Increase In Surface Free Energy Research Articles

Effect of Electrolytic Plasma Polishing on Surface Properties of Titanium Alloy

Electrolytic plasma polishing (EPPo) is an advanced metal surface finishing technology with high quality and environmental protection that has broad application prospects in the biomedical field. However, the effect of EPPo on surface properties such as corrosion resistance and the wettability of biomedical titanium alloys remains to be investigated. This paper investigated the changes in surface roughness, surface morphology, microstructure, and chemical composition of Ti6Al4V alloy by EPPo and their effects on surface corrosion resistance, wettability, and residual stress. The results showed that Ra decreased from 0.3899 to 0.0577 μm after EPPo. The surface crystallinity was improved, and the average grain size increased from 251 nm to more than 800 nm. The oxidation behavior of EPPo leads to an increase in surface oxygen content and the formation of TiO2 and Al2O3 oxide layers. EPPo can significantly improve the corrosion resistance and wettability of titanium alloy in simulated body fluid and eliminate the residual stress on the sample surface. The surface properties are enhanced not only by the reduction in surface roughness but also by the formation of a denser oxide film on the surface, changes in the microstructure, an increase in surface free energy, and the annealing effect developed during EPPo. This study can provide guidance and references for applying EPPo to biomedical titanium alloy parts.

Effect of surface plastic deformation of tool steel on ion-plasma nitriding in glow discharge

In this paper the influence of surface plastic deformation of P6M5 tool steel on the characteristics of the hardened layer after ion-plasma nitriding in the glow discharge is investigated. P6M5 tool steel annealed at 850 °C was used for the study. The annealed samples were preliminarily subjected to severe plastic deformation by torsion, with cold settling by 43 % and torsion by 1.5 turns, under hydrostatic compression of 4 GPa. Ion-plasma nitriding was carried out in a gas mixture of 50 % argon, 35 % nitrogen and 15 % hydrogen, at a gas pressure of 200 Pa and a temperature of 450 °C, for 2, 4 and 6 hours. The microhardness of the surface layer of the samples was investigated by the Vickers method on inclined slides. To reveal the microstructure, the studied samples were subjected to chemical etching for 10 s with a solution of acids: C2H5OH (80 ml), HNO3 (10 ml), HCl (10 ml) and C6H3N3O7 (1 g). The thickness of the nitride zone was estimated from the obtained optical images of microstructures. It was found that surface plastic deformation of steel contributes to an increase in the rate of nitrogen diffusion into the depth of the material due to an increase in the density of dislocations and the formation of microdefects due to a highly fine-grained structure. It was found that the surface plastic deformation of steel before ion-plasma nitriding leads to an increase in the thickness of the hardened layer of tool steel P6M5 in a2 times, due to an increase in surface free energy, which contributes to the increase in adsorption of the saturating element and the formation of nitrides in the near-surface layer of nitrided material.

Effect of Atomic-Layer-Deposited Hydroxyapatite Coating on Surface Thrombogenicity of Titanium

This study aimed to evaluate the surface characteristics of a nanocrystalline hydroxyapatite coating made through atomic layer deposition (ALD-HA) on titanium surfaces and to investigate its effect on blood coagulation and platelet adhesion. Grade 2 square titanium discs (0.7 cm, 1 mm thick) were used (n = 108). Half of the substrates (n = 54) were coated with ALD-HA, and the other half were used as the non-coated control. Surface free energy (SFE), contact angle (CA), surface roughness (Ra), and chemical composition were evaluated. Blood thrombogenic properties were assessed on ALD-HA and non-coated surfaces using the kinetic clotting time method. The platelets’ adhesion and morphology were also evaluated. The ALD-HA-coated surfaces demonstrated significantly higher polar SFE (p < 0.001) and lower CA (p < 0.001) values compared to the non-coated surfaces. In addition, the surface roughness was significantly lower for the ALD-HA (p < 0.001) than for the non-coated surfaces. Platelets adhered to both surfaces; however, there was variability in platelet morphologies in different areas with higher platelet density on the ALD-HA surfaces. There was no significant difference in the overall absorbance values of the hemolyzed hemoglobin for both substrates, and the total clotting time was achieved at 60 min. It can be concluded that the ALD-HA coating of titanium can enhance surface wettability, increase surface free energy, and support blood coagulation and platelet adhesion.

Effect of pretreatment on the interfacial bonding strength between modified polyolefin and aluminum foil treated with trivalent chromium chemical conversion: Experimental, quantum chemical calculations and molecular dynamics simulation

Good adhesive strength and joint durability are necessary for aluminum (Al)/polymer laminated film for lithium-ion battery packages. A pretreatment method involving alkaline degreasing followed by acid pickling was employed to treat the Al foil surface to facilitate the deposition of trivalent chromium [Cr(III)] conversion coating on the surface. The adhesive strength between propylene-based elastomer grafted glycidyl methacrylate (GMA-g-PBE) and Cr(III)-converted Al foil pretreated with 0.5 M HF pickling was 51% higher than Cr(III)-converted Al foil without pretreatment. Moreover, the effect of different pretreatments on the interfacial bond strength of GMA-g-PBE/Cr(III)-converted Al foil was studied from macroscopic to microscopic perspectives. The results indicate that the pretreatment of 0.5 M HF pickling results in complete coverage of the Cr(III) compounds and the formation of a thicker Cr(III) conversion coating on the Al foil compared to other pretreatments. A higher content of Cr(III) compounds results in an increased surface free energy of Cr(III)-converted Al foil, improving the wettability of adhesive melt on the substrate and enhancing the adhesion strength. Moreover, quantum chemical calculations and molecular dynamics simulations were used to investigate the interface bonding mechanism, and the results indicate that GMA in the adhesive exhibits a higher binding energy with Cr(III) oxides and hydroxides compared to Al oxides and hydroxides.

Performance degradation mechanism of γ-ray irradiated sol-gel silica film

γ-ray radiation effect on sol-gel silica films was investigated at different absorbed doses ranging from 10 kGy to 1000 kGy. The defect and microstructure evolutions of silica films were analyzed to understand the performance degradation behavior and mechanism of the γ-ray irradiated silica films. The cracks appear on the silica film surface and further expand at larger γ-ray absorbed dose, while surface roughness slightly decreases. During γ-ray irradiation, the thermal effect and the increased rate of diffusion-controlled process lead to the condensation of Si-OH groups and the recombination of ODCs. However, the ionization of atoms leads to generation and accumulation of E′ centers and NBOHCs. γ-ray irradiation leads to the reductions of bond lengths and bond angles of Si-O-Si groups, thus causing the densification of films. The refractive index and mechanical property firstly enhance and then reduce with the increase of absorbed dose associated with the change of silica film density. After γ-ray irradiation, the decreased contact angle and increased surface free energy indicate the reduction of anti-pollution ability of silica films. The dose-dependent surface quality, defects and mechanical properties determine the variation in laser-induced damage threshold (LIDT) of silica film. The results provide a reference to control the structural damage and performance degradation of silica films, which is very important for the research of safe operation of high-power laser facilities for inertial confinement fusion (ICF).

Physical effect of ultrasonic on leaching system of zinc oxide dust containing germanium

Abstract Insufficient reaction between dust and sulfuric acid during leaching of zinc oxide dust containing germanium is a major reason for the low leaching efficiency of germanium. This paper makes use of the unique physical effect of ultrasonic wave to play an important role in strengthening the leaching process. Research found that with ultrasonic enhanced leaching, on the one hand, the surface tension and viscosity of the leaching solution decreased by 5.94 and 32.73 %, respectively; on the other hand, for the leached mineral, the contact angle decreases, the surface free energy increases by 9.43 %, the particle size decreases 40.92 %, and the specific surface area and pore volume respectively increase 94.10 and 54.05 %, which reduces the contact resistance between sulfuric acid and dust, making the reaction between them more completely and in-depth. Therefore, the leaching rate is accelerated and the germanium leaching efficiency is increased. Under ultrasonic condition, the leaching efficiency of germanium is enhanced by 3.94 % and the time to reach equilibrium is shortened by about 40.00 %. The above findings can provide theoretical guidance for the extended application of ultrasound in hydrometallurgy and the efficient leaching of germanium-containing zinc oxide dust.

Effects of DBD Direct Air Plasma and Gliding Arc Indirect Plasma Activated Mist on Germination, and Physiological Parameters of Rice Seed

AbstractRice seeds (Oryza sativa L.) have been treated with cold atmospheric plasma in air both directly in a dielectric barrier discharge and indirectly by gliding arc discharge with plasma activated mist. Comparisons of impacts of the two methods on rice seeds germination and physiological parameters are presented.Plasma has been found to increase seeds hydrophilization and water uptake through decrease of liquid contact angle and increase of total surface free energy of seed’s coat. Germination of treated seeds and their seedling growth parameters are enhanced by plasma application. After 20 min of seeds direct and indirect exposures respectively, germination potential increases by 36.73 and 50.4%, germination rate by 26.0 and 30.0%, and germination index by 25.92 and 36.53%. Also, total shoot length increases by 42.2 and 48.5%, and total root length by 15.93 and 22.42%. Plasma enhances physiological changes by increasing nonenzymatic antioxidants substances which in turn increase the tolerance against abiotic stresses. After 20 min for direct and indirect exposures respectively, free proline increases by 30.0 and 40.0%, total soluble carbohydrates by 49.7 and 54.6%. Also, cellular reactive oxygen species (ROS) increase by 52.0 and 60.0%, and malondialdehyde (MDA) decreases by 68.0 and 88.0%. Indirect exposure of rice seeds by plasma activated mist shows enhanced effects on germination and physiological parameters compared to direct one and could be more practical when applied to large scale seeds plasma treatment.

Interfacial and interlayer enhancement of highly hydrophilic dual-affinity waterborne polyurethane sizing agent acting on carbon fiber/epoxy resin composites

Dual-affinity waterborne polyurethane (WPU) sizing agents with different solid concentrations were designed to achieve two-stage interfacial properties of carbon fiber (CF) and epoxy resin (EP) reinforced composites. The effects of hydrophilic monomer content on the emulsion dispersion of WPU sizing agents and the thermal properties of the coating films were investigated, and the best performing component was selected as the sizing agent of CF to prepare WPU treated-CF. The analysis focuses on the changes of surface morphology and roughness, ionic group types, tensile strength of CF before and after WPU sizing, and the interfacial properties, interfacial strengthening mechanism of CF/EP composites. Compared with conventional commercial CF, the WPU treated-CF shows a 4 % increase in surface free energy and a noticeable improvement in surface roughness and morphology. The wettability, compatibility and adhesion of WPU treated-CF/EP composites were improved according to the strong polar “similarity intermiscibility” between the strong polar functional groups in WPU and EP. Most importantly, the interfacial shear properties (IFSS) of WPU treated-CF/EP composites were improved by 17.2 % and the interlaminar shear properties (ILSS) were improved by 23.8 %. The dual-affinity WPU sizing agent optimizes the practical effect of CF/EP composites for applications such as instrument components and surface coatings used in new energy vehicles, high-speed rail trains, aerospace and provides a boost to the development of new environmentally friendly high-performance chemical coatings.

Surface structuring of β-TCP and transition to α-TCP induced by femtosecond laser processing

Tricalcium phosphate (Ca3(PO4)2, TCP), is one of the most studied and used as material for bioresorbable implants. The β phase has a slower dissolution dynamic and ensures mechanical support for a longer time in biological environment, while a faster release of ions characterize the α phase that trigger a stronger biological response. In this work a femtosecond laser system was used to process β-TCP pellets surface. The femtosecond laser processing results in surface morphology modification, by turning the flat mirror polished surface into a rough and opaque one. The morphological and phisycochemical characteristics of material surface were studied by means of SEM, AFM, Raman, XRD and contact angle measurement. The processed surface showed the formation of micro and nano roughness alongside, furthermore a partial phase transformation from β-TCP to α-TCP was detected. A significant improvement in surface wettability for three different liquids (i.e.water, ethylene glycol and diiodo-methane) is reported. This implies an increase in surface free energy as well. The combination of α and β phase, together with the increased roughness obtained by laser processing, could positively affect the cell adhesion and metabolic activity.

Effect of drying conditions on adhesion strength of a pressure-sensitive adhesive

ABSTRACT Regular surface roughness could be created on the surface of a pressure-sensitive adhesive (PSA) film through Marangoni flow during the drying process. Therefore, tailoring of both surface and bulk characteristics of the PSA and consequently its adhesion strength could be expected by controlling the drying conditions. Herein, surface and bulk properties of a water-based PSA dried at various temperatures and humidities were scrutinized. Increase in the drying temperature improved the adhesion strength of the PSA to poly(ethylene terephthalate) due to enhanced surface nanoroughness of its film. At constant humidity, the higher the Péclet number, the higher the Marangoni number and the rougher the PSA film surface. Drying humidity rise, however, improved the adhesion strength due to more uniform distribution of copolymers constituting the PSA, better interdiffusion of chains through the interface of polymer particles in a prolonged drying process, and increased surface free energy of the film. The adhesion strength of the PSA, similar to the here-defined viscoelastic dissipation ability, demonstrated a power dependence on the film surface nanoroughness. This newly-defined parameter considers taking advantage of the real viscoelastic dissipation of the PSA regarding its potentiality through thorough wetting of the substrate surface with the PSA.

High-Translucency Zirconia Following Chemical Vapor Deposition with SiH4: Evidence of Surface Modifications and Improved Bonding.

To evaluate the effect of plasma-enhanced chemical vapor deposition (PECVD) with silicon hydride (SiH4) at different times on HT-zirconia surface characteristics and bonding of composite cement before and after thermocycling. Blocks of HT zirconia were obtained, polished, sintered and divided into five groups, according to PECVD time (n = 31): Zr-30 (30 s), Zr-60 (60 s), Zr-120 (120 s) and Zr-300 (300 s). The control group (Zr-0) did not receive PECVD. X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), energy dispersive spectroscopy (EDS) in conjunction with field-emission scanning electron microscopy (FE-SEM), x-ray photoelectron spectroscopy (XPS), goniometry, and profilometry tests were used for chemical and topographic characterization. Monobond N silane (Ivoclar Vivadent) was applied to the surface, and a cylinder of composite cement (Variolink N) was made (3 x 3 mm). Half of the specimens of each group were stored for 24 h or subjected to thermocycling (6 x 103 cycles). A shear bond strength (SBS) test was performed. Results were subjected to one-way ANOVA and Tukey's tests (α = 0.05). For experimental groups, XPS showed that formation of Si-O bonds contributed to increased surface free energy (SFE). FE-SEM and EDS showed that the longer the deposition time, the greater the amount of silicon on the surface. Zr-60 and Zr-300 presented higher and lower surface roughnesses, respectively. The silicon penetrated the microstructure, causing higher stress concentrations. The bond strength to composite cement was improved after all PECVD deposition times. The PECVD technique with SiH4, associated with chemical treatment with primer based on silane methacrylate, is a solely chemical surface treatment capable of maintaining bonding between composite cement and HT zirconia.

Morphology Transition of Te-Doped InAs Nanowire on InP(111)B Grown Using MOCVD Method

In this paper, we reported changes in the growth morphology of n+InAs nanowires (NWs) doped with Te which were selectively grown on nano-hole patterned InP(111)B substrates using an MOCVD method. While the vertical growth of InAs NWs in the <111> direction was extremely suppressed, their lateral growth was enhanced when the diethyl-tellurium (DETe) flow rate was increased as they grew. Moreover, the sidewall planes evolved from (11¯0) (90° against the (111) plane) to a reverse-tapered morphology, which had a 62° slope against the InP (111)B plane, when the Te flow rate and growth time were increased. This indicates that the surfactant effect of adsorbed Te atoms on InAs changes the relative growth rate between (111) and (11¯0) due to the increase in surface free energy in the growth plane.

Surface Properties of Ti6Al7Nb Alloy: Surface Free Energy and Bacteria Adhesion.

The laser micro-machining was carried out on a station equipped with a TruMicro 5325c laser emitting ultraviolet radiation (343 nm wavelength) in picosecond pulses. On the surface of the Ti6Al7Nb alloy, dimple texturing with a constant diameter of ~200 μm, different depths (from ~5 to ~78 μm) and density (from 10% to 50%) were produced. The value of surface free energy was determined with the Owens–Wendt method using two measuring liquids: distilled water and diodomethane. The Staphylococcus epidermidis strain was used to test the adhesion of bacteria. It was found that the surface free energy value is influenced by both of the texture parameters (density, depth). The density also affects the potential for biofilm formation. Based on the analysis, it was shown that with an increase in surface free energy, the number of adhering microorganisms increases exponentially. Moreover, the study shows that there is a correlation between the number of adhering microorganisms and surface free energy.

Application of Nitrogen Piezoelectric Direct Discharge for Increase in Surface Free Energy of Polymers

The subject of this study is the application of the piezoelectric direct discharge (PDD) operated with nitrogen to control the surface free energy (SFE) of polymers. The activation area, defined as the area of the zone reaching the SFE of 58 mN/m for high-density polyethylene (HDPE) and poly (methyl methacrylate) (PMMA), is characterized. For HDPE, the activation area was characterized as a function of the distance from 1 to 16 mm, the nitrogen flow from 5 to 20 SLM, and the treatment time from 1 to 32 s. For larger distances, where SFE does not exceed 58 mN/m, the water contact angle is evaluated. The activation area for nitrogen PDD is typically a factor of 3 higher than for air with all other conditions the same. A maximum static activation area of 15 cm2 is reached. The plasma treatment of lens panels made of PMMA is presented as application example.

Vol4 num2-16 CFRP advanced surface characterization prior to adhesive bonding. Peel ply treatment vs UV laser

Surface treatment is one of the most important issues for obtaining high quality adhesive bonding. The main objective of this treatment is the removal of surface contaminants, the modification of surface roughness and the increase of surface free energy, without damaging the surface of the composite material. Nowadays, the treatments which are approved by the aeronautical sector for the surface preparation of CFRP prior to adhesive bonding are manual and some of them depend on the skills of the operator. Because of this, different automatable alternatives are being studied in order to substitute these traditional methods. One of these alternatives is the use of UV laser radiation. In this work the advanced surface characterization of CFRP surfaces treated with peel ply and processed with UV laser have been performed. Advanced techniques have been used in order to evaluate the changes that occur in the surface and which can be related to adhesiveness. Thus, techniques such as scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), surface free energy determination and 3D optical confocal profilometry have been used to evaluate chemical and physical properties of treated surfaces. Obtained results show that UV laser radiation leads to surface changes which would improve the adhesiveness of the surfaces, although these changes suggest that the mechanism by which adhesion happens is different from the one which is related to peel ply. &nbsp

Confinement synthesis in porous molecule-based materials: a new opportunity for ultrafine nanostructures.

A balance between activity and stability is greatly challenging in designing efficient metal nanoparticles (MNPs) for heterogeneous catalysis. Generally, reducing the size of MNPs to the atomic scale can provide high atom utilization, abundant active sites, and special electronic/band structures, for vastly enhancing their catalytic activity. Nevertheless, due to the dramatically increased surface free energy, such ultrafine nanostructures often suffer from severe aggregation and/or structural degradation during synthesis and catalysis, greatly weakening their reactivities, selectivities and stabilities. Porous molecule-based materials (PMMs), mainly including metal–organic frameworks (MOFs), covalent organic frameworks (COFs) and porous organic polymers (POPs) or cages (POCs), exhibit high specific surface areas, high porosity, and tunable molecular confined space, being promising carriers or precursors to construct ultrafine nanostructures. The confinement effects of their nano/sub-nanopores or specific binding sites can not only effectively limit the agglomeration and growth of MNPs during reduction or pyrolysis processes, but also stabilize the resultant ultrafine nanostructures and modulate their electronic structures and stereochemistry in catalysis. In this review, we highlight the latest advancements in the confinement synthesis in PMMs for constructing atomic-scale nanostructures, such as ultrafine MNPs, nanoclusters, and single atoms. Firstly, we illustrated the typical confinement methods for synthesis. Secondly, we discussed different confinement strategies, including PMM-confinement strategy and PMM-confinement pyrolysis strategy, for synthesizing ultrafine nanostructures. Finally, we put forward the challenges and new opportunities for further applications of confinement synthesis in PMMs.

Adhesion of water-based paint on plasma-treated high-density polyethylene sheets

In this study, high-density polyethylene (HDPE) surfaces were treated with plasma to enhance the adhesion of a water-based paint. A custom-built cold atmospheric pressure plasma jet (CAPPJ) device using a neon transformer as its power source was developed and used in the surface treatment. The jet nozzle of the device was made from polytetrafluoroethylene with two bare stainless-steel electrodes positioned laterally through the nozzle and opposite each other with a 1 mm gap. Gas was allowed to pass through the nozzle, exiting through a 1 mm diameter hole where a plasma jet is ejected through the arc from the electrodes. The effect of plasma treatment on HDPE surfaces was determined. Air and nitrogen were used as the process gases and exposure times were also varied. Hydrophilicity of the surface increased with longer plasma exposure with a corresponding 50% increase in surface free energy compared to the untreated surface. From Fourier transform infrared and x-ray photoelectron spectroscopy analysis, it was seen that plasma treatment introduced oxygen containing functionalities onto the surface. Increase in adhesion of a water-based paint was observed for plasma-treated HDPE sheets.

What Happens to Wood after a Tree Is Attacked by a Bark Beetle?

Advancing climate change is affecting the health and vitality of forests in many parts of the world. Europe is currently facing spruce bark beetle outbreaks, which are most often caused by wind disturbances, hot summers, or lack of rainfall and are having a massive economic impact on the forestry sector. The aim of this research article was to summarize current scientific knowledge about the structure and physical and mechanical properties of wood from bark beetle-attacked trees. Spruce stands are attacked by a number of beetles, of which Ips typographus is the most common and widespread in Central Europe. When attacking a tree, bark beetles introduce ophiostomatoid fungi into the tree, which then have a greater effect on the properties of the wood than the beetles themselves. Fungal hyphae grow through the lumina of wood cells and spread between individual cells through pits. Both white rot and brown rot fungi are associated with enzymatic degradation of lignin or holocellulose, which is subsequently reflected in the change of the physical and mechanical properties of wood. Wood-decay fungi that colonize wood after infestation of a tree with bark beetles can cause significant changes in the structure and properties of the wood, and these changes are predominantly negative, in the form of reducing modulus of rupture, modulus of elasticity, discolouration, or, over time, weight loss. In certain specific examples, a reduction in energy consumption for the production of wood particles from beetle-attacked trees, or an increase in surface free energy due to wood infestation by staining fungi in order to achieve better adhesion of paints or glues, can be evaluated positively.

Insight into the role of exopolysaccharide in determining the structural stability of aerobic granular sludge

Extracellular polymeric substances (EPS) have a critical contribution to the stability of aerobic granular sludge (AGS), but the mechanism and details of EPS composition and function are far from clear. This work investigated the contribution of exopolysaccharide (PS) to maintaining the structural stability of AGS. The results revealed that PS hydrolysis induced by α-amylase, dextranase and cellulase significantly decreased the granular stability, whereas a substantial content reduction of extracellular protein (PN) was also observed. It was also found that hydrolysis of PS led to a decrease of sludge hydrophobicity, granular gel mechanical strength by 14.09 %, 38.67 %, respectively, and an increase of surface free energy by 49.59 %, which is not conducive to granular stability. Through fluorescent staining, existence of large amounts of PS and PN conjugates in EPS matrix was verified. It was proposed that these conjugates with PS as skeleton (PS-PN) dominate granular stability by affecting hydrophobicity interactions and hydrogen bonds system, which are two important parameters to gel properties, constituting a crucial finding of this work. This study offers an supplementation of EPS system theory and granular stability mechanism.

Improved interfacial adhesion in carbon fiber/poly (ether ether ketone) composites with the sulfonated poly (ether ether ketone) sizing treatment

AbstractA water‐soluble sulfonated poly (ether ether ketone) (SPEEK) sizing agent is prepared and applied to improve the interfacial adhesion of carbon fiber/poly (ether ether ketone) (CF/PEEK) composites. The surface morphology, surface roughness, surface chemistries, and surface free energy of SPEEK sized CF are obtained to understand the sizing effect. The results reveal the increased surface free energy and surface roughness of SPEEK sized CF. In addition, a chemical reaction between the CF surface and sizing layer is proved based on the results of XPS, IR, and 1H NMR. The interfacial structure of CF/PEEK composites is further ascertained by AFM and the appearance of gradient interface could be verified for SPEEK sized CF/PEEK composites. The formation of the gradient interface is due to the chemical reaction between the CF and sizing agent as well as the improved compatibility between the sized CF and matrix, which benefits the improvement of interfacial adhesion.