Durable Low-Emissivity Coating for Vacuum Glass and Glazing Surfaces Exposed to the Environment

Vacuum glazing requires a scratch-resistant Low-E coating. Microscopic pane spacers are required to prevent the two panes from touching under external pressure, but create high contact stresses which can scratch glass and existing Low-E coatings during pane movement with temperature change. Hard pyrolytic coatings can be used, but allow four times more radiant heat loss than sputtered coatings, compromising R-value. Lack of a scratch resistant Low-E coating is one of the key issues which have impeded successful commercialization of vacuum glazing for more than two decades. This project will study the viability of using a vacuum deposition process that produces a graded interface extending well into the glass surface, rather than just on it. Such coatings have proven scratch-resistant since the 1970s, but have not been studied for use as Low-E coatings. A bench top vacuum chamber will be modified and used to apply a highly energetic non-sputtered coating to square panes of common window glass. The coating process will be evaluated for 1) spectral performance, 2) scratch resistance on a cyclic tribological tester, and visual damage using Scanning Electron Microscopy.Commercial Application and Other Benefits: A successful coating will produce vacuum glazing with almost three times less heat loss than the vacuum glazing currently on the market. It will enable commercial production of windows having the same R-value as a wall as early as 2013 and which cost no more to make than todays argon-filled Low-E coated glazing. Simply changing our window glazing can reduce total US energy use (and greenhouse gas emissions) by 5% or more over the next 20 years. Buildings use 55% of our nations natural gas, so the impact of vacuum windows extends to reducing groundwater pollution from natural gas production, most notably by fracturing shale. It will create many jobs in manufacturing as well as the retrofit of existing buildings