Nanomechanics of Materials and Structures
This book is derived from the proceedings of the International Workshop on Nanomechanics held at Asilomar Conference Grounds in Pacific Grove, California on July 14-17, 2004. Approximately 70 leading experts from academia, government and industrial sector
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S. Guruzu, G. Xu, and H. Liang Department of Mechanical Engineering, Texas A&M University, College Station, TX 778433123
Abstract:
Experimental investigation of friction induced nucleation of nanocrystals was conducted. A series of interfacial interactions were experimentally examined, including pressing, light sliding, and heavy sliding. Results showed that only under a certain sliding conditions, nucleation of crystalline features were formed. Compressing along with heavy sliding caused either melting or severe wear. This preliminary research demonstrated the feasibility of using a friction-stimulation process combined with phase transformation to generate nanostructured materials. The possible nucleation mechanisms are frictional energy induced melting and strain-related nucleation. It leads to the future study of nucleation theory.
Key words:
wear, nanocrystals, phase transformation, asperity, nucleation.
1.
INTRODUCTION
The development in microelectro mechanical systems (MEMS), the atomically ordered nanostructures such as Nano-MOSFETs, and tiny fluid power devices for bio-applications, etc., have challenged manufacturing precision products such as micro-pumps, micro-engines, and micro-robots [1-14]. There are existing methods, such as surface coatings, lithographic techniques, self-assembly, etc., developed to fabricate small devices. Yet, the synthesis of precisely defined artificial molecular architectures beyond 25 nm in length is often unattainable, due to solubility, material throughput, and characterization constraints [15-20]. Generating nanoscaled phases with 45 T. J. Chuang et al. (eds.), Nanomechanics of Materials and Structures, 45–54. © 2006 Springer. Printed in the Netherlands.
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S. Guruzu, G. Xu, and H. Liang
desired size, shape, and crystal structure is critically important for nanotechnology development. The motivation of this research is to investigate the doping/nucleation mechanisms of low-temperature systems through friction triggered atomic doping and nucleation. This paper reports our findings from experiments. It has been widely accepted that friction activates the surface reaction sites by bond stretching, bond breaking, and reformation [21-30]. Using an AFM, experimental evidence supports the mechanism involving mechanical stimulation-enhanced mass transport of ions to nucleation sites [31-32]. Due to friction, spontaneous, heterogeneous nucleation produces nanodeposits on brushite surfaces. In this research, effects of friction on interactions of Ga and Si are investigated. Doping Ga into Si, the surface and phase changes under the friction stimulation are studied. Due to the small nature of asperity contact, small features are expected to form that are potentially useful for nanoscale study. The doping takes place when Ga is rubbing against a Si substrate in ambient conditions. The Ga has a low melting point (29.78 oC) and Si has a high one (1410 oC). This material pair undergoes eutectic phase transformation at temperatures around 29 oC. Due to the low equilibrium conce
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