Thorium Oxide Buy

Thoria exists as two polymorphs. One has a fluorite crystal structure. This is uncommon among binary dioxides. (Other binary oxides with fluorite structure include cerium dioxide, uranium dioxide and plutonium dioxide.)[clarification needed] The band gap of thoria is about 6 eV. A tetragonal form of thoria is also known.

thorium oxide buy

Thorium dioxide is more stable than thorium monoxide (ThO).[7] Only with careful control of reaction conditions can oxidation of thorium metal give the monoxide rather than the dioxide. At extremely high temperatures, the dioxide can convert to the monoxide either by a disproportionation reaction (equilibrium with liquid thorium metal) above 1,850 K (1,580 C; 2,870 F) or by simple dissociation (evolution of oxygen) above 2,500 K (2,230 C; 4,040 F).[8]

Thorium dioxide (thoria) can be used in nuclear reactors as ceramic fuel pellets, typically contained in nuclear fuel rods clad with zirconium alloys. Thorium is not fissile (but is "fertile", breeding fissile uranium-233 under neutron bombardment); hence, it must be used as a nuclear reactor fuel in conjunction with fissile isotopes of either uranium or plutonium. This can be achieved by blending thorium with uranium or plutonium, or using it in its pure form in conjunction with separate fuel rods containing uranium or plutonium. Thorium dioxide offers advantages over conventional uranium dioxide fuel pellets, because of its higher thermal conductivity (lower operating temperature), considerably higher melting point, and chemical stability (does not oxidize in the presence of water/oxygen, unlike uranium dioxide).

Thorium dioxide can be turned into a nuclear fuel by breeding it into uranium-233 (see below and refer to the article on thorium for more information on this). The high thermal stability of thorium dioxide allows applications in flame spraying and high-temperature ceramics.

Thorium dioxide is used as a stabilizer in tungsten electrodes in TIG welding, electron tubes, and aircraft gas turbine engines. As an alloy, thoriated tungsten metal is not easily deformed because the high-fusion material thoria augments the high-temperature mechanical properties, and thorium helps stimulate the emission of electrons (thermions). It is the most popular oxide additive because of its low cost, but is being phased out in favor of non-radioactive elements such as cerium, lanthanum and zirconium.

Thorium dioxide has almost no value as a commercial catalyst, but such applications have been well investigated. It is a catalyst in the Ruzicka large ring synthesis. Other applications that have been explored include petroleum cracking, conversion of ammonia to nitric acid and preparation of sulfuric acid.[14]

Thorium dioxide was the primary ingredient in Thorotrast, a once-common radiocontrast agent used for cerebral angiography, however, it causes a rare form of cancer (hepatic angiosarcoma) many years after administration.[15] This use was replaced with injectable iodine or ingestable barium sulfate suspension as standard X-ray contrast agents.

Another major use in the past was in gas mantle of lanterns developed by Carl Auer von Welsbach in 1890, which are composed of 99 percent ThO2 and 1% cerium(IV) oxide. Even as late as the 1980s it was estimated that about half of all ThO2 produced (several hundred tonnes per year) was used for this purpose.[16] Some mantles still use thorium, but yttrium oxide (or sometimes zirconium oxide) is used increasingly as a replacement.

When added to glass, thorium dioxide helps increase its refractive index and decrease dispersion. Such glass finds application in high-quality lenses for cameras and scientific instruments.[17] The radiation from these lenses can darken them and turn them yellow over a period of years and degrade film, but the health risks are minimal.[18] Yellowed lenses may be restored to their original colourless state by lengthy exposure to intense ultraviolet radiation. Thorium dioxide has since been replaced by rare-earth oxides such as lanthanum oxide in almost all modern high-index glasses, as they provide similar effects and are not radioactive.[19]

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Thorium is a naturally occurring radioactive metal that is found in soil, rock, and water. It is formed by the radioactive decay of uranium. Minerals such as monazite, thorite, and thorianite are rich in thorium and may be mined for the metal.

Thorium has coloring properties that have made it useful in ceramic glazes. Thorium also has been widely used in lantern mantles for the brightness it imparts (though alternatives are replacing it), and in welding rods, which burn better with small amounts of added thorium. Until the 1950s, thorium dioxide was used as a contrast agent (called Thorotrast) in medical radiology.

The primary ways people are exposed to thorium are inhalation, intravenous injection, ingestion, and absorption through the skin. More than 2.5 million people worldwide were exposed to thorium in Thorotrast between 1930 and 1950. Once injected, Thorotrast remains in the body, resulting in lifelong exposure to thorium.

Although thorium is widespread in the environment, most people are not exposed to dangerous levels of the metal. However, people who live near thorium-mining areas or facilities that manufacture products with thorium may have increased exposure, especially if their water comes from a private well. Analytical laboratories can test water for thorium content.

Studies of patients who received intravascular injections of Thorotrast found an increased risk of liver tumors among these individuals. And there is research evidence that inhaling thorium dust increases the risk of lung and pancreatic cancer. Individuals exposed to thorium also have an increased risk of bone cancer because thorium may be stored in bone.

Occasionally, household items may be found to contain thorium, such as some older ceramic wares in which uranium was used in the glaze, or gas lantern mantles. Although these exposures generally do not pose serious health risks, such household items should be retired from use to avoid unnecessary exposures. A radiation counter is required to confirm if ceramics contain thorium. 041b061a72