Layers Of Stearic Acid Research Articles

Effect of surface layers of stearic acid on the fatigue strength of metals

The fatigue failure of metals begins, as a rule, at the surface as a result of physicochemical processes that take place under the influence of the moisture and oxygen in the air. It is known that even the ordinary laboratory atmosphere may have a harmful effect on the fatigue resistance of aluminum alloys [i]. In a number of cases thin, ultimately monomolecular, water-repellent films of organic substances may act as an effective barrier against the adsorption of water and oxygen molecules from the atomosphere on the metal surface [2-5]. In this connection investigations have been carried out on octyl and dodecyl alcohols and dodecyl and octadecyl amines, among polar substances. In a study of the endurance of a number of metals (steel 4340, a beryllium alloy, aluminium alloy 6061-T6, and stainless steel 17-7RN), it has been found [2] that after the application of a film of dodecyl alcohol to their surface the limited endurance of these materials increases By 2.5 times.

Concentration and removal of liquid microlayers from a seawater surface by bursting bubbles1

A monomolecular layer of radioactive stearic acid has been used to determine the concentration and transport of surface liquid microlayers from a natural seawater surface. The monolayer was prepared by allowing drops of a 0.08 mM solution of stearic acid dissolved in hexane to spread over the sample area, and then laterally compressing the resultant monomolecular layer with a castor oil film. The surface microlayers were sampled by collecting the top drop resulting from a gas bubble bursting at the air‐liquid interface.The ratio of surface liquid to bulk liquid in a drop increases with decreasing drop size, supporting our previous model. The measurements also show that small drops (diameters of 28–108 µm) are effective for removing organic surface‐active material from a seawater surface.

Studies on built-up films by means of the polarized infrared ATR spectrum I.: Built-up films of stearic acid

The infrared attenuated total reflection (ATR) spectra of molecular layers of stearic acid built upon the germanium plate by the Blodgett method were studied by using the polarized radiations with the electric vectors parallel and perpendicular to the plane of incidence. It is concluded that the built-up films are made of an assembly of crystallites of the monoclinic system, and that the crystallites are oriented so that their crystallographical c-axis may form angles from ca. 27° to 35° with the z-axis (the axis perpendicular to germanium-stearic acid interface) depending upon the number of layers, but at random around the z-axis (uniaxial orientation with respect to the z-axis) irrespective of the direction of withdrawal of the plate in the film preparation. From penetration depth of the totally reflected radiation and changes in reflectivity with the number of layers, the thickness of a single monomolecular layer is estimated to be ca. 23.8 Å, showing a good agreement with the values previously proposed by Blodgett and by Müller.

Initial events in interactions of blood with a foreign surface.

AbstractThe nature of the events occurring immediately after exposing foreign surfaces to fresh flowing blood was assessed using a combination of MAIR infrared spectroscopy, ellipsometry, and contact angle measurements. Within the first 5 sec after contact with blood issuing from the jugular veins of lightly anesthesized dogs, germanium prisms were uniformly coated with strongly adherent proteinaceous filsm having an average optical thickness equivalent to 2 layers of stearic acid (approx. 50 Å) and having critical surface tensions of about 36 dyne/cm. A contact time of 60 sec led to a less uniform coating of average optical thickness equivalent to 5 layers of stearic acid (approx. 125 A), but with similar MAIR spectrum and wettability. The internal refelection spectra were consistent with the presence of either alpha‐helical or random‐chain configurations, but not with the extended chain beta‐structure for proteins. Films cast from purified fibrinogen on platinum foils gave similar spectra and exhibited similar wetting properties; these observations are consistent with the hypotehsis that initial adsorptive events are dominated by fibrinogen deposition. The involvement of small amounts of lipid or other protein remains a distinct possibility, however.

金属表面上における鉱油潤滑油留分の接触角について

Contact angle of an oil droplet placed on a horizontal metal surface is used one of the characteristic values of such clock oil, lubricant fraction of mineral oil, rust preventive oil, etc. This value shows the adhesion wetting of test oil against metal surface. And it is necessary to standardize the dropping method, the drop volume and the time after deposit on toget its reproducibility. It is better to use a small wire immersed in test oil, draw out and trickle the drop let on the test surface, for better reproducibility. The volume of drop is about 0.004ml. The contact angle of oil is measured after 3 minutes by means of a goniometer eyepiece constructed by the author. When the metal surface is absorbed and coated by oleophobic molecular layers of such stearic acid or its derivatives etc., an oil drop on it shows a large contact angle of 40-50°. But the contact angle of oil drop for bare metal surface is less than 10°.The difference between new polished surface by emery paper and its aged surface about 24 hours can be distinguished by the contact angle of distilled water drop, but it can not be distinguished by that of oil drop. Surface tention of mineral oil is scarcely changed by addition of 4-5% of the polar type rust preventive additives.

Radioactive tracer studies of monolayers: II. Comparison of floating and built-up monolayers

The composition of built-up calcium stearate stearic acid layers has been studied with Ca 45. The results diverge from those obtained by conventional chemical analysis of the floating layers (“H-layers”), from which the built-up layers were formed. Similar discrepancies have been observed when building layers of fatty acids on a hypophase containing bivalent organic cations. In all these instances the cations seem to form an integral part of the H-film, but are eliminated, probably by exchange against protons, during the building-up operation.

Local anaesthetics. V. The action of local anaesthetics on monomolecular layers of stearic acid.

Local anaesthetics. V. The action of local anaesthetics on monomolecular layers of stearic acid.

Structure of Molecular Films of Stearic Acid on Copper

ELECTRON diffraction patterns, obtained during an investigation of the effect of temperature on mono- and multi-molecular layers of stearic acid on copper have produced evidence for the existence of crystallites of a metal soap on the copper surface.

Electron Diffraction and Surface Structure

IN opening the discussion on electron diffraction and surface structure before a joint meeting of the Physical and Chemical Societies held on March 17, Prof. G. I. Finch compared electron diffraction with other methods of surface structure examination, and cited cases where the microscope or X-rays may give a wrong impression of the structure of deposits and of the size, shape and chemical nature of thin crystalline films. He described, among others, a striking experiment on the orientation of fatty acids by friction, which seems to have a direct bearing on the nature of the mechanism of lubrication. Thus the previously unorientated molecules in a stearic acid layer deposited on a metal surface can be made to point in a common direction by rubbing. If the surface be rubbed in all manner of ways, it is the last stroke only which determines the final direction of orientation of the stearic acid chains. Prof. Finch also gave an account of new experiments which confirm the conclusions previously arrived at by electron diffraction as to the structure of the polish layer on calcite. Sodium nitrate crystals were found to orientate in such a way as virtually to continue the structure of calcite when deposited on the polish layer on a cleavage face and which electron diffraction had shown to be of single crystal structure integral with the main crystal. A calcite surface cut and polished in such a manner as to be steeply inclined to all cleavage planes, however, gives a halo pattern characteristic of an amorphous layer, and on such a surface the nitrate crystals do not orientate but point in all directions just as they do when grown, for example, on a glass surface. After heating, which causes this amorphous polish layer to recrystallize, the sodium nitrate crystals orientate once more.