Formation Of Hydrogen Bubbles Research Articles

Hydrogen effect on low-field magnetic properties of amorphous alloys

The irreversible effect produced by hydrogen charging on the magnetic properties, at low magnetic field, of high magnetostrictive amorphous ribbons has been studied. The experimental measurements show irreversible effects on the propagation field in as-cast samples and very low effect in annealed samples. These results have been explained by the formation of hydrogen bubbles inside the sample.

Catalytic hydrogen evolution in the presence of sulfide and cobalt ions. A study by cathodic stripping voltammetry on the hanging mercury drop electrode

AbstractTraces of sulfide ion produce a cathodic peak on the HMDE at about −1.50 V (vs. SCE) after preconcentration at −0.5 V in the borax buffer containing 0.01 mM CoII. This peak is due to the catalytic hydrogen evolution, as demonstrated by the influence of the buffer concentration, the effect of water substitution by deuterium oxide and by the formation of hydrogen bubbles on the electrode. The effect of sulfide ion concentration, deposition time and deposition potential demonstrate that a positively charged cobalt complex is adsorptively accumulated during the deposition step. The reduction of CoII in this species produces a catalytically active compound which is involved in the reduction of the hydrogen ion according to the proposed mechanism. The potential analytical applications of this process for the determination of the sulfide ion have been assessed. The peak current is directly proportional to the concentration of the sulfide ion enabling the application of the standard addition method. The detection limit (using either normal or derivative LSV) is about 1 nM for 10 min accumulation time. The accuracy and reproducibility are fairly good and some of the common interferences in CSV of sulfide ion are removed or at least diminished.

Inhibition of pyramid formation in the etching of Si p(100) in aqueous potassium hydroxide-isopropanol

Production of smooth, defect-free silicon surfaces is essential for the fabrication of precise three-dimensional devices. Micromachining usually involves anisotropic etching in alkaline media such as potassium hydroxide-isopropanol mixtures (KOH/IPA). The quality of the etched surfaces is highly dependent on the etching conditions and surface inhomogeneities such as micropyramids or pits can present major problems, In the present investigation, the purity of the reagents used in the etchant and the effects of dissolved gases, such as oxygen and nitrogen, on surface finish have been evaluated for KOH/IPA baths. The purity of both the water and KOH used was found to be extremely important; the best surfaces were obtained with baths prepared with the lowest impurity content. Dissolved gases had marked effects on surface finish. Pyramid-free surfaces were obtained in oxygen-saturated etchants; this is attributed to the rapid reaction of oxygen with hydrogen produced at the surface during etching, thereby decreasing hydrogen bubble formation. The opposite was seen in solutions saturated with nitrogen where pyramid formation increased. The presence of IPA in the nitrogen-saturated bath improved the surface finish but did not prevent pyramid formation whereas with oxygen and IPA, defects were completely eliminated and surfaces with a roughness of less than 5 nm were obtained.

Use of video techniques to study the electrochemical activation and corrosion of aluminium alloys

In situ video techniques have been used to examine the galvanostatic initiation of pits on two Al–Mg–Sn–Ga alloys and an Al-In alloy demonstrating the switch-on of the anodic-discharge reaction. Surface magnifications in the range ×25 to ×200 have been employed. Surface effects were studied during electrochemical activation and deactivation of the alloys and during the voltage-oscillation phenomenon observed with Al–In alloys when under discharge in alkaline solutions. Alloys undergoing non-superactive behaviour exhibited a much more crystallographic pitting behaviour than those displaying superactive behaviour, the latter showing much more rounded smooth-sided pits. The time required for battery alloys to activate fully, i.e. switch-on, was related to the number of pits per unit area generated. The formation of hydrogen bubbles during switch-on caused a very noisy voltage transient. The voltage oscillatory behaviour of Al–In under discharge was explained by use of the observation that during voltage rise and fall there was sympathetic growth and dissolution of a surface film. This cyclic film growth and dissolution was proposed to cause the voltage oscillation through its oscillatory effect on the specimen area undergoing corrosion.

Quenching of dilute Be [sbnd]H alloys: A TEM study

Be is a relevant material in nuclear and reactor technology. It has recently gained additional prominence as a coating material for Tokamak fusion devices. In this latter context, the reactions of Be with the hydrogen isotopes are very important. Recently, rather precise hydrogen solubility measurements both in {alpha}-Be and in {beta}-Be became available. This paper presents an adapted form the solubility of H in Be in the {alpha}-phase. The solubility in terms of the atom ratio H/M can be expressed by: S = 1.723 {times} 10{sup {minus}4} sq. root p exp({minus}16700/RT) (H){sub (M)} where p is the pressure in MPa, T the temperature and R the gas constant. Thus, {alpha}-Be is an endothermic occluder of hydrogen. Another endothermic occluder of H is, for instance, Cu where TEM techniques showed the quenching of dilute Cu-H alloys from high temperatures leads to the formation of hydrogen bubbles around room temperature. Matter is ejected from the growing bubble by prismatic dislocation loop punching. In other TEM studies, it was established that quenching of the exothermic occluder of hydrogen, Mg, does not lead to bubble precipitation but to the formation of small hydride particles.

Design of the Veslefrikk wellhead jacket: Blair-Fish, P. M., Baerheim, M. and Austin, C. W.Steel Constr. Today Aug. 1989 3, (4), 103–108

Magnesium, as a biomaterial has the potential to replace conventional implant materials owing to its numerous advantages. However, high corrosion rate is a major obstacle that has to be addressed for its implementation as implants. This study aims to evaluate the feasibility and effects of High Repetition Laser Shock Peening (HRLSP) on biocompatibility and corrosion resistance of Mg samples and as well as to analyze the effect of operational parameters such as peening with overlap on corrosion rate. From the results obtained using hydrogen evolution and mass loss methods, it was found that corrosion rates of both 0% overlap and 66% overlap peened samples reduced by more than 50% compared to that of unpeened sample and sample peened with 66% overlap exhibited least corrosion. The biocompatibility of peened Mg samples was also enhanced as there was neither rapid pH variation nor large hydrogen bubble formation around samples.

The effect of nickel on the mechanism of the initial stages of zinc electrowinning from sulphate electrolytes. Part I. Investigations on a spectrally pure aluminium cathode

The effect of nickel ions on the mechanism of the initial stages of zinc electrowinning was studied using scanning electron microscopy (SEM) and cyclic voltammetry. It is shown that nickel ions are deposited simultaneously onto the zinc crystals which are being formed and onto the still exposed aluminium cathode. As a result of the catalytic activation of the hydrogen ion discharge during the initial stages of the process, conditions are created for the formation of hydrogen bubbles on the uncovered aluminium cathode.

NDE Observations of Hydrogen Effects in 4340 Steel

AbstractCathodic charging of hydrogen into 4340 steel produces drastic deterioration of mechanical properties such as the notch tensile strength, depending on current density, charging time, and the poison used as an inhibitor of hydrogen recombination and bubble formation at the specimen surface. Fusion of charged samples permitted hydrogen content to be measured and revealed a linear increase in the latter with charging current density. The change in the Doppler spectrum sharpness parameter Δ(P/W) deviates negatively with cathodic charging time but inversely with the charging current density (fugacity). Thus a low-fugacity hydrogen charging appears merely to screen existing positron trap sites, whereas a high-fugacity charge also creates new defect traps. This would result in a lesser net screeninig effect which would be seen as a smaller negative deviation in Δ(P/W) as observed. For cumulative charging, however, one finds oscillatory behavior in (P/W) as in earlier cumulative charging experiments with Ni. This behavior indicates that hydrogen screening of positron traps was followed by new positron trap site creation and that this sequence of events occurred repeatedly and in that order.

Hydrogen Gas Evolution from Cathodically Protected Surfaces

Abstract An experimental study on the formation of hydrogen bubbles on a mill-scaled steel surface was conducted near the entrance to a crevice that simulated a disbonded pipeline coating surrounding a holiday and contained a carbonate-bicarbonate solution. The study showed that the growth rate of bubbles and their effects on the potential along the crevice are a function of the potential applied at the holiday and the crevice thickness, while the orientation of the simulated crevice and the temperature had little further effect on bubble formation. Because of IR drops along the crevice, the rate of hydrogen release is lower for creviced surfaces than for noncreviced ones exposed to the same applied potential. Thus, for both situations, the highest (least negative) potential for hydrogen release is between −1.05 and −1.1 V (SCE), when the potential is made successively more negative from about −0.8 V at daily intervals. However, when the noncreviced surfaces that had been held previously for extensive per...

Hydrogen bubble formation by pulse heating in vanadium-Hydrogen alloys

Hydrogen bubble formation is a well known phenomenon in endothermic occluders of hydrogen (e.g. Cu) which are quenched and annealed. In that case, hydrogen is introduced at high temperatures. Quenching then leads to supersaturation of hydrogen and—diffusivities permitting—to precipitation in form of bubbles. In the present work, the reverse case is investigated. An exothermic occluder (here V) was hydrogen charged to elevated concentrations (c ≃5 … 20 pct) at a low temperature. The samples were subsequently pulse heated in vacuum to temperatures not far from the melting point. Under these conditions, a very large hydrogen supersaturation was produced which corresponded to equilibrium pressures of a few thousand bars. Also, only a minor fraction of the hydrogen could escape to the adjacent surfaces during the pulse. Inspection of the pulse heated samples revealed the morphology of bubbles and cavities arising from the precipitation of hydrogen. Interestingly, the density of bubbles was so high in some regions that actually “metal foam” was formed. The implications of the present results are also discussed.

Formation and annihilation of lithium colloids and hydrogen bubbles in irradiated LiH

Formation and annihilation of Li colloids and hydrogen bubbles in LiH have been studied with optical absorption ESR and thermoluminescence. The optical absorption measurements of irradiated LiH gave S- and colloid bands as well as a broad band. The theoretical calculation using Mie theory shows that the observed S- and colloid bands can be ascribed to large and small Li colloids with radii of 220 and 50 AA, respectively. Extended calculation of light scattering by bubbles or voids indicates that the observed broad band is due to hydrogen bubbles with radii less than 600 AA. The colloids and bubbles are annealed out above 80 degrees C; accompanying thermoluminescence follows second-order kinetics. The possible models of the annihilation of colloids and bubbles in LiH are presented.

Measurements of the acoustic emission in a steam sodium interaction

The acoustic emissions from the interaction of steam and sodium have been measured in the Argonne Core Components test loop for liquid sodium temperatures of 204 °C and 482 °C, liquid sodium flow rates of 0.23 m/s and 0.69 m/s and steam injection rates between 1.67 and 16.7 mg/s. These measurements were performed with a calibrated high temperature lithium niobate microphone which has a flatresponse to 25 kHz with a sensitivity 0.011 PC/Pa and rises at 12 dB per octave between 30 and 90 kHz to a peak of 0.062 PC/Pa. These data were observed to have low frequency (less than 10 kHz) and higher frequency (greater than 20 kHz) components. The lower frequency data was found to be consistent with hydrogen bubble formation and oscillation. The higher‐frequency component was observed to consist of transient events with center frequencies between 20 and 40 kHz. The amplitude of the individual events appeared independent of injection rate; however, the repetition of the transient events was found to be proportional ...

Water Vapour Embrittlement and Hydrogen Bubble Formation in Al–Zn–Mg Alloys

AbstractIt has been found by transmission electron microscope observations that lens-shaped bubbles form on grain boundaries of Al–6% Zn–3% Mg alloy specimens pre-exposed to moist air but not in specimens pre-exposed to dry air. The bubbles are surrounded by strong elastic strain fields and their density depends on the time and temperature of pre-exposure, the grain boundary plane and mis-orientation, the specimen thickness, composition and presence of stress. In aged alloys the bubbles form preferentially on grain boundary precipitates. The bubbles are believed to result from the precipitation of molecular hydrogen formed by reaction between the specimen and the water vapour. The pressure of hydrogen in the bubbles is sufficient to propagate intergranular cracks even in the absence of an externally applied stress. However, the experimental observations suggest that it is the hydrogen in solution on the grain boundaries between the bubbles that is particularly damaging and not the hydrogen precipitated in...

Water Vapour Embrittlement and Hydrogen Bubble Formation in Al–Zn–Mg Alloys

Water Vapour Embrittlement and Hydrogen Bubble Formation in Al–Zn–Mg Alloys

Deformation of magnesium and its alloys on oxidation

Experiments have been carried out on the mechanisms by which magnesium alloys are deformed by oxidation at 500°C in carbon-dioxide-based environments. The composition of the gas and heterogeneous gas reactions are important factors. Slight deformation combined with some enhanced oxidation occurs with water vapour present, these effects being greatly enhanced by the additional presence of hydrocarbons in the gas and by carbon deposits on the specimens. Carbon dioxide appears to act in the main as an inert carrier. The deformation is derived from a compressive stress within the oxide scale which grows by the transport of both magnesium and oxygen through it by, it is believed, gaseous or surface diffusion through cracks or open pores. The formation of magnesia and/or hydrogen bubbles within the scale has been postulated to explain the generation of the compressive stress. In agreement with basic considerations, contamination of the solid corrosion products with sodium and roughening the metal surface reduce deformation for at least short term exposures to gas containing hydrocarbons.

DETACHMENT OF THE RETINA

In May 1934, I suggested a method of closing a hole in the retina by multiple momentary punctures with the electrolysis needle (cathode) in the margin of the hole and in the hole itself. The anode, a small ball, lies on the eyeball. This method is the most delicate and most successful operative procedure for detachment of the retina. Instead of extreme heat or sodium hydroxide solution, a current intensity of only from 0.5 to 1 ma. is necessary. The application is momentary and can be repeated many times until the hole has been completely treated. This new operation does not produce cicatricial bands in the retina and secondary holes from too intense heat. In contradistinction to diathermy, cathode electrolysis is active at the point of the needle, and thereby avoids the danger of perforating the detached retina and producing new holes without cauterization. The formation of hydrogen bubbles at