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Powders, Volume 4, Issue 3 (September 2025) – 5 articles

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27 pages, 10150 KiB  
Article
Numerical Simulation and Experimental Study of the Thermal Wick-Debinding Used in Low-Pressure Powder Injection Molding
by Mohamed Amine Turki, Dorian Delbergue, Gabriel Marcil-St-Onge and Vincent Demers
Powders 2025, 4(3), 22; https://doi.org/10.3390/powders4030022 - 1 Aug 2025
Abstract
Thermal wick-debinding, commonly used in low-pressure injection molding, remains challenging due to complex interactions between binder transport, capillary forces, and thermal effects. This study presents a numerical simulation of binder removal kinetics by coupling Darcy’s law with the Phase Transport in Porous Media [...] Read more.
Thermal wick-debinding, commonly used in low-pressure injection molding, remains challenging due to complex interactions between binder transport, capillary forces, and thermal effects. This study presents a numerical simulation of binder removal kinetics by coupling Darcy’s law with the Phase Transport in Porous Media interface in COMSOL Multiphysics. The model was validated and subsequently used to study the influence of key debinding parameters. Contrary to the Level Set method, which predicts isolated binder clusters, the Multiphase Flow in Porous Media method proposed in this work more accurately reflects the physical behavior of the process, capturing a continuous binder extraction throughout the green part and a uniform binder distribution within the wicking medium. The model successfully predicted the experimentally observed decrease in binder saturation with increasing debinding temperature or time, with deviation limited 3–10 vol. % (attributed to a mandatory brushing operation, which may underestimate the residual binder mass). The model was then used to optimize the debinding process: for a temperature of 100 °C and an inter-part gap distance of 5 mm, the debinding time was minimized to 7 h. These findings highlight the model’s practical utility for process design, offering a valuable tool for determining optimal debinding parameters and improving productivity. Full article
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29 pages, 9521 KiB  
Article
The Chemical Fingerprint of Smokeless Powders: Insights from Headspace Odor Volatiles
by Miller N. Rangel, Andrea Celeste Medrano, Haylie Browning, Shawna F. Gallegos, Sarah A. Kane, Nathaniel J. Hall and Paola A. Prada-Tiedemann
Powders 2025, 4(3), 21; https://doi.org/10.3390/powders4030021 - 29 Jul 2025
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Abstract
Smokeless powders are a commonly used low explosive within the ammunition industry. Their ease of purchase has allowed criminals to use these products to build improvised explosive devices. Canines have become a vital tool in locating such improvised devices. With differing fabrication processes, [...] Read more.
Smokeless powders are a commonly used low explosive within the ammunition industry. Their ease of purchase has allowed criminals to use these products to build improvised explosive devices. Canines have become a vital tool in locating such improvised devices. With differing fabrication processes, one of the most difficult challenges for canine handlers is the optimal selection of training aids to choose as odor targets to allow for broad generalization. Several studies have been underway to understand the chemical odor characterization of smokeless powders, which can help provide canine teams with essential information to understand odor signatures from powder varieties. In this study, a SPME method optimization was conducted using unburned smokeless powders to provide a chemical odor profile assessment. Concurrently, statistical analysis using PCA and Spearman’s rank correlations was performed to explore whether odor volatile composition depicted associations between and within powder brands. The results showed that a longer extraction time (24 h) was optimal across all powders, as this yielded higher compound abundance and number of extracted odor volatiles. The optimal SPME fiber varied per powder, depicting the complexity of powder composition. There were 66 highly frequent compounds among the 18 powders, including 2-ethyl-1-hexanol, diphenylamine (DPA), and dibutyl phthalate. Principal component analysis (PCA) showed that while powders may be of the same type (single/double base), they can still portray clustering differences across and within brands. The Spearman’s rank correlation within powder type suggested that the double-base powders had a slightly higher similarity index when compared with the single-base powder types. Understanding the volatile odor profiles of various smokeless powders can enhance canine training by informing the selection of effective training aids and supporting odor generalization. Full article
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23 pages, 7060 KiB  
Article
Deposition: A DPM and PBM Approach for Particles in a Two-Phase Turbulent Pipe Flow
by Alkhatab Bani Saad, Edward Obianagha and Lande Liu
Powders 2025, 4(3), 20; https://doi.org/10.3390/powders4030020 - 4 Jul 2025
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Abstract
Particle deposition is a phenomenon that occurs in many natural and industrial systems. Nevertheless, the modelling and understanding of such processes are still quite a big challenge. This study uses a discrete phase model (DPM) to determine the deposition constant for the particles [...] Read more.
Particle deposition is a phenomenon that occurs in many natural and industrial systems. Nevertheless, the modelling and understanding of such processes are still quite a big challenge. This study uses a discrete phase model (DPM) to determine the deposition constant for the particles in a liquid phase flowing in a horizontal pipe. This study also develops a steady-state population balance equation (PBE) for the particles in the flow involving deposition and aggregation and an unsteady-state PBE for particles depositing on the wall. This establishes a mathematical relationship between the deposition constant and velocity. An industrial setting of a 1000 m long pipe of 0.5 m in diameter was used for the population balance modelling (PBM). Based on the extracted deposition constant from the DPM, it was found that the particle deposition velocity increases with the continuous flow velocity. However, the number and volume of the deposit particles on the wall reduce with the increase of the continuous flow velocity. The deposition was found mainly taking place in the inlet region and reduces significantly towards the pipe outlet. The deposition was also found driven by advection of particles. Calculated deposit thickness showed that increasing the continuous flow velocity from 1 m s−1 to 5 m s−1, the thickness at the inlet would reduce to nearly 1/40th. With a 10 m s−1 flow, this would be 1/80th. Full article
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28 pages, 5228 KiB  
Article
Selective Separation of SiO2 and SnO2 Particles in the Submicron Range: Investigating Salt and Surfactant Adsorption Parameter
by Claudia Heilmann, Lisa Ditscherlein, Martin Rudolph and Urs Alexander Peuker
Powders 2025, 4(3), 19; https://doi.org/10.3390/powders4030019 - 3 Jul 2025
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Abstract
The separation of particles smaller than 1 µm either by composition or by size is still a challenge. For the separation of SiO2 and SnO2, the creation of a selective separation feature and the specific adsorption of salts and surfactants [...] Read more.
The separation of particles smaller than 1 µm either by composition or by size is still a challenge. For the separation of SiO2 and SnO2, the creation of a selective separation feature and the specific adsorption of salts and surfactants were investigated. The adsorption of various salts, e.g., AlCl3, ZnCl2, MnCl2 and MgCl2 were therefore analyzed, and the necessary concentration for the charge reversal of the material was determined. It was noticed that the investigated materials differ in their isoelectric point (IEP) and therefore in their adsorption behavior because only ZnCl2 and MgCl2 are suitable for a charge reversal of both metal oxides. The phase transfer of the pure material at different pH values with ZnCl2 or MgCl2 and sodium dodecyl sulfate (SDS) revealed that the adsorption behavior of the particle has an influence on the phase transfer. As a result, the phase transfer of SiO2 is pH dependent, whereas the phase transfer of SnO2 operates over a wider pH range. This allowed the separation of SiO2 and SnO2 to be controlled by the salt and surfactant concentration as well as pH. The separation of SiO2 and SnO2 was investigated for various parameters such as salt and surfactant concentration, particle concentration and composition of the mixture. Also, pH 8, where a selective phase transfer for SiO2 occurs, and pH 6, where the greatest difference between the materials exists, were also investigated. By comparing the parameters, it was found that the combination of ZnCl2/SDS and MgCl2/SDS enables a selective separation of the materials. Furthermore, it was also found that the concentration of SDS has a significant effect on the separation, as the formation of a bilayer structure is important for the separation, and therefore, higher SDS concentrations are required at higher particle concentrations to increase the separation efficiency. Full article
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12 pages, 3481 KiB  
Article
Formation of Layered Structure in Ceramics Based on Alumina Nanopowder Under Effect of Induction Heating
by Lina L. Sartinska
Powders 2025, 4(3), 18; https://doi.org/10.3390/powders4030018 - 20 Jun 2025
Viewed by 424
Abstract
The effect of induction heating on alumina ceramics and alumina ceramic composites based on α-Al2O3 nanopowders (additives: SiC, Si3N4, SiO2, ZrO2) has been examined. Various factors such as the structure, grain size, [...] Read more.
The effect of induction heating on alumina ceramics and alumina ceramic composites based on α-Al2O3 nanopowders (additives: SiC, Si3N4, SiO2, ZrO2) has been examined. Various factors such as the structure, grain size, distribution of elements, hardness, fracture toughness, and wear rate of hot-pressed ceramic materials were assessed. Despite achieving improved densification of alumina ceramics at a higher temperature of 1720 °C, there is a consistent trend toward a decline in hardness and fracture toughness. Heating at lower temperatures of 1300–1500 °C results in the development of a strengthened surface layer with a fine-grained structure enriched with carbon. Therefore, the wear rate behavior of such ceramics differs from the behavior of samples made at higher temperatures of 1600–1720 °C. This fact indicates the presence of a non-thermal microwave effect of induction heating. The incorporation of additives to alumina leads to the formation of novel structures with altered crack propagation patterns. The optimal ceramic composite, containing 5 wt. % SiC, displayed superior hardness and the lowest wear rate when compared to pure alumina ceramics. Across all investigated composites, a short dwell time at 1700 °C results in an enhancement of the mechanical properties. Full article
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