Environmental Engineering Reference
In-Depth Information
This.topic.focuses.on.a.subset.of.materials.that.are.in.or.have.the.potential.to.be.
in.the.widest.use.at.the.nano.scale:
Titanium.dioxide:.particles.of.TiO 2 .at.the.nanometer.scale.
Zero-valent.iron:.particles.of.Fe 0 .
Silver:.particles.of.Ag.
Carbon.black:.particulate.form.of.elemental.carbon.
Carbon.nanotube:.hollow.tube,.commonly.made.of.a.single.layer.of.carbon.
atoms.(single-walled.carbon.nanotube).or.multiple.layers.(multi-walled.car-
bon.nanotube)..Nanotubes.also.can.incorporate.materials.other.than.carbon.
Fullerene:.also.known.as.a.“buckminsterfullerene”.or.“buckyball,”.a.fuller-
ene.is.a.hollow.sphere..The.term.commonly.refers.to.C60.fullerenes.com-
prising.60.carbon.atoms..Other.fullerene.structures,.such.as.C70.and.C120,.
exist.
Information.about.this.subset.of.nanomaterials.will.provide.the.reader.with.an.
overview.of.the.range.of.manufacturing.processes,.physical.characteristics,.and.toxi-
cological. effects. of. nanoscale. materials.. Table.2.1. summarizes. information. about.
the. structure. and. composition. of. the. speciied. nanomaterials. and. indicates. some.
of.their.uses..The.focus.on.these.materials.continues.through.subsequent.chapters.
of.this.topic.on.the.manufacture.of.nanomaterials,.fate.and.transport,.and.potential.
toxicological.effects.
The.sections.that.follow.provide.more.information.about.the.classiication,.prop-
erties,.and.uses.of.common.nanomaterials.
.  ClassiFiCation oF nanosCale MateRials
Classiication.schemes.used.to.describe.nanomaterials.continue.to.evolve,.but.gener-
ally.recognize.the.origin.of.the.material,.whether.it.is.ixed.in.a.structure.or.free,.its.
shape,.and/or.its.composition.
2.2.1  O rigin
Some. nanoscale. materials. occur. naturally.. Examples. include. volcanic. ash. and.
viruses.. Human. activities. can. generate. nanoscale. materials. as. incidental. byprod-
ucts..Diesel.exhaust.particles.and.byproducts.of.welding,.for.example,.can.be.in.the.
nanoscale.range.[3,.5]..This.topic.focuses.on.intentionally.manufactured.nanoscale.
materials,.however,.and.not.on.these.naturally.occurring.or.incidental.materials.
2.2.2  C OmpOsitiOn and  s truCture
Nanoscale. materials. can. be. made. of. elemental. carbon,. carbon-based. compounds,.
metals.or.metal.oxides,.or.ceramics..They.can.take.many.shapes..These.generally.
include.the.following.structures:
Particles.or.crystals
Tubes,.wires,.or.rods
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