Some features of the evaporation of magnesium and lead by quasi-cw laser radiation

Abstract

Neutron diffraction and 31 P nuclear magnetic resonance spectroscopy were used to probe the structure of phosphate glass biomaterials of general composition (CaO) 0.5−x (Na 2 O) x (P 2 O 5 ) 0.5 (x = 0, 0.1 and 0.5). The results suggest that all three glasses have structures based on chains of Q 2 phosphate groups. Clear structural differences are observed between the glasses containing Na 2 O and CaO. The P-O bonds to bridging and non-bridging oxygens are less well resolved in the neutron data from the samples containing CaO, suggesting a change in the nature of the bonding as the field strength of the cation increases Na + → Ca 2+ . In the (CaO) 0.5 (P 2 O 5 ) 0.5 glass most of the Ca 2+ ions are present in isolated CaO x polyhedra whereas in the (Na 2 O) 0.5 (P 2 O 5 ) 0.5 glass the NaO x polyhedra share edges leading to a Na-Na correlation. The results of the structural study are related to the properties of the (CaO) 0.4 (Na 2 O) 0.1 (P 2 O 5 ) 0.5 biomaterial.

Experimental determination of temperature threshold for melt surface deformation during laser interaction on iron at atmospheric pressure

“…This question is very important, since this temperature determines limit of energy efficiency of various processes. Although there exist a few experimental measurements of the recoil pressure for several metal species [3][4][5][6][7], these are limited to the ablation regime with high laser intensity (typically > 1 MW/cm 2 for iron) well above the threshold of the ejection process. It should be noted also that in these studies, the recoil pressure was determined only as a function of laser intensity and it could not be related to the surface temperature.…”

The reactive element effect on high-temperature oxidation of magnesium

“…The quantitative evaluation of evaporation rate of magnesium is based on analysis of the metal droplets, which flow during a welding sequence. [208][209][210] Modelling of magnesium evaporation during vacuum electron beam welding found that evaporation of Mg preceded Zn. 211 It also shows that evaporation rates of alloying elements are not only dependent on their boiling point but also on thermal diffusivity and latent heats of melting and evaporation.…”