Journal of Materials Science最新文献

In the present study, Inconel 686 thick-wall part manufactured utilizing gas metal arc welding-based wire arc directed energy deposition (WA-DED) was examined. The microstructure and mechanical properties of the fabricated Inconel 686 component across different sections, such as bottom, middle, and top, were explored, and the influence of cryogenic treatments, such as shallow and deep, on the properties of the fabricated specimens was examined. The optical and scanning electron microscopy revealed differences in microstructure across various regions of the deposited metal. The bottom region showed a columnar structure, the intermediate region displayed a combination of cellular structures, and the top layer featured an equiaxed structure. These variations contribute to heterogeneity and anisotropy in the mechanical characteristics. Moreover, the microstructure of the deep cryogenic treatment (DCT)-treated samples exhibited a finer grain structure in contrast to both the as-built and shallow cryogenic treatment (SCT)-treated WA-DED samples attributed to grain refinement. X-ray diffraction analysis observed that applying DCT decreased grain size, with the average grain size of the DCT-treated sample measuring 22.81 nm, while concurrently increasing the dislocation density to 19.22 × 10^–4 nm^–2. Energy-dispersive X-ray spectroscopy point analysis, elemental mapping, and line mapping were conducted to study the microsegregation and spatial distribution of alloying elements in the grain boundaries and interdendritic regions. Results indicated intensified segregation tendencies of alloying elements molybdenum (Mo) and tungsten (W) with increasing deposited height, peaking in the lowermost region. However, DCT samples exhibit reduced elemental segregation compared to as-built and SCT samples. The tensile strength and microhardness showed substantial differences across various areas. Cryogenic treatments considerably improved the mechanical properties of WA-DED specimens compared to their as-built state. As a result, the tensile strength improved by 7.23%, and the hardness strength increased by 8.98%.

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The accuracy of electron-excited X-ray microanalysis with energy-dispersive spectrometry (EDS) has been tested in the low beam energy range, specifically at an incident beam energy of 5 keV, which is the lowest beam energy for which a useful characteristic X-ray peak can be excited for all elements of the periodic table, excepting H and He. Elemental analysis results are reported for certified reference materials (CRM), stoichiometric compounds, minerals, and metal alloys of independently known or measured composition which had microscopic homogeneity suitable for microanalysis. Two-hundred sixty-three concentration measurements for 39 elements in 113 materials were determined following the k-ratio protocol and using the EDS analytical software NIST DTSA-II. The accuracy of the results, as characterized by the relative deviation from expected value (RDEV) metric, was such that more than 98% of the results were found to be captured within a range of ±5% RDEV, while 82% of the results fell in the range -2% to 2% RDEV.

Hydrophobic, elastic, and conductive (HEC) aerogels have significant potential in electronic devices. Herein, we propose a new method to fabricate an HEC aerogel with excellent mechanical and sensing performances from TEMPO-oxidized bacterial cellulose (O-BC) and conductive MXene nanosheets via directional freeze-drying and silanization modification. O-BC with a high aspect ratio can interweave with each other to form continuous layers, while MXene can induce a regular and flat structure and provide good conductivity. The silanization modification ensures high hydrophobicity and high elasticity, which can prevent the aerogel from structural collapse by avoiding adhesion among lamellae. The resulting aerogel can withstand compressive strain high up to 90% and long-term compression for 10,000 cycles at 50% strain due to the elastic and hydrophobic lamellar structure. It also offers a precise electrical response to stress signals in a broad detection range of 0–40 kPa and can accurately detect biological signals from humans. These structural and mechanical performance benefits make the HEC aerogel valuable in the field of pressure sensing.

Toluene solubles (TS) play a crucial role in mesophase pitch (MP), but their influence on the spinnability of MP and the properties of carbon fiber remains unclear. In this work, a solvent extraction method is employed to regulate the TS content in MP for improving its spinnability, and the MPs with different TS contents are prepared. The results show that TS, characterized as a small molecule (I_OS = 0.337) with an alkyl side chain length index (Abs1460/Abs1380) of 2.012, can significantly improve the flowability of the system. Following comprehensive characterization, a unique molecular structure model is constructed. The removal of a portion of TS increases the regularity of the microcrystalline structure to a certain extent (d₀₀₂ = 3.447 Å, L_c = 8.86 nm), further optimizing the spinning performance of compounded MPs with different TS contents, and improving the tensile strength and thermal conductivity of their carbon fibers. The compounded sample MP-TS-17, containing 17 wt% TS, shows superior spinning performance at a high rotary speed of 315 rpm, accompanying with an average and even diameter of 12.60 μm. The carbon fiber derived from MP-TS-17 perform an impressive tensile strength of 2.39 GPa and a high thermal conductivity of 612 W·m⁻¹·K⁻¹. Compared with the carbon fiber from the raw material MP, its mechanical strength and thermal conductivity are improved by 97.4% and 120%, respectively, demonstrating a promising approach for preparing high-performance petroleum-based mesophase pitch carbon fiber.

Developing an efficient and green electrode material is vital for energy storage. Herein, a kind of lignin-based porous carbon material with different pore size distribution and high electrochemical properties was prepared by using alkali lignin as a carbon precursor doped with heteroatoms. The effects of different temperature gradients and pore structure on the properties of porous carbon with lignin as precursor were studied. The prepared material has high specific surface area of 1168.4 m²/g, rich pore size distribution, which was conducive to electron transfer and storage, and high nitrogen doping also improved the electrochemical properties of the carbons. The prepared lignin-based carbon material has a considerable specific capacitance of 302 F/g and higher level of cycle stability. The study not only provided a potential strategy for the preparation of cost-effective heteroatom-doped materials from lignin, but also offered a new insight for lignin valorization.

MnZn ferrite powders were prepared, based on the novel nano-in-situ composite method and through chemical sol–spray–calcination technology. Different dosage of CTAB were used, and the influences on the precursor sol solutions and precursor powders were studied. Also, the selected precursor powders (P-0.1CTAB) were calcined at 1060 °C in air for 3 h, and the sample (S-0.1CTAB) was considered to further exploration. The results indicated that the precursor sol and precursor powders were in their optimal state when adding 0.1 wt.% CTAB. Under this condition, the Zeta potential of the sol was 10.7 mV, and the colloidal particle size was 91.63 nm. The corresponding precursor powders can still maintain a nanoscale fine particle composition and be well dispersed. The S-0.1CTAB sample with hollow spherical shell composed of small particles of several hundred nanometers had pure MnZn ferrite phase, and the maximum value of saturation magnetization (M_s) was 53.46 emu/g. Moreover, there are three stages of the formation of MnZn ferrite during the CTAB-assisted synthesis process which are CTAB ionization and (Mn, Zn, Fe)(OH)(NO₃)(H₂O) formation stage, CTA + adsorption and colloidal particle formation stage, and (Mn, Zn, Fe)(OH)(NO₃)(H₂O) decomposition stage.

Water-soluble polysaccharides generally have the problem of not resistant to high temperature, which limits their application. CMC-LAP nanocomposites were prepared by silanization of sodium carboxymethyl cellulose (CMC) and introduction of nanomaterial laponite (LAP) by APTES. It was found that both the polysiloxane structures formed by APTES and LAP interacted with CMC. Their dual protection of CMC makes the dense network structure still exist in aqueous solution after aging at 150°C. It is very important to maintain the normal rheological properties of drilling fluid. CMC-LAP has great effect as rheological modifier of drilling fluid. The viscosity reduction rate of CMC-LAP drilling fluid after aging at 180°C was only 35%, while that of CMC was 75%. When CMC-LAP is partially degraded at high temperature for a long time in drilling fluid, LAP can play a bridging role in the system through its strong hydrogen bond and electrostatic adsorption. After the system is stable, the network structure will still recover. This network structure enhances the rheological properties of the drilling fluid and improves the ability of the drilling fluid to suspend cuttings and clean the wellbore. We provide a new method to greatly improve the temperature resistance of sodium carboxymethyl cellulose in aqueous solution and maintain normal rheological behavior. The combination of LAP nanomaterials is also a new direction for the study of water-soluble polysaccharides. The materials prepared in this study also show strong application potential in environmentally friendly water-based drilling fluids.

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We report on the dispersion and gelling mechanisms of Al₂O₃ and Si₃N₄ suspensions fabricated via gelcasting. These systems were prepared by introducing bivalent ions into a gelcasting system known as ISOBAM, a water-soluble copolymer of isobutylene and maleic anhydride. The addition of metal ions negatively affects viscosity, while the influence of bivalent ions on the storage modulus is closely related to the microscopic configuration of ISOBAM. This configuration is altered due to the competition between particles and metal ions in the suspension to adsorb ISOBAM. An increase in the ionic potential of metal ions accelerates the gelling rate of Al₂O₃ suspensions and increases the surface area of ISOBAM self-assembly around the particles, thereby extending the microscopic conformation. In Si₃N₄ suspensions, the surface area of ISOBAM around the particles initially decreases and then increases, primarily due to pH changes resulting from the hydrolysis of metal ions and Si₃N₄.

Cu/Mo codoped NiO semiconductors exhibited a visible light efficient photo-removal performance for diclofenac sodium and methylene blue waste. A simple and low-cost methodology was used to synthesize NiO, Ni_0.95Cu_0.03Co_0.02O, and Ni_0.95Cu_0.03Mo_0.02O nanocatalysts. The crystal structure verified the formation of a cubic NiO single phase. The scanning electron microscopy (SEM) micrographs of all samples have shown a homogenous spherical particle distribution. The harvesting of visible light from NiO semiconductors was significantly enhanced after the addition of Cu/Co and Cu/Mo ions. The X-ray photoelectron spectra confirmed that Cu dopant has a +2-oxidation state while Mo dopant has +3 and +4 as mixed oxidation states. Ni_0.95Cu_0.03Co_0.02O and Ni_0.95Cu_0.03Mo_0.02O have shown high dielectric constant values at low frequencies. For purification of wastewater, the visible light photocatalytic efficiencies of Cu/Mo codoped NiO catalyst for the removal of 20 mg/L methylene blue (MB) and 20 mg/L diclofenac sodium (DS) were 98 and 95% after 50 min, respectively. The MB and DS molecules were converted to CO₂ and H₂O as confirmed by total organic carbon and chemical oxygen demand analyses. Besides, this nanocatalyst showed a high reusability for MB and DS pollutants until four cycles.

Graphical Abstract

Extensive research has focused on green and renewable energies to address the increasing demand for flexible, reliable, and self-sustaining advanced technology and electrical supplies. Piezoelectric nanogenerators (PENGs) have garnered significant interest as a pioneering energy-harvesting technology, due to their notable advancements and capacity to effectively capture and convert mechanical energy from the environment into electrical power. This review article seeks to cover the latest developments and innovations in piezoelectric materials for PENG applications. It explores key topics, such as the strategic selection of piezoelectric materials to optimize energy-harvesting efficiency, advancements in fabrication techniques, and the evaluation of PENGs performance. Throughout this manuscript, critical points are highlighted that require further investigation in the field of high-performance piezoelectric material fabrication. Ongoing research is crucial for improving the flexibility and durability of functional materials, thus advancing the development of superior electronic devices with enhanced piezoelectric properties. Furthermore, addressing enhancements in the electromechanical properties of current piezoelectric materials is imperative. This review article aims to support researchers in their quest for a comprehensive understanding of piezoelectric mechanisms and offers valuable insights for the progression and refinement of PENGs, which have broad potential applications.

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An overview of the PENGs applications, piezoelectric materials selection, fabrication methods and PENGs performance discussed in this review paper.