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A remarkable increase in global ambient temperature is resulting in a high demand for human thermal comfort. The space cooling and heating requirements are increasing worldwide. Currently, conventional vapor compression refrigeration systems are dominating the market share in building air conditioning. These systems are high consumers of electrical energy largely dependent on fossil fuels, thus causing global warming. Therefore, there is a dire need for a sustainable and environmentally friendly solution for air conditioning, like solar-assisted desiccant evaporative cooling systems. Solar desiccant air conditioning systems are considered alternative solutions due to their separate control of latent and sensible loads. However, the climate conditions strongly influence the performance and output behavior of such systems. In this research, a solar desiccant evaporative cooling system is extensively tested through integration of a specially designed climate-controlled chamber to provide different control input conditions. Detailed experimental analysis is presented in terms of system’s coefficient of performance, cooling capacity, moisture removal rate, dehumidification effectiveness, supply outlet air temperature and outlet air humidity. The results show the maximum coefficient of performance and cooling capacity of the system 1.25 and 2.3 kW, respectively, at a regeneration temperature of 80 °C. At a constant inlet temperature of 30 °C, the moisture removal rate increased from 0.80 g/s to 1.41 g/s, corresponding to an increase in inlet humidity from 12 g/kg to 18 g/kg. Moreover, it is found that by increasing the process inlet temperature from 25 °C to 45 °C, considering constant inlet humidity of 14 g/kg, increases the coefficient of performance from 0.54 to 1.29 and the cooling capacity from 1.01 to 2.18 kW. It can be observed that the solar desiccant evaporative cooling system has proven a significant solution to overcome the humidity and cooling loads to ensure human thermal comfort requirements for diverse climatic conditions.

Nanocrystalline (similar to 10 nm) singe-fcc CoCrFeNiGax (x = 0.5, 1.0) high entropy alloy (HEA) particles with excellent structural and compositional homogeneity were prepared from elemental powders using single-step, short-term (190 min) high energy ball milling (HEBM) at room temperature (RT). Both HEA powders exhibit paramagnetic behaviour at RT with a small ferromagnetic contribution at low fields (saturation magnetization M-s= 4.5 - 7.5 Am-2/kg; average Curie temperature T-c = 130 K - 150 K). They are thermally stable up to 1295 K-1305 K despite the low melting temperature of Ga (302.9 K). Heat treatment up to 1000 K enhances M-s to 59.9 Am-2/kg and T-c to 740 K for the CoCrFeNiGa HEA powder due to an irreversible fcc -> bcc structural transformation, whereas the magnetic properties of CoCrFeNiGa0.5 do not show this enhancement. In-situ TEM heating reveals nanosized sigma-phase Cr-rich precipitates (< 50 nm) at 875 K only for the CoCrFeNiGa HEA powder. Spark plasma sintering (SPS) of powders produces homogeneous nanocrystalline bulk HEAs. SPS at 1073 K of the CoCrFeNiGa0.5 powder increased the crystallinity of the fcc phase. Three-dimensional local compositional mapping at atomic resolution by atom probe tomography indicates a homogeneous distribution of all elements. Bulk HEAs exhibit similar magnetic behavior as heat-treated HEA powders. Combining HEBM and SPS yields homogeneous bulk HEAs with low-melting Ga and enhanced structural, composition, and thermal stability, as well as improved magnetic properties (M-s = 55Am(2)/kg and T-c = 750 K), which is 45% and 47 K higher, respectively, compared to conventional melting approaches.

Off-axis Electron Holography and Electron Magnetic Circular Dichroism are powerful Transmission Electron Microscopy (TEM) techniques capable of mapping magnetic information with near-atomic spatial resolution. However, the magnetic signals obtained is semi-quantitative due to factors such as thickness variations and local crystallographic changes. Precise determination of spatial thickness variations can make these techniques more quantitative. Electron Energy Loss Spectroscopy (EELS) provides a method to measure thickness variations within a region of interest. The absolute thickness depends on reliable estimates of the inelastic mean free path (lambda), which is often unknown for many materials. Alternative techniques, such as Scanning Electron Microscopy (SEM) and Convergent Beam Electron Diffraction (CBED), either lack spatial resolution in thickness mapping or are accurate only within a limited thickness range. Here, we present a straightforward approach to precisely determine the inelastic mean free path (lambda), enabling accurate thickness measurements from EELS maps. We compare these thickness measurements with CBED-and SEM-based methods, identifying discrepancies, particularly in thinner samples (< 100 nm). Finally, we demonstrate how this calibrated thickness measurement can provide quantitative magnetic maps using TEM-based magnetic measurements.

Magnetism originates from the spin and orbital angular momenta of electrons and their coupling. These interactions occur at subatomic scales and a comprehensive understanding of such phenomena relies on characterization techniques capable of probing the spin and orbital moments at atomic resolution. Although electron energy loss magnetic chiral dichroism has previously enabled the detection of magnetic moments at atomic scales, it was limited to a chromatic-aberration-corrected transmission electron microscope. Although possible, the detection of atomic-scale electron energy loss magnetic chiral dichroism in a scanning transmission electron microscope remains elusive due to challenges associated with convergent beam setups. Here we demonstrate the detection of atomic-scale electron energy loss magnetic chiral dichroism signals in a probe-corrected scanning transmission electron microscope. We not only determine the orbital-to-spin moments ratio for individual atomic planes of an iron crystal but also reveal its local variations at subatomic scales. These findings open the possibility of resolving magnetism down to the orbital level in future studies.

Electron magnetic circular dichroism (EMCD) is a powerful technique for estimating element-specific magnetic moments of materials on nanoscale with the potential to reach atomic resolution in transmission electron microscopes. However, the fundamentally weak EMCD signal strength complicates quantification of magnetic moments, as this requires very high precision, especially in the denominator of the sum rules. Here, we employ a statistical resampling technique known as bootstrapping to an experimental EMCD dataset to produce an empirical estimate of the noise-dependent error distribution resulting from application of EMCD sum rules to bcc iron in a 3-beam orientation. We observe clear experimental evidence that noisy EMCD signals preferentially bias the estimation of magnetic moments, further supporting this with error distributions produced by Monte-Carlo simulations. Finally, we propose guidelines for the recognition and minimization of this bias in the estimation of magnetic moments.

Cellulose, being a renewable and abundant biopolymer, has garnered significant attention for its unique properties and potential applications in hybrid materials. Understanding the hierarchical arrangement of cellulose nanofibers is crucial for developing cellulose-based materials with enhanced mechanical properties. In this study, the use of Scanning Electron Diffraction (SED) is presented to map the nanoscale orientation of cellulose fibers in a bio-composite material with a preserved wood cell structure. The SED data provides detailed insights into the ordering of cellulose with an extraordinary resolution of ≈15 nm. It enables a quantitative analysis of the fiber orientation over regions as large as entire cells. A highly organized arrangement of cellulose fibers within the secondary cell wall is observed, with a gradient of orientations toward the outer part of the wall. The in-plane fiber rotation is quantified, revealing a uniform orientation close to the middle lamella. Transversely sectioned material exhibits similar trends, suggesting a layered cell wall structure. Based on the SED data, a 3D model depicting the complex helical alignment of fibers throughout the cell wall is constructed. This study demonstrates the unique opportunities SED provides for characterizing the nanoscale hierarchical arrangement of cellulose nanofibers, empowering further research on a range of hybrid materials.

The need to acquire multiple angle-resolved electron energy loss spectra (EELS) is one of the several critical challenges associated with electron magnetic circular dichroism (EMCD) experiments. If the experiments are performed by scanning a nanometer to atomic-sized electron probe on a specific region of a sample, the precision of the local magnetic information extracted from such data highly depends on the accuracy of the spatial registration between multiple scans. For an EMCD experiment in a 3-beam orientation, this means that the same specimen area must be scanned four times while keeping all the experimental conditions same. This is a non-trivial task as there is a high chance of morphological and chemical modification as well as non-systematic local orientation variations of the crystal between the different scans due to beam damage, contamination and spatial drift. In this work, we employ a custom-made quadruple aperture to acquire the four EELS spectra needed for the EMCD analysis in a single electron beam scan, thus removing the above-mentioned complexities. We demonstrate a quantitative EMCD result for a beam convergence angle corresponding to sub-nm probe size and compare the EMCD results for different detector geometries.

When magnetic properties are analysed in a transmission electron microscope using the technique of electron magnetic circular dichroism (EMCD), one of the critical parameters is the sample orientation. Since small orientation changes can have a strong impact on the measurement of the EMCD signal and such measurements need two separate measurements of conjugate EELS spectra, it is experimentally non-trivial to measure the EMCD signal as a function of sample orientation. Here, we have developed a methodology to simultaneously map the quantitative EMCD signals and the local orientation of the crystal. We analyse, both experimentally and by simulations, how the measured magnetic signals evolve with a change in the crystal tilt. Based on this analysis, we establish an accurate relationship between the crystal orientations and the EMCD signals. Our results demonstrate that a small variation in crystal tilt can significantly alter the strength of the EMCD signal. From an optimisation of the crystal orientation, we obtain quantitative EMCD measurements.

The strength of the interlayer exchange coupling in [Fe/MgO]N(001) superlattices with 2 <= N <= 10 depends on the number of bilayer repeats (N). The exchange coupling is antiferromagnetic for all the investigated thicknesses while being nine times larger in a sample with N = 4 as compared to N = 2. The sequence of the magnetic switching in two of the samples (N = 4, N = 8) is determined using polarized neutron reflectometry. The outermost layers are shown to respond at the lowest fields, consistent with having the weakest interlayer exchange coupling. The results are consistent with the existence of quantum well states defined by the thickness of the Fe and the MgO layers as well as the number of repeats (N) in [Fe/MgO]N(001)superlattices.