Browsing by Author "Ahadian, Hamidreza"
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- Cyclic Pressing as a Viable Approach for Dewatering and Controlling Shrinkage of Micro-Nanofabricated Cellulose Films
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2024-06-27) Zamani, Elaheh Sharifi; Ahadian, Hamidreza; Maloney, ThaddeusCellulose films, predominantly consisting of micro-nanocelluloses, are a new type of product with interesting properties for functional packaging applications. However, the potentially scalable production methodology has not yet been elucidated. Poor dewatering and high web shrinkage are issues that need solutions beyond what is available in conventional paper production. This research investigates a cyclic pressing method that shows potential in cellulose film consolidation. Cyclic pressing allows the MNFC films to be dewatered to about 90% solids while yielding a smooth, flat product. The results show no inherent physical limits for mechanical dewatering these high swelling webs, even at very high solids. Cyclic pressing allows controlled restraint during consolidation, which could be adjusted in an industrial setup to produce even films with desirable product characteristics. - Fast dewatering of high nanocellulose content papers with in-situ generated cationic micro-nano bubbles
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-08-01) Ahadian, Hamidreza; Sharifi Zamani, Elaheh; Phiri, Josphat; Maloney, ThaddeusHerein, an innovative method to improve the dewatering of micro- and nanofibrillated cellulose (MNFC) containing furnishes is proposed. This method is based on fiber flotation in which cationic bubbles are injected into the furnish to separate fibers from liquid medium and accumulate them on the surface of the furnish. These cationic bubbles are generated by pressurizing a solution of Hexadecyltrimethylammonium chloride in deionized water in a dissolved air flotation (DAF) tank. The drainage properties of the furnishes with MNFC content from 0% to 25% were studied. With the help of the cationic bubbles, drainage rate of 0% and 15% MNFC furnish increased from 183 ml/s to 210 ml/s and 38 ml/s to 113 ml/s, respectively. The final couch solids content of these furnishes also increased from 16 wt% to 23 wt% and from 21 wt% to 24 wt%, respectively. Cationic bubbles flocculate MNFC fibers and increase retention. Sheets characteristics including morphology, permeability, mass distribution and surface profilometry were investigated. Cationic bubbles help structure fiber elements and improve the sheet formation. - The Influence of Physical Mixing and Impregnation on the Physicochemical Properties of Pine Wood Activated Carbon Produced by One-Step ZnCl2 Activation
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-03) Phiri, Josphat; Ahadian, Hamidreza; Sandberg, Maria; Granström, Karin; Maloney, ThadIn this study, two different sample preparation methods to synthesize activated carbon from pine wood were compared. The pine wood activated carbon was prepared by mixing ZnCl2 by physical mixing, i.e., “dry mixing” and impregnation, i.e., “wet mixing” before high temperature carbonization. The influence of these methods on the physicochemical properties of activated carbons was examined. The activated carbon was analyzed using nitrogen sorption (surface area, pore volume and pore size distribution), XPS, density, Raman spectroscopy, and electrochemistry. Physical mixing led to a slightly higher density carbon (1.83 g/cm3) than wet impregnation (1.78 g/cm3). Raman spectroscopy analysis also showed that impregnation led to activated carbon with a much higher degree of defects than physical mixing, i.e., ID/IG = 0.86 and 0.89, respectively. The wet impregnated samples also had better overall textural properties. For example, for samples activated with 1:1 ratio, the total pore volume was 0.664 vs. 0.637 cm3/g and the surface area was 1191 vs. 1263 m2/g for dry and wet mixed samples, respectively. In the electrochemical application, specifically in supercapacitors, impregnated samples showed a much better capacitance at low current densities, i.e., 247 vs. 146 F/g at the current density of 0.1 A/g. However, the physically mixed samples were more stable after 5000 cycles: 97.8% versus 94.4% capacitance retention for the wet impregnated samples. - Production of low-density and high-strength paperboards by controlled micro-nano fibrillation of fibers
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2023-11) Ahadian, Hamidreza; Ceccherini, Sara; Sharifi Zamani, Elaheh; Phiri, Josphat; Maloney, ThaddeusOne of the critical challenges in the fiber-based packaging industry is to produce low-density paperboards with high functionality and attractive cost structure. In this study, we examine how control of the hierarchical fiber swelling can be used to enhance bonding and generate a low-density fiber network with excellent strength properties. Here, the osmotic pressure inside the cell wall is increased by adding phosphate groups with a deep eutectic solvent (DES) functional drying method. Together with mechanical refining, this process causes the fibril aggregates to split and swell up massively. This effect was measured by a novel thermoporosimetry analysis method. The treated fibers have enhanced external fibrillation, fibrillar fines and bonding potential. When mixed with relatively stiff, unrefined fibers, a well-bonded sheet with lower density than a conventionally refined reference sheet was achieved. The results suggest that pulp fibers can be “nanoengineered” to enhance performance without the complications of producing and adding nanocellulose. - Sheet sealing in single and multilayer nanopapers
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-09) Ahadian, Hamidreza; Sharifi Zamani, Elaheh; Phiri, Josphat; Coelho, Miguel Alexandre Salvador; Maloney, ThaddeusThis study addresses one of the limiting factors for producing micro and nanofibrillated cellulose (MNFC)-containing papers: poor water removal properties. We focus on the sheet sealing phenomenon during dewatering. A modified dynamic drainage analyzer (DDA) is used to examine both multilayer and single layer forming of MNFC and pulp mixtures. It was found that a thin layer of pulp fibers on the exit layer with the grammage as low as 5 gsm was enough to significantly improve the dewatering of MNFC. For example, the dewatering rate of a furnish with 50% MNFC increased from 0.6 mL/s for a mixed system to 2 mL/s for multilayer system. However, the sheet sealing behavior was completely different when a lower proportion of MNFC was used. For the furnishes with less than 20% MNFC content, the mixed furnishes dewatered faster because the high amount of pulp fibers were able to prevent MNFC from enriching on the exit layer. Surprisingly, we found that very high final solids content (couch solids) could sometimes be achieved when MNFC was used. The highest solids contents achieved were 34 and 29% for the mixed systems. This compares to the 15–20% range typical of standard papermaking furnishes without MNFC. Overall, the results show that contrary to current thinking MNFC containing papers may lead, under some circumstances, to enhanced wire section dewatering. - Twin-roll forming, a novel method for producing high-consistency microfibrillated cellulosic films
A1 Alkuperäisartikkeli tieteellisessä aikakauslehdessä(2022-12) Sharifi Zamani, Elaheh; Ahadian, Hamidreza; Maloney, ThaddeusMicro-nano fibrillated cellulose (MNFC) films have the potential for applications in, e.g., packaging and printed electronics. However, the production paradigm for these types of products has still not been established. This study uses twin-rollers to form films from high consistency (15% w/w) micro fibrillated cellulose furnishes. MFC furnishes were produced at 20% wt dry matter content with enzymatic hydrolysis and PFI refining. We used the twin-roller method to spread the material over a supporting substrate by repeatedly passing between two parallel rollers with decreasing nip. Rheological behavior and physical properties of furnishes were analyzed. We found that only some furnishes with relatively short fiber lengths were formable. Refining improved the formation of the sheets. Roll-formed sheets showed comparable strength and formation to conventional wet-laid hand sheets.