Twist disclinations in the carbonaceous mesophase

White, J.L.; Zimmer, J.E.

doi:10.1016/0008-6223(78)90094-5

Cited by 16 publications

(2 citation statements)

References 9 publications

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“…Optical evidence of twist disclinations in the carbonaceous mesophase comes from studies of the lamellar microconstituent of the mesophase [39]. This type of disclination appears to be common, but the twist character is readily distinguishable only on favorable sections through the lamellar morphology.…”

Section: Twist Disclinationsmentioning

confidence: 99%

Disclination Structures in the Carbonaceous Mesophase

Zimmer

White

1982

Advances in Liquid Crystals

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Section: Twist Disclinationsmentioning

confidence: 99%

Disclination Structures in the Carbonaceous Mesophase

Zimmer

White

1982

Advances in Liquid Crystals

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“…The moderate aromaticity most likely maintains a low viscosity, which leads to the development of anisotropic flow texture. Some of these anisotropic structures are characterized by internal disclinations (defects caused by the folding patterns of aromatic layers) . When mesophase pitches are sufficiently fluid, as in this case, they can be readily deformed by the percolation of gas bubbles or by mechanical deformation at the early stages of coalescence .…”

Section: Resultsmentioning

confidence: 99%

Interaction of Clay Additives with Mesophase Formed during Thermal Treatment of Solid-Free Athabasca Bitumen Fraction

Rahimi¹,

Gentzis²,

Fairbridge³

1999

Energy Fuels

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The coking propensity (mesophase appearance time and size) of a fraction of mineral-matterfree Athabasca bitumen vacuum bottoms was investigated using hot-stage (high-temperature and high-pressure) microscopy. The following variables were studied: (1) gas atmosphere (hydrogen and nitrogen); (2) different clay minerals and concentrations (kaolinite at 2 wt % and 5 wt %, illite at 5 wt %, and montmorillonite at 5 wt %). The results of repeated experiments indicated that the mesophase induction period was relatively insensitive to the gas atmosphere. However, the size of the mesophase measured over the same time period was larger and the growth was uninhibited under hydrogen compared with nitrogen. It was also observed that the use of different clays at different concentrations did not significantly affect the mesophase induction period. Kaolinite, at the same concentration, had a significant effect in reducing the size of the mesophase compared with illite and montmorillonite. The effect was more pronounced at higher concentrations of kaolinite. The formation of a small-size mesophase in the case of kaolinite can be explained in terms of the increasing apparent viscosity of the isotropic matrix. The possible mechanism of the clay-mesophase interaction is envisaged as follows: Clays stabilize the layer structure of mesophase, thus inhibiting the shear that is the characteristic form of mesophase deformation. The presence of kaolinite clay prevents the molecules in the pitch matrix from acting as lubricants and restricts the coalescence of the mesophase. Differences in the physical properties of the clays (shape, size, surface charge, and hydrophilicity) may explain the differences in the observed interactions between these clays and the mesophase. The present findings may have significant implications in delayed coking operations and in the prevention of foulant adhesion to the internal wall of furnaces and superheaters.

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