title: The local physical structure of amorphous hydrogenated boron carbide: insights from magic angle spinning solid-state NMR spectroscopy.
abstract: Magic angle spinning solid-state nuclear magnetic resonance spectroscopy techniques are applied to the elucidation of the local physical structure of an intermediate product in the plasma-enhanced chemical vapour deposition of thin-film amorphous hydrogenated boron carbide (B(x)C:H(y)) from an orthocarborane precursor. Experimental chemical shifts are compared with theoretical shift predictions from ab initio calculations of model molecular compounds to assign atomic chemical environments, while Lee-Goldburg cross-polarization and heteronuclear recoupling experiments are used to confirm atomic connectivities. A model for the B(x)C:H(y) intermediate is proposed wherein the solid is dominated by predominantly hydrogenated carborane icosahedra that are lightly cross-linked via nonhydrogenated intraicosahedral B atoms, either directly through B-B bonds or through extraicosahedral hydrocarbon chains. While there is no clear evidence for extraicosahedral B aside from boron oxides, ∼40% of the C is found to exist as extraicosahedral hydrocarbon species that are intimately bound within the icosahedral network rather than in segregated phases.
authors.affiliation: Department of Physics, University of Missouri-Kansas City, Kansas City, MO 64110, USA.
authors.forename: Michelle M
authors.initials: MM
authors.lastname: Paquette
authors.forename: Wenjing
authors.initials: W
authors.lastname: Li
authors.forename: M
authors.initials: M
authors.lastname: Sky Driver
authors.forename: Sudarshan
authors.initials: S
authors.lastname: Karki
authors.forename: A N
authors.initials: AN
authors.lastname: Caruso
authors.forename: Nathan A
authors.initials: NA
authors.lastname: Oyler