bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spontaneous Crystalline Multilayer Formation in Ni Implanted Al at 100 K
Authors: Cuenat Alexandre , Hessler-Wyser Aicha , Döbeli Max , Gotthardt Rolf 
Published: April 2011

AbstractThe microstructure evolution of aluminum implanted with nickel at 5 MeV and at 100 K to a local concentration of 25 at. % is described. Transmission Electron Microscopy (TEM) observa- tions and Rutherford Backscattering Spectrometry (RBS) experiments are conducted to deter-mine the Ni profile and the microstructure of the implanted samples. For lower Ni concentration, it has been previously observed that Al0.75Ni0.25 amorphous precipitates are formed together with a high dislocation density. When the Ni concentration reaches 25 at. %, a new crystalline multi-layered microstructure is observed: the TEM observations reveal the presence of well-defined crystalline layers separated by sharp interfaces. To our knowledge, it is the first time that such a structure is observed without further annealing of the implanted sample. A series of mechanisms describing the formation of the crystalline multilayer are briefly discussed. It is argued that its formation is the result of a recrystallization front produced by the exothermal amorphous to crystal transformation.
Time-Resolved X-Ray Scattering Study of Co Surface Evolution during Low-Energy Ion Irradiation
Authors: Malis O. , Pomeroy J. M. , Headrick R. L. , Brock J. D. 
Published: April 2011

AbstractThe sputter-erosion of hcp Co (0001) single crystal with Ar+ ions in the 100 to 700 eV energy range was investigated using in-situ time-resolved x-ray scattering. At temperatures above 300°C the surface remains relatively smooth, erosion evolving through a layer-by-layer or step flow mechanism. In this regime the ions have a smoothening effect on the surface and the resulting roughness decreases with increasing ion energy. Below 300°C the surface develops a pattern of mounds or pits with a characteristic wavelength. The time, ion energy and temperature dependence of this wavelength were studied in detail. Epitaxial Co thin films thermally evaporated on sapphire were also sputtered through in order to synthesize self-assembled arrays of Co nanoclusters with a narrow size distribution. The degree of local order within the Co dot arrays was examined using atomic force microscopy.
Shear Modulation Force Microscopy Studies on Cross-linked Elastomer Thin Films
Authors: Zhang Y. , Ge S. , Rafailovich M.H. , Sokolov J.C. , Peiffer D.G. , Dias A.J. 
Published: April 2011

ABSTRACTThe atomic force microscope in the shear force modulation microscopy (SMFM) mode has been used to characterize the surface modulus and cross-link density of elastomer thin films, where standard rheological methods cannot be applied. Brominated poly(isobutylene-co-4-methylstyrene) (BIMS) is a synthetic terpolymer which can be stoichiometrically cross-linked by N, N'-dicinnamylidene-1,6-hexanediamine. The results on several types of BIMS elastomers with different bromide content are reported. The cross-linking reaction at the surface is found to be significantly faster than that of bulk. The estimated shear moduli of the thin films were found to be proportional to the cross-link density, as expected from the rubber elasticity theory for bulk materials.
3D FIB and AFM mapping of Nanoindentation Zones
Authors: Steer T.J. , Möbus G. , Kraft O. , Wagner T. , Inkson B.J. 
Published: April 2011

ABSTRACTA novel technique has been developed to examine site-specific, subsurface microstructures in three dimensions. A 3D data set is collected by successive cross-sectional slicing using a gallium focused ion beam (FIB) and imaging using ion-induced secondary electrons, enabling a 3D microstructure map to be generated using computer-based reconstruction techniques. In the first instance, this 3D FIB mapping technique has been applied to copper-based epitaxial metal multilayer coatings which have been deformed by nanoindentation. It is possible to produce 3D profiles of the deformed subsurface interfaces. These individual interface maps allow analysis of the deformation in terms of both the thickness of individual layers and that of the entire film. Material flow, which is seen as pile-up and residual indent zones around the indent, can thus be precisely characterised. The site at which the sectioning is to be carried out can be chosen with high spatial resolution; consequently, nanoscale mechanical properties can be linked directly with an area's microstructure.In an attempt to examine the errors involved in this 3D mapping method the 3D FIB map of the surface of a residual indent has been compared to an atomic force microscopy (AFM) scan of the same region. The sources and significance of the errors are discussed with reference to ways in which they might be reduced.
Mechanical Deformation of Crystalline Silicon During Nanoindentation
Authors: Bradby J.E. , Williams J.S. , Wong-Leung J. , Swain M.V. , Munroe P. 
Published: April 2011

ABSTRACTDeformation during spherical and pointed indentation in (100) crystalline silicon usig a UMIS-2000 nanoindenter has been studied using cross-sectional transmission electron microscopy (XTEM), atomic force microscopy (XTEM), atomic force microscopy and Raman microspectroscopy. XTEM samples were prepard by focused ion beam milling to accurately position the cross-section through the indentations. Indentation loads were chosen below an above the yield point for silicon to investigate the modes of plastic deformation. Slip planes are visible in XTEm micrographs for all indentation loads studied but slip is not the main avenue for plastic deformation. A thin layer of poly-crystalline material has been identified (indexed as Si-XII from diffraction patterns) on the low load indentation, just prior to yield (pop-in during loading). For loading above the yield point, a large region of amorphous silicon was observed directly under the indenter when fast unloading conditions were used. The various microstructures and phase observed below indentations are correlated with load/unload data.
Nanomechanics Using an Ultra-Small Amplitude AFM
Authors: Hoffmann Peter M. , Jeffery Steve , Oral Ahmet , Grimble Ralph A. , Özer H. özgür , Pethica John B. 
Published: April 2011

ABSTRACTA new type of AFM is presented which allows for direct measurements of nanomechanical properties in ultra-high vacuum and liquid environments. The AFM is also capable of atomic-scale imaging of force gradients. This is achieved by vibrating a stiff lever at very small amplitudes of less than 1 Å (peak-to-peak) at a sub-resonance amplitude. This linearizes the measurement and makes the interpretation of the data straight-forward. At the atomic scale, interaction force gradients are measured which are consistent with the observation of single atomic bonds. Also, atomic scale damping is observed which rapidly rises with the tip-sample separation. A mechanism is proposed to explain this damping in terms of atomic relaxation in the tip. We also present recent results in water where we were able to measure the mechanical response due to the molecular ordering of water close to an atomically flat surface.
Matrix Damage in Iron
Authors: Nicol A C , Jenkins M L , Kirk M A 
Published: April 2011

ABSTRACTWe present results of a weak-beam transmission electron microscopy study of “matrix damage” in two nearly-pure irons (designated alloys 1A and 2A) produced by neutron irradiation to a fluence of 0.06 dpa at 280°C. The matrix damage in both materials was found to consist of small (2-6 nm) dislocation loops. About 80 % have Burgers vectors b = a<100>, and the remainder have b = a/2<111>. The loops in alloy 1A have a mean image size dmean = 2.8± 0.1 nm and a mean maximum image size dmax = 4.2± 0.3 nm, while those in 2A have d mean = 3.4± 0.1 nm and d max = 4.5± 0.3 nm. The number densities are about 8.5 × 1021 m−3 in alloy 1A, and 6.6 × 1021 m−3 in 2A. It can be shown that the loops can account for the observed irradiation hardening. At least some loops are stable under thermal annealing to temperatures of at least 430°C. This and other indirect evidence suggests that their nature is interstitial.
Identification of Defects In Ferritic/Martensitic Steels Induced by Low Dose Irradiation
Authors: Schäublin R. , Victoria M. 
Published: April 2011

ABSTRACTThe ferritic/martensitic steels which are candidates for the first wall of the future fusion reactor are investigated in TEM. While the irradiation doses expected in this reactor are in the range of 100 dpa per year, there is still a lack of knowledge on the nature of the irradiation induced defects for the low doses at which hardening is already occuring. This hardening depends strongly on the type of interaction between the moving dislocations and the defects. The early defects, which start to appear as black dots in TEM, are expected to be either three dimensional clusters of interstitials or vacancies, or dislocation loops. The nature and size of these defects is carefully studied in the F82H steel for doses ranging from about 0.5 dpa to 9 dpa and irradiation temperatures ranging from 40°C to 330°C. For that purpose, various weak beam techniques are explored at the limit of resolution of a TEM used in diffraction mode. Results are presented here for the cases of a 1.7 dpa and a 8.8 dpa irradiation.
High Energy Proton Irradiation of Pure Titanium
Authors: Leguey Teresa , Bailat Claude , Baluc Nadine , Victoria Max 
Published: April 2011

ABSTRACTPolycrystalline specimens of hcp pure titanium have been irradiated at 300-320 K with 590 MeV protons to doses ranging between 10-3 and 3×10-2 dpa. Combination of tensile deformation experiments and transmission electron microscopy observations revealed that irradiation produces slight hardening of the material, related to the irradiation-induced formation of defect clusters, but not significant loss of ductility. Plastic deformation of irradiated titanium is homogeneous. It occurs via propagation of dislocations through a cloud of defect clusters, leading to their annihilation and the formation of a cellular dislocation structure together with twins. This mechanical behavior is similar to what was previously observed for pure fcc metals, the formation of twins being however intrinsic to deformation of hcp titanium.
Dynamical Behavior of Voids in Neutron-irradiated Copper at Elevated Temperature
Authors: Mukouda Ichiro , Shimomura Yoshiharu 
Published: April 2011

ABSTRACTWe reported previously an experimental result which shows that voids can move in neutron-irradiated copper at elevated temperature. To study the detailed behavior of voids, we carried out annealing experiments and in-situ observations in neutron-irradiated copper. Neutron irradiation was carried out in the temperature controlled capsule at KUR (Kyoto University Reactor). Neutron irradiation was performed at 300°C to damage levels between 10-4 to 10-3 dpa. The annealing temperature was 250°C for 10, 20, 30 min sequentially for neutron- irradiated copper. After annealing TEM observation was carried out at room temperature. Experimental results show that voids moved along the [110] direction. Voids moved during 250°C annealing but small stacking fault tetrahedra (SFT) were not changed. We observed 37 voids and 8 voids moved, the others vanished during annealing. The images of in-situ observation, void contrast images were recorded on VTR tape and analyzed frame by frame. At room temperature observation voids were static and were seen as white circles; however at 300°C the contrast changed to an oval shape and sometimes disappeared. After 7 sec contrast was a white circle and moved slightly and similar phenomena were observed quite frequently at 300°C. It is concluded that void moved with dynamical structural relaxation at elevated temperature.
Effect of Annealing and Re-irradiation on the Copper-enriched Precipitates in a Neutron-irradiated Pressure Vessel Steel Weld
Authors: Miller M. K. , Russell K. F. , Pareige P. 
Published: April 2011

ABSTRACTAn atom probe tomography study has been performed to estimate the matrix composition, and the size, composition and number density of the ultrafine copper-enriched precipitates that formed under neutron irradiation in a submerged arc weld (Weld 73W). This high copper (0.27 at. % Cu) weld was examined after a typical stress relief treatment of 40 h at 607°C, after neutron irradiation to a fluence of 1.8 × 1023 n m-2 (E > 1 MeV) at a temperature of 288°C, after irradiation and thermal annealing for 168 h at 454°C, and after irradiation, thermal annealing and re-irradiation to an additional fluence of 0.8 × 1023 n m-2 (E > 1 MeV). A high number density of ultrafine copper-enriched precipitates were found to form on irradiation. These precipitates were found to coarsen and decrease in number density after the annealing treatment at 454°C. These precipitates were present after re-irradiation and some additional subnanometer diameter copper- enriched precipitates were also observed. Segregation of nickel, manganese, silicon, copper and phosphorus atoms to dislocations was also observed.
The Size Distribution of Ge Nanocrystals in Implanted and Annealed Silica
Authors: Dowd Annette R. , Llewellyn David , Gerald John D. Fitz , Elliman Robert G. 
Published: April 2011

ABSTRACTThis study examines the effect of implantation and annealing parameters on the formation of Ge crystallites in ion-implanted silica. Samples were implanted at room temperature or −196oC with 1.0 MeV Ge+ ions to fluences in the range from 0.6 to 3×1017 Ge.cm−2. Ge nanocrystals were not observed in samples implanted at −196°C but were observed in samples irradiated at room temperature. Nanocrystals were observed in all samples after annealing and their size distribution was found to be almost independent of the implant fluence. The distributions were also shown to be asymmetrical with depth, with smaller nanocrystals located on the near-surface side of the implant distribution.
Molecular Dynamics Simulations of Cluster Ion Impact on Diamond Surface
Authors: Aoki Takaaki , Matsuo Jiro , Takaoka Gikan , Yamada Isao 
Published: April 2011

ABSTRACTMolecular dynamics (MD) simulations of various cluster ions impacting on solid targets were performed in order to examine the implant and damage formation processes. Ne and Ar rare gas cluster with various cluster sizes, and fullerene (C60) were impacted on diamond (001) surface. It was shown that the impact process of cluster ion depends on the cluster size. When the cluster size is small and incident energy-per-atom is high, such as Ar15 with 800eV/atom, all incident Ar atoms penetrate the surface and reside in the substrate. As the cluster size increases and the incident energy-per-atom decreases, the implant depth decreases and the profile of the displacement becomes shallower. A large cluster, such as Ar60 with 200eV/atom, shows a shallower implant depth and a higher sputtering yield than Ar15. However, Ar240 with 50eV/atom shows a shallower implant depth, but less sputtering yield than Ar60.These results suggest that there is proper cluster size and incident energy where the maximum sputtering yield is achieved.
Microstructural Evolution of Ni-doped Ferritic/martensitic Steels Irradiated in the HFIR
Authors: Hashimoto Naoyuki , Klueh Ronald L. , Robertson Janet P. 
Published: April 2011

ABSTRACTThe microstructures of reduced-activation ferritic/martensitic steels, 9Cr-2WVTa and 9Cr-2WVTa doped with 2% Ni, irradiated at 400oC up to 12 dpa in the High Flux Isotope Reactor (HFIR), were investigated by transmission electron microscopy. Specimens were tempered at two different temperatures in order to investigate the effects of tempering on microstructural evolution during irradiation. Before irradiation, the lath width of Ni-doped 9Cr-2WVTa was somewhat narrower and the dislocation density tended to be higher compared with 9Cr-2WVTa. Dislocation density of specimens tempered at 750°C was lower than that tempered at 700°C. In all steels, precipitates on grain and/or lath boundaries were mainly M23C6, and there were a few TaC along dislocations in the matrices. Irradiation-induced cavities were observed in all the steels. The cavity number density of the Ni-doped 9Cr-2WVTa was higher than that of 9Cr-2WVTa due to the higher concentration of helium; however, swelling in each steels was < 0.1% because cavity sizes were so small. There was no difference of cavity number density between the steels tempered at 700°C and 750°C, but the mean size of the cavities in the steels tempered at 750°C was larger than that tempered at 700°C. Irradiation-induced a0<100> and (a0/2)<111> type dislocation loops were observed in all steels; number density and mean diameter of a0<100> type loops was higher and larger than that of (a0/2)<111> type loops. There was a tendency for the number density of loops in Ni-doped 9Cr-2WVTa to be slightly higher than that in 9Cr-2WVTa. In addition, the mean size of loops in the steels tempered at 750°C was larger than for those tempered at 700°C, while there was not much difference of number density between them. In the steels doped with Ni, irradiation-produced precipitates, identified as M6C(η)-type carbide, were found in the matrices. In this experiment, the change in tensile properties and the δDBTT of the 9Cr-2VWTa-2Ni was greater than for 9Cr-2WVTa. The microstructural evidence suggests that these differences in mechanical behavior are related to the formation of radiation-induced precipitates and cavities in the Ni-doped alloy; further analysis of the data using barrier hardening models is in progress.
Radiation Effects on the Plasticity and Microstructure of Ti-Al-V Alloys Containing β Phase
Authors: Sawai Tomotsugu , Tabuchi Masayuki , Wakai Eiichi , Hishinuma Akimichi 
Published: April 2011

ABSTRACTTensile properties of Ti-35Al-15V and Ti-30Al-10V alloys were examined. These alloys contain β phase with ordered bcc structure. The total elongation of Ti-35Al-15V alloy abruptly changes from 10% to 60% around 620 ºC. Many transformation bands were observed in β grains that were highly deformed above this temperature. The hexagonal α2-phase grains in bands and the β–phase grains in bands and matrix were in Burgers type of orientation relationship. The ductility of Ti-30Al-10V alloy was highly affected by neutron irradiation. The specimens irradiated and tested at 400 °C showed almost no ductility. The total elongation of specimens irradiated and tested at 600 °C was about 10 %, while that of unirradiated ones was larger than 60 %. Specimens irradiated at 400 °C were also tested at 600 °C and the elongation was only 6 %, showing little recovery in ductility. This embrittlement suggests phase decomposition during irradiation.
The primary damage in Fe revisited by Molecular Dynamics and its binary collision approximation
Authors: Becquart C.S. , Hou M. , Souidi A. 
Published: April 2011

ABSTRACTMolecular Dynamics (MD) is a very powerful tool for studying displacement cascades initiated by the neutrons when they interact with matter and thus evaluate the primary damage. The mean number of point defects created can be obtained with a fair standard error with a reasonable number of cascade simulations (10 to 20 [1]), however other cascades characteristics (spatial distribution, size and amount of defect clusters …) display a huge variability. Therefore, they may need to be studied using faster methods such as the Binary Collision Approximation (BCA) which is several order of magnitude less time consuming. We have investigated the point defect distributions subsequent to atomic collision cascades by both MD (using EAM potentials for Fe) and its BCA. MD and its BCA lead to comparable point defect predictions. The significant similarities and differences are discussed.
Effect of Bulk Phosphorus Content on Hardening, Non-Equilibrium Segregation and Embrittlement in Neutron Irradiated Iron-Based Alloys
Authors: Nishiyama Y. , Bloomer T. E. , Kameda J. 
Published: April 2011

ABSTRACTThe effect of bulk P contents on hardening, non-equilibrium intergranular segregation and embrittlement has been studied in Mn-doped ferritic alloys subjected to neutron irradiation (E>0.1MeV: fluence of 1 × 1025 n/m2 at 711K for 2120 h) or irradiation-equivalent thermal aging. Neutron irradiation-induced intergranular P segregation became more prominent with decreasing bulk P content. Thermal aging slightly enhanced the amount of segregated P independent of the bulk P content. Intergranular C segregation in all the alloys was suppressed by the irradiation. An alloy with low bulk P content showed only moderate irradiation-induced hardening. The ductile-brittle transition temperature (DBTT) in alloys with low and intermediate amounts of P increased by the same shift during the irradiation but not at all during the thermal aging. Doping high bulk P led to a high DBTT in the as-heat-treated alloy while the irradiation decreased the DBTT. The irradiation effect on the DBTT in the model ferritic alloys containing the different levels of P is discussed in light of embrittling or toughening effects caused by the changes in the P or C segregation, and hardness.
Hardening and Microstructure of Model Reactor Pressure Vessel Steel Alloys Using Proton Irradiation
Authors: Yu Q. , Was G. S. , Wang L. M. , Odette R. , Alexander D. E. 
Published: April 2011

ABSTRACTAs part of a broad effort to understand the mechanisms of irradiation embrittlement in reactor pressure vessels steels, irradiation hardening and microstructural evolution in simple model Fe-0.9Cu-1.0Mn, Fe-0.9Cu and Fe alloys irradiated with 3.2 MeV protons at 300°C are compared to the corresponding changes in hardening produced by neutron irradiation over a similar dose range of 0.0004 to 0.015 dpa. In the case of the proton irradiated samples, Vickers hardness was measured at a 25 g load and the microstructures were characterized using small angle x-ray scattering (SAXS). In spite of the much higher dpa rate for protons (3 × 10−7dpa/s compared to neutron rates of about 10−9to 10−10dpa/s) as well as very different primary recoil spectra, the observed hardening-dose response is very similar in both cases. The large increase in hardness in the alloys with 0.9% copper, and the SAXS data are consistent with precipitation of coherent copper-rich features accelerated by irradiation enhanced diffusion, as well as a much smaller contribution presumably from defect clusters that do not require the presence of copper.
Nanophase Composites Produced by Ion Implantation: Properties, Problems, and Potential
Authors: Meldrum A. , Boatner L. A. , White C. W. , Haglund R. F. 
Published: April 2011

ABSTRACTIon implantation has become a versatile and powerful technique for synthesizing nanometer-scale clusters and crystals embedded in the near-surface region of a variety of hosts. The resulting nanocomposite materials often show unique optical, magnetic, and electronic properties. Here we review some of the principal features of this nanophase materials synthesis technique and discuss the outstanding experimental difficulties that currently hamper the development of devices based on the many unique properties of these nanocomposite materials. Possible solutions to these problems and future research directions are discussed.