[Show abstract][Hide abstract] ABSTRACT: The possibility to align diamond nanoparticles has a number of potential technological applications, but there are few methods by which this can be achieved, and research in this field can be considered to be in its infancy. Hitherto, two methods which have been commonly used are lithography and chemical vapour deposition (CVD), but these methods are both complex and have poor effectiveness. In this paper, we present a new technique for particle alignment, which is simpler and avoids particle structural damage. The method works by functionalising the nanodiamonds of size 5 nm by attaching 1-undecene onto the nanodiamond surfaces; the particles are then evaporated using UHV and deposited onto TEM grids and mica surfaces at 200 °C. XPS, SERS, HRTEM, luminescence spectroscopy and luminescence micro-imaging have been applied to characterise samples both before and after evaporation. Deposition of nanodiamond onto a mica surface resulted in particle alignment with length scales of 500 µm. The XPS and Raman spectra confirmed the absence of non-diamond carbon (sp2-hybridized carbon). Moreover, photoluminescence (emitting in the range of 2.48–1.55 eV; 500–800 nm) which is characteristic for nanodiamond with size of 5 nm was also observed, both before and after evaporation of the functionalised nanodiamonds.
[Show abstract][Hide abstract] ABSTRACT: An oxygen transport membrane made from La0.6Sr0.4Co0.2Fe0.8O3 − δ (LSCF6428) has been tested for air separation by oxygen permeation at 900 °C with the introduction of sulfur in the form of hydrogen sulfide. 200 ppm of hydrogen sulfide was fed either in the sweep-side (argon-side) or the air-side. The membrane was exposed to hydrogen sulfide for 100 h. Results show that the presence of hydrogen sulfide negatively influenced the oxygen permeation due to the formation of strontium sulfate blocking the oxygen permeation pathway. When the hydrogen sulfide was removed from the system, the oxygen permeation was partially restored in the case of argon-side contamination, while being fully restored in the case of air-side contamination.
[Show abstract][Hide abstract] ABSTRACT: Undoped, cast films of PolyBenzoImadazole (PBI) were investigated as a function of humidity using both H2O and D2O, and as a function of temperature up to 100 °C in order to better understand the infrared response of this polymer, as well as to provide benchmark data for subsequent studies on acid doped PBI. Marked changes across the mid-IR range were observed during the uptake of water and D2O. The use of D2O proved extremely useful in terms of deconvoluting the complex IR response observed and allowed the IR data to be rationalised in terms of the disruption of the N-H…N inter-chain hydrogen bonded network and changes in the morphology of the polymer.
[Show abstract][Hide abstract] ABSTRACT: This work reports an investigation on mass transfer by ultrasound agitation during electrodeposition on electrodes separated by a narrow inter-electrode gap. Polarisation experiments were performed to identify the mass transfer limiting current. The limiting current density was used to calculate mass transfer boundary layer thicknesses which were used to develop mass transfer correlations. Experiments were carried out using a cell with parallel copper discs which were positioned at gaps of 1, 0.5 and 0.15 cm. The distance between the ultrasonic probe and electrodes was varied between 3 and 1.5 cm. The polarisation data showed clear limiting current plateaux when the distance between the electrodes was larger, however significant distortions were observed when the gap was 0.15 cm. It was found that lower ultrasound powers of 9–18 W/cm2 provided more effective agitation at narrower electrode gaps than powers exceeding 18 W/cm2. Sherwood correlations showed that in this system, developing turbulence occurs for larger inter-electrode spacing, whereas for narrow electrode gaps fully turbulent correlations were obtained. A 2-D current distribution model showed that potential distortions that were observed in the polarisation data were caused by the close placement of the metallic US probe to the two parallel electrodes.
[Show abstract][Hide abstract] ABSTRACT: A more robust kinetic model of base-catalysed transesterification than the conventional reaction scheme has been developed. All the relevant reactions in the base-catalysed transesterification of rapeseed oil (RSO) to fatty acid methyl ester (FAME) were investigated experimentally, and validated numerically in a model implemented using MATLAB. It was found that including the saponification of RSO and FAME side reactions and hydroxide–methoxide equilibrium data explained various effects that are not captured by simpler conventional models. Both the experiment and modelling showed that the “biodiesel reaction” can reach the desired level of conversion (>95%) in less than 2 min. Given the right set of conditions, the transesterification can reach over 95% conversion, before the saponification losses become significant. This means that the reaction must be performed in a reactor exhibiting good mixing and good control of residence time, and the reaction mixture must be quenched rapidly as it leaves the reactor.
[Show abstract][Hide abstract] ABSTRACT: The rechargeable Li-air battery has a key role to play as a storage system for renewable energy and as the power system for electric vehicles. Effective cathode materials are required to improve its capacity, cycling ability and rate capability. In this work, an ionic conductive Li-Nafion® binder and Li-Nafion® membrane materials were fabricated and used to construct a novel rechargeable Li-O2/air and all-solid battery. The battery achieved a high capacity over 1000 mA h (g solids)−1 with good rate capability and capacity retention were achieved. Insight into the improved performance has been explored with the aid of TEM, XRD, galvanostatic charge discharge test and impedance analysis.
[Show abstract][Hide abstract] ABSTRACT: Cu electroplating was carried out using a pure ethaline melt, a 1:2 ratio of choline chloride and ethylene glycol, at room temperature by potentiostatic and galvanostatic methods. Hydrated cupric chloride was added to the pure ethaline melt. Polarisation data for cupric ion reduction to copper was collected using an RDE to determine where metal deposition was feasible. Smooth Cu deposits were obtained at − 4.7 × 10− 3 A/cm2 using 0.2 M CuCl2·2H2O at 25 °C at a current efficiency of (95 ± 5)% at a rotation speed of 700 rpm. XRD analysis of the deposit showed a polycrystalline face centred cubic structure with (111) texture. The crystalline size was 66 ± 10 nm with some internal strain. EDX analysis showed the presence of carbon and chlorine with copper in the deposit, which was due to the break-down of the DES. Several deposition processes were carried out from a single bath to examine bath stability. The bath was found to be stable when a soluble anode was employed, and became unstable when an insoluble anode was used due to other reactions proceeding at the cathode.
Surface and Coatings Technology 01/2014; 238:165–173.
[Show abstract][Hide abstract] ABSTRACT: Titanium-based and cobalt-chrome alloys have been widely used in orthopaedic applications as these materials can significantly enhance the quality of human life as implant materials. The longevity of these materials is highly influenced by their mechanical properties. In some devices cobalt chrome components articulate with titanium alloy counter faces (e.g. in the taper connections of stems and femoral heads in modern modular designs) and damage has been reported of the harder cobalt chrome by the softer titanium alloy component. This study attempts to understand why this might occur by investigating bulk and surface mechanical properties (such as hardness and Young's modulus) of a number of hip implants and test samples using a Hysitron Triboindenter. AFM images were also obtained to determine the contact area and hence, pile-up correction factors.
The results were compared for samples before being used in the body, to account for surface mechanical response due to implant manufacture, and after, to account for the materials response to long-term cyclic loads. To assess the effects of oxidation, the alloys were treated electrochemically with Sodium-Chloride (NaCl) solution at body temperature. It was found that titanium oxidised preferentially compared with cobalt-chrome alloys. Furthermore, the oxidised titanium showed significantly higher hardness values therefore damaging the un-oxidised cobalt-chrome material. The implications for device design and manufacture are discussed.
Thin Solid Films 12/2013; 549:79–86.
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