Effect of particle refinement on return loss and bandwidth performance of TiCN/NiFe₂O₄ composite patch antennas

Abstract

Titanium carbonitride/nickel ferrite (TiCN/NiFe₂O₄) composite-based microstrip patch antennas (MPAs) were investigated to determine how controlled TiCN particle refinement affects measured impedance matching and bandwidth. TiCN powder was subjected to ball-milling durations of 0, 2, 4, 6, and 8 h, while nominal NiFe₂O₄ powder was prepared by a solid-state reaction followed by calcination at 1100 °C. The materials were characterized using dynamic light scattering, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy, scanning electron microscopy with energy-dispersive X-ray spectroscopy, Brunauer-Emmett-Teller analysis, and thermogravimetric analysis. The TiCN Z-average particle size decreased from 887.3 nm for the unmilled powder to 278.9–297.4 nm after milling. XRD revealed hematite-dominant patterns and did not conclusively confirm the formation of single-phase spinel NiFe₂O₄. Five TiCN/NiFe₂O₄ composite-based MPAs were subsequently fabricated by screen printing and evaluated using a vector network analyzer over 5–20 GHz. Sample 4, containing TiCN milled for 6 h, achieved the most negative measured reflection coefficient (S₁₁) of -42.90 dB at 12.53 GHz, with an impedance bandwidth of 1.70 GHz and a voltage standing-wave ratio of 1.01. Sample 5 exhibited dual-band operation at 7.60 and 13.07 GHz and produced the widest measured bandwidth of 3.83 GHz at the higher resonance. Although Sample 3 had the smallest TiCN particle size, Sample 4 provided the best impedance matching, indicating that particle size alone did not govern the measured response. Because independent replicate particle-size measurements and antenna prototypes were not available, experimental uncertainty could not be statistically established. These preliminary results demonstrate that the TiCN milling condition can modify the input-matching and bandwidth characteristics of screen-printed TiCN/NiFe₂O₄ composite antennas.