 | |
| Names | |
|---|---|
| IUPAC name Americium(IV) oxide | |
| Identifiers | |
3D model (JSmol) | |
| ChemSpider | |
| ECHA InfoCard | 100.031.324 |
| EC Number |
|
| |
| |
| Properties | |
| AmO2 | |
| Molar mass | 275 g·mol−1 |
| Appearance | Black crystals |
| Density | 11.68 g/cm3 |
| Melting point | 2,113 °C (3,835 °F; 2,386 K)[1] |
| Structure[1] | |
| Fluorite (cubic),cF12 | |
| Fm3m, No. 225 | |
a = 537.6 pm | |
Formula units (Z) | 4 |
| Related compounds | |
Othercations | Plutonium(IV) oxide Curium(IV) oxide |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Americium dioxide (AmO2) is a black[2] compound ofamericium. In the solid state, AmO2 adopts afluorite structure (likeCaF2).[3] It is used as a source ofalpha particles.
The demand for americium dioxide stems from the difficulty of storing the element americium as a solution ofamericium(III) chloride because the alpha radiation andhydrochloric acid decomposes storage containers over time. To solve the liquid storage problem, scientists atOak Ridge National Laboratory devised a synthesis to turn liquid americium–acid solution into a precipitated form of americium for safer handling and more efficient storage.[4]
Synthesis of americium dioxide, as described by the Oak Ridge National Laboratory in 1960, starts by dissolving americium in hydrochloric acid, and then neutralizing the excess acid withammonium hydroxide (NH
4OH). Then, saturatedoxalic acid solution (C
2H
2O
4) is added to the now neutralized solution to precipitate dull pink americium(III)oxalate crystals; once complete precipitation is achieved, additionaloxalic acid is added to make a slurry. The slurry of americium oxalate and oxalic acid is next agitated before the americium oxalate is filtered out, washed with water, and partially dried in air.[4]
The americium oxalate is thencalcinated in aplatinum boat. It is first dried in a furnace at 150 °C (302 °F) and then heated to 350 °C (662 °F). When decomposition begins to occur, the oxalate will turn into the desired black americium dioxide; to ensure no oxalate remains in the newly forming dioxide, the oven temperature is increased and held at 800 °C (1,470 °F) then slowly allowed to cool to room temperature.[4]
Americium dioxide is the most widely used americium compound in ionising smoke detectors. The dioxide form is insoluble in water, making it relatively safe to handle in production.
In the late 2010s, americium dioxide has been of interest toESA as power source forradioisotope thermoelectric generators (RTGs) fordeep space exploration spacecraft andsatellites. A fully automatedchemical process to produce americium dioxide was developed by nuclear researchers from theUniversity of Bristol to be implemented on theSellafield nuclear site inCumbria,UK. It is based on the same principles as the historic production method developed at Oak Ridge National Laboratory.[5]
Americium-aluminium alloys can be formed by melting americium dioxide with aluminium and an additionalfluxing agent.[6] The created alloy can undergo neutron irradiation to produce othertransuranicnuclides.[7]
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