D Electro-Deposits of Cu-Sn Alloy

Shown in Fig. 8 is a typical copper-tin foam stmcture prepared in an electrolyte of 1.5 M sulfuric acid containing 0.24 M copper sulfate and 0.20 M tin sulfate. The electro-deposit is characterized by typical foam stmcture like copper and tin. Moreover, the foam wall is highly-porous and full of numerous small grains. Pores of less than a few microns in foam wall are possibly caused by the hydrogen gas evolution on newly-developed copper-tin deposits, similar to the case of copper deposition. The atomic ratio of copper to tin of the deposit was estimated to be 1.18 using energy-dispersive X-ray spectroscopy and the X-ray diffraction analysis showed the deposit was ri -CueSus, a low-temperature variation of CueSns.  

The grain shape of the deposits is particularly noteworthy. Both the ramified character of copper branches and dendritic feature of tin branches totally disappear. Instead, the wall contains spherical grains of the order of hundreds of nanometers. This indicates the growth habit of the deposits is drastically modified when copper and tin are electrochemically co-deposited. Copper-tin alloy is a promising option to substitute the graphite for negative 

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