Advanced Powder Technology最新文献

Porosity variations have an impact on the disintegration behavior of tablets whereas the influence on the disintegration characteristics of natural plant product (NPP) tablets has not been extensively studied. Revealing the pore structure of NPP tablets provides a new and important clue to elucidate the phenomenal behavior and underlying mechanisms of tablet disintegration. In this study, the effect of porosity variation on disintegration of NPP tablets was evaluated for the first time. The disintegration performance of NPP tablets was evaluated using tablet attributes, disintegration kinetics, and the wicking process. Mercury intrusion porosimetry (MIP) and X-ray computed microtomography (XμCT) were used to characterize the microstructure of the tablets. Curcuma Longa Linn. extractions were compacted into tablets with different solid fractions. Tablet qualities changed significantly with increasing porosity. An increase in the wicking rate with porosity changed by visualizing the wicking process. The disintegration kinetics of tablets showed a sensitive variation after an increase in porosity. The pore structure of tablets including parameters such as pore size distribution, tortuosity, and connectivity were identified as direct drivers of wicking and disintegration. The current study provides new insights into the disintegration mechanism of dissolved NPP tablets by exploring the evolution of the pore microstructure.

The paper studied the structural features and physicomechanical properties of the WC–4wt.%TiC–3wt.%TaC–12wt.%Co composite refractory hard alloy system obtained by spark plasma sintering (SPS) from a preliminarily mechanically activated powder. It has been shown that preliminary mechanical activation in a planetary mill contributed to the comminution of agglomerates and the formation of a monomodal particle size distribution with a predominance of the submicron fraction, which intensifies the densification processes during subsequent consolidation by the SPS method. Kinetic analysis of the SPS process showed a two-stage sintering pattern with intense densification at temperatures above 790 °C due to rearrangement of WC, TiC, TaC particles and melting of the cobalt binder. It has been found that the SPS method does not lead to the formation of undesirable secondary phases in the entire sintering temperature range. A sintering temperature of 1200 °C is optimal for achieving the best structural homogeneity, density and mechanical properties, providing optimal distribution of carbide phases and the cobalt binder. The microstructure of the sample obtained at 1200 °C represents a refractory skeleton of WC grains with TiC and TaC carbide particles uniformly distributed throughout the volume. Improved fluidity of the melted cobalt binder and its mobile redistribution contribute to increased compactness of the structure and reduced porosity of the material. Samples sintered at 1200 °C possess high physicomechanical characteristics: relative density 99.99 %, hardness HV30 1623.2, bending strength 1125.1 MPa, fracture toughness 10.5 MN⋅m^1/2. The abrasive wear resistance of a newly synthesized hard material was evaluated through a turning operation. Results showed durability, indicating promise for cutting tool applications and the need for further research to fully characterize the performance of this novel material.

The remarkable differences in the metallurgical processes of copper and zinc require their host minerals to be separated as far as possible during beneficiation. For chalcopyrite and sphalerite, the primary host minerals of copper and zinc, their green and efficient separation in the beneficiation stage remains a great challenge. This work is the first to employ environmentally friendly pullulan polysaccharide (PP) as a sphalerite depressant to assist in the concentration of chalcopyrite. Flotation experiments have revealed that PP possesses a selective depression action on sphalerite without having a large influence on the recovery of chalcopyrite. Characterization analysis has revealed that PP can be adsorbed onto chalcopyrite and sphalerite surfaces, but with a different response to subsequent sorption collectors. PP adsorbs to the Zn atoms on sphalerite surfaces via its O atoms in the C−O−H group and thus prevents the adsorption of sodium butyl xanthate (BX). The Fe sites on the chalcopyrite surface can adsorb PP, but this process does not affect the BX adsorption as the Cu sites remain exposed. Hence, PP can enhance the hydrophilicity of sphalerite without interfering with the hydrophobicity of chalcopyrite, resulting in a desirable separation effect. Overall, this work offers a promising scheme for the concentration of chalcopyrite from sphalerite during beneficiation, thereby contributing to the efficient exploitation of copper and zinc resources.

FeSiAl/(Al₂O₃-Ni) soft magnetic composites (SMCs) were prepared by sintering FeSiAl/NiO composite powders, and the formation mechanism of the Al₂O₃-Ni composite coating and performance of the FeSiAl SMCs with different NiO coating content were studied. During sintering, high temperature promoted a reaction between Al and NiO at the FeSiAl/NiO interface, resulting in the in-situ formation of a composite coating comprising Al₂O₃ coating with high integrity and ferromagnetic Ni coating. The interdiffusion of Al and O^2– toward the interface ensured the continuation of the reaction and growth of the composite coating. The composite coating thickened with the increasing NiO coating content, thus showing reduced real part of permeability. Saturation magnetization considerably increased until the NiO coating content exceeded 12.5 wt% owing to residual NiO. Excessive NiO coating content led to the generation of a large amount of Ni, which was not conducive to the integrity of the Al₂O₃ coating and increased magnetic loss. The FeSiAl SMCs with 5.0 wt% NiO coating content exhibited exceptional performance with high saturation magnetization (135.3 emu/g), good frequency stability of permeability, and low magnetic loss (63.7 W/kg at 0.05 T/20 kHz).

Aiming at explaining the short-time dust emission from belt conveyors, an analytical scaling law model framework is introduced, employing the same assumptions and wall models as traditional numerical simulations. Further, assuming a piecewise mean velocity profile, the Lagrangian mean velocity of dust particles can be written as a general expression. This expression is validated in various cases, including the 2D Belt, 3D Belt, 2D Tire, and 3D Tire cases. Numerical results show that the theoretical prediction, with key parameters fixed at $u_s=5,\kappa =0.4187$, and $E=9.793$, fits well with the simulated Lagrangian mean velocity profiles. For example, in the 2D Belt case, short-time agreement is achieved within $t⩽1$ s, indicating the model’s effectiveness in predicting dust dispersion within this time frame.

This experimental study aims to enhance the understanding of the correlation among equivalent particle diameters measured using two analytical techniques: optical analysis (assisted by computer aided image analysis) and permeability tests. The presence or absence of a specific analytical method or instrument can lead to the use of an incorrect equivalent diameter. Therefore, it can be beneficial to establish conversion rules between different equivalent particle diameters obtained through various methods and instruments. The optical analysis returns an equivalent diameter value inherently independent of particle arrangement since it deals with isolated particles. In contrast, the permeability test offers an equivalent mean diameter dependent not only on the size of the particles but also on their packed arrangement. A suitable correlation between the two diameters has been proposed, shown to be a decreasing function of porosity following a power law.

An unexpected outcome of the comparison between the optical method and permeametry is the possibility to isolate and characterize the effect that the packing arrangement has on pressure losses and to characterize it in terms of the tortuosity of the path that the fluid must travel through the packed bed. Our findings confirm a strong alignment between our tortuosity model, which contains the ratio between the two equivalent diameters considered here, and an empirical correlation from literature often utilized for predicting packed bed tortuosity.

This study presents an innovative approach for synthesizing hierarchical porous carbon materials (HPCMs) tailored for high-performance supercapacitors. The proposed method combines oxidative foaming with self-activation, in-situ template, in-situ activation and template synthesis, respectively, utilizing glucose reactions with oxidizing agents like ammonium persulfate (APS), magnesium nitrate hexahydrate (MNH), and potassium persulfate (KPS). The process involves two stages: low-temperature foaming to initiate macropore formation and high-temperature annealing to create meso/micropores through in-situ template and activation. Generally, increasing the ratio of oxidant to glucose in the synthesis process can notably enhance the high specific surface area and pore volume of the HPCMs with a combination of micro/meso/macropores, exhibiting maximum values of 821 m²/g and 0.61 cm³/g (APS), 2077 m²/g and 3.05 cm³/g (MNH), 1845 m²/g and 1.29 cm³/g (KPS), respectively. Furthermore, the O and N, or S elements, can also be in-situ doped in the carbon framework. The hierarchical porous structure and the doping elements enhance the electrochemical performance of supercapacitors. The APS@4, with a high mass loading of 3.2 mg/cm², exhibits a superior specific capacitance of 144 F/g and an areal capacitance of 456 mF/cm² at a current density of 1 A/g. It demonstrates excellent cycling stability based on a capacitance retention of 100 % after 10,000 cycles.

In this study, an eco-friendly compound, carrageenan, was employed as a depressant for the selective separation of chalcopyrite and pyrite. The depressant performance and mechanism were comprehensively investigated. The results of the flotation experiments demonstrated that carrageenan exhibited selective depression towards pyrite as opposed to chalcopyrite, achieving flotation recoveries of 88.57 % for chalcopyrite and 9.57 % for pyrite with the combination of 2 × 10^-5 mol/L SIBX and 20 mg/L carrageenan. The results of AFM and contact angle measurements revealed that carrageenan exhibited selective adsorption on pyrite surface, resulting in an enhancement in surface hydrophilicity. In contrast, the adsorption of carrageenan on chalcopyrite surface was found to be negligible. Zeta potential and XPS analyses further confirmed the chemisorption of carrageenan on the pyrite surface, indicating the reaction involving sulfuric acid and hydroxyl groups on carrageenan and Fe sites on pyrite. Therefore, carrageenan holds potential as a promising depressant for the selective separation of chalcopyrite from pyrite.

In this study, modified low rank coal water slurry (M-LRCWS) was prepared by using diesel modified low rank coal (LRC) and compared with low LRC water slurry (LRCWS) to investigate the slurry formation mechanism and combustion characteristics of coal water slurry. Meanwhile, the combustion kinetics of coal-water slurry was investigated using kinetic methods to probe the combustion reaction mechanism. The results showed that the slurry formation concentration of LRC was 70 %, while the slurry formation concentration of M-LRCWS was 72 %, which was an increase of 2 %. The diesel modification positively affected the stability of CWS. The comprehensive combustion characteristics index of the same slurry deteriorated with increasing heating rate. At the same heating rate, M-LRCWS has better combined combustion performance, higher flammability and more stable ignition performance. Combustion kinetics calculations showed that the reaction activation energies were 105.50 kJ/mol for M-LRCWS and 99.59 kJ/mol for LRCWS using the FWO method, and 93.48 kJ/mol for M-LRCWS and 92.68 kJ/mol for LRCWS using the Starink method. The activation energy of M-LRCWS is slightly higher than that of LRCWS, which indicates that the diesel fuel is encapsulated in the coal particles and it is difficult to activate the substance. As a result, the dispersion system is more stable and favorable for storage and transportation. The physical functions of LRCWS and M-LRCWS were calculated using the Achar differential equation and the Coats-Redfern integral equation, and the results showed that both LRCWS and M-LRCWS followed the tertiary reaction (F3) mechanism.

Poor wettability and weak graphene/Cu interface limit the mechanical properties’ enhancement in graphene/Cu composites. This study devised an interface enhancement approach by Ag decoration of graphene nanoplatelets (Ag-GNPs) and Ag decorated nitrogen doped graphene (Ag-N-GNP) without oxide (during decoration) and carbide (during sintering) formation. Sonication was used to functionalize GNPs for decoration with Ag nanoparticles (NPs) and Cu composites (Ag-GNP/Cu and Ag-N-GNP/Cu) were fabricated using cold pressing (low-pressure) and sintering. 2-Ag-GNP/Cu (2 vol% of Ag-GNPs) and 2-Ag-N-GNP/Cu (2 vol% of Ag-N-GNPs) possessed highest sintered density. In addition, 2-Ag-GNP/Cu and 1-Ag-N-GNP/Cu showed highest microhardness and tensile strength (theoretical), respectively. Higher concentration of Ag NPs on GNPs in Ag-N-GNP (oxygen and nitrogen functionalization) showed lower mechanical properties for Ag-N-GNP/Cu compared to Ag-GNP/Cu with limited Ag NPs on GNPs (oxygen functionalization). Interface modification strategy with noble metal NPs bridging between GNP and Cu suggests controlled functionalization and noble metal NPs’ attachment on GNPs for effective mechanical properties’ enhancement in graphene Cu composites.