Study On The Preparation And Properties Of Fecl₃-nicl₂-gics And Its Reduction Products

Ternary FeCl3-NiCl2-GICs were synthesized by molten salts method in quantitative air. The natural graphite powder was used as host material and the mixture of NiCl2 and FeCl3 was as intercalant. The paper discussed the influence of reaction condition such as particle size of graphite, reaction temperature and reaction time, as well as chlorides molar ratios on the stage structure of the products. The results show that the glass tube was sealed by fusing in air, Ternary FeCl3-NiCl2-GICs with different stage structure can be obtained by changing the condition of reaction. With prolonging the reaction time,lifting the reaction temperature and minishing the graphite size, the stage structure of the products decreases gradually. When the reaction temperature is too high and the size of graphite is too small, the intercalant will be pull out. With the rise of NiCl2/FeCl3 molar ratio and the amount of graphite increased, the stage structure of the products ascended gradually. The regularities of the alteration of the FeCl3- NiCl2-GICs structure were similar to the alteration of the FeCl3-NiCl2-GICs structure prepared in the glass tube was sealed by fusing in airvoid. The low-volume ternary FeCl3-NiCl2-GICs were prepared by the stainless steel container that designed and manufactured by ourself.The electrical conductivity and microwave absorption properties of FeCl3- NiCl2-GICs with different stage and size were tested. The results of researches show that the electrical conductivity of FeCl3-NiCl2-GICs are better than that of host graphite. With rise of the stage, the electrical conductivity of the 2st stage FeCl3-NiCl2-GIC is the highest that is 3.7 times of graphite, and the electrical conductivity of the FeCl3-NiCl2-GICs increase first, then decrease. When the size of FeCl3-NiCl2-GIC is 100 meshes, the electrical conductivity that is 1.5 times of graphite is the highest. FeCl3-NiCl2-GICs that has properties of microwave absorption and they are relate to its electrical conductivity are dielectric loss microwave absorption materials. When the electrical conductivity is too high, the properties of microwave absorption descend. The microwave absorption of FeCl3-NiCl2-GICs are influenced by the stage structure and size. They both are the main factors. When the stage is rised, the maximum theoretical reflection loss decreased first, then increased. The law that electrical conductivity changed with the stage was opposite. The maximum theoretical reflection loss of the 1st stage FeCl3-NiCl2-GIC which size is 100 meshes is -10.3 dB. The microwave absorption properties of 200 meshes FeCl3-NiCl2-GIC is the best in the lower frequency region.FeCl3-NiCl2-GICs were reduced by H2. And the influence of temperature and time and the particle size of graphite on the stage structure and C/(Fe+Ni) molar ratio were studied. The results show that the content of the proportion Cl in the reduction product is decreased with the increasing of reduction temperature, the prolonging of reduction time and the minishing the particle size of FeCl3-NiCl2- GICs. FeCl3-NiCl2-GICs which the particle size is 325 meshes is reduced by H2 at the condition that H2 pressure was1.8×105 Pa, temperature was 600℃, reaction time was 72h. The atom% proportion Cl in the reduction product was 26.32%。The key reason why FeCl3-NiCl2-GICs cannot be reduced thoroughly is that a part of FeCl3 was reduced to FeCl2. When FeCl3-NiCl2-GICs was reduced by H2 ,the FeNi alloy was generated, amount of FeNi alloy concentrate nearby the edge of graphite layer, and few is located in the graphite layer. With the reduced temperature 400℃to elevate to 600℃, the FeNi alloy pellet number increased, the particle size increased from 100~300nm to approximately 3μm. The process that FeCl3-NiCl2-GICs was reduced by H2 was regard as the result of which the FeCl3, NiCl2 pull out and H2 diffuse in the graphite layer together.The microwave absorption propertiesof reduction product were tested. The result showed that the microwave absorption properties of reduction product were better than graphite. When the reduced temperature enhanced, the matching frequency tends to shift to lower frequency region. The reduction product generate at 600℃is microwave absorption compound material which are dielectric loss and magnetic loss coexistent. The pellet number and the particle size of the FeNi alloy which was generated at the reducing increased by reduced temperature rising. It is the main factor that the reduction product has magnetic loss.