Qingrong Yao

Investigation of the isothermal section of the Ce-Co-Al ternary system at 573 K

The isothermal section of the Ce-Co-Al ternary system at 573 K was investigated by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) techniques. It consisted of 19 single-phase regions, 46 two-phase regions and 25 three-phase regions. Four ternary compounds, namely CeCoAl, Ce2Co15Al2, CeCoAl4, CeCo2Al8, were confirmed in this system. At 573 K, the maximum solid solubilities of Co in CeAl2 and Al in CeCo2 were about 10.4 at.% and 10.0 at.%, respectively. The homogeneity range of CoAl phase extended from about 46.0 to 56.0 at.% Al.

Preparation and microwave absorption properties of NdFeB alloys

In order to improve the microwave absorbing properties of NdFeB alloys, as-jet milled powders were further processed in a planetary mill. The phase structure, morphology and particle size of the alloy powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser diffraction-based particle size analyzer, respectively. The saturation magnetization and electromagnetic parameters of the powders were determined by a vibrating sample magnetometer (VSM) and a vector network analyzer (VNA), respectively. The results showed that the saturation magnetization decreased as the milling time increased. The minimum absorption peak frequency shifted towards the lower region and the reflection loss values increased with increasing the ball milling time. The minimum absorption peak value of the powders milled for 15 h on the basis of jet milling reached −44.4 dB at 11.04 GHz, and the bandwidth of R<-10 dB was 1.2 GHz with the best matching thickness of 1.8 mm.

Crystal structure and magnetic behavior of the La0.1Bi0.9FeO3 compound

Abstract The nano-crystalline La 0.1 Bi 0.9 FeO 3 compound was successfully synthesized by starch-based combustion method. The crystal structure and magnetic behavior were studied by temperature-dependent X-ray diffraction (XRD), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and magnetic measurements. The La 0.1 Bi 0.9 FeO 3 compounds crystallized in a rhombohedrally distorted perovskite structure with space group R 3 c . The substitution of La for Bi reduced the rhombohedral distortion. The structural phase transitions in La 0.1 Bi 0.9 FeO 3 driven by temperature showed that the extraordinary two-phase coexistence state of BiFeO 3 and LaFeO 3 was observed in a narrow temperature range of 630–700 °C. The magnetization of the La 0.1 Bi 0.9 FeO 3 sample was improved by heat treatment in the temperature range. When the heat treatment temperatures rose from 25 to 600 °C, the remanence ( M r ) and coercivity ( H c ) of the La 0.1 Bi 0.9 FeO 3 compound almost remained the same, and increased rapidly to 0.134 emu/g and 7.1 KOe on further increasing the heat treatment temperature to 650 °C.

Effect of rapid solidification treatment on structure and electrochemical performance of low-Co AB5-type hydrogen storage alloy

The effect of rapid solidification on structure and electrochemical performance of the LaNi4.5Co0.25Al0.25 hydrogen storage alloy was investigated by X-ray powder diffraction and a simulated battery test, including maximum capacity, cycling stability, self-discharge, and high-rate discharge ability (HRD). All the melt-spun alloys were single-phase with the CaCu5-type structure (space group P6/mmm). In comparison to the as-cast alloy, the rapidly quenched alloys manifested an improved homogeneity of composition and expanded lattice parameters. The electrochemical measurements showed that the activation property, cycling stability and self-discharge of the alloy electrodes were also improved for the rapid solidified alloys. The HRD of the as-cast alloy was better than those of all the rapidly solidified alloys. As the quenching rate increased, the HRD and exchange current density first decreased and then increased.

Effects of cobalt substitution on structure and microwave absorption properties of PrNi5 alloy

The polycrystalline samples PrNi5–xCox (x=0.0, 0.1, 0.2, 0.3, 0.4) were synthesized by arc smelting and high energy ball milling method. The phase structure, morphology, saturation magnetization and electromagnetic parameters of the alloy powders were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM) and vector network analyzer (VNA), respectively. The results revealed that the lattice parameter a and c and unit-cell volume V increased with the increasing amount of Co substitution. The saturation magnetization increased as Co content increased. The minimum absorption peak frequency shifted towards lower frequency region with the increasing amount of Co substitution. And the minimum reflection loss of the PrNi5–xCox powders increased first and then decreased with the increasing amount of Co substitution. The PrNi5–xCox alloys possessed the excellent microwave absorbing properties. The minimum reflection loss of the PrNi4.9Co0.1 alloy all could reach −20.0 dB with the coating thickness ranging from 1.8 to 3 mm. The minimum reflection loss of PrNi4.9Co0.1 powders was −36.20 dB at 7.76 GHz, and the frequency bandwidth of R<–10 dB reached about 1.50 GHz with the best matching condition d=2.0 mm.

Crystal structure and phase relations of Pr2Fe14B-La2Fe14B system

Abstract The crystal structure and phase relations of the Pr 2 Fe 14 B-La 2 Fe 14 B system were investigated by X-ray powder diffraction (XRD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDS). The crystal structure parameters were determined by full-profile Rietveld refinements. The results revealed that all alloys of (Pr 1– x La x ) 2 Fe 14 B crystallized the Nd 2 Fe 14 B-type structure with the space group P 4 2 / mnm and formed a continuous solid solutions between x =0.0 and 1.0. The lattice parameter a, c , unit-cell volume V and c/a ratio increased linearly with the La concentration. Determined by thermogravimetry analysis, the Curie temperature ( T C ), phase transition temperature and melting temperature of (Pr 1– x La x ) 2 Fe 14 B decreased linearly upon the La content. Based on the results of DSC measurements and X-ray powder diffraction examinations, the phase diagram of the Pr 2 Fe 14 B-La 2 Fe 14 B system was built up.