Gels with hierarchical well-defined macropores and supramolecularly templated mesopores have been synthesized in the systems of pure silica as well as organic-inorganic hybrids. Cationic surfactants such as alkyltrimethylammonium salts and nonionic surfactants such as poly(ethyleneglycol)-poly(propyleneglycol)- poly(ethyleneglycol) triblock copolymers, EOPOEO, were found to be effective for pure silica system both in inducing the phase separation to give macroporous morphology and in templating the mesopores within a narrow distribution width. The partial introduction of methyl-modified alkoxide into the pure silica system lead to increased phase separation tendency accompanied by the disturbance of the supramolecular templating of mesopores. By contrast, in the 1,2-bis(trimethoxysilyl)ethane systems, poly(ethylene glycol) and EOPOEO were much better additive to induce phase separation in spite of the presence of internal hydrocarbon chain. Combination of well-defined macropores and supramolecularly templated mesopores has been achieved by selecting an appropriate molecular weight and concentration of EOPOEO in the starting composition.

Carbon/Nafion® nanocomposite thin films developed through a low-cost procedure were shown to function as high-sensitivity, low-noise, high-throughput laser desorption-ionization mass spectroscopy substrates for small molecule detection without the need of organic matrices. Our nanocomposite approach combines the strong light absorption feature of amorphous carbon with Nafion®'s efficient protonating capability to yield superior laser desorption-ionization.

Highly oriented, near single-crystal lamellar triblock copolymer films with alternating rubbery-glassy layer morphology possess an interesting anisotropy in their mechanical behavior, which can prove to be attractive for various applications. Here, the deformation micromechanics of highly oriented styrene-butadiene-styrene (SBS) lamellar triblock copolymers are investigated. The competing roles of the glassy (PS) and rubbery (PB) phases in the layered configuration are studied with micromechanical finite element based representative volume element (RVE) models subjected to tensile loading at different directions to the lamellar plane. The calculated material response is compared to x-ray and microscopy data from the literature, and proves to be successful in linking the macroscopic material response to the underlying physics of the microstructural evolution. Moreover, the RVE simulations are successful in reproducing the mechanical behavior of highly oriented nano-clay block copolymer nanocomposites. The response of layered-silicate models having 2wt% clay content is compared to the behavior of the respective neat block copolymer (BCP) and to existing experimental data. The ultimate objective is to facilitate these micromechanical models to design hierarchically ordered materials with properties, which will be optimally tailored for different classes of applications.

The electrochemical polymerization of conducting polymers, such as polypyrrole, generally requires the incorporation of an anionic dopant to balance the positive charge on the oxidized conducting polymer chains. The susceptibility of multiwalled carbon nanotube (MWNT) surfaces to functionalization makes them exciting candidates for a new class of dopant for conducting polymers. In this work, the doping of polypyrrole with functionalized MWNTs is investigated using a combination of electrochemical impedance spectroscopy, scanning electron microscopy, and quartz crystal microbalance work. The findings described here are particularly relevant in light of recent reports indicating that carbon nanotube-conducting polymer composites hold great promise for use in electrochemical capacitors, also known as supercapacitors [1,2].

One of the many forms of carbon, diamondlike carbon (DLC), consists mainly of sp3-bonded carbon atoms. DLC coatings possess properties close to diamond in terms of hardness, atomic bonding, and chemical inertness. Unfortunately, DLC exhibits poor adhesion to metals and polymers. The adhesion of the DLC film is determined by internal stresses in the film and by interfacial bonding. This work involves processing, characterization and modeling of diamondlike composite films on metal and polymer substrates to improve adhesion and wear properties. A novel target design was adopted to incorporate metal (silver or titanium) atoms into DLC films during pulsed laser deposition. STEM of the DLC/metal nanocomposites has shown that the metals that do not form carbides (e.g., silver) form 2–10 nm inclusions within the DLC matrix. Wear resistance measurements made on these samples have demonstrated that DLC/metal nanocomposites possess exceptional wear resistance. Diamond-like carbon nanocomposites also exhibit significantly enhanced adhesion. Careful analysis of the Raman data also indicated a significant shift to shorter wavelength in DLC nanocomposite films, indicating a reduction in compressive stress within these films. The sp3 content of these films was studied using electron energy loss spectroscopy (EELS). By varying the metal concentration as a function of distance from the interface, we have created functionally gradient DLC nanocomposites. These DLC/metal nanocomposite coatings have multiple biomedical applications.

A simple mechanical stirring process leads to charge-stabilised dispersions of aligned, substrate-grown, CVD-grown multi-wall carbon nanotubes in an epoxy resin. Subsequent sample processing, after the addition of the hardener, can be used to induce the nanotube agglomeration necessary to achieve electrically conductive bulk composites at low loading fractions. Both the nanotube percolation threshold and the resulting bulk conductivity can be adjusted by selection of suitable processing parameters and nanotube aspect ratio. This behaviour of aligned CVD-grown multi-wall carbon nanotubes allows lower electrical percolation thresholds than are possible with entangled multi-wall carbon nanotubes, single-wall carbon nanotube bundles, or carbon black in an epoxy matrix. Furthermore, the application of electric fields during composite processing induces the formation of aligned multi-wall carbon nanotube networks between electrodes dipped into the dispersion. Such composites show an electrical conductivity above the anti-static level and retain a degree of optical transmissivity.

As the individual layer of Ti is reduced in thickness in a Ti/Nb multilayered thin film structure, the Ti layer can undergo a change in phase stability from hcp to bcc. Due to its high spatial resolution, atom probe tomography (APT) is ideally suited to characterize the compositional variations in such thin film structures. A series of hcp Ti / bcc Nb and bcc Ti / bcc Nb multilayers have been sputtered deposited and prepared as APT specimens using a Focus Ion Beam (FIB) milling procedure. The APT results have shown a substantial interdiffusion of Nb into the bcc Ti layers to a pseudo-equilibrium concentration of approximately Ti-20at%Nb while maintaining a compositionally modulated interface. In contrast, the hcp Ti layers indicated little Nb interdiffusion within the layers. Thermodynamic volumetric free energy modeling has indicated that this unexpected Nb interdiffusion facilitated the bcc phase stability. The coupling of APT results to the pseudomorphic bcc Ti phase demonstrates the capability APT has in quantifying the compositional characteristics in these types of multilayered nanocomposite systems.

The present paper describes a new concept of synthesizing nanoporous carbons that allows control not only of the pore structure, but also of the molecular structure of the internal surfaces. Interfacial molecular control is achieved through the use of discotic liquid crystalline precursors whose molecular orientation on the substrate material is known or can be determined by simple measurements on flat substrate test samples. Here a suite of nanoporous (mesoporous) carbons are synthesized from various porous glass and silica gel templates, and a model is developed to predict the carbon properties from template properties thus allowing systematic template selection.

In the present work, a novel method of synthesis has been developed to obtain highly dispersed oxide powders. This method is based on the combination of hydrothermal and ultrasonic treatment and uses the effect of acoustic cavitation.

Hydrothermal-ultrasonic treatment was carried out under the following conditions: T= 423 - 523 K, t = 10 min. -3 h. and ultrasonic frequency ν = 21.5 kHz. The control experiments (without ultrasound) were performed under the same conditions. The products were characterized by X-ray diffraction (XRD), thermal analysis (TGA), transmission electron microscopy (TEM). The specific surface area was determined by the BET method.

It was found that high-temperature hydrolysis of cobalt (II) nitrate in ultrasonic field results in formation of considerably smaller particles of Co3O4 in comparison with conventional high-temperatures hydrolysis (mean particle size decreases from 600–650 nm to 60–70 nm). It must be noted that Co3O4 samples obtained by hydrothermal-ultrasonic treatment possess mesoporous structure.

Ultrasonic-hydrothermal processing of amorphous gels of zirconyl and titanyl hydroxides leads to significant raise of the rate of crystallization process and formation of nanopowders of zirconia and titania (mean particle size 7–16 nm).

It must be pointed that the use of ultrasonic treatment during hydrothermal processing of amorphous gel of zirconyl hydroxide and 0.3 M aqueous solution of H2TiO(C2O4)2 leads to increase of the content of thermodynamically stable phases in the products of synthesis.

The mechanisms underlying stabilization of the metastable tetragonal (t)-phase in sol-gel derived, nanocrystalline ZrO2 were studied by high-resolution analytical electron microscopy, utilizing parallel electron-energy loss (PEEL) and energy-dispersive X-ray spectroscopies. The powders were synthesized by hydrolysis of Zr (IV) n-propoxide at ratios of molar concentration of water to Zr n-propoxide, R=5 and 60, respectively, followed by calcination at 400°C. Dense particles of the as-precipitated ZrO2 (R=5) revealed 4–11 nm-sized nanocrystals embedded in the amorphous matrix that may serve as nuclei for the t-phase during calcination. The calcined particles consist of 10–100 nm–sized t-crystals. For as-precipitated ZrO2 (R=60), week aggregates (50–100 nm) of largely amorphous 4–20 nm-sized particles after calcination yield a mixture of t-and monoclinic (m-) nanocrystals. PEELS fingerprints of the band structure with the intensity threshold matching the expected position of a direct bandgap at 4–5 eV allow to differentiate between the amorphous and nanocrystalline ZrO2. Stabilization of t-phase (R=5) with sizes up to 16 times larger than reported earlier is likely due to strain-induced confinement from surrounding growing grains, which suppress the volume expansion associated with the martensitic t-m transformation. For R=60, loose nanoparticle agglomerates cannot suppress the transformation. In this case, the t-phase may be partially stabilized due to a crystal size effect and /or to the presence of m-phase.

The evolution during growth and subsequent annealing of the <111> fiber texture in magnetron-sputtered nanocrystalline Au films has been studied experimentally using X-ray diffraction with synchrotron radiation. To quantitatively investigate this fiber texture, grain orientation distributions were recorded in situ during growth and during subsequent annealing using Bragg-Brentano geometry. The (111) diffraction intensity was measured as a function of the sample tilt χ, the tilt axis lying at the intersection of the film surface and the scattering plane. As a quantitative measure of the texture, we used the width of the orientation distributions. The grain-orientation distributions narrowed during annealing. The activation energy for the process behind this texture change was found to be 0.64 ± 0.05 eV, close to the activation energy for grain boundary self-diffusion in nanocrystalline Au. This and the narrowing of the grain orientation distributions led us to suggest that the observed changes in texture originated from grain rotations and not from grain growth. Grain growth did not take place at the lower temperatures, where changes in orientation distributions were observed.

Nanoporous thermosets are used as polyelectrolytes in fuel cells, separation membranes, and sensors and actuators, etc. Design of nanoporous thermosets for such applications entails controlling permeability by tailoring the pore size and pore chemistry. Usually free radically polymerizing and simultaneously phase separating systems are used to synthesize porous thermosets. A novel method of synthesizing nanoporous polymeric materials is employed in this work. This technique involves the synthesis of nanoporous thermosets by reactive encapsulation of an inert solvent using step-growth crosslinking polymerization reaction carried out until completion without phase separation into macroscopic phases. Key structural features of the porous materials synthesized by the reactive encapsulation technique were investigated by Scanning Electron Microscopy (SEM) after extraction and supercritical drying using carbon dioxide. Micrographs of the materials synthesized using the reactive encapsulation technique showed that the porous materials of pore size less than 100nm are obtained. Micrographs also showed that the reactive encapsulation technique can be employed to synthesize nanoporous polymeric materials of desired porosity and pore size by changing the solvent content. In addition, porous thermosets were also synthesized using free radical chemistry and phase separating system. The differences in the porous morphology of both these systems were enunciated using SEM micrographs.

Mo doped vanadium oxide nanotubes (VONT) were formed via a rheological phase reaction followed by self-assembling process and were heated at 400 □ in an inert atmosphere. The nanotubes were characterized by SEM, HRTEM, XRD, FTIR, electrochemical investigation, etc. In contrast to the undoped VONTs, the interlayer distance between oxide layers in the (V0.99Mo0.01)xONTs increases owing to replacement of some V in nanotubes by Mo with a larger ionic radius, resulting in a shorten diffusion length of Li ions and an improved electrochemical performance. The electrochemical performance of (V0.99Mo0.01)xONTs is further enhanced by removing the residual organic template by heating in an inert atmosphere.

Silver single crystals (Ag(100), Ag(111)) were exposed to 5eV hyperthermal atomic oxygen, created by a laser detonation of molecular oxygen at a substrate temperature of 220°C for 7 hours. Oxide scales of more than ten microns formed on both Ag (100) and Ag (111) substrates. The microstructural investigation of the oxide layers by high resolution transmission electron microscopy (HRTEM) revealed that the “oxide” scales are predominately composed of nanosized polycrystalline silver grains (5–100nm) as well as a small amount of nanosized silver oxides. The results were remarkably different than the O2 oxidation. The HRTEM investigation suggested that the grains of polycrystalline silver were first carved off from the substrate into “oxide” scale by lattice expansion and decohesion, which are driven by atomic oxygen diffusion in Ag lattice, occupation of oxygen atoms at the interstitial sites of Ag lattice, and partially internal oxidation. The grains in the scale were also subject to continuing oxidations with the atomic oxygen--secondary poly-crystallization, and changed to smaller grains. The preferred oxidation fronts in silver lattice is along the {111} planes.

This study investigated the microstructural characteristics of directionally solidified freeze-dried silica sols. Porous structures were formed by depositing silica sol on silicon (100) single crystals. The deposited sols were unidirectionaly solidified by placing the silicon substrate on a copper block immersed in liquid nitrogen and then subsequently freeze-dried. Freeze drying removal of ice crystals created three-dimensional pore channels ranging from 3 to10 micrometers in diameter aggregated in grain like colonies 50–100 micrometers in diameter. Pore size, spacing, colony size and microstructure were determined using optical microscopy (OM) and scanning electron microscopy (SEM) while the structure of the amorphous SiO2 was characterized by X-ray diffraction (XRD). The microstructure results are compared and contrasted with silica aerogel obtained through conventional processing using supercritical CO2.

Silicon nanotips, grown via electron cyclotron resonance plasma chemical vapour deposition, with apex diameters of ∼2nm and lengths of 1000 nm and densities of 1011/cm2 were used as a new substrate for surface enhanced Raman spectroscopy. Ion beam sputtered gold and silver self assemble on these substrates as nanoparticulates of 4–10 nm diameter and these metallic nanoparticulates assist in the surface enhancement of Raman signals of analytes. Molecules such as Rhodamine 6G and bis-Pyridyl ethylene of varied concentrations, in the range of 10-6-10-10 M, has been studied on these substrates and enhancements in the range of 106-108 were observed.

The structure of a Re(5 nm)/(Co(2 nm)/Re(3 nm))19 sample grown via magnetron sputtering was thoroughly analyzed via x-ray reflectivity (XRR) and transmission electron microscopy (TEM). Cross-sectional TEM results indicate that the sample is epitaxial, with the in-plane c-axis of the superlattice pointing along the c-axis of the substrate. A quantitative analysis of XRR yielded an average thickness of each layer and an interface roughness ∼ 0.4 nm between the Co and Re layers. A careful analysis of the TEM data reveals that the in-plane lattice parameters for Co, Re and Al2O3 are approximately 0.24 nm, 0.43 nm; 0.26 nm, 0.44 nm; and 0.24 nm, 0.44 nm, respectively. The lattice spacings of Al2O3 correspond to a/2 and c/3, where a, and c are lattice parameters, respectively. Interestingly, both high resolution and Z-contrast images show a very uniform period thickness. Z-contrast images, however, show that the initial interface roughness between the Re buffer layer and the first Co layer is amplified as the layers get farther away from the substrate. A high magnification TEM analysis shows that the bottom Co-Re interface roughness is about 0.2 nm, whereas the top Re-Co interface roughness is about 0.7 nm. Previous anistropic magnetoresistance measurements are discussed in light of these new structural data.

The flame retardancy of nylon 6/laponite and nylon 6/montmorillonite nanocomposites was investigated. The pronounced effect of layered silicates on heat release and mass loss rates of nylon 6 was examined. We found that nylon 6/laponite has 46 % and nylon 6/montmorillonite has 52.5 % lower peak heat release rates than that of neat nylon 6. The 6.5 % difference between the peak heat release rates of laponite- and montmorillonite-based nanocomposites was attributed to differences in aspect ratio and surface charge density of the nanoparticles.

The barrier properties of nanocomposite chars was evaluated by examining the peak heat release and mass loss rate reductions of stacks of layers, with the bottom layer being neat nylon 6 polymer and the top layers being nanocomposites that formed chars during the experiments. We observed that the peak heat release rate of a 10×10×0.3 cm neat nylon 6 slab was reduced by about 45 % when protected with a char-forming nylon 6/montmorillonite slab of same dimensions. The dramatic reduction of the peak heat release rate of neat nylon 6 when covered with a nanocomposite char was consistent with the notion that the flame retardancy of polymer/clay nanocomposites is affected by the (thermal and/or mass) barrier properties of the char. In order to test the thermal insulation of the char, temperature profiles of the layered samples were measured during cone calorimeter experiments. We observed that the nanocomposite char that brought about a 44.5 % reduction in peak heat release and mass loss rates reduced the heating rate of the same neat nylon 6 by about 31.2 %. The reduction in the heating rate increased with the amount of nanocomposite char formed.

A unique nanocomposite of poly (3-methylthiophene) with functionalized multiwalled carbon nanotubes (MWNT) has been synthesized that shows selective sensing for halogenated methanes. The sensor has been found to give the highest response for chloroform and none for methane. A tentative model has been proposed for this selective sensing of halogenated methanes.

To find an alternative for CVD diamond films and carbon nanotubes for low-field electron emission sources and cold cathode applications, we have designed a novel class of nanomaterials with excellent field emission properties – dielectric/carbon nanocomposites, in which different insulating nanoparticles such as silicon oxide, boron nitride in cubic and hexagonal forms, and nanodiamond were used inside a pyrocarbon matrix. The thickness of pyrocarbon shells covering the dielectric particles can be controlled in a wide range during the CVD process. The best samples of the nanocomposites with all four kinds of dielectric material show excellent field emission properties with threshold fields of as low as 0.5–1 V/μm, good surface uniformity and long-term stability. An effect of post-growth treatment with oxygen and hydrogen plasma on the emission was also studied. A mechanism of the emission is discussed basing on quantum properties of nanostructured thin (two-dimensional) carbon covering the dielectric particles. The mechanism could be suitable for wide range of nanostructured sp2-bonded carbon objects.