Sustainable high-strength and dimensionally stable composites through in situ regulation and reconstitution of bamboo-derived lignin and hemicellulose contents.

The development of modern construction and transportation industries demands increasingly high requirements for thin, lightweight, high-strength, and highly tough composite materials, such as metal carbides and concrete. Bamboo is a green, low-carbon, fast-growing, renewable, and biodegradable material with high strength and toughness. However, the density of its inner layer is low due to the functional gradient (the volume fraction of vascular bundles decreases from the outer layer to the inner layer), resulting in low performance, high compressibility, and significant amounts of bamboo waste. We utilized chemical and mechanical treatments of bamboo's low-density, low-strength inner layers to create lightweight, ultra-thin, high-strength, and high-toughness composites. The treatment included the partial removal of lignin and hemicellulose to alter the chemical components, followed by mechanical drying and hot pressing. The treated bamboo had 100.8 % higher tensile strength (150.35 MPa), 47.7 % higher flexural strength (97.67 MPa), and 132.0 % higher water resistance and was approximately 68.9 % thinner than the natural bamboo. The excellent physical and mechanical properties of the treated bamboo are attributed to the contraction of parenchyma cells during delignification, the interlocking due to the collapse of parenchyma cells during mechanical drying, and an increase in the density of hydrogen bonds between cellulose molecular chains during hot pressing. Our research provides a new strategy for obtaining sustainable, ultra-thin, lightweight, high-strength, and high-toughness composite materials from bamboo for construction and transportation applications.

Biomass 3D Printing: Principles, Materials, Post-Processing and Applications.

Under the background of green and low-carbon era, efficiently utilization of renewable biomass materials is one of the important choices to promote ecologically sustainable development. Accordingly, 3D printing is an advanced manufacturing technology with low energy consumption, high efficiency, and easy customization. Biomass 3D printing technology has attracted more and more attentions recently in materials area. This paper mainly reviewed six common 3D printing technologies for biomass additive manufacturing, including Fused Filament Fabrication (FFF), Direct Ink Writing (DIW), Stereo Lithography Appearance (SLA), Selective Laser Sintering (SLS), Laminated Object Manufacturing (LOM) and Liquid Deposition Molding (LDM). A systematic summary and detailed discussion were conducted on the printing principles, common materials, technical progress, post-processing and related applications of typical biomass 3D printing technologies. Expanding the availability of biomass resources, enriching the printing technology and promoting its application was proposed to be the main developing directions of biomass 3D printing in the future. It is believed that the combination of abundant biomass feedstocks and advanced 3D printing technology will provide a green, low-carbon and efficient way for the sustainable development of materials manufacturing industry.

Nanoemulsion containing Yellow Monascus pigment : Fabrication, characterization, storage stability, and lipase hydrolytic activity in vitro digestion.

The natural pigment of monascus is favored by human for its special coloring and physiological activity, and its development and application have attracted much attention. In this study, a novel corn oil-based nanoemulsion encapsulated with Yellow Monascus Pigment crude extract (CO-YMPN) was successfully prepared via the phase inversion composition method. The fabrication and stable conditions of the CO-YMPN including Yellow Monascus pigment crude extract (YMPCE) concentration, emulsifier ratio, pH, temperature, ionic strength, monochromatic light and storage time were investigated systemically. The optimized fabrication conditions were the emulsifier ratio (5:3 ratio of Tween 60 to Tween 80) and the YMPCE concentration (20.00% wt%)). Additionally, the DPPH radical scavenging capability of the CO-YMPN (19.47 ± 0.52%) was more excellent than each YMPCE or corn oil. Moreover, the kinetic analysis results based on Michaelis-Menten equation and constant revealed that CO-YMPN could improve lipase hydrolysis capacity. Therefore, the CO-YMPN complex had excellent storage stability and water solubility in the final water system, and the YMPCE showed brilliant stability.

Chitosan-based oxygen-doped activated carbon/graphene composite for flexible supercapacitors.

Flexible supercapacitors have attracted widespread attention from many researchers as a type of portable energy storage device. As a unique carbon material, graphene has shown great potential in supercapacitor electrodes, mainly due to its large theoretical specific surface area, high conductivity and chemical stability. Therefore, reasonable design of graphene-based hydrogels with low cost, high specific surface area, and excellent mechanical properties is of great significance for flexible and wearable energy storage device applications. Oxygen-doped activated carbon/graphene composite hydrogels have been fabricated using a one-step hydrothermal method. In the hybrid hydrogel, the activated carbon derived from chitosan with high specific surface area and oxygen-containing groups which were introduced by using a facile room-temperature oxidation strategy with HNO3 are assembled into the framework of reduced graphene oxide (rGO) to effectively prevent the restacking of rGO nanosheets and result in high specific surface area and high conductivity of the composite hydrogels, thereby leading to an excellent energy storage performance. The optimal sample displayed a high specific capacitance of 375.7 F g-1 in 1 M H2SO4 electrolyte at a current density of 1 A g-1. Furthermore, the assembled flexible supercapacitor showed an ideal cycling stability of 83% after 5000 charge/discharge cycles at 10 A g-1. The facile strategy developed in this work is of significance for the performance improvement of supercapacitor electrode materials.

Lightweight, strong, and form-stable cellulose nanofibrils phase change aerogel with high latent heat.

Phase change material (PCM) is promising for energy storage and release. However, the deformation and leaking during phase change generally limit its application. Herein, a lightweight, strong, and form-stable PCM aerogel was fabricated using Pickering emulsion templating technique. Cellulose nanofibrils (CNFs) were used to stabilize PCM into Pickering emulsion, which was further integrated into a 3D interconnected CNF network forming CNF/PCM composite aerogel. The composite aerogel is strong that can support over 5000 times of its own weight, and demonstrates exceptional form stability at 80 °C, showing no leakage after 20 heating/cooling cycles. The latent heat of CNF/PCM composite aerogel could reach 173.59 J·g-1, approximately 84.4% of the paraffin. The CNF/PCM composite aerogel showed relatively low thermal conductivity of 32.0-37.7 mW·m-1·K-1. The sustainability and impressive thermal regulating properties of the CNF/PCM composite aerogel make it an ideal candidate for applications in smart textile, smart building, batteries, and electronic devices.

Thermogravimetric Analysis-Fourier Transform Infrared Spectroscopy Study on the Effect of Extraction Pretreatment on the Pyrolysis Properties of Eucalyptus Wood Waste.

Eucalyptus wood is one of the important hardwood resources with attractive properties of rapid growth and good quality, which are widely used for the manufacture of wood-based boards, furniture, pulp and paper, and so on. In order to explore the potential of sawdust waste from the eucalyptus wood furniture factory as a bioenergy feedstock, its pyrolysis properties after different solvent extractions were examined using thermogravimetric analysis coupled with Fourier transform infrared spectrometry. The mass ratio of extractives in eucalyptus wood sawdust by benzene-alcohol, hot water, and sodium hydroxide solution was 4.25, 9.68, and 16.11%, respectively. After extraction, the thermal decomposition process of eucalyptus wood was promoted with a higher weight loss rate, lower activation energy, and lower residue content compared to the raw sample without pretreatment, and the promotion level was positively correlated to the strength of extracting solvent. CO2, CO, CH4, H2O, acids, aldehydes, aromatics, ethers, and alcohols were identified as the important intermediates in pyrolysis vapors, which can be tuned by different extraction pretreatments. In terms of typical gas products, benzene-alcohol enhanced the release of carbon dioxide, and hot water enhanced the water generation from dehydration reactions and slightly increased the production of carbon monoxide, while sodium hydroxide promoted the formation of methane at the early stage under 280 °C and later stage over 460 °C during the pyrolysis of eucalyptus wood. It is believed that the extraction pretreatment can not only obtain the bioactive extractive products but also benefit the pyrolysis process by lowering the energy barrier and tuning the composition of pyrolysis products.

Flexible and Super Thermal Insulating Cellulose Nanofibril/Emulsion Composite Aerogel with Quasi-Closed Pores.

Because of the prevailing environment and energy challenges, there has been a growing interest in biobased materials for thermal insulation application. Although cellulose aerogel has been considered as an excellent thermal insulating material, its thermal conductivity is generally negatively affected by the interconnected internal pores. Herein, it is demonstrated that a cellulose nanofibril (CNF)/emulsion composite aerogel with quasi-closed internal pores can be facilely fabricated by Pickering emulsion templating and solvent exchange methods. The CNF-stabilized oil-in-water Pickering emulsion (with an average diameter of 1.3 µm) can be converted into quasi-closed pores by sequential solvent exchange to acetone and tert-butanol (TBA), followed by freeze-drying from TBA to suppress the formation of large ice crystals. The presence of quasi-closed pores from emulsion templating is verified by both confocal microscopy and scanning electron microscopy images and is confirmed to reduce thermal conductivity to as low as 15.5 mW/(m K). Compared to the CNF aerogel, increasing emulsion content can lead to better volume retention with significantly reduced density (11.4 mg/cm3), increased mesoporosity, and enhanced specific modulus (18.2 kPa/(mg/cm3)) and specific yield strength (1.6 kPa/(mg/cm3)). In addition, the CNF/emulsion composite aerogel also demonstrates superb flexibility and infrared shielding performance.

The Dynamic Mechanical Analysis of Highly Filled Rice Husk Biochar/High-Density Polyethylene Composites.

In this study, rice husk biochar/high-density polyethylene (HDPE) composites were prepared via melt mixing followed by extrusion. Effects of biochar content and testing temperature on the dynamic mechanical analysis (DMA) of the composites were studied. Morphological analysis of the rice husk biochar and composites were evaluated by scanning electron microscopy (SEM). The results showed that biochar had a positive effect on dynamic viscoelasticity, creep resistance and stress relaxation properties of the composites, but the creep resistance and stress relaxation of the composites decreased with the increase of temperature. SEM analysis showed that HDPE components were embedded in the holes of the rice husk biochar, and it is believed that strong interaction was achieved.

The Preparation and Characterization of Pyrolysis Bio-Oil-Resorcinol-Aldehyde Resin Cold-Set Adhesives for Wood Construction.

Resorcinol-formaldehyde (RF) resin is a kind of excellent exterior-grade wood structural adhesive, which can be conveniently cold-set for various applications. In order to decrease the production cost, pyrolysis bio-oil from renewable bioresources was used to replace resorcinol to synthesize the bio-oil-resorcinol-aldehyde (BRF) resin. The effect of replacing resorcinol with bio-oil on the properties, bonding performance, and characterization of resorcinol-aldehyde resin was comparatively investigated. A higher solid content and viscosity, albeit a lower shear strength, was found when the replacement ratio of bio-oil increased. The bonding performance of BRF with 10 and 20 wt % bio-oil was close to that of the pure RF resin. However, the trends of being less cross-linked, more easily decomposed, but more porous were found when the substitution ratio of bio-oil was higher than 20 wt %. Interestingly, it was found that the wood failure values of the BRF resins with bio-oil of no more than 20 wt % were slightly higher than that of the pure RF resin. On the whole, BRF resins with 20 wt % bio-oil is recommended as a wood structural adhesive, comprehensively considering the bio-oil substitution ratio and resin properties. The results obtained here showed that pyrolysis bio-oil is a promising green raw material for the production of RF resin with lower cost.

Optimization Extraction, Preliminary Characterization and Antioxidant Activities of Polysaccharides from Semen Juglandis.

The optimization extraction process, preliminary characterization and antioxidant activities of polysaccharides from Semen Juglandis (SJP) were studied in this paper. Based on the Box-Behnken experimental design and response surface methodology, the optimal extraction conditions for the SJP extraction were obtained as follows: temperature 88 °C, extraction time 125 min and ratio of liquid to solid 31 mL/g. Under these conditions, experimental extraction yield of SJP was (5.73 ± 0.014)% (n = 5), similar to the predicted value of 5.78%. Furtherly, the purified SJP obtained from SJP extract by DEAE-52 and Sephacryl S-100 chromatography was analyzed to be rhamnose, galacturonic acid, galactose, arabinose and fucose in the molar ratio of 1:6.34:1.38:3.21:1.56. And the weight-average molecular weight and radius of gyration of the purified SJP in 0.1 M NaCl were determined to be 2.76 × 104 g/mol and 122 nm by SEC-MALLS, respectively. More importantly, it exhibited appreciable antioxidant activities compared to the standard Vc, such as DPPH radical scavenging activity (IC50 0.21 mg/mL), strong reducing power, ABTS radical scavenging activity (IC50 0.29 mg/mL), and hydroxyl radical scavenging activity (IC50 0.38 mg/mL). These results indicate that SJP may be useful for developing functional health products or natural antioxidant.

Optimization of the solid-state fermentation and properties of a polysaccharide from Paecilomyces cicadae (Miquel) Samson and its antioxidant activities in vitro.

The culture conditions for the yield of a polysaccharide (PCPS) produced by Paecilomyces cicadae (Miquel) Samson on solid-state fermentation were investigated using response surface methodology (RSM). Plackett-Burman design (PBD) was applied to screen out significant factors, followed by the paths of steepest ascent to move to the nearest region of maximum response. Then Box-Behnken design (BBD) was conducted to optimize the final levels of the culture conditions. After analyzing the regression equation and the response surface contour plots, relative humidity 56.07%, inoculum 13.51 mL/100 g and temperature 27.09°C were found to be the optimal key parameters for PCPS production. The maximum predicted yield of PCPS was 10.76 mg/g under the optimized conditions. The resulting PCPS (FPCPS) generated at optimal conditions was purified by chromatography column and found to be composed of mannose (43.2%), rhamnose (32.1%), xylose (14.5%) and arabinose (10.2%). Based on the size exclusion chromatography combined with multi-angle laser light scattering (SEC-MALLS) analysis, FPCPS adopted a Gaussian coil conformation in 0.1 M NaNO3 solution with 3.75 × 10(6) g/mol of the weight-average molar mass (Mw) and 41.1 nm of the root-mean square radius (Rg(2))z (1/2). Furthermore, both of the polysaccharides were revealed to have strong antioxidant activities by evaluating in DPPH radical, superoxide radicals and hydroxyl radical assay. These data suggest the polysaccharides of Paecilomyces cicadae (Miquel) Samson produced by solid-state fermentation could be explored as potential natural antioxidants.

Thermogravimetric investigation on the degradation properties and combustion performance of bio-oils.

The degradation properties and combustion performance of raw bio-oil, aged bio-oil, and bio-oil from torrefied wood were investigated through thermogravimetric analysis. A three-stage process was observed for the degradation of bio-oils, including devolatilization of the aqueous fraction and light compounds, transition of the heavy faction to solid, and combustion of carbonaceous residues. Pyrolysis kinetics parameters were calculated via the reaction order model and 3D-diffusion model, and combustion indexes were used to qualitatively evaluate the thermal profiles of tested bio-oils for comparison with commercial oils such as fuel oils. It was found that aged bio-oil was more thermally instable and produced more combustion-detrimental carbonaceous solid. Raw bio-oil and bio-oil from torrefied wood had comparable combustion performance to fuel oils. It was considered that bio-oil has a potential to be mixed with or totally replace the fuel oils in boilers.

[TG-fTIR study of the thermal-conversion properties of holo-cellulose derived from woody biomass].

Thermal-conversion properties of cellulose, hemi-cellulose and holo-cellulose derived from woody biomass were studied using TG-FTIR, and also compared to those of avicel cellulose and xylan. 3-D diffusion model was applied to calculate the kinetic parameters of thermal-conversion reaction of biomass materials, such as the activation energy, pre-exponential factors, etc, which showed good regression results. With the analysis of three-dimensional IR spectra of gas products, featured peaks of HzO, CO, CO2, CH4, and oxygenates were obviously observed where showing up with the maximum weight-loss rate in DTG curves. The possible forming routes of major gaseous products were analyzed and discussed. The order of releasing amounts for gaseous productions was approximately as CO2 > H2O > CO CH4. Based on the comprehensive understanding and comparative analysis of the whole results, it is concluded that the thermal conversion process of holo-cellulose was the result of interaction between cellulose and hemi-cellulose under the dominant role of cellulose.

[Analysis of pyrolysis process and gas evolution rule of larch wood by TG-FTIR].

The weight-loss character and gas evolution rule of larch wood at different heating rates were investigated by TG-FTIR (thermogravimetric analyzer coupled to a Fourier transform infrared spectrometer), and the results were compared with those of larch wood model-component mixture. The main weight-loss area of larch wood was wider than larch wood model-component mixture, and the residual char yield of larch wood (18.97%) was lower than larch wood model-component mixture (29.83%). During the pyrolysis process, the activation energy of larch wood model-component mixture was higher than the larch wood's in the low-temperature region, but there was little difference between the two segments in high temperature region. Larch wood came through several stages of water extraction, main component decomposition, charring during its pyrolysis process, and gas precipitation mainly happening at near 375 degrees C. The order of main gas products generated from the larch wood pyrolysis reaction was CO2 > H2O > CH4 > CO, and the gas product yield was significantly increased when the heating rate increased. The larch wood model-component mixture had the similar basic rules of producing gas to larch wood, but the former had relatively higher precipitation density than the latter.