WordNet

a soft silvery-white tetravalent radioactive metallic element; isotope 232 is used as a power source in nuclear reactors; occurs in thorite and in monazite sands (同)Th, atomic number 90
an oxide containing two atoms of oxygen in the molecule

PrepTutorEJDIC

トリウム(金属元素;化学記号は『Th』)
二酸化物

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2014/04/21 04:03:47」(JST)

wiki en

Thorium dioxide (ThO₂), also called thorium(IV) oxide is a crystalline solid, often white or yellow in color. It was formerly known as thoria or thorina. It is produced mainly as a by-product of lanthanide and uranium production.^[1] Thorianite is the name of the mineralogical form of thorium dioxide. It is moderately rare and crystallizes in isometric system. The melting point of thorium oxide is 3300 °C – the highest of all known oxides. Only a few elements (including tungsten and carbon) and a few compounds (including tantalum carbide) have higher melting points.).^[2]

Chemistry

The compound is radioactive due to the radioactivity of thorium. Thorium dioxide can be used as a nuclear fuel. (Refer to the article of thorium for more information on this application.) The high thermal stability of thorium dioxide allows applications in flame spraying and high temperature ceramics. Thorium dioxide was the primary ingredient in the X-ray contrast medium Thorotrast. Use of Thorotrast was abandoned when it was found to be a carcinogen, sometimes causing cholangiocarcinoma. Today, barium sulfate is the standard X-ray contrast agent. Thoria has the fluorite crystal structure. This is uncommon among binary dioxides (other examples include cerium dioxide, hafnium dioxide, uranium dioxide and plutonium dioxide). The band gap of thoria is about 6 eV.

Applications

Thorium dioxide is used as a stabilizer in tungsten electrodes in TIG welding, electron tubes, and aircraft 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.

A major use in the past was in gas mantles of lanterns, which were frequently 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.^[3] Some mantles still use thorium, but yttrium oxide (or sometimes zirconium oxide) is used increasingly as a replacement.

Thorium dioxide was formerly added to glasses during manufacture to increase their refractive index, producing thoriated glass with up to 40% ThO₂ content. These glasses were used in the construction of high-quality photographic lenses. However, the radioactivity of the thorium caused both a safety and pollution hazard and self-degradation of the glass (turning it yellow or brown over time). Lanthanum oxide has replaced thorium dioxide in almost all modern high-index glasses.

Thorium dioxide is a Welsbach material. It has been suggested^[4] that these chemicals could be sprayed into the upper atmosphere to reflect sunlight and thus lower the global temperature.

Thorium dioxide is a catalyst in many chemical reactions, including the Ruzicka large ring synthesis, petroleum cracking, conversion of ammonia to nitric acid and preparation of sulfuric acid.^[5]

Thoria dispersed nickel finds its applications in various high temperature operations like combustion engines because it is a good creep resistant material. It can also be used for hydrogen trapping.^[6]^[7]

References

^ Yamashita, Toshiyuki; Nitani, Noriko; Tsuji, Toshihide; Inagaki, Hironitsu (1997). "Thermal expansions of NpO₂ and some other actinide dioxides". J. Nucl. Mat. 245 (1): 72–78. doi:10.1016/S0022-3115(96)00750-7.
^ Emsley, John (2001). Nature's Building Blocks ((Hardcover, First Edition) ed.). Oxford University Press. p. 441. ISBN 0-19-850340-7.
^ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 1425, 1456. ISBN 0-08-022057-6.
^ Chang, David B; Shih, I-fu "Stratospheric Welsbach seeding for reduction of global warming", US Patent No. 5003186.
^ Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. p. 931. ISBN 0-07-049439-8. Retrieved 2009-06-06.
^ Mitchell, Brian S (2004). An Introduction to Materials Engineering. and Science for Chemical and Materials.. p. 473. ISBN 978-0-471-43623-2.
^ Robertson, Wayne M. (1979). "Measurement and evaluation of hydrogen trapping in thoria dispersed nickel". Metallurgical and Materials Transactions A 10 (4): 489–501. doi:10.1007/BF02697077.

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 原発性骨髄線維症における病態 pathogenetic mechanisms in primary myelofibrosis
2. 悪性肝腫瘍の病理 pathology of malignant liver tumors
3. 悪性胸膜中皮腫の疫学 epidemiology of malignant pleural mesothelioma

English Journal

Radioactive characterization of the main materials involved in the titanium dioxide production process and their environmental radiological impact.

Mantero J, Gazquez MJ, Bolivar JP, Garcia-Tenorio R, Vaca F.SourceGrupo Física Nuclear Aplicada, Departamento Física Aplicada II, Universidad de Sevilla, E.T.S.A., Avenida Reina Mercedes, 241012 Sevilla, Spain.
Journal of environmental radioactivity.J Environ Radioact.2013 Jun;120:26-32. doi: 10.1016/j.jenvrad.2013.01.002. Epub 2013 Feb 12.
A study about the distribution of several radionuclides from the uranium and the thorium series radionuclides along the production process of a typical NORM industry devoted to the production of titanium dioxide has been performed. With this end the activity concentrations in raw materials, final pr
PMID 23416226

Anomalous bulk compression behaviour in a hyperstoichiometric uranium-dioxide-thorium-dioxide solid solution.

Tschauner O, Ma C, Grubor-Urosevic O, Chen YJ.SourceHigh Pressure Science and Engineering Center, UNLV, NV, USA. Department of Geoscience, UNLV, NV, USA. Department of Physics, UNLV, NV, USA.
Journal of physics. Condensed matter : an Institute of Physics journal.J Phys Condens Matter.2013 Mar 18;25(16):162201. [Epub ahead of print]
The compression behaviour of a solid solution of ThO2 and hyperstoichiometric UO2 was examined up to 11 GPa hydrostatic pressure using x-ray diffraction. We observed a distortive phase transition above 3 GPa from fluorite-type to a structure isotypic with t-zirconia. The transition is tentatively
PMID 23503105

Japanese Journal

本当に二酸化炭素は減らすべきか?

藤井義明
Journal of MMIJ : journal of the Mining and Materials Processing Institute of Japan 128(4), 218-223, 2012-03-25
… In order to clarify whether we should reduce anthropogenic carbon dioxide emission or not, interaction between 5 potential problems to survival of human, namely, water shortage, food crises, exhaustion of energy and mineral resources, global warming and population increase were investigated. … Unreasonable reduction of carbon dioxide is harmful to human future and should be stopped. …
NAID 10030516847

The Relationship between Internally Deposited Alpha-particle Radiation and Subsite-specific Liver Cancer and Liver Cirrhosis:an Analysis of Published Data

Sharp Gerald B.
Journal of radiation research 43(4), 371-380, 2002-12
… Chronic exposure to high LET radiation has been shown to cause liver cancer in humans based on studies of patients who received Thorotrast, a colloidal suspension of thorium dioxide formerly used as a radiological contrast agent, and on studies of Russian nuclear weapons workers exposed to internally ingested plutonium. …
NAID 110002334202

Comparison of the Burnup Characteristics and Radiotoxicity Hazards of Rock-like Oxide Fuel with Different Types of Additives

Shelley Afroza,Akie Hiroshi,Takano Hideki [他],SEKIMOTO Hiroshi
Journal of nuclear science and technology 38(2), 134-142, 2001-02-25
NAID 10005148776

Related Pictures

★リンクテーブル★

リンク元	「トロトラスト」「二酸化トリウム」
関連記事	「dioxide」「thorium」

「トロトラスト」

Thorium dioxide
	IUPAC name Thorium dioxide; Thorium(IV) oxide
	Other names thoria; thorium anhydride
Identifiers
CAS number	1314-20-1
PubChem	14808
Jmol-3D images	Image 1
	SMILES O=[Th]=O ;
	InChI InChI=1S/2O.Th ;
Properties
Molecular formula	ThO2
Molar mass	264.04 g/mol
Appearance	white solid
Odor	odorless
Density	10.00 g/cm3
Melting point	3,390 °C (6,130 °F; 3,660 K)
Boiling point	4,400 °C (7,950 °F; 4,670 K)
Solubility in water	insoluble
Solubility	insoluble in alkali; slightly soluble in acid
Refractive index (nD)	2.200 (thorianite)
Structure
Crystal structure	Fluorite (cubic), cF12
Space group	Fm3m, No. 225
Lattice constant	a = 559.74(6) pm
Coordination; geometry	Tetrahedral (O2–); cubic (ThIV)
Thermochemistry
Std molar; entropy So298	65.2(2) J K−1 mol−1
Std enthalpy of; formation ΔfHo298	−1226(4) kJ/mol
Hazards
EU Index	Not listed
Flash point	Non-flammable
LD50	400 mg/kg
Related compounds
Other cations	Hafnium(IV) oxide; Cerium(IV) oxide
Related compounds	Protactinium(IV) oxide; Uranium(IV) oxide
	Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
	(verify) (what is: /?)
	Infobox references

　　[★]

英: thorotrast
関: 二酸化トリウム thorium dioxide、トリウム

二酸化トリウムを主成分とする血管造影剤;現在は使われない
肝腫瘍との関連：胆管細胞癌、血管肉腫、肝細胞癌

「二酸化トリウム」

　　[★]

英: thorium dioxide
関: トロトラスト

「dioxide」

　　[★]

二酸化物、ジオキシド　　

「thorium」

　　[★] トリウム Th 　　

[1] Yamashita, Toshiyuki; Nitani, Noriko; Tsuji, Toshihide; Inagaki, Hironitsu (1997). "Thermal expansions of NpO₂ and some other actinide dioxides". J. Nucl. Mat. 245 (1): 72–78. doi:10.1016/S0022-3115(96)00750-7.

[2] Emsley, John (2001). Nature's Building Blocks ((Hardcover, First Edition) ed.). Oxford University Press. p. 441. ISBN 0-19-850340-7.

[3] Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 1425, 1456. ISBN 0-08-022057-6.

[4] Chang, David B; Shih, I-fu "Stratospheric Welsbach seeding for reduction of global warming", US Patent No. 5003186.

[patnaik-5] Patnaik, Pradyot (2003). Handbook of Inorganic Chemical Compounds. McGraw-Hill. p. 931. ISBN 0-07-049439-8. Retrieved 2009-06-06.

[6] Mitchell, Brian S (2004). An Introduction to Materials Engineering. and Science for Chemical and Materials.. p. 473. ISBN 978-0-471-43623-2.

[7] Robertson, Wayne M. (1979). "Measurement and evaluation of hydrogen trapping in thoria dispersed nickel". Metallurgical and Materials Transactions A 10 (4): 489–501. doi:10.1007/BF02697077.

匿名

検索

案内

案内

thorium dioxide