Experimental verification of the formal nucleation and growth rate equations – initial UH3 development on uranium surface

The very initial stage of hydride formation on polycrystalline gadolinium

“…Unlike GC's formation which is clearly displayed by the in situ optical microscope observations [1][2][3][4][5][6][7], the formation of the tiny sub-micron precipitates is not directly detected within magnification scales of HSM (magnification of up to ×50). In some cases the coloring of the surface is observed during this stage.…”

“…Hydrogen exposure experiments were performed in a high-vacuum chamber (base pressure of about 10 −4 Pa) of a Hot Stage Microscope (HSM), utilized in previous studies of the GC's kinetics (described in detail in references [5,6]). …”

Elastic fields generated by a semi-spherical hydride particle on a free surface of a metal and their effect on its growth

“…Several experimental observations [15,22,23] described the microstructural evolution and kinetics of hydrides growth on surfaces. Initially, many small sub-micron hydride precipitates are nucleated and tend to cluster.…”

UD3formation on uranium: evidence for grain boundary precipitation

“…The initial development of hydrides on metallic surfaces is observed to occur in isolated zones or 'spots' [6], [10], [11], [12], [13], [14], indicating that certain areas favour the onset of hydride forming reactions. It follows that these zones experience shorter induction times than elsewhere on the sample surface, which may be attributed to the effects of defects or cracks in the oxide layer, localised thinning, regions of enhanced hydrogen species permeability or regions of enhanced hydrogen surface dissociation (although the exact nature of the hydrogen species which transport through the surface oxide film is currently unknown) [15].…”