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  1. Nanocomposites By Milind Arbatti Instructor: Dr. Tzeng 7970 Nanocomposites

  2. Introduction • What are Composite materials? • Theory behind Composites • Limitations of Composite materials • Welcome to the world of nanocomposites! • Theory behind nanocomposites • Making of nanocomposites • Properties of nanocomposites • Applications • Limitations • Questions Nanocomposites

  3. Multiphase material Usually exhibits properties of both phases Usually improves performance over either individual phase Composites have already been discussed Multiphase metal alloys, or ceramics or polymers Example, pearlitic steels, alt. layers a + Fe3C There are also composites spanning materials classes (e.g. ceramic and metals) Definition of Composite Materials 7%20-%20Composites.ppt Nanocomposites

  4. Theory! • Composites often have only two phases • Matrix phase • continuous - surrounds other phase • Dispersed phase • discontinuous phase Matrix (light) Dispersed phase (dark) 7%20-%20Composites.ppt Nanocomposites

  5. Classification of Artificial Composites Composites Particulate Fiber Structural Large Dispersion Laminates Sandwich Particle Strengthened Panels Continuous Discontinuous Aligned Random 7%20-%20Composites.ppt Nanocomposites

  6. Properties of Composites Dependent on: • constituent phases • relative amounts • geometry of dispersed phase • shape of particles • particle size • particle distribution • particle orientation For a given matrix/dispersed phase system: • Concentration • Size • Shape • Distribution • Orientation 7%20-%20Composites.ppt Nanocomposites

  7. 7%20-%20Composites.ppt Parameters Concentration Orientation Distribution Size Shape Nanocomposites

  8. Rule of Mixtures Actual Values Upper bound * * E - particulate * * * E- matrix * * Lower bound conc. of particulates Nanocomposites

  9. Technologically, the most important type of composite. Characterized in terms of specific strength or specific modulus = strength (or E) per weight usually want to maximize specific strength and modulus Subclasses: Short fiber and continuous fiber lengths Fiber Phase Requirements for the fiber The small diameter fiber must be much stronger than the bulk material High tensile strength (Wiskers, Fibres, Wires) Matrix Phase Function Binds fibers together Acts as a medium through which externally applied stress is transmitted and distributed to the fibers Protects fiber from surface damage Separates fibers and prevents a crack from one fiber from propagating through another Fiber-Reinforced Composites Nanocomposites

  10. Influence of Fiber Length • Mechanical properties depend on: • mechanical properties of the fiber • how much load the matrix can transmit to the fiber • depends on the interfacial bond between the fiber and the matrix • Critical fiber length - depends on • fiber diameter, fiber tensile strength • fiber/matrix bond strength Critical fiber length - lc lc = sfd/2tc where d = fiber diameter tc = fiber-matrix bond strength sf = fiber yield strength 7%20-%20Composites.ppt Nanocomposites

  11. Influence of Fiber Orientation • Fiber parameters • arrangement with respect to each other • distribution • concentration • Fiber orientation • parallel to each other • totally random • some combination 7%20-%20Composites.ppt Nanocomposites

  12. Limitations of Composites • Properties of material are highly anisotropic due to orientation fibers • Modulus in direction of alignment is a function of the volume fraction of the E of the fiber and matrix • Modulus perpendicular to direction of alignment is considerably less (the fibers do not contribute) • Loss of transparency • Loss Optical/Electrical/Chemical (barrier) Properties Nanocomposites

  13. Welcome to the “Nano”World !!! • A broad class of materials, with microstructures modulated in zero to three dimensions on length scales less than 100 nm. • Materials with atoms arranged in nanosized clusters, which become the constituent grains or building blocks of the material • Any material with at least one dimension in the 1-100m range Nanocomposites

  14. Classes of nanostructured materials • Range, from zero dimensional atom clusters to three dimensional equiaxed grain structure.  Each class has at least one dimension in the nanometer range zero modulation dimensionalitythree dimensionally modulated Nanocomposites

  15. Properties • Tiny particels with very high aspect ratio, and hence larger surface area. • Larger surface area enables better adhesion with the matrix/surface. • Improvement in the mechanical performance of the parent material. • Better transparency due to small size(>wavelength of light). Nanocomposites

  16. Nanoparticles • A lot of research literature in this area. • Common in everyday life. • Examples include film materials, catalyst, ion exchangers, nanocrystals, semiconductors - quantum dots, molecular diodes. Source: Nanocomposites

  17. Nanoclays • Silicates layers separated by an interlayer or gallery. • Silicates layers are ~ 1 nm thick, 300 nm to microns laterally. • Polymers as interlayers. • Tailor structural, optical properties Nanocomposites

  18. Nanofibers - Nanotubes • Nanotubes in metal, metal oxide and ceramic matrix have also been fabricated. • Typical fabrication process is by hot-pressing the powdered matrix with the nanotubes. • Nanotubes in polymer matrices by mixing, then curing. • Most important filler category in nanocpomposites Nanocomposites

  19. Nanocomposites • Constituents have at least one dimension in the nanometer scale. • Nanoparticles (Three nano-scale dimensions) • Nanofibers (Two nano-scale dimensions) • Nanoclays (One nano-scale dimensions) Nanocomposites

  20. Typical Nano-materials Nanocomposites

  21. Characteristics Nanocomposites

  22. Characteristics of Polymer Layered Silicates • Due to the layer orientation, polymer-silicate nanocomposites exhibit stiffness, strength and dimensional stability in two dimensions (rather than one). In addition, because of the length scale involved that minimizes scattering, nanocomposites are usually transparent. Furthermore, PLS [Polymer-Layered Silicate] nanocomposites exhibit a significant increase in thermal stability as well as self-extinguishing characteristics. • Uniform dispersion of these nanoscopically sized filler particles (or nanoelements) produces ultra-large interfacial area per volume between the nanoelement and host polymer. This immense internal interfacial area and the nanoscopic dimensions between nanoelements fundamentally differentiate PNCs from traditional composites and filled plastics. Thus, new combinations of properties derived from the nanoscale structure of PNCs provide opportunities to circumvent traditional performance trade-offs associated with conventional reinforced plastics, epitomizing the promise of nano-engineered materials. Nanocomposites

  23. Nanocomposites • Multi-constituent materials. • Superior overall properties compared to constituent properties e.g. optical clarity, strength, stiffness, permeability. • Ability to tailor properties. Nanocomposites

  24. Continued…… • From the structural point of view, the role of inorganic filler, usually as particles or fibers, is to provide intrinsic strength and stiffness while the polymer matrix can adhere to and bind the inorganic component so that forces applied to the composite are transmitted evenly to the filler. Meanwhile, the polymer matrix can also protect the surface of the filler from damage and keep the particle apart to hinder crack propagation. • Nanocomposite materials can achieve much better properties than just the sum of its components as a result of interfacial interaction between the matrix and filler particles. Nanocomposites

  25. Chemical Synthesis: Gas Phase Synthesis Chemical Vapor Condensation Combustion Flame Synthesis Liquid Phase Synthesis Others – Mechanical Deformation Thermal recrystallization Synthesis of Nanocomposites Nanocomposites

  26. The nano powder formed normally has the same composition as the starting material. The starting material, which may be a metallic or inorganic material is vaporized using some source of energy The metal atoms that boil off from the source quickly loose their energy. These clusters of atoms grow by adding atoms from the gas phase and by coalescence A cold finger is a cylindrical device cooled by liquid nitrogen. The nano particles collect on the cold finger The cluster size depends on the particle residence time and is also influenced by the gas pressure, the kind of inert gas, i.e. He, Ar or Kr and on the evaporation rate of the starting material. The size of the nano particle increases with increasing gas pressure, vapor pressure and mass of the inert gas used. Gas Phase Synthesis(Synthesis of ultra pure metal powders and compounds of metal oxides(ceramics) ) Nanocomposites

  27. Chemical Vapor Condensation • the precursor vapor is passed through a hot walled reactor. The precursor decomposes and nano particles nucleate in the gas phase. The nano particles are carried by the gas stream and collected on a cold finger. The size of the nano particles is determined by the particle residence time, temperature of the chamber, precursor composition and pressure. Nanocomposites

  28. Combustion Flame Synthesis • Energy to decompose the precursor may be supplied by burning a fuel-air mixture with the precursor. In order to reduce agglomeration of the particles in the flame, the flame is specially designed to be low pressure. • If you have observed the flame of a candle, you would have noticed that the flame consist of a blue center and a yellow to red periphery. This is because the temperature in the flame varies with position in the flame. Such a variation in the temperature profile of the flame would cause nanoparticles of different sizes to grow in the different regions of the flame. This is avoided by designing the flame to have a 'flat temperature profile' i.e. a constant temperature across its width. Nanocomposites

  29. Liquid Phase Synthesis • Two chemicals are chosen such that they react to produce the material we desire • An emulsion is made by mixing a small volume of water in a large volume of the organic phase. A surfactant is added. The size of the water droplets are directly related to the ratio of water to surfactant. The surfactant collects at the interface between the water and the organic phase. If more surfactant were to be added, smaller drops would be produced and therefore, as will become apparent, smaller nano-particles. Nanocomposites

  30. Carbon nanotubes • Tubular form of carbon with nanoscale diameter • Folding a 2D sheet of graphene in different directions • Electronic properties depend on direction of folding • Doping of semiconducting carbon nanotubes From: Nanocomposites

  31. Laser ablation method to fabricate carbon nanotubes • Laser vaporises target (graphite + catalyst) • Carbon nanotubes from cooling mixture particles • Proportion of catalyst controls type of nanotubes Nanocomposites

  32. Park et. al., Block copolymer lithography: Periodic arrays of ~1011 holes in 1 square centimeter, Science, 276, 1401-1404, 1997 APPLICATIONS • Composite Industry – Drastic improvement in the mechanical performance of materials. Estimated Modulus Nanocomposites

  33. Barrier Properties • The silicate blocks are arranged alternately. Imagine a drop of water trying to get through the PLS barrier compared to a conventional filled polymer. The water drop would face more barrier going through the PLS nanocomposites because of the layered silicates arrangement. • Uses:  Packaging in food, medical and pharmaceutical industry Nanocomposites

  34. Thermal Barrier Coatings(TBC) for Aircraft Gas Turbine Engines Protection Required against: • High temperatures (gas T's up to approximately 2000 C and component T's of approximately 1200 C!) • High partial pressures of oxygen • High heat fluxes TBC’s such as Alumina, Pt-Aluminide Higher gas temperatures ==> higher engine efficiency • Lower component temperatures (so they don't fail) • Reduced cooling air requirements • Moderation of thermal transients • A decrease in the severity of engine hot spots by 80-150C below normal values. Nanocomposites

  35. Nanocrystalline Diamond Thin Films • Uses based on Physical Strength Cutting Tools Protective Coatings Composite Additives Nanocomposites

  36. Membranes • Commonly made from Alumina, (Al2O3 ), Titania, (TiO2) , and Zirconia, (ZrO2) • Membranes made of nanometer sized grains are stronger, less brittle and have higher temperature resistance than bulk ceramics. Pore sizes are on the order of 3-5 nanometers. • Current uses: Hemodialysis, Plasmapheresis - Separation of blood components and plasma from whole blood • Potential uses: High temp catalytic reactions , solid oxide fuel cells Nanocomposites

  37. Drug Delivery Attributes of Nanoparticulate Systems • provide a better penetration of the particles inside the body. • can be used for intramuscular or subcutaneous applications • minimizes the irritant reactions at the injection site. • exhibit greater stability, in both longer shelf storage lives and uptake times. • and can be designed to elicit the desired kinetics, uptake, and response from the body(i.e. Biocompatibility). Nanocomposites

  38. Medical • Nanoceramics have already shown outstanding osteoblast proliferation (Webster et al.). • If a hierarchical approach that mimics natural bone can be created for nanomaterials, these cellular interactions may be improved even further. • Additionally, the corresponding increase in mechanical properties may allow previously unsuitable materials to become viable options for future implants. Nanocomposites

  39. Summary of Applications • Nanocomposite materials and coatings: • Thermal and environmental barriers • Wear resistant coatings and parts • Tailored optical barriers • Flame retardant plastics • High surface area nanostructures: • Catalysts (molecule specific) • Energy storage media (nanoparticles, nanotubes) Nanocomposites

  40. Hierarchical Nanostructures • Ultrahigh-strength, tough structural materials • Ductile and strong cements • Net-shape formed ceramic parts • Magnetic/thermoelectric thermal management • New materials for MEMS • Smart materials with embedded sensors and actuators Nanocomposites

  41. Limitations! • To date one of the few disadvantages associated with nanoparticle incorporation has concerned toughness and impact performance. Nanoclay modification of polymers such as polyamides, could reduce impact performance. • Research will be necessary to develop a better understanding of formulation/structure/property relationships, better routes to platelet exfoliation and dispersion etc. • Economically feasible. Nanocomposites

  42. My Questions • Which geometrical factor plays an important role in nanocomposites? • Mention the processes for the synthesis of nanocomposites and explain any one of them in detail. Nanocomposites

  43. Questions? Nanocomposites

  44. 1.Date:06/20/2003 • 2.Presenter’s name: Milind Arbatti • 3.Title of presentation:Nanocomposites • The following is for the class to fill out and turn in at the end of each class: • Name of student turning in this form _______________________ • 4.From 1 to 10 (ten being the best), how do you grade the materials presented? ______ • 5.From 1 to 10 (ten being the best), were complete references given for each side? ______ • 6.From 1 to 10 (ten being the best), how well is the presentation understandable? _______ • 7.From 1 to 10 (ten being the best), how are the glossary, questions and problems presented? ______ • 8.Suggestion: Nanocomposites