Morphology of Electrophoretically Deposited Films on Electrode Strips

Pascall, Andrew J.; Sullivan, Kyle T.; Kuntz, Joshua D.

doi:10.1021/jp306447n

Cited by 23 publications

(22 citation statements)

References 33 publications

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“…The cross sectional profi le of a representative deposited strip with the 1.25 mm mask is presented in Figure 2 d. In this case, the deposit is approximately 9 µm thick at the center and 14 µm thick at the edges. This is a characteristic of deposits on electrode strips as observed by Pascall et al, [ 35 ] and, as they showed, is a result of a singularity in the electric fi eld that results from a discontinuity in the electric boundary conditions at the edge of the electrode, or in this case, at the boundary between the illuminated and dark areas of the photoconductive electrode. This is a characteristic of deposits on electrode strips as observed by Pascall et al, [ 35 ] and, as they showed, is a result of a singularity in the electric fi eld that results from a discontinuity in the electric boundary conditions at the edge of the electrode, or in this case, at the boundary between the illuminated and dark areas of the photoconductive electrode.…”

Section: Communicationmentioning

confidence: 69%

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Light‐Directed Electrophoretic Deposition: A New Additive Manufacturing Technique for Arbitrarily Patterned 3D Composites

et al. 2014

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patterned deposits from collections of particles, nearly universally, these methods rely on AC electric fi elds and the particles are manipulated through dielectrophoresis, as with optoelectronic tweezers, [23][24][25] or electrohydrodynamic fl ows. [ 26 ] Perhaps the closest technique to light-directed EPD described in the literature is the report of Hayward et al. [ 27 ] on the assembly of 2D patterned colloidal crystals using DC fi elds and UV light, but the method of action points to near-surface electrohydrodynamic fl ows, [ 28 ] which limits the ability to form thick 3D deposits. To our knowledge, there have been no reports that demonstrate fabrication of 3D patterned multimaterial composites using DC electric fi elds.Light-directed EPD has the potential to elevate EPD from its traditional role as a coating process to a true additive manufacturing technique. By automating the fl uid handling and light delivery systems, light-directed EPD will allow rapid patterning of multiple materials over large areas and can produce composites to near net shape from a diverse set of materials, including metals, ceramics, polymers, and biological materials. Controlled voids can also be incorporated into the composite by utilizing a fugitive material that is removed with subsequent post-processing. These capabilities are unique among current additive manufacturing processes. [ 29 ] A typical multimaterial light-directed EPD process is depicted in Figure 1 . The space between the photoconductive electrode and counter electrode is fi lled with a suspension of particles that will be deposited. The photoconductive electrode consists of a photoconductive layer of titania nanorods hydrothermally grown on an fl uorine-doped tin oxide (FTO) coated glass substrate. A photomask is placed on the back side of the photoconductive electrode and illuminated with a light source. An electrical potential difference is imposed between the FTO layer of the photoconductive electrode and the counter electrode. In the regions illuminated by the light source defi ned by the clear regions of the photomask, the conductivity of the photoconductive fi lm increases. Electric fi eld lines are concentrated in these regions and particles in suspension move long the fi eld lines and attach to the surface of the electrode forming a deposit (Figure 1 a). The suspension composition and the photomask pattern can be changed to deposit another material in a different location within the same layer (Figure 1 b). The process can be repeated to build subsequent layers to form an arbitrarily patterned 3D composite (Figure 1 c). Finally, the suspension can be removed from the chamber yielding a dry deposit while retaining the precise patterning.Electrophoretic deposition (EPD) is a process in which electrically charged colloids are forced to deposit onto the surface of an electrode due to an electric fi eld. EPD was originally developed nearly a century ago for applying paint to metal surfaces. [ 1 ] Since then, EPD has been used to deposit a wide range of materials...

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Section: Communicationmentioning

confidence: 69%

“…The origin of increased thickness of the edges is described by Pascall et al[ 35 ] b) Feature size reproduction of the technique with mask feature widths ranging from 0.25 to 5 mm.…”

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confidence: 99%

Light‐Directed Electrophoretic Deposition: A New Additive Manufacturing Technique for Arbitrarily Patterned 3D Composites

et al. 2014

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“…It is worth noting that, even though the observed microstructures are representative for the layers obtained from the different suspensions under the conditions here defined, the modification of the deposition conditions lead to a different morphology of the as-deposited samples and to a different sintering behavior. For instance, the increase in the deposition time for a defined suspension, which gives place to thicker deposits with a less pronounced U-shape according to Pascall et al, 25 results in sintered films with diverse microstructures. Further focused studies are in progress in order to investigate the effect of the film thickness on the microstructure of PZT-Nb thick films.…”

Section: Influence Of the Co-solvents In The Properties Of The Suspenmentioning

confidence: 99%

PZT-Based Thick Films Prepared by Electrophoretic Deposition from Suspensions with Different Alcohol-Based Solvents

Bernardo¹,

Malič²,

Kuščer³

2015

J. Electrochem. Soc.

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Niobium-doped lead zirconate titanate (PZT-Nb) thick films have been prepared by electrophoretic deposition from suspensions with different alcohol-based solvents, namely ethanol or mixtures of ethanol and 10 vol.% of a co-solvent: butanol or 2-butoxyethanol. The co-solvent addition results in a modification of the suspension's properties. As a consequence, under the same deposition conditions the rate of deposit formation changes for the suspensions with different solvents. The deposits show a homogeneous packing of the particles without any appreciable variation in their green density regardless of the variations in the deposition rate. Nevertheless, the deposits with a similar mass prepared from the different suspensions show distinct morphologies, some of them being considerably thicker at the edges than at the centre. The peculiarities in the thickness uniformity observed for the as-deposited layers are ascribed to changes in the resistivity of the deposits. After sintering, the thick films obtained from the different suspensions show particular microstructures which may be related to the morphology of the as-deposited layers. Dense films with a grain size of about 2-3 μm and an enhanced ferroelectric response were obtained from the suspension containing butanol.Lead zirconate titanate (PZT) based materials with composition near the morphotropic phase boundary are widely used for the fabrication of sensors, actuators and transducers because of their excellent piezoelectric properties. To miniaturize the devices these materials are patterned in the form of thick films. Such structures can be processed by an electrophoretic deposition (EPD) method that is based on the mobility of electrically charged particles dispersed in a solvent toward an oppositely charged electrode as a result of an external electric field. The possibility of preparing different PZT coatings such as thick films on flat substrates 1-4 or on complex-shaped ones, 5,6 nanowires 7 or patterned structures 8,9 by EPD has already been reported in the literature. However, difficulties like particle agglomeration, an inappropriate morphology of the coatings or the formation of cracks during the drying or sintering are also frequently reported and require further optimization of the dispersions, the deposition process and the post-deposition procedures.In order to obtain PZT-based thick films with a homogeneous microstructure and a defined geometry, which are suitable for practical applications, the processing conditions have to be carefully controlled. The parameters affecting the EPD can be classified in those related to the particles and the suspensions and those related to the process including the physical parameters such as the electrical conductivity and the size of the electrodes, the electrical conditions, i.e.. the voltage/intensity relationship and the deposition mode (constant voltage, constant current, pulse mode, etc.), the deposition time, etc.. 10 As described by Hamaker, 11 the rate of deposit formation is directly proportional to ...

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“…[3,4] Recently, there has been a focus on manufacturing energetic thin films for material synthesis applications [5][6][7][8][9] and creating tailored shapes for customized power generation applications. [10] Processing energetic materials for tailored shapes can be achieved through quiescent sol-gel synthesis, [11] vapor/spray deposition, [12,13] blade casting, [14,15] or through additive manufacturing techniques. [16,17] All of these processes require combining energetic materials with a polymer binder and carrier fluid that acts to disperse the reactant matrix into a polydisperse colloidal slurry.…”

Section: Introductionmentioning

confidence: 99%

Effects of Shear Rate during Energetic Material Processing on Reactivity

et al. 2019

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Energetic materials are often processed at high rates of deformation as colloidal slurries and then cured. The slurries are non-Newtonian colloidal solutions that exhibit changes in microstructure with variations in applied flow. This study shows that changes to microstructure due to applied flow affect the reactivity of energetic thin films. Energetic thin films of identical composition and geometry are prepared with different applied shear rates, which produce variations in the film microstructure by segregating smaller particles toward surfaces. Results show that films exhibit significant gains in flame speed with increasing shear rate. The differences in flame speed are linked to variations in microstructure. Specifically, densification of smaller particles near a boundary promote increased flame speeds. However, when particles become segregated, larger particles tend to contribute less to the overall reaction because they burn slowly compared to the smaller particles. When segregated, the larger particles may not be adding chemical energy to the reaction front because propagation is dominated by the more ignition sensitive smaller particles. This study demonstrates explicit changes in reactivity arising from changes in processing conditions that affect microstructure. Controlling applied shear rate introduces a new approach to regulating energetic material reactivity when processed using extrusion-based advanced manufacturing techniques.

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Morphology of Electrophoretically Deposited Films on Electrode Strips

Cited by 23 publications

References 33 publications

Light‐Directed Electrophoretic Deposition: A New Additive Manufacturing Technique for Arbitrarily Patterned 3D Composites

Light‐Directed Electrophoretic Deposition: A New Additive Manufacturing Technique for Arbitrarily Patterned 3D Composites

PZT-Based Thick Films Prepared by Electrophoretic Deposition from Suspensions with Different Alcohol-Based Solvents

Effects of Shear Rate during Energetic Material Processing on Reactivity

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