Flow and Fracture of Dental Alloys Determined by a Microbend Tester
The microstructure of an alloy is the fundamental variable on which the mechanical properties of an alloy depend. For testing the mechanical properties, however, common tests, such as tensile strength or hardness, are generally used. This may be due to the fact that the microstructure study is more complicated and time-consuming. The common method of microstructure study is to perform a series of tensile tests and then obtain the microstructure of the specimens after the tests are completed so as to correlate the structure with the performance data. The actual contribution of each observable microstructure to flow and fracture is rather difficult to detect. When the structure is examined after the fracture has taken place, some of the evidence is lost that would have been available if continuous observation of the structure had been possible. In 1955 Flinn and Trojan' developed an apparatus by means of which the microstructure of an alloy under stress can be studied. The stress can be increased while the microstructure is under observation. Thus any changes that may take place can be detected in any of the phases. When an alloy with a complicated microstructure is studied, the microbend test shows its main advantage, since it is rather difficult to predict how the different phases of a complicated structure will behave under different stresses. With this test the effect of such stress on various phases may be continuously watched under the microscope. The purpose of this study was to observe the behavior of different phases of cobalt-base and gold alloys used in dentistry for partial denture framework when they were subjected to bending stresses.
Review of dental research, 1962
The series of annual reviews, sponsored by the Council on Dental Research, enters its eighth year with this presentation. The Council’s objective is to provide the practitioner with an authoritative condensation of recent research developments in major fields of dental interest. It is impossible to cover all areas of dentistry with any degree of adequacy in a few short reviews. Instead, the Council selects a few disciplines for major emphasis each year, and attempts to cover the main categories of dental interest in the course of three or four years. Accordingly, the reviews which follow contain some informa­ tion that was published before 1962. The Council is grateful to Samuel Dreizen, Robert E. Gillis, Irving Glickman, Gustav O. Kruger, David B. Mahler, and Louis S. Hansen for preparing reviews in their respective specialties. The Council welcomes constructive comment with a view toward improving the usefulness of future reviews to the profession.
Inhibition of Mild Steel Corrosion Using L-tryptophan and Synergistic Surfactant Additives
The corrosion inhibition characteristics of nitrogen containing amino acid L-tryptophan on mild steel in 0.1 M HCl solution, in the temperature range of 30-50 o C, was studied by weight loss and potentiodynamic polarization measurements. L-tryptophan significantly reduces the corrosion rates of mild steel; the maximum inhibition efficiency being 83% at 50 o C in presence of inhibitor concentration of 500 ppm. The effect of the addition of very small concentrations of anionic surfactant, sodium dodecyl sulfate (SDS), and of cationic surfactant, cetyl trimethyl ammonium bromide (CTAB), on the corrosion inhibition behavior of L-tryptophan was also studied. The inhibition efficiency (IE) of L-tryptophan significantly improved in presence of both surfactants. The effect of SDS and CTAB on the corrosion inhibition behavior of L-tryptophan appears to be synergistic in nature, the values of synergism parameter being greater than unity. The adsorption of inhibitors on mild steel surface obeyed Langmuir’s adsorption isotherm. The calculated thermodynamic parameters for adsorption reveal a strong interaction between the inhibitors and the mild steel surface. The results obtained by electrochemical studies are consistent with the results of the weight loss measurements. L-tryptophan acts more anodic than cathodic inhibitor.