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| The first gem-quality stones were always yellow to brown in color because of contamination with [[nitrogen]]. [[Inclusion (mineral)|Inclusions]] were common, especially "plate-like" ones from the nickel. Removing all nitrogen from the process by adding aluminum or [[titanium]] produced colorless "white" stones, and removing the nitrogen and adding [[boron]] produced blue ones.<ref name=burns>{{cite journal|last1=Burns|first1=R. C.|last2=Cvetkovic|first2=V.|last3=Dodge|first3=C. N.|title =Growth-sector dependence of optical features in large synthetic diamonds| doi = 10.1016/0022-0248(90)90126-6 |journal =Journal of Crystal Growth |volume= 104 |year =1990 |pages = 257–279| issue= 2|bibcode = 1990JCrGr.104..257B | last4= Evans | first4=D. J. F. | last5= Rooney | first5= Marie-Line T. | last6= Spear | first6=P. M. | last7=Welbourn | first7=C. M. }}</ref> Removing nitrogen also slowed the growth process and reduced the crystalline quality, so the process was normally run with nitrogen present. | The first gem-quality stones were always yellow to brown in color because of contamination with [[nitrogen]]. [[Inclusion (mineral)|Inclusions]] were common, especially "plate-like" ones from the nickel. Removing all nitrogen from the process by adding aluminum or [[titanium]] produced colorless "white" stones, and removing the nitrogen and adding [[boron]] produced blue ones.<ref name=burns>{{cite journal|last1=Burns|first1=R. C.|last2=Cvetkovic|first2=V.|last3=Dodge|first3=C. N.|title =Growth-sector dependence of optical features in large synthetic diamonds| doi = 10.1016/0022-0248(90)90126-6 |journal =Journal of Crystal Growth |volume= 104 |year =1990 |pages = 257–279| issue= 2|bibcode = 1990JCrGr.104..257B | last4= Evans | first4=D. J. F. | last5= Rooney | first5= Marie-Line T. | last6= Spear | first6=P. M. | last7=Welbourn | first7=C. M. }}</ref> Removing nitrogen also slowed the growth process and reduced the crystalline quality, so the process was normally run with nitrogen present. |
| Although the GE stones and natural diamonds were chemically identical, their physical properties were not the same. The colorless stones produced strong [[fluorescence]] and [[phosphorescence]] under short-wavelength ultraviolet light, but were inert under long-wave UV. Among natural diamonds, only the rarer blue gems exhibit these properties. Unlike natural diamonds, all the GE stones showed strong yellow fluorescence under [[X-ray]]s.<ref>[[#Barnard|Barnard]], p. 166</ref> The [[De Beers]] [https://rockrush.com/ Diamond Research Laboratory has grown] stones of up to {{convert|25|carat|g}} for research purposes. Stable HPHT conditions were kept for six weeks to grow high-quality diamonds of this size. For economic reasons, the growth of most synthetic diamonds is terminated when they reach a mass of {{convert|1|carat|mg}} to {{convert|1.5|carat|mg}}.<ref name=bars /> | Although the GE stones and natural diamonds were chemically identical, their physical properties were not the same. The colorless stones produced strong [[fluorescence]] and [[phosphorescence]] under short-wavelength ultraviolet light, but were inert under long-wave UV. Among natural diamonds, only the rarer blue gems exhibit these properties. Unlike natural diamonds, all the GE stones showed strong yellow fluorescence under [[X-ray]]s.<ref>[[#Barnard|Barnard]], p. 166</ref> The [[De Beers]] Diamond Research Laboratory has grown stones of up to {{convert|25|carat|g}} for research purposes. Stable HPHT conditions were kept for six weeks to grow high-quality diamonds of this size. For economic reasons, the growth of most synthetic diamonds is terminated when they reach a mass of {{convert|1|carat|mg}} to {{convert|1.5|carat|mg}}.<ref name=bars /> |
| In the 1950s, research started in the Soviet Union and the US on the growth of diamond by [[pyrolysis]] of hydrocarbon gases at the relatively low temperature of {{cvt|800|C}}. This low-pressure process is known as [[chemical vapor deposition]] (CVD). William G. Eversole reportedly achieved vapor deposition of diamond over diamond substrate in 1953, but it was not reported until 1962.<ref>[[#Spear|Spear and Dismukes]], pp. 25–26</ref><ref>Eversole, W. G. (April 17, 1962) "Synthesis of diamond" {{US patent|3030188}}</ref> Diamond film deposition was independently reproduced by Angus and coworkers in 1968<ref>{{cite journal| title = Growth of Diamond Seed Crystals by Vapor Deposition| doi = 10.1063/1.1656693 |journal= J. Appl. Phys. |volume= 39 |year =1968|page = 2915| issue = 6| last1 = Angus| first1 = John C.|bibcode = 1968JAP....39.2915A | last2 = Will| first2 = Herbert A.| last3 = Stanko| first3 = Wayne S.}}</ref> and by Deryagin and Fedoseev in 1970.<ref>[[#Spear|Spear and Dismukes]], p. 42</ref><ref>{{cite journal| last1 = Deryagin | first1 = B. V. | last2 = Fedoseev | first2 = D. V. |title = Epitaxial Synthesis of Diamond in the Metastable Region| journal = Russian Chemical Reviews|year =1970|pages = 783–788| doi = 10.1070/RC1970v039n09ABEH002022| volume = 39| issue = 9|bibcode = 1970RuCRv..39..783D | s2cid = 250819894 }}</ref> Whereas Eversole and Angus used large, expensive, single-crystal diamonds as substrates, Deryagin and Fedoseev succeeded in making diamond films on non-diamond materials ([[silicon]] and metals), which led to massive research on inexpensive diamond coatings in the 1980s.<ref>[[#Spear|Spear and Dismukes]], pp. 265–266</ref> | In the 1950s, research started in the Soviet Union and the US on the growth of diamond by [[pyrolysis]] of hydrocarbon gases at the relatively low temperature of {{cvt|800|C}}. This low-pressure process is known as [[chemical vapor deposition]] (CVD). William G. Eversole reportedly achieved vapor deposition of diamond over diamond substrate in 1953, but it was not reported until 1962.<ref>[[#Spear|Spear and Dismukes]], pp. 25–26</ref><ref>Eversole, W. G. (April 17, 1962) "Synthesis of diamond" {{US patent|3030188}}</ref> Diamond film deposition was independently reproduced by Angus and coworkers in 1968<ref>{{cite journal| title = Growth of Diamond Seed Crystals by Vapor Deposition| doi = 10.1063/1.1656693 |journal= J. Appl. Phys. |volume= 39 |year =1968|page = 2915| issue = 6| last1 = Angus| first1 = John C.|bibcode = 1968JAP....39.2915A | last2 = Will| first2 = Herbert A.| last3 = Stanko| first3 = Wayne S.}}</ref> and by Deryagin and Fedoseev in 1970.<ref>[[#Spear|Spear and Dismukes]], p. 42</ref><ref>{{cite journal| last1 = Deryagin | first1 = B. V. | last2 = Fedoseev | first2 = D. V. |title = Epitaxial Synthesis of Diamond in the Metastable Region| journal = Russian Chemical Reviews|year =1970|pages = 783–788| doi = 10.1070/RC1970v039n09ABEH002022| volume = 39| issue = 9|bibcode = 1970RuCRv..39..783D | s2cid = 250819894 }}</ref> Whereas Eversole and Angus used large, expensive, single-crystal diamonds as substrates, Deryagin and Fedoseev succeeded in making diamond films on non-diamond materials ([[silicon]] and metals), which led to massive research on inexpensive diamond coatings in the 1980s.<ref>[[#Spear|Spear and Dismukes]], pp. 265–266</ref> |
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