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Ice XVII
Ice XVII is a metastable form of ice with a hexagonal structure and Helix, helical channels that was discovered in 2016. It can be formed by freezing water with hydrogen molecules at high pressure to form a filled ice, and then removing the hydrogen molecules from the structure. The form has potential for being used in hydrogen storage. Ice XVII made from heavy water can also be reduced to pure cubic ice. Discovery In 2016, the discovery of a new form of ice was announced. Characterized as a "porous water ice metastable at atmospheric temperatures", this new form was discovered by taking a filled ice and removing the non-water components, leaving the crystal structure behind, similar to how ice XVI, another porous form of ice, was synthesized from a clathrate hydrate. To create ice XVII, the researchers first produced filled ice in a stable phase named C from a mixture of hydrogen (H) and water (HO), using temperatures from and pressures from . The filled ice ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Desorbed
Desorption is the physical process where a previously adsorbed substance is released from a surface. This happens when a molecule gains enough energy to overcome the activation barrier of the bounding energy that keeps it in the surface. There are a lot of different types of desorption, depending on the mechanism that separates the adsorbate from the substrate; therefore there is no one equation that describes the process. Note that desorption is the opposite of adsorption, which differs from absorption because it refers to substances being stuck to the surface, as opposed to being absorbed into the bulk. Desorption can occur after a reaction between a catalyst and an adsorbed compound; or during stripping or chromatography which are types of separation processes. Desorption mechanisms Depending on the nature of the adsorbent-to-surface bond, there are a multitude of mechanisms for desorption. The surface bond of a sorbant can be cleaved thermally, through chemical react ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Storage
Hydrogen storage can be accomplished by several existing methods of holding hydrogen for later use. These include mechanical approaches such as using high pressures and low temperatures, or employing chemical compounds that release H2 upon demand. While large amounts of hydrogen are produced by various industries, it is mostly consumed at the site of production, notably for the synthesis of ammonia. For many years hydrogen has been stored as compressed gas or cryogenic liquid, and transported as such in cylinders, tubes, and cryogenic tanks for use in industry or as propellant in space programs. Interest in using hydrogen for on-board storage of energy in zero-emissions vehicles is motivating the development of new methods of storage, more adapted to this new application. The overarching challenge is the very low boiling point of H2: it boils around 20.268 K (−252.882 °C or −423.188 °F). Achieving such low temperatures requires expending significant energy. Es ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrogen Clathrate
A hydrogen clathrate is a clathrate containing hydrogen in a water lattice. It is not possible to store commercial quantities of hydrogen by this method hydrogen in a hydrogen economy. A recent review that accounts the state-of-the-art and future prospects and challenges of hydrogen storage as clathrate hydrates is reported by Veluswamy et al. (2014). Another unusual characteristic is that multiple hydrogen molecules can occur at each cage site in the ice, one of only a very few guest molecule that forms clathrates with this property. The maximum ratio of hydrogen to water is 6 H2 to 17 H2O. It can be formed at 250K in a diamond anvil at a pressure of 300MPa (3000 Bars). It takes about 30 minutes to form, so this method is impractical for rapid manufacture. The percent of weight of hydrogen is 3.77%. The cage compartments are hexakaidecahedral and hold from two to four molecules of hydrogen. At temperatures above 160K the molecules rotate around inside the cage. Below 120K the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clathrate Hydrate
Clathrate hydrates, or gas hydrates, clathrates, hydrates, etc., are crystalline water-based solids physically resembling ice, in which small non-polar molecules (typically gases) or polar molecules with large hydrophobic moieties are trapped inside "cages" of hydrogen bonded, frozen water molecules. In other words, clathrate hydrates are clathrate compounds in which the host molecule is water and the guest molecule is typically a gas or liquid. Without the support of the trapped molecules, the lattice structure of hydrate clathrates would collapse into conventional ice crystal structure or liquid water. Most low molecular weight gases, including , , , , , , , , and , as well as some higher hydrocarbons and freons, will form hydrates at suitable temperatures and pressures. Clathrate hydrates are not officially chemical compounds, as the enclathrated guest molecules are never bonded to the lattice. The formation and decomposition of clathrate hydrates are first order phase t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molar Ratio
In chemistry, the mole fraction or molar fraction (''xi'' or ) is defined as unit of the amount of a constituent (expressed in moles), ''ni'', divided by the total amount of all constituents in a mixture (also expressed in moles), ''n''tot. This expression is given below: :x_i = \frac The sum of all the mole fractions is equal to 1: :\sum_^ n_i = n_\mathrm ; \ \sum_^ x_i = 1. The same concept expressed with a denominator of 100 is the mole percent, molar percentage or molar proportion (mol%). The mole fraction is also called the amount fraction. It is identical to the number fraction, which is defined as the number of molecules of a constituent ''Ni'' divided by the total number of all molecules ''N''tot. The mole fraction is sometimes denoted by the lowercase Greek letter (chi) instead of a Roman ''x''. For mixtures of gases, IUPAC recommends the letter ''y''. The National Institute of Standards and Technology of the United States prefers the term amount-of-substance fraction o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Physisorption
Physisorption, also called physical adsorption, is a process in which the electronic structure of the atom or molecule is barely perturbed upon adsorption. Overview The fundamental interacting force of physisorption is Van der Waals force. Even though the interaction energy is very weak (~10–100 meV), physisorption plays an important role in nature. For instance, the van der Waals attraction between surfaces and foot-hairs of geckos (see Synthetic setae) provides the remarkable ability to climb up vertical walls. Van der Waals forces originate from the interactions between induced, permanent or transient electric dipoles. In comparison with chemisorption, in which the electronic structure of bonding atoms or molecules is changed and covalent or ionic bonds form, physisorption does not result in changes to the chemical bonding structure. In practice, the categorisation of a particular adsorption as physisorption or chemisorption depends principally on the binding en ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Van Der Waals Force
In molecular physics, the van der Waals force is a distance-dependent interaction between atoms or molecules. Unlike ionic or covalent bonds, these attractions do not result from a chemical electronic bond; they are comparatively weak and therefore more susceptible to disturbance. The van der Waals force quickly vanishes at longer distances between interacting molecules. Named after Dutch physicist Johannes Diderik van der Waals, the van der Waals force plays a fundamental role in fields as diverse as supramolecular chemistry, structural biology, polymer science, nanotechnology, surface science, and condensed matter physics. It also underlies many properties of organic compounds and molecular solids, including their solubility in polar and non-polar media. If no other force is present, the distance between atoms at which the force becomes repulsive rather than attractive as the atoms approach one another is called the van der Waals contact distance; this phenomenon resul ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chemisorption
Chemisorption is a kind of adsorption which involves a chemical reaction between the surface and the adsorbate. New chemical bonds are generated at the adsorbent surface. Examples include macroscopic phenomena that can be very obvious, like corrosion, and subtler effects associated with heterogeneous catalysis, where the catalyst and reactants are in different phases. The strong interaction between the adsorbate and the Substrate (chemistry), substrate Interface (matter), surface creates new types of electronic chemical bond, bonds. In contrast with chemisorption is physisorption, which leaves the chemical species of the adsorbate and surface intact. It is conventionally accepted that the energetic threshold separating the binding energy of "physisorption" from that of "chemisorption" is about 0.5 eV per adsorbed Chemical species, species. Due to specificity, the nature of chemisorption can greatly differ, depending on the chemical identity and the surface structural properties ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liquid Hydrogen
Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form. To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully liquid state at atmospheric pressure, H2 needs to be cooled to .IPTS-1968 iupac.org, accessed 2020-01-01 A common method of obtaining liquid hydrogen involves a compressor resembling a jet engine in both appearance and principle. Liquid hydrogen is typically used as a concentrated form of . Storing it as liquid takes less space than storing it as a gas at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Compressed Hydrogen
Compressed hydrogen (CH2, CGH2 or CGH2) is the gaseous state of the element hydrogen kept under pressure. Compressed hydrogen in hydrogen tanks at 350 bar (5,000 psi) and 700 bar (10,000 psi) is used for mobile hydrogen storage in hydrogen vehicles. It is used as a fuel gas. Infrastructure Compressed hydrogen is used in hydrogen pipeline transport and in compressed hydrogen tube trailer transport. See also *Cryo-adsorption *Gas compressor *Gasoline gallon equivalent *Hydrogen compressor *Hydrogen safety *Liquid hydrogen *Liquefaction of gases *Metallic hydrogen *Slush hydrogen *Standard cubic foot *Timeline of hydrogen technologies This is a timeline of the history of hydrogen technology. Timeline 16th century * c. 1520 – First recorded observation of hydrogen by Paracelsus through dissolution of metals (iron, zinc, and tin) in sulfuric acid. 17th century * 1625 – Fi ... References External links COMPRESSED HYDROGEN INFRASTRUCTURE PROGRAM ("CH2IP") Hydrogen physics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Environmental Technology
Environmental technology (envirotech) or green technology (greentech), also known as ''clean technology'' (''cleantech''), is the application of one or more of environmental science, green chemistry, environmental monitoring and electronic devices to monitor, model and conserve the natural environment and resources, and to curb the negative impacts of human involvement. The term is also used to describe sustainable energy generation technologies such as photovoltaics, wind turbines, etc. Sustainable development is the core of ''environmental technologies''. The term ''environmental technologies'' is also used to describe a class of electronic devices that can promote sustainable management of resources. Purification and waste management Examples *Biofiltration *Bioreactor *Bioremediation *Desalination *Thermal depolymerization *Composting toilet *Pyrolysis Water purification Water purification: The whole idea/concept of having dirt/germ/pollution free water flowing throughou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
