Preparation and characterization of Fe-doped TiO<SUB>2</SUB> powders for solar light response and photocatalytic applications

Different amounts of Fe-doped TiO2 (with 0.1 to 10 wt.% Fe) powders were prepared at temperatures in the range of 400 and 800 °C following a conventional co-precipitation technique and were thoroughly characterized by means of X-ray diffraction (XRD), Fourier-transform infrared (FT-IR), Fourier-transform Raman (FT-Raman), diffuse reflectance spectroscopy (DRS), BET surface area, zeta potential and flat band potential measurements. Photocatalytic ability of Fe-doped TiO2 powders was evaluated by means of methylene blue (MB) degradation experiments conducted under the irradiation of simulated solar light. Characterization results suggested that as a dopant Fe stabilized TiO2 in the form of anatase phase, reduced its band gap energy and adjusted its flat band potentials in such a way that these powders can be employed for photoelectrolysis of water into hydrogen and oxygen in photoelectrochemical (PEC) cells. The 0.1 wt.% Fe-doped TiO2 exhibited highest activity in the photocatalytic degradation of MB. The kinetic studies revealed that the MB degradation reaction follows the Langmuir-Hinshelwood first order reaction rate

TEM analysis and molecular dynamics simulation of graphene coated Al-Cu micro joints

This study compares friction-stir spot welds (FSSW) of pure Al to Cu, with and without graphene interlayer (GL), for tensile load and electrical conductivity (σ). The weld interface of Al-Cu fabricated without a GL is found with brittle intermetallic compounds (IMC) like Al2Cu. The presence of brittle IMCs significantly affects the tensile load and σ. In contrast, the sample with GL suppresses the brittle IMCs and enhances the formation of Al4C3 IMC. The presence of Al4C3 strengthens the weld joint by 26.94 % concerning the without GL samples. Further, it was observed that thinner and high-density twins are formed in the samples with GL. The formation of thinner deformation twins is also possible for increased tensile load and σ. The thicker twins in the samples without GL inhibit the electron flow and increase electrical resistivity. The molecular dynamics (MD) simulation was performed to study the in-situ formation of deformed twins. In addition, the MD simulation provides insight into the influence of graphene during the formation of IMCs based on diffusion coefficients of individual atoms. The σ of the Al-Cu joint can be estimated using a cluster Nernst-Einstein equation, which is dependent on the diffusion coefficient obtained from MD simulation

Molecular dynamics simulation of atomic diffusion in friction stir spot welded Al to Cu joints

Dissimilar metals joining, especially Aluminum (Al) to copper (Cu), have gained importance in batteries for electric vehicles. Although friction stir spot welding (FSSW) has recently been used for welding dissimilar materials, progress has been very slow toward understanding the effect of temperature on diffusion condition between the two materials with the same FCC crystal structure. The thermo-mechanical modeling has been used to define the trajectory of Al and Cu particles at the weld interface, but it had a limitation to quantified the diffusion coefficient. Hence, the molecular dynamics (MD) study has been used to investigate the atomic interdiffusion of Al and Cu. The transmission electron microscopy results are used to validate the MD simulation outcome to understand the formation of dislocations and intermetallic compounds. The MD results implicated the formation of γ-phase (BCC), i.e., Al4Cu9 IMC toward the Cu side. Further, the In-situ investigation of non-FCC phase formation at FSSW condition has also been studied