Preparation and photocatalytic activity of PANI/TiO2 composite film

1. Introduction As an advanced oxidation technique (AOT), photocatalytic oxidation of semiconductor nanopar-ticles has been widely investigated by several groups during the past two decades [1-2]. Among all types of oxide semiconductor photocatalysts, nano-TiO2 is a very important photocatalyst for its strong oxidiz-ing power, nontoxicity, and long-term photostability [3]. Some researchers have reviewed the photocata-lytic mechanism of nano-TiO2 [4-5]. Generally, when the surface of TiO2 i…     

Synthesis,structure, and properties of a bentonite–magnetite composite

A bentonite–magnetite composite is obtained by means of bentonite intercalation with iron oxide Fe₃O₄. Using the methods of electron microscopy, low-temperature nitrogen vapor adsorption–desorption, and XRD phase analysis, the composite morphology, structure, and texture have been investigated. It is shown that the synthesized bentonite–magnetite composite can be used as a sorbent for wastewater purification from organic pollutants.     

Laser and resistance joining of aluminum–graphite composite

This research investigates welding and brazing of Al–Gr composite using different joining techniques. Limited success is obtained for laser welding since laser degrades the mechanical properties at the weld due to defects in the resolidified aluminum matrix, delamination of graphite fibers, and formation of brittle aluminum carbide Al₄C₃. Brazing is the preferred technique since the low brazing temperature of filler material suppresses the formation of Al₄C₃ while minimizing shrinkage cavities in the joint. Microstructural study and shear testing confirms the success of joining Al–Gr by laser brazing and resistance brazing with Zn–Al filler.     

Compressive behavior and energy absorption of metal porous polymer composite with interpenetrating network structure

Interpenetrating phase composites （IPCs） are a new class of composite materials with improved combinations of mechanical and physical properties. This study was performed on a new type of IPC called metal porous polymer composite （MPPC） with an interpenetrating network structure. Aluminum-polypropylene （Al-PE） and Aluminum-epoxy resin （Al-Ep） composites were produced by infiltrating the polymer in the aluminum foam. The composite microstructures were characterized using SEM observation. The compressive behavior and energy absorption characteristics of MPPC were investigated and compared with the aluminum foams. The compressive modulus of composite was compared with the VOIGT-REUSS bounds and HASHIN-SHTRIKMAN （H-S） bounds models. The experimental modulus of compressive tests falls well within the theoretical models.     

Mechanical Properties and Microstructural Behaviour of Microwave Sintered WC–Co

Metals and Materials International - Cemented carbides have been of great interest within industrially manufacturable hard materials for their mechanical properties. Microwave sintering is known...     

Designed synthesis of wide range microwave absorption Fe3O4–carbon sphere composite

Fe₃O₄–carbon sphere composite was synthesized by a simple hydrothermal method. The as-synthesized products were characterized by field-emission scanning electron microscopy (FE-SEM), energy dispersive spectrum (EDS), X-ray diffraction (XRD), vibrating sample magnetometer (VSM), and Raman spectrum. The complex permittivity and permeability of paraffin wax and Fe₃O₄–carbon sphere composite with different volume fraction of the composite were measured by vector network analysis. A wide region of microwave absorption was achieved due to dual dielectric and magnetic losses. When the matching thickness is 4 mm, the calculated reflection loss of the sample with 70% volume fraction of Fe₃O₄–carbon sphere composite exhibits a broad microwave absorption ranging from 2.5 to 18 GHz.     

Microwave permittivity of SiC-Al2O3 composite powder prepared by sol-gel and carbothermal reduction

SiC-Al2O3 composite powder was prepared by sol-gel and carbothermal reduction method. The powder synthesized was characterized by X-ray diffraction（XRD） and scanning electron microscopy（SEM） to confirm the phase formation, and the thermodynamic analysis was performed systematically. Moreover, the variation of its microwave permittivity with different atomic ratio of Al/Si was investigated in the frequency range of 8.2-12.4 GHz. The results show that, the powder obtained consists of spherical particles of 300-400 nm in diameter, which are composed of SiC and Al2O3 microcrystal with the grain size of approximately 45 nm. The results of XRD accord with those of the thermodynamic analysis. It is impossible for Al atoms to dissolve in the lattice of SiC during the carbothermal reduction process. Along with the increase of atomic ratio of Al/Si in the xerogel, the amount of Al2O3 in the powder synthesized increases, which reduces both ε＇, the real part of complex permittivity, and tg δ（ε＂/ε＇）, the dissipation factor, where ε＂ is the imaginary part of complex permittivity.     

Microwave sintering of nanocrystalline WC–12Co: Challenges and perspectives

Microwave sintering of microcrystalline and nanocrystalline WC–12Co powder compacts was carried out employing different time–temperature schedules. The microcrystalline powder compacts were made from powders with particle sizes ranging from 5 to 45 μm by using methyl cellulose as the lubricant. The nanocrystalline powder compacts were made from powders having a mean WC grain size of 38 nm, without employing any lubricant. The sintered samples were characterized with respect to their densities, Vickers hardness, fracture toughness and microstructures and the challenges encountered during microwave sintering of the WC–12Co powders are discussed.     

Electrochemical corrosion behaviour and surface morphology of electrodeposited zinc,zinc–cobalt and their composite coatings

Abstract

The electrochemical behaviour as well as the surface morphology characteristics of electrodeposited Zn and Zn-Co (≈3 wt-%) alloy coatings on low carbon steel samples, with and without included nanoparticles of organic co-polymers in their structure, are discussed. Their corrosion resistance and protective properties were studied in a model corrosion medium, 5 wt-% NaCl, using electrochemical methods such as polarisation resistance (R _p) measurements and potentiodynamic (PD) polarisation curves. Scanning electron microscopy (SEM) was performed to examine the surface morphology changes of the samples before and after the corrosion treatment. Some conclusions are drawn about the influence and importance of the organic nanoparticles on the corrosion behaviour of the coatings presented.     

Friction and wear behaviors of reciprocatingly extruded Al–SiC composite

This study focuses on the friction and wear behaviors of reciprocatingly extruded Al–SiC composites. To increase the strength of metal matrix composites and refine the grains of the matrix some deformation processes can be applied, such as reciprocating extrusion (RE). For this reason, RE was carried out on a 6061 Al matrix by a SiC (20 μm) reinforced composite one. The billets were extruded under a pressure of 17.5 MPa at 573 K with a 10:1 extrusion ratio. The reciprocating extrusions were carried out by using up to 15 passes.     

Structure and oxidation resistance of W1–xAlxN composite films

A series of W_1–xAl_xN films (0<x<38.6%, mole fraction) were deposited by reactive magnetron sputtering. The composition, microstructure, mechanical properties and oxidation resistance of the films were characterized by EPMA, XRD, XPS, nano-indentation, SEM and HRTEM. The effect of Al content on the microstructure and oxidation resistance of W_1–xAl_xN films was investigated. The results show that WN film has a face-centered cubic structure. The preferred orientation changes from (111) to (200). The W_1–xAl_xN films consist of a mixture of face-centered cubic W(Al)N and hexagonal wurtzite structure AlN phases. The hardness of the W_1–xAl_xN films first increases and then decreases with the Al content increasing. The maximum hardness is 36 GPa, which is obtained at 32.4% Al (mole fraction). Compared with WN film, the W_1-xAl_xN composite films show much better oxidation resistance because of the formation of dense Al₂O₃ oxide layer on the surface.     

Preparation and corrosion behavior of electrodeposited Ni–TiN composite coatings

Ni–TiN composite coatings were successfully prepared by direct current (DC), pulse current (PC) and ultrasonic pulse current (UPC) deposition methods. The morphology, mechanical properties and the corrosion behavior of Ni–TiN composite coatings were investigated using atomic force microscope (AFM), scanning electronic microscope (SEM), X-ray diffraction (XRD) and gravimetric analysis. The results show that the Ni–TiN composite coatings synthesized by UPC deposition method possess a compact and exiguous surface morphology. The XRD results demonstrate that the average grain diameter of Ni and TiN in composite coating prepared by UPC deposition is 52.6 and 35.7 nm, respectively. In the corrosion tests, the coating prepared by UPC deposition exhibits the best corrosion resistance, whereas the coating fabricated by DC deposition suffers the most serious damage.     

Microstructure and sliding wear assessment of Co–TiC composite materials

Monolithic Co and Co based composites reinforced by TiC precipitates were fabricated by vacuum arc melting process. The ratio of hexagonal to cubic phase cobalt was affected by the presence of the TiC precipitates. The microstructure of the produced materials was also associated with the presence of TiC crystals. The TiC primary precipitates are characterised by a strong faceted morphology which is explained in terms of Jackson’s theory of crystal growth. The solidification progress was altered by the presence of the TiC crystals. The sliding wear behaviour of the produced composites was assessed in terms of wear track and debris examination and compared to that of Co29Cr5Mo alloy.     

Microstructure and mechanical properties of hot pressed Mo–Cr–Si–Ti in-situ composite,and oxidation behavior with silicide coatings

The present study deals with the synthesis of Mo–16Cr–4Si–0.5Ti (wt.%) alloy by means of the reactive hot pressing method. The microstructure of the synthesized alloy consisted of (Mo, Cr, Ti)₃Si, and the discontinuous α-(Mo, Cr, Ti)_SS phases. The isothermal oxidation behavior of the alloy was investigated in air at 1273 K for 50 h. The alloy exhibited superior oxidation behavior in comparison with single phase molybdenum alloys, because of the formation of SiO₂ and Cr₂O₃ over the alloy surface. The flexural strength determined from three-point bend testing of single edge notch bend specimens was 615 ± 15 MPa. The dominant mechanism of fracture was identified as transgranular mode of crack propagation. To extend the life of the alloy under oxidizing atmosphere, silicide based oxidation resistant coatings were developed, using halide activated pack cementation process. The kinetic behavior of growth of the coating was established and the activation energy of the coating process was determined to be 52.5 kJ/mol. Isothermal oxidation tests of the coated alloy at 1273 K for 50 h, revealed a small weight gain at the initial stages of oxidation followed by no change of weight, indicating the protective nature of the coating.     

Microstructure,fracture, and thermal stability of Ni–Fe–Cu–P–B two-phase amorphous composite produced from the double-chamber crucible

The purpose of the work was investigation of the final microstructure and properties of the melt-spun Ni–Fe–Cu–P–B, Ni–Fe–B, and Ni–Cu–P alloys ejected as uniform liquid from the standard single-chamber crucible and from the double-chamber crucible as flux composed of the two Ni–Fe–B and Ni–Cu–P liquids cooled on a copper roller before formation of a uniform mixture. The methods applied in this study for microstructural investigations include scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and Mössbauer spectroscopy. Thermal stability of the melt-spun alloys was tested using differential scanning calorimetry (DSC) and tensile test were performed. The results of the investigations are described and discussed in terms of the unique features of the two component melt spinning (TCMS) amorphous microstructure.     

Annealing hardening and deformation behavior of layered gradient Zr–Ti composite

To investigate potential strengthening approaches, multi-layered zirconium–titanium (Zr–Ti) composites were fabricated by hot-rolling bonding and annealing. The microstructures of these composites were characterized using scanning electron microscopy with energy dispersive spectroscopy (SEM–EDS) and electron backscatter diffractometry (EBSD). Their mechanical properties were evaluated by uniaxial tension and compression measurements. It was found that the fabricated Zr–Ti composites are composed of alternating Zr/diffusion/Ti layers, and chemical compositions of Zr and Ti showed a gradient distribution in the diffusion layer. Compared with as-rolled samples, annealing can strengthen the layered gradient Zr–Ti composite, and this is mainly caused by solid-solution strengthening and microstructure refinement-induced strengthening. Compared with the raw materials, a synergistic improvement of strength and ductility is achieved in the Zr–Ti composite as a result of the layered gradient microstructure. Tension–compression asymmetry is observed in the Zr–Ti composites, which may be attributed to twinning and microvoids induced by unbalanced diffusion.     

In-situ synthesis of WC–Co composite powder and densification by sinter-HIP

In the present study, a complete route which integrates in-situ synthesis of WC–Co composite powder and sinter-HIP is proposed to prepare the ultrafine tungsten carbides. Owing to the in-situ reduction and carbonization reactions of WO_2.9, Co₃O₄ and carbon black powders at 1000 °C, the composite powder with pure phase constitution and ultrafine particle size is synthesized with a rapid procedure. The WC–Co bulk material prepared by the sinter-HIP densification of the composite powder exhibits homogeneous and ultrafine microstructure, as well as the excellent mechanical properties. The proposed method shows potential to be developed as a promising industrial route owing to its advantages of low-cost raw materials and short-term in-situ reactions.     

Preparation and sintering of silica-coated ultrafine diamonds–vitrified bond composite powders

The oxidation resistance of ultrafine diamonds (UFDs) was improved by encapsulating UFDs into silica shells forming core/shell structures with a PVP-aided method. Meanwhile, the dispersion stability of the UFDs in the inorganic salt aqueous solution was also improved greatly. In addition, adopting the silica-coated UFD aqueous suspension including multi-component inorganic salts, the coated UFDs–vitrified bond composite powders with higher homogeneity were obtained by using a polyacrylamide gel method, which was used for manufacturing the vitrified-bonded UFD wheels. The porous specimens of the UFD grinding wheels were fabricated with the above composite powders at low temperature in the air and in a muffle furnace. The results suggested that the porosity, bulk density and bending strength of the specimens were 36.3%, 1.71 g/cm^− 3 and 62.9 MPa, respectively. Moreover, no obvious aggregation and degradation of UFDs were observed in the above UFD specimens. These results demonstrate a new pathway of preparing multifunctional nanostructure with a low-aggregation and high oxidation resistance that can be applied for manufacturing vitrified-bonded UFD wheels.