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Scientific and Technological Challenges in the Production of Nanostructured Ceramics

Scientific and Technological Challenges in the Production of Nanostructured Ceramics. Pradip Tata Research Development & Design Centre, Pune, India pradip.p@tcs.com. Bangalore Nano 2007. “Research to Reality” in Nanotechnology.

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Scientific and Technological Challenges in the Production of Nanostructured Ceramics

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  1. Scientific and Technological Challenges in the Production of Nanostructured Ceramics Pradip Tata Research Development & Design Centre, Pune, India pradip.p@tcs.com Bangalore Nano 2007

  2. “Research to Reality” in Nanotechnology However, today there is a nanotechnology center in practically every institution in the country, and worldwide research in nanomaterials is booming………………….There certainly is a lot of hype about nanotechnology. Except for the tremendous advances in the semiconductor chip industry, which in any case were already there before the launch of the nanotechnology initiative, currently there are not many innovations in the market place based on nanotechnology. The projections about the potential market being as large as $1 trillion sounds really exaggerated. From an engineering point of view, before this field can really be called a technology, much more needs to be done with respect to the reliability, reproducibility, standardization, productivity and engineering scale-up so that laboratory claims or successes can actually be scaled-up and realized in practice. Certainly major effort should be undertaken to understand the environmental, health and safety impacts of engineered nanoparticles.

  3. Contd……. Producing nanotubes, nanorods, hollow nanoparticles, core and shell nanoparticles are certainly results of innovative chemistry and physics in the laboratory but to claim this as a technology is not correct. One sees excellent TEM/SEM photographs of these particles but to produce them reproducibly even at the kg scale currently is not an easy task. It is the involvement of process engineers and the applications of process engineering tools which will take this to the next stage. Pioneering work done by mineral processing engineers to understand the modeling and scale-up issues related to particle processing needs to be emulated by those working in the nano area. One problem is that not very many engineers are currently associated with this field, but chemical engineers appear to be realizing the opportunities this field offers. DW Fuerstenau, AIChE Particle Technology Forum - Life Time Achievement Award, 2006

  4. Research to Reality - NNI • From investigation of single phenomena and creating single nano-components to complex, active nanostructures • From scientific discovery to technological innovation in advanced materials, nanostructured chemicals, electronics and pharma • Expanding to new areas of relevance such as energy, food and agriculture, nanomedicine and engineering simulations from the nanoscale (multi-scale modeling) • Accelerating development Rocco, 2007

  5. Large Scale Production of Carbon Nanotubes • Fluidized Bed Reactor for production of CNT’s in tons per day (Tsinghua University, China) – Prof. Wei Fei’s group • CVD method to produce high purity single-walled carbon nanotubes (SWNTs) and multi-walled carbon nanotubes (MWNTs) with various diameters and narrow diameter distribution; Facilities to produce 1.5kg high purity SWNTs per day and 20kg MWNTs (10-20nm in diameter) per day. The production facilities can be scaled up easily to produce MWNTs with purity more than 98wt% max. [The Chengdu Institute of Organic Chemistry, Chinese Academy of Sciences: R&D Centre for Carbon Nanotubes]

  6. Microemulsions Nanogels Aerosol Flame Reactors Titania Carbon Black Drug Delivery Coatings Metals/Metal Oxides Semiconductors Silica Microfluidics Nanofluids Engineered Nanostructured Components Engine Coolants Transmission Fluids PolymerNanocomposites Transparent Alumina Advanced Ceramics Ink-jet Printing Rapid Prototyping Population Balance Modeling Molecular Modeling Computational Fluid Dynamics Particulate Processing Rheology Surface Science Linkages with Appropriate Industrial Partners Nanomaterials Research Program at TRDDC

  7. Fabrication of Nanostructured Ceramics Components • Full consolidation of nano-powders into fully dense, defect free large engineering components while retaining nanostructures • Challenge in consolidation of nano-crystalline particles: grain coarsening ; loss of desired nano structure during processing & fabrication • Fast sintering/densification inversely proportional to pore size. Densification rate is dictated by the instantaneous pore size not the initial pore size and hence pores should remain small throughout. • Close control of pore size and pore size distribution (narrow) is the key to restrict grain growth and thus retain nano structures Joanna Groza, Int. J. Powder Metallurgy, Vol. 35(7), 1999, pp 59-66]

  8. Non Conventional Sintering To enhance densification & prevent grains growth • Hot Pressing • Hot Isostatic Pressing (HIP) • Sintering Forging • Hot Extrusion • Ultra high Pressure Sintering • Microwave Sintering • Field Assisted Sintering Techniques (FAST) • Pulsed current discharge and resistance heating also known as • Plasma activated sintering (PAS) • Spark Plasma Sintering • Pulse electro-discharge consolidation • Dynamic Magnetic Compaction (DMC) (short high pressure pulses) • Shockwave Consolidation

  9. Nanoparticles Suspensions Dispersion Consolidation Dispersed Conc. Slurry Green Compact Sintering Dense Homogeneous compacts Colloidal Processing of Nanoparticles and Production of Sintered Nanostructured Ceramics Design of Dispersants Slip/tape/gel casting/ pressure filtration Design of Sintering Time – Temperature Cycles Challenges: Close control of pore size distribution Restrict grain growth Retain nano-structures

  10. Rational Design of Additives • Experiments • Dispersion/flocculation • Rheology • Flotation • Adsorption • Molecular Modeling • Atomistic • Ab- initio/DFT • Molecular Dynamics (MD) • Dissipative Particle Dynamics (DPD) • Self assembly at interfaces • Colloidal stability • Wettability

  11. Molecular Modeling Methods Quantum Mechanics • Ab initio (HF, MP2) • DFT • Semi-empirical EHMO, CNDO, MINDO, MNDO, ZINDO Molecular Dynamics • NVE • NVT Force Field • MM2 • AMBER • OPLS • UFF • Drieding • COMPASS

  12. Oleic Acid OLA Octanoic Acid OCA Polyhydroxy Stearic Acid PHS Emphos PS-21A EPS Menhaden Fish Oil MFO Zonyl-A ZNL Alkazine – O AIME Dispersants for Tape Casting of Barium Titanate

  13. Molecular Dynamics Simulation Expt BaTiO3(001) /Glycerol trioleate /AcetoneMD Simulation300 °K and 300 ps Theory Data from: Bergstrom et.al. (1997) J. Am. Ceram. Soc., 80, pp. 291 Pradip et al., Ferroelectrics, 306, 2004, 195-208

  14. Population Balance Modeling of SinteringPrediction of Microstructure Evolution during Sintering • Extensive research /published literature on idealized systems available on the mechanisms of sintering but difficult to translate into commercial solutions • Need exists for a quantitative approach to optimize sintering cycles • What kind of green body microstructure is desirable for desired properties in the final product? • Is it possible to embed our fundamental mechanistic understanding in a mathematical representation (model) of commercial sintering process (size distribution) so as to be able to optimize practical systems • Population balance paradigm offers such a possibility

  15. Sintering Stages Initial Stage Rapid interparticle neck growth by diffusion, vapor transport, plastic or viscous flow Intermediate Stage Pores reach equilibrium shape as dictated by interfacial free energy. A network of grain and pores defines the microstructure whose evolution is driven by trajectories of pore and grain size distributions. This stage normally covers the major part of sintering process Final Stage Pores may get pinched off and exist in isolation at grain corners or and within the grains. Abnormal grain growth can occur

  16. Changes due to convection in physical space Accumulation Term Jump changes due to discrete events Continuous changes in property space Population Balance Paradigm

  17. An Operational Approach to Intermediate Stage of Solid State Sintering • In coupled population balance equations for evolution of pore and grain size spectra, incorporate semi-empirical velocity or convective terms for: • Pore Shrinkage • Grain Shrinkage and Growth density

  18. Pore Shrinkage and Evolution of Pore Size Spectra I • Continuity eqaution • Shrinkage “velocity”  n(r,t) is number of pores of radius r at sintering time t.  m is a floating exponent that need not represent any one particular surface or bulk diffusion mechanism of shrinkage.  k is a specific rate constant that follows an Arrhenius type relationship.  Pore coalescence can be incorporated in the continuity equation.

  19. Pore Shrinkage and Evolution of Pore Size Spectra II • Solution • Total pore volume • Normalized cumulative pore volume distribution

  20. Grain Growth and Evolution of Grain Size Spectra I • Continuity equation • Growth “velocity”  H(r,t) is number of grains of radius r  rc is critical radius  n is a floating exponent that depends on transport mechanism(s)  CG is a specific rate constant that conforms with an Arrhenius type relationship   is a coupling parameter. Any alternate plausible coupling relationship can be employed

  21. Model Validation • Alumina, zirconia powders sintered at different temperatures for varying times • Pore size distributions, porosity, grain size distribution as a function of time and temperature determined for parameter estimation • Model is adequate to describe the pore shrinkage and grain growth (essence of sintering kinetics) and hence can be used to simulate sintering for different conditions.

  22. Test of Pore Shrinkage Model I: Alumina A16 At 1400ºC S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  23. Test of Pore Shrinkage Model II: Zirconia Syp 5.2 At 1400ºC S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  24. Test of Grain Growth Model II: Zirconia Syp 5.2, At 1500ºC S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  25. 800 oC hold Application: Sintering By Pre-coarsening Hold I. Alumina At 1450ºC (Lin Data) S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  26. Sintering by Pre-coarsening Hold II. Simulated and Measured Density & Grain Size S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  27. Sintering by Precoarsening Hold III. Simulated Alumina Grain Size Distributions S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  28. Simulation of Heating Cycles I S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  29. Simulation of Heating Cycles II S. Manjunath, PC Kapur and Pradip, Materials Chemistry and Physics, 2001, 17-24

  30. d50 (measured by laser light scattering) 738nm Agglomerated received powder Zirconia Nano Powder Dispersion • Reported average Zirconia particle size is (30 -60nm) • Received powder is in the form of aggregates confirmed from TEM and laser light scattering measurements

  31. 1300oC, 0.5hour, 99.5% Density Consolidation (300kPa) Sintering Finer particles Mamata Pradhan, PC Kapur and Pradip, APT 2007

  32. Densification: Effect of Particle Size With use of a simple technique, starting from 70 nm size particles we produced fully densified nano structured products with grains < 100nm Mamata Pradhan, PC Kapur and Pradip, APT 2007

  33. Microstructure of Sintered Samples : Effect of Particle Size Coarser one, Density 94% Sintered at 1300oC, 1hour Finer one, Density 99.5% Sintered at 1300oC, 1hour

  34. Concluding Remarks • Process engineering and scale up issues are critical • Application driven product development in partnership with industry • Innovative use of existing knowledge to meet application needs • Innovative business model to convert scientific discoveries and inventions into commercial succeses

  35. Thank You

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