Preparation of waterborne dispersions of epoxy resin by ultrasonic-assisted supercritical CO2 nanoemulsification technique

Influence of ultrasonic combined supercritical-CO2 electrodeposition process on copper film fabrication: Electrochemical evaluation

Introducing ultrasound irradiation to the electrodeposition process can significantly improve the physical and chemical properties of deposited films. Meanwhile, the beneficial effects from supercritical-CO_2, such as high diffusivity, high permeability, low surface tension, etc., would improve the electrodeposition process with better surface quality. In the shed of the light, the present work deals with the preparation of copper (Cu) films using the integrated techniques, i.e., ultrasonic-assisted supercritical-CO₂ (US-SC-CO₂) electrodeposition approach. For comparison, Cu films were also prepared by normal supercritical-CO₂ (SC-CO₂) and conventional electrodeposition methods. To investigate the characteristics of Cu films, surface morphology analysis, roughness analysis, X-ray diffraction studies (XRD), Linear polarization, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry (CV) were performed. In this work, EIS analysis was utilized for interfacial charge transfer resistance analysis with 5 mM [Fe(CN)₆]^-3/-4 redox system and corrosion analysis with 3.5 wt% NaCl solution. The observed results revealed that the film prepared with the US-SC-CO₂ method have superior properties than those produced by normal SC-CO₂ and conventional methods. Due to the combination of US-SC-CO₂, the cavitation implosion occurs rapidly that enriches the deposited film quality, such as sufficient grain size, smoother surface, enhanced corrosion resistance, and charge carrier dynamics. On the other hand, the ultrasound effect with SC-CO₂ helped to remove the weakly adhered metal ions on the electrode's surface.

Ultrasonic-assisted supercritical-CO2 electrodeposition of Zn-Co film for high-performance corrosion inhibition: A greener approach

The ultrasonic-assisted electrodeposition process significantly improves the mechanical and electrochemical properties. Meanwhile, supercritical fluid technology also enhances the electrodeposition process with increased benefits, such as low surface tension, permeability, high diffusivity, and density, which improves the surface quality through grain refinement. In this study, Zn-Co films were prepared using the ultrasonic-assisted supercritical-CO2 (US-SC-CO2) electrodeposition approach, and its pressure effect on the film was evaluated. The films were also prepared by the conventional and typical supercritical-CO2 (SC-CO2) methods for a comparison study. All the prepared films were characterized by morphological studies, elemental composition, crystal structure orientation, and microhardness tests. Later, the fabricated films were examined by potentiodynamic polarization technique and electrochemical impedance technique (EIS) with 3.5 wt.% NaCl solution for corrosion evaluation. Based on results, Zn-Co film prepared through the US-SC-CO2 process shows a spherical nodule like structure with reduced grain size and significantly enhanced hardness property. In XRD studies, the shift in diffracted peak's position reveals the increased proportion of Co ions. Further, EDX results also confirm the same with the characteristic peaks. Finally, compared to the other methods, the corrosion resistance was more efficient in the US-SC-CO2 process by 73.75%.

Ultrasound-Assisted Preparation of Exopolysaccharide/Nystatin Nanoemulsion for Treatment of Vulvovaginal Candidiasis

PURPOSE

As one of the classic anti-Canidia albicans (CA) and vulvovaginal candidiasis (VVC) drugs, nystatin (NYS) is limited by poor water solubility and easy aggregation. Traditional NYS vaginal delivery formulations do not fully adapt to the specific environment of the vaginal cavity. The use of exopolysaccharides (EPS) has great application potential in emulsifiers, but its use has not been reported in nanoemulsions. In this work, an EPS/NYS nanoemulsion (ENNE) was developed to improve the activities of NYS against CA and VVC.

METHODS

The ENNE was prepared by ultrasonic method using EPS as an emulsifier, liquid paraffin oil as an oil phase, PEG400 as a co-emulsifier, and NYS as the loaded drug. ENNE preparation was optimized by response surface method. After optimization, in vitro and in vivo analysis of the anti-CA activity; animal experiments; staining with propidium iodide (PI), periodic acid-schiff (PAS), and hematoxylin-eosin (H&E); and cytokine experiments were performed to investigate the therapeutic ability against VVC.

RESULTS

The optimal formulation and preparation parameters of ENNE were determined as follows: EPS content of 1.5%, PEG400 content of 3.2%, NYS content of 700 μg/mL, paraffin oil content of 5.0%, ultrasonic time of 15 min, and ultrasonic amplitude of 35%. The ENNE showed an encapsulated structure with an average particle size of 131.1 ± 4.32 nm. ENNE exhibited high storage and pH stability, as well as slow release. The minimum inhibitory concentration (MIC) of ENNE against CA was only 0.125 μg/mL and the inhibition zone was 19.0 ± 0.5 mm, for greatly improved anti-CA effect. The prepared ENNE destroyed the membrane of CA cells, and exhibited good anti-CA effect in vivo and therapeutic ability against VVC.

CONCLUSION

The results of this study will promote the application of EPS in nanotechnology, which should lead to new and effective local drug formulations for treating VVC.

Fabrication and application of complex microcapsules: a review

The development of new functional materials requires cutting-edge technologies for incorporating different functional materials without reducing their functionality. Microencapsulation is a method to encapsulate different functional materials at nano- and micro-scales, which can provide the necessary protection for the encapsulated materials. In this review, microencapsulation is categorized into chemical, physical, physico-chemical and microfluidic methods. The focus of this review is to describe these four categories in detail by elaborating their various microencapsulation methods and mechanisms. This review further discusses the key features and potential applications of each method. Through this review, the readers could be aware of many aspects of this field from the fabrication processes, to the main properties, and to the applications of microcapsules.

Ultrasonic nano-emulsification - A review

The emulsions with nano-sized dispersed phase is called nanoemulsions having a wide variety of applications ranging from food, dairy, pharmaceutics to paint and oil industries. As one of the high energy consumer methods, ultrasonic emulsification (UE) are being utilized in many processes providing unique benefits and advantages. In the present review, ultrasonic nano-emulsification is critically reviewed and assessed by focusing on the main parameters such pre-emulsion processes, multi-frequency or multi-step irradiations and also surfactant-free parameters. Furthermore, categorizing aposematic data of experimental researches such as frequency, irradiation power and time, oil phase and surfactant concentration and also droplet size and stability duration are analyzed and conceded in tables being beneficial to indicate uncovered fields. It is believed that the UE with optimized parameters and stimulated conditions is a developing method with various advantages.

The effects of ultrasonic agitation on supercritical CO2 copper electroplating

Applying ultrasound to the electroplating process can improve mechanical properties and surface roughness of the coating. Supercritical electroplating process can refine grain to improve the surface roughness and hardness. However, so far there is no research combining the above two processes to explore its effect on the coating. This study aims to use ultrasound (42kHz) in supercritical CO₂ (SC-CO₂) electroplating process to investigate the effect of ultrasonic powers and supercritical pressures on the properties of copper films. From the results it was clear that higher ultrasonic irradiation resulted in higher current efficiency, grain refinement, higher hardness, better surface roughness and higher internal stress. SEM was also presented to verify the correctness of the measured data. The optimal parameters were set to obtain the deposit at pressure of 2000psi and ultrasonic irradiation of 0.157W/cm³. Compared with SC-CO₂ electroplating process, the current efficiency can be increased from 77.57% to 93.4%, the grain size decreases from 24.34nm to 22.45nm, the hardness increases from 92.87Hv to 174.18Hv, and the surface roughness decreases from 0.83μm to 0.28μm. Therefore, this study has successfully integrated advantages of ultrasound and SC-CO₂ electroplating, and proved that applied ultrasound to SC-CO₂ electroplating process can significantly improve the mechanical properties of the coating.

Shear-Assisted Production of Few-Layer Boron Nitride Nanosheets by Supercritical CO2 Exfoliation and Its Use for Thermally Conductive Epoxy Composites

Boron nitride nanosheets (BNNS) hold the similar two-dimensional structure as graphene and unique properties complementary to graphene, which makes it attractive in application ranging from electronics to energy storage. The exfoliation of boron nitride (BN) still remains challenge and hinders the applications of BNNS. In this work, the preparation of BNNS has been realized by a shear-assisted supercritical CO₂ exfoliation process, during which supercritical CO₂ intercalates and diffuses between boron nitride layers, and then the exfoliation of BN layers is obtained in the rapid depressurization process by overcoming the van der Waals forces. Our results indicate that the bulk boron nitride has been successfully exfoliated into thin nanosheets with an average 6 layers. It is found that the produced BNNS is well-dispersed in isopropyl alcohol (IPA) with a higher extinction coefficient compared with the bulk BN. Moreover, the BNNS/epoxy composite used as thermal interface materials has been prepared. The introduction of BNNS results in a 313% enhancement in thermal conductivity. Our results demonstrate that BNNS produced by supercritical CO₂ exfoliation show great potential applications for heat dissipation of high efficiency electronics.