In our previous studies, we have developed a wet process to synthesize a copper-single walled carbon nanotube (Cu–SWCNT) metal nanocomposite with excellent mechanical properties. The nanostructure of this Cu–SWCNT composite was confirmed independently by energy-dispersive X-ray spectroscopy mapping, spectroscopy measurements, and Transmission Electron Microscope (TEM) images with discernable SWCNT clusters in nano sizes. However, TEM images with discernable nano-sized SWCNT clusters are rare. In this paper, we present analysis of indirect TEM image patterns, such as moiré fringes, to infer the existence of SWCNT clusters within the copper matrix. Moiré fringes or patterns in the TEM images of a Cu–SWCNT nanocomposite could be generated due to the overlapping of more than one thin crystals with similar periodic arrangements of atoms, promoted by SWCNT clusters. However, the presence of moiré patterns is not a sufficient or a necessary condition for the existence of SWCNT clusters. It was found that based on the overlapping angle of two periodic arrangements, it is feasible to distinguish the moiré fringes induced by SWCNT clusters from those by other factors, such as dislocations. The ability to identify SWCNTs within the copper matrix based on indirect TEM moiré patterns helps to widen the usability of TEM images.

In this paper, feasibility studies are presented on microneedle fabrication by using a multiple-pulse laser microhole drilling technique to drill an axial hole into a thin nitinol wire of 150 μm in diameter. Nitinol is chosen for its biocompatibility and excellent super-elasticity to eliminate breakage risk. One potential use of this microneedle is for drawing a small amount of blood for glucose monitoring. The critical factor for drilling microholes into a thin nitinol wire axially is the restoration of the semi-infinite material condition, which is the key to prevent the thin wire from being melt away by the laser due to excessive heat transfer in the radial direction. The results show that holes, up to 607 μmin depth, can be drilled into a thin nitinol wire of 150 μm in diameter using 18 repetitions of a 3-pulse group with 13 μs pluses. However, hole quality is poor. The challenges for improving hole qualities, such as centering, hole blockage, through holes, and process parameters, are discussed.

A copper–single-walled carbon nanotube (Cu–SWCNT) metal nanocomposite could be an ideal material if it can substantially improve the strength of copper while preserving the metal's excellent thermal and electrical properties. However, synthesis of such a nanocomposite is highly challenging, because copper and SWCNTs do not form intermetallic compounds and are insoluble; as a result, there are serious issues regarding wettability and fine dispersion of SWCNTs within the copper matrix. In this paper we present a novel wet process, called the laser surface implantation process (LSI), to synthesize Cu–SWCNT nanocomposites by mixing SWCNTs into molten copper. The LSI process includes drilling several microholes on a copper substrate, filling the microholes with SWCNTs suspended in solution, and melting the copper substrate to create a micro-well of molten copper. The molten copper advances radially outward to engulf the microholes with pre-deposited SWCNTs to form the Cu–SWCNT implant upon solidification. Rapid and non-equilibrium solidification is achieved due to copper's excellent heat conductivity, so that SWCNTs are locked in position within the copper matrix without agglomerating into large clusters. This wet process is very different from the typical dry processes used in powder metallurgy. Very high hardness improvement, up to 527% over pure copper, was achieved, confirmed by micro-indentation tests, with only a 0.23% SWCNT volume fraction. The nanostructure of the nanocomposite was characterized by TEM imaging, energy-dispersive x-ray spectroscopy mapping and spectroscopy measurements. The SWCNTs were found to be finely dispersed within the copper matrix with cluster sizes in the range of nanometers, achieving the goal of molecular-level mixing.

Lack of complete knowledge of process characteristics, particularly uncertainties associated with milling processes and spindle behavior, severely limits the reliability of high speed spindles to support high speed machining. Attempts to regulate high speed milling processes based on sensing spindle power and controlling feed rate to prevent spindle stalls have not been successful, mainly due to the fact that power is often not the limiting factor. Instead, problems such as chatter, cutter and/or part deflection, milling forces, and its effects on the rapid wear of the taper of the tool holder and the spindle bearings can easily lead to scrapped parts and/or spindle breakdowns unless extreme care is taken. This paper addresses the stability analysis and design of a novel, robust, nonlinear milling controller implemented at Boeing Co. This controller is aimed at driving an end mill at the highest possible feedrate without damaging the cutter and the spindle. The successful implementation of this controller at Boeing has significantly reduced spindle failures in their extremely demanding high speed machining production lines.