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Precipitation-hardened Sm 2 Co 17 based sintered permanent magnet has been attracting a great deal of attention due to its distinguished high temperature magnetic properties, extremely low temperature coefficient, excellent corrosion resistance and oxidation resistance [1]–[3]. In this study, magnetic properties and microstructures of Sm-Co 17 -based sintered permanent magnets with the nominal composition Sm(Co bal Fe 0.245 Cu 0.07 Zr 0.02 ) 7.8 have been investigated. The magnets were prepared using the conventional powder metallurgy method, in which the pulverizing of powder is jet-milling and ball-milling, respectively. The typical demagnetization curves of the sintered magnets obtained by jet-milled and ball-milled powders are shown in Fig. 1. The corresponding magnetic properties of the magnets made of ball-milled powders (the magnet is designated as $\mathrm{M}_{\mathrm{b}})$ , are: the remanent magnetic polarization intensity J r =1.157 T (11.57 kGs), the intrinsic coercivity $\mathrm{H}_{\mathrm{c}\mathrm{j}}=752$ kA/m (9.46 kOe), and the maximum magnetic energy product $(\text{BH})_{\max}=221$ kJ/m3(27.8 MGOe), while that of jet-milled powder (the magnet is designated as M j ) are: $\mathrm{J}_{\mathrm{r}}=1.146$ T (11.46 kGs), $\mathrm{H}_{\mathrm{c}\mathrm{j}}=2497$ kA/m (31.37 kOe), and $(\text{BH})_{\max}=251.7$ kJ/m3(31.64 MGOe). The cause of such a significant difference between the two kinds of samples is expected as the existed deviation in effective chemical compositions, due to the different oxygen contents introduced during fabrication for the two kinds of magnets: ∼2800 and ∼1300 ppm.

A (Ce,Nd)-Fe boundary phase with low melting-point was obtained in the sintered Ce9Nd21FebalB1 magnets by the two powders blending method. Ce element enriched in the boundary phase and decreased the melting point. The melting-point of the boundary phase decreases with the increase of Ce content. Thus, the high performance magnets with fine grain and low oxygen content can be obtained by low temperature sintering. The sintered Ce9Nd21FebalB1 magnet with 600 PPM oxygen content and magnetic property of Br = 13.5 kGs, Hci =9.5 kOe and (BH)max =42.8 MGOe has been fabricated by the low melting-point phase formation and low temperature sintering method. Microstructure and chemistry composition of the magnet and the low melting-point boundary phase were investigated by SEM and TEM.

Similar to a diesel engine, the main vibration sources of an air-compressor are to and fro inertial forces of its piston, rod, and crankshaft. An active vibration isolation system is developed for an air-compressor in a tug boat. This system consists of four inertial actuators and a DSP processor. A four-input and four-output adaptive control strategy is applied and the reference input signal comes from a laser tachometer on the shaft of the motor. The active vibration isolation experiment is conducted in a tug boat when only the air-compressor is working. The experimental results demonstrate that good vibration reductions are obtained at not only error sensor's locations but also the hull under the compressor. Some discussion and conclusions are given at last.

The effect of the atomic disorder–order transformation on the interaction mechanisms in isotropic PtCo alloys has been studied by isothermal annealing at 953 K, well below the transformation temperature, for 5–30 min after quenching from 1273 K. The transmission electron microscopy (TEM) testing showed that the ordered regions grew with prolonging heat treatment time. Investigation of the interaction mechanisms in PtCo alloys has been made using analysis of the δM(H) plot. The results of the δM(H) plot and TEM indicate that the interaction mechanisms are changed by the size of the magnetically soft and hard phases. The Kneller–Hawig model was used to explain the continuously changing degree of exchange coupling between the magnetically soft and hard phases.