We report tensile experiments on Ni80P20 metallic glass samples fabricated via a templated electroplating process and via focused ion beam milling, which differed only in their surface energy states: Ga-ion-irradiated and as-electroplated. Molecular dynamics simulations on similar Ni80Al20 systems corroborate the experimental results, which suggest that the transition from brittle to ductile behavior is driven by sample size, while the extent of ductility is driven by surface state.

Nanometallic Glasses: Size Reduction Brings Ductility, Surface State Drives Its Extent

This in-depth overview examines a number of key considerations relating to environmental effects on today’s advanced materials. While certainly not inclusive of all environmental issues, the article does investigate high-temperature corrosion and crack growth in ceramics and ceramic composites, hydrogen effects on ceramics, hydrogen effects on fracture of intermetallics, and corrosion and hydroen effects in amorphous or glassy metals.

Environmental Effects on Advanced Materials

Binary iron group (IG)-rare earth (RE) and ternary IG-RE-B alloys were codeposited from aqueous chloride and sulfamate solutions containing glycine as the complexing agent. The effects of solution composition and deposition conditions on deposit composition, coercivity, and morphology were investigated using dc and pulse current electrodeposition, resulting in nanocrystalline deposits approaching amorphism (grain size, ∼5 nm). Continuing research indicates substantially increased RE deposit contents have been achieved with modifications in solution composition and ratios of IG and RE to glycine with applied current density ≥ 300 mA cm -2 and vigorous agitation; e.g., CoSm deposits containing 15-18 atom % Sm have been obtained. A mechanism for the codeposition of the alloys is proposed. It involves hetero-nuclear glycinato coordination complexes as a result of the zwitterionic characteristics of glycine. The complexes adsorbed on the cathode provide step-wise reduction of the depositing metals with surface adsorbed H atoms and/or direct electron transfer, resulting in alloy deposits.

Electrodeposition of Iron Group-Rare Earth Alloys from Aqueous Media

We report on a new electroless codeposition system for fabricating hard magnetic NdFeB particle–NiP alloy magnets for magnetic micro-electro-mechanical systems (MEMS) actuators. In the newly developed electroless codeposition process, an NdFeB hard magnetic particle, which cannot be independently deposited from aqueous electrolytes, is added to an acidic NiP alloy electroless plating electrolyte. An NdFeB (particle)-NiP (matrix) composite thin film has been successfully obtained using an optimized electroless codeposition technique. In addition, NdFeB–NiP microarrays magnets with a thickness of 20 μm have been realized by surface micro-machining techniques. These micromachined magnets exhibit good magnetic properties such as a large ( BH ) max and a high perpendicular coercivity ( H c ) that are particularly well suited for magnetic MEMS actuators. This deposition technique is compatible with many MEMS fabrication processes since it does not demand high processing temperatures.

Norimiki Usuzaka

Papers

Preparation and magnetic properties of CoGd amorphous alloy films by the electroplating method