Electrodeposition activation

The theoretical value of the stress generated at the contact interface between the electrodeposited active material and substrate was calculated to obtain the order of magnitude of the stress generated by lithiation. As it has been reported from previous studies,the actual electrode is not a uniform material and is expected to contain and/or form voids and cracks with lithiation. It has also been shown by in situ atomic force microscopy (AFM) observations that the electrode experiences plastic deformation, and the thickness of the electrode changes irreversibly to some extent with the lithiation and delithiation process. Because of such indeterminate nature of the assumptions, the absolute value of the calculated stress is not the subject of discussion. 

Wrought and cast nickel anodes and sulfur-activated electrodeposited rounds are used widely for nickel electro deposition onto many base metals. 

It was quite recently reported that La can be electrodeposited from chloroaluminate ionic liquids [25]. Whereas only AlLa alloys can be obtained from the pure liquid, the addition of excess LiCl and small quantities of thionyl chloride (SOCI2) to a LaCl3-sat-urated melt allows the deposition of elemental La, but the electrodissolution seems to be somewhat Idnetically hindered. This result could perhaps be interesting for coating purposes, as elemental La can normally only be deposited in high-temperature molten salts, which require much more difficult experimental or technical conditions. Furthermore, La and Ce electrodeposition would be important, as their oxides have interesting catalytic activity as, for instance, oxidation catalysts. A controlled deposition of thin metal layers followed by selective oxidation could perhaps produce cat-alytically active thin layers interesting for fuel cells or waste gas treatment. 

The use of electrodeposited metals to protect corrodible basis metals from their service environments has been well established for many years and accounts for by far the larger part of the activities of the plating industry. There are many reasons for using an electroplated metal finish in preference to an organic finish or to making the articles concerned from inherently corrosion-resistant materials. 

The metal to be plated is first cleaned carefully and then activated with a weak acid. Steel can be treated with 3-5% HCl, whilst a 10% fluoboric acid solution is suitable for copper alloys. It is then ready for the electrodeposition process. 

Early measurements of " Th were on seawater samples and Th was co-precipitated from 20-30 L of seawater with iron hydroxide (Bhat et al. 1969). This procedure may not recover all of the " Th in the sample, and an alpha emitting Th isotope (e g., °Th or Th) is added as a yield monitor. Following chemical purification of the Th fraction by ion exchange chromatography, the Th is electrodeposited onto platinum or stainless steel planchets. The planchets are then counted in a low background gas-flow beta detector to measure the beta activity and subsequently with a silicon surface barrier detector to determine the alpha activity of the yield monitor. The " Th activity is thus determined as ... 

Measurements of " Th in sediment samples (Aller and Cochran 1976 Cochran and Aller 1979) used much the same approach as outlined above. In this case, the dried sediment sample ( 10 g) was leached with strong mineral acid (HCl) in the presence of a yield monitor (generally Th, an artificial Th isotope resulting from the decay of Th that is produced by neutron capture on Th). Thorium was separated from U and purified by ion exchange chromatography, and electrodeposited onto stainless steel planchets. Counting and determination of " Th activity followed the procedure outlined above. 

If one considers the electrodeposit to be of pure silver and pure copper, then the activities of silver and copper can both be taken as unity. Therefore, the co-deposition condition can be expressed as... 

Electrodeposition is more flexible than electroless deposition, in that it is not limited by the requirement of having a catalytically active surface. Electrodeposition allows a wider variation in the alloy composition and in the deposit properties than does electroless deposition. This flexibility has not been widely exploited, however, and most of the electrodeposited alloys have had compositions similar to those obtained by electroless deposition (i.e. CoP or CoNiP). 

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