Quiz 2 (ch 4 and 5) Flashcards
singly bonded carbon atom to 4 other atoms
Saturated Hydrocarbons
Double or triple bonded carbon atoms
Unsaturated hydrocarbons
hydrocarbon atoms with the same compositions
isomerism
Process of forming solid polyethylene
gas at atmospheric Temp and Pressure
average number of repeated units in a polymer
Degree of Polymerization
Molecular weight increase will also increase:
melt viscosity, tensile strength, and impact resistance
The physical properties of polymers depend on:
Molecular weight, molecular shape, and structure of molecular chains
How do you change molecular configurations?
break bonds
2 categories of isomerism
stereoisomerism and geometrical isomerism
all R groups on the same side
isostatic
R group alternate sides
syndiotactic
R groups randomly positioned
Atactic
h atom and CH3 group on the same side
Cis
H atom and CH3 group on opposite sides
Trans
Soft when heated, hard when cold; heat allows secondary bonds to break, primarily linear
Thermoplastic
During initial heating material is permanently set; cross links are formed that prevent molecular motion, harder, stronger, and brittle
Thermosetting
4 groups of copolymers
Random, alternating, block, and gaft
polymer with chain folds at the faces
polymer crystallinity
The degree of crystallinity is determined by:
The rate of cooling during soldification
Main goal of materials science engineering:
to control the defects to better manipulate materials
Process of adding defects manually to improve material
Soldification
Anything that disrupts the regular crystalline structure
Micro-defects
Two categories of point defects in solids
vacancies and self interstitials
Location in solid structure that indicate an absence of atom
vacancy
Location in solid structure where the is an inserted atom that seems unnatural and tends to be larger or smaller than base atom
Self interstitial
foreign atoms present within an atom
impurities
Most metals are what?
alloys
when the parent metal is replaced by atoms of the alloying metal
substitutional solid solution
Atoms of the parent or solvent metal are larger than the atoms of the alloying metal
interstitial solid solution
Maximum concentration of carbon to form a solid solution
2%
Possible for cations and anions in ceramics
vacancies
Possible for only cations due to anions being much larger in nature
Interstitials
When a cation vacancy and cation interstitial pair exist
Frankel Defect
When a cation vacancy and an anion vacancy pair exist
Shottky defect
What must be balanced in order for a solid solution when impurities are present
electronegativity
Antimony atom surrounded by covalent bonded silicon; free electron
N-type Semiconductor
Boron atom surrounded by 4 silicon atoms (covalent bonds) with a hole in of the shells
P-type Semiconductor
