Characterization of sp carbon produced by plasma deposition on gamma-TiAl alloys

Surfaces of two gamma-TiAl alloys, Ti-47%Al-2%Nb-2%Cr (MJ12) and Ti-47%Al-2%Nb-2%Mn + 0.8%TiB₂ (MJ47), were modified by acetylene plasma deposition at −3 kV bias voltage for 0.5-4 h. By using GIXRD and SAED, C (n-diamond), TiC, Al, AlTi, AlTi₂, AlTi₃, Al_0.64Ti_0.36 and Al₂Ti were detected on both alloys. Additional TiB₂ was detected on MJ47. XPS and Raman analyses revealed the presence of sp³ and sp² carbon deposited on the alloy surfaces with their binding energies of 283.9-284.8 eV for MJ12 and 283.9-285.0 eV for MJ47. Both sp³ and sp² contents were increased with the increase in the exposure times. The increasing rate of the first was less than that of the second, due to the stress developed in the films. Moiré fringe and crystallographic planes were detected using TEM. Knoop hardness of the deposited alloys, influenced by sp³ carbon, was increased with the increase in the exposure time. Those of MJ12 and MJ47 with 4 h deposition are 1.88 and 1.57 times of the corresponding untreated alloys, respectively.     

Surface modification of γ-TiAl alloys by acetylene plasma deposition

Surfaces of two γ-TiAl alloys, Ti-47 at% Al-2at% Nb-2 at% Cr (MJ12) and Ti-47 at% Al-2 at% Nb-2 at% Mn + 0.8 at% TiB₂ (MJ47), have been modified by acetylene plasma deposition at bias voltages of −4, −5 and −6 kV for 3.6 × 10³ s (1 h) and 1.44 × 10⁴ s (4 h). Knoop hardness (HK) of the alloys is increased with the increase of bias voltage and prolonged time for the deposition. HK of MJ12 and MJ47 deposited at −6 kV for 1.44 × 10⁴ s is, respectively, 3.36 and 3.32 times as hard as the untreated alloys. SEM and AFM analyses show that the deposited alloys compose of a number of nano-dots which reflect their surface properties. The phases analyzed by XRD are in accord with the elements analyzed by EDX.     

Microwave-assisted hydrothermal synthesis of BiOBr/BiOCl flowerlike composites used for photocatalysis

Research on Chemical Intermediates - BiOBr/BiOCl flowerlike composites were successfully synthesized in different solutions containing 0.00–1.50 g polyvinylpyrrolidone (PVP) by...