Use the link below to share a full-text version of this article with your friends and colleagues. Learn more. Critical modification on the model is proposed and applied in this work as a result of critical assessment of model application in solute solubility prediction in supercritical carbon dioxide.
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Two relationships were obtained for S 12 that must be implemented together with this equation of state. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors.
Estimation and determination of steroid solubility in supercritical carbon dioxide
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The solubility of water in carbon dioxide as well as the vapor phase density are measured. In order to measure the mass of water and volume of gas in the vapor phase, in each experiment the vapor phase of a L-V equilibrium system is transferred to an equilibrium flash separator equipped with a desiccant and a gasometer.
The gas volume is converted to the mass and density based on the ideal behavior of gases at standard conditions. However, the Gillespie and Wilson low pressure data are in good agreement with the new experimental data. There is no consistency between the Takenouchi and Kennedy data and generated data in this work. The produced data for vapor phase density in this study accurately follow the characteristic trend.
Due to the interconnectivity between density data and water content data in the designed experimental procedure, it is believed that the new water content data obtained in this experimental study are reliable. Todheide, K. This application is a divisional of U. Insulator oxide films, particularly silicon oxide films, have conventionally been made by methods such as thermal oxidation of silicon, physical vapor deposition and chemical vapor deposition, most typically chemical vapor deposition.
However, chemical vapor deposition requires high temperatures, e. Newer, lower temperature techniques, known as Chemical Fluid Deposition CFD , are based on chemical deposition of the oxide films from a supercritical fluid solution have been developed. Either the reagent is capable of reacting with, or is a precursor of, a compound capable of reacting with the solvent to form the desired product, or at least one additional reagent is included in the supercritical solution and is capable of reacting with, or is a precursor of, a compound capable of reacting with the first reagent or with a compound derived from the first reagent to form the desired material.
The supercritical solution is expanded to produce a vapor or aerosol and a chemical reaction is induced in the vapor or aerosol so that a film of the desired material resulting from the chemical reaction is deposited on the substrate surface. In an alternate embodiment, the supercritical solution containing at least one reagent is expanded to produce a vapor or aerosol which is then mixed with a gas containing at least one additional reagent.
A chemical reaction is induced in the resulting mixture so that a film of the desired material is deposited. The invention also includes similar methods for depositing material particles into porous solids, and films of materials on substrates or porous solids having material particles deposited in them. By supplying organometallic complexes and carbon dioxide in a supercritical state into the housing, a BST thin film is formed on a platinum thin film, while at the same time, carbon compounds, which are produced when the BST thin film is formed are removed.
Supercritical Solubility Database (search results)
The solubility of carbon compounds in the supercritical carbon dioxide is very high, and yet the viscosity of the supercritical carbon dioxide is low. Accordingly, the carbon compounds are removable efficiently from the BST thin film. An oxide or nitride film may also be formed by performing oxidation or nitriding at a low temperature using water in a supercritical or subcritical state, for example.
By supplying organometallic complexes and carbon dioxide in a supercritical state into the housing, a BST thin film is formed on a platinum thin film, while at the same time, carbon compounds, which are produced when the BST thin film is formed, are removed.
Although these methods of chemical deposition form supercritical fluid solutions provide advantages over conventional deposition techniques, they can still be improved. Also, providing a broader array of precursors and reagents would also be advantageous. A hallmark of the present invention is the rapid deposition of oxide formations via acid or base catalyzed CFD processes.
In one embodiment, the invention is a method for forming an insulating structure, the method comprising hydrolyzing an alkoxide in a supercritical fluid in the presence of an acid catalyst or a base catalyst such that an insulating oxide material is deposited from the supercritical fluid to form the insulating structure.
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Another embodiment of the invention is a composition comprising a solution of an alkoxide and either an acid or a base in supercritical carbon dioxide. A further embodiment of the invention is a method of forming a material having a high dielectric content, the method comprising the steps of forming a solution of a hydrolysable alkoxide and a catalyst, the catalyst comprising an acid or a base, in supercritical carbon dioxide; and, reacting the hydrolysable alkoxide with water to deposit an oxide having a dielectric constant at least about Another embodiment of the invention is a method of producing an insulating film, the method comprising forming a solution of a hydrolysable alkoxide and a catalyst, the catalyst comprising an acid or a base, in supercritical carbon dioxide; contacting a substrate with the supercritical carbon dioxide solution; and, reacting the hydrolysable alkoxide with water to deposit a film of an oxide having a dielectric constant at least equal to silicon dioxide.
Yet another embodiment is a method for producing fine structures of an insulating material, the method comprising forming a solution of a hydrolysable alkoxide and a catalyst, the catalyst comprising an acid or a base, in supercritical carbon dioxide; contacting a substrate with the supercritical carbon dioxide solution, wherein the substrate comprises structures having high aspect ratios of at least 5; and, reacting the hydrolysable alkoxide with water to deposit an oxide having a dielectric constant at least equal to silicon dioxide, wherein the oxide fills the high aspect ratio structures.
In a further embodiment, the invention is a method of increasing the solubility of acids in supercritical carbon dioxide, the method comprising combining supercritical carbon dioxide, a Lewis base that is soluble in supercritical carbon dioxide, and an acid that is substantially insoluble in supercritical carbon dioxide such that the Lewis base and the acid form a complex that is soluble in supercritical carbon dioxide.
Another embodiment is a method of increasing the solubility of bases in supercritical carbon dioxide, the method comprising combining supercritical carbon dioxide, a Lewis acid that is soluble in supercritical carbon dioxide, and a base that is substantially insoluble in supercritical carbon dioxide such that the Lewis acid and the base form a complex that is soluble in supercritical carbon dioxide.
Yet another embodiment is a method for increasing the solubility of water in supercritical carbon dioxide, the method comprising combining supercritical carbon dioxide with an acid or base, wherein the acid or base is soluble, or solubilizable, in supercritical carbon dioxide and the acid or base interacts with water to solubilize the water in the supercritical carbon dioxide.
Still yet another embodiment is a method of forming a material having a low dielectric content, the method comprising the steps of forming a solution of a hydrolysable alkoxide and a catalyst, the catalyst comprising an acid or a base, in supercritical carbon dioxide, and reacting the hydrolysable alkoxide with water to deposit an oxide having a dielectric constant less than about 3. Various other features, objects and advantages of the present invention will be made apparent from the following detailed description and the drawings. In the following detailed description, references made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced.
These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the spirit and scope of the present invention. This invention is an improved method of conducting chemical reactions in supercritical, or near supercritical, carbon dioxide SCD. In one preferred embodiment, the invention is a method for producing metal or semi-metal oxide deposits by hydrolysis of at least one hydrolysable precursor in supercritical carbon dioxide SCD.
Specifically, the hydrolysis reaction can be catalyzed by the presence of either an acid or a base. The hydrolysable precursor is a typically a hydrolysable metallic compound. The semi-metals are typically considered to be boron, silicon, germanium, arsenic, antimony, tellurium, and polonium.
Supercritical carbon dioxide: a solvent like no other
The hydrolysable metallic compound precursor must be soluble or partially soluble in supercritical carbon dioxide SCD. Unlike a normal fluid solvent, SCD has virtually no surface tension. As such, SCD is freely miscible with all gases because of the mutual lack of surface tension. The SCD may include one or more co-solvents such as an alcohol e. Additionally, this method could be applicable to reverse micelle structures that contain a CO 2 immiscible solvent that is the carrier for one or more of the reactants.
Some typical surfactants for a reverse micelle in SCD are bis- 2-ethylhexyl sulfosuccinate AOT , Zonyl FSJ contains one or more fluoroalkylphosphate ester salt , and poly 1,1,-dihydroperfluoro octyl acrylate -b-poly ethylene oxide and others in review article: Helen M. Woods, Marta M. Shakesheff and Stven M. Howdle, Materials processing in supercritical carbon dioxide: surfactants, polymers and biomaterials, J.
Generally, the hydrolysable metallic compounds known from the field of Sol-Gel chemistry should be appropriate for use in this inventive method under the right processing conditions.
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Examples of such compounds are:. Preferably, M is at least one of silicon, boron, hafnium, aluminum, phosphorus, zirconium, titanium, barium, lanthanum, or yttrium. Typically, R is a methyl, ethyl, propyl, or butyl group. These and other metallic alkoxides are commercially available, such as from Gelest, Inc. More than one metallic alkoxide precursor may be used when a complex oxide, e. M-O-M linkages can exist in these materials, as well. Included are reaction products of metal alkoxides with organic hydroxy compounds such as alcohols, silanols R 3 SiOH, glycols OH CH 2 n OH, carboxylic and hydroxycarboxylic acids, hydroxyl surfactants etc.
Non-hydrolytic condensation reactions are also possible with these Sol-Gel materials. Building-up of the M-O-M network can also be achieved by condensation reactions between species with different ligands. Metal alkoxides and carboxylates elimination of ester, equation 1 , metal halides MX n and alkoxides formation of alkylhalide—equation 2 or elimination of dialkylether equation 3 as the source of the oxo ligand are examples.
Metal alkoxides can also be used as precursors of non-oxide materials.
Study of Metal Complexes’ Solubility in Supercritical Carbon Dioxide
Metal fluorides may result from these precursors depending on thermal treatment. The reactivity of the M-OR bond also provides ascention to phosphatessulfides or oxysulfides materials. The hydrolysable metallic alkoxide precursors are selected so that they yield the desired metallic oxide material. The metallic oxide materials may have high k values dielectric constant , baseline values, or low k values.