Carbonaceous chemical composition

The chemical composition of the SEI formed on carbonaceous anodes is, in general, similar to that formed on metallic lithium or inert electrodes. However some differences are expected as a result of the variety of chemical compositions and morphologies of carbon surfaces, each of which can affect the i() value for the various reduction reactions differently. Another factor, when dealing with graphite, is solvent co-intercalation. Assuming Li2C03 to be a major SEI building material, the thickness of the SEI was estimated to be about 45 A [711. 

Now, apart from the planets, many meteorites were formed, moving in quite different orbits and of quite different chemical composition. In particular, the so-called C-l meteorites composed of carbonaceous chondrites have a composition of elements much closer to that of the Sun. It is proposed (see for example Harder and also Robert in Further Reading) that many of these meteorites collided with very early Earth and became incorporated in it, so that eventually some 15% of Earth came from this material (see Section 1.11). Other planets such as Mars and the Moon could have had similar histories, but the remote planets and Venus are very different. 

Microprobe laser desorption laser ionisation mass spectrometry (/xL2MS) is used to provide spatial resolution and identification of organic molecules across a meteorite sample. Tracking the chemical composition across the surface of the meteorite requires a full mass spectrum to be measured every 10 p,m across the surface. The molecules must be desorbed from the surface with minimal disruption to their chemical structure to prevent fragmentation so that the mass spectrum consists principally of parent ions. Ideally, the conventional electron bombardment ionisation technique can be replaced with an ionisation that is selective to the carbonaceous species of interest to simplify the mass spectrum. Most information will be obtained if small samples are used so that sensitivity levels should be lower than attomolar (10—18 M) fewer than 1000 molecules can be detected and above all it must be certain that the molecules came from the sample and are not introduced by the instrument itself. 

The Murchison meteorite shown in Figure 6.7, like all meteorites, is named after the place from which it was recovered and in this case it is the town of Murchison, Victoria in Australia about 100 km north of Melbourne. The fall occurred in 1969 and was followed by an analysis of the chemical composition in some considerable detail. The Murchison meteorite is a carbonaceous chondrite containing about 2 per cent carbon, some as inorganic carbonates, and some as soluble compounds such as amino acids but the bulk as a macromolecular heterogeneous material referred to as kerogen. 

Relative to the controversy associated with the mechanism of SEI formation, there is less uncertainty in the knowledge about the chemical composition of the SEI, due mainly to the exhaustive surface spectroscopic studies carried out by Aurbach and coworkers on carbonaceous anodes in various nonaque-ous electrolytes, adopting both in situ and ex situ approaches. Table 6 lists the chemical... 

In a further effort to identify the active intermediate that initiates the reaction, they tested the effect of a few possible ingredients on the production of EMC based on the knowledge about the chemical composition of the SEI on carbonaceous anodes. These model compounds included Li2C03, LiOCHs, and LiOH, while lithium alkyl carbonate was not tested due to its instability and therefore rare avail-ability. The results unequivocally showed that LiOCHs effectively catalyzes the ester exchange. 

When conducting a differential scanning calorimetry (DSC) study on the stability of carbonaceous anodes in electrolytes, Tarascon and co-workers found that, before the major reaction between lithiated carbon and fluorinated polymers in the cell, there was a transition of smaller thermal effect at 120 °C, marked peak (a) in Figure 28. They ascribed this process to the decomposition of SEI into Li2C03, based on the previous understanding about the SEI chemical composition and the thermal stability of lithium alkyl carbonates.Interestingly, those authors noticed that the above transition would disappear if the carbonaceous anode was rinsed in DMC before DSC was performed, while the other major processes remained (Figure 28). Thus,... 

Ambersorb carbonaceous adsorbents (Rohm and Haas Company) are a new class of synthetic adsorbents which show interesting collection properties (37,38). The chemical composition is intermediate between that of activated carbon and polymeric sorbents. Ambersorb sorbents are available in various pore sizes and surface areas. 

Table 12.2 Average chemical compositions of hydrated carbonaceous chondrite groups...

Both Ambersorb XE-340 and XE-348 are members of a carbonaceous polymer product line currently manufactured exclusively by Rohm and Haas. The chemical composition of these sorbents is generally regarded to be intermediate between that ascribed to either activated carbon or a purely polymeric sorbent (9,10). 

Materials. To satisfy the requirements for models for pyrolysis studies, it was necessary to select compounds that were of high purity and well-defined structure which would produce carbonaceous residues when subjected to high temperatures. Commercially available organic dyestuffs proved to be a ready source of model compounds containing various heterocyclic structures. It was necessary to purify these dyes by recrystallization and extraction to remove small quantities of organic impurities and residual inorganic contaminants. The identity, structure, and chemical composition of the model compounds can be seen in Table I and Figure 1. 

In Fig. 4 an overview of the chemical composition , already grouped according to source processes, of PM10 in Germany is shown. The unaccounted PM mass in these mass closures is frequently around 10-20% which can reasonably be assigned to particle bound water and analytical uncertainties. Higher unaccounted mass fractions in most cases also comprise the mineral dust fraction since analyses of silicon and aluminium are scarcely done in routine. In some studies only the main ionic PM constituents were analysed, and the unaccounted mass then became the major fraction and comprises carbonaceous particles as well. 

The monitoring network in EMB compared to those established in Central and North Europe or even with the Western Mediterranean Basin (e.g. Spain) is rather insufficient. Particularly there is a lack of data on continuous or long-term monitoring of the chemical composition of particulate matter [12], For some substances (e.g. carbonaceous aerosol), the variability is expected to be much larger than can be resolved by integrating the available measurements and the research studies need to be supported by assessment of the local scale variability. In order to understand the temporal evolution (trends) there is also a particular need for aerosol measurements at additional sites with little influence from local and regional emission sources. 

The chemical composition of PM10 shows a considerable conformity in these countries. Always, secondary inorganic aerosols (SIA) are the major constituent ( 40%) followed by the carbonaceous compounds ( 25%). Contributions of sea salt and mineral dust vary between 10% and 15% depending on presence and distance of respective sources. The unidentified mass is some 15% indicating that the composition of PM10 in this region is fairly well known. 

Atmospheric particles in the troposphere are composed of a complex mixture of highly water-soluble inorganic salts, insoluble mineral dust, and carbonaceous material (which includes organic compounds plus elemental carbon) (Jacobson et al., 2000). Studies in which the chemical composition has been determined as a function of particle size demonstrate a correlation between the chemical composition and the size mode of atmospheric aerosols (Meszaros et al., 1997 Krivacsy and Molnar, 1998 Alves et al.,2000 Maenhaut et al.,2002 Smolik et al., 2003 Samara andVoutsa, 2005). 

A most remarkable result in the chemical study of ancient morphologies is the complex chemical composition, comprizing carbonaceous materials and different inorganic materials such as carbonates, iron sulphides and iron oxides. It can be shown that most of the inorganic constituents are biominerals produced directly or indirectly by the life activity of the involved organisms. So also these products are chemical fossils and, therefore, merit adequate consideration in our analyses. 

The find is associated with other specimens of the same kind and together with non-structured carbonaceous debris of similar chemical composition. The assemblages are arranged along bedding planes or other primary patterns of the sediment which is a chert, stromatolite, banded iron formation, shale or related rock. 

Black carbon is a general denomination for materials such as soot, graphitic carbon and carbon black. The incomplete combustion of fossil fuels and biomass releases enormous quantities of these materials into the atmosphere, about 13Tgyear 1 on a global basis [55]. Both natural and anthropogenic processes contribute to this input. The chemical composition of the carbonaceous particles in the atmosphere is highly variable, as it depends on their formation process and ageing. 

The Apollo 11 rocks contain large amounts of ilmenite, as can be seen from Tables 2 and 3 (high titanium content). We have plotted the chemical composition of rock sample 12018 in Fig. 3a vs. that of the carbonaceous chondrites (the most primitive of all meteorites), in Fig. 3b vs. the basaltic achondrite (eucrite) Juvinas (a class of meteorites which have undergone magmatic differentiation) and in Fig. 4 vs. the average composition of the Earth s... 

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