A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

The acid-base properties of titanium 6-4 plates (low surface area) were investigated after three different pretreatments, namely Turco, phosphate-fluoride and Pasa-Jell. A series of indicators was used and color changes were detected using diffuse reflectance visible spectroscopy. Electron spectroscopy for chemical analysis was used to examine the indicator on the Ti 6-4 surface. Specular reflectance infra-red spectroscopy was used to study the adsorption of stearic acid from cyclohexane solutions on the Ti 6-4 surface

An investigation of adhesive/adherend and fiber matrix interactions

Research during the report period focused on continued scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) of lap shear samples and flatwise tensile specimens and on the surface characterization of TiO2, Ti 6-4, and Ti powders with particular emphasis on their interaction with primer solutions of both polyphenylquinoxaline and LaRC-13 polyimide. The use of SEM and XPS in the analysis of Ti 6-4 adherend surfaces is described as well as differences in Ti 6-4 surface composition after different chemical pretreatments. Analysis of fractured surfaces is used to established the failure mode. The surface acidity of Ti 6-4 coupons can be established by reflectance visible spectroscopy using indicator dyes

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

Several techniques were used to study pretreated Ti 6-4 surfaces including scanning electron microscopy (SEM), electron spectroscopy of chemical analysis (ESCA), and, reflectance visible spectroscopy. Each pretreatment type gave a characteristic surface morphology as seen by SEM. Elemental analysis of the Ti 6-4 surfaces was done using ESCA. Trace residual contaminants from particular chemical pretreatments were identified readily. Results indicate that reflectance visible spectroscopy using indicator dyes placed on Ti 6-4 surfaces appears to be a feasible approach to establish surface acidity. Differences in surface acidity were observed using bromthymol blue on Ti 6-4 surfaces pretreated by two different methods

A fundamental approach to adhesion: Synthesis, surface analysis, thermodynamics and mechanics

Pretreated and primed Ti 6-4 surfaces were characterized by scanning electron microscopy/energy dispersive analysis of X-rays (SEM/EDAX) and electron spectroscopy for chemical analysis (ESCA). Fractured lap shear bonded Ti 6-4 specimens were also characterized by SEM/EDAX and ESCA. A number of surface techniques were used to characterize Ti02 powders

Influence of Shrinkage and Swelling Properties of Coal on Geologic Sequestration of Carbon Dioxide

The potential for enhanced methane production and geologic sequestration of carbon dioxide in coalbeds needs to be evaluated before large-scale sequestration projects are undertaken. Geologic sequestration of carbon dioxide in deep unmineable coal seams with the potential for enhanced coalbed methane production has become a viable option to reduce greenhouse gas emissions. The coal matrix is believed to shrink during methane production and swell during the injection of carbon dioxide, causing changes in tlie cleat porosity and permeability of the coal seam. However, the influence of swelling and shrinkage, and the geomechanical response during the process of carbon dioxide injection and methane recovery, are not well understood. A three-dimensional swelling and shrinkage model based on constitutive equations that account for the coupled fluid pressure-deformation behavior of a porous medium was developed and implemented in an existing reservoir model. Several reservoir simulations were performed at a field site located in the San Juan basin to investigate the influence of swelling and shrinkage, as well as other geomechanical parameters, using a modified compositional coalbed methane reservoir simulator (modified PSU-COALCOMP). The paper presents numerical results for interpretation of reservoir performance during injection of carbon dioxide at this site. Available measured data at the field site were compared with computed values. Results show that coal swelling and shrinkage during the process of enhanced coalbed methane recovery can have a significant influence on the reservoir performance. Results also show an increase in the gas production rate with an increase in the elastic modulus of the reservoir material and increase in cleat porosity. Further laboratory and field tests of the model are needed to furnish better estimates of petrophysical parameters, test the applicability of thee model, and determine the need for further refinements to the mathematical model

Regenerable Sorbent Development for Sulfur, Chloride and Ammonia Removal from Coal-Derived Synthesis Gas

A large number of components in coal form corrosive and toxic compounds during coal gasification processes. DOE’s NETL aims to reduce contaminants to parts per billion in order to utilize gasification gas streams in fuel cell applications. Even more stringent requirements are expected if the fuel is to be utilized in chemical production applications. Regenerable hydrogen sulfide removal sorbents have been developed at NETL. These sorbents can remove the hydrogen sulfide to ppb range at 316 °C and at 20 atmospheres. The sorbent can be regenerated with oxygen. Reactivity and physical durability of the sorbent did not change during the multi-cycle tests. The sorbent development work has been extended to include the removal of other major impurities, such as HCl and NH3. The sorbents for HCl removal that are available today are not regenerable. Regenerable HCl removal sorbents have been developed at NETL. These sorbents can remove HCl to ppb range at 300 °C to 500 °C. The sorbent can be regenerated with oxygen. Results of TGA and bench-scale flow reactor tests with both regenerable and non-regenerable HCl removal sorbents will be discussed in the paper. Bench-scale reactor tests were also conducted with NH3 removal sorbents. The results indicated that the sorbents have a high removal capacity and good regenerability during the multi-cycle tests. Future emphasis of the NETL coal gasification/cleanup program is to develop multi-functional sorbents to remove multiple impurities in order to minimize the steps involved in the cleanup systems. To accomplish this goal, a regenerable sorbent capable of removing both HCl and H2S was developed. The results of the TGA conducted with the sorbent to evaluate the feasibility of both H2S and HCl sorption will be discussed in this paper

Oxidation and sulfidation resistant alloys with silicon additions

The Albany Research Center (ARC) has considerable experience in developing lean chromium, austenitic stainless steels with improved high temperature oxidation resistance. Using basic alloy design principles, a baseline composition of Fe-16Cr-16Ni-2Mn-1Mo alloys with Si and Al addition at a maximum of 5 weight percent was selected for potential application at temperatures above 700ºC for supercritical and ultra-supercritical power plant application. The alloys were fully austenitic. Cyclic oxidation tests in air for 1000 hours were carried out on alloys with Si only or combined Si and Al additions in the temperature range 700ºC to 800ºC. Oxidation resistances of alloys with Si only additions were outstanding, particularly at 800ºC (i.e., these alloys possessed weight gains 4 times less than a standard type-304 alloy). In addition, Si alloys pre-oxidized at 800ºC, showed a zero weight gain in subsequent testing for 1000 hours at 700ºC. Similar improvements were observed for Si only alloy after H2S exposure at 700ºC compared with type 304 stainless steel. SEM and ESCA analysis of the oxide films and base material at the oxide/base metal interface were conducted to study potential rate controlling mechanisms at ARC. Depth profile analysis and element concentration profiles (argon ion etching/x-ray photoelectron spectroscopy) were conducted on oxidized specimens and base material at the National Energy Technology Laboratory

Hydrogen Separation Membranes Annual Report for FY 2006.

The objective of this work is to develop dense ceramic membranes for separating hydrogen from other gaseous components in a nongalvanic mode, i.e., without using an external power supply or electrical circuitry. This goal of this project is to develop two types of dense ceramic membrane for producing hydrogen nongalvanically, i.e., without electrodes or external power supply, at commercially significant fluxes under industrially relevant operating conditions. The first type of membrane, hydrogen transport membranes (HTMs), will be used to separate hydrogen from gas mixtures such as the product streams from coal gasification, methane partial oxidation, and water-gas shift reactions. Potential ancillary uses of HTMs include dehydrogenation and olefin production, as well as hydrogen recovery in petroleum refineries and ammonia synthesis plants, the largest current users of deliberately produced hydrogen. The second type of membrane, oxygen transport membranes (OTMs), will produce hydrogen by nongalvanically removing oxygen that is generated when water dissociates at elevated temperatures. This report describes progress that was made during FY 2006 on the development of OTM and HTM materials

The Pitfalls of Central Clearing in the Presence of Systematic Risk

Through the lens of market participants' objective to minimize counterparty risk, we provide an explanation for the reluctance to clear derivative trades in the absence of a central clearing obligation. We develop a comprehensive understanding of the benefits and potential pitfalls with respect to a single market participant's counterparty risk exposure when moving from a bilateral to a clearing architecture for derivative markets. Previous studies suggest that central clearing is beneficial for single market participants in the presence of a sufficiently large number of clearing members. We show that three elements can render central clearing harmful for a market participant's counterparty risk exposure regardless of the number of its counterparties: 1) correlation across and within derivative classes (i.e., systematic risk), 2) collateralization of derivative claims, and 3) loss sharing among clearing members. Our results have substantial implications for the design of derivatives markets, and highlight that recent central clearing reforms might not incentivize market participants to clear derivatives