Surface diffusion of hydrogen on platinum was detected by permeation of H2 and inert gases in porous Pt.Below 1 Torr at 60-75°C surface transport was substantial in comparison with gas-phase transport. Surface diffusivities Ds were about 10-6 cm2/sec and the activation energy was 5.7 kcal/mole! Comparison of these and literature values of Ds showed a relation between Ds and the heat of adsorption q. Three classes of behavior were found, and differences were attributed to differences in the type of gas-surface bonding. Numbers m were assigned to each bond type and a general correlation was produced, Da = 0.016•
Surface transport is described in terms of the hopping of adsorbed molecules between adjacent sites of different adsorption strength. The change in surface diffusivity with surface concentration is attributed to a change in the strength of adsorption, as evidenced by a change in the differential heat of adsorption, q, with concentration. The correlating equation predicts that the surface diffusivity varies as exp(~aq/RT), where a is an experimental constant. New data on the flow of C02, S02, and NH3 in porous glass are presented and are correlated successfully by the above equation. In addition, literature data for five other systems are correlated well by this method.
Thin film
TiO2
was produced at 150°C by chemical vapor deposition using hydrolysis of tetraisopropyl titanate. Films were amorphous as grown, but annealing in air caused crystallization, with anatase formed beginning at 350°C and rutile at 700°C. Density and index of refraction increased substantially with increasing anneal temperature, while etch susceptibility in
HF
and
H2SO4
decreased. Comparison with literature data showed two groups of processes. One group yields films having properties that gradually approach those of rutile with increasing process temperature. The other group gives rutile directly at moderate temperatures. Deposition of amorphous film, followed by etching and annealing is suggested as a means for pattern definition.
From these studies, it can be concluded that cocurrent contacting of vapor and liquid streams is a very satisfactory method to utilize for the design of a multistage vapor-liquid equilibrium unit.A contactor, six in. in length, with an annular space of %or %-in., packed with Metex screen, will be 100% efficient at throughputs up to 1000 grams per hr per cm2, which corresponds, respectively, to 6 and 28 liters of liquid per hr.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.