Functional Nanoparticles and Films made in the Gas-Phase
Sunday June 1, 2008, 8:00 am - 6:00 pm, Boston, Massachusetts
We will start with the fascinating history of this technology from ink production in ancient China and Greece to the Bible printing by Gutemberg in Mainz and to the current manufacture of optical fibers, carbon blacks, filamentary nickel, pigments and fumed silica through valiant Edisonian research. Opportunities for aerosol synthesis of functional materials are highlighted. An overview of flame and hot-wall reactors for synthesis of metal, alloys, ceramics as well as their composites is given. Fundamental physical and chemical phenomena that control these processes are presented along with engineering design principles combining fluid and particle dynamics.
Emphasis is placed on scalable flame reactors that dominate both by value and volume today’s manufacture of nanostructured materials. In particular, it is highlighted the versatile flame spray pyrolysis process for synthesis of metal/ceramic particles for catalysts (CeO2/ZrO2, Pt/Al2O3, TiO2/SiO2) biomaterials such as translucent and radio-opaque Ta2O5/SiO2. Synthesis of solid nano- or hollow micro-particles of Bi2O3, CeO2 or Al2O3 by combustion spraying of solutions, emulsions or slurries will be shown along with process design criteria. Next, the course highlights specific cases for hot-wall synthesis of selected metals (Al, Bi, Pd and Zn) and even co-production of solar H2. Scale-up will be discussed showing how design correlations are developed with reactors of various sizes along with principles for synthesis of aggregates and agglomerates. Gas-phase coating with oxide or carbon films will be discussed.
A scalable, dry technology for synthesis of high purity nanoparticles with closely controlled characteristics is presented. This is advantageous over classic wet chemistry technologies (sol-gel or precipitation) as it does not use their multiple processing steps (e.g. washing, drying, calcination etc.) and high volumes of liquid byproducts. In addition, particle collection is easier from gas than liquid streams, high purity products (e.g. optical fibers) with unique morphology (e.g. fumed silica) and phase composition can be made in the gas-phase Today industry uses dry technology for manufacture of carbon blacks and simple oxides after several years of evolutionary research. As a result, it is practically impossible to use these units for synthesis of functional inorganic (mixed ceramic or metal-ceramic) nanoparticles without going through the same costly and time-consuming cycle as shareholders have no patience or stomach for it.
Recent major breakthroughs in understanding aerosol processes have placed dry synthesis of nanoparticles on a firm scientific basis allowing now production of these materials in appreciable volumes and competitive prices creating renewed interest in dry processes and products. The focus now shifts to product performance rather than mere particle characteristics through close interaction of particle specialists with end users. Special emphasis is placed on the degree of particle agglomeration and its control as well as on nanoparticle morphology and even layered composition.
This course will introduce aerosol process technology and show its accessibility and potential for manufacture of functional nanoparticles. It will go through its history to show how it survived the “death valley of scale-up” from laboratory to manufacturing for selected products. The most important theories will be presented along with tangible examples so one can use them for a specific product with systematic reasoning and use of the pertinent literature. Diverse examples will be given through analyzing and discussing a number of old and new products and processes using dry technologies in a relaxed atmosphere and through motivating lectures.
1. Overview and History (1h)
Nanoparticles: Origins, Significance and Applications. The evolution of industry for manufacture of carbon blacks, fumed silica, pigmentary titania, ZnO, filamentary nickel, optical fibers and, most recently, for metallic and ceramic nanoparticles. Flame and hot-wall reactors.
2. Fundamentals (1h)
Definitions and Particle size Distribution. Brownian Motion and Particle Diffusion. Thermophoretic Sampling and Particle Characterization. Aerosol Coagulation in the Continuum and Free-Molecular Regimes, Self-Preserving Distributions, Agglomeration, Fractal-like Particles. Critical, Kelvin or minimum Particle Size, Condensation and Nucleation.
3. Principles for Process Design and Operation (1.5h)
Controlled flame synthesis of nanoparticles. Chemistry affects particle characteristics. Reactor design by computational fluid and particle dynamics. Process Scale-up and correlations. Aggregates and Agglomerates.
4. Novel Products and Applications (2.5h)
4.1 Flame-made catalysts for DeNOx removal (V2O5/TiO2), polymer synthesis (TiO2/SiO2) and chiral pharmaceuticals (Pt/Al2O3) manufacture, automotive CeO2/ZrO2 and Pt/Ba/Al2O3.
4.2 Sensors: Flame synthesis of sensing particles (Pt/SnO2 and TiO2) and their direct deposition of highly porous, self-assembled lace-like or cauliflower-like films.
4.3 Mixed ceramics: Stable ZnO Quantum Dots for UV-filters by doping with silica, Dental nanocomposites (non-agglomerated SiO2) or Translucent Ta2O5/SiO2 in polymer matrices.
4.4 Hot-wall reactors for metal (Bi, Pd, Al, Zn) and non-oxide (AlN, B4C) nanoparticles and even for co-production of solar H2.
4.5 Coatings: Carbon or ceramic oxide films on titania or silica nanoparticles.
Who Should Attend
The course is aimed for scientists (chemistry and physics) and engineers (chemical -mechanical) in research and development of processes involving fine particles for batteries, films, phosphors, catalysts, polishing, medical and dental nanocomposite materials (prosthetics), pigments, optical fibers, precious metals (Ag, Au, Pt, Pd), sunscreens, cosmetics, fuel cells, solar energy storage.
Dr. Sotiris E. Pratsinis is Professor and Head of the Department of Mechanical and Process Engineering as well as Adjunct Professor in the Materials Science Department and Director of the Particle Technology Laboratory (www.ptl.ethz.ch) at ETH Zurich, Switzerland (the Swiss Federal Institute of Technology). His research focuses on aerosol processing of nanoparticles with applications in catalysts, ceramics, sensors, batteries, bio and nutritional materials. His program has been funded by the U.S. and Swiss National Science Foundations as well as by DuPont, Nestle, Toyota, Clariant etc. Prior to this, he was Professor and Interim Head of Chemical Engineering at the University of Cincinnati, Ohio (1985-98). He received his PhD on particulate air pollution engineering from the University of California, Los Angeles in 1985 and his Diploma in Chemical Engineering from the Aristotle University of Thessaloniki, Greece in 1977.
Prof. Pratsinis has graduated 20 and currently supervises nine PhD students with whom he has published over 200 refereed articles and book chapters on synthesis of nano-TiO2, SiO2, ZnO, CeO2 as well nanocomposites, lightguides and noble metal – ceramics. He has been awarded eight patents that have been licensed to Dow Chemical, Degussa, Hosokawa-Micron and Ivoclar-Vivadent and has contributed to creation of four spinoffs from his laboaratory. He has received the 1988 Kenneth T. Whitby Award of the American Association for Aerosol Research, the 1989 Presidential Young Investigator Award by the U.S. National Science Foundation and the 1995 Marian Smoluchowski Award by the European Aerosol Association and the 2003 Thomas Baron Award by the American Institute of Chemical Engineers (AIChE). In 2005-06 he was appointed Springer Professor of Mechanical Engineering at University of California, Berkeley. He is on the Editorial Boards of the Journal of Nanoparticle Research, Powder Technology, Journal of Aerosol Science, Advanced Powder Technology, Particle and Particle Systems Characterization and KONA Powder and Particle as well as on the Advisory Board of the Australian Research Council Centre on Functional Nanomaterials and on the Science Advisory Board, Harvard School of Public Health- International Initiative for the Environment and Public Health.