Elastic properties of materials and their changes with temperature are important for their applications in engineering. In the present study the influence of phase composition and temperature of AISI 4130 alloy on Young’s modulus (E_d), shear modulus (G_d), and damping (Q⁻¹) was carried out by the impulse excitation technique (IET). The material characterization was performed using confocal microscopy, XRD, SEM, HV, and dilatometry. A stable structure, composed of ferrite (BCC) and pearlite (α-Fe + Fe₃C), was obtained by annealing. Metastable structure of martensite (BCT) was obtained by quenching. The E_d, G_d, and Q⁻¹ were measured by varying the temperature from RT to 900 °C. The values of E_d and G_d, at RT, were determined as 201.5 and 79.2 GPa (annealed) and 190.13 and 76.5 GPa (quenched), respectively. In the annealed steel, the values E_d and G_d decrease linearly on heating up to 650 °C, with thermal expansion. In the quenched steel, weak changes occurred in the dilatometric curve, E_d, G_d, and Q⁻¹, in the range of 350–450 °C, which indicated decompositions of the martensitic phase. A sharp decrease in the moduli and high peak of Q⁻¹ were observed for both samples around 650–900 °C, revealing low lattice elastic stability of the phases during transformations α(BCC) + Fe₃Cγ(FCC).

The development of efficient catalysts for hydrogen photoproduction is a significant research field, as the demand for clean energy increases. In this context, we have successfully applied an innovative synthesis protocol for TiO₂/Cu₂O heterojunctions, designed to be carried out at low temperature and ambient pressure without the need for addition of a special stabilizing agent, offering a novel and efficient approach to fabricating these materials. The TiO₂/Cu₂O heterojunction demonstrated a notable increase of over 280 times in photocatalytic hydrogen (H₂) production under sunlight compared to neat TiO₂ (8.51 mmol h^–1 g^–1 vs. 0.03 mmol h^–1 g^–1), maintaining reasonable photostability, with ∼15% reduction in activity after the fifth cycle. Furthermore, the material was characterized by XRPD, scanning electron microscopy (SEM), transmission electron microscopy (TEM), DRS, EIS, and N₂ physisorption. Interestingly, TEM analysis revealed that the applied synthesis protocoldespite not employing any specific capping or stabilizing agentsuccessfully achieved an excellent dispersion of ultrasmall Cu₂O species (<2 nm) on the TiO₂ support. This remarkable dispersion is responsible for the efficiency of the heterojunction interface and provides a key explanation for the outstanding photocatalytic performance observed. The present study represents a step forward in developing photocatalysts for H₂ generation by demonstrating the potential of a straightforward, low-temperature, capping or stabilizing agent-free, and environmentally benign synthesis protocol to prepare a TiO₂/Cu₂O heterojunction as an efficient catalyst for sustainable H₂ photoproduction.

Herein, amorphous carbon particles were synthesized from pumpkin seed biomass as a coproduct of a carbon quantum dot preparation route. The material was subsequently investigated as an electrocatalyst for the selective two-electron oxygen reduction reaction (2e^– ORR) toward hydrogen peroxide production. The results demonstrate selectivity and stability comparable to those of conventional commercial carbon, while being obtained through a simple waste-valorization strategy without additional activation or external doping steps. SEM analysis revealed fragmented particles with irregular morphology and predominantly external surface area, consistent with the low porosity quantified by N₂ adsorption (14.2 m² g^–1; pore volume 0.00597 cm³ g^–1), while XPS analyses demonstrated the presence of oxygenated surface functionalities and verified endogenous nitrogen incorporation (∼1%), indicating successful self-doping derived solely from the precursor composition. Rotating disk electrode experiments showed an onset potential of 0.738 V vs RHE, and Koutecký–Levich analyses indicated an electron transfer number close to 2, in contrast to Vulcan XC-72, which displayed mixed 2–3e^– behavior. Rotating ring-disc electrode measurements were also performed and confirmed high stability and selectivity, with an average H₂O₂ yield of ∼91.8% across 1.0–0.22 V and an average electron transfer number of 2.16. Additionally, chronoamperometry demonstrated outperforming compared to several reported carbon-based electrocatalysts. Thus, the results demonstrate that pumpkin seed-derived amorphous carbon is a sustainable and low-cost electrocatalyst with strong potential for decentralized H₂O₂ production via the 2e^– ORR pathway.