Adjust The Curie Temperatures By Hydrogen Absorption And Desorption For Preparing（la,Ce）（fe,si）₁₃H_y Compounds

La(Fe,Si)13-based alloys which belong to cubic structure of NaZn13have win thegood graces of many researchers, due to the advantages of their low cost, relativelystable chemical property, a large magnetocaloric effect and environmentally friendlyproperty. This kind of compounds will be a promising magnetic refrigerantmaterials andmay be widely used in refrigeration. The Curie temperature of the La(Fe,Si)13-basedalloys will reach above room temperature after hydrogen absorption processing, we canobtain a large isothermal magnetic entropy change at the same time. There is a biggestproblem which is difficult to control the amount of hydrogen when the alloys absorbhydrogen, as a result, it is not controlling the Curie temperatureeffectively. Although theamount of onetime hydrogen absorption can be adjusted by changing temperature,pressure and time of experiments, the repeatability of hydrogen absorption process isdifficult because of many uncontrollable factors such as: the purity of raw materials,environmental changes and production equipment. Thus, it is an important researchcontent to effectively regulate the Curie temperature of the La(Fe,Si)13-based alloys.Hence, in this research, we will focus on studying the Curie temperature and magneticthermal properties of the La(Fe,Si)13-based alloys.The isothermal magnetic entropy change of the La(Fe,Si)13-based alloys can beimproved after adding Ce element, so we select rare earth Ce as an alternative element.La1-xCexFe11.44Si1.56(x=0,0.1,0.2,0.3,0.4) series parent phase alloys are produced byindustrial bulk raw material, with smelting and annealing in the experiments. Theresearch for La1-xCexFe11.44Si1.56(x=0,0.1,0.2,0.3,0.4) alloys show: the Curietemperature of the alloys decreases and the maximum isothermal magnetic entropychange gradually increases while Ce content increases, the maximum isothermalmagnetic entropy change can reach24.71J/kgK with0-1.5T external magnetic field. La1-xCexFe11.44Si1.56(x=0,0.1,0.2,0.3,0.4) alloys absorb hydrogen for5hoursunder the conditions of0.1MPa (relative pressure) and280℃, the results ofresearch showed that: the Curie temperature of the La1-xCexFe11.44Si1.56Hy alloys areraised over100K and some alloys can reach room temperature, despite the maximumisothermal magnetic entropy change become lower, it is still3times as large as metalGd.La0.9Ce0.1Fe11.44Si1.56Hyalloy is incubated for180min respectively at200℃,210℃,220℃,230℃,240℃and250℃in the vacuum heat treatment furnace chamberwhich is evacuated to1.9×10-3Pa befor filled with argon; then in this wayLa0.8Ce0.2Fe11.44Si1.56Hyalloy is respectively incubated for90min,180min,270min,360min，450min and540min at210℃. The experiment results show that the Curietemperature of the alloys can be continuously changed and a large isothermal magneticentropy change can be maintained at the same time by altering the hydrogen desorptiontime at certain temperature; yet the Curie temperature of the alloy can drop to272K bychanging the temperature of the hydrogen desorption process under a certain time, andthe maximum isothermal magnetic entropy change decreased with the hydrogendesorption temperature raised.Two way of hydrogen desorption process mentioned above fine control thehydrogen content in oder to adjust the Curie temperature of the alloy variedcontinuously between272K-316K, so the Curie temperature of the alloy can beeffectively adjusted to achieve the practical required temperature range by means ofselecting appropriate temperature or time of hydrogen desorption.