Copper-coated titanium diboride articles
New copper-coated titanium diboride electrodes are disclosed. The copper-coated titanium diboride electrodes may be used in an aluminum electrolysis cell. In one embodiment, a method includes installing the copper-coated titanium diboride electrode in the aluminum electrolysis cell and operating the aluminum electrolysis cell. During start-up, the aluminum electrolysis cell may be preheated and a bath may be formed from a molten electrolyte. Alumina (Al 2 O 3 ) may in the added to the bath and reduced to aluminum metal. At least some of the copper film of the copper-coated titanium diboride electrode may be replaced by an aluminum film, thereby forming an aluminum-wetted titanium diboride electrode.
1 . A method comprising:
(a) making a titanium diboride electrode;
(i) wherein the making comprises sintering of a titanium diboride powder at a temperature of from 1400° C. to 2100° C.;
(ii) wherein the titanium diboride electrode comprises a density of from 80 to 99% of theoretical and an apparent porosity of from 0.01 to 20%; and
(b) forming a copper-based film on the titanium diboride electrode, thereby forming a copper-coated titanium diboride electrode;
(i) wherein the forming comprises at least one of electroless deposition and electroplating of copper onto at least a portion of a surface of the titanium diboride electrode; and
(ii) wherein the copper-based film predominately comprises copper.
2 . The method of claim 1 , wherein, after the forming step (b), the copper-based film comprises a nominal thickness of from 10 to 200 micrometers.
3 . The method of claim 1 , wherein the copper-based film is continuous and at least partially covers the outer surface of the titanium diboride electrode.
4 . The method of claim 1 , wherein the copper-based film comprises a uniform thickness, wherein a maximum and minimum thickness of the copper-based film are within 50% of an average thickness of the copper-based film.
5 . The method of claim 1 , comprising:
preparing the titanium diboride electrode for the forming step (b), wherein the preparing comprises at least one of:
(i) cleaning of the titanium diboride electrode; and
(ii) rinsing of the titanium diboride electrode.
6 . The method of claim 5 , wherein the cleaning step comprises contacting the titanium diboride electrode with one or more acids and at temperature of from room temperature to 95° C.
7 . The method of claim 6 , wherein the rinsing comprises contacting the titanium diboride electrode with water.
8 . The method of claim 1 , comprising:
using the copper-coated titanium diboride electrode in an aluminum electrolysis cell.
9 . The method of claim 8 , wherein the using comprises using the copper-coated titanium diboride electrode as an anode.
10 . The method of claim 8 , wherein the using comprises using the copper-coated titanium diboride electrode as a cathode.
11 . The method of claim 8 , wherein the using comprises using the copper-coated titanium diboride electrode as a sidewall.
12 . The method of claim 8 , wherein the using comprises:
prior to operating the aluminum electrolysis cell, installing the copper-coated titanium diboride electrode in the aluminum electrolysis cell; and
starting-up the aluminum electrolysis cell, wherein the starting-up comprises:
preheating the aluminum electrolysis cell;
adding a molten electrolyte to the aluminum electrolysis cell, thereby forming a bath;
applying DC current, via the copper-coated titanium diboride electrode, to the bath;
dissolving alumina (Al 2 O 3 ) in the bath;
reducing the dissolved alumina to aluminum metal; and
replacing at least some of the copper-based film of the copper-coated titanium diboride electrode with an aluminum film, thereby forming an aluminum-wetted titanium diboride electrode, wherein the replacing comprises:
dissolving at least a portion of the copper-based film via the aluminum metal of the bath.
13 . The method of claim 12 , comprising:
after the starting-up step, making commercial purity aluminum in the aluminum electrolysis cell via the aluminum-wetted titanium diboride electrode.
14 . The method of claim 13 , wherein the using comprises using the copper-coated titanium diboride electrode in a vertical orientation.
15 . The method of claim 14 , wherein the replacing step comprises:
producing aluminum metal at or near outer surfaces of the vertically oriented, aluminum-wetted titanium diboride electrode; and
flowing the aluminum metal down the vertically oriented, aluminum-wetted titanium diboride electrode.
16 . The method of claim 12 , wherein the preheating the aluminum electrolysis cell comprises heating to a temperature of at least 600° C.
17 . The method of claim 12 , comprising:
dissolving, via the bath, copper oxides on surfaces of the copper-coated titanium diboride electrode.
18 . The method of claim 12 , wherein, during the reducing the dissolved alumina to aluminum metal step, the copper-coated titanium diboride electrode is at least partially submerged in the bath.
19 . The method of claim 12 , wherein the dissolving step comprises dissolving a first portion of the copper-based film of the copper-coated titanium diboride electrode, wherein the method comprises:
maintaining a second portion of the copper-based film of the copper-coated titanium diboride electrode during the operating the aluminum electrolysis cell step.
20 . The method of claim 1 , wherein the titanium diboride electrode consists essentially of titanium diboride.