摘要
本文以二氧化硅为壳层材料,以纳米铁以及羰基铁粒子为核层材料,制备一种新型的吸收剂粒子。用FTIR,TEM,SEM,XPS,XRD表征了复合粒子的结构,利用VSM,TG-DTA,网络矢量分析仪等分析了材料结构改变对材料磁性能,热性能,结晶性能,电磁参数等性能进行了分析。
对纳米复合铁粒子研究表明,在APS改性的铁纳米粒子表面硅烷偶联剂氨基一端连接铁粒子,另一端对铁粒子外面,能与活性硅聚合。铁纳米复合粒子颗粒表面光滑致密。核壳复合粒子表面主要由Si,O组成,伴随着微量的C,H元素的峰,核壳复合粒子表面氧对硅有富余。铁纳米复合粒子为结晶态,纳米粒子在6000C,氮气保护下,纳米粒子不重新结晶,壳层二氧化硅包裹在纳米铁表面阻断了纳米粒子之间的重新原子排列。纳米铁包裹二氧化硅后,抗氧化性能提高,氧化为一个过程,同时伴随着材料纳米铁氧化的放热峰,材料表面没有吸附水和结晶水。铁纳米粉浓度对核壳粒子的磁性能分析表明,随着纳米铁加入量的变大,材料饱和磁化强度与剩磁呈现相似性,都均匀地增大。而矫顽力先有微弱上升然后逐渐减小,随着TEOS加入量的变大,材料饱和磁化强度与剩磁逐渐降低,包裹后,随着包裹厚度不一样,矫顽力变化不大。随着纳米粒子表面二氧化硅含量,复合粒子介电常数实部逐渐减小,介电常数虚部在2GHZ-10GHZ处随着二氧化硅包裹层厚增大而变小,在10GHZ-18GHZ形成一个峰值,随着包裹层厚的增大,峰位逐渐向低频移动。磁导率变化规律不明显。
对微米级复合粒子的研究表明,发现二氧化硅包裹微米铁方式与纳米铁不同,表现出来为纳米微米包裹现象。研究不同TEOS投入量,即二氧化硅的表观包裹层包裹量对材料静磁性能的影响。随着TEOS的投料的增加,材料饱和磁化强度呈下降趋势,微米粒子磁化曲线通过原点,表面包裹后,剩磁与矫顽力变化很小对于微米铁粉,其磁畴变化较快,没有剩磁与矫顽力。从XPS测试结果可以看出,在核壳复合粒子的XPS谱图上没有铁的结合峰。复合粒子表面主要由Si,O元素组成,伴随着少量的C,H元素。C元素由TEOS
武汉理工大学硕士学位论文
的水解引来。核壳复合粒子热重分析表明,微米铁复合粒子氧化分
为三个步骤,作为核层材料的铁氧化为氧化亚铁,氧化亚铁在空气
中仍不稳定,温度升高,氧化亚铁进一步氧化为四氧化三铁,四氧
化三铁相对稳定,在温度进一步升高,四氧化三铁完全氧化为三氧
化二铁。
This text attempts to regard silica as shell materials,regard nanometer iron and carbonyl iron particle as core materials to prepare a kind of new-type absorbent.The structur of the core-shell particles were characterized by FTIR, TEM, SEM, XPS, XRD etc.The properties of magnetism,heat,crystalization,ectromagnetic were characterized by VSM, TG-DTA, Network Vectorial Analysis Instrument.
The study on the core-shell particles shows,one extrenity of silane coupling agents at the surface of the composite particles after adding APS are connected with the Fe particles.and the other extrenity outside can polymerize with the active silica.The slick and compact surface of the composite particles shows the obvious core-shell structure.The surface of the composite particles are composed of the combined apex of the element Si,O,C,H.The element O is superfluous to the element Si. The silica coated nanometer particles after containning in N2 for 2h within 600 C is the crystallization form.thus it can sufficiently work the nano effect.The surface of the composite particles has no crystal water and no absorbing water.The anti-oxidation ability increase after coating. The saturation magnetism and the remnant magnetism of the composite particles increase while the coersive increase then decrease with the feed content of nano Fe particles increase.With the feed content of TEOS increase, the saturation magneti
sm and the remnant magnetism of the composite particles decrease, While the coersive changed little.The real part of the permittivity decrease with the shell of particles increase. The imaginary part decrease with the shell of particles increase at 2GHZ-10GHZ.The apex move toward the low frequency at 10GHZ-18GHZ.
The TEM shows lots of nano silica particles circumfuse on the surface of the micro Fe particles after the micro Fe coated by silica.The SEM analysis shows the same result. The VSM shows the micro Fe particles have almost no remnant magnetism and coesive. The saturation magnetization decrease with the feed content of TEOS
remenant magnetization and coesive are little. The XPS shows there is no combined apex of the Fe element because of the great thickness of the shell
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