Iranian Journal of Materials Science and Engineering

Nanoreactor-Enabled Formation of Graphitic Film from a Non-Graphitizing Precursor at Low-Temperature

Aliyeh Afzalalghom

Gas-phase methods for graphite/graphene production, such as chemical vapor deposition (CVD), yield high-quality products but demand catalysts, substrates, high-purity hydrocarbon gases, specialized furnaces, and temperatures exceeding 1000 °C. Here, we demonstrate the synthesis of highly graphitized films with crystalline domains via low-temperature carbonization (900 °C) of nanoporous polydivinylbenzene (PDVB) microspheres, without reliance on a CVD system or catalysts. The films formed on the inner surface of the furnace quartz tube and were characterized by Raman spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, X-ray Diffraction (XRD), and high-resolution transmission electron microscopy (HRTEM). Raman spectrum revealed a high graphitization degree (I_D1/I_G = 0.78), surpassing reported values for catalyst-free plasma- or low-pressure-assisted CVD. XRD showed a sharp diffraction peak at 2θ = 26.37° (d = 3.37 Å), exactly matching the (002) plane of Graphite-2H, while HRTEM and selected area electron diffraction confirmed crystalline domains with p63/mmc symmetry. We propose that the intricate network of nanopores as nanoreactors in PDVB microspheres enables the generation and controlled release of fused benzene rings into the quartz tube, where they condense to form crystalline films. This approach reveals how a nanoscale confinement can be translated into a macroscopic, scalable route, offering a low-cost and facile method for graphite or graphene production.

The Synergistic Effect of Molybdenum Dopant Content and Pressure on the Optoelectronic and Mechanical Performance of CeO2: DFT+U Study

Hussein Miran

This contribution investigates the structural, opto-electronic, and mechanical properties of cerium oxide (CeO₂) and molybdenum-included cerium oxide (Ce_1-xMo_xO₂) under hydrostatic pressures of 0, 25, 50, 75, and 100 GPa. The computed results were executed by the state of the art density functional theory (DFT+U). The generalized gradient approximation (GGA) supported by the PBE functional has been utilized. Initially, the lattice dimensions of the cubic CeO₂ phase accounts to 5.438 Å. The electronic characteristics have inspected by assessing the band gap of the pure CeO₂ unit cell, which amounts to 3.134 eV. Incorporating Mo element into the host CeO₂ lattice declines the band gap to 2.045 eV of Ce_0.75Mo_0.25O₂. This value is more dropped when applying hydrostatic pressure till reaching 1.808 eV at 100 GPa. The projected density of states (PDOS) findings reveal a hybridization between CeO₂ and Mo with key contributions of Ce-4f, O-2p, and Mo-3d states. Furthermore, the assessed negative formation energy magnitudes of Ce_0.75Mo_0.25O₂under zero and applied hydrostatic stress evidence the thermodynamic stability, proposing the possible experimental fabrication of such system. Absorption curves examinations reveal a blue shift for the inspected structures. Under applied pressures, an enhancement in the absorption spectra has been observed by shifting toward the ultraviolet (UV) wavelength region, indicating the potential applications in optoelectronic devices.