In-situ Hrem Heating Experiments at Very High Temperatures

1995 ◽  
Vol 404 ◽  
Author(s):  
T. Kamino ◽  
H. Saka
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Atomic Resolution ◽  
Very High

AbstractA specimen-heating holder which allows an observation of reactions of more than one materials, in a controlled manner, at such a high temperature as 1723K has been developed. Facet-unfacet transformation and reconstruction of Au-deposited Si surfaces have been observed at very high temperatures at near-atomic resolution.

scholarly journals Asymmetric Pd-NHC*-catalyzed coupling reactions

2012 ◽  
Vol 84 (8) ◽  
pp. 1741-1748 ◽  
Author(s):  
E. Peter Kündig ◽  
Yixia Jia ◽  
Dmitry Katayev ◽  
Masafumi Nakanishi
Keyword(s):  
High Temperature ◽  
Coupling Reactions ◽  
Structural Studies ◽  
Methylene Unit ◽  
Asymmetric Coupling ◽  
New Applications ◽  
Very High

Very high asymmetric inductions result in the Pd-catalyzed intramolecular arylation of amides to give 3,3-disubstituted oxindoles when new in situ-generated chiral N-heterocyclic carbene (NHC*) ligands are employed. Structural studies show that conformational locking to minimize allylic strain is the key to understanding the function of these ligands. New applications of these ligands in the frontier area of asymmetric coupling reactions involving C(sp3)–H bonds are detailed. Highly enantioenriched fused indolines are accessible using either preformed- or in situ-generated Pd-NHC* catalysts. Remarkably, this occurs at high temperature (140–160 °C) via excellent asymmetric recognition of an enantiotopic C–H bond in an unactivated methylene unit.

Characteristics and aging of SiC MOSFETs operated at very high temperatures

2014 ◽  
Vol 1693 ◽  
Author(s):  
Dean P. Hamilton ◽  
Michael R. Jennings ◽  
Craig A. Fisher ◽  
Yogesh K. Sharma ◽  
Stephen J. York ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Threshold Voltage ◽  
Thermal Aging ◽  
Ohmic Contacts ◽  
Stress Tests ◽  
Temperature Capability ◽  
Temperature Constant ◽  
Voltage Management ◽  
Very High

ABSTRACTSilicon carbide power devices are purported to be capable of operating at very high temperatures. Current commercially available SiC MOSFETs from a number of manufacturers have been evaluated to understand and quantify the aging processes and temperature dependencies that occur when operated up to 350°C. High temperature constant positive bias stress tests demonstrated a two times increase in threshold voltage from the original value for some device types, which was maintained indefinitely but could be corrected with a long negative gate bias. The threshold voltages were found to decrease close to zero and the on-state resistances increased quite linearly to approximately five or six times their room temperature values. Long term thermal aging of the dies appears to demonstrate possible degradation of the ohmic contacts. This appears as a rectifying response in the I-V curves at low drain-source bias. The high temperature capability of the latest generations of these devices has been proven independently; provided that threshold voltage management is implemented, the devices are capable of being operated and are free from the effects of thermal aging for at least 70 hours cumulative at 300°C.

scholarly journals Nanoscaled eutectic NiAl-(Cr,Mo) composites with exceptional mechanical properties processed by electron beam melting

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Andreas Förner ◽  
S. Giese ◽  
C. Arnold ◽  
P. Felfer ◽  
C. Körner ◽  
...  
Keyword(s):  
Electron Beam ◽  
High Temperature ◽  
Electron Beam Melting ◽  
Lamellar Microstructure ◽  
High Hardness ◽  
Additive Process ◽  
In Situ Composites ◽  
Selective Electron Beam Melting ◽  
Very High

Abstract Eutectic NiAl-(Cr,Mo) composites are promising high temperature materials due to their high melting point, excellent oxidation behavior and low density. To enhance the strength, hardness and fracture toughness, high cooling rates are beneficial to obtain a fine cellular-lamellar microstructure. This can be provided by the additive process of selective electron beam melting. The very high temperature gradient achieved in this process leads to the formation of the finest microstructure that has ever been reported for NiAl-(Cr,Mo) in-situ composites. A very high hardness and fracture toughening mechanisms were observed. This represents a feasibility study towards additive manufacturing of eutectic NiAl-(Cr,Mo) in-situ composites by selective electron beam melting.

scholarly journals Forging, textures, and deformation systems in a B2 FeAl alloy

1999 ◽  
Vol 14 (3) ◽  
pp. 715-728 ◽  
Author(s):  
P. Zhao ◽  
D. G. Morris ◽  
M. A. Morris Munoz
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Slip System ◽  
High Temperatures ◽  
Low Temperatures ◽  
High Speed ◽  
Deformation Texture ◽  
Slip Systems ◽  
Feal Alloy ◽  
Very High

High-temperature forging experiments have been carried out by axial compression testing on a Fe–41Al–2Cr alloy in order to determine the deformation systems operating under such high-speed, high-temperature conditions, and to examine the textures produced by such deformation and during subsequent annealing to recrystallize. Deformation is deduced to take place by the operation of 〈111〉 {110} and 〈111〉{112} slip systems at low temperatures and by 〈100〉{001} and 〈100〉{011} slip systems at high temperatures, with the formation of the expected strong 〈111〉 textures. The examination of the weak 〈100〉 texture component is critical to distinguishing the operating slip system. Both texture and dislocation analyses are consistent with the operation of these deformation systems. Recrystallization takes place extremely quickly at high temperatures (above 800 °C), that is within seconds after deformation and also dynamically during deformation itself. Recrystallization changes the texture such that 〈100〉 textures superimpose on the deformation texture. The flow stress peak observed during forging is found at a very high temperature. Possible origins of the peak are examined in terms of the operating slip systems.

In-Situ Observations of the Effect of Electron Irradiation on the Defect Microstructure of Alumina

1997 ◽  
Vol 3 (S2) ◽  
pp. 601-602
Author(s):  
S.-J. Chen ◽  
U. Dahmen ◽  
D.G. Howitt
Keyword(s):  
High Temperature ◽  
Electron Irradiation ◽  
Shear Bands ◽  
Valuable Insight ◽  
High Velocity Impact ◽  
Dislocation Densities ◽  
In Situ Observations ◽  
Very High ◽  
Insight Into

The interaction of radiation produced point defects with a dislocation microstructure at high temperature is of considerable interest and careful high voltage microscopy experiments can provide valuable insight into the mechanisms. Veyssière and Westmacott carried out in-situ experiments monitoring the partial dislocation climbs in Ni3Al induced by thermal vacancies as well as by Frenkel pairs produced during irradiation.1 We report here the results of some preliminary experiments we performed on alumina (A12O3) single crystals with high dislocation densities to study the modification of the microstructure by electron irradiation at high temperature.The dislocation microstructures were produced by shock wave deformation using a high-velocity impact technique. The technique is capable of producing a very high density of defects consisting primarily of basal twins, and slips on the basal, pyramidal and rhombohedral planes in alumina. The dislocations are all of glide type, mostly forming shear bands. A typical microstructure prior to irradiation is shown in figure la.

scholarly journals High-temperature decomposition of Cu2BaSnS4 with Sn loss reveals newly identified compound Cu2Ba3Sn2S8

2020 ◽  
Vol 8 (22) ◽  
pp. 11346-11353
Author(s):  
José A. Márquez ◽  
Jon-Paul Sun ◽  
Helena Stange ◽  
Hasan Ali ◽  
Leo Choubrac ◽  
...  
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Fluorescence Analysis ◽  
Decomposition Mechanism ◽  
Temperature Decomposition

The decomposition mechanism of Cu2BaSnS4 is studied by in situ diffraction and fluorescence analysis revealing “Sn loss” and Cu2Ba3Sn2S8 at high temperatures.

Integrity assessment of the high temperature engineering test reactor (HTTR) control rod at very high temperatures

1997 ◽  
Vol 172 (1-2) ◽  
pp. 93-102 ◽  
Author(s):  
Y. Tachibana ◽  
S. Shiozawa ◽  
J. Fukakura ◽  
F. Matsumoto ◽  
T. Araki
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Control Rod ◽  
Integrity Assessment ◽  
Test Reactor ◽  
Very High
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