Surface Free Energy Values Research Articles

Argon Ion Implantation as a Method of Modifying the Surface Properties of Wood-Plastic Composites.

Wood-plastic composites (WPCs) combine the properties of plastics and lignocellulosic fillers. A particular limitation in their use is usually a hydrophobic, poorly wettable surface. The surface properties of materials can be modified using ion implantation. The research involved using composites based on polyethylene (PE) filled with sawdust or bark (40%, 50%, and 60%). Their surfaces were modified by argon ion implantation in three fluencies (1 × 1015, 1 × 1016, and 1 × 1017 cm-2) at an accelerating voltage of 60 kV. Changes in the wettability, surface energy, and surface colour of the WPCs were analysed. It was shown that argon ion implantation affects the distinct colour change in the WPC surface. The nature of the colour changes depends on the filler used. Implantation also affects the colour balance between the individual variants. Implantation of the WPC surface with argon ions resulted in a decrease in the wetting angle. In most of the variants tested, the most significant effect on the wetting angle changes was the ion fluence of 1 × 1017 cm-2. Implantation of the WPC surface also increased the surface free energy of the composites. The highest surface free energy values were also recorded for the argon ion fluence of 1 × 1017 cm-2.

Mikrostruktur dan Karakteristik Permukaan Kayu Pinus Scots (Pinus sylvestris L.) Termodifikasi Gliserol dan Asam Sitrat

Scots pine (Pinus sylvestris L.) wood is one of the most popular timber export products. However, its low durability can reduce the potential and utilization of the wood. Chemical modification is one of the solutions to overcome this drawback. Chemical modification using non-biocide materials such as glycerol and citric acid was carried out to improve the inferior properties of wood. The study aimed to observe the microstructure and evaluate the surface characteristics of glycerol and citric acid-modified scots pine wood. Scots pine wood was modified using glycerol and citric acid with weight percent gain (WPG) values of 20% and 46%. Surface characteristics were measured, including surface roughness, surface free energy (SFE), wettability, and bonding quality. The results show that chemical modification using glycerol and citric acid resulted in the structure of the pine wood being more filled and denser. The modification could also reduce the roughness of the wood surface, resulting in decreased SFE value, increased contact angle, and decreased wettability on the wood surface. It might cause a decrease in the bonding quality because the wood did not have the strength to mechanically lock with the paint. Glycerol and citric acid modified-scots pine wood can be considered for exterior application. Keywords: citric acid, glycerol, microstructure, scots pine, surface characteristics

Research on the adhesion mechanism and compatibility of acrylate composite polyurethane binder − aggregate based on surface free energy theory

The raw materials selection and design of waterproof polymer concrete for steel bridge deck paving lack clarity regarding the adhesion mechanism and optimal compatibility between acrylate composite polyurethane binder (APUB) and various aggregates. This study systematically investigates these issues based on surface free energy (SFE) theory. Initially, Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) techniques are utilized to characterize chemical structure of APUB. Subsequently, obtaining the SFE parameters of APUB and aggregates through contact angle tests, and establishing the evaluation indices compatibility ratios ERs (ER1 and ER2) for the most compatible APUB-aggregate pairs. Finally, the correlation between ERs and the water stability of the APUB-aggregate pair is verified through shear tests conducted on sandwich specimens immersed in water. The findings reveal that APUB exhibits both acidic and non-polar surface properties. The SFE values of all aggregates surpasses that of APUB, indicating APUB's ability to wet the surfaces of all aggregates. Under dry conditions, non-polar basalt and limestone aggregates exhibit strong adhesion to APUB. This is primarily due to the combined effects of acid-base chemical reactions and the principle of compatibility, with the former predominating. Under wet conditions, APUB on non-polar basalt and limestone surfaces exhibits reduced susceptibility to displacement and detachment by water. The closer the polarity component of polar aggregates is to that of water, the easier water can displace APUB from the polar aggregate surfaces. Correlation analysis between the maximum shear force of the immersed specimens and the ER2 indicates that the APUB-basalt pair has the best compatibility. The cohesive work of APUB is crucial in establishing compatibility indicators for evaluating APUB-aggregate pairs. This study provides a theoretical basis for the raw material selection and design of polymer concrete for steel bridge deck paving.

Effect of surface treatment strategies on bond strength of additively and subtractively manufactured hybrid materials for permanent crowns

ObjectivesThe purpose of this study is to evaluate the bond strength of different computer-aided design / computer-aided manufacturing (CAD/CAM) hybrid ceramic materials following different pretreatments.MethodsA total of 306 CAD/CAM hybrid material specimens were manufactured, n = 102 for each material (VarseoSmile Crownplus [VSCP] by 3D-printing; Vita Enamic [VE] and Grandio Blocs [GB] by milling). Each material was randomly divided into six groups regarding different pretreatment strategies: control, silane, sandblasting (50 μm aluminum oxide particles), sandblasting + silane, etching (9% hydrofluorics acid), etching + silane. Subsequently, surface roughness (Ra) values, surface free energy (SFE) were measured. Each specimen was bonded with a dual-cured adhesive composite. Half of the specimens were subjected to thermocycling (5000 cycles, 5–55 °C). The shear bond strength (SBS) test was performed. Data were analyzed by using a two-way analysis of variance, independent t-test, and Mann-Whitney-U-test (α = 0.05).ResultsMaterial type (p = 0.001), pretreatment strategy (p < 0.001), and the interaction (p < 0.001) all had significant effects on Ra value. However, only etching on VSCP and VE surface increased SFE value significantly. Regarding SBS value, no significant difference was found among the three materials (p = 0.937), while the pretreatment strategy significantly influenced SBS (p < 0.05). Etching on VSCP specimens showed the lowest mean value among all groups, while sandblasting and silane result in higher SBS for all test materials.ConclusionsThe bond strength of CAD/CAM hybrid ceramic materials for milling and 3D-printing was comparable. Sandblasting and silane coupling were suitable for both millable and printable materials, while hydrofluoric etching should not be recommended for CAD/CAM hybrid ceramic materials.Clinical relevanceSince comparable evidence between 3D-printable and millable CAD/CAM dental hybrid materials is scarce, the present study gives clear guidance for pretreatment planning on different materials.

Evaluation of the electrochemical interaction in the asphalt emulsion-aggregate system of cold mix asphalt through zeta potential and surface free energy analysis

ABSTRACT The interaction in the emulsion-aggregate system is well known and influences the Cold Mix Asphalt (CMA) performance. However, the electrochemical interaction indexes for the emulsion-aggregate systems are still not well understood. Therefore, the present investigation focussed on evaluating the electrochemical interaction in the Asphalt Emulsion-Aggregate system (AEA-S) of Cold Mix Asphalt (CMA). Zeta Potential (ZP), X-ray diffraction (XRD), and Surface Free Energy (SFE) analysis were carried out in three slow-setting cationic asphalt emulsions and three common Colombian aggregates (alluvial and quarried) to determine the electrical potential and interaction in the emulsion-aggregate system. Zeta Potential analysis shows both dependence on the chemical compounds of the aggregates and variation in pH conditions. Moreover, Zeta Potential shows negative values for all three aggregates in the entire pH range variation and decreases with asphalt emulsions pH associated with SiO 2 / Al 2 O 3 ratio. Through chemical identification and electrokinetic forces is feasible to conclude that high Zeta Potential (ZP) and Surface Free Energy (SFE) values improve the electrochemical ad of the asphalt emulsion-aggregate system (AEA-S), demonstrating that high polarity is an essential factor in Cold Mix Asphalts (CMA).

Characteristics of Si (C,N) Silicon Carbonitride Layers on the Surface of Ni-Cr Alloys Used in Dental Prosthetics.

Chromium- and cobalt-based alloys, as well as chrome-nickel steels, are most used in dental prosthetics. Unfortunately, these alloys, especially nickel-based alloys, can cause allergic reactions. A disadvantage of these alloys is also insufficient corrosion resistance. To improve the properties of these alloys, amorphous Si (C,N) coatings were deposited on the surfaces of metal specimens. This paper characterizes coatings of silicon carbide nitrides, deposited by the magnetron sputtering method on the surface of nickel-chromium alloys used in dental prosthetics. Depending on the deposition parameters, coatings with varying carbon to nitrogen ratios were obtained. The study analyzed their structure and chemical and phase composition. In addition, a study of surface wettability and surface roughness was performed. Based on the results obtained, it was found that amorphous coatings of Si (C,N) type with thicknesses of 2 to 4.5 µm were obtained. All obtained coatings increase the value of surface free energy. The study showed that Si (C,N)-type films can be used in dental prosthetics as protective coatings.

UV-mediated photochemical synthesis and investigation of the antiviral properties of Silver nanoparticle-polyvinyl butyral nanocomposite coatings as a novel antiviral material with high stability and activity

Effectively developing new antimicrobial surfaces for viral diseases requires considerable research, money, and time. Moreover, new species of microorganisms and pathogens are constantly appearing or entering from other regions, which can cause epidemics or pandemics. The ongoing presence of SARS-CoV-2 underscores the need to develop new antimicrobial materials. In this context, a novel UV-irradiated photochemical in-situ synthesis method is introduced for producing durable, long-lasting antiviral silver-polymer (AgNP-PVB) nanocomposite coatings. These coatings are intended to mitigate infectious disease transmission across various frequently touched surfaces, such as door handles, keypads, bank encoders, telephone locks, lift buttons, etc. Additionally, the significance of the size and concentration of AgNP in influencing the physical and antiviral properties of these nanocomposite coatings is illustrated. Detailed studies of AgNP-PVB coatings were conducted using X-ray diffraction, Raman spectroscopy, atomic force microscopy (AFM), and ultraviolet-visible-near-infrared spectroscopy, and contact angle measurements. The antiviral properties of the coatings were evaluated by a one-step reverse transcription real-time polymerase chain reaction (one-step qRT‒PCR) using synthetic SARS-CoV-2 RNA. Raman spectra signatures confirm AgNPs in the PVB matrix by matching identified peaks in X-ray diffractograms. AFM analysis revealed a reduction in AgNP size in the nanocomposite with an increase in the irradiation duration from 5 to 30 min. Spectroscopic results corresponding to AFM measurements highlighted specific wavelengths related to different AgNP size ranges. Contact angle measurements suggest that antiviral activity can be predicted by calculating the surface free energy (SFE) of the sample. As the SFE value increases, antiviral activity decreases. Nanocomposite coatings (with concentrations of 150, 200, 500, and 1000 ppm AgNP) are effective in reducing the activity of SARS-CoV-2, indicating their potential as long-acting preventive agents against viral infections. A methodology incorporating a specialized algorithm was devised for the application of the investigated coatings, which also integrates 3D scanning and printing techniques for fabricating complex geometry flexible protective cover. Subsequently, this coating was applied to produce a protective cover for the widely utilized public object, the door handle, employing 3D printing technology. As a result of the work, a long-term, durable antiviral AgNP-PVB nanocomposite coating with varying AgNP sizes (ranging from 15 to 118 nm) and concentrations (150, 200, 500, and 1000 ppm) was successfully developed.

Effect of hydrophobic nano-silica content on the surface properties of corn-starch films

Starch-based films can be used for applications such as single-use packaging for food with a short shelf life. Hence, starch-based films could be a green alternative to some plastic packaging. This study analyzes the influence of hydrophobic silica content on mechanical properties, surface free energy, surface roughness, and morphology of corn starch-based films. For this purpose, commercially available amorphous hydrophobic nano-silica, Aerosil® R972, was used. The lowest value of surface free energy was observed for the starch films with the lowest glycerol and silica content (57 ± 1 mJ·m–2 for CG40S2.5), while the highest value was with the highest glycerol and silica content (73 ± 2 mJ·m–2 for CG80S5.0). The influence of silica content on the tensile strength decreases and elongation at break was investigated. The results showed that the surface roughness increases when the silica content increases. The SEM and EDS observation confirmed the homogeneity of the developed materials. This study shows that the commercially available Areosil® type of silica can be successfully used to change the performance of starch films.

The Influence of the Chemical Composition of Flax and Hemp Fibers on the Value of Surface Free Energy.

The article presents the exploration of flax and hemp fibers' surface free energy depending on the chemical composition of the fiber, which is closely related to the plant variety and the method of extracting the fiber. For this purpose, tests of the surface free energy (SFE), evaluation of the percentage content of individual fiber components and FTIR analyses were conducted. The research was carried out with the use of fibrous materials prepared in three different ways: 1. To analyze the effect of subsequent stages of flax fibers refining process on chemical composition and SFE, 2. to explore the dependence of fiber SFE on hemp variety, the water-retting hemp fibers were used, 3. To evaluate the influence of the retting method of hemp fibers BIAŁOBRZESKIE variety on SFE, the fibers extracted with the use of dew and water retting were used as the research material. The study confirmed that the content of individual components in the fiber influenced its sorption capacity and therefore determined its hydrophilic properties. The values of Pearson's linear correlation coefficients determined in the statistical analysis proved that the surface free energy was strongly correlated with the content of individual components in the fibers. Understanding the wettability characteristics of bast fibers will allow modeling the properties of products made of these fibers and designing surface modification processes in order to obtain specific functionality of textile products, depending on their intended utilization.

The effect of Aceria litchii (Keifer) infestation on the surface properties of litchi leaf hosts.

The wettability of target crop surfaces affects pesticide wetting and deposition. The structure and properties of the leaf surface of litchi leaves undergo severe changes after infestation by Aceria litchii (Keifer). The objective of this study was to systematically investigate the surface texture and wettability of litchi leaves infested. Firstly, the investigation focused on the surface structure and physicochemical properties of litchi leaves infested with Aceria litchii. Subsequently, different levels of Contact Angle (CA) were measured individually on the infested litchi leaves. Lastly, Surface Free Energy (SFE) and its polar and dispersive components were calculated using the Owens-Wendt-Rabel-Kaelble (OWRK) method. The outcomes revealed distinctive 3D surface structures of the erineum at various stages of mycorrhizal growth. At stage NO. 1, the height of the fungus displayed a peaked appearance, with the skewness value indicating a surface characterized by more crests. In contrast, at stages NO. 2 and NO. 3, the surface appeared relatively flat. Furthermore, post-infestation of litchi leaves, the CA of droplets on the abaxial surface of diseased leaves exhibited an increase, while the SFE value on the abaxial surface of leaves decreased significantly, in contrast to the abaxial surface of healthy leaves. The infestation behavior of Aceria litchii changed the surface structure and chemistry of litchi leaves, which directly affected the CA value of foliar liquids and the SFE value of leaves, changing the surface wettability of litchi leaves from hydrophobic to superhydrophobic. This study provides useful information for improving the wetting and deposition behavior of liquid droplets on the surface of infested leaves. © 2024 Society of Chemical Industry.

Atomic Diffusion Bonding in Air Using Oxide Films

Atomic diffusion bonding (ADB) of wafers is a promising process to achieve room-temperature wafer bonding [1]. For ADB processing, thin films are fabricated on two flat wafer surfaces using sputter deposition, with subsequent bonding of the two films on the wafers in vacuum. In addition to thin metal films [1], both oxide [2] and nitride [3] thin films are useful for bonding.For this study, after demonstrating ADB “in air” using oxide films, we compared the resultant bonding performance to that obtained using ADB “in vacuum” with the oxide films. Table 1 presents the surface free energy values at the bonded interface γ for quartz glass wafers bonded using 5-nm-thick Y2O3 film on each side. Using ADB in vacuum, great bonding strength was achieved for as-bonded wafers: the blade could not be inserted between the wafers. Using ADB in air, γ for as-bonded wafers was small, only 0.25 J/m2, but low-temperature annealing at 150 °C enhanced γ to 1.6 J/m2. At 200 °C, γ becomes greater than 2 J/m2. The annealing was conducted in air using a hot plate. Figure 2 portrays STEM cross-section images of Y2O3(5 nm)/Y2O3(5 nm) films (A) bonded in vacuum (as-bonded) and (B) bonded in air (annealed at 150 °C). The bonded interface is not visible in image (A). However, a slightly low-density bonded interface is partially visible in image (B). The difference of the bonded interface structure is consistent with that of γ presented in Table 1.Various oxide films such as TiO2, ITO, SiO2, and WO3 are useful for ADB in air, as is true also for ADB in vacuum, although post-bonded annealing at a low temperature of 150 °C is necessary for ADB in air to achieve γ greater than 1 J/m2. The bonding process of ADB in air is more convenient to execute than that in vacuum. Moreover, any mirror-polished wafer can be bonded using ADB in air, as is true also using ADB in vacuum. It is likely that H2O gas in air can adsorb on the fresh surface of oxide films efficiently and that well-hydrophilic films surfaces can be obtained easily when the deposited oxide films are removed from the vacuum chambers; in fact, low-temperature annealing at 150 °C enhanced γ remarkably. ADB in air using oxide films is useful for some applications if post-bonded annealing at low temperatures is acceptable for bonding processes. T. Shimatsu and M. Uomoto, ECS Trans., 33 (4), 61 (2010).T. Shimatsu, H. Yoshida, M. Uomoto, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. p.51 (2021).M. Uomoto, H. Yoshida, T. Shimatsu, T. Saito, T. Moriwaki, N. Kato, Y. Miyamoto, and K. Miyamoto, Proceedings of Seventh LTB-3D 2021. p.45 (2021). Figure 1

Superhydrophobic Coatings for Corrosion Protection of Stainless Steel

Corrosion is a persistent challenge in the aviation industry, affecting the safety, performance, and maintenance costs of aircraft. While composite materials have gained widespread use due to their lightweight properties and corrosion resistance, certain critical parts, such as the wing and empennage leading edges and the engine inlet, demand alternative solutions. Aluminum, titanium, and stainless steel emerge as mandatory materials for such components, given their exceptional strength and durability. However, protecting these metallic components from corrosion remains crucial. In this paper, we present a study aimed at evaluating the corrosion resistance of stainless steel, employed as an erosion shielding panel for a composite vehicle’s wing, layered with a superhydrophobic coating. The samples with and without coating have been characterized by contact angle measurements, microscopy (optical and electronic), and visual inspection after immersion in two solutions, NaCl and NaOH, respectively. The application of the superhydrophobic coating demonstrated a significant reduction in corrosion extent, especially in the demanding NaCl environment. This was evidenced by diminished formation of ripples and surface roughness, decreased iron oxide formation from oxidative processes, and a lower Surface Free Energy value in both liquid environments. Notably, the surface maintained its superhydrophobic properties even following an 8-day immersion in NaCl and NaOH solutions, demonstrating the reliability of the superhydrophobic coating offering as a potential solution to enhance the longevity and reliability of aircraft structures.

Biofilm formation of C. albicans on occlusal device materials and antibiofilm effects of chitosan and eugenol

Microbial adhesion on occlusal devices may lead to oral diseases such as candidiasis. Whether chitosan and eugenol provide antibiofilm effects is unclear. The purpose of this in vitro study was to evaluate the biofilm formation of C. albicans strains on occlusal device materials and the antibiofilm effects of chitosan and eugenol against C. albicans on these surfaces. A total of 88 specimens (5×10×2mm) were produced from occlusal device materials with 4 production techniques: vacuum-formed thermoplastic (Group V), head-press (Group H), computer-aided design and computer-aided manufacture (CAD-CAM) (Group C), and 3-dimensionally (3D) printed (Group D) (n=22). After various finishing procedures, the surface properties of the specimens were evaluated by using surface free energy (SFE), surface roughness (SR) measurements, and elemental and topographic analysis. Biofilm formation of C. albicans strain and the antibiofilm effects of chitosan and eugenol against biofilm formation on these surfaces were also examined with a crystal violet assay. The distribution's normality was statistically analyzed with the Kolmogorov-Smirnov test. One-way and two-way analysis of variance with post hoc Tukey tests were used for statistical evaluations (α=.05). Surface roughness values in Groups D and H were significantly higher than in other groups (P<.05). While the highest surface free energy values (except γp) were in Group V, Group C had the highest γp. The lowest biofilm value appeared in Group H. Chitosan exhibited an antibiofilm effect in all groups except Group H, while eugenol was effective in all groups. The production method affected the susceptibility of occlusal device materials to the adhesion of C. albicans. Eugenol was an effective antibiofilm agent for device materials.

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 &lt; 0.001) and lower CA (p &lt; 0.001) values compared to the non-coated surfaces. In addition, the surface roughness was significantly lower for the ALD-HA (p &lt; 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.

Physical-chemical influences and cell behavior of natural compounds on titanium dental surfaces.

The present study evaluated the influence of carvacrol, terpinene-4-ol, and chlorhexidine on the physical-chemical properties of titanium surfaces, cell viability, proliferation, adhesion, and spreading of fibroblasts and osteoblasts in vitro. Titanium surfaces (Ti) were treated with Carvacrol (Cvc), Terpinen-4-ol (T4ol), Chlorhexidine (CHX), DMSO, and ultrapure water (Control group). Physical-chemical modifications were evaluated by surface wettability, the surface free energy (SFE) calculated from the contact angle values using the Owens-Wendt-Rabel-Kaeble (OWRK) equation, scanning electron microscopy (SEM) and energy dispersive spectrometry probe (EDS) system. Cells were seeded onto Ti-treated surfaces and incubated for 24 h and 72 h, then evaluated by Alamar blue assay and fluorescence microscopy. Surfaces treated with Cvc and T4ol showed the presence of Na, O, and Cl. All surfaces showed hydrophilic characteristics and SFE values between 5.5 mN/m and 3.4 mN/m. On the other hand, EDS peaks demonstrated the presence of O and Cl after CHX treatment. A reduction of cell viability and adhesion was noted on titanium surfaces treated with CHX after 24 and 72h. In conclusion, the results indicate that the decontamination with Cvc and T4ol on Ti surfaces does not alter the surface proprieties and allows an adequate interaction with cells involved in the re-osseointegration process such as fibroblasts and osteoblasts.

Blade Test in Atmospheric-Pressure Ar Gas to Characterize Bonded Interface Fabricated Using Atomic Diffusion Bonding

A blade test was applied in atmospheric-pressure Ar gas for wafers bonded using atomic diffusion bonding processing. We assessed the variation of the values of surface free energy at the bonded interface γ calculated, for convenience, from the debonding length. For interfaces bonded using thin Zr and Ti films, γ measured in Ar maintained the initial value γ0(Ar) in the initial region of observation time t and started decreasing as t increased further. Results indicate that γ0(Ar) corresponds to the value without water stress corrosion effects. The initial value of γ measured in air with a higher blade insertion-speed was almost equal to γ0(Ar). Result obtained for wafers bonded using Al2O3 films were almost identical to those obtained using metal films. However, γ for wafers bonded using ZrO2 films did not maintain their initial values. They decreased gradually as t increased, even in Ar, suggesting high water stress corrosion effects.

Tunable Wettability with Stretchable Microstructured Surfaces

Analyzing the wettability of stretchable microstructured surfaces is crucial in applications like soft robotics, wearable biosensors, stretchable electronics, and electronic skin (e‐skin). However, it remains unclear how stretching affects the surface free energy (SFE) of these stretchable surfaces. In this article, stretchable microstructured surfaces are designed and fabricated, enabling liquid droplets to stay on top of the surface gaps. The corresponding SFE values are quantified as a function of both micropillar geometry and strain. It is observed that stretching could significantly affect their SFE and wettability. For instance, for the microstructured surface with pillar and gap dimensions of 10 μm, increasing the strain from 0% to 50% causes a sevenfold increase in the effective SFE. Interestingly, reversible decreasing of the strain decreases SFE to its original value, suggesting that the SFE remains unchanged after a complete stretching and releasing cycle. This trend agrees with the measurement of apparent contact angle (CA) as a function of strain. The results demonstrate stretching's capacity to significantly increase the wettability of microstructured surfaces, leading to a decrease in the CA and an increase in SFE. These findings further shed light on understanding the tunable wettability of microstructured surfaces under various deformation conditions.

Surface Free Energy for the Evaluation of Asphalt Binder Stripping

Stripping is one of the major distresses within asphalt concrete pavements caused due to penetration of water within the interface of asphalt-aggregate matrix. In this work, one grade of asphalt cement (40-50) was mixed with variable percentages of three types of additives (fly ash, fumed silica, and phosphogypsum) to obtained an modified asphalt cement to resist the effect of stripping phenomena .The specimens have been tested for physical properties according to AASHTO. The surface free energy has been measured by using two methods namely, the wilhelmy technique and the Sessile drop method according to NCHRP-104 procedures. Samples of asphalt concrete using different asphalt cement and modified asphalt cement percentages(4.1,4.6 and 5.6) were prepared and tested for stripping phenomena by using Marshall Immersion method (The index of retained stability test(I.R.S) ≥75 %. When using Sessile drop method the value of surface free energy of asphalt cement grade (40-50) was about 8.8 ergs/cm2, while when using Wilhelmy technique the value of surface free energy of asphalt cement was 30.71 ergs/cm2. Finally, a mathematical relationship was obtained by using (SPSS) Software between the strippingasphalt concrete using conditioned and unconditioned specimens data (I.R.S) %, the contact angle, the total surface free energy for asphalt cement and modified asphalt cement with fume silica.

Evaluation of Surface Free Energy Inducing Interfacial Adhesion of Amphiphilic Cellulose Nanofibrils.

Cellulose nanofibrils (CNFs) have been studied extensively over the past decade. Their applications, e.g., as fillers for nanocomposites, stabilizers for Pickering emulsions, and scaffolds for cell culture, are mostly dictated by interfacial adhesion. In general, the individual surface free energy values of the constituents of a material correlate with its adsorption and desorption behaviors. In the present study, we estimated the surface free energy values of thin films composed of CNFs using traditional contact angle methods based on the Wenzel equation and van Oss-Chaudhury-Good theory. The accuracy and utility of the estimated surface free energy values were verified by close matching between the obtained adhesion energy values and the actual interfacial adsorption behaviors of the CNFs. Therefore, the evaluated surface energy values are expected to be a feasible tool for designing of interfacial interactions between CNF surfaces and other materials.

Study of mineralization of lithium calcium phosphosilicate glass ceramics in vivo during bone tissue regeneration

Prospective directions for the creation of biologically active substitutes for bone tissue were analyzed. The effectiveness of the use of calcium phosphosilicate materials modified with CuO, ZnO, Ag2O, Fe2O3, TiO2, SrO and Nb2O5 to ensure high biocompatibility and antibacterial properties of bone endoprostheses has been established. The prospective use of lithium calcium phosphate silicate glass ceramics for obtaining strengthened, biologically active bone implants was substantiated. The main criteria for the development of biocompatible glass-ceramic materials regarding their composition, structure, texture, and surface properties have been established. The influence of differences in the structure and resorption of calcium phosphosilicate glass ceramics on the mechanism of formation of an apatite-like layer in vivo was analyzed. The features of mineralization of calcium phosphosilicate glass ceramics in vivo during bone tissue regeneration were determined, and the effectiveness of the use of glass ceramics based on hydroxyapatite and lithium disilicate in bone tissue replacement was established to reduce the rehabilitation period and long-term use of endoprostheses under variable loads. The developed OS-7 calcium phosphosilicate glass-ceramic material is characterized by the content of crystalline phases of 10 vol.% lithium disilicate and 55 vol.% hydroxyapatite with a ratio of CaO/P2O5=1.67, surface microrelief of 6 m, surface free energy value of 75 mJ/m2 and crack resistance of 6.0 MPam1/2. This material is biocompatible due to the formation of carbonate hydroxyapatite crystals already on the 14th day, which allows us to consider its promising use in the treatment of fractures, defects of long bones and in the replacement of short or tubular bones.