Surface Energy Of Coatings Research Articles

A comparative parametric investigation of thin diamond-like and polymer-like carbon coatings to explore carbonate anti-scaling performance

Five coatings, among diamond-like carbon (DLC), polymer-like carbon (PLC), and a polymer composite (PPS-based) were applied to a corrosion-resistant alloy substrate and characterized to determine major material parameters that influence carbonate scale deposition. A comparative parametric investigation was carried out using information on microstructures, mechanical properties, tribological characteristics, surface roughness, surface energy (hydrophobicity), and chemical properties. Both uncoated (bare metal) and coated substrates were repeatedly tested under static and hydrodynamic scaling conditions and analyzed for their scaling tendency, specifically mass gains, crystal morphology, adhesion strength. All selected coatings were confirmed to reduce scale deposition compared to the uncoated metal surfaces. The morphology and size of the calcium carbonate crystals (calcite) were primarily influenced by both the coating surface energy and the scaling conditions. The results also revealed a significant correlation between the coefficient of friction of DLCs and the scale deposition tendency, especially in hydrodynamic conditions. While the polymer composite coating outperformed other coatings due to its smallest scaling tendency, the DLC coatings offered a plurality of technical advantages, with several DLC coating parameters newly identified to predominantly influence carbonate scaling.

Evolution via friction of properties of DLC nanofilms on steel

The results of the diamond-like carbon (DLC) coatings surface investigation with thickness of 100, 300 and 500 nm, applied on hardened steel via laser ablation methods and pulse arc discharge are presented. Topography, roughness, adhesion forces and specific surface energy of coatings before and after tribotests were studied using atomic force microscopy (AFM). The changes in the elastic modulus E and microhardness H of the surface after dry sliding friction have been established by nanoindentation method (NI).

Fabrication of AlTiN coatings deposited on the ultrasonic rolling textured substrates for improving coatings adhesion strength

This paper aims to provide a method in improving the adhesion strength of the AlTiN coating/steel substrate system, which is considerable for tribological applications. The surface pre-treatment was implemented by the ultrasonic surface rolling technology to fabricate linear micro-textures with different spacing. Then the AlTiN coatings were subsequently deposited on the polished and textured AISI 1045 steel surfaces. The scratch tests and reciprocating sliding wear tests were conducted to assess the adhesion strength and the wear performance of different coatings. Results revealed that the adhesion of AlTiN coatings deposited on textured substrates with the micro-groove spacing of 150 μm was improved and the anti-adhesive wear property of AlTiN coating against GCr15 steel ball was greatly improved with the aid of ultrasonic rolling texturing pre-treatment than that of the polished one. The contribution of ultrasonic rolling texturing was primarily providing a mechanical locking and a large interfacial contact area, a narrowing difference between the interactions in coating surface energy, an ideal surface residual compressive stress, and a highly active substrate, thus enhancing the adhesion strength and anti-adhesive wear performance of the hard coating/soft substrate system.

Dynamic wetting behavior of droplets on the surface of porous materials with micro-airflow

<p indent=0mm>The dynamic wetting behavior characteristic of droplets is of significant importance in various industrial applications and high technologies, such as surface self-cleaning, surface drag reduction, anti-frosting, and droplet directional transportation. The modifications of coating surface energy and micro/nano structures on substrate surfaces are the conventional and indirect ways to manipulate the droplet dynamic wetting behavior. At present, many direct and external incentive ways, like substrate vibration, electrowetting and additional magnetic field, also have been proposed to control the droplet dynamic wetting behavior. In the present study, inspired from the phenomenon of droplet floating in the air without gravity, an innovative manipulation method had been proposed, which utilized the additional micro-airflow field as a momentum field to control the force distribution and wetting characteristic of droplets. The core idea of this innovative manipulation method was similar as the Leidenfrost phenomenon, which used the gas buoyancy to counter the droplet gravity effect. A porous substrate sintered by copper particles was used as the experimental sample, a micro-airflow field was located at the down side of porous substrate, and a droplet was wetted on the up side of porous substrate. The magnitude of upright momentum force could be changed by adjusting the pressure of micro-airflow field. Under different pressure of micro-airflow field, the dynamic wetting behaviors of droplets on porous substrate were visualized, and the change regulations of dynamic wetting parameters as a function of wetting time were analyzed. According to the results, three different dynamic wetting modes of droplets on the surface of porous materials with micro-airflow were identified, namely, intact infiltration mode, broken infiltration mode and non-infiltration mode. In the intact infiltration mode and broken infiltration mode, the droplets were finally in the state of complete infiltration, while in the non-infiltration mode, the droplets always maintained the suspension state similar as the super-hydrophobic wetting state. When the droplet was in the intact infiltration mode on the surface of the porous sample, the corresponding dynamic wetting process was simultaneously affected by gravity, surface tension, lifting force, adhesion force and capillary force. In this mode, the apparent contact angle and volume of droplet decreased exponentially at the initial stage during the dynamic wetting process. At the following stage, the decreasing amplitude of two dynamic wetting parameters became slower and presented a linear declining trend. The wetting area at the bottom of droplet rapidly increased to the maximum value at the initial stage, and then decreased slowly. However, when the ratio of droplet height to bottom diameter was less than 0.03, the decreasing amplitude of bottom wetting area increased rapidly, and the droplet would quickly approach to the state of complete infiltration. Besides, the maximum wetting area at the bottom of droplet increased with the increase of pressure difference driven by micro-airflow. The larger the pressure difference was, the smaller the changing range of apparent contact angle and volume of droplet in the same wetting time was, but the longer the whole dynamic wetting period was.

Experimental measurement and Numerical Simulation of Particle Deposition on super–hydrophobic surface

Airborne dust deposition on a large number of energy devices would cause serious efficiency and lifetime reduction, such as solar photovoltaic panels, heat exchanger surfaces and fan blades. Mechanicalor manual cleaning using water is still the main method of mitigating dust deposition damage on theserelated energy equipment, which is commonly expensive and frequent. As a kind of self-cleaningmaterial,super–hydrophobic coating may become a new effective way to mitigating the dust deposition issue. Super–hydrophobic coatings with low surface energy and unique micro-nano secondary structure can significantly reduce dust deposition rate. However, mechanism of dust deposition on super-hydrophobic surfaces remains unclear. Thus it is difficult to develop high performance self-cleaning coating. This paper aims to investigate dust deposition behaviors and mechanisms on super-hydrophobic surface by experimental measurement and numerical simulation. Lattice Boltzmann Method-Discrete Particle Method (LBM–DPM) will be developed to predict dust particle deposition process including settling, collision adhesion and rebound behaviors. The mechanisms and interactions between coating surface energy, particle characteristics, particle incident velocity and particle adhesion or rebound behavior will be studied carefully. The findings and results may be useful to guide the development of high performance self-cleaning super– hydrophobic coating.

A comparative study on surface morphology and electrochemical behaviour of hydroxyapatite-calcium hydrogen phosphate composite coating synthesized in-situ through electro chemical process under various deposition conditions

Coating surface energy and morphology play an essential role to decide on cell attachment and subsequent faster-uniform-interconnected cell growth over the coated orthopaedic metallic implant surfaces. It has been observed that during the process of electro-chemical deposition, the in-situ formed bond energy and deposited morphology greatly depend on few controllable process parameters namely reaction over potential, pulsed time and cathode current density. Keeping in view of this, this work aimed to study and compare the surface morphology and electrochemical corrosion resistance behaviour with respect to various depositions kinetics and nucleation mechanism achieved with the help of variable current density, voltage and time.SEM micrographs of the electrodeposited surfaces depict the formations of altogether different structures of coating surfaces, varying from surface parallel flakes to concentric bars along with sub-micron dots and nano pores on its surfaces. It is observed that with increasing nucleation rate vis-à-vis increasing deposition potential, the presence of calcium orthophosphate phase is decreased along with increased rate of hydroxyapatite phase in the coating. The presence of various phosphate bond structures is evident from IR spectroscope, which seems to be accountable for the formation of various morphologies along with the varying structure of hydroxyapatite. The electrochemical impedance spectroscopy study under contact with simulated body fluid (SBF) compared their performance regarding corrosion resistance capability of coating surface after implantation in the human body.

Improvement of Surface Properties of Micro-Mold via SAM Coating for Fabrication of Microfluidic Device

N-octadecyltrichlorosilane [OTS, CH3(CH2)17SiCl3] self-assembled monolayer (SAM) coatings were deposited on Si micromolds by dip-coating. Chemical composition, surface roughness, friction coefficient, thermal stability and surface energy of coatings were investigated. OTS coated silicon (Si) micromolds were used to fabricate PMMA microfluidic devices by hot-embossed process. All OTS coatings were thermally stable up to 180 °C, which is higher than hot-embossing temperature of PMMA. OTS coated micromolds had low friction coefficient, adhesion and superior molding efficiency, which improved lifetime of a uncoated Si micromold from 3 to 27 times.

New fluorine-containing alkoxysilane with branched cyclic substituent for preparing protective coatings with low refractive index

The search for new protective antireflection coat� ings for silicon solar cells, luminescent solar concen� trators, optical lenses, optical integrated circuit ele� ments, and laser crystals are currently in progress. The materials of such a kind should have a relatively low refractive index (less than 1.4), be capable of self� cleaning, which is characterized by the low surface energy of coatings. These properties allow antireflec� tion coatings to enhance the energy efficiency of opti� cal devices. They should also be sufficiently strong to function as protective coatings. Alkoxysilanes that are used at present as components for making these coatings contain organofluorine sub� stituents with a large relative content of fluorine atoms: R F = -CH 2 CH 2 (CF 2 ) n -CF 3 , where n = 1-8, or -CF(CF3)O(-CF2CF(CF3)O)n-C3F7, where n = 0-50 (1-4). At the same time, it is known from the lit� erature that the coatings of organic polymers obtained on the basis of monomers with branched or cyclic sub� stituents provide a possibility to reach the lowest values

Correlation between sol–gel reactivity and wettability of silica films deposited on stainless steel

Sol–gel silica films were deposited on 316L and 409 stainless steel substrates in order to investigate their wettability properties. These films were deposited by dip-coating varying some parameters of the sol–gel process, including the acid used in the synthesis, its concentration, and the heat treatment temperature. Water and oil contact angles were measured on the surfaces and discussed regarding the physico-chemical and morphological properties of the prepared films. The findings shown in this work allow correlating the wettability behavior of silica coatings with the sol–gel reactivity of sols prepared using various amounts of nitric acid. It was observed that the more reactive the silica sol, the more hydrophilic and oleophilic the prepared coating. The presence in the films of alkoxy residues due to an incomplete condensation reaction could decrease both the polar and dispersive components of the coating surface energy, respectively responsible for water and oil wetting.

Influence of the chemical structure of fluorinated radicals in acrylated derivatives of Boltorn™ H20 hyperbranched polyesterpolyol on the surface energy of coatings prepared from UV-curable powder formulations

The surface and physicomechanical properties of polymeric coatings prepared from UV-curable powder formulations based on oligoester dimethacrylates were studied in relation to the chemical structure of a series of synthesized fluorinated modifiers of new generation, based on Boltorn™ H20 hyperbranched polyesterpolyol. The surface energy of the coatings depends on the chemical structure of the derivatives obtained. The fluorinated derivatives of Boltorn™ H20 are effective in low concentrations, 0.5–1.0 wt %.

Evaluation of commercially available materials to mitigate insect residue adhesion on wing leading edge surfaces

Surface contamination from insect strikes on aircraft wing leading edges can induce localized boundary layer transition from laminar to turbulent flow, resulting in increased aerodynamic drag and reduced fuel efficiency. As aviation fuel costs continue to climb, strategies to reduce fuel burn using laminar flow have led to renewed interest in surface modifications to minimize the effects of insect residue adhesion on aircraft wings. Under NASA's Environmentally Responsible Aviation Program, insect residue adhesion-resistant coatings are being studied as an approach for drag reduction. A series of aluminum alloy test surfaces were coated with commercially available materials and characterized using contact angle goniometry. The surfaces were subsequently subjected to controlled impact of crickets using a custom-built pneumatic insect delivery device. Impact events were recorded and analyzed using high-speed digital photography and characterized using optical surface profilometry. Residue adhesion was observed on all of the coatings investigated. The cricket impact event was related to liquid droplets impacting surfaces at high velocities and was analyzed as such. Coating surface energy was determined to influence residue adhesion.

Anti-Sticking Properties of PVD CrWN&lt;sub&gt;x&lt;/sub&gt;, CrO&lt;sub&gt;x&lt;/sub&gt; and ZrO&lt;sub&gt;x&lt;/sub&gt; Coatings on Medical Electrode Application

The side effect of electrosurgery includes tissue charring, smoke generation and the adhesion of tissue to electrodes. These effects prolong surgery and interfere with effective coagulation. In this paper, CrWNx, CrOx and ZrOx coating were prepared by an unbalanced magnetron sputtering. The microstructure of films was characterized using XRD, XPS, TEM and AFM. The hydrophobicity and surface energy of coatings were calculated by contact angle measurement and Wu harmonic mean approach. Anti-sticking in vitro test was performed by monopolar electrosurgery using pork liver tissue. The hardness of CrWNx , ZrOx and CrOx coatings were 44 GPa, 26.3 GPa and 20.7 GPa, respectively. The CrOx coating had the lowest surface energy 33.5 mN/m and the highest contact angle of water as high as 103°. The high surface O-H bonds density of CrOx coating and N-H bonds density of CrWNx coating could explain about their lower polar component of surface energy. All the three PVD coatings remarkably reduced the quantity of tissue adhesion on the electrode from about 2 times (ZrOx and CrWNx coatings) to 4.88 times (CrOx coating) than uncoated SUS304 electrode.

Effect of Titanium Oxide Nanoparticle Incorporation into nm Thick Coatings Deposited Using an Atmospheric Pressure Plasma

This study reports on the use of an atmospheric plasma technique to incorporate metal oxide nanoparticles into nm thick siloxane coatings. Titanium dioxide (TiO2) particles with diameters of 30-80 nm, were mixed with a number of different siloxanes-polydimethylsiloxane, hexamethyldisiloxane and tetraethylorthosilicate (TEOS). The TiO2/TEOS mixture was found to give the most stable suspension, possibly due to the higher surface tension of TEOS compared with the other siloxanes. TiO2/TEOS mixtures with 2 to 10% by weight of the metal oxide were prepared and were then nebulised into a helium/oxygen atmospheric plasma. Polyethylene terepthalate (PET) and silicon wafer substrates were passed through this plasma using a reel-to-reel substrate manipulation system. SEM combined with EDX was used to examine the distribution of the metal oxide particles in the resultant coatings. The TEOS coating thickness without TiO2 addition was 9 nm. The composite coating consisted of a relatively homogeneous distribution of small agglomerates of the TiO2 nanoparticles in TEOS. A linear increase in the titanium surface concentration was observed with increase in the quantity of TiO2 added into the siloxane precursor. The chemical functionality of the siloxane coating was examined using FTIR spectroscopy and no significant spectrum differences was observed with the incorporation of the different concentrations of TiO2 into the polymer. There were also no changes observed in coating surface energy with TiO2 incorporation. Coating morphology was examined using optical profilometry and surface roughness (Ra) values increased from typical values of 0.8 nm for the TEOS coating to 4.1 nm for the TiO2/TEOS coating. The adhesion of the deposited coatings was compared using fragmentation tests. These were carried out through uniaxial tensile loading. The coating cracking pattern after applied strain of 20% was not observed to change significantly with the addition of TiO2 into the siloxane.

Highly Liquid-Repellent, Large-Area, Nanostructured Poly(vinylidene fluoride)/Poly(ethyl 2-cyanoacrylate) Composite Coatings: Particle Filler Effects

Super-repellent nanostructured composite coatings applied over large areas by spray and subsequent thermal treatment are reported. Solution blending of poly(vinylidene fluoride) and poly(ethyl 2-cyanoacrylate) is implemented to formulate filler particle dispersions used to apply these coatings. The wettability of these coatings is manipulated using hydrophobic poly(tetrafluoroethylene) and hydrophilic zinc oxide particle fillers or their combination. The resulting coatings feature contact angles up to 164 degrees for water and 154 degrees for a water and isopropyl alcohol mixture (9:1 weight ratio; surface tension approximately 40 mN/m). A self-cleaning ability is revealed by droplet roll-off angles below 10 degrees . The results show that the fillers affect the coating surface energy and surface roughness, in turn influencing the wettability of the coatings.

Influence of reducers on nanostructure and surface energy of silver coatings and bacterial adhesion

Abstract The high incidence of infections caused by the use of implanted biomedical devices has a severe impact on human health and health care costs. Many studies suggest a strong antimicrobial activity of silver-coated medical devices. However no studies have been reported on the effect of surface energy of silver coatings on bacterial adhesion. In this paper, 4 types of silver coatings with various surface energies were prepared on stainless steel plates using AgNO 3 based electroless plating solutions with four different reducing agents, formaldehyde, hydrazine, glucose and potassium sodium tartrate tetrahydrate, respectively. The morphology and surface energy of the silver coatings were characterized with an Atomic Force Microscope and a Dataphysics OCA-20 contact angle analyzer, respectively. The anti-bacterial performance of the silver coatings was evaluated with Pseudomonas aeruginosa PA01, which frequently causes medical device-associated infections. The experimental results showed that bacterial adhesion decreased with the total surface energy of the coatings decreasing, but decreased with the electron donor component increasing. All the silver coatings performed much better than stainless steel in reducing bacterial attachment. The extended DLVO theory was used to explain bacterial adhesion behavior.

Deposition of Biodegradable Polycaprolactone Coatings Using an In‐line Atmospheric Pressure Plasma System

AbstractPolycaprolactone (PCL) is a biodegradable and bioresorbable polymer with applications ranging from use in packaging to medical sutures. In this study, the use of an atmospheric pressure plasma to deposit plasma polymerised PCL (P‐PCL) coatings from a PCL diol precursor is evaluated. Fourier transform infrared spectroscopy demonstrated the retention of PCL functional groups in the deposited coating. Changes in coating surface energy were monitored with time after deposition using the contact angle technique. The rate of degradation of 500 nm thick P‐PCL coatings was assessed after immersion in a phosphate‐buffered saline (PBS) solution at 37 °C. It was observed that slower rates of P‐PCL coating degradation were obtained for coatings deposited at higher applied powers and lower precursor flow rates.

Increased endothelial cell adhesion on plasma modified nanostructured polymeric and metallic surfaces for vascular stent applications

Techniques to regenerate the vasculature have risen considerably over the last few decades due to the increased clinical diagnosis of artery narrowing and blood vessel blockage. Although initially re-establishing blood flow, current small diameter vascular regenerative materials often eventually cause thrombosis and restenosis due to a lack of initial endothelial cell coverage on such materials. The objective of this in vitro study was to evaluate commonly used vascular materials (specifically, polyethylene terephthalate, polytetrafluoroethylene, polyvinyl chloride, polyurethane, nylon, commercially pure titanium, and a titanium alloy (Ti6Al4V)) modified using an ionic plasma deposition (IPD) process and a nitrogen ion implantation plasma deposition (NIIPD) process. Such surface modifications have been previously shown to create nanostructured surface features which mimic the natural nanostructured surface features of blood vessels. The modified and unmodified surfaces were characterized by scanning electron microscopy, atomic force microscopy and surface energy measurements. Furthermore, in vitro endothelial cell adhesion tests (a key first step for vascular material endothelialization) demonstrated increased endothelial cell adhesion on many modified (with IPD and NIIPD + IPD) compared to unmodified samples. In general, endothelial cell adhesion increased with nanoroughness and surface energy but demonstrated a decreased endothelial cell adhesion trend after an optimal coating surface energy value was reached. Thus, results from this study provided materials and a versatile surface modification process that can potentially increase endothelialization faster than current unmodified (conventional) polymer and metallic vascular materials.

Evaluation of the mechanical behaviour of nanometre-thick coatings deposited using an atmospheric pressure plasma system

This study evaluated the use of pin-on-disc wear testing as a technique to examine the mechanical behaviour of nanometre thick plasma deposited coatings. The coatings were deposited onto polyethylene terephthalate and silicon wafer substrates by directly injecting an aerosol of siloxane liquid precursors into a helium/oxygen atmospheric pressure plasma. The siloxane precursors examined were hexamethyldisiloxane, polydimethylsiloxane and tetramethyldisiloxane. The mechanical performance of 21 (± 3) nm thick coatings was compared using a pin-on-disc wear test technique and fragmentation tests. An increase in the level of precursor plasma exposure was found to be associated with an increase in coating surface energy and a reduction in coating roughness and resulted in enhanced wear resistance. Fragmentation tests revealed a transition from ductile failure to brittle failure as the level of plasma exposure increased. This correlated with the reduction in coating wear rates. Wear track depth and proximity to the coating/substrate interface were both found to influence the rate or wear. A simple correlation between wear rate and applied force is presented as a method for comparing coating performance using pin-on-disc wear testing.

Synthesis and antimicrobial activity of quaternary ammonium-functionalized POSS (Q-POSS) and polysiloxane coatings containing Q-POSS

An array of quaternary ammonium-functionalized POSS (Q-POSS) compounds were synthesized and their antimicrobial properties toward the Gram-negative bacterium, Escherichia coli, and the Gram-positive bacterium, Staphylococcus aureus, determined in aqueous solution. Using Q-POSS compositions that exhibited broad spectrum antimicrobial activity in solution, the utility of the Q-POSS compounds as an antimicrobial additive for polysiloxane coatings was determined. The results of the investigation showed that Q-POSSs possessing a relatively low extent of quaternization and longer alkyl chain lengths provided the highest antimicrobial activity in solution. For polysiloxane coatings containing Q-POSS molecules as an antimicrobial additive, coating surface energy, surface morphology, and antimicrobial properties were found to be strongly dependent on Q-POSS composition. Coatings based on Q-POSSs possessing the lowest extent of quaternization displayed antimicrobial activity while analogous coatings produced using Q-POSSs possessing the highest extent of quaternization showed no antimicrobial activity. The lack of antimicrobial activity exhibited by coatings possessing Q-POSSs with a relatively high extent of quaternization was attributed to agglomeration of Q-POSS molecules through the formation of intermolecular interactions involving the quaternary ammonium moieties. Agglomeration would be expected to reduce diffusivity and inhibit interaction of the Q-POSS molecules with microbial cells.

Relationship between surface chemistry and surface energy of different shape pigment blend coatings

The influence of pigment shapes and pigment blends on the surface energy was investigated and compared with the surface chemistry of pigmented latex coatings. The coatings were made of different volume ratios of two pigments: plate-like kaolin clay pigment and prismatic precipitated calcium carbonate (PCC) pigment. These were mixed together with carboxylated styrene–butadiene–acrylonitrile latex (SBA), and applied over nonabsorbent substrates as well as absorbent substrates. The composition of the surface of the coatings was investigated by X-ray photoelectron spectroscopy (XPS). Two approaches were used to estimate the total surface energy and the components of the coatings: a conventional approach—“the Kaelble approach”—and a more modern approach—“the van Oss approach.” Pigment blends with different shapes and increments caused a change in the surface chemistry and the surface energy of the latex coatings. As the prismatic PCC pigment particles increased in the kaolin/SBA coating system, the SBA latex content at the coating surface increased and the total surface energy of the coating decreased. This is valid for both nonabsorbent as well as absorbent substrates. It was found that there was a strong correlation between the surface energy and the surface composition. The surface energy of the coatings estimated by the Van Oss approach was always lower than that estimated by the Kaelble approach. Colloidal interactions between pigment–pigment and/or pigment–binder were thought to play an essential role in determining the final coating surface energy and its components. Changes in the surface latex content and the surface energy due to the different pigment blends investigated were found to fit straight-line equations.