Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Sivaraman, Deeptanshu; Siqueira, Gilberto; Maurya, Anjani K.; Zhao, Shanyu; Koebel, Matthias M.; Nyström, Gustav; Lattuada, Marco; Malfait, Wim J.

doi:10.1016/j.carbpol.2022.119675

Cited by 20 publications

(7 citation statements)

References 95 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A minimum of the total effective thermal conductivity as a function of density is observed, which results from opposing density dependent trends of the solid and radiative/gas phase contributions. This general picture has been proposed and was confirmed already decades ago for organic aerogels [29], and has subsequently been confirmed for many aerogel compositions [29][30][31][32][33].…”

Section: Heat Transfer Mechanisms In Porous Materialssupporting

confidence: 58%

The poor reliability of thermal conductivity data in the aerogel literature: a call to action!

Malfait,

Ebert,

Brunner

et al. 2024

J Sol-Gel Sci Technol

Self Cite

View full text Add to dashboard Cite

Aerogels are an exciting class of materials with record-breaking properties including, in some cases, ultra-low thermal conductivities. The last decade has seen a veritable explosion in aerogel research and industry R&D, leading to the synthesis of aerogels from a variety of materials for a rapidly expanding range of applications. However, both from the research side, and certainly from a market perspective, thermal insulation remains the dominant application. Unfortunately, continued progress in this area suffers from the proliferation of incorrect thermal conductivity data, with values that often are far outside of what is possible within the physical limitations. This loss of credibility in reported thermal conductivity data poses difficulties in comparing the thermal performance of different types of aerogels and other thermal superinsulators, may set back further scientific progress, and hinder technology transfer to industry and society. Here, we have compiled 519 thermal conductivity results from 87 research papers, encompassing silica, other inorganic, biopolymer and synthetic polymer aerogels, to highlight the extent of the problem. Thermal conductivity data outside of what is physically possible are common, even in high profile journals and from the world’s best universities and institutes. Both steady-state and transient methods can provide accurate thermal conductivity data with proper instrumentation, suitable sample materials and experienced users, but nearly all implausible data derive from transient methods, and hot disk measurements in particular, indicating that under unfavorable circumstances, and in the context of aerogel research, transient methods are more prone to return unreliable data. Guidelines on how to acquire reliable thermal conductivity data are provided. This paper is a call to authors, reviewers, editors and readers to exercise caution and skepticism when they report, publish or interpret thermal conductivity data. Graphical Abstract

show abstract

Section: Heat Transfer Mechanisms In Porous Materialssupporting

confidence: 58%

The poor reliability of thermal conductivity data in the aerogel literature: a call to action!

Malfait,

Ebert,

Brunner

et al. 2024

J Sol-Gel Sci Technol

Self Cite

View full text Add to dashboard Cite

show abstract

“…This is mainly due to the improved nanoporosity of the cell walls and the fibrillated networks in the lumen. Figure e compares the λ radial of NW-Aerogel to those of commercial insulation materials (polystyrene (PS), extruded polystyrene (XPS), polyurethane (PU) foam, and Rockwool), − cellulosic aerogels, , and regenerated cellulose/lignin aerogel . The all-wood NW-Aerogel shows great strength at the given λ value.…”

Section: Resultsmentioning

confidence: 99%

“…Third row: digital photographs of each respective sample used for SEM analysis. (d) Thermal conductivity in radial and axial directions of NW and NW-Aerogel based on balsa and (e) comparison of yield strength and thermal conductivity to cellulosic aerogels, , regenerated lignin/cellulose aerogel, and some commercially used thermal insulators. − The NW-Aerogel was prepared via freeze-drying for thermal property measurements.…”

Section: Resultsmentioning

confidence: 99%

Strong, Shape-Memory Lignocellulosic Aerogel via Wood Cell Wall Nanoscale Reassembly

et al. 2023

View full text Add to dashboard Cite

Polymer shape-memory aerogels (PSMAs) are prospects in various fields of application ranging from aerospace to biomedicine, as advanced thermal insulators, actuators, or sensors. However, the fabrication of PSMAs with good mechanical performance is challenging and is currently dominated by fossil-based polymers. In this work, strong, shape-memory bio-aerogels with high specific surface areas (up to 220 m2/g) and low radial thermal conductivity (0.042 W/mK) were prepared through a one-step treatment of native wood using an ionic liquid mixture of [MTBD]+[MMP]−/DMSO. The aerogel showed similar chemical composition similar to native wood. Nanoscale spatial rearrangement of wood biopolymers in the cell wall and lumen was achieved, resulting in flexible hydrogels, offering design freedom for subsequent aerogels with intricate geometries. Shape-memory function under stimuli of water was reported. The chemical composition and distribution, morphology, and mechanical performance of the aerogel were carefully studied using confocal Raman spectroscopy, AFM, SAXS/WAXS, NMR, digital image correlation, etc. With its simplicity, sustainability, and the broad range of applicability, the methodology developed for nanoscale reassembly of wood is an advancement for the design of biobased shape-memory aerogels.

show abstract

“…These include thermal insulators [ 25 ], acoustic insulators [ 26 ], batteries’ electrodes [ 27 ], supercapacitors [ 28 ], piezoelectric transducers [ 29 ], CO 2 captures [ 30 ], absorbents [ 31 ], drug carriers [ 32 ], catalyst supports [ 33 ], and food packaging [ 22 ]. Several bio-aerogels were studied for their thermal insulation properties, and materials based on nanocellulose, starch, and pectin were shown to fall in the superinsulating area [ 16 , 21 , 34 , 35 ]. Among them, pectin aerogels possess density around 0.1 g cm −3 , specific surface area up to 600 m 2 g −1 and thermal conductivity in ambient conditions as low as 0.015 W m −1 K −1 , which is very close to the thermal conductivity of the best silica aerogels [ 21 ].…”

Section: Introductionmentioning

confidence: 99%

Hydrophobic Modification of Pectin Aerogels via Chemical Vapor Deposition

Effraimopoulou,

Jaxel,

Budtova

et al. 2024

Polymers

View full text Add to dashboard Cite

Pectin aerogels, with very low density (around 0.1 g cm−3) and high specific surface area (up to 600 m2 g−1), are excellent thermal insulation materials since their thermal conductivity is below that of air at ambient conditions (0.025 W m−1 K−1). However, due to their intrinsic hydrophilicity, pectin aerogels collapse when in contact with water vapor, losing superinsulating properties. In this work, first, pectin aerogels were made, and the influence of the different process parameters on the materials’ structure and properties were studied. All neat pectin aerogels had a low density (0.04–0.11 g cm−1), high specific surface area (308–567 m2 g−1), and very low thermal conductivity (0.015–0.023 W m−1 K−1). Then, pectin aerogels were hydrophobized via the chemical vapor deposition of methyltrimethoxysilane using different reaction durations (2 to 24 h). The influence of hydrophobization on material properties, especially on thermal conductivity, was recorded by conditioning in a climate chamber (25 °C, 80% relative humidity). Hydrophobization resulted in the increase in thermal conductivity compared to that of neat pectin aerogels. MTMS deposition for 16 h was efficient for hydrophobizing pectin aerogels in moist environment (contact angle 115°) and stabilizing material properties with no fluctuation in thermal conductivity (0.030 W m−1 K−1) and density for the testing period of 8 months.

show abstract

Superinsulating nanocellulose aerogels: Effect of density and nanofiber alignment

Cited by 20 publications

References 95 publications

The poor reliability of thermal conductivity data in the aerogel literature: a call to action!

The poor reliability of thermal conductivity data in the aerogel literature: a call to action!

Strong, Shape-Memory Lignocellulosic Aerogel via Wood Cell Wall Nanoscale Reassembly

Hydrophobic Modification of Pectin Aerogels via Chemical Vapor Deposition

Contact Info

Product

Resources

About