Adsorption Properties of Nanocrystalline/Nanoporous Gallium Nitride Powders
Jerzy F. Janik,
A diverse pool of six semiconductor GaN nanopowders was synthesized by the thermally-driven pyrolysis of gallium imide at
various temperatures. The XRD-derived average crystallite sizes for the nanopowders were in the range 1-17 nm. Standard nitrogen adsorption
measurements at 77 K yielded the basic characteristics of the powder pore structures including the BET surface areas that
spanned 23-287 m2/g. Rare studies of adsorption of water vapor, carbon dioxide, and hydrogen on the nitride nanopowders were carried
out. The data on water vapor adsorption at 295 K supported chemisorption of water molecules on the primary adsorption centers and physisorption
on the secondary centers. The data on carbon dioxide adsorption at 273 K and hydrogen adsorption at 77 K were used to determine
the selectivity of adsorption for these gases defined as the ratio of the respective Henry's constants calculated from the Langmuir
equation. The GaN nanopowders showed remarkably diverse pore structure characteristics and adsorption properties that could be linked
to the nitride's average crystallite size and crystallite agglomeration, the latter supported by helium density data.
Keywords: Nanocrystalline, GaN, adsorption, water vapor, hydrogen, carbon dioxide.
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