Sample Topography Research Articles

Deposition of Zinc Oxide Coatings on Wood Surfaces Using the Solution Precursor Plasma Spraying Process

In the present work, the solution precursor plasma spray (SPPS) process was used to deposit zinc oxide (ZnO) coatings on wood surfaces using zinc nitrate solution as precursor to improve the hydrophobicity and the color stability of European beech wood under exposure to ultraviolet (UV) light. The surface morphology and topography of the wood samples and the coatings were characterized by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The formation of ZnO was detected with the help of X-ray photoelectron spectroscopy (XPS) and by Fourier transform infrared (FTIR) spectroscopy. The FTIR spectra of the coated samples showed the typical Zn–O band at 445 cm−1. According to the XPS analysis, the coatings consist of two different Zn-containing species: ZnO and Zn(OH)2. Variation of the deposition parameters showed that the most significant parameters affecting the microstructure of the coating were the solution concentration, the deposition scan speed, and carrier gas flow rate. The wettability behaviors of the coated wood were evaluated by measuring the water contact angle (WCA). The coatings that completely covered the wood substrates showed hydrophobic behaviors. UV-protection of wood surfaces after an artificial UV light irradiation was evaluated by color measurements and FTIR spectroscopy. The ZnO-coated wood surfaces were more resistant to color change during UV radiation exposure. The total color change decreased up to 60%. Additionally, the FTIR spectra showed that the wood surfaces coated with ZnO had more stability. The carbonyl groups formation and C=C-bonds consumption were significantly lower.

Development of a Topographic Z-Correction Algorithm for 3D Depth Profiling Nanosims Images

Seasonal epidemics caused by the influenza virus, are responsible for thousands of deaths each year throughout the world. Anti-viral therapeutics that target the host cell components critical for its infectivity could reduce antiviral resistance. Cellular lipids such as sphingolipids and cholesterol are attractive targets because influenza a virus infectivity is sensitive to their abundance. Studies indicate the influenza a viral envelope is enriched with cholesterol and sphingolipids, and depletion of these components is detrimental to virus infectivity. Interestingly, influenza virus infection is also correlated with an accumulation of cholesterol within certain organelles in cells. The ability to produce intracellular three-dimensional images that show the abundance of cholesterol within distinct organelles could improve understanding of the role of intracellular cholesterol in influenza virus infectivity. Metabolically incorporated, rare stable isotope-labeled cholesterol and sphingolipids within intracellular compartments can be visualized by performing NanoSIMS imaging in a depth profiling mode. This depth profiling produces a series of NanoSIMS images that show the same location on the cell, but at increasing depth from its surface. Unfortunately, stacking the NanoSIMS images creates a three-dimensional (3D) image in which all the component-specific signals detected in a single scan are positioned at the same height. In contrast, the components that produced these ions were located at different distances from the substrate due to the cell's nonplanar topography. This poster describes an algorithm we developed that enables reshaping the 3D NanoSIMS images stacks to correct for sample topography in the absence of atomic force microscopy (AFM) data.

Unveiling surfaces for advanced materials characterisation with large-area electrochemical jet machining

Surface preparation for advanced materials inspection methods like electron backscatter diffraction (EBSD) generally involve laborious and destructive material sectioning and sequential polishing steps, as EBSD is sensitive to both sample topography and microstrain within the near-surface. While new methodologies, like focussed ion beam and femtosecond laser milling are capable of removing material in a layer-by-layer manner to enable the construction of tomographic datasets within the electron microscope, such techniques incur high initial capital cost for slow removal and reconstruction rates. In this study, ambient condition electrochemical slot jets are applied to rapidly etch (e.g. 31 s) large surface areas (e.g. 160 mm2) at controlled depths (e.g. 20 μm) with no in-process monitoring. Unveiled surfaces are conducive to measurement by EBSD (raw index rates between 75 and 95%), despite topographic anisotropy arising both from the process and the material. The mechanisms of topography formation during dissolution under the slot jet are analysed and understood. It is proposed that this slot jet method can be applied to create measurement surfaces for analysis with optical-based microstructural measurement routines reliant on topography and directional reflectance, at a significantly lower cost and time intervention than electron beam-based analysis methods.

A MEMS Nanopositioner With Integrated Tip for Scanning Tunneling Microscopy

Slow Z-axis dynamics of Scanning Tunneling Microscope (STM) is a key contributing factor to the slow scan speed of this instrument. A great majority of STM systems use piezotube nanopositioners for scanning. The piezotube bulkiness along with the mass of STM tip assembly restrict the overall Z-axis bandwidth of the system to about 1 kHz. This limited bandwidth slows down the STM response to the sample topography changes. In this paper, we report a microfabrication process to build a Microelectromechanical-System (MEMS) nanopositioner for Z-axis positioning in STM with a tenfold bandwidth, and a similar range of motion. The MEMS device features an integrated nanometer-sharp in-plane Si tip, compatible with conventional batch fabrication processes. In addition, a novel electrical isolation technique is developed to electrically isolate the tip from the rest of this device. This enables us to provide a separate routing for tunneling current signal, enabling potential applications in parallelism. The fabricated MEMS device achieves 1.6 μm motion with its first in-plane resonance beyond 10 kHz. The capability of this MEMS nanopositioner to replace the Z-axis of STMs is demonstrated through establishing controlled and stable tunneling current on a graphite sample in ambient conditions. [2020-0345]

Image acquisition for trolling-mode atomic force microscopy based on dynamical equations of motion

Trolling mode atomic force microscopy (TR-AFM) can considerably reduce the liquid-resonator interaction forces, and hence, has overcome many imaging problems in liquid environments. This mode increases the quality factor (QF) significantly compared with the conventional AFM operation in liquid; therefore, the duration to reach the steady-state periodic motion of the oscillating probe is relatively high. As a result, utilizing conventional imaging techniques, which are based on measuring the amplitude and phase, are significantly slower when compared to our proposed method. This research presents a high-speed scanning technique based on an estimation law to obtain the topography of various samples utilizing a two-degree-of-freedom model of TR-AFM. The effect of the nanoneedle tip horizontal displacement on the estimation process is investigated, and a solution to compensate for its undesirable effect is also presented.

High-spatial-resolution measurements of iron isotopes in pyrites by secondary ion mass spectrometry using the new Hyperion-II radio-frequency plasma source.

Iron isotopic signatures in pyrites are considered as a good proxy for reconstructing paleoenvironmental and local redox conditions. However, the investigation of micro-pyrites less than 20 μm in size has been limited by the available analytical techniques. The development of a new brighter radio-frequency plasma ion source (Hyperion-II source) enhances the spatial resolution by increasing the beam density 10 times compared with the Duoplasmatron source. Here we present high-spatial-resolution measurements of iron isotopes in pyrites using a 3 nA-3 μm primary 16 O- beam on two Cameca IMS 1280-HR2 ion microprobe instruments equipped with Hyperion sources at CRPG-IPNT (France) and at SwissSIMS (Switzerland). We tested analytical effects, such as topography and crystal orientation, that could induce analytical biases perceptible through variations of the instrumental mass fractionation (IMF). The δ56 Fe reproducibility for the Balmat pyrite standard is ±0.25‰ (2 standard deviations) and the typical individual internal error is ±0.10‰ (2 standard errors). The sensitivity on 56 Fe+ was 1.2 × 107 cps/nA/ppm or better. Tests on Balmat pyrites revealed that neither the crystal orientation nor channeling effects seem to significantly influence the IMF. Different pyrite standards (Balmat and SpainCR) were used to test the accuracy of the measurements. Indium mounts must be carefully prepared with a sample topography less than 2 μm, which was checked using an interferometric microscope. Such a topography is negligible for introducing change in the IMF. This new source increases the spatial resolution while maintaining the high precision of analyses and the overall stability of the measurements compared with the previous Duoplasmatron source. A reliable method was developed for performing accurate and high-resolution measurements of micrometric pyrites. The investigation of sedimentary micro-pyrites will improve our understanding of the processes and environmental conditions during pyrite precipitation, including the contribution of primary (microbial activities or abiotic reactions) and secondary (diagenesis and/or hydrothermal fluid circulation) signatures.

Experimental study on the surface and interface phenomenon changes by means of contact angle measurement on slot milled nimonic 263 alloy

The primary aim of this work is to analyze the interaction behavior between the machining process and surfaces and interface phenomenon of slot milled nimonic 263 alloy. In this investigation, the quantitative contribution of the cutter nomenclature such as cutter with variations in Radial Rake Angle (RRA) and the machining parameters on the surface energy and the wettability of the machined samples are examined through surface roughness and contact angle measurement over the slot milled surface. From the above experimentation, it is stated that the cutter with the Negative RRA machined sample has shown better and significant changes in surface energy which leads to increase the surface wettability related to the nascent nimonic sample. In addition to the above, the surface morphology variations are examined using scanning electron microscope to investigate the impact of slot milling process over the surface topography of the machined samples.

Reinforcing effect of polyurethane sizing on properties of acrylonitrile–butadiene–styrene composites involving short carbon fiber

In this study, we present the influence of sizing layer of short carbon fiber (CF) to the basic properties of CF reinforced acrylonitrile–butadiene–styrene (ABS) composites. Composite samples are prepared with four different loading ratio of 5, 10, 15 and 20% by weight using melt-compounding. Surface topography, elemental analysis and surface functionality of CF samples are confirmed by atomic force microscopy (AFM), energy-dispersive X-ray (EDX) and infrared (FTIR) spectroscopy techniques, respectively. Characterizations of composites are performed based on mechanical, thermo-mechanical, melt-flow (MFI) and morphological performances of composites. According to test results, mechanical properties of ABS are enhanced with CF additions. Polyurethane (PU) sized CF containing composites display higher tensile strength, modulus and hardness compared to desized ones. CF additions lead to increase in glass transition temperature of ABS copolymer. MFI values of composites are found to be in narrow range, hence CF additions cause no effect for processing conditions of ABS. According to SEM analysis, CF surfaces are covered by polymer matrix thanks to PU sizing layer of CF, whereas debondings are formed for desized CF-filled ABS matrix. Results indicate that PU-sizing is suitable for ABS/CF composite system.

Development of a Bioinspired, Self-Adhering, and Drug-Eluting Laryngotracheal Patch.

Novel laryngotracheal wound coverage devices are limited by complex anatomy, smooth surfaces, and dynamic pressure changes and airflow during breathing. We hypothesize that a bioinspired mucoadhesive patch mimicking how geckos climb smooth surfaces will permit sutureless wound coverage and also allow drug delivery. ex-vivo. Polycaprolactone (PCL) fibers were electrospun onto a substrate and polyethylene glycol (PEG) - acrylate flocks in varying densities were deposited to create a composite patch. Sample topography was assessed with laser profilometry, material stiffness with biaxial mechanical testing, and mucoadhesive testing determined cohesive material failure on porcine tracheal tissue. Degradation rate was measured over 21 days in vitro along with dexamethasone drug release profiles. Material handleability was evaluated via suture retention and in cadaveric larynges. Increased flocking density was inversely related to cohesive failure in mucoadhesive testing, with a flocking density of PCL-PEG-2XFLK increasing failure strength to 6880 ± 1810 Pa compared to 3028 ± 791 in PCL-PEG-4XFLK density and 1182 ± 262 in PCL-PEG-6XFLK density. The PCL-PEG-2XFLK specimens had a higher failure strength than PCL alone (1404 ± 545 Pa) or PCL-PEG (2732 ± 840). Flocking progressively reduced composite stiffness from 1347 ± 15 to 763 ± 21 N/m. Degradation increased from 12% at 7 days to 16% after 10 days and 20% after 21 days. Cumulative dexamethasone release at 0.4 mg/cm2 concentration was maintained over 21 days. Optimized PCL-PEG-2XFLK density flocked patches were easy to maneuver endoscopically in laryngeal evaluation. This novel, sutureless, patch is a mucoadhesive platform suitable to laryngeal and tracheal anatomy with drug delivery capability. NA Laryngoscope, 131:1958-1966, 2021.

The analysis of EDM electrodes wear in corners and edges

Die-sinking electrical discharge machining is an unconventional technology that allows to machine all at least minimally electrically conductive materials regardless of their physical and mechanical properties. Despite the fact that it is not a conventional technology, the tool gets also worn out, which is a tool electrode. The wear of the electrode does not only mean its loss but also the degradation of the shapes that are transferred to the resulting workpiece. For this reason, a design of experiments was conducted with 6 input factors, 2 were categorical: the electrode material (copper, graphite) and workpiece material (steel 1.2363 and steel 1.2343ESR) and 4 were numerical: Open-voltage, Pulse current, Pulse on-time, and Pulse off-time. In the framework of this design of experiments, the wear of the used graphite and copper electrodes at their corners and edges was evaluated, which was made possible by the use of electron microscopy and the use of approximation circles. Furthermore, the eroding speed, the topography of the machined samples, and the morphology of the surfaces of the used electrodes were investigated. It has been recognized that the use of a graphite electrode will allow for more accurate workpiece shapes and less wear.

ADAPTATION OF THE SMM-2000 INSTALLATION TO STUDENTS SCIENTIFIC WORKS ON STUDYING THE SURFACE OF VARIOUS MATERIALS

This paper presents the capabilities of the device "Scanning multi-microscope SMM-2000" as one of the most modern methods for measuring the characteristics of materials and diagnostics of features of small-size systems. The SMM-2000 scanning multi-microscope is designed for measuring geometric and physical parameters of the surface topography of samples with nanometer spatial resolution. The principle of operation of the device is briefly described and the parameters of manual and automatic settings are presented. On the example of scanning sample No. 2 - gold on mica, graphical results are shown that show sectional analysis for the selected area of the frame, and the results of the surface roughness parameters of the selected area are also shown. Described the possibility of carrying out Fourier analysis, morphological analysis, correlation analysis, fractal analysis, etc.

Characterization of weld seam surface and corrosion behavior of laser-beam-welded AISI 2205 duplex stainless steel in simulated body fluid

In this study, AISI 2205 duplex stainless steel was joined with laser welding. Base material and laser-welded samples were kept in simulated body fluid (SBF) for 1, 3, 7, 14, 21, and 28 days. This research investigated microstructure, hydroxyapatite (HA) structure formed on surfaces, surface topography, and corrosion properties of samples which were kept in SBF. Characterization studies were performed by using microhardness, optical microscope, macroscope, SEM–EDS, XRD, and atomic force microscope. According to results, it was found out that HA accumulation was higher on base material surface when compared to weld seam surface, and also calcium-deficient carbonate HA structure with low crystallinity was observed on all surfaces. Very low corrosion rates due to very low weight losses were detected in all samples kept in SBF. The results showed us that heat input changes had an important effect on surface roughness values (Ra), apatite morphology on weld seam surfaces, and corrosion behaviors. Overall, it is considered that laser-welded duplex stainless steel can be used as an implant material depending on surface characterization and corrosion behaviors.

Numerical analyses of molten pool evolution in laser polishing Ti6Al4V

Abstract As one advanced manufacturing process, laser polishing has been widely used in precision machining of metal or nonmetal materials. However, the evolution mechanism of molten pool formed during polishing process has not been thoroughly studied. This paper studies the polishing process of Ti6Al4V with a continuous wave (CW) fiber laser under the top-hat distributed heat source. A two-dimensional (2D) axisymmetric numerical transient model is established to simulate the formation process of the surface of Ti6Al4V after laser heating to form a molten pool and then cooling. It reveals that the evolution mechanism of physical processes involved in heat transfer, heat radiation, heat convection, melting and solidification during the polishing process. Particularly, the capillary and thermocapillary regimes (Marangoni flow) play a key role in smoothing the free-form surface of molten pool. The freedom surface can be smoothed effectively before the solidification of molten pool. In order to verify the correctness of the simulation model and explore the influence of laser irradiation duration on the material, the surface topography of the polished sample was investigated. It is found that the errors of the depth and width of the remelting zone are respectively less than 8 % and 22 % by the comparison of simulation and experimental results. Likewise, the depth and width of molten pool expand with the laser radiation duration increasing. Meanwhile, the polished surface topography becomes smoother.

Surface Quality Evaluation of Removable Thermoplastic Dental Appliances Related to Staining Beverages and Cleaning Agents

(1) Background: Thermoplastic materials are not inert and subject to changes in the oral environment, which affect their surface quality. Color stability and topographic characteristics of clear thermoplastic appliances are critical considerations. The study aimed to evaluate the optical changes and surface topography of different thermoplastic materials related to staining beverages and cleaning agents. (2) Methods: Thermoplastic polyethylene terephthalate glycol (PET-G) material specimens were selected for the study: S (Duran, Scheu-Dental GmbH, Iserlohn, Germany), D (Biolon, Dreve Dentamid GmbH, Unna, Germany), and B (Crystal, Bio Art Dental Equipment, Sao Carlos, Brazil). Four different media were involved for immersion: coffee (C) and black tea (T) at 55 °C, Coca-Cola (K) at 5 °C, and distilled water (W) at 22 °C. As for cleaning, chemical options and mechanical brushing were selected (P-powder, T-tablets, and X-brushing). Color changes, and mean surface roughness were measured at 24 h, 48 h, and after 7 days. Statistical analysis was performed. After the testing period, atomic force microscopy (AFM) analyses and SEM images were registered in order to characterize the surface topography. (3) Results: Quantitative color change evaluations revealed a slight change in color after 24 h and an extremely marked change after 48 h, respective 7 days. Mean roughness values are kept below the clinically acceptable limit of 0.20 µm for all samples. Related to mean nanoroughness values Sa, and 3D evaluations of the surface quality, Biolon samples have demonstrated the most constant behavior, while Crystal samples are visibly influenced by water immersion. Related to the cleaning method, the topography of Duran samples was influenced by mechanical brushing. (4) Conclusions: Nanoscale investigations provided high accuracy and more realistic surface quality examinations of the examined samples compared to profilometry. Both SEM and AFM should be used for a more detailed description of the surface topography.

Effect of Heat Treatment and Plasma Arc Welding on the Mechanical and Metallurgical Properties of Hastelloy C276

Hastelloy is a superalloy which contains nickel, chromium, iron and molybdenum as its major constituents which possess outstanding high temperature strength and oxidation resistance. The objective of this work is to study the heat treatment effect on mechanical and metallurgical properties of Hastelloy C276. A total of four samples are prepared at two different temperatures (700°C and 900°C) and at two different soaking times (4 and 8 hours). Tensile strength, percentage elongation and hardness were measured for the heat-treated samples. Further plasma arc welding was carried out on the heat-treated samples to understand its effect on tensile strength and hardness. The results indicate that there is significant increase in tensile strength and hardness of the hastelloy after heat treatment. Sample processed at 900°C and 8 hours soaking time has the maximum tensile strength and hardness of 378 MPA and 197 HV respectively. There is slight increase in tensile strength of the plasma arc welded samples. The percentage elongation of heat-treated samples is reduced after the welding process. The XRD pattern of the alloy revealed that the alloy is amorphous or microcrystalline in structure. The SEM image reveals the surface topography of the aged samples which confirms the experimental results.

About the reliability of EBSD measurements: Data enhancement

An extensive set of information about the diffracting volume is carried by EBSD patterns: the crystal lattice, the reciprocal lattice, the crystal structure, the crystal symmetry, the mean periodic number of the diffracting phase, the source point from where it has been projected (projection centre), the crystal orientation, the sample topography (local tilt), the (preparation) quality or defect density of the crystal, and possible pattern overlaps. Some of this information is used regularly in conventional EBSD analyses software while others are still waiting for a more widespread application. Despite the wealth of information available, the accuracy and precision of the data that are presently extracted from conventional EBSD patterns are often well below the actual physical limits. Using a selection of example applications, we will demonstrate the gain in angular resolution possible using relatively low-resolution patterns of approximately 20k pixels in combination with pattern matching (PM) approaches. In this way, fine details in a microstructure can be revealed which would otherwise be hidden in the orientation noise.

Morphological and Mechanical Characterization of DNA SAMs Combining Nanolithography with AFM and Optical Methods.

The morphological and mechanical properties of thiolated ssDNA films self-assembled at different ionic strength on flat gold surfaces have been investigated using Atomic Force Microscopy (AFM). AFM nanoshaving experiments, performed in hard tapping mode, allowed selectively removing molecules from micro-sized regions. To image the shaved areas, in addition to the soft contact mode, we explored the use of the Quantitative Imaging (QI) mode. QI is a less perturbative imaging mode that allows obtaining quantitative information on both sample topography and mechanical properties. AFM analysis showed that DNA SAMs assembled at high ionic strength are thicker and less deformable than films prepared at low ionic strength. In the case of thicker films, the difference between film and substrate Young’s moduli could be assessed from the analysis of QI data. The AFM finding of thicker and denser films was confirmed by X-Ray Photoelectron Spectroscopy (XPS) and Spectroscopic Ellipsometry (SE) analysis. SE data allowed detecting the DNA UV absorption on dense monomolecular films. Moreover, feeding the SE analysis with the thickness data obtained by AFM, we could estimate the refractive index of dense DNA films.

The influence of the process parameters of drag finishing on the surface topography of aluminium samples

Tribofinishing techniques are superfinishing processes that enable surface roughness improvement due to the mechanical action of abrasive media. A wide variety of kinematics can be employed and these abrasive media can have various trajectories and speeds when impacting the treated surface (normal, oblique, tangential, etc.). This work focuses on the drag finishing process, and in particular on the effect of spherical abrasive media impacting normally the surface of an aluminium part (6061T6). It investigates first the influence of the initial surface roughness and the diameter of spherical media when a lubricant is used. Secondly, it analyses the effect of a chemical accelerator surrounding abrasive media and the surface. An original experimental set-up was designed to observe the evolution of various surface roughness parameters and to identify local physical and chemical mechanisms. The results show that the final surface finishing greatly depends on the size of the abrasive media, and that a chemical additive can accelerate the material removal rate and improve the roughness when compared to a lubricant.

Impact of industrially applied surface finishing processes on tribocorrosion performance of 316L stainless steel

This investigation addresses the effect provided by industrial surface finishes on the tribocorrosion properties of 316L stainless steel exposed to NaCl solution. Three distinct surface treatments were evaluated: passivation (SSO), electropolishing-passivation (SSEP) and micro-undulation (SSM mechano-chemical + electropolishing + passivation). For the tribocorrosion tests, a potentiostatic approach was considered in order to highlight the alloy behavior under two opposite situations, where repassivation of the surface would be thermodynamically possible or not (anodic or cathodic polarization, respectively). The outcomes demonstrated that the surface treatments were either harmful (SSEP) or beneficial (SSM) in terms of resulting tribocorrosion resistance. The specific topography of the micro-undulated sample decreased the real contact area and improved the surface lubrication in aqueous medium. SSEP presented the highest chemical wear and several factors seemed to have contributed for it, including the chemical, mechanical and structural properties of the passive film. Regardless the surface treatment, the tribocorrosion response was modified by the applied potential and more severe damage was determined under anodic polarization. At this potential, calculations of the total surface degradation suggested that volume loss was mainly dominated by chemical wear.

A High Accuracy Ion Conductance Imaging Method Based on the Approach Curve Spectrum

Scanning ion conductance microscopy (SICM), as an emerging non-contact in situ topography measurement tool with nano resolution, has been increasingly used in recent years in biomedicine, electrochemistry and materials science. In the conventional measurement method of SICM, the sample topography is constructed according to the position of the probe at the feedback threshold of the ion current. Nevertheless, for different structures, a constant threshold cannot maintain a constant probe-sample distance. This phenomenon makes the measurement topography inconsistent with the real sample surface. In order to solve this problem and improve the measurement accuracy of SICM, a new ion conductance imaging method based on the approach curve spectrum is proposed in this work. In the new method, the local feature around the measurement point is firstly evaluated according to the change rate of ion current. Secondly, based on the local feature, the corresponding approach curve is searched from the prior approach curve spectrum to accurately evaluate the distance between the probe and the sample. Finally, the sample topography is constructed by the probe position subtracting the probe-sample distance. In this paper, we verify the feasibility of the new imaging method by combining finite element theory and experiments. To examine the measurement accuracy, the standard strip silicon and cylindrical polydimethylsiloxane (PDMS) samples are tested, and the improved imaging method can obtain the topography closer to the real samples and reduce the volumetric measurement error by 5.4%. The implementation of the new imaging method will further promote SICM application in related research fields.