million for packaging, buoyancy materials, and other miscellaneous uses. A large percentage of t h e total market for rigid plastic foams uses their thermal insulating properties. T h e future demand for rigid foams in these applications is estimated on the basis of the thermal conductivity. Some of the new foams have 30 t o 50',; lower thermal conductivity. If these new materials take over t h e insulation market by 1965, t h e total estimate of 105 million cubic feet of rigid foams might be cut to 7 0 or 80 million. Estimates of 80 million to 105 million cubic feet equal between 100 and 200 million pounds of rigid plastic foam based on densities of the various foams, says Dr. Goggin. > Coatings. Use of aikyd resins in alkyd-based paints is likely to grow from 4S7 million pounds in 1958 to 580 million pounds in 1965, says Dr. Maurice H. Bigelow of Allied Chemical. Consumption of binder resins for latex paints should advance from 130 million pounds in 1958 to 200 million in 1965, Or. Bigelow predicts. Currently, about 2 pounds of binder resin are used per gallon of latex paint. This figure, however, is likely to decline t o about 1.5 pounds per gallon, h e says. • Variety of Elastomers. About 2.4 billion pounds of synthetic rubber will b e consumed in the U.S. this year, compared to about 5 billion pounds of plastics, says Kendall Greene of Goodrich-Gulf Chemicals. In 1965, U.S. consumption of synthetic rubber should hit 3.1 billion pounds, including 224 million to 336 million pounds of polyisoprene and polybutadiene, Mr. Greene says. • Synthetic Fiber Usage. Nylon, the first high-polymer synthetic fiber, is still in t h e forefront, with annual production of 300 million pounds of filament and 30 million pounds of staple, says Clare W. Bendigo of Werner Textile Consultants. Output of acrylic fibers this year will be about 175 million pounds. T h e Cinderella fiber is, of course, polypropylene. "So far, no olefin fibers have been even reasonably successful/' says Mr. Bendigo, "and we do not expect any polypropylene fiber w e have seen in use to date to b e a commercial success. However, w e feel about the olefins as we did about the acrylics 11 years ago . . . sooner or later the olefins cannot help b u t become major fibers . . . the potentials are admittedly in the hundreds of millions of pounds." 24
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N O V . 2 3, 1 9 5 9
Diamond M a k i n g Process R e v e a l e d Catalyst a n d design of pressure equipment critical f a c tors in making industrial stones . D I A M O N D S can be made by man. This
the public has known since 1955, when General Electric announced the achievement. But the techniques used to reach this goal of somewhat more than a century of experimental effort have only very recently been revealed. The process, using a specially designed ultrahigh pressure and high temperature assembly, a metal catalyst, a n d a pyrophyllite capsule, can now produce diamonds at a rate that assures the U.S. of a domestic source of these important tools. Since October 1957, GE's metallurgical products department in Detroit, Mich., has been making diamonds commercially. Until recently the process has been covered by a secrecy order from the U.S. Government. G E released some of the details directly to the press and further details appear in an article in t h e Oct. 10 issue of Nature, which was a month late in appearing because of press strike problems. Original work on man-made diamonds was done by D r . Francis P, Bundy, Dr. H. Tracy Hall, Dr. Herbert M. Strong, and Dr. Robert Wentorf, working at GE's chemical research department under the direction of Dr. A. L . Marshall and A. J. Nerad. • Catalyst Critical. One of the critical elements in the process is the cata-
lyst and its physical relation to the carbon to b e converted. Any of several molten metals, or their salts that will give the metals, can be used. At diamond-forming temperatures t h e thin filin of metal exists at t h e interface b e tween the unconverted carbon and t h e growing diamond crystal. T h e diamond forms on the side of the catalyst film away from the carbon. If the film should happen to break, diamond formation stops. W i t h o u t this catalytic action it is e s timated that pressures of 3 million p.s.i. a n d temperatures over 7000° F . a r e needed. The GE system accomplishes diamond formation "within a few minutes" at pressures ranging from 800,000 to 1,800,000 p.s.i. a n d temperatures ranging from 2200° to 4400° F . T h e products are usually less than a tenth of a carat in weight and often a r e five-pointed stars. They have excellent quality, says GE, with t h e qualities for many industrial uses superior to those of natural diamonds. O n e of the primary achievements in developing the G E technique has been t h e design of a pressure device, called t h e "belt." I t makes use of conical carbide pistons that push into each end of a specially shaped chamber. T h e conical piston h a s much greater strength than the usual cylindrical piston of
INSIDE STORY. Exploded view of GE's assembly for making diamonds shows holder for graphite and catalyst ( c e n t e r ) , a n d components of gasket a n d current-
THE C O V E R : G E unveils its process f o r making diamonds* Five-pointed stars, only t w o cases of which h a v e been r e ported In n a t u r e , o f t e n occur
IN THE ROUGH. GE says its diamonds are b e t t e r than natural ones for many industrial uses. Photomicrograph shows diamond w i t h catalyst film removed high-pressure equipment, a n d the doughnut- or belt-shaped structure supporting t h e c h a m b e r consists of several stressed binding rings which give support. Conical gaskets of pyrophyllite, a naturally occuring form of a l u m i n u m silicate, are used in t h e hole of t h e doughnut for pressure sealing, yet allowing motion through compression a n d flow. Pyrophyllite is unique in that pressure raises its melting point from 2 4 0 0 ° to 4800° F. • Variety of Materials Work. Carbon is charged into the pyrophyllite capsule. Graphite is t h e preferred form, h u t other materials, such as car-
bon blacks, sugar charcoal, or carburizing coin pound, may b e used. Catalyst is placed a t both ends of the carbon charge. X h e metal catalyst can be chromium, manganese, iron, cobalt, nickel, ruthenium, rhodium, palladium, osmium, iridium, or platinum. Tantalum is particularly effective for inducing the growth of small diamond crystals, but it is n o t always a s active as some of the other catalysts. T h r o u g h this sample assembly an electric current is passed, producing t h e high temperatures n e e d e d . T h e conical pistons simultaneously converge, creating the pressure needed. As t h e metallic catalvst melts, a thin
film is formed b e t w e e n the carbon and the catalyst and diamond formation begins on the side of the metallic film away from the carbon. N o seed crystals a r e necessary. G r o w t h rates at least as high as 0.1 millimeter per minu t e have been observed. T h e thin film of catalyst—a vital p a r t of t h e p r o c e s s should be on something of t h e order of about 0.1 millimeter. W h e n t h e film breaks, diamond growth ceases. Also, it is difficult to grow diamonds buried in molten catalyst even to a depth of 1 millimeter away from the source of carbon. Crystal habit varies according to the temperature of formation. Cubes predominate at the lowest temperatures, with mixed cubes, c u b o - o c t a h e d r a , and dodecahedra at i n t e r m e d i a t e temperatures. Octahedra a r e formed at the highest t e m p e r a t u r e . No tetrahedra have been found. At high growth rates o c t a h e d r a are frequently twinned t h r o u g h an octahedron face as a mirror plane. This often results in twinned five-pointed stars which are slightly imperfect. Close observation usually shows a spur on the side of one of the points of t h e star. Color varies with t e m p e r a t u r e . The diamonds are black at low temperatures, passing t h r o u g h dark green, light green, yellow, to w h i t e at the highest temperature.
mm
CATALYST METAL
MIXTURE OF METAL, CARBIDES, AND NEW DIAMOND UNCHANGED CARBON HEATED Br ELECTRIC CURRENT
XARB0N
transmitting element (right a n d left). D i a m o n d forms on side of catalyst away from carbon (diagram at right)
.CATALYST FILM
WE
-NEW DIAMOND
NOV.
2 3,
1959
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