N--H Interaction in Nitrided Fe--Nb Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 4987-4992
Author(s):  
Masatoshi Sakamoto
Keyword(s):  
Internal Friction ◽  
Room Temperature ◽  
Diffusion Rate ◽  
Interstitial Site ◽  
Torsion Pendulum ◽  
Nitriding Temperature ◽  
Octahedral Interstitial Site ◽  
Snoek Peak ◽  
Strong Affinity ◽  
Temperature Side

Internal friction of nitrogen in α iron has known as Snoek peak of N atom resolv ed in the octahedral interstitial site of bcc. When M atom ( Mn, Mo, Si, et.al) which has the affinity bigger than Fe were added ,another peaks due to the jump of N from Fe-Fe site to Fe-M site appear in the upper temperature side and complicate the Snoek peak curve of N. In this paper, the Snoek peak curve was studied in Fe-0.4wt%Nb-0.02wt%N alloys. This alloy showed no other peaks in the upper side to 373K and had only the single peak of N in Fe-Fe site. Internal friction measured by torsion pendulum method at about 1 Hz. After that this alloy was cooled from 373K to room temperature and reheated to 373K, but Snoek peak of N which showed on the first measurement just after nitriding disappeared completely and internal friction was only background. One of the reasons of it is the precipitation of Fe16N2 under heating and resolved N atoms disappeared. So these specimens were reheated to 873K and quenched, but Snoek peak of N was not measured. This shows the disappearance of N atom from Fe-Fe site. The mixture gas of a few % NH3 and H2 was used in this study. Therefore after nitriding much of H atoms were resolved in α iron alloys. Because the diffusion rate of H atom in α iron is bigger than N atom , it expected that H atoms can combine with Nb atoms before coming N atoms. And the appearance of Snoek peak of N in these alloys is considered. After that, in the heating to 373K H atom leave Nb and go away from the surface, and N atoms combine with Nb in place of H atoms. Nb has the very strong affinity with N, so these alloys have no peaks. When they reheated to the nitriding temperature N atoms can not diffuse from Fe-Nb site to Fe-Fe site. Then Snoek peak of N can not appears again in these alloys. Therefore, when Fe-Nb alloys were nitrided in NH3 and H2 mixture gas H atom plays very important part and it needs that the interaction of N-H atoms will be considered in these nitrided Fe-Nb alloys.

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.

The IF Spectrum of Fe-C-N and Fe-17%Cr-C-N Alloys Measured by the Impulse Excitation Technique

2012 ◽  
Vol 184 ◽  
pp. 209-214 ◽  
Author(s):  
I. Jung ◽  
Bruno C. De Cooman
Keyword(s):  
Internal Friction ◽  
Strong Dependence ◽  
Gas Jet ◽  
Torsion Pendulum ◽  
Snoek Peak ◽  
Temperature Range ◽  
Impulse Excitation ◽  
Cold Rolled ◽  
Hot Rolled ◽  
Undeformed Sample

The temperature dependence of the dynamic Young’s modulus, E, and the damping, Q-1, of Fe-C-N and Fe-17%Cr-C-N alloys with different C, N contents were studied in the temperature range of 25°C to 600°C by the impulse excitation internal friction technique at 1KHz. Hot rolled samples were cold rolled to a thickness of 1.2mm and recrystallization annealed at 820°C for 30sec then gas jet cooled (-50°C/sec). Samples were subsequently tensile strained 6% and 16%. A Snoek peak was observed at 120°C in the undeformed sample and a Snoek-Koster peak was observed at 400°C after deformation. In the case of the Fe-Cr-C-N alloy, a high damping background due to magneto-mechanical damping was observed in the temperature range of 25°C to 400°C. A broaden Snoek peak in FeCr was observed at 300°C. The internal friction peaks observed in this study showed the strong dependence of the amount of interstitial contents and deformation and were well correlated to previous internal friction studies measured mainly by torsion pendulum and inverted torsion pendulum.

Snoek-Type and Zener Relaxation in Fe-Si-Al Alloys

2008 ◽  
Vol 137 ◽  
pp. 69-82 ◽  
Author(s):  
Igor S. Golovin ◽  
S. Jäger ◽  
V.A. Semin ◽  
G.V. Serzhantova ◽  
H.R. Sinning ◽  
...  
Keyword(s):  
Internal Friction ◽  
Peak Height ◽  
Al Alloys ◽  
Ternary Alloys ◽  
Mechanical Spectroscopy ◽  
Temperature Dependent ◽  
High Temperature Side ◽  
Mutual Compensation ◽  
Snoek Peak ◽  
Temperature Side

Carbon-containing Fe - Si and Fe - Si - Al alloys were studied with respect to the carbonrelated Snoek-type and Zener relaxation using different mechanical spectroscopy techniques. In all alloys the temperature-dependent profile of the Snoek peak, relative to that in pure iron, is modified on its high-temperature side by the substitutional atoms. At least two components, an Fe - C - Fe (which correspond to C atom jumps (diffusion) in areas where it is surrounded by Fe atoms only) and Fe - C - Me peaks, where Me = Si, Al, can be distinguished in the Snoek-peak profile. In both binary Fe - Al and Fe - Si and ternary Fe - Si - Al alloys, a higher annealing temperature prior to quenching leads to an increase in the Fe - C - Fe and a decrease in the Fe - C - Me component of the Snoek peak. Heating to 1173K and above often lowers the peak height due to thermal vacancies. Low-temperature (<670K) ageing of quenched Fe - Si - Al and Fe – Si specimens reduces both the Fe – C - Fe and Fe – C – Al / Si peaks. Ageing at T > 670 K changes the temperature- as well as the amplitude-dependent parts of internal friction due to a redistribution of carbon between solid solution and dislocations. Both the Snoek-type peak height and the dislocation mobility – as can be concluded from the slope of the amplitude-dependent internal friction – increase, and a new peak appears at temperatures higher than that of the Snoek peak, which probably is a Snoek-Köster peak resulting from the motion of weakly pinned dislocations. A Zener peak appears if the concentration of substitutional atoms is > 6 at. %. The Zener peak relaxation strength is much lower in ternary alloys than in the binary ones probably due to mutual compensation of elastic distortions in presence of Al and Si atoms which are bigger and smaller, respectively, than Fe atoms.

Magnetic Volume Effect of Hydrogen Diffusion in Palladium

2020 ◽  
Vol 310 ◽  
pp. 29-33
Author(s):  
Sarantuya Nasantogtokh ◽  
Xin Cui ◽  
Zhi Ping Wang
Keyword(s):  
Transition Metal ◽  
Density Of States ◽  
Density Functional ◽  
Hydrogen Diffusion ◽  
Magnetic Moments ◽  
Interstitial Site ◽  
Volume Effect ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Octahedral Interstitial Site

The electronic and magnetic properties of palladium hydrogen are investigated using first-principles spin-polarized density functional theory. By studying the magnetic moments and electronic structures of hydrogen atoms diffusing in face-centered cubic structure of transition metal Pd, we found that the results of magnetic moments are exactly the same in the two direct octahedral interstitial site-octahedral interstitial site diffusion paths-i.e. the magnetic moments are the largest in the octahedral interstitial site, and the magnetic moments are the lowest in saddle point positions. We also studied on the density of states of some special points, with the result that the density of states near the Fermi level is mainly contributed by 4d electrons of Pd and the change of magnetic moments with the cell volume in the unit cell of transition metal Pd with a hydrogen atom.

Effect of Boron and Hydrogen on the Electronic Structure of Ni3Al

1993 ◽  
Vol 319 ◽  
Author(s):  
N. Kioussis ◽  
H. Watanabe ◽  
R.G. Hemker ◽  
W. Gourdin ◽  
A. Gonis ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Charge Density ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Interstitial Site ◽  
Octahedral Interstitial Site ◽  
Interstitial Region ◽  
Ordered Intermetallic ◽  
Lmto Method ◽  
Structure Calculations

AbstractUsing first-principles electronic structure calculations based on the Linear-Muffin-Tin Orbital (LMTO) method, we have investigated the effects of interstitial boron and hydrogen on the electronic structure of the L12 ordered intermetallic Ni3A1. When it occupies an octahedral interstitial site entirely coordinated by six Ni atoms, we find that boron enhances the charge distribution found in the strongly-bound “pure” Ni3AI crystal: Charge is depleted at Ni and Al sites and enhanced in interstitial region. Substitution of Al atoms for two of the Ni atoms coordinating the boron, however, reduces the interstitial charge density between certain atomic planes. In contrast to boron, hydrogen appears to deplete the interstitial charge, even when fully coordinated by Ni atoms. We suggest that these results are broadly consistent with the notion of boron as a cohesion enhancer and hydrogen as an embrittler.

A bioprinted composite hydrogel with controlled shear stress on cells

2020 ◽  
pp. 095441192097668
Author(s):  
Amirhossein Bakhtiiari ◽  
Rezvan Khorshidi ◽  
Fatemeh Yazdian ◽  
Hamid Rashedi ◽  
Meisam Omidi
Keyword(s):  
Shear Stress ◽  
Cell Viability ◽  
Room Temperature ◽  
Degradation Rate ◽  
Diffusion Rate ◽  
Sol Gel ◽  
Three Dimensional ◽  
Simulation Software ◽  
Sol Gel Transition ◽  
Gel Transition

In recent decades, three dimensional (3D) bio-printing technology has found widespread use in tissue engineering applications. The aim of this study is to scrutinize different parameters of the bioprinter – with the help of simulation software – to print a hydrogel so much so that avoid high amounts of shear stress which is detrimental for cell viability and cell proliferation. Rheology analysis was done on several hydrogels composed of different percentages of components: alginate, collagen, and gelatin. The results have led to the combination of percentages collagen:alginate:gelatin (1:4:8)% as the best condition which makes sol-gel transition at room temperature possible. The results have shown the highest diffusion rate and cell viability for the cross-linked sample with 1.5% CaCl2 for the duration of 1 h. Finally, we have succeeded in printing the hydrogel that is mechanically strong with suitable degradation rate and cell viability.

scholarly journals First-Principles Investigation of Atomic Hydrogen Adsorption and Diffusion on/into Mo-doped Nb (100) Surface

2018 ◽  
Vol 8 (12) ◽  
pp. 2466 ◽  
Author(s):  
Yang Wu ◽  
Zhongmin Wang ◽  
Dianhui Wang ◽  
Jiayao Qin ◽  
Zhenzhen Wan ◽  
...  
Keyword(s):  
First Principles ◽  
Atomic Hydrogen ◽  
Energy Barrier ◽  
Hydrogen Adsorption ◽  
Hydrogen Permeation ◽  
Diffusion Path ◽  
Interstitial Site ◽  
Octahedral Interstitial Site ◽  
Tetrahedral Interstitial Site ◽  
And Diffusion

To investigate Mo doping effects on the hydrogen permeation performance of Nb membranes, we study the most likely process of atomic hydrogen adsorption and diffusion on/into Mo-doped Nb (100) surface/subsurface (in the Nb12Mo4 case) via first-principles calculations. Our results reveal that the (100) surface is the most stable Mo-doped Nb surface with the smallest surface energy (2.75 J/m2). Hollow sites (HSs) in the Mo-doped Nb (100) surface are H-adsorption-favorable mainly due to their large adsorption energy (−4.27 eV), and the H-diffusion path should preferentially be HS→TIS (tetrahedral interstitial site) over HS→OIS (octahedral interstitial site) because of the correspondingly lower H-diffusion energy barrier. With respect to a pure Nb (100) surface, the Mo-doped Nb (100) surface has a smaller energy barrier along the HS→TIS pathway (0.31 eV).

Effect of H-Doping on Damping Capacity of Various NiTi-Based Alloys at kHz Frequencies

2006 ◽  
Vol 128 (3) ◽  
pp. 254-259 ◽  
Author(s):  
B. Coluzzi ◽  
A. Biscarini ◽  
G. Mazzolai ◽  
F. M. Mazzolai ◽  
A. Tuissi
Keyword(s):  
Internal Friction ◽  
Twin Boundary ◽  
Room Temperature ◽  
Mechanical Energy ◽  
Noise Pollution ◽  
Metal Alloy ◽  
Maximum Efficiency ◽  
Damping Capacity ◽  
Good Opportunity ◽  
Hydrogen Doping

The internal friction Q−1 and the Young’s modulus E of NiTi based alloys have been measured as a function of temperature after various thermomechanical and hydrogen-doping treatments given to the materials. Hydrogen is found to play a major role introducing tall damping peaks associated with Snoek-type and H-twin boundary relaxations. Levels of Q−1 as high as 0.08 have been detected, which are among the highest to date measured in metal alloy systems. For appropriate alloy compositions, these peaks occur at around room temperature (for acoustical frequencies), thus providing a good opportunity to reduce machinery vibrations and noise pollution. In the paper, the conditions are highlighted under which maximum efficiency can be reached in the conversion of mechanical energy into heat.

scholarly journals Internal Friction and Young's Modulus Measurements on SiO2 and Ta2O5 Films Done with an Ultra-High Q Silicon-Wafer Suspension

2015 ◽  
Vol 60 (1) ◽  
pp. 365-370 ◽  
Author(s):  
M. Granata ◽  
L. Balzarini ◽  
J. Degallaix ◽  
V. Dolique ◽  
R. Flaminio ◽  
...  
Keyword(s):  
Thin Films ◽  
Internal Friction ◽  
Silicon Wafer ◽  
Room Temperature ◽  
Suspension System ◽  
Cryogenic Temperatures ◽  
Resonant Frequencies ◽  
High Q ◽  
Key Features ◽  
Q Factors

Abstract In order to study the internal friction of thin films a nodal suspension system called GeNS (Gentle Nodal Suspension) has been developed. The key features of this system are: i) the possibility to use substrates easily available like silicon wafers; ii) extremely low excess losses coming from the suspension system which allows to measure Q factors in excess of 2×108 on 3” diameter wafers; iii) reproducibility of measurements within few percent on mechanical losses and 0.01% on resonant frequencies; iv) absence of clamping; v) the capability to operate at cryogenic temperatures. Measurements at cryogenic temperatures on SiO2 and at room temperature only on Ta2O5 films deposited on silicon are presented.

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