Showing papers on "Sessile drop technique published in 1980"

Interfacial tension from height and diameter of a single sessile drop or captive bubble

Abstract: The silhouette of a sessile drop submerged in a transparent bulk phase appears to possess a contact angle of 180° with a plane solid support, when the drop is separated from the solid surface by a thin film of surrounding fluid. A computer-aided analysis of the generalized sessile drop form leads to an explicit equation for interfacial tension dependent only on drop height (from apex to solid support) and the magnitude of the drop equatorial diameter. The equation is valid for a wide range of physically realizable drops. Measurements of drop profile coordinates or the location of the drop equator are not required for the use of the method, leading to improvements in accuracy relative to current practice. Le contour d'une goutte sessile, immergee dans une phase transparente, semble avoir un angle de contact de 180° avec un support solide plan, lorsqu'un film mince de fluide entourant cette goutte la separe de la surface solide. Une analyse numerique de la forme generalisee de la goutte sessile, fournit une relation explicite pour la tension superficielle, fonction unique de la hauteur de la goutte (distance de l'apex au support solide) et du diametre equatorial de la goutte. L'equation s'applique a une grande gamme de gouttes physiquement realisables. L'emploi de cette methode n'exige pas la determination precise du contour de la goutte ni la localisation de son equateur; cette methode est plus precise que celle couramment utilisee.

Effects of varying oxygen partial pressure on molten silicon-ceramic substrate interactions

Abstract: The silicon sessile drop contact angle was measured on hot pressed silicon nitride, silicon nitride coated on hot pressed silicon nitride, silicon carbon coated on graphite, and on Sialon to determine the degree to which silicon wets these substances. The post-sessile drop experiment samples were sectioned and photomicrographs were taken of the silicon-substrate interface to observe the degree of surface dissolution and degradation. Of these materials, silicon did not form a true sessile drop on the SiC on graphite due to infiltration of the silicon through the SiC coating, nor on the Sialon due to the formation of a more-or-less rigid coating on the liquid silicon. The most wetting was obtained on the coated Si3N4 with a value of 42 deg. The oxygen concentrations in a silicon ribbon furnace and in a sessile drop furnace were measured using the protable thoria-yttria solid solution electrolyte oxygen sensor. Oxygen partial pressures of 10 to the minus 7 power atm and 10 to the minus 8 power atm were obtained at the two facilities. These measurements are believed to represent nonequilibrium conditions.