Pub Date : 2024-10-22DOI: 10.1016/j.apt.2024.104689
A design method for wet stirred ball milling by the simulation using the Discrete Element Method (DEM) was developed. The method optimized milling conditions for wet stirred ball milling by using the simulation to search for the optimal milling condition that maximizes a milling performance indicator. The milling performance indicator was defined in such a manner that the value of the indicator was maximized when more target particles with the desired particle diameter were produced in less milling time and with lower power consumption and less contamination. Furthermore, it was confirmed that the optimal milling condition estimated by the simulation agreed with the experiments. Therefore, it was suggested that the developed method has the potential to design the milling conditions of the wet stirred ball milling.
{"title":"Development of design method for wet stirred ball milling by simulation using DEM","authors":"","doi":"10.1016/j.apt.2024.104689","DOIUrl":"10.1016/j.apt.2024.104689","url":null,"abstract":"<div><div>A design method for wet stirred ball milling by the simulation using the Discrete Element Method (DEM) was developed. The method optimized milling conditions for wet stirred ball milling by using the simulation to search for the optimal milling condition that maximizes a milling performance indicator. The milling performance indicator was defined in such a manner that the value of the indicator was maximized when more target particles with the desired particle diameter were produced in less milling time and with lower power consumption and less contamination. Furthermore, it was confirmed that the optimal milling condition estimated by the simulation agreed with the experiments. Therefore, it was suggested that the developed method has the potential to design the milling conditions of the wet stirred ball milling.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528120","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-22DOI: 10.1016/j.apt.2024.104694
In order to address the key question of how the thickness of the C shell affects the microwave absorption properties of metal-C core–shell nanoparticles, FeCo-C core–shell nanoparticles, with identical metal cores but varied carbon shell thicknesses, were synthesized by simply annealing FeCo-C core–shell nanoparticles in air. The free electronic-polarization theory was employed, and thus the polarization storage dependence of the loss plot, i.e., was introduced to elucidate the underlying microwave absorption mechanism. It was found that permittivities, conduction and polarization losses degrade as the carbon shell becomes thinner. Meanwhile, the thickness of the C shells was well adjusted to tune the magnetic resonance frequencies and intensities of the nanoparticles. Notably, a thicker C shell enhances the complete polarization relaxation process and increases polarization loss. Due to optimal dielectric and magnetic properties, FeCo-C nanoparticles exhibit an optimal reflection loss value up to −72.2 dB and an effective absorption bandwidth of 7.6 GHz at 3.5 mm. These results indicate that the synthesized FeCo-C core–shell nanoparticle is a promising candidate for microwave absorption applications. Furthermore, the introduction of plot is expected to have a significant impact on the field of microwave absorption.
{"title":"Microwave absorption of FeCo-C core–shell nanoparticles with tunable thickness of C shells and the underlying mechanism","authors":"","doi":"10.1016/j.apt.2024.104694","DOIUrl":"10.1016/j.apt.2024.104694","url":null,"abstract":"<div><div>In order to address the key question of how the thickness of the C shell affects the microwave absorption properties of metal-C core–shell nanoparticles, FeCo-C core–shell nanoparticles, with identical metal cores but varied carbon shell thicknesses, were synthesized by simply annealing FeCo-C core–shell nanoparticles in air. The free electronic-polarization theory was employed, and thus the polarization storage dependence of the loss plot, <em>i.e.</em>, <span><math><mrow><msubsup><mi>ε</mi><mrow><mi>p</mi></mrow><mo>′</mo></msubsup><mo>-</mo><msubsup><mi>ε</mi><mrow><mi>p</mi></mrow><mrow><mo>\"</mo></mrow></msubsup></mrow></math></span> was introduced to elucidate the underlying microwave absorption mechanism. It was found that permittivities, conduction and polarization losses degrade as the carbon shell becomes thinner. Meanwhile, the thickness of the C shells was well adjusted to tune the magnetic resonance frequencies and intensities of the nanoparticles. Notably, a thicker C shell enhances the complete polarization relaxation process and increases polarization loss. Due to optimal dielectric and magnetic properties, FeCo-C nanoparticles exhibit an optimal reflection loss value up to −72.2 dB and an effective absorption bandwidth of 7.6 GHz at 3.5 mm. These results indicate that the synthesized FeCo-C core–shell nanoparticle is a promising candidate for microwave absorption applications. Furthermore, the introduction of <span><math><mrow><msubsup><mi>ε</mi><mrow><mi>p</mi></mrow><mo>′</mo></msubsup><mo>-</mo><msubsup><mi>ε</mi><mrow><mi>p</mi></mrow><mrow><mo>\"</mo></mrow></msubsup></mrow></math></span> plot is expected to have a significant impact on the field of microwave absorption.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528121","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-21DOI: 10.1016/j.apt.2024.104696
This study introduces a novel one-pot reaction system that efficiently converts greenhouse gases into methanol while simultaneously processing polyethylene terephthalate (PET) into dimethyl terephthalate (DMT) and ethylene glycol (EG). Our approach involves the development of hybrid materials derived from metal-organic frameworks (MOFs) using an aerosol-assisted synthesis method. These catalysts, which include a Cu/ZnO active phase on various supports, are optimized for the hydrogenation of both carbon monoxide (CO) and carbon dioxide (CO2). By integrating PET methanolysis with the (CO2 + CO) hydrogenation process, we achieved a significant enhancement in conversion ratios, exceeding 2.5 times their individual values. This synergistic approach effectively addresses the challenges posed by both plastic waste and greenhouse gas emissions. An impressive space–time yield of 5.6 mmol gcat−1h−1 and selectivity of 92 % for DMT production were achievable under optimized conditions. These results highlight the effectiveness of MOF-derived catalyst materials in facilitating complex chemical transformations and contribute significantly to environmental sustainability. This dual-function system offers a practical solution for the utilization of plastic waste and greenhouse gases, marking an important step toward a circular economy.
{"title":"Combined (CO2 + CO) hydrogenation with methanolysis using aerosol metal-organic framework-derived hybrid catalysts","authors":"","doi":"10.1016/j.apt.2024.104696","DOIUrl":"10.1016/j.apt.2024.104696","url":null,"abstract":"<div><div>This study introduces a novel one-pot reaction system that efficiently converts greenhouse gases into methanol while simultaneously processing polyethylene terephthalate (PET) into dimethyl terephthalate (DMT) and ethylene glycol (EG). Our approach involves the development of hybrid materials derived from metal-organic frameworks (MOFs) using an aerosol-assisted synthesis method. These catalysts, which include a Cu/ZnO active phase on various supports, are optimized for the hydrogenation of both carbon monoxide (CO) and carbon dioxide (CO<sub>2</sub>). By integrating PET methanolysis with the (CO<sub>2</sub> + CO) hydrogenation process, we achieved a significant enhancement in conversion ratios, exceeding 2.5 times their individual values. This synergistic approach effectively addresses the challenges posed by both plastic waste and greenhouse gas emissions. An impressive space–time yield of 5.6 mmol g<sub>cat</sub><sup>−1</sup>h<sup>−1</sup> and selectivity of 92 % for DMT production were achievable under optimized conditions. These results highlight the effectiveness of MOF-derived catalyst materials in facilitating complex chemical transformations and contribute significantly to environmental sustainability. This dual-function system offers a practical solution for the utilization of plastic waste and greenhouse gases, marking an important step toward a circular economy.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142528119","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.apt.2024.104690
An innovative method for fabrication and investigating the effect of mechanical activation duration (MAD) on the properties of TiAl alloys was developed. The study employs an efficient implementation of combustion reactions in a compressed, mechanically activated mixture of titanium and aluminum, leading to the synthesis of titanium aluminide (TiAl). The induction-activated method initiates an exothermic reaction between Ti and Al, facilitating simultaneous preheating and ignition under an argon gas atmosphere. The accomplishment of the synthesis process lasted very short times, and the products were characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) techniques. The investigation focuses on samples with MAD durations ranging from 1 to 10 h, revealing that higher MADs (4 to 10 h) result in an innovative microstructure with α2 (Ti3Al)/γ (TiAl) round-shape lamellar grains embedded in the γ (TiAl) matrix. This microstructure enhances the toughness of TiAl alloys while maintaining comparable hardness. The study indicates that increasing MAD from 1 to 10 h improves reaction kinetics, leading to a rise in reaction front velocity from 3.95 to 5.02 mm s−1 and a reduction in α2 (Ti3Al)/γ (TiAl) round-shape lamellar grain size from 215.804 to 172.709 μm in a more homogeneous arrangement. Furthermore, corrosion behavior analysis for samples with 1 and 10 h MAD reveals an increase in the resistance of the oxide layer (Rf) value from 702.9 to 43111 Ω.cm2 and the charge transfer resistance (Rct) value from 41.84 to 18520 Ω.cm2.
{"title":"Investigating the effect of mechanical activation duration (MAD) on the microstructure and corrosion behavior of TiAl intermetallic compounds","authors":"","doi":"10.1016/j.apt.2024.104690","DOIUrl":"10.1016/j.apt.2024.104690","url":null,"abstract":"<div><div>An innovative method for fabrication and investigating the effect of mechanical activation duration (MAD) on the properties of TiAl alloys was developed. The study employs an efficient implementation of combustion reactions in a compressed, mechanically activated mixture of titanium and aluminum, leading to the synthesis of titanium aluminide (TiAl). The induction-activated method initiates an exothermic reaction between Ti and Al, facilitating simultaneous preheating and ignition under an argon gas atmosphere. The accomplishment of the synthesis process lasted very short times, and the products were characterized using X-ray diffraction (XRD), energy dispersive X-ray (EDX), scanning electron microscopy (SEM), and electrochemical impedance spectroscopy (EIS) techniques. The investigation focuses on samples with MAD durations ranging from 1 to 10 h, revealing that higher MADs (4 to 10 h) result in an innovative microstructure with α<sub>2</sub> (Ti<sub>3</sub>Al)/γ (TiAl) round-shape lamellar grains embedded in the γ (TiAl) matrix. This microstructure enhances the toughness of TiAl alloys while maintaining comparable hardness. The study indicates that increasing MAD from 1 to 10 h improves reaction kinetics, leading to a rise in reaction front velocity from 3.95 to 5.02 mm s<sup>−1</sup> and a reduction in α<sub>2</sub> (Ti<sub>3</sub>Al)/γ (TiAl) round-shape lamellar grain size from 215.804 to 172.709 μm in a more homogeneous arrangement. Furthermore, corrosion behavior analysis for samples with 1 and 10 h MAD reveals an increase in the resistance of the oxide layer (R<sub>f</sub>) value from 702.9 to 43111 Ω.cm<sup>2</sup> and the charge transfer resistance (R<sub>ct</sub>) value from 41.84 to 18520 Ω.cm<sup>2</sup>.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445951","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.apt.2024.104695
Eu3+-doped and Li+/Na+ co-doped K3Y(BO2)6 (KYBO) phosphors were synthesized through a microwave-assisted sol–gel method, and their structural and photoluminescent (PL) characteristics were examined. X-ray diffraction (XRD) and Rietveld refinement confirm effective dopant incorporation and preservation of the crystalline structure. Fourier Transform Infrared (FTIR) spectroscopy indicates the maintenance of the borate structure, confirming the structural integrity of the phosphors upon doping. The addition of Li+ and Na+ co-dopants notably enhances luminescent efficiency and thermal stability, making these phosphors promising candidates for solid-state lighting (SSL) applications. PL analysis reveals strong red emission peaks at 612 nm, attributed to the 5Do → 7F2 transition of Eu3+ ions. The study indicates that electric dipole-quadrupole interactions are the primary mechanism for energy migration, with a critical distance of approximately 22.68 Å. This mechanism contributes to concentration quenching at higher doping levels. High temperature PL measurements indicated an activation energy of 0.1389 eV for thermal quenching in the Li+ co-doped sample. Additionally, the Na+ co-doped sample exhibited an abnormal thermal stability behavior, with an even higher activation energy of 0.2536 eV. This suggests that Na+ co-doping significantly enhances the thermal resilience of the phosphor, making it more suitable for high-power light-emitting applications that operate under extreme conditions. CIE chromaticity diagrams highlight the potential for optimizing Eu3+ doping levels, combined with Li+ and Na+ co-doping, to improve luminescent performance and thermal stability for advanced SSL applications.
{"title":"Enhancement of luminescence and thermal stability in Eu3+-doped K3Y(BO2)6 with Li+ and Na+ co-doping","authors":"","doi":"10.1016/j.apt.2024.104695","DOIUrl":"10.1016/j.apt.2024.104695","url":null,"abstract":"<div><div>Eu<sup>3+</sup>-doped and Li<sup>+</sup>/Na<sup>+</sup> co-doped K<sub>3</sub>Y(BO<sub>2</sub>)<sub>6</sub> (KYBO) phosphors were synthesized through a microwave-assisted sol–gel method, and their structural and photoluminescent (PL) characteristics were examined. X-ray diffraction (XRD) and Rietveld refinement confirm effective dopant incorporation and preservation of the crystalline structure. Fourier Transform Infrared (FTIR) spectroscopy indicates the maintenance of the borate structure, confirming the structural integrity of the phosphors upon doping. The addition of Li<sup>+</sup> and Na<sup>+</sup> co-dopants notably enhances luminescent efficiency and thermal stability, making these phosphors promising candidates for solid-state lighting (SSL) applications. PL analysis reveals strong red emission peaks at 612 nm, attributed to the <sup>5</sup>D<sub>o</sub> → <sup>7</sup>F<sub>2</sub> transition of Eu<sup>3+</sup> ions. The study indicates that electric dipole-quadrupole interactions are the primary mechanism for energy migration, with a critical distance of approximately 22.68 Å. This mechanism contributes to concentration quenching at higher doping levels. High temperature PL measurements indicated an activation energy of 0.1389 eV for thermal quenching in the Li<sup>+</sup> co-doped sample. Additionally, the Na<sup>+</sup> co-doped sample exhibited an abnormal thermal stability behavior, with an even higher activation energy of 0.2536 eV. This suggests that Na<sup>+</sup> co-doping significantly enhances the thermal resilience of the phosphor, making it more suitable for high-power light-emitting applications that operate under extreme conditions. CIE chromaticity diagrams highlight the potential for optimizing Eu<sup>3+</sup> doping levels, combined with Li<sup>+</sup> and Na<sup>+</sup> co-doping, to improve luminescent performance and thermal stability for advanced SSL applications.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445950","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-18DOI: 10.1016/j.apt.2024.104699
Low-rank coal is naturally hydrophilic, and the traditional hydrocarbon collectors often have poor performance in its flotation. In this study, the modification of diesel was conducted using an instantaneous gasification-oxidation-condensation device for the expected improvement of collector’s performance. Experimental analyses and interfacial interaction calculation were performed to explore the mechanism of enhancing flotation of long-flame coal by diesel modification. It indicated that the flotation of coal sample can be greatly enhanced by the modified diesel, and a combustible matter recovery of 90.52 % could be attained only consuming 6 kg/t of modified diesel which was far better than the flotation effect consuming 100 kg/t of common diesel. The improved flotation effect of the coal sample could be attributed to the increased polarity of collector from 0.48 % to 9.76 % resulted from the newly added oxygenated functional groups after the oxidation of diesel, which significantly enhanced the adsorption capacity of the collector on the long-flame coal surface reflected by the FTIR and XPS analyses. Furthermore, the calculated results of interfacial interaction between the coal sample and the common/modified diesel suggested that the efficient adsorption of modified diesel on the coal sample was achieved through the bridging role acted by water molecules. This research may give some insight into enhancing flotation of low-rank coal.
{"title":"Exploration on the mechanism of enhancing flotation of long-flame coal by diesel modification via oxidation","authors":"","doi":"10.1016/j.apt.2024.104699","DOIUrl":"10.1016/j.apt.2024.104699","url":null,"abstract":"<div><div>Low-rank coal is naturally hydrophilic, and the traditional hydrocarbon collectors often have poor performance in its flotation. In this study, the modification of diesel was conducted using an instantaneous gasification-oxidation-condensation device for the expected improvement of collector’s performance. Experimental analyses and interfacial interaction calculation were performed to explore the mechanism of enhancing flotation of long-flame coal by diesel modification. It indicated that the flotation of coal sample can be greatly enhanced by the modified diesel, and a combustible matter recovery of 90.52 % could be attained only consuming 6 kg/t of modified diesel which was far better than the flotation effect consuming 100 kg/t of common diesel. The improved flotation effect of the coal sample could be attributed to the increased polarity of collector from 0.48 % to 9.76 % resulted from the newly added oxygenated functional groups after the oxidation of diesel, which significantly enhanced the adsorption capacity of the collector on the long-flame coal surface reflected by the FTIR and XPS analyses. Furthermore, the calculated results of interfacial interaction between the coal sample and the common/modified diesel suggested that the efficient adsorption of modified diesel on the coal sample was achieved through the bridging role acted by water molecules. This research may give some insight into enhancing flotation of low-rank coal.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142535152","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-17DOI: 10.1016/j.apt.2024.104691
Large eddy simulation of dense particle flow in fluidized bed is an advanced strategy to acquire a better understanding mechanism of gas-particle two-phase turbulent flow. A novelty particle stress model at subgrid scale level based on the Euler-Euler two-fluid frame is proposed to consider the effect of gas flow on particle dynamics. Anisotropic dispersion of interactions between gas and particle is modeled by a developed second-order moment approach, the four-way coupling is used to combine the particle–particle collisions by using the particle granular temperature based on the kinetic theory of granular flow. Numerical simulation is carried out in a small-scale fluidized bed and predictions are well agreed with the experimental data. Results show that the evolution of core-annular flow structure is captured. Increased superficial gas velocity is favorable for the enhancement of bubble hydrodynamics and anisotropic particle dispersions. At the 4umf, Bubblelike granular temperature is 11.2 times larger than particle granular temperature, and mean and standard deviation values of axial particle velocity are approximately 2.2 times and 1.5 times larger than those of 2umf. Bubble motions have a great effect on the heterogeneous flow pattern, particle dynamics and the redistribution of particle Reynolds stresses.
{"title":"A Euler-Euler hydrodynamic modelling and simulation of dense particle flow in a small-scale fluidized bed","authors":"","doi":"10.1016/j.apt.2024.104691","DOIUrl":"10.1016/j.apt.2024.104691","url":null,"abstract":"<div><div>Large eddy simulation of dense particle flow in fluidized bed is an advanced strategy to acquire a better understanding mechanism of gas-particle two-phase turbulent flow. A novelty particle stress model at subgrid scale level based on the Euler-Euler two-fluid frame is proposed to consider the effect of gas flow on particle dynamics. Anisotropic dispersion of interactions between gas and particle is modeled by a developed second-order moment approach, the four-way coupling is used to combine the particle–particle collisions by using the particle granular temperature based on the kinetic theory of granular flow. Numerical simulation is carried out in a small-scale fluidized bed and predictions are well agreed with the experimental data. Results show that the evolution of core-annular flow structure is captured. Increased superficial gas velocity is favorable for the enhancement of bubble hydrodynamics and anisotropic particle dispersions. At the 4u<sub>mf</sub>, Bubblelike granular temperature is 11.2 times larger than particle granular temperature, and mean and standard deviation values of axial particle velocity are approximately 2.2 times and 1.5 times larger than those of 2u<sub>mf</sub>. Bubble motions have a great effect on the heterogeneous flow pattern, particle dynamics and the redistribution of particle Reynolds stresses.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445318","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.apt.2024.104692
Particle gradation effect on the shear-dilatancy of granular soils was studied through a series of drained triaxial tests using the discrete element and finite difference methods (PFC3D-FLAC3D). Spherical particles with different coefficients of uniformity Cu and median particle sizes D50 were assembled to exclude the strong size-shape correlation in natural sands. Four groups of Cu and four groups of D50 at the same void ratio ec prior to shearing, and seven more groups with the same void ratio e0 prior to isotropic compression were tested. Various mechanical behaviors were analyzed, including the stress–strain response, the stress-dilatancy response, friction angle, and fabric anisotropy. Cu significantly influences the peak friction angle, the maximum dilation angle, and the anisotropies of normal contact force and contact normal, whereas these are almost independent of D50. The contribution of the maximum rate of dilation to the excess friction angle is largely independent of Cu and D50 for spherical particles.
利用离散元和有限差分方法（PFC3D-FLAC3D），通过一系列排水三轴试验研究了颗粒级配对粒状土剪切膨胀性的影响。试验采用不同均匀系数 Cu 和中值粒径 D50 的球形颗粒，以排除天然砂中粒径-形状的强烈相关性。在剪切前测试了四组空隙率 ec 相同的 Cu 和四组 D50，在各向同性压缩前又测试了七组空隙率 e0 相同的 Cu 和 D50。分析了各种力学行为，包括应力-应变响应、应力-膨胀响应、摩擦角和织物各向异性。铜对峰值摩擦角、最大扩张角以及法向接触力和接触法线的各向异性有很大影响，而这些因素几乎与 D50 无关。对于球形颗粒而言，最大扩张率对过大摩擦角的贡献在很大程度上与铜和 D50 无关。
{"title":"DEM investigation of particle gradation effect on the stress-dilatancy behavior of granular soil","authors":"","doi":"10.1016/j.apt.2024.104692","DOIUrl":"10.1016/j.apt.2024.104692","url":null,"abstract":"<div><div>Particle gradation effect on the shear-dilatancy of granular soils was studied through a series of drained triaxial tests using the discrete element and finite difference methods (PFC<sup>3D</sup>-FLAC<sup>3D</sup>). Spherical particles with different coefficients of uniformity <em>C<sub>u</sub></em> and median particle sizes <em>D</em><sub>50</sub> were assembled to exclude the strong size-shape correlation in natural sands. Four groups of <em>C<sub>u</sub></em> and four groups of <em>D</em><sub>50</sub> at the same void ratio <em>e<sub>c</sub></em> prior to shearing, and seven more groups with the same void ratio <em>e</em><sub>0</sub> prior to isotropic compression were tested. Various mechanical behaviors were analyzed, including the stress–strain response, the stress-dilatancy response, friction angle, and fabric anisotropy. <em>C<sub>u</sub></em> significantly influences the peak friction angle, the maximum dilation angle, and the anisotropies of normal contact force and contact normal, whereas these are almost independent of <em>D</em><sub>50</sub>. The contribution of the maximum rate of dilation to the excess friction angle is largely independent of <em>C<sub>u</sub></em> and <em>D</em><sub>50</sub> for spherical particles.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441769","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-16DOI: 10.1016/j.apt.2024.104698
MFI-topology nanosheets with a b-axis-oriented structure are valuable catalysts in diffusion-controlled acid-catalyzed reactions. Therefore, b-axis-oriented ZSM-5 nanosheets were synthesized herein in a fluoride-free solution without using special additives and complex methods. The initial gel pH of mixed raw materials was adjusted to approximately 5–7 (weak acidity) to direct nanosheet structure formation. The target ZSM-5 zeolite with a b-axis-oriented structure was achieved through the synergistic effect between the involved gel pH and seed solution. The seed solution directed the formation of an MFI structure, and the low alkalinity of the gel limited crystal growth in the b plane, thereby affording b-axis-oriented thin sheets. The ratio of the lengths of the c and b axes of the obtained ZSM-5 could be effectively tuned by adjusting the pH of the initial gel. Compared with the nanosized hexagonal ZSM-5 sample synthesized in a strong-basic system, the as-synthesized b-axis-oriented ZSM-5 exhibited a lower coking rate and higher propylene yield during the considered 1-hexene cracking reaction.
具有 b 轴定向结构的 MFI 拓扑纳米片是扩散控制酸催化反应中的重要催化剂。因此，本文在无氟溶液中合成了以 b 轴为方向的 ZSM-5 纳米片，无需使用特殊添加剂和复杂方法。为了引导纳米片结构的形成，混合原料的初始凝胶 pH 值被调至约 5-7（弱酸性）。通过所涉及的凝胶 pH 值和种子溶液之间的协同效应，实现了具有 b 轴方向结构的 ZSM-5 目标沸石。种子溶液引导 MFI 结构的形成，而凝胶的低碱度限制了晶体在 b 平面的生长，从而获得了面向 b 轴的薄片。通过调节初始凝胶的 pH 值，可以有效地调整所得到的 ZSM-5 的 c 轴和 b 轴的长度比。与在强碱体系中合成的纳米六方 ZSM-5 样品相比，合成的 b 轴定向 ZSM-5 在所考虑的 1- 己烯裂解反应中表现出更低的结焦率和更高的丙烯产率。
{"title":"Fluoride- and OSDA-free synthesis of ZSM-5 with controllable b-axis orientation: Insights into the role of medium alkalinity and seed induction","authors":"","doi":"10.1016/j.apt.2024.104698","DOIUrl":"10.1016/j.apt.2024.104698","url":null,"abstract":"<div><div>MFI-topology nanosheets with a b-axis-oriented structure are valuable catalysts in diffusion-controlled acid-catalyzed reactions. Therefore, b-axis-oriented ZSM-5 nanosheets were synthesized herein in a fluoride-free solution without using special additives and complex methods. The initial gel pH of mixed raw materials was adjusted to approximately 5–7 (weak acidity) to direct nanosheet structure formation. The target ZSM-5 zeolite with a b-axis-oriented structure was achieved through the synergistic effect between the involved gel pH and seed solution. The seed solution directed the formation of an MFI structure, and the low alkalinity of the gel limited crystal growth in the b plane, thereby affording b-axis-oriented thin sheets. The ratio of the lengths of the c and b axes of the obtained ZSM-5 could be effectively tuned by adjusting the pH of the initial gel. Compared with the nanosized hexagonal ZSM-5 sample synthesized in a strong-basic system, the as-synthesized b-axis-oriented ZSM-5 exhibited a lower coking rate and higher propylene yield during the considered 1-hexene cracking reaction.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142441770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-10-12DOI: 10.1016/j.apt.2024.104687
The development of light-emitting diode (LED) technology has intensified the requirements for the particle size of the K2SiF6:Mn4+ phosphor. However, the synthesis technology of the K2SiF6:Mn4+ phosphor possessing small particle sizes remains underdeveloped, rendering it difficult to fulfill the development requirements of display technology. This study presents an ammonium salt–assisted synthesis strategy for the rapid and hydrofluoric acid–free synthesis of submicron-sized K2SiF6:Mn4+, achieving an internal quantum yield of 98 % and average particle size of ∼ 200 nm. The synthesized material demonstrates excellent thermal stability, and its luminous intensity at 423 K is 136 % higher than that at 298 K, which is attributed to a negative thermal quenching effect. A high-performance white LED prepared using the as-developed material as the red-light-generation component exhibited a luminous efficacy of 113 lm/W and color rendering index of 93. Furthermore, the fluorescent inks developed using the prepared submicron phosphors can be utilized for screen printing. In summary, this study introduces a method for the ecofriendly, efficient, and cost-effective synthesis of submicron Mn4+-doped fluoride phosphors. Moreover, it presents a potential red fluorescent material for application in the development of full-color micro-LEDs.
发光二极管（LED）技术的发展提高了对 K2SiF6:Mn4+ 荧光粉粒径的要求。然而，具有小粒径的 K2SiF6:Mn4+ 荧光粉的合成技术仍不发达，难以满足显示技术的发展要求。本研究提出了一种铵盐辅助的合成策略，可快速、无氢氟酸地合成亚微米尺寸的 K2SiF6:Mn4+ ，内量子产率达到 98 %，平均粒径为 ∼ 200 nm。合成材料具有出色的热稳定性，其在 423 K 时的发光强度比 298 K 时高 136%，这归功于负热淬效应。使用所开发的材料作为红光生成元件制备的高性能白光 LED 的光效为 113 lm/W，显色指数为 93。此外，利用所制备的亚微米荧光粉开发的荧光油墨还可用于丝网印刷。总之，本研究介绍了一种环保、高效、低成本合成亚微米掺杂 Mn4+ 的氟化物荧光粉的方法。此外，它还提出了一种潜在的红色荧光材料，可用于开发全彩色微型 LED。
{"title":"Rapid synthesis of environmentally friendly submicron K2SiF6:Mn4+ phosphors: Advancing micro-LED technology","authors":"","doi":"10.1016/j.apt.2024.104687","DOIUrl":"10.1016/j.apt.2024.104687","url":null,"abstract":"<div><div>The development of light-emitting diode (LED) technology has intensified the requirements for the particle size of the K<sub>2</sub>SiF<sub>6</sub>:Mn<sup>4+</sup> phosphor. However, the synthesis technology of the K<sub>2</sub>SiF<sub>6</sub>:Mn<sup>4+</sup> phosphor possessing small particle sizes remains underdeveloped, rendering it difficult to fulfill the development requirements of display technology. This study presents an ammonium salt–assisted synthesis strategy for the rapid and hydrofluoric acid–free synthesis of submicron-sized K<sub>2</sub>SiF<sub>6</sub>:Mn<sup>4+</sup>, achieving an internal quantum yield of 98 % and average particle size of ∼ 200 nm. The synthesized material demonstrates excellent thermal stability, and its luminous intensity at 423 K is 136 % higher than that at 298 K, which is attributed to a negative thermal quenching effect. A high-performance white LED prepared using the as-developed material as the red-light-generation component exhibited a luminous efficacy of 113 lm/W and color rendering index of 93. Furthermore, the fluorescent inks developed using the prepared submicron phosphors can be utilized for screen printing. In summary, this study introduces a method for the ecofriendly, efficient, and cost-effective synthesis of submicron Mn<sup>4+</sup>-doped fluoride phosphors. Moreover, it presents a potential red fluorescent material for application in the development of full-color micro-LEDs.</div></div>","PeriodicalId":7232,"journal":{"name":"Advanced Powder Technology","volume":null,"pages":null},"PeriodicalIF":4.2,"publicationDate":"2024-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142428039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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