scholarly journals Resistance to Helium Bubble Formation in Amorphous SiOC/Crystalline Fe Nanocomposite

Materials ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 93 ◽  
Author(s):  
Qing Su ◽  
Tianyao Wang ◽  
Jonathan Gigax ◽  
Lin Shao ◽  
Michael Nastasi
Keyword(s):  
Bubble Formation ◽  
Secondary Phase ◽  
Silicon Oxycarbide ◽  
Helium Bubble ◽  
Helium Bubbles ◽  
Transmission Electron ◽  
Bubble Density ◽  
Secondary Phase Formation ◽  
Helium Ion ◽  
Fission Reactors

The management of radiation defects and insoluble He atoms represent key challenges for structural materials in existing fission reactors and advanced reactor systems. To examine how crystalline/amorphous interface, together with the amorphous constituents affects radiation tolerance and He management, we studied helium bubble formation in helium ion implanted amorphous silicon oxycarbide (SiOC) and crystalline Fe composites by transmission electron microscopy (TEM). The SiOC/Fe composites were grown via magnetron sputtering with controlled length scale on a surface oxidized Si (100) substrate. These composites were subjected to 50 keV He+ implantation with ion doses chosen to produce a 5 at% peak He concentration. TEM characterization shows no sign of helium bubbles in SiOC layers nor an indication of secondary phase formation after irradiation. Compared to pure Fe films, helium bubble density in Fe layers of SiOC/Fe composite is less and it decreases as the amorphous/crystalline SiOC/Fe interface density increases. Our findings suggest that the crystalline/amorphous interface can help to mitigate helium defect generated during implantation, and therefore enhance the resistance to helium bubble formation.

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.

A transmission electron microscopy study of the crystallinity and secondary phase formation in melt-processed YBa2Cu3O7−δ

1996 ◽  
Vol 11 (12) ◽  
pp. 2990-2999 ◽  
Author(s):  
Y. Yan ◽  
D. A. Cardwell ◽  
A. M. Campbell ◽  
W. M. Stobbs
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Secondary Phase ◽  
High Resolution Electron Microscopy ◽  
Microscopy Study ◽  
Electron Microscopy Study ◽  
Transmission Electron ◽  
Resolution Electron ◽  
Secondary Phase Formation ◽  
Layer Stacking

The microstructure of large grain melt-processed YBa2Cu3O7−δ containing 10 molar% excess Y2BaCuO5 prepared and oxygenated under atmospheric pressure has been investigated by transmission electron microscopy (TEM) and optical microscopy. These materials always contain parallel structural and microscopic platelet-like features in the crystallographic a-b plane of a few microns spacing which have been variously described as grain boundaries or microcracks. We have observed such features, which clearly influence the flow of current in melt-processed YBCO, to consist of copper deficient, impurity phase material which can be either amorphous or crystalline in nature. A variety of defects have been observed by high-resolution electron microscopy (HREM) in the vicinity of these platelet boundaries, including double and triple CuO layer stacking faults, which may constitute effective flux pinning sites.

A Transmission Electron Microscopy Study of the Effect of Interfaces on Bubble Formation in He-Implanted Cu-Nb Multilayers

2012 ◽  
Vol 18 (1) ◽  
pp. 152-161 ◽  
Author(s):  
D. Bhattacharyya ◽  
M.J. Demkowicz ◽  
Y.-Q. Wang ◽  
R.E. Baumer ◽  
M. Nastasi ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Layer Thickness ◽  
Bubble Diameter ◽  
Bubble Formation ◽  
Nuclear Reaction Analysis ◽  
Cross Sectional ◽  
Helium Bubbles ◽  
Transmission Electron ◽  
Pure Cu

AbstractMagnetron sputtered thin films of Cu, Nb, and Cu-Nb multilayers with 2.5 and 5 nm nominal layer thickness were deposited on Si and implanted with 4He+ and 3He+ ions. Secondary ion mass spectroscopy and nuclear reaction analysis, respectively, were used to measure the 4He+ and 3He+ concentration profile with depth inside the films. Cross-sectional transmission electron microscopy was used to characterize the helium bubbles. Analysis of the contrast from helium bubbles in defocused transmission electron microscope images showed a minimum bubble diameter of 1.25 nm. While pure Cu and Nb films showed bubble contrast over the entire range of helium implantation, the multilayers exhibited bubbles only above a critical He concentration that increased almost linearly with decreasing layer thickness. The work shows that large amounts of helium can be trapped at incoherent interfaces in the form of stable, nanometer-size bubbles.

Ni+ and He+ Implantation Effects on the Hardness and Microstructure of Heat-Treated X750 Superalloy

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Maisaa N. Tawfeeq ◽  
Robert J. Klassen
Keyword(s):  
Electron Microscopy ◽  
Indentation Hardness ◽  
Hardness Testing ◽  
Strengthening Phase ◽  
Tem Analysis ◽  
Helium Bubbles ◽  
Implantation Damage ◽  
Transmission Electron ◽  
Heat Treated ◽  
Helium Ion

Abstract Nickel and Helium ion implantation-induced hardening and microstructural evolution of X750 in the heat-treated (HT) and solution annealed (SA) conditions were investigated using nano-indentation hardness testing and electron microscopy (scanning electron microscopy (SEM) and transmission electron microscopy (TEM)). Irradiation crystal damage up to ψ = 5 dpa was invoked with Ni+ implantation while He+ implantation up to CHe = 5000 appm was performed on samples the HT and SA conditions. The X750 alloy displayed generally increasing hardness with increasing Ni+ implantation damage but a perturbation in the trend occurred when ψ ≤ 0.5 dpa, and the hardness dropped by about 30% and 2% for the HT and the SA samples, respectively. TEM analysis indicated that this softening was associated with disordering and dissolution of the γ′ strengthening phase. The hardening behavior observed at higher implantation damage (ψ = 1 dpa) resulted in reformation of Al/Ti-rich regions within the microstructure phase. The hardness of the X750 increased continuously with increasing implanted He+ up to CHe = 1000 appm. This was associated with the formation of helium bubbles as observed by TEM. Slight drop in hardness in the HT condition at CHe = 5000 appm indicated that high levels of He+ implantation destabilize the γ′ precipitates as was confirmed with TEM observed disappearance of γ′ super-lattice reflections.

scholarly journals COMPARATIVE STUDY OF HELIUM BUBBLE FORMATION IN Cr-Fe-Ni-Mn HIGH-ENTROPY ALLOY AND 18Cr10NiTi STEEL AFTER IRRADIATION AND POST-IRRADIATION ANNEALING

2019 ◽  
pp. 25-29
Author(s):  
А.S. Kalchenko ◽  
S.A. Karpov ◽  
I.E. Kopanets ◽  
M.A. Tikhonovsky ◽  
G.D. Tolstolutskaya
Keyword(s):  
Room Temperature ◽  
Ion Irradiation ◽  
Identical Condition ◽  
Bubble Formation ◽  
Austenitic Stainless Steels ◽  
High Entropy Alloy ◽  
Helium Bubble ◽  
High Entropy ◽  
Helium Ion ◽  
Displacement Per Atom

High entropy alloys (HEAs) are considered for applications in nuclear reactors due to their promising mechanical properties, corrosion and radiation resistance. In order to understand the irradiation effects in HEAs and to demonstrate their potential advantages over conventional austenitic stainless steels, we performed helium ion irradiation experiments with 20Cr-40Fe-20Ni-20Mn high-entropy alloy and 18Cr10NiTi steel under an identical condition. Both alloys have been irradiated to a dose of 4.8 displacement per atom (dpa) and a helium concentration of 11.7 at.% at room temperature. After subsequent annealing at 500 °C the microstructure evolution of irradiated materials was examined. The irradiation promotes the formation of a high density of bubbles in HEA and steel. Comparison of parameters of helium porosity in these materials has been done.

scholarly journals Helium Bubbles and Blistering in a Nanolayered Metal/Hydride Composite

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5393
Author(s):  
Caitlin A. Taylor ◽  
Eric Lang ◽  
Paul G. Kotula ◽  
Ronald Goeke ◽  
Clark S. Snow ◽  
...  
Keyword(s):  
Ex Situ ◽  
Metallic Multilayers ◽  
Helium Bubble ◽  
Helium Bubbles ◽  
Transmission Electron ◽  
The Matrix ◽  
Multilayered Composites ◽  
Helium Implantation ◽  
Thin Film Composites

Helium is insoluble in most metals and precipitates out to form nanoscale bubbles when the concentration is greater than 1 at.%, which can alter the material properties. Introducing controlled defects such as multilayer interfaces may offer some level of helium bubble management. This study investigates the effects of multilayered composites on helium behavior in ion-implanted, multilayered ErD2/Mo thin film composites. Following in-situ and ex-situ helium implantation, scanning and transmission electron microscopy showed the development of spherical helium bubbles within the matrix, but primarily at the layer interfaces. Bubble linkage and surface blistering is observed after high fluence ex-situ helium implantation. These results show the ability of metallic multilayers to alter helium bubble distributions even in the presence of a hydride layer, increasing the lifetime of materials in helium environments.

scholarly journals Statistical analysis of helium bubbles in transmission electron microscopy images based on machine learning method

2021 ◽  
Vol 32 (5) ◽  
Author(s):  
Zhong-Hang Wu ◽  
Ju-Ju Bai ◽  
Di-Da Zhang ◽  
Gang Huang ◽  
Tian-Bao Zhu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Machine Learning ◽  
Transmission Electron Microscopy ◽  
Image Resolution ◽  
Structure Identification ◽  
Machine Learning Method ◽  
Learning Method ◽  
Helium Bubble ◽  
Helium Bubbles ◽  
Transmission Electron

AbstractHelium bubbles, which are typical radiation microstructures observed in metals or alloys, are usually investigated using transmission electron microscopy (TEM). However, the investigation requires human inputs to locate and mark the bubbles in the acquired TEM images, rendering this task laborious and prone to error. In this paper, a machine learning method capable of automatically identifying and analyzing TEM images of helium bubbles is proposed, thereby improving the efficiency and reliability of the investigation. In the proposed technique, helium bubble clusters are first determined via the density-based spatial clustering of applications with noise algorithm after removing the background and noise pixels. For each helium bubble cluster, the number of helium bubbles is determined based on the cluster size depending on the specific image resolution. Finally, the helium bubble clusters are analyzed using a Gaussian mixture model, yielding the location and size information on the helium bubbles. In contrast to other approaches that require training using numerous annotated images to establish an accurate classifier, the parameters used in the established model are determined using a small number of TEM images. The results of the model formulated according to the proposed approach achieved a higher F1 score validated through some helium bubble images manually marked. Furthermore, the established model can identify bubble-like objects that humans cannot facilely identify. This computationally efficient method achieves object recognition for material structure identification that may be advantageous to scientific work.

Observation of solid-state reaction between a thin yttria film and a (0001) α-alumina substrate

1994 ◽  
Vol 52 ◽  
pp. 644-645
Author(s):  
J. R. Heffelfinger ◽  
C. B. Carter
Keyword(s):  
Electron Microscopy ◽  
Solid State ◽  
Solid State Reaction ◽  
Yttrium Aluminum Garnet ◽  
Secondary Phase ◽  
Ceramic Composites ◽  
Alumina Substrate ◽  
Transmission Electron ◽  
Alumina Fibers ◽  
Optical Applications

Transmission-electron microscopy (TEM), scanning-electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS) were used to investigate the solid-state reaction between a thin yttria film and a (0001) α-alumina substrate. Systems containing Y2O3 (yttria) and Al2O3 (alumina) are seen in many technologically relevant applications. For example, yttria is being explored as a coating material for alumina fibers for metal-ceramic composites. The coating serves as a diffusion barrier and protects the alumina fiber from reacting with the metal matrix. With sufficient time and temperature, yttria in contact with alumina will react to form one or a combination of phases shown by the phase diagram in Figure l. Of the reaction phases, yttrium aluminum garnet (YAG) is used as a material for lasers and other optical applications. In a different application, YAG is formed as a secondary phase in the sintering of AIN. Yttria is added to AIN as a sintering aid and acts as an oxygen getter by reacting with the alumina in AIN to form YAG.

Sign in / Sign up

Export Citation Format

Share Document