Search Results (182)

This review provides a comprehensive analysis of modern strategies for the synthesis, functionalization, and application of carbon nanotubes (CNTs) and graphene for the development of high-performance polymer composites in the field of strain sensing. The paper systematically organizes key synthesis methods for CNTs and graphene (chemical vapor deposition (CVD), such as arc discharge, laser ablation, microwave synthesis, and flame synthesis, as well as approaches to their chemical and physical modification aimed at enhancing dispersion within polymer matrices and strengthening interfacial adhesion. A detailed examination is presented on the structural features of the nanofillers, such as the CNT aspect ratio, graphene oxide modification, and the formation of hybrid 3D networks and processing techniques, which enable the targeted control of the nanocomposite’s electrical conductivity, mechanical strength, and flexibility. Central focus is placed on the fundamental mechanisms of the piezoresistive response, analyzing the role of percolation thresholds, quantum tunneling effects, and the reconfiguration of conductive networks under mechanical load. The review summarizes the latest advancements in flexible and stretchable sensors capable of detecting both micro- and macro-strains for structural health monitoring, highlighting the achieved improvements in sensitivity, operational range, and durability of the composites. Ultimately, this analysis clarifies the interrelationship between nanofiller structure (CNTs and graphene), processing conditions, and sensor functionality, highlighting key avenues for future innovation in smart materials and wearable devices. Full article

Laser cladding is an effective surface engineering technique to enhance the high-temperature performance of metallic materials. In this work, a Cr-Al-C composite coating was in situ fabricated on H13 steel by laser cladding to alleviate the performance degradation of H13 steel under severe thermomechanical conditions, particularly in high-temperature piercing applications. The phase composition, microstructure, microhardness, high-temperature oxidation behavior, and tribological performance of the coating were systematically investigated. The coating is mainly composed of a B2-ordered Fe-Cr-Al phase reinforced by uniformly dispersed M₃C₂/M₇C₃-type carbides, which provides a synergistic combination of oxidation protection and mechanical strengthening, offering a microstructural design that differs from conventional Cr-Al or Cr₃C₂-based laser-clad coatings. Cyclic oxidation tests conducted at 800–1000 °C revealed that the oxidation behavior of the coating followed parabolic kinetics, with oxidation rate constants significantly lower than those of the H13 substrate, attributed to the formation of a dense and adherent Al₂O₃/Cr₂O₃ composite protective scale acting as an effective diffusion barrier. Benefiting from the stable oxide layer and the thermally stable carbide-reinforced microstructure, the wear rate of Cr-Al-C coating is significantly reduced compared to H13 steel. At room temperature, the wear rate of the coating is 6.563 × 10⁻⁶ mm³/(N·m), about two orders of magnitude lower than 8.175 × 10⁻⁴ mm³/(N·m) for the substrate. When the temperature was increased to 1000 °C, the wear rate of the coating remained as low as 5.202 × 10⁻⁶ mm³/(N·m), corresponding to only 1.9% of that of the substrate. This work demonstrates that the Cr-Al-C laser-cladded coating can effectively improve the high-temperature oxidation resistance and wear resistance of steel materials under extreme service conditions. Full article

The research and development of new accident-tolerant fuel cladding materials has emerged as a critical focus in international academic and engineering fields following the Fukushima nuclear accident. Due to the outstanding resistances in corrosion and radiation as well as high-temperature creep properties, oxide dispersion-strengthened (ODS) FeCrAl alloys have been studied extensively during the past decade. Current review articles in this field have primarily focused on the effects of chemical composition on the anti-corrosion performance and species of nano-oxide. However, several key issues have not been given adequate attention, including processing methods and parameters, high-temperature stability mechanisms, post-deformation microstructural evolution and high-temperature mechanical properties. This paper reviews the progress of basic research on ODS FeCrAl alloys, including preparation methods, the effects of preparation parameters, the thermal stability and irradiation stability of oxides, the microstructural deformation, and the mechanical properties at elevated temperatures. The aspects mentioned above not only provide valuable references for understanding the effects of preparation parameters on the microstructure and properties of ODS FeCrAl alloys but also offer a comprehensive framework for the subsequent optimization of ODS FeCrAl alloys for nuclear reactor applications. Full article

To improve the comprehensive performance of indium oxide (In₂O₃) thermoelectric materials, this study systematically investigates the regulatory effects of tantalum (Ta) doping on their electrical transport characteristics, thermoelectric conversion efficiency, and mechanical properties. The results show that Ta doping achieves synchronous optimization of multiple properties through precise regulation of crystal structure, electronic structure, and microdefects. In terms of electrical transport, the electron doping effect of Ta⁵⁺ substituting In³⁺ and the introduction of impurity levels lead to a continuous increase in carrier concentration; lattice relaxation and impurity band formation at high doping concentrations promote mobility to first decrease and then increase, resulting in a significant growth in electrical conductivity. Although the absolute value of the Seebeck coefficient slightly decreases, the growth rate of electrical conductivity far exceeds the attenuation rate of its square, increasing the power factor from 1.83 to 5.26 μWcm⁻¹K⁻² (973 K). The enhancement of density of states near the Fermi level not only optimizes carrier transport efficiency but also provides electronic structure support for synergistic performance improvement. For thermoelectric conversion efficiency, the substantial increase in power factor collaborates with thermal conductivity suppression induced by lattice distortion and impurity scattering, leading to a leapfrog increase in ZT value from 0.055 to 0.329 (973 K). In terms of mechanical properties, lattice distortion strengthening, formation of strong Ta-O covalent bonds, and dispersion strengthening effect significantly improve the Vickers hardness of the material. Ta doping breaks the bottleneck of mutual property constraints in traditional modification through an integrated mechanism of “electronic structure regulation-carrier transport optimization-multiple performance synergistic enhancement”, providing a key strategy for designing high-performance indium oxide-based thermoelectric materials and facilitating their practical application in the field of green energy conversion. Full article

The direct synthesis of long-chain α-olefins from syngas offers a strategically vital pathway for producing high-value chemicals from alternative carbon resources. However, achieving high selectivity toward C₅₊ olefins remains challenging due to competing paraffin formation and difficulties in precisely regulating chain growth kinetics. To mitigate these critical challenges, a series of Rh-promoted Co-Mn catalysts supported on SiO₂ were synthesized using a carbon-mediated impregnation strategy for the direct conversion of syngas to long-chain α-olefins (C₅₊). The introduction of Rh significantly enhanced both catalytic activity and C₅₊ olefin selectivity. The optimal 1.1 wt% Rh-loaded catalyst achieved 24.6% CO conversion and 46.0% total olefin selectivity, with 34.2% of the selectivity toward C₅₊ olefins, while maintaining low CH₄ (6.2%) and CO₂ (<1%) selectivity. Comprehensive characterization techniques, including XRD, H₂-TPR, XPS, and TEM/HAADF-STEM, revealed that the carbon-mediated method facilitated the formation of highly dispersed Co₃O₄ nanoparticles with abundant oxygen vacancies and strengthened the Co-MnO_x interface. Rh promotion modulated the cobalt speciation (Co⁰/Co²⁺), improved reducibility, and enhanced the metal-support interaction. This promoted chain growth and olefin desorption while suppressing over-hydrogenation. This study demonstrates the efficacy of Rh promotion and carbon mediation in designing high-performance Fischer-Tropsch catalysts for selective α-olefin synthesis, offering new insights into the design of efficient metal-oxide interfacial catalysts. Full article

In order to improve the high-temperature wear resistance of mold copper plates, this study used laser cladding technology to prepare a high-wear-resistant composite coating with Inconel 718 and WC(Tungsten carbide) particles. The phase composition, microstructure, microhardness, and tribological properties at 400 °C were systematically analyzed using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Vickers microhardness tester, and high temperature friction and wear tester. The results indicate that the Inconel 718/WC coating is free of pores and cracks and exhibits a metallurgical bond with the substrate. Its phases mainly consist of a γ-Ni solid solution and various hard carbide reinforcing phases, such as MC, M₃W₃C, and W₂C. The average microhardness of the coating reaches 851.7 HV_0.5, which is 11.5 times than that of the substrate (74 HV_0.5). At 400 °C, the wear rate of the coating is 3.48 × 10⁻⁴·mm³·N⁻¹·m⁻¹, only 35.7% of the substrate’s wear rate. The dominant wear mechanism is abrasive wear, accompanied by oxidative wear. The outstanding performance of the coating is attributed to the combined effects of grain refinement strengthening, solid solution strengthening, and second-phase strengthening induced by the various hard carbides. Full article

In this study, we demonstrated chloroprene rubber (CR)-based composites with the addition of synthesized alumina nanofibers (AONF) with a high aspect ratio (>1000). AONF were characterized using transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). AONF were introduced by pre-dispersion. The resulting chloroprene rubber/aluminum oxide nanofiber (CR/AONF) composites were subjected to tensile and shear adhesive bonding tests. The tensile test results for the CR/AONF composites are 81% greater than those of the original CR composite (0.85 MPa and 1.54 MPa, respectively). Shear adhesive bonding tests were conducted for glass and steel. CR/AONF demonstrates a 213% (for steel) and 262% (for glass) increase in shear strength. The main strengthening mechanisms are reinforcement, CR adsorption on the AONF surface, and crack arrest. These results may expand our understanding of the potential of sealant strengthening using AONF. Full article

We report a scalable route to hybrid aluminum matrix composites (AMCs) based on Al6060 (as-fabricated condition) reinforced with 2 wt.% TiB₂ and 1 wt.% microsilica, fabricated by ultrasonically assisted stir casting (UASC) followed by radial-shear rolling (RSR). Premixing and preheating of powders combined with acoustic cavitation/streaming during UASC ensured uniform, non-sedimentary particle dispersion and low-defect cast billets. X-ray diffraction of the as-cast composite shows fcc-Al with weak TiB₂ reflections and no reaction products; microsilica remains amorphous. Electron microscopy and EBSD after RSR reveal full erasure of cast dendrites, fine equiaxed grains, weakened texture, and a high fraction of high-angle boundaries due to the concurrent action of particle-stimulated nucleation (micron-scale TiB₂) and Zener pinning/Orowan strengthening (50–350 nm microsilica). Mechanical testing shows that, in the cast state—comparing cast monolithic Al6060 to the cast hybrid-reinforced composite—yield strength (YS) increases from 61.7 to 77.2 MPa and ultimate tensile strength (UTS) from 103.4 to 130.7 MPa, without loss of ductility. After RSR to Ø16 mm (cumulated true strain ≈ 0.893), the hybrid attains YS 101.2 MPa, UTS 150.6 MPa, and elongation ≈ 22.0%, i.e., comparable strength to rolled Al6060 (UTS 145.1 MPa) while restoring/raising ductility by ~9.7 percentage points. Microhardness follows the same trend, increasing from 50.2 HV0.2 to 73.1 HV0.2 when comparing the base cast condition with the rolled hybrid. The route from UASC to RSR thus achieves a favorable mechanical strength–ductility balance using an economical, eco-friendly oxide/boride hybrid reinforcement, making it attractive for formable AMC bar and rod products. Full article

An ambit of enhancing heat transfer throughout thermal convection in a cavity is explored numerically in this study, contemplating the heat dispersal from a segmental heat source circumscribed in a square-vented porous cavity with a moving lid. The cavity can be used as a heat sink for electronic cooling, material processing, and convective drying. Aluminum $10$ PPI metal foam saturated by aluminum oxide–water nanofluid is occupied in this lid-driven vented cavity system. The bottom cavity wall is fully and partially heated by a heat source of specific length $L_H$, and the left wall and inlet fluid are kept at the same cold temperature, while the right wall and top-driven wall are thermally insulated. Thermal dispersion and local thermal non-equilibrium effects are included in an energy equation, and continuity and Darcy–Brinkmann–Forchheimer momentum equations are implemented and resolved by utilizing the finite volume method with the aid of a vorticity–stream function approach operation. The inspirations behind pertinent parameters, including the Reynolds number ($Re=10–50$), Grashof number ($Gr={10}^3–{10}^6$), inlet and outlet ports’ aspect ratio ($D/H=0.1–0.4$), outlet port location ratio ($S/H=0.25–0.75$), and discrete partial heating ratio ($L_H/L=0.25–1$) are scrutinized. The baseline circumstance corresponds to full-length heating $L_H/L=1$ and the outlet port location ratio $S/H=0.25$. The results reveal that the fluid and heat flow domains are addressed mostly via these specification alterations. For $Gr={10}^3$, increasing $Re$ from $10$ to $40$ does not alter streamlines or the isotherm field, but when $Re=50$ it is detected that streamlines increase monotonically. Streamlines are not altered when $L_H/L$ and $S/H$ are amplified but strengthened more when the opening vent aspect ratio is increased. A greater temperature difference occurs as $L_H/L$ is raised from $0.25–0.75$ and isotherms are intensified, and the thermal boundary layer becomes more distinct when $S/H$ is augmented. The average Nusselt number rises as $Re$, $Gr$, $L_H/L$, and $D/H$ are increased by about $30\%$, $3.5\%$, $23\%$, and $19.4\%$, respectively, and it decreases with $S/H$ amplifying is increased by around $5.5\%$. Full article

This study investigates the enhancement of tribological performance in coarse-grained (CG) 42CrMo steel through the development of gradient-structured (GS) samples using double-sided symmetrical surface mechanical rolling treatment (D-SMRT). Dry reciprocating sliding wear tests are performed against a GCr15 steel counter ball to evaluate the influence of normal load on the wear resistance of CG and D-SMRT samples. Results demonstrate that D-SMRT significantly improves wear resistance under a 5 N load, attributed to the synergistic effects of surface strengthening and microstructure refinement. Characterization of worn surfaces via scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) confirms oxidative wear and abrasive wear as the dominant mechanisms at 5 N. With increasing load, wear transitions to abrasive and fatigue wear for the CG sample, while adhesive wear and plastic deformation dominate in the GS sample. This work concludes that D-SMRT technology effectively enhances the tribological properties of 42CrMo steel under normal loads below 10 N. Full article

Food waste is a global challenge, with nearly 40% of food discarded annually, leading to economic losses, food insecurity, and environmental harm. Major factors driving spoilage include microbial contamination, enzymatic activity, oxidation, and excessive ethylene production. Active packaging offers a promising solution by extending shelf life through the selective absorption or release of specific substances. In this study, polyvinyl alcohol (PVA) films incorporating metal-organic frameworks (MOFs) were prepared via solvent casting to enhance their mechanical and barrier properties. Five MOFs (HKUST-1, MIL-88A, BASF-A520, UiO-66, and MOF-801) were embedded in the PVA matrix and analyzed for their physical, mechanical, and optical characteristics. The incorporation of TEMPO-oxidized cellulose nanofibers (CNF) improved MOF dispersion, significantly strengthening film performance. Among the formulations, PVA-CNF-MOF-801 exhibited the best performance, with a 130% increase in tensile strength, a 50% reduction in water vapor permeability, and a 168% improvement in UV protection compared with neat PVA films. Ethylene adsorption tests with climacteric fruits confirmed that CNF-containing films retained ethylene more effectively than those without CNFs, although the differences among the MOFs were minimal. These results highlight the potential of PVA-CNF-MOF composite films as sustainable active packaging materials, providing an effective strategy to reduce food waste and its environmental impact. Full article

Oxide dispersion-strengthened (ODS) alloys are regarded as one of the most promising materials for Generation IV nuclear fission systems, owing to their exceptional attributes such as high strength, corrosion resistance, and irradiation tolerance. The traditional methods for fabricating oxide dispersion-strengthened (ODS) alloys are both time-consuming and costly. In contrast, additive manufacturing (AM) technologies enable precise control over material composition and geometric structure at the nanoscale, thereby enhancing the mechanical properties of components while reducing their weight. This novel approach offers significant advantages over conventional techniques, including reduced production costs, improved manufacturing efficiency, and more uniform distribution of oxide nanoparticles. This review begins by summarizing the state of the art in Fe-based and Ni-based ODS alloys fabricated via traditional routes. Subsequently, it examines recent progress in the AM of ODS alloys, including Fe-based, Ni-based, high-entropy alloys, and medium-entropy alloys, using powder bed fusion (PBF), directed energy deposition (DED), and wire arc additive manufacturing (WAAM). The microstructural characteristics, including oxide particle distribution, grain morphology, and alloy properties, are discussed in the context of different AM processes. Finally, critical challenges and future research directions for laser-based AM of ODS alloys are highlighted. Full article

A key issue with lead-cooled fast reactors is the corrosion vulnerability of fuel cladding and core components, which will endanger the structural materials’ integrity and the operational safety of the reactor system. The FeCrAlTi-ODS (Oxide Dispersion Strengthened) alloy coatings are prepared by the Magnetron Sputtering technique under different bias voltages to shield structural elements in lead-cooled fast reactors from corrosion caused by lead-bismuth eutectic (LBE). A comprehensive study examines their mechanical attributes and resistance to LBE-induced corrosion. Compared to the bare substrate of austenitic 316L steel, the FeCrAlTi-ODS alloy coatings exhibit significantly improved binding force and hardness. The hardness (H) reaches 11.52 GPa (twice that of the bare substrate), and the elastic modulus (E) reaches 172.89 GPa. After the corrosion of bare substrate 316L steel by LBE, the oxygen element penetrated was obvious, and the Nickel element underwent selective migration. The FeCrAlTi-ODS alloy coatings show promising LBE corrosion resistance, and the FeCrAlTi-ODS alloy coating prepared under different bias can effectively protect the substrate material, which is attributed to the formation of protective FeCr₂O₄ film on the surface. The compact oxide film significantly prevents the further infiltration of the oxygen element and the migration of metal elements. Full article

Shape memory alloys (SMAs) are known for their exceptional mechanical properties, particularly their superior wear resistance compared to conventional alloys with similar surface hardness. Rare earth oxides are often used as additives to further improve these characteristics. This study investigates the effects of different CeO₂ (cerium dioxide) concentrations (0.01 wt.%, 0.1 wt.%, 0.5 wt.%, and 1.0 wt.%) on the properties of CuAlMnFe alloys produced via powder metallurgy (PM). Various analyses were performed, including scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), X-ray diffraction (XRD), as well as hardness, wear, and corrosion tests. The increase in wear rate is closely related to the formation of precipitates from CeO₂ addition. Improvements in wear resistance and hardness are attributed to the effects of grain refinement and solid solution strengthening due to CeO₂. Specifically, the wear rate increased from 1.5 × 10⁻³ mm³/(Nm) to 3.4 × 10⁻³ mm³/(Nm) with higher CeO₂ content. Additionally, the friction coefficient of the CuAlMnFe alloy was reduced with CeO₂ addition, indicating enhanced frictional properties. The optimal CeO₂ concentration of 0.5% was found to improve grain uniformity, resulting in better wear resistance. Incorporating CeO₂ particles into CuAlMnFe alloy enhances hardness and reduces wear rate when used in appropriate amounts. Additionally, it exhibits superior corrosion resistance, as evidenced by a positive shift in corrosion potential in Tafel measurements in solutions and a decrease in corrosion current density. The C0.5 specimen showed the highest corrosion potential (E_corr, −588 V) and the lowest corrosion current density (i_corr, 6.17 μA/cm²) during electrochemical corrosion in 3.5 wt.% NaCl solution. Full article

In this paper, the different effects of laser shock peening (LSP) and laser shock peening without coating (LSPwC) on the morphology, microhardness and fretting-wear behavior of DD6 Ni-based single-crystal superalloy are investigated. The results show that the surface roughness of DD6 decreases slightly after LSP, while it increases after LSPwC due to surface remelting. Shock wave strengthening during LSP and LSPwC results in plastic deformation of the surface layer of DD6 samples. However, besides work hardening from shock wave, dispersion strengthening of oxide particles also occurs during LSPwC. Therefore, after LSPwC, the microhardness of the DD6 surface layer increases by 38.8%, higher than the increase of 27.7% after LSP. The fretting wear resistance of DD6 increases by about 42.8% and 58% after LSP and LSPwC, respectively. The surface roughness only affects the friction coefficient at the initial stage of fretting wear. The hardness increase caused by work hardening and the dispersion strengthening of surface oxides after laser strengthening is the key to the improvement of fretting wear resistance. The main wear mechanisms of untreated and LSP sample are oxidation wear, abrasive wear and adhesive wear, while the main wear mechanisms of LSPwC sample are oxidation wear and adhesive wear. Full article