Estimation Of Film Thickness Research Articles

The estimation of cement film thickness by an in vivo technique.

The estimation of cement film thickness by an in vivo technique.

Estimation of the film thickness from the cohesive pressure at the air water interface

The pressure-area curves for neutral monolayers of butyric, valeric, caproic and caprylic acids at the airwater interface were obtained from the surface tension concentration data. Similar curves for the charged monolayers of sodium octanoate and sodium lauryl sulphate in the presence and absence of excess neutral salts were constructed on the basis of the results on surface tension. From the comparison of the pressure area curves of each of these monolayers at air-water and oil-water interfaces under identical conditions, the cohesive pressures of the monolayer at the air-water interface were calculated for different areas per adsorbed molecule using the equation ofDavies. The cohesive pressure was observed to vary linearly with the square of the reciprocal area per adsorbed molecule or ion. From the slope of such linear plot, magnitude of the two-dimensionalvan der Waals constant in each case was estimated. The thickness of the interfacial film was estimated from the comparison of the values of two- and three-dimensionalvan der Waals constants. This is, however, found to be considerably greater than the length of the stretched molecules adsorbed at the interface. When correction for entropy, as suggested byGershfeld is introduced, the film thickness becomes identical with the length of the molecule.

Lubricant Films in Rolling Contact of Rough Surfaces

An experimental and mathematical study of elastohydrodynamic film formation is described for a rolling four-ball configuration utilizing steel bearing balls. Wear rates are determined in the microgram range, using a radiotracer tagged ball. Existence and interruptions of elastohydrodynamic films are observed by measurement of electrical conductivity through the Hertzian contact. Surface microgeometry of the rolling tracks on the balls is statistically analyzed by processing electrical analogs of surface profiles through on-line computing equipment. Defining electrical contacts as asperity approaches through a separating film, the average duration and frequency of such approaches is computed from surface microgeometry statistics. A comparison of computed and observed values of contact conductivity parameters shows good order of magnitude agreement and yields estimates of average film thickness as a function of speed and load which agree, satisfactorily with the order of film thickness predicted by elastohy...

Fibrous Growth of NaClO3

It has been observed by Kato [J. Phys. Soc. Japan, 1024 (1955)] that fine fibers of NaClO3 form on moist massive crystals of NaClO3 which are slowly desiccated. It is proposed that the growth occurs by a uniaxial screw dislocation mechanism in which the material transport occurs by hydrodynamic flow in an adherent film of solution on the fiber surface. The tractive force for film flow is furnished by a gradient in surface tension. The film solution becomes more concentrated during its flow to the fiber tip and the gradient in solute concentration causes a gradient in surface tension. The estimated film thickness is about 100 A. Periodic bends in the fiber can be accounted for by periodic precipitation of a minor impurity with limited solid solubility in NaClO3.