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Publications (10 of 48) Show all publications
Guccini, V., Carlson, A., Yu, S., Lindbergh, G., Wreland Lindström, R. & Salazar-Alvarez, G. (2019). Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells. Journal of Materials Chemistry A
Open this publication in new window or tab >>Highly proton conductive membranes based on carboxylated cellulose nanofibres and their performance in proton exchange membrane fuel cells
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2019 (English)In: Journal of Materials Chemistry A, ISSN 2050-7488Article in journal (Refereed) Epub ahead of print
Abstract [en]

The performance of thin carboxylated cellulose nanofiber-based (CNF) membranes as proton exchange membranes in fuel cells has been measured in situ as a function of CNF surface charge density (600 and 1550 μmol g−1), counterion (H+ or Na+), membrane thickness and fuel cell relative humidity (RH 55 to 95%). The structural evolution of the membranes as a function of RH, as measured by Small Angle X-ray Scattering, shows that water channels are formed only above 75% RH. The amount of absorbed water was shown to depend on the membrane surface charge and counter ions (H+ or Na+). The high affinity of CNF for water and the high aspect ratio of the nanofibers, together with a well-defined and homogenous membrane structure, ensures a proton conductivity exceeding 1 mS cm−1 at 30 °C between 65 and 95% RH. This is two orders of magnitude larger than previously reported values for cellulose materials and only one order of magnitude lower than Nafion 212. Moreover, the CNF membranes are characterized by a lower hydrogen crossover than Nafion, despite being ≈30% thinner. Thanks to their environmental compatibility and promising fuel cell performance the CNF membranes should be considered for new generation proton exchange membrane fuel cells.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-263094 (URN)10.1039/C9TA04898G (DOI)
Note

QC 20191030

Available from: 2019-10-29 Created: 2019-10-29 Last updated: 2019-10-30Bibliographically approved
Ohm, W., Rothkirch, A., Pandit, P., Koerstgens, V., Mueller-Buschbaum, P., Rojas, R., . . . Roth, S. V. (2019). Morphological and crystalline properties of airbrush spray-deposited enzymatic cellulose thin films. Paper presented at National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL. Abstracts of Papers of the American Chemical Society, 257
Open this publication in new window or tab >>Morphological and crystalline properties of airbrush spray-deposited enzymatic cellulose thin films
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2019 (English)In: Abstracts of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 257Article in journal, Meeting abstract (Other academic) Published
Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2019
National Category
Paper, Pulp and Fiber Technology
Identifiers
urn:nbn:se:kth:diva-257617 (URN)000478860502739 ()
Conference
National Meeting of the American-Chemical-Society (ACS), MAR 31-APR 04, 2019, Orlando, FL
Note

QC 20190918

Available from: 2019-09-18 Created: 2019-09-18 Last updated: 2019-09-18Bibliographically approved
Karlsson, R.-M. P., Larsson, P. T., Yu, S., Pendergraph, S. A., Pettersson, T., Hellwig, J. & Wågberg, L. (2018). Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers. Journal of Colloid and Interface Science, 519, 119-129
Open this publication in new window or tab >>Carbohydrate gel beads as model probes for quantifying non-ionic and ionic contributions behind the swelling of delignified plant fibers
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2018 (English)In: Journal of Colloid and Interface Science, ISSN 0021-9797, E-ISSN 1095-7103, Vol. 519, p. 119-129Article in journal (Refereed) Published
Abstract [en]

Macroscopic beads of water-based gels consisting of uncharged and partially charged beta-(1,4)-D-glucan polymers were developed to be used as a novel model material for studying the water induced swelling of the delignified plant fiber walls. The gel beads were prepared by drop-wise precipitation of solutions of dissolving grade fibers carboxymethylated to different degrees. The internal structure was analyzed using Solid State Cross-Polarization Magic Angle Spinning Carbon-13 Nuclear Magnetic Resonance and Small Angle X-ray Scattering showing that the internal structure could be considered a homogeneous, non-crystalline and molecularly dispersed polymer network. When beads with different charge densities were equilibrated with aqueous solutions of different ionic strengths and/or pH, the change in water uptake followed the trends expected for weak polyelectrolyte gels and the trends found for cellulose-rich fibers. When dried and subsequently immersed in water the beads also showed an irreversible loss of swelling depending on the charge and type of counter-ion which is commonly also found for cellulose-rich fibers. Taken all these results together it is clear that the model cellulose-based beads constitute an excellent tool for studying the fundamentals of swelling of cellulose rich plant fibers, aiding in the elucidation of the different molecular and supramolecular contributions to the swelling.

Place, publisher, year, edition, pages
Academic Press, 2018
Keywords
Swelling, Water uptake, Hydrogel, Cellulose, Small-angle X-ray scattering, Solid state NMR, Atomic force microscopy
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-226733 (URN)10.1016/j.jcis.2018.02.052 (DOI)000429633500013 ()29486431 (PubMedID)2-s2.0-85042413398 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20180503

Available from: 2018-05-03 Created: 2018-05-03 Last updated: 2019-04-25Bibliographically approved
Ohm, W., Rothkirch, A., Pandit, P., Koerstgens, V., Mueller-Buschbaum, P., Rojas, R., . . . Roth, S. V. (2018). Morphological properties of airbrush spray-deposited enzymatic cellulose thin films. Paper presented at 13th Coatings Science International Conference (COSI), JUN 26-30, 2017, Noordwijk, NETHERLANDS. JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, 15(4), 759-769
Open this publication in new window or tab >>Morphological properties of airbrush spray-deposited enzymatic cellulose thin films
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2018 (English)In: JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH, ISSN 1945-9645, Vol. 15, no 4, p. 759-769Article in journal (Refereed) Published
Abstract [en]

We investigate the layer formation of enzymatic cellulose by airbrush spray coating on silicon oxide surfaces. The layer structure and morphology of enzymatic cellulose films in the thickness range between 86 nm and 2.1 A mu m is determined as a function of the spray coating procedures. For each spray coating step, layer buildup, surface topography, crystallinity as well as the nanoscale structure are probed with atomic force microscopy and surface-sensitive X-ray scattering methods. Without intermittent drying, the film thickness saturates; with intermittent drying, a linear increase in layer thickness with the number of spray pulses is observed. A closed cellulose layer was always observed. The crystallinity remains unchanged; the nanoscale structures show three distinct sizes. Our results indicate that the smallest building blocks increasingly contribute to the morphology inside the cellulose network for thicker films, showing the importance of tailoring the cellulose nanofibrils. For a layer-by-layer coating, intermittent drying is mandatory.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-232911 (URN)10.1007/s11998-018-0089-9 (DOI)000439757000011 ()2-s2.0-85046905803 (Scopus ID)
Conference
13th Coatings Science International Conference (COSI), JUN 26-30, 2017, Noordwijk, NETHERLANDS
Note

QC 20180808

Available from: 2018-08-08 Created: 2018-08-08 Last updated: 2018-08-08Bibliographically approved
Liu, D., Pallon, L. K. H., Pourrahimi, A. M., Zhang, P., Diaz, A., Holler, M., . . . Gedde, U. W. (2017). Cavitation in strained polyethylene/aluminium oxide nanocomposites. European Polymer Journal, 87, 255-265
Open this publication in new window or tab >>Cavitation in strained polyethylene/aluminium oxide nanocomposites
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2017 (English)In: European Polymer Journal, ISSN 0014-3057, E-ISSN 1873-1945, Vol. 87, p. 255-265Article in journal (Refereed) Published
Abstract [en]

The incorporation of metal oxide (e.g. Al2O3) nanoparticles has a pronounced positive effect on low-density polyethylene (LDPE) as an insulating material for high-voltage direct-current (HVDC) cables, the electrical conductivity being decreased by one to two orders of magnitude and charge species being trapped by the nanoparticles. The risk of debonding between the nanoparticles and the polymer matrix leading to electrical treeing via electrical discharges in the formed cavities was the motivation for this study. Scanning electron microscope (SEM), small-angle X-ray scattering (SAXS) and X-ray ptychographic tomography were used to study a series of LDPE nanocomposites which contained Al2O3 nanoparticles treated with silanes having terminal alkyl groups of different lengths (methyl, octyl and octadecyl). When specimens were subjected to a tensile strain (a typical specimen stretched beyond the onset of necking consisted of three zones according to SEM of specimens that were studied after removal of the external force: an essentially cavitation-free zone with low local plastic strain, a transitional zone in which local plastic strain showed a marked increase and the revealed concentration of permanent cavities increased with increasing plastic strain and a highly strained zone with extensive cavitation), the cavitation occurred mainly at the polymer-nanoparticle interface according to SEM and X-ray ptychographic tomography and according to SEM progressed with increasing plastic strain through an initial phase with no detectable formation of permanent cavities to a period of very fast cavitation and finally almost an order of magnitude slower cavitation. The polymer/nanoparticle interface was fractal before deformation, as revealed by the profile of the Porod region in SAXS, presumably due to the existence of bound polymers at the nanoparticle surface. A pronounced decrease in the interface fractal dimension was observed when the strain exceeded a critical value; a phenomenon attributed to the stress-induced de-bonding of nanoparticles. The strain-dependence of the interface fractal dimension value at low strain levels between composites containing differently treated nanoparticles seems to be an indicator of the strength of the nanoparticle-polymer interface.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Aluminium oxide, Cavitation, Low-density polyethylene, Nanocomposites, Aluminum, DC power transmission, Electric discharges, Fractal dimension, Fractals, HVDC power transmission, Low density polyethylenes, Metal nanoparticles, Metals, Nanoparticles, Plastic deformation, Polyethylenes, Scanning electron microscopy, Silanes, Tomography, X ray scattering, Electrical conductivity, Electrical discharges, Fractal-dimension value, High voltage direct current, Low density polyethylene(LDPE), Nanoparticle surface, Polymer nanoparticles, Tensile strain
National Category
Polymer Technologies
Identifiers
urn:nbn:se:kth:diva-201939 (URN)10.1016/j.eurpolymj.2016.12.021 (DOI)000395210900022 ()2-s2.0-85008230710 (Scopus ID)
Note

Funding text: The Swedish Foundation for Strategic Research (grant EM11-0022) is thanked for the financial support.

QC 20170307

Available from: 2017-03-07 Created: 2017-03-07 Last updated: 2017-11-29Bibliographically approved
Li, Y., Yu, S., Veinot, J. G., Linnros, J., Berglund, L. & Sychugov, I. (2017). Luminescent Transparent Wood. Advanced Optical Materials, 5(1), Article ID 1600834.
Open this publication in new window or tab >>Luminescent Transparent Wood
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2017 (English)In: Advanced Optical Materials, ISSN 2195-1071, Vol. 5, no 1, article id 1600834Article in journal (Refereed) Published
Abstract [en]

Luminescent transparent wood is prepared by combining the complementary properties of naturally grown anisotropic porous wood and luminescent quantum dots. The wood structure introduces strong diffused luminescence and waveguiding, which can potentially be exploited for optoelectronic and photovoltaic applications, such as for planar illumination sources and luminescent buildings/furniture. Images below show the transparency, haze, and luminescence of quantum dot wood.

Place, publisher, year, edition, pages
John Wiley & Sons, 2017
Keywords
concentrators, diffused luminescence, LED, quantum dot, transparent wood
National Category
Materials Engineering
Identifiers
urn:nbn:se:kth:diva-202236 (URN)10.1002/adom.201600834 (DOI)000393203600010 ()2-s2.0-85004065408 (Scopus ID)
Note

Funding text: Y.L. and S.Y. contributed equally to this work. The authors acknowledge financial support by Knut and Alice Wallenberg foundation through the Wallenberg Wood Science Center at KTH Royal Institute of Technology, and by the Swedish Research Council (VR) through an individual contract (VR 2015-04064) and ADOPT Center of Excellence. Regina Sinelnikov is acknowledged for providing some starting material. QC 20170320

Available from: 2017-03-20 Created: 2017-03-20 Last updated: 2018-01-17Bibliographically approved
Pallon, L. K. H., Nilsson, F., Yu, S., Liu, D., Diaz, A., Holler, M., . . . Gedde, U. W. (2017). Three-Dimensional Nanometer Features of Direct Current Electrical Trees in Low-Density Polyethylene. Nano letters (Print), 17(3), 1402-1408
Open this publication in new window or tab >>Three-Dimensional Nanometer Features of Direct Current Electrical Trees in Low-Density Polyethylene
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2017 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 17, no 3, p. 1402-1408Article in journal (Refereed) Published
Abstract [en]

Electrical trees are one reason for the breakdown of insulating materials in electrical power systems. An understanding of the growth of electrical trees plays a crucial role in the development of reliable high voltage direct current (HVDC) power grid systems with transmission voltages up to 1 MV. A section that contained an electrical tree in low-density polyethylene (LDPE) has been visualized in three dimensions (3D) with a resolution of 92 nm by X-ray ptychographic tomography. The 3D imaging revealed prechannel-formations with a lower density with the width of a couple of hundred nanometers formed around the main branch of the electrical tree. The prechannel structures were partially connected with the main tree via paths through material with a lower density, proving that the tree had grown in a step-by-step manner via the prestep structures formed in front of the main channels. All the prechannel structures had a size well below the limit of the Paschen law and were thus not formed by partial discharges. Instead, it is suggested that the prechannel structures were formed by electro-mechanical stress and impact ionization, where the former was confirmed by simulations to be a potential explanation with electro-mechanical stress tensors being almost of the same order of magnitude as the short-term modulus of low-density polyethylene.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2017
Keywords
Electrical tree, ptychography, DC-tree, HVDC, polyethylene
National Category
Chemical Sciences
Identifiers
urn:nbn:se:kth:diva-204068 (URN)10.1021/acs.nanolett.6b04303 (DOI)000396185800013 ()28177252 (PubMedID)2-s2.0-85014927866 (Scopus ID)
Note

QC 20170329

Available from: 2017-03-29 Created: 2017-03-29 Last updated: 2017-11-29Bibliographically approved
Wu, Q., Yu, S., Kollert, M., Mtimet, M., Roth, S. V., Gedde, U. W., . . . Hedenqvist, M. S. (2016). Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids. ACS SUSTAINABLE CHEMISTRY & ENGINEERING, 4(4), 2395-2404
Open this publication in new window or tab >>Highly Absorbing Antimicrobial Biofoams Based on Wheat Gluten and Its Biohybrids
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2016 (English)In: ACS SUSTAINABLE CHEMISTRY & ENGINEERING, ISSN 2168-0485, Vol. 4, no 4, p. 2395-2404Article in journal (Refereed) Published
Abstract [en]

This paper presents the absorption, mechanical, and antimicrobial properties of novel types of biofoams based on wheat-gluten (WG) and its biohybrids with silica. The hybrid WG foams were in situ polymerized with silica using two different silanes. When immersed in water, the 90-95% porous WG and silica-modified hybrid WG foams showed a maximum water uptake between 32 and 11 times the original sample weight. The maximum uptake was only between 4.3 and 6.7 times the initial weight in limonene (a nonpolar liquid) but showed reversible absorption/desorption and that the foams could be dried into their original shape. The different foams had a cell size of 2-400 mu m, a density of 60-163 kg/m(3), and a compression modulus of 1-9 MPa. The integrity of the foams during swelling in water was improved by cross-linking with glutaraldehyde (GA) or by a thermal treatment at 130 degrees C, which polymerized the proteins. In the never-dried state, the foam acted as a sponge, and it was possible to squeeze out water and soak it repeatedly. If the foam was dried to its glassy state, then the cells collapsed and did not open again even if the solid foam was reimmersed in water, saving as a sensor mechanism that can be used to reveal unintended exposure to polar liquids such as water under a product's service life. Small-angle X-ray scattering revealed that the gliadin-correlated structure expanded and then disappeared in the presence of water. The foam was made antimicrobial by impregnation with a Lanasol solution (a bromophenol existing in algae). It was also shown that the foam can act as a transfer/storage medium for liquids such as natural oils (rapeseed oil) and as a slow-release matrix for surfactant chemicals.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keywords
Protein, Freeze-drying, Swelling, Sponge, Lanasol
National Category
Chemical Sciences Chemical Engineering
Identifiers
urn:nbn:se:kth:diva-185985 (URN)10.1021/acssuschemeng.6b00099 (DOI)000373554600061 ()2-s2.0-84964378085 (Scopus ID)
Note

QC 20160504

Available from: 2016-05-04 Created: 2016-04-29 Last updated: 2017-05-29Bibliographically approved
Li, Y., Fu, Q., Yu, S., Yan, M. & Berglund, L. (2016). Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance. Biomacromolecules, 17(4), 1358-1364
Open this publication in new window or tab >>Optically Transparent Wood from a Nanoporous Cellulosic Template: Combining Functional and Structural Performance
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2016 (English)In: Biomacromolecules, ISSN 1525-7797, E-ISSN 1526-4602, Vol. 17, no 4, p. 1358-1364Article in journal (Refereed) Published
Abstract [en]

Optically transparent wood (TW) with transmittance as high as 85% and haze of 71% was obtained using a delignified nanoporous wood template. The template was prepared by removing the light-absorbing lignin component, creating nanoporosity in the wood cell wall. Transparent wood was prepared by successful impregnation of lumen and the nanoscale cellulose fiber network in the cell wall with refractive-index-matched prepolymerized methyl methacrylate (MMA). During the process, the hierarchical wood structure was preserved. Optical properties of TW are tunable by changing the cellulose volume fraction. The synergy between wood and PMMA was observed for mechanical properties. Lightweight and strong transparent wood is a potential candidate for lightweight low-cost, light-transmitting buildings and transparent solar cell windows.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2016
Keywords
Solar-Cells, Nanofiber Paper, Scattering, Efficient, Fibers, Film
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-187074 (URN)10.1021/acs.biomac.6b00145 (DOI)000374076900013 ()26942562 (PubMedID)2-s2.0-84964600674 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation
Note

QC 20160518

Available from: 2016-05-18 Created: 2016-05-17 Last updated: 2018-02-21Bibliographically approved
Chen, S., Grandfield, K., Yu, S., Engqvist, H. & Xia, W. (2016). Synthesis of calcium phosphate crystals with thin nacreous structure. CrystEngComm, 18(6), 1064-1069
Open this publication in new window or tab >>Synthesis of calcium phosphate crystals with thin nacreous structure
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2016 (English)In: CrystEngComm, ISSN 1466-8033, E-ISSN 1466-8033, Vol. 18, no 6, p. 1064-1069Article in journal (Refereed) Published
Abstract [en]

Nacre-like structures have attracted great interest in recent years due to their outstanding toughness, stiffness and impact resistance. However, there is a challenge associated with engineering nacre-like calcium phosphate crystals. In this study, thin nacreous-like monetite sheets were synthesized in solutions guided by a surfactant. The influence of temperature, initial pH, Ca/P ratio, stirring time and the concentration of cetyltrimethylammonium bromide (CTAB) on the nacre-like structure has been studied. Findings showed that a nacre-like structure could only be formed at a high temperature (90 °C), high initial pH (11), sufficient stirring time (3 h), and under the presence of CTAB. A small-angle X-ray scattering experiment carried out at a synchrotron radiation facility showed that the distance between nanolayers was around 2.6 nm and TEM confirmed the fine sheet-like structure. The mechanism of the formation the nacre-like structure and its characterization were discussed.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2016
National Category
Ceramics
Identifiers
urn:nbn:se:kth:diva-180732 (URN)10.1039/C5CE02078F (DOI)000369609800025 ()2-s2.0-84956926056 (Scopus ID)
Note

QC 20160304

Available from: 2016-01-21 Created: 2016-01-21 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-9663-7705

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