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Material Science > Chapter 3 Structure of Crystalline Solids > Flashcards

Chapter 3 Structure of Crystalline Solids Flashcards

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1
Q

energy and packing

why do atoms assemble in ordered/ crystal structures

A
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2
Q

crystalline materials

A

atoms pack in periodic arrays

  • metals many ceramics, some polymers
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3
Q

single crystal

A

atoms are in a repeating/ periodic array over the entire material

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4
Q

polycrystalline

A

comprised of many single-crystal grains

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5
Q

noncrystalline (amorphous) materials

A

atoms have no periodic packing

  • occurs for complex structures, rapid cooling
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6
Q

unit cell

A

is a structural unit/ building block that repeated in 2D or 3D, generates the crystal structure

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7
Q

7 types of crystal systems

A

In total there are seven crystal systems:

triclinic

monoclinic

orthorhombic

tetragonal

trigonal

hexagonal

cubic

A crystal family is determined by lattices and point groups.

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8
Q

* quick reference *

crystal systems bravais lattices

A
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9
Q

crystal structure lattice

A

A crystal lattice is the arrangement of these atoms, or groups of atoms, in a crystal.

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10
Q

*quick reference *

crystal structure lattice

A
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11
Q

metallic bonding

A

nondirectional, ion cores glued together by an electron cloud, hence can be arranged in dense packing schemes

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12
Q

three types of unit cells

A

face-centered cubic (FCC)

body-centered cubic(BCC)

hexagonal close-packed (HCP)

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13
Q

* quick reference *

BCC

A
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14
Q

*quick reference *

BCC part 2

A
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15
Q

atomic packing factor

A

atomic packing factor, packing efficiency, or packing fraction is the fraction of volume in a crystal structure that is occupied by constituent particles

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16
Q

atomic packing factor BCC

A
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17
Q

FCC lattice characteristics

A
18
Q

closed packed structure

A

refers to the most tightly packed or space-efficient composition of crystal structures (lattices)

19
Q

FCC stacking sequence

A
20
Q

hexagonal close-packed structure

stacking sequence

A
21
Q

theoretical density

A

is defined as the maximum density of a material or element that could be achieved assuming there are no voids or contaminants in the overall material

22
Q

theoretical density example

A
23
Q

densities of material classes

metals

ceramics

polymers

composites

A

metals - have close packing (metallic bonding) (often large atomic masses)

ceramics - have less dense packing (often lighter elements )

polymers - have a low packing density ( often amorphous, lighter elements )

composites - have intermediate values

24
Q

single crystals vs polycrystals

A

single crystals - properties vary with direction (anisotropic)

polycrystals - properties may/may not vary with direction

isotropic - if grains are randomly oriented

anisotropic - if grains are textured

25
Q

anisotropic vs isotropic

A

Isotropic materials show the same properties in all directions.

Anisotropic materials show different properties in different directions.

26
Q

examples of isotropic materials

A

Glass, crystals with cubic symmetry, diamonds, metals

27
Q

examples of anisotropic materials

A

Wood, composite materials, all crystals (except cubic crystal)

28
Q

* quick reference *

polycrystals (iso vs aniso )

A
29
Q

polymorphism vs allotropy

A

Polymorphism is defined as the ability of a solid material to exist in more than one form or crystal structure, whereas allotropy is defined as the property of some chemical elements to exist in two or more different forms

30
Q

point coordinates

A
31
Q

crystallographic directions

A

Refers to directions in the various crystal systems that correspond with the growth of the mineral and often with the direction of one of the faces of the original crystal itself

32
Q

linear density of an atom

A
33
Q

Miller indices

A

group of three numbers that indicates the orientation of a plane or set of parallel planes of atoms in a crystal.

34
Q

miller indices example

A
35
Q

crystallographic planes algorithm

A

1) read of intercepts of the plane with axes in terms a, b, c
2) take reciprocals of intercepts
3) reduce to the smallest integer values
4) enclose in parentheses no commas (hkl)

36
Q

crystallographic plane example

A
37
Q

planar density

A

is a measure of packing density in crystals.

38
Q

planar density example

A
39
Q

diffraction

A

is a powerful nondestructive technique for characterizing crystalline materials

40
Q

X-ray diffraction

A
41
Q

x-ray diffraction pattern

A
42
Q

Summary of this chapter

A

Material Science (17 decks)

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