Vacuum outgassing

Vacuum Outgassing and Permeability. Under vacuum, modified ethylene—tetrafluoroethylene copolymers give off Htde gas at elevated temperatures. The loss rate is about one-tenth of the acceptable maximum rates for spacecraft uses. Exposing 750-pm specimens for 24 h at 149°C to a high vacuum results ia a maximum weight loss of 0.12% volatile condensible material is less than 0.02%. 

Sample cells were fabricated from tungsten. Additional crucibles composed of a Pt-40 w/o Rh-8 w/o W alloy were also used in experiments on the PuPt phase. Each tungsten cell was vacuum outgassed at 1800 for 1 h before an experiment. The cell temperature was determined during the measurements by sighting with a pyrometer (Pyrometer Instrument Co.) onto a blackbody hole in each cell base. The pyrometer and sight glasses were calibrated with an NBS standard lamp. 

K did not produce tiny new paramagnetic species, despite FTIR observations confirming appearance of IR features attributable to adsorbed NjO (2234 and 1256 cm in Fig. 4a) upon contact with N2O at 300 K. Stepwise decreases in magnitude of those IR features were, however, observed in each of a sequence of FTIR spectra taken after separate NjO adsorptions at increasing adsorption temperatures (TJ up to 573 K (Fig. 4b-d). From these FTIR observations it could be inferred that increased T, for contact between N,0 and vacuum-outgassed CeOj resulted in increased fractional decomposition of the N O introduced. FTIR spectra did not show bands due to peroxide species after N,0 adsorption. 

Evidence emerges from both the microcatalytic and spectroscopic studies for enhanced dissociative interaction of N,0 with preoxidised RhO,/CeO, materials exposed to helium-flush or vacuum-outgassing at T > 573 K. This is consistent with generation of reduced active-sites, such as electron-vacancy complexes, by such treatments. 

After elimination of moisture, the vacuum outgassing of certain polyimides is sufficiently low to be usable in space. 

Because the gravimetric and volumetric apparatus use vacuum systems it is convenient to outgas by vacuum. Outgassing in a continuous flow apparatus is accomplished by purging. 

The pressure exerted on the silver halide grains actually is increased by vacuum outgassing of emulsion coatings because... 

The most effective method of hypersensitization by hydrogen is to keep the vacuum-outgassed film or plate in contact with the gas for a time to be determined by experiment, and then... 

Although S-sensitization decreases low intensity reciprocity failure it usually does not eliminate it. In our experiments with monodisperse fine-grain silver bromide emulsion, vacuum outgassing of the S-sensitized emulsion eliminated the LIRF, just as it did for the unsensitized emulsion. Moreover, the sensitivities of the two emulsions under vacuum were nearly the same. Whatever may be the role of S-sensitization in this emulsion, it became inconsequential for exposures made under vacuum. However, the degree of increase in sensitivity caused by S-sensitization of the fine grain emulsions for exposures in air is much smaller than can be achieved with coarse-grain poly-disperse emulsions. 

The sensitivity of our (S+Au)-sensitized emulsions was increased by vacuum outgassing, and the low intensity reciprocity failure was nearly eliminated (108). When the vacuum out-gassed emulsion was equilibrated with water vapor before exposure, sensitivity decreased to a minimum at 40-60% RH, then increased at higher RH, unlike the behavior of emulsions with other types of sensitization where sensitivity continued to decrease. The cause of the increase at high humidities is uncertain. One possibility is that incorporation of gold into the latent image takes place more readily at the high humidities. 

Loss of photoelectrons and silver atoms to oxygen and moisture can be studied by the vacuum outgassing methods already described. The use of thinly coated emulsion layers is preferred. In the monodisperse fine-grain emulsions, loss to mobile... 

The dyes with the least negative Er are extremely sensitive to oxygen and moisture. If, after vacuum outgassing, the film was removed from vacuum into room air before exposure, sensitivity decreased by more than two orders of magnitude in less than a minute. 

The effect of moisture alone on spectral sensitization has been studied to only a limited extent. Moist oxygen generally causes greater desensitization than dry oxygen, just as in the undyed emulsions. However, moisture alone can cause effects in some dyed emulsions that are not found in the undyed emulsions. Absorptance measurements made on several emulsions showed that vacuum outgassing decreased the absorptance in the region of the... 

FIGURE 9. Changes in the absorption spectrum of 5,5 -dichloro-3,3, 9-triethylthiacarbocyanine (dye 3) adsorbed on Lippmann emulsion grains. Solid curve, measured in air dashed curve, measured after 16-hr vacuum outgassing dotted curve, measured after readmission of room air (266). 

Figure 3.18 Vacuum outgassing from a bulb for adsorption manometry (left) or from the sample container of an adsorption nucrobalance (right).

Outgassing the adsorbent sample 79 Aim of the outgassing 79 Conventional vacuum outgassing 80 Controlled vacuum outgassing by means of CRT A 81 Outgassing with a carrier gas 83... 

Immersion calorimetry requires a vacuum outgassing, in order to avoid the wetting of the pores to be partly prevented by the presence of a gas. 

Berger and Weir reported that 9-phenylxanthen-9-ol adsorption on silica gel results in formation of the 9-phenylxanthyl cation 1, as indicated by a characteristic absorption band at approximately 380 nm using diffuse reflectance spectroscopy [32]. A vacuum-outgassed sample produced a strong luminescence characteristic of the cation. Excitation spectra indicated that the cation luminescence derives from two sources from adiabatic photodehydroxylation of the alcohol and from direct excitation of cation thermally formed on the silica gel surface. 

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