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Uniform Bi2Te3−xSex nanowires (NWs) with tunable components are synthesized by a modified solution method free of any template, and inter-diffusion mechanism is proposed for the growth and transformation of ternary nanowires. Spark plasma sintering is adopted to fabricate the pellets of Bi2Te3−xSex NWs and thermoelectric transport properties are measured. As compared to Bi2Te3 pellets, Se doping results in lowered electrical conductivity because of the reduced carrier concentration, both the Seebeck coefficient and the power factor are enhanced substantially. The Bi2Te2.7Se0.3 pellet exhibits the highest power factor at room temperature as a result of optimized carrier concentration (4.37 × 1019 cm−3) and mobility (60.22 cm2 V−1 s−1). As compared to Bi2Te3, the thermal conductivity of Bi2Te3−xSex is lowered owing to the enhanced phonon scattering by dopants and grain boundaries. As a result, the ZT value at 300 K is substantially improved from 0.045 of Bi2Te3 to 0.42 of Bi2Te2.7Se0.3. It is suggested that Se doping is an effective way to enhance the thermoelectric performance of Bi2Te3 based materials. [ABSTRACT FROM AUTHOR]

We report here, for the first time, a novel multi-scaled hybrid orthopedic implant material consisting of a macroporous Ti scaffold, whose macropores' walls have a microporous titania layer which is fully covered with nanofibers of Sr-doped hydroxyapatite (Sr-HA). The microporous titania layer is formed on and within the Ti scaffold by micro-arc oxidation, which firmly binds to the Ti substrate and contains Ca2 + , Sr2 + and PO43 [?] ions. It is then hydrothermally treated to form Sr-HA nanofibers. During the hydrothermal treatment, Sr-HA nanoprisms nucleate from Ca0.5Sr0.5TiO3 pre-formed on the TiO2 and grow in length to nanofibers at the expense of Ca2 + , Sr2 + and PO43 [?] ions that migrate from the TiO2. These Sr-HA nanofibers construct a network structure similar to the hierarchical organization of bone extracellular matrix (ECM), and the resulting nanofibrous surface displays a firm adhesion to substrate, superhydrophilicity and apatite-inducing ability. The induced apatite prefers to nucleate on the basal-faceted surfaces of Sr-HA nanofibers. The nanofiber-walled scaffold has a great potential for load-bearing orthotopic use. [ABSTRACT FROM AUTHOR]

Ti-Si-C-N coatings with different Si contents were synthesized by means of pulsed direct current plasma-enhanced chemical vapor deposition using a TiCl4, SiCl4, CH4, N2, H2 and Ar gas mixture. A complex phase transition has been identified which is strongly controlled by the silicon content in the coatings. Transmission electron microscopy (TEM) and x-ray diffraction (XRD) results indicate that increasing Si content leads to a phase transition from a solid solution (Ti, Si)(C, N) to a dual-phase Ti (C,N)+TiSi2 structure, and then to a two-phase Ti (C,N)+SiC structure, and that the changes in grain size and lattice parameter coincide with the phase transition. The Ti-Si-C-N coatings with high Si contents ([?]4.3 at.%) possess a superhigh hardness (43-52 GPa) due to grain refinement/grain boundary hardening and compressive stress/dispersion hardening of the hard, nanosized crystalline TiSi2 or SiC dispersed in the matrix. [ABSTRACT FROM AUTHOR]