Uniform Particle Distribution Research Articles

Hierarchical structure Fe@CNFs@Co/C elastic aerogels with intelligent electromagnetic wave absorption

AbstractDeveloping intelligent electromagnetic wave (EMW) absorption materials with real‐time response‐ability is of great significance in complex application environments. Herein, highly compressible Fe@CNFs@Co/C elastic aerogels were assembled through the electrospinning method, achieving EMW absorption through pressure changes. By varying the pressure, the effective absorption bandwidth (EAB) of Fe@CNFs@Co/C elastic aerogels shows continuous changes from low frequency to high frequency. The EAB of Fe@CNFs@Co/C elastic aerogels is 14.4 GHz (3.36–17.76 GHz), which covers 90% of the range of S/C/X/Ku bands. The theoretical simulation indicates that the external pressure prompts a reduction in the spacing between the fiber layers in the aerogels and facilitates the formation of a 3D conductive network with enhanced attenuation ability of EMW. The uniform distribution of metal particles and appropriate layer spacing can effectively optimize the impedance matching to achieve the best EMW absorption performance. This work state clearly that the hierarchically assembled elastic aerogels composed of metal–organic frameworks (MOFs) derivatives and carbon fibers are ideal dynamic EMW absorption materials for intelligent EMW response.image

Studies on Dry Sliding Wear Mechanisms of Al7075/Si3N4 Composites

Abstract In this investigation, Al7075 aluminum alloy reinforced with Si3N4 particles (3, 6, 9, and 12 wt%) was used as reinforcements to manufacture composites through a stir-casting approach. The microstructural characteristics have shown significant grain refinement owing to the presence of Si3N4 particle distribution during the solidification. SEM micrographs confirm the uniform distribution of Si3N4 particles with considerably fewer particle agglomerations throughout the matrix alloy. The reinforcement particle cluster formation is relatively increased for increasing the Si3N4 content. The SEM and EDS analyses showed good integrity at the matrix–refinement interface with no interfacial compound formation. The mechanical properties, such as hardness (up to 118 BHN), tensile strength (up to 281 MPa), and yield strength (up to 178 MPa), were enhanced by 30.69% and 20.27%, respectively. The wear-rate and coefficient of friction of the composites were evaluated with increasing percentages of Si3N4 content. The average wear-rate of the composites is 0.019, 0.0085, 0.0075, and 0.0065 mm3/m, respectively, for the increased Si3N4 ceramic particulate content from 3 to 12 wt%, while the average COF of the composites is 0.45, 0.37, 0.32 and 0.28 respectively. With the addition of Si3N4 particulate content, the wear resistance performance of the composites at 30 N has shown up to 46% enhancement and increased from 0.0052 to 0.0103 mm3/m with the increasing sliding velocity from 1.5 to 3.5 m/s for varying Si3N4 particulate content from 3 to 12 wt%, while reducing the COF up to 65%, and from 0.43 to 0.27. Different wear mechanisms are characterized by identifying the typical features of wear on the SEM micrographs of the worn surfaces. The dominant wear mechanisms of the composites are typically observed as abrasion, oxidation, delamination and melt wear. The mechanism and behavior of composites under dry sliding conditions are analyzed through the construction of wear maps. The windows of wear mechanisms and progression in terms of load and sliding velocity for the composites with various wt% of Si3N4 content were identified, analyzed, and presented.

Spontaneous combustion coal gangue-based composite cement: Compressive performance and environmental benefits under grinding kinetics control

This study aims to tackle the environmental pressure of spontaneous combustion coal gangue by using its active silica-alumina content to create eco-friendly composite cement through a low-energy process. The Divas-Aliavden grinding kinetics equation was established, and powder characteristics were analyzed using particle size distribution, the Rosin-Rammler-Bennett model, and fractal dimension theory. The compressive performance of the coal gangue-based composite cement was tested. A comprehensive evaluation model linked grinding time, powder characteristics, compressive performance, and energy consumption, while also analyzing hydration products and environmental impact. Results showed that initial grinding stages had larger particle sizes and higher energy utilization efficiency. As grinding progressed, energy consumption increased. A grinding time of 35 min achieved optimal balance between energy efficiency and compressive performance, improving particle distribution uniformity and complexity. The compressive performance of the composite cement reached 95 % of ordinary Portland cement after 28 days of curing. The evaluation model indicated that specific surface area, d50, and fractal dimension are key factors influencing energy efficiency, determining energy consumption and particle distribution during grinding. Environmental assessment revealed that substituting 30 % of cement with coal gangue could reduce CO2 emissions by 250 kg CO2/t, achieving a reduction rate of 29.5 %. This study supports the large-scale application of spontaneous combustion coal gangue, contributing to efficient resource utilization and environmental protection.

Impact of Variable Device Structural Changes on Particle Deposition Distribution in Multi-Rotor UAV

The aim of this study was to investigate the effect of structural changes in variable fertilizer application devices on the distribution of particle deposition in UAVs. With the rapid development of drone technology, particularly in particulate spreading, drones have demonstrated significant potential due to their efficiency and precision. This paper evaluates the impact of different variable adjustment modes of the device on particulate deposition distribution through drone spreading experiments and particulate deposition data analysis. In this study, device structure change is the main variable factor, and flight altitude, flight speed and ambient wind speed are single quantitative factors. Experiments were conducted by varying the structure of the device to test the detailed deposition distribution of the device under group a, b, and c structures. Experimental results indicate that by choosing different variable combinations, the spreading device can achieve various fertilizer deposition states to meet regional needs. Among all 27 variable groups, the fertilizer particle deposition data for group b1b2b3 is relatively uniform, with three-quarters of particulate deposition values being 3 g/m2 and the maximum value being 4 g/m2. However, even with a relatively uniform distribution of fertilizer particles, the coefficient of variation for group b1b2b3 remains high (36.5%), with a range of 4.5% to 41%. Under different group adjustments, the particle distribution shows the smallest variability range in group b1b2b3, with a range of 15.71–26.44% and a variability difference of 10.73%. The particle distribution shows the largest variability range in group a1a2b3, with a range of 0.78–35.06% and a variability difference of 34.28%. These research conclusions provide important guidance for the study and practice of drone spreading systems.

Enhancing Herbal Efficacy: Synthesis and Evaluation of Nanosuspension from Withania somnifera Root Extract

Background: Ayurveda emphasizes the balance of mind, body, and spirit, drawing on ancient texts that highlight the medicinal properties of herbs like Withania somnifera, known for its wide range of therapeutic applications and pharmacological benefits. Commonly referred to as Indian ginseng or Ashwagandha, Withania somnifera, demonstrates a variety of therapeutic effect , including anti-inflammatory, antitumor, sedative, hypnotic, deobstruent effects, narcotic, antioxidant, tonic, antistress, diuretic, aphrodisiac, immunomodulatory, and rejuvenating properties. Nanotechnology, particularly through the development of nanosuspensions, offers a significant advancement in medicine, addressing challenges like poor solubility and low bioavailability of lipophilic drugs. Nanosuspensions can enhance drug safety and efficacy by improving solubility and altering pharmacokinetics. Methods: This study focuses on formulating and characterizing a nanosuspension using an ethanolic extract of Withania somnifera roots. The nanosuspension (NSWS) underwent comprehensive characterization, utilizing techniques such as FT-IR spectroscopy, particle size analysis, zeta potential measurement, polydispersity index (PDI) assessment, Field emission scanning electron microscopy (FESEM), X-ray diffraction analysis, pH measurement, and stability testing. This study seeks to explore the potential of nanosuspensions, aiming to integrate nanotechnology with herbal medicine to improve the safety and efficacy of herbal formulations. Results: The nanosuspension (NSWS) shown particle size about 133.09 nm, and its uniform particle distribution was indicated by a Polydispersity Index (PDI) about 0.27. Stability and uniformity were further supported by the zeta potential, particle size, and PDI values. Conclusion: Nanosuspension formulations represents a versatile strategy to improve the therapeutic efficacy of hydrophobic drugs across various routes of administration. Keywords: Withania somnifera, Nanosuspension, Characterization, FT-IR, PDI, FESEM

Improvement of the microstructure and corrosion behavior of Ni-TiO2 composite coatings electrodeposited at various amounts of TiO2 powder

The purpose of this study was to produce efficient Ni-TiO2 composite coatings at different concentrations of TiO2 particles to enhance BS2 microstructure and corrosion resistance in 3.5 wt. % NaCl. % NaCl solution. EDS analysis shows that the Ti and O content increases by increasing the amount of TiO2. XRD results reveal that the preferential growth plane of pure Ni is (100), which corresponds to the (111) and (100) planes for Ni-TiO2 composite coatings. SEM shows that the substrates are coated homogeneously. In addition to the microstructural improvements, the corrosion resistance efficiency was enhanced significantly with the inclusion of TiO2 particles. Specifically, the study showed that 10 g/L of TiO2 provided the optimal balance, achieving a corrosion resistance efficiency of 74.6%, along with a marked reduction in porosity. Furthermore, the surface morphology confirmed a uniform and defect-free distribution of the TiO2 particles, contributing to the overall anti-corrosion properties. These findings suggest that Ni-TiO2 composite coatings are a promising candidate for industrial applications, particularly in environments where materials are exposed to harsh conditions, such as marine environments. The outcomes of this research have the potential to inform the development of advanced anti-corrosion strategies for various industries.

Processes of Metal Oxides Catalyst on Conversion of Spent Coffee Grounds into Rich-Synthesis Gas by Gasification

Spent coffee grounds (SCGs), a waste product of the coffee industry, present a significant untapped resource for fuel production. This study aims to optimize the gasification of SCG using various metal catalysts (NiO, MnO2, Al2O3, and Fe2O3) to maximize syngas yield. SCG samples were gasified at different temperatures (800 °C, 900 °C, 1000 °C) and analyzed using Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TG-DTA), and Fourier Transform Infrared (FTIR) spectroscopy to evaluate catalyst performance and reaction mechanisms. The findings indicated that utilizing mixing techniques for physical contact to introduce catalysts led to a uniform distribution of catalyst particles throughout the sample. The decomposition rate of the gasification experiment after adding the catalyst was 24% faster than that of the pure SCGs. In the gasification experiment, the MnO2 catalyst showed the highest CO production, which was 71% higher than that of NiO under the same conditions. At this temperature, MnO2 generated around 171% more CO than at 800 °C, surpassing the yields observed with other catalysts. The study concludes that Mn emerged as the most promising catalyst, significantly improving both CO and CH4 yields. Selecting the appropriate metal catalyst and optimizing operational temperatures are crucial for enhancing the efficiency of SCG gasification.

Wear micromechanics, mechanisms and wear map of Al-12.6Si-0.25Fe-XMn alloy: The role of Al15(Mn,Fe)3Si2 intermetallic and microstructure modification

Abstract The study investigates the microstructural evolution and wear behaviour of Al-12.6Si-0.25Fe-xMn alloys (x = 0, 1, 2, and 3 wt.%) in dry sliding wear experiments. Manganese (Mn) considerably modifies the microstructure by modifying primary and eutectic silicon particles, changing Fe-rich intermetallic compounds, and increasing the overall wear resistance of Al-12.6Si-0.25Fe. The microstructural investigation demonstrates the production of Al15(Mn,Fe)3Si2 intermetallic phases, as well as a more uniform Si particle distribution. Wear experiments at varied loads (20 N, 40 N, and 60 N) show that Mn addition significantly reduces wear rates and specific wear rates, especially at lower loads. The findings highlight Mn's significance in increasing the hardness and wear resistance of Al-Si-Fe alloys, making them better suited to automotive applications.

Enhanced solar interfacial evaporation through lignin-polyaniline composite coatings on Balsa wood substrates

Solar interfacial evaporation employing wood-derived substrates is increasingly acknowledged as a viable desalination and wastewater treatment technique. This study presents an optimized method that enhances the efficiency of solar interfacial evaporation by applying a coating of lignin-polyaniline composites (EHL-PANI) onto balsa wood substrates. Initial assessments involved comparing evaporators made from various kinds of wood, identifying balsa wood-based photothermal evaporators as the most effective, with an evaporation rate of 1.63 kg·m−2·h−1 and an efficiency of 72.7 %. Photothermal properties were further improved through the chemical oxidation of enzymatic hydrolysis lignin (EHL) with polyaniline, producing a composite with notably high dispersion stability and uniform particle distribution. This modification resulted in reduced particle size and enhanced stability of the polyaniline, which is crucial for boosting photothermal activity. Additionally, the EHL-PANI composites demonstrated exceptional light absorption, exceeding 95 %, and significant photothermal conversion efficiency across a broad wavelength range, attributable to polyaniline's broadband light absorption characteristics. A prototype evaporator, featuring the EHL-PANI coated on a balsa wood substrate, was constructed to assess performance, achieving a water evaporation rate of 2.10 kg·m−2·h−1 and an efficiency of 80.7 % under solar illumination of 1 kW·m−2.

Application of precursor with ultra-small particle size and uniform particle distribution for ultra-high nickel single-crystal cathode materials by coprecipitation method

Ultra-high nickel single-crystal cathode materials have become the most promising for lithium-ion batteries. However, the preparation of ultra-high nickel single-crystal precursors by a continuous coprecipitation method has the disadvantages of large particle size, wide distribution, poor morphology. The extent of the inhomogeneous reactions can be more severe in single-crystal cathodes with larger particle size. Herein, the coprecipitation method with a solid concentrator was adopted, and citrate sodium was used as a complexing agent to improve the physical properties of precursors and electrochemical performance of single-crystal cathode materials. By analyzing the morphology and agglomeration mechanism of the precursor nucleuses under different pH values, it was found that hexagonal nanosheets grew along the 101 direction, and the primary particles showed thicker at pH of 11.4. The hexagonal nanosheets grew along the 001 direction, and the primary particles showed finer at pH of 12.2. The morphology and particle size uniformity of the secondary particles formed by agglomeration at these two pH values showed poor. However, hexagonal nanosheets grew synergistically along the 001 and 101 directions at pH of 11.8, so the primary particles with uniform particle size gradually agglomerated, and then the secondary particles with ultra-small particle size and uniform distribution obtained. Compared to materials prepared by the traditional continuous coprecipitation method, the precursor displays a smaller particle size(D50 = 1.8 µm), higher sphericity, uniformity and denser internal structure. In order to evaluate the performance of Ni0.94Co0.04Mn0.02(OH)2 with ultra-small particle size, the sintering conditions of LiNi0.94Co0.04Mn0.02O2 need to be explored. It was found that the LiNi0.94Co0.04Mn0.02O2 cathode material prepared at 790 °C exhibited higher discharge capacity, cycle and rate performance, compared to materials prepared at 760 °C and 820 °C. We further utilized TEM, EPMA, and XPS to test the internal structure and valence state of LiNi0.94Co0.04Mn0.02O2 cathode material. The results show that the LiNi0.94Co0.04Mn0.02O2 calcined at 790 °C has a good single crystal structure. The LiNi0.94Co0.04Mn0.02O2 cathode materials inherited the structure and particle size of Ni0.94Co0.04Mn0.02(OH)2 precursors, and displayed discharge capacity of 194.7 mAh/g and capacity retention rate of 89.8 % after 100 cycles at 1 C. The microstructure and phase transition of the as-prepared cathode material are well-maintained after long-term cycling, without obvious inter-crystalline micro-crack. The results indicate that its electrochemical performance is better than that of cathode materials with precursors prepared by a continuous coprecipitation method. This work provides new insights for the preparation of small-particle-size precursor and single-crystal cathode materials.

Optimization of process parameters in fabricating AA6082/Nip surface composite using friction stir processing technique

Abstract In this present study, an attempt was made to improve the Ultimate Tensile Strength (UTS) and Microhardness (MH) of friction stir-processed AA 6082 with Nip surface composites without affecting the ductility of the Base Metal (BM). Nip micron particle with an average size of 149 μm (99.99 purity) was utilized as reinforcement and AA6082 as a matrix for fabricating the surface composites. Process parameters namely rotational speed, transverse speed, and volume fraction with three levels considered as input parameters for this study. Moreover, ultimate tensile strength, microhardness, and wear rate were determined as process output. For this study, experiments were conducted as per Taguchi’s L9 orthogonal array (OA) by repeating each trial three times and the average values were used for further analysis. ANOVA was performed to ensure the influential process parameter and the results exhibited that the volume fraction of Nip exhibited the most influential parameter among the three process parameters. Additionally, Grey relational analysis (GRA) was used to grade the rank of the experimental samples using the Grey Relation Coefficient (GRC). Based on this method, the optimal process parameters (Rotational Speed = 1250 rpm, Transverse Speed = 40 mm min−1, Volume Fraction = 18%) were chosen and the optimal sample (Rank 1) attained a UTS of 247 MPa and MH of 100 HV. The results revealed that the fabricated composite (AA6082/Nip) demonstrated an improvement in UTS (26.02%), MH (56.25%), and wear rate (57.38%) as compared to BM (AA6082). Eventually, the surfaces of the optimized samples were also analyzed by x-ray diffraction (XRD), energy dispersive x-ray analysis (EDAX), and field emission-scanning electron microscopy (FE-SEM) methods to confirm the composition of surface composite and the uniform distribution of particles.

Slot‐Die‐Printed Electroactive Polymer Actuators with High‐Strain Sensitivity for Soft Robotic Applications

AbstractIonic electroactive polymer gels are widely employed as actuators in soft robotics due to their ability to undergo rapid mechanical deformation under low‐voltage. How to improve the performance of the ionic electroactive polymer actuators is always the focus of research in this field. Optimizing the migration of ions within the actuator is crucial for enhancing the actuation performance. In this regard, this study innovatively introduces slot‐die‐printing technology to fabricate gel actuation layers characterized by high smoothness and uniform particle distribution, achieving seamless integration between the electrodes and gel actuation layers, while mitigating issues associated with ion accumulation due to polymer clustering. Furthermore, this study attempts to add lactic acid to the traditional CS‐PVA‐IL gel, effectively strengthening the connection between CS and PVA, and promoting smooth ion transport within the gel. The results demonstrate that the actuators prepared in this study achieved a high‐bending‐strain of 0.35%, with a retention rate of 91% for actuation displacement after 10 000 cycles, showcasing superior actuation performance compared to existing research. The fabrication method proposed in this study is simple and highly reproducible, making it suitable for widespread industrial application, and providing a new approach for future industrial production of soft robotics.

Ultrasonic-microwave assisted extraction of selenium-rich rice bran protein: a study on its structural and physicochemical properties

This study explores the effects of different extraction methods on the physicochemical properties and functional performance of selenium-rich rice bran protein (Se-RBP). Four extraction techniques—alkaline extraction (AAE), microwave extraction (MAE), ultrasonic extraction (UAE), and ultrasonic-assisted microwave extraction (UMAE)—were assessed for their efficiency and impact on protein structure, solubility, and functional properties, including emulsifying and foaming capacities. The results demonstrate that UMAE significantly enhances the functional properties of Se-RBP, achieving an emulsion stability index of 86.76% and a foaming capacity of 188.63%, both of which outperform the other methods. Furthermore, UMAE-treated Se-RBP exhibited a 35.43% increase in selenium bioavailability following gastrointestinal digestion. UMAE also delivered the highest antioxidant activity, reducing the IC50 for DPPH radical scavenging to 0.85 mg/mL. These improvements are attributed to UMAE’s ability to achieve a finer, more uniform particle distribution and increased exposure of bioactive compounds. This study reveals the potential of UMAE in optimizing the extraction and functional utilization of Se-RBP.

Effect of inclusion complex formation and mechanoactivation on the structure and rheological behavior of starch-oleic acid mixtures

In the present work, for the first time, mechanical activation implemented in a rotor-stator device (RSD) has been used to enhance the formation of the amylоse-fatty acid complex in gelatinized starch at a moderate temperature (40 °C) using oleic acid (ОА) as a model guest compound. Mechanical activation was found to cause an increase in the complexing index from 10 to 30 % for non-activated mixtures to 83–92 %. The study of aqueous and dried starch-OA mixtures using optical and AFM microscopy and dynamic light scattering methods revealed a uniform distribution of amylose-OA complex particles with a size of 125–260 nm in the starch matrix. The freeze-dried starch-ОА sample prepared using mechanical activation exhibited a V-type crystalline structure. By rotational viscometry and dynamic rheometry, it was found that mechanical activation causes the gelation of aqueous starch-OA mixtures, which accompanies a decrease in their fluidity and an increase in elasticity. The developed method can be recommended for large-scale production of thickening and texture modifying materials based on gelatinised starch containing a fatty acid as a nutritional or structuring additive.

Fabrication of high-performance biomedical rare-earth magnesium alloy-based WE43/hydroxyapatite composites through multi-pass friction stir processing

Magnesium-based composites with bioactive ceramic particles addition are promising materials for biomedical implant applications. Nevertheless, the agglomeration of bioactive ceramic particles remains a challenge for fabricating high-performance biomedical magnesium-based composites. Herein, a novel high-performance biomedical rare-earth magnesium alloy-based WE43/hydroxyapatite (HA) composite is successfully fabricated via multi-pass friction stir processing (MP-FSP). Systematic investigations reveal that MP-FSP leads to a uniform distribution of HA particles and efficient elimination of defects. The microstructural analysis shows a significant grain refinement in the WE43 alloy from 49.4 μm to 2.4 μm under triple-passes FSP. The mechanical properties of the composite are enhanced significantly under triple-passes FSP, with yield strength, ultimate tensile strength, and elongation reaching 236.2 MPa, 278.6 MPa, and 14.2% respectively. Corrosion resistance is also improved, with a 30% reduction in the corrosion rate in SBF solution compared to the unprocessed alloy. Moreover, the MP-FSP fabricated composites exhibit superior corrosion-wear resistance, characterized by slight abrasive wear compared to the abrasive wear and severe pitting corrosion observed in the base WE43 alloy. These improvements are attributed to the synergistic effects of grain refinement, dispersion strengthening, enhanced interfacial bonding, and texture modification. Overall, these findings provide significant quantitative insights into the advanced fabrication techniques of magnesium-based composites for biomedical implant applications, highlighting the effectiveness of MP-FSP in enhancing both mechanical and corrosion-related properties.

Development of anti-corrosion, structural, and optoelectronic potential of Capsicum annuum-Doped AA6063 alloy for marine applications

The study explores the potential of incorporating pepper waste as a reinforcement material in aluminium AA6063 composites, with focussing on the morphological, mechanical, electrochemical, and optoelectric properties. Pepper wastes, including stalks and seeds, were carbonised, pulverized, and sieved to yield 75 μm particulates. These were mixed with molten AA6063 alloy via stir casting, with the pepper content ranging from 0% to 25% by weight. The composites were characterised using hardness testing, electrochemical evaluation, optoelectrical analysis, and morphological analysis. Hardness tests revealed that the 25% pepper-reinforced sample exhibited the highest hardness value of 37 HRB, a 31.7% increase over the control sample. Electrochemical evaluations showed significant improvements in corrosion resistance, with the corrosion potential (Ecorr) of the 25% pepper-reinforced sample reducing to −0.59 V and the corrosion rate decreasing to 7.69 mm/yr. Optoelectrical testing indicated enhanced conductivity in samples with higher pepper content, with the 25% reinforcement achieving a conductivity of 0.1979 (Ωm)⁻1. Morphological tests, such as SEM and XRD, revealed the uniform distribution of pepper particles and the occurrence of several phases that contribute to the composite's improved properties.

Fabrication of Three-Dimensional Dendritic Ag Nanostructures: A SERS Substrate for Non-Invasive Detection.

This paper discusses the fabrication of three-dimensional dendritic Ag nanostructures, showcasing pronounced Localized Surface Plasmon Resonance (LSPR) effects. These nanostructures, employed in surface-enhanced Raman scattering (SERS), function as sensors for lactic acid in artificial sweat. The dendritic structures of the silver nanoparticles (AgNPs) create an effective SERS substrate, with additional hotspots at branch junctures enhancing LSPR. We achieve differential LSPR effects by varying the distribution and spacing of branches and the overall morphology. Adjustments to electrodeposition parameters, such as current and plating solution protective agents on an anodized aluminum oxide (AAO) base, allow for precise control over LSPR intensities. By pre-depositing AgNPs, the electron transmission paths during electrodeposition are modified, which leads to optimized dendritic morphology and enhanced LSPR effects. Parameter optimization produces elongated rods with main and secondary branches, covered with uniformly sized, densely packed, non-overlapping spherical AgNPs. This configuration enhances the LSPR effect by generating additional hotspots beyond the branch tips. Fine-tuning the electrodeposition parameters improved the AgNPs' morphology, achieving uniform particle distribution and optimal spacing. Compared to non-SERS substrates, our structure amplified the Raman signal for lactic acid detection by five orders of magnitude. This method can effectively tailor SERS substrates for specific analytes and laser-based detection.

The structure, magnetic properties, magnetotransport and temperature coefficient of resistivity of hexagonal 4H-SrMnO3 manganite

The perovskite hexagonal SrMnO3 manganite with four layers (4H-SrMnO3) have been one of the hot topics in materials science due to the physical characteristics of antiferromagnetic, ferroelectric, and thermoelectric effects. The transport properties and magnetoresistance (MR) effect of 4H-SrMnO3 have seldom been reported. The structure, temperature coefficient of resistivity (TCR), magnetic and magnetotransport properties of the 4H-SrMnO3 SrMnO3 manganite obtained by solid state reaction have been investigated in this work. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements at room temperature reveal that the SrMnO3 sample exhibits a pure hexagonal symmetric structure, with uniform distribution of particles and elements. Under applied magnetic fields of 2000 Oe, the SrMnO3 sample exhibits a transition from antiferromagnetic (AFM) to paramagnetic (PM) behavior at approximately 280 K, known as the Néel temperature (TN). The resistance is influenced by the magnetic field, but overall exhibits an insulating state. Remarkably, the SrMnO3 sample shows significant MR effect near room temperature. The negative MR near room temperature varies from 5.8 % with 1 T field to 16.8 % with 6 T field, indicating an existence of obvious MR in the hexagonal AFM SrMnO3 manganite. Furthermore, the maxmium value of TCR reaches 4.34 % K−1 near room temperature. These findings of room-temperature TCR and room-temperature MR in the AFM 4H-SrMnO3 hold immense value for the research and potential application of the AFM spintronics and devices.

Fabrication of a ZIF-8/PVA Membrane on PVDF Fiber by Spray for the Highly Efficient Separation of Oil-in-Water Emulsions.

In human life and production, excessive oily wastewaters containing detergents are produced and discharged, causing severe environmental pollution and water resource problems. A metal-organic framework (MOF)-based membrane is an economical and environmentally friendly tool for emulsion separation but is limited by a complex preparation process and poor flexibility. Herein, we developed a simple method to synthesize a MOF-based mixed-matrix membrane (MMM) by spray and fabricated the membrane on poly(vinylidene fluoride) (PVDF) fibers via postdeposition and in situ growth manners. The prepared ZIF-8/PVA MMMs have uniform distribution of ZIF-8 particles and poly(vinyl alcohol) (PVA) on the PVDF fibers. PVA improved the adhesion between the ZIF-8 particles and between the MOF layer and PVDF fiber, endowing the separation membrane with high flexibility and bendability. The prepared ZIF-8/PVA membrane exhibited hydrophilicity and underwater superoleophobicity, which showed high separation efficiency and considerable water flux for emulsions, emulsion containing dye, and surfactant-stabilized emulsion. In addition, the fabricated ZIF-8/PVA/PVDF fibers exhibited good antifouling property and flexibility and can maintain stable separation efficiency after working several times and even under bending, demonstrating the stability and potentiality of the ZIF-8/PVA/PVDF fibers in practical applications. This work paves a new avenue for the synthesis and application of MOF-based MMMs.

The effect of melt thermal-rate treatment on precipitation hardening and mechanical properties of Al–Si–Mg alloys

In this study, we investigate the age-hardening behavior and mechanical properties of direct chill (DC)-cast Al–10Si-0.35 Mg alloys subjected to melt thermal rate treatment (TRT). Our findings reveal that TRT refines the microstructure and precipitation morphology. Grain analysis indicates the prevalence of twin dendritic grains in both TRT and non-TRT (NTRT) alloys during casting, with the TRT billet exhibiting smaller grains. The microstructural analysis demonstrates that TRT reduces the size of secondary dendrite arm spacing and eutectic phases while ensuring a uniform distribution of intermetallic particles. The precipitation mechanism in both alloys remains consistent, with the TRT alloy exhibiting a higher density of fine precipitates. Additionally, we observe a novel coprecipitation mechanism of Si and β″ phase, attributed to a lower misfit between (003)β″ and (011)Si compared to that between (003)β″ and (0 2‾ 0)Al. Furthermore, the TRT alloy displays slower precipitation kinetics due to homogeneous solute distribution, resulting in higher activation energy for precipitation nucleation. Consequently, a single age-hardening peak is observed in TRT alloys during aging. TRT alloys exhibit higher hardness and tensile strength after artificial aging at 190 and 210 °C, while maintaining comparable elongation to NTRT alloys. Theoretical calculations of precipitation strengthening also show higher values for TRT alloys, consistent with experimental results. Thus, our findings comprehend the underlying mechanisms of melt treatments crucial for improving precipitation hardening behavior and mechanical properties of Al–Si–Mg alloys.