Browsing by Author "Budtova, Tatiana"

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  • Acoustic Properties of Aerogels: Current Status and Prospects
    (2023-03) Budtova, Tatiana; Lokki, Tapio; Malakooti, Sadeq; Rege, Ameya; Lu, Hongbing; Milow, Barbara; Vapaavuori, Jaana; Vivod, Stephanie
     A2 Katsausartikkeli tieteellisessä aikakauslehdessä
    Noise reduction remains an important priority in the modern society, in particular, for urban areas and highly populated cities. Insulation of buildings and transport systems such as cars, trains, and airplanes has accelerated the need to develop advanced materials. Various porous materials, such as commercially available foams and granular and fibrous materials, are commonly used for sound mitigating applications. In this review, a special class of advanced porous materials, aerogels, is examined, and an overview of the current experimental and theoretical status of their acoustic properties is provided. Aerogels can be composed of inorganic matter, synthetic or natural polymers, as well as organic/inorganic composites and hybrids. Aerogels are highly porous nanostructured materials with a large number of meso- and small macropores; the mechanisms of sound absorption partly differ from those of traditional porous absorbers possessing large macropores. The understanding of the acoustic properties of aerogels is far from being complete, and experimental results remain scattered. It is demonstrated that the structure of the aerogel provides a complex three-dimensional architecture ideally suited for promising high-performance materials for acoustic mitigation systems. This is in addition to the numerous other desirable properties that include low density, low thermal conductivity, and low refractive index.
  • All-cellulose composite aerogels and cryogels
    (2020-10) Korhonen, Oona; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Porous all-cellulose composites were prepared from pulps dissolved in 8 wt-% NaOH-water and dispersed softwood kraft fibers. Freeze-drying and drying with supercritical CO2 were used to vary the morphology of the composites. As cellulose dissolution in NaOH-water is known to be limited by pulp degree of polymerization, the latter was varied to obtain different amounts of non-dissolved fractions in solution. The goal of the work was to understand the influence of fibers originating from the incomplete dissolution and/or from added kraft fibers on the morphology and properties of porous all-cellulose composites. Density, porosity, pore volume, specific surface area and mechanical properties under compression were determined and correlated with the composite formulations and morphology.
  • All-cellulose composites from alfa and wood fibers
    (2019-01-01) Labidi, Khaled; Korhonen, Oona; Zrida, Montassar; Hamzaoui, Ahmed Hichem; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    All-cellulose composites (ACCs) in which both matrices and reinforcing fibers are made from lignocellulose were successfully obtained from alfa (Stipa tenacissima L) and wood (Genus Betula) fibers. Matrices were prepared either from alfa or wood pulps that were dissolved in 8 wt% NaOH-water, while reinforcing fibers were alfa in both matrices. Prior to the dissolution, alfa and wood pulps were acid hydrolyzed in order to decrease cellulose degree of polymerization to 149 and 145, respectively. The degree of cellulose dissolution was 95–96% for both alfa and wood dissolving pulps. X-ray diffraction (XRD) analysis confirmed the coexistence of cellulose I and II. The adhesion between the reinforcing fibers and both matrices was investigated using Scanning Electron Microscopy (SEM) and was found to be excellent. The density of ACCs decreased with the increase of the reinforcing fiber content for both types of matrices and ranged from 0.6 to 1.0 g.cm−3 leading to remarkably low-density ACCs. Young's modulus reached 3.8 and 4.2 GPa for the composites based on alfa and wood dissolving pulps, respectively, while yield stress reached 16 and 13.9 MPa, respectively.
  • All-cellulose composites via short-fiber dispersion approach using NaOH–water solvent
    (2019-05-30) Korhonen, Oona; Sawada, Daisuke; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Abstract: All-cellulose composites were prepared by dispersing short softwood kraft fibers in dissolving pulp-8 wt% NaOH–water. The degree of polymerization of the dissolving pulp used for the matrix and the concentration of reinforcing fibers were varied. Morphology, density, crystallinity, cellulose I content and mechanical properties of the composites were investigated. A special attention was paid on the presence of non-dissolved fibers originating from incomplete dissolution of pulp in 8 wt% NaOH–water thus decreasing the actual concentration of dissolved cellulose in matrix solution. This “lack of matter” induced the formation of pores, which strongly influenced the morphology of composites. Density was shown to be the main parameter contributing to the mechanical properties of the prepared all-cellulose composites. The results demonstrate the complexity of the system and the need in taking into account the dissolution power of the solvent. Graphical abstract: Morphology of all-cellulose composites: matrix is from low-DP dissolving pulp (a) and from high-DP pulp (b).[Figure not available: see fulltext.].
  • The European Polysaccharide Network of Excellence (EPNOE) research roadmap 2040 : Advanced strategies for exploiting the vast potential of polysaccharides as renewable bioresources
    (2024-02-15) Gericke, Martin; Amaral, Adérito J.R.; Budtova, Tatiana; De Wever, Pieter; Groth, Thomas; Heinze, Thomas; Höfte, Herman; Huber, Anton; Ikkala, Olli; Kapuśniak, Janusz; Kargl, Rupert; Mano, João F.; Másson, Már; Matricardi, Pietro; Medronho, Bruno; Norgren, Magnus; Nypelö, Tiina; Nyström, Laura; Roig, Anna; Sauer, Michael; Schols, Henk A.; van der Linden, John; Wrodnigg, Tanja M.; Xu, Chunlin; Yakubov, Gleb E.; Stana Kleinschek, Karin; Fardim, Pedro
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Polysaccharides are among the most abundant bioresources on earth and consequently need to play a pivotal role when addressing existential scientific challenges like climate change and the shift from fossil-based to sustainable biobased materials. The Research Roadmap 2040 of the European Polysaccharide Network of Excellence (EPNOE) provides an expert's view on how future research and development strategies need to evolve to fully exploit the vast potential of polysaccharides as renewable bioresources. It is addressed to academic researchers, companies, as well as policymakers and covers five strategic areas that are of great importance in the context of polysaccharide related research: (I) Materials & Engineering, (II) Food & Nutrition, (III) Biomedical Applications, (IV) Chemistry, Biology & Physics, and (V) Skills & Education. Each section summarizes the state of research, identifies challenges that are currently faced, project achievements and developments that are expected in the upcoming 20 years, and finally provides outlines on how future research activities need to evolve.
  • Exploring digital image correlation technique for the analysis of the tensile properties of all-cellulose composites
    (2021-05) Chen, Feng; Sawada, Daisuke; Pradille, Christophe; Hummel, Michael; Sixta, Herbert; Budtova, Tatiana; Bouvard, Jean-Luc
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Abstract: All-cellulose composites (ACCs) were prepared from filter paper via partial dissolution in the ionic liquid 1-ethyl-3-methylimidazolium acetate, and material tensile properties were investigated using various approaches. One is based on data directly taken from a tensile testing machine, and the other uses two-cameras stereovision with digital image correlation (DIC) technique. In the latter case, virtual extensometer with different locations on the sample and averaging over sample surface were tested. Nominal and true stress–strain dependences were built and Young's modulus, tensile strength, elongation at maximal stress and toughness were evaluated as a function of ACC density. A minor difference was observed for the stress–strain dependences derived from different approaches which use the DIC technique, most probably because of low ACC deformation. However, the results reveal that the nominal stress–strain curve from DIC is significantly different from that which is directly derived from the data provided by machine sensors thus strongly impacting Young’s modulus and elongation at break values. This study provides an insight into the evaluation of the mechanical properties of ACCs. Graphic abstract: [Figure not available: see fulltext.]
  • Exploring Large Ductility in Cellulose Nanopaper Combining High Toughness and Strength
    (2020-09-22) Chen, Feng; Xiang, Wenchao; Sawada, Daisuke; Bai, Long; Hummel, Michael; Sixta, Herbert; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Cellulose nanopaper is a strong lightweight material made from renewable resources with a wide range of potential applications, from membranes to electronic displays. Most studies on nanopaper target high mechanical strength, which compromises ductility and toughness. Herein, we demonstrate the fabrication of highly ductile and tough cellulose nanopaper via mechanical fibrillation of hemicellulose-rich wood fibers and dispersion of the obtained cellulose nanofibrils (CNFs) in an ionic liquid (IL)–water mixture. This treatment allows hemicellulose swelling, which leads to dissociation of CNF bundles into highly disordered long flexible fibrils and the formation of a nanonetwork as supported by cryogenic transmission electron microscopy (cryo-TEM) imaging. Rheology of the suspensions shows a 300-fold increase in storage and loss moduli of CNF–IL–water suspensions, compared to their CNF–water counterparts. The nanopaper prepared by removing the IL–water shows a combination of large elongation (up to 35%), high strength (260 MPa), and toughness as high as 51 MJ/m3, because of efficient interfibrillar slippage and energy dissipation in the highly disordered isotropic structure. This work provides a nanostructure-engineered strategy of making ductile and tough cellulose nanopaper.
  • Gelation of cellulose-NaOH solutions in the presence of cellulose fibers
    (2019-08-01) Korhonen, Oona; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    It is well known that when cellulose is dissolved in aqueous NaOH-based solvent, solutions are gelling with increasing time and temperature. The goal of this work was to understand if the presence of non-dissolved cellulose fibers influences gelation behavior of the whole system. One of the motivations is to control gelation when making all-cellulose composites with short fibers dispersed in cellulose-NaOH-water solutions. Gelation kinetics of cellulose(dissolving pulp)-NaOH-water solutions with added softwood kraft fibers were investigated using dynamic rheology. Fiber concentration, dissolving pulp degree of polymerization and solution temperature were varied. In all cases the addition of kraft fibers accelerates gelation and increases modulus at gel point while the presence of “inert” carbon fibers does not influence solution gelation kinetics. It was suggested that acceleration of gelation and reinforcement of cellulose gels is due to the interactions between dissolved and non-dissolved cellulose.
  • Swelling and dissolution kinetics of natural and man-made cellulose fibers in solvent power tuned ionic liquid
    (2020-09-01) Chen, Feng; Sawada, Daisuke; Hummel, Michael; Sixta, Herbert; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    The kinetics of the dissolution and swelling of different cellulose fibers in the ionic liquid 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]) was studied by varying solvent power and temperature. Natural fiber, flax, and man-made fibers, Cordenka and Lyocell-type (Ioncell) were used with one Ioncell fiber containing lignin and hemicelluloses. Through the addition of water, the solvent power was modified from very good (neat ionic liquid), to moderate (with 5 wt% water) and weak (15 wt% water). The temperature was varied to correlate the fiber dissolution rate with the solvent viscosity. All fibers were characterized by chemical composition, crystallinity, molecular weight distribution and dynamic vapor sorption. It was demonstrated that while the rate of fiber dissolution in neat ionic liquid depends on fiber accessibility and solvent viscosity, the water-induced decreased solvent power dominates the general fiber behavior. Flax appeared to be the most “sensitive” to the solvent power due to its hierarchical structure. The fastest dissolution or swelling was recorded for Ioncell and the slowest for Cordenka.
  • Unidirectional All-Cellulose Composites from Flax via Controlled Impregnation with Ionic Liquid
    (2020-05-01) Chen, Feng; Sawada, Daisuke; Hummel, Michael; Sixta, Herbert; Budtova, Tatiana
     A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä
    Mechanically strong all-cellulose composites are very attractive in the terms of fully bio-based and bio-degradable materials. Unidirectional flax-based all-cellulose composites are prepared via facile room-temperature impregnation with an ionic liquid, 1-ethyl-3-methyl imidazolium acetate. To determine the optimal processing conditions, the kinetics of flax dissolution in this solvent is first studied using optical microscopy. Composite morphology, crystallinity, density, the volume fraction of cellulose II and tensile properties are investigated, indicating that flax dissolution should be within certain limits. On the one hand, the amount of cellulose II formed through dissolution and coagulation should be high enough to “fuse” flax fibers, resulting in a density increase. On the other hand, only the surface layer of the fibers should be dissolved to maintain the strength provided by the inner secondary layer and avoid a detrimental decrease in crystallinity. The highest Young’s modulus and strength, 10.1 GPa and 151.3 MPa, respectively, are obtained with a crystallinity of 43% and 20 vol% of cellulose II.