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Gels
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Preparation and Characteristics of Aerogel-Based Materials
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Preparation and Characteristics of Aerogel-Based Materials

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

Deadline for manuscript submissions: closed (31 August 2024) | Viewed by 9143

Special Issue Editor

Dr. Xiaodong Wu

E-Mail Website
Guest Editor
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Materials Science and Engineering, Nanjing Tech University, Nanjing 211816, China
Interests: thermal insulation; photocatalysis; electrocatalysis; aerogels; density functional theory
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Aerogels are porous materials consisting of nanoparticles or polymer chains with low density, high specific surface area, and high porosity, which are derived by replacing the pore liquids by air via the supercritical drying, the freezing drying, ambient pressure drying, as well as the 3D printing technique. Aerogel materials can be classified as single-component aerogels and composite aerogels, among which the single-component aerogels can be composed of oxide-based aerogels, carbide-based aerogels, nitride-based aerogels, graphene-based aerogels, quantum dots-based aerogels, polymer-based organic aerogels, biomass-based organic and carbon aerogels, etc. The composite aerogels are composed of several kinds of single-component aerogels, as well as the reinforcement by the fibers, whiskers, and nanotubes, etc. Benefitting from their inherent structural merits, aerogels have been widely used in the fields of aerospace, petrochemical engineering, environmental remediation, building energy saving, energy storage and conversion, etc. In addition, during the past few years, the carbon-based and metal-based aerogels have been considered as one of the most promising candidates in the fields of photocatalysts and electrocatalysts due to their excellent electric conductivity, high porosity, exposed reactive sites, and abundant reactants tunnels for the intermediates during catalysis process. 

This Special Issue will provide an international forum for researchers around the world to discuss the most recent studies regarding the preparation, characterization, and applications of different kinds of aerogels. Through this Special Issue, the present state and future will be discussed by a wide range of authors.

Dr. Xiaodong Wu
Guest Editor

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 2100 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
  • electrocatalysis
  • photocatalysis
  • thermal insulation
  • density functional theory

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Published Papers (6 papers)

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Research

12 pages, 9479 KiB  
Article
An Efficient and Economic Approach for Producing Nanocellulose-Based Aerogel from Kapok Fiber
by Minjie Hou, Qi Wang, Shunyu Wang, Zeze Yang, Xuefeng Deng and Hailong Zhao
Gels 2024, 10(8), 490; https://doi.org/10.3390/gels10080490 - 25 Jul 2024
Viewed by 930
Abstract
Cellulose nanofibers (NF) were extracted from kapok fibers using TEMPO oxidation, followed by a combination of mechanical grinding and ultrasonic processing. The TEMPO-mediated oxidation significantly impacted the mechanical disintegration behavior of the kapok fibers, resulting in a high NF yield of 98%. This [...] Read more.
Cellulose nanofibers (NF) were extracted from kapok fibers using TEMPO oxidation, followed by a combination of mechanical grinding and ultrasonic processing. The TEMPO-mediated oxidation significantly impacted the mechanical disintegration behavior of the kapok fibers, resulting in a high NF yield of 98%. This strategy not only improved the fibrillation efficiency but also reduced overall energy consumption during NF preparation. An ultralight and highly porous NF-based aerogel was successfully prepared using a simple ice-templating technique. It had a low density in the range of 3.5–11.2 mg cm−3, high compressional strength (160 kPa), and excellent thermal insulation performance (0.024 W m−1 K−1). After silane modification, the aerogel displayed an ultralow density of 7.9 mg cm−3, good hydrophobicity with a water contact angle of 128°, and excellent mechanical compressibility with a high recovery of 92% at 50% strain. Benefiting from the silene support structure, it showed a high oil absorptive capacity (up to 71.4 g/g for vacuum pump oil) and a remarkable oil recovery efficiency of 93% after being reused for 10 cycles. These results demonstrate that our strategy endows nanocellulose-based aerogels with rapid shape recovery and high liquid absorption capabilities. Full article
(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials)
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16 pages, 8278 KiB  
Article
Ag Nanoparticles Deposited onto BaTiO3 Aerogel for Highly Efficient Photodegradation
by Jun Wu, Wen Yan, Mengyuan Xie, Kai Zhong, Sheng Cui and Xiaodong Shen
Gels 2024, 10(6), 378; https://doi.org/10.3390/gels10060378 - 31 May 2024
Viewed by 728
Abstract
Given the increasingly severe environmental problems caused by water pollution, the degradation of organic dyes can be effectively achieved through the utilization of photocatalysis. In this work, metal alkoxides and a combination of alcohol/hydrophobic solvents are employed to prepare BaTiO3 aerogels via [...] Read more.
Given the increasingly severe environmental problems caused by water pollution, the degradation of organic dyes can be effectively achieved through the utilization of photocatalysis. In this work, metal alkoxides and a combination of alcohol/hydrophobic solvents are employed to prepare BaTiO3 aerogels via a liquid-phase and template-free synthetic route. The preparation process of the aerogels solely entails facile agitation and supercritical drying, eliminating the need for additional heat treatment. The binary solvent of ethanol and toluene is identified as the optimal choice, resulting in a significantly enhanced surface area (up to 223 m2/g) and an abundant pore structure of BaTiO3 aerogels compared to that of the BaTiO3 nanoparticles. Thus, the removal efficiency of the BaTiO3 aerogel sample for MO is nearly twice as high as that of the BaTiO3 nanoparticles sample. Noble metal Ag nanoparticles’ deposition onto the BaTiO3 aerogel surface is further achieved via the photochemical deposition method, which enhances the capture of photogenerated electrons, thereby ensuring an elevated level of photocatalytic efficiency. As a result, Ag nanoparticles deposited on BaTiO3 aerogel can degrade MO completely after 40 min of illumination, while the corresponding aerogel before modification can only remove 80% of MO after 60 min. The present work not only complements the preparatory investigation of intricate aerogels but also offers a fresh perspective for the development of diverse perovskite aerogels with broad applications. Full article
(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials)
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12 pages, 3122 KiB  
Article
Fabrication of the SiC/HfC Composite Aerogel with Ultra-Low Thermal Conductivity and Excellent Compressive Strength
by Wei Wang, Qi You, Zhanwu Wu, Sheng Cui and Weimin Shen
Gels 2024, 10(5), 292; https://doi.org/10.3390/gels10050292 - 24 Apr 2024
Cited by 4 | Viewed by 1279
Abstract
Aerogels, as a new type of high-temperature-resistant insulation material, find extensive application in aerospace, high-temperature industrial furnaces, new energy batteries, and various other domains, yet still face some limitations such as inadequate temperature resistance and pronounced brittleness. In this work, SiC/HfC composite aerogels [...] Read more.
Aerogels, as a new type of high-temperature-resistant insulation material, find extensive application in aerospace, high-temperature industrial furnaces, new energy batteries, and various other domains, yet still face some limitations such as inadequate temperature resistance and pronounced brittleness. In this work, SiC/HfC composite aerogels were prepared through a combination of sol-gel method, atmospheric pressure drying technique, and carbothermal reduction reaction. The effects of different molar ratios, calcination time, and temperatures on the microstructural features and physicochemical properties of the resulting SiC/HfC composite aerogels were investigated. The aerogel exhibited an elevated BET-specific surface area of 279.75 m2/g, while the sample displayed an extraordinarily low thermal conductivity of 0.052 W/(m·K). Most notably, the compressive strength reached an outstanding 5.93 MPa after a carbonization temperature of 1500 °C, far exceeding the values reported in prior aerogel studies. This research provided an innovative approach for advancing the development of carbide aerogels in the realm of high-temperature applications. Full article
(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials)
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13 pages, 3284 KiB  
Article
Facile Preparation of a Novel HfC Aerogel with Low Thermal Conductivity and Excellent Mechanical Properties
by Wei Wang, Zhanwu Wu, Shicong Song, Qi You, Sheng Cui, Weimin Shen, Guoqing Wang, Xuanfeng Zhang and Xiaofei Zhu
Gels 2023, 9(10), 839; https://doi.org/10.3390/gels9100839 - 23 Oct 2023
Cited by 1 | Viewed by 1759
Abstract
Aerogels emerge as captivating contenders within the realm of high-temperature thermal resistance and thermal insulation. Nevertheless, their practical applications are usually constrained by their inherent brittleness when subjected to rigorous conditions. Herein, employing hafnium dichloride oxide octahydrate (HfOCl2·8H2O) as [...] Read more.
Aerogels emerge as captivating contenders within the realm of high-temperature thermal resistance and thermal insulation. Nevertheless, their practical applications are usually constrained by their inherent brittleness when subjected to rigorous conditions. Herein, employing hafnium dichloride oxide octahydrate (HfOCl2·8H2O) as the hafnium source and resorcinol–formaldehyde (RF) as the carbon precursor, hafnium carbide (HfC) aerogels are fabricated via the sol-gel method complemented with carbothermal reduction reaction. Investigations are conducted into the effects of various molar ratios, duration, and temperatures of calcination on the microstructural features and physico-chemical characteristics of the as-prepared HfC aerogel. The aerogel shows a high BET-specific surface area (601.02 m2/g), which is much larger than those of previously reported aerogels. Furthermore, the HfC aerogel exhibits a low thermal conductivity of 0.053 W/(m·K) and a compressive strength of up to 6.12 MPa after carbothermal reduction at 1500 °C. These excellent thermal insulation and mechanical properties ensure it is ideal for the utilization of high-temperature thermal resistance and thermal insulation in the fields of aerospace. Full article
(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials)
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14 pages, 3171 KiB  
Article
Tuning the Electronic Structure of a Novel 3D Architectured Co-N-C Aerogel to Enhance Oxygen Evolution Reaction Activity
by Chunsheng Ni, Shuntian Huang, Tete Daniel Koudama, Xiaodong Wu, Sheng Cui, Xiaodong Shen and Xiangbao Chen
Gels 2023, 9(4), 313; https://doi.org/10.3390/gels9040313 - 7 Apr 2023
Cited by 1 | Viewed by 1562
Abstract
Hydrogen generation through water electrolysis is an efficient technique for hydrogen production, but the expensive price and scarcity of noble metal electrocatalysts hinder its large-scale application. Herein, cobalt-anchored nitrogen-doped graphene aerogel electrocatalysts (Co-N-C) for oxygen evolution reaction (OER) are prepared by simple chemical [...] Read more.
Hydrogen generation through water electrolysis is an efficient technique for hydrogen production, but the expensive price and scarcity of noble metal electrocatalysts hinder its large-scale application. Herein, cobalt-anchored nitrogen-doped graphene aerogel electrocatalysts (Co-N-C) for oxygen evolution reaction (OER) are prepared by simple chemical reduction and vacuum freeze-drying. The Co (0.5 wt%)-N (1 wt%)-C aerogel electrocatalyst has an optimal overpotential (0.383 V at 10 mA/cm2), which is significantly superior to that of a series of M-N-C aerogel electrocatalysts prepared by a similar route (M = Mn, Fe, Ni, Pt, Au, etc.) and other Co-N-C electrocatalysts that have been reported. In addition, the Co-N-C aerogel electrocatalyst has a small Tafel slope (95 mV/dec), a large electrochemical surface area (9.52 cm2), and excellent stability. Notably, the overpotential of Co-N-C aerogel electrocatalyst at a current density of 20 mA/cm2 is even superior to that of the commercial RuO2. In addition, density functional theory (DFT) confirms that the metal activity trend is Co-N-C > Fe-N-C > Ni-N-C, which is consistent with the OER activity results. The resulting Co-N-C aerogels can be considered one of the most promising electrocatalysts for energy storage and energy saving due to their simple preparation route, abundant raw materials, and superior electrocatalytic performance. Full article
(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials)
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17 pages, 7008 KiB  
Article
Electronic Modulation of the 3D Architectured Ni/Fe Oxyhydroxide Anchored N-Doped Carbon Aerogel with Much Improved OER Activity
by Jiaxin Lu, Wenke Hao, Xiaodong Wu, Xiaodong Shen, Sheng Cui and Wenyan Shi
Gels 2023, 9(3), 190; https://doi.org/10.3390/gels9030190 - 28 Feb 2023
Cited by 9 | Viewed by 2190
Abstract
It remains a big challenge to develop non-precious metal catalysts for oxygen evolution reaction (OER) in energy storage and conversion systems. Herein, a facile and cost-effective strategy is employed to in situ prepare the Ni/Fe oxyhydroxide anchored on nitrogen-doped carbon aerogel (NiFeOx [...] Read more.
It remains a big challenge to develop non-precious metal catalysts for oxygen evolution reaction (OER) in energy storage and conversion systems. Herein, a facile and cost-effective strategy is employed to in situ prepare the Ni/Fe oxyhydroxide anchored on nitrogen-doped carbon aerogel (NiFeOx(OH)y@NCA) for OER electrocatalysis. The as-prepared electrocatalyst displays a typical aerogel porous structure composed of interconnected nanoparticles with a large BET specific surface area of 231.16 m2·g−1. In addition, the resulting NiFeOx(OH)y@NCA exhibits excellent OER performance with a low overpotential of 304 mV at 10 mA·cm−2, a small Tafel slope of 72 mV·dec−1, and excellent stability after 2000 CV cycles, which is superior to the commercial RuO2 catalyst. The much enhanced OER performance is mainly derived from the abundant active sites, the high electrical conductivity of the Ni/Fe oxyhydroxide, and the efficient electronic transfer of the NCA structure. Density functional theory (DFT) calculations reveal that the introduction of the NCA regulates the surface electronic structure of Ni/Fe oxyhydroxide and increases the binding energy of intermediates as indicated by the d-band center theory. This work provides a new method for the construction of advanced aerogel-based materials for energy conversion and storage. Full article
(This article belongs to the Special Issue Preparation and Characteristics of Aerogel-Based Materials)
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