Showing papers on "Sessile drop technique published in 1984"

Profile and contact angle of small sessile drops. A more general approximate solution

Abstract: The second-order differential equation describing the profile of a sessile drop has been derived in polar coordinates using the criterion of minimum free energy and applying the calculus of variations. Application of a form of perturbation theory leads to an approximate solution valid for drops of sufficiently small maximum diameter. In the case of drops of contact angle > 90°, this solution can be exploited directly to obtain the contact angle from a knowledge of drop height, maximum diameter and diameter at the plane of contact with the solid. If this last datum is lacking, the contact angle can still be obtained by a reiterative method or graphically. For contact angles < 90° this last procedure must be used and thus little advantage is gained over a solution previously obtained in cartesian coordinates. Although the solution is less accurate than data obtained from numerical integration, its relative simplicity should prove useful for the objective determination of contact angles.

A Critical Comparison of Hanging Mercury Drop Electrode and Long Lasting Sessile Drop Mercury Electrode in A.C. Anodic Stripping Voltammerty

Abstract: The hanging mercury drop electrode (HMDE) and the long lasting sessile drop mercury electrode (LLSDME) currently used in trace metal analysis are critically compared. Alternating current anodic stripping voltammetry (AC-ASV) and alternating current linear sweep voltammetry (AC-LSV) respectively are employed for the determination of Zn,Cd, Pb, Cu and Fe. The influence of the electrolysis time, stirring rate, a.c. amplitude, frequency and scan rate on the peak current is evaluated. Analytical measurements were carried out by the standard addition method, using 0.02 mol/l HClO4 + 0.1 mol/l NaClO4 (Zn, Cd, Pb, Cu) and 0.1 mol/l (COONa)2, (Fe), respectively as supporting electrolytes.

Effect of ZrO2 on the alkali feldspar-aluminosilicate interface

Abstract: The contact angles of the alkali feldspars containing 0, 4, 8 and 12 vol % ZrO2 on the aluminosilicate substrate were measured by sessile drop method. During the heating from 1350 to 1520° C and the holding at 1350° C, the contact angles were generally increased with increasing ZrO2 content. 8 vol % ZrO2 in the melt drop was very effective to raise the contact angles and 12 vol % ZrO2 was barely sufficient to maintain the contact angles at around 90° or larger at elevated temperatures. The SEM micrographs indicated that ZrO2 particles were scattered throughout the drop and also located in the interface between the drop and substrate. The dissolution of the substrate by liquid feldspar and the diffusion of ZrO2 in the substrate were also observed. The cause of the increase in contact angle with increasing ZrO2 content are discussed.

The Wetting of Ceramic Opaque Suspensions on Oxidized Alloy Surfaces

Abstract: : Liquid mediums used with opaque porcelain powders are crucial in the application of opaque slurries to oxidized metal surfaces To augment the effective application of opaque porcelain, liquid mediums should wet oxidized metal surfaces well (indicated by a low contact angle) The liquid-metal-surface interaction is a critical factor in the wetting of alloys by liquid suspensions A multifactorial treatment design was used to evaluate the effects of various metals, liquids, surface preparation, and possible interactions on wetting Five opaque liquid mediums were evaluated photographically by sessile drop contact angle measurements on five oxidized metal surfaces