Line patterning of graphite and the fabrication of cheap, inexpensive, “throw-away” sensors

A new simple method (“line patterning technique”) using only standard office equipment is described whereby clearly defined, electrically conducting patterns of graphite can be deposited on polymer (plastic) or paper substrates. The properties of the conductive patterns have been characterized by electrical conductivity and SEM measurements. Sensors were constructed by using interdigitated patterns of graphite deposited on plastic and paper, and coated with a thin film of conducting electronic polymer, e.g. polyaniline emeraldine salt.     

Effects of SiC nanoparticles with and without Ni on the hydrogen storage properties of MgH2

In this work, MgH₂–SiC–Ni was prepared by magneto-mechanical milling in hydrogen atmosphere. Scanning electron microscope mapping images showed a homogeneous dispersion of both Ni and SiC among MgH₂ particles. Based on the differential scanning calorimetry traces, the temperature of desorption is reduced by doping MgH₂ with SiC and Ni. Hydrogen absorption/desorption behaviour of the samples was investigated by Sievert's method at 300 °C, and the results showed that both capacity and kinetics were improved by adding SiC and Ni. The hydrogen desorption kinetic investigation indicated that for pure MgH₂, the rate-determining step is surface controlled and recombination, while for the MgH₂–SiC–Ni sample it is controlled as described by the Johnson–Mehl–Avrami 3D model (JMA 3D).     

Anodic titania films as anode materials for lithium ion batteries

Titania thin films were prepared through the anodisation of titanium metal in a 1.0 M sulphuric acid solution at 80 °C utilising a series of pulsed dc constant currents of increasing magnitude. Films were then tested as a potential anode material for lithium batteries using a variety of techniques. Electrochemical testing revealed that the films (3.8 cm²) offered good rate capabilities affording a constant capacity of 48 μAh for a constant current of 10 μA which decreased to 25 μAh on increasing the current to 1250 μA. Cyclic voltammetry was conducted over a range of scan rates from which capacitive currents were examined and rate constants, transfer coefficients and diffusion coefficients calculated. Electrochemical impedance spectroscopy was conducted over six potentials in the range 0.1-2.7 V with the experimental data successfully modelled using an equivalent circuit with the notation R(Q(RW))C. TEM observation of focussed ion beam milled cross-sections showed significant structural differences between the as-anodised film and those cycled in a lithium battery. Raman spectroscopy showed that the films had an anatase character that transformed into an unidentified lithium-containing, titanate phase on cycling. Based on a film thickness of 100 nm, and assuming density of 4 g cm⁻³ such films offered a stable capacity of 316 mAh g⁻¹.     

Composites with needle-like inclusions exhibiting negative thermal expansion: A preliminary investigation

In this work a simple cylindrical structure with a stiff needle-like inclusion embedded within a much softer matrix is presented and analysed with the aim of obtaining a system with tunable thermal expansion properties. It is shown that by the correct combination of the thermal and mechanical properties of the matrix and inclusion, it is possible to design a system which can be tailor-made to exhibit particular values of the coefficient of thermal expansion (CTE) in the radial direction and also negative thermal expansion (NTE). In particular an analytical model to quantify the radial strain with changes in temperature is derived and verified through finite element analysis. The model is used to find correct property combinations which lead to particular values of thermal expansion which could also be negative or zero.     

Oxidation of Glycerol Using Supported Gold Catalysts

A series of supported gold catalysts (0.25, 0.5, 1.0 wt% Au/graphite) have been investigated for the oxidation of glycerol and propan-1,2-diol. The 1 wt% Au/graphite catalyst is found to give 100% selectivity to the mono acid product, isolated as the sodium salt, as long as NaOH is present. The catalysts are characterized by TEM and cyclic voltammetry. By TEM, active catalysts all comprise fairly broad-size distributions (5–50 nm diameter) for the gold nanoparticles, although most are ca. 25 nm in diameter. An inactive 1 wt% Au/graphite is shown to have considerably larger particle sizes (>50 nm) and this indicates that there may be an optimum particle size for the desired catalysis. Characterization using cyclic voltammetry of active Au/graphite catalysts carried out in NaOH reveals the presence of an oxide species that may be responsible for the observed catalysis. In contrast, the inactive 1 wt% Au/graphite catalyst shows no oxidation in the cyclic voltammetry experiments.     

Simplifying the reaction system for the preparation of polyaniline nanofibers: Re-examination of template-free oxidative chemical polymerization of aniline in conventional low-pH acidic aqueous media

In this study, several polyaniline samples were prepared by oxidative chemical polymerization using only aniline, (NH₄)₂S₂O₈ and HCl in aqueous media at room temperature for morphological studies by SEM (scanning electron microscopy). The results show that polyaniline nanofibers can be obtained by template-free oxidative chemical polymerization in a conventional low-pH acidic aqueous medium (pH ～ 0) at room temperature. The study indicates that it is crucial to employ a mild post-polymerization processing procedure, such as dialysis, to preserve the as-formed morphology of polyaniline nanofibers. Our study also suggests that polyaniline could adopt the nanofiber structure as its intrinsic morphology when it is synthesized in a simple oxidative chemical polymerization system consisting of only aniline, (NH₄)₂S₂O₈ and HCl in an aqueous medium at room temperature.     

Recovery of polyphenols from camu-camu (Myrciaria dubia H.B.K. McVaugh) depulping residue by cloud point extraction

In this study the potential of cloud point extraction formed by a non-ionic surfactant was used in order to separate polyphenols from industrial residues of camu-camu. The effects of operational conditions of the cloud point extraction (CPE) on the polyphenol recovery and volumetric ratio were investigated. The results showed a maximum recovery of 95.71% that was obtained using 7.0 wt% Triton X-114, native pH (3.25), and 80 wt% polyphenol extract at 30 °C. The use of cloud point extraction was successful to recover the polyphenols from agroindustrial residue since it is a simple as well as of low-cost technique.