Everything from a grain of sand to this 6-cylinder engine block can be nondestructively examined in the LC-SEM, which has the world’s largest chamber and an array of diagnostic tools. Photo: Y-12 National Security Complex

Have you ever wanted to take a large-chamber scanning electron microscope (LC-SEM) for a test run? You just might if you've ever wanted to know why that aircraft turbine blade cracked, whether that new material actually improves pacemakers or what is creating wear on that diamond crystal.

Whether you work for an aircraft company, medical manufacturer or in the tool grinding industry, the Y-12 National Security Complex is offering free use of what is being hailed as "the largest LC-SEM in the world" from February through May 6 at Technology 2020 in Oak Ridge, TN.

A key advantage of scanning electron microscopy is the combination of a high lateral resolution with a large depth of focus. Microanalysis of the sample composition also can be achieved. The LC-SEM represents a new class in scanning electron microscopy in that, unlike conventional solutions, the electron optics and detector are positioned freely in the large vacuum chamber with the sample left unaffected and opening up new applications for scanning electron microscopy.

A new class

"This is one of the most exciting projects we've been involved in," Steve Dekanich, LC-SEM project lead at the Y-12 Complex, says. "There are other smaller-chamber SEMs in operation in the world-seven in Germany and one in Japan. With this larger instrument, we're now able to conduct nondestructive testing of full-sized parts. We've never before had the capability to do this."

The LC-SEM, by Visitec (Greves-muehlen, Germany) allows for the examination of parts and components virtually, regardless of geometry, volume and weight. It features a compact electron optics column with advanced tungsten filament technology capable of a lateral resolution of up to 10 nanometers and with a magnification range of 10 times to 200,000 times for samples measuring up to 1 meter high by 1 meter in diameter and weighing up to 300 kilograms.

Dekanich explains that manufacturers can examine areas repeatedly because of a backlash-free positioning device associated with an electron optics column. The combination of mechanical and electronic beam adjustment allows a given area to be positioned with an accuracy of less than 10 nanometers.

The LC-SEM also is fitted with a Channeltron detector, characterized by its good signal-to-noise ratio. "Key features of the LC-SEM design are that it accommodates special fixtures for in-situ studies and opens up new horizons in the world of microscopy and microanalysis," says Arash Behzadi, director of sales and marketing at Qualitest USA (Plantation, FL), distributor of the microscope. "Magnifications from the instrument's variable-pressure feature allows for critical surface characterization studies of conductive and nonconductive surfaces such as steel and ceramics."

The LC-SEM's analytical capabilities include a backscatter detector for compositional contrast and an electron backscatter diffraction (EBSD) for mapping of crystalline compound orientations and phase identification of small particles. The instrument also features an energy-dispersive X-ray spectrometer for simultaneous analysis of the elements boron to uranium; a Fourier transform infrared spectrometer for analysis of chemical bonds in thin films on metals; and a focused ion beam for dual-beam operation, three-dimensional reconstruction and ion milling and preparation of surfaces for EBSD.

Such capabilities help to take the mystery out of determining how corrosion came about, what corrupted a chemical composition or why a part snapped in two, Dekanich says. "This literally is a one-stop materials characterization laboratory in one instrument." Although the LC-SEM provides critical information about the characteristics of materials used in the U.S. weapons program, because of its size, it is well suited to a broad range of applications. Areas of potential application include everything from electronics to medical implants, with investigations focusing on materials behavior, wear, product failures and more, Dekanich says.

For example, medical manufacturers can use the LC-SEM for nondestructive evaluation of implants, proposed implant materials and the interface of implants coupled with exterior components. In the aerospace industry, the instrument can be used to evaluate compressor blades and small spacecraft or spacecraft components and, on a smaller scale, circuit boards, atmospheric particulate contamination and solar dust. In the automotive industry, the microscope can help to evaluate everything from failed engine blocks to pistons to drive shafts. In addition to performing failure evaluations, the LC-SEM can provide morphological and chemical analysis of the failure surface.

A microscope adapts

The LC-SEM also adapts to its surroundings. The microscope is mounted in an active vibration isolation system. The temperature of the electron optics column is controlled by a cooling circuit, and protection from external magnetic fields is ensured by multi-layered chamber walls. The instrument also can be prepared for use in a cleanroom environment.

The vacuum system consists of three pumps. Rotary vane and rotary lobe pumps for the low vacuum, and a powerful cryopump for the high-vacuum application with capacity to deal with out-gassing samples. The LC-SEM also can be equipped with a separate sample transfer device.

The instrument's control is based on the Microsoft Windows user interface and supports operations in the manufacturer's work environment. Vacuum control, optics positioning, sample analysis and image processing all are performed directly from the personal computer.

Developed according to ergonomic and safety criteria, microscopic analysis can be conducted efficiently using the LC-SEM, with shape and function complemented to each other. With its intuitive controls, both beginners and experienced SEM users can see the benefits.

At the Y-12 complex

"This demonstration of the LC-SEM is a great opportunity for the technical community," Dekanich says, including the aircraft and automotive industries, medical manufacturers, government agencies such as NASA and the FBI, the U.S. Army and other military branches, universities and even museums.

The Y-12 complex is hosting the demonstration in part to fulfill its mission to advance U.S. science and technology and support community economic development programs.

sidebar: Quality Specs

• The LC-SEM allows for the nondestructive examination of full-size components.

• The instrument accommodates samples measuring 1 meter in diameter by 1 meter high and weighing up to 300 kilograms.

• The microscope allows for magnification from 10 times to 200,000 times.

• Variable pressure allows critical surface characterization studies of conductive and nonconductive surfaces.