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J.w. Rogers – One of the best experts on this subject based on the ideXlab platform.

  • Initial stages of AlN thin‐film growth on alumina using trimethylamine Alane and ammonia precursors
    Journal of Applied Physics, 1994
    Co-Authors: D. C. Bertolet, Herng Liu, J.w. Rogers
    Abstract:

    A novel precursor combination, trimethylamine Alane (TMAA) and ammonia (NH3), has been investigated for the low‐temperature chemical vapor‐deposition of AlN thin films. The initial stages of AlN growth on alumina powder substrates were studied by Fourier transform infrared specspectroscopy and x‐ray photoelectron specspectroscopy. Upon exposure of TMAA to the alumina surface at 300 K, infrared data show the presence of molecular trimethylamine Alane on the surface. NH3 reacts with the TMAA derivatized surface at 300 K, removing all of the trimethylamine, and leaving a four‐coordinate ‐NH2‐ species bound to aluminum in extended networks. Concurrently, the population of Alane on the surface is greatly reduced as a result of reaction with NH3 to form ‐NH2‐ and liberate H2. Subsequent exposure of TMAA leads to reaction with the surface ‐NH2‐ species and the further adsorption of TMAA. These reactions continue to propagate following additional alternating exposures of NH3 and TMAA, although with decreasing efficiency….

  • initial stages of aln thin film growth on alumina using trimethylamine Alane and ammonia precursors
    Journal of Applied Physics, 1994
    Co-Authors: D. C. Bertolet, Herng Liu, J.w. Rogers
    Abstract:

    A novel precursor combination, trimethylamine Alane (TMAA) and ammonia (NH3), has been investigated for the low‐temperature chemical vapor‐deposition of AlN thin films. The initial stages of AlN growth on alumina powder substrates were studied by Fourier transform infrared specspectroscopy and x‐ray photoelectron specspectroscopy. Upon exposure of TMAA to the alumina surface at 300 K, infrared data show the presence of molecular trimethylamine Alane on the surface. NH3 reacts with the TMAA derivatized surface at 300 K, removing all of the trimethylamine, and leaving a four‐coordinate ‐NH2‐ species bound to aluminum in extended networks. Concurrently, the population of Alane on the surface is greatly reduced as a result of reaction with NH3 to form ‐NH2‐ and liberate H2. Subsequent exposure of TMAA leads to reaction with the surface ‐NH2‐ species and the further adsorption of TMAA. These reactions continue to propagate following additional alternating exposures of NH3 and TMAA, although with decreasing efficiency….

Jason Graetz – One of the best experts on this subject based on the ideXlab platform.

  • Effect of Titanium Doping of Al(111) Surfaces on Alane Formation Mobility, and Desorption
    The Journal of Physical Chemistry C, 2011
    Co-Authors: Irinder S. Chopra, Jason Graetz, Santanu Chaudhuri, Jean François Veyan, Yves J. Chabal
    Abstract:

    Alanes are critical intermediates in hydrogen storage reactions for mass transport during the formation of complex metal hydrhydrides. Titanium has been shown to promote hydrogen desorption and hydrogenation, but its role as a catalyst is not clear. Combining surface infrared (IR) spectroscopy and density funcfunctional theory (DFT), the role of Ti is explored during the interaction of atomic hydrhydrogen with Ti-doped Al(111) surfaces. Titanium is found to reduce the formation of large Alanes, due to a decrease of hydrogen mobility and to trapping of small Alanes on Ti sites, thus hindering oligomerization. For high doping levels ({approx}0.27 ML Ti) on Al(111), only chemisorbed AlH{sub 3} is observed on Ti sites, with no evidence for large Alanes. Titanium also dramatically lowers the desorption temperature of large Alanes from 290 to 190 K, due to a more restricted translational motion of these Alanes.

  • thermochemistry of Alane complexes for hydrogen storage a theoretical and experimental investigation
    Journal of Physical Chemistry C, 2011
    Co-Authors: Bryan M. Wong, David Lacina, Jason Graetz, Ida M. B. Nielsen, Mark D. Allendorf
    Abstract:

    Knowledge of the relative stabilities of Alane (AlH(3)) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for 38 Alane complexes with NH(3-n)R(n) (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH(2-n)R(n) (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and Alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amineAlane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine and obtaining upper limits of ΔG° for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the Alane complex. On the basis of this, we conclude that only a subset of the tertiary aminamine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an Alane-based hydrogen storage system.

  • Thermochemistry of Alane Complexes for Hydrogen Storage: A Theoretical and Experimental Comparison
    The journal of physical chemistry. C Nanomaterials and interfaces, 2011
    Co-Authors: Bryan M. Wong, David Lacina, Jason Graetz, Ida M. B. Nielsen, Mark D. Allendorf
    Abstract:

    Knowledge of the relative stabilities of Alane (AlH3) complexes with electron donors is essential for identifying hydrogen storage materials for vehicular applications that can be regenerated by off-board methods; however, almost no thermodynamic data are available to make this assessment. To fill this gap, we employed the G4(MP2) method to determine heats of formation, entropies, and Gibbs free energies of formation for thirty-eight Alane complexes with NH3-nRn (R = Me, Et; n = 0-3), pyridine, pyrazine, triethylenediamine (TEDA), quinuclidine, OH2-nRn (R = Me, Et; n = 0-2), dioxane, and tetrahydrofuran (THF). Monomer, bis, and selected dimer complex geometries were considered. Using these data, we computed the thermodynamics of the key formation and dehydrogenation reactions that would occur during hydrogen delivery and Alane regeneration, from which trends in complex stability were identified. These predictions were tested by synthesizing six amineAlane complexes involving trimethylamine, triethylamine, dimethylethylamine, TEDA, quinuclidine, and hexamine, and obtaining upper limits of delta G for their formation from metallic aluminum. Combining these computational and experimental results, we establish a criterion for complex stability relevant to hydrogen storage that can be used to assess potential ligands prior to attempting synthesis of the Alane complex. Based on this, we conclude that only a subset of the tertiary aminamine complexes considered and none of the ether complexes can be successfully formed by direct reaction with aluminum and regenerated in an Alane-based hydrogen storage system.

D. C. Bertolet – One of the best experts on this subject based on the ideXlab platform.

  • Initial stages of AlN thin‐film growth on alumina using trimethylamine Alane and ammonia precursors
    Journal of Applied Physics, 1994
    Co-Authors: D. C. Bertolet, Herng Liu, J.w. Rogers
    Abstract:

    A novel precursor combination, trimethylamine Alane (TMAA) and ammonia (NH3), has been investigated for the low‐temperature chemical vapor‐deposition of AlN thin films. The initial stages of AlN growth on alumina powder substrates were studied by Fourier transform infrared spectroscopy and x‐ray photoelectron spectroscopy. Upon exposure of TMAA to the alumina surface at 300 K, infrared data show the presence of molecular trimethylamine Alane on the surface. NH3 reacts with the TMAA derivatized surface at 300 K, removing all of the trimethylamine, and leaving a four‐coordinate ‐NH2‐ species bound to aluminum in extended networks. Concurrently, the population of Alane on the surface is greatly reduced as a result of reaction with NH3 to form ‐NH2‐ and liberate H2. Subsequent exposure of TMAA leads to reaction with the surface ‐NH2‐ species and the further adsorption of TMAA. These reactions continue to propagate following additional alternating exposures of NH3 and TMAA, although with decreasing efficiency….

  • initial stages of aln thin film growth on alumina using trimethylamine Alane and ammonia precursors
    Journal of Applied Physics, 1994
    Co-Authors: D. C. Bertolet, Herng Liu, J.w. Rogers
    Abstract:

    A novel precursor combination, trimethylamine Alane (TMAA) and ammonia (NH3), has been investigated for the low‐temperature chemical vapor‐deposition of AlN thin films. The initial stages of AlN growth on alumina powder substrates were studied by Fourier transform infrared spectroscopy and x‐ray photoelectron spectroscopy. Upon exposure of TMAA to the alumina surface at 300 K, infrared data show the presence of molecular trimethylamine Alane on the surface. NH3 reacts with the TMAA derivatized surface at 300 K, removing all of the trimethylamine, and leaving a four‐coordinate ‐NH2‐ species bound to aluminum in extended networks. Concurrently, the population of Alane on the surface is greatly reduced as a result of reaction with NH3 to form ‐NH2‐ and liberate H2. Subsequent exposure of TMAA leads to reaction with the surface ‐NH2‐ species and the further adsorption of TMAA. These reactions continue to propagate following additional alternating exposures of NH3 and TMAA, although with decreasing efficiency….

M. E. Gross – One of the best experts on this subject based on the ideXlab platform.

  • Aluminum thin film growth by the thermal decomposition of triethylamine Alane
    Surface Science, 1991
    Co-Authors: L.h. Dubois, B. R. Zegarski, M. E. Gross, Ralph G. Nuzzo
    Abstract:

    Abstract Triethylamine Alane (TEAA) decomposes on an Al(111) single crystal surface at temperatures above ∼310 K to yield pure aluminum thin films, liberating hydrogen and triethylamine into the gas phase. Aluminum deposition is epitaxial and clean (no carbon or nitrogen containing species are observed by Auger elecelectron specspectroscopy). The film growth rate is limited by the rate of the recombinative desorption of hydrogen from the surface. These results are compared to similar data from experiments on the surface-mediated thermal decodecomposition of trimethylamine Alane.

  • Liquid source metalorganic chemical vapor deposition of aluminum from triethylamine Alane
    Journal of Applied Physics, 1991
    Co-Authors: M. E. Gross, C. G. Fleming, K.p. Cheung, L. A. Heimbrook
    Abstract:

    Low‐pressure metalorganic chemical vapovaporosition (MOCVD) of aluminum using triethylamine Alane (TEAA) is reported. This liquid source combines the chemical advantages of adduct precursors such as solid trimethylamine Alane (TMAA), with the processing and handling advantages of liquid precursors such as triisobutyl aluminum (TIBA). High‐purity Al films were deposited on TiN and thin in situ evaporated Cu and Ti films, which serve as activators for nucleation of Al. The electrical resistivities of the Al films on TiN were close to the 3 μΩ cm of sputtered Al. In the case of depositions on Cu, the Cu diffuses readily into the Al and serves to improve the electromigration resistance of the latter. The Al deposition rates using TEAA are 2–4 times those using TIBA at 250 °C, although the TEAA process is not fully optimized at this point and further work is needed to improve the film morphologies.

Minh Tho Nguyen – One of the best experts on this subject based on the ideXlab platform.

  • Hydrogen Release from Ammonia Alane-Based Materials: Formation of Cyclotrialazane and Alazine
    The Journal of Physical Chemistry C, 2015
    Co-Authors: Vinh Son Nguyen, D. Majumdar, Jerzy Leszczynski, Minh Tho Nguyen
    Abstract:

    In previous papers (Nguyen et al. J. Phys. Chem. C 2008, 112, 5662–5667 and J. Phys. Chem. C 2009, 113, 18914–18926), formation of H2 molecules from ammonia Alane monomer (AAl) and dimers (AAl)2 was shown to be facilitated by the addition of one or more Alane or ammonia molecules that can play the role of efficient bifunctional catalyst. Ammonia Alane emerges as a good starting compound for building up materials for chemical hydrhydrogenrage (CHS). Further exploration of the products based on the H2 release from ammonia Alane were carried out using coupled-cluster theory computations together with the aug-cc-pVTZ basis set (based on MP2/aug-cc-pVDZ optimized geometries). Our ab initio MO calculations for the first time led to the identification of cyclotrialazane [(H2AlNH2)3], alazine [(HAlNH)3], and its oligomer [H2Al(HNAlH)2NH2] that are produced along the multistep dehydrogenation processes from the reactions of ammonia Alane and AlH3NH2AlH2NH3. The formation of alazine (homologue of borazine) as the f…

  • Hydrogen release from systems containing phosphine, borane, Alane and gAlane: A mechanistic study
    Chemical Physics Letters, 2013
    Co-Authors: Vinh Son Nguyen, D. Majumdar, Jerzy Leszczynski, Minh Tho Nguyen
    Abstract:

    Abstract The H 2 release mechanism from phosphine borane and phosphine Alane was investigated using quantum chemical methods (MP2/aug-cc-pVTZ geometry optimization and coupled-cluster energies were obtained through complete basis set extrapolation, CCSD(T)/CBS). The effect of catalysts borane, Alane and gAlane on the processes was also explored. As the energy barriers for the release of H 2 from BH 3 PH 3 and AlH 3 PH 3 are much higher than the B–P and Al–P bond energies, the presence of inherent catalysts can reduce substantially such energy barriers (using BH 3 for BH 3 PH 3, while AlH 3 and GaH 3 for AlH 3 PH 3 ), and these systems could be useful as probable hydrogen source.

  • the effect of the nh2 substituent on nh3 hydrazine as an alternative for ammonia in hydrogen release in the presence of boranes and Alanes
    Physical Chemistry Chemical Physics, 2009
    Co-Authors: Minh Tho Nguyen, Myrna H. Matus, Nguyen Vinhson, Saartje Swinnen, David A. Dixon
    Abstract:

    Potential energy surfaces for H2 release from hydrazine interacting with borane, Alane, diborane, diAlane and boraneAlane were constructed from MP2/aVTZ geometries and zero point energies with single point energies at the CCSD(T)/aug-cc-pVTZ level. With one borane or Alane molecule, the energy barrier for H2-loss of ∼38 or 30 kcal mol−1 does not compete with the B–N or Al–N bond cleacleavage (∼30 or ∼28 kcal mol−1). The second borane or Alane molecule can play the role of a bifunctional catalyst. The barrier energy for H2-elimination is reduced from 38 to 23 kcal mol−1, or 30 to 20 kcal mol−1 in the presence of diborane or diAlane, respectively. The mixed boraneAlane dimer reduces the barrier energy for H2 release from hydrazine to ∼17 kcal mol−1. A systematic comparison with the reaction pathways from ammonia borane shows that hydrazine could be an alternative for ammonia in producing borane amine derivatives. The results show a significant effect of the NH2 substituent on the relevant thermodynamics. The B–N dative bond energy of 31 kcal mol−1 in NH2NH2BH3 is ∼5 kcal mol−1 larger than that of the parent BH3NH3. The higher thermodynamic stability could allow hydrazineborane to be used as a material for certain energetic H2 storage applications.