Chemistry: analytical and immunological testing – Hydrogen – per se
Reexamination Certificate
2003-01-29
2004-04-20
Snay, Jeffrey R. (Department: 1743)
Chemistry: analytical and immunological testing
Hydrogen, per se
C436S167000, C422S086000, C422S091000
Reexamination Certificate
active
06723566
ABSTRACT:
TECHNICAL FIELD
The invention relates to a Pd/Ni WO
3
(palladium/tungsten-doped nickel oxide) anodic double layer gasochromic device in which the palladium layer functions as a catalyst material that facilitates reaction with hydrogen gas. The hydrogen gas is disassociated on the Pd catalyst into H atoms, which diffuse into the Ni—WO
3
film. The Ni—WO
3
thin film exhibits an anodic coloration with H
+
or Li
+
insertion. The Ni—WO
3
thin film is more stable than WO
3
films in air, due to the fact that Ni oxide based materials, unlike WO
3
, forms a hydroxide upon absorption of water vapor. Even after forming the hydroxide, the Ni—W hydroxide thin film still shows a strong color change. By use of the gasochromic response upon exposure to hydrogen gas, hydrogen gas monitoring of the anodic double layer device of the invention can be detected via optical detection schemes such as a fiber-optic type H
2
sensor.
1. Background Art
Hydrogen is a plentiful, clean, non-polluting fuel. Hydrogen is currently used in many industries, and the US demand for hydrogen is approximately 140 billion cubic feet per year and growing. However, hydrogen is explosive at 4% in air. Therefore, it is critical to measure, monitor and control hydrogen wherever it is used.
In the gasochromic art where sensors and measurement instrumentation for hydrogen gases detect and/or measure hydrogen, typically there is required a portable sensing device, a kit (where hydrogen gas detection and/or measurement is required in existing equipment), and sensor heads installed at points where hydrogen leaks are possible, or where monitoring is necessary (i.e., in internal combustion engines which operate using hydrogen as a fuel).
The problems associated with current H
2
gasochromic devices are that these devices are not of adequate durability in that they degrade quickly with cycling and time, are too moisture sensitive, and react too slowly in response to the presence of H
2
to produce an optical absorption change with a lengthy time constant in the vicinity of 30 seconds.
2. Description of the Related Art
At present, optical detection of H
2
is widely accomplished through the use of Pd/WO
3
hydrogen detecting gasochromic devices. However, several problems or drawbacks are associated with the use of Pd/WO
3
hydrogen detecting gasochromic devices. These problems are: they are of inadequate durability; they respond slowly to the presence of H
2
; and there is a conflicting cathodic-anodic optical response that results in a weak color change.
Inadequate durability problems are occasioned by the fact that the Pd/WO
3
hydrogen detecting gasochromic device degrades quickly with cycling and time, and is unduly moisture sensitive.
The slow response of the Pd/WO
3
hydrogen detecting gasochromic device in the presence of a H
2
leak is due to the hydrogen reaction in H
x
WO
3
which produces a slow optical absorption change within a lengthy room temperature time constant of about 30 seconds.
Also, there is a conflicting optical response upon detection of H
2
by the Pd/WO
3
gasochromic device due to the fact that the WO
3
exhibits a cathodic response and the Pd exhibits an opposite anodic response.
3. Disclosure of Invention
One object of the present invention is to provide an anodic double layer H
2
detecting gasochromic device of improved durability that shows little degradation with cycling and time.
A further object of the present invention is to provide an anodic double layer H
2
detecting gasochromic device that responds more swiftly to detection of H
2
gas by producing faster optical absorption change within a room temperature time constant of about 10 seconds.
Another object of the present invention is to provide an anodic double layer H
2
detecting gasochromic device comprising complementary coloring layers in which both of the layers consist of an anodic coloration material.
In general, the invention is accomplished by providing a palladium/tungsten-doped nickel oxide anodic double layer gasochromic device in which, a Ni—WO
3
thin film is prepared on a glass substrate by reactive sputtering. Thereafter, a palladium layer is evaporated onto the Ni—WO
3
thin film. The palladium layer serves as a catalyst material that facilitates reaction with hydrogen gas. That is, the hydrogen gas is dissociated on the Pd catalyst into H atoms, which readily diffuse into the Ni—WO
3
film. The Ni—WO
3
thin film exhibits an anodic coloration with insertion of either H
+
or Li
+
.
The Ni—WO
3
thin films arc more stable than WO
3
films in air due to the fact that Ni oxide based materials, unlike WO
3
, form a hydroxide upon absorption of water vapor. Even after formation of the hydroxide, Ni—W hydroxide thin films still show a strong color change. By use of this gasochromic response upon exposure to hydrogen gas, hydrogen gas can be monitored via optical detection schemes such as fiber-optic type H
2
sensors.
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Patent Abstracts of Japan, vol. 012, No. 136(P-694), Apr. 26, 1988 & JP 62 257047 A(Hochiki Corp.), Nov. 9, 1987, abstract.
Shen , P.K. et al., “The Performance of Electrochromic Tungsten Trioxide Films Doped with Cobalt or Nickel” Journal of the Electrochemical Society, Electrochemical Society, Manchester, New Hampshire, US, vol. 138, No. 9, Sep. 1, 1991, pp. 2778-2783, XP000248209.
Lee, S-H. et al., “Characterization of Ni-W Oxide Thin Film Electrodes”, Solid State Ionics, North Holland Pub. Co. Amsterdam, NL, vol. 109, No. 3-4, Jun. 2, 1998, pp. 303-310, XP004124974.
Lee Se-Hee
Liu Ping
Pitts J. Roland
Tracy C. Edwin
Midwest Research Institute
Snay Jeffrey R.
White Paul J.
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