In-depth mesocrystal formation analysis of microwave-assisted synthesis of LiMnPO4nanostructures in organic solution

In the present work, we report on the preparation of LiMnPO4 (lithiophilite) nanorods and mesocrystals composed of self-assembled rod subunits employing microwave-assisted precipitation with processing times on the time scale of minutes. Starting from metal salt precursors and H3PO4 as phosphate source, single-phase LiMnPO4 powders with grain sizes of approx. 35 and 65 nm with varying morphologies were obtained by tailoring the synthesis conditions using rac-1-phenylethanol as solvent. The mesocrystal formation, microstructure and phase composition were determined by electron microscopy, nitrogen physisorption, X-ray diffraction (including Rietveld refinement), dynamic light scattering, X-ray absorption and X-ray photoelectron spectroscopy, and other techniques. In addition, we investigated the formed organic matter by gas chromatography coupled with mass spectrometry in order to gain a deeper understanding of the dissolution\u2013precipitation process. Also, we demonstrate that the obtained LiMnPO4 nanocrystals can be redispersed in polar solvents such as ethanol and dimethylformamide and are suitable as building blocks for the fabrication of nanofibers via electrospinning

A study of the observed shift in the peak position of olivine Raman spectra as a result of shock induced by hypervelocity impacts

Kuebler et al. (2006) identified variations in olivine Raman spectra based upon the composition of individual olivine grains, leading to identification of olivine composition from Raman spectra alone. However, shock on a crystal lattice has since been shown to result in a structural change to the original material, which produces a shift in the Raman spectra of olivine grains compared with the original un-shocked olivine (Foster et al., 2013). This suggests that the use of the compositional calculations from the Raman spectra, reported in Kuebler et al. (2006), may provide an incorrect compositional value for material that has experienced shock. Here we have investigated the effect of impact speed (and hence peak shock pressure) on the shift in the Raman spectra for San Carlos olivine (Fo91) impacting Al. foil. Powdered San Carlos olivine (grain size 1 to 10 ?m) was fired at a range of impact speeds from 0.6 – 6.1 km s-1 (peak shock pressures 5 – 86 GPa) at Al. foil to simulate capture over a wide range of peak shock pressures. A permanent change in the Raman spectra was found to be observed only for impact speeds greater than ~5 km s-1. The process that causes the shift is most likely linked to an increase in the peak pressure produced by the impact, but only after a minimum shock pressure associated with the speed at which the effect is first observed (here 65 – 86 GPa). At speeds around 6 km s-1 (peak shock pressures ~86 GPa) the shift in Raman peak positions is in a similar direction (red shift) to that observed by Foster et al. (2013) but of twice the magnitude

A Raman Spectroscopic Study of Humite Minerals

Raman spectroscopy has been used to study the structure of the humite mineral group ((A2SiO4)n - A(OH, F)2 where n represents the number of olivine and brucite layers in the structure and is 1,2,3 or 4 and A2+ is Mg, Mn, Fe or some mix of these cations). The humite group of minerals forms a morphotropic series with the minerals olivine and brucite. The members of the humite group contain layers of the olivine structure that alternate with layers of the brucite-like sheets. The minerals are characterized by a complex set of bands in the 800 to 1000 cm-1 region attributed to the stretching vibrations of the olivine (SiO4)4- units. The number of bands in this region is influenced by the number of olivine layers. Characteristic bending modes of the (SiO4)4- units are observed in the 500 to 650 cm-1 region. The brucite sheets are characterized by the OH stretching vibrations in the 3475 to 3625 cm-1. The position of the OH stretching vibrations is determined by the strength of the hydrogen bond formed between the brucite-like OH units and the olivine silica layer. The number of olivine sheets and not the chemical composition determines the strength of the hydrogen bonds