Английская Википедия:Ice XVII
Шаблон:Short description Шаблон:Use American English
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 waterШаблон:Efn can also be reduced to pure cubic ice.
Discovery
In 2016, the discovery of a new form of ice was announced.Шаблон:R 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.Шаблон:R
To create ice XVII, the researchers first produced filled ice in a stable phase named CШаблон:Sub from a mixture of hydrogen (HШаблон:Sub) and water (HШаблон:SubO), using temperatures from Шаблон:Cvt and pressures from Шаблон:Cvt.Шаблон:RШаблон:Efn The filled ice is then placed in a vacuum, and the temperature gradually increased until the hydrogen frees itself from the crystal structure.Шаблон:RШаблон:Efn The resulting form is metastable at room pressure while under Шаблон:Cvt, but collapses into [[ice Ih|ice IШаблон:Sub]] (ordinary ice) when brought above Шаблон:Cvt.Шаблон:R The crystal structure is hexagonal in nature, and the pores are helical channels with a diameter of about Шаблон:Cvt.Шаблон:R
Hydrogen storage
The discovery announcement also mentioned that ice XVII could repeatedly adsorb and release hydrogen molecules without degrading its structure.Шаблон:R 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 millibarsШаблон:Efn if the temperature is under Шаблон:Cvt.Шаблон:R The adsorbed hydrogen molecules can then be released, or desorbed, through the application of heat.Шаблон:R 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.Шаблон:R
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).Шаблон:R The storage method used by ice XVII falls in the latter category, physisorption.Шаблон:R 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".Шаблон:R
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.Шаблон:R In addition, ice XVII has shown the ability to store hydrogen at an HШаблон:Sub to HШаблон:SubO molar ratio above 40%, higher than the theoretical maximum ratio for sII clathrate hydrates, another potential storage medium.Шаблон:R However, if ice XVII is used as a storage medium, it must be kept under a temperature of Шаблон:Cvt or risk being destabilized.Шаблон:R
Cubic ice
It was reported in 2020 that cubic ice based on heavy water (DШаблон:SubO) can be formed from ice XVII.Шаблон:R This was done by heating specially prepared DШаблон:SubO ice XVII powder.Шаблон:R The result was free of structural deformities compared to standard cubic ice, or ice IШаблон:Sub.Шаблон:R This discovery was reported around the same time another research group announced that they were able to obtain pure DШаблон:SubO cubic ice by first synthesizing filled ice in the CШаблон:Sub phase, and then decompressing it.Шаблон:RШаблон:Efn
See also
Notes
References
