This paper reports on the results of measurements of the conductivity in MnSe and MnTe polycrystalline samples under thermal cycling in the temperature range 80 < T < 300 K in magnetic fields of up to 5 kOe. Manganese selenide MnSe is found to exhibit a magnetoresistive behavior below the Néel temperature. The specific features revealed in the temperature dependences of the magnetic susceptibility and the electrical resistivity in some temperature ranges are accounted for in terms of magnetic ordering, which is mediated by the interaction of the pseudoorbital moments with spins.
The temperature dependences of the specific magnetization σ and the electrical resistivity ρ of MexMn1 − xS single crystals (Me= Co, Gd; x= 0.05) have been studied in the temperature range 80 K < T < 1000 K. The samples under study have revealed the presence of a spontaneous magnetic moment below the Néel temperature (TN) and ferromagnetic clusters in Gd0.05Mn0.95S in the temperature range 146 K < T < 680 K. Substitution of gadolinium for manganese initiates a transition from p-type to n-type conduction. The change in the conduction type is accompanied by an increase in the electrical resistivity at 300 K by approximately one order of magnitude and, accordingly, by a decrease in the activation energy. The magnetic and electrical properties of the crystals under study have been interpreted in terms of the cluster model with temperature-dependent ferromagnetic exchange and an electron localized in this cluster.
Hydrogen absorption in transition metals has received enormous attention for applications such as the hydrogen storage, sensing and corrosion. In particular, the Pd‐H system is a simple and classical metal hydride system that serves as a platform for a deeper understanding of hydrogen behavior. In the past few years, Pd‐H has been reported as electrocatalyst in multiple reactions, whereas the impact of hydrogen absorption/desorption in electrocatalytic applications remains unclear. Therefore, in this concept, factors influencing the hydrogen adsorption/desorption of palladium in the gas phase, such as facet engineering, ligand effects, and alloying effects, are summarized. Subsequently, in the context of electrocatalysis, factors affecting electrochemical hydrogen adsorption/desorption are outlined. Particularly, prospects for the further investigation of electrochemical hydrogen adsorption/desorption in catalysis are discussed.
1 January 2024 in Journal of the Brazilian Chemical Society
Sintered NdFeB magnets possess excellent magnetic properties, but behave passively in alkaline and saline media and are susceptible to corrosion in acidic environments. The corrosion behavior of NdFeB magnets in industrial environments: potassium hydroxide (KOH), perchloric acid (HClO4) and sodium chloride (NaCl), was investigated by immersion and electrochemical tests. The immersion test concluded that the most corrosive electrolyte of the three studied was HClO4. Electrochemical tests showed that the NdFeB sample without magnetic order had better corrosion resistance. Metallographic microscopy and scanning electron microscopy support the obtained corrosion data. X-ray photoelectron spectroscopy indicates that the main elements on the surface of the analyzed sample (Nd, Fe, B) are in the oxidized state after corrosion.