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Revision as of 20:53, 14 May 2011 editLamro (talk | contribs)Autopatrolled, Extended confirmed users84,339 edits {{Rhenium compounds}}← Previous edit		Latest revision as of 18:34, 11 September 2024 edit undoDMacks (talk | contribs)Edit filter managers, Autopatrolled, Administrators187,066 edits acs-link surgery
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	{{chembox		{{Chembox
			| Watchedfields = changed
	| verifiedrevid = 406468085		| verifiedrevid = 429136924
	| ImageFile =		| ImageFile =
	| ImageFile2 = Magnesium-diboride-3D-balls.png		| ImageFile2 = Magnesium-diboride-3D-balls.png
	| IUPACName = Rhenium diboride		| IUPACName = Rhenium diboride
		⚫	|Section1={{Chembox Identifiers
	| OtherNames =
			| CASNo_Ref = {{cascite|correct|??}}
⚫	| Section1 = {{Chembox Identifiers
	| CASNo = 12355-99-6		| CASNo = 12355-99-6
	| PubChem =		| PubChem = 57418167
	| SMILES =		| SMILES = B##B
			| EC_number = 234-959-3
⚫	}}
			| InChI = InChI=1S/2B.Re
⚫	| Section2 = {{Chembox Properties
			| InChIKey = OLXPHXSOQYDZNT-UHFFFAOYSA-N
	| Formula = ReB<sub>2</sub>
		⚫	}}
⚫	| MolarMass = 207.83 g/mol
		⚫	|Section2={{Chembox Properties
⚫	| Appearance = black powder
	| Density = 12.7 g/cm<sup>3</sup>		| Formula = ReB<sub>2</sub>
		⚫	| MolarMass = 207.83 g/mol
	| MeltingPt = 2400 °C <ref>{{cite journal|journal = Soviet powder metallurgy and metal ceramics| volume = 7| page = 112–114 | year =1968}}</ref>
		⚫	| Appearance = black powder
⚫	| BoilingPt =
			| Density = 12.7 g/cm<sup>3</sup>
⚫	| Solubility = none
			| MeltingPtC = 2400
⚫	}}
			| MeltingPt_ref = <ref>{{cite journal|doi=10.1007/BF00775787|title=Forward slip in the rolling of strip from metal powders|year=1968|last1=Gaidar'|first1=L. M.|last2=Zhilkin|first2=V. Z.|journal=Soviet Powder Metallurgy and Metal Ceramics|volume=7|issue=4|page=258|s2cid=135565681}}</ref>
⚫	| Section3 = {{Chembox Structure
		⚫	| BoilingPt =
		⚫	| Solubility = none
		⚫	}}
		⚫	|Section3={{Chembox Structure
	| CrystalStruct = ], Space group P6<sub>3</sub>/mmc.		| CrystalStruct = ], Space group P6<sub>3</sub>/mmc.
	| Coordination =		| Coordination =
	}}		}}
	| Section7 = {{Chembox Hazards		|Section7={{Chembox Hazards
	| MainHazards =		| MainHazards =
	| FlashPt =		| FlashPt =
	| Autoignition =		| AutoignitionPt =
			| GHSPictograms = {{GHS07}}<ref name=sds>{{cite web|title = Rhenium Diboride|url = https://www.americanelements.com/rhenium-diboride-12355-99-6|website = ]|accessdate = 2018-08-02}}</ref>
⚫	}}
			| GHSSignalWord = Warning<ref name=sds />
	| Section7 = {{Chembox Hazards
			| HPhrases = {{H-phrases|315|319|335}}<ref name=sds />
	| MainHazards =
			| PPhrases = {{P-phrases|261|280|305+351+338|304+340|405|501}}<ref name=sds />
	| FlashPt =
		⚫	}}
	| Autoignition =
	}}
	}}		}}
	'''] diboride''' (]]<sub>2</sub>) is a synthetic ]. It was first synthesized in 1962<ref>S. J. La Placa, B. Post "The crystal structure of rhenium diboride" </ref> and re-emerged recently due to hopes of achieving high hardness comparable to that of ].<ref name="Chung">{{cite journal | last = Chung | first = Hsiu-Ying | coauthors = ''et al.'' | date = April 20, 2007 | title = Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure | journal = Science | volume = 316 | issue = 5823 | pages = 436 | doi = 10.1126/science.1139322 | url = http://www.sciencemag.org/cgi/content/abstract/316/5823/436 | pmid = 17446399}}</ref> However, the ultrahigh hardness has not been confirmed.<ref name=comment/>		'''Rhenium diboride''' (ReB<sub>2</sub>) is a synthetic high-] material that was first ] in 1962.<ref>{{cite journal|doi=10.1107/S0365110X62000298|title=The crystal structure of rhenium diboride|year=1962|last1=La Placa|first1=S. J.|last2=Post|first2=B.|journal=Acta Crystallographica|volume=15|issue=2|pages=97|doi-access=free|bibcode=1962AcCry..15...97L }}</ref><ref name=":0">{{Cite journal |last1=Dubrovinskaia |first1=Natalia |last2=Dubrovinsky |first2=Leonid |last3=Solozhenko |first3=Vladimir L. |date=2007-12-07 |title=Comment on "Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure" |url=https://www.science.org/doi/10.1126/science.1147650 |url-status= |format= |journal=Science |language=en |volume=318 |issue=5856 |pages=1550 |bibcode=2007Sci...318.1550D |doi=10.1126/science.1147650 |issn=0036-8075 |oclc=264200699 |pmid=18063772 |s2cid=1640087 |access-date=2024-01-27}}</ref> The compound is formed from a mixture of ], noted for its resistance to high pressure, and ], which forms short, strong ]s with rhenium. It has regained popularity in recent times in hopes of ] that possesses hardness comparable to ].<ref name="Chung">{{cite journal |last1=Chung |first1=Hsiu-Ying |last2=Weinberger |first2=M. B. |last3=Levine |first3=J. B. |last4=Kavner |first4=A. |last5=Yang |first5=J.-M. |last6=Tolbert |first6=S. H. |last7=Kaner |first7=R. B. |last8=Kaner |first8=RB |display-authors=1 |date=April 20, 2007 |title=Synthesis of Ultra-Incompressible Superhard Rhenium Diboride at Ambient Pressure |url=http://www.sciencemag.org/cgi/content/abstract/316/5823/436 |journal=Science |volume=316 |issue=5823 |pages=436–9 |bibcode=2007Sci...316..436C |doi=10.1126/science.1139322 |pmid=17446399 |s2cid=10395879}}</ref>
			Unlike other high-hardness synthetic materials, such as the c-BN, rhenium diboride can be synthesized at ],<ref name=":0" /> potentially simplifying a ]. However, the high cost of rhenium and commercial availability of alternatives such as ] ], make a prospect of large-scale applications less likely.<ref name=":0" />
	The production method of this material does not involve high pressures as with other hard synthetic materials, such as ], which makes production cheap. However, rhenium itself is an expensive metal.
	The compound is formed from a mixture of ], noted for its resistance to high pressure, and ], which forms short, strong ]s with rhenium.
	== Synthesis ==		== Synthesis ==
			]
	ReB<sub>2</sub> can be synthesized by at least three different methods at atmospheric pressure: solid-state ], melting in an ], and direct heating of the elements.<ref name="Chung" />		ReB<sub>2</sub> can be synthesized by at least three different methods at standard atmospheric pressure: solid-state ], melting in an ], and direct heating of the elements.<ref name="Chung" />
	In the metathesis reaction, ] and ] are mixed and heated in an inert atmosphere and the ] byproduct is washed away. Excess boron is needed to prevent formation of other phases such as Re<sub>7</sub>B<sub>3</sub> and Re<sub>3</sub>B.		In the metathesis reaction, ] and ] are mixed and heated in an inert atmosphere and the ] byproduct is washed away. Excess boron is needed to prevent the formation of other phases such as Re<sub>7</sub>B<sub>3</sub> and Re<sub>3</sub>B.
	In the arc-melting method, rhenium and boron powders are mixed and a large electric current (80 ]s) is passed through the mixture, also in an inert atmosphere.		In the arc-melting method, rhenium and boron powders are mixed and a large electric current is passed through the mixture, also in an inert atmosphere.
	In the direct reaction method, the rhenium-boron mixture is sealed in a vacuum and held at a high temperature over a longer period (1000&nbsp;°C for five days).		In the direct reaction method, the rhenium-boron mixture is sealed in a vacuum and held at a high temperature over a longer period (1,000&nbsp;°C for five days).
	At least the last two methods are capable of producing pure ReB<sub>2</sub> without any other phases, as confirmed by ].		At least the last two methods are capable of producing pure ReB<sub>2</sub> without any other phases, as confirmed by ].
	== Properties ==		== Hardness ==
			Rhenium diboride is occasionally, and controversially,<ref name=":0" /><ref name="comment">{{cite journal |last1=Qin |first1=Jiaqian |last2=He |first2=Duanwei |last3=Wang |first3=Jianghua |last4=Fang |first4=Leiming |last5=Lei |first5=Li |last6=Li |first6=Yongjun |last7=Hu |first7=Juan |last8=Kou |first8=Zili |last9=Bi |first9=Yan |year=2008 |title=Is Rhenium Diboride a Superhard Material? |journal=Advanced Materials |volume=20 |issue=24 |pages=4780 |bibcode=2008AdM....20.4780Q |doi=10.1002/adma.200801471 |s2cid=98327405}}</ref> cited as a "]" due to its high hardness level. However, tested in the asymptotic-hardness region, as recommended for hard and superhard materials,<ref name=":0" /> rhenium diboride demonstrates a ] of only 30.1&nbsp;±&nbsp;1.3&nbsp;GPa at 4.9&nbsp;N, well below the generally-accepted threshold of 40&nbsp;GPa or more needed to classify it as "superhard".<ref name=":0" /> Another research has estimated the {{Abbr|H<sub>v</sub>|Hardness, Vickers}} of full-dense ReB<sub>2</sub> at about 22&nbsp;GPa under an applied load of 2.94&nbsp;N,<ref name="comment" /> comparable to that of ], ], ] or ].<ref name="comment" />
	The hardness of ReB<sub>2</sub> exhibits considerable ] because of its hexagonal layered structure (see structure model). Its value (H<sub>V</sub> ~ 22 GPa)<ref name=comment>J. Qin et al. "Is Rhenium Diboride a Superhard Material?" </ref> is much lower than that of diamond and is comparable to that of ], ], ] or ].<ref name=comment>J. Qin et al. "Is Rhenium Diboride a Superhard Material?" Adv. Mater. 20 (2008) 4780</ref>
			Values greater than 40&nbsp;GPa have been observed only in tests with very low loads, which is not a suitable testing method for this type of solids.<ref name=":0" /> In one test, the lowest tested load of 0.49&nbsp;N yielded the ''average'' hardness of 48&nbsp;±&nbsp;5.6 GPa and a ''maximum'' hardness of 55.5&nbsp;GPa, which is comparable to the hardness of ] (c-BN) under an equivalent load.<ref name="Chung" /> Such phenomenon of inverse relationship between the applied load and hardness is known as the ].<ref name="Chung" />
	ReB<sub>2</sub> slowly reacts with water, converting into a hydroxide.
			In recent times, there has been a significant amount of research into improving the hardness and other properties of the ReB<sub>2</sub>. In one study, the hardness for the ReB<sub>2</sub>(R-3m) ] was estimated at 41.7&nbsp;GPa, while for the ReB<sub>2</sub>(P6<sub>3</sub>/mmc) it was placed at c.a. 40.6&nbsp;GPa.<ref>{{Cite journal |last1=Maździarz |first1=Marcin |last2=Mościcki |first2=Tomasz |date=2015-10-12 |title=Structural, mechanical, optical, thermodynamical and phonon properties of stable ReB<sub>2</sub> polymorphs from density functional calculations |url=https://www.sciencedirect.com/science/article/abs/pii/S092583881531389X |format= |journal=Journal of Alloys and Compounds |language=en |publication-date=2016-02-05 |volume=657 |pages=878–888 |doi=10.1016/j.jallcom.2015.10.133 |issn=0925-8388 |oclc=5937517569 |s2cid=138931858 |access-date=2024-01-27}}</ref> In another study, a fully dense ]-{{Abbr|27]|27% by weight}}ReB<sub>2</sub> ceramic composite nanopowder was fabricated by ]. It has exhibited a ] of 50&nbsp;±&nbsp;3&nbsp;GPa under a 49&nbsp;N load in the asymptotic-hardness region and had a 3.2&nbsp;g/cm<sup>3</sup> density, comparable with the hardness and density of the c-BN.<ref>{{Cite journal |last1=Mnatsakanyan |first1=R. |last2=Davtyan |first2=D. |last3=Minasyan |first3=T. |last4=Aydinyan |first4=S. |last5=Hussainova |first5=I. |date=2021-02-15 |title=Superhard B4C-ReB2 composite by SPS of microwave synthesized nanopowders |journal=Materials Letters |volume=285 |pages=129163 |doi=10.1016/j.matlet.2020.129163 |issn=0167-577X |oclc=8885940810 |s2cid=229404472 |doi-access=free}}</ref>
⚫	Two factors contribute to ReB<sub>2</sub>'s high hardness: a high density of ]s, and an abundance of short ]s.<ref name="Chung"/><ref>{{cite journal | title = Electronic, dynamical, and thermal properties of ultra-incompressible superhard rhenium diboride: A combined first-principles and neutron scattering study | author =W. Zhou, H. Wu, and T. Yildirim | url = http://link.aps.org/abstract/PRB/v76/e184113 | doi = 10.1103/PhysRevB.76.184113 | journal = Phys. Rev. B | volume = 76 | issue = 18 | pages = 184113–184119 | year =2007}}</ref> Rhenium has one of the highest valence electron densities of any transition metal (476 electrons/nm<sup>3</sup>, compare to 572 electrons/nm<sup>3</sup> for ] and 705 electrons/nm<sup>3</sup> for diamond<ref name="Cumberland">{{cite journal | last = Cumberland | first = Robert W. | coauthors = ''et al.'' | date = April 27, 2005 | title = Osmium Diboride, An Ultra-Incompressible, Hard Material | journal = Journal of the American Chemical Society | volume = 127 | issue = 20 | pages = 7264 | doi = 10.1021/ja043806y | url = http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2005/127/i20/abs/ja043806y.html | pmid = 15898746}}</ref>). The addition of boron requires only a 5% expansion of the rhenium lattice, because the small boron atoms fill the existing spaces between the rhenium atoms. Furthermore, the ] of rhenium and boron are close enough (1.9 and 2.04 on the ]) that they form covalent bonds in which the electrons are shared almost equally.
		⚫	The hardness of ReB<sub>2</sub> exhibits considerable ] because of its hexagonal layered ], being greatest along the ''c'' axis. Two factors contribute to the high hardness of ReB<sub>2</sub>: a high density of ]s, and an abundance of short ]s.<ref name="Chung"/><ref>{{cite journal | title = Electronic, dynamical, and thermal properties of ultra-incompressible superhard rhenium diboride: A combined first-principles and neutron scattering study |author1=W. Zhou |author2=H. Wu |author3=T. Yildirim |name-list-style=amp | doi = 10.1103/PhysRevB.76.184113 | journal = Phys. Rev. B | volume = 76 | issue = 18 | pages = 184113–184119 | year =2007|arxiv=0708.3694 |bibcode=2007PhRvB..76r4113Z |s2cid=16343415 }}</ref> Rhenium has one of the highest valence electron densities of any transition metal (476 electrons/nm<sup>3</sup>, compare to 572 electrons/nm<sup>3</sup> for ] and 705 electrons/nm<sup>3</sup> for diamond<ref name="Cumberland">{{cite journal | last1 = Cumberland | first1 = Robert W. | date = April 27, 2005 | title = Osmium Diboride, An Ultra-Incompressible, Hard Material | journal = Journal of the American Chemical Society | volume = 127 | issue = 20 | pages = 7264–5 | doi = 10.1021/ja043806y | pmid = 15898746 | display-authors = 1 | last2 = Weinberger | first2 = Michelle B. | last3 = Gilman | first3 = John J. | last4 = Clark | first4 = Simon M. | last5 = Tolbert | first5 = Sarah H. | last6 = Kaner | first6 = Richard B.}}</ref>). The addition of boron requires only a 5% expansion of the rhenium lattice because the small boron atoms fill the existing spaces between the rhenium atoms. Furthermore, the ] of rhenium and boron are close enough (1.9 and 2.04 on the ]) that they form covalent bonds in which the electrons are shared almost equally.
⚫	== References ==
	{{reflist}}
	==See also==		==See also==
	*]		* ]
			* ]
	*]		* ]
		⚫	== References ==
			{{Reflist|2}}
	{{Rhenium compounds}}		{{Rhenium compounds}}
			{{Borides}}
		⚫	]
	]		]
⚫	]
	]		]
			]
	]
	]
	]
	]
	]