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The polyol process and the parameters influencing the synthesis of metal and alloy nanoparticle are discussed. Then, the synthesis strategies to obtain hard (Fe-Pt) and soft (Fe-Co) nanoparticles by using polyol process is presented. Under optimum synthesis conditions, partially ordered Fe-Pt nanoparticles with an average grain diameter of 8 nm exhibited a coercivity of 460 kA/m in the as-synthesized state. In the case of Fe-Co alloy particles, synthesis technique to prepare particles with varying Fe concentration in the size ranging between 300 and 50 nm is reported. Index Terms--Co alloys, FeCo, FePt, polyol process, soft magnetic materials.

A combination of wet grinding, hydrothermal treatment and oxidation process are used to describe a purification technique for multi-walled carbon nanotubes (MWNTs). This purification technique is believed to be able to revive research interest in MWNTs and bring about major advances in their application.

An experiment was conducted to extract dimeric fullerene oxides in the fullerene soot by using hydrothermally initiated dynamic extraction process. This process requires treating the soot hydrothermally before the extraction by organic solvent. Compared to Soxhlet extraction with organic solvents, this process was 40 times more efficient. Moreover, the analyses showed that the extract includes higher fullerene oxides in addition to dimeric fullerene oxides. Purification procedures for individual fullerene oxide are discussed.

The successful synthesis of Fe-Co nanoparticles by using a modified polyol process is reported. The formation of the alloy nanoparticles was confirmed by X-ray diffraction and X-ray extended absorption fine structure analyses. The concentration of iron in these particles could be varied between 40% and 90% by controlling the reaction conditions such as initial Fe/Co ratio, reaction temperature and hydroxyl ion concentration. The shape of the particles changed from spherical to cubic when the concentration of Fe was increased from 40 to above 60 at. %. The highest magnetization of 225 emu/g was recorded for [Fe.sub.70][Co.sub.30] nanoparticles. The magnetization of these particles decreased by about 20% when exposed to severe oxidizing atmosphere for seven days. Index Terms--Chemical synthesis, Fe-Co nanoparticles, polyol process, soft magnetic materials.

The synthesis strategies of Ni, Co and FePt magnetic nanoparticles with controlled particle size and structure through a modified polyol process are examined. The deceleration of reaction kinetics resulted in FePt nanoparticles with particle diameter below 10 nm and with fcc and a mixture of fcc and fct phases.

The synthesis technique based on heterogeneous nucleation to increase the average particle diameter of Mn-Zn ferrite and thereby increase the magnetic volume force of the temperature sensitive magnetic fluid is reported. The higher magnetization resulted in a higher magnetization-temperature gradient, which serves as a potential candidate for the preparation of temperature sensitive magnetic fluid.

Applications of Co[Fe.sub.2][O.sub.4] are limited due to the lack of synthesis technique to produce monodispersed, single domain and high coercivity ([H.sub.c]) nanoparticles. Here, we describe the growth dominant co-precipitation process to achieve high [H.sub.c] with moderate magnetization at room temperature (RT) in Co[Fe.sub.2][O.sub.4] nanoparticles. It is well known that the particle size is closely related to the relative interdependence between the nucleation and growth steps, which in turn can strongly be affected by the solution chemistry and precipitation conditions. Based on this premise, the effect of 1) reaction temperature, 2) NaOH concentration, and 3) feeding rate of metal ions into the alkali solution were evaluated. The maximum [H.sub.c] of 2.29 kOe (RT) was observed for the Co[Fe.sub.2][O.sub.4] prepared at 98[degrees]C, 1.13-mol NaOH, and the metal ion feeding rate of 0.00103 M/min. To improve the coercivity, single domain Co[Fe.sub.2][O.sub.4] nanoparticles were produced by in situ growth of the Co[Fe.sub.2][O.sub.4]seeds followed by size separation method. A coercivity of 4.3 kOe was achieved at RT for 40-nm single domain Co[Fe.sub.2][O.sub.4] nanoparticles, which is close to the theoretical value of 5.3 kOe. Index Terms--Coercivity, Co[Fe.sub.2][O.sub.4], ferrites, nanoparticles.

We have succeeded in the synthesis of nanometer size monodispersed Ni-Co metal particles through the modified-polyol process. Ni-Co metal particles of about 40 and 100 nm with Co-rich core and NJ-rich shell were produced by the manipulation of the reaction kinetics through a suitable selection of hydroxyl ion concentration in the ethylene glycol-Ni--Co system. Furthermore, core-shell structured (NiCo)O(AFM)-NiCo(FM) was produced by oxidizing particles at 533 K in air for different times. The magnetic properties, especially the exchange-bias ([H.sub.E]) fields of 40 and 100-nm core-shell structured particles synthesized under similar conditions behaved differently. However, their behavior was explained considering exchange biased interactions at (NiCo)O(AFM)-NiCo(FM), and (Co)O(AFM)-Co(FM) interfaces with two different exchange coupling constants. The 40 nm particles oxidized for 4 h and composed of (NiCo)O(AFM)-NiCo(FM), exhibited a maximum [H.sub.E] field of 36 and 201 Oe at 298 and 77 K, respectively. Index Terms--Core-shell structured nanoparticles, exchange-bias, nanocrystalline Ni-Co particles, polyol process.

Nanostructured CdFe2O4 spinel powders were investigated to observe ferrimagnetic ordering.

Encapsulation of fine metal particles by graphite would not only provide an oxidation protective layer but also acts as a solid lubricant that enables high speed scanning of magnetic tapes against a writing/recording head. In this paper, we propose a novel method to produce the graphite layer on the surface of magnetic particles. First, the surfactant is adsorbed onto the particle and then reduced/decomposed by bombardment with ionized He atoms in the arc discharge chamber. As a result of this treatment, the magnetite particles are uniformly coated with a graphite layer of a few nanometers thick.

Radial single-walled carbon nanotubes (radial SWCNTs) are formed by using a direct current (dc) arc discharge when carbon and metal atoms are mixed in a gas phase after the vaporization and cooled together in a liquid droplet. Since SWCNTs sprout through the precipitation of saturated carbon atoms from liquid droplets during cooling, a mass synthesis of radial SWCNTs can be achieved when a large number of liquid droplets are generated. In order to understand the effects of arc peripheral plasma parameters (electrons, ions, radical atoms, and molecules) on the growth of radial SWCNTs, the optimum production efficiency of radial SWCNTs is investigated by superimposing a radio-frequency (rf) plasma on the thermal arc plasma and controlling the arc peripheral plasma density. Two parameters—the rf power and the dc potential—of the rf electrode, which is equipped above 20 mm from the center of an arc-discharge point, are changed with the constant He pressure (200 Torr), dc arc current (75 A), and power (2000 W). The production yield of radial SWCNTs is found to be enhanced under the condition of the rf power of 100 W and the dc component of the rf electrode voltage of -22 V, revealing that the optimum ion flux and ion bombardment energy are important key parameters for the formation of radial SWCNTs. [ABSTRACT FROM AUTHOR]

Extended x-ray-absorption fine structure studies of the structure of coprecipitated ZnFe2O4 suggest that the zinc ions occupy both tetrahedral and octahedral sites. The resulting cation distribution increases the magnetization in coprecipitated zinc ferrite. The occupation of Zn ions in octahedral sites leads to a structural deformation that decreases the periodicity of the structure, reducing the radial structure function amplitude.

The Ni nanoparticles with face-centered-cubic (fcc) or hexagonal-close-packed (hcp) phases are synthesized in tetrathylene glycol by using the modified polyol process. The hcp Ni particles show nonmagnetic behavior and thermally stable below 673 K.

The structural and magnetic properties of monolayer film of the CoPt nanoparticles are reported. The monolayer film of CoPt nanoparticles is fabricated by the application of APTS as a coupling layer to find that the grain growth is well controlled even after annealing at higher temperatures.

The synthesis protocol for CoPt alloy particles is done by polyol process and their magnetic properties are reported. DSC studies showed that the ordering temperature was about 550 degree centigrade and that annealing above this temperature induced high degree of atomic ordering and magnetic properties.

Direct synthesis of fct-FePt particles is done by controlling the reaction kinetics of the chemical process. Regulating parameters such as reaction temperature and type of polyol could pave the way for further reduction in transformation temperature and consequently lead to direct synthesis of fct-FePT.

A method to synthesize CrO2 by reacting Cr(III) with Cr(VI) compounds mechanochemically is presented. This synthesis method is of practical importance for its simplicity, especially since there is no requirement for the high pressure used in traditional methods.

The observation of an anomaly in the optical luminescence excitation spectrum of oxygen in the region of the oxygen K edge is reported. Dispersed luminescence spectra were obtained for x-ray excitation at the pi and sigma resonances, at the anomaly, and in the continuum. These spectra indicate enhanced production of O2+2 ions at both the sigma resonance and at the anomaly. The anomaly thus is attributed to a shake-up or shake-off state associated with an antibonding sigma molecular orbital of oxygen. This work also demonstrates that optical luminesence spectra provide state-specific information about the products of core hole excitation and relaxation. [ABSTRACT FROM AUTHOR]