Structural, chemical, and electronic characterization of nickel-titanium shape-memory alloys

Miscellaneous · Wed Jan 01 00:00:00 EST 1992

OSTI ID:5522870

Gisser, K R.C.

An overview of the thermoelastic martensitic phase transformation that gives rise to the shape-memory effect is presented in Chapter 1. In Chapter 2, normally chemically inert nickel-titanium (NiTi) alloys having composition Ni[sub x]Ti[sub 1[minus]x] (0.47 [le] x [le] 0.51) react with wet methanolic Br[sub 2] and I[sub 2] solutions to yield crystalline nickel halides and uncharacterized titanium-containing products. The crystalline products are independent of whether NiTi is in its high temperature (austenite) or low temperature (martensite) phase. Reaction rates were measured for austenitic NiTi in bromine and iodine solutions. For the Br[sub 2]/MeOH reaction, kinetic studies were conducted with samples of pure martensite, pure austenite, or mixtures of these phases. In Chapter 3 nickel-titanium films, 0.5 to 10 microns thick, were prepared on silicon substrates by sputter deposition. Three annealing methods were used to crystallize the amorphous as-deposited films. All three methods produced crystalline films that exhibit the B2 to B19[prime] phase transformation, as confirmed by resistance-temperature and X-ray diffraction-temperature measurements. Films deposited onto a heated substrate were highly oriented, whereas films annealed in a second step were polycrystalline. The film structure was the same for all of the annealing methods: A substantial s([approximately]3,000[angstrom]) layer of amorphous nickel and titanium silicides grows between the nickel-titanium film and the silicon. Chapter four. The current-voltage characteristics of nickel-titanium junctions on n-type silicon were measured. Although the junctions do rectify current, they deviate from ideal behavior even at moderate forward bias voltages ([approximately]0.4 volts). Neither the barrier height, nor the series resistance for the diodes showed any dependence on the crystal structure of the NiTi film; this insensitivity is discussed in the context of the structural results from Chapter Three.

• Research Organization: Wisconsin Univ., Madison, WI (United States)
• OSTI ID: 5522870
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
74 ATOMIC AND MOLECULAR PHYSICS
NICKEL ALLOYS
PHASE STUDIES
SHAPE MEMORY EFFECT
STRUCTURAL CHEMICAL ANALYSIS
TITANIUM ALLOYS
AUSTENITE
BINARY ALLOY SYSTEMS
CRYSTAL STRUCTURE
CRYSTAL-PHASE TRANSFORMATIONS
ELECTRONIC STRUCTURE
FILMS
HALIDES
MARTENSITE
SPUTTERING
TITANIUM SILICIDES
ALLOY SYSTEMS
ALLOYS
CARBON ADDITIONS
HALOGEN COMPOUNDS
IRON ALLOYS
PHASE TRANSFORMATIONS
SILICIDES
SILICON COMPOUNDS
TITANIUM COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
360102* - Metals & Alloys- Structure & Phase Studies
360604 - Materials- Corrosion
Erosion
& Degradation
664000 - Atomic & Molecular Physics- (1992-)