Dear Colleagues,
Aerogels are advanced materials with outstanding properties, including a high specific surface area and porosity, and a low thermal conductivity, density, dielectric constant, and refractive index. Due to their outstanding properties, aerogels were listed among the top 10 most promising themes of investigation in science and technology in the 21st century. Aerogels can be widely applied in thermal insulation, acoustic insulation, optics, hypervelocity particle capture, environmental protection, biomedical engineering, fire protection, etc. Among these applications, thermal insulation is currently the dominant market. However, according to the reports from MarketResearch.biz and the China Insulation & Energy Efficiency Materials Association, aerogels only accounted for 1.1–2.6% of the global market share of thermal insulation materials from 2016 to 2020. Therefore, despite this intense interest and the remarkable rate of research advancement, the commercialization and expansion of aerogels into diversified industries have not developed as quickly as expected. Why does the application of aerogels remain unrealized in these reported sectors? Below are the challenges for aerogel application that need to be discussed: (1) high costs, (2) low mechanical strength, (3) fragile texture, (4) the fire safety of aerogel products, and (4) environmental issues in aerogel production, among others.
Aerogels are part of a broad family, including silica, alumina, ceramics, nanocarbons, 2D materials, (bio-)polymers, metals, metal chalcogenides, etc. Each aerogel possesses a suitable preparation process, properties, difficulties to overcome, and perspectives in practical applications. Moreover, the downstream applications of aerogel products are also diverse, including coatings, sheets, boards, special structures, etc., They are also used as core materials of vacuum insulation panels, or thermal functional components of insulation and decoration integrated panels, fabrics, or batteries. For instance, the emerging applications of silica aerogels are in electric vehicles and building insulation. On the one hand, driven by policies related to carbon emission reduction and global warming prevention, electric and hybrid electric vehicles have been developed quickly in recent years and are expected to replace traditional gasoline-powered vehicles. Currently, lithium-ion batteries are the dominant power source for a variety of portable electronic devices. However, they have a narrow operational temperature range and poor thermal stability. Their failure may cause fire and, under certain circumstances, an explosion. The composite material system consists of silica aerogel papers and cooling materials that have been proven to positively prevent the thermal runaway of lithium-ion battery packs. On the other hand, nearly zero-energy buildings have become mainstream in the building sector, which has driven the development and application of superinsulation materials such as efficiently insulated interior and exterior walls and energy-saving windows in buildings. Due to having a remarkably lower thermal conductivity (∼0.013 W/(m·K)) than the other commercial thermal insulation materials and flexible designability, silica aerogels are considered one of the most promising thermal insulation materials for building applications. Silica aerogels will continue to grow in applications in the form of coatings, boards, blanks, concrete, rendering, and transparent and insulating aerogel glazings in buildings.
This Special Issue aims to analyze the potential solutions to facilitate translational research and the industrial adoption of aerogels based on the aerogel formation chemistries, structure, and properties, especially with the recent research and technological advances. Particular attention will be paid to the established sol–gel chemistries, newly developed synthesis processes, and characterization tools. Based on this analysis, a cost and downstream application analysis of aerogels and insights into the most promising development directions in academia and industry are also appreciated. The publication of original research articles, rapid communications, and reviews in this Special Issue will contribute to the development of aerogel materials and their advanced applications.
Prof. Dr. Zhaofeng Chen
Dr. Chengdong Li
Dr. Zhi Li
Guest Editors
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