| 1. |
- Munier, Pierre, 1993-, et al.
(författare)
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Rheo-SAXS study of shear-induced orientation and relaxation of cellulose nanocrystal and montmorillonite nanoplatelet dispersions
- 2022
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Ingår i: Soft Matter. - : Royal Society of Chemistry (RSC). - 1744-683X .- 1744-6848. ; 18:2, s. 390-396
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Tidskriftsartikel (refereegranskat)abstract
- The development of robust production processes is essential for the introduction of advanced materials based on renewable and Earth-abundant resources. Cellulose nanomaterials have been combined with other highly available nanoparticles, in particular clays, to generate multifunctional films and foams. Here, the structure of dispersions of rod-like cellulose nanocrystals (CNC) and montmorillonite nanoplatelets (MNT) was probed using small-angle X-ray scattering within a rheological cell (Rheo-SAXS). Shear induced a high degree of particle orientation in both the CNC-only and CNC:MNT composite dispersions. Relaxation of the shear-induced orientation in the CNC-only dispersion decayed exponentially and reached a steady-state within 20 seconds, while the relaxation of the CNC:MNT composite dispersion was found to be strongly retarded and partially inhibited. Viscoelastic measurements and Guinier analysis of dispersions at the shear rate of 0.1 s−1 showed that the addition of MNT promotes gel formation of the CNC:MNT composite dispersions. A better understanding of shear-dependent assembly and orientation of multi-component nanoparticle dispersions can be used to process materials with improved mechanical and functional properties.
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| 2. |
- Ruiz-Caldas, Maria-Ximena, 1991-, et al.
(författare)
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Anisotropic foams derived from textile-based cellulose nanocrystals and xanthan gum
- 2024
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Ingår i: Carbohydrate Polymers. - 0144-8617 .- 1879-1344. ; 338
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Tidskriftsartikel (refereegranskat)abstract
- The upcycling of discarded garments can help to mitigate the environmental impact of the textile industry. Here, we fabricated hybrid anisotropic foams having cellulose nanocrystals (CNCs), which were isolated from discarded cotton textiles and had varied surface chemistries as structural components, in combination with xanthan gum (XG) as a physical crosslinker of the dispersion used for foam preparation. All CNCs had crystallinity indices above 85 %, zeta potential values below -40 mV at 1 mM NaCl, and true densities ranging from 1.61 to 1.67 g center dot cm(-3). Quartz crystal microbalance with dissipation (QCM-D) measurements indicated weak interactions between CNC and XG, while rheology measurements showed that highly charged CNCs caused the XG chains to change from an extended to a helicoidal conformation, resulting in changes the in viscoelastic properties of the dispersions. The inclusion of XG significantly enhanced the compression mechanical properties of the freeze-casted foams without compromising their thermal properties, anisotropy, or degree of alignment. CNC-XG foams maintained structural integrity even after exposure to high humidity (91 %) and temperatures (100 degrees C) and displayed very low radial thermal conductivities. This research provides a viable avenue for upcycling cotton-based clothing waste into high-performance materials.
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| 3. |
- Schiele, Carina, 1993-, et al.
(författare)
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Hybrid Foams based on Multi-Walled Carbon Nanotubes and Cellulose Nanocrystals for Anisotropic Electromagnetic Shielding and Heat Transport
- 2024
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Ingår i: Advanced Materials Interfaces. - 2196-7350. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Lightweight and mechanically robust hybrid foams based on cellulose nanocrystals (CNC) and multi-walled carbon nanotubes (MWCNT) with an anisotropic structure are prepared by directional ice-templating. The anisotropic hybrid CNC-MWCNT foams displayed a combination of highly anisotropic thermal conductivity and an orientation-dependent electromagnetic interference (EMI) shielding with a maximum EMI shielding efficiency (EMI-SE) of 41–48 dB between 8 and 12 GHz for the hybrid foam with 22 wt% MWCNT. The EMI-SE is dominated by absorption (SEA) which is important for microwave absorber applications. Modelling of the low radial thermal conductivity highlighted the importance of phonon scattering at the heterogeneous CNC-MWCNT interfaces while the axial thermal conductivity is dominated by the solid conduction along the aligned rod-like particles. The lightweight CNC-MWCNT foams combination of an anisotropic thermal conductivity and EMI shielding efficiency is unusual and can be useful for directional heat transport and EMI shielding.
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| 4. |
- Schiele, Carina, 1993-, et al.
(författare)
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Hybrid Foams based on Multi-Walled Carbon Nanotubes and Cellulose Nanocrystals for Anisotropic Electromagnetic Shielding and Heat Transport
- 2024
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Ingår i: Advanced Materials Interfaces. - : Wiley-VCH Verlagsgesellschaft. - 2196-7350. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Lightweight and mechanically robust hybrid foams based on cellulose nanocrystals (CNC) and multi-walled carbon nanotubes (MWCNT) with an anisotropic structure are prepared by directional ice-templating. The anisotropic hybrid CNC-MWCNT foams displayed a combination of highly anisotropic thermal conductivity and an orientation-dependent electromagnetic interference (EMI) shielding with a maximum EMI shielding efficiency (EMI-SE) of 41–48 dB between 8 and 12 GHz for the hybrid foam with 22 wt% MWCNT. The EMI-SE is dominated by absorption (SEA) which is important for microwave absorber applications. Modelling of the low radial thermal conductivity highlighted the importance of phonon scattering at the heterogeneous CNC-MWCNT interfaces while the axial thermal conductivity is dominated by the solid conduction along the aligned rod-like particles. The lightweight CNC-MWCNT foams combination of an anisotropic thermal conductivity and EMI shielding efficiency is unusual and can be useful for directional heat transport and EMI shielding.
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| 5. |
- Church, Tamara L., et al.
(författare)
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A Stiff, Tough, and Thermally Insulating Air- and Ice-Templated Plant-Based Foam
- 2022
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Ingår i: Biomacromolecules. - : American Chemical Society (ACS). - 1525-7797 .- 1526-4602. ; 23:6, s. 2595-2602
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Tidskriftsartikel (refereegranskat)abstract
- By forming and directionally freezing an aqueous foam containing cellulose nanofibrils, methylcellulose, and tannic acid, we produced a stiff and tough anisotropic solid foam with low radial thermal conductivity. Along the ice-templating direction, the foam was as stiff as nanocellulose–clay composites, despite being primarily methylcellulose by mass. The foam was also stiff perpendicular to the direction of ice growth, while maintaining λr < 25 mW m–1 K–1 for a relative humidity (RH) up to 65% and <30 mW m–1 K–1 at 80% RH. This work introduces the tandem use of two practical techniques, foam formation and directional freezing, to generate a low-density anisotropic material, and this strategy could be applied to other aqueous systems where foam formation is possible.
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| 6. |
- Di, Andi, 1992-, et al.
(författare)
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Thermally Insulating and Moisture-Resilient Foams Based on Upcycled Aramid Nanofibers and Nanocellulose
- 2023
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 35:48
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Tidskriftsartikel (refereegranskat)abstract
- Low-density foams and aerogels based on upcycled and bio-based nanofibers and additives are promising alternatives to fossil-based thermal insulation materials. Super-insulating foams are prepared from upcycled acid-treated aramid nanofibers (upANFA) obtained from Kevlar yarn and tempo-oxidized cellulose nanofibers (CNF) from wood. The ice-templated hybrid upANFA/CNF-based foams with an upANFA content of up to 40 wt% display high thermal stability and a very low thermal conductivity of 18–23 mW m−1 K−1 perpendicular to the aligned nanofibrils over a wide relative humidity (RH) range of 20% to 80%. The thermal conductivity of the hybrid upANFA/CNF foams is found to decrease with increasing upANFA content (5–20 wt%). The super-insulating properties of the CNF-upANFA hybrid foams are related to the low density of the foams and the strong interfacial phonon scattering between the very thin and partially branched upANFA and CNF in the hybrid foam walls. Defibrillated nanofibers from textiles are not limited to Kevlar, and this study can hopefully inspire efforts to upcycle textile waste into high-performance products.
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| 7. |
- Hadi, Seyed Ehsan, 1993-
(författare)
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Colloidal Processing and Alignment of Wood-Based Dispersions and Hybrid Functional Foams
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents novel methods and approaches for designing, preparing/fabricating, and characterizing wood-based nanomaterials. It investigates how modifications in structure, process variables, and composition can enhance functional properties. It employs advanced characterization techniques to analyze process-structure-property relationships and utilizes innovative colloidal processing approaches such as controlled nanoparticle incorporation, Layer-by-Layer self-assembly, and unidirectional ice-templating to improve the functional properties of wood-based nanomaterials.A novel approach has been developed to fabricate lightweight, highly porous hybrid foams using iron oxide nanoparticles (IONP) and TEMPO-oxidized cellulose nanofibers (TOCNF). The addition of tannic acid (TA) and the application of a magnetic field-enhanced unidirectional ice-templating technique (MFUIT) enhanced processability, mechanical, and magnetic characteristics of the foams. The hybrid foam containing 87% IONPs exhibited a saturation magnetization of 83.2 emu g–1, which is equivalent to 95% of the magnetization value observed in bulk magnetite.Hybrid, anisotropic foams have been prepared by incorporation of reduced graphene oxide (rGO) onto the macropore-walls of anisotropic TOCNF foams using a liquid-phase Layer-by-Layer self-assembly method. These hierarchical rGO-TOCNF foams exhibit lower radial thermal conductivity (λr) across a wide range of relative humidity compared to control TOCNF foams.The shear-induced orientations and relaxations of multi-component dispersions containing cellulose nanocrystals (CNC) and montmorillonite nanoplatelets (MNT) have been studied by rheological small-angle X-ray scattering (Rheo-SAXS). The addition of MNT resulted in gelation and changes in flow behavior, shear responses, and relaxation dynamics. Rheo-SAXS measurements showed that CNC and MNT aligned under shear, creating aligned structures that relaxed upon shear removal. Gaining insights into shear-induced orientations and relaxation dynamics can aid in the development of advanced wood-based nanocomposite materials.Transmission Electron Microscopy (TEM) was employed to characterize lignin oleate nanoparticles (OLNPs) derived from abundant lignin waste. TEM analysis revealed that the OLNPs had a spherical shape and a core-shell structure. Upon drying, the particles tended to agglomerate due to the loss of electrostatic repulsion forces. This agglomeration behavior indirectly supports the hypothesis that oleate chains act as a hydration barrier, preventing water permeation into the particles. Finally, a comprehensive study showed that TEMPO-oxidized lignocellulose nanofibers (TOLCNF)-based foams made from unbleached pulp can be used to prepare anisotropic, light-weight ice-templated foams with high mechanical strength. TOLCNF foams utilize lignin and hemicellulose to enhance properties while require less energy for production compared to TOCNF-based foams. This study emphasizes the potential for developing sustainable wood-based nanomaterials using TOLCNF.The results presented in this thesis offer valuable insights for further advancements of wood-based nanomaterials.
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