Impact of Hydrogen Content on the Thermal Stability of Hydride Phases in Zirconium Alloys

2018 ◽  
Vol 941 ◽  
pp. 1318-1323
Author(s):  
Egle Conforto ◽  
Patrick Girault ◽  
Cyril Berziou ◽  
Guillaume Lotte ◽  
Rémy Milet ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
Hydrogen Diffusion ◽  
Zirconium Alloys ◽  
Nuclear Industry ◽  
Orientation Relationships ◽  
Hydrogen Atoms ◽  
Diffusion Controlled ◽  
Zirconium Hydrides ◽  
Thermal Stability Of

The fast and spontaneous hydrogen diffusion in HCP structures leads to the hydride precipitation. It is often pointed as causing embrittlement and rupture in zirconium alloys for applications in the nuclear industry. In our previous works TEM, DSC, SEM-EBSD and XRD were used to study the hydride stability after many precipitation-dissolution thermal cycles as well as the crystallographic hydride phase nature and the hydride-substrate crystallographic orientation relationships as a function of the hydrogen content. Results showed that the evolution of the dissolution and precipitation energies is correlated to the concentration of hydrogen atoms available to reprecipitate, which is submitted to a diffusion controlled by the misfit dislocation migration. In the present workin-situTEM thermal cycling was performed in order to locally investigate the crystallographic stability of zirconium hydrides of different structures after many dissolution-reprecipitation cycles.

Formation and Dissolution of Hydride Precipitates in Zirconium Alloys: Crystallographic Orientation Relationships and Stability after Temperature Cycling

2016 ◽  
Vol 879 ◽  
pp. 2330-2335 ◽  
Author(s):  
Egle Conforto ◽  
Stephane Cohendoz ◽  
Cyril Berziou ◽  
Patrick Girault ◽  
Xavier Feaugas
Keyword(s):  
Hydrogen Content ◽  
Hydrogen Diffusion ◽  
Zirconium Alloys ◽  
Temperature Cycling ◽  
Nuclear Industry ◽  
X Rays ◽  
Orientation Relationships ◽  
Hydrogen Distribution ◽  
Cycle Number ◽  
Hydride Phases

Hydride precipitation due to the spontaneous and fast hydrogen diffusion is often pointed as causing embrittlement and rupture in zirconium alloys used in the nuclear industry. Transmission Electron Microscopy (TEM) and X-Rays Diffraction (XRD) have been used to study the precipitation of hydride phases in zirconium alloys as a function of the hydrogen content. The orientation relationships observed between the hydride phase and the substrate were similar to those previously observed in Titanium hydrides grown on Titanium. Dislocation emission from the hydride precipitates has been directly related to the relaxation of the misfit stresses appearing during the transformation. The stability of the hydride phases after several dissolution-reprecipitation cycles have been studied by DSC, TEM and XRD for different total hydrogen content in several alloys. The energy of precipitation observed is lower than that of the dissolution in each case studied. The temperature associated with these two processes slightly increase as a function of the cycle number, as a result of the homogenizing hydrogen distribution in the alloy bulk. The same hydrides phases present before cycling were also observed after 20 cycles. However, transition phases poorer in hydrogen than the dominant one may precipitate at the interface with the substrate. The evolution of these transitions phases with the temperature increase will be investigated by TEM in-situ heating in the next future.

In situ HREM of interface interactions

1993 ◽  
Vol 51 ◽  
pp. 830-831
Author(s):  
Robert Sinclair ◽  
Toyohiko J. Konno
Keyword(s):  
Amorphous Material ◽  
Equilibrium Phase ◽  
High Resolution Electron Microscopy ◽  
Atomic Scale ◽  
Orientation Relationships ◽  
Interface Reactions ◽  
Diffusion Controlled ◽  
Resolution Electron

We have applied in situ high-resolution electron microscopy (HREM) to the study of interface reactions, particularly in metal-semiconductor systems. There is contrasting behavior whether or not the manufactured interface undergoes a chemical reaction. The in situ technique allows determination of the reaction mechanisms on an atomic scale.Reactive interfaces are characterized by systems in which new chemical compounds are formed (e.g., silicides for metal-silicon interfaces, metal gallides and arsenides for GaAs, etc.). We found that the equilibrium phase formation is often preceded by a solid-state amorphization reaction. In situ observations allow very precise measurement of the reaction rate in a sufficient temperature range to confirm that this process is diffusion controlled. Crystallization of the amorphous material can be followed as well as the development of any crystallographic orientation relationships. A ledge growth mechanism can easily be distinguished from a random process.It might be expected that non-reactive interfaces are stable upon heating.

Anisotropy of Hydrogen Diffusivity in ZnO

2013 ◽  
Vol 333 ◽  
pp. 39-49 ◽  
Author(s):  
Jakub Čížek ◽  
František Lukáč ◽  
Marián Vlček ◽  
Martin Vlach ◽  
Ivan Procházka ◽  
...  
Keyword(s):  
Plastic Deformation ◽  
Hydrogen Concentration ◽  
Hydrogen Diffusion ◽  
Surface Region ◽  
Nuclear Reaction Analysis ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
Slow Positron ◽  
X Ray

Hydrogen absorption and diffusivity in high quality ZnO crystals were investigated in this work by X-ray diffraction combined with slow positron implantation spectroscopy and electrical resistometry. ZnO crystals were covered by a thin Pd over-layer and electrochemically charged with hydrogen. It was found that absorbed hydrogen causes plastic deformation in a sub-surface region. The depth profile of hydrogen concentration introduced into the crystal was determined by nuclear reaction analysis. Enhanced hydrogen concentration was found in the sub-surface region due to excess hydrogen atoms trapped at defects introduced by plastic deformation. Hydrogen diffusion in ZnO crystals with various orientations was studied by in-situ electrical resistometry. It was found that hydrogen diffusion in the c-direction is faster than hydrogen diffusion in the a-direction most probably due to open channels existing in the wurtzite structure along the c-axis.

scholarly journals A Review of Hydride Precipitates in Titanium and Zirconium Alloys: Precipitation, Dissolution and Crystallographic Orientation Relationships

2020 ◽  
Vol 321 ◽  
pp. 11042
Author(s):  
Egle CONFORTO ◽  
Xavier FEAUGAS
Keyword(s):  
Zirconium Alloys ◽  
Zirconium Hydride ◽  
Misfit Dislocations ◽  
Orientation Relationships ◽  
Ti Alloys ◽  
Local Plastic Strain ◽  
Bulk Scale ◽  
Hydride Phases ◽  
Zr Alloys

This work proposes a review of recent results on the formation and dissolution of hydrides in HCP alloys (Ti and Zr alloys) correlated to the nature of crystallographic hydride phases and their ORs. The crystallographic coherence observed between the surface hydride layer and the substrate is very important for many applications as for biomaterials devices. Five particular orientation relationships (OR) were identified between titanium/zirconium hydride precipitates and the oc-Ti and a-Zr substrates. In addition, the nature of hydrides have a large implication on the ductility, the strain hardening, and the local plastic strain accommodation in the Ti alloys. Our studies using XDR, TEM and SEM-EBSD have been demonstrating that the nature of the hydride phase precipitates depends on the hydrogen content. DSC has been used to obtain the hydride dissolution and precipitation energy values at the bulk scale, whose difference can be associated to misfit dislocations. Local in-situ TEM dissolution observations show the depinning of part of misfit dislocations during dissolution process. Hydride reprecipitation is thus possible only if hydrogen is not driven away during heating by misfit dislocations depinning.

scholarly journals NANOINDENTATION OF HYDROGEN ENRICHED Zr-1Nb ZIRCONIUM ALLOY NUCLEAR FUEL CLADDINGS

2020 ◽  
Vol 27 ◽  
pp. 155-159
Author(s):  
Ondřej Libera ◽  
Patricie Halodová ◽  
Petra Gávelová ◽  
Jakub Krejčí
Keyword(s):  
Nuclear Fuel ◽  
Hydrogen Content ◽  
Zirconium Alloy ◽  
Nuclear Reactors ◽  
Bulk Material ◽  
Surface Preparation ◽  
Zirconium Alloys ◽  
High Hydrogen ◽  
Operation Conditions ◽  
Zirconium Hydrides

Zirconium alloys are being commonly used as a material of choice for nuclear fuel claddings in water cooled nuclear reactors for decades due to their good corrosion resistance and low neutron absorption. However, the increasing operation conditions of next generation nuclear reactors (Gen-V) in terms of higher temperatures, pressures and higher neutron flux requires evaluation of further Zr cladding usability. The embrittlement of Zr claddings due to hydrogen pickup from reactor coolant is one of the issues for its potential use in Gen-IV reactors. Nanoindentation is an effective tool for analysis of the change of mechanical properties of hydrogen enriched Zr claddings from localised material volume. Zirconium alloy Zr-1Nb (E110) with experimentally induced hydrides was analysed by the means of nanoindentation. Zirconium hydrides were formed in the material after exposure in high temperature water autoclave. The optimized methodology of surface preparation suitable for nanoindentation is described and the resulting surface quality is discussed. The nanoindentation measurements were performed as an array of 10x10 indents across areas with hydrides. Depth dependent hardness and reduced modulus values measured by nanoindentation were compared between the material with no hydrogen content, low hydrogen content (127 ppm H) and high hydrogen content (397 ppm H). Complementary microhardness measurements at HV 0.1 were performed on all materials for bulk material hardness comparison.

Ex-situ and in-situ Neutron Radiography Investigations of the Hydrogen Uptake of Nuclear Fuel Cladding Materials During Steam Oxidation at 1000°C and Above

2010 ◽  
Vol 1262 ◽  
Author(s):  
Mirco Grosse ◽  
Marius van den Berg ◽  
Eberhard Helmar Lehmann ◽  
Burkhard Schillinger
Keyword(s):  
Hydrogen Diffusion ◽  
Neutron Radiography ◽  
Zirconium Alloys ◽  
Hydrogen Uptake ◽  
Steam Oxidation ◽  
Ex Situ ◽  
In Situ Experiments ◽  
Nuclear Fuel Cladding ◽  
Non Destructive

AbstractNeutron radiography is a powerful tool for the investigation of the hydrogen uptake of zirconium alloys. It is fast, fully quantitative, non-destructive and provides a spatial resolution of 30 μm. The non-destructive character of neutron radiography provides the possibility of in-situ investigations. The paper describes the calibration of the method and delivers results of ex-situ measurements of the hydrogen concentration distribution after steam oxidation, as well as in-situ experiments of hydrogen diffusion in β-Zr and in-situ investigations of the hydrogen uptake during steam oxidation.

Hydrogen Diffusion in Zr-Cu-Ni-Al Metallic Glasses

2003 ◽  
Vol 801 ◽  
Author(s):  
Tomaz Apih ◽  
Lioba Jastrow ◽  
Lyudmila Lyubenova ◽  
Janez Dolinšek ◽  
Daniela Zander ◽  
...  
Keyword(s):  
Hydrogen Content ◽  
Metallic Glasses ◽  
Hydrogen Diffusion ◽  
Spin Echo ◽  
Diffusion Constant ◽  
Superconducting Magnet ◽  
Inhomogeneous Magnetic Field ◽  
Fringe Field ◽  
Hydrogen Atoms ◽  
Self Diffusion

AbstractZr-based metallic glasses are known to absorb high amounts of hydrogen, but exhibiting less severe embrittlement than their crystalline counterparts; therefore, they might be useful for hydrogen storage application. In order to understand kinetics of hydrogen absorption and desorption in more detail, data on hydrogen diffusion are necessary. The aim of this paper is to present hydrogen diffusivities in melt-spun amorphous Zr69.5Cu12Ni11Al7.5 alloys.Hydrogen charging was performed electrochemically in a 2:1 glycerin-phosphoric acid electrolyte. Hydrogen contents were measured by a microbalance with accuracy of ±1 μg as well as by LECO. Diffusivities of hydrogen atoms were measured at different temperatures by the technique of Nuclear Magnetic Resonance (NMR) diffusion in a static fringe field of a superconducting magnet. The diffusion of hydrogen nuclei in an inhomogeneous magnetic field is accompanied by the change of its NMR resonance frequency, which produces motional destruction of the spin echo signal. The analysis of the echo damping allows a model-independent determination of the hydrogen self-diffusion constant, with the low limit of sensitivity D>10−10 cm2/s.Within the temperature interval between room temperature and 420 K diffusivities in the range between 4×10−8 and 1.2×10−9 cm2/s were observed. The Arrhenius-type temperature dependence indicate a simple classical over-barrier-hopping hydrogen diffusion; the activation energy increases slightly with the hydrogen content. Whereas in a number of metallic glasses hydrogen diffusion is known to increase with the hydrogen content, in Zr69.5Ni12Cu11Al7.5 the opposite effect was observed, at least for hydrogen contents between H/M = 0.2 and 1.2. The results will be compared with other measurements known for Zr-based metallic glasses (e.g., Zr-Ni) and discussed in detail, e.g. in regard to the density of the glass.

scholarly journals In Situ Neutron Radiography Investigations of Hydrogen Related Processes in Zirconium Alloys

2021 ◽  
Vol 11 (13) ◽  
pp. 5775
Author(s):  
Mirco Grosse ◽  
Burkhardt Schillinger ◽  
Anders Kaestner
Keyword(s):  
Zirconium Alloy ◽  
High Temperature Oxidation ◽  
Hydrogen Diffusion ◽  
Neutron Radiography ◽  
Zirconium Alloys ◽  
Hydrogen Uptake ◽  
Temperature Oxidation ◽  
Diffusive Processes ◽  
Kinetics Of

In situ neutron radiography experiments can provide information about diffusive processes and the kinetics of chemical reactions. The paper discusses requirements for such investigations. As examples of the zirconium alloy Zircaloy-4, the hydrogen diffusion, the hydrogen uptake during high-temperature oxidation in steam, and the reaction in nitrogen/steam and air/steam atmospheres, results of in situ neutron radiography investigations are reviewed, and their benefit is discussed.

In situ TEM observations of melting in nanosized eutectic Pb-Cd inclusions embedded in Al

1996 ◽  
Vol 54 ◽  
pp. 986-987
Author(s):  
S. Hagège ◽  
U. Dahmen ◽  
E. Johnson ◽  
A. Johansen ◽  
V.S. Tuboltsev
Keyword(s):  
Electron Microscope ◽  
Melt Spinning ◽  
Ternary Alloys ◽  
Solid Matrix ◽  
Eutectic System ◽  
In Situ Tem ◽  
In Situ Observation ◽  
Orientation Relationships ◽  
Transmission Electron

Small particles of a low-melting phase embedded in a solid matrix with a higher melting point offer the possibility of studying the mechanisms of melting and solidification directly by in-situ observation in a transmission electron microscope. Previous studies of Pb, Cd and other low-melting inclusions embedded in an Al matrix have shown well-defined orientation relationships, strongly faceted shapes, and an unusual size-dependent superheating before melting.[e.g. 1,2].In the present study we have examined the shapes and thermal behavior of eutectic Pb-Cd inclusions in Al. Pb and Cd form a simple eutectic system with each other, but both elements are insoluble in solid Al. Ternary alloys of Al (Pb,Cd) were prepared from high purity elements by melt spinning or by sequential ion implantation of the two alloying additions to achieve a total alloying addition of up to lat%. TEM observations were made using a heating stage in a 200kV electron microscope equipped with a video system for recording dynamic behavior.

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