Micro & Nano Letters最新文献

Traditional tertiary oil recovery methods are fraught with challenges such as significant reagent adsorption, voluminous injection requirements, limited sweep efficiency, and inadequate intelligent targeting. These issues lead to suboptimal displacement of residual oil, resulting in the inability to mobilize substantial crude oil resources and thus yielding low recovery rates. Microcapsules—spherical particles with micron or nanometer scale diameters—have been extensively utilized across various sectors, including food storage, targeted drug encapsulation, and fragrance containment, owing to their distinct advantages in controlled release, isolation, and targeted delivery. These applications have successfully achieved industrialization and commercialization. In recent years, numerous researchers have explored the application of microcapsule preparation processes to diverse facets of oil extraction, with the aim of further enhancing oil recovery (EOR). This article elucidates the mechanism of action of microcapsules, their preparation methods (encompassing in situ polymerization, interfacial polymerization, spray drying, solvent evaporation, phase separation, and supercritical CO₂-assisted techniques), characterization and evaluation methodologies, among other aspects. It encapsulates the current status and principal challenges associated with the application of microcapsule preparation processes in oilfield development and probes the potential and pivotal research directions for their oilfield applications.

The paper proposes a single antenna that can generate dual-mode plane spiral orbital angular momentum (PS-OAM) beams. Six Vivaldi antennas placed in a tangential circular array make up the antenna, and the antenna is etched onto a substrate material and has a flat design, allowing for easy integration with other system components. The neighbouring ports of the antenna elements have phase differences, so phase-shifting in the feeding network is unnecessary. When fed with the same phase and amplitude, the antenna can produce PS-OAM beams with mode +1 at 7 GHz and mode +2 at 14 GHz, and the measured purity is 80.6% and 63%, respectively. The method may provide a new way to produce multi-mode orbital angular momentum.

The tribological behaviors of nanoparticles (NPs) have attracted widespread attention in the fields of nano-lubrication and ultra-precision manufacturing. The frictional and dynamic behaviors of SiO₂ NPs acting with the single asperity were studied on silicon surface utilizing atomic force microscope. The friction forces of NPs, both static and kinetic, exhibit an initial decrease followed by an increase as the normal load increases (0–300 nN). The nonmonotonic load-dependence of friction behavior corresponds to the dynamic transformation of “sliding-rolling-sliding” motion state of the manipulated NPs, which can be predicted by a Double-Hertz model and further confirmed by nanoindentation-marked NPs. This research has a significant implication for regulating dynamic behaviors of NPs in contemporary three-body abrasive tribology.

Nitrogen and phosphorus co-doped porous carbon plate (NPCP) was prepared by simple pyrolysis carbonization and alkali activation of biomass duckweed NPCP displays the largest specific surface area (SSA) of 2023 m² g⁻¹, and is rich in pyridine N and P doping, which makes the metal-free carbon have excellent electrocatalytic oxygen reduction performance. The best NPCP2 shows a half-wave potential of 0.19 V vs. Ag/AgCl in alkaline electrolyte, and its activity is equivalent to that of commercial platinum carbon (Pt/C). In addition, it shows excellent methanol toxicity resistance and continuous catalytic stability. The experimental results show that the heteroatom doping method obtained by biomass hydroponics has great advantages and great application value in the catalytic field of porous carbon materials.

This study explores the effect of incorporating steel fibres and fly ash into self-compacting concrete (SCC) in various combinations on its mechanical properties. The study begins with thoroughly investigating the fresh properties to ensure compliance with SCC standards when adding steel fibres. Subsequently, mixes that meet SCC standards are evaluated for their mechanical properties. The study aims to enhance the mechanical properties of SCC while maintaining its flowability, filling ability, and passing ability. The research findings provide valuable insights into the optimal combination of steel fibres and fly ash for improving the mechanical properties of SCC. The addition of hooked end type steel fibres increases the compressive strength. When compared to crimped type the mechanical properties increased to 14.4%; however, the strength decreases beyond 1% of steel fibres. Satisfactory results are obtained for fresh properties test.

Multi-needle electrospinning is a simple and general method for mass preparation of nanofiber membrane, which has great industrial potential. However, the bending instability produced in the electrospinning process makes that the deposition uniformity of the nanofiber is still a big concern, resulting in non-uniform nanofiber membrane, which seriously affects the application of electrospun membrane in environmental filtration, new energy and medical fields. In order to improve the uniformity of nanofiber deposition in multi-needle electrospinning, an auxiliary flow field system (AFF) is proposed, which can effectively improve the uniformity of nanofiber deposition. After image processing, the uniformity of nanofiber deposition is quantified with the index of grey distribution, and the effectiveness of this method is verified. Combined with the multi-physical field analysis, the influence mechanism of cross-wind field on the uniformity of fibre deposition was revealed. By optimizing the experimental parameters, the non-uniformity of nanofiber deposition was reduced by 49.19%. Based on multi-needle electrospinning technology, a reliable idea (AFF) and experimental basis are provided for the uniform preparation of nanofiber membrane.

Nickel cobalt layered double hydroxides (NiCo LDHs) have emerged as ideal electrode materials for supercapattery due to their high specific surface area and excellent cycling stability. Morphology control plays a unique role in regulating the performance of the NiCo LDHs. Herein, the morphology of NiCo-LDHs electrode is optimized for enhancing energy storage by a simple activation process with different concentrations of the electrolyte. During the activation process, electrochemical morphology reconstruction occurs on the electrode surface. With a 2 m KOH electrolyte, the NiCo-LDH electrode transforms from nanosheets to nanoflower, which aids in reducing the distance of ion transport. The reconstructed NiCo-LDH exhibits an ultra-high specific capacity of 2809 C g⁻¹ at a current density of 1 A g⁻¹, outperforming most of NiCo LDHs. At a high current density of 10 A g⁻¹, the capacity retention rate remains above 72.7% after 3000 cycles. An asymmetric supercapacitor is fabricated with activated carbon material as the negative electrode, the energy density is 36 Wh kg⁻¹ at the power density of 732 W kg⁻¹. The strategy proposed in the study, which involves concentration-controlled morphology optimization for energy storage enhancement, holds great practical significance for the field of supercapatteries.

The wavelength tunability of a general transmittance function (GTF) is investigated in a first-order fibre multiwavelength filter based on a polarisation-diversified fibre loop, which utilised a composite combination of wave retarders. The filter consists of a polarisation beam splitter, two equal-length high birefringence fibre (HBF) segments, and two different sets of wave retarders with each set positioned before each HBF segment. Specifically, a combination of a set of dual quarter-wave retarders (QWRs) and another set of a QWR and a half-wave retarder is focused upon. By considering the effect of the four wave retarders and two HBF segments on the output polarisation state (OPS) of each element in the filter, the four wave retarder angles (WRAs) are identified that caused all polarisation states on the OPS trace of the second HBF move in the direction of wavelength decrease, resulting in a redshift of the GTF. 360 WRA sets are derived that enabled tuning the GTF by one free spectral range S_R. For eight sets chosen from the WRA sets, inducing a wavelength shift of S_R/8 for each set order, wavelength-shifted spectra are calculated. Finally, this theoretical prediction is experimentally verified, confirming the wavelength tunability of the GTF of the filter.

Silver (Ag) nanoparticles (NPs) are perceiving remarkable progress during the past few periods due to its exclusive properties in many applications. Recently, green synthesis method of NPs is racing against traditional chemical and physical methods by avoiding the use of many toxic chemicals, and expensive devices. Accordingly, in this study, dry and fresh Portulaca-oleracea L. leaf extract has been employed for producing AgNPs as a reducing, capping and stabilizing agents. This process is simple, eco-friendly and green. UV–vis spectra showed the formation of AgNPs represented by the change of a colorless liquid to brownish solution. The crystallinity of the AgNPs, was confirmed by X-ray diffraction (XRD). The contribution of the available functional groups of the leaf extract in the reduction and capping process of NPs was demonstrated using Fourier transform infrared spectroscopy (FTIR). This study showed that fresh Portulaca-oleracea L. leaf extract provides better NPs in terms of stability, purity, degree of crystallinity and spherical shape. The biosynthesized AgNPs from both procedures were coated on the indium tin oxide (ITO) glass substrates to enhance the reflectivity property. It has been shown that the utilized AgNPs, from fresh Portulaca-oleracea L. extract, has smaller size and negligeable agglomeration, consequently lower light transmittance.

Multi-walled carbon nanotubes (MWCNTs) were successfully synthesized and functionalized by chemical vapour deposition and acid reflux methods, respectively. Chitosan (CTS) was prepared by a chemical extraction method from waste prawn shells. Various weight fractions of functionalized multi-walled carbon nanotubes (f-MWCNTs) have been used as reinforcing agent in CTS biopolymer matrix. Fourier transform infrared spectroscopy analysis was done, which confirms the presence of absorption bands of the various functional groups of chitin, CTS, and MWCNTs. Raman spectra revealed the quality of MWCNTs, the extent of their functionalization, and the quality of nanocomposites. The X-ray diffraction analysis showed the distinctive peaks for f-MWCNTs’ and also revealed the formation of CTS/f-MWCNTs nanocomposites. Transmission Electron Microscopy (TEM) analysis also exhibited that the CTS/f-MWCNTs nanoparticles have a well-defined crystalline structure. The highest coercivity and magnetization (Ms) of the CTS/5%f-MWCNTs nanocomposite are 602 Oe and 0.1202 emu/g, respectively that have been enhanced by 3.83 and 5.27 times compared to the pure CTS respectively. It showed that the conductivity is getting higher with the addition of f-MWCNTs in the CTS matrix. CTS/5% f-MWCNTs composites exhibit the highest conductivity than other composites and the conductivity of CTS/5% f-MWCNTs composite is 4.0×10⁻⁴ S/m.