Environmental Scanning Electron Microscopy Research Articles

Self-healing and wave-absorbing functional coupling of nano-Fe3O4 hybridized microcapsules

As a common high-performance wave absorber, the application prospect of nano-Fe3O4 in cementitious materials is limited due to its defects such as easy agglomeration and possible hydration reaction with cement clinker. In this study, self-healing and wave-absorbing functional coupling materials were synthesized by nano-Fe3O4 hybridized microcapsules. The physical and chemical properties of nano-Fe3O4 hybridized microcapsules were characterized by ESEM (Environmental scanning electron microscopy), XRD (X-ray diffractometer) and FTIR (Fourier transform infrared spectrum), etc. The self-healing properties of microcapsules were assessed. The electromagnetic parameters of microcapsules were measured, and the wave-absorbing performance of microcapsules with different matching thicknesses was assessed. The function coupling mechanism of self-healing and wave-absorbing of microcapsules hybridized by nano-Fe3O4 was revealed. The findings revealed that the residual weights of FM0 and FM40 were 1.28 % and 16.44 %, respectively. The hybrid microcapsules demonstrated the amorphous structure of self-healing microcapsules and the crystal structure characteristics of nano-Fe3O4. The highest strength healing rate of cement mortar mixed with microcapsules was 34.2 %. The minimum reflection loss and the corresponding effective bandwidth of the nano-Fe3O4 hybridized microcapsules with a thickness of 3 mm were −20.32 dB and 7.07 GHz, respectively. The nano-Fe3O4 hybridized microcapsules with core–shell structure exhibit excellent wave-absorbing performance through the functional coupling of dielectric loss and magnetic loss.

Cnicus Benedictus roots as a low-cost adsorbent for methylene blue dye removal from aqueous solution: kinetic and equilibrium studies

In this research, Cnicus Benedictus roots powder (CBRP) was utilized as a low-cost adsorbent for removing methylene blue (MB) as a cationic dye from aqueous solution. Characterization of CBRP by Boehm titration method, Fourier transform infrared (FT-IR) and environmental scanning electron microscope (ESEM) indicates the presence of different types of functional groups and a very rough surface filled with cavities, suitable for MB adsorption. The effect of various parameters such as CBRP dose (0.2–2 g/1L), contact time (0–180 min), initial pH (1–10), coexisting anions/cations and the initial MB concentration (100–500 mg L−1) on MB adsorption were examined, the results showed that MB uptake depends on the pH of solution, the electrostatic attraction forces, the formation of H-bonds and π–π interactions are the possible CBRP–MB interaction mechanisms. Adsorption kinetic of MB on CBRP was best represented by linear and non-linear form of the pseudo-second order model. The experimental equilibrium data were best described by linear and non-linear forms of Langmuir and Redlich–Peterson isotherm models (R 2> 0.98) with a maximum MB adsorption capacity of 85.47 mg g−1 at 25 °C, the adsorption efficiency R (%) was greater than 90 (%). MB adsorption-desorption experiments showed the reusability of CBRP for five consecutive cycles. According to the obtained results, CBRP can be used as a natural adsorbent material for cationic dyes removal from aqueous solution.

Gelatin-Based Polymers Can Be Processed to Highly Resilient Biocompatible Porous Hydrogel Scaffolds for Soft Tissue Regeneration Applications

Tissue regeneration relies on the mechanical properties of the surrounding environment, and it has already been shown that mechanostimulation is highly dependent on the stiffness of the native biological tissue. The main advantage of injectable hydrogels in medical applications is their ability to be delivered through minimally invasive techniques. Natural polymer-based hydrogels have been widely used in biomedical applications, due to their high biocompatibility, low immunogenicity, and similarity to soft tissues. However, the crucial combination of low stiffness with high resilience has not been achieved for natural polymers. The current study focuses on the development of novel gelatin-based injectable hydrogels for soft tissue regeneration applications, elucidating the effects of the formulation parameters on the resilience, microstructure, biocompatibility, and mechanical properties. Non-foamed hydrogels demonstrated resilience of at least 95%, while porous hydrogels maintained resilience above 90%, allowing them to withstand mechanical stresses and dynamic conditions within the body. The adjustable modulus of these hydrogels provides the necessary flexibility to mimic the mechanical properties of soft and very soft tissues, without compromising resilience. Environmental Scanning Electron Microscopy (ESEM) observations of the porous hydrogels indicated round interconnected pore structures, desired for cell migration and nutrient flow. Biocompatibility tests on fibroblasts and pre-adipocytes confirmed high biocompatibility, both directly and indirectly. In summary, structuring these new hydrogels for achieving adjustable stiffness, along with the excellent resilience and biocompatibility, is expected to enable this new technology to fit various soft tissue regeneration applications.

Extraction, Characterization, and Encapsulation of Cinnamon Hydrosol Obtained via Microwave-Assisted Hydrodistillation: Analysis of Antioxidant and Antimicrobial Activities

Microwave-assisted hydrodistillation (MAHD) method was employed to extract cinnamon oil and hydrosol (a byproduct). The total polyphenol content (TPC) of the cinnamon hydrosol (CH) was determined using the Folin-Ciocalteu method, and its antioxidant power was assessed through the DPPH radical reduction method. Gas chromatography was utilized to quantify the main bioactive compound (cinnamaldehyde). The disc agar diffusion method was applied to evaluate the inhibition of pathogenic microorganisms. To protect the bioactive compound, an encapsulation method involving cross-linking with calcium alginate was utilized. The capsules were examined using environmental scanning electron microscopy (ESEM). The TPC content was found to be 15.63 ± 0.21 mg gallic acid/g dry matter, and the DPPH radical inhibition rate was 84.26 ± 1.35%. CH exhibited a significant inhibitory effect against Escherichia coli, and a moderate inhibition effect against Shigella flexneri, Salmonella spp., Salmonella typhimurium, and Escherichia coli EPEC. Finally, successful encapsulation of CH was achieved using sodium alginate, resulting in bead sizes ranging between 1.75 and 2.75 mm.

Fouling Resistant Liquid-Infused membranes for oil separations

Bioinspired membranes offer an alternative approach to improving the fouling resistance of commercial membranes for oil separations. Here, two perfluoropolyether oils, a lower viscosity Krytox 103 (K103) and a higher viscosity Krytox 107 (K107), were infused into commercial polyvinylidene fluoride (PVDF) ultrafiltration membranes to mimic the Nepenthes pitcher plant. The transmembrane pressure required to perform long-term oil permeance tests was optimized by testing the liquid-infused membranes at different applied pressures. Crystal violet staining and variable pressure scanning electron microscopy qualitatively suggest that the oil layer remained on the membranes after the oil separation experiments were conducted. Over 5 cycles, K103- and K107- liquid-infused membranes exhibited a consistent permeance of ∼ 30000 L m-2h−1 bar−1 at 1.0 bar and ∼ 14500 L m-2h−1 bar−1 at 0.5 bar, respectively. The steady performance further supports a long-lasting oil layer persists on the membrane surface and inside membrane’s pores. Next, experiments were conducted to determine the stability of the Krytox oil post accelerated cleaning tests using bleach. No structural changes to the Krytox oils were detected by thermogravimetric analysis or nuclear magnetic resonance spectroscopy. Dynamic fouling experiments using Escherichia coli K12 revealed that the liquid-infused membranes had higher flux recovery ratios (∼95 %) than the bare PVDF control membranes (∼55 %). Our results demonstrate that liquid-infused membranes exhibit chlorine stability and superior fouling resistance, presenting a promising bioinspired membrane that can be used in pressure-driven oil separation applications.

High temperature environmental scanning electron microscopy characterization of transient phase formation during conversion of simulated nuclear waste feed to glass

In-situ High-Temperature Environmental Scanning Electron Microscopy (HT-ESEM) is used to characterize the transient phases formed during the melting of complex glass batch mixtures representing simulated nuclear waste feeds. The first phenomenon that occurs is the formation of oxyanionic salt melt, followed by the reaction of oxyanionic salts with refractory grains containing Si, Al, or Mg through surface reactions to form a molten alkali-alumino-boro-silicate phase. The onset temperatures of gas bubble formation and primary foaming are directly determined from the HT-ESEM measurements. The formation of sulfate lakes as well as the formation of high-temperature transient phases floating at the sample surface are also directly observed and identified. Convection currents are observed and their consequences on glass homogenization are discussed.

Enrichment of strontium and magnesium improves the physical, mechanical and biological properties of bioactive glasses undergoing thermal treatments: New cues for biomedical applications

Bioactive glasses (BGs) have emerged as invaluable resources for bone tissue engineering due to their remarkable properties such as bioactivity, resorbability, cell compatibility, and osteoconductivity. However, these materials exhibit certain limitations when subjected to high temperatures, for their tendency to crystallize, thus leading to diminished bioactivity, reduced mechanical strength, and altered dissolution kinetics. One promising approach to counteract this problem is to reduce the alkaline element content in BGs while simultaneously adding strontium and magnesium. Building on previous studies of Bio_MS, a recently developed experimental formulation, we investigated the contributions of strontium and magnesium to the thermal, mechanical, and biological properties of various bioactive glasses, including commercially available options. Differential thermal analysis, heating microscopy, X-ray diffractometry, environmental scanning electron microscopy, measurement of the Young's modulus, simulated body fluid testing, cytotoxicity tests, cell viability, growth, adhesion and morphology were assessed through an integrated approach and compared for a complete evaluation of BGs, and of doped BGs, also undergoing thermal treatments. The results demonstrated improved thermal, mechanical and biological behaviors of the magnesium-strontium-doped BGs, thus paving the way for the development of BGs with enhanced biomedical perspectives.

Taste characterization and molecular docking study of novel umami flavor peptides in Yanjin black bone Chicken meat

Five polypeptides with a potential umami taste were isolated and purified from Yanjin black bone chicken. However, the flavor characteristics and umami mechanism have not been clarified. The umami properties of these five peptides were investigated in this work using a range of analytical techniques, computer simulation, and sensory evaluation. HE-10 and TP-7 exhibited the strongest umami flavors. Furthermore, dose-response experiments showed that the umami peptides enhanced umami by generating peptide mineral chelates. Environmental scanning electron microscopy (ESEM) microstructural analyses supported this finding. The molecular docking results indicated that the five polypeptides bind to four critical amino acid residues, namely Glu217, Glu148, Asp216, and His145, of the T1R1/T1R3 receptor. The binding occurred through van der Waals, electrostatic interactions, hydrogen bonding, and hydrophobic interactions. The main surface forces implicated include aromatic interactions, hydrogen bonding, hydrophilicity, and solvent accessibility.

Biodegradation mechanism of asphalt by microbial consortia in asphalt pavement of forest area road

To study the degradation behaviors of asphalt by microorganisms and reveal biodegradation mechanism of asphalt, 16S rRNA full-length sequencing was utilized to analyze the collected samples from three forest areas. Five strains, namely Sphingomonas polyaromaticivorans, Pseudomonas putida, Pseudomonas fluorescens, Bacillus cereus, and Bacillus subtilis, were selected for compounding microbial consortium to study its degradation effects on asphalt. The micromorphology, elemental chemical states, micromechanical properties, molecular weight distribution, and functional groups of degraded asphalt were studied using environmental scanning electron microscopy, X-ray photoelectron spectroscopy, atomic force microscopy, gel permeation chromatography, and Fourier transform infrared spectroscopy. The results show that the biodegradation of asphalt by microbial consortium increases the surface roughness of asphalt and reduces surface adhesion. Asphalt is used as the sole carbon source by microbial consortium, resulting in a continuous decrease in the contents of C and N elements, while the content of O element is continuously increased. Simultaneously, under the action of microbial enzymes, C-C/C-H bonds which are combined with molecular oxygen in asphalt are continuously broken and converted to C-O-C/C-O-H bonds. The continuous reductions in methylene index and butadiene index of asphalt, as well as the production of carbonyl functional groups confirm the oxidative degradation of asphalt by microbial consortium. Additionally, with the extension of degradation time, the large molecular substances in asphalt are gradually degraded by microbial consortium, leading to a more concentrated molecular weight distribution. This study is of great importance to understand biodegradation mechanism of asphalt.

Ultrahigh Subcooling Dropwise Condensation Heat Transfer on Slippery Liquid-like Monolayer Grafted Surfaces.

Rapid and continuous droplet shedding is crucial for many applications, including thermal management, water harvesting, and microfluidics, among others. Superhydrophobic surfaces, though effective, suffer from droplet pinning at high subcooling temperature (Tsub). Conversely, slippery liquid-like surfaces covalently bonded with flexible hydrophobic molecules show high stability and low droplet adhesion attributed to their dense and ultrasmooth water repellent polymer chains, enhancing dropwise condensation and rapid shedding. In this work, linear poly(dimethylsiloxane) chains of various viscosities are covalently bonded onto silicon substrates to form thin and smooth monolayer coated surfaces. The formation of the monolayer is characterized by cryogenic transmission electron microscopy. On these surfaces a very low contact angle hysteresis is reported within wide surface temperature ranges as well as continuous dropwise condensation at ultrahigh Tsub of 60 K. In particular, one of the highest condensation heat fluxes of 1392.60 kW·m-2 and a heat transfer coefficient of 23.21 kW·m-2·K-1 at ultrahigh Tsub of 60 K is reported. The experimental heat transfer performance is further compared to the theoretical heat transfer via the individual droplets with the droplet distribution elucidated via both macroscopic observations as well as environmental scanning electron microscopy. Finally, only a mild decrease in the heat transfer coefficient of 20.3% after 100 h of condensation test at Tsub of 60 K is reported. Slippery liquid-like surfaces promote droplet shedding and sustain dropwise condensation at high Tsub without flooding empowered by the lower frictional forces, addressing challenges in heat transfer performance and durability.

Synthesis and performance study of amphoteric polymer suspension stabilizer for cementing slurry at ultra-high temperature

As the number of ultra-deep wells increases, maintaining the suspension stability of cement slurry at ultra-high temperatures becomes increasingly challenging; the development of a suspension stabilizer suitable for ultra-high temperature environments is imperative. Therefore, this study synthesized a temperature-resistant polymer suspension stabilizer (LHAP) using 2-acrylamide-2-methylpropanesulfonic acid (AMPS), N, N-dimethyl acrylamide (DMAA), 4-acryloylmorpholine (ACMO), and quaternary ammonium cationic hydrophobic long-chain monomer hexadecyl dimethylallyl ammonium chloride (DMAAC-16) as raw materials. It was applied to maintain the suspension stability of cement slurry at ultra-high temperatures. The molecular structure and molecular weight of LHAP were characterized and tested using infrared spectroscopy, nuclear magnetic hydrogen spectroscopy, and Ubbelohde viscometer. The thermal stability and viscosity-temperature performance of LHAP were measured using thermogravimetric analysis and rheometer, respectively. Through the segmented density difference testing of cement stone columns, the suspension stability effect of LHAP on cement slurry under high temperature was evaluated. The suspension stabilization mechanism of LHAP was studied through fluorescence probe testing, variable temperature UV visible light testing, variable temperature particle size distribution testing, Zeta potential analysis, Environmental Scanning Electron Microscopy (ESEM) analysis, and scanning electron microscopy (SEM) analysis. The results indicated that the polymer suspension agent LHAP had excellent temperature resistance, and the molecules didn’t undergo significant thermal degradation below 302 ℃. At high temperatures of 220 ℃, LHAP could maintain the suspension stability of cement slurry, and the segmented density difference of cement columns was less than 0.01 g/cm3. Mechanism analysis revealed that in addition to enhancing temperature resistance by introducing sulfonic acid groups and rigid rings, LHAP also effectively maintains the stability of the slurry suspension at ultra-high temperatures by coordinating electrostatic interactions and molecular associations. LHAP can effectively solve the settlement instability problem of cement slurry under ultra-high temperature, which is beneficial for improving the safety and quality of cementing construction in ultra-deep wells.

Deseeded sunflower fractions and their anatomy and cell morphology

Deseeded sunflower is a heterogeneous lignocellulosic biomass that has not been well utilized due to the incomplete understanding of its biological structure. In this study, deseeded sunflower was fractioned into the stalk rind, stalk pith, receptacle, bract, bractlet, leaf blade, and petiole, and their anatomy, cell morphology, and fiber dimension were studied using light microscope, environmental scanning electron microscope, and fiber quality analyzer. The results showed that the major fractions were the stalk rind and receptacle (49.4 wt% and 28.1 wt%, respectively) and each of the other fractions was less than 10 wt% of the total biomass. The pith was only composed of parenchyma tissue, and the other fractions were composed of epidermal, parenchyma, and vascular tissues. The arrangement and number of vascular tissues were different among fractions. The fiber length in the stalk rind was 0.823 mm, the width was 21.3 μm, and the aspect ratio was 38.6. The content of fiber fines in other fractions was higher than 50%, and these fractions should be developed for other uses. Fractionation was judged to be an effective way to achieve high value utilization of deseeded sunflower.

An Advanced Surface Treatment Technique for Coating Three-Dimensional-Printed Polyamide 12 by Hydroxyapatite

Polymer 3D printing has is used in a wide range of applications in the medical field. Polyamide 12 (PA12) is a versatile synthetic polymer that has been used to reconstruct bony defects. Coating its surface with calcium phosphate compounds, such as hydroxyapatite (HA), could enhance its bonding with bone. The aim of this study was to coat 3D-printed polyamide 12 specimens with hydroxyapatite by a simple innovative surface treatment using light-cured resin cement. Polyamide 12 powder was printed by selective laser sintering to produce 80 disc-shaped specimens (15 mm diameter × 1.5 mm thickness). The specimens were divided randomly into two main groups: (1) control group (untreated), where the surface of the specimens was left without any modifications; (2) treated group, where the surface of the specimens was coated with hydroxyapatite by a new method using a light-cured dental cement. The coated specimens were characterised by both Fourier transform infrared spectroscopy (FTIR) and Transmission Electron Microscopy (TEM), (n = 10/test). The control and treated groups were further randomly subdivided into two subgroups according to the immersion in phosphate-buffered saline (PBS). The first subgroup was not immersed in PBS and was left as 3D-printed, while the second subgroup was immersed in PBS for 15 days (n = 10/subgroup). The surfaces of the control and treated specimens were examined using an environmental scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDXA) before and after immersion in PBS. Following the standard American Society for Testing and Materials (ASTM D3359), a cross-cut adhesion test was performed. The results of the FTIR spectroscopy of the coated specimens were confirmed the HA bands. The TEM micrograph revealed agglomerated particles in the coat. The SEM micrographs of the control 3D-printed polyamide 12 specimens illustrated the sintered 3D-printed particles with minimal porosity. Their EDXA revealed the presence of carbon, nitrogen, and oxygen as atomic%: 52.1, 23.8, 24.1 respectively. After immersion in PBS, there were no major changes in the control specimens as detected by SEM and EDXA. The microstructure of the coated specimens showed deposited clusters of calcium and phosphorus on the surface, in addition to carbon, nitrogen, and oxygen, with atomic%: 9.5, 5.9, 7.2, 30.9, and 46.5, respectively. This coat was stable after immersion, as observed by SEM and EDXA. The coat adhesion test demonstrated a stable coat with just a few loose coating flakes (area removed <5%) on the surface of the HA-coated specimens. It could be concluded that the 3D-printed polyamide 12 could be coated with hydroxyapatite using light-cured resin cement.

Electrochemical Performance of Deposited LiPON Film/Lithium Electrode in Lithium-Sulfur Batteries.

This paper presents a composed lithium phosphate (LiPON) solid electrolyte interface (SEI) film which was coated on a lithium electrode via an electrodeposit method in a lithium-sulfur battery, and the structure of the product was characterized through infrared spectrum (IR) analysis, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), environment scanning electron microscope (ESEM), etc. Meanwhile, the electrochemical impedance spectrum and the interface stability of the lithium electrode with the LiPON film was analyzed, while the coulomb efficiency and the cycle life of the lithium electrode with the LiPON film in the lithium-sulfur battery were also studied. It was found that this kind of film can effectively inhibit the charge from transferring at the interface between the electrode and the solution, which can produce a more stable interface impedance on the electrode, thereby improving the interface contact with the electrolyte, and effectively improve the discharge performance, cycle life, and the coulomb efficiency of the lithium-sulfur battery. This is of great significance for the further development of solid electrolyte facial mask technology for lithium-sulfur batteries.

Biodegradation of low-density polyethylene by mixed fungi composed of Alternaria sp. and Trametes sp. isolated from landfill sites

With the development of industry and modern manufacturing, nondegradable low-density polyethylene (LDPE) has been widely used, posing a rising environmental hazard to natural ecosystems and public health. In this study, we isolated a series of LDPE-degrading fungi from landfill sites and carried out LDPE degradation experiments by combining highly efficient degrading fungi in pairs. The results showed that the mixed microorganisms composed of Alternaria sp. CPEF-1 and Trametes sp. PE2F-4 (H-3 group) had a greater degradation effect on heat-treated LDPE (T-LDPE). After 30 days of inoculation with combination strain H-3, the weight loss rate of the T-LDPE film was approximately 154% higher than that of the untreated LDPE (U-LDPE) film, and the weight loss rate reached 0.66 ± 0.06%. Environmental scanning electron microscopy (ESEM) and Fourier transform infrared spectroscopy (FTIR) were used to further investigate the biodegradation impacts of T-LDPE, including the changes on the surface and depolymerization of the LDPE films during the fungal degradation process. Our findings revealed that the combined fungal treatment is more effective at degrading T-LDPE than the single strain treatment, and it is expected that properly altering the composition of the microbial community can help lessen the detrimental impact of plastics on the environment.

Microplastic evidence assessment from water and sediment sampling in a shallow tropical lake.

Microplastics (MPs) severely threaten inland waterbodies due to the direct impact of human activities. In the present study, spatial and temporal patterns of MPs in a shallow tropical lake were assessed, describing their size, morphology, and polymer types. Water and sediment samples were collected from Lake Chapala during three seasons, and MPs were quantified with a stereomicroscope. The structure, elemental composition, and polymeric composition were determined via environmental scanning electron microscopy and Fourier transform infrared spectroscopy. The highest average concentration of microplastics in Lake Chapala was detected during the low-water period in April 2022 (2.35 items/L), exceeding the July 2022 rainy season concentration (1.8 items/L) by 0.25 items/L, and sediment concentrations were also higher in April 2022 (219 items/kg) compared to July 2022 (210 items/kg). This study highlights the significant pollution of Lake Chapala with microplastics, emphasizing the need for urgent measures to manage plastic waste and mitigate its environmental impact on aquatic ecosystems. PRACTITIONER POINTS: Microplastic contamination was evaluated in Lake Chapala. The distribution profiles of microplastics were different in each area. Heavy metals osmium, tellurium, and rhodium were found associated with the PMs. Polymers were found in this study.

Study on synthesis and mechanism of high temperature resistant suspension stabilizer for spacer fluid

With 2-acrylamido-2-methylpropanesulfonic acid (AMPS), YX-1 (a monomer containing an amide group) as the main chain, DX-2 (a monomer containing a hydrophobic group), N-vinylpyrrolidone (NVP) as the side chain, the high temperature resistant suspension stabilizer for spacer was prepared by free radical aqueous solution polymerization and characterized. The structure was characterized by fourier transform infrared (FTIR) spectroscopy and thermogravimetry-differential thermal analysis (TG-DTA), which proved that the synthesized product was the target product. The performance of the copolymer was evaluated. The experimental results showed that it could be used in the spacer fluid at 30 ∼ 210 °C, and its sedimentation performance could also meet the requirements in the spacer fluid system containing saturated brine. In order to explore the mechanism of the polymer, the polymer solution was tested by six-speed rotational viscometer, pyrene fluorescence probe test, environmental scanning electron microscopy (ESEM) test, and the isolation solution containing the copolymer was tested by Zeta potential test and X-ray diffraction (XRD). Based on the above test results, it is shown that the suspension stabilizer synthesized in this paper has the characteristics of thickening, physical plugging, chemical and physical adsorption, which can effectively ensure that the spacer fluid has excellent suspension performance at high temperature.

Extraction and identification of plastic debris in Sargassum spp. from the beaches of Cancun and Cozumel, Mexico

The beaches of the Mexican Caribbean have been affected by the arrival of pelagic sargassum since 2011, which has caused economic losses in the area. This research consisted on the evaluation and identification of recovered plastic particles (Rpp) from pelagic sargassum collected at eleven beaches in Cancun and Cozumel. The Rpp were extracted manually before and after washing the sargassum, as well as by filtering the water used to wash it. The Rpp were classified by their size and color using optical microscopy; obtaining that these corresponded to secondary shape plastics and are mostly white in color (35.56 %). They were classified as microplastics (90 %), mesoplastics (9 %) and macroplastics (1 %). Also, Rpp were analyzed by Fourier transform infrared spectroscopy (FTIR) and compared with FTIR spectra of standard plastics, namely, polyethylene (PE), polypropylene (PP) and polystyrene (PS); It was found that the Rpp corresponded to PE (47 %) and PP (41 %). Finally, to corroborate wear or changes in the morphology of the Rpp, they were evaluated by environmental scanning electron microscopy; and wear, fractures and holes were observed on the surface of the particles; this result could be attributed to mechanical wear by ocean waves, as well as exposure to solar radiation for long periods.

Corrosion mechanisms of Escherichia coli and Pseudomonas fluorescens on carbon steel based on biofilm perspective

Corrosion mechanisms of Escherichia coli, Pseudomonas fluorescens and E. coli–P. fluorescens on carbon steel were researched by the corrosion weight loss, electrochemical impedance, microbial inoculation culture, biofilm three-dimensional layer scanning, environmental scanning electron microscope, infrared spectroscopy and other methods. It was found that the corrosion rate in E. coli condition was 1.37–1.48 times higher than that in P. fluorescens condition and 1.23–1.33 times higher than that in E. coli–P. fluorescens condition. Although the types of functional groups contained in the EPS secreted by E. coli and P. fluorescens were the same, the hydrogen bonding was weaker in the former, resulting in a loose biofilm structure. Meanwhile, the metabolic corrosion of E. coli itself dominated in the corrosion. On the contrary, P. fluorescens condition and E. coli–P. fluorescens condition had stronger hydrogen bonding of functional groups, so their biofilm structure was tighter. For P. fluorescens condition, the corrosion behaviour was dominated by inhibitory action of EPS in late. For E. coli–P. fluorescens condition, the corrosion behaviour was dominated by metabolic corrosion of E. coli–P. fluorescens itself in early. However, corrosion behaviour was dominated by inhibitory corrosion of EPS in middle. E. coli–P. fluorescens itself and EPS had comparable roles in late.

New interpretation model of the effect of short PE fibers in TRM on tensile behavior

An experimental investigation was conducted on the tensile behavior of textile reinforced mortar (TRM) composites containing different volumes of short polyethylene (PE) fibers in a cementitious matrix to improve the tensile strength and cracking mode of TRM. This investigation mainly aimed to study the action mechanism of short fibers and propose a reasonable textile-short fiber-matrix interface model. The short fiber content was varied, as was the matrix type and the number of grid layers. Ten groups of TRM tensile specimens subjected to the monotonic uniaxial tensile loading were fabricated and tested to examine their tensile characteristics. The results showed that the multiple-cracking behavior and failure mode of TRM were significantly improved by adding PE fibers into the matrix. The tensile strength was increased by 25.8–167.2 %. After the uniaxial tensile tests, the microscopic investigation of the interface between the textile and matrix was conducted on the tensile specimens using an environmental scanning electron microscope (ESEM). The significant influence of the short PE fibers on the improvement of the interface bonding between the textile and matrix was confirmed. More importantly, based on the ESEM results, a novel interface model was proposed to promote understanding of the action mechanism of short fibers.