Steric stabilization of inorganic suspensions in carbon dioxide

Calvo, Lourdes; Holmes, Justin D.; Yates, Matthew Z.; Johnston, Keith P.

doi:10.1016/s0896-8446(99)00036-4

Cited by 44 publications

(67 citation statements)

References 35 publications

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“…The particles were dispersed with an ultrasonic bath for ∼30 s. The silica and hexane were then injected into a high-pressure variable volume cell using a syringe. The variable volume cell was equipped with sapphire windows for turbidity measurements as has been described previously (23). Carbon dioxide was added to the view cell to make a 15 wt% hexane/85 wt% CO 2 mixture.…”

Section: Procedures For Stability Measurementsmentioning

confidence: 99%

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Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

Yates

Shah

Johnston

et al. 2000

Journal of Colloid and Interface Science

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Section: Procedures For Stability Measurementsmentioning

confidence: 99%

“…Turbidity measurements were taken at the highest pressure first (usually 345 bar), then the pressure was lowered in increments until the colloid flocculated. At each pressure, turbidity readings were taken for 15 min, following a procedure described previously (23).…”

Section: Procedures For Stability Measurementsmentioning

confidence: 99%

Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

Yates

Shah

Johnston

et al. 2000

Journal of Colloid and Interface Science

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“…We note that the slight agglomeration in water is consistent with the fluorinated silica being CO 2 -philic and not well dispersible in water. 30,31 To demonstrate that the method is applicable to other oxides beyond silica a suspension of alumina was reacted with perfluorooctyl triethoxysilane (TES) as a coupling agent in the presence of the ionic liquid. Thermogravimetric analysis shows a weight loss of 10%, which is equal to the weight loss (and thus grafting density) of the silica nanoparticles.…”

mentioning

confidence: 99%

An improved process for the surface modification of SiO2 nanoparticles

Livi

Giannelis

2012

Green Chem.

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A phosphonium ionic liquid is used as an activator of silanol groups to improve the surface functionalization of silica nanoparticles with fluorosilanes in supercritical CO 2 .Due to their excellent optical, electrical and mechanical properties as well as their unique advantages such as high surface area, nanoparticles can play a key role in many nanotechnology applications. 1,2 For example, significant R&D resources have been devoted to nanoparticle technology in diverse fields including electronic and biomedical devices, automotive parts, coatings, drug delivery, gene delivery, catalysis and polymers. [3][4][5][6][7][8][9][10][11][12][13][14] For several of these applications surface functionalization is an important requirement. For example, to change the polarity of the nanoparticles and promote dispersion in organic solvents or polymers chemical treatment by cation exchange or grafting using organosilanes has been extensively practiced. [15][16][17] In addition, surface functionalization has been used to improve the stability of the nanoparticles and avoid aggregation in various media. 18,19 Surface functionalization is typically carried out in the presence of organic solvents. In some instances and to make the process greener, supercritical CO 2 (scCO 2 ) has been used in place of conventional solvents. However, the grafting density tends to be relatively low. It has been reported that small amounts of a highly basic ionic liquid (<0.5 wt%) can generate silanoates on the surface of silica. We combine here the use of an ionic liquid in scCO 2 to increase the grafting density of fluorosilane on silica. The process results in doubling of the grafting densities with the resulting nanoparticles exhibiting CO 2 -philic behavior. In addition to the increased reactivity and higher grafting density the new process offers the following additional advantages: (i) this is a one-step process, (ii) the use of organic solvents is completely eliminated, (iii) the lengthy steps of purification and drying of the silica are replaced by dilution and filtration, (iv) the ionic liquid can be recovered and reused.We note that our process differs from previous reports using scCO 2 in that low pressures (80 instead of 400 bar) and less amounts of silane (only 10 wt% compared to a 3-10 times molar excess of the corresponding coupling agents used in the literature) are required. 20,21 In addition, previous reports utilizing scCO 2 were limited to dry, fumed silica instead of aqueous dispersions used in our approach. While the primary particles of fumed silica are small and comparable to that of colloidal silica, drying tends to lead to particle agglomeration.While the method can be applicable to different oxides we demonstrate it here using colloidal silica and three different fluorosilanes: (i) perfluorooctyl-methyldimethoxysilane (DMS), (ii) perfluorooctyl-trichlorosilane (TCS), and (iii) perfluorooctyltriethoxysilane (TES). Triphenyloctadecyltriphenylphosphonium iodide (C 18 P I − ) was used as the surface activator. The synthesi...

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“…al. [49] have developed a fundamental understanding of the stability of inorganic solid suspension in CO2 which is sterically stabilized with surfactant. To prevent flocculation from van der Waals forces, the surfactant must be adsorbed on the silica surface, and the steric layer must be sufficiently thickened.…”

Section: Applications Of Co 2 -Based Solvent Cleaningmentioning

confidence: 99%

Cleaning Using CO₂‐Based Solvents

Zhang¹,

Han

2007

CLEAN Soil Air Water

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Cleaning with hierarchy of CO 2 -based solvents is advantageous from an environmental point of view because CO 2 is non-flammable, virtually inert, and abundant. After cleaning, the only waste stuffs generated are the contaminants that are removed from the cleaned parts. The technology is especially well suited for precision cleaning applications in which parts have intricate geometries or for applications in which parts are sensitive to water or high temperature. This review will first introduce aqueous cleaning concepts and mechanism, which is helpful to understand how to design cleaning systems using high pressure CO 2 . Recent microelectronic processes for cleaning and rising of circuit wafers using CO 2 -based solvents are the main focus of the review. Additional cleaning topics include dry cleaning, separation of dyestuffs, and extraction of contaminations from soils and regeneration of catalysts.

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Steric stabilization of inorganic suspensions in carbon dioxide

Cited by 44 publications

References 35 publications

Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

An improved process for the surface modification of SiO2 nanoparticles

Cleaning Using CO₂‐Based Solvents

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Steric stabilization of inorganic suspensions in carbon dioxide

Cited by 44 publications

References 35 publications

Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

Steric Stabilization of Colloids by Poly(dimethylsiloxane) in Carbon Dioxide: Effect of Cosolvents

An improved process for the surface modification of SiO2 nanoparticles

Cleaning Using CO2‐Based Solvents

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Product

Resources

About

Cleaning Using CO₂‐Based Solvents