Radiative cooling is the process by which a body loses heat by thermal radiation. As Planck's law describes, every physical body spontaneously and continuously emits electromagnetic radiation.
Nanomaterials describe, in principle, materials of which a single unit small sized between 1 and 100 nm.
Graphene is an allotrope of carbon consisting of a single layer of atoms arranged in a two-dimensional honeycomb lattice. The name is a portmanteau of "graphite" and the suffix -ene, reflecting the fact that the graphite allotrope of carbon consists of stacked graphene layers.
A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 100 nm in only two directions. At the lowest range, metal particles smaller than 1 nm are usually called atom clusters instead.
Auxetics are structures or materials that have a negative Poisson's ratio. When stretched, they become thicker perpendicular to the applied force. This occurs due to their particular internal structure and the way this deforms when the sample is uniaxially loaded. Auxetics can be single molecules, crystals, or a particular structure of macroscopic matter.
In materials science, the sol–gel process is a method for producing solid materials from small molecules. The method is used for the fabrication of metal oxides, especially the oxides of silicon (Si) and titanium (Ti). The process involves conversion of monomers into a colloidal solution (sol) that acts as the precursor for an integrated network of either discrete particles or network polymers. Typical precursors are metal alkoxides.
Ceramic engineering is the science and technology of creating objects from inorganic, non-metallic materials. This is done either by the action of heat, or at lower temperatures using precipitation reactions from high-purity chemical solutions. The term includes the purification of raw materials, the study and production of the chemical compounds concerned, their formation into components and the study of their structure, composition and properties.
Nanocomposite is a multiphase solid material where one of the phases has one, two or three dimensions of less than 100 nanometers (nm) or structures having nano-scale repeat distances between the different phases that make up the material.
Scanning probe lithography (SPL) describes a set of nanolithographic methods to pattern material on the nanoscale using scanning probes. It is a direct-write, mask-less approach which bypasses the diffraction limit and can reach resolutions below 10 nm. It is considered an alternative lithographic technology often used in academic and research environments. The term scanning probe lithography was coined after the first patterning experiments with scanning probe microscopes (SPM) in the late 1980s.
Zirconium diboride (ZrB2) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB2 is an ultra high temperature ceramic (UHTC) with a melting point of 3246 °C. This along with its relatively low density of ~6.09 g/cm3 (measured density may be higher due to hafnium impurities) and good high temperature strength makes it a candidate for high temperature aerospace applications such as hypersonic flight or rocket propulsion systems. It is an unusual ceramic, having relatively high thermal and electrical conductivities, properties it shares with isostructural titanium diboride and hafnium diboride.
A colloidal crystal is an ordered array of colloid particles and fine grained materials analogous to a standard crystal whose repeating subunits are atoms or molecules. A natural example of this phenomenon can be found in the gem opal, where spheres of silica assume a close-packed locally periodic structure under moderate compression. Bulk properties of a colloidal crystal depend on composition, particle size, packing arrangement, and degree of regularity. Applications include photonics, materials processing, and the study of self-assembly and phase transitions.
Multiphoton lithography of polymer templates has been known for years by the photonic crystal community. Similar to standard photolithography techniques, structuring is accomplished by illuminating negative-tone or positive-tone photoresists via light of a well-defined wavelength. The fundamental difference is, however, the avoidance of reticles. Instead, two-photon absorption is utilized to induce a dramatic change in the solubility of the resist for appropriate developers.
An acoustic metamaterial, sonic crystal, or phononic crystal, is a material designed to control, direct, and manipulate sound waves or phonons in gases, liquids, and solids. Sound wave control is accomplished through manipulating parameters such as the bulk modulus β, density ρ, and chirality. They can be engineered to either transmit, or trap and amplify sound waves at certain frequencies. In the latter case, the material is an acoustic resonator.
Ultralight materials are solids with a density of less than 10 mg/cm3, including silica aerogels, carbon nanotube aerogels, aerographite, metallic foams, polymeric foams, and metallic microlattices. The density of air is about 1.275 mg/cm3, which means that the air in the pores contributes significantly to the density of these materials in atmospheric conditions. They can be classified by production method as aerogels, stochastic foams, and structured cellular materials.
A metallic microlattice is a synthetic porous metallic material consisting of an ultra-light metal foam. With a density as low as 0.99 mg/cm3 (0.00561 lb/ft3), it is one of the lightest structural materials known to science. It was developed by a team of scientists from California-based HRL Laboratories, in collaboration with researchers at University of California, Irvine and Caltech, and was first announced in November 2011. The prototype samples were made from a nickel-phosphorus alloy. In 2012, the microlattice prototype was declared one of 10 World-Changing Innovations by Popular Mechanics. Metallic microlattice technology has numerous potential applications in automotive and aeronautical engineering. A detailed comparative review study among other types of metallic lattice structures showed them to be beneficial for light-weighting purposes but expensive to manufacture.
Mechanical metamaterials are artificial structures with mechanical properties defined by their structure rather than their composition. They can be seen as a counterpart to the rather well-known family of optical metamaterials. They are often also termed elastodynamic metamaterials and include acoustic metamaterials as a special case of vanishing shear. Their mechanical properties can be designed to have values which cannot be found in nature.
SiC–SiC matrix composite is a particular type of ceramic matrix composite (CMC) which have been accumulating interest mainly as high temperature materials for use in applications such as gas turbines, as an alternative to metallic alloys. CMCs are generally a system of materials that are made up of ceramic fibers or particles that lie in a ceramic matrix phase. In this case, a SiC/SiC composite is made by having a SiC matrix phase and a fiber phase incorporated together by different processing methods. Outstanding properties of SiC/SiC composites include high thermal, mechanical, and chemical stability while also providing high strength to weight ratio.
Tube-based nanostructures are nanolattices made of connected tubes and exhibit nanoscale organization above the molecular level.
An aluminum polymer composite (APC) material combines aluminum with a polymer to create materials with interesting characteristics. In 2014 researchers used a 3d laser printer to produce a polymer matrix. When coated with a 50-100 nanometer layer of aluminum oxide, the material was able to withstand loads of as much as 280 megapascals, stronger than any other known material whose density was less than 1,000 kilograms per cubic metre (1,700 lb/cu yd), that of water.
Microscale structural metamaterials are synthetic structures that are aimed to yield specific desired mechanical advantages. These designs are often inspired by natural cellular materials such as plant and bone tissue which have superior mechanical efficiency due to their low weight to stiffness ratios.
