In the paper the results of 3D micromachining of silicon using nanosecond (1064 nm), picosecond (343 nm) and femtosecond (343 nm) laser pulses are presented. Effective laser processing demands repeated scanning of the laser beam and overlapping of paths what generate many phenomena which do not occur by impact of individual laser pulses. Thermal incubation effect and shielding of laser beam by ejected particles compete and decide on the final result of ablative micromachining. Applying femto and picosecond laser pulses does not directly guarantee expected quality and effectiveness.
Laser surface texturing is currently the most developed technique of producing in a completely repetitive way microcavities on the surface of machine elements. From the point of view of the technology of making textures, a very important aspect is the appropriate selection of process parameters in order to obtain texture elements with desirable and repeatable geometries and physicochemical properties. Surface texturing increases the resistance to scuffing and wear through fretting, and is also used wherever the adhesive properties of surface layers are of importance (printing techniques, joining materials, biological and chemical activity of the surface, coating, etc.) [7]
The TiO2 coatings were prepared by simple sol-gel method and modified by UV pulsed laser. TiO2, also know as titania, is a ceramic compound, existing in numerous polymorphic forms, mainly as tetragonal rutile and anatase, and rhomboidal brookite. Rutile is the most stable form of titanium dioxide, whereas anatase is a metastable form, created in lower temperatures than rutile. Anatase is marked with higher specific surface area, porosity and a higher number of surface hydroxyl groups as compared to rutile. The unique optical and electronic properties of TiO2 results in its use as semiconductors dielectric mirrors, sunscreen and UV-blocking pigments and especially as photocatalyst.
In this paper, the tetraisopropoxide was used as Ti precursor according to sol-gel method. An organic base was applied during sol preparation. Prepared gel was coated on glass substrates and calcined in low temperature to obtain amorphous phase of titania. Prepared coatings were modified by UV picosecond pulse laser with different pulse repetition rate and pulse power. Physical modification of the coatings using laser pulses was intended in order change the phase content of the produced material. Raman spectroscopy (RS) method was applied to studies of modified coatings as it is one of the basic analytical techniques, supporting the identification of compounds and obtaining information about the structure. Especially, RS is a useful method for distinguishing the anatase and rutile phases. In these studies, anatase to rutile transformation was observed, depending on laser parameters.
In modern machines for realization of goals like lubrication intesyfication, heat flow intensyfiacation, microflow simulation; more and more often surface texturing is used. It became possible due to develepment of technologies that use sources of concentrated energy stream like microlasers. The paper shows results of experimental investigation on seal rings made of silicon carbide. Experiments were conducted using seal rings without surface modifications and a seal rings with a geometrical surface textures made with Nd:Yag laser.
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