Materials Science Forum Vol. 1103

Abstract: This study investigates the effect of a chain extender on the properties of recycled polyethylene terephthalate (rPET) for 3D printing filament. The research focuses on the melt flow index (MFI), mechanical properties, thermal behavior, and crystallinity of rPET blends with varying chain extender concentrations. MFI analysis reveals that the viscosity of rPET is influenced by the grade and sources of the PET bottles. The addition of the chain extender decreases MFI, indicating increased viscosity. Mechanical testing shows a slight decrease in impact strength with increasing chain extender concentration, suggesting the presence of limitations or constraints within the material. Thermal analysis demonstrates that the chain extender elevates the glass transition temperature (T_g) and melting temperature (T_m) of rPET, indicating enhanced rigidity and thermal resistance. However, the crystallinity (X_c) decreases as the chain extender disrupts the regular packing of polymer chains within the crystalline regions. These findings provide valuable insights into the influence of the chain extender on the properties of rPET for 3D printing filament. The research contributes to the development of sustainable manufacturing practices and promotes the utilization of recycled materials in additive manufacturing applications, furthering the goals of the circular economy and environmental sustainability.

Abstract: In this work, the Cu-alginate/graphene aerogels were prepared by using alginate, graphene and copper chloride as precursors by a freeze-drying process. Finally, N-doped carbon aerogels supported by Cu nanoparticles (NPs) (Cu/N-CAs) were obtained through annealing in the NH₃ atmosphere. The morphology, microstructures, specific surface area, and pore size distribution were studied by SEM, XRD, and BET analysis. The results showed that a significant amount of Cu NPs were uniformly disseminated on the aerogels’ surface, and the catalysts’ specific surface area reached 141 m²/g. Electrochemical tests revealed good catalytic capabilities for the oxygen reduction reaction (ORR) of the as-obtained Cu/N-CAs. Compared to the commercial 20%Pt/C, the Cu/N-CAs exhibited comparable catalytic performance, superior catalytic stability and methanol resistance. The transfer of 3.94 electrons indicated that the Cu/N-CAs were undergoing a four-electron (4e^-) ORR process.

Abstract: Spinel copper ferrite nanoparticles have wide spread technological applications. Polycrystalline copper ferrite nanoparticles is prepared by sonochemical method. The structural property is investigated by X-ray diffraction study, which reveals cubic spinel structure of copper ferrite NPs with average crystalline size of 20 nm. The temperature variation of DC conductivity of copper ferrite nanoparticles is studied. The conductivity is observed to increase with temperature which implies semiconducting nature of copper ferrite. The Mott study reveals that conduction process is three dimensional in present case. Again, p-n junction formation in the ferrite system is observed from the current voltage (I-V) study. This study further shows that the trap height increases with temperature. Ideality factor with values greater than 1 has been observed in present case.

Abstract: Different sand quarries used to build construction in Morelia, México were analyzed, the optimum mortar configuration was obtained based in the analysis of sand aggregates. Different mixes mortar configuration with Portland cement, masonry mortar, lime, sand, and water, were elaborated and characterized. Two different configurations were proposed, one with the addition of 1/4 of lime and the second with 1/2 of mortar masonry in relation to cement ratio. 3 different quarries were studied, and the proportion of sand were from 2.25 to 4. All the samples were analyzed by flowability and wet electrical characterization. The flowability of all different mix configuration pastes was studied to comprehend the sand-water relation of the mortar mix and to observe the different water requirements in function of the sands proportion and quarry origin. The results shows that the sand proportion 2.25 and 3.25 in configuration 1 (1/4 lime) had 123 and 124 % respectively, the highest values. The flowability of sand proportion in configuration 2 (1/2 masonry mortar) were closed and above 100%. The mortar samples were also characterized by the electric resistivity test to analyze the porosity of the mortar in relation to the sand aggregate. All the sand proportion of configuration 1 were under the minimum limit, the 2.5 sand proportion were the closest with 9.51 kΩ-cm. With the configuration 2, 3.5 sand proportion at 7 days from bank J show the highest value 15.48 kΩ-cm.

Abstract: The addition of silicon-aluminium materials can improve the strength of geopolymers, but its effect on the durability of geopolymers has not been confirmed. In this paper, chemical corrosion resistance and freeze-thaw cycle tests were carried out on fly ash geopolymer and metakaolin/mineral slag-fly ash geopolymer, and the reaction mechanism was determined by microscopic analysis. In the chemical corrosion resistance tests, three groups of specimens were immersed in different corrosive solutions, and the corrosion resistance of the specimens was measured by testing the compressive strength and quality change of the specimens immersed in the solution for different times. The results show that the addition of silicon-alumina materials can improve the chemical corrosion resistance of geopolymers in a certain extent, and the mineral slag shows better improvement effect. In the freeze-thaw cycle tests, three groups of materials were put into the freeze-thaw test machine, and their freezing-thawing resisting performance was measured by testing their mass loss rate and compressive strength after different cycles. The results showed that the strength loss of the specimens was improved with the addition of the silicon-aluminium materials, but the mass loss rate of the specimens became higher with the addition of metakaolin.

Abstract: This research focuses on the modification of Natural Rubber Latex (NRL) for its application in soil-cement pavement. The NRL was modified with Coumarone-Indene (CI) and various tests were conducted to evaluate the effects of this modification. The degree of swelling test showed that the NRL's ability to absorb and retain toluene solvent was influenced by the addition of CI. The tensile tests revealed that the inclusion of CI improved the tensile modulus and tensile strength of the NRL up to an optimal content, beyond which there was a decrease. Peel strength tests demonstrated that the incorporation of CI initially increased peel strength up to an optimal CI content, after which it decreased. The splitting tensile test and the unconfined compressive test indicated that soil-cement blends containing modified NRL with CI 8 phr exhibited higher splitting tensile strength and unconfined compressive strength compared to those with neat NRL. Overall, the modification of NRL with CI showed promise in enhancing the properties of soil-cement pavement materials. The findings contribute to the understanding of modifying NRL for pavement applications and provide insights for further research and development in this field.

Abstract: Stress concentration factor (SCF) is usually used to estimate the fatigue life of an offshore joint. Historically, parametric equations were used to estimate SCF based on a statistical analysis of experimental and finite element analysis (FEA) results, to reduce cost and time. These equations give the SCF at the saddle/crown position for simple joints and basic load cases. However, for modified or defective joints, the location of the maximum SCF can change. In such circumstances, the single-point SCF equation cannot be used to estimate the maximum value of SCF, as its location may have changed from saddle/crown. To our knowledge, there are no general expressions to estimate SCF around the brace axis accurately. As artificial neural networks (ANN) can approximate the trend of complex phenomena better than conventional data fitting, a mathematical model based on ANN is proposed to estimate SCF based on the weights and biases of trained ANN. Nine hundred thirty-seven finite element simulations were performed to generate SCF data for training the ANN. This ANN was used to model an empirical equation for SCF. The proposed empirical model can estimate SCF around the brace axis with less than 5% error. The current study provides a roadmap to using FEA and ANN for empirical modeling of SCF in tubular joints, and this approach can be applied to any joint type, with or without design modification or damage. Once a database of similar equations is available, it can be utilized for quickly estimating SCF instead of costly experimentation and FEA. Optimization of the ANN can further improve the accuracy of the developed mathematical model.