Scanning Electron Microscope-energy Dispersive Spectrometer Research Articles

Effect of Rare Earth Ce on Structure and Properties in 7CrSiMnMoV Die Steel Castings

In this study, rare earth (RE) Ce is used to modify the interaction between atoms in 7CrSiMnMoV die steel castings. The tensile properties are performed, and strengthening mechanism are analyzed by investigated fracture surface, and microstructure by optical microscopy (OM) and scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS). And ab initio molecular dynamics (AIMD) is used to simulate the effect of the Ce element on the local atomic structure of the FeCeC system alloy steel. The results indicate the strength can increase from 722.55 to 1074.27 MPa, and the elongation can increase from 24.86% to 44.22% with a RE Ce concentration of 0.009%. It is attributed to that doping of Ce can inhibit the formation of network eutectic cementite, refine the lamellar spacing of pearlite, and even form granular cementite and martensite structures. AIMD simulation results show that C atoms tend to be surrounded by Fe, and the strong chemical bonds of FeC make the Fe‐centered C more stable with an increase in RE Ce concentration. And doping Ce can introduce new local topological and chemical orderings such that the FeCFe triplets predominantly form small and big angles shifting from near 75° and 136° to 47° and 81°, respectively.

Study on the influence parameters and anti‐abrasion performance of steam‐cured hydraulic concrete for prefabricated water conveyance channel

AbstractExcessive sediment concentration in water can cause damage to prefabricated concrete channels. This study evaluates the impact of sediment‐laden water flow on the mass loss of concrete after abrasion, incorporating scanning electron microscope‐energy dispersive spectrometer (SEM‐EDS) and X‐ray diffraction (XRD) analyses to assess the effects of four steam‐curing parameters—delay time, heating rate, constant temperature duration, and steam curing temperature—on the abrasion resistance of concrete used in enterprise prefabricated water conveyance channels. The results indicate that the abrasion resistance of concrete for prefabricated channels improves gradually with increases in delay time and constant temperature duration. When the delay time exceeds 3 h and the constant temperature time exceeds 4 h, the concrete's abrasion resistance can reach more than 5 h(g/cm2)−1. Rapid heating rates and excessively high steam curing temperatures adversely affect the concrete's abrasion resistance. However, when the heating rate is controlled within 20°C/h and the steam curing temperature does not exceed 70°C, the concrete's abrasion resistance can achieve more than 5 h(g/cm2)−1. In compliance with the standard DL/T5201‐2021 requirements, it is recommended that concrete with high demands for abrasion resistance should preferentially select steam‐curing parameters within these ranges.

Study on the adsorption process and kinetic, thermodynamic of bio-based waste cattle hair powder toward acidic complex dye.

In this paper, cattle hair waste (CHW) was collected and physically milled into different meshes of ultrafine cattle hair powder (UCHP). The reuse of CHW reaches the purpose of treating pollution with waste by using bio-base adsorbent. It was characterized by using scanning electron microscope-energy dispersive spectrometer (SEM-EDS), Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), and X-ray diffraction (XRD). The adsorption studies were carried out under different conditions of temperature, time, pH, concentration of dye solution, mesh size, and dosage of cattle hair powder, respectively. The pseudo-first and pseudo-secondary kinetics and intra-particle diffusion models were employed to analyze the adsorption kinetic. The Langmuir, Freundlich, and Temkin adsorption isotherm was used to analyze the adsorption isotherm. The results showed that the adsorption capacity of UCHP for acidic metal complex (Trupoxane Brown R6) dyes increased with the decreasing pH solution. The adsorption capacity of 200 mesh UCHP was 379.5mg.g-1 when the adsorption conditions were as follows: 100mL dye solution with the initial concentration of 1000mg·L-1, the dosage of adsorbent was 0.1g, the pH was 3 for 12h at 40°C. The kinetic model fitting results showed that the adsorption of dyes by UCHP conformed to the pseudo-second-order kinetic model. Adsorption thermodynamics study showed that the Langmuir model has the highest fitting result. The amino group contained on the surface of cattle hair powder and the amide bond contained in the molecular chain of peptide chain have better electrostatic adsorption binding force for acid metal complex dyes, and the binding between them is mainly electrostatic attraction. The experimental results show that the ultrafine powder has better adsorption property, which provides a high-value conversion way for recycling waste cattle hair.

Efficient elimination of 3-monochloropropane-1,2-diol fatty acid ester from palm oil via using activated carbon grafted with Tween80.

In the current study, we attempt to remove 3-monochloropropane-1,2-diol fatty acid ester (3-MCPD ester) from palm oil with developed composite adsorbent (Tween80 modified activated carbon [AC]), and scanning electron microscopy-energy dispersive spectrometer, Fourier transform-infrared spectroscopy, X-ray diffraction, nitrogen content adsorption-desorption and thermogravimetric analysis were used to characterize the modifications. We further examined the adsorption capability of the composite adsorbent for 3-MCPD ester and found that the highest removal efficiency was 87.36% (5.3% of adsorbent dose at 104°C for 29min). This is approximately three times higher than that of pristine AC, implying that the composite can be employed as a novel adsorbent for 3-MCPD ester reduction. Along with the adsorption mechanism of Langmuir, Freundlich, Dubinin-Radushkevich, and Temkin models were also tested. It has been suggested that Freundlich model could best describe the adsorption process. Adsorption was found to be well-fitted by pseudo-second-order kinetics according to the kinetic study. An endothermic and spontaneous adsorption mechanism was demonstrated by the thermodynamic studies.

Evaluation of calcium carbonate production and cementitious characteristics of enzymatically induced carbonate precipitation during environmental adjustment

Enzymatically induced carbonate precipitation (EICP) is an emerging and eco-friendly technology, which is considered a green alternative to traditional cement in soil stabilization. When stabilizing soil use one-phase grouting method, the activity of urease is often adjusted, leads to changes in the composition and cementitious characteristics of CaCO3. Previous studies primarily focused on the mechanical properties of solidified soil samples, while the production and cementitious characteristics of CaCO3 influenced by the control of urease activity is rarely discussed. This study investigated production and cementitious characteristics of CaCO3 under different reaction environment (pH adjustment, temperature adjustment, and addition of inhibitors), during which the urease activity tests, pH tests, CaCO3 production tests and ultrasonic oscillation tests are conducted. Meanwhile, the morphological characteristics and mineral composition of CaCO3 are revealed through Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS) tests and X-ray Diffraction (XRD) test. The results demonstrate that all three one-phase grouting methods can delay the production of CaCO3 at early-stage of EICP, while the pH should be maintained above 4 to prevent significant urease deactivation. The CaCO3 generated in EICP mainly consists of calcite and vaterite, and the size of CaCO3 increases with the urease activity increased. The cementitious characteristics of CaCO3 is mainly determined by the percentage composition of calcite and vaterite, where higher vaterite content results in weaker cementitious characteristics. This study provides insights for evaluating the cementitious characteristics of CaCO3, which is beneficial for guiding the promotion and application of one-phase grouting method.

Study on Thermal Cycling Reliability of Epoxy-Enhanced SAC305 Solder Joint.

In this work, epoxy was added into commercial Sn-3.0Ag-0.5Cu (SAC305) solder paste to enhance the thermal cycling reliability of the joint. The microstructure and fracture surface were observed using a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a shear test was performed on the thermally cycled joint samples. The results indicated that during the thermal cycling test, the epoxy protective layer on the surface of the epoxy-enhanced SAC305 solder joint could significantly alleviate the thermal stress caused by coefficients of thermal expansion (CTE) mismatch, resulting in fewer structural defects. The interfacial compound of the original SAC305 solder joints gradually coarsened due to the accelerated atomic diffusion, but epoxy-enhanced SAC305 solder joints demonstrated a thinner interfacial layer and a smaller IMC grain size. Due to the reduced stress concentration and the additional mechanical support provided by the cured epoxy layer, epoxy-enhanced SAC305 solder joints displayed superior shear performance compared to the original joint during the thermal cycling test. After 1000 thermal cycles, Cu-Sn IMC regions were observed on the fracture surfaces of the original SAC305 solder joint, exhibiting brittle fracture characteristics. However, the fracture of the SAC305 solder joint with 8 wt.% epoxy remained within the solder bulk and exhibited a ductile fracture mode. This work indicates that epoxy-enhanced SAC305 solder pastes display high thermal cycling reliability and could meet the design needs of advanced packaging technology for high-performance electronic packaging materials.

In Situ Analysis of Binder Degradation during Catalyst-Accelerated Stress Test of Polymer Electrolyte Membrane Fuel Cells.

High-oxygen-permeability ionomers (HOPIs) are being actively developed to enhance the performance and durability of high-power polymer electrolyte membrane fuel cells (PEMFCs). While methods for evaluating binder performance are well-established, techniques for assessing binder durability and measuring its degradation in situ during the AST process remain limited. This study examines the distribution of relaxation times (DRT) and Warburg-like response (WLR) methods as in situ analysis techniques during the catalyst-accelerated stress test (AST) process. We conducted catalyst-ASTs (0.6-0.95 V cycling) for 20,000 cycles, monitoring changes using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV). Contrary to expectations, during the catalyst-AST, the ion transport resistance of the binder decreased, indicating no binder degradation. Scanning electron microscopy/energy dispersive spectrometer (SEM/EDS) analysis revealed that the degradation rate of the catalyst and the support was relatively higher than that of the binder, leading to a reduction in catalyst layer thickness and improved binder network formation. By applying the DRT method during the catalyst-AST process, we were able to measure the increase in oxygen reduction reaction (ORR) resistance and the decrease in proton transport resistance in situ. This allowed for the real-time detection of the reduction in catalyst layer thickness and improvements in ionomer networks due to catalyst and support degradation. These findings provide new insights into the complex interplay between catalyst degradation and binder performance, contributing to the development of more durable PEMFC components.

Graphene nanoplatelet reinforced Al-based composites prepared from recycled powders via mechanical alloying and pressureless sintering

This study reports on the powder metallurgy preparation and characterization of aluminum-graphene nanoplatelet (Al-GNP) composites synthesized using recycled Al powders. Recycled Al and GNP powders (0.1–1 wt%) were mechanically alloyed (MA'd) for 4 h, followed by cold pressing (at 450 MPa) and pressureless sintering at 590 °C for 2 h. Starting powders were analyzed using an optical emission spectrometer (OES) and a Raman spectrometer. Also, MA'd powders and sintered samples were characterized using an X-ray diffractometer (XRD), a scanning electron microscope/energy dispersive spectrometer (SEM/EDS), and a differential scanning calorimeter (DSC). Particle size analyses, pycnometer, and Archimedes' densities, Vickers microhardness, dry-sliding wear, and compression tests were also conducted. The Al4C3 formation was observed in the XRD patterns of sintered compositions. The highest and lowest relative densities were measured for the 1 wt% and 0.1 wt% GNP reinforced samples as 97 % and 92 %, respectively. The highest hardness value was obtained as approximately 1.31 GPa for 1 wt% GNP reinforced. With the addition of reinforcement GNP, the wear rate developed to approximately 0.00225 mm3/Nm. The compressive strength increased from nearly 70 MPa to 162 MPa.

Lanthanum ferrite modified filling materials and its enhancement for phosphorus and COD removal: Performance and mechanism

Previous studies have developed numerous adsorption composite materials demonstrating substantial removal efficiencies for phosphorus (P) and chemical oxygen demand (COD). However, most of materials targeted single contaminant and were inconvenient to apply in real water bodies owing to size limitation. In the current study, three composite materials‑lanthanum ferrite-modified Quartz balls/Maifan stones/Honeycomb ceramics-were synthesized using one step co-precipitation method. Structural and morphological changes of pre- and post-adsorption were examined through Scanning Electron Microscope - Energy Dispersive Spectrometer (SEM-EDS) and X-ray diffraction (XRD). Kinetics, thermodynamics, and isotherm models were simulated for the analysis of P and COD adsorption. X-ray photoelectron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR) were employed to elucidate the adsorption mechanisms. The results demonstrated that these materials achieved P maximal removal rate of 99.56 % and COD maximal removal rate up to 94.82 %. The second-order kinetic model for P adsorption was more excellent than that of the first-order model, and the intra-particle diffusion model more accurately described the COD adsorption. Both the Langmuir and Freundlich were used to fit the adsorption isotherm data for P and COD. XPS and FTIR revealed that the adsorption mechanisms for P were ligand exchange and chemical precipitation. Whereas the adsorption mechanisms for COD were ligand exchange and physical adsorption. The materials in the actual farmland drainage performed excellent and effectively reduced the concentration of P and COD up to 68.58 % and 53.98 %, respectively. The lanthanum ferrite-modified fillers provide accessible, universal and bifunctional option for controlling agricultural non-point source pollution.

Microscopic Mechanism and Road Performance Analysis of MgO Carbonation–Solidification of Dredged Sediment

MgO carbonization is a green and low-carbon soil improvement technology. The use of MgO carbonization to solidify dredged sediment and transform it into road-building materials has significant environmental sustainability advantages. A series of microscopic characterization tests, including X-ray Diffraction (XRD), Scanning Electron Microscope–Energy Dispersive Spectrometer (SEM-EDS), and Mercury-in-Pressure (MIP) tests, were conducted to elucidate the evolution characteristics of mineral composition, microscopic morphology, and pore structure of sediment under carbonation. Based on the results, the mechanism of MgO carbonation–solidification of dredged sediment was explored. In order to verify the improvement of carbonation on the road performance of sediment, comparative tests were carried out on sediment, non-carbonated sediment, and carbonated sediment. The results indicate a significant improvement in the solidification of MgO-treated sediment through carbonation, with enhanced macroscopic strength and densified microscopic structure. This can be attributed to the encapsulation, cementation, and pore-filling effects of the hydration products and carbonation products of MgO on soil particles. The rebound modulus and splitting strength of carbonated sediment were 3.53 times and 2.16 times that of non-carbonated sediment, respectively. Additionally, the carbonated sediment showed improved saturated stability, resistance to salt solution wet–dry cycles, and resistance to freeze–thaw cycles.

Preparation and evaluation of GCD-1 lunar regolith simulant based geopolymer activated by solid sodium silicate

In this study, a new lunar regolith simulant, named "GCD-1", was formulated by combining various minerals, such as anorthite, albite, pyroxene, ilmenite, slag, and fly ash. Through X-ray fluorescence spectroscopy (XRF) and X-ray diffraction (XRD) analysis, it was verified that the main mineral composition of GCD-1 was basically the same as that of the lunar soil at the Apollo 14 landing site, in which the deviation in the main compound (i.e., SiO2 and Al2O3) was within 0.5%. Furthermore, GCD-1 based geopolymer was prepared by the one-part method, which was a mixture of solid GCD-1 precursor, solid sodium silicate (SS) activator, and water. The average daytime temperature at the lunar equator, which was calculated to be 60°C, was set as the curing temperature for the GCD-1 based geopolymer. The strength development of the GCD-1 based geopolymer was then characterized by unconfined compressive strength (UCS) for 3, 7, and 12 curing days to consider the effectiveness of the factors (solid SS to lunar regolith simulant [S/L] and water to binder ratio [W/B]). The micro-analysis tests including scanning electron microscope-energy dispersive spectrometer (SEM-EDS), mercury intrusion porosimetry (MIP), and brunner-emmet-teller (BET), were further conducted to investigate the microstructural development of the GCD-1 based geopolymer. Results showed that the increase of the W/B ratio in the GCD-1 based geopolymer tended to increase the total porosity of the sample, thereby inducing a lower UCS. At the same time, for a fixed W/B ratio, the higher S/L ratio had a certain inhibition effect on the hydration reaction, which caused the reduction in the UCS of the sample. The highest UCS of the GCD-1 based geopolymer reaching 30.54 MPa, was achieved under the simulated lunar equatorial daytime temperature for 12 days with W/B and S/L ratios set at 0.25 and 0.18, respectively. Microstructure and mineralogy analyses indicated that the hydrated sodium aluminosilicate (N-A-S-H) gels contributed to reducing the sample's porosity, thereby enhancing the UCS. The relationship between the UCS and total porosity of GCD-1 based geopolymer was then derived. The results of the current study are crucial for lunar base construction with in-situ resources.

Hydration, strength, and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds ultra-early strength cementitious system

Improving the very early age strength of precast concrete components at ambient temperature and ensuring the development of later strength is of significant engineering importance. This objective was successfully achieved by incorporating a specific percentage of 0–3% CSH seeds (CSHs) and 5%-20% calcium sulphoaluminate cement (CSA) into Portland cement (PC). The hydration, strength and microstructure evolution of Portland cement-calcium sulphoaluminate cement-CSH seeds cementitious system were investigated. Hydration heat tests reveal that CSHs effectively accelerated the early hydration of the slurry within the first 12 h without affecting its later hydration. CSHs and CSA acted synergistically to enhance hydration kinetics. However, it is crucial to control the proportion of CSA within the range of 5%-10%; exceeding this ratio can severely inhibit the hydration of silicates. Strength tests indicate that the addition of CSHs and CSA can increase the compressive and flexural strengths of mortar within the first 12 h by 282% and 208%, respectively, without impacting the development of its later-age strength. Together, they synergistically provide favorable support for the strength and toughness of matrix. Based on linear regression analysis and nitrogen adsorption and desorption tests, it was concluded that CSHs enhance the hydration dependence of matrix strength, while CSA diminishes this characteristic. This is because CSHs refine the pore size distribution of the paste, increasing the proportion of micropores, whereas CSA promotes the formation of more mesopores and macropores, leading to coarser pores; however, 5% CSA is beneficial for further refining the pore structure. The microcosmic phase evolution of the early-strength cementitious system was analyzed through X-ray diffraction and scanning electron microscope-energy dispersive spectrometer experiments. Results demonstrate that low proportions of CSA and CSHs promote the co-growth of ettringite and C-S-H gel, ensuring a more rapid formation of a dense hydration network in the early stages, thereby accelerating strength development. These findings provide a reference for the design and preparation of precast concrete.

Synthesis and Characterization of Fluorapatite-Copper(II) Oxide with Sol-Gel Method as an Antibacterial Biomaterial

One of the calcium phosphate compounds that can be used as an antibacterial material for coating dental implants is fluorapatite (FAp). This research aims to synthesize FAp at three different sintering temperatures (600, 800, and 1000°C), copper(II) oxide (CuO), and fluorapatite-copper(II) oxide (FAp-CuO) using the sol-gel method, and test the antibacterial properties of the synthesized products. The sol-gel technique proved successful in synthesizing FAp, with optimal results observed at a sintering temperature of 1000°C, achieving a crystallinity level of 90%. Analyses conducted using X-ray diffractometer, Fourier-transform infrared spectrometer, and scanning electron microscope-energy dispersive X-ray spectrometer revealed FAp as the dominating phase, exhibiting Ca/P and P/F ratios of 1.84 and 4.67, respectively. In FAp-CuO, replacing Ca2+ with Cu2+ ions lowered the average crystallite size, crystallinity, and Ca/P ratio. FAp, CuO, and FAp-CuO all displayed antibacterial activities against S. aureus and E. coli, with FAp-CuO having the maximum average inhibitory zone diameters of 0.243 and 1.397 mm, respectively.

Improving the Flotation of Unoxidized and Oxidized Molybdenite Fines Using Dodecylamine as a Collector: Flotation Tests and Interaction Mechanism

The flotation of unoxidized and oxidized molybdenite fines is a challenging job worldwide. In this work, dodecylamine (DDA) was developed as a potential collector to improve the flotation of molybdenite fines with and without oxidation. The flotation behaviors and interaction mechanisms were probed through flotation tests, contact angle, Zeta potential, Scanning Electron Microscope-Energy Dispersive Spectrometer(SEM-EDS), and X-ray Photoelectron Spectroscopy (XPS). The flotation tests revealed that DDA improved the flotation of unoxidized or oxidized molybdenite fines efficiently. The results of Zeta potential, contact angle, and SEM-EDS uncovered that a substantial number of DDA species adsorbed on both fresh and oxidized molybdenite faces and edges, thus enhancing their hydrophobicity. XPS analysis further manifested that RNH2 and RNH3+ adsorbed on the S atoms of fresh faces through hydrogen bonding. Meanwhile, RNH2 and RNH3+ mainly adsorbed on fresh edges via chemical bonding between amine groups and Mo sites and electrostatic force. For oxidized molybdenite, RNH2 and RNH3+ interacted with oxidized faces through hydrogen bonding while adsorbed on oxidized edges via hydrogen bonding and electrostatic interaction.

Innovations in prosthetic foot design enhancing durability, functionality and comfort through PLA composite filament 3D printing

Purpose The number of people with special needs, including citizens and military personnel, has increased as a result of terrorist attacks and challenging conditions in Iraq and other countries. With almost 80% of the world’s amputees having below-the-knee amputations, Iraq has become a global leader in the population of amputees. Important components found in lower limb prostheses include the socket, pylon (shank), prosthetic foot and connections. Design/methodology/approach There are two types of prosthetic feet: articulated and nonarticulated. The solid ankle cushion heel foot is the nonarticulated foot that is most frequently used. The goal of this study is to use a composite filament to create a revolutionary prosthetic foot that will last longer, have better dorsiflexion and be more stable and comfortable for the user. The current study, in addition to pure polylactic acid (PLA) filament, 3D prints test items using a variety of composite filaments, such as PLA/wood, PLA/carbon fiber and PLA/marble, to accomplish this goal. The experimental step entails mechanical testing of the samples, which includes tensile testing and hardness evaluation, and material characterization by scanning electron microscopy-energy dispersive spectrometer analysis. The study also presents a novel design for the nonarticulated foot that was produced with SOLIDWORKS and put through ANSYS analysis. Three types of feet are produced using PLA, PLA/marble and carbon-covered PLA/marble materials. Furthermore, the manufactured prosthetic foot undergoes testing for dorsiflexion and fatigue. Findings The findings reveal that the newly designed prosthetic foot using carbon fiber-covered PLA/marble material surpasses the PLA and PLA/marble foot in terms of performance, cost-effectiveness and weight. Originality/value To the best of the author’s knowledge, this is the first study to use composite filaments not previously used, such as PLA/wood, PLA/carbon fiber and PLA/marble, to design and produce a new prosthetic foot with a longer lifespan, improved dorsiflexion, greater stability and enhanced comfort for the patient. Beside the experimental work, a numerical technique specifically the finite element method, is used to assess the mechanical behavior of the newly designed foot structure.

Solidification Mechanism and Strength Characteristics of Alkali-Activated Tannery Sludge–Slag Geopolymer

The aim of this article is to reduce the environmental harm caused by industrial solid waste, specifically tannery sludge, and enable its reutilization. This study prepared an alkali-activated tannery sludge–slag solidification product (ATSSP) with high mechanical properties using blast furnace slag and tannery sludge as raw materials. The response surface methodology (RSM) was used to optimize the product mix ratio. The hydration mechanism and solidification method of ATSSP for Cr in tannery sludge were studied using X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometer (SEM-EDS), and Fourier transform infrared reflection (FT-IR). The results indicate that the compressive strength regression model established through RSM has high accuracy and credibility. When the ratio of activator to binder is 0.2174, the alkali activation modulus is 1.02, and the water-to-cement ratio is 0.37; the 28 d compressive strength of ATSSP can reach 71.3 MPa. The sulfate in tannery sludge can promote the secondary hydration reaction of slag, and the generated hydrated calcium silicate and calcite greatly improve the strength of the ATSSP. The reducing substances contained in slag can reduce Cr (VI) in tannery sludge to Cr (III) in the form of uvarovite. The total Cr and Cr (VI) precipitation concentrations of the product are far less than the specification requirements.

Study on the performance of alkali-activated phosphorus slag cemented paste backfill material: Effect of activator type and amount

Effective disposal of phosphorus slag (PS) is crucial for ecosystem protection. Herein, this study proposed that Na2SO4 (SS), Na2SiO3 (NS), Na2CO3 (SC) and NaOH (NH) were performed to prepare alkali-activated phosphorus slag cemented paste backfill material (AAPS-PB). The evolution mechanisms of setting time, rheological behavior and mechanical properties at different contents of various activators were systematically investigated. The mineral compositions, bonding structure, micromorphology and pore structure characteristics of AAPS-PB hydration products were further clarified by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), scanning electron microscopy-energy dispersive spectrometer (SEM-EDS) and mercury intrusion porosimeter (MIP). Results indicated that activators were proved to significantly promote the dissolution of PS at appropriate content. NH had stronger alkali activation ability in the early hydration period, whereas NS sufficiently improved the later strength, enhanced the denseness of hydration products and refined the pore structure characteristics. This study expands the avenues for high-value applications of PS.

The Properties of High-Performance Concrete with Manganese Slag under Salt Action.

Manganese slag (MS) containing a certain amount of active hydration substances may be used as a kind of cementitious material. In the present study, we measured the mass, the relative dynamic modulus of elasticity (RDME), and the flexural and compressive strengths of MS high-performance concrete (MS-HPC) with added basalt fibers exposed to NaCl freeze-thaw cycles (N-FCs), NaCl dry-wet alternations (N-DAs), and Na2SO4 dry-wet alternations (NS-DAs). Scanning electron microscope energy-dispersive spectrometer (SEM-EDS) spectra, thermogravimetric analysis (TG) curves, and X-ray diffraction spectroscopy (XRD) curves were obtained. The mass ratio of MS ranged from 0% to 40%. The volume ratio of basalt fibers varied from 0% to 2%. We found that, as a result of salt action, the mass loss rate (MLR) exhibited linear functions which were inversely correlated with the mass ratio of MS and the volume ratio of basalt fibers. After salt action, MLR increased by rates of 0~56.3%, but this increase was attenuated by the addition of MS and basalt fibers. Corresponding increases in RDME exhibited a linear function which was positively correlated with MS mass ratios in a range of 0~55.1%. The addition of MS and basalt fibers also led to decreased attenuation of mechanical strength, while the addition of MS led to increased levels of flocculent hydration products and the elements Mn, Mg, and Fe. CaClOH and CaSO4 crystals were observed in XRD curves after N-DA and NS-DA actions, respectively. Finally, the addition of MS resulted in increased variation in TG values. However, the opposite result was obtained when dry-wet actions were exerted.

Chloride ion permeability of concrete containing recycled composite powder from building demolition waste

Buildings in the marine environment are vulnerable to chloride ion erosion, which threatens the service life of concrete structures. To facilitate the application of concrete containing construction demolition waste in the marine environment, recycled composite powder concrete (RCPC) was prepared using recycled composite powder as cement substitute. The chloride ion permeability of RCPC was evaluated by chloride ion diffusion test and rapid chloride ion migration test (RCM). The chloride ion permeability of RCPC continued to enhance with growing content of recycled composite powder. During the immersion age, the surface chloride ion content of the samples containing recycled composite powder increased by an average of 18.3–65.3% over the control group, with a corresponding average increase in chloride ion diffusion coefficients ranging from 17.0% to 31.5%. The chloride ion migration coefficients in the RCM test raised by 9.5–24.7%. A series of microscopic tests such as nuclear magnetic resonance (NMR), X-ray diffraction (XRD) and scanning electron microscope-energy dispersive spectrometer (SEM-EDS) suggested that the total porosity increased by 11.9–29.5% with the addition of recycled composite powder. The chloride ion diffusion coefficients exhibited a linear increase with growing total porosity and porosity of capillary pores, whereas an exponential increase with the porosity of transitional pores. The poor reactivity of the recycled composite powder resulted in a looser microstructure and weakened chloride binding capacity, and these factors boosted chloride ion transport. A chloride ion diffusion model of RCPC considering the time dependence of chloride ion transport was developed, and the reliability of the model was verified by experimental data.

Investigation of phenol adsorption performance and mechanism using Na2EDTA-modified activated biochars produced from a fluidized bed pyrolysis system

The study investigated the characteristics and mechanisms of phenol adsorption in three types of modified activated biochars (rice straw, rice husk, and sawdust) obtained through fluidized bed pyrolysis system, particularly focusing on biochars activated with KOH and modified with Na2EDTA. The experimental comprehensively analyzed the morphology of biochars through nitrogen adsorption-desorption (BET), Fourier Transform Infrared Spectroscopy (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Scanning Electron Microscope-Energy Dispersive Spectrometer (SEM-EDS), while employed mathematical descriptions with isotherm, adsorption kinetics, and thermodynamics models. The adsorption process could be better described by the pseudo-second-order kinetic model and Langmuir isotherm model, indicating the spontaneous and exothermic reaction. After being activated by KOH, results showed that KOH could generate potassium vapor for etching carbon layers at high temperatures, forming a microporous structure. With the KOH activation and Na2EDTA modification, the amino (-NH2) and carboxyl (-COOH) groups were effectively loaded on the adsorbents. Especially, after Na2EDTA modification, an N1s peak appeared in the XPS spectrum, the peak area ratios of pyrrolic-N and graphitic-N drop from 54.20 % to 21.45%–49.15% and 16.62%, while that of pyridinic-N and nitrogen oxides correspondingly increased, indicating the presence and alteration of nitrogen-containing functional groups, promoting the formation of π-π bonds, and strengthening of π-π dispersion effects. Meanwhile, the specific surface area reaches 1143.60 m2/g to 1337.20 m2/g, the maximum adsorption capacities reach 156.29 mg/g to 195.17 mg/g, which outperform the commercial activated biochars. This finding suggests that Na2EDTA -modified biochars by fluidized bed could enhance the adsorption capacity for phenol, and offer economic feasibility and high production technical for the environmental protection and wastewater treatment.