Dynamical behavior of copper atoms in a carbon nanotube channel

The transportation of copper atoms along a carbon nanotube (CNT) channel, which consists of a junction, is studied using molecular dynamics simulations. A bias voltage is applied along the channel to induce an electromigration force on copper atoms. The study focuses on the flow of copper atoms by varying the voltage gradient and the temperature of copper. The results show that the temperature increase due to electromigration forces is lower when the initial temperature of copper is higher. A higher temperature results in larger thermal vibrations of copper atoms, which partly contributes to a change in the atomic arrangement of copper when copper is transported along the channel. This change occurs due to the existence of the CNT channel junction. Besides this, the interactive forces between copper and the CNT channel are significant when copper is approaching the junction. The effect of temperature on the interactive forces at the junction of the channel is more prominent than the effect of electromigration forces. The resistive forces on copper produced by the CNT channel are quite insignificant for a straight channel, but are more prominent when copper is flowing against the obstruction of the CNT channel junction.     

Electrochemical doping of graphene with toluene

The electrical properties of graphene are known to be modified by chemical species that interact with it. We investigate the effect of doping of graphene-based devices by toluene (C₆H₅CH₃). We show that this effect has a complicated character. Toluene is seen to act as a donor, transferring electrons to the graphene. However, the degree of doping is seen to depend on the magnitude and polarity of an electric field applied between the graphene and a nearby electrode. This can be understood in terms of an electrochemical reaction mediated by the graphene crystal.     

Influence of the inorganic phase concentration and geometry on the viscoelastic properties of latex coatings through the glass-transition

The mechanical properties of artists’ acrylic (latex) paint films containing different volume fractions of TiO₂, CaCO₃ and kaolin were measured in uni-axial tension over a broad range of temperatures and crosshead speeds. Young’s modulus results in the glassy region were first compared with several micromechanics theories for particle-filled composites containing elastic phases. It was found that the Mori-Tanaka theory slightly under-predicted the modulus enhancement, while the Lielens approach provided the most accurate results. A nonlinear viscoelastic material model involving a Prony series and the neo-Hookean hyperelastic function was used to represent the tensile data up to relatively small strains of a few percent. From the experimental data, the material model was calibrated and the required parameters were determined. The derived parameters were then used to re-construct relaxation modulus plots, which were compared with the approximations given by Clements and Mas for the viscoelastic Mori-Tanaka theory in the time-domain. It was found that the experimentally observed modulus enhancement was much stronger than the predicted values in the rubbery region. Mechanisms such as constrained polymer at the inorganic particle interface, and the possible formation of a percolation network are discussed.     

Towards solving the crystal structure of polytype 3R2 Mg–Al layered double hydroxides

An analysis of the crystal structure of polytype 3R₂ layered double hydroxides has been carried out based on XRPD diffractograms. Measurement of the transmission-XRPD pattern carried out in a spinning and tilting capillary using synchrotron radiation has been shown to diminish the preferred orientation effect of the sample. In order to approach the structure of polytype 3R₂, structural models, based on possible interlayer anion arrangement as revealed by FT-IR, 27-Al solid state NMR and XRPD, were constructed. A structural model is proposed that is consistent with the by XRPD measured interlayer distance, in which tetrahedral aluminate ions are grafted with their apical oxygen ions onto the octahedral sheet. The presence of a measured extra reflection at 2θ value of 6.3, which is not predicted by this structure, can be obtained however by enlargement of the unit cell to a′ = a√3 = 0.5279 nm and c′ = c = 2.1985 nm, which simulates the aluminate anions ordering in the interlayer.     

Dissociation pressure and Gibbs energy of formation of Y3Fe5O12 and YFeO3

Compounds in the ternary system Y  Fe  O are of significant interest due to their magnetic properties. Electrochemical solid state galvanic cell techniques have been employed to study their thermodynamic properties in the temperature range from 900 to 1250 °C. The following oxygen dissociation pressures were obtained: log P_O2$\text{[}\text{Pa}\text{] = ?}\text{26365}\text{T}\text{+ 17.13}$ for yttrium iron garnet, Y₃Fe₅O₁₂, in the entire temperature range, log P_O2$\text{[}\text{Pa}\text{] = ?}\text{29345}\text{T}\text{+ 13.00}$ for perovskite, YFeO₃, below 1080 °C and log P_O2$\text{[}\text{Pa}\text{] = ?}\text{39375}\text{T}\text{+ 20.43}$ for YFeO₃ above 1080 °C. The standard Gibbs energies of formation from metallic iron, yttria (Y₂O₃) and oxygen were determined to be $\text{2}\text{G}{}^{\mathrm{o}}\text{= ? 2078.2 + 0.5850·}\text{T kJ}\text{/}\text{mol}$ for the formation of Y₃Fe₅O₁₂ and $\text{2}\text{G}{}^{\mathrm{o}}\text{= ? 421.3 + 0.1148·}\text{T kJ}\text{/}\text{mol}$ for the formation of YFeO₃. The standard enthalpies and entropies of formation are ? 2078.2 kJ/mol and ? 585.0 J/mol·K for Y₃Fe₅O₁₂ and ? 421.3 kJ/mol and ? 114.8 J/mol·K for YFeO₃, respectively.     

Fatigue crack growth in polyurethane foam

The growth of fatigue cracks in compact tension specimens of rigid polyurethane foam has been studied at room temperature under conditions of constant load-amplitude cycling. The growth of the cracks at the frequencies employed (0.2 Hz) is found to be reasonably reproducible and the growth rate can be related to the cyclic stress intensity range in the conventional way. The rate of growth of the cracks is also found to depend on the mean stress level and an attempt has been made to separate out the effects of stress-intensity range, K, and the maximum stress intensity in each cycle, K _max, by combining the data obtained under a variety of loading conditions.