Smart Materials

This ppt. is the first session of my class about Smart Materials.

1. Special Technologies An Introduction to SMART MATERIALS Mehrshad Mehrpouya [email protected] Sapienza University of Rome Department of Mechanical and Aerospace Engineering

2. Mehrshad Mehrpouya PhD . Fellow Industrial Production Engineering Sapienza University of Rome, Rome, Italy M.Sc . Manufacturing Systems Engineering University Putra Malaysia (UPM ) LinkedIn : www.linkedin.com/in/mehrpouya Email : [email protected] Office no: 16 Sapienza University of Rome Department of Mechanical and Aerospace Engineering

3. Department of Mechanical and Aerospace Engineering Special Technology Types of Materials - Metals - Ceramics - Polymers - Composites - Semiconductors

4. Department of Mechanical and Aerospace Engineering Special Technology A metal is a material (an element, compound, or alloy) that is typically hard, opaque, shiny, and has good electrical and thermal conductivity . Example: several uses of steel and pressed aluminum as shown in the pictures. Metals

5. Department of Mechanical and Aerospace Engineering Special Technology METALS FERROUS METALS NON-FERROUS METALS

6. Department of Mechanical and Aerospace Engineering Special Technology

7. Department of Mechanical and Aerospace Engineering Special Technology

8. Department of Mechanical and Aerospace Engineering Special Technology Ceramics exhibit very strong ionic and/or covalent bonding (stronger than the metallic bond) and this confers the properties commonly associated with ceramics: high hardness, high compressive strength, low thermal and electrical conductivity and chemical inertness . Examples : glass, porcelain . Ceramics Ceramic

9. Department of Mechanical and Aerospace Engineering Special Technology Ceramics Ceramic Engineering ceramics are used to fabricate components for applications in many industrial sectors, including ceramic substrates for electronic devices, turbocharger rotors, and tappet heads for use in automotive engines. Ceramic substrates for electronic devices Ceramic turbocharger rotor assembly made from silicon nitride Courtesy of NGK/NTK Spark Plug Co.

10. Department of Mechanical and Aerospace Engineering Special Technology A polymer is a large molecule, or macromolecule, composed of many repeated subunits . Because of their broad range of properties, both synthetic and natural polymers play an essential and ubiquitous role in everyday life . Polymers range from familiar synthetic plastics such as polystyrene to natural biopolymers such as DNA and proteins that are fundamental to biological structure and function. Polymers also include “Plastics” and rubber materials. Polymers

11. Department of Mechanical and Aerospace Engineering Special Technology Polymers are bound by covalent forces and also by weak van der Waals forces, and usually based on C and H. They decompose at moderate temperatures (100 – 400 C), and are lightweight. Examples: plastics rubber . Polymers

12. Department of Mechanical and Aerospace Engineering Special Technology Polymer composite materials: reinforcing glass fibers in a polymer matrix. Composites A  composite material   is a material made from two or more constituent materials with significantly different   physical  or  chemical properties  that, when combined, produce a material with characteristics different from the individual components.

13. Department of Mechanical and Aerospace Engineering Special Technology Semiconductors The bonding is covalent (electrons are shared between atoms). Their electrical properties depend strongly on minute proportions of contaminants. Examples: Si, Ge, GaAs . This behavior and the interactions between charge carriers and photons and phonons allows semiconductors to store binary information , form logic gates, and convert between voltage , light, heat, and force as sensors and emitters . Silicon  crystals are the most common semiconducting materials used in  microelectronics and photovoltaics .

14. Department of Mechanical and Aerospace Engineering Special Technology Semiconductors Semiconductors are a special case of electronic material that combines two differently electrically conductive materials . A semiconductor is also known as a P-N junction , where one material allows ‘loose’ electrons to move through an ordered structure, and the other allows holes (where an electron could be, but is not) to move in the same way .

15. Department of Mechanical and Aerospace Engineering Special Technology Smart Materials

16. Department of Mechanical and Aerospace Engineering Special Technology What are smart materials? Smart materials are materials that have one or more properties that can be significantly altered in a controlled fashion by external stimuli, such as stress , temperature , moisture , pH , electric or magnetic fields .

17. Department of Mechanical and Aerospace Engineering Special Technology What are the examples? Piezoelectric materials Shape memory alloys Magnetic shape memory alloys Magnetorheological PH sensitive polymers Halochromic materials Thermochromic materials Chromogenic systems Electrochromic Smart Grease

18. Department of Mechanical and Aerospace Engineering Special Technology What are Piezoelectric materials? 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 the sample. Suitably designed structures made from these materials can therefore be made that bend, expand or contract when a voltage is applied.

19. Department of Mechanical and Aerospace Engineering Special Technology Piezoelectric materials have the ability to generate an electrical charge. A mechanical stress is applied to the smart material. This causes a small electrical charge to be generated. In return, the shape of the solid changes by a small amount. A car’s cigarette lighter is a good example of how piezoelectric materials are used in a every day application.

20. What are Piezoelectric materials?

21. Department of Mechanical and Aerospace Engineering Special Technology What are shape memory alloys? Shape memory alloys and shape memory polymers are thermo-responsive materials where deformation can be induced and recovered through temperature changes.

22. What are shape memory alloys?

23. Department of Mechanical and Aerospace Engineering Special Technology Shape memory alloys change shape at set temperatures. One of the most common alloys is a combination of nickel and titanium . This shape memory alloy can be treated so that when it reaches a set temperature it contracts. When it cools it then returns to its original shape. They become deformed once heated above the transformation temperature, but regain their shape as they cool.

24. Department of Mechanical and Aerospace Engineering Special Technology Shape memory alloy wire is called smart wire as it remembers its shape. When a small electrical current passes through the wire it becomes smart. It remembers to change shape. The wire becomes shorter. This shortening can be used to control a robotic hand. In the future, this may help scientists produce artificial motion that is more similar to the range of human movement.

25. Department of Mechanical and Aerospace Engineering Special Technology Magnetic shape-memory alloys (MSMAs), or ferromagnetic shape-memory alloys (FSMAs), are ferromagnetic materials which exhibit large strains under the influence of an applied magnetic field due to martensitic phase transformation. Magnetic shape-memory alloys (MSMAs )

26. Magnetic shape-memory alloys (MSMAs )

27. Department of Mechanical and Aerospace Engineering Special Technology Magnetorheological Magnetorheological fluid (MR fluid) is a type of smart material that has the ability to change state when placed in a magnetic field. These fluids are composed of iron-like particles. In their normal state they are fluid. When placed in a magnetic field the particles are attracted to each other and join up to form a solid. Currently, these materials are not widely used. It is thought of as a more futuristic smart material.

28. Department of Mechanical and Aerospace Engineering Special Technology PH sensitive polymers pH sensitive or pH responsive polymers are materials which will respond to the changes in the pH of the surrounding medium by varying their dimensions. Such materials increase its size (swell) or collapse depending on the pH of their environment. This behavior is exhibited due to the presence of certain functional groups in the polymer chain

29. Department of Mechanical and Aerospace Engineering Special Technology PH sensitive polymers The sensor is prepared by entrapping within a polymer matrix a pH sensitive dye that responds, through visible colour changes (see the Figure) to spoilage volatile compounds that contribute to a quantity known as Total Volatile Basic Nitrogen (TVB-N).

30. Department of Mechanical and Aerospace Engineering Special Technology Halochromic Materials Halochromic materials are commonly materials that change their colour as a result of changing acidity. One suggested application is for paints that can change colour to indicate corrosion in the metal underneath them.

31. Department of Mechanical and Aerospace Engineering Special Technology Thermochromic materials Thermochromic materials react to changes in temperature. Tiny capsules in thermochromic ink contain liquid crystals. As the temperature changes these crystals move. The reorientation of the crystals causes a change in colour at a specific temperature. This sensitivity causes them to temporarily change colour when they are exposed to heat.

32. Department of Mechanical and Aerospace Engineering Special Technology Thermochromic Colour-changing thermochromic pigments are now routinely made as inks for paper and fabrics – and incorporated into injection moulded plastics. A new type of phosphorescent pigment, capable of emitting light for up to 10 hours, has opened up entirely new design opportunities for instrumentation, low-level lighting systems etc. Warm Cool

33. Thermochromic

34. Thermochromic

35. Department of Mechanical and Aerospace Engineering Special Technology Chromogenic systems Chromogenic systems change colour in response to electrical, optical or thermal changes . These include electrochromic materials, which change their colour or opacity on the application of a voltage (e.g. liquid crystal displays), thermochromic materials change in colour depending on their temperature, and photochromic materials, which change colour in response to light - for example, light sensitive sunglasses that darken when exposed to bright sunlight.

36. Department of Mechanical and Aerospace Engineering Special Technology Photochromic materials This causes them to undergo a reversible change of colour when exposed to a certain amount of light. Photochromic lenses become dark when they are exposed to UV radiation . Once the UV radiation is removed, the lenses gradually return to their normal state. They can be made of either glass or plastic.

37. Department of Mechanical and Aerospace Engineering Special Technology Electrochromic Electrochromism is the phenomenon displayed by some materials of reversibly changing colour by using bursts of charge to cause electrochemical redox reactions in electrochromic materials. Various types of materials and structures can be used to construct electrochromic devices, depending on the specific applications.

38. Department of Mechanical and Aerospace Engineering Special Technology Electrochromic

39. Department of Mechanical and Aerospace Engineering Special Technology Electrochromic Flip a switch and an electrochromic window can change from clear to fully darkened or any level of tint in-between. The action of an electric field signals the change in the window's optical and thermal properties. Once the field is reversed, the process is also reversed. The windows operate on a very low voltage -- one to three volts -- and only use energy to change their condition, not to maintain any particular state, like Boeing 787 Dreamliner .

40. Department of Mechanical and Aerospace Engineering Special Technology Smart Grease Smart grease is a particularly sticky and viscous gel with almost magical shear characteristics. It can be used in prototype applications to improve performance or it can be used in novel applications such as wound-up motors to provide uniform speed and torque output . The example illustrated here is a simple elastic band motor comprising a pill container, elastic, wheel and securing/winding rod. If, under normal circumstances, the wheel is wound up and released, it will spin rapidly and slow down. If a tiny amount of smart grease is added between the friction surfaces, the wheel will turn at a uniform (very slow) speed and the stored energy will be released uniformly.

41. Smart Grease

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