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Journal articles on the topic 'Vacancy segregation'

Author: Grafiati

Published: 6 September 2023

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1

Shen, Kun, Yixuan Wang, Jun Zhang, Yi Zong, Gengwei Li, Changchun Zhao, and Hao Chen. "Revealing the effect of grain boundary segregation on Li ion transport in polycrystalline anti-perovskite Li3ClO: a phase field study." Physical Chemistry Chemical Physics 22, no. 5 (2020): 3030–36. http://dx.doi.org/10.1039/c9cp06055c.

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Phase field calculated effective diffusivity D_eff of Li vacancy in anti-perovskite Li₃OCl is shown as a function of average grain sizes. Li vacancy segregation reinforces the negative contribution of grain boundaries on the overall Li diffusion.

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2

Wang, Xiao Wei, Hong Yan Zhang, and Ai Qing Sun. "Influence of Vacancy Formation and Mg Migration on Cracking in Spot Welding AA5754 Alloys." Materials Science Forum 539-543 (March 2007): 433–37. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.433.

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Al alloys with Mg as the major alloying element constitute a group of non-heat treatable alloys with medium strength, high ductility, excellent corrosion resistance and weldability. However, the segregation of Mg may adversely affect the performance of these materials if they are exposed to rapid heating and cooling environments such as resistance spot welding. The formation and migration of vacancy is an important factor affecting Mg segregation. In this paper, the amount and distribution of Mg were measured by electron probe microanalysis and the vacancy formation energy in AA5754 alloys was measured by positron annihilation lifetime spectroscopy. The results indicated that the segregation of Mg at cracks, occurring under suitable temperature and stress conditions, is related to the formation and migration of vacancies, and may promote crack initiation and propagation.

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3

Cho, Eunae, Bora Lee, Choong-Ki Lee, Seungwu Han, Sang Ho Jeon, Bae Ho Park, and Yong-Sung Kim. "Segregation of oxygen vacancy at metal-HfO2 interfaces." Applied Physics Letters 92, no. 23 (June 9, 2008): 233118. http://dx.doi.org/10.1063/1.2943322.

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4

Melikhova, Oksana, Jakub Čížek, Ivan Procházka, Tetyana E. Konstantinova, and Igor A. Yashchishyn. "Inhibition of Positronium Formation in Yttria Stabilized Zirconia Nanopowders Modified by Addition of Chromia." Materials Science Forum 733 (November 2012): 249–53. http://dx.doi.org/10.4028/www.scientific.net/msf.733.249.

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The effect of chromia additive on defects in yttria stabilized zirconia (YSZ) nanopowders was investigated in this work. It was found that positrons are trapped at vacancy-like misfit defect at grain boundaries and at larger defects situated at triple points. Moreover, a long-lived ortho-positronium contribution was found in YSZ nanopowder without chromia. Addition of chromia prolongs the lifetime of positrons trapped at vacancy-like misfit defects which indicates segregation of Cr ions at grain interfaces and interaction of Cr with vacancy-like misfit defets. Moreover addition of chromia completely suppresses formation of positronium.

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5

Ismunandar, Brendan J. Kennedy, and Brett A. Hunter. "Surface Segregation and Oxygen Vacancy Ordering in Defect Pyrochlores." Journal of Solid State Chemistry 130, no. 1 (April 1997): 81–89. http://dx.doi.org/10.1006/jssc.1997.7271.

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6

Shitara, K., A. Kuwabara, C. A. J. Fisher, T. Ogawa, T. Asano, Y. Kaneko, A. Omote, and H. Moriwake. "Effect of oxygen vacancy segregation in Au or Pt/oxide hetero-interfaces on electronic structures." RSC Advances 7, no. 57 (2017): 36034–37. http://dx.doi.org/10.1039/c7ra04804a.

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We investigated the effects of oxygen vacancy segregation on electronic structures in the vicinity of hetero-interfaces between noble metals (Au and Pt) and yttria stabilized zirconia by performing first-principles calculations and Bader analysis.

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7

Skelton, R., C. Nowak, X. W. Zhou, and R. A. Karnesky. "Tritium segregation to vacancy-type basal dislocation loops in α-Zr from molecular dynamics simulations." Journal of Applied Physics 131, no. 12 (March 28, 2022): 125103. http://dx.doi.org/10.1063/5.0078048.

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Tritium interactions with irradiation-induced defects in α-Zr are important for understanding getter performance in tritium-producing burnable absorbed rods. Vacancy-type basal loops are prominent in α-Zr irradiated at high dose rates. As they generate substantial tensile strain fields, such loops can trap tritium atoms. For this reason, vacancy-type basal dislocation loops are potentially important for tritium transport, tritium solubility, and tritide precipitation. We perform molecular dynamics simulations of tritium distributions around vacancy-type basal dislocation loops of different sizes, across a temperature range of 700–1200 K. Tritium preferentially segregates to the dislocation core and, to a lesser extent, the stacking fault. Segregation energies are estimated by inverting the tritium concentration distributions by assuming that the Boltzmann distribution adequately describes partitioning between the bulk and core environments. Agreement between molecular dynamics calculated segregation energies and predictions from elasticity theory using the stress field obtained by spatially averaging the atomic virial stresses suggests that elastic interactions dominate the interaction between tritium and basal loops. We also find an attractive tritium–tritium interaction. This attractive interaction can increase the stability of tritium in the dislocation core, resulting in a higher relative tritium concentration as the overall tritium concentration of the system increases. This suggests that vacancy-type basal dislocation loops can increase tritium solubility in irradiated α-Zr and may serve as preferential sites for tritide precipitation.

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8

Qiao, Ying Jie, Hong Bo Fu, and Chun Kai Li. "Study on the Diffusion Coefficient in NGS under Low Tensile Stress." Key Engineering Materials 525-526 (November 2012): 317–20. http://dx.doi.org/10.4028/www.scientific.net/kem.525-526.317.

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In this paper, the diffusion coefficient of vacancy-solute complex and diffusion coefficient of solute atoms, P, in non-equilibrium grain-boundary segregation under low tensile stress in steel 12Cr1MoV are calculated based on the model developed by Xu. Both the simulation and experimental kinetics curves are achieved. Results show that the calculated result with the kinetic equations perfectly fits with the experimental observations for phosphorus in steel 12Cr1MoV under low tensile stress. In the segregation process, the rate of phosphorus segregation is high due to a large diffusivity of the complex. In the de-segregation process, the level of phosphorus segregation decreases with increasing stress aging time. But the rate of phosphorus desegregation from grain boundaries to centre is slower compared with that in segregation for the diffusion coefficient of phosphorus atoms is far lower than the complexes.

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9

Terblans, J. J., and G. N. van Wyk. "The effect of vacancy formation energy on surface segregation kinetics." Radiation Effects and Defects in Solids 156, no. 1-4 (December 2001): 87–93. http://dx.doi.org/10.1080/10420150108216877.

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10

Mizoguchi, Teruyasu, Yukio Sato, James P. Buban, Katsuyuki Matsunaga, Takahisa Yamamoto, and Yuichi Ikuhara. "Sr vacancy segregation by heat treatment at SrTiO3 grain boundary." Applied Physics Letters 87, no. 24 (December 12, 2005): 241920. http://dx.doi.org/10.1063/1.2146051.

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11

Klie, R. F., Y. Ito, S. Stemmer, and N. D. Browning. "Observation of oxygen vacancy ordering and segregation in Perovskite oxides." Ultramicroscopy 86, no. 3-4 (February 2001): 289–302. http://dx.doi.org/10.1016/s0304-3991(00)00120-0.

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12

Mastrikov, Yuri A., Denis Gryaznov, Maksim N. Sokolov, Guntars Zvejnieks, Anatoli I. Popov, Roberts I. Eglitis, Eugene A. Kotomin, and Maxim V. Ananyev. "Oxygen Vacancy Formation and Migration within the Antiphase Boundaries in Lanthanum Scandate-Based Oxides: Computational Study." Materials 15, no. 7 (April 6, 2022): 2695. http://dx.doi.org/10.3390/ma15072695.

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The atomic structure of antiphase boundaries in Sr-doped lanthanum scandate (La1−xSrxScO3−δ) perovskite, promising as the proton conductor, was modelled by means of DFT method. Two structural types of interfaces formed by structural octahedral coupling were constructed: edge- and face-shared. The energetic stability of these two interfaces was investigated. The mechanisms of oxygen vacancy formation and migration in both types of interfaces were modelled. It was shown that both interfaces are structurally stable and facilitate oxygen ionic migration. Oxygen vacancy formation energy in interfaces is lower than that in the regular structure, which favours the oxygen vacancy segregation within such interfaces. The calculated energy profile suggests that both types of interfaces are advantageous for oxygen ion migration in the material.

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13

Eglitis, Roberts I., Juris Purans, Anatoli I. Popov, and Ran Jia. "Tendencies in ABO3 Perovskite and SrF2, BaF2 and CaF2 Bulk and Surface F-Center Ab Initio Computations at High Symmetry Cubic Structure." Symmetry 13, no. 10 (October 12, 2021): 1920. http://dx.doi.org/10.3390/sym13101920.

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We computed the atomic shift sizes of the closest adjacent atoms adjoining the (001) surface F-center at ABO3 perovskites. They are significantly larger than the atomic shift sizes of the closest adjacent atoms adjoining the bulk F-center. In the ABO3 perovskite matrixes, the electron charge is significantly stronger confined in the interior of the bulk oxygen vacancy than in the interior of the (001) surface oxygen vacancy. The formation energy of the oxygen vacancy on the (001) surface is smaller than in the bulk. This microscopic energy distinction stimulates the oxygen vacancy segregation from the perovskite bulk to their (001) surfaces. The (001) surface F-center created defect level is nearer to the (001) surface conduction band (CB) bottom as the bulk F-center created defect level. On the contrary, the SrF2, BaF2 and CaF2 bulk and surface F-center charge is almost perfectly confined to the interior of the fluorine vacancy. The shift sizes of atoms adjoining the bulk and surface F-centers in SrF2, CaF2 and BaF2 matrixes are microscopic as compared to the case of ABO3 perovskites.

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14

Williams, D. B., and A. D. Romig. "Measurement of solute segregation to grain boundaries in the AEM: A review." Proceedings, annual meeting, Electron Microscopy Society of America 46 (1988): 606–7. http://dx.doi.org/10.1017/s0424820100105096.

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The segregation of solute or imparity elements to grain boundaries can occur by three well-defined processes. The first is Gibbsian segregation in which an element of minimal matrix solubility confines itself to a monolayer at the grain boundary. Classical examples include Bi in Cu and S or P in Fe. The second process involves the depletion of excess matrix solute by volume diffusion to the boundary. In the boundary, the solute atoms diffuse rapidly to precipitates, causing them to grow by the ‘collector-plate mechanism.’ Such grain boundary diffusion is thought to initiate “Diffusion-Induced Grain Boundary Migration,” (DIGM). This process has been proposed as the origin of eutectoid transformations or discontinuous grain boundary reactions. The third segregation process is non-equilibrium segregation which result in a solute build-up around the boundary because of solute-vacancy interactions.All of these segregation phenomena usually occur on a sub-micron scale and are often affected by the nature of the grain boundary (misorientation, defect structure, boundary plane).

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15

Hin, Céline, Frédéric Soisson, and Philippe Maugis. "Atomistic Monte Carlo Simulations of Homogeneous and Heterogeneous Precipitation on Grain Boundaries of NbC in Steels." Defect and Diffusion Forum 237-240 (April 2005): 721–26. http://dx.doi.org/10.4028/www.scientific.net/ddf.237-240.721.

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The precipitation of niobium carbides in industrial steels is commonly used to control the recrystallization process or the amount of interstitial atoms in solid solution. It is then important to understand the precipitation kinetics and especially the competition between homogeneous and heterogeneous precipitation, since both of them have been observed experimentally, depending on the alloy composition, microstructure and thermal treatments. We propose Monte Carlo simulations of NbC precipitation in α-iron, based on a simple atomic description of the main parameters which control the kinetic pathway : - realistic diffusion properties, with a rapid diffusion of C atoms by interstitial jumps and a slower diffusion of Fe and Nb atoms by vacancy jumps - a simple model of grain boundaries which reproduces the equilibrium segregation properties of Nb and C - a point defect source which drives the vacancy concentration towards its equilibrium value. Depending on the precipitation conditions, MC simulations predict different kinetic behaviours, including homogeneous and heterogeneous NbC precipitation, early segregation of C atoms and its importance as a first stage for NbC precipitation, wetting phenomena on grain boundaries and transient precipitation of metastable carbides.

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16

Lindman, Anders, Edit E. Helgee, B. Joakim Nyman, and Göran Wahnström. "Oxygen vacancy segregation in grain boundaries of BaZrO3 using interatomic potentials." Solid State Ionics 230 (January 2013): 27–31. http://dx.doi.org/10.1016/j.ssi.2012.07.001.

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17

Geng, Chengwei, and Long-Qing Chen. "Computer simulation of vacancy segregation during spinodal decomposition and Ostwald ripening." Scripta Metallurgica et Materialia 31, no. 11 (December 1994): 1507–12. http://dx.doi.org/10.1016/0956-716x(94)90065-5.

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18

Sun, Sen, Nan Qiu, Kun Zhang, PingNi He, YongJun Ma, FuJun Gou, and Yuan Wang. "Segregation of Al1.5CrFeNi high entropy alloys induced by vacancy-type defects." Scripta Materialia 161 (March 2019): 40–43. http://dx.doi.org/10.1016/j.scriptamat.2018.10.014.

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19

Klie, R. F., and N. D. Browning. "Atomic scale characterization of oxygen vacancy segregation at SrTiO3 grain boundaries." Applied Physics Letters 77, no. 23 (December 4, 2000): 3737–39. http://dx.doi.org/10.1063/1.1330572.

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20

Zhang, Yifan, Xiaoyuan Sun, Bing Ma, Jing Wang, Laima Luo, and Yucheng Wu. "Investigation of the Y Effect on the Microstructure Response and Radiation Hardening of PM V-4Cr-4Ti Alloys after Irradiation with D Ions." Metals 13, no. 3 (March 8, 2023): 541. http://dx.doi.org/10.3390/met13030541.

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In the current work, an analysis of the effects of Y on the radiation hardening and microstructure response of a V-4Cr-4Ti alloy has been conducted after 30 keV D ion irradiation at room temperature using transmission electron microscopy (TEM) and nanoindentation. The results show that the formation of large Y2O3 and small Y2V2O7 nanoparticles was confirmed, indicating that the addition of Y reduces the amount of dissolved oxygen. The addition of Y has been shown to affect the radiation-induced dislocation loops, radiation hardening, and Ti-rich segregation of the V-4Cr-4Ti alloy. With the addition of Y, the mean size of the radiation-induced dislocation loop decreased, which may result from the strong sink strength of the nanoparticle/matrix interface, interactions between Y atoms and SIA clusters, and the strong binding energy of vacancy–oxygen pairs. Some particles with core–shell structures were observed after ion irradiation, where Ti-rich segregations at the nanoparticle/matrix interface were confirmed. These results indicate that Y might promote abnormal segregation. Possible causes for this include the lower interface energy at the particle/matrix interface and the interaction between oxygen and solute atoms.

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21

Huntington, David. "Urban Shrinkage and Socio-Economic Segregation in Medium-Sized Cities: The Case of Schwerin (Germany)." Quaestiones Geographicae 40, no. 4 (December 1, 2021): 29–46. http://dx.doi.org/10.2478/quageo-2021-0036.

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Abstract Although past studies have found that processes of urban shrinkage may act as a catalyst for socio-economic segregation, these relationships remain underexplored outside the context of large cities and capitals. Moreover, cities at lower-tiers of the urban hierarchy in post-socialist Europe have been doubly excluded from the critical discourse on the socio-spatial effects of shrinkage. Hence, this article examines how shrinkage affects socio-economic segregation in the medium-sized post-socialist city of Schwerin, employing segregation indices to assess levels of spatial unevenness and location quotients to map intra-urban patterns of vulnerable population groups over time. Results indicate processes of shrinkage may exacerbate socio-economic segregation in medium-sized cities and that the spatial heterogeneity of shrinkage intersects with uneven distributions of affluence and poverty. However, suggesting that legacies of state socialism shape contemporary socio-spatial change, segregation in Schwerin is strongly conditioned by its socialist-era housing estates, which are generally characterised by the highest rates of population decline, vacancy, and vulnerable groups.

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22

Creuze, Jérome, F. Berthier, Robert Tétot, and B. Legrand. "Vacancy Segregation at Surface Grain Boundaries and their Intersection: an Atomistic Study." Defect and Diffusion Forum 194-199 (April 2001): 1217–22. http://dx.doi.org/10.4028/www.scientific.net/ddf.194-199.1217.

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23

Zimmermann, Janina, Mike W. Finnis, and Lucio Colombi Ciacchi. "Vacancy segregation in the initial oxidation stages of the TiN(100) surface." Journal of Chemical Physics 130, no. 13 (April 7, 2009): 134714. http://dx.doi.org/10.1063/1.3105992.

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24

Borkovska, L. V., R. Beyer, M. Hoffmann, A. Holzhey, N. Korsunska, Yu G. Sadofyev, and Joerg Weber. "Role of Cation Vacancy-Related Defects in Self-Assembling of CdSe Quantum Dots." Defect and Diffusion Forum 230-232 (November 2004): 55–66. http://dx.doi.org/10.4028/www.scientific.net/ddf.230-232.55.

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In this chapter we present the results of the photoluminescent and optical investigations of the influence of cation vacancy-related defects on CdSe/ZnSe quantum dot organization. Selfassembling growth was achieved under molecular beam epitaxy with subsequent annealing step. Number of cation vacancies was controlled by the intensity of the emission band connected with complex that includes cation vacancy and shallow donor. For the first time it is shown that increase of number of cation vacancy related defects results in the reduction of potential fluctuations in the QD layer. In this case a relatively uniform dense array of QDs with shallow localization potential is organized. It is proposed that generation of cation vacancies during the growth suppresses both Cd segregation and Cd surface diffusion as well as facilitates Cd/Zn interdiffusion. Interdiffusion process is proved by the changes in the photoluminescence and optical reflection spectra of ZnSe layers. It is showned that Cd/Zn interdiffusion can play an important role in CdSe/ZnSe intermixing during the QD formation at least under such growth conditions which can stimulate generation of cation vacancies.

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25

Goeller, Peter T., Boyan I. Boyanov, Dale E. Sayers, Robert J. Nemanich, Alline F. Myers, and Eric B. Steel. "Germanium segregation in the Co/SiGe/Si(001) thin film system." Journal of Materials Research 14, no. 11 (November 1999): 4372–84. http://dx.doi.org/10.1557/jmr.1999.0592.

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Cobalt disilicide contacts to silicon–germanium alloys were formed by direct deposition of pure cobalt metal onto silicon–germanium films on Si(001) substrates. Segregation of germanium was observed during the reaction of the cobalt with the silicon–germanium alloy. The nature of the Ge segregation was studied by transmission electron microscopy, energy dispersive spectroscopy, and x-ray diffraction. In the case of cobalt films deposited onto strained silicon–germanium films, the Ge segregation was discovered to be in the form of Ge-enriched Si1−xGex regions found at the surface of the film surrounding CoSi and CoSi2 grains. In the case of cobalt films deposited onto relaxed silicon–germanium films, the Ge segregation was dependent on formation of CoSi2. In samples annealed below 800 °C, where CoSi was the dominant silicide phase, the Ge segregation was similar in form to the strained Si1−xGex case. In samples annealed above 800 °C, where CoSi2 was the dominant silicide phase, the Ge segregation was also in the form of tetrahedron-shaped, Ge-enriched, silicon–germanium precipitates, which formed at the substrate/silicon– germanium film interface and grew into the Si substrate. A possible mechanism for the formation of these precipitates is presented based on vacancy generation during the silicidation reaction coupled with an increased driving force for Ge diffusion due to silicon depletion in the alloy layer.

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26

Divinski, Sergiy V. "Systematics of Grain Boundary Diffusion and Solute Segregation in Copper Poly- and Bicrystals." Defect and Diffusion Forum 273-276 (February 2008): 168–75. http://dx.doi.org/10.4028/www.scientific.net/ddf.273-276.168.

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Recent results on radiotracer grain boundary diffusion of different solutes in the same high-purity polycrystalline copper are reviewed. The measurements were performed in extended temperature intervals satisfying Harrison’s B and C regime conditions at higher and lower temperatures, respectively. In the B regime, the triple product P = sδDgb was determined, while the grain boundary diffusivity Dgb was directly measured in the C regime (s is the segregation factor and δ the grain boundary width). Consequently, the segregation of different solutes in the copper matrix was determined for the true dilute limit conditions. The results on grain boundary diffusion and segregation are analysed in relation to the solute – solvent binding and solute – vacancy interaction in the bulk and in the grain boundaries. By increasing amount of the applied radiotracer the effect of solute concentration on grain boundary diffusion can thoroughly be examined. Grain boundary diffusion experiments on well-characterised bicrystals have been shown to be most suitable for such a study. In a radiotracer experiment, the complete solute segregation isotherm can be measured beginning already from a dilute solution in both, bulk and grain boundary.

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27

Seymour, Ieuan David, and Ainara Aguadero. "Suppressing void formation in all-solid-state batteries: the role of interfacial adhesion on alkali metal vacancy transport." Journal of Materials Chemistry A 9, no. 35 (2021): 19901–13. http://dx.doi.org/10.1039/d1ta03254b.

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28

Xiao, W., C. S. Liu, Z. X. Tian, and W. T. Geng. "Effect of applied stress on vacancy segregation near the grain boundary in nickel." Journal of Applied Physics 104, no. 5 (September 2008): 053519. http://dx.doi.org/10.1063/1.2975939.

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29

Browning, N. D., J. P. Buban, Y. Ito, R. F. Klie, and Y. Lei. "Atomic Scale Analysis of Oxygen Vacancy Segregation At Grain Boundaries in Ceramic Oxides." Microscopy and Microanalysis 7, S2 (August 2001): 308–9. http://dx.doi.org/10.1017/s1431927600027616.

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The properties of ceramic oxides being developed for such varied applications as fuel cells, ionic transporting membranes, high-Tc superconductors, ferroelectrics and varistors are dominated by the presence of grain boundaries. Key to controlling the electronic properties of the grain boundaries in these materials is a fundamental understanding of the complex relationship between structure, composition and local electronic structure. The ability to characterize and directly correlate these parameters on the atomic scale is afforded by the combination of Z-contrast imaging and electron energy loss spectroscopy (EELS) in the scanning transmission electron microscope (STEM). Furthermore, the recent development of in-situ heating capabilities in the JEOL 201 OF STEM/TEM permits atomic resolution analysis to be performed at elevated temperatures and the interactions of grain boundaries with the oxygen vacancies determined.Figure 1 shows an example of the type of experiment that can be performed using these methods.

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30

Duan, Guohua, Xiangyan Li, Yichun Xu, Yange Zhang, Yan Jiang, Congyu Hao, C. S. Liu, et al. "Clustering and segregation of small vacancy clusters near tungsten (0 0 1) surface." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 414 (January 2018): 29–37. http://dx.doi.org/10.1016/j.nimb.2017.10.007.

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Yoshiya, Masato, and Takashi Oyama. "Impurity and vacancy segregation at symmetric tilt grain boundaries in Y2O3-doped ZrO2." Journal of Materials Science 46, no. 12 (February 15, 2011): 4176–90. http://dx.doi.org/10.1007/s10853-011-5352-8.

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32

Wang, Tianjiao, Te Zhu, Dandan Wang, Peng Zhang, Yamin Song, Fengjiao Ye, Qianqian Wang, et al. "Effect of Vacancy Behavior on Precipitate Formation in a Reduced-Activation V−Cr−Mn Medium-Entropy Alloy." Materials 16, no. 1 (December 23, 2022): 153. http://dx.doi.org/10.3390/ma16010153.

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In this work, we studied the evolution of vacancy-like defects and the formation of brittle precipitates in a reduced-activation V−Cr−Mn medium-entropy alloy. The evolution of local electronic circumstances around Cr and Mn enrichments, the vacancy defects, and the CrMn3 precipitates were characterized by using scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, and positron annihilation spectroscopy. The microstructure measurements showed that the Mn and Cr enrichments in the as-cast sample significantly evolved with temperature, i.e., from 400 °C, the Cr/Mn-segregated regions gradually dissolved into the matrix and then disappeared, and from 900 °C to 1000 °C, they existed as CrMn3 precipitates. The crystallite size of the phase corresponding to CrMn3 precipitates was about 29.4 nm at 900 °C and 43.7 nm at 1000 °C. The positron annihilation lifetime results demonstrated that the vacancies mediated the migration of Cr and Mn, and Cr and Mn segregation finally led to the formation of CrMn3 precipitates. The coincidence Doppler broadening results showed that the characteristic peak moved to the low-momentum direction, due to an increase in the size of the vacancy defects at the interface and the formation of CrMn3 precipitates.

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33

Soisson, Frédéric, and Chu Chun Fu. "Atomistic Simulations of Copper Precipitation and Radiation Induced Segregation in α-Iron." Solid State Phenomena 139 (April 2008): 107–12. http://dx.doi.org/10.4028/www.scientific.net/ssp.139.107.

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We present Monte Carlo simulations of the first stages of the coherent precipitation of Cu in α-Fe during thermal ageing and under irradiation. The simulations are based on a diffusion model by vacancy and self-interstitial jumps, the parameters of which are fitted on ab initio calculations. The simulations of precipitation kinetics during thermal ageing are compared with experimental ones. They reveal that precipitates containing up to several tens of atoms can be much more mobile than individual copper atoms, due to the trapping of vacancies in Cu. Monte Carlo simulations are also used to analyze the coupling between fluxes of point defects and Cu which occurs under irradiation and the possible resulting radiation induced segregation phenomena.

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34

Koizumi, Yuichiro, Samuel M. Allen, Masayuki Ouchi, Yoritoshi Minamino, and Akihiko Chiba. "Phase-Field Simulation of D0₃-Type Antiphase Boundary Migration in Fe₃Al with Vacancy and Solute Segregation." Solid State Phenomena 172-174 (June 2011): 1313–19. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.1313.

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Segregation of solute atoms and vacancies to migrating D03–type antiphase boundaries (APBs) in Fe3Al of the stoichirometric and an Al-rich compositions has been investigated in detail by a phase-field method developed in the previous study [Koizumi et al. Acta Mater 2009;57:3039] focusing on the quantitative relationship among the segregation, APB energy, driving-force, drag-force and APB mobility. It has been revealed that the drag-force by solute segregation depends considerably on the alloy composition and is responsible for the significant composition dependence of the migration kinetics of D03-APB whereas the composition dependences of driving-force and mobility are negligibly small.

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35

Ebihara, Ken-ichi, and Tomoaki Suzudo. "Molecular Dynamics Study of Phosphorus Migration in Σ3(111) and Σ5(0-13) Grain Boundaries of α-Iron." Metals 12, no. 4 (April 13, 2022): 662. http://dx.doi.org/10.3390/met12040662.

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Phosphorus atoms in steels accumulate at grain boundaries via thermal and irradiation effects and induce grain boundary embrittlement, which is experimentally confirmed by an increase in the ductile-brittle transition temperature. Quantitative prediction of phosphorus segregation at grain boundaries under various temperature and irradiation conditions is essential for preventing embrittlement. To develop a model of grain boundary phosphorus segregation in α-iron, we studied the migration of a phosphorus atom in two types of symmetrical tilt grain boundaries (Σ3[1-10](111) and Σ5[100](0-13) grain boundaries) using molecular dynamics simulations with an embedded atom method potential. The results revealed that, in the Σ3 grain boundary, phosphorus atoms migrate three-dimensionally mainly in the form of interstitial atoms, whereas in the Σ5 grain boundary, these atoms migrate one-dimensionally mainly via vacancy-atom exchanges. Moreover, de-trapping of phosphorus atoms and vacancies was investigated.

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36

Evans, Prescott E., Hae-Kyung Jeong, and Peter A. Dowben. "Sulfur Segregation and Surface Site Vacancy Compensation During Methanol to Methoxy Reactions on MoS2." MRS Advances 4, no. 15 (December 27, 2018): 873–78. http://dx.doi.org/10.1557/adv.2018.634.

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ABSTRACTSulfur loss from the surface of MoS2(0001) is observed following the adsorption of methanol on MoS2 at 86 K and subsequent annealing of MoS2 near 300 K. This sulfur loss, at the MoS2 surface, leads to suppression of inverse photoemission features characteristic of the unoccupied states associated with MoS2. This sulfur loss is counteracted by further annealing to 350 K, as is evident in the temperature dependent sulfur to molybdenum integrated X-ray photoemission intensity ratios near 300 to 350 K. Upon further annealing to 350 K, inverse photoemission additionally indicates a reestablishment of characteristic features associated with the unoccupied states of MoS2. These results are indicative of sulfur segregation to the surface and compensation of surface vacancy sites.

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Otani, Ryuken, Shin Kiyohara, Kiyou Shibata, and Teruyasu Mizoguchi. "Prediction of interface and vacancy segregation energies at silver interfaces without determining interface structures." Applied Physics Express 13, no. 6 (May 13, 2020): 065504. http://dx.doi.org/10.35848/1882-0786/ab8b6c.

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Wróbel, J. S., D. Nguyen-Manh, K. J. Kurzydłowski, and S. L. Dudarev. "A first-principles model for anomalous segregation in dilute ternary tungsten-rhenium-vacancy alloys." Journal of Physics: Condensed Matter 29, no. 14 (March 3, 2017): 145403. http://dx.doi.org/10.1088/1361-648x/aa5f37.

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39

Bhatia, M. A., and K. N. Solanki. "Energetics of vacancy segregation to symmetric tilt grain boundaries in hexagonal closed pack materials." Journal of Applied Physics 114, no. 24 (December 28, 2013): 244309. http://dx.doi.org/10.1063/1.4858401.

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40

Hu, Shenyang, Yulan Li, Shunli Shang, Zi-Kui Liu, Douglas Burkes, and David J. Senor. "Microstructure-dependent rate theory model of defect segregation and phase stability in irradiated polycrystalline LiAlO₂." Modelling and Simulation in Materials Science and Engineering 30, no. 2 (December 21, 2021): 025005. http://dx.doi.org/10.1088/1361-651x/ac4001.

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Abstract Gamma lithium aluminate (LiAlO2) is a breeder material for tritium and is one of key components in a tritium-producing burnable absorber rod (TPBAR). Dissolution and precipitation of second phases such as LiAl5O8 and voids are observed in irradiated LiAlO2. Such microstructure changes cause the degradation of thermomechanical properties of LiAlO2 and affect tritium retention and release kinetics, and hence, the TPBAR performance. In this work, a microstructure-dependent model of radiation-induced segregation (RIS) has been developed for investigating the accumulation of species and phase stability in polycrystalline LiAlO2 structures under irradiation. Three sublattices (i.e. [Li, Al, V]I [O, Vo]II [Lii, Ali, Oi, Vi]III), and concentrations of six diffusive species (i.e. Li; vacancy of Li or Al at [Li, Al, V]I sublattice, O vacancy at [O, Vo]II sublattice, and Li, Al and O interstitials at [Lii, Ali, Oi, Vi]III interstitial sublattices; are used to describe spatial and temporal distributions of defects and chemistry. Microstructure-dependent thermodynamic and kinetic properties including the generation, reaction, and chemical potentials of defects and defect mobility are taken into account in the model. The parametric studies demonstrated the capability of the developed RIS model to assess the effect of thermodynamic and kinetic properties of defects on the segregation and depletion of species in polycrystalline structures and to explain the phase stability observed in irradiated LiAlO2 samples. The developed RIS model will be extended to study the precipitation of LiAl5O8 and voids and tritium retention by integrating the phase-field method.

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Symington, A. R., M. Molinari, N. A. Brincat, N. R. Williams, and S. C. Parker. "Defect segregation facilitates oxygen transport at fluorite UO 2 grain boundaries." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 377, no. 2152 (July 8, 2019): 20190026. http://dx.doi.org/10.1098/rsta.2019.0026.

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An important challenge for modelling transport in materials for energy applications is that in most applications they are polycrystalline, and hence it is critical to understand the properties in the presence of grain boundaries. Moreover, most grain boundaries are not pristine stoichiometric interfaces and hence dopants are likely to play a significant role. In this paper, we describe our recent work on using atomistic molecular dynamics simulations to model the effect of doped grain boundaries on oxygen transport of fluorite structured UO 2 . UO 2 , much like other fluorite grain boundaries, are found to be sinks for oxygen vacancy segregation relative to the grain interior, thus facilitating oxygen transport. Fission products further enhance diffusivity via strong interactions between the impurities and oxygen defects. Doping produces a striking structural alteration in the Σ 5 class of grain boundaries that enhances oxygen diffusivity even further. This article is part of a discussion meeting issue ‘Energy materials for a low carbon future’.

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42

Itoh, Yuta, Hirotaka Watanabe, Yuto Ando, Emi Kano, Manato Deki, Shugo Nitta, Yoshio Honda, Atsushi Tanaka, Nobuyuki Ikarashi, and Hiroshi Amano. "Effect of beam current on defect formation by high-temperature implantation of Mg ions into GaN." Applied Physics Express 15, no. 2 (January 20, 2022): 021003. http://dx.doi.org/10.35848/1882-0786/ac481b.

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Abstract We evaluated the beam current dependence of defect formation during Mg ion implantation into GaN at a high temperature of 1100 °C with two beam currents. Photoluminescence spectra suggest that low-beam-current implantation reduced the vacancy concentration and activated Mg to a greater extent. Moreover, scanning transmission electron microscopy analysis showed that low-beam-current implantation reduced the density of Mg segregation defects with inactive Mg and increased the density of intrinsic dislocation loops, suggesting decreases in the densities of Ga and N vacancies. The formation of these defects depended on beam current, which is an important parameter for defect suppression.

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43

GESARI, S. B., M. E. PRONSATO, and A. JUAN. "GRAIN BOUNDARY SEGREGATION OF HYDROGEN IN BCC IRON: ELECTRONIC STRUCTURE." Surface Review and Letters 09, no. 03n04 (June 2002): 1437–42. http://dx.doi.org/10.1142/s0218625x02003998.

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The electronic properties of H impurity in an Fe Σ = 5, 53.1° [100] (012) symmetrical tilt grain boundary (GB) were studied using qualitative electronic structure calculations in the framework of the atom superposition and electron delocalization molecular orbital (ASED-MO) theory. A large cluster containing 197 Fe atoms was used to simulate the local environment of the boundary. The most stable positions for one H atom and two H atoms at the GB core were determined. The total energy of the cluster decreases when the H atoms are at that location, making it a possible site for H accumulation. The binding energy found was less than that of a Σ = 5 [100] (013) GB. An analysis of the orbital interaction reveals that H–Fe bonding involves mainly the Fe 4s and H 1s orbitals. A higher contribution of d orbitals is present, which show a different behavior when compared with mixed dislocation and vacancy in the bulk Fe. The interatomic bonding along the Fe atom chains via H atoms is very inefficient, thus resulting in significant weakening of the interatomic bonding. H–H interaction was also analyzed.

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Joakim Nyman, B., Edit E. Helgee, and Göran Wahnström. "Oxygen vacancy segregation and space-charge effects in grain boundaries of dry and hydrated BaZrO3." Applied Physics Letters 100, no. 6 (February 6, 2012): 061903. http://dx.doi.org/10.1063/1.3681169.

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KIRCHHEIM, R. "Reducing grain boundary, dislocation line and vacancy formation energies by solute segregation. I. Theoretical background." Acta Materialia 55, no. 15 (September 2007): 5129–38. http://dx.doi.org/10.1016/j.actamat.2007.05.047.

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46

Procházka, Ivan, Jakub Čížek, Oksana Melikhova, Jan Kuriplach, Wolfgang Anwand, Gerhard Brauer, Tetyana E. Konstantinova, Igor A. Danilenko, and Igor A. Yashchishyn. "Defect Behaviour in Yttria-Stabilised Zirconia Nanomaterials Studied by Positron Annihilation Techniques." Defect and Diffusion Forum 331 (September 2012): 181–99. http://dx.doi.org/10.4028/www.scientific.net/ddf.331.181.

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Recent experimental and theoretical investigations on a variety of yttria-stabilised zirconia (YSZ) nanomaterials are reviewed. The investigations were conducted within the frame of a collaboration of three institutions: (i) Charles University in Prague, (ii) Helmholtz Centre Dresden-Rossendorf and (iii) Donetsk Institute for Physics and Engineering of the NAS of Ukraine, Materials studied involved pressure-compacted nanopowders of binary and ternary (with Cr2O3 additive) YSZ and YSZ ceramics obtained by sintering the nanopowders. The nanopowders were prepared by the co-precipitation technique. Positron annihilation spectroscopy including the conventional positron lifetime (LT) and coincidence Doppler broadening (CDB) techniques was employed as the main experimental tool. Slow positron implantation spectroscopy (SPIS) was used in investigation of commercial YSZ single crystals for reference purposes. Extended state-of-art theoretical ab-initio calculations of positron response in the ZrO2 lattice were carried out for various vacancy-like defect configurations. It was suggested by these calculations that none of the oxygen-vacancy related defects are capable to trap positrons. On the other hand, zirconium vacancy was demonstrated by the calculations to be a deep positron trap, even in the case that a hydrogen atom is attached to the vacancy. The measured positron LT data clearly indicated that positrons annihilate in nanopowders predominantly from trapped states at defects of two kinds: (a) the vacancy-like misfit defects concentrated in layers along the grain boundaries and characterised with lifetimes of 0.180 ns, and (b) the larger defects of open volume comparable to clusters of a few vacancies which are situated at intersections of three (or more) grain boundaries (characteristic lifetimes of 0.380 ns). The intensity ratio of LT components corresponding to these two kinds of defects was found to be correlated with the mean particle size. This correlation reconfirms the above interpretation of LT components and, moreover, the measured ratios could be used to estimate changes of the mean particle size with chromia content or sintering temperature. It was shown in this way that chromia addition to the YSZ nanopowder leads to a smaller particle size compared to the binary YSZ. Similarly, grain growth during sintering could be monitored via this intensity ratio. A portion of 10 % of positrons was found to form positronium (Ps) in compacted binary YSZ nanopowders. The observed ortho-Ps lifetimes correspond to Ps pick-off annihilation in cavities of 3 nm size which may be expected to occur between the primary nanoparticles. On the other hand, an addition of chromia at a concentration as low as 0.3 mol.% appeared to be sufficient to suppress Ps formation below the detection limit. Similarly, Ps formation could not be detected in binary YSZ sintered for 1 hour at a temperature of 1000 °C or higher. The former effect indicates an enhanced concentration of Cr cations at the particle surfaces, while the latter one appears to be due to a decrease of cavity concentration induced by sintering. The measured CDB data supported the idea that vacancy-like trapping centres are similar to zirconium vacancies and gave further evidence of a strong segregation of Cr segregation at particle interfaces. SPIS was further involved in a trial experiment on binary YSZ nanopowders and sintered ceramics. This experiment clearly demonstrated that SPIS may reveal valuable information about changes of depth profiles of microstructure during sintering, e.g. a sintering induced diffusion of defects from sample interior to its surface.

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47

Tauer, Tania, Ryan O'Hayre, and J. Will Medlin. "Computational investigation of defect segregation at the (001) surface of BaCeO3 and BaZrO3: the role of metal–oxygen bond strength in controlling vacancy segregation." Journal of Materials Chemistry A 1, no. 8 (2013): 2840. http://dx.doi.org/10.1039/c2ta01297a.

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48

Tingdong, Xu, Song Shenhua, Shi Huazhong, Yuan Zhexi, and W. Gust. "The Diffusion Coefficient of Vacancy-Boron Complexes during the Segregation of Boron Atoms to Grain Boundaries." Materials Science Forum 94-96 (January 1992): 519–24. http://dx.doi.org/10.4028/www.scientific.net/msf.94-96.519.

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49

Garza, Richard, Jiyoung Lee, Mai Nguyen, Andrew Garmon, Meng Li, Danny Perez, Graeme Henkelman, Judith Yang, and Wissam Saidi. "Multiscale vacancy and dislocation-mediated surface segregation in CuNi alloy up to microsecond timescales with accelerated dynamics." Microscopy and Microanalysis 27, S1 (July 30, 2021): 2408–10. http://dx.doi.org/10.1017/s143192762100862x.

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50

Feibelman, Peter J. "First-principles calculational methods for surface-vacancy formation energies, heats of segregation, and surface core-level shifts." Physical Review B 39, no. 8 (March 15, 1989): 4866–72. http://dx.doi.org/10.1103/physrevb.39.4866.

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