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Tongbaite
Tongbaite is a rare mineral that has the chemical formula Cr3C2, or chromium carbide. It was first described in 1983 for an occurrence in Liu village, Tongbai County (桐柏县), Henan Province, China and named for the locality. It occurs in an ultramafic rock deposit. It has also been found in the Tibet Autonomous Region and the Isovsky District, in the Urals of Russia. References

Carbide minerals Chromium minerals Orthorhombic minerals Minerals in space group 62 Minerals described in 1983 {{Mineral-stub ...
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Chromium Carbide
Chromium(II) carbide is a ceramic compound that exists in several chemical compositions: Cr3C2, Cr7C3, and Cr23C6. At standard conditions it exists as a gray solid. It is extremely hard and corrosion resistant. It is also a refractory compound, which means that it retains its strength at high temperatures as well. These properties make it useful as an additive to metal alloys. When chromium carbide crystals are integrated into the surface of a metal it improves the wear resistance and corrosion resistance of the metal, and maintains these properties at elevated temperatures. The hardest and most commonly used composition for this purpose is Cr3C2. The mineral form of the Cr3C2 compound is tongbaite. Isovite, , is a related mineral. Both are extremely rare. Yet another chromium-rich carbide mineral is yarlongite, Cr4Fe4NiC4.Mindat, http://www.mindat.org/min-35899.html Properties There are three different crystal structures for chromium carbide corresponding to the three diff ...
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Orthorhombic
In crystallography, the orthorhombic crystal system is one of the 7 crystal systems. Orthorhombic Lattice (group), lattices result from stretching a cubic crystal system, cubic lattice along two of its orthogonal pairs by two different factors, resulting in a rectangular Prism (geometry), prism with a rectangular Base (geometry), base (''a'' by ''b'') and height (''c''), such that ''a'', ''b'', and ''c'' are distinct. All three bases intersect at 90° angles, so the three lattice vectors remain mutually orthogonal. Bravais lattices There are four orthorhombic Bravais lattices: primitive orthorhombic, base-centered orthorhombic, body-centered orthorhombic, and face-centered orthorhombic. For the base-centered orthorhombic lattice, the primitive cell has the shape of a right rhombic prism;See , row oC, column Primitive, where the cell parameters are given as a1 = a2, α = β = 90° it can be constructed because the two-dimensional centered rectangular base layer can also be descr ...
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Ångström
The angstrom (; ) is a unit of length equal to m; that is, one ten-billionth of a metre, a hundred-millionth of a centimetre, 0.1 nanometre, or 100 picometres. The unit is named after the Swedish physicist Anders Jonas Ångström (1814–1874). It was originally spelled with Swedish letters, as Ångström and later as ångström (). The latter spelling is still listed in some dictionaries, but is now rare in English texts. Some popular US dictionaries list only the spelling ''angstrom''. The unit's symbol is Å, which is a letter of the Swedish alphabet, regardless of how the unit is spelled. However, "A" or "A.U." may be used in less formal contexts or typographically limited media. The angstrom is often used in the natural sciences and technology to express sizes of atoms, molecules, microscopic biological structures, and lengths of chemical bonds, arrangement of atoms in crystals, wavelengths of electromagnetic radiation, and dimensions of integrated circuit part ...
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Tongbai County
Tongbai County () is a county in the south of Henan province, China, bordering Hubei province to the south. The easternmost county-level division of the prefecture-level city of Nanyang, it has an area of and a population of 420,000. Administrative divisions As of 2012, this county is divided to 9 towns and 7 townships. ;Towns ;Townships Climate Transport *China National Highway 312 China National Highway 312 (312国道), also referred to as Route 312, is a key east-west route beginning in Shanghai and ending at Khorgas, Xinjiang in the Ili River valley, on the border with Kazakhstan. In total it spans , passing through Ji ... References {{authority control County-level divisions of Henan Nanyang, Henan ...
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Henan Province
Henan; alternatively Honan is a province in Central China. Henan is home to many heritage sites, including Yinxu, the ruins of the final capital of the Shang dynasty () and the Shaolin Temple. Four of the historical capitals of China, Luoyang, Anyang, Kaifeng and Zhengzhou, are in Henan. While the province's name means 'south of the river', approximately a quarter of the province lies north of the Yellow River. With an area of , Henan covers a large part of the fertile and densely populated North China Plain. Its neighboring provinces are Shaanxi, Shanxi, Hebei, Shandong, Anhui, and Hubei. Henan is China's third-most populous province and the most populous among inland provinces, with a population of over 99 million as of 2020. It is also the world's seventh-most populous administrative division; if it were a country by itself, Henan would be the 17th-most populous in the world, behind Egypt and Vietnam. People from Henan often suffer from regional discrimination. ...
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China
China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after India, representing 17.4% of the world population. China spans the equivalent of five time zones and Borders of China, borders fourteen countries by land across an area of nearly , making it the list of countries and dependencies by area, third-largest country by land area. The country is divided into 33 Province-level divisions of China, province-level divisions: 22 provinces of China, provinces, 5 autonomous regions of China, autonomous regions, 4 direct-administered municipalities of China, municipalities, and 2 semi-autonomous special administrative regions. Beijing is the country's capital, while Shanghai is List of cities in China by population, its most populous city by urban area and largest financial center. Considered one of six ...
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Ultramafic
Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are usually composed of greater than 90% mafic minerals (dark colored, high magnesium and iron content). Earth's mantle is composed of ultramafic rocks. Ultrabasic is a more inclusive term that includes igneous rocks with low silica content that may not be extremely enriched in Fe and Mg, such as carbonatites and ultrapotassic igneous rocks. Intrusive ultramafic rocks Intrusive ultramafic rocks are often found in large, layered ultramafic intrusions where differentiated rock types often occur in layers. Such cumulate rock types do not represent the chemistry of the magma from which they crystallized. The ultramafic intrusives include the dunites, peridotites and pyroxenites. Other rare varieties include troctolite which has a greater pe ...
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Tibet Autonomous Region
The Tibet Autonomous Region (TAR), often shortened to Tibet in English or Xizang in Pinyin, Hanyu Pinyin, is an Autonomous regions of China, autonomous region of the China, People's Republic of China. It was established in 1965 to replace the Tibet Area (administrative division), Tibet Area, a former administrative division of the Republic of China (1912–1949), Republic of China. The current borders of the Tibet Autonomous Region were generally established in the 18th century and include about half of Tibet, cultural Tibet, which was at times independent and at times under Mongol or Chinese rule. The TAR spans more than and is the second-largest Administrative divisions of China, province-level division of China by area. Due to its harsh and rugged terrain, it has a total population of only 3.6 million people or approximately . Names and etymologies Tibet Autonomous Region is often shortened to Tibet in English or Xizang in Hanyu Pinyin. The earliest official record of the ...
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Urals
The Ural Mountains ( ),; , ; , or simply the Urals, are a mountain range in Eurasia that runs north–south mostly through Russia, from the coast of the Arctic Ocean to the river Ural (river), Ural and northwestern Kazakhstan.Ural Mountains
, Encyclopædia Britannica on-line
The mountain range forms part of the Boundaries between the continents of Earth, conventional boundary between the continents of Europe and Asia, marking the separation between European Russia and Siberia. Vaygach Island and the islands of Novaya Zemlya form a further continuation of the chain to the north into the Arctic Ocean. The average altitudes of the Urals are around , the highest point being Mount Narodnaya, which reaches a height of . The mountains lie within the Ural (region), Ural geographical region and significantl ...
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Carbide Minerals
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece. Interstitial / Metallic carbides The carbides of the group 4, 5 and 6 transition metals (with the exception of chromium) are often described as interstitial compounds. These carbides have metallic properties and are refractory. Some exhibit a range of stoichiometries, being a non-stoichiometric mixture of various carbides arising due to crystal defects. Some of them, including titanium carbide and tungsten carbide, are important industrially and are used to coat metals in cutting tools. The long-held view is that the carbon atoms fit into octahedral interstices in a close-packed metal lattice when the metal atom radius is greater than approximately 135 pm: *When the metal atoms are cubic close-packed, (ccp), then filling all of the octahedral interstices with carbon achieves 1:1 stoichi ...
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