63Cu and 65Cu NMR spectra from cluster-assembled nanophase copper with an average grain size between 5 and 10nm show a broadened peak, at the normal Knight-shifted frequency for copper metal, which arises from only the central 1/2 to -1/2 transition. A very broad background is observed on either side of that peak. Some samples exhibit a second broad peak at a position normally associated with non-metallic copper. Pulsed NMR measurements of the central peak show that virtually all the copper signals are significantly broadened and have a spin-spin relaxation time longer than larger grained copper samples. Line shape measurements, using spin echoes, as a function of delay between rf excitation and measurement show there are a number of copper sites with longer relaxation times which have a significantly larger broadening. Those sites are tentatively identified as being at or near a grain boundary or free surface. A small orientation effect is observed indicating an anisotropy within the samples. An isochronal anneal of one sample showed significant, but not complete, line narrowing after an anneal at 450°C consistent with other nanophase metals which show grain growth above 40-50% of the melting temperature.

Catalysts consisting of ultra-fine gold particles supported on iron oxide have been synthesized by the coprecipitation method. Subsequent to preparation, each sample was heat treated in air at four different temperatures, ranging from 473 K to 773 K. Steady state carbon monoxide oxidation was carried out over each sample. Upon extended reaction, catalyst deactivation took place over three of the catalysts whose respective surface compositions (e.g., gold to iron atomic ratio) were altered appreciably from their initial state. Surface structure analyses performed on all the unreacted catalysts have revealed variations in physical properties (e.g., degree of crystallinity and particle size). In addition, lattice parameters of gold were observed to increase up to 20 % from the bulk value. In contrast, XPS showed both gold and iron to be in essentially the same chemical states for all catalysts, irrespective of heat treatment temperatures. The importance of surface sensitive parameters to catalytic function are discussed.

The thermal properties of the nanocrystalline metal Ag (n-Ag), with the average grain size of 10 run, synthesized by an inert gas condensation and in situ compacting technique under different pressures of 0.2 to 1.5 GPa were studied. The thermal stable temperature for asprepared state is 373K, above which the grain growth appears at different rates. An exothermal peak and an endothermal peak occur on the DSC curves of the n-Ag. The enthalpy of both peaks are dependent upon the compacting pressure. Tht enhancement of the specific heat in going from the polycrystalline to the nanocrystalline state varies between 5.4% and 3.6% in the temperature range of 380K to 540K. The thermal diffusivity at room temperature increases with grain growth, and approaches to the corresponding value of the polycrystalline Ag.

Silicon powder has been produced by means of square-wave modulated rf silane plasma. The plasma conditions were: 30°C of reaction chamber temperature, 70 Pa of pressure, 80 W of rf power and 0. 1 Hz of square-wave modulation frequency. The gas flow rate was varied from 5 to 90 sccm.

The distribution and size of the powder grains were determined by transmission electron microscopy. The compositional and microstructural analysis of the powder was performed by FTIR spectroscopy. This analysis has revealed the dominant presence of SiH2 groups (2100 cm−1), in a highly polymeric form (850 and 890 cm−1), as well as the existence of an absorption band (1000-1100 cm−1) associated with oxidation of the powder.

These results have shown the great influence of the flow rate, through the gas residence time, on the composition and microstructure of silicon powder.

Nanocrystalline Fe (α and γ phases), Fe-carbide (Fe3C, Fe7C3 ), Fe-sulfide (Fel-xS), Fe-nitride (Fe3N and Fe4N) particles with narrow size distributions have been produced using a CO2 laser pyrolysis of vapor mixtures of Fe(CO)5 with C2H4, H2S or NH3. Typical production rates of ∼ 1 - 3 g/hr were observed. The chemical phase and size of these nanoscale particles can be controlled by reaction parameters such as laser intensity and gas composition. Pyrolytic carbon coatings were found to be present on the Fe-carbide particles, but absent in the Fe-sulfide and -nitride particles.

Atom-probe techniques have been used to characterise nanostructured metallic materials prepared by thermal evaporation and by sputtering. Multilayer samples of Fe-Cr have been prepared by sputter deposition and analysed using the Oxford position-sensitive atom probe. This has made it possible to observe the quality of interfaces in the material, and also accurately determine local compositions at each layer within the multilayer stack. Preliminary experiments aimed at producing dual phase nanocrystalline films by thermal evaporator deposition are also reported.

This paper discusses the effects residual porosity may have on some properties of nanocrystalline materials. The two examples considered here are Young's modulus and saturation magnetization. It will be shown that the large variations observed for these properties may be explained, at least in part, on the basis of the residual porosity in thematerials which may vary considerably depending on the production techniques used to synthesize nanostructured materials.

Nanocrystalline Pt (nc-Pt) thin film was prepared by R. F. sputtering on liquid N2 cooled substrate. Transmission Electron Microscopy (TEM)analyses clearly show that the as prepared film is constructed by numerous nanometer sized particles with average diameter of about 8-9nm. The interfaces between particles can be clearly seen and the interface width is about nmm. Electron Diffraction (ED) photograph and X-ray Diffraction (XRD) spectroscopy both confirm that the nanometer sized particles in the film are ultra fine crystallites with a cubic structure. The crystallite size increases gradually with annealing temperature. The temperature coefficient of resistance (TCR) of nc-Pt film are much lower than that of polycrystalline Pt film. DC conductivity and TCR also increase gradually with the increase of annealing temperature. It is suggested that the interfaces between the nanoorystallites greatly influence the properties of nc-Pt thin film.

A new group of nanostructured composites with chromium silicide and silicon carbide has been developed. These composite powders which are about 20-40 rm in size were prepared by the chemical synthesis route and were characterized by UV, DTA/TGA, XRD, FTIR and SEM. Chemical reaction and phase formation versus the processing temperatures have been investigated and discussed. The particle size and the lattice parameter of the synthesized composite have been found to be dependent on the processing temperatures. A possible reaction mechanism of the nanostructured silicon oxide to silicon carbide is proposed.

Electroplating is one of the most technologically advanced methods to synthesize nanophase materials both as coatings and in bulk form. This paper demonstrates the formulation of a processing “window” for nanocrystalline Co-W alloys using factorial design. The microstructural evolution from polycrystalline to nanocrystalline to amorphous Co-W microstructures is shown for electrodeposits produced from a bath containing cobalt sulphate, sodium tungstate, Rochelle salt and ammonium chloride. The effect of operating variables such as temperature and current density is discussed.

We have studied the structure of the Co-Ag granular system across the entire composition range, as well as the annealed samples, using transmission electron microscopy (TEM) and x-ray diffraction. GMR, as much as 80% at 5K and 25% at room temperature, have been observed. The absolute values of the resistivity (ρ) and the change of the resistivity (δρ) as functions of the magnetic Co concentration and the annealing temperature have been determined. A linear relation between δρ and I/rco, where rco is Co particle size, has been found. This result suggests that the magnetic scattering at the interfaces is crucial to GMR.

Nanocrystalline and amorphous Fe-Ti at or close to the equiatomic composition have been prepared by ball milling, starting either from the elemental components or from the pre-melted intermetallic. The final structure, whose evolution has been monitored by Xray diffraction and transmission electron microscopy, is found to be critically dependent on milling conditions and contamination level.

Hydrogen absorption properties of both the amorphous and nanocrystalline alloys have been investigated. These properties are substantially modified by the reduction in grain size. We will also discuss the influence of the activation process and repeated hydrogen charging on substitutional disorder and grain size.

Ball milling has been used to mechanically induce the displacement reaction 3Fe3O4 + 8 Al → 9 Fe + 4 A12O3, in which fine magnetite particles (Fe3O4) are reduced to nanophase iron particles. The presence of initial, intermediate, and final phases are easily identified by Mössbauer spectroscopy on samples taken at various stages of the milling process.

Our measurements confirm the gradual progress of the above reaction and also verify the presence of FeAl2O4 at intermediate milling times. The concentration of this phase reaches a maximum of 42% at a milling time of 100 minutes. After five hours, the sample is fully reduced and contains ferromagnetic bcc-iron and superparamagnetic iron particles. Further milling reduces the amount of ferromagnetic iron and increases the proportion of the superparamagnetic phase.

Amorphous and nanocrystalline Nil-xMox alloys have been prepared by mechanical alloying of pure Ni and Mo elemental powders in an atmosphere containing various amounts of oxygen. Metastable fcc solid solutions are formed when the Mo content is less than 30 at.%. The amorphization of the supersaturated solid solution occurs when the Mo concentration exceeds 30 at.%. The electrocatalytic properties of the nanocrystalline alloys for the hydrogen evolution reaction in alkaline solutions have been investigated. High electrocatalytic activity is found when the average crystal size is below 10 nm and when the supersaturated solid solution contains some oxygen.

To clarify the relation between high magnetic permeability and magnetic phases of Fe73.5Cu1Nb3Si13.5B9 ribbons, the process of precipitation was investigated by using the Xray diffraction, DTA, VSM and the Mössbauer spectra at various annealing temperatures. The volume fraction of each magnetic phase was estimated. The sample annealed at 853K which shows maximum permeability is composed of partially ordered Fe3Si(70%), Fe(B) solid solution(10%) and amorphous(20%) phases. The relative permeability of the sample annealed below 853K increases with increasing the volume fraction of both of the Fe3Si partially ordered and the Fe(B) solid solution phases. The relationship between tile permeability and the volume fraction is interpreted by the random anisotropy model.

Using mechanical attrition (milling) which also transforms the material into nanocrystalline form, various L12 or γ-type Ni3 A1-Fe alloys have been prepared in metastable-γ form and their magnetisations M(γ) and M(γ) and Curie temperatures Tc(γ) and Tc(γ) measured.

Using magnetic properties we determine isothermal ordering kinetics in the nanocrystalline γstate and find that the ordering reaction cannot propagate across the nanograin boundaries. Each grain must obtain its own γ nucleus thus resulting in a Johnnson-Mehl-Avrami exponent n =1.

In this paper we make clear distinctions from the terms nanophase, nanocrystalline and deal only with nanocomposites defined as an interacting mixture of two phases, one of which is in the nanometer size range in at least one dimension. The author's origins of development of the idea that nanocomposites are a virtually infinite class of new materials are described.

Then we refer to the results of our extensive studies of nanocomposites derived by solution-solgel techniques to illustrate the properties of such materials in the area of chemical and thermal reactivity.

Finally it is pointed out that in the last few years nanocomposite materials have become a major part of new materials synthesis all over the world for applications ranging from mechanical to optical, to magnetic to dielectric.

Silica particles were produced by the well known “Stbber” process. The silica core size as well as the coating thickness could be varied by the reaction conditions. Respectively, yttria core particles or coatings on silica nuclei were synthesized by the ureadecomposition method, previously described in general by Matijevic or Akinc et al.

The (silica or yttria) core size (86 to 400 nm) as well as the coating thickness (monolayer to 100 nm) was varied systematically. Green compacts of about 50 to over 60 % thD. were produced either by sedimentation, centrifugation, or pressure filtration of well dispersed slurries.

The results demonstrated the enhanced densification of coated powders. A two step shrinkage process was observed for some of the samples. TEM micrographs and X-ray analysis exemplify the microstucture and phase development during sintering.

The narrow, intense emission bands of europium(III) make its compounds of interest for various optical source applications. Previous studies have shown that europium thenoyltrifluoroacetonate complexes, e.g. Eu(TTFA)3, have superior fluorescence properties in select media with respect to inorganic salts like EuCl3. It has been shown that such complexes may be incorporated into solid-state matrices via the sol-gel process. The present research examines the luminescence behavior of a metalorganic complex (Eu(TTFA)3) doped into a sol-gel derived silica-acrylate ORMOSIL host and extends our earlier work on doped silica gel materials. The present study focuses on the effects of dopant concentration and dopant-matrix interaction, and seeks to compare the behavior of Eu(ITFA)3 in silica and ORMOSIL gel host materials.

Opto-chemical transducers, which exhibit changes in luminescence and/or absorption characteristics as a function of local conditions, are currently of great interest for use in performing quantitative chemical analyses. Present research is focused on the preparation and characterization of novel optrode materials which may be remotely interrogated via optical fiber carriers. The approach under investigation involves preparation of sol-gel derived films which are sensitized by the entrapment of analyte-complexing organic probe molecules. Zn(II)aq induced perturbations to the luminescence behavior of a porphyrin derivative entrapped within a porous sol-gel derived host matrix are detailed.