Functional Group Modification and Bonding Characteristics of Ti3 C2 MXene-Organic Composites from First-Principles Calculations.

The unique physical structure and abundant surface functional groups of MXene make the grafted organic molecules exhibit specific electrical and optical properties. This work reports the results of first-principles calculations to investigate the composite systems formed by different organic molecular monomers, namely acrylic acid (AA), acrylamide (AM), 1-aziridineethanol (1-AD) and glucose, and Ti3 C2 MXene saturated with different functional groups, namely -OH, -O and -F. The results show that the interaction between organic molecules and the MXene surface depends on the type of functional groups of the organic molecules, while the strength of the interaction is determined by the type of surface functional groups and the number of hydrogen bonds. The bare Ti3 C2 and Ti3 C2 (OH)2 can readily form strong chemical and hydrogen bonds with AA and AM molecules, leading to strong adsorption energy and a large amount of charge transfer, while the interaction between organic molecules and MXene saturated by -F or -O groups mainly exhibits physical interactions, accompanied by low adsorption energy and a small amount of charge transfer. This research provides theoretical guidance for the synthesis of high-performance MXene organic composite systems.

New insight into binary TiO2@C nanocomposites: the crucial effect of an interfacial microstructure.

Combining with carbon materials is a common and efficient strategy to improve the photocatalytic performance of TiO2. But the fundamental nature of the interfacial microstructures between carbon and TiO2 and how they affect the photocatalysis process remain controversial. In this work, hybrid TiO2@C nanocomposites with different carbon contents are synthesized. It is found that an interfacial disorder region with interfacial Ti-O-C bonds and abundant defects (oxygen vacancies, VO) can be generally formed from the chemical interactions between carbon and Ti-O-Ti skeletons. These interfacial VO sites are well stabilized by the carbon complex coating, and maintain their intrinsic nature in visible light absorption and electron trapping. Moreover, the synergistic effect of interfacial bonding, defective sites and the components on the visible photocatalysis of TiO2@C composites has been carefully investigated, and a corresponding mechanism is also proposed.

Microstructure and Quantitative Micromechanical Analysis of Wood Cell-Emulsion Polymer Isocyanate and Urea-Formaldehyde Interphases.

Emulsion polymer isocyanate (EPI) and urea-formaldehyde (UF) were selected as typical resin systems to investigate the microstructure of wood-adhesive interphases by fluorescence microscopy (FM) and confocal laser scanning microscopy (CLSM). Further, a quantitative micromechanical analysis of the interphases was conducted using nanoindentation. The FM results showed that the UF resin could penetrate the wood to a greater extent than the EPI resin, and that the average penetration depth for these two resin systems was higher in the case of latewood. CLSM allowed visualization of the resin distribution with contrasting colors, showing that the EPI resin could not penetrate the cell wall, whereas UF resin could enter the cell walls. The micromechanical properties of the cell walls were almost unaffected by EPI penetration but were significantly affected by UF penetration, especially in the first cell wall from the glueline. This further confirmed that only cell walls with resin penetration can improve the mechanical properties of the interphase regions.

A robust salt-tolerant superoleophobic aerogel inspired by seaweed for efficient oil-water separation in marine environments.

Oil-water separation has recently become an important subject due to the increasing incidence of oil spills. Materials with underwater superoleophobic properties have aroused considerable interest due to their cost-effectiveness, environmental friendliness and anti-fouling properties. This paper presents a robust salt-tolerant superoleophobic aerogel inspired by seaweed used without any further chemical modification for oil-seawater separation. The green aerogel is prepared by freeze-drying of sodium alginate (SA)-nanofibrillated cellulose (NFC) using Ca2+ ions as the crosslinking agent. The three-dimensional (3D) interconnected network structure of the developed aerogel ensures its high mechanical strength and good flexibility. The natural hydrophilicity of the polysaccharides contained in the aerogel ensures its excellent underwater superoleophobicity, antifouling and salt-tolerance properties. More impressively, the as-prepared aerogel can even keep its underwater superoleophobicity and high hydrophilicity after being immersed in seawater for 30 days, indicating its good stability in marine environments. Furthermore, the aerogel could separate oil-seawater mixtures with a high separation efficiency (of up to 99.65%) and good reusability (at least 40 cycles). The facile and green fabrication process combined with the excellent separation performance and good reusability makes it possible to develop engineering materials for oil-water separation in marine environments.

Versatile fabrication of a superhydrophobic and ultralight cellulose-based aerogel for oil spillage clean-up.

To deal with marine oil spillage and chemical leakage issues, a highly efficient absorbent (cellulose based aerogel) with a low density (ρ < 0.034 g cm-3, φ > 98.5%) and high mechanical strength was fabricated via a novel physical-chemical foaming method, plasma treatment and subsequent silane modification process. This aerogel has a perfect 3D skeleton and interconnected pores similar to honeycomb, which are favorable to oil adsorption and storage. More importantly, without introducing additional micro/nanoparticles, the rough micro/nano structure of the surface was directly constructed using plasma irradiation in this study. The low surface energy substrate was further introduced using a simple physical-soaking method and the resulting aerogel exhibited excellent superhydrophobicity (WCA > 156°) and superoleophilicity (OCA = 0°), which can selectively and efficiently absorb various oils or organic solvents from polluted water. In addition, this aerogel has a high storage capacity and absorption capacity (up to 4300% and 99% of its weight and volume, respectively). More interestingly, this aerogel exhibits excellent mechanical abrasion resistance and corrosion resistance even in strong acid, alkali solution and salt marine environment. The aerogel could be reused more than 30 times after removal of the absorbed oil by rinsing with ethanol.

Enhancing supercapacitor electrochemical performance through acetate-ion intercalation in layered nickel-cobalt double hydroxides.

Enhancing the performance of layered nickel-cobalt double hydroxides (NiCo-LDH) as electrode materials for supercapacitors represents a promising strategy for optimizing energy storage systems. However, the complexity of the preparation method for electrode materials with enhanced electrochemical performance and the inherent defects of nickel-cobalt LDH remain formidable challenges. In this study, we synthesized acetate-ion-intercalated NiCo-LDH (NCLA) through a simple one-step hydrothermal method. The physical and chemical structural properties and supercapacitor characteristics of the as-prepared NCLA were systematically characterized. The results indicated that the introduction of Ac- engendered a distinctive tetragonal crystal structure in NiCo-LDH, concomitant with a reduced interlayer spacing, thus enhancing structural stability. Electrochemical measurements revealed that NCLA-8 exhibited a specific capacitance of 1032.2 F g-1 at a current density of 1 A g-1 and a high specific capacitance of 922 F g-1 at 10 A g-1, demonstrating a rate performance of 89.3%. Furthermore, NCLA-8 was used to construct the positive electrode of an asymmetric supercapacitor, while the negative electrode was composed of activated carbon. This configuration resulted in an energy density of 67.7 Wh kg-1 at a power density of 800 W kg-1. Remarkably, the asymmetric supercapacitor retained 82.8% of its initial capacitance following 3000 charge-discharge cycles at a current density of 10 A g-1. Thus, this study demonstrates the efficacy of acetate-ion intercalation in enhancing the electrochemical performance of NiCo-LDH, establishing it as a viable electrode material for supercapacitors.

Towards high performance wood composites through interface customization with cellulose-based adhesive.

How to efficiently produce high performance plywood is of particular interest, while its sensitivity to moisture is overcome. This paper presents a simple and scalable strategy for the preparation of high-performance plywood based on the chemical bonding theory; a wood interfacial functionalized platform (WIFP) based on (3-aminopropyl) triethoxysilane (APTES) was established. Interestingly, the APTES-enhanced dialdehyde cellulose-based adhesive (DAC-APTES) was able to effectively establish chemically active adhesive interfaces; the dry/wet shear strength of WIFP/DAC-APTES adhesive was 3.15/1.31 MPa, which was much higher than 0.7 MPa (GB/T 9846-2015). The prepared plywood showed excellent wood-polymer interface adhesion, which exceeded the force that the wood itself could withstand. In addition, the DAC-APTES adhesive exhibits moisture evaporation-induced curing behavior at room temperature and can easily support the weight of an adult weighing 65.7 Kg. This research provides a novel approach for functionalized interface design of wood products, an effective means to prepare high-performance plywood.

Correction: Preparation of gypsum/sawdust green composite with spray coating.

[This corrects the article DOI: 10.1039/C5RA18707A.].

Binary additives of polyamide epichlorohydrin-nanocellulose for effective valorization of used paper.

This paper presents a binary reinforcement system of polyamide polyamine epichlorohydrin with nanocellulose (PAE-NC) for effectively modification of the reclaimed fibres for paper production, and based on the improvement of physical and mechanical properties of cellulosic fibres together with PAE-NC self-crosslinking networks, the strengthening mechanisms of recycled papers are examined. The PAE-NC binary system was applied directly to old corrugated container (OCC) and softwood bleached kraft pulp (SWBKP), and handsheets are prepared with varying amounts of PAE/NC/PAE-NC, namely 0.05, 0.1, 0.3, 0.5, 0.75, 1.0, 1.5, 2.0 wt% (dry pulp). The results showed that the studied additives improved the performance of recycled fibres, whether SWBKP or OCC pulp, and handsheets in solely or combined mechanisms except for the air permeability of the handsheets. The treatment of PAE-NC combination was significantly more effective than those of PAE or NC alone for both OCC and SWBKP, although the combined PAE-NC treatment results in better performance enhancement for OCC than SWBKP handsheets, and the NC alone is more effective than PAE for SWBKP recycled paper and conversely for OCC recycled paper. SEM observations further confirmed that the combined PAE-NC addition treatment imparted a relatively uniform surface structure to the handsheet.

Fungal Selectivity and Biodegradation Effects by White and Brown Rot Fungi for Wood Biomass Pretreatment.

The biodegradation path and mechanism of wood varies depending on diverse fungi and tree species, as fungi possess selectivity in degradation of versatile wood components. This paper aims to clarify the actual and precise selectivity of white and brown rot fungi and the biodegradation effects on different tree species. Softwood (Pinus yunnanensis and Cunninghamia lanceolata) and hardwood (Populus yunnanensis and Hevea brasiliensis) were subjected to a biopretreating process by white rot fungus Trametes versicolor, and brown rot fungi Gloeophyllum trabeum and Rhodonia placenta with various conversion periods. The results showed that the white rot fungus Trametes versicolor had a selective biodegradation in softwood, which preferentially convert wood hemicellulose and lignin, but cellulose was retained selectively. Conversely, Trametes versicolor achieved simultaneous conversion of cellulose, hemicellulose and lignin in hardwood. Both brown rot fungi species preferentially converted carbohydrates, but R. placenta had a selectivity for the conversion of cellulose. In addition, morphological observation showed that the microstructures within wood changed significantly, and the enlarged pores and the improved accessibility could be beneficial for the penetration and accessibility of treating substrates. The research outcomes could serve as fundamental knowhows and offer potentials for effective bioenergy production and bioengineering of bioresources, and provide a reference for further application of fungal biotechnology.

Microstructural architecture and mechanical properties of empowered cellulose-based aerogel composites via TEMPO-free oxidation.

This paper describes the development of cellulose-based aerogel composites enhanced via a new refinement process. The behaviour and microstructure of treated cellulose aerogel composites are examined including, how the constituents interact and contribute to the overall aerogel composite mechanism. The various forms of cellulose such as treated microcrystalline cellulose (MCT), nanofibrillated cellulose (NFC) and nanocrystalline cellulose (NCC) are also compared. Treated cellulose/Polyvinyl alcohol (PVA) aerogel composites show reinforced microstructural systems that enhance the mechanical property of the aerogels. The specific modulus of treated cellulose aerogels could be increased five-fold compared to the stiffness of untreated cellulose aerogels, reaching specific moduli of 21 kNm/kg. The specific strength of treated cellulose aerogels was also increased by four folds at 1.7 kNm/kg. These results provide insight into the understanding of the morphology and structure of treated cellulose-based aerogel composites.

Construction of advanced zeolitic imidazolate framework derived cobalt sulfide/MXene composites as high-performance electrodes for supercapacitors.

The Ti3C2Tx with excellent conductivity is used in a novel cobalt-based ZIF-67/Ti3C2Tx composites, sulfide derivative (Co3S4/Ti3C2Tx) of which is then applied as an active supercapacitor material. The specific capacitance of ZIF-67/Ti3C2Tx is significantly higher than that of unmodified ZIF-67. The sulfide-containing derivatives of these compounds demonstrated pseudocapacitance. The specific capacitance of an electrode containing Co3S4/Ti3C2Tx as an active material is very high and equal to 602F/g at 1 A/g, which is 2.6 times higher than of a ZIF-67/Ti3C2Tx-containing electrode. The supercapacitor based on Co3S4/Ti3C2Tx maintained 81.6% of its original capacitance even at 10 A/g current density. Thus, the introduction of Ti3C2Tx into the ZIF-67 improves not only the electrical conductivity of the hybrid material but also its structural stability, which allows to act as support. An asymmetric Co3S4/Ti3C2Tx//AC supercapacitor (ASC) containing activated carbon (AC) as an anode showed a high energy density equal to 44.9 Wh/kg at 800.3 W/kg power density. This ASC also demonstrated high rate-performance (equal to 79.2%) and excellent cycling stability (with 88.3% capacitance retention and 99.23% Coulombic efficiency after 5000 cycles). The excellent electrochemical performance of our novel composite and conductivity, as well as the stability of its three-dimensional (3D) structure, make it a very promising material for energy storage applications.

Interfacial structure and property of eco-friendly carboxymethyl cellulose/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biocomposites.

This paper investigates the interface bonding of the novel carboxymethyl cellulose (CMC)/poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biocomposites, and the influence of coupling agents on the structure and properties of the biocomposites. The chemical structure, crystallisation behaviour and microstructure of the untreated and coupling agent treated biocomposites were examined by using FTIR, XRD and SEM respectively. The results suggested that maleic anhydride (MA) and vinyltrimethoxysilane (VTMS) covalently bonded to both CMC and PHBV macromolecules owing to their intrinsic multifunctionality, and promoted the distribution and embedment of the CMC in PHBV matrix, leading to a superior interfacial bonding of the resulted biocomposites. The enhanced interfacial bonding between the CMC and PHBV gave rise to a significant increase of tensile and flexural properties (i.e. tensile and flexural stress increased by up to 71% and 117% respectively, Young's and flexural modulus increased by up to 17% and 18% respectively) as well as thermal stability of the biocomposites.

Effect of morphology and phase engineering of MoS2 on electrochemical properties of carbon nanotube/polyaniline@MoS2 composites.

This paper rationally designs the morphology and phase structure of carbon nanotube/polyaniline@MoS2 (CNT/PANI@MoS2) composites, with MoS2 conductive wrapping growing vertically on the outer layer of the composites via hydrothermal method. The crystalline nature and chemical properties are characterized by X-ray diffraction (XRD), Flourier transformation infrared spectroscopy (FT-IR), Raman spectroscopy (Raman), X-ray photoelectron spectroscopy (XPS). Morphology and microstructures are determined by Scanning electric microscopy (SEM), Transmission electron microscope (TEM) and Brunauer-Emmett-Teller (BET). The developed composites possess excellent electrochemical properties (the specific capacitance is substantially increased by ~119%, reaching 700.0 F g-1 after wrapping by MoS2) and good cycling stability (after over 5000 cycles retains 80.8% capacitance) in three-electrode systems, which indicating that the unique morphology of MoS2 shells endow the channels to composites for rapid charge transport and ionic diffusion. Furthermore, symmetric supercapacitors devices assembled with the CNT/PANI@MoS2 composites achieve specific capacitance of 459.7 F g-1 at 1 A g-1, capacitance retention is 97.4% after 10,000 cycles and reach superior energy density of 40.9 Wh kg-1 at the power density of 400 W kg-1. This strategy of three-dimensional wrapping method may open up a new potential to relieve the dilemma of degraded performance of supercapacitor, while improving the capacitance and stability for supercapacitors.

Improved wet shear strength in eco-friendly starch-cellulosic adhesives for woody composites.

Development of eco-friendly adhesives from renewable biomass has attracted considerable attention in recent years. Here, we present a novel approach via combination of waste newspaper (WNP) powder, oxidized glutinous rice starch, and polyamidoamine-epichlorohydrin (PAE) to prepare a formaldehyde-free starch-cellulosic adhesive (SCA) for woody composites. The oxidation treatment made the carboxyl/carbonyl groups more available in starch. Plywood bonded by the optimum SCA with 50 wt% of the WNP powder showed a wet shear strength of 0.83 MPa exceeding that of the oxidized starch adhesive by 130.5 %. During the curing process of SCA, the oxidized starch and WNP fiber participated into the crosslinking reaction with PAE via ester and ether bonds, as evidenced by FTIR analysis. The resulting cured adhesive had enhanced crystalline structures, thermal properties, hydrophobicity, wet-cohesion, rheological properties, and adhesiveness to wood. The SCA showed great potential in wood composites as an alternative to formaldehyde-derived adhesives.

Cost-Effective Monolithic Hierarchical Carbon Cryogels with Nitrogen Doping and High-Performance Mechanical Properties for CO2 Capture.

Cost-effective nitrogen-doped monolithic hierarchical carbon cryogels with excellent mechanical properties and carbon dioxide (CO2) adsorption performance were prepared from phenol, melamine, and formaldehyde (PMF) by the sol-gel, freeze-drying, and then, pyrolysis processes under an inert atmosphere. The morphology, mechanical properties, pore structure, and chemical characteristics of these cryogels were investigated. The results showed that the dilution ratio played a crucial role in the preparation of nitrogen-doped PMF carbon cryogels with controlled structures. The prepared carbon cryogels were a kind of monolithic materials composed of a hierarchical pore structure and had high compression properties (0.67 and 9.4 MPa for strength and modulus), porosity (97.6%), surface area (1406 m2/g), and heteroatom nitrogen content (0.98-2.09%). CO2 adsorption capacities up to 5.75 mmol/g at 0 °C and 4.50 mmol/g at 25 °C under 1 bar were obtained, which is at a high level among N-doped carbon materials and far better than resorcinol-based carbon gels reported. These superior CO2 adsorption capacities, high isosteric adsorption heat (Qst), and good CO2/N2 adsorption selectivity were ascribed to the synergistic effect of high surface area, appropriate pore size, and also heteroatom doping.

A circular economy use of recovered sludge cellulose in wood plastic composite production: Recycling and eco-efficiency assessment.

This paper presents a novel development of sludge cellulose plastic composite (SPC) in line with the circular economy concept by using recovered sludge cellulose from wastewater treatment plant (WWTP). Bearing the aim of replacing the wood in wood plastic composite (WPC) with sludge cellulose, WPC was developed in parallel for determining the substitution potentials. In order to maximise the integration of properties, maleic anhydride (MA) and vinyltrimethoxysilane (VTMS) coupling agents were employed to refine the interfacial bonding of both SPC and WPC. In line with the main aim of circular economy - to decouple the economic value from the environmental impact, eco-efficiency analysis was performed for the developed process. The results showed that the tensile and flexural strength of the composites were substantially enhanced after both treatments, while MA appeared to be more efficient than VTMS in the refinery of interfacial bonding. Scanning electron microscope (SEM) analysis confirmed the improvement of interface by identifying well embedded and firmly bonded wood flour or sludge cellulose in the matrix. WPC was marginally more thermally stable than SPC, while SPC suggested comparable flexural properties. Eco-efficiency assessment results showed that the SPC had better environmental and economic performance than the WPC. The latter turns sludge cellulose as a promising sustainable alternative to wood or natural fibres in the production of WPC.

Synthesis of activated carbon from biowaste of fir bark for methylene blue removal.

Activated carbon (AC) was successfully prepared from low-cost forestry fir bark (FB) waste using KOH activation method. Morphology and texture properties of ACFB were studied by scanning and high-resolution transmission electron microscopies (SEM and HRTEM), respectively. The resulting fir bark-based activated carbon (ACFB) demonstrated high surface area (1552 m2 g-1) and pore volume (0.84 cm3 g-1), both of which reflect excellent potential adsorption properties of ACFB towards methylene blue (MB). The effect of various factors, such as pH, initial concentration, adsorbent content as well as adsorption duration, was studied individually. Adsorption isotherms of MB were fitted using all three nonlinear models (Freundlich, Langmuir and Tempkin). The best fitting of MB adsorption results was obtained using Freundlich and Temkin. Experimental results showed that kinetics of MB adsorption by our ACFB adsorbent followed pseudo-second-order model. The maximum adsorption capacity obtained was 330 mg g-1, which indicated that FB is an excellent raw material for low-cost production of AC suitable for cationic dye removal.

Effect of PVC film pretreatment on performance and lamination of wood-plastic composite plywood.

In order to solve the practical problem of heat transfer during the hot pressing process of a novel wood-plastic composite plywood, this paper investigates the perforation treatment of polyvinyl chloride (PVC) plastic films and their plywood composites. The PVC films were pretreated by the physical punching method, and the effects of PVC perforation diameter, hot pressing time and hot pressing temperature on the mechanical properties of the plywood composites were investigated by orthogonal experimental design. The results showed that the optimum hot pressing time was 7 min, the hot pressing temperature was 170 °C, and the PVC perforation diameter was 15 mm for the optimum mechanical properties. The punching pretreatment of PVC films gave rise to a reduction of the hot pressing time by 51 s due to improved heat transfer and heat loss by 5.06%, and allowed an increase in the initial moisture content of the veneer by 2-3%, thereby cutting down the drying cost in the veneer production process, which is conducive to energy conservation and environmental protection.

Revealing the Interface Structure and Bonding Mechanism of Coupling Agent Treated WPC.

This paper presents the interfacial optimisation of wood plastic composites (WPC) based on recycled wood flour and polyethylene by employing maleated and silane coupling agents. The effect of the incorporation of the coupling agents on the variation of chemical structure of the composites were investigated by Attenuated total reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and Solid state 13C Nuclear Magnetic Resonance spectroscopy (NMR) analyses. The results revealed the chemical reactions that occurred between the coupling agents and raw materials, which thus contributed to the enhancement of compatibility and interfacial adhesion between the constituents of WPC. NMR results also indicated that there existed the transformation of crystalline cellulose to an amorphous state during the coupling agent treatments, reflecting the inferior resonance of crystalline carbohydrates. Fluorescence Microscope (FM) and Scanning Electron Microscope (SEM) analyses showed the improvements of wood particle dispersion and wettability, compatibility of the constituents, and resin penetration, and impregnation of the composites after the coupling agent treatments. The optimised interface of the composites was attributed to interdiffusion, electrostatic adhesion, chemical reactions, and mechanical interlocking bonding mechanisms.