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Pure silicon nano-powder was successfully synthesized via gas-phase sodium reduction of silicon tetrachloride, exhibiting 100% conversion of the reactants and achieving >95% yield of the final product. The interactions of the process conditions and tin-doping with the particle morphology were investigated. The produced powders were analyzed by nitrogen adsorption, transmission and scanning electron microscopy, X-ray diffraction, inert gas fusion analysis and glow discharge mass spectroscopy. The washed polycrystalline silicon particles had a BET surface area in the range of 23–44 m 2 /g. The silicon aciniform aggregates consisted of relatively homogeneous primary particles in the range of 20–100 nm. The silicon was protected by a 2–3 nm thick passivation layer established during the washing step resulting in an oxygen content of less than 3 wt.%. Electrochemical testing demonstrated a high inherent capacity for the pure Si powders. The initial capacity and 1st cycle charge efficiency of Si-containing anode electrodes was dependent on the initial powder surface area. The highest capacity was achieved for Si powders with intermediate BET surface area of 28.5 m 2 /g and cells with this anode material delivered capacity of 2651 mA h/g (normalized to Si) and 82.4% efficiency at first charge.

Chemical vapor co-deposition of Cu–Co films has been demonstrated using (1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)Cu(II) [Cu(hfac)2] [hfac=hexafluoroacetylacetonate] and (acetylacetonate)Co(II) [Co(acac)2] [acac=acetylacetonate] as precursors. The deposition was performed at the substrate temperature of 270°C in a warm-wall impinging jet type reactor. The precursor Co(acac)2 was sublimed at 140°C to achieve reasonable precursor delivery rates and avoid decomposition of precursor in the sublimator. Films with varying Cu content from 17 wt.% to 98 wt.% were deposited by subliming Cu(hfac)2 in the temperature range of 40–100°C with a fixed Co(acac)2 delivery rate. The morphologies and crystallinities of the binary films were strongly dependent on the film stoichiometry. Overall, this study provides insights into the mechanism of Cu–Co binary film formation by CVD.

The role of surface reaction in the synthesis of titanium dioxide from TiCl 4 in aerosol reactors was studied theoretically using a one-dimensional log-normal model in which particle growth occurred by coagulation and surface reaction. The surface reaction kinetics were obtained from chemical vapor deposition studies of TiO 2 from TiCl 4 reported in the literature and the gas-phase kinetics from data for aerosol reactors. The effect of surface reaction rate on the TiO 2 particle size distribution was studied for different axial temperature profiles and for laboratory and industrial conditions. Within the inlet TiCl 4 concentration range of 4.7 × 10 −8 −5.5 × 10 −6 mol cm −3 and gas velocities of 30 cm s −1 −20 m s −1 at atmospheric pressure, surface reaction did not affect the average TiO 2 particle size or the spread of the distribution. Two dimensionless quantities were identified which enable the determination of the significance of surface reaction in aerosol synthesis of particles. In general, for any system where homogeneous gas-phase reaction directly forms particles, and particle growth occurs by surface reaction and coagulation, it is not possible in practice to obtain a final particle size distribution with a geometric standard deviation less than the asymptotic geometric standard deviation determined by the coagulation kinetics (e.g. 1.32 for spherical particles with a log-normal size distribution in the continuum regime (Lee, 1983), which is the value determined by coagulation kinetics)

A new thermal dry etch process for copper (Cu) is reported which results in isotropic removal of Cu at high rates, does not involve the use of halogens such as chlorine, and results in formation of a volatile etching product. Applications include cleaning of chemical vapor deposition reactors and the back-side of wafers. The process involves oxidation of copper by hydrogen peroxide (H2O2) vapor to form either copper(I) or copper(II) oxide depending on the etch temperature and removal of the copper oxides by reaction with hexafluoroacetylacetone (hfacH) to form volatile copper(bis-hexafluoroacetylacetonate) (Cu(hfac)2) and water. Copper was etched at temperatures as low as 150 °C and at rates of up to ~ 1 μm min−1 at 190 °C by simultaneous flow of H2O2 and hfacH over a heated substrate. The etch rate increased with substrate temperature, etchant flow rates, and chamber pressure over the range of the parameters studied. The rate-limiting regime was identified by observing the film color during etching; a dark-brown color suggested fast oxidation with slow removal of copper oxide as the rate limiting step while a copper color suggested fast removal of copper oxide from the surface with oxidation as the rate-limiting step. The partially etched copper films were less reflective and exhibited higher surface roughness compared with the sputter-deposited copper used for etching.

A new process has been developed to produce patterned copper films with small feature sizes on polytetrafluoroethylene (PTFE). In the first step a sodium naphthalenide etching solution was used to chemically modify PTFE and also create a rough surface which provided good adhesion characteristics. In the second step a KrF excimer laser irradiated the substrate through a mask, ablating the etched layer and leaving a pattern. The typical total absorbed laser energy required to ablate the etched layer was 575 mJ cm−2 and X-ray photoelectron spectroscopy (XPS) analysis showed that the ablated region had a composition similar to that of unmodified PTFE. In the third step, high purity copper was deposited selectively on the unablated regions in a cold wall reactor using (hfac)Cu(VTMS) (hfac [ hexafluoroacetylacetonate; VTMS [ vinyltrimethylsilane) at deposition rates up to 1 μm min−1 at 180 °C and 10 mTorr partial pressure of (hfac)Cu(VTMS) to give films 15–20 μm thick of high purity copper on PTFE. Film resistivities were near bulk values. There are several advantages to this procedure compared with conventional approaches: (1) wet etching and liquid wastes are avoided; (2) conducting paths with dimensions less than 20 μm can be produced; (3) excellent adhesion is obtained; (4) owing to the high energy density available from an excimer laser, rapid throughput is possible.

The selective chemical vapor deposition (CVD) of Cu was studied using (hfac)Cu(VTMS) (hfac  1,1,1,5,5,5-hexafluoro-acetylacetonate; VTMS [ vinyltrimethylsilane) in the absence and presence of water during CVD with SiO2 surface passivation, derived from the silylating agent hexamethyldisilazane (HMDS), as a function of the nature of the carrier gas, HMDS and water vapor flow rates and chamber pressure. For CVD of Cu in the absence of water, pre-dosing with HMDS in the absence of water gave selective deposition. The deposition was feed rate limited and dense, smooth copper films were deposited selectively at rates of about 600 A min−1. The selectivity for CVD of Cu in the presence of water depended on the pre-dosing conditions. Pre-dosing with both HMDS and water vapor gave selective deposition at rates of about 1200 A min−1 in the presence of water, a factor of 2 higher compared with CVD in the absence of water vapor. Dense films with near-bulk resistivities were deposited selectively in the trenches on an underlying tungsten layer at the optimum water vapor flow rate and chamber pressure. Higher water vapor flow rates and chamber pressures resulted in porous, discontinuous films with significantly higher resistivities. An integration scheme utilizing selective CVD of Cu is proposed that allows formation of fully encapsulated copper lines without the need for a copper etch.

Nanometer-size fullerene particles were generated via vapor condensation in a continuous flow system starting from pure C60 and mixed fullerene extract (C60/C70). Vapor condensation was carried out by cooling a nitrogen gas stream containing fullerene vapors from 400–650°C to room temperature. Particles were partly amorphous at 400°C, and became crystalline C60 when processed above 500°C. The average particle diameter and particle number concentration increased with increasing processing temperature. The particles had average sizes of 30, 35 and 40 nm and total number concentrations of 2.2 × 106, 3.5 × 106, and 5.0 × 106 #/cm3, respectively at 500, 525 and 550°C.

The influence of precursor design on gas-phase and liquid/solid-phase (spray pyrolysis) aerosol materials synthesis is described. The necessity for the incorporation of reaction mechanisms that lead to complete removal of organic by-products is emphasized by the examples of aerosol-assisted CVD of Cu and Ag films and the formation of ZnS films and powders. The role of “single-source” precursors in the formation of complex materials including ZnS, perovskite phase PbTiO3 and yttrium aluminum garnet, Y3Al5O12 is described.

The process of spray pyrolysis was investigated theoretically using a model that describes the evolution of the droplet size, solvent vapor concentration in the carrier gas, and both droplet and gas temperatures along the reactor axis. The model also accounts for solute concentration profiles and solute precipitation in the solution droplets. The model was used to describe the evaporation of sodium chloride aqueous solution droplets in diffusion dryers and hot-wall reactors as a function of reactor residence time, droplet size (a few microns), solution molality (up to 2 M), droplet concentration (10 6 –10 7 cm −3 ), relative humidity of the carrier gas (0–50%) and reactor wall conditions. Decreasing initial droplet size and solution molality accelerated droplet evaporation and resulted in smaller droplets at the onset of solute nucleation. Decreasing droplet concentration and carrier gas inlet relative humidity as well as increasing wall temperature (up to 350°C) or axial wall temperature gradient (up to 100°C cm −1 ) increased the droplet evaporation rate, but did not change appreciably the droplet size at the point of precipitation for a given droplet size and solute concentration. Thus, control of droplet size at the onset of solute nucleation by varying process parameters other than the solution concentration and initial droplet size is limited.

The compound (hfac)Ag(1,5-cod) was synthesized by the reaction of 1,1,1,5,5,5-hexafluoroacetylacetone (hfacH) with Ag2O and 1,5-cyclooctadiene (1,5-cod) and characterized in the solid state by single-crystal X-ray diffraction. In contrast to the corresponding copper(I) compound (hfac)Ag(1,5-cod) exhibited lower volatility and was found to be dimeric in the solid state, containing the two unusual β-diketonate coordination modes, namely, μ4-η2-hfac and μ2-hfac. The deterioration of the crystal and extensive disorder precluded a detailed comparison of the metrical parameters of this compound with other literature data. However, the solid-state FTIR data showed substantial differences in the ν(CO) and ν(CC) stretching regions compared with the chelated hfac ligand in (hfac)Cu(1,5-cod). These data will be useful in assigning the coordination mode of β-diketonate ligands in metal-organic β-diketonate complexes by FTIR.

Solid, spherical, micron-sized silver metal particles were produced by spray pyrolysis from a silver nitrate solution. The effects of reaction temperature, carrier gas type, solution concentration, and aerosol droplet size on the characteristics of the resultant silver particles were examined. Pure, dense, unagglomerated particles were produced with an ultrasonic generator at and above 600° C using N 2 carrier gas, and at and above 900°C using air as the carrier gas. Solid particle formation at temperatures below the melting point of silver (962°C) was attributed to sufficiently long residence times (3.5–54 s) which allowed aerosol-phase densification of the porous silver particles resulting from reaction of the precursor.

A series of copper(I) compounds of the general formula (fod)CuL, where fod = 2,2-dimethyl-6,6,7,7,8,8,8-heptafluoro-3,5-octanedione, and L  PMe 3 , PEt 3 , 1,5-cyclooctadiene (1,5-COD), vinyltrimethylsilane (VTMS), 2-butyne, bis(trimethylsilyl)acetylene (BTMSA), have been prepared by the reaction of Na[fod] with CuCl in the presence of the appropriate amount of the Lewis base, L. All the compounds were characterized by elemental analysis, 1 H, 13 C, 19 F, 31 P and IR spectroscopies. The spectroscopic data are consistent with the chelation of the β- diketonate ligand through its oxygen atoms to the copper(I) center. The analytical data are consistent with the empirical formula (fod)CuL. One compound, (fod)CuPMe 3 , was characterized in the solid-state by single-crystal X-ray diffraction which confirmed the empirical formula and revealed the monomeric nature of this species in the solid state. The distorted trigonal planar coordination environment observed for this species is common to these species. The CuO distances are significantly different within the limits of error on the data possibly as a result of inductive effects of the different β-diketonate substituents. Crystal data: Triclinic space group P 1, a = 10.052(2) A, b = 11.871 (2) A, c = 16287(3) A, α = 109.84(1)°, β = 92.18(2)°, γ = 90.34(2)°, V = 1826.5(6) A 3 , Z = 4, R F , = 7.09% and R wF = 7.28%. Hot- and cold-wall chemical vapor deposition experiments revealed that these species are generally not suitable as precursors for the deposition of copper due to their low thermal stability. While pure copper films could be deposited, as determined by Auger electron spectroscopy, from the compounds (fod)CuL, where L = PMe 3 , 2-butyne and BTMSA, heating the precursors to increase their vapor pressures resulted in significant thermal decomposition in the source reservoir. As a result, deposition rates of only 100 A/min were achieved. No selectivity was observed on W versus SiO 2 substrates under the conditions employed. The other compounds, (fod)CuL, where L = 1,5-COD, VTMS, were too thermally unstable for CVD experiments.

Spray pyrolysis was used to produce dense, spherical palladium metal particles at and above 900 °C in air and 800 °C in nitrogen, well below the melting point of palladium (1554 °C). Palladium oxide particles were produced at lower temperatures. At 500 °C the PdO particles were composed of nanocrystalline grains 5 to 15 nm in diameter and had surface areas of 30.2 to 32.8 m2/g. The particles became less porous and less polycrystalline as temperature increased. At 800 °C the PdO particles were polycrystalline with grains of 20 to 50 nm and a surface area of 3.23 m2/g. The Pd particles produced at 900 °C by decomposition of the oxide were single-crystalline and fully-dense. These observations are consistent with the formation of porous but not hollow aggregates of PdO at lower temperatures, which can be densified in the gas phase to form solid particles of Pd above 900 °C.

Two new chemical approaches to etching copper have been identified recently. The first involves oxidizing copper films with halogens and then generating various Lewis base adducts of CuX where X scmsim; Cl or Br (LnCuX, where n = 1 or 2 ). The second approach involves the reaction of Cu films with Cu(hfac)2 (where hfac ≿ 1,1,1,5,5,5- hexafluoro -2,4- pentanedione ) and various Lewis bases to form two equivalents of (hfac)CuL ( L ≿ ligand ) . Spontaneous etching experiments have been carried out in a hot-wall reactor which showed that etch rates up to 1 μm min−1 can be achieved at temperatures below 420 K. The high etch rates are the result of the high vapor pressures of the LnCuX and (hfac)CuL which are on the order of 0.1–1 Torr at 330–370 K. The interaction of Cl2 and triethyl phosphine (PEt3) with a single-crystal copper surface was studied under ultrahigh vacuum conditions to provide a better understanding of the etching process. At temperatures above 320 K, PEt3 reacts rapidly with a heavily chlorinated copper surface (10 000 L exposure ( 1 L ≿ 1 langmuir ≿ 1 × 10 −6 Torr s ) of Cl2 at 300 K). The mass spectrum of the desorbing product is similar to that of CuCl(PEt3)2, suggesting that etching of copper occurs by reaction with Cl2 and PEt3 to form gaseous CuCl(PEt3)2. Subsequent examination of the substrate by Auger electron spectroscopy showed removal of chlorine (and presumably copper). Finally, the reactions of copper oxide with hfacH were investigated as a method for etching copper oxide films. Etch rates of up to 1 μm min−1 at an hfacH partial pressure of 1 Torr and temperature of 540 K were obtained in a differential cold-wall reactor.

The compound Pb(O2CCH3)2(18-crown-6) · 3H2O was synthesized via the reaction of either an aqueous solution of lead(II) acetate with 18-crown-6 or by reaction of lead(II) carbonate with acetic acid and 18-crown-6 in water. The product was shown to be monomeric in the solid state, as determined by single-crystal X-ray diffraction. The molecule is markedly asymmetric with both acetate ligands chelating to the same side of the 10-coordinate lead(II) centre. Solid-state FTIR of a crystalline sample revealed a difference, Δ, in νasym(CO) and νsym(CO) of 612 cm−1. Solution 207Pb NMR spectroscopy was consistent with coordination of the 18-crown-6 ligand to the lead centre in aqueous solution. Thermogravimetric analysis studies showed that Pb(O2CCH3)2(18-crown-6)·3H2O thermally decomposed in air to form crystalline PbO at 380°C.

A hybrid process, aerosol-assisted chemical vapor deposotion (AACVD), is described for reproducible preparation of superconducting thin films of YBa 2 Cu 3 O 7−χ . The process consists of atomizing a toluene solution of the Y, Ba, and Cu tetramethylheptanedionato complexes using an aerosol generator. The aerosol is transported into a CVD reactor where solvent and precursor evaporation and deposition occur at atmospheric pressure on heated substrates. The process provides stable evaporation rates for all three precursors, yielding constant film stoichiometry throughout the deposition period and from film to film. Superconducting films may be deposited in-situ at substrate heater temperatures above 825°C, or may be formed at lower temperatures by deposition followed by post-deposition annealing at higher temperatures. The microstructure and quality of films are highly dependent on the conditions employed in deposition and in the case of films deposited below 825°C, the post-deposition annealing conditions. Superconducting films prepared by the AACVD/post-annealing process have a metallic normal state resistivity signature with a zero resistance temperature typically above 88K, and are highly c -axis oriented. Transport critical current densities measured at 75 K on polycrystalline films prepared by the AACVD process are 220 000 A/cm 2 and 84 000 A/cm 2 at self-field and 0.1 T, respectively.

We have generated 0.1–0.5 μm aggregates that consist of nanocrystalline P d O and V 2 O 5 . The particles were generated by reacting aerosol particles that are composed of metal nitrates in a hot flowing gas stream. The microstructure of the particles was controlled by varying the temperature. Nanophase materials were formed at temperatures low enough to avoid grain growth in each particle, but sufficiently high to fully react the precursors. This process allows reasonable production rates of nanophase materials. Generation of multicomponent materials is also possible.

We have generated 0.1-0.5 μm particles that consist of nanophase PdO and V2O5. The particles were produced by an aerosol decomposition technique in which droplets containing precursors were passed through a hot-wall flow system in which the solvent evaporated and the precursors decomposed within the particles to form the product. By controlling the temperature and residence time, grain-growth in the particle could be minimized to allow formation of nanometer-sized crystallites. Advantages of this approach include the ability to form nanophase complex metal oxides with high purity at high production rates.

Spray Pyrolysis allows generation of small, unagglomerated, high-purity ceramic particles including multicomponent oxide and non-oxide powders. The primary disadvantage of this technique is that the particles are often hollow and porous. These morphologies occur using certain precursors and reactor conditions, while under other conditions, the particles are dense. We have examined approaches for generation of solid particles. The effects of controlled drying, addition of colloidal seed particles, and high reactor temperatures on particle morphology were studied. Controlled drying and additions of colloidal seed particles to Mg(NO 3 ) 2 ·6H 2 O and Zn(NO 3 ) 2 ·6H 2 O solutions produced hollow ZnO and MgO particles. Titania (TiO 2 ) particles were added to BaTiO 3 and SrTiO 3 precursor solutions. The BaTiO 3 and SrTiO 3 particles changed from hollow shells to agglomerates of crystallites on the order of 10 nm as the percentage of titanium from TiO 2 increased. Particles of BaTiO 3 and SrTiO 3 underwent aerosol-phase densification at higher reactor temperatures.

We are examining new routes to vapor-phase generation of multi-component particles with controlled stoichiometry. Generally, gas phase reaction processes use two or more reactants which must be fed simultaneously into a reactor to form such materials. This method can result in the formation of chemically nonuniform particles having different compositions. We have demonstrated a new approach to producing particles by gas-to-particle conversion using volatile single-source compounds that contain all the elements needed to form the final compound. This technique was used to form both Ge-Mn and ZnS particles. By reacting 1,1-bis-(pentacarbonylmanganio)-3,4-dimethylgermacylclopent-3-ene in both nitrogen (at 600°C) and H 2 -N 2 (at 400, 500, 600, and 700 °C), 30 nm Ge-Mn particles were formed. By reacting Zn(S 2 CNEt 2 ) 2 (TMEDA) in nitrogen at 500, 600, and 700 °C, 30 to 50 nm ZnS particles were produced.

A fine-scale dispersion of Y2BaCuO5 (“211”) particles ( ∼8000 A average diam.) within the YBa2Cu3O7-δ supercondu ctor (“123”) has been achieved by local melt-texture processing of off-stoichiometric Y-Ba-Cu-O prepared by the aerosol decomposition technique. The presence of such fine particles significantly reduces the thickness of the superconductor plate to below ∼ 7000 A. The plate thickness almost linearly with 211 particle size. The observed scaling relationship is most likely caused by the 211 inclusions serving as effective nucleation sites for 123 crystallization as well as restricting the plate coarsening below the peritectic temperature. The submicron-sized 211 particles tend to reduce microcracks and segregation of impurity phases at the plate boundaries, however, their effect on flux pinning appears to be insignificant.

The compounds (β-diketonate)Cu(1,5-COD) have been prepared by the reaction between [(1,5-COD)CuCl]2 and Na(β-diketonate) for β-diketonate = hexafluoroacetylacetonate (hfac), trifluoroacetylacetonate (tfac) and acetylacetonate (acac) and 1,5- COD = 1,5-cyclooctadiene. These compounds were characterized spectroscopically and (hfac)Cu(1,5-COD) was characterized, in the solid state, by single-crystal X-ray diffraction. Crystal data: empirical formula, C13,H13CuF6O2; crystal system, monoclinic; space group, P21/c; a = 10.011(2), b = 9.777(3), c = 15.658(3) A and β = 107.88(2)° and Z = 4. The coordination of the copper centre is best described as “3+1” with an asymmetrically coordinated 1,5-COD ligand where the Cu:C(6):C(7) centroid and Cu:C(10):C(11) centroid distances are 1.953 and 2.418 A, respectively. The quantitative disproportionation, according to the equation 2(hfac)Cu(1,5-COD) → Cu+Cu(hfac)2+2(1,5-COD) to produce copper metal and volatile by-products, was observed at 200°C.

The synthesis of submicron YBa 2 Cu 3 O 7−γ (1-2-3) and composite 1-2-3/CuO powders using aerosol decomposition of nitrate solutions and the behavior of those powders during subsequent processing were investigated. Transmission Electron Microscopy (TEM) revealed that 1-2-3 and 1-2-3/CuO particles produced at 800°C (residence time of 15 s) were polycrystalline and hollow, while solid particles were produced at temperatures greater than 900°C. Solvent evaporation led to a hollow particle morphology which was retained unless the reactor temperature exceeded 900°C, where densification was rapid enough to result in collapse of the hollow particles within the reactor residence time. Single-phase 1-2-3 powder with a critical temperature ( T c ) of 92K was produced using reactor temperatures of 900–1000°C. Dry-pressed 1-2-3 pellets densified rapidly at 800–900°C to 89% of theoretical density, which is considerably below the temperatures required for coarser powders produced by other techniques. 1-2-3/CuO particles produced at 800°C consisted of 25–50 nm crystallites of 1-2-3 and CuO, and pellets formed from that powder could be converted to single-phase YBa 2 Cu 4 O 8 (1-2-4) by heating in atmospheric-pressure oxygen at 750°C for 24 h, followed by 800°C for 24 h. Larger grained 1-2-3/CuO powder (100–250 nm) produced at 900 and 1000°C showed no conversion to 1-2-4 with the same treatment, demonstrating the critical importance of the small grain sizes obtained by aerosol decomposition for rapid conversion of 1-2-3/CuO to 1-2-4.

A series of (β-diketonate)Cu(PMe3), where β-diketonate = acetylacetonate (acac) (1), trifluoroacetylacetonate (2) and hexafluoroacetylacetonate (3), compounds have been prepared by the reaction of β-diketones with (η5-C5H5)CuPMe3. A single crystal X-ray diffraction study of (tfa)CuPMe3 reveals that it is monomeric in the solid state with a trigonal planar copper coordination environment. All three new compounds are volatile and soluble in hydrocarbon solvents.

Gold crystals were grown on alumina substrates using photothermal laser-induced chemical vapor deposition with dimethyl gold hexafluoroacetylacetonate as the gold precursor. The overall shape of the deposits and the size of the crystallites in the deposit depended strongly on the laser power, buffer gas partial pressure and buffer gas type. Addition of oxygen or air resulted in a large increase in the size of the crystallites in the deposit, while addition of inert buffer gas resulted in the formation of dendritic structures.

A novel aerosol flow reactor is described in which the core of a laminar flow of premixed reactants is irradiated to produce particles along the axis of the flow. The reactor was studied experimentally by irradiating an NH 3 /C 3 H 6 /NO 2 /air mixture to produce NH 4 NO 3 aerosol. A theory developed for particle formation and growth in the core reactor, accounting for radial diffusion of the condensing species and the parabolic velocity profile, explained the behavior of the system. The theory was formulated in terms of moments of the particle size distribution. The formation of NH 4 NO 3 particles from HNO 3 and NH 3 vapors followed classical nucleation theory with HNO 3 considered as the monomer. Values of the surface tension of the solid NH 4 NO 3 and the rate of HNO 3 formation were determined by comparing theory and experiment.

Production of Knudsen aerosols from gaseous precursors in the absence of coagulation is analyzed in reactors with laminar flow. Tubular, annular and parallel plates configurations are considered. Annular and parallel plate reactor geometries can produce more monodisperse aerosols than tubular reactors at the expense of lower yields. For equivalent conditions, these geometries give more vapor deposition and lower rates of particle formation than tubular reactors, a result of importance in chemical vapor deposition.

A theoretical study of the performance of continuous stirred tank and tubular flow aerosol reactors is presented. In all reactors considered, the aerosol properties are determined by chemical reaction, nucleation and aerosol growth in the free molecule regime in the absence of coagulation. Three to five dimensionless groups, depending on reactor type, affect the product aerosol characteristics (polydispersity, concentration, average size, surface area and yield). The uniformity of the product aerosol can be substantially improved by seeding. Aerosol reactors can be used in powder production or in chemical vapor deposition.

YBa 2 Cu 3 O 7−δ (1-2-3) powders containing silver have been prepared by aerosol decomposition for the first time. The primary phase observed by X-ray diffractometry and transmission electron microscopy (TEM) is 1-2-3. Metallic Ag grains have also been identified by using energy-dispersive spectroscopy and diffraction pattern analysis in the TEM. For reactor operating temperatures of 1000° C, each YBa 2 Cu 3 O 7−δ particle has associated with it a single Ag grain which does not wet the superconductor. Thus, the Ag is contained in discrete grains dispersed uniformly throughout the powder. Both materials are nanocrystalline with a grain size on the order of 10 to 80 nm.