We report detailed measurements of the low temperature magnetic phase diagram of Er2Ti2O7. Heat capacity and time-of-flight neutron scattering studies of single crystals reveal unconventional low-energy states. Er3+ magnetic ions reside on a pyrochlore lattice in Er2Ti2O7, where local XY anisotropy and antiferromagnetic interactions give rise to a unique frustrated system. In zero field, the ground state exhibits coexisting short and long-range order, accompanied by soft collective spin excitations previously believed to be absent. The application of finite magnetic fields tunes the ground state continuously through a landscape of noncollinear phases, divided by a zero temperature phase transition at micro{0}H{c} approximately 1.5 T. The characteristic energy scale for spin fluctuations is seen to vanish at the critical point, as expected for a second order quantum phase transition driven by quantum fluctuations.

An ultrasonic imaging technique has been developed to investigate the internal changes of pouch cells nondestructively. The local ultrasonic transmittance of pouch cells has been measured and used for imaging with a new ultrasonic scanning machine designed and built in-house. The wetting process of the cells is clearly observed via such ultrasonic imaging techniques. Furthermore, ultrasonic transmission images of fresh cells and aged cells with different electrolytes and cycling conditions exhibit very different ultrasonic transmittance, which can be caused by electrolyte dry-out or ''unwetting'' due to cell swelling. The ultrasonic imaging technique is a very sensitive method to probe failure mechanisms in Li-ion pouch cells.

Thermal conductivity of carbon nanotube (CNT) films and micro-fibres synthesised by floating catalyst chemical vapour deposition was measured by the parallel thermal conductance method. CNT films showed in-plane thermal conductivities of 110 W m 1 K 1. Online condensation into a micro-fibre morphology-a two-dimensional reduction in the transverse plane, including some axial stretching during solvent evaporation-resulted in room-temperature thermal conductivity values as high as 770 ± 10 W m 1 K 1 , which is the highest thermal conductivity reported for CNT bulk materials to date. In specific terms, this matches the maximum thermal conductivity of heattreated carbon fibre, but with a higher onset temperature for Umklapp scattering processes (300 K rather than 150 K). We selected four sample types to investigate effects of alignment, purity, and single-or multi-wall character on their thermal conductivity. For both the electrical and thermal conductivity of as-spun material, i.e. without any post-synthesis treatment, we show that the density and quality of CNT bundle alignment are still the predominant factors affecting these properties, outweighing the influence of single-or multi-walled character of the nanotubes. This raises the promise that, with optimal alignment and junction points, even higher values of thermal conductivity are achievable for macroscopic CNT fibres.

A set of LiNi 0.5 Mn 0.3 Co 0.2 O 2 /graphite lithium-ion cells underwent 750 charge-discharge cycles during about 8 months at 55 • C to upper cutoff potentials of 4.0, 4.1, 4.2, 4.3, and 4.4 V. The electrolyte in these cells was extracted using a centrifuge method and studied using gas chromatography/mass spectrometry to determine the changes to the solvents and by inductively coupled plasma-mass spectrometry to determine the changes to the salt content in the electrolyte. The negative electrodes from the cells were harvested and studied by micro-X-ray fluorescence to quantify the amount of transition metals which migrated from the positive electrode to the negative electrode during the testing. Emphasis is given to a detailed description of the quantitative methods used in the hope that others will adopt them in similar studies of different types of aged lithium-ion cells. The cells studied here initially had 1.1 molal LiPF 6 ethylene carbonate (EC): ethyl methyl carbonate (EMC) (3:7 by weight) electrolyte. The aged cells showed increasing amounts of dimethyl carbonate and diethyl carbonate created by transesterification as the upper cutoff potential increased. Only extremely small amounts of Mn, less than 0.1% of the total Mn in the positive electrode, were found on the negative electrode after this aggressive testing. Lithium-ion batteries are currently used in a wide range of applications: cell phones, power tools, vehicles and even grid energy storage.

The Pbcn orthorhombic phase of Y 2 Mo 3 O 12 has been examined through high-resolution X-ray powder diffraction (10-450 K), heat capacity determination (2-390 K), and differential scanning calorimetry (103-673 K). No phase transition was found over this temperature range. The overall thermal expansion is negative, and the average linear thermal expansion coefficient, R l , is -9.02 Â 10 -6 K -1 averaged over T = 20-450 K. From a thorough analysis of the structure of Y 2 Mo 3 O 12 , we find that the YO 6 octahedra and MoO 4 tetrahedra are increasingly distorted with increasing temperature. The inherent volume distortion parameter (υ) of AO 6 has been introduced to quantitatively evaluate polyhedral distortion and it is observed that this parameter is strongly correlated with the linear coefficient thermal expansion (R l ) of different members of the A 2 M 3 O 12 family. We attribute the negative thermal expansion to the reduction of the mean Y-Mo nonbonded distances and Y-O-Mo bond angles with increasing temperature, the joint action of high-energy optical and low-energy translational and librational modes.