Surface Energy Analysis Research Articles

Fabrication of MoS2 thin films on oxide‐dielectric‐covered substrates by chemical solution process

The chemical solution process of MoS2 on high‐k oxide films has been systematically investigated. The source solution used in this work is made of (NH4)2MoS4 powder dissolved in N‐methyl‐2‐pyrrolidone. We have spin‐coated the solution on various kinds of dielectric oxide films and shown that the coating properties strongly depend on the kind of dielectric, which can be understood by surface energy analysis, following this, the growth of high quality of MoS2 film is confirmed by Raman scattering spectroscopy and X‐ray diffraction. It is demonstrated that the MoS2 film can be grown on Nb doped ZrO2 using a solution with a two‐step annealing process, where the first annealing is performed at 450 °C in H2/Ar (5:95) atmosphere for 20 min and the second annealing at 1000 °C in Ar atmosphere with S vapor for 20 min. In addition, conformal growth of a MoS2 layered structure on the curved surface of the oxide film is confirmed by transmission electron microscope observations. A further conclusion is that the thickness of MoS2 can be controlled by the concentration of a source solution and that two‐layer MoS2 is obtained when the concentration of source solution is 0.00625 mol kg−1. The measured Hall mobility of the solution‐derived MoS2 film, annealed at 1000 °C is approximately 25 cm2 V−1s−1.

Colonization by Staphylococcus aureus of Nano-Structured Fluorinated Surfaces, Formed by Different Methods of Ion-Plasma Technology.

Colonization of fluorinated surfaces produced by ion-plasma technology by Staphylococcus aureus was studied by scanning electron microscopy and surface energy analysis. It was shown that the intensity of colonization was determined by the surface relief and fluorine content. Formation of nanostructured surfaces accompanied by a sharp decrease in the surface energy prevented adhesion of Staphylococcus aureus cells to the fluorine-containing surface.

Specific surface free energy component distributions and flotabilities of mineral microparticles in flotation—An inverse gas chromatography study

In fundamental flotation studies often the contact angle with water is used to describe wettability of a mineral surface and it is correlated with flotability. A more fundamental parameter however is the specific surface free energy related to the contact angle via Young’s equation. Inverse gas chromatography (iGC) has recently been proven to be a suitable method to determine specific surface free energy components and their distributions of particulate surfaces. In this study the pure minerals quartz (SiO2), fluoro-apatite (Ca5[F,(PO4)3]), and magnetite (Fe3O4) are examined for flotabilities and surface energy component distributions considering different methods of sample treatment and the effect of the collectors sodium oleate and dodecyl ammonium acetate. The parameter of specific net free energy of interaction between bubbles and particles immersed in water ΔGpwb resulting from the complex surface energy analyses is introduced and used to evaluate the hydrophobicity of the mineral surface in correlation to microflotation recoveries. The results lead to the hypothesis that only small fractions of the surface and their change of wettability by flotation reagent adsorption will inherently define the flotability of minerals. Consequently, the main purpose of the amphiphilic collector molecules seems to be the reduction of high specific surface free energies of small fractions of the surface that lead to a strong attraction between particle surface sites and water molecules rather than the hydrophobization of the entire mineral surface, a new paradigm in flotation science.

Structure–property relationships of elementary bamboo fibers

Natural fibers are promising alternatives to synthetic fibers because of their sustainability, low environmental footprint and specific properties desirable for a wide range of technical engineering applications. The industrial implementation of fine grade natural bamboo fibers, including technical (100–200 microns) and elementary fibers (<30 microns) has been of increasing interest in recent times because these fibers offer a unique set of properties including high tensile strength, antibacterial and UV absorption. However to date, very little scientific effort has been devoted to fully understand the inter-correlation between their mechanical, physico-chemical, microstructural and morphological properties. In this paper, we report for the first time the structure–property relationship of elementary bamboo fibers. The impact of the inner microstructural organization of fibers (including the micro-fibrils angle) and physico-chemical factors such as the cellulose content and crystallinity index, on the tensile performance of these fibers is discussed in detail. This work also provides an insight into the application of bamboo fibers as natural and low-cost sorbent material for the removal of Cu2+ metal ions from model industrial wastewater. The metal ion adsorption properties of the fibers are correlated to surface energy analysis obtained from inverse gas chromatography.

Influence of low pressure cold plasma on cooking and textural properties of brown rice

Abstract The aim of this research is to study the effect of low pressure cold plasma on the cooking and textural properties of brown rice at two different power levels (40 and 50 W) and different treatment times (5 and 10 min). Cold plasma processing of foods is an emerging non thermal technology mainly used to change surface properties of substrates and microbial inactivation. Proximate composition, cooking properties and textural characteristics of plasma processed brown rice were investigated. SEM, contact angle and surface energy analysis were done to study the changes in surface morphology of plasma treated rice. It was observed that after the plasma treatment the cooking time was reduced significantly from 29.1 min to 21.1 min with respect to plasma power and time of treatment. The increase in degree of gelatinization of the cooked samples supported the decrease in cooking time. The water uptake was increased from 2.2 to 2.36 g/g after the treatment. Textural parameters showed there is decrease in hardness from 40.47 N to 30.09 N and chewiness. The extent of plasma treatment was observed as decrease in contact angle and increase in surface energy, making surface more hydrophilic and thus rice grains absorbs more water resulting in lesser cooking time. Based on the results it can be concluded that plasma application can significantly change cooking and textural properties. Industrial relevance The present work is suitable for the instant rice production industries. This technology can be used by the industries designing rice cooker. This can also be used by the countries for cooking rice, where resources are scarcity.

In vitro analysis of different properties of acrylic resins for ocular prosthesis submitted to accelerated aging with or without photopolymerized glaze

The effect of a photopolymerized glaze on different properties of acrylic resin (AR) for ocular prostheses submitted to accelerated aging was investigated. Forty discs were divided into 4 groups: N1 AR without glaze (G1); colorless AR without glaze (G2); N1 AR with glaze (G3); and colorless AR with glaze (G4). All samples were polished with sandpaper (240, 600 and 800-grit). In G1 and G2, a 1200-grit sandpaper was also used. In G3 and G4, samples were coated with MegaSeal glaze. Property analysis of color stability, microhardness, roughness, and surface energy, and assays of atomic force microscopy, scanning electron microscopy, and energy-dispersive spectroscopy were performed before and after the accelerated aging (1008h). Data were submitted to the ANOVA and Tukey Test (p<0.05). Groups with glaze exhibited statistically higher color change and roughness after aging. The surface microhardness significantly decreased in groups with glaze and increased in groups without glaze. The surface energy increased after the aging, independent of the polishing procedure. All groups showed an increase of surface irregularities. Photopolymerized glaze is an inadequate surface treatment for AR for ocular prostheses and it affected the color stability, roughness, and microhardness. The accelerated aging interfered negatively with the properties of resins.

Interfacial characterization and reinforcing mechanism of novel carbon nanotube – Carbon fibre hybrid composites

Carbon nanotube (CNT) deposition onto carbon fibre resulting in hybrid surface structures with various morphologies were successfully carried out using electrospray technique. In terms of tensile testing and Weibull analysis this process did not degrade fibre mechanical properties. When incorporated into composites, the interfacial shear strength (IFSS), as measured by single fibre fragmentation testing, increased by up to 124%. Experimental work was carried out to develop a deeper understanding of the interfacial reinforcing mechanism. Contact angle measurements demonstrated that the CNT deposition resulted in good wettability by the resin. Significant increases in roughness, friction and surface area were also found after CNT deposition, especially for the sample prepared using the parameter of 20 kV/10 cm at 100 °C. Surface energy analysis revealed that an increase in the dispersive surface energy due to the CNTs likely contributed to the improvement of interaction between fibre and matrix. Fractographic analysis revealed that the length of fibre pull-out and the size of cracks between the fibre and matrix were markedly decreased in the hybrid CNT surface structure, indicating that the stress transfer and interfacial shear strength have been improved. Finally, the potential for further improvement in interfacial composite properties by this approach was assessed.

DFT study on the water molecule adsorption and the surface dissolution behavior of Mg alloys

Mg-based alloys have a strong potential for various structural and biomedical applications. A critical issue associated with Mg-based alloys is their high degradation (corrosion) rates in oxidation environments. It is known that both the internal crystal structures and the impurity compositions/contents in the Mg alloys can affect the degradation rates. In the present work, we employed the density-functional theory (DFT) computation technique to understand the surface degradation behaviors with different crystallographic orientations and impurity elements from an atomistic point of view. Here, we studied the adsorption response of a water molecule to the Mg alloy surface and the dissolution of surface atoms that can be potentially applied to describe the degradation behavior of Mg/Mg alloy. The tendency for water molecule adsorption was quantified for Mg-based slab systems with low-index surface planes and various alloying elements including Al, Zn, Ca, and Y. The trends for surface degradation from these systems were examined using surface energy analysis and electrode potential shift analysis. The results show that adding Ca and/or Y increases the propensity to attract a water molecule to the alloy surface. Also, it was generally found that the relative electrode potential shift of Mg-Y alloys is positive while those of all other alloys are negative.

Wetting behavior of patterned micro-pillar array predicted by an equivalent surface tension model

Micro-pillar array is widely applied to manipulate the wettability of surfaces. Cases where liquid has infiltrated such pillar arrays completely are drawing increased attention in miniaturized systems. An equivalent surface tension model is proposed to characterize the driving force of liquid evolution in patterned micro-pillar arrays after the Young-Laplace equation and surface energy analysis are applied on both the pillar unit and bulk liquid levels. The effects of local menisci induced from the wetting of pillars are bounded and treated as “equivalent liquid-vapor surface tension”, through which the bulk liquid profile is then obtained based on the principle of minimal surface energy. The model is found to be computationally efficient and can be easily obtained through numerical methods. A typical sample case is presented to demonstrate its advantages and simplicity. The bulk profile that considers the effects of pillar array is compared with the result without pillars. The influencing effects, including apparent tilt angle, pillar spacing, and pillar shape, are addressed.

Analysis of surface energy and mass balance in the accumulation zone of Qiyi Glacier, Tibetan Plateau in an ablation season

Previous work on glaciers in the Tibetan Plateau has focused mainly on the ablation zone, while only a modest amount of work has been done on surface energy balance in the accumulation zone on glaciers. To better understand glacial melting in the accumulation zone of high-altitude continental glaciers, a physically based energy-balance model was used to investigate characteristics of the surface energy budget and mass balance on Qiyi Glacier, at the northern margin of the Tibetan Plateau, from 30 July to 9 October 2011. The model was validated by comparing the computed and observed mass variation. The result shows that modeled cumulative mass balance was −60.5 mm w.e. and the measured one was −69.6 mm w.e. The modeled and measured accumulated mass balances compared well in August (r = 0.98, p < 0.001), but less so in September due to the influence of precipitation (r = 0.73, p < 0.01). Improved precipitation observation will therefore be needed. In August, the month of greatest melting, net radiation, R n, was the primary component of the SEB, dominating the total surface energy heat fluxes (67 %), followed by turbulent sensible heat flux (13 %), latent heat flux (9 %) and conductive heat flux (11%). However, in September, the contribution of R n sharply decreased (15 %), and sensible heat flux (40 %) was the primary component of the surface energy balance. Over the observation period, R n accounted for only 51 % of the total heat flux. Strong sublimation was found in the accumulation zone during the study summer period, and positive latent heat flux during several days further illustrates that the glacier is occasionally influenced by monsoon activity.

Atomic relaxation, stability and electronic properties of Mg2Sn (100) surfaces from ab-initio calculations

Abstract Mg 2 Sn (100) surfaces were investigated using ab-initio method based on density functional theory in order to explore the surface properties. It is found that both the eleven-layers for Mg-termination surfaces and the nine-layers for Sn-termination surfaces are all converged very well. The effects of relaxation mainly occurred within the three outermost atomic layers for both Mg and Sn terminations during the surface relaxation. Mg-termination surfaces are more stable than Sn-termination surfaces according to the analysis of surface energy. The density of states reveals the metallic property of both Mg-termination and Sn-termination surfaces. Covalent bonding exists in Mg 2 Sn (100) surfaces according to the analysis of partial density of states.

Aging effect of atmospheric air on lithium disilicate ceramic after nonthermal plasma treatment

Statement of problemNonthermal plasma (NTP) treatment is an alternative technique for promoting the adhesion of resin cement to lithium disilicate ceramic. However, no study has evaluated whether the surface modifications are affected by atmospheric air aging. PurposeThe purposes of this in vitro study were to characterize the lithium disilicate surface after depositing an organosilicon film with NTP treatment and to verify the surface energy before and after atmospheric air aging up to 30 days. Material and methodsSixteen lithium disilicate disks (10×3 mm) were prepared, and their surfaces were treated with a mixture of hexamethyldisiloxane and argon, followed by oxygen plasma treatment, both for 30 minutes. The lithium disilicate surface was characterized through scanning electron microscopy, energy-dispersive spectroscopy, and atomic force microscopy. Surface energy analysis was performed before (T0) and immediately after NTP treatment (T1) and after atmospheric air aging for 7 (T2), 15 (T3), and 30 days (T4). Data were submitted to analysis of variance followed by the Tukey HSD test (α=.05). ResultsCarbon, oxygen, and silicon were identified on the disilicate surface after NTP treatment, suggesting organosilicon film adhesion. Air aging did not modify the film morphology. At T1, the surface energy was significantly higher compared with other periods, and the water contact angle on the disilicate surface was reduced to 0 degrees. Similar surface energy was observed for T0, T2, T3, and T4. ConclusionsOn the basis of the results of this in vitro study, NTP treatment can promote bonding to lithium disilicate surfaces because of its high surface wettability. However, after air aging, the wettability was not durable.

Effect of nonthermal plasma treatment on the surface of dental resins immersed in artificial saliva

Abstract This study aimed (1) to use scanning electron microscopy associated with energy-dispersive spectroscopy (SEM-EDS) to characterize the surface of dental resins after nonthermal plasma (NTP) treatment and (2) to use surface energy analysis to evaluate whether NTP treatment protects the microhardness of the resins against the degradative effects of saliva. Twenty-eight acrylic and composite resin discs were fabricated and divided into four groups. Two groups received no surface treatment [control acrylic resin (Co/AR) and control composite resin (Co/CR] and two groups [NTP-treated acrylic resin (NTP/AR) and NTP-treated composite resin (NTP/CR)] were treated with NTP. One disc from each group was analyzed using SEM-EDS. Ten discs were subjected to surface energy analysis (before and after NTP) and microhardness assessments (at various time points). p&lt;0.05 was used to determine statistical significance. Surface energy decreased after NTP treatment. Microhardness was reduced after 30 days in the Co/AR group and between 15 and 30 days in the NTP/AR group. Microhardness decreased in the Co/CR group after 15 and 30 days, whereas there was no difference after 30 days in the NTP/CR group. SEM images showed the presence of cracks and holes after 30 days in both Co/AR and NTP/AR groups. Cracks and silicon particles were observed after 30 days in the Co/CR group. Both the acrylic and composite resins exhibited hydrophobic properties after NTP treatment. The reduction in microhardness of the acrylic resin after NTP treatment was lower than that of the composite resin.

Self-assembled oleamide layer applied for cathode buffer layer of bulk heterojunction solar cells based on PTB7:PC71BM

In this work, bulk heterojunction solar cells based on poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b′]dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl)carbonyl]thieno[3,4-b]-thiophenediyl]] and phenyl-C71-butyric-acid-methyl-ester were fabricated using 1,2-dichlolobenzene solutions containing different weight ratios of oleamide. The oleamide layers were self-assembled on the active layer surfaces during the solidification of the active layer after spin coating. A significant increase in open-circuit voltage was observed after the introduction of oleamide at the expense of short-circuit current density. The optimal performance of the solar cell was obtained by spin coating the active layer at 1000 rpm for 60 s using a 1,2-dichlolobenzene solution containing 3% oleamide. The solar cell exhibited a short-circuit current density, an open circuit voltage, a fill factor, and a power conversion efficiency of 13.95 mA/cm2, 0.79 V, 0.47, and 5.22%, respectively. These solar cell behaviors are discussed on the basis of results of morphological analysis by optical microscopy, atomic force microscopy, and surface energy analysis.

Effect of hydrothermal dewatering on the physico-chemical structure and surface properties of Shengli lignite

Shengli lignite from China was treated by hydrothermal dewatering (HTD) under 200–300°C. The changes of physico-chemical structure and surface properties of Shengli lignite were tested and the relationship between these changes was analyzed. The equilibrium moisture content of Shengli lignite decreased from 29.75% in raw coal to 7.40% in HTD-300 (the sample treated by HTD under 300°C) due to the decomposition of oxygen functional groups and the alternation of hydrophilic property of the coal sample. The coal upgrading by the HTD process was shown through the decrease in atomic ratios of oxygen to carbon (O/C) and hydrogen to carbon (H/C) due to the decomposition of functional groups and side-chains, which should be the important reason for the change of pore size distribution. The analysis of surface energy showed that the decrease of hydrophilicity was mainly caused by the reduction of acidic components, which provides another evidence for that the decomposition of carboxyl and hydroxyl resulted in the decrease of equilibrium moisture content.

Facile dielectric surface-modification methodology for high-performance polymer transistors via thermal evaporation of polydimethylsiloxane

Here we demonstrate a novel surface-modification methodology for dielectric layers to be used for high-performance organic field-effect transistors (OFETs). Instead of conventional solution-processed polymeric thin films or self-assembled monolayers such as octadecyltrichlorosilane, we introduce thermally evaporated thin films of polydimethylsiloxane (PDMS) processed at atmospheric conditions. The thermally evaporated PDMS (TEP) thin film possesses various merits compared to other surface-treated films in terms of surface hydrophobicity, smoothness, reproducibility, and large-area deposition. From surface energy analyses, X-ray photoelectron spectroscopy, near-edge X-ray absorption fine structure spectroscopy, grazing incident X-ray diffraction, and atomic force microscopy analyses, we prove the overall superiority of TEP over other surface-treated films for OFETs. Using a conventional semiconducting polymer of poly(2,5-bis(3-hexadecylthiophen-2-yl)thieno[3,2-b]thiophene) (PBTTT), OFETs with TEP dielectric layers are demonstrated to have higher charge carrier mobility, better on/off ratio, and superior reproducibility compared to OFETs with other buffer layers. The relationships between dielectric surface properties and OFET performance are fully discussed in conjunction with the above-mentioned analyses. In addition, the reproducibility of the TEP-based OFET is demonstrated by long-term fabrication and measurement analyses.

Inverse gas chromatography a tool to follow physicochemical modifications of pharmaceutical solids: Crystal habit and particles size surface effects

Powders are complex systems and so pharmaceutical solids are not the exception. Nowadays, pharmaceutical ingredients must comply with well-defined draconian specifications imposing narrow particle size range, control on the mean particle size, crystalline structure, crystal habits aspect and surface properties of powders, among others. The different facets, physical forms, defects and/or impurities of the solid will alter its interaction properties. A powerful way of studying surface properties is based on the adsorption of an organic or water vapor on a powder. Inverse gas chromatography (IGC) appears as a useful method to characterize the surface properties of divided solids.The aim of this work is to study the sensitivity of IGC, in Henry’s domain, in order to detect the impact of size and morphology in surface energy of two crystalline forms of an excipient, d-mannitol. Surface energy analyses using IGC have shown that the α form is the most energetically active form. To study size and shape influence on polymorphism, pure α and β mannitol samples were cryomilled (CM) and/or spray dried (SD). All forms showed an increase of the surface energy after treatment, with a higher influence for β samples (γsd of 40–62mJm−2) than for α mannitol samples (γsd of 75–86mJm−2). Surface heterogeneity analysis in Henry’s domain showed a more heterogeneous β-CM sample (62–52mJm−2). Moreover, despite its spherical shape and quite homogeneous size distribution, β-SD mannitol samples showed a slightly heterogeneous surface (57–52mJm−2) also higher than the recrystallized β pure sample (∼40mJm−2).

Aging Effect of Atmospheric Air on Zirconia Surfaces Treated by Nonthermal Plasma.

The purpose of this study was twofold: 1) to characterize the zirconia (Y-TZP) surfaces through scanning electronic microscopy associated with energy-dispersive spectroscopy and atomic force microscopy after the deposition of a thin organosilicon film by nonthermal plasma (NTP) treatment, and 2) to determine the zirconia surface hydrophilicity, before and after aging, through surface energy analysis. Surfaces of 16 zirconia disks (10 x 3 mm) were treated for 30 min each with hexamethyldisiloxane and argon plasmas, followed by oxygen plasma. Disks were analyzed before NTP treatment, immediately after NTP treatment, and after aging for 7, 15, and 30 days. The surface energy of the Y-TZP disks was measured with a goniometer. Quantitative data were submitted to statistical analysis using ANOVA and Tukey's test (p < 0.05). Immediately after NTP treatment, the surface energy of the zirconia disks was significantly higher than at any other tested period (p < 0.001), and the water contact angle on the zirconia disks was reduced to 0 degrees. Similar surface energy results were obtained before NTP treatment and after 15 or 30 days of aging (p > 0.05; Tukey's test). Energy-dispersive spectroscopy results revealed the presence of carbon, oxygen, and silicon on the surface after NTP treatment. NTP treatment was useful for treating the zirconia surface for cementation procedures, as it produced a high level of hydrophilicity on the zirconia surface. However, this high level of hydrophilicity did not persist after aging.

Thermal behavior, surface energy analysis, and hemocompatibility of some polycarbonate urethanes for cardiac engineering

The understanding of basic surface properties and the relationships between temperature and the configuration of the polymer surface are the key to further understand the first interaction mechanism of the polymer with the body. To this end, some poly(carbonate tetramethylene ether)urethane (PCEU), poly(carbonate siloxane tetramethylene ether)urethane (PCSiEU), and their 1:1 gravimetric mixture (PCEU/PCSiEU) membranes were prepared. In order to establish the relationships between temperature and the chemical structure of polymer surface, the polyurethane (PU) membranes were analyzed by attenuated total reflectance–Fourier transform infrared spectroscopy. The temperature has a significant influence on these PU surface structures. Surface characteristics such as wettability and surface free energy were also analyzed since the interaction between biomaterials and blood occurs at their interface. The preliminary cytotoxicity screening showed no cytotoxicity of these PU membranes. The PU samples do not accelerate the clot formation mechanisms under the tested conditions. The results suggest that these PU membranes are promising materials for the preparation of cardiovascular scaffolds.

Bulk Heterojunction Solar Cell with Nitrogen-Doped Carbon Nanotubes in the Active Layer: Effect of Nanocomposite Synthesis Technique on Photovoltaic Properties

Nanocomposites of poly(3-hexylthiophene) (P3HT) and nitrogen-doped carbon nanotubes (N-CNTs) have been synthesized by two methods; specifically, direct solution mixing and in situ polymerization. The nanocomposites were characterized by means of transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray dispersive spectroscopy, UV-Vis spectrophotometry, photoluminescence spectrophotometry (PL), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermogravimetric analysis, and dispersive surface energy analysis. The nanocomposites were used in the active layer of a bulk heterojunction organic solar cell with the composition ITO/PEDOT:PSS/P3HT:N-CNTS:PCBM/LiF/Al. TEM and SEM analysis showed that the polymer successfully wrapped the N-CNTs. FTIR results indicated good π-π interaction within the nanocomposite synthesized by in situ polymerization as opposed to samples made by direct solution mixing. Dispersive surface energies of the N-CNTs and nanocomposites supported the fact that polymer covered the N-CNTs well. J-V analysis show that good devices were formed from the two nanocomposites, however, the in situ polymerization nanocomposite showed better photovoltaic characteristics.