Effect Of Environment Humidity And PH On Friction And Wear Behaviors Of Nuclear Borosilicate Glass

With the rapid development of the nuclear energy industry,the reasonable disposal of highly radioactive nuclear waste has gradually attracted widespread attention from scientists.At present,nuclear waste glass curing technology is regarded as the most mature treatment solution,and borosilicate glass has become the most common curing substrate due to its strong mechanical and chemical stability.However,during the geological storage process of the solidified structure of nuclear waste,the glass matrix will be affected by mechanical stress and multiple environmental factors.Therefore,researching the damage evolution law of borosilicate glass under different conditions will play an important role in perfecting the wear mechanism of borosilicate glass,meanwhile,it will provide theoretical support for reducing the damage of borosilicate glass during deep geological storage.The current research only considers the corrosion effect of water molecules on borosilicate glass.The damage evolution law and wear mechanism of borosilicate glass due to mechanical action and different acidic solution environments have not been well-explained.This paper systematically research the wear mechanism of borosilicate glass under the synergistic effect of mechanical factors and chemical corrosion.Based on the tribological experiment methods to simulate the storage state of the actual borosilicate glass solidified structure,and then study the influence of different humidity and various solution pH on the friction and wear mechanism of borosilicate glass.Meanwhile,this paper further explores the evolution law and competitive relationship of borosilicate glass surface damage and subsurface damage,and proposes technical measures to prevent borosilicate glass damage,which deepens the understanding of the mechanism of the damage of glass materials under different effects.Through the above studies,the main conclusions of this paper are as follows:（1）Based on the study of the friction and wear properties of borosilicate glass under different environmental humidity,it can be found that at the same applied load,as the environmental humidity increases,the steady-state friction coefficient and wear of the borosilicate glass is gradually reduced during the friction process.When in dry atmosphere,mechanical abrasion is the main form of wear of borosilicate glass,and tribochemical reactions is the main form of wear of glass under conditions of humid and liquid water.Researches have shown that the tribochemical reactions and lubricating effects of water molecules are the direct cause of lower wear in humid than in dry environments.The substantial reduction of the frictional interface shear force is the main reason that the wear and subsurface damage of the borosilicate glass in liquid water are much milder than that in the dry and humid environments.（2）Based on the study of the friction and wear properties of borosilicate glass under various solution pH,it can be found that as the solution pH increases from 1 to7,the friction coefficient of the friction interface,the wear of the borosilicate glass and the stainless steel ball present the same evolution law.It shows increase at first and then decrease.Further researches indicate that the wear of borosilicate glass at different solution pH is closely related to the interface charge effect and contact conditions.When the pH of the solution is equal to the isoelectric point of the glass(pH_pzc),the borosilicate glass and the stainless steel ball are in direct contact during the friction process,which leads to the largest wear volume.When the pH is less than pH_pzc,the repulsive force of the contact interface reduces the direct contact and shear stress,resulting in the lower wear volume of the materials.When the pH of the solution is greater than the pH_pzc,the attractive force of the contact interface causes the formation of an interface hydration layer,thereby reducing the wear volume.（3）Based on the HF corrosion experiment of borosilicate glass with different friction damage types,it can be found that with the increase of corrosion time,the surface topography features will transition from concave to convex,and the corresponding critical times are:Scratch zone～5 min,Cracking zone～2 min,Debris zone～1 min.The corrosion rate of borosilicate glass corresponding to different friction damage types is:Pristine glass>Scratch zone>Cracking zone>Debris zone.Further analysis indicates that during the HF corrosion of borosilicate glass,the surface damage characteristics and the subsurface densification characteristics present a competitive relationship with the changes in the corrosion rate.Compared with the pristine glass surface and Scratch zone,the fluorine-based precipitate formed by the chemical reaction of metal ions effectively reduces the corrosion rate in the Cracking zone,and the stubborn wear debris significantly inhibits the corrosion rate of the borosilicate glass in the Debris zone.