Predicting the viscosity and electrical conductivity of ionic liquids on the basis of theoretically calculated ionic volumes

Selected physical properties of the ionic liquids might be quantitatively predicted based on the volumes of the ions these systems are composed of. It is demonstrated that the ionic volumes calculated using relatively simple theoretical quantum chemistry methods can be utilised to estimate the viscosities and electrical conductivities of various commonly used ionic liquids. The fitting formulas of the exponential form are offered and their predictive usefulness is verified. The quality of such predictions is discussed on the basis of several ionic liquids involving [Tf₂N]^? and [BF₄]^? anions and 16 various cations. The dependence of the viscosity and electrical conductivity of the ionic liquids on the temperature is also investigated and the temperature-dependent equations are derived and compared to the experimentally measured values.     

Metastable Linkage Isomerism in [Ni(Et(4) dien)(NO(2) )(2) ]: A Combined Thermal and Photocrystallographic Structural Investigation of a Nitro/Nitrito Interconversion

One way or another: The N-bound NO(2) group in [Ni(Et(4) dien)(η(2) -O,ON)(η(1) -NO(2) )] (see structure Ni turquoise, N blue, O red) has been shown to undergo reversible conversion into the O-bound nitrito linkage isomer under both thermal and photoactivation of a single crystal. Et(4) dien=N,N,N',N'-tetraethyldiethylenetriamine.     

N2O concentration and isotope signature along profiles provide deeper insight into the fate of N2O in soils†

Nitrous oxide is an important greenhouse gas and its origin and fate are thus of broad interest. Most studies on emissions of nitrous oxide from soils focused on fluxes between soil and atmosphere and hence represent an integration of physical and biological processes at different depths of a soil profile. Analysis of N₂O concentration and isotope signature along soil profiles was suggested to improve the localisation of sources and sinks in soils as well as underlying processes and could therefore extend our knowledge on processes affecting surface N₂O fluxes. Such a mechanistic understanding would be desirable to improve N₂O mitigation strategies and global N₂O budgets. To investigate N₂O dynamics within soil profiles of two contrasting (semi)natural ecosystem types (a temperate acidic fen and a Norway spruce forest), soil gas samplers were constructed to meet the different requirements of a water-saturated and an unsaturated soil, respectively. The samplers were installed in three replicates and allowed soil gas sampling from six different soil depths. We analysed soil air for N₂O concentration and isotope composition and calculated N₂O net turnover using a mass balance approach and considering diffusive fluxes. At the fen site, N₂O was mainly produced in 30–50 cm soil depth. Diffusion to adjacent layers above and below indicated N₂O consumption. Values of δ¹⁵N and δ¹⁸O of N₂O in the fen soil were always linearly correlated and their qualitative changes within the profile corresponded with the calculated turnover processes, suggesting further reduction of N₂O. In the spruce forest, highest N₂O production occurred in the topsoil, but there was also notable production occurring in the subsoil at a depth of 70 cm. Changes in N₂O isotope composition as to be expected from local production and consumption processes within the soil profile did hardly occur, though. This was presumably caused by high diffusive fluxes and comparatively low net turnover, as isotope signatures approached values measured for ambient N₂O towards the topsoil. Our results demonstrate a highly variable influence of diffusive versus production/consumption processes on N₂O concentration and isotope composition, depending on the type of ecosystem. This finding indicates the necessity of further N₂O concentration and isotope profile investigations in different types of natural and anthropogenic ecosystems in order to generalise our mechanistic understanding of N₂O exchange between soil and atmosphere.     

Meeting Report: Australia's First Users Workshop

The Australian Synchrotron Research Program (ASRP) and the Australian Synchrotron (AS) held their first joint Users Workshop over three days in December 2005. The ASRP has been providing access for Australian users to the APS, NSRRC and the Photon Factory since 1996; the AS is under construction in Melbourne and at press time was scheduled to open in early 2007. The joint user workshop is one of an increasing number of collaborative projects between the two programs as they move forward towards an eventual combined Australian user program.     

Effects of graphene and carbon nanotube fillers on the shear properties of epoxy

The effects of quantity of graphene and carbon nanotube‐based fillers and their pendant functional groups on the shear properties of a thermoset epoxy were investigated. Two novel functionalized graphenes, one with epoxy functionality and the other with an amine, are synthesized for this purpose. Nanocomposites are prepared at concentrations of 0.5, 1, 2, 3, 5, and 10 wt % and the effects of functionalization on the homogeneity of dispersion and the shear mechanical properties are investigated. The properties of the epoxy nanocomposites containing epoxy‐ and amine‐functionalized graphene are compared with those containing graphene oxide, Claisen‐functionalized graphene, neat multiwalled carbon nanotubes (MWNTs), three types of epoxy‐functionalized MWNT (EpCNT), and the unfilled epoxy. One of the EpCNT ( EpCNT3 ) was found to increase the plateau shear storage modulus by 136% (1.67–3.94 MPa) and the corresponding loss modulus by almost 400% at a concentration of 10 wt %. Several other fillers were also found to increase shear properties at certain concentrations. A hybrid system of EpCNT3 and graphite was also studied, which improved the storage modulus by up to 51%. SEM images reveal a correlation between thorough dispersion of the additive and enhancement of shear modulus. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 997–1006     

Authentication of Cereal Flours by Multivariate Analysis of GC–MS Data

In this work flour samples of various cereal species, a group of different cultivars of small grain species (wheat, Triticum spp.; barley, Hordeum vulgare; oat, Avena sativa; rye, Secale cereale; triticale, Triticosecale) and cultivars of corn species, Zea Mays, growing in the same period and in the same geographical area, were selected to establish differences between each other, using a new rapid method: a comparison of derivatized hexane extracts by GC–MS and multivariate analysis, using the characteristic fragmentation ion m/z 74, without performing qualitative and quantitative analysis of eluting components. Obtained results were compared with the results obtained using a common electron microscopy method. Flour samples made of every corn and oat cultivar showed complete differences compared to flour samples of each wheat, barley, rye and triticale cultivar investigated in this study. The GC–MS approach combined with multivariate analysis outperforms the standard electron microscopy method in a faster and easier way, and may be used to verify flour types in the market.