D.P. Weston

The electrodeposition of silver composites using deep eutectic solvents.

Silver is an important metal for electronic connectors, however, it is extremely soft and wear can be a significant issue. This paper describes how improved wear resistant silver coatings can be obtained from the electrolytic deposition of silver from a solution of AgCl in an ethylene glycol/choline chloride based Deep Eutectic Solvent. An up to 10-fold decrease in the wear volume is observed by the incorporation of SiC or Al(2)O(3) particles. The work also addresses the fundamental aspect of speciation of silver chloride in solution using EXAFS to probe solution structure. The size but not the nature of the composite particles is seen to change the morphology and grain size of the silver deposit. Grain sizes are shown to be consistent with previous nucleation studies. The addition of LiF is found to significantly affect the deposit morphology and improve wear resistance.

Nanostructured Co–W coatings produced by electrodeposition to replace hard Cr on aerospace components

Abstract Co–W alloys with 12–26 at.-%W (25–45 wt-%W) can be produced by electrodeposition from complexed aqueous plating baths. The deposits can be in the amorphous or nanostructured conditions, depending on the plating bath operations. Most recent attention has been focused on the nanocrystalline conditions which have hardness values in excess of 850 kg mm−2, which makes them competitive with hard engineering chromium. This may allow the coatings to replace hard Cr which is produced from hexavalent chromium baths having associated health and safety problems. Co–W coatings, 2–120 μm thick, can be deposited with a low incidence of cracking, with good corrosion and wear properties (dry and lubricated) when deposited on a variety of steel substrates. The underlying reasons, i.e. the amount of tungsten in solution, the density of grain boundaries and the reduction in bonding between coating and counterface under dry sliding conditions, which account for these enhanced properties are discussed. Potential applications are in many sectors of engineering including aerospace, hydraulics and automobile.

Ternary lithium nitridocuprates, Li3−x−yCuxN: crystal growth, bulk synthesis, structure and magnetic properties

Abstract Systematic studies within the ternary Li–Cu–N system have examined the effects of varying starting materials, transition metal stoichiometry, reaction temperature/duration and cooling rate on crystal growth and bulk phase formation of ternary nitridocuprates. Resulting lithium transition metal compounds, Li 3− x − y □ y Cu x N (□=Li vacancy), have been characterised by single crystal and powder XRD. The maximum copper substituent level ( x ≈0.45) and vacancy level, y , appear insensitive to reaction temperature. Both vacancies and copper are disordered with Li when reaction mixtures are quenched (α-Li 3 N-type: P6/mmm , a ≈3.7 A, c ≈3.8 A, Z =1), whereas evidence of copper and/or vacancy ordering exists on slow cooling. Morphology of crystallites has been evaluated by SEM and magnetic properties have been investigated using squid magnetometry. Magnetic data show compounds exhibit temperature dependent paramagnetism in contrast to the parent nitride, Li 3 N.

Production of A356/TiB2 Nanocomposite Feedstock for Thixoforming by an Ultrasonic Method

Metal matrix nanocomposites (MMNCs) are promising materials to produce engineering components for the automotive and aerospace industry. This study aims to determine the feasibility of Al/TiB2 nanocomposite fabrication by the combination of the ultrasonic method and flux-assisted particle incorporation for the production of thixoforming feedstock material. Flux assistance has been invoked to attempt to overcome challenges with the presence of oxide on the surface of the foil in the aluminium foil capsulate method. A356 alloy has been reinforced with 0.25 wt.% TiB2 nanoparticles using different methods; 1. Flux-assisted casting, 2. Flux-assisted casting with ultrasonic cavitation, and 3. The Al foil capsulate method for particle feeding with ultrasonic cavitation. The composite fabricated by the ultrasonic method with the use of flux agent provided a non-dendritic microstructure which is the requirement for thixoforming. It was found that the flux-assisted casting method is not appropriate for achieving nanoparticle entry into the melt in MMNC fabrication due to the buoyancy forces of nanoparticles, unlike micron-sized particles.

New metathesis routes to layered dichalcogenides: synthesis, crystal growth and structure of NayNbX2 (y=0.5, X = S, Se)

Separated reactant metathesis methods using ternary oxide precursors and yttrium chalcogenides have been used to prepare powders and crystals of alkali metal niobium dichalcogenides, AyNbX2 (X = S, Se). The structure of Na0.5NbSe2 has been solved unambiguously for the first time from single crystal X-ray data (hexagonal space group P63/mmc (no. 194), a = 3.4762(7), c = 15.342(2) A, U = 160.55(5) A3, Z = 2). Similarly, the structure of Na0.5NbS2 has also been determined (hexagonal space group P63/mmc, a = 3.3533(4), c = 14.547(3) A, U = 141.66(4) A3, Z = 2). Products have been characterised further by powder X-ray diffraction, scanning electron microscopy and energy dispersive X-ray analysis. Magnetic measurements describe temperature-independent paramagnetic behaviour for both dichalcogenides, with no superconducting transitions above 1.8 K.

Measurement and Modeling of Pitting Depth Distribution for Phosphor Bronze Tapes Used in Underground Power Transmission Cables

Phosphor bronze tapes used in underground power transmission cables are affected by pitting corrosion that can lead to cable failures. In the present work, the probability distribution of corrosion...

Life prediction of phosphor bronze reinforcing tape used in underground power cables

Phosphor bronze tape is a key protection component of underground power transmission cables. During the service life, it is affected by both corrosion and fatigue effects, leading to the failure of...