Journal of Materials Science最新文献

Graphene has attracted increasing attention due to its unique properties and widespread applications in various sectors, including its use as a nanofiller in polymer matrices. However, its poor dispersion within the matrix compromises the desired nanocomposite properties, making chemical functionalization a viable strategy to enhance its applicability. This study evaluates the dispersion of reduced graphene oxide (rGO) functionalized with different organosilanes in an epoxy matrix. Initially, graphene oxide (GO) was synthesized and functionalized with 3-aminopropyltriethoxysilane (APTES), 3-aminopropyltrimethoxysilane (APTMS), 3-glycidoxypropyltrimethoxysilane (GPTMS), and triethoxymethylsilane (MTES), followed by thermal reduction to obtain the corresponding functionalized rGO. Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy, thermogravimetric analysis (TGA), dispersion stability in solvent, and scanning electron microscopy (SEM) were used to confirm functionalization and assess its efficiency. The results demonstrated successful covalent functionalization with all silanes, ensuring the permanence of their molecules on the rGO basal plane. Subsequently, nanocomposites were prepared with 0.5 wt.% of each functionalized rGO to evaluate their dispersion within the polymer matrix. SEM analysis of fracture surfaces revealed that nanocomposites containing functionalized rGO exhibited improved distribution, dispersion, and interfacial bonding compared to those with non-functionalized rGO. Among the tested organosilanes, rGO functionalized with APTES presented the most satisfactory results.

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The Ruddlesden–Popper (RP) layered perovskite family is well known for its diverse functionalities. RP members are amenable to structural changes when subjected to a change in temperature. A minor change in the structure of a given RP member substantially influences the resultant functionality of each structural variant. It is therefore essential to decipher such preferred structural variations, planar defects, and their morphology in the as-synthesized sample at ambient conditions, prior to its use for functional applications. Ca₃Mn₂O₇ (n = 2) RP member is synthesized through the Pechini citrate gel technique. X-ray diffraction and transmission electron microscopy techniques have been used to demonstrate the coexistence of orthorhombic A2₁am (SG# 36) and Acaa (SG# 68) structural phases in the as-synthesized sample at ambient conditions. The experimental observation is supported by density functional theory calculations. This confirms that the A2₁am and Acaa orthorhombic Ca₃Mn₂O₇ structural phases are energetically comparable and structurally stable. A 90° oriented merohedral twin variant of the orthorhombic A2₁am phase is experimentally observed along the [001] axis. The nano-lamellae type morphology of these variants is observed with interfaces parallel to the (001) plane. The lamellae are stacked along the [001] direction. The two coexisting phases differ structurally by a variation in octahedral tilting distortion and A-cation displacement.

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In the preparation of Ce-Mn oxide catalysts for low-temperature NH₃-SCR reactions, conventional sintering methods often lead to surface agglomeration of the catalysts, making it difficult to fully expose their active components. In this study, a series of Mn–Ce catalysts were prepared via microwave sintering, which exhibited excellent catalytic activity and good resistance to H₂O and SO₂ in the selective catalytic reduction of NO with NH₃. Among them, the Mn–Ce 0.06 catalyst achieved the highest NO conversion at 250 °C, outperforming the control sample (Mn–Ce 0.06-M) sintered in the muffle furnace. This superior performance was mainly attributed to its uniform pore structure, excellent reducibility, abundant acidic sites, as well as higher contents of Mn⁴⁺, surface active oxygen (O_α), and Ce³⁺. These characteristics promoted the formation of oxygen vacancies and enhanced oxygen migration capability, thereby facilitating the SCR reaction. In situ DRIFTs results demonstrated that the SCR reaction over the Mn–Ce 0.06 catalyst followed both the Eley–Rideal (E-R) mechanism and the Langmuir–Hinshelwood (L-H) mechanism, with Lewis acid sites being the primary acidic sites on the catalyst. This study provides new insights into the microwave-assisted synthesis of high-performance SCR catalysts.

MXene, a two-dimensional layered nanomaterial analogous to graphene, stands out due to its scalable top-down synthesis and exceptional intrinsic properties, among which are high specific surface area, excellent mechanical strength, high-temperature stability, and tunable abundant surface functional groups. These unique characteristics make MXene a promising reinforcement candidate for structural composites, such as polymers, metals and ceramic matrices. However, critical challenges, including the dispersion, agglomeration and interfacial interaction, as well as the need to maintain structural integrity within various matrices, restrict the potential of MXene. This review systematically evaluates the current manufacturing methods, analyzes their limitations, and highlights recent advancements in overcoming the above issues. A comprehensive examination of mechanical properties after MXene reinforcement across different matrices is also provided. Meanwhile, despite considerable progress, no existing processing strategy can simultaneously address the bottlenecks associated with MXene industry. In view of the above, research directions, emphasizing hybrid processing strategies and targeted interfacial engineering, are proposed as the alternative. These routes aim to guide the development of next-generation MXene-enhanced structural composites with optimized performance and broader applicability.

The intermittent nature of solar radiation prevents interfacial evaporation systems from operating continuously around the clock. To overcome the limitation, this study developed a phase change microcapsule material (MPCMs) with excellent comprehensive performance for water evaporators. In this work, nano-tungsten carbide (nano-WC) hybrid melamine-urea–formaldehyde (MUF) resin was used as the shell to wrapped capric acid core material to prepare hybrid MPCMs. The MPCMs and EP (epoxy resin) were mixed and solidified by ultrasonic stirring to form a composite material for seawater evaporation test. At a 6 wt.% nano-WC loading, the microcapsules achieved optimal performance with an encapsulation efficiency of 66.0% and a 76.40% improvement in thermal conductivity. Specifically, the microcapsule sample achieved a photo-thermal conversion efficiency of 75.96% in photo-thermal conversion experiments. The composite sample showed excellent durability, maintaining an evaporation efficiency of 98.70% in six circulating water evaporation tests, and the average evaporation rate was 1.41 kg m⁻² h⁻¹. The evaporation efficiencies for samples were 82.30%. Compared with the traditional sample without phase change material, the evaporated water of the developed phase change microcapsule composite plate sample increased by 25.30 g m⁻² within 10 min after the light stopped. This photo-thermal conversion and energy storage composite material provides a viable strategy for developing uninterrupted solar-thermal water evaporators, showcasing broad application prospects in sustainable desalination and energy-efficient water purification.

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Single crystal tungsten, a high-temperature refractory metal with exceptional properties, is widely used in aerospace, military, and nuclear fusion applications. Understanding its nanoscale mechanical behavior is crucial for advanced material design and extreme environment applications. This study employs molecular dynamics simulations to investigate the nanoindentation behavior of single crystal tungsten, with a focus on the edge effect. The results reveal that surface atomic stacking exhibits a non-monotonic trend as the indentation position shifts from the center to the edge, while the number of side extruded atoms increases monotonically near the edge. The edge region demonstrates reduced resistance to deformation, lower hardness, and pronounced plastic flow. Stress and temperature distributions further confirm that edge constraints lead to localized stress concentration and thermal gradients. These findings provide critical insights into the nanoscale mechanical behavior of tungsten, aiding in the optimization of high-performance materials for extreme conditions.

Pitting potential (Ep) and stress corrosion cracking potential (ESCC) of super duplex stainless steel (SDSS) grade (UNS S32760) were determined using potentiodynamic polarization and slow strain rate test (SSRT) methods at 130⁰ C. SSRT tests were conducted at controlled applied potentials (EAPP) from + 0 to + 1200 mV (Ag/AgCl) in 15 and 1000 ppm chloride to determine the stress corrosion cracking (SCC) resistance response of SDSS material. Potentiodynamic polarization tests were also conducted at 130C in chloride concentration from 15, 100, 1000, 10,000 & 22,000 ppm, showed pitting resistance of SDSS material decrease with increase in chloride concentration. SSRT results indicate that isolated microcracks initiate at applied potentials below ~ 500 mV, with crack coalescence occurring near E_SCC (~ 500 mV) and rapid degradation dominated by localized galvanic and pitting corrosion at higher potentials. Microstructural characterization using SEM and EBSD revealed that damage below Ep and E_SCC is associated with short cracks and selective phase attack, whereas at potentials exceeding Ep by ~ 200 mV, pit–crack interactions become dominant. Grain size distribution, phase morphology, and phase continuity particularly along the rolling direction were found to influence pit growth and crack propagation.

Given the complex operational conditions in engineering, this article investigates the effects of Zn and SO₂ on the SCR performance of the CeO₂-TiO₂ catalyst, a promising candidate for the commercialized V₂O₅-WO₃/TiO₂ system. The loading of Zn or the treatment with SO₂ interfered with SCR catalysis, with the operational temperature range (> 90% NO_x conversion) narrowed by approximately 100 °C. The reduced surface area, pore volume, acidity, NO adsorption capacity, and oxidizability collectively accounted for the declined NO_x conversion of the Zn-poisoned sample, while the excessively strong acidity, together with the damaged textural structures, weakened oxidative ability, and inhibited NO adsorption, contributed to the deactivation of the SO₂-treated catalyst. For the Zn and SO₂ co-poisoned samples, the proceeding of the SCR reaction was further prohibited, with > 90% NO_x conversion achieved only between 350 and 450 °C. This was largely ascribed to the declined specific surface area and pore volume. Even though the synergistic effects between SO₂ and Zn could further deactivate the CeTi catalyst, the relevant mechanisms might provide valuable guidance for the wide commercialization of this system.

A high-carbon-steel/Cu nanolamellar composite was fabricated via accumulative roll bonding and wire drawing. Cu layers inhibited martensite grain growth during hot-press and hot-rolling, yielding ~ 70-nm-thick steel layers containing single-variant nanotwins (~ 3.5 nm thick). The in situ XRD analysis revealed the deformation mechanism of the martensite, characterized by dynamic evolution of its tetragonality (c/a ratio) under uniaxial tensile strain. The nanolamellar/nanotwinned martensite obtained a maximum lattice strain of 2.0%, corresponding to 1400 MPa tensile strength of the composite. Ultrahigh strength in martensite is achieved through a high aspect ratio, nanoscale confinement, and Cu-layer crack suppression. Nanolamellar confinement with nanotwinning is a promising strengthening pathway.