Spinel Formation for Stabilizing Simulated Nickel-Laden Sludge with Aluminum-Rich Ceramic Precursors

The use of Si3N4, alloys for high temperature, high stress structural applications has prompted numerous studies of the oxynitride glasses which exist as intergranular phases in their microstructures. Oxynitride glasses have been investigated recently in their bulk form in order to understand their crystallization behavior for subsequent Si3N4 applications and to investigate their worth as glass-ceramic precursors. This research investigates the crystallization sequence of a glass having a normalized composition of Y26Si30Al11 ON11 and lying in the A1N-Y2O3-SiO2 section of the Y-Si-Al-O-N system. Such glasses exist as intergranular phases in the technologically important Y2O3/Al2O3-fluxed Si3N4 alloys.

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The crystallization of thin-film ceramics

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100122095 ◽

1992 ◽

Vol 50 (1) ◽

pp. 338-339

Author(s):

J.M. Schwartz ◽

L.F. Francis ◽

L.D. Schmidt ◽

P.S. Schabes-Retchkiman

Keyword(s):

Thin Films ◽

Grain Size ◽

Sol Gel ◽

Processing Route ◽

Small Areas ◽

Ceramic Thin Films ◽

Complex Shapes ◽

Sol Gel Process ◽

Ceramic Precursors ◽

Crystalline Ceramic

Ceramic thin films and coatings are of interest for electrical, optical, magnetic and thermal barrier applications. Critical for improved properties in thin films is the development of specific microstructures during processing. To this end, the sol-gel method is advantageous as a versatile processing route. The sol-gel process involves depositing a solution containing metalorganic or colloidal ceramic precursors onto a substrate and heating the deposited layer to form a crystalline or non-crystalline ceramic coating. This route has several advantages, including the ability to create tailored microstructures and properties, to coat large or small areas, simple or complex shapes, and to more easily prepare multicomponent ceramics. Sol-gel derived coatings are amorphous in the as-deposited state and develop their crystalline structure and microstructure during heat-treatment. We are particularly interested in studying the amorphous to crystalline transformation, because many key features of the microstructure such as grain size and grain size distribution may be linked to this transformation.

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Heterogeneous Nucleation of Ordered Mesoporous Materials

MRS Proceedings ◽

10.1557/proc-371-111 ◽

1994 ◽

Vol 371 ◽

Cited By ~ 2

Author(s):

Jun Liu ◽

Jud W. Virden ◽

Anthony Y. Kim ◽

Bruce C. Bunker

Keyword(s):

Mesoporous Materials ◽

Heterogeneous Nucleation ◽

Colloidal Particles ◽

Co Adsorption ◽

Surfactant Solution ◽

Nucleation Process ◽

Ordered Mesoporous Materials ◽

Ordered Mesoporous ◽

Ceramic Precursors ◽

Heterogenous Nucleation

AbstractRecently we proposed that heterogenous nucleation is an important phenomenon for the preparation of ordered mesoporous materials. In this paper we further investigate the effect of colloidal particles on the nucleation process of mesoporous materials. Based on the change of the electrical mobilities of the particles in the surfactant solution, we suggest that the adsorption and co-adsorption of surfactant and ceramic precursors changes local structural and chemistry on the particle surfaces, and favors the nucleation events within these regions.

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Thermodynamical Calculations and Experimental Confirmation about the Mg-Al-Spinel Reaction Path in the Sol-Gel-Process

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.317-318.135 ◽

2006 ◽

Vol 317-318 ◽

pp. 135-138 ◽

Cited By ~ 1

Author(s):

Wilfried Wunderlich ◽

Krupathi Vishista ◽

Francis D. Gnanam ◽

Daniel Doni Jayaseelan

Keyword(s):

Thermal Analysis ◽

Reaction Path ◽

Sol Gel ◽

Chemical Processing ◽

Aluminium Isopropoxide ◽

Spinel Formation ◽

Sol Gel Process ◽

Wet Chemical ◽

Enthalpy Data ◽

Good Agreement

The aim of this research is, to clarify which route the sol-gel-process is taking in the case of a Al-Mg-spinel slurry, in particular, whether the hydrolysis reaction or the spinel formation is faster and which of the intermediate hydroxide phases Al(OH)3, and Mg(OH)2, or MgO and Al2O3 or MgAl2O4H2O are formed during the spinel formation. The spinel-alloy was produced using the polymeric route during wet chemical processing. Aluminium-isopropoxide was hydrolyzed in order to form the boehmite-sol and then the same amount of magnesia was added and mixed. This sol precipitated as boehmite (AlOOH) and brucite (Mg(OH)2) after ageing for 12h as confirmed by differential thermal analysis (DTA), and differential thermal gravity (DTG) measurements. After that, the powders were subsequently annealed at 900oC for 3h in air and observed by TEM. Calculations using thermodynamic enthalpy data are in good agreement with the experiments and can be used to predict reaction paths in other system as well.

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Spinel Formation from Magnesium Aluminium Double Alkoxides

MRS Proceedings ◽

10.1557/proc-73-111 ◽

1986 ◽

Vol 73 ◽

Cited By ~ 27

Author(s):

Kenneth Jones ◽

Thomas J. Davies ◽

Harold G. Emblem ◽

Peter Parkes

Keyword(s):

Nmr Spectroscopy ◽

General Formula ◽

Metal Atom ◽

Vacuum Distillation ◽

Viscosity Measurements ◽

Spinel Formation ◽

Bonding Phase ◽

Xrd Studies ◽

Aluminium Alkoxide

ABSTRACTDouble alkoxides of the general formula Mg[Al(OR)4]2 where R is iso-Pr or sec-Bu were prepared by reacting aluminium and magnesium metals together with the alcohol ROH and purified by vacuum distillation. They were characterised by IR, proton and 27Al NMR spectroscopy and MW determination. A magnesium aluminium double alkoxide was also prepared by treating the commercially available aluminium alkoxide ‘Aliso B’ [a mixed aluminium (iso-propoxide)(sec-butoxide)] with magnesium and iso-propanol. Treatment of magnesium aluminium double alkoxides with water and an alkanolamine (preferably triethanolamine) gives a rigid coherent gel. Viscosity measurements and 27Al NMR spectroscopy suggest that the double alkoxide does not break down to its constituents during hydrolysis. The air-dried gel was shown by XRD to convert quantitatively to spinel on firing to 1500°C. The resistance of the double alkoxide moiety to hydrolysis explains the ease of conversion to spinel on firing. The gel has been used to bind alumina and magnesia grain. Gels suitable for binding refractory grain were obtained only when the alkanolamine content corresponded to one alkanolamine group per metal atom. Electron micrographic and XRD studies showed that in fired refractory pieces, the bonding phase was spinel.

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Oxide scale behavior of Al–7.5 mass%Mg alloy containing trace Ca during short-term oxidation

Materials Express ◽

10.1166/mex.2021.2090 ◽

2021 ◽

Vol 11 (11) ◽

pp. 1881-1886

Author(s):

Seong-Ho Ha ◽

Young-Ok Yoon ◽

Bong-Hwan Kim ◽

Hyun-Kyu Lim ◽

Sung-Hwan Lim ◽

...

Keyword(s):

Electron Microscopy ◽

Transmission Electron Microscopy ◽

Oxide Film ◽

Phase Diagrams ◽

Film Formation ◽

Mg Alloy ◽

Short Term ◽

Spinel Formation ◽

Transmission Electron ◽

Significant Difference

In this study, using transmission electron microscopy and phase diagrams from thermodynamic calculations, we investigated the oxide film formation of Al–7.5 mass%Mg alloy containing Ca traces during short-term oxidation in terms of the thermodynamic stability and multi-element oxides by inter-diffusion based on the results of analysis for the oxide film. For the oxidation test at 515 ˚C, for 1 h, its results showed that there is no significant difference between the Ca-added and Ca-free Al–7.5 mass%Mg alloys was observed, while further exposure caused the Ca-free alloy to gain significant weight. Based on the standard Gibbs free energy for oxide production calculated in this study, CaO was the most preferential product among the single metal oxides examined. As per calculations for MgAl2O4-spinel formation reactions, the spinel formation from MgO was thermodynamically the most favorable. According to the phase diagrams calculated in this study, various multi-element oxides including Ca could possibly form in the oxide layer of Ca-added alloy. The analysis results of transmission electron microscopy confirmed that MgO is the primary oxide in the Al–Mg binary alloys. In oxidation tests conducted for less than 1 h, the spinel was rarely found. The outmost areas of oxide layers correspond to MgO and CaO in Ca-free and Ca-added alloys, respectively. However, in the Ca-added alloy, the inner layer contains certain amounts of Ca, Al, and Mg.

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