HRTEM of 1DSnTe@SWNT nanocomposite located on thin layers of graphite

The method for imaging of highly sensitive nanostructures unstable under electron beam irradiation is introduced. To reduce charge and thermally generated beam damage, highly conductive multilayered graphene or thin graphite layers were used as supports for nanostructures. Well‐defined crystalline structure of graphite layers enables image reconstruction by Fourier filtering and allows maintaining high quality of images. The approach was tested for imaging of highly sensitive quasi one‐dimensional SnTe nanocrystals hosted inside single‐walled carbon nanotubes. Relying on the filtered images and the image simulation, the structure of one‐dimensional SnTe was established as a chain of fcc NaCl type unit cells, connected by the [001] edges with <110> direction coinciding with nanotube axis.     

The structure of 1D CuI crystals inside SWNTs

Nanocomposites consisting of one‐dimensional CuI crystals inside single‐walled carbon nanotubes were obtained using the capillary technique. high‐resolution transmission electron microscopy investigations of the atomic structure of the encapsulated 1D CuI crystals revealed two types of 1D CuI crystals with growth direction <001> and relative to the bulk hexagonal CuI structure. Atomic structure models were proposed based on the high‐resolution transmission electron microscopy images. According to the proposed models and image simulations, the main contrast in the 1D crystal images arises from the iodine atoms whereas copper atoms, with lower atomic number giving lower contrast, are thought to be statistically distributed.     

EXERGY ANALYSIS OF AMMONIA-BASED SOLAR THERMOCHEMICAL POWER SYSTEMS

The reversible dissociation of ammonia is one of the candidate reactions for use in closed loop solar thermochemical energy storage systems. The major determinant of achievable performance for such a system is the degree of thermodynamic irreversibility associated with the heat recovery process. Exergy analysis of a semi realistic 30 MPa isobaric system has revealed that the major irreversibilities occur within the exothermic reactor and the counterflow heat exchanger between ingoing and outgoing reactants. In this study, optimum reactor control yielded exergetic efficiencies up to 71%, which should translate to overall solar to electric conversion efficiencies of around 20%.     

THAI experimental research on hydrogen risk and source term related safety systems

In the defense-in-depth concept employed for the safety of nuclear installations, maintaining integrity of containment as the last barrier is of high importance to limit the release of radioactivity to the environment in case of a severe accident. The active and passive safety systems implemented in containments of light water reactors (LWRs) are designed to limit the consequences of such accidents. Assessing the performance and reliability of such systems under accident conditions is critical to the safety of nuclear installations. In the aftermath of the Fukushima accident, there has been focus on re-examining the existing safety systems to demonstrate their capabilities for a broader range of boundary conditions comprising both the early as well as the late phases of an accident. In addition to the performance testing of safety systems, their interaction with containment atmosphere needs detailed investigations to evaluate the effects of operation of safety systems on H₂ risk and fission product (FP) behavior in containment, which may ultimately have an impact on the source term to the environment.In this context, an extensive containment safety related experimental research has been conducted in a thermal-hydraulics, hydrogen, aerosols, and iodine test facility (THAI, 60 m³, single vessel)/(THAI⁺, 80 m³, two interconnected vessels). Related to the subject of this paper, experimental investigations covered performance testing of various safety and mitigation systems, i.e., containment spray, passive autocatalytic recombiner (PAR), pressure suppression pool (water pools), and effects of their operation on H₂ risk and in-containment FP behavior. The experimental results have provided a better phenomenological understanding and database for validation and further improvement of a safety analysis tool based on computation fluid dynamic (CFD) and lumped parameter (LP) modeling approach. This paper summarizes the main insights obtained from the aforesaid THAI experimental research covering safety systems installed in containments of LWRs. The relevance of experimental outcomes for reactor safety purpose is also discussed.     

Extraction and parametrization of grain boundary networks in glacier ice,using a dedicated method of automatic image analysis

Microstructure analysis of polar ice cores is vital to understand the processes controlling the flow of polar ice on the microscale. This paper presents an automatic image processing framework for extraction and parametrization of grain boundary networks from images of the NEEM deep ice core. As cross‐section images are acquired using controlled surface sublimation, grain boundaries and air inclusions appear dark, whereas the inside of grains appears grey. The initial segmentation step of the software is to separate possible boundaries of grains and air inclusions from background. A Machine learning approach is utilized to gain automatic, reliable classification, which is required for processing large data sets along deep ice cores. The second step is to compose the perimeter of section profiles of grains by planar sections of the grain surface between triple points. Ultimately, grain areas, grain boundaries and triple junctions of the later are diversely parametrized. High resolution is achieved, so that small grain sizes and local curvatures of grain boundaries can systematically be investigated.     

Element specific imaging with high lateral resolution: an experimental study on layer structures

Planar defects and individual layers in ceramic material are chemically imaged by high resolution energy-filtering TEM using a post-column imaging electron energy filter. Objects are barium layers in the cuprate superconductor NdBa₂Cu₃O_7−δ (isostructual to YBa₂Cu₃O_7−δ) as well as planar defects and precipitates of β-WB in tungsten- and chromium-doped TiB₂. The barium layers with a spacing of 0.42 nm in the cuprate are resolved in jump-ratio images using the Ba_N edge. In the boride system the β-WB precipitates with thickness of 0.8 nm can be chemically imaged in elemental maps of B_K, Ti_L ,Cr_L and W_M. The B as well as the Ti map show a decrease in intensity at the precipitates, whereas in the W map an increase in intensity is observed. The boron-deficient layers with a spacing of 0.38 nm in the β-WB precipitate can be resolved in boron jump-ratio images. Additionally, defects containing single boron-deficient layers are chemically imaged. Hence structures in the dimension of interatomic distances can be imaged with respect to their elemental constituents. Although high resolution electron spectroscopic images contain strong interference contrast from elastic scattering, after normalization or background subtraction the element specific images are dominated by chemical contrast.