Three-dimensional Cross-linked Structure Research Articles

Insight into the effect of structural differences among pitch fractions on sodium storage performance of pitch-derived hard carbons

Pitch is an excellent precursor of hard carbons (HCs) with low-cost and high carbon content, enabling its commercial-scale application in sodium-ion batteries. Pre-oxidation is the key to obtaining pitch-derived HCs with disordered microstructures. However, pitch is a mixture of fractions with different molecular weights and structures. With the introduction of oxygen, the cross-linked structure established by each fraction could be different, the effect of which on the microstructure and sodium storage performance of HCs remains unclear. Here, we separate pitch into three fractions and further pre-oxidize and carbonize to produce HCs, in order to systematically investigate the effects of structural differences among pitch fractions on the cross-linking mechanism and microstructure of as-obtained HCs. It is found that tetrahydrofuran-insoluble (THFI) enables the enrichment of polar oxygen functional groups, thus enhancing its oxidative activity to obtain more oxygen for the construction of abundant three-dimensional cross-linked structure. It is conducive to preventing the rearrangement of carbon layers and promoting the development of micropores during high-temperature carbonization process, which facilitates the storage of sodium ions in the low-voltage plateau region. The resulting hard carbon (THFI-1400) has significantly improved overall sodium storage performances. This work provides a new strategy to prepare low-cost and high-performance HCs.

A facile and efficient solvothermal degradation route for carbon fiber reinforced epoxy resin composite waste

Carbon fiber reinforced epoxy resin composite (CF/EP) is widely used in aerospace applications, automotive industry, construction engineering and many other important sectors, for it has excellent mechanical properties and corrosion resistance. However, the three-dimensional cross-linked structure of the cured epoxy resin determines its insolubility and non-melting characteristics, which makes it challenging to efficiently degrade CF/EP waste and recycle the high-value carbon fibers. In this study we propose a strategy that degrades the CF/EP waste via a facile and efficient solvothermal degradation route. The results showed that the degradation ratio of the resin increased significantly with the rise in reaction temperature. When the reaction temperature reached 180 °C there were no obvious resin residues on the surface of the recycled carbon fibers. It was found that the recycled carbon fibers were not obviously damaged during the solvothermal degradation process, as shown by the scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman analyses.

Facile, catalyst-free, and high enthalpy PEG-based phase change composite for use in photothermal conversion and waste heat recovery

The poor shape stability, low thermal storage density, and complex process confronted in fabricating high-performance phase change composites (PCCs) via the chemical cross-linking technology. Herein, PEG-based shape stability PCC (SSPCC) with high enthalpy and good shape stability was obtained using a facile one-pot method without additional catalysts. The reliable three-dimensional cross-linked structure formed by the interaction of epoxy resin and curing agent binds the movement of PEG molecular chains, which simultaneously in coupled with the stronger hydrogen bonding between PEG and cross-linked products to endow the as-prepared SSPCC with excellent shape stability, thermal stability, durability, and high thermal storage density (160.8 J/g). Moreover, the Raman spectra clearly presented the interaction force and phase morphology distribution between PEG and the skeleton structure. SSPCC with the high relative enthalpy efficiency and melt enthalpy can play an essential role in photothermal applications, while the facile manufacturing process free from additional organic solvents or high temperature, highlighting its green and sustainable features. Additionally, the photothermal transport and thermostatic effects of the SSPCCs show great potential for application in waste heat recovery, which can maintain higher temperatures for a long time. Totally, such SSPCC with reliable and distinguished phase change properties ensure a wide range of potential applications, while the easy-to-prepare and low-cost fabrication method provides an inspiring strategy for alternative SSPCC development.

Macromolecular grafting of carboxyl polymers on the surface of non-woven fabrics and their adsorption behavior on metal cations

In order to address the issues of the time-consuming, the low density of functional groups and the instability of mussel-inspired adsorbents, an efficient in situ cross-linked mussel-inspired coating-assisted macromolecular grafting strategy was proposed to prepare a polyacrylic acid (PAA) grafted polypropylene nonwoven (PP-g-PAA) for the efficient removal of heavy metal ions. The mussel-inspired coating was formed by rapid deposition in the presence of oxidizing agents and polyamines, and then thiol-terminated polyacrylic acid (PAA-SH) prepared by thiol-ene click reaction and glutaraldehyde were added in situ, and then PAA brushes were introduced on the surface of the polypropylene nonwoven via the Michael addition Schiff base reaction between the thiol and o-benzoquinone, and the improvement of the stability of the adsorbent was achieved through in situ formation of the three-dimensional cross-linked structure. A high density carboxyl group functionalized adsorbent with a grafting rate up to 38.98% was obtained, which also exhibited unprecedented tolerance to strong acid, alkali and polar organic solvents. Meanwhile, grafting on polyester nonwovens, sponges and PVDF membrane substrates confirmed the versatility of the proposed method. The PP-g-PAA was characterized by SEM, IR and XPS, and the adsorption behaviors of the adsorbent for Pb2+, Cu2+ and Cd2+ were systematically investigated. The results showed that the adsorption capacity of PP-g-PAA was nearly twice as high as that of the mussel-inspired adsorbent. The adsorption mechanism was also well investigated.

Effective and eco-friendly safe self-antimildew strategy to simultaneously improve the water resistance and bonding strength of starch-based adhesive

Starch adhesive, as a sustainable biomass-based adhesive, could be used to solve environmental problems from petroleum-derived adhesive. But its application is hindered by poor water resistance, mildew resistance, and storage stability. Here, a fully bio-based citric acid-starch adhesive (CASt) with high properties was successfully introduced by a simple method. Liquid chromatography/mass spectrometry (LC-MS), and Fourier Transform Infrared spectroscopy (FT-IR) determined that esterification of citric acid (CA) and starch (St) occurred to form a stable three-dimensional crosslinking structure, which strengthened water resistance and bonding strength of the starch adhesive. Compared with native starch (100 %), the soluble content of cured CASt was 1–16 %. CASt adhesive has well storage stability and high mildew resistance. Even after being stored for 5 months, the CASt-1 adhesive (mass ratio of CA/St = 1:1, and reaction time = 1 h) still have good liquidity. And its hot water strength (1.05 ± 0.22 MPa) also satisfied the standard requirements (≥0.7 MPa). The exhibited CASt adhesive is eco-friendly with components from plant resources, which performed as a bright alternative that can substitute petroleum-based adhesives in the artificial board industry.

Boosting sodium storage performance of hard carbons by regulating oxygen functionalities of the cross-linked asphalt precursor

Pre-oxidation treatment is a key process to produce carbon anodes for sodium ion batteries from pitch because it governs the orientation of carbon layers during subsequent carbonization. However, the relationship between the oxygen functionalities in the oxidized pitch and the evolution of carbon structure during carbonization remains unclear. Herein, cross-linked asphalts with differentiated oxygen functionalities such as C–O and C(O)–O (ester group and anhydride), are synthesized to explore their effects on the evolution of carbon structure. The planar cross-linked structures constructed by thermally stable C–O fail to prevent the sliding of carbon layer, leading the formation of short-range order carbon structures with lager lateral size. In contrast, the three-dimensional cross-linked structures constructed by C(O)–O effectively prevent the rearrangement of asphalt at early pyrolysis. Owing to the gas generated by C(O)–O removal during subsequent carbonization, the as-formed more disorder carbon structures with small microcrystalline sizes can generate more closed pores and ultra-micropores, which enhances the low-voltage plateau capacity from 96.06 to 132.2 mAh g−1. The insights for the differentiated oxygen functionalities in regulating the carbon structural conversion pave the way for further development of pitch-based hard carbons with higher performance and their practical applications in SIBs.

Comparative assessment of modified bentonites as retardation barrier: adsorption performance and characterization

Modified bentonites for the anti-seepage system have been attracting global attention. At the same time, the performances of modified bentonite containing retardation barrier exposed to organic–heavy metal pollutants have not been fully reported. In this study, the adsorption performances (one of the key evaluation indicators of retardation barrier) of nine kinds of commonly used modified bentonites on multiple contaminants were comparatively investigated. The x-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analyses were also performed to unravel the adsorption mechanisms. Results show that the adsorption of modified bentonites on phenol and Pb(II) follows the order of SB-16 > PVA > CTAB > APAM > CTAB + PAC > PAC > CPAM > CTAB + PAC > CTAB + CPAM + APAM. Among all the samples, the bentonite modified with SB-16 showed the highest adsorption capacities for phenol and Pb(II). The surfactant molecules inserted in the interlayer space of montmorillonite increase the substrate spacing, which changes the structural properties of the bentonite from hydrophilic to hydrophobic and increases the adsorption of organic contaminants. On the other hand, the polymer has functional groups such as hydroxyl and carboxyl that can form a spatial three-dimensional cross-linking structure on the bentonite surface, providing more adsorption sites for heavy metal ions. These findings indicate the potential industrial applications of modified bentonite in a contaminant barrier system.

SYNTHESIS OF CARBOXYLATE TYPE SORBENT BASED ON COOLIGOMERS OF 2-PROPENYLPHENOL AND FORMALDEHYDE AND STUDY OF THEIR FUNCTIONAL PROPERTIES FOR SORPTION OF URANYL IONS IN MODEL SYSTEMS

Alkaline synthesis of double co-oligomers of 2-propenylphenol and formaldehyde (synthons) was carried out at 92-950C, for 3 hours and ratio of 1:2.5 mol (their yield are 93% of theory)Interaction of maleic anhydride with the obtained olygomers at 800C in the presence of 0.5% benzoyl peroxide for 10 hours produced copolymers of a three-dimensional cross-linked structure (with a yield of 90%). By treating them with hot water, a sorbent was obtained to contain both propenyl and carboxylate fragments in the structure - active centers of chemisorption. The functional sorption properties of the copolymer were studied under static conditions, in model water systems. The influence of the pH of the medium, the concentration of uranyl ions and the exposure time on the degree of their sorption at room temperature were studied and it was found that the best results are achieved at pH 6 and for 24 hours (R=93%). Uranyl ions can be easily desorbed with mineral acid and the crosslinked copolymers can be reused.

Sifat Mekanik dan Densitas Ikatan Silang Hidrogel berbasis Tapioka Nanopartikel

Tapioca is a natural polymer that is widely used as a raw material for hydrogels. In order to improve the mechanical properties of tapioca-based hydrogels, this research modified tapioca by acid hydrolysis method for 2 hours and 24 hours and by ethanol precipitation method. This modified tapioca was further treated with epichlorohydrin with various concentrations of 0, 5, 10, and 20% to produce a three-dimensional cross-linked structure. The results showed that the increasing of epichlorohydrin concentration led to an increasing in the mechanical properties of the hydrogels consisting of hardness, stress, modulus of elasticity, and cross-linked density. The hydrogel from tapioca hydrolyzed for 24 hours and 20% epichlorohydrin was the sample with the best mechanical properties with a hardness of 19.78 mJ, a stress of 78.65 kPa, a modulus of elasticity of 233.84 mJ, and a cross-linked density of 57.61 × 1024 m-3.

Highly Stretchable Composite Foams via Sustainable Utilization of Waste Tire Rubbers for Temperature-Dependent Electromagnetic Wave Absorption.

Recently, the sustainable utilization of waste resources has become a low-cost and effective strategy to design high-performance functional materials to solve the increasingly serious environmental pollution problem. Herein, the flexible and highly stretchable polyurethane (PU) composite foams assisted by one-dimensional carbon nanotubes (CNTs) and zero-dimensional Fe3O4 were fabricated using waste tire rubbers (WTRs) as reinforcements during a simple self-foaming process. The collaborative introduction of conductive CNTs, magnetic Fe3O4, and WTRs with three-dimensional cross-linked structures enabled the construction of an efficient electronic transmission path and heterointerfaces inside the composite foam. The resulting composite foam possessed a desired minimum reflection loss (RLmin) of −47.43 dB, and also exhibited superior mechanical properties with a tensile strength of >3 MPa and multiple tensile deformation recovery abilities. In addition, increasing the temperature could significantly improve the electromagnetic wave absorption performance of the composite foam. This comprehensive composite foam derived from WTRs has shown a promising development potential for using waste materials to relieve electromagnetic pollution.

Total synthesis of merodesmosine

Elastin is an important extracellular matrix protein responsible for the elasticity of tissues such as ligamentum, arteries, and lungs. Its three-dimensional crosslinking structure plays an important role in its elasticity. However, the precise structure has not yet been clarified since it is difficult to analyze due to its insoluble nature. Merodesmosine is one of the possible crosslinking amino acids in elastin. In this work, the first total synthesis of merodesmosine was achieved in five steps in 21% overall yield from protected allysine. This achievement will aid in the elucidation of the crosslinking structure of elastin.

Programmable shape deformation actuated bilayer hydrogel based on mixed metal ions

The intelligent hydrogel actuators that respond to temperature have great application prospects in many fields. At the same time, the intelligent hydrogel actuators still have challenges in driving force, deformation intensity, and programming deformation. Herein, we fabricated a bilayer hydrogel actuator using a two-step photopolymerization method, which consists of a poly(N-isopropylacrylamide)-chitosan-N-2-hydroxypropyl trimethylammonium chloride (PNIPAm-HACC) layer with an LCST-type volume phase change and an alginate-polyacrylamide (SA-PAm) layer. We employed mixed metal ions (trivalent/divalent cations) to cross-link alginate-based hydrogels to construct two-dimensional and three-dimensional cross-linked structure units, resulting in a synergistic effect. The Zn2+/Fe3+(1:1)-SA-PAm/PNIPAm-HACC bilayer-actuated hydrogels have excellent antibacterial properties, shape fixation (85.4 %), fatigue resistance, and reversibility, and showed rapid, reversible, and reproducible thermoresponsive bending/unbending properties, which can be prepared as an actuator, such as a gripper to capture, transport, and release an object, or a temperature-controlled device to turn on and off indicator lights. Overall, this hybrid ion-crosslinked bilayer hydrogel can provide new insights into the design and fabrication of smart actuators.

Degradation of Flame-Retardant Cross-Linked Polyethylene Caused by Heat, Gamma-Rays, and Steam

Various kinds of polymers are used for electrical insulation in nuclear power plants. They are subjected to thermal and radioactive stresses, depending on their locations. They are also subjected to high-temperature steam in the event of an accident. Regarding this, sheets of flame-retardant cross-linked polyethylene (FR-XLPE) were subjected to heat, gamma-rays, and steam exposure, and their infrared absorption spectra, stress-strain relations, indenter moduli, and permittivity spectra were measured. As a result, we have made clear various degradation-induced property changes of FR-XLPE. In addition, it has also become clear that cross-linked structures are formed by the gamma-ray irradiation in FR-XLPE. In this regard, some aspects of degradation due to subsequent steam exposure are suppressed by the formation of firm three-dimensional cross-linked structures.

Corrosion assisted the formation of unique structure transition metal oxides/carbon nanofibers with fast and high lithium storage

In this work, a facile and universal synthetic strategy is proposed to synthesize carbon nanofibers/ transition metal oxide composites with a three-dimensional cross-linked structure. The character of its morphology is the carbon nanofiber framework, based on which transition metal oxide nanoparticles and nanosheets (nanoparticles, nanoneedles) can be compounded inside and outside the nanofiber, respectively. The synthesis of this special morphology is achieved by electrospinning, heat treatment, and corrosion. By using this method, a series of hybrid materials including Co3O4/C nanofibers @ Co3O4 nanosheets (Co3O4/CFs @ Co3O4), ZnO/C nanofibers @ ZnO nanoparticles (ZnO/CFs @ ZnO), and CuO/C nanofibers @ CuO nanoneedles (CuO/CFs @ CuO) can be successfully synthesized. The capacity of Co3O4/CFs @ Co3O4 can reach 842.4 mAh g−1 after 150 cycles, and ZnO/CFs @ ZnO and CuO/CFs @ CuO also show well cycle stability and high specific capacity as 650 mAh g−1 and 544 mAh g−1 after 600 cycles at 1 A g−1. This work can inspire the research of carbon nanofibers framework composite transition metal oxide nanostructure materials for outstanding lithium storage.

Carbon-Reinforced Nb2CTx MXene/MoS2 Nanosheets as a Superior Rate and High-Capacity Anode for Sodium-Ion Batteries.

Sodium-ion batteries operating at room temperature have emerged as a generation of energy storage devices to replace lithium-ion batteries; however, they are limited by a lack of anode materials with both an adequate lifespan and excellent rate capability. To address this issue, we developed Nb2CTx MXene-framework MoS2 nanosheets coated with carbon (Nb2CTx@MoS2@C) and constructed a robust three-dimensional cross-linked structure. In such a design, highly conductive Nb2CTx MXene nanosheets prevent the restacking of MoS2 sheets and provide efficient channels for charge transfer and diffusion. Additionally, the hierarchical carbon coating has a certain level of volume elasticity and excellent electrical conductivity to guarantee the intercalation of sodium ions, facilitating both fast kinetics and long-term stability. As a result, the Nb2CTx@MoS2@C anode delivers an ultrahigh reversible capacity of 530 mA h g-1 at 0.1 A g-1 after 200 cycles and very long cycling stability with a capacity of 403 mA h g-1 and only 0.01% degradation per cycle for 2000 cycles at 1.0 A g-1. Moreover, this anode has an outstanding capacity retention rate of approximately 88.4% from 0.1 to 1 A g-1 in regard to rate performance. Most importantly, the Nb2CTx@MoS2@C anode can realize a quick charge and discharge at current densities of 20 or even 40 A g-1 with capacities of 340 and 260 mAh g-1, respectively, which will increase the number of practical applications for sodium-ion batteries.

Hemostatic Compositions Based on Chitosan Complexes with Calcium Ions

The production of new effective hemostatic materials based on a polymer composition of modified chitosan with a three-dimensional cross-linked structure as a polymer matrix and calcium ions coordinated to it is addressed. The optimum concentration of calcium ions in the chitosan-based composition was established as 10 – 20 mM and ensured an effective in vitro blood coagulation time of 40 sec. Compositions of chitosan succinate and chloride in addition to chitosan in solutions with nicotinic acid were shown to have effective hemostatic activity. Statistical differences in the effects of various calcium salts on the blood coagulation time were not found. In vivo tests showed that a chitosan-based composition was effective for stopping bleeding of any degree of severity, both with external and internal injuries to tissues.

Construction and selective removal of Cd ion based on diatom-based Cd (II) ion-imprinted composite adsorbent

The present work displays diatom as an ecofriendly material replace to the conventional costly synthetic matrixes for surface imprinting technology. In this study, novel green Cd (II) ion-imprinted composite adsorption material (SH/DE-IIP) was synthesized by surface ion-imprinting technique for selective removal of cadmium ions from aqueous solutions. Various characterization methods have confirmed the structural transformation on the diatom surface. The changes in surface morphology and structure were characterized by SEM. N2 adsorption-desorption analysis revealed the adsorption material possessed microporous structure. XRD and FTIR spectra have shown the functional monomers were successfully introduced into the surface of diatom by observing changes in characteristic functional groups. XPS spectra have shown the bonding relationship of the material with a coordination S-Cd bond, effectively utilizing the surface-active structure characteristic of diatom, and the three-dimensional cross-linked structures were presented after the cross-linking reaction. Due to the unique pore structure provided by diatoms, the mass transfer of the SH/DE-IIP was enhanced after functional modification, and SH/DE-IIP exhibited significantly improved adsorption efficiency for Cd(II) ions. Combined with XPS quantitative analysis, the calculation formula of grafting percentage for the diatoms and the functional monomers was derived, while a grafting model was constructed to evaluate the removal effect. The calculated grafting percentage indicated that the SH/DE-IIP provided a good compounding effect. The adsorption studies revealed the SH/DE-IIP possessed a good adsorption performance for Cd (II), and the adsorption equilibrium was reached in 30 min. The adsorption behaviors followed the pseudo-second-order kinetic model and the adsorption isotherms are described well by Langmuir isotherm adsorption model. The relative selectivity coefficients for Cd(II)/Ni(II), Cd(II)/Zn(II), and Cd(II)/Cu(II) were 1.56, 1.67, and 1.50, respectively. The more results showed that the SH/DE-IIP has the excellent selectivity and the good reusability. The obtained Cd ion-imprinted composite adsorption material exhibited a good directional removal performance for Cd (II) from aqueous solutions. This work not only provides a new material strategy for preparation of ion-imprinted materials, but also provides new insights into the structure of imprinted materials.

MWCNTs-GONRs/Co3O4 electrode with needle-like arrays for outstanding supercapacitors

Multiwalled carbon nanotubes-graphene oxide nanoribbons (MWCNTs-GONRs) exhibit high specific surface area and good electroconductivity because of their unique three-dimensional cross-linking structure with the properties of both CNTs and GONRs. In this study, a hydrothermal method was employed to anchor MWCNTs–GONRs onto a Ni foam (NF) to obtain a precursor substrate. Subsequently, Co3O4 arrays were grown on the NF substrate to synthesize a MWCNTs–GONR/Co3O4 electrode. The electrode showed a capacitance of 846.2 F g−1 at 1 A g−1 and a capacitance retention of 90.1% after 3000 cycles. Furthermore, MWCNTs–GONRs/Co3O4 and active carbon (AC) were used as the positive and negative electrodes, respectively, to assemble a supercapacitor, which delivered a maximum energy density of 38.23 W h kg−1 and a high power density of 6.80 kW kg−1. In addition, the specific capacitance of the device reached a maximum of 91.5% after 9000 cycles. Thus, the MWCNTs–GONRs/Co3O4 electrode showed huge potential for supercapacitor applications.

Modified Carbon Fiber Paper-Based Electrodes Wrapped by Conducting Polymers with Enhanced Electrochemical Performance for Supercapacitors.

An easy approach to fabricating carbon fiber paper (CFP) based electrodes has been developed. This method can be mainly divided into two steps, for which the mixture of cellulose nanofibers (CNFs) and carbon nanotubes (CNTs) was first deposited on the surface of carbon fiber paper through a vacuum filtration device followed by immersing the hybrid paper into concentrated aniline solution to polymerize polyaniline (PANI). Compared to carbon fiber paper, the acid-treated carbon fiber paper (A-CFP)-based electrode provides more active sites, which are beneficial for the polymerization of polyaniline. The mixture of CNFs and CNTs could coat on the A-CFP by vacuum-filtration due to the high hydrophilicity of A-CFP improved by acid-treatment. PANI with different polymerization time was in-situ synthesized on the surface of the hybrid paper to form a three-dimensional cross-linked structure that greatly enhanced the electrochemical performance of the electrode by improving high capacitance, high rate-capability, and long cycle-life. Moreover, the assembled symmetrical supercapacitor showed a high area capacitance of 626 mF·cm−2 and an energy density of 87 µWh·cm−2. This facile, easy performed, and low-cost strategy may provide a feasible method for the production of supercapacitor electrodes.

Synthesis of three-dimensional cross-linked MnO@C composite as high-performance anode material for lithium-ion batteries

MnO@C composites with three-dimensional cross-linked structure were designed and fabricated through hydrothermal treatment. Cation exchange resin was used as the precursor to create a three-dimensional cross-linked porous carbon structure, which was evenly decorated by nanosized MnO particles. When compared with pristine MnO, those MnO@C composites showed much better stability during charge-discharge cycling, retaining a specific capacity of 615 mAh g−1 (62.5 wt% MnO) after 100 cycles at a current density of 0.2 A g−1. This could be ascribed to the special three-dimensional cross-linked porous carbon that not only accelerated the transport of Li+ ions but also buffered the volume change and prevented agglomeration of MnO particles during the repeated lithiation and delithiation process.