Correlation between Structure, Electrical, and Magnetic Properties of Some Alkali-Oxide Materials

In this chapter, the correlation between structure and electrical properties of Na2MP1.5As0.5O7 (MII = Co and Cu) are treated. The structural study shows that the cobalt and copper isotype materials can be crystallized in the tetragonal and monoclinic systems, respectively. The electrical study using impedance spectroscopy technique showed that these mixed diphosphate diarsenates are fast electrical conductors; however, the cobalt material exhibited more conductive property than the copper compound. In addition, the powder perovskite manganites La0.7M0.2M’0.1MnO3 (M = Sr, Ba and M’ = Na, Ag and K) have been prepared using the conventional solid-state reaction. The structural, magnetic, and magnetocaloric properties of these perovskite manganites compounds were studied extensively by means of X-ray powder diffraction (XRD) and magnetic measurements. These samples were crystallized in the distorted rhombohedral system with R3c space group. The variation of magnetization (M) vs. temperature (T) reveals that all compounds exhibit a second-order ferromagnetic to paramagnetic phase transition in the vicinity of the Curie temperature (TC). A maximum magnetic entropy change, ΔSMMax, of 4.07 J kg−1 K−1 around 345 K was obtained in La0.7Sr0.2Na0.1MnO3 sample upon a magnetic field change of 5 T. The ΔSMMax values of La0.7Ba0.2M’0.1MnO3 are smaller in magnitude compared to La0.7Sr0.2M’0.1MnO3 samples and occur at lower temperatures

Synthesis and Structure of New Mixed Silver Cobalt(II)/(III) Diphosphate - Ag3.68Co2(P2O7)2. Silver(I) Transport in the Crystal

International audienceA new silver cobalt diphosphate, Ag3.68Co2(P2O7)2, is synthesized by solid-state reaction route. Crystal structure and Ag+pathways simulation are studied by single-crystal X-ray diffraction and Bond Valence Site Energy (BVSE) model, respectively. The title material crystallizes in the triclinic system, space group P-1 with a = 6.521(4) Å, b = 9.623(6) Å, c = 10.969(7) Å, =64.23(2) ̊, = 80.14(3) ̊ and = 72.10(2) ̊. The structure presents Co4P4O28groups formed by two Co2O11units and two P2O7groups. The junction between these groups is assured by two pyrophosphates to create a three-dimensional anionic framework showing interconnecting tunnels in a, band caxis. The obtained structural model is supported by two validations tools: Charge Distribution (CHARDIT) analysis and Bond Valence Sum (BVS) calculation which validated the presence of Co2+and Co3+in the same sites. The Ag+cations balanced the negative charge with partial site occupations. The Ag+ pathways simulation, using the Bond Valence Site Energy(BVSE) model, identified the mobile species and proposed migration pathways of the monovalent cations according vast tunnels in three dimensions. The material must be a 3D average ionic conductor, with theoretical activation energy about 1.7 eV. Correlation between structure and electricalproperties has been discussed

Evaluation of 2-Mercaptobenzimidazole Derivatives as Corrosion Inhibitors for Mild Steel in Hydrochloric Acid

This research aimed to develop a better understanding of the corrosion inhibition of the mild steel in acidic medium by new organic molecules. For this purpose, two new compounds namely, 2,3-dihydrobenzo[4,5]imidazo[2,1-b]thiazole (2-BIT) and 3,4-dihydro-2H-benzo[4,5]imidazo[2,1-b]thiazole (3-BIT) were synthesized and evaluated for mild steel (MS) corrosion in HCl. Analyses were carried out using weight loss measurements, electrochemical techniques, and scanning electron microscope (SEM). The adsorption of inhibitors onto the steel surface follows the Langmuir adsorption model. Generally, results showed that the corrosion inhibition efficiency of the investigated molecules was found to increase with increased concentration of inhibitors. Electrochemical tests, i.e., electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) techniques, showed that the addition of our investigated inhibitors decreases the dissolution of the metal and generally act as mixed-type inhibitors. In addition, the influence of temperature (from 303 to 333 K) on the corrosion inhibition was studied, and the results demonstrated that with an increase in temperature, the inhibition efficiency decrease. SEM results confirmed that the inhibition process is due to a protective film that prevents corrosion. Similarly, the results showed that the inhibitory efficiencies reach 93% at 5 × 10−3 M in the case of inhibitor 3-BIT. These results revealed that this compound could effectively control and reduce the corrosion rate of mild steel in the corrosion test solution