- Email: [email protected]
Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy
Accepted Manuscript Title: Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy Authors: Andrey A. Mikhaylov, Tatiana S. Priamushko, Maria N. Babikhina, Victor N. Kudiiarov, Rene Heller, Roman S. Laptev, Andrey M. Lider PII: DOI: Reference:
S0169-4332(17)31846-9 http://dx.doi.org/doi:10.1016/j.apsusc.2017.06.191 APSUSC 36391
To appear in:
APSUSC
Received date: Revised date: Accepted date:
31-10-2016 29-4-2017 18-6-2017
Please cite this article as: Andrey A.Mikhaylov, Tatiana S.Priamushko, Maria N.Babikhina, Victor N.Kudiiarov, Rene Heller, Roman S.Laptev, Andrey M.Lider, Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy, Applied Surface Sciencehttp://dx.doi.org/10.1016/j.apsusc.2017.06.191 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy Andrey A. Mikhaylov1, Tatiana S. Priamushko*,1, Maria N. Babikhina1, Victor N. Kudiiarov1, Rene Heller2, Roman S. Laptev1, Andrey M. Lider1 1 – Department of General Physics, Tomsk Polytechnic University, Tomsk, Russia 2 – Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany *[email protected], 15b, Usova Street, Tomsk, Russia, 634034 Highlights
Creation of Zr-Nb-H standard samples includes hydrogenation and incubation in Ar atmosphere. Incubation after hydrogenation makes hydrogen distribution from the surface to the depth uniform. The calibration of GD-OES was performed at the first time with the use of 7 samples. All calibration curves are straight lines, all the points are on the lines. The range of hydrogen concentrations in the samples is from 0.034 to 0.51 % mass.
Abstract: To study the hydrogen distribution in Zr-1Nb alloy (Э110 alloy) GD-OES was applied in this work. Qualitative analysis needs the standard samples with hydrogen. However, the standard samples with high concentrations of hydrogen in the zirconium alloy which would meet the requirements of the shape, size are absent. In this work method of Zr+H calibration samples production was performed at the first time. Automated Complex Gas Reaction Controller was used for samples hydrogenation. To calculate the parameters of post-hydrogenation incubation of the samples in an inert gas atmosphere the diffusion equations were used. Absolute hydrogen concentrations in the samples were determined by melting in the inert gas atmosphere using RHEN602 analyzer (LECO Company). Hydrogen distribution was studied using nuclear reaction analysis (HZDR, Dresden, Germany). RF GD-OES was used for calibration. The depth of the craters was measured with the help of a Hommel-Etamic profilometer by Jenoptik, Germany. 1. Introduction Keywords: Glow discharge optical emission spectroscopy (GD-OES); Hydrogen; Standard samples; Zirconium alloy; Calibration. Zirconium (Zr) is well-known for having low thermal neutron absorption cross section, good mechanical properties at high temperatures and its alloys are well-known for having had good resistance to corrosion. For these reasons, zirconium alloys are commonly employed as the base material for structural components of today's thermal reactors, including the fuel cladding in their cores [1]. While in service, the fuel cladding material is gradually degraded by different environmentally induced factors including hydrogen uptake from the surrounding light/heavy water acting as moderator and irradiation damage caused by persistent bombardment by high-
energy particles which are released in the fission process [2, 3]. Technical characteristics of metals and alloys heavily depend on the concentration of gas-forming impurities, such as hydrogen. Penetration and accumulation of hydrogen can lead to significant changes in mechanical properties of materials and even lead to its destruction. The presence of hydrogen can have a detrimental effect on the longevity of zirconium. This can be attributed to different degrading mechanisms, including the formation of brittle hydrides [4], delayed hydride cracking (DHC) [5] and hydrogen enhanced local plasticity [6]. Hydrides form because of the low hydrogen solid solubility limit of zirconium, which promotes its formation even at relatively low hydrogen concentrations [7]. Dissolution of hydrogen in metal is characterized by its non-uniform distribution from the surface to the depth [8]. This non-uniform hydrogen distribution explains the various degrees of material damage from the surface to the depth. In this case, many world laboratories develop and study new protective coatings from the penetration of hydrogen. Due to this, it is very important to carry out an elemental analysis of the composite structure and surface layers. Research on high-performance materials characterization poses new analytical challenges requiring new enabling techniques. Among them, glow discharges (GD) coupled to optical emission spectrometry (OES) [9, 10] is of growing present importance. In particular, GD-OES is a rather well-established technique allowing high depth resolution, multi-element analysis, high sample throughput and low limits of detection with minimal matrix effects [11]. The main advantages of GD-OES in this research are the ability to determine hydrogen and high speed of analysis. Unfortunately, GD-OES has a number of disadvantages such as geometric shape, size and conductivity. Nowadays the standard samples with high concentrations of hydrogen in the zirconium alloy are absent. In this work the creation of Zr-1Nb+H standard samples method has done at the first time. 2. Materials and methods 2.1 Sample preparation and hydrogenation The samples of Zr-1Nb alloy (Table 1) with the size of 2 mm thickness and 20 mm diameter and rectangular samples with the size of 20×20×1 mm were polished to the average roughness Ra of 0.045 μm due to the fact that the surface condition has a strong influence on the penetration of hydrogen into the material. Samples with the size of 2 mm thickness and 20 mm diameter were annealed at Ta=580 °C for ta=180 minutes to remove internal stresses and structural defects. Hydrogenation was performed from hydrogen atmosphere at a temperature Th=600 °С and the pressure Ph=0.66 atm). Hydrogenation was carried out using automated complex Automated Complex Gas Reaction
Controller [12] using Sievert's method. Hydrogenation was performed to obtain 6 different concentrations. The average sorption rate was 5.02∙10-8 m3∙H2(STP)/(cm2∙sec).
Fig.1. The dependence of hydrogen concentration on the hydrogenation time After saturation in order to achieve a uniform distribution of hydrogen by volume samples were incubated in an inert gas atmosphere at a temperature of Ti=650 °C and pressure Pi=0.66 atm for ti=5 hours, after which the temperature decreased with the rate 2 °C/minute during 3 hours. Hydrogen concentrations were determined by volumetric and gravimetric methods. 2.2 Characterization The absolute hydrogen concentration in the samples was determined by melting in argon atmosphere using hydrogen analyzer RHEN602 by LECO, volumetrically and calculated from the weight changing. The determination of hydrogen distribution was carried out with the use of NRA. The process parameters for NRA were: 15N primary ions with the charge +2, incident angle 45˚, ion current 20 nA. Measurements were carried out at the following thicknesses (the corresponding energies are given in parentheses): 212 nm (7495 keV), 354 nm (8235 keV), 530 nm (9160 keV) and 707 nm (10085 keV). 2.3 Optimization and Calibration of RF-GD-OES Samples with size 20x20x1 mm were used for the selection of the optimal Zr-1Nb alloy sputtering parameters, as well as determining the sputtering rate. For these aims, GD Profiler2 by Jobin Yvon Emission Horiba Group (Longjumeau Cedex, France) was used. The instrument is equipped with a standard JY GD source with an anode of 4 mm internal diameter and two optical
spectrometers (poly- and monochromator). One of the spectrometers is a 0.5 m Paschen Runge polychromator with a concave grating of 2400 lines mm−1. The optical path of the spectrometer is nitrogen purged. Also, the system is equipped with a Czerny-Turner monochromator (0.64 m focal length, blazed planar holographic grating of 2400 lines mm−1), which allows the expansion of the instrument’s capabilities to any wavelength of the spectral range. Table 2 collects the analytical emission lines monitored. The samples were cooled at 10 ˚C by a cold liquid circulating between the sample and the RF power input. Obtained samples were used for RF-GD-OES instrument calibration. The depth of the craters was measured with the help of a Hommel-Etamic profilometer by Jenoptik Germany. To construct a 3D-image of craters was used three-dimensional non-contact profilometer MicroMeasure 3D Station. 3. Results and discussion 3.1 Characterization of the hydrogenated samples The results of the hydrogen concentration determination by three different methods are shown in Table 3. Hydrogen concentrations, determined by different methods, correlate with sufficient accuracy. Concentration values calculated from the weight changing and concentrations values determined by the volumetric method have the greatest convergence with each other. The difference between the values, in this case, does not exceed 1%. By comparing the concentration determined by melting in an inert gas atmosphere, with concentrations obtained by other methods, it was found that the maximum difference between the values is approximately 27%. It can be attributed to the fact that the calibration of RHEN602 analyzer is carried out with the usage of the samples with hydrogen concentrations in the range of 0.0004-0.0007% mass. Due to the calibration with low hydrogen concentrations, the determination of high hydrogen concentrations can be carried out without sufficient accuracy. The values of hydrogen concentration determined by the weight changing and volumetric method are in good correlation, but the value determined by weight changing is slightly higher due to the peculiarity of hydrogenation procedure. This peculiarity is related to the presenting of short period of time, when hydrogenation stopped, but hydrogen still is not evacuated. Moreover, sorption of some extra part of hydrogen takes place. That is why for calibration of RF-GD-OES the value of hydrogen concentration was taken as a value of hydrogen concentration determined by weight changing. The results of hydrogen distribution determination are shown in Figure 2. As can be seen, the distribution of hydrogen in the samples is relatively uniform. There are no sharp peaks of hydrogen signal at the surface layer as it was observed in our previous research. Small fluctuations of hydrogen signal are observed. However, these deviations from a straight line are valid because
the investigated depth is less than 1 μm. In these depths, the state of the surface has a strong influence on the analysis. Samples 2 and 3 have the greatest uniformity. The samples 4 and 5 have the least uniformity. It is shown that the number of gamma rays highest the highest hydrogen concentration in the sample (Table 3). Data on the hydrogen concentration obtained with the help of NRA, poorly correlated with the data obtained by other methods. However, these data were used to confirm the uniformity of hydrogen distribution. The reasons for not matching the data require further research.
Fig.2. Hydrogen distribution in the hydrogenated samples obtained by NRA 3.2 Optimization of pulsed GD operating conditions High-quality GD analysis of coated samples mostly depends on the depth resolution and, therefore, on the experimental conditions selected for the analysis [14, 15]. As it is well known, the crater bottom must be flat and with the crater walls perpendicular to the sample surface for optimal depth resolution, because in this case a constant sputtering rate over the entire sputtered area (4 mm) is achieved. During the optimization, the power was changed with the step of 5 Wt and the pressure was changed with the step of 50 Pa. Figure 3 shows the difference in crater shape between the 35 Wt, 650 Pa (the lowest values – a) and 50 Wt, 750 Pa (the highest values – b), sputtering time was 60 s. The power of 35 Wt and the pressure of 650 Pa were chosen as the optimal parameters.
To establish the dependence between the time and the rate of sputtering it requires sputter the samples for different times to reach the crater depths of 10-30 microns. Then the calculation of the sample erosion rate was determined as a ratio the crater depth / sputtering time. Sputtering rates, evaluated as mass loss per unit time during the sputtering, were calculated by measuring the penetration depths per unit time and considering the crater diameter and material density. The mean of four sputtered replicates was always used. The value of the sputtering rate was 4.67 μm/min. 3.3 Calibration of RF-GD-OES Most of the elements curves are the straight lines due to their identical concentrations in the samples. Figure 4 presents the calibration curve of Mn (257.614). It is shown that the intensity changes by an amount equal to 0.01 V. Such changing are unessential for metals. Cl (134.730), C (156.149), Pb (220.357), Cd (228.806), B (249.682), Cr (II) (267.720), Fe (I) (271.445), Hf (286.641), Si (288.162), Cu (324.759), Ni (341.482), Ti (365.355), Fe (II) (371.999), Mo (386.416), Al (396.157), Ca (422.679), Cr (I) (425.439), Li (670.800), K (766.500) have similar calibration curve and the intensity changing. The concentrations of these elements determined due to the calibration are similar to the announced concentrations. Zr (339.203), Nb (316.345), O (130.492), H (121.574) have changing of the concentrations and the intensity (Figure 5). The concentration of Zr (Figure 5a) changes from 98.165 to 98.676 % mass. These values are similar to the announced. Zirconium concentration decreased with the increasing of the sample number (from 7 to 1) due to the increasing of the impurities concentrations. Figure 5b presents the calibration curve of Nb. The range of niobium concentrations is 0.92-1.02 % mass. The changing caused by the impermanent content from sample to sample. Determined Nb concentrations are in the boundaries of acceptable values the manufacturer designated (Table 1). Oxygen has similar situation of the concentration changing – the range is from 0.09 to 0.10 % mass. The maximum does not exceed the announced value (Table 1). Hydrogen calibration curve has the concentration changing from 0.034 to 0.498 % mass. These values are nearly identical to the announced (Table 3). All the points lie on a straight line, the sequence of the samples is from the lowest hydrogen concentration (sample 1) to the highest (sample 7). However, samples 2 and 3 break this sequence (Figure 5d). Conclusion In this work method of Zr+H calibration samples production was performed at the first time. Samples of Zr-1Nb alloy were chosen for research. The hydrogenation and the incubation were performed with the use of Automated Complex Gas Reaction Controller. The temperature of hydrogenation was Th=600 °С and the pressure was Ph=0.66, the temperature of the incubation
was Ti=600 °С at the same pressure. Hydrogen distribution was studied by NRA; the absolute hydrogen concentrations were determined by melting in the inert gas atmosphere, volumetric method and calculated from the weight changing. Thus, as a result of this work is a set of standard Zr-1Nb+H samples, hydrogen concentrations are in the range of 0.034-0.51 wt%. The distribution of hydrogen in the samples is uniform, the geometric shape and dimensions meet the requirements of GD-OES. The optimization and calibration of RF-GD-OES were carried out, sputtering rate of the Zr-1Nb alloy was determined. The power of 35 Wt and the pressure of 650 Pa were chosen as the optimal parameters. The value of the sputtering rate is 4.67 μm/min. The calibration curves are the straight lines for all elements. Acknowledgements The study was performed within the framework of the Programme of improving the competitiveness of the National Research Tomsk Polytechnic University among the world's leading research and education centers. Project: VIU_ENIN_25_2016. Authors would like to express their gratitude to Dr. Markus Wilde, The University of Tokyo, for the assistant with the processing of NRA research data and the presentation of the results. References [1]
M. P. Puls, The effect of hydrogen and hydrides on the integrity of zirconium alloy
components: delayed hydride cracking, Springer Science & Business Media, 2012. [2]
J. P. Mardon, A. Lesbros, C. Bernaudat, N. Waeckel, Recent data on M5 (TM) alloy under
RIA and LOCA conditions. In Proceedings of International Meeting on LWR Fuel Performance: (2004) 507-515. [3]
S.J. Oh, C. Jang, J.H. Kim, Y.H. Jeong, Microstructure and hydride embrittlement of
zirconium model alloys containing niobium and tin, Materials Science and Engineering: A. 528(10) (2011) 3771-3776. [4]
P.A.T. Olsson, K. Kese, A.M.A. Holston, On the role of hydrogen filled vacancies on the
embrittlement of zirconium: An ab initio investigation, Journal of Nuclear Materials. 467 (2015) 311-319. [5]
D.O. Northwood, U. Kosasih, Hydrides and delayed hydrogen cracking in zirconium and
its alloys, International Metals Reviews. 28(1) (1983) 92-121. [6]
S.M. Myers, M.I. Baskes, H.K. Birnbaum, J.W. Corbett, G.G. Deleo, S.K. Estreicher, E.E.
Haller, P. Jena, N.M. Johnson, R. Kirchheim, S.J. Pearton, M.J. Stavola, Hydrogen interactions with defects in crystalline solids, Reviews of Modern Physics 64(2) (1992) 559-617. [7]
C. Varvenne, O. Mackain, L. Proville, E. Clouet, Hydrogen and vacancy clustering in
zirconium, Acta Materialia, 102 (2016) 56-69.
A. M. Lider, N. S. Pushilina, V.N. Kudiiarov, M. Kroening, Investigation of hydrogen
[8]
distribution from the surface to the depth in technically pure titanium alloy with the help of glow discharge optical emission spectroscopy, Applied Mechanics and Materials 302 (2013) 92-96. P. Sánchez, B. Fernández, A. Menéndez, J. Orejas, R. Pereiro, A. Sanz-Medel, Quantitative
[9]
depth profile analysis of metallic coatings by pulsed radiofrequency glow discharge optical emission spectrometry, Analytica chimica acta, 684(1) (2011) 47-53. [10]
Th. Nelis, R. Payling, Glow Discharge Optical Emission Spectroscopy: A Practical Guide,
RSC Analytical Spectroscopy Monographs, Cambridge (UK), 2003. [11]
R.K. Marcus, J.A.C. Broekaert, Glow Discharge Plasmas in Analytical Spectroscopy, John
Wiley & Sons Ltd., England, 2003. [12]
V.N. Kudiiarov, A.M. Lider, S.Y. Harchenko, Hydrogen accumulation in technically pure
titanium alloy at saturation from gas atmosphere, Advanced Materials Research 880 (2014) 68-73. [13]
Chepetsky Mechanical Plant, information about manufactured products, Е110 alloy ingots:
http://www.chmz.net/en/product/zr/slitki/ [14]
V. Hoffmann, R. Dorka, L. Wilken, V.D. Hodoroaba, K. Wetzig, Present possibilities of
thin‐layer analysis by GDOES. Surface and interface analysis 35(7) (2003) 575-582. [15]
C. Yang, K. Ingeneri, M. Mohill, W.W. Harrison, Influence of discharge parameters on the
resolution of depth profiling by pulsed glow discharge atomic emission spectrometry, Journal of Analytical Atomic Spectrometry 15(1) (2000) 73-78.
a
b
Fig. 3. Consideration of the crater forms achieved by: a – 35 Wt, 650 Pa, b – 50 Wt, 750 Pa, sputtering time is 60 s
Fig. 4. Calibration curve of Mn (257.614)
a
b
c
d
Fig. 5. Calibration curves of a – Zr (339.203), b – Nb (316.345), c – O (130.492), d – H (121.574)
Table 1. Elemental composition of Zr-1Nb alloy (Е110 alloy [13]) Element
Content,
Element
Content,
% mass.
Element
% mass.
Content,
Element
% mass.
Content, % mass.
Zr
≈98.68
Si
0.02
Ni
0.007
Ti
0.005
Nb
0.9-1.1
Cr
0.02
N
0.006
K
0.004
O
0.1 (max) C
0.02
Cu
0.005
Cl
0.002
Fe
0.05
Ca
0.01
Mo
0.005
Mn
0.002
Hf
0.05
Al
0.008
Pb
0.005
Li
0.0008
Table 2. Analytical emission lines selected Element Wavelength, Element Wavelength, Element Wavelength, Element Wavelength, nm
nm
nm
nm
H
121.574
B
249.682
Nb
316.345
Mo
386.416
O
130.492
Mn
257.614
Cu
324.759
Al
396.157
Cl
134.730
Cr (II)
267.720
Zr
339.203
Ca
422.679
C
156.149
Fe (I)
271.445
Ni
341.482
Cr (I)
425.439
Pb
220.357
Hf
286.641
Ti
365.355
Li
670.800
Cd
228.806
Si
288.162
Fe (II)
371.999
K
766.500
Table 3. Results of hydrogen concentration determination Sample
Initial (1) Hydrogen concentration 0.004 by RHEN602 LECO, % ±0.002 mass. Hydrogen concentration by weight changing, % mass. Hydrogen concentration by volumetric method, % mass.
2
3
4
5
6
7
0.089 ±0.002
0.099 ±0.002
0.162 ±0.002
0.282 ±0.002
0.358 ±0.002
0.562 ±0.002
0.069 ±0.001
0.072 ±0.001
0.129 ±0.001
0.282 ±0.001
0.302 ±0.001
0.515 ±0.001
0.069 ±0.010
0.072 ±0.010
0.129 ±0.010
0.280 ±0.010
0.300 ±0.010
0.510 ±0.010
S0169-4332(17)31846-9 http://dx.doi.org/doi:10.1016/j.apsusc.2017.06.191 APSUSC 36391
To appear in:
APSUSC
Received date: Revised date: Accepted date:
31-10-2016 29-4-2017 18-6-2017
Please cite this article as: Andrey A.Mikhaylov, Tatiana S.Priamushko, Maria N.Babikhina, Victor N.Kudiiarov, Rene Heller, Roman S.Laptev, Andrey M.Lider, Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy, Applied Surface Sciencehttp://dx.doi.org/10.1016/j.apsusc.2017.06.191 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Hydrogen calibration of GD-spectrometer using Zr-1Nb alloy Andrey A. Mikhaylov1, Tatiana S. Priamushko*,1, Maria N. Babikhina1, Victor N. Kudiiarov1, Rene Heller2, Roman S. Laptev1, Andrey M. Lider1 1 – Department of General Physics, Tomsk Polytechnic University, Tomsk, Russia 2 – Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany *[email protected], 15b, Usova Street, Tomsk, Russia, 634034 Highlights
Creation of Zr-Nb-H standard samples includes hydrogenation and incubation in Ar atmosphere. Incubation after hydrogenation makes hydrogen distribution from the surface to the depth uniform. The calibration of GD-OES was performed at the first time with the use of 7 samples. All calibration curves are straight lines, all the points are on the lines. The range of hydrogen concentrations in the samples is from 0.034 to 0.51 % mass.
Abstract: To study the hydrogen distribution in Zr-1Nb alloy (Э110 alloy) GD-OES was applied in this work. Qualitative analysis needs the standard samples with hydrogen. However, the standard samples with high concentrations of hydrogen in the zirconium alloy which would meet the requirements of the shape, size are absent. In this work method of Zr+H calibration samples production was performed at the first time. Automated Complex Gas Reaction Controller was used for samples hydrogenation. To calculate the parameters of post-hydrogenation incubation of the samples in an inert gas atmosphere the diffusion equations were used. Absolute hydrogen concentrations in the samples were determined by melting in the inert gas atmosphere using RHEN602 analyzer (LECO Company). Hydrogen distribution was studied using nuclear reaction analysis (HZDR, Dresden, Germany). RF GD-OES was used for calibration. The depth of the craters was measured with the help of a Hommel-Etamic profilometer by Jenoptik, Germany. 1. Introduction Keywords: Glow discharge optical emission spectroscopy (GD-OES); Hydrogen; Standard samples; Zirconium alloy; Calibration. Zirconium (Zr) is well-known for having low thermal neutron absorption cross section, good mechanical properties at high temperatures and its alloys are well-known for having had good resistance to corrosion. For these reasons, zirconium alloys are commonly employed as the base material for structural components of today's thermal reactors, including the fuel cladding in their cores [1]. While in service, the fuel cladding material is gradually degraded by different environmentally induced factors including hydrogen uptake from the surrounding light/heavy water acting as moderator and irradiation damage caused by persistent bombardment by high-
energy particles which are released in the fission process [2, 3]. Technical characteristics of metals and alloys heavily depend on the concentration of gas-forming impurities, such as hydrogen. Penetration and accumulation of hydrogen can lead to significant changes in mechanical properties of materials and even lead to its destruction. The presence of hydrogen can have a detrimental effect on the longevity of zirconium. This can be attributed to different degrading mechanisms, including the formation of brittle hydrides [4], delayed hydride cracking (DHC) [5] and hydrogen enhanced local plasticity [6]. Hydrides form because of the low hydrogen solid solubility limit of zirconium, which promotes its formation even at relatively low hydrogen concentrations [7]. Dissolution of hydrogen in metal is characterized by its non-uniform distribution from the surface to the depth [8]. This non-uniform hydrogen distribution explains the various degrees of material damage from the surface to the depth. In this case, many world laboratories develop and study new protective coatings from the penetration of hydrogen. Due to this, it is very important to carry out an elemental analysis of the composite structure and surface layers. Research on high-performance materials characterization poses new analytical challenges requiring new enabling techniques. Among them, glow discharges (GD) coupled to optical emission spectrometry (OES) [9, 10] is of growing present importance. In particular, GD-OES is a rather well-established technique allowing high depth resolution, multi-element analysis, high sample throughput and low limits of detection with minimal matrix effects [11]. The main advantages of GD-OES in this research are the ability to determine hydrogen and high speed of analysis. Unfortunately, GD-OES has a number of disadvantages such as geometric shape, size and conductivity. Nowadays the standard samples with high concentrations of hydrogen in the zirconium alloy are absent. In this work the creation of Zr-1Nb+H standard samples method has done at the first time. 2. Materials and methods 2.1 Sample preparation and hydrogenation The samples of Zr-1Nb alloy (Table 1) with the size of 2 mm thickness and 20 mm diameter and rectangular samples with the size of 20×20×1 mm were polished to the average roughness Ra of 0.045 μm due to the fact that the surface condition has a strong influence on the penetration of hydrogen into the material. Samples with the size of 2 mm thickness and 20 mm diameter were annealed at Ta=580 °C for ta=180 minutes to remove internal stresses and structural defects. Hydrogenation was performed from hydrogen atmosphere at a temperature Th=600 °С and the pressure Ph=0.66 atm). Hydrogenation was carried out using automated complex Automated Complex Gas Reaction
Controller [12] using Sievert's method. Hydrogenation was performed to obtain 6 different concentrations. The average sorption rate was 5.02∙10-8 m3∙H2(STP)/(cm2∙sec).
spectrometers (poly- and monochromator). One of the spectrometers is a 0.5 m Paschen Runge polychromator with a concave grating of 2400 lines mm−1. The optical path of the spectrometer is nitrogen purged. Also, the system is equipped with a Czerny-Turner monochromator (0.64 m focal length, blazed planar holographic grating of 2400 lines mm−1), which allows the expansion of the instrument’s capabilities to any wavelength of the spectral range. Table 2 collects the analytical emission lines monitored. The samples were cooled at 10 ˚C by a cold liquid circulating between the sample and the RF power input. Obtained samples were used for RF-GD-OES instrument calibration. The depth of the craters was measured with the help of a Hommel-Etamic profilometer by Jenoptik Germany. To construct a 3D-image of craters was used three-dimensional non-contact profilometer MicroMeasure 3D Station. 3. Results and discussion 3.1 Characterization of the hydrogenated samples The results of the hydrogen concentration determination by three different methods are shown in Table 3. Hydrogen concentrations, determined by different methods, correlate with sufficient accuracy. Concentration values calculated from the weight changing and concentrations values determined by the volumetric method have the greatest convergence with each other. The difference between the values, in this case, does not exceed 1%. By comparing the concentration determined by melting in an inert gas atmosphere, with concentrations obtained by other methods, it was found that the maximum difference between the values is approximately 27%. It can be attributed to the fact that the calibration of RHEN602 analyzer is carried out with the usage of the samples with hydrogen concentrations in the range of 0.0004-0.0007% mass. Due to the calibration with low hydrogen concentrations, the determination of high hydrogen concentrations can be carried out without sufficient accuracy. The values of hydrogen concentration determined by the weight changing and volumetric method are in good correlation, but the value determined by weight changing is slightly higher due to the peculiarity of hydrogenation procedure. This peculiarity is related to the presenting of short period of time, when hydrogenation stopped, but hydrogen still is not evacuated. Moreover, sorption of some extra part of hydrogen takes place. That is why for calibration of RF-GD-OES the value of hydrogen concentration was taken as a value of hydrogen concentration determined by weight changing. The results of hydrogen distribution determination are shown in Figure 2. As can be seen, the distribution of hydrogen in the samples is relatively uniform. There are no sharp peaks of hydrogen signal at the surface layer as it was observed in our previous research. Small fluctuations of hydrogen signal are observed. However, these deviations from a straight line are valid because
the investigated depth is less than 1 μm. In these depths, the state of the surface has a strong influence on the analysis. Samples 2 and 3 have the greatest uniformity. The samples 4 and 5 have the least uniformity. It is shown that the number of gamma rays highest the highest hydrogen concentration in the sample (Table 3). Data on the hydrogen concentration obtained with the help of NRA, poorly correlated with the data obtained by other methods. However, these data were used to confirm the uniformity of hydrogen distribution. The reasons for not matching the data require further research.
To establish the dependence between the time and the rate of sputtering it requires sputter the samples for different times to reach the crater depths of 10-30 microns. Then the calculation of the sample erosion rate was determined as a ratio the crater depth / sputtering time. Sputtering rates, evaluated as mass loss per unit time during the sputtering, were calculated by measuring the penetration depths per unit time and considering the crater diameter and material density. The mean of four sputtered replicates was always used. The value of the sputtering rate was 4.67 μm/min. 3.3 Calibration of RF-GD-OES Most of the elements curves are the straight lines due to their identical concentrations in the samples. Figure 4 presents the calibration curve of Mn (257.614). It is shown that the intensity changes by an amount equal to 0.01 V. Such changing are unessential for metals. Cl (134.730), C (156.149), Pb (220.357), Cd (228.806), B (249.682), Cr (II) (267.720), Fe (I) (271.445), Hf (286.641), Si (288.162), Cu (324.759), Ni (341.482), Ti (365.355), Fe (II) (371.999), Mo (386.416), Al (396.157), Ca (422.679), Cr (I) (425.439), Li (670.800), K (766.500) have similar calibration curve and the intensity changing. The concentrations of these elements determined due to the calibration are similar to the announced concentrations. Zr (339.203), Nb (316.345), O (130.492), H (121.574) have changing of the concentrations and the intensity (Figure 5). The concentration of Zr (Figure 5a) changes from 98.165 to 98.676 % mass. These values are similar to the announced. Zirconium concentration decreased with the increasing of the sample number (from 7 to 1) due to the increasing of the impurities concentrations. Figure 5b presents the calibration curve of Nb. The range of niobium concentrations is 0.92-1.02 % mass. The changing caused by the impermanent content from sample to sample. Determined Nb concentrations are in the boundaries of acceptable values the manufacturer designated (Table 1). Oxygen has similar situation of the concentration changing – the range is from 0.09 to 0.10 % mass. The maximum does not exceed the announced value (Table 1). Hydrogen calibration curve has the concentration changing from 0.034 to 0.498 % mass. These values are nearly identical to the announced (Table 3). All the points lie on a straight line, the sequence of the samples is from the lowest hydrogen concentration (sample 1) to the highest (sample 7). However, samples 2 and 3 break this sequence (Figure 5d). Conclusion In this work method of Zr+H calibration samples production was performed at the first time. Samples of Zr-1Nb alloy were chosen for research. The hydrogenation and the incubation were performed with the use of Automated Complex Gas Reaction Controller. The temperature of hydrogenation was Th=600 °С and the pressure was Ph=0.66, the temperature of the incubation
was Ti=600 °С at the same pressure. Hydrogen distribution was studied by NRA; the absolute hydrogen concentrations were determined by melting in the inert gas atmosphere, volumetric method and calculated from the weight changing. Thus, as a result of this work is a set of standard Zr-1Nb+H samples, hydrogen concentrations are in the range of 0.034-0.51 wt%. The distribution of hydrogen in the samples is uniform, the geometric shape and dimensions meet the requirements of GD-OES. The optimization and calibration of RF-GD-OES were carried out, sputtering rate of the Zr-1Nb alloy was determined. The power of 35 Wt and the pressure of 650 Pa were chosen as the optimal parameters. The value of the sputtering rate is 4.67 μm/min. The calibration curves are the straight lines for all elements. Acknowledgements The study was performed within the framework of the Programme of improving the competitiveness of the National Research Tomsk Polytechnic University among the world's leading research and education centers. Project: VIU_ENIN_25_2016. Authors would like to express their gratitude to Dr. Markus Wilde, The University of Tokyo, for the assistant with the processing of NRA research data and the presentation of the results. References [1]
M. P. Puls, The effect of hydrogen and hydrides on the integrity of zirconium alloy
components: delayed hydride cracking, Springer Science & Business Media, 2012. [2]
J. P. Mardon, A. Lesbros, C. Bernaudat, N. Waeckel, Recent data on M5 (TM) alloy under
RIA and LOCA conditions. In Proceedings of International Meeting on LWR Fuel Performance: (2004) 507-515. [3]
S.J. Oh, C. Jang, J.H. Kim, Y.H. Jeong, Microstructure and hydride embrittlement of
zirconium model alloys containing niobium and tin, Materials Science and Engineering: A. 528(10) (2011) 3771-3776. [4]
P.A.T. Olsson, K. Kese, A.M.A. Holston, On the role of hydrogen filled vacancies on the
embrittlement of zirconium: An ab initio investigation, Journal of Nuclear Materials. 467 (2015) 311-319. [5]
D.O. Northwood, U. Kosasih, Hydrides and delayed hydrogen cracking in zirconium and
its alloys, International Metals Reviews. 28(1) (1983) 92-121. [6]
S.M. Myers, M.I. Baskes, H.K. Birnbaum, J.W. Corbett, G.G. Deleo, S.K. Estreicher, E.E.
Haller, P. Jena, N.M. Johnson, R. Kirchheim, S.J. Pearton, M.J. Stavola, Hydrogen interactions with defects in crystalline solids, Reviews of Modern Physics 64(2) (1992) 559-617. [7]
C. Varvenne, O. Mackain, L. Proville, E. Clouet, Hydrogen and vacancy clustering in
zirconium, Acta Materialia, 102 (2016) 56-69.
A. M. Lider, N. S. Pushilina, V.N. Kudiiarov, M. Kroening, Investigation of hydrogen
[8]
distribution from the surface to the depth in technically pure titanium alloy with the help of glow discharge optical emission spectroscopy, Applied Mechanics and Materials 302 (2013) 92-96. P. Sánchez, B. Fernández, A. Menéndez, J. Orejas, R. Pereiro, A. Sanz-Medel, Quantitative
[9]
depth profile analysis of metallic coatings by pulsed radiofrequency glow discharge optical emission spectrometry, Analytica chimica acta, 684(1) (2011) 47-53. [10]
Th. Nelis, R. Payling, Glow Discharge Optical Emission Spectroscopy: A Practical Guide,
RSC Analytical Spectroscopy Monographs, Cambridge (UK), 2003. [11]
R.K. Marcus, J.A.C. Broekaert, Glow Discharge Plasmas in Analytical Spectroscopy, John
Wiley & Sons Ltd., England, 2003. [12]
V.N. Kudiiarov, A.M. Lider, S.Y. Harchenko, Hydrogen accumulation in technically pure
titanium alloy at saturation from gas atmosphere, Advanced Materials Research 880 (2014) 68-73. [13]
Chepetsky Mechanical Plant, information about manufactured products, Е110 alloy ingots:
http://www.chmz.net/en/product/zr/slitki/ [14]
V. Hoffmann, R. Dorka, L. Wilken, V.D. Hodoroaba, K. Wetzig, Present possibilities of
thin‐layer analysis by GDOES. Surface and interface analysis 35(7) (2003) 575-582. [15]
C. Yang, K. Ingeneri, M. Mohill, W.W. Harrison, Influence of discharge parameters on the
resolution of depth profiling by pulsed glow discharge atomic emission spectrometry, Journal of Analytical Atomic Spectrometry 15(1) (2000) 73-78.
a
b
a
b
c
d
Fig. 5. Calibration curves of a – Zr (339.203), b – Nb (316.345), c – O (130.492), d – H (121.574)
Table 1. Elemental composition of Zr-1Nb alloy (Е110 alloy [13]) Element
Content,
Element
Content,
% mass.
Element
% mass.
Content,
Element
% mass.
Content, % mass.
Zr
≈98.68
Si
0.02
Ni
0.007
Ti
0.005
Nb
0.9-1.1
Cr
0.02
N
0.006
K
0.004
O
0.1 (max) C
0.02
Cu
0.005
Cl
0.002
Fe
0.05
Ca
0.01
Mo
0.005
Mn
0.002
Hf
0.05
Al
0.008
Pb
0.005
Li
0.0008
Table 2. Analytical emission lines selected Element Wavelength, Element Wavelength, Element Wavelength, Element Wavelength, nm
nm
nm
nm
H
121.574
B
249.682
Nb
316.345
Mo
386.416
O
130.492
Mn
257.614
Cu
324.759
Al
396.157
Cl
134.730
Cr (II)
267.720
Zr
339.203
Ca
422.679
C
156.149
Fe (I)
271.445
Ni
341.482
Cr (I)
425.439
Pb
220.357
Hf
286.641
Ti
365.355
Li
670.800
Cd
228.806
Si
288.162
Fe (II)
371.999
K
766.500
Table 3. Results of hydrogen concentration determination Sample
Initial (1) Hydrogen concentration 0.004 by RHEN602 LECO, % ±0.002 mass. Hydrogen concentration by weight changing, % mass. Hydrogen concentration by volumetric method, % mass.
2
3
4
5
6
7
0.089 ±0.002
0.099 ±0.002
0.162 ±0.002
0.282 ±0.002
0.358 ±0.002
0.562 ±0.002
0.069 ±0.001
0.072 ±0.001
0.129 ±0.001
0.282 ±0.001
0.302 ±0.001
0.515 ±0.001
0.069 ±0.010
0.072 ±0.010
0.129 ±0.010
0.280 ±0.010
0.300 ±0.010
0.510 ±0.010