White Light Interferometery Research Articles

Effect of Laser Surface Texturing on Coating Adherence and Tribological Properties of CuNiIn and MoS2 Coating

Copper nickel indium (CuNiIn) and Molybdenum disulphide (MoS2) duplex coating is used in aero engine compressor blades of Ti6Al4V to prevent fretting failure. Surface before coating is roughened by grit blasting process for coating adhesion. In present study, in place of grit blasting, laser surface texturing (LST) process is used for surface preparation and compared with grit blasted surface. Four different elliptical and square patterns are created by LST on Ti6Al4V. Difference of surface topography between LST and grit blasted surface is analyzed by SEM and white light interferometery. CuNiIn is deposited on Ti6Al4V by atmospheric plasma spray. MoS2 lubricating coating is deposited on top of CuNiIn by spray painting and curing. Effect of difference in surface preparation on coating microstructure as well as on tribological properties is studied. The results showed that geometry and dimensions of LST pattern influence the coating adherence and wear performance. LST process can be optimized for better performance and explored as an alternative surface preparation process in industry for thermal spray coatings.

Investigation the effect of weathering on chemically strengthened flat glasses

Present work discusses weathering behavior of chemically strengthened flat glasses. With this aim, different soda-lime silicate and sodium aluminosilicate glasses were subjected to weathering tests before and after chemical strengthening to simulate possible scenarios that toughened glass products face and effect of weathering on topographical, optical, structural and mechanical properties were investigated. Topographical evaluations were made through roughness measurements and topography images using white light interferometery and atomic force microscopy techniques. Depth profiling was accomplished by time of flight secondary ion mass spectroscopy. Optical transmittance spectra were recorded with ultraviolet-visible-near infrared spectrophotometer. Structural properties were analzyed by Fourier-transform infrared spectroscopy. Mechanical testing was realized by applying biaxial bending and Vickers indentation tests. Experimental results revealed that soda-lime silicate glasses are more prone to corrosion when weathering takes place after chemical strengthening due to formation of alteration layers. This behavior can be altered by increasing alumina content in the glass composition.

Effect of Coating and Polishing of Cutting Tool on Machined Surface Quality in Dry Machining of Aluminium Alloy

Surface quality is one of the major concerns in any machining process. To achieve the higher surface finish, mostly concentrated on machining parameter optimisation. This study has been carried out to study the effect of coating and polishing of flute surface of the solid carbide (WC-Co) endmill cutters on machined surface quality obtained during dry machining of Aluminium alloy 24345WP. Experiments were conducted on Aluminum workpieces with Ø6 mm 2 flute end- mill cutter with and without coating/polishing and their effect on surface quality studied for linear as well as areal surface roughness parameters using white light interferometery. The study concludes that polished flute tool, despite their non-sharp cutting edges, gives considerably better surface finish due to its lowering of chip tool friction. This was also supported by the results obtained from scanning electron microscopy of the cutting tool edge as well as optical microscopy of the obtained machined surface.

Nanoscale piezoelectric surface modulation for adaptive extreme ultraviolet and soft x-ray optics.

Extreme ultraviolet and soft x-ray wavelengths have ever-increasing applications in photolithography, imaging, and spectroscopy. Adaptive schemes for wavefront correction at such a short wavelength range have recently gained much attention. In this Letter we report, to the best of our knowledge, the first demonstration of a functional actuator based on piezoelectric thin films. We introduce a new approach that allows producing a gradually varying surface deformation. White light interferometery is used to show the level of control in generating arbitrary surface profiles at the nanoscale.

The influence of the topography and physico-chemical properties of the cuticle surface on the wettability and adhesive properties of the elytra of the dung beetle Geotrupes stercorarius (Coleoptera, Scarabaeidae)

The elytral surface of dung beetles is generally accepted to be self-cleaning due to its anti-adhesive properties. In this article, the wettability and adhesive properties of elytral surface (intact and treated with Acetone and Ethanol) of the beetle Geotrupes stercorarius were characterized. Since these properties are influenced by the surface structure and chemistry, the micro- and nanostructure of the elytra were observed using scanning electron microscopy and the surface roughness were estimated with white light interferometery, whereas the water contact angle and adhesion force of the elytra were evaluated using contact angle measurement device and force transducer, respectively. The results show that the microstructure of the elytra changed greatly after different chemical treatments and the changes in wettability were mainly related to the changes of elytra roughness after treatments. The differences in adhesion force between differently treated elytra and wet sand indicate that the molecular polarity of the elytral surface is decisive for its anti-adhesive (self-cleaning) property.

White light Sagnac interferometer—a common (path) tale of light

White or polychromatic light sources are vastly abundant in nature and lie in our most basic understanding of the theory of light, beginning from stars like our Sun and extending to every common household light bulb or street lamp. In this paper, I present concepts of white light interferometery using a common-path Sagnac interferometer, manifested in a straightforward laboratory experiment. I further show the use of this as a Fourier transform spectrometer while presenting a basic overview of the theoretical concepts and spectrum of different light sources obtained experimentally. This work, both experimentally and analytically, is suitable for upper-level undergraduate physics or engineering courses where electromagnetic theory and optics are discussed. The experiment and theory presents important deep concepts and aspects in modern optics and physics that every science student should acquire.

Rapid prototyping by consolidation of stainless steel powder using an electrical arc

PurposeThe purpose of this paper is to investigate the feasibility of using a pulsed Tungsten inert gas arc to fully melt and consolidate stainless steel powder onto a stainless steel substrate. The technology aims to bridge the gap between selective laser sintering or laser melting and wire fed weld deposition by providing good quality and better resolution at a lower cost.Design/methodology/approachCurrent settings between 5 and 30 A and frequencies between 0 and 200 Hz were used to consolidate stainless steel powder onto a substrate. Results were catalogued based on surface roughness using white light interferometery to develop a process map.FindingsVelocity independent thresholds of current (17 A minimum) and frequency (20 Hz minimum) were found, with better quality achieved at higher pulse frequencies. The microstructure of the samples were examined showing grain sizes of ≈3 μm for equiaxed grains and up to 20 μm for the columnar grains. Vickers hardness measurements showed only a 20 point average hardness increase in the HAZ compared to the substrate.Research limitations/implicationsThe study showed that although it was possible to deposit stainless steel tracks, it was not possible to reduce the track resolution to less than 400 μm at any of the process settings.Originality/valueThe research aims to investigate the use of a readily available, low cost, heat source to consolidate metal powder. The suitability of such a heat source for rapid prototyping is investigated using a variety of objective tests to provide a balanced view of its capabilities and limitations.

Practice-oriented evaluation of lateral resolution for micro- and nanometre measurement techniques

In the past few years, micro topography measuring techniques, such as atomic force microscopy (AFM) and white light interferometery (WLI), have been adopted by industry for quality assurance of micro structures. Since many factors influencing the uncertainty of measurements performed with these technologies are still unknown, the reliability of the measurement instruments is mostly done by comparison of different instruments at a given task. Among other things, to have a similar resolution of the instruments is an important pre-requisite. To provide a method for the evaluation of resolution, the Siemens-Star, which is widely applied in evaluation of 2D camera resolution, has been modified and applied to micro- and nano-measurement techniques. It is shown that this (non-calibrated) structure can be applied to quite different measuring techniques in order to investigate a wide range of resolutions, approximately from 0.1 µm to 6 µm. The applicability of the concept has been shown with WLI and AFM. Based on a suggested evaluation method, experimental results have been compared with the manufacturer specifications. Additionally, the lateral resolution of WLI measurements has been investigated at different positions of the field of view. Other resolution-influencing factors, such as the number of pixels and scan direction, have also been investigated. This concept also shows that it is possible to compare calibrated optical and stylus measurement devices whose resolution can vary in a wide range using non-calibrated structures.

Preparation and Evaluation of Damage Free Surfaces on Silicon Carbide

A new chemical mechanical polishing process (ACMP) has been developed by the Penn State University Electro-Optics Center for producing damage free surfaces on silicon carbide substrates. This process is applicable to the silicon face of semi-insulating, conductive, 4H, 6H, onaxis and off-axis substrates. The process has been optimized to eliminate polishing induced selectivity and to obtain material removal rates in excess of 150nm/hour. The wafer surfaces and resultant subsurface damage generated by the process were evaluated by white light interferometery, Transmission Electron Microscopy (TEM), Atomic Force Microscopy (AFM), and epitaxial layer growth. Residual surface damage induced by the polishing process that propagates into the epitaxial layer has been significantly reduced. Total dislocation densities measured on the ACMP processed wafers are on the order of the densities reported for the best as grown silicon carbide crystals [1]. Characterization of high electron mobility transistors (HEMTs) grown on these substrates indicates that the electrical performance of the substrates met or exceeded current requirements [2].

Femtosecond laser ablation of diamond-like carbon films

Diamond-like carbon (DLC) coatings were deposited on Si substrates using a hot filament diode discharge and they were irradiated with ultrashort laser pulses (800nm, 150fs, <4J/cm2). The laser-treated films were examined using optical microscopy, Raman spectroscopy, SEM, AFM and white-light interferometery. Damage threshold of 0.16J/cm2 and ablation rates below 110nm/pulse were determined. Changes in the structure of the laser-irradiated films were showed by means of Raman investigations. The laser-treated samples were etched and the depths of modified material layers were determined. Ablation experiments with longer laser pulses (1064nm, 100ns, <3J/cm2) were also performed and the irradiated DLC films were afterwards analyzed using the same procedures. Dissimilarities in the structure changes induced by fs-and ns-laser irradiation were observed and comments are given.