Multiple dip-coating

Multiple dip-coating removes defects present in the first layer as shown in Fig. 8.5 for a three-layer y-alumina membrane system. 

A test series was carried out to determine the effects of multiple dip-coating cycles on the PFOM thickness on slider rows. It was necessary to measure the substrate optical constants and for each row before dip coating because of the significant variation from one row to another. These values for the uncoated slider rows are listed in table 4.2. The slider rows were dip coated and the PFOM thickness was measured. This procedure was repeated until some of the rows had been dipped up to four times (4x). The PFOM thickness measured after each dip-coating cycle is given in table 4.3. 

A test was done to study the effects of multiple dip-coating cycles with baking in between on the PFOM thickness. Slider rows were dipped the PFOM film thickness... 

PFOM Thickness as Measured by Ellipsometry on Carbon-Overcoated Slider Rows Showing the Effect of Multiple Dip Coatings... 

The external diffusion process is based upon the fabrication of a Nb-Cu-Ta composite in a manner analogous to the processing used for NbTi. The surface of a wire strand is plated or dip-coated with Sn which is then diffused and reacted to form NbaSn. The cost of this process is lower than that of current bronze processes, since the use of a Cu matrix removes the need for repeated anneals during drawing, and multiple extrusions are not required. Because the amount of Sn is not restricted to 13 wt.% of the matrix, a high overall critical current density can be achieved without the need for thin reaction layers and very fine filaments (--2 pm in diameter). Thus, a single extrusion with several hundred filaments, compared with thousands for the bronze process, is all that is required to obtain a high critical current density in an external diffusion conductor. 

PEDOTiPSS dispersions can be deposited by multiple techniques including spin coating, doctor blading, dip coating or ink jetting. Spin coating is regarded as the most reliable technique to obtain uniform thin layers. 

The high transfer efficiency of this coating process resnlts from little dragout and consequently no dripping. This method is nsed to apply heavy coats, 3-10 mil, in one dip, uniformly to complex-shaped prodncts. The film thickness is dependent on the powder chemistry, preheat temperature, and dwell time. It is possible to build a film thickness of 100 mil by using higher preheat temperatures and multiple dips. 

Dip coating cannot be used multiple times to build up thicker layers of acrylic coating, since solvent in the bath will loosen or dissolve previously applied layers of acrylic. 

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