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In the current research, we successfully prepared TiO2/Ni–Cu–Zn ferrite composite powder for magnetic photocatalyst. The core Ni–Cu–Zn ferrite powder was synthesized using the steel pickling liquor and the waste solution of electroplating as the starting materials. The shell TiO2 nanocrystal was prepared by sol-gel hydrolysis precipitation of titanium isopropoxide [Ti(OC3H7)4] on the Ni–Cu–Zn ferrite powder followed by heat treatment. From transmission electron microscopy (TEM) image, the thickness of the titania shell was found to be approximately 5 nm. The core of Ni–Cu–Zn ferrite is spherical or elliptical shape, and the particle size of the core is in the range of 70–110 nm. The magnetic Ni–Cu–Zn ferrite nanopowder is uniformly encapsulated in a titania layer forming core-shell structure of TiO2/Ni–Cu–Zn ferrite powder. The degradation efficiency for methylene blue (MB) increases with magnetic photocatalyst (TiO2/Ni–Cu–Zn ferrite powder) content. When the magnetic photocatalyst content is 0.40 g in 150 mL of MB, the photocatalytic activity reached the largest value. With a further increase in the content of magnetic photocatalyst, the degradation efficiency slightly decreased. This occurs because the ultraviolet (UV) illumination is covered by catalysts, which were suspended in the methylene blue solution and resulted in the inhibition in the photocatalytic reaction. The photocatalytic degradation result for the relationship between MB concentration and illumination revealed a pseudo first-order kinetic model of the degradation with the limiting rate constant of 1.717 mg/L·min and equilibrium adsorption constant 0.0627 L/mg. Furthermore, the Langmuir–Hinshelwood model can be used to describe the degradation reaction, which suggests that the rate-determining step is surface reaction rather than adsorption is in photocatalytic degradation.

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The microstructure, lattice parameters, mechanical properties, and electrical conductivity mechanisms for Co, Mn co-doped (La 0.8 Ca 0.2 )CrO 3Àd have been systematically investigated. In this study, the concept of defect chemistry is used to explain the relationship between the compensation mechanisms and the electrical conductivity. In air, the hole concentration at high oxygen activity (p ¼ 0.2-u) is larger than that at low oxygen activity (p ¼ 0.2-u-2d 1 ). Therefore, the electrical conductivity decreased with increasing Mn-doping level, and the compensation mechanism is significantly dominated by electrical compensation. In 5% H 2 -95% Ar, the transformation temperature occurred in Mn-doped (La 0.8 Ca 0.2 )(Cr 0.9 Co 0.1 )O 3Àd specimens, which indicates that the prevailing compensation mechanism is changed. Above the transformation temperature, the prevailing compensation mechanism changes from electrical to ionic compensation. The effect of atmospheres on fracture toughness and microhardness for specimens is also investigated in this study. It is found that when the specimens were exposed to 5% H 2 -95% Ar at 1000 C, the cracks appeared in Mn-doped (La 0.8 Ca 0.2 )(Cr 0.9 Co 0.1 )O 3Àd specimens. Presumably, the ionic radii were changed and generated stress that increased brittleness and leaded to cracking. With the increase in the Mn-doping level, the degree of cracking was increased. This indicates these materials could not be used as interconnects at high temperature in the reducing atmosphere.

The microstructure, lattice parameters, electrical conductivity, thermal expansion, and mechanical properties of (La 0.8 Ca 0.2 )(Cr 0.9-x Co 0.1 Ni x )O 3-d (x = 0.03, 0.06, 0.09, 0.12) were systematically investigated in this work. Nickel doping of (La 0.8 Ca 0.2 )(Cr 0.9 Co 0.1 ) O 3-d is an effective way of increasing the thermal expansion coefficient (TEC) and stabilizing the high-temperature phase transformation from rhombohedral to tetragonal. As the nickel-doped content increases, the TEC increases parabolically by TEC (x) (ppm/ C) = 10.575 + 63.3xÀ240x 2 (x = 0.03À0.12). The electrical conductivity of (La 0.8 Ca 0.2 )(Cr 0.9-x Co 0.1 Ni x )O 3-d specimens increases systematically with increasing nickel substitution in the range of 0.03 x 0.09 and reaches a maximum for the composition of (La 0.8 Ca 0.2 )(Cr 0.81 Co 0.1 Ni 0.09 )O 3-d (s 850 C $60.36 S/cm). There is a slight increase in the fracture toughness with increasing nickel doping content, and the fracture toughness is strongly affected by the grain size. It seems that there is an increase in the fracture toughness with decreasing grain size. However, the microhardness does not significantly depend on the grain size in this study. The (La 0.8 Ca 0.2 )(Cr 0.81 Co 0.1 Ni 0.09 )O 3-d specimen shows high electrical conductivity, a moderate thermal expansion coefficient, and nearly linear thermal expansion behavior from room temperature to 800 C. It will be suitable for interconnect materials for intermediate temperature solid oxide fuel cells (IT-SOFCs).

The microstructure, lattice parameters, and electrical conductivity mechanisms for Fe doping on B-site of (La 0.8 Ca 0.2 ) (Cr 0.9 Co 0.1 )O 3 -d were systematically investigated. The oxygen nonstoichiometry was measured by means of thermogravimetry as a function of oxygen partial pressure. In this study, the concept of defect chemistry is used to explain the relationship between the concentration of electron hole with the electrical conductivity. Based on the result of electrical conductivity in air, it is concluded that the concentration of electron hole at high oxygen activity is larger than that at low oxygen activity. This is due to the fact that (La 0.8 Ca 0.2 )CrO 3 -d -based ceramics are p-type conductors, the electrical conductivity is dominated by the concentration of hole. At higher Fe-doping level, the compensation mechanism at high oxygen activity is significantly dominated by the formation of oxygen vacancy, that is, ionic compensation. The compensation mechanism at low oxygen activity is significantly dominated by the formation of the formation of Cr 4+ , that is, electrical compensation at lower Fe-doping level. Based on oxygen nonstoichiometry data, it is found that with increasing Fe-doping amount on B-site of (La 0.8 Ca 0.2 )(Cr 0.9 Co 0.1 )O 3 -d specimens, the initial weight-stable temperature shifted to lower temperature which might be highly related with the change in compensation mechanism at the temperature.