Materials Science Forum Vol. 1181

Abstract: The aim of this research is to obtain activated carbon from the solid residue generated in the pyrolysis process of used tires, using microwave technology for its activation. In the first phase, the tires were subjected to thermal pyrolysis at 575°C to obtain a carbonaceous residue (CR). This residue was then activated using potassium hydroxide (KOH) in a 1:3 ratio and exposed to a conventional microwave oven at a power of 700 W for 3 minutes without pauses, obtaining activated carbon (AC) as a result. To evaluate the adsorption capacity, tests were conducted with both carbons (CR and AC) using three concentrations of carbon, with a contact time of 300 minutes and agitation at 400 RPM. The results showed that CR achieved a maximum adsorption of 57.13% at a concentration of 0.2 g, while AC exhibited values greater than 90%. It is concluded that microwave activation is an effective and cost-efficient process to convert the carbonaceous residue from used tire pyrolysis into an adsorbent material with high arsenic removal capacity.

Abstract: The performance of polymer electrolyte can be improved through various approaches, including the addition of filler and dopant salt, in which has demonstrated significant potential for enhancing performance in electrochemical applications. The purpose of this study was to investigate the ionic conductivity and structural studies of 49% poly (methyl methacrylate) grafted natural rubber (MG49)-graphene oxide (GO) integrated with ammonium triflate (NH₄CF₃SO₃) based polymer electrolytes. The highest ionic conductivity, 4.42 x 10^-6 Scm^-1, was achieved with 25 wt.% of NH₄CF₃SO_3. ATR-FTIR analysis showed a reduction in C=O peak intensity, indicating interaction between the polymer matrix and salt, while optical microscopy (OM) revealed that the 25 wt.% sample had the smoothest surface and the most amorphous structure, correlating with the highest ionic conductivity. These results suggest that nanocomposite polymer electrolytes based on MG30-GO-NH₄CF₃SO₃ have potential for energy storage applications.

Abstract: We report double scaling electrical transport in (Fe₃O₄)_1-x/(BaTiO₃)ₓ nanoparticle-composite sinters (NPCSs), where charge conduction arises from the coexistence of variable range hopping and percolation. Understanding the interplay between these mechanisms is essential for designing composite materials in which microstructural connectivity and carrier localization can be tuned for targeted electronic properties. The NPCSs were synthesized via low-temperature hydrogen reduction and sintering of α-Fe₂O₃ and BaTiO₃ nanoparticles (average diameter ~100 nm) at 500 °C for 3 h in an Ar (90%)/H₂(10%) atmosphere, yielding x values from 0.0 to 0.7. X-ray diffraction and scanning electron microscopy confirmed phase purity, the coexistence of Fe₃O₄ and BaTiO₃, and systematic grain-size evolution with BaTiO₃ content. Electrical resistivity increased with x and followed 3D Mott’s variable range hopping behavior, with ln ρ vs. T ⁻¹ᐟ⁴ (ρ: electrical resistivity; T: temperature) remaining linear and slopes increasing with x, consistent with shorter hopping lengths and enhanced carrier localization. Percolation analysis in the 150–300 K range yielded a conductivity critical exponent of ~3, significantly higher than the ~2 predicted for simple 3D percolation, indicating that geometric connectivity alone cannot explain the transport. These results provide compelling evidence that charge conduction in these composites is governed by a double scaling mechanism, in which variable range hopping and percolation coexist and jointly control electronic transport through the combined influence of microstructure and composition.

Abstract: I report a first-principles investigation of nickel-doped magnetite as a candidate for thermoelectric applications. Substituting Ni at the octahedral Fe sites preserves the inverse spinel framework while introducing Ni 3d impurity levels near the Fermi energy. Using Boltzmann transport theory in the constant-relaxation-time approximation, I calculate temperature and carrier-concentration-dependent transport properties, namely, electrical conductivity, the Seebeck coefficient, the power factor, and electronic thermal conductivity for both n-type and p-type doping. I find that conductivity increases significantly with increasing doping level, while the Seebeck coefficient shows large peaks and even changes sign at moderate carrier densities. Notably, I observed a very large power factor that exceeds that of the commonly used thermoelectric materials at higher temperatures. However, the accompanying rise in electronic thermal conductivity highlights the need for phonon engineering to limit total heat transport. These results demonstrate that Ni substitution provides an effective route to tune the electronic structure and optimize the thermoelectric performance of magnetite under realistic operating conditions.

Abstract: The partial substitution of cement with ground blast furnace slag (GGBS) and silica fume (HS) in the concrete mix has the potential to reduce the carbon footprint associated with cement production. The objective of this study is to evaluate the feasibility of this partial replacement as a strategy to promote greater sustainability in construction. The research looks at four replacement percentages with different ratios: 10% HS, 10% GGBS, a combination of 10% GGBS and 10% HS, and 13% GGBS with 10% HS. The results indicate that the mixtures obtained not only reach but exceed the required strength of f´c=280 kg/cm² and have a reduced carbon footprint compared to conventional concrete. This highlights the environmental benefits of using industrial by-products as partial replacements in concrete manufacturing, helping to mitigate the negative impacts of cement production.

Abstract: Under the current research project, the feasibility of reducing the carbon footprint of masonry restoration mortars was investigated, by means of replacing a part of cement with emery. A two-fold advantage is offered by following this strategy: (i) to develop more sustainable restoration mortars and (ii) to validate the use of a rock that can potentially offer greater resistance to depletion/ weathering. Emery, a naturally occurring rock was characterized via X-ray fluorescence and stereo microscopy. The reference mortar was prepared according to EN 196-1:2016, with a CEMII/B-M(P-LL)42.5R cement targeting a flow table spread of 12-16±1 mm (in accordance with EN1015-3:1999+A1). Consequently, (i) a 20% and (ii) a 50% CEMII replacement with corundum powder was materialized. The mean compressive strength was reduced, as originally intended, by approximately 50% for the 50% replacement, allowing the mortar to be used for restoration purposes, where natural, low strength materials are preferred, which not exceeding the strength of masonry stones. Interestingly, flexural strength did not fall drastically. A number of complications arise on setting the flow spread as the basic design parameter and discussion on mix design is elaborated upon and correlated with the 7-and 28-day strength tests (in accordance with EN1015-11:1999+A1). Furthermore, the pore structure of the surface of the specimens was investigated via stereo microscopy and interesting observations pave the way for more sustainable mortar design.