scholarly journals Numerical Interpretation of Hydrogen Thermal Desorption Spectra for Iron with Hydrogen-Enhanced Strain-Induced Vacancies

2020 ◽  
Vol 52 (1) ◽  
pp. 257-269
Author(s):  
Ken-ichi Ebihara ◽  
Yuri Sugiyama ◽  
Ryosuke Matsumoto ◽  
Kenichi Takai ◽  
Tomoaki Suzudo
Keyword(s):  
Thermal Desorption ◽  
Vacancy Cluster ◽  
Hydrogen Atoms ◽  
High Temperature Side ◽  
Vacancy Clusters ◽  
Static Calculation ◽  
Iron Specimen ◽  
Atomistic Calculations ◽  
Enhanced Strain ◽  
Temperature Side

AbstractWe obtained thermal desorption spectra of hydrogen for a small-size iron specimen to which strain was applied during charging with hydrogen atoms. In the spectra, a shoulder-shaped peak in the high-temperature side was enhanced compared with the spectra of the specimen to which only strain was applied. We also observed that the peak almost disappeared by aging processes at ≥ 373 K. Then, assuming that the shoulder-shaped peak results from hydrogen atoms released by vacancies, we simulated the thermal desorption spectra using a model incorporating the behavior of vacancies and vacancy clusters. The model considered up to vacancy cluster $${{V_9}}$$ V 9 , which is composed of nine vacancies, and employed the parameters based on atomistic calculations, including the H trapping energy of vacancies and vacancy clusters that we estimated using the molecular static calculation. As a result, we revealed that the model could, on the whole, reproduce the experimental spectra, except two characteristic differences, and also the dependence of the spectra on the aging temperature. By examining the cause of the differences, the possibilities that the diffusion of clusters of $${V_2}$$ V 2 and $${V_3}$$ V 3 is slower than the model and that vacancy clusters are generated by applying strain and H charging concurrently were indicated.

Change in the Positron Annihilation Lifetime of Vacancy Clusters Containing Hydrogen Atoms in Electron-Irradiated F82H

2021 ◽  
Vol 1024 ◽  
pp. 71-78
Author(s):  
Koichi Sato ◽  
Yohei Kondo ◽  
Masakiyo Ohta ◽  
Qiu Xu ◽  
Atsushi Yabuuchi ◽  
...  
Keyword(s):  
Theoretical Calculation ◽  
Positron Annihilation ◽  
Room Temperature ◽  
Vacancy Cluster ◽  
Hydrogen Atoms ◽  
Positron Annihilation Lifetime ◽  
Vacancy Clusters ◽  
Hydrogen Charging ◽  
Trapping Effect ◽  
Before And After

The change in the positron annihilation lifetime (PAL) of vacancy clusters before and after electrolysis hydrogen charging was determined using PAL measurements in electron-irradiated F82H. The experimental change indicated 8 hydrogen atoms were trapped in vacancy clusters; whereas the theoretical calculation resulted in approximately 14 atoms. As the samples were left at room temperature for 5 min until the start of the PAL measurements, the de-trapping effect of hydrogen atoms was also considered; approximately 13 hydrogen atoms were captured at each vacancy cluster. The PAL decreased after annealing at 148 K, which could not be explained theoretically. Therefore, further experiments and discussions are needed to obtain a precise change in the PAL of vacancy clusters containing hydrogen atoms in F82H.

Search for High Damping Metallic Glasses

2006 ◽  
Vol 319 ◽  
pp. 151-156 ◽  
Author(s):  
Y. Hiki ◽  
M. Tanahashi ◽  
Shin Takeuchi
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Internal Friction ◽  
Metallic Glass ◽  
Room Temperature ◽  
Temperature Stability ◽  
Temperature Peak ◽  
High Temperature Side ◽  
Side Slope ◽  
Temperature Side

In a hydrogen-doped metallic glass, there appear low-temperature and high-temperature internal friction peaks respectively associated with a point-defect relaxation and the crystallization. The high-temperature-side slope of low-temperature peak and also the low-temperature-side slope of high-temperature peak enhance the background internal friction near the room temperature. A hydrogen-doped Mg-base metallic glass was proposed as a high-damping material to be used near and somewhat above the room temperature. Stability of the high damping was also checked.

scholarly journals Relationship between the Behavior of Hydrogen and Hydrogen Bubble Nucleation in Vanadium

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 322
Author(s):  
Zhengxiong Su ◽  
Sheng Wang ◽  
Chenyang Lu ◽  
Qing Peng
Keyword(s):  
Hydrogen Atom ◽  
First Principles ◽  
Bound States ◽  
Hydrogen Molecule ◽  
Vacancy Cluster ◽  
Bubble Nucleation ◽  
Hydrogen Bubble ◽  
First Principles Calculations ◽  
Hydrogen Atoms ◽  
Macroscopic Deformation

Hydrogen plays a significant role in the microstructure evolution and macroscopic deformation of materials, causing swelling and surface blistering to reduce service life. In the present work, the atomistic mechanisms of hydrogen bubble nucleation in vanadium were studied by first-principles calculations. The interstitial hydrogen atoms cannot form significant bound states with other hydrogen atoms in bulk vanadium, which explains the absence of hydrogen self-clustering from the experiments. To find the possible origin of hydrogen bubble in vanadium, we explored the minimum sizes of a vacancy cluster in vanadium for the formation of hydrogen molecule. We show that a freestanding hydrogen molecule can form and remain relatively stable in the center of a 54-hydrogen atom saturated 27-vacancy cluster.

Strain-Rate Dependence of Vacancy Cluster Size in Hydrogen-Charged Martensitic Steel AISI410 under Tensile Deformation

2017 ◽  
Vol 373 ◽  
pp. 171-175 ◽  
Author(s):  
Kazuki Sugita ◽  
Yasumasa Mutou ◽  
Yasuharu Shirai
Keyword(s):  
Strain Rate ◽  
Positron Lifetime ◽  
Tensile Deformation ◽  
Martensitic Steel ◽  
Vacancy Cluster ◽  
Rate Dependence ◽  
Strain Rate Dependence ◽  
Strain Rates ◽  
Vacancy Clusters ◽  
Positron Lifetime Spectroscopy

The strain-rate dependence of vacancy cluster sizes in hydrogen-charged martensitic steel AISI410 under tensile deformation was investigated using positron lifetime spectroscopy. The vacancy-cluster sizes in hydrogen-charged samples tended to increase with decreasing strain rates during the tensile deformations. The vacancy-cluster sizes significantly correlated to the tensile elongations to fracture. It was revealed that the presence of large-sized vacancy-clusters can cause the degradation of mechanical properties and followed by brittle fracture.

Moisture-dependent orthotropic viscoelastic properties of Chinese fir wood during quenching in the temperature range of 20 to −120°C

Holzforschung ◽  
2019 ◽  
Vol 74 (1) ◽  
pp. 10-19 ◽  
Author(s):  
Zhu Li ◽  
Jiali Jiang ◽  
Jianxiong Lyu
Keyword(s):  
Cell Wall ◽  
Viscoelastic Properties ◽  
Wood Cell Wall ◽  
Bound Water ◽  
Free Water ◽  
Chinese Fir ◽  
High Temperature Side ◽  
Temperature Spectrum ◽  
Β Relaxation ◽  
Temperature Side

AbstractAn understanding of wood’s moisture-dependent viscoelastic properties under various temperature conditions is important for assessing its utilization and product quality. In this study, we investigated the influence of moisture content (MC) on the orthotropic viscoelasticity of Chinese fir wood (Cunninghamia lanceolata [Lamb.] Hook.) during quenching ranging from 20 to −120°C. The storage modulus (E′) and loss factor (tan δ) of the longitudinal (L), radial (R) and tangential (T) specimens were determined for nine MC levels ranging from 0.6 to 60.0%. The results showed that E′ generally decreased with increasing amount of bound water in all orthotropic directions, regardless of the temperature. In contrast, a sharp increase in E′ was observed at temperatures below 0°C when free water was present, due to the formation of ice within the cell lumens. The γ-relaxation and β-relaxation were observed in the temperature spectrum. A comparison demonstrates that the β-relaxation showed evident grain orientation. When only bound water was present in the wood cell wall, one clear γ-relaxation was found for all orthotropic directions. In contrast, only the high-temperature side of the γ-relaxation was observed in the three anatomic directions in specimens with free water, which might be related to the amorphous wood cell wall coupling with the frozen free water during the quenching process. In addition, the differences in peak temperatures of the γ-relaxation among the three main directions diminished with increasing bound water.

Tourmaline and boron as indicators of the presence, segregation and extraction of melt in pelitic migmatites: examples from the Ryoke metamorphic belt, SW Japan

2004 ◽  
Vol 95 (1-2) ◽  
pp. 111-123 ◽  
Author(s):  
Tetsuo Kawakami
Keyword(s):  
High Temperature ◽  
Partial Melting ◽  
Correct Recognition ◽  
High Temperature Side ◽  
Metamorphic Belt ◽  
Melt Extraction ◽  
Mode Of Occurrence ◽  
Temperature Side ◽  
Sw Japan

The mode of occurrence of borosilicates and the breakdown fronts of prograde tourmaline (tourmaline-out isograd) in three anatectic migmatite regions of the Ryoke metamorphic belt, SW Japan, are reported. The breakdown of tourmaline in the migmatite zones and release of boron into the melts, followed by the extraction of the boron-bearing melts from the migmatite zones occurred throughout the Ryoke metamorphic belt. Retrograde, magmatic tourmaline in interboudin partitions filled with leucosome is useful for calculating the degree of partial melting in the migmatites. Using boron contents in the leucosomes and pelitic schists, the degree of partial melting at the migmatite front of the Aoyama area is estimated to be 12 wt.%. Extraction of the boron-bearing melt is suggested by the boron-depleted nature of the migmatites. Connection of boudinage structures probably supplied the vertical pathways of the segregated melts, and major transport of the melts was accomplished by dyking. Irregularly shaped, amoeboid tourmaline locally occurs on the high-temperature side of the tourmaline-out isograds in the Yanai and Komagane areas, implying incomplete extraction of boron-bearing melts from those areas. Discriminating retrograde from prograde tourmaline enables correct recognition of the tourmaline-out isograd. The amount of retrograde tourmaline in migmatites can potentially be used as an indicator of the degree of melt extraction from them.

Comparison of Hydrogen Thermal Desorption Analysis Curves of Electron-Irradiated F82H and Creep-Ruptured Pure Fe Obtained by Experiments and Simulations

2021 ◽  
Vol 1024 ◽  
pp. 135-144
Author(s):  
Takuya Kamimura ◽  
Hayato Yamashita ◽  
Koichi Sato ◽  
Tsunakazu Ohyama ◽  
Yoshinori Kimoto ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Thermal Desorption ◽  
Rate Theory ◽  
Hydrogen Atoms ◽  
Positron Annihilation Lifetime ◽  
Solute Atoms ◽  
Simulation Results ◽  
Diffusion Of Hydrogen ◽  
Trapping Sites ◽  
Thermal Desorption Analysis

Herein, we compared thermal desorption analysis (TDA) curves obtained by conducting experiments and simulations. In addition, we discussed the validation of our simulations and trapping sites of hydrogen atoms. In as-received F82H, when the samples contained solute atoms, grain boundaries, dislocations, and precipitates, the experimental curve corresponded to the simulated curve. In positron annihilation lifetime (PAL) measurements, di-vacancies were detected in the electron-irradiated F82H. When we changed the growth and the concentration of vacancy-type defects during temperature increase using the rate theory, the simulation results agreed with experiment results. In creep-ruptured Fe, only dislocations were detected by the PAL measurements. However, the existence of a type of defect, which was related to grain boundaries, must be assumed to fit the simulation curve to the experimental one. In the next step, the diffusion of hydrogen atoms on grain boundaries should be added to simulation program.

SPECIFIC HEAT ANOMALY FOR H ≥ 28.5 T IN CeIrIn5

2002 ◽  
Vol 16 (20n22) ◽  
pp. 3014-3017
Author(s):  
J. S. KIM ◽  
J. ALWOOD ◽  
P. KUMAR ◽  
G. R. STEWART
Keyword(s):  
High Temperature ◽  
Single Crystal ◽  
Specific Heat ◽  
Single Crystals ◽  
Hybrid Magnet ◽  
High Temperature Side ◽  
And Shifts ◽  
Temperature Side

Recently Takeuchi reported a weak, 'metamagnetic-like' increase in the magnetization around 42 T in single crystals of CeIrIn 5 for field in the c-direction. We report specific heat measurements on single crystal CeIrIn 5, H parallel c-axis, measured in the dc hybrid magnet at NHMFL in Tallahassee between 1.4 and 10 K. A clear anomaly in C/T in 35 T is observed to peak at 1.8 K, with an entropy of 6% of RIn2. This anomaly grows in size and shifts upwards in temperature (both monotonically) with increasing H until at 45 T T peak =4.1 K , with the entropy associated with the transition equal to 14% of RIn2. C/T data at 32 T show3 only the high temperature side of the peak occurring above 1.4 K, while C/T data at 28.5 T show no anomaly down to 1.4 K. This is consistent with our Tpeak vs H data, which imply T peak → 0 at 26 T.

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