Introduction to Material Science and Engineering

Transcription

1 Introduction to Material Science and Engineering

2 Introduction What is materials engineering? the understanding and modification of the structure and properties of materials to improve the performance and processing of the material What is a material scientist/engineer? A person who uses his/her combined knowledge of physics, chemistry and metallurgy to exploit property-structure combinations for practical use.

3 What are materials? What do we mean when we say materials? 1. Metals - aluminum - copper - steel (iron alloy) - nickel - titanium 2. Ceramics - clay - silica glass - alumina - quartz 3. Polymers - polyvinyl chloride (PVC) - Teflon - various plastics - glue (adhesives) - Kevlar 4. Composites - wood - carbon fiber resins - concrete semiconductors (computer chips, etc.) = ceramics, composites nanomaterials = ceramics, metals, polymers, composites

4 Classes of Materials metals polymers ceramics composites

5 Stone Age up to around 3000 B.C. tools and weapons of stone, copper (some silver and gold) used mostly for ornamental purposes, but too soft for much else

6 Bronze Age 3000 BC to 1000 BC tools and weapons made from a combination of copper and tin

7 Iron Age 1000 BC to present weaker than bronze, but didn t require being alloyed with another metal, also could be sharpened Later combined with carbon to create steel, a much stronger metal

8 Definitions Elastic deformation Reversible alteration of the form or dimensions of a solid body under stress. Plastic deformation - Irreversible alteration of the form or dimension of a solid body under stress. Brittle Ability of a material to break, snap, crack or fail easily when subjected to external loads. Ductile Ability of a material to undergo permanent deformation through cross-section reductions and elongation without fracture.

9 Metals Metal alloys are mixtures of two or more metal and nonmetal elements (for example, aluminum and copper, Cu-Ni alloy, steel) Properties: Electrically conductive (free electrons) Thermally conductive High strength large capacity to carry load over crosssection area (stress) Ductile endure large amounts of deformation before breaking. Magnetic Medium melting point

10 Metal Applications Electrical wire: aluminum, copper, silver Heat transfer fins: aluminum, silver Plumbing: copper Construction beams (bridges, sky scrapers, rebar, etc.): steel Cars: steel Consumer goods: soup cans appliances (stainless steel sheet metal) utensils tools Many, many, many more

11 Polymers Polymers consist of various hydro-carbon (organic elements) with select additives to bring out specific properties Properties: ductile: can be stretched up to 1000% of original length lightweight: Low densities medium strength: Depending on additives chemical stability: inert to corrosive environments low melting point

12 Polymer Applications Car tires: vulcanized polymer (added sulfur) Ziploc bags Food storage containers Plumbing: polyvinyl chloride (PVC) Kevlar Aerospace and energy applications: Teflon Consumer goods: calculator casings TV consuls shoe soles cell phone casings Elmer s Glue (adhesives) contact lenses Many, many. many more

13 Ceramics Consist of metal and non metal elements Typically a mixture of elements in the form of a chemical compound, for example Al 2 O 3 or glass Properties: wear resistant (hard) chemical stability: corrosion resistant high temperature strength: strength retention at very high temperatures high melting points good insulators (dielectrics)

14 Ceramic Applications Window glassaerospace, energy and automotive industry heat shield tiles engine components reactor vessel and furnace linings Consumer products: pottery dishes (fine china, plates, bowls) glassware (cups, mugs, etc.) eye glass lenses

15 Composites A mixture of two different materials to create a new material with combined properties Types of composites: Particulate reinforced Whisker/rod reinforced Fiber reinforced Laminated composites - layered structures (surf boards, skate boards) Properties: Depends on composites High melting points with improved high temperature strength: ceramic-ceramic High strength and ductile with improved wear resistance: metal-ceramic High strength and ductile: polymer-polymer

16 Composites: Applications Wood: naturally occurring biological material consists of very strong fibers imbedded in a soft matrix Plywood: laminated wood for buildings Concrete: basements, bridges, sidewalks Fiberglass: boats Carbon fiber resins: bicycle frames

17 Additional Properties of Materials Electrical Properties Conductivity how well electricity flows through a material Resistivity how well a material resists the flow of electricity Magnetic Properties high magnetic permeability = magnetic flow

18 Additional Properties of Materials Chemical Properties Flammability how easy it is to ignite Corrosion reaction between material and environment that leads to deterioration Thermal Properties Thermal Conductivity how well heat is transferred Thermal Resistance how well heat is resisted Expressed with an R-Value High R-value = less heat flow

19 Additional Properties of Materials Optical Properties Reflection/Absorption if something is blue it absorbs all other light but blue, which is reflected back Acoustic Properties Absorption more porous materials absorb more sound Reflection Smoother materials reflect sound in one direction Rough materials reflect sound in multiple directions

20 Nanotechnology Nanotechnology the design of new materials and devices at the scale of a single nanometer Nanoparticles between 1nm and 100nm, at the nanoscale material properties can be different than in larger scales (i.e. gold can melt at room temperature) Nanowires small strands designed to transmit light or electricity Nanotubes lightweight and stronger than steel Buckyball most round molecule known to man, ideal for carrying other atoms or particles