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Lecture Presentation
Chapter 23
Metals and
Metallurgy
Sherril Soman
Grand Valley State University
© 2014 Pearson Education, Inc.
Vanadium
• Petroleum is often contaminated with vanadium.
– It’s believed that some ancient forms of life that
decomposed to form oil used vanadium compounds for
oxygen transport.
• Vanadium and many of its compounds are toxic
and regulated by the EPA.
• Vanadium must be removed from petroleum before
it is sold.
• Research is currently ongoing to use metallurgy to
economically remove and recover vanadium so it
can be sold and used in other ways.
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What Do We Need Vanadium For?
• Vanadium is a soft, ductile, silver-gray metal.
• Vanadium has good resistance to corrosion.
• Vanadium is unreactive with alkalis, sulfuric acid,
and hydrochloric acids.
• Vanadium is oxidized in air at
about 660 ° C, although an oxide layer
forms even at room temperature.
• Most vanadium is used to alloy with
iron to increase the strength of steel.
• V2O5 is a catalyst used in the production
of sulfuric acid, the largest chemical industry.
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General Properties and Structure of Metals
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Opaque
Good conductors of heat and electricity
High malleability and ductility
In the electron sea model, each metal atom
releases its valence electrons to be shared by all
the atoms in the crystal.
• The valence electrons occupy an energy band
called the valence band that is delocalized over the
entire solid.
• However, each metal has its own unique properties
to be accounted for.
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Properties of Some Metals
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Distribution of Metals in Earth
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Metals make up about 25% of Earth’s crust.
Aluminum is the most abundant.
Alkali and alkali earth metals make up about 1%.
Iron is only the transition metal > 5%.
Only Ni, Cu, Ag, Au, Pd, Pt are found in native form.
– Noble metals
• Most metals are found in minerals.
– Minerals are natural, homogeneous crystalline
inorganic solids.
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Mineral Sources of Common Metals
• NaCl = halite; KCl = sylvite
 Both recovered from evaporated sea water
• Fe2O3 = hematite; TiO2 = rutile; SnO2 = cassiterite
• PbS = galena; HgS = cinnabar; ZnS = sphalerite;
MoS = molybdenite; VS4 = patronite
• [Pb5(VO4)3Cl] = vanadinite
 Found mainly at upper levels of galena mines
• [K2(UO2)2(VO4)2 · 3 H2O] = carnotite
 Found as crusts or flakes with sandstone
 Source of V, U, and Ra (because Ra is found with U)
• [Fe(NbO3)2] = columbite; [Fe(TaO3)2] = tantalite
 Found in mixed deposits
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Metallurgy
• A rock containing a high concentration of a
particular mineral is called an ore.
• The mineral must first be separated from the
surrounding ore material by physical means.
• Extractive metallurgy consists of chemical
processes that separate a metal from its mineral.
• Refining consists of processes that purify the
metal for use.
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Separation
• The first step is to crush the ore into small particles.
• The mineral is then separated from the gangue by
physical means.
– The gangue – the undesirable material in the ore
– Using cyclonic winds to separate by density
– Froth flotation in which the mineral is treated with a
wetting agent to make it more attracted to the froth and
floated off the mineral
– Electrostatic separation of polar minerals
– Magnetic separation of magnetic minerals
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Separation Methods
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Pyrometallurgy
• In pyrometallurgy, heat is used to extract the metal
from the mineral.
• Some minerals can be decomposed on heating into
volatile materials that will vaporize easily, leaving
the metal behind—this is called calcination.
– Or drive off the water of hydration
• Pyrometallurgy is an expensive process due to the
high cost of the heat energy required.
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Pyrometallurgy
• Heating a mineral so that it will react
with furnace gases is called roasting.
• If the roast product is a liquid, it’s
called smelting.
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Pyrometallurgy
• If some byproduct of the roasting doesn’t
volatilize and escape, a flux can be added to
react with the nonvolatile gangue to create a low
melting waste product that is easy to separate.
 A flux is a chemical that reacts with a material to form a
lower melting or highly volatile material.
• The waste liquid is called the slag.
• The slag separates from the molten metal
by density.
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Hydrometallurgy
• The use of aqueous solutions to extract the metal
from its mineral is called hydrometallurgy.
• Gold is often extracted by dissolving it in NaCN(aq).
4 Au(s) + 8 CN−(aq) + O2 (g) + 2 H2O(l) → 4 Au(CN)2−(aq) + 4 OH−(aq)
– Leaching
– After the impurities are filtered off, the Au is reduced back
to the metallic form.
2 Au(CN)2−(aq) + Zn(s) → Zn(CN)42−(aq) + 2 Au(s)
• Some minerals dissolve in acidic, basic,
or salt solutions.
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Electrometallurgy
• Using electrolysis to reduce the metals from the
mineral is called electrometallurgy.
• The Hall process is a method for producing
aluminum metal by reducing it from its mineral
bauxite (Al2O3 · nH2O).
– Bauxite melts at a very high temperature.
– To reduce the energy cost, bauxite is dissolved in the
molten mineral cryolite (Na3AlF3).
– Electrolysis of the solution produces molten Al.
• Electrolysis is also used to refine metals extracted by
other methods.
– For example, copper
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Production of Aluminum
• Bauxite is separated from other minerals by
reacting it with a concentrated NaOH(aq) solution
at high pressure and 150–200 ° C.
 The Bayer process
 Hydrometallurgy
• The solution is filtered to remove the gangue.
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Production of Aluminum
• Al(OH)3 is precipitated out.
• Al(OH)3 is converted to Al2O3 by heating.
• Al2O3 is mixed with the mineral cryolite (Na3AlF6)
and heated to 1000 ° C.
Al2O3 · n H2O(s) + 2 NaOH(aq) + 2 H2O(l) → 2 NaAl(OH)4(aq)
• Electrolysis of the molten mixture produces molten
aluminum.
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Hall Process − Electrolysis of Al2O3
Dissolved in Molten Cryolite
Oxidation: C(s,gr) + 2 O2−(dissolved) → CO2(g) + 4 e−
Reduction: Al3+(dissolved) + 3 e− → Al(l)
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Production of Copper
• Crushed copper minerals are separated from gangue by froth flotation.
 Main mineral chalcopyrite, CuFeS2
• This concentrated mixture is then dried and fed into a furnace for roasting.
 Or fed directly onto a reactor bed for flash smelting
2 CuFeS2(s) + 3 O2(g) → 2 FeO(s) + 2 CuS(s) + SO2(g)
• Limestone and silica are added and the mixture is smelted to remove iron.
 The iron oxides and sulfides are converted to slag and floated.
• The remaining copper sulfides are converted to blister copper by blowing
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hot air through the molten sulfides.
The copper blister is refined by electrolysis.
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Electrolytic Refining of Copper
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Powder Metallurgy
• Micron-sized powdered metal particles are
compressed into a component.
– Oxidized powdered mill scraps are reduced.
– Or, a stream of pure molten metal is atomized by blasting it
with a stream of cold water.
• The component is heated until the metal particles
fuse—called sintering.
– The particles never get hot enough to completely melt.
– This increases the strength and density of the metal.
• Advantages over milling or casting
– It produces no scrap.
– Intricate pieces can be made that would be difficult to cast.
– It allows for making pieces from high melting metals that
would require very high heat to cast.
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Structures of Metals
• Metal structures are generally the closest packing
of spheres.
– Most are cubic closest packed, hexagonal closest packed, or
body-centered cubic.
• The exact crystal structure may change with
temperature and pressure.
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Structures of Metals
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Alloys
• Alloys are metals that contain more than one type
of material.
– A base metal and alloying materials
• Alloys show metallic properties.
• Most common physical properties of alloys are
often averages of the component metals.
• However, engineering properties may be quite
different than the components.
– Like tensile strength and shear strength
• Most melt over a large temperature range rather
than having a fixed melting point.
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Alloy Composition
• Some alloys are solid solutions with variable
composition.
– Steel = Fe, C, and other metals
– Brass = Cu and Zn
– Bronze = Cu and Sn
• Some have fixed composition like a compound.
– Intermetallic compounds – solids with different crystal
structures than any of their components
– Alnico − used for its magnetic properties
– NiTi − memory metal
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Types of Alloys
• In substitutional alloys, one metal atom
substitutes for another.
– Crystal structure may stay the same or change
– Brass
• In interstitial alloys, an atom fits between the
metal atoms in the crystal.
– Usually a small nonmetal atom
– At low concentrations, best described as a solution
– At high concentrations, better described with a
stoichiometric formula
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Substitutional Alloy: Substituting Nickel
into Copper
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Binary Phase Diagrams
• These diagrams show the
phase an alloy is in at
different temperatures
and alloy composition.
• The area above the phase
boundary line is the
liquid state.
• The phase boundary line is the
melting point curve for the solid
solution.
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Substitutional Alloys: Miscible Solid
Solutions
• The phase-composition
diagram for Cu–Ni alloys
shows a smooth increase
in melting point from the
lower melting Cu to the
higher melting Ni.
• The alloys all have the
face-centered cubic
crystal structure as the Cu
and Ni are similar sizes.
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Substitutional Alloys: Miscible Solid
Solutions
• The phase-composition
diagram for Cr–V alloys do
show a smooth increase in
melting point.
• The dip in the curve
indicates that some of the
alloys melt below either of
the pure metals.
• The composition that gives
the lowest melting point is
called the eutectic mixture.
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Substitutional Alloys: Limited Solubility
Solid Solutions
• Because of their
different crystal
structures, some metals
are not miscible.
• At some intermediate
composition, the crystal
structure has to
change.
• The result is alloys with
two different crystal
structures and
intermediate area(s)
where both exist.
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Substitutional Alloys: Two Phase Region
• At point A, the alloy is
50 mole percent Ni and
50 mole percent Cr.
• There is too much Cr to
all fit into the facecentered cubic structure
of the Ni.
– Pure Cr is body centered.
• The extra Cr form their
own body-centered cubic
crystals with some
substituted Ni.
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Substitutional Alloys: The Lever Rule
• The lever rule tells us that
in a two-phase region,
whichever phase is closest
to the composition of the
alloy is the more
abundant phase.
• Because point A is closer
to the face-centered cubic
region than to the bodycentered cubic region,
there are more fcc crystals
in the solid alloy.
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Interstitial Alloys
• H, B, N, C can often fit in the holes in a closest
packed structure.
• Formula of alloy depends on the number and type
of holes occupied.
• Interstitial alloys are often harder and denser than
the base metals because more of the space in the
crystal is occupied.
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Octahedral Hole
An atom with maximum radius 41.4% of the metal
atom’s radius can fit in an octahedral hole.
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Tetrahedral Holes
An atom with maximum radius 23% of the metal
atom’s radius can fit in a tetrahedral hole.
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Interstitial Alloys
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Titanium
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Ninth most abundant element on Earth
Fourth most abundant metal
Minerals rutile (TiO2) and ilmenite (FeTiO3)
Very reactive
Oxidizes in the presence of O2 and N2
– Needs to be arc-welded under inert atmosphere
• Resists corrosion because of a tightly held oxide coat
• Stronger than steel, but half the density
• Denser than aluminum, but twice as strong
– Used to make jet engine parts
• Alloyed with 5% Al and trace amounts of Fe, Cr, Mo
• Most common use is as TiO2 in paint as white pigment
– Large rutile TiO2 crystals resemble diamonds.
– It is produced from ilmenite.
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Chromium
• Forms many compounds with different colors
• Mineral chromite (FeCr2O4)
– Which is reduced with Al
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White, hard, lustrous, brittle
Cr dissolves in HCl and H2SO4, but not HNO3
Mainly used as alloy to make stainless steel
Compounds used as pigments and wood
preservatives
• Toxic and carcinogenic
• Oxidation states +1 to +6
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Chromium
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Manganese
• Mineral pyrolusite (MnO2), hausmannite (Mn3O4)
and rhodochrosite MnCO3
– Which is reduced with Al or Na
– Heating impure pyrolusite with C produces alloy
ferromanganese
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Mn very reactive, dissolves in acids
Used as alloy to make stainless steel
Compounds used as glass additives
Oxidation states +1 to +7
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Cobalt
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Mineral cobaltite (CoAsS)
Ferromagnetic
Mn very reactive, dissolves in acids
Used as alloy to make high-strength steels
– Carbaloy
• Used to make magnets
• Compounds with deep blue colors, used in pigments
and inks
• Covitamin of B12
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Copper
• Found in its native form
• Minerals are chalcopyrite (CuFeS2), malachite (Cu2(OH)2CO3)
• Reddish color
– Used in ornamentation and jewelry
• High abundance and concentration = useful industrially
• Easy to recycle
• Second best electrical conductor – used in electrical wiring
and devices
• High heat conductivity – used in heat exchangers
• Used in water piping because of its resistance to corrosion
• Long exposure to environment produces a green patina –
mainly malachite and brohchanite (Cu4SO4(OH)6)
• Strong metal – so used to alloy with metals where strength
is needed
– Bronze = Cu and Sn
– Brass = Cu and Zn
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Brass – a Mixture
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Copper
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Nickel
• Comes from meteor crater in Ontario
• Nickel sulfides roasted in air to form oxides, and
then reduced with carbon
• Separated by converting to volatile Ni(CO)4, which
is later heated to decompose back to Ni
• Ni not very reactive and resistant to corrosion
• Used as an alloying metal in stainless steel,
especially where corrosion resistance is important
– Monel metal
– Used in armor plating
• Ni metal plated onto other metals as protective coat
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Zinc
• Minerals sphalerite (ZnS), smithsonite (ZnCO3), and
franklinite (Zn, Fe, and Mn oxides)
• Minerals roasted in air to form oxides, and then reduced
with carbon
• Used in alloys with Cu (brass) and Cu and Ni (German brass)
• Reactive metal
• Resists corrosion because it forms an adhering oxide coat
• Galvinizing – plating Zn onto other metals to protect them
from corrosion
– Both coating and sacrificial anode
• Zinc compounds used in paints for metals
– If scratched, becomes sacrificial anode
• Zinc phosphate used to coat steel so that it may be painted
• Considered safe – used to replace Cr and Pb additives
– Though some evidence it may be an environmental hazard
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Zinc Phosphate Adhering to Steel Surface
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