SiO2/Ni核壳结构纳米粒子的制备及其磁性

背景:包覆层的存在能够阻止纳米粒子氧化、晶体长大、腐蚀和团聚,并赋予特殊的性能.目的:制备SiO2/Ni核壳结构纳米粒子,并评估复合粉体的磁性能.设计、时间及地点:观察性实验,于2005-11/2006-03在大连理工大学纳米复合材料研究实验室完成.材料:应用直流电弧等离子体法制备纳米镍粉,硅酸钠由天津市石英钟厂霸州市化工分厂生产.方法:以硅酸钠为主要原料,通过液相沉淀法在纳米镍粉表面包覆了一层SiO2.主要观察指标:应用X射线衍射仪、傅里叶红外光谱仪、透射电镜、振动样品磁强计、热重分析仪等对复合粉体的结构、形貌和磁性能进行检测.结果:SiO2以非晶态的形式包覆在纳米镍粒子表面,形成了核壳结构,降低了纳米粉体的团聚现象.经SiO2包覆后纳米镍粉氧化温度由287℃提高到385℃.磁性分析结果表明,粉体包覆前由于表面氧化层(NiO)的存在,粉体的磁滞回线偏移;包覆后的粉体由于SiO2的存在,饱和磁化强度降低,矫顽力升高.结论:成功制备了SiO2/Ni核壳结构纳米粒子,SiO2的包覆提高了纳米粉体的抗氧化性,且纳米镍粉具有很好的铁磁性能,矫顽力升高.

Preparation of SiO2/Ni core-shell type nanoparticles and their magnetic properties

BACKGROUND: Inhibitory coating can prevent nanoparticle oxidation, grain growth, corrosion and agglomeration, and endow nanoparticle with special properties. ABJECTIVE: To prepare SiO2/Ni core-shell type nanoparticles and assess their magnetic properties. DESIGN, TIME AND SETTING: The observation experiment was performed between November 2005 and March 2006 at Nanometer Compound Material Research Laboratory of Dalian University of Technology, Dalian, Liaoning Province, China. MATERIALS: Nanometer nickel powder prepared by DC arc plasma jet method, Na2SiO3 produced by Bazhou Chemical Industry Branch Factory of Tianjin Quartz Clock Factory (China).METHODS: SiO2/Ni core-shell type nanoparticles were synthesized by coating a layer of SiO2 on the surface of manometer nickel powder via liquid deposition method using Na2SiO3 as the main source material. MAIN OUTCOME MEASURES: Their microstructures and material properties were investigated by X-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscopy, thermo-gravimetric analysis, differential scanning calorimetry and vibrating sample magnetometer. RESULTS: The experimental results showed that SiO2 shell was in an amorphous state around Ni cores and it avoided agglomeration of the Ni nanoparticles. The oxidation temperature of nanometer nickel powder coated by SiO2 elevated from 287 ℃ to 385 ℃. The analysis result of magnetic properties indicated that the hysteresis loop of Ni had an excursion for the existence of anti-ferromagnetic NiO, the silica coating reduced the saturation magnetization and improved the coercivity. CONCLUSION: Preparation of SiO2/Ni core-shell type nanopartieles was successful; silica coating improved the oxidation resistance of nanometer nickel powder, endowed nanometer nickel powder better ferromagnetism and improved the coercivity.