Volume 2 Issue 4
Authors: Chris Yang; Shreyes N. Melkote; Steven Danyluk; Frank Mess
Abstract: This paper discusses the influence of tribology on the mechanical properties of cutting, shaping and forming silicon wafers. These processes, such as multi wire slurry sawing, diamond wire sawing, lapping and grinding, Chemical Mechanical Polishing (CMP), and dicing, utilize either a two-body or a three-body material removal, where the fundamental cutting process results from micro-fracturing of silicon by the hard abrasives. There are specific types of defects and related fracture strength characteristics for each process. The associated surface and subsurface damage, especially microcracks, have a dominant effect on the fracture strength of the silicon substrates, even playing a more significant role than edge chipping. There is a need to reduce the surface and subsurface damage, possibly through ductile regime machining/polishing, to improve the mechanical strength.
Keywords: Fracture Strength; Defects; Microcracks; Silicon
Authors: Yevgen Bilotsky
Abstract: Evaluation of internal energy and the inter-atomic or ionic interactions in a crystal lattice usually requires precise calculation of lattice sums. This in the case of small nano-particles (as space-limited domains) presents several challenges, as conventional methods are usually valid only for infinite lattices, tailored for a specific potential. In this work, a new method has been developed for calculation of atomic interactions based on the radial density function with the geometric probability approach, extended to arbitrary fixed lattices and potentials in a nano-particle. The derived radial density function (RDF) combines terms for a uniform particles distribution, for non-uniform spherical symmetry and the last one for an additional, angle-dependent term. The second term originates from Walfisz-like formula for lattice sums. The RDF with these three terms is explicitly integrated for spherical lattice domains resulting in the internal energy of the system with a prescribed interaction potential. The application of the method was demonstrated for Wigner model of electrons lattice interacting with compensating positive jelly in finite lattice sphere, which interacting energy between lattice and jelly was evaluated. The excess of this energy caused by space-limitation of the lattice was explicitly expressed in the terms of absolutely convergent lattice sums.
Keywords: Nanocrystals; Energy; Geometric Probability; Surface; Convergent Lattice Sums
Authors: S.A. Al Kahtani
Abstract: A new means of obtaining fine Si particles is through the use of a melt thermal treatment (MTT), where the mixing of low and high temperature alloy melts produces a fine Si structure. Modification is achieved by nuclei resulting from the degeneration of large atom clusters and some refractory solids in the low temperature melt when it is heated by the high temperature melt. This is a relatively recent technique which demonstrates promise as an alternative to Sr-modification, as it requires no element addition, thus reducing the risk of increased porosity normally associated with the addition of strontium to the melt. The use of melt superheat is also found to produce refinement of the eutectic Si structure. In this case, the high melt temperature assists in the degeneration of atom clusters, providing more nuclei for α-Al dendrite formation, and a resulting refinement of the microstructure.
Keywords: Melt Thermal Treatment; Melt Superheat; Sr Modification Eutectic Si Particle Characteristics
Authors: Hironori Matsuoka; Takahiro Ryu; Takashi Nakae; Shuuichi Shutou; Tsukuru Kodera
Abstract: This paper deals with the influence of hardness of work materials on flank wear, crater wear and finished surface roughness when using two types of high-speed steel (HSS) hob tool materials coated with (Al, Ti)N film. Specifically, hobbing with a minimal quantity lubrication (MQL) system is compared with dry hobbing. Experiments were conducted by simulating hobbing by fly tool cutting on a milling machine. The results are summarized as follows. (1) With SCM415 work material changed to hardness HB131, HB144 and HB161 by heat treatment, flank wear and crater wear of the tool are small when cutting comparatively hard HB161 work material, irrespective of the change in hob materials and cutting speeds. (2) With SCM435 work material changed to hardness HB172, HB195 and HB214, flank wear and crater wear tend to be small when cutting annealed HB172 work material. (3) When cutting SCM415 of hardness HB161 and SCM435 of hardness HB172, the finished surface roughness is small and the surface roughness of SCM415 is smaller than that of SCM435. (4) SCM415 of hardness HB161 is suitable for an MQL system in hobbing in terms of flank wear, crater wear and finished surface roughness.
Keywords: Gear; Cutting; Gear; Hobbing; MQL; Work Material; Hardness; Fly Tool; Flank Wear; Crater Wear; Finished Surface Roughness