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Application of in-situ ion irradiation TEM and 4D tomography to advanced scintillator materials

Proceedings of SPIE - The International Society for Optical Engineering

Pratt, Sarah H.; Hattar, Khalid M.; Boyle, Timothy; Villone, Janelle; Yang, Pin; Doty, F.P.; Hernandez-Sanchez, Bernadette A.

Scintillating nanomaterials are being investigated as replacements for fragile, difficult to synthesize single crystal radiation detectors, but greater insight into their structural stability when exposed to extreme environments is needed to determine long-term performance. An initial study using high-Z cadmium tungstate (CdWO4) nanorods and an in-situ ion irradiation transmission electron microscope (I3TEM) was performed to determine the feasibility of these extreme environment experiments. The I3TEM presents a unique capability that permits the real time characterization of nanostructures exposed to various types of ion irradiation. In this work, we investigated the structural evolution of CdWO4 nanorods exposed to 50 nA of 3 MeV copper (3+) ions. During the first several minutes of exposure, the nanorods underwent significant structural evolution. This appears to occur in two steps where the nanorods are first segmented into smaller sections followed by the sintering of adjacent particles into larger nanostructures. An additional study combined in-situ ion irradiation with electron tomography to record tilt series after each irradiation dose; which were then processed into 3D reconstructions to show radiation damage to the material over time. Analyses to understand the mechanisms and structure-property relationships involved are ongoing. © 2012 SPIE.

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TYPE Conference YEAR 2012
OSTIScopus

Nanoindentation and TEM Characterization of Ion Irridiated 316L Stainless Steels

Energy Technology 2012: Carbon Dioxide Management and Other Technologies

Hattar, Khalid M.; Buchheit, Thomas E.; Kotula, Paul G.; Mcginnis, Alexander; Brewer, Luke

Understanding the effects of extensive radiation damage in structural metals provides necessary insight for predicting the performance of those metals considered for application in the extreme radiation environment. Predicting mechanical performance after long term radiation exposure is of great importance to extending the life of current nuclear reactors and for developing future materials for the next generation of reactors. A combination of finite element modeling, nanoindentation, and TEM characterization were used to rapidly determine the microstructure and mechanical properties influences of ion irradiation on a standard 316L stainless steel sample. The results of this study found that ion irradiation and small scale mechanical property testing can be used to characterize extensive levels of radiation damage structure, only when significant consideration is given to ion irradiation depth, surface roughness and polishing condition, the irradiation temperature, and.many other experimental parameters. © 2012 The Minerals, Metals, & Materials Society. All rights reserved.

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TYPE Conference YEAR 2012
ScopusOSTI

Fast neutron environments

Hattar, Khalid M.; Puskar, J.D.; Doyle, B.L.; Boyce, Brad L.; Buchheit, Thomas E.; Foiles, Stephen M.; Lu, Ping; Clark, Blythe C.; Kotula, Paul G.; Goods, Steven H.

The goal of this LDRD project is to develop a rapid first-order experimental procedure for the testing of advanced cladding materials that may be considered for generation IV nuclear reactors. In order to investigate this, a technique was developed to expose the coupons of potential materials to high displacement damage at elevated temperatures to simulate the neutron environment expected in Generation IV reactors. This was completed through a high temperature high-energy heavy-ion implantation. The mechanical properties of the ion irradiated region were tested by either micropillar compression or nanoindentation to determine the local properties, as a function of the implantation dose and exposure temperature. In order to directly compare the microstructural evolution and property degradation from the accelerated testing and classical neutron testing, 316L, 409, and 420 stainless steels were tested. In addition, two sets of diffusion couples from 316L and HT9 stainless steels with various refractory metals. This study has shown that if the ion irradiation size scale is taken into consideration when developing and analyzing the mechanical property data, significant insight into the structural properties of the potential cladding materials can be gained in about a week.

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TYPE SAND Report YEAR 2011
DOIOSTI

Influence of anisotropy on thermal boundary conductance at solid interfaces

Physical Review B - Condensed Matter and Materials Physics

Hopkins, Patrick E.; Beechem, Thomas E.; Duda, John C.; Hattar, Khalid M.; Ihlefeld, Jon F.; Rodriguez, Mark A.; Piekos, Edward S.

We investigate the role of anisotropy on interfacial transport across solid interfaces by measuring the thermal boundary conductance from 100 to 500 K across Al/Si and Al/sapphire interfaces with different substrate orientations. The measured thermal boundary conductances show a dependency on substrate crystallographic orientation in the sapphire samples (trigonal conventional cell) but not in the silicon samples (diamond cubic conventional cell). The change in interface conductance in the sapphire samples is ascribed to anisotropy in the Brillouin zone along the principal directions defining the conventional cell. This leads to resultant phonon velocities in the direction of thermal transport that vary nearly 40% based on crystallographic direction. © 2011 American Physical Society.

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TYPE Journal Article YEAR 2011
DOIOSTIScopus

Reduction in thermal boundary conductance due to proton implantation in silicon and sapphire

Applied Physics Letters

Hopkins, Patrick E.; Hattar, Khalid M.; Beechem, Thomas E.; Ihlefeld, Jon F.; Medlin, Douglas L.; Piekos, Edward S.

We measure the thermal boundary conductance across Al/Si and Al/ Al 2 O3 interfaces that are subjected to varying doses of proton ion implantation with time domain thermoreflectance. The proton irradiation creates a major reduction in the thermal boundary conductance that is much greater than the corresponding decrease in the thermal conductivities of both the Si and Al2 O3 substrates into which the ions were implanted. Specifically, the thermal boundary conductances decrease by over an order of magnitude, indicating that proton irradiation presents a unique method to systematically decrease the thermal boundary conductance at solid interfaces. © 2011 American Institute of Physics.

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TYPE Journal Article YEAR 2011
DOIOSTIScopus

In situ TEM investigation into the thermal stability of nanograined FCC metals

Hattar, Khalid M.; Knapp, J.A.

Nanostructured materials often display very unique properties related to their far-from-equilibrium nature. Due to these unique structures, many of these materials transform into other, more stable microstructures with minimal thermal excitation. This work will highlight examples of the unexpected routes taken during the microstructural evolution of pulsed-laser deposited (PLD) free-standing face-centered cubic (FCC) thin films as a function of deposition condition and annealing temperatures. A direct comparison between the grain growth dynamics observed during in situ TEM annealing experiments in PLD films of high-purity aluminum, copper, gold and nickel films, as well as aluminum-alumina alloys shows a multitude of kinetics. For high-purity systems film thickness, void density, grain size distribution, and deposition temperature were found to be the primary factors observed controlling the rate, extent, and nature of the grain growth. The growth dynamics ranged from nearly classical normal grain growth to abnormal grain growth resulting in a bimodal grain size distribution. The grain growth rate was found to be highly dependent on the materials system despite all of the films being nanograined FCC metals produced by similar PLD parameters. The investigation of the aluminum-alumina alloys produced under various compositions and deposition parameters suggests that particle pinning can be used to maintain nanostructured films, even after annealing treatments at high homologous temperatures. In addition to investigating the grain growth dynamics and the resulting grain size distribution, the variety of internal microstructures formed from thermal annealing were evaluated. These structures ranged from intergranular voids to stacking-fault tetrahedra. An unexpected, metastable hexagonal-closed packed phase was indentified in the high-purity nickel films. These in situ TEM observations have provided key insight into the microstructural evolution of nanograined free-standing metal films and the defect structure present in the grains resulting from various growth dynamics, in addition to suggesting multiple methods to tailor the structure and the resulting properties of nanostructured free-standing films.

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TYPE Conference YEAR 2010
OSTI

Nanomechanics and nanometallurgy of boundaries

Boyce, Brad L.; Clark, Blythe C.; Foiles, Stephen M.; Hattar, Khalid M.; Holm, Elizabeth A.; Knapp, J.A.

One of the tenets of nanotechnology is that the electrical/optical/chemical/biological properties of a material may be changed profoundly when the material is reduced to sufficiently small dimensions - and we can exploit these new properties to achieve novel or greatly improved material's performance. However, there may be mechanical or thermodynamic driving forces that hinder the synthesis of the structure, impair the stability of the structure, or reduce the intended performance of the structure. Examples of these phenomena include de-wetting of films due to high surface tension, thermally-driven instability of nano-grain structure, and defect-related internal dissipation. If we have fundamental knowledge of the mechanical processes at small length scales, we can exploit these new properties to achieve robust nanodevices. To state it simply, the goal of this program is the fundamental understanding of the mechanical properties of materials at small length scales. The research embodied by this program lies at the heart of modern materials science with a guiding focus on structure-property relationships. We have divided this program into three Tasks, which are summarized: (1) Mechanics of Nanostructured Materials (PI Blythe Clark). This task aims to develop a fundamental understanding of the mechanical properties and thermal stability of nanostructured metals, and of the relationship between nano/microstructure and bulk mechanical behavior through a combination of special materials synthesis methods, nanoindentation coupled with finite-element modeling, detailed electron microscopic characterization, and in-situ transmission electron microscopy experiments. (2) Theory of Microstructures and Ensemble Controlled Deformation (PI Elizabeth A. Holm). The goal of this Task is to combine experiment, modeling, and simulation to construct, analyze, and utilize three-dimensional (3D) polycrystalline nanostructures. These full 3D models are critical for elucidating the complete structural geometry, topology, and arrangements that control experimentally-observed phenomena, such as abnormal grain growth, grain rotation, and internal dissipation measured in nanocrystalline metal. (3) Mechanics and Dynamics of Nanostructured and Nanoscale Materials (PI John P. Sullivan). The objective of this Task is to develop atomic-scale understanding of dynamic processes including internal dissipation in nanoscale and nanostructured metals, and phonon transport and boundary scattering in nanoscale structures via internal friction measurements.

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TYPE Conference YEAR 2010
OSTI

Heavy ion radiation effects studies with ion photon emission microscopy

Hattar, Khalid M.; Powell, Cody J.; Doyle, B.L.

The development of a new radiation effects microscopy (REM) technique is crucial as emerging semiconductor technologies demonstrate smaller feature sizes and thicker back end of line (BEOL) layers. To penetrate these materials and still deposit sufficient energy into the device to induce single event effects, high energy heavy ions are required. Ion photon emission microscopy (IPEM) is a technique that utilizes coincident photons, which are emitted from the location of each ion impact to map out regions of radiation sensitivity in integrated circuits and devices, circumventing the obstacle of focusing high-energy heavy ions. Several versions of the IPEM have been developed and implemented at Sandia National Laboratories (SNL). One such instrument has been utilized on the microbeam line of the 6 MV tandem accelerator at SNL. Another IPEM was designed for ex-vacu use at the 88 cyclotron at Lawrence Berkeley National Laboratory (LBNL). Extensive engineering is involved in the development of these IPEM systems, including resolving issues with electronics, event timing, optics, phosphor selection, and mechanics. The various versions of the IPEM and the obstacles, as well as benefits associated with each will be presented. In addition, the current stage of IPEM development as a user instrument will be discussed in the context of recent results.

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TYPE Conference YEAR 2010
OSTI
Results 501–600 of 613
Results 501–600 of 613