Amorphous Nanocomposite Materials Presented by: Renée E. Gordon Advisor: Professor Michael McHenry Graduate Student: Changyong Um

Melt Spinning Process Amorphous Nanocomposite Material. –FINEMET, NANOPERM, and HITPERM. –Nanocrystals are embedded in an amorphous matrix. Rapid Solidification Technique. –Cooling rate: 1 Million Kelvin per second. (10 6 K/sec) Produces Amorphous Metastable Material. –Material is not stable at higher temperatures. –If occurs, material is thermally activated and can turn to Crystalline phase. Application: Inductive Component of electronic devices. –Good soft magnetic properties.

Indenter is only 100nm in size. Area of Berkovich Tip : θ = 65.3° (semi-angle of Berkovich indenter) hp= plastic depth of penetration Berkovich Hardness: Nano-Indentation

Theory Begins Fully Amorphous. Gradually becomes paramagnetic (losing magnetic change). Crystallization begins at ~500 o C. –Increase in magnetization. Curie Temperature of Nanocrystalline phase: 610 o C. Note there are 2 different Curie temperatures. Curie transition Primary crystallization onset temperature Nanocrystalline Curie Temperature FINEMET

Theory Increase in annealing temperature increases the rate of crystallization. Morphology Index (n) can be determined from Johnson-Mehl-Avrami Kinetic model. This (n) indicates the mechanism and dimension of nucleation and growth. Volume Fraction Transformed: –k o JMA = rate constant coefficient –Q JMA = activation energy Volume fracture increase is proportional to the magnetization increase. Isothermal Magnetization Kinetic Data of FINEMET

Results Shows Hardness as a function of Volume Fraction that has been Crystallized. When crystallization occurs, nanocrystals form. These nanocrystals are harder than the amorphous matrix. The more nanocrystals, the harder the overall material. Fully Amorphous, Hardness=7-8 GPa. Saturated (top right), Hardness=14 GPa. HITPERM expected to act similar to FINEMET and NANOPERM.

Results Thickness-Dependent Magnetization Curve (from VSM). Increased thickness results in slower crystallization. As thickness decreases crystallization occurs faster. 100 nm reading has “noise” % Volume Fraction of the material crystallizes. NANOPERM

Acknowledgements Changyong UmChangyong Um Professor McHenryProfessor McHenry MRSECMRSEC Wright Patterson Air Force BaseWright Patterson Air Force Base Magnetics, A Division of Spang and Co.Magnetics, A Division of Spang and Co.

Thank you for your time. Questions and Comments.

Extras Composition of HITPERM: –(Fe,Co) 88 M 7 B 4 Cu 1 ; (M=Zr,Nb,Hf) Composition of NANOPERM: –Fe 88 Zr 7 B 4 Cu 1 Composition of FINEMET: –Fe 73.5 Si 13.5 B 9 Nb 3 Cu 1