Search Results (947)

Double-shell ZnO/Al₂O₃ submicron hollow fibers were successfully fabricated through a combined electrospinning and atomic layer deposition (ALD) approach. Polyvinyl alcohol (PVA) fibers were first produced by electrospinning and subsequently coated with a conformal Al₂O₃ barrier layer via low-temperature ALD employing trimethylaluminum (TMA) and deionized (DI) H₂O to preserve the integrity of the temperature-sensitive polymer core. The inner polymer was then removed using two different techniques—thermal annealing and water dissolution—to compare their effects on the fiber morphology. Finally, a functional ZnO layer was deposited by thermal ALD with diethylzinc (DEZ) and DI H₂O. It was found that the polymer removal method critically determined the final structural and morphological characteristics of the fibers. Thermal annealing resulted in smooth, shrunken fibers, while water dissolution led to diameter expansion and the formation of a highly rough, bubble-like surface structure due to swelling-induced micro-cracking. The selection of the polymer removal method offers a precise and controllable route for tailoring the fiber morphology. The resulting high-aspect-ratio (HAR) structures, particularly the rough and expanded fibers, exhibit enhanced specific surface area, making them highly promising for applications in sensing, catalysis, and filtration. Full article

In light of the recent advances in hollow-core fiber (HCF) design and manufacturing, wide-scale deployments of this fiber type to realize next-generation optical transport networks may become viable in the foreseeable future, with benefits in terms of lower latency and improved capacity/reach. Nevertheless, several uncertainties remain regarding the properties of HCF that can be manufactured at scale, as well as the specifications of optical amplifiers developed to leverage the negligible low linearity of this fiber type. This work evaluates the performance of HCFs considering a wide range of potential fiber and amplifier parameters and compares them with traditional standard single-mode fiber (SSMF) and pure-silica-core fiber (PSCF). The resulting analysis allows us to determine, at a system and network level, the combination of fiber and amplifier parameters that will allow HCF to become a competitive transmission medium for next-generation optical transport networks. Full article

This study presents the techno-economic optimization of a hybrid distillation-membrane process for the complete fractionation of liquefied petroleum gas (LPG), targeting high-purity propane, n-butane, and isobutane recovery. The process employs an initial distillation column to separate propane (99% purity) from a propane-enriched stream, which is subsequently fed to a two-stage membrane system using an MFI zeolite hollow-fiber membrane for n-butane/isobutane separation. Through systematic simulation and sensitivity analysis, different membrane configurations were evaluated. The two-stage process with a partial residue-side reflux configuration demonstrated superior economic performance, achieving a total operating cost of 31.58 USD/h. Key membrane parameters—area, permeance, and separation factor—were optimized to balance separation efficiency with energy consumption and cost. The analysis identified an optimal configuration: a membrane area of 800 m², an n-butane permeance of 0.9 kg·m⁻²·h⁻¹, and a separation factor of 40. This setup ensured high n-alkane recovery while effectively minimizing energy use and capital investment. The study concludes that the optimized distillation-membrane hybrid process offers a highly efficient and economically viable strategy for the full utilization of LPG components. Full article

Membrane separation is a promising, low-energy technology for purifying turquoise hydrogen from methane pyrolysis streams. However, there is a critical knowledge gap between the performance of membrane materials and the practical application of large-scale modules under realistic process conditions. This study evaluates commercial polyimide and polysulfone hollow fiber membranes for H₂/CH₄ separation. The effect of feed composition and pressure on the membrane separation performance were studied, revealing that the separation efficiency is overwhelmingly dominated by concentration polarization, which reduced the H₂/CH₄ separation factor by up to 80% compared to ideal values. Despite this, by optimizing process conditions, we successfully achieved a permeate purity of 99.3% H₂ at 85% recovery. Furthermore, Aspen Plus simulations of an integrated pyrolysis reactor with the membrane unit and a recycle stream demonstrate significant process benefits. The integration increased the H₂ production rate from 10.3 to 17.6 kmol/h and substantially reduced the specific energy consumption from 40.3 to 24.9 kJ/g H₂ compared to non-integrated systems. This work shows that a membrane process can improve not only the product H₂ purity but also the overall energy efficiency of a turquoise hydrogen production process. Full article

Virus filtration is an essential unit operation used to validate clearance of adventitious virus during the manufacture of biopharmaceutical products such as monoclonal antibodies. Obtaining at least a 10,000-fold reduction in virus particles in the permeate is challenging as monoclonal antibodies are about half the size of the virus particles. Minute virus of mice, FDA-recommended model adventitious virus, was labeled with a fluorescent dye. Laser scanning confocal microscopy was used to determine the location of virus entrapment within the virus filtration membrane. Three different hollow fiber membranes made of regenerated cellulose and polyvinylidene fluoride were tested. Feed streams consisted of MVM spiked in buffer and MVM spiked in 5 g L⁻¹ bovine serum albumin known to contain aggregates similar in size to the MVM. After filtering the feed, a buffer flush was used, with and without 30 min pause before the buffer flush. For all virus filters, a 30 min process pause led to broadening and movement of the virus entrapment zone deeper into the membrane. The presence of aggregates led to greater broadening of the entrapment zone. Both effects could lead to reduced virus clearance. Visualization of virus entrapment helps improve understanding of the behavior of virus filtration membranes. Full article

Carbon fiber reinforced silicon carbide (C/SiC) composite material exhibits exceptional properties, including high strength, high stiffness, low density, outstanding high-temperature performance, and corrosion resistance. Consequently, they are widely used in aerospace, defense, and automotive engineering. However, their anisotropic, high hardness, and brittle characteristics make them a typical difficult-to-machine material. This paper focuses on achieving high-quality micro hole machining of C/SiC composite material via electrical discharge machining. It systematically investigates electrical discharge machining characteristics and innovatively develops a hollow internal flow helical electrode reaming process. Experimental results reveal four typical chip morphologies: spherical, columnar, blocky, and molten. The study uncovers a multi-mechanism cutting process: the EDM ablation of the composite involves material melting and explosive vaporization, the intact extraction and fracture of carbon fibers, and the brittle fracture and spalling of the SiC matrix. Discharge energy correlates closely with surface roughness: higher energy removes more SiC, resulting in greater roughness, while lower energy concentrates on m fibers, yielding higher vaporization rates. C fiber orientation significantly impacts removal rates: processing time is shortest at θ = 90°, longest at θ = 0°, and increases as θ decreases. Typical defects such as delamination were observed between alternating 0° and 90° fiber bundles or at hole entrances. Cracks were also detected at the SiC matrix–C fiber interface. The proposed hole-enlargement process enhances chip removal efficiency through its helical structure and internal flushing, reduces abnormal discharges, mitigates micro hole taper, and thereby improves forming quality. This study provides practical references for the EDM of C/SiC composite material. Full article

Improving electronic and ionic transport and the structural stability of electrode materials is essential for the development of advanced lithium-ion batteries. Despite its great potential as a high-power anode, Ti₂Nb₁₀O₂₉ (TNO) still underperforms due to its unsatisfactory electronic and ionic conductivity. Here, a TNO/carbon microtube (TNO@CMT) composite is constructed via an ethanol-assisted solvothermal process and controlled annealing. The hollow carbon framework derived from kapok fibers provides a lightweight conductive skeleton and abundant nucleation sites for uniform TNO growth. By tuning precursor concentration, the interfacial structure and loading are precisely regulated, optimizing electron/ion transport. The optimized TNO@CMT-2 exhibits uniformly dispersed TNO nanoparticles anchored on both inner and outer CMT surfaces, enabling rapid electron transfer, short Li⁺ diffusion paths, and high structural stability. Consequently, it delivers a reversible capacity of 314.9 mAh g⁻¹ at 0.5 C, retains 75.8% capacity after 1000 cycles at 10 C, and maintains 147.96 mAh g⁻¹ at 40 C. Furthermore, the Li⁺ diffusion coefficient of TNO/CMT-2 is 5.4 × 10⁻¹¹ cm² s⁻¹, which is nearly four times higher than that of pure TNO. This work presents a promising approach to designing multi-cation oxide/carbon heterostructures that synergistically enhance charge and ion transport, offering valuable insights for next-generation high-rate lithium-ion batteries. Full article

Supramolecular proteins have emerged as promising templates for guiding metal ion mineralization into well-defined nanomaterials because of their structural versatility and chemical diversity. However, the precise control of metal ion nucleation on the different reactive sites of protein templates remains challenging. In this study, a genetically engineered hollow tobacco mosaic virus protein fiber (TMVF) with excellent structural stability was employed to achieve selective mineralization of noble metal nanostructures either on its external surface or within its internal channel. Moreover, the Pt/Pd bimetallic nanowire (NW) was also successfully prepared by co-depositing Pt and Pd on the TMVF. The bimetallic NWs demonstrated a peroxidase-like activity, which enabled their application for cholesterol detection by cooperating with cholesterol oxidase. Full article

Today, reducing carbon footprints requires the development of technologies to utilize CO₂, particularly by converting it into valuable chemical products. One approach is plasma-catalytic CO₂ splitting into CO and O₂. The task of separating such a ternary mixture is nontrivial and requires the development of an efficient method. In this paper, we have developed a comprehensive scheme for the separation of a CO₂/CO/O₂ mixture using membrane technology. The novelty of this work lies in the development of a complete scheme for separating the products of plasma-chemical decomposition of CO₂ to produce a CO concentrate. The calculations utilized the principle of a reasonable balance between the recovery rate and the energy consumption of the separation process. This scheme allows production of a CO stream with a purity of 99%. To achieve this goal, we have proposed the sequential use of CO₂-selective membranes based on polysiloxane with oligoethyleneoxide side groups (M-PEG), followed by polysulfone (PSF) hollow-fiber membranes to separate CO and O₂. For these membranes, we measured the CO permeability for the first time and obtained the selectivity for CO₂/CO and O₂/CO. The potential of membrane separation was demonstrated through a three-stage process, which includes recycling of the CO removal stream and concentration after CO₂ plasmolysis. This process was calculated to yield a highly pure CO stream containing 99 mol% with a recovery rate of 47.9–69.4%. The specific energy consumption for the separation process was 30.31–0.83 kWh per 1 m³ of feed mixture, and the required membrane area was between 0.1 m² for M-PEG and 42.5–107 m² for PSF, respectively. Full article

This study investigates the design factors of stress wave barrier zones intended for manufacturing machines under impulse loading, using polymer discontinuously reinforced composites with specified internal microstructures, which effectively suppress stress at the wave front, promote uniform stress distribution, improve impact resistance, and reduce vibrations and noise. Two-dimensional representative unit cells and explicit finite element simulations were used to analyze stress wave propagation under impulse loading. The effects of inclusion shape, orientation, distribution, interlayer, and size of the interface on stress wave scattering and attenuation were examined. In our models, hollow inclusions demonstrated 20.6% higher attenuation compared to solid inclusions, with the hollow fiber inclusion showing the most significant improvement. Inclusion orientation relative to the stress wave direction affected attenuation by 18.5%, while redistribution of inclusions and addition of a compliant interlayer contributed additional increments of 3–11%. These results highlight the critical role of microscale topology in stress barrier zone designing, such that the combined adjustment of inclusion shape, orientation, interlayer presence, and spatial distribution provides an effective strategy to maximize stress wave attenuation. Full article

A novel anti-resonant hollow-core fiber (AR-HCF) is proposed. The fiber uses cross-nested circular cladding tubes including single-nested and non-nested tubes in the near-infrared spectral region of 1.3–1.7 μm. All the anti-resonant tubes are used to minimize the confinement loss (CL) of the LP₀₁ core mode. The non-nested tubes are also employed to achieve single-mode performance through strong mode coupling between the cladding mode and the LP₁₁ core mode. The impact of the structural parameters on the CL of the modes is analyzed by using the finite element method (FEM). Optimization results indicate that the CLs of the LP₀₁ mode and the LP₁₁ mode are 0.18 dB/km and 5.88 × 10³ dB/km at 1.55 μm. Consequently, the higher-order mode extinction ratio (HOMER) achieves 3.27 × 10⁴. Additionally, the mode field area of the fiber exceeds 4720 μm² and the corresponding mode field diameter of the LP₀₁ mode is more than 77 μm across the spectral region of 1.3–1.7 μm. In the practical applications, the fabrication tolerance is analyzed. The collapse of anti-resonant tubes within 0–2 μm and positional offsets between 0° and 4° both have minimal impact on fiber performance, thereby ensuring the stability of the system. Compared with other reported fibers, the proposed fiber demonstrates superior performance. Full article

Varied types of particulate matter (PM) persist in the environment and exert a harmful impact on public health. The aim of this review article is to explore the key role of membrane technology in the separation of PM from ambient air. Nanofibrous, microporous, Janus, photocatalytic and hollow fiber membranes have found significant utilization in the effective separation of PM. Recent advancements in membrane technology and their key properties such as antibacterial activity, flame retardancy, wettability, thermal stability and reusability have been underscored in this review article. Moreover, the principles of PM separation have been discussed in detail to understand the working pathway of a membrane air filter via physical, chemical or biological approaches. A brief comparison between the conventional air filters and membrane air filters is provided in terms of cost, separation principle and respective merits and demerits to understand the importance of membranes in the realm of PM separation. This study also highlighted the commercial status of PM air filters with respect to their cost and scalability. By focusing on the innovations in membrane filters, this review article has highlighted the futuristic approaches such as green fabrication techniques, highly efficient material incorporation, use of AI/ML, etc., to overcome the challenges associated with conventional air filters. Full article

Fiber lasers operating at 1.7 μm have significant application value in fields such as gas detection and material processing due to their characteristics, including compact structure and ease of thermal management. Based on the stimulated Raman scattering (SRS) of gas molecules in hollow-core fibers (HCFs), fiber gas Raman lasers (FGRLs) are a novel and effective method for generating 1.7 μm fiber lasers. We report here, to the best of our knowledge, the first FGRL based on the anti-resonant hollow-core fiber (AR-HCF) filled with sulfur hexafluoride (SF₆) molecules. A nanosecond pulsed fiber amplifier tunable from 1540 to 1560 nm was used to pump a 17.8-m-long AR-HCF filled with SF₆ molecules. By virtue of the vibrational SRS of SF₆ molecules, laser output in the range of 1748–1774 nm was achieved. At a gas pressure of 15 bar, a maximum average power output of ~3 W was obtained, corresponding to an optical-to-optical conversion efficiency of ~22%. The output linewidth of the Raman laser was measured to be approximately 2.1 GHz using a Fabry–Pérot (F-P) scanning interferometer. The research results enriched the methods for 1.7 μm fiber laser output. Full article

A hollow fiber-supported polymeric mixed-matrix membrane, consisting of a Pebax-1657 matrix and graphene nanoplatelet (GNP) fillers as the selective layer, was tested for CO₂/CH₄ gas separation at transmembrane pressures up to 30 bar(a). Using a custom, novel, membrane module, we simultaneously performed permeability/selectivity and in situ electric impedance spectroscopy measurements. This in situ technique is proposed here for the first time. Furthermore, stable mixed-gas selectivities, for 10% CO₂ in CH₄ gas, reaching up to 61.4 (M0) and 68.5 after heat treatment (M2) were observed at 20–30 bar(a), whereas the stressed state (M1) dropped to ~22. Throughout the whole procedure of the three (initial, degraded, and restored) membrane testing assessments, a gradual decline in gas permeability coupled with a corresponding increase in the membrane’s AC resistance, due to membrane compaction, was evident. More specific, the membrane’s AC resistance, R₁, increased from ~96–147 ΜΩ (M0) to ~402–435 ΜΩ (M1) and ~5390–5700 ΜΩ (M2), while the peak-phase frequency f_p decreased from ~1.25 kHz (M0) to ~340 Hz (M1) and ~115 Hz (M2). Overall, this work proposes a new tool/method for connecting membrane’s deterioration phenomena with AC resistance and demonstrates that a facile heat treatment can restore selectivity following compaction, despite the absence of full permeance recovery. Full article

Membrane distillation (MD) is a promising technology for reducing the volume of high-salinity brines generated from desalination plants, yet limited knowledge exists regarding its fouling behavior under long-term operation. In this study, fouling was investigated through the autopsy of a hollow fiber MD module operated for 120 days in a direct contact membrane distillation (DCMD) configuration using real desalination brine. Despite stable salt rejection exceeding 99%, a gradual decline in flux and permeability was observed, indicating progressive fouling and partial wetting. Post-operation analyses, including SEM, EDS, ICP-OES, and FT-IR, revealed that the dominant foulants were inorganic scales, particularly calcium carbonate (CaCO₃), with minor contributions from suspended particles (SiO₂, Fe) and organic matter. Fouling was more severe in the inlet and inner regions of the module due to intensified temperature and concentration polarization, which promoted supersaturation and scale deposition. These combined effects led to a reduction in membrane hydrophobicity and liquid entry pressure, ultimately accelerating partial wetting and performance deterioration. The findings provide valuable insights into the spatial fouling behavior and mechanisms in MD systems, highlighting the importance of hydrodynamic optimization and fouling mitigation strategies for long-term brine concentration applications. Full article