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Marcio S. Carvalho - One of the best experts on this subject based on the ideXlab platform.
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dynamic wetting failure in curtain Coating comparison of model predictions and experimental observations
Chemical Engineering Science, 2019Co-Authors: Marcio S. Carvalho, Satish KumarAbstract:Abstract In this work dynamic wetting failure of Newtonian liquids in a curtain Coating geometry is studied using a hydrodynamic model developed in our prior work (Liu et al., 2016b). The model is used to predict the onset of wetting failure with curtain heights consistent with prior experimental setups. In the model, a Navier-slip boundary condition and constant contact angle are used to describe the dynamic contact line (DCL). The governing equations are solved with the Galerkin finite-element method and the critical substrate speed is identified at which wetting failure occurs. A boundary of a Coating Window is constructed which outlines the critical substrate speed for different flow rates of the liquid curtain. The model predictions are compared with prior experimental observations reported by Blake et al. (1999) and Marston et al. (2009). The model reproduces the non-monotonic behavior of the critical speed as the liquid flow rate increases. When surfactants are absent, our results suggest that the experimental observations can largely be explained with a model that uses the simplest boundary conditions at the DCL (Navier-slip and constant contact angle) and accounts for the air stresses there to accurately calculate interface shapes. When surfactants are present, our results suggest that a decrease in the equilibrium surface tension may not be the only mechanism responsible for changes in the shape of the Coating Window. In particular, Marangoni stresses may play an important role.
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Uncovering Slide Coating Window with Theoretical Modeling
2015Co-Authors: Kristianto Tjiptowidjojo, Marcio S. CarvalhoAbstract:Slide Coating is a method used for rapidly depositing multilayer of Coating onto a moving substrate or web simultaneously. This method is commonly used in the manufacturing of photographic products, magnetic recording media, and optical films. Slide Coating is a premetered Coating method, in which the thickness of the Coating is set by the liquid flow rate and web speed only and independent of the other operating parameters, making it the method of choice for precision Coating. However, the nature of the flow in the Coating bead and therefore the uniformity of the liquid layer deposited on the substrate can be affected by the other operating parameters. The region in the operating parameters of a Coating process where the applied liquid layer is adequately uniform is referred to the Coating Window and that is the focus of this study. Fundamentals of slide Coating Window, even for single-layer, are not completely understood. Incomplete slide Coating Windows with some of the modes of Coating bead breakdown are described in Chen (1992) and Hens and van Abbenyen (1997). Mechanisms, however, have not been addressed and the effects of die-lip geometry have not been explored. In contrast, slot Coating Window is much better understood, mechanisms of bead breakdown have been identified (Romero et al 2004) and the effects of die-lip geometry have been studied (Gates 1999). Our goa
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two layer tensioned web over slot die Coating effect of operating conditions on Coating Window
Chemical Engineering Science, 2010Co-Authors: Marcio S. CarvalhoAbstract:Abstract Tensioned-web-over-slot die (TWOSD) Coating deploys elastohydrodynamic interaction to control the distance between the moving substrate and the Coating die lip surface in order to be able to coat an ultra-thin liquid layer. Dual slot TWOSD Coating is designed to deposit two thin uniform liquid layers onto a moving web simultaneously. Like in the fixed-gap dual slot Coating, the interlayer separation point needs to be at the downstream corner of the mid lip in order to prevent Coating defects. Different flow features, like weeping, bead breakup and feed slot vortices, limit the range of operating parameters that ensures uniform Coating, and define the operating Window of the process. In this study, we analyze dual slot TWOSD Coating flow by solving the Navier–Stokes equation coupled with thin cylindrical shell equation using the finite element method. The boundaries in the parameter space that define the operating Window or vortex-free Window are automatically computed by a direct tracking method of flow features. The effect of operating conditions, such as liquid viscosity, web tension and web speed, on the critical layer thickness at which the Coating becomes non-uniform is determined by this study.
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two layer tensioned web over slot die Coating effect of die lip geometry
Chemical Engineering Science, 2010Co-Authors: Marcio S. CarvalhoAbstract:Abstract Tensioned-web-over-slot die Coating (TWOSD) takes advantage of the elastohydrodynamic interaction between the curved web under tension and the Coating liquid to sustain a very small Coating gap that enables ultra thin Coating at relatively high speed. When the product requires two liquid layers, dual slot TWOSD Coating can be used to coat those layers simultaneously. In this case, the liquid pressure along the Coating bead sets not only the web configuration and meniscus locations but also the interlayer separation point. An easy way to control the pressure distribution is through the die lip geometry. Here, we analyze the effect of four different die lip geometric parameters, e.g. the downstream lip radius, the mid lip radius, the downstream lip offset and the mid lip apex point, on the Coating Window of the dual slot TWOSD Coating. Using the model proposed by Nam and Carvalho (2009c) and a direct tracking of flow features, the boundaries of the vortex-free operating Window, area inside the parameter spaces that ensure a uniform Coating without vortex inside the flow, were obtained and compared for each die lip configuration. We found that the mid lip radius is one of the important parameters to control the location of the upstream meniscus. Also the location of the interlayer separation point can be controlled by the lip offset and location of the apex point.
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flow in tensioned web over slot die Coating effect of die lip design
Chemical Engineering Science, 2010Co-Authors: Marcio S. CarvalhoAbstract:Abstract Tensioned-web-over-slot die (TWOSD) Coating is one of the most successful high-speed liquid Coating process. It deploys elastohydrodynamic interaction to control the distance between the moving substrate and the Coating die lip surface in order to be able to coat an ultra-thin liquid layer. However, flow instabilities that come from the gas–liquid interface and microvortices inside the flow may lead to Coating defects. Therefore, the range of operating conditions of uniform Coating is limited. The operating Window of the process is a strong function of the geometry of the die. However, this relationship and, in general, the fundamental mechanisms of the elastohydrodynamic interaction are not known. In this study, we analyze TWOSD Coating flow by solving the Navier–Stokes equation coupled with thin cylindrical shell equation using the finite element method. The boundaries that define the regions in the parameter space of uniform Coating are automatically computed by a direct tracking method, based on multi-parameter continuation. The results show that the Coating Window of the process can be enlarged by designing the appropriate lip geometry.
Kristianto Tjiptowidjojo - One of the best experts on this subject based on the ideXlab platform.
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Mapping Slide Coating Window with Flow Visualization
2015Co-Authors: Kristianto Tjiptowidjojo, Wieslaw J. SuszynskiAbstract:The complete understanding of the mechanisms of Coating processes failures is usually the result of detailed flow visualization and theoretical modeling. In slot Coating process, these tools have been used to successfully describe and determine the operating parameters of bead break-up at low-vacuum, high vacuum and low flow limit for Newtonian and non-Newtonian liquids. The Coating Window of slide Coating is not as well understood. The currently best available information appears to be Hens & Van Abbenyen (1997) and Chen (1992). They describe some of the Coating defects that define the boundary of the operability Window of the process. However, flow mechanisms associated with the different defects have not been addressed. One reason is that the break-up modes have not been perceptively viewed through a transparent back-up roll in a systematic flow visualization study. In this work, we are extending Romero et al (2004) analysis of slot Coating to slide Coating. We are probing the bead breakup mechanisms with the aid of through-the-roll viewing of the bead at low-vacuum, high-vacuum, and low-flow limits. We are investigating the flow states that lie beyond the operability limits and operating parameters, such as web speed, vacuum pressure, gap height and slide inclination, which set them u
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Uncovering Slide Coating Window with Theoretical Modeling
2015Co-Authors: Kristianto Tjiptowidjojo, Marcio S. CarvalhoAbstract:Slide Coating is a method used for rapidly depositing multilayer of Coating onto a moving substrate or web simultaneously. This method is commonly used in the manufacturing of photographic products, magnetic recording media, and optical films. Slide Coating is a premetered Coating method, in which the thickness of the Coating is set by the liquid flow rate and web speed only and independent of the other operating parameters, making it the method of choice for precision Coating. However, the nature of the flow in the Coating bead and therefore the uniformity of the liquid layer deposited on the substrate can be affected by the other operating parameters. The region in the operating parameters of a Coating process where the applied liquid layer is adequately uniform is referred to the Coating Window and that is the focus of this study. Fundamentals of slide Coating Window, even for single-layer, are not completely understood. Incomplete slide Coating Windows with some of the modes of Coating bead breakdown are described in Chen (1992) and Hens and van Abbenyen (1997). Mechanisms, however, have not been addressed and the effects of die-lip geometry have not been explored. In contrast, slot Coating Window is much better understood, mechanisms of bead breakdown have been identified (Romero et al 2004) and the effects of die-lip geometry have been studied (Gates 1999). Our goa
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operability limits of slide Coating
Chemical Engineering Science, 2011Co-Authors: Kristianto TjiptowidjojoAbstract:Abstract Slide Coating is one of the pre-metered methods used for high precision single and multilayer Coatings. The thickness of each liquid layers is set by the flow rate and web speed only and it is independent of other process parameters. The uniformity of the deposited layer, however, is affected by the operating conditions. In the design of Coating processes, it is crucial to know the set of conditions at which the deposited layer is adequately uniform, i.e. to define the operability Window of the process. We developed a theoretical model of slide Coating flow by solving the full two-dimensional Navier–Stokes equations and used it to uncover the mechanisms of Coating bead breakdown at low vacuum, high vacuum, and low flow limits. With full understanding of the bead breakup processes, we then constructed a theoretical Coating Window as a function of Coating thickness, web speed, and applied vacuum. A simple stability criterion was used to predict the onset of ribbing instability and deployed to add the onset of ribbing limit inside the Coating Window.
W Schabel - One of the best experts on this subject based on the ideXlab platform.
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slot die processing of lithium ion battery electrodes Coating Window characterization
Chemical Engineering and Processing, 2013Co-Authors: Marcel Schmitt, Michael Baunach, Lukas Wengeler, K Peters, Pascal Junges, Philip Scharfer, W SchabelAbstract:Abstract Slot-die Coating is actually the most used Coating method for the manufacturing of lithium-ion battery electrodes. An easy way of reducing production costs is to increase the line capacity. Thus, the relatively high-viscous slurries are coated at continuously increasing velocities. Facing these higher and higher velocities, the main processing challenge is to ensure that the surface quality stays constant. Therefore we investigated Coating of high-viscous anode slurries consisting of large graphite particles. Systematically detected conditions for which Coating defects occurred were discussed and compared with different theoretical limits for stable Coating conditions. Thereby the uniformity of the stable wet film was analyzed and logged with a two dimensional laser sensor system. Even though the detected break-up lines are, in some regions, congruent with the applied viscocapillary models, the appearing Coating defects are not as expected in the literature. Furthermore, large particles and agglomerations may provoke an additional film break-up at small film thicknesses regardless of the Coating speed. For stable conditions the roughness of the film increases when the dimensionless gap width increases.
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slot die processing of lithium ion battery electrodes Coating Window characterization
Chemical Engineering and Processing, 2013Co-Authors: Marcel Schmitt, Michael Baunach, Lukas Wengeler, K Peters, Pascal Junges, Philip Scharfer, W SchabelAbstract:Abstract Slot-die Coating is actually the most used Coating method for the manufacturing of lithium-ion battery electrodes. An easy way of reducing production costs is to increase the line capacity. Thus, the relatively high-viscous slurries are coated at continuously increasing velocities. Facing these higher and higher velocities, the main processing challenge is to ensure that the surface quality stays constant. Therefore we investigated Coating of high-viscous anode slurries consisting of large graphite particles. Systematically detected conditions for which Coating defects occurred were discussed and compared with different theoretical limits for stable Coating conditions. Thereby the uniformity of the stable wet film was analyzed and logged with a two dimensional laser sensor system. Even though the detected break-up lines are, in some regions, congruent with the applied viscocapillary models, the appearing Coating defects are not as expected in the literature. Furthermore, large particles and agglomerations may provoke an additional film break-up at small film thicknesses regardless of the Coating speed. For stable conditions the roughness of the film increases when the dimensionless gap width increases.
Hyun Wook Jung - One of the best experts on this subject based on the ideXlab platform.
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operability Coating Window of dual layer slot Coating process using viscocapillary model
Chemical Engineering Science, 2016Co-Authors: Ho Suk Ji, Ilyoung Kwon, Hyun Wook JungAbstract:Abstract The viscocapillary model for predicting the operability Windows in a dual-slot Coating process for two Newtonian liquids has been derived by means of a lubrication approximation technique from two-dimensional (2-D) Navier-Stokes equations. The flow rates per width and the pressure differences simplified in several sub-regions within the Coating bead regime have been integrated together with approximations of the upstream and downstream menisci and the interlayer between the top and bottom layers. Coating limits or onsets for leaking and bead break-up defects have been determined on the basis of the position of upstream meniscus of the bottom layer as an indicator. Operability Coating Windows predicted from the viscocapillary model show a good agreement with those by 2-D CFD solver and experiments. In addition, the pressure profiles within the Coating bead regime compared between the viscocapillary and 2-D models are qualitatively similar. This simplified model can be applied as a fast tool for usefully manipulating the stable operations in dual-layer slot Coating systems.
Tequila A L Harris - One of the best experts on this subject based on the ideXlab platform.
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slot die Coating of polybenzimiazole based membranes at the air engulfment limit
Journal of Power Sources, 2013Co-Authors: Kanthi Latha Bhamidipati, Sima Didari, Tequila A L HarrisAbstract:Abstract The objective of the current study is to analyze the slot die Coating process of highly viscous (1–20 Pa s), shear-thinning solutions. The upper and lower Coating boundaries are determined with respect to various non-dimensional parameters. Polyphosphoric acid doped polybenzamidazole (PPA/PBI) solutions are used as the test solutions. Simulations are performed using 2D, volume-of-fluid (VOF) model available in FLUENT 6.3.26 to predict the Coating Windows. The numerically predicted Coating Window compared within ±4% of the experimental data. Design of Experiments (DOE) is performed to understand the impact of operational and processing conditions on the Coating Windows. It is observed that the air engulfment could be delayed by using smaller Coating gaps and higher processing temperatures, which would facilitate faster processing of thin films, an important attribute during industrial scale processing. One major contribution from the study is the development of a semi-empirical model, in which operational and processing parameters are supplied as inputs to predict the air engulfment velocity within ±10% accuracy.