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.

Fabrication and Ablation Behavior of a Novel 3D Orthogonal Woven C/C-SiC-HfC Composite by I-CVI, SI, and LSI Combined Process

Amin Rezaei Chekani

A C/C-SiC-HfC composite was fabricated using a three-dimensional orthogonally woven (3DW) preform, and the effect of HfC ultra-high temperature ceramic (UHTC) particles on the microstructure and ablation properties of the composite was evaluated. First, pyrolytic carbon (PyC) was infiltrated into the 3DW preform by the I-CVI method. Then, impregnation of a suspension composed of HfC particles and phenolic resin into the 3DW preform. Next, liquid Si alloy was infiltrated into the C/C-HfC porous structure at 1650 °C to form a C/C composite with a SiC-HfC matrix. HfC particles and the continuous SiC phase among carbon fibers were saturated and during the oxyacetylene test, covered the surface of the C/C-SiC-HfC composite as a dense continuous SiO₂-HfO₂ layer. This layer acted as a barrier against the diffusion of oxygen into the bulk parts of the C/C-SiC-HfC composite. The results of the oxyacetylene flame test at 2500 °C for 120 s showed that the mass and linear ablation rates of the C/C-SiC composite were 4.8 mg/s and 3.75 µm/s, respectively. After the addition of HfC and the formation of the C/C-SiC-HfC composite, these rates decreased to 1.6 mg/s and 0.98 µm/s, respectively.

Catalytic Oxidation of Nitrite to Nitrate in Aquas Solution by Carbonate-Activated Charcoal

Sumrit Mopoung

Activated charcoals were prepared by activation with 600 W microwave irradiation in combination with pretreatments of tamarind wood derived charcoal in boiling mixtures with NaOH (1 g : 0 g - 1 g: 0.12 g). The samples were characterized by FTIR, XRD, SEM-EDS, and BET, and used for catalytic nitrite c oxidation under air atmosphere in the absence of light at 30°C, pH 6.5, and 120 rpm shanking for improved efficiency. The results show that the percent yields of tamarind wood derived activated charcoals (ACCs) were 88.51% - 94.66 %. The main carbonate compounds of ACCs are present in the materials after activation. Na⁺ ions and water molecules could be inserted into the graphitic layers during pretreatment and efficiently effected surface cracking of ACCs by 600 W microwave irradiation. The surface cracklings and porosities of ACCs increased with increasing concentration of NaOH from 1 M to 3 M with optimum at 2 M NaOH. The final products are mesopore materials containing macro and meso hole channels. It was found that the nitrite conversions exhibit high reaction rates and are completed within 20 min. The reactions proceed via catalytic oxidations and their rates increase with increasing concentrations of NaOH activation, while nitrite conversions via the disproportionation reaction wereinhibited.

Galvanostatic Deposition of Iron Powder from Sulfate Electrolytes: Experimental Analysis and Empirical Modeling

Daniela Grigorova

Producing high-purity iron powders with controlled particle morphology is essential for advanced powder metallurgy, additive manufacturing, and functional materials. However, achieving precise morphological control in environmentally benign, additive-free electrolytes remains challenging. This study systematically investigates the galvanostatic electrodeposition of iron powder from sulfate-based electrolytes containing 10.0 and 50.0 g·L⁻¹ Fe²⁺, focusing on the interplay between current density, pH evolution, deposition efficiency, and particle structure. A clear transition from compact, adherent deposits at low current densities to dendritic, easily detachable powders at higher values was observed. SEM analysis revealed well-defined dendritic aggregates at 7 A·dm⁻² (30–80 μm), whereas highly fragmented, porous agglomerates formed at 10 A·dm⁻², accompanied by fine-scale fragmentation driven by intense hydrogen evolution. XRD confirmed pure α-Fe for current densities up to 7 A·dm⁻², while partial oxidation to Fe₃O₄ occurred at 10 A·dm⁻²; EDX mapping further supported this surface oxidation. The deposited mass increased linearly with current density for both Fe²⁺ concentrations, with regression models yielding R² values above 0.96. Current efficiency decreased at high current densities due to enhanced parasitic reactions. Overall, the results demonstrate that galvanostatic electrodeposition in additive-free sulfate media enables controlled synthesis of iron powders, with tunable morphology and phase purity governed primarily by current density and electrolyte composition.

Preparation, Characterization and Antimicrobial Properties of Ag2O Nanoparticles Composited with Reduced Graphene Oxide

Layth Hayder Hameed kazem Al_Tmamimi

Researchers have increasingly investigated hybrid nanocomposites that mix physical and chemical properties of carbonaceous materials and metal/metal oxides. In this work, a nanocomposite composed of reduced graphene oxide and silver (I) oxide, rGO@Ag₂O, was prepared using ascorbic acid as a green reducing agent. The Ag₂O nanoparticles were synthesized by means of a controlled precipitation process in water. The carbonaceous material of rGO was obtained through a modified Hummers' approach. After being combined with a solvent, the Ag₂O and rGO in ethanol were dried with heat. The resultant nanocomposite was structurally and optically examined using different characterization techniques.
The results showed that GO has been successfully reduced, Ag₂O revealed a crystalline structure, and Ag₂O nanostructures were found on the surface of rGO sheets. Disk diffusion assay was adopted in order to evaluate antibacterial activity of nanocomposite against both Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative) bacteria. The Ag₂O nanostructures in the composite form exhibited inhibition zone with higher diameter compared to their uncomposited counterparts. Higher antibacterial activity of rGO@Ag₂O was attributed to the role of negatively charged oxygen-containing groups present on the surface of rGO in slightly improvement in the stability of Ag₂O nanostructures.
Our findings show that rGO@Ag₂O could be a useful antimicrobial material for biomedical surfaces, as a coating, and in systems that clean water. It could be a good option for future research in nano-enabled antimicrobial technology because it can destroy bacteria, is made in an environmentally benign way, and could be made on a larger scale.