Closure to “Discussion of ‘Factors Affecting The Formation of Anodic Oxide Coatings’ [M. S. Hunter and P. Fowle (pp. 514–519)]”

Hunter, M. S.; Fowle, P.

doi:10.1149/1.2430083

Cited by 23 publications

(37 citation statements)

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“…The porous layer is assumed to have a homogeneous porosity. The saturation concentration inside the porous layer will be allowed to increase above the initial saturation value due to local resistance heating (10,14). Dilute-solution theory (15) will be used to relate the derivative of the concentration at the electrode surface to the current density.…”

Section: Description Of Modelmentioning

confidence: 99%

“…The solution to Eq. [7][8][9][10][11][12] will first be examined for small ~ by expressing A and 0 as a power series in T.…”

Section: Mathematical Formulationmentioning

confidence: 99%

“…[7][8][9][10][11][12], the unknown coefficients can be determined. The result is given by A = ~ --~2/2 -5 5"~3/6 --17z4/8 -5 827z5/120 + 0(T s) [15] o Let us now determine if -% --~1/2 at long times, which would be characteristic of unrestricted semiinfinite diffusion from an electrode.…”

Section: + D(x)z 4 + O(t 5) [14]mentioning

confidence: 99%

“…The change of variables used to obtain Eq. [7][8][9][10][11][12] was useful in obtaining the short-time solution. For the development of the long-time solution, the following change of variables will be used in Eq.…”

Section: + D(x)z 4 + O(t 5) [14]mentioning

confidence: 99%

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Growing Porous Layers

Tiedemann¹,

Newman²

1972

J. Electrochem. Soc.

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The precipitation of ions generated at an electrode, operating at a constant current, with ions of the adjacent electrolytic solution has been modeled as a growing porous layer. The thickness of the layer as a function of time for short times is given by a power series expansion of time. The long-time solution was determined by a numerical calculation on a digital computer. A criterion for linear growth rate as a function of time is given.Moving boundary problems, such as melting-freezing, evaporation-condensation, and purification of materials, involving heat and mass transfer have been treated in depth (1-7). A moving boundary problem is encountered in the field of electrochemistry when ions being generated at an electrode, operating at a constant current, form a precipitate with ions of the adjacent electrolytic solution. The resulting precipitate forms a growing porous layer on the electrode. Studies of anodic dissolution of various metals which form porous coatings (8) can be considered examples of growing porous layers. In the case of silver, a porous layer occurs only after a nonporous layer has been formed or when large currents are employed (9, 10). Jackson and Blomgren (11) studied the anodic dissolution of lithium in a 1M solution of A1C13 in propylene carbonate and observed a growing porous layer of LiC1. Other examples of growing porous layers are the oxidation of tungsten (12) and the scaling of metals (13). In the following analysis, the thickness of a growing porous layer as a function of time is determined, and a criterion for linear growth rate as a function of time is given.

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Section: Description Of Modelmentioning

confidence: 99%

“…The solution to Eq. [7][8][9][10][11][12] will first be examined for small ~ by expressing A and 0 as a power series in T.…”

Section: Mathematical Formulationmentioning

confidence: 99%

Section: + D(x)z 4 + O(t 5) [14]mentioning

confidence: 99%

Section: + D(x)z 4 + O(t 5) [14]mentioning

confidence: 99%

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Growing Porous Layers

Tiedemann¹,

Newman²

1972

J. Electrochem. Soc.

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“…In order to achieve higher specific capacity, the surface areas of the foils are increased by means of etching [1].…”

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confidence: 99%

Thermogravimetric studies on aluminium foils for electrolytic capacitors

Kőmives

Gál

Tomor

et al. 1983

Journal of Thermal Analysis

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Thermogravimetry was applied in studies .of aluminium foils for electrolytic capacitors. Scanning electron microscopy, X-ray diffraction and surface area determination were also used in the interpretation of the results.Both the specific surface area and the capacity of the foils showed a linear relationship to the height of the oxidation step measured by TG, which was found suitable for following the processes of anodic oxidation and thermal treatment of the foils as well.Electrolytic capacitors consist of cathode and anode foils, an aluminium oxide insulating layer and a paper soaked by the electrolyte. In order to achieve higher specific capacity, the surface areas of the foils are increased by means of etching [1].Erdey and coworkers [2, 3] developed a derivative thermogravimetric method combined with X-ray diffraction measurements for phase analysis of the insulating layer in the presence of the aluminium base metal. Dorsey [3] determined the amount of water evolved during the thermal treatment of anodically oxidized foils in a thermal conductivity cell, and described the character of the water bonding by means of IR reflectance spectroscopy.In the present paper mainly the oxidation step in the TG curve of capacitor foils is discussed. Additional information was obtained with scanning electron microscopy (SEM), X-ray diffraction and surface area determination. ExperimentalThe samples included

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Color Fine‐Tuning of CNTs@AAO Composite Thin Films via Isotropically Etching Porous AAO Before CNT Growth and Color Modification by Water Infusion

Zhao

Meng

et al. 2010

Advanced Materials

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Optical interference structures exist in nature, e.g., in feathers of birds and wings of insects, and exhibit vivid colors, which originate from the mechanism of optical interference and thus can vary notably with the viewing-angle and the refractive index of the dielectric medium surrounding the optical interference structures. [1][2][3] Because of the attractive applications of optical interference structures in color display, decoration, anti-counterfeiting and liquid sensors, considerable attention has been paid to the construction of man-made systems with interference colors, such as multilayer structures, [4] silicon dimple arrays, [5] and anodic aluminum oxide (AAO) thin films embedded with metal. [6,7] Recently, it has been reported that AAO thin films embedded with carbon nanotubes (CNTs) (denoted as CNTs@AAO composite thin films) display brilliant colors, which stem from the interference between the reflected light from the AAO top planar surface and the emergent light reflected on the AAO-Al interface.[8] As colors of the CNTs@AAO composite thin films are mainly determined by the interference band with the maximum reflectance (B max ) in the visible region, and B max shifts by changing the AAO film thickness, color tuning of the CNTs@AAO composite thin films can be attained by varying the AAO film thickness in the anodization. However, B max is very sensitive to the thickness of the AAO film, and the pore growth rate of the AAO in the anodization is very fast, so it would be difficult for this approach to tune the color of the CNTs@AAO composite thin film in a well-controlled manner. In addition, the as-prepared CNTs@AAO composite thin films are hydrophobic and thus prohibit water infusion.[9] If the CNTs@AAO composite thin films can be changed into hydrophilic, the composite thin films might be used as water sensors. Here, by applying wetchemical etching to porous AAO thin films to thin the AAO films and widen the AAO pores isotropically before CNTs growth, controllable precise color tuning of the CNTs@AAO composite thin films has been achieved. Moreover, via further plasma cleaning, the CNTs@AAO composite thin films with large AAO pore diameter can change their colors remarkably after water infusion. Additionally, via applying wet-chemical etching to different areas of one piece of AAO film for rationally different durations, patterned CNTs@AAO composite thin film with each area showing a unique color has been obtained. The details of the fabrication of the AAO, the etching of the AAO, and the growth of the CNTs are given in the Experimental section. Figure 1a and b are SEM images of the CNTs released from the CNTs@AAO composite thin films. Figure 1a shows free-standing CNTs aggregating into clumps and formed inside the pores of the AAO films without being etched. Figure 1b Figure 1d is the TEM image of the CNTs from Figure 1b. The outer diameter and wall thickness of the CNTs are estimated to be 90 and 6 nm, respectively. Therefore, etching AAO films before CNTs growth can cause remarkable increase ...

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Closure to “Discussion of ‘Factors Affecting The Formation of Anodic Oxide Coatings’ [M. S. Hunter and P. Fowle (pp. 514–519)]”

Cited by 23 publications

References 0 publications

Growing Porous Layers

Growing Porous Layers

Thermogravimetric studies on aluminium foils for electrolytic capacitors

Color Fine‐Tuning of CNTs@AAO Composite Thin Films via Isotropically Etching Porous AAO Before CNT Growth and Color Modification by Water Infusion

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