Graded index antireflective coatings for glass. Second annual report

Technical Report · Thu May 01 00:00:00 EDT 1980

DOI:https://doi.org/10.2172/5140005· OSTI ID:5140005

Haggerty, J S

M.I.T. is conducting research which will lead to a process for forming broad band antireflective (AR) coatings on glass. Use of these coatings increases the extractable heat from flat-plate solar collectors by 30 to 50% compared with their performance under equivalent solar flux, surface temperature and ambient conditions without broad band AR coatings. Graded index surface films can virtually eliminate reflection losses if controlled properly. Graded index films on a borosilicate glass (Corning Glass Works No. 7740, Pyrex) has been demonstrated. While glass treated this way exhibited adequate optical properties, the glass itself, cannot be fabricated by the float glass process because of excessive working temperatures, and consequently is too expensive for solar applications. The objective of this work is to define glass compositions and processing steps which will result in graded index surface films (which exhibit broad band AR characteristics) on glasses which can be fabricated by the float glass process. The mechanism by which these graded index surface films are produced on glass surfaces consists of preferentially etching one phase from a phase separated glass. The film which remains consists of a porous structure in which the fraction of solid phase increases continuously from the free surface toward the bulk glass. Scattering effects are eliminated by limiting the size of the pore structure to dimensions which are substantially less than the wavelength of light. With this structure, the local index of refraction is proportional to the fraction of solid phase which is present. Characterizations are intended to define the microstructural and chemical nature of the surface film throughout its thickness. Progress is reported. (WHK)

• Research Organization: Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
• DOE Contract Number: AS02-78ER05003
• OSTI ID: 5140005
• Report Number(s): DOE/ER/05003-T1
• Country of Publication: United States
• Language: English

Related Subjects

14 SOLAR ENERGY
ANTIREFLECTION COATINGS
FABRICATION
FLAT PLATE COLLECTORS
COVERINGS
GLASS
AUGER ELECTRON SPECTROSCOPY
BORON SILICATES
ELECTRON MICROSCOPY
ETCHING
FATIGUE
FILMS
ION MICROPROBE ANALYSIS
MATERIALS TESTING
MICROSTRUCTURE
OPTICAL PROPERTIES
REPLICAS
RESEARCH PROGRAMS
SCANNING ELECTRON MICROSCOPY
STRESSES
BORON COMPOUNDS
CHEMICAL ANALYSIS
COATINGS
CRYSTAL STRUCTURE
ELECTRON SPECTROSCOPY
EQUIPMENT
MECHANICAL PROPERTIES
MICROANALYSIS
MICROSCOPY
NONDESTRUCTIVE ANALYSIS
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
SILICATES
SILICON COMPOUNDS
SOLAR COLLECTORS
SOLAR EQUIPMENT
SPECTROSCOPY
SURFACE FINISHING
TESTING
141000* - Solar Collectors & Concentrators