Structure and Mechanical Properties of Electrodeposited Nanocrystalline Ni-Fe Alloys

The electrodeposition of NiFe nanowires-with the length ∼3.0 μm and diameter 200 nm-using the porous anodized aluminum oxide (AAO) templates on the sputtered Au-back electrode (300 nm) using sulfate/chloride electrolyte solution and potential pulsed deposition. The electrode area of Au-AAO template, determined by the reversible one-electron transfer oxidation of K 4 Fe(CN) 6 , used as a probe in CV, was found to be ∼2.4 times larger than Au-thin film electrode. The anomalous codeposition phenomenon known as a ,,volcano" type curve-with a maximum in Fe-content in NiFe as a function of the applied potential-was observed in the literature. The observed results were explained through the limited mass transport of Fe +2 ions after the peak. This explanation is partially correct, but not complete. The electrodeposition of NiFe nanowire in this work resulted in a similar "volcano" type curve. The alternative explanation of anomalous codeposition-through the surface concentration of H + dependent adsorption/desorption of FeOH + and NiOH + electroactive species-was proposed. The electrodeposition of NiFe nanowire arrays using a designed pulse potential method produced fcc NiFe nanowires with 5-55% Fe with controlled composition, length, and uniformity.The distinct decrease of parallel coercivity of NiFe nanowire arrays having the same length was observed with increase of Fe-content in NiFe, which also correlates with the increase of their magnetic saturation. 12 The studies on magnetic properties of NiFe nanowire arrays were intensified during last 15 years. [13][14][15][16][17][18][19][20] The electrodeposition of NiFe alloys exhibits a phenomenon known as an anomalous codeposition, which is characterized by the anomaly that less noble metal, i.e. Fe, deposits preferentially. 21 The extent of anomalous codeposition can be evaluated by the "selectivity ratio" (SR), which is defined as an atomic ratio of Fe/Ni in the deposit to the molar ratio of Fe +2 /Ni +2 in the electrolyte. 22 The SR is dependent on solution condition (pH, presence of organic additives, concentration of electrolytes, temperature, etc), method of electrodeposition (constant current density, controlled potential, pulsed current or potential), and the thickness of deposit. The value of SR ranges from 1.0 (for non-anomalous codeposition) to 15 (for anomalous codeposition). The variation of composition of NiFe films affects the following properties of deposit: (i) stress, 23 (ii) magnetostriction, 24 (iii) crystal structure, 25 and (iv) grain size. 26 Thereby, the resulting changes profoundly influence the magnetic behavior of electrodeposited NiFe alloys, which was demonstrated recently. 27The present work describes the method of electrodeposition of NiFe nanowires into anodized aluminum oxide (AAO) templates with the controlled elemental composition using designed potential pulse electrodeposition. We report here a new explanation for the observed anomalous codeposition of NiFe in nanowires, through the surface concentration of H + dependent adsorption/...

Section: Magnetic Properties Of Nife Nanowire Arrays With 8-55%fe-mentioning

confidence: 66%

Anomalous Codeposition offccNiFe Nanowires with 5–55% Fe and Their Morphology, Crystal Structure and Magnetic Properties

Dragos

Chiriac

Lupu

et al. 2015

“…To date, with respect to the formation of a metastable bcc phase in the electroplated Fe-Ni alloy in the Invar composition range, several mechanisms related to hydrogen generation and hydride formation during electroplating have been proposed; 46 however, we have yet to discover the details of such mechanisms. It has been reported that hydrogen generation and hydride formation during the Invar alloy electroplating generate high-density structural defects, which may induce a metastable bcc structure.…”

Section: Alloy Composition Deposition Rate Surface Morphology and Cry...mentioning

confidence: 99%

Thermal Expansion and Thermal Stress Behavior of Electroless-Plated Fe–Ni–B Alloy Thin Film for High-Density Packaging

Yamamoto

Nagayama

Nakamura

2018

Fe-Ni-B alloy thin films were prepared by using an electroless plating method, and their thermal-expansion behavior, thermal-stress generation, and crystal structure were evaluated. By heating from 30 • C to 300 • C, the electroless-plated Ni-5 wt%B alloy film showed a marked increase in tensile stress at approximately 270 • C, which is caused by a phase separation from the amorphous Ni-B alloy into a highly crystalline Ni and Ni 3 B compound. The coefficient of thermal expansion (CTE) of electroless-plated Ni-B alloy film from 300 • C to 30 • C, after heating to 300 • C, was 14 ppm/K. In contrast, the electroless-plated Fe-Ni-B alloy film in the Invar composition range had a small CTE (8 ppm/K to 9 ppm/K) and no substantial change in crystal structure during heating to 300 • C. As a result, the Fe-Ni-B alloy film on the silicon substrate (CTE = 3 ppm/K) exhibited a low thermal stress compared with the electroless-plated Ni-B alloy film. Thus, it is suggested that the electroless-plated Invar Fe-Ni-B alloy films are suitable as an under-bump metal layer from the viewpoint of the thermal-expansion behavior.

“…[4][5][6][7][8][9][10][11] These properties are largely dependent upon the structure and morphology of the electrodeposit, which in the case of cobalt can vary dramatically with overpotential, electrolyte pH, and the presence of strongly adsorbing anions. 2,[12][13][14][15][16] …”

mentioning

confidence: 99%

In Situ Stress Measurements during Cobalt Electrodeposition on (111)-Textured Au

Fayette

Bertocci

Stafford

2016

Cantilever curvature was used to examine stress generation during the electrodeposition of Co onto (111)-textured Au from 0.1 mol/L NaClO 4 + 0.001 mol/L Co(ClO 4 ) 2 (pH = 4.8) in films measuring less than 25 nm in thickness and at Co current efficiencies ranging from 65% to 90%. XRD analysis indicates that the Co is face-centered cubic and maintains the (111) texture of the Au substrate, suggesting epitaxial but not pseudomorphic growth on the Au. The stress-thickness product showed a −0.2 N/m compression in the first monolayer followed by increasing tensile stress as the film thickened. The initial compressive stress is most likely due to surface and interface stresses that dominate at submonolayer coverage. Steady state tensile stress, ranging from 0 to +450 MPa, developed in continuous Co films and showed a strong dependence on electrode potential. However, over this potential range there is no change in grain size or growth rate, factors typically associated with tensile stress. We attribute the tensile stress and its potential dependence to the formation of hydrogen stabilized vacancies, defects found to be quite stable in fcc Fe-group metals and alloys deposited under conditions of H + discharge. The use of electrodeposited Co-based materials has attracted much attention over the past several decades owing in part to their interesting magnetic 1-3 and catalytic properties. [4][5][6][7][8][9][10][11] These properties are largely dependent upon the structure and morphology of the electrodeposit, which in the case of cobalt can vary dramatically with overpotential, electrolyte pH, and the presence of strongly adsorbing anions. 2,[12][13][14][15][16]