CARBON COATING OF METAL AND METAL OXIDE PARTICLES BY ARC DISCHARGE

用碳包覆金属颗粒可以解决金属颗粒表面在氧化性气氛中的不稳定性。在本计画中，我们提出一种在粒子表面产生类石墨碳层的新方法。为了获得几纳米厚的类石墨层，首先，表面活性剂被吸附到颗粒上，然后通过在电弧放电室中用电离的He原子轰击来还原/分解。在该项目的初始阶段，代替金属颗粒，在电弧室中处理涂覆有油酸酯的磁铁矿颗粒（10 nm），并使用TEM、FTIR、SEM和SEM表征处理后的颗粒。XRD和XPS分析结果表明，表面活性剂的处理只影响了粒子的表面，表面活性剂被还原，在粒子周围形成石墨状的包覆层，包覆粒子在酸中溶解与未处理的颗粒相比，溶液的溶解度更低。在下一阶段，实验在磁性材料上进行。 关于我们 微米大小的颗粒。原因是为了接近磁记录等中使用的实际尺寸，并使使用SEM直接观察颗粒表面成为可能。结果与我们用10 nm大小的磁铁矿获得的结果相似。最后，研究了不同表面活性剂对铁粒子的影响以及合成层对铁粒子的保护作用。对于表面活性剂，我们使用油酸钠和Aerosol OT（磺基琥珀酸二-2-乙基己酯钠）。即使在金属颗粒的情况下，也可以在表面上观察到类似的碳。此外，当经处理的颗粒暴露于氧化气氛（HCl蒸气）并溶解在稀HCl中时，与未经处理的颗粒相比，饱和磁化强度随暴露时间的降低减缓，并且溶解速率也降低。油酸钠上级优于OT气雾剂。该方法的主要问题是为了提高保护性，必须重复多次处理。我们相信，这可以通过选择在金属和碳表面上强烈吸附并且具有大横截面积和长链的表面活性剂来解决。少

The unstability of the metal particle surface in oxidizing atmosphere can be solved by coating the particle with carbon. In this project, we propose a novel method to produce the graphite like carbon layr on the surface of the particles. To obtain a graphite like layr of a few nanometer thick, first, the surfactant is adsorbed onto the particle and then reduced/decomposed by bombardment with ionized He atoms in the arc discharge chamber. In the initial stages of the project, instead of metal particles, magnetite particles (10nm) coated with oleate was treated in the arc chamber and the treated particles were characterized using TEM,FTIR,XRD and XPS.The results suggested that only the surface of the particle is influenced by the treatment and the surfactant is reduced to produce a graphite like layr around the particle and the dissolution of the coated particles in acid solution was lower compared to the non-treated particles. In the next stage, the experiments were performed on magneti … More te particle of micrometer size. The reason was to get closer to practical size used in magnetic recording etc., and make direct observation of the particle surface using SEM possible. The results were similar to the one we obtained with 10nm size magnetite. In the final stage, we studied the influence of different surfactants and protectiveness of the synthesized layr on iron particles. As for the surfactants, we used sodium oleate and Aerosol OT (Di-2-ethyl-hexyl Sodium Sulfosuccinate). Even in the case of metal particle, it was possible observe the carbon like later on the surface. Further, when the treated particles were exposed to oxidizing atmosphere (HCl vapor) and dissolution in diluted HCl, the decrease in saturation magnetization with time of exposure slowed down and the dissolution rate was also reduced compared to the non-treated particles. Sodium oleate was superior to Aerosol OT.The main problem of this method is that to improve the protectiveness, the treatment has to be repeated a number of times. We believe that this could be solved by selecting the surfactant that adsorbs strongly on metal and carbon surfaces and has large cross-sectional area and long chains. Less