Uhlíkové nanotrubice. Rozdělení, struktura. Eva Košťáková KNT, FT, TUL

Transkript

1 Uhlíkové nanotrubice Rozdělení, struktura Eva Košťáková KNT, FT, TUL

2 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.

3 Formy uhlíkových materiálů Diamant Grafit Fuleren C 60 Fuleren C250 Amorfní uhlík Nanotrubice

4 Formy uhlíkových materiálů Čistý uhlík je obecně znám ve dvou molekulárních formách: diamant, grafit. Diamant Krystalizace v kubické struktuře nejčastěji v osmistěnech. Grafit Ve formě grafitu uhlík krystalizuje ve vrstvách.

5 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.

6 Fullereny Představují třetí známou formu uhlíku! Od C20 dále (mimo C22)

7 C20 C60

8 Uhlíkové nanomateriál - Fullereny Pak téměř pro každý sudý počet atomů uhlíku (vyjma 22) existuje další fulleren. C540 Nejméně stabilní C 20 pravidelný dvanáctistěn jehož stěny jsou pětiúhelníky. Fulereny jsou kulovité (často mnohostěnné) obří molekuly tvořené dvaceti a více atomy uhlíku.

9 Uhlíkové nanomateriály kulovité fullereny Fuleren C 60 Uhlík je čtyřmocný! Výjimečné postavení má C60 nejkulatější, nejsymetričtější. Nejobvyklejší fuleren C 60 (povrchové napětí) Mezi šestiúhelníky musí být pětiúhelníkové poruchy vytvoření uzavřeného prostorového útvaru. CENA: Sigmaaldrich.com C60 25mg = 1300Kč (97% čistota), 1kg = 21000Kč

10 Jméno fulleren dle podoby ke kopulím geodetických budov architekta Richard Buckminster Fullera == Buckminsterfullerene C60 The first fullerene to be discovered, and the family's namesake, was buckminsterfullerene C 60, 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. Nobelova cena za chemii

11 Fulereny jsou kulovité (často mnohostěnné) obří molekuly tvořené dvaceti a více atomy uhlíku. nano-onions Fullerene (Buckyball) colloids, 1,000,000X. The nucleus to nucleus diameter of a C 60 molecule is about 0.71 nm

12 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 Sumio Iijima (born 1939) is a Japanese physicist, often cited as the discoverer of carbon nanotubes.

13 SWNTs (single wall nanotubes) jednostěnné uhlíkové nanotrubice Diameter of SWNTs Optimal 1,4nm Possible 0,4 2,5 nm

14 TEM microstructure of SWNT-rope

15 Carbon nanotubes - struktura a) Zigzag structure b) Armchair structure c) Chiral structure 3. CARBON NANOTUBES, NANOFIBERS AND NANOWIRES 1

16 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".

17 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

18 A "zig-zag" carbon nanotube. A chiral" carbon nanotube. A arm-chair" carbon nanotube.

19 chiral" "zig-zag"

20 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 singlewalled 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.

21 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

22 1 Postup při kreslení nanotrubic CH 3 CH

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25 MWNTs (multi wall nanotubes)

26 TEM microstructure of MWNTs and nanoparticle

27 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

28 c-mwnts (multi wall nanotubes) cb-mwnts (bamboo multi wall nanotubes) Vícestěnná uhlíková trubice typu bambus

29 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.

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31 h-mwnts ( herringbonemwnts rybí kost) hb-mwnts (bamboo herringbone multi wall nanotubes)

32 Hetero-nanotubes or - 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.

33 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.

34 Under electron irradiation in TEM mesurements, the fullerenes become mobile and merge to a second tube inside the tube

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36 Nanotrubice se dají plnit oxidy kovů Ni, Co, Fe, Zr, Cd, Sn atd. a čistými kovy Ag, Au, Pd, Rh atd a fulereny. Ag MWNT Snaha o výrobu extrémně jemných kovových drátků významné zlepšení elektrických vlastností.

37 Cena uhlíkových nanotub SWNTs 70%purity 1g = 300Euro MWNTs 90%purity 1kg = 1000Euro MWNTs 95%purity 1g = 40 Euro MWNTs 95%purity surface modified 1g = 50-65Euro

38 Orientace MWNTs

39 ZÁKLADNÍ VLASTNOSTI CNTs Comparison of mechanical properties [ Material Young's Modulus Tensile strength Elongation at break (%) (TPa) (GPa) SWNT ~1 (from 1 to 5) E 16 Armchair SWNT 0.94 T T 23.1 Zigzag SWNT 0.94 T 94.5 T Chiral SWNT 0.92 MWNT E E Stainless Steel ~0.2 ~ Kevlar ~0.15 ~3.5 ~2 Kevlar T E Experimental observation; T Theoretical prediction

40 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 A/cm 2 which is more than 1,000 times greater than metals such as copper [25].

41 Carbon nanofibers: no hollow, diameter - between nm, 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. 3. CARBON NANOTUBES, NANOFIBERS AND NANOWIRES 32