Nanoscopic Materials Atomď Molecules 1 Nanoscale Particles 125 70,000 Condensed Matter 6x106 oc N° Atoms Quantum Chemistry 1 ^ 10 ■ 100 oc Diameter(nm) Solid State Physics Nanomaterials 1 Nanostructural Materials "Prey", the latest novel by Michael Crichton, author of "Jurassic Park". The horrible beasties threatening humanity in this new thriller are not giant dinosaurs, but swarms of minute "nanobots" that can invade and take control of human bodies. Last summer, a report issued by a Canadian environmental body called the action group on erosion, technology and concentration took a swipe at nanotechnology. It urged a ban on the manufacture of new nanomaterials until their environmental impact had been assessed. The group is better known for successfully campaigning against biotechnology, and especially against genetically modified crops. The research, led by a group at the National Aeronautics and Space Administration's Johnson Space Centre in Houston, has found in preliminary studies that inhaling vast amounts of nanotubes is dangerous. Since they are, in essence, a form of soot, this is not surprising. But as most applications embed nanotubes in other materials, they pose little risk in reality. Nanomaterials 2 ■ .. ■ .. ■ .. ■ .. Room at the Bottom What I want to talk about is the problem of manipulating and controlling things on a small scale ... As soon as I mention this, people tell me about miniaturization, and how far it has progressed today. They tell me about electric motors that are the size of the nail on your small finger. And there is a device on the market, they tell me, by which you can write the Lord's Prayer on the head of a pin. But that's nothing; that's the most primitive, halting step in the direction I intend to discuss. It's a staggeringly small world that is below. In the year 2000, when they look back at this age, they will wonder why it was not until the year 1960 that anybody began seriously to move in this direction...... Prof. Richard Feynman in "There's plenty of room at the bottom", lecture delivered at the annual meeting of the APS, Caltech, 29 December, 1959. Nanomaterials Nanoscale Writing i Dip-Pen Nanolithography AFM Tip \ WrtOnfl if taction Watvr Nanoscale writing with an AFM (Mirkin et al.) 3 Sijori os I ment Tor. T-h's* people tel ! me atoj^ m'niortür' zať on, and nov.- rar *"•: ^as progf^ň^rd *-uííoy. TI ŕLj rŕl1 m* obout frfec^rlc mor or = f,K3tr or ŕ T-n? &íz* rf *he na r I on uolf" small Finger. Rr,J 0 t-re ía a device ir"» T. Ke r*1 irket. ^ney *. 11 "ie. b^ ».-.'h'ch Hej :3n i^ítŕ t he Ldrďe Prayer oci t, h e head i p "n. B^t chart's npfeMng) vhaťb +.-Se "los** prfm"l fwf. hnj| t. ; ruj iVtľp I" th^- d*reů^-tOn X "^*ra3 ta d'scu-sä. 1^ F« o &^. cnA*ŕ " ng ' lj srna1 í ',-yjr'd t^-a't is befow. In Tne year 20G0, when *n^ij ,ook bork at- +,rťift "jo*?- tní'ij '-ví t I wOndp'- .jhu 'I u«j!t nat unTvl I the uear Í^EO Jth,ííJ|L- orybudy, be^ar ítrToosty ta mow* In this dľF 400 nm Rrthard P. reunrr.an. 13E0 Nanomaterials Nanoscopic Materials How big is nano? smaller - 10 million times ------------------► smaller d = 10 nm i What Changes? Size is another variable to change physical and chemical properties Nanomaterials 5 5871 Nanoscopic Materials Small Negligible light scattering New optics Quantum size effects Information technology, Storage media High surface area Catalysts, Adsorbents Large Interracial area New composites Surface modifications Targeted Drug Delivery Nanomaterials 6 ■ .. ■ .. ■ .. ■ .. Nanoscopic Materials Nanoscale regime Size 1 - 100 nm (traditional materials > 1 |um) Physical and chemical properties depend on the size !! Natural examples: © Human teeth, 1-2 nm fibrils of hydroxyapatite Ca5(P04)3(OH) + collagen ©Asbestos, opals, calcedon © Primitive meteorites, 5 nm C or SiC, early age of the Solar system Nanomaterials 7 ■ .. ■ .. ■ .. ■ .. Nanoscopic Materials Nanoparticles 1 - 100 nm 5 nm itional materials > 1 |um 1 jim I 1 um Z/tm Nanomaterials . . texture / morphology V 0.] mm 0-5 Dm 1,0 n m L5 Dim 3.0 am 8.0 nm 0.8 |im Mill tun NMR XRll TEM EXAFS STM KANES EKR UV SAXS SEM OM Nanomaterials The nano-Family At least one dimension is between 1-100 nm 0-D structures (3-D confinement): • Quantum dots • Nanoparticles 1-D structures (2-D confinement) • Nanowires • Nanorods • Nanotubes CdTe NPs < 100 nm II Si/Ge/Si/Ge Superlattice 2-D structures (1-D confinement): • Thin films • Planar quantum wells • Superlattices Nanomaterials 10 CARBON NANOTUBES 1. A unique species somewhere between traditional carbon fibers and novel farms Of carbon Such as lulleren». 2. A seamless cylindrical-sheet cf-graphite whose diameter is ao small anrf hba aa* ptct rile o töiam rter n. I enslh) li-ia great that it < an be con side >ed ftom ihe electronic point oľview as a cnr-dimr nsiorcil structure. There are two sorts -of carbon nariotubts. One is muln-shellnanotubes andth* other is slnejlt-snelinanotubes. The Former nav* two or «or* layers such as the leňVside figure b*low and about 2 to 20 nm diameterwhileihe latter have only one layer and about 1 to 2 nm diameter. Both are a few tens of microns long. In mul: - sh(i I nanotupes. the wer layer spa< ma it "9,34 nm. in K etn cases. * seh < arten ?tom 15 cpmpkíf ly bonded to p right o mi n carbon atoms throuali sp* nybridiza,-tion to form a seamless shelf.Tn the absence of external strain, carbon nanotubes are always straight unless t arbon rings having a number of cartons defiant: horn sl» (pentagons, nepteaons. eetaaons. etc] are present in the ne-xetjonel netweiK. mrtfubq Eakdn using FEM cir^nn ranylktes and EHrtt^li-y (S0(|iCe1(lnD' P U Anfín] [So^ĎS (řWI ĎI H M ^IW) Nanomaterials Coherence Length k. a) XRD patterns of iron oxide nanocrystals of 4, 6, 8, 9,10,11,12,13, and 15 nm (311) [440] -í- 15 nm 13 nm ^^----------12 nm •11 nm b) O^ ___ -10 «0 t I I I I II 32 33 3J 35 3£ 17 3ft 39 20 — ------------► E0------ ---------¥ . Nanomaterials . 12 - Surface Effects Decreasing grain size = Increasing volume fraction of grain boundaries (50% for 3 nm particles) BBS* 100 Ü t 3 C/> C O 3 CD 90- 90 O < 20 ^----------------------- Bulk Atoms Surface Atoms '**•••« •***• 10 —f— IS -1-20 25 —f— Jí 3£ Particle Size(nm) Nanomaterials 13 Surface Effects Dispersion F = the fraction of atoms at the surface F is proportional to surface area divided by volume N = total number of atoms V ~ r3 ~ N F 1 1 \[Ň F ■n Q (ň t_ CJ G. 1.0- 0,8- . k 0.6-0-4 0.2 0-0 ■ - ■ \ 20 A 0 n = N 1-3 80 MX n = number of atoms at the cube edge Nanomaterials 14 Surface Effects Atoms at surfaces have fewer neighbours than atoms in the bulk lower coordination and unsatisfied bonds surface atoms are less stabilized than bulk atoms The smaller a particle the larger the fraction of atoms at the surface, and the higher the average binding energy per atom. the melting and other phase transition temperatures scale with surface-to-volume ratio and with the inverse size Example: the melting point depression in nanocrystals 2.5 nm Au particles 930 K bulk Au 1336 K Nanomaterials 15 ■ .. ■ .. ■ .. ■ .. coordination number . 10 -z. z. V 3 6 D.I Surface Effects 309 N 103 55 N 1.'3 23 Q.15 0.2 0.25 0.3 0.35 0.4 Calculated mean coordination number as a function of inverse radius, represented by N~1/3 for Mg clusters (triangles = icosahedra, squares = decahedra, diamonds = hep Nanomaterials Surface Effects Atom binding (vaporization) energies lower in nanoparticles, ■ fewer neighbors to keep atoms from escaping Plasticity of nanocrystalline ceramics ■ ■ Nanomaterials 17 Surface Effects Properties of grain boundaries >Lower coordination number of atoms > Reduced atomic density (by 10 - 30 %) >Broad spectrum of interatomic distances . Experimental evidence >HREM >EXAFS, reduced number of nearest and next-nearest neighbors > Raman spectroscopy > Mössbauer spectroscopy, quadrupole splitting distribution broadened >Diffusivity enhanced by up to 20 orders of magnitude !! > Solute solubility in the boundary region ^Si Ag (fee) and Fe (bec) immiscible in (s) or (1), but do form solid solution as nanocrystalline alloy >EPR, nano-Si gives a sharp signal Nanomaterials 18 m_____m_ rpb m Gibbs-Thomson Equation ■Bfcft i in nanopartiqles.fionfinfirtin ,por, ej,,, 2V'r mol f si m Tm = mp of the cluster with radius r Tmb = mp of the bulk Vmo/ = the molar volume of the liquid y sl = the interfacial tension between the s and 1 surface AHm = the bulk latent heat of melting 0 - DSC a) d-SOi nm t>)d = 34,3nm c) d~ J2.8 nm d) d=5.6 nm .,. .. ■ ...J-, ,al .,,,J-.--------- -lj' ■--■■■ ■! ■ ■- ■-------■ I--.......I-. .-■ . Nanomaterials - 375 3S5 395 405 415 425 435 445 Temperature (K) Phase Transitions Phase transitions are collective phenomena With a lower number of atoms in a cluster a phase transition is less well defined, it is therefore broadened Small clusters behave more like molecules than as ° bulk matter 435 ■ i ' ::__:___:__:____bd líc; 425 • InCPG 415 ^»v« ° Tn VyCOť j S 405 H ■ 395 *^^. tt$ 'iTí b} ■ J f J 000 0.05 0.10 0,15 0,20 l/d (1/nm) o - IPIIPIIIIJII I P I I I ■ I j ■ I II I 1 I I 1| IPI I Jl II I I I II MPIPI|PMIMIII|II1I II I IP a) d-S0i nm t>) d = 34,3 nm c)d-J2.3nm á) d=5.6 nm ■ ■■■ .. ■ .-.É_. ■-. .--.J-. . .1.. .. ■■ 375 3S5 395 405 415 425 435 445 Temperature (K) '■ Surface Effects Correlation between the unit-cell volume (cubic) and the XRD particle size in y-Fe203 nanoparticles 80 120 XRD porticLe size Nanomaterials 21 Surface Effects The inter-ionic bonding in nanoparticles has a directional character ions in the outermost layer of unit cells possess unpaired electronic orbitals associated electric dipole moments, aligned roughly parallel to each other point outwards from the surface the repulsive dipolar interactions increase in smaller particles reduced by allowing unit cell volume to increase Nanomaterials 22 ■ .. ■ .. Quantum Confinement Effects Physical and chemical properties depend on the size !! 1 ® Finite-size effects [ MO to Band transition \ Conduction J Band CT* ____ i ^o =. LUMO v»v sp3----------- ! ^ s' HOMO •-'" Bond Gap Eg u / /// /A Valence ^—\ ^^= \ 3 y/y// *P3 Local 5iH ' y^^^ Atomic Bond Molecular Orbitals Hybrid Basis Orbitals Density of States Si Atom Si2 Diatonic Si/« Crystalline Si Nanomaterials 23 Metal-to-Insulator Transition EF 5 = 0 6kT bulk metal S»kT metallic clusters insulating clusters atoms & & particles & particles molecules increasing diameter n u cle arity decreasing Nanomaterials 24 Bulk Mciais C _u Nanocrystal Isolated atom r :Fermi S Semiconductors E? :z u Unoccupied Occupied Density of states • * ■*■«•* Unoccupied -'Fermi Occupied Density of states Nanomaterials 25 Metal-to-Insulator Transition Band gap increases with decreasing size ■. 10 100 1000 10,000 Particle diameter (d/A) iNaiiumaieiiais Metallic behavior Single atom cannot behave as a metal nonmetal to metal transition 100-1000 atoms Magnetic behavior Single domain particles large coercive field 26 Metal-to-Insulator Transition \ * STM 1-0 1 \% O HREM ~~l*>- J 1 1 1 1 i_ VO 2-0 3.0 4.0 5-0 5-0 dia /nm The increase in the core-level binding energy in small particles poor screening of the core charge the size-induced metal-nonmetal transition in nanocrystals Variation of the shift, AZľ, in the core-level binding energy (relative to the bulk metal value) of Pd with the nanoparticle diameter Nanomaterials 27 Electrical Conductivity Bulk value Particle size Nanomaterials 28 6s HOMO c S u _Ü I o ^rr 10 15 30 65 100 180 250 I I V E í j.^. JĽ±- E I1 i' M 5 4 s: 6 5 4 3 2 Bincfing Energy/eV 6p LUMO 1 o Photoelectron spectra of Hg clusters of nuclearity n The 6p peak moves gradually towards the Fermi level the band gap shrinks with increase in cluster size Nanomaterials 29 a) a) Absorption spectra of CdSe nanocrystals (at 10 K) of various diameters b) Wavelength of the absorption threshold and band gap as a function of the particle diameter for various semiconductors. The energy gap in the bulk state in parenthesis 1 21 Á diameter 2.4 2good sinterability >high catalytic activity > difficult handling > adsorption of gases and impurities >poor compressibility PREPARATION METHODS Top-down: from bulk to nanoparticles Bottom-up: from atoms to nanoparticles Nanomaterials 33 ■ .. ■ .. ■ .. a) Variation of the nonmetallic band gap with nanocrystal size b) in CdS nanocrystals a) 2.2 e 1 B g IS 1 M 1 7 Un □ S + ^ GO oah ' ' ' ■ ti- _ i □ Pd + Cd AA9 I J J.M1 0.1 TŮ SO 100 150 200 25D Volume rnmJ b) 5 uj 4 - 3- d.'nm Nanomaterials Nanoscopic Materials NANO -particles, crystals, powders -films, patterned films -wires, rods, tubes -dots Nanostructured materials = nonequilibrium character >good sinterability >high catalytic activity > difficult handling > adsorption of gases and impurities >poor compressibility PREPARATION METHODS Top-down: from bulk to nanoparticles Bottom-up: from atoms to nanoparticles Nanomaterials 35 ■ .. ■ .. ■ .. Bottom-up Synthesis: Atom Up Sixteen componenls assemble into supramolecular mgcrocyde O-Cu- Nanomaterials 36 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis ${ Atom Aggregation Method GEM - gas evaporation method 4- evaporation by heating - resistive, laser, plasma, electron beam, arc discharge -$- the vapor nucleates homogeneously owing to collisions with the cold gas atoms -$- condensation in an inert gas (He, Ar, IkPa) on a cold finger, walls - metals, intermetallics, alloys, SiC, C60 in a reactive gas 02 Ti02, MgO, A1203, Cu20 N2, NH3 nitrides in an organic solvent matrix Nanomaterials 37 ■ .. ■ .. ■ .. NANOSTRUCTURAL MATERIALS Bottom-up Synthesis SMAD - the solvated metal atom dispersion 1 - 2 g of a metal, 100 g of solvent, cooled with liquid N2 more polar solvent (more strongly ligating) gives smaller particles Ni powder: THF < toluene < pentane = hexane Carbide formation 77 to 300 K 180 °C> octane TVi/Vl + nrntnnr k IVi C TT k IVi C J^i^fe/ peil um e w rMix^yXiz w w\^^ Nanomaterials 38 NANOSTRUCTURAL MATERIALS Bottom-up Synthesis *& Thermal or Sonocative Decomposition of Precursors Fe(CO)5 ---------► nc-Fe + 5 CO sono [Co(en)3]W04 _____► nc-WC - 23% Co Ar, 1500 °C PhSi(OEt)3 + Si(OEt)4 + H20 --------► gel----------------► ß-SiC (CH3SiHNH)n (1) ---------► Si3N4 + SiC laser 3on-4nn°r M(BH4)4 (g) ___________^ borides MB2+X (M = Ti, Zr, Hf) Si(OEt)4 + Ag+ or Cu2+ + H20 --------► Si02/Ag+/Cu2+ H2,550°C -------------------► Si02/Ag/Cu Nanomaterials 39 ■ .. ■ .. ■ .. NANOSTRUCTURAL MATERIALS Bottom-up Synthesis ^ Reduction of Metal Ions Borohydride Reduction - Manhattan Project Aqueous, under Ar 2 Co2+ + 4 BH4 + 9 H20 -----► Co2B + 12.5 H2 + 3 B(OH)3 Under air d Cn R + ^ O k S Cn + *> R O t \^U2i» ~ J w2 ™ o KsU i £ r>2v^3 Nonaqueous Co + dH4 + diglyme + to + H2 + B2rl6 . TiCl4 + 2 NaBH4 ------------► TiB2 + 2 NaCl + 2 HCl + H2 ifV _i_ n "IVľlí ÍTrlľ* TT1 k T\T _i_ XTTÍ Y _i_ n TÍIľ + _i_ n H TT IVlAjj + n IM K.4 [1511/1311] r 1V1 + IM K.4A + n KH^ + n/Z tl2 M = group 6 to 11; n = 2,3; X = Cl, Br mixed-metal particles Nanomaterials 40 - NANOSTRUCTURAL MATERIALS Bottom-up Synthesis Au colloidal particles HAuCl4 + NaBH4 in toluene/H20 system, TOABr as a phase transfer agent, Au particles in the toluene layer, their surface covered with Br, addition of RSH gives stable Au colloid \ fee / s- «CIV8 ,s s Nanomaterials 41 Bottom-up Synthesis Arrested Growth Atomization -i> Growth H> Quenching -$ Stabilization SHi Nanomaterials 42 Two-dimensional array of thiol-derivatised Au particles (mean diam 4.2 nm) jfi 5.2 ŮS diam*Ur(rim] Nanomaterials d = t.5nm Ô (degrees) 43 TEM micrograph of hexagonal arrays of thiolized Pd nanocrystals: a) 2.5 nm, octane thiol b) 3.2 nm, octane thiol Nanomaterials 44 C/í nm d /nm C4 /0.8 Cg/u ci2/u c,e/2.i ! 1.8 2.5 2,3 á 3.1 /Ľ.l 1.5 ^.'2 ft 1 *v 3.2 \ 4.0 • 2.7 U LSI 1 K, 4.5 r» .6 6.0 ,7.5 5.0 3Ä""'ü^2.«^r The í/-/ phase diagram for Pd nanocrystals thiolized with different alkane thiols. The mean diameter, oř, obtained by TEM. The length of the thiol, /, estimated by assuming an a\\-irans conformation of the alkane chain. The thiol is indicated by the number of carbon atoms, Cn. The bright area in the middle encompasses systems which form close-paced organizations of nanocrystals. The surrounding darker area includes disordered or low-order arrangements of nanocrystals. The area enclosed by the dashed line is derived from calculations from the soft sphere model Nanomaterials 45 NANOSTRUCTURAL MATERIALS Alkali Metal Reduction in dry anaerobic diglyme, THF, ethers, xylene NiCl2 + 2 K -> Ni + 2 KCl AICI3 + 3K^ Al + 3 KCl Reduction by Glycols or Hydrazine "Organically solvated metals" K + Mg Nanomaterials Alkalide Reduction 13 K+(15-crown-5)2Na- + 6 FeCl3 + 2CBr4 THF -30 °C 2 Fe3C (nano) + 13 K(15-crown-5)2Cl0 43Br0 57 + 13 NaCl ■ Anealed at 950 °C / 4 h 3 *t~JÉÍ ••• * Fe3C: 2-15nm * * • • • 4 * • ■já ^BFJ 47 Nanomaterials . ■ ' NANOSTRUCTURAL MATERIALS Bottom-up Synthesis 1% Reactions in Porous Solids - Zeolites, Mesoporous materials Ion exchange in solution, reaction with a gaseous reagent inside the cavities M2+ + H2E --------►ME M = Cd,Pb;E = S,Se Ship-in-the-Bottle Synthesis Ru3+ + Na-Y--------► Ru(III)-Y Ru(III)-Y + 3 bpy---------► Ru(bpy)32+ reduction of Ru(III) Conducting carbon wires Acrylonitrile introduced into MCM-41 (3 nm diam. channels) Radical polymerization Pyrolysis gives carbon filaments Nanomaterials 48 - NANOSTRUCTURAL MATERIALS Bottom-up Synthesis 3<: Gel or Polymer Matrices # Sol-Gel Method Aerogels, supercritical drying 1% Aerosol Spray Pyrolysis Aqueous solution, nebulization, droplet flow, solvent evaporation, chemical reaction, particle consolidation, up to 800 °C 3Gd(N03)3 + 5 Fe(N03)3 --------► Ga3Fe5012 + 6 02 + 24 N02 MnCl2 + 2 FeCl3 + 4 H20 ---------► MnFe204 + 8 HCl Mn(N03)2 + Fe(N03)3 no go, why? Nanomaterials 49 ■ .. ■ .. ■ .. NANOSTRUCTURAL MATERIALS ${ Inverse Micelles Bottom-up Synthesis o H20 + octane IIIMIIIMIIII -o ° o............ o Cd o oH2o iiiiiiiiiii IIIMIIIMIIII Se2" '"O Ô O'........... O H20 O p0q llllllllllllll IIMIIIMIII "oXo-...... O (cdSejO- PhSeSiMe3 ©-(CdSe Nanomaterials 50 254 1 Éiw/A* ** * * i **" 9 nm Number of comited particles: 204 Average size: 9.04 mn Standard deviation: 0.33 nm (3.7%) 55 50 45 43 35 % 30 25 2ZI 15 1G 7-7.5 7.5-8 8-8.5 8.5-9 9-9.5 9.5- 10- 10.5- 10 10.5 11 Size (nm) Nanomaterials 51 NANOSTRUCTURAL MATERIALS Properties on Nanostructured Materials ® Metallic behavior Single atom cannot behave as a metal nonmetal to metal transition : 100-1000 atoms ® Magnetic behavior Single domain particles, large coercive field ® Depression of melting points in nanocrystals bulk Au mp 1064 °C 10 nm Au 550 °C Nanomaterials 52 - LaMer mechanism Supersaturated solution Burst of nucleation Slow growth of particles without additional nucleation Separation of nucleation and growth Nanomaterials 53 ■ .. ■ .. ■ .. ■ .. Watzky-Finke mechanism Slow continuous nucleation Fast autocatalytic surface growth Nanomaterials 54 Seed-mediated mechanism Au nanoclusters as seeds Bi, Sn, In, Au, Fe, Fe304 Nanomaterials 55 Other mechanisms Digestive rippening Surfactant exchange Nanomaterials 56 Thermal Decomposition of Precursors 350 °C, 1 h Fe(CO) oleic acid trioctylamine - Fe 350 °C, lh Me3NO Fe203 6 nm ön m Separation of nucleation and growth Fe(CO)5 thermal decomposition at 100 °C contributes to nucleation VCtí Fe(oleate) thermal decomposition at 350 °C contributes to growth 5 nrtfv ■- o Nanomaterials 57 Top-down Synthesis: Bulk Down Nanomaterials 58 NANOSTRUCTURAL MATERIALS Top-down Synthesis: Bulk Down 5Z Introduction of Crystal Defects (Dislocations, Grain Boundaries) ^High-Energy Ball Milling final size only down to 100 nm, contamination -♦■ Extrusion, Shear, Wear ^High-Energy Irradiation -♦■ Detonative Treatment 1% Crystallization from Unstable States of Condensed Matter *♦• Crystallization from Glasses -^Precipitation from Supersaturated Solid or Liquid Solutions Nanomaterials 59 ■ .. ■ .. a) XRD patterns of iron oxide nanocrystals of 4, 6, 8, 9,10,11,12,13, and 15 nm (311) [440] -1- —r— -1-60 b) CW> ___ 4nm firm >■ — Sum ft - - flnm j!; —- 10nrn í i _._ 11 nm I &k------- 12rirn 13nm #s\nk —r" ~ 15nm i* V- m 41 *H I"- 1 1 1U /■ V U íl! * A' JL * íŕ^wfe T^/ ^3*&» Ü ~" i ■ 32 33 34 35 3E 17 3ft 34 2íř se— Nanomaterials 60 --------v Nanomaterials 61 NANOSTRUCTURAL MATERIALS ® Optical properties nc-Ti02 is transparent Blue shift in optical spectra of nanoparticles 1.2 10Ä 300 60 A T 400 500 600 Wavelength (nm) Nanomaterials 62 NANOSTRUCTURAL MATERIALS ©Atom binding (vaporization) energies lower in nanoparticles, fewer neighbors to keep atoms from escaping (E) Plasticity of nanocrystalline ceramics Nanomaterials 63 Electrical conductivity 1 _<_<__ _ _ -_ B kompaktu i My* 10 i '''r- Nanomaterials 64 Applications Destruction of dangerous organic compounds (organophosphates - VX, chlorinated - PCB) 400 °C 800 °C 850°C II C2H* ^/ || CH3 O 750oc O Ú í HEAT HEAT Figure 3. Cleavages of bonds in (C3HsO)sP(0) and DMMP under thermal decomposition condition. 170°C /C2H5 600°C 170°CX II MgO Figure 4. Cleavages of bonds of (C2H50)3P{0) and DMMP on MgO, Nanomatenals Asymmetrie heterogeneous catalysis on nanoparticles ■ . ■ _ * OH.............o ] O R + CH3NO2- AM rr NHr ...■> OH Nanomaterials 66 CNT growth 67