Abbott Andrew P, Ballantyne Andrew, Harris Robert C, Juma Jamil A, Ryder Karl S
Materials Centre, Department of Chemistry, University of Leicester, Leicester, LE1 7RH, UK.
Phys Chem Chem Phys. 2017 Jan 25;19(4):3219-3231. doi: 10.1039/c6cp08720e.
Organic and inorganic additives are often added to nickel electroplating solutions to improve surface finish, reduce roughness and promote uniform surface morphology of the coatings. Such additives are usually small molecules and often referred to as brighteners or levellers. However, there have been limited investigations into the effect of such additives on electrodeposition from ionic liquids (ILs) and deep eutectic solvents (DESs). Here we study the effect of four additives on electrolytic nickel plating from an ethyleneglycol based DES; these are nicotinic acid (NA), methylnicotinate (MN), 5,5-dimethylhydantoin (DMH) and boric acid (BA). The additives show limited influence on the bulk Ni(ii) speciation but have significant influence on the electrochemical behaviour of Ni deposition. Small concentrations (ca. 15 mM) of NA and MN show inhibition of Ni(ii) reduction whereas high concentrations of DMH and BA are required for a modest difference in behaviour from the additive free system. NA and MN also show that they significantly alter the nucleation and growth mechanism when compared to the additive free system and those with DMH and BA. Each of the additive systems had the effect of producing brighter and flatter bulk electrodeposits with increased coating hardness but XRD shows that NA and MN direct crystal growth to the [111] orientation whereas DMH and BA direct crystal growth to the [220] orientation.
有机和无机添加剂经常被添加到镍电镀液中，以改善表面光洁度、降低粗糙度并促进镀层表面形态均匀。这类添加剂通常是小分子，常被称为光亮剂或整平剂。然而，关于这类添加剂对离子液体（ILs）和深共熔溶剂（DESs）中电沉积的影响的研究有限。在此，我们研究了四种添加剂对基于乙二醇的DES中电解镀镍的影响；这些添加剂是烟酸（NA）、甲基烟酸酯（MN）、5,5 - 二甲基乙内酰脲（DMH）和硼酸（BA）。添加剂对本体Ni(ii)的形态影响有限，但对Ni沉积的电化学行为有显著影响。低浓度（约15 mM）的NA和MN对Ni(ii)的还原有抑制作用，而与无添加剂体系相比，DMH和BA需要高浓度才能使行为有适度差异。与无添加剂体系以及含有DMH和BA的体系相比，NA和MN还表明它们能显著改变成核和生长机制。每个添加剂体系都有使本体电沉积物更光亮、更平整且镀层硬度增加的效果，但X射线衍射表明，NA和MN使晶体生长定向到[111]晶面，而DMH和BA使晶体生长定向到[220]晶面。
