X-ray Photoemission Study of Graphite
EMSL Project ID
18591
Abstract
The energy requirement of many industrial processes is met through utilization of reactions of carbon and carbonaceous materials with oxygen, steam, carbon dioxide and hydrogen. The mechanisms of the gas reactions of carbon/graphite are not well established and the properties of carbonaceous materials have not been studied extensively in the past. And this is primarily due to the lack of experimental techniques that can be used for the detailed characterization of these materials. Retarding the gas-carbon reaction would be beneficial to many industrial processes. For example, when carbon is used as an electrode material, it is desirable to have minimum reaction of the carbon with the carbon dioxide produced by the reduction of the ore or with the ambient atmosphere. In this research, we plan to carry out X-ray photoemission spectroscopy (XPS) depth profiling of several oxidized graphite samples in order to study the different phases of oxidized graphite. This research will also provide us with a better understanding of mass transport of the reacting gas from the exterior surface to an active site beneath the surface. The carbon surface is composed of defect sites generated by holes and dislocations. Moreover, carbon is a multi-crystalline material where the surface is composed of more than one crystallographic plane. Such heterogeneity plays an important role in the mechanisms of gas reactions. Oxidation of graphite occurs not only at the external surface but also at the internal pores. This research will help identify the oxidation states of carbon at the exterior surface as well as the active site beneath the surface. Part of this effort will also include characterization of a variety of graphite samples using XPS depth profiling to better understand the oxidation states of carbon at various phases as well as the defect sites and trace impurities in these materials. We have studied the structure of graphite extensively in the past using XRD (X-ray diffraction), XRF (X-ray fluorescence), thermal and mechanical techniques and our goal is to correlate the XPS results with the other property data, thus to obtain improved quality control methods and optimum performance. GrafTech International Inc. is the world leader in the manufacture of carbon and graphite products with facilities in four continents and approximately 4000 employees. The research and development center of Graftech is one of the premier technology centers in the world for the study and application of carbon and graphite. EMSL at PNNL offers state of the art XPS/AES (Kratos) and XPS High Resolution (Quantum) Spectrometers that we do not have at our Graftech research facility. This proposed research will allow us to study the structure of graphite as well as the reaction mechanisms of oxidation of graphite, which will lead to precise control of catalytic activity and selectivity of several of our manufacturing processes.
Project Details
Project type
Exploratory Research
Start Date
2006-07-24
End Date
2007-01-08
Status
Closed
Released Data Link
Team
Principal Investigator