are characteristic of the sample composition. 6 Using XRF, the average metalliccomposition of the Persian daric wasfound to be 95.1 percent gold, 2.8 percentcopper and 2.1 percent silver.
Replicated mirrors were produced using
Darius’ alloy. The intent was to compara-
tively characterize the surface hardness
and wear resistance of this unique alloy
against virgin gold and to spectrophoto-
metrically measure its infrared reflectivity.
If improved hardness was evident, thenthe alloy might be an ideal candidate forfurther surface hardening using a room-temperature deposited protective film.
For comparative hardness measure-
ments, the moderate abrasion methods per
MIL-M-13508C were used by abrading
dry cheesecloth across a mirror’s surfaces
using a 1-lb force. Virgin gold suffered vi-
sual damage after one test stroke; Darius’
alloy survived eight to 12 strokes.
Reflectivity was measured on PerkinElmer Lambda 950 UV/VIS and Lambda983 infrared spectrophotometers. In the1300- to 15,000-nm region, alloy mirrorswere basically indistinguishable from virgin gold (> 99 percent reflectivity).
These alloy-replicated mirrors thereforewere excellent candidates for further surface modifications.
Reactive ion plating deposition
Established as a means to produce high-quality optical filters, Newport’s StabilifeReactive Low Voltage Ion Plating(RLVIP) process was used to deposit hardadherent silicon protective films upon thealloy mirror’s surfaces. 7 The process produces optical thin films possessing thephysical density, amorphous microstructure and optical properties approachingthose of bulk materials. These homogeneous films are free of the physical poresand columnar structure typically seen in
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