Environmental Scanning Electron Microscopy Research Articles

Removal of Aflatoxin B1 Using Alfalfa Leaves as an Adsorbent Material: A Comparison between Two In Vitro Experimental Models.

An adsorbent material derived from alfalfa leaves was prepared and further characterized, and its efficacy for removing aflatoxin B1 (AFB1) was investigated. Characterization consisted of the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), environmental scanning electron microscopy (ESEM), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), point of zero charge (pHpzc), zeta potential (ζ-potential), UV-Vis diffuse reflectance spectroscopy, and spectral analysis. To determine the adsorption capacity against AFB1 (250 ng AFB1/mL), pH-dependent and avian intestinal in vitro models were used. The adsorbent inclusion percentage was 0.5% (w/w). In general, the pH-dependent model gave adsorption percentages of 98.2%, 99.9%, and 98.2%, evaluated at pH values of 2, 5, and 7, respectively. However, when the avian intestinal model was used, it was observed that the adsorption percentage of AFB1 significantly decreased (88.8%). Based on the characterization results, it is proposed that electrostatic, non-electrostatic, and the formation of chlorophyll-AFB1 complexes were the main mechanisms for AFB1 adsorption. From these results, it can be concluded that the adsorbent derived from alfalfa leaves could be used as an effective material for removing AFB1 in in vitro digestion models that mimic the physiological reality.

Investigation on the working performance of a non-dispersible grouting material for the crack repairment of underwater structures

Underwater structure repair is highly susceptible to various factors, including the pressure of the underwater environment and dynamic water flow. Traditional materials used for repairs are prone to dilution and dispersion, resulting in a subpar repair outcome. To address the limitations of traditional grouting materials, specifically their poor retention rate and vulnerability to erosion caused by dynamic water, an underwater non-dispersible crack repair grouting material was developed. It is composed of liquid epoxy resin, curing agent, and aggregate (ECA). Comprehensive and systematic testing was conducted to evaluate the performance of ECA grout. The results show that optimized ECA grouting material has advantages such as a high retention rate under dynamic water erosion, strong adhesion, high fluidity, high early strength, and suitable setting time. The ECA grout demonstrates excellent underwater working performance. In addition, the microstructure was analyzed using X-ray diffractometry (XRD), Fourier-transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM). The results show that the addition of aggregates to the epoxy resin does not cause any chemical reaction. Furthermore, the aggregates are bonded together by epoxy resin. Due to the formation of cross-linked microstructures, the microstructure becomes more compact. The addition of aggregates during the curing process has good compatibility and stability, which enhance the performance of the ECA grout. The material has been successfully applied in a restoration project of underwater cultural relics protection facilities, effectively addressing and repairing the existing defects. Its potential value as a reference for similar projects is substantial.

Oleic-acid functionalized mesoporous silica nanoparticles with a hydroxyapatite core enhanced growth of the hydrocarbon degrader Dietzia maris at oil–water interfaces

Rapid biodegradation of poorly water-soluble hydrocarbons as nonaqueous (oil) phases in contaminated aquatic environments is enabled by attachment of hydrocarbon-degrading bacteria to the oil–water interface. Herein, we report the synthesis of nanoparticles comprising a hydroxyapatite (Ca5(PO4)3(OH)) core encapsulated in a mesoporous silica shell and surface-modified with oleic acid (OA–nHAP@MSN) for targeted binding at the oil–water interface and to supply P to bacteria at the interface. P is an essential and often limiting nutrient for bacteria in hydrocarbon-contaminated environments. In microcosm experiments, where the hydrocarbon-degrading bacteria, Dietzia maris strain NWWC4, and OA–nHAP@MSN were inoculated in mineral media in contact with pure liquid hexadecane (sole C source), there was 419.6–fold growth at the hexadecane-water interface, compared to 31.2-fold in identical, but NP-free microcosms. The continuous release of P from the hydroxyapatite core in OA–nHAP@MSN to water was demonstrated in separate experiments in well mixed batch systems and was found to be pH-sensitive. Environmental Scanning Electron Microscopy showed significantly larger cell aggregates and dense biofilms in the OA–nHAP@MSN–amended systems, compared to NP-free systems. Our results demonstrate a strategy for enhancing oil–spill bioremediation using NPs targeting nutrient supply to hydrocarbon-degrading bacteria at oil-water interfaces.

Multi-supramolecular and double-network strategy improves rheological properties and oil displacement efficiency of polymers

In enhanced oil recovery (EOR), the application of polymer systems in harsh reservoir conditions is limited. This study conducted a proof-of-concept study of multi-supramolecular interactions and dual-network strategies, motivated by the desire to gain insights into the effectiveness of these higher-order self-assembled polymer flooding. Xanthan gum dual network supramolecular polymer (DN-HXG) system was obtained by multi-supramolecular cross-linking of polyacrylamide and xanthan gum, and compared with hydrophobic polyacrylamide/hydrophobic xanthan gum (HMPAM/MXG) mixture and polyacrylamide/xthan gum (HPAM/XG) mixture. The thickening and temperature and salt tolerance mechanisms of DN-HXG were analyzed by environmental scanning electron microscopy (ESEM), dynamic light scattering (DLS) and fluorescence spectra. The results show that the DN-HXG system has excellent viscoelastic and shear resistance. Due to the presence of multiple supramolecular interactions and rigid xanthan gum molecular chains, DN-HXG can withstand environments of more than 120 ℃ and 50 g/L salinity, which has good applicability in harsh reservoirs. In laboratory oil displacement experiments, DN-HXG shows obvious advantages in low-permeability core, and the recovery rate of DN-HXG is more than 20 % higher than that of conventional polymer. These experiments show that the strategies described can be applied to other synthetic polymers and biopolymers to improve their oil displacement properties.

Reducing starch digestibility of white rice by structuring with hydrocolloids

Controlling starch digestion in high glycaemic index staple foods such as white rice is of interest as it has been associated with reduced risk for conditions such as obesity and type-2 diabetes mellitus. Addition of hydrocolloids has been proposed to reduce the rate of post-prandial glucose by controlling the rate of starch hydrolysis. In this work, the potential of a range of hydrocolloids to modify starch digestibility when added (at 1 % maximum concentration) during cooking of white rice was first investigated. Low acyl gellan gum (LAG) showed the highest potential (in-vitro estimated Glycaemic Index reduced by about 20 %, from 94 in the control to 78 in the LAG rice) and was investigated further. While the grains of rice control and rice with LAG appeared similar, SEM images revealed a gel-like layer (a few micrometers in thickness) on the surface of the treated samples. Addition of LAG appeared to also have an effect on the breakdown of a simulated cm-sized bolus. During gastric digestion, bolus breakdown of the rice control was completed after 30 min, while the rice LAG bolus appeared intact after 1 h of observation. This was attributed to strengthening of the LAG gel in the acidic environment of the stomach. During intestinal digestion, rice samples containing 1 % LAG appeared to be less susceptible to breakdown when seen under a microscope and in environmental SEM, while they showed larger rice particle aggregates, compared to rice control. Overall, LAG showed potential to control starch digestion kinetics of white rice with a mechanism that may involve formation of a protective layer on the rice grains (um) that reduces bolus break down (cm) and enzymatic hydrolysis (nm). Outcomes of this work will be used to identify conditions for further relevant in-vitro and in-vivo investigations.

The Effect of Water-Based Primer Pretreatment on the Performance of Water-Based Inkjet Coatings on Wood Surfaces

Wood surface staining suffers from volatile organic gas (VOC) emissions and uneven staining at knots, and these environmental and decorative performance issues are the main restrictions in the application of wood products, indoors and outdoors. Herein, the method of wood-based panel surface staining is presented for improving environmental and decorative performance using environmentally friendly water-based inks, water-based primers, and digital inkjet coloring technology. The wood-based panels’ dye coatings were prepared with oak plank as the sample substrate, a one-component water-based primer as the interfacial adhesive, and a water-based ink as a coating agent. The application amount of water-based primer was 15 g per square meter, applied twice by a roller, and the coating thickness reached approximately 20 μm. The influence of the one-component water-based primer on the interfacial properties of water-based inkjet coatings was investigated via Fourier-transform infrared (FTIR) spectroscopy, a video contact angle analyzer, and environmental scanning electron microscopy (SEM). The results showed that the one-component water-based primer connected the plain board to the inkjet-printed coating. The addition of a water-based primer coating reduced the contact angle of the wood surface from 41.69° to 37.28° and increased wettability. This helped enhance the adhesion of the water-based inkjet coating, and the primer treatment in the semi-closed state covered the scar defects of the plain board while preserving the path of grain holes on the wood surface. With image editing and inkjet dyeing, the surface of the oak plank obtained a uniform staining effect on the primer coating while maintaining the original natural pore texture of the wood. This study proves that a one-component water-based primer pretreatment process for water-based inkjet printing coatings on wood surfaces has excellent modification ability and interface adhesion. It provides a feasible method of color modification for artificial panel surfaces.

Chemical-physical investigations of nine types of nasopharyngeal swabs for the PCR analyses

During the SARS-Cov-2 pandemic, a test of samples collected through naso/oropharyngeal swab was set up; for this aim new swabs were developed. Materials and methods: The laboratory New Nanodiagnostics srl (Modena - Italy) analyzed nine different types of swabs used to collect human organic material for PCR diagnostic test for the SARS-CoV-2 infection. The swabs were observed under Optical Microscope and analyzed by Field Emission Gun Environmental Scanning Electron Microscope (FEGE-SEM) coupled with an Energy Dispersive System (EDS), to verify their morphology and chemical composition. Three different morphologies and nanostructures, along with their chemical composition were identified. Surprisingly enough, the presence of identified chemical contaminants like Titanium-Silicon-Aluminum or Silicon- Aluminium-Chromium-Manganese does not be understandable nor is it explained in the data sheet. Some fibers also present a nanostructured coating of Silicon-Zirconium. This might be of concern, as their presence could invalidate the accuracy of the PCR testing. In addition to that, the biocompatibility of the medical devices is discussed since a particular tendency of the glassy fibers to break has been verified. The presence of broken fibers in the nasal and oropharyngeal mucosa can cause irreversible damages. Finally, after their use, the swabs must be incinerated and their fumes contribute to the increase of the environmental pollution.

Hybrid MWCNT/TiO2 nanoparticles based high-temperature quinary nitrate salt mixture for thermal energy storage applications

This study developed an advanced thermal energy storage (TES) material consisting of a quinary nitrate salt mixture doped with hybrid MWCNT/TiO2 nanoparticles. The structural, morphology, and thermophysical properties of hybrid MWCNT/TiO2 and hybrid MWCNT/TiO2 doped quinary nitrate salt mixture was characterized using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), laser flash analysis (LFA), viscosity measurement, X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Raman spectroscopy and Field environmental scanning electron microscopy and Energy dispersive X-ray (FESEM-EDX) analysis. Furthermore, levelized cost of electricity (LCOE) of concentrated solar power (CSP)-parabolic trough collector (PTC) power plant using the optimized sample as the TES materials were calculated using the “physical trough model” in system advisor model (SAM) software. Based on the result, 0.05 wt% dosage of hybrid MWCNT/TiO2 nanoparticles in the quinary nitrate salt mixture has the most favorable thermophysical properties, with 17.655 % enhancement in average specific heat capacity, 37.769 % enhancement in latent heat, 25.412 % enhancement in average thermal conductivity and 94.77 % decrement in viscosity. Furthermore, SAM simulation studies also showed that the developed TES material could reduce LCOE of the CSP power plant by 1.29 % to 0.1687 USD/kWh. Therefore, in the efforts of replacing the coal-fired electricity generation with the CSP-PTC power plants, it is also possible to achieve a potential annual saving of up to 552 million USD compared to commercial TES materials.

In-Situ Microscale Compression Testing of Li-Si Micropillars

Silicon is considered as an ideal anode material for high-capacity Li-ion batteries (LIB) thanks to its high theoretical capacity, but the commercial viability is severely hampered by considerable volume expansion of Si upon lithiation that can lead to mechanical failure (e.g., cracks and delamination). Hence, understanding the mechanical behaviors of the Li-Si system is of high interest, but the experimental studies have been limited to thin film electrodes by means of wafer curvature measurements or nanoindentation. In this work, we for the first time present in-situ microscale compression testing of Li-Si micropillars and extract the key mechanical properties (e.g., Young’s modulus, yield strength, and fracture energy) from the resulting stress-strain curves. Prior to testing, Si micropillars of various sizes/shapes and oriented at different crystal directions were lithiated/delithiated at room temperature. We then performed the microscale compression testing on these lithiated Si micropillars using a flat-head indenter in environmental scanning electron microscope (ESEM) while obtaining live video images for data-image correlation. The results suggest that the measured elastic moduli of the Li-Si system agree with the values obtained from the standard nanoindentation experiments but with much smaller variance. The precise nature of these experiments allows us to observe the mechanical properties dependent on the crystal orientation of Si and lithiation rate. In addition, various failure behaviors of Li-Si under compressive stresses will be presented, which is difficult to be obtained through the existing experimental techniques.

Comparison of arterial wall integration of different flow diverters in rabbits: The CICAFLOW study

Background and purposeNew coated flow diverters (FDs) claim antithrombotic properties and increased arterial wall integration. The aim of this study is to compare in vivo endothelial coverage of coated and uncoated FD in the context of different antiplatelet regimens. MethodsDifferent FDs (Silk Vista – SV, Pipeline with Shield technology – PED shield and Surpass Evolve – SE) were implanted in the aorta of rabbits, all 3 in each animal with 3 different antiplatelet regimens: no antiplatelet therapy, aspirin alone, or aspirin and ticagrelor. Four weeks after FD implantation, angiography, flat-panel CT, and optical coherence tomography (OCT) were performed before harvesting the aorta. Extensive histopathology analyses were performed including environmental scanning electron microscopy (ESEM), multiphoton microscopy (MPM) and histological staining with qualitative and/or quantitative assessment of device coverage. ResultsAll 23 FDs that were implanted remained patent without hyperplasia. Qualitative stent coverage assessment revealed that there were no statistically significant differences between the FD groups (p = 0.19, p = 0.45, p = 0.40, and p = 0.84 for OCT, ESEM, MPM and histology, respectively). Quantitative neointimal measurement of histological sections also showed similar results in all 3 FD groups (p = 0.70). However, there were significant differences between the 3 groups of antiplatelet regimens (p = 0.07) with a higher rate in the no antiplatelet group (p = 0.05 versus aspirin alone and p = 0.03 versus aspirin and ticagrelor). ConclusionOur study provides evidence that FD integration into the arterial wall is similar with coated (PED shield) and uncoated devices (SV, SE), regardless of the antiplatelet regimen. FD integration with specific surface coverage should be promoted. Trial registrationAPAFIS #2022011215518538.

Research on the performance evolution of concrete under the coupling effects of sulfate attack and carbonation

In this study, three coupled modes of coupling effect of sulfate attack and carbonation of concrete were carried out to investigate the change of mass, mechanical properties and apparent morphology. The phase composition, microstructure and morphological characteristics of erosion products were also studied by using environment scanning electron microscope (ESEM-EDS), Fourier infrared spectrometer (FTIR), and X-ray diffraction (XRD). The results indicated that the coupled mode played an obvious effect on the performance and microstructures of specimen due to effects of coupled mode on the deterioration mechanism and erosion products. The surface feature of specimen became worse with carbonation time, and plenty of surface efflorescence and desquamation of products were observed under the coupled mode of carbonation followed by sulfate attack. The relative compressive strength and dynamic elastic modulus of concrete specimen first increased and then decreased with carbonation time, and there existed relationship of a cubic function of single variable between them. The relative mass of concrete specimen increased with the increase of the erosion age of sulfate attack. The difference of the carbonation time per period test played a significant effect on the relative compressive strength and dynamic elastic modulus of concrete specimen, which was due to the dominant effect of carbonation.

Phase evolutions, microstructure and physico-mechanical properties of ceramics from Meiganga kaolin: effect of Na/K2O and CaO addition

ABSTRACT This paper examines the potential use of pegmatite and marble as additives in amalgamation with Meiganga kaolin to produce stoneware products capable to resist high temperatures as well as enhancement the mechanical characteristics. Two series of ceramic products were formulated by partly replacing kaolin with 0, 3, 5 and 7 wt% of both pegmatite and marble wastes. The specimens were sintered at 1000°C, 1050°C and 1100°C. Fired ceramic samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and the microstructure of the products was determined using an environmental scanning electron microscope and energy-dispersive X-ray spectroscopy. Also, the physico-mechanical properties were evaluated. Results divulged that, the addition of pegmatite or marble to kaolin enhances the strength of the ceramic body and act as a fluxing agent by promoting vitrification and glassy phase in clay after firing. The highest flexural strength results were observed with 7 wt% of pegmatite added at 1100 °C, with an increase ~ 35% compared to the control sample. High silica and alumina contents in pegmatite fill in voids, providing densification matrices. The incorporation of pegmatite allows to obtain a ceramic with better mechanical properties and energy saving as compared by the conventional ceramic.

Micro-scale wettability of carbonate rocks via high-resolution ESEM imaging

The wettability of several materials has been traditionally quantified using macro-scale contact angles. However, precise identification of the three-phase contact (TPC) line is often difficult due to the resolution limit of macro-scale setups. Moreover, micro-level surface chemical heterogeneities can have a notable impact on the predicted wetting behavior which limits macro-scale contact angles. Thus, here, we investigate the micro-scale water wettability of condensed micro-droplets on carbonate rock surfaces via a high-resolution Environmental Scanning Electron Microscopy (ESEM). Macro- and micro-scale contact angles were evaluated under three conditions: 1) natural carbonate surfaces, 2) surfaces aged in crude oil, and 3) surfaces aged in cationic surfactant to allow for a broader insight of the impact of rock composition and surface morphology on wettability.At the macro-scale, carbonate rocks were preferentially oil-wet to intermediate-wet. However, a profound variability was observed in wetting behavior at the micro-scale where a weakly water-wet state (50° ≥ θ ≥ 80°) was prevalent with evidence of minor oil-wet patches too. At the micro-scale, for the 100% dolomite sample, the contact angle (θ) varied from ∼66° to 76° under natural conditions, while the same sample aged in crude oil depicted a remarkable variability, i.e., θ ranged from 58° to 132° with the majority of micro-droplets having θ of ∼85° – thus suggesting a mixed-wet behavior. For the same sample aged in surfactant, θ was <5° at micro and macro-scales, with few micro-droplets having θ of ∼89°. However, the macro-scale θ values were 105° (natural) and 90° (oil-aged) – suggesting notable variability at macro- and micro-scales.These findings reflect: a) significant differences among macro- and micro-scale contact angles, and b) surface wetting at the micro-scale captures physical and chemical properties of the rock, i.e., surface roughness, pore size and distribution, and chemical composition. The study herein presents qualitative and semi-quantitative analyses of the non-uniform wetting behavior of carbonate rocks and the associated rock/fluid interactions through a multi-scale perspective and thus have broader implications for flow in porous medium.

Effect of incorporation of nano-graphene oxide on physicochemical, mechanical, and biological properties of tricalcium silicate cement

ObjectiveEvaluation of setting time, compressive strength, pH, calcium ion release, and antibacterial activity of mineral trioxide aggregate (MTA) after modification with three different concentrations of nano-graphene oxide (GO) powder compared to unmodified Biodentine as a commercial control. MethodsGO powder, unhydrated and hydrated cements were characterized using Environmental Scanning Electron Microscope (ESEM) with Energy Dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Raman Spectroscopy, and Fourier Transform Infrared spectroscopy (FTIR). GO was also analyzed using Scanning Transmission Electron Microscope (STEM) to determine average lateral dimensions. Specimens were prepared and grouped according to the concentration of GO added to Rootdent MTA (control, 1, 3, and 5 wt%) and the material used (MTA and unmodified Biodentine) into five groups. Setting time was evaluated using Gillmore penetrometer (n = 5). Compressive strength was evaluated using universal testing machine (n = 7). pH and calcium ion release were assessed using pH meter and Induced Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) at 1, 7, 14, and 28 days (n = 7). Antibacterial activity was evaluated against Streptococcus mutans using direct contact test (n = 7). One-way and repeated measures ANOVA followed by Tukey's post hoc test were used for data analysis with significance level set at p ≤ 0.05. ResultsAddition of GO to MTA reduced both initial and final setting time. GO modified MTA groups and unmodified Biodentine showed significantly increased calcium ion release at 14 and 28 days. All cements showed alkaline pH of the storage media at all tested time intervals. 1 wt% GO recorded the highest compressive strength values in MTA modified groups. The increased concentration of GO from 1 to 5 wt% successively increased antibacterial activity of MTA, with Biodentine showing the lowest significant value. ConclusionAddition of 1 wt% GO can significantly improve the tested properties of tricalcium silicate-based cements without compromising their compressive strength. Clinical significanceGO is a promising modification for tricalcium silicate cements to improve setting time, compressive strength, and antibacterial activity to provide a variety of materials for different clinical situations. This in turn can reduce the risk of reinfection and allow placement of the final restoration in a single visit.

Comparison between clinical evaluations and laboratory findings and the impact of biofilm on antimicrobial susceptibility in vitro in canine otitis externa.

In canine otitis externa (OE), biofilm-producing bacteria are frequently present but biofilm may be underdiagnosed clinically. The study aimed to investigate an association between clinical and cytological findings with bacteriological data from dogs with OE, to establish, through Environmental Scanning Electron Microscope (ESEM) examination, whether the presence of biofilm in vivo can be predicted and to evaluate the impact of biofilm on antimicrobial susceptibility tests. Fifty-six dogs showing clinical signs of OE were enrolled. One cotton swab each was collected for ESEM, bacterial culture and susceptibility testing and for cytology. Staphylococcus pseudintermedius (n = 42, 48.8%) and Pseudomonas aeruginosa (n = 26, 30.2%) were tested for their ability to form biofilm. Minimum Inhibitory Concentrations (MIC), Minimal Biofilm Inhibitory Concentrations (MBIC) and Minimal Biofilm Eradication Concentrations (MBEC) towards enrofloxacin, gentamicin, polymyxin B and rifampicin were determined. Pseudomonas aeruginosa was positively associated with the biofilm clinical evaluation (p < 0.01) and neutrophils (p < 0.05), nuclear streaks (p < 0.01) and rods bacteria (p < 0.01) on cytology. S. pseudintermedius was associated with a low presence of neutrophils. There was a statistical correlation between clinical and cytological biofilm presence (p ≤ 0.01), but none with the biofilm production assay nor ESEM biofilm detection. No differences were found comparing the results of MIC and MBIC. MBEC results showed higher values than MIC and MBIC for all antimicrobials tested (p ≤ 0.001). Biofilm presence in OE was often underdiagnosed. Even if there is no specific clinical or cytological pattern related to biofilm, its presence should always be suspected.

Direct observation for relative-humidity-dependent mixing states of submicron particles containing organic surfactants and inorganic salts

Abstract. Aerosol mixing state plays an important role in heterogeneous reactions and cloud condensation nuclei (CCN) activity. Organic surfactants could affect aerosol mixing state through bulk–surface partitioning. However, the mixing state of surfactant-containing particles remains unclear due to the lack of direct measurements. Here, direct characterizations of the mixing state for 20 kinds of submicron particles containing inorganic salts (NaCl and (NH4)2SO4) and atmospheric organic surfactants (organosulfates, organosulfonates, and dicarboxylic acids) were conducted upon relative humidity (RH) cycling by environmental scanning electron microscopy (ESEM). As the RH increased, the surfactant shells inhibited water diffusion being exposed to the inorganic core, leading to notably increased inorganic deliquescence RH (88.3 %–99.5 %) when compared with pure inorganic aerosol. Meanwhile, we directly observed an obvious Ostwald ripening process (that is, the growth of larger crystals at the expense of smaller ones) in 6 out of 10 NaCl–organic surfactant systems. As a result of water inhibition by the organic surfactant shell, Ostwald ripening in all systems occurred at RH above 90 %, which were higher than the reported RH range for pure NaCl measured at 27 ∘C (75 %–77 %). As RH decreased, eight systems underwent liquid–liquid-phase separation (LLPS) before efflorescence, showing a strong dependence on the organic molecular oxygen-to-carbon ratio (O:C). Quantitatively, LLPS was always observed when O:C≤0.43 and was never observed when O:C&gt;∼0.57. Separation RH (SRH) of inorganic salt–organic surfactant mixtures generally followed the trend of (NH4)2SO4 &lt; NaCl, which is consistent with their salting-out efficiencies reported in previous studies. Solid-phase separations were observed after efflorescence for systems without LLPS. Our results provide a unique insight into the consecutive mixing processes of the inorganic salt–organic surfactant particles, which would help improve our fundamental knowledge of model development on radiative effect.

Transient melt formation and its effect on conversion phenomena during nuclear waste vitrification – HT‐ESEM analysis

AbstractAlthough the vitrification of nuclear waste has a decades‐long history, numerous opportunities still exist to improve its efficiency and to increase the waste loading in glass. This is especially true for the vitrification of low‐activity waste (LAW), which has been historically treated by other immobilization technologies and is less mature than high‐level waste (HLW) vitrification. In this work, we address one of the least understood phenomena during the conversion of nuclear waste feeds to glass—the formation of molten salt and transient glass‐forming melt. Using high‐temperature environmental scanning electron microscopy (HT‐ESEM) in combination with X‐ray diffraction, thermogravimetry, and evolved gas analysis, we have analyzed the complex chemical reactions and phase transitions as they occur during melting of representative HLW and LAW melter feeds. We evaluated the compositions of amorphous phases and the fractions of salt components, and estimated the fractions of molten salt phases present in the feeds as a function of temperature. We show that the maximum fraction of molten salts is ∼4 % and ∼28 % during HLW and LAW feed melting, respectively, and discuss the possibility of molten salt migration in LAW feeds. We also argue that the presence of significant fractions of molten salt phase can hinder the retention of rhenium (and, hence, radioactive technetium), and discuss how the properties of molten salt phase and transient glass‐forming melt are related to primary foam formation and behavior. Finally, we summarize key unanswered questions requiring further research to increase the understanding of the conversion process and enhance the nuclear waste vitrification efficiency.

In Situ Nanoindentation at Elevated Humidities

AbstractNanoindentation is one of the most widespread methods to measure the mechanical performance of complex materials systems. As it allows for local characterization of composite architectures with sub‐micron spatial features and a large range of properties, nanoindentation is commonly used to measure the properties of biological materials. In situ nanoindentation, a further development of the approach, is a powerful tool for the analysis of plastic deformation and failure of materials. Here, samples can be mechanically manipulated using the indenter, while their behavior is monitored with the resolution of a scanning electron microscope (SEM). Indeed, numerous studies demonstrate the potential of this approach for studying the most fundamental material characteristics. However, so far, these measurements are performed in high‐vacuum conditions inherent to the conventional electron microscopy method, which are irrelevant when studying biological structures that evolved to perform in hydrated conditions. In this work, the ability to conduct nanoindentation experiments under controlled humidity and temperature inside an environmental SEM is developed. This technique has the potential to become crucial for materials design and characterization in many domains where humidity has a significant impact on performance. These include organic/polymer systems, microelectronic and optoelectronic devices, materials for catalysis, batteries, and many more.

Mineralogical Characteristics and Arsenic Release of High Arsenic Coals from Southwestern Guizhou, China during Pyrolysis Process

Coal is the primary energy source in China, and coal pyrolysis is considered an essential and efficient method for clean coal utilization. Three high arsenic coals collected from the southwestern Guizhou province of China were chosen in this study. Low-temperature ashing plus X-ray diffraction analysis (XRD) was used to identify the minerals in coals. The three coals were pyrolyzed in a tube furnace in an N2 atmosphere at 950 °C, 1200 °C, and 1400 °C, respectively. Environment scanning electron microscope (ESEM), XRD, X-ray fluorescence analysis (XRF), and inductively coupled plasma-mass spectrometry (ICP-MS) were adopted to determine the morphology, mineral compositions, and element compositions and arsenic contents of the coal pyrolysis ashes, respectively. It can be found that minerals in coal are mainly composed of quartz, pyrite, muscovite, and rutile. The minerals in the ashes generated from coal pyrolysis mainly contain quartz, dehydroxylated muscovite, iron oxide minerals, mullite, and silicon nitride. Oldhamite and gupeite exist at 950 °C and 1400 °C, respectively. The morphologies of oldhamite and gupeite at these temperatures are irregular block-shaped particles and irregular spherical particles, respectively. The mineralogical transformations in the process of coal pyrolysis affect coal utilization. The arsenic release rate is higher than 87% during pyrolysis at 1400 °C. The arsenic in organic matter is more able to be volatilized than mineral components. The retention time can slightly influence the arsenic release rate, and the influence of temperature is much more significant than the influence of retention time. The understanding of mineral evolution and arsenic environmental emission is helpful for the safety of high-arsenic coal pyrolysis.

Rheological, Mechanical, Microscopic, and Chemical Characterization of Asphalt Binders at Extended Aging Levels

This study aims to connect asphalt binder mechanical properties to their dynamic microscopic morphology and chemical indices to provide a more thorough and fundamental picture of aging and cracking phenomena. Unmodified and modified asphalt binders were aged to five levels for a comprehensive representation of the asphalt binder service life. Rheological indices used covered linear viscoelastic cracking indicators and nonlinear parameters including fatigue life obtained by the linear amplitude sweep test. A recently validated asphalt binder cracking test, the poker chip test, was used to provide new insight into the mechanical performance of asphalt binders as they stretch into the nonlinear regime and experience cavitation damage. Rheological and mechanical properties were compared to static surface topography from atomic force microscopy (AFM) and time-sensitive asphalt binder microstructure based on electron beam loading using an environmental scanning electron microscope (ESEM). Results indicated that the parameters based on linear viscoelastic analysis and fatigue life derived from the linear amplitude sweep (LAS) test are not adequate to delineate the evolution of asphalt binder behavior with aging among different asphalt binders, due to poor ranking based on known phenomena. However, it was confirmed that the poker chip test was sensitive to longer aging cycles and could capture the total degradation of the asphalt binder’s ductility for both modified and unmodified asphalt binders. The consistency between ESEM and AFM was ensured by observing static surface structures; however, quantification of the fibril formation in ESEM images was the most critical morphological observation when it came poker chip results, because both sharing similar deformation mechanisms. Chemical characterization using Fourier transform infrared spectroscopy was also able to capture asphalt binder aging well, and could be best related to the strength of the asphalt binder. Overall, it was established that the surface microstructure has some relationship to mechanical properties, but not a definitive one, and that using ESEM as an energy absorption indicator was most similar to the comprehensive results from mechanical and chemical testing.