Mohamed Abdullah Abdullah Mohamed

Substrate-mediated CVT growth enables highly crystalline 3R-TaSe ₂ nanocrystals exhibiting charge density wave behavior at ∼100 K and superconductivity below 2.2 K.

The design of van der Waals (vdW) heterostructures by integrating distinct two-dimensional (2D) materials remains a central strategy for tailoring novel functionalities or enhancing intrinsic properties beyond those of their...

In this work, Cu₂O nanopyramids and CuO nanoflakes are synthesized using simple co-precipitation and hydrothermal methods, respectively. The XRD and Rietveld refinement results show that the synthesized samples are pure single phases of cubic Cu₂O and monoclinic CuO. The field emission scanning electron microscope (FE-SEM) is used to figure out the size, shape and surface morphology of the materials. The alternating current (AC) conductivity (σ _ac) of the Cu₂O and CuO nanostructures was investigated and explained in the framework of the correlated barrier hopping model. Maxwell–Wagner model was applied to explain the behavior of the dielectric constant as a function of frequency. The impedance spectra show that the grain boundaries play an important role in the dielectric relaxation processes. The obtained Cole-Cole diagrams were explained using the Maxwell- Wagner capacitor model.

In this work, pure and Mg-doped CuO (Cu_1−xMg_xO, x = 0.0, 0.02, 0.04 and 0.08) nanoflakes were synthesized by a surfactant-free hydrothermal method. X-ray diffraction patterns confirmed the formation of the single-phase monoclinic CuO crystal structure. The morphological investigations using field emission scanning electron microscopy showed that the samples possessed ultrathin nanoflake-like morphology. The internal microstructure was highlighted using high-resolution transmission electron microscopy and selected area electron diffraction investigations. Raman spectroscopy investigation confirmed the chemical bonding, structure, and phase purity of the samples. DC conductivity measurements revealed two thermally activated conduction mechanisms in low- and high-temperature ranges caused by charge carrier transitions from shallow and deep donor levels, respectively. The AC electrical conductivity and dielectric parameters were analyzed in the temperature range of 303–403 K and frequency range of 10 Hz–1 MHz. The frequency and temperature dependencies of the AC conductivity were explained in the framework of Jonscher's power law and correlated barrier hopping model. The dielectric constant and dielectric loss were analyzed as functions of frequency and temperature and the behavior coincided with Koops’ theory. Also, the study of the impedance spectra and Cole–Cole diagrams illustrated the significant role of grain boundaries in the dielectric relaxation processes.

We report in the context of lithium-rich antiperovskite cathode materials outstanding electrochemical properties of (Li₂Fe)SeO, which for the first time was synthesized via direct ball-milling. The unique structured material displays an electrochemical cycling performance of 250 mA h g⁻¹ at 0.1C when used as a cathode in lithium-ion batteries. Comprehensive electrochemical analysis combined with detailed transmission electron microscopy studies reveal that, above 2.5 V, the multi electron storage mechanism involves conversion of (Li₂Fe)SeO to Fe_1−xSe_x. Our results furthermore demonstrate the general relevance of our findings to the whole class of antiperovskite cathode materials and present a route to strongly enhance their cell performance by avoiding the degradation path deciphered by our studies.

Green and scalable mechanochemical synthesis of antiperovskite (Li ₂ Fe)SO cathode.