NMR Chemical Shift and Quadrupolar Interaction Parameters of Carbon‐Coordinated ²⁷Al in Aluminium Carbide, Al₄C₃

Abstract

Aluminium carbide, Al 4 C 3 , was characterised by 13 C and 27 Al solid-state NMR spectroscopy. The 13 C NMR spectra display two resonances with an intensity ratio of 1:2, which is in agreement with the reported crystal structure. The 27 Al NMR spectra of Al 4 C 3 under both static and MAS conditions were deconvoluted into two spectral components, belonging to the two aluminium species Al1 and Al2 in the crystal structure of Al 4 C 3 . The spectral fit allowed for determination of the relatively large quadrupolar coupling constants (χ ≈ 16 MHz) of both 27 Al species. One aluminium species displayed a

Atomic scale structure of amorphous aluminum oxyhydroxide, oxide and oxycarbide films probed by very high field27Al nuclear magnetic resonance

“…4), which is a chemical shift more positive than the typical positions of AlO 4 units found in pure alumina. This indicates the formation of a tetrahedral environment including an element less electronegative than O like C. 27 Al SSNMR on aluminum carbide (Al 4 C 3 ) has been investigated by Bräuniger et al 45 and the corresponding experimental chemical shifts as well as quadrupolar coupling constants are in good agreement with our spectrum reconstruction (d iso ¼ 98:5 ppm, C Q ¼ 14 MHz). In the present work, the carbon content does not exceed 7 at% (vs. 42.8 at% in Al 4 C 3 ) which suggests that the first coordination sphere of aluminum may not only be filled with carbon atoms, but also with oxygen ones.…”

Synthesis of Mg2C: A Magnesium Methanide

“…This agrees with the antifluorite structure, which contains only one unique crystallographic position for carbon. The chemical shift is significantly higher than that of C 4À in Al 4 C 3 (34 and 51 ppm for C atoms in two crystallographically different sites), [18] and agrees well with higher degree of covalent character of AlÀC bonding as compared with MgÀC. The absence of J coupling in the observed NMR spectrum suggests that carbon within the compound is primarily ionic; increased covalency would be manifested by the presence of J coupling.…”

Convenient Preparation of Ternary Carbidoaluminates – The Example MgAl2C2

“…The small peak at δ ≈ 250 ppm is a spinning side band. The resonance is almost the same as that of one of the two crystallographically nonequivalent carbon atoms in the aluminium trigonal antiprisms of Al 4 C 3 with space group R $\bar {3}$ m ( δ = 50.5 ppm); the other carbon atom in the Al 4 C 3 structure is surrounded by a distorted trigonal‐bipyramidal arrangement of aluminium atoms ( δ = 33.9 ppm) 22. The peak position of the carbon resonance in silicon carbides appears at lower fields ( δ =15.2–25 ppm)23–25 and that of TiC at higher fields ( δ =560 ppm) 23…”