Topic
Sessile drop technique
About: Sessile drop technique is a research topic. Over the lifetime, 2827 publications have been published within this topic receiving 68943 citations.
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TL;DR: Anisotropic wetting behavior was established for a range of crystalline systems: paracetamol polymorphs, aspirin, and ibuprofen racemates, and the hydrophilicity/hydrophobicity of facets reflects the presence of functional groups at surfaces to form hydrogen bonds with external molecules.
Abstract: The purpose of this study was to establish the link between the wetting behavior of crystalline pharmaceutical solids and the localized surface chemistry. A range of conventional wetting techniques were evaluated and compared with a novel experimental approach: sessile drop contact angle measurements on the individual facets of macroscopic (>1 cm) single crystals. Conventional measurement techniques for determining surface energetics such as capillary rise and sessile drops on powder compacts were found not to provide reliable results. When the macroscopic crystal approach was used, major differences for advancing contact angles, theta(a), of water were observed-as low as 16 degrees on facet (001) and as high as 68 degrees on facet (010) of form I paracetamol. theta(a) trends were in excellent agreement with X-ray photoelectron spectroscopy surface composition and known crystallographic structures, suggesting a direct relationship to the local surface chemistry. Inverse gas chromatography (IGC) was further used to probe the surface properties of milled and unmilled samples, as a function of particle size. IGC experiments confirmed that milling exposes the weakest attachment energy facet, with increasing dominance as particle size is reduced. The weakest attachment energy facet was also found to exhibit the highest theta(a) for water and to be the most hydrophobic facet. This anisotropic wetting behavior was established for a range of crystalline systems: paracetamol polymorphs, aspirin, and ibuprofen racemates. theta(a) was found to be very sensitive to the local surface chemistry. It is proposed that the hydrophilicity/hydrophobicity of facets reflects the presence of functional groups at surfaces to form hydrogen bonds with external molecules.
56 citations
TL;DR: Although plasma treatment was found to increase the wettability of griseofulvin it was not found to increasing the dissolution rate as the treatment caused surface fusion of the material.
56 citations
TL;DR: In this paper, the surface tension of molten silicon was measured using both the oscillating drop method and an improved sessile drop method, and the result was expressed by the following equation: γ = −733 −−−0.062(T −−1687) where T is the temperature.
56 citations
TL;DR: In this paper, a chemical system where interfacial reactions and oxide film effects could be isolated was used to evaluate the wetting of ceramic surfaces by aluminum alloys, and the system Al-Mg-O was chosen since it is technologically important and high-purity, well-characterized materials are readily available.
Abstract: The wetting of ceramic surfaces by aluminum alloys has been reexamined using a chemical system where interfacial reactions and oxide film effects could be isolated. The system Al–Mg–O was chosen since it is technologically important and high-purity, well-characterized materials are readily available. Magnesium alloyed with the aluminum sessile drop and silicon picked up from the experimental apparatus cause an initial reduction in contact angle by altering the protective nature of the oxide film formed on the sessile drop. Evidence of spreading is observed as an intermediate process in the reactive sessile drop pairs. Reaction products formed between the Al–Mg alloys and sapphire (Al2O3), spinel (MgAl2O4), or periclase (MgO) can be interpreted with predicted phase equilibria and the measured loss of magnesium from the sessile drop. Only the rate of the periclase alloy interaction was rapid enough to result in a continuous product layer after 24 h at 800 °C. The volatilization of all of the magnesium from the sessile drop resulted in the formation of a true Al–Al2O3 interface. The contact angle for a true Al–Al2O3 interface is 88 ± 5 deg at 800 °C. The liquid-solid interfacial energy is 1688 ergs/cm2.
55 citations
TL;DR: Sessile drop contact angles between liquid aluminum alloys and solid beryllium, boron carbide, and graphite were measured to 840°C under vacuum and in helium as discussed by the authors.
Abstract: Sessile drop contact angles between liquid aluminum alloys and solid beryllium, boron carbide, and graphite were measured to 840°C under vacuum and in helium. Little wetting occurred between most of the combinations, but at 20% magnesium the contact angle on beryllium decreased to 68°. Low contact angles were noted for the binary aluminum alloys on graphite coated with titanium.
55 citations