Diamond Coating Offers Many Uses
The Broadway song that claims diamonds are a girl’s best friend may need rewriting to include business.
The astounding combination of mechanical, electrical and optical properties of diamonds make them a prime candidate for industrial applications. Uniquely hard and inert, a diamond surface is as friction-free as Teflon but much tougher. Its thermal conductivity is four times greater than copper and 20 times that of silicon. Diamond “doped” with the proper impurities becomes an excellent semiconductor, and diamond is transparent to light, from infrared through ultraviolet frequencies.
Unfortunately, in its natural form, diamond is both extremely expensive and nearly impossible to process physically.
As a result, cost has limited natural diamond’s role more or less to grinding wheels, oil drilling bits and jewelry.
In recent months, however, a surge in industrial interest has energized the field of man-made diamond technology, particularly in using a process similar to growing crystals to create a diamond film on various substances.
Last summer, Beamalloy Corp. announced that it would apply synthetic diamond coatings to objects submitted by clients. In the three months following, the company received more than 2,000 industrial inquiries.
Beamalloy Vice President Robert Partyka bragged: “We’ve put coatings on the natural surfaces of emeralds and opals. We’ve coated rock drills, computer disks, stamping punches, watch crystals, plastic eyeglasses--all kinds of things. We even have an order from a physician to put a diamond coating on a set of dentures to improve their compatibility with a patient’s tissue.”
Diamond’s properties make man-made coatings suitable for a mind-boggling array of applications, from the mundane to the highly sophisticated.
Coatings on optical surfaces (eyeglasses, lenses, mirrors, watch crystals, etc.) make them highly scratch-resistant.
A coating on a computer memory hard disk could prevent damage from “head crashes.”
Coatings on cutting edges (machine tools, surgical knives, household knives, razor blades, etc.) make them last longer and wear better, and coatings can protect softer gemstones such as emeralds. Ball bearings can exploit the friction-free property of diamond surfaces. Diamond’s chemical inertness makes it useful as a corrosion-resistant coating for materials used in corrosive environments.
For instance, diamond-coated in-line sensors could measure paper thickness during production or measure gas composition in the combustion chamber of an automobile engine. Diamond’s strength and transparency make it suitable for use in X-ray detection equipment and some medical instruments. A look at current activity in diamond-film research reveals a discouragingly familiar pattern. Only 10 U.S. companies are actively involved in the technology, with a total funding of $15 million. But more than 80 Japanese companies, funded at $100 million, are active in the field.
In the past five years, Japanese firms won 488 patents in the technology, while U.S. companies managed only 28.
On the brighter side, the U.S. government spends $6 million a year on synthetic diamond research, and Pennsylvania State University manages a diamond-film research consortium that has attracted 25 members.
Essentially, diamond coatings remain in the development stage, but a renewed interest in their capabilities has begun to bring new applications to market.
Sumitomo Electric manufactures a high-quality loudspeaker tweeter whose sounding surface is coated with diamond film for rigidity. The tweeter is incorporated into a top-of-the-line Sony speaker system. Crystallume Corp. of Menlo Park, Calif., markets an ultra-thin diamond window for use in X-ray analyzers. Reportedly, four Japanese companies--Mitsubishi, Idemitsu, Toshiba and Sumitomo--will soon test-market diamond-coated machine tools. They expect to go commercial within a year.
Diamond film technology appears ready for the market. Inexpensive raw materials and fast, low-temperature coating processes should enable man-made diamond to penetrate a broad variety of “low-technology” areas. The adaptation of a well-understood, existing semiconductor technology to grow single-crystal diamond films on silicon should accelerate development of a diamond semiconductor market--the most exciting potential application of the technology.
Some scientists say the development of synthetic diamond films could be the greatest advance in materials since the invention of plastics. We appear to be on the verge of finding out whether diamond films can realize that promise.
