Argon Degassing Research Articles

Effect of Ultrasonic-Assisted Casting on the Hydrogen and Lithium Content of Al-Li Alloy.

Dehydrogenation of the 2195 Al–Li alloy was accomplished using argon degassing, ultrasonic degassing, and vacuum degassing. The concentration of hydrogen, its microstructure, and its mechanical characteristics were all investigated. The hydrogen content in the 2195 Al–Li alloy is high. The degassing process significantly improved the mechanical properties of the cast alloy, owing the removal of hydrogen. Among the three degassing techniques, ultrasonic argon treatment was an efficient dehydrogenation approach and an effective procedure for enhancing the microstructure while minimizing lithium loss in the Al–Li alloy. On the one hand, ultrasonic waves can dissolve purged argon bubbles, allowing them to degas more efficiently. On the other hand, ultrasonic waves may cause a large number of cavitation bubbles to form in the melt, which should be the cause of the microstructure refinement. The dynamics of rising argon bubbles and ultrasonic effects are involved in ultrasonic argon treatments such as cavitation and flow.

Thermal evolution of Venus with argon degassing

Decades-old measurements of atmospheric and elemental surface composition constrain the history of Venus. In this study, we search for a model featuring continuous evolution in the stagnant-lid regime that predicts the present-day atmospheric mass of radiogenic argon and satisfies the other available constraints. For comparison, we also consider the end-member scenario of a single catastrophic resurfacing event. Thermal evolution simulations are performed that track the mass transport of argon and potassium and include a simple model of upwelling mantle plumes. Sensitivity analyses and linear regression are used to quantify the range of initial conditions that will produce desired values for key model output parameters. Decompression melting of passively upwelling mantle causes considerable mantle processing and crustal growth during the early evolution of Venus. Mantle plumes have negligible effects on recent crustal production, but may be important to local surface features. For a wide range of initial conditions, continuous evolution in the stagnant-lid regime predicts the correct amount of argon degassing, along with the absence of a global magnetic field, crustal and lithosphere thicknesses matching modern estimates, and volcanism consistent with the cratering record. Argon degassing does not uniquely constrain mantle dynamics, but the success of simple stagnant-lid models diminishes the need to invoke dramatic changes like catastrophic resurfacing.

Effect of ultrasonic argon degassing on dissolved hydrogen in aluminium alloy

Ultrasonic degassing has been shown to be a reasonably efficient way of degassing a melt. Similarly, vacuum degassing has also been proven to be beneficial in producing high quality products. However, neither method is sufficiently efficient. Moreover, a combination of these techniques does not respond well to large volumes of melt. In this article, a novel approach, using ultrasonic assisted argon degassing was examined and compared with vacuum and argon degassing. The results indicate that the ultrasonic-argon degassing process is a faster method and can be used for large volumes of melt, thus overcoming the restrictions of the other two methods.

Oxidative DNA damage following photoexcitation of daunomycin: Direct role of oxygen

The chemistry of the photoactivation of daunomycin–DNA complexes is reported and the mechanism is elucidated. We quantitatively assessed the type of DNA damage, such as strand breaks, oxidized bases, and abasic sites, that arise using a plasmid relaxation assay coupled with DNA repair endonucleases. Photoexcitation of daunomycin leads to oxidative DNA damage in a dose- and irradiation time-dependent manner and guanine-specific oxidized purines are substantially produced under these conditions. Oxidative DNA base damage was also inhibited by argon degassing, indicating that guanine-specific damage arises from an oxygen-dependent mechanism. In addition, photoexcitation of daunomycin–DNA complexes leads to superoxide anion radical formation. From these studies of the actual product formed, we conclude that a charge transfer is a main driving force of the mechanism.

Argon degassing models of Mars

ON July 20, 1976 Viking I lander made a soft landing on the martian surface. Atmospheric pressure recorded on the surface by the lander was 7.7 mbar and main constituents of the atmosphere were 95% CO2 2–3% N2, 1–2% Ar and 0.3–0.4% O2 (ref. 1). The (40Ar/36Ar) isotopic ratio was 2,750±500 as measured by a mass spectrometer1. This high isotopic ratio suggests an unique history for the evolution of the martian atmosphere. The possible mechanisms of argon degassing models of Mars are discussed here.

Argon degassing of seamless tubular steels

Argon degassing is effective in removing oxygen, nitrogen, and nonmetallic inclusions from liquid teel to a degree comparable to vacuum degassing.

Argon Degassing of Steel

Previously reported experimental data show that argon injection is effective for deoxidizing steel in 10-lb induction furnace heats. Present tests, conducted in a covered ladle with argon injected either through a lance or a bottom-mounted device, indicate that it is possible on a 1-ton scale to closely approach the results of the smaller experimental heats. In addition, data are presented showing removal of both hydrogen and nitrogen by argon injection.