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Development and experimental–Numerical investigation of alumina powder spheroidization and hollow sphere formation using a novel conical RF-ICP torch.

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Title: Development and experimental–Numerical investigation of alumina powder spheroidization and hollow sphere formation using a novel conical RF-ICP torch.
Authors: Ebrahimi, Ali1 (AUTHOR), Alavi, Sina1 (AUTHOR), Mostaghimi, Javad1 (AUTHOR) javad.mostaghimi@utoronto.ca
Source: Ceramics International. Jul2026, Vol. 52 Issue 17, p32290-32307. 18p.
Subjects: Plasma materials processing, Ceramic powders, Plasma jets, Magnetohydrodynamics
Abstract: A novel conical radio-frequency inductively coupled plasma (RF–ICP) torch is developed and systematically evaluated for alumina powder spheroidization. Magnetohydrodynamic (MHD) simulations coupled with discrete particle tracking are integrated with in-flight diagnostics (DPV-2000) and post-process characterization (SEM, XRD, particle sizing) to quantify how torch geometry and operating parameters govern plasma structure, particle thermal histories, and final morphology. Relative to a conventional cylindrical RF–ICP torch at the same RF power (15 kW), the conical design reduces total gas consumption by 25–50%, increases volumetric power density by ∼13%, extends the axial high-temperature zone by ∼27%, and increases particle residence time in the effective heating region by ∼70%, thereby strengthening particle–plasma coupling and widening the operating window for complete melting. Parametric trends show that spheroidization improves with increasing RF power, whereas excessive carrier-gas flow and high powder feed rates reduce melting efficiency through plasma cooling and reduced residence time. Experimental measurements and microstructural analyses validate numerical predictions and demonstrate highly spherical alumina particles under optimized conditions with narrow morphological distributions. The role of carrier-gas composition is further examined: nitrogen enhances particle heating and spheroidization relative to argon and enables controlled formation of hollow alumina spheres. Cross-sectional analyses (ion milling/FIB-SEM) show uniform shell thicknesses of ∼1.5–2.5 μm, and size-based analysis indicates that hollow particles form predominantly from individual precursor particles rather than agglomeration. Overall, the conical RF–ICP torch provides an energy-efficient and versatile platform for advanced ceramic powder processing. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
Description
Abstract:A novel conical radio-frequency inductively coupled plasma (RF–ICP) torch is developed and systematically evaluated for alumina powder spheroidization. Magnetohydrodynamic (MHD) simulations coupled with discrete particle tracking are integrated with in-flight diagnostics (DPV-2000) and post-process characterization (SEM, XRD, particle sizing) to quantify how torch geometry and operating parameters govern plasma structure, particle thermal histories, and final morphology. Relative to a conventional cylindrical RF–ICP torch at the same RF power (15 kW), the conical design reduces total gas consumption by 25–50%, increases volumetric power density by ∼13%, extends the axial high-temperature zone by ∼27%, and increases particle residence time in the effective heating region by ∼70%, thereby strengthening particle–plasma coupling and widening the operating window for complete melting. Parametric trends show that spheroidization improves with increasing RF power, whereas excessive carrier-gas flow and high powder feed rates reduce melting efficiency through plasma cooling and reduced residence time. Experimental measurements and microstructural analyses validate numerical predictions and demonstrate highly spherical alumina particles under optimized conditions with narrow morphological distributions. The role of carrier-gas composition is further examined: nitrogen enhances particle heating and spheroidization relative to argon and enables controlled formation of hollow alumina spheres. Cross-sectional analyses (ion milling/FIB-SEM) show uniform shell thicknesses of ∼1.5–2.5 μm, and size-based analysis indicates that hollow particles form predominantly from individual precursor particles rather than agglomeration. Overall, the conical RF–ICP torch provides an energy-efficient and versatile platform for advanced ceramic powder processing. [ABSTRACT FROM AUTHOR]
ISSN:02728842
DOI:10.1016/j.ceramint.2026.05.269