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1. IMPREFECTION IN TRADITIONAL & SMART MATERIALS The Report Submitted By Eng. AHMED MOHAMED IBRAHIM REFAAT Teacher Assistant, Canadian International College (CIC)   Under Supervision Of   Prof . Mohamed Shenawy Dept. of Mechanical Engineering, Helwan University

2. Imperfection In Solids For Traditional Material Point Defect (Zero dimensional defect ) Linear Defects or Dislocation ( One-Dimensional imperfection) Planar Defects – Two-Dimensional Imperfections

3. Point Defect (Zero dimensional defect) The Vacancy : is simply an unoccupied atom site in the crystal structure. The interstitial : is an atom occupying an interstitial site not normally occupied by an atom in the perfect crystal structure or an extra atom inserted into the perfect crystal structural such that two atoms occupy positions close to a singly occupied atomic site in the perfect structure . The Frenkel Defect is a vacancy- interstitialcy combination. This defect happens when some of the ions of the lattice occupy interstitial sites leaving lattice vacant.

4. Point Defect (Zero dimensional defect)

5. Point Defect (Zero dimensional defect)

6. Point Defect (Zero dimensional defect) 4. The Schottky Defect is a pair of oppositely charged ion vacancies.

7. Calculating the No. of Vacancies The equilibrium number of vacancies N v for a given quantity of material Depends on and increases with temperature according to Where N v = equilibrium number of vacancies N = total no. of atomic sites (it depends on density) = energy required for vacancy formation. K = Boltzmann’s constant (the value of k 1.38 x 10 -23 J/atom-K ) T = the absolute temperature  

8. Linear Defects or Dislocation ( One-Dimensional imperfection ) Linear Defects (Dislocation), which are one dimensional, are associated primarily with mechanical deformation. Were the atoms are out of position in the crystal structural. The motion of dislocations allows slip-plastic deformation to occur. The Linear defect is commonly designed by the “inverted T” symbol (┴) which represents the edge of an extra half-plane of atoms .

9. Edge Dislocations The edge defect can be easily visualized as an extra half-plane of atoms in a lattice. Linear Defects or Dislocation ( One-Dimensional imperfection )

10. The edge dislocation moves parallel to the direction of stress. Linear Defects or Dislocation ( One-Dimensional imperfection )

11. 2. Screw Dislocations The screw dislocation is slightly more difficult to visualize. The motion of a screw dislocation is also a result of shear stress, but the defect line movement is perpendicular to direction of the stress and the atom displacement, rather than parallel. Linear Defects or Dislocation ( One-Dimensional imperfection )

12. the screw dislocation will move upward which is perpendicular to direction of the stress. Linear Defects or Dislocation ( One-Dimensional imperfection )

13. Planar Defects – Two-Dimensional Imperfections 1) A twin region: a change over many atomic spacing’s . 2) A Grain Boundary is a general planar defect that separates regions of different crystalline orientation (i.e. grains) within a polycrystalline solid.

14. Twin boundary Defect A twin boundary is a special type of grain boundary across which there is a specific mirror lattice symmetry; that is, atoms on one side of the boundary are located in mirror-image positions of the atoms on the other side Planar Defects – Two-Dimensional Imperfections

15. Twin boundary Defect image showing (a) the twinning zone (b ) contraction twinning boundary, (c) double twinning boundary, and (d) tension twinning boundary. 

16. 2. Grain Boundaries Defects A Grain Boundary is a general planar defect that separates regions of different crystalline orientation (i.e. grains) within a polycrystalline solid. The atoms in the grain boundary will not be in perfect crystalline arrangement. Planar Defects – Two-Dimensional Imperfections

17. Grain Boundaries Defects Micrograph  of a  polycrystalline  metal; grain boundaries evidenced by acid etching.

18. Intrinsic Defects Intrinsic defects of self-assembled colloidal crystals: (a) vacancy defect pointed by arrow; (b) interstitial defect; (c) crack defect due to stacking fault; (d) grain boundary defect due to dislocation. Reproduced with permission from  ref. 28 , Copyright 2003, American Chemical Society.

19. Smart Materials What are Smart Materials? Types Examples Application

20. Definition Smart Materials are designed materials that have one or more properties that can be significantly changed in a controlled fashion by external Motivation. Such as : Stress Temperature Moisture Electric Fields Magnetic Fields

21. Types of smart material Piezoelectric  materials are materials that produce a voltage when stress is applied. Since this effect also applies in the reverse manner, a voltage across the sample will produce stress within sample.

22. 2. Shape-memory alloys  are materials in which large deformation can be induced and recovered through temperature changes or stress changes . Types of smart material

23. Shape-memory alloys An armored tire That tire is the Shape Memory Alloy (SMA) tire. It's essentially a chain mail tire made up of stoichiometric nickel titanium, an alloy that remembers its original shape after it has rolled over something. https://youtu.be/KLpCrfBO_e4

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