When sheets of metal are plated or plastic fibers are formed in large quantities on the production line, the actual composition of these materials is not known until after a batch has been produced and analyzed. If part of the batch has the incorrect composition, it is discarded. Then the production process is altered to correct the composition for the next run.

Production could be made more efficient by determining the composition of industrial materials during manufacture, detecting compositional variations, making midproduction corrections, and otherwise controlling the process to achieve the desired composition. In this way, a larger percentage of the products would meet customer requirements, reducing waste, saving money and energy, and increasing the competitiveness of American industry.

New photonic methods for improving manufacturing efficiency are being developed through a collaborative effort among ORNL, the Y-12 Plant, and the University of Tennessee at Knoxville (UTK). Principal investigators are Eric Wachter, a physical-analytical chemist in ORNL's Health Sciences Research Division; Jennings Cline, a physical-analytical chemist in the Development Division of the Y-12 Plant; and Marion Hansen, a professor of chemical engineering at UTK.

This research team is adapting Raman spectroscopy, normally a complex laboratory technique, to the industrial environment. Through use of this technique, the composition of many industrial materials can be monitored in real time on the production line. In addition, the production process can be controlled while materials are being produced rather than after a batch is completed.

"Timely control of production offers several advantages,"Wachter says. "They include improved product consistency, reduced waste generation, and increased energy efficiency. These improvements will help maintain industrial profitability in a competitive global marketplace."

Raman spectroscopy is based on the Raman effect, discovered by the Indian physicist C. V. Raman in 1928. In this phenomenon, light of a single frequency (color) is scattered by each target molecule in a transparent medium. The scattered light undergoes a change in frequency based on the characteristic energies of rotation and vibration of each target molecule. In Raman spectroscopy, the measured intensities and frequencies of scattered light are used to identify and quantify different molecules in the medium.

The ORNL, Y-12 Plant, and UTK team are hoping to find applications for Raman analysis in the metal plating, aluminum, and organic polymer industries. These areas were selected as a result of discussions with industrial representatives. Such industries could benefit from improved control of composition during production. Such control could be achieved by relaying the real-time results of Raman analysis to a computer programmed to adjust the production process in response to messages about compositional variations.

How would this technique be useful in the polymer business? According to Wachter, "Physical properties of organic polymers, such as flexibility or hardness, are often determined by varying the proportion of constituents incorporated during fabrication. Traditionally, components have been added at roughly the desired levels, and then the batch is analyzed after production. If the composition is not correct, the batch often must be scrapped. Real-time Raman analysis allows polymer composition to be monitored and adjusted during production to avoid errors in formulation of the final product."

Although current local efforts are focused on these applications, the lessons learned can be applied to numerous other industrial needs for measurement. "Raman analysis is an extremely flexible method that can solve complex characterization problems in a timely and cost-effective manner," Wachter says. "The different backgrounds and capabilities of the our team have proven critical for effectively and rapidly applying Raman spectroscopy to industrial problems. We expect further successes."

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