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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Sequentially Executed Model Evaluation Framework

Provides a message passing framework between generic input, model and output drivers, and specifies an API for developing such drivers. Also provides batch and real-time controllers which step the model and 1/0 through the time domain (or other discrete domain), and sample 1/0 drivers. This is a Framework library framework, and does not, itself, solve any problems or execute any modelling. The SeMe framework aids in development of models which operate on sequential information, such as time-series, where evaluation is based on prior results combined with new data for this iteration. Ha) applications in quality monitoring, and was developed as part of the CANARY-EDS software, where real-time water quality data is being analyzed

Hart, David↗
DOE OSTI2017

Environmental Risk Implications of Metals in Sludges from Waste Water Treatment Plants: The Discovery of Vast Stores of Metal-Containing Nanoparticles

Nanoparticle (NP) assessment in sludge materials, although of growing importance in eco- and biotoxicity studies, is commonly overlooked and, at best, understudied. In the present study, sewage sludge samples from across the mega-city of Shanghai, China were investigated for the first time using a sequential extraction method coupled with single particle inductively coupled plasma mass spectrometry (SP-ICP-MS) to quantify the abundance of metal-containing NPs in the extraction fractions and transmission electron microscopy to specifically identify the nanophases present. In general, most sludges observed showed high concentrations of Cr, Cu, Cd, Ni, Zn, and Pb, exceeding the maximum permitted values in the national application standard of acid soil in China. NPs in these sludges contribute little to the volume and mass but account for about half of the total particle number. Based on electron microscopy techniques, various NPs were further identified, including Ti-, Fe-, Zn-, Sn-, and Pb-containing NPs. All NPs, ignored by traditional metal risk evaluation methods, were observed at a concentration of 107 -1011 particles/g within the bioavailable fraction of metals. These results indicate the underestimate or misestimation in evaluating the environmental risks of metals based on traditional sequential extraction methods. A new approach for the environmental risk assessment of metals, including NPs, is urgently needed.

Oxides, Metals, Nanoparticles, Sludges↗
DOE OSTI2016

Zinc Corrosion in Borated, Buffered Post-LOCA Solutions

This current research provides a broad assessment of recently evaluated zinc corrosion in simulated non-buffered and buffered post-LOCA solution as a function of pH, temperature, velocity, boron concentration and surface area. Corrosion rates obtained can be used for further zinc borate formation analysis or to plan further zinc corrosion studies. Experiments are conducted utilizing a three-electrode electrochemical system in a glass cell. Aqueous solutions used in testing simulate reactor containment building (RCB) pool water under various LOCA scenarios that are representative of US PWR RCB pool water: boric acid only, boric acid with trisodium phosphate, boric acid with sodium hydroxide, and boric acid with sodium tetraborate. The specimens used in this work are machined from 99.6% pure zinc rods that are used as a surrogate for the high purity zinc layer of galvanized steel. Prior to the experiment, the specimens are first polished and then left exposed to the atmosphere for approximately one day at room temperature. Prior to each test, the zinc specimen are sequentially rinsed with deionized water and acetone, and then dried by evaporation in air at room temperature. Prepared samples are then mounted in the glass cell test apparatus and rotated on a spindle at a desired velocity for a specified duration. Instantaneous corrosion rate as a function of time and total zinc mass corroded, which may either be released into solution or incorporated into surface scale, is determined by electrochemical impedance spectroscopy (EIS) analysis. Corrosion rates after 24 hours of immersion are determined from a full potential dynamic scan and from weight loss measurements of descaled post-test samples. The solution zinc concentration resulting from zinc corrosion is determined by inductively coupled plasma optical emission spectroscopy (ICP-OES). Preliminary results show that zinc corrosion with a zinc surface area-to-liquid volume ratio of 0.0003 m2/L in a borated, buffered solution (55 deg. C, pH 7.2) exposed to a velocity of 0.5 ft/s is between 4.9 X to 2.3 X less than that obtained by the Kyrk et al study, which examines a lower temperature, lower pH with a 5.5 X larger surface area-to-volume ratio. This initial finding suggests that the corrosion of zinc, which supplies a zinc source term to form zinc borates, may not be insignificant under conditions of interest (borated, buffered post-LOCA solutions). Further experiments are currently underway that evaluate the influence of pH, velocity, temperature, buffer type, boron concentration and surface area-to-volume ratio on zinc corrosion. Preliminary results suggest two of the three buffer types examined as conditions of interest to US PWRs likely produce zinc corrosion within the range observed by Kyrk et al. Current preliminary results indicate that buffer type, temperature, pH and velocity each have an impact on the zinc corrosion rate. Quantification of zinc mass lost to solution and incorporated into scale is currently underway, as is the characterization of velocity and boric acid effects on zinc corrosion.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Topological insulator thin films starting from the amorphous phase-Bi{sub 2}Se{sub 3} as example

We present a new method to obtain topological insulator Bi{sub 2}Se{sub 3} thin films with a centimeter large lateral length. To produce amorphous Bi{sub 2}Se{sub 3} thin films, we have used a sequential flash-evaporation method at room temperature. Transmission electron microscopy has been used to verify that the prepared samples are in a pure amorphous state. During annealing, the samples transform into the rhombohedral Bi{sub 2}Se{sub 3} crystalline structure which was confirmed using X-ray diffraction and Raman spectroscopy. Resistance measurements of the amorphous films show the expected Mott variable range hopping conduction process with a high specific resistance compared to the one obtained in the crystalline phase (metallic behavior). We have measured the magnetoresistance and the Hall effect at different temperatures between 2 K and 275 K. At temperatures T ≲ 50 K and fields B ≲ 1 T, we observe weak anti-localization in the MR; the Hall measurements confirm the n-type character of the samples. All experimental results of our films are in quantitative agreement with results from samples prepared using more sophisticated methods.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Effect of helium on dispersoid evolution under self-ion irradiation in a dual-phase 12Cr oxide-dispersion-strengthened alloy

As one candidate alloy for future Generation IV and fusion reactors, a dual-phase 12Cr oxide-dispersion-strengthened (ODS) alloy was developed for high temperature strength and creep resistance and has shown good void swelling resistance under high damage self-ion irradiation at high temperature. However, the effect of helium and its combination with radiation damage on oxide dispersoid stability needs to be investigated. In this study, 120 keV energy helium was preloaded into specimens at doses of 1 × 10 15 and 1 × 10 16 ions/cm 2 at room temperature, and 3.5 MeV Fe self-ions were sequentially implanted to reach 100 peak displacement-per-atom at 475 °C. He implantation alone in the control sample did not affect the dispersoid morphology. After Fe ion irradiation, a dramatic increase in density of coherent oxide dispersoids was observed at low He dose, but no such increase was observed at high He dose. The study suggests that helium bubbles act as sinks for nucleation of coherent oxide dispersoids, but dispersoid growth may become difficult if too many sinks are introduced, suggesting that a critical mass of trapping is required for stable dispersoid growth.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Kinetics study of the evolution of oxygen-related defects in mono-crystalline silicon subjected to electron-irradiation and thermal treatment

The diffusion and dissociation mechanisms governing the evolution of oxygen and vacancy-oxygen defects in Czochralski-grown Si samples have been studied. The samples were irradiated at (i) room temperature or (ii) elevated temperature (350 °C) by MeV electrons and then isothermally annealed at 8 different temperatures in the range of 300 °C to 500 °C. The evolution of the concentrations of oxygen complexes (O{sub n}, n ≤ 3) and mono-vacancy-oxygen defects (VO{sub n}, n ≤ 4) have been followed by infrared absorption measurements of local vibrational modes originating from the individual defects. The experimental kinetics data have been compared with simulation results based on the theory for diffusion limited reactions, assuming a model where sequential build-up of the VO{sub n} defects is a key ingredient. A close quantitative agreement is obtained for both sets of samples despite quite different initial conditions prior to the annealing, which adds evidence to the validity of the model. Values for the diffusivity and dissociation rates of VO{sub n} (n ≤ 4) and O{sub n} (n ≤ 3) have been deduced and in general, the mobility and stability of VO{sub n} decrease and increase with n, respectively. For all the defects, partial dissociation appears as a prevailing process during diffusion, while full dissociation of VO{sub n} is limited by an energy barrier identical to that of interstitial oxygen (O{sub i}) diffusion (∼2.55 eV). The oxygen dimer and trimer are fast diffusers but slower than substitutional oxygen, i.e., VO; VO is found to be the most mobile species, whilst O{sub i} is the slowest one with a difference in diffusivity of up to 7 orders of magnitude in the studied temperature range.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2023

Commissioning of a two-target DC cylindrical magnetron sputter coater for depositing Nb 3 Sn film on Nb superconducting radiofrequency cavities

A DC cylindrical magnetron sputter coater was commissioned and used to coat Nb 2.6 GHz superconducting radiofrequency (SRF) cavity with Nb 3 Sn. The sputter coater has two identical cylindrical magnetrons that can move, with a controlled speed, along the axis of the SRF cavity to coat the inside surface of the cavity. The design of the sputter coater is discussed, along with its performance. Initially, a sample holder that allows coating on flat substrates at positions similar to the equator and beam tubes of a 2.6 GHz SRF cavity was used to test conditions for fabricating Nb 3 Sn layers. Multilayers of Nb and Sn were sequentially sputtered on flat Nb and sapphire substrates mounted on the equivalent positions of the cavity's beam tubes and the equator using the two identical cylindrical magnetrons. Then, the Nb/Sn multilayers were annealed at 950 °C for 3 h. Here, the ~1.2 μm thick Nb 3 Sn film did not show any other Nb–Sn compounds and had a superconducting transition temperature of 17.61–17.76 K. The 2.6 GHz SRF cavity was coated using similar conditions as flat samples. Cryogenic RF testing of the Nb 3 Sn-coated cavity demonstrated a quality factor of 3.2 × 10 8 at an accelerating gradient of 5 MV/m at 4.4 K.

43 PARTICLE ACCELERATORS↗
DOE OSTI2015

Sodium silicate treatment for uranium (vi) bearing groundwater systems at f/h area at savannah river site - 15709

The Savannah River Site (SRS) was one of the most significant manufacturing facilities during the Cold War era for producing nuclear materials. At the end of the Cold War, the Site's mission changed to support the environmental restoration of the Site due to over six decades of research, development, and production of nuclear weapons. Currently SRS is a major hazardous waste management facility responsible for nuclear materials storage, and remediation of contaminated soil and groundwater from radionuclides. This research focuses on controlling the mobilization of the contaminants, specifically uranium (VI) located in groundwater plumes at the Site's F/H Area Seepage Basin, where approximately 1.8 billion gallons of hazardous waste were deposited. Objective: To evaluate the potential use of sodium silicate for uranium removal from the aqueous phase, as well as to restore the pH of the treatment zone. Adding sodium silicate increases the pH of the treatment zone and uranium precipitation is achieved, therefore immobilizing the contaminant. Through a series of experiments the optimal concentration of sodium silicate was investigated. Part 1: An experiment was conducted in order to determine the effect of sodium silicate on the pH of a solution containing Savannah River Site soil and synthetic groundwater replicated after the Site's natural groundwater composition. Each sample was spiked with the appropriate volume from the sodium silicate stock solution in order to achieve final desired sodium silicate concentrations of 10, 20, 40,50,60,70, and 80 parts per million. The samples were placed on a platform shaker for three days during which pH readings were collected in regular intervals to determine which silicate concentration produced a pH in the neutral range (6 > pH < 8). Part 2: A sequential experiment was conducted specifically using 40 and 50 ppm of sodium silicate with Savannah River Site soil, synthetic groundwater, and 0.5 ppm of uranium (VI), in order to investigate the removal of uranium in the aqueous phase via precipitation. Samples were extracted and categorized into a filtered and non-filtered control group. Each sample was diluted 1:20 with 1% nitric acid and analyzed using the Kinetic Phosphorescence Analyzer (KPA) in order to measure uranium concentrations in the supernatant. By measuring the concentration of uranium in the supernatant the percent removal is obtained for the comparison between the filtered and non-filtered samples, revealing the amount of uranium precipitation that occurred for each silicate concentration. Results: A sodium silicate concentration of between 40-50 ppm proved ideal for achieving uranium precipitation and creating a circum-neutral pH environment in the aqueous phase. 50 ppm achieved the larger percent of uranium precipitation with a range of 30-50% removal for the filtered samples and between 60-95% removal for the non-filtered samples. A large difference between the removal of filtered and non- filtered samples from the same day was observed for both sodium silicate concentrations tested, indicating that there is a considerable amount of uranium species retained in the filter. The addition of sodium silicate proved effective in the removal of uranium precipitation from the aqueous phase. Future work: Determine potential re-solubilization of uranium concentrations; Examine mineralogy and surface morphology of dried precipitate using XRD and SEM/EDS.

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2020

Ghost imaging second harmonic generation microscopy

Second harmonic generation (SHG) microscopy is useful for visualizing interfaces and sub-structures within a wide range of materials due to the propensity for SHG to occur in non-centrosymmetric environments. However, since SHG is a nonlinear process generally necessitating small focal sizes for higher peak powers, a raster scanning approach is usually needed to build an SHG image over a significant sample size. While raster scanning is effective, there is a cost in terms of the time needed to acquire the image and, also, some materials cannot withstand the higher optical intensities within the small focal volume. As such, we describe a SHG microscopy approach based on ghost imaging (GI), which enables imaging data to be collected in parallel rather than sequentially as in raster scanning techniques. We experimentally demonstrate the approach and combine GI-SHG with compressive sensing to make further substantial gains in reducing the amount of sampling required for image reconstruction. Furthermore, GI-SHG is shown to have significant advantages for imaging in highly scattering environments, partly because GI is a background-free approach requiring spatial correlations between photons that travel two paths, with one path entirely devoid of sample interaction. This basic property of GI means that only the photons that travel unimpeded through the sample preserve the spatial correlations needed to reconstruct the image, while more scattered photons do not contribute to the overall GI signal. Finally, we compare the image quality and sampling properties of three different reconstruction algorithms used for compressive sensing.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Microscale mechanical modeling of deformable geomaterials with dynamic contacts based on the numerical manifold method

Abstract Micromechanical modeling of geomaterials is challenging because of the complex geometry of discontinuities and potentially large number of deformable material bodies that contact each other dynamically. In this study, we have developed a numerical approach for micromechanical analysis of deformable geomaterials with dynamic contacts. In our approach, we detect contacts among multiple blocks with arbitrary shapes, enforce different contact constraints for three different contact states of separated, bonded, and sliding, and iterate within each time step to ensure convergence of contact states. With these features, we are able to simulate the dynamic contact evolution at the microscale for realistic geomaterials having arbitrary shapes of grains and interfaces. We demonstrate the capability with several examples, including a rough fracture with different geometric surface asperity characteristics, settling of clay aggregates, compaction of a loosely packed sand, and failure of an intact marble sample. With our model, we are able to accurately analyze (1) large displacements and/or deformation, (2) the process of high stress accumulated at contact areas, (3) the failure of a mineral cemented rock samples under high stress, and (4) post-failure fragmentation. The analysis highlights the importance of accurately capturing (1) the sequential evolution of geomaterials responding to stress as motion, deformation, and high stress; (2) large geometric features outside the norms (such as large asperities and sharp corners) as such features can dominate the micromechanical behavior; and (3) different mechanical behavior between loosely packed and tightly packed granular systems.

58 GEOSCIENCES↗
DOE OSTI2018

Sequential chemical separations and multiple ion counting ICP-MS for 241 Pu– 241 Am– 237 Np dating of environmental collections on a single aliquot

In this study, we have developed a combined sequential chemical separation procedure and multiple ion counting ICP-MS measurement method for isotopic measurements of Am in environmental samples. This, in conjunction with established resin bead TIMS measurements for Pu and Np, allows us to measure long-lived Pu–Np–Am nuclides in environmental samples on a single solution aliquot. This single aliquot method reduces time lines and maximizes sample utility for the measurements, improving sensitivity, precision, and accuracy over prior methods. Finally, we have evaluated this new method with environmental reference materials and have obtained accurate results on samples with > 3E6 atoms 241 Am.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2018

Precursor and Neutral Loss Scans in an RF Scanning Linear Quadrupole Ion Trap

Methodology for performing precursor and neutral loss scans in an RF scanning linear quadrupole ion trap is described and compared to the unconventional ac frequency scan technique. In the RF scanning variant, precursor ions are mass selectively excited by a fixed frequency resonance excitation signal at low Mathieu q while the RF amplitude is ramped linearly to pass ions through the point of excitation such that the excited ion’s m/z varies linearly with time. Ironically, a nonlinear ac frequency scan is still required for ejection of the product ions since their frequencies vary nonlinearly with the linearly varying RF amplitude. In the case of the precursor scan, the ejection frequency must be scanned so that it is fixed on a product ion m/z throughout the RF scan, whereas in the neutral loss scan, it must be scanned to maintain a constant mass offset from the excited precursor ions. Both simultaneous and sequential permutation scans are possible; only the former are demonstrated here. The scans described are performed on a variety of samples using different ionization sources: protonated amphetamine ions generated by nanoelectrospray ionization (nESI), explosives ionized by low-temperature plasma (LTP), and chemical warfare agent simulants sampled from a surface and analyzed with swab touch spray (TS). We lastly conclude that the ac frequency scan variant of these MS/MS scans is preferred due to electronic simplicity. In an accompanying manuscript, we thus describe the implementation of orthogonal double resonance precursor and neutral loss scans on the Mini 12 using constant RF voltage. .

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2022

Direct Fabrication of Vertically Stacked Double Barrier Tunnel Junctions Based on Graphene and h-BN

Direct manufacturing of two-dimensional material-based double barrier (DB) tunnel junctions, based on a lithography-free approach was developed. Graphene/h-BN/Graphene/h-BN/Graphene devices were deposited on Si/SiO2 substrates by employing a plasma enhanced chemical vapor deposition technique in a sequential manner. DB tunneling junctions with varying barrier widths (by varying the thickness of the second graphene layer) were studied. Samples were characterized using Raman, Atomic Force Microscopy and X-ray photoemission spectroscopy. The I–V characteristics of tunneling current showed resonant tunneling behavior at room temperature with a negative differential conductance. The behavior could be explained with quantum mechanical double barrier tunneling model in which analytic solutions to Schrödinger’s equation were obtained in each region of the system. Resonances in transmission probability coefficient for varying barrier widths were evaluated and compared with the experimental results.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A review of rare earth elements and yttrium in coal ash: Content, modes of occurrences, combustion behavior, and extraction methods

Rare earth elements and yttrium (REY) have attracted considerable attention over the last decade because of their vital roles in clean energy, consumer product, national defense and security applications, among other uses. Due to the retention of REY during coal burning, coal combustion ash is considered as potential alternative sources for REY. Understanding the content, speciation, retention and/or transformation behavior of REY during coal combustion not only expands our knowledge of the combustion behavior of the trace elements in coal, but also provides basis for modeling REY partitioning during coal combustion and for developing economically viable REY recovery technologies. This review makes a critical summary of recent progress in the study of REY in coal ash. The contents and the extraction potentials of REY in coal ash derived from 15 major coal-producing countries worldwide were summarized and evaluated. Various analytical methods for determining REY bulk contents and speciation, together with the solid sample pretreatment, analytical accuracy and precision, advantages and disadvantages were summarized and compared. Modern analytical approaches combined indirect methods (e.g., sequential extraction) shed light on the physical distribution, mineralogy, and the chemical state of REY in coal ash. Three types of REY occurrences in coal ash, including Si-Al glassy association, discrete minerals or compounds, and organic association (bound with unburned carbon) were defined in the review. The glassy association can be further divided into REY minerals closely bound to glass phases and dispersed throughout the glassy structure. REY partitioning in various emission streams, the size distribution, and their enrichment behavior in coal ash were discussed. Additionally, thermal behavior and transformation of various REY forms in coal during combustion process, including organic-associated REY, REY phosphates, REY carbonates, clay-bound REY and among others were summarized. Two possible retention mechanisms of REY by aluminosilicate glass at boiler temperature were proposed: the incorporation of the individual REY phases into the glass as inclusions and the diffusion of REY phases throughout Si-Al glass structures in the melting process. Feed coal mineral types, mineral-mineral associations, boiler conditions, and other factors control the retention process. After coal combustion, the speciation of REY in fly ash may be modified by the reactions of REY phases with flue gas components. Further, an overview of REY transformation mechanisms during coal combustion was deeply discussed. Finally, current extraction techniques for REY recovery from coal combustion ash were introduced. Future outlooks and research problems were also identified.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Unsupervised Segmentation and Clustering Workflow for Efficient Processing of 4D-STEM and 5D-STEM Data

Four-dimensional scanning transmission electron microscopy (4D-STEM) enables mapping of diffraction information with nanometer-scale spatial resolution, offering detailed insight into local structure, orientation, and strain. However, as data dimensionality and sampling density increase, particularly for in situ scanning diffraction experiments (5D-STEM), robust segmentation of structurally consistent behavior across sequential measurements becomes essential for efficient and physically meaningful analysis. Here, we introduce a clustering framework that identifies crystallographically distinct domains from 4D-STEM datasets. By using local diffraction-pattern similarity as a metric, the method extracts closed contours delineating spatially contiguous regions. This approach produces cluster-averaged diffraction patterns that improve signal quality while reducing data volume by orders of magnitude, enabling rapid and accurate orientation, phase, and strain mapping. We demonstrate the applicability of this approach to in situ liquid-cell 4D-STEM data of gold nanoparticle growth. Our method provides a scalable and generalizable route for spatially coherent segmentation, data compression, and quantitative structure–strain mapping across diverse 4D-STEM modalities. The full analysis code and example workflows are publicly available to support reproducibility and reuse.

4D-STEM↗
DOE OSTI2015

Morphology-dependent phase transformation of y-Al2O3

The phase transformations of platelet- and rod-shaped ?-Al2O3 were investigated and compared to that of a commercial sample by XRD, BET surface area measurements, Transmission Electron Microscopy (TEM), solid state 27Al-NMR and ethanol temperature programmed desorption (TPD) after sequential annealing in air up to 1100 oC. After annealing at 1100 oC, commercial ?-Al2O3 mostly transformed into a-Al2O3 with drastic surface area reduction (from 200 m2/g to 25 m2/g). Interestingly, platelet- and rod-shaped ?-Al2O3 which showed exactly the same XRD patterns transformed into different phases upon the high temperature calcinations. Platelet-shaped ?-Al2O3 transformed into ?-phase while the rod-shaped ?-Al2O3 transformed into the d-phase and not to the a-polymorph. Both platelet- and rod-shaped aluminas retained significantly higher surface area (~60 m2/g) than the commercial one after the same treatment at 1100 oC. These results suggest that the phase transformation in ?-Al2O3 is strongly affected by not only the crystal structure of the starting material, but its morphology as well. Ethanol TPD from platelet- and rod-shaped alumina after 1100 oC annealing, showed significantly different desorption profiles which suggest different surface characteristics even though they had almost the same surface areas. These different phase transformations were also supported by solid state 27Al-NMR. After 1100oC annealing commercial alumina showed the presence of mostly octahedral Al3+ ions, but the other two samples displayed even higher number of tetrahedral Al3+ ions than the initial ?-Al2O3. Morphological changes were also confirmed by TEM. All these results consistently suggest the morphology-dependent phase transformations of ?-Al2O3 and the improved thermal stability of platelet- and rod- shaped ?-Al2O3 in comparison to a commercial ?-Al2O3. J.Sz. acknowledges the US Department of Energy (DOE), Office of Science, Office of Basic Energy Sciences (BES), Division of Chemical Sciences, Geosciences & Biosciences for the support of this work.

Lee, Jaekyoung↗
DOE OSTI2019

Chapter 11: Combined and Sequential Accelerated Stress Testing for Derisking Photovoltaic Modules

Application of stress factors in the combinations and sequences as they occur in the natural environment better reproduces failures seen in the field. Further, choice of sample type for testing that best represents the final product is most likely to yield relevant results. Tests meeting these criteria are more likely to discover potential weaknesses that are not a priori known in new module designs, reduce risk, accelerate time to market, achieve bankability and reduce costly overdesign.

14 SOLAR ENERGY↗
DOE OSTI2016

Lattice modification in KTiOPO{sub 4} by hydrogen and helium sequentially implantation in submicrometer depth

We investigated lattice modification and its physical mechanism in H and He co-implanted, z-cut potassium titanyl phosphate (KTiOPO{sub 4}). The samples were implanted with 110 keV H and 190 keV He, both to a fluence of 4 × 10{sup 16 }cm{sup −2}, at room temperature. Rutherford backscattering/channeling, high-resolution x-ray diffraction, and transmission electron microscopy were used to examine the implantation-induced structural changes and strain. Experimental and simulated x-ray diffraction results show that the strain in the implanted KTiOPO{sub 4} crystal is caused by interstitial atoms. The strain and stress are anisotropic and depend on the crystal's orientation. Transmission electron microscopy studies indicate that ion implantation produces many dislocations in the as-implanted samples. Annealing can induce ion aggregation to form nanobubbles, but plastic deformation and ion out-diffusion prevent the KTiOPO{sub 4} surface from blistering.

36 MATERIALS SCIENCE↗