Search

The powder immersion reaction assisted coating (PIRAC) method was used to fabricate a coating on the graphite surface. The graphite was immersed into Cr powder and annealed at 1173–1373 K. The iodine powder was admixed with the Cr powder to investigate the contribution of iodine to the growth and mechanical properties of the coating. After 4 h of PIRAC treatment with or without iodine, Cr7C3- and Cr23C6-based coatings were formed, respectively. The iodinated samples had a higher hardness and thickness, and the friction coefficient was slightly higher than that of the iodine-free sample. The mechanisms for the formation of PIRAC-chromium carbide coatings are explained, and the variations in the produced coatings are discussed. [ABSTRACT FROM AUTHOR]

Single-phase high-entropy perovskite ceramics (Ln 0.2 Gd 0.2 La 0.2 Nd 0.2 Sm 0.2)MnO 3 (Ln-GLNSMO HEPCs) have been synthesized using solid-state reactions. The effect of A-site rare-earth ions (Ln = Eu, Ho, Yb) on the structure and magnetic properties was systematically investigated. The results show that all samples are orthorhombic phases (with a space group of Pbnm) and exhibit a strong crystallization trend sintered at 1300 °C for 16 h. All the HEPCs are composed of irregular spherical particles with smooth surfaces and show obvious hysteresis effects at T = 5 K. The changing Mn–O bond distance, Mn–O–Mn bond angle and the increase of Mn4+ ion concentration enhance the double exchange effect of Mn3+-O2--Mn4+, leading to different magnetic interactions. The residual magnetization M r (coercivity H c) of the samples is significantly enhanced, which is increasing from 0.13 emu/g (16.34 Oe) to 3.17 emu/g (97.07 Oe) due to the increase of configuration entropy, lattice distortion and the double exchange effect (DE). In addition, there is a strong relationship between the magnetic properties and the average radius of the A-site ions, in which Ho-GLNSMO HEPCs have a high M s magnetism. This work is a valuable reference for the magnetic regulation of high-entropy ceramics based on rare-earth and entropy-stabilized perovskite types. [ABSTRACT FROM AUTHOR]

In this work, single-phase (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 2-δ high-entropy fluorite oxides (HEFOs) were successfully prepared by conventional solid-phase reaction method and crystal structure and microstructure were studied in-depth. Single-phase (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 2-δ is formed at 1600 °C for 12 h, and five cationic elements are uniformly distributed without any segregation at the micrometer and nanometer scales. And the XRD patterns with Rietveld refinement reveal the formation of single-phase fluorite structure of (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 2-δ. The SAED patterns on the [0 1 ‾ 1] band axes are similar to the diffraction patterns of face-centered cubic fluorite structure, and the standard deviation of the cation radius (coordination VIII) distribution of the specimens is 0.1277, which is again identified as forming a single-phase fluorite structure. The bulk specimens are solid compacts free of obvious cracks with randomly distribution porosity at a rare level, and the powder specimens are irregular fragmented shapes with an average particles size of 5.41 μm. The average cation radius and interplanar spacings becomes larger compared with standard fluorite structure of CeO 2 due to the cation radius of La3+, Sm3+ and Nd3+ are larger than that of Ce4+, leading to an increase in lattice parameters of the HEFOs. In addition, the concentration of Ce3+ in the Ce cation is only 8.1 %, and the δ -value is calculated to be 0.3081 based on the content of all cations per mole of the substance, which indicates that the composition of the prepared specimen is (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 1.6919. [ABSTRACT FROM AUTHOR]

In this work, single-phase (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 2-δ high-entropy fluorite oxides (HEFOs) were successfully prepared by conventional solid-phase reaction method and crystal structure and microstructure were studied in-depth. Single-phase (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 2-δ is formed at 1600 °C for 12 h, and five cationic elements are uniformly distributed without any segregation at the micrometer and nanometer scales. And the XRD patterns with Rietveld refinement reveal the formation of single-phase fluorite structure of (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 2-δ. The SAED patterns on the [0 1 ‾ 1] band axes are similar to the diffraction patterns of face-centered cubic fluorite structure, and the standard deviation of the cation radius (coordination VIII) distribution of the specimens is 0.1277, which is again identified as forming a single-phase fluorite structure. The bulk specimens are solid compacts free of obvious cracks with randomly distribution porosity at a rare level, and the powder specimens are irregular fragmented shapes with an average particles size of 5.41 μm. The average cation radius and interplanar spacings becomes larger compared with standard fluorite structure of CeO 2 due to the cation radius of La3+, Sm3+ and Nd3+ are larger than that of Ce4+, leading to an increase in lattice parameters of the HEFOs. In addition, the concentration of Ce3+ in the Ce cation is only 8.1 %, and the δ -value is calculated to be 0.3081 based on the content of all cations per mole of the substance, which indicates that the composition of the prepared specimen is (Ce 0.2 Zr 0.2 La 0.2 Sm 0.2 Nd 0.2)O 1.6919. [ABSTRACT FROM AUTHOR]