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APSC278 by Warren Poole and Anoush Poursartip
Bonding and Properties
8/13/2019 2. Bonding and Properties
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APSC278 by Warren Poole and Anoush Poursartip
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APSC278 by Warren Poole and Anoush Poursartip
Competition in Product Development
1) between groupsmetal alloys vs. ceramics vs. polymers
e.g. – beverage containers
2) within groups
steel vs. aluminum vs. titanium
e.g. bicycles, autos
3) between producers of the same material
e.g. Alcan vs. Alcoa
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QUESTION ??
What are the designrequirements that need
to be considered forbeverage containers ?
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For any givenproperty, we canthen comparedifferent materials,and choose the bestone(s)
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Question
• What are the factors which control theproperties of materials ?
– Composition – what it is made from – Bonding – Crystal structure – arrangement of atoms – Temperature – Pressure
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Bonding controls
• Melting temperature• Density• Thermal and Electrical Conductivity• Coefficient of Thermal Expansion• Stiffness
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Types of Bonds
• Primary Bonds – Ionic Bonds – Covalent Bonds – Metallic Bonds
• Secondary Bonds – Van der Waals Bonds – Hydrogen Bonds
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Acrobat Document
Bond Energy Diagram
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Ionic Bond
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Ionic Bond Formation
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Covalent Bonds
The formation of a covalent bond – in this case between twohydrogen atoms, making a hydrogen molecule
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Covalent Bonds are Directional
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Metallic Bonds
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Secondary Bonds
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Hydrogen Bonds
From Wikipedia.org
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APSC278 by Warren Poole and Anoush Poursartip
Bond Energies
Type of Bond Bonding Energy
(kJ/mol) Ionic 600-1500 (strong)
Covalent 100-800 (med.)Primary
Metallic 70-850 (med.)
Van derWaals 10-50 (weak)
Secondary
Hydrogen 10-50 (weak)
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Presence of Bonds
Type of Bond Material
Ionic Covalent Metallic Van der Waals
Metals X X
Polymers X X
Some Ceramics X X
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Bonding Type Substance Bonding Energy(kJ/mol)
MeltingTemperature(deg C)
Ionic NaCl 640 801MgO 1000 2800
Covalent Si 450 1410C (diamond) 713 >3550
Metallic Hg 68 -39 Al 324 660Fe 406 1538W 849 3410
van der Waals Ar 7.7 -189
Cl2 31 -101Hydrogen NH3 35 -78
H2O 51 0
Bonding Energies and MeltingTemperatures
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Presence of Bonds
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Thermal Expansion Coefficient
• Decreases withincrease in bond
energy• Controlled by the
shape of the bondenergy diagram
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Coefficient of Thermal Expansion
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APSC278 by Warren Poole and Anoush Poursartip
Effect of Temperature onbond spacing