Deformation Mechanisms of Aluminum at High Temperatures: in situ Straining Experiments in H.V.E.M.

1975 ◽  
Vol 33 ◽  
pp. 56-57
Author(s):  
D. Caillard ◽  
P. Muchin ◽  
J. L. Martin
Keyword(s):  
High Temperature ◽  
Dislocation Density ◽  
Single Crystals ◽  
High Temperatures ◽  
Room Temperature ◽  
Dislocation Climb ◽  
Deformation Mechanisms ◽  
High Angle ◽  
The One

Aluminium single crystals have been deformed on a straining holder between room temperature and 550° C in a H.V.E.M. Observations are recorded on still photographs or movies.Evidence is shown of crosslip and dislocation climb.1) The formation of dislocation subboundaries has been observed at high temperature and low stresses. The increase with time of dislocation density of each boundary is explained and the coalescence of low angle subboundaries into high angle ones, is described on the basis of our observations by a model involving dislocation climb, different from the one proposed formerly by Dunn and Hibbard.

scholarly journals In Situ Hyperspectral Raman Imaging of Ternesite Formation and Decomposition at High Temperatures

Minerals ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 287 ◽  
Author(s):  
Nadine Böhme ◽  
Kerstin Hauke ◽  
Manuela Neuroth ◽  
Thorsten Geisler
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Temperature Stability ◽  
Dicalcium Silicate ◽  
Raman Imaging ◽  
Cement Industry ◽  
Solid State Reactions ◽  
High Temperature Stability ◽  
The One

Knowledge of the high-temperature properties of ternesite (Ca5(SiO4)2SO4) is becoming increasingly interesting for industry in different ways. On the one hand, the high-temperature product has recently been observed to have cementitious properties. Therefore, its formation and hydration characteristics have become an important field of research in the cement industry. On the other hand, it forms as sinter deposits in industrial kilns, where it can create serious problems during kiln operation. Here, we present two highlights of in situ Raman spectroscopic experiments that were designed to study the high-temperature stability of ternesite. First, the spectra of a natural ternesite crystal were recorded from 25 to 1230 °C, which revealed a phase transformation of ternesite to the high-temperature polymorph of dicalcium silicate (α’L-Ca2SiO4), while the sulfur is degassed. With a heating rate of 10 °C/h, the transformation started at about 730 °C and was completed at 1120 °C. Using in situ hyperspectral Raman imaging with a micrometer-scale spatial resolution, we were able to monitor the solid-state reactions and, in particular, the formation properties of ternesite in the model system CaO-SiO2-CaSO4. In these multi-phase experiments, ternesite was found to be stable between 930 to 1020–1100 °C. Both ternesite and α’L-Ca2SiO4 were found to co-exist at high temperatures. Furthermore, the results of the experiments indicate that whether or not ternesite or dicalcium silicate crystallizes during quenching to room temperature depends on the reaction progress and possibly on the gas fugacity and composition in the furnace.

Analyses of Eutectoid Phase Transformations in Nb–SilicideIn SituComposites

2004 ◽  
Vol 10 (4) ◽  
pp. 470-480 ◽  
Author(s):  
B.P. Bewlay ◽  
S.D. Sitzman ◽  
L.N. Brewer ◽  
M.R. Jackson
Keyword(s):  
Crystal Structure ◽  
Phase Transformation ◽  
High Temperature ◽  
Room Temperature ◽  
Bulk Composition ◽  
High Strength ◽  
Eutectoid Decomposition ◽  
Quaternary Alloys ◽  
Temperature Fracture

Nb–silicide in situ composites have great potential for high-temperature turbine applications. Nb–silicide composites consist of a ductile Nb-based solid solution together with high-strength silicides, such as Nb5Si3and Nb3Si. With the appropriate addition of alloying elements, such as Ti, Hf, Cr, and Al, it is possible to achieve a promising balance of room-temperature fracture toughness, high-temperature creep performance, and oxidation resistance. In Nb–silicide composites generated from metal-rich binary Nb-Si alloys, Nb3Si is unstable and experiences eutectoid decomposition to Nb and Nb5Si3. At high Ti concentrations, Nb3Si is stabilized to room temperature, and the eutectoid decomposition is suppressed. However, the effect of both Ti and Hf additions in quaternary alloys has not been investigated previously. The present article describes the discovery of a low-temperature eutectoid phase transformation during which (Nb)3Si decomposes into (Nb) and (Nb)5Si3, where the (Nb)5Si3possesses the hP16 crystal structure, as opposed to the tI32 crystal structure observed in binary Nb5Si3. The Ti and Hf concentrations were adjusted over the ranges of 21 to 33 (at.%) and 7.5 to 33 (at.%) to understand the effect of bulk composition on the phases present and the eutectoid phase transformation.

1700V, 5.5mOhm-cm2 4H-SiC DMOSFET with Stable 225°C Operation

2014 ◽  
Vol 778-780 ◽  
pp. 903-906 ◽  
Author(s):  
Kevin Matocha ◽  
Kiran Chatty ◽  
Sujit Banerjee ◽  
Larry B. Rowland
Keyword(s):  
High Temperature ◽  
Temperature Stress ◽  
High Temperatures ◽  
Threshold Voltage ◽  
Room Temperature ◽  
Gate Bias ◽  
Threshold Voltage Shift ◽  
Device Reliability ◽  
Bias Temperature Stress ◽  
High Temperature Operation

We report a 1700V, 5.5mΩ-cm24H-SiC DMOSFET capable of 225°C operation. The specific on-resistance of the DMOSFET designed for 1200V applications is 8.8mΩ-cm2at 225°C, an increase of only 60% compared to the room temperature value. The low specific on-resistance at high temperatures enables a smaller die size for high temperature operation. Under a negative gate bias temperature stress (BTS) at VGS=-15 V at 225°C for 20 minutes, the devices show a threshold voltage shift of ΔVTH=-0.25 V demonstrating one of the key device reliability requirements for high temperature operation.

Facile in situ synthesis of zeolite-encapsulating Cs2SiF6:Mn4+ for application in WLEDs

2019 ◽  
Vol 7 (5) ◽  
pp. 1345-1352 ◽  
Author(s):  
Suqian Meng ◽  
Yayun Zhou ◽  
Wei Wan ◽  
Shi Ye ◽  
Qinyuan Zhang
Keyword(s):  
High Temperature ◽  
Luminous Efficiency ◽  
In Situ Synthesis ◽  
Stability Test ◽  
High Humidity ◽  
The One ◽  
Testing Condition

Stability test shows that the luminous efficiency of WLED with CSFM-Y reduces only 4% after duration of 120 h in the testing condition of high humidity (85%) and high temperature (85 °C), while the one with pure CSFM declines 28%.

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.

scholarly journals Improvement of High Temperature Wear Behavior of In-Situ Cr3C2-20 wt. % Ni Cermet by Adding Mo

Crystals ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 682
Author(s):  
Liang Sun ◽  
Wenyan Zhai ◽  
Hui Dong ◽  
Yiran Wang ◽  
Lin He
Keyword(s):  
Wear Resistance ◽  
High Temperature ◽  
Wear Mechanism ◽  
Room Temperature ◽  
Wear Behavior ◽  
Ceramic Particle ◽  
High Temperature Wear ◽  
The Coefficient Of Friction ◽  
Mo Content

Cr3C2-Ni cermet is a kind of promising material especially for wear applications due to its excellent wear resistance. However, researches were mainly concentrated on the experiment condition of room temperature, besides high-temperature wear mechanism of the cermet would be utilized much potential applications and also lack of consideration. In present paper, the influence of Mo content on the high-temperature wear behavior of in-situ Cr3C2-20 wt. % Ni cermet was investigated systematically. The friction-wear experiment was carried out range from room temperature to 800 °C, while Al2O3 ceramic was set as the counterpart. According to experimental results, it is indicated that the coefficient of friction (COF) of friction pairs risen at the beginning of friction stage and then declined to constant, while the wear rate of Cr3C2-20 wt. % Ni cermet risen continuously along with temperature increased, which attributes to the converted wear mechanism generally from typical abrasive wear to severe oxidation and adhesive wear. Generally, the result of wear resistance was enhanced for 13.4% (at 400 °C) and 31.5% (at 800 °C) by adding 1 wt. % Mo. The in-situ newly formed (Cr, Mo)7C3 ceramic particle and the lubrication phase of MoO3 can effectively improve the wear resistance of Cr3C2-20 wt. % Ni cermet.

scholarly journals The High-Temperature Transformation from 1T- to 3R-LixTiS2 (x = 0.7, 0.9) as Observed in situ with Neutron Powder Diffraction

2015 ◽  
Vol 229 (9) ◽  
Author(s):  
Dennis Wiedemann ◽  
Suliman Nakhal ◽  
Anatoliy Senyshyn ◽  
Thomas Bredow ◽  
Martin Lerch
Keyword(s):  
High Temperature ◽  
Powder Diffraction ◽  
Electrode Material ◽  
Room Temperature ◽  
Lithium Ion ◽  
Neutron Powder Diffraction ◽  
Titanium Disulfide ◽  
Temperature Transformation

AbstractLayered titanium disulfide is used as lithium-ion intercalating electrode material in batteries. The room-temperature stable trigonal 1T polymorphs of the intercalates Li

Applications: Light My Fire

1982 ◽  
Vol 75 (1) ◽  
pp. 53-55
Author(s):  
George Knill ◽  
George Fawceti
Keyword(s):  
High Temperature ◽  
High Temperatures ◽  
Low Temperatures ◽  
Chemical Process ◽  
Room Temperature ◽  
Very High

Everyone knows that wood bums at a very high temperature. This burning is a chemical process that combines oxygen and carbon. The process occurs at very low temperatures as well as at very high ones. At high temperatures the process is spectacular-fire. At low temperatures (room temperature) you won’t even notice it, although it is still going on. Wood is always burning.

Crystal structures and high-temperature vibrational spectra for synthetic boron and aluminum doped hydrous coesite

2020 ◽  
Author(s):  
Yu Ye ◽  
Yunfan Miao ◽  
Joseph R. Smyth ◽  
Junfeng Zhang
Keyword(s):  
High Pressure ◽  
High Temperature ◽  
Single Crystals ◽  
Vibrational Spectra ◽  
Fourier Transformation ◽  
Ambient Pressure ◽  
Al Content ◽  
Al Substitution ◽  
Long Time

<p>Coesite, a high-pressure SiO2 polymorph, has drawn extensive interest from the mineralogical community for a long time. In this study, we synthesized hydrous coesite samples with different B and Al concentrations at 5 and 7.5 GPa (1273 K). The B concentration could be more than 400 B/10<sup>6</sup>Si with about 300 ppmw. H2O, while the Al content can be as much as 1200 ~ 1300 Al/10<sup>6</sup>Si with CH2O restrained to be less than 10 ppmw. Hence, B-substitution may prefer the mechanism of Si<sup>4+</sup> = B<sup>3+</sup> + H<sup>+</sup>, whereas Al-substitution could be dominated by 2Si<sup>4+</sup> = 2Al<sup>3+</sup> + O<sub>V</sub>. The doped B<sup>3+</sup> and Al<sup>3+</sup> cations may be concentrated in the Si1 and Si2 tetrahedra, respectively, and make noticeable changes in the Si-O4 and Si-O5 bond lengths. In-situ high-temperature Raman and Fourier Transformation Infrared (FTIR) spectra were collected at ambient pressure. The single crystals of coesite were observed to be stable up to 1500 K. The isobaric Grüneisen parameters (ϒ<sub>i<em>P</em></sub>) of the external modes (< 350 cm<sup>-1</sup>) are systematically smaller in the Al-doped samples, as compared with those for the Al-free ones, while most of the OH-stretching bands shift to higher frequencies in the high temperature range up to ~ 1100 K</p>

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