Characterization of Crystalline structures – SEM-EBSD vs TEM-PED
Besides images provided by SEM and TEM, different attachments can be added to reveal crystalline information, including (SEM-EBSD) and TEM (TEM-PED).
The Versatility and Usefulness of Aerogels
Thermal resistance and its complement, thermal conductance, are fundamental concepts in thermodynamics, thermal engineering, and heat transfer. They describe the ability of a material to insulate (resistance) or transfer (conductance) heat. Thermal resistivity is important in industries like aerospace, automotive, building &
construction, biomedical applications, and energy storage, among others. At one end of the spectrum of thermal properties are metals which typically exhibit high conductance and low resistance, for example, a copper coil immersion chiller used to transfer heat out of a liquid. At the other end of the spectrum are thermal insulators like fiberglass and polyurethane foam. There are, however, more exotic materials that exhibit more extreme properties. Diamond and boron arsenide are both much more conductive than the most conductive metal – silver. Silica aerogel is about 33% less conductive than
expanded polyurethane foam (The Engineering ToolBox). Aside from being exceptional insulators, aerogels have other fascinating properties that make them well-suited for unique applications.
What Are Aerogels?
Aerogels are synthesized rigid, porous substances formed by substituting the liquid portion of a gel with a gaseous element while retaining its construction. This process yields unique characteristics such as ultra-low density (0.003-0.5g/cm3), extraordinary surface area
(500-1200m2g-1), very high porosity (80-99.8%), and excellent thermal insulation capabilities. Some silica-based aerogels are nearly transparent and weigh less than four times as much as the equivalent volume of dry air. Different types of aerogels exhibit exceptional physical features such as low dielectric constants, low refractive indices, high thermal insulation, and solar light transmission (Nazia Rodoshi Khan, 2024). On a more evocative note, traditional silicon-based aerogels have been described as ”solid air” and ”frozen smoke”. Aerogels also encompass materials based on carbon nanoparticles, polymers, and metal oxides, among additional more exotic varieties.
How Can Aerogels Be Used?
Due to their unusual features, aerogels can be used for biomedical, acoustic, food packaging, electrochemical energy storage, thermal insulation, environmental, water treatment, catalysis, and aerospace applications. For biomedical and pharmaceutical applications specifically, aerogels can be used for diagnostic instruments, implantable devices, biosensing, wound repair, regenerative medicine, and delivery of medications. In astronautical applications, aerogels have a variety of uses including thermal insulation, high-velocity particle capture (e.g, cosmic dust collection), cryogenic fluid containment, fire retardation, acoustics, thermal barriers, etc. (Nazia Rodoshi Khan, 2024).
The Future of Aerogels
A research group from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences recently developed aerogel materials with higher temperature resistance, strength, and insulation performance. Aerogels are traditionally made with SiO2, but in this group’s study, researchers introduced small amounts of ZrO2 crystalline phase to one-dimensional SiO2 fibers (Liu Cui, 2024), which increased their temperature resistance. Additionally, they investigated the potential use of biomass aerogels for eco-friendly building insulation materials, developing sodium alginate aerogels that were able to support 2600 times their own weight and possessed flame retardancy and self-extinguishing properties. This recent research has helped provide solutions for efficient heat insulation.
EAG's Expertise in Analyzing Aerogels
The characterization of synthesized aerogels typically emphasizes structural and materials properties rather than elemental or molecular composition. EAG is well-equipped to undertake Surface Area (Brunauer, Emmett and Teller equation) and Pore Size Determination (Barrett, Joyner, Halenda or Density Functional Theory methods) measurements of aerogels. For aerogels that are being deployed for purposes such as capturing high-velocity particles in a spacecraft or carrying calcium, zinc and silver cations for wound care, mapping the distribution of chemical composition is an important application. Scanning Electron Microscopy – Energy Dispersive Spectroscopy and Laser Ablation – Inductively Coupled Plasma – Mass Spectrometry are both spatially resolved elemental chemistry techniques well-suited to mapping aerogels. Bulk compositional analysis of aerogels, such as before and after testing of aerogels used to harvest uranium from sea water, can be accomplished using Inductively Coupled Plasma – Optical Emission Spectroscopy or Inductively Coupled Plasma – Mass Spectrometry. EAG scientists and engineers are ready to work with you to develop application-specific protocols to meet your aerogel needs.
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