Hydrogen atmosphere, effect

Purification. Tellurium can be purified by distillation at ambient pressure in a hydrogen atmosphere. However, because of its high boiling point, tellurium is also distilled at low pressures. Heavy metal (iron, tin, lead, antimony, and bismuth) impurities remain in the still residue, although selenium is effectively removed if hydrogen distillation is used (21). 

Operating limits for steels in atmospheres containing hydrogen. 66 Effect of temperature on the tensile strength of copper ... 

Pure ruthenium powder or mixed ruthenium-molybdenum powders have been found able to effect good joints between molybdenum and tungsten. A eutectic melting above 1 900°C is formed, and joints produced in hydrogen atmospheres at 2 100°C operate satisfactorily at 1 500°C. A cobalt-palladium-gold alloy has also been reported to be useful in brazing molybdenum. 

We should note that this effect of the hydrogen on electric conductivity is related neither to reduction of oxide nor to the volume dissolution of hydrogen in oxide. The first option was ruled out due to initial heating of adsorbent in hydrogen atmosphere up to establishing the stationary value of electric conductivity at the temperature exceeding the maximum temperature of experiment (Theati 400 420 C). The con-... 

Kohn and Taylor (40) also studied the influence of illumination on the hydrogen-deuterium exchange reaction using specimens of barium, calcium, lithium, and sodium hydrides. If the specimens were annealed in the hydrogen atmosphere, the photocatalytic effect on these specimens was positive. And if the specimens of the same hydrides were preliminarily calcined in vacuum, the irradiation of these specimens retarded the reaction. 

If the positive effect is observed on a specimen deposited in the hydrogen atmosphere, then after the specimen is calcined in vacuo, this being accompanied by an increase of es, it is replaced by the negative effect (transfer from the point A to the point F in Fig. 9). Such an inversion (change of sign) of the photocatalytic effect due to the calcination of the specimen in vacuo (after it is annealed in hydrogen) was observed by Kohn and Taylor (40) who worked with hydrides of various metals. 

Molecular hydrogen atmosphere is the less aggressive method but, as we shall see, decomposition of the H2 molecules at the surface is the limiting process for its introduction. In this section, we shall present mainly results concerned with hydrogen plasma introduction. Comparison will be made with other introduction methods. We shall present also the effect of nonin-tentional introduction of hydrogen in these semiconductors. 

We also examined the effects of various heat treatments in both reducing and oxidizing atmospheres. An indochinite reduced for 12 hours in a hydrogen atmosphere at 950 °C. yielded the Mossbauer spectrum displayed in Figure 5. The curve shown is the result of the computer fit the data points are not given, but the closeness of fit is about the same as in the other spectra. The spectrum clearly shows that a certain amount of the original tektite remains the two broad lines at —0.11 and 1.83 mm./sec. match the original tektite lines closely. There is also clear evidence of the presence of metallic iron since the six narrow... 

At the end of the experiment, the reaction bed was allowed to cool in a hydrogen atmosphere. In some experiments, nitrogen was used instead of hydrogen to confirm that the effects observed were in fact associated with hydrogenation of the coal rather than with high pressure effects. 

The third form of inorganic sulfur - the sulfate variety - is realitively unimportant in energy conversion. Fresh coal contains very little sulfate its presence is usually indicative of a weathered (oxidized) feedstock. Additionally, sulfate may be formed to a minor degree from other types of sulfur by moderate heating of the feedstock, by reaction with the bound oxygen in that feed. This effect can even occur under a hydrogen atmosphere. ... 

Stockmann found that tempering zinc oxide in a hydrogen atmosphere at 250°C increased its conductivity and changed the shape of the resulting time-temperature-conductivity curve. The effect of hydrogen on zinc oxide will be discussed in the next section. 

Figure 3. Pressure effect on kerogen recovery from rich shale in pure hydrogen atmospheres...

Keywords ultrafine diamond, structural effects, treatment, hydrogen atmosphere, sintering, thermal-baric action. 

Furthermore, since the C4 cuts employed exhibit a 1-butcne percentage of about 10 to 15 per cent weight, this graph also shows that, to achieve effective conversion, it is necessary to operate at less than ISO C. In practice, the operation is conducted at about lOCPC, which maintains a residual 1-butene content of about 5 per cent weight in the effluenL la these conditions, however, the reaction rate becomes slow. Catalysts are used to accelerate it, usually based on precious metals deposited on inert alumina (palladium, rhodium etc.), whose operation is considerably improved in a hydrogen atmosphere. This also permits the selective hydrogenation of the residual butadiene, and explains why this conversion is called hydroisomerization. 

Effect of Oxygen on the Platinum Functions. On the basis of the mechanism of sintering in a non-hydrogen atmosphere (2) and in order to protect the platinum functions of the catalysts, we treated them at 482 494°C with different oxygen concentration from 0 to 21% in N2 for 4 8 hrs. The results are shown in Table III. 

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