Introduction: Although third-generation advanced high-strength steels with medium-manganese quenching and partitioning processes have shown promise for use in the automotive industry, many knowledge gaps exist regarding the effect of partitioning temperature on the microstructural evolution of medium-Mn steel. This study systematically investigated the effect of partitioning temperature (330°C and 560°C) on the morphology and distribution of Martensite/retained Austenite (M/A) islands and the volume fraction of retained austenite in medium-Mn QP steel. Methodology: Microstructural characterizations were performed using optical microscopy, field emission scanning electron microscopy, and X-ray diffraction analysis after austenitization at 950°C, quenching at 100°C, and partitioning at 330°C and 560°C. Results: The amount of retained austenite increased by 53% in relative terms, from 9.8% at 330°C to 15.0% at 560°C, as confirmed by the X-ray diffraction data. At the elevated partitioning temperature QP560, tempered martensite was converted, whereas the retained austenite content increased to 15%, M/A islands decreased, and filmlike retained austenite increased along the martensite plate boundaries. Discussion: Carbon atoms migrate from martensite to austenite as the temperature increases; thus, increased diffusivity enhances carbon migration. The partitioning temperature has a pronounced effect on the microstructural properties, with higher temperatures resulting in a lower brittle M/A phase content and higher stabilized retained austenite content. Conclusion: The partitioning temperature plays a crucial role in tailoring the strength-ductility synergistic behavior of medium-Mn Q&P steels, justifying the ongoing research into the development of third-generation advanced high-strength automotive steels.
Abstract: Natural fiberreinforced composites (FRC) are very popular because they are better for the environment than synthetic FRC, as they can be biodegraded and reused. Natural FRC can't be used as much because their mechanical and interfacial properties aren't good enough. Since 2011, a type of polymer composite that combines natural lignocellulosic fibers (NLFs) with a graphene-based material has become increasingly popular. Graphene and its derivatives can improve the mechanical properties of natural fibers and reduce their environmental impact by altering their surfaces to form natural FRC. A short summary of graphene's properties and the method of its extraction from graphite is provided. Graphene oxide (GO), reduced graphene oxide (rGO), graphite nanoplatelet (GNP)/exfoliated graphene, and nanographene (NG) are some of the materials made from graphene that are being successfully added to natural fiber composites (NLFs). Some studies examine how these materials improve protection against impacts and heat, and increase strength. An intriguing aspect of this combination is that graphene's amphiphilic nature provides a more effective means to enhance interfacial adhesion between the hydrophobic polymer matrix and hydrophilic NLFs. Two primary approaches to inclusion have been implemented. In the first approach, NLFs and a hybrid filler comprising NG, GNP, GO, and rGO to reinforce polymer composites are discussed. The second method employs GO and rGO coatings on NLFs to enhance molecular bonding, followed by incorporation into a polymeric matrix. Both approaches are helping pave the way for innovations in energy storage, medication delivery, biosensors, wearable electronics, medical implants, and bulletproof armor.
Introduction: Polymer electrolyte membranes (PEMs) are increasingly being considered for flexible electronics, electromagnetic interference (EMI) shielding, fuel cells, and biosensors because of their electrical tunability and mechanical flexibility. In this study, the dielectric and electrical properties of a PVA/PVP/ PAMPS-based polymer electrolyte membrane filled with the ionic dopant AgNO3 are examined. Methods: Flexible polymer electrolyte membranes (PEMs) were prepared by solution casting. The membranes were made from polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS), and different concentrations of silver nitrate (AgNO3) were used to explore the mechanisms of ion transport and polarization; the dielectric properties, dielectric loss, AC conductivity, and impedance characteristics were examined at frequencies between 20 Hz and 10 MHz. results: The comprehensive electrical characterization of PVA/PVP/PAMPS/AgNO3 polymer blend membranes reveals a strong dependence of dielectric and conductive behaviour on the concentration of silver nitrate (AgNO3) incorporated into the matrix. The frequency-resolved evaluation of dielectric constant (ε′), dissipation factor (tan δ), and AC conductivity (σ) yields pivotal insights into the ion transport mechanisms and polarization dynamics within the polymer system Results: The optimized polymer composition was 0.6 gm of PAMPS and 0.3 gm of PVP. Significant frequency- and ionic-concentration-dependent behavior was observed in dielectric analysis. The highest electrical performance and dielectric constant were found in the membrane containing 0.8 gm of AgNO3. At the low frequencies, there was a significant rise in the permittivity arising from the interfacial and space-charge polarization effects. The AC conductivity was found to increase with frequency, suggesting improved bulk ion transport. The conductivity of all the membranes containing AgNO3 decreased at low frequencies, as revealed by impedance spectroscopy. Discussion: The improved dielectric and conductive performance of the 0.8 gm AgNO3 membrane is believed to be related to the optimum ionic charge carrier concentration and polymer chain mobility, as such frequency dependence is in agreement with the known polarization and ion-hopping mechanisms in polymer electrolytes. Conclusion: The PVA/PVP/PAMPS/AgNO3 polymer electrolyte membranes had better dielectric and electrical properties as the AgNO3 content was increased. The membrane with a concentration of 0.8 gm AgNO3 showed the highest performance among the studied samples and can be used in the development of advanced flexible electronic and electrochemical devices. AgNO3.
Introduction: This study optimizes the mix proportion of toughness-enhanced mortar to obtain excellent toughness and mechanical properties. Methods: Modified mortars were prepared using SBR latex, PVA fibers, and silica fume. Based on an L9(34) orthogonal array experiment, the effects of different admixtures on fluidity, setting time, mechanical strength, and toughness of mortar are studied, and then multi-objective optimization is carried out by using Gray correlation analysis. Results: The result is that the optimal mix proportion is A1B3C3 (5% SBR latex, 0.3% PVA fibers, and 15% silica fume). The 28-day flexural-to-compressive strength ratio achieved 0.23, which is far beyond ordinary mortar. Discussion: The findings demonstrate that the toughened mortar achieves superior toughness while retaining high compressive strength. Conclusion: SEM shows that the excellent toughness comes from the synergistic network. PVA fiber bridging and the bonded polymer film together prevent crack propagation and prevent spalling. The GRA method provides a reliable framework for multi-objective optimization in material design.
Introduction: Asphalt binders exhibit strong viscoelastic behavior at intermediate temperatures (15-35°C), where rutting is no longer the dominant pavement distress. Instead, repeated traffic loading leads to fatigue cracking that progressively reduces pavement performance. Such cracks typically initiate within the bitumen mastic or at the bitumen–aggregate interface, indicating that mixture fatigue behavior is largely controlled by binder properties. Therefore, understanding binder fatigue characteristics is essential for evaluating asphalt mixture durability. Appropriate material selection and binder modification strategies are crucial for evaluating asphalt mixture durability in pavements. Methods: Utilizing Linear Amplitude Sweep (LAS) and Time Sweep (TS) tests, the damage characteristic relationships for modified asphalt with varying Cu2O dosages under multiple aging conditions were determined. This revealed the influence of modifier content on material stiffness and damage mechanics. The dynamic mechanical behavior within the Linear Viscoelastic (LVE) region was comprehensively characterized using dynamic modulus and phase angle master curves. Results: Fatigue resistance exhibited a non-monotonic trend with increasing nanoparticle content, reaching an optimum at 3% concentration, where peak fatigue life was achieved. Performance degradation beyond this threshold is postulated to result from reduced effective reactive surface area due to nanoparticle agglomeration. Discussion: Nano-Cu2O agglomeration at higher dosages limits modification efficacy, highlighting the need for optimized dispersion techniques. The study did not investigate the chemical reaction mechanisms between nano-Cu2O and asphalt or their long-term fatigue effects, introducing uncertainty regarding field performance. Conclusion: Nano-Cu2O significantly improved binder fatigue life under both unaged and aged conditions, with optimal performance at 3% dosage, producing a 16.8% increase. Higher contents caused particle agglomeration and reduced interfacial stability. LAS results indicated broader stress peaks and higher yield.
