688:, starts to form, and the support is slowly moved downward, allowing the base of the boule to crystallise, while its cap always remains liquid. The boule is formed in the shape of a tapered cylinder, with a diameter broadening away from the base and eventually remaining more or less constant. With a constant supply of powder and withdrawal of the support, very long cylindrical boules can be obtained. Once removed from the furnace and allowed to cool, the boule is split along its vertical axis to relieve internal pressure, otherwise the crystal will be prone to fracture when the stalk is broken due to a vertical
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between the melted product and support to as small an area as possible. The average commercially produced boule using the process is 13 mm (0.51 in) in diameter and 25 to 50 mm (0.98 to 1.97 in) long, weighing about 125 carats (25.0 g). The process can also be performed with a custom-oriented seed crystal to achieve a specific desired
918:. A Dissertation Submitted to the Graduate Facility of the Louisiana State University and Agricultural and Mechanical College In partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Chemical Engineering: Louisiana State University and Agricultural & Mechanical College.
711:
Crystals produced by the
Verneuil process are chemically and physically equivalent to their naturally occurring counterparts, and strong magnification is usually required to distinguish between the two. A telltale characteristic is the Verneuil crystal is curved growth lines (curved striae) form, as
406:
merchant in 1880. These "Geneva rubies" were dismissed as artificial at the time, but are now believed to be the first rubies produced by flame fusion, predating
Verneuil's work on the process by 20 years. After examining the "Geneva rubies", Verneuil came to the conclusion that it was possible to
695:
When initially outlining the process, Verneuil specified a number of conditions crucial for good results. These include: a flame temperature that is not higher than necessary for fusion; always keeping the melted product in the same part of the oxyhydrogen flame; and reducing the point of contact
415:
By 1910, Verneuil's laboratory had expanded into a 30-furnace production facility, with annual gemstone production by the
Verneuil process having reached 1,000 kg (2,200 lb) in 1907. By 1912, production reached 3,200 kg (7,100 lb), and would go on to reach 200,000 kg
407:
recrystallise finely ground aluminium oxide into a large gemstone. This realisation, along with the availability of the recently developed oxyhydrogen torch and growing demand for synthetic rubies, led him to design the
Verneuil furnace, where finely ground purified alumina and
716:, while the equivalent lines in natural crystals are straight. Another distinguishing feature is the common presence of microscopic gas bubbles formed due to an excess of oxygen in the furnace; imperfections in natural crystals are usually solid impurities.
656:
This starting material is finely powdered, and placed in a container within a
Verneuil furnace, with an opening at the bottom through which the powder can escape when the container is vibrated. While the powder is being released,
451:
The process was designed primarily for the synthesis of rubies, which became the first gemstone to be produced on an industrial scale. However, the
Verneuil process could also be used for the production of other stones, including
669:
occurs, with a flame of at least 2,000 °C (3,630 °F) at its core. As the powder passes through the flame, it melts into small droplets, which fall onto an earthen support rod placed below. The droplets gradually form a
387:, has long been a prime candidate. In the 19th century, significant advances were achieved, with the first ruby formed by melting two smaller rubies together in 1817, and the first microscopic crystals created from alumina (
411:
were melted by a flame of at least 2,000 °C (3,630 °F), and recrystallised on a support below the flame, creating a large crystal. He announced his work in 1902, publishing details outlining the process in 1904.
609:
One of the most crucial factors in successfully crystallising an artificial gemstone is obtaining highly pure starting material, with at least 99.9995% purity. In the case of manufacturing rubies, sapphires or
399:
chemist
Auguste Verneuil collaborated with Frémy on developing the method, but soon went on to independently develop the flame fusion process, which would eventually come to bear his name.
487:
Despite some improvements in the method, the
Verneuil process remains virtually unchanged to this day, while maintaining a leading position in the manufacture of synthetic corundum and
649:
are added, such as chromium oxide for a red ruby, or ferric oxide and titania for a blue sapphire. Other starting materials include titania for producing rutile, or titanyl double
1114:
395:
had devised an effective method for commercial ruby manufacture by using molten baths of alumina, yielding the first gemstone-quality synthetic stones. The
31:
1122:
1180:
213:
503:, where a much higher quality of crystals is required than the Verneuil process can produce. Other alternatives to the process emerged in 1957, when
484:
pioneered the use of the
Verneuil process for creating such star sapphires, until production was discontinued in 1974 owing to overseas competition.
950:
142:
1088:
864:
519:. In 1989 Larry P Kelley of ICT, Inc. also developed a variant of the Czochralski process where natural ruby is used as the 'feed' material.
172:
1185:
894:
826:
661:
is supplied into the furnace, and travels with the powder down a narrow tube. This tube is located within a larger tube, into which
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402:
One of
Verneuil's sources of inspiration for developing his own method was the appearance of synthetic rubies sold by an unknown
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851:. Solid Mechanics and Its Applications. Vol. 221. Springer Science & Business Media. pp. 113–177.
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for producing strontium titanate. Alternatively, small, valueless crystals of the desired product can be used.
199:
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cone on the rod, the tip of which is close enough to the core to remain liquid. It is at that tip that the
508:
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152:
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912:"A Study of the Influences of Bayer Process Impurities on the Crystallization of Alumina Trihydrate"
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and spinel. The principle of the process involves melting a finely powdered substance using an
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371:
A sketch of an early furnace used by Verneuil to synthesise rubies using the Verneuil process.
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428:, founded in 1914. The most notable improvements in the process were made in 1932, by
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through the next 20 years. A large production capability was also established in the
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263:
187:
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432:, who helped establish the capability for producing high-quality sapphires in the
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Depending on the desired colouration of the crystal, small quantities of various
532:
516:
425:
416:(440,000 lb) in 1980 and 250,000 kg (550,000 lb) in 2000, led by
306:
282:
137:
1058:
Scheel, H. J. (April 2000). "Historical aspects of crystal growth technology".
703:
605:
A small ruby boule, still attached to the rod, produced by the Verneuil process
464:
to be used in place of chromium oxide, as well as more elaborate ones, such as
666:
379:
began, there have been attempts to synthetically produce precious stones, and
55:
671:
504:
448:
were in high demand for their military applications such as for timepieces.
665:
is supplied. At the point where the narrow tube opens into the larger one,
472:) was added and the boule was kept in the heat longer, allowing needles of
242:, was the first commercially successful method of manufacturing synthetic
815:
Dobrovinskaya, Elena R.; Lytvynov, Leonid A.; Pishchik, Valerian (2009).
662:
461:
289:. The process is considered to be the founding step of modern industrial
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132:
45:
1021:
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615:
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1123:"Dangerous Curves: A Reexamination of Verneuil Synthetic Corundum"
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the cylindrical boule grows upwards in an environment with a high
702:
646:
600:
592:
396:
366:
457:
380:
255:
1089:"What is the procedure by which synthetic rubies are produced?"
967:
Nassau, K. (October 1969). "'Reconstructed' or 'Geneva' ruby".
842:
Pelleg, Joshua (2016). "Diffusion in Alumina Single Crystals".
618:
impurities is especially undesirable, as it makes the crystal
526:
300:
626:
from which alumina is obtained is most likely by way of the
491:
gemstones. Its most significant setback came in 1917, when
1037:
Levin, I. H. (June 1913). "Synthesis of precious stones".
996:
Harris, D. C. (September 2003). Tustison, Randal W (ed.).
678:
eventually forms. As more droplets fall onto the tip, a
886:
Introduction to Crystal Growth: Principles and Practice
642:) particular attention must be paid to the feedstock.
998:"A peek into the history of sapphire crystal growth"
285:
flame, and crystallising the melted droplets into a
1039:
The Journal of Industrial and Engineering Chemistry
777:"The Chemical News and Journal of Physical Science"
104:
63:
37:
21:
1117:, McGraw-Hill AccessScience, January 2002, Page 2.
293:technology, and remains in wide use to this day.
444:, when European sources were not available, and
818:Sapphire: Material, Manufacturing, Applications
781:Revue Générale des Sciences Pures et Appliquées
499:, which has found numerous applications in the
1121:Hughes, R. W.; Koivula, J. I. (October 2005).
207:
8:
614:, this material is alumina. The presence of
597:A simplified diagram of the Verneuil process
391:) in a laboratory in 1837. By 1877, chemist
16:Manufacturing process of synthetic gemstones
561:. Unsourced material may be challenged and
335:. Unsourced material may be challenged and
783:vol 2, number 1, 15 January 1891]: 96.
214:
200:
18:
923:
821:. Springer Science & Business Media.
581:Learn how and when to remove this message
355:Learn how and when to remove this message
878:
876:
945:
943:
916:LSU Historical Dissertations and Theses
767:
476:to crystallise within it. In 1947, the
797:
786:
775:Verneuil, Auguste (20 February 1891).
254:. It is primarily used to produce the
1004:. Window and Dome Technologies VIII.
630:(the first stage of which introduces
246:, developed in the late 1883 by the
7:
559:adding citations to reliable sources
333:adding citations to reliable sources
173:Shaping processes in crystal growth
925:10.31390/gradschool_disstheses.761
14:
1181:Science and technology in France
951:"Verneuil / Flame-Fusion Method"
779:[translated from the French
531:
305:
29:
953:. Gemstone Buzz. Archived from
143:Fractional crystallization
1:
1080:10.1016/S0022-0248(99)00780-0
989:10.1016/0022-0248(69)90035-9
910:Kelly, James Leslie (1962).
857:10.1007/978-3-319-18437-1_11
746:Laser-heated pedestal growth
698:crystallographic orientation
163:Laser-heated pedestal growth
726:Bridgman–Stockbarger method
634:in order to separate the Al
456:, which required oxides of
153:Hydrothermal synthesis
118:Bridgman–Stockbarger method
1202:
889:. CRC Press. p. 173.
383:, being one of the prized
1186:Methods of crystal growth
1060:Journal of Crystal Growth
969:Journal of Crystal Growth
195:
123:Van Arkel–de Boer process
109:
68:
42:
28:
1102:(5): 6–8. Archived from
148:Fractional freezing
128:Czochralski method
796:Cite journal requires
708:
606:
598:
501:semiconductor industry
372:
105:Methods and technology
1113:R. T. Liddicoat Jr.,
1087:Imel, D. (May 2005).
845:Diffusion in Ceramics
706:
604:
596:
370:
1171:Industrial processes
1109:on October 25, 2005.
957:on 21 November 2008.
555:improve this section
511:, and in 1958, when
509:hydrothermal process
329:improve this section
1072:2000JCrGr.211....1S
1051:10.1021/ie50054a022
1014:2003SPIE.5078....1H
1002:Proceedings of SPIE
981:1969JCrGr...5..338N
883:Bhat, H.L. (2014).
497:Czochralski process
418:Hrand Djevahirdjian
375:Since the study of
97:Single crystal
77:Crystal growth
1151:Chemical processes
1096:The Rock Collector
756:Shelby Gem Factory
751:Micro-pulling-down
736:Float-zone silicon
731:Czochralski method
709:
707:Synthetic Corundum
622:. But because the
607:
599:
478:Linde Air Products
373:
279:strontium titanate
236:Verneuil technique
168:Micro-pulling-down
1166:French inventions
1022:10.1117/12.501428
866:978-3-319-18436-4
741:Kyropoulos method
591:
590:
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468:, where titania (
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364:
357:
272:diamond simulants
270:, as well as the
224:
223:
158:Kyropoulos method
87:Seed crystal
82:Recrystallization
51:Crystal structure
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1125:. Archived from
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232:Verneuil process
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515:introduced the
513:Carroll Chatham
507:introduced the
495:introduced the
493:Jan Czochralski
389:aluminium oxide
361:
350:
344:
341:
326:
310:
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238:), also called
228:Verneuil method
220:
183:Verneuil method
72:Crystallization
23:Crystallization
17:
12:
11:
5:
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1045:(6): 495–500.
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975:(5): 338–344.
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466:star sapphires
420:'s factory in
409:chromium oxide
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628:Bayer process
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571:February 2021
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540:This section
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482:Union Carbide
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454:blue sapphire
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438:United States
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385:cardinal gems
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345:February 2021
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314:This section
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266:varieties of
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1131:. Retrieved
1127:the original
1104:the original
1099:
1095:
1063:
1059:
1042:
1038:
1005:
1001:
972:
968:
955:the original
915:
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885:
844:
837:
817:
810:
789:cite journal
780:
770:
710:
694:
683:
676:seed crystal
655:
644:
632:caustic soda
612:padparadscha
608:
577:
568:
553:Please help
541:
486:
480:division of
450:
442:World War II
434:Soviet Union
414:
401:
393:Edmond Frémy
374:
351:
342:
327:Please help
315:
264:padparadscha
240:flame fusion
239:
235:
231:
227:
225:
188:Zone melting
182:
38:Fundamentals
682:, called a
517:flux method
430:S. K. Popov
426:Switzerland
283:oxyhydrogen
138:Flux method
1156:Mineralogy
1145:Categories
1133:2011-06-22
762:References
667:combustion
56:Nucleation
1030:109528895
934:103735465
542:does not
505:Bell Labs
316:does not
244:gemstones
1176:Crystals
1161:Gemology
1008:: 1–11.
720:See also
663:hydrogen
462:titanium
397:Parisian
268:corundum
260:sapphire
250:chemist
64:Concepts
1068:Bibcode
1010:Bibcode
977:Bibcode
651:oxalate
624:bauxite
563:removed
548:sources
523:Process
440:during
422:Monthey
404:Genevan
377:alchemy
337:removed
322:sources
297:History
133:Epitaxy
46:Crystal
1028:
932:
893:
863:
825:
672:sinter
659:oxygen
647:oxides
620:opaque
616:sodium
489:spinel
474:rutile
446:jewels
275:rutile
248:French
113:Boules
1107:(PDF)
1092:(PDF)
1026:S2CID
930:S2CID
849:(PDF)
685:boule
287:boule
1006:5078
891:ISBN
861:ISBN
823:ISBN
802:help
546:any
544:cite
460:and
458:iron
381:ruby
320:any
318:cite
262:and
256:ruby
230:(or
226:The
1115:Gem
1100:105
1076:doi
1064:211
1047:doi
1018:doi
985:doi
920:doi
853:doi
557:by
331:by
234:or
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1094:.
1074:.
1062:.
1041:.
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