Rozdělení, struktura¡sk… · 20 –pravidelný dvanáctistěn jehož stěny jsou...
Transcript of Rozdělení, struktura¡sk… · 20 –pravidelný dvanáctistěn jehož stěny jsou...
Uhlíkové nanotrubice
Rozdělení, struktura
Eva Košťáková
KNT, FT, TUL
UHLÍK
Uhlík je chemický prvek, tvořící základní kámen všech
organických sloučenin a tím i všech živých organizmů.
Charakteristickou vlastností atomů uhlíku je schopnost
vytvářet řetězce, což je dáno mimořádnou pevností
jednoduché a dvojné vazby C-C.
Diamant Grafit
Fuleren C60 Fuleren C250
Amorfní uhlíkNanotrubice
Formy uhlíkových materiálů
Diamant Grafit
Formy uhlíkových materiálů
Čistý uhlík je obecně znám ve dvou molekulárních formách: diamant, grafit.
Krystalizace v kubické struktuře
nejčastěji v osmistěnech. Ve formě grafitu uhlík krystalizuje ve vrstvách.
Grafit
Struktura grafitu je vysoce anizotropní.
Je tvořen grafenovými vrstvami.
V jejich rovině jsou atomy pojeny pevnými
kovalentními vazbami
Ve směru kolmém na tyto vrstvy jsou
slabé vazby – Van der Waalsovy.
Fullereny
Představují třetí známou formu uhlíku!
Od C20 dále (mimo C22)
C20 C60
Uhlíkové nanomateriál - Fullereny
Nejméně stabilní C20 – pravidelný dvanáctistěn jehož stěny jsou
pětiúhelníky.
Fulereny jsou „kulovité“ (často mnohostěnné)
obří molekuly tvořené dvaceti a více atomy uhlíku.
Pak téměř pro každý sudý
počet atomů uhlíku (vyjma 22)
existuje další fulleren.
C540
Uhlíkové nanomateriály – kulovité fullereny
Fuleren C60
Uhlík je čtyřmocný!
Výjimečné postavení má C60 – nejkulatější, nejsymetričtější.
Nejobvyklejší fuleren C60 (povrchové napětí)
Mezi šestiúhelníky musí být pětiúhelníkové poruchy –
vytvoření uzavřeného prostorového útvaru.
CENA: Sigmaaldrich.com C60 25mg = 1300Kč (97% čistota), 1kg = 21000Kč
Jméno fulleren – dle podoby ke kopulím geodetických budov architekta
Richard Buckminster Fullera == Buckminsterfullerene C60
Nobelova cena za chemii - 1996
The first fullerene to be discovered, and the family's
namesake, was buckminsterfullerene C60, made in 1985 by
Robert Curl, Harold Kroto and Richard Smalley.
By 1991, it was relatively easy to produce gram-sized samples
of fullerene powder
Kroto, Curl, and Smalley were awarded the 1996 Nobel Prize
in Chemistry for their roles in the discovery of this class of
compounds.
Fullerene (Buckyball) colloids, 1,000,000X.
http://www.nature.com/nnano/journal/v1/n2/full/nnano.2006.62.html
The nucleus to nucleus diameter of a
C60 molecule is about 0.71 nm
nano-onions
Fulereny jsou „kulovité“ (často mnohostěnné)
obří molekuly tvořené dvaceti a více atomy
uhlíku.
Uhlíkové nanomateriál – válcovité
fullereny - Nanotrubice
A large percentage of academic and popular
literature attributes the discovery of hollow,
nanometer-size tubes composed of graphitic carbon
to Sumio Iijima in 1991.
Sumio Iijima (born 1939) is a Japanese physicist,
often cited as the discoverer of carbon nanotubes.
SWNTs (single wall nanotubes) –
jednostěnné uhlíkové nanotrubice
Diameter of SWNTs
Optimal 1,4nm
Possible 0,4 – 2,5 nm
TEM microstructure of SWNT-rope
3. CARBON NANOTUBES, NANOFIBERS AND NANOWIRES 1
Carbon nanotubes - struktura
a) Zigzag structure
b) Armchair structure
c) Chiral structure
Most single-walled nanotubes (SWNT)
have a diameter of close to 1 nanometer,
with a tube length that can be many
millions of times longer. The structure of a
SWNT can be conceptualized by wrapping
a one-atom-thick layer of graphite called
graphene into a seamless cylinder. The
way the graphene sheet is wrapped is
represented by a pair of indices (n,m)
called the chiral vector. The integers n and
m denote the number of unit vectors along
two directions in the honeycomb crystal
lattice of graphene. If m = 0, the nanotubes
are called "zigzag". If n = m, the nanotubes
are called "armchair". Otherwise, they are
called "chiral".
Multi-walled nanotubes (MWNT) consist of multiple rolled layers
(concentric tubes) of graphite. There are two models which can be used
to describe the structures of multi-walled nanotubes. In the Russian Doll
model, sheets of graphite are arranged in concentric cylinders, e.g. a
(0,8) single-walled nanotube (SWNT) within a larger (0,10) single-walled
nanotube
A "zig-zag" carbon nanotube.
A „arm-chair" carbon nanotube.
A „chiral" carbon nanotube.
The end caps of a nanotube are
one of a half bucky ball and the
repeating axial hexagonal
patterns are graphite structures;
however, the electrical
properties of nanotubes are
dependent on the precise
orientation[5] of the repeating
hexagons. The nanotubes can
be semiconductors (similar to
“doped silicon” used in
integrated circuits) or metal-like
conductors (such as copper
used as electric wiring). The
inset micrographs show the
orientation axes that distinguish
between these electronic
behaviors. These micrographs
also show another important
development – that of single-
walled nanotubes or SWNT.
Using optimum synthesis
conditions one can make SWNT
tubes with diameters of 1.38 ±
0.02 nm, very close to the
diameter of geometrically ideal
nanotubes.
Optimální průměr SWNT = 1,4nm
Kolik šestiúhelníků je v obvodu takové
trubice, např. při uspořádání zig-zag?
Vzdálenost atomů uhlíku v
šesterečné struktuře je 1,44 Å
CH3
CH3
1
2
34
5
Postup při kreslení nanotrubic
MWNTs (multi wall nanotubes)
TEM microstructure of MWNTs and nanoparticle
the multi-walled nanotubes
are concentric (a good
analogy is a Russian
babushka doll). The inset
diagram shows micrographs
for 5, 2 and 7 MWNT
respectively from left to right
c-MWNTs (multi wall nanotubes)
cb-MWNTs (bamboo multi wall nanotubes)
Vícestěnná uhlíková trubice typu „bambus“
Typical TEM images of BCNTs grown at 850 ºC using a 10 wt.% Cu/Mo/MgO catalyst: (a) low magnification TEM image of BCNTs, (b) TEM image of catalyst particles located inside and at the tips of
the nanotubes, (c) TEM image of carbon nanotubes filled with a catalyst nanoparticle which is responsible for the formation of BCNTs with an outer diameter of 20 nm, (d) a high-resolution TEM
image of a BCNT with the curved graphite sheets.
www.azonano.com/Details.asp?ArticleID=2037
www.materials.ox.ac.uk/peoplepages/grobert.html
h-MWNTs ( herringboneMWNTs – rybí kost)
hb-MWNTs (bamboo herringbone multi wall nanotubes)
Hetero-nanotubes
X@SWNT or X@MWNT - Hybrid carbon nanotubes
An uncapped single-wall carbon nanotube with
encapsulated buckyballs. This type of tube is
sometimes referred to as a ‘peapod’ carbon nanotube.
Nanotube peapod – hrachový lusk
If the nanotube is big enough, there
is room for metal atoms, molecules,
and even fullerenes to fit inside.
A nanotube filled with fullerenes is
known as a "peapod". A model of a
peapod is shown below.
Under electron irradiation in TEM mesurements, the fullerenes
become mobile and merge to a second tube inside the tube
http://iffwww.iff.kfa-juelich.de/~cmeyer/filling/fillCNTs.html
Nanotrubice se dají „plnit“ oxidy kovů Ni, Co,
Fe, Zr, Cd, Sn atd. a čistými kovy Ag, Au, Pd,
Rh atd a fulereny.
http://gtresearchnews.gatech.edu/newsrelease/NANOTUBE.html
MWNT
Ag
Snaha o výrobu extrémně jemných kovových drátků – významné zlepšení elektrických vlastností.
SWNTs – 70%purity 1g = 300Euro
MWNTs – 90%purity 1kg = 1000Euro
MWNTs – 95%purity 1g = 40 Euro
MWNTs – 95%purity surface modified 1g = 50-65Euro
Cena uhlíkových nanotub
Orientace MWNTs
ZÁKLADNÍ VLASTNOSTI CNTs
Comparison of mechanical properties[
Material Young's Modulus
(TPa)
Tensile strength
(GPa)
Elongation at break (%)
SWNT ~1 (from 1 to 5) 13–53E
16
Armchair SWNT 0.94T
126.2T
23.1
Zigzag SWNT 0.94T
94.5T
15.6–17.5
Chiral SWNT 0.92
MWNT 0.8–0.9E
11–150E
Stainless Steel ~0.2 ~0.65–3 15–50
Kevlar ~0.15 ~3.5 ~2
KevlarT
0.25 29.6
EExperimental observation; TTheoretical prediction
ZÁKLADNÍ VLASTNOSTI CNTs
Because of the symmetry and unique electronic structure of
graphene, the structure of a nanotube strongly affects its electrical
properties. For a given (n,m) nanotube, if n = m, the nanotube is
metallic; if n − m is a multiple of 3, then the nanotube is
semiconducting with a very small band gap, otherwise the nanotube
is a moderate semiconductor. Thus all armchair (n = m) nanotubes
are metallic, and nanotubes (5,0), (6,4), (9,1), etc. are
semiconducting. In theory, metallic nanotubes can carry an
electrical current density of 4 × 109 A/cm2 which is more than 1,000
times greater than metals such as copper[25].
3. CARBON NANOTUBES, NANOFIBERS AND NANOWIRES 32
Carbon nanofibers: no hollow, diameter -
between 50-200nm, length – several
micrometers.
Carbon nanotubes: presence of hollow, -
from 1nm to several tens of micrometers (It
depends on number of walls), length – several
micrometers.
Nanowires: presence of hollow, - Not from
CARBON, from 1nm to several tens of
micrometers (It depends on number of walls),
length – several micrometers.