Effect of reaction conditions on size and morphology of ultrasonically prepared Ni(OH)(2) powders

Magnesium and magnesium alloy dissolution by high intensity focused ultrasound: erosion/cavitation vs. Wave propagation

The dissolution of metals, influenced by mechanical and chemical factors, plays a crucial role in various applications. Ultrasonic irradiation has been explored for its ability to enhance dissolution rates and modify surface characteristics. In this study, we investigate the dissolution of magnesium (Mg) and magnesium alloys under high-intensity focused ultrasound (HIFU) conditions with frequency sweeping (wobbling). Our findings reveal distinct effects of cavitation and acoustic streaming on the dissolution process. For pure magnesium, ultrasonic treatment significantly increases dissolution rates compared to silent conditions. Negative frequency sweeps result in the highest dissolution rates, linked to increased cavitation activity, while positive sweeps reduce dissolution rates but maintain acoustic streaming effects. The removal of surface oxides is accelerated in all sonication conditions. Macro- and micro-roughness patterns on the surface correspond to the wobbling frequency range, with wavelengths matching the average ultrasonic frequency. However, dissolution is not uniform across the sample, and preferential attack occurs at the focal point during negative frequency sweeps. In contrast, magnesium alloys exhibit lower dissolution rates than pure Mg. The alloy's mechanical properties make it less susceptible to cavitation erosion but more sensitive to acoustic streaming-induced dissolution. Grain boundaries are preferentially attacked, revealing differences between ductile pure Mg and the harder, more cavitation-resistant, alloy. This study highlights the complex interplay between cavitation and acoustic streaming in the dissolution of magnesium and its alloys under HIFU conditions, shedding light on the limits and potential applications of this technique, particularly in microstructure analysis.

A Disposable Screen Printed Electrodes with Hexagonal Ni(OH)2 Nanoplates Embedded Chitosan Layer for the Detection of Depression Biomarker

Serotonin (5-hydroxytryptamine (5-HT)) is one of the important neurotransmitters which is released from the endocrine system. An abnormal level of this biomarker leads to several neurological diseases. The accurate assessment of serotonin is the utmost option to start treatment in the early stages of the disease. The current work is focused on the development of a disposable, screen-printed electrochemical sensor for the depression biomarker, serotonin in the physiological pH medium (pH 7.4) with the aid of a hexagonal, Ni(OH)₂-nanoplate (NH-HNP)-embedded chitosan (Chit) and modified, screen-printed carbon electrode (SPCE). Initially, hexagonal nanoplates of Ni(OH)₂ were synthesized by an eco-friendly and simple hydrothermal method. The prepared materials were well characterized by advanced analytical techniques to examine the physicochemical properties of the synthesized Ni(OH)₂ hexagonal nanoplates. From the cyclic voltametric (CV) analysis, it was found that the oxidative current response of 5-HT at a NH-HNP-modified SPCE has about fivefold higher current values than over bare SPCE. The scan rate studies of NH-HNP-Chit/SPCE electrodes revealed that the oxidation mechanism of 5-HT is controlled by the diffusion behavior of the analyte. Differential pulse voltammetric tests of the NH-HNP-Chit/SPCE electrode exhibited a linear response in the dynamic concentration range of 0.1 to 30 µM, with a detection limit of about 60 nM. The sensor response is very reproducible from electrode to electrode, and the deactivation or surface-fouling of the sensor was not observed within the several experimental measurements. The sensor exhibited excellent storage stability over a period of twenty days. Finally, the fabricated, disposable SPCE sensor has shown respectable activity for the detection of depression biomarker 5-HT from synthetic urine and saliva samples.

Ultrasound assisted preparation, characterization and adsorption study of ternary chitosan-ZnO-TiO2 nanocomposite: Advantage over conventional method

In the present work, the synthesis of ternary chitosan/zinc oxide/titanium dioxide (CTS-ZnO-TiO₂) nanocomposite was carried out with the use of mechanical stirring (conventional) and ultrasound assisted method. The characterization of prepared CTS-ZnO-TiO₂ adsorbent was carried out using XRD, TEM, FTIR and the results of these analysis methods proved the successful preparation of ternary nanocomposite. Crystal violet (CV) dye was used as a pollutant to observe the adsorption ability of the prepared nanocomposite and the nanocomposite prepared by ultrasonic-assisted method proved to be a better adsorbent. The CV dye adsorption was significant for CTS-ZnO-TiO₂ nanocomposite synthesized with the use of ultrasound assisted method compared to that prepared by conventional method. It is due to the physical effects of the ultrasonic irradiations due to which formation of finely dispersed nanocomposite takes place than that by conventional method. For batch adsorption the effect of various operating parameters such as initial dye concentration, time, temperature and adsorbent dose has been evaluated. The obtained data were processed using isotherm models, adsorption kinetics and the thermodynamic behavior of the cationic dye adsorption was also studied. The isotherm data was correlated reasonably well by the Temkin adsorption isotherm. Pseudo-second-order kinetic model provided a better correlation for the experimental data compared to pseudo first order, Elovich model and power function kinetics model. Thermodynamic parameters for adsorption indicated that the dye adsorption was spontaneous and endothermic in nature.

Enhanced electrochemical performance of lamellar structured Co–Ni(OH)2/reduced graphene oxide (rGO) via hydrothermal synthesis

Lamellar Co–Ni(OH)₂/rGO structures were synthesized and electrochemical properties were improved due to the unique structure and enhanced crystallinity. Also, exhibited long term stability even if high mass loading was used in electrode fabrication.

Ultrasound precipitation of manganese carbonate: the effect of power and frequency on particle properties

The influence of ultrasonic frequency and intensity on particle shape, tap density and particle size distribution was investigated during the precipitation of manganese carbonate. For the first time, a broad frequency range of 94 till 1135 kHz was studied in one single reactor setup. Smaller and more spherical particles were observed during sonication compared to silent conditions. Lower frequencies and increased intensities result in smaller and more spherical particles. The most spherical particles with superior tap densities are obtained at the lowest frequency and most elevated intensity. Moreover, the results indicate that a particle size threshold exists, below which the particle size cannot be reduced by a further increase of the ultrasonic intensity or reduction of the frequency. Sonication of already formed spherical powders resulted in particles with smaller sizes but unaffected shapes. Finally, one test with pulsed ultrasonic irradiation resulted in equally sized particles with similar sphericity as the ones produced under continuous sonication.

Synthesis, spectroscopic and electrochemical performance of pasted β-nickel hydroxide electrode in alkaline electrolyte

β-Nickel hydroxide (β-Ni(OH)2) was successfully synthesized using precipitation method. The structure and property of the β-Ni(OH)2 were characterized by X-ray diffraction (XRD), Fourier Transform infra-red (FT-IR), Raman spectra and thermal gravimetric-differential thermal analysis (TG-DTA). The results of the FTIR spectroscopy and TG-DTA studies indicate that the β-Ni(OH)2 contains water molecules and anions. The microstructural and composition studies have been performed using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray (EDX) analysis. A pasted-type electrode is prepared using β-Ni(OH)2 powder as the active material on a nickel sheet as a current collector. Cyclic voltammetry (CV) and Electrochemical impedance spectroscopy (EIS) studies were performed to evaluate the electrochemical performance of the β-Ni(OH)2 electrode in 6M KOH electrolyte. CV curves showed a pair of strong redox peaks as a result of the Faradaic redox reactions of β-Ni(OH)2. The proton diffusion coefficient (D) for the present β-Ni(OH)2 electrode material is found to be 1.44×10(-12) cm(2) s(-1). Further, electrochemical impedance studies confirmed that the β-Ni(OH)2 electrode reaction processes are diffusion controlled.

Influence of ultrasound on the instantaneous synthesis of tridimensional α-Ni(OH)2 nanostructures and derived NiO nanoparticles

Nickel hydroxides present an extraordinary importance in the development of electrochemical devices.