Nanoparticles to Improve Mass Transport Inside Deep Recesses

Abstract

A high pH citrate electrolyte was used to electrodeposit Ni-Cu alloys and Ni-Cu-␥-Al 2 O 3 nanocomposites into recessed microelectrodes and onto rotating cylinder electrodes. The patterned, recessed substrates were 500 m deep with a 187 ϫ 187 m cross section, produced by X-ray radiation at the LSU synchrotron facility, Center for Advanced Microstructures and Devices. Copper deposition was diffusion controlled and used as a probe to assess changes in mass transport. Nickel deposition was kinetically controlled by keeping the nickel ions in comparable excess to the concentration of copper ions. In the micropost, the copper deposit concentration increased along the height indicative of a changing boundary layer thickness regardless if the particles were present or absent. The addition of alumina nanoparticles in the electrolyte led to an enhancement of copper concentration in the deposit, and hence an enhancement of its mass-transport rate.Electrodeposited alloys and nanocomposites, in numerous applications, have superior properties over their constituent metals. 1-6 In particular, nanocomposites offer an attractive method to combine properties of alloys and nonreactive nanoparticles. For example, nickel-copper alloys have superior corrosion resistance 7 and alumina incorporation is expected to increase hardness and wear resistance as demonstrated by the elemental Cu-Al 2 O 3 8-13 and Ni-Al 2 O 3 13-18systems. While some studies have focused on the parameters that effect particle incorporation, 9,19-21 few involve the influence of the particle on the metal rate. Webb and Robinson 22 have shown that the nickel deposition rate can be inhibited by the presence of low concentrations of submicrometer alumina particles ͑on the order of 10 g/L͒ in the electrolyte. The same has been noted for copper by Stojak and Talbot, 23 for low alumina electrolyte concentrations, but the opposite effect, an enhancement of the copper rate, was also observed with very high particle loadings ͑exceeding 100 g/L͒. The electrodeposition of alloys and composites is favorable for microelectromechanical systems ͑MEMS͒ and high-aspect-ratio deposition due to its cost effective nature and capability for depositing into recessed substrates. There exist few examples of alloy and composite deposition into recessed geometries. A review of alloy electrodeposits realized in recesses can be found by Ehrfeld et al. 24 Electrodeposition of submicrometer SiC-Ni and Al 2 O 3 -Ni composites into LIGA electrodes has been demonstrated by Yeh et al. 25 and Wang, 26 respectively, into LIGA electrodes. Jakob et al. 27 have codeposited nanometric TiO 2 and Al 2 O 3 into microstructures.In this paper, the electrodeposition of graded Ni-Cu alloys and Ni-Cu-Al 2 O 3 nanocomposites into recessed electrodes made using X-ray lithography is presented; and to the authors' knowledge has not been hitherto reported. Experiments using rotating cylinder electrodes ͑RCEs͒ are used to interpret the compositional changes in the recesses. ExperimentalThe electrolyte used for electr...

Metal Matrix Composite Coatings of Cupronickel Embedded with Nanoplatelets for Improved Corrosion Resistant Properties

“…By systematic control of these parameters, microstructure and property performance can be optimized for the composites. Researchers have used majority of the work has focused on applications for MEMS devices or mechanical properties [38][39][40]. Previous work on 70-30 Cu-Ni composites reported an increase in the corrosion resistance and mechanical properties [41].…”

Deposition of TiO2 nanoparticles in surfactant-containing aqueous suspension by a pulsed DC charging-mode electrophoresis

“…14),18), 21) Furthermore, this method can achieve transportation leading selective particle growth in a uniform size. 7),13),15),16), 20) However, most of the methods developed by previous workers were independence of particle stability and were absolutely a need agitation.…”

Effect of Microstructure on the Solid Particle Erosion Properties of Ni Plating

“…In electrode plating process with CNTs two mechanisms can be involved: first, the randomly suspending CNTs in the electrolyte contact the substrate and are deposited by van der Waals force, and are further buried with the incoming ions; second, the suspending CNTs in the electrolyte attach to the ions in the electrolyte and move toward the substrate by Columbic force. It is believed that the combinations of both mechanisms contribute to the deposition process and impart changes to the nucleation and formation of new grain ( Ref 2,5).…”