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Powders, Volume 5, Issue 1 (March 2026) – 10 articles

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18 pages, 2614 KB  
Article
Porcelain Polishing Residue as a Supplementary Cementitious Material in Self-Compacting Concrete: Pozzolanic Activity and Performance Assessment
by Alexandre Serafim, Elaine Antunes, Gláucia Dalfré and Ricardo de Almeida
Powders 2026, 5(1), 10; https://doi.org/10.3390/powders5010010 - 5 Mar 2026
Cited by 2 | Viewed by 944
Abstract
The increasing demand for sustainable construction materials has intensified research on supplementary cementitious materials capable of reducing Portland cement consumption and associated CO2 emissions. In this context, porcelain polishing residue (PPR), a fine ceramic waste generated by the tile industry, presents potential [...] Read more.
The increasing demand for sustainable construction materials has intensified research on supplementary cementitious materials capable of reducing Portland cement consumption and associated CO2 emissions. In this context, porcelain polishing residue (PPR), a fine ceramic waste generated by the tile industry, presents potential for valorization in cement-based composites. This study investigates the use of PPR as a supplementary cementitious material in self-compacting concrete (SCC), focusing on its pozzolanic activity and its influence on fresh, physical, and mechanical properties. Pozzolanic behavior was evaluated using strength-based indices with lime and Portland cement, as well as the modified Chapelle method. SCC mixtures were produced with partial replacement of cement by PPR at different levels and assessed in terms of self-compactability, compressive strength, elastic modulus, water absorption, and void index. The results showed that, although PPR did not meet strength-based pozzolanicity criteria at early ages, it exhibited significant calcium hydroxide consumption, indicating latent pozzolanic potential. Fresh-state properties were preserved in all mixtures, and an optimal replacement level of 20% resulted in improved long-term mechanical performance, reduced void content, and enhanced matrix compactness. These findings demonstrate that PPR can be effectively used as a functional supplementary cementitious material in SCC, contributing to more sustainable and eco-efficient concrete production. Full article
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20 pages, 4652 KB  
Article
Effect of YB4 Reinforcement on the Microstructural Evolution and Mechanical Behaviour of AISI 420 Composites Produced by Vacuum Induction Melting
by M. Sadhasivam, Mainak Saha, L. John Berchmans, S.P. Kumaresh Babu and SankaraRaman Sankaranarayanan
Powders 2026, 5(1), 9; https://doi.org/10.3390/powders5010009 - 3 Mar 2026
Cited by 1 | Viewed by 1006
Abstract
The influence of YB4 particle addition on the microstructure and the associated thermal and mechanical properties of AISI 420 stainless steel composites fabricated using the vacuum induction melting technique was investigated. Microstructural analysis using scanning electron microscopy (SEM) confirmed the presence of [...] Read more.
The influence of YB4 particle addition on the microstructure and the associated thermal and mechanical properties of AISI 420 stainless steel composites fabricated using the vacuum induction melting technique was investigated. Microstructural analysis using scanning electron microscopy (SEM) confirmed the presence of YB4 particles within the BCC-structured martensitic matrix and also along the grain boundaries across all weight fractions. In addition, YB4 addition resulted in a pronounced refinement of the martensitic matrix, as evidenced by a progressive reduction in the size of the packets, i.e., a group of martensitic laths/plates sharing the same habit plane variants with the parent austenite grain. The presence of YB4 particles induced internal stresses and microstrains, leading to peak shifting and broadening of the X-ray diffraction (XRD) peaks corresponding to that of the martensitic matrix phase. The coefficient of thermal expansion (CTE) decreased significantly from 13.4 × 10−6 K−1 for monolithic AISI 420 to 8.06 × 10−6 K−1 for the AISI 420/4 wt.% YB4 composite and was attributed to the excellent dimensional stability of YB4 particles. The maximum hardness (913.12 HV) and tensile strength (930 MPa) were achieved for the AISI 420/4 wt.% YB4 composite. Fractographic analysis using SEM indicated a transition from ductile to brittle fracture with increasing YB4 content, suggesting a reduction in strain-hardening capacity. The contributions of various strengthening mechanisms were quantified using the summation of strengthening and modified Clyne models, revealing that strengthening due to load bearing is dominant across all composites. Insights gained from these results are important to strategize the design of boride-based metal-matrix composites with enhanced strength–ductility synergy for structural applications. Full article
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19 pages, 1152 KB  
Review
Adaptive Powder Behavior Model for Dispersion and Recovery in Metal Additive Manufacturing
by Daniel Onuț Badea
Powders 2026, 5(1), 8; https://doi.org/10.3390/powders5010008 - 3 Mar 2026
Cited by 2 | Viewed by 705
Abstract
Metal additive manufacturing relies on fine powders whose properties influence flow, spreading, and airborne release during processing, yet published data on powder characteristics, reuse effects, and emissions remain fragmented and difficult to compare. This study reviews quantitative measurements reported for metallic feedstocks used [...] Read more.
Metal additive manufacturing relies on fine powders whose properties influence flow, spreading, and airborne release during processing, yet published data on powder characteristics, reuse effects, and emissions remain fragmented and difficult to compare. This study reviews quantitative measurements reported for metallic feedstocks used in laser powder bed fusion and directed energy deposition. A numerical evaluation model is developed to connect powder properties, process conditions, dispersion tendency, and material recovery. Particle size distribution values, density metrics, flow test results, reuse-related oxidation, and nanoparticle counts were compiled from the literature and normalized on a 0–1 scale. Four independent indices were defined: Material Fingerprint, process–powder interaction, airborne dispersion potential, and recovery. Adaptiveness refers to index sensitivity to changes in powder, reuse, and process conditions. The results indicate stable spreading for gas-atomized feedstocks, while wider particle size distributions and rougher surfaces increase cohesion and agglomeration, particularly under humid conditions and during reuse. Emission data indicate nanoparticle formation during processing, with recovery efficiency dependent on cyclone or high-efficiency particulate air filtration selection. The proposed model offers a screening approach for comparing powders and planning recovery strategies using data already available in the literature. Full article
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16 pages, 13843 KB  
Article
Phase Evolution and Microstructural Changes in Air-Sintered Alumina/SiC Composites
by Amal Elzubair Eltom, Pedro de Farias Vanzan, Thiago Calheiros de Souza Barbosa, João Paulo de Souza Silva, Nathan Rodrigues Mendes de Souza, Gustavo Ferreira de Rezende, Luis Gustavo Fontoura dos Santos, Luiz Felipe Santiago Proença, Pedro Henrique Poubel Mendonça da Silveira and Marcelo Henrique Prado da Silva
Powders 2026, 5(1), 7; https://doi.org/10.3390/powders5010007 - 10 Feb 2026
Viewed by 902
Abstract
The use of monolithic alumina is limited by its intrinsic brittleness, which is commonly addressed through second-phase reinforcement. Silicon carbide (SiC) is an attractive reinforcement due to its high-temperature stability; however, its oxidation behavior strongly influences composite processing and properties. In this study, [...] Read more.
The use of monolithic alumina is limited by its intrinsic brittleness, which is commonly addressed through second-phase reinforcement. Silicon carbide (SiC) is an attractive reinforcement due to its high-temperature stability; however, its oxidation behavior strongly influences composite processing and properties. In this study, alumina/SiC composites containing 1, 5, and 10 wt.% SiC were prepared by conventional powder mixing, calcined at 800 °C for 1 h, and pressureless sintered at 1400 °C in air. Phase evolution, microstructure, densification, and mechanical properties were investigated using XRD, SEM/EDS, density–porosity measurements, and flexural testing. Air sintering led to SiC oxidation and the formation of silica-rich glassy phase and mullite, which significantly affected densification. The composite containing 1 wt.% SiC exhibited the best performance, with a flexural strength of 248.7 MPa, a Weibull modulus of 5.7, an average grain size of 1.86 µm, and a porosity of 11.08%. Higher SiC contents resulted in excessive porosity and severe degradation of mechanical properties. Full article
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12 pages, 3495 KB  
Article
Photosensitization of TiO2 with Copper for the Photodegradation of Organic Contaminants in Water
by Dafne Rubi Porras-Herrera, Debany Yulissa Rincón-Salazar, María Teresa Maldonado-Sada, Carlos Adrián Calles-Arriaga, José Adalberto Castillo-Robles and Enrique Rocha-Rangel
Powders 2026, 5(1), 6; https://doi.org/10.3390/powders5010006 - 4 Feb 2026
Viewed by 923
Abstract
Photocatalysis is a process in which a material utilizes light energy to degrade contaminants through oxidation reactions that decompose impurities upon contact with its surface. Titanium dioxide is one of the most widely used semiconductor materials due to its abundance, chemical stability, and [...] Read more.
Photocatalysis is a process in which a material utilizes light energy to degrade contaminants through oxidation reactions that decompose impurities upon contact with its surface. Titanium dioxide is one of the most widely used semiconductor materials due to its abundance, chemical stability, and non-toxicity. However, its relatively wide bandgap restricts its photocatalytic activity to the ultraviolet region of the solar spectrum, limiting its overall efficiency under natural sunlight. The incorporation of copper nanoparticles into the TiO2 matrix enhances light absorption by extending its activity into the visible range, thereby improving its energy conversion efficiency. In this study, undoped and Cu-doped TiO2 powders were synthesized using the mechanochemical method. The characteristics of the prepared photocatalyst material were determined by XRD, SEM, absorbance, and chemical analysis. XRD analysis showed the formation of TiO2 in its anatase and rutile phases. Sphere-like shapes with a size of 100 nm were inferred from SEM images. The photocatalytic tests revealed that the Cu-doped TiO2 nanoparticles exhibited high photocatalytic activity in degrading contaminated water. This enhancement can be attributed to the formation of oxygen vacancies, which promote the photodegradation of organic compounds. Full article
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18 pages, 666 KB  
Review
The Equation of Motion of Particles in Fluids—An Historical Perspective
by Efstathios E. Michaelides
Powders 2026, 5(1), 5; https://doi.org/10.3390/powders5010005 - 2 Feb 2026
Cited by 1 | Viewed by 1716
Abstract
This is a review article that covers the history of the development of the equation of motion for solid particles in fluids, starting with the early work, before the Navier–Stokes equations were developed. Particular emphasis is placed on the development of the transient [...] Read more.
This is a review article that covers the history of the development of the equation of motion for solid particles in fluids, starting with the early work, before the Navier–Stokes equations were developed. Particular emphasis is placed on the development of the transient equation of motion, which features the history (or memory) term and the added mass (virtual mass) term. The salient features of the equation and the methods of their derivation are pointed out. Creeping, non-inertia flows as well as advective flows are surveyed, with particular emphasis on their effects on the functional form of the history term. Modifications to the hydrodynamic force due to possible interface slip are also examined. The review also deals with the inclusion of the weaker lateral (lift) forces and the inclusion of the effects of Brownian movement, which gives rise to thermophoresis—an important source of nanoparticle movement and surface deposition. The drag on irregularly shaped particles—another important feature of nanoparticles—is also examined. The review concludes with a short section on significant unknown issues and work that may be carried out in the near future for the theoretical and computational development of the subject. Full article
25 pages, 3613 KB  
Article
Flow Behavior of Co-Processed Excipients Using Lactose and Microcrystalline Cellulose as Bulk Fillers
by Paulo J. Salústio, Daniel Cingel, Telmo Nunes, José Catita, José P. Sousa e Silva and Paulo J. Costa
Powders 2026, 5(1), 4; https://doi.org/10.3390/powders5010004 - 22 Jan 2026
Cited by 1 | Viewed by 1967
Abstract
Powder flow is a constant concern in the production of solid dosage forms. Its concise and reliable determination and improvement are challenges for the pharmaceutical industry. Lactose (Lac) and microcrystalline cellulose (MCC) are both widely used pharmaceutical fillers either alone or mixed. In [...] Read more.
Powder flow is a constant concern in the production of solid dosage forms. Its concise and reliable determination and improvement are challenges for the pharmaceutical industry. Lactose (Lac) and microcrystalline cellulose (MCC) are both widely used pharmaceutical fillers either alone or mixed. In this study, flow determination was performed through methods described on the European Pharmacopoeia. The results obtained showed poor flow and cohesive behavior for Lac and MCC powders and their mixtures (co-processed excipients). The 50% Lac_MCC mixture, with colloidal silicon dioxide (CSD) as the glidant in different proportions, showed relevant improvements in flow. In addition, the effective angle of wall friction (φx), the effective angle of internal friction (φe), arching, and ratholing were also determined, demonstrating the flow behavior in the discharge equipment. Outlet diameters that prevent blockages or insufficient powder flow were also determined. With this study, it was concluded that it was possible to prepare a co-processed excipient with optimal flow behavior composed of Lac_MCC and CSD as a glidant. Full article
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15 pages, 3128 KB  
Article
Ammonium Paratungstate Production from Scheelite Ore: Process Study, Morphology and Thermal Stability
by Maria José Lima, Fernando E. S. Silva, Cleber da Silva Lourenço, Ariadne Silva, Jussier Vitoriano, Kivia Araujo, Matheus Silva, Marco Morales and Uílame Gomes
Powders 2026, 5(1), 3; https://doi.org/10.3390/powders5010003 - 16 Jan 2026
Cited by 1 | Viewed by 2354
Abstract
Ammonium paratungstate (APT) was synthesized from scheelite ore concentrates from the Brejuí Mine in Currais Novos, Rio Grande do Norte, Northeast Brazil. The process involved acid leaching to obtain tungstic acid (H2WO4), followed by its conversion to APT. A [...] Read more.
Ammonium paratungstate (APT) was synthesized from scheelite ore concentrates from the Brejuí Mine in Currais Novos, Rio Grande do Norte, Northeast Brazil. The process involved acid leaching to obtain tungstic acid (H2WO4), followed by its conversion to APT. A 23 factorial design evaluated the influence of temperature, HCl concentration, and reaction time on the leaching efficiency, revealing temperature and acid concentration as significant variables. Tungsten extraction reached 98.6% under moderate time and temperature conditions. The resulting H2WO4 phase exhibited a lamellar and porous morphology, facilitating its rapid dissolution and crystallization into APT at 60 °C. The produced nanometric APT exhibited high purity, a mixed rod-like/cubic morphology, and thermal stability above 600 °C. This work adds value to the Brazilian tungsten deposits by supporting more efficient and sustainable extraction routes for obtaining APT. Full article
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19 pages, 3413 KB  
Article
Assessment of Brazilian Type F Fly Ash: Influence of Chemical Composition and Particle Size on Alkali-Activated Materials Properties
by Adriano G. S. Azevedo
Powders 2026, 5(1), 2; https://doi.org/10.3390/powders5010002 - 1 Jan 2026
Cited by 4 | Viewed by 1003
Abstract
This study assesses two Brazilian Type F fly ash samples (FA-A and FA-B), collected from the same thermoelectric complex in different years, to investigate their influence on the production of alkali-activated materials (AAMs). FA-A exhibited a slightly higher SiO2/Al2O [...] Read more.
This study assesses two Brazilian Type F fly ash samples (FA-A and FA-B), collected from the same thermoelectric complex in different years, to investigate their influence on the production of alkali-activated materials (AAMs). FA-A exhibited a slightly higher SiO2/Al2O3 ratio (3.52 vs. 3.34) and a finer average particle size (D50 = 19.7 μm vs. 30.8 μm) than FA-B. X-ray diffraction revealed that FA-A presented a broad amorphous halo between 15° and 35° (2θ), indicative of phases with low atomic ordering, which are more susceptible to dissolution and capable of supplying Si- and Al-rich species for the formation of alkali activation products. These differences directly affected reactivity and mechanical performance. After 1 day of curing, FA-A-based matrices achieved 88.5 MPa in compressive strength—approximately 100% higher than FA-B (44.2 MPa). However, FA-A suffered a 19.6% strength reduction after 28 days of curing, whereas FA-B showed only a 3.8% decrease over the same period, reflecting better long-term stability. FTIR confirmed Na2CO3 formation in FA-A, associated with excess sodium (Na/Al = 2.07 after 28 days), while SEM revealed unreacted spheres persisting in FA-B, consistent with its lower dissolution rate. Water absorption was also significantly different, with FA-B matrices reaching values up to 52% lower than FA-A after 7 days of curing. These results demonstrate that even slight variations in chemical composition and atomic ordering, even for ashes from the same plant, strongly influence the reactivity, microstructure, and mechanical performance of alkali-activated binders. Full article
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20 pages, 4863 KB  
Article
Zeolite Synthesis from Spodumene Leach Residue and Its Application to Heavy Metal Removal from Aqueous Solutions
by Sofi Buzukashvili, Justin Paris, Helmi F. Kalahari, Sidney Omelon and Kristian E. Waters
Powders 2026, 5(1), 1; https://doi.org/10.3390/powders5010001 - 26 Dec 2025
Cited by 2 | Viewed by 1679
Abstract
This study presents an approach to synthesizing LTA-type zeolite from spodumene residue generated during a lithium extraction process. A residue was obtained after leaching β-spodumene with 2 mol/L phosphoric acid. After solid–liquid separation, the delithiated residue was first treated with 2 mol/L sodium [...] Read more.
This study presents an approach to synthesizing LTA-type zeolite from spodumene residue generated during a lithium extraction process. A residue was obtained after leaching β-spodumene with 2 mol/L phosphoric acid. After solid–liquid separation, the delithiated residue was first treated with 2 mol/L sodium hydroxide and then subjected to hydrothermal synthesis using sodium aluminate as an additional aluminum source. The resulting material was characterized by XRD, SEM-EDS, XPS, and FTIR, which collectively confirmed the formation of a crystalline material exhibiting the structural features, elemental composition, and morphological characteristics consistent with LTA-type zeolite. Additional analyses, including BET surface area, particle size distribution, and zeta potential measurements, were performed to further evaluate the physicochemical properties of the synthesized zeolite. The spodumene leach residue (SLR)-derived zeolite was further tested for its adsorption performance in heavy metal ions removal from a mixed ion solution containing Pb2+, Cu2+, Zn2+, and Ni2+ ions. The zeolite demonstrated a high selectivity for Pb2+, followed by moderate uptake of Cu2+, while Zn2+ and Ni2+ adsorption was minimal. These findings demonstrate that spodumene residue, a waste by-product of lithium processing, can be effectively upcycled into LTA zeolite suitable for heavy metal remediation in water treatment applications. Full article
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