The Magnetocaloric Effect And Catalytic Performance Of Fe-based Amorphous Alloys

Nowadays,it is urgent to promote sustainable development for humankind's requirements,because of increasingly serious resource scarcities,energy shortages and environmental problems.The demand for materials is not only the performance,but also the compatibility with the environment.On one hand,Fe-based amorphous alloy exhibits good magnetic refrigeration capacity near room temperature with appropriate composition design and has the potential to act as magnetic refrigeration.On the other hand,Fe-based amorphous alloy could be applied as the catalyst for wastewater degradation,on account of a large number of zero-valent iron in amorphous state and high chemical activity,.As Fe-based amorphous alloy combines above-mentioned two properties,it could be a promising environmental material.In the thesis,composition design and microalloying technology were used to construct Fe-based amorphous alloys for improvement of magnetocaloric effect.Furthermore,the Fe-based amorphous-oxalic acid UV-Fenton reaction system was developed using the prepared Fe-based amorphous alloys as a catalyst,and the effects of various parameters on the reaction were investigated.Based on Fe-Zr-B amorphous alloys,the added alloying elements?Ni,Co,Al or Ti?,improved the peak values of magnetic entropy change of the alloys.Ni and Co enhanced the Curie temperature and saturation magnetization of the alloys,while Al and Ti caused the Curie temperature to decrease.Taking into account of the refrigeration capacity,Fe₈₈Zr₇B₄Co₁ and Fe₈₈Zr₇B₄Ti₁ amorphous alloys showed excellent property which is comparable with the benchmark material-Gd.By studying the effects of alloying elements Ni,Co,Al and Ti on the Curie temperature and magnetocaloric performance,it provides a reference for alloying Fe-based amorphous alloys with low boron content.In order to promoting the magnetocaloric performance of Fe-based amorphous alloys while ensuring their Curie temperature in the room temperature range,Fe₈₈Zr₁₁B₁amorphous alloy with a low B content was designed and prepared,and the alloying elements Ni and Co were used to modify the magnetocaloric response.In comparison with the precursor alloy,the Curie temperature keeps in the range of room temperature,and the saturation magnetization and magnetic refrigeration capacity of the alloyed samples have been improved.The substitution of alloying elements for Fe has a greater effect on the Curie temperature and the saturation magnetization than the substitution for Zr,indicating that the elements with large atomic radius play a more significant role in magnetic properties of Fe-Zr-B amorphous alloys.Fe₈₇Zr₁₁B₁Ni₁ and Fe₈₈Zr₉B₁Co₂ exhibited optimal magnetic refrigeration in their respective series.The Fe-based amorphous alloys with narrow temperature span were composited,which greatly enhanced the temperature span and the magnetic refrigeration capacity of the composites.The maximum refrigeration capacity of the composite consisted with Fe₈₈Zr₁₁B₁ and Fe₈₆Zr₁₁B₁Co₂ is 38.6%higher than that of each single constituent.Y element with large atomic radius was added into amorphous alloys to enlarge their temperature span.The temperature span of Y-added amorphous alloys increased significantly,resulting in an increase in magnetic refrigeration capacity.The field dependence of peak values of entropy change also increased,and there was a correlation between the degree of amorphous disorder and the temperature span of amorphous alloys.Fe-based amorphous alloys were shown to be an efficient catalyst of the photo-decomposition of rhodamine B when illuminated with UV light.Oxalic acid and zero-valent iron in the amorphous state were applied to generate photosensitive Fe-oxalate complexes and then generate active radical hydroxyl under UV irradiation.The produced hydroxyl radical could degrade the rhodamine B.The catalyst dosage and the wavelength and intensity of the light source were all found to strongly influence the reaction rate.The influence of addition amount of Fe-based amorphous alloy is most obvious.For 20 mgL^-1 of rhodamine B,90%degradation can be achieved within 10 minutes under optimal experimental conditions and complete degradation within 15 minutes.Fe-based amorphous alloys still maintain catalytic activity and amorphous structure after multiple reactions.