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At least 19 records

Porous article with surface functionality and method for preparing same

Porous organic articles having no surface functionality may be treated by remote plasma discharge to thereby introduce functionality to the surface of the article. The functionality is introduced throughout the article's surface, including the exterior surface and the surfaces of the pores. Little or no degradation of the porous organic article occurs as a result of the functionalization. Amino, hydroxyl, carbonyl and carboxyl groups may be introduced to the article. In this way, an essentially inert hydrophobic porous article, made from, for example, polyethylene, can have its surface modified so that the surface becomes hydrophilic. The remote plasma discharge process causes essentially no change in the bulk properties of the organic article. The remote plasma discharge process is preferably conducted so that no photons, and particularly no ultraviolet radiation, is transmitted from the plasma glow to the porous article. The surface-functionalized article may be used, for example, as a solid support in organic synthesis or in the chromatographic purification of organic or biochemicals.

Koontz, Steven L.↗

Porous article with surface functionality and method for preparing same

Porous organic articles having no surface functionality may be treated by remote plasma discharge to thereby introduce functionality to the surface of the article. The functionality is introduced throughout the article's surface, including the exterior surface and the surfaces of the pores. Little or no degradation of the porous organic article occurs as a result of the functionalization. Amino, hydroxyl, carbonyl and carboxyl groups may be introduced to the article. In this way, an essentially inert hydrophobic porous article, made from, for example, polyethylene, can have its surface modified so that the surface becomes hydrophilic. The remote plasma discharge process causes essentially no change in the bulk properties of the organic article. The remote plasma discharge process is preferably conducted so that no photons, and particularly no ultraviolet radiation, is transmitted from the plasma glow to the porous article. The surface-functionalized article may be used, for example, as a solid support in organic synthesis or in the chromatographic purification of organic or biochemicals.

Koontz, Steven L.↗

Plasma Surface Functionalization of AFP Manufactured Composites for Improved Adhesive Bond Performance

Application of carbon fiber reinforced polymer (CFRP) as a high-performance structural material has widespread application in the present aerospace industry. However, as-processed composite materials require a comprehensive surface treatment prior to bonding to remove contaminants and impart surface functionality and topography to overcome their poor adhesion properties. Atmospheric pressure plasma jet treatment (APPJT) has been increasingly garnering attention as an alternate method for surface preparation of CFRP. This method has been reported to achieve success in imparting favorable polar functional groups into the composite surfaces enhancing wettability and surface energy of the bonded surfaces. In some cases, APPJT has been demonstrated to remove contaminants or, in the case of silicones, convert them to silica. In this study, an atmospheric pressure plasma jet (APPJ) system was used for surface activation of a composite laid-up by an automated fiber placement (AFP) machine. Surface modifications prior to and after treatment were characterized using water contact angle (WCA) measurements, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and atomic force microscopy (AFM). Double cantilever beam (DCB) tests were performed to quantify the bonding performance of the composites. The results show a marked enhancement of the mode I interlaminar fracture toughness with the application of APPJT.

Sarikaya, Ibrahim↗

Low-work-function surfaces produced by cesium carbonate decomposition

Cesium carbonate (Cs2CO3) was heated to the decomposition temperature of approximately 600 C. The nonvolatile decomposition products were condensed on a nickel substrate while the carbon dioxide was removed by pumping. The deposited material is characterized by an effective work function of between 1.05 and 1.15 eV at 450 K and by photoemission in the visible and near-infrared region of the spectrum. It is suggested that the deposited material consists of Cs2O, possibly Cs2O2, and adsorbed cesium. Silver, evaporated from a heated silver bead, produced the typical photoemissive and thermionic properties of a silver-oxygen-cesium (S-1) photocathode. The material may be of interest for thermionic energy converters and for the formation of silver-oxygen-cesium photocathodes.

Briere, T. R.↗

The role of cesium suboxides in low-work-function surface layers studied by X-ray photoelectron spectroscopy - Ag-O-Cs

The oxidation of cesium on silver substrates has been studied using photoyield measurements and X-ray photoelectron spectroscopy. The occurrence of two O1s peaks in the core-level spectrum at 527.5 and 531.5-eV binding energy for cesium and oxygen exposures giving the optimum photoyield proves that two oxides of cesium exist in high-photoyield surfaces, and not Cs2O alone as previously thought. From the shape and position of the cesium peaks and the Auger parameter, the assignment of the O1s peaks at 527.5- and 531.5-eV binding energies to oxygen in Cs2O and Cs11O3, respectively, can be made. Hence the total cesium-oxygen layer is a mixed phase consisting of Cs2O + Cs11O3, approximately 20-40 A thick.

Yang, S.-J.↗

A new surface impedance function for the aperture surface of a conducting body with a dielectric-filled cavity

A surface impedance function (SIF) appropriate for use on the aperture surface of a conducting body with a dielectric-filled cavity, is presented. Unlike the usual SIFs that might be used on an aperture, this SIF takes into account not only the wave transmitted through the aperture but also the wave reflected from the inside of the cavity the shape of the aperture and cavity, and the polarization and direction of the incident wave. The SIF is derived heuristically from the series-reflection solution for a plane wave normally incident on an infinite flat conducting plate with a flat dielectric coating. The SIF was developed and used in a combined method of moments (MM) solution for the scattered fields due to an incident plane wave. This combined technique greatly reduces the number of current expansion coefficients to be determined using the method of moments and hence also reduces the number of impedance elements required for calculation in the method of moments. Application of the SIF in a combined method is illustrated for a two-dimensional object.

Goggans, Paul M.↗

Measuring Skew in Average Surface Roughness as a Function of Surface Preparation

Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces polishing time, saves money and allows the science requirements to be better defined. This study characterized statistics of average surface roughness as a function of polishing time. Average surface roughness was measured at 81 locations using a Zygo white light interferometer at regular intervals during the polishing process. Each data set was fit to a normal and Largest Extreme Value (LEV) distribution; then tested for goodness of fit. We show that the skew in the average data changes as a function of polishing time.

Stahl, Mark↗

Measuring Skew in Average Surface Roughness as a Function of Surface Preparation

Characterizing surface roughness is important for predicting optical performance. Better measurement of surface roughness reduces grinding saving both time and money and allows the science requirements to be better defined. In this study various materials are polished from a fine grind to a fine polish. Each sample's RMS surface roughness is measured at 81 locations in a 9x9 square grid using a Zygo white light interferometer at regular intervals during the polishing process. Each data set is fit with various standard distributions and tested for goodness of fit. We show that the skew in the RMS data changes as a function of polishing time.

Stahl, Mark T.↗