Influence of heat treatment on strength and ductility improvement of high nitrogen dissolved in α-Ti alloy The SPS process following by extrusion process of Ti powder with high nitrogen concentrations exhibit the features of the non-uniform microstructure including equiaxed grains and elongated grains, resulting by nitrogen agglomeration in some area. After applying pre-treatment, XRD patterns show α-Ti peaks greater shifted to the lower angle due to the lattice parameter expansion by nitrogen

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... tom solid solution between the crystal structure. According to EBSD analysis, the final microstructures after extrusion process show the fine equiaxed grain structure which the average grain size was significantly reduced from 16.35 µm, 19.04 µm and 18.29 µm to 11.57 µm, 11.18 µm and 10.35 µm for nitrogen content at 0.3wt%, 0.5wt%, and 0.7wt%, respectively. The stress-strain curves show the improvement of mechanical properties achieving by homogenization of nitrogen elements in Ti-(N) materials. The yield stress, ultimate tensile strength and elongation were 957 MPa, 1117 MPa, and 15.1%, respectively, at high 2019 12 Abstract Oral presentation title: "Preparation of anatase titanium dioxide powder having strong antibacterial activity under dark conditions by co-doping of K and P" Among three kinds of crystal structures of titanium dioxide, such as anatase (α-TiO 2 ), rutile and brookite, it has been reported up to now that the antibacterial activity of α-TiO 2 needs ultraviolet, i.e., this activity can be performed only under sunlight. However, α-TiO 2 having antibacterial activity even under dark conditions has been newly developed. Fine α-TiO 2 powders with a small amount of dopants (K 2 O and P 2 O 5 ) have been prepared using solid state reaction by heating at 973 K for 3.6×10 3 s in air. Thus prepared α-TiO 2 powders can emit extraordinary much reactive oxygen species (ROS) such as 1 O 2 and H 2 O 2 without ultraviolet, this phenomenon has been confirmed using chemical luminescence (CL) observation under dark conditions at room temperature. Their antibacterial activity is strongly depended on the amount of (K and P) and combined compounds of dopants. Moreover, the physicochemical properties of doped TiO 2 powders and their antibacterial mechanism also have been investigated. It was found that doped anatase (α-TiO 2 ) powders could submit ROS even under dark and the amounts of ROS are much higher than the previous antibacterial ZnO powders. Besides, the preparation process is simple with low cost. Especially, CL values of co-doped (1·K+3·P) anatase samples after heating in O 2 at 973 K for 3.6×10 3 s were highly improved (5 times higher) comparing to the samples which heated in air. Bio-test was also conducted on E. Coli bacteria at 36°C for 24 hours under dark conditions, the results show that doped (1·K+3·P) anatase sample gave higher antibacterial activity than the other doped samples.