Investigation of the Splat Deposition Behavior onto a Composite Coating in Cold Spray

The splat test is usually generated by low feed rate cold spraying of particles onto an as-polished substrate and it can be considered as a monolayer coating deposition. In this study, in order to investigate cold spray deposition mechanisms, Fe splats were sprayed onto the cold-sprayed single component 316L, Fe, and a composite 90Fe coatings. Results showed that although there is only 3.6 vol.% of 316L in the composite 90Fe coating, Fe splats exhibit a much better deposition behavior onto the 90Fe as compared with the single component Fe coating. To explain this observation, Fe splat samples were characterized using the scanning electron microscope (SEM), optical profilometry, splat adhesion tests, and splat nanoindentation. Finally, a preliminary explanation towards the Fe splat deposition behavior onto the composite coating was drawn.

The Contact Pressure Distribution and its Effects on the Magnetic Disc Substrate Surface Profiles in Chemical Mechanical Polishing

In order to obtain the contact pressure distribution between the hard disc substrate and the polishing pad and its effects on the profile of polished substrate surface, the elastic contact mechanical model and mathematical equations on the chemical mechanical polishing of the hard magnetic disc substrate are established, and also the relevant boundary conditions are put forward. The contact pressure distribution is calculated with FEM, the polishing experiments are carried out and the surface profiles of polished substrates are obtained. The study results show that the contact pressure distribution on the substrate surface is non-uniformity and the contact pressure in the substrate edge present biggish undulation. Choosing properly the Young’s modulus of the polishing pads and decreasing its Poisson’s ratios can make the uniform area of the contact pressure distribution enlarging and improve the flatness of polished substrate.

CMP Behavior of α-Alumina-g-Polyvinylpyrrolidone Composite Abrasive on Hard Disk Substrate

A novel α-alumina-g-polyvinylpyrrolidone (α-Al2O3-g-PVP) composite abrasive was prepared by surface grafting polymerization. The chemical mechanical polishing (CMP) performances of the composite abrasive on hard disk substrate were investigated with a UNIPOL-1502 polishing machine. Analyses on the surface of polished substrate indicated that the α-Al2O3-g-PVP composite abrasive exhibited lower surface roughness, less scratch, and improved post-CMP cleaning performances than pure α-alumina abrasive under the same testing conditions.

Evaporation of Adherent Al-Films on Single Crystalline LiNbO3Substrates

LiNbO3is used as a single crystalline substrate material for the manufacturing of surface acoustic wave devices as frequency selective components. On the polished substrate wafer, Al with a film thickness of about 400 nm is evaporated in a high vacuum.The difficulties of the inadequate adhesion of the structured Al-film were eliminated by systematical investigations. Films that were adherent to the total surface could be prepared by evaporating an intermediate film of Cr or SiOxor, otherwise, a mixed film of Al with Si.An ultrasonic test for adhesion strength was developed that results in an assessment of local and also large-area film adhesion.