Browsing by Author "Yazdani, Maryam R."
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Item Cellulose Nanofibrils Endow Phase-Change Polyethylene Glycol with Form Control and Solid-to-gel Transition for Thermal Energy Storage(AMERICAN CHEMICAL SOCIETY, 2021-02-10) Yazdani, Maryam R.; Ajdary, Rubina; Kankkunen, Ari; Rojas, Orlando J.; Seppälä, Ari; Department of Mechanical Engineering; Department of Bioproducts and Biosystems; Energy Conversion; Bio-based Colloids and MaterialsGreen energy-storage materials enable the sustainable use of renewable energy and waste heat. As such, a form-stable phase-change nanohybrid (PCN) is demonstrated to solve the fluidity and leakage issues typical of phase-change materials (PCMs). Here, we introduce the advantage of solid-to-gel transition to overcome the drawbacks of typical solid-to-liquid counterparts in applications related to thermal energy storage and regulation. Polyethylene glycol (PEG) is form-stabilized with cellulose nanofibrils (CNFs) through surface interactions. The cellulosic nanofibrillar matrix is shown to act as an organogelator of highly loaded PEG melt (85 wt %) while ensuring the absence of leakage. CNFs also preserve the physical structure of the PCM and facilitate handling above its fusion temperature. The porous CNF scaffold, its crystalline structure, and the ability to hold PEG in the PCN are characterized by optical and scanning electron imaging, infrared spectroscopy, and X-ray diffraction. By the selection of the PEG molecular mass, the lightweight PCN provides a tailorable fusion temperature in the range between 18 and 65 °C for a latent heat storage of up to 146 J/g. The proposed PCN shows remarkable repeatability in latent heat storage after 100 heating/cooling cycles as assessed by differential scanning calorimetry. The thermal regulation and light-to-heat conversion of the PCN are confirmed via infrared thermal imaging under simulated sunlight and in a thermal chamber, outperforming those of a reference, commercial insulation material. Our PCN is easily processed as a structurally stable design, including three-dimensional, two-dimensional (films), and one-dimensional (filaments) materials; they are, respectively, synthesized by direct ink writing, casting/molding, and wet spinning. We demonstrate the prospects of the lightweight, green nanohybrid for smart-energy buildings and waste heat-generating electronics for thermal energy storage and management.Item Hollow Filaments Synthesized by Dry-Jet Wet Spinning of Cellulose Nanofibrils: Structural Properties and Thermoregulation with Phase-Change Infills(AMERICAN CHEMICAL SOCIETY, 2022-04-08) Reyes, Guillermo; Ajdary, Rubina; Yazdani, Maryam R.; Rojas, Orlando J.; Department of Bioproducts and Biosystems; Department of Mechanical Engineering; Bio-based Colloids and Materials; Energy ConversionWe use dry-jet wet spinning in a coaxial configuration by extruding an aqueous colloidal suspension of oxidized nanocellulose (hydrogel shell) combined with airflow in the core. The coagulation of the hydrogel in a water bath results in hollow filaments (HF) that are drawn continuously at relatively high rates. Small-angle and wide-angle X-ray scattering (SAXS/WAXS) reveals the orientation and order of the cellulose sheath, depending on the applied shear flow and drying method (free-drying and drying under tension). The obtained dry HF show Young's modulus and tensile strength of up to 9 GPa and 66 MPa, respectively. Two types of phase-change materials (PCM), polyethylene glycol (PEG) and paraffin (PA), are used as infills to enable filaments for energy regulation. An increased strain (9%) is observed in the PCM-filled filaments (HF-PEG and HF-PA). The filaments display similar thermal behavior (dynamic scanning calorimetry) compared to the neat infill, PEG, or paraffin, reaching a maximum latent heat capacity of 170 J·g-1 (48-55 °C) and 169 J·g-1 (52-54 °C), respectively. Overall, this study demonstrates the facile and scalable production of two-component core-shell filaments that combine structural integrity, heat storage, and thermoregulation properties.Item Leakage-free porous cellulose-based phase change cryogels for sound and thermal insulation(ELSEVIER SCIENCE B.V., 2023-07-01) Le, Wendy T.; Kankkunen, Ari; Rojas, Orlando J.; Yazdani, Maryam R.; Department of Bioproducts and Biosystems; Department of Mechanical Engineering; Bio-based Colloids and Materials; Energy Conversion and Systems; Department of Bioproducts and BiosystemsLeakage-free phase change materials (PCM) are used as passive energy storage systems that thermoregulate indoor environments. In this research, we synthesized highly porous hybrid materials based on non-covalent physical interactions between (poly)ethylene glycol (PEG) and modified cellulose nanofibrils (CNF), namely lignin-containing CNF (LCNF) or acetylated CNF (ACNF). The PEG/CNF hybrid, termed phase change nanohybrids (PCN), were ultra-lightweight (0.022–0.043 g/cm3), mechanically resilient, and displayed a high latent energy storage, up to 204 J/g. The PCN systems (specific heat capacity as high as 2.24 J/g K) were effective in thermal regulating 2.23 °C with a 1 mm thickness coverage while maintaining thermal stability. The PCN also demonstrated favorable thermal management under excess solar heating, providing 33.5 °C of insulative protection with a 1.5 cm thick system. The PCNs have exceptional acoustic absorbance (100% absorbance for 1600 Hz and 50% at lower frequencies, 500 Hz). Trace metal oxide (TiO2) nanoparticles improved the PCN thermoregulating abilities, revealing desirable opportunities in multi-functional applications. Our biobased PCN is a promising insulation and passive energy storage alternative for thermal protection in smart building, electronic, packaging, energy storage system and aerospace sectors.Item Leakage-proof microencapsulation of phase change materials by emulsification with acetylated cellulose nanofibrils(ELSEVIER SCI LTD, 2021-02-15) Shi, Xuetong; Yazdani, Maryam R.; Ajdary, Rubina; Rojas, Orlando J.; Department of Bioproducts and Biosystems; Department of Mechanical Engineering; Bio-based Colloids and Materials; Energy Conversion; Department of Bioproducts and BiosystemsWe use acetylated cellulose nanofibrils (AcCNF) to stabilize transient emulsions with paraffin that becomes shape-stable and encapsulated phase change material (PCM) upon cooling. Rheology measurements confirm the gel behavior and colloidal stability of the solid suspensions. We study the effect of nanofiber content on PCM leakage upon melting and compare the results to those from unmodified CNF. The nanostructured cellulose promotes paraffin phase transition, which improves the efficiency of thermal energy exchange. The leakage-proof microcapsules display high energy absorption capacity (ΔHm = 173 J/g) at high PCM loading (up to 80 wt%), while effectively controlling the extent of supercooling. An excellent thermal stability is observed during at least 100 heating/cooling cycles. Degradation takes place at 291 °C, indicating good thermal stability. The high energy density and the effective shape and thermal stabilization of the AcCNF-encapsulated paraffin points to a sustainable solution for thermal energy storage and conversion.Item Nano-cellulose based insulation biomaterials for thermal regulation purposes(2021-10-19) Le, Wendy; Yazdani, Maryam R.; Perustieteiden korkeakoulu; Rojas, OrlandoThere is a growing urgency to develop more sustainable solutions to address climate change impacts. Energy consumption from building thermal regulation is a large contributor to CO2 emissions from heating and cooling units. Phase change materials (PCM), such as polyethylene glycol (PEG), can thermoregulate and alleviate the intensive use of heating and cooling of buildings. Commercial PCMs used for thermo-regulation in buildings still have the problem of leakage from the transformation of solid-liquid phase. Nanocellulose (CNF) is successful in providing physical encapsulation with PEG, referred to as a phase change nanohybrid. In this study, a novel phase change nanocellulose hybrid (PCN) is introduced and characterized. Modified CNF (TEMPO-oxidized, acetylated and lignin, and TiO2 additive containing CNFs) and different processing techniques (3D printing, freeze templating and casting) are explored to observe their effects on the insulating qualities of the PCN. The PCNs exhibited very low bulk densities (0.022-0.043〖g /cm〗^3) and high porosity (95.8-98.1%). Scanning electron microscope (SEM) and porosity analysis measured with BJH methods revealed structural properties. Differential scanning calorimetry (DSC) measured latent energy storage (100-160 J/g) and specific heat capacity (up to 2.10 J/gK). The PCN demonstrated stable PEG encapsulation of up to 80 ℃ and 200 ℃ surface temperatures without leakage; imaged with a thermal IR camera. Thermocouple sensors revealed heat transfer behavior and low thermal conductivity (0.035-0.039 W/mK) was determined. Surprisingly, impedance testing revealed sound absorption capability, and compressive dynamic mechanical analysis (DMA) indicated the PCN’s structural reformation ability.Item Synthesis and efficiency comparison of reed straw-based biochar as a mesoporous adsorbent for ionic dyes removal(Elsevier, 2024-01-30) Tomin, Oleksii; Vahala, Riku; Yazdani, Maryam R.; Department of Built Environment; Department of Mechanical Engineering; Water and Environmental Eng.; Energy Conversion and SystemsThe reed straw is assessed as a potential source of widely available renewable biomass for biochar production and compared with two other waste-based biomasses, namely fruit stones blend, and brewery spent grains. The biochars were activated via steam and CO2. While steam activation yielded 12 % carbon from reed biomass, CO2 activation resulted in biomass degradation. The characterization of reed biochar showed a mesoporous structure and a high surface area of 514 m2/g. The adsorption tests displayed a decent adsorption capacity of biochar, with values of 92.6 mg/g for methylene violet dye and 35.7 mg/g for acid green dye. Only 1 g/L dosage of reed biochar was able to remove 99 % of the 50 mg/L methylene violet solution in 15 min and 60 % of the 50 mg/L acid green solution in 10 min. The obtained results demonstrate reed biomass as a suitable source for biochar production as well as reed-based biochar as a promising dye adsorbent.
