Showing papers on "Sessile drop technique published in 1971"

Surface tension measurements on pure liquid iron and nickel by an oscillating drop technique

Abstract: A novel experimental technique for the measurement of surface tension of molten metals has been developed. It is based on the Rayleigh equation which relates frequency and surface tension for an oscillating drop. A systematic study has shown this equation to be valid for a liquid metal droplet levitated electromagnetically in an inert flowing gas with no prior calibration required. It is, therefore, an absolute method. The frequencies of oscillation of droplets of pure iron and nickel in a 6 pct H2-He gas mixture were measured by high speed cinematography. Surface tensions were obtained for temperatures of 1550° to 1780°C for iron and 1475° to 1650°C for nickel.

The surface tension of liquid silver alloys: Part I. Silver-gold alloys

Abstract: The sessile drop technique has been used to determine the surface tension of silver-gold alloys. The techniques of data reduction are discussed and an improved one is presented. The measurements are in good agreement with previous data reported in the literature for pure silver and gold. The surface tension of alloys at 1108‡C was found to behave according to the prediction of the perfect solution model.

Wetting of Ceramics by Liquid Metals

Abstract: A linear relation is established between the cosine of the contact angle and the temperature of a liquid metal sessile drop resting on a ceramic substrate. This relation is demonstrated for many liquid metal/ceramic systems. The work of adhesion and the effects of surface roughness, porosity, chemical reactions, and structural transformations in the substrate surface are also discussed.

The surface tension of liquid silver alloys: Part II. Ag−O alloys

Abstract: The surface tensions of liquid Ag-O alloys have been determined by the sessile drop method. The surface activity of oxygen, as measured by −(dσ/dX O)XO→0j, where σ is the surface tension of the metal andX O the mole fraction of oxygen, is quite large and equals 3.80×105 dyne per cm at 980°C and 1.35×105 dyne per cm at 1108°C. The heat of adsorption of oxygen is estimated to be of the order of 30 kcal per mole. Application of the monolayer approximation shows that liquid silver becomes saturated with oxygen when each adsorbed oxygen atom occupies an area of 33±5A2. Small additions of platinum to silver do not change the characteristics of the adsorption of oxygen appreciably. An analysis of the data is consistent with the conclusion that saturation of the surface of liquid silver with oxygen results from the formation of an ionic two-dimensional compound at the surface. This hypothesis is tested in the case of several other systems and yields satisfactory results. The structure of these compounds is discussed. In the case of the Ag-O system, it appears to correspond to the stoichiometry Ag3O.

Critical Surface Tension for Spreading in the Systems (Al‐Mg)/Graphite and (Cu‐O)/Sapphire

Abstract: According to Zisman and co-workers, in organic systems the cosine of the contact angle of a sessile drop increases with the decreasing surface tension of the drop at room temperature. The applicability of the Zisman relation to liquid metal-ceramic systems is discussed using the systems (Al-Mg)/graphite and (Cu-O)/sapphire. Also discussed is the significance of the critical surface tension for spreading, γc, in the systems where the surface tension of the liquid is greater than that of the solid substrate; γc is 230 dynes/cm for graphite at 720°C and 440 dynes/cm for sapphire at 1230°C.

Copper diffusion in iron during high-temperature tensile creep

Abstract: The diffusion of liquid copper in iron from a notched surface has been studied by metallographic, microanalysis, and sessile drop techniques. The diffusivity of copper was found to be 0.59×10−6 sq cm per sec at 1100°C and 0.97×10−6 sq cm per sec at 1130°C. The diffusion factor,D0 was 0.78×10−3 sq cm per sec and the activation energy 19.0 kcal per mole. The predominant mode of copper penetration was along grain boundaries, but when larger volumes of copper at the iron surface were used, surface diffusion increased and grain boundary penetration remained constant. The most frequently occurring dihedral angle for liquid copper was 34 deg at 1100° and 1130°C. The liquid copper/austenite interfacial energy was found to be 444 ergs per sq cm between 1100 and 1130°C. From sessile drop measurements, the contact angle was determined as 35 deg at 1100°C and 28 deg at 1130°C, from which values the respective interfacial energies were calculated to be 387 ergs per sq cm and 301 ergs per sq cm.

Stability of a pendent liquid drop on horizontal and inclined solid surfaces

Abstract: 1. Equilibrium equations have been derived for a pendent drop on a horizontal and an inclined solid surface. 2. The weight of an equilibrium drop depends on the slope of the surface, the surface tension of the liquid, the angle of contact, and the drop surface area. It is shown that, other things being equal, a pendent drop is less stable on an inclined surface than on a horizontal surface. 3. An equation has been derived for the full energy of a two-dimensional pendent drop. Minimization of this equation makes it possible to determine, with the aid of a computer, the approximate ratio of the drop diameter to the maximum drop thickness (maximum distance from the solid surface) for each specific case.