Zhang Zhiming¹， Zhang Haoyu¹， Wang Jiabo²， Wang Yigang¹

1.College of Automotive and Energy Engineering， Tongji University， Shanghai 201804， China； 2.School of Innovation and Entrepreneurship， Xi’an University of Science and Technology， Xi’an 710054， China

Abstract

Objective The primary engineering bottlenecks and core goals of this study are outlined. Silicon carbide （SiC）， as a representative third-generation semiconductor material， has been widely applied in modern new energy vehicles， high-frequency systems， and high-performance power electronics due to its superior physical and chemical properties. However， the electrical consistency， switching characteristics， and thermal reliability of SiC-based devices are strictly restricted by the morphological irregularities and inherent defects of raw powder particles during manufacturing. Therefore， high-precision and efficient morphological sorting of micron-scale powders is recognized as a critical link in the semiconductor manufacturing chain. While conventional sorting technologies have achieved success in particle size classification above 100 μm， specialized techniques for pure morphological sorting remain scarce and inefficient. As particle sizes scale down to the micro-level， the dominant mechanical regime transitions from macroscopic gravity and inertial forces to microscopic interfacial adhesion forces， leading to uncontrollable particle agglomeration and unexpected dynamic behavior. Therefore， this study aims to explicitly identify the critical physical failure boundary for effective morphological sorting under micro-scale conditions. The interference mechanisms and patterns of micro-scale interfacial forces on macroscopic sorting behavior are systematically elucidated. Solid theoretical support and a scientific pathway are provided for overcoming the technical bottlenecks in sorting even finer particles， thereby avoiding empirical trial-and-error and minimizing the development cycle in engineering practice.

Methods To investigate the mechanical limitations of morphological separation， a comprehensive methodology combining theoretical derivation， discrete element method （DEM） simulation， and experimental verification was adopted. First， a theoretical framework for particle vibrational dynamics on an inclined plate was established. The spatial Lissajous trajectories， harmonic excitation forces， and instantaneous accelerations delivered by the vibrating substrate were analytically resolved under a near-resonance frequency. The three orthogonal excitation components were configured with specific amplitudes and corresponding maximum directional accelerations along the three axes. The translational and rotational states of the particles were governed by Newton-Euler equations. Second， a high-fidelity DEM simulation system replicating actual working conditions was constructed. The Johnson-Kendall-Roberts （JKR） contact mechanics model was coupled with a triboelectric charging model and a classical electrostatic model to precisely capture micro-scale interfacial contact forces and particle cohesion. Third， ideal spherical particles and elongated particles—reconstructed via a multi-sphere clump method with specified aspect ratios and typical micro-scale diameters—were modeled to differentiate their motion trajectories. The background cell grid sizes were optimized to resolve the computational bottlenecks of large-scale simulations. To ensure numerical stability， the fixed simulation time step was restricted to a small fraction of the Rayleigh time step over a predetermined total duration， thereby accumulating a sufficient number of iterations. Fourth， system verification experiments were performed using a multi-degree-of-freedom adjustable flat-plate vibrating classifier. Multiple distinct particle size groups covering the micro-scale range were tested at the designated excitation frequency. The feeding smoothness and spatial distribution of the powders on the plate were recorded and compared with the simulation datasets. Finally， theoretical failure criterion inequalities for normal， longitudinal， and transverse motions were derived by incorporating a peeling reduction coefficient， the Hamaker constant， and the surface charge density to evaluate the exact boundary mathematically.

Results and Discussion A high degree of consistency was observed between the experimental results and the numerical simulation results， validating the reliability of the established boundary parameters. For the 100 μm and 80 μm particle groups， highly effective morphological sorting was achieved. The feeding stream exhibited a continuous fluid-like state without visible agglomeration， and a distinct fan-like scattering pattern was formed on the plate surface. Due to high geometric symmetry， the spherical particles experienced minimal eccentric torque， causing them to slide stably along the maximum longitudinal slope. Conversely， the elongated particles generated intense non-central collisions， which triggered violent three-dimensional flipping and random transverse jumping， forcing them to migrate toward the lateral wings of the plate. For the 60 μm particle size group， the morphological sorting capacity failed completely. The initial projectile trajectories of the elongated particles were abruptly truncated， and a collective co-directional slide movement was observed. The micro-scale van der Waals forces and the high-frequency contact-induced Coulomb electrostatic forces escalated rapidly， surpassing the macroscopic inertial detachment forces. Consequently， the individual dynamic characteristics of different morphologies were completely obscured， and particles were locked onto the substrate， forming dense wave-like profiles. For the 40 μm particle size group， an extreme state of microscopic force locking occurred. The feeding channel was severely clogged， and a permanent， irreversible solid-like powder adhesion layer was deposited on the plate surface， which could not be broken even by maximizing the vibration amplitude. Ultimately， the critical physical threshold for effective separation was determined to be a particle diameter of 60 μm， which exceeded the internationally recognized dry mesh screening limit by 20%. The derived theoretical formula yielded a normal failure threshold diameter of 60.56 μm， which perfectly matched the experimental and numerical results.

Conclusion Several critical conclusions are drawn regarding the physical limitations of dry mechanical sorting systems. First， the root cause of morphological separation failure and severe powder agglomeration in ultra-fine SiC particles is identified as the fundamental reversal of the underlying mechanical regime. The dominant forces transition from macroscopic gravitational and inertial forces to microscopic interfacial adhesion forces （van der Waals and electrostatic interactions）. This transition deprives fine particles of their degrees of freedom for three-dimensional rotation and high-frequency vertical bouncing. Second， a definitive engineering boundary for conventional pure harmonic flat-plate vibrating classifiers is established at a critical particle diameter threshold of 60 μm. This study shows that any attempt to separate ultra-fine powders below 60 μm utilizing pure mechanical vibration faces an insurmountable physical barrier. Third， it is demonstrated that merely increasing the mechanical excitation intensity is ineffective for overcoming microscopic interfacial adhesion forces. Instead， such adjustments amplify high-frequency friction， which accelerates triboelectric charge accumulation and intensifies powder agglomeration. Finally， these findings successfully reveal the underlying physical mechanisms and physical limitations of plate vibration methods， providing a solid theoretical reference and a scientific framework for guiding the transition from traditional mechanical vibration to advanced multi-field coupled micropowder sorting technologies.

Keywords： morphological sorting； flat-plate vibrating classifier； silicon carbide particle； particle vibrational dynamics； van der Waals forcen

Get Citation:Zhang Zhiming， Zhang Haoyu， Wang Jiabo， et al. Experimental study on morphological sorting of micron-sized silicon carbide particles and analysis of its limitations［J］. China Powder Science and Technology， 2026， 32（5）： 173-185.

Received：2026-04-20， Revised： 2026-08-13， Online： 2026-08-28。

Funding： The research was supported by the National Key R&D Program of China (Grant No. 2024YFB4007402).

CLC No.:TB4； TQ022.1

Type Code：A

Serial No.:1008-5548（2026）05-0173-13