An Overview of Parameters Controlling the Decomposition and Degradation of Ti-Based Mn+1AXn Phases

Structure, Morphology, Heat Capacity, and Electrical Transport Properties of Ti3(Al,Si)C2 Materials

A study of Ti₃Al_1−xSi_xC₂ (x = 0 to x = 1) MAX-phase alloys is reported. The materials were obtained from mixtures of Ti₃AlC₂ and Ti₃SiC₂ powders with hot pressing sintering technique. They were characterised with X-ray diffraction, heat capacity, electrical resistivity, and magnetoresistance measurements. The results show a good quality crystal structure and metallic properties with high residual resistivity. The resistivity weakly varies with Si doping and shows a small, positive magnetoresistance effect. The magnetoresistance exhibits a quadratic dependence on the magnetic field, which indicates a dominant contribution from open electronic orbits. The Debye temperatures and Sommerfeld coefficient values derived from specific heat data show slight variations with Si content, with decreasing tendency for the former and an increase for the latter. Experimental results were supported by band structure calculations whose results are consistent with the experiment concerning specific heat, resistivity, and magnetoresistance measurements. In particular, they reveal that of the s-electrons at the Fermi level, those of Al and Si have prevailing density of states and, thus predominantly contribute to the metallic conductivity. This also shows that the high residual resistivity of the materials studied is an intrinsic effect, not due to defects of the crystal structure.

Rice Crust-Like ZnO/Ti3C2Tx MXene Hybrid Structures for Improved Photocatalytic Activity

Novel two-dimensional ZnO/Ti3C2Tx hybrid photocatalysts with modified surface areas were prepared using a simple calcination technique. The microstructures, crystalline features, and bonding states of the ZnO structure-covered Ti3C2Tx MXenes were closely characterized using various tools. The photoluminescence intensity of the hybrid photocatalyst was greatly reduced compared to the pristine ZnO, while its Brunauer-Emmett-Teller (BET) surface area increased by more than 100 times. Under solar light illumination, the photocatalytic degradation efficiency of the hybrid photocatalyst for organic pollutants (MO, RhB) appeared to be three-fold larger as compared to pristine ZnO. The superb photocatalytic performance of the photocatalyst was attributed to several factors, such as ideal band alignment, Schottky barrier formation, and large surface area. Moreover, the ZnO/Ti3C2Tx hybrid photocatalyst showed excellent cycling stability. These results suggest that the novel hybrid structure may be a potential candidate for removing organic pollutants in wastewater.