Let's face the liquid-liquid interface

The demand for energy consumption, limited availability of fossil fuels, and pollution caused by the energy production industry challenge scientists to find new, more cost-effective, and greener solutions to produce power. ...

Fatal flaw uncovered in green pigmented concrete

As Xi'an Jiaotong-Liverpool University researchers completed their research on colored architectural concrete, they found a surprising result—green pigmented cement had impurities that produced porous, poor quality concrete. ...

A new theory to explain the transparency of metallic oxides

The electrons of some metal oxides, due to their large effective mass when coupled with the ionic lattice of the material, cannot follow the electric field of light and allow it to pass through the material. Transparent and ...

Stimulating blood vessel formation with magnetic fields

Magnetic fields can be used to stimulate blood vessel growth, according to a study published in the journal Science and Technology of Advanced Materials. The findings, by researchers at the Tecnico Lisboa and NOVA School ...

Thumb-sized device quickly 'sniffs out' bad breath

No one wants bad breath—not when visiting friends and family, at a job interview, and especially not on a first date. Smelly breath can make things awkward, but it also is a natural warning sign, indicating that serious ...

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Oxide

An oxide ( /ˈɒksaɪd/) is a chemical compound that contains at least one oxygen atom in its chemical formula. Metal oxides typically contain an anion of oxygen in the oxidation state of −2.

Most of the Earth's crust consists of solid oxides. Oxides result when elements are oxidized by oxygen in air. Combustion of hydrocarbons affords the two principal oxides of carbon, carbon monoxide and carbon dioxide. Even materials that are considered to be pure elements often contain a coating of oxides. For example, aluminium foil has a thin skin of Al2O3 that protects the foil from further corrosion.

Virtually all elements burn in an atmosphere of oxygen, or an oxygen rich environment. In the presence of water and oxygen (or simply air), some elements—lithium, sodium, potassium, rubidium, caesium, strontium and barium—react rapidly, even dangerously, to give the hydroxides. In part for this reason, alkali and alkaline earth metals are not found in nature in their metallic, i.e., native, form. Caesium is so reactive with oxygen that it is used as a getter in vacuum tubes, and solutions of potassium and sodium, so called NaK are used to deoxygenate and dehydrate some organic solvents. The surface of most metals consists of oxides and hydroxides in the presence of air. A well known example is aluminium foil, which is coated with a thin film of aluminium oxide that passivates the metal, slowing further corrosion. The aluminium oxide layer can be built to greater thickness by the process of electrolytic anodising. Although solid magnesium and aluminium react slowly with oxygen at STP, they, like most metals, will burn in air, generating very high temperatures. Finely grained powders of most metals can be dangerously explosive in air. Consequently, they are often used in Solid-fuel rockets.

In dry oxygen, iron readily forms iron(II) oxide, but the formation of the hydrated ferric oxides, Fe2O3−2x(OH)x, that mainly comprise rust, typically requires oxygen and water. The production of free oxygen by photosynthetic bacteria some 3.5 billion years ago precipitated iron out of solution in the oceans as Fe2O3 in the economically important iron ore hematite.

Due to its electronegativity, oxygen forms chemical bonds with almost all elements to give the corresponding oxides. Noble metals (such as gold or platinum) resist direct chemical combination with oxygen, and substances like gold(III) oxide must be generated by indirect routes.

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