jpsmith123
December 6th, 2007, 05:21 PM
For the last few weeks I've been trying to make a cobalt oxide coated titanium anode for chlorate and perchlorate production; so far without much luck. (There is a detailed discussion about it at sciencemadness).
Most of my attempts so far have involved anodic electrodeposition from both cobalt (II) sulfate and acetate solutions. (If I get any good results I will post them here, since I know many people here may be interested).
The problem is that, regardless of how the surface is prepared, the product just doesn't seem to adhere very well. Most of the deposited material can be wiped off with a rag, and if that's not done beforehand, it seems to come off like slime after a short period of exposure to the salt brine.
Anyway, I'm wondering if anyone might have access to the following papers? These sound like they may have some useful information.
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A new cobalt oxide electrodeposit bath for solar absorbers
Solar Energy Materials and Solar Cells, Volume 51, Issue 1, 1 February 1998, Pages 69-82
Enrique Barrera, Ignacio González and Tomás Viveros
A study was carried out in a Hull cell in order to optimize the deposition conditions of cobalt oxide (black cobalt) in an electrolytic bath, which uses cobalt nitrate for direct obtention of black cobalt. Thermal stability of the material was surveyed on several samples of black cobalt prepared on stainless-steel with a thickness of approximately of 2.5 μm. It was found that the optical properties change, in respect to the initial values, with time of treatment until an equlibrium is reached. This equilibrium depends on the substrate and the temperature of the treatment used.
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Black cobalt solar absorber coatings
Solar Energy Materials, Volume 22, Issue 4, August 1991, Pages 293-302
S. John, N. Nagarani and S. Rajendran
A new electrolyte has been proposed for the deposition of black cobalt selective absorber coatings. These coatings are used in solar collectors for photothermal conversion of solar energy. We have studied the influence of electrolyte composition and operating parameters on the properties of the black cobalt coatings including optical (α, ε;) and electcical properties. Thermal stability and corrosion resistance tests showed good durability of black cobalt selective coatings for high temperature applications.
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Preparation of selective surfaces of black cobalt by the sol-gel process
Renewable Energy, Volume 9, Issues 1-4, September-December 1996, Pages 733-736
E. C. Barrera, T. G. Viveros and U. Morales
Black cobalt, Co3O4, thin solid coatings on stainless steel and glass substrates have been prepared by the dip coating technique via the sol-gel route using a CoCl2 precursor. The coatings produced on substrates exhibit a blue to black colours as a function of the film thickness. Sols have been made from a cobalt acetate precursor 0.1 M, and for such conditions, the dip coating process gives 0.08–0.25 μm thick uniform films per dipping, depending on the viscocity of the sol.
################################################## #################################
Cobalt oxide thin films prepared by chemical vapor deposition from cobalt (II) acetate
Solar Energy Materials, Volume 23, Issue 1, November 1991, Pages 25-29
Toshiro Maruyama and Tsuyoshi Nakai
Cobalt oxide thin films were prepared by a low-temperature atmospheric-pressure chemical vapor deposition method. The raw material was cobalt (II) acetate which is non-toxic and easy to handle. Polycrystalline films were obtained at a reaction temperature above 300°C. From near-normal reflection measurements it follows that the films have solar absorptance α = 0.73 and thermal emittance ε = 0.089.
Most of my attempts so far have involved anodic electrodeposition from both cobalt (II) sulfate and acetate solutions. (If I get any good results I will post them here, since I know many people here may be interested).
The problem is that, regardless of how the surface is prepared, the product just doesn't seem to adhere very well. Most of the deposited material can be wiped off with a rag, and if that's not done beforehand, it seems to come off like slime after a short period of exposure to the salt brine.
Anyway, I'm wondering if anyone might have access to the following papers? These sound like they may have some useful information.
###################################
A new cobalt oxide electrodeposit bath for solar absorbers
Solar Energy Materials and Solar Cells, Volume 51, Issue 1, 1 February 1998, Pages 69-82
Enrique Barrera, Ignacio González and Tomás Viveros
A study was carried out in a Hull cell in order to optimize the deposition conditions of cobalt oxide (black cobalt) in an electrolytic bath, which uses cobalt nitrate for direct obtention of black cobalt. Thermal stability of the material was surveyed on several samples of black cobalt prepared on stainless-steel with a thickness of approximately of 2.5 μm. It was found that the optical properties change, in respect to the initial values, with time of treatment until an equlibrium is reached. This equilibrium depends on the substrate and the temperature of the treatment used.
################################################## ############################
Black cobalt solar absorber coatings
Solar Energy Materials, Volume 22, Issue 4, August 1991, Pages 293-302
S. John, N. Nagarani and S. Rajendran
A new electrolyte has been proposed for the deposition of black cobalt selective absorber coatings. These coatings are used in solar collectors for photothermal conversion of solar energy. We have studied the influence of electrolyte composition and operating parameters on the properties of the black cobalt coatings including optical (α, ε;) and electcical properties. Thermal stability and corrosion resistance tests showed good durability of black cobalt selective coatings for high temperature applications.
################################################## ################################
Preparation of selective surfaces of black cobalt by the sol-gel process
Renewable Energy, Volume 9, Issues 1-4, September-December 1996, Pages 733-736
E. C. Barrera, T. G. Viveros and U. Morales
Black cobalt, Co3O4, thin solid coatings on stainless steel and glass substrates have been prepared by the dip coating technique via the sol-gel route using a CoCl2 precursor. The coatings produced on substrates exhibit a blue to black colours as a function of the film thickness. Sols have been made from a cobalt acetate precursor 0.1 M, and for such conditions, the dip coating process gives 0.08–0.25 μm thick uniform films per dipping, depending on the viscocity of the sol.
################################################## #################################
Cobalt oxide thin films prepared by chemical vapor deposition from cobalt (II) acetate
Solar Energy Materials, Volume 23, Issue 1, November 1991, Pages 25-29
Toshiro Maruyama and Tsuyoshi Nakai
Cobalt oxide thin films were prepared by a low-temperature atmospheric-pressure chemical vapor deposition method. The raw material was cobalt (II) acetate which is non-toxic and easy to handle. Polycrystalline films were obtained at a reaction temperature above 300°C. From near-normal reflection measurements it follows that the films have solar absorptance α = 0.73 and thermal emittance ε = 0.089.