This Review gives an overview of precursor systems, their processing, and the final precursor-dependent structure of carbon fibers (CFs) including new developments in precursor systems for low-cost CFs. The following CF precursor systems are discussed: poly(acrylonitrile)-based copolymers, pitch, cellulose, lignin, poly(ethylene), and new synthetic polymeric precursors for high-end CFs. In addition, structure-property relationships and the different models for describing both the structure and morphology of CFs will be presented.
Different softwood lignin O‐acyl derivatives, i.e., methacrylated, hexanoylated, benzoylated, methoxybenzoylated, and cinnamoylated lignin are synthesized and subjected to melt spinning. In the presence of spinning aids such as vanillin and ethylene glycol dimethacrylate, multifilament melt spinning is accomplished with spinning speeds up to 500 m min−1, which allowed for realizing uniform precursor fibers 17 μm in diameter. Out of all acyl‐derivatives of softwood lignin investigated, cinnamoylated softwood lignin (CL) turned out to be superior in terms of processability. CL‐derived precursor fibers are oxidatively thermostabilized and then carbonized applying carbonization temperatures up to 2200 °C. Carbon fiber structure formation is followed in detail by wide‐angle X‐ray scattering and Raman spectroscopy. An orientation ≤53% and a d
002 spacing of 0.353 nm is achieved. According to small angle X‐ray scattering, carbon fibers have a porosity of ≈38%. CL‐derived carbon fibers are also characterized in terms of mechanical properties. Tensile strengths up to 0.93 GPa (average 0.75 GPa) are obtained and follow Weibull statistics. Elastic moduli are ≤66.5 GPa (average 41.1 GPa).
Dieser Aufsatz gibt einen Überblick über Präkursorsysteme, deren Verarbeitung und die resultierenden Eigenschaften der Carbonfasern (CF) in Abhängigkeit des Präkursors und berücksichtigt dabei die neuesten Entwicklungen auf dem Gebiet der alternativen Präkursoren für die Herstellung von preisgünstigeren CF. Es werden folgende Präkursoren behandelt: Polyacrylnitril‐basierte Copolymere, Pech, Cellulose, Lignin, Polyethylen und neue synthetische Polymerpräkursoren für hochwertige CF. Außerdem werden Zusammenhänge zwischen Struktur und Eigenschaften aufgezeigt, und es werden verschiedene Modelle vorgestellt, die sowohl die Struktur als auch die Morphologie von CF beschreiben.
The blue title compound, long assumed to be an olefin
complex on the basis of an apparently single unresolved CN stretching
band in the IR spectrum, has been identified by experiment and through
DFT analysis as a σ complex with the tungsten atom coordinated
to one of the nitrile N centers. The previously reported data are
reinterpreted in light of the new structural assignment, and spectroelectrochemical
results (UV–vis, IR, EPR) are presented.
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