Porous Skeleton Research Articles

Safe and Efficient Strategy for Directly Preparing Azide Aerogels for Microinitiation Device.

The main bottlenecks limiting the practical application of primary explosives are the contradiction between safety and detonation performance, as well as the inherent brittleness of powder charge. Traditional methods to improve sensitivity performance such as adding carbon nanomaterials or embedding metal-organic framework (MOF) structure methods are mostly powders, which are inherently brittle and unsafe. Here, we report three types of typical azide aerogels that can be directly prepared and obtained in this paper by combining electrospinning with aerogel. Their electrostatic sensitivity and flame sensitivity were significantly improved and could be detonated successfully at an initiation voltage of 25 V, demonstrating good ignition performance. This enhancement is primarily due to the porous carbon skeleton structure evolved from a three-dimensional nanofiber aerogel, which has good thermal and electrical conductivity characteristics and can also uniformly load azide particles, contributing to improved explosive system sensitivity. The most important aspect of this method is that it can directly prepare molded explosives, which can be matched with the micro-electrical-mechanical system (MEMS) process, and it offers a new idea for the preparation of high-security molded explosives.

Long-Lasting Zinc-Iodine Batteries with Ultrahigh Areal Capacity and Boosted Rate Capability Enabled by Nickel Single-Atom Electrocatalysts.

Zinc-iodine (Zn-I2) batteries have garnered significant attention for their high energy density, low cost, and inherent safety. However, several challenges, including polyiodide dissolution and shuttling, sluggish iodine redox kinetics, and low electrical conductivity, limit their practical applications. Herein, we designed a highly efficient electrocatalyst for Zn-I2 batteries by uniformly dispersing Ni single atoms (NiSAs) on hierarchical porous carbon skeletons (NiSAs-HPC). In situ Raman analysis revealed that the conversion of soluble polyiodides (I3- and I5-) was significantly accelerated using NiSAs-HPC because of the remarkable electrocatalytic activity of NiSAs. The resulting Zn-I2 batteries with NiSAs-HPC/I2 cathodes delivered exceptional rate capability (121 mAh g-1 at 50 C), and ultralong cyclic stability (over 40 000 cycles at 50 C). Even under 11.6 mg cm-2 iodine, Zn-I2 batteries still exhibited an impressive cyclic stability with a capacity retention of 93.4% and 141 mAh g-1 after 10 000 cycles at 10 C.

Thermal behaviors and performance of phase change materials embedded in sparse porous skeleton structure for thermal energy storage

Thermal behaviors and performance of phase change materials embedded in sparse porous skeleton structure for thermal energy storage

Construction of MoS2@reduced graphene oxide/carbon nanotubes three-dimensional network structure and its application in lithium-sulfur batteries

In order to enhance the electrochemical performance of lithium-sulfur batteries, reduced graphene oxide (rGO), and carbon nanotubes (CNTs) were used to construct a conductive and mechanical skeleton of the overall electrode composite. And molybdenum disulfide (MoS2) grew on the skeleton in situ. Thus, a composite MoS2@rGO/CNTs with a three-dimensional (3D) network structure was constructed. A series of corresponding structural characterizations and electrochemical performance tests were carried out. And the results showed that the 3D porous skeleton composed of rGO and CNTs could act as a 3D conductive network, which not only significantly improved the conductivity and structural stability of the cathode material for lithium-sulfur batteries but also provided a large number of active sites for the active substance S. MoS2 had a strong chemisorption effect on lithium polysulfides, which could effectively hinder their shuttle behavior. So, the MoS2@/CNTs/rGO/S cathode material showed good electrochemical performance. Its first discharge specific capacity was up to 1417.8 mAh/g at 0.1 C. After 200 cycles at 0.5 C, its capacity decay rate per cycle was only 0.09%. Its discharge capacity could still maintain at 803.2 mAh/g at 3 C, showing a good application prospect.

The Loss of Structural Integrity of 3D Chitin Scaffolds from Aplysina aerophoba Marine Demosponge after Treatment with LiOH.

Aminopolysaccharide chitin is one of the main structural biopolymers in sponges that is responsible for the mechanical stability of their unique 3D-structured microfibrous and porous skeletons. Chitin in representatives of exclusively marine Verongiida demosponges exists in the form of biocomposite-based scaffolds chemically bounded with biominerals, lipids, proteins, and bromotyrosines. Treatment with alkalis remains one of the classical approaches to isolate pure chitin from the sponge skeleton. For the first time, we carried out extraction of multilayered, tube-like chitin from skeletons of cultivated Aplysina aerophoba demosponge using 1% LiOH solution at 65 °C following sonication. Surprisingly, this approach leads not only to the isolation of chitinous scaffolds but also to their dissolution and the formation of amorphous-like matter. Simultaneously, isofistularin-containing extracts have been obtained. Due to the absence of any changes between the chitin standard derived from arthropods and the sponge-derived chitin treated with LiOH under the same experimental conditions, we suggest that bromotyrosines in A. aerophoba sponge represent the target for lithium ion activity with respect to the formation of LiBr. This compound, however, is a well-recognized solubilizing reagent of diverse biopolymers including cellulose and chitosan. We propose a possible dissolution mechanism of this very special kind of sponge chitin.

Facile fabrication of few-layer nanostructured MoSe2 entrenched on N-doped carbon as a superior anode material for high-performance potassium-ion hybrid capacitors

As an emerging class of advanced capacitor-battery hybrid energy storage and transformation devices, potassium ion hybrid capacitors (PIHCs) have become the next generation of electrochemical energy storage systems owing to their abundant ratio of raw materials and inexpensive potassium resources. However, potassium ions have backward kinetics because of their ionic radius. Therefore, the improvement of applicable materials with powerful capacity and rapid charge and discharge capabilities remains a large challenge. Here, we design simple hydrothermal synthesis methods to anchor MoSe2 nanosheets into a 3-dimensional N-doped porous carbon skeleton as a fast, durable electrode to boost energy storage for PIHCs. Specifically, highly conductive 3-dimensional N-doped porous carbon skeleton materials can efficiently alleviate the accumulation of MoSe2 nanosheets and facilitate electron diffusion. It is demonstrated that MoSe2/NC utilized as potassium ion battery anodes exhibits a reversible capacity (415.1 mA h g−1 at 100 mA g−1) and a superior rate performance (212.4 mAh g−1 at 5000 mA g−1) as a result of its unique nanostructure and powerful chemical interactions between MoSe2 nanosheets and N-doped carbon skeletons. As a result of its use of an anode of MoSe2/NC and a cathode of activated carbon, the PIHCs can provide an extremely high energy density of 136.8 Wh kg−1 accompanied by a power density of 400 W kg−1 excellent rate performance and an exceptionally long-cycle lifespan.

Self-Activated SiO2/C Nanocomposite from Silica-Rich Marine Mucilage for Supercapacitor Applications

Bioresources are continually being explored as potential precursors for sustainable supercapacitor electrode materials. In this work, diatom-rich marine mucilage (MM) collected from the Marmara Sea, Turkey was used as a biomass source and converted to SiO2/Carbon nanocomposite (SiO 2 /C) through pyrolysis and acid etching. Diatom frustules acted as a highly porous silica source while algal organic matter delivered the carbonaceous part of the composite. The natural salts found in marine mucilage served as a self-activating agent and avoided the use of corrosive chemicals for the development of pores. The SiO 2 /C exhibited a competitive capacitance of 210 F g–1 at a current rate of 0.5 A g–1 in 1 M sodium sulfate (Na2SO4) aqueous electrolyte solution. The porous and durable silica skeleton improved capacitance by expanding the electrode/electrolyte interface, and the interconnected hierarchical pores ensured high electrochemical stability during long-term cycling. The mucilage-derived nanocomposite retained 80% and 70% of its capacitance after 4000 and 10,000 charge–discharge cycles, respectively. This work presents a potential solution for the management of marine mucilage by converting it into a high-value electrode material.

In situ encapsulation of phase change material by synergistic interaction of polymethyl methacrylate and nano-TiO2

The widespread utilization of conventional porous skeleton adsorption strategies is often limited by the inhomogeneous and inadequate encapsulation due to the surface tension between skeleton and phase change material. Therefore, it remains challenging to achieve high compatibility between the support material and phase change material. Herein, for the first time, we reported a breakthrough on phase change materials encapsulation strategy, paraffin wax was encapsulated by Polymethyl methacrylate-enhanced nano-TiO2. Methyl methacrylate forms a porous support structure with nano-TiO2 as the backbone node, providing advantages for encapsulation of paraffin wax. TiO2 enhances the compatibility and thermal conductivity between polymethyl methacrylate and phase change materials, and solves the problem of phase separation that occurs during the polymerization process. The preparation features straightforward operation and high environmental metrics with no emission, requires only stirring and heating. A thermal conductivity enhancement of one time than that of paraffin wax is achieved along with a light-thermal conversion efficiency of 47.31 % and with a latent heat of 102.52 J/g without leakage.

Study of the effect of phase state on the interfacial thermal conductance between PCMs and ceramic skeletons

ABSTRACT Composite phase change materials with sugar alcohol as the phase change material and highly thermally conductive ceramics as the porous skeleton are widely used in various thermal storage systems. The interfacial thermal conductance (ITC) between the phase change materials under different phases and the skeleton is an important factor affecting the rate of heat storage (release) in thermal storage systems. The ITC between ceramics(AlN, SiC) and sugar alcohols (mannitol and galactitol) in the solid and liquid states is investigated by means of both time-domain thermoreflectance and molecular dynamics simulations. The results show that the ITC between phase change materials and ceramic is better in liquid state than in solid state, and that the ITC between mannitol and ceramic is better, and that the ITC betweenAlN and sugar alcohol is better. More low-frequency phonons are involved in the thermal transport of the sugar alcohols in the liquid state, with an average overlap energy of about 9.5% higher than that of the solid state and an average phonon participation rate of about 6.8% higher. It was also found that it isthe H atom in the sugar alcohol that is linked to the C atom that governs the ITC.

Pushing electromagnetic interference shielding self-enhanced based on smart Ti3C2Tx-WVO2 thermal management composite

Aerogel materials have shown tremendous vistas in electromagnetic interference (EMI) of intelligentized electronics and armaments. However, it is challenging to simultaneously achieve self-enhanced shielding performance and release the accumulation thermal. Herein, an intelligent tunable shielding composite was demonstrated through synergistic dynamic interactions between Ti3C2Tx and tungsten doped VO2 (WVO2), tactfully transforming the accumulation thermal energy to superiority for enhanced shielding. Additionally, the performances of meticulously engineered Ti3C2Tx-WVO2 composite from thermal conversion to enhanced electromagnetic shielding have been hierarchically dissected. The composite possessed highly sensitive and dynamically tunable shielding performance (ΔSE = 13.9 dB, X-band = 8–12 GHz) and high-efficiency thermal management characteristic by virtue of three-dimensional porous Ti3C2Tx skeleton, the phase transition of WVO2 and energy transformation between Ti3C2Tx and WVO2. Furthermore, the composite provides excellent shielding performance (EMI SE = 42.8 dB). Therefore, this Ti3C2Tx-WVO2 composite can be a potential candidate in both EMI shielding and tunable shielding fields.

Hierarchical porous photosensitizers with efficient photooxidation

Photosensitizers (PSs) with nano- or micro-sized pore provide a great promise in the conversion of light energy into chemical fuel due to the excellent promotion for transporting singlet oxygen (1O2) into active sites. Despite such hollow PSs can be achieved by introducing molecular-level PSs into porous skeleton, however, the catalytic efficiency is far away from imagination because of the problems with pore deformation and blocking. Here, very ordered porous PSs with excellent 1O2 generation are presented from cross-linking of hierarchical porous laminates originated by co-assembly of hydrogen donative PSs and functionalized acceptor. The catalytic performance strongly depends on the preformed porous architectures, which is regulated by special recognition of hydrogen binding. As the increasing of hydrogen acceptor quantities, 2D-organized PSs laminates gradually transform into uniformly perforated porous layers with highly dispersed molecular PSs. The premature termination by porous assembly endows superior activity as well as specific selectivity for the photo-oxidative degradation, which contributes to efficient purification in aryl-bromination without any postprocessing.

Facile synthesis of NiCo2 nanoparticles grown on rice husk waste-derived porous carbon for high-efficiency microwave absorption

Herein, rice husk waste-derived porous carbon decorated with NiCo2 nanoparticles (NiCo2/C) was simply prepared by impregnation method combined with an annealing process. From the SEM images, 0-dimensional (0D) NiCo2 nanoparticles (NPs) are uniformly dispersed on the surface of three-dimensional (3D) porous rice husk carbon (PRC). The porous carbon skeleton with high graphitization not only extends the propagation path of electromagnetic waves, but also improves the conductive loss. Upon increasing the NiCo2 NPs content, the conductive loss initially decreases and then aggrandizes, while the polarization relaxation shows a monotonic increase. Benefiting from the specific structure (0D NiCo2 nanoparticles decorated 3D porous carbon construction) and the synergistic effect of excellent attenuation capacity and good impedance matching, NiCo2/C exhibits remarkably increased microwave absorption capability relative to pure PRC. By controlling the content of metallic NiCo2 NPs, the minimum RL of most samples exceeds −20 dB (＞99% attenuation) in wide EM wave ranges (4.64–18 GHz) with the variation of the absorber thickness from 1.0 to 5.0 mm. In detail, the reflection loss (RL) value is up to −55.62 dB with a thickness of 3.57 mm, and the effective absorption bandwidth (EAB) reaches 4.24 GHz with a thin thickness of only 1.5 mm. This work gives a new guideline for the development of magnetic biomass carbon composite absorbers.

Improving the performance of flexible composites based on 3-3 interconnected skeletons for piezoelectric energy harvesting

With the rapid development of microelectronics and portable devices, flexible piezoelectric electricity generators (FPEGs) as self-powered devices have attracted extensive attention. Piezoelectric ceramic-polymer composites with good flexibility is the core component of FPEGs. Having high d33 and g33 values is also essential for power generation. Herein, the porous ceramic skeleton is prepared using PZT based as the ceramic powder and polyurethane sponge as the template, followed by compounding the porous ceramic skeleton with polydimethylsiloxane (PDMS) by vacuum impregnation to prepare a 3-3 interconnected composite. When the ratio of ceramic phase in the ceramic slurry is 75 wt%, the volume fraction of the ceramic phase in the composite can achieve 37 vol%. Before compounding PDMS, porous ceramics are polarised, which is called pre-polarisation. The d33 value of the pre-polarised composites can reach 158 pC/N as compared to not polarising the porous ceramic and then polarising it after composite; the improvement is 48%. In addition, the g33 value of the pre-polarized composites is up to 144 mV m/N. Moreover, the 3.0 × 1.2 × 0.2 cm3 FPEG can generate a maximum output voltage of 15 V and a maximum short circuit current of 167 nA at 9% compression strain. The maximum instantaneous power density is 990 nW/cm2, thereby providing a new idea for piezoelectric power generation.

Electrostatically reinforced and sealed nanocellulose-based macrosphere by alginate/chitosan multi-layer coatings for delivery of probiotics

Probiotic supplements have been widely employed to change gut microbiome compositions for the treatment of numerous human disorders since gut flora has a tight association with human health and disease. However, the viability of probiotics has been a major barrier to the application of probiotic products. Here, we developed an electrostatically reinforced and sealed nanocellulose-based macrosphere for probiotic encapsulation. The inside porous gel sphere provides abundant and relatively independent porous spaces for probiotics to live in. The introduction of chitosan hydrochloride (CHC) and alginate (ALG) strengthened the gel structure and contributed to the formulation of a multi-layered structure with pH-responsive properties. The mild strengthening and coating processes avoid severe damage to the sensitive probiotics in the processing process, and the synthesized multi-layer macrospheres could protect probiotics from gastric acid and bile salt conditions. In addition, the dissolvability of the outer shell and the stable inner porous skeleton in intestinal conditions allow the gradual release of the entrapped probiotics in targeted environments. Overall, this work suggests the electrostatically reinforced and sealed nanocellulose-based macrospheres are ideal materials for the probiotic delivery application.

Carbon foams with Fe-organic network-derived Fe3O4 for efficient electromagnetic shielding

Carbon-based functional materials have attracted extensive attention of the materials research community in recent years. They are expected to be used in flexible wearable devices due to their certain remarkable properties such as light-weight, ability to form thin films and excellent electromagnetic shielding performance. Herein, we report a novel CNTs/Fe3O4/Melamine-based carbon foam functional materials which can be utilized for efficient electromagnetic shielding. The synthesis of this material relies on the in-situ growth of the metal-organic skeleton on the carbon-based skeleton structure and the subsequent heat treatment process. This method is effective in in-situ doping of Fe3O4 nanoparticles on the carbon matrix. Electromagnetic shielding performance experiments demonstrate that the total shielding effectiveness (SET) of a functional material with the thickness of 3 mm is as high as 46.41 dB in the X-band. It is reflection-dominated accounting for as high as reflection coefficient of 0.67. In addition, this material also exhibits good compression cycle performance. Even after 50 compression cycles, its SET remains 33.80 dB. Compared to the Melamine-based carbon foam, the electromagnetic shielding performance of the functional material is significantly improved, which is effectuated mainly due to innovative structural design of the functional material. The high conductivity CNTs, magnetic Fe3O4 and porous carbon skeleton structure form the synergistic effect of dielectric and magnetic losses, which significantly improves the electromagnetic shielding performance of the functional material.

Hierarchical structure design of sea urchin Shell-Based evaporator for efficient omnidirectional Solar-Driven steam generation

Solar-driven steam generation (SSG) is regarded as a feasible solution to the problem of fresh water scarcity. Although several attempts have been devoted to increase the efficiency of solar-to-steam conversion, it remains difficult to fabricate cost-effective, steady, and multi-angle sunlight-absorbing evaporators from readily available biomass materials. Herein, a novel hierarchical structured SSG evaporator (PDA@Shell-NaClO) is developed through a simple, low-cost, and scalable etching treatment on discarded sea urchin (SU) shells. Attributing to the dedicatedly designed microneedles array structure and porous skeleton structure of the SU shell, this PDA@Shell-NaClO evaporator shows an outstanding average light absorption performance (>90%) in a broad range of angles from 0° to 60° and exceedingly high evaporation rate of 2.81 kg m-2 h−1 under one sun condition. Furthermore, the prepared evaporator also maintains an overall stable evaporation performance and exhibits an excellent durability for a long time of up to two weeks in actual seawater. This full-ocean biomass-based SSG evaporator with plentiful raw material availability offers innovative opportunities for large-scale fresh water production.

Insight into the origin of oxidation behaviors of carbon fiber reinforced carbon aerogel composites with different porous skeletons

Carbon fiber reinforced carbon aerogel (C/CA) composites are promising lightweight insulators for the thermal protection of aerospace vehicles at ultra-high temperatures. However, it is seriously lack of understanding their oxidation behaviors despite its importance for the applications in oxygen-containing environments. Herein, we fabricate two kinds of C/CA using resorcinol-formaldehyde (RF) and phenolic resin (PR) as precursors and investigate the effects of original and heat-treated skeletons on their oxidation behaviors. The results show that the composites derived from RF have the lower mass losses at 600−800 °C after 35-min oxidation with an apparent activation energy of 50.80 kJ mol−1 than the counterparts derived from PR with the value of 40.14 kJ mol−1. It can be explained by the existence of more impurities and macropores as well as the larger residual tensile stress in C/CA from PR. The temperature-dependent oxidation morphology evolution is similar to the time-dependent evolution, changing from the gradually enlarged pores, to the formed grooves and even island-like structure. However, the composites from RF have reversely the higher mass losses when they were heat treated at 1600 and 2300 °C, which is attributed to its relatively lower crystallinity and larger mesopore surface area. The significant increase in crystallinity and decrease in impurities and specific surface area are the main explanations for the remarkably lower oxidation rates after heat treatment. The oxidation behaviors of C/CA are jointly governed by the carbon-oxygen reaction and diffusion within pores; and the residual stress exerts a role to different extent.

Superior mechanical properties of multilayer covalent-organic frameworks enabled by rationally tuning molecular interlayer interactions

Two-dimensional (2D) covalent-organic frameworks (COFs) with a well-defined and tunable periodic porous skeleton are emerging candidates for lightweight and strong 2D polymeric materials. It remains challenging, however, to retain the superior mechanical properties of monolayer COFs in a multilayer stack. Here, we successfully demonstrated a precise layer control in synthesizing atomically thin COFs, enabling a systematic study of layer-dependent mechanical properties of 2D COFs with two different interlayer interactions. It was shown that the methoxy groups in COFTAPB-DMTP provided enhanced interlayer interactions, leading to layer-independent mechanical properties. In sharp contrast, mechanical properties of COFTAPB-PDA decreased significantly as the layer number increased. We attributed these results to higher energy barriers against interlayer sliding due to the presence of interlayer hydrogen bonds and possible mechanical interlocking in COFTAPB-DMTP, as revealed by density functional theory calculations.

Strengthening performance of Al-stabilized, CaO-based CO2 sorbent pellets by the combination of impregnated layer solution combustion and graphite-moulding

Calcium looping (CaL) process is recognized as one of the most promising CO2 capture technologies. However, the CaO-based sorbents commonly encounter serious sintering and elutriation problem during CO2 capture cycles. In this work, Al-stabilized, CaO-based sorbents were synthesized by the impregnated layer solution combustion method, and cigarette butt was selected as the porous reactive skeleton. The Al-stabilized, CaO-based sorbent containing 15 wt% of Al2O3 exhibits the highly stable CO2 capture performance, whose CO2 capture capacity after 20 cycles is almost the same as its initial capacity, ∼0.354 g/g. It is mainly attributed to the synergistic effect of thermal pretreatment (cigarette butt-assisted combustion) and incorporation of Al-based stabilizer (i.e., Ca12Al14O33) provide a stable inert framework for the synthetic sorbents, ensuring their highly stable capability for CO2 sorption during cycles. Further, graphite-moulding is a facile and energy-saving approach to make Al-stabilized, CaO-based sorbent powders into pellets to enhance its resistance to elutriation. The produced sorbent pellets (85 wt% CaO/15 wt% Al2O3) exhibit excellent long-term CO2 capture capacity (∼0.248 g/g after 49 cycles) and high compression strength of 18.47 ± 3.47 MPa. Therefore, the combined method involved of impregnated layer solution combustion and graphite-moulding is promising to produce highly efficient CaO-based CO2 sorbent pellets used in CaL.

A hierarchical SiO2-microsphere-graphene host enabling superior long-term cycling for lithium-metal anodes

Metallic lithium (Li) is considered to be one of the most promising anodes for Li-ion batteries due to its high theoretical capacity and low reduction potential. However, dendritic growth and substantial volume variations during battery operation make it difficult for commercialization. Here, a graphene and SiO2 composites material was presented as a lithiophilic host to enable superior long-term cycling for Li-metal anode. The porous skeleton of graphene with excellent electronic conductivity can effectively reduce the actual current density and suppress the volume expansion. And the SiO2 particles with excellent ionic conductivity can significantly suppress the growth of Li dendrites and regulate the nucleation sites. So doping SiO2 nanoparticles between graphene sheets can significantly suppress the growth of Li dendrites and the volume expansion effect of metallic Li deposition, while also providing good electrochemical performance. Benefitting from these synergistic effects, the Li-GF@SiO2 battery exhibits excellent electrochemical reversibility over 500 cycles depositing 1 mAh cm−2 of metallic Li at a current density of 1 mA cm−2, and the coulombic efficiency of the Li-GF@SiO2 battery is still as high as 97%, but the Li-Cu battery decays after 75 cycles. So this hierarchical SiO2-microsphere-graphene host demonstrates great potential for Li batteries.