Magnetic Submicron Mullite Coatings with Oriented SiC Whiskers

Abstract

Addressing the challenge of making ceramic thin films with the in-plane-oriented nanorods, we propose to decorate the nanorods with magnetic nanoparticles and orient them using the external magnetic field. As an illustration, the mullite thin films with embedded and oriented SiC nanorods were synthesized. The SiC nanorods were decorated with the FeO nanoparticles. A two-step processing route was developed when the nanorods are first oriented in a sacrificial polymer layer. Then, the polymer film with the aligned nanorods was removed by heat-treatment. In the second step, a sol-gel/dip-coating method was applied to produce the mullite composite film. The main challenge was to guarantee that all of the nanorods that were initially randomly distributed in the polymer would have time to rotate toward the field direction before complete solidification of the sacrificial layer. Theoretical and experimental analyses of the orientational distribution of the nanorod axes were conducted to identify a relationship between the polymer viscosity and processing parameters of the system. In contrast to the ferromagnetic nanorods, the rate of rotation of paramagnetic nanorods and their time of alignment are more sensitive to the magnetic field. This methodology allows manufacturing of different ceramic films with aligned nanorods and making nonmagnetic ceramic coating magnetic.

The mechanism of tuning filler orientation degree in composites based on AC electric field assist: from microscopic dynamical model to macroscopic electrical properties

“…Researchers have explored various approaches to tune switch-field stress and nonlinear coefficients without compromising the matrix's intrinsic insulating properties. One promising solution is inducing high aspect ratio filler orientation using methods such as magnetic field [15], electrostatic spinning [16], shear flow [17], and AC electric field [18]. Among these methods, the AC electric field has several advantages: (1) applicable to a wider range of material types: compared to magnetic field induction, the AC electric field utilizes the polarization effect of the particles for alignment, eliminating the need for magnetizing the particles.…”

Magnetic Alignment for Plasmonic Control of Gold Nanorods Coated with Iron Oxide Nanoparticles

“…Magnetic alignment of anisotropic micro‐ and nanostructures has been demonstrated by depositing spherical magnetic NPs on their surfaces, including Al 2 O 3 microplatelets, [ 54 ] cellulose microcrystals, [ 55 ] high‐aspect‐ratio CaSO 4 nanorods, [ 54 ] polymer microrods, [ 56 ] SiC whiskers, [ 57,58 ] Te nanorods, [ 59 ] Ag nanowires, [ 60 ] and carbon nanotubes. [ 61 ] Hybrid nanorods composed of spherical magnetic and plasmonic NPs formed using templates can also be aligned in magnetic fields.…”

“…[49,50] Magnetic alignment and manipulation of GNRs and related anisotropic structures have been applied in magnetochromic sensors, [46,51] photothermal actuators, [52] gyromagnetic imaging, [53] and nanoelectromechanical systems like nanomotors for controlled drug release. [43] Magnetic alignment of anisotropic micro-and nanostructures has been demonstrated by depositing spherical magnetic NPs on their surfaces, including Al 2 O 3 microplatelets, [54] cellulose microcrystals, [55] high-aspect-ratio CaSO 4 nanorods, [54] polymer microrods, [56] SiC whiskers, [57,58] Te nanorods, [59] Ag nanowires, [60] and carbon nanotubes. [61] Hybrid nanorods composed of spherical magnetic and plasmonic NPs formed using templates can also be aligned in magnetic fields.…”