Preparation of Intermetallic Compound Silicide Film by Electrodeposition Using Molten Salt as Medium

本工作以熔盐为电沉积介质，对硅化物中最引人注目的超高温材料--硅化钼薄膜的制备进行了尝试。本工作中制备硅钼酸钼薄膜的原计划是：硅和钼交替沉积，在高温熔盐中进行合金化。结果，在金属衬底上形成了硅化钼薄膜。首先考察了Si和Mo的电沉积行为，明确了它们的沉积条件。结果表明，用含K_2SiF_6的NaC_1-KCl熔体在还原K_2SiF_6的电位区进行恒电位阴极极化，可使沉积的Si和Ni基片合金化形成硅化镍薄膜。另一方面，为了沉积Mo，用含Li_2MoO_4和K_2SiF_6的NaC_1-KCl熔体进行恒电位阴极极化，在低电位区极化沉积金属钼。根据硅和钼的沉积条件，依次进行了电沉积。当在硅沉积后再沉积Mo时，可以在NiSiliside上形成Mo3Si薄膜。相反，在Mo沉积后再沉积Si时，形成了树枝状的MoSi2，该MoSi2具有良好的高温性能。结果发现，采用熔盐电沉积法制备了硅化钼薄膜。

In this work, the preparation of films of molybdenum silicides, which is the most remarkable as a super high-temperature material among silicides, was attempted by the electrodeposition using molten salt as a medium. The original plan to prepare the molybdenum silisides film in this work was as follows ;Si and Mo are deposited by turns, and their alloying can be proceeded in the molten salt at high temperature. As a result, molybdenum silicide film is formed on metal substrate. First the electrodeposition behaviors of Si and Mo were examined to clarify the deposition conditions of them. It was found that Si could be deposited in a film shape to form nickel silicide film by alloying of deposited Si and Ni substrate when the potentiostatic cathodic polarizations were carried out at the potential regions, at which K_2SiF_6 was reduced, using molten NaC1-KC1 containing K_2SiF_6. In order to deposit Mo, the other hand, the potentiostatic cathodic polarization was carried out using molten NaC1-KC1 containing Li_2Mo0_4 and K_2SiF_6. As a result, metallic Mo was deposited by the polarization at lower potential region. In accordance with their deposition conditions of Si and Mo, the electrodepositions of them were carried out by turns. When Mo was deposited after the Si deposition, Mo_3Si film could be formed on nickel siliside. Conversely, when Si was deposited after the Mo deposition, MoSi_2, which has a superior high-temperature properties, was formed in a dendrite shape. Consequently, it was found that molybdenum silicide films were prepared by the electrodeposition using molten salts.