Conventional Electrophoretic Deposition Research Articles

Pulsed Electrophoretic Deposition of Nanocarbons and Their Optical, Thermal, and Electrical Applications

Electrophoretic deposition (EPD) is a well-established, scalable industrial manufacturing technology for depositing a wide variety of coatings across a broad range of substrates, geometries and sizes. Conventional electrophoretic deposition (EPD) is the migration of small, suspended particles in a liquid driven by a constant electrical potential difference. As a subset of electrodeposition, EPD has been used to deposit layers on various conducting and semiconducting surfaces from polar, aqueous, and non-polar suspensions. On the other hand, state of the art developments within nanoscience and nanotechnology has opened a new vista for the field of nanocarbon materials. Nanostructured carbon materials, such as carbon nanotubes, graphene, carbon quantum dots, etc., exhibit excellent physical and chemical properties, and have been gaining attention in both fundamental research and technological applications.In this invited presentation, Faraday Technology will discuss an innovative electrophoretic deposition (EPD) manufacturing process, based on the use of pulsed electric fields, for controlled, reproducible, scalable deposition of a wide variety of nanocarbon based coatings across a broad range of substrates, geometries and sizes (Figure 1). The effects of waveforms, electrolytes, substrates, etc. on the formation of robust and uniform coating will be discussed in this talk. The optical and electrical properties, and environmental survivability of nanocarbon coatings will be demonstrated via a variety of testing or characterizations. Faraday will also introduce their applications ranging from low-reflective coatings, solar absorber, high emissivity coatings, to thin film electrodes for energy storage.In summary, a scalable EPD manufacturing process for fabricating nanocarbon based coatings have been developed at Faraday for various applications ranging from optical, thermal, to electrical fields. Acknowledgements: The financial support from NASA SBIR program through contracts No. 80NNSC18P2062 & 80NSSC19C0177, DOD DMEA STTR program through grant No. HQ0727-21-P-0029, DARPA SBIR program through grant No. W31P4Q-22-C-0014, DOD MDA STTR program through grant No. HQ0147-19-C-7065, DOD Air Force SBIR program through grant No. FA9453-19-P-0573, NASA SBIR program through contracts No. 80NSSC20C0287 are acknowledged. Figure 1

Nanofiber Architecture Engineering Implemented by Electrophoretic-Induced Self-Assembly Deposition Technology for Flash-Type Memristors.

Electrophoretic deposition (EPD) has been recognized as a promising large-scale film preparation technology for industrial application. Inspired by the conventional EPD method and the crystal diffusion growth strategy, we propose a modified electrophoretic-induced self-assembly deposition (EPAD) technique to control the morphologies of organic functional materials. Here, an ionic-type dye with a conjugated skeleton and strong noncovalent interactions, celestine blue (CB), is chosen as a module molecule for EPAD investigation. As expected, CB molecules can assemble into different nanostructures, dominated by applied voltage, concentration effect, and duration. Compared to a nanopillar layered packing structure formed by the traditional spin-coating method, the EPAD approach can produce a nanofiber structure under a fixed condition of 10 V/10 min. Intriguingly, a memristor device based on a pillar-like nanostructure exhibits WORM-type behavior, while a device based on nanofibers presents Flash memory performance. The assemble process and the memory mechanism are uncovered by molecular dynamics simulations and density-functional theory (DFT) calculations. This work endows the typical EPD technique with a fresh application scenario, where an in-depth study on the growth mechanism of nanofibers and the positive effect of unique morphologies on memristor performance are offered.

Elucidating the role of electrophoretic mobility for increasing yield in the electrophoretic deposition of nanomaterials

HypothesisCatalysts, chemical, gas, and bio- sensing devices fabricated from porous nanoparticle films show better performance and sensitivity than their bulk material counterparts because of their high specific surface area. Electrophoretic deposition (EPD) technique is a cost-effective, fast, versatile, and easy to perform method to fabricate porous nanoparticle films. However, conventional EPD is currently limited by the fact that the deposition rate decreases with time, resulting in an eventual plateau in the deposit yield. Here, we sought to overcome this limitation by establishing and leveraging the critical role of the particle’s electrophoretic mobility in EPD kinetics. ExperimentsTo identify the impact of electrophoretic mobility on EPD yield we used alumina nanoparticles suspended in ethanol as a model system. Changes in particle mobility were monitored via changes in the effective pH (pHe) of the suspension during EPD. We also developed a new suspension replenish EPD approach that allows us to maintain near-constant particle mobility and particle concentration with time thereby increasing yield. FindingsWe observed that in conventional EPD the particle mobility of the alumina nanoparticles decreased with time, resulting in a halting of deposition. Further, using the suspension replenish EPD, we observed a linear increase in the mass of the deposited film with time, overcoming the plateau limitation of conventional EPD.

Improvement in magnetic and microwave absorption properties of nano-Fe3O4@CFs composites using a modified multi-step EPD process

In this research, structural, magnetic and microwave absorption properties of multifunctional nano-Fe3O4@carbon fibers (CFs) composites in the frequency range of 8.2–18GHz were investigated. The nano-Fe3O4 particles (30nm) were successfully prepared using co-precipitation method. These particles were then deposited on CFs using two conventional and modified multi-step electrophoretic deposition (EPD) processes to investigate the contributing effects of uniformity of coating on their magnetic and microwave absorption properties. The magnetic properties measurements represented that the coercivity (Hc), saturation magnetization (Ms) and residual magnetization (Mrs) values of the coated CFs using the conventional EPD process were 531.4Oe, 15.2emu/g and 5.2emu/g, respectively, while for the CFs coated with modified EPD process these values were 167.8Oe, 33.1emu/g and 1.7emu/g, respectively. It was found that by employing conventional EPD process, the maximum reflection loss (RL) of −9.87dB was obtained for the composite containing 20wt.% nano-Fe3O4@CFs and 80wt.% epoxy-resin with the thickness of 2mm, while by using the modified multi-step EPD process, due to enhancement of deposited coating quality, the achieved maximum RL was approximately increased by −0.64dB and reached to −10.51dB with an effective absorption bandwidth of about 4GHz for the similar sample with the same thickness and weight ratio of nano-Fe3O4@CFs composites to epoxy 828.

Role of the Electric Field Affected Zone (EFAZ) on the Electrophoretic Deposition of TiO2 Nanoparticles under Symmetric Low-Frequency AC Electric Fields

In the present study, electrophoretic deposition (EPD) of TiO(2) nanoparticles under the application of symmetric AC fields was investigated. In the first step, EPD of TiO(2) nanoparticles under a DC field at 50 V resulted in the particles' deposition on one electrode, consistent with conventional EPD principles. However, no deposits were formed on any of the electrode surfaces for symmetric sinusoidal waves at 1 Hz. In this case, enhancing the electric field strength through the application of higher potentials was considered to extend the electric field affected zone (EFAZ) in front of the electrode, increasing the particles' opportunity to deposit. A kinetic model was then derived based on the Hamaker approach to calculate the deposited mass under an AC electric field. Although this model was found to be in agreement with experimental results at 1 Hz above 200 V, some deviation was detected at lower voltages. This trend shows that there is a threshold field strength below which EFAZ is not wide enough to let particles deposit under an AC electric field.

Electrophoretic deposition onto an insulator for thin film preparation toward electronic device fabrication

An electrostatic film fabrication method utilizing the dielectric layer, entitled dielectric barrier electrophoretic deposition (DBEPD) has been proposed. We demonstrated the fabrication of uniform organic semiconductor thin film onto any kind of substrate by DBEPD. Optical absorption spectra of colloidal poly(3-hexylthiophene) (P3HT) film prepared by DBEPD exhibited the clear vibrational structure attributed to highly ordered domains. It was in contrast to the relatively disordered structure as shown in the case of P3HT film prepared by conventional electrophoretic deposition (EPD). Organic field effect transistors fabricated by each method showed similar organic field effect transistor characteristics, however, the uniformity of DBEPD film was superior to EPD film.

Pulse Electric Fields for EPD of Thermal Barrier Coatings

Conventional electrophoretic deposition is being combined with pulse electric fields to deposit yttria stabilized zirconia from ethanol based suspensions onto bondcoated turbine alloys for thermal barrier coatings. The addition of the pulse electric fields to the electrophoretic process has demonstrated the capability to decrease the coating roughness, minimize hydrolysis, and decrease coating edge effects commonly encountered in electrokinetic and electrochemical deposition processes. Subsequent to the electrophoretic deposition process the green body coatings were subjected to a combined binder burnout and sintering process for further coating densification. The coatings have been qualified in terms of surface roughness as well as microstructure and experiments have been performed to show that the pulse EPD process can deposit TBC materials onto turbine components.

Preparation of Barium Titanate Nanoparticle Thin Films by the Electrophoretic Deposition Method Using Polyacrylic Acid as a Charge-Compensating Agent

Using the electrophoretic deposition (EPD) method, we prepared barium titanate nanoparticle (BT-NP) thin films by depositing BT-NP monodispersed in ethylene glycol monomethyl ether (EGMME) onto an electrically conductive substrate coated with polyacrylic acid (PAA). Deposition efficiency was increased compared to conventional EPD, and the uniformity of the film thickness was also improved as a result of the BT-NPs cohesion effect of the PAA coating on the substrate in addition to the electrophoretic deposition effect of the electric field. When low-molecular-weight PAA was used, the film was reinforced since PAA, which coats the substrate, diffused close to the surface of the BT-NP film during film formation. A crack-free BT-NP film was produced with a film thickness of several micrometers.

Novel Reproducible Fabrication of MgTiO3 Nanoparticles by Electrodeposition

Abstract While a high supply voltage (>15 V) is needed in the conventional EPD (electrophoretic deposition) methods, we propose a novel method in which deposition of dielectric films can be carried out using a low voltage (<10 V); we have used this method for the deposition of MgTiO3 films. MgTiO3 powder was dispersed in a solution of ethanol–Ti4+ with 3–9 V. Subsequently, the deposition of a MgTiO3 film with spherical nano-particles in aggregated random shape particles was observed at the anode.

Preparation of TiO<sub>2</sub> Nanorod Arrays by Electrophoretic Deposition of Titania Nanoparticles

The TiO2 nanorod arrays were fabricated by the electrophoretic deposition (EPD) of the 4.5 and 7 nm-sized anatase titania nanoparticles using the anodized aluminum oxide (AAO) as the template. Each of the TiO2 nanoparticle was plus-charged by adjusting the pH of the electrolyte. The growth rate of TiO2 nanorod arrays with this new method was dramatically higher than that of the arrays obtained from the conventional EPD method employing sol-gel solutions. In addition, the robust anatase-phase TiO2 nanorod arrays were obtained without post-thermal treatment. The scanning electron microscope (SEM) images showed that the titania nanoparticles were tightly interconnected to form the highly uniform and well-organized TiO2 nanorod arrays. The diameter of the TiO2 nanorod arrays was 55~58 nm with the length of 15 0m, which corresponded to the size of AAO templates.