Influence of additive material to surface roughness in turning of sintered steels is not well known. In this study, effect of manganese sulfide (MnS), silica and alumina powder was investigated on a viewpoint of material characteristics near turned surface. The surface roughness of the sintered steel added with MnS was smaller than the others. MnS was extended and dispersed finely in the deformed layer near the turned surface, while silica and alumina were localized but not extended. Nano indentation test showed that the deformed layer of the sintered steel added with MnS had lower hardness in comparison with others. We considered that a tear mark of the cutting chip separated from deformed layer was lowered by MnS and the trace of torn chips, namely the surface roughness became relatively small. However, the deformed layer of the sintered steel added with silica or alumina was close to that of the additive-free sintered steel and the surface roughness became similar to these cases.

In recent years, in fields of an eco-friendly automobile, an advanced industrial machine, and a precision electronic device, controlling of vibration damping behavior of the sintered materials is required. In this paper, vibration damping analysis of Cu-Sn/Carbon fiber sintered composite materials was performed by frequency response function of FFT analyzer, and the results was compared with Cu-Sn/Graphite sintered composite materials.

Cu, Sn elemental powders and Carbon fiber were used as initial substances. The powders and the fiber were mixed and pressed into a plate shaped compact with 200 MPa. Using a vacuum furnace, the green compact was sintered at 825-1075°C for 1 hour. By changing the mixing ratio and the sintering temperature, some kinds of the composite material plates were prepared. For the composite material obtained, microstructure, Vickers hardness, compression strength and vibration behavior were investigated.

The composite materials were consisted from the crystal grain of 17-70 μm, and the mixed Carbon fiber were dispersed in the microstructure. Twin crystal was also found in the composite materials obtained. Vibration damping behavior of the Cu-Sn/Carbon fiber sintered composite material was affected by solubility element, grain boundary, dispersed Carbon fiber, and twin crystal in composite material.

Exchange-coupled nanocomposite magnets (NCMs) consisting of hard and soft magnetic phases have attracted much attention as novel permanent magnets. We previously succeeded in fabrication of L1₀-FePd/α-Fe NCMs by the reductive annealing of Pd/γ-Fe₂O₃ heterostructured nanoparticles. Herein we explain the structural optimization of L1₀-FePd/α-Fe NCMs by adjusting the volume fraction of hard/soft phases and the temperature of reductive annealing to obtain large maximum energy products ((BH)_max). The sample with a hard/soft volume ratio of 82/18 formed by annealing at 773 K had the largest (BH)_max = 10.3 MGOe. In these L1₀-FePd/α-Fe NCMs with the large (BH)_max, the interface between the hard and soft phases was coherent and the phase sizes were optimized, both of which effectively induced exchange coupling. This exchange coupling was directly observed by visualizing the magnetic interaction between the hard and soft phases using a first-order reversal curve (FORC) diagram.

FePt thin films with L1₀ ordered structure are candidates for high-density magnetic recording media because of their high uniaxial magnetic anisotropy energy. The (Fe_0.395Pt_0.395Cu_0.15P_0.02Pd_0.04)_100–xSb_x thin films with various x were deposited directly on quartz glass substrates by a sputtering method. FePt ordered alloy thin films with (001) preferential orientation were achieved in Sb content of x ≥ 8.0 at.% with post-annealing at 600°C for 1 hour under reduced pressure in a H₂ atmosphere. However, the coercivity of these thin films decreased dramatically due to growing of the crystal grains. Therefore, in this study, we prepared the PdSb-FePt-(C₄F₈)_n granular thin films to improve the coercivity. The Fe_0.44Pt_0.44Pd_0.04Sb_0.08-(C₄F₈)_n granular thin film deposited at C₄F₈ partial pressure of 0.1 mTorr then annealed at 700°C for 1 hour under reduced pressure in a H₂ atmosphere exhibited a large coercivity of 30 kOe.

The present paper describes a fabrication of magnetic composite of Fe-Pt nanoparticles and hydroxylpropyl cellulose (HPC) for magnetically guided drug delivery system with a capability of thermo-responsive controlled release. The composites are fabricated by a synthesis of Fe-Pt nanoparticles in a reaction solution containing HPC coated silica particles; Fe-Pt nanoparticles are grown on HPC deposited on the silica particles. The island-like composites of HPC and Fe-Pt NPs are observed to be densely deposited on the silica particles by transmission electron microscopy. Thermal responsiveness is evaluated by temperature-dependence of particle size distribution using dynamic light scattering; the thermal responsiveness is successfully confirmed even after the thermal history up to 533 K during synthesis.

In this study, magnetic nanoparticles were prepared by the arc plasma deposition (APD). The monodisperse Fe-Pt nanoparticles (5~10 nm) were obtained on the surface of SiO₂ nanoparticles. Deposition voltage and shot counts can control particle size of Fe-Pt. The coercivity of Fe-Pt/SiO₂ composite particles increased after annealing at 300°C, and the maximum coercivity value reached to 583 kA·m⁻¹. In the selected area diffraction pattern obtained by transmission electron microscopy (TEM), amount of the order L1₀ phase was increased by annealing at 300°C. The Mn-Bi nanoparticles (5~20 nm) were also prepared by APD. The Mn-Bi was deposited on Fe nanoparticles, which were prepared by hydrogen-plasma-meta-reaction (HPMR) method, and monodisperse Mn-Bi particles were obtained on the Fe nanoparticles. Consequently, the arc plasma deposition is effective process to prepare composite magnetic nanoparticles.

Synthesis of magnetic iron oxide (Fe_3−xO₄) nanosheets using iron oleate complex via hydrothermal methods were investigated, and the obtained Fe_3−xO₄ nanosheets had 500 to 2000 nm in lateral size. Since the thickness of Fe_3−xO₄ nanosheets was 10 nm, the estimated aspect ratio was 50 to 200. On the other hands, Fe_3−xO₄ nanocubes are obtained only in solvothermal treatment. These results suggest that liquid-liquid interface between aqueous solution and non-polar organic solvent plays an important role to synthesize iron oxide nanosheets with large lateral dimensions.

Y-type ferrite substituted with a combination of non-magnetic lithium and aluminum, Ba₂Zn_2–2xLi_xAl_xFe₁₂O₂₂, was synthesized by polymerized complex method and the effects of substitution on their magnetic properties were investigated. The monophasic Y-type ferrite was obtained at the composition range up to x = 0.6 and their lattice parameters decreased isotropically by the substitution. The saturation magnetization at 10 K decreased and Curie temperature increased with increasing composition x. As a result, the saturation magnetization at room temperature showed maximum at x = 0.2 and the relative complex permeability of sintered Y-type ferrite also showed same tendency. The substituion with a combination of non-magnetic ions could enhanced the magnetic properties of Y-type ferrite through lattice contraction and/or site occupation of iron ions.

Preparation of spinel Mn-doped Fe(Al_1−xMn_x)₂O₄ (0 ≤ x ≤ 0.9) ferrite powders, in which B-site Al³⁺ were replaced partially by Mn³⁺, has been tried via a modified citric acid route. Fe and Al nitrate salts and fine MnO₂ powder were used as starting materials. Homogeneous mixed solutions containing Fe³⁺, Al³⁺ ions and MnO₂ were added to the mixed solution of citrate acid (CA) and ethylene glycol (EG) at room temperature with stirring. After boiling and continuous drying, thus obtained precursors were heated in air to burn out the organic substances and calcined at 1173 K (900°C) for 7.2 × 10³ s (2 h) under nitrogen atmosphere with a small amount of hydrogen to control the valances of Fe and Mn in the ferrite powders. Single spinel B-site Mn-doped Fe(Al_1−xMn_x)₂O₄ powders with the compositions of x = 0.0, 0.2, and 0.6 ~ 0.9 have been obtained. With increasing x value, the magnetic property of spinel powder changed from paramagnetism (x = 0) to ferrimagnetism (x = 0.2, 0.6 ~ 0.9) at room temperature. Neutron-diffraction analysis measured at room temperature proved that some of Mn ions occupied B-site and on the contrary Fe did A-site. Magnetic properties also supported this configuration determined by XRD and NRD.