Surface Techniques Research Articles

Characterization of aperiodic surfaces with mesh-based parameters

For technical surfaces, it is important to know their functional purpose and to characterize them accordingly. Therefore, ISO 21920–2 in 2D and ISO 25178–2 in 3D offer parameters that can assess surface functional properties. The topographic portions of a surface, for example hills and dales, can be classified as features and evaluated using feature parameters. However, no parameter exists to describe the spatial distribution of features with regard to the degree of homogeneity for aperiodic surfaces. Here we show the application of the Delaunay triangulation to quantify the spatial distribution respectively the geometric relationship of features. Therefore, the feature points are determined by watershed analysis and the resulting point cloud is meshed in 2D. Based on that mean and standard deviation of the triangle side lengths and the area disorder (AD) are calculated as new parameters. The method is demonstrated for sandblasted and chrome-plated specimens. In addition simulation is used to generate more data for analysis. With the proposed approach the distinction and extent of uniform, homogeneous or inhomogeneous spatial distributions of features with parameter AD can be determined.

Oil adsorbing and transporting surfaces: a simulative determination of parameters for bionic functional textiles

Certain superhydrophobic plants, such as Salvinia molesta, are able to adsorb oil films from water surfaces and thus separate the oil from the water. There are first attempts to transfer this phenomenon to technical surfaces, but the functional principle and the influence of certain parameters are not yet fully understood. The aim of this work is to understand the interaction behavior between biological surfaces and oil, and to define design parameters for transferring the biological model to a technical textile. This will reduce the development time of a biologically inspired textile. For this purpose, the biological surface is transferred into a 2D model and the horizontal oil transport is simulated in Ansys Fluent. From these simulations, the influence of contact angle, oil viscosity and fiber spacing/diameter ratio was quantified. The simulation results were verified with transport tests on spacer fabrics and 3D prints. The values obtained serve as a starting point for the development of a bio-inspired textile for the removal of oil spills on water surfaces. Such a bio-inspired textile provides the basis for a novel method of oil–water separation that does not require the use of chemicals or energy. As a result, it offers great added value compared to existing methods.

Biomimetic, antiadhesive surface structure inspired by the calamistra setae of cribellate spiders for electrospun nanofiber handling

IntroductionDue to their excellent surface-to-volume ratio, nanofibers (i.e., fibers with a diameter of approximately 10 to 800 nm) are of increasing interest to engineers and scientists in a broad spectrum of applications. However, due to van der Waals forces, these nanofibers tend to adhere strongly to any surface, which makes further processing very challenging. In nature, we find animals that can easily handle nanofibers: Cribellate spiders use a comb-like structure, the so-called calamistrum, to produce, handle, and process nanofibers. Due to a fingerprint-like surface nanostructure, nanofibers do not adhere to the calamistrum. The principle interaction between this fingerprint-like surface nanostructure and single nanofibers has recently been described in a publication. The fingerprint-like surface structure was replicated on a technical metal surface using laser-induced periodic surface structures, which resulted in material properties resembling those of the natural model.MethodsWe went a step further and took a closer look on an additional structural feature of the calamistrum much larger than the fingerprint-like surface structure. A theoretical approach to describing the influence of a fiber preload, which may become a dominant effect if the fiber dimensions are small compared to the surface structure dimensions, on the adhesion of the fiber to these large surface structures was derived. Our theory was verified experimentally for artificial electrospun polyamide 6 nanofibers on surface-structured samples made of titanium alloy.Results and ConclusionA dramatic reduction in adhesion compared to unstructured, flat surfaces was proven. Therefore, such a surface structure can be used for tools or parts of tools during nanofiber production (e.g., as part of the electrospinning process) to reduce the adhesion of the nonwoven fabric and thus facilitate the handling and processing of the nanofibers during production.

Jet Cleaning of Filter Cloths Used in Solid‐Liquid Separation: A High‐Speed Video Evaluation

AbstractCleaning avoids cross‐contamination and sustains production safety and efficiency. While there have been discoveries for technical surfaces, data on activities for filter cloth are still in the early stages. In the food industry, there is a lack of knowledge and innovative ideas on how to clean cloths efficiently. This study combined high‐speed recordings with cleaning experiments. Cleaning of eleven filters was captured, enabling time‐resolved analysis of the cleaning degree, the cleaning homogeneity, and insights into the mechanisms. The findings divide cloth cleaning into three phases, each significantly influenced by the properties of the cloth. Exemplarily, close‐mesh cloths have smoother surfaces that facilitate cleaning. Coarse structures with flow channels on the cloth surface can complicate cleaning.

Robust surface profile envelope estimation using a beam-surface contact model

An important tool for the functional characterization of technical surfaces are envelope estimation techniques. This paper describes a new method for generating profile envelope lines based on a simplified beam-surface contact model with intuitive parameterization. The method is closely related to spline filters and shares some of their positive characteristics such as smoothness and robustness against isolated outliers. Unlike spline filters, the proposed method does not calculate mean lines, but envelope lines. Several examples of calculated profile envelopes of sintered surfaces are shown and a comparison with morphological methods, the state-of-the-art method for envelope estimation, is presented.

Electron conditioning of technical surfaces at cryogenic and room temperature in the 0–1 keV energy range

In the superconducting magnets of the Large Hadron Collider (LHC) at CERN, most of the beam-induced heat load is intercepted by a beam-screen (BS) cryogenically cooled to 5–20 K. When circulating the bunched proton beam, an electron cloud (EC) can form and bombard the BS copper surface with high doses of predominantly low-energy electrons, which desorb gas and consequently increase the pressure. The beam-induced pressure rise decreases during operation as the electron irradiation diminishes the secondary electron yield (SEY) and the electron-stimulated desorption (ESD) yield, a phenomenon referred to as ‘beam conditioning’. Low ESD and SEY values achieved rapidly are requisite to mitigate EC and maintain UHV in storage rings. We report data on ESD and SEY electron conditioning completed at cryogenic temperature with 0–1 keV electrons up to an electron dose of 5.10−3 C mm−2. Our results show that SEY conditioning depends on the primary electron energy and also that ESD yield significantly decreases with temperature. At 15 K, the amorphous-carbon coating and laser-treated copper present SEY below 1.1 and have initial ESD yields 3–6 times lower than OFE copper. Our results conform to the SEY and ESD's general understanding and extend it towards cryogenic temperatures.

Deliberate Surface Treatment of Zirconium Dioxide with Abrasive Brushing Tools

Brushing with bonded abrasives is a flexible finishing process used to reduce the roughness of technical surfaces. Although industrially widespread, especially for the finishing of metallic surfaces, insufficient knowledge of the motion, the material removal, and the wear behavior of the abrasive filaments complicates predictions of the work result. In particular, the reliable finishing of ceramics with bonded diamond grains proves difficult due to increased material removal rates, quickly leading to undesirable changes in the workpiece geometry. Based on technological investigations with abrasive brushing tools, this article provides insights into the surface finishing of zirconium dioxide with a focus on finding compromises between reduction in the surface roughness and alteration of the workpiece shape.

Design of a biomimetic, small-scale artificial leaf surface for the study of environmental interactions.

The cuticle with its superimposed epicuticular waxes represents the barrier of all aboveground parts of higher plant primary tissues. Epicuticular waxes have multiple effects on the interaction of plants with their living and non-living environment, whereby their shape, dimension, arrangement, and chemical composition play significant roles. Here, the ability of self-assembly of wax after isolation from the leaves was used to develop a small-scale wax-coated artificial leaf surface with the chemical composition and wettability of wheat (Triticum aestivum) leaves. By thermal evaporation of extracted plant waxes and adjustment of the evaporated wax amounts, the wettability and chemical character of the microstructure of the surface of wheat leaves were transferred onto a technical surface. For the use of these artificial leaves as a test system for biotic (e.g., germination of fungal pathogens) and non-biotic (e.g., applied surfactants) interactions on natural leaf surfaces, the chemical composition and the wetting behavior should be the same in both. Therefore, the morphology, chemistry, and wetting properties of natural and artificial surfaces with recrystallized wax structures were analyzed by scanning electron microscopy, gas chromatography–mass spectrometry, and by the determination of water contact angles, contact angle hysteresis, and tilting angles. Wheat leaves of different ages were covered exclusively with wax platelets. The extracted wheat wax was composed of alcohols, aldehydes, esters, and acids. The main component was 1-octacosanol. The waxes recrystallized as three-dimensional structures on the artificial surfaces. The three tested wetting parameters resembled the ones of the natural surface, providing an artificial surface with the chemical information of epicuticular waxes and the wetting properties of a natural leaf surface.

Roll‐to‐roll structuring and PECVD coating of polymer foils

SummaryIn the innovation field “Functional Surfaces and Materials” at the Fraunhofer IGB, research is being carried out to tailor the surface properties of PU foils and other materials via roll‐to‐roll processes. The goal is to save considerable costs by applying a unique and resource‐saving structures and coatings to self‐adhesive, transparent and erosion‐resistant PU foils to equip various technical devices with water and ice repellency. We are now able to obtain such surfaces in two separate roll‐to‐roll processes using low‐pressure plasma (pressure p < 100 Pa) in combination with a microstructuring process. Through structure and coating, the contact area and adhesion are minimized. Compared to an untreated reference surface, we are able to increase water contact angles from 76° to 157°. The structuring and coating of polymer foils make it therefore possible to open up new fields of application at lower cost than direct treatment of the various technical surfaces.

ANALYSIS OF THE WEAR PROCESS OF SURFACE LAYERS AFTER BURNISHING

The paper presents the results of an analysis of the wear process under conditions of dry technical friction of surface layers after selecting external surface pressure burnishing methods. The possibility of making changes in the burnishing process leading to an increase in resistance to wear under conditions of a simulated exploitation process is described. The possibility of conscious control of the process of material deformation in the zone of contact between the tool and the workpiece in the course of the surface layer formation process by changing the method and technological parameters of the pressure burnishing process is used. The course and results of the wear process of surfaces pressure burnished with a rolling ball, disc, and sliding ball are analysed. A description of the wear mechanism and comparative results of the wear of the surfaces tested are presented.

The Interaction of Waterborne Epoxy/Dicyandiamide Varnishes with Metal Oxides

For delayed crosslinking of waterborne epoxy varnishes, dicyandiamide (DICY) is often used as a latent curing agent. While, for amine-based curing agents such as diaminoethane (DAE), chemical interactions with metal oxides are well described, so far, no studies have been performed for DICY and waterborne epoxy varnishes. Hence, in this work X-ray photoelectron spectroscopy (XPS) was used to investigate reactions of DICY and varnishes with technical surfaces of Al, Zn, and Sn. To directly study the reaction of DICY with metal oxides, immersion tests in a boiling solution of DICY in pure water were performed. A clear indication of the formation of metal–organic complexes was deduced from the change in the N1s peak of DICY. To understand the interfacial interaction and consequently the interphase formation during coating of waterborne epoxy varnishes, advanced cryo ultra-low-angle microtomy (cryo-ULAM) was implemented. Interestingly, a comparable reaction mechanism and the formation of metal complexes were confirmed for varnishes. The coatings exhibited a pronounced enrichment of the DICY hardener at the metal oxide–polymer interface.

Atmospheric pressure matrix‐assisted laser desorption/ionization mass spectrometry of engine oil additive components

RationaleThe efficiency of lubricants strongly depends on the content of functional additives. In order to assess the chemical and structural changes taking place in the lubricating oil and its additives during operation, it is essential to develop a method for simple and prompt analysis.MethodsTwo single additives as well as a fully formulated engine oil were analysed using an atmospheric pressure matrix‐assisted laser desorption/ionization (AP‐MALDI) source coupled to a linear trap quadrupole Orbitrap XL hybrid tandem mass spectrometer and compared with results obtained by means of electrospray ionization (ESI) including additional low‐energy collision‐induced dissociation (LE‐CID). The identification of additives directly from technical surfaces was simulated by using steel substrates as AP‐MALDI targets with varying roughness.ResultsAfter assessment and selection of the most suited AP‐MALDI matrix it was found that pure additives such as calcium sulfonate and zinc dialkyldithiophosphates (ZDDPs) could well be identified with abundant signal intensity based on their elemental composition. Molecular identification was corroborated by LE‐CID in ESI mode. Additionally, additives present in the fully formulated commercial oil such as ZDDPs and salicylates could be reliably identified based on the elemental composition of the deprotonated molecules by means of the Orbitrap unit on different substrates including steel surfaces with high roughness.ConclusionsAP‐MALDI is an efficient technique for determination of lubricant additives directly from commercial oil blends. Identification of additive components was also achieved on steel surfaces with high roughness as applied in tribological systems and thus it is expected that it will be possible to assess additive degradation in real applications, enabling more effective and timely maintenance measures.

СОВРЕМЕННЫЕ ТЕНДЕНЦИИ В РАЗВИТИИ МЕТОДОВ И СРЕДСТВ ЭКСПЕРИМЕНТАЛЬНОЙ МЕХАНИКИ. ЧАСТЬ 2

The article considers a number of new directions in the development of methods and means of experimental mechanics. They are: the unification of test and calculation methods; the development of equipment and test methods in extreme conditions; the widespread use of acoustic emission methods and video recording during testing; the creation and development of equipment and methods for complex testing (for example, wear-fatigue) of materials and products. The achievements of Belarusian scientists are also noted in the field of experimental mechanics of contact interaction, including: an adhesiometer for measuring the molecular interaction of technical surfaces; a millitribometer for measuring friction forces under loads which are characteristic of a precision contact; an onboard tribometer for testing materials for friction and wear in extreme conditions of the action of space factors.

New methodology for discrimination of topography diversity of engineering surfaces – Case of grinding

The paper presents the methodology of assessing the degree of differentiation of machined technical surfaces based on the empirical probability distribution of the roughness parameters. The methodology allowed to determine the differentiation level of the analysed surfaces morphology based on the influence of the machining process features on the variability of roughness parameters. The minimum sample size necessary to obtain a statistically significant differentiation level in roughness parameters of the compared surfaces was also determined. The conducted analyses made it possible to determine the information content (indicating the ability to differentiate the features of the analysed surfaces) of the roughness parameters. The robustness of the methodology has been demonstrated. The described methodology was used to evaluate the information content on the example of the grinding process of 100Cr6 bearing steel and Ti-6Al-4V titanium alloy.

A Review of Factors Affecting the Effectiveness of Phishing

Phishing has become the most convenient technique that hackers use nowadays to gain access to protected systems. This is because cybersecurity has evolved and low-cost systems with the least security investments will need quite advanced and sophisticated mechanisms to be able to penetrate technically. Systems currently are equipped with at least some level of security, imposed by security firms with a very high level of expertise in managing the common and well-known attacks. This decreases the possible technical attack surface. Nation-states or advanced persistent threats (APTs), organized crime, and black hats possess the finance and skills to penetrate many different systems. However, they are always in need of the most available computing resources, such as central processing unit (CPU) and random-access memory (RAM), so they normally hack and hook computers into a botnet. This may allow them to perform dangerous distributed denial of service (DDoS) attacks and perform brute force cracking algorithms, which are highly CPU intensive. They may also use the zombie or drone systems they have hacked to hide their location on the net and gain anonymity by bouncing off around them many times a minute. Phishing allows them to gain their stretch of compromised systems to increase their power. For a normal hacker without the money to invest in sophisticated techniques, exploiting the human factor, which is the weakest link to security, comes in handy. The possibility of successfully manipulating the human into releasing the security that they set up makes the life of the hacker very easy, because they do not have to try to break into the system with force, rather the owner will just open the door for them. The objective of the research is to review factors that enhance phishing and improve the probability of its success. We have discovered that hackers rely on triggering the emotional effects of their victims through their phishing attacks. We have applied the use of artificial intelligence to be able to detect the emotion associated with a phrase or sentence. Our model had a good accuracy which could be improved with the use of a larger dataset with more emotional sentiments for various phrases and sentences. Our technique may be used to check for emotional manipulation in suspicious emails to improve the confidence interval of suspected phishing emails.

Principles of discrete-event modeling of physical processes during technical surfaces contact interaction

The article discusses the advantages and disadvantages of computer modeling used in physical experiments field on rough surfaces contact interaction. Methods for constructing the software model are given. The description of a single irregularity in the form of revolution ellipsoid segment is presented and an algorithm for rough surface three-dimensional modeling based on it is proposed. Some assumptions made for generating surface topography do not significantly affect the simulation validity. Taking into account the individual parameters of each irregularity and the algorithm for their distribution make it possible to create inhomogeneous rough surfaces that are close to real ones relative to the physical experiments being carried out. The general principles of the software architecture and the data storage model of discrete-event modeling system of rough surface contact interaction are described. The developed software can be used for modeling the rough surfaces contact interaction, for researching of tribo-interface units’ parameters, predicting the characteristics of frictional interaction and tribotechnical tests computer simulation.

Fringe analysis approach for imaging surface undulations on technical surfaces

Automated defect inspection is becoming increasingly important for advanced manufacturing. The ability to automatically inspect for critical defects early in the production cycle can reduce production costs and resources on unnecessary manufacturing steps. While there are many inspection techniques available, samples from early in a production workflow can prove challenging as they may still have systematic tooling marks, causing preferential scattering and hindering defect extraction. We propose a new imaging technique that exploits the preferential scattering from a technical surface to generate predictable fringe patterns on the sample's surface using only an array of LEDs. The patterns from this adapted fringe projection technique are imaged, and phase shifting algorithms are used to recover surface undulations on the sample. We implement this technique in the context of Hard Disk Drive platters that exhibit tooling marks from the lapping process and show that it is possible to image both highly scattering pits and scratches, as well as slow surface undulations with the same apparatus.

Quantifying flux residues after soldering on technical copper using ultraviolet visible (UV–Vis) spectroscopy and multivariate analysis

Employing diffuse reflection ultraviolet visible (UV–Vis) spectroscopy we developed an approach that is capable to quantitatively determine flux residues on a technical copper surface. The technical copper surface was soldered with a no-clean flux system of organic acids. By a post-solder cleaning step with different cleaning parameters, various levels of residues were produced. The surface was quantitatively and qualitatively characterized using X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Fourier transform infrared spectroscopy (FTIR) and diffuse reflection UV–Vis spectroscopy. With the use of a multivariate analysis (MVA) we examined the UV–Vis data to create a correlation to the carbon content on the surface. The UV–Vis data could be discriminated for all groups by their level of organic residues. Combined with XPS the data were evaluated by a partial least squares (PLS) regression to establish a model. Based on this predictive model, the carbon content was calculated with an absolute error of 2.7 at.%. Due to the high correlation of predictive model, the easy-to-use measurement and the evaluation by multivariate analysis the developed method seems suitable for an online monitoring system. With this system, flux residues can be detected in a manufacturing cleaning process of technical surfaces after soldering.

Copper alginate surface for perpetual Self-Polishing and Anti-Biofouling compound release

Biofouling is a severe problem for many applied technical surfaces ranging from ships and piers to water inlets and medicine. Here we investigate the physical–chemical properties of divalent copper and divalent calcium alginate bulk films and their anti-biofouling properties on the example of Chlorella vulgaris and in a natural river water environment. Physical-chemical characterization includes mechanical characterization of different mixing ratios, oil contact angles, and equilibrium water contents, self-polishing properties and copper ion release of copper alginate and copper-calcium alginate compositions. The results prove highly composition dependent physical–chemical properties. This causes highly composition dependent antibiofouling properties against Chlorella vulgaris, which changes significantly over time due to copper ion release and self-polishing resulting into up to 100 times lower biofouling compared to glass slides. Extending the test to river water, less Chlorella vulgaris compared to pure Chlorella vulgaris solution were determined. The total biofouling, which reached however, saturation of 25% and 35% coverage for copper, and calcium alginate respectively, which is comparable to glass.

Use of Hyperspectral Imaging for the Quantification of Organic Contaminants on Copper Surfaces for Electronic Applications

To correctly assess the cleanliness of technical surfaces in a production process, corresponding online monitoring systems must provide sufficient data. A promising method for fast, large-area, and non-contact monitoring is hyperspectral imaging (HSI), which was used in this paper for the detection and quantification of organic surface contaminations. Depending on the cleaning parameter constellation, different levels of organic residues remained on the surface. Afterwards, the cleanliness was determined by the carbon content in the atom percent on the sample surfaces, characterized by XPS and AES. The HSI data and the XPS measurements were correlated, using machine learning methods, to generate a predictive model for the carbon content of the surface. The regression algorithms elastic net, random forest regression, and support vector machine regression were used. Overall, the developed method was able to quantify organic contaminations on technical surfaces. The best regression model found was a random forest model, which achieved an R2 of 0.7 and an RMSE of 7.65 At.-% C. Due to the easy-to-use measurement and the fast evaluation by machine learning, the method seems suitable for an online monitoring system. However, the results also show that further experiments are necessary to improve the quality of the prediction models.