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Laser-induced graphitization (LIG) is a method of converting a carbon-rich precursor into a highly conductive graphite-like carbon by laser scribing. This method has shown great promise as a versatile and low-cost patterning technique. Here we show for the first time how an ink based on cellulose and lignin can be patterned using screen printing followed by laser graphitization. Screen printing is one of the most commonly used manufacturing techniques of printed electronics, making this approach compatible with existing processing of various devices. The use of forest-based materials opens the possibility of producing green and sustainable electronics. Pre-patterning of the ink enables carbon patterns without residual precursor between the patterns. We investigated the effect of the ink composition, laser parameters, and additives on the conductivity and structure of the resulting carbon and could achieve low sheet resistance of 3.8 Ω sq−1 and a high degree of graphitization. We demonstrated that the process is compatible with printed electronics and finally manufactured a humidity sensor which uses lignin as the sensing layer and graphitized lignin as the electrodes.

Redox flow batteries represent a remarkable alternative for grid-scale energy storage. They commonly employ carbon felts or carbon papers, which suffer from low activity towards the redox reactions involved, leading to poor performance. Here we propose the use of electrospun freestanding carbon materials derived from lignin as alternative sustainable electrodes for all-vanadium flow batteries. The lignin-derived carbon electrospun mats exhibited a higher activity towards the VO2+/VO2+ reaction than commercial carbon papers when tested in a three-electrode electrochemical cell (or half-cell), which we attribute to the higher surface area and higher amount of oxygen functional groups at the surface. The electrospun carbon electrodes also showed performance comparable to commercial carbon papers, when tested in a full cell configuration. The modification of the surface chemistry with the addition of phosphorous produced different effect in both samples, which needs further investigation. This work demonstrates for the first time the application of sustainably produced electrospun lignin-derived carbon electrodes in a redox flow cell, with comparable performance to commercial materials and establishes the great potential of biomass-derived carbons in energy devices.

Upscaling lignin-based precursor fibre production is an essential step in developing bio-based carbon fibre from renewable feedstock. The main challenge in upscaling of lignin fibre production by melt spinning is its melt behaviour and rheological properties, which differ from common synthetic polymers used in melt spinning. Here, a new approach in melt spinning of lignin, using a spin carrier system for producing bicomponent fibres, has been introduced. An ethanol extracted lignin fraction from LignoBoost process of commercial softwood kraft black liquor was used as feedstock. After additional heat treatment, melt spinning was performed in a pilot-scale spinning unit. For the first time, biodegradable polyvinyl alcohol (PVA) was used as a spin carrier to enable the spinning of lignin by improving the required melt strength. PVA-sheath/lignin-core bicomponent fibres were manufactured. Afterwards, PVA was dissolved by washing with water. Pure lignin fibres were stabilized and carbonized, and tensile properties were measured. The measured properties, tensile modulus of 81.1 ± 3.1 GPa and tensile strength of 1039 ± 197 MPa, are higher than the majority of lignin-based carbon fibres reported in the literature. This new approach can significantly improve the melt spinning of lignin and solve problems related to poor spinnability of lignin and results in the production of high-quality lignin-based carbon fibres. This article is part of the theme issue ‘Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 2)’.

An important factor in the development of sodium-ion batteries (SIBs) is the use of cheap and sustainable materials. Sodium lignosulfonate, a lignin derivative, is demonstrated here as an attractive, “green”, water-soluble, and potentially cost-effective binder for use in hard carbon anodes for SIBs. A comparison of its battery cycling performance is made against other binders including sodium carboxymethyl cellulose and lignin, obtained from the kraft process, as well as sodium alginate, derived from algae. Apart from lignin, which requires processing in N-methyl-2-pyrrolidone, the other three binders are water-soluble. Lignosulfonate shows comparable or better performance, with high capacity retention and stability, when using 1 M NaPF6 in propylene carbonate or ethylene carbonate:diethyl carbonate electrolytes for both half- and full-cells (against a Prussian white cathode). Further improvements are observed when including styrene-butadiene rubber as a co-binder. X-ray photoelectron spectroscopy demonstrates similar solid electrolyte interphase compositions after the initial sodium insertion for both lignosulfonate and carboxymethyl cellulose binders. However, after subsequent cycling, the surface layer composition and thickness are found to be dependent on the binder. For the lignosulfonate-based electrode, the layer appears thicker but comprises a smaller fraction of carbon–oxygen species.

Sodium ion batteries (SIBs) are emerging as an alternative battery technology to lithium ion batteries because they have the potential of having a similar energy density and the advantage of sodium ...

In this study, a renewable reinforcement, namely cellulose nanocrystals (CNC), was used to develop a bio-based nanocomposite UV-cured coating system with improved performance. CNC was modified in order to be compatible with the nonpolar polymer matrix (acrylated epoxidized soybean oil (AESO)). The CNC was modified by two methods, with acryloyl chloride or a cationic surfactant (HDTMA). The mechanical properties and structure of bionanocomposites were evaluated. The addition of CNC increased modulus of elasticity (MOE) and tensile strength of the cured film coatings. Use of CNC modified by HDTMA and acrylated CNC led to a higher increase in tensile strength and MOE, relative to un-modified CNC. Best performance enhancement was in hardness and reduced elastic modulus (Er), measured by the nanoindentation technique, which were improved several fold by CNC addition. Hardness, Er, MOE and tensile strength increased with CNC loading level in the matrix. Hardness measurements of cured film coating by pencil hardness test methods confirmed that CNC improved the hardness of the films. Studying the morphology of the nanocomposites revealed that surface modification method of CNC affected nanocomposite film structure and thus the mechanical properties.

Demand for durable clear wood coatings is on the rise. Cellulose nanocrystals (CNC) constitute an organic nanomaterial widely studied in polymer composites for its reinforcing effect. In this study, CNC was used to enhance the performance of a UV curable high-solid content coating system intended for indoor environments. The CNC surface was modified by a cationic surfactant since the coating system was hydrophobic resin-based requiring hydrophobic nanomaterial reinforcement. Modified CNC was mixed with the coating system using a high-speed mixer and the ultrasonication technique. Mechanical, thermal and morphological properties and curing behavior of the newly developed UV-curing coatings were assessed. Inclusion of CNC in the coating increased the mechanical properties (hardness and reduced modulus) of the coating system to a large extent. Thermal stability of the coating system was also improved by CNC addition. The CNC did not affect the curing behavior of the coating, in contrast to most inorganic nanomaterials. The CNC dispersed well in the matrix at 1% loading. Results of this study show that CNC can be used successfully with high-solid content coating systems.

The process of stabilization is essential in the production of carbon fibers from lignins. During stabilization, the initially thermoplastic lignin polymer is converted to a thermoset polymer allowing for high-temperature treatment without a change in shape. In this work, hardwood (HKL) and softwood (SKL) Kraft lignins were stabilized in air at temperatures between 190 and 340 °C before carbonization at 800 °C in a nitrogen atmosphere. Due to the differences in side-chain linkages, functional groups and molar mass, the lignins exhibit different structural changes upon stabilization and hence develop different porosities upon carbonization. Both lignins undergo major crosslinking reactions in the side chains at low temperatures and degradation reactions at high temperatures during stabilization. Crosslinking gives rise to narrow pore size distributions with mainly (sub-) nanometer pores, whereas degradation reactions lead to a more open pore structure with additional mesoporosity (>2 nm). When both types of reactions take place simultaneously, highly accessible (sub-) nanoporosity can be effectively created, which boosts the performance of supercapacitors operating in 6 M KOH(aq). This effect terminates when the crosslinking reactions cease and mainly degradation reactions take place, which occurs in HKL at 340 °C. SKL shows both a lower degree of crosslinking and degradation and hence develops less specific surface area. The optimum performance in an aqueous alkaline supercapacitor is achieved with HKL stabilized at 310 °C. It shows a specific gravimetric capacitance of 164 F g−1 at 0.1 A g−1 and 119 F g−1 at 250 A g−1 with a capacitance retention of more than 90% after 10 000 cycles. M. J. M. L. and D. C. A. thank Spanish Ministry of Science, Innovation and Universities and FEDER (project RTI2018-095291-B-I00) for financial support. C. P. G. and C. O'K. thank Shell. MMT and PS thank RISE AB for co-funding Philipp Schlee's PhD position.

Lignin was extracted from Alamo switchgrass (Panicum virgatum) and yellow polar (Liriodendron tulipifera) by organosolv fractionation at different pretreatment temperatures, and its chemical structure was studied by means of elemental analysis and spectroscopy. Thermal properties of lignins were investigated using thermogravimetric analysis and differential scanning calorimetry. Lignin fibers were produced via melt-spinning by a twin-screw extruder with a custom spinneret. Fibers were thermostabilized at different rates and finally carbonized. In both species, lignin obtained from higher severity organosolv fractionation had fewer impurities, higher content of phenolic hydroxyl groups, and more condensed structures as a result of extensive cleavage of aryl ether linkages. Higher organosolv severity improved the ability to spin fibers; in the case of switchgrass, only the high severity sample was spinnable. High severity also decreased thermostabilization time and increased tensile strength and modulus of ...

A very simple method to enhance the low volumetric energy density of free-standing carbon nanofiber electrodes., We have discovered a very simple method to address the challenge associated with the low volumetric energy density of free-standing carbon nanofiber electrodes for supercapacitors by electrospinning Kraft lignin in the presence of an oxidizing salt (NaNO3) and subsequent carbonization in a reducing atmosphere. The presence of the oxidative salt decreases the diameter of the resulting carbon nanofibers doubling their packing density from 0.51 to 1.03 mg cm–2 and hence doubling the volumetric energy density. At the same time, the oxidative NaNO3 salt eletrospun and carbonized together with lignin dissolved in NaOH acts as a template to increase the microporosity, thus contributing to a good gravimetric energy density. By simply adjusting the process parameters (amount of oxidizing/reducing agent), the gravimetric and volumetric energy density of the resulting lignin free-standing carbon nanofiber electrodes can be carefully tailored to fit specific power to energy demands. The areal capacitance increased from 147 mF cm–2 in the absence of NaNO3 to 350 mF cm–2 with NaNO3 translating into a volumetric energy density increase from 949 μW h cm–3 without NaNO3 to 2245 μW h cm–3 with NaNO3. Meanwhile, the gravimetric capacitance also increased from 151 F g–1 without to 192 F g–1 with NaNO3.

Organosolv fractionation is a promising pathway to separate cellulosic biomass into high purity cellulose, hemicelluloses, and lignin. This work specifically investigates the properties of lignins isolated at specific time points as fractionation progressed, with the intent of correlating fractionation time with lignin purity, yield, thermal and chemical properties. Yellow poplar (Liriodendron tulipifera) was fractionated using a mixture of methyl isobutyl ketone, ethanol, and water with sulfuric acid as catalyst at 140 °C over a two-hour period. Aliquots of the liquor were collected by sampling every 15 min during the fractionation to generate a series of lignins. The results showed that with increased fractionation time, lignin purity improved from 90.3 to 94.6% and the glass transition temperature increased from 117 to 137 °C. The loss of aliphatic OH and increase of phenolic OH with fractionation time led to an increase in condensed structures and increased polydispersity at times greater than 90 min. Principal component analysis of Fourier transform infrared spectroscopic data confirmed the shift to higher purity and more condensed chemical structures with increasing fractionation time. Overall, this study demonstrates that thermal and chemical properties of lignin change with the organosolv fractionation time.

Lignin/lignin blends were used to improve fiber spinning, stabilization rates, and properties of lignin-based carbon fibers. Organosolv lignin from Alamo switchgrass (Panicum virgatum) and yellow poplar (Liriodendron tulipifera) were used as blends for making lignin-based carbon fibers. Different ratios of yellow poplar:switchgrass lignin blends were prepared (50:50, 75:25, and 85:15 w/w). Chemical composition and thermal properties of lignin samples were determined. Thermal properties of lignins were analyzed using thermogravimetric analysis and differential scanning calorimetry. Thermal analysis confirmed switchgrass and yellow poplar lignin form miscible blends, as a single glass transition was observed. Lignin fibers were produced via melt-spinning by twin-screw extrusion. Lignin fibers were thermostabilized at different rates and subsequently carbonized. Spinnability of switchgrass lignin markedly improved by blending with yellow poplar lignin. On the other hand, switchgrass lignin significantly improved thermostabilization performance of yellow poplar fibers, preventing fusion of fibers during fast stabilization and improving mechanical properties of fibers. These results suggest a route towards a 100% renewable carbon fiber with significant decrease in production time and improved mechanical performance.

Replacing petroleum by biomass can be economically feasible by generating revenue from the three primary biomass constituents., The production of renewable chemicals and biofuels must be cost- and performance- competitive with petroleum-derived equivalents to be widely accepted by markets and society. We propose a biomass conversion strategy that maximizes the conversion of lignocellulosic biomass (up to 80% of the biomass to useful products) into high-value products that can be commercialized, providing the opportunity for successful translation to an economically viable commercial process. Our fractionation method preserves the value of all three primary components: (i) cellulose, which is converted into dissolving pulp for fibers and chemicals production; (ii) hemicellulose, which is converted into furfural (a building block chemical); and (iii) lignin, which is converted into carbon products (carbon foam, fibers, or battery anodes), together producing revenues of more than $500 per dry metric ton of biomass. Once de-risked, our technology can be extended to produce other renewable chemicals and biofuels.

Lab-processed cellulose nanofibrils (CNF-L), commercial cellulose nanofibrils (CNF-C), and cellulose nanocrystals (CNC) were used in this study as reinforcing materials in phenol formaldehyde (PF) resin. The mechanical modification of adhesives and cell wall layers (S2 and compound corner-middle lamellae [CCML]) by the three types of cellulose particles was investigated by nanoindentation. Results showed that cellulose nano-materials can improve the mechanical properties of both adhesives and the cell wall structure. CNF-C had the most obvious reinforcing effect on the elastic modulus (Er) and hardness within the glue line. With modification, the Er and hardness reached 13.0 and 0.436 GPa, respectively, in the S2 layer far from the glue line. In comparison, the control sample had an Er and hardness of 7.31 and 0.256 GPa, respectively.

The collision-activated fragmentation pathways and reaction mechanisms of 34 deprotonated model compounds representative of lignin degradation products were explored experimentally and computationally. The compounds were evaporated and ionized by using negative-ion mode electrospray ionization doped with NaOH to produce abundant deprotonated molecules. The ions were isolated and subjected to collision-activated dissociation (CAD). Their fragment ions were then isolated and also subjected to CAD. This was repeated until no further fragmentation was observed (up to MS6 ). This approach enabled the identification of characteristic reaction pathways and delineation of reasonable fragmentation mechanisms for deprotonated molecules containing various functional groups. The varying fragmentation patterns observed for different types of compounds allow for the identification of the functionalities in these compounds. This information was utilized to identify the presence of specific functionalities and their combinations in molecules in an organosolv lignin sample.

In this study nanocrystalline cellulose (NCC) was used to improve the performance of polyvinyl acetate (PVA) as a wood adhesive. NCC was added to PVA at different loadings (1%, 2% and 3%) and the blends were used as binder for wood. Block shear tests were done to evaluate bonding strength of PVA at different conditions; dry and wet conditions, at the elevated temperature (100 °C). The mechanical properties of PVA film and its composites with NCC were measured by nanoindentation technique. Thermal stability and structure of nanocomposites were studied by thermogravimetric analysis and atomic force microscopy (AFM). The block shear tests demonstrate that NCC can improve bonding strength of PVA in all conditions. Hardness, modulus of elasticity (MOE) and creep of PVA film were also changed positively by the addition of NCC. Thermal stability of PVA was significantly improved as NCC was added to PVA. Structural studies revealed that variations in shear strength and other properties can be related to the quality of NCC dispersion in the PVA matrix.

Hygroscopicity, low durability, and low thermal resistance are disadvantages of lignocellulosic materials that also plague wood–plastic composites (WPCs). Hemicellulose is the most hydrophilic wood polymer and is currently considered as a sugar source for the bioethanol industry. The objective of this research is to extract hemicellulose from woody materials and enhance the properties of WPC by diminishing the hydrophilic character of wood. Hemicellulose of Southern Yellow Pine was extracted by hot-water at three different temperatures: 140, 155, and 170 °C. Wood flour was compounded with polypropylene in an extruder, both with and without a coupling agent. Injection molding was used to make tensile test samples. The thermal stability of wood flour was found to have increased after extraction. Extraction of hemicellulose improved the tensile strength and water resistance of composites, which may indicate a decrease in the hygroscopicity of wood flour, better compatibility, and interfacial bonding of the filler and matrix.

To find out the penetration of PF into the wood cell wall and its effects onthe mechanical properties in the cellular level, the elastic modulus and hardness of secondary wall (S2layer) and compound corner middle lamella (CCML) near PF bond line region were determined by nanoindentation. Compare to the reference cell walls (unaffected by PF), PF penetration into the wood tissues showed improved elastic modulus and hardness. And the mechanical properties decreased slowly with the increasing the distance from the bond line, which are attributed to the effects of PF penetration into S2layer and CCML. The reduced elastic modulus variations were from18.8 to 14.4 GPa for S2layer, and from10.1 to 7.65 GPa for CCML. The hardness was from 0.67 to 0.52 GPa for S2layer, and from 0.65 to 0.52 GPa for CCML. In each test viewpoint place, the average hardness of CCML was almost as high as that of S2layer, but the reduced elastic modulus was about 50% less than that of S2layer. But the increase ratio of mechanical properties was close. All the results showed PF penetrates into the CCML. The penetration behavior and penetration depth from bond line were similar in both S2layer and CCML.

Hot-water pretreatment was performed on wood strands to investigate effects of the extraction of hemicellulose under different temperature (140, 155, and 170 °C) and time durations (30 and 60 min) conditions. Hydrolysate was analyzed by means of high-performance liquid chromatography. Chemical changes in the surface of wood strands were studied by infrared spectroscopy. The effects of hemicellulose extraction on the wettability of wood strands were studied by measuring the contact angle and surface free energy. The mechanical properties of wood cell walls before and after treatment were studied by nanoindentation. Among the extracted monosaccharides, mannose was found in the highest concentration. The mechanical properties of cell walls showed little decrease after extraction. The chemical changes in the surface of the wood strands reduced wettability of wood surface by water and produced hydrophobic characteristics after extraction.

Hemicellulose is the most hydrophilic polymer of wood, and as a polysaccharide, it has potential applications in conversion to biofuels. The objective of this study was to enhance properties of flakeboard by extracting hemicellulose. Hot-water pretreatment was performed to extract hemicellulose under different temperatures (140°C, 155°C, and 170°C) and times (30 and 60 min). The flakes were blended with 5 percent liquid phenol-formaldehyde resin and 1 percent wax emulsion. The mat was pressed at 200°C for 5 minutes. The physical and mechanical properties and the susceptibility of flakeboard to mold were studied. Panels made from the hemicellulose-extracted flakes showed remarkable decreases in water absorption and thickness swelling without a decrease in mechanical properties. Resistance of the panels to the mold growth also increased with increasing mass loss due to extraction. The most severe condition of extraction (170°C, 60 min), in addition to having the lowest water absorption and thickness swelling, showed the highest mold resistance.

The use of nanocrystalline cellulose (NCC) has become increasingly prevalent in recent years, with limited studies on the the time-dependent characteristics of wood-adhesive composite reinforced by it. To analyze the viscoelasticity of control phenol formaldehyde (PF) resin and wood-resin composites added with three types of NCC, the micro-creep properties of control phenol formaldehyde (PF) resin and PF resin with cellulose nanofibrils (CNF), cellulose microfibrils (CMF), and cellulose nanocrystals (CNC) were investigated by nanoindentation (NI). The sample creep curves proved that adding CNC, CMF, and CNF into the PF resin remarkably impacted the creep properties of the wood-resin sample interface. The cured resin sample had the lowest strength and the most deformation, and the pure wood sample performed slightly better. Among the three NCC-added wood-resin samples, the CNF-added wood-resin sample has the least deformation in the same load and the least permanent deformation after unloading followed by CMF-added and CNC-added wood-resin samples. In the derivative of creep curve function, the depth tendency of CNC-added and CNF-added wood-resin samples showed a gently increasing slope with time in contrast to CMF-added ones. Furthermore, scanning probe microscopy (SPM) images supported that PF resin had filled up the pores of the wood microstructures and strengthened the wood-resin sample in the company of NCC, which was then able to carry the load.

Organosolv switchgrass lignin (SGL) and hardwood lignin (HWL) polymers are used as precursors to prepare low cost carbon fibers (CFs). Lignin powder and fiber samples are stabilized and carbonized at different conditions to investigate the effect of HCl on thermal-oxidative stabilization time, mass yield, fiber diameter, and mechanical properties. The results show that HCl can accelerate stabilization and reduce the stabilization time from many hours to 75 min for the SGL fibers, and to 35 min for the HWL fiber. The rate of rapid stabilization in HCl/air is at least four times faster than conventional stabilization in air. The CFs prepared with two different stabilization methods have almost the same strength and modulus, but higher carbon yield is obtained with the rapid stabilization due to a short time of oxidation. Pores and defects observed on the surface and the cross-section of the CFs across all stabilization conditions contribute to low fiber strength. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017, 134, 45507.