Surface Wettability Measurements Research Articles

Effects of combined zinc chloride-ultrasound pretreatment and thermal modification on the physicochemical properties of Moso bamboo

BackgroundTo save energy and reduce emissions during the thermal modification of Moso bamboo, this study investigated the effect of the combined zinc chloride-ultrasound pretreatment and thermal modification on the physicochemical properties of Moso bamboo. MethodsSamples were pretreated using 5% (w/w) ZnCl2 solution and 40 kHz ultrasonic waves, followed by heat treatment at 160 °C. The samples were characterized by moisture absorption measurements, X-ray diffraction, Fourier-transform infrared spectroscopy, surface wettability measurements, thermogravimetric analysis, and colorimetry. FindingsThe results showed that the combined pretreatment method reduced the moisture absorption by 10.15% and increased the relative crystallinity of Moso bamboo cellulose by 4.4%. It also increased the surface contact angle by 25.2%, lowered the onset of thermal decomposition, reduced the temperature required for hemicellulose to reach its maximum thermal degradation rate by 49 °C, and increased the color change (∆E*ab) by 23.60.

Effect of different inorganic draw solutes on SiNPs-TFN membrane for forward osmosis desalination

Forward osmosis (FO) is the most promising upcoming desalination technique which requires more detailed researches to reduce its challenges like low pure water flux and high reverse solute flux. This paper represents the fabrication of thin-film nanocomposite polyethersulfone membrane with 0.005 wt% of silica nanoparticle (SiNPs) loading and analysis of FO performance of the fabricated TFN membrane. The nanoparticle was incorporated into the polyamide active rejection layer by interfacial polymerization. Membrane characterizations like ATR-FTIR, SEM, and wettability analysis were done. Successful nanoparticle incorporation was confirmed by ATR-FTIR analysis. Rise in hydrophilicity of TFN membrane was confirmed surface wettability measurements. The effect on draw solution concentration as well as cross-flow rate on membrane performance was analyzed. Comparison of forward osmosis performance with various inorganic draw solutes was also tested. The draw solutes considered were KCl, NaCl, and CaCl2 due to its various applications in fertigation and desalination. The filtration parameters of the fabricated membranes are analyzed and enlisted. The membrane FO performance under AL-FS and AL-DS modes of operation was tested. Results show that fabricated TFN membrane obtains a maximum flux of 23.93LMH in AL-DS mode, and salt rejection was 91%.

Appraisal of surface preparation in adhesive bonding of additive manufactured substrates

This work emphasizes the critical need of surface preparation to improve the performance of adhesively bonded 3D printed Acrylonitrile Butadiene Styrene (ABS) adherends obtained using Fused Filament Fabrication (FFF). In particular, mechanical abrasion and two different plasma pre-treatments, i.e., Atmospheric Pressure Plasma (APP) and Low-Pressure Plasma (LPP), were compared through the qualitative analysis of surface wettability, using static and dynamic contact angle measurements, and the quantitative evaluation of surface roughness measured using optical profilometry. In addition, mechanical tests were carried out using the single lap joint configuration and the interaction between the treated ABS substrates and three different adhesive materials, epoxy, polyurethane and modified silane, were carefully ascertained. The results indicated that the plasma process at low pressure (LPP) enabled a substantial decrease of contact angle (θ < 10o), with little modifications of surface morphology and topography with respect to the reference solvent cleaned surface (θ > 80o). The improved wetting was accompanied by a relevant increase in the joint strength. The actual mechanism of fracture shifted from adhesive failure, typical of solvent cleaned and abraded surfaces, to full cohesive failure within either the substrates of the adhesive layer. Besides, a strong influence of the adhesive selected for manufacturing was reported. Indeed, using a tough bi-component epoxy adhesive in conjunction with the LPP pre-treatment led to substrate failure, representing the largest possible enhancement of joint strength. The shear strength was over 300% of that obtained with reference solvent cleaned, and 80% larger than that recorded on abraded surfaces.

The role of the spatial heterogeneity and correlation length of surface wettability on two-phase flow in a CO2-water-rock system

This study characterized and modeled heterogeneous surface wettability in sandstone and investigated the role of spatial heterogeneity and correlation length of surface wettability on relative permeability in a supercritical CO2 (scCO2)-brine-rock system. Understanding the role of wettability heterogeneity on relative permeability is essential to geological CO2 sequestration, oil and gas recovery, and contaminated groundwater remediation. Although numerous studies have attempted to understand the influences of surface wettability, capillary number (Ca), and viscosity ratio, the role of the spatial variation and correlation length of surface wettability on two-phase flow in three-dimensional (3D) porous media has not been unraveled due to the challenges in the measurement and representation of realistic rock surface wettability. In this work, we conducted in-situ measurements of surface contact angle (CA) in a Bentheimer sandstone after CO2 flooding using micro-computed tomography (micro-CT), and found that the pore-scale CA distribution on rock surfaces followed a log-normal distribution associated with a spatial correlation length. Based on the statistical information from CT scanning, a Gaussian random field was used to model CA distributions that had desired standard deviations and spatial correlation lengths, which were then adjusted within a certain range of values for sensitivity analyses to study their combined effects on the two-phase flow in the porous medium using the lattice Boltzmann (LB) method. The LB two-phase flow simulation was accelerated using hybrid, multicore parallel computing to overcome the challenges in simulating multiphase flow in a large 3D domain having 800 × 800 × 600 nodes. The simulation results showed that the surface wettability heterogeneity (i.e., standard deviation of CA) had a lesser effect on the relative permeability of the wetting fluid (water) but a more significant impact on the relative permeability of the non-wetting fluid (scCO2). The Corey model was used to fit the LB-simulated relative permeability curves of water and scCO2 and showed that the variations in the relative permeability curves for both water and scCO2 increased as the standard deviation and spatial correlation length of CA increased. This study illustrated that the assumption of homogeneous surface wettability may cause errors in multiphase flow simulations. The impacts of both the standard deviation and spatial correlation length of CAs should be accounted for. This is the first study that explored the spatial correlation lengths associated with CA distributions on sandstone surfaces and comprehensively investigated the roles of both spatial variation and correlation length of CA on two-phase flow properties in 3D porous media. The optimized LB multiphase flow model was proved a powerful tool to study the interplays and combined effects of these statistical parameters, which had critical applications in numerous natural and engineering processes that involved multiphase flow in porous media.

Vitamin B12-loaded polycaprolacton/gelatin nanofibrous scaffold as potential wound care material

The current study aimed to develop a potential wound dressing using vitamin B12-loaded polycaprolacton/gelatin nanofibrous scaffold. In order to produce wound dressings, 1000 mcg of vitamin B12 was added to polycaprolacton/gelatin solution and the nanofibrous scaffolds were fabricated through electrospinning method. The obtained scaffolds were studied regarding their hydrophobicity, microstructure, amount of water absorption, water vapor permeability, tensile strength, release test, and cellular proliferation assay. In vitro studies revealed that the incorporation of vitamin b12 into polycaprolacton/gelatin scaffolds could significantly augment L929 cells proliferation at 1 and 3 days post-seeding. However, there was not statistically significant difference between Vitamin B12-containing and polymer-only scaffolds in tensile strength study, surface wettability measurement, water vapor transmission test, the capacity for water absorption, and nanofiber's diameter. Both vitamin containing and free dressings were applied on the full-thickness excisional wound in rat model to compare their healing potential. Our results showed that after 14 days, vitamin B12 containing dressing could significantly enhance wound closure compared to vitamin B12 free scaffolds (92.27 ± 6.84% vs. 64.62 ± 2.96%). Furthermore, histopathological examinations showed significantly greater epithelial thickness in polycaprolacton/gelatin/vitamin B12 group compared to other experimental groups. This preliminary study suggest potential applicability of the proposed dressing to treat skin wounds in clinic.

The Effect of 45S5 Bioglass and Ag, Cu, or Zn Addition on the Crystal Structure, Properties, and Antibacterial Effect of Bulk Ti23Zr25Nb Biocomposites

In the present study, the crystal structure, microstructure, mechanical, corrosion properties, and wettability of bulk Ti23Zr25Nb-x45S5 Bioglass (x = 0, 3, 6, 9 wt.%) and Ti23Zr25Nb—9 wt.% 45S5 Bioglass composites with the addition of 1 wt.% Ag, Cu, or Zn were synthesized and their properties studied. The hardness of these biomaterials is at least two times higher and the elastic modulus lower in comparison to commercial purity (CP) microcrystalline α-Ti. The mechanically alloyed Ti23Zr25Nb—9 wt.% 45S5 Bioglass composite was more corrosion resistant in Ringer’s solution than the bulk Ti23Zr25Nb alloy. Surface wettability measurements revealed the higher surface hydrophilicity of the bulk synthesized composites. The antibacterial activity of Ti23Zr25Nb-based composites containing silver, copper, or zinc against reference strain Streptococcus mutans ATCC 25175 was studied. In vitro bacterial adhesion indicated a significantly reduced number of S. mutans on the bulk Ti23Zr25Nb-BG-Ag (or Cu, Zn) plate surfaces in comparison to the microcrystalline Ti plate surface. Ultrafine-grained Ti23Zr25Nb-BG-Ag (or Cu, Zn) biomaterials can be considered to be the next generation of dental implants.

Properties of Binary Mixture of Cetyl Diphenyl Ether Disulfonate and Linear Alkylbenzene Sulfonate

Abstract The surface properties of the binary mixture of cetyl diphenyl ether disulfonate (C16-MADS) and linear alkylbenzene sulfonate (LAS) have been investigated by salinity and hardness tolerance, equilibrium surface tension, wettability, foam and emulsification measurements. The results show that with increasing mass ratio of LAS in the C16-MADS/LAS mixed system, the ability to reduce the surface tension of the solution is improved. The wetting performance is also improved. The critical micelle concentration (CMC) values are increased first, then decreased, and are higher than the ideal CMC values, which indicates that there is an antagonistic effect that is not conducive to the formation of mixed micelles between C16-MADS and LAS. In addition, the C16-MADS/LAS system improves the hard water resistance of LAS and reduces the foam properties of LAS.

Ion irradiation effects on Cr-coated zircaloy-4 surface wettability and pool boiling critical heat flux

The concept of coating the currently used nuclear fuel cladding (zirconium-based alloy, typically Zircaloy-4 or Zirc-4) with an oxidation preventive layer is a progressing Accident tolerant Fuel (ATF) candidate alloys. The coated Zirc-4-based alloys could be a solution to suppress undesirable fast reaction kinetics with high-temperature steam. Zirc-4 has been the most preferred cladding material in pressurized water reactors (PWRs). Chromium (Cr) based alloys as a coating material provides excellent corrosion protection and good strength and wear resistance. This paper presents the surface wettability measurements and pool boiling Critical Heat Flux (CHF) for Cr-coated Zirc-4 claddings pre- and post-exposure to an ion irradiation environment.The wettability measurements, including static contact angle (contact angle, θ) and average surface roughness (surface roughness, Ra), are introduced for samples of different coating thicknesses (5–30 μm thick). The coatings fabricated by the cold spray of Cr-Al particles to 10 mm × 10 mm × 1.95 mm Zirc-4 substrates. Post fabrication, a Pilgering (cold rolling) process, was applied to finalize the coating thickness and resulted in a significant reduction in surface roughness of initially fabricated rough surfaces. The process produced three distinguished samples 5-μm unpolished (as machined), 5-μm, and 30-μm polished (cold rolled). The measurements are presented for the three surfaces and bare Zirc-4 as a baseline surface. The contact angle analyses were implemented in theoretical models from the literature to predict pool boiling CHF. Pool boiling experiments were conducted to measure the pool boiling CHF values and compare them to the predicted values. Scanning Electron Microscope (SEM) images and Energy Dispersive X-ray Spectroscopy (EDS) analysis was performed to characterize the surfaces for better understanding and interpreting the results.The SEM images showed localized surface damage due to ion irradiation. No recognized change in the measured surface roughness due to ion irradiation. The contact angles of irradiated Cr-coated surfaces are consistently higher (10°) than pre-irradiated surfaces. Decreasing the Cr-coating layer thickness resulted in lower contact angle pre- and post- ion irradiation. The predicted pool boiling CHF using the Kandlikar model is in good agreement with the experimentally measured CHF values within ±12% for all samples.

Effect of hydroxyapatite and Ag, Ta2O5 or CeO2 addition on the properties of ultrafine-grained Ti31Mo alloy

In the present study, the crystal structure, microstructure, mechanical and corrosion properties of bulk Ti31MoxHA composites (x = 0, 2.5, 5 and 10 wt %) were investigated. The sintering of Ti31MoxHA powders led to the formation of a bulk composite with grain size of approx. 1 μm. All these composites have elastic modulus lower than CP microcrystalline α-Ti, and their hardness is two times higher. The ultrafine Ti31Mo5HA composite was more corrosion resistant in Ringer solution than the bulk Ti31Mo alloy. Surface wettability measurements revealed the higher surface hydrophilicity of the bulk ultrafine-grained Ti31Mo10HA sample in comparison to microcrystalline Ti sample. Ti31Mo5HA composites with the addition of 1 wt % Ag, 2 wt % Ta2O5 or 2 wt % CeO2 were synthesized, too. The antibacterial activity of Ti31Mo5HA composite containing silver (Ag), tantalum (V) oxide (Ta2O5) or cerium (IV) oxide (CeO2) against Staphylococcus aureus was studied. In vitro bacterial adhesion, study indicated a significantly reduced number of S. aureus on the bulk ultrafine-grained Ti31Mo5HA-Ag (Ce2O3) plate surfaces in comparison to microcrystalline Ti plate surface. Ultrafine-grained Ti31Mo5HA - Ag or CeO2 biomaterials can be considered to be the future generation of medical implants.

Mussel inspired bacterial denitrification of water using fractal patterns of polydopamine

Nitrate is currently one of the most significant causes of water pollution in many parts of the world due to its detrimental effects on humans and the environment. The purpose of this study was to find a novel immobilization method based on bacterial adsorption to adhesive coating material, for use in water denitrification. The fractal formation capability of polydopamine (PDA) allowed coating of the surface of in-house asymmetric polyethersulfone (PES) beads (1.65–2.35 mm in diameter), and immobilizing the denitrifying bacteria Pseudomonas stutzeri with noticeable denitrification potential, on the surface of hyper-branched PDA coated beads. For surface characterization, SEM, wettability measurement, and ATR-FTIR spectroscopy were performed. Nitrate and nitrite concentrations were measured by APHA standard method 4500-NO3−-B and a colourimetric method using two reagents respectively. The effects of temperature, pH and different carbon sources (Acetic acid, methanol, and ethanol) on the denitrification process were also investigated. The results revealed that the bacterial immobilization on PES surface with fractal patterns of PDA (with fractal dimension (Df) value of 1.57) was successful, and the optimum parameters for nitrate removal were established as 25 °C, pH = 8, and 420 mg/L ethanol as the carbon source. Finally, this research showed that under the optimum conditions the immobilized bacteria exhibited 100 % removal efficiency for 28 mg of NO3–N in 22 h (removal rate: 8.06 mg NO3-N/h/mg biomass of bacteria). We found that the immobilization of bacteria on the PDA coated beads is practicable and that the denitrification rate is adequate.

Evaluation of protein adsorption to diamond-like carbon (DLC) and fluorinedoped DLC films using the quartz crystal microbalance method.

The aim of the present study was to evaluate albumin adsorption to stainless steel (SUS), diamond-like carbon (DLC) and fluorinedoped DLC (F-DLC) films using the quartz crystal microbalance (QCM) method. Each sensor was characterized using atomic force microscopy, surface roughness and surface wettability measurements and surface free energy calculations. Adsorbed amounts of bovine serum albumin on DLC and F-DLC were significantly lower than that on SUS (p<0.05). The apparent first-order reaction rate, kobs, of F-DLC was significantly larger than those of SUS and DLC (p<0.05). Moreover, significantly lower total surface free energies of DLC and F-DLC influenced the albumin absorbed amounts and kobs. Furthermore, a clear correlation was found between the albumin absorbed amounts and the hydrogen bond component of the total surface free energy. Thus, DLC or F-DLC coating is effective for preventing protein adsorption on orthodontic appliances.

Changes in wettability of wood surface using electron beam irradiation

ABSTRACT This study deals with the influence of electron beam irradiation (EBI) on the wettability of Norway spruce surface samples. To evaluate this possible effect in detail, the changes in chemistry and wood structure were analysed using the methods of IR spectroscopy and Scanning Electron Microscopy (SEM). The surface wettability was determined by the contact angle measurement method. The results of infrared spectra show decreased relative numbers of available hydrophilic groups (e.g. hydroxyl and carbonyl groups) in the wood surfaces due to the electron beam irradiation. This behaviour is consistent with the values from the surface wettability measurements. Structural differences of the wood surfaces after electron beam irradiation were not detectable. Based on these findings pre-treatment of wood surfaces for industrial usages can be a potential field of application of this technology.

Surface wettability and pool boiling Critical Heat Flux of Accident Tolerant Fuel cladding-FeCrAl alloys

Abstract Surface wettability analysis, including measurements of static (θ) advance (θ A ), and receding (θ r ) contact angles, and surface roughness, Ra, are effective parameters used in the literature to predict changes in the pool boiling Critical Heat Flux (CHF). The CHF is an important aspect of the thermal hydraulic performance that needs to be investigated for new Accident Tolerant Fuel (ATF) cladding materials, such as iron-chromium-aluminum alloys (FeCrAl). Surface wettability of FeCrAl samples oxidized under different simulated Light Water Reactor (LWR) water chemistry conditions was measured. These measurements were compared to as-machined and oxidized Zircaloy-4 (Zirc-4), the reference cladding material in LWRs, under the same conditions. Theoretical models were used to predict the pool boiling CHF using surface wettability measurements. Pool boiling experiments were conducted using the same samples to measure the CHF. The measured and predicted CHF data were compared for model validation. The obtained results showed no significant difference in the measured static contact angle and hence the predicted CHF between the as-machined samples of FeCrAl, 310 SS, and Zirc-4. The contact angles (static, advance, and receding angles) for corroded FeCrAl samples under different LWR water chemistry conditions are lower, and the measured surface roughness values are higher than Zirc-4 corroded under the same conditions. Existing models in the literature predicted higher pool boiling CHF of corroded FeCrAl compared to 310 stainless steel (SS), and Zirc-4. The measured pool boiling CHF for oxidized FeCrAl samples was higher than Zirc-4 samples. The measured and predicted CHF values are in good agreement. The CHF and the Departure from Nucleate Boiling Ratio (DNBR) were calculated using the Consortium for Advanced Simulation of Light Water Reactors (CASL) subchannel code COBRA-TF (CTF) for a one-eighth model of a 17 × 17 Pressurized Water Reactor (PWR) fuel assembly. The inlet conditions are consistent with typical PWR values except for the power, which was set 50% higher than is typical to represent possible accident conditions more accurately. The calculated distributions for the CHF and DNBR for oxidized FeCrAl showed significantly higher values throughout the fuel assembly octant compared to as machined Zirc-4 and as machined FeCrAl. These preliminary results show that oxidized FeCrAl may be able to withstand the proposed accident conditions without leading to a boiling crisis.

The relationship between enthalpy of immersion and flotation response

The enthalpy of immersion is the heat change arising from the replacement of the solid-gas interface with the solid-liquid interface when a solid surface is immersed in a liquid. Although immersion calorimetry has been established as a reliable means of determining wettability of solid surfaces, it has found only limited applications in flotation research where wettability of mineral ores is a key variable. In this study, precision solution calorimetry was employed to measure the enthalpies of immersion of different minerals in water. These values were then related to the first-order flotation rate constants as determined by microflotation. The same measurements were also made on sulphide minerals whose surfaces were modified using different percentage coverages of potassium amyl xanthate collector.It was found that there was a strong inverse relationship between the enthalpy of immersion of the minerals studied and their wettability as indicated by their rates of flotation in a microflotation cell. In addition, a critical enthalpy of immersion (CEI) value was observed, above which no flotation occurred. The variance in the inverse relationship between enthalpy of immersion and rate of flotation decreased when the data was normalized with respect to particle density which was the only variable in the flotation studies with respect to bubble-particle encounter efficiency. These results have shown that the enthalpy of immersion is an excellent indicator of both the natural mineral hydrophobicity and of the extent to which collectors render a mineral hydrophobic. This technique has considerable potential to be used as a highly sensitive measure of mineral surface wettability in predicting flotation performance.

Multi-functional thin film coatings formed via nanogrinding

Nanostructured thin films of silicon and titanium disilicide are produced using a nanoscale or colloidal grinding technique based on planetary ball milling in solution. High-purity micron-scale powders are dispersed in solvent and milled at 200–1000 rpm for 10 min to several hours. The resulting films are cast from solution on planar and curved surfaces with individual particle sizes reaching below 100 nm after approximately 45 min of grinding at 400 rpm. X-ray analysis and Raman spectroscopy shows that the crystalline structure of the starting materials is maintained following grinding, with carbon and oxygen species appearing, as grinding time is increased likely the result of surface reactions occurring during the milling process. Surface wettability measurements show the contact angle of nanostructured Si, and TiSi2 films can be tuned from approximately 10 to over 100 degrees resulting in hydrophobic or hydrophilic surfaces depending upon grinding time, speed and solvent. Two-terminal electronic transport data of the thin films show that electrical resistivity can be tuned by more than one order of magnitude depending on grinding conditions. In general, coatings created via nanogrinding possess unique and varied structural, surface, electrical and optical properties, which can be used for advanced multi-functional materials and devices.

Fabrication and characterization of multilayered kafirin/gelatin film with one-way water barrier property

A tri-layered film with blend kafirin/gelatin film as core layer, kafirin and gelatin films as skin layers was obtained by layer-by-layer solvent casting method. The surface and cross-section morphology, molecular interactions, mechanical properties, surface wettability and water vapor barrier property of multilayered film were extensively investigated. The cross-section morphology displayed distinguishable individual layers, and heterogenous distribution of spherical aggregations in the intermediate layer was observed. Intermolecular interactions between kafirin and gelatin in the blended film were identified via FTIR. Lamination enhanced the UV protection property while keeping transparency, and the multilayered film made up to the weakness of blend film in tensile strength. Surface wettability measurement demonstrated that kafirin layer possessed lower contact angle than gelatin film surface. Yet, the kafirin layer was more effective in inhibiting moisture penetration than gelatin layer as revealed by the dynamic water absorption analysis and water vapor permeability measurement. Different structural responses of kafirin and gelatin moieties in multilayered films in response to water penetration might explain this phenomenon: while gelatin matrix swelled readily after contact with water, solvent induced aggregation of kafirin moieties led to changes in the compactness of film matrix. Such insights are particularly important in engineering multilayered films with rational designed one-way water barrier property, which is quite useful in fresh fruit and vegetable packaging industry.

Fouling mitigation and cleanability of TiO2 photocatalyst-modified PVDF membranes during ultrafiltration of model oily wastewater with different salt contents.

In the present study, TiO2-coated ultrafiltration membranes were prepared and used for oily water filtration (droplet size < 2μm). The aim of this work was to investigate the effect of different salt contents on fouling and filtration properties of neat and TiO2-coated membranes during oil-in-water emulsion filtration. The effect of the TiO2 coating on the flux, surface free energy, and retention values was measured and compared with the neat membrane values. The cleanability of the fouled TiO2-coated membranes by UV irradiation was also investigated by measuring flux recovery and contact angles, and the chemical changes during cleaning were characterized by ATR-IR. It was found that increasing the salt content of the model wastewaters, oil-in-water emulsions, increased the zeta potential and the size of the droplets. The presence of the TiO2 coating decreases the membrane fouling during oily emulsion filtration compared to the neat membrane, due to the hydrophilicity of the coating regardless of the salt content of the emulsions. The neat and coated membrane oil retention was similar, 96 ± 2%. The coated membrane can be effectively cleaned with UV irradiation without additional chemicals and a significant flux recovery can be achieved. Monitoring of the cleaning process by following the membrane surface wettability and ATR-IR measurements showed that the recovery of flux does not mean the total elimination of the oil layer from the membrane surface.

Effect of gluten on the properties of ternary biopolymers based on gluten, whey protein concentrate, and kaolinite

The aim of the research was to investigate the effect of different gluten (Gl) concentration on ternary biopolymers with whey protein concentrate (WPC) and kaolinite (KAO). Distilled water dispersions of Gl (10–30%), WPC (7%), and KAO (5%) were heated at 80 °C for 30 min. The concentration of WPC and KAO was based on previous research with montmorillonite. Rheological properties of produced wet biopolymers were evaluated by dynamic rheology and ultrasound viscometry. The obtained biopolymers were dried in the thermostatic cabinet for 24 h at 45 °C. The texture was determined using the puncture test and the microstructure was analyzed by scanning electron microscopy. Surface properties of dried biopolymers were analyzed by surface wettability and roughness measurements. The increase in gluten concentration caused an increase in moduli and viscosity of the obtained wet biopolymers and in the puncture force for dry biopolymers. For the ternary biopolymer, layers with intercalation and exfoliation are observed in comparison with the biopolymer obtained without KAO. With the increasing Gl content in the biopolymer, the number of surface hydrophobic groups with carbon decreased and the number of surface hydrophilic groups increased. Higher Gl concentration produced less porous structure, although there are differences in the micro and nano-scale roughness. Water contact angle decreased with the increased Gl concentration, which is in agreement with less porous microstructure of the surface. The apparent surface free energy increased with the increasing of Gl concentration. The best plastic properties and the best shape of a pot were obtained for the ternary biopolymer with the 15% Gl concentration.

Tuning the Band Bending and Controlling the Surface Reactivity at Polar and Nonpolar Surfaces of ZnO through Phosphonic Acid Binding.

ZnO is a prime candidate for future use in transparent electronics; however, development of practical materials requires attention to factors including control of its unusual surface band bending and surface reactivity. In this work, we have modified the O-polar (0001̅), Zn-polar (0001), and m-plane (101̅0) surfaces of ZnO with phosphonic acid (PA) derivatives and measured the effect on the surface band bending and surface sensitivity to atmospheric oxygen. Core level and valence band synchrotron X-ray photoemission spectroscopy was used to measure the surface band bending introduced by PA modifiers with substituents of opposite polarity dipole moment: octadecylphosphonic acid (ODPA) and 3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctylphosphonic acid (F13OPA). Both PAs act as surface electron donors, increasing the downward band bending and the strength of the two-dimensional surface electron accumulation layer on all of the ZnO surfaces investigated. On the O-polar (0001̅) and m-plane (101̅0) surfaces, the ODPA modifier produced the largest increase in downward band bending relative to the hydroxyl-terminated unmodified surface of 0.55 and 0.35 eV, respectively. On the Zn-polar (0001) face, the F13OPA modifier gave the largest increase (by 0.50 eV) producing a total downward band bending of 1.00 eV, representing ∼30% of the ZnO band gap. Ultraviolet (UV) photoinduced surface wettability and photoconductivity measurements demonstrated that the PA modifiers are effective at decreasing the sensitivity of the surface toward atmospheric oxygen. Modification with PA derivatives produced a large increase in the persistence of UV-induced photoconductivity and a large reduction in UV-induced changes in surface wettability.

Preparation and characterization of superhydrophobic organic-inorganic hybrid cotton fabrics via γ-radiation-induced graft polymerization

A new kind of non-fluorine-based organic-inorganic hybrid superhydrophobic cotton fabric was successfully prepared by simultaneous radiation-induced graft polymerization of γ-methacryloxypropyl trimethoxy silane (MAPS) and subsequent end-capping modification with hexamethyldisilazane (HMDS). The chemical structure and surface topography of the pristine and modified cotton fabrics were investigated in detail by ATR-FTIR, XPS, 29Si NMR, SEM and TGA to confirm that the graft reaction and end-capping modification had taken place. The above results demonstrated that the grafting polymerization and following end-capping reaction were completed, and a grafting layer was immobilized onto the surface of the cotton fabric. Surface wettability measurement and oil-water separation showed that the modified cotton surface not only exhibited the superhydrophobicity with a water contact angle of 165°, but also afforded a high efficiency of oil-water separation (96%). In particular, this modified cotton fabric retains superhydrophobicity even after 30 laundering cycles or 400 cycles of abrasion.