Precise Focal Spot Positioning on an Opaque Substrate Based on the Diffraction Phenomenon in Laser Microfabrication.

The precise positioning of the laser focal spot on the substrate is an important issue for laser microfabrication. In this work, a diffraction pattern-based focal spot positioning method (DFSPM) is proposed to achieve the precise positioning of the laser focal spot on opaque substrates. A series of diffraction patterns of laser focus under-positioning, exact positioning and over-positioning were obtained to investigate the cross-section light distribution of the laser focal spot. According to the monotonic tendency of FWHM to exhibit light intensity at the focal spot cross-section away from the focal plane, the FWHM threshold of polynomial fitted curves was used to determine the exact positioning of laser focus. The ascending scanning method was used to obtain the diffraction patterns at various vertical positions and the FWHM threshold of light distribution at the exact position. The polynomial fitted curves verify the FWHM monotonic tendency of light intensity distribution at the focal spot cross-section along the optical axis. Precise positioning can be achieved with a 100 nm adjustment resolution. This work was expected to provide references for laser microfabrication on opaque materials.

Design and Performance Analysis of a Micro-Displacement Worktable Based on Flexure Hinges.

The flexure hinge is a kind of micro-displacement adjustment device with application prospects because of its high displacement resolution, positioning accuracy and repeatability. In this study, a micro-displacement worktable with four degrees of freedom (X→, Z→, X︵, Z︵) was designed. The micro-displacement worktable was composed of three different flexure hinges. The adjustment ranges and adjustment accuracy of flexure hinges in terms of their respective degrees were improved. The micro-displacement worktable performance was examined by FEA (Finite Element Method). The maximum displacement that was adjusted in X→ and Z→ was 1.67 µm and 1.74 µm. The maximum angle adjusted in the X︵ and Z︵ direction was 14.90° and 18.58°. A test platform was developed for micro-displacement worktable performance tests. The simulation results showed a good agreement with the experimental results.

Influence of Sintering Process on Microstructure and Mechanical Properties of Ti(C,N)-Based Cermet.

In this study, a Ti(C,N)-based cermet material was prepared through vacuum sintering. The research also investigates how holding time and maximum sintering temperature influence the material microstructure and mechanical properties. X-ray diffraction (XRD), energy dispersive spectroscopy (EDS) were used to analyze the composition of the cermet. The microstructure of the cermet was analyzed and examined using a scanning electron microscope (SEM). A Vickers hardness tester was used to test the mechanical properties of the materials. As indicated by testing results, the hardness of the material decreases as the temperature of sintering increases, and its fracture toughness increases gradually as holding time increases. Ti(C,N)-based cermet manifested the optimal mechanical properties when sintering was conducted under 1400 °C with 80 min of holding time. Moreover, the material microstructure is significantly affected by the sintering process. The grain size of Ti(C,N) cermets increases as the sintering temperature increases. The microstructure tends to be uniform and the complete core-rim structures are established as the holding time increases.