Electron Microscopy Observations Research Articles

Improving membrane distillation performance by Fe(II) activated sodium percarbonate oxidation during the treatment of shale gas produced water

Membrane distillation (MD) offers promise for recycling shale gas produced water (SGPW), while membrane fouling is still a major obstacle in standalone MD. Herein, sodium percarbonate (SPC) oxidation was proposed as MD pretreatment, and the performance of the single MD, SPC-MD hybrid process and Fe(II)/SPC-MD hybrid process for SGPW treatment were systematically evaluated. Results showed that compared to raw SGPW, the application of SPC and Fe(II)/SPC led to the decrease of the fluorescent organics by 28.54% and 54.52%, respectively. The hydrophobic fraction decreased from 52.75% in raw SGPW to 37.70% and 27.20% for SPC and Fe(II)/SPC, respectively, and the MD normalized flux increased from 0.19 in treating raw SGPW to 0.65 and 0.81, respectively. The superiority of SPC oxidation in reducing the deposited membrane foulants and restoring membrane properties was further confirmed through scanning electron microscopy observation, attenuated total reflection fourier transform infrared, water contact angle and surface tension analyses of fouled membranes. Correlation analysis revealed that hydrophobic/hydrophilic matters and fluorescent organics in SGPW took a crucial role in MD fouling. The mechanism of MD fouling mitigation by Fe(II)/SPC oxidation was attributed to the decrease in concentrations and hydrophobicity of organic by synergistic oxidation, coagulation and adsorption.

Synthesizing a novel cerium-modified graphene powder to achieve long-term anticorrosion performance of epoxy powder coatings

Graphene with extremely large specific surface area possesses great loading capacity for various kinds of corrosion inhibitors to obtain long-term anticorrosion properties. In this study, the corrosion inhibitor cerium nitrate was employed to modify graphene on which the cerium species were loaded. The as-synthesized cerium-modified graphene (Ce-Gr) was introduced into epoxy powder coating to provide long-effective corrosion protection on steel. X-ray photoelectron spectroscopy (XPS) analysis implies that cerium species were successfully loaded on graphene in the form of cerium nitrate and cerium oxide. Scanning electron microscopy (SEM) observation exhibited that Ce-Gr improved structural density and reduced the porosity in coating matrix. Electrochemical measurements demonstrated incredibly high impedance values of 1010.5 Ω cm2 for the epoxy powder coatings containing Ce-Gr after immersion in 3.5% NaCl solution for 45 days. Additionally, the smallest average corrosion propagation width of only 0.60 mm on the substrate at scratch after salt spray test, the shorter cathodic disbondment diameter of 3.49 mm and the fewest corrosion oxidation products with extremely low oxygen content of 3 wt% on substrate after salt solution immersion for 120 days implied that the coating with the addition of 0.05 wt% Ce-Gr possessed the most effective corrosion inhibition property to protect the steel substrate for a long period.

Improved camptothecin encapsulation and efficacy by environmentally sensitive block copolymer/chitosan/fucoidan nanoparticles for targeting lung cancer cells

In this study, thermo-sensitive poly(N-isopropyl acrylamide) (PNP) was polymerized with pH-sensitive poly(acrylic acid) (PAA) to prepare a PAA-b-PNP block copolymer. Above its cloud point, the block copolymer self-assembled into nanoparticles (NPs), encapsulating the anticancer drug camptothecin (CPT) in situ. Chitosan (CS) and fucoidan (Fu) further modified these NPs, forming Fu-CPT-NPs to enhance biocompatibility, drug encapsulation efficiency (EE), and loading content (LC), crucially facilitating P-selectin targeting of lung cancer cells through a pulmonary drug delivery system. The EE and LC reached 82 % and 3.5 %, respectively. According to transmission electron microscope observation, these Fu-CPT-NPs had uniform spherical shapes with an average diameter of ca. 250 nm. They could maintain their stability in a pH range of 5.0–6.8. In vitro experimental results revealed that the Fu-CPT-NPs exhibited good biocompatibility and had anticancer activity after encapsulating CPT. It could deliver CPT to cancer cells by targeting P-selectin, effectively increasing cell uptake and inducing cell apoptosis. Animal study results showed that the Fu-CPT-NPs inhibited lung tumor growth by increasing tumor cell apoptosis without causing significant tissue damage related to generating reactive oxygen species in lung cancer cells. This system can effectively improve drug-delivery efficiency and treatment effects and has great potential for treating lung cancer.

Cutibacterium acnes biofilm formation is influenced by bone microenvironment, implant surfaces and bacterial internalization

BackgroundThe bacterial persistence, responsible for therapeutic failures, can arise from the biofilm formation, which possesses a high tolerance to antibiotics. This threat often occurs when a bone and joint infection is diagnosed after a prosthesis implantation. Understanding the biofilm mechanism is pivotal to enhance prosthesis joint infection (PJI) treatment and prevention. However, little is known on the characteristics of Cutibacterium acnes biofilm formation, whereas this species is frequently involved in prosthesis infections.MethodsIn this study, we compared the biofilm formation of C. acnes PJI-related strains and non-PJI-related strains on plastic support and textured titanium alloy by (i) counting adherent and viable bacteria, (ii) confocal scanning electronic microscopy observations after biofilm matrix labeling and (iii) RT-qPCR experiments.ResultsWe highlighted material- and strain-dependent modifications of C. acnes biofilm. Non-PJI-related strains formed aggregates on both types of support but with different matrix compositions. While the proportion of polysaccharides signal was higher on plastic, the proportions of polysaccharides and proteins signals were more similar on titanium. The changes in biofilm composition for PJI-related strains was less noticeable. For all tested strains, biofilm formation-related genes were more expressed in biofilm formed on plastic that one formed on titanium. Moreover, the impact of C. acnes internalization in osteoblasts prior to biofilm development was also investigated. After internalization, one of the non-PJI-related strains biofilm characteristics were affected: (i) a lower quantity of adhered bacteria (80.3-fold decrease), (ii) an increase of polysaccharides signal in biofilm and (iii) an activation of biofilm gene expressions on textured titanium disk.ConclusionTaken together, these results evidenced the versatility of C. acnes biofilm, depending on the support used, the bone environment and the strain.

Delamination bridging response of Z‐pins under mixed mode loading: The influence of carbon and Kevlar Z‐pins

AbstractThis paper presents the effect of varying the type of Z‐pin on the delamination bridging performance of unidirectional composite laminates. Carbon and Kevlar Z‐pins were inserted in thick composite laminates using the pre‐hole insertion Z‐pinning process and their bridging performance characterized across the different mode‐mixity range. The bridging response indicated that Kevlar Z‐pin experienced load reduction driven by interfacial friction (Stage III), which was absent in the Carbon Z‐pin. When Mode II dominated the bridging crack, Kevlar Z‐pin showed partial pullout and fiber shear cracking, while the Carbon Z‐pin exhibited clean transverse fracture. Although the bridging load obtained by the Carbon Z‐pin was twice that of Kevlar Z‐pin, the Kevlar Z‐pin provided a higher interlaminar fracture energy. The superior bridging performance of Kevlar Z‐pin is correlated with the enhanced ductility. Moreover, the resin‐rich area was involved in deformation and provided the extra axial load of Z‐pin.Highlights The comparison of mixed‐mode bridging mechanism between Kevlar Z‐pin and Carbon Z‐pin. Reveal the variation of multi‐directional load and energy consumption with mixed‐mode angle in thick laminates. Detailed scanning electron microscope observation to understand failure characteristics of ductile Z‐pin. Evidence that the extra axial load of Z‐pin provided by resin‐rich area.

Designing a Stable Alloy Interlayer on Li Metal Anodes for Fast Charging of All-Solid-State Li Metal Batteries

The deposition of a thin LixSny alloy layer by plasma vapor deposition (PVD) on the surface of a Li foil is reported. The formation of a Li-rich alloy is confirmed by the volume expansion (up to 380%) of the layer and by the disappearance of metallic Sn peaks in the X-ray diffractogram. The layer has a much higher hardness than bare Li and can withstand aggressive cycling at 1C. Post-mortem scanning electron microscope observations revealed that the alloy layer remains intact even after fast cycling for hundreds of cycles. A concept of double modification by adding a thin ceramic/polymer layer deposited by a doctor blade on top of the LixSny layer was also reported to be efficient to reach long-term stability for 500 cycles at C/3. Finally, a post-treatment after Sn deposition consisting of a plasma cleaning of the LixSny alloy layer led to a strong improvement in the cycling performance at 1C. The surface is smoother and less oxidized after this treatment. The combination of a Li-rich alloy interlayer, the increase in hardness at the electrolyte/Li interface, and the absence of dissolution of the layer during cycling at high C-rates are reasons for such an improvement in electrochemical performance.

Scanning Acoustic Microscopy Characterization of Cold-Sprayed Coatings Deposited on Grooved Substrates

AbstractThe effect of non-planar substrate surface on homogeneity and quality of cold-sprayed (CS) deposits was studied by scanning acoustic microscopy (SAM). Fe coatings were cold-sprayed onto Al substrates containing artificially introduced grooves of square- and trapezoid-shaped geometries, with flat or cylindrical bottoms. The Al substrates were either wrought or cold-sprayed, to comprehend their prospective influence on the Fe coatings buildup. SAM was then used to assess morphological properties of the materials from the cross-view and top-view directions. The microstructure below the surface of the studied samples was visualized by measuring the amplitudes of the reflection echoes and the velocity of the ultrasonic waves. The SAM analysis revealed that the regions of coating imperfections around the grooves are larger than what is suggested by standard scanning electron microscopy (SEM) observations. Furthermore, we found that the seemingly non-influenced coating regions that appear perfectly homogeneous and dense in SEM do, in fact, possess heterogeneous microstructure associated with the individual CS nozzle passes.

Frictional resistance and delamination mechanisms in 2D tungsten diselenide revealed by multi-scale scratch and in-situ observations

Friction phenomena in two-dimensional (2D) materials are conventionally studied at atomic length scales in a few layers using low-load techniques. However, the advancement of 2D materials for semiconductor and electronic applications requires an understanding of friction and delamination at a few micrometers length scale and hundreds of layers. To bridge this gap, the present study investigates frictional resistance and delamination mechanisms in 2D tungsten diselenide (WSe2) at 10 µm length and 100–500 nm depths using an integrated atomic force microscopy (AFM), high-load nanoscratch, and in-situ scanning electron microscopic (SEM) observations. AFM revealed a heterogenous distribution of frictional resistance in a single WSe2 layer originating from surface ripples, with the mean increasing from 8.7 to 79.1 nN as the imposed force increased from 20 to 80 nN. High-load in-situ nano-scratch tests delineated the role of the individual layers in the mechanism of multi-layer delamination under an SEM. Delamination during scratch consists of stick-slip motion with friction force increasing in each successive slip, manifested as increasing slope of lateral force curves with scratch depth from 10.9 to 13.0 (× 103) Nm−1. Delamination is followed by cyclic fracture of WSe2 layers where the puckering effect results in adherence of layers to the nanoscratch probe, increasing the local maximum of lateral force from 89.3 to 205.6 µN. This establishment of the interconnectedness between friction in single-layer and delamination at hundreds of layers harbors the potential for utilizing these materials in semiconductor devices with reduced energy losses and enhanced performance.

Synergetic Effect of Chemical Components in a Tungsten CMP Slurry and the Evolution of Tungsten Surface Species

Abstract A novel slurry containing 50 ppm Fe3+, 2 wt.% H2O2, 75 ppm oxalic acid, and abrasive nano-silica particles were utilized in a W chemical mechanical planarization process. Using this slurry, a W material removal rate of 710 Å/min and surface roughness of 1 nm were achieved. According to X-ray photoelectron spectroscopy data, surface W was first transformed to WO2 via its dissolution in H2O2, and then Fe3+ ions serving as a catalyst promoted the conversion of tungsten to WO3 through the WO2 intermediate in the presence of H2O2. Oxalic acid was added to coordinate with H2O2 and thus improve the slurry stability through a “wrapping” mechanism without decreasing the W material removal rate. Scanning electron microscopy and atomic force microscopy observations revealed that the W surface morphology changed first from coarse elongated grains to a discontinuous structure after the uneven oxidation by H2O2 and then to a wrinkled soft surface by Fe3+ and H2O2. Finally, it was ground with abrasive nano-silica particles to achieve a high degree of flatness.

Biocontrol potential and growth-promoting effect of endophytic fungus Talaromyces muroii SD1-4 against potato leaf spot disease caused by Alternaria alternata

BackgroundAlternaria alternata is the primary pathogen of potato leaf spot disease, resulting in significant potato yield losses globally. Endophytic microorganism-based biological control, especially using microorganisms from host plants, has emerged as a promising and eco-friendly approach for managing plant diseases. Therefore, this study aimed to isolate, identify and characterize the endophytic fungi from healthy potato leaves which had great antifungal activity to the potato leaf spot pathogen of A. alternata in vitro and in vivo.ResultsAn endophytic fungal strain SD1-4 was isolated from healthy potato leaves and was identified as Talaromyces muroii through morphological and sequencing analysis. The strain SD1-4 exhibited potent antifungal activity against the potato leaf spot pathogen A. alternata Lill, with a hyphal inhibition rate of 69.19%. Microscopic and scanning electron microscope observations revealed that the strain SD1-4 grew parallel to, coiled around, shrunk and deformed the mycelia of A. alternata Lill. Additionally, the enzyme activities of chitinase and β-1, 3-glucanase significantly increased in the hyphae of A. alternata Lill when co-cultured with the strain SD1-4, indicating severe impairment of the cell wall function of A. alternata Lill. Furthermore, the mycelial growth and conidial germination of A. alternata Lill were significantly suppressed by the aseptic filtrate of the strain SD1-4, with inhibition rates of 79.00% and 80.67%, respectively. Decrease of leaf spot disease index from 78.36 to 37.03 was also observed in potato plants treated with the strain SD1-4, along with the significantly increased plant growth characters including plant height, root length, fresh weight, dry weight, chlorophyll content and photosynthetic rate of potato seedlings.ConclusionThe endophyte fungus of T. muroii SD1-4 isolated from healthy potato leaves in the present study showed high biocontrol potential against potato leaf spot disease caused by A. alternata via direct parasitism or antifungal metabolites, and had positive roles in promoting potato plant growth.

A Combined Metabolome and Transcriptome Reveals the Lignin Metabolic Pathway during the Developmental Stages of Peel Coloration in the 'Xinyu' Pear.

Sand pear is the main cultivated pear species in China, and brown peel is a unique feature of sand pear. The formation of brown peel is related to the activity of the cork layer, of which lignin is an important component. The formation of brown peel is intimately associated with the biosynthesis and accumulation of lignin; however, the regulatory mechanism of lignin biosynthesis in pear peel remains unclear. In this study, we used a newly bred sand pear cultivar 'Xinyu' as the material to investigate the biosynthesis and accumulation of lignin at nine developmental stages using metabolomic and transcriptomic methods. Our results showed that the 30 days after flowering (DAF) to 50DAF were the key periods of lignin accumulation according to data analysis from the assays of lignin measurement, scanning electron microscope (SEM) observation, metabolomics, and transcriptomics. Through weighted gene co-expression network analysis (WGCNA), positively correlated modules with lignin were identified. A total of nine difference lignin components were identified and 148 differentially expressed genes (DEGs), including 10 structural genes (PAL1, C4H, two 4CL genes, HCT, CSE, two COMT genes, and two CCR genes) and MYB, NAC, ERF, and TCP transcription factor genes were involved in lignin metabolism. An analysis of RT-qPCR confirmed that these DEGs were involved in the biosynthesis and regulation of lignin. These findings further help us understand the mechanisms of lignin biosynthesis and provide a theoretical basis for peel color control and quality improvement in pear breeding and cultivation.

Unified Solid Solution Product of [Nb][C] in Nb-Microalloyed Steels with Various Carbon Contents.

In this work, the solid solution product of [Nb][C] in the Nb-microalloyed steels with various carbon contents in the range of 0.20~1.80 wt.% was investigated by means of the extraction phase analysis method. The results showed that the Nb content in austenite tended to first decrease and then increase with the increase of carbon content in the steels. A unified solid solution product of [Nb][C] in austenite at different temperatures was obtained according to the results of the experimental steels. The Nb content in austenite of the experimental steels with high carbon contents was lower than that calculated by Ohtani's equation. The existence of NbC precipitates in the case and the core of the specimens carburized at 930 °C and 980 °C were verified by transmission electron microscopy (TEM) observations. The pinning effect of NbC precipitates on austenite grain growth was calculated according to the size and amount of NbC precipitates in the carburized case and the core of the carburized specimens. The calculated results of prior austenite grain sizes were in good agreement with the experimental results, which indicated that the unified solid solution product of [Nb][C] in Nb-microalloyed steels with various carbon contents was applicable for the low-pressure carburizing process.

O-096 Human fallopian tube organoids provide a favorable environment for sperm motility

Abstract Study question Does a human fallopian tube (HFT) organoid model offer a favorable apical environment for human sperm survival and motility? Summary answer The apical compartment of a new model of human fallopian tube organoids provides after differentiation a favorable environment for sperm motility. What is known already Human fallopian tubes are the site of major events that are crucial for achieving an ongoing pregnancy, such as gamete survival and competence, fertilization steps, and preimplantation embryo development. In order to better understand the tubal physiology and tubal factors involved in these reproductive functions, and to improve still suboptimal in vitro conditions for gametes preparation and embryo culture during In Vitro Fertilization IVF, we sought to develop a human fallopian tube organoid model from isolated adult stem cells allowing spermatozoa coculture in the apical compartment. Study design, size, duration Over a two-year period, fallopian tube tissues were collected for organoid culture purposes from 10 “donor” patients undergoing bilateral salpingectomy by laparoscopy for definitive sterilization. After tissue digestion, adult stem cells from the isthmus and ampulla regions were separately seeded in 3D Matrigel and cultured with conventional growth factors for organoid culture and specific factors for differentiation of the female genital tract. Participants/materials, setting, methods HFT organoids were characterized by light microscopy, scanning and transmission electron microscopy, immunofluorescence and transcriptomic analysis. Following simultaneous organoid culture on specific inserts, spermatozoa from five donors were placed either in control media or in the apical compartment of colon or HFT organoids (isthmus and ampulla separately) for 96 hours. Vitality and motility were assessed at 0, 48, and 96 hours on 200 spermatozoa in each condition and in duplicate and compared using Wilcoxon test. Main results and the role of chance Specific fallopian tube differentiation of our model was confirmed by immunofluorescence, transcriptome analysis and electron microscopy observations that exhibited ciliary and secretory cells. We succeeded in releasing spermatozoa in the apical compartment of HFT organoids and in recovering them for sperm analysis. Sperm vitality values are similar in HFT organoids and in commercial sperm media. We demonstrated a superiority of HFT organoid apical compartment for sperm motility compared with other controls (colon organoids, organoid culture media, and conventional commercial sperm washing and fertilization media). At 48 hours of incubation, progressive sperm motility was higher in the apical compartment of HFT organoids (ampulla 30.6% ±17.3, isthmus 29.3% ±14.8) than in commercial fertilization media (15.3% ±14.6) (p < 0.05) and compared with all other conditions. At 96 hours progressive sperm motility was almost nil (<1%) in all conditions except for spermatozoa within HFT organoids (p < 0.05): 11.5% ±14.7 and 12.9% ±16.9 in ampulla and isthmus organoids, respectively. Limitations, reasons for caution This was an in vitro study in which conditions of organoid culture could not exactly mimic the in vivo environment of extracellular matrix and the vascularization of fallopian tubes. Wider implications of the findings This work opens up perspectives for better understanding of HFT physiology. For the first time, it highlights the possibility of developing HFT organoids for reproductive purposes. In the future, it could help us to improve gametes fertilizing abilities and culture conditions of embryos during human assisted reproductive technologies. Trial registration number not applicable

Study on Antibacterial Durability of Waterproof Coatings with Different Base Materials

Microbial corrosion of waterproof coatings causes structural damage to buildings and renovation materials and severely threatens human health. In practical applications, coatings with different base materials show different durabilities to external environmental influences. There is little literature on the antimicrobial durability performance of waterproof coatings. Therefore, this paper selected four standard waterproofing coatings, including polyurethane coatings, cement-based coatings, asphalt-modified polymer coatings, and polymer emulsion coatings, as the main body of this study. Their antimicrobial abilities against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, Candida albicans, and mold were tested after experiencing three kinds of harsh environments: Ultraviolet ray (UV), water immersion, and low temperature. The results show that the extreme climates significantly reduced the ability of the four coatings to resist mold, and the highest growth rate of bacteria was 54.64%. Under UV conditions, the polymer emulsion coatings were significantly more resistant to Candida albicans, and the optical density of the bacterial liquid showed a negative growth trend. The microstructural integrity of the polymer emulsion coatings was found to be damaged by Scanning Electron Microscope (SEM) observation. This work improves the durability application research on these coatings and provides a valuable reference for developing new environmentally friendly, antibacterial, and anticorrosive waterproof coatings.

Influence of peat-derived humic acid on the growth of agarwood seedlings

Humic acid (HA) is widely used in agriculture as a biostimulant to enhance plant growth and nutrient uptake. Studies on the early growth promotion of agarwood seedlings using plant biostimulants have not been explored. Therefore, the objective of this study was to extract and characterize peat-derived HA and to determine the optimum rate that would exert biostimulant action on the early growth of agarwood seedlings at the nursery stage. HA was extracted from peat soil using a modified rapid alkaline hydrolysis method. Produced peat humic acid (PHA) was compared with commercial humic acid (CHA) for its chemical and spectroscopic characteristics. One-month-old agarwood seedlings were treated with PHA at different rates (0, 20, 40, 80, 160 and 320 mg kg−1) before the commencement of the experiment. The study was conducted for four months. The C/N ratio of both PHA and CHA were 25.85 and 26.93, respectively. Scanning electron microscope (SEM) and fourier-transform infrared spectroscopy (FTIR) spectra observation reveals that PHA and CHA have similar surface morphology and functional groups respectively. Results revealed that agarwood seedlings treated with 80 mg kg−1 of PHA significantly increased the plant height, stem diameter, the number of leaves, leaf area, dry matter weight, N and P concentrations in plant tissues, and N, P and K uptakes. Based on the findings, incorporation of PHA at the rate of 80 mg kg−1 with planting medium could be used as an optimum rate to enhance the growth of agarwood seedlings in the nursery stage.

Interaction between dislocation and heterogeneous interface in Cu/Fe laminated composites based on discrete dislocation dynamics

Bimetal laminated composites (BLCs) exhibit more outstanding mechanical properties than traditional alloys due to the interaction between heterogeneous interface boundary (HIB) and dislocation. However, the underlying physics of the dislocation motion and the strengthening effect has not been uncovered at mesoscopic scale. In this study, the detailed microstructure of the Cu/Fe HIB was obtained by transmission electron microscope (TEM) observation. The dislocation model was established using discrete dislocation dynamics (DDD), and several interactions between the dislocation and HIB were focused on, as well as the intrinsic strengthening mechanisms of the HIB. The results show that different HIB characteristics induce different interaction mechanisms such as absorption, slip transmission, slip on the HIB, emission from HIB and reflection by HIB, resulting in different strengthening effect on the BLCs. The HIB promotes slip of the dislocation emitted from the Fe, while prevents movement of the dislocation emitted from Cu. Since dislocation slip is more difficult in Fe, greater elastic deformation occurs before large-scale expansion of the dislocation, resulting in larger nominal yield strength. The presence of HIB increases the difficulty of dislocation movement compared to the single crystal structure, which in turn improves the overall strength of BLCs. Due to the different dislocation motion and strain gradient, the mechanism of that dislocation slip absorption by the HIB has optimal strengthening effect relative to other interaction mechanisms. The strengthening effect of other interaction mechanisms is influenced by the position of the dislocation emission, the type of interaction mechanism, and the angle between adjacent slip planes, etc. The outcome of present research sheds important insights into the design of HIB strengthening materials, such as multi- and nano- laminated composites.

Germanium nanostructures by helium plasma irradiation

The effects of helium plasma irradiation, which has been widely studied on metals, on germanium have been experimentally investigated. The irradiation temperature ranges from 430 to 720 K, and the incident ion energy ranges from 30 to 100 eV. From the scanning electron microscope (SEM) observation, it was found that various morphological changes including pits, nanocones, nanopillars, and roughened surfaces occur. The spatial scale of the morphological change was analyzed by applying fast Fourier transform to SEM micrographs. Thermal desorption spectroscopy analysis suggests that He atoms implanted on Ge play major roles in forming roughened surfaces at a surface temperature higher than 500 K.

Bacterial activity and cementation pattern in biostimulated MICP-treated sand-bentonite mixtures

The application of microbially induced carbonate precipitation (MICP) in clayey soils has attracted much attention, and many studies used clay as an additive to enhance microbial mineralization efficiency in sandy soils. Within the sand-clay-bacteria-calcite system, the property and content of clay play crucial roles in affecting bacterial growth and calcite formation. More important, bentonite is particularly sensitive to changes in the geochemical environment. In this study, the sand-bentonite mixtures were treated by biostimulated MICP, aiming to provide insights into the behavior of this system. The bacterial activity and cementation pattern at different bentonite contents were evaluated through a series of tests such as enrichment tests, unconfined compressive strength (UCS) tests, cementation content measurements, mercury intrusion porosimetry (MIP) tests, scanning electron microscopy (SEM) observations, and energy dispersive X-ray spectroscopy (EDS) analyses. The findings showed that the bentonite presence promoted the enrichment of indigenous ureolytic bacteria, with lower bentonite levels enhancing ureolytic activity. Macroscopic and microscopic characterization indicated that the bentonite-coating sand structure was more conducive to the formation of large-sized calcite crystals capable of cementing soil particles compared to sand-supported and bentonite-supported structures. Additionally, excessive calcium ions (Ca2+) concentrations in the cementitious solution would lead to predominant calcite deposition on soil particle surfaces, contributing minimally to strength improvement.

Investigating Degradation in Extrusion-Processed Bio-Based Composites Enhanced with Clay Nanofillers

This research investigates the extrusion-based fabrication and characterization of nanocomposites derived from bio-sourced polypropylene (PP) and poly(butylene succinate) (PBS: a biodegradable polymer derived from renewable biomass sources such as corn or sugarcane), incorporating Cloisite 20 (C20) clay nanofillers, with a specific focus on their suitability for electrical insulation applications. The research includes biodegradation tests employing the fungus Phanerochaete chrysosporium to evaluate the impact of composition and extrusion conditions. These tests yield satisfactory results, revealing a progressive disappearance of the PBS phase, as corroborated by scanning electron microscopy (SEM) observations and a reduction in the intensity of Fourier transform infrared spectroscopy (FTIR) peaks associated with C-OH and C-O-C bonds in PBS. Despite positive effects on various properties (i.e., barrier, thermal, electrical, and mechanical properties, etc.), a high clay content (5 wt%) does not seem to enhance biodegradability significantly, highlighting the specific sensitivity of the PBS phase to the addition of clay during this process. This study provides valuable insights into the complex interplay of factors conditioning nanocomposite biodegradation processes and highlights the need for an integrated approach to understanding these processes. This is the first time that research has focused on studying the degradation of nanocomposites for electrical insulation, utilizing partially bio-sourced materials that contain PBS.

Synergetic Effect of Chemical Components in a Tungsten CMP Slurry and the Evolution of Tungsten Surface Species

A novel slurry containing 50 ppm Fe3+, 2 wt% H2O2, 75 ppm oxalic acid, and abrasive nano-silica particles were utilized in a W chemical mechanical planarization process. Using this slurry, a W material removal rate of 710 Å min−1 and surface roughness of 1 nm were achieved. According to X-ray photoelectron spectroscopy data, surface W was first transformed to WO2 via its dissolution in H2O2, and then Fe3+ ions serving as a catalyst promoted the conversion of tungsten to WO3 through the WO2 intermediate in the presence of H2O2. Oxalic acid was added to coordinate with H2O2 and thus improve the slurry stability through a “wrapping” mechanism without decreasing the W material removal rate. Scanning electron microscopy and atomic force microscopy observations revealed that the W surface morphology changed first from coarse elongated grains to a discontinuous structure after the uneven oxidation by H2O2 and then to a wrinkled soft surface by Fe3+ and H2O2. Finally, it was ground with abrasive nano-silica particles to achieve a high degree of flatness.