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Below 912 °C (1,674 °F), iron has a body-centered cubic (bcc) crystal structure and is known as α-iron or ferrite.It is thermodynamically stable and a fairly soft metal. α-Fe can be subjected to pressures up to ca. 15 GPa before transforming into a high-pressure form termed ε-Fe discussed below.
Diamond and graphite are two allotropes of carbon: pure forms of the same element that differ in crystalline structure.. Allotropy or allotropism (from Ancient Greek ἄλλος (allos) 'other' and τρόπος (tropos) 'manner, form') is the property of some chemical elements to exist in two or more different forms, in the same physical state, known as allotropes of the elements.
Plutonium in the delta (δ) phase [8] normally exists in the 310 °C to 452 °C range but is stable at room temperature when alloyed with a small percentage of gallium, aluminium, or cerium, enhancing workability and allowing it to be welded in weapons applications. The δ phase has more typical metallic character and is roughly as strong and ...
Contrary to other phases, which are semiconductors, this phase is a metal and becomes a superconductor with a critical temperature increasing from 6 K at 160 GPa to 11 K at 250 GPa. [48] This structural transformation occurs at pressures at which theory predicts the icosahedra will dissociate. [ 49 ]
It has been described as slightly harder than graphite with a reflection color of grey to white. However, the existence of carbyne phases is disputed – see the article on chaoite for details. D-carbon: D-carbon was proposed by theorists in 2018. [33] D-carbon is an orthorhombic sp 3 carbon allotrope (6 atoms per cell).
Iron is the base metal of steel. Depending on the temperature, it can take two crystalline forms (allotropic forms): body-centred cubic and face-centred cubic. The interaction of the allotropes of iron with the alloying elements, primarily carbon, gives steel and cast iron their range of unique properties.
Austenite, also known as gamma-phase iron (γ-Fe), is a metallic, non-magnetic allotrope of iron or a solid solution of iron with an alloying element. [1] In plain-carbon steel , austenite exists above the critical eutectoid temperature of 1000 K (727 °C); other alloys of steel have different eutectoid temperatures.
Upon sublimation at 616 °C, the gas phase arsenic molecules lose this packing arrangement and form small clusters of As 4, As 2, and As, though As 4 is by far the most abundant in this phase. [1] If these vapors are condensed swiftly onto a cold surface (<200 K), solid yellow arsenic (As 4 ) results due to the lack of energy required to form ...