Microstructure and morphology of Si crystals grown in pure Si and Al-Si melts

2021 ◽  
Author(s):  
Liubov Toropova ◽  
Dmitri Alexandrov ◽  
Markus Rettenmayr ◽  
Dongmei Liu
Keyword(s):  
Transition Zone ◽  
Shape Function ◽  
High Growth ◽  
Electromagnetic Levitation ◽  
Primary Si ◽  
Microstructural Transition ◽  
Dendritic Structures ◽  
Good Agreement

Abstract Microstructure of Al-40 wt%Si samples solidified in electromagnetic levitation furnace is studied at high melt undercooling. Primary Si with feathery and dendritic structures is observed. As this takes place, single Si crystals either contain secondary dendrite arms or represent faceted structures. Our experiments show that at a certain undercooling, there exists the microstructural transition zone of aceted to non-faceted growth. Also, we analyze the shape of dendritic crystals solidifying from liquid Si as well as from hypereutectic Al-Si melts at high growth undercoolings. The shapes of dendrite tips grown at undercoolings >100 K along the surface of levitated Al-40 wt%Si droplets are compared with pure Si dendrite tips from the literature. The dendrite tips are digitized and superimposed with theoretical shape function recently derived by stitching the Ivantsov and Brener solutions. We show that experimental and theoretical dendrite tips are in good agreement for Si and Al-Si samples.

Influence of Interfacial Transition Zone on Local and Overall Fracture Response of Cementitious Composites

2018 ◽  
Vol 784 ◽  
pp. 97-102 ◽  
Author(s):  
Vojtěch Zacharda ◽  
Jiří Němeček ◽  
Hana Šimonová ◽  
Barbara Kucharczyková ◽  
Michal Vyhlídal ◽  
...  
Keyword(s):  
Transition Zone ◽  
Interfacial Transition Zone ◽  
Cement Matrix ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fine Grained ◽  
Bulk Matrix ◽  
Electron Microscopes ◽  
Microstructure Measurements ◽  
Good Agreement

Mechanical fracture properties of interfacial transition zone (ITZ) of fine-grained composite based on cement matrix with different types – basalt, granite, marble and amphibolite – of rock inclusion were studied. Specimens with the initial stress concentrator were tested in standard three-point bending configuration. Fracture surfaces were examined with light and electron microscopes. Local ITZ response was characterized by nanoindentation in the vicinity of rock inclusions. Local elasticity, hardness and viscous properties were assessed. It has been shown that the ITZ is mechanically weaker compared to the bulk matrix in the region of ca. 0–20 μm from the inclusion for all specimen’s types. It exhibits gradual increase of elastic modulus and hardness, which can be approximately expressed by a power law. On the other hand, the creep in ITZ was found to be higher compared to the bulk matrix. The results of nanoindentation measurements are in a good agreement with overall mechanical properties, fracture response and microstructure measurements done by scanning electron microscopy.

scholarly journals Rayleigh's quotient for multiple cracked beam and application

2011 ◽  
Vol 33 (1) ◽  
pp. 1-12 ◽  
Author(s):  
Nguyen Tien Khiem ◽  
Tran Thanh Hai
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Analysis ◽  
Crack Detection ◽  
Natural Frequencies ◽  
Shape Function ◽  
Detection Problem ◽  
Cracked Beam ◽  
Rayleigh’S Quotient ◽  
Good Agreement

Rayleigh's quotient for Euler-Bernoulli multiple cracked beam with different boundary conditions has been derived from the governed equation of free vibration. An appropriate choosing of approximate shape function in terms of mode shape of uncracked beam and specific functions satisfying conditions at cracks and boundaries leads to an explicit expression of natural frequencies through crack parameters that can simplify not only the analysis of natural frequencies of cracked beam but also the crack detection problem. Numerical analysis of natural frequencies of the cracked beam by using the obtained expression in comparison with the well-known methods such as the characteristic equation and finite element method shows their good agreement. The analytical expression of natural frequencies applied to the crack detection problem allows the result of detection to be improved.

scholarly journals Kinetic Aspects of Phosphorus Removal from Electromagnetically Levitated 600 MPa Steel Droplets

Metals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1460
Author(s):  
Qi Jiang ◽  
Guifang Zhang ◽  
Yindong Yang ◽  
Alexander McLean ◽  
Lei Gao
Keyword(s):  
Gas Phase ◽  
Flow Rate ◽  
Phosphorus Removal ◽  
Gas Flow ◽  
Electromagnetic Levitation ◽  
Effect Of Temperature ◽  
Gas Flow Rate ◽  
Electromagnetically Levitated ◽  
Rate Controlling Step ◽  
Good Agreement

A kinetic model was developed to study the dephosphorization of 600 MPa steel droplets under electromagnetic levitation conditions. The relationships which were derived from the model between dephosphorization and the influence of temperature and gas flow rate were in good agreement with experimental data. Both temperature and gas flow rate were conducive to the evaporation of phosphorus, with the effect of temperature having a greater influence than that of the gas velocity. The results show that the rate-controlling step for the dephosphorization process was diffusion within the gas phase. This work aims to provide a theoretical basis for process optimization during the dephosphorization of 600 MPa steel.

scholarly journals Optimization of Thick Film Resistors for Low Drift

1980 ◽  
Vol 7 (1-3) ◽  
pp. 87-91 ◽  
Author(s):  
Gunnar Björklund ◽  
Lars Linde
Keyword(s):  
Theoretical Model ◽  
Thick Film ◽  
Transition Zone ◽  
Experimental Results ◽  
Film Resistor ◽  
Theoretical Predictions ◽  
Thick Film Resistor ◽  
Theoretical Results ◽  
Low Drift ◽  
Good Agreement

In order to minimize drift in a thick film resistor both printing and trimming parameters have to be optimized carefully.With the aid of a linear theoretical model it is shown how the resistance drift in the bulk transition zone and terminals of the resistor can be calculated for both trimmed and untrimmed resistors.The theoretical results are used for optimization of laser trimmed high ohmic resistors. The experimental results are in good agreement with the theoretical predictions and confirm that thick film resistors can be optimized for low drift.

Flash photolysis of alkali metal anions in tetrahydrofuran and dimethoxyethane

1979 ◽  
Vol 57 (14) ◽  
pp. 1792-1800 ◽  
Author(s):  
W. A. Seddon ◽  
J. W. Fletcher ◽  
F. C. Sopchyshyn ◽  
E. B. Selkirk
Keyword(s):  
Pulse Radiolysis ◽  
Shape Function ◽  
Flash Photolysis ◽  
Ion Pairs ◽  
Ion Pair ◽  
Parent Metal ◽  
Initial Formation ◽  
Extinction Coefficients ◽  
Best Fit ◽  
Good Agreement

Flash photolysis of K−, Rb−, and Cs− in tetrahydrofuran (THF) produces the corresponding ion-pairs (K+, es−), (Rb+, es−), and (Cs+, es−), followed by the regeneration of the parent metal anion, M−. In mixed-metal solutions containing Na and M where M is K, Rb, or Cs, photolysis of Na− also forms the (M+, es−) ion-pair and M−, but with the latter then reforming Na− on an extended time scale. Similar results were obtained in dimethoxyethane (DME) at 213 K, but in this case with the initial formation of a loose ion-pair, (M+, es−)loose.Based on a Gaussian–Lorenztian shape function, the 'best-fit' optical bands for the (M+, es−) and M− species were used to simulate the experimental spectra and deduce the corresponding extinction coefficients in both solvents.The overall mechanism is complex but is in good agreement with previous interpretations deduced by pulse radiolysis.

Oscillator Strength Measurements in the Vacuum-Ultraviolet by the Emission Method

1988 ◽  
Vol 102 ◽  
pp. 353-356
Author(s):  
C. Goldbach ◽  
G. Nollez
Keyword(s):  
Oscillator Strength ◽  
Vacuum Ultraviolet ◽  
Oscillator Strengths ◽  
Emission Method ◽  
Absolute Scale ◽  
Good Agreement

AbstractThe principles and the realization of an experiment devoted to oscillator strength measurements in the vacuum-ultraviolet by the emission method are briefly presented. The results obtained for the strong multiplets of neutral nitrogen and carbon in the 1200-2000 Å range yield an absolute scale of oscillator strengths in good agreement with the most recent calculations.

A High Voltage Electron Microscopy Study of Sub-Oxide Formation in Vanadium

1971 ◽  
Vol 29 ◽  
pp. 212-213
Author(s):  
R. H. Geiss ◽  
R. L. Ladd ◽  
K. R. Lawless
Keyword(s):  
High Vacuum ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Ultra High Vacuum ◽  
Pure Oxygen ◽  
Pressure Oxidation ◽  
High Voltage Electron Microscopy ◽  
Oxidation Study ◽  
Voltage Electron ◽  
Good Agreement

Detailed electron microscope and diffraction studies of the sub-oxides of vanadium have been reported by Cambini and co-workers, and an oxidation study, possibly complicated by carbon and/or nitrogen, has been published by Edington and Smallman. The results reported by these different authors are not in good agreement. For this study, high purity polycrystalline vanadium samples were electrochemically thinned in a dual jet polisher using a solution of 20% H2SO4, 80% CH3OH, and then oxidized in an ion-pumped ultra-high vacuum reactor system using spectroscopically pure oxygen. Samples were oxidized at 350°C and 100μ oxygen pressure for periods of 30,60,90 and 160 minutes. Since our primary interest is in the mechanism of the low pressure oxidation process, the oxidized samples were cooled rapidly and not homogenized. The specimens were then examined in the HVEM at voltages up to 500 kV, the higher voltages being necessary to examine thick sections for which the oxidation behavior was more characteristic of the bulk.

Diagnostic Value of Electron Microscopy in Soft Tissue Tumors

1970 ◽  
Vol 28 ◽  
pp. 220-221
Author(s):  
Gerald Fine ◽  
Azorides R. Morales
Keyword(s):  
Cardiac Myxoma ◽  
Osteogenic Sarcoma ◽  
Diagnostic Value ◽  
Soft Tissue Tumors ◽  
Amelanotic Melanoma ◽  
Growth Patterns ◽  
Light Microscopic Level ◽  
Mesenchymal Tumors ◽  
Good Agreement

For years the separation of carcinoma and sarcoma and the subclassification of sarcomas has been based on the appearance of the tumor cells and their microscopic growth pattern and information derived from certain histochemical and special stains. Although this method of study has produced good agreement among pathologists in the separation of carcinoma from sarcoma, it has given less uniform results in the subclassification of sarcomas. There remain examples of neoplasms of different histogenesis, the classification of which is questionable because of similar cytologic and growth patterns at the light microscopic level; i.e. amelanotic melanoma versus carcinoma and occasionally sarcoma, sarcomas with an epithelial pattern of growth simulating carcinoma, histologically similar mesenchymal tumors of different histogenesis (histiocytoma versus rhabdomyosarcoma, lytic osteogenic sarcoma versus rhabdomyosarcoma), and myxomatous mesenchymal tumors of diverse histogenesis (myxoid rhabdo and liposarcomas, cardiac myxoma, myxoid neurofibroma, etc.)

Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Surface reconstructions of (001) cleaved GdBa2Cu3O7-δ

1992 ◽  
Vol 50 (1) ◽  
pp. 106-107
Author(s):  
H.W. Zandbergen ◽  
M.R. McCartney
Keyword(s):  
Electron Microscopy ◽  
Copper Oxide ◽  
Grain Boundaries ◽  
Atomic Structure ◽  
Oxygen Deficiency ◽  
Surface Layers ◽  
Layer Sequence ◽  
Surface Reconstructions ◽  
Good Agreement

Very few electron microscopy papers have been published on the atomic structure of the copper oxide based superconductor surfaces. Zandbergen et al. have reported that the surface of YBa2Cu3O7-δ was such that the terminating layer sequence is bulk-Y-CuO2-BaO-CuO-BaO, whereas the interruption at the grain boundaries is bulk-Y-CuO2-BaO-CuO. Bursill et al. reported that HREM images of the termination at the surface are in good agreement with calculated images with the same layer sequence as observed by Zandbergen et al. but with some oxygen deficiency in the two surface layers. In both studies only one or a few surfaces were studied.

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