metals with minimla chemical reactivity - resits oxidation, corrosion, tarnsih

metals Flashcards by Abigail Cook

noble metal

metals with minimla chemical reactivity

resits oxidation, corrosion, tarnsih

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precious metal

have intrinsic value, noble +silver

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base/ non-precious metal

inexpensive non noble metals

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Pt stands for

platinum (platinum group of noble)

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Pd stands for

Palladium (platinum group of noble)

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Ir stands for

Iridium (platinum group of noble)

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Rh stands for

Rhodium (platinum group of noble)

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Os stands for

Osmium (platinum group of noble)(platinum group of noble)

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Ru stands for

Ruthenium (platinum group of noble)

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Au stands for

Gold

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characteristics of gold

soft, malleable, primary compoennt of alloys

resistant to oxidation / corrosion

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gold in contact with what causes problem?

maybe next to amalgam

- current set up and get mercury release

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carat and fineness of gold

100% =
75%

24K = 100% - 1000 fine

18K = 18/24=75% Au = 75 fine

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Tm of gold

1063 degrees celcius

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effects of adding platinum

tough, ductile, malleable, alloy with gold to INCREASE HARDNESS AND STRENGTH 
improve color (its silver) 
Tm = 1755

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palladium addition?

similar to platinum
- substituted for pt in alloys to increase strength
silver alloy inhibits corrosion and absorbs H during casting

Tm = 1555

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iridium and ruthenium addition?

GRAIN REFINERS

0.0005%
SMALLER CRYSTALS AND HIGHER CRYSTAL CONTENT –> IMPROVED MECHANICAL PROPERTIES

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Rhodium addition?

allow with pt- thermocouples

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what type of metal is silver
abbreviation?
highest/best what?
reactive with?

Ag - precious metal
- malleable, ductile, best electrical and thermal conductor

very reactive with sulfur, chlorine, and phosphorus

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silver often in combination with?

Palladium

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base metal that is used a lot?

copper

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Cu is?

Copper

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charactersitics of copper

good thermal/ electrical conductor

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Cu-Zn alloy is?

Brass

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copper and gold form

different crystal structures - depending on treatment of the casting (like heat treating) can adjust the properties HEAT HARDENING / SOFTENING WITH THIS SO SOLID SOLUTION WITH AU

PHASE OF AU-CU IS DEPENDENT ON? what are they

the temperature 1. solid solution - when >424 (above) degrees celcius 2. intermetallic ordered phase when <424 AuCu3 ALTERS MECHANICAL PROPERTIES

solid solution of Au and Cu

random orientation | material that is more flexible

ordered phase of Au and Cu

material is stronger and less flexible

SOLID SOLUTION ARRANGEMENT

more random

intermetallic compoiunf alloy

secific composition - single phase stronger but more brittle

heat treatment to soften?

QUENCH in water immediatley | 700 celcius for 10 minutes

heat treatment to harden

450 celcius for 2 minutes cool to 250 celcius in 30 minutes

if want to seal margins? want to amke something stiffer

quench, cast , throw in water cool and then put into water

heat treatment effect on hardening

1. increased tensile strength 2. increased yield strength 3. increased hardness 4. decreased elongation

Type I -IV detnal gold casting | properties as go from I-IV

Au content decreases from I-IV - harndess increases - strenght increaeses - mechnical properties increase - Cu content increases - can increase size of restoration usually - metling range decreases - changing mechanical properties

best mechanical properties in what type of alloy?

Type IV goes up from type I - to type IV IV -- brdiges and partial denture framework

Type I can be used for restoring?

Class III and V | - small restorations

Type II can be used for restoring?

medium harness, inlays

Type III can be used for restoring?

inlays onlays crowns bridges

Type IV can be used for restoring?

crowns, bridges, partial denture framework

ability tomburnish harden as go from type I to type IV

``` decreases I -- maximal II- yes III- some IV - minimal ```

ability to heat harden from type I to type IV?

``` increases I- none II- minimal III - moderate IV - maximal (50%) ```

long spanding bridge impliciation

more deformation that is likely to occur | so increase the elastic modulus to decrease the deformation

T/F you can heat harden to increase the elastic modulus?

YES -- so consider doing this for a bridge framework

Bridges take into account what law? stress =? deformation=?

Law of beams stress = 3x load x length /2x width x thickness deformation = loadx length / 4x elastic modulus x width x thickness

low noble metal alloys used for?

PFMs | Type A, B, and C

general properties of low noble metal allows of type A, B, and C

1. higher mechanicla properties than type IV 2. low elongation 3. high hardness 4. high strenght Type C has lowest yield strength

are low noble metal allows burnishable? resitant to corrosion?

not burnishible but corrosion resistant

* quenching a casting in water versus slow cooling

quench = malleable -- like sealing the margins slow cool = harden --> resist deformation like in bridges

can you seal the margins / want to seal the margins?

ask lab to quench it

when / why harden a casting?

bridge

type what for bridge? wtype for inlay?

type III / IV - bridge inlay I (small) or type II

globing warming is caused by

lack of pirates

Types of alloys for metal-ceramic restorations

type 1-6 alloys noble metal allloys 1-3 non-noble types 4-6

mechanical properties and usual makeup of noble metal ceramic alloys

usually gold, platinum, palladium, easy to work with, adjust, and nice bonds formed

*what is used to bond the surface of the metal to the porcelain/ ceramic?

oxide layer -- by adding alloys added indian or tin

type 4-6

base metals type 4 - Ni-Cr type 5 - Co- Cr Type 6 - titanium alloy

base metals usually create what type of oxide layer?

thick - so resoration may be hard to look esthetics can create problems with fracture if too thick

importance of In or Sn

noble- metal- ceramic alloys and are primarily added to improve the bonding to the porcelain by creating an oxide layer

Pt and Pd with effect with noble metal - ceramic alloys

increase mechanical properties | - alter the thermal expansion coefficient and increase melting range

T/F base metals are difficult to cast

true

*True or false base metal- ceramic alloys may contain Ni

TRUE | - allergies to the base metals

reason for porcelain de-bonding with base metal ceramic alloys

oxide bonding layer too think also leads to poor estehtics due to dark oxide layer on the metal

what are base metals used for?

PFM's

Composition of base metal alloys

cast cobalt - chromium- nickel alloys Minimum 85% Co Cr and Ni minimum 20% Cr

yield strenght of base metals

500 MPa

what is major use of cromium in base metals

prevent corrosion

uses of Co-Cr-Ni

removable partial denture framework crown and bridge bone plates, screws

implication of nickel

allergies!

do vitallium and nobillium have nickel?

does ticonium have nickel

yes (no Co) | this is a lot!

what happens if there is too much carbon?

the framework can become too brittle and break more easily

*RPD alloys commonly used?

1. Vitallium 2. Ticonium (contains Ni!!) 3. Nobilium