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Time horizons for nuclear materials development and qualification must be shortened to realize future nuclear energy concepts. Inspired by the Materials Genome Initiative, we present an integrated approach to materials discovery and qualification to insert new materials into service.

A gas-phase approach to form Zn coordination sites on metal-organic frameworks (MOFs) by vapor-phase infiltration (VPI) was developed. Compared to Zn sites synthesized by the solution-phase method, VPI samples revealed approximately 2.8 % internal strain. Faradaic efficiency towards conversion of CO2 to CO was enhanced by up to a factor of four, and the initial potential was positively shifted by 200-300 mV. Using element-specific X-ray absorption spectroscopy, the local coordination environment of the Zn center was determined to have square-pyramidal geometry with four Zn-N bonds in the equatorial plane and one Zn-OH2 bond in the axial plane. The fine-tuned internal strain was further supported by monitoring changes in XRD and UV/Visible absorption spectra across a range of infiltration cycles. The ability to use internal strain to increase catalytic activity of MOFs suggests that applying this strategy will enhance intrinsic catalytic capabilities of a variety of porous materials.

Recent advances in design and processing technology have made possible commercialization of polycrystalline (px)-CdTe as a photovoltaic absorber. Grain boundaries (GBs) are the most prominent struc...

This work presents a thorough analysis of the grain growth behavior of gadolinium doped yttria stabilized zirconia (YSZ). The effect of the dopant on the thermodynamics as well as on the kinetics of the process is reported by providing extensive experimental data. While normal grain growth following a parabolic growth relation was observed, gadolinium inhibited the process proportionally to its concentration. By using microcalorimetry, we showed that the dopant decreases the grain boundary energy of YSZ, and hence reduces the driving force for growth. Analysis of the growth profile at different temperatures and times indicate that gadolinium does not significantly affect the grain boundary mobility or the activation energy for grain growth. The results rationalize that the dopant is acting on a mostly thermodynamic basis and opens good perspective for design of coarsening control focused on the system energetics.

Mitigating corrosion remains a daunting challenge due to localized, nanoscale corrosion events that are poorly understood but are known to cause unpredictable variations in material longevity. Here, the most recent advances in liquid-cell transmission electron microscopy were employed to capture the advent of localized aqueous corrosion in carbon steel at the nanoscale and in real time. Localized corrosion initiated at a triple junction formed by a solitary cementite grain and two ferrite grains and then continued at the electrochemically-active boundary between these two phases. With this analysis, we identified facetted pitting at the phase boundary, uniform corrosion rates from the steel surface, and data that suggest that a re-initiating galvanic corrosion mechanism is possible in this environment. These observations represent an important step toward atomically defining nanoscale corrosion mechanisms, enabling the informed development of next-generation inhibition technologies and the improvement of corrosion predictive models.

We present progress to develop low-cost interdigitated back contact solar cells with pc-Si/SiO2/c-Si passivated contacts formed by plasma immersion ion implantation (PIII). PIII is a lower-cost implantation technique than traditional beam line implantation due to its simpler design, lower operating costs, and ability to run high doses (1E14–1E18 cm−2) at low ion energies (20 eV–10 keV). These benefits make PIII ideal for high throughput production of patterned passivated contacts, where high-dose, low-energy implantations are made into thin (20–200 nm) a-Si layers instead of into the wafer itself. For this work symmetric passivated contact test structures (~100 nm thick) grown on n-Cz wafers with pH3 PIII doping gave implied open circuit voltage (iVoc) values of 730 mV with Jo values of 2 fA/cm2. Samples doped with B2H6 gave iVoc values of 690 mV and Jo values of 24 fA/cm2, outperforming BF3 doping, which gave iVoc values in the 660–680 mV range. Samples were further characterized by SIMS, photoluminescence, TEM, EELS, and post-metallization TLM to reveal micro- and macro-scopic structural, chemical and electrical information.

We investigated potential-induced degradation (PID) in silicon mini-modules that were subjected to accelerated stressing to induce PID conditions. Shunted areas on the cells were identified with photoluminescence and dark lock-in thermography (DLIT) imaging. The identical shunted areas were then analyzed via time-of-flight secondary-ion mass spectrometry (TOF-SIMS) imaging, 3-D tomography, and high-resolution transmission electron microscopy. The TOF-SIMS imaging indicates a high concentration of sodium in the shunted areas, and 3-D tomography reveals that the sodium extends more than 2 μm from the surface below shunted regions. Transmission electron microscopy investigation reveals that a stacking fault is present at an area identified as shunted by DLIT imaging. After the removal of surface sodium, tomography reveals persistent sodium present around the junction depth of 300 nm and a drastic difference in sodium content at the junction when comparing shunted and nonshunted regions.

Pyrochlores have long been considered as host phases for long-term immobilization of radioactive waste nuclides that would undergo α-decay for hundreds of thousands of years. This work utilizes ion-beam irradiations to examine the combined effects of radiation damage and He accumulation on bubble formation in Gd2Ti2O7 over relevant waste-form timescales. Helium bubbles are not observed in pre-damaged Gd2Ti2O7 implanted with 2 × 1016 He/cm2, even after post-implantation irradiations with 7 MeV Au3+ at 300, 500, and 700 K. However, He bubbles with average diameters of 1.5 nm and 2.1 nm are observed in pre-damaged (amorphous) Gd2Ti2O7 and pristine Gd2Ti2O7, respectively, after implantation of 2 × 1017 He/cm2. The critical He concentration for bubble nucleation in Gd2Ti2O7 is estimated to be 6 at.% He.

We introduce the concept of electrophobic interaction, analogous to hydrophobic interaction, for describing the behavior of impurity atoms in a metal, a “solvent of electrons”. We demonstrate that there exists a form of electrophobic interaction between impurities with closed electron shell structure, which governs their dissolution behavior in a metal. Using He, Be and Ar as examples, we predict by first-principles calculations that the electrophobic interaction drives He, Be or Ar to form a close-packed cluster with a clustering energy that follows a universal power-law scaling with the number of atoms (N) dissolved in a free electron gas, as well as W or Al lattice, as Ec ∝ (N2/3−N). This new concept unifies the explanation for a series of experimental observations of close-packed inert-gas bubble formation in metals, and significantly advances our fundamental understanding and capacity to predict the solute behavior of impurities in metals, a useful contribution to be considered in future material design of metals for nuclear, metallurgical, and energy applications.

Pyrochlores have long been considered as potential candidates for advanced ceramic waste-forms for the immobilization of radioactive waste nuclides. This work provides evidence that Gd2Zr2O7, often considered the most radiation tolerant pyrochlore, could be susceptible to radiation damage in the form of bubble nucleation at the highest He doses expected over geological time. Ion irradiations were utilized to experimentally simulate the radiation damage and He accumulation produced by alpha-decay. Samples were pre-damaged using 7 MeV Au3+ to induce the pyrochlore to defect-fluorite phase transformation, which would occur due to alpha-recoil damage within several hundred years of storage in a Gd2Zr2O7 waste form. These samples were then implanted to various He concentrations in order to study the long-term effects of He accumulation. Helium bubbles 1-3 nm in diameter were observed in TEM at a concentration of 4.6 at.% He. Some bubbles remained isolated, while others formed chains 10-30 nm in length parallel to the surface. GIXRD measurements showed lattice swelling after irradiating pristine Gd2Zr2O7 with 7 MeV Au3+ to a fluence of 2.2 x 10(15) Au/cm(2). An increase in lattice swelling was also measured after 2.2 x 10(15) Au/cm(2) + 2 x 10(15) He/cm(2) and 2.2 x 10(15) Au/cm(2) + 2 x 10(16) He/cm(2). A decrease in lattice swelling was measured after irradiation with 2.2 x 1015 Au/cm2 + 2 x 1017 He/cm2, the fluence where bubbles and bubble chains were observed in TEM. Bubble chains are thought to form in order to reduce lattice strain normal to the surface, which is produced by the Au and He irradiation damage. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Kesterite Cu2ZnSn(S,Se)4 (CZTSSe) is a sustainable material for thin-film photovoltaics with device efficiencies greater than 12% have been demonstrated. Despite similar crystal structure and polycrystalline film microstructures, there is widespread evidence for larger-amplitude potential and bandgap fluctuations in CZTS than in the analogous Cu(In,Ga)Se2 (CIGSe) chalcopyrite material. This disorder is believed to account for a sizable part of the larger open-circuit voltage (VOC) deficit in CZTS devices, yet the detailed origins and length scales of these fluctuations have not been fully elucidated. Herein, we present a transmission electron microscopy study focusing on composition variation within bulk multicrystals of CZTS grown by the travelling heater method (THM). In these slow-cooled, solution grown crystals we find direct evidence for spatial composition fluctuations of amplitude

The composition and crystal structure of the “Joint Oxyde Gaine” (JOG) has been investigated by means of electron microscopy. Microstructural characterization reveals a highly heterogeneous porous structure with inclusions containing both fission products and cladding components. Major fission products detected, other than Cs and Mo, are Te, I, Zr and Ba. The layer is composed by sub-micrometric crystallites. The diffraction data refinement, together with chemical mapping, confirms the presence of Cs2MoO4, which is the major component of the JOG. However, combinatorial analyses reveal that other non-stoichiometric phases are possible, highlighting the complex nature of the crystalline structure of the JOG. Fe is found in metallic Pd-rich precipitates with structure compatible with the tetragonal structure of FePd alloy. Cr is found in different locations of the JOG, in oxide form, but no structural data could be obtained due to local beam sensitization of the sample in those areas.

Uranium-free nonfertile Pu-based alloys, including Pu–40Zr and Pu-12Am–40Zr, represent two candidate fuel alloys for Generation IV (GEN-IV) and transuranic (TRU) type burner reactors. Before their acceptance in these applications, the chemical compatibility and interaction layer growth between these alloys and suggested HT-9 cladding must be reported in detail to facilitate their acceptance in advanced reactor concepts. In this study, each alloy was studied at 700 °C (973 K) for a variable period of time between 100 and 200 h in a diffusion couple geometry with Cr and V. Comparing the 100–200 h tests between Pu-12Am–40Zr fuel and Cr with V suggests a weakening in the interfacial growth rate as a function of annealing time. A quantitative study on the solid-state behavior and evolution of Pu-Am-Zr interacting with both Cr and V barriers at 700 °C (973 K) is reported.

From serving as the primary host material from near-ideal neutron moderators to high-capacity discharge electrodes, graphite is a ubiquitous material for a number of advanced applications. The focus of this work, however, is on those applications requiring high-purity fine-grained densified graphite monoliths fabricated to scale with minimal effort. To date, graphite monoliths have been constrained to lower final part densities and purities due to the technical challenges associated with mainly hot pressing and extrusion, that ultimate limit these attributes. In this study, we report on the use of spark plasma sintering as an alternate method for fabrication at temperatures below 1,200 °C and less than 300 MPa without the use of binders, additional resins, or post-thermal treatments. Formed part sizes from few to several millimeters in size, we report highly dense (2.095 g/cm3), well-bonded, and low-defect-ridden graphite with uniform composition examined by detailed X-ray and electron-based microscopy. The results are an initial report on the use this technique to sinter graphite under moderate conditions that may support small to moderate-scale technical production needs that require low-cost, high-purity, and high-density graphite.

Simultaneously capturing material structure and chemistry in the form of accessible data is often advantageous for drawing correlations and enhancing our understanding of measurable materials behavior and properties. Unfortunately, in many cases, accessing data at the scale required, is highly multidimensional and sparse by the historical and evolving nature of materials science. To mitigate difficulties, we develop and employ methods of data analytics in conjunction with open accessible chemistry and structure datasets, to classify and reduce the amount of data needed for extracting useful descriptors from multidimensional techniques. The construction and systematic ablation of our model highlights the potential for dimensional reduction in data sampling, improved classification, and identification of correlations among material crystallography and chemistry.

Deep learning provides an efficient cross-validation tool for crystallography with no preferred orientation or magnification., While machine learning has been making enormous strides in many technical areas, it is still massively underused in transmission electron microscopy. To address this, a convolutional neural network model was developed for reliable classification of crystal structures from small numbers of electron images and diffraction patterns with no preferred orientation. Diffraction data containing 571,340 individual crystals divided among seven families, 32 genera, and 230 space groups were used to train the network. Despite the highly imbalanced dataset, the network narrows down the space groups to the top two with over 70% confidence in the worst case and up to 95% in the common cases. As examples, we benchmarked against alloys to two-dimensional materials to cross-validate our deep-learning model against high-resolution transmission electron images and diffraction patterns. We present this result both as a research tool and deep-learning application for diffraction analysis.

Organic–inorganic perovskites have emerged as an important class of next generation solar cells due to their remarkably low cost, band gap, and sub-900 nm absorption onset. Here, we show a series of in situ observations inside electron microscopes and X-ray diffractometers under device-relevant synthesis conditions focused on revealing the crystallization process of the formamidinium lead-triiodide perovskite at the optimum temperature of 175 °C. Direct in situ observations of the structure and chemistry over relevant spatial, temporal, and temperature scales enabled identification of key perovskite formation and degradation mechanisms related to grain evolution and interface chemistry. The lead composition was observed to fluctuate at grain boundaries, indicating a mobile lead-containing species, a process found to be partially reversible at a key temperature of 175 °C. Using low energy electron microscopy and valence electron energy loss spectroscopy, lead is found to be bonded in the grain interior with iodine in a tetrahedral configuration. At the grain boundaries, the binding energy associated with lead is consequently shifted by nearly 2 eV and a doublet peak is resolved due presumably to a greater degree of hybridization and the potential for several different bonding configurations. At the grain boundaries there is adsorption of hydrogen and OH− ions as a result of residual water vapor trapped as a non-crystalline material during formation. Insights into the relevant formation and decomposition reactions of formamidinium lead iodide at low to high temperatures, observed metastabilities, and relationship with the photovoltaic performance were obtained and used to optimize device processing resulting in conversion efficiencies of up to 17.09% within the stability period of the devices.

Oxide dispersion strengthened ferritic/martensitic alloys have attracted significant attention for their potential uses in future nuclear reactors and storage vessels, as the metal/oxide interfaces act as stable high-strength sinks for point defects while also dispersing helium. Here, in order to unravel the evolution and interplay of interface structure and chemistry upon irradiation in these types of materials, an atomically sharp FeCr/MgO interface was synthesized at 500 °C and separately annealed and irradiated with Ni3+ ions at 500 °C. After annealing, a slight enrichment of Cr atoms was observed at the interface, but no other structural changes were found. However, under irradiation, sufficient Cr diffuses across the interface into the MgO to form a Cr-enriched transition layer that contains spinel precipitates. First-principles calculations indicate that it is energetically favorable to incorporate Cr, but not Fe, substitutionally into MgO. Furthermore, our results indicate that irradiation can be used to form new phases and complexions at interfaces, which may have different radiation tolerance than the pristine structures.

Cr diffusion in trilayer thin films of 100 nm Fe–18Cr/125 nm TiO2−x/100 nm Fe–18Cr deposited on MgO substrates at 500 °C was studied by either annealing at 500 °C or Ni3+ ion irradiation at 500 °C. Microchemistry and microstructure evolution at the metal/oxide interfaces were investigated using (high-resolution) transmission electron microscopy, energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy. Diffusion of Cr into the O-deficient TiO2 layer, with negligible segregation to the FeCr/TiO2−x interface itself, was observed under both annealing and irradiation. Cr diffusion into TiO2−x was enhanced in ion-irradiated samples as compared to annealed. Irradiation-induced voids and amorphization of TiO2−x was also observed. The experimental results are rationalized using first-principles calculations that suggest an energetic preference for substituting Ti with Cr in sub-stoichiometric TiO2. The implications of these results on the irradiation stability of oxide-dispersed ferritic alloys are discussed.

Individually, alloying and ion irradiation are two avenues for modifying the chemical and phase structure at solid-state interfaces. Both can lead to the phenomena of alloying, intermixing, and, when combined, radiation-induced elemental redistribution. Thus, understanding how each independently influences the structure of interfaces provides insight into the chemical morphologies at the interface, the possible formation of secondary phases, and the basic mechanisms necessary for understanding alloying. Within the analytical framework provided by electron microscopy, we study changes in structure and chemistry in connection with the formation of composite layered interfaces following alloying and ion irradiation at metal-oxide interfaces. In particular, the chemical evolutions of as-deposited Fe/Cr and irradiated Fe thin films on $$\hbox {TiO}_{2}$$ are characterized to reveal structural and chemical changes associated with physical interactions induced by either alloying or irradiation. The results of the study conclude by comparing the effects of alloying with radiation-induced intermixing. We find that the extent of Fe intermixing into the $$\hbox {TiO}_{2}$$ substrate is similar for both irradiated and alloyed films, indicating that both can lead to the formation of similar complex nanoscale morphologies at the interface. Our results highlight the complex and competing phenomena that dictate the structure and chemistry at these interfaces.

Here we report on the material chemistry following crystallization in the presence of water vapor of chlorinated formamidinium lead-triiodide (NH2CH = NH2PbI3−xClx) perovskite films. We found in-situ exposure to water vapor reduces, or possibly eliminates, the retention of chlorine (Cl) inside NH2CH = NH2PbI3−xClx crystals. There is a strong tendency toward Cl volatility, which indicates the sensitivity of these materials for their integration into solar cells. The requisite for additional efforts focused on the mitigation of water vapor is reported. Based on the in situ results, hot casting (

Nickel ferrite (NiFe2O4) is a major constituent of the corrosion deposits formed on the exterior of nuclear fuel cladding tubes during operation. NiFe2O4 has attracted much recent interest, mainly due to the impact of these deposits, known as CRUD, on the operation of commercial nuclear reactors. Although advances have been made in modeling CRUD nucleation and growth under a wide range of conditions, the thermophysical properties of NiFe2O4 at high temperatures have only been approximated, thereby limiting the accuracy of such models. In this study, samples of NiFe2O4 were synthesized to provide the thermal diffusivity, specific heat capacity, and thermal expansion data from room temperature to 1300 K. These results were then used to determine thermal conductivity. Numerical fits are provided to facilitate ongoing modeling efforts. The Curie temperature determined through these measurements was in slight disagreement with literature values. Transmission electron microscopy investigation of multiple NiFe2O4 samples revealed that minor nonstoichiometry was likely responsible for variations in the Curie temperature. However, these small changes in composition did not impact the thermal conductivity of NiFe2O4, and thus are not expected to play a large role in governing reactor performance.

The present disclosure relates to a composition that includes, in order: a first layer that includes MAw; a second layer that includes MOyAz; and a third layer that includes MOx, where M includes a transition metal, A includes at least one of sulfur, selenium, and/or tellurium, w is between greater than zero and less than or equal to five, x is between greater than zero and less than or equal to five, y is between greater than zero and less than or equal to five, and z is between greater than zero and less than or equal to five. In some embodiments of the present disclosure, the transition metal may include at least one of molybdenum and/or tungsten. In some embodiments of the present disclosure, A may be sulfur.

Under irradiation, chemical species can redistribute in ways not expected from equilibrium behavior. In oxide-dispersed ferritic alloys, the phenomenon of irradiation-induced Cr redistribution at the metal/oxide interfaces has drawn recent attention. Here, the thermal and irradiation stability of the FeCr/Y2O3 interface has been systematically studied. Trilayer thin films of 90 nm Fe - 20 at.% Cr (1st layer)/100 nm Y2O3 (2nd layer)/135 nm Fe - 20 at.% Cr (3rd layer) were deposited on MgO substrates at 500 °C. After irradiation, Cr diffuses towards and enriches the FeCr/Y2O3 interface. Further, correlated with Cr redistributed into the oxide, an amorphous layer is generated at the interface. In the Y2O3 layer, the original cubic phase is observed to transform to the monoclinic phase after irradiation. Meanwhile, nanosized voids, with relatively larger size at interfaces, are also observed in the oxide layer. First-principles calculations reveal that Cr substitution of Y interstitials in Y2O3 containing excess Y interstitials is favored and the irradiation-induced monoclinic phase enhances this process. Our findings provide new insights that may aid in the development of irradiation resistant oxide-dispersed ferritic alloys.

Observation of growth, synthesis, dynamics, and electrochemical reactions in the liquid state is an important yet largely unstudied aspect of nanotechnology. The only techniques that can potentially provide the insights necessary to advance our understanding of these mechanisms is simultaneous atomic-scale imaging and quantitative chemical analysis (through spectroscopy) under environmental conditions in the transmission electron microscope. In this study we describe the experimental and technical conditions necessary to obtain electron energy loss (EEL) spectra from a nanoparticle in colloidal suspension using aberration-corrected scanning transmission electron microscopy (STEM) combined with the environmental liquid stage. At a fluid path length below 400 nm, atomic resolution images can be obtained and simultaneous compositional analysis can be achieved. We show that EEL spectroscopy can be used to quantify the total fluid path length around the nanoparticle and demonstrate that characteristic core-loss signals from the suspended nanoparticles can be resolved and analyzed to provide information on the local interfacial chemistry with the surrounding environment. The combined approach using aberration-corrected STEM and EEL spectra with the in situ fluid stage demonstrates a plenary platform for detailed investigations of solution-based catalysis.

We have derived ambient black carbon (BC) concentrations and estimated emission factors for on-road diesel vehicles from archived Coefficient of Haze (COH) data that was routinely collected beginning in 1967 at 11 locations in the San Francisco Bay Area. COH values are a measure of the attenuation of light by particles collected on a white filter, and available data indicate they are proportional to BC concentrations measured using the conventional aethalometer. Monthly averaged BC concentrations are up to five times greater in winter than summer, and, consequently, so is the population?s exposure to BC. The seasonal cycle in BC concentrations is similar for all Bay Area sites, most likely due to area-wide decreased pollutant dispersion during wintertime. A strong weekly cycle is also evident, with weekend concentrations significantly lower than weekday concentrations, consistent with decreased diesel traffic volume on weekends. The weekly cycle suggests that, in the Bay Area, diesel vehicle emissions are the dominant source of BC aerosol. Despite the continuous increase in diesel fuel consumption in California, annual Bay Area average BC concentrations decreased by a factor of ~;;3 from the late 1960s to the early 2000s. Based on estimated annual BC concentrations, on-road diesel fuel consumption, and recent measurements of on-road diesel vehicle BC emissions, diesel BC emission factors decreased by an order of magnitude over the study period. Reductions in the BC emission factor reflect improved engine technology, emission controls and changes in diesel fuel composition. A new BC monitoring network is needed to continue tracking ambient BC trends because the network of COH monitors has recently been retired.

The properties and performance of metal/oxide nanocomposites are governed by the structure and chemistry of the metal/oxide interfaces. Here we report an integrated theoretical and experimental study examining the role of interfacial structure, particularly misfit dislocations, on solute segregation at a metal/oxide interface. We find that the local oxygen environment, which varies significantly between the misfit dislocations and the coherent terraces, dictates the segregation tendency of solutes to the interface. Depending on the nature of the solute and local oxygen content, segregation to misfit dislocations can change from attraction to repulsion, revealing the complex interplay between chemistry and structure at metal/oxide interfaces. These findings indicate that the solute chemistry at misfit dislocations is controlled by the dislocation density and oxygen content. Fundamental thermodynamic concepts – the Hume-Rothery rules and the Ellingham diagram – qualitatively predict the segregation behavior of solutes to such interfaces, providing design rules for novel interfacial chemistries.

Ordered Ni3Al intermetallic precipitates constitute the main hardening sources of Ni-based superalloys. Here, we report the interdiffusion and precipitation behavior in a Ni/Ni3Al model system. The deposition of Ni3Al on a pure Ni layer at 500°C generated L12-structured γ′ (Ni3Al) precipitates, preferentially at the interface. After annealing at 800°C for 1 h, interdiffusion between Ni and Ni3Al layers occurred, and the γ′ precipitates that grew near the parent Ni/Ni3Al interface are ∼2.8 times larger in size than those formed in the matrix. Monte Carlo simulations indicate that vacancies preferentially diffuse along the Ni/Ni3Al interface, increasing the probability of precipitation.

Exploiting the promise of nanocomposite oxides necessitates a detailed understanding of the dislocation structure at the interfaces, which governs diverse and technologically relevant properties. Here we report atomistic simulations demonstrating a strong dependence of the dislocation structure on the termination chemistry at the SrTiO3/MgO heterointerface. The SrO- and TiO2-terminated interfaces exhibit distinct nearest neighbour arrangements between cations and anions, leading to variations in local electrostatic interactions across the interface that ultimately dictate the dislocation structure. Networks of dislocations with different Burgers vectors and dislocation spacing characterize the two interfaces. These networks in turn influence the overall stability of and the behaviour of oxygen vacancies at the heterointerface, which will dictate vital properties such as mass transport at the interface. To date, the observed correlation between the dislocation structure and the termination chemistry at the interface has not been recognized, and offers novel avenues for fine-tuning oxide nanocomposites with enhanced functionalities.

Recent developments within the nuclear materials community have lead researchers to predict nanocrystalline materials can plausibly address concerns regarding nucleation, growth, migration, waste storage, and fission product evolution at higher temperatures and radiation environments. From the work so far in the community, it is not clear how these phases of material impact waste form evolution and behavior. Advanced microscopy allows for unprecedented insights into the underlying physical mechanisms responsible for the improved performance of these materials, especially through the use and study of evolving decaying isotopes. To extend our understanding of nuclear materials after service, in particular waste forms, we have studied the fundamental evolution of these materials induced by the decay of radioisotopes by coupling the use of accelerated aging and analytical microscopy.

We observe interfacial ferromagnetism in superlattices of the paramagnetic metal ${\mathrm{LaNiO}}_{3}$ and the antiferromagnetic insulator ${\mathrm{CaMnO}}_{3}$. ${\mathrm{LaNiO}}_{3}$ exhibits a thickness dependent metal-insulator transition and we find the emergence of ferromagnetism to be coincident with the conducting state of ${\mathrm{LaNiO}}_{3}$. That is, only superlattices in which the ${\mathrm{LaNiO}}_{3}$ layers are metallic exhibit ferromagnetism. Using several magnetic probes, we have determined that the ferromagnetism arises in a single unit cell of ${\mathrm{CaMnO}}_{3}$ at the interface. Together these results suggest that ferromagnetism can be attributed to a double exchange interaction among Mn ions mediated by the adjacent itinerant metal.

Earth‐abundant sustainable inorganic thin‐film solar cells, independent of precious elements, pivot on a marginal material phase space targeting specific compounds. Advanced materials characterization efforts are necessary to expose the roles of microstructure, chemistry, and interfaces. Herein, the earth‐abundant solar cell device, Cu2ZnSnS(4– x )Sex, is reported, which shows a high abundance of secondary phases compared to similarly grown Cu2ZnSnSe4.

Semiconducting CdZnTe or "CZT" crystals are very suitable for use as a room temperature-based gamma radiation spectrometer. During the last decade, modifications in growth methods for CZT have significantly improved the quality of the produced crystals however there are material features that can influence the performance of these materials as radiation detectors. For example, various structural heterogeneities within the CZT crystals, such as, pipes, voids, polycrystallinity, and secondary phases (SP) can have a negative impact on the detector performance. In this study, a CZT material was grown by the modified vertical Bridgman growth (MVB) method with zone leveled growth in the absence of excess Te in the melt. Numerous SP were imaged using transmission IR at a volume % of 0.002. Samples from this material were analyzed using various analytical techniques to evaluate its electrical properties, purity and detector performance as radiation spectrometers and to determine the morphology, dimension and elemental /structural composition of one of the SP in this material. This material was found to have a high resistivity and good radiation spectrometer performance. It had SPs that were rich in calcium (Ca), carbon (C) and oxygen (O) (possibly CaCO3) or only C and O that were 5 μm or less in diameter.

In this paper, we compare constructed records of concentrations of black carbon (BC)--an indicator of anthropogenic aerosols--with observed surface temperature trends in California. Annual average BC concentrations in major air basins in California significantly decreased after about 1990, coincident with an observed statewide surface temperature increase. Seasonal aerosol concentration trends are consistent with observed seasonal temperature trends. These data suggest that the reduction in anthropogenic aerosol concentrations contributed to the observed surface temperature increase. Conversely, high aerosol concentrations may lower surface temperature and partially offset the temperature increase of greenhouse gases.

Extended abstract of a paper presented at Microscopy and Microanalysis 2013 in Indianapolis, Indiana, USA, August 4 – August 8, 2013.

Extended abstract of a paper presented at Microscopy and Microanalysis 2012 in Phoenix, Arizona, USA, July 29 – August 2, 2012.