Americium dioxide

Last updated
Americium dioxide
Americium oxide.png
Names
IUPAC name
Americium(IV) oxide
Identifiers
3D model (JSmol)
ECHA InfoCard 100.031.324 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 234-471-0
PubChem CID
  • InChI=1S/Am.2O/q+4;2*-2 X mark.svgN
    Key: GABXYUQCUHMHDP-UHFFFAOYSA-N X mark.svgN
  • [O--].[O--].[Am+4]
Properties
AmO2
Molar mass 275 g·mol−1
AppearanceBlack 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
4
Related compounds
Other cations
Plutonium(IV) oxide
Curium(IV) oxide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Americium dioxide (AmO2) is a black [2] compound of americium. In the solid state, AmO2 adopts a fluorite structure (like CaF2). [3] It is used as a source of alpha particles.

Contents

Historical context

The demand for americium dioxide stems from the difficulty of storing the element americium as a solution of americium(III) chloride because the alpha radiation and hydrochloric acid decomposes storage containers over time. To solve the liquid storage problem, scientists at Oak 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

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 with ammonium hydroxide (NH
4
OH
). Then, saturated oxalic acid solution (C
2
H
2
O
4
) is added to the now neutralized solution to precipitate dull pink americium(III) oxalate crystals; once complete precipitation is achieved, additional oxalic 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 then calcinated in a platinum 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]

Modern applications

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 to ESA as power source for radioisotope thermoelectric generators (RTGs) for deep space exploration spacecraft and satellites. A fully automated chemical process to produce americium dioxide was developed by nuclear researchers from the University of Bristol to be implemented on the Sellafield nuclear site in Cumbria, UK. It is based on the same principles as the historic production method developed at Oak Ridge National Laboratory. [5]

Americium-aluminium alloys

Americium-aluminium alloys can be formed by melting americium dioxide with aluminium and an additional fluxing agent. [6] The created alloy can undergo neutron irradiation to produce other transuranic nuclides. [7]

Related Research Articles

<span class="mw-page-title-main">Americium</span> Chemical element with atomic number 95 (Am)

Americium is a synthetic chemical element; it has symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element europium and was thus named after the Americas by analogy.

<span class="mw-page-title-main">Berkelium</span> Chemical element with atomic number 97 (Bk)

Berkelium is a synthetic chemical element; it has symbol Bk and atomic number 97. It is a member of the actinide and transuranium element series. It is named after the city of Berkeley, California, the location of the Lawrence Berkeley National Laboratory where it was discovered in December 1949. Berkelium was the fifth transuranium element discovered after neptunium, plutonium, curium and americium.

<span class="mw-page-title-main">Curium</span> Chemical element with atomic number 96 (Cm)

Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium.

<span class="mw-page-title-main">Nitric acid</span> Highly corrosive mineral acid

Nitric acid is an inorganic compound with the formula HNO3. It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into oxides of nitrogen. Most commercially available nitric acid has a concentration of 68% in water. When the solution contains more than 86% HNO3, it is referred to as fuming nitric acid. Depending on the amount of nitrogen dioxide present, fuming nitric acid is further characterized as red fuming nitric acid at concentrations above 86%, or white fuming nitric acid at concentrations above 95%.

<span class="mw-page-title-main">Aqua regia</span> Mixture of nitric acid and hydrochloric acid in a 1:3 molar ratio

Aqua regia is a mixture of nitric acid and hydrochloric acid, optimally in a molar ratio of 1:3. Aqua regia is a fuming liquid. Freshly prepared aqua regia is colorless, but it turns yellow, orange or red within seconds from the formation of nitrosyl chloride and nitrogen dioxide. It was so named by alchemists because it can dissolve noble metals like gold and platinum, though not all metals.

<span class="mw-page-title-main">Radioisotope thermoelectric generator</span> Electrical generator that uses heat from radioactive decay

A radioisotope thermoelectric generator, sometimes referred to as a radioisotope power system (RPS), is a type of nuclear battery that uses an array of thermocouples to convert the heat released by the decay of a suitable radioactive material into electricity by the Seebeck effect. This type of generator has no moving parts and is ideal for deployment in remote and harsh environments for extended periods with no risk of parts wearing out or malfunctioning.

Neodymium(III) chloride or neodymium trichloride is a chemical compound of neodymium and chlorine with the formula NdCl3. This anhydrous compound is a mauve-colored solid that rapidly absorbs water on exposure to air to form a purple-colored hexahydrate, NdCl3·6H2O. Neodymium(III) chloride is produced from minerals monazite and bastnäsite using a complex multistage extraction process. The chloride has several important applications as an intermediate chemical for production of neodymium metal and neodymium-based lasers and optical fibers. Other applications include a catalyst in organic synthesis and in decomposition of waste water contamination, corrosion protection of aluminium and its alloys, and fluorescent labeling of organic molecules (DNA).

<span class="mw-page-title-main">Vanadium(V) oxide</span> Precursor to vanadium alloys and industrial catalyst

Vanadium(V) oxide (vanadia) is the inorganic compound with the formula V2O5. Commonly known as vanadium pentoxide, it is a dark yellow solid, although when freshly precipitated from aqueous solution, its colour is deep orange. Because of its high oxidation state, it is both an amphoteric oxide and an oxidizing agent. From the industrial perspective, it is the most important compound of vanadium, being the principal precursor to alloys of vanadium and is a widely used industrial catalyst.

<span class="mw-page-title-main">Magnesium silicide</span> Chemical compound

Magnesium silicide, Mg2Si, is an inorganic compound consisting of magnesium and silicon. As-grown Mg2Si usually forms black crystals; they are semiconductors with n-type conductivity and have potential applications in thermoelectric generators.

<span class="mw-page-title-main">Plutonium(IV) oxide</span> Chemical compound

Plutonium(IV) oxide, or plutonia, is a chemical compound with the formula PuO2. This high melting-point solid is a principal compound of plutonium. It can vary in color from yellow to olive green, depending on the particle size, temperature and method of production.

A salt metathesis reaction is a chemical process involving the exchange of bonds between two reacting chemical species which results in the creation of products with similar or identical bonding affiliations. This reaction is represented by the general scheme:

<span class="mw-page-title-main">Sodium oxalate</span> Chemical compound

Sodium oxalate, or disodium oxalate, is a chemical compound with the chemical formula Na2C2O4. It is the sodium salt of oxalic acid. It contains sodium cations Na+ and oxalate anions C2O2−4. It is a white, crystalline, odorless solid, that decomposes above 290 °C.

<span class="mw-page-title-main">Curium(III) oxide</span> Chemical compound

Curium(III) oxide is a compound composed of curium and oxygen with the chemical formula Cm2O3. It is a crystalline solid with a unit cell that contains two curium atoms and three oxygen atoms. The simplest synthesis equation involves the reaction of curium(III) metal with O2−: 2 Cm3+ + 3 O2− ---> Cm2O3. Curium trioxide can exist as five polymorphic forms. Two of the forms exist at extremely high temperatures, making it difficult for experimental studies to be done on the formation of their structures. The three other possible forms which curium sesquioxide can take are the body-centered cubic form, the monoclinic form, and the hexagonal form. Curium(III) oxide is either white or light tan in color and, while insoluble in water, is soluble in inorganic and mineral acids. Its synthesis was first recognized in 1955.

<span class="mw-page-title-main">Kipp's apparatus</span> Laboratory device for preparing gases

Kipp's apparatus, also called a Kipp generator, is an apparatus designed for preparation of small volumes of gases. It was invented around 1844 by the Dutch pharmacist Petrus Jacobus Kipp and widely used in chemical laboratories and for demonstrations in schools into the second half of the 20th century.

<span class="mw-page-title-main">Neptunium(IV) oxide</span> Chemical compound

Neptunium(IV) oxide, or neptunium dioxide, is a radioactive, olive green cubic crystalline solid with the formula NpO2. It emits both α- and γ-particles.

<span class="mw-page-title-main">Lead compounds</span> Type of compound

Compounds of lead exist with lead in two main oxidation states: +2 and +4. The former is more common. Inorganic lead(IV) compounds are typically strong oxidants or exist only in highly acidic solutions.

<span class="mw-page-title-main">Magnesium oxalate</span> Magnesium compound

Magnesium oxalate is an organic compound comprising a magnesium cation with a 2+ charge bonded to an oxalate anion. It has the chemical formula MgC2O4. Magnesium oxalate is a white solid that comes in two forms: an anhydrous form and a dihydrate form where two water molecules are complexed with the structure. Both forms are practically insoluble in water and are insoluble in organic solutions.

<span class="mw-page-title-main">Americium(III) hydroxide</span> Chemical compound

Americium(III) hydroxide is a radioactive inorganic compound with the chemical formula Am(OH)3. It consists of one americium atom and three hydroxy groups. It was first discovered in 1944, closely related to the Manhattan Project. However, these results were confidential and were only released to the public in 1945. It was the first isolated sample of an americium compound, and the first americium compound discovered.

Americium compounds are compounds containing the element americium (Am). These compounds can form in the +2, +3, and +4, although the +3 oxidation state is the most common. The +5, +6 and +7 oxidation states have also been reported.

<span class="mw-page-title-main">Terbium(III) oxalate</span> Chemical compound

Terbium(III) oxalate is the oxalate of terbium with the chemical formula Tb2(C2O4)3. Its decahydrate can be obtained by reacting terbium(III) chloride and oxalic acid in an aqueous solution. Its decahydrate gradually loses water when heated and becomes anhydrous. Continued heating obtains terbium(III,IV) oxide. It decomposes in isolation from air to form terbium(III) oxide. The decomposed gas products are carbon monoxide and carbon dioxide. It reacts with hydrochloric acid to obtain H[Tb(C2O4)2]·6H2O.

References

  1. 1 2 Christine Guéneau; Alain Chartier; Paul Fossati; Laurent Van Brutzel; Philippe Martin (2020). "Thermodynamic and Thermophysical Properties of the Actinide Oxides". Comprehensive Nuclear Materials 2nd Ed. 7: 111–154. doi:10.1016/B978-0-12-803581-8.11786-2. ISBN   9780081028667. S2CID   261051636.
  2. Greenwood, Norman N. & Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Pergamon Press. p. 1267. ISBN   978-0750633659. LCCN   97036336. OCLC   1005231772. OL   689297M.
  3. Wells, Alexander Frank (1984). Structural inorganic chemistry. Oxford: Clarendon Press. ISBN   978-0-19-855370-0.
  4. 1 2 3 "Preparation of Americium Dioxide by Thermal Decomposition of Americium Oxalate in Air" (PDF). Oak Ridge National Laboratory. December 1960. Retrieved 2 May 2013.[ permanent dead link ]
  5. Verbelen, Yannick; Megson-Smith, David; Holland, Erin (2020). "Am2RTG: Am2RTG: Fully Autonomous, Rad-Hard Americium Nitrate to Americium Dioxide Conversion Process Flow for Radioisotope Thermoelectric Generators". doi:10.13140/RG.2.2.28490.80320.{{cite journal}}: Cite journal requires |journal= (help)
  6. "Preparation of Americium-Aluminium Alloys". KERNFORSCHUNG GMBH GES FUER. January 1974. Archived from the original on 2013-06-29. Retrieved May 3, 2013.
  7. "Toxicological profile for americium" (PDF). U.S. Department of Health and Human Services. April 2004. Retrieved 15 January 2011.