Modification Of Surface Properties Research Articles

Saponaria officinalis L. extract: Surface active properties and impact on environmental bacterial strains

Plant-derived surfactants are characterised by low toxicity, high biodegradability and environmental compatibility. They therefore have many applications; for instance, they can be used in bioremediation to accelerate biodegradation processes, especially of hydrophobic pollutants. This paper analyses the properties of an extract from Saponaria officinalis L. containing saponins and its impact on bacterial strains isolated from soil, as well as its potential for application in hydrocarbon bioremediation. The tested extract from Saponaria officinalis L. contains gypsogenin, hederagenin, hydroxyhederagenin and quillaic acid aglycone structures and demonstrates good emulsification properties. Contact with the extract led to modification of bacterial cell surface properties. A decrease in cell surface hydrophobicity and an increase in membrane permeability were recorded in the experiments. An increase of up to 63% in diesel oil biodegradation was also recorded for Pseudomonas putida DA1 on addition of 1gL−1 of saponins from Saponaria officinalis L. Saponaria extract showed no toxic impact on the tested environmental bacterial strains at the concentration used in the biodegradation process.

Impact of sodium hypochlorite (NaClO) on polysulfone (PSF) ultrafiltration membranes: The evolution of membrane performance and fouling behavior

Abstract This paper presents a study on the impact of sodium hypochlorite (NaClO) on the performance and fouling behavior of polysulfone (PSF) membranes. The performance of aged PSF membranes was studied under different transmembrane pressures (TMPs), and three critical TMPs including the pressure corresponding to critical flux (P C ), the pressure corresponding to critical filtration efficiency (P V ), and the pressure corresponding to the greatest retention ability (P R ) were innovatively proposed. In terms of an aged membrane, the filtration efficiency (η v ) and retention ability (R) were decreased, while, the enhanced sieving capacity (η s ) were experimentally proved. These are strongly related to modified surface properties and enlarged pore diameters of aged PSF membranes. The fitting results of Hermia’s model and critical flux analysis mutually verified that the formation of cake layer fouling on an aged PSF membrane surface was delayed. However, the specific fouling results indicated the aged membrane suffered a more severe pore block fouling. Moreover, the target plot also implied that the critical parameters (P C , P V and P R ) can serve as indicators of the evolution of membrane performance and fouling behaviors.

Improvement of surface and mechanical properties of high strength metallic alloys by laser shock processing

Profiting by the increasing availability of laser sources delivering intensities above 109 W/cm2 with pulse energies in the range of several Joules and pulse widths in the range of nanoseconds, laser shock processing (LSP) is being consolidated as an effective technology for the improvement of surface mechanical and corrosion resistance properties of metals and is being developed as a practical process amenable to production engineering. The main acknowledged advantage of the LSP technique consists on its capability of inducing a relatively deep compression residual stresses field into metallic alloy pieces allowing an improved mechanical behaviour. Following a short description of the theoretical/computational and experimental methods developed by the authors for the predictive assessment and experimental implementation of LSP treatments, experimental results on the residual stress profiles and associated surface properties modification successfully reached in typical materials (specifically Al and Ti alloys) under different LSP irradiation conditions are presented.

Surface characterisation and wetting properties of single basalt fibres

Basalt fibres are claimed to show better high temperature resistance compared to glass fibres, suggesting better prospects to survive an end-of-life composite thermal recycling process while preserving an adequate reinforcing efficiency. It is well known that sizing agents affect impregnation of fibre reinforcements during composite manufacturing, which influences the overall mechanical behaviour of the resulting composites. However, with the exception of some studies about coupling agent effects on the adhesion between basalt fibres and matrix, no information are present in literature on the wetting characteristics of basalt fibres. The main contribution of this study is the analysis of the surface properties and wetting behaviour of basalt fibres with sizing optimised for both thermoset and thermoplastic matrices. Measurements of static contact angles were performed with a tensiometric procedure designed for singles fibres, in order to determine their surface energy and its components. Modifications of surface properties due to chemical treatments and high temperature exposure were also investigated and discussed.

Modification of the Wood Surface Properties of Tsoongiodendron odorum Chun with Silicon Dioxide by a Sol-gel Method

A sol-gel method was employed to improve wood surface properties by generating SiO2 with tetraethoxysilane and methyl triethoxysilane as co-precursors. The effect of SiO2 on the wood surface properties was studied by the analysis of size stability, ultraviolet radiation aging resistance, and contact angle of the modified wood. The improvement mechanism was explored using scanning electron microscopy (SEM), energy dispersive X-ray (EDAX), and Fourier transform infrared spectroscopy (FT-IR). The results showed that the water absorption and the hygroscopic expansion rate of the modified wood were less than those of the control samples. The discoloration resistant properties were improved 1.5 times more than that of the control samples. The thickness of SiO2 on the wood surface was approximately 60 μm, and the silicon content increased as the dipping time increased. The contact angle of modified wood showed that it was more hydrophobic than that of the control sample, and this increased as the dipping time increased. The variation in contact angle of the modified wood was less than that of the control sample before and after aging. The anti-aging performance of the modified wood surface was also improved.

The effect of alcohol type on the thickness of silica layer of Co3O4@SiO2 core-shell particle

Silica layer was deposited on the spherical Co3O4 particles, which were prepared by the thermal decomposition of cobalt nitrate, by the hydrolysis and condensation of tetraethylorthosilicate (TEOS) in the presence of cetyltrimethylammonium bromide (CTAB) in alcohol (methanol, ethanol, propanol or butanol). The products were characterized by X-ray diffraction (XRD), scanning and transmission electron microscopies (SEM and TEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric/differential thermal analysis (TG-DTA), UV–vis absorption spectroscopy, and vibrating sample magnetization (VSM). The result showed that the spherical Co3O4 particles with the average diameter of 242nm were coated with silica layer (the thickness of 12–27nm). The thickness of the silica shell varied depending on alcohols, methanol gave thicker silica shell than ethanol, butanol and propanol. Irrespective of the thickness of the silica shell, all the present Co3O4@SiO2 core-shell particles showed a soft ferromagnetic with narrow hysteresis loops, not much different from that of pristine Co3O4, suggesting possible applications as magnetic particles with modified surface properties. The core-shell particles were stable in acidic solution (pH=1) to extend the potential of magnetic Co3O4.

Wetting characteristics of 3-dimensional nanostructured fractal surfaces

This article reports the fabrication and wetting characteristics of 3-dimensional nanostructured fractal surfaces (3DNFS). Three distinct 3DNFS surfaces, namely cubic, Romanesco broccoli, and sphereflake were fabricated using two-photon direct laser writing. Contact angle measurements were performed on the multiscale fractal surfaces to characterize their wetting properties. Average contact angles ranged from 66.8° for the smooth control surface to 0° for one of the fractal surfaces. The change in wetting behavior was attributed to modification of the interfacial surface properties due to the inclusion of 3-dimensional hierarchical fractal nanostructures. However, this behavior does not exactly obey existing surface wetting models in the literature. Potential applications for these types of surfaces in physical and biological sciences are also discussed.

Surface Microstructure and High Temperature Oxidation Resistance of Thermal Sprayed NiCoCrAlY Bond-Coat Modified by Cathode Plasma Electrolysis

The surface properties of the air-plasma sprayed bond-coat have been modified by cathode plasma electrolysis (CPE). After modification, a re-melted layer without obvious pores and oxide stringers is formed, the gain size of re-melted layer is approximately 80–120 nm. It is shown, from cyclic oxidation at 1100 °C, that a thin oxide scale mainly composed of α-Al2O3 has been formed on the modified bond-coat and the oxidation resistance of the modified bond-coat has been significantly improved. Such beneficial result can be attributed to following effects: during CPE process, the plasma discharges with high temperature take place on the bond-coat surface. With plasma discharge treatment, the surface is melted and quickly re-solidified, the grain size decreases, and the pores and oxide stringers disappear. During cyclic oxidation, owing to the above modification of surface properties, the critical content of Al for selective oxidation is significantly decreased. Therefore, a continuous Al2O3 scale is formed.

Nanopowders of gallium nitride GaN surface functionalized with manganese

Four GaN nanopowders of systematically varying surface properties, prepared via an anaerobic synthesis method from gallium imide (ammonia assisted decomposition in the range 600–975 °C), were subjected to functionalization with manganese centers. Each powder was slurried in a diluted hexane solution of manganese (II) bis{bis[trimethylsilyl]amide} Mn{N[Si(CH3)3]2}2 and stirred overnight at ambient conditions. This was followed by filtering out of the solid, rinsing it with hexane to remove excess of the manganese precursor, and evacuating volatiles. The raw solid with some adsorbed Mn precursor was then subjected to transamination/deamination chemistry at 200 °C, 18 h, under a flow of ammonia to afford Mn surface-functionalized GaN nanopowders. The powders were thoroughly characterized including investigation of their magnetic properties with a SQUID magnetometer. They were confirmed to have tightly bound manganese and significantly modified surface properties with relatively decreased BET specific surface areas and helium densities. Magnetic measurements were consistent with the formation of a paramagnetic surface (Ga,Mn)N-type of phase and some antiferromagnetic by-product, the latter formed from adventitious oxidation of excessive quantities of the manganese precursor.

Dynamic Analysis of Banana Fibre Reinforced Hybrid Polymer Matrix Composite Using ANSYS and Optimization of Design Parameters

In the recent scenario, the focus for the environmental pollution and the piling of products from non-renewable and non-biodegradable resources has forced many researchers to develop new eco-friendly and biodegradable materials. In this work, banana fiber reinforced hybrid polymer matrix composite is fabricated and tested. Banana fiber is treated with various alkali solutions to modify surface properties in order to improve mechanical properties. Hybrid polymer is made from CNSL (Cashew Nut Shell Liquid) and Isotholic Polyester. Dynamic behavior of banana fibre reinforced hybrid polymer matrix composite is investigated by means of experimental and finite element analysis. Simulation of frequency response and dynamic displacement are carried out on banana fibre reinforced hybrid polymer matrix composite by ANSYS and it is compared with experimental results. Optimization of design parameter is carried out using ANOVA technique and design of experiment of Taguchi method is employed for better combination of the parameter.

Modification of Orientation, Surface and Optical Properties of ZnO Films by Cesium and Erbium Codoping Using Sol–Gel Method

Modification of Orientation, Surface and Optical Properties of ZnO Films by Cesium and Erbium Codoping Using Sol–Gel Method

(Invited) ALD to Prevent Metal Transfer from Implants

The interest about coatings devoted to biomedical applications has been continuously increasing during the last years. Several literature studies address the modification of surface properties, and the improvement of biocompatibility of implant surfaces by coatings. Among the other properties, adhesion and uniform coverage are desired. Another challengeable issue for biomedical applications is metal release from implant alloy into tissue environment. Indeed, severe adverse reactions may occur, including inflammation, fibrosis, thrombosis, infections and, last but non least, metallosis. Clinical cases of this pathology have been already observed with orthopaedic implants made with CoCrMo alloys. On these purposes several materials and coating techniques have been investigated. Recently, nanomaterials have also been considered. Atomic Layer Deposition (ALD) is a synthesis technique for nanomaterials, that is raising interest in the field of biomedical application, due to its unique properties. ALD allows conformal coating by ultrathin layers with high adhesion and well-defined thickness, at the nanometer scale. Oxide compounds may be easily deposited by ALD, even at low temperature. Among these, TiO2 is one of the most attractive functional oxide for such application, due to its high durability, good corrosion resistance, and well-tested biocompatibility. Indeed, TiO2 is already used to coat biomedical alloys and implants to improve short and long term body responses. In this work we study the effect of TiO2 layers deposited by ALD against metal release from CoCrMo alloy implants. Implant samples are coated with different thicknesses of TiO2, ranging from 10 to 200nm. Micro X-Ray Fluorescence is used to map the metal distribution in the bone surrounding the implant, after 1 and 2 months respectively from implantation. It is observed that the presence of TiO2 may prevent the metal transfer into the bone. Results show that Co and Cr has cluster distribution in the tissue surrounding the uncoated implant, with a number of particles that significantly increases with time. While, a decreasing gradient distribution from the alloy surface is evident in all the coated implant samples. In particular, the thicker the coating layer, the lower is the metal concentration in the surrounding tissue. The distribution of Mo is much uniform and extended with respect to Co and Cr. Metal transport increases with time, only in uncoated samples. It is also observed that corrosion of coated implants is delayed. The content of metals at a fixed distance from the implant surface increases with time. However, the mechanism of metal transport through the coating layer is not clear. For this reason a further "proof of concept" test is designed, to study the transport kinetics of ionic species into water through TiO2 coatings, deposited by ALD. Results show zero order kinetics. This model experiment demonstrates that the release of ionic species occur by a mechanism of diffusion through a continuous layer. This work figures out two important benefits of TiO2 coating obtained by ALD on the surface of CoCrMo implant: i. it shows a barrier effect against metal movement from the implant toward the tissue; ii. it protects the implant material against corrosion in this biological environment. Clinical benefits or antibacterial effects should be further investigated. From another point of view, this study highlights that ALD allows a very precise control of ionic species diffusion by means of layer thickness. This ability can be strongly exploited in the field of controlled release. The combination of these effects may be successfully used to obtain layer by layer structures with tunable properties, making ALD a powerful tool for biomedical applications.

Corrosion inhibition by the trace amount of sulphide ion in CO2-saturated brine solutions

By accurately controlling the concentration of sulphide ion in CO2-saturated solutions, it was demonstrated that the corrosion behaviour of mild steel was sensitive to the trace amount of sulphide ion additions. An obvious inhibition effect on cathodic reactions was observed at an extremely low level of sulphide ion, while a detrimental effect on corrosion was gradually emerged as its dosage increased higher than 0.5 mg L−1. These positive and negative synergy effects would be strengthened after immersing for longer time. The sensitivity of CO2 corrosion to sulphide ion was attributed to the modification of surface properties by the presence of iron sulphides.

Azido Platform Surfaces for Post‐Functionalization with Aromatic Groups Using the Huisgen Reaction to Obtain High Water Adhesion

In this work, platform post‐modifications using the Huisgen reaction are reported. Various platform surfaces are developed and post‐functionalized with aryl side chains. The development of different conducting polymer platforms allows the study of the impact of the starting surface on the modified surface properties. Also in this work, different aryl side chains are investigated (with one, two, three, or four aromatic rings) in order to investigate the impact of the side chain on the final surface feature. All the combinations (surface vs aryl side chain) are investigated for their wettability. Highly hydrophobic features are observed with apparent contact angles θ higher than 140° and extremely high water adhesion. Surface morphologies are also investigated and important changes in morphology are observed after surface post‐functionalization. The reported strategy to develop various highly hydrophobic surfaces with high water adhesion feature can be a powerful strategy for water trap elaboration. image

Aluminum surface wettability changes by pool boiling of nanofluids

Boiling of colloidal suspensions has been found to modify surface properties, which can lead to enhancements in heat transfer processes. In this paper, a systematic study of the surface modification after nanofluid boiling is reported. Aluminium substrates of different initial roughness were used to study the roughness effect on the wettability after boiling in various nanofluid concentrations, boiling durations and heat fluxes. Experimental results show that these parameters are significant to surface wettability changes. Extending boiling duration and increasing nanofluid concentration exhibits positive impact on the surface wettability enhancement, while roughness has a more complex influence. The mechanism of the wettability modification is revealed by microscopy and goniometry. It was found that the enhanced wettability on aluminium surfaces after boiling in Al2O3 nanoparticle aqueous suspensions is due to the growth of hydroxides and the deposition of particles during the boiling process, so both chemical and topographical modifications were caused by nanofluid boiling on aluminium surface. Scanning electron microscope (SEM) images demonstrate that, micro and nano multi-scale structures were introduced to the surface after the treatment, which contributes to the enhancement of wettability, and improves longevity. The good agreement of roughness factor obtained by atomic force microscopy (AFM) and water contact angle experiment indicates Wenzel wetting state on the surface.

NH3-treated MoS2 nanosheets as photocatalysts for enhanced H2 evolution under visible-light irradiation

MoS2 is widely applied in photocatalytic H2 evolution to function as an efficient cocatalyst, whereas it is not yet reported that this material acted as an effective host photocatalyst in this field. Herein, MoS2 nanosheets were prepared by a general hydrothermal process at first, and then treated with flowing NH3 at temperatures from 400 to 900 °C to develop a series of novel MoS2-based photocatalysts, which showed considerable photocatalytic activities for H2 evolution under visible-light irradiation. It was deduced from different instrumental characterizations on the physicochemical properties of photocatalysts that the enhancement of photocatalytic activity by high-temperature NH3 treatment could be mainly attributed to the modification of surface properties (such as electric property and acid-base properties) by N, which promoted the adsorption of reactants and further accelerated photocatalytic reaction. This work presented an effective route to explore new H2-evolution photocatalysts by modifying the appropriate materials that were commonly employed as cocatalysts.

The role of solvent type, size and chemical composition of bioactive glass particles in modulating material properties of poly(ε-caprolactone) based composites

The role of solvent type (dichloromethane, 1,4-dioxane, tetrahydrofuran), size (<45, <3μm) and chemical composition (silica-rich, calcium-rich) of bioactive glass (BG) particles in modulating surface properties, crystallinity, mechanical properties and in vitro bioactivity of poly(ε-caprolactone) based composite films was investigated. Films were prepared by solvent casting method. Bioactive glasses from the SiO2–CaO–P2O5 system were obtained by sol-gel method. The particle size and solvent type played an important role in nucleation and crystallisation kinetics of PCL, affecting morphology, topography and wettability of films. In contrast to BG particles of <45μm size, the smaller ones (<3μm) were exposed on the surfaces of films and consequently have improved hydrophilicity and have provided crystallisation of carbonated hydroxyapatite after incubation in SBF. Type of the solvent, by affecting surface properties, influenced hydroxyapatite crystallisation process. The addition of BG particles of both sizes resulted in enhanced modulus and drastic decrease in elongation at break.

Adsorption of hydrophobin/β-casein mixtures at the solid-liquid interface

The adsorption behaviour of mixtures of the proteins β-casein and hydrophobin at the hydrophilic solid-liquid surface have been studied by neutron reflectivity. The results of measurements from sequential adsorption and co-adsorption from solution are contrasted. The adsorption properties of protein mixtures are important for a wide range of applications. Because of competing factors the adsorption behaviour of protein mixtures at interfaces is often difficult to predict. This is particularly true for mixtures containing hydrophobin as hydrophobin possesses some unusual surface properties. At β-casein concentrations ⩾0.1wt% β-casein largely displaces a pre-adsorbed layer of hydrophobin at the interface, similar to that observed in hydrophobin-surfactant mixtures. In the composition and concentration range studied here for the co-adsorption of β-casein–hydrophobin mixtures the adsorption is dominated by the β-casein adsorption. The results provide an important insight into how the competitive adsorption in protein mixtures of hydrophobin and β-casein can impact upon the modification of solid surface properties and the potential for a wide range of colloid stabilisation applications.

Modification in surface properties of poly-allyl-diglycol-carbonate (CR-39) implanted by Au+ions at different fluences

AbstractIon implantation has a potential to modify the surface properties and to produce thin conductive layers in insulating polymers. For this purpose, poly-allyl-diglycol-carbonate (CR-39) was implanted by 400 keV Au+ions with ion fluences ranging from 5 × 1013ions/cm2to 5 × 1015ions/cm2. The chemical, morphological and optical properties of implanted CR-39 were analyzed using Raman, Fourier transform infrared (FT-IR) spectroscopy, atomic force microscopy (AFM) and UV-Vis spectroscopy. The electrical conductivity of implanted samples was determined through four-point probe technique. Raman spectroscopy revealed the formation of carbonaceous structures in the implanted layer of CR-39. From FT-IR spectroscopy analysis, changes in functional groups of CR-39 after ion implantation were observed. AFM studies revealed that morphology and surface roughness of implanted samples depend on the fluence of Au ions. The optical band gap of implanted samples decreased from 3.15 eV (for pristine) to 1.05 eV (for sample implanted at 5 × 1015ions/cm2). The electrical conductivity was observed to increase with the ion fluence. It is suggested that due to an increase in ion fluence, the carbonaceous structures formed in the implanted region are responsible for the increase in electrical conductivity.

Enhancing Durability of Hot Work Tool Steel by Duplex Treatments: A Review

The abrasive wear unitedly with thermo-mechanical fatigue and plastic deformation is a critical factor of the process of failure of forging dies during the forging of components with close tolerances and not subject to further mechanical treatment. The failure rate of forging dies are also greatly influenced by the variety of the shapes of the forging and the precision with which these are made. The effective way to improve the durability of forging dies is a modification of surface properties by the constitution of layers or coatings having appropriate properties. Among huge available techniques; Plasma nitriding along with suitable coating formed by physical vapor deposition (PVD) technique; commonly known as Duplex/Hybrid treatment; is widely used, allows control of surface microstructure, enhance wear resistance, corrosion resistance and fatigue resistance. This had been noted that Duplex Treatment can increase the wear resistance of the tool/die up to 30%. The tribological behaviours of duplex treated dies in hot forging are reviewed and presented here. Some commonly used surface treatments as well as coatings in hot forging dies are given. Eventually, xperimental results obtained by various researchers could be used in theory and model developments for hot forging process and die materials at high temperatures. The review also showed the great potential in further investigations in tribology.