TY - JOUR
T1 - Al27 and H1 MAS NMR and Al27 multiple quantum studies of Ti-doped NaAlH4
AU - Herberg, Julie L.
AU - Maxwell, Robert S.
AU - Majzoub, Eric H.
N1 - Previous X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) studies on Ti-doped NaAlH4 revealed the reaction products of two heavily doped (...
PY - 2006/6/1
Y1 - 2006/6/1
N2 - Previous X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) studies on Ti-doped NaAlH4 revealed the reaction products of two heavily doped (33.3 at.%) samples. This investigation revealed that nano-crystalline or amorphous Al2O3 forms from the possible coordination of aluminum with the oxygen atom of the furan ring system from added tetrahydrofuran (THF) in solvent-mixed samples, and that TiAl3 forms in mechanically-milled samples [E.H. Majzoub, J.L. Herberg, R. Stumpf, R.S. Maxwell, J. Alloys Compd. 394 (2005) 265], indicating the importance of understanding the processing conditions of these potentially important hydrogen storage materials. The present paper provides a more sophisticated NMR investigation of these materials and resolves some unanswered questions. On heavily doped (33.3 at.%) solvent-mixed samples, Al27 Magic Angle Spinning (MAS) NMR Al27 multiple quantum MAS (MQMAS) indicates the presence of an oxide layer of Al2O3 on the surfaces of potentially bulk nanocrystalline Ti, nanocrystalline TiAl3, and/or metallic aluminum. The H1 MAS NMR data also indicate the possible coordination of aluminum with oxygen atoms in the THF molecules. In addition, the H1 MAS NMR and H1 spin-lattice relaxation (T1) measurements are consistent with the presence of TiH2. These results are in agreement with recent XAFS measurements indicating both Al and H within the first few coordination shells of Ti in the doped alanate.
AB - Previous X-ray diffraction (XRD) and nuclear magnetic resonance (NMR) studies on Ti-doped NaAlH4 revealed the reaction products of two heavily doped (33.3 at.%) samples. This investigation revealed that nano-crystalline or amorphous Al2O3 forms from the possible coordination of aluminum with the oxygen atom of the furan ring system from added tetrahydrofuran (THF) in solvent-mixed samples, and that TiAl3 forms in mechanically-milled samples [E.H. Majzoub, J.L. Herberg, R. Stumpf, R.S. Maxwell, J. Alloys Compd. 394 (2005) 265], indicating the importance of understanding the processing conditions of these potentially important hydrogen storage materials. The present paper provides a more sophisticated NMR investigation of these materials and resolves some unanswered questions. On heavily doped (33.3 at.%) solvent-mixed samples, Al27 Magic Angle Spinning (MAS) NMR Al27 multiple quantum MAS (MQMAS) indicates the presence of an oxide layer of Al2O3 on the surfaces of potentially bulk nanocrystalline Ti, nanocrystalline TiAl3, and/or metallic aluminum. The H1 MAS NMR data also indicate the possible coordination of aluminum with oxygen atoms in the THF molecules. In addition, the H1 MAS NMR and H1 spin-lattice relaxation (T1) measurements are consistent with the presence of TiH2. These results are in agreement with recent XAFS measurements indicating both Al and H within the first few coordination shells of Ti in the doped alanate.
KW - doped
KW - multiple quantum studies
UR - https://www.sciencedirect.com/science/article/pii/S0925838805014805
UR - https://www.researchgate.net/publication/248177043_and_MAS_NMR_and_multiple_quantum_studies_of_Ti-doped_NaAlH4
U2 - 10.1016/j.jallcom.2005.09.047
DO - 10.1016/j.jallcom.2005.09.047
M3 - Article
VL - 417
JO - Journal of Alloys and Compounds
JF - Journal of Alloys and Compounds
ER -