Surface Modification Of Various Materials Research Articles

Novel Application of Diffuse Coplanar Surface Barrier Discharge: Fast, Efficient and Controlled Surface Functionalization

Plasma chemistry is currently an interesting approach to surface modification of materials. In general plasma treatment is a fast process, affecting only the units of nanometers of the surface layer without altering the bulk properties. and has many potential benefits such as minimal waste and control of surface functionality. It represents a dry and environmentally friendly process that can achieve comparable results to wet chemical treatment. The research and development of plasma sources, mainly operating at atmospheric pressure, has been the main activity of the centre CEPLANT, Brno, Czech Republic for several decades. Our development is generally aimed at fast, efficient, and low-cost plasma treatments, easily implementable in industry, and flexibly responds to industrial requirements and current trends.One of our most versatile plasma source, the so-called Diffuse Coplanar Surface Barrier Discharge (DCSBD) has been developed for in-line surface modification of various materials, primarily for fabric materials. DCSBD produces a 0.3 mm thin layer of non-equilibrium, cold macroscopically diffuse plasma at atmospheric pressure (Fig. 1) in any working gas, including oxygen, hydrogen, or even water vapors. Due to its strongly non-equilibrium nature, operation at atmospheric pressure, and low temperatures, the DCSBD represents a unique plasma source suitable for surface modification of low-cost and temperature-sensitive materials [1-4].Unique results have been achieved in research on the practical application of flexible conductive layers on glass, with a focus on the deposition of transparent organic polymer coatings on ultra-thin flexible glass (UTFG). We have developed and optimized efficient and fast dry non-contact cleaning and activation of fragile and lightweight conductive glasses using DCSBD. The high-speed plasma treatment corresponding to the exposure times in the order of units of seconds leads to a synergistic balance between the efficient removal of impurities (carbohydrates) adsorbed on the UTFG surface and the formation of oxygen-based functional groups. Subsequent PEDOT:PSS-based coatings sprayed on plasma-treated UTFG surfaces achieve significantly higher electrical conductivity compared to the standard liquid-purified samples. This method combined with the unique properties of UTFG provides prospective results applicable in microelectronics, and optoelectronic devices like sensors or displays.In the field of composite materials research, we have discovered that plasma treatment of reinforcing fibers leads to improvement of the mechanical properties of laminated fiber-reinforced polymer (FRP) composites. Efficient functionalization of various commonly used reinforcement fibers (flax, aramid and glass) in atmospheric low-temperature DCSBD increases the interfacial adhesion at the fiber-matrix interface, which has a provable positive effect on the resulting mechanical properties.DCSBD plasma can also be utilized for the initiation of reducing chemical reactions. We have developed a simple and fast chemical-free fabrication method of 2D and 3D reduced graphene oxide (rGO) structures using an electrical plasma-triggered reduction & exfoliation of 3D porous graphene oxide (GO) aerogel-like materials [4] and also 2D GO paper-like films starting at temperatures not higher than 100 oC [5]. The plasma triggered the self-propagating reduction & exfoliation fast modification of GO into rGO, while the rGO structures retained their original shape without abrupt disintegration. We observed an approximately 105 fold decrease of the rGO paper resistivity compared to the unmodified GO paper. This novel method opens new opportunities for the production of conductive rGO and rGO-based composites for modern industrial applications.Innovative results were achieved in the fabrication of ZnO nanofibers by a novel calcination approach assisted by DCSBD. Exposition of the polyvinyl pyrrolidone/zinc acetate fibers to DCSBD before the thermal processing leads to the gentle low-temperature removal of organic material. Plasma pre-treated nanofibers are characterized by a smaller diameter and retain a defined fibrous structure during heat treatment. Moreover, the ZnO nanofibers prepared by a combination of plasma and heat treatment exhibited considerably higher photodegradation activity increasing with decreasing calcination temperature [6]. The low-temperature and high oxidation potential of plasma makes plasma-assisted calcination of the inorganic nanofibers an attractive alternative to conventional thermal annealing with potential application in optoelectronics or biosensors.The mentioned applications are only a small fragment of available cases of utilization of the DCSBD, which is now commonly established and applied in the field of surface modification of various materials (glass, metals, non-woven fabrics, polymers, paper, nanofibres) and biomaterials (seeds, grains, wood, natural leather).[1] M. Černák et al., Plasma Physics and Controlled Fusion 53 (2011) 1-8[2] R. Talviste et al., Surface and Interface 16 (2019) 2468-0230[3] T. Morávek et al., Open Chemistry 13 (2015) 236-244[4] R. Krumpolec et al., Flatchem 35 (2022)[5] F. Zelenák , Carbon N. Y. 215 (2023) 118436[6] V. Medvecká et al., Applied Surface Science, 581 (2022) 152384 Figure 1

Threshold of Surface Initiator Concentration for Polymer Brush Growth by Surface-Initiated Atom Transfer Radical Polymerization.

The surface modification of various materials by grafting functional molecules has attracted much attention from fundamental research to practical applications because of its ability to impart various physical and chemical properties to the surfaces. One promising approach is the use of polymer brushes synthesized by atom transfer radical polymerization (ATRP) from surface-tethered initiators (SIs). In this study, for the purpose of controlling the grafting amounts/densities of polymer brushes, we developed a facile method to precisely regulate SI concentrations of SI layers (SILs) by serial dilution based on a sol-gel method. By simply mixing organosilanes terminated with and without an initiator group ((p-chloromethyl) phenyltrimethoxysilane (CMPTMS) and phenyltrimethoxysilane (PTMS), respectively) with tetraethoxysilane (TEOS), SI concentrations of SILs could be arbitrarily tuned precisely by varying dilution factors of (CMPTMS + PTMS)/CMPTMS (DFs, 1-107). The resulting SILs prepared at different DFs were highly smooth and transparent. X-ray photoelectron spectroscopy (XPS) also confirmed that the SIs were homogeneously distributed at the topmost surface of the SILs and their concentrations were proven to be accurately and precisely controlled from high to extremely low, comparable to theoretical values. Subsequent SI-ATRP in air ("paint-on" SI-ATRP) of two different types of monomers (hydrophobic/nonionic (2,3,4,5,6-pentafluorostyrene) and hydrophilic/ionic (sodium 4-styrenesulfonate)) demonstrated that polymer brushes with different grafting amounts/densities were successfully grafted only from SILs with DFs of 1-104 (theoretical SI concentrations: 3.9 × 10-4 ∼ 3.5 units/nm2), while at DFs of 105 and above (theoretical SI concentrations: <3.9 × 10-5 units/nm2), no sign of polymer brush growth was confirmed by thickness, XPS, and water contact angle data. Therefore, we are the first to gather evidence that the approximate threshold of SI concentration required for "paint-on" SI-ATRP might be on the order of 10-4 ∼ 10-5 units/nm2.

Dynamic Characteristics Determination of the Radiation Power Control System for the Industrial CO2 Laser Excited by а Nonself-Sustained Glow Discharge

In the article, an automatic system for radiation power control of lasers excited by а nonself-sustained glow discharge is studied using industrial lasers of the Lantan series as an example. They are designed for cutting, welding and surface modification of various materials as part of laser machines. The power of laser radiation is one of the most important parameters of a laser that determines its technological capabilities. The radiation power is controlled by changing the ionization pulses frequency of high voltage pulses with duration of 100 ns, given with a frequency of 1-5 kHz. The step response of the laser is experimentally obtained. Laser radiation is fed to a thermoelectric mirror-detector with thermo-EMF anisotropy, which measures its power. After preliminary amplification, the differential signal from the mirror-detector is recorded by a digital oscilloscope. A delay in the change in the laser radiation power relative to the control signal was established. The delay is 1487 ms that is explained by the fact that several ionization pulses are required for the initial exciting of the gas volume before the start of radiation generation. The initial section of the step response and damped oscillations are explained by the presence of a protective choke in the main discharge source connection circuit. The choke slows down the rise in current during the short circuit of discharge, allowing circuit breakers to turn off the power supply. To simulate the transient process, the step response of the oscillating circuit is used. The original signal was filtered to remove noise that does not al[1]low determining the parameters of the step response. To determine the spectrum of the step response, fast Fourier transform is carried out, frequencies introducing noise were cut out, and the inverse fast Fourier transform is performed. According to the step response obtained after filtering, the parameters of the modeling step response are determined. Based on the parameters of the step response, the laser transfer function is calculated. It makes possible to proceed to the calculation of the optimal radiation power controller, which ensures the best quality of the transient process.

Dopamine‐assisted wet spinning and mechanical reinforcement of graphene oxide fibers

AbstractBioinspired polydopamine coatings have been widely used for the surface modification of various materials because of their strong adhesion, facile application method, and functionalization ability. However, dopamine has not been previously utilized as a coagulation agent for graphene oxide fibers (GOFs). In this study, we performed the wet spinning of GOFs using dopamine as a coagulation agent (denoted as DA‐GOFs) and successive polymerization of dopamine inside the fibers. The polymerized DA‐GOFs (pDA‐GOFs) exhibited enhanced mechanical properties with a 97% higher tensile strength than that of the fibers coagulated with CaCl2. The described dopamine‐assisted wet spinning and polymerization process were simple but effective method for preparing mechanically strong fibers, which can be potentially employed in flexible and wearable electronic applications.

Application of diffuse coplanar surface barrier plasma discharge to polymeric materials

AbstractThe KPR 200 mm plasma reactor is a device designed for the surface modification of various materials. Such a modification occurs by applying a unique type of plasma – plasma generated on a ceramic dielectric. The ceramic dielectric is a durable system with which it is possible to continuously modify the surfaces of materials with such a plasma. The advantage of applying this unique type of plasma is that the modification of the materials occurs at room temperature and atmosphere. However, it is necessary to monitor and observe certain parameters, for example: the selected power, the exposure time of the surfaces of the modified materials, and the distance of the surface from the ceramic dielectric itself. Therefore, in the present paper, the effect of diffuse coplanar surface barrier discharge (DCSBD) plasma discharge on selected polymeric materials was investigated. Plasma impact assessment was also performed using image analysis, that could provide relevant information in the process of plasma‐chemical modification. Changes in the surfaces of the investigated thin polyvynil chloride material, before and after exposure to plasma discharge, were also observed (changes in contact angle, atomic force microscopy).

Effects of ultraviolet irradiation on beta-tricalcium phosphate as a bone graft substitute.

Surface modification of various materials using ultraviolet (UV) irradiation improves their wettability. The purpose of this study was to investigate the wettability of a β-tricalcium phosphate (TCP) surface and the composition changes and bioactivity of β-TCP after UV irradiation. We applied 172nm UV treatment to a β-TCP surface and measured the contact angle before and after UV irradiation. Energy-dispersive X-ray and Fourier transform infrared spectroscopy examinations were performed on the β-TCP disk with or without UV treatment. In an adhesion test of bone marrow cells using β-TCP disks with and without UV irradiation, cell attachment was measured 10, 30, 50, and 70h after β-TCP insertion. UV-irradiated β-TCP osteogenesis and absorption of bone substitutes were evaluated using hematoxylin and eosin and tartrate-resistant acid phosphatase (TRAP) staining in a rabbit sinus model. The contact angle on the TCP surface decreased from 70° to 10° owing to UV irradiation. Conversely, UV irradiation did not change the composition of carbon, oxygen, and phosphorus. In the cell adhesion test, UV-irradiated β-TCP significantly increased cell adhesion compared with UV-unirradiated β-TCP after 10 to 30h of culture. In the rabbit sinus model, TRAP staining showed that UV-irradiated β-TCP significantly increased the number of TRAP-positive cells compared with unirradiated β-TCP granules in the central part of β-TCP. Our results indicate that the UV irradiation of β-TCP improves its clinical utility for surgical bone augmentation in the oral and maxillofacial region.

Preparing potato starch nanocrystals assisted by dielectric barrier discharge plasma and its multiscale structure, physicochemical and rheological properties

Non-thermal plasma has increasingly been used for surface modification of various materials as a novel green technology. In this study, we prepared potato starch nanocrystals (SNCs) assisted by dielectric barrier discharge plasma technology and investigated its multiscale structure, physicochemical properties and rheology. Plasma treatment did not change the morphology and crystalline pattern of SNCs but reduced the crystallinity. The amylose content, swelling power, gelatinization temperature, and apparent viscosity of SNCs decreased after the plasma process by depolymerizing the amylopectin branch chains and degrading SNCs molecules. Besides, plasma increased the rapidly digestible starch and resistant starch content. Changes in rheological properties of plasma treated SNCs suggested that the plasma process increased the flowing capacity. The effective structural and functional changes of plasma treated SNCs confirm that plasma technology has great potential for modification of SNCs.

Effect of Under Surface Cooling in Friction Stir Processing of Aluminum Alloy 6082: A Review

Friction Stir processing (FSP) is a new technique of Friction Welding. This technology is used in automobile and aerospace industries because it reduces the defects produces by conventional fusion welding techniques. Now in days Friction Stir Processing is introduced as a new process for microstructural surface modification of various materials or for changing the properties of metal by producing intense localized plastic deformation in the material. The main principle of this technique is based on FSW. The tool pin plunged in the plate and plastic deformation is produced by heat is generated due to rotational motion of too. Cooling of specimen during FSP is also a new research to improve the mechanical properties of base metal. The present investigation shows the effect of cooling of specimen on mechanical properties during FSP. It has been observed from this review paper that the effect of cooling of specimen greatly affected the mechanical properties of metal as compared to dry conditions. It has been observed that the values of yield strength and micro hardness increases in cooled region of welded joint.

A Two‐Stage Kinetics Model for Polydopamine Layer Growth

AbstractSince its introduction, polydopamine coating has played a significant role in the surface modification of various materials, yet a persistent gap exists in understanding its polymerization process. Applying Gompertz' equation, this paper proposes a kinetics model based on the data reported in the literature and obtained at different temperatures and on various substrates. Along with a statistically good regression, the selection of Gompertz' equation is supported by the observed trend in the reported data: regardless of the substrate and the system temperature, the point where 37–40% of the final film thickness is reached precisely coincides with the inflection point of the Gompertz' curve. The proposed kinetics model suggests a two‐stage polymerization process, with the maximum growth rate occurring at 37–40% of the final film thickness. The maximum growth rate increases with temperature. However, at higher temperatures, the system needs more time to reach the maximum growth rate.

SURFACE CHARACTERIZATION OF TITANIUM ALLOYS FOR NITROGEN ION IMPLANTATION

Ion implantation is one of the modern methods of the surface modification of various materials. Industrially used Ti–6Al–4V titanium alloy and commercially pure Ti grade 2 were characterized using the X–ray diffraction methods. Texture of the material and dependence of the microstructural properties on the method of the surface modification were examined in order to determine suitable conditions for application of the process in the industry. The structure of Ti–6Al–4V alloy before and after the nitrogen ion implantation process is discussed and observed surface hardening is explained.

Nano titanium dioxide/PAoQ-coated polybenzoxazol fibers for enhancing anti-ultraviolet performance

Inspired by the composition of adhesive in mussels, polydopamine has been widely used for surface modification of various materials. In accord with the formation mechanism of polydopamine coating, the catechol containing two o-phenol groups and triethylenetetramine (TETA) containing two primary amine groups were used to copolymerize and deposit a polyamine-o-benzoquinone polymers (PAoQ) film on the polybenzoxazol (PBO) fibers. In order to enhance the anti-ultraviolet performance of PBO fibers, rutile nano titanium dioxide particles (TiO2) were also decorated on the PBO fibers by the layer-by-layer self-assembling technique. The optimum modification conditions were obtained by orthogonal method. Morphological structure and chemical composition of the modified fibers were studied using scanning electron microscopy with energy dispersive X-ray, and Fourier transform infrared spectroscopy. The UV-aging test results showed that under 144 h UV-light exposure at 340 nm, the modified PBO fibers’ strength retention was promoted to 80.8%, 34.4% higher than that of the original PBO fiber. The thermal stability of the modified fibers had no obvious change after modification with TiO2/PAoQ, while their carbon residue rate increased slightly.

Promising Soft Coating Material for Protection of Foldable Substrates Exposed to Corrosive Environment

Surface modification of various materials is important to impart the desired surface characteristics to them for their improved performance for industrial as well as domestic use. Preparation of suitable coating materials to enhance the efficacy of the substrates of engineering importance is necessary for offering wide spectrum of applications. Performance evaluation of the coating material for foldable materials is indeed important to justify its compatibility with the substrates. Here we demonstrate the potential of the soft polymeric coating especially for the foldable material to impart resistance towards highly corrosive environment. Polydimethylsiloxane (PDMS) was used with the cross-linking agent to prepare the coating material. The experiments were performed to explore the effects of the polymeric coating on the foldable aluminium foils exposed to corrosive environment for wide pH range and long exposure time. The experiments with the contact angle measurements revealed the potential of flexible PDMS coatings for the foldable materials to enhance their surface characteristics. The durability of the polymeric coating was also justified with the surface morphology demonstrated by the micrographs obtained using scanning electron microscope equipped with an energy dispersive X-ray spectroscopy detector. The findings of the present work confirm the suitability of the cost effective and biocompatible soft polymeric coating materials especially for the surface modification of foldable substrates for variety of applications, and open up new research direction to improve the adhesion of soft polymeric coating materials with tunable viscoelasticity on to the flexible substrates.

Effect of Under Surface Cooling on Tensile Strength of Friction Stir Processed Aluminium Alloy 6082

Friction stir welding (FSW) is a new upgraded version of friction welding. This technology is used worldwide especially in automobile and aerospace industries due to some of its advantages over conventional fusion welding techniques. Friction stir processing (FSP) has recently emerged as a new technique for microstructural surface modification of various materials or for changing the properties of metal by producing intense localized plastic deformation in the material. Friction stir processing is proved to be a viable tool for improving the mechanical properties of materials. This technique works on the principles of FSW. The plastic deformation is produced by same way as in FSW by inserting a non-consumable shouldered pin tool in the work piece and by providing lateral movement to the tool. FSP also used as a method for depositing materials like tool steels, stainless steels and hard facings materials to improve the quality of an underlying metallic base material. Simultaneous cooling of the specimen during FSP is a new approach to further improve the microstructural properties.The results of tensile testing show that the tensile strength can be improved with simultaneous under-surface cooling in FSP.

Mussel Inspired Modification of Polypropylene Separators by Catechol/Polyamine for Li-Ion Batteries

Inspired by the remarkable adhesion of mussel, dopamine, a mimicking adhesive molecule, has been widely used for surface modification of various materials ranging from organic to inorganic. However, dopamine and its derivatives are expensive which impede their application in large scale. Herein, we replaced dopamine with low-cost catechol and polyamine (only 8% of the cost of dopamine), which could be polymerized in an alkaline solution and deposited on the surfaces of various materials. By using this cheap and simple modification method, polypropylene (PP) separator could be transformed from hydrophobic to hydrophilic, while the pore structure and mechanical property of the separator remained intact. The uptake of electrolyte increased from 80% to 270% after the hydrophilic modification. Electrochemical studies demonstrated that battery with the modified PP separator had a better Coulombic efficiency (80.9% to 85.3%) during the first cycle at a current density of 0.1 C, while the discharging current density increased to 15 C and the discharge capacity increased by 1.4 times compared to the battery using the bare PP separator. Additionally, the modification allowed excellent stability during manifold cycles. This study provides new insights into utilizing low-cost chemicals to mimic the mussel adhesion and has potential practical application in many fields.

Synthesis of Photoreactive Phospholipid Polymers for Use in Versatile Surface Modification of Various Materials to Obtain Extreme Wettability

We synthesized photoreactive phospholipid polymers for use in the versatile surface modification of various materials. The photoreactive methacrylate derivative 2-methacryloyloxyethyl-4-azidobenzoate (MPAz) was synthesized. MPAz was copolymerized with 2-methacryloyloxyethyl phosphorylcholine (MPC) to obtain poly(MPC-co-MPAz) (PMPAz) and with both MPC and n-butyl methacrylate (BMA) to obtain poly(MPC-co-BMA-co-MPAz) (PMBPAz). PMPAz and PMBPAz were bound to the surfaces of various materials, including polymers, glass, and metals, by exposure to ultraviolet irradiation. The azide groups in the MPAz units played a role in the surface anchoring; the polymer was bound covalently to the substrate. After the photoreaction, the surfaces were converted from hydrophobic to superhydrophilic, and their cell adhesion was effectively suppressed.

Plasma electron source for the generation of wide-aperture pulsed beam at forevacuum pressures

This article reports on design and application of wide-aperture pulsed beam source, based on hollow cathode discharge. The source is intended for electron beam generation in pressure range 2-15 Pa. Multi-aperture extraction system, used in a source, provided beam cross-section uniformity of 10% on diameter 40 mm. The limiting values of the current density, pulse duration, and accelerating voltage are 350 mA∕cm(2), 250 μs, and 10 kV, respectively. These parameters are sufficient for surface modification of various materials, including non-conducting matters.

Solvent-free surface modification by initiated chemical vapor deposition to render plasma bonding capabilities to surfaces

A versatile solvent-free method for surface modification of various materials including both metals and polymers is described. Strong irreversible bonds were formed when substrates modified by initiated chemical vapor deposition (iCVD) of poly(1,3,5-trivinyltrimethylcyclotrisiloxane) or poly(V3D3) and exposed to an oxygen plasma were brought into contact with plasma-treated poly(dimethylsiloxane) (PDMS). The strength of these bonds was quantified by burst pressure testing microfluidic channels in the PDMS. The burst pressures of PDMS bonded to various coated substrates were in some cases comparable to that of PDMS bonded directly to PDMS. In addition, porous PTFE membrane coated with poly(V3D3) was successfully bonded to a PDMS microfluidic device and withstood pressures of over 300 mmHg. Bond strength was shown to correlate with surface roughness and quality of the bond between the coating and substrate. This work paves a methodology to fabricate microfluidic devices that include a specifically tailored membrane. Furthermore, the bonded devices exhibited hydrolytic stability; no dramatic change was observed even after immersion in water at room temperature over a period of 10 days.

SURFACE MODIFICATION BY DEPOSITION AND THERMAL DECOMPOSITION OF TRANSITION METAL CLUSTER HALIDES

The surface modification of various materials with small particles of sizes down to the nano scale is technologically very important. In this article we report about the use of metal-rich niobium halide cluster compounds to modify surfaces. In a deposition and subsequent decomposition procedure, small metallic particles of the refractory high-melting metal niobium are produced. These particles offer several potential areas of applications, like in heterogeneous catalysis or as hard-surface coating materials. Overall, a new, easy-to-use method for surface modifications is described.

Small signal frequency response studies for plasma electrolytic oxidation

Plasma assisted electrochemical treatments provide new possibilities in surface modification of various materials including light weight alloys. However, their large-scale application is still restricted, mainly due to poor understanding of the process mechanisms and consequent limitations in process control and automation. This problem can be resolved if the frequency response (FR) of the system is known and applied for process diagnostics. Our previous work has shown the effectiveness of the large signal mode for FR studies of plasma electrolytic oxidation (PEO) of aluminium. This research is dedicated to FR measurements during PEO of Al in the small signal mode corresponding to small perturbations of voltage signal around large DC values. The study was carried out during PEO of Al at DC voltages which were varied from 450 to 600 V. The FR obtained is a frequency dependent admittance of the PEO electrolyser; this complex number is represented by a modulus and a phase angle. Under potentiostatic conditions, the modulus evolution strongly correlates with the average current value; therefore, it bears insufficient amounts of independent information. The FR phase angle measured within this study was never obtained before. Depending on the frequency, it varies between 0° and 70 ° in the capacitive domain. One of the most notable features of this characteristic is low values at 500–5000 Hz when microdischarges appear during PEO. The other feature is a correlation with the coating growth. As a result, a new diagnostic tool was developed and shown to be effective for evaluation of microdischarges and surface properties during the treatment, thus decreasing the uncertainty in the system.

Plasma-Needle Treatment of Substrates With Respect to Wettability and Growth of Escherichia coli and Streptococcus mutans

In this paper, surface modification of various materials exposed to a nonthermal atmospheric plasma is investigated. The used source is the plasma needle: a radio-frequency-driven nonthermal atmospheric microplasma. A number of substrates (Perspex and polystyrene) were treated with the plasma needle. The modification of materials was subsequently identified as hydrophilization of the surface and was experimentally validated by water-contact-angle measurements. Furthermore, the effect of this modification on the growth of two bacterial species, which are the Escherichia coli and Streptococcus mutans, is studied. The bacteria were cultured on treated and nontreated polystyrene 96-well plates; the growth of E. coli on the treated substrates was enhanced, while for S. mutans, it was reduced. An explanation of these effects is provided