Electron Microscopy Technology Research Articles

Research on the Compression Performance and Damage Mechanism of Larix Wood With Smooth Grain

In order to investigate the compression performance and damage mechanism of fallen wood in the down-grain direction, northeast larix was taken as the research object. Through the monotonic compression test of 12 specimens, the deformation characteristics, damage mode, and stress-strain curve properties of larix wood under compression in the direction of the smooth grain were analyzed; scanning electron microscope technology was used to analyze the damage and fracture characteristics of wood fibers from the microscopic point of view to further reveal the damage mechanism of wood monotonic compression. The results showed that larix wood compressed in the paragons produced three damage modes of end collapse, shear damage and paragons splitting after the peak load, and the shear damage usually occurred at the junction of the early and late wood tubular cells due to the difference between the early and late wood tubular cells. On this basis, an isomorphic model was established to describe the compression of larix wood in the smooth grain.

Novel interface characteristics and strengthening mechanisms in extruded fiber(Ti)-reinforced Al-based composites

Tailoring Al/Ti composites with high toughness and tensile plasticity requires a comprehensive understanding of multi-scale interface microstructures and element diffusion behaviors. In this study, Al/Ti composites are produced by a novel continuous extrusion technique. Interfacial microstructures, elemental diffusion, and mechanical characteristics are systematically investigated using up-to-date electron microscope technology. The interlayer thickness grows from 0.8 to 4.2 µm when the annealing duration is increased from 6 to 48 h. The interlayer growth behavior exhibits a mixed reaction–diffusion process and is dominated by the interfacial chemical reaction. Elements Si and Mg are aggregated at the Ti/TiAl3 and Al/TiAl3 heterogeneous interfaces, respectively, where the diffusion of Al and Ti is inhibited. A gradient structure at the interface is generated via severe thermal and mechanical effects during extrusion, including fine Ti grains, superfine Al grains, and coarse Al grains. Deformation-induced dislocations and nanograins are observed near the welding interface. Micro-scale interlocking and nano-scale intermixing structures are formed under strong welding pressure. Compared with the conventional Al bar, the ultimate tensile strength and plasticity of the extruded composite Al bar are enhanced by 5.7% and 32.2%, respectively. This work provides new strategies for developing Al/Ti composites with exceptional strength and ductility.

Pore development characteristics and controlling factors of Lower Cambrian Qiongzhusi shale gas reservoir in Sichuan Basin, China

Recently, the shale gas exploration of Lower Cambrian Qiongzhusi Formation in Sichuan Basin has made a great breakthrough. However, the pore characteristics and controlling factors of the shale-gas reservoir in the Qiongzhusi Formation are not clear, which hinders further exploration and development of shale gas. This paper focuses on the Qiongzhusi Formation in the Lower Cambrian of the Sichuan Basin. On the basis of mineral composition and the lithofacies types of shale-gas reservoirs in Qiongzhusi Formation were classified by microscopic observation. Additionally, focused ion beam-scanning electron microscope (FIB-SEM), advanced mineral identification and characterization system (AMICS) analysis, large-field stitching scanning electron microscope technology (MAPS) and nitrogen adsorption experiment were employed to comprehensively determine the differential characteristics and controlling factors of pore development. The results indicate that the pore types in Qiongzhusi Formation are mainly composed of interparticle pores and intercrystalline pores. The pore structure of Qiongzhusi Formation is complex. Significant differences in pore structure parameters are observed among different lithofacies. Quartz and feldspar contribute to the preservation of primary pores due to their strong compressive resistance. Clay minerals and carbonate minerals impede pore development by occluding pores. The influence of organic matter on the pore development is relatively small. According to the mineral composition and pore parameters, laminated shale is a relatively favorable reservoir facies among different lithofacies types.

Magnetic biochar-supported layered double hydroxide for simultaneous remediation of As and Cd in soil: Effectiveness, retention durability, and insight into a new immobilization mechanism

Immobilization/stabilization is a common technique for remediating As and Cd-contaminated soil. However, the effectiveness of employed stabilizer plays a crucial role in determining the fate of these contaminants. This study investigated the effectiveness and durability of a magnetic biochar-supported Ca–Mg–Al layered double hydroxide composite (FLBC) and its components in simultaneous remediation of As and Cd in Phaeozem (BS) and Krasnozem soils (RS). Results demonstrated that 5 wt% FLBC amendment immobilized >85% of As and Cd and converted them into immobile fractions even in a reduction environment. Moreover, FLBC treatment effectively resisted leaching of As and Cd by > 70% under acidic rainwater filtration, thus displaying excellent retention durability. The new immobilization mechanisms were proved using transmission electron microscope technology, where layered double hydroxide (LDH) acted as a nano-bridge to bind FLBC and soil colloids ensuring FLBC stability and synergistic immobilization. During this process, X-ray photoelectron analysis demonstrated the re-oxidation of As(III) to As(V) driven by ferric reduction that resulted in the formation of multiple stable species on the soil surface via the confirmation of X-ray absorption near fine structure and extended X-ray absorption fine structure. This species included Ca/Fe/Cd–As(V) and γ-Cd(OH)2 co-precipitation, as well as As(V)–O–Fe(III)/Ca and As–Fe tridentate-hexanuclear corner-sharing complexes. Furthermore, FLBC amendment favored the immobilization of As and Cd in RS soil compared to BS soil due to a weaker reduction potential and an increased participation of metal-(hydr)oxides for As and Cd complexation. This study provides valuable references for predicting the impact of LDH-coupled magnetic biochar technology on the fate of As and Cd in actual soil environments.

Electrochemical investigation of niobium doped nickel selenide nanostructure for supercapacitor devices

A significant challenge in the research and development of supercapacitors is the creation of nanoscale structures in metal chalcogenide with improved chemically active surfaces, faster ion/charge transport kinetics and shorter ion-diffusion routes. A metal doping strategy has successfully resolved the transition metal chalcogenides issue and provides a larger surface area, faster migration of ions and good thermal and structural stability. In this study, a series of nanostructures comprising pure NiSe and Nb doped NiSe are synthesized across various compositions. Systematic research has been carried out to ascertain the impact of doping on physical and electrochemical traits. Using the X-ray diffraction (XRD) analysis, the confirmation of phase purity was accomplished. The morphology of the nanostructures underwent a dramatic change, as shown by the use of scanning electron microscope (SEM) technology. The specific capacitance (Cs) of Nb0.06NS is measured to be 1482 F/g at 1 A/g. Additionally, cyclic voltammetry (CV) study suggests that the nanostructures obtained in their original state exhibit pseudocapacitive behavior. The GCD of Nb0.06NS demonstrated exceptional charging/discharging performance, showing greater stability and rate capability. Specifically, after undergoing the 5000th GCD cycle, the GCD displayed outstanding performance, and after the 5000th GCD cycle, it retained 96.62 % of its initial performance. Numerous studies have revealed that nanoflakes with extremely high capacitance and stability make excellent candidates for usage as supercapacitor component parts.

Wear mechanism and leakage failure analysis of the mechanical seal end face of an oil transfer pump

The John Crane 48 V mechanical seal is a long-distance oil transfer pump station shaft end seal; its sealing effect directly affects pipeline production safety. However, it has been found that there is oil leakage at the shaft end of the pump station. In order to explore the oil transfer pump mechanical seal abnormal leakage failure causes, to ensure the safety and stability of production, the end face of the 48 V mechanical seal was analyzed by white light interference and scanning electron microscope technology. The failure mechanism of the 48 V mechanical seal was explored from the perspective of the wear mechanism of moving and stationary rings. Results showed that the wear mechanism of the 48 V mechanical seal stationary ring was mainly abrasive wear, and substantial furrows, bulges, and depressions existed on the wear surface. The material removal mechanism was brittle spalling, and the roughness of the wear surface increased with the increase in wear depth and decreased with the increase in wear average width. Uneven wear occurred on the end face of the stationary ring of the mechanical seal, resulting in the leakage of the sealing medium from the end cover of the mechanical seal. The working condition could be improved by adding a spring compensation device to the stationary ring or increasing the gap between the stationary ring and the shaft sleeve.

Preparation of CuO/g-C3N4 and its effect on the removal of phenol

In this paper, CuO/g-C3N4 catalyst was prepared by one-step hydrothermal calcination, characterized, and analyzed by scanning electron microscope, X-ray diffraction, and X-ray photoelectron technology to test the activation effect and regeneration properties, and to investigate the effect of photocatalytic removal of phenol from the water after activation of sulfate with this material. A xenon lamp was used to simulate the visible light source, and the self-prepared phenol wastewater was used as the treated water sample to observe the treatment effect of the test under different test systems. The results show that the morphology of CuO/g-C3N4 and various energy peaks meet the requirements and have good photoactivation characteristics. The stability and recyclability of the catalyst were good, and the treatment of phenol reached 76 % after five tests. The phenol removal rate was 86.71 % at a reaction temperature of 40 °C, a catalyst dosage of 1 g/L, a persulfate concentration of 4 mM, and pH=5. In conclusion, CuO/g-C3N4 has a broad application prospect as a catalyst.

Method of defining rock damage variable on the basis of wave impedance

AbstractA method of determining rock damage variable from wave impedance, which is suitable for the study of dynamics, is presented. The determined variable provides a more reasonable quantitative description of the degree of rock damage. First, the Taylor model of mesoscopic damage mechanics is used to derive the relationship between the velocity of longitudinal waves and the density of rock materials. Based on the measured data of rock samples with different lithology and the same lithology, the relationship between the longitudinal wave velocity and density of rock materials is studied. It is demonstrated that using the wave impedance to define the rock damage variable has advantages over using the P‐wave velocity. Second, the relationship between the wave impedance and degree of damage to the rock material is studied using an electron microscope and ultrasonic testing technology, and the microstructure of rock samples with a wave impedance gradient and time–frequency‐domain characteristics of the ultrasonic signals are compared and analyzed. It is found that it is feasible to determine the damage degree of the rock from the wave impedance. Finally, a method of defining rock damage variable with the wave impedance is further proposed and its rationality verified. The research results show that there is a good positive correlation between the longitudinal wave velocity and density of rock materials, and there is a strong correlation between the degree of rock damage and its wave impedance. The damage variable defined by wave impedance can better reflect the damage state and damage evolution process of rock.

The crack-healing and strength recovery mechanisms for the new developed Ti(C,N)-TiSi2-WC composite ceramic tool materials with crack-healing ability

Because the ceramic tool life will be reduced due to the crack growth, it is necessary to develop the new ceramic tools with crack-healing ability for improving the ceramic tool life. Ti(C,N)-TiSi2-WC composite ceramic tools were fabricated by vacuum hot pressing sintering technology. The Vickers hardness tester was used to prefabricate cracks with different lengths. The crack-healing abilities of materials were researched by air and vacuum heat treatments. The effects of different healing conditions on crack-healing behaviors were investigated based on the strength recovery and microstructure of crack morphology. The healing conditions included healing temperature, healing time, crack length and healing atmosphere. It could be found that the surface cracks were entirely healed after air heat treatment, but locally healed after vacuum heat treatment. After air heating at 800 °C for 90 min, the restoration ratio of flexural strength of the crack-healed samples returned to 109.02% compared to that of the smooth specimen. The strength of the crack-healed specimen would be fully recovered when the crack length was less than 400 μm. After vacuum heating at 1000 °C for 60 min, the recovery of the flexural strength of the crack-healed samples returned to 49.73%. X-ray diffraction and scanning electron microscope technology were used to analyze compositions and microstructure of crack-healed specimens. In the air atmosphere, the liquid filling of SiO2 and TiO2 and crack closure caused by WSi2 and MoSi2 were confirmed as the crack-healing mechanisms. SiO2 and TiO2 were produced by high temperature oxidation reaction of TiSi2 and WSi2. WiS2 and MoSi2 were new phases formed during sintering and heat treatment, and their formation could be explained by thermodynamically feasible reactions. In the vacuum atmosphere, local filling of the crack with silicide solid solutions such as WSi2, MoSi2 and NiSi was the main crack-healing mechanism.

Microstructure and phase correlation of DySZ-Polyester abradable seal coating after thermal exposure

Advanced gas turbine blade/shroud clearance control system requires abradable seal coatings with a high-temperature capacity above 1000 ℃ to accommodate the increasing turbine inlet temperature requirements. Dysprosia-stabilized-zirconia (DySZ) based abradable seal Coatings were fabricated on the Ni-based single-crystal superalloy via the atmospheric plasma spraying technique. The microstructure of the DySZ-based coating before and after thermal ageing was characterized using high-contrast SEM. The phase composition and distribution of the coatings were measured by XRD and Raman spectroscopy, respectively. Focused ion beam (FIB) and Scanning transmission electron microscope (STEM) technologies were employed for the phase confirmation. The results indicated that phase transformation from tetragonal to monoclinic ZrO2 was observed in the DySZ-Polyester after 300 h thermal exposure. Based on the different concentrations of Dy element in the monoclinic and tetragonal phases, the morphology and distribution of the monoclinic phase in the coating were observed intuitively using high-contrast BSE images and further corroborated by the Raman spectra mapping results. During heat treatment, the polyester added to the feedstock was oxidized to form amorphous carbon, which is mainly distributed in the gaps of interlamellar cracks and big pores. In addition, numerous Dy2O3 precipitates added to the feedstock were detected in the as-sprayed coating, and some reacted with ZrO2 to form the Dy2Zr2O7 phase during thermal spraying and thermal ageing. The correlation between Dy concentration and phase structure was then discussed.

Low‐velocity impact and self‐healing behavior of CFRP laminates with poly(ethylene‐co‐methacrylic acid) filament reinforcement

AbstractAn experimental study is performed to explore the low‐velocity impact (LVI) and self‐healing behavior of carbon‐fiber‐reinforced‐polymer (CFRP) laminates reinforced by thermoplastic poly(ethylene‐co‐methacrylic acid) (EMAA) filaments. Firstly, differential scanning calorimetry (DSC), thermos‐gravimetric analysis (TGA) and dynamic mechanical analysis (DMA) are used to determine the process parameters. Thereafter, the unreinforced laminates and EMAA reinforced laminates are prepared via phased hot‐processing curing process. The LVI tests with four energy levels (5, 15, 25 and 35 J) are then carried out on the two types of specimens. In these energy cases, the peak‐force values of the reinforced specimens are 2.2%, 1.9%, 2.3% and 7.5% higher than those of the unreinforced ones, while the energy‐absorption‐rate values of the reinforced ones are 6.02%, 3.53%, 4.24% and 2.32% lower. The comparisons demonstrate the impact‐resistance enhancement of EMAA. Moreover, multiple LVI tests are performed on the unhealed and healed specimens. In 15 and 25 J cases, around 6.92% higher peak load and 4.58% lower absorbed energy are observed within the healed specimens, which is attributed to the healing effect. The healing mechanism is investigated by utilizing attenuated total reflectance Fourier transform infrared spectroscopy (ATR‐FTIR), scanning electron microscope (SEM) and optical microscope (OM) technologies. It reveals that EMAA flows into the delaminations and cracks during the healing process, and thus accomplishing self‐healing behavior effectively.

Experimental Study on Mechanical Properties of Polyurethane Cement Composite (PUC) Under Various Temperatures

This paper aims to investigate the mechanical properties of polyurethane cement (different ratios) at different ambient temperatures. The temperature and proportion which affect the constitutive relation of the material were analyzed by axial tensile test. The microstructure and failure mode of polyurethane cement were studied using scanning electron microscope technology. At -40oC ~40oC, the stress-strain curves of polyurethane cement with different proportions were roughly similar. When the temperature was higher than 40oC, with the rise of temperature, the ultimate tensile strength of polyurethane cement specimens would decrease but the ultimate strain would increase. When the temperature was lower than -40oC, with the decline of temperature, the ultimate strain and tensile strength of polyurethane cement specimens would decrease. The ultimate stress of polyurethane cement with different ratios was different. With the rise of the proportion of polyurethane components, the ultimate stress would increase but the elastic modulus would decrease. Macroscopically, the failure modes of polyurethane specimens were different with the change of temperature. Brittle fracture occurred at low temperatures. At high temperatures, the specimen did not fracture, but a large number of �V�shaped cracks appeared at the edge. The higher the temperature, the more obvious this phenomenon was. At the microscopic level, the fibers didn t break at high temperatures, and there were obvious cracks and more stubble on the surface of cracks at room temperature.

Correlative light-electron microscopy: integrating dynamics to structure

A challenge of classical electron microscopy (EM) modalities is the static and limited view they present of dynamic biological processes. Correlative light and EM (CLEM) pairs the precise imaging of the cellular location in light microscopy (LM) and EM, taking advantage of both methods. Recent advances in protein labeling, fluorescent markers, super-resolution microscopy, and EM technologies have allowed widespread application in modern biological research. Because of the wide versatility of CLEM, it is difficult to describe a single workflow. In general, samples are prepared and imaged by LM before EM preparation and imaging, with software utilized for the correlation of the two images. Fluorescent tags can help to select and localize structures for EM or add dynamics through live-cell imaging. Future developments in multimodal probes showing electron density and fluorescence activity will allow greater integration of the modalities and high-throughput workflows. Can be paired with focused ion beam-scanning EM (FIB-SEM), cryo-EM, transmission EM (TEM), and serial block-face SEM (SBF-SEM), as well as structured illumination microscopy (SIM), stimulated emission depletion (STED), and total internal reflection fluorescence (TIRF). Amenable to live-cell imaging, in part due to advances that can quickly freeze a sample for cryo-EM. Systems to pair with microscopic X-ray computed tomography to provide non-destructive forms of 3D imaging alongside high-resolution micrographs obtained by TEM and fluorescence. Sensitive enough for applications such as virus–host cell membrane interactions. Alongside other techniques, can localize the distribution of specific proteins or structures within a sample and correlate this information with the ultrastructural details provided by EM. Finding the appropriate FM and EM microscopes may be difficult and expensive. Preparing samples for both modalities requires careful planning and optimization so they are properly preserved, labeled, and processed for the chosen application. The growth of cells on the grid during the LM phase can make correlational positioning difficult. Aligning LM and EM micrographs can be challenging and time-consuming due to differences in resolution and sample shrinkage. Lower throughput and smaller region-of-interest size than traditional FM techniques due to being reliant on EM acquisition and additional sample preparation times. We thank Kit Neikirk for his thoughtful suggestions and edits to the manuscript. Funding by the UNCF/Bristol-Myers Squibb E.E. Just Faculty Fund, BWF Career Awards at the Scientific Interface Award, BWF Ad-hoc Award, National Institutes of Health (NIH) Small Research Pilot Subaward to 5R25HL106365-12 from the NIH PRIDE Program, DK020593, Vanderbilt Diabetes and Research Training Center for DRTC Alzheimer’s Disease Pilot & Feasibility Program. CZI Science Diversity Leadership grant number 2022- 253529 from the Chan Zuckerberg Initiative DAF, an advised fund of Silicon Valley Community Foundation (to A.H.). The images were arranged using BioRender and all representative images are original. The authors have no interests to declare.

Effect of interaction between catechin and glycated porcine hemoglobin on its antioxidant functional and structural properties

This study aimed to investigate the interaction between catechins and glycated porcine hemoglobin (G-PHb). The effects of the interaction on the antioxidant function and structural characteristics of the complex (CG-PHb) of catechin and G-PHb were discussed. Porcine hemoglobin (PHb) and G-PHb were used as controls. The solubility, turbidity, emulsifying property, surface hydrophobicity, and oxidation resistance of CG-PHb were studied. The structural characteristics of the CG-PHb were analyzed via UV–visible spectroscopy, fluorescence spectrometry, fourier transform infrared spectroscopy, scanning electron microscope and molecular docking technology. Compared with the control group, these properties of the CG-PHb are significantly improved. The UV absorption peak of CG-PHb had a larger peak and a slight red shift. The fluorescence peak intensity was in the following order: CG-PHb > PHb > G-PHb. The β-sheet content of CG-PHb increased significantly (P < 0.05). Moreover, SEM showed that the structure of CG-PHb had changed. The surface pore structure increased, which facilitated its functional properties. Molecular docking showed that catechin likely interacted with PHb residues HEM-950, PHE-41, GLU-43, ARG-40 and LEU-96. Catechin and PHb formed a more stable complex because of hydrogen bonds. This study can provide new ideas for protein modification research and provide theoretical basis and reference for the property changes of the CG-PHb during food processing.

The effect of salt water ageing on the mechanical and rheological properties of magnetorheological elastomer

This paper aims to investigate the mechanical and rheological properties of magnetorheological elastomer (MRE) in marine ecosystems. The prepared samples comprised silicone rubber (SR) and 70 wt% micron-sized carbonyl iron particles (CIPs), immersed in an artificial marine ecosystem using salt water (Natrium Chloride) for 30 days. The mechanical properties of MRE samples were evaluated using hardness and quasi-static tensile tests. While the rheometer was used to investigate the rheological properties of their storage modulus condition with magnetic field stimulation. Further analysis of the defects and damages caused by salt water ageing was done through morphological observation using scanning electron microscope (SEM) technology. The results showed that the hardness and tensile strength of MRE samples that were soaked in salt water were affected over time. Lower values of hardness and tensile strength were obtained after 30 days due to the presence of Na+ and Cl−, which acted as an accelerator to the hydrolyzation process of the MRE. The process then, enhanced the water ingress capability into the matrix to cause the molecular changes. Interestingly, for rheological properties, 30 days of salt water ageing allowed the water molecules to move the MRE matrix molecular chains apart, a process known as plasticization and thus increasing the MR effect. Furthermore, morphological evidence was established to determine the MRE changes during salt water ageing. The research findings should greatly contribute to a better understanding of the effect of salt water on the performance of MRE.

Quantitative analysis of the structural evolution in Si anode via multi-scale image reconstruction

Despite the high theoretical capacity, silicon (Si) anode suffers from dramatical capacity loss, due to its massive volume swings (up to 300%) during cycling. Hence, thorough understanding of the structural evolution mechanism is necessary and essential for performance optimization of Si anode. Herein, a multi-scale three-dimensional (3D) image reconstruction technique is firstly applied to visualize the structural evolution process of Si anodes. Three key components (Si particles, inactive components, and voids) in the electrode are quantitatively analyzed by the focused ion beam and scanning electron microscope (FIB-SEM) technology. Furthermore, the average sizes of Si particles were run statistics during the cycling. By combining the componential observation within the electrode (macroscopic information) and the 3D models of the particle with solid electrolyte interphase (SEI) layer (microscopic information), the failure mechanism of Si anode is vividly demonstrated. This work establishes a new methodology to quantitatively analyze the structural and compositional evolution of Si anode, which could be further applied for the studies of many other electrode materials with similar issues.

Effect of polyurea coating with different mechanical properties on blast resistance of aluminum alloy circular tube structures: Experiments vs numerical simulations

Polyurea has attracted extensive attention in the field of anti-blast protection over the past few years. Two types of polyurea were prepared and their quasi-static and dynamic mechanical properties were examined to investigate the effect of polyurea coating with different mechanical properties on the blast resistance of the metal circular tube structure. A set of automatic spray equipment was designed and manufactured to spray polyurea efficiently on the circular tube structure. On that basis, the anti-blast test was performed using the two types of polyurea coated on the surface of 6063-T5 aluminum alloy circular tubes with different thicknesses. The macro and micro damage characteristics of polyurea coated aluminum tubes were obtained using the field tests, the metallographic microscope and the scanning electron microscope (SEM) technology. Numerical simulation models were built to elucidate the dynamic response process. The results suggest that polyurea is capable of significantly enhancing the blast resistance performance of the aluminum alloy circular tube. In contrast, polyurea with better energy absorption effect under high dynamic load may not exhibit higher protective efficiency. Whether the polyurea and the aluminum tube can always maintain the adhesion relationship and deformation together under the action of blast has been confirmed as a vital factor. Lastly, the energy absorption mechanism and influence mechanism of different kinds of polyurea were revealed using the Fourier Transform Infra-Red (FTIR) technology in accordance with the stress wave theory.

Selectively sequestrating aqueous Bi(III) with titanium pyrophosphate polyhedral submicro-particles

Titanium pyrophosphate (TiP2O7) adsorbent was prepared by sol–gel combined with sintering method. The products were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), Raman, transmission and scan electron microscope (TEM/SEM) technologies. The results showed that the cubic phase of TiP2O7 has a uniform polyhedral morphology, and most particles are 200–600 nm in size. The submicron scale TiP2O7 particles were first assessed to adsorb aqueous Bi(III) ions. It is found that TiP2O7 micro-particles exhibited excellent capture capability (Qm = 42.54 mg g−1, 298.5 K), fast adsorption rates (>99 % within 30 min) for toxic Bi(III) and high Bi(III) selectivity (KdBi = 5.6 × 104 mL g−1) in the presence of various competitive ions, with the order of Bi(III) ≫ Pb(II) ≫ Cu(II) > Fe(II) > Al(III) > Zn(II). The adsorption kinetics conformed to the pseudo-second-order model, equilibrium adsorption satisfied the Langmuir equation, and the adsorption process was thermodynamically spontaneous. Chemisorption was inferred as the adsorption mechanism, and surface hydroxylated functional groups were considered the adsorptive sites. The reusability and testing of actual samples demonstrated the practicality of TiP2O7 adsorbents in water environment treatment.

Mechanical and microstructural properties of 3D-printed aluminate cement based composite exposed to elevated temperatures

Investigation into the mechanical performances of 3D-printed composite exposed to elevated high-temperatures is of great significance for broadening the engineering application field of 3D printing. Aluminate cement-based composite was developed for 3D printing. The setting time, flowability, and printability of the composite material were adjusted by adding proper dosages of retarder. Then the compressive and flexural properties of the 3D-printed aluminate cement-based composites were evaluated, as well as the residual mechanical properties after heat-treatment at 200, 400, 600, 800, and 1000 °C, respectively. The pore distribution characteristics and the difference between the interface and matrix areas of 3D-printed composites after heat-treatment were systematically quantified through CT microscopic examinations and their relationship with the mechanical anisotropy was clarified. Additionally, the microstructural evolution were investigated by scanning electron microscope (SEM), X-ray diffraction (XRD) and thermogravimetric-differential scanning calorimetry (TG-DSC) technologies. The results indicate that high temperature has a more significant effect on the interfaces of 3D-printed concrete, and the increase of porosity at interfaces was 23 % higher than that at the matrix after exposure to 1000 °C. At different temperatures, the average porosity in the Y direction was lower than that in the X and Z directions, and therefore result in the damage anisotropy.

Failure analysis of water liquid nitrogen cyclic jet impacting concrete

As a flexible crushing technology, the high-pressure water jet breaking concrete has unique advantages in the aspect of safety, quality and environment protection in contrast with mechanical or blasting crushing methods, but there are still problems with the high pump pressure and the limited effective cracking range, etc. So a new method of water-liquid nitrogen (W-LN2) jet breaking concrete is originally proposed in this paper, and the crushing rules and crack characteristics of concrete at macro and micro under the cyclic impact of W-LN2 jet were comprehensively revealed by the quantitative method of fragmentation degree, scanning electron microscope (SEM) technology and three-dimensional X-ray microscopic (3D-XRM) technology and so on. The results show that compared with pure water jet (PWJ) impacting concrete, the width of the crushing pit under the cyclic impact of W-LN2 jet increases by 139.25%, with the depth of 21.65% and crushing volume by 59.68% in this experiment. And there are more significant microcracks in concrete under W-LN2 jet cyclic impact with typical tear traces on the fracture surface, and the concrete presents higher penetration degree in comparison with under PWJ impact. In addition, the numerical model of W-LN2 jet cyclic impacting concrete was established, systematically considering the jet erosion and low-temperature deterioration effects of LN2, and it quantitatively revealed the damage distribution rule of concrete under W-LN2 jet cyclic impact, based on the digital imaging method. The results show that the damage distribution area of concrete under W-LN2 jet cyclic impact is 5.33 times that under PWJ impact. The damage attenuation trend along the jet radial direction includes three stages of slow, fast and slow, with the difference in attenuation rate of 12.50 times between the fastest attenuation area and the slowest attenuation area, while the damage attenuation along the jet axial direction firstly increases rapidly and then drops slowly, and the attenuation amplitude of the fastest attenuation area is 23.86 times that of the slowest attenuation area.