| 1. |
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| 2. |
- Alimohammadzadeh, Rana, et al.
(författare)
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Scalable Improvement of the Strength Properties of Chemimechanical Pulp Fibers by Eco-Friendly Catalysis
- 2018
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Ingår i: IMPC 2018. - Trondheim, Norway.
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Konferensbidrag (refereegranskat)abstract
- The sustainable improvement of the strength properties of chemimechanical pulp by eco-friendlycatalysis is disclosed. Significant research activities have been performed on the use of cationic starchand polyelectrolyte complexes for improving the strength properties of cellulose-based materials. Herewe apply an eco-friendly strategy based on catalysis for significantly improving the strength propertiesof sheets made from chemimechanical pulp (CTMP) and bleeched sulphite pulp (BSP) using sustainablepolyelectrolyte complexes as the strength additives and organocatalysis. This surface engineeringstrategy significantly increased the strength properties of the assembled sheets (up to 100% in the caseof Z-strength). We also developed a catalytic selective colour marking of the cationic potato starch (CS)and carboxymethylcellulose (CMC) in order to elucidated how the specific strength additives aredistributed on the sheets. It revealed that the strength additives were more evenly distributed on thesheets made from CTMP as compared to BSP sheets. This is most likely attributed to the presence oflignin in the former lignocellulosic material. It also contributes to the increase in strength (up to 100%,Z-strength) for the CTMP derived sheets. The selective colour marking method also revealed that morestrength additives had been bound to the pulps in the presence of the catalyst.
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| 3. |
- Alimohammadzadeh, Rana, et al.
(författare)
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Sustainable Surface Engineering of Lignocellulose and Cellulose by Synergistic Combination of Metal‐Free Catalysis and Polyelectrolyte Complexes
- 2019
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Ingår i: Global Challenges. - : Wiley. - 2056-6646. ; 3
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Tidskriftsartikel (refereegranskat)abstract
- A sustainable strategy for synergistic surface engineering of lignocellulose and cellulose fibers derived from wood by synergistic combination of metal‐free catalysis and renewable polyelectrolyte (PE) complexes is disclosed. The strategy allows for improvement and introduction of important properties such as strength, water resistance, and fluorescence to the renewable fibers and cellulosic materials. For example, the “green” surface engineering significantly increases the strength properties (up to 100% in Z‐strength) of chemi‐thermomechanical pulp (CTMP) and bleached sulphite pulp (BSP)‐derived sheets. Next, performing an organocatalytic silylation with a nontoxic organic acid makes the corresponding lignocellulose and cellulose sheets hydrophobic. A selective color modification of polysaccharides is developed by combining metal‐free catalysis and thiol‐ene click chemistry. Next, fluorescent PE complexes based on cationic starch (CS) and carboxymethylcellulose (CMC) are prepared and used for modification of CTMP or BSP in the presence of a metal‐free catalyst. Laser‐scanning confocal microscopy reveals that the PE‐strength additive is evenly distributed on the CTMP and heterogeneously on the BSP. The fluorescent CS distribution on the CTMP follows the lignin distribution of the lignocellulosic fibers.
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| 4. |
- Andres, Britta, 1986-, et al.
(författare)
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Cellulose binders for electric double-layer capacitor electrodes : The influence of cellulose quality on electrical properties
- 2018
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Ingår i: Materials & design. - : Elsevier BV. - 0264-1275 .- 1873-4197. ; 141, s. 342-349
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose derivatives are widely used as binders and dispersing agents in different applications. Binders composed of cellulose are an environmentally friendly alternative to oil-based polymer binding agents. Previously, we reported the use of cellulose nanofibers (CNFs) as binders in electrodes for electric double-layer capacitors (EDLCs). In addition to good mechanical stability, we demonstrated that CNFs enhanced the electrical performance of the electrodes. However, cellulose fibers can cover a broad range of length scales, and the quality requirements from an electrode perspective have not been thoroughly investigated. To evaluate the influence of fiber quality on electrode properties, we tested seven samples with different fiber dimensions that are based on the same kraft pulp. To capture the length scale from fibers to nanofibrils, we evaluated the performance of the untreated kraft pulp, refined fibers, microfibrillated cellulose (MFC) and CNFs. Electrodes with kraft pulp or refined fibers showed the lowest electrical resistivity. The specific capacitances of all EDLCs were surprisingly similar, but slightly lower for the EDLC with CNFs. The same electrode sample with CNFs also showed a slightly higher equivalent series resistance (ESR), compared to those of the other EDLCs. Graphite dispersions with MFC showed the best dispersion stability.
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| 5. |
- Andres, Britta, 1986-
(författare)
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Low-Cost, Environmentally Friendly Electric Double-Layer Capacitors : Concept, Materials and Production
- 2017
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Today’s society is currently performing an exit from fossilfuel energy sources. The change to sustainable alternativesrequires inexpensive and environmentally friendly energy storagedevices. However, most current devices contain expensive,rare or toxic materials. These materials must be replaced bylow-cost, abundant, nontoxic components.In this thesis, I suggest the production of paper-based electricdouble-layer capacitors (EDLCs) to meet the demand oflow-cost energy storage devices that provide high power density.To fulfill the requirements of sustainable and environmentallyfriendly devices, production of EDLCs that consist of paper,graphite and saltwater is proposed. Paper can be used as aseparator between the electrodes and as a substrate for theelectrodes. Graphite is suited for use as an active material in theelectrodes, and saltwater can be employed as an electrolyte.Westudied and developed different methods for the productionof nanographite and graphene from graphite. Composites containingthese materials and similar advanced carbon materialshave been tested as electrode materials in EDLCs. I suggest theuse of cellulose nanofibers (CNFs) or microfibrillated cellulose(MFC) as a binder in the electrodes. In addition to improvedmechanical stability, the nanocellulose improved the stabilityof graphite dispersions and the electrical performance of theelectrodes. The influence of the cellulose quality on the electricalproperties of the electrodes and EDLCs was investigated.The results showed that the finest nanocellulose quality is notthe best choice for EDLC electrodes; MFC is recommended forthis application instead. The results also demonstrated thatthe capacitance of EDLCs can be increased if the electrodemasses are adjusted according to the size of the electrolyte ions.Moreover, we investigated the issue of high contact resistancesat the interface between porous carbon electrodes and metalcurrent collectors. To reduce the contact resistance, graphitefoil can be used as a current collector instead of metal foils.Using the suggested low-cost materials, production methodsand conceptual improvements, it is possible to reduce the material costs by more than 90% in comparison with commercialunits. This confirms that paper-based EDLCs are apromising alternative to conventional EDLCs. Our findings andadditional research can be expected to substantially supportthe design and commercialization of sustainable EDLCs andother green energy technologies.
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| 6. |
- Blomquist, Nicklas, 1987-, et al.
(författare)
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Effects of Geometry on Large-scale Tube-shear Exfoliation of Multilayer Graphene and Nanographite in Water
- 2019
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Industrially scalable methods for the production of graphene and other nanographites are needed to achieve cost-efficient commercial products. At present, there are several available routes for the production of these materials but few allow large-scale manufacturing and environmentally friendly low-cost solvents are rarely used. We have previously demonstrated a scalable and low-cost industrial route to produce nanographites by tube-shearing in water suspensions. However, for a deeper understanding of the exfoliation mechanism, how and where the actual exfoliation occurs must be known. This study investigates the effect of shear zone geometry, straight and helical coil tubes, on this system based on both numerical simulation and experimental data. The results show that the helical coil tube achieves a more efficient exfoliation with smaller and thinner flakes than the straight version. Furthermore, only the local wall shear stress in the turbulent flow is sufficient for exfoliation since the laminar flow contribution is well below the needed range, indicating that exfoliation occurs at the tube walls. This explains the exfoliation mechanism of water-based tube-shear exfoliation, which is needed to achieve scaling to industrial levels of few-layer graphene with known and consequent quality.
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| 7. |
- Blomquist, Nicklas, 1987-, et al.
(författare)
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Influence of Substrate in Roll-to-roll Coated Nanographite Electrodes for Metal-free Supercapacitors
- 2020
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 10:1
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Tidskriftsartikel (refereegranskat)abstract
- Due to the high electric conductivity and large surface area of nanographites, such as graphene and graphite nanoplatlets, these materials have gained a large interest for use in energy storage devices. However, due to the thin flake geometry, the viscosity of aqueous suspensions containing these materials is high even at low solids contents. This together with the use of high viscosity bio-based binders makes it challenging to coat in a roll-to-roll process with sufficient coating thickness. Electrode materials for commercial energy storage devices are often suspended by organic solvents at high solids contents and coated onto metal foils used as current-collectors. Another interesting approach is to coat the electrode onto the separator, to enable large-scale production of flat cell stacks. Here, we demonstrate an alternative, water-based approach that utilize slot-die coating to coat aqueous nanographite suspension with nanocellulose binder onto the paper separator, and onto the current collector as reference, in aqueous metal-free supercapacitors. The results show that the difference in device equivalent series resistance (ESR) due to interfacial resistance between electrode and current collector was much lower than expected and thus similar or lower compared to other studies with a aqueous supercapacitors. This indicates that electrode coated paper separator substrates could be a promising approach and a possible route for manufacturing of low-cost, environmentally friendly and metal-free energy storage devices.
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| 8. |
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| 9. |
- Blomquist, Nicklas, 1987-
(författare)
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Large-Scale Graphene Production for Environmentally Friendly and Low-Cost Energy Storage : Production, Coating, and Applications
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- There is great demand for energy-efficient, environmentally sustainable, and cost-effective electrical energy storage devices. One important aspect of this demand is the need for automotive electrification to achieve more energy-efficient transportation at a reasonable cost, thus supporting a fossil-fuel free society. Another important aspect is the requirement for energy storage in the growing field of renewable energy production from wind and solar sources, which generates an irregular supply of electricity due to weather conditions.Much of the research in this area has been conducted in the field of battery technology with impressive results, but the need for rapid storage devices such as supercapacitors is growing. Due to the excellent ability of supercapacitors to handle short peak power pulses with high efficiency along with their long lifetime and superior cyclability, their implementations range from small consumer electronics to electric vehicles and stationary grid applications. Supercapacitors also have the potential to complement batteries to improve pulse efficiency and lifetime of the system, however, the cost of supercapacitors is a significant issue for large-scale commercial use, leading to a demand for sustainable, low-cost materials and simplified manufacturing processes. An important way to address this need is to develop a cost-efficient and environment-friendly large-scale process to produce highly conductive nanographites, such as graphene and graphite nanoplatelets, along with methods to manufacture low-cost electrodes from large area coating.In this thesis, I present a novel process to mechanically exfoliate industrial quantities of nanographite from graphite in an aqueous environment with low energy consumption and at controlled shear conditions. The process is based on hydrodynamic tube-shearing and can produce both multilayer graphene and nanometer-thick and micrometer-wide flakes of nanographite. I also describe the production of highly conductive and robust carbon composites based on the addition of nanocellulose during production; these are suitable as electrodes in applications ranging from supercapacitors and batteries to printed electronics and solar cells.Furthermore I demonstrate a scalable route for roll-to-roll coating of the nanographite-nanocellulose electrode material and propose a novel aqueous, low-cost, and metal-free supercapacitor concept with graphite foil functioning as the current collector. The supercapacitors possessedmore than half the specific capacitance of commercial units but achieved a material cost reduction of more than 90 %, demonstrating anenvironment-friendly, low-cost alternative to conventional supercapacitors.
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| 10. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Base Sheet Structures that Control Coating Uniformity: Effects of Length Scale
- 2008
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Ingår i: TAPPI Advanced Coating Fundamentals Symposium Proceedings. - : TAPPI Press. - 1595101748 - 9781595101747 ; , s. 124-133
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Konferensbidrag (refereegranskat)abstract
- Characterization of the base sheet properties and coating layer properties was performed by using scanning electron microscope (SEM) images of paper cross-sections and image analysis. Frequency analysis was used to study how the base sheet properties affect coating thickness uniformity at different length scales. Samples analysed were Lightweight Coated (LWC) base sheets blade-coated on only one side with coat weights of 12 and 22 g/m2. A number of images were taken in sequence giving a total length of more than 6 mm. The results showed that the surface height variations of the base sheet control coating uniformity in the entire examined length scale, but with different mechanisms. At short wavelengths the coating mechanism was “level coating” where the coating suspension fills small pores (“levels”), whereas at longer wavelengths the coating suspension follows the surface profile and “contour coating” becomes more prevalent. In other words, the level- and contour-coatings represent the coating mechanisms in different length scales. Surface height variations can be explained by base sheet thickness only at short wavelengths, but at all other wavelengths the surface height variations were very much independent of the base sheet structure properties measured.
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| 11. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Coating Microstructures : Binder Distributions
- 2012
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Ingår i: 12th TAPPI Advanced Coating Fundamentals Symposium Proceedings, Co-located with the 16th International Coating Science and Technology Symposium, ISCST 2012. - : Tappi. - 9781595102201 ; , s. 250-257
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Non-uniformities within the coating layer, such as porosity variations and binder distributions, are known to affect print uniformity and barrier properties. However, in the literature the results on coating microstructures are rather limited or sometimes conflicting.We obtained high quality images of coated paper cross sections using field emission scanning electron microscopy in combination with a new argon ion beam milling technique to directly observe and analyse the binder and pore distribution. This technique produces high quality images that allow microstructure characterisation of the coating layer.The binder distribution measurements showed that the binder is almost exclusively filling up the small pores, whereas the larger pores are mainly empty and depleted of binder.
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| 12. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Ion conductivity through TEMPO-mediated oxidated and periodate oxidated cellulose membranes
- 2020
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Ingår i: Carbohydrate Polymers. - : ELSEVIER SCI LTD. - 0144-8617 .- 1879-1344. ; 233
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose in different forms is increasingly used due to sustainability aspects. Even though cellulose itself is an isolating material, it might affect ion transport in electronic applications. This effect is important to understand for instance in the design of cellulose-based supercapacitors. To test the ion conductivity through membranes made from cellulose nanofibril (CNF) materials, different electrolytes chosen with respect to the Hofmeister series were studied. The CNF samples were oxidised to three different surface charge levels via 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), and a second batch was further cross-linked by periodate oxidation to increase wet strength and stability. The outcome showed that the CNF pre-treatment and choice of electrolyte are both crucial to the ion conductivity through the membranes. Significant specific ion effects were observed for the TEMPO-oxidised CNF. Periodate oxidated CNF showed low ion conductivity for all electrolytes tested due to an inhibited swelling caused by the crosslinking reaction.
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| 13. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Microstructure Variations in Paper Coating : Direct Observations
- 2012
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 51:24, s. 8246-8252
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Tidskriftsartikel (refereegranskat)abstract
- Non-uniformities in the coating layer, such as porosity variations and binder distributions, are known to affect print uniformity and barrier properties. However, in the literature the results are rather scarce or sometimes conflicting.We acquired high quality images of coated paper cross sections using field emission scanning electron microscopy in combination with a new argon-ion-beam milling technique to directly observe and analyse the coating microstructures in relation to underlying base sheet structures.The results showed that coating porosity varied with mass density of the underlying base sheet for the relatively bulky clay/GCC coating, whereas for the more compact clay coating, the effect was small. Areas with more fibres in the base sheet were more compressed by calendering, resulting in a decreased coating porosity. A unique binder enriched layer of less than 500 nm thickness was found at the coating surface as well as at the coating/base sheet interface.
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| 14. |
- Dahlström, Christina, 1977-, et al.
(författare)
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New Insights into Coating Uniformity and Base Sheet Structures
- 2009
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 48:23, s. 10472-10478
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Tidskriftsartikel (refereegranskat)abstract
- Base sheet structures, such as surface roughness and mass density distribution (formation), have been known to affect coating uniformity. However, the literature is not necessarily consistent in determining which structure controls coating uniformity. This study employed scanning electron microscopy (SEM) and image analysis, combined with autocorrelation and frequency analyses, to investigate the fundamental mechanisms of coating and to resolve some of the controversies in the literature regarding the base sheet effects. The results showed that coating thickness variation resembles a process of random deposition with leveling. At small length scales (in the size of fiber width), leveling causes a very strong dependence of coating thickness variations on the surface profile of the base sheet, whereas at larger length scales, coating thickness variation diminishes in its intensity by the same leveling effect, but still retains a significant correlation with base sheet structure, particularly formation. Frequency analyses clearly showed that the discrepancies in the results for the base sheet effects in the literature are due to the length scales used in the experiments, that is, the sampling area and the resolution of the measurements.
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| 15. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Regenerated cellulose properties tailored for optimized triboelectric output and the effect of counter-tribolayers
- 2024
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Ingår i: Cellulose. - : Springer Nature. - 0969-0239 .- 1572-882X. ; 31:4, s. 2047-2061
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose has shown great potential in the development of green triboelectric nanogenerators. Particularly, regenerated cellulose (R-cellulose) has shown remarkably high output power density but the structural features and key parameters that explain such superior performance remain unexplored. In this work, wood cellulose fibers were dissolved in a LiOH(aq)-based solvent to produce a series of R-cellulose films. Regeneration in different alcohols (from methanol to n-pentanol) was performed and the films’ structural features and triboelectric performance were assessed. Nonsolvents of increased hydrophobicity led to R-cellulose films with a more pronounced (1–10) diffraction peak. An open-circuit voltage (VOC) of up to ca. 260 V and a short-circuit current (ISC) of up to ca. 150 µA were measured for R-cellulose against polytetrafluoroethylene (as negative counter-layer). However, R-cellulose showed an increased VOC of 175% (from 88.1 V) against polydimethylsiloxane when increasing the alcohol hydrocarbon chain length from methanol to n-pentanol. The corresponding ISC and output power also increased by 76% (from 89.9 µA) and by 382% (from 8.8 W m–2), respectively. The higher R-cellulose hydrophilicity, combined with soft counter-tribolayer that follow the surface structures increasing the effective contact area, are the leading reasons for a superior triboelectric performance.
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| 16. |
- Dahlström, Christina, 1977-
(författare)
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Sample Preparation Using Argon Ion Beam Milling
- 2013
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Ingår i: Argon: Production, Characteristics and Applications. - Hauppauge, NY : Nova Science Publishers, Inc.. - 9781626182042 ; , s. 223-240
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Surface and cross section analysis can provide important information on material properties. It has, however, been difficult to characterise the internal structure at a micro scale using cross sections prepared with conventional methods, such as e.g. mechanical grinding and polishing, because these procedures can damage the surface and introduce artefacts. A few years ago, a new precision argon ion beam cross section polisher was shown to be a suitable sample preparation technique for microstructure characterisation. It produces high quality cross sections free from artefacts and distortions. This technique can be used for cross section preparation of a wide variety of materials including composites, metals, ceramics and polymers. Argon ion beam milling can also be used in combination with focused ion beam (FIB) as a final step to remove FIB-damaged layers before nano- and microstructure characterisation in high resolution transmission electron microscopy (HRTEM).
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| 17. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Surface Evolution of Pigment Coating
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- We studied the surface evolution of coating by using a random deposition model of particles. In order to capture the real coating structure development, we included a volume exclusion effect to represent particle-particle interaction, and a levelling effect to represent surface tension effect. In this study we investigated three cases: (1) random deposition on a flat surface, (2) random deposition on a flat surface with levelling, and (3) random deposition on a rough surface with levelling.When plotting in logarithmic scale, the roughness initially increased linearly with average number of particles deposited for all three cases but reached saturation after a certain amount of deposited particles. The result resembles a ballistic deposition process where agglomerates are developed over the surface due to lateral growth. Even a flat, uniform surface creates roughness during random deposition of particles.Autocorrelation analysis showed that the correlation length continues to increase with the number of particles deposited. The aggregated structures were easily seen in the autocorrelation function.Experimental and simulated data on the rough surface were compared and they were in agreement, confirming that the coating process is essentially a random process with some local correlation in the length scale of a typical fibre width.
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| 18. |
- Dahlström, Christina, 1977-, et al.
(författare)
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Triboelectric Performance Of Regenerated Cellulose
- 2023
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Ingår i: Book of Abstracts EPNOE 2023. - : Graz University of Technology. ; , s. 116-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Cellulose has shown great potential in the development of green triboelectric nanogenerators (TENG) [1]. Particularly, regenerated cellulose (R-cellulose) has shown remarkably high output power density but the structural features and key parameters that explain such superior performance remain unexplored. In this work, wood cellulose fibers were dissolved in a LiOH(aq)-based solvent to produce a series of R-cellulose films. Regeneration in different alcohols (from methanol to n-pentanol) was performed and the films’ structural features and triboelectric performance were assessed. Nonsolvents of increased hydrophobicity led to R-cellulose films with higher hydrophilic character; the films showed a (1- 10) diffraction peak of larger amplitude and higher apparent crystallinity. An open-circuit voltage (VOC) of up to ca. 260 V and a short-circuit current (ISC) of up to ca. 150 μA were measured for R-cellulose against polytetrafluoroethylene (as negative counter-layer). However, R-cellulose showed an increased VOC of 175% (from 88.1 V) against polydimethylsiloxane from methanol to n-pentanol. The corresponding ISC and output power also increased by 76% (from 89.9 μA) and by 382% (from 8.8 W m–2), respectively. The higher R-cellulose hydrophilicity, combined with soft counter-layer that follow the surface structures increasing the effective contact area, are the leading reasons for a superior triboelectric performance.[1] Zhang, R., Dahlström, C., Zou, H., Jonzon, J., Hummelgård, M., Örtegren, J., Blomquist, N., Yang, Y., Andersson, H., Olsen, M., Norgren, M., Olin, H. & Wang, Z.L. Adv. Mater. 32, 2002824, 2020; https://doi.org/10.1002/adma.202002824
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| 19. |
- Eivazihollagh, Alireza, et al.
(författare)
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Controlled Synthesis of Cu and Cu2O NPs and Incorporation of Octahedral Cu2O NPs in Cellulose II Films
- 2018
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- In this study, Cu and Cu2O nanoparticles (NPs) were synthesized through chemical reduction of soluble copper-chelating ligand complexes using formaldehyde as a reducing agent. The influence of various chelating ligands, such as ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and a surface-active derivative of DTPA (C12-DTPA), as well as surfactants (i.e., hexadecyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium chloride (DoTAC), sodium dodecyl sulfate (SDS), and dimethyldodecylamine-N-oxide (DDAO)), on morphology and the composition of produced NPs was investigated. In the absence of surfactants, spherical copper particles with polycrystalline structure could be obtained. X-ray diffraction (XRD) analysis revealed that, in the presence of EDTA, the synthesized NPs are mainly composed of Cu with a crystallite size on the order of 35 nm, while with DTPA and C12-DTPA, Cu2O is also present in the NPs as a minority phase. The addition of ionic surfactants to the copper–EDTA complex solution before reduction resulted in smaller spherical particles, mainly composed of Cu. However, when DDAO was added, pure Cu2O nano-octahedrons were formed, as verified by high-resolution scanning electron microscopy (HR-SEM) and XRD. Furthermore, a hybrid material could be successfully prepared by mixing the octahedral Cu2O NPs with cellulose dissolved in a LiOH/urea solvent system, followed by spin-coating on silica wafers. It is expected that this simple and scalable route to prepare hybrid materials could be applied to a variety of possible applications.
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| 20. |
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| 21. |
- Forsberg, Viviane, 1981-, et al.
(författare)
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Liquid Exfoliation of Layered Materials in Water for Inkjet Printing
- 2016
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Ingår i: Printing for Fabrication 2016. - USA : Curran Associates, Inc.. - 9780892083220 - 9780892083237 - 9780892083213 ; 60:4, s. 1-7
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Konferensbidrag (refereegranskat)abstract
- MoS2 is a layered material which is abundant and non-toxic and has been increasingly studied during the last few years as a semiconducting alternative to graphene. While most studies have been performed on single MoS2 nanosheets, for example to demonstrate high-performance electronic transistors, more work is needed to explore the use of MoS2 in printed electronics. The importance of using MoS2 as a printed electronic material could be understood by considering the several orders higher electron mobility in MoS2, even in several nanometer thick layers, compared to the organic and other materials used today. In the few studies performed so far on printing MoS2, the developed dispersions used mainly organic solvents that might be detrimental for the environment. Here, we show an environmentally friendly liquid-based exfoliation method in water where the solution was stabilized by sodium dodecyl sulfate (SDS) surfactant. The dispersions consisted of very thin MoS2 nanosheets with average lateral size of about 150 nm, surface tension of 28 mN m-1 and a shelf life of a year. Although both the concentration and viscosity was less than optimal, we were able to inkjet print the MoS2 solution on paper and on PET films, using multiple printing passes. By tuning the concentration/viscosity, this approach might lead to an environmentally friendly MoS2 ink suitable for printed electronics.
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| 22. |
- Forsberg, Viviane, 1981-, et al.
(författare)
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Printability of functional inkjet inks onto commercial inkjet substrates and a taylor made pigmented coated paper
- 2018
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Printed electronics are of increasing interest. The substrates used have primarily been plastics although the interest for cellulose-based substrates is increasing due to the environmental aspect as well as cost. The requirements of substrates for electronically active inks differs from graphical inks and therefore we have investigated a custom-made pigment based coated paper and compared it to commercial photo-papers and a coated PE film.Our goal with the study of different substrates was to select the most suitable substrate to print water based 2D materials inkjet inks for flexible electronics.The discovery of graphene, a layered material achieved from the exfoliation of graphite, has resulted in the study of other materials with similar properties to cover areas where graphene could not be used due to the absence of a bandgap in the material. For example in thin film transistors (TFT) a semiconductor layer is essential to enable turn on and off the device. This semiconductor layer can be achieved using various materials but particular interest have been dedicated to abundant and cheap 2D materials such as the transition metal dichalcogenide (TMD) molybdenum disulfide (MoS2). To date, most of the dispersions based on TMDs use organic solvents or water solutions of surfactants. Previously we focus on the study of environmental friendly inks produced by liquid phase exfoliation (LPE) of MoS2 in water using cellulose stabilizers such as ethyl cellulose (EC), cellulose nanofibrils (CNF) and nanofibrilcellulose (NFC). We have study various aspects of the ink fabrication includi ng pH range, the source of MoS2, nanosheets thickness, particle size distribution, ink stabilizers, ink concentration, viscosity and surface tension. These inks have very low concentration requiring a number of printing passes to cover the substrate. Therefore the substrate selection is crucial as a large amount of solvent is to be absorb by the substrate. Our goal was to use such an ink to print electrodes of MoS2 into a paper substrate after substrate selection.Commercial photo papers, a commercial coated PE film and a tailor made multilayer pigment coated paper substrate were used for the substrate selection analysis. We print the substrates using a DIMATIX inkjet printer with a 10 pL printing head using the distillated water waveform supplied by the printer manufacturer. The voltage used was 23V and 4 nozzles were used for the print outs. The inkjet ink used was the organic PEDOT:PSS. We printed lines ranging from 1 pixel to 20 pixels with 1, 2 and 3 printing passes. The printing quality was evaluated through measurements of the waviness of the printed lines measured after imaging the printed samples with a SEM microscope. The line width measurement was done using the software from the SEM.We also evaluated the structure of the coatings using SEM and topography measurements. The ink penetration through the substrates was evaluated using Raman Spectroscopy. For the pigmented coated sample we measured 4% of ink penetration through the substrate for the 1pxl printed line printed once onto the paper. Cross-section SEM images of the printed lines were made to visualize the ink penetration into the substrate.Regarding the electrical conductivity of the printed samples, the differences in resistivity varying the width of the printed lines and the number of printed passes were evaluated. The resistivity of the printed electrodes was evaluated using the 2-points probe method. Before the resistivity measurements, the printed substrates were heated at 50°C and 100°C for 30 minutes in an oven.We choose the PEDOT:PSS ink because it is a low price ink compared to metal nanoparticles inks for printed electronics. The print outs had low resistivity at a few printing passes with no need for sintering at high temperatures. The MoS2 ink has a very high resistance at a few printing passes due to lower coverage of the substrate therefore for this ink these measurements were not possible to be made. The main pigment composition of the paper coatings of the substrates was evaluated using FT-IR and EDX, these data plus the coating structure evaluated by SEM was related to the print quality.The best in test papers were used to print MoS2 electrodes. After the printing tests, another step for the optimization of the MoS2 ink properties shall be carried out in future studies for better print quality. We also evaluated the surface energy of the substrates through contact angle measurements to match the surface tension of the PEDOT:PSS ink and later the MoS2 ink. Although the pigmented coated printing substrate did not show better results than the commercial photo papers and PE foil in terms of line quality, it shows the lowest resistivity and sufficient results for low cost recyclable electronics, which do not require high conductivity. Nevertheless, the substrate was very thin and it could even be used in magazines as traditional lightweight coated papers (LWC) are used but with the additional of a printed electronic feature.
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| 23. |
- Koppolu, Rajesh, et al.
(författare)
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High-Throughput Processing of Nanographite-Nanocellulose-Based Electrodes for Flexible Energy Devices
- 2020
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Ingår i: Industrial & Engineering Chemistry Research. - : American Chemical Society (ACS). - 0888-5885 .- 1520-5045. ; 59:24, s. 11232-11240
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Tidskriftsartikel (refereegranskat)abstract
- The current work aims at understanding factors that influence the processability of nanographite-nanocellulose suspensions onto flexible substrates for production of conductive electrodes. A custom-built slot-die was used in a continuous rollto-roll process to coat the nanomaterial suspension onto substrates with varying surface smoothness, thickness, pore structure, and wet strength. The influence of a carboxymethyl cellulose (CMC) additive on suspension rheology, water release properties, and coating quality was probed. CMC addition reduced the suspension yield stress by 2 orders of magnitude and the average pore diameter of the coated electrodes by 70%. Sheet resistances of 5-9 Omega sq(-1) were obtained for the conductive coatings with a coat weight of 12-24 g m(-2). Calendering reduced the sheet resistance to 1-3 Omega sq(-1) and resistivity to as low as 12 mu Omega m. The coated electrodes were used to demonstrate a metal-free aqueous-electrolyte supercapacitor with a specific capacitance of 63 F g(-1). The results increase our understanding of continuous processing of nanographite-nanocellulose suspensions into electrodes, with potential uses in flexible, lightweight, and environmentally friendly energy devices.
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| 24. |
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| 25. |
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| 26. |
- Kumar, Vinay, et al.
(författare)
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Conductive nanographite-nanocellulose coatings on paper
- 2017
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Ingår i: Flexible And Printed Electronics. - : IOP Publishing. - 2058-8585. ; 2:3
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Tidskriftsartikel (refereegranskat)abstract
- Paper products with active and functional coatings have attracted interest in recent years to counter the stagnating demand for traditional graphic paper grades. Conductive coatings have potential uses in various energy generation and storage applications, e.g. in batteries, supercapacitors, and photovoltaics. The current work aims to demonstrate large-scale production of flexible low-cost nanographite coatings on paper-based substrate. The large aspect ratio of graphene present in the suspension limits solids content to very low values, which makes it challenging to create thick coating layers required for high conductivity. The use of nanocellulose binder together with a custom-built slot-coating device enables roll-to-roll coating of thick conductive coatings on paper. The rheological and water-retention properties of nanographite-nanocellulose suspensions are reported. The influence of coat weight, carbon black addition, and calendering on coating structure and the resulting conductivity of the coatings is investigated. Impact of humidity and bending/creasing of coated samples on their electrical performance is explored as well. The lowest surface resistances obtained were in the range 1-2 Ohm/square, for 15 g m(-2) coat weight. Increasing the coat weight and calendering nip load resulted in higher conductivity of coatings. Carbon black addition deteriorated the conductivity somewhat, probably due to increased porosity of coatings. Moisture and creasing did not affect significantly the conductivity of high coat weight and calendered samples. The results reported are very encouraging for future research on further improving the electrical performance of such carbon coatings.
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| 27. |
- Mattsson, Amanda
(författare)
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Characterisation of Time-dependent Statistical Failure of Fibre Networks : Applications for Light-weight Structural Composites
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The future of a sustainable society requires that materials not only be renewable, but also leave as small a carbon foot-printin the environment as possible. One such product is light-weight composite material for transportation packages. Cellulose fibres have been and will continue to be ideal for this purpose.The strength design of light-weight composites is becoming increasingly important. The challenge is to neither over- nor under-design, but instead to target the right strength underrealistic loading conditions. The question then is: What is right strength? Under realistic loading conditions (e.g., fatigue, random loading, and creep), materials fail differently from what one expects from tests of static strength: materials often fail at much lower stresses than are measured in these tests, the failure is time-dependent, and time to failure is highly variable. Therefore, to answer the above question, we have set up the following objectives: (1) theoretically formulate time-dependent statistical failure (TSF), and examine the validity of the model; (2) define material parameters describing the multi-faceted strength characteristics based on this formulation; (3) develop an experimental method to determine the material parameters; (4) investigate the impacts of fibre properties and network structures; and finally (5) characterise containerboard (the fibre material used in corrugated boxes) samples in terms of the new material parameters. The results for these five objectives are presented below, one by one.(1) A general formulation of TSF, originally proposed byColeman [1] for fibre failures, has been used. We have found that this model is indeed valid, even at the fibre network level, with only two restrictions: the existence of a lower bound onweakest-link scaling and an approximate nature of the Weibull distribution.(2) Accordingly, we have defined three material parameters that characterise different aspects of material strength: shortterm strength, durability/brittleness, and reliability. We call these parameters the new strength metrics.(3) Although the newly defined material parameters are most comprehensive, it takes up to several months to determine them by using creep tests. We have developed a new method, using constant loading rate (CLR) tests, that not only gives values comparable to those from creep tests, but also requires only about one day, allowing a drastic reduction in the testing time.(4) Monte-Carlo simulations of lattice networks have been performed to determine the basic relationships between fibre properties and network failures. The brittleness of an individual fibre (or a breaking element) influenced both brittleness and reliability of the fibre network, the higher the brittleness, the lower the reliability. Reliability, on the other hand, exhibited more intricate relationships with fibre properties and network structures. Several important analytical relationships have been derived.(5) Finally, using the CLR tests, we have characterised commercial containerboards in terms of the new strength metrics. Containerboard, as a cellulose fibre network, is quite comparable to typical stiff polymer-based fibre composites (e.g., glassfibres and aramid fibres). However, the reliability and durability/brittlenessof containerboard varied considerably within the operating windows, suggesting ample opportunities to fine-tune these properties even using current papermaking practices.The fact that the multi-faceted nature of strength can be expressed by three parameters is remarkable, and the implications are profound for how materials are designed and new materials developed. It is the author’s hope that this thesis will be of some use when it comes to redefining materials for a sustainable society, particularly the renewable alternative –cellulose fibres.
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| 28. |
- Norgren, Magnus, 1967-, et al.
(författare)
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Perspectives on the Lindman Hypothesis and Cellulose Interactions
- 2023
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Ingår i: Molecules. - : MDPI. - 1431-5157 .- 1420-3049. ; 28:10
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Forskningsöversikt (refereegranskat)abstract
- In the history of cellulose chemistry, hydrogen bonding has been the predominant explanation when discussing intermolecular interactions between cellulose polymers. This is the general consensus in scholarly textbooks and in many research articles, and it applies to several other biomacromolecules’ interactions as well. This rather unbalanced description of cellulose has likely impacted the development of materials based on the processing of cellulose—for example, via dissolution in various solvent systems and regeneration into solid materials, such as films and fibers, and even traditional wood fiber handling and papermaking. In this review, we take as a starting point the questioning of the general description of the nature of cellulose and cellulose interactions initiated by Professor Björn Lindman, based on generic physicochemical reasoning about surfactants and polymers. This dispute, which became known as “the Lindman hypothesis”, highlights the importance of hydrophobic interactions in cellulose systems and that cellulose is an amphiphilic polymer. This paper elaborates on Björn Lindman’s contribution to the subject, which has caused the scientific community to revisit cellulose and reconsider certain phenomena from other perspectives.
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| 29. |
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| 30. |
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| 31. |
- Stolpe, Amanda, et al.
(författare)
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Regenerated cellulose TENG with colour printed surface for increased performance
- 2023
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Ingår i: Book of Abstracts EPNOE 2023. - : Graz University of Technology. ; , s. 132-
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Triboelectric nanogenerators (TENGs) are ideal to meet the increasing need for green and efficient energy solutions, e.g., in small wireless and/or wearable applications. Regenerated cellulose is an exemplary material regarding both power output and mechanical performance, and it is environmentally friendly and economically favourable. To further improve the triboelectric performance of the cellulose, colour printing was done on the surface with conventional laser printing. Printer toners commonly contain substances with different triboelectric properties. [1] In this work, cellulose fibres were dissolved using a LiOH/urea solvent and regenerated in an ethanol bath and eventually dried under controlled conditions. Thereafter the resulting transparent cellulose films were run through a conventional laser paper printer to apply toners of different colour and patterns on the surface. Cyan, magenta, yellow and black was printed in one layer. In addition, black was printed in certain patterns from low to high coverage and in several layers to evaluate the effect of applied amount. The samples were analysed using SEM, AFM, XRD, FTIR and a TENG was assembled in the contact-separation mode to investigate the triboelectric performance. The printed cellulose films were found to give enhanced triboelectric output. The results show an interesting and simple processing route to enhance the performance of cellulose- based TENG materials that can be useful in the development of cheap and sustainable small wireless electrical generators or sensors.[1] Zhang, R.; Hummelgård, M.; Örtegren, J.; Andersson, H.; Olsen, M.; Chen, W.; Wang, P.; Eivazi, A.; Dahlström, C.; Norgren, M., Adv. Engin. Mater., 2023, in press, https://doi.org/10.1002/adem.202300107
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| 32. |
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| 33. |
- Yang, Jiayi, et al.
(författare)
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pH-responsive cellulose–chitosan nanocomposite films with slow release of chitosan
- 2019
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Ingår i: Cellulose. - : Springer Science and Business Media LLC. - 0969-0239 .- 1572-882X. ; 26:6, s. 3763-3776
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Tidskriftsartikel (refereegranskat)abstract
- Cellulose–chitosan films were preparedusing a physical method in which cellulose andchitosan were separately dissolved via freeze thawingin LiOH/urea and mixed in different proportions, theresulting films being cast and regenerated in water/ethanol. X-ray diffraction and Fourier transforminfrared spectroscopy (FT-IR) spectroscopy verifiedthe composition changes in the nanocomposites due todifferent mixing ratios between the polymers. Tensilestress–strain measurements indicated that the mechan-ical performance of the cellulose–chitosan nanocom-posites slightly worsened with increasing chitosancontent compared with that of films comprisingcellulose alone. Field emission scanning electronmicroscopy revealed the spontaneous formation ofnanofibers in the films; these nanofibers were subse-quently ordered into lamellar structures. Water uptakeand microscopy analysis of film thickness changesindicated that the swelling dramatically increased atlower pH and with increasing chitosan content, thisbeing ascribed to the Gibbs–Donnan effect. Slowmaterial loss appeared at acidic pH, as indicated by aloss of weight, and quantitative FT-IR analysisconfirmed that chitosan was the main componentreleased.Asample containing 75% chitosan reached amaximum swelling ratio and weight loss of 1500%and 55 wt%, respectively, after 12 h at pH 3. Thestudy presents a novel way of preparing pH-responsivecellulose–chitosan nanocomposites with slow-releasecharacteristics using an environmentally friendlyprocedure and without any chemical reactions.
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| 34. |
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| 35. |
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| 36. |
- Zhang, Renyun, et al.
(författare)
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Cellulose-Based Fully Green Triboelectric Nanogenerators with Output Power Density of 300 W m−2
- 2020
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Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 32:38
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Tidskriftsartikel (refereegranskat)abstract
- Triboelectric nanogenerators (TENGs) have attracted increasing attention because of their excellent energy conversion efficiency, the diverse choice of materials, and their broad applications in energy harvesting devices and self-powered sensors. New materials have been explored, including green materials, but their performances have not yet reached the level of that for fluoropolymers. Here, a high-performance, fully green TENG (FG-TENG) using cellulose-based tribolayers is reported. It is shown that the FG-TENG has an output power density of above 300 W m−2, which is a new record for green-material-based TENGs. The high performance of the FG-TENG is due to the high positive charge density of the regenerated cellulose. The FG-TENG is stable after more than 30 000 cycles of operations in humidity of 30%–84%. This work demonstrates that high-performance TENGs can be made using natural green materials for a broad range of applications.
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| 37. |
- Zhang, Renyun, et al.
(författare)
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Energy Harvesting Using Wastepaper-Based Triboelectric Nanogenerators
- 2023
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Ingår i: Advanced Engineering Materials. - : Wiley. - 1438-1656 .- 1527-2648. ; 25:11
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Tidskriftsartikel (refereegranskat)abstract
- Inks and toners used for printing contain materials, such as polyester, with strong triboelectric properties to enhance the binding effects, making wastepaper, such as magazines and newspapers, good candidates for triboelectric materials. Herein, high-output power triboelectric nanogenerators (TENGs) that utilize wastepaper as triboelectric layers (wastepaper-based triboelectric nanogenerators (WP–TENGs)) are reported. Journal paper and office copy paper wastes are investigated. The results show that the maximum power densities of the WP–TENGs reach 43.5 W m−2, which is approximately 250 times the previously reported output of the TENG with a recycled triboelectric layer made from wastepaper. The maximum open circuit voltage (V OC) and short circuit current (I SC) are 774 V and 3.92 mA (784 mA m−2), respectively. These findings can be applied to extend the life cycle of printed papers for energy harvesting, and they can later be applied for materials recycling to enhance the sustainable development of our society.
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| 38. |
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| 39. |
- Zhang, Renyun, et al.
(författare)
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Triboelectric nanogenerators with ultrahigh current density enhanced by hydrogen bonding between nylon and graphene oxide
- 2023
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Ingår i: Nano Energy. - 2211-2855 .- 2211-3282. ; 115
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Tidskriftsartikel (refereegranskat)abstract
- The triboelectric properties of the tribolayers are essential factors affecting the current density of triboelectric nanogenerators (TENGs). To enhance the current density, composites have been developed to tune their triboelectric properties. Previous studies have reported enhanced TENG performance with composite materials, primarily based on their composition, while chemical interactions between the components have been less analyzed. In this study, we report a novel approach to improve the current density of a TENG by introducing dipole-dipole interactions between a nylon filter membrane and graphene oxide (GO) through hydrogen bonds. The Raman spectroscopy confirmed the occurrence of the interactions resulting from hydrogen bonding. The enhancing mechanisms of hydrogen bonds were further analyzed by Kelvin probe force microscope (KPFM) measurement, which demonstrated that hydrogen bonding could influence the surface potential of the coated GO, leading to increased output of the nylon/GO@NFM TENG (NGN-TENG). Our results show that an ultrahigh current density of 1757 mA·m−2 was obtained with a 2 × 2 cm2 NGN-TENG. Additionally, we demonstrated the feasibility of using the NGN-TENG as a motion sensor to sense finger motions. These findings suggest that the introduction of hydrogen bonds in TENG composites can provide a promising route for improving their performance.
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| 40. |
- Zhang, Renyun, et al.
(författare)
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Wastepaper-based Triboelectric Nanogenerators
- 2023
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Ingår i: Book of Abstracts EPNOE 2023. - : Graz University of Technology.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- nks and toners used for printing contain materials, such as polyester, with strong triboelectric properties to enhance the binding effects, making wastepaper, such as magazines and newspapers, good candidates for triboelectric materials. In this study, we report high- output power triboelectric nanogenerators (TENGs) that utilize wastepaper as triboelectric layers (wastepaper-based triboelectric nanogenerators (WP–TENGs)) [1]. Journal paper and office copy paper wastes are investigated. The results show that the maximum power densities of the WP–TENGs reach 43.5 W·m-2, which is approximately 250 times the previously reported output of the TENG with a recycled triboelectric layer made from wastepaper [2]. The maximum open circuit voltage (VOC) and short circuit current (ISC) are 774 V and 3.92 mA (784 mA m-2), respectively. These findings can be applied to extend the life cycle of printed papers for energy harvesting, and they can later be applied for materials recycling to enhance the sustainable development of our society.[1] Zhang, R., Hummelgård, M., Örtegren, J., Andersson, H., Olsen, M., Chen, W., Wang, P., Eivazi, A., Dahlström, C. & Norgren, M. Adv. Engin. Mater., in press, 2023; https://doi.org/10.1002/adem.202300107[2] Zhang, Z., Jie, Y., Zhu, J., Zhu, Z., Chen, H, Lu, Q., Zeng, Y., Cao, X., Wang, N. & Wang, Z. Nano Res. 15, 1109, 2022; https://doi.org/10.1007/s12274-021-3612-8
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