Дисертації з теми "Aluminyl Anion"

Size selective reactivity has been observed in pure aluminum cluster anions as a result of Lewis acid and base pairs. Using this a starting point, the goal of this study has been to explore how reactivity is affected with the addition of one or more ligand, which may induce active sites on the surface of the metal clusters. To study this, a theoretical investigation was undertaken on Al13Ix- and Al14Iy- (x=0-2, y=2-4) and their reactivity with methanol. The hypothesis was that iodine can induce a Lewis base site on the opposite side of the cluster, which may enhance reactivity. In results that are consistent with preliminary experimental data, it was found that the Al13Ix- series has a large energy barrier with respect to the cleavage of the O-H bond of methanol. The clusters of the series act as an extremely poor Lewis acids, and as a result, these clusters are relatively inert to methanol etching. On the other hand, the Al14Iy- series has a low barrier and is expected to react rapidly with methanol. The series is found to be most reactive at an aluminum adatom that is bound to an iodine due to the iodine extracting charge from the aluminum cluster creating a strong Lewis acid site.

We use cryogenic ion trap vibrational spectroscopy in combination with quantum chemical calculations to study the structure of mono- and dialuminum oxide anions. The infrared photodissociation spectra of D2-tagged AlO1-4 − and Al2O3-6 − are measured in the region from 400 to 1200 cm−1. Structures are assigned based on a comparison to simulated harmonic and anharmonic IR spectra derived from electronic structure calculations. The monoaluminum anions contain an even number of electrons and exhibit an electronic closed-shell ground state. The Al2O3-6 − anions are oxygen-centered radicals. As a result of a delicate balance between localization and delocalization of the unpaired electron, only the BHLYP functional is able to qualitatively describe the observed IR spectra of all species with the exception of AlO3 −. Terminal Al–O stretching modes are found between 1140 and 960 cm−1. Superoxo and peroxo stretching modes are found at higher (1120-1010 cm−1) and lower energies (850-570 cm−1), respectively. Four modes in-between 910 and 530 cm−1 represent the IR fingerprint of the common structural motif of dialuminum oxide anions, an asymmetric four-member Al–(O)2–Al ring.

Ce travail s'inscrit dans un cadre de recherches qui a pour objectif essentiel l'étude de l'effet des éléments réactifs sur l'oxydation à haute température (1373 K) d'alliages alumino-formaurs de type FeCrAl. Un alliage modèle, ne contenant pas d'éléments mineurs d'addition, a été utilisé pour cette étude. L'originalité de cette étude réside dans l'utilisation de la technique de revêtement sol-gel contenant le lanthane, le cérium ou l'yttrium. Les échantillons revêtus de sol-gel ont été recuits sous argon aux températures de 600, 800 et 1000°C. Les tests de cyclage thermiques montrent que les dépôts sol-gel de lanthane recuits à 1000°C et de cérium recuits à 600°C apportent une protection efficace à l'alliage. Le dépôt sol-gel d'yttrium n'a pas d'effet bénéfique sur le comportement à haute température même après recuit sous argon. L'analyse par la thermogravimétrie (ATG) montre que les recuits sous argon provoquent les prises de masse les plus importantes. Ceci est dû à l'augmentation de la diffusion anionique au stade initial de l'oxydation. L'utilisation de la DRX in situ nous permet de suivre l'évolution des réactions d'oxydation en identifiant les phases formées sur la surface des alliages. Après recuit ou exposition à 1100°C, le lanthane peut former des oxydes mixtes avec l'aluminium : LaAlO3 et LaAl11O18, le cérium ne forme aucun oxyde mixte avec les éléments d'alliages. L'yttrium est l'élément qui a l'affinité avec l'alumine la plus élevée. Pendant les recuits ou expositions à 1100°C, il peut former des oxydes mixtes avec l'aluminium : YAlO3 et Y3Al5O12. Les micro-observations montrent que la couche d'alumine développée sur l'alliage recouvert des dépôts sol-gel est généralement convolutée. Cette morphologie est le résultat de la formation des nouveaux oxydes dans la couche existante dû à un processus de diffusion mixte. Cette étude montre que les éléments réactifs lanthane, cérium et yttrium se localisent toujours à l'interface externe de la couche d'oxyde

Thesis (Ph. D.)--Chemical and Biomolecular Engineering, Georgia Institute of Technology, 2007.
Kohl, Paul, Committee Chair ; Bottomley, Lawrence, Committee Member ; Eckert, Charles, Committee Member ; Fuller, Tom, Committee Member ; Teja, Amyn, Committee Member.

Etude des groupes superficiels de l'alumine et des cites d'adsorption. Etude de l'adsorption des alcools sur l'alumine degussa c, des sites d'adsorption et de l'acidite induite. Donnees, enfin, sur les alumines modifiees par des ions na+ ou f-

Photoelectron spectroscopy of negatively, charged clusters of aluminum, copper, silver, and gold reveals electronic shell structure and electron energy band development. Photodetachment experiments on Au$\sb6\sp-$ also suggests that an image-bound state of the anion exists at the detachment threshold. Al$\sb{\rm x}$, Cu$\sb{\rm x}$, Ag$\sb{\rm x}$, and Au$\sb{\rm x}$ all show closed shells in their electron affinities for clusters with x $<$ 21. The electron affinities of Au$\sb{\rm x}$ for 20 $<$ x $<$ 60 have three spherical shells at x = 20, 34, and 58, all of which are dramatically manifested in dips of 1.2, 0.65, and 0.75 eV when compared to their adjacent lower mass neighbors. The photoelectron spectra of Ag$\sb{\rm x}\sp-$, 30 $<$ x $<$ 58, have cleanly resolved peaks that are a result of level structure in the density-of-states and they are predicted by the Nilsson-Clemenger formalism of shell theory. Copper clusters in the same size range show similar behavior although not as pronounced. The onset of the 3d-band in copper is monotonically increasing with cluster size and at Cu$\sb{410}$ the band is only 0.6 eV from its bulk value. The monotonic increase is a result of the expanding sphere of charge that induces a dipole as the electron leaves the vicinity of the cluster. Sharp features in the 3d-band onset are very similar to bulk photoemission spectra and suggest that these structures are beginning to show crystalline character. The induced dipole also causes at least one weakly bound state to exist for Au$\sb6\sp-$ at the detachment threshold. Photodetachment spectroscopy shows a 30 cm$\sp{-1}$ phase shift between the 1- and 2-photon ejected electrons. The phase shift may be due to a sequence congestion of vibrational states between the ground and image-bound electronic states of Au$\sb6\sp-$.

Hydrogen desorption mechanisms on hydrogenated silicon surface such as H/Si(1 00)-1x1, H/Si(l00)-2xl and H/Si(100)-3x1 surfaces have been explored by theoretical calculations with slab models. Similar desorption mechanisms have been identified for three hydrogenated surfaces and the calculated barriers were in agreement with experimental values. More interestingly, a common bridge structure has been identified as an intermediate. Its unique electronic structure is analyzed in detail. The identification of such a structure provides an alternative account for previous experimental results on STM tip-induced desorption.
Metal atom clusters are nanoscale intermediates between metal atoms and the bulk metal. Al13- can be regarded as a cluster model for Al(111) due to its special electronic and geometric structures. The reaction between Al13- and O2 was explored by various DFT methods such as BLYP, PW91, PBE, B3LYP and BHHLYP and post-HF methods such as CCSD and QCISD(T). The calculation results demonstrated that the reaction was exothermic and thermodynamically quite favorable, and the reason for the stability of Al13- towards oxygen exposure was kinetic, due to the presence of a reaction barrier. True to the expectation of Al13- as a molecular model for the Al surface, the identification of this barrier resolved a long standing puzzle in the initial chemisorption of O2 on Al(111): a barrier was identified in experiment but not in any theoretical calculations on the ground state potential surface.
Reactions on solid surfaces play a crucial role in many technologically important areas such as corrosion, adhesion, synthesis of new materials and heterogeneous catalysis. Theoretical studies on chemical reactions at surfaces can provide much useful information to understand and control these chemical processes. The present project is devoted to explore chemical reactions occurred on the aluminum cluster of Al13- and on the Si(100) surface by first principle calculations, using Gaussian 03 and Vienna Ab Initio Simulation Package (VASP).
The Al13-+HX reactions, with HX being either HCl or HI, are explored by first principle calculations and two importance dynamic factors are identified. Firstly, there was a barrier to the dissociative adsorption of FIX on the surface of an Al13- cluster, which involved charge transfer from Al13-. Secondly, the H atom could be bonded to the cluster in multiple ways, similar to the top, bridge and hollow adsorption sites on Al(111) surface. With a large amount of energy (>40 kcal/mol) deposited during the formation of Al13 -HX-, the H atom could easily migrate among these sites, similar to the diffusion of H on metal surfaces. The two dynamic factors were therefore important considerations in the formation and dissociation of Al 13-HX- And moreover, these dynamic factors make Al13- a fascinating model to probe the dynamic aspect of surface reactions, which should be an important consideration in the reactivity of other metal clusters.
Yuan, Qinghong.
"October 2009."
Source: Dissertation Abstracts International, Volume: 72-01, Section: B, page: .
Thesis (Ph.D.)--Chinese University of Hong Kong, 2010.
Includes bibliographical references.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
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Abstract also in Chinese.

碩士
國立臺灣大學
農業化學研究所
88
The polynuclear species of aluminum (including Al13) in Al partially hydrolytic soltuion influence the soil genesis, plant toxicity, and waste water process of the natural environment. The orgainic ligands in soil can be complexed with aluminum to inhibit the toxicity of aluminum. Many scholars are interested in the mechanisms of the organic ligands complexd with aluminum and their roles influence the Al partially hydrolytic solution. The objective of this study is focusing on the influences of aluminum hydrolytic reaction with and without citrate anion, and to assess the qualitative and quantitative relation to aluminum species by combining ferron method, 27Al NMR, MinteqA2 chemical species speciation program, XRD, AFM techniques etc. The speciation of aluminum in Al partially solution without citrate anions at pH = 4, monomeric Al species hydrolyze to Al13 complexes. The NMR chemical shift of Al13 is at 62.5 ppm, and the XRD d-spacings of Al13 with sulfate precipitates are 12.06 Å and 9.82 Å. As the hydroxy anions are added, the Al13 complexes transfer slowly to colloidal phase or precipitated of Al complexes. The size of the sulfuric precipitates of colloid or precipitated Al complexes is around 0.5 μm. Some Al-hydroxy-sulfate complexes aggregate together. When citrate anions exist, citrate anions will be complexed with aluminum and form Al-citrate and Al-citrate2 complexes. Their NMR chemical shift is near 6 ppm. As the hydroxy anions are added, citrate anions are partiallyly replaced and form hydroxy-citrate-colloid or precipitated of Al complexes. The shape of the sulfuric precipitates of hydroxy- citrate-colloid or precipitated of Al complexes is rhomboid or triangle. The partcile size is 1μm and its XRD d-spacings are 4.64 Å, 4.43 Å, 4.24 Å, 4.10 Å, and 3.89 Å, respectively。

Five new metalloporphyrins, $\rm \lbrack Al\sp{III} (TPPCM)Cl\rbrack,$ $\rm \lbrack Al\sp{III} (TPPCN)Cl\rbrack,$ $\rm \lbrack Al\sp{III} (TPPC)Cl\rbrack,$ $\rm \lbrack Cr\sp{III} (TPPCM)Cl\rbrack,$ and $\rm \lbrack Cr\sp{III} (TPPCN)Cl\rbrack,$ have been synthesized and characterized as a first step toward the bulk synthesis of water-soluble C$\sb{60}\sp{.-}$ salts. According to a literature report, Cr$\rm \sp{II}$(TPP) and (Al$\rm \sp{III}$(TPP)$\sp{.-}\rbrack$ (TPP$\sp{2{-}}$ = tetraphenylporphyrinato) reduce C$\sb{60}$ to C$\sb{60}\sp{.-}$ under proper solvent conditions to form an insoluble $\rm \lbrack Cr\sp{III}(TPP)\rbrack\sp+(C\sb{60}\sp{.-})$ or (Al$\rm \sp{III}$(TPP)$\rbrack\sp+$(C$\sb{60}\sp{.-})$ salt. Here it is proposed to derivatize these Cr$\rm \sp{II}$ and Al$\rm \sp{III}$ tetraphenylporphyrins with substituents on the phenyl rings to produce water-soluble $\rm \lbrack Cr\sp{III} (TPPR)\rbrack\sp+(C\sb{60}\sp{.-})$ and $\rm \lbrack Al\sp{III} (TPPR)\rbrack\sp+(C\sb{60}\sp{.-})$ salts. Initial electrochemical data for precursor $\rm \lbrack Al\sp{III} (TPPCM)Cl\rbrack,$ $\rm \lbrack Al\sp{III} (TPPCN)Cl\rbrack,$ $\rm \lbrack Al\sp{III} (TPPC)Cl\rbrack,$ $\rm \lbrack Cr\sp{III} (TPPCM)Cl\rbrack,$ and $\rm \lbrack Cr\sp{III} (TPPCN)Cl\rbrack$ compounds suggest that adding water-solubilizing substituents does not interfere with the electron transfer between the reduced Al$\rm \sp{III}$ and C$\rm \sp{II}$ metalloporphyrins and C$\sb{60}.$ Hence, there is potential to produce bulk amounts of water-soluble C$\sb{60}\sp{.-}$ by this method. The radical anion has 150 A$\sp2$ of paramagnetic surface area (S = 1/2), and possible utility as a new magnetic resonance imaging contrast agent.

碩士
東海大學
化學系
107
In recent years, aluminum has been considered as suitable candidate for electrochemical storage devices due to its high volumetric and gravimetric capacities besides its high abudance. The high capacity of aluminum ion battery is attributed to trivalent electrochemical redox reaction (Al3++3e-↔Al). Moreover, it is supported by its density which is around four times the lithium and it can be handled under the air leading to enormous advantages for the battery application, thus extremely improves the safety level of electrochemical storage system. We investigated the electrochemical performance of different graphite materials as cathode for aluminum-ion battery by using in-situ X-ray diffraction and in-situ Raman techniques. The two analytical methods demonstrated that crystallinity of the graphite materials will influence the storage mechanism of AlCl4-. Furthermore, we synthesized expanded graphite (EG) by simple acid treatment and followed by high temperature annealing.The high capacity displayed by EG can be attributed to integreated intercalation and adsorption mechanisms. In-situ XRD and in-situ Raman techaniques were used to speculate the different mechanisms adopted by EG during cycling.