Liquid Crystals and Carbon Materials

Abstract

Carbon atoms can be found in a variety of structures, including the tetrahedra of diamond, the stacked planes of graphite, and the celebrated fullerene spheres and nanotubes. The graphite family alone includes a rich variety of materials, ranging from pencil “lead” to interstellar dust to chimney soot, and from metallurgical coke to activated charcoal for water filtration to lightweight composites for aerospace components—such as the nose cone of the space shuttle, for which carbon composites were chosen because of their high strength at elevated temperatures.

Preparation of Different Carbon Materials by Thermochemical Conversion of Lignin

“…Thus, during stabilization, the gradual increase in T g by cross-linking reactions leads to the formation of rigid oxidized segments (Braun et al, 2005) that, although are necessary to avoid fiber swelling and fusion and may increase the carbon yields, could be detrimental to structural carbon order (Hurt and Chen, 2000). However, it has been recently reported that the interconnection in fused CFs enhances the mechanical properties of both the thermostabilized and carbonized materials (Dallmeyer et al, 2014a).…”

Liquid crystal engineering of carbon nanofibers and nanotubes

“…Coating optical substrates with concentrated lyotropic solutions in a manner that flow-aligns the rods is known to produce, upon drying, dichroic organic layers upon drying 17 . Dried films of indanthrone disulfonate have a density of 1.69 g/cm 3 by picnometry 17 and XRD analysis reveals crystallinity with a d-spacing of 0.336 nm in the _-stacks and molecular order parameters from 0.86-0.91 17 . For the present work indanthrone disulfonate was acquired as an ammonium salt solution from the firm Optiva (South San Francisco), which uses the solutions for fabrication of thin film organic polarizers 17 .…”

“…3 is the uniform perpendicular alignment, which establishes the unique crystal orientation that characterizes this nanomaterial. Heat treatment of these phases can coalesce the layers and produce longer and straighter fringes, but does not alter the basic crystal symmetry established in the young, lowtemperature carbon material 3 . Figure 3.…”

“…The tube wall structure consists of short (2-3 nm) graphene layers with a statistical meandering about mean perpendicular orientation. These short meandering layers are typical for a low-temperature carbon derived from a liquid crystal precursor 3,14 , and reflect the structure of the liquid crystalline phase at the point of solidification. The key feature in Fig.…”

“…These platelet, herringbone, and cup-shaped nanofibers are inferior to "conventional" nanotubes/fibers in mechanical strength and conductivity, but contain exposed graphene edge sites that make them attractive for complementary applications such as catalysis 6,7 and Li intercalation electrochemistry 8 . A long term goal in carbon synthesis is to develop techniques for systematic control of graphene layer arrangement in order to fabricate "designer" materials and nanomaterials with crystal structures preprogrammed for specific applications 3 .…”