High Rate Evaporation of Alloys

摘要

Although thermal evaporation is very suitable for large area coatings, this technology is still restricted to the evaporation of pure metals since vapor pressures of the alloy components can be decades apart. As mixing in the liquid phase is not thorough enough and subsequent evaporation of the separate alloy components will require diffusive mixing in the solid deposit, mixing is best done in the vapor phase. An efficient alloy-mixing device has been constructed and demonstrated using separate heating chambers forthe separate alloy components. The device is designed on the basis of gas dynamics calculations and combines several sonic orifices to physically separate the evaporating chambers and allow mixing in the gaseous phase before the gas mixture is allowed to pass the final orifice and deposit onto the substrate. It will be shown that the use of sonic orifices has a further advantage in allowing close proximity between the evaporator and substrate, thereby greatly enhancing the vapor utilization rate. From the basic calculations, the design rules for the efficient vapor handling and mixing will be demonstrated. The device has been demonstrated for the Zn-Mg alloy evaporation. Results from these tests will be shown.