminar shear strength has been reported and discussed. Limited topological studies have also been conducted to understand the nature of material fracture and its dependence on the notch orientation. The results thus obtained are analysed and discussed in detail to elucidate: (i) alignment of fibre and its influence on the anisotropy in strength and fracture resistance, (ii) dependence of notch root radii on the apparent fracture toughness and concurrence to strain-controlled fracture and (iii) finally, the nature of J–R curves. The results thus obtained have revealed that the resistance to fracture is significantly increased with the addition of amino-functionalized MWCNTs and carbon fibres. In the hybrid composite, fracture resistance is greater in the longitudinal orientation of fibres than in the transverse orientation and it exhibits a significantly higher strength–fracture toughness combination.     

Fabrication and characterization of microcapsules with polyamide–polyurea as hybrid shell

Well-defined microcapsules with polyamide–polyurea as a hybrid shell have been described for biomedical applications. Interfacial polymerization method with surfactant and cosurfactant was developed for the preparation of the hybrid microcapsules. After reaction, centrifugation, and freeze drying processes, the polyamide–polyurea hybrid microcapsules with porous membranes were successfully fabricated. Compared with previous researches of the single polyamide or polyurea microcapsules, experimental data showed that the hybrid microcapsules have a thicker shell and excellent mechanical property. Various diameters and morphologies for the hybrid microcapsules can be obtained by changing the stirring rate, drying method, and surfactant content.     

Fabrication,physiochemical and optoelectronic characterization of SiO2/CdS core–shell nanostructures

Silica/CdS core–shell nanostructures have been developed using a simple wet chemical route. This method utilizes silica spheres formation followed by successive ionic layer adsorption and reaction method assisted CdS shell layer formation. The morphological studies revealed the uniformity in size distribution with core size of 250 nm and shell thickness of 9 nm. The electron microscopic images also indicate the irregular morphology of CdS shell layer. The structural studies indicate the simple cubic system of CdS shell with no other trace for impurities in the crystal structure. This CdS layer exhibit the band gap energy of 2.66 eV, due to weak quantum confinement and numerous defects presence. The studies on room temperature photoluminescence measurement indicate the emission properties and the corresponding electronic energy levels of defect states. Further, the physiochemical understanding of core–shell formation mechanism clearly matches with the motive behind the defects present in the CdS shell layer.     

Combinatorial Electroless Plating Characteristics for Dense Pd–PSS Composite Membrane Fabrication

Emphasizing upon a process–product combinatorial perspective, this article addresses the role of rate enhanced electroless plating baths for the fabrication of dense Pd/porous stainless steel composite membranes. Adopting phasewise contacting pattern of the reducing agent, plating experiments have been carried out with variegated Pd electroless plating baths at a palladium solution concentration of 0.005 M with a loading ratio of 203 cm²/L for the plating time of 2–6 h. Amongst all processes, surfactant and sonication coupled electroless plating baths provided optimal combinations of combinatorial plating process characteristics for dense Pd composite membrane fabrication.     

Analytical-geometrical percolation network model for piezoresistivity of hybrid CNT–CB polymer nanocomposites using Monte Carlo simulations

International Journal of Mechanics and Materials in Design - A 3D Monte Carlo simulation and percolation network model for hybrid nanocomposites reinforced by carbon nanotubes (CNTs) and carbon...     

A tribological and biomimetic study of PI–CNT composites for cartilage replacement

This article presents an investigation into the possible matching of mechanical properties of a polyimide (PI)–carbon nanotube (CNT) composite system to natural cartilage tissue. Currently used ultrahigh molecular weight polyethylene (UHMWPE) used in total joint replacements presents certain drawbacks due to a mismatch in mechanical and tribological properties with those of a natural bone joint. Natural cartilage tissue is a composite material itself, being composed of collagen fibers, hydrophilic proteoglycan molecules, cells and other constituents. The current investigation attempts to mimic the mechanical and tribological properties of natural cartilage tissue by varying the CNT concentration in a PI matrix. Nanoindentation and pin-on-flat tribological tests were conducted for this purpose. It was found that the coefficient of friction (COF) reached a minimum at a concentration of 0.5% CNT (by volume) when articulated against Ti6Al4V alloy. When articulated against Ti6Al4V alloy in the presence of a lubricant, the minimum COF was obtained at a concentration of 0.2% CNT. The maximum penetration depth under nanoindentation varied with CNT concentration and indicated that the mechanical properties could be tailored to match that of cartilage tissue. A closer investigation into this behavior was carried out using scanning electron, transmission electron, and atomic force microscopy. It was noticed that there is good bonding between the CNTs and polyimide matrix. There was a ductile to brittle transition as the concentration of CNT was increased. Competing interactions between nanotube–matrix and nanotube–nanotube are possible reasons for the deformation and friction behavior identified.     

Fabrication of graphene–platinum nanocomposite for the direct electrochemistry and electrocatalysis of myoglobin

In this paper a platinum (Pt) nanoparticle decorated graphene (GR) nanosheet was synthesized and used for the investigation on direct electrochemistry of myoglobin (Mb). By integrating GR–Pt nanocomposite with Mb on the surface of carbon ionic liquid electrode (CILE), a new electrochemical biosensor was fabricated. UV-Vis absorption and FT-IR spectra indicated that Mb remained its native structure in the nanocomposite film. Electrochemical behaviors of Nafion/Mb–GR–Pt/CILE were investigated with a pair of well-defined redox peak appeared, which indicated that direct electron transfer of Mb was realized on the underlying electrode with the usage of the GR–Pt nanocomposite. The fabricated electrode showed good electrocatalytic activity to the reduction of trichloroacetic acid in the linear range from 0.9 to 9.0 mmol/L with the detection limit as 0.32 mmol/L (3σ), which showed potential application for fabricating novel electrochemical biosensors and bioelectronic devices.     

Fabrication and properties of titanium–hydroxyapatite nanocomposites

Titanium–hydroxyapatite nanocomposites with different HA contents (3, 10, 20 vol%) were produced by the combination of mechanical alloying (MA) and powder metallurgical process. The structure, mechanical and corrosion properties of these materials were investigated. Microhardness test showed that the obtained material exhibits Vickers microhardness as high as 1030 and 1500 HV_0.2, which is more than 4–6 times higher than that of a conventional microcrystalline titanium. Titanium nanocomposite with 10 vol% of HA was more corrosion resistant (i_C = 1.19 × 10⁻⁷ A cm⁻², E_C = −0.41 V vs. SCE) than microcrystalline titanium (i_C = 1.31 × 10⁻⁵ A cm⁻², E_C = −0.36 V vs. SCE). Additionally, the electrochemical treatment in phosphoric acid electrolyte results in porous surface, attractive for tissue fixing and growth. Mechanical alloying and powder metallurgy process for the fabrication of titanium–ceramic nanocomposites with a unique microstructure are developed.     

Fabrication of poly- and single-crystalline platinum nanostructures using hole-mask colloidal lithography, electrodeposition and annealing

Colloidal lithography (CL) is a generic name for a collection of nanolithographic techniques, based on using colloidal nanoparticles as pattern (mask)-defining entities to produce various nanostructures. A key step in CL processes is the deposition, usually by evaporation or sputtering, of the material that makes up the final nanostructures. We have for the first time combined a special version of CL, called hole-mask colloidal lithography (HCL), with electrodeposition. We demonstrate how electrodeposition of Pt onto Au and carbon substrates, through a lithographic mask, can be used to prepare well-defined nanostructured surfaces. The results are compared with evaporated structures and characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and cyclic voltammetry. Specific results are: (i) electrodeposition generates structures with very good adhesion, (ii) due to differences in the deposition mechanism, structures with much larger aspect (height/width) ratio can be made with electrodeposition than with evaporation and (iii) the originally deposited polycrystalline nanoparticles can be annealed into single crystals, as demonstrated by electron diffraction, SEM and TEM, before and after annealing, which is of great value for fundamental (electro)catalysis studies.     

Synthesis and characterization of bismaleimide–polyetherimide–titania hybrid

Ternary hybrids of bismaleimide–polyetherimide–titania were synthesized by sol–gel reaction and characterized by Scanning Electron Microscope, Energy Dispersive X-ray Analysis, Thermogravimetric Analysis and Differential Scanning Calorimeter. Moreover, their mechanical properties were also measured.The results indicated that titania could be introduced into the blends of bismaleimide–polyetherimide(BMI/PEI) by sol–gel reaction. Although, the titania content in BMI-rich phase was higher than that in PEI-rich phase, the titania particles dispersed in the hybrids were almost uniform. The introduction of titania actually changed the ultimate phase structure of the PEI modified BMI system because of the chelate complex formation between o,o′-diallyl bisphenol A and dibutoxy bis(acetylacetonato) titanium (IV), which was proved by their ultraviolet spectra. If the content of titania was increased under a specific PEI content, the morphology of the bismaleimide–polyetherimide–titania hybrids remained unaffected apparently, while its mechanical properties were obviously improved.     

Fabrication and evaluation of chitosan–gelatin based buckling implant for retinal detachment surgery

The traditional nonabsorbable silicone buckling implant (buckle) may cause some long-term complications when it is used in the retinal detachment surgery. In this study we fabricated a chitosan–gelatin based buckling implant to replace the traditional one. We evaluated its biocompatibility with human scleral fibroblasts (HSF) in vitro and its cytotoxicity with L929 cell. To evaluate elasticity and hardness of the blends buckle, the mechanical properties of the chitosan–gelatin buckle were compared with the traditional silicone buckle. The light and electron microscopy coupled with immunocytochemistry demonstrated that chitosan–gelatin blends supported the survival and growth of primarily cultured HSF without significant cytotoxic effects. MTT analysis and cell cycle analysis indicated that chitosan–gelatin blends promoted the proliferation of HSF. A preliminary in vivo implantation test indicated that chitosan–gelatin buckling implant were compatible with the surrounding tissue. The results collectively demonstrated that chitosan–gelatin blends could be a candidate biodegradable material for scleral buckling surgery.     

Fabrication and characterization of porous Ti–7.5Mo alloy scaffolds for biomedical applications

Porous titanium and titanium alloys are promising scaffolds for bone tissue engineering, since they have the potential to provide new bone tissue ingrowth abilities and low elastic modulus to match that of natural bone. In the present study, porous Ti–7.5Mo alloy scaffolds with various porosities from 30 to 75 % were successfully prepared through a space-holder sintering method. The yield strength and elastic modulus of a Ti–7.5Mo scaffold with a porosity of 50 % are 127 MPa and 4.2 GPa, respectively, being relatively comparable to the reported mechanical properties of natural bone. In addition, the porous Ti–7.5Mo alloy exhibited improved apatite-forming abilities after pretreatment (with NaOH or NaOH + water) and subsequent immersion in simulated body fluid (SBF) at 37 °C. After soaking in an SBF solution for 21 days, a dense apatite layer covered the inner and outer surfaces of the pretreated porous Ti–7.5Mo substrates, thereby providing favorable bioactive conditions for bone bonding and growth. The preliminary cell culturing result revealed that the porous Ti–7.5Mo alloy supported cell attachment.     

Design and analysis of longitudinal–flexural hybrid transducer for ultrasonic peen forming

Ultrasonic peen forming (UPF) is an emerging technology that exhibits great superiority in both its flexible operating modes and the deep residual stress that it produces compared with conventional plastic forming methods.Although ultrasonic transducers with longitudinal vibration have been widely studied,they have seldom been incorporated into UPF devices for machining in confined spaces.To meet the requirements of this type of machining,a sandwich-type piezoelectric transducer with coupled lon...     

Comparisons of Co–C and Pd–C Eutectic-Point Cells for Thermocouple Calibration Between NMIA and NMIJ

Comparisons between NMIA and NMIJ on the melting temperatures of the Co–C eutectic point and the Pd–C eutectic point were performed using an NMIJ high-temperature furnace. The eutectic-point cells were constructed by NMIA and NMIJ following two different specifications. NMIA designed two miniature crucibles, one for Co–C and one for Pd–C eutectic-point cells. NMIJ designed larger eutectic-point cells, one for Co–C and one for Pd–C eutectic-point cells. Prior to performing the comparisons, the effect of conductive heat flow through the thermocouple stem was evaluated during the melting. The comparisons of the Co–C eutectic-point cells and of the Pd–C eutectic-point cells were performed using types R, B and Pt/Pd thermocouples. Despite the different cell designs and different material sources, the melting temperatures of the Co–C and Pd–C eutectic-point cells under investigation agreed within 0.1 \(\,{^{\circ }}\hbox {C}\).     

Design and synthesis of inorganic–organic hybrid microstructures

Vanadium oxide–polypyrrole (V₂O₅–PPy) hybrid aerogels were prepared using three different strategies. These approaches were focused on either sequential or consecutive polymerization of the inorganic and organic networks. The hybrid microstructure differed greatly depending on which synthesis approach was used. Microcomposite aerogels were synthesized by encapsulating a dispersion of preformed PPy in a V₂O₅ gel. In the second approach, pyrrole was polymerized and doped within the pore volume of a preformed V₂O₅ gel. The hybrid microstructure of these materials was nanometer scaled but inhomogeneous. When the inorganic and organic precursors were allowed to polymerize simultaneously, the resulting gels exhibited a nanometer-scaled microstructure with a homogeneous distribution of the PPy and the V₂O₅. Through this route, a suitable microstructure and composition for a lithium secondary battery cathode were obtained. Undoped material with a composition of [PPy]_0.8V₂O₅ exhibited a lithium intercalation capacity comparable to that of V₂O₅ aerogel. For the full benefit of the PPy phase to be achieved, a suitable doping procedure is still required to oxidize the PPy into its high conductivity state while preserving the inorganic structure.