Thermal Decomposition of Aluminum Alkoxides<sup>1</sup>

Shulman, Garson P.; Trusty, Monty; Vickers, John

doi:10.1021/jo01039a005

Cited by 34 publications

(17 citation statements)

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“…Most of the above-mentioned studies take for granted that the film composition is Al 2 O 3 whatever the processing conditions, in contrast to the results reported by the authors' group. [1][2][3] Lee et al, [12] operating in conditions close to the ones investigated in the present study, inferred that 3 as molecular species in the vapor phase, [13] however ATI has long been shown to be a tetramer ([Al(O i Pr)] 4 ) in the solid state, and to exist mainly as tetramer molecules in the vapor phase. [3] This is a key feature to consider when proposing relevant transitional species forming in the vapor phase.…”

supporting

confidence: 61%

Local Kinetic Modeling of Aluminum Oxide Metal‐Organic CVD From Aluminum Tri‐isopropoxide

Vergnes

Samélor

Gleizes

et al. 2011

Chemical Vapor Deposition

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Due to numerous allotropic modifications and to the subsequent large spectrum of structure-properties relationships, aluminum oxides in the form of films and coatings are of major technological interest for a wide range of applications, e.g., optics and microelectronic components, wear resistance, catalyst support, protection against corrosion, and high temperature oxidation. Metal-organic (MO)CVD is a potentially attractive technique for the processing of such coatings, especially on complex-in-shape, temperature-sensitive parts. In this context, processingstructure relationships were established and the feasibility of such a process was proven, on the laboratory scale, in a series of papers recently published by the authors. [1][2][3] It is recalled that, using aluminum tri-isopropoxide (ATI) as the precursor and operating in a hot-wall reactor in the temperature range 350-415 8C, under 5 Torr, with dry N 2 as a carrier/dilution gas results in partially hydroxylated films AlO 1þx (OH) 1-2x ; x varies from 0 (AlOOH) at 350 8C to 0.5 (Al 2 O 3 ) at 415 8C. Films processed between 415 8C and 650 8C are composed of amorphous Al 2 O 3 ; nanostructured gamma-alumina films are obtained at a deposition temperature of 700 8C. In parallel, promising barrier properties were demonstrated for such amorphous coatings, especially for the protection of titanium alloys from oxidation and corrosion at temperatures up to 600 8C. [4][5][6] These works revealed that, despite its instability and trend to ageing, ATI can be used for reproducibly depositing aluminum oxide provided that it is stored in a glove box, and renewed in the bubbler after a few hours of use. The next step towards industrial implementation of this process is the insight into the involved chemical reactions, and the determination of the corresponding reaction kinetics. Such knowledge allows process modeling, and hence controlling, and consequently optimizing, the relation between macroscopic processing conditions and the local deposition rates.There are very few reports on local kinetic modeling of the MOCVD processes. This blank spot in processing science is due to the often complex chemical mechanisms involved, combining poorly known homogeneous and heterogeneous chemical reactions. The main difficulty then is to find representative chemical reactions and the related kinetic laws. Concerning the MOCVD of alumina from ATI, Kawase et al. experimentally investigated reaction kinetics in a hot-wall tubular reactor under 30 Torr total pressure in the temperature range 830-1160 8C.[7] Assuming a firstorder reaction in ATI, they found an activation energy of 179 kJ mol À1 . They also obtained different deposition rates in two different tubular reactor diameters and concluded that the dominant reaction mechanism was the homogeneous pyrolysis of ATI. Hofman et al. performed CVD and mass spectroscopic experiments in this system operating under 3 Torr between 220 8C and 450 8C.[8] The authors showed that propene is a deposition by-product, and that the rate-limiting step...

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supporting

confidence: 61%

Local Kinetic Modeling of Aluminum Oxide Metal‐Organic CVD From Aluminum Tri‐isopropoxide

Vergnes

Samélor

Gleizes

et al. 2011

Chemical Vapor Deposition

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“…At very low levels of water vapour, some scattering in the deposition rate occurred, probably owing to the inaccuracy of the mass-flow controllers used. The effect of thermal and hydrolytic decomposition of aluminum alkoxides can be explained by the reactions proposed by Schulman et al [25]: …”

Section: Discussionmentioning

confidence: 99%

Properties of alumina films prepared by metal-organic chemical vapour deposition at atmospheric pressure in the presence of small amounts of water

Haanappel

Rem

Corbach

et al. 1995

Surface and Coatings Technology

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Thin alumina films were deposited on stainless steel, type AISI 304. The deposition process was carried out in nitrogen with low partial pressures of water (0-2.6 x 10 -2 kPa (0-0.20 mmHg)) by metal-organic chemical vapour deposition (MOCVD) with aluminium-tri-sec-butoxide (ATSB) as the precursor. Also results are presented regarding the alumina deposition in the presence of small amounts of 2-butanol. The film properties, including the protection of the underlying substrate against aggressive gas compounds such as sulphur at high temperatures, the chemical composition, the microstructure, and the refractive index were investigated as a function of the water vapour pressure.In contrast with the results of stress reduction in silica films by the addition of small amounts of water to the deposition process, no significant effect on the internal stress in alumina films was found. TEM analysis showed that extremely fine grains of ~-A1203/A10(OH) were formed, in agreement with the refractive index. Only an increase of the OH groups was found if water was added to the process, which also was the only impurity in the oxide film. Carbon was not detected.

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“…A first-order or pseudo-first-order mechanism with respect to precursor vapor concentration is encountered in the high-temperature oxidation of Tic& and Sic& in excess O2 (Powers, 1978;French et al, 1978;Suyama and Kato, 1976) and in thermal decomposition of metal alkoxides (Schulman et al, 1963). Such a reaction mechanism has also been used to facilitate modeling of particle dynamics (Okuyama et al, 1986).…”

Section: Theorymentioning

confidence: 99%

Gas-phase manufacture of particulates: interplay of chemical reaction and aerosol coagulation in the free-molecular regime

Landgrebe¹,

Pratsinis²

1989

Ind. Eng. Chem. Res.

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A theoretical analysis of gas-phase manufacture of particulates is presented using a discrete model for particulate dynamics in the free-molecular regime. Regardless of the reaction order and process conditions, two dimensionless groups suffice to determine the particle size distribution a t isothermal conditions. These groups are (1) the dimensionless reaction time, which is proportional to the ratio of the characteristic time for chemical reaction to the characteristic time for aerosol coagulation, and (2) the dimensionless residence time, which is proportional to the ratio of the residence time to the characteristic time for coagulation. The size distribution of a reaction-produced coagulating aerosol evolves to an asymptotic self-preserving size distribution that has a geometric standard deviation of 1.46. When the reaction is instantaneous, good agreement is obtained between model predictions and literature values for the time needed for the size distribution to obtain its asymptotic geometric standard deviation (self-preserving form). For noninstantaneous reactions, a self-preserving map is created in which the required time for attainment of the self-preserving form is given as a function of the dimensionless reaction time. The employed numerical model provides an accurate solution of the coagulation equations. This solution can be used to evaluate the accuracy of approximate models of aerosol dynamics that employ monodisperse, self-preserving, log-normal, or discrete-sectional representations of the aerosol size distribution.

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Thermal Decomposition of Aluminum Alkoxides¹

Cited by 34 publications

References 0 publications

Local Kinetic Modeling of Aluminum Oxide Metal‐Organic CVD From Aluminum Tri‐isopropoxide

Local Kinetic Modeling of Aluminum Oxide Metal‐Organic CVD From Aluminum Tri‐isopropoxide

Properties of alumina films prepared by metal-organic chemical vapour deposition at atmospheric pressure in the presence of small amounts of water

Gas-phase manufacture of particulates: interplay of chemical reaction and aerosol coagulation in the free-molecular regime

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Thermal Decomposition of Aluminum Alkoxides1

Cited by 34 publications

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Local Kinetic Modeling of Aluminum Oxide Metal‐Organic CVD From Aluminum Tri‐isopropoxide

Local Kinetic Modeling of Aluminum Oxide Metal‐Organic CVD From Aluminum Tri‐isopropoxide

Properties of alumina films prepared by metal-organic chemical vapour deposition at atmospheric pressure in the presence of small amounts of water

Gas-phase manufacture of particulates: interplay of chemical reaction and aerosol coagulation in the free-molecular regime

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Thermal Decomposition of Aluminum Alkoxides¹