Materials Science Forum Vols. 534-536

Abstract: This paper compares the effect of using different types of iron powders for the preparation of Sm2Fe17 by calciothermic reduction-diffusion (CRD). Three types of iron powder were used: carbonyl, sponge and water atomized. The results show that, when immediately nitrogenated after the CRD process, Sm2Fe17 prepared from sponge and water atomized iron powders yield Sm2Fe17N3-magnets with a high degree of texture. However, after a suitable treatment with hydrogen followed by nitrogenation, Sm2Fe17-powders made from Carbonyl iron produce magnets with the best quality regarding coercivity, remanence and degree of texture.

Abstract: Recently, SMC(Soft Magnetic Composite) materials were studied for their applications in many fields. We have developed a superior SMC for use as motor cores and are studying their applying effects [1]. It shows almost the same motor output power as laminated Si-steels of 0.35mm in thickness, although core loss of SMC is about 1.5 times that of the laminations. As shown in the results, the SMC motor core is sufficient for real use as a motor core. Furthermore, a 3-D shaped motor core made of SMC can improve approximately 20% of the output compared with the same size motor made of laminations.

Abstract: TiB2-43vol.%Cu nanocomposite powders with titanium diboride particle size 50-100 nm were cold and detonation sprayed in order to fabricate coatings on a copper substrate. The powders were produced by self-propagating high-temperature synthesis (SHS) followed by mechanical milling. The temperatures during spraying were calculated and the change in the nanostructure of the powders during spraying was studied: in cold sprayed coatings the size of TiB2 particles was well retained, in detonation sprayed coatings the growth of the particles was observed, the mode of spraying greatly affecting the microstructure and the size of the particles. The hardness of cold sprayed coatings was higher compared to detonation sprayed coatings. This research shows the future potential for development of coatings with submicron and nanostructure by cold and detonation spraying of powders produced by mechanical milling.

Abstract: The effect of working temperature on microstructure and mechanical properties of ultrafine grained monolithic Al and Al-5vol.%SiCp composite processed by accumulative roll bonding (ARB) was studied. The ARB was performed up to eight cycles (an equivalent strain of ~6.4) without lubricant. The working temperature was varied from ambient temperature to 200
C. The samples processed at temperatures below 100
C exhibited an ultrafine grained structure over almost all regions. However, the samples processed at 200
C showed an inhomogeneous structure in which a few coarse grains due to an occurrence of conventional recrystallization is partially seen. The tensile strength of both the monolithic Al and the composite decreased with increasing the ARB working temperature. The variation of microstructure and mechanical properties of the composite with the working temperature was compared to that of the monolithic aluminum.

Abstract: Nano-particulates are being used in conjunction with Direct Write Technologies for fabrication of electronic devices, sensors, and in tissue engineering. The materials being used in Direct Write Technologies predominately are suspensions, solutions or pastes comprised from nano-particulate metals, oxides or organics. This paper will present a comparison of several nano-particle silver inks being evaluated for use by one of these Direct Write Technologies, Maskless Meso-Scale Material Deposition (M3D) being developed by Optomec, Inc., Albuquerque, NM. USA. The silver inks in this case were deposited by the M3D process and then cured by sintering by both oven and by laser. Optical microscopy and Scanning Electron Microscopy (SEM) were used to examine the resultant cured material. The surface resistivity of these deposits was determined as a measure of their quality. A soft magnetic inductor material was also fabricated through a combination of nickel and iron oxide nano-particles. The results obtain with this inductor material are also discussed.

Abstract: Magnetic properties of nanostructured materials are affected by the microstructures such as grain size (or particle size), internal strain and crystal structure. Thus, it is necessary to study the synthesis of nanostructured materials to make significant improvements in their magnetic properties. In this study, nanostructured Fe-20at.%Co and Fe-50at.%Co alloy powders were prepared by hydrogen reduction from the two oxide powder mixtures, Fe2O3 and Co3O4. Furthermore, the effect of microstructure on the magnetic properties of hydrogen reduced Fe-Co alloy powders was examined using XRD, SEM, TEM, and VSM.

Abstract: Combining nano-designed plasma source ion implantation and deposition (PSII&D) method has been developed with the pulsed cathodic arc plasma to make a processing system suitable for surface modification of materials such as metals, plastics and ceramics. By controlling the arc plasma pulse and the target pulse, the surface modification can be changed from plasma deposition to ion implantation. Various versions of applying high-voltage pulse bias are described and compared with other methods. Microstructural changes of the nanometered gold films with/without a high voltage bias, concentration profiles of implanted aluminum ions on the surfaces of complex-shaped trench are discussed.

Abstract: Nanostructured aluminum powders were obtained by means of planetary ball milling with methanol as the Process Control Agent (PCA). The behavior, during milling, was considered measuring the microhardness and grain size at different milling times. Bulk near-full density samples were sintered using the Spark Plasma Sintering technology with different schedules: temperature of 500°C and 550°C, pressure of 30 MPa and 60 MPa and different modes of applying the pressure were changed in order to understand the behavior during sintering. The samples sintered at 500°C showed a density of about 2.4-2.61 g/cm3 while for that sintered at 550°C it was 2.65-2.67 g/cm3 depending on the applied pressure. All the samples retained their nanostructure with an increase of the grain size from about 46 up to 70-90 nm. Using X-ray diffraction and metallography the formation of Al4C3 carbides was detected for samples sintered at highest temperatures.