What is mesophase pitch?
Mesophase pitch consists of a large variety of polycyclic aromatic hydrocarbons and maintains the molecular ordering (i.e., optical anisotropy), which is an important precursor for high-performance industrial carbon materials.
What is nematic mesophase?
In the nematic mesophase, disk molecules tend to align with their symmetry axes parallel to each other and have spatial distribution of their centers of mass (Table 2). Disk-shaped molecules can be assembled in columns packed parallel on a two-dimensional (2D) lattice symmetry of the columnar packing.
What is a cholesteric phase?
[kə′les·tə·rik ‚fāz] (physical chemistry) A form of the nematic phase of a liquid crystal in which the molecules are spiral.
What is a mesophase in chemistry?
In chemistry and chemical physics, a mesophase is a state of matter intermediate between liquid and solid. Gelatin is a common example of a partially ordered structure in a mesophase. Further, biological structures such as the lipid bilayers of cell membranes are examples of mesophases.
What is a nematic crystal?
A nematic liquid crystal is a transparent or translucent liquid that causes the polarization (that is, the focusing in a plane) of light waves to change as the waves pass through the liquid. The extent of the change in polarization depends on the intensity of an applied electric field .
What is meant by nematic ordering?
The nematic phase is characterized by one-dimensional orientational order of the molecules by virtue of correlations of the long molecular axes, although the orientational order is not polar. There is no translational order within the nematic phase.
What is nematic and smectic liquid crystal?
The key difference between nematic smectic and cholesteric liquid crystals is that nematic liquid crystals have no ordered structure of molecules, and smectic liquid crystals have a layered molecular structure, whereas cholesteric liquid crystals have molecules in a twisted and chiral arrangement.
What is the meaning of mesomorphic?
Definition of mesomorphic 1 : of or relating to the component in W. H. Sheldon’s classification of body types that measures especially the degree of muscularity and bone development. 2 : having a husky muscular body build.
What is nematic and smectic liquid crystals?
What is mesophase pitch in Xray diffraction?
Mesophase pitch is a precursor material of graphite. Accordingly, the X-ray diffraction pattern of the mesophase pitch, as is shown in Fig. 4(A), shows a peak at around 26° which is related to interlayer spacing between the graphite-like planes.
How do you spin mesophase pitches?
mesophase pitch has a heterogeneous structure consisting of anisotropic regions. Several spinning modes such as centrifugal spinning, jet spinning, and conventional melt spinning have been used to spin mesophase pitches. Continuous multifilament mesophase fibers are obtained using commercial melt spinning equipment.
What is the difference between isotropic and mesophase pitch-based carbon fibers?
Mesophase pitch-based carbon fibers have much higher oxidation resistance in carbon dioxide in comparison with isotropic pitch-based carbon fibers (Wang and Inagaki, 1999).
What is the tensile strength of mesophase pitch?
The as-spun mesophase pitch fiber is quite weak with a tensile strength of about 40–60 MPa and a modulus of less than 5 GPa ( Mochida et al., 1988a,b; McHugh et al., 1992 ). Stabilization improves the properties; however, the fibers are still weak.