Physical Properties of Nanoparticles Lecture PDF

what is the nanotechnology? It creating materials, it is dimension measured in nanometers to become intermediate size between isolated molecules & bulk materials. These structure has changed physical & chemical properties than atoms, molecules & bulk  Physical Properties Optical Pro...

what is the nanotechnology? It creating materials, it is dimension measured in nanometers to become intermediate size between isolated molecules & bulk materials. These structure has changed physical & chemical properties than atoms, molecules & bulk  Physical Properties Optical Properties (Absorption, Emission,, And Band gap) Electric Properties (Conductivity and resistivity) Magnetic Properties ( Magnetic Field, Magnetic Intensity, susceptibility, Retentivity and Coercivity) Thermal Properties (thermal conductivity, melting point, heat capacity) Mechanical Properties (Hardness, Yield Strength, Tensile Strength, Ductility, Toughness) Classification of nanostructures Classification of nanostructure depend on number of dimensions which lie in the nanometer range Quantum Quantum Quantum Bulk Well Wire Dot  15 Optical Properties The reduction of materials' dimension has pronounced effects on the optical properties. The size dependence can be generally classified into two groups. One is due to the increased energy level spacing as the system becomes more confined (Semiconductor), and the other is related to surface plasmon resonance (Metal). Energy gap of materials Energy gap of materials  Confinement length In semiconductor If length of any dimension (a) less than Bohr Radius (ar )( which is distance between electron (in conduction band) and hole (in valance band) ,this dimension is confinement In metal If length of any dimension (a) less than Mean free path of electron (which is the average distance between two successive collision of free electron in metal ) , this dimension is confinement  Type of confinment a < ar strong confinment regime a ~ ar Intermediate confinement regime a > ar weak confinment regime Metal Nanoparticles What is a Surface Plasmon Absorption? electrons + + + + - - - - + + - - light electric field - - - - - - + + + + ++ ionic core surface charges time t time t + T / 2 Excitation of a dipolar surface plasmon oscillation by the electric field of an incident light wave of frequency  = 1 / T Collective excitation of the free electrons of a metal cluster leading to a coherent oscillation What is a Surface Plasmon Absorption? electrons + + + + - - - - + + - - light electric field - - - - - - + + + + ++ ionic core surface charges time t time t + T / 2 Excitation of a dipolar surface plasmon oscillation by the electric field of an incident light wave of frequency  = 1 / T Collective excitation of the free electrons of a metal cluster leading to a coherent oscillation Rayleighy and Mie scattering  Size and Shape Dependence of the Surface Plasmon Absorption 1.0 22 nm longitudinal SP 0.9 2.0 48 nm 0.8 99 nm 0.7 1.5 Absorbance absorbance 0.6 Transverse SP 0.5 At 520 nm 1.0 0.4 0.3 0.5 0.2 0.1 Spheres Rods 0.0 350 400 450 500 550 600 650 700 750 800 400 600 800 1000 wavelength  / nm Wavelength (nm)  Size Dependence R=2 (i) of the Surface Plasmon Absorption of Gold Nanorods Absorbance / a.u. R = 2.6 (ii) R = 3.5 (iii) R = 4.3 (iv) R = 5.4 (v) 300 400 500 600 700 800 900 1000 1100 1200 Wavelength / nm  Energy level of semiconductor Energy of electron in C.B  2l2,n Ele,n  E g  2 e a 2 Energy of hole in V.B  2l2,n Elh,n   2 h a 2 Ele,,nh  1 a2  Confinement length In semiconductor If length of any dimension (a) less than Bohr Radius (ar ) ,this dimension is confinement aB = єħ2 / µre2 where µr reduced mass of exciton  Type of confinment a < ar strong confinment regime a ~ ar Intermediate confinement regime a > ar weak confinment regime  Effect of nanometer scale Confinement length effect on energy system & structure system. Those lead to change physical & chemical properties Quantum Quantum Quantum Bulk Well Wire Dot r2D(E) r1D(E) r3D(E) r0D(E) e1e2 e3 e4 e1,1 e1,2 e1,3 Energy Energy Energy Energy  The density of states In model of free-electron gas Density of states in bulk dN ( E ) dN ( K ) dK D3d ()    E 1 E E d (E) dK dE dN ( ) D3d ( )   2 d ( ) Atomic Bulk leveles bands  Two-Dimensional Systems (quantum well) dN ( E ) dN ( K ) dK D2 d ( E )    E 1 1 dE dK dE E dN ( K ) D2 d ( K )  K dK  One-Dimensional Systems (Quantum Wires) dN ( E ) dN ( K ) dK D1d ( E )    1 1  1 dE dK dE E E dN ( K ) D1d ( K )  1 dK Zero-Dimensional system ( Quanum Dots)  Energy Levels of a Semiconductor Quantum Dot    nl  2 2 where χnl is the spherical Bessel function E e,h nl  E  e,h   c ,v 2m  R  n l name 0 1 1s 0 2 1p 0 3 1d 1 1 2s 1 2 2p 1 3 2d Optical Properties of Quantum Dots the optical properties of nanostructure are tunable due to the size effect Decreasing size of semiconductor nanoparticles lead to increase in bandgap then change in fluorescence color of emission of sample  Allowed Optical Transitions in Strong Confinement Semiconductor Nanocrystals Effective mass approximation and confinement strong confinement gives:  2 2 1 1.786e 2 1 E  Eg   2  2 a  a µ: reduced effective mass, a: particle radius Eg: band gap energy of the bulk, : dielectric constant The large stock shift between the absorption and emission spectra S1/2e S3/2h The absorbing state is different than the emitting state  Allowed Optical Transitions and the Nature of Emitting State Exchan A-B ge splittin splitting 1S1/2(e) 1/2 -1/2 B g Fe=1/2,Fh=3 /2 δAB 1S3/2(h) A 1/2 -1/2 3/2 -3/2 Dark Exciton The absorbing state is different than the emitting state and so there is a large stock shift between the The eight fold degenerate of the lowest absorption and emission spectra. excited state (1Se 1S3/2 ) is lifted by: In semiconductor nanocrystals the radiative -The crystal field structures of the lifetime (~ 1µsec at 10K) is very long compared to hexagonal lattice. bulk semiconductor (1 ns). - The particle shape -Electron-hole exchange interaction. Bright state Dark state Biexciton Effect 1Pe Surface 1Se trap hole state 1Sh STS 1Ph (i) Single Exciton (ii) G.S Biexciton (iii) Negative Trion 1ps (iv) Excited Biexciton ST S (v) Triexciton (vi) Charged Biexciton  Ahmed Mahmoud Saad CORE /SHELL NANOPARTICLES  DIFFERENT SHAPED NANOPARTICLES a) spherical core/shell nanoparticles; b) hexagonal core/shell nanoparticles; c) multiple small core materials coated by single shell material; d) nano matryushka material; e) movable core within hollow shell material. The properties of nanoparticles are not only size dependent but are also linked with the actual shape. Other nanoparticle physical and chemical properties such as catalytic activity and selectivity, electrical and optical properties, sensitivity to surface-enhanced Raman scattering (SERS) and the plasmon resonance and melting point are also all highly shape- dependent classification of core shell NPs Silica core/shell Ag\SiO2 , Au\SiO2 , NPs ZnO\SiO2 Nonsilica Ag/Au, Fe/C, core/shell NPs Zn/ZnO inorganic- inorganic Semiconductor CdSe/CdTe, core/shell NPs CdSe/ZnO, Core shell Lanthanide Au/SiO2/Y2O3:EU+3 Fe/dextran, Fe3O4/ MPEG, Inorganic-organic Au/PSMA, SiO2/chitosan organic-inorganic PS/Ag, organic-organic PTBA/PS  The choice of shell material of the core/shell nanoparticle is generally strongly dependent on the end application and use.  Multiple core core/shell particles are formed when a single shell material is coated onto many small core particles together  Inorganic/Inorganic Silica Core/Shell Nanoparticles C2H5OH a 1.0 Ag NPs Ag-SiO2 NPs 0.8 Absorpation (Arb. unit) 0.6 0.4 0.2 0.0 300 400 500 600 Wavelength (nm) Silica shell enhances Ag plasmonic  Silica coating is the more basic and advantageous as compared with other inorganic (metal or metal oxide) or organic coatings as it reduces the bulk conductivity and increases the suspension stability of the core particles. In addition, silica is the most chemically inert material available; it can block the core surface without interfering in the redox (reduction– oxidation reaction).  Surface Plasmon Amplification by Stimulated Emission of Radiation (SPASER) or plasmonic laser In 2003 David J. Bergman and Mark I. Stockman photon Surface plasmon (SP) modes dielectrical metal are localized in dimension much smaller than optical wavelength. These modes oscillation as optical frequencies. Local field amplitude in the V-shaped inclusion plane for eigenmodes with highest gains in the regions of two spectral maxima for the case of thin active medium.  Gain medium dielectrical metal metal Gain medium dielect rical metal Schematic of levels and transitions in a spaser. The external radiation excites a transition into electron–hole (e–h) pairs (vertical black arrow). The e–h pairs relax to excitonic levels (green arrow). The exciton recombines and its energy is transferred (without radiation) to the plasmon excitation of the metal nanoparticle (nanoshell) through resonant coupled transitions (red arrows). Ref:- Mark I. Stockman, Nature 2, 327-329(2008). Plasmon-based nanolasing. A) The laser structure developed by Noginov and colleagues consists of a gold core surrounded by a silica shell in which organic dye molecules are embedded. The molecules provide the laser’s optical gain. The energy (photons) pumped into the system is transferred to the collective motion of the electrons on the gold core’s surface and stimulates the coherent emission and amplification of so-called surface-plasmon waves. These waves are ultimately converted into laser light of wavelength 531 nm. B) Oulton and co-workers’ laser, whose working principle is also based on surface-plasmon waves, consists of a cadmium sulphide nanowire separated from a silver surface by a 5-nm insulating gap made of magnesium fluoride. The emergent, 489-nm-wavelength laser light is emitted from a strongly confined spot within the gap region. Inorganic/Inorganic Nonsilica Core/Shell Nanoparticles Increase shell thickness lead to Plasmon of core is blue shifted also increase absorbance Inorganic Inorganic Semiconductor Core/Shell Nps Classify to  Semiconductor- Semiconductor core shell (CdTe-CdSe, CdS-PbS, …..), and it dived to two types, core shell type I and core shell type II  Semiconductor- nonsemiconductor core shell (CdSe-SiO2, CdS-TiO2,……) Core Shell Type I No change in photoluminescence (PL) Increase in quantum yield (QY) Type I Core Shell Type II Change in wavelength of PL (big red shift) Increase in QY Type II  5 drop/min Cd steart CdTe + TOPO + HDA CdTe/CdSe core time shell quantum dots SeTOP 5 drop/min  CdTe cdte\cdsecoreshell 2.4 1.4 2.2 1.2 2.0 645 1.8 1.0 1.6 Intensity/A.U Intensity/A.U 0.8 1.4 1.2 0.6 780.09314 1.0 554 618 0.8 0.4 0.6 0.2 0.4 865 0.2 874 560.18634 0.0 0.0 400 450 500 550 600 650 700 750 800 400 450 500 550 600 650 700 750 800 850 900 wavelength /nm wavelength /nm Quantum yield 40-60 % Quantum yield 70-90 % TEM image of CdTe / CdSe core shell Inorganic/Inorganic Lanthanide Core/Shell Nanoparticles The term "lanthanide" was introduced by Victor Goldschmidt in 1925 Lanthanide series comprises the fifteen metallic chemical elements with atomic numbers 57 through 71, from lanthanum through lutetium Inorganic/Inorganic Lanthanide Core/Shell Nanoparticles Y, Eu(OH)CO3.H2O Y2O3: Eu Y(NO3)3 annealing Eu(NO3)3 Au/SiO2 +Urea Emission spectrum of SiO2@Y2O3:Eu3+ (600 °C) (a), SiO2@Y2O3:Eu3+ (800 °C) (b) and Au@SiO2@Y2O3:Eu3+ (c). Inorganic/Inorganic Lanthanide Core/Shell Nanoparticles * Lanthanide Core/Shell Nanoparticles have high quantum yield (QY) of upconversion and that is promsing in bio sensing Inorganic/Inorganic Lanthanide Core/Shell Nanoparticles Draw Schema of synthesis for one of the following then discusses the properties of it: Ag\Au core shell, Ag\SiO2 core shell, CdSe\CdS core shell, CdSe\ZnS core shell, metal/semiconductor core shell, core shell of metal\silica doped with dye , Lanthanide Core/Shell Nanoparticles Thermal Properties of Nanomaterials Mechanical Properties of Nanomaterials Nanocomposite Ahmed Mahmoud Saad  Nanocomposite  Definition:- Nanocomposite are broad range of materials consisting of two or more components, with at least one component having dimensions in the nm regime (i.e. between 1 and 100 nm)  Nanocomposite consist of two phases (i.e nanocrystalline phase + matrix phase) Phase may be inorganic-inorganic, inorganic-organic or organic-organic  Nanocomposite means nanosized particles (i.e metals, semiconductors, dielectric materials, etc) embedded in different matrix materials (ceramics, metal, glass, polymers, etc).  Small size effect Physical sensitivity Quantum confinement effect Higher gas absorption features of Nanocomposites Increased nonstoichiometry Regrowth Chemical reactivity Rotation and orientation Sub graining Assembly Physical sensitivity  Small size effect: When the particle sizes in composite materials approach lengths of physical interaction with energy, such as light wave, electromagnetic waves, the periodic boundry conditions of coupling interaction with energy would behave different from its microscopic counterparts, which results in unusual properties  Quantum confinement effect: When electrons are confined to a small domain, such as a nanoparticles, the electrons behave like “particles in a box” and their resulting new energy levels are determined by quantum confinement effect. These new energy levels give rise to the modification of optoelectronic properties such as “blue shift” light emitting diode  Higher gas absorption: large specific area of nanopartilces can easily absorb gaseous species  Increased nonstoichiometry phases: Nanomaterials easily form chemically unsaturated bonds and nonstoichiometry compounds  Regrowth: Nanomaterials are probably easier to recrystallise and regrow in processing and service conditions than traditional materials  Rotation and orientation: Crystallographic rotation and orientation of nanoparticles have been found in processing of nanocomposites  Sub-grain: Nanoparticles enveloped into larger particles act as dispersed pinholes to divide the large particles into several parts.  Assembly Nanoparticles are easy to aggregate and assemble in liquid or gaseous media  Classification of nanocomposite Types Features Nanocomposites Nanocomposites Ceramic Good wear resistance and Enhanced mechanical properties matrix high thermal and chemical including Fracture toughness, stability. But they are brittle Stiffness & Strength due to the (low toughness ). crack bridging role of nanofillers Metal matrix Ductile, toughness with high High strength in shear/compression strength and modulus, processes , high electrical and electrical and heat thermal stability, Wear and conductivity. But highly Chemical resistance. corrosive. Polymer Polymers/ inorganic compounds matrix Widely used in industry due increases heat and impact to their ease of production, resistance, flame retardancy & lightweight and ductility. mechanical strength & decreases Some disadvantages, such gas permeability with respect to as low modulus and oxygen and water vapour. strength. Polymer/metal or ceramic offer striking magnetic, electronic, optical or catalytic properties. Dramatic improvement in biodegradability.  Different type of nanocomposite Class Examples Table 2. Different types of Metal nanocomposites. Fe-Cr/Al2O3, Ni/Al2O3, Co/Cr, Class Examples Fe/MgO, Al/CNT, Mg/CNT Metal Fe-Cr/Al2O3, Ni/Al2O3, Co/Cr, Fe/MgO, Al/CNT, Mg/CNT Ceramic Ceramic Al2O3/SiO2, SiO2/Ni, Al2O3/SiO2, SiO2/Ni, Al2O3/TiO2, Al2O3/SiC, Al2O3/TiO2, Al2O3/SiC, Al2O3/CNT Al2O3/CNT Polymer Polymer Thermoplastic/thermosetThermoplastic/thermoset polymer/layered silicates, polymer/layered silicates, polyester/TiO2, polymer/CNT, polyester/TiO2, polymer/CNT, polymer/ layered double hydroxides. polymer/ layered double hydroxides. Material having ceramic as a matrix material in composites called as Ceramic Matrix Composite (CMC). Properties of CMC  Tensile & Compressive Behaviour No sudden failure in CMC as like in Ceramics. Certain amount of Elongation in CMC improves the tensile and compressive property.  Fracture Toughness It limits to ceramics, but for CMC’s fracture toughness increases due to reinforcement.  Fatigue Resistance Fatigue occurs due to cyclic loading, in case of CMC’s cracks arrested by reinforcement. So higher Fatigue Resistance.  Thermal Response It can withstand high temperature.  Chemical Inertness Ceramic do not react with chemicals.  Corrosion Resistance  Excellent wear and corrosion resistance in a wide range of environments and temperature  Higher strength to weight ratio  Higher strength retention at elevated temperature  Higher chemical stability  Non-catastrophic failure  High hardness  Lightweight  Processing routes for CMCs involve high temperatures – can only be employed with high temperature reinforcements.  CMCs are designed to improve toughness of monolithic ceramics, the main disadvantage of which is brittleness.  High processing temperature results in complexity in manufacturing and hence expensive processing.  Difference in the coefficients of thermal expansion between the matrix and the reinforcement lead to thermal stresses on cooling from the processing temperatures. Method System Procedure i) Selection of raw materials [mostly powders - small Powder Al2O3/SiC average size, uniformity and high purity]; ii) Mixing Process by wet ball milling or attrition milling techniques in organic or aqueous media; iii) Drying by heating, using lamps and/or ovens, or by freeze-drying; iv) consolidation of the solid material by either hot pressing or gas pressure sintering or slip casting or injection moulding and pressure filtration. Polymer Al2O3/SiC, SiN/SiC Mixing a Si-polymeric precursor with the matrix Precursor material → Pyrolysis of the mixture using a Process microwave oven, generating the reinforcing particles. Sol-Gel SiO2/Ni, ZnO/Co, Hydrolysis and polycondensation reactions of an Process TiO2/ Fe2O3, (in)organic molecular precursor dissolved in organic La2O3/TiO2, Al2O3/ media. Reactions lead to the formation of three- SiC, TiO2/Al2O3, Al2O3/SiO2, dimensional polymers containing metal-oxygen Al2O3/SiO2/ ZrO2, bonds (sol or gel) → drying to get a solid material TiO2/Fe2 TiO5, and further consolidation by thermal treatment. NdAlO3/Al2O3  Ball-milling Drying under (α)Al2O3 Ultrasonic with ZrO2 balls infrared +(β)SiC bath in methanol lamp (48 hours) Schema of Powder Al2O3/SiC Hot pressing Processing nanocomposi at 1700 °C te under N2 (α)Al2O3 + Coated Pyrolysis at 1500 polymer (α)Al2O3 Coating/drying °C: SiC (polycarbosila powder nanoparticles ne) Schema of Polymer Al2O3/SiC Hot pressing Precursor Process nanocomposite at 1700 °C Quiz  Draw Schema of sol gel Processing for one of the following:  SiO2/Ni, ZnO/Co, TiO2/ Fe2O3, La2O3/TiO2, Al2O3/ SiC, TiO2/Al2O3, Al2O3/SiO2, Al2O3/SiO2/ ZrO2, TiO2/Fe2 TiO5, NdAlO3/Al2O3  Advantages and limitations of ceramic nanocomposite processing methods. Method Advantages Limitations Powder Low formation rate, high Process Simple temperature, agglomeration, poor phase dispersion, formation of secondary phases in the product. Polymer Possibility of preparing finer particles; Inhomogeneous and Precursor better reinforcement dispersion phase-segregated Process materials due to agglomeration and dispersion of ultra-fine particles Sol-Gel Simple, low processing temperature; Greater shrinkage and Process versatile; high chemical homogeneity; lower amount of voids, rigorous stoichiometry control; high purity compared to the mixing products; formation of three dimensional method. polymers containing metal-oxygen bonds. Single or multiple matrices. Applicable specifically for the production of composite materials with liquids or with viscous fluids that are derived from alkoxides. 1) Cutting Tools 2) Aerospace 3) Jet Engine 4) Burner 5) Turbine Blade 6) Hot Fluid Channel Process Syste Procedure m Spray Fe/Mg i) Dissolution of the inorganic precursors (starting Pyrolysis O, materials) in a suitable solvent to get the liquid W/Cu source; ii) Generation of a mist from this liquid source using an ultrasonic atomizer; iii) Use of a carrier gas to carry the mist into a pre-heated chamber. iv) Vaporisation of the droplets in the chamber and trapping with a filter, promoting their decomposition to give the respective oxide materials; v) Selective reduction of the metal oxides to produce the respective metallic materials. Liquid Pb/Cu, i) Mixing of fine reinforcement particles with the Infiltration Pb/Fe, matrix metal material; ii) Thermal treatment, whereby W/Cu/ the matrix melts and surrounds the reinforcements by Nb/Cu, liquid infiltration; iii) Further thermal treatment below Nb/Fe, Al-C60 the matrix melting point, to promote consolidation and eliminate internal porosity. Process System Procedure Rapid Al/Pb, Al/X/Zr i) Melting of the metal components together; ii) Keeping the Solidification (X = Si, Cu, melt above the critical line of the miscibility gap between the Process(RSP) Ni), Fe alloy different components to ensure homogeneity; iii) Rapid solidification of the melt by any process, such as melt spinning. RSP with Use of ultrasonics for mixing and for improving wettability ultrasonics Al/SiC between the matrix and the reinforcements. High Energy Milling the powders together till the required nanosized alloy is Ball Milling Cu-Al2O3 obtained → Nanocomposite. Chemical Al/Mo, Cu/W, PVD: i) Sputtering/evaporation of different components to vapor Cu/Pb produce a vapour-phase; ii) Supersaturation of the vapour deposition(C phase in an inert atmosphere to promote the condensation of VD) or metal nanoparticles; iii) Consolidation of the nanocomposite by physical thermal treatment under inert atmosphere. vapor CVD: Use of chemical reactions to get vapours of materials, deposition followed by consolidation. (PVD ) High Energy Ball Milling Chemical vapor deposition(CVD) https://www.youtube.com/watch?v=XGR2CObCWi4&ab_channel= Physics%2CMaterialsScienceandNanoLectureSeries Process System Procedure Chemical Ag/Au, Colloidal Method: i) Chemical reduction of inorganic salts Processes Fe/SiO2, in solution to synthesize metal particles; ii) Consolidation (Sol-gel, Au/Fe/Au of the dry material; iii) Drying and thermal treatment of Colloidal) the resulting solid in reducing atmosphere, such as H2, in order to promote selective oxide reduction and generate the metal component. Sol-gel process: i) Preparation of two micelle solutions using mesoporous silica containing 0.1 M HAuCl4 (aq.) and 0.6 M NaBH4 (aq.); ii) Mixing under ultraviolet light till complete reduction of the gold. For Fe/Au-containing nanocomposites: i) Synthesis of the iron shell; ii) Preparation of the second shell and drying of the powders after second gold coating; iii) Pressing of the mixture to get the final material.. Method Advantages Limitations Spray Effective preparation of ultra fine, High cost associated Pyrolysis spherical and homogeneous powders with producing large in multicomponent systems, quantities of uniform, reproductive size and quality. nanosized particles. Liquid Short contact times between Use of high Infiltrat matrix and reinforcements; moulding temperature; ion into different and near net shapes of segregation of different stiffness and enhanced wear reinforcements; resistance; rapid solidification; both formation of undesired lab scale and industrial scale products during production. processing. Rapid Process (RSP) Simple; effective. Only metal-metal Solidific nanocomposites; ation induced agglomeration and non-homogeneous distribution of fine particles. Method Advantages Limitations RSP with Good distribution without agglomeration, ultrasoni even with fine particles. cs High Milling Homogeneous mixing and Energy uniform distribution. Ball CVD/PVD Capability to produce highly dense Optimization of many and pure materials; uniform thick parameters; cost; relative films; adhesion at high deposition complexity. rates; good reproducibility. Chemical Simple; low processing Weak bonding, low Processe temperature; versatile; high chemical wear-resistance, high s homogeneity; rigorous stoichiometry permeability and (Sol-Gel, control; high purity products. difficult control of Colloidal) porosity. Process System Procedure Intercalation Clay with PCL, Employed for layered reinforcing material in which / PLA, HDPE, the polymer may intercalate. Mostly for layered Prepolymer PEO, PVA, PVP, silicates, with intercalation of the polymer or pre- from PVA, etc. Solution polymer from solution. Use of a solvent in which the polymer or pre-polymer is soluble and the silicate layers are swellable. Montmorillonate Encasing of the layered silicate within the In-situ with N6/PCL/ Intercalative PMMA liquid monomer or a monomer solution → Polymerizatio /PU/Epoxy formation of polymer between the n intercalated sheets. Polymerization by heat or radiation, by diffusion of a suitable initiator or by a catalyst fixed through cation exchange inside the interlayer, before the swelling step. Process System Procedure Montmorillonate Annealing of a mixture of the polymer and the Melt with Intercalation PS/PEO/PP/ layered host above the softening point of the PVP, Clay-PVPH polymer, statically or under shear. Diffusion of polymer chains from the bulk polymer melt into the galleries between the host layers during annealing Hectorite with In situ formation of the layered structure of Template PVPR, HPMC, Synthesis PAN, PDDA, the inorganic material in an aqueous solution PANI containing the polymer. The water soluble polymer acts as a template for the formation of layers. Widely used for the synthesis of Layered double hydroxides (LDH )nanocomposites, but less developed for layered silicates. Process System Procedure (a) Mixing PVA)/Ag; PMMA/Pd (a) Mixing of either polymer or monomer with (b) In situ Polyester/ TiO2 reinforcing materials; polymerizatio PET/CaCO3, Epoxy (b1) Dispersion of inorganic particles into a n vinyl ester/ Fe3O4 ; precursor of the polymeric matrix (monomer); (b2) Epoxy vinyl ester/γ- Polymerization of the mixture by addition of an Fe2O3; Poly (acrylic appropriate catalyst; acid)(PAA)/Ag, PAA/ Ni (b3) Processing of this material by conventional and PAA/Cu moulding technologies. AgNO3, NiSO4 and Use of ultrasonics for dispersion in epoxy systems. CuSO4; Exposition of Ag systems to Co60 γ-ray to promote simultaneous polymerization and metal nanoparticle formation. Sol-Gel Polyimide/SiO2; 2- Embedding of organic molecules and monomers on Process hydroxyethyl acrylate sol-gel matrices; introduction of organic groups by (HEA)/SiO2, formation of chemical bonds → In-situ formation of polyimide/ silica. sol-gel matrix within the polymer and/or PMMA/ SiO2, simultaneous generation of inorganic /organic polyethylacrylate/ networks. SiO2, polycarbonate / SiO2 and poly (amide- imide)/TiO2 Method Advantages Limitations Intercalati Synthesis of intercalated nanocomposites Industrial use of large amounts on / based on polymers with low or even no of solvents. Prepolyme polarity. Preparation of homogeneous r from dispersions of the filler. Solution In-situ Easy procedure, based on the dispersion of the Difficult control of intra gallery Intercalati filler in the polymer precursors. polymerization. Limited ve applications. Polymeriz ation Melt Environmentally benign; use of polymers not Limited applications to Intercalati suited for other processes; compatible with polyolefins, who represent the on industrial polymer processes. majority of used polymers. Template Large scale production; easy procedure. Limited applications; based Synthesis mainly in water soluble polymers, contaminated by side products. Chemical Simple; low processing temperature; versatile; Weak bonding, low wear- Processes high chemical homogeneity; rigorous resistance, high permeability and (Sol-Gel, stoichiometry control; high purity products. difficult control of porosity. Colloidal)