Uranium trioxide (UO
3), also called
uranyl
The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula . It has a linear structure with short U–O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands may ...
oxide, uranium(VI) oxide, and uranic oxide, is the hexavalent
oxide
An oxide () is a chemical compound that contains at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion of oxygen, an O2– (molecular) ion. with oxygen in the oxidation state of −2. Most of the E ...
of
uranium
Uranium is a chemical element with the symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium is weak ...
. The solid may be obtained by heating
uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
to 400 °C. Its most commonly encountered
polymorph, γ-UO
3, is a yellow-orange powder.
Production and use
There are three methods to generate uranium trioxide. As noted below, two are used industrially in the reprocessing of nuclear fuel and uranium enrichment.
![Uranium-trioxide-formation](https://upload.wikimedia.org/wikipedia/commons/b/b0/Uranium-trioxide-formation.png)
# U
3O
8 can be oxidized at 500 °C with oxygen. Note that above 750 °C even in 5 atm O
2 UO
3 decomposes into U
3O
8.
#
Uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
, UO
2(NO
3)
2·6H
2O can be heated to yield UO
3. This occurs during the
reprocessing of nuclear fuel. Fuel rods are dissolved in
HNO3 to separate
uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
from
plutonium
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibi ...
and the fission products (the
PUREX
PUREX (plutonium uranium reduction extraction) is a chemical method used to purify fuel for nuclear reactors or nuclear weapons. PUREX is the ''de facto'' standard aqueous nuclear reprocessing method for the recovery of uranium and plutonium ...
method). The pure uranyl nitrate is converted to solid UO
3 by heating at 400 °C. After reduction with hydrogen (with other inert gas present) to
uranium dioxide
Uranium dioxide or uranium(IV) oxide (), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear rea ...
, the uranium can be used in new
MOX fuel
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material, usually consisting of plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an al ...
rods.
#
Ammonium diuranate or
sodium diuranate
Sodium diuranate, Na2U2O7·6H2O, is a uranium salt also known as the yellow oxide of uranium. Sodium diuranate is commonly referred to by the initials SDU. Along with ammonium diuranate it was a component in early yellowcakes. The ratio of the tw ...
(Na
2U
2O
7·6H
2O) may be decomposed.
Sodium diuranate
Sodium diuranate, Na2U2O7·6H2O, is a uranium salt also known as the yellow oxide of uranium. Sodium diuranate is commonly referred to by the initials SDU. Along with ammonium diuranate it was a component in early yellowcakes. The ratio of the tw ...
, also known as
yellowcake
Yellowcake (also called urania) is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined but before f ...
, is converted to uranium trioxide in the
enrichment of uranium.
Uranium dioxide
Uranium dioxide or uranium(IV) oxide (), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear rea ...
and
uranium tetrafluoride
Uranium tetrafluoride is the inorganic compound with the formula UF4. It is a green solid with an insignificant vapor pressure and low solubility in water. Uranium in its tetravalent ( uranous) state is important in various technological process ...
are intermediates in the process which ends in
uranium hexafluoride
Uranium hexafluoride (), (sometimes called "hex") is an inorganic compound with the formula UF6. Uranium hexafluoride is a volatile white solid that reacts with water, releasing corrosive hydrofluoric acid. The compound reacts mildly with alumin ...
.
Uranium trioxide is shipped between processing facilities in the form of a gel, most often from
mines to conversion plants. When used for conversion, all uranium oxides are often called
reprocessed uranium
Reprocessed uranium (RepU) is the uranium recovered from nuclear reprocessing, as done commercially in France, the UK and Japan and by nuclear weapons states' military plutonium production programs. This uranium makes up the bulk of the material s ...
(RepU).
Cameco Corporation
Cameco Corporation (formerly Canadian Mining and Energy Corporation) is the world's largest publicly traded uranium company, based in Saskatoon, Saskatchewan, Canada. In 2015, it was the world's second largest uranium producer, accounting for 18 ...
, which operates at the world's largest uranium refinery at
Blind River, Ontario
Blind River is a town situated on the North Channel of Lake Huron in the Algoma District, Ontario, Canada. The town, named after the nearby Blind River, celebrated its centennial in 2006.
History
French explorers discovered the North Channel a ...
, produces high-purity uranium trioxide.
It has been reported that the corrosion of uranium in a silica rich aqueous solution forms
uranium dioxide
Uranium dioxide or uranium(IV) oxide (), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear rea ...
, uranium trioxide, and
coffinite
Coffinite is a uranium-bearing silicate mineral with formula: U(SiO4)1−x(OH)4x.
It occurs as black incrustations, dark to pale-brown in thin section. It has a grayish-black streak. It has a brittle to conchoidal fracture. The hardness of coffini ...
. In pure water,
schoepite
Schoepite, empirical formula (UO2)8O2(OH)12•12(H2O) is a rare alteration product of uraninite in hydrothermal uranium deposits. It may also form directly from ianthinite. The mineral presents as a transparent to translucent yellow, lemon yello ...
(UO
2)
8O
2(OH)
12·12(H
2O) is formed in the first week and then after four months
studtite
Studtite, chemical formula UO2)O2(H2O)2·2(H2O) or UO4·4(H2O), is a secondary uranium mineral containing peroxide formed by the alpha-radiolysis of water during formation. It occurs as pale yellow to white needle-like crystals often in acicular, ...
(UO
2)O
2·4(H
2O) was produced. This alteration of uranium oxide also leads to the formation of
metastudtite
Studtite, chemical formula UO2)O2(H2O)2·2(H2O) or UO4·4(H2O), is a secondary uranium mineral containing peroxide formed by the alpha-radiolysis of water during formation. It occurs as pale yellow to white needle-like crystals often in acicular, ...
,
a more stable uranyl peroxide, often found in the surface of spent nuclear fuel exposed to water. Reports on the corrosion of uranium metal have been published by the
Royal Society
The Royal Society, formally The Royal Society of London for Improving Natural Knowledge, is a learned society and the United Kingdom's national academy of sciences. The society fulfils a number of roles: promoting science and its benefits, re ...
.
Health and safety hazards
Like all hexavalent uranium compounds, UO
3 is hazardous by inhalation, ingestion, and through skin contact. It is a poisonous, slightly radioactive substance, which may cause shortness of breath, coughing, acute arterial lesions, and changes in the chromosomes of
white blood cell
White blood cells, also called leukocytes or leucocytes, are the cell (biology), cells of the immune system that are involved in protecting the body against both infectious disease and foreign invaders. All white blood cells are produced and de ...
s and
gonads
A gonad, sex gland, or reproductive gland is a mixed gland that produces the gametes and sex hormones of an organism. Female reproductive cells are egg cells, and male reproductive cells are sperm. The male gonad, the testicle, produces sperm ...
leading to
congenital malformations
A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can r ...
if inhaled.
[abstract]
/ref> However, once ingested, uranium is mainly toxic for the kidney
The kidneys are two reddish-brown bean-shaped organs found in vertebrates. They are located on the left and right in the retroperitoneal space, and in adult humans are about in length. They receive blood from the paired renal arteries; blood ...
s and may severely affect their function.
Structure
Solid state structure
The only well characterized binary trioxide of any actinide
The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
is UO3, of which several polymorphs are known. Solid UO3 loses O2 on heating to give green-colored U3O8: reports of the decomposition temperature in air vary from 200–650 °C. Heating at 700 °C under H2 gives dark brown uranium dioxide
Uranium dioxide or uranium(IV) oxide (), also known as urania or uranous oxide, is an oxide of uranium, and is a black, radioactive, crystalline powder that naturally occurs in the mineral uraninite. It is used in nuclear fuel rods in nuclear rea ...
(UO2), which is used in MOX
Mixed oxide fuel, commonly referred to as MOX fuel, is nuclear fuel that contains more than one oxide of fissile material, usually consisting of plutonium blended with natural uranium, reprocessed uranium, or depleted uranium. MOX fuel is an al ...
nuclear fuel rods.
Alpha
Beta
Gamma
Delta
High pressure form
There is a high-pressure solid form with U2O2 and U3O3 rings in it.
Hydrates
Uranium Trioxides.jpg, Hydrous and anhydrous forms of UO3
UO3 Anhydrous.jpg, Anhydrous forms of UO3
Several hydrates
In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...
of uranium trioxide are known, e.g., UO3·6H2O.
Bond valence parameters
It is possible by bond valence The bond valence method or mean method (or bond valence sum) (not to be mistaken for the valence bond theory in quantum chemistry) is a popular method in coordination chemistry to estimate the oxidation states of atoms. It is derived from the bond v ...
calculations to estimate how great a contribution a given oxygen atom is making to the assumed valence of uranium. Bond valence calculations use parameters which are estimated after examining a large number of crystal structures of uranium oxides (and related uranium compounds), note that the oxidation states which this method provides are only a guide which assists in the understanding of a crystal structure.
The formula to use is
The sum of the ''s'' values is equal to the oxidation state of the metal centre.
For uranium binding to oxygen, the constants RO and B are tabulated in the table below. For each oxidation state use the parameters from the table shown below.
It is possible to do these calculations on paper or software.
Molecular forms
While uranium trioxide is encountered as a polymeric solid under ambient conditions, some work has been done on the molecular form in the gas phase, in matrix isolations studies, and computationally.
Gas phase
At elevated temperatures gaseous UO3 is in equilibrium with solid U3O8 and molecular oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...
.
::2 U3O8(s) + O2(g) 6 UO3(g)
With increasing temperature the equilibrium is shifted to the right. This system has been studied at temperatures between 900 °C and 2500 °C. The vapor pressure of monomeric UO3 in equilibrium with air and solid U3O8 at ambient pressure, about 10−5 mbar (1 mPa) at 980 °C, rising to 0.1 mbar (10 Pa) at 1400 °C, 0.34 mbar (34 Pa) at 2100 °C, 1.9 mbar (193 Pa) at 2300 °C, and 8.1 mbar (809 Pa) at 2500 °C.
Matrix isolation
Infrared spectroscopy of molecular UO3 isolated in an argon matrix indicates a T-shaped structure (point group
In geometry, a point group is a mathematical group of symmetry operations (isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every p ...
''C2v'') for the molecule. This is in contrast to the commonly encountered ''D3h'' molecular symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain m ...
exhibited by most trioxides. From the force constants the authors deduct the U-O bond lengths to be between 1.76 and 1.79 Ã… (176 to 179 pm).
Computational study
Calculations predict that the point group of molecular UO3 is ''C2v'', with an axial bond length of 1.75 Å, an equatorial bond length of 1.83 Å and an angle of 161° between the axial oxygens. The more symmetrical ''D3h'' species is a saddle point, 49 kJ/mol above the ''C2v'' minimum. The authors invoke a second-order Jahn–Teller effect
The Jahn–Teller effect (JT effect or JTE) is an important mechanism of spontaneous symmetry breaking in molecular and solid-state systems which has far-reaching consequences in different fields, and is responsible for a variety of phenomena in sp ...
as explanation.
Cubic form of uranium trioxide
The crystal structure of a uranium trioxide phase of composition UO2·82 has been determined by X-ray powder diffraction techniques using a Guinier-type focusing camera. The unit cell is cubic with a = 4·138 ± 0·005 kX. A uranium atom is located at (000) and oxygens at (View the MathML source), (View the MathML source), and (View the MathML source) with some anion vacancies. The compound is isostructural with ReO3. The U-O bond distance of 2·073 Å agrees with that predicted by Zachariasen for a bond strength S = 1.
Reactivity
Uranium trioxide reacts at 400 °C with freon-12 to form chlorine
Chlorine is a chemical element with the Symbol (chemistry), symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate betwee ...
, phosgene
Phosgene is the organic chemical compound with the formula COCl2. It is a toxic, colorless gas; in low concentrations, its musty odor resembles that of freshly cut hay or grass. Phosgene is a valued and important industrial building block, espe ...
, carbon dioxide
Carbon dioxide (chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is transpar ...
and uranium tetrafluoride
Uranium tetrafluoride is the inorganic compound with the formula UF4. It is a green solid with an insignificant vapor pressure and low solubility in water. Uranium in its tetravalent ( uranous) state is important in various technological process ...
. The freon-12 can be replaced with freon-11 which forms carbon tetrachloride
Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVAC ...
instead of carbon dioxide. This is a case of a hard perhalogenated freon
Freon ( ) is a registered trademark of the Chemours Company and generic descriptor for a number of halocarbon products. They are stable, nonflammable, low toxicity gases or liquids which have generally been used as refrigerants and as aerosol prop ...
which is normally considered to be inert being converted chemically at a moderate temperature.
:2 CF2Cl2 + UO3 → UF4 + CO2 + COCl2 + Cl2
:4 CFCl3 + UO3 → UF4 + 3 COCl2 + CCl4 + Cl2
Uranium trioxide can be dissolved in a mixture of tributyl phosphate
Tributyl phosphate, known commonly as TBP, is an organophosphorus compound with the chemical formula (CH3CH2CH2CH2O)3PO. This colourless, odorless liquid finds some applications as an extractant and a plasticizer. It is an ester of phosphoric ac ...
and thenoyltrifluoroacetone
Thenoyltrifluoroacetone, C8H5F3O2S, is a chemical compound used pharmacology, pharmacologically as a chelating agent. It is an inhibitor of cellular respiration by blocking the respiratory chain at complex II.
Perhaps the first report of TTFA as ...
in supercritical carbon dioxide, ultrasound was employed during the dissolution.
Electrochemical modification
The reversible insertion of magnesium
Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ta ...
cations into the lattice
Lattice may refer to:
Arts and design
* Latticework, an ornamental criss-crossed framework, an arrangement of crossing laths or other thin strips of material
* Lattice (music), an organized grid model of pitch ratios
* Lattice (pastry), an orna ...
of uranium trioxide by cyclic voltammetry
Cyclic voltammetry (CV) is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment, the working electrode potential is ramped linearly versus time. Unlike in linear sweep voltammetry, after the set potential is r ...
using a graphite
Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...
electrode modified with microscopic particles of the uranium oxide has been investigated. This experiment has also been done for U3O8. This is an example of electrochemistry
Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...
of a solid modified electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials de ...
, the experiment which used for uranium trioxide is related to a carbon paste electrode A carbon-paste electrode (CPE) is made from a mixture of conducting graphite powder and a pasting liquid. These electrodes are simple to make and offer an easily renewable surface for electron exchange. Carbon paste electrodes belong to a special ...
experiment. It is also possible to reduce uranium trioxide with sodium
Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable iso ...
metal to form sodium uranium oxides.
It has been the case that it is possible to insert lithium
Lithium (from el, λίθος, lithos, lit=stone) is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid el ...
into the uranium trioxide lattice by electrochemical means, this is similar to the way that some rechargeable
A rechargeable battery, storage battery, or secondary cell (formally a type of energy accumulator), is a type of electrical battery which can be charged, discharged into a load, and recharged many times, as opposed to a disposable or prim ...
lithium ion batteries
A lithium-ion or Li-ion battery is a type of rechargeable battery which uses the reversible reduction of lithium ions to store energy. It is the predominant battery type used in portable consumer electronics and electric vehicles. It also sees ...
work. In these rechargeable cells one of the electrodes is a metal oxide which contains a metal such as cobalt
Cobalt is a chemical element with the symbol Co and atomic number 27. As with nickel, cobalt is found in the Earth's crust only in a chemically combined form, save for small deposits found in alloys of natural meteoric iron. The free element, pr ...
which can be reduced, to maintain the electroneutrality for each electron which is added to the electrode material a lithium ion enters the lattice of this oxide electrode.
Amphoterism and reactivity to form related uranium(VI) anions and cations
Uranium oxide is amphoteric
In chemistry, an amphoteric compound () is a molecule or ion that can react both as an acid and as a base. What exactly this can mean depends on which definitions of acids and bases are being used.
One type of amphoteric species are amphiproti ...
and reacts as acid
In computer science, ACID ( atomicity, consistency, isolation, durability) is a set of properties of database transactions intended to guarantee data validity despite errors, power failures, and other mishaps. In the context of databases, a sequ ...
and as a base, depending on the conditions.
;As an acid:
:UO3 + H2O → + 2 H+
Dissolving uranium oxide in a strong base like sodium hydroxide
Sodium hydroxide, also known as lye and caustic soda, is an inorganic compound with the formula NaOH. It is a white solid ionic compound consisting of sodium cations and hydroxide anions .
Sodium hydroxide is a highly caustic base and alkali ...
forms the doubly negatively charged uranate
A uranate is a ternary oxide involving the element uranium in one of the oxidation states 4, 5 or 6. A typical chemical formula is MxUyOz, where M represents a cation. The uranium atom in uranates(VI) has two short collinear U–O bonds and eithe ...
anion
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
(). Uranates tend to concatenate, forming diuranate, , or other poly-uranates.
Important diuranates include ammonium diuranate ((NH4)2U2O7), sodium diuranate
Sodium diuranate, Na2U2O7·6H2O, is a uranium salt also known as the yellow oxide of uranium. Sodium diuranate is commonly referred to by the initials SDU. Along with ammonium diuranate it was a component in early yellowcakes. The ratio of the tw ...
(Na2U2O7) and
magnesium diuranate (MgU2O7), which forms part of some yellowcake
Yellowcake (also called urania) is a type of uranium concentrate powder obtained from leach solutions, in an intermediate step in the processing of uranium ores. It is a step in the processing of uranium after it has been mined but before f ...
s. It is worth noting that uranates of the form M2UO4 do ''not'' contain ions, but rather flattened UO6 octahedra, containing a uranyl group and bridging oxygens.
;As a base:
:UO3 + H2O → + 2 OH−
Dissolving uranium oxide in a strong acid like sulfuric or nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
forms the double positive charged uranyl
The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula . It has a linear structure with short U–O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands may ...
cation
An ion () is an atom or molecule with a net electrical charge.
The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...
. The uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
formed (UO2(NO3)2·6H2O) is soluble in ether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be c ...
s, alcohols
In chemistry, an alcohol is a type of organic compound that carries at least one hydroxyl () functional group bound to a saturated carbon atom. The term ''alcohol'' originally referred to the primary alcohol ethanol (ethyl alcohol), which is ...
, ketone
In organic chemistry, a ketone is a functional group with the structure R–C(=O)–R', where R and R' can be a variety of carbon-containing substituents. Ketones contain a carbonyl group –C(=O)– (which contains a carbon-oxygen double bo ...
s and ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides ar ...
s; for example, tributylphosphate. This solubility is used to separate uranium from other elements in nuclear reprocessing
Nuclear reprocessing is the chemical separation of fission products and actinides from spent nuclear fuel. Originally, reprocessing was used solely to extract plutonium for producing nuclear weapons. With commercialization of nuclear power, the ...
, which begins with the dissolution of nuclear fuel rods in nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
. The uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
is then converted to uranium trioxide by heating.
From nitric acid
Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...
one obtains uranyl nitrate
Uranyl nitrate is a water-soluble yellow uranium salt with the formula . The hexa-, tri-, and dihydrates are known. The compound is mainly of interest because it is an intermediate in the preparation of nuclear fuels.
Uranyl nitrate can be prepa ...
, ''trans''-UO2(NO3)2·2H2O, consisting of eight-coordinated uranium with two bidentate nitrato ligands and two water ligands as well as the familiar O=U=O core.
Uranium oxides in ceramics
UO3-based ceramics become green or black when fired in a reducing atmosphere and yellow to orange when fired with oxygen. Orange-coloured Fiestaware
Fiesta is a line of ceramic glazed dinnerware manufactured and marketed by the Fiesta Tableware Company of Newell, West Virginia since its introduction in 1936, with a hiatus from 1973 to 1985. Fiesta is noted for its Art Deco styling and its ra ...
is a well-known example of a product with a uranium-based glaze. UO3-has also been used in formulations of enamel, uranium glass
Uranium glass is glass which has had uranium, usually in oxide diuranate form, added to a glass mix before melting for colouration. The proportion usually varies from trace levels to about 2% uranium by weight, although some 20th-century piec ...
, and porcelain
Porcelain () is a ceramic material made by heating substances, generally including materials such as kaolinite, in a kiln to temperatures between . The strength and translucence of porcelain, relative to other types of pottery, arises mainl ...
.
Prior to 1960, UO3 was used as an agent of crystallization in crystalline coloured glazes. It is possible to determine with a Geiger counter
A Geiger counter (also known as a Geiger–Müller counter) is an electronic instrument used for detecting and measuring ionizing radiation. It is widely used in applications such as radiation dosimetry, radiological protection, experimental ph ...
if a glaze or glass was made from UO3.
References
{{Oxides
Uranium(VI) compounds
Oxides
Amphoteric compounds