Ultrastrong nanocrystalline steel with exceptional thermal stability and radiation tolerance

Du, Congcong; Jin, Shenbao; Fang, Yuan; Li, Jin; Hu, Shenyang; Yang, Tingting; Zhang, Ying; Huang, Jianyu; Sha, Gang; Wang, Yugang; Shang, Zhongxia; Zhang, Xinghang; Sun, Baoru; Xin, Shengwei; Shen, Tongde

doi:10.1038/s41467-018-07712-x

Title: Ultrastrong nanocrystalline steel with exceptional thermal stability and radiation tolerance

Journal Article · 19 December 2018 · Nature Communications

DOI: https://doi.org/10.1038/s41467-018-07712-x · OSTI ID:1489222

Du, Congcong ^[1]; Jin, Shenbao ^[2]; Fang, Yuan ^[3]; Li, Jin ^[4]; Hu, Shenyang ^[5]; Yang, Tingting ^[1]; Zhang, Ying ^[1]; Huang, Jianyu ^[1]; Sha, Gang ^[2]; Wang, Yugang ^[3]; Shang, Zhongxia ^[4];

^[4]; Sun, Baoru ^[1]; Xin, Shengwei ^[1];

^[1]

Yanshan Univ., Qinhuangdao (China)
Nanjing Univ. of Science and Technology (China)
Peking Univ., Beijing (China)
Purdue Univ., West Lafayette, IN (United States)
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)

Nanocrystalline (NC) metals are stronger and more radiation-tolerant than their coarse-grained (CG) counterparts, but they often suffer from poor thermal stability, i.e., nanograins coarsen significantly when heated to 0.3 to 0.5 of their melting temperature (T_m). Here we report an NC austenitic stainless steel (NC-SS) containing 1 at% lanthanum with an average grain size of 45 nm and an ultrahigh yield strength of ~ 2.5 GPa that exhibits exceptional thermal stability up to 1000 oC (0.75 Tm). In-situ irradiation to 40 dpa at 450 oC and ex-situ irradiation to 108 dpa at 600 oC produce neither significant grain growth nor void swelling, in contrast to significant void swelling of CG-SS at similar doses. This thermal stability is due to segregation of elemental lanthanum and (La, O, Si)-rich nanoprecipitates at grain boundaries. Microstructure dependent cluster dynamics show grain boundary sinks effectively reduce steady-state vacancy concentrations to suppress void swelling upon irradiation.

View Accepted Manuscript (DOE)

Cite

Export

Save

Research Organization:: Pacific Northwest National Laboratory (PNNL), Richland, WA (United States)

Sponsoring Organization:: USDOE

Grant/Contract Number:: AC05-76RL01830

OSTI ID:: 1489222

Report Number(s):: PNNL-SA-139907

Journal Information:: Nature Communications, Vol. 9, Issue 1; ISSN 2041-1723

Publisher:: Nature Publishing GroupCopyright Statement

Country of Publication:: United States

Language:: English

References (83)

Radiation damage in nanostructured materials Zhang, Xinghang; Hattar, Khalid; Chen, Youxing Progress in Materials Science, Vol. 96 https://doi.org/10.1016/j.pmatsci.2018.03.002	journal	July 2018
Theory and experimental background on dimensional changes in irradiated alloys Mansur, L. K. Journal of Nuclear Materials, Vol. 216 https://doi.org/10.1016/0022-3115(94)90009-4	journal	October 1994
Materials challenges in nuclear energy Zinkle, S. J.; Was, G. S. Acta Materialia, Vol. 61, Issue 3 https://doi.org/10.1016/j.actamat.2012.11.004	journal	February 2013
Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries in α -Fe Tschopp, M. A.; Solanki, K. N.; Gao, F. Physical Review B, Vol. 85, Issue 6 https://doi.org/10.1103/PhysRevB.85.064108	journal	February 2012
Recent Developments in Irradiation-Resistant Steels Odette, G. R.; Alinger, M. J.; Wirth, B. D. Annual Review of Materials Research, Vol. 38, Issue 1, p. 471-503 https://doi.org/10.1146/annurev.matsci.38.060407.130315	journal	August 2008
Radiation damage in helium ion irradiated nanocrystalline Fe Yu, K. Y.; Liu, Y.; Sun, C. Journal of Nuclear Materials, Vol. 425, Issue 1-3 https://doi.org/10.1016/j.jnucmat.2011.10.052	journal	June 2012
Correlation between Milling Parameters, Structural and Mechanical Properties of Nanostructured Austenitic Y₂O₃ Strengthened Steels Koncz, Péter; Horváth, Ákos; Balázsi, Katalin Materials Science Forum, Vol. 729 https://doi.org/10.4028/www.scientific.net/MSF.729.409	journal	November 2012
Alloy effects in nanostructures Weissmüller, J. Nanostructured Materials, Vol. 3, Issue 1-6 https://doi.org/10.1016/0965-9773(93)90088-S	journal	January 1993
Irradiation-tolerant nanostructured ferritic alloys: Transforming helium from a liability to an asset Odette, G. R.; Hoelzer, D. T. JOM, Vol. 62, Issue 9 https://doi.org/10.1007/s11837-010-0144-1	journal	September 2010
Methodology for determining void swelling at very high damage under ion irradiation Getto, E.; Sun, K.; Taller, S. Journal of Nuclear Materials, Vol. 477 https://doi.org/10.1016/j.jnucmat.2016.05.026	journal	August 2016
Solute-Derived Thermal Stabilization of Nano-sized Grains in Melt-Spun Aluminum Baker, A. H.; Sanders, P. G.; Lass, E. A. Metallurgical and Materials Transactions A, Vol. 47, Issue 8 https://doi.org/10.1007/s11661-016-3551-2	journal	June 2016
Grain coarsening inhibited by solute segregation Kirchheim, Reiner Acta Materialia, Vol. 50, Issue 2 https://doi.org/10.1016/S1359-6454(01)00338-X	journal	January 2002
Radiation damage tolerant nanomaterials Beyerlein, I. J.; Caro, A.; Demkowicz, M. J. Materials Today, Vol. 16, Issue 11 https://doi.org/10.1016/j.mattod.2013.10.019	journal	November 2013
Stabilization of nanocrystalline grain sizes by solute additions Koch, C. C.; Scattergood, R. O.; Darling, K. A. Journal of Materials Science, Vol. 43, Issue 23-24 https://doi.org/10.1007/s10853-008-2870-0	journal	December 2008
Unusual size-dependent strengthening mechanisms in helium ion-irradiated immiscible coherent Cu/Co nanolayers Chen, Y.; Liu, Y.; Fu, E. G. Acta Materialia, Vol. 84 https://doi.org/10.1016/j.actamat.2014.10.061	journal	February 2015
Influence of injected interstitials on the void swelling in two structural variants of 304L stainless steel induced by self-ion irradiation at 500 °C Sun, C.; Garner, F. A.; Shao, L. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Vol. 409 https://doi.org/10.1016/j.nimb.2017.03.070	journal	October 2017
Alloy thermodynamics in nanostructures Weissmüller, Jörg Journal of Materials Research, Vol. 9, Issue 1 https://doi.org/10.1557/JMR.1994.0004	journal	January 1994
Grain growth in nanocrystalline TiO2 and its relation to vickers hardness and fracture toughness Höfler, H. J.; Averback, R. S. Scripta Metallurgica et Materialia, Vol. 24, Issue 12 https://doi.org/10.1016/0956-716X(90)90101-L	journal	December 1990
Ultrastrong steel via minimal lattice misfit and high-density nanoprecipitation Jiang, Suihe; Wang, Hui; Wu, Yuan Nature, Vol. 544, Issue 7651 https://doi.org/10.1038/nature22032	journal	April 2017
The Deformation and Ageing of Mild Steel: III Discussion of Results Hall, E. O. Proceedings of the Physical Society. Section B, Vol. 64, Issue 9 https://doi.org/10.1088/0370-1301/64/9/303	journal	September 1951
An in-situ tem study of the thermal stability of nanocrystalline NiP Boylan, K.; Ostrander, D.; Erb, U. Scripta Metallurgica et Materialia, Vol. 25, Issue 12 https://doi.org/10.1016/0956-716X(91)90144-P	journal	December 1991
Grain growth and chemical ordering in (Fe,Mn)3Si Bansal, C.; Gao, Z. Q.; Fultz, B. Nanostructured Materials, Vol. 5, Issue 3 https://doi.org/10.1016/0965-9773(95)00236-8	journal	March 1995
Comparison of swelling and irradiation creep behavior of fcc-austenitic and bcc-ferritic/martensitic alloys at high neutron exposure Garner, F. A.; Toloczko, M. B.; Sencer, B. H. Journal of Nuclear Materials, Vol. 276, Issue 1-3 https://doi.org/10.1016/S0022-3115(99)00225-1	journal	January 2000
The impact of swelling on fusion reactor first wall lifetime Mattas, R. F.; Garner, F. A.; Grossbeck, M. L. Journal of Nuclear Materials, Vol. 122, Issue 1-3 https://doi.org/10.1016/0022-3115(84)90601-9	journal	May 1984
Formation mechanism and the role of nanoparticles in Fe-Cr ODS steels developed for radiation tolerance Hsiung, Luke L.; Fluss, Michael J.; Tumey, Scott J. Physical Review B, Vol. 82, Issue 18 https://doi.org/10.1103/PhysRevB.82.184103	journal	November 2010
Defect and void evolution in oxide dispersion strengthened ferritic steels under 3.2 MeV Fe+ ion irradiation with simultaneous helium injection Kim, I. -S; Hunn, J. D.; Hashimoto, N. Journal of Nuclear Materials, Vol. 280, Issue 3 https://doi.org/10.1016/S0022-3115(00)00066-0	journal	August 2000
Efficient Annealing of Radiation Damage Near Grain Boundaries via Interstitial Emission Bai, X. M.; Voter, A. F.; Hoagland, R. G. Science, Vol. 327, Issue 5973 https://doi.org/10.1126/science.1183723	journal	March 2010
High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions Li, Lulu; Saber, Mostafa; Xu, Weizong Materials Science and Engineering: A, Vol. 613 https://doi.org/10.1016/j.msea.2014.06.099	journal	September 2014
Phase-Field Models for Microstructure Evolution Chen, Long-Qing Annual Review of Materials Research, Vol. 32, Issue 1 https://doi.org/10.1146/annurev.matsci.32.112001.132041	journal	August 2002
Defect-interface interactions Beyerlein, I. J.; Demkowicz, M. J.; Misra, A. Progress in Materials Science, Vol. 74 https://doi.org/10.1016/j.pmatsci.2015.02.001	journal	October 2015
Microstructural observation and tensile properties of ODS-304 austenitic steel Wang, Man; Zhou, Zhangjian; Sun, Hongying Materials Science and Engineering: A, Vol. 559 https://doi.org/10.1016/j.msea.2012.08.099	journal	January 2013
The radiation damage tolerance of ultra-high strength nanolayered composites Misra, A.; Demkowicz, M. J.; Zhang, X. JOM, Vol. 59, Issue 9 https://doi.org/10.1007/s11837-007-0120-6	journal	September 2007
An experimental investigation of extrapolation methods in the derivation of accurate unit-cell dimensions of crystals Nelson, J. B.; Riley, D. P. Proceedings of the Physical Society, Vol. 57, Issue 3 https://doi.org/10.1088/0959-5309/57/3/302	journal	May 1945
Ideal sinks are not always ideal: Radiation damage accumulation in nanocomposites Uberuaga, Blas Pedro; Choudhury, Samrat; Caro, Alfredo Journal of Nuclear Materials, Vol. 462 https://doi.org/10.1016/j.jnucmat.2014.11.073	journal	July 2015
Micro-engineered first wall tungsten armor for high average power laser fusion energy systems Sharafat, Shahram; Ghoniem, Nasr M.; Anderson, Michael Journal of Nuclear Materials, Vol. 347, Issue 3, p. 217-243 https://doi.org/10.1016/j.jnucmat.2005.08.012	journal	December 2005
Interface Structure and Radiation Damage Resistance in Cu-Nb Multilayer Nanocomposites Demkowicz, M. J.; Hoagland, R. G.; Hirth, J. P. Physical Review Letters, Vol. 100, Issue 13 https://doi.org/10.1103/PhysRevLett.100.136102	journal	April 2008
The stabilization of nanocrystalline copper by zirconium Atwater, Mark A.; Scattergood, Ronald O.; Koch, Carl C. Materials Science and Engineering: A, Vol. 559 https://doi.org/10.1016/j.msea.2012.08.092	journal	January 2013
Voids in Irradiated Stainless Steel Cawthorne, C.; Fulton, E. J. Nature, Vol. 216, Issue 5115 https://doi.org/10.1038/216575a0	journal	November 1967
High dislocation density–induced large ductility in deformed and partitioned steels He, B. B.; Hu, B.; Yen, H. W. Science, Vol. 357, Issue 6355 https://doi.org/10.1126/science.aan0177	journal	August 2017
Effect of grain size on void formation during high-energy electron irradiation of austenitic stainless steel Singh, B. N. The Philosophical Magazine: A Journal of Theoretical Experimental and Applied Physics, Vol. 29, Issue 1 https://doi.org/10.1080/14786437408213551	journal	January 1974
Design of Stable Nanocrystalline Alloys Chookajorn, T.; Murdoch, H. A.; Schuh, C. A. Science, Vol. 337, Issue 6097 https://doi.org/10.1126/science.1224737	journal	August 2012
Effect of grain boundary character on sink efficiency Han, W. Z.; Demkowicz, M. J.; Fu, E. G. Acta Materialia, Vol. 60, Issue 18 https://doi.org/10.1016/j.actamat.2012.08.009	journal	October 2012
Design of Radiation Tolerant Materials Via Interface Engineering Han, Weizhong; Demkowicz, Michael J.; Mara, Nathan A. Advanced Materials, Vol. 25, Issue 48 https://doi.org/10.1002/adma.201303400	journal	September 2013
Structural materials for fission & fusion energy Zinkle, Steven J.; Busby, Jeremy T. Materials Today, Vol. 12, Issue 11 https://doi.org/10.1016/S1369-7021(09)70294-9	journal	November 2009
Void-swelling in irons and ferritic steels Little, E. A.; Stow, D. A. Journal of Nuclear Materials, Vol. 87, Issue 1 https://doi.org/10.1016/0022-3115(79)90123-5	journal	November 1979
Enhanced thermal stability of nanograined metals below a critical grain size Zhou, X.; Li, X. Y.; Lu, K. Science, Vol. 360, Issue 6388 https://doi.org/10.1126/science.aar6941	journal	May 2018
Grain-size stabilization in nanocrystalline FeZr alloys Darling, Kris A.; Chan, Ryan N.; Wong, Patrick Z. Scripta Materialia, Vol. 59, Issue 5 https://doi.org/10.1016/j.scriptamat.2008.04.045	journal	September 2008
Advanced oxide dispersion strengthened and nanostructured ferritic alloys Miller, M. K.; Parish, C. M.; Li, Q. Materials Science and Technology, Vol. 29, Issue 10 https://doi.org/10.1179/1743284713Y.0000000207	journal	October 2013
Microstructure and strength of nanocrystalline copper alloy prepared by mechanical alloying Morris, D. G.; Morris, M. A. Acta Metallurgica et Materialia, Vol. 39, Issue 8 https://doi.org/10.1016/0956-7151(91)90144-P	journal	August 1991
A review: applications of the phase field method in predicting microstructure and property evolution of irradiated nuclear materials Li, Yulan; Hu, Shenyang; Sun, Xin npj Computational Materials, Vol. 3, Issue 1 https://doi.org/10.1038/s41524-017-0018-y	journal	April 2017
Stainless steel in construction: A review of research, applications, challenges and opportunities Baddoo, N. R. Journal of Constructional Steel Research, Vol. 64, Issue 11 https://doi.org/10.1016/j.jcsr.2008.07.011	journal	November 2008
In Situ Study of Defect Migration Kinetics and Self-Healing of Twin Boundaries in Heavy Ion Irradiated Nanotwinned Metals Li, J.; Yu, K. Y.; Chen, Y. Nano Letters, Vol. 15, Issue 5 https://doi.org/10.1021/nl504677z	journal	April 2015
Void swelling and irradiation creep in light water reactor (LWR) environments Garner, F. A. Understanding and Mitigating Ageing in Nuclear Power Plants https://doi.org/10.1533/9781845699956.2.308	book	January 2010
Superior radiation-resistant nanoengineered austenitic 304L stainless steel for applications in extreme radiation environments Sun, C.; Zheng, S.; Wei, C. C. Scientific Reports, Vol. 5, Issue 1 https://doi.org/10.1038/srep07801	journal	January 2015
Design of Radiation Tolerant Materials Via Interface Engineering Han, Weizhong; Demkowicz, Michael J.; Mara, Nathan A. Advanced Materials, Vol. 25, Issue 48 https://doi.org/10.1002/adma.201303400	journal	September 2013
Stabilization of nanocrystalline grain sizes by solute additions Koch, C. C.; Scattergood, R. O.; Darling, K. A. Journal of Materials Science, Vol. 43, Issue 23-24 https://doi.org/10.1007/s10853-008-2870-0	journal	December 2008
The radiation damage tolerance of ultra-high strength nanolayered composites Misra, A.; Demkowicz, M. J.; Zhang, X. JOM, Vol. 59, Issue 9 https://doi.org/10.1007/s11837-007-0120-6	journal	September 2007
Irradiation-tolerant nanostructured ferritic alloys: Transforming helium from a liability to an asset Odette, G. R.; Hoelzer, D. T. JOM, Vol. 62, Issue 9 https://doi.org/10.1007/s11837-010-0144-1	journal	September 2010
The impact of swelling on fusion reactor first wall lifetime Mattas, R. F.; Garner, F. A.; Grossbeck, M. L. Journal of Nuclear Materials, Vol. 122, Issue 1-3 https://doi.org/10.1016/0022-3115(84)90601-9	journal	May 1984
Theory and experimental background on dimensional changes in irradiated alloys Mansur, L. K. Journal of Nuclear Materials, Vol. 216 https://doi.org/10.1016/0022-3115(94)90009-4	journal	October 1994
Grain growth and chemical ordering in (Fe,Mn)3Si Bansal, C.; Gao, Z. Q.; Fultz, B. Nanostructured Materials, Vol. 5, Issue 3 https://doi.org/10.1016/0965-9773(95)00236-8	journal	March 1995
Effect of grain boundary character on sink efficiency Han, W. Z.; Demkowicz, M. J.; Fu, E. G. Acta Materialia, Vol. 60, Issue 18 https://doi.org/10.1016/j.actamat.2012.08.009	journal	October 2012
Unusual size-dependent strengthening mechanisms in helium ion-irradiated immiscible coherent Cu/Co nanolayers Chen, Y.; Liu, Y.; Fu, E. G. Acta Materialia, Vol. 84 https://doi.org/10.1016/j.actamat.2014.10.061	journal	February 2015
Stainless steel in construction: A review of research, applications, challenges and opportunities Baddoo, N. R. Journal of Constructional Steel Research, Vol. 64, Issue 11 https://doi.org/10.1016/j.jcsr.2008.07.011	journal	November 2008
Micro-engineered first wall tungsten armor for high average power laser fusion energy systems Sharafat, Shahram; Ghoniem, Nasr M.; Anderson, Michael Journal of Nuclear Materials, Vol. 347, Issue 3, p. 217-243 https://doi.org/10.1016/j.jnucmat.2005.08.012	journal	December 2005
Radiation damage in helium ion irradiated nanocrystalline Fe Yu, K. Y.; Liu, Y.; Sun, C. Journal of Nuclear Materials, Vol. 425, Issue 1-3 https://doi.org/10.1016/j.jnucmat.2011.10.052	journal	June 2012
Ideal sinks are not always ideal: Radiation damage accumulation in nanocomposites Uberuaga, Blas Pedro; Choudhury, Samrat; Caro, Alfredo Journal of Nuclear Materials, Vol. 462 https://doi.org/10.1016/j.jnucmat.2014.11.073	journal	July 2015
Methodology for determining void swelling at very high damage under ion irradiation Getto, E.; Sun, K.; Taller, S. Journal of Nuclear Materials, Vol. 477 https://doi.org/10.1016/j.jnucmat.2016.05.026	journal	August 2016
Radiation damage tolerant nanomaterials Beyerlein, I. J.; Caro, A.; Demkowicz, M. J. Materials Today, Vol. 16, Issue 11 https://doi.org/10.1016/j.mattod.2013.10.019	journal	November 2013
Microstructural observation and tensile properties of ODS-304 austenitic steel Wang, Man; Zhou, Zhangjian; Sun, Hongying Materials Science and Engineering: A, Vol. 559 https://doi.org/10.1016/j.msea.2012.08.099	journal	January 2013
High-temperature grain size stabilization of nanocrystalline Fe–Cr alloys with Hf additions Li, Lulu; Saber, Mostafa; Xu, Weizong Materials Science and Engineering: A, Vol. 613 https://doi.org/10.1016/j.msea.2014.06.099	journal	September 2014
Influence of injected interstitials on the void swelling in two structural variants of 304L stainless steel induced by self-ion irradiation at 500 °C Sun, C.; Garner, F. A.; Shao, L. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Vol. 409 https://doi.org/10.1016/j.nimb.2017.03.070	journal	October 2017
Defect-interface interactions Beyerlein, I. J.; Demkowicz, M. J.; Misra, A. Progress in Materials Science, Vol. 74 https://doi.org/10.1016/j.pmatsci.2015.02.001	journal	October 2015
Radiation damage in nanostructured materials Zhang, Xinghang; Hattar, Khalid; Chen, Youxing Progress in Materials Science, Vol. 96 https://doi.org/10.1016/j.pmatsci.2018.03.002	journal	July 2018
In Situ Study of Defect Migration Kinetics and Self-Healing of Twin Boundaries in Heavy Ion Irradiated Nanotwinned Metals Li, J.; Yu, K. Y.; Chen, Y. Nano Letters, Vol. 15, Issue 5 https://doi.org/10.1021/nl504677z	journal	April 2015
Voids in Irradiated Stainless Steel Cawthorne, C.; Fulton, E. J. Nature, Vol. 216, Issue 5115 https://doi.org/10.1038/216575a0	journal	November 1967
Ultrastrong steel via minimal lattice misfit and high-density nanoprecipitation Jiang, Suihe; Wang, Hui; Wu, Yuan Nature, Vol. 544, Issue 7651 https://doi.org/10.1038/nature22032	journal	April 2017
Effect of grain size on void formation during high-energy electron irradiation of austenitic stainless steel Singh, B. N. The Philosophical Magazine: A Journal of Theoretical Experimental and Applied Physics, Vol. 29, Issue 1 https://doi.org/10.1080/14786437408213551	journal	January 1974
An experimental investigation of extrapolation methods in the derivation of accurate unit-cell dimensions of crystals Nelson, J. B.; Riley, D. P. Proceedings of the Physical Society, Vol. 57, Issue 3 https://doi.org/10.1088/0959-5309/57/3/302	journal	May 1945
Design of Stable Nanocrystalline Alloys Chookajorn, T.; Murdoch, H. A.; Schuh, C. A. Science, Vol. 337, Issue 6097 https://doi.org/10.1126/science.1224737	journal	August 2012
High dislocation density–induced large ductility in deformed and partitioned steels He, B. B.; Hu, B.; Yen, H. W. Science, Vol. 357, Issue 6355 https://doi.org/10.1126/science.aan0177	journal	August 2017
Enhanced thermal stability of nanograined metals below a critical grain size Zhou, X.; Li, X. Y.; Lu, K. Science, Vol. 360, Issue 6388 https://doi.org/10.1126/science.aar6941	journal	May 2018
Phase-Field Models for Microstructure Evolution Chen, Long-Qing Annual Review of Materials Research, Vol. 32, Issue 1 https://doi.org/10.1146/annurev.matsci.32.112001.132041	journal	August 2002

Cited By (2)

Recent Studies on the Microstructural Response of Nanotwinned Metals to In Situ Heavy Ion Irradiation Yu, K. Y.; Fan, C.; Chen, Y. JOM, Vol. 72, Issue 1 https://doi.org/10.1007/s11837-019-03883-0	journal	November 2019
Response of solidification cellular structures in additively manufactured 316 stainless steel to heavy ion irradiation: an in situ study Shang, Z.; Fan, C.; Xue, S. Materials Research Letters, Vol. 7, Issue 7 https://doi.org/10.1080/21663831.2019.1604442	journal	April 2019