Airtightness is an important functional requirement for additively manufactured enclosures intended for sealed or pressure-controlled building-envelope applications. This preliminary study compared the short-term vacuum-retention behavior of Fused Deposition Modeling enclosures manufactured using four material–process combinations: carbon-fiber-reinforced polyethylene terephthalate (PET-CF), polyethylene terephthalate glycol-modified (PETG), lightweight foaming polylactic acid (PLA-Aero), and conventional polylactic acid (PLA Basic). Three independently manufactured enclosures were evaluated for each combination, resulting in 12 experimental units. Each enclosure had nominal internal dimensions of mm, a nominal wall thickness of 6 mm, and a nominal cavity volume of 27 ml. The enclosures were evacuated to an initial nominal gauge-pressure differential of approximately 0.70 bar. After isolation from the vacuum pump, the residual gauge-pressure differential was recorded at 20, 40, and 60 min. PET-CF showed no gauge-resolvable vacuum loss during the 60 min observation period, PLA Basic showed partial pressure recovery, and PETG and PLA-Aero had reached atmospheric equilibrium by the first scheduled observation at 20 min. The primary statistical outcome was the cumulative vacuum loss after 60 min, , with one enclosure-level observation included for each independently manufactured specimen ((N = 12); (n = 3) per material–process group). An exploratory Kruskal–Wallis test indicated an overall difference among the four groups, , (p = 0.013). Dunn’s post-hoc comparisons with Bonferroni adjustment identified exploratory differences between PET-CF and PETG and between PET-CF and PLA-Aero for both comparisons). The remaining pairwise comparisons were not statistically significant after adjustment and should not be interpreted as demonstrating equivalence. The inferential findings were interpreted cautiously because only three independent enclosures were available per group and the observations included ties, gauge-resolution limitations, and interval-censored rapid pressure loss. Qualitative optical microscopy provided morphological context but did not confirm continuous leakage pathways. Because the total pneumatic volume and background leakage of the complete isolated circuit were not quantified metrologically, the results represent apparatus-dependent comparisons of vacuum-retention behavior rather than validated specimen-only leak rates or intrinsic material permeability.

Rare-earth (RE)-microalloyed Q235RE steel and conventional Q235 low-carbon steel were subjected to two carburizing–quenching routes: gas carburizing followed by oil quenching, and low-pressure carburizing followed by high-pressure gas quenching. The microstructures, grain sizes, hardness profiles, and elemental distributions of the carburized specimens were systematically compared. The results showed that RE microalloying significantly improved the hardenability of Q235RE steel. The surface hardness of Q235RE specimens exceeded 700 HV0.1 under both conditions, whereas the low-pressure-carburized Q235 specimen formed a troostitic layer with a maximum hardness of only 386 HV0.1. However, RE microalloying did not increase the carbon diffusion depth. This result was attributed to carbon trapping by RE inclusions at inclusion/matrix interfaces, which reduced the number of carbon atoms available for inward diffusion.

To improve the prediction accuracy (PC) of phase selection in multi-principal element alloys (MPEAs), this study focuses on amorphous alloys (AM) and intermetallic compounds (IM), utilizing input features that combine parametric descriptors with potential energy distribution characteristics. The number of hidden layer nodes in the artificial neural network (ANN) model was systematically optimized to enhance predictive performance. As a result, the PC values for IM phases exceeded 90%, while those for AM phases typically reached approximately 88%. Comparative analysis of mean square error (MSE) and correlation coefficient (R) further confirmed the high predictive accuracy of the ANN model for IM phase selection. To experimentally validate the model, phase selection predictions were performed for three Ti–Co–Ni–Zr and four novel Ti–Cu–Ni–Ta MPEAs. The predicted results indicated a stronger tendency toward IM phase formation over AM phase formation in all seven alloys. Subsequently, the microstructure and mechanical properties of the new Ti–Cu–Ni–Ta alloys, which exhibited high strength, were experimentally characterized. Overall, this study demonstrates that the adopted ANN model can effectively predict the phase selection probability for bulk amorphous and IM alloys from given compositions, thereby significantly reducing the ‘trial-and-error’ costs associated with extensive experimental exploration of composition–phase relationships.

In this study, the effects of post-aging conditions on the mechanical properties, deformation behavior, and fracture characteristics of 6082-T6 aluminum alloy sheets were investigated, using tensile testing supported by DIC. Post-aging treatments were performed at 100 °C, 200 °C, 300 °C, and 400 °C, with holding times of 30, 60, and 90 min at each temperature. The following parameters were determined from the tensile tests: yield strength, tensile strength, strain-hardening exponent, uniform elongation, total elongation, and energy absorption capacity. Microstructural and fracture analyses were performed using optical microscopy and scanning electron microscopy, while x-ray diffraction was used to evaluate phase-related structural changes. Hardness variations were assessed by Vickers hardness testing. Fracture-surface dimple morphologies were quantitatively evaluated using average dimple diameter and standard deviation values to assess the temperature- and time-dependent variation in fracture behavior. The results showed that aging at 200 °C for 60 min provided a highly favorable strength–ductility balance and was identified as the most efficient processing condition in terms of the combined mechanical response, with a yield strength of approximately 289 MPa, tensile strength of about 400 MPa, uniform elongation of 15.9%, total elongation of 17.4%, hardness of 115.6 HV, and energy absorption of 61.36 MJ m−3. At 300 °C–400 °C, pronounced overaging occurred as precipitate coarsening reduced the effectiveness of precipitation strengthening, leading to significant degradation in mechanical performance. The strain-hardening response and energy absorption capacity were found to be strongly dependent on the aging condition. The results indicate a transition from relatively homogeneous deformation to strain-localized behavior as aging temperature increases, consistent with reduced deformation stability at elevated temperatures. Overall, these findings demonstrate that controlled post-aging can tailor the strength–ductility balance and fracture response of AA6082-T6 sheets.

Pumice-based lightweight mortars generally exhibit high porosity, which adversely affects their engineering performance. This study investigated the influence of graphene nanoplatelets (GNPs) on the fresh, physical, mechanical, and microstructural properties of pumice-based lightweight mortars. GNPs were incorporated at dosages of 0, 0.01, 0.03, 0.05, and 0.10 wt.% of cement, and the mortars were evaluated through flow diameter (FD), water absorption (WA), compressive strength (CS), flexural strength (FS), scanning electron microscopy (SEM), and ImageJ-based microstructural analysis. Increasing the GNP dosage from 0 to 0.10 wt.% reduced the FD from 207 to 186 mm, corresponding to a 10.1% decrease. Among the investigated mixtures, the mixture containing 0.03 wt.% GNP exhibited the best overall performance. At this dosage, WA decreased from 12.82% to 12.23%, representing a 4.60% reduction relative to the control mixture. The 28 d CS increased from 27.84 to 31.23 MPa, while the FS increased from 4.28 to 4.81 MPa, corresponding to improvements of 12.18% and 12.38%, respectively. ImageJ analysis showed that the two-dimensional void area decreased from 10.21% in the control mixture to 7.47% in the mixture containing 0.03 wt.% GNP, corresponding to a 26.84% reduction. SEM observations also indicated a denser and more homogeneous cementitious matrix at this dosage. Higher GNP dosages were associated with slight performance reductions and localized agglomeration of nanoplatelets. Overall, 0.03 wt.% GNP was the best-performing dosage among those investigated, improving the engineering performance and microstructural compactness of pumice-based lightweight mortars.

This study investigates the grinding performance of WC–12Co plasma-sprayed coatings on Ti17 alloy, focusing on the combined effects of abrasive characteristics and process parameters on surface integrity. To achieve this, surface roughness, hardness, and microstructural evolution were systematically evaluated under varying abrasive grain size, concentration, spindle speed, and feed rate. The experimental results demonstrate that increasing abrasive concentration significantly improves surface finish while enhancing surface hardness due to intensified plastic deformation and strain hardening; however, it also promotes microcrack formation, indicating a trade-off between quality and integrity. Furthermore, spindle speed strongly influences surface morphology; while hardness values plateau beyond a critical speed, higher speeds lead to increased microcrack formation, which—based on surface morphological evidence—indicates the dominating role of thermo-mechanical loading during high-speed contact, though direct in-situ thermal measurements were not recorded. At elevated feed rates, a transition in the material removal mechanism from plastic deformation to brittle fracture and material pull-out causes severe surface degradation. In conclusion, these findings indicate that surface integrity in the grinding of WC–12Co coatings cannot be adequately assessed based solely on roughness or hardness, but is governed by the complex interplay between mechanical loading, thermal effects, and material removal mechanisms.

Flexible and wearable sensors based on sustainable materials are gaining significant attention for next-generation sensing applications. In this work, biomass derived piezoresistive textile sensor was developed using biochar derived from Caryota urens biomass and deposited onto various textile substrates, including polyester, cotton, denim, and wool, via a dip coating technique. Structural characterization using x-ray diffraction revealed disordered carbon with limited short-range structural ordering, while morphological and elemental analyses (field emission scanning electron microscope-energy-dispersive x-ray spectroscopy) confirmed the distribution of biochar particles on the fiber surfaces. The electromechanical performance of the fabricated sensors was systematically evaluated through bending and cyclic repeatability tests. The sensors exhibited a clear and consistent change in resistance with bending angle, demonstrating typical piezoresistive behavior governed by bending-induced compression of the conductive biochar network. Among the investigated compositions, optimal sensing performance was observed at intermediate filler loadings, above the onset of conductive pathway formation but below network saturation, particularly at 5 wt% for polyester and around 10 wt% for cotton, denim, and wool substrates. The devices also showed stable and repeatable responses across the 100 bending cycles tested, with minimal signal drift; the optimized polyester sensor exhibited a hysteresis error of approximately 4.9%, indicating good short-term repeatability and reversibility; extended cyclic testing toward 500–1000 cycles is identified as future work to confirm long-term durability for wearable deployment. Overall, this study highlights the potential of biochar as a sustainable conductive filler for developing low-cost, flexible textile-based sensors and providing insights into the role of substrate type and filler concentration in tuning sensing performance, with potential for future flexible and wearable electronics applications.

Multifunctional oxide materials continue to fascinate researchers and industries due to the ability to tune their optical, electrical, catalytic, electrochemical, thermal, and biological properties by adjusting composition, defect engineering, morphology, interfaces, and processing conditions. The Focus Collection on Multi-Functional Oxide Materials in Materials Research Express presents a range of studies on optoelectronics, solar energy, photocatalysis, antimicrobial materials, heat storage systems, fuel cells, dosimetry, gas sensors, supercapacitors, and composites. The overview of this collection shows that the properties of materials are influenced not only by composition but also by production methods, defect characteristics, interfacial properties, and the ability to control the microstructure. The editorial outlines the findings of the collection and highlights future trends in the design of materials for sustainable production and application-oriented multifunctionality.

Lanthanum hexaboride (LaB6) is a refractory ceramic widely used in electron-emission applications, whereas its potential as a nitrogen-modified protective coating for engineering steels remains insufficiently explored. This study presents, for the first time, a systematic nitrogen flow rate series of Cr/CrN/LaB6-N coatings on AISI 4130 steel by hybrid DC/pulsed-DC closed-field unbalanced magnetron sputtering (0–8 sccm N2; R1–R4). With increasing N2, scanning electron microscopy/energy-dispersive x-ray spectroscopy showed a columnar-to-dense transition and rising nitrogen content (0.2–40.4 at. %), while x-ray diffraction revealed progressive amorphization of the LaB6 phase and a new BN-related reflection at 8 sccm. x-ray photoelectron spectroscopy confirmed a shift toward more ionic La–N/Cr-N and B–N/B–O bonding. Nanoindentation showed a non-monotonic hardness trend, peaking at 28 GPa (R3, 4 sccm) before declining to 19.8 GPa (R4), while scratch adhesion peaked at R2 (Lc = 50 N). Dry-sliding friction increased monotonically from 0.31 (R1) to 0.39 (R4). These results identify N2 flow rate as an effective tailoring parameter, with 2–4 sccm offering the best combination of hardness and adhesion for wear-resistant coating applications.

Sustainable biomass valorization has emerged as an attractive strategy for developing carbon-based electrode materials for electrochemical energy-storage applications. In this study, naturally biologically pretreated ovine digestive biomass was investigated as an unconventional carbon precursor for the synthesis of graphene oxide (GO) intended for supercapacitor electrodes. Activated carbon (AC) was first obtained by carbonization of the digestive biomass and subsequently converted into GO through a modified Hummers’ oxidation process. The resulting materials were characterized by SEM–EDS, Raman spectroscopy, x-ray diffraction, FT-IR, Brunauer–Emmett–Teller surface area analysis, and inductively coupled plasma (ICP) analysis, while their electrochemical performance was evaluated by electrochemical impedance spectroscopy and cyclic voltammetry in 6.0 M KOH. The characterization results confirmed the successful formation of oxygen-functionalized GO with preserved graphitic domains, expanded interlayer spacing, and surface functionalities associated with hydroxyl, epoxy, carbonyl, and carboxyl groups. ICP analysis further indicated reduced inorganic impurity content in the digestive biomass, supporting the role of natural biological pretreatment in precursor purification. Electrochemical optimization identified 1 wt% GO as the optimum loading for the graphite electrode. Under these conditions, the GO/graphite electrode exhibited a specific capacitance of 50.84 F g−1 at 100 mV s−1 and retained 105.9% of its initial capacitance after 500 cycles, indicating stable capacitive behaviour accompanied by progressive electrochemical activation. Although the present system does not target record-high capacitance values, the study demonstrates that ovine digestive biomass can serve as a naturally preconditioned precursor for GO-based supercapacitor electrodes and highlights a sustainable precursor-engineering approach that integrates natural biological pretreatment, AC-to-GO conversion, and electrochemical structure–property correlation within a single biomass valorization framework. The present investigation constitutes a three-electrode electrochemical screening of this newly proposed precursor-engineered electrode material, undertaken to establish its structure–property relationships prior to full two-electrode device fabrication; galvanostatic charge–discharge evaluation and symmetric/asymmetric device assembly are identified as the immediate next steps of this research programme.