1 Intimate mixing of components in solution, precipitation, filtration, washing, drying, calcination High degree of homogenization Large contact area Reduction of diffusion distances Faster reaction rates Lower reaction temperatures Metastable phases, smaller grain size, larger surface area Precursor Methods 2 Coprecipitation Method Coprecipitation applicable to nitrates, acetates, oxalates, hydroxides, alkoxides, beta-diketonates Requires: similar salt solubilities similar precipitation rates no supersaturation Washing: water, organic solvents Drying: evaporation azeotropic distillation freeze-drying Disadvantage: difficult to prepare high purity, accurate stoichiometric phases if solubilities do not match 3 Spinels oxalates: Zn(CO2)2/Fe2[(CO2)2]3/H2O 1 : 1 mixing, H2O evaporation, salts coprecipitation Solid-solution mixing on atomic scale, filter, calcine in air Zn(CO2)2 + Fe2[(CO2)2]3 ZnFe2O4 + 4CO + 4CO2 Al2O3 Bayer Process bauxite Al(OH)4 - Al(OH)3 -Al2O3 Fe(OH)3, TiO2, SiO2 BaTiO3 BaCl2 + TiOCl2 + 2 H2C2O4 + 4 H2O + Ln dopants BaTiO(C2O4)2.4H2O + 4 HCl filtration, washing, drying, calcination @ 730 °C NaOH, p CO2 1500 °C Coprecipitation Method 4 Spinel Al(NO3)3 + Mg(NO3)2 + H2O freeze-drying gives amorphous mixture, calcination @ 800 °C !!! low T Mg(NO3)2 + 2 Al(NO3)3 MgAl2O4 + 6 NOx + (10-3x)O2 random Ruby Ion exchange Al(NO3)3 + Cr(NO3)3 Al(OH)3 + Cr(OH)3 sol freeze drying gives solid (Al/Cr)(OH)3 @ LN2 temperature, 5 Pa anealing @ 950 °C for 2.5 h gives solid solution Al2-xCrxO3 Zirconia ZrSiO4(zircon) + NaOH Na2ZrO3 + Na2SiO3 ZrOCl2 Zr(OH)4 / Y(OH)3 nano-Y/ZrO2 HCl OH- , YCl3 azeot. dist. calcination Coprecipitation Method 5 High-Tc Superconductors La3+ + Ba2+ + Cu2+ + H2C2O4 ppt La1.85Ba0.15CuO4 Magnetic garnets, tunable magnetic materials Y(NO3)3 + Gd(NO3)3 + FeCl3 + NaOH YxGd3-xFe5O12 Firing @ 900 o C, 18-24 hrs, pellets, regrinding, repelletizing, repeated firings, removes REFeO3 perovskite impurity Isomorphous replacement of Y3+ for Gd3+ on dodecahedral sites, solid solution, similar rare earth ionic radii complete family accessible, 0 < x < 3, 2Fe3+ Oh sites, 3Fe3+ Td sites, 3RE3+ dodecahedral sites 1373 K Coprecipitation Method 6 COOH COOH COOH HO Pechini and Citrate Gel Method Aqueous solution of metal ions Chelate formation with citric acid Polyesterification with polyfunctional alcohol on heating further heating leads to resin, transparent glassy gel calcination provides oxide powder control of stoichiometry by initial reagent ratio complex compositions, mixture of metal ions good homogeneity, mixing at the molecular level low firing temperatures 7 BaTiO3 by conventional powder method at 1200 °C Ba2+ + Ti(Oi Pr)4 + citric acid at 650 °C Sc2O3 + 6 HCOOH 2Sc(HCOO)3 + 3 H2O MnCO3 + 2 HCOOH Mn(HCOO)2 + CO2 + H2O added to citric acid, water removal, calcination @ 690 °C gives ScMnO3 without citric acid only mixture of Sc2O3 and Mn2O3 is formed Pechini and Citrate Gel Method 8 Chromite spinel Precursor Ignition T, o C MgCr2O4 (NH4)2Mg(CrO4)2.6H2O 1100-1200 NiCr2O4 (NH4)2Ni(CrO4)2.6H2O 1100 MnCr2O4 MnCr2O7.4C5H5N 1100 CoCr2O4 CoCr2O7.4C5H5N 1200 CuCr2O4 (NH4)2Cu(CrO4)2.2NH3 700-800 ZnCr2O4 (NH4)2Zn(CrO4)2. 2NH3 1400 FeCr2O4 (NH4)2Fe(CrO4)2 1150 Double salts of known and controlled stoichiometry such as: Ni3Fe6(CH3COO)17O3(OH).12Py Burn off organics 200-300 oC, then 1000 oC in air for 2-3 days Product highly crystalline phase pure NiFe2O4 spinel Good way to make chromite spinels, important tunable magnetic materials Juggling the electronic-magnetic properties of the Oh and Td ions in the spinel lattice Double Salt Precursors 9 Compounds containing desired elements in a proper stoichiometric ratio Easy chemical pathway for ligand removal M O Si O O O H2O + (M-O-SiO3) x Single Source Precursor 10 Vegard law behavior: Any property P of a solid-solution member is the atom fraction weighted average of the end-members The composition of the A1-xBx alloy can be calculated from Vegard's law The lattice parameter of a solid solution alloy will be given by a linear dependence of lattice parameter on composition: a(A1-xBx) = x a(B) + (1-x) a(A) Vegard's Law 11 Vegard's Law c(CdSe1-xSx) = x c(CdS) + (1-x) c(CdSe) 12 P (YxCe!-xRhIn5) = x P (YxCe!-xRhIn5) + (1-x) P (YxCe!-xRhIn5) Any property P of a solid-solution member is the atom fraction weighted average of the end-members Vegard's Law Tetragonal lattice constant a as a function of Y concentration x for the Ce1-xYxRhIn5 system 13 Vegard's Law A linear relationship exists between the concentration of the substitute element and the size of the lattice parameters The direction of the linear relationship, increasing or decreasing, depends upon the system being analyzed As the concentration of Y is increased, lattice constant a decreases, implying the cell is contracting along the a axis 14 Vegard's Law Vegard law behavior: P (YxGd3-xFe5O12) = x/3 P (Y3Fe5O12) + (3-x)/3 P (Gd3Fe5O12) Any property P of a solid-solution member is the atom fraction weighted average of the end-members 15 Tunable magnetic properties by tuning the x value in the binary garnet YxGd3-xFe5O12 3 Td Fe3+ sites, 5 UPEs 2 Oh Fe3+ sites, 5UPEs Ferrimagnetically coupled material, oppositely aligned electron spins on the Td and Oh Fe3+ magnetic sublattices Counting spins Y3Fe5O12 ferrimagnetic at low T: 3 x 5 - 2 x 5 = 5UPEs Counting spins Gd3Fe5O12 ferrimagnetic at low T: 3 x 7 - 3 x 5 + 2 x 5 = 16 UPEs YxGd3-xFe5O12 creates a tunable magnetic garnet that is strongly temperature and composition dependent, applications in permanent magnets, magnetic recording media, magnetic bubble memories and so forth, similar concepts apply to magnetic spinels 16 Molten salts (inert or reactive), oxides, metals MNO3, MOH, (M = alkali metal) FLINAK: LiF-NaF-KF M2Qx (M = alkali metal, Q = S, Se, Te) molten salts ionic, low mp, eutectics, completely ionized act as solvents or reactants, T = 250-550 °C enhanced diffusion, reduced reaction temperatures in comparison with powder method products finely divided solids, high surface area (SA) slow cooling to grow crystals separation of water insoluble product from a water soluble flux incorporation of the molten salt ions in product prevented by using salts with ions of much different sizes than the ones in the product (PbZrO3 in a B2O3 flux) Flux Method 17 Lux-Flood formalism oxide = strong base acid = oxide acceptor A + OB AO + B base = oxide donor Zr(SO4)2 + eut. (Li/K)NO3 ZrO2 Zr(SO4)2 + eut. (Li/K)NO2 ZrO2 ZrOCl2 + eut. (Na/K)NO3 ZrO2 amorph. t- ZrO2 ZrOCl2 + YCl3 + eut. (Na/K)NO3 ZrO2 BaCO3 + SrCO3 + TiO2 + eut. (Na/K)OH cubic-Ba0.75 Sr0.25TiO3 700 K 540 K 520 K 720 K 570 K Flux Method 18 fly ash (aluminosilicates) NaOH, NH4F, NaNO3 zeolites (sodalite, cancrinite) NH4H2PO4 + (Na/K)NO3 + M(NO3)2 (Na/K)MPO4 4 SrCO3 + Al2O3 + Ta2O5 Sr2AlTaO6 900 °C in SrCl2 flux 1400 °C required for a direct reaction K2Tex + Cu K2Cu5Te5 K2Tex reactive flux, 350 °C Flux Method 19 Electrolysis in molten salts Reduction of TiO2 pellets to Ti sponge in a CaCl2 melt at 950 °C O2- dissolves in CaCl2, diffuses to the graphite anode insulating TiO2 TiO2-x conductive graphite anode anodic oxidation 2 O2- O2 + 4 e- cathode TiO2 pellet cathodic reduction Ti4+ + 4 e- Ti Flux Method 20 Organic cations (containing N, P) Inorganic anions: Cl- , AlCl4 - , Al2Cl7 - , Al3Cl10 - , PF6 - , SnCl3 - , BCl3 - , BF4 - , NO3 - , OSO2CF3 - (triflate), CH3C6H4SO3 - , N(SO2CF3)2 - , PO4 3- N N N N (CH2 )n NN N N N HO OH Ionic Liquids 21 Oldest known (1914) : EtNH3 + NO3 - mp 12 °C Liquids at room temperature or low mp Thermal operating range from -40 °C to 400 °C Higly polar, noncoordinating, completely ionized Nonvolatile ­ no detectable vapor pressure Nonflamable, nonexplosive, nonoxidizing, high thermal stability Electrochemical window > 4V (not oxidized or reduced) Immiscible with organic solvents Hydrophobic IL immiscible with water Ionic Liquids 22 Ionic Liquids 23 Synthesis of Ionic Liquids NR3 + RCl [NR4]+ Cl- Aluminates [NR4]+ Cl- + AlCl3 [NR4]+ [AlCl4]- Metal halide elimination [NR4]+ Cl- + MA MCl + [NR4]+ A- Reaction with an acid [NR4]+ Cl- + HA HCl + [NR4]+ A- Ion exchange [NR4]+ Cl- + Ion exchanger A [NR4]+ A- 24 Halogenoaluminate(III) Ionic Liquids The most widely studied class of IL High sensitivity to moisture ­ handling under vacuum or inert atmosphere in glass/teflon RCl + AlCl3 R+ [AlCl4]- 2 [AlCl4]- [Al2Cl7]- + Cl- autosolvolysis Keq = 10-16 to 10-17 at 40 C 2 [Al2Cl7]- [Al3Cl10]- + [AlCl4]- Acidic: excess of AlCl3 as [Al2Cl7]- x(AlCl3) > 0.5 Basic: excess of Cl- x(AlCl3) < 0.5 Neutral: [AlCl4]- x(AlCl3) = 0.5 25 Equilibria in Halogenoaluminate(III) IL Equilibria in IL X1 = Cl- X4 = [AlCl4]- X7 = [Al2Cl7]- X10 = [Al3Cl10]- X13 = [Al4Cl13]- X6 = Al2Cl6 26 Halogenoaluminate(III) Ionic Liquids 2 [AlCl4]- [Al2Cl7]- + Cl- autosolvolysis Keq = 10-16 to 10-17 at 40 C Acidic IL with an excess of AlCl3 HCl + [Al2Cl7]- H+ + 2 [AlCl4]- Proton extremely poorly solvated = high reactivity Superacid [EMIM]Cl/AlCl3/HCl H0 = -19 (HSO3F: H0 = -15) Latent acidity MCl + [Al2Cl7]- M+ + 2 [AlCl4]- buffered IL B + M+ + [AlCl4]- MCl + B-AlCl3 27 Superacidity 28 Superacidic [EMIM]Cl/AlCl3/HCl log Kb in HF I = not protonated II = slightly protonated III and IV = 10-20 % V = 75-90% VI-VIII = nearly completely IX and X = completely 29 Compound mp (K) Compound mp (K) Na13[La(TiW11O39)2] 253.0 Na13[Tm(TiW11O39)2] 260.2 Na13[Ce(TiW11O39)2] 263.0 Na13[Yb(TiW11O39)2] 267.2 Na13[Pr(TiW11O39)2] 253.0 Na5[CrTiW11O39] 261.5 Na13[Sm(TiW11O39)2] 256.0 Na5[MnTiW11O39] 253.0 Na13[Gd(TiW11O39)2] 265.1 Na5[FeTiW11O39] 257.6 Na13[Dy(TiW11O39)2] 265.2 Na6[ZnTiW11O39] 257.4 Na13[Er(TiW11O39)2] 261.0 Completely inorganic ionic liquids Ionic Liquids 30 Melting Point of Ionic Liquids Phase diagram of [EMIM]Cl/AlCl3 Melting point is influenced by: Cation ­ low symmetry, weak imtermolecular interactions, good distribution of charge Anion ­ increasing size leads to lower mp Composition ­ Phase diagram 31 Melting Point of Ionic Liquids 32 Density of Ionic Liquids The density of IL decreases as the bulkiness of the organic cation increases: 33 Viscosity of Ionic Liquids The viscosity of IL depends on: van der Waals interactions H-bonding 34 Solubility in/of Ionic Liquids Variation of the alkyl group Increasing nonpolar character of the cation increases solubility of nonpolar solutes. Water solubility depends on the anion water-soluble [BMIM] Br, CF3COO, CF3SO3 Water-immiscilble [BMIM] PF6 (CF3SO2)2N IL miscible with organic solvent IF their dielectric constant is above a certain limit given by the cation/anion combination Polarity by E(T)(30) scale [EtNH3][NO3] 0.95 between CF3CH2OH and water [BMIM] PF6 as methanol 35 Solubility in/of Ionic Liquids 36 Applications of Ionic Liquids Electrodeposition of metals and alloys (also nanoscopic) Al, CoAlx, CuAlx, FeAlx, AlTix Semiconductors Si, Ge, GaAs, InSb, CdTe Electrodeposition of a Bi-Sr-Ca-Cu alloy (precursor to SC oxides) Melt of MeEtImCl at 120 C BiCl3, SrCl2, CaCl2, CuCl2 dissolve well Constituent BiCl3 SrCl2 CaCl2 CuCl2 Concentration 0.068 0.50 0.18 0.050 (mol kg-1 MeEtImCl) Substrate Al -1.72 V vs the Ag/Ag+ reference electrode 37 Biphasic solvent systems Preparation of aerogels 2 HCOOH + Si(OMe)4 ag-SiO2 + 2 MeOH + 2 HCOOMe Natural gas sweetening (H2S, CO2 removal) Electrolytes in batteries or solar cells Dissolving spent nuclear fuel (U4+ oxidized to U6+ ) Extraction Enyzme activity Applications of Ionic Liquids 38 Applications of Ionic Liquids Olefin polymerization Ethene + TiCl4 + AlEtCl2 in acidic IL Ethene + Cp2TiCl2 + Al2Me3Cl3 in acidic IL Cp2TiCl2 + [cation]+[Al2Cl7]- [Cp2TiCl] + + [cation]+ + 2 [AlCl4]- Olefin hydrogenation Cyclohexene + H2 + [RhCl(PPh3)3] (Wilkinson's catalyst) 39 Sound Sound = pressure wave, periodic compression/expansion cycles traveling through a medium possessing elastic properties (gas, liqud, solid) Liquids and gases ­ longitudinal pressure waves ­ compression/rarefaction Solids ­ longitudinal and transverse waves The energy is propagated as deformations in the media The molecules oscillate about their original positions and are not propagated The propagation of a sound wave = the transfer of vibrations from one molecule to another 40 Sound In a typical liquid, the speed of sound decreases as the temperature increases, at all temperatures. The speed of sound in water is almost five times greater than that in air (340 m s-1) 41 Longitudinal Pressure Waves 42 Pa = PA sin 2 f t Pa acoustic pressure PA pressure amplitude f sound frequency c = f (for 20 kHz, = 7.5 cm) Ptotal = Pa + Ph Ph hydrostatic pressure Acoustic Pressure 43 44 Acoustic Pressure cIPA 2= PA = driving pressure amplitude [Pa] I = irradiation intensity [W m-2] = liquid density [kg m-3] c = sound velocity in liquid [m s-1] (Water 1482 m s-1) 45 Speed of Sound Substance Speed of sound [m s-1] Air 343 Helium 965 Water 1482 Lead 1960 Steel 5960 Granite 6000 46 The speed of sound The speed of sound (u) u2 = 1/S = [P/]S ~ 1/(<(V)2>) where S is the adiabatic compressibility is the density and P the pressure. 47 Sound Intensity Sound Intensity = Power / area = Watts/m2 Source of Sound Intensity (W/m2) Sound level (dB) Jet Airplane 30 m away 102 140 Air-raid Siren, nearby 1 120 Threshold of Pain 10-1 120 Concert ~10-1 115 Riveter 10-3 100 Busy Traffic 10-5 70 Normal Conversations 10-6 60 Whisper 10-10 20 Threshold of Hearing 10-12 0 0 dB (10-12 W/m2) 10 dB = 10 as intense 20 dB = 102 as intense 30 dB = 103 as intense 120 dB = 1012 as intense 48 Ultrasound Frequencies from 20 kHz to 50 MHz , Hz 49 Sonochemistry Suslick, K. S.; Price, J. P. Ann. Rev. Mater. Sci. 1999, 29, 295-326. Mason, T. J.; Lorimer, J. P. Applied Sonochemistry, Wiley-VCH, Weinheim, 2002. Gedanken, A. Ultrason. Sonochem. 2004, 11, 47-55. Mastai, Y.; Gedanken, A. In: Rao, C.N.R.; Mueller, A.; Cheetham, A. K. (Eds.), The Chemistry of Nanomaterials, Wiley-VCH, NY, 2004, 113-169. 50 Sonochemical Reactions No direct interaction of US field with molecules Liquid phase reactions ­ chemical reactions driven by cavitation effects Solid state reactions ­ introduction of defects = speeding up diffusion 51 Hydrodynamic Cavitation the passage of liquid through (an orifice plate) the kinetic energy/velocity of the liquid increases at the expense of the pressure throttling causes the pressure to fall below the threshold pressure for cavitation (vapor pressure) cavities are generated the liquid jet expands, the pressure recovers the collapse of the cavities 52 Cavitation effects = creation, growth, and implosive collapse of bubbles in a liquid Acoustic Cavitation stable cavitation - bubbles oscillate for many cycles transient cavitation - transient cavities expand rapidly collapse violently 53 Bubble formation = overcoming tensile strength of the liquid (pure water 1500 bar, only 50 bar available) Weak spots = dissolved gas molecules, solid particles, trapped gases slow bubble growth (300 s), energy absorption, size oscillations critical size (170-300 m) = most efficient energy absorption, rapid growth, inefficient energy absorption, collapse Acoustic Cavitation 54 Microjet - bubble implosion Bubble collapse = implosion ( 1 ns) ˇ HOMOGENEOUS liquid: spherically symmetrical implosion, shear forces Hot spots = adiabatic compression, life time 2 s temperature of the gas inside bubble 5 000 ­ 20 000 °C, surrounding liquid layer 2000 °C pressure 500 ­ 1000 bar cooling rate 1010 K s-1 red hot steel poured into water 2500 K s-1 ˇ HETEROGENEOUS liquid-solid interface: asymmetrical implosion, high speed microjets of liquid (400 km h-1) Cavitation 55 Homogeneous Sonochemistry Two-Site Mechanism Inside the cavity gases and vapors temperatures 5 000 ­ 20 000 °C pressure 500 ­ 1000 bar Surrounding liquid layer temperatures 2000 °C Bulk liquid shear forces 56 Two-site Mechanism 57 Solid surfaces = implosion, microjets, shock waves 200 m minimum particle size at 20 kHz for microjets surface erosion removal of unreactive coatings (oxides, nitrides, carbonaceous) fragmentation of brittle materials, increased surface area Heterogeneous Sonochemistry 58 Heterogeneous Sonochemistry 59 Solid particles in liquid = shock waves high speed interparticle collisions (500 km/s) surface smoothing, surface coating removal localized melting of metal particles at the impact point fragmentation, increased surface area intercalation rates enhanced Heterogeneous Sonochemistry 60 SONOCHEMICAL METHOD Solid particles in liquid = shock waves, high speed interparticle collisions (500 km/s) surface smoothing, surface coating removal Ni catalytic activity in hydrogenation increased 105 fold by NiO removal localized melting of metal particles at the impact point fragmentation, increased surface area intercalation rates enhanced 200 fold in layered oxides and sulfides (V2O5, MoO3, MoS2, ZrS2, TaS2) 61 Metal powders Cr (mp 2130 K) and Mo (mp 2890 K) agglomerate W (mp 3683 K) does not temperature at the point of impact 3000 °C Heterogeneous Sonochemistry 62 SONOCHEMICAL METHOD Metal powders Cr (mp 2130 K) and Mo (mp 2890 K) agglomerate W (mp 3683 K) does not temperature at the point of impact 3000 °C 63 Cavitational Corrosion of the Tip 64 Control of sonochemical reactions frequency 20-40 kHz, the higher the frequency, the higher power needed to actuate cavitation, rarefaction phase shortens at high freq. volatile reactants, primary reaction site inside the bubbles, diameter 200 m, 5000 °C, easier bubble formation, more vapors inside bubbles, but the cavitation is cushioned nonvolatile reactants, reaction in the thin layer (200 nm) surrounding the bubble, 2000 °C, less cushioning, more energetic cavitation (collapse) use high boiling solvents, high vapor pressure inside the bubble cushions the implosion less cavitation in viscous liquids, viscosity resists shear forces reaction rates decrease with increasing temperature, more vapors in bubbles low surface tension facilitates cavitation, in water add surfactants 65 Cavitation in Water The frequency dependence of the intensity required to produce cavitation for degassed water at room temperature. The intensity required to produce vaporous cavitation above the frequency of 100 kHz rises rapidly. 66 The effect of temperature on cavitation The effect of temperature on cavitation and its associated hysteresis effect for tap water. The increase in intensity as the temperature is increased can be observed before it falls away at the boiling point. When the temperature is allowed to fall an increase in intensity is found in the region of 50-60 °C. This is quite a significant effect and appears to occur in all liquids. 67 Control of sonochemical reactions ambient gas important energy developed on bubble collapse: monoatomic (Ar) > diatomic (N2) > triatomic (CO2) Xe: low thermal conductivity, heat of the collapsing cavity retained He: high thermal conductivity, heat of the collapsing cavity dissipitated, no reaction external pressure, higher pressure suppresses bubble formation but makes cavitation more energetic, optimum pressure for given frequency temperature, higher temperature increases vapor pressure of a medium, lowers viscosity and surface tension, many bubbles formed at temps. close to solvent boiling point, a barrier to sound transmission intensity, minimum intensity for cavitation threshold, depends on freq., optimum intensity for given reaction conditions, at high powers great number of bubbles hinder sound transmission, decoupling of a liquid from the source, breakdown of transducer material sound attenuation is proportional to the frequency, more power needed at high freq. 68 a transducer - device converting one type of energy into other gas driven whistle (F. Galton), liquid atomizer siren liquid driven liquid whistle homogeniser, a jet of liquid passed through an orifice on a thin metal blade, vibrations, cavitation, mixing of immiscible liquids, ketchup, mayonnaise electromechanical magnetostrictive, Ni, Co/Fe, Al/Fe, Tb/Dy/Fe alloys shrink when placed in mg. field, solenoid, pulses, upper limit 100 kHz, cooling piezoelectric, oposite charges applied on crystal sides, contraction/expansion, quartz, Pb(Zr/Ti)O3 ceramics (PZT), up to MHz Generation of Ultrasound 69 Generation of Ultrasound 70 Sonochemical Reactor 71 SONOCHEMICAL METHOD Ti alloy horn, minimum lenght is a half-wavelength of sound in a material, 26 cm for 20 kHz in Ti, multiples of 13 cm vibration amplitude 5 - 50 m 72 Sandwich transducer operating at 1-200 kHz PZT wafers 73 Ultrasound Processor VCX 500 W Frequency 20 kHz 0 to 40 °C Argon (flow rate 62 cm3 min-1) TIME of ultrasound treatment PULSE irradiation and a dwell time 2:2 TEMP maximum temperature 50 °C AMPL amplitude 50 % Sonochemical Reactor 74 SONOCHEMICAL METHOD Liquids = heating/cooling by cavity implosions H2O H. + OH. H2 + H2O2 precursor decomposition: metals Fe(CO)5 Fe + 5 CO oxides Ga3+ + H2O Ga(O)(OH), diaspore nitrides, carbides, sulfides alkane cracking polymer degradation, lower MW, surface modification emulsification of immiscible liquids (oil-water, Hg-organics, polymer-inorganics) 75 SONOCHEMICAL METHOD Solid surfaces = implosion, microjets, shock waves 200 m minimum particle size at 20 kHz for microjets surface erosion removal of unreactive coatings (oxides, nitrides, carbonaceous) fragmentation of brittle materials, increased surface area Li, Mg, Zn, Al, Cu react at room temperature MCl5 + Na + CO M(CO)5 - (M = V, Nb, Ta) Mo + 6 CO Mo(CO)6 r. t., 1 bar, normally needs 300 bar, 300 °C R2SiCl2 + Li [-SiR2-SiR2-]n + LiCl monomodal MW distribution Protein microspheres diameter 2 m, hollow emulsification, crosslinking cysteine -S-S- by superoxide 76 SONOCHEMICAL METHOD