Researchers at Purdue University (West Lafayette, Indiana, USA) have created a hybrid technique to fabricate a new form of nickel, with a goal of boosting the corrosion resistance of medical devices, high-tech devices, and vehicles.
The Purdue technique involves a process where high-yield electrodeposition is applied on conductive substrates. According to the researchers, one of the biggest challenges for manufacturers with nickel is dealing with places within the metals where crystalline grains intersect, known as the boundary areas. These conventional grain boundaries can strengthen metals for high-strength demand.
However, these boundaries often act as stress concentrators, and they are vulnerable sites for electron scattering and corrosion attack. As a result, conventional boundaries often decrease ductility, corrosion resistance, and electrical conductivity, according to the team.
Another specific type of boundary—though it is much less common in metals due to high-stacking fault energy—is called a twin boundary. The unique nickel in a single-crystal-like form contains high-density ultrafine twin structure but few conventional grain boundaries.
This particular nickel has been shown by the Purdue researchers to promote strength, ductility, and improve corrosion resistance. Those properties are important for manufacturers across industries such as automotive, oil and gas, and micro-electro-mechanical devices.
“We developed a hybrid technique to create nickel coatings with twin boundaries that are strong and corrosion-resistant,” says Xinghang Zhang, a professor of materials engineering. “We want our work to inspire others to invent new materials with fresh minds.”
The solution of the Purdue researchers is to use a single crystal substrate as a growth template, in conjunction with a designed electrochemical recipe to promote the formation of twin boundaries and inhibit the formation of conventional grain boundaries. The high-density twin boundaries contribute a high mechanical strength exceeding 2 GPa, a low corrosion current density of 6.91 × 10-8A cm-2 , and high polarization resistance of 516 kΩ.
“Our technology enables the manufacturing of nanotwinned nickel coatings with high-density twin boundaries and few conventional grain boundaries, which leads to superb mechanical, electrical properties and high corrosive resistance, suggesting good durability for applications at extreme environments,” says Qiang Li, a research fellow in materials engineering. “Template and specific electrochemical recipes suggest new paths for boundary engineering, and the hybrid technique can be potentially adopted for large-scale industrial productions.”
Potential applications include the semiconductor and automotive industries, which require metallic materials with advanced electric and mechanical properties for manufacturing. The nanotwinned nickel could be applied in the form of corrosion-resistant coatings for the automobile and oil and gas industries, according to the researchers, who are currently seeking partners for further development with the technology.
The nickel-hybrid technique could also be potentially integrated into the micro-electro-mechanical system industry after careful engineering designs. The relevant pressure sensors and other functional small-scale components in these devices require the use of materials with superior mechanical and structural stability and chemical reliability, the researchers explain.
The research was funded by the U.S. Department of Energy’s Basic Energy Science program, and the Purdue team worked with scientists from Sandia National Laboratories (Albuquerque, New Mexico, USA( on the technology.
Source: Purdue University, www.purdue.edu.