| 词条 | Anatase |
| 释义 |
| name = Anatase | category = Oxide minerals | boxwidth = | boxbgcolor = | image = Anatase Oisans.jpg | alt = | caption = | formula = TiO2 | molweight = 79.88 g/mol | strunz = 4.DD.05 | system = Tetragonal | class = Ditetragonal dipyramidal (4/mmm) H-M symbol: (4/m 2/m 2/m) | symmetry = I41/amd | unit cell = a = 3.7845, c = 9.5143 [Å]; Z = 4 | color = Black, reddish to yellowish brown, dark blue, gray | habit = Pyramidal (crystals are shaped like pyramids), tabular (form dimensions are thin in one direction). | twinning = Rare on {112} | cleavage = Perfect on [001] and [011] | fracture = Subconchoidal | tenacity = Brittle | mohs = 5.5–6 | luster = Adamantine to splendent, metallic | refractive = nω = 2.561, nε = 2.488 | opticalprop = Uniaxial (-), anomalously biaxial in deeply colored crystals | birefringence = δ = 0.073 | pleochroism = Weak | streak = pale yellowish white | gravity = 3.79–3.97 | melt = | fusibility = | diagnostic = | solubility = | diaphaneity = Transparent to nearly opaque | other = | references = [1][2][3] }} Anatase is a mineral form of titanium dioxide (TiO2). The mineral is almost always encountered as a black solid, although the pure material is colorless or white. Two other mineral forms of TiO2 are known, brookite and rutile. Anatase is always found as small, isolated and sharply developed crystals, and like rutile, a more commonly occurring modification of titanium dioxide, it crystallizes in the tetragonal system; but, although the degree of symmetry is the same for both, there is no relation between the interfacial angles of the two minerals, except in the prism-zone of 45° and 90°. The common pyramid of anatase, parallel to the faces of which there are perfect cleavages, has an angle over the polar edge of 82°9', the corresponding angle of rutile being 56°52½'. It was on account of this steeper pyramid of anatase that the mineral was named, by René Just Haüy in 1801, from the Greek anatasis, "extension", the vertical axis of the crystals being longer than in rutile. There are also important differences between the physical characters of anatase and rutile: the former is less hard (5.5–6 vs. 6–6.5 Mohs) and dense (specific gravity about 3.9 vs. 4.2). Also, anatase is optically negative whereas rutile is positive, and its luster is even more strongly adamantine or metallic-adamantine than that of rutile.[4] Crystal habitTwo growth habits of anatase crystals may be distinguished. The more common occurs as simple acute double pyramids with an indigo-blue to black color and steely luster. Crystals of this kind are abundant at Le Bourg-d'Oisans in Dauphiné, where they are associated with rock-crystal, feldspar, and axinite in crevices in granite and mica-schist. Similar crystals, but of microscopic size, are widely distributed in sedimentary rocks, such as sandstones, clays, and slates, from which they may be separated by washing away the lighter constituents of the powdered rock.[4] The (101) plane of anatase is the most thermodynamically stable surface and is thus the most widely exposed facet in natural and synthetic anatase.[5] Crystals of the second type have numerous pyramidal faces developed, and they are usually flatter or sometimes prismatic in habit; the color is honey-yellow to brown. Such crystals closely resemble xenotime in appearance and, indeed, were for a long time supposed to belong to this species, the special name wiserine being applied to them. They occur attached to the walls of crevices in the gneisses of the Alps, the Binnenthal near Brig in canton Valais, Switzerland, being a well-known locality. Naturally occurring pseudomorphs of rutile after anatase are also known.[4] While anatase is not an equilibrium phase of TiO2, it is stable near room temperature. At temperatures between 550 and about 1000 °C, anatase converts to rutile. The temperature of this transformation strongly depends on the impurities or dopants as well as on the morphology of the sample.[6] Synthetic anataseDue to its potential application as a semiconductor, anatase is often prepared synthetically. Crystalline anatase can be prepared in laboratories by chemical methods such as sol-gel method. Examples include controlled hydrolysis of titanium tetrachloride (TiCl4) or titanium ethoxide. Often dopants are included in such synthesis processes to control the morphology, electronic structure, and surface chemistry of anatase.[7] Alternate and obsolete namesAnother name commonly in use for this mineral is octahedrite, a name which, indeed, is earlier than anatase, and given because of the common (acute) octahedral habit of the crystals. Other names, now obsolete, are oisanite and dauphinite, from the well-known French locality.[4] See also{{commons category|Anatase}}
References1. ^Anatase, Handbook of Mineralogy {{Titanium minerals}}2. ^Anatase, Mindat.org 3. ^{{cite web| url = http://webmineral.com/data/Anatase.shtml| title = Anatase| accessdate = 2009-06-06| publisher = Webminerals}} 4. ^1 2 3 {{EB1911|inline=y|wstitle=Anatase|volume=1|pages=919–920|first=Leonard James|last=Spencer|authorlink=Leonard James Spencer}} 5. ^{{cite journal |last1= Assadi | first1=MHN | last2=Hanaor | first2 = DAH | title= The effects of copper doping on photocatalytic activity at (101) planes of anatase TiO 2: A theoretical study| url=https://www.researchgate.net/publication/304714130 |journal= Applied Surface Science | volume= 387| pages=682–689|year=2016 | doi=10.1016/j.apsusc.2016.06.178| arxiv=1811.09157 }} 6. ^{{cite journal| last1=Hanaor| first1=Dorian A. H.| last2=Sorrell| first2=Charles C.| title= Review of the anatase to rutile phase transformation| journal= Journal of Materials Science| year=2011| volume=46| issue=4| pages=855–874| doi=10.1007/s10853-010-5113-0| url=https://link.springer.com/content/pdf/10.1007%2Fs10853-010-5113-0.pdf}} 7. ^{{cite journal |last1=Jeantelot |first1=Gabriel |last2=Ould-Chikh |first2=Samy |last3=Sofack-Kreutzer |first3=Julien |last4=Abou-Hamad |first4=Edy |last5=Anjum |first5=Dalaver H. |last6=Lopatin |first6=Sergei |last7=Harb |first7=Moussab |last8=Cavallo |first8=Luigi |last9=Basset |first9=Jean-Marie |title=Morphology control of anatase TiO2 for well-defined surface chemistry |journal=Physical Chemistry Chemical Physics |date=2018 |volume=20 |issue=21 |pages=14362–14373 |doi=10.1039/C8CP01983E |pmid=29767182 }} 3 : Titanium minerals|Oxide minerals|Tetragonal minerals |
| 随便看 |
|
开放百科全书收录14589846条英语、德语、日语等多语种百科知识，基本涵盖了大多数领域的百科知识，是一部内容自由、开放的电子版国际百科全书。