Poor Wetting Properties Research Articles

Application of hydroxypropyl methylcellulose to improve the wettability of chitosan coating and its preservation performance on tangerine fruits

Hydroxypropyl methylcellulose (HPMC) was employed as an intermediate layer to enhance interfacial interaction between chitosan (CS) coating and tangerine fruits, thereby improving the preservation effect. Owing to the low surface tension of tangerine fruit (26.04 mN/m), CS coating solutions showed poor wetting properties on fruit peels (contact angle > 100°). However, by applying a 1.0 % (w/v) HPMC coating on fruits, the contact angle of CS solutions with concentrations of 0.5 %, 1.0 %, and 1.5 % (w/v) decreased to 47.0°, 47.4°, and 48.5°, respectively, whereas the spreading coefficient increased to −16.0 mN/m, −17.6 mN/m and −19.8 mN/m, respectively. Subsequently, the effects of the coatings on fruit quality were investigated. The results demonstrated the promising performance of HPMC-CS two-layer coating in inhibiting fruit respiration, reducing decay rate, and maintaining nutrient content. Notably, HPMC-1.5%CS coating not only reduced the decay rate of tangerine fruit by 45 % and 31 %, in comparison to the uncoated group (CK) and pure CS coating respectively, but also maintained a high content of ascorbic acid. Therefore, this study confirmed that the use of amphiphilic polymers for improving the surface properties of fruits can effectively facilitate the wetting of hydrophilic coatings on fruits, and significantly improve the fresh-keeping performance of edible coatings.

Enhanced dosage delivery of pesticide under unmanned aerial vehicle condition for peanut plant protection: tank-mix adjuvants and formulation improvement.

Suspension concentrate (SC) is one of the most widely used formulations for agricultural plant protection. With the rapid development of unmanned aerial vehicle (UAV) plant protection, the problems of spray drift, droplet rebound and poor wettability in the application of SC from UAVs have attracted wide attention. Although some tank-mix adjuvants have been used to enhance dosage delivery for UAV, their effects and mechanisms are not fully clear, and few formulations are specifically designed for UAV. The type and concentration of tank-mix adjuvant affect the dosage delivery of SC. MO501 can significantly reduce DV<100μm , and inhibit droplet rebound on peanut leaves at concentrations ≥0.5%. Silwet 408 can achieve complete wetting and superspreading after adding ≥0.2% concentrations, but only ≥0.5% can inhibit rebound. XL-70 shows excellent regulation ability even at low concentration, and 0.2% concentration can simultaneously suppress impact and promote spreading. Besides, the formulation oil dispersion (OD) can significantly reduce the driftable fine fraction and inhibit rebound at dilution ratios of ≤250-fold, thus enhancing dosage delivery. SC is prone to rebound on hydrophobic leaf surfaces and shows poor wetting and spreading properties. Appropriate types and concentrations of tank-mix adjuvants and formulation improvement are two effective strategies for improving the dosage delivery of pesticides, whereas the addition of inappropriate adjuvants may cause potential risks instead. These findings provide guidance for the rational selection of tank-mix adjuvants and potential applications of OD for UAV plant protection. © 2023 Society of Chemical Industry.

Ultra-Low Concentration Electrolyte Enabling LiF-Rich SEI and Dense Plating/Stripping Processes for Lithium Metal Batteries.

The interface structure of the electrode is closely related to the electrochemical performance of lithium‐metal batteries (LMBs). In particular, a high‐quality solid electrode interface (SEI) and uniform, dense lithium plating/stripping processes play a key role in achieving stable LMBs. Herein, a LiF‐rich SEI and a uniform and dense plating/stripping process of the electrolyte by reducing the electrolyte concentration without changing the solvation structure, thereby avoiding the high cost and poor wetting properties of high‐concentration electrolytes are achieved. The ultra‐low concentration electrolyte with an unchanged Li+ solvation structure can restrain the inhomogeneous diffusion flux of Li+, thereby achieving more uniform lithium deposition and stripping processes while maintaining a LiF‐rich SEI. The LiIICu battery with this electrolyte exhibits enhanced cycling stability for 1000 cycles with a coulombic efficiency of 99% at 1 mA cm–2 and 1 mAh cm–2. For the LiIILiFePO4 pouch cell, the capacity retention values at 0.5 and 1 C are 98.6% and 91.4%, respectively. This study offers a new perspective for the commercial application of low‐cost electrolytes with ultra‐low concentrations and high concentration effects.

Performance evaluation of electrochemical capacitors with activated carbon spheres as electrode material and aqueous electrolyte

The model activated carbon spheres (ACSs) were optimized to be used as negative electrode in asymmetric electrochemical capacitors (ECs). A microporous commercial activated carbon was used as positive electrode.Carbon spheres (CSs) were synthesized by precipitation polymerization at room temperature followed by pyrolysis and activation. By enhancing the carbon:KOH ratio from 1:2 to 1:4, an increase in the specific surface area from 380 m2 g−1 to 2835 m2 g−1 (1:4) was achieved along with an increase in pore volume/size. Consequently, the electrochemical performance in the aqueous electrolyte was improved. After activation, low-temperature-pyrolyzed polymer spheres (400 °C) result in random-like particles with macroporous structure, while intermediate- and high-temperature-pyrolyzed materials (550 °C and 700 °C) lead to partially and totally conserved spheres.The interaction between the electrode material and electrolyte is important and is related to the texture, morphology, and surface chemistry of ACS. In 1 mol L−1 H2SO4, capacitance and rate handling are mostly affected by electrode morphology and wettability with the electrolyte. In 1 mol L−1 Li2SO4 electrolyte solution, texture and surface chemistry of the electrode material are crucial to obtain high-performance EC. Regardless of morphology, poor wetting properties of synthesized materials were found in Li2SO4, compared to the H2SO4 solution.

Comparative study of solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum laser soldering joint

Cu-based component/aluminum substrate solder joint is achieved through laser soldering technology in this paper. The solder wettability on aluminum substrate and microstructure-properties of Cu-based component/aluminum substrate laser soldering joint are studied. The results show that the presence of the high melting point Al2O3 oxide film (∼18.45 nm thickness) isolates the contact between the molten Sn-based solder and the aluminum substrate, which results in the poor wetting properties of aluminum substrate. The surface modification of aluminum substrate can significantly improve wettability (110°→14°). Anisotropic Sn dendrites appear in the brazing area of laser soldering joints, and Ag3Sn is precipitated in the β-Sn matrix. The (Cu, Ni)6Sn5 IMC is formed near the Ni layer side. Due to the extremely fast cooling rate, the IMC thickness is less than 5 μm, and a continuous (Cu, Ni)6Sn5 region with a thickness of less than 1 μm appears at the interface near the Ni layer side. The average maximum linear load of the laser soldering joints is 95.2 N/mm. The laser soldering joint fracture occurs along the brittle (Cu, Ni)6Sn5 IMC formed at the Ni layer interface, and the fracture mode is mainly ductile fracture.

In-situ generated graphene from wheat flour for enhancing mechanical and electrical properties of copper matrix composites

Graphene, with its excellent mechanical properties and electrical conductivity, has been considered as an effective reinforcement phase for copper matrix composites. However, due to its easy agglomeration and poor wetting properties in the copper matrix, it is difficult to simultaneously enhance strength, ductility and conductivity of graphene matrix copper composites using a low cost and efficient method. In this paper, we proposed a new methodology to use wheat flour as a solid carbon source to in-situ generate graphene-coated copper (Gr@Cu) composite powders. These powders were then used as strengthening phases to fabricate Gr@Cu copper composites through wet mixing and spark plasma sintering (SPS) processes. Results showed that not only high-quality graphene layer was obtained and serious agglomeration of graphene was avoided, but also a strong interfacial bonding between graphene and copper matrix was achieved. The fabricated composites showed excellent properties, e.g., a maximum density of 99%, enhanced micro-hardness (15%–22% higher than that of pure copper), and excellent strength/ductility. The maximum tensile strength and yield strength were obtained in the 0.70 wt.%Gr@Cu/Cu composites (e.g., 252 MPa and 132 MPa, respectively). These values are ∼23% and ∼110% higher than those of pure copper, and the elongation rate was maintained at ∼30%. In addition, the composites showed excellent conductivity.

Robust liquid repellency by stepwise wetting resistance

Maintaining both high static liquid repellency and large dynamic pressure resistance is highly preferred for a myriad of applications, such as energy conversion, anti-icing, and antifouling. However, these two merits are mutually exclusive in conventional surface design: Sparse structures with reduced solid–liquid contact area yield high static liquid repellency, which in turn inevitably suffer from poor dynamic wetting properties as exemplified by low wetting resistance and easy Cassie-to-Wenzel transition. Here, we circumvent this trade-off by designing a springtail cuticle-inspired surface consisting of multilayered, doubly reentrant posts with increasing diameter from top to bottom, which simultaneously imparts high static wetting and multiple energy barriers for the gradual liquid penetration in a stepwise mode. Particularly, the synergy between the doubly reentrant structure, which increases the breakthrough pressure, and the multilayered architecture sustains a robust liquid repellency in a broad range of conditions otherwise challenging on conventional structures. Our findings provide an important insight for the rational design of robust superliquid-repellent surfaces.

Improving through‐thickness conductivity of carbon fiber reinforced polymer using carbon nanotube/polyethylenimine at the interlaminar region

AbstractThe through‐thickness conductivity of carbon fiber reinforced polymer (CFRP) composite was increased by incorporating multiwalled carbon nanotubes in the interlaminar region. Carbon nanotubes (CNTs) were dispersed in a polyethylenimine (PEI) binder, which was then coated onto the carbon fiber fabric. Standard vacuum‐assisted resin infusion process was applied to fabricate the composite laminates. This modification technique aims to enhance the electrical conductivity in through‐thickness direction for the purpose of nondestructive testing, damage detection, and electromagnetic interference shielding. CNT concentrations ranging from 0 to 0.75 wt% were used and compared to pristine CFRP samples (reference). The through‐thickness conductivity of the CFRP exhibited an improvement of up to 781% by adopting this technique. However, the dispersion of CNT in PEI led to a viscosity increase and poor wetting properties which resulted in the formation of voids/defects, poor adhesion (as shown in scanning electron micrographs) and the deterioration of the mechanical properties as manifested by interlaminar shear strength and dynamic mechanical analysis measurements.

Selection of surfactants for enhancing the wettability of powder formulations of Beauveria bassiana (bals.-criv.) vuill. (1912) (ascomycota: Cordycipitaceae)

Entomopathogenic fungal products, such as formulations made with Beauveria sp., are recognized for their effectiveness in controlling insect pests. Due to their high hydrophobicity, however, fungal agents require the addition of surfactants to diminish particle aggregation in water during field applications. The aim of the present study was to select surfactants to enhance the wettability of Beauveria bassiana formulations without affecting fungal viability. In a first experiment, formulations prepared with 24 different surfactants were tested for viability after 30 days of storage at 25 °C. Five surfactants provided the best results and were selected for further experiments. New formulations were prepared and evaluated in terms of surface tension, wetting time, conidial germination, and viability during three months of storage. The biological index was also evaluated. The shortest wetting time (1.61 min) and lowest surface tension (38 mN/m) were obtained using Emulsogen TS 200 at 5%. Four of the five formulations led to a 50% decrease in germination after two months of storage. The exception was Surfon D. After three months of storage, the control formulation (without surfactant) and formulations prepared using Surfom D had germination rates of 0% and 55%, respectively. The highest viability (1.14 × 109 colony-forming units/g) was obtained with Surfom D. B. bassiana was found to be compatible with 5% Emulsogen TS 200 and Surfom D. Emulsogen TS 200 was more effective at reducing surface tension but decreased fungal viability and conidial germination. Surfom D exhibited poor wetting properties but increased the germination rate of B. bassiana. Therefore, the use of both surfactants is promising for the formulation of B. bassiana pest control products.

Role of wetting agents and disintegrants in development of danazol nanocrystalline tablets.

Poor wetting and/or particle aggregation are the shortcomings of the dried nanocrystalline suspensions, which subsequently might hinder the superior dissolution performance of the nano-crystalline suspensions. The objective of this study was to evaluate the effect of wetting agents and disintegrants on the dissolution performance of dried nanocrystals of an active pharmaceutical ingredient (API) with poor wetting property. Danazol, a BCS Class II compound with high LogP and low polar surface area, was chosen as a model compound for this study. Danazol nanocrystalline suspension was prepared by wet-media milling and converted into powder via spray granulation either with mannitol or microcrystalline cellulose as carriers at a drug: carrier ratio of 1:9 w/w. Danazol nanocrystalline suspension showed a superior dissolution performance compared to an un-milled danazol suspension. Dried danazol nanocrystals suffered from poor wetting leading to hindered dissolution performance i.e.~40% and~15% drug dissolution within 15min for the mannitol and microcrystalline cellulose-based granules, respectively. Addition of a lipophilic surfactant (i.e. docusate sodium) at a surfactant: drug ratio of 0.015: 1 w/w during granulation helped in retaining the superior drug dissolution rates i.e. more than 80% drug dissolution within 15min for mannitol-based granules by enhancing the wettability of dried danazol nanocrystals when compared to a hydrophilic surfactant (i.e. poloxamer 188) or disintegrant (i.e. sodium starch glycolate or croscarmellose sodium). The fast-dissolving mannitol-based granules containing danazol nanocrystals and docusate sodium were compressed into a tablet dosage form. The tablets containing danazol nanocrystals with docusate sodium showed a superior dissolution performance compared to a tablet containing un-milled danazol with docusate sodium.

Microstructure and mechanical properties of cold metal transfer welded galvanized steel/magnesium alloy dissimilar joints

The joining of magnesium alloy to galvanized steel was realized by cold metal transfer method with AZ31 magnesium alloy welding wire. Weld appearance, microstructure and tensile properties of Mg–steel joints under various welding parameters were investigated with different welding heat inputs. The results showed that magnesium alloy-steel brazed joints had good weld appearance. When the welding heat input was 141 J/mm, Zn elements were enriched in the Zn-rich zone (ZRZ), and the interface layer was composed of a large portion of Mg–Zn phases and minor Mg–Al phases. With the increase of welding heat input, Zn elements in the ZRZ gradually decreased, Fe/Al phase appeared in the interface layer, and the strength of welding joint increased. When the welding heat input was 159 J/mm, the tensile strength of welding joint reached the maximum value of 198 MPa. However, when the welding input was increased to 181 J/mm, Zn element in the ZRZ was burnt and volatilized seriously, resulting in poor wetting and spreading properties of liquid phase at the interface zone of the steel.

Investigation of large enhancement of spin hall angle in heterostructures of Ag nanoparticles randomly grown in Pt

The spin Hall angle (SHA) represents the efficiency of the conversion between spin current into charge current and vice-versa. In this paper, we report the experimental detection of large enhancement of the effective SHA in heterostructures of yttrium iron garnet (YIG)/[Pt-Ag]/Pt and YIG/[Pt-Ag], when compared with measurements in YIG/Pt bilayers. The notation [Pt-Ag] represents the nanoparticles island formation of Ag in the Pt film. In order to investigate the role played by the metallic nanoparticles in the spin-to-charge conversion process, we carried out microwave spin pumping measurements in the following samples: YIG/Ag(3 nm)/Pt(6 nm), YIG/[Pt(3 nm)-Ag(3 nm)]/Pt(3 nm) and YIG/[Pt(6 nm)-Ag(3 nm)]. By means of high-resolution scanning electron microscope (HR-SEM) investigation, we confirmed that layers of Ag exhibit islands nanoparticle structures when grown on the surface of the Pt, which are characterized by the Volmer-Weber mode. The spin pumping results show that the Ag nanoparticles can enhance the charge current created by the inverse spin Hall effect (IISHE) up to three times larger than the single Pt layer. Also, by analyzing atomic force microscopy (AFM) images, obtained for samples with different thickness of the Ag layer, we conclude that the roughness plays an important role in the enhancement of the IISHE. Therefore, taking advantage of poor wetting properties of Ag over Pt layer, it was possible to create nanoscopic particles of Ag randomly grown in the Pt layer. The nanoparticles serve as nanoscopic molds to locally increase the SHA. This feature represents an improvement in searching more efficient methods of the spin-to-charge conversion and opens up the possibility of tuning the SHA by controlling the size and shape of the Ag nanoparticles.

Wetting improvement of plastic working plate for liquid desiccant dehumidification systems

Liquid desiccant dehumidification is promising because it removes extra excess effectively and environmentally. By affecting the contact area between desiccant and air, the mass transfer performance is significantly influenced by the wettability on inner working surfaces of the dehumidifier. Non-metallic surfaces such as plastics are considered as good alternatives due to their anticorrosion characteristics. However, poor wetting properties severely limited the application. In this study, a silica super-hydrophilic coating on pre-etched plastic surfaces was developed by the sol-gel method to enhance wetting performance. Coating properties were test on samples made of acrylic with a 40% LiBr solution and deionized water. Results showed that with the pre-etching and super-hydrophilic coating, water droplets could completely spread within 3 seconds, which means that the contact angle could be reduced to about 0 degrees. Furthermore, the durability test showed that after 48 hours of continuous scouring under 0.01 Mpa water pressure (approximately 1000 times that of that in common liquid desiccant systems), the droplet could fully spread within 22s and the contact angle remained was maintained at 0°. Therefore, the novel coating on pre-etched surfaces developed in this study could effectively increase the wetting performance on plastic surfaces, which is helpful to the mass transfer of liquid desiccant dehumidification systems.

The influence of titanium addition on wettability of high-chromium white cast iron-matrix composites

The mining industry exerts ever increasing demand for components with high wear resistance to the extent that plain ferrous alloys are falling short. Innovative metal-matrix composites non-ferrous metals have been widely researched and used. Casting composites based on ferrous alloys pose monumental challenges in casting. First, the density differential results in large buoyant forces on the ceramic such that unless a rigid structure is configured, the less dense ceramic floats on the metal stream. Second, the poor wetting properties between metal and ceramic will result in inferior bonding of the matrix, hence separation of solids in service. The paper attempts to improve the bonding characteristics of zirconia and alumina through wettability studies. High-chromium white cast iron was used as a substrate. The wetting behavior of molten iron on the substrates of zirconia and alumina was investigated. The study shows that alumina is poorly wetted with copper and nickel; the wetting angles were higher than 90°. Thus, the envisaged coating of alumina with copper or nickel prior to casting of ferrous melts will not significantly alter or improve wettability of alumina. Between copper and nickel, nickel has better bonding with alumina than copper. Titanium in high-chromium white cast iron was found to improve the wetting characteristics on alumina. The wetting angle decreased with increased titanium content.

Highly efficient solution-processed inverted polymer light emitting diodes with uniformly coated poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) layers on a hydrophobic emission layer using a dilution method

Inverted polymer light emitting diodes (PLEDs), where solution-processed multi-layers were sandwiched between indium tin oxide and thermally evaporated aluminum electrodes, were fabricated and their characteristics were measured. In order to achieve high performance in the inverted PLEDs, there is a need for additional functional layers such as a hole transport layer and hole injection layer (HIL) on an emission layer (EML), but formation of the solution-processed layers on the hydrophobic EML have been rarely reported due to the extremely poor wetting property of a poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) solution, which is a widely used HIL. Non-wetting phenomena such as the formation of islands or radiation patterns in PEDOT:PSS films on the EML caused by their poor wetting property have been completely removed using a dilution method. By diluting PEDOT:PSS solutions with ethanol and analyzing a wetting envelope, we found the optimized dilution condition (10:1) and fabricated highly efficient inverted PLEDs with the uniformly coated PEDOT:PSS HIL, showing a current efficiency of 9.73 cd/A at 1000 cd/m2 and uniform light emission simultaneously.

Covalent Surface Functionalization of Boron Nitride Nanotubes Fabricated with Diazonium Salt

The chemical inertness and poor wetting properties of boron nitride nanotubes (BNNTs) hindered their applications. In this work, BNNTs have been functionalized with aniline groups by reacting with diazonium salt and the graft content of aniline component was calculated as high as 71.4 wt.%. The chemical structure, composition, and morphology of functionalized BNNTs were carefully characterized to illustrate the modification. The anilinocarbocation generated by decomposition of diazonium salt reacted not only with NH2 sites, but also with B-OH sites on the surface of BNNTs. Meanwhile, the reaction applied a hot strong acid environment, which would help to open parts of B-N bonds to produce more reactive sites and enrich the functional groups grafted on the surface of BNNTs. Consequently, the functionalized BNNTs exhibited significantly improved dispersion stability in chloroform compared with pristine BNNTs. Amino surface functionalization of BNNTs offered more possibilities for surface chemical design of boron nitride and its practical application.

Improved performance of molten carbonate fuel cells with (Li/Na)2CO3 electrolytes by using BYS coated cathode at low operating temperatures

In order to improve the stack life time of MCFCs, it is necessary to reduce the operating temperature of MCFCs below 600 °C, because reduced operating temperature minimizes electrolyte loss due to evaporation and corrosion. However, at the low operating temperature below 600 °C, the cell performance of MCFCs with (Li/Na)2CO3 electrolyte is too low to operate the fuel cell stack and system. In this study, we have performed wettability control of the liquid molten carbonate electrolyte by coating NiO cathodes with poor wetting property of the mixed ionic and electronic conductor (MIEC) such as BYS (Bi1.5Y0.3Sm0.3O3-δ). From experiments with symmetrical cells, each polarization component with various temperatures and gas conditions were studied. To investigate effects of the BYS coated cathode on the performance of MCFCs, a 100 cm2 single cell of MCFCs was employed. The performance of a 100 cm2 single cell with BYS coated cathode was better than that with conventional cathode by a factor of 1.84, because BYS coated cathode reduces activation polarization and mass transfer resistance greatly.

Flowability and wetting behaviour of milk protein ingredients as influenced by powder composition, particle size and microstructure

This work aimed to provide a comprehensive characterisation of several physicochemical properties of different milk protein powders frequently used as ingredients in dairy‐based food formulations, in particular flowability and wettability. The flow and wetting properties were influenced mainly by the powder composition, less than by other physicochemical properties, such as particle size and microstructure. Powders with high fat content had poor flow and wetting properties. The wetting properties were also influenced by the protein content (mainly by the casein content) of the powders and were poor for powders having poor release of ionic calcium.

Reconstruction and thermal performance analysis of die-bonding filling states for high-power light-emitting diode devices

This paper proposed a half-experimental model to reconstruct the die-bonding thermal path of high-power light-emitting diodes (HP-LEDs). In this model, the partially insufficient filling of bonding materials and their directional/random distributions (“filling state” for short) have been taken into consideration. Both the silver-paste structure and the Au/Sn-eutectic structure were analyzed and compared. Finite element analysis (FEA) indicated that qualified die-bonding with uniform filled areas would lead to much better thermal performance. Hotspots have been observed above the insufficiently filled regions. The simulated thermal resistances of the defective bonding were 5.4 times and 2.1 times higher than those of the qualified samples under conditions of Au/Sn-eutectic and silver-paste, respectively. Transient thermal resistance measurements further demonstrated that the devices with different filling states would result in distinct thermal resistances. Interestingly, it was noted that although the qualified silver-paste bonding had a larger filled area, the measured thermal resistance remained higher than that of the defective Au/Sn-eutectic bonding because of the high contact thermal resistance caused by poor wetting properties. Furthermore, defectively bonded LED devices revealed a poor maintenance of luminous flux after 500 h of aging, which was consistent with the results of thermal performance analysis on the reconstructed die-bonding models.

Cold plasma effect on short glass fibre reinforced composites adhesion properties

The low surface energy and poor wetting properties of polymers make it necessary to modify prior to achieve adhesive bonding. This work is focused on the creation of wettable glass fibre reinforced epoxy and polyester composites, thus improving their adhesion performance. The key to evaluate this parameter as a function of the treatment with an atmospheric pressure plasma torch (APPT) device is the surface energy value. The chemical and morphological effects of APPT on the substrates are characterised by infrared and X-ray photoelectron spectroscopy, while etching of APPT is studied by scanning electron and atomic force microscopy. Benefits of APPT on the composites adhesive behaviour are evaluated through mechanical pull-off tests. Experimental results show an improvement in polarity and Lewis base behaviour of the surfaces as well as the creation of a rougher topography, which would be greatly helpful in the bonding process.