Cold densification rolling of porous copper strip obtained directly from cuprous oxide perform

Abstract

The densification of porous copper strips obtained from the combined reduction and sintering of cuprous oxide preforms by cold rolling has been discussed. It has been shown that such strips, although containing a relatively large amount of porosity, exhibit no problems during cold rolling and, in general, have good workability. Although it is possible to subject the strip to cold rolling thickness deformations of the order of 75%, without any intermediate annealing, rolling with annealing after every 35–40% cold rolling reduction yields better results. The efficiency of densification and changes in the pore morphology during the cold rolling of the porous strip have also been discussed.

MST/670     

Copper/copper oxide nanoparticles synthesis using Stachys lavandulifolia and its antibacterial activity

Nanoparticles of copper/cuprous oxide (Cu/Cu₂ O) were successfully synthesised by a green chemistry route. The synthesis process was carried out using an extract of Stachys lavandulifolia as both reducing and capping agents with a facile procedure. The nanoparticles were characterised by different techniques including X‐ray diffraction, indicating that the synthesised sample comprised both copper and cuprous oxide entity. The nanoparticles had a mean size of 80 nm and represented an impressive bactericidal effect on Pseudomonas aeruginosa.Inspec keywords: copper, copper compounds, nanoparticles, nanofabrication, nanomedicine, antibacterial activity, X‐ray diffractionOther keywords: nanoparticles synthesis, Stachys lavandulifolia, antibacterial activity, green chemistry route, reducing agents, capping agents, X‐ray diffraction, bactericidal effect, Pseudomonas aeruginosa, Cu‐Cu₂ O     

Daguerreotypes on copper

Abstract

The history of photography is dominated by accounts of various processes which utilize the light sensitivity of silver halides. It is less well known that cuprous halides are also light sensitive, and that they share with silver halides the ability to retain a latent image¹. It is helpful to review the history of light-sensitive processes based on cuprous halides before describing a new process for making daguerreotype-like images on copper.     

Effects of aluminium powder content and cold rolling on foaming behaviour of xAlp/Al5Si4Cu4Mg/0.8TiH2 composites

Abstract

Aluminium foams were produced by applying powder metallurgy technology. The process began by making aluminium powder and mixing it with alloy powder (Al5Si4Cu4Mg) and foaming agent (TiH₂). The mix was compacted to the form of a billet by cold pressing and then it was hot extruded to a dense foamable strip, which was cold rolled to give 40% thickness reduction. The resulting precursor composites of both the extruded strip and the extruded plus rolled strip were then freely foamed without a mould at a constant temperature of 700°C for different foaming times. The effects of aluminium powder content and cold rolling on the foaming characteristics of the foamable composite strip were studied. It is noted that aluminium powder fibre in the extruded composite strip acts as a barrier to pore initiation and evolution due to the higher melting point of pure aluminium fibre than that of the alloy matrix. Cold rolling promotes foaming of the composite strip due to the TiH₂ cracking and debonding between TiH₂ particles and metal matrix. The morphological and microstructural evolution of composite foams was also investigated. The foaming mechanism can be described by the following sequence: cracklike pore nucleation between elongated powder fibres; ellipsoidal, spherical, and polygonal pore growth; and the collapse of pores as a result of coalescence.     

Making tungsten targets using tungsten oxide powder

A straightforward method of making tungsten targets from tungsten oxide powder on Cu backing is presented. A ceramic crucible containing WO₃ powder placed on a copper foil is heated in hydrogen atmosphere at temperatures ranging from 650 up to 850 °C. The resulting thickness of tungsten deposited in our trials was in the range of 0.5-3.4 mg/cm².     

γ-Cu2(OH)3Cl as precursor in the preparation of copper (I) and (II) oxides and copper powder

When-Cu₂(OH)₃Cl is decomposed in air or nitrogen flow, different amounts of cuprous oxide are obtained as final product depending on both the heating rate and the ambient atmospheres. However, the temperature of formation of cuprous oxide only appears to depend on the partial pressure of oxygen. When thermal decomposition is carried out under dynamic vacuum in the X-ray high-temperature diffraction chamber, using a tantalum strip as the heating element, copper is obtained as final product at a comparatively low temperature.     

Sustainable GQDs for potential application in engineering using corn powder as green precursor

Abstract

An alternative way to produce Graphene Quantum Dots (GQDs) economically is proposed in this study where corn powder was used as a green precursor to fabricate GQDs in a hassle less one-step route. These GQDs showed a stable, size-dependent in aqueous solution. The size of GQDs obtained from this work is approximately measure from 0.21 to 5.20?nm. The XRD patterns showed a broad peak at 22?Å. Furthermore, the UV-vis absorption spectrum has a broad peak around the range of 250–350?nm which is ascribed to the typical absorption of n-π* transition of the carbonyl groups. The said sample also exhibited bright green photoluminescence under an UV light. The Raman spectra displayed a D band around 1375?cm^?1 and G band around 1578?cm^?1. The performed analysis confirms that the GQDs by this method has a similar result compared to the other methods. This suggests that corn powder as a precursor can be used to fabricate GQDs in a simplistic and environment-friendly way for potential application in sensors, very large scale integration and energy generation technology.     

Bonding between aluminium and copper in cold spraying: story of asymmetry

Abstract

The bonding mechanism in cold spraying is still a matter of some debate, which requires further investigation. In the present work, aluminium powder was cold sprayed onto a copper substrate and copper powder was cold sprayed onto an aluminium substrate using the same process gas and spray parameters. Separate experiments were performed to produce thick (～400 μm) coatings and isolated particle impacts. Deposits were characterised using scanning electron microscopy and image analysis. The coating–substrate interfacial bonding was assessed via a method in which, following a short heat treatment at 400°C, intermetallics grow at the interface where metal to metal contact has been established. In addition, the bond strength values of deposits were determined using a standard pull-off test. It was found that the copper particles deposited onto an aluminium substrate resulted in significant substrate deformation, whereas aluminium particles caused minimal deformation of the copper substrate. Furthermore, the former displayed a higher degree of metallurgical bonding at the coating/substrate interface in comparison with the latter. These results suggest that the removal of oxide films from the surfaces was greater when copper was the material being sprayed rather than aluminium. The impact behaviour of the two materials and the removal of oxide due to deformation at high strain rate are discussed with the aid of the Johnson–Cook plasticity model.     

Comparison analysis of graphene oxide reduction methods

Abstract

Graphene oxide was reduced by aspartic acid, β-mercaptoethanol in the acidic mixture, hydrothermal method and by atomic hydrogen (deuterium and tritium). Raman spectroscopy and FTIR indicate high reduction efficiency of hydrothermal method. FTIR indicates that atomic hydrogen results in the formation C_sp3H-bonds on the graphene surface. Graphene oxide can be effectively reduced by β-mercaptoethanol in the acidic mixture even at room temperature.     

超细球形铜粉的制备工艺研究

以水合肼为还原剂,采用液相化学法对超细铜粉的制备工艺进行了研究。结果表明,直接还原Cu2O获得的铜粉粒度分布很不均匀,抗氧化性能差。在添加微量亚铁氰化钾和2,2’-联吡啶后,铜粉的形貌、粒度分布以及抗氧化性能得到很大改善。经两步还原硫酸铜可制备平均粒度0.5μm以下且分布范围窄的近球形铜粉,热分析表明,该粉末在空气中120℃以下无氧化。     

Low-cost synthesis of hollow Cu2O octahedra with more than one shell

Inorganic materials with hollow and multilayer structures have attracted many interests because of their special applications. In this paper we reported a low-cost synthetic route for hollow cuprous oxide octahedra with more than one shell. Various characterizations identified the as-obtained powder as pure, uniform, and monodispersed Cu₂O octahedra wrapped by the {111} faces. To determine the formation mechanism, the time-dependent experiments were conducted and the results showed that the intermediate phase, CuO, precipitated out first and its reduction by amino acids led to the formation of hollow Cu₂O structures.     

A Comparative Analysis of Catalysts for the Preparation of Germanium through Hydrogen Reduction of Germanium Tetrachloride

We have synthesized catalysts for the hydrogen reduction of germanium tetrachloride: a catalyst based on multiwalled carbon nanotubes and a hybrid catalyst based on multiwalled carbon nanotubes whose surface was decorated with copper-containing nanoparticles. The hybrid catalyst has been characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results demonstrate that it consists of multiwalled carbon nanotubes whose surface is decorated with copper nanoparticles in a cuprous oxide shell (Cu₂O/Cu/MWCNTs). The catalytic activity of the hybrid catalyst exceeds that of the as-prepared MWCNTs. The use of the Cu₂O/Cu/MWCNT hybrid catalyst as a catalyst for the hydrogen reduction of germanium tetrachloride allows the reaction temperature to be lowered and ensures 95.7% germanium tetrachloride conversion at 873 K.     

Damping properties of porous AZ91 magnesium alloy reinforced with copper particles

Abstract

The well distributed open porous AZ91 magnesium alloy reinforced with copper particles was successfully prepared through powder metallurgy route based on space holder method. Its damping properties were characterised by internal friction and the internal friction measurement in a temperature range from room temperature to 100°C was performed by a multifunction internal friction apparatus. Experimental results revealed that the damping capacity of the porous AZ91 magnesium alloy was increased as a result of the addition of copper particle and the increase was further enhanced with increasing volume fraction of copper particle. Attempt is performed to correlate the increase in damping with the microstructural change arising due to the addition of copper particles. It was suggested that the increase should be related to the appearance of plastic zone and thus an increase in dislocation density at the matrix particles interfaces.     

Controlling the Formation of Nanocavities in Kirkendall Nanoobjects through Sequential Thermal Ex Situ Oxidation and In Situ Reduction Reactions

Controlling the porosity, the shape, and the morphology of Kirkendall hollow nanostructures is the key factor to tune the properties of these tailor‐made nanomaterials which allow in turn broadening their applications. It is shown that by applying a continuous oxidation to copper nanowires following a temperature ramp protocol, one can synthesize cuprous oxide nanotubes containing periodic copper nanoparticles. A further oxidation of such nanoobjects allows obtaining cupric oxide nanotubes with a bamboo‐like structure. On the other hand, by applying a sequential oxidation and reduction reactions to copper nanowires, one can synthesize hollow nanoobjects with complex shapes and morphologies that cannot be obtained using the Kirkendall effect alone, such as necklace‐like cuprous oxide nanotubes, periodic solid copper nanoparticles or hollow cuprous oxide nanospheres interconnected with single crystal cuprous oxide nanorods, and aligned and periodic hollow nanospheres embedded in a cuprous oxide nanotube. The strategy demonstrated in this study opens new avenues for the engineering of hollow nanostructures with potential applications in gas sensing, catalysis, and energy storage.     

The controlled reduction of copper tungstate in H2O/H2 mixtures

The controlled reductions of copper tungstate, copper tungstate plus blue tungsten oxide and CuO plus WO₃ have been studied at temperatures of 500, 600 and 700C using H₂/H₂O mixtures in a glass thermobalance. The copper-tungsten oxide composite powder products have been characterized by X-ray diffraction analysis and scanning electron microscopy. The morphologies of the copper-tungsten oxide products have been related to the morphologies of copper-tungsten powders obtained by dry hydrogen reduction. It is shown that widely varying copper-tungsten oxide morphologies may be obtained as precursors for metal powder production by control of the H₂/H₂O ratio in the reducing gas mixture.     

Green chemistry synthesis of nano‐cuprous oxide

Green chemistry and a central composite design, to evaluate the effect of reducing agent, temperature and pH of the reaction, were employed to produce controlled cuprous oxide (Cu₂ O) nanoparticles. Response surface method of the ultraviolet–visible spectroscopy is allowed to determine the most relevant factors for the size distribution of the nanoCu₂ O. X‐ray diffraction reflections correspond to a cubic structure, with sizes from 31.9 to 104.3 nm. High‐resolution transmission electron microscopy reveals that the different shapes depend strongly on the conditions of the green synthesis.Inspec keywords: nanostructured materials, copper compounds, nanofabrication, pH, response surface methodology, ultraviolet spectra, X‐ray diffraction, transmission electron microscopyOther keywords: green chemistry synthesis, nanocuprous oxide, reducing agent, reaction pH, response surface method, ultraviolet‐visible spectroscopy, size distribution, cubic structure, high‐resolution transmission electron microscopy, X‐ray diffraction reflection, central composite design, Cu₂ O     

Synthesis of Nanophase WC Powder by Displacement Reaction

ABSTRACT

Conventional thermochemical processing of nanophase WC powder involves hydrogen reduction of a tungsten precursor compound to form high surface area α-W. followed by gas phase carburization to develop WC. This two-step process inevitably leads to some coarsening of the nanophase WC powder product. Recently, we have developed a new method, called “displacement reaction processing”, in which the two steps (reduction and carburization ) are combined into a single step, leading to a much finer nanostruciure for the product WC powder. The one-step process is particularly favored when H₂ reduction of the precursor compound results in the formation of an amorphous oxygen-rich intermediate. The resulting nanophase WC has a particle size < 10 nm. In this talk, the procedures that must be followed to promote one-step WC powder processing, starting from different tungsten-based precursors, will be described, and the mechanisms discussed.     

Processing of Ti-SiC metal matrix composites by tape casting

Abstract

Titanium-silicon carbide (Ti-SiC) continuous fibre composites are very attractive for aerospace applications. Although development of various components is under way, a cost effective method to manufacture the material still has to be identified. Here, a tape casting technique is investigated as a viable method of producing the composites. It involves relatively large inexpensive titanium powder and simple apparatus. Furthermore, the powder particles ensure good fibre distribution, reduced consolidation time, and little damage to the reinforcement. It is shown that uniform powder tapes with good packing density can be readily produced using appropriate casting parameters. Both thermogravimetry and mass spectrometry are used to analyse the burnout process of a fugitive binder system used to produce the tapes. Removal of the organics is found to take place in two stages, separated by over 100 K. composite materials processed by the tape casting route exhibit good fibre distribution and no signs of fibre damage.     

Green synthesis of copper oxide nanoparticles and its effective applications in Biginelli reaction,BTB photodegradation and antibacterial activity

Metal/metal oxide nanoparticles have gained much attention in the field of organic catalysis and photocatalysis reactions for development of greener methodology. In the present work, copper oxide nanoparticles (CuO NPs) were synthesized by a greener route using Cordia sebestena (C. sebestena) flower aqueous extract. The nanoparticles were evaluated for their catalytic efficiency. The green synthesized CuO NPs were characterized using various analytical studies. A UV–Visible spectrum with peak at 267?nm and the peaks in their FT-IR spectrum at 431 and 542?cm^?1 showed reduction by the plant metabolites. FESEM-EDX analysis of CuO NPs shows an agglomerated spherical shape with signatures of Cu and O and XRD reveals characteristic crystallinity. TEM and DLS analyses showed particle size between 20 and 35?nm and TEM-SAED pattern ensured crystallinity. A Zeta potential of ?26?mV demonstrates moderate stability. The CuO NPs acted as a catalyst in the Biginelli reaction to produce 3,4-dihydropyrimidinones rapidly and at high yield. The NPs also degraded bromothymol blue (BTB) by photocatalysis with hydrogen peroxide. 100% dye removal efficiency was achieved by 3?h exposure of BTB to natural sunlight inferring it as economy, ecofriendly and effective catalyst. This finding illustrates that the NPs could be used in photolysis to remove water pollutants. Moreover, the biological significance of green synthesized CuO NPs was assessed by antibacterial activity against selected pathogenic bacterial organisms.     

Influence of water vapor on the reduction of cuprous chloride to copper microfibers

Reduction of cuprous chloride has been examined in various atmospheres, mostly at 600°C, to produce copper microfibers that can be applied as a filler for electromagnetic interference shielding and electron conductive paste composites. The reduction with hydrogen resulted in formation of a large amount of copper films, but fine particles and short filaments were obtained when carbon black was mixed into the raw material. The most promising copper microfibers with dimensions of several mm length and 1–10 m thickness could be produced with the system CuCl — C — H₂O using argon as a carrier gas, where H₂ and CO formed then probably reduced the vaporized CuCl molecules. Introduction of hydrogen gas into this system increased the yield of copper microfibers, though they became more bent, curved and kinked in shape. However, the morphology of the microfibers is still acceptable as a filler.