Part IV - Visualization techniques and parameters for characterizing three-dimensional surface topography

Study on the three-dimensional topography of the machined surface in laser-assisted machining of Si3N4 ceramics under different material removal modes

In metallic fusion devices, parasitic light originating from multiple reflections on the wall is a major problem for the interpretation of optical diagnostics. Strong stray light affects several optical diagnostics in ITER. One possibility to cope with this reflected light is to use photonic simulation, which can accurately predict the behavior of light within complex 3D geometry. A prerequisite is to get a good description of the reflection model, represented by the Bidirectional Reflectance Distribution Function (BRDF), based on optical measurements of in-vessel materials. To avoid complicated measurements using goniophotometer to get the BRDF, one possibility is to link surface optical properties and topography characteristics, such as roughness measurements, for example, using the classical Bennett’s formula. Measurements were performed using two experimental goniophotometers to fully characterize the BRDF of tungsten samples with different roughness values. Surface topography was measured using a three-dimensional laser scanning confocal microscope. Several parameters were extracted from these measurements including the arithmetic average roughness (Ra), the root mean square roughness (RMS), the Surface Inclination Angle Distribution and furthermore its mean value δm and the power spectral density (PSD). The correlations of BRDF model parameters deduced from the measurements are compared with the previous topographic parameters. The initial results on several tungsten samples show that Ra, which is the usual measure of surface roughness, is not the most suitable metric to link with the reflection behavior of the surface. In contrast, the PSD and the surface inclination angle are interesting metrics for describing the reflected light.

Lateral adhesion forces are a fundamental property of liquid-solid interactions and a key aspect of dynamic droplet mobility. But, commonly applied conventional wetting analysis is limited to static and quasi-static methods and cannot resolve dynamic and spatial liquid-solid interactions. However, droplet mobility is assumed to be affected by chemical and topographic surface inhomogeneities introduced by femtosecond laser treatment. In this study, we used a customized droplet adhesion force instrument to determine lateral adhesion forces on various femtosecond laser-structured surface designs to obtain a deeper understanding of the dynamic droplet motion with regard to chemical and topographic surface features. We show that the droplet motion was highly affected by the chemical and topographical surface design and local inhomogeneities. The droplet mobility on femtosecond laser-structured surfaces could be classified into a static, a transfer, and a kinetic regime, which is essential for designing surfaces with extreme wetting characteristics and a wide range of scientific and industrial processes. Furthermore, with proper tailoring of surface structures and chemical modification, we were able to provoke adhesion forces on self-organized laser microstructures similar to those found on the natural lotus leaves.

Three-dimensional surface characterization for orthopaedic joint prostheses.

The complex surface topography of a scraped surface is studied quantitatively. The scraped surfaces are composed of the surface elements which are formed by each scraping operation, distribute in the depth direction, and have many asperities. Based on this model, the microscopic contacting problem between two scraped surfaces and static frictional characteristics are investigated under boundary lubrication. As a result, it is clarified that the ellipsoidal shape of the asperity tip of scraping surface may be regarded as optimal from the point of static friction, and the static friction characteristics are considerably influenced by the scraping directions.

The relation between static friction characteristics and surface topography of contacting scraped surfaces are theoretically examined under boundary lubrication. As a result, it is clarified that the topographic effects on static friction of a scraped surface can be evaluated quantitatively by a nondimensional parameter (coefficient of surface topography). The sliding characteristics of scraped surface slideway can be improved by using surfaces having a large coefficient of surface topography.

The goal of this study was to reproducibly generate samples with complex surface topographies and chemistries identical to a "master surface" and to test their response in cell culture using rat calvarial cells. Negative replicas of dual-type topography were fabricated using dental impression material with half of the surface exhibiting smooth and rough topography, respectively. Positive epoxy resin replicas were cast from the same negative replica eight times consecutively and coated with a 60-nm thin film of titanium dioxide using a vapor deposition technique. Atomic force microscopy, scanning electron microscopy, confocal white light microscopy, and X-ray photoelectron spectroscopy indicated that TiO(2)-coated epoxy replicas had surface topographical features and surface compositions nearly indistinguishable from the original titanium master surfaces. The described technique showed high reproducibility over at least eight generations of replication using the same negative replica. Rat calvarial osteoblasts proliferated just as well on dual topography surfaces as on single topography surfaces. The advantage of the dual-type substrates is that they facilitate comparison within a single culture dish, thus eliminating dish-to-dish variation as well as saving material, time and costs compared to the usual method of evaluating surfaces in separate dishes.

Topographic features of cylinder liners — an application of three-dimensional characterization techniques

Study on wear state evaluation of friction stir welding tools based on image of surface topography

Differences in microscale surface contours of metallic targets subjected to laser shock

The Cu-2 wt% Sb alloy was prepared and exposed to various heat treatments at temperatures ranging from 573 to 973 K to get distinct grain diameters. Different samples of various grain diameters were individually sputtered in an argon glow discharge for various times (0.5, 1, 2 h) using a DC magnetron sputtering device. The surface topography and microstructural features of a Cu-2 wt% Sb alloy were examined utilizing an optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD). The Cu3Sb\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$Cu_{3} Sb$$\\end{document} IMC phase was found to segregate at the grain boundaries. Results showed that the topographical features of sputtered samples (grain boundaries, tiny cones, cratered cones, and etch pits) were mainly affected by grain size and sputtering time. Moreover, the mechanical properties of a Cu-2 wt% Sb alloy were examined. The parameters of the stress–strain curves (Young modulus Y, 0.2% offset stress σy0.2, fracture stress σf, parabolic work-hardening coefficient χp\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upchi }_{{\ ext{p}}}$$\\end{document}, and ductility εf\\%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upvarepsilon }_{{\ ext{f}}} {\ ext{\\% }}$$\\end{document}) were measured under different testing conditions. Generally, these stress parameters decrease as the grain diameter increases. These parameters, with the exception of εf\\%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upvarepsilon }_{{\ ext{f}}} {\ ext{\\% }}$$\\end{document}, increase as the strain rate increases, while εf\\%\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\upvarepsilon }_{{\ ext{f}}} {\ ext{ \\% }}$$\\end{document} decreases as the strain rate increases. Additionally, selective samples of the present alloy were irradiated using γ-radiation with different doses 0.5, 1, 1.5, and 2 MGy. The Vickers microhardness of annealed and irradiated samples lowered as the grain size augmented, while it increased as the irradiation dose increased. Based on the obtained activation energy Q value of 20.65 kJ/mol., it is indicated that the predominant deformation mechanism in the Cu-2 wt% Sb alloy is the motion of dislocation through the Cu-matrix.

Excitonic properties of the polar faces of bulk ZnO after wet etching

With the remarkable success of the Cassini‐Huygens mission, considerable new knowledge has been obtained regarding the surface topography, composition and atmospheric characteristics of Titan. However, Cassini‐Huygens represents only a bold beginning for the exploration of Titan, as high resolution mapping will have been performed for only a small fraction of the surface of Titan by the end of the nominal mission. Large gaps in knowledge will remain in key scientific areas including global surface topography, atmospheric and surface composition, precipitation rates, and the density, thickness, and formation processes of clouds. This study details a conceptual follow‐on Titan orbiter mission that would provide full global topographic coverage, surface imaging, and meteorological characterization of the atmosphere over a nominal 2‐year science mission duration. The reference power requirement is ∼1 kWe at EOM and is driven by a high power radar instrument that would provide 3‐dimensional measurements of atmospheric clouds, precipitation, and surface topography. While this power level is moderately higher than that of the Cassini spacecraft, higher efficiency advanced RPSs could potentially reduce the plutonium usage to less than 1/3 of that used on the Cassini spacecraft. The Titan Orbiter mission is assumed to launch in 2015. It would utilize advanced RPSs to provide all on‐board power, and would employ an aeroshell to aerocapture into Titan orbit. A conceptual advanced Stirling RPS was selected due to its high specific power and conversion efficiency which enabled the ability to include a 500 kg “black box” deployed entry probe.

Elemental surface topography information in microscopic material characterization contributes to a better understanding of surfaces, interfaces, substrates, and their applications. Here, a general approach based on microbeam proton-induced X-ray emission (micro-PIXE) to reconstruct the three-dimensional (3D) elemental surface topography using the annular multisegment silicon drift detector has been demonstrated. The proposed method includes four main steps: acquiring four two-dimensional elemental concentration maps using the multichannel spectrometer, reconstructing the local inclination angle from the atomic model of ion-matter interaction, calculating the two independent topography gradient components, and numerical surface topography integration. In this study, the general algorithm to obtain the gradient components has been successfully tested on a four-segment configuration to reconstruct the 3D surface topography of compound alloys with different microstructure scales. In synchrotron and accelerator facilities dealing with elemental X-ray mapping where the development of customized multisegment detectors is needed, the introduced method is applicable to elemental surface/interface roughness reconstruction in microscale for cultural heritage samples, fusion plasma-facing materials, and microelectronic devices.

The specific topography of biomaterials plays an importantrolein their biological interactions with cells and thus the safety ofmedical implants. Antifouling materials can be engineered with topographicfeatures to repel microbes. Meanwhile, undesired topographies of implantscan cause complications such as breast implant-associated anaplasticlarge cell lymphoma (BIA-ALCL). While the cause of BIA-ALCL is notwell understood, it is speculated that textured surfaces are proneto bacterial biofilm formation as a contributing factor. To guidethe design of safer biomaterials and implants, quantitative screeningapproaches are needed to assess bacterial adhesion to different topographicsurface features. Here we report the development of a high-throughputmicroplate biofilm assay for such screening. The assay was used totest a library of polydimethylsiloxane (PDMS) textures composed ofvarying sizes of recessive features and distances between featuresincluding those in the range of breast implant textures. Outliersof patterns prone to bacterial adhesion were further studied usingreal-time confocal fluorescence microscopy. The results from theseanalyses revealed that surface area itself is a poor predictor foradhesion, while the size and spacing of topographic features playan important role. This high-throughput biofilm assay can be appliedto studying bacteria–material interactions and rational developmentof materials that inhibit bacterial colonization.