Li(Ni 1-x-y Co x Mn y)O 2 (NCM) materials, which are the cathode active material for lithium ion batteries, have been developed and widely used as an alternative to lithium cobalt oxide, because of the high cost of cobalt. To synthesize high quality NCM materials, it is important to control the process manufacturing of the NCM precursor. We synthesized a precursor for LiNi 0.6 Co 0.2 Mn 0.2 O 2 with high capacity through the co-precipitation method using the Taylor reactor. First, it was confirmed that the optimum concentration of ammonia water, which is complexing agent, was 2 M, for uniform particle contribution. The average particle size distributions of the synthesized NCM precursors, and the analysis of the crystal phase and the composition of the NCM precursor, were investigated using a Taylor reactor which is capable of a continuous production process. A reference sample fabricated at a stirring rate of 1,000 rpm showed a composition similar to the target NCM material. When the reaction time was more than 24 hours, the concentration in the Taylor reactor reached a constant steady state, and it was confirmed that continuous production is possible after a reaction time of 24 hours. The use of Taylor reactors can be an effective process because the NCM precursor can be continuously produced, and it is possible to reduce agitation time.

Abstract:The Al-Ni system is known as a high energy density materials (HEDM) because of its highly exothermic nature during intermetallic compound (IMC) formation. In this study, elemental Al and Ni powder were milled to explore the effect of cryomilling atmosphere on the microstructure and exothermic behavior. Scanning electron microscope (SEM) observations show continuous structural refinement up to 8 h of cryomilling. No IMC phase was detected in the X-ray diffraction (XRD) spectrum. Differential thermal analyzer (DTA) results show two exothermic peaks for 8 h cryomilled powder as compared to that of powder milled for 1 h. The ignition temperature of prepared powder mixture also decreased due to gradual structural refinement. The activation energy was also calculated and correlated with the DTA and SEM results. The cryomilled Al-Ni powder is composed of fine Al-Ni metastable junctions which improve the reactivity at a lower exothermic reaction temperature.

There is a continuous demand for multi-disciplinary design approaches for the development of new implant materials. A potential biomaterial that is suitable for vascular stents and catheters is Ni–Ti alloy (Nitinol), which exhibits excellent biocompatibility, superelasticity, and shape memory effects. Corrosion resistance of Ni–Ti vascular stents in body fluids is significantly dependent on its surface finishing characteristics. In the study, as-drawn Ni–Ti wires were electropolished from a methanolic sulfuric acid electrolyte. The effect of various electropolishing (EP) parameters, i.e., current density, electropolishing time, and electrode gap, on the surface properties of Ni–Ti wires were examined. The surface morphology and topography of the Ni–Ti wires were characterized via scanning electron microscopy (SEM) and atomic force microscopy (AFM). The root mean square (Ra) surface roughness of electropolished Ni–Ti wires was also measured using AFM. The results indicated that the surface finishing of Ni–Ti alloy exhibited maximum sensitivity to electropolishing current density. An optimum combination of surface morphology and roughness was obtained at a parameter set with current density of approximately 0.5 A/cm2, polishing time of 10 s, and electrode gap of 1.0 cm.

MA956 (Fe-Cr-Al) alloy powder was high-energy ball milled with various amount of yttria contents (1,2,3, and 4 wt.%) to fabricate an oxide dispersion strengthened alloy. The milled powders were then consolidated using hot press sintering at 1150°C. The surface morphology and crystal structure of MA956 powder during the high-energy milling depending on the yttria contents was investigated using particle size analysis, X-ray diffraction, and scanning electron microscopy. The microstructural analysis of sintered alloy was performed using transmission electron microscopy and energy dispersive spectroscopy to evaluate the dispersion behavior of yttrium oxide. The results showed that, as yttria contents increased, the oxide particles became finer and are uniformly distributed during the high-energy milling. However, after the sintering, the oxide particles were coarsened with more than 3 wt.% of yttria addition.