Sessile-drop technique

Sessile drop technique -wettability measurements [CONTACT LENSES] (Vol 7)... 

The chemical structure and composition of films deposited onto the Al substrates was determined by X-ray photoelectron spectroscopy (XPS) using a Perkin Elmer PHI 548 instrument. Measurement of advancing and receding water contact angles (aa and or, to 3°) were carried out by the sessile drop technique, using a Rame Hart contact angle goniometer (10 ). 

Wetting experiments with liquid tin on heterogeneous surfaces composed of oxide glass ceramic (a) and molybdenum (/ ) with 0 = 125° and 0 = 18° were performed using the sessile drop technique (Voitovich 1992, Naidich et al. 1995). 

Only the two first methods allow measurement of the temperature coefficient of the surface energy. The maximum bubble pressure technique is well-adapted for metals with low and intermediate melting points and specially for oxidizable metals, while the sessile drop technique has been applied with success to measure ctlv values up to 1500°C. The drop weight method is particularly useful for very high melting-point metals because it avoids liquid contact with container materials. This is also true for the recently developed levitation drop technique that analyses the oscillation spectrum of a magnetically levitated droplet. 

Figure 6.25. Variation of contact angle with the A1 molar fraction for the Cu-AI/AI2O3 system at 1423 K in high vacuum. Circles in an alumina furnace using the sessile drop technique (Li et al. 1987-88). Squares in a metal chamber furnace using the dispensed drop technique (Labrousse et al., to be published). All points represented by circles for 0 < XAi < 0.3 are for oxidised drops.

Kwok, D.Y., Gietzelt, T., Grundke, K., Jacobasch, H.J., and Neumann, A.W. (1997). Contact angle measurements and contact angle interpretation. 1. Contact angle measurements by axisymmetric drop shape analysis and a goniometer sessile drop technique. Langmuir, 13, 2880-2894. 

There are several methods for interfacial tension measurement. However, at high temperatures, the choice of the measurement technique is limited. Since most high temperature liquids are corrosive and often non-transparent to visible light, the sessile drop technique can rarely be used. However, by the use of the X-ray beam, the shape of sessile drops immersed in another liquid may be determined. This technique was used by Utigard and Toguri (1985) in the measurement of interfacial tension of aluminum in cryolite melts. On the basis of the curvature of the drop and the density difference between the metal and the salt. X-rays lead to a fuzzy outline of the drop shape and together with the sensitivity of the drop outline on the interfacial tension, this technique is limited to an accuracy of about 5-10%. 

The medium used was MilliQ water. The angle between water droplet surface and membranes was measured using a light microscope, thus the convendonal sessile drop technique was applied. The methods have been reviewed in Chapter 3. 

Interfacial tension studies are conducted with various concentrations of micellar solution components to determine optimal concentration ranges. Measurements are usually made with the spinning drop, pendent drop, or sessile drop techniques. 

Muk] Sessile drop technique, surface tension, wettability 1550°C, low oxygen activity, 16 mass% Cr... 

Two methods can be used for the assessment of y and its components contact angle measurements and inverse gas chromatography (IGC) [31]. Chibowski and Perea-Carpio [32] reviewed the problems encountered when attempting to determine the surface free energy of powered solids, like silica particles, using the contact angle technique. Wu reviewed the different techniques that can be employed to measure the surface tension of polymer melts [30]. These techniques are based on the pendant and sessile drop techniques that require density data or contact angle measurements. 

Temperature dependence of interfacial tension of demixed polystyrene/poly (dimethylsiloxane) melts was studied by Nose (1997) using the sessile drop technique. The results were described as a scaled relation of reduced interfacial tension versus reduced segregation strength. The scaled relation was discussed on the basis of the mean-field theory, and a semiempirical expression has been presented for the scaled relation covering a wide temperature range. 

The most commonly used method for the determination of surface tension of polymers is the sessile drop technique. A droplet of a purified hquid is placed on a surface using a syringe. The angle formed by adding hquid to the... 

The purpose of this chapter is to present the LAD performance experiments carried out in room temperature liquids. Bubble point and reseal pressure tests for a 325x2300, 450 X 2750, and 510 x 3600 Dutch Twill screen are conducted in storable liquids, methanol, acetone, IPA, water, and binary methanol/water mixtures of various methanol concentrations. First screen pore diameters are estimated based on analysis from scanning electron microscopy and historical data. Experimental results are used to compare methods for determining effective pore diameter. Next, contact angles are measured for both pure and binary mixture fluids using a modified version of the Sessile Drop technique. Then, the equation of state analysis from Neumann and Good (1979) is used to determine the critical Zisman surface tension for stainless steel LAD screens, which... 

The surface energy of the elucidated samples was estimated by means of observing the contact angle by sessile drop technique, while the moistening liquids were water and saline (0.9% mass solution of NaCl). The surface irregularities were estimated through the atomic force microscopy investigation. 

Fig. 9. The surface free energy of Cu vs. temperature. The melting temperature T is indicated hy the dashed vertical Hne, data in the solid state have been obtained by the zero creep techniqne [49Udi], data of the liquid by the sessile drop technique [59All]. The jump of y at the melting temperature is ascribed to the heat of fusion. The slope of the solid line in the liquid range is -0.00031 Nm K (data from [59AH]).

Measurements of the change in the interfacial tension across the transitional inversion have been made by several workers. Kunieda and Shinoda used a sessile drop technique to show that Antonoff s relationship for the interfacial tensions between three phases held for conditions near the PIT. Cayais et al. measured the interfacial tension across a transitional inversion directly using a spinning drop apparatus. Their results are shown in Figure 6.8 (EACN = 8 is equivalent to SAD = 0, EACN < 8 is equivalent to SAD and EACN > 8 is equivalent to SAD" conditions). It is to be noted that some authors have quoted values as low as 10" Nm". ... 

Contact angles on "Mylar" films were measured using the sessile drop technique H. Surface tensions were measured by the null-buoyancy Wilhelmy plate method using a roughened glass plate showing zero contact angle to water. The plate was supported from an electronic microbalance and the values are quoted to 0.1 mNm l. 

The two most common techniques for the quantitative and qualitative assessment of the wetting and spreading performance of solders are the wetting balance and the sessile drop technique. Each method possesses certain advantages over the other and is discussed in Secs. 3.4 and 3.5. However, there are certain experimental conditions that are common to either method and merit brief consideration. 

The chapter authors feel that the sessile drop technique represents a more precise and versatile tool for quantifying wetting, particularly in high-temperature systems where environmental control is imperative. For solderability assessment, the technique involves placing a solder alloy on a preheated substrate either as a molten (Uquid) drop or as a solid mass that subsequently melts. Wetting in the sessile drop method is spontaneous rather than forced. Therefore, it shares a strong similarity with the conditions that prevail in many commercial soldering processes. 

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