Joydip Joardar

A Ti–6Al–7Nb–0.3Y spherical powder was produced by ultrasonic atomization (UA), and its < 63 µm (d₅₀ ≈ 53 µm) and 63–125 µm (d₅₀ ≈ 82 µm) fractions were characterized for laser powder-bed fusion (LPBF) of patient–specific biomedical implants. Both fractions show near-ideal sphericity (1.01) with no satellites or internal pores, flow times of 26.8–28.0 s/50 g and bulk densities of 2.35–2.45 g/cm³ (51–53% of true density), matching commercial powder-bed feedstocks. XRD revealed only hexagonal α(α′)-Ti with a microstrain of 0.45–0.55%. Nanoindentation showed a hardness of 4.55–4.90 GPa, exceeding that of laser-powder-bed-fused Ti–6Al–4V (3.66 GPa), and an elastic modulus of 119–148 GPa on rigidly supported particles. Simultaneous thermal analysis showed stability up to 450 °C in all atmospheres, oxidation in air above 720 °C (E_a ≈ 160–170 kJ/mol) and mass gains at 1195 °C of 23.2–25.7% (air), 4.9–6.8% (N₂) and 1.7–2.1% (Ar). The Ti–6Al–7Nb–0.3Y powder contains 0.69–0.74 wt.% Oxygen, far beyond the scavenging capacity of the retained 0.11–0.12 wt.% Yttrium, as well as 0.09–0.12 wt.% Nitrogen and 0.013–0.015 wt.% Hydrogen.

The paper focuses on materials characterization and in vivo biocompatibility tests of Ti–6Al–7Nb–0.3REE wt.% alloys (REEs—Y, Ce, La) for use as a promising material to produce personalized medical implants and shed light on possible toxicity effects of REE alloy microdoping. All alloys were produced by the electric arc melting method and characterized by scanning electron microscopy (SEM), optical microscopy (OM), energy-dispersive X-ray spectroscopy analysis (EDX), X-ray diffraction (XRD), true density analysis, micro- and nanoindentation methods, and reducing/oxidation melting techniques. True density of alloys increased in the following order: Ti−6Al−7Nb−0.3Y (4.4563 ± 0.1075 g/cm³) < Ti−6Al−7Nb−0.3Ce (4.7255 ± 0.2853 g/cm³) < Ti−6Al−7Nb−0.3La (4.8019 ± 0.0111 g/cm³). XRD analysis indicated that Ti–6Al–7Nb–0.3Y alloy consisted of single α–Ti phase in comparison with Ti–6Al–7Nb–0.3La (α–Ti to β–Ti = 82 to 18) and Ti–6Al–7Nb–0.3Ce (α–Ti to β–Ti = 90.5 to 9.5). The single-phase Ti–6Al–7Nb–0.3Y alloy had the finest α–Ti phase crystallites (22.32 nm); the larger α–Ti crystallites in the dual-phase Ti–6Al–7Nb–0.3Ce and Ti–6Al–7Nb–0.3La (30.77 nm and 29.83 nm, respectively) suggested the presence of the β–Ti phase (23.34 nm and 25.61 nm, respectively). REE microdoping of alloys changed the lattice volume (∆V): α–Ti phase—0.269% for Ti–6Al–7Nb–0.3Y, 1.799% for Ti–6Al–7Nb–0.3Ce, 0.595% for Ti–6Al–7Nb–0.3La; and β–Ti phase—0.334% for Ti–6Al–7Nb–0.3Ce, 0.670% for Ti–6Al–7Nb–0.3La. Nanohardness (H) and elastic modulus (E) increased in the following order: Ti−6Al−7Nb−0.3La (4.01 GPa and 135 GPa, respectively) < Ti−6Al−7Nb−0.3Y (4.39 GPa and 137 GPa, respectively) < Ti−6Al−7Nb−0.3Ce (4.67 GPa and 146 GPa, respectively). In vivo tests were conducted using 46 sexually mature male Wistar rats by means of skin implantation of samples with d = 11 mm and h = 1 mm. Our research shows that Ti–6Al–7Nb–0.3La alloy (Group 2) and Ti–6Al–7Nb–0.3Ce alloy (Group 3) induced sustained hepatotoxic and nephrotoxic effects. Ti–6Al–7Nb–0.3Y alloy induced a slight local inflammatory response; however, serum biochemical analysis suggested this effect was compensated.

The paper focuses on materials characterization and «in vivo» biocompatibility tests of Ti6Al7Nb alloys microdoped by 0.3 wt. % of rareearth elements (REE) to use it as perspective materials to produce personalized medical implants. All Ti6Al7Nb0.3REE alloys (REE Y, Ce, La) were produced by electric arc melting method and characterized by scanning electron microscopy (SEM), optical microscopy (OM), energy-dispersive Xray spectroscopy analysis (EDX), helium pycnometer as well as reducing/oxidation melting methods. The measured true densities increased in the order: Ti−6Al−7Nb−0.3Y (4.4563 ± 0.1075 g/cm³) < Ti−6Al−7Nb−0.3Ce (4.7255 ± 0.2853 g/cm³) < Ti−6Al−7Nb−0.3La (4.8019 ± 0.0111 g/cm³). Diffraction analysis was performed to indicate phases composition and calculate crystallites sizes, crystal orientation and lattice parameters that confirmed REEmicrodoping due to increase of lattice volume. The single-phase Ti6Al7Nb0.3Y alloy had the finest αTi crystallites (22.32 nm), the larger αTi crystallites in the dualphase Ti6Al7Nb0.3Ce and Ti6Al7Nb0.3La (30.77 nm and 29.83 nm, respectively) suggest that the presence of the βTi phase. Hardness (H) and elastic modulus (E) were indicated by nanoindentation and increased in the order: Ti−6Al−7Nb−0.3La (4.01 GPa and 17.7 GPa respectively) < Ti−6Al−7Nb−0.3Y (4.39 GPa and 137 GPa respectively ) < Ti−6Al−7Nb−0.3Ce (4,67 GPa and 146 GPa respectively). In vivo tests showed that Ti6Al7Nb0.3La alloy had statistically significant increase of local inflammation at the one-week mark needed to further research and explanation as well, that could be indicator of toxicity in comparison with other studied alloys.

Low temperature synthesis of V ₃ S ₄ nanoflakes using a unique gas–solid reaction route.

Hydrothermally synthesized nanostructured MoS ₂ was immobilized over large area graphite paper (5 × 5 mm ² ) to fabricate electrode for hydrogen evolution application. The chemical optimization via. variation in hydroxylamine hydrochloride(HAH) concentration, led to nanosheets containing surface over the micro-balls, with a 1T and 2H phase of MoS ₂ . A physicochemical and electrochemical characterization yielded a lowest Tafel slope of ∼67 mV dec ⁻¹ , a lowest over potential of 0.19 V with a significant electrocatalytic stability in acidic. An electrocatalytic hydrogen evolution over optimized MoS ₂ evolved 2 times (∼46 μ mol h ⁻¹ ) of hydrogen gas as compared to that from MoS ₂ synthesized without HAH. The improved performance of electrocatalyst can be attributed to the combination of phase, and electrochemical properties 2D structure of MoS ₂ .