Engineering topics
Publications and source records attributed to Morrison, S. R..
The preparation of a matrix of 48 samples consisting of pigments and pigmented paints is described. The results obtained from testing these samples by electron spin resonance and by in situ spectral reflectance measurements in space simulation tests are presented. Conclusions and recommendations for further research are given.
Various redox couple surface additives are studied which increase the photostability of coprecipitated zinc orthotitanate pigment. The electron spin resonance technique was used to examine the characteristic photodamage centers. Results indicate that cerium surface redox additive completely passivates the pigment at the surface concentrations studied. Less passivation occurs with the iridium chloride and the iron cyanide redox couples.
Five powders were received for plasma calcining during this report period. The particle size using a fluid energy mill, and obtained pigments that could be plasma calcined. Optimum results are obtained in the plasma calcining of zinc orthotitanate when finely dispersed particles are subjected to a calculated plasma temperature of 1670 C. Increasing the plasma calcining time by using multiple passes through the plasma stabilized the pigment to vacuum UV irradiation was evidenced by the resulting ESR spectra but slightly decreased the whiteness of the pigment. The observed darkening is apparently associated with the formation of Ti(+3) color centers.
Two experimental techniques were developed. In the first, an electrochemical method was used with a single crystal ZnO electrode and with the material of interest dissolved in the electrolyte. In the other an electron spin resonance method was used so that measurements related to thermal control coatings could be made with the ZnO in the form of powder, either alone or in formulation of a binder. A simplified model regarding the relationship between the electron density and time is considered.
Ferricyanide/ferrocyanide couple prevents zinc oxide pigment degradation in thermal control coatings. Chemical couple retards physical optical property changes.
The oxidation by ZnO holes of vehicle components in thermal control coatings has been examined to develop experimental methods to study such reactions and to identify what components to avoid because of their instability when in the presence of u.v.-produced holes. Two methods were used that show consistent results. An electrochemical technique with a single crystal ZnO anode was used for quantitative comparisons, and electron spin resonance was used to study more practical powder/vehicle systems. Alcohols and dioxane were shown to be readily oxidized by ZnO holes, whereas acetonitrile, neopentane, and ethyl acetate were oxidation resistant. Some resistance to the photooxidation was provided by recombination centers.
Surface recombination centers protecting against discoloration of thermal control coatings due to chemical changes induced by photoproduced holes and electrons in oxide pigments
Iron cyanide additive for surface stabilization of ZnO irradiated with UV in vacuum
Thermal control coating degradation under vacuum and ultraviolet radiation by chemical change of photoproduced holes and electrons
Electron reactivity of one equivalent oxidizing agents at ZnO surface by electrochemical reduction
Ferrocyanide and ferricyanide additives for prevention of optical degradation of coatings by ultraviolet radiation and vacuum
Current-voltage characteristics of cathodic reduction of aqueous ferricyanide ion, using single crystal of n-type semiconductor zinc oxide
Additives used to provide surface recombination centers on thermal control coatings and thus stop optical degradation
Thermal control coatings, cathodic processes on semiconductor zinc oxide, and semiconductor electrolyte interface capacitance
Cathodic reduction of aqueous ferricyanide ion on single crystal zinc oxide electrode