Ice XVII is a metastable form of ice with a hexagonal structure and 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 [lower-alpha 1] can also be reduced to pure cubic ice.
In 2016, the discovery of a new form of ice was announced. [1] 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. [2] [1] [3] [4] [5]
To create ice XVII, the researchers first produced filled ice in a stable phase named C0 from a mixture of hydrogen (H2) and water (H2O), using temperatures from 100 to 270 K (−173 to −3 °C; −280 to 26 °F) and pressures from 360 to 700 MPa (52,000 to 102,000 psi; 3,600 to 6,900 atm). [1] [lower-alpha 2] The filled ice is then placed in a vacuum, and the temperature gradually increased until the hydrogen frees itself from the crystal structure. [1] [3] [lower-alpha 3] The resulting form is metastable at room pressure while under 120 K (−153 °C; −244 °F), but collapses into ice Ih (ordinary ice) when brought above 130 K (−143 °C; −226 °F). [1] [3] The crystal structure is hexagonal in nature, and the pores are helical channels with a diameter of about 6.10 Å (6.10×10−10 m; 2.40×10−8 in). [1] [3]
The discovery announcement also mentioned that ice XVII could repeatedly adsorb and release hydrogen molecules without degrading its structure. [1] The total amount of hydrogen that ice XVII can adsorb depends on the amount of pressure applied, but hydrogen molecules can be adsorbed by ice XVII even at pressures as low as a few millibars [lower-alpha 4] if the temperature is under 40 K (−233.2 °C; −387.7 °F). [1] [6] The adsorbed hydrogen molecules can then be released, or desorbed, through the application of heat. [6] This was an unexpected property of ice XVII, and could allow it to be used for hydrogen storage, an issue often mentioned in environmental technology. [1] [6]
Aside from storing hydrogen via compression or liquification, it can also be stored within a solid substance, either via a reversible chemical process (chemisorption) or by having the hydrogen molecules attach to the substance via the van der Waals force (physisorption). [6] The storage method used by ice XVII falls in the latter category, physisorption. [6] In physisorption, there is no chemical reaction, and the chemical bond between the two atoms within a hydrogen molecule remains intact. Because of this, the number of adsorption–desorption cycles ice XVII can withstand is "theoretically infinite". [1] [6]
One significant advantage of using ice XVII as a hydrogen storage medium is the low cost of the only two chemicals involved: hydrogen and water. [6] In addition, ice XVII has shown the ability to store hydrogen at an H2 to H2O molar ratio above 40%, higher than the theoretical maximum ratio for sII clathrate hydrates, another potential storage medium. [1] However, if ice XVII is used as a storage medium, it must be kept under a temperature of 130 K (−143 °C; −226 °F) or risk being destabilized. [6]
It was reported in 2020 that cubic ice based on heavy water (D2O) can be formed from ice XVII. [7] This was done by heating specially prepared D2O ice XVII powder. [7] The result was free of structural deformities compared to standard cubic ice, or ice Isd. [7] [8] This discovery was reported around the same time another research group announced that they were able to obtain pure D2O cubic ice by first synthesizing filled ice in the C2 phase, and then decompressing it. [9] [1] [lower-alpha 2]
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 32 °F, 0 °C, or 273.15 K. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.
The term cryostasis was introduced to name the reversible preservation technology for live biological objects which is based on using clathrate-forming gaseous substances under increased hydrostatic pressure and hypothermic temperatures.
Methane clathrate (CH4·5.75H2O) or (8CH4·46H2O), also called methane hydrate, hydromethane, methane ice, fire ice, natural gas hydrate, or gas hydrate, is a solid clathrate compound (more specifically, a clathrate hydrate) in which a large amount of methane is trapped within a crystal structure of water, forming a solid similar to ice. Originally thought to occur only in the outer regions of the Solar System, where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of the Earth. Methane hydrate is formed when hydrogen-bonded water and methane gas come into contact at high pressures and low temperatures in oceans.
Clathrate hydrates, or gas hydrates, clathrates, or hydrates, are crystalline water-based solids physically resembling ice, in which small non-polar molecules 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 O2, H2, N2, CO2, CH4, H2S, Ar, Kr, and Xe, 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 transitions, not chemical reactions. Their detailed formation and decomposition mechanisms on a molecular level are still not well understood. Clathrate hydrates were first documented in 1810 by Sir Humphry Davy who found that water was a primary component of what was earlier thought to be solidified chlorine.
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understood.
The self-ionization of water (also autoionization of water, and autodissociation of water) is an ionization reaction in pure water or in an aqueous solution, in which a water molecule, H2O, deprotonates (loses the nucleus of one of its hydrogen atoms) to become a hydroxide ion, OH−. The hydrogen nucleus, H+, immediately protonates another water molecule to form a hydronium cation, H3O+. It is an example of autoprotolysis, and exemplifies the amphoteric nature of water.
In chemistry, noble gas compounds are chemical compounds that include an element from the noble gases, group 18 of the periodic table. Although the noble gases are generally unreactive elements, many such compounds have been observed, particularly involving the element xenon.
A clathrate is a chemical substance consisting of a lattice that traps or contains molecules. The word clathrate is derived from the Latin clathratus, meaning ‘with bars, latticed’. Most clathrate compounds are polymeric and completely envelop the guest molecule, but in modern usage clathrates also include host–guest complexes and inclusion compounds. According to IUPAC, clathrates are inclusion compounds "in which the guest molecule is in a cage formed by the host molecule or by a lattice of host molecules." The term refers to many molecular hosts, including calixarenes and cyclodextrins and even some inorganic polymers such as zeolites.
Titanium hydride normally refers to the inorganic compound TiH2 and related nonstoichiometric materials. It is commercially available as a stable grey/black powder, which is used as an additive in the production of Alnico sintered magnets, in the sintering of powdered metals, the production of metal foam, the production of powdered titanium metal and in pyrotechnics.
Several methods exist for storing hydrogen. 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.
Carbon dioxide hydrate or carbon dioxide clathrate is a snow-like crystalline substance composed of water ice and carbon dioxide. It normally is a Type I gas clathrate. There has also been some experimental evidence for the development of a metastable Type II phase at a temperature near the ice melting point. The clathrate can exist below 283K (10 °C) at a range of pressures of carbon dioxide. CO2 hydrates are widely studied around the world due to their promising prospects of carbon dioxide capture from flue gas and fuel gas streams relevant to post-combustion and pre-combustion capture. It is also quite likely to be important on Mars due to the presence of carbon dioxide and ice at low temperatures.
Ice Ic is a metastable cubic crystalline variant of ice. Hans König was the first to identify and deduce the structure of ice Ic. The oxygen atoms in ice Ic are arranged in a diamond structure and is extremely similar to ice Ih having nearly identical densities and the same lattice constant along the hexagonal puckered-planes. It forms at temperatures between 130 and 220 kelvins upon cooling, and can exist up to 240 K (−33 °C) upon warming, when it transforms into ice Ih.
Ice VII is a cubic crystalline form of ice. It can be formed from liquid water above 3 GPa (30,000 atmospheres) by lowering its temperature to room temperature, or by decompressing heavy water (D2O) ice VI below 95 K. (Different types of ice, from ice II to ice XVIII, have been created in the laboratory at different temperatures and pressures. Ordinary water ice is known as ice Ih in the Bridgman nomenclature.) Ice VII is metastable over a wide range of temperatures and pressures and transforms into low-density amorphous ice (LDA) above 120 K (−153 °C). Ice VII has a triple point with liquid water and ice VI at 355 K and 2.216 GPa, with the melt line extending to at least 715 K (442 °C) and 10 GPa. Ice VII can be formed within nanoseconds by rapid compression via shock-waves. It can also be created by increasing the pressure on ice VI at ambient temperature. At around 5 GPa, Ice VII becomes the tetragonal Ice VIIt.
Magnesium hydride is the chemical compound with the molecular formula MgH2. It contains 7.66% by weight of hydrogen and has been studied as a potential hydrogen storage medium.
Water is a polar inorganic compound that is at room temperature a tasteless and odorless liquid, which is nearly colorless apart from an inherent hint of blue. It is by far the most studied chemical compound and is described as the "universal solvent" and the "solvent of life". It is the most abundant substance on the surface of Earth and the only common substance to exist as a solid, liquid, and gas on Earth's surface. It is also the third most abundant molecule in the universe.
A Bjerrum defect is a crystallographic defect which is specific to ice, and which is partly responsible for the electrical properties of ice. It was first proposed by Niels Bjerrum in 1952 in order to explain the electrical polarization of ice in an electric field. A hydrogen bond normally has one proton, but a hydrogen bond with a Bjerrum defect will have either two protons or no proton. D-defects are more energetically favorable than L-defects. The unfavorable defect strain is resolved when a water molecule pivots about an oxygen atom to produce hydrogen bonds with single protons. Dislocations of ice Ih along a slip plane create pairs of Bjerrum defects, one D defect and one L defect.
A hydrogen clathrate is a clathrate containing hydrogen in a water lattice. This substance is interesting due to its possible use to store 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 molecules stop racing around the cage, and below 50K are locked into a fixed position. This was determined with deuterium in a neutron scattering experiment.
Ice XVI is the least dense experimentally obtained crystalline form of ice. It is topologically equivalent to the empty structure of sII clathrate hydrates. It was first obtained in 2014 by removing gas molecules from a neon clathrate under vacuum at temperatures below 147 K. The resulting empty water frame, ice XVI, is thermodynamically unstable at the experimental conditions, yet it can be preserved at cryogenic temperatures. Above 145–147 K at positive pressures ice XVI transforms into the stacking-faulty ice Ic and further into ordinary ice Ih. Theoretical studies predict ice XVI to be thermodynamically stable at negative pressures.
Solid nitrogen is a number of solid forms of the element nitrogen, first observed in 1884. Solid nitrogen is mainly the subject of academic research, but low-temperature, low-pressure solid nitrogen is a substantial component of bodies in the outer Solar System and high-temperature, high-pressure solid nitrogen is a powerful explosive, with higher energy density than any other non-nuclear material.
Nitrogen clathrate or nitrogen hydrate is a clathrate consisting of ice with regular crystalline cavities that contain nitrogen molecules. Nitrogen clathrate is a variety of air hydrates. It occurs naturally in ice caps on Earth, and is believed to be important in the outer Solar System on moons such as Titan and Triton which have a cold nitrogen atmosphere.
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