Moisture Effects on Gold Nanowear
- PDF / 137,592 Bytes
- 6 Pages / 612 x 792 pts (letter) Page_size
- 17 Downloads / 235 Views
1085-T05-10
Moisture Effects on Gold Nanowear Megan Pendergast1, Alex A. Volinsky1, Xiaolu Pang1,2, and Robert Shields1 1 Department of Mechanical Engineering, University of South Florida, 4202 E. Fowler Ave. ENB118, Tampa, FL, 33620 2 Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing, 100083, China, People's Republic of ABSTRACT The addition of water results in the higher wear rate of gold compared to experiments performed in the ambient environment (approximately 60% humidity). This higher wear rate in water has been observed with the AFM, Hysitron Triboindenter, and additionally in single pass scratch tests performed with the Taber Shear/Scratch tester. These tests were preformed using silicon nitride cantilevers in the AFM and a diamond tip in Hysitron and in the Taber instrument. Tests performed in the ambient atmosphere resulted in slightly reduced surface roughness, while much higher wear rate was observed in water. Ambient scratch tests consistently produced slightly shallower scratch trenches than wet scratches as a function of increasing normal load. Single scan lines provide valuable information about the mechanisms and progression of the nanoscale wear. The different components of scratch friction are investigated to explore the main contributors to the nanoscale scratching of gold. INTRODUCTION Abrasive wear resistance generally correlates with a material’s hardness, however, this correlation was found not to hold true for thin coatings [1]. Additionally, many common wheel-based wear testers are too harsh for coatings. Scratch testing can provide a better evaluation of material abrasive resistance that is deposited as a thin coating. In many small scale applications, thin gold films are used as interconnects for electrical devices, therefore a scratch test can be a valuable experiment in evaluating gold wear properties. Technology continually strives to achieve smaller products, which pushes to reduce coating thickness. However, these coatings are still expected to provide the same tribological performance [2]. Much of scratch testing is devoted to providing information about a coating’s practical adhesion, but wear resistance is equally significant [3]. In terms of quantifying material’s scratch resistance, several definitions have been proposed, such as dynamic hardness, tangential hardness, and specific grooving energy. Recently an ASTM scratch standard was produced; however problems still lie in the reproducibility and the terms definitions [4]. To apply the definitions for scratch hardness, most often the contact area needs to be calculated, a difficult task if working with a material that can recover a large percentage of deformation upon unloading [5]. A scratch test is most often performed with a diamond tip scratching along the surface with a constant normal load. The depth of scratch is then analyzed to provide information about the material’s scratch resistance. Another method useful in very thin
films is to constantly ramp up the normal l
Data Loading...
