Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
39 Cards in this Set
- Front
- Back
Ceramics: compounds
|
compounds between metallic and non metallic elements
Ex. Oxides, nitrides, silicates |
|
Ceramics: Bonding
|
ionic and covalent
|
|
Ceramics: Structure
|
Crystalline
Amorphus(glass) |
|
Ionic Bonding
|
Metal(+) and non metal(negative)
|
|
Properties of Ionic Bonding:
MP/BP Electrical conductivity |
high MP/BP-->high thermal energy to separate ions
low electrical conductivity (no free electrons) * strong bonds = hard to disassociate = high MP/BP |
|
Properties of Ionic Compounds
Hardness Compressive Strength Brittleness |
High for all! Not strong tensile, not ductile-->easy to fracture
|
|
Covalent Bonding:
Electrical conductivity? |
Sharing a pair of valence elctrons
low |
|
Biocompatibility of Ceramics:
Biointerness Examples: |
Bioinertness: non reactive to minimize toxic effects and inflammatory responses
Dental Crowns/Bridges: Alumina: Al2O3 Silica: SiO2 Zirconia: ZrO2 Titania: TiO2(implants! anticorrosive not novel but high resistance to corrosion) |
|
Ceramics:
Basic units? Allotropic forms? Dental Applications? |
SiO2 in differ forms
Fused Silica(non crystalline, glass) Cristobalie(crystalline) Tridymite(Crystalline) Quartz(Crystalline Dental Applications |
|
Structure of Ceramics
|
Crystalline: long range order
Non-crystalline: amorphous |
|
Crystal Melting Transition:
properties |
Sharp change at a definite melting point
Discontinuity in specific volume specific volume = density Ordered crystall structure= high packing density Disordered liquid= low packing density *see solid-solid transitions for SiO2 |
|
Amorphous Properties
structure? How to make phase change? |
No long range periodicty
Rapid cooling of metled sand to avoid crystallization NO SHARP PHASE CHANGE from solid to liquid at definite MP, gradual softening |
|
Solid-Solid Transition
|
Sharpe changes in specific volume at definite temperatures
|
|
Glass Transition
|
No sudden increase in volume
gradual increase becomes more rapid above transition temp |
|
Formation of Crystalline Solid
|
Crystalline solid: slow cooling of molten cilica
|
|
Glass formation:Glass
|
Rapid cooling of molten silica(vitrification)-->doesn't allow time for rearrangement and growth of crystal nucllei
|
|
Glass formation:Devertrification
|
small amount of crystalization of glass
Reorganization of molecules at elevated temp for a long time(annealing)-->translucent |
|
Polymers: Synthetic EX
|
Polyethylene
PCV(polyvinyl chloride) |
|
Acrylic Resins: what are they
EX? |
Derivative of ethylene
Acrylic Acid: COOH Methaccrylic Acid: COOH + CH3 on same carbon |
|
Polymer Bonding
|
1. hydrogen
2. van der walls |
|
Glass formation:Glass
|
Rapid cooling of molten silica(vitrification)-->doesn't allow time for rearrangement and growth of crystal nucllei
|
|
Glass formation:Devertrification
|
small amount of crystalization of glass
Reorganization of molecules at elevated temp for a long time(annealing)-->translucent |
|
Polymers: Synthetic EX
|
Polyethylene
PCV(polyvinyl chloride) |
|
Acrylic Resins: what are they
EX? |
Derivative of ethylene
Acrylic Acid: COOH Methaccrylic Acid: COOH + CH3 on same carbon |
|
Polymer Bonding:
|
Primary: Covalent monomer-monomer
Secondary 1. hydrogen 2. van der walls |
|
Hydrogen bonding
|
weak
NH, OH, FH in polymers |
|
Van Der Waals
|
weak,
Iner Gasses: He, Ne, Ar |
|
Molecular Weight Definition
|
# of repeating unit x molecular weight of repeating unit
|
|
Average Molecular Weight
why? types? |
many different chains, only average can be defined
Number Average mol. weight Weight Average molecular weight |
|
Number Average Molecular Weight
|
# molecules in a given weight
Mx=Der xi/Mi |
|
Number Average Molecular Weight
|
Sum of:
Mean Molecular Weight Range x Xi(occurence) essentially mean/average of molecular weights of individual macromolecules |
|
Weight average molecular weight
|
Sum of:
Mean wt range x Wi(occurence) |
|
Degree of Polymerization:
Number Average dgree of polymerization Weight Average degree of polymerization |
# of repeating unit
Number: Mn/molecular weight Weight: Mw/molecular weight |
|
Degree of Poly Generalizations:
High: Lower: |
High: fewer, longer chains, more rigid less soluble
Low: More, shorter chains, less rigid, more soluble |
|
Molecular Weight
<100g/mol =1000g/mol >10,00g/mol |
liquid
waxy solid solid |
|
Polymer Structure of 1 vs. 2 compounds
|
See notebook
Homo-->linear, branched Copolymer-->linear(blk/random), Branched(random, graft) |
|
Spatial Structure of Polymers
|
Linear-vanderwals
Branched-inefficient packing Crosslinked-covalent Network |
|
Thermoplastic Polyers
|
reversible
softens upon heating, harden cooling flexible linear w/ some branches most dental resin |
|
Thermoset
|
Irreversible crosslinks
hardens heated crosslinked-networked harder, stronger, more brittle than thermoplastics |