.......spray nozzles, ultrasonic spray nozzles, screen printers, manual brushing, and “nozzle-less” ultrasonic spray heads. There are many limitations with traditional coating methods for the application of coatings used in fuel cells. With dip coating techniques, it is difficult to control both thickness and uniformity. Air atomizing spray valves produce overspray, have a tendency to clog easily, produce a non-uniform spray pattern and have difficulty maintaining accurate control of the liquid flow rate. Ultrasonic spray nozzles produce a softer, more efficient spray but produce non-uniform coating layers due to difficulties with control of the spray pattern shape and inability to precisely start and stop the liquid spray. Screen printing techniques are best suited to applying thick coating layers and have very limited ability to apply thin layers. Manual brushing techniques are inherently subjective because of the dependence on operator skills. There are also difficulties with material handling for coatings used in fuel cells. Many of the coatings are suspensions, which have a tendency to separate or “fall out” quickly. This condition causes the coating properties to change over time, which further limits the ability to apply a uniform coating layer to the substrate. An automated method for the precise application of fuel cell coating materials has been developed that utilizes a “nozzle-less” ultrasonic spray head and a precision X-Y-Z-q-Æ’…….continue
