scholarly journals Primary and secondary dendrite spacing of Ni-based superalloy single crystals

2009 ◽  
Vol 74 (1) ◽  
pp. 61-69 ◽  
Author(s):  
Slobodanka Kostic ◽  
Aleksandar Golubovic ◽  
Andreja Valcic
Keyword(s):  
Crystal Growth ◽  
Temperature Gradient ◽  
Single Crystals ◽  
Gradient Method ◽  
Dendrite Spacing ◽  
Published Data ◽  
Bridgman Technique ◽  
Spontaneous Nucleation ◽  
Vertical Furnace ◽  
Growth Experiments

Ni-based superalloy single crystals were grown by different methods (gradient method and Bridgman technique with spontaneous nucleation and with seed). In all crystal growth experiments using the Bridgman technique, the temperature gradient along the vertical furnace axes was constant (G = 33.5 ?C/cm). The obtained single crystals were cut, mechanical and chemical polished, and chemically etched. Using a metallographic microscope, the spacing of the primary and secondary dendrites was investigated. The dendrite arm spacing (DAS) was determined using a Quantimet 500 MC. The obtained results are discussed and compared with published data.

The Effect of Modified Crucible Design and Seed Attachment on SiC Crystal Grown by PVT

2013 ◽  
Vol 740-742 ◽  
pp. 77-80
Author(s):  
Jung Young Jung ◽  
Sang Il Lee ◽  
Mi Seon Park ◽  
Doe Hyung Lee ◽  
Hee Tae Lee ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Temperature Gradient ◽  
Single Crystals ◽  
Crystal Quality ◽  
Full Width ◽  
Half Maximum ◽  
Radial Temperature Gradient ◽  
Radial Temperature ◽  
Better Than

The present research was focused to investigate the effect of internal crucible design that influenced the 4H-SiC crystal growth onto a 6H-SiC seed by PVT method. The crucible design was modified to produce a uniform radial temperature gradient in the growth cell. The seed attachment was also modified with a use of polycrystalline SiC plate. The crystal quality of 4H-SiC single crystals grown in modified crucible and grown with modified seed attachment was revealed to be better than that of crystal grown in conventional crucible. The full width at half maximum (FWHM) values of grown SiC crystals in the conventional crucible, the modified seed attachment and the modified crucible were 285 arcsec, 134 arcsec and 128 arcsec, respectively. The micropipe density (MPD) of grown SiC crystals in the conventional crucible, the modified seed attachment and the modified crucible were 101ea/cm^2, 81ea/cm^2 and 42ea/cm^2, respectively.

Single-crystal growth and characterization of the Pb0.5Sr2.5Y1−xCaxCu2Oy system

1995 ◽  
Vol 10 (9) ◽  
pp. 2211-2215 ◽  
Author(s):  
H. Jin ◽  
N.L. Wang ◽  
Y. Chong ◽  
M. Deng ◽  
L.Z. Cao ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Oxygen Partial Pressure ◽  
Partial Pressure ◽  
Single Crystals ◽  
Single Crystal Growth ◽  
Optimum Conditions ◽  
Flux Method ◽  
Ca Doping ◽  
Spontaneous Nucleation

Two kinds of methods such as spontaneous nucleation from flux-free stoichiometric melt and CuO flux method have been used for the growth of Pb0.5Sr2.5Y1−xCaxCu2Oy single crystals. The morphologies, phases, and compositions occurring in the crystals grown from the two kinds of methods were compared systematically. Optimum conditions for the growth of larger 1212 phase single crystals are x =0.15, 0.25, and 0.35. The lattice parameters of the crystals with the 1212 phase were found to be increasing upon Ca doping. The resistivity behavior of the PbSrYCaCuO single crystals with the 1212 phase both in the state of as-grown and after extended annealings under various oxygen partial pressure was also discussed briefly.

Features of morphogenesis of diamond single crystals more than 2 carats grown by temperature gradient method

2020 ◽  
Vol 550 ◽  
pp. 125890
Author(s):  
V.V. Lysakovskyi ◽  
S.O. Ivakhnenko ◽  
V.M. Kvasnytsya ◽  
A.V. Burchenia ◽  
T.V. Kovalenko ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Single Crystals ◽  
Gradient Method ◽  
Diamond Single Crystals ◽  
Temperature Gradient Method

Crystal Growth and Scintillation Properties of CeF3

1994 ◽  
Vol 348 ◽  
Author(s):  
J.L. Allain ◽  
M. Couchaud ◽  
B. Ferrand ◽  
Y. Grange ◽  
B. Utts ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Single Crystals ◽  
Radiation Hardness ◽  
Bridgman Technique ◽  
Vertical Bridgman

ABSTRACTLarge single crystals of CeF3, 40 mm in diameter up to 140 mm in length, have been grown using the vertical Bridgman technique. Their optical and scintillation properties and their radiation hardness have been measured.

Crucible Selection in AlN Bulk Crystal Growth

2003 ◽  
Vol 798 ◽  
Author(s):  
Rafael Dalmau ◽  
Balaji Raghothamachar ◽  
Michael Dudley ◽  
Raoul Schlesser ◽  
Zlatko Sitar
Keyword(s):  
Mass Spectrometry ◽  
Crystal Growth ◽  
Single Crystals ◽  
Secondary Ion Mass Spectrometry ◽  
X Ray Diffraction ◽  
Bulk Crystal Growth ◽  
Growth Environment ◽  
X Ray ◽  
Spontaneous Nucleation ◽  
Bulk Single Crystals

ABSTRACTGrowth of AlN bulk single crystals by sublimation of AlN powder was carried out in a resistively heated reactor at temperatures up to 2300°C. A variety of crucible materials, such as BN, W, Ta, Re, ZrO2, TaN, and TaC, were evaluated. Our studies have shown that the morphology of crystals grown by spontaneous nucleation strongly depends on the growth temperature and contamination in the reactor. Crucible selection had a profound effect on contamination in the crystal growth environment, thus influencing nucleation, coalescence, and crystal morphology. Spontaneously grown single crystals up to 15 mm in size were characterized by x-ray diffraction (XRD), x-ray topography (XRT), glow discharge mass spectrometry (GDMS), and secondary ion mass spectrometry (SIMS). Average dislocation densities were on the order of 103 cm−3, with extended areas virtually dislocation-free, while high-resolution XRD showed rocking curves as narrow as 7 arcsec.

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