The thermal conductivity of clear fused silica was measured over the temperature range 300–2100°K in an experiment which minimized radiative energy transport. This was a steady-state experiment involving the measurement of the electric current and voltage drop through a fine tungsten wire which was embedded along the axis of a cylindrical silica rod. The wire served both as a heating element and as a resistance thermometer. Thermal conductivities were calculated by graphical evaluation of the rate of change of electric power with temperature at different temperatures. The experiment yielded thermal conductivities between 2.6×10−3 and 2.9×10−3 cal/cm sec°K at room temperature, and between 4.5×10−3 and 5.5×10−3 cal/cm sec°K over the temperature range 1000–2100°K.

A shock-tube program was carried out in which the NO concentration was followed as a function of time behind the shock front by absorption of 1270 A radiation, where ground vibrational state O2 and N2 are essentially transparent. The absorption coefficients of the species NO, O2, and N2 as functions of the respective vibrational temperatures were determined by measuring the absorption by the shock-heated gas at a point in the time history corresponding to complete vibrational relaxation but before the onset of dissociation. Time history analyses were made on a total of 42 shock-tube runs covering a temperature range of 3000°—8000°K on the following six mixtures: ½% NO, ½% NO+¼% O2, 10% NO, 50% NO, 20% air, and 100% air—the diluent in all cases being argon. An IBM 704 computer was programmed to integrate the vibrational and chemical rate equations as a function of time behind the shock front, subject to the constraints of the conservation equations. The pertinent rate constants were varied in a systematic trial-and-error manner in order to get the best fit to all the data.

A shock tube study of the thermal decompositions of acetaldehyde and ethylene oxide AIP Conf.Recent thermal decomposition studies of SF6 have led to interest in its principal oxidation product, sulfuryl difluoride. In the present study the thermal stability of S02F2 at high temperatures has been investigated. Highly dilute S02F2-Ar mixtures (~0.1 %) were shock heated in a conventional 1.5" stainlesssteel shock tube. The S02F2 concentration was monitored as a function of time behind the incident shock wave by its infrared emission at 11. 7 p. utilizing a liquid helium cooled eu: Ge detector. The initial pressure in the shock tube was varied from 30 to 600 torr and the temperature range covered was 1900-2300 o K. The monitored radiation was shown to be transparent over the range of densities employed. Effective first-order rate constants were evaluated from the logarithmic initial slopes of the radiation decay curves. For the 30-torr data, a unimolecular rate constant fit to the data is keff= 2.1 X 1011 exp ( -39 200jT) seCI. The data are analyzed in the light of several modern unimolecular rate theories, yielding ~81 kcal as the endothermicity for the reaction S02F2+Ar->S02F+F+Ar.

The vibrational relaxation time of nitric oxide in NO–Ar mixtures was determined over the temperature range 1500°—7000°K. An ultraviolet absorption technique using 1270-A radiation was employed to monitor the vibrational temperature as a function of time after these mixtures were shock heated to high translational temperatures. P10, the transition probability per oscillator per collision for transition between vibrational levels 1 and 0 calculated from the measured relaxation times ranged from 1.0×10—3 at 1500°K to 2.8×10—2 at 7000°K for NO–NO collisions. Argon is about 1/50 as efficient as NO. The results are compared with the lower temperature (400°—1500°K) work of Robben and with the adiabatic theory of Schwartz, Slawsky, and Herzfeld and the nonadiabatic theory of Nikitin.

No abstract