We present the first direct experimental test of the complex ion structure in liquid carbon at pressures around 100 GPa, using spectrally resolved x-ray scattering from shock-compressed graphite samples. Our results confirm the structure predicted by ab initio quantum simulations and demonstrate the importance of chemical bonds at extreme conditions similar to those found in the interiors of giant planets. The evidence presented here thus provides a firmer ground for modeling the evolution and current structure of carbon-bearing icy giants like Neptune, Uranus, and a number of extrasolar planets.

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The melt-shear organization technique for tailor-made polystyrene-co-polyacrylonitrile (PSAN) shell and silica core particles is investigated yielding easy-scalable carbonaceous porous films after etching and appropriate thermal treatment.

Abstract.Here we report on the high-temperature piezoresistivity of carbon-containing silicon oxycarbide nanocomposites (C / SiOC). Samples containing 13.5 vol% segregated carbon have been prepared from a polysilsesquioxane via thermal cross-linking, pyrolysis and subsequent hot-pressing. Their electrical resistance was assessed as a function of the mechanical load (1-10 MPa) and temperature (1000-1200 • C). The piezoresistive behavior of the C / SiOC nanocomposites relies on the presence of dispersed nanocrystalline graphite with a lateral size ≤ 2 nm and non-crystalline carbon domains, as revealed by Raman spectroscopy. In comparison to highly ordered carbon (graphene, HOPG), C / SiOC exhibits strongly enhanced k factor values, even upon operation at temperatures beyond 1000 • C. The measured k values of about 80 ± 20 at the highest temperature reading (T = 1200 • C) reveal that C / SiOC is a primary candidate for high-temperature piezoresistive sensors with high sensitivity.

Polymer-derived silicon oxycarbides exhibiting¯1 and 10 vol.% of segregated carbon finely dispersed within a glassy Si x O y C z matrix have been investigated by UV Raman spectroscopy using a laser excitation of 4.8 eV ( = 256.7 nm). Carbon exists as amorphous sp 2 sp 3 bonded component in SiOC/C (¯1 vol.%) pyrolyzed at 1100°C in H 2 , including CC single bonds, polymeric chains and small polycyclic aromatic hydrocarbons (PAHs). The formation of nanocrystalline carbon at T > 1400°C is seen in the Raman spectra of SiOC/C (¯1 vol.%) and SiOC/C (10 vol.%) by the appearance of the G band of graphite. Tempering at 1600°C increases the degree of order within the carbon phase. However, the slight narrowing of the G peak with processing temperature (by about 5%) indicates still not well-crystallized carbon: the Raman results can be best explained by turbostratic carbon (with a lateral size L a of µ2 nm) and do not support the model description in literature as a network of single layer graphene.