Theodore Wydeven

Combination Moisture Resistant and Antireflection Plasma Polymerized Thin Films for Optical Coatings

The technique of plasma polymerization under vacuum conditions at ~0.1 Torr has been employed to produce highly moisture resistant, thin polymer films on hygroscopic alkali metal halide crystal materials. The polymer film is fluorocarbon in nature. In addition to the moisture resistance, the films also exhibit antireflection properties and have only one absorption band over the range 25,000-250 cm(-1) centered at 1200 cm(-1).

Reactions of atomic oxygen (O/3P/) with various polymer films

Abstract Thin films of various polymers were exposed at ambient temperature to ground-state oxygen atoms (O( 3 P)) downstream from a radio-frequency O 2 plasma or glow discharge. The polymer films examined were a polyimide (Kapton), poly(ethylene terephthalate), polystyrene, high- and low-density polyethylenes, poly(vinyl fluoride), poly(vinylidene fluoride), alternating tetrafluoroethylene-ethylene copolymer, polytetrafluoroethylene, and tetrafluoroethylene-hexafluoropropylene copolymer. The relative etch rates for the various polymer films exposed ‘out of the glow’ to O atoms with 0·04 eV translational energy are compared with corresponding literature values obtained from low-pressure, oxygen discharge studies involving exposure ‘in the glow’ and from the Space Shuttle STS-8 flight (with O atoms in low Earth orbit having collisional energy of ≈ 5 eV). The etch rate for Kapton exposed ‘out of the glow’ to 0·04-eV O atoms is also compared with etch rates obtained from various neutral and ion beam experiments (with O O + having impact energies ranging from 0·14 to 800 eV). The etch rate data for Kapton fit reasonably well a logarithmic plot, with positive slope, of reaction probability versus O( 3 P) impact energy. ESCA spectra of Kapton before and after reaction with O( 3 P) indicated steady-state competition between surface recession (etching) and oxidation.

Antireflection coating prepared by plasma polymerization of perfluorobutene-2

Plasma-polymerized coatings of perfluorobutene-2 were found to be effective single-layer antireflection coatings for polymethylmethacrylate. In the range of 400-700 nm, light transmittance of these lenses, when coated on both sides with perfluorobutene-2, was about 4% higher than with uncoated lenses. Also, the transmittance curve of the coated lenses was essentially flat from 400 nm to 700 nm.

ESCA study of several fluorocarbon polymers exposed to atomic oxygen in low Earth orbit or within or downstream from a radio-frequency oxygen plasma

Abstract The ESCA (electron spectroscopy for chemical analysis) spectra of films of poly(vinyl fluoride) (Tedlar), tetrafluoroethylene-hexafluoropropylene copolymer (in the form of a Teflon FEP coating on Kapton H, i.e. Kapton F) and polytetrafluoroethylene (Teflon or Teflon TFE) exposed to atomic oxygen (O( 3 P)) - either in low Earth orbit (LEO) on the STS-8 Space Shuttle or within or downstream from a radio-frequency oxygen plasma - were compared. The major difference in surface chemistry of Tedlar induced by the various exposures to O( 3 P) was a much larger uptake of oxygen when etched either in or out of the glow of an O 2 plasma than when etched in LEO. In contrast, Kapton F exhibited very little surface oxidation during any of the three different exposures to O( 3 P), while Teflon was scarcely oxidized.

Synthesis of Reverse Osmosis Membranes by Plasma Polymerization of Allylamine

The polymerization of allylamine in a radio-frequency electrodeless plasma to form thin polymer films on microporous filter media provides very effective dry composite membranes for reverse osmosis. Salt and urea rejections as high as 98 percent and 46 percent, respectively, have been achieved from a solution containing 10 grams of sodium chloride per liter and 10 grams of urea per liter. The plasma conditions and polymerization technique are discussed.

Plasma-enhanced CVD silicon nitride antireflection coatings for solar cells

Abstract Multilayer plasma-enhanced chemical vapor deposition (PECVD) silicon nitride antireflection coatings were deposited on space quality silicon solar cells. Preliminary experiments indicated that multilayer coatings decreased the total reflectance of polished silicon from 35 per cent to less than 3 per cent over the spectral range 0.4–1.0 μm. The solar cell energy conversion efficiency was increased from an average of 8.84 per cent to an average of 12.63 per cent.

Plasma polymerized coating for polycarbonate: single layer, abrasion resistant, and antireflection

Plasma polymerized vinyltrimethoxy silane films were deposited on transparent polycarbonate substrates. The adherent, clear films protected the substrates from abrasion and also served as antireflection coatings. Posttreatment of the vinyltrimethoxy silane films in an oxygen glow discharge further improved the abrasion resistance. ESCA (electron spectroscopy for chemical analysis) and ir transmission spectra of some films were recorded, and an elemental analysis of the films was obtained.

Wet oxidation of a spacecraft model waste

Wet oxidation was used to oxidize a spacecraft model waste under different oxidation conditions. The variables studied were pressure, temperature, duration of oxidation, and the use of one homogeneous and three heterogeneous catalysts. Emphasis is placed on the final oxidation state of carbon and nitrogen since these are the two major components of the spacecraft model waste and two important plant nutrients.

Development of a water recovery subsystem based on Vapor Phase Catalytic Ammonia Removal (VPCAR)

An integrated engineering breadboard subsystem for the recovery of potable water from untreated urine was designed, fabricated and tested. It was fabricated from commercially available components without emphasis on weight, volume and power requirement optimization. Optimizing these parameters would make this process competitive with other spacecraft water recovery systems. Unlike other phase change systems, this process is based on the catalytic oxidation at elevated temperatures of ammonia and volatile hydrocarbons to innocuous products; therefore, no urine pretreatment is required. The testing program consisted of parametric tests, one month of daily tests, and a continuous run of 165 hours. The recovered water is low in ammonia, hydrocarbons and conductivity and requires only adjustment of its pH to meet drinking water standards.

Solute rejection by porous glass membranes. II. Pore size distributions and membrane permeabilities

Abstract The pore size distributions of porous glass hyperfiltration membranes were calculated from nitrogen desorption isotherm data. Pore volume distributions of unused porous glass membranes peaked sharply between 19 and 22A pore radius. Membranes from batches with higher solute rejection appeared to have sharp cut-offs of the pore volume distribution tail for larger pores and median pore radius under 20 A. The small differences may include “skin” effects, as it was found that etching of membrane-effluent solution interface greatly reduced solute rejection, although etching of the membrane-feed solution interface had no effect on rejection. A permeability equation with a tortuosity term was used to relate porous glass membrane permeabilities to the pore size distributions. Tortuosities of 2.6–3.4 allowed such agreement for new membranes. Membranes that lost solute rejection capability during hyperfiltration life tests with sodium chloride and urea feed solutions showed a marked broadening of the pore volume distribution and, in the case of the test with sodium chloride feed, a new pore volume distribution peak at 60–80 A radius. The addition of 1.7 gm/liter aluminum chloride to a 10 gm/liter sodium chloride feed solution minimized changes in pore size distribution during a hyperfiltration life test. Electron micrographs showed apparent flow paths of the right order of tortuosity and surface area calculated from particle dimensions were less than BET areas for unused membranes but equivalent to BET areas after hyperfiltration testing.