Materials Science Exam 1 PDF

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materials science exam 1...

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Materials Science and Engineering – CENG 3120 Chapter 1 Solid materials have been conveniently grouped into three basic categories: metals, ceramics, and polymers. This scheme is based primarily on chemical makeup and atomic structure, and most materials fall into one distinct grouping or another. Metals Polymers/Plastics Ceramics Strong, ductile Covalent bonding (share e-), Ionic bonding – compounds of similar EN nonmetal/metal (oxides, nitrides, High thermal/electrical etc.) requires electron transfer, conductivity, opaque/ reflective Soft, ductile, low strength/ btwn + and – ions density, thermal/electrical insulators Brittle, glassy, elastic, Nonconducting (insulator) Electronegativity: L to R increasing, Bot to Top increasing, He highest, Fr lowest EN Difference Bond Ex 0.00-0.40 Covalent (non-polar) H-H 0.41-1.00 Covalent (slightly polar) H-Cl 1.01-2.00 Covalent (very polar) H-F 2.01 – higher Ionic Na+ClChapter 2 Electronic Structure • Orbitals and quantum numbers Energy states • Occupy the lowest possibly, cannot be in between • N-shell: n=4 • M-shell: n=3 • L-shell: n=2 • K-shell n=1 Electropositive elements, readily give up electrons to become ions • Columns IA, IIA, IIB give up 1e-, 2e-, 3e Electronegative elements. readily acquire electrons to become ions • last 3 columns. VIA, VIIA, and 0 accept 2e-, accept 1e-, He/Ne/Ar… become inert gasses Energy and Packing Dense, ordered packed structures tend to have lower energies. As the atoms are brought closer together, the energy drops. Energy $ " Net Potential energy between two adjacent ions 𝐸! = − # + # ! "

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Attractive and repulsive energy 𝐸" = − # , 𝐸% = # ! From a plot of interatomic separation versus force for two atoms/ions, the equilibrium separation corresponds to the value at zero force. From a plot of interatomic separation versus potential energy for two atoms/ions, the bonding energy corresponds to the energy value at the minimum of the curve. Intermolecular forces For hydrogen bonding, highly polar molecules form when hydrogen covalently bonds to a nonmetallic element such as fluorine.

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Chapter 3 Structure Body Center Cubic Face Center Cubic Hexagonal Closst PackedE

Abbrev. BCC FCC HCP

# atoms/ unit cell 2 4 6

Atomic radius / lat. par. 4R=a√3 4R=a√2 2R=a

𝜌&'()*+ > 𝜌,'#)&-,+ > 𝜌./*0&'#+ METALS: close packing, metallic bonding, often larger atomic masses CERAMICS; less dense packing, often lighter elements POLYMERS; low packing density, often amorphous, lighter elements, C, H, O COMPOSITES; intermediate values Chapter 4 Chapter 5 Chapter 6 Homework

APF 0.68 0.74 0.74

Materials Science and Engineering – CENG 3120

N lambda =2dsin theta

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120

Materials Science and Engineering – CENG 3120...