| 1. |
- Pakharenko, Viktoriya, et al.
(författare)
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Cellulose nanofiber thin-films as transparent and durable flexible substrates for electronic devices
- 2021
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Ingår i: Materials & design. - : Elsevier. - 0264-1275 .- 1873-4197. ; 197
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Tidskriftsartikel (refereegranskat)abstract
- This work reports for the first time an exceptionally high thermal stability of cellulosic nanofibers films at 190 °C after a 5 h exposure, a threshold required for their design and manufacturing in flexible electronic devices. A long-term durability validation of a flexible cellulose nanofiber over a period of 10 years exposure under ambient condition validated their life-span over a long period of operating condition. Arresting quinoid oxidative reactions pathways and thermal degradation of lignin or lignin-less cellulose are demonstrated to be two fundamental routes to enhance thermal processing of cellulose nanofiber substrates and to achieve long service life of energy devices made from them. One of the main highlights of this work is the first time validation of a long operating service life for a light-emitting device made from a cellulose nanofibers substrate, while continuously illuminating the fabricated prototype under ambient condition for an equivalent of 10 years. The unique durability of this flexible substrate will have potential applications in flexible lighting, energy and sensing devices. © 2020 The Authors
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| 2. |
- Pakharenko, Viktoriya, et al.
(författare)
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Chemical and molecular structure transformations in atomistic conformation of cellulose nanofibers under thermal environment
- 2022
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Ingår i: npj Materials Degradation. - : Springer Nature. - 2397-2106. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- The structural changes of the glucopyranose chain and the chemical compositional response of cellulose nanofibers (CNFs) under thermal exposure (at 190 °C for 5 h) have remained a significant gap in the understanding of the long-term performance of nanocellulose. Herein, CNF films with different chemical compositions were investigated to confirm the structural transformation of glucopyranose (coupling constant of OH groups changed up to 50%) by nuclear magnetic resonance (NMR) analysis. Remarkably, the glucopyranose rings underwent partial dehydration during the thermal exposure resulting in enol formation. This study confirms the chain mobility that could lead to the conformational and dimensional changes of the CNFs during thermal exposure. The broad range of conformations was defined by the dihedral angles that varied from ±27° to ±139° after thermal exposure. Investigation into the mechanism involving chemical transformation of the substrates during heating is important for the fabrication of the next generation of flexible electrical materials.
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| 3. |
- Pakharenko, Viktoriya, et al.
(författare)
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Thermoconformational Behavior of Cellulose Nanofiber Films as a Device Substrate and Their Superior Flexibility and Durability to Glass
- 2021
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Ingår i: ACS Applied Materials and Interfaces. - : American Chemical Society (ACS). - 1944-8244 .- 1944-8252. ; 13:34, s. 40853-40862
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Tidskriftsartikel (refereegranskat)abstract
- The design and high-throughput manufacturing of thin renewable energy devices with high structural and atomic configurational stability are crucial for the fabrication of green electronics. Yet, this concept is still in its infancy. In this work, we report the extraordinary durability of thin molecular interlayered organic flexible energy devices based on chemically tuned cellulose nanofiber transparent films that outperform glass by decreasing the substrate weight by 50%. The nanofabricated flexible thin film has an exceptionally low thermal coefficient of expansion of 1.8 ppm/K and a stable atomic configuration under a harsh fabrication condition (over 190 °C for an extended period of 5 h). A flexible optoelectronic device using the same renewable cellulose nanofiber film substrate was found to be functionally operational over a life span of 5 years under an intermittent operating condition. The success of this device’s stability opens up an entirely new frontier of applications of flexible electronics.
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| 4. |
- Patel, Mitul Kumar
(författare)
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Improving properties of poly(lactic acid) biopolymer for use in food packaging
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The petroleum-based plastics are widely used for food packaging applications because of their low cost, easy processability, and tunable properties to meet the specific needs of food packaging. However, these polymers are non-biodegradable, leading to a substantial amount of plastic waste in both land and marine ecosystems. Therefore, it is crucial to find biodegradable polymers from renewable resources to achieve the sustainability goals set by the United Nations. In this context, poly(lactic acid) (PLA) biopolymer is a potential candidate due to its biodegradability, low toxicity, and eco-friendly behavior; it also has excellent mechanical properties, transparency, and economic viability in comparison to many other biopolymers. However, despite the aforementioned benefits, PLA has disadvantages that limit its use in food packaging applications. These include inherent brittleness, poor melt strength, and moderate gas barrier performance. The primary objective of this thesis was to improve these properties of PLA by producing nanocomposites with biopolymer, processing aids, and nano-size reinforcement, as well as modifying by processing to meet the requirements for food packaging applications.In this work, PLA and PLA-poly(hydroxybutyrate) (PHB) blend nanocomposites with chitin nanocrystal (ChNC) were prepared via a liquid-assisted extrusion process. Glyceroltriacetate (GTA), triethyl citrate (TEC), and lactic acid oligomer (OLA) were used as plasticizers/compatibilizers, dispersing, and processing aids. The effect of the addition of PHB, chitin nanocrystals (ChNCs), and dispersing agents on the properties of PLA was studied. The effect of different processing techniques, such as iso-thermal crystallization as well as the melt-state and solid-state drawing on the properties of the PLA nanocomposites were also investigated. In addition, the influence of ChNCs and liquid assisted extrusion on the processing and properties of blown films were assessed.The results of the first study demonstrated that the dispersion and distribution of ChNCs in the PLA matrix progressively improved with increasing TEC dispersing aid content, with the effect being most pronounced in the nanocomposite containing 15 wt% plasticizers. PLA with 15 wt% of TEC resulted in enhanced flexibility and toughness, but negatively influenced its mechanical and thermal properties; however, the incorporation of 1 wt% ChNCs minimizes these effects. In the second study, it was shown that the polymer chain orientation of PLA/ChNC nanocomposite achieved via a combination of melt state and solid-state drawing resulted in a material with excellent mechanical properties, including an increase in toughness of nearly 100-fold compared to that of unoriented nanocomposite film. The orientation of the nanocomposite also enhanced the material's crystallinity. In the third and fourth studies, it was found that the crystallinity of PLA was increased by using an isothermal crystallization process and the addition of 25 wt% PHB. The crystallinity was further enhanced by the addition of a very small amount of ChNC (1 wt%), which acted as a nucleation agent, resulting in a faster crystallization rate and enhanced crystallinity in both cases. The nanocomposites PLA/ChNC or PLAPHB/ChNC with ChNCs, higher crystallinity, and/or orientation created a more tortuous path for gas molecules resulting in significant improvements in the O2 and CO2 barrier performance. In the final study, it was demonstrated that the PLA-PHB/ChNCs nanocomposite produced by liquid-assisted extrusion exhibited a stable process during the film-blowing operation and exhibited smooth and homogenous surface film compared to the nanocomposite produced via conventional melt compounding. Moreover, the blown film exhibited comparable mechanical properties with petroleum polymers and also degraded within 45 days under standard composting conditions.In conclusion, this thesis shows that the properties of PLA can be tailored through the composition of the blend and nanocomposite, or during the processing of the material to make it suitable for food packaging applications. It was also demonstrated that the processing technique in this study can be a step forward for the large-scale production of bionanocomposites.
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| 5. |
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| 6. |
- Saadat, Nazmus, et al.
(författare)
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Enhancing performance of advanced fuel cell design with functional energy materials and process
- 2023
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Ingår i: Journal of Materials Research and Technology. - : Elsevier. - 2238-7854 .- 2214-0697. ; 26, s. 1723-1735
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Tidskriftsartikel (refereegranskat)abstract
- Efficiency enhancement of hydrogen based electric powertrain is becoming highly relevant for medium to heavy duty transportation due to advantages of eminent electrochemical cell design and advances in infrastructure accessibility. Herein, a facile and highly effective fabrication process has been reported for the first time to demonstrate an outstanding mechanical strength and electrical conductivity simultaneously in the carbon rich composite designed to enhance the fuel cell performance. Improvement of composites with different advanced reinforced materials such as carbon veil, recycled carbon fiber as well as functional additives such as carbon black, multiwalled nanotube, etc. Was investigated through a holistic approach of optimized parameters. Advanced composite plates have been designed to be mechanically flexible, electrically conductive and cost effective; this newly designed composite for bipolar plate supersedes by far the US Department of Energy (DOE) target for fuel cell bipolar plate with a flexural strength of over 64Â MPa and exceeding electrical conductivity of 200Â S/cm. Notably, tuned process parameters as well as novel architecture of materials such as continuous carbon fiber and carbon veil can facilitate the fabrication of a light-weight high-performance carbon polymer composite for a wide range of applications including battery electrodes, supercapacitors, fuel cells and solar cell.
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| 7. |
- Semeniuk, Maria, et al.
(författare)
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Catalytically Transformed Low Energy Intensive 2D-Layered and Single Crystal-Graphitic Renewable Carbon Cathode Conductors
- 2021
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Ingår i: Carbon. - : Elsevier. - 0008-6223 .- 1873-3891. ; 183, s. 243-250
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Tidskriftsartikel (refereegranskat)abstract
- This is the first study of the catalytic graphitization of Black Spruce (Picea mariana) which has successfully discovered the formation of single crystal graphitic carbon structures with a very high conductivity over 850 S/m implemented in the cathode of a coin cell battery. Renewable carbon with this conductivity is suitable for use in bio-electronics, organic thin film transistors, fuel cells, organic batteries, supercapacitors and sensing device applications. The P. mariana was doped with iron nitrate nanoparticle precursor, and sequentially thermo-catalyzed in presence of helium at temperatures between 300-800 ˚C. Transmission electron micrographs reveal formation of graphitic structures with an interplanar distance of ∼0.33 nm resembling single crystal graphite structure. Raman spectroscopy and X-ray diffraction studies confirm the presence of nano-layered carbon, and the high conductivity was observed in Fe-free residual graphite. Thus, using iron nitrate as a catalyst promotes the formation of single crystal graphitic structures at a significantly reduced thermal energy than traditional pyrolysis treatment and opening a new frontier for sustainable bio-electronics and energy materials manufacturing.
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| 8. |
- Thomas, Bony, et al.
(författare)
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Electrochemical Properties of Biobased Carbon Aerogels Decorated with Graphene Dots Synthesized from Biochar
- 2021
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Ingår i: ACS Applied Electronic Materials. - : American Chemical Society (ACS). - 2637-6113. ; 3:11, s. 4699-4710
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Tidskriftsartikel (refereegranskat)abstract
- Carbon aerogels prepared from low-cost renewable resources are promising electrode materials for future energy storage applications. However, their electrochemical properties must be significantly improved to match the commercially used high-carbon petroleum products. This paper presents a facile method for the green synthesis of carbon aerogels (CAs) from lignocellulosic materials and graphene dots (GDs) from commercially available biochar. The produced carbon aerogels exhibited a hierarchical porous structure, which facilitates energy storage by forming an electrical double-layer capacitance. Surprisingly, the electrochemical analyses of the GD-doped carbon aerogels revealed that in comparison to pristine carbon aerogels, the surface doping of GDs enhanced the electrochemical performance of carbon aerogels, which can be attributed to the combined effect from both double-layer capacitance and pseudocapacitance. Herein, we designed and demonstrated the efficacy of a supercapacitor device using our green carbon electrode as a sustainable option. These green carbon aerogels have opened a window for their practical use in designing sustainable energy storage devices.
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| 9. |
- Thomas, Bony, et al.
(författare)
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Hetero-Porous, High-Surface Area Green Carbon Aerogels for the Next-Generation Energy Storage Applications
- 2021
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Ingår i: Nanomaterials. - : MDPI. - 2079-4991. ; 11:3
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Tidskriftsartikel (refereegranskat)abstract
- Various carbon materials have been developed for energy storage applications to address the increasing energy demand in the world. However, the environmentally friendly, renewable, and nontoxic bio-based carbon resources have not been extensively investigated towards high-performance energy storage materials. Here, we report an anisotropic, hetero-porous, high-surface area carbon aerogel prepared from renewable resources achieving an excellent electrical double-layer capacitance. Two different green, abundant, and carbon-rich lignins which can be extracted from various biomasses, have been selected as raw materials, i.e., kraft and soda lignins, resulting in clearly distinct physical, structural as well as electrochemical characteristics of the carbon aerogels after carbonization. The obtained green carbon aerogel based on kraft lignin not only demonstrates a competitive specific capacitance as high as 163 F g−1 and energy density of 5.67 Wh kg−1 at a power density of 50 W kg−1 when assembled as a two-electrode symmetric supercapacitor, but also shows outstanding compressive mechanical properties. This reveals the great potential of the carbon aerogels developed in this study for the next-generation energy storage applications requiring green and renewable resources, lightweight, robust storage ability, and reliable mechanical integrity.
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| 10. |
- Thomas, Bony, et al.
(författare)
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Ice-Templating of Lignin and Cellulose Nanofiber-Based Carbon Aerogels: Implications for Energy Storage Applications
- 2022
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Ingår i: ACS Applied Nano Materials. - : American Chemical Society (ACS). - 2574-0970. ; 5:6, s. 7954-7966
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Tidskriftsartikel (refereegranskat)abstract
- Hierarchically porous carbon aerogels (CAs) were synthesized by following a green, facile preparation route involving ice-templating and lyophilization followed by carbonization. For the first time, we report CAs prepared with a cooling rate of 7.5 K/min, demonstrating a very high specific surface area (SSA) of 1260 m2 g–1 without any physical or chemical activation steps, and the electrode prepared using the latter aerogel showed superior electrochemical performance with a specific capacitance of 410 F g–1 at 2 m V s–1 with a cyclic stability of 94% after 4500 charge–discharge cycles. The effects of the ice-templating cooling rate and the solid content of lignin and cellulose nanofibers (CNFs) in the suspension on the structure and electrochemical performance of the CAs were investigated. The ice-templating process and the cooling rate were found to have a large effect on the generation of the nanoporous structure and the specific surface area of carbon aerogels, while the solid content of the lignin-nanocellulose suspension showed negligible effects. When assembled as a supercapacitor (SC), a remarkable specific capacitance of 240 F g–1 at 0.1 A g–1 was achieved. The relaxation time constant for the prepared SC was 1.3 s, which shows the fast response of these SCs. In addition, an energy density of 4.3 Wh kg–1 was also obtained at a power density of 500 W kg–1. Thus, this study opens new perspectives for the preparation of green, environment-friendly, free-standing, high-performance CA electrodes for future energy storage applications.
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