Chemisorption of hydrogen on aluminum oxide

Arbuzova, L. A.; Slovetskaya, K. I.; Rubinshtein, A. M.; Kunin, L. L.; Danilkin, V. A.

doi:10.1007/bf00849340

Cited by 3 publications

(2 citation statements)

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“…The molar mass of aluminum oxide is 102 g/mol, while that of hydrogen is 1 g/mol. Thus, hydrogen absorption by the aluminum oxide surface corresponds, on average, to the correlation Al 2 O 3 × 3.46 H, which allows-even considering the model approximation (of the incomplete collapse of oxide spots to cubic particles)-no more than a monoatomic hydrogen layer on the aluminum oxide surface; that is, there is, in fact, the chemical absorption shown in paper [28]. The results of paper [29] also demonstrate the reduction in pore formation in the presence of small-size products of the oxide film collapse.…”

Section: Resultsmentioning

confidence: 89%

Dehydrogenation of AlSi7Fe1 Melt during In Situ Composite Production by Oxygen Blowing

Finkelstein

Schaefer

Dubinin

2021

Metals

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The technology of producing a composite material in situ envisages the pre-saturation of an AlSi7Fe1 melt with hydrogen; afterwards, the melt is blown with oxygen until the hydrogen dissolved in the melt is burned out. The hydrogen content was researched during the manufacturing process of the composite material; before oxygen blowing, and at incomplete and complete burning out of the dissolved hydrogen. The interrelation between the absorbed hydrogen content and the aluminum oxide fraction was identified. A mathematical model was proposed which demonstrated that during the saturation process of the melt with oxide particles, hydrogen was absorbed on their surface as a layer close to monoatomic, which does not lead to the realization of the pores’ heterogeneous nucleation mechanism. Due to this, castings produced from the researched composite material are leakless. Incomplete burning out of hydrogen dissolved in the melt leads to the formation of significant hydrogen porosity. The proposed method of prevention of gas porosity in cast composites is an alternative to the conventional one and offers not only the purging of the melt from oxide inclusions but, on the contrary, a significant increase in their specific surface, which allows for the reduction in hydrogen content on the inclusion surface to the monoatomic level.

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Section: Resultsmentioning

confidence: 89%

Dehydrogenation of AlSi7Fe1 Melt during In Situ Composite Production by Oxygen Blowing

Finkelstein

Schaefer

Dubinin

2021

Metals

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“…oxides in liquid Al or Mg, serve as hydrogen concentrators as well as the cavitation nuclei. Experimental results [74] show that pure alumina and even more so alumina contaminated with transition metals adsorbs hydrogen in considerable quantities that makes these particles efficient cavitation nuclei and decreases the cavitation threshold.…”

Section: Degassingmentioning

confidence: 99%

High-Frequency Vibration and Ultrasonic Processing

Eskin

Tzanakis

2018

Springer Series in Materials Science

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Chapter 5 High-frequency vibration and ultrasonic processing D.G. Eskin, I. Tzanakis 5.1 Historical overview of ultrasonic cavitation science and applications The application of ultrasound to the processing of liquids and slurries has a long history. The theory of oscillations was developed by Lord Rayleigh who laid the foundation for nonlinear acoustics. He also theoretically quantified the pressure pulse resulted from the imploding cavitation bubble and suggested that the acoustic pressure is directly related to the wave energy and velocity [1], which was experimentally confirmed by W.J. Altberg [2]. Significant contribution to the theory of cavitation was made by Ya.I. Frenkel [3] and E.N. Harvey [4] who explained why the cavitation threshold in liquids is well below the theoretical tensile strength of the liquid phase, suggesting a model of cavitation nuclei in real liquids as stable gas pockets at the surface imperfections of suspended particles. The pulsation of a cavitation bubble was described analytically by B.E. Nolting and E.A. Neppiras [5]. They introduced the resonance radius of the bubble. The bubble smaller that and around the resonance size will rapidly grow and then implode within one or two sound wave cycles. Each of the imploded bubble will generate large pressure pulse and create many even smaller bubbles, starting a chain reaction of bubble multiplication. The bubble larger than the resonance size will not implode but, being relatively stable, will pulsate around its size. The product of the number of cavitation bubbles in the unit volume and the maximum volume of a single bubble is called cavitation index. When this index approaches unity the amount of bubbles in the unit volume becomes so big that they substitute the liquid phase and the ultrasonic power transmitted to the liquid declines rapidly [6, 7]. This is the base of so-called shielding effect of the cavitation region, when the acoustic energy rapidly attenuates within the cavitation zone and does not propagate to the liquid volume. The practical aspects of ultrasonic cavitation started to attract the attention of physicists, chemists and other applied scientists and researchers. R. Wood and A. Loomis (1927) observed intensive acoustic streaming and fountaining, ultrasonic degassing, emulsification and atomization, cavitation damage of organic tissue, etc. [8]. The direct observation of cavitation became possible with the development of high-speed film cameras, high-brilliance impulse lamps and, eventually, laser illumination in the 1950s-1960s [9, 10, 11, 12, 13, 14]. The images taken with the exposure 0.5 to 5 msec enabled the in-situ study of the cavitation development, bubbles collapse and sonoluminescence. In recent years, in-situ studies of cavitation in liquid metals became possible using synchrotron radiation [15, 16, 17]. The application of vibrations to treating metals dates back to the 1870s when D.K. Chernov reported that shaking molten steel solidifying in a mold resulted in the formation of very fine crystals [18]. The ...

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