Correlating the Energetics and Atomic Motions of the Metal-Insulator Transition of M1 Vanadium Dioxide

Materials that undergo reversible metal-insulator transitions are obvious candidates for new generations of devices. For such potential to be realised, the underlying microscopic mechanisms of such transitions must be fully determined. In this work we probe the correlation between the energy landscape and electronic structure of the metal-insulator transition of vanadium dioxide and the atomic motions occurring using first principles calculations and high resolution X-ray diffraction. Calculations find an energy barrier between the high and low temperature phases corresponding to contraction followed by expansion of the distances between vanadium atoms on neighbouring sub-lattices. X-ray diffraction reveals anisotropic strain broadening in the low temperature structure's crystal planes, however only for those with spacings affected by this compression/expansion. GW calculations reveal that traversing this barrier destabilises the bonding/anti-bonding splitting of the low temperature phase. This precise atomic description of the origin of the energy barrier separating the two structures will facilitate more precise control over the transition characteristics for new applications and devices.Comment: 11 Pages, 8 Figure

Phase effects in zirconia catalysed glucose conversion to 5‐hydroxy methylfurfural

5-(hydroxymethyl)furfural (HMF) is a key biomass derived platform chemical used to produce fuel precursors or additives and value-added chemicals, synthesised by the cascade isomerisation of glucose and subsequent dehydration of reactively formed fructose to HMF over Lewis and Bronsted acid catalysts respectively. Zirconia is a promising catalyst for such reactions; however, the impact of acid properties of different zirconia phases is poorly understood. In this work, we unravel the role of the zirconia crystalline phase in glucose isomerisation and fructose dehydration to HMF. The Lewis acidic monoclinic phase of zirconia is revealed to preferentially facilitate glucose isomerisation, while the nanoparticulate tetragonal phase possesses Brønsted acid sites which favour fructose dehydration. Synergy between both zirconia phases facilitates cascade HMF production, with both catalysts investigated as physical mixtures in batch and flow reactor configurations. Using a physical mixture of only 15 wt% m-ZrO2 with 85 wt% t-ZrO2 in either batch or packed bed reactor configuration is sufficient to reach equilibrium conversion of glucose for subsequent dehydration by the t-ZrO2 component. Under continuous flow, a six-fold increase in HMF production was obtained when operating with a physical mixture of m- and t-ZrO2 compared to that from a single bed of t-ZrO2.<br/

Controlling Homogenous Spherulitic Crystallization for high-efficiency Planar Perovskite Solar Cells fabricated under ambient high-humidity conditions

The influence of precursor solution properties, fabrication environment, and antisolvent properties on the microstructural evolution of perovskite films is reported. First, the impact of fabrication environment on the morphology of methyl ammonium lead iodide (MAPbI3) perovskite films with various Lewis‐base additives is reported. Second, the influence of antisolvent properties on perovskite film microstructure is investigated using antisolvents ranging from nonpolar heptane to highly polar water. This study shows an ambient environment that accelerates crystal growth at the expense of nucleation and introduces anisotropies in crystal morphology. The use of antisolvents enhances nucleation but also influences ambient moisture interaction with the precursor solution, resulting in different crystal morphology (shape, size, dispersity) in different antisolvents. Crystal morphology, in turn, dictates film quality. A homogenous spherulitic crystallization results in pinhole‐free films with similar microstructure irrespective of processing environment. This study further demonstrates propyl acetate, an environmentally benign antisolvent, which can induce spherulitic crystallization under ambient environment (52% relative humidity, 25 °C). With this, planar perovskite solar cells with ≈17.78% stabilized power conversion efficiency are achieved. Finally, a simple precipitation test and in situ crystallization imaging under an optical microscope that can enable a facile a priori screening of antisolvents is shown

Thermal analysis, nuclear magnetic resonance spectroscopy, and impedance spectroscopy of N,N-dimethyl-pyrrolidinium iodide: An ionic solid exhibiting rotator phases

N,N-dimethyl-pyrrolidinium iodide has been investigated using differential scanning calorimetry, nuclear magnetic resonance (NMR) spectroscopy, second moment calculations, and impedance spectroscopy. This pyrrolidinium salt exhibits two solid-solid phase transitions, one at 373 K having an entropy change, Delta S, of 38 J mol(-1) K-1 and one at 478 K having Delta S of 5.7 J mol(-1) K-1. The second moment calculations relate the lower temperature transition to a homogenization of the sample in terms of the mobility of the cations, while the high temperature phase transition is within the temperature region of isotropic tumbling of the cations. At higher temperatures a further decrease in the H-1 NMR linewidth is observed which is suggested to be due to diffusion of the cations. (C) 2005 American Institute of Physics

3 years of liraglutide versus placebo for type 2 diabetes risk reduction and weight management in individuals with prediabetes: a randomised, double-blind trial

Background: Liraglutide 3·0 mg was shown to reduce bodyweight and improve glucose metabolism after the 56-week period of this trial, one of four trials in the SCALE programme. In the 3-year assessment of the SCALE Obesity and Prediabetes trial we aimed to evaluate the proportion of individuals with prediabetes who were diagnosed with type 2 diabetes. Methods: In this randomised, double-blind, placebo-controlled trial, adults with prediabetes and a body-mass index of at least 30 kg/m2, or at least 27 kg/m2 with comorbidities, were randomised 2:1, using a telephone or web-based system, to once-daily subcutaneous liraglutide 3·0 mg or matched placebo, as an adjunct to a reduced-calorie diet and increased physical activity. Time to diabetes onset by 160 weeks was the primary outcome, evaluated in all randomised treated individuals with at least one post-baseline assessment. The trial was conducted at 191 clinical research sites in 27 countries and is registered with ClinicalTrials.gov, number NCT01272219. Findings: The study ran between June 1, 2011, and March 2, 2015. We randomly assigned 2254 patients to receive liraglutide (n=1505) or placebo (n=749). 1128 (50%) participants completed the study up to week 160, after withdrawal of 714 (47%) participants in the liraglutide group and 412 (55%) participants in the placebo group. By week 160, 26 (2%) of 1472 individuals in the liraglutide group versus 46 (6%) of 738 in the placebo group were diagnosed with diabetes while on treatment. The mean time from randomisation to diagnosis was 99 (SD 47) weeks for the 26 individuals in the liraglutide group versus 87 (47) weeks for the 46 individuals in the placebo group. Taking the different diagnosis frequencies between the treatment groups into account, the time to onset of diabetes over 160 weeks among all randomised individuals was 2·7 times longer with liraglutide than with placebo (95% CI 1·9 to 3·9, p&lt;0·0001), corresponding with a hazard ratio of 0·21 (95% CI 0·13–0·34). Liraglutide induced greater weight loss than placebo at week 160 (–6·1 [SD 7·3] vs −1·9% [6·3]; estimated treatment difference −4·3%, 95% CI −4·9 to −3·7, p&lt;0·0001). Serious adverse events were reported by 227 (15%) of 1501 randomised treated individuals in the liraglutide group versus 96 (13%) of 747 individuals in the placebo group. Interpretation: In this trial, we provide results for 3 years of treatment, with the limitation that withdrawn individuals were not followed up after discontinuation. Liraglutide 3·0 mg might provide health benefits in terms of reduced risk of diabetes in individuals with obesity and prediabetes. Funding: Novo Nordisk, Denmark

Modification of ZrB₂ powders by a sol-gel ZrC precursor-A new approach for ultra high temperature ceramic composites

AbstractA simple method of integrating a powder processing technique with a sol–gel process to produce ultra high temperature ceramic (UHTC) composites is reported. ZrB2 powder was treated with a zirconium oxide-carbon sol–gel coating. Carbothermal reduction produced nanosized crystalline ZrC grains on the surface of ZrB2 powder. Detailed refinement of carbon content in the sol–gel coating was necessary to control the oxide reduction on the ZrB2 surface, while providing intrinsic carbon for the nanoparticle sol–gel phase. Microstructures and crystalline phases were analyzed using TEM, SEM, and XRD. It was found that carbothermal reduction of ZrO2 to form nano ZrC can be completed on the surface of ZrB2 at 1450°C. The sol–gel coating creates a homogenous mix of ~200nm ZrC in close proximity to the ZrB2 surface. Densification of the ZrB2-ZrC composite can be achieved by spark plasma sintering at 1800°C. The amount of carbon added to the sol–gel precursor needs to be carefully tailored to dictate the final porosity and grain size of sintered composites

LiI-doped N,N-Dimethyl-Pyrrolidinium iodide, an archetypal rotator-phase ionic conductor

N,N-Dimethyl-pyrrolidinium iodide, and the effect of doping with LiI, has been investigated using DSC, NMR, and impedance spectroscopy. It was found that the addition of a small amount of LiI enhances the ionic conductivity by up to 3 orders of magnitude for this ionic solid. Furthermore, a slight decrease in phase transition onset temperatures, as well as the appearance of a superimposed narrow line in the 1H NMR spectra with dopant, suggest that the LiI facilitates the mobility of the matrix material, possibly by the introduction of vacancies within the lattice. 7Li NMR line width measurements reveal a narrow Li line width, decreasing in width and increasing in intensity with temperature, indicating mobile Li ions.<br /

Electrochemical and Surface Characterisation of Carbon Steel Exposed to Mixed Ce and Iodide Electrolytes

The protection of ferrous metals in acidic environments is important in many industries. Extending the pH range of organic inhibitors to low pH has been achieved with the addition of iodide ions, which facilitate adsorption. It was of interest to see whether similar outcomes could be achieved with inorganic inhibitors. To this end, this paper examines the influence of potassium iodide addition on the level of corrosion protection provided by Ce(NO3)3 in 3.5% NaCl electrolytes over a pH range of 2.5 to 8. Potentiodynamic polarization was used to assess percentage inhibitor efficiency (IE%), and scanning electron microscopy, energy dispersive X-ray spectrometry, and X-ray photoelectron spectroscopy were used to characterize the corrosion product. It was found that KI alone provided only poor corrosion inhibition except at pH 2.5, where nearly 85IE% was achieved. Its addition to the cerium electrolytes was generally in excess of 90% and over 97% for the optimum concentration. The addition of KI seemed to change the mechanism of formation of corrosion products from predominantly Fe2O3 to a mixture of FeOOH, Fe3O4, and Fe2O3, which were more adherent. Corrosion protection was extended to pH 4, but under the conditions explored here, no additional protection was evident at pH 2.5