Ultrasonic Mixing Research Articles

Inherently Chiral 6,7-Diphenyldibenzo[ e,g ][1,4]diazocine: Enantioselective Synthesis and Application as a Ligand Platform

Inherently Chiral 6,7-Diphenyldibenzo[ <i>e,g</i> ][1,4]diazocine: Enantioselective Synthesis and Application as a Ligand Platform

Synthesis and characterization of MWCNTs/Al6082 nanocomposites through ultrasonic assisted stir casting technique

The objectives of this work are to investigate the microstructural characterization of multi-walled carbon nanotubes (MWCNTs) produced by chemical vapor deposition method and to prepare Al6082/MWCNT nanocomposites by stir casting method. MWCNTs were developed and then ball milled with aluminum powder to obtain its coating on MWCNTs to improve wettability. Similarly, ultrasonic mixing was used to de-agglomerate the bundled MWCNTs during the stir casting process. MWCNTs were added to molten Al6082 with varying weight percentages (0.3–1.2 wt. %) during the stirring process, and microstructural characterization was performed with field emission scanning electron microscope (FESEM) along with energy dispersive X-ray spectrometer (EDX) for evaluation of elements. EDX analysis of the developed and purified MWCNTs revealed the absence of nickel and other impurities after purification. The Results from the microstructure of nanocomposites indicate that MWCNTs were uniformly distributed for up to 0.9 wt. % of MWCNT and on further increment of MWCNTs, agglomeration was noticed.

Improving the immunoassay for procalcitonin detection using an aeroelastic agitator: A feasibility study

Procalcitonin (PCT) is an important biomarker of bacterial infections. Detection of serum PCT is of great significance in diagnosis and therapy of a variety of diseases. In this work it is measured through immunoassay using antibody-conjugated fluorescent microspheres. To improve the binding efficiency of PCT antigen and antibody, an aeroelastic agitator is designed. Through alternate perturbations, it produces chaotic advection to enhance the fluid mixing. The influences of key design and operating factors are analyzed, including the geometrical parameters, the driving pressure, and the alternating period. Then the agitator is applied for PCT detection and its performance is compared with an ultrasonic mixer. Results show that the chaotic mixing significantly improves the capturing efficiency of PCT antigen, leading to a better detection consistency and reliability. The fluorescence intensity correlates fairly well with the serum PCT concentration in the range of 0.02 ng/ml–49.56 ng/ml.

Simultaneous Electrochemical Sensing of Indole-3-Acetic Acid and Salicylic Acid on Poly(L-Proline) Nanoparticles-Carbon Dots-Multiwalled Carbon Nanotubes Composite-Modified Electrode.

Sensitive simultaneous electrochemical sensing of phytohormones indole-3-acetic acid and salicylic acid based on a novel poly(L-Proline) nanoparticles–carbon dots composite consisting of multiwalled carbon nanotubes was reported in this study. The poly(L-Proline) nanoparticles–carbon dots composite was facilely prepared by the hydrothermal method, and L-Proline was used as a monomer and carbon source for the preparation of poly(L-Proline) nanoparticles and carbon dots, respectively. Then, the poly(L-Proline) nanoparticles–carbon dots–multiwalled carbon nanotubes composite was prepared by ultrasonic mixing of poly(L-Proline) nanoparticles–carbon dots composite dispersion and multiwalled carbon nanotubes. Scanning electron microscope, transmission electron microscope, Fourier transform infrared spectroscopy, ultraviolet visible spectroscopy, energy dispersive spectroscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and linear sweep voltammetry were used to characterize the properties of the composite. poly(L-Proline) nanoparticles were found to significantly enhance the conductivity and sensing performance of the composite. Under optimal conditions, the composite-modified electrode exhibited a wide linear range from 0.05 to 25 μM for indole-3-acetic acid and from 0.2 to 60 μM for salicylic acid with detection limits of 0.007 μM and 0.1 μM (S/N = 3), respectively. In addition, the proposed sensor was also applied to simultaneously test indole-3-acetic acid and salicylic acid in real leaf samples with satisfactory recovery.

Physical, Thermal Transport, and Compressive Properties of Epoxy Composite Filled with Graphitic- and Ceramic-Based Thermally Conductive Nanofillers.

Epoxy polymer composites embedded with thermally conductive nanofillers play an important role in the thermal management of polymer microelectronic packages, since they can provide thermal conduction properties with electrically insulating properties. An epoxy composite system filled with graphitic-based fillers; multi-walled carbon nanotubes (MWCNTs), graphene nanoplatelets (GNPs) and ceramic-based filler; silicon carbide nanoparticles (SiCs) was investigated as a form of thermal-effective reinforcement for epoxy matrices. The epoxy composites were fabricated using a simple fabrication method, which included ultrasonication and planetary centrifugal mixing. The effect of graphite-based and ceramic-based fillers on the thermal conductivity was measured by the transient plane source method, while the glass transition temperature of the fully cured samples was studied by differential scanning calorimetry. Thermal gravimetric analysis was adopted to study the thermal stability of the samples, and the compressive properties of different filler loadings (1–5 vol.%) were also discussed. The glass temperatures and thermal stabilities of the epoxy system were increased when incorporated with the graphite- and ceramic-based fillers. These results can be correlated with the thermal conductivity of the samples, which was found to increase with the increase in the filler loadings, except for the epoxy/SiCs composites. The thermal conductivity of the composites increased to 0.4 W/mK with 5 vol.% of MWCNTs, which is a 100% improvement over pure epoxy. The GNPs, SiCs, and MWCNTs showed uniform dispersion in the epoxy matrix and well-established thermally conductive pathways.

Use of ultrasonic dual-mode mixing for graphene infusion to make hybrid GFRPs: Study on mechanical performance

Optimized process parameters of a top–down approach via the ultrasonic dual-mode mixing process are adopted to disperse and exfoliate graphene nanoplatelets uniformly in the epoxy resin and fabricate hybrid GFRP laminates. The in-plane tensile and out-of-plane flexural behavior of the hybrid GFRPs made with different concentration of GNPs have been investigated. The test results show that ∼39.47% and ∼40.87% enhancement in tensile strength and flexural strength has been attained for the hybrid GFRPs made with 1 wt% of GNPs. In addition, the enhancement of ∼117% in absorbed failure energy and ∼28.56% in work of fracture is also achieved. Mori Tanaka Method has been used to calculate the modulus of the GNP-epoxy composite system, and these results are used further to predict the modulus of the hybrid GFRPs. The theoretical moduli so obtained are used to compare the experimental modulus of the hybrid GFRPs as a function of GNP concentration. Fractography examination of the fractured hybrid GFRPs reveals it reduced interlaminar delamination, which is governed by the effective load transferability of GNP-infused epoxy network.

Investigation of the mechanical and thermal stability of ultra-high molecular weight polyethylene by using amide-multi-walled carbon nanotubes as a reinforcement material

In this research, an investigation of the thermal and mechanical properties of ultra-high molecular weight polyethylene (UHMWPE) reinforced with pristine and modified multi- walled carbon nanotubes (Amide-MWCNTs)-MWCNTs nanocomposite was conducted. The nanocomposites were prepared by ultra-sonication mixing and hot press moulding methods. The MWCNTs surface was functionalised with amide group. The prepared nanocomposites were characterised based on structure, thermal, and mechanical properties by x-ray diffraction (XRD), differential scanning calorimeter (DSC), and universal testing machine, respectively. The crystallinity, crystal size, space between atomic lattice and lattice constant were calculated from the XRD patterns. Results showed the decrease in UHMWPE crystallinity without affecting the crystal structure of UHMWPE when adding pristine MWCNTs and Amide-MWCNTs (1−5 wt%). Tensile test results showed an increase in the composites stiffness for all percentages in the range of 19%–65%, while the elongation at break for the 3 wt% Amide-MWCNT nanocomposite increased up to 71%. This indicates that the interfacial adhesion was enhanced by the amide group.

Facile fabrication of high nanofiller-content natural rubber nanocomposites for reversible plasticity shape memory polymers

Reversible plasticity shape memory (RPSM) polymers that undergo a large deformation at room temperature and subsequently recover to their original shape upon heating is a new type of shape memory material just discovered in recent years. Herein, the RPSM polymers based on crosslinked natural rubber (NR) composites were fabricated by a simple ultrasonic mixing of zwitterionic chitin slurry, the precursor of chitin nanofibers (ChNFs), and sulfur-prevulcanized natural rubber latex (NRL) in aqueous media. The results showed that with the increase of the nanofiller content, the elastomer deformation of ChNFs/NR composites turned to plasticity deformation under uniaxially stretching. Meanwhile, the room-temperature plasticity deformation of ChNFs/NR composites with high nanofiller loading (>20 wt%) could be rapidly recovered in hot water (90 °C). Interestingly, it was also found that the stretch-induced crystallization of NR occurred at low strain (λ = 1) for the plasticity deformed ChNFs/NR composites, which is far lower than that of neat NR (λ > 4). Moreover, the stretch-induced crystals even persisted in the stretched high-content ChNFs/NR composites when the stress was unloaded. The significantly advanced stretch-induced crystallization of NR indicated the presence of strong interfacial interaction between ChNFs and NRL. To explain the RPSM behavior of as-prepared ChNFs/NR composites, the formation of ChNFs network and its water-induced softening mechanism were proposed to resist or give way to the recovery force of chemical crosslinking network in NR. This work provides a new insight into the fabrication of RPSM composites for promising applications.

Controllable synthesis of silver nanoparticles using an acoustofluidic micromixer based on ultrasonic vibration

Combined liquid-phase reduction method and ultrasonic vibration mixing technology, a new method for controllable synthesis of silver nanoparticles (AgNPs) using an acoustofluidic micromixer is proposed. First, the working mechanism of the acoustofluidic micromixer and the basic principle of the liquid-phase reduction method were briefly described. Then, based on the finite element theory, the simulation software COMSOL was utilized to analyze the vibration pattern and acoustic streaming field of the device. Finally, a series of AgNPs synthesis experiments were carried out using a self-made prototype. Controllable synthesis was achieved by adjusting the control parameters of the device and changing the reagent dosage. And the synthesized AgNPs were characterized by UV spectroscopy and transmission electron microscopy (TEM). Simulation and experimental results show that rapid and homogeneous mixing reaction inside a microchannel is demonstrated via the acoustic streaming phenomenon induced by the interdigital transducers (IDT). The driving voltage, reductant, and protectant concentration have significant effects on the synthesis of AgNPs. Ultrasonic vibration combines with a proper protectant dosage can effectively inhibit particle agglomeration and ensure that the synthesized AgNPs have good homogeneity and monodispersity. When the working voltage is 30–40 V and the concentration ratio of reductant to the precursor is 2:1, the quality of the synthesized AgNPs is better. The samples are approximately spherical, without a large number of agglomerates, and high monodispersity. At this point, the average particle size is about 24.4 nm and the deviation is below 5.01 nm. The excellent and fast mixing reaction performance makes the proposed acoustofluidic micromixer a promising candidate for a wide variety of applications.

Synthesis, characterization, and modelling the behavior of in-situ ZrO2 nanoparticles dispersed epoxy nanocomposite

The cured epoxy has poor toughness owing to highly cross-linked nature. The present work reports inclusion of ZrO2 nanoparticles with epoxy via ultrasonic mixing process for improving the toughness. The developed nanocomposites are characterized using mechanical tests, fractographic analysis and dynamic mechanical thermal analysis (DMTA). The mode-1 fracture toughness (K1C), fracture energy (G1C), storage modulus (E') and glass transition temperature (Tg) for different filler concentration are evaluated. A theoretical explanation for improved ZrO2-epoxy nanocomposite behaviour is reported by analyzing the fracture parameters and morphology of fractured samples. A micromechanical finite element (FE) model is constituted for predicting macroscopic elastic properties of composites using numerical homogenization scheme. The model predicted location of fracture initiation under triaxial and uniaxial loading conditions. The SEM micrographs and modelling results collectively explained the fracture mechanism. The experimentation and modelling results are compared.

Photoelectrochemical sandwich immunoassay of CYFRA21-1 based on In2O3/WO3 type-II heterojunction and CdS quantum dots-polydopamine nanospheres labeling.

Using an In2O3/WO3 type-II heterojunction modified fluorine-doped tin oxide (FTO) electrode as the photoanode and CdS quantum dots (QDs)-polydopamine nanospheres (PDA NSs) as the secondary antibody (Ab2) label, the photoelectrochemistry (PEC) sandwich immunosensing of the lung cancer marker CYFRA21-1 was studied. WO3 nanoplates were prepared by a hydrothermal method, In2O3 nanoporous spheres were prepared by a hydrothermal method followed by calcination, and the In2O3/WO3 type-II heterojunction with high PEC activity was prepared by ultrasonic mixing and cast-coating. PDA NSs with a high surface area can be loaded with abundant Ab2 molecules and many CdS QDs with an energy level well matched with the heterojunction, so the photocurrent signal can be amplified by the formation of a sandwich immunostructure. Through the simulation experiments of photoelectrode-modified chitosan films of varying thickness, the effective transport distance of photogenerated charges is preliminarily discussed. Under the optimized conditions, the photocurrent was linear with the common logarithm of CYFRA21-1 concentration from 100 fg mL-1 to 50 ng mL-1, with a limit of detection of 56 fg mL-1 (S/N = 3). The immunoassay of CYFRA21-1 in human serum samples gave satisfactory recovery results.

Determining influences of different stirring methods for encapsulating stearic acid with SiO2 shell for thermal energy storage applications

ABSTRACTStearic acid was encapsulated successfully with SiO2 shell in nanoscale by in situ emulsion interfacial hydrolysis and poly-condensation techniques. The influence of using different mixing techniques on these techniques was investigated. Morphologic, thermal and crystal structure analysis results show that the ultrasonic mixing technique is suggested for synthesis of SiO2 nanocapsules. Ultrasonic vibrations lead to more homogeneous covering of the oil droplets without residuals by effectively orienting SiO2 molecules during polymerization.

An electrochemical sensor based on a MOF/ZnO composite for the highly sensitive detection of Cu(ii) in river water samples.

Cu(ii) ions are one of the most common forms of copper present in water and can cause bioaccumulation and toxicity in the human body; therefore, sensitive and selective detection methods are required. Herein, a copper ion sensor based on a UiO-66-NH2/ZnO composite material is proposed. The UiO-66-NH2/ZnO nanocomposite was prepared by an ultrasonic mixing method. The morphology and structure of the nanocomposite were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The sensitivity to Cu(ii) is 6.46 μA μM−1 and the detection limit is 0.01435 μM. The composite material is rich in –OH and –NH2 groups, which are active sites for Cu(ii) adsorption. The UiO-66-NH2/ZnO-modified electrode has good repeatability and anti-interference ability. The sensor was successfully used for the determination of Cu(ii) in an actual water sample.

Thermal properties of surface-modified nano-Al2O3/Kevlar fiber/epoxy composites

The mechanical and thermal properties of Kevlar fiber reinforced polymer composites are favorable. Researchers have extensively studied to improve these composites' mechanical characteristics, but research into improving their thermal properties is still limited. The aim of this study is to further improve the thermal properties of Kevlar fiber reinforced epoxy composite using surface modified Al2O3 nanoparticles. Vacuum-assisted resin infusion method (VARIM) was used to produce nanocomposite laminates. The surface of Al2O3 nanoparticles was modified with a silane coupling agent. Ultrasonication and magnetic mixing were used to incorporate Al2O3 at various wt.% (1, 2, 3, 4 and 5) into epoxy. Thermal stability was determined by performing differential scanning calorimetric (DSC) and thermogravimetric analysis (TGA) and measuring thermal conductivity and thermal diffusivity. The results obtained revealed that the surface-modified Al2O3 nanoparticles exhibit good thermal barrier properties and improve thermal stability. In terms of degradation temperature and specific heat capacity, the thermal stability of Kevlar composites is best at 3 wt% Al2O3. SEM images and EDX processing were used to determine the morphological characteristics. The chemical composition was confirmed by EDX analysis, and SEM images revealed that the failure occurred in fiber and matrix-related mechanisms. Fourier transform infrared (FT-IR) spectra were recorded using a FT-IR spectrophotometer. It was seen that three new peaks appear with the addition of surface-modified Al2O3.

Epoxy/SIO2 nanocomposite mechanical properties and tribological performance

In this study, a systematic review was conducted to evaluate the performance of nanocomposites of the epoxy matrix of Sio2 nanoparticles embedded in epoxy resin. Ultrasonic mixing is used to achieve uniform dispersion of these epoxy resin nanoparticles. Numerous experiments have been performed in three methods, such as three-dimensional experiments, Izod effect tests and annual tests, to evaluate the composition and performance of epoxy nanocomposites. In addition, the introduction of Sio2 nanoparticles into the low epoxy resin matrix resulted in a significant reduction in the flow rate and the rate of friction.

Cubic nonlinearity parameter measurement and material degradation detection using nonlinear ultrasonic three-wave mixing

Early detection of accumulated damage or material degradation in structures is important to ensure their structural safety. Nonlinear ultrasonic techniques are widely used to measure the quadratic nonlinearity parameter that represents the third-order elastic constants of materials for material degradation detection. In addition, there are ongoing efforts to exploit both the third- and fourth-order elastic constants that describe the cubic nonlinearity parameter to detect material degradation. This study develops a nonlinear ultrasonic three-wave mixing technique to generate and measure third-order combined harmonics (TOCH) in plate-like structures and to measure cubic nonlinearity parameter. The proposed three-wave mixing technique generates three primary Lamb waves in the target structure and measures the TOCH produced by nonlinear cross-interaction of the primary Lamb waves. A theoretical model is developed to describe the generation of TOCH in a nonlinear elastic and homogeneous plate, and the effectiveness of the theoretical model is validated experimentally. Measurements of the TOCH are conducted for intact and degraded aluminum specimens with different degradation levels. Because inherent material nonlinearity and material degradation alter the third- and fourth-order elastic constants of a structure, the three-wave mixing technique for measuring the TOCH can be used to identify the inherent material nonlinearity and material degradation. In particular, the experimental results indicate that the proposed technique is more sensitive to early-stage material degradation than existing nonlinear ultrasonic techniques such as two-wave mixing, and third harmonic generation techniques.

Constant volume combustion properties of Al/Fe2O3/RDX nanocomposite: the effects of its particle size and chemical constituents

A potential novel lead-free primary explosive:Al/Fe2O3/RDX nanocomposites, were prepared by the ultrasonic mixing method, and their ignition and constant volume combustion properties in the electric detonator were analyzed. Results show the constant volume combustion properties are a function of the specific surface area and proportions of their ingredients. A small amount of Al/Fe2O3 nanothermite could accelerate the constant volume combustion of nanocomposites, and make the ignition delay time and pressure rise time decrease. When nano-Fe2O3 with high specific surface area was used as oxidizer, or both cyclohexane and acetone as the solvent, the ignition and combustion properties show a dramatic improvement. Al/Fe2O3/RDX nanocomposites with faster combustion velocity than RDX and enough detonation output power to explode other explosives could be obtained by adjusting their particle sizes and the amount of their constituents.

Flexible synthesis of high-performance electrode materials of N-doped carbon coating MnO nanowires for supercapacitors

The MnO/C composites were obtained by co-precipitation method, which used Mn3O4 nanomaterials as precursors and dopamine solution after ultrasonic mixing and calcination under N2 atmosphere at different temperatures. By studying the difference of MnO/C nanomaterials formed at different temperatures, it was found that with the increase of calcination temperature, the materials appear obvious agglomeration. The optimal calcination temperature is 400 °C, and the resulting MnO/C is a uniformly dispersed slender nanowire structure. The specific capacitance of MnO/C nanowires can reach 356 F g−1 at 1 A g−1. In the meantime, the initial capacitance of MnO/C nanowires remains 106% after 5000 cycles. Moreover, the asymmetric supercapacitor was installed, which displays a tremendous energy density of 30.944 Wh kg−1 along with a high power density of 10 kW kg−1. The composite material reveals a promising prospect in the application of supercapacitors.

Effect of glass nanofibers on mode I interlaminar fracture toughness of glass/epoxy composites

The idea of using glass nanofibers was proposed to overcome the weakness of out-of-plane properties of glass/epoxy composites. Glass nanofibers were produced by electrospinning solution of tetraethyl orthosilicate and polyvinylpyrrolidone as carrying polymer and dispersing the nanofibers in resin using an ultrasonic mixer. Various percentages of glass nanofibers were mixed with the resin and its effect on the tensile properties was investigated. Based on the tensile strength, the optimal percentage of nanofiber in the matrix was optimized. Finally, the hybrid composite was produced with unidirectional glass fabric using the optimized glass nanofibers content in resin. Interlaminar fracture toughness in mode I test was performed to investigate the effect of the addition of glass nanofibers on composites' mechanical properties. Results showed a significant increase (up to 91%) in interlaminar fracture toughness at the crack initiation state and caused a slight increase in the crack propagation load.

A review on nondestructive testing of bonding interface using nonlinear ultrasonic technique

<p indent="0mm">As an important complement to traditional mechanical connections, bonded structures are widely used in industry. Under the combined effect of external loads and environmental factors, the performance of the bonding interface will deteriorate, which seriously affects the safe use of bonding structures. Therefore, the performance evaluation of bonding interfaces has always been a hot and difficult issue in the field of non-destructive testing. Traditional linear ultrasonic technology can effectively detect damage such as delamination and debonding in the bonding interface, but it is difficult to detect and quantitatively evaluate the early degradation of the bonding interface (such as closed defects and weak bonding). However, the nonlinear ultrasonic technology can overcome the low sensitivity of the traditional linear ultrasonic technology and is expected to be an effective means for nondestructive testing of early deterioration of bonding interface performance. In this paper, we review the recent development of nonlinear ultrasonic technology for bonding interface detection from theoretical models and testing experiments. From the perspectives of contact nonlinearity of the interface and material nonlinearity of the interlayer, we introduce relevant theoretical models for nonlinear ultrasonic inspection of bonded interfaces, such as nonlinear spring model, interface contact model and contact model considering the thickness of the interlayer. These models can be used for the description of various acoustic nonlinear effects (such as second harmonic generation, wave mixing and nonlinear resonance) generated by ultrasonic waves at weak bonding interfaces, but the ability of different models to characterize the nonlinear propagation behavior of ultrasonic waves at weak bonding interfaces needs to be further investigated. Meanwhile, we review the progress of three nonlinear techniques of nonlinear ultrasonic resonance, wave mixing and second harmonic generation in the experimental testing of bonding interface properties. The nondestructive testing of bonding interface using nonlinear ultrasonic resonance technique remains relatively limited. Mixing technology is of great interest because of its flexibility and selectability of excitation frequency, mode and area of action, and its ability to effectively avoid the effects of system nonlinearity. Among the nonlinear ultrasonic methods, harmonic techniques are the most widely used, and have been used for damage detection and performance evaluation of bonding interfaces, such as bonding thickness measurement, debonding detection, bond strength and fatigue life evaluation. The harmonic technique is considered as a possible solution for the quantitative detection of the interface properties of multilayer bonded structures. However, how to distinguish the harmonics generated by weakly bonded interfaces from those generated by detection systems has been a challenge for its application. Finally, we provide an outlook for the development of nonlinear ultrasonic detection technology for early degradation of bonding interfaces.