Search Results (5)

M²⁺N⁴⁺Nb₂O₈-type ceramics (where M = Mg, Ca, Mn, Co, Ni, Zn and N = Ti, Zr) are essential for satellite communication and mobile base stations due to their medium relative permittivity (ε_r) and high quality factor (Q × f). Although ZnTi_0.2Zr_0.8Nb₂O₈ ceramic exhibits impressive microwave dielectric properties, including an ε_r of 29.75, a Q × f of 107,303 GHz, and a τ_f of −24.41 ppm/°C, its sintering temperature of 1150 °C remains a significant barrier for integration into low-temperature co-fired ceramic (LTCC) technologies. To overcome this limitation, a strategy involving the partial substitution of Zn²⁺ with Cu²⁺ and the addition of LiF as a sintering aid was devised for ZnTi_0.2Zr_0.8Nb₂O₈. The dual impact of Cu²⁺ partial substitution and LiF as a sintering enhancer facilitated the successful sintering of Cu_0.3Zn_0.7Ti_0.2Zr_0.8Nb₂O₈ ceramics at a reduced temperature of 950 °C using the conventional solid-state reaction method. These ceramics exhibited excellent microwave dielectric properties. Notably, Cu_0.3Zn_0.7Ti_0.2Zr_0.8Nb₂O₈ ceramic with 40 mol% LiF addition demonstrated optimal microwave dielectric properties without any reaction with a silver electrode at a sintering temperature of 950 °C, yielding ε_r = 32, Q × f = 45,543 GHz, and τ_f = −43.5 ppm/°C. Full article

The work presented in this paper describes the preparation and the electrochemical application of functionalized chitosan-entrapped carbon paste electrodes (CH/CPE) for lead ions (Pb²⁺) detection in industrial wastewater. The chitosan was first functionalized using TiO₂ and CuO, which were both metal oxides that were obtained by extracting it from waste products derived from shrimp shells. The analytical performance of the as-prepared electrodes, CH/CPE, TiO₂-CH/CPE, and NiO-CH/CPE, for the detection of lead (II) was examined using electrochemical impedance spectroscopy (EIS) technique in the 0.1 M KNO₃ electrolyte solution. The effect of experimental conditions, including polarization potential, frequency, and pH, are optimized to maximize the sensitivity of the measurements. The developed impedimetric sensors provided a linear response over a concentration range of 10⁻⁶ to 10⁻⁴ M with a detection limit of 3.10⁻⁷ M based on S/N = 3. The DFT computational analysis demonstrated that chitosan biopolymer possesses the ability to adsorb Pb (II) ions that are present in wastewater. Chitosan and the derivatives of chitosan, have the potential to remove heavy metals from industrial effluent in a manner that is both economical and eco-friendly to the environment. Chitosan is a biopolymer that is abundantly renewable. Full article

The mechanism of the material destruction under discharge pulses and material removal mechanism based on the thermochemical nature of the electrical erosion during electrical discharge machining of conductive materials were researched. The experiments were conducted for two structural materials used in the aerospace industry, namely austenite anticorrosion X10CrNiTi18-10 (12kH18N10T) steel and 2024 (D16) duralumin, machined by a brass tool of 0.25 mm in diameter in a deionized water medium. The optimized wire electrical discharge machining factors, measured discharge gaps (recommended offset is 170–175 µm and 195–199 µm, respectively), X-ray photoelectron spectroscopy for both types of materials are reported. Elemental analysis showed the presence of metallic Zn, CuO, iron oxides, chromium oxides, and 58.07% carbides (precipitation and normal atmospheric contamination) for steel and the presence of metallic Zn, CuO, ZnO, aluminum oxide, and 40.37% carbides (contamination) for duralumin. For the first time, calculating the thermochemistry parameters for reactions of Zn(OH)₂, ZnO, and NiO formation was produced. The ability of Ni of chrome–nickel steel to interact with Zn of brass electrode was thermochemically proved. The standard enthalpy of the Ni₅Zn₂₁ intermetallic compound formation (erosion dust) ΔH⁰₂₉₈ is −225.96 kJ/mol; the entropy of the crystalline phase S^c_int is 424.64 J/(mol·K). Full article

The development of visible-light-responsive semiconductor-based photoelectrodes is a prerequisite for the construction of efficient photoelectrochemical (PEC) cells for solar water splitting. Surface modification with an electrocatalyst on the photoelectrode is effective for maximizing the water splitting efficiency of the PEC cell. Herein, we investigate the effects of surface modification of Ta₃N₅ photoanodes with electrocatalysts consisting of Ni, Fe, and Co oxides, and their mixture, on the PEC oxygen evolution reaction (OER) performance. Among the investigated samples, NiFeO_x-modified Ta₃N₅ (NiFeO_x/Ta₃N₅) photoanodes showed the lowest onset potential for OER. A PEC cell with a parallel configuration consisting of a NiFeO_x/Ta₃N₅ photoanode and an Al-doped La₅Ti₂Cu_0.9Ag_0.1S₅O₇ (LTCA:Al) photocathode exhibited stoichiometric hydrogen and oxygen generation from water splitting, without any external bias voltage. The solar-to-hydrogen energy conversion efficiency (STH) of this cell for water splitting was found to be 0.2% at 1 min after the start of the reaction. In addition, water splitting by a PEC cell with a tandem configuration incorporating a NiFeO_x/Ta₃N₅ transparent photoanode prepared on a quartz insulating substrate as a front-side electrode and a LTCA:Al photocathode as a back side electrode was demonstrated, and the STH was found to be 0.04% at the initial stage of the reaction. Full article

In the industrial field, electric discharge machining (EDM) is the most commonly used non-traditional machining process because it has the potential to machine electrically conductive materials of high hardness. To satisfy the need for rapid and economical fabrication of EDM electrodes, techniques that use the addition of more metal in the manufacturing process are gaining in popularity. This study presents an investigation of the characterization of ternary metals (Cu–Ni–TiN) for EDM electrodes by using powder metallurgy, which leads to enhancement of the mechanical properties, such as the hardness, electrical properties, and other properties, for the formation of Cu in Ni-TiN electrodes using a cold press at pressures of 18, 20, and 22 MPa. The influences of the parameters of this process were identified for the betterment of Cu–Ni–TiN on the surface. The specimens were calcined in a furnace at 1100 °C for 1 h, with a mixture of argon and hydrogen gas as a controlled gas in the ratio of 95:5. The specimens were investigated in terms of hardness, electric resistivity, apparent density, and porosity. The results show that the 80% Cu–3% Ni–17% TiN electrode at 18 MPa had the highest hardness (124.38 HV) and the lowest electric resistivity (0.39188 cm), while the specimen increased Cu with a ratio of 85% Cu–3% Ni–12% TiN, and a pressure of 20 MPa was found to have the highest density (8.5472 g/cm³) and the lowest porosity (6.2922%). As a further confirmation of the above results, the X-ray diffraction (XRD) patterns of the surfaces of the specimens exhibited major phases that supported the ternary Cu–Ni–TiN phase. However, we also achieved the successful use of Cu–Ni–TiN electrodes as a titanium source (as an alternative to the conventional metal powder) to provide a novel approach to fabricating composite electrodes through the EDM process. Full article