Study On Interfacial Misfit Dislocation Nucleation In Nanostructured Materials With Surface/Interface Effects

Nano materials due to their excellent physical and mechanical properties,received high attention in science and technology and extensive application. Themechanical properties of nano composites are greatly affected by the surface andinterface effects. Interface of misfit dislocation nucleation mechanism is one of thekey scientific problems about composite material strength performance and damagefailure. Based on nanopore and core-shell nanowires as the research object, Using theelastic complex potential theory, the explicit solutions to the complex variablefunctions of above problems are provided. The dependence of elastic energy onmaterials’ properties and surface/interface parameters are calculated and discussed.Research results are as follows:1. The nanopore in elastic and piezoelectric material interface of misfitdislocation nucleation mechanism is investigated. The critical formation condition ofscrew misfit dislocation which locates in cylindrical nanopore surface with interfacestress is investigated. The dependence of elastic energy on surface/interface effectwith different materials parameters and thickness of thin film are calculated anddiscussed. The results show that surface/interface effects on the nanoscale have greateffect on misfit dislocation formation, when the composite substrate and film of therelative shear modulus exceeds a certain value, screw misfit dislocation can form onlyconsidering negative surface/interface effects. Misfit dislocation form easier whenconsidering the negative surface/interface effects in smaller film thickness, The largerfilm thickness, the more prone to the formation of misfit dislocation under thesurface/interface effects. The formation of screw dislocation in the surface during thepiezoelectric matrix nanopore film is investigated. The dependence of piezoelectricelastic energy on piezoelectric materials properties and eigen strain are calculated anddiscussed. The larger the piezoelectric constant ratio, the smaller the critical thicknessof thin film; the larger eigen strain, the smaller the critical thickness of thin film.2. The core-shell nanowires in elastic and piezoelectric material interface ofmisfit dislocation nucleation mechanism is investigated. The critical formationcondition of screw misfit dislocation which locates in core-shell nanowires surfacewith different surface/interface residual stress and surface/interface effects isinvestigated. The positive(negative) surface/interface residual stress willincrease(decrease) the extent of critical film thickness, the positive(negative) surface/interface effects will increase(decrease) the critical film th ickness and thecritical misfit strain. The critical formation condition of piezoelectric misfitdislocation which locates in core-shell nanowires surface with differentsurface/interface effects is investigated. Applied force electric coupling constitutiveequation, the piezoelectric thin film regional stress field of complex potential functionanalytic solutions, exporting the dislocation nucleation critical condition of theproblem. Mainly study the material constants of misfit dislocation nucleation imp act,and compared with elastic material core-shell nanowires in the interface of misfitdislocation nucleation. The dipoles of piezoelectric misfit dislocation in annularcoating layer on a cylindrical nanowire are investigated. The possibility of dipolesmisfit dislocation nucleation within the coating is discussed. The smaller thepiezoelectric constant ratio, the more possibility of dipoles misfit dislocation form,the dipoles of piezoelectric misfit dislocation can’t form if they close to the core.