Surface Microtexture Research Articles

Prediction of Contact and Lubrication Characteristics of Micro-textured Surface Under Thermal Line Contact EHL

In this study, a method combining numerical surface generation technology and three-dimensional hot-line contact EHL is employed to evaluate the contact characteristics of micro-textured surfaces under high-load line contact. Based on numerical simulation, the film thickness, film pressure, friction coefficient and surface flashing temperature of the virtual texture surface with different cross-sectional shapes and sizes are studied. On this basis, the subsurface stress at the contact point is calculated by the DC-FFT algorithm. The results show that, compared with a smooth surface, the micro-textures of different shapes all increase the average oil film thickness of the surface and reduce the friction coefficient, but at the same time lead to an increase in the contact stress of the surface. By changing the width and depth of the texture, the maximum film pressure has changed by 11.4 and 18.5%, respectively.

Analyzing the surface dynamics of titanium thin films using fractal and multifractal geometry

Titanium thin films are prepared by DC magnetron sputtering on the glass substrate with varying sputtering power. The nanoscale surface morphology and nanotexture are captured via atomic force microscopy (AFM). The value of average roughness and interface width show the increasing trend with sputtering power. The autocorrelation and height-height correlation function are applied to characterize the formation of the self-affine and mounded surfaces. The roughness (or Hurst) exponent and fractal dimension are estimated by height-height correlation function while lateral correlation length is measured by autocorrelation. It is found that the surface complexity is affected with various sputtering power. The value of Hurst exponent of the topography greater than 0.5 indicates a persistent behavior and such system shows memory effect. The fractal lacunarity, succolarity and surface entropy is used for investigating the surface microtexture and percolation. The 2D Multifractal Detrended Fluctuation Analysis (2D MFDFA) method is used to study the multifractal nature of thin-film surfaces. Computed Δα and Δf show an increase with sputtering power indicating a surface with many characteristic scale patterns. Furthermore, the thin film deposited with the highest sputtering power has greater topographic uniformity, lower surface percolation and greater homogeneity of the surface microtexture.

Micromorphology of metallic surfaces for hydrophobicity by waterjet-guided laser processing

Waterjet-guided laser processing is a novel machining technique for metallic materials. To investigate and analyse the effects of processing parameters on surface topography change, micro-texturing evolution, and hydrophobicity, micromorphology machining experiments were conducted on stainless steel using self-developed waterjet-guided laser processing equipment. Nd:DPSS laser system with repetition frequency of 20–120 kHz and maximum power of 50W is used in the equipment. A scanning electron microscope (SEM) is used to measure surface topography. Energy-dispersive spectrometer (EDS) is used to evaluate the material composition of processing zone and no processing zone. The effects of grid spacing and laser power coupled into the jet are examined and processing conditions for hydrophobicity are provided. There was oxidation and no crack on the kerf edge. The surface contact angle dramatically increases from 92.94 to 138.41° with the decreasing of the grid size. It has been shown that waterjet-guided laser processing yields textures with a hydrophobic surface and is suit for micro-texture micro-machining.

Integration of finishing and surface treatment of Inconel 718 alloy using high-speed ultrasonic vibration cutting

The successful implementation of high-speed ultrasonic vibration cutting (HUVC) to improve the machinability of the Inconel 718 alloy has been reported in literature. However, the influence of HUVC on the surface integrity of the Inconel 718 alloy has not been investigated. In this context, this study is the first attempt to integrate cutting operations and mechanical surface treatment into one step via HUVC. To this end, an experiment was performed to compare the surface integrity of conventional cutting (CC) and HUVC using coated carbide tools at high cutting speeds (80–240 m/min). The experiment revealed that HUVC led to a lower surface roughness, regular surface micro-texture, deeper subsurface deformation zone (up to 104.47 μm), higher surface micro-hardness rate (by up to ~50%), and higher surface compressive residual stress (−1772 to −2323 MPa) compared to CC. In some occasions, a single HUVC step can be used to satisfy requirements originally addressed over two distinct steps (cutting operation and mechanical surface treatment) by improving surface integrity.

Preparation of Monoclinic Pyrrhotite by Thermal Decomposition of Jarosite Residues and Its Heavy Metal Removal Performance

Jarosite residues produced by zinc hydrometallurgical processing are hazardous solid wastes. In this study, monoclinic pyrrhotite (M-Po) was prepared by the pyrolysis of jarosite residues in H2S atmosphere. The influence of gas speed, reaction temperature, and time was considered. The mineral phase, microstructure, and elemental valence of the solids before and after pyrolysis were analyzed using X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy, respectively. The performances of the prepared M-Po on the removal of Zn and Pb from aqueous solution were evaluated. The results show M-Po to be the sole product at the reaction temperatures of 550 to 575 °C. Most of the M-Po particles are at the nanometer scale and display xenomorphic morphology. The phase evolution process during pyrolysis is suggested as jarosite → hematite/magnetite → pyrite → pyrite+M-Po → M-Po+hexagonal pyrrhotite (H-Po) → H-Po. The formation rate, crystallinity, and surface microtexture of M-Po are controlled by reaction temperature and time. Incomplete sulfidation may produce coarse particles with core–shell (where the core is oxide and the shell is sulfide) and triple-layer (where the core is sulfate, the interlayer is oxide, and the shell is sulfide) structures. M-Po produced at 575 °C exhibits an excellent heavy metal removal ability, which has adsorption capacities of 25 mg/g for Zn and 100 mg/g for Pb at 25 °C and pH ranges from 5 to 6. This study indicates that high-temperature sulfidation is a novel and efficient method for the treatment and utilization of jarosite residues.

Anti-icing capability of textured silicone rubber surfaces via laser processing

ABSTRACT It is an undisputable fact that surface texture has a profound influence on the functional behavior of products. A method is proposed for manufacturing an anti-icing surface on silicone rubber composite material. Using a multi-function laser engraving machine, cylindrical micro-textures with different size and depth parameters are processed on the umbrella skirt surface of composite insulator samples. The optimal dimensional parameter of the surface micro-texture was determined by the best superhydrophobic property. By analyzing the freezing time of droplets, the influence of texture depth parameters on the anti-icing performance of the silicone rubber surface was investigated, which clearly confirmed that the contact angle affected anti-icing performance. Studying on adhesion of the ice on the sample surface and changing of the water contact angle after ice coating demonstrated the influence of texture-depth parameter on the deicing performance of silicone rubber surface. Thus, the characteristics and optimality of the texture specimen were obtained.

Micro-texturing by femtosecond laser ablation of a carbonaceous anode for production of fluorine by electrolysis

Micro-texturing of the carbon surface of the anode used for the production of fluorine gas by electrolysis is achieved by ablation using a pulsed laser in the femtosecond range; this avoids oxidation of the carbon during ablation. Samples microstructured on the surface via a grid of parallel and perpendicular grooves were prepared and then studied from an electrochemical point of view coupled with ultra-fast image acquisition to visualize the effect of micro-texturing on the dynamics of the fluorine bubbles. In addition, the quantity of gas formed was measured using an incremental flowmeter on an electrolysis cell. Surface micro-texturing controls both the dynamics and shape of the fluorine bubbles, as well as the electroactive zone. The bubbles, then spherical due to the controlled roughness, have a short residence time (about 1 s) and small sizes (a few mm). These observed changes suggest a different wettability of the carbonaceous anode surface by the fluorine gas or the KF-2 H F electrolyte with a beneficial effect on the electrode performance in terms of Faraday efficiency as opposed to the anode voltage which changes slightly. In addition, thanks to the particular dynamics of the fluorine bubbles, very high current densities of up to 75 A dm−² can be applied.

Numerical Simulation and Experimental Study on Flow Forming of Laser Concave–Convex Microtexture of Cr12 Steel Surface

In this paper, Cr12 steel was taken as the research object, and laser micro melting model was established in comsol software based on physical equations such as laser heat source, convection heat transfer, evaporation mobility, recoil pressure, Marangoni effect. The forming mechanism and evolution law of concave–convex microtexture morphology were studied by numerical simulation. The research reveals the changing process of the velocity of the flow field inside the material during the surface deformation. In addition, it can be found from the temperature field changes under different power that the higher the power is, the faster the surface temperature of Cr12 material increases in the process of thermal deformation. And the hardness of the microtexture was greatly improved after the material experienced sudden heat and cold in a very short time. By comparing the numerical simulation results and the experimental results, it can be found that with the increase of power, the height, depth and diameter of the concave–convex microtexture morphology all show an increasing trend, and the surface geometry obtained through numerical simulation matches well with the experimental results. It indicates that the numerical simulation has high feasibility and can effectively reflect the forming process and morphology of concave-convex microtexture.

A comparison of bioinspired slippery and superhydrophobic surfaces: Micro-droplet impact

Slippery lubricant impregnated surfaces (SLIPSs/LISs) exhibit remarkable features of repellency and droplet mobility to a broad range of complex fluids. Their performance in micro-droplet repellency has received less attention. In this study, the anti-wetting performance of SLIPSs in comparison to superhydrophobic surfaces (SHSs) is investigated for the micro-droplet impact on different textured surfaces. Different series of square-pillar arrays are modeled to consider the effect of surface morphology on droplet hydrodynamics. A multiphase numerical model in conjunction with an accurate contact angle method has been implemented to analyze details of three immiscible phases during the droplet impact on the SLIPS. Our findings revealed that on the SLIPS with a low-density micro-textured surface where the effect of lubricant is more significant, droplet repellency and mobility are improved compared to SHSs. It was illustrated that on the SLIPS, droplet pinning decreased significantly and in low Weber number cases where the effect of lubricant is more noticeable, partial bouncing occurred. It was also observed that slippery surfaces with a low-density of micro-pillars exhibit bouncing behavior, which indicated the repellency effect of lubricant in droplet hydrodynamics. Although micro-droplets failed to recoil at a higher Weber number (We≃160) on both the SHS and the SLIPS, droplet penetration within the micro-structured surface was considerably smaller on the SLIPS.

Prospective randomized clinical trial evaluating the effects of two different implant collar designs on peri-implant healing and functional osseointegration after 25 years.

Evaluate the effects of two different machined-collar lengths and designs on peri-implant healing. An implant with a microtextured surface and 3.6mm-long internal-connection machined collar was compared to two implants that had an identical 1.2mm-long external-connection machined collar, but one had the microtextured surface while the other's was machined. Participants received the three implants, with microgap at the crest, alternately at five sites between mental foramen, and a full-arch prosthesis. Peri-implant bone levels were measured after 23 to 26years of function. Keratinized tissue height, plaque, probing depth, bleeding, and purulence were also evaluated. Descriptive and mixed models for repeated\measures analyses were used, with Bonferroni correction for pairwise comparisons. Twenty-two participants (110 implants) were evaluated at the 25-year examination. Microtextured implants with the longer machined collar had significantly greater mean marginal bone loss (-1.77mm±0.18, mean±SE) than machined (-0.85mm±0.18, p < .001) and microtextured (-1.00±0.18mm, p < .001) implants with the shorter machined collar. Keratinized tissue height was greater for internal-connection (0.74mm±0.10) versus external-connection (0.51±0.08, p= 0.01) microtextured implants. No differences were observed for plaque (p=0.78), probing depth (p=0.42), bleeding (p = 0.07), and purulence (p=1.00). Implant survival rate was 99%. Implants with the 1.2mm machined collar limited bone loss to 1mm, while those with the longer machined collar showed>1.5mm loss after 25years of function with microgap at the crest. Internal-connection design and fixture surface microtexturing did not result in greater bone preservation. ClinicalTrials.gov Identifier: NCT03862482.

Stereometric characterization of Dinizia excelsa Ducke wood from Amazon rainforest using atomic force microscopy.

Dinizia excelsa Ducke under three different cut conditions were carefully analyzed. The morphology and stereometry of different wood cutting surfaces (longitudinal radial, longitudinal tangential, and transversal) were studied by SEM and AFM. The results obtained in this study suggest that both the height parameters and the advanced stereometric parameters of the surfaces did not reveal a significant difference, indicating that the spatial patterns do not change according to the type of cut. In this way, the surface microtexture does not vary depending on the cut type. Similarly, the Hurst's coefficients did not show any significant difference in the spectrum of the PSD fractal region. On the other hand, Minkowski functionals presented a morphological difference between the samples. These results showed that the microtexture of the wood surface does not change as a function of the type of cut submitted to the same polishing process.

Nanoscale morphology and fractal analysis of TiO2 coatings on ITO substrate by electrodeposition.

In this paper, we introduced an advanced discussion of the 3D morphology of TiO2 coatings deposited on ITO substrate by electrodeposition under different deposition times. Atomic force microscopy was applied for obtaining topographic images of the samples. The images were processed using the MountainsMap 8.0 commercial software according to ISO 25178-2:2012. Moreover, fractal theory was applied to study the surface microtexture of coatings. The morphology was affected by the deposition time, where the grain size decreased with the increase of the time, making film's surfaces smoother. In addition, the surface roughness exhibited a random behaviour, but does not presented significant difference between samples. The fractal dimension showed similar values for all coatings. In contrast, surface texture isotropy also exhibited random behaviour. However, advanced fractal parameters revealed that when the deposition time increased, the coatings microtexture has become uniform and less porous. Furthermore, all coatings presented high topographic uniformity, regardless of deposition time. These results revealed that the morphology and microtexture of TiO2 -based coatings can be controlled by the deposition time. LAY DESCRIPTION: An advanced characterization on the micromorphology of 3D morphology, using AFM images, of Titanium dioxide (TiO2 ) coatings deposited on ITO substrate by electrodeposition under different deposition times. TiO2 is one of the most studied semiconductors to make photovoltaic devices. The versatility of this semiconductor is associated with low toxicity, high photochemical stability, abundance, and the facility to obtain by conventional synthesis routes. The obtention of a homogeneous and stable layer in the semiconductor TiO2 film deposition is a crucial stage in the assembly of sensitized photovoltaic devices. Atomic Force Microscopy (AFM) is a technique which can magnify up to a billion times and it uses a tip or probe which touches the sample surface point by point. The tip deflection is interpreted as the surface topography by the software, producing 2D or 3D images that generate several tribological parameters such as roughness in respect to a scanned area, has been a technique widely reported in the morphological characterization, determination of thickness, roughness, and particle size in thin films. Therefore, in this paper, the morphology was studied by atomic force microscopy using MountainsMap commercial software. The main goal was to study the influence of the deposition time on the morphology and microtexture of the material. New parameters such as surface entropy, fractal succolarity and fractal lacunarity were obtained for studying coatings microtexture's complexity.

Icephobic Performance of Multi-Scale Laser-Textured Aluminum Surfaces for Aeronautic Applications.

Ice-building up on the leading edge of wings and other surfaces exposed to icing atmospheric conditions can negatively influence the aerodynamic performances of aircrafts. In the past, research activities focused on understanding icing phenomena and finding effective countermeasures. Efforts have been dedicated to creating coatings capable of reducing the adhesion strength of ice to a surface. Nevertheless, coatings still lack functional stability, and their application can be harmful to health and the environment. Pulsed laser surface treatments have been proven as a viable technology to induce icephobicity on metallic surfaces. However, a study aimed to find the most effective microstructures for reducing ice adhesion still needs to be carried out. This study investigates the variation of the ice adhesion strength of micro-textured aluminum surfaces treated using laser-based methods. The icephobic performance is tested in an icing wind tunnel, simulating realistic icing conditions. Finally, it is shown that optimum surface textures lead to a reduction of the ice adhesion strength from originally 57 kPa down to 6 kPa, corresponding to a relative reduction of ~90%. Consequently, these new insights will be of great importance in the development of functionalized surfaces, permitting an innovative approach to prevent the icing of aluminum components.

Enhancement of heavy-duty friction and wear characteristics of cast-iron surface by electrolytic micro-textures filled with MoS2

Cylinder liners made of cast iron are widely used in heavy-duty diesel engines. With the continuous strengthening of heavy-duty conditions of diesel engine, surface modifying technologies of piston ring and cylinder liner are gaining more attention. Two types of modified surfaces were prepared using cast-iron cylinder liner. One was a micro-texture prepared by electrolytic machining technology and the other was a MoS2-filled micro-texture prepared by cathodic reduction of thiosulfate. Modified cast-iron cylinder liners matched with chromium-based ceramic composite coated (CKS) rings were compared using the piston ring reciprocating liner test rig. Friction coefficient and wear depth of MoS2-filled microtextured liner were 8.4% and 51.5% lower than those of the microtextured liner under the simulated conditions of 50 MPa, 200 r/min and 250 °C, respectively. XPS of the MoS2-filled micro-textured surface revealed that both zinc dialkyl dithiophosphates (ZDDP) in the lubricating oil and MoS2 in the micro-textures were involved in the formation of the tribofilm with a good synergistic interaction. Typical compositions of friction-reducing and wear-resistant tribofilm on the platform area between the MoS2-filled micro dimples contained some amount of the zinc compounds ZnO, the short chain polyphospahtes FePO4, the unoxidized molybdenum compounds MoS2 and the sulfides FeS.

Lubrication dynamics of swollen silicones to limit long term fouling and microbial biofilms.

Bacterial contamination and biofilm formation on medical devices remain a costly and serious healthcare problem. Silicone (polydimethylsiloxane, PDMS) elastomers are common biomaterials but are susceptible to bacterial surface contamination and biofilm growth. 'Self-lubricated' PDMS elastomers (iPDMS) have the potential to greatly reduce rates of cell attachment, biofilm formation and infection. Cross-linked PDMS elastomers immersed in PDMS oil swell to an equilibrium concentration to form a swollen network, and then form a surface liquid layer through syneresis. Herein we have measured the swelling and syneresis kinetics as a function of time, viscosity (1.5 to 10 cSt), and cross-linking density to optimize the surface lubricant layer formation, and resistance to biofouling. The lubricant layer thickness was measured in situ (optical profilometry and AFM) for flat and micro-textured surfaces, as a function of time and swelling ratio, to be in a range from 0.1 to 1 μm, and continuously increases with time. We show this continuous generation is likely due to a gradual, dynamic re-structuring of the elastomer network. Long term antifouling properties of (10 cSt) iPDMS were tested for Pseudomonas aeruginosa growth in a flow culture bioreactor, and after 30 d showed a 103 to 104 reduction of bacterial cell density for iPDMS compared to conventional PDMS elastomers. This long term performance and non-specific activity makes them highly suitable for biomedical devices, such as urinary catheters.

Influence of maskless electrochemical micromachining process parameters during microtexturing

Abstract Maskless electrochemical micromachining (EMM) is a prospective procedure for elevated precision microtexturing. Particularly the microtexturing of substrates without any mechanical influence or heat affect is a substantial characteristic for this process. Moreover, the anodic dissolution performance of job material is only characterized by its electrochemical features. This creates maskless EMM an alternative procedure for electrochemically hard to machine materials. Maskless EMM method with developed vertical cross flow method has been recommended involving microtexturing with higher symmetrical uniformity that are produced on stainless steel (SS304) surface. In this paper, maskless EMM method is a promising cost-efficient substitute for microtexturing containing rectangular micropatterns. The advanced setup has the developed machining cell, flow system and unique electrical connection unit. The machining unit has fixturing arrangements of electrodes, flow system, and electrical connection arrangement. Within the machining unit, the advanced flow scheme is a vertical cross flow system that aids in the fabrication of high-quality microtextured surface. One coated textured tool can produce many rectangular micropatterns with high quality. The effect of process parameters such as electrolyte concentration, machining time, and inter electrode gap (IEG) is evaluated on surface roughness (Ra), length overcut, machining depth and width overcut when fabricating micropatterns is investigated. The best process variables i.e., 50 μm IEG, 6 s machining time and 15 g/l electrolyte concentration manufacture good quality micropatterns.

Thermal modeling of laser surface micro-texturing: Investigation on effects of laser parameters on dimple-texture dimensions and aspect ratio

Micro-texturing on the rake/flank face of the tool to obtain higher service life has emerged as a promising area of research. Micro-texturing assists in reducing contact area, and in-turn lowering wear and frictional heat. There are several methods to obtain micro-textures on tools. However, the quality of micro-texture depends largely on the manufacturing method used. Laser-induced surface texturing has been found more accurate and a cost-effective solution to enhance tribological properties and efficiency of the cutting tool. Ultra-short laser pulses can produce controlled ablation and micro-textures. However, obtaining accurate and ultra-clean micro-textures on cutting tools depends on the type of laser source, set of laser process parameters, and physical and mechanical properties of the cutting tool material. Several ablation models have been developed to predict the optimized set of laser parameters. This paper illustrates the simulation of laser surface texturing with the help of the finite element model and its experimental validation with a fiber laser. Thermal modeling and 2-D laser ablation have been presented for tungsten carbide (WC) tool material. Dimple textures have been created on the side rake face with equidistant spacing. Laser parameters like frequency and power have been varied to investigate their effect on texture dimensions and aspect ratio. Sample experimental validation results have also been discussed presenting the degree of agreement to simulation results.

Evidences of an unknown debris avalanche event (

Azufral volcano is an active composite volcano located in SW Colombia, whose edifice is mostly formed by pyroclastic deposits and lava flows. Recent road works in the region, NE of the volcano, revealed unknown deposits, one of them related to a debris avalanche event. This deposit, herein named San Roque debris avalanche deposit, outcrops along a 13 km section in the Túquerres - Samaniego road. Using this long exposure, the deposit was studied through sedimentological, grain size, microtextural and mineralogical analyses. The deposit is massive, varicolored, poorly sorted, with a predominance of gravel and sand-sized clasts; it contains angular megaclasts some of them with jigsaw cracks, and exhibits injections, faults, and horsts-and-graben structures. Surface microtextures in some clasts evidence collisions and shearing interactions among them, while mineralogy evidences the collapsed material involved in the avalanche. Based on stratigraphic relationships, the collapse occurred between 0.58 Ma and ~18 ka. The San Roque debris avalanche deposit covers an area of 56.01 km2, has an estimated volume of 0.51 km3, an approximated runout of 11 km, and an apparent friction coefficient H/L of 0.109; these parameters are indicative of a large and very mobile flow. Its main transport mechanism responded to a dynamic disintegration of the larger clasts and a subsequent interaction by contact or collision (inertial-granular flow model), although some zones moved in a cushioned way remaining coherent over long distances (multi-shear model).

Geometry mediated friction reduction in Taylor-Couette flow

Periodic surface microtextures inspired by textures of shark denticles can alter the frictional response of a solid wall in flow. Using 3D-printed texture-covered rotors in a bespoke Taylor-Couette cell, the effect of the geometry of the textures and flow dynamics on the frictional torque measurements in Couette flow and Taylor vortex flow regimes are investigated. The changes in the torque measurements show direct dependence on the geometric features of the textures in both flow regimes, while the effect of the Reynolds number is only seen in the Taylor vortex flow.

A study on tribological properties of textured Co-Cr-Mo alloy for artificial hip joints

Co-Cr-Mo alloys are widely applied in the field of artificial hip joints. However, the service life of artificial hip joints is limited to 10–15 years due to its poor wear resistance. Thus, more and more patients have to replace the damaged artificial hip joints by revision surgery, which leaves the patient in pain. The surface micro-textures manufactured on the surfaces of artificial joints is an established method to improve its tribological behaviors such as coefficient of friction (COF), wear and scratches etc. However, most of researches about textured Co-Cr-Mo were limited to simple dimple shaped micro-textures. In this study, innovative patterned surface micro-textures, i.e., arrays of groove, hexagon and concentric circles were manufactured on Co-Cr-Mo alloy by laser surface texturing (LST). Results showed that the hardness and wettability of Co-Cr-Mo alloy were improved. The rotating friction tests were carried out under bovine serum albumin (BSA) lubricants by a ball-on-disc type friction machine. Frictional experiments showed that the tribological properties of concentric circles micro-textures were best. And, under the 10 N loading conditions, the COF and weight loss of PEEK ball of concentric circles sliding against concentric circles micro-textured sample with 20% density (C-20) were reduced by 49.22% and 52.3% compared to untextured sample, respectively. Meanwhile, the relationship between surface wettability and COF of the textured Co-Cr-Mo alloy was discussed and the mechanism for the effects of the surface micro-textures was revealed.