@inproceedings{KashkarovSutyginaNikitenkovetal., author = {Kashkarov, Egor B. and Sutygina, Alina and Nikitenkov, Nikolay and Syrtanov, Maxim S. and Obrosov, Aleksei}, title = {Microstructure changes and hydrogenation behaviour of Zr-1Nb alloy after plasma immersion titanium implantation at different time of exposure}, series = {American Advanced Materials Congress 2016}, booktitle = {American Advanced Materials Congress 2016}, editor = {Tiwari, Ashutosh}, publisher = {VBRI Press}, address = {Link{\"o}ping}, isbn = {978-91-88252-03-6}, abstract = {Zirconium alloys are the main construction materials of water-cooled nuclear reactors. Zirconium is used in the core of nuclear reactors as fuel element claddings due to low thermal-neutron capture cross section. Hydrogen is released in the process of water radiolysis or high-temperature oxidation of fuel claddings under loss of coolant accident (LOCA) conditions. The penetration and accumulation of hydrogen in zirconium alloys lead to degradation of their physical and mechanical properties caused by hydrogen embrittlement and delayed hydride cracking [1, 2]. Plasma immersion ion implantation (PIII) is widely used to improve the mechanical properties, corrosion and erosion resistance as well as to decrease hydrogen absorption rate of zirconium [3, 4]. During PIII, a plasma ions are accelerated by high voltage pulsed bias applied to the target. The accelerated ions penetrate in the bulk of the target and modify the deeper layers of materials. Previous studies shown that PIII of titanium improves the protection properties of Zr-2.5Nb alloy from hydrogenation [5]. Moreover, the microdroplets and ion energy have significant impact on hydrogen absorption of the alloys. However, it is necessary to understand the mechanism of hydrogen interaction with the modified layers depending on the time of implantation. In this study, titanium ions were implanted into Zr-1Nb alloy target using filtered vacuum arc source and high frequency short pulser. Coaxial plasma filter was used to reduce the number and size of microdroplets evaporated from the cathode spots. The implantation parameters are: 70 A arc current, 0.15 Pa argon pressure, 1500 V pulsed bias, 100 kHz repetition frequency, 5 μs pulse length and 5-30 min implantation time. Gas-phase hydrogenation was performed at 623 K and 2 atm. hydrogen pressure for 60 min. Surface morphology, phase composition and depth distribution of elements were investigated using scanning electron and atomic force microscopies (SEM and AFM), X-ray diffraction and glow-discharge optical emission spectroscopy (GDOES). It was revealed that the microdroplets and craters with the size of several microns are formed after titanium implantation. The number and size of craters are increased with implantation time from 5 to 30 minutes. It is assumed that the presence of craters on the surface caused by bombardment of an accelerated ion clusters, which is formed due to incorporation (condensation) and ionization of evaporated atoms near the cathode region. Furthermore, the surface becomes rougher and the microstructure changes to fine-grained with an average grain size of 50-100 nm with increase of implantation time. Hydrogenation behaviour depends on the implantation time and differs from the non-treated Zr-1Nb alloy. Hydrogen absorption rate decreases by two times with increase in implantation time from 5 to 30 min. Furthermore, hydrogen preferably accumulates in the modified layer at higher implantation time. The distribution of hydrogen tends to decrease in the depth of implanted layer. The phase state of the alloy has not changed after implantation, however, the extensive distortions of the crystal lattice are observed after hydrogenation of the non-treated and implanted for 5 min Zr-1Nb alloys.}, language = {en} } @misc{KashkarovNikitenkovSutyginaetal., author = {Kashkarov, Egor B. and Nikitenkov, Nikolay and Sutygina, Alina and Laptev, Roman and Bordulev, Yuriy and Obrosov, Aleksei and Liedke, Maciej O. and Zak, Andrzej and Weiß, Sabine}, title = {Microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb treated by plasma immersion Ti ion implantation and deposition}, series = {Journal of Alloys and Compounds}, volume = {732}, journal = {Journal of Alloys and Compounds}, issn = {0925-8388}, doi = {10.1016/j.jallcom.2017.10.151}, pages = {80 -- 87}, abstract = {The effect of low energy plasma immersion ion implantation and deposition of titanium on microstructure, defect structure and hydrogen trapping in zirconium alloy Zr-1Nb was studied. Defect structure and distribution were analyzed by Doppler broadening using slow positron beam. The surface microstructure after modification is represented by nanostructured Ti grains with random orientation. The gradient distribution of titanium as well as vacancy type defects were analyzed. The concentration of vacancy type defects is rising with increasing bias voltage. Gas-phase hydrogenation of the Ti-modified Zr-1Nb alloy was performed at 400 °C for 60 min. The strong interaction of hydrogen with vacancy type defects was demonstrated. Two different changes in the defect structure after hydrogenation were observed: when a titanium film is formed on the surface (after deposition at 500 V) hydrogen trapping occurs with the formation of titanium hydride phases, while in the implanted layer (deposition at 1000 and 1500 V) hydrogen is trapped due to interaction with vacancy type defects. The physical basis of Ti diffusion and its influence on the evolution of defect structure after surface modification and hydrogenation were discussed.}, language = {en} } @misc{KashkarovNikitenkovSutyginaetal., author = {Kashkarov, Egor B. and Nikitenkov, Nikolay and Sutygina, Alina and Obrosov, Aleksei and Manakhov, Anton and Polčak, Josef and Weiß, Sabine}, title = {Hydrogen absorption by Ti-implanted Zr-1Nb alloy}, series = {International journal of hydrogen energy}, volume = {43}, journal = {International journal of hydrogen energy}, number = {4}, issn = {0360-3199}, doi = {10.1016/j.ijhydene.2017.12.003}, pages = {2484 -- 2491}, abstract = {This paper describes the hydrogenation behavior of Zr-1Nb alloy Ti-implanted by plasma immersion ion implantation (PIII). Hydrogen sorption kinetics of the Ti-modified alloy was investigated under gas-phase hydrogenation at 400 °C for 1 h. The influence of implantation time on the protective properties of the modified layer was shown. The lowest hydrogen absorption as well as the highest hydrogen trapping efficiency was achieved after PIII for 30 min. The main contribution to the reduction of hydrogen permeation is the formation of an oxide layer consisting of mixed TiO2 and ZrO2 on the modified surface of the alloy. X-ray photoelectron spectroscopy (XPS) revealed that PIII titanium oxide exists on the surface in the form of TiO2, which transforms to mixed Ti2O3 and TiO2 after hydrogenation. The thickness of the modified layer increases with implantation time that improves the efficiency of hydrogen trapping. All the absorbed hydrogen is gradually distributed in the modified layer and no hydrides are formed after hydrogenation in Ti-modified Zr-1Nb for 15 and 30 min.}, language = {en} } @misc{KashkarovNikitenkovSutyginaetal., author = {Kashkarov, Egor B. and Nikitenkov, Nikolay and Sutygina, Alina and Syrtanov, Maxim S. and Zakharchenko, S. and Obrosov, Aleksei}, title = {Influence of Plasma-Immersion Titanium-Ion Implantation on the Kinetics of Hydrogen Penetration into E110 Zirconium Alloy}, series = {Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques}, volume = {12}, journal = {Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques}, number = {3}, issn = {1819-7094}, doi = {10.1134/S102745101803031X}, pages = {570 -- 575}, abstract = {The influence of plasma-immersion titanium-ion implantation on the hydrogen saturation of E110 zirconium alloy is described. Titanium ions are implanted from the metal plasma of an arc discharge at an accelerating-pulse bias potential of 1.5 kV (the pulse-repetition frequency is 100 kHz, and the pulse length is 5 μs) for 30 min. The phase composition, morphology, and valence state of the alloy surface layer are studied. Comparative analysis of changes in the hardness and wear resistance of the alloy subjected to implantation is performed. It is demonstrated that the rate of hydrogen penetration into the surface-doped alloy decreases substantially at a gas-phase hydrogenation temperature of 400°C.}, language = {en} }