Characterization of transient cavitation activity during sonochemical modification of magnesium particles

Abstract

Investigation of the cavitation activity during ultrasonic treatment of magnesium particles during nanostructuring has been performed. Cavitation activity is recorded in the continuous mode after switching the ultrasound on with the use of ICA-5DM cavitometer. It has been demonstrated that this characteristic of the cavitationzonemaybevariedinawiderangeofconstantoutputparametersofthegenerator.Thespeedand natureofthecavitationactivityalterationdependedontheconcentrationofMgparticlesinthesuspensionand the properties of the medium in which the sonochemical treatment has been performed. Three stages of the cavitation area evolution can be distinguished: 1 – the initial increase in cavitation activity, 2 – reaching a maximumwithasubsequentdecrease,and3–reachingtheplateau(ortherepeatedcycleswithfeedbackloops ofenlargement/reductionofthecavitationactivity). Theultrasonicallytreatedmagnesiumparticleshavebeencharacterizedbyscanningelectronmicroscopy,Xraydiffractionanalysisandthermalanalysis.Dependingonthenatureofthedispersedmediumtheparticlescan be characterized by the presence of magnesium hydroxide (brucite) and magnesium hydride. It is possible to reachtheincorporationofmagnesiumhydrideinthemagnesiumhydroxide/magnesiummatrixbyvaryingthe conditionsofultrasonictreatment(durationoftreatment,amplitude,dispersedmediumetc.).Theinfluenceof the magnesium reactivity is also confirmed by the measurements of cavitation activity in organic dispersed media(ethanol,ethyleneglycol)andtheiraqueousmixtures.