Environmental Scanning Electron Microscopy Images Research Articles

Real-time imaging of oil shale pyrolysis dynamics at nanoscale via environmental scanning electron microscopy

Pyrolysis is a promising technology to increase pore and fracture connectivity in oil shale and thereby accomplish commercial recovery of unconventional hydrocarbons. Herein, real-time oil shale pyrolysis dynamics are imaged at nanoscale via environmental scanning electron microscopy (imaging resolution of 58 nm/pixel, imaging speed of 1 frame per second, and heating temperature up to 750 °C). It is counterintuitively observed that 1) inorganic nano-fractures started to appear below 100 °C; 2) inorganic nano-fracture width had a non-monotonous relationship with temperature; and 3) organic kerogen areas decreased monotonously with increasing temperature. These findings will establish a standard benchmark for unconventional resource recovery, promote fundamental understanding of oil shale pyrolysis dynamics at nanoscale and provide key guidance on oil shale extraction at reservoir scale.

Integrating continuous mineral-impregnated carbon fibers into digital fabrication with concrete

Digital concrete technologies, such as 3D concrete printing, have the potential to be game changers in the construction industry by reducing material consumption and offering a high level of automation. This not only provides a solution to the shortage of qualified workers but also makes construction sites more attractive workplaces. However, a significant challenge lies in integrating reinforcement, as traditional methods quickly reach their limits, particularly in geometrically complex, material-minimized structures. A potential solution is the use of mineral-impregnated carbon fibers (MCF) reinforcement, which offers high flexibility for 3D printing and better bonding to concrete compared to polymer coating, among other advantages. This article presents the integration of both freshly impregnated and cured MCF into two different concretes in the context of digital fabrication: 3D-printed concrete (3DPC) and self-compacting concrete (SCC). A particular focus was on the mechanical performance of MCF and MCF-reinforced concrete, as well as on the bond behavior between MCF and concrete. The second focus was on the production method. Therefore, samples were conventionally cast with SCC, while layered pouring or printing were used for producing specimens with 3DPC. It was found that the cured MCF exhibited a notably better bond, enhanced by 50%, to both 3DPC and SCC compared to freshly impregnated yarns. Subsequently, when subjected to uniaxial tensile loading, a significantly higher crack density and more uniform crack distribution could be observed in composites with cured MCF using digital image correlation (DIC). This effect was particularly pronounced in printed specimens and confirmed with computed tomography (CT) and environmental scanning electron microscope (ESEM) images.

Development of Curcumin and Turmerone Loaded Solid Lipid Nanoparticle for Topical Delivery: Optimization, Characterization and Skin Irritation Evaluation with 3D Tissue Model.

Curcuma longa L., commonly known as turmeric, is renowned for its therapeutic benefits attributed to bioactive compounds, namely curcumin (Cur) and aromatic turmerone (Tur), present in its rhizome. These compounds exhibit diverse therapeutic properties, including anti-inflammatory, antioxidant, and anti-tumor effects. However, the topical application of these compounds has a significant potential for inducing skin irritation. This study focuses on formulating solid lipid nanoparticle (SLN) carriers encapsulating both Cur and Tur for reduced irritation and enhanced stability. SLN formulations were prepared by a method using homogenization followed by ultrasonication procedures and optimized by applying response surface methodology (RSM). The optimized SLN formulation demonstrated entrapment efficiencies, with 77.21 ± 4.28% for Cur and 75.12 ± 2.51% for Tur. A size distribution of 292.11 ± 9.43 nm was obtained, which was confirmed to be a spherical and uniform shape via environmental scanning electron microscopy (ESEM) images. The in vitro release study indicated cumulative releases of 71.32 ± 3.73% for Cur and 67.23 ± 1.64% for Tur after 24 hours under sink conditions. Physical stability tests confirmed the stability of formulation, allowing storage at 4°C for a minimum of 60 days. Notably, in vitro skin irritation studies, utilizing the reconstructed human epidermal model (EPI-200-SIT), revealed a significant reduction in irritation with the SLN containing Cur and Tur compared to nonencapsulated Cur and Tur. These findings collectively endorse the optimized SLN formulation as a favorable delivery system for Cur and Tur in diverse topical uses, offering enhanced stability, controlled release and reduced irritation.

Interfacial properties of high-strength, limestone-calcined clay cement (LC3) matrix and PE fibers, surface-modified using dopamine and tannic acid

Polyethylene (PE) fibers exhibit superb mechanical and geometrical properties with respect to their use as dispersed reinforcement in cement-based materials. However, the fiber–matrix interaction in such composites is known to be poor due to the lack of active functional groups on the fibers’ polymeric backbones, leading to the limited affinity of PE fibers toward water-based, cementitious matrices. Therefore, to exploit the reinforcing effect of PE fibers in cementitious composites fully, fiber–matrix interactions need to be enhanced by functionalizing the fibers with hydrophilic polar groups. In the article at hand, the effects of dopamine (DA) and tannic acid (TA) surface functionalization and their combinations on interfacial properties with a high-strength, limestone-calcined clay cement (LC3) matrix have been explored. To assess the morphological changes as well as the physical–chemical properties of the fibers under investigation, they were characterized by environmental scanning electron microscopy (ESEM), Energy-dispersive X-ray spectroscopy (EDX), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and zeta-potential (ZP). The presence of a DA and TA (DA/TA) coating layer was confirmed by ESEM and AFM images for modified samples, which showed rougher surfaces along with uniform coating distributions, proven via mapping images as well. TGA results yielded coating amounts of 7.8, 1.5, 1.5, 2.3 and 1.0 wt% for samples with DA/TA portions of 100/0, 70/30, 50/50 and 30/70 and 0/100, respectively. Compared with the pristine PE fiber, the DA/TA surface modification of PE fibers improved the tensile strength and modulus of elasticity values by 29% and 36%, respectively. According to micromechanical investigations, maximum pullout force and interfacial shear strength in specimens with modified fibers were three times higher than for the reference fibers, while fiber pullout energy was as much as six times higher

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.

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.

In Situ Polycondensation Synthesis of NiS-g-C3N4 Nanocomposites for Catalytic Hydrogen Generation from NaBH4.

The nanocomposites of S@g-C3N4 and NiS-g-C3N4 were synthesized for catalytic hydrogen production from the methanolysis of sodium borohydride (NaBH4). Several experimental methods were applied to characterize these nanocomposites such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and environmental scanning electron microscopy (ESEM). The calculation of NiS crystallites revealed an average size of 8.0 nm. The ESEM and TEM images of S@g-C3N4 showed a 2D sheet structure and NiS-g-C3N4 nanocomposites showed the sheet materials that were broken up during the growth process, revealing more edge sites. The surface areas were 40, 50, 62, and 90 m2/g for S@g-C3N4, 0.5 wt.% NiS, 1.0 wt.% NiS, and 1.5 wt.% NiS, respectively. The pore volume of S@g-C3N4 was 0.18 cm3, which was reduced to 0.11 cm3 in 1.5 wt.% NiS owing to the incorporation of NiS particles into the nanosheet. We found that the in situ polycondensation preparation of S@g-C3N4 and NiS-g-C3N4 nanocomposites increased the porosity of the composites. The average values of the optical energy gap for S@g-C3N4 were 2.60 eV and decreased to 2.50, 2.40, and 2.30 eV as the NiS concentration increased from 0.5 to 1.5 wt.%. All NiS-g-C3N4 nanocomposite catalysts had an emission band that was visible in the 410-540 nm range and the intensity of this peak decreased as the NiS concentration increased from 0.5 to 1.5 wt.%. The hydrogen generation rates increased with increasing content of NiS nanosheet. Moreover, the sample 1.5 wt.% NiS showed the highest production rate of 8654 mL/g·min due to the homogeneous surface organization.

Inhibition of multi-species biofilm formation using chitosan-based film supplemented with essential oils

The biofilm development following microbial attachment on food-grade surfaces represents a main problem in the food sector, leading to significant economic losses. To overcome that, the present investigation aimed to develop biodegradable films that protect against heterogeneous biofilms using chitosan and essential oils (EOs). First, the cross-streak method revealed the absence of antagonism between Staphylococcus aureus, Enterococcus hirae, Escherichia coli, and Pseudomonas aeruginosa strains. The contact angle findings revealed a drop in the electron acceptor (γ+) and qualitative hydrophobicity (θw) associated with an increase in the Lifshitz-van Der Waals component (γLW) and electron donor (γ−) regarding the treated chitosan-based films (CH-films). The environmental scanning electron microscopy (ESEM) images showed that among all the treatments, the CH-film treated with the Pelargonium asperum EO exhibited the weakest antiadhesion activity (73.89 ± 1.42% of the covered surface) while the CH-film treated with the Pelargonium asperum, Thymus satureioides, Cinnamomum zeylanicum, and Eugenia caryophyllus EOs mixture had the strongest activity (9.23 ± 1.66% of the covered surface). From these results, the CH-film containing the EOs mixture presents a high potential for utilization in the food industry as an active coating and packaging that prevent the microorganisms' attachment and the eventual biofilm development.

The use of a time-fractional transport model for performing computational homogenisation of 2D heterogeneous media exhibiting memory effects

In this work, a two-dimensional time-fractional subdiffusion model is developed to investigate the underlying transport phenomena evolving in a binary medium comprised of two sub-domains occupied by homogeneous material. We utilise an unstructured mesh control volume method to validate the model against a derived semi-analytical solution for a class of two-layered problems. This generalised transport model is then used to perform computational homogenisation on various two-dimensional heterogenous porous media. A key contribution of our work is to extend the classical homogenisation theory to accommodate the new framework and show that the effective diffusivity tensor can be computed once the cell problems reach steady state at the microscopic scale. We verify the theory for binary media via a series of well-known test problems and then investigate media having inclusions that exhibit a molecular relaxation (memory) effect. Finally, we apply the generalised transport model to estimate the bound water diffusivity tensor on cellular structures obtained from environmental scanning electron microscope (ESEM) images for Spruce wood and Australian hardwood. A highlight of our work is that the computed diffusivity for the heterogeneous media with molecular relaxation is quite different from the classical diffusion cases, being dominated at steady-state by the material with memory effects.

Alleviation of metal stress in rape seedlings (Brassica napus L.) using the antimony-resistant plant growth-promoting rhizobacteria Cupriavidus sp. S-8-2

This study investigated an effective strategy for remediating antimony (Sb)-contaminated soil using the bacterial strain screened from Sb-contaminated fern rhizospheres due to its superior growth-promoting, heavy-metal(loid) resistant, and antibiotic-tolerant characteristics. The strain that belongs to Cupriavidus sp. was determined by 16S rRNA sequencing and showed no morphological changes when grown with high concentrations of Sb (608.8 mg/L). The strain showed prominent indole acetic acid (IAA), phosphate-solubilizing abilities, and ACC deaminase activity under Sb stress. Moreover, IAA and soluble phosphate levels increased in the presence of 608.8 mg/L Sb. Inoculation of rape seedlings with Cupriavidus sp. S-8-2 enhanced several morphological and biochemical growth features compared to untreated seedlings grown under Sb stress. Inoculation of Cupriavidus sp. S-8-2 increased root weight by more than four-fold for fresh weight and over two-fold for dry weight, despite high environmental Sb. The strain also reduced Sb-mediated oxidative stress and malondialdehyde contents by reducing Sb absorption, thus alleviating Sb-induced toxicity. Environmental Scanning Electron Microscope (ESEM) imaging and dilution plating technique revealed Cupriavidus sp. S-8-2 is localized on the surface of roots. Identifying the Sb-resistant plant growth-promoting bacterium suggested its usefulness in the remediation of contaminated agricultural soil and for the promotion of crop growth. We highly recommend the strain for further implementation in field experiments.

Pore‐scale simulation of mucilage drainage

AbstractCompared with bulk soil, rhizosphere has different properties because of the existence of root mucilage, which affects physical, chemical, and microbial processes. The slow response of rhizosphere to changes in water potential buffers water content changes and leads the rhizosphere to be wetter than bulk soil during drying. By affecting connectivity of the liquid and gas phases, mucilage can also influence solute transport and gas diffusion. Overview of the literature and previous models shows the lack of a model that describes the connectivity between different phases in the rhizosphere pore space during wetting and drying processes. A major challenge is that mucilage shows a complex behavior, which at low concentrations is more like a liquid, whereas at higher concentration, dry mucilage becomes a solid. In between, a viscoelastic state is observed where mucilage can be considered as a hydrogel. In this study a three‐dimensional pore‐scale model based on the lattice spring method is introduced and used to simulate drying of mucilage between two soil particles. The model is capable of reproducing spider‐web‐like structures that are specific for mucilage. This three‐dimensional mucilage drying model is qualitatively validated via environmental scanning electron microscopy (ESEM) images of dry mucilage between glass beads. The proposed model may provide us with a new perspective on hydrodynamic processes within the pore space of the rhizosphere. In addition, the model may help to better understand further important processes that strongly depend on rhizosphere hydraulic dynamics, such as solute transport, connectivity of the liquid phase, root penetration resistance, rhizosheath formation, and microbial activity.

Surface aspects and multifractal features of 3D spatial patterns of low-cost Amazon açaí-loaded kefir microbial films.

In this study, açaí-loaded kefir microbial films obtained in solutions containing demerara sugar, a low-cost and relatively organic sugar, were prepared. Environmental scanning electron microscopy (ESEM), atomic force microscopy (AFM), stereometric and multifractal analyses were applied to study the influence of the concentration of açaí over the surface morphology as well as its multifractal nature. The ESEM and AFM images showed that low concentrations of acai berry form surface covered by bacteria, while higher concentrations promote yeast growth. The autocorrelation function suggested that the degree of surface anisotropy changes as the concentration of açaí increases, while the Minkowski Functionals confirmed that the sample with the highest content has a different morphology than the samples containing 10-40 ml. The multifractal analysis revealed that the surfaces have a strong multifractal behavior, where the multifractal singularity strength was higher in the sample containing the highest concentration of açaí. The sample with the highest concentration was then mapped to have a greater vertical growth of its spatial patterns. These results prove that image analysis using mathematical tools can be very useful for the characterization of biological-based systems for application in the biomedicine field. We characterized the micromorphology of the 3D surface of the kefir biofilms associated with Acai extract. The 3D surface analysis of the samples was performed using by environmental scanning electron microscope and atomic force microscopy. We determined the multifractal and Minkowski Functionals of the analyzed samples.

Evaluation of Different Agitation Techniques on Smear Layer Formation and Dentine Erosions- An In Vitro Study.

This study was performed to assess smear layer formation and erosion after final irrigation protocols with metal and non-metal tips in the apical third of root canals. Forty mandibular premolars were instrumented with ProTaper Gold files up to F3 and embedded in a closed silicone flask system. The teeth were subsequently cleaved and 4 sequential indentations (1 to 4 mm from the apical foramen) were prepared on the buccal root canal walls to standardize sites for environmental scanning electron microscopy (ESEM) imaging. The samples were cleaned in an ultrasonic bath and observed under ESEM (controls), reassembled and divided into four groups (n=10 each) and subjected to different final irrigation protocols; XPF Group (XP-endo Finisher) and PUI Group (passive ultrasonic irrigation) with metal tips; EA Group (EndoActivator) and MDA Group (Manual dynamic agitation) with non-metal tips. The smear layer formation and dentine erosion were evaluated using ESEM. The data were analyzed with Kruskal-Wallis test with Bonferroni correction. In comparison to the control groups, XPF group had significantly increased smear layer formation at 1 and 2 mm (P<0.05). PUI group had significantly higher smear layer (P<0.05) formation at 3mm while EA and MDA groups did not present with significantly higher smear layer at all levels. Erosion was significantly higher (P<0.05) in MDA, XPF and PUI groups at all levels when compared to controls while EA group presented with significantly more erosion only at 2 and 3 mm. Final irrigation protocol using EA and MDA with non-metal tips did not result in significant smear layer formation. Dentine erosion was observed after all experimental irrigation protocols. (EEJ-2021-12-194).

Chitosan-Based Functional Films Integrated with Magnolol: Characterization, Antioxidant and Antimicrobial Activity and Pork Preservation.

The aims of this study were to develop the magnolol–chitosan films and study the positive effect of the combination of magnolol and chitosan. The addition of magnolol made the magnolol–chitosan films exhibit higher density (1.06–1.87 g/cm3), but the relatively lower water vapor permeability (12.06–7.36 × 10−11·g·m−1·s−1·Pa−1) and water content (16.10–10.64%). The dense and smooth surface and cross-section of magnolol–chitosan films were observed by environmental scanning electron microscopy (ESEM) images. The interaction of magnolol and chitosan was observed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). After the addition of magnolol, the antioxidant capacity of magnolol–chitosan films was increased from 18.99 to 82.00%, the growth of P. aeruginosa was inhibited and the inhibition percentage of biofilm formation was increased from 30.89 to 86.04%. We further verified that the application of magnolol–chitosan films on chilled pork significantly reduced the increases in pH value, inhibited the growth of microorganisms and extended the shelf life. Results suggest that magnolol had a positive effect on magnolol–chitosan films and could be effectively applied to pork preservation.

Characterization of Eocene flint

Eocene flint 48–56.0 million years old (mya) from the Negev desert (Israel) was characterized using a suite of analytical techniques. High-resolution transmission electron microscopy (HR-TEM) and selected area electron diffraction (SAED) of the inorganic component showed the texture, morphology, size, and distribution of two silica polymorphs: α–quartz and moganite. While euhedral forms were attributed to α-quartz, moganite crystals were comprised of spherulitic grains. An electron less-dense amorphous material (no scattering under SAED) was found between the siliceous crystallites. Energy dispersive X-rays (EDS) and electron energy loss spectroscopy (EELS) demonstrated that this electron less-dense amorphous material is composed solely of carbon. Low vacuum, low energy backscattered environmental scanning electron microscopy (BSE-eSEM) imaging of flint surfaces showed the presence of micrometer-sized organic inclusions randomly distributed throughout the siliceous matrix. Energy-dispersive X-ray studies (EDS) demonstrated that these organic micro-inclusions were composed of carbon, sulfur, and nitrogen with a C/N ratio attributed to marine sources. These micro-inclusions were not directly associated with hard-shell fossils. BSE-eSEM imaging conditions allowed the identification of entrapped carbon-rich organic material, which is not possible when applying commonly used electron microscopy conditions that require carbon coating and high acceleration voltages, rendering carbon-rich features electron-transparent. Phase contrast-enhanced micro-computed tomography (PC-μCT) showed that these organic micro-inclusions were randomly distributed throughout the siliceous matrix.Time-of-flight secondary ion mass spectrometry (ToF-SIMS), nano-Fourier transform infrared spectroscopy (nano-FTIR), and scanning probe microscopy (SPM) were used to further characterize these organic micro-inclusions. These three in situ analytical techniques with nanometer resolution provided complementary information on the chemical composition and structure of the organic material. Specifically, ToF-SIMS analysis revealed amino acid and hydrocarbon mass spectra fingerprints inside the organic micro-inclusions. While the former were exclusively found in the organic micro-inclusions, the mass spectral fingerprints for hydrocarbons were also found in the siliceous matrix in agreement with the HR-TEM/EDS/EELS results, where pure carbon was found between the siliceous nanocrystals. While ToF-SIMS provides chemical information, it does not provide structural information. Nano-FTIR analysis showed the presence of amide I and II infrared vibrations exclusively on the organic micro-inclusions. The scanning probe microscopy (SPM) techniques Peak Force Quantitative Nanomechanics (PF-QNM) and Contact Resonance Atomic Force Microscopy (CR-AFM) were used to assess the mechanical properties. PF-QNM measurements on the organic micro-inclusions, under dry and liquid conditions, demonstrated that the organic micro-inclusions swell upon hydration and soften, pointing toward the presence of hydrophilic molecules in agreement with nano-FTIR and ToF-SIMS results. CR-AFM allows in situ determination of the mechanical properties of materials with high stiffness at nanometer resolution. This technique, rarely used in a geological context, revealed that the organic micro-inclusions had an unusually high stiffness atypical for modern organic material, which was attributed to molecular cross-linking promoted by diagenesis.This work provided a comprehensive view of the inorganic and organic components of Eocene flint from the Negev desert with implications for paleontology and archaeology. It offers a roadmap of novel complementary techniques that can be used in the exploration of entrapped organic material in flint.

Characterization of the Microstructure of the Cement-Rock Interface Using Environmental Scanning Electron Microscopy and Micro-Computed Tomography Scan

Summary Cement-rock interface is a major component of the wellbore barrier system. Leakage may result from the poor bonding between cement and rock interface. In this paper we investigate possible factors that may affect the cement-rock interface bonding. More specifically, integrity of the cement-rock interface was characterized using micro-computed tomography (CT) and environmental scanning electron microscopy (ESEM). Hollow cylinder rock samples were prepared by using rock samples (e.g., Banff dolostone, Pekisko limestone, Doig sandstone, Notikewin siltstone, Montney siltstone, and Wilrich siltstone) collected from different Alberta wells at various depths. Two abandonment cement blends were injected into the rock open hole. After curing the cement-rock samples in water at ambient temperature (≈21°C) and 1,500 psi for 7 days, the samples were then processed into thin sections. By using ESEM (0.05-µm resolution) and micro-CT (11.92-µm resolution) techniques, the 2D and 3D models of the cement-rock interface were developed. Energy-dispersive X-ray spectroscopy (EDS) was conducted to analyze chemical characteristic of the cement-rock samples. Using the CT images, computational fluid dynamics (CFD) models were built to simulate fluid flow through the cement-rock samples. For both cement and rock, there is a nonuniform porosity distribution in radial and axial directions. For most of the cement-rock samples, the highest porosity region in the cement column was found at the cement-rock interface. Optimizing the chemistry of the cement system enhances the cement-rock interface bond by effectively reducing the gap between cement and rock observed in ESEM images. Although cement migration was observed in the rough rock surface in porous rocks, the rock interface and matrix zones have almost identical element concentrations. For the investigated samples, the chance for significant chemical reaction at the cement-rock interface is minimal. CFD simulation based on digital cement models showed that the cement-rock interface has more chance to act as the main flow pathway when intact (low permeability) caprock exists. The sample preparation, image analysis and simulation methods used in this study can be also applied to other cement interface studies (e.g., cement-casing, casing-cement-rock). From the practical field application point of view, the results presented here would help to have a better understanding of the requirements for designing optimum cement formulations to establish effective zonal isolation and reduce the greenhouse gas emissions from oil and gas wells.

In situ evaluation of desensitizing toothpastes for protecting against erosive tooth wear and its characterization

This five-phase, single-blind, crossover in situ trial evaluated the effects of desensitizing or anti-erosive toothpastes on dentin erosive wear and tubule occlusion. Some characteristics such as relative dentin abrasivity (RDA), viscosity (V), cytotoxicity, and fluoride and calcium (Ca) availability of the toothpastes were also tested. Samples were positioned on removable intraoral appliances from 15 volunteers (n=4), according to the groups, C-control (0 ppm fluoride), F-sodium monofluorophosphate (MFP), A-MFP and arginine+calcium carbonate, CSP-calcium sodium phosphosilicate, and CS-MFP and calcium silicate+sodium phosphate. Erosion-abrasion cycling was performed (1% citric acid, 2min, 6×/day; toothbrushing, 5s, 2×/day). Surface loss (SL) was evaluated by optical profilometry. Environmental scanning electron microscopy images (ESEM) counted the number of open dentin tubules (ODTs). Data were statistically analyzed (α=0.05). There were no significant differences in SL among groups (p=0.468). The ODT for CSP, CS, and A groups were significantly lower than the control. CSP and CS presented significantly less ODT than F, but they did not significantly differ from A. F and CS were more abrasive than all the other toothpastes; CSP was more abrasive than A, and C was the least abrasive. CSP presented higher V (p<0.05). All toothpastes presented lower cell viability than the control without toothpaste exposure. F and A presented significantly higher values of F- (p<0.05). All fluoride toothpastes had similar amount of Ca, differing from the control (p<0.05). Although the toothpastes caused similar degree of erosive wear, CSP and CS were able to occlude the dentin tubules. Desensitizing toothpastes containing calcium, sodium, phosphate, and silicate could be a suitable option for treating dentin hypersensitivity.

Formula optimization of thermosensitive biological sol–gel carrier for EOR surfactants by rheological investigation

Adsorption loss of surfactants by rock formations reduces surfactant efficiency and increases cost. We propose a new approach to solve this problem. Xanthan gum/locust bean gum (XLB) and xanthan gum/konjac glucomannan (XKG) were chosen as surfactant carriers. Both XLB and XKG are thermosensitive; they are in a gel state at low temperature and sol state at high temperature. When the temperature near an injection well is low, gelled carriers can shield surfactant charge and reduce adsorption loss of surfactants by the formation. A high temperature deep in the reservoir transforms the carriers into a sol state to release the surfactants. In this way, the transport distance of the surfactants is increased, which enables the surfactants to contact more crude oil. The effects of ratio, pH, and salinity on the rheological properties of the XLB and XKG systems were evaluated to optimize the formulation and define the sol–gel transition temperature (Tsol/gel). The storage modulus and loss modulus of the system was affected by the ratio of rigid glue (XG) and flexible glue (LBG and KGM). Adding acid or base weakened the shear modulus, CaCl2 and NaCl had little effect on the shear modulus, and KCl significantly increased this property. The shear modulus of these two systems was greatest when the two biogels were mixed in equal proportion, the pH was not adjusted, and 3% KCl was added. Environmental scanning electron microscopy images revealed that KCl transformed the loose porous crosslinked structure into a dense lamellar structure. Sodium lauryl sulfate (SDS) and hexadecyl dimethylamine betaine had little influence on the shear modulus of the system, while cetyl trimethyl ammonium bromide prevented the systems from gelatinizing. The zeta potential and surface tension of XLG (XLB with 2% KCl) and XKG (XKG with 2% KCl) with 3% SDS were measured. The absolute values of their zeta potentials in the gel state were smaller than those in the sol state, which indicates that XLG and XKG effectively shielded surfactant charge. The surface tension decreased with increasing temperature. When the temperature was higher than the Tsol/gel, the gel melted completely and the surface tension was almost unchanged. This indicates that the surfactants were released slowly by the carriers before melting was complete. Both XLG and XKG proved to be efficient carriers for surfactants that are used for oil displacement.

Studying the anti-ageing performance of road asphalt based on penetration and ductility

The existing research on modified asphalt is primarily focused on how to improve the high- and low-temperature performances (high-temperature rutting and low-temperature cracking) of asphalt, but the improvement of the anti-ageing performance of asphalt is also important. The research objects of the present study were equivalent-penetration (high-temperature performance) and equivalent-ductility (low-temperature performance) asphalt specimens, and the anti-ageing performances of different specimens were compared from both the macro- and micro-perspectives. From the macro-perspective, taking the penetration, ductility, viscosity and softening point of asphalt as the experimental indexes, the anti-ageing performances of different asphalt specimens were compared and analysed based on the changes in different indicators at different ageing times. From the micro-perspective, the macro-test results of asphalt specimens with different durabilities were verified by an asphalt component test and the analysis of environmental scanning electron microscopy images. The research results have certain theoretical value for scientifically understanding the technical characteristics of different modifiers, the research and development of modifiers and the formation mechanism of modified asphalt.

Irrigant Agitation Techniques versus Passive Ultrasonic Irrigation for Removing Debris from Curved Root Canals: An Environmental Scanning Electron Microscopic Study.

The aim of this study was to compare the efficacy of passive ultrasonic irrigation (PUI) versus mechanical agitation of the irrigant promoted by the EasyClean (EC) and XP-Endo Finisher (XP-F) systems in removing debris from root canal walls, using environmental scanning electron microscopy (ESEM). Twelve curved mesiobuccal canals of mandibular molars were prepared with the ProTaper Next system up to file X2 (25/0.06). The specimens were embedded in flasks containing silicone putty, sectioned lengthwise, and a 4-mm long groove was made on the canal wall of the buccal half of the specimen, extending from 2 mm up to 6 mm short of the apex. Five cross-sectional markings were made along this groove to establish standardized locations for imaging. The same specimens were used to prepare a negative control group (without debris), a positive control group (completely covered by debris), and 3 experimental groups according to the final irrigation protocol employed: PUI, EC or XP-F. ESEM images were obtained and evaluated by 3 examiners. The amount of debris observed on the images was classified according to a 4-category scoring system. The kappa test was used to assess inter-examiner agreement, and the Kruskal-Wallis and Dunn tests were used to compare the scores (P<0.05). The scores attributed to the PUI, EC, and XP-F groups were statistically similar to those attributed to the negative control group (P>0.05). Based on this in-vitro study, the mechanical agitation of the irrigant promoted by EC and XP-F was as effective as using PUI to remove debris from the root canal walls.