UTMUNIVERSITI TEKNOLOGI MALAYSIAINTRODUCTION & ATOMIC STRUCTURE

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1-*Introduce the field of Materials Science and Engineering

Provide introduction to the classification of materials

Identify and distinguish between the types of atomic bonding

COURSE LEARNING OBJECTIVES

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1-*Historical OverviewWhat is Materials Science & EngineeringClassification of MaterialsAtomic StructureAtomic Bonding

CHAPTER OUTLINE

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1-*Chapter Outline Stone Age (40,000 to 100,000 yrs ago): Stone tools, clay pots, skin

Copper Age (5,000 to 10,000 yrs ago): Copper ornaments, earthenware, metal smelting

Bronze Age (3,000 to 5,000 yrs ago): Bronze (Cu/Sn), glass, iron smelting

Iron Age (1000 3000 yrs ago): Carburized Iron, improved forging, porcelain

Steel and concrete (100 1000 yrs ago)

Advanced Materials (beginning early 1900s): polymers, ceramics, composites, semiconductors

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1-*MATERIALS

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1-*MATERIALS

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1-*Chapter OutlinePropertiesProcessingStructurePerformanceMaterials Science Investigating the relationship between structure and properties of materials.Materials Engineering Designing the structure to achieve specific properties of materials. Processing Structure Properties Performance

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1-*Chapter Outline

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1-*Properties Properties are the way materials responds to external forces or the environment

MechanicalElectrical and magneticOptical Chemical

To obtain the desired properties the material must have the appropriate structureProcessing can produce the appropriate structure

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1-*Properties Composition, bonding, crystal structure, and microstructure define materials properties

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1-*Classification of Materials Metals

Ceramics

Polymers: Thermoplastics and Thermosets

Semiconductors

Composite Materials

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1-*Classification of Materials

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1-*Engineering Materials

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1-*Functional Classification of Materials Aerospace Biomedical Electronic Materials Energy Technology and Environmental Technology Magnetic Materials Photonic or Optical Materials Smart Materials Structural Materials

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1-*Atomic StructureAtomic structure is made of:

Protons: positive (+) charge Neutrons: no charge (neutral)Electrons: negative (-) charge

The nucleus contains the mass of an atom: Protons + Neutrons

Layers of electrons that orbit around the nucleus are called orbitals or energy-level shells.

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1-*Atomic Structure

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1-*Periodic Table of ElementsAtomic Number (# of protons)Atomic weight = # protons + average # neutrons

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1-*Electronegativity Electronegativity is defined as the measure of how willing atoms are to accept electrons

Subshells with one electron: low electronegativitySubshells with one missing electron: high electronegativity

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1-*Periodic Table of ElementsLow electronegativityHigh electronegativity

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1-*IonsWhen an atom loses or gains an electron to or from another atom, it is called an ion

Types of Ions:CATIONS a loss of electrons: positive (+) chargeANIONS a gain of electrons: negative (-) charge

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1-*Atomic BondingAtomic bonding is the formation of compounds by combining two or more elements

In an atomic bonding electrons are gained, lost or shared

There are 4 main types of bonding:

Ionic bondingCovalent bondingMetallic bondingVan der waals

Primary BondingSecondary Bonding

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1-*Ionic BondingIonic bonding occurs between + and ions

Requires electron transfer between atoms forming attracting ions

Example: sodium chloride (NaCl)

Other compounds having ionic bonding: MgO, CsCl

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1-*Ionic BondingCharacteristics of Ionic Bonding

Ionic compounds are usually hard, rigid and brittle: the results of ions being held in specific positions

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1-*Covalent BondingIn covalent bonding the electrons are shared between atoms

Covalent bonds are more stable and stronger than ionic bonds

e.g; Diamond (Carbon)

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1-*Metallic BondingMetallic bonding:Valence electrons are detached from atoms, and spread in an electron sea that glues the ions together

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1-*Metallic BondingCharacteristics of metallic bonding

Metallic bonds occur between metalsGood conductors of electricity and heat (due to the mobility of electrons)Malleability (can be shaped) and Ductility (can be drawn into wires)Brightness and strong light reflectionExamples: copper (Cu), gold (Au), silver (Ag)

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1-*Metallic Bonding

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1-*Secondary BondingAtomic bonding without electron transfer or sharingArises from interaction between dipoles

Fluctuating dipoles

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1-*Secondary Bonding Permanent dipoles-molecule induced-general case:-ex: liquid H2O

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1-*Secondary Bonding-ex: Polymer (PVC)

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1-*Summary: Atomic BondingExamples of bonding in materials

Metals:metallic bondingModerate Tm and ECeramics:ionic/covalent high Tm and high EPolymers:covalent and secondarySmall Tm and small E Semiconductors:covalent and covalent/ionic Tm: melting temperature, E: stiffness

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