Search2023 Vol. 30, No. 7
Display Method:
2023, vol. 30, no. 7, pp.
1227-1243.
https://doi.org/10.1007/s12613-023-2607-8
Abstract:
Understanding the in situ stress state is crucial in many engineering problems and earth science research. The present article presents new insights into the interaction mechanism between the stress state and faults. In situ stresses can be influenced by various factors, one of the most important being the existence of faults. A fault could significantly affect the value and direction of the stress components. Reorientation and magnitude changes in stresses exist adjacent to faults and stress jumps/discontinuities across the fault. By contrast, the change in the stress state may lead to the transformation of faulting type and potential fault reactivation. Qualitative fault reactivation assessment using characteristic parameters under the current stress environment provides a method to assess the slip tendency of faults. The correlation between in situ stresses and fault properties enhances the ability to predict the fault slip tendency via stress measurements, which can be used to further refine the assessment of the fault reactivation risk. In the future, stress measurements at greater depths and long-term continuous real-time stress monitoring near/on key parts of faults will be essential. In addition, much attention needs to be paid to distinguishing the genetic mechanisms of abnormal stress states and the type and scale of stress variations and exploring the mechanisms of pre-faulting anomaly and fault reactivation.
Understanding the in situ stress state is crucial in many engineering problems and earth science research. The present article presents new insights into the interaction mechanism between the stress state and faults. In situ stresses can be influenced by various factors, one of the most important being the existence of faults. A fault could significantly affect the value and direction of the stress components. Reorientation and magnitude changes in stresses exist adjacent to faults and stress jumps/discontinuities across the fault. By contrast, the change in the stress state may lead to the transformation of faulting type and potential fault reactivation. Qualitative fault reactivation assessment using characteristic parameters under the current stress environment provides a method to assess the slip tendency of faults. The correlation between in situ stresses and fault properties enhances the ability to predict the fault slip tendency via stress measurements, which can be used to further refine the assessment of the fault reactivation risk. In the future, stress measurements at greater depths and long-term continuous real-time stress monitoring near/on key parts of faults will be essential. In addition, much attention needs to be paid to distinguishing the genetic mechanisms of abnormal stress states and the type and scale of stress variations and exploring the mechanisms of pre-faulting anomaly and fault reactivation.
2023, vol. 30, no. 7, pp.
1244-1260.
https://doi.org/10.1007/s12613-023-2615-8
Abstract:
In the past few decades, microbubble flotation has been widely studied in the separation and beneficiation of fine minerals. Compared with conventional flotation, microbubble flotation has obvious advantages, such as high grade and recovery and low consumption of flotation reagents. This work systematically reviews the latest advances and research progress in the flotation of fine mineral particles by microbubbles. In general, microbubbles have small bubble size, large specific surface area, high surface energy, and good selectivity and can also easily be attached to the surface of hydrophobic particles or large bubbles, greatly reducing the detaching probability of particles from bubbles. Microbubbles can be prepared by pressurized aeration and dissolved air, electrolysis, ultrasonic cavitation, photocatalysis, solvent exchange, temperature difference method (TDM), and Venturi tube and membrane method. Correspondingly, equipment for fine-particle flotation is categorized as microbubble release flotation machine, centrifugal flotation column, packed flotation column, and magnetic flotation machine. In practice, microbubble flotation has been widely studied in the beneficiation of ultrafine coals, metallic minerals, and nonmetallic minerals and exhibited superiority over conventional flotation machines. Mechanisms underpinning the promotion of fine-particle flotation by nanobubbles include the agglomeration of fine particles, high stability of nanobubbles in aqueous solutions, and enhancement of particle hydrophobicity and flotation dynamics.
In the past few decades, microbubble flotation has been widely studied in the separation and beneficiation of fine minerals. Compared with conventional flotation, microbubble flotation has obvious advantages, such as high grade and recovery and low consumption of flotation reagents. This work systematically reviews the latest advances and research progress in the flotation of fine mineral particles by microbubbles. In general, microbubbles have small bubble size, large specific surface area, high surface energy, and good selectivity and can also easily be attached to the surface of hydrophobic particles or large bubbles, greatly reducing the detaching probability of particles from bubbles. Microbubbles can be prepared by pressurized aeration and dissolved air, electrolysis, ultrasonic cavitation, photocatalysis, solvent exchange, temperature difference method (TDM), and Venturi tube and membrane method. Correspondingly, equipment for fine-particle flotation is categorized as microbubble release flotation machine, centrifugal flotation column, packed flotation column, and magnetic flotation machine. In practice, microbubble flotation has been widely studied in the beneficiation of ultrafine coals, metallic minerals, and nonmetallic minerals and exhibited superiority over conventional flotation machines. Mechanisms underpinning the promotion of fine-particle flotation by nanobubbles include the agglomeration of fine particles, high stability of nanobubbles in aqueous solutions, and enhancement of particle hydrophobicity and flotation dynamics.
2023, vol. 30, no. 7, pp.
1261-1277.
https://doi.org/10.1007/s12613-023-2608-7
Abstract:
The macroscopic characteristics of molten salts are governed by their microstructures. Research on the structures of molten salts provides the foundation for a full understanding of the physicochemical properties of molten salts as well as a deeper analysis of the microscopic electrolysis process in molten salts. Information about the microstructure of matter can be obtained with the help of several speculative and experimental procedures. In this review, the advantages and disadvantages of the various test procedures used to determine the microstructures of molten salts are compared. The typical coordination configurations of metal ions in molten salt systems are also summarized. Furthermore, the impact of temperature, anions, cations, and metal oxides (O2−) on the structures of molten salts is discussed in detail. The accuracy and completeness of the information on molten salt structures need to be investigated by the integration of multiple methods and interdisciplinary fields. Information on the microstructure and coordination of molten salts deepens the understanding of the elementary elements of the microstructure of matter. This paper, which is based on the review of the coordination states of metal ions in molten salts, is hoped to inspire researchers to explore the inter-relationship between the microstructure and macroscopic properties of materials.
The macroscopic characteristics of molten salts are governed by their microstructures. Research on the structures of molten salts provides the foundation for a full understanding of the physicochemical properties of molten salts as well as a deeper analysis of the microscopic electrolysis process in molten salts. Information about the microstructure of matter can be obtained with the help of several speculative and experimental procedures. In this review, the advantages and disadvantages of the various test procedures used to determine the microstructures of molten salts are compared. The typical coordination configurations of metal ions in molten salt systems are also summarized. Furthermore, the impact of temperature, anions, cations, and metal oxides (O2−) on the structures of molten salts is discussed in detail. The accuracy and completeness of the information on molten salt structures need to be investigated by the integration of multiple methods and interdisciplinary fields. Information on the microstructure and coordination of molten salts deepens the understanding of the elementary elements of the microstructure of matter. This paper, which is based on the review of the coordination states of metal ions in molten salts, is hoped to inspire researchers to explore the inter-relationship between the microstructure and macroscopic properties of materials.
Surface metal-matrix composites based on AZ91 magnesium alloy via friction stir processing: A review
2023, vol. 30, no. 7, pp.
1278-1296.
https://doi.org/10.1007/s12613-022-2589-y
Abstract:
This monograph presents an overview of friction stir processing (FSP) of surface metal-matrix composites (MMCs) using the AZ91 magnesium alloy. The reported results in relation to various reinforcing particles, including silicon carbide (SiC), alumina (Al2O3), quartz (SiO2), boron carbide (B4C), titanium carbide (TiC), carbon fiber, hydroxyapatite (HA), in-situ formed phases, and hybrid reinforcements are summarized. AZ91 composite fabricating methods based on FSP are explained, including groove filling (grooving), drilled hole filling, sandwich method, stir casting followed by FSP, and formation of in-situ particles. The effects of introducing second-phase particles and FSP process parameters (e.g., tool rotation rate, traverse speed, and the number of passes) on the microstructural modification, grain refinement, homogeneity in the distribution of particles, inhibition of grain growth, mechanical properties, strength–ductility trade-off, wear/tribological behavior, and corrosion resistance are discussed. Finally, useful suggestions for future work are proposed, including focusing on the superplasticity and superplastic forming, metal additive manufacturing processes based on friction stir engineering (such as additive friction stir deposition), direct FSP, stationary shoulder FSP, correlation of the dynamic recrystallization (DRX) grain size with the Zener–Hollomon parameter similar to hot deformation studies, process parameters (such as the particle volume fraction and external cooling), and common reinforcing phases such as zirconia (ZrO2) and carbon nanotubes (CNTs).
This monograph presents an overview of friction stir processing (FSP) of surface metal-matrix composites (MMCs) using the AZ91 magnesium alloy. The reported results in relation to various reinforcing particles, including silicon carbide (SiC), alumina (Al2O3), quartz (SiO2), boron carbide (B4C), titanium carbide (TiC), carbon fiber, hydroxyapatite (HA), in-situ formed phases, and hybrid reinforcements are summarized. AZ91 composite fabricating methods based on FSP are explained, including groove filling (grooving), drilled hole filling, sandwich method, stir casting followed by FSP, and formation of in-situ particles. The effects of introducing second-phase particles and FSP process parameters (e.g., tool rotation rate, traverse speed, and the number of passes) on the microstructural modification, grain refinement, homogeneity in the distribution of particles, inhibition of grain growth, mechanical properties, strength–ductility trade-off, wear/tribological behavior, and corrosion resistance are discussed. Finally, useful suggestions for future work are proposed, including focusing on the superplasticity and superplastic forming, metal additive manufacturing processes based on friction stir engineering (such as additive friction stir deposition), direct FSP, stationary shoulder FSP, correlation of the dynamic recrystallization (DRX) grain size with the Zener–Hollomon parameter similar to hot deformation studies, process parameters (such as the particle volume fraction and external cooling), and common reinforcing phases such as zirconia (ZrO2) and carbon nanotubes (CNTs).
Effect of dissolved components of malachite and calcite on surface properties and flotation behavior
2023, vol. 30, no. 7, pp.
1297-1309.
https://doi.org/10.1007/s12613-023-2606-9
Abstract:
In general, malachite is recovered via sulfidization–xanthate flotation, although many unsatisfactory flotation indexes are frequently obtained as a result of the presence of associated calcite. This phenomenon occurs because the dissolved components of malachite and calcite affect the flotation behavior of both minerals. In this study, the effect of the dissolved components derived from malachite and calcite on the flotation behavior and surface characteristics of both minerals was investigated. Flotation tests indicated that malachite recovery decreased when the calcite supernatant was introduced, while the presence of the malachite supernatant increased the recovery of calcite. Dissolution and adsorption tests, along with zeta potential measurements, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and time-of-flight secondary ion mass spectrometry demonstrated that the Ca species in the calcite supernatant were adsorbed on the malachite surface, which hindered the interaction of Na2S with malachite, thereby resulting in the insufficient adsorption of sodium isoamyl xanthate (NaIX) on the surface of malachite. By contrast, the Cu species in the malachite supernatant were adsorbed on the calcite surface, and they provided active sites for the subsequent adsorption of Na2S and NaIX.
In general, malachite is recovered via sulfidization–xanthate flotation, although many unsatisfactory flotation indexes are frequently obtained as a result of the presence of associated calcite. This phenomenon occurs because the dissolved components of malachite and calcite affect the flotation behavior of both minerals. In this study, the effect of the dissolved components derived from malachite and calcite on the flotation behavior and surface characteristics of both minerals was investigated. Flotation tests indicated that malachite recovery decreased when the calcite supernatant was introduced, while the presence of the malachite supernatant increased the recovery of calcite. Dissolution and adsorption tests, along with zeta potential measurements, X-ray photoelectron spectroscopy, Fourier transform infrared spectrometry, and time-of-flight secondary ion mass spectrometry demonstrated that the Ca species in the calcite supernatant were adsorbed on the malachite surface, which hindered the interaction of Na2S with malachite, thereby resulting in the insufficient adsorption of sodium isoamyl xanthate (NaIX) on the surface of malachite. By contrast, the Cu species in the malachite supernatant were adsorbed on the calcite surface, and they provided active sites for the subsequent adsorption of Na2S and NaIX.
2023, vol. 30, no. 7, pp.
1310-1319.
https://doi.org/10.1007/s12613-022-2582-5
Abstract:
The flotation separation of chalcopyrite and talc is challenging due to their similar natural floatability characteristics. Besides, it is usually difficult to effectively inhibit talc by adding sodium carboxymethyl cellulose (CMC) alone during chalcopyrite flotation. Here, a combined inhibitor comprising acidified sodium silicate (ASS) and CMC was employed to realize effective flotation separation of chalcopyrite and talc, and the combined inhibition mechanism was further investigated. Microflotation results showed that adding ASS strengthened the inhibitory effect of CMC on talc and improved the separation of chalcopyrite and talc. The zeta potential, Fourier transform infrared, and X-ray photoelectron spectroscopy analysis indicated that CMC was mainly adsorbed on the talc surface via hydroxyl and carboxyl groups. Moreover, the addition of ASS improved the adsorption of carboxyl groups. Furthermore, the adsorption experiments and apparent viscosity measurements revealed that adding ASS dispersed the pulp well, which reduced the apparent viscosity, improved the adsorption amount of CMC on the talc surface, and enhanced the inhibition of talc in chalcopyrite flotation.
The flotation separation of chalcopyrite and talc is challenging due to their similar natural floatability characteristics. Besides, it is usually difficult to effectively inhibit talc by adding sodium carboxymethyl cellulose (CMC) alone during chalcopyrite flotation. Here, a combined inhibitor comprising acidified sodium silicate (ASS) and CMC was employed to realize effective flotation separation of chalcopyrite and talc, and the combined inhibition mechanism was further investigated. Microflotation results showed that adding ASS strengthened the inhibitory effect of CMC on talc and improved the separation of chalcopyrite and talc. The zeta potential, Fourier transform infrared, and X-ray photoelectron spectroscopy analysis indicated that CMC was mainly adsorbed on the talc surface via hydroxyl and carboxyl groups. Moreover, the addition of ASS improved the adsorption of carboxyl groups. Furthermore, the adsorption experiments and apparent viscosity measurements revealed that adding ASS dispersed the pulp well, which reduced the apparent viscosity, improved the adsorption amount of CMC on the talc surface, and enhanced the inhibition of talc in chalcopyrite flotation.
2023, vol. 30, no. 7, pp.
1320-1328.
https://doi.org/10.1007/s12613-023-2621-x
Abstract:
The low-reactivity mold flux with low SiO2 content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO2 in mold flux. However, the traditional low-reactivity mold flux still presents some problems such as high viscosity and strong crystallization tendency. In this study, the co-addition of Li2O and B2O3 in CaO–Al2O3–10wt%SiO2 based low-reactivity mold flux was proposed to improve properties of mold flux for high-aluminum steel, and the effect of Li2O replacing B2O3 on properties of mold flux was investigated. The viscosity of the mold flux with 2wt% Li2O and 6wt% B2O3 reached a minimum value of 0.07 Pa·s. The break temperature and melting point showed a similar trend with the viscosity. Besides, the melt structure and precipitation of the crystalline phase were studied using Raman and X-ray diffraction spectra to better understand the evolution of viscosity. It demonstrated that with increasing Li2O content in the mold flux from 0 to 6wt%, the degree of polymerization of aluminate and the aluminosilicate network structure increased because of increasing Li+ released by Li2O, indicating the added Li2O was preferentially associated with Al3+ as a charge compensator. The precipitation of LiAlO2 crystalline phase gradually increased with the replacement of B2O3 by Li2O. Therefore, Li2O content should be controlled below 2wt% to avoid LiAlO2 precipitation, which was harmful to the continuous casting of high-aluminum steels.
The low-reactivity mold flux with low SiO2 content is considered suitable for the continuous casting of high-aluminum steel since it can significantly reduce the reaction between Al in steel and SiO2 in mold flux. However, the traditional low-reactivity mold flux still presents some problems such as high viscosity and strong crystallization tendency. In this study, the co-addition of Li2O and B2O3 in CaO–Al2O3–10wt%SiO2 based low-reactivity mold flux was proposed to improve properties of mold flux for high-aluminum steel, and the effect of Li2O replacing B2O3 on properties of mold flux was investigated. The viscosity of the mold flux with 2wt% Li2O and 6wt% B2O3 reached a minimum value of 0.07 Pa·s. The break temperature and melting point showed a similar trend with the viscosity. Besides, the melt structure and precipitation of the crystalline phase were studied using Raman and X-ray diffraction spectra to better understand the evolution of viscosity. It demonstrated that with increasing Li2O content in the mold flux from 0 to 6wt%, the degree of polymerization of aluminate and the aluminosilicate network structure increased because of increasing Li+ released by Li2O, indicating the added Li2O was preferentially associated with Al3+ as a charge compensator. The precipitation of LiAlO2 crystalline phase gradually increased with the replacement of B2O3 by Li2O. Therefore, Li2O content should be controlled below 2wt% to avoid LiAlO2 precipitation, which was harmful to the continuous casting of high-aluminum steels.
2023, vol. 30, no. 7, pp.
1329-1337.
https://doi.org/10.1007/s12613-023-2597-6
Abstract:
This study investigated the influence of band microstructure induced by centerline segregation on carbide precipitation behavior and toughness in an 80 mm-thick 1 GPa low-carbon low-alloy steel plate. The quarter-thickness (1/4t) and half-thickness (1/2t) regions of the plate exhibited similar ductility and toughness after quenching. After tempering, the 1/4t region exhibited ~50% and ~25% enhancements in both the total elongation and low-temperature toughness at −40°C, respectively, without a decrease in yield strength, whereas the toughness of the 1/2t region decreased by ~46%. After quenching, both the 1/4t and 1/2t regions exhibited lower bainite and lath martensite concentrations, but only the 1/2t region exhibited microstructure bands. Moreover, the tempered 1/4t region featured uniformly dispersed short rod-like M23C6 carbides, and spherical MC precipitates with diameters of ~20–100 nm and <20 nm, respectively. The uniformly dispersed nanosized M23C6 carbides and MC precipitates contributed to the balance of high strength and high toughness. The band microstructure of the tempered 1/2t region featured a high density of large needle-like M3C carbides. The length and width of the large M3C carbides were ~200–500 nm and ~20–50 nm, respectively. Fractography analysis revealed that the high density of large carbides led to delamination cleavage fracture, which significantly deteriorated toughness.
This study investigated the influence of band microstructure induced by centerline segregation on carbide precipitation behavior and toughness in an 80 mm-thick 1 GPa low-carbon low-alloy steel plate. The quarter-thickness (1/4t) and half-thickness (1/2t) regions of the plate exhibited similar ductility and toughness after quenching. After tempering, the 1/4t region exhibited ~50% and ~25% enhancements in both the total elongation and low-temperature toughness at −40°C, respectively, without a decrease in yield strength, whereas the toughness of the 1/2t region decreased by ~46%. After quenching, both the 1/4t and 1/2t regions exhibited lower bainite and lath martensite concentrations, but only the 1/2t region exhibited microstructure bands. Moreover, the tempered 1/4t region featured uniformly dispersed short rod-like M23C6 carbides, and spherical MC precipitates with diameters of ~20–100 nm and <20 nm, respectively. The uniformly dispersed nanosized M23C6 carbides and MC precipitates contributed to the balance of high strength and high toughness. The band microstructure of the tempered 1/2t region featured a high density of large needle-like M3C carbides. The length and width of the large M3C carbides were ~200–500 nm and ~20–50 nm, respectively. Fractography analysis revealed that the high density of large carbides led to delamination cleavage fracture, which significantly deteriorated toughness.
2023, vol. 30, no. 7, pp.
1338-1352.
https://doi.org/10.1007/s12613-023-2602-0
Abstract:
The corrosion behavior of 304L stainless steel (SS) in 3.5wt% NaCl solution after different cavitation erosion (CE) times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques. It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods. The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS. Over the rising period of CE, the 304L SS experienced a transition from passivation to depassivation, leading to the massive growth of metastable pitting and stable pitting. The depassivation of 304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.
The corrosion behavior of 304L stainless steel (SS) in 3.5wt% NaCl solution after different cavitation erosion (CE) times was mainly evaluated using electrochemical noise and potentiostatic polarization techniques. It was found that the antagonism effect resulting in the passivation and depassivation of 304L SS had significant distinctions at different CE periods. The passive behavior was predominant during the incubation period of CE where the metastable pitting initiated at the surface of 304L SS. Over the rising period of CE, the 304L SS experienced a transition from passivation to depassivation, leading to the massive growth of metastable pitting and stable pitting. The depassivation of 304L SS was found to be dominant at the stable period of CE where serious localized corrosion occurred.
2023, vol. 30, no. 7, pp.
1353-1362.
https://doi.org/10.1007/s12613-023-2598-5
Abstract:
Natural minerals-based energy materials have attracted enormous attention because of the advantages of good materials consistency, high production, environmental friendliness, and low cost. The uniform distribution of grains can effectively inhibit the aggregation of active materials, improving lithium storage performance. In this work, natural graphite is modified by polyvinylpyrrolidone to obtain modified graphite with reduced size and better dispersion. Natural pyrite composite polyvinylpyrrolidone-modified graphite (pyrite/PG) material with uniform particle distribution is obtained by the ball milling process. The subsequent calcination process converts pyrite/PG into Fe1−xS compounded with polyvinylpyrrolidone-modified graphite (Fe1−xS/PG). The homogeneous grain distributions of active material can facilitate the faster transfer of electrons and promote the efficient utilization of active materials. The as-prepared Fe1−xS/PG electrode exhibits a remarkably reversible specific capacity of 613.0 mAh·g−1 at 0.2 A·g−1 after 80 cycles and an excellent rate capability of 523.0 mAh·g−1 at 5 A·g−1. Even at a higher current density of 10 A·g−1, it can deliver a specific capacity of 348.0 mAh·g−1. Moreover, the dominant pseudocapacitance in redox reactions accounts for the impressive rate and cycling stability. This work provides a low-cost and facile method to fabricate natural mineral-based anode materials and apprise readers about the impact of uniform particle distribution on lithium storage performance.
Natural minerals-based energy materials have attracted enormous attention because of the advantages of good materials consistency, high production, environmental friendliness, and low cost. The uniform distribution of grains can effectively inhibit the aggregation of active materials, improving lithium storage performance. In this work, natural graphite is modified by polyvinylpyrrolidone to obtain modified graphite with reduced size and better dispersion. Natural pyrite composite polyvinylpyrrolidone-modified graphite (pyrite/PG) material with uniform particle distribution is obtained by the ball milling process. The subsequent calcination process converts pyrite/PG into Fe1−xS compounded with polyvinylpyrrolidone-modified graphite (Fe1−xS/PG). The homogeneous grain distributions of active material can facilitate the faster transfer of electrons and promote the efficient utilization of active materials. The as-prepared Fe1−xS/PG electrode exhibits a remarkably reversible specific capacity of 613.0 mAh·g−1 at 0.2 A·g−1 after 80 cycles and an excellent rate capability of 523.0 mAh·g−1 at 5 A·g−1. Even at a higher current density of 10 A·g−1, it can deliver a specific capacity of 348.0 mAh·g−1. Moreover, the dominant pseudocapacitance in redox reactions accounts for the impressive rate and cycling stability. This work provides a low-cost and facile method to fabricate natural mineral-based anode materials and apprise readers about the impact of uniform particle distribution on lithium storage performance.
2023, vol. 30, no. 7, pp.
1363-1374.
https://doi.org/10.1007/s12613-023-2618-5
Abstract:
Novel graphitic carbon nitride (g-C3N4) nanosheet/Bi5O7Br/NH2-MIL-88B (Fe) photocatalysts (denoted as GCN-NSh/Bi5O7Br/Fe-MOF, in which MOF is metal–organic framework) with double S-scheme heterojunctions were synthesized by a facile solvothermal route. The resultant materials were examined by X-ray photoelectron spectrometer (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflection spectroscopy (UV-vis DRS), photocurrent density, electrochemical impedance spectroscopy (EIS), and Brunauer–Emmett–Teller (BET) analyses. After the integration of Fe-MOF with GCN-NSh/Bi5O7Br, the removal constant of tetracycline over the optimal GCN-NSh/Bi5O7Br/Fe-MOF (15wt%) nanocomposite was promoted 33 times compared with that of the pristine GCN. The GCN-NSh/Bi5O7Br/Fe-MOF (15wt%) nanocomposite showed superior photoactivity to azithromycin, metronidazole, and cephalexin removal that was 36.4, 20.2, and 14.6 times higher than that of pure GCN, respectively. Radical quenching tests showed that •O\begin{document}${}_2^- $\end{document} ![]()
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Novel graphitic carbon nitride (g-C3N4) nanosheet/Bi5O7Br/NH2-MIL-88B (Fe) photocatalysts (denoted as GCN-NSh/Bi5O7Br/Fe-MOF, in which MOF is metal–organic framework) with double S-scheme heterojunctions were synthesized by a facile solvothermal route. The resultant materials were examined by X-ray photoelectron spectrometer (XPS), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence spectroscopy (PL), Fourier transform infrared spectroscopy (FT-IR), UV-Vis diffuse reflection spectroscopy (UV-vis DRS), photocurrent density, electrochemical impedance spectroscopy (EIS), and Brunauer–Emmett–Teller (BET) analyses. After the integration of Fe-MOF with GCN-NSh/Bi5O7Br, the removal constant of tetracycline over the optimal GCN-NSh/Bi5O7Br/Fe-MOF (15wt%) nanocomposite was promoted 33 times compared with that of the pristine GCN. The GCN-NSh/Bi5O7Br/Fe-MOF (15wt%) nanocomposite showed superior photoactivity to azithromycin, metronidazole, and cephalexin removal that was 36.4, 20.2, and 14.6 times higher than that of pure GCN, respectively. Radical quenching tests showed that •O
2023, vol. 30, no. 7, pp.
1375-1387.
https://doi.org/10.1007/s12613-023-2605-x
Abstract:
As a heat-resistant wave-absorbing material, silicon carbide (SiC) aerogel has become a research hotspot at present. However, the most common silicon sources are organosilanes, which are costly and toxic. In this work, SiC aerogels were successfully prepared by using water glass as the silicon source. Specifically, the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process, and the effect on SiC aerogel microwave absorption properties was investigated. The SiC aerogels prepared with Si : C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity, with a minimum reflection loss value of −46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 GHz. They also have good physical properties, such as the density of 0.0444 g/cm3, the thermal conductivity of 0.0621 W/(m·K), and the specific surface area of 1099 m2/g. These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.
As a heat-resistant wave-absorbing material, silicon carbide (SiC) aerogel has become a research hotspot at present. However, the most common silicon sources are organosilanes, which are costly and toxic. In this work, SiC aerogels were successfully prepared by using water glass as the silicon source. Specifically, the microstructure and chemical composition of SiC aerogels were controlled by adjusting the Si to C molar ratio during the sol–gel process, and the effect on SiC aerogel microwave absorption properties was investigated. The SiC aerogels prepared with Si : C molar ratio of 1:1 have an effective electromagnetic wave absorption capacity, with a minimum reflection loss value of −46.30 dB at 12.88 GHz and an effective frequency bandwidth of 4.02 GHz. They also have good physical properties, such as the density of 0.0444 g/cm3, the thermal conductivity of 0.0621 W/(m·K), and the specific surface area of 1099 m2/g. These lightweight composites with microwave-absorbing properties and low thermal conductivity can be used as thermal protection materials for space shuttles and reusable carriers.
2023, vol. 30, no. 7, pp.
1388-1397.
https://doi.org/10.1007/s12613-023-2599-4
Abstract:
CoFe2O4 has been widely used for electromagnetic wave absorption owing to its high Snoek limit, high anisotropy, and suitable saturation magnetization; however, its inherent shortcomings, including low dielectric loss, high density, and magnetic agglomeration, limit its application as an ideal absorbent. This study investigated a microstructure regulation strategy to mitigate the inherent disadvantages of pristine CoFe2O4 synthesized via a sol–gel auto-combustion method. A series of CoFe2O4 foams (S0.5, S1.0, and S1.5, corresponding to foams with citric acid (CA)-to-Fe(NO3)3·9H2O molar ratios of 0.5, 1.0, and 1.5, respectively) with two-dimensional (2D) curved surfaces were obtained through the adjustment of CA-to-Fe3+ ratio, and the electromagnetic parameters were adjusted through morphology regulation. Owing to the appropriate impedance matching and conductance loss provided by moderate complex permittivity, the effective absorption bandwidth (EAB) of S0.5 was as high as 7.3 GHz, exceeding those of most CoFe2O4-based absorbents. Moreover, the EAB of S1.5 reached 5.0 GHz (8.9–13.9 GHz), covering most of the X band, owing to the intense polarization provided by lattice defects and the heterogeneous interface. The three-dimensional (3D) foam structure circumvented the high density and magnetic agglomeration issues of CoFe2O4 nanoparticles, and the good conductivity of 2D curved surfaces could effectively elevate the complex permittivity to ameliorate the dielectric loss of pure CoFe2O4. This study provides a novel idea for the theoretical design and practical production of lightweight and broadband pure ferrites.
CoFe2O4 has been widely used for electromagnetic wave absorption owing to its high Snoek limit, high anisotropy, and suitable saturation magnetization; however, its inherent shortcomings, including low dielectric loss, high density, and magnetic agglomeration, limit its application as an ideal absorbent. This study investigated a microstructure regulation strategy to mitigate the inherent disadvantages of pristine CoFe2O4 synthesized via a sol–gel auto-combustion method. A series of CoFe2O4 foams (S0.5, S1.0, and S1.5, corresponding to foams with citric acid (CA)-to-Fe(NO3)3·9H2O molar ratios of 0.5, 1.0, and 1.5, respectively) with two-dimensional (2D) curved surfaces were obtained through the adjustment of CA-to-Fe3+ ratio, and the electromagnetic parameters were adjusted through morphology regulation. Owing to the appropriate impedance matching and conductance loss provided by moderate complex permittivity, the effective absorption bandwidth (EAB) of S0.5 was as high as 7.3 GHz, exceeding those of most CoFe2O4-based absorbents. Moreover, the EAB of S1.5 reached 5.0 GHz (8.9–13.9 GHz), covering most of the X band, owing to the intense polarization provided by lattice defects and the heterogeneous interface. The three-dimensional (3D) foam structure circumvented the high density and magnetic agglomeration issues of CoFe2O4 nanoparticles, and the good conductivity of 2D curved surfaces could effectively elevate the complex permittivity to ameliorate the dielectric loss of pure CoFe2O4. This study provides a novel idea for the theoretical design and practical production of lightweight and broadband pure ferrites.
2023, vol. 30, no. 7, pp.
1398-1406.
https://doi.org/10.1007/s12613-023-2619-4
Abstract:
A polymer-derived ZrC ceramic with excellent electromagnetic interference (EMI) shielding performance was developed to meet ultra-high temperature requirements. The thermal decomposition process of ZrC organic precursor was studied to reveal the evolution of phase composition, microstructure, and EMI shielding performance. Furthermore, the carbothermal reduction reaction occurred at 1300°C, and the transition from ZrO2 to ZrC was completed at 1700°C. With the increase in the annealing temperature, the tetragonal zirconia gradually transformed into monoclinic zirconia, and the transition was completed at the annealing temperature of 1500°C due to the consumption of a large amount of the carbon phase. The average total shielding effectiveness values were 11.63, 22.67, 22.91, 22.81, and 34.73 dB when the polymer-derived ZrC was annealed at 900, 1100, 1300, 1500, and 1700°C, respectively. During the thermal decomposition process, the graphitization degree and phase distribution of free carbon played a dominant role in the shielding performance. The typical core–shell structure composed of carbon and ZrC can be formed at the annealing temperature of 1700°C, which results in excellent shielding performance.
A polymer-derived ZrC ceramic with excellent electromagnetic interference (EMI) shielding performance was developed to meet ultra-high temperature requirements. The thermal decomposition process of ZrC organic precursor was studied to reveal the evolution of phase composition, microstructure, and EMI shielding performance. Furthermore, the carbothermal reduction reaction occurred at 1300°C, and the transition from ZrO2 to ZrC was completed at 1700°C. With the increase in the annealing temperature, the tetragonal zirconia gradually transformed into monoclinic zirconia, and the transition was completed at the annealing temperature of 1500°C due to the consumption of a large amount of the carbon phase. The average total shielding effectiveness values were 11.63, 22.67, 22.91, 22.81, and 34.73 dB when the polymer-derived ZrC was annealed at 900, 1100, 1300, 1500, and 1700°C, respectively. During the thermal decomposition process, the graphitization degree and phase distribution of free carbon played a dominant role in the shielding performance. The typical core–shell structure composed of carbon and ZrC can be formed at the annealing temperature of 1700°C, which results in excellent shielding performance.
2023, vol. 30, no. 7, pp.
1407-1416.
https://doi.org/10.1007/s12613-023-2614-9
Abstract:
Tetragonal barium titanate was synthesized from barium hydroxide octahydrate and titanium tetrachloride through a simple one-step hydrothermal method. The effect of different solvents on the crystal structure and morphology of barium titanate nanoparticles during the hydrothermal process was investigated. Except for ethylene glycol/water solvent, impurity-free barium titanate was synthesized in pure water, methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents. Compared with other alcohols, ethanol promotes the formation of a tetragonal structure. In addition, characterization studies confirm that particles synthesized in methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents are smaller in size than those synthesized in pure water. In the case of alcohol-containing solvents, the particle size decreases in the order of isopropanol, ethanol, and methanol. Among all the media used in this study, ethanol/water is considered the optimum reaction media for barium titanate with high tetragonality (defined as the ratio of two lattice parameters c and a, c/a = 1.0088) and small average particle size (82 nm), which indicates its great application potential in multilayer ceramic capacitors.
Tetragonal barium titanate was synthesized from barium hydroxide octahydrate and titanium tetrachloride through a simple one-step hydrothermal method. The effect of different solvents on the crystal structure and morphology of barium titanate nanoparticles during the hydrothermal process was investigated. Except for ethylene glycol/water solvent, impurity-free barium titanate was synthesized in pure water, methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents. Compared with other alcohols, ethanol promotes the formation of a tetragonal structure. In addition, characterization studies confirm that particles synthesized in methanol/water, ethanol/water, and isopropyl alcohol/water mixed solvents are smaller in size than those synthesized in pure water. In the case of alcohol-containing solvents, the particle size decreases in the order of isopropanol, ethanol, and methanol. Among all the media used in this study, ethanol/water is considered the optimum reaction media for barium titanate with high tetragonality (defined as the ratio of two lattice parameters c and a, c/a = 1.0088) and small average particle size (82 nm), which indicates its great application potential in multilayer ceramic capacitors.
2023, vol. 30, no. 7, pp.
1417-1426.
https://doi.org/10.1007/s12613-022-2594-1
Abstract:
Manganese-substituted magnetite ferrofluids (FFs) MnxFe1−xFe2O4 (x = 0–0.8) were prepared in this work through a chemical co-precipitation reaction. The controlled growth of FF nanomaterials for antibacterial activities is challenging, and therefore, very few reports are available on the topic. This research focuses on stabilizing aqueous FFs with the tetramethylammonium hydroxide surfactant to achieve high homogeneity. Morphological characterization reveals nanoparticles of 5–11 nm formed by the chemical reaction and nanocrystalline nature, as evident from structural investigations. Mn-substituted magnetic FFs are analyzed for their structural, functional, and antibacterial performance according to the Mn-substituent content. Optical studies show a high blue shift for Mn2+-substituted MnxFe1−xFe2O4 with the theoretical correlation of optical band gaps with the Mn content. The superparamagnetic nature of substituted FFs causes zero coercivity and remanence, which consequently influence the particle size, cation distribution, and spin canting. The structural and functional performance of the FFs is correlated with the antibacterial activity, finally demonstrating the highest inhibition zone formation for MnxFe1−xFe2O4 FFs.
Manganese-substituted magnetite ferrofluids (FFs) MnxFe1−xFe2O4 (x = 0–0.8) were prepared in this work through a chemical co-precipitation reaction. The controlled growth of FF nanomaterials for antibacterial activities is challenging, and therefore, very few reports are available on the topic. This research focuses on stabilizing aqueous FFs with the tetramethylammonium hydroxide surfactant to achieve high homogeneity. Morphological characterization reveals nanoparticles of 5–11 nm formed by the chemical reaction and nanocrystalline nature, as evident from structural investigations. Mn-substituted magnetic FFs are analyzed for their structural, functional, and antibacterial performance according to the Mn-substituent content. Optical studies show a high blue shift for Mn2+-substituted MnxFe1−xFe2O4 with the theoretical correlation of optical band gaps with the Mn content. The superparamagnetic nature of substituted FFs causes zero coercivity and remanence, which consequently influence the particle size, cation distribution, and spin canting. The structural and functional performance of the FFs is correlated with the antibacterial activity, finally demonstrating the highest inhibition zone formation for MnxFe1−xFe2O4 FFs.
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