Verneuil process

Because of the small volume of liquid phase, the Verneuil process is predestined to the growth of graded materials. The development of the flux-Verneuil technique [4] enables the variation of the material support to the growing crystal. In this way, a specific influence on the stoichiometry of the liquid phase is possible. 

Briefly describe how ruby could be produced by the Czochralski (Cz) process. Under what situations, if any, would it be preferable to use the Cz process rather than the Verneuil process for ruby growth ... 

Description. Sapphire occurs in a wide range of colors such as blue, pink, padparadscha orange, yellow, green, purple, black. Color is due to trace impurities of FeG Fe , Ti, and yellow color centers. The most expensive color is an intense cornflower blue these are sometimes referred to as Kashmir sapphires having a highly saturated, slightly milky, violet blue color. Padparadscha is next in value, followed by pink, then orange, purple and yellow, respectively. Nowadays 400-500 tonnes of synthetic sapphire are produced by the Verneuil process each year. 

Boule. A fused mass of material, pear-shaped, particularly as produced by the VERNEUIL PROCESS (q.v.). Sapphire... 

Sapphire. Single-crystal alumina sapphire boules can be made by the VERNEUiL PROCESS (q.v.) and find use as bearings and thread guides. 

Verneuil Process. A method for the production of ceramic boules (q.v.) by feeding powdered material, e.g. AI2O3, into an oxy-hydrogen flame. (A. Verneuil, Ann. Chim. Phys., 3, 20,1904.) Versatran. A programmable machine for positioning, transfer and handling or objects, suitable for bricks. (Licensed from the American Machine Foundry Co). 

Single crystals of pure and doped alumina can be grown using well-established techniques such as flame fusion (Verneuil process), Czochralski crystal puUing, and top-seeded solution growth (TSSG), as well as under hydrothermal conditions and from the vapor phase (Franke et al., 1968). Some of these applications will be... 

Other temperature measurements in the Verneuil process have been reported by Ikornikova and Popova [18] and by Khambatta et al. [20]. 

Verneuil et al. (Verneuil, V.S., P. Yan, and F. Madron, Banish Bad Plant Data, Chemical Engineering Progress, October 1992, 45-51) emphasize the importance of proper model development. Systematic errors result not only from the measurements but also from the model used to analyze the measurements. Advanced methods of measurement processing will not substitute for accurate measurements. If highly nonlinear models (e.g., Cropley s kinetic model or typical distillation models) are used to analyze unit measurements and estimate parameters, the Hkelihood for arriving at erroneous models increases. Consequently, resultant models should be treated as approximations. 

Verneuil A process for growing single crystals of refractory compounds. The powdered material is dropped through an oxy-hydrogen flame and the product, consisting of microscopic molten droplets, is collected on a seed crystal. As the liquid mass reaches a cooler zone, it crystallizes in the form of a single crystal, known as a boule. Invented by A.V.L. Verneuil at the Museum of Natural History, Paris, who made synthetic rubies and sapphires in this way. 

Leibovici, C.F, VS. Verneuil, Jr., and P. Yang, Improve Prediction with Data Reconciliation, Hydrocarbon Processing, October 1993, 79-80. 

August Verneuil develops a process for making synthetic rubies... 

Brannock, N.F., V.S. Verneuil, and Y.L. Wang, PROCESS Simulation Program—A Comprehensive Flowsheeting Tool for Chemical Engineers. Comput. Chem. Eng., v.3, p. 329 (1979). 

Describe the Verneuil method for producing ruby. What are the advantages and disadvantages of this process ... 

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