scholarly journals Heterogeneity of the Dendrite Array Created in the Root of Cored SX Turbine Blades during Initial Stage of Crystallization

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 80
Author(s):  
Robert Paszkowski ◽  
Jacek Krawczyk ◽  
Włodzimierz Bogdanowicz ◽  
Dariusz Szeliga ◽  
Jan Sieniawski
Keyword(s):  
Transverse Section ◽  
Turbine Blades ◽  
Lateral Growth ◽  
X Ray Diffraction ◽  
Dendrite Branching ◽  
X Ray ◽  
Initial Stage ◽  
Vertical Bridgman ◽  
Lateral Dendrite ◽  
Root Connection

The roots of cored single-crystalline turbine blades made of a nickel-based CMSX-4 superalloy were studied. The casts were solidified by the vertical Bridgman method in an industrial ALD furnace using the spiral selector and selector continuer situated asymmetrically in the blade root transverse section. Scanning electron microscopy, the Laue diffraction and X-ray diffraction topography were used to visualize the dendrite array and the local crystal misorientation of the roots. It has been stated that heterogeneity of the dendrite array and creation of low-angle boundaries (LABs) are mostly related to the lateral dendrite branching and rapid growth of the secondary and tertiary dendrites near the surface of the continuer–root connection. These processes have an unsteady character. Additionally, the influence of the mould walls on the dendrite array heterogeneity was studied. The processes of the lateral growth of the secondary dendrites and competitive longitudinal growth of the tertiary dendrites are discussed and a method of reducing the heterogeneity of the root dendrite array is proposed.

scholarly journals Defect Creation in the Root of Single-Crystalline Turbine Blades Made of Ni-Based Superalloy

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 870 ◽  
Author(s):  
Jacek Krawczyk ◽  
Robert Paszkowski ◽  
Włodzimierz Bogdanowicz ◽  
Aneta Hanc-Kuczkowska ◽  
Jan Sieniawski ◽  
...  
Keyword(s):  
Turbine Blades ◽  
Lateral Growth ◽  
X Ray Diffraction ◽  
Single Crystalline ◽  
X Ray ◽  
Positron Annihilation Lifetime ◽  
The Creation ◽  
Misorientation Angles ◽  
Axial Growth ◽  
Root Connection

An analysis of the defects in the vicinity of the selector–root connection plane occurring during the creation of single-crystalline turbine blades made of CMSX-6 Ni-based superalloy was performed. X-ray diffraction topography, scanning electron microscopy, and positron annihilation lifetime spectroscopy were used. Comparing the area of undisturbed axial growth of dendrites to the area of lateral growth concluded that the low-angle boundaries-like (LAB-like) defects were created in the root as a result of unsteady-state lateral growth of some secondary dendrite arms in layers of the root located directly at the selector–root connection plane. Additional macroscopic low-angle boundaries (LABs) with higher misorientation angles were created as a result of concave curvatures of liquidus isotherm in platform-like regions near selector–root connections. Two kinds of vacancy-type defects, mono-vacancies and vacancy clusters, were determined in relation to the LABs and LAB-like defects. Only mono-vacancies appeared in the areas of undisturbed axial growth. Reasons for the creation of macroscopic LABs and LAB-like defects, and their relationships with vacancy-type defects were discussed.

scholarly journals The Influence of the Cooling Bores on the Dendritic Structure and Crystal Orientation in Single-Crystalline Cored CMSX-4 Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3966
Author(s):  
Jacek Krawczyk ◽  
Włodzimierz Bogdanowicz
Keyword(s):  
Crystal Orientation ◽  
Turbine Blades ◽  
Dendritic Structure ◽  
X Ray Diffraction ◽  
Vertical Temperature ◽  
Single Crystalline ◽  
X Ray ◽  
Vertical Bridgman ◽  
The Relationship

Single-crystalline cored CMSX-4 blades obtained at a withdrawal rate of 3 mm/min by the vertical Bridgman method were analyzed. The dendritic structure and crystal orientation near the cooling bores of the blades were studied through Scanning Electron Microscopy, the X-ray diffraction measurements of α and β angular components of the primary crystal orientation, and the γ angular component of the secondary crystal orientation. Additionally, the primary arm spacing (PAS) was studied in areas near and far from the cooling bores. It was found that in the area approximately 3–4 mm wide around the cooling bores, changes occurred in the α, β, and γ angles, as well as in the PAS. The PAS determined for the transverse section of the root and the linear primary arm spacing (LPAS) determined for the longitudinal sections, as well as their relationship, have been defined for the areas located near the cooling bores and those at a distance from them. The vertical temperature gradient of 29.5 K/cm was estimated in the root areas located near the cooling bores based on the PAS values. The value of this gradient was significantly higher compared to the growth chamber operating gradient of 16 K/cm. The two-scale analysis applied in this study allowed for the determination of the relationship between the process of dendrite array creation proceeding on a millimeter scale, which is associated with the local changes in crystal orientation near the cooling bores, and that which proceeds on a scale of tens of millimeters, associated with the changes in crystal orientation in the whole blade cast.

scholarly journals The Influence of the Cooling Bores on Crystal Orientation and Lattice Parameter in Single-Crystalline Cored Turbine Blades

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3842
Author(s):  
Jacek Krawczyk ◽  
Włodzimierz Bogdanowicz ◽  
Jan Sieniawski
Keyword(s):  
Solidification Front ◽  
Crystal Orientation ◽  
Turbine Blades ◽  
Lattice Parameter ◽  
Growth Direction ◽  
X Ray Diffraction ◽  
Single Crystalline ◽  
X Ray ◽  
Vertical Bridgman ◽  
Α Angle

The areas located near the cooling bores of single-crystalline cored turbine blades made of nickel-based CMSX-4 superalloy were studied. The blades were solidified by the vertical Bridgman technique in the industrial ALD furnace. Longitudinal sections of the blades were studied by Scanning Electron Microscopy, X-ray diffraction topography, X-ray diffraction measurements of the γ′-phase lattice parameter a, and the α angle of the primary crystal orientation. The local changes in α were analyzed in relation to the changes of the dendrite’s growth direction near the cooling bores. It was found that in the area approximately 3 ÷ 4 mm wide around the cooling bores, changes of α and a, both in the blade root and in the airfoil occurred. The local temperature distribution near the cooling bores formed a curved macroscopic solidification front, which caused changes in the chemical composition and, consequently, changes in the a value in a range of 0.002 Å to 0.014 Å. The mechanism of alloying elements segregation by tips of the dendrites on the bent solidification front was proposed. The multi-scale analysis that allows determining a relation between processes proceed both on a millimeter-scale and a micrometric and nanometric scale, was applied in the studies.

scholarly journals Variation of Crystal Orientation and Dendrite Array Generated in the Root of SX Turbine Blades

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4126 ◽  
Author(s):  
Włodzimierz Bogdanowicz ◽  
Jacek Krawczyk ◽  
Robert Paszkowski ◽  
Jan Sieniawski
Keyword(s):  
Crystal Orientation ◽  
Crystallization Front ◽  
Turbine Blades ◽  
Crystallographic Direction ◽  
Lateral Growth ◽  
Primary Crystal ◽  
X Ray Diffraction ◽  
Bridgman Technique ◽  
X Ray ◽  
Complex Wave

The variation of the crystal orientation and the dendrite array generated in the root of the single-crystalline (SX) turbine blades made of CMSX-4 superalloy were studied. The blades with an axial orientation of the [001] type were solidified by the industrial Bridgman technique using a spiral selector at a withdrawal rate of 3 mm/min. The analysis of the crystal orientation and dendrite arrangement was carried out using scanning electron microscopy, X-ray diffraction topography, and Laue diffraction. It was found that the lateral growth of such secondary dendrite arms, which are defined as “leading” and grow in the root at first, is related to the rotation of their crystal lattice, which is the reason for creation of the low-angle boundary (LAB) type defects. The primary crystal orientation of the selector extension (SE) area determines the areas and directions of the lateral growth of the leading arms. Additionally, it was found that in the SE areas of the root, near the connection with the selector, the spatial distribution of the [001]γ′ crystallographic direction has a complex wave-like character and may be related to the shape of the crystallization front.

scholarly journals Photoconductivity of the Single Crystals Pb4Ga4GeS12 and Pb4Ga4GeSe12

Proceedings ◽  
2020 ◽  
Vol 62 (1) ◽  
pp. 4
Author(s):  
Hadj Bellagra ◽  
Oksana Nyhmatullina ◽  
Yuri Kogut ◽  
Halyna Myronchuk ◽  
Lyudmyla Piskach
Keyword(s):  
Ternary Systems ◽  
Semiconductor Materials ◽  
Tetragonal Symmetry ◽  
Bandgap Energy ◽  
Experimental Measurements ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vertical Bridgman ◽  
Symmetry Space ◽  
Symmetry Space Group

Quaternary semiconductor materials of the Pb4Ga4GeS(Se)12 composition have attracted the attention of researchers due to their possible use as active elements of optoelectronics and nonlinear optics. The Pb4Ga4GeS(Se)12 phases belong to the solid solution ranges of the Pb3Ga2GeS(Se)8 compounds which form in the quasi-ternary systems PbS(Se)−Ga2S(Se)3−GeS(Se)2 at the cross of the PbGa2S(Se)4−Pb2GeS(Se)4 and PbS(Se)−PbGa2GeS(Se)6 sections. The quaternary sulfide melts congruently at 943 K. The crystallization of the Pb4Ga4GeSe12 phase is associated with the ternary peritectic process Lp + PbSe ↔ PbGa2S4 + Pb3Ga2GeSe8 at 868 K. For the single crystal studies, Pb4Ga4GeS(Se)12 were pre-synthesized by co-melting high-purity elements. The X-ray diffraction results confirm that these compounds possess non-centrosymmetric crystal structure (tetragonal symmetry, space group P–421c). The crystals were grown by the vertical Bridgman method in a two-zone furnace. The starting composition was stoichiometric for Pb4Ga4GeS12, and the solution-melt method was used for the selenide Pb4Ga4GeSe12. The obtained value of the bandgap energy for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals is 1.86 and 2.28 eV, respectively. Experimental measurements of the spectral distribution of photoconductivity for the Pb4Ga4GeS12 and Pb4Ga4GeSe12 crystals exhibit the presence of two spectral maxima. The first lies in the region of 570 (2.17 eV) and 680 nm (1.82 eV), respectively, and matches the optical bandgap estimates well. The locations of the admixture maxima at about 1030 (1.20 eV) and 1340 nm (0.92 eV), respectively, agree satisfactorily with the calculated energy positions of the defects vs. and VSe.

Interdiffusion in Co/Ta Multilayer Thin Films

2005 ◽  
Vol 237-240 ◽  
pp. 554-559 ◽  
Author(s):  
Hui Myeong Lee ◽  
Byeong Seon Lee ◽  
Chan Gyu Lee ◽  
Yasunori Hayashi ◽  
Bon Heun Koo
Keyword(s):  
Structural Relaxation ◽  
Multilayer Thin Films ◽  
X Ray Diffraction ◽  
Stress Release ◽  
X Ray ◽  
Angle Measurements ◽  
Peak Intensity ◽  
Straight Line ◽  
Initial Stage ◽  
Interdiffusion Coefficients

We will discuss the stress release phenomena, structural relaxation and interdiffusion processes during annealing. The [Co(4nm)/Ta(4nm)]38 multilayers were prepared by dc magnetron sputtering on Si substrate. The multilayers were annealed at various temperatures (523 - 673K) in vacuum (under 10-5 torr) furnace. The effective interdiffusion coefficients were determined from the slope of the best straight line fit of the first peak intensity versus annealing time [d ln(I(t)/I(0)) /dt] by X-ray diffraction (XRD) low angle measurements. The drastic decrease of the relative intensity in the initial stage shown due to the structural relaxation was excluded in the calculation of effective interdiffusion coefficients. The temperature dependence of interdiffusion in the range of 523 - 673K is described by D = 3.2×10-19 exp(-0.51±0.11 eV/kT) m2s-1.

Otosclerotic Stapes: Morphological and Microchemical Correlates

1977 ◽  
Vol 86 (4) ◽  
pp. 525-540 ◽  
Author(s):  
David J. Lim ◽  
William H. Saunders
Keyword(s):  
Calcium Salt ◽  
Mineral Deposit ◽  
Ground Substance ◽  
X Ray Diffraction ◽  
Typical Pattern ◽  
X Ray ◽  
Initial Stage ◽  
Electron Microscopes ◽  
Sclerotic Lesions ◽  
Scanning Electron Microscopes

A total of 32 otosclerotic stapes is thin-sectioned without decalcification and examined using transmission and scanning electron microscopes, with a nondispersive x-ray analyzer attached to the latter. These otosclerotic stapes are classified as spongiotic, sclerotic, or preotosclerotic, according to their pathologic characteristics and state of mineralization. Either diffuse or patchy demineralization in the ground substance appears to be the initial stage of otosclerosis, and this area coincides with preotosclerotic lesions (also known as blue mantle) in light microscopy. Therefore, it is interpreted that demineralization precedes the destruction of ground substance in the preotosclerotic lesion. Bone mineral deposits in new otosclerotic bone appear to be related to the collagen fibrils that are embedded in the ground substance. No mineral deposit could be seen without the ground substance deposition; therefore, it is suggested that this ground substance is the single most important factor in the poor mineralization of the otosclerosis. The sclerotic lesions are well mineralized and show a typical pattern of hydroxyapatite by x-ray diffraction study. We could not confirm the notion that the sclerotic lesion is hypermineralized as compared to the normal stapes. The spongiotic lesions are poorly mineralized, with low calcium salt. Using the Ca/P ratio and x-ray diffraction pattern as criteria, it was determined that spongiotic lesions belong to unstable, immature bone.

Investigation Of Nucleation And Initial Stage Of Gan Growth By Atomic Force Microscopy And X-Ray Diffraction

1997 ◽  
Vol 482 ◽  
Author(s):  
P. W. Yip ◽  
S.-Q. Wang ◽  
A. J. Drehman ◽  
L. D. Zhu ◽  
P. E. Norris
Keyword(s):  
Atomic Force Microscopy ◽  
Surface Morphology ◽  
Deposition Temperature ◽  
Yellow Luminescence ◽  
X Ray Diffraction ◽  
Rocking Curve ◽  
X Ray ◽  
Force Microscopy ◽  
Atomic Force ◽  
Initial Stage

AbstractThe nucleation and initial stage of GaN growth on sapphire was investigated by atomic force microscopy, X-ray diffraction and photoluminescence. A 15 to 30 nm thick GaN buffer layer deposited at proper conditions was extremely smooth and nearly amorphous. Proper post deposition annealing resulted in the buffer crystallized. The buffer layer deposition temperature, thickness and annealing time and temperature must be coordinated. Low deposition temperature and/or insufficient annealing of the buffer results in a GaN wafer which has fine spiking surface morphology with an RMS of 3.4 nm for 1.4 μm wafer, strong yellow luminescence and wide xray rocking curve FWHM. High deposition temperature, longer crystallization time, and a low growth rate results in a wafer which exhibits strong band edge luminescence without noticeable yellow luminescence, and a narrow (002) diffraction rocking curve. However, the surface morphology exhibits well developed hexagonal feature with RMS roughness of 14.3 nm for a 570 nm thick layer. X-ray rocking curve analysis revealed buffer crystallization, domain coalescence and alignment process. The FWHM of the ω–scan of GaN (101) diffraction was 1700–2000 arc seconds for 200–1400 nm wafers which indicates that the twist of the domains is not changing much with the growth.

Thermoelectric Properties of Pb1-xCdxSe Crystals Grown by Vertical Bridgman Method

2012 ◽  
Vol 194 ◽  
pp. 148-152
Author(s):  
Horng Jyh Gau ◽  
Yih Jye Chiou ◽  
Ching Cherng Wu ◽  
Yung Kang Kuo ◽  
Ching Hwa Ho
Keyword(s):  
Figure Of Merit ◽  
Carrier Transport ◽  
Sem Analysis ◽  
Bridgman Method ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vertical Bridgman Method ◽  
Temperature Dependences ◽  
Type Semiconductor ◽  
Vertical Bridgman

Single crystals of Pb1-xCdxSe compounds with x = 0, 0.01, 0.03, 0.05, 0.07 and 0.1 were grown by vertical Bridgman method. The crystalline phase and stochiometry for these crystals were investigated by X-ray diffraction, SEM and electron-probe microanalysis (EPMA). The thermoelectric behaviors for the Pb1-xCdxSe crystals were studied by means of thermal and carrier transport measurements in the temperature range between 50K and 400K. X-ray diffraction and SEM analysis confirmed that as-grown Pb1-xCdxSe crystals are simgle phase. The experimental results showed that the PbTe sample is p-type semiconductor but Pb1-xCdxSe samples with x = 0.01, 0.03, 0.05, 0.07 and 0.1 are n-type semiconductors. Temperature dependences of resistivity, Seebeck coefficient, and thermal conductivity for the various compositions of Pb1-xCdxSe were analyzed. The dimensionless thermoelectric figure of merit ZT for these compounds was evaluated and discussed. It was found that Pb0.95Cd0.05Se exhibits the best thermoelectric performance. The maximum figure of merit (ZT) of Pb0.95Cd0.05Se is about 0.47 at 290 K.

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