Controlled Pore Structure Research Articles

Effect of pore plugging on transpiration cooling performance implemented with perforated flat plates

Transpiration cooling is expected to be one of the most effective cooling technologies for gas turbine blades. However, dust deposition can easily lead to pore plugging, which limits its practical application in engineering. The plugging of pores in conventional porous media models is difficult to predict, so it is essential to construct computational models with finely controllable porous structures. In this study, a transpiration cooling configuration with straight holes perforated with a diameter of 0.5 mm was adopted. The effects of plugging ratio and region on flow and heat transfer under different coolant injection ratios and pump power conditions were investigated by numerical simulation. The results showed that at constant mass flow rate, the overall cooling performance increased as the plugging ratio increased at low injection ratios. At high injection ratios, the opposite was true. With a certain pump power, as the plugging rate increased, the flow loss coefficient rose, leading to a decrease in cooling efficiency. Transpiration cooling efficiency was also highly sensitive to the distribution of plugged holes at the same plugging ratio. When the coolant flow was sufficient, the farther the plugged area was from the leading edge, the smaller the reduction in cooling efficiency.

High-performance radiative cooling PVDF-HFP film based on controllable porous structure

The preparation of porous films by nonsolvent-induced phase separation (NIPS) for efficient radiation cooling has attracted considerable attention. However, the thermodynamic uncertainty in the NIPS phase separation process may cause film formation to fail. Furthermore, the existing research on the pore size of porous films prepared by the phase separation method is inadequate. This study used the NIPS and vapor-induced phase separation (VIPS) techniques to ensure the stable formation of porous PVDF-HFP film (PPF). The pore size of the PPF was studied. The experimental results indicated that the film tended to obtain larger micropores at a concentration of 12 wt% and an immersion time of 12 h. The simulation results demonstrate that the scattering efficiency of 1.322 μm micropores is approximately three orders of magnitude higher than that of 0.077 μm nanopores. The porous film with the largest micropore exhibits high solar reflectivity (96.4 %) and long-wave infrared emissivity (95 %). It allows the sub-ambient temperature to drop by approximately 10.2 °C at a solar intensity of 514 W/m2. It retained 96.1 % reflectivity and a porous structure, after 480 h of fluorescent lamp irradiation. This work constitutes a supplement to preparing porous films by the phase separation method.

Microfluidic Precision Manufacture of High Performance Liquid Chromatographic Microspheres

AbstractA key bottleneck in developing chromatographic material is the chemically entangled control of morphology, pore structure, and material chemistry, which holds back precision material manufacture in order to pursue advanced separation performance. In this work, a precision manufacture strategy based on droplet microfluidics was developed, for production of highly efficient chromatographic microspheres with independent control over particle morphology, pore structure and material chemistry. The droplet‐synthesized microspheres display extremely narrow particle size distribution (CV<3 %), enabling a 100 % production yield due to complete elimination of sieving steps. More importantly, the size of the droplet‐synthesized microspheres is freely adjustable without the need for re‐optimizing chemical recipes or reaction conditions. The resulting materials exhibit excellent separation efficiencies, achieving a reduced plate height of hmin=1.67. This precision manufacture strategy also allows for flexible pore design and continuous pore size adjustment across three orders of magnitudes, providing a novel vehicle for resolution fine‐tuning targeting protein separation. Besides traditional silica, organic–inorganic hybrid silica, zirconia, and titania microspheres can also be precisely synthesized on the same platform, supporting various separation applications and operating conditions. Powered by precision manufacture, super‐throughput production, and versatile chemistry, the high‐performance droplet‐synthesized separation material will pave the way towards green and precision chromatographic industry.

Microfluidic Precision Manufacture of High Performance Liquid Chromatographic Microspheres.

A key bottleneck in developing chromatographic material is the chemically entangled control of morphology, pore structure, and material chemistry, which holds back precision material manufacture in order to pursue advanced separation performance. In this work, a precision manufacture strategy based on droplet microfluidics was developed, for production of highly efficient chromatographic microspheres with independent control over particle morphology, pore structure and material chemistry. The droplet-synthesized microspheres display extremely narrow particle size distribution (CV<3 %), enabling a 100 % production yield due to complete elimination of sieving steps. More importantly, the size of the droplet-synthesized microspheres is freely adjustable without the need for re-optimizing chemical recipes or reaction conditions. The resulting materials exhibit excellent separation efficiencies, achieving a reduced plate height of hmin=1.67. This precision manufacture strategy also allows for flexible pore design and continuous pore size adjustment across three orders of magnitudes, providing a novel vehicle for resolution fine-tuning targeting protein separation. Besides traditional silica, organic-inorganic hybrid silica, zirconia, and titania microspheres can also be precisely synthesized on the same platform, supporting various separation applications and operating conditions. Powered by precision manufacture, super-throughput production, and versatile chemistry, the high-performance droplet-synthesized separation material will pave the way towards green and precision chromatographic industry.

Multifunctional Ti3C2Tx/Fe3O4/glass fiber paper composites for flexible microwave absorption materials with ultralow filling ratio

The preparation of multifunctional microwave absorbing materials with the characteristics of stronger absorption, wider bandwidth, lighter weight, higher strength and thinner thickness is an urgent research direction. Due to the difficulty of controllable distribution of absorbers, excellent microwave absorption performance is usually accompanied by large absorber amount and thickness, which can result in microwave absorption composite materials lack flexibility, mechanical properties, and adaptability to the environment. In this study, Ti3C2Tx/Fe3O4/glass fiber paper composite was prepared by vacuum-assisted filtration. The controllable pore structure constructed by glass fiber enables uniform distribution of MXene/Fe3O4 and effectively spreading of MXene monolayer film, enhancing conductivity loss and interface loss. By controlling the diameter of glass fiber, the pore size and the distribution of absorber can be regulated, thereby achieving a minimum reflection loss of up to −57.2 dB at an ultra-low filling ratio of 1.66 wt%. With the addition amount of 1.90 wt%, the effective absorption bandwidth can cover the whole X-band. The ultra-low specific reflection loss exceeds most of fabric materials and MXene-based absorbers. Meanwhile, the composite material exhibited excellent mechanical properties with a tensile strength of 3.054 kN/m and a burst resistance of 290 kPa. In addition, the adhesion between the filler and the glass fiber was increased by adding acrylic resin-based aqueous adhesive, and the surface grafting functional group (-F) made the composite material superhydrophobic. This work provides a new strategy to synthesize multifunctional absorbing material with low filling ratio and strong environmental practicality.

Supermolecule-opitimized defect engineering of rich nitrogen-doped porous carbons for advanced zinc-ion hybrid capacitors.

Pitch-based porous carbons with adjustable surface chemical property and controllable pore structure are regarded as promising cathode materials for aqueous zinc-ion hybrid capacitors (ZIHCs), while its disordered carbon matrix and microstructure as well as insufficient surface defects often result in low Zn2+-storage capacity and poor rate capability of ZIHCs. Herein, a synergetic strategy of self-assembled supermolecule and enriched defective carbon engineering was developed to achieve ultrahigh edge-nitrogen doping for ZIHCs. The crystallite defects and surface structure of porous carbon could be effectively achieved through grafting electronegative oxygen-containing small molecules and high-level nitrogen-containing functional groups between modified polycyclic aromatic hydrocarbon and supermolecule framework. The optimized three-dimensional carbon structure delivered high capacity of 218 mAh g-1 at 0.2 A g-1, fast charge/discharge capability, enhanced energy density (165.4 Wh kg-1) and superior cycling stability (95% retention after 10000 cycles as cathode of ZIHCs). This provided new insight into the controllable synthesis of carbon cathodes for ZIHCs and expects to prepare functional porous carbon by supermolecules and special precursors.

Cellulose-Templated Nanomaterials for Nanogenerators and Self-Powered Sensors.

Energy crisis inspires the development of renewable and clean energy sources, along with related applications such as nanogenerators and self-powered devices. Balancing high performance and environmental sustainability in advanced material innovation is a challenging task. Addressing the global challenges of sustainable development and carbon neutrality lead to increasedinterest in biopolymer research. Nanocellulose materials, derived from biopolymers, demonstrate potential as template candidates for advanced materials, due to their unique properties, including high strength, high surface area, controllable pore structures and high-water retention. In recent years, cellulose-templated nanomaterials enable delicate nano-/microscale structural construction, thus promoting developments in the field of nanogenerators and self-powered sensors. However, there is still a limited number of reviews focused on cellulose-templated nanomaterials for applications in nanogenerators and self-powered sensors. This review aims to fill this research gap by introducing various cellulose-templated nanomaterials and providing a detailed analysis of their fashionable applications in nanogenerators and self-powered sensors. The goal is to present cellulose-templated nanomaterials as highly promising template and guest materials for templating technologies, offering sustainable nano-/microscale control over advanced materials for the foreseeable future. This potential is promising for new applications in the fields of nanogenerators and self-powered sensors.

Self-exothermic reaction behavior and pore structures of Ni-Al intermetallics with more than 70% porosity

Abstract In this study, high-porosity Ni-Al alloys with complete shape and controllable pore structures were prepared by combining the self-exothermic reaction with the space holder method. The observations show that porous Ni-Al sintered discs appeared to melt and deform after a violent reaction without adding space holder particles. The link between the volume content of urea particles and macroscopic morphology, combustion behavior, phase composition and pore structures of porous Ni-Al compounds were studied. The space holder pores acts as a heat absorber, greatly increasing the open porosity to 76.0% when adding 50 vol% urea particles. This leachable space holder method can be an effective strategy to regulate the sample shape and pore characteristics of porous Al-containing intermetallics.

Supramolecular Polymer Frameworks with Controlled and Uniform Pore Apertures.

Porous frameworks with controlled pore structure and tunable aperture are greatly demanded. However, precise synthesis of this kind of materials is a formidable challenge. Herein, we report the fabrication of two-dimensional (2D) supramolecular polymer frameworks using a precisely synthesized rod-like helical polyisocyanide as link. Four three-arm star-shaped polyisocyanides with the degree of the polymerization of 10, 20, 30 and 40, and having 2-ureido-4[1H]-pyrimidinone (UPy) terminals were synthesized. 2D-Crystalline polymer frameworks with apertures of 5.3, 10.1, 13.9, and 19.1 nm were respectively obtained through intermolecular hydrogen bonding interaction between the terminal Upy units. The pore aperture is dependent on the length of polyisocyanide backbone. Thus, well-defined supramolecular polymer frameworks with controlled and uniform hexagonal pores were obtained, as proved by small-angle X-ray scattering (synchrotron radiation facility), atomic force microscopy, and Brunauer-Emmett-Teller analyses. The frameworks with uniform large pore aperture were used to purify nanomaterials and immobilize biomacromolecules. For instance, the membranes of the polymer frameworks could size-fractionation of silver nanoparticles into uniform nanoparticles with very low dispersity. The frameworks with large aperture facilitated the inclusion of myoglobin and enhanced the stability and catalytic activity.

Wrinkled hierarchical porous carbon spheres with interconnected multi-cavity for ultrahigh capacitive deionization

As one of the most promising electrode materials for capacitive deionization (CDI), the development of carbon materials with controllable pore structure and continuous mass production is essential for their practical application. Herein, a facile ultrasonic spray pyrolysis method was developed to synthesize surface-functionalized wrinkled hierarchical porous carbon spheres (HCS) with unique interconnected multi-cavity structures. The wrinkled and interconnected multi-cavity hierarchical pores of the HCS play a crucial role in providing accessible ion adsorption sites and promoting ion diffusion and storage in the “multi-cavity warehouse”. The carboxyl groups on the surface of HCS generate a negative charge that promotes the adsorption of cations. The optimized HCS possesses outstanding desalination capacity (114.25 mg g−1), fast adsorption rate (6.57 mg g−1 min−1), and superior cycling stability (95%). Meanwhile, the HCS exhibited impressive desalination capacities in brackish water. Furthermore, the density functional theory calculation results confirmed that the synergistic effect of carboxyl groups and defects significantly enhanced the Na+ adsorption capacity and facilitated ion diffusion. This study extends the synthesis method of surface-functionalized hierarchical porous carbon, which is expected to facilitate the development of CDI electrode materials.

Amphiphilic silica monomers induced superhydrophilic and flexible silica aerogels for radiative cooling and atmospheric water harvesting

Silica aerogels have attracted extensive attention owing to their exceptional porous structures and crucial applications for sustainable environments. However, the inherent fragility and complex manufacturing process of silica aerogels present a challenge for their prolonged applications. In this study, an amphiphilic silica monomer, triethoxysilane end-capped poly(ethylene oxide) (PEO-TES), is designed and synthesized, which can co-gelled with methyltrimethoxysilane in water and gives birth to flexible and superhydrophilic silica aerogels via ambient pressure drying (APD). PEO-TES plays a dual role as both co-monomers and surfactants, effectively stabilizing the sol–gel transition, adjusting the porous structure of hydrogels, and imparting superhydrophilicity. The silica aerogel has low density (0.147 g cm−3), zero water contact angle, high elasticity (80 % compression), high solar reflectance (0.888), and high IR emissivity (0.967). These features make them robust all-day passive radiative cooling materials with 10.5 °C sub-ambient cooling capacity and atmospheric water harvesting capacities for both vapor (a water harvesting rate of 0.041 kg m−2h−1) and fog (harvesting capacity of 2.9 g g−1). The strategy provides a simple APD method for synthesizing flexible and superhydrophilic silica aerogels with controllable porous structures, passive cooling, and water harvesting performance, which may help address global climate change and water scarcity challenges.

Enhancing mechanical strength and porosity of alumina extrudates through composite processing

Industrial alumina supports need to possess both high mechanical strength and porosity, but these requirements often conflict with each other. In this work, differences in powder properties such as particle shape, flowability, and peptizability were utilized to composite for extrusion. When globoid pseudo-boehmite was composited with sheet-like alumina at a mass ratio of 3:1, the extrudate exhibited a mechanical strength of 183 N·cm−1 and a porosity of 62.24%, representing a 46.4% and 4.5% increase, respectively, when compared to using globoid alone. Multiscale characterizations revealed that the composite extrudate possessed rich and interconnected mesopores and macropores. The outcome of DEM indicated that the composited extrudates had higher porosity and particle average coordination numbers than the single powder extrudates. This study revealed a correlation between powder properties and extrudate structures, providing design insights for the targeted control of mechanical strength and pore structure.

Supramolecular Polymer Frameworks with Controlled and Uniform Pore Apertures

AbstractPorous frameworks with controlled pore structure and tunable aperture are greatly demanded. However, precise synthesis of this kind of materials is a formidable challenge. Herein, we report the fabrication of two‐dimensional (2D) supramolecular polymer frameworks using a precisely synthesized rod‐like helical polyisocyanide as link. Four three‐arm star‐shaped polyisocyanides with the degree of the polymerization of 10, 20, 30 and 40, and having 2‐ureido‐4[1H]‐pyrimidinone (UPy) terminals were synthesized. 2D‐Crystalline polymer frameworks with apertures of 5.3, 10.1, 13.9, and 19.1 nm were respectively obtained through intermolecular hydrogen bonding interaction between the terminal Upy units. The pore aperture is dependent on the length of polyisocyanide backbone. Thus, well‐defined supramolecular polymer frameworks with controlled and uniform hexagonal pores were obtained, as proved by small‐angle X‐ray scattering (synchrotron radiation facility), atomic force microscopy, and Brunauer–Emmett–Teller analyses. The frameworks with uniform large pore aperture were used to purify nanomaterials and immobilize biomacromolecules. For instance, the membranes of the polymer frameworks could size‐fractionation of silver nanoparticles into uniform nanoparticles with very low dispersity. The frameworks with large aperture facilitated the inclusion of myoglobin and enhanced the stability and catalytic activity.

Fabrication of fabric-based piezoresistive sensors based on chemically deposited fabric silver electrodes and PDMS-MWCNTs/CB composite films with thermally expandable microspheres

Optimizing the fabrication process of fabric electrodes and creating active layers with a controlled pore structure is crucial for advancing high-performance flexible pressure sensors. This work proposes an approach to manufacturing fabric-based piezoresistive sensors. Specifically, it utilizes the liquid-phase chemical reduction method with microdroplet jetting technology and the thermally expandable microsphere foaming method. The impact of conductive material filling content and the microsphere expansion process on the active layer performance was investigated. Additionally, the electrical properties of fabric metal silver electrodes were evaluated, along with the sensing capabilities and applications of the sensors. The results reveal that the electrodes exhibit an average sheet resistance of 0.023 Ω sq−1. The sensor displays a sensitivity of 0.21 kPa−1, with a response-recovery time of approximately 300/200 ms and repeatability over 5000 s. Human motion signal tests of the sensor demonstrate its potential in healthcare and sports monitoring applications.

Regulating pore structure of diatomite with alkali dissolution and its influence on humidity control performance

Alkali dissolution is an effective method to regulate the pore structure of porous mineral material. The main chemical composition of diatomite is amorphous SiO2, which can be dissolved in alkali dissolution. The diatomite samples with alkali dissolution treatment were systematacially characterized by the particle size analysis, low temperature nitrogen adsorption, MIP, fractal theory, SEM, TEM, XRD, FTIR and surface hydroxyl density to analyze the pore structure and surface properties. And the humidity control performance of diatomite was tested under different temperatures and relative humidities. The relationship among pore structure, surface properties and humidity control performance were analyzed. The results show that alkali dissolution can regulate the mesoporous and macroporous of diatomite, and some new microporous can generate at high alkali dosage. The specific surface area, mesoporous pore volume, proportion of macroporous volume, surface roughness, heterogeneity of pore structure and number of hydroxyl groups on the surface of diatomite are important factors which determining the humidity control performance. The humidity control performance of diatomite is positively correlated with the specific surface area, mesoporous volume, surface roughness, heterogeneity of pore structure and number of hydroxyl groups on the surface, while is negatively correlated with the proportion of macroporous volume.

Preparation of cost-effective and self-reinforced porous mullite ceramics for advanced heat insulation and sound absorption applications

Self-reinforcing porous mullite ceramics have attracted considerable attention in the field of insulation and sound absorption materials, due to their precise and controllable porous structure, high temperature and corrosion resistance, and low thermal conductivity. However, the high cost and relatively low performance obstruct their practical applications. In this work, self-reinforcing porous mullite ceramics were fabricated by utilizing construction waste via foam-gel casting and freeze-drying methods, and the impact of blowing agent dosage and sintering temperatures on the microstructures, sound absorption, and thermal insulation properties were systematically investigated. In addition, the related mechanism was also discussed in detail. The results show that, at a sintering temperature of 1000 °C and blowing agent dosage of 0.10 wt%, the self-reinforcing porous mullite ceramics can be successfully obtained, which exhibited a bulk density as low as 0.24 g/cm³ and porosity more than 90 %. Consequently, at a frequency of 2000 Hz, its absorption coefficient reached about 0.81. Furthermore, its thermal conductivity also decreased to about 0.06266 W/(m·K). This development not only unveils innovative avenues for the cost-effective fabrication of porous ceramics but also significantly broadens their potential applications within high-performance thermal insulation and sound absorption domains.

N-doped one-dimensional carbon framework embedded with CoSe2 nanoparticles as superior electrode for advanced sodium ion storage

Cobalt selenide (CoSe2) is acknowledged as a negative electrode material for sodium-ion batteries (SIBs) due to its high theoretical capacity. However, the significant volume change and inadequate electrochemical performance during charge and discharge processes have limited its practical use in batteries. In this investigation, a straightforward and practical electrospinning method combined with selenization reaction was utilized to fabricate CoSe2 nanoparticles enclosed in nitrogen-doped carbon nanofibers with a three-dimensional self-supporting network structure (CoSe2/N-PCNFs).The CoSe2/N-PCNFs electrode has self-supporting and high conductivity properties, as an anode material for sodium-ion batteries, the discharge capacity of the composite material can reach 450.1 mAh/g after 100 cycles at a current density of 0.2 A/g, and can still maintain a large discharge capacity of 396.9 mAh/g after 500 cycles at a high current density of 1 A/g. The outstanding electrochemical performance is mainly attributed to the superior specific surface area, controllable porous structure, and high pore volume of CoSe2/N-PCNFs Experimental and density functional theory calculations both indicate that the heterojunction interface between CoSe2 and nitrogen-doped carbon can not only promote the adsorption of Na+, but also facilitate electron transfer to significantly improve the rate capability of the material.

Fluorine Incorporation for Enhanced Gas Separation Performance in Porous Organic Polymers: Investigating Reaction Pathways and Pore Structure Control.

The precise control of pore structures in porous organic polymer (POP) materials is of paramount importance in addressing a wide range of challenges associated with gas separation processes. In this study, we present a novel approach to optimize the gas separation performance of POPs through the introduction of fluorine groups and figure out an important factor of reaction decision that whether the AlCl3-catalyzed polymerization is Scholl reaction or Friedel-Crafts alkylation. In the chloroform system, the steric hindrance of function groups could make direct coupling between the benzene rings difficult, which would lead to part solvent knitting (Friedel-Crafts alkylation) instead. The fluorinated polymers show enhanced surface area and pore size characteristics. Notably, the fluorinated polymers exhibited significantly improved adsorption and separation performance for SF6, as evidenced by an ideal adsorbed solution theory selectivity (SF6/N2, v: v = 50:50, 273 K) increase of 75.0, 668.8, and 502.8% compared to the nonfluorinated POPs. These findings highlight the potential of fluorination as a strategy for tailoring the properties of POP materials for advanced gas separation applications.

In-situ growth of novel iron oxide/iron organic framework composites as efficient electroactive materials of battery supercapacitor hybrids

Iron oxide (Fe2O3) with a high theoretical capacitance, wide potential ranges and easy availability has attracted much attentions as the electrode material of battery supercapacitor hybrids (BSH). Metal–organic framework (MOF) is one of the promising potential energy storage materials due to its large surface area and controllable pore structures. In this work, novel iron oxide/iron organic framework composites (Fe2O3/FeMOF) are in-situ grown on the Ni foam as efficient energy storage electrodes of BSH. By tuning the solvothermal durations, the morphology changes from random sizes of sheets, regular grown vertical sheets, to flower-like structures. The d-spacing also increases for the Fe2O3/FeMOF synthesized using longer solvothermal durations. The optimal Fe2O3/FeMOF electrode synthesized using 9 h shows a high areal capacitance of 10.97 F/cm2 along with an areal capacity of 5.49 F/cm2 at the current density of 35 mA/cm2, owing to the most regular growth of sheets, the large d-spacing, and the smallest charge-transfer resistances. A BSH composed of the Fe2O3/FeMOF positive electrode and a graphene negative electrode shows a maximum energy density of 0.76 mWh/cm2 at 22.5 mW/cm2. The excellent long-term cycling stability with the capacitance retention of 85% and Coulombic efficiency of 98% are also achieved after 10,000 charge/discharge cycles.

Preparation Method and Application of Porous Poly(lactic acid) Membranes: A Review.

Porous membrane technology has garnered significant attention in the fields of separation and biology due to its remarkable contributions to green chemistry and sustainable development. The porous membranes fabricated from polylactic acid (PLA) possess numerous advantages, including a low relative density, a high specific surface area, biodegradability, and excellent biocompatibility. As a result, they exhibit promising prospects for various applications, such as oil-water separation, tissue engineering, and drug release. This paper provides an overview of recent research advancements in the fabrication of PLA membranes using electrospinning, the breath-figure method, and the phase separation method. Firstly, the principles of each method are elucidated from the perspective of pore formation. The correlation between the relevant parameters and pore structure is discussed and summarized, subsequently followed by a comparative analysis of the advantages and limitations of each method. Subsequently, this article presents the diverse applications of porous PLA membranes in tissue engineering, oil-water separation, and other fields. The current challenges faced by these membranes, however, encompass inadequate mechanical strength, limited production efficiency, and the complexity of pore structure control. Suggestions for enhancement, as well as future prospects, are provided accordingly.