Preparing low-oxygen Ti-6Al-4V alloy powder through direct reduction of oxides and its synergistic reaction mechanism

Ti-6Al-4V alloy powder was prepared through a two-step reduction of a mixture of TiO_(2),V_(2)O_(5) and Al_(2)O_(3) in this study.The oxide mixture was first reduced by Mg in MgCl_(2) at 750℃ in argon,where oxygen was reduced to 2.47 wt%from 40.02 wt%.The oxygen content in the final powder was eventually reduced to an extremely low level(0.055 wt%)using calcium at 900℃ in argon,and the final powder had the composition of 90.12 wt%Ti,5.57 wt%Al,and 3.87 wt%V,which meets the standard specification of Ti-6Al-4V(ASTM F1108-09).Between the two reductions,a heat treatment step was designed to help controlling the specific surface area and particle size.The effect of the heat treatment temperature on the morphology,and composition uniformity of the powder was investigated in detail.Heat treatment above 1300℃ attributed to a dense powder with a controlled specific surface area.Thermodynamic modeling and experimental results indicated that onlyα-Ti enriched with Al andβ-Ti enriched with V exist in the final powder,and other possible phases including Al-Mg and Al-V were excluded.This study also offers a triple-step thermochemical process for producing high-purity Ti-based alloy powder.

Supramolecular precursor derived loofah sponge-like Fe_(2)O_(x)/C for effective synergistic reaction of Fenton and photocatalysis

Fenton or photocatalytic degradations of organic contaminants are recognized as promising approaches to address the increasing environmental pollution issues.Herein,we develop the effective synergistic catalysis reaction of Fenton and photocatalysis based on a loofah sponge-like Fe_(2)O_(x)/C nanocomposite,which exhibits excellent nitrobenzene photocatalytic degradation property.It is noted that Fe2O3 nanoparticles with surface Fe^(2+) species were encapsulated with an ultrathin carbon layer(denoted as Fe_(2)O_(x)/C)via a supramolecular self-sacrificing template and following thermal treatment process.The experimental results indicated that the thin layer carbon coating not only inhibited the Fe iron leaching from the Fe_(2)O_(x)but also prompted the separation and transferring of electrons–hole pairs.The introduction of Fe_(2)O_(x)/C enables the Fenton reaction to induce a rapid Fe^(2+)/Fe^(3+)cycle,and meanwhile,together with the photocatalytic reaction to produce continuous active substances for the subsequent degradation catalytic reaction without successive H2O2,resulting in the inexpensive and the effective photocatalytic procedure.As a result,100%nitrobenzene(100 mg/L)was degraded and 97%of the organic carbon was mineralized in 90 min using the Fe_(2)O_(x)/C(0.1 g/L)at a low H_(2)O_(2) dosage(0.50 mM),under air mass(AM)1.5 irradiation.Theoretical calculations confirmed that the Fe_(2)O_(x)/C-600 with thin carbon layer promoted the dissociation of H2O2 and the·OH desorption.The synergistic catalysis of this work may provide new ideas for low-cost and more efficient treatment of pollutants.