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Engström, Ann-Christine
Publications (10 of 12) Show all publications
Kumar, V., Forsberg, S., Engström, A.-C., Nurmi, M., Dahlström, C. & Toivakka, M. (2017). Conductive carbon-nanocellulose coatings on paper. In: Paper Conference and Trade Show, PaperCon 2017: Renew, Rethink, Redefine the Future. Paper presented at Paper Conference and Trade Show: Renew, Rethink, Redefine the Future, PaperCon 2017, Minneapolis, United States, 23 April 2017 through 26 April 2017 (pp. 26-35). TAPPI Press
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2017 (English)In: Paper Conference and Trade Show, PaperCon 2017: Renew, Rethink, Redefine the Future, TAPPI Press , 2017, p. 26-35Conference paper, Published paper (Refereed)
Place, publisher, year, edition, pages
TAPPI Press, 2017
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-32867 (URN)2-s2.0-85041529982 (Scopus ID)9781510847286 (ISBN)
Conference
Paper Conference and Trade Show: Renew, Rethink, Redefine the Future, PaperCon 2017, Minneapolis, United States, 23 April 2017 through 26 April 2017
Available from: 2018-02-20 Created: 2018-02-20 Last updated: 2018-02-20Bibliographically approved
Kumar, V., Forsberg, S., Engström, A.-C., Nurmi, M., Andres, B., Dahlström, C. & Toivakka, M. (2017). Conductive nanographite-nanocellulose coatings on paper. Flexible And Printed Electronics, 2(3), Article ID aa728e.
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2017 (English)In: Flexible And Printed Electronics, ISSN 2058-8585, Vol. 2, no 3, article id aa728eArticle in journal (Refereed) Published
Abstract [en]

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.

Keywords
nanographite, nanofibrillated cellulose, paper electronics, carbon black, calendering, roll-to-roll conductive coating
National Category
Chemical Engineering
Identifiers
urn:nbn:se:miun:diva-31882 (URN)10.1088/2058-8585/aa728e (DOI)000410630500004 ()2-s2.0-85041007089 (Scopus ID)
Available from: 2017-10-17 Created: 2017-10-17 Last updated: 2018-02-20Bibliographically approved
Forsberg, S., Kumar, V., Engström, A.-C., Maristiina, N., Dahlström, C. & Martti, T. (2016). Effect of calendering and coating formulations on conductivity in paper-based electrodes. In: : . Paper presented at TAPPI Advanced Coating Symposium 2016, October 4-6, 2016, Stockholm.
Open this publication in new window or tab >>Effect of calendering and coating formulations on conductivity in paper-based electrodes
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2016 (English)Conference paper, Oral presentation with published abstract (Refereed)
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:miun:diva-29691 (URN)
Conference
TAPPI Advanced Coating Symposium 2016, October 4-6, 2016, Stockholm
Available from: 2016-12-20 Created: 2016-12-20 Last updated: 2016-12-20Bibliographically approved
Andres, B., Engström, A.-C., Blomquist, N., Forsberg, S., Dahlström, C. & Olin, H. (2016). Electrode Mass Balancing as an Inexpensive and Simple Method to Increase the Capacitance of Electric Double-Layer Capacitors. PLoS ONE, 11(9), 1-12, Article ID e0163146.
Open this publication in new window or tab >>Electrode Mass Balancing as an Inexpensive and Simple Method to Increase the Capacitance of Electric Double-Layer Capacitors
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2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 9, p. 1-12, article id e0163146Article in journal (Refereed) Published
Abstract [en]

Symmetric electric double-layer capacitors (EDLCs) have equal masses of the same active material in both electrodes. However, having equal electrode masses may prevent the EDLC to have the largest possible specific capacitance if the sizes of the hydrated anions and cations in the electrolyte differ because the electrodes and the electrolyte may not be completely utilized. Here we demonstrate how this issue can be resolved by mass balancing. If the electrode masses are adjusted according to the size of the ions, one can easily increase an EDLC's specific capacitance. To that end, we performed galvanostatic cycling to measure the capacitances of symmetric EDLCs with different electrode mass ratios using four aqueous electrolytes-Na2SO4, H2SO4, NaOH, and KOH (all with a concentration of 1 M)-and compared these to the theoretical optimal electrode mass ratio that we calculated using the sizes of the hydrated ions. Both the theoretical and experimental values revealed lower-than-1 optimal electrode ratios for all electrolytes except KOH. The largest increase in capacitance was obtained for EDLCs with NaOH as electrolyte. Specifically, we demonstrate an increase of the specific capacitance by 8.6% by adjusting the electrode mass ratio from 1 to 0.86. Our findings demonstrate that electrode mass balancing is a simple and inexpensive method to increase the capacitance of EDLCs. Furthermore, our results imply that one can reduce the amount of unused material in EDLCs and thus decrease their weight, volume and cost.

Keywords
Mass balancing, capacitance, electric double layer capacitor, EDLC, electrode, electrolyte, electrode mass ratio, ion size ratio
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:miun:diva-29083 (URN)10.1371/journal.pone.0163146 (DOI)000383893200073 ()2-s2.0-84992186879 (Scopus ID)
Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2017-11-30Bibliographically approved
Blomquist, N., Engström, A.-C., Hummelgård, M., Andres, B., Forsberg, S. & Olin, H. (2016). Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water. PLoS ONE, 11(4), Article ID e0154686.
Open this publication in new window or tab >>Large-Scale Production of Nanographite by Tube-Shear Exfoliation in Water
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2016 (English)In: PLoS ONE, ISSN 1932-6203, E-ISSN 1932-6203, Vol. 11, no 4, article id e0154686Article in journal (Refereed) Published
Abstract [en]

The number of applications based on graphene, few-layer graphene, and nanographite is rapidly increasing. A large-scale process for production of these materials is critically needed to achieve cost-effective commercial products. Here, we 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. This process, based on hydrodynamic tube shearing, produced nanometer-thick and micrometer-wide flakes of nanographite with a production rate exceeding 500 gh-1 with an energy consumption about 10 Whg-1. In addition, to facilitate large-area coating, we show that the nanographite can be mixed with nanofibrillated cellulose in the process to form highly conductive, robust and environmentally friendly composites. This composite has a sheet resistance below 1.75 Ω/sq and an electrical resistivity of 1.39×10-4 Ωm and may find use in several applications, from supercapacitors and batteries to printed electronics and solar cells. A batch of 100 liter was processed in less than 4 hours. The design of the process allow scaling to even larger volumes and the low energy consumption indicates a low-cost process.

Place, publisher, year, edition, pages
Nicklas Blomquist, 2016
Keywords
Nano-graphite, Graphite, Graphene, Nanomaterials, Composite materials
National Category
Natural Sciences
Identifiers
urn:nbn:se:miun:diva-27600 (URN)10.1371/journal.pone.0154686 (DOI)000375212600060 ()2-s2.0-84966389426 (Scopus ID)
Projects
KEPS
Funder
Swedish Energy Agency
Available from: 2016-05-09 Created: 2016-05-09 Last updated: 2019-05-02Bibliographically approved
Osong, S. H., Dahlström, C., Forsberg, S., Andres, B., Engstrand, P., Norgren, S. & Engström, A.-C. (2016). Nanofibrillated cellulose/nanographite composite films. Cellulose (London), 23(4), 2487-2500
Open this publication in new window or tab >>Nanofibrillated cellulose/nanographite composite films
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2016 (English)In: Cellulose (London), ISSN 0969-0239, E-ISSN 1572-882X, Vol. 23, no 4, p. 2487-2500Article in journal (Refereed) Published
Abstract [en]

Though research into nanofibrillated cellulose (NFC) has recently increased, few studies have considered co-utilising NFC and nanographite(NG) in composite films, and, it has, however been a challenge to use high-yield pulp fibres (mechanical pulps) to produce this nanofibrillar material. It is worth noting that there is a significant difference between chemical pulp fibres and high-yield pulp fibres, as the former is composed mainly of cellulose and has a yield of approximately 50 % while the latter is consist of cellulose, hemicellulose and lignin, and has a yield of approximately 90 %. NFC was produced by combining TEMPO (2,2,6,6-tetramethypiperidine-1-oxyl)-mediated oxidation with the mechanical shearing of chemi-thermomechanical pulp (CTMP) and sulphite pulp (SP); the NG was produced by mechanically exfoliating graphite. The different NaClO dosages in the TEMPO system differently oxidised the fibres, altering their fibrillation efficiency. NFC-NG films were produced by casting in a Petri dish. We examine the effect of NG on the sheet-resistance and mechanical properties of NFC films. Addition of 10 wt% NG to 90 wt% NFC of sample CC2 (5 mmol NaClO CTMP-NFC homogenised for 60 min) improved the sheet resistance, i.e. from that of an insulating pure NFC film to 180 Omega/sq. Further addition of 20 (CC3) and 25 wt% (CC4) of NG to 80 and 75 wt% respectively, lowered the sheet resistance to 17 and 9 Omega/sq, respectively. For the mechanical properties, we found that adding 10 wt% NG to 90 wt% NFC of sample HH2(5 mmol NaClO SP-NFC homogenised for 60 min) improved the tensile index by 28 %, tensile stiffness index by 20 %, and peak load by 28 %. The film's surface morphology was visualised using scanning electron microscopy, revealing the fibrillated structure of NFC and NG. This methodology yields NFC-NG films that are mechanically stable, bendable, and flexible.

Keywords
Nanofibrillated cellulose, Nanographite, Nanocomposites, TEMPO, High-speed homogenisation
National Category
Engineering and Technology
Identifiers
urn:nbn:se:miun:diva-28778 (URN)10.1007/s10570-016-0990-2 (DOI)000380089300017 ()2-s2.0-84975467623 (Scopus ID)
Available from: 2016-09-14 Created: 2016-09-14 Last updated: 2017-11-21Bibliographically approved
Andres, B., Dahlström, C., Engström, A.-C., Forsberg, S., Blomquist, N. & Olin, H. (2015). Cellulose-based binder systems for electrochemical electrodes. In: : . Paper presented at 2015 E-MRS Spring Meeting.
Open this publication in new window or tab >>Cellulose-based binder systems for electrochemical electrodes
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2015 (English)Conference paper, Poster (with or without abstract) (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-26560 (URN)
Conference
2015 E-MRS Spring Meeting
Available from: 2015-12-16 Created: 2015-12-16 Last updated: 2015-12-18Bibliographically approved
Henshaw Osong, S., Dahlström, C., Forsberg, S., Andres, B., Engstrand, P., Norgren, S., . . . Engström, A.-C. (2015). Development of CTMP-based nanofibrillated Cellulose /nanographite composites for paper applications. In: : . Paper presented at 9th International Fundamental Mechanical Pulp Research Seminar, 19-20May, Trondheim, Norway.
Open this publication in new window or tab >>Development of CTMP-based nanofibrillated Cellulose /nanographite composites for paper applications
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2015 (English)Conference paper, Oral presentation only (Other academic)
National Category
Other Chemical Engineering Composite Science and Engineering
Identifiers
urn:nbn:se:miun:diva-26561 (URN)
Conference
9th International Fundamental Mechanical Pulp Research Seminar, 19-20May, Trondheim, Norway
Available from: 2015-12-16 Created: 2015-12-16 Last updated: 2017-07-03Bibliographically approved
Forsberg, S., Andres, B., Blomquist, N., Dahlström, C., Engström, A.-C. & Olin, H. (2015). Paper-based supercapacitors. In: : . Paper presented at 2015 E-MRS Spring Meeting, May 11-15, 2015, Lille, France.
Open this publication in new window or tab >>Paper-based supercapacitors
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2015 (English)Conference paper, Oral presentation only (Other academic)
National Category
Physical Sciences
Identifiers
urn:nbn:se:miun:diva-26559 (URN)
Conference
2015 E-MRS Spring Meeting, May 11-15, 2015, Lille, France
Available from: 2015-12-16 Created: 2015-12-16 Last updated: 2015-12-17Bibliographically approved
Dahlström, C., Andres, B., Faria, G. C., Engström, A.-C., Duong, D. T. & Salleo, A. (2015). Structural Change of Cellulose Nanofibers in Supercapacitor Electrodes during Galvanostatic Cycling. In: : . Paper presented at 2015 MRS Fall Meeting & Exhibit. Boston
Open this publication in new window or tab >>Structural Change of Cellulose Nanofibers in Supercapacitor Electrodes during Galvanostatic Cycling
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2015 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Graphene and other carbon-based materials are often used as electrodes in electrochemical double-layer supercapacitors (EDLCs), due to their ability to store electrical energy. Cellulose nanofibers (CNF) have been proven to be suitable as a dispersion agent and binder in graphite based electrodes for supercapacitor applications, especially due to their capability to improve the wet and dry strength of the electrode. At the same time the capacitance is maintained or even increased with addition of CNF. It is reasonable to believe that the addition of CNF manages to stabilize smaller graphite particles in the dispersion which results in larger internal surface area in the dry material.

 

When the amount of CNF is around 20 wt%, (in ratio to the total mass of active material), both scanning electron microscopy and XPS analysis showed that the surface is almost completely covered with the nano-cellulose. Even with this isolating layer of cellulose it is interesting to note that the capacitance is as high as 90 F/g, compared to around 50 F/g for the lowest CNF amount of 5 wt%. However, by applying voltage pulses during the galvanostatic cycling procedure for capacitance measurements, an initial transient behavior is observed during the first cycles. Therefore the capacitance is calculated after 4000 charge and discharge curves, when curves are completely stabilized. We found that the electrode structure changes significantly during this capacitance measurement and already after a short pulse of 10 s and 0.3 V the structural change is noticeable. After cycling for 24 hours, a completely new structure emerges where large fiber-like structures are developed with diameters around 20-30 µm. The galvanostatic cycling procedure has created fiber-like cellulose structures around 1000 times larger than the initial size of the nano-cellulose.

 

Structural properties of the electrode have often been related to the electronic properties in the supercapacitor. Our result shows that due to this change in the CNF structure, the electrode properties after galvanostatic cycling are indeed also of interest to study. This structural change might be critical to device performance and durability.    

Place, publisher, year, edition, pages
Boston: , 2015
National Category
Composite Science and Engineering
Identifiers
urn:nbn:se:miun:diva-26412 (URN)
Conference
2015 MRS Fall Meeting & Exhibit
Available from: 2015-12-12 Created: 2015-12-11 Last updated: 2015-12-18Bibliographically approved
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