Chemical & Chemical Engineering News (80th Anniversary Issue), Vol. 81, No. 36, 2003, Sept. Edited by X. Lu Introduction

My personal introduction to tungsten as a structural material was at Kennametal, a producer of tungsten carbide metal-cutting tools, where I took an internship in my senior year while studying chemistry at a small liberal arts college in Latrobe, Pa. The position involved sample preparation for X-ray fluorescence. During visits to the powder metallurgy laboratory, I noticed paint cans on the storage shelves, many without handles. Curiosity led me to remove a can from a shelf, only to be surprised when gravity quickly dragged it to the ground, barely missing my toes. Although the can was less than half full of powder, it weighed almost 35 lb. The powder was tungsten for fabricating heavy-metal alloys.

Later, I went to Oak Ridge National Laboratory while I studied for a graduate degree in metallurgy. I specialized in vapor-phase processing of high-temperature materials, primarily structural coatings and composites. Once again, tungsten entered my life when I became involved in a project to develop a small fiber-reinforced ceramic can with a tungsten layer deposited on its outer diameter. The cans were to be used as thermionic emitters in advanced space power systems.

I became intimately involved with tungsten during the development of powder-metal replacements for lead in small-arms ammunition, in other words, during the investigation of "green bullets." A perusal of the periodic table reveals very few candidates for replacing lead. Bismuth, tin, and zinc are interesting, but each has deficiencies. Tungsten is heavy and commonly used in ordnance but unfortunately is much too hard for most small-arms applications.

One approach to the problem seemed quite straightforward: Build a composite that combined the properties of different elements to produce a leadlike material. A light, ductile metal like tin could be used as the binder with tungsten included for mass. But tungsten is not easy to process, and bullets had to be cheap. A review of the tungsten binary-phase diagrams revealed fewer than 40 systems, with few intermetallic compounds. Most of the soft metals with low melting points do not wet tungsten, and, in addition, significant differences in density make casting impossible. There had to be a method to combine tungsten and a ductile metal binder.

After World War I, resourceful window and curtain manufacturers sprinkled tungsten particulates onto the surface of tin sheets, which were subsequently fed through a rolling mill to produce high-density, pliable sheets that could be used to make weights. The solution to the lead-replacement problem was actually very simple. Powder blends without additives were pressed at room temperature to produce dense compacts. It wasn't rocket science, but it worked, and the tungsten-tin composite is a leading candidate for replacing lead in small-caliber bullets and for a variety of other applications.

Although we may not realize it, tungsten continues to be a part of our lives because it is still used in lighting and electrical contacts; in electronics, including cell phones and pagers; in cutting tools and engine components; in radiation shielding; and now in sporting goods such as golf balls and shot.

Rick Lowden is a metallurgist and senior research engineer at Oak Ridge National Laboratory. Although his primary area of expertise is vapor-phase processing of materials, he has been intimately involved in the development of powder-metal replacements for lead in ammunition--and being an avid shooter, it's been a dream come true.

TUNGSTEN AT A GLANCE

Name: From the Swedish tung sten, meaning heavy stone. The symbol is from mineral wolframite, from which the element was originally isolated.

Atomic mass: 183.84.

History: Isolated in 1783 by Spanish chemists Juan José and Fausto Elhuyar.

Occurrence: China has 75% of the world's tungsten ores.

Appearance: Silvery white metal.

Behavior: Tungsten has the highest melting point and highest boiling point of all metals.

Uses: Tungsten is used in high-temperature applications such as heating elements and lightbulb filaments.

SEABORGIUM

ERIC SEABORG, CHARLOTTESVILLE, VA.

What's in a name?

In the case of seaborgium, the story goes back to World War II. My father, Glenn T. Seaborg, was a 30-year-old chemist who'd had the good fortune to discover a secret element that would become known as plutonium. He'd taken a leave of absence from the University of California to work at the code-named Metallurgical Laboratory at the University of Chicago. The mission: to develop a process to isolate plutonium so it could be used in a theoretical weapon, the atomic bomb.

He was scrambling to assemble a staff when a letter arrived asking him for a recommendation for the Navy. The correspondent, Albert Ghiorso, repaired the Geiger counters at Berkeley's Radiation Laboratory. He was a nodding acquaintance of my father's, but my mother knew him well--he'd married one of her best friends. "Al is much too independent; he wouldn't last a day in the Navy," she told my father. "You should offer him a job here."

My father invited Ghiorso to Chicago, unable to reveal the nature of their project, except to say that it was important. Ghiorso agreed to come on the condition that his work wouldn't involve wiring circuits, which was what he was trying to get away from. He was promptly put to work wiring circuits.

NAMESAKE Glenn T. Seaborg points to the element named in honor of him.