X-ray Spectroscopy Experiments Research Articles

Compact vacuum transfer devices for highly air-sensitive materials in scanning electron microscopy

Surface analysis experiments on air-sensitive substances are challenging to avoid their contact with air, leading to inaccurate results due to oxidation or hygroscopicity. To address this issue, we designed a compact vacuum transfer device (VTD) and applied it to scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) experiments. Our VTD features a split structure that can be opened and separated in the SEM specimen exchange chamber via magnetic control. This design allows the SEM manufacturer's stub to be fed directly into the SEM specimen chamber, preventing damage to the instrument's internal components and avoiding restrictions on specimen height. Additionally, the compact design maximizes the utilization of sample accommodation space. Besides, it can be flexibly customized in different sizes and types of stubs to adapt electron microscopes from various manufacturers. To confirm the reliability of our device, we applied it to several highly air-sensitive samples for morphology and chemical composition analysis by SEM and EDS. The EDS results showed that the atomic percentage of Na reaches 94.55 % after 14 minutes and 93.44 % after 30 minutes of storage when transferring metallic sodium. Furthermore, our VTD enables airtight recycling and re-transfer of samples after the SEM (-EDS) experiments. These results demonstrate that our device has excellent practicality and airtightness, making it suitable for medium- and long-distance sample transfer between laboratories on the campus.

Osseointegration Potential Assessment of Bone Graft Materials Loaded with Mesenchymal Stem Cells in Peri-Implant Bone Defects.

Many studies have been exploring the use of bone graft materials (BGMs) and mesenchymal stem cells in bone defect reconstruction. However, the regeneration potential of Algipore (highly purified hydroxyapatite) and Biphasic (hydroxyapatite/beta-tricalcium phosphate) BGMs combined with bone marrow-derived mesenchymal stem cells (BMSCs) remains unclear. Therefore, we evaluated their osseointegration capacities in reconstructing peri-implant bone defects. The cellular characteristics of BMSCs and the material properties of Algipore and Biphasic were assessed in vitro. Four experimental groups-Algipore, Biphasic, Algipore+BMSCs, and Biphasic+BMSCs-were designed in a rabbit tibia peri-implant defect model. Implant stability parameters were measured. After 4 and 8 weeks of healing, all samples were evaluated using micro-CT, histological, and histomorphometric analysis. In the energy-dispersive X-ray spectroscopy experiment, the Ca/P ratio was higher for Algipore (1.67) than for Biphasic (1.44). The ISQ values continuously increased, and the PTV values gradually decreased for all groups during the healing period. Both Algipore and Biphasic BGM promoted new bone regeneration. Higher implant stability and bone volume density were observed when Algipore and Biphasic BGMs were combined with BMSCs. Biphasic BGM exhibited a faster degradation rate than Algipore BGM. Notably, after eight weeks of healing, Algipore with BSMCs showed more bone-implant contact than Biphasic alone (p < 0.05). Both Algipore and Biphasic are efficient in reconstructing peri-implant bone defects. In addition, Algipore BGM incorporation with BSMCs displayed the best performance in enhancing implant stability and osseointegration potential.

Unravelling the complex speciation of halozincate ionic liquids using X-ray spectroscopies and calculations.

Using a combination of liquid-phase X-ray spectroscopy experiments and small-scale calculations we have gained new insights into the speciation of halozincate anions in ionic liquids (ILs). Both core and valence X-ray photoelectron spectroscopy (XPS) experiments were performed directly on the liquid-phase ILs, supplemented by Zn 1s X-ray absorption near edge structure (XANES) spectroscopy. Density functional theory (DFT) calculations were carried out on both 1- and 2- halozincate anions, in both a generalised solvation model SMD (Solvation Model based on Density) and the gas phase, to give XP spectra and total energy differences; time-dependent DFT was used to calculate XANES spectra. Speciation judgements were made using a combination of the shape and width of the experimental spectra, and visual matches to the calculated spectra. For 2- halozincate anions, excellent matches were found between the experimental and calculated XP spectra, clearly showing that only 2- halozincate anions were present at all zinc halide mole fractions, x, studied. At specific values of x (0.33, 0.50, 0.60) only one halozincate anion was present; equilibria of different halozincate anions at those values of x were not observed. All findings show that chlorozincate anion and bromozincate anion speciation matched at the same x. Based on the results, predictions are made of the halozincate anion speciation for all values of x up to 0.67. Caution is advised when using differences in calculated total energies obtained from DFT to judge halozincate anion speciation, even when the SMD was employed, as predictions based on total energy differences did not always match the findings from the experimental and calculated spectra. Our findings clearly establish that the combination of high-quality experimental data from multiple spectroscopies and a wide range of calculated structures are essential to have high confidence in halozincate anion speciation identification.

Materials Mitigation Strategies and Anode Catalyst Durability in Low Temperature Electrolysis

Hydrogen has unique advantages as an energy carrier, with a high energy density and capacity to facilitate both long term storage and conversion between electricity and chemical bonds. Although hydrogen currently has a significant role in transportation and agriculture, its use in the general energy landscape has been limited. With decreasing electricity prices, electrolysis cost reductions can be achieved and will enable an opportunity for greater use.[1] While load-following renewable power sources can reduce feedstock costs, further cost reductions can be achieved by reducing the platinum group metal (PGM) content.[2]Efforts are needed and underway to understand electrolyzer degradation and develop accelerated stress tests when accounting for lower PGM loadings and intermittent operation. In this presentation, studies related to different catalysts and catalyst layer properties, and their impact on electrolyzer performance and durability will be discussed. Catalysts with high metal content and less stable elements were generally found to be more susceptible to mobility and migration.[3] Materials have been evaluated, however, that can address catalyst degradation. These include catalyst development strategies such as crystallinity, structured morphologies, and supports, and electrode design strategies such as coating techniques and pore formers. In some cases this has led to increased site utilization and the spread of operational stressors through a larger portion of the catalyst layer, lessening performance losses over time. Testing of these materials has included more continuous operation and with applied accelerated stress tests, and it was found that certain materials may address load fluctuations in different ways. Perspectives on anode catalyst development will be discussed as they relate to the current status of materials mitigation strategies and anode catalyst layer degradation.[1] B. Pivovar, N. Rustagi and S. Satyapal, The Electrochemical Society Interface, 27, 47 (2018).[2] K. Ayers, N. Danilovic, R. Ouimet, M. Carmo, B. Pivovar and M. Bornstein, Annual Review of Chemical and Biomolecular Engineering, 10, 219 (2019).[3] Pivovar, B. S.; Boardman, R., H2NEW: Hydrogen (H2) from Next-generation Electrolyzers of Water. 2022.Acknowledgements: This research is supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Hydrogen and Fuel Cell Technologies Office under the auspices of the H2NEW consortium. Electron microscopy was performed at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility at Oak Ridge National Laboratory. The X-ray spectroscopy experiments were performed at beamline 10-ID at the APS, which is operated by the Materials Research Collaborative Access Team (MRCAT). MRCAT operations are supported by the Department of Energy and the MRCAT member institutions. The APS is a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.

Frequency and spatially chirped free-electron laser pulses

We have produced hard x-ray free-electron laser (FEL) pulses, which are chirped both in photon energy and in spatial position. The experiments have been carried out at the hard x-ray beamline Aramis at SwissFEL, located at the Paul Scherrer Institute in Switzerland. The FEL beamline was operated without any external focusing and with a tilted, energy-chirped electron bunch, whose properties are then transferred to the photon beam. The resulting FEL pulses were used for a single-shot absorption x-ray spectroscopy experiment at the Alvra endstation. But, as will be outlined, applications of this type of tailored FEL pulse go beyond such experiments, allowing for x-ray pulse compression and control of the transverse coherence within the pulse.Received 13 May 2022Accepted 22 February 2023DOI:https://doi.org/10.1103/PhysRevResearch.5.L022009Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Physical SystemsFree-electron lasersAccelerators & Beams

Structural Evolution in an Annealed (Eu, Tb)-Doped ZnO/Si Nanoscale Junction: Implication for Red LED Development

Codoped (Tb,Eu) ZnO films grown by magnetron sputtering on a silicon substrate and annealed up to 1200 °C showed intense photoluminescence (PL) emission from Eu3+ ions. The high-temperature annealing led to diffusion and segregation of rare earth (RE) elements toward the bottom of the film, which induced the formation of nanometric Zn-free inclusions responsible for remarkable PL emission intensity. Combined electron diffraction, chemical contrast imaging, and optical studies of these nanometric phases have been carried out. Large inclusions of zinc silicates and RE silicates a few hundreds of nanometers in size were observed, embedded in a silica phase. The structural determination of these RE-rich inclusions was carried out by combining atomic Z contrast imaging (high-angle annular dark-field imaging) and precession electron diffraction data. Upon annealing at 1200 °C, it appeared that the structure was related to an F-type disilicate structure. Energy-dispersive X-ray spectroscopy and electron energy loss spectroscopy experiments were carried out to determine the ratios between elements and the oxidation states of the RE elements in the abovementioned inclusions. A (Tb,Eu)2Si2O7 formulation is proposed from dynamical precession electron diffraction tomography refinements, leading to a +III valence state for the RE species in agreement with spectroscopic results. PL modeling is also in good agreement with the experimental data. These results complete those obtained at 1100 °C for which the inclusions were identified as some RE10–x(SiO4)6O2–x oxyapatite structures and pointed out a combined structural and PL properties’ evolution between 1100 and 1200 °C annealing temperatures.

Ξ − atomic X-ray spectroscopy using a counter-emulsion hybrid method

Abstract Ξ− atomic X-ray spectroscopy is one of the most useful methods for investigation of the Ξ–nucleus strong interaction. Since the X-ray energy is shifted and/or broadened due to the Ξ–nucleus strong interaction compared to those calculated from electromagnetic interaction alone, the measurement of the energy shift, ΔE, and the width, Γ, give us information on the Ξ–nucleus potential. A serious problem in the measurement is the significant background derived from in-flight Ξ− decay. A novel method of identifying stopped Ξ− events using the nuclear emulsion was developed to realize the first Ξ− atomic X-ray spectroscopy experiment as the J-PARC E07 experiment, which also aimed at searching for ΛΛ and Ξ− hypernuclei in the emulsion. The X-rays emitted from Ξ− Br and Ξ− Ag atoms were measured using germanium detectors. No clear peaks were observed in the obtained spectra. However, we succeeded in reducing the background to 1/170 by this method employing coincidence measurements using nuclear emulsion and X-ray detectors.

Biosorption of zinc (II) from synthetic wastewater by using Inula Viscosa leaves as a low-cost biosorbent: Experimental and molecular modeling studies

The use of biosorption as a strategy for lowering the amount of pollution caused by heavy metals is particularly encouraging. In this investigation, a low-cost and efficient biosorbent, Inula Viscosa leaves were used to remove zinc ions (Zn2+) from synthetic wastewater. A Fourier transform infrared spectroscopy experiment, a scanning electron microscopy experiment, and an energy dispersive X-ray spectroscopy experiment were used to describe the support. Several different physicochemical factors, such as the beginning pH value, contact duration, initial zinc concentration, biosorbent dose, and temperature, were investigated in this study. When the Langmuir, Freundlich, Temkin, Toth, and Redlich-Peterson models were used to match the data from the Inula Viscosa leaves biosorption isotherms, it was found that the biosorption isotherms correspond most closely with the Langmuir isotherm. On the other hand, the kinetic biosorption process was investigated using pseudo-first-order, pseudo-second-order (PS2), and Elovich models. The PS2 model was the one that provided the most accurate description of the biosorption kinetics. The thermodynamics process shows the spontaneous and endothermic character of Zn2+ sorption on Inula Viscosa leaves, which also entails the participation of physical interactions. In addition, the atom-in-molecule analysis, density functional theory, and the conductor like screening model for real solvents, were used to investigate the relationship that exists between quantum calculations and experimental outcomes.

Comparison of One-Part and Two-Part Alkali-Activated Metakaolin and Blast Furnace Slag

One-part alkali-activated materials prepared with solid-form alkali activator are gaining attention in the construction industry, as they are an easier and safer approach for cast-in-situ applications in comparison with two-part approach (i.e., involving the use of alkali-activator solutions). The present study compares the one-part and conventional two-part mixing methods with two aluminosilicate precursors, metakaolin and ground granulated blast-furnace slag, using identical mix designs (in terms of molar ratios of SiO2, Al2O3, and Na2O) with both preparation methods. The results revealed that using one-part mix delays the setting time, increases the heat of reaction, decreases the shrinkage, and reaches between 80 and 85% of the compressive strength of the two-part mix. In addition, scanning electron microscopy, thermogravimetric analysis, and X-ray diffraction analysis showed no major differences between one- and two-part. However, energy-dispersive X-ray spectroscopy and magic angle spinning nuclear magnetic resonance experiments indicated that the extent of reaction in two-part alkali-activated mixes is higher than for one-part.Graphical

Designing Hybrid Mesoporous Pr/Tannate-Inbuilt ZIF8-Decorated MoS2 as Novel Nanoreservoirs toward Smart pH-Triggered Anti-corrosion/Robust Thermomechanical Epoxy Nanocoatings.

For the first time, organic tannic acid (TA) molecules and then inorganic praseodymium (Pr) cations as corrosion inhibitors were successfully loaded into a zeolitic imidazolate framework (ZIF8)-type porous coordination polymer (PCP) decorated on molybdenum disulfide, MoS2, (MS)-based transition metal dichalcogenides (TMDs) to create novel hybrid mesoporous Pr/TA-ZIF8@MS nanoreservoirs. Thereafter, the hybrid nanoreservoirs were embedded into the epoxy matrix for the preparation of smart pH-triggered nanocoatings. Characterizations of the Pr/TA-ZIF8@MS nanoreservoirs via Fourier transform infrared (FT-IR), X-ray diffraction (XRD), thermogravimetric (TG), Brunauer-Emmett-Teller (BET), and field emission-scanning electron microscopy (FE-SEM)/energy-dispersive X-ray spectroscopy (EDS) experiments confirmed the fabrication of mesoporous structures comprising Pr/TA interfacial interactions with ZIF8-decorated MS nanoplatelets possessing high thermal stability and compact/dense configuration features with a framework reorientation. A remarkable smart release of the inhibited cations (Pr3+ and Zn2+) in the presence of inbuilt TA at both acidic and alkaline media was achieved under inductively coupled plasma (ICP) examination. The superior pH-triggered self-healing inhibition through the smart controlled-release of Pr, tannate, Zn, and imidazole inhibited species/complexes from EP/Pr-TA-ZIF8@MS via ligand exchange was obtained from electrochemical impedance spectroscopy (EIS) assessments of the scratched coatings during 72 h of saline immersion. In addition, the long-term barrier-induced corrosion prevention (log |Z|10mHz = 10.49 Ω·cm2 after 63 days) of the EP/Pr-TA-ZIF8@MS was actualized. Moreover, efficient increments of the coating cross-link density (56.45%), tensile strength (63.6%), and toughness value (56.5%) compared to the Neat epoxy coating revealed noticeable thermomechanical properties of the EP/Pr-TA-ZIF8@MS.

Principal Component Analysis as a Tool for Electrochemical Characterization of Modified Electrodes: A Case Study

Characterizing electrodes surface is a mandatory step in developing any electrochemical methodology, especially when electrode modification is performed. One or two electrochemical techniques are often used, and their results are evaluated separately, leading to the loss of valuable information. Principal Component Analysis (PCA) is presented as an appealing strategy to optimize the electrochemical characterization of the modified-electrode’s surface. The developed strategy was applied for the characterization of glassy carbon (GC) electrode modified with reduced graphene oxide (GC/RGO), RGO with gold nanoparticles (GC/RGO/AuNP), and RGO with copper nanoparticles (GC/RGO/CuNP). The electrochemical characterization techniques used were differential pulse voltammetry (DPV), linear scan voltammetry (LSV), and electrochemical impedance spectroscopy (EIS). The PCA showed the data from the four electrodes separately, and it was possible to determine that the GC/RGO/AuNP electrode had the most efficient surface for charge transfer. By scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) experiments, the metal:RGO ratio was determined, and by normalizing the results with this ratio, GC/RGO/CuNP and GC/RGO/AuNP presented similar responses. With the proposed methodology, it was possible to evaluate simultaneously and straightforwardly all data, making this propose an innovative method for a robust electrochemical characterization based on usual electrochemical techniques.

Effect of the Ti-6Al-4V powder size on the microstructure and mechanical properties of composites with nickel-coated graphene nanoflakes

In this study, 0.5 wt% Ni-P@GNF/ Ti-6Al-4V composites with different particle sizes (0–25, 15–53 and 53–150 μm) were fabricated via chemical nickel plating and speak plasma sintering. The plasma sintering temperature and the sintering pressure were 900 °C and 50 MPa, respectively. The microstructure and mechanical properties of the three composites were investigated via optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy and compression experiments. The results showed that the microstructures of the composites were refined, and the compressive strength of the Ti-6Al-4V incorporated with graphene nanosheets was higher than that of the pure Ti-6Al-4V. Herein, with 0–25 μm Ti-6Al-4V powder, the compressive strength of 0.5 wt% Ni-P@GNFs/TC4 composite reaches 1339 MPa, which was an increase of 37.91% versus Ti-6Al-4V alloy (970 MPa). Moreover, with increasing spherical powder particle size, the size of the reinforcing phase of the network structure was coarser, and the plasticity was improved. • Ni addition could decrease the interfacial reaction of composites. • The particle size was beneficial for grain refinement of composites. • The homogeneous dispersion of GNFs lead to load strengthening and network structure

Results of the 𝚵− atomic X-ray measurement in J-PARC E07

Ξ− atomic X-ray spectroscopy is one of the most useful methods for investigation of the Ξ-nucleus strong interaction. A serious problem in the measurement is the significant background coming from in-flight Ξ− decay. For the first Ξ− atomic X-ray spectroscopy experiment, a novel method of identifying stopped Ξ− events using nuclear emulsion was developed to reject background photons from in-flight Ξ− decay. We succeeded in reducing the background to 1/170 by this method employing coincidence measurements using the nuclear emulsion and X-ray detectors.

Soft X-Ray Spectroscopy of Low-Valence Nickelates

Low-valence nickelates—including infinite-layer (IL) and trilayer (TL) compounds—are longstanding candidates for mimicking the high-temperature superconductivity of cuprates. A recent breakthrough in the field came with the discovery of superconductivity in hole-doped IL nickelates. Yet, the degree of similarity between low-valence nickelates and cuprates is the subject of a profound debate for which soft x-ray spectroscopy experiments at the Ni L- and O K-edge provided critical input. In this review, we will discuss the essential elements of the electronic structure of low-valance nickelates revealed by x-ray absorption spectroscopy (XAS) and resonant inelastic x-ray scattering (RIXS). Furthermore, we will review magnetic excitations observed in the RIXS spectra of IL and TL nickelates, which exhibit characteristics that are partly reminiscent of those of cuprates.

How electron beam melting tailors the Al-sensitive microstructure and mechanical response of a novel process-adapted [formula omitted]-TiAl based alloy

Additive manufacturing of lightweight intermetallic γ-TiAl based alloys combines process-related freedom of design with material-specific excellent high-temperature properties. Nevertheless, where locally melting the powder by an electron beam, there is a risk that Al evaporates due to its high vapor pressure, causing compositional and microstructural variations. This work investigates the impact of different process parameters on the total and local Al-content as well as the resulting as-built and heat-treated microstructure in a complex multiphase Ti-44.8Al-4.1Nb-0.7W-1.1Zr-0.4Si-0.5C-0.1B (at.%) alloy. The examinations applied are complementary, employing electron microscopy, X-ray spectroscopy and diffraction experiments with synchrotron X-ray radiation, supported by numerical simulations. The mechanical anisotropy of the heat-treated microstructure was analyzed by micro-hardness measurements. The results demonstrate that the amount of γ-TiAl phase decreases with increasing energy input of the electron beam in the as-built and heat-treated microstructure owing to the total and local loss of Al. Besides, the investigations of the crystal orientations within the multiphase alloy reveal a preferred orientation of the γ phase at high energy inputs. This follows from the fact that the preferred γ orientation is inherited through directional solidification of the β phase. The obtained process-microstructure-property relationships show that tailor-made material properties of additively manufactured γ-TiAl components are achievable.

Control and Impact of Metal Loading Heterogeneities at the Nanoscale on the Performance of Pt/Zeolite Y Catalysts for Alkane Hydroconversion.

The preparation of zeolite-based bifunctional catalysts with low noble metal loadings while maintaining optimal performance has been studied. We have deposited 0.03 to 1.0 wt % Pt on zeolite H-USY (Si/Al ∼ 30 at./at.) using either platinum(II) tetraammine nitrate (PTA, Pt(NH3)4(NO3)2) or hexachloroplatinic(IV) acid (CPA, H2PtCl6·6H2O) and studied the nanoscale Pt loading heterogeneities and global hydroconversion performance of the resulting Pt/Y catalysts. Pt/Y samples prepared with PTA and a global Pt loading as low as 0.3 wt % Pt (nPt/nA = 0.08 mol/mol, where nPt is the number of Pt surface sites and nA is the number of acid sites) maintained catalytic performance during n-heptane (T = 210–350 °C, P = 10 bar) as well as n-hexadecane (T = 170–280 °C, P = 5 bar) hydroisomerization similar to a 1.0 wt % Pt sample. For Pt/Y catalysts prepared with CPA, a loading of 0.3 wt % Pt (nPt/nA = 0.08 mol/mol) sufficed for n-heptane hydroisomerization, whereas a detrimental effect on n-hexadecane hydroisomerization was observed, in particular undesired secondary cracking occurred to a significant extent. The differences between PTA and CPA are explained by differences in Pt loading per zeolite Y crystal (size ∼ 500 nm), shown from extensive transmission electron microscopy energy-dispersive X-ray spectroscopy experiments, whereby crystal-based nPt/nA ratios could be determined. From earlier studies, it is known that the Al content per crystal of USY varied tremendously and that PTA preferentially is deposited on crystals with higher Al content due to ion-exchange with zeolite protons. Here, we show that this preferential deposition of PTA on Al-rich crystals led to a more constant value of nPt/nA ratio from one zeolite crystal to another, which was beneficial for catalytic performance. Use of CPA led to a large variation of Pt loading independent of Al content, giving rise to larger variations of nPt/nA ratio from crystal to crystal that negatively affected the catalytic performance. This study thus shows the impact of local metal loading variations at the zeolite crystal scale (nanoscale) caused by different interactions of metal precursors with the zeolite, which are essential to design and synthesize optimal catalysts, in particular at low noble metal loadings.

Site-Specific Electronic Properties of [Ag25 (SR)18 ]- Nanoclusters by X-Ray Spectroscopy.

Silver nanoclusters (NCs) are of significant interest owing to their interesting structural, electronic, and catalytic properties. Among these NCs, Ag25 (SR)18 is particularly attractive due to its identical geometry as its Au counterpart, Au25 (SR)18 . Herein, the site-specific electronic properties of Ag25 (SR)18 and Au25 (SR)18 using X-ray spectroscopy experiments and quantum simulations are presented. To overcome the final state effect observed in X-ray photoelectron spectroscopy (XPS), a unique method is developed to reliably analyze the charge transfer behavior of the NCs. Density functional theory calculations are combined with XPS to provide more insight into the electronic properties of the NCs. The differences in the XPS valence bands of these two NCs are further compared and interpreted using the relativistic effect. The first derivative of the X-ray absorption near-edge structure (XANES) spectrum is further used as a tool to sensitively probe the bonding properties of Ag25 (SR)18 . By combining the experimental XANES data and their site-specific quantum simulations, the large impact of the staple motif on the bonding properties of the NC is demonstrated. These findings highlight the unique electronic properties of each atomic site in Ag25 (SR)18 ; the effective X-ray analysis techniques developed here can offer new opportunities for the site-specific study of other NCs.

Electronic structure and optical constants of CsPbCl3: The effect of approaches within ab initio calculations in relation to X-ray spectroscopy experiments

We report on experimental and theoretical studies of the electronic structure and optical properties of cesium lead chloride, CsPbCl3. We employ X-ray photoelectron spectroscopy (XPS) to determine binding energies of core-level electrons of as-grown surface of CsPbCl3 crystal and to measure the energy distribution of electronic states in the valence band region. To achieve the best agreement between the shape and energy positions of peculiarities of the XPS valence-band spectrum and the curve of total density of states, we used various approaches treating exchange-correlation potential. In particular, we have realized that the fair agreement is derived when performing calculations within a density functional theory framework using modified Becke-Johnson potential and treating the Hubbard parameter U and spin-orbit coupling. Using possibilities of this technique, we study in detail curves of partial density of states, energy band dispersion, and principal optical constants of CsPbCl3.

Characterisation of Ge micro-strip sensors with a micro-focused X-ray beam

Germanium micro-strip sensors were selected as the sensor technology to take data in energy dispersive X-ray spectroscopy experiments at the Extremely Brilliant Source (EBS) in Grenoble (FR). It is important for this experimental technique to use sensors with a large uniform area and a fine pitch. The former determines the range of energy detectable with a single sensor. The latter improves spectral resolution. A high stopping power is also important to perform studies with hard X-rays.The device under test in this measurement was a germanium micro-strip sensor made of 1024 strips with 50μm pitch. The bulk was 1.5 mm thick. The sensor was assembled into a prototype cryostat part of the XH detector system. The device was tested at the B16 beamline at the Diamond Light Source (DLS) in Didcot (UK). The objective of the test-beam was to characterise charge-sharing between strips. In fact, this effect limits the spectral resolution of the device.To carry out this test, the sensor was scanned over a subset of strips with micro-focused X-rays under different settings. These were beam energy and intensity, sensor temperature and bias voltage. Results are presented in this paper. It was measured that the full width half maximum of the charge-sharing profile across different strips was ∼90μm for settings which were indicative of the experimental conditions at the EBS. This was a signal current per unit area on the sensor of ∼1.66×10−8 A/μm2, a bias voltage of −180 V and a temperature of −159 oC.

A feasible approach efficiently redisperse dried cellulose nanofibrils in water: vacuum or freeze drying in the presence of sodium chloride

Cellulose Nanofibrils (CNFs) were exposed to a certain amount of sodium chloride (NaCl) before being subjected to two types of drying methods (freeze drying and vacuum drying). The effect of two drying methods on water redispersibility of CNFs was investigated by characterizing product morphology, particle size distribution, water stability, and surface chemistry. The results showed that vacuum drying was favorable for the redispersion of CNFs with NaCl resulted in more homogenous fibril structure with lower mean particle sizes and higher water stability. Fourier transform-infrared spectroscopy (FT-IR) and Energy-dispersive X-ray Spectroscopy (EDX) experiments indicated that vacuum drying at pH 8 was more conducive to complexation between Na+ and carboxyl, hydroxyl groups favorable for CNF redispersion. Furthermore, NaCl is cheap, and the process is very straightforward which does not require any organic solvents or hazardous chemicals. Therefore, vacuum drying with NaCl may be considered as a green and economically feasible method for preparation of water redispersible dried CNFs.