Formation Of Nanocomposite Structure Research Articles

Influence of quenching rate on the microstructure and magnetic properties of melt-spun L10-FePt∕Fe2B nanocomposite magnets

The quenching rate, which is dependent on the surface velocity (Vs) of Cu wheel during melt spinning, has significant influence on the formation of nanocomposite structure in the Fe52Pt32B18 melt-spun ribbons. The L10-FePt∕Fe2B hard magnetic nanocomposite structure was formed at Vs=20–37m∕s, while the soft magnetic fcc-FePt+amorphous phases were formed at Vs=40–50m∕s. The ribbons melt spun at Vs=37m∕s exhibit in-plane coercivity (Hci)=760kA∕m, remanence (Br)=0.71T, and energy product (BH)max=93.4kJ∕m3. The Br=0.74–0.77T, Hci=681–718kA∕m, and (BH)max=101–108kJ∕m3 were obtained for the ribbons melt spun at Vs=50m∕s and annealed at 748–773K for 900s. The improvement in hard magnetic properties is due to the formation of more finer and homogeneous nanocomposite structure, which results in the enhancement in exchange coupling among the nanosized hard L10-FePt and soft Fe2B magnetic phases.

Conditions of nanocomposite structure formation from the vapour phase in Ti–Y system

In this study the method of electron beam deposition of a mixture of titanium and yttrium vapours was used to produce condensates at different ratios of elements in the substrate temperature range from 200 to 800 °C. Condensates consist of grains of yttrium and titanium, the dimensions of which are reduced from the submicron to nanosize scale at lowering of substrate temperature. The temperature of composite transition into the nanosized state depends on yttrium content and can be 200–300 °C higher than in the case of pure titanium. Such structural changes are accompanied by an abrupt increase of microhardness. At the change of yttrium content the microhardness of condensates deposited at the same temperature changes non-monotonically. Possible causes of non-monotonic variation of concentration dependencies in Ti–Y condensate microhardness are discussed.

Phase Stability of Crystalline and Amorphous Phases and Formation of Nanostructure in Zr-Pd and Zr-Pt Alloys Under Electron Irradiation

AbstractElectron irradiation induced phase transition behavior of Zr-Pd and Zr-Pt alloys was investigated focusing on phase selection in crystallization by thermal annealing and electron irradiation. Nano quasi-crystalline (QC) phase was formed by thermal crystallization in Zr66.7Pd33.3 and Zr80Pt20 alloys, while nano two-type f.c.c. super-saturated solid solutions were formed by irradiation induced crystallization at 298K. In Zr66.7Pt33.3 alloy, polycrystalline Zr5Pt3 and Zr9Pt11 phases transformed to two-type f.c.c. nano-crystalline phase through an amorphous state by crystal-to-amorphous-to-crystal (C-A-C) transition during electron irradiation. Nano-composite phase composed of f.c.c. super-saturated solid solution and residual amorphous phase was stable rather than an amorphous single phase, thermal equilibrium crystalline phase and quasi-crystalline phase under 2.0MV electron irradiation at 298K, resulting in the formation of nano-composite structure by irradiation induced amorphization and crystallization.

Effects of organomontmorillonite concentration on the structure formation of nanocomposites with 5CB liquid crystal

Heterosystems consisting of an organic substance and inorganic nanoparticles are being intensively studied by various physical methods, due to the wide applications of such composites in modern nan...

Control of a Nanocomposite Structure in Fe<SUB>86</SUB>Nd<SUB>9</SUB>B<SUB>5</SUB> Alloy by Electron Irradiation

Change in nanocomposite structure in rapidly solidified Fe 86 Nd 9 B 5 alloy during electron irradiation was investigated. Nanocrystalline structure composed of α-Fe, Fe 3 B, Nd 2 Fe 14 B and Nd 2 Fe 23 B 3 crystalline phases was formed by rapid solidification. Electron irradiation can introduce amorphization of intermetallic compounds and crystallization of an amorphous phase, resulting in the formation of a novel nanocomposite structure in which α-Fe and Nd 2 Fe 14 B nanocrystals are embedded in the amorphous matrix. The mechanism of nanocomposite structure formation was discussed based on the phase stability of amorphous and crystalline phases under electron irradiation.

Relationship between the physical and structural properties of NbzSiyNx thin films deposited by dc reactive magnetron sputtering

The optical and electrical properties of NbzSiyNx thin films deposited by dc reactive magnetron sputtering have been investigated as a function of the Si content (CSi). Optical properties were studied by both specular reflectivity and spectroscopic ellipsometry. Electrical resistivity was measured by the van der Pauw method at room temperature and as a function of the temperature down to 10K. Both the optical and electrical properties of NbzSiyNx films are closely related with the chemical composition and microstructure evolution caused by Si addition. For CSi up to 4at.% the Si atoms are soluble in the lattice of the NbN crystallites. In this compositional regime, the optical and electrical properties show little dependence on the Si content. Between 4 and 7at.% the surplus of Si atoms segregates at the grain boundaries, builds an insulating SiNx layer, and originates important modifications in the optical and electrical properties of these films. Further increase of CSi leads to the formation of nanocomposite structures. The electrical properties of these films are well described by the grain-boundary scattering model with low probability for electrons to cross the grain boundary. The appearance of the intragranular-insulating SiNx layer and the reduction of the grain size are noticed in the dielectric function mainly as a strong damping of the plasma oscillation.

Computer Simulation of the Structure of Porous Electrodes with an Immobilized Enzyme and Nanosized Support Particles

The efficiency of the operation of a porous electrode with an immobilized enzyme is defined, in particular, by a lucky structure of its active layer, which can contain nanosized particles of the support. The composites of such a kind are prepared with the aid of methods of colloidal chemistry. The aim of this particular investigation is to perform a computer simulation of processes of coagulation of particles of the support and their possible heterocoagulation with molecules of the enzyme. Algorithms of the formation of nanocomposite structures in solution are suggested. Calculations show that the concentration of the enzyme molecules in the nanocomposite structures cannot exceed a certain critical value. On the other hand, at a fixed value of the concentration of the enzyme molecules, the concentration of the support particles must not fall below a certain threshold quantity, which provides for the passing of current through the active layer. In order for all the enzyme molecules, rather than for a fraction of these, in the composite to take part in the process of bioelectrocatalysis, the concentration of support particles must be increased even higher, to an optimum value.

ナノメータコンポジット材料 反応スパッタ法により作製したＴｉ‐Ａｌ‐Ｓｉ‐Ｎナノコンポジット膜の特性

The influence of Si addition on the microstructure, mechanical properties and oxidation resistance of Ti-Al-Si-N was investigated using XRD, XPS, SEM and ultra-microindentaion. The composite targets consisting of a Ti50Al50 plate and Si chips were sputtered in a mixture of argon and nitrogen. Ti-Al-Si-N films were prepared in an r.f. sputtering apparatus of the Facing Target-type Sputtering. During the deposition, the substrate was heated from room temperature up to -573 K without substrate bias application. The total results of XRD, XPS and SEM revealed that the Ti-Al-Si-N films have a nano-composite structure consisting of nanocrystalline Ti-Al-N and an amorphous phase containing Si3N4. The highest hardness of 38 GPa was obtained for films with 3.5%Si. The films were subjected to an oxidation test, where they were exposed to a temperature in the range of 873 K to 1193 K for 1 ks. The hardness of Ti-Al-Si-N films hardly decreased after oxidation test up to 973 K, whereas the hardness of Ti-Al-N films decreased 7% at 973 K. Only a small TiO2 peak was observed for the Ti-Al-Si-N films oxidized at 973 K, whereas many TiO2 peaks were observed in the Ti-Al-N film. SEM & EDS observation revealed that the inside of the Ti-Al-Si-N film was not oxidized even after oxidation test at 1193 K. These improvements of Ti-Al-Si-N films could be attributed to the formation of nano-composite structure.

Influence of sputtering conditions on the structure and properties of Ti–Si–N thin films prepared by r.f.-reactive sputtering

The influence of Si content and sputtering conditions on the microstructure and mechanical properties (hardness and Young's modulus) of Ti–Si–N were investigated using XRD, XPS and nano-indentation. The composite targets consisting of a Ti plate and Si or Si 3N 4 chips were sputtered in a mixture of argon and nitrogen. Ti–Si–N films were prepared in an r.f. sputtering apparatus of the facing target-type. During the deposition, the substrate was heated from room temperature up to ∼573 K and a bias of d.c. up to −100 V was applied. Without substrate heating and bias, the hardness of the films increased from 30 GPa for a binary system, reaching a maximum of 37 GPa for a ternary system with a small amount (3–8 at.%) of Si. It then decreased to lower values than those of binary systems when Si was more than 10 at.%. The tendency to grow columnar grains was strongest at approximately 5 at.% of Si. The hardness of Ti–Si–N films increased and reached to a maximum value of 42 GPa around at a bias of −10 V, but the crystallite size of the film remained larger than 23 nm. The increase of hardness with small amounts of Si in TiSiN films was probably associated with the lattice distortion. On the other hand, the increment of hardness of films containing 20 at.% of Si by the negative bias application could be attributed to the formation of nano-composite structure.