Wtastite-magnetite and magnesia-magnesioferrite nanocrystalline ceramics have been prepared by mechanical milling and spark plasma sintering. As-milled powders have a nanocrystal-line structure in both systems. Low energy milling gives rise to an increasingly higher volume fraction of wfistite as a function of milling time in the Fe1−xO-Fe3O4 system. Similar results are obtained in the MgO-MgFe2O4 system with increasingly larger amounts of MgFe2O4 produced by milling. Composites of magnetic particles (Fe3O4 or MgFe2O4) in a nonconductive matrix (FeO or MgO, respectively) are found in the sintered samples. Measurement of magnetic properties can be used to determine conclusively the nature of the developed phases and the effect of grain size.

Mechanical alloying of ternary SmFe11−xCoxTi (x = 0, 0.5, 1, 1.5, 2) alloys was carried out under an Ar atmosphere. Milled samples were annealed for 30 min in a vacuum at different temperatures Ta from 650 °C to 1150 °C. The effects of heat treatment, on structure and magnetic property changes, have been investigated by means of x-ray diffraction using the Rietveld method, Mössbauer spectroscopy and differential sample magnetometer. Tetragonal ThMn12-type structure is observed for samples annealed at Ta > 900 °C. For 650<Ta<800 °C the TbCu7 type phase was identified as the major phase. Between these two regions a mixture of TbCu7 and ThMn12-type nanocrystalline phases is obtained with a maximum of the coercive field Hc (Hc > 5kOe). The Mössbauer spectra relative to the hexagonal phase show sextuplets broadened by the statistical occupancies of the iron sites. An enhancement of the magnetic properties results from the Co substitution.

The reduction in grain size of a metal can lead to significant improvement in mechanical properties. Mechanical alloying (MA) with a second phase is a possible route to producing fine-grained, particulate reinforced material. This study describes the microstructural development of Ti-6%Al-4%V milled with increasing concentrations of boron. Mechanical milling of Ti-6%Al-4%V powder produces a nanocrystalline material. MA of Ti-6%Al-4%V with boron results in the alloying of the two to form either a boride or an amorphous phase when the local concentration of boron is ∼ 50 at.%. During milling, the boron tends to remain near to its original particle form and in these boron-rich regions TiB is formed. Beyond these regions small amounts of boron (a few at.%) mix with the titanium matrix and reduce further the grain size of the titanium. An increase in the global concentration of boron increases the volume fraction of boride produced.

The nature of the steady state reached during ball milling of CuxAg1−x powders (x=35 to 75) is studied as a function of the milling temperature (85K≤T≤503K). The characterization of the powders is performed by using x-ray diffraction, differential calorimetry and atom probe field ion microscopy. A steady-state phase diagram is built. Three-phase coexistence is shown to generally take place at intermediate milling temperatures. Atom probe data reveals that the solid solution stabilized by low milling temperature is nearly random, where as milling at elevated temperatures results in the decomposition of the elements at a lengthscale of 20∼30 nm.

METGLAS alloy #2826 (Fe40Ni40P14B6) is a eutectic alloy. Its melt can undergo metastable liquid state spinodal decomposition deep in the undercooling regime ΔT defined as ΔT = T1 - T where T1 is the liquidus of the alloy and T is the temperature at which the decomposition reaction takes place. Micrographs of undercooled Fe40Ni40P14B6 of ΔT = 209, 260 and 307 K were displayed. All of them exhibit refined microstructures, esp. the one with the largest ΔT.

We present the characterization of supersonic cluster beam deposition as a viable technique for the synthesis of nanostructured materials. Stable and intense cluster beams can be obtained with a pulsed microplasma cluster source. This technique has been applied to produce TiNi nanostructured thin films on various substrates at room temperature. The morphology and the structure of the film are strongly influenced by the precursor clusters. Films characterized by crystallite sizes of a few tens of nanometers can be grown without recrystallization by thermal annealing. The stoichiometry of the original TiNi alloy is maintained.

Highly mono-dispersed CdSe/CdS core-shell and CdSe/CdS composites have been prepared by a novel route involving thermolysis in TOPO using Cd(Se2CNMe(nHex))2 and Cd(S2CNMe(nHex))2. The absorption band edge (652 nm, 1.90 eV) of the CdSe-CdS core-shell structure is red shifted (22 nm, 0.0 17 eV) as compared to the CdSe nanoparticles (630 nm, 1.96 eV) whereas the absorption spectrum of the CdSe-CdS composites shows the absorption band edge at (584 nm, 2.12 eV), blue shifted (46 nm, 0.037 eV) as expected. Photoluminescence (PL, λex = 400 nm) of both the core-shell (622 nm) and the composites (588 nm) show values close to band edge emission. A sharper emission maximum with a considerable increase of intensity is observed for core-shell structure as compared to that of CdSe whereas the composite showed a broader emission maximum. The TEM images of the CdSe/CdS core-shell nanoparticles show crystalline, spherical particles with the average size of 53 Å (±7 %), a increase of 8 Å than the average size of CdSe (45 Å) nanoparticles, with a narrow size distribution. The High Resolution Transmission Electron Microscopy (HRTEM) showed lattice spacing intermediate between those for CdSe and CdS as is observed by Selected Area Electron Diffraction (SAED) and X-ray patterns (hexagonal phase). As expected no interface can be observed by HRTEM between CdSe core and CdS shell. The TEM image of the CdSe-CdS composites show particles with an average size of 48.7 Å (±10%).

Magnetocaloric effect of nanocomposites composed of iron-oxide or iron-nitride grains dispersed in a silver matrix was studied by calculating magnetic entropy change ΔS induced by a change in applied magnetic field H. These nanocomposites were synthesized by the inert gas condensation technique and nitridation by heat treatment in an ammonia gas stream. Average sizes of the iron-containing grains were 10-35 nm. Magnetic phases in the materials were Fe3O4 or γ -Fe2O3 for the oxide-composites and γ-Fe4N or ε -Fe3N for the nitride-composites. Values of the ΔS were obtained by applying a thermodynamic Maxwell's relation, (∂S / ∂H)T = (∂M / ∂T)H, to data set of magnetization M measured at various temperatures T. They clearly indicated significant enhancement due to the nanostructure as predicted.

The surface residual stress state induced by grinding and polishing an alumina/silicon carbide nanocomposite and monolithic alumina has been investigated using Hertzian indentation and fluorescence spectroscopy. Specimens were ground and then polished with diamond slurry with grit sizes ranging between 8 μm and 1 μm. The results show that the surface residual stress state in the nanocomposites is more sensitive to surface treatment than that in the monolithic alumina. Surfaces of both ceramics were examined in cross-section by TEM and direct observations were made of the plastic deformation induced by different surface treatments. There is a change in the predominant deformation micromechanism from twinning in the alumina to dislocation generation in the nanocomposites.

Nematic liquid crystal filled with Aerosil particles prospective inorganic-organic nanocom-posite material for optoelectronic application has been investigated by broadband dielectric spectroscopy (BDS) and photon correlation spectroscopy (PCS). The aerosil particles of diameter ≈ 10 nm in filled nematic liquid crystals form a network structure with linear size of LC domains about 250 nm and with random distribution of the director orientation of each domain. This material has a very developed liquid crystal-solid particle interface that makes the role of the surface layers of LC important in the determination of the properties of the material. BDS provides information on reorientational motion of polar molecules of liquid crystal while PCS probes dynamics of collective modes associated with director fluctuations. We found that the properties of 5CB are considerably affected by the network. Two bulk-like dielectric modes due to the rotation of molecules around short axes and the tumbling motion were observed in filled 5CB. Additionally, a low frequency relaxation process and dispersion of dielectric permittivity due to conductivity were observed. The treatment of the surface of filling particles has strongest influence on the properties of the slow process and it is less important for molecular modes. PCS experiment shows that two new relaxation processes appear in filled 5CB in addition to the director fluctuations process in bulk.

The structure and surface properties of composites based upon high-surface-area framework zirconium phosphates with supported WO3, MoO3 and Pt nanoparticles were studied by using combination of structural and spectral methods. The effect of these promoters on performance of zirconium phosphates in the reaction of pentane and hexane isomerization is considered.

In course of further development of our generic concept for the design of novel superhard nanocomposites [1,2] we have recently developed new multi-phase ultrahard nano-composite coatings with Vickers mirohardness of 80 to 105 GPa which is in the range of natural diamond. The coatings show a high elastic recovery of up to 90% upon a relatively large indentation deformation. The hardness measured by the depth sensing technique agree with those calculated from the area of the remaining pseudoplastic deformation. The very high apparent fracture toughness is illustrated by the absence of any radial cracks upon in-dentation with a large load of I N into 10.3 p.m thick film [3]. The unusual combination of high hardness, elastic recovery and apparent fracture toughness was attributed to the ample possibility of cracks deflection, meandering and termination during loading and cracks closure upon unloading [1,2,4]. The suggested nanostructure of the coatings has been elucidated on a basis of a complex analysis by means XRD, EDX, ERD, XPS and HR TEM.

Alumina/silicon carbide nanocomposites are known to show their highest strength levels after surface grinding followed by annealing. After annealing in flowing argon, nanocomposites with very coarsely ground surfaces have strengths exceeding those with a finely polished surface. Specimens with lapped surfaces also show a small improvement in strength on annealing. TEM investigations of annealed cross-sections show that the annealing process leads to surface crack healing. The chemical composition of the subsurface region has been studied, and reactive products on and close to the nanocomposite surface after annealing have been investigated by energy dispersive X-ray analysis in the STEM.

We have investigated the synthesis and the structural and magnetic properties of Fe nanoparticles embedded in Al2O3 matrix, a granular nanocomposite prepared by sol-gel processing. Samples with volumetric Fe content ranging from 20 to 62% were obtained starting from Al nitrate and Fe sulfate as precursors and the preparation method results initially in a mixture of Fe- and Al oxides. The conversion of Fe oxides into metallic Fe was done by calcination at 800°C followed of reduction at 600°C for 2 hours, in H2 atmosphere. Our results indicated the following phases in the amorphous alumina matrix, after reduction: α-Fe, the main phase, α- and γ-Fe2O3, Fe3O4 and some interstitial Fe2+ and substitutional Fe3+ atoms in the Al2O3 lattice. For the investigated system, Fe reduction rate was very sensitive to the sample porosity and, with the applied method, we have obtained reductions of the Fe atoms into metallic Fe ranging from 45 to 68%, preserving the mean diameter of the oa-Fe nanoparticles between 55 and 80 nm. VSM measurements at room temperature resulted in coercivity between 450 and 630 Oe and saturation magnetization between 40 and 110 emu/g. Magneto-transport measurements in samples with 25% metallic Fe (and 51% total Fe) reveal ΔR/R close to 2% at room temperature.

TiC and Ti-W-C films have been produced by chemical vapor deposition (CVD). A fractional factorial design was used to study the effects of deposition temperature, C:Ti input, H:Ti input, reactor pressure, and total mass flow on TiC film composition. Statistical models were developed for both titanium at.% and C:Ti in the film. It was found that the most significant affect on titanium at.% was the interaction of temperature, pressure and total mass flow. The most important affect on the C:Ti in the deposited film was the interaction C:Ti input, H:Ti, and total mass flow. Ti-W-C films have been deposited at 1050°C at various (TiCl4+W(CO)6)/CH4 inlet ratios ranging from 0.53 to 1.01. The characterization of the films revealed that the changes in deposition rate, crystallinity, film orientation, and morphology of various Ti-W-C compositions were affected by (TiCl4+W(CO)6)/CH4 inlet ratios.

This work describes the study of the surface reduction of ceria zirconia mixed oxides (CeZrO) as either thin films or powders, both with and without Pt present. XPS was used to measure the composition of the surface and the oxidation states of all metals contained within the material. The thin films of CeZrO showed little reactivity towards the reducing conditions used. Grazing incidence angle XRD showed the presence of Ce0.75Zr0.25O2. The thin films prepared with Pt showed that surface reduction of Ce4+ occurred under reducing conditions. The size of the Pt clusters was also determined from the data. The Pt was found to always exist in the metallic state. The Zr4+ was not seen to change during all treatments. For the powder samples the Ce4+ was readily reduced to approximately 60%. Pt was found to be initially oxidised with the % of metallic Pt increasing with reduction temperature. Again no change in the Zr was observed.

The formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at the nanophase level have been probed by photon and electron transmission and neutron scattering techniques to help elucidate the basis for structural integrity together with the small entity sizes that permit transparency in the visible range. They also help with understanding the chemical reactivities of the metal-containing sites in these very high surface area materials. These results are discussed in connection with new reaction studies.

Sol-gel method was used to prepare nickel oxide-silica and iron oxide-silica nanocomposites materials in form of aerogels and xerogels. The samples were characterized by thermal analysis, X-ray diffraction, N2 physisorption and transmission electron microscopy techniques. The variation of the supercritical solvent extraction conditions gives rise to differences in the morphological characteristics of the aerogels. These differences influence the size of the nickel oxide nanoparticles in nickel containing aerogels. On the other hand they do not affect the structure and size of the iron oxide nanoparticles in iron containing aerogels. The differences between the xerogel and aerogel nanocomposites are discussed.

Chemically functionalized alumina nanoparticles (carboxylate-alumoxanes) are used as the inorganic component of a new class of inorganic-organic hybrid materials. Lysine- or para- hydroxybenzoic acid-derivatized alumoxanes are readily prepared from the reaction of boehmite, [Al(O)(OH)]n, with the appropriate carboxylic acid. The peripheral organic hydroxides and amines of these carboxylate-alumoxanes either react directly with epoxide resins, such as the diglycidyl ether of bisphenol-A (DER 332), to form a hybrid material, or in the presence of an organic resin and hardener system to form a composite material. SEM and AFM show a uniform distribution of alumina nanoparticles within the resin matrix. The properties and cure times of the alumoxane hybrid and composite materials are distinct from both the pure resins and from a physical blend of the resins with traditional ceramic fillers. A significant increase in thermal stability and tensile strength is observed for both the hybrid and composite resin systems. In addition, both carbon fiber and carbon/Kevlar® matting have been successfully incorporated into the hybrid resin systems resulting in further property improvements.

Replacing the current on-chip dielectric materials such as silicon dioxide, which has a dielectric constant of approximately 4.0, with low dielectric constant materials can greatly improve the performance of high density VLSI device by reducing crosstalk and capacitive delay. Polytetrafluoroethylene (PTFE) has the lowest dielectric constant (k < 2.0) of any full density material, which makes it a promising candidate for this IC application. Pure PTFE thin films cast from PTFE nanoemulsion containing sub-20nm PTFE particles, though thermally stable, have some inherent sub-optimal properties. These include adhesion to other inorganic materials and mechanical strength at high processing temperatures. In order to improve these properties, we have developed a PTFE / silicon compound nanocomposite material. Initial tests have shown that this nanocomposite material has significantly improved high temperature mechanical properties and interfacial properties between the composite and inorganic materials such as silicon, silicon oxide, silicon nitride and some metals. The surface roughness of the thin film coatings is also reduced compared to pure PTFE thin film coatings. The coatings require no separate adhesion promoter to be applied to the substrate prior to deposition. Characterization work has been carried out with different techniques such as DMA, ToF-SIMS, XPS and AFM with hydrofluoric acid (HF) selective etching, in order to understand this novel nanocomposite and its surface and interfacial properties.