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Nanocrystalline (NC) metals are a subdivision of the family of nanostructural materials. Nanostructural materials are single phase or multi-phase polycrystals, the crystal size of which is of the order of a few (typically 1-100) nanometers in at least one dimension. Nanocrystalline materials have many interesting physical and chemical properties which attract researchers. Particularly in catalyst’s utility, it can provide a large specific surface area and active sites. Its size efficiency (Kubo efficiency) may create different electron energy gap which permits us to do other functional designs. Some phenomenons contribute to attractiveness of nanocrystalline material as catalysts or sensors. The interfacial study between NC metal and oxides became an important issue to evaluate the performance of the these applications.Gas-condensation technique is used to produce the nanophase WO3 or TiO2 by evaporating the tungsten in 10 mbar O2 atmosphere or pure titanium in (10 mbar O2/90 mbar He) atmosphere, respectively.

This paper presents recent result on the observation of microstructure of nanocrystalline platinum. Nanocrystalline powders of Pt are made by gas condensation method, and examined by using TEM and HRTEM. Twin structure is found first within the individual particle of as evaporated nanophase Pt particles which form twin during the nucleation and growth of particle. Twin also appears while neck growth take place during the sintering of as evaporated pt with Al2O3. The formation of these twins during sintering was due to the fact that the neck growth will induce a tensile stress which is high enough to pull the nanocrystalline powders to form twin structure. Twin plane of nanophase sintering Pt powder was identified by using the Fourier transformation as {111} plane. It is the same as usually found in fcc bulk materials.The pure nanocrystalline Pt particles with a diameter less than 100 nm had been produced by the gas evaporation in helium atmosphere.

Polyetheretherketone (PEEK) is a crystallizable thermoplastic used as composite matrix materials in application which requires high yield stress, high toughness, long term high temperature service, and resistance to solvent and radiation. There have been several reports on the crystallization behavior of neat PEEK and of CF/PEEK composite. Other reports discussed the effects of crystallization on the mechanical properties of PEEK and CF/PEEK composites. However, these reports were all concerned with the crystallization or melting processes at or close to atmospheric pressure. Thus, the effects of high pressure on the crystallization of CF/PEEK will be examined in this study.The continuous carbon fiber reinforced PEEK (CF/PEEK) laminate composite with 68 wt.% of fibers was obtained from Imperial Chemical Industry (ICI). For the high pressure experiments, HIP was used to keep these samples under 1000, 1500 or 2000 atm. Then the samples were slowly cooled from 420 °C to 60 °C in the cooling rate about 1 - 2 degree per minute to induce high pressure crystallization. After the high pressure treatment, the samples were scanned in regular DSC to study the crystallinity and the melting temperature. Following the regular polishing, etching, and gold coating of the sample surface, the scanning electron microscope (SEM) was used to image the microstructure of the crystals. Also the samples about 25mmx5mmx3mm were prepared for the 3-point bending tests.

Alternative phases which are other than the most stable crystalline phase can be formed from highly supercooled liquids. Phase selection occurs during nucleation which is strongly affected by the extent of supercooling. A large supercooling in the liquid is generally needed in order to nucleate alternative phases. Supercooling will increase with suppression of heterogeneous nucleation and with increasing cooling rate. Thus, high cooling rate and isolation of the heterogeneous catalytic sites should be simultaneously reaLized in order to achieve large supercooling. From a practical point of view, production of very small liquid droplets in high vacuum using electrohydrodynamic (EHD) atomization is a very effective way to achieve large liquid supercoolings.Seventeen pure elements have been studied previously by using the electrohydrodynamic (EHD) process. The results show that pure nickel forms an amorphous phase in the smallest (< 10 nm diameter) submicron spheres.

Spherical submicron particles of materials produced by electrohydrodynamic (EHD) atomization have been used to study a variety of materials processes including nucleation of alternative crystallization phases in iron-nickel and nickel-chromium alloys, amorphous solidification in submicron droplets of pure metals, and quasi-crystal formation in nickel-chromium alloys. Some experiments on pure nickel, nickel oxide single crystals, the nickel/nickel(II) oxide interface, and grain boundaries in nickel monoxide have been performed by STEM. For these latter studies, HREM is the most direct approach to obtain particle crystal structures at the atomic level. Grain boundaries in nickel oxide have also been investigated by HREM. In this paper, we present preliminary results of HREM observations of NiO growth on submicron spheres of pure nickel.Small particles of pure nickel were prepared by EHD atomization. For the study of pure nickel, 0.5 mm diameter pure nickel wire (99.9975%) is sprayed directly in the EHD process. The liquid droplets solidify in free-flight through a vacuum chamber operated at about 10-7 torr.

Kelly et. al. have processed submicron spherical particles of iron-nickel alloys and pure elements by using electrohydrodynamic (EHD) atomization. The liquid droplets solidify in free-flight through a vacuum chamber operated at about 10-5 Pa. Each droplet is a separate nucleation experiment in which the droplet diameter is readily determined. Both high cooling rates and extreme isolation of heterogeneous catalytic sites are realized in the EHD process. Thus, rapid quenching of submicron spherical particles by using EHD process in Ni-Cr alloy may provide an opportunity to produce segregation-free alternative crystal phases (ACP) with low chromium contents.In this study, Ni-10, 20 and 30 at%Cr alloys were atomized and several samples of each composition were prepared for scanning transmission electron microscopy (VG HB501 STEM) analysis. EDS spectra from about ten different sphere sizes were recorded for each sample. Table I shows the average composition and standard deviation of the EDS measurements. The results indicate that each sphere composition deviates less than two percent. The X-ray counting times of chromium peak are greater than 1000 times in each sampling.