Effects of Welding Electropolished Stainless Steel as Used in Ultra-Pure Fluid Delivery Systems for the Semiconductor and Pharmaceutical Industries

In the semiconductor and pharmaceutical industries, care is taken to prevent any contribution to product contamination or corrosion from the fluid delivery systems. Electropolished 316L stainless steel has become the industry standard due to its superior corrosion resistance. However, welding of the tubing often leads to discoloration in the heat affected zone (HAZ) which can lead to corrosion. Electropolished specimens from various lots of 316L stainless steel tubing were welded under identical parameters, but with varying concentrations of oxygen leaked into the argon purge gas during the welding, simulating on-site welding conditions. Various levels of discoloration were observed in the HAZ after welding. The chemical composition and thickness of the discoloration and an adjacent clean reference area on each specimen were analyzed by Auger Electron Spectroscopy. The cause of the discoloration was due to an iron-enriched oxide layer in the HAZ in the sensitizing temperature range. The thickness and level of discoloration depended upon the concentration of oxygen in the purge gas. The presence of this oxide layer is due to the rapid growth kinetics of FeO compared to that of C^C^. The composition of the original steel was found to be only a minor factor in the extent of the discoloration

In-Situ Resource Utilization for the Moon, Mars and Beyond...

For any future manned exploration to the moon, Mars, or beyond, there is a significant need to reduce the cost and logistics of transporting the raw materials such as oxygen, water, and fuel required to sustain human activity. Current research at Kennedy Space Center is focused on utilizing the resources at the destination to produce these requirements on-site, i.e. to live off the land. This program, known as In-situ Resource Utilization (ISRU), is the focus of the Applied Science and Technology research group here at KSC. This slide presentation will introduce the laboratories and highlight current research in ISRU to produce oxygen, water, and fuel components from lunar and Martian regolith

NanoBio2006-18031 EFFECT OF SURFACE TREATMENT ON SURFACE CHARACTERISTICS AND BIOCOMPATIBILITY OF AISI 316L STAINLESS STEEL

ABSTRACT Surface characteristics are essential in determining the biocompatibility of medical implants. Surface treatments such as mechanical polishing, electropolishing, passivation and plastic strain of AISI 316L stainless steel was found to affect the critical surface tension, with the combined electropolishing and passivation treatment resulting in the most desirable critical surface tension for biocompatibility. AES and XPS analysis showed that electropolishing results in changing the surface chemical composition significantly. There is significant Cr enrichment on the surface, compared to the bulk. The surface Cr and Fe exist as a combination of oxides and hydroxides

Application of Glow Discharge Plasma to Alter Surface Properties of Materials

Some polymer materials that are considered important for spaceport operations are rendered noncompliant when subjected to the Kennedy Space Center (KSC) Standard electrostatic testing. These materials operate in stringent environmental conditions, such as high humidity. Treating materials that fail electrostatic testing and altering their surface properties so that they become compliant would result in considerable cost savings. Significant improvement in electrostatic dissipation of Saf-T-Vu PVC after treatment with air Atmospheric Plasma Glow Discharge (APGD) was observed and the material now passed the KSC electrostatic test. The O:C ratio on the surface, as monitored by X-ray Photoelectron Spectroscopy, increased from 0.165 tO 0.275 indicating enhanced oxidation, and surface contact angle measurements decreased from 107.5 to 72.6 showing increased hydrophilicity that accounted for the increased conductivity. Monitoring of the aging showed that the materials hydrophobic recovery resulted in it failing the electrostatic test 30 hours after treatment. This was probably due to the out-diffusion of the added Zn, Ba, and Cd salt stabilizers detected on the surface and/or diffusion of low molecular weight oligomers. On going work includes improving the long term hydrophilicity by optimizing the APGD process with different gas mixtures. Treatment of other spaceport materials is also presented

Electrostatic Separator for Beneficiation of Lunar Soil

A charge separator has been constructed for use in a lunar environment that will allow for separation of minerals from lunar soil. In the present experiments, whole lunar dust as received was used. The approach taken here was that beneficiation of ores into an industrial feedstock grade may be more efficient. Refinement or enrichment of specific minerals in the soil before it is chemically processed may be more desirable as it would reduce the size and energy requirements necessary to produce the virgin material, and it may significantly reduce the process complexity. The principle is that minerals of different composition and work function will charge differently when tribocharged against different materials, and hence be separated in an electric field

Carbon Nanotube Coatings as Used in Strain Sensors for Composite Tanks

The next generation of cryogenic fuel tanks, crew habitats and other components for future spacecraft will focus on the usc of lightweight carbon fiber composite materials. A critical issue in the design and optimization of such tanks and structures will bc in structural health monitoring, however, current strain sensors have limitations. In this study, a novel carbon nanotube thin film was applied to carbon fiber composites for structural monitoring. Applying a load using a 3-point bend test to simulate bowing of a tank wall, induced significant increases in the film's electrical resistance at small deflections. Upon release of the load, the resistance returned to its approximate start value and was reproducible over multiple tests. The results show that a carbon nanotube thin film has great potential for the health monitoring of composite structures

Electronic Surface Structures of Coal and Mineral Particles

Surface science studies related to tribocharging and charge separation studies were performed on electrostatic beneficiation of coal. In contrast to other cleaning methods, electrostatic beneficiation is a dry cleaning process requiring no water or subsequent drying. Despite these advantages, there is still uncertainty in implementing large scale commercial electrostatic beneficiation of coal. The electronic surface states of coal macerals and minerals are difficult to describe due to their chemical complexity and variability [1]. The efficiency in separation of mineral particles from organic macerals depends upon these surface states. Therefore, to further understand and determine a reason for the bipolar charging observed in coal separation, surface analysis studies using Ultra-violet Photoelectron Spectroscopy (UPS) and X-ray Photoelectron Spectroscopy (XPS) were performed on coal samples and several materials that are used or considered for use in tribocharging. Electrostatic charging is a surface phenomenon, so the electronic surface states of the particles, which are influenced by the environmental conditions, determine both polarity and magnitude of tribocharging. UPS was used to measure the work function of the materials as typically used in ambient air. XPS was used to determine the surface chemistry in the form of contamination and degree of oxidation under the same environmental conditions. Mineral bearing coals are those amenable to electrostatic beneficiation. Three types of coal, Illinois No. 6, Pittsburgh No. 8, and Kentucky No. 9 were investigated in this study. Pulverized coal powder was tribocharged against copper. Pyritic and other ashes forming minerals in coal powders should charge with a negative polarity from triboelectrification, and organic macerals should acquire positive charge, according to the relative differences in the surface work functions between the material being charged and the charging medium. Different types of minerals exhibit different magnitudes of negative charge and some may also charge positively against copper [2]. Only the mineral sulfur fraction of the total sulfur content is accessible by the electrostatic method since organic sulfur is covalently bound with carbon in macerals. The sizes of mineral constituents in coal range from about 0.1 to 100 {micro}m, but pyrites in many coals are on the lower end of this scale necessitating fine grinding for their liberation and separation. A ready explanation for coal powder macerals to charge positively by triboelectrification is found in the large numbers of surface carbon free radicals available to release electrons to form aromatic carbocations. There is evidence that these cationic charges are delocalized over several atoms [3]. Only perhaps one in one hundred thousand of the surface atoms is charged during triboelectrification [4], making it difficult to predict charging levels since the data depends upon the surface chemical species involved in charging. Based on the high electron affinity of oxygen atoms, oxidation is expected to decrease the extent of a coal particle to charge positively. Also, ion transfer may contribute to the increasingly negative charging character of oxidized coal carbons. A variety of oxidized surface functional groups may influence charge properties. For example, carboxylic acid functions can lose protons to form carboxylate anions. The samples of coal investigated in this study showed differing degrees of beneficiation, consistent with a more extensively oxidized Illinois No. 6 coal sample relative to that of Pittsburgh No. 8. Even though oxygen in air is deleterious to coal stored prior to beneficiation, other gases might favorably influence charge properties. To this end, coal exposed to vapors of acetone, ammonia, and sulfur dioxide also were beneficiated and analyzed in this study