Porous Skeleton Research Articles

Supercooling suppression and thermal conductivity enhancement of erythritol using graphite foam with ultrahigh thermal conductivity for thermal energy storage

The application of erythritol to medium-temperature latent heat energy storage systems is limited by its low thermal conductivity and large supercooling. Three types of graphite foams (GFs) with different thermal conductivities were used as the porous skeleton for encapsulating erythritol via vacuum impregnation, and the erythritol/GF composites were investigated using different methods to solve the aforementioned problems. The GF pores were effectively filled with erythritol via vacuum impregnation, and the filling rate of erythritol reached more than 90%. The thermal conductivity of the erythritol/GF composites was 73.80, 35.05, and 13.30 W/m·K. The thermal conductivity of the erythritol/GFs was improved by 26–158 times over that of pure erythritol. The subcooling degree of the erythritol/GF composites was reduced from 64.1 °C to 59.4 °C, facilitating the release of latent heat. The erythritol/GF composites had remarkably boosted thermal stability compared with that of pure erythritol. The developed erythritol/GF phase-change composite material exhibits excellent heat transfer and storage properties, and it has broad prospects in the field of phase-change heat storage at intermediate temperatures.

Boron-doped three-dimensional porous carbon framework/carbon shell encapsulated silicon composites for high-performance lithium-ion battery anodes

Deleterious volumetric expansion and poor electrical conductivity seriously hinder the application of Si-based anode materials in lithium-ion batteries (LIBs). Herein, boron-doped three-dimensional (3D) porous carbon framework/carbon shell encapsulated silicon (B-3DCF/Si@C) hybrid composites are successfully prepared by two coating and thermal treatment processes. The presence of 3D porous carbon skeleton and carbon shell effectively improves the mechanical properties of the B-3DCF/Si@C electrode during the cycling process, ensures the stability of the electrical contacts of the silicon particles and stabilizes the solid electrolyte interface (SEI) layer, thus enhancing the electronic conductivity and ion migration efficiency of the anode. The developed B-3DCF/Si@C anode has a high reversible capacity, excellent cycling stability and outstanding rate performance. A reversible capacity of 1288.5 mAh/g is maintained after 600 cycles at a current density of 400 mA g−1. The improved electrochemical performance is demonstrated in a full cell using a LiFePO4-based cathode. This study presents a novel approach that not only mitigates the large volume expansion effects in LIB anode materials, but also provides a reference model for the preparation of porous composites with various functionalities.

Unraveling the Nucleation and Growth Mechanism of Potassium Metal on 3D Skeletons for Dendrite-Free Potassium Metal Batteries.

Designing three-dimensional (3D) porous carbonaceous skeletons for K metal is one of the most promising strategies to inhibit dendrite growth and enhance the cycle life of potassium metal batteries. However, the nucleation and growth mechanism of K metal on 3D skeletons remains ambiguous, and the rational design of suitable K hosts still presents a significant challenge. In this study, the relationships between the binding energy of skeletons toward K and the nucleation and growth of K are systematically studied. It is found that a high binding energy can effectively decrease the nucleation barrier, reduce nucleation volume, and prevent dendrite growth, which is applied to guide the design of 3D current collectors. Density functional theory calculations show that P-doped carbon (P-carbon) exhibits the highest binding energy toward K compared to other elements (e.g., N, O). As a result, the K@P-PMCFs (P-binding porous multichannel carbon nanofibers) symmetric cell demonstrates an excellent cycle stability of 2100 h with an overpotential of 85 mV in carbonate electrolytes. Similarly, the perylene-3,4,9,10-tetracarboxylic dianhydride || K@P-PMCFs cell achieves ultralong cycle stability (85% capacity retention after 1000 cycles). This work provides a valuable reference for the rational design of 3D current collectors.

Influence of Starting Reagents on the Formation of Ti3SiC2 Porous Skeleton by SHS in Air

Influence of Starting Reagents on the Formation of Ti3SiC2 Porous Skeleton by SHS in Air

Vertical and Horizontal Double Gradient Design for Super‐Slippery and High‐Bearing Hydrogel Skeleton

AbstractHydrogels with excellent hydrophilicity, high water content, outstanding biocompatibility, and lubrication properties are among the promising articular cartilage replacement materials. Despite extensive research focus on lubrication of hydrogels, realization of bioinspired materials with high load‐bearing, low‐friction, extraordinary lubrication, and anti‐wear properties is challenging. Herein, robust lubrication can be realized by structuring vertical and horizontal dual gradient surfaces, with structural design in vertical direction gradually transitioning from an anisotropic tubular to a compact body to provide load‐bearing, and a surface rigid porous polymer skeleton and a filled loose lubricating polymer structural design to provide lubrication in horizontal direction. What is more, gradient transition region in vertical direction greatly weakens gradient layer interface stress to increase load‐bearing, and gradient surface in horizontal direction is constructed by interconnected surface rigid polymer skeleton containing “pockets” that house highly hydrated and mechanically fragile soft lubrication polymer to prevent removal of lubrications under high load and wear. The designed hydrogel has an extremely low coefficient of friction (COF) with hard steel (COF ≈0.0036, 50 N, 35,000 cycles) and achieves a balance between lubrication and load bearing. The work opens up an avenue for rational design of high load‐bearing and ultralow friction soft material surfaces.

Seaweed─Modification of Si by Natural Nitrogen-Doped Porous Biochar for High-Efficiency Lithium Batteries.

Due to the porous structure and high electrical conductivity of carbon materials, lithium-ion batteries (LIBs) frequently employ carbon cladding to modify silicon anodes. However, the high cost and convoluted manufacturing process have prevented widespread use of carbon-based materials. Due to the abundance of seaweed (Gelidium amansii: GAm), there is a developing interest in seaweed's additional uses. We present, for the first time in lithium-ion batteries, the modification of silicon anodes by algal biomass carbon, which was thoroughly analyzed morphologically, structurally, and electrochemically. Seaweed's biomass carbon is porous and highly linked, making it ideal for evenly enclosing silicon nanoparticles and supplying the porous carbon skeleton with sufficient nitrogen after annealing. The Si@ self-encapsulated naturally nitrogen-doped biochar prepared from seaweed composites displayed reversible capacities of 1111.61 mAh g-1 after 500 cycles at a high current of 1 A g-1 and 714.08 mAh g-1 after 1000 cycles at the same current density.

Ultra-stable hollow nanotube conjugated microporous polymer incorporating fluorenyl moieties for Co-capture of PM and CO2

Conjugated microporous polymers have a highly delocalized π-π conjugated porous skeleton connected by covalent bonds, which can combine their excellent stability with high adsorption, in order to be applied to the study of co-capture of harmful particulate matter (PM) and carbon dioxide (CO2) under high temperature and high humidity conditions. In this paper, fluorene-based coupled conjugated microporous polymers (D-CMPs) with functionalized hollow nanotubes and abundant microporous structures were proposed. Through mechanism exploration and molecular electrostatic potential (MESP) calculation, the capture efficiency, adsorption capacity and selectivity of PM and CO2 in the waste gas stream of carbon-based combustion were analyzed. The results indicate that D-CMPs, with their rigid carbon-based π-conjugated framework, exhibit excellent tolerance under prolonged high-humidity conditions, with a capture efficiency exceeding 99.87% for PM0.3 and exceeding 99.99% for PM2.5. Meanwhile, based on its chemical/thermal stability, it can realize the recycling of adsorption-regeneration. On this basis, the "slip effect" induced by the open three-dimensional hierarchical porous structure of D-CMPs significantly enhances airflow dispersion and improves gas throughput (with a minimal permeation resistance of only 15 Pa). At a pressure of 1 bar and a temperature of 273.15 K, D-CMP-2 exhibited a CO2 adsorption capacity of up to 2.69 mmol g−1. The fitting results of three isothermal adsorption models demonstrate that D-CMPs exhibit an outstanding equilibrium selectivity towards CO2. Therefore, prior to the widespread adoption of low-carbon and clean energy technologies, porous solid materials exhibiting excellent structural stability, equilibrium selectivity, environmental tolerance, and high adsorption capacity emerge as optimal candidates for the treatment of industrial waste gases.

Direct synthesis of porous aluminum nitride foams for enhancing heat transfer and anti-leakage performance of phase change materials

Organic phase change materials (PCMs) suffer from low thermal conductivity and easy leakage, which limit their application in heat storage and thermal management. In this work, porous AlN skeletons were synthesized to solve these problems of paraffin PCM. Using Al powders as raw material, porous AlN skeletons were prepared through the ice-templated method and the direct nitridation reaction. The skeletons were impregnated with paraffin to prepare phase change composites (PCCs). The thermal conductivity of the PCC with 55.6 wt% AlN reaches 9.1 W m−1 K−1 in the axial direction, which is 4550 % of paraffin. This PCC retains a high enthalpy of 105 J g−1 and has good thermal stability. Moreover, the porous AlN skeletons can effectively absorb paraffin so that all PCCs maintain a stable shape. This study provides a simple and efficient method to synthesize porous AlN and to solve the heat conduction and leakage issues of PCMs.

Fabrication of MAX‐Phase Composites by Novel Combustion Synthesis and Spontaneous Metal Melt Infiltration: Structure and Tribological Behaviors

In this work, a new scheme is developed and experimentally tested for fabricating family of MAX–metal composites. This scheme combines the combustion synthesis (CS) process to obtain a porous MAX‐phase skeleton and process of metal melt infiltration spontaneously, which is then used to fabricate Ti3SiC2–TiC–Sn and Ti3SiC2–TiC–(Sn–Pb) composites. The resultant composite samples have an uneven density along the length, which steadily decrease from the point of contact of the sample with the molten tin to the opposite edge. Existence of Ti3SiC2, TiC, Sn, and (Sn and Pb) phases in the composite samples is confirmed using X‐ray diffraction and energy‐dispersive spectroscopy analyses. Comparative tribological characterizations are performed on fabricated Ti3SiC2–TiC–Sn and Ti3SiC2–TiC–(Sn–Pb) composite samples. Herein, these results are compared against standalone Sn and Sn–Pb samples as baseline and reveal major differences in friction and wear mechanisms due to addition of select MAX phases via novel CS process. As a whole, in the present study, a novel synthesis process is established to fabricate MAX‐phase composites and its enhanced tribological behavior and wear mechanisms which can have plethora of applications ranging from aerospace, automotive to biomedical sectors, are validated.

MnO2 porous carbon composite from cellulose enabling high gravimetric/volumetric performance for supercapacitor

Preparing electrode material integrated with high gravimetric/volumetric capacitance and fast electron/ion transfer is crucial for the practical application. Owing to the structural contradiction, it is a big challenge to construct electrode material with high packing density, sufficient ion transport channels, and fast electronic transfer pathways. Herein, MnO2 porous carbon composite with abundant porous structure and 3D carbon skeleton was facilely fabricated from Linum usitatissimum. L stems via NaOH activation and MnO2 introduction. The in-situ introduced MnO2 not only increases the packing density and the electrical conductivity of the porous carbon but also provides more active sites for oxidation reactions. These unique characteristics endow the resultant MnO2 porous carbon composite with remarkable gravimetric capacitance of 549 F g−1, volumetric capacitance of 378 F cm−3, and capacitance retention of 54.9 %. Giving the simple process and low cost, this work might offer a new approach for structural design and the practical application of high-performance electrode materials.

Pore-scale Simulation of Two-phase Flow in Foamed Porous Materials

This paper establishes a pore cell model of foamed silicon carbide material based on a tetradecahedron structure, and uses FLUENT software to numerically study the flow rate and pressure drop changes in the porous structure at different flow rates and the gas-liquid two-phase flow state of the channel. The research results show that the porous skeleton structure has a great influence on the velocity and pressure distribution in the calculation domain; the inlet flow velocity has a certain impact on the gas-liquid mixing zone and gas-liquid interface area in two-phase flow. The application of tetradecahedral porous media increases the thickness of the gas-liquid mixing zone and the phase interface area are increased, with a maximum increase of 11.5%, thus promoting gas-liquid heat and mass transfer.

Preparation of lithium iron phosphate battery by 3D printing

Three-dimensional (3D) printed batteries are considered a special class of energy storage devices that allow flexible control of the electrode structure on a microscopic scale, which is crucial to improving the energy density of miniaturized devices. In this study, lithium iron phosphate (LFP) porous electrodes were prepared by 3D printing technology. The results showed that with the increase of LFP content from 20 wt% to 60 wt%, the apparent viscosity of printing slurry at the same shear rate gradually increased, and the yield stress rose from 203 Pa to 1187 Pa. The rheological property and printability of the slurry show that the printing slurry of 40 wt% LFP has excellent conformal property and self-supporting property. Due to the porous skeleton shortening the transfer distance of ions and electrons and enhancing the efficiency of the electrode reaction, the rate performances and cycle stability of LFP batteries were improved. The 3D-printed battery containing an active material loading of 15.9 mg cm−2 achieved a specific capacity of 121.7 mA h g−1 at 0.5C after 200 cycles and coulombic efficiency higher than 99.7 %, and the LFP battery had an energy density of 350 W h kg−1. These results suggest that 3D printing is an effective strategy for developing batteries with high active material loadings and energy densities at micro sizes.

Structure and properties study of magnesium oxide porous ceramics prepared by Organic Foam Template Method

Magnesium oxide (MgO) porous ceramics with high porosity, compressive strength and low thermal conductivity were prepared by Organic Foam Template Method. The effects of the sintering temperature, polycarboxylic acid (PCE) dispersant and pore size of organic foam template on the properties of MgO porous ceramics were investigated. The experiment results showed that with the increase of sintering temperature, the MgO porous ceramic shrinkage, skeleton density and compressive strength increased. PCE could increase the fluidity of slurry and make the framework clearer, as well as reduce the cracks formed in the process of drying effectively. When the content of PCE was 0.5 wt-%, the porosity, compressive strength and thermal conductivity of MgO porous ceramics were 88.5%, 1.6 MPa and 0.045 W/(m·K), respectively. In addition, as the pore size of the organic foam template decreased, the porosity decreased, and the resistance increased and the thermal conductivity increased.

Bismuth Nanoparticles Encapsulated in a Porous Carbon Skeleton as Stable Chloride-Storage Electrodes for Seawater Desalination

Cost-effective bismuth (Bi) boasts a high theoretical capacity and exceptional selectivity towards Cl- ion storage, making it a promising material for desalination batteries (DBs). However, the substantial volume expansion and low conductivity severely hinder the cycling performance of Bi-based DBs. In this study, a carbon-layer-coated Bi nanocomposite (Bi@C) was synthesized by pyrolyzing a metal–organic framework (Bi-MOF) containing Bi using a straightforward method. The results show that the Bi@C synthesized under the condition of annealing at 700 °C for 2 h has the optimum properties. The Bi@C has good multiplication performance, and the desalination capacity is 106.1 mg/g at a high current density of 1000 mA/g. And the material exhibited a high desalination capacity of 141.9 mg/g at a current density of 500 mA/g and retained 66.9% of its capacity after 200 cycles. In addition, the Bi@C can operate at a wide range of NaCl concentrations from 0.05 to 2 mol/L. The desalination mechanism analysis of the Bi@C revealed that the carbon coating provides space for Bi particles to expand in volume, thereby mitigating the issues of electrode material powdering and shedding. Meanwhile, the porous carbon skeleton establishes electron and ion channels to enhance the electrode material’s conductivity. This research offers a promising strategy for the application of chloride-storage electrode materials in electrochemical desalination systems.

Facile construction of superhydrophobic/superoleophilic melamine sponges with durability and antifouling for selective oil absorption and effective oil/water separation

The manufacturing techniques of superhydrophobic/superoleophilic materials typically involve complicated processes. To address the issue, tannic acid, 3–aminopropyltriethoxysilane, and hexadecyltrimethoxysilane were used as primary ingredients to construct 3D superhydrophobic/superoleophilic melamine sponges by a facile one–step biomimetic method. The surface morphologies and functional composition of the modified 3D melamine sponges were characterized by scanning electron microscope, energy dispersive spectrometer, Fourier transform infrared spectroscopy, and X–ray photoelectron spectroscopy, respectively. The wetting performance of the modified 3D melamine sponge was estimated by measuring the water contact angle and oil contact angle. The water and oil contact angle were determined to be 155.4° and 0°, suggesting that the modified sponge showed superhydrophobic/superoleophilic performance. The modified sponge also presented remarkable self-cleaning and antifouling performance. As a result of porous skeleton and resilience of the melamine sponge, the superhydrophobic/superoleophilic sponge possessed outstanding oil absorption capacity and recycling durability. The modified sponge exhibited absorption capacities ranging from 38.43 g/g to 194.62 g/g for the chosen absorbents. The recycling absorption capacity for diesel and chloroform remained at 94.32% and 97.76% of their initial absorption capacity after 20 cycles. In addition, the modified sponge could also be used to separate oil and water continuously. The continuous separation efficiency for the mixture of diesel/water and chloroform/water could reach 98.52% and 99.42%, respectively. Therefore, the modified sponge shows considerable potential for practical application in oil/water separation.

Constructing a novel porous skeleton based on polycarbonate/expandable graphite for phase change materials with improved flame retardancy and shape stability

Phase change materials (PCMs) have been utilized in thermal management to stabilize the temperature and improve the fire safety of operating electronics. Paraffin wax (PW) is usually used as PCMs due to its high latent heat, stable performance, environmental friendliness, and low cost. However, PW has inherent weakness of easy leakage and high flammability. In this work, a porous skeleton composed of polycarbonate (PC) and expandable graphite (EG) was innovatively fabricated, and then the skeleton was applied to construct PCMs with enhanced flame retardancy and reduced leakage of PW by absorbing PW and triphenyl phosphate (TPP) into the PC-EG skeleton. The phase change performance, fire safety, and thermal management capacity of the PC-based PCMs were characterized. The results showed that at the loading ratio of PW/TPP = 3/1, the PC-based PCMs had a leakage ratio of only 0.26 % and a latent heat of 94.1 J g−1. The peak heat release rate (pHRR) and total heat release (THR) of the PC-EG/(PW/TPP-3:1) sample were decreased by 58.8 % and 39.1 %, respectively compared with that of the PC-EG/PW sample. The char residue was increased to 10.0 % from 5.0 % by the presence of TPP. The as-prepared PCMs exhibited high thermal management ability in the pouch cell operation. It is suggested that the PC/EG skeleton have never been used in PCMs for the improvement of flame retardancy and shape stability. This work provides a feasible method to fabricate PC-based PCMs with excellent flame retardancy, shape stabilization, and high phase change efficiency, which has great potential to produce ideal thermal management materials.

Honeycomb-like porous copper with pleated surface for supporting phase change material with enhanced thermal conductivity and solar thermal storage performance

Paraffin wax (PW) is concerned in the field of thermal storage because of its high thermal storage density, but it generally has problems such as low thermal conductivity, poor shape stability, and low solar absorption, which limit its application in solar thermal storage and thermal management. In this study, a honeycomb-like 3D porous Cu skeleton with a pleated surface was prepared by the salt template method, and the phase change composites (PCCs) were prepared using this 3D thermal conductive skeleton to support PW. The honeycomb-like porous structure with pleated surface has positive effects on the shape stability and solar-thermal conversion of PW. The thermal conductivity, leakage resistance, and solar-thermal conversion efficiency of the PCCs were significantly improved. Among them, the thermal conductivity of PW@PSHCPC2 reached 3.3 Wm−1 K−1, which was 16.5 times higher than that of PW, and the solar-thermal conversion efficiency reached 89.2 %, and a stable current of 61.8 mA was generated in the solar thermal power generation experiment. These results show that these PCCs have great potential for applications in several fields such as solar thermal storage, waste heat recovery, solar power generation, and electronic thermal management.

Research on preparation and related properties of macro-micro porous mullite ceramic skeletons via twice pore-forming technology.

A lot of solid waste coal gangue is produced every year in the process of coal mining and coal washing, which poses a great threat to human health. How to deal with coal gangue properly is still a serious problem. In this study the macro-micro composite porous mullite ceramic skeletons were successfully prepared using solid waste coal gangue and α-Al2O3 as main raw materials via twice pore-forming technology. The main phase composition of the porous ceramic skeletons was mullite tested by X-ray Diffractometer (XRD). The morphology and microstructure of the porous ceramic skeletons were analyzed by Scanning Electron Microscope (SEM). The results show that the microstructure of porous ceramic skeletons was mainly composed of mullite whiskers. With the increase of sintering temperature from 1200 °C to 1350 °C, the maximum length of mullite whiskers grew up from 2.68 μm to 8.10 μm and their average length grew up from 0.78 μm to 2.98 μm. The maximum compressive strength of the porous ceramic skeletons with 30 PPI and 45 PPI were 1.25 MPa and 1.54 MPa tested by Universal Testing Machine (UTM) at the sintering temperature of 1250 °C, respectively. The linear shrinkage, bulk density and pore stem density of the porous ceramic skeletons became larger with the rising of sintering temperatures from 1150 °C to 1350 °C. However, the corresponding performance values of 45 PPI porous ceramic skeletons were greater than that of 30 PPI at the same sintering temperature. The prepared porous ceramic skeletons will be used in ceramic-metal wear-resistant composites for the later research and the study provides a new idea for coal gangue on the comprehensive utilization with high added value and brings both good environmental and economic benefits.

Distribution of growth lines in the tube wall of serpulids (Polychaeta, Annelida)

Abstract The frequency of growth increments in the tube wall of the Mesozoic and Cenozoic serpulids is in the range of modern species (i.e. 7–37 growth lines per 50 μm). The growth increments of serpulids do not show correlation with the water temperature and presumably cold water and warm water serpulid species are growing on average with similar speed in terms of number of growth lines per 50 μm. The large serpulid species have usually significantly larger growth increments than smaller species and presumably also grew faster than smaller species. The species with denser skeletons have lower growth rates than species with more porous skeletons. It is possible that serpulids do not have to calcify faster to produce thicker growth increments with lower density.

Revolutionizing energy storage with advanced reduced graphene oxide-wrapped MnSe@CoSe@FeSe2 nanowires.

Thanks to their good redox activity properties and exceptional conductivity, metal selenides (MSs) have attracted great attention as prospective positive electrodes for hybrid supercapacitors. However, they demonstrate low-rate capacities and poor endurance. Nanomaterials fabricated from MSs and reduced graphene oxide (rGO) with a porous skeleton can effectively mitigate the above-mentioned problems. Herein, porous MnSe@CoSe@FeSe2 nanowires wrapped with rGO on nickel foam (NF@MCFS-rGO) are manufactured as a binder-free electrode for a hybrid supercapacitor. The obtained NF@MCFS-rGO, acting as a positive electrode, has distinct advantages such as (1) the porous nanowires are helpful for fast electrolyte penetration, (2) the conductivity of the MCFS is further improved when combined with rGO, and (3) wrapping MCFS within the rGO endows the nanomaterial with much better structural durability. Capitalizing on the high conductivity of the rGO and the porous morphology, the fabricated NF@MCFS-rGO manifests impressive characteristics with a capacitance of 1830 F g-1 at 1 A g-1 and only 6.75% capacitance loss within 10 000 cycles. By matching NF@MCFS-rGO with activated carbon (AC), the fabricated apparatus (AC\\NF@MCFS-rGO) reveals an energy density (ED) of 64.6 W h kg-1 and a long lastingness of 90.55% after 10 000 cycles.