Environmental Scanning Electron Microscopy Research Articles

Speciation-specific chromium bioaccumulation and detoxification in fish using hydrogel microencapsulated biogenic nanosilver and zeolite synergizing with biomarkers.

Grass carp intestinal waste-mediated biosynthesized nanosilver (AgNPs) was valorized using guaran and zeolite matrices, resulting in AgNPs-guaran, AgNPs-zeolite, and AgNPs-guaran -zeolite composites. The valorized products were examined using Environmental Scanning Electron Microscopy, Energy Dispersive X-ray analysis and X-ray Diffraction analysis to confirm uniform dispersion and entrapment of AgNPs within the matrixes. These valorized products were evaluated for their efficacy in detoxifying the ubiquitous and toxic hexavalent chromium (Cr6+) in aquatic environments, with Anabas testudineusexposed to 2mgl-1 of Cr6+ for 60days. Remarkable reduction of Cr6+ concentration to 0.86 ± 0.007mgl-1 was achieved with AgNPs-guaran-zeolite composite, indicating successful reclamation of contaminated water and food safety assurance. Consistency in results was further corroborated by minimal stress-related alterations in fish physiological parameters and integrated biomarker response within the experimental group treated with the AgNPs-guaran-zeolite composite. Despite observed chromium accumulation in fish tissues, evidence of physiological stability was apparent, potentially attributable to trivalent chromium accumulation, serving as an essential nutrient for the fish. Additionally, the challenge study involvingAnabas testudineus exposed to Aeromonas hydrophila exhibited the lowest cumulative mortality (11.11%) and highest survival rate (87.5%) within the same experimental group. The current study presents a novel approach encompassing the valorization of AgNPs for Cr6+ detoxification under neutral to alkaline pH conditions, offering a comprehensive framework for environmental remediation.

Study on Chalcopyrite Dissolution Mechanism and Bioleaching Community Behavior Based on Pulp Concentration Gradient at 6 °C

Low-temperature bioleaching is relevant to the recovery of metals in alpine mines, but its development has been constrained by low bioleaching rates at high pulp concentrations. To this end, the bioleaching effect of the microbial community after the domestication of pulp concentration at 6 °C was studied. Domestication improved the bioleaching rate of copper. Environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), and electrochemical measurements revealed that the domestication process aggravated the corrosion of the chalcopyrite surface by accelerating its dissolution reaction. High-throughput sequencing technology indicated that Acidithiobacillus spp., Leptospirillum spp., and Acidiphilium spp. were the major lineages of the domesticated microbial community. The analysis of the microbial community revealed that domestication changed the microbial structure, enhancing the adaptability of the microbial community to pulp concentrations and acidic conditions. This study uncovered the mechanism by which domestication enhanced the bioleaching efficiency of the microbial community at low temperatures.

Study on Chalcopyrite Dissolution Mechanism and Bioleaching Community Behavior Based on Pulp Concentration Gradient at 6 °C

Low-temperature bioleaching is relevant to the recovery of metals in alpine mines, but its development has been constrained by low bioleaching rates at high pulp concentrations. To this end, the bioleaching effect of the microbial community after the domestication of pulp concentration at 6 °C was studied. Domestication improved the bioleaching rate of copper. Environmental scanning electron microscopy (ESEM), X-ray diffraction (XRD), and electrochemical measurements revealed that the domestication process aggravated the corrosion of the chalcopyrite surface by accelerating its dissolution reaction. High-throughput sequencing technology indicated that Acidithiobacillus spp., Leptospirillum spp., and Acidiphilium spp. were the major lineages of the domesticated microbial community. The analysis of the microbial community revealed that domestication changed the microbial structure, enhancing the adaptability of the microbial community to pulp concentrations and acidic conditions. This study uncovered the mechanism by which domestication enhanced the bioleaching efficiency of the microbial community at low temperatures.

Plants with silver nanoparticles to improve electrical conductivity: an innovative approach in biology

AbstractThis paper shows the effect of electrical conductivity on the vascular system of plants through the utilization of silver nanoparticles supported by nanocellulose. The plant Epipremnum aureum, also known as pothos, was used in the experimentation. The main characteristics of the plant are its vigorous growth, remarkable adaptability to thrive in both soil and aquatic environments, simple propagation, and noteworthy resilience against diseases. The experiment used a polarization voltage ranging from − 1.5 to 1.5 V and shunt resistors of 1, 10, 100, and 1000 ohms. The scan polarization rate was 15 mV/s. Methods like environmental scanning electron microscopy and energy-dispersive X-ray analysis were used for chemical and structural analysis. The findings demonstrate that adding silver nanoparticles held together by nanocellulose enhances the vascular system's capacity to conduct electricity. Moreover, the Wilcoxon signed-rank test results revealed no statistically significant difference between the root-steam and stem-leaf output voltage values. These findings imply that silver nanoparticles are distributed throughout the vascular system and act as conductive pathways in plants. Additionally, electrolysis-Faraday's law was used to calculate the recovery of silver material, yielding 40 mg/mm2 per hour. These discoveries open new avenues for comprehending and manipulating plant physiological processes, potentially leading to beneficial outcomes in agriculture and contaminant recovery.

The Combined ICP-MS, ESEM-EDX, and HAADF-STEM-EDX Approach for the Assessment of Metal Sub-Micro- and Nanoparticles in Wheat Grain.

Metal sub-microparticles (SMPs) and nanoparticles (NPs) presence in food is attributable to increasing pollution from the environment in raw materials and finished products. In the present study, a multifaceted analytical strategy based on Environmental Scanning Electron Microscopy and High-Angle Annular Dark-Field-Scanning Transmission Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (ESEM-EDX, HAADF-STEM-EDX) and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was proposed for the detection and characterization of metal and metal-containing SMPs and NPs in durum wheat samples, covering a size measurement range from 1 nm to multiple µm. ESEM-EDX and ICP-MS techniques were applied for the assessment of SMP and NP contamination on the surface of wheat grains collected from seven geographical areas characterized by different natural and anthropic conditions, namely Italy, the USA, Australia, Slovakia, Mexico, Austria, and Russia. ICP-MS showed significant differences among the mean concentration levels of metals, with the USA and Italy having the highest level. ESEM-EDX analysis confirmed ICP-MS concentration measurements and measured the highest presence of particles < 0.8 µm in size in samples from Italy, followed by the USA. Less marked differences were observed when particles < 0.15 µm were considered. HAADF-STEM-EDX was applied to a selected number of samples for a preliminary assessment of internal contamination by metal SMPs and NPs, and to expand the measurable particle size range. The multifaceted approach provided similar results for Fe-containing SMPs and NPs. ICP-MS and ESEM-EDX also highlighted the presence of a significant abundance of Ti- and Al-containing particles, while for STEM-EDX, sample preparation artifacts complicated the interpretation. Finally, HAADF-STEM-EDX results provided relevant information about particles in the low nm range, since, by applying this technique, no particles smaller than 50 nm were observed in accordance with ESEM-EDX.

Compositional and Microstructural Investigations of Prehistoric Ceramics from Southern Romania (Middle Neolithic Pottery)

In this paper, based on our previous expertise on ceramic artifacts, several archaeometric methods applied to some samples collected from the Dudești archaeological site (Oltenia region, Romania) are reported for the first time in the literature. The chemical composition, and microstructural and morphological characterization of these samples offer important conclusions about the processing conditions. Some specific techniques such as X-ray diffraction (XRD), wavelength-dispersive X-ray fluorescence (WDXRF), optical microscopy (OM), stereomicroscopy, environmental scanning electron microscopy (ESEM), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy provide compositional information about composition and the decay processes. Additionally, the Brunauer–Emmett–Teller (BET) method helps to estimate pore sizes and specific surface areas. A thermogravimetric analysis (TGA/TDG) was used to establish details regarding the production technology and also the raw materials source used to make the ceramics. The obtained results indicated that the ceramics are based on a paste of muscovite and feldspar, with high plasticity, together with quartz and hematite/goethite and calcite, the latter in very low concentrations. According to the obtained results, we could assume that clays from the investigated samples had a low concentration of calcium. Gypsum is present as paste in a very low concentration, identified by the presence of a sulphate group in WDXRF. In the same context, iron oxides have a significant impact on the firing atmosphere of iron-rich clay, resulting in blackening under reducing conditions and a reddish coloration under oxidative conditions. The use of hematite and gypsum as pigments further contributes to the color variations in the pottery. The consistent firing temperature range of 200–600 °C in Dudești pottery implies a standardized production process, the variation in color being dependent on the specific reducing/oxidative regime conditions (reducing atmosphere followed by rapid oxidation). This relationship between clay composition and local sources suggests a connection to Neolithic pottery production in the region and their color depending on the reducing/oxidative regime conditions.

Experimental study on the comparison of mechanical properties of different types of glutenite in the Ma'nan area

This study delves into the mechanical properties of various rock types found in glutenite reservoirs in the Ma'nan area of the Xinjiang oilfield. It bridges a knowledge gap by exploring the mechanical deformation and failure patterns among different glutenite types. Employing porosity-permeability tests, ultrasonic wave velocity measurements, and triaxial compression tests, this research scrutinizes physical parameters, mechanical properties, deformation, and failure modes of dolomitic sandstone, calcareous coarse sandstone, calcareous fine siltstone, and glutenite. Results highlight a porosity increase from dolomitic sandstone to glutenite, with calcareous coarse sandstone having the lowest permeability and glutenite the highest. Shear wave velocity is greater in dolomitic sandstone and calcareous coarse sandstone compared to calcareous fine siltstone, while longitudinal wave velocity is higher in dolomitic sandstone than in glutenite. Deformation behavior varies: dolomitic sandstone is primarily elastic, and calcareous sandstone and glutenite show elastoplastic characteristics. Dolomitic sandstone boasts the highest compressive strength, elastic modulus, and Poisson's ratio. Calcareous fine siltstone's compressive strength and elastic modulus fall below dolomitic sandstone, while the Poisson's ratio of calcareous coarse sandstone is three-quarters that of dolomitic sandstone. Main failure modes observed are shear failure in dolomitic sandstone, calcareous coarse sandstone, and glutenite, and axial splitting failure in calcareous fine siltstone. Microscopic analyses, including environmental scanning electron microscopy and mineral composition, shed light on the mechanical differences among the rocks. In sum, this research yields crucial insights into the mechanical traits of glutenite reservoir rocks, essential for optimizing hydraulic fracturing strategies in such reservoirs.

Osteoinductive and regenerative potential of premixed calcium‐silicate bioceramic sealers on vascular wall mesenchymal stem cells

AbstractAimThe osteogenic potential of new premixed calcium‐silicate‐containing bioceramic sealers (Ca‐Si sealers) was tested with porcine vascular wall‐mesenchymal stem cells (pVW‐MSCs).MethodologyTwo Ca‐Si‐containing sealers: Ceraseal (MetaBiomed, Cheong‐si, South Korea) and AH Plus Bioceramic (Maruchi, Wonju‐si, South Korea), and an epoxy resin sealer (AH Plus; Dentsply, Konstanz, Germany) as a control, were prepared according to the manufacturers' indications. All samples were allowed to set for 100% of their setting time in a sterile humid cabinet at 37°C and 95% relative humidity. pVW‐MSC seeding efficiency and osteogenic differentiation were analysed as marker of gene/protein expression for up to 12 days. Mineralization assay and immunofluorescence staining were performed and evaluated over a period of 21 days. Statistical analyses were conducted using one‐way analysis of variance (p &lt; .05). Additional samples were prepared and stored under the same conditions and inspected using an environmental scanning electron microscope equipped with an energy dispersive X‐ray spectroscopy system.ResultsSignificantly higher cell seeding efficiency (p &lt; .05) was observed for both Ca‐Si sealers from day 8. pVW‐MSCs showed a significant shift towards the osteogenic lineage only when seeded in contact with Ca‐Si sealers. Gene expression of osteopontin was upregulated significantly. Collagen I and osteocalcin were clearly expressed by cells in contact with Ca‐Si sealers. Mineralization granules were observed in Alizarin red assays and confocal laser scanning microscopy analysis of both Ca‐Si sealers. No gene expression or granule mineralization were observed on the epoxy resin sealer.ConclusionsPremixed Ca‐Si sealers displayed a higher potential for osteogenic activity on pVW‐MSCs. Epoxy resin sealer was unable to induce any osteogenic activity. The properties of both Ca‐Si sealers suggest their potential as osteoinductive platforms for vascular MSCs in periapical bone.

Anisotropic Icephobic Mechanisms of Textured Surface: Barrier or Accelerator?

Icing has been seen as an economic and safety hazard due to its threats to aviation, power generation, offshore platforms, etc., where passive icephobic surfaces with a surface texturing design have the potential to address this problem. However, the intrinsic icephobic principles associated with the surface textures, energy, elasticity, and hybrid effects are still unclear. To explore the anisotropic wettability, ice nucleation, and ice detaching behaviors, a series of textured poly(dimethylsiloxane) (PDMS)-based coatings with various texture orientations were proposed through a simple stamping method with surface functionalization. The anisotropic hydrophobic/icephobic phenomena and mechanisms were discovered from wettability evaluation, experimentally studied by icing/deicing experiments, and finally verified by microscopic numerical simulations. One-way analysis of variance (one-way ANOVA analysis) was used to analyze the effect of surface textures on hydrophobic/icephobic properties, which assisted in understanding anisotropic phenomena. Typical anisotropic ice nucleation and growth on the textured coatings were clarified using in situ environmental scanning electron microscope (ESEM) characterization. The ice/coating interfacial stress responses were studied by numerical stimulation at the microscopic level, further verifying the localized, amplified, and propagated stress at the ice/coating interface. The theoretical anisotropic responses, barrier effect, and accelerating effect were verified to interpret the anisotropic wettability and icephobicity, depending on the specific surface conditions. This study revealed the basics of the anisotropic icephobic mechanisms of textured icephobic surfaces, further facilitating the R&D of passive icephobic surfaces.

Analysis of the manufacturing craft of the painted gold foils applied on the lacquerware of the Jin Yang Western Han Dynasty tomb in Taiyuan, Shanxi, China

Seven pieces of gold foils for surface decoration of the lacquerware were excavated in the late Western Han Dynasty tomb in the area of the Jin Yang (晋阳) Ancient City site in Taiyuan (太原), Shanxi (山西), China. These gold foils portray images of the carriage, the leopard, the tigers, the ox, and the dancer with fluttering sleeves, etc., with black lines outlining the contours and red paint depicting vivid patterns. The study used Stereo Microscopes, Metallurgical Microscopy, Environmental Scanning Electron Microscopy coupled with Energy-Dispersive X-ray Spectroscopy (ESEM-EDS), and Laser Raman Spectroscopy (LRS) to analyse the thickness of the gold foils, the alloy composition, the composition of the paint and other surface attachments, and investigate the manufacturing process. As the results show, the thickness of the gold foils is about 26 μm. The composition is a gold-silver alloy with about 96% Au/(Au + Ag) (surface) and 98% Au/(Au + Ag) (cross-section). The metallurgical observation shows that the gold foils underwent heating and forging. The black lines on the front side are Chinese ink lines, with cracking and peeling phenomenon, and parallel polishing lines can be seen at the peeling places, while no polishing lines are observed on the back side. Some red paint made of cinnabar is above the black lines, and the binder is organic. Some lacquer residues are found on the back. According to the results of the study, the manufacturing process of the gold foils applied on the lacquerware is as follows: the gold foils are obtained by heating and forging, the front sides of the gold foils are polished, the shapes are carved out, and the gold foils are pasted on the lacquerware when the lacquerware’s surface is not yet dry. The gold foils are painted with black Chinese ink and red cinnabar pigment. The study’s results offer important references for understanding the manufacturing craft of the gold foils applied on the lacquerware in the late Western Han Dynasty of China and guide the conservation of the lacquerware decorated with painted gold foils.

Environmental Scanning Electron Microscopy of copper alloy artefacts from unidentified shipwreck sites: Clues to the identity of shipwrecks on Kenn Reef, Coral Sea

This study investigates the use of Environmental Scanning Electron Microscopes (ESEM) as a tool for identification of historic shipwrecks. Copper alloy fasteners from unidentified shipwreck on Kenn Reef in the Coral Sea, were sampled and analysed to determine the chemical composition of each artefact. When combining this data with known evolution of copper alloying for wooden ship construction, historical and archaeological data, the results provided valuable insight into the possible date range for these wrecks. Specifically, comparison to known wrecks in the vicinity of Kenn Reef could be linked to these previously unidentified sites. Results are promising and ESEM analyses proved to provide valuable, reliable data, yet also highlighted limitations and areas for further investigation and research.

Condensation or Desublimation: Nanolevel Structural Look on Two Frost Formation Pathways on Surfaces with Different Wettabilities.

Processes of water condensation and desublimation on solid surfaces are ubiquitous in nature and essential for various industrial applications, which are crucial for their performance. Despite their significance, these processes are not well understood due to the lack of methods that can provide insight at the nanolevel into the very first stages of phase transitions. Taking advantage of synchrotron grazing-incidence wide-angle X-ray scattering (GIWAXS) and environmental scanning electron microscopy (ESEM), two pathways of the frosting process from supersaturated vapors were studied in real time for substrates with different wettabilities ranging from highly hydrophilic to superhydrophobic. Within GIWAXS, a fully quantitative structural and orientational characterization of the undergoing phase transition reveals the information on degree of crystallinity of the new phase and determines the ordering at the surfaces and inside the films at the initial stages of water/ice nucleation from vapor onto the substrates. The diversity of frosting scenarios, including direct desublimation from the vapor and two-stage condensation-freezing processes, was observed by both GIWAXS and ESEM for different combinations of substrate wettability and vapor supersaturations. The classical nucleation theory straightforwardly predicts the pathway of the phase transition for hydrophobic and superhydrophobic substrates. The case of hydrophilic substrates is more intricate because the barriers in Gibbs free energy for nucleating both liquid and solid embryos are close to each other and comparable to thermal energy kBT. At that end, classical nucleation theory allows concluding a relation between contact angles for ice and water embryos on the basis of the observed frosting pathway.

Macro-micro mechanical behavior of saturated cemented sands during drained triaxial shearing

To enhance the understanding of the macro-micro mechanical behavior of cemented sands, a series of drained triaxial shearing tests were conducted on saturated cemented sands with varying cement contents and confining stresses. These tests incorporated high-performance acoustic emission (AE) monitoring and an environmental scanning electron microscope (ESEM) technique. The results yielded quantitative interpretations of macro-mechanical response, microstructural variation, and AE behaviors. Specifically, increasing cement content led to an exponential reduction in porosity (or pore area ratio) and a power increase in pore number, possibly due to the production of hydration products that segment large pores. Relationships were established among peak strength (or AE hits), cement content, and confining stress. However, AE trends diverged from those observed in peak strength due to microstructural modifications under different cement contents and their resulting differences in micromechanical behavior during shearing. General relationships between AE rate and mechanical parameters were established during the initial shearing stage, regardless of cement content and confining stress. Moreover, AE evolution efficiently characterized subtle variations in failure patterns due to its high sensitivity to failure-induced structural modifications. These contributions have the potential to establish a non-destructive field evaluation framework and provide guidelines for the efficient utilization of cemented soils in geological and geotechnical engineering applications.

Long-term behavior of mortars experiencing delayed ettringite formation

Ettringite formation is an expansive reaction that causes cracking in the hydrated cementitious materials. This research has investigated the mechanisms of ettringite formation by examining the chemical and physical structure of the reactants and products involved in the process of late age (over 15 years) ettringite formation, and subsequent expansion and cracking. For this, seven different types of commercially available cement with their unique composition, and an elevated heat curing temperature of up to 100 °C were applied. The physical expansion of mortar bars due to delayed ettringite formation was monitored by the length change comparator. Environmental scanning electron microscopy (ESEM) was used to qualify and quantify changes in the microstructure and chemical composition of the cementitious matrix. Results revealed that the high-temperature heat curing accelerated the onset of expansion but limited the over-magnitude of the expansion. Results also revealed that the expansion may take years to initiate, likely due to a critical pore size threshold necessary to induce stresses. If expansion is delayed, the expansion magnitude is greater than those that expanded immediately.

Mathematical Physics Analysis of Nozzle Shaping at the Gas Outlet from the Aperture to the Differentially Pumped Chamber in Environmental Scanning Electron Microscopy (ESEM).

A combination of experimental measurement preparations using pressure and temperature sensors in conjunction with the theory of one-dimensional isentropic flow and mathematical physics analyses is presented as a tool for analysis in this paper. Furthermore, the subsequent development of a nozzle for use in environmental electron microscopy between the specimen chamber and the differentially pumped chamber is described. Based on experimental measurements, an analysis of the impact of the nozzle shaping located behind the aperture on the character of the supersonic flow and the resulting dispersion of the electron beam passing through the differential pumped chamber is carried out on the determined pressure ratio using a combination of theory and mathematical physics analyses. The results show that nozzle shapes causing under-expanded gas outflow from the aperture to the nozzle have a worse impact on the dispersion of the primary electron beam. This is due to the flow velocity control. The controlled reduction in the static pressure curve on the primary electron beam path thus causes a significantly higher course of electron dispersion values than variants with shapes causing over-expanded gas outflow.

Study on physicochemical properties of polysaccharides and glycosides from Rehmannia glutinosa under different processing conditions

AIM: The physicochemical properties of polysaccharides and changes in the glycoside composition under different processing conditions of Rehmannia glutinosa were studied. METHODS: High-pressure processing temperature, processing time, processing frequency, and thickness of fresh Rehmannia glutinosa slices were taken as factors, and the contents of polysaccharides, catalpol, and rehmannioside D were taken as evaluation indexes. The physicochemical properties and the inhibition of α-glucosidase were characterized via ion chromatography, Fourier transform infrared spectroscopy, and environmental scanning electron microscopy. RESULTS: The parameter values for the highest polysaccharide content were as follows: processing temperature of 110 ℃, processing time of 4 h, processing frequency of 2 times, and slice thickness of 1.0–1.5 cm. The parameter values for the highest α-glucosidase inhibition rate were as follows: processing temperature of 120 ℃ and processing time of 2 h. The surface morphology of polysaccharides from Rehmannia glutinosa showed irregular fragments, and glucose and galactose were dominant. The α-glucosidase inhibitory activity of polysaccharides from processed Rehmannia glutinosa reached 60% at a low concentration of 0.05 mg/mL.

Towards the icephobicity evolution of metallic surfaces affected by transitional wettability

In light of the escalating demands for ice protection related applications in diverse fields, including wind energy, power lines and aerospace, there is a notable surge in interest and attention toward the icephobic materials. The increased focus reflects a growing recognition of the crucial role of materials that demonstrate superior resistance to icing phenomenon. However, the intricate correlation between material wettability and icephobicity remains inadequately elucidated. This study aimed to investigate the factors that influence the relationship between icephobicity and different wetting states. The impact of varying surface topographies was examined within the scope of this investigation. A comprehensive analysis was conducted to evaluate the anti-icing and de-icing performances of the surfaces, encompassing anti-frost, ice shear adhesion strength and electro-thermal heating de-icing aspects. Furthermore, the static and dynamic wettability, along with surface free energy measurements, were also performed to enhance the comprehension of icephobicity variation. The detailed water condensation on various surfaces was meticulously observed using environmental scanning electron microscopy (ESEM). The findings elucidated a strong correlation between the icing behaviour and surface topography. It was observed that the surface topography acted as an amplifier, intensifying the deteriorating effect in icephobicity: the formed glaze per unit area exhibited a significant increase with rough asperities; the ice adhesion strength suffered an obvious increase with rough surface and lower hydrophobicity as well as the prolonged ice detachment and overall energy consumption. Therefore, careful consideration should be devoted to the tailoring of surface morphology and wettability when designing and fabricating icephobic surfaces.

Towards dynamic in situ observation of flax fibres under varying water contents through environmental SEM and X-ray tomography

Flax fibre represents one of the most promising natural components for the development of new innovative high-performance biobased composite materials. Their properties are closely related to the lumen, the central cavity of the fibre, which was only studied, to date, under unrealistic environments as in dry conditions. The objective of the current study is to characterise, at a micrometre-scale, the surface and volume modifications induced by exposure of fibres to humid atmospheres. Different dynamic characterization strategies have shown a significant opening of the hydrated lumen "channel". Values of this opening rate are discussed in the light of potential biases linked to the investigation technique (SEM versus X-ray tomography), and to the adopted acquisition approach (in situ versus ex situ). By eSEM, after a 5 min. exposure to the water-saturated environment for instance, the lumen opening value was measured at 36 ± 2% for ex-situ hydration of the bundles with a subsequent delamination of the fibre, while it was only 15 ± 2% when hydration was progressively conducted into the SEM chamber. By microtomography, the lumen swelling for the single fibre was estimated to be within the same order of magnitude, about 7%, after hydration and measurements performed under realistic atmospheric pressure.

Microscopic insights of phase-transition-induced vapor transport enhancement in porous media

Vapor transport in porous media, often associated with liquid-vapor phase change, is an fundamental process in many emerging underground energy storage and extraction processes (i.e., seasonal solar thermal aquifer storage, geothermal extraction, extraterrestrial in-situ water extraction). By jointly using experimental imaging and numerical modeling at the micro-scale, we conduct mechanistic pore scale investigation of capillarity-dominated phase change dynamics and its influence on vapor transport in partially saturated porous rock micromodel. Strongly linked to surface roughness and wettability condition, the capillarity hinders water vaporization from rock surface micro/nano-structures as observed under the environmental scanning electron microscope. By varying the contact angle of 0°, 60°, and 120°, the lattice Boltzmann simulation shows the wettability-dependent vaporization process of capillary-hold water, where pores with hydrophilic surfaces contains significantly more liquid water than that of the hydrophobic ones under the same temperature. When saturated vapor flows through rock porous patterns, capillarity further induces water condensation on the strongly water-wet surfaces. Water condensation, yet forming water bridges/islands and causing the blockage of vapor diffusion, enhances the vapor diffusion ability counterintuitively. The reduction of diffusion path is revealed as the main reason by assessing the local vapor pressure distribution before and after the pore filling by condensate. The findings support the debatable enhancement mechanisms postulated by Philip and de Vries. This work offers the insightful interfacial hydrodynamics of vapor transport in porous media and potentially provides operational guidance for geothermal applications and beyond.

Enhancing microbial-induced carbonate precipitation (MICP) sand consolidation with alkali-treated jute fibers

Recent research has focused on reinforcing sand consolidated through microbial-induced carbonate precipitation (MICP) with alkali-treated fibers to enhance its mechanical properties and mitigate brittleness. This research investigated how modified fiber affected the microstructure and properties of MICP solid sand. The fiber content (0, 0.5, 1, 3, and 5%), pretreatment concentration (0, 1, 5, 10, and 20%), pretreatment time (0, 0.5, 1, 2, and 4 h), and pretreatment temperature (25, 35, 45, and 55 °C) required for the experiment were determined by MICP testing. The interactions between fiber, sand, and calcium carbonate(CaCO3) were analyzed by calcium carbonate content(CaCO3(%)), unconfined compressive strength (UCS), environmental scanning electron microscopy (ESEM), and X-ray diffraction (XRD). The specimen without added fiber had a UCS of 2.13 MPa, the UCS of the added fiber sample was 2.8 MPa, which was 31.46% more than that of the specimen without added fiber, and the UCS of the specimen with added alkali-treated fiber was 3.62 MPa, which was 70% more than that of the specimen without added fiber and 28.57% more than that of the added untreated fiber. The optimum content of jute fibers was 0.5%, and the optimum concentration of alkali treatment of jute fibers was 10% for one hour.