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Crystal structure of CH 3 NH 3 PbX 3 perovskites (X=I, Br and/or Cl). The methylammonium cation (CH 3 NH 3 +) is surrounded by PbX 6 octahedra. [13]The name "perovskite solar cell" is derived from the ABX 3 crystal structure of the absorber materials, referred to as perovskite structure, where A and B are cations and X is an anion.
Naturally occurring vanadium is composed of one stable isotope, 51 V, and one radioactive isotope, 50 V. The latter has a half-life of 2.71×10 17 years and a natural abundance of 0.25%. 51 V has a nuclear spin of 7 ⁄ 2 , which is useful for NMR spectroscopy . [ 25 ]
Its melting point of 180.50 °C (453.65 K; 356.90 °F) [13] and its boiling point of 1,342 °C (1,615 K; 2,448 °F) [13] are each the highest of all the alkali metals while its density of 0.534 g/cm 3 is the lowest. Lithium has a very low density (0.534 g/cm 3), comparable with pine wood. [14]
Graphene (/ ˈ ɡ r æ f iː n /) [1] is a carbon allotrope consisting of a single layer of atoms arranged in a honeycomb planar nanostructure. [2] [3] The name "graphene" is derived from "graphite" and the suffix -ene, indicating the presence of double bonds within the carbon structure.
Weak oxidation of molybdenum starts at 300 °C (572 °F); bulk oxidation occurs at temperatures above 600 °C, resulting in molybdenum trioxide. Like many heavier transition metals, molybdenum shows little inclination to form a cation in aqueous solution, although the Mo 3+ cation is known to form under carefully controlled conditions.
A pipe one inch in diameter and two feet long can transfer 3.7 kW (13,000 BTU/h) at 1,800 °F (980 °C) with only 18 °F (10 °C) drop from end to end. [14] Some heat pipes have demonstrated a heat flux of more than 23 kW/cm 2 , about four times the heat flux through the surface of the Sun. [ 15 ]