Porous Composite Materials Research Articles

Synergistic Effects of Fe3O4/N-Doped Porous Carbon Nanospheres for Enhanced Oxygen Reduction Reaction.

Designing transition metal oxide (TMO)/porous carbon composite materials for the oxygen reduction reaction (ORR) is a promising strategy in high-performance fuel cell technology. In this study, we used the isolation effect and pore-creating properties of Zn2+ to fabricate a composite material comprising ultrasmall Fe3O4 particles anchored on hierarchically N-doped porous carbon nanospheres. This material, referred to as CPZ1.0-Fe0.1, serves as an efficient ORR electrocatalyst in alkaline fuel cells. CPZ1.0-Fe0.1 exhibits outstanding ORR catalytic activity with a half-wave potential of 0.86 V in a 0.1 M KOH solution, surpassing that of the Pt/C catalyst (0.82 V). Furthermore, CPZ1.0-Fe0.1 exhibited excellent stability with minimal current degradation after 18 h of continuous testing. The superior ORR catalytic performance can be attributed to the synergistic effect between the catalytic sites and the high conductivity of porous carbon. The porous carbon nanospheres effectively address the low conductivity of Fe3O4 nanoparticles, while the ultra-small Fe3O4 nanoparticles anchored on the carbon surface provide efficient catalytic sites for the ORR.

Spatial confinement of MoS2 nanoparticles in jellyfish-inspired open-mouthed spheres for high-capacity and ultrafast-rate sodium-ion capture

Rational nanoscale structure engineering of electroactive nanoarchitecture is a very promising strategy for designing advanced capacitive deionization (CDI) materials. Herein, inspired by jellyfish physiological structure, open-mouthed MoS2/C hierarchical porous spheres were fabricated via direct-spray pyrolysis by adopting a strategy of coupling defective MoS2 with locally conductive network graphene quantum dots. Such a well-developed open-mouthed interconnected porous structure significantly stimulated the permeation of electrolyte ion the deep internal spaces of electrode, facilitated fast ion diffusion and provided abundant electrochemical adsorption sites, endowing the MoS2/C electrode with a remarkable desalination capacity of 118.83 mg g−1, an impressively rapid desalination rate of 51.35 mg g−1 min−1, and a good long-term cycle stability of 82 % after 50 cycles. This work inspires the design hierarchically porous composite materials with unique micro-nanostructures, offering a new viable route for the continuous and efficient production of CDI electrode materials.

PDMS-in-water emulsions stabilized by cellulose/chitin/starch nanoparticles for fabrication of oil adsorbents: A comparison study.

Pickering emulsion template has aroused attention in the fabrication of porous composite materials. In this work, six nanoparticles including cellulose nanofiber/nanocrystal (CNF/CNC), chitin nanofiber/nanocrystals (ChNF/ChNC) and waxy/normal corn nanocrystal (WSNC/CSNC) were comparatively studied for their performance in fabricating porous composites with PDMS via Pickering emulsion templates. Among all, CNF and ChNF exhibited best emulsion stabilizing ability, while ChNF and ChNC at optimized concentrations enabled the formation of high internal phase emulsions with long-term stability of over 300days. WSNC and CSNC with poorest emulsion stabilizing ability failed to obtain porous composites while the other four particles all formed porous composites with PDMS. The ChNF and ChNC composites displayed highest hydrophobicity, followed by the CNC composite. As adsorbents for diesel oil, the ChNF composite showed the highest adsorption capacity and adsorption selectivity, which could be easily recycled by simple mechanical squeezing. At optimized PDMS fractions, the ChNF composite could achieve continuous oil-water separation under vacuum with a highest separation efficiency of 98.9% at high flux of 8862L/h·m2. This study revealed the association between nanoparticles and their composite materials fabricated from Pickering emulsion template, hopefully broadening the application of natural polymers in water treatment and related fields.

Determination of Crack Depth in Brickworks by Ultrasonic Methods: Numerical Simulation and Regression Analysis

Ultrasonic crack detection is one of the effective non-destructive methods of structural health monitoring (SHM) of buildings and structures. Despite its widespread use, crack detection in porous and heterogeneous composite building materials is an insufficiently studied issue and in practice leads to significant errors of more than 40%. The purpose of this article is to study the processes occurring in ceramic bricks weakened by cracks under ultrasonic exposure and to develop a method for determining the crack depth based on the characteristics of the obtained ultrasonic response. At the first stage, the interaction of the ultrasonic signal with the crack and the features of the pulse propagation process in ceramic bricks were considered using numerical modeling with the ANSYS environment. The FEM model allowed us to identify the characteristic aspects of wave propagation in bricks and compare the solution with the experimental one for the reference sample. Further experimental studies were carried out on ceramic bricks, as the most common elements of buildings and structures. A total of 110 bricks with different properties were selected. The cracks were natural or artificially created and were of varying depth and width. The experimental data showed that the greatest influence on the formation of the signal was exerted by the time parameters of the response: the time when the signal reaches a value of 12 units, the time of reaching the first maximum, the time of reaching the first minimum, and the properties of the material. Based on the regression analysis, a model was obtained that relates the crack depth to the signal parameters and the properties of the material. The error in the predicted values according to this model was approximately 8%, which was significantly more accurate than the existing approach.

Drying Kinetics and Sorption Isotherms of Biocomposite Materials: Experimental Investigation and Modeling Analysis.

Modern materials science has made significant progress in creating new materials and processes for waste recovery. One such advancement involves the development of a new porous composite material made from clay and an environmentally sustainable eggshell powder. In this study, the dynamic behavior of water vapor during desorption and adsorption processes within this composite material was investigated. The moisture diffusivity coefficient was determined within the clay/eggshell powder composite material. The drying kinetic data were analyzed using various models such as Newton, Page, and Wan and Singh. The static gravimetric vapor adsorption/desorption experiments were conducted at different temperatures (30, 40, 50, 60, and 70 °C) to depict the material's capacity for absorbing and releasing moisture over time. The experimental isotherm data were fitted using different mathematical models (Guggenheim, Anderson, and De Boer, Peleg, Adam and Shove, Oswin, and Modified Henderson). The findings suggest that integrating eggshell powder with clay can significantly influence the behavior and characteristics of the resultant material. The combination of eggshell powder and clay reduces moisture sorption and accelerates the drying process. Consequently, this affects the porosity, permeability, and response to humidity changes.

Porous flexible molecular-based piezoelectric composite achieves milliwatt output power density

Molecular ferroelectrics have made breakthrough progress in intrinsic piezoelectric response that can be on par with advanced inorganic piezoelectric ceramics. However, their successful applications in high-density energy harvesting and self-powered flexible devices have been great challenge, owing to the low elastic moduli, intrinsically brittle, and fracture proneness of such material systems under mechanical loading. Here, we have developed a flexible porous composite piezoelectric material by using soft thermoplastic polyurethane (TPU) and molecular ferroelectric materials. Benefiting from the porous structure of TPU, the flexible piezoelectric composites enable effectively large doping ratio (50%) of [Me3NCH2Cl]CdCl3 (TMCM-CdCl3) and highly efficient stress absorption, coupled with the excellent piezoelectric properties of TMCM-CdCl3, to realize a superior power density (636.9 µW cm−2 or 1273.9 µW cm−3). This output is 2000 times higher than that of flexible piezoelectric materials represented by poly(vinylidene fluoride) (PVDF). We believe that the outstanding performance of the porous composite piezoelectric material would pave a feasible way for real industrial applications of molecular ferroelectrics.

Characterisation and simulation of a general ventilation filter based on a double porosity approach

The air filters installed in ventilation systems are designed for collecting dust and particles. These filters usually consist in folded paper or textile, arranged either as a flat slab or in a V-shape frame. Some of them may also contain activated carbon in order to remove molecular compounds. Experimental results show that they can significantly attenuate the upstream sound sources such as fans or other regenerated noise. Though, these acoustic properties are not strictly speaking designed and often result from the tailored filtering capacities. The present work proposes a three-stage methodology to design and optimize the acoustic performance of these filters. The first stage is the characterization of the intrinsic acoustic parameters of the paper or textile. The second stage consists in the validation of these parameters regarding sound attenuation as measured in impedance tube. This includes analytical and finite element computations to correctly account for the mounting conditions of the specimen in the impedance tube. The final stage consists in predicting the sound attenuation measured on the full-size filter, set in shape using the porous composite material theory. The obtained results provide a satisfactory correspondence allowing for an accurate design at an early stage of the project.

Preparation of Porous Composite Materials through Silicon Component Foaming and Special Heat Treatment.

This study proposes a foaming method along with calcination to produce silica-based porous materials. The high-silicon-content waste residue reacts with sodium hydroxide for hydrogen evolution foaming reactions. Then, the foaming green bodies are embedded and calcined in the calcination powder consisting of silicon, silicon carbide, graphite, and activated carbon at 1200 °C. The calcination powder creates a reducing atmosphere and prevents adhesion of the foaming green bodies to the crucible during calcination. Furthermore, the addition of activated carbon and calcination improve the macroporosity issue of the prepared sample through a gas-liquid-solid transformation. The BET surface area measurement is 64.197 m2/g, and the mercury intrusion porosimetry measurement indicates a porosity of 56.48%, with an average pore diameter of 396.48 nm. The porous composite materials exhibit the capability to adsorb methylene blue in solution. The porous materials possessing functional groups suggest promising potential for future development and application prospects.

Multiscale dynamic behavior of imperfect hybrid matrix/fiber nanocomposite nested conical shells with elastic interlayer

This investigation delves into the free vibration characteristics of coupled nested conical shells (CNCSs) made of porous composite materials. These two conical shells are connected by a mid-layer of elastic springs. The composite materials used in the shells consist of epoxy, nanofillers, and fibers. Two types of nanofillers are considered: Graphene Nanoplatelets (GNPs) and Carbon Nanotubes (CNTs), while E-glass fiber is used as the fiber. The nanofillers are distributed in four different patterns within the shell section. Porosity is uniformly distributed along the shell section and characterized by a coefficient. The rule of mixtures is employed to ascertain the equivalent material properties of the hybrid materials, while the Chamis approach is utilized for three-phase materials. First-order shear deformation theory (FSDT) and Donnell's theory are utilized for modeling the conical shells. The governing equations of motion are established through Hamilton's principle are solved using the generalized differential quadrature method (GDQM). Seven different boundary conditions (BCs) are considered to encompass the full range of BCs for CNCSs and four type of BCs for single truncated conical shell (STCS). The solution's accuracy is verified, and the effects of various parameters on the natural frequency parameter (NFP) of the shell are investigated, such as BCs, circumferential wave number (n), nanofillers pattern, semi-vertex angle, nanofillers angle, and mid-layer stiffness. Initially, a comprehensive investigation into the vibration behavior of a STCS is presented, followed by an analysis of the NFP of the CNCSs. The results demonstrate that the stiffness of the elastic mid-layer significantly influences the NFP of the system. The orientation of the nanofillers in the shell can increase or decrease the NFP. Additionally, the relationship between mode number and n depends on the type of BCs of the shells.

Fundamental mechanical relations of open-cell metal foam composite materials with reticular porous structure

The compressive behavior is one of the most fundamental mechanical properties for engineering materials. In this paper, the octahedral structure model of porous materials is used to evolve the mechanical analysis model under compressive loading for the porous composite materials, which are resulted from reticular metal foams with pore struts presenting multilayered structure. Starting from this analysis model, some fundamental mechanical relationships, including those of the safe load-bearing and overall strength, have been deduced for these porous composite materials. The compressive strength has been characterized for the porous composite body, corresponding to the overall failure caused by the prior breakage of the strut core and by the prior breakage of the strut shell, respectively. The nickel foam products manufactured on the production line of enterprise were used to make porous composite materials by coating the pore struts with epoxy resin, and the metal foam composite material was obtained with the composite pore-struts of metal/resin multilayered structure. Using this porous composite material for compression experiments, it is found that the experimental data match well with the mathematical relationship from the present theoretical model. The results verify the feasibility of this analysis model and the practicality of the relevant mathematical relationship.

Selective electro-capacitive deionization of Yb(III) by nanospherical N-doped carbon supported nickel‑iron bimetallic oxide, nitride and phosphide

The separation of rare earth elements from the mining waste water is highly important but still facing challenge. In this study, three different porous composite electrode materials were well-designed by decorating the nickel‑iron bimetallic oxide, nitride or phosphide onto nitrogen-doped carbon nanosphere, respectively (termed as NiFeO@NC, NiFeN@NC and NiFeP@NC), and utilized in capacitive deionization device for electrosorption of Yb(III) from water under the low-voltage electric field. The characterization and electrochemical results indicated that the incorporation of N or P atom lead to the reduced specific surface area and the enhanced electrochemical properties (i.e., larger specific capacitance, lower charge transfer resistance). In addition, NiFeN@NC and NiFeP@NC exhibited the excellent electrosorption capacities of Yb(III) with 105.24 mg·g−1 and 90.31 mg·g−1, respectively, under conditions of a flow rate of 20 mL·min−1, a voltage of 1.2 V, and pH of 5.0, which was extremely higher than NiFeO@NC (i.e., 50.7 mg·g−1). Moreover, all these three materials also demonstrated the remarkable electrosorption selectivity of Yb(III) from the mixed solution, and the robust durability with over 90 % of initial capacities after ten consecutive electrosorption-desorption cycles. Furthermore, the XPS characterizations and electrosorption results revealed that the electrosorption mechanism mainly depended on the synergistic effects of intrinsic Faraday redox reaction, electric double layer capacitance and active binding sites. Therefore, this work provided a feasible strategy for the separation of rare earth elements from aqueous solution, and the prospective applications related to the recovery of rare earth elements from mining wastes or spent permanent magnets in future life.

Study on Two Inorganic Consumables in PMMA Electrochromic Devices Based on Work Function Differences

In electrochromic devices, the dielectric layer is not only an electrode dielectric, but also can provide compensating ions for electrochromism. In this paper, three composite porous materials, PMMA/SiO2, PMMA/TiO2, and PMMA/SiO2/TiO2, were prepared and assembled using polymethyl cellulose (PMMA) as the polymer matrix, impurity medium (SiO2) and titanium dioxide (TiO2) inorganic polymers, and the effect of doping two inorganic porous materials on the electrochromic performance was studied. The optical recovery and cycle stability of electrochromic wear of the PMMA/SiO2/TiO2 composite structure are significantly improved compared with the loss of other ceramic structures. Cyclic voltammetry analysis shows that the lithium ion diffusion coefficient of the electrochromic device using the PMMA/SiO2/TiO2 composite ceramic structure is the largest, which is 2.5 × 10−14 cm2​ s−1 . The improvement of electrochromic performance is mainly due to the difference in work function between SiO2 and TiO2 on the figure of merit diagram, which leads to the directional movement of the resonator, accelerates the transmission rate of Li+ and further optimizes the electrochemical properties of the composite ceramic. This study provides an effective method to improve the performance of electrochromic devices.

Clarifying the Impact of Electrode Material Heterogeneity on the Thermal Runaway Characteristics of Lithium‐Ion Batteries

The safety and efficiency of lithium‐ion batteries (LIBs) suggest a promising future for this technology, particularly in the automobile industry. However, thermal runaway—wherein a LIB undergoes an uncontrollable increase in temperature that may result in smoke, fire, or explosion—represents an important and widely studied failure type. Since the electrodes of LIBs are manufactured from porous composite materials, their heterogeneity can significantly influence the effective material characteristics and microscale behaviors of LIBs during operation. Microstructure geometric and electrochemical–thermal models are typically used to investigate these impacts. Herein, a microstructure geometric model is constructed of LIB's electrodes. A virtual multiphysics model is used to simulate the overcharging thermal runaway condition. The model's accuracy is validated through real‐world experiments. The model shows greater accuracy compared to the result from a conventional homogeneous geometric model and better reflects the heterogeneous internal phenomenon. The model is applied to a variable analysis in order to investigate how the varying heterogeneity of the cathode's porosity impacts the cell during overcharging thermal runaway behavior. Our results indicate that decreasing porosity heterogeneity at the cathode may delay thermal runaway, owing to the heterogeneous impact on particle diffusion behaviors and the side reaction rate.

Multifunctional Chitosan Nanofiber-Based Sponge Materials Using Freeze-Thaw and Post-Cross-Linking Method.

The fabrication of porous sponge materials with stable structures via cross-linking diverse polymers presents significant challenges due to the simultaneous requirements for phase separation as a pore-forming step and cross-linking reactions during the fabrication process. To address these challenges, we developed a sponge material solely from natural-based polymers, specifically chitosan nanofibers (CSNFs) and dialdehyde carboxymethyl cellulose (DACMC), employing a straightforward, eco-friendly technique. This technique integrates a facile freeze-thaw method with subsequent cross-linking between CSNFs and DACMC. This method effectively addresses the difficulties associated with pore formation in materials, which typically arise from the rapid formation and precipitation of polyionic complexes during the mixing of anionic and cationic polymers, using ice crystals as a rigid template. The resultant sponge materials exhibit remarkable shape recoverability in their wet state and maintain light, stable porosity in the dry state. Furthermore, in comparison to commonly used commercial foams, this composite porous material demonstrates superior fire retardancy and thermal insulation properties in its dry state. Additionally, it shows effective adsorption capacities for both cationic and anionic dyes and metal ions. This method of using biobased polymers to produce porous composites offers a promising avenue for creating multifunctional materials, with potential applications across various industries.

Unraveling the impact of pore length on the conversion reaction of Fe3O4/carbon anodes in lithium-ion batteries

Despite numerous studies investigating Fe3O4/porous carbon anode materials for high-performance lithium-ion batteries (LIBs), the inherent limitations of the Fe3O4 conversion reaction, such as low reversibility and sluggish kinetics, continue to pose significant challenges. While modifying the porous structure of Fe3O4 anodes has demonstrated considerable promise in overcoming these limitations, the precise relationship between the porous structure and Fe3O4 conversion behavior still remains unclear. Here, we explore the impact of the pore length of the anode active material on the electrochemical performance of LIBs. Using two different composites of Fe3O4 and porous carbon with varying pore lengths as model materials, we conduct various in-depth electrochemical and ex-situ analyses. Our findings confirm that a shorter pore length facilitates higher Li+ ion diffusivity compared to longer pore length. Consequently, the conversion reaction of Fe3O4 to Fe and Li2O during lithiation process can be expedited, leading to a decrease in the resistance at the solid electrolyte interphase. As a result, we demonstrate that shortening the pore length of the porous anode composite materials can enhance the initial Coulombic efficiency (CE), reversible capacity, and rate capability of LIBs.

Endowing Three-Dimensional Porous Wood with Hydrophobicity/Superhydrophobicity Based on Binary Silanization.

Wood, as a natural biomass material, has long been a research focus. Superhydrophobic modified wood, in particular, has shown great promise in a myriad of engineering applications such as architecture, landscape, and shipbuilding. However, commercial development has encountered significant resistance due to preparation difficulties and sometimes unsatisfactory performance. In this study, hydrophobic/superhydrophobic wood comodified with methyltrimethoxysilane (MTMS) and 1H,1H,2H,2H-perfluorodecyltrimethoxysilane (PFDTMS) was fabricated by a one-step sol-gel method that uses an in situ growth process. Low-molecular-weight MTMS was allowed to permeate the three-dimensional porous wood interior. Then, acid-base catalysts were used to regulate the hydrolytic condensation process of MTMS and PFDTMS composite silanes to generate micro/nano hierarchical structures with low surface energy on the wood surface. The physicochemical characteristics of modified wood were investigated and the reaction mechanism established. The modified wood displayed excellent internal hydrophobicity/surface superhydrophobicity, water-moisture resistance, and dimensional stability at low fluorine concentrations. The resulting superhydrophobic surface provided stain resistance, self-cleaning ability, and loading capacity in water while exhibiting good mechanochemical stability; wood mechanical strength was also enhanced. This methodology created a superhydrophobic surface and bulk hydrophobization of wood in one step. Beyond wood, this approach is expected to provide a promising approach for functional modification of other porous composite materials.

Synthesis and characterization of Ag/Cu dual-metal-functionalized porous Bi2WO6 microsphere with enhanced N2 photofixation

Semiconductor photocatalytic nitrogen reduction reaction (PNRR) stands as a promising clean technique for ammonia synthesis, yet it confronts numerous challenges. In this study, Ag nanoparticle-modified Cu-doped Bi2WO6 (ACB) porous composite materials with varying mass percentages were successfully synthesized using a solvothermal reduction approach. The incorporation of transition metal Cu effectively modulates the energy band position of Bi2WO6. Furthermore, the introduction of Ag nanoparticles significantly suppresses the recombination of photogenerated carriers. Without adding sacrificial agent, the photocatalytic nitrogen fixation yield of ACB reaches an impressive 184.93 μmol·g−1·h−1, which is 5.44 times higher than that of pristine Bi2WO6. A comprehensive analysis of the experimental results reveals that the combined effect of Cu doping and Ag nanoparticle loading endows ACB with an increased exposure of active sites, thereby significantly enhancing its photocatalytic nitrogen fixation performance. This research offers a promising approach for the design of metal nanoparticle-supported catalysts for PNRR, holding significant implications for the advancement of other material systems.

The synthesis of multi-level porous MOF composite materials with different MOF contents

To address the inherent limitations of current MOF synthesis, where pore size is restricted to micropores or small mesopores, we successfully synthesized MOF composite materials with well-developed porous structures using a self-template approach. These pores encompass not only the intrinsic micropores or small mesopores of MOFs but also the template-induced large pores. During the experimental process, we achieved the synthesis of composite materials with varying MOF contents by modifying experimental conditions. Through this design, we not only achieved selective adsorption of guest molecules but also significantly increased the porosity, thereby enhancing the mass transfer efficiency of guest molecules and the utilization rate of materials. This research breakthrough offers new insights and solutions for addressing critical issues in fields such as gas separation, energy storage, and catalysis.

The influence of B4C content on the pore structure of reaction-synthesized porous Ti3AlC2-TiB2 composite ceramics

Using a mixture of TiH2, Al, B4C, and graphite powders with a molar ratio of 3+2 m/1.2/m/2-m (where m ranges from 0 to 0.25, with increments of 0.05), porous Ti3AlC2-TiB2 composite ceramics were successfully synthesized through activated reaction sintering. The effect of B4C content on the phase composition, volumetric expansion, microstructure, and pore structure parameters (including pore size, porosity, and permeability) was systematically studied. When the molar ratio of B4C was less than 0.1, the volumetric expansion rate, average pore size, and permeability increased with the addition of B4C, reaching maximum values of −5.46 %, 2.23 μm, and 92.4 m3 m−2·10 kPa−1 h−1, respectively. Conversely, when the B4C molar ratio exceeded 0.1, the parameters related to the pore structure of the porous Ti3AlC2-TiB2 composite ceramics decreased, with minimum values of −10.40 %, 1.46 μm, and 68 m3 m−2·10 kPa−1 h−1, respectively. In addition, the pore formation mechanism of the porous Ti3AlC2-TiB2 composite ceramics was systematically explored. The revolution tendency of pores is related to the decomposition of TiH2, Kirkendall partial diffusion, diffusion between B and C, and the transition process of the final phase Ti3AlC2-TiB2. This research work could provide a reference for the preparation of the MAX phase composite porous materials.

Experimental Study on Convection Heat Transfer of CO2 in C/SiC Composite Porous Material at Subcritical, Transcritical, and Supercritical States

Using C/SiC as the structure for transpiration cooling is prospective for new hypersonic vehicles, based on clarification of heat transfer process in porous media. But there are still gaps due to the complexity of pore structure of C/SiC, together with the effects of capillary force and strong variation of thermophysical properties for subcritical and supercritical flow. In this study, heat transfer analysis for C/SiC with CO2 as the coolant is presented by experiments. Heat transfer characteristics in typical C/SiC sample under various mass flow rates (0.003–0.018 kg/s), inlet fluid temperatures (20–40 °C) and pressures (5.9–10 MPa) are analyzed. Heat transfer and pressure drop correlations have been developed. The results show heat transfer coefficient at supercritical state behaves non-monotonic under varying flow rates caused by the combined effect of sharp increase of specific heat and the change of flow rate. The effect of pressure on heat transfer can be neglected compared to that of flow rate, while for Reynolds number (Re) >100, the pressure drop of supercritical cases are smaller than that of phase-change cases under similar Re, due to the effect of capillary force in C/SiC. This study can provide basic support for further study of transpiration cooling using C/SiC and CO2.