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HISTORICAL NOTE painfully slow; craftsmen chipped away ship for naval battles. Despite a successful Perfect with hammer and chisel for hours on a engagement by the French captain Des­ rough block until it became somewhat chiens in 1690-in which his single ship round. Even after the advent of metal shot, drove off four British vessels and, later, two though, stone continued to be used be­ Dutch through the use of exploding Spheres cause it remained cheaper than expensiv~ shells-no other naval commander used iron and bronze, and also because stone cast-iron shells until 1788, when Sir Sam­ Manufacturing perfectly round geomet­ shot was lighter than equivalent metal uel Bentham (formerly of England, and rical shapes from solid materials requires spheres, thereby requiring smaller charges then working in the service of the tsar of specialized techniques and careful crafts­ of gunpowder. (This not only proved less Russia) used hollow iron shells to gain a manship. Humans first "mass-produced" expensive and safer, but also increased the great victory singlehandedly against an en­ crude spheres as projectiles to be thrown in lifetime of the fragile cannons of the per­ tire Turkish fleet. Still, neither the Russians siege machinery; later these spheres be­ iod.) or the British put Bentham's (re)discovery came smaller and better shaped as ammu­ However, large stone shot tended to to practice, until General Henri Paixhans of nition in weapons and, in the industrial break when it struck a stone wall, and so France implemented exploding shells as age, as bearings in machinery. Recently, on new materials were needed to penetrate part of the French navy's weaponry. flights of the space shuttles Columbia and defensive walls. Petrarch describes how While large round shot was used to great Challenger, microgravity experiments the Italians began using bronze shot in effectiveness in cannons to batter walls and with the Monodisperse Latex Reactor pro­ 1344. At the same time, soldiers in France buildings, a single cannon ball could do lit­ duced millions of identical perfect spheres were using spherical lead projectiles. Iron tle against massed troops. Occasional!~ only 10 micrometers across. shot came into general use for hand and small lead balls and other shrapnel were Though darts and arrows had been used shoulder weapons during the reign of packaged in canisters and then fired, as projectiles for centuries, they proved to Charles VIII of France (1483-1498), though which scattered the shot over a wide area. be ballistically unsound when launched it was mentioned as early as 1350. All these In another system, called grape shot, iron from a firearm. The next alternative was spheres were cast in molds and worked balls were arranged three layers separated round shot, spherical ammunition that re­ into a reasonably round shape. Over the by metal plates, producing composite pro­ mained the most popular type of projectile course of about a century, iron, lead, and jectile with wide dispersion. until the 19th century, when rifled gun bar­ bronze spheres were used interchange­ Small hand and shoulder firearms used rels came into use. ably. individual projectiles, which came to be The first spherical projectiles fired with Hollow spheres of cast iron were filled known as bullets, from the French word gunpowder were made of stone, which with gunpowder and fired from cannons "boulette;' which means "small ball:' was readily available everywhere and had as explosive "shells" of metal. The Nether­ Early bullets, usually made from soft lead, previously been used in the catapult and lands and Venice seem to have indepen­ ranged from 0.6 to 0.8 inches in diameter the ballista as far back as Roman days. The dently developed this idea in the late 14th (1.5 to 2 em). first references to stone ammunition century. Many other countries rapidly Although early lead bullets varied some­ spheres can be found in France in 1346, in adopted the concept for land battles, what in shape, they were usually round. Italy 18 years later, and in England 12 years though the risks of exploding metal shells One method for making small lead ammu­ after that. Making the stone spheres was were considered too great to be used on a nition was swaging, or cold-shaping, ex- truded wire in suitable dies, but small shot ---------------------------------,was most commonly made on a "shot tower:' Small lead spheres could be formed in large quantities by pouring the molten READY-TO-USE HV AND UHV PUMPING SYSTEM metal through a sieve at the top of a Highly Mobile TMP Pumping System wooden or brick tower. The oldest shot towers rose 50 to 100 ft high (15 to 30 m), Complete and Ready to Plug-in and Operate though current ones reach 190 f. (58 m). • Hydrocarbon-Free High Ultimate Since the lowest energy configuration Vacuum- 10"9 mbar with CF Flange for the molten lead droplets minimizes the surface area per volume, the surface ten­ • High Effective Pumping Speed sion draws each shot into a ball as it falls. • Small Footprint, Simple Operation The lead droplets formed perfect spheres • Integral Vacuum Vacuum Gauge by the time they reached the bottom, Controller where they plunged into a pool of water. The fallen shot was collected from the wa­ For more Information, dlal1-800-433-4021 ter, dried, and sorted by size and spheric­ ity. The primary size of lead shot LEYBOLD VACUUM PRODUCTS, INC. manufactured this way could be varied by 5700 Mellon Road, Export, PA 15632-8900 increasing or decreasing the gap size in the sieve at the top of the tower. Lead for shot is usually an alloy contain­ '--VBOLD~ ing 2 to 6% antimony and 1% arsenic. The Inn o v a ti v e Va c u u m Tech n o I o g Y !!!!!!!!!!!!!!!!!!EAEDegEuEssaEcEomEpaEny!!!!::=:- additions increase the lead's tensile strength (by up to four times) and also Circle No. 31 on Reader Service C.rd. lower its melting point. 84 MRS BULLETIN/APRIL 1991 HISTORICAL NOTE A technique similar to the shot tower is used in modem manufacturing to make microscopic spheres. A monodisperse aerosol generator, consisting of a vibrating membrane and a screen, creates a mist where all particulates are approximately the same size. On Earth, the largest uni­ form size of spherical particles that can be manufactured by an aerosol reaches only about three micrometers in diameter. However, in the microgravity environ­ ment of the U.S. space shuttle orbiting the Earth, the Monodisperse Latex Reactor (MLR), can produce identical, perfectly spherical particles up to about 10 microme­ ters in diameter. In a chamber in the shuttle The Journal in an evolving Field bay, the MLR sprays a solution of liquid latex through four aerosol generators, Editor-in-Chief: J. E. Greene which create millions of tiny spheres. University of Illinois, The MLR was tested and flown on four Urbana, I L, U.S.A. of the first nine Shuttle flights: STS-3 and STS-4 on the Columbia in March and June 1982, and STS-6 and STS-7 on the Chal­ lenger in April and June 1983. Results showed that such small particles could be made at larger sizes, perhaps up to 20 mi­ crometers in diameter, and still maintain a consistent size. Once hardened, these la­ tex spheres can be used in many applica­ tions back on Earth. The tiny beads can be applied in indus­ try for calibrating instruments used to International Journal on the measure within tolerances. In medical ap­ Science and Technology plications, the latex spheres can be used to of Condensed Matter Films carry medication or radioactive isotopes through the bloodstream to tumor sites; they can also be used to determine the Aims and Scope sizes of lesions in the eye or the intestine. The journal Thin Solid Films is in a unique position Demand for the space-manufactured la­ to both reflect developments in the evolving field of tex spheres grew so great among souvenir thin films and to provide guidance and coherence. seekers that NASA took to sealing small The study of thin films is, by nature, highly inter­ samples of them inside glass slides, leav­ disciplinary, requiring knowledge in areas of physics, ing the bulk of them for the uses to which chemistry, engineering, and, in some cases, biology. they had been conceived. Interests of those in the field span the full spectrum Spheres are also used for hardness test­ from fundamental studies of adatom/surface inter­ ing. The Brinell hardness test presses a actions and interfacial reactions to device and user­ hardened steel ball, 10 mm in diameter, related applications. Examples of the latter include into the surface of a test piece, measuring such diverse specialties as optoelectronics, super­ the depth of penetration of the ball under a conductivity, information storage media, hard load of up to 3,000 kg. The test was devel­ wear-resistant coatings, fuel cells, and bio-com­ oped in the late 1800s by Johan August patible coatings. Brinell of Sweden, and his hardness mea­ suring apparatus was first displayed in Please send me a free sample 1900 at the Paris Exposition. The test is still copy and subscription one of the most widely used measure­ It: ~ ELSEVIER information on ~ EL VIER ments of hardness. SEQUOIA S.A. Thin Solid Films Small glass spheres the size of a pea (5 P.O. Box 564 ~~ mm in diameter) are doped with deute­ CH-1001 Lausanne 1. ~ rium and tritium and used in tests for iner­ Switzerland Tel.: 021/20 73 81 Ol tial confinement fusion power. Each fusion (f) Name:: ____________~-------------------~ target contains about 5 mg of deuterium For customers in the U.S.A.

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