Accession Number : AD0672575

Title :   STUDY OF THE REACTION OF MAGNESIUM VAPOR AND OXYGEN AT THE SURFACE OF MGO DEPOSITS BY ATOMIC-ABSORPTION SPECTROPHOTOMETRY,

Corporate Author : PURDUE UNIV LAFAYETTE IND PROJECT SQUID HEADQUARTERS

Personal Author(s) : Markstein,G. H.

Report Date : JUL 1968

Pagination or Media Count : 34

Abstract : A method for investigating surface reactions of metal vapors by means of atomic-absorption spectrophotometry was developed. In this technique, the beam of resonance radiation used in the absorption measurement is confined to a thin sheet parallel to the reacting plane surface, and the optical system is provided with means for varying the distance Z between the radiation sheet and the surface. The reaction of magnesium vapor and oxygen was found to be first-order in magnesium concentration. In this case, a linear relationship between absorbance and distance Z is obtained near the surface, and the ratio k/D of the rate constant and the diffusion coefficient can be determined from the slope of a plot of absorbance vs. distance without need for an absolute calibration of the absorption measurement. Previously reported methods of growing magnesium oxide deposits and of measuring their rate of growth by recording of interference fringes were employed in the present work. Within the accuracy of the measurements, the rate constant with respect to magnesium-vapor concentration was independent of pressure and of oxygen concentration, but decreased markedly with increasing surface temperature. The corresponding collision efficiency decreased from unity at 410K to about 0.02 at 840K. (Author)

Descriptors :   (*COMBUSTION, MAGNESIUM), (*MAGNESIUM, ATOMIC SPECTROSCOPY), OXYGEN, CHEMICAL REACTIONS, VAPORS, ABSORPTION SPECTRA, MAGNESIUM OXIDES, VAPOR PLATING, SUBSTRATES, NICKEL ALLOYS, CHROMIUM ALLOYS, THERMOCHEMISTRY

Subject Categories : Atomic and Molecular Physics and Spectroscopy
      Combustion and Ignition

Distribution Statement : APPROVED FOR PUBLIC RELEASE