Nonthermal Plasma Synthesis of Metallic Ti Nanocrystals.

Nanoscale metallic titanium (Ti) offers unique energetic and biocompatible characteristics for the aerospace and biomedical industries. A rapid and sustainable method to form purified Ti nanocrystals is still in demand due to their high oxygen affinity. Herein, we report the production of highly purified Ti nanoparticles with a nonequilibrium face center cubic (FCC) structure from titanium tetrachloride (TiCl4) via a capacitively coupled plasma (CCP) route. Furthermore, we demonstrate a secondary H2 treatment plasma as an effective strategy to improve the air stability of a thin layer of nanoparticles by further removal of chlorine from the particle surface. Hexagonal and cubic-shaped Ti nanocrystals of high purity were maintained in the air after the secondary H2 plasma treatment. The FCC phase potentially originates from small-sized grains in the initial stage of nucleation inside the plasma environment, which is revealed by a size evolution study with variations of plasma power input.

3D Periodic and Interpenetrating Tungsten-Silicon Oxycarbide Nanocomposites Designed for Mechanical Robustness.

Metal-ceramic nanocomposites exhibit exceptional mechanical properties with a combination of high strength, toughness, and hardness that are not achievable in monolithic metals or ceramics, which make them valuable for applications in fields such as the aerospace and automotive industries. In this study, interpenetrating nanocomposites of three-dimensionally ordered macroporous (3DOM) tungsten-silicon oxycarbide (W-SiOC) were prepared, and their mechanical properties were investigated. In these nanocomposites, the crystalline tungsten and amorphous silicon oxycarbide phases both form continuous and interpenetrating networks, with some discrete free carbon nanodomains. The W-SiOC material inherits the periodic structure from its 3DOM W matrix, and this periodic structure can be maintained up to 1000 °C. In situ SEM micropillar compression tests demonstrated that the 3DOM W-SiOC material could sustain a maximum average stress of 1.1 GPa, a factor of 22 greater than that of the 3DOM W matrix, resulting in a specific strength of 640 MPa/(Mg/m3) at 30 °C. Deformation behavior of the developed 3DOM nanocomposite in a wide temperature range (30-575 °C) was investigated. The deformation mode of 3DOM W-SiOC exhibited a transition from fracture-dominated deformation at low temperatures to plastic deformation above 425 °C.