scholarly journals In-Situ TEM Annealing Observation of Helium Bubble Evolution in Pre-Irradiated FeCoNiCrTi0.2 Alloys

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3727
Author(s):  
Huanhuan He ◽  
Zhiwei Lin ◽  
Shengming Jiang ◽  
Xiaotian Hu ◽  
Jian Zhang ◽  
...  
Keyword(s):  
Vacuum Arc ◽  
In Situ Tem ◽  
Face Centered Cubic ◽  
Helium Bubble ◽  
High Entropy ◽  
Helium Bubbles ◽  
Transmission Electron ◽  
Bubble Evolution ◽  
Face Centered

The FeCoNiCrTi0.2 high-entropy alloys fabricated by vacuum arc melting method, and the annealed pristine material, are face centered cubic structures with coherent γ’ precipitation. Samples were irradiated with 50 keV He+ ions to a fluence of 2 × 1016 ions/cm2 at 723 K, and an in situ annealing experiment was carried out to monitor the evolution of helium bubbles during heating to 823 and 923 K. The pristine structure of FeCoNiCrTi0.2 samples and the evolution of helium bubbles during in situ annealing were both characterized by transmission electron microscopy. The annealing temperature and annealing time affect the process of helium bubbles evolution and formation. Meanwhile, the grain boundaries act as sinks to accumulate helium bubbles. However, the precipitation phase seems have few effects on the helium bubble evolution, which may be due to the coherent interface and same structure of γ’ precipitation and matrix.

In-Situ UHV TEM Investigations of the Initial Stages of Cu(001) Oxidation

1997 ◽  
Vol 3 (S2) ◽  
pp. 583-584
Author(s):  
J. C. Yang ◽  
M. Yeadon ◽  
B. Kolasa ◽  
J. M. Gibson
Keyword(s):  
High Vacuum ◽  
Copper Film ◽  
Ultra High Vacuum ◽  
Native Oxide ◽  
In Situ Tem ◽  
Face Centered Cubic ◽  
Free Standing ◽  
Transmission Electron ◽  
Face Centered

We studied the beginning oxidation stage of a model metal system by in-situ transmission electron microscopy (TEM) in order to gain insights into the initial kinetics of oxidation. In-situ TEM experiments can distinguish between nucleation and growth since individual oxide islands are imaged. We chose to investigate Cu, since it is a simple face-centered cubic metal. Also, Cu is a highly promising metal interconnect material because of its low resistivity and good electromigration properties as compared to Al.Single crystal -1000Å 99.999% purity copper films were grown on irradiated NaCl in an UHV e-beam evaporator system. The free-standing copper film was placed on a specially designed holder, which permits resistive heating of the sample. The microscope used for this experiment is a modified ultra-high vacuum, with base pressure of 10−9 torr, JEOL200CX, operated at l00kV. To remove the native oxide formed during exposure in air, the Cu film was annealed at ∼350°C

In situ tEM observation of C49 to C54 TiSi2 transformation

1992 ◽  
Vol 50 (2) ◽  
pp. 1356-1357
Author(s):  
K. Barmak ◽  
L.E. Levine ◽  
D.A. Smith ◽  
Y. Komemt
Keyword(s):  
High Resistivity ◽  
In Situ Tem ◽  
Video Tape ◽  
Furnace Annealing ◽  
Plan View ◽  
Transmission Electron ◽  
In Situ Heating ◽  
Face Centered ◽  
Si Wafer

The reaction of thin films of Ti with Si results in the formation of the high resistivity (≃150 μΩcm) base-centered orthorhombic C49 phase prior to the low resistivity (≃15-20 μΩcm) face-centered orthorhombic C54 phase. In our experiments, 30 nm of Ti was evaporated onto a < 100 > oriented Si wafer cleaned in a 10:1 H2O:HF solution. The wafer had been previously implanted with As to a dose of 5×l015 cm−2. Mixed C49/C54 phase films were obtained by furnace annealing at 700°C for 10 min. Plan view transmission electron microscopy (TEM) specimens were prepared by dimpling and etching in a 10:6:6 HNO3:HF:CH3COOH solution. The sample was initially studied in a JEOL 4000FX and in situ heating experiments were carried out in a Philips 430 operating at 300 kV. The progress of the transformation was recorded on video tape. The temperature was raised relatively quickly to 700°C and then more slowly to 750°C.

Microstructure and Mechanical Properties of the W-Ni-Co System Refractory High-Entropy Alloys

2015 ◽  
Vol 816 ◽  
pp. 324-329 ◽  
Author(s):  
Hui Jiang ◽  
Li Jiang ◽  
Yi Ping Lu ◽  
Tong Min Wang ◽  
Zhi Qiang Cao ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Vacuum Arc ◽  
High Entropy Alloys ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Melting Temperatures ◽  
Arc Melting ◽  
Microstructure And Mechanical Properties ◽  
The Matrix ◽  
Face Centered

The elements Mo, Cr and V were added to the W-Ni-Co system high entropy alloys, the effects of these added elements on microstructure and mechanical properties of these alloys were studied. The alloys were produced by vacuum arc melting. The compositions were W0.5Ni2Co2VMo0.5,W0.5Ni2Co2VCr0.5and W0.5Ni2Co2CrMo0.5(denoted as Alloy 1, Alloy 2 and Alloy 3) respectively. The theoretical melting temperatures were higher than 2000 K. X-ray diffraction, SEM and energy dispersive spectroscopy (EDS) results indicated that the matrix of the alloys is face-centered cubic (FCC) solid-solution, the alloys showed dendrite crystal structure. Ni, Co elements were enriched in the dendrite areas, the W, Mo were enriched in the inter-dendrite regions ,while V, Cr elements were uniform distribution. The Vickers hardness of these alloys was 376.1 HV, 255.88 HV and 306.8 HV, respectively. The yield strength values (σ0.2) of Alloy 1, Alloy 2 and Alloy 3 were approximately 1000MPa, 750MPa, 250MPa, respectively. The alloys show good compression plasticity deformation capacity at RT.

scholarly journals A Sequence of Phase Transformations and Phases in NiCoFeCrGa High Entropy Alloy

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1076
Author(s):  
Ádám Vida ◽  
János Lábár ◽  
Zoltán Dankházi ◽  
Zsolt Maksa ◽  
Dávid Molnár ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Phase Transitions ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
High Entropy ◽  
Transmission Electron ◽  
Temperature Ranges ◽  
Face Centered ◽  
Electron Energy Loss

The present investigation is directed to phase transitions in the equimolar NiCoFeCrGa high entropy alloy, which is a mixture of face-centered cubic (FCC) and body-centered cubic (BCC) crystalline phases. The microstructure of the samples was investigated by using scanning electron microscopy (SEM), time-of-flight secondary ion mass spectroscopy (TOF-SIMS), transmission electron microscopy-based energy-dispersive spectroscopy (EDS) and electron energy loss spectroscopy (EELS), as well as X-ray diffraction (XRD) measurements. Based on the phases observed in different temperature ranges, a sequence of the phase transitions can be established, showing that in a realistic process, when freely cooling the sample with the furnace from high to room temperature, a microstructure having spinodal-like decomposition can also be expected. The elemental mapping and magnetic behaviors of this decomposed structure are also studied.

scholarly journals Investigating Helium Bubble Nucleation and Growth through Simultaneous In-Situ Cryogenic, Ion Implantation, and Environmental Transmission Electron Microscopy

Materials ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 2618 ◽  
Author(s):  
Caitlin A. Taylor ◽  
Samuel Briggs ◽  
Graeme Greaves ◽  
Anthony Monterrosa ◽  
Emily Aradi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Implantation ◽  
Nucleation And Growth ◽  
Bubble Nucleation ◽  
Face Centered Cubic ◽  
Helium Bubble ◽  
Palladium Hydride ◽  
Transmission Electron

Palladium can readily dissociate molecular hydrogen at its surface, and rapidly accept it onto the octahedral sites of its face-centered cubic crystal structure. This can include radioactive tritium. As tritium β-decays with a half-life of 12.3 years, He-3 is generated in the metal lattice, causing significant degradation of the material. Helium bubble evolution at high concentrations can result in blister formation or exfoliation and must therefore be well understood to predict the longevity of materials that absorb tritium. A hydrogen over-pressure must be applied to palladium hydride to prevent hydrogen from desorbing from the metal, making it difficult to study tritium in palladium by methods that involve vacuum, such as electron microscopy. Recent improvements in in-situ ion implantation Transmission Electron Microscopy (TEM) allow for the direct observation of He bubble nucleation and growth in materials. In this work, we present results from preliminary experiments using the new ion implantation Environmental TEM (ETEM) at the University of Huddersfield to observe He bubble nucleation and growth, in-situ, in palladium at cryogenic temperatures in a hydrogen environment. After the initial nucleation phase, bubble diameter remained constant throughout the implantation, but bubble density increased with implantation time. β-phase palladium hydride was not observed to form during the experiments, likely indicating that the cryogenic implantation temperature played a dominating role in the bubble nucleation and growth behavior.

scholarly journals Controlling the Amorphous and Crystalline State of Multinary Alloy Nanoparticles in An Ionic Liquid

Nanomaterials ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 903 ◽  
Author(s):  
Alba Garzón-Manjón ◽  
Hajo Meyer ◽  
Dario Grochla ◽  
Tobias Löffler ◽  
Wolfgang Schuhmann ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Electron Beam ◽  
Crystalline State ◽  
Ex Situ ◽  
Alloy Nanoparticles ◽  
Face Centered Cubic ◽  
Transmission Electron ◽  
Cubic Structure ◽  
Face Centered

Controlling the amorphous or crystalline state of multinary Cr-Mn-Fe-Co-Ni alloy nanoparticles with sizes in the range between ~1.7 nm and ~4.8 nm is achieved using three processing routes. Direct current sputtering from an alloy target in the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide leads to amorphous nanoparticles as observed by high-resolution transmission electron microscopy. Crystalline nanoparticles can be achieved in situ in a transmission electron microscope by exposure to an electron beam, ex situ by heating in vacuum, or directly during synthesis by using a high-power impulse magnetron sputtering process. Growth of the nanoparticles with respect to the amorphous particles was observed. Furthermore, the crystal structure can be manipulated by the processing conditions. For example, a body-centered cubic structure is formed during in situ electron beam crystallization while longer ex situ annealing induces a face-centered cubic structure.

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