Search Results (751)

Magnetotactic bacteria (MTB), a unique group of Gram-negative prokaryotes, have the remarkable ability to biomineralize magnetic nanoparticles (MNPs) intracellularly, making them promising candidates for various biomedical applications such as biosensors, drug delivery, imaging contrast agents, and cancer-targeted therapies. To fully exploit the potential of MTB, a precise understanding of the structural, surface, and functional properties of these biologically produced nanoparticles is required. Given these concerns, this review provides a focused synthesis of the most widely used microscopic and spectroscopic methods applied in the characterization of MTB and their associated MNPs, covering the latest research from January 2022 to May 2025. Specifically, various optical microscopy techniques (e.g., transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AFM)) and spectroscopic approaches (e.g., localized surface plasmon resonance (LSPR), surface-enhanced Raman scattering (SERS), and X-ray photoelectron spectroscopy (XPS)) relevant to ultrasensitive MTB biosensor development are herein discussed and compared in term of their advantages and disadvantages. Overall, the novelty of this work lies in its clarity and structure, aiming to consolidate and simplify access to the most current and effective characterization techniques. Furthermore, several gaps in the characterization methods of MTB were identified, and new directions of methods that can be integrated into the study, analysis, and characterization of these bacteria are suggested in exhaustive manner. Finally, to the authors’ knowledge, this is the first comprehensive overview of characterization techniques that could serve as a practical resource for both younger and more experienced researchers seeking to optimize the use of MTB in the development of advanced biosensing systems and other biomedical tools. Full article

This study investigates the development of a fully rubberized fine-aggregate engineered geopolymer composite (R-EGC) by replacing quartz sand with waste rubber particles (RPs). The influence of the rubber aggregate-to-binder mass ratio (A/B) on the performance of the R-EGC was systematically examined from both macroscopic and microscopic perspectives. Quantitative analysis of crack width and number was conducted using binarized image-processing techniques to elucidate the crack propagation patterns. Moreover, scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were employed to analyze the interfacial transition zone (ITZ) between the rubber aggregates and the geopolymer matrix under varying A/B ratios, aiming to explore the underlying failure mechanisms of the R-EGC. The research results indicated that the flowability of the R-EGC decreased gradually with increasing A/B ratio. The flowability of R-0.1 was 73.5%, outperforming R-0.2 and R-0.3 (66% and 65%, respectively). R-0.1 achieved the highest compressive strength of 35.3 MPa (compared to 31.2 MPa and 28.4 MPa for R-0.2 and R-0.3, respectively). R-0.3 demonstrated the most effective crack-control capability, with a tensile strength of 3.96 MPa (representing increases of 11.9% and 3.7% compared to R-0.1 and R-0.2, respectively) and the smallest crack width of 104 μm (indicating reductions of 20.6% and 43.5% compared to R-0.1 and R-0.2, respectively). R-0.2 exhibited the best ductility, with an ultimate tensile strain of 8.33%. Microstructural tests revealed that the interfacial transition zone (ITZ) widths for R-0.1, R-0.2, and R-0.3 were 2.47 μm, 4.53 μm, and 1.09 μm, respectively. An appropriate increase in the ITZ width was found to be beneficial for enhancing tensile ductility, but it compromised the crack-control ability of the R-EGC, thereby reducing its durability. Overall, this study clarifies the fundamental influence of the A/B ratio on the mechanical performance of the R-EGC. The findings provide valuable insights for future research in this field. Full article

This study presents an innovative solution to improve the mechanical performance of traditional cemented tailings backfill (CTB) by incorporating 3D-printed polymer lattice (3DPPL) reinforcements. We systematically investigated three distinct 3DPPL configurations (four-column FC, six-column SC, and cross-shaped CO) through comprehensive experimental methods including Brazilian splitting tests, digital image correlation (DIC), and scanning electron microscopy (SEM). The results show that the 3DPPL reinforcement significantly enhances the CTB’s tensile properties, with the CO structure demonstrating the most substantial improvement—increasing the tensile strength by 85.6% (to 0.386 MPa) at a cement-to-tailings ratio of 1:8. The 3DPPL-modified CTB exhibited superior ductility and progressive failure characteristics, as evidenced by multi-stage load-deflection behavior and a significantly higher strain capacity (41.698–51.765%) compared to unreinforced specimens (2.504–4.841%). The reinforcement mechanism involved synergistic effects of macroscopic truss behavior and microscopic interfacial bonding, which effectively redistributed the stress and dissipated energy. This multi-scale approach successfully transforms CTB’s failure mode from brittle to progressive while optimizing both strength and toughness, providing a promising advancement for mine backfill material design. Full article

Previous research on geopolymers has not fully established their porosity and its influence on the matrix structure, as well as its relevance to mechanical and durability properties, supporting the potential of this material as a sustainable alternative to traditional construction materials. In this study, three geopolymer mortar (GM) mixtures were prepared: the first was obtained with fly ash (FA) without mechanical grinding (GM_FA), the second with FA that required crushing and sieving through a #200 sieve (GM_FA_200), and the third was a GM with FA that required crushing and sieving through a #325 sieve (GM_FA_325). The main objective was to evaluate the porosity of the geopolymeric paste and the interfacial transition zone (ITZ) between the aggregate and the geopolymerization products. Due to the susceptibility of this area to develop higher porosity, which leads to reduced mechanical properties and durability, it has become a significant focus of investigation in materials such as concrete and mortar. These analyses were carried out using physical adsorption of gases (PAG), and a methodology for image analysis of GM microporosity was implemented using micrographs obtained from a scanning electron microscope (SEM) and processed with the NI Vision Assistant 8.6 software (VA). The results from both image analysis and physical adsorption demonstrated that the GM_FA_325 matrix exhibited 19% less porosity compared to the GM_FA matrix. The results confirmed that GMs are predominantly mesoporous. It was observed that GM_FA_325 has the lowest total porosity, resulting in a denser and more compact microstructure, which is a key factor in its mechanical performance and potential applications as an eco-friendly construction material for coatings and precast elements such as blocks, panels, and similar products. In addition, image analysis using VA is highlighted as an efficient, cost-effective, and complementary technique to PAG, enabling robust results and resource optimization. Full article

Grouting is an effective method for enhancing the stability of poor strata such as sand layers. The performance of the grouting materials directly influences the effect of stratum reinforcement. To meet the urgent demand for efficient grouting materials, this study selected a high-permeability, flexible polymer (PFP) as the grouting material. The influences of the PFP content, curing time, and dry density on the mechanical and impermeable properties of PFP-improved sand were systematically analyzed via unconfined compressive tests, split tensile tests, and variable head permeability tests. Moreover, the section morphology and pore characteristics of the PFP-improved sand were qualitatively described and quantitatively analyzed by scanning electron microscopy (SEM) and image processing software. The results indicated that the mechanical properties and impermeability of the test sand were significantly improved by adding the PFP, and the improvement effect continued to increase with increasing PFP content, curing time, and dry density. The compressive strength and splitting tensile strength of PFP30 (PFP content of 30%, curing time of 28 d, dry density of 1.5 g/cm³) reached 8.3 MPa and 1.4 MPa, respectively. The permeability coefficient reduced to 5.41 × 10⁻⁶ cm/s. The microscopic results revealed that the PFP effectively cemented the isolated sand particles through bridging, filling, and encapsulation as well as substantially filled the internal pores of the test sand. The percentage of the pore area, the total number of pores, and the maximum pore diameter of the test sand were significantly reduced. The pore area percentage, the total number of pores, and the maximum pore diameter of PFP30 were reduced to 0.124, 30, and 213.84 μm, respectively. This study reveals that PFP has potential for application in the grouting construction of poor strata, such as sand layers. Full article

A flexible and highly sensitive piezoresistive strain sensor was fabricated through the application of CO₂ laser ablation on a composite film composed of multi-walled carbon nanotubes, carbon black, and polydimethylsiloxane (MWCNT/CB/PDMS). The results of scanning electron microscopy (SEM) surface analysis shows that the “bush-like” conductive structure on the PDMS-based composite material membrane post-laser ablation is formed. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) spectra of the ablation products indicated the formation of an amorphous carbon layer on the surface of carbon nanomaterials due to laser ablation. Experimental findings revealed that the sensitivity (GF) value of the sensor based on CNT0.6CB1.0-P3.0 is up to 584.7 at 5% strain, which is approximately 14% higher than the sensitivity 513 of the sensor previously prepared by the author using CO₂ laser ablation of MWCNT/PDMS composite films. The addition of a very small volume fraction of CB particles significantly enhances the piezoresistive sensitivity of the sensor samples. Combined with the qualitative analysis of microscopic morphology characterization, CB and MWCNT synergistically promote the deposition of amorphous carbon. This phenomenon increases the probability of tunnel effect occurrence in the strain response region of the sensor, which indirectly confirms the synergistic enhancement effect of the combined action of CB and MWCNT on the piezoresistive sensitivity of the sensor. Full article

Although diverse and abundant, the phylum Bryozoa has been the subject of few studies in Costa Rica. Nearly 50 years have passed since Banta and Carson identified, described, and published twenty-four bryozoan species, including scanning electron microscope (SEM) images. To expand the knowledge of bryozoan diversity in the region, we sampled shallow coastal waters along the northern Pacific coast of Costa Rica and extracted tissue for DNA barcoding using the mitochondrial COI marker. Photographs of living specimens and SEM images were taken for morphological identification. We identified fifteen individuals belonging to nine bryozoan species from the orders Cyclostomatida and Cheilostomatida. Five of these species represent new records for Costa Rica (Savignyella lafontii, Bugula neritina, Watersipora arcuata, Smittipora levinseni, and Biflustra tenuis), while the remaining four (Disporella sp., Parasmittina crosslandi, Cigclisula sp., and Biflustra sp.) had been previously reported. Full article

In this study, multi-walled carbon nanotubes (MWCNTs) were uniformly applied to polyethylene terephthalate (PET) film using a bar-coating method to fabricate conductive thin films, and their transmittance, surface morphology, and effects on the heating and electrical properties of cement composites were analyzed. The experimental parameters considered were the mixing method, MWCNT concentrations, use or absence of coating films, applied voltages, and electrode spacings. Considering these parameters, the cement composites were divided into a total of four groups and then fabricated. Group 1 is a method for fabricating plain cement composites (PCCs), while Group 2 is a method for fabricating PCC using only MWCNT-coated films. Group 3 is a method for fabricating PCC by adding only MWCNT dispersion, and finally, Group 4 is a method for fabricating PCC using both MWCNT dispersion and MWCNT-coated films. Furthermore, field emission scanning electron microscope (FE-SEM) image analysis confirmed that MWCNT were evenly distributed across the entire front surface of the PET film and formed a dense network structure. The experimental results of cement composites using these showed that when both MWCNT dispersion and MWCNT-coated films were used, the electrical resistance was significantly reduced and the heating performance was improved. In particular, when the electrode spacing was 40 mm and the applied voltage was 30 V, the MDCF-0.75 specimen exhibited the highest heating performance and the lowest electrical resistance. Full article

Sandstone reservoirs exhibit strong heterogeneity and complex microscopic pore structures, presenting challenges for quantitative characterization. This study investigates the Chang 8 tight sandstone reservoir in the Jiyuan, Ordos Basin through analyses of its physical properties, high-pressure mercury injection (HPMI), casting thin sections (CTS), and scanning electron microscopy (SEM). Deep learning techniques were employed to extract the geometric parameters of the pores from the SEM images. Fractal geometry was applied for the combined quantitative characterization of pore parameters and fractal dimensions of the tight sandstone. This study also analyzed the correlations between the fractal dimensions, sample properties, pore structure, geometric parameters, and mineral content. The results indicate that the HPMI-derived fractal dimension (D_MIP) reflects pore connectivity and permeability. D_MIP gradually increases from Type I to Type III reservoirs, indicating deteriorating pore connectivity and increasing reservoir heterogeneity. The average fractal dimensions of the small and large pore-throats are 2.16 and 2.52, respectively, indicating greater complexity in the large pore-throat structures. The SEM-derived fractal dimension (D_SEM) reflects the diversity of pore shapes and the complexity of the micro-scale geometries. As the reservoir quality decreases, the pore structure becomes more complex, and the pore morphology exhibits increased irregularity. D_MIP and D_SEM values range from 2.21 to 2.49 and 1.01 to 1.28, respectively, providing a comprehensive quantitative characterization of multiple pore structure characteristics. The fractal dimension shows negative correlations with permeability, porosity, median radius, maximum mercury intrusion saturation, mercury withdrawal efficiency, and sorting factor, while showing a positive correlation with median and displacement pressures. Among these factors, the correlations with the maximum mercury intrusion saturation and sorting factor are the strongest (R² > 0.8). Additionally, the fractal dimension is negatively correlated with pore circularity and major axis length, but positively correlated with pore perimeter, aspect ratio, and solidity. A higher proportion of circular pores and fewer irregular or long-strip pores correspond to lower fractal dimensions. Furthermore, mineral composition influences the fractal dimension, showing negative correlations with feldspar, quartz, and chlorite concentrations, and a positive correlation with carbonate content. This study provides new perspectives for the quantitative characterization of pore structures in tight sandstone reservoirs, enhances the understanding of low-permeability formation reservoir performance, and establishes a theoretical foundation for reservoir evaluation and exploration development in the study area. Full article

This study takes limestone crushed stone concrete as the research object and systematically investigates its mechanical property changes and microstructural damage characteristics under different confining pressures using triaxial compression tests, scanning electron microscope (SEM) tests, and digital image processing techniques. The results show that, in terms of macro-mechanical properties, as the confining pressure increases, the peak strength increases by 192.66%, the axial peak strain increases by 143.66%, the elastic modulus increases by 133.98%, and the ductility coefficient increases by 54.61%. In terms of microstructure, the porosity decreases by 64.35%, the maximum pore diameter decreases by 75.69%, the fractal dimension decreases by 19.56%, and the interfacial transition zone cracks gradually extend into the aggregate interior. The optimization of the microstructure makes the concrete more compact, reduces stress concentration, and thereby enhances the macro-mechanical properties. Additionally, the failure characteristics of the specimens shift from diagonal shear failure to compressive flow failure. According to the Mohr–Coulomb strength criterion, the calculated cohesion is 6.96 MPa, the internal friction angle is 38.89°, and the breakage angle is 25.53°. A regression analysis established a quantitative relationship between microstructural characteristics and macro-mechanical properties, revealing the significant impact of microstructural characteristics on macro-mechanical properties. Under low confining pressure, early volumetric expansion and rapid volumetric strain occur, with microcracks mainly concentrated at the aggregate interface that are relatively wide. Under high confining pressure, volumetric expansion is delayed, volumetric strain increases slowly, and microcracks extend into the interior of the aggregate, becoming finer and more dispersed. Full article

Carbonate rock slopes in reservoir environments are increasingly exposed to dissolution-induced deterioration due to water level fluctuations. However, the influence of internal structures—particularly calcite veins—on dissolution behavior remains inadequately understood. The acid-induced dissolution of limestone by a sulfuric acid solution leads to the removal of soluble minerals and changes to the rock structure. Natural variation in rock structures—particularly in the presence, density, and morphology of calcite veins—can significantly affect the dissolution process and its outcomes. In this study, we obtained three types of Triassic limestone from the same host rock but with varying vein structures from the Three Gorges Reservoir area. Cylindrical rock specimens were prepared to investigate the acid-induced dissolution behavior of limestone in a sulfuric acid solution. We identified and analyzed the macrostructures on the rock specimens before and after the interaction. Additionally, SEM was employed to observe the microstructures of the specimens before and after the acid-induced dissolution, and fractal dimension analysis was conducted on the SEM images to quantify surface complexity. Furthermore, we used a focused ion beam–scanning electron microscope (FIB-SEM) with an automatic mineral identification and characterization system, as well as mineral roundness calculation, for mineral identification and analysis. Based on the experiments and analyses, we determined the following: The contact surfaces between the host rock and the calcite veins increase the dissolution areas between the limestone and the sulfuric acid solution, intensifying the dissolution reactions, enhancing the connectivity of the original microstructural planes, and generating new, highly extended dissolution fissures. The calcite veins facilitate the entry of sulfuric acid solution into the limestone, intensifying the dissolution of the edges and corners of dolomite and resulting in the gradual rounding of dolomite shapes. Quantitatively, the limestone with dense, fine calcite veins exhibited the most severe dissolution, with water absorption rates nearly twice as high as the non-veined samples (0.13% vs. 0.07%), a 2.2% reduction in fractal dimension, and a 19.53% increase in dolomite roundness with the 1 ≤ R ≤ 3 interval, indicating significantly enhanced surface complexity and mineral reshaping. In summary, the presence of more calcite veins, regardless of their width, leads to more severe rock dissolution. Full article

The corrosion mechanism of concrete structures in landfills in cold regions is complex, and there are few existing studies that address multifactorial coupled deterioration scenarios. Since loading and freeze-thaw cycles affect concrete deterioration, this study included three test groups—landfill leachate, loaded-landfill leachate, and freeze-thaw cycles-loaded-landfill leachate—and three different corrosion scenarios—gas-liquid, liquid-solid, and gas-liquid-solid. The physico-mechanical changes in concrete in terms of mass, compressive strength, and dynamic elasticity modulus were analyzed, and the deterioration mechanism of concrete was elaborated by its apparent morphology and scanning electron microscope (SEM) images. The study showed that the most serious damage to concrete was caused by freeze-thaw cycles, loading, and landfill leachate coupled in multifactorial situations. The compressive strength and dynamic elastic modulus decreased; the endpoints decreased by 15.75% and 7.42%, respectively, and increased by 12.51% and 6.74% compared with the unapplied load group. The concrete in the gas-liquid-solid test group had the most serious damage among the corrosion scenarios, with a 21.63% decrease in compressive strength. This study determined the most unfavorable corrosion conditions for concrete structures in landfills in cold regions and the corrosion mechanism of concrete exposed to landfill leachate and provides a technical reference for the construction of landfill facilities. Full article

Advanced packaging represents a crucial technological evolution aimed at overcoming limitations posed by Moore’s Law, driving the semiconductor industry from two-dimensional toward three-dimensional integrated structures. The increasing complexity and miniaturization of electronic devices have significantly heightened the challenges associated with failure analysis during process development. The focused ion beam–scanning electron microscope (FIB-SEM), characterized by its high processing precision and exceptional imaging resolution, has emerged as a powerful solution for the fabrication, defect localization, and failure analysis of micro- and nano-scale devices. This paper systematically reviews the innovative applications of FIB-SEM in the research of core issues, such as through-silicon-via (TSV) defects, bond interfacial failures, and redistribution layer (RDL) electromigration. Additionally, the paper discusses multimodal integration strategies combining FIB-SEM with advanced analytical techniques, such as high-resolution three-dimensional X-ray microscopy (XRM), electron backscatter diffraction (EBSD), and spectroscopy. Finally, it provides a perspective on the emerging applications and potential of frontier technologies, such as femtosecond-laser-assisted FIB, in the field of advanced packaging analysis. Full article

When using supplementary cementitious materials to replace cement partially, the carbon emissions of cement products can be reduced, but it often leads to reduced strength. This study explores the application potential of carbide slag (CS) and calcined coal gangue (CCG), byproducts of acetylene production, to partially replace cement. The effects of these two materials on the macroscopic properties and microstructure of cement-based materials were analyzed through systematic experiments. The compressive strength, ultrasonic pulse velocity, and electrical resistivity test results showed that replacing 20% of cement with CCG did not cause significant changes in the test results of the specimens. An X-ray diffraction (XRD) analysis showed that these two materials can produce additional hydration products. Scanning electron microscopy images (SEM) further revealed that CCG produces hydration products to fill microscopic pores. Thermogravimetric analysis (TG) results after 28 days showed that with the addition of supplementary cementitious materials, calcium hydroxide (CH) in CS reacts with CCG, resulting in the consumption of CS. Finally, the environmental impact of CS and CCG was assessed. It was found that CS is more favorable for reducing carbon emissions compared to CCG. However, when considering the effect of cement replacement on compressive strength, combining these two materials is more advantageous for sustainable development. Overall, the use of CS and CCG demonstrated good performance in promoting sustainable development. Full article

Extreme ultraviolet (EUV) imagers are key tools to monitor the space environment and forecast space weather. EUV filters are important components to block radiation in the ultraviolet (UV), visible, and near-infrared (IR) regions. In this study, various characterization methods were proposed for the nickel mesh-supported indium (In) filter, and their spectral characteristics were comprehensively studied. The material and thickness of the filter were chosen based on atomic scattering principles, determined through theoretical calculation and software simulation. The metal film was deposited using the vacuum-resistive thermal evaporation method. The measured transmission of the filter was 10.06% at 83.4 nm. The surface elements of the sample were analyzed using X-ray photoelectron spectroscopy (XPS). The surface and cross-sectional morphologies of the filter were observed using a scanning electron microscope (SEM). The impact of the oxide layer and carbon contamination on the filter’s transmittance was investigated using an ellipsometer. A multilayer “In-In₂O₃-C” model was established to determine the thickness of both the oxide layer and carbon contamination layer on the filter. This model introduces the filling factor based on the original model and considers the diffusion of the contamination layer, resulting in more accurate fitting results. The transmittance of the filter in the visible light range was measured using a UV-VIS spectrophotometer, and the measurement error was analyzed. This article provides preparation methods and test methods for the 83.4 nm EUV filter and conducts a detailed analysis of the spectral characteristics of the prepared optical filters, which hold significant value for space exploration applications. Full article