Three minimum wet thickness regions of slot die coating

An experimental study was carried out to investigate slot die coating of dilute suspensions. Polymethyl methacrylate (PMMA) particles of different sizes were added to glycerol solutions as test fluids. The coating flow experiment was performed on a lab coater. The operating window, which is a domain in which only a stable and uniform coating solution is possible, was determined experimentally. It was found that adding particles has little effect on the physical properties of glycerol solutions, as only the fluid viscosity increases slightly. Two coating defects are commonly observed; ribbing which is caused by flow instability refers to lateral waves on the coated surface, and air entrainment which implies that air bubbles are trapped in the coating solution. Adding particles has little effect on the operating window if the coating defect is ribbing. However, the operating window can be expanded substantially if the coating defect is air entrainment. Higher the particle concentration, or the smaller the particle size, more significant is the expansion of the operating window. The maximum coating speed may increase to 80% for high suspension particle density number. A previous study reported that there exists an optimal particle size which has the largest operating window for a given pure solution; this was not found in the present work. 

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“…Recently Chang et al . [8] reported that the minimum wet thickness may go down, go up or be independent of Reynolds number.…”

Section: Introductionmentioning

confidence: 99%

Slot die coating of dilute suspensions

Lin

Chu

Liu

2008

Asia-Pacific J Chem Eng

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“…In the current experimental setup, no vacuum system was applied; the effect of bead vacuum was investigated and reported elsewhere. 20 The experimental procedure for the determination of the minimum wet thickness for a given coating solution was the same as the one used by Chang et al 16 Two critical coating speeds V min and V max can be identified for a coating solution, below V min or above V max , no good coating is possible. Between V min and V max , the coating window as shown in Fig.…”

Section: Methodsmentioning

confidence: 99%

“…They also found that there exists a critical capillary number, above which the minimum wet thickness is independent of Ca. Recently, Chang et al 16 demonstrated experimentally that the minimum wet thickness may go up with, go down with or be independent of Reynolds numbers. However, the shapes of the limiting coating beads were not reported in these experiments.…”

Section: Introduction Smentioning

confidence: 99%

Operating windows of slot die coating: Comparison of theoretical predictions with experimental observations

et al. 2010

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ABSTRACT:The objective of the present study is to examine the validity of the theoretical predictions on the operating windows of slot die coating. The operating window is defined as a domain inside which stable and uniform coating is possible; different types of coating defects are found outside the window. A flow visualization technique was applied to observe the coating bead, particularly the positions and shapes of the downstream and upstream menisci, just before and after coating defects appear at high coating speeds. Special features of coating bead shapes, which lead to onsets of ribbing and air entrainment, were identified. The two-dimensional flow in the coating bead region was computed by the commercial software package FLOW-3D ® . Critical features observed experimentally for the onset of coating defects were used to judge whether the coating flow was within the operating window. The theoretically evaluated operating windows were found to be much larger than

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“…The success to obtain a uniform film is conditioned by the stability of the coating bead that fills the gap between the slot-die and the aluminum foil. The coating speed can be increased by applying vacuum underneath the coating bead [47]. The horizontal position of the slot-die provides the best combination of air purging at start-up and clean operation that are mandatory to make sure that the deposited film is free of any impurity.…”

Section: Deposition On the Current Collectormentioning

confidence: 99%

Technology of the Li-Ion Batteries

Julien¹,

Mauger²,

Vijh

et al. 2016

Lithium Batteries

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585reversible capacity measured after the first or second cycle of the half cell, since it is the capacity that can be delivered during the life of the battery. In any case, the coulombic efficiency after the two first cycles for a battery of interest (i.e., already commercialized or under investigation in research laboratories) is close to 100 %. Negative/Positive Capacity RatioThe negative electrode/positive electrode ratio N/P is also called the balance of the battery. To understand the importance of this parameter, let us first consider the case of a negative electrode with initial capacity 100 mAh with irreversible capacity 10 mAh. This means that, in an experience made on a cell with this electrode and Li-metal as the counter-electrode, the measurements have shown that the formation of the SEI has consumed 10 mAh, so that the capacity delivered by the electrode after formation of the SEI is 90 mAh. For this half-cell, the formation of the SEI has no consequence, and does not limit the capacity of the half-cell, because the metalLi is a reservoir that can provide as much of Li + ions as we need. This, however, is not true for the full cell. To see the effect, let us consider now the full cell with this negative electrode, and a positive electrode with an initial capacity 100 mAh and irreversible capacity 20 mAh, so that its reversible capacity is 80 mAh. During the first charge, the capacity of the positive electrode is just sufficient to allow for the formation of the SEI that consumes 10 mAh, plus fully charge the negative electrode with an amount of Li + ions corresponding to a capacity of 90 mAh. Upon discharging, these Li + ions will be delivered by the negative electrode to the positive electrode, so that only the amount of lithium inside the positive electrode now corresponds to a capacity of 100-10 ¼ 90 mAh. However, a part of them corresponding to the irreversible capacity 20 mAh will be trapped, so that the capacity of the battery will be 90-20 ¼ 70 mAh, while the negative electrode has a larger capacity. Therefore, the formation of the SEI has now contributed to a decrease of the reversible capacity of the full cell.It might be tempting to increase the amount of active product in the positive electrode to increase the capacity of the battery. However, this may be not a good idea. Let us assume for instance that we increase the capacity of the positive electrode by 50 %. Then the initial capacity of the positive electrode is 150 mAh, and the irreversible capacity is 30 mAh. During the first charge, 100 mAh out of the 150 mAh available will be delivered by the positive electrode like before. Actually, if the charge is stopped at this stage, then, during the first discharge, 90 mAh will return to the negative electrode. The amount of lithium that the positive electrode can deliver in the second charge corresponds to a capacity of 140-30 ¼ 110 mAh capacity available to proceed reversibly upon cycling, larger than the 90 mAh that the negative electrode can absorb, so that the reversible capacity is sim...

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Three minimum wet thickness regions of slot die coating

Cited by 83 publications

References 19 publications

Slot die coating of dilute suspensions

Slot die coating of dilute suspensions

Operating windows of slot die coating: Comparison of theoretical predictions with experimental observations

Technology of the Li-Ion Batteries

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