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Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation

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A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Processing and Engineering".

Deadline for manuscript submissions: 15 September 2024 | Viewed by 6156

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Special Issue Editors

Dr. Beatriz Merillas

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Guest Editor

1. Cellular Materials Laboratory (CellMat), Department of Condensed Material Physics, Facultad de Ciencias, University of Valladolid, 47011 Valladolid, Spain
2. Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, University of Coimbra, 3000-370 Coimbra, Portugal
Interests: polyurethane; nanoporous materials; aerogels; thermal insulation; bio-aerogels

Dr. Luísa Durães

E-Mail Website
Guest Editor

Chemical Process Engineering and Forest Products Research Centre, Department of Chemical Engineering, University of Coimbra, 3000-370 Coimbra, Portugal
Interests: aerogels; nanoparticles; sol-gel; soft-solution synthesis; functional nanomaterials; environmental remediation; thermal insulation
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Special Issue Information

Dear Colleagues,

This Special Issue on “Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation” is dedicated to recent innovative studies on the synthesis procedures and distinctive characteristics of aerogels for the referred applications.

The huge relevance of this topic in the development of advanced materials for our increasingly technological society promotes the high number of papers that are currently being published in scientific journals. Therefore, this Special Issue is gathering research describing the production of aerogels through different methods and an exhaustive characterization in terms of textural properties, chemical composition, thermal insulation, mechanical properties, and uncommon adsorptive/catalytic performance, among others.

Aerogels usually present a unique combination of properties that can be tuned through changes in the production process that significantly alter their nanostructures. There are several procedures for tailoring the final properties of these materials by modifying the formulations, inducing changes in the structure through different processing steps, adding different fillers, etc.

Thus, papers describing structure–property relationships, heat transfer modelling, mechanical reinforcing techniques, and adsorptive- or catalytic-enhancing modifications of aerogels are widely welcomed. Moreover, the presented works may provide an approach to different applications in the fields of building, aerospace, energy management, medicine, and environmental remediation.

We encourage authors to contribute to this Special Issue, which hopefully will provide valuable knowledge for the aerogel community.

Dr. Beatriz Merillas
Dr. Luísa Durães
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Gels is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

aerogels
thermal insulation
mechanical properties
porous structure
environmental remediation

Published Papers (5 papers)

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Research

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15 pages, 12099 KiB

Open AccessArticle

Silica-Poly(Vinyl Alcohol) Composite Aerogel: A Promising Electrolyte for Solid-State Sodium Batteries

by João Pedro Vareda, Ana Clotilde Fonseca, Ana Cristina Faria Ribeiro and Ana Dora Rodrigues Pontinha

Gels 2024, 10(5), 293; https://doi.org/10.3390/gels10050293 - 25 Apr 2024

Viewed by 362

Abstract

The transition from fossil fuels is in part limited by our inability to store energy at different scales. Batteries are therefore in high demand, and we need them to store more energy, be more reliable, durable and have less social and environmental impact. Silica-poly(vinyl alcohol) (PVA) composite aerogels doped with sodium perchlorate were synthesized as novel electrolytes for potential application in solid-state sodium batteries. The aerogels, synthesized by one-pot synthesis, are light (up to 214 kg m⁻³), porous (~85%), exhibit reduced shrinkage on drying (up to 12%) and a typical silica aerogel microstructure. The formation of a silica network and the presence of PVA and sodium perchlorate in the composite were confirmed by FTIR and TGA. The XRD analysis also shows that a predominantly amorphous structure is obtained, as crystalline phases of polymer and salt are present in a very reduced amount. The effects of increasing polymer and sodium salt concentrations on the ionic conductivity, assessed via electrochemical impedance spectroscopy, were studied. At a PVA concentration of 15% (w/w silica precursors), the sodium conduction improved significantly up to (1.1 ± 0.3) × 10⁻⁵ S cm⁻¹. Thus, this novel material has promising properties for the envisaged application. Full article

(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation)

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22 pages, 6890 KiB

Open AccessArticle

High Modulus, Strut-like poly(ether ether ketone) Aerogels Produced from a Benign Solvent

by Glenn A. Spiering, Garrett F. Godshall and Robert B. Moore

Gels 2024, 10(4), 283; https://doi.org/10.3390/gels10040283 - 22 Apr 2024

Viewed by 555

Abstract

Poly(ether ether ketone) (PEEK) was found to form gels in the benign solvent 1,3-diphenylacetone (DPA). Gelation of PEEK in DPA was found to form an interconnected, strut-like morphology composed of polymer axialites. To our knowledge, this is the first report of a strut-like morphology for PEEK aerogels. PEEK/DPA gels were prepared by first dissolving PEEK in DPA at 320 °C. Upon cooling to 50 °C, PEEK crystallizes and forms a gel in DPA. The PEEK/DPA phase diagram indicated that phase separation occurs by solid–liquid phase separation, implying that DPA is a good solvent for PEEK. The Flory–Huggins interaction parameter, calculated as χ₁₂ = 0.093 for the PEEK/DPA system, confirmed that DPA is a good solvent for PEEK. PEEK aerogels were prepared by solvent exchanging DPA to water then freeze-drying. PEEK aerogels were found to have densities between 0.09 and 0.25 g/cm³, porosities between 80 and 93%, and surface areas between 200 and 225 m²/g, depending on the initial gel concentration. Using nitrogen adsorption analyses, PEEK aerogels were found to be mesoporous adsorbents, with mesopore sizes of about 8 nm, which formed between stacks of platelike crystalline lamellae. Scanning electron microscopy and X-ray scattering were utilized to elucidate the hierarchical structure of the PEEK aerogels. Morphological analysis found that the PEEK/DPA gels were composed of a highly nucleated network of PEEK axialites (i.e., aggregates of stacked crystalline lamellae). The highly connected axialite network imparted robust mechanical properties on PEEK aerogels, which were found to densify less upon freeze-drying than globular PEEK aerogel counterparts gelled from dichloroacetic acid (DCA) or 4-chlorphenol (4CP). PEEK aerogels formed from DPA were also found to have a modulus–density scaling that was far more efficient in supporting loads than the poorly connected aerogels formed from PEEK/DCA or PEEK/4CP solutions. The strut-like morphology in these new PEEK aerogels also significantly improved the modulus to a degree that is comparable to high-performance crosslinked aerogels based on polyimide and polyurea of comparable densities. Full article

(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation)

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Review

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21 pages, 1081 KiB

Open AccessReview

Bio-Based Aerogels for the Removal of Heavy Metal Ions and Oils from Water: Novel Solutions for Environmental Remediation

by Antonella Caterina Boccia, Monica Neagu and Alfio Pulvirenti

Gels 2024, 10(1), 32; https://doi.org/10.3390/gels10010032 - 30 Dec 2023

Cited by 1 | Viewed by 1549

Abstract

Contamination of the aqueous environment caused by the presence of heavy metal ions and oils is a growing concern that must be addressed to reduce their detrimental impact on living organisms and safeguard the environment. Recent efficient and environmentally friendly remediation methods for the treatment of water are based on third-generation bioaerogels as emerging applications for the removal of heavy metal ions and oils from aqueous systems. The peculiarities of these materials are various, considering their high specific surface area and low density, together with a highly porous three-dimensional structure and tunable surface chemistry. This review illustrates the recent progress in aerogels developed from cellulose and chitosan as emerging materials in water treatment. The potential of aerogel-based adsorbents for wastewater treatment is reported in terms of adsorption efficacy and reusability. Despite various gaps affecting the manufacturing and production costs of aerogels that actually limit their successful implementation in the market, the research progress suggests that bio-based aerogels are ready to be used in water-treatment applications in the near future. Full article

(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation)

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27 pages, 949 KiB

Open AccessReview

Hybrid Materials of Bio-Based Aerogels for Sustainable Packaging Solutions

by Urška Vrabič-Brodnjak

Gels 2024, 10(1), 27; https://doi.org/10.3390/gels10010027 - 28 Dec 2023

Viewed by 1497

Abstract

This review explores the field of hybrid materials in the context of bio-based aerogels for the development of sustainable packaging solutions. Increasing global concern over environmental degradation and the growing demand for environmentally friendly alternatives to conventional packaging materials have led to a growing interest in the synthesis and application of bio-based aerogels. These aerogels, which are derived from renewable resources such as biopolymers and biomass, have unique properties such as a lightweight structure, excellent thermal insulation, and biodegradability. The manuscript addresses the innovative integration of bio-based aerogels with various other materials such as nanoparticles, polymers, and additives to improve their mechanical, barrier, and functional properties for packaging applications. It critically analyzes recent advances in hybridization strategies and highlights their impact on the overall performance and sustainability of packaging materials. In addition, the article identifies the key challenges and future prospects associated with the development and commercialization of hybrid bio-based aerogel packaging materials. The synthesis of this knowledge is intended to contribute to ongoing efforts to create environmentally friendly alternatives that address the current problems associated with conventional packaging while promoting a deeper understanding of the potential of hybrid materials for sustainable packaging solutions. Full article

(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation)

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32 pages, 3750 KiB

Open AccessReview

Rheology in Product Development: An Insight into 3D Printing of Hydrogels and Aerogels

by Raquel V. Barrulas and Marta C. Corvo

Gels 2023, 9(12), 986; https://doi.org/10.3390/gels9120986 - 17 Dec 2023

Cited by 1 | Viewed by 1794

Abstract

Rheological characterisation plays a crucial role in developing and optimising advanced materials in the form of hydrogels and aerogels, especially if 3D printing technologies are involved. Applications ranging from tissue engineering to environmental remediation require the fine-tuning of such properties. Nonetheless, their complex rheological behaviour presents unique challenges in additive manufacturing. This review outlines the vital rheological parameters that influence the printability of hydrogel and aerogel inks, emphasising the importance of viscosity, yield stress, and viscoelasticity. Furthermore, the article discusses the latest developments in rheological modifiers and printing techniques that enable precise control over material deposition and resolution in 3D printing. By understanding and manipulating the rheological properties of these materials, researchers can explore new possibilities for applications such as biomedicine or nanotechnology. An optimal 3D printing ink requires strong shear-thinning behaviour for smooth extrusion, forming continuous filaments. Favourable thixotropic properties aid viscosity recovery post-printing, and adequate yield stress and G′ are crucial for structural integrity, preventing deformation or collapse in printed objects, and ensuring high-fidelity preservation of shapes. This insight into rheology provides tools for the future of material design and manufacturing in the rapidly evolving field of 3D printing of hydrogels and aerogels. Full article

(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation)

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