Sintered and aged Dy-doped NdFeB magnets were investigated. The magnetic properties, the microstructures and the compositions were characterized by hysteresis loop instrument, thermal field emission scanning electron microscopy (TFESEM) and energy disperse spectroscopy (EDS), respectively. The results indicate that Dy element is mainly distributed in the Nd-rich phase, Nd-Dy oxides and Dy-rich particles located at the grain boundaries of the sintered magnets, in addition to the main crystal phase Nd2Fe14B. The optimized aging process is beneficial to promote a reasonable diffusion and distribution of Dy element. The Dy contents of Nd-riched phases, Nd-Dy oxide, and Dy-riched particle decrease successively in the sintered, the high temperature aged and the optimally two-stage aged Dy-doped NdFeB permanent magnets. The measurements demonstrate that the enhancement of the coercivity of the aged Dy-doped NdFeB Magnet is caused mainly by the Dy element reasonable distribution.

The magnetic performance and mechanical properties including hardness, brittleness, fracture toughness and strength characteristics of the as-sintered and the optimal aged Nd-Fe-B magnets were examined in this work. A new method of Vickers hardness indentation combined with acoustic emission was used to test the brittleness of the magnets.The results show that the magnetic properties of the magnets could be improved through aging treatment, especially the intrinsic coercive force. But it is accompanied by a decrease of strength and fracture toughness. Theoretical calculation confirms that acoustic emission energy accumulated count value could be used to characterize the material brittleness. The bending fracture morphologies of the as-sintered and the optimal aged NdFeB magnets were investigated with the emphasis on the relationship between mechanical properties and microstructure using a field emission scanning electron microscopy (FE-SEM). The research results indicate that the intergranular fracture is the primary fracture mechanism for both as-sintered and optimal aged NdFeB magnets. Aging treatment changes the morphology and distribution of the Nd-rich phases, reducing the sliding resistance between Nd2Fe14B main crystal grains and lowers the grain boundary strength, which is the main reason for the strength and fracture toughness decrease of the aged Nd-Fe-B magnets.

Diamond-like carbon (DLC) films have excellent mechanical and chemical properties similar to those of crystalline diamond giving them wide applications as protective coatings. So far, a variety of methods are employed to deposit DLC films. In this study, DLC films with different thicknesses were deposited on Si and glass substrates using RF magnetron PECVD method with C4H10 as carbon source. The bonding microstructure, surface morphology and tribological properties at different growing stages of the DLC films were tested. Raman spectra were deconvoluted into D peak at about 1370 cm−1 and G peak around 1590 cm−1, indicating typical features of the DLC films. A linear relationship between the film thickness and the deposition time was found, revealing that the required film thickness may be obtained by the appropriate tune of the deposition time. The concentration of sp3 and sp2 carbon atoms in the DLC films was measured by XPS spectra. As the films grew, the sp3 carbon atoms decreased while sp2 atoms increased. Surface morphology of the DLC films clearly showed that the films were composed of spherical carbon clusters, which tended to congregate as the deposition time increased. The friction coefficient of the films was very low and an increase was also found with the increase of film thickness corresponding to the results of XPS spectra. The scratch test proved that there was good bonding between the DLC films and the substrates.

H-terminated DLC layers were synthesized on SiO2 substrate by radio frequency (RF) magnetron plasma-enhanced chemical vapor deposition (PECVD) in a conventional reactor using C4H10 as carbon source. As-deposited DLC films were characterized by Raman spectroscopy, scanning electron microscopy (SEM) as well as atomic force microscopy (AFM). The chemical reactivity of the obtained DLC surface was further investigated by exposing the photochemically oxidized DLC surface to a silane reagent. The course of the reaction was followed using water contact angle and X-ray photoelectron spectroscopy.

A carbon/carbon composite scaffold for bone tissue reconstruction was prepared. The surface morphology and trace elements of the scaffold were analyzed and its biological behavior was studied both in vitro and in vivo. It was found that the scaffold had a good biocompatibility, not only resulting from its high purity and mild cell toxicity, but also from the excellent integration of the bone tissue with the composite scaffold during the reconstruction.