Materials Research & Technology News 1998 Fall MRS Meeting highlights

High honor At this years Fall MRS Meeting, the soci- ety bes towed their highest honor on Larry L. Hench, of the University of London, for his p ioneer ing work in the field of glass and ceramics.

The pres t ig ious Yon Hippe l Award acknowledged Hench's many notable achievements , including demonst ra- t ion of the In'st bioactive glass, called Bioglass®; showing that nuclear waste could be encapsulated in glass/ceram- ic matrices; and developing sol gel pro- cessing to p roduce optical and dielec- tric materials of ultra high puri ty and having control led microstructures.

Bioglass, discovered by Hench 30 years ago whilst at the University of Florida, was the first fabricated material that bonded to living tissues. Bioactive glass- es, ceramics and glass-ceramics are today used clinically to replace many different body parts including the middle ear bone, teeth, vertebrae, orbit of the eye and knees. Hench and colleagues recently discovered active compositions that can enhance bone proliferation suf- ficiently to prevent loss of teeth from peridontal disease and stimulate repair of bone after failed hip and knee replacement surgery.

Research since 1976 has focused on the safe storage of high-level nuclear waste (HLW). With Florida University cog leagues, Hench applied new surface analysis techniques to show how and how fast encapsulant materials would be degraded by HLW He worked inter- nationally to establish policies and pro- cedures, as a result of which several countries have since selected borosili- cate glass as their disposal medium.

Over the last decade, Hench's research has led to a new generation of gel-glass products, including diffractive optics of

specified shape, and porous optical matri- ces for environmental sensors and hybrid optics. One of several commercial results is a sensor used to protect health and safety by detecting carbon monoxide.

New carbon devices Also at the MRS, distinguished chemistry Nobel prize winner Richard Smalley of Rice University, delivered the plenary talk, on 'Bucky tubes, New Materials and New Devices from Carbon'.

Smalley is well known for his discovery, wi th Kroto and Curl, of C60 known as buckminsterful lerene. C60, or 'bucky balls', have not yet lived up to their early applications promise. However, bucky tubes or nanotubes could be another matter, having demonstrated impressive mechanical and electronic properties. As Smalley indicated, for example, grow- ing tubular extens ions of carbon fullerenes in long ropes could yield fibres 100 times as strong as steel, at only one-sixth the weight.

Metal Failure and the Titanic In contrast, the hypnot ic allure of the Titanic he lped t empt a wide variety of part ic ipants to a press conference on Fracture and Failure of Metals. Tim Foecke from the National Institute of Standards and Technology, Gaithers- berg MD, dramatically illustrated his presenta t ion on 'What Sank the RMS Titanic' by displaying an 801b, four square foot p iece of the ship's hu l l He revealed that steel used for the hull, though state of the art in 1911, turns brit t le at tempera tures be low 70°E Such steel, embri t t led in chilly ocean waters, would fracture on collision wi th ice, ra ther than bend ing and yielding. Also, w r o u g h t i ron rivets ins ta l led hydraul ica l ly had a w e a k head-shaft interface, causing rows of

them to p o p off, so unzipping large gashes in Titanic's hull.

Maintaining the interest in failure mech- anisms, Robert Odette (University of Catifornia, Santa Barbara) reviewed the different approaches used to study and predict fracture of structural materials. Robert Wei and Gary Harlow (Lehigh University) highlighted degredations, from pitt ing to cracking, that are a growing issue in aging airliner fleets, a theme that is also of pressing interest for the US Air Force and in aircraft engines. Diana Farkas from Virginia Tech showed how the fracture and deforma- t ion of metals can be simulated at microscopic scale and what can be learned from such studies.

Priya Vashishta, Louisiana State University, was concerned wi th frac- ture in ceramics and glasses, descr ibed h o w the p o w e r of con tempora ry par- allel comput ing can be harnessed for mode l ing at a tomic scale the way cracks propagate during fracture.

Metallic glass Bill Johnson, California Inst i tute of Technology, was honored for pioneer- ing a n e w class of structural materials based on alloys that readily form a glass phase on cooling from the melt. His receipt of the 1998 MRS Medal fol- lowed two decades of fundamental work on amorphous alloys.

He and A Peker, also at Caltech, found that samples of zirconium, ti tanium, copper, nickel and beryl l ium alloyed by induc t ion mel t ing sol idif ied on freezing, into crystal-free glassy ingots. Significantly, cooling rates of less than 10 ° K pe r second are sufficient to form the metallic glass in areas up to several cm2.This compares wi th 10 to 100[xm 2 typically achieved previously by high- rate quenching of ribbons and powders .

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If earlier alloys had limited glass forming ability, Johnson and Peker's examples resist crystallization strongly, facilitating such formation. The research team is current ly col laborat ing wi th several other laboratories and companies to develop applications for metallic glasses and metallic glass matrix composites. The 'undercoo led l iquid' state, says Johnson, presents opportunit ies for the manufacture of inexpensive net-shape metal components of superior quality with high strength to weight ratio, frac- ture toughness, fatigue resistance and resistance to wear and corrosion.

Plasma and films Environmental concerns were acknowl- edged during a symposium on Plasma Deposition and Treatment of Polymers. Fracassi discussed the impact of cu~en t processes on the production of green- house gases and on global warming. Other contributions dealt with use of plasma polymer films in micro-electro mechanical systems (MEMS) and bio- medical applications, use of microwave

plasmas to destroy fungal spores, a tech- nique for embedding nanostructured sil- ver particles in non-fouling organic films for medical implants and catheters, and a novel approach to diagnostics of plas- mas used for transparent barrier coat- ings. Such coatings, on PET plastic - of interest in food packaging - were the conce rn of da Silva Sobrinho w h o addressed defects evaluation.

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'Electric" catalyst An intriguing multifunctional material h ighl ighted at the Meeting was a porous form of manganese oxide mate- rial that can serve as a selective catalyst, as a molecular sieve membrane or filter, or as a semiconductor. This suits it to applications ranging from formation of chemicals from petrochemical stock to use as a bat tery material. Stephen Sulb repor ted the bulk preparat ion of the material, which is characterized by a unique asymmetric pore structure.

Other catalysts, wi th potent ial use in the bulk plastics industry, were men-

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t ioned by Murphy w h o has used com- binatorial chemistry to achieve them, and by Cong whose similar methods have yielded catalysts that can be used to reduce air pollution.

The role of chemist ry in developing novel inorganic materials was clear in a presenta t ion from Susan Kauzilarich (University of California, Davis) on the d iscovery of colossal magnetoresis- tance in certain rare ear th transit ion meta l c o m p o u n d s . CMR mater ia l known as Permalloy, current ly used in compute r read heads, is of l imited sen- sitivity. Increasing the CMR effect by an order of magni tude would make the heads much more sensitive, increasing the scope for miniaturization. Recent discovery of the rare ear th compounds holds out hope that materials wi th greater intrinsic CMR can be found.

Further in format ion abou t the 1997

MRS Fall Meeting can be f o u n d at

w w w . mrs. org.

George Marsh

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Materials T o d a y Volume 2 Issue 2 June 1999

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