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Engineering topics

Smith, D. T.

Publications and source records attributed to Smith, D. T..

Modeling of HiPco Process for Carbon Nanotube Production

High-pressure carbon monoxide (HiPco) reactor, developed at Rice University, is used to produce single-walled carbon nanotubes (SWNT) from gas-phase reactions of iron carbonyl and nickel carbonyl in carbon monoxide at high pressures (10 - 100 atm). Computational modeling is used to better understand the HiPco process. In the present model, decomposition of the precursor, metal cluster formation and growth, and carbon nanotube growth are addressed. Decomposition of precursor molecules is necessary to initiate metal cluster formation. The metal clusters serve as catalysts for carbon nanotube growth. Diameter of metal clusters and number of atoms in these clusters are some of the essential information for predicting carbon nanotube formation and growth, which is then modeled by Boudouard reaction (2CO ---> C(s) + CO2) with metal catalysts. The growth kinetic model is integrated with a two-dimensional axisymmetric reactor flow model to predict reactor performance.

Gokcen, T.↗

Analysis of suspended solids by single-particle scattering

Light scattering by individual particulates is used in a multiple-detector system to categorize the composition of suspended solids in terms of broad particulate categories. The scattering signatures of red clay and taconite tailings, the two primary particulate contaminants in western Lake Superior, along with two types of asbestiform fibers, amphibole and chrysolite, were studied in detail. A method was developed to predict the concentration of asbestiform fibers in filtration plant samples for which electron microscope analysis was done concurrently. Fiber levels as low as 50,000 fibers/liter were optically detectable. The method has application in optical categorization of samples for remote sensing purposes and offers a fast, inexpensive means for analyzing water samples from filtration plants for specific particulate contaminants.

Diehl, S. R.↗

Cosmic-ray decreases and the occurrence of solar flares.

Results are presented of a more extensive study of the relationship between the occurrence of cosmic-ray decreases and solar flares. In particular, it is considered whether it is possible to relate all large cosmic-ray decreases to flare-producing regions on the sun, and whether there is any compelling evidence relating the time of a large flare and the occurrence of a decrease to substantiate the long-standing hypothesis that at least some large cosmic-ray decreases are due to the effects of a single energetic flare. It is concluded that existing flare evidence significantly favors the hypothesis that all large cosmic-ray decreases can be accounted for by interplanetary structure associated with active flare-producing regions.

Ballif, J. R.↗