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Sun N.K.,Shenyang Ligong University | Guo J.,Shenyang Ligong University | Zhao X.G.,CAS Shenyang Institute of Metal Research | Si P.Z.,China Jiliang University | And 2 more authors.
Applied Physics Letters

La(Fe, Si)13 hydride is regarded as one of the most promising room-temperature refrigerants. However, to use the alloys in an active magnetic regenerator machine, it is vital to prepare thin refrigerants. In this work, a high H2 gas pressure of 50 MPa was employed to suppress the desorption of hydrogen atoms during the sintering process of plate-shaped La0.5Pr0.5Fe11.4Si1.6 hydrides. At 330 K, a high-density sintered thin plate shows a large magnetic-entropy change ΔSm of 15.5 J/kg K (106 mJ/cm3K) for a field change of 2 T. The volumetric ΔSm is almost twice as large as that of bonded La(Fe,Si)13 hydrides. Favorably, hysteresis is almost absent due to the existence of micropores with a porosity of 0.69% which has been analyzed with high-resolution X-ray microtomography. © 2015 AIP Publishing LLC. Source

Phan T.-L.,Chungbuk National University | Zhang Y.D.,Baotou Research Institute of Rare Earths | Yang D.S.,Chungbuk National University | Nghia N.X.,Vietnam Academy of Science and Technology | And 3 more authors.
Applied Physics Letters

Though ZnO is known as a diamagnetic material, recent studies have revealed that its nanostructures can be ferromagnetic (FM). The FM origin has been ascribed to intrinsic defects. This work shines light on an alternate method based on mechanical milling to induce defect-related ferromagnetism in ZnO nanoparticles (NPs) from initial diamagnetic ZnO powders. Our idea is motivated by the fact that mechanical milling introduces more defects to a ground material. We point out that the FM order increases with increasing the density of defects in ZnO NPs. The experimental results obtained from analyzing X-ray absorption, electron spin resonance, and Raman scattering spectra demonstrate that the ferromagnetism in ZnO NPs is due to intrinsic defects mainly related to oxygen and zinc vacancies. Among these, zinc vacancies play a decisive role in introducing a high FM order in ZnO NPs. © 2013 American Institute of Physics. Source

Chen Y.-X.,Baotou Research Institute of Rare Earths
Chinese Rare Earths

This paper summarizes the development process of using fluoride salt electrolysis to produce rare earth metals at home and abroad, analyses the researches on physico-chemical properties and electrochemical properties of rare-earth fluoride electrolyte and reviews study progress of numerical simulation on the process. Source

Liu B.,Inner Mongolia University | Li C.,Inner Mongolia University | Zhang Y.,Inner Mongolia University | Liu Y.,Inner Mongolia University | And 4 more authors.
Applied Catalysis B: Environmental

A colloidal crystal template method coupled with a precursor complexion process was developed to create three-dimensionally ordered macroporous (3DOM) Au/CeO 2 catalyst. The resultant Au/CeO 2 catalyst possesses well-defined 3DOM structure, and shows enhanced catalytic performance for formaldehyde (HCHO) oxidation with 100% HCHO conversion at ∼75°C. The catalytic mechanism of HCHO catalytic oxidation over 3DOM Au/CeO 2 catalyst was systematically investigated by means of gas chromatograph (GC), H 2-temperature programmed reduction (H 2-TPR), temperature programmed surface reaction (TPSR), CO 2-temperature programmed desorption (TPD), and Fourier transform infra-red (FT-IR) spectroscopy. GC results indicate that HCOOH intermediate is generated during HCHO catalytic oxidation. TPD and TPSR tests show that the weak absorption ability of CO 2 over 3DOM Au/CeO 2 catalyst and the existence of Au active species in ionic and metallic states in 3DOM Au/CeO 2 catalyst largely improve the catalytic activity, favoring the enhanced HCHO catalytic oxidation. FT-IR tests prove that the carbonate and hydrocarbonate formed on the surface of 3DOM Au/CeO 2 catalyst during HCHO catalytic oxidation may account for its deactivation. Based on the above investigation, a new catalytic mechanism of enhanced HCHO catalytic oxidation over 3DOM Au/CeO 2 catalyst is proposed. The mechanism may afford the scientific guidance for preparing high efficiency oxide supported noble metal catalysts and present a solution for solving their deactivation problem. © 2011 Elsevier B.V. Source

Kong F.,Baotou Research Institute of Rare Earths
Electrochimica Acta

In this paper, micrometer Co 3O 4 materials are synthesized via a method of chemical synthesis in combination with calcinations. The effect of calcination temperature on the morphology, structure and catalytic performance as air/oxygen electrode materials are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) spectroscopy and electrochemical techniques. The SEM observation reveals that the morphology of the Co 3O 4 products changes to a beadlike shape from the rod shape after calcinated at temperature of 700 °C. The XRD measurements show that the both morphology Co 3O 4 products exhibit a cubic phase of Co 3O 4 spinel with a space group of Fd3m. But the beadlike Co 3O 4 product has better crystallinity. The electrochemical measurements show that the beadlike Co 3O 4 material has better active properties for electrochemical O 2 reduction and O 2 generation reactions. Also it exhibits the bi-functional performance in the oxygen-diffusion electrodes and has potential applications in rechargeable metal-air batteries and regenerative fuel cells. © 2012 Elsevier Ltd. All rights reserved. Source

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