Electrophoretic Deposition Technique Date: 18/12/2023 | Views: 445

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Electrophoretic Deposition (EPD), a traditional processing method in the ceramic industry, is gaining an increase interest both in academia and in the industrial sector for production of new materials. Consequently, a wide range of novel applications of EPD in the processing of advanced monolithic materials, composites and coatings is emerging. The interest in the EPD technique is based not only on its high versatility to be used with different materials and combinations of materials, but also its a cost- effective method usually requiring simple equipment. With EPD particulate deposits can be made in seconds on suitable surfaces of planar or more complex geometry. Moreover, EPD has a high potential for scaling up to large product volumes and sizes, as well as to a variety of product shapes and 3D complex structures. As well as, some advantages like being faster, less expensive, more uniform deposited coatings on complex substrate shapes, high purity of deposits and no phase transformation during coating process would be related to EPD process.
EPD consists of two different steps. In the first step (named electrophoresis) charged particles in suspension move towards an oppositely charged substrate under the influence of an applied electric field. In the second one (the deposition itself) the particles coagulate to create a coherent and homogeneous coating on the surface of the conductive substrate. Once the liquid solvents are evaporated, the coating is dried, different steps, e.g. sintering, can be applied to consolidate the coating. This march is required mainly for ceramic coatings, but can be avoided for organic/inorganic coatings where the organic phase acts as binder. EPD is achieved via the motion of charged particles dispersed in a suitable liquid towards an electrode under an applied electric field. Deposit formation on the electrode occurs via particle coagulation. Electrophoretic motion of charged particles during EPD results in the accumulation of particles and formation of a homogeneous and rigid deposit at the relevant electrodes.
An EPD setup contains a power source, two electrodes (anode and cathode) and a EPD cell carrying the suspension with homogeneously dispersed particles or macromolecules. According to the direction of deposits, the EPD can be separated into anodic EPD, and cathodic EPD, as schematically shown in Figure. Particles having a positive surface charge will be deposited on the cathode and negative charged particles be deposited on the anode under the electric field. The current supplied to electrodes can either be direct current (DC) or alternating current (AC). The nature of the suspension and processing parameters affecting electrophoretic deposition then reviewed. Suspension parameters such as the particle size, dielectric constant, conductivity and zeta potential determine the quality of the suspension, while physical parameters such as the voltage, deposition time and conductivity of the substrate determine the success of the EPD deposition. Lower surface charged particles tend to attract each other and the deposited coating is found to be porous, and particles with a high surface charge produce a strong electrostatic repulsion force at the time of deposition, thereby producing a dense coating. Hence, a uniform particle suspension with a proper conductivity and medium dielectric constant results in better deposition.