Project Title:

Rapid Sensor to Detect Leaks During Fueling Operations

94-1	13.01	4844	A	

Rapid Sensor to Detect Leaks During Fueling Operations

Abstract:

An innovative microelectronic gas sensor utilizing plasma enhanced 
chemical vapor deposited (PECVD) diamond in conjunction with a 
catalytic metal has been fabricated and demonstrated in the 
laboratory to detect hydrogen gas. The device is fabricated in a 
layered Pd/i-diamond/p-diamond Schottky diode configuration. Test 
results indicate that the technology will allow rapid detection of 
hydrogen leaks during fueling operations. The same technology with 
modifications can provide a similar capability for detecting 
oxygen. The objective of this Phase I project is to develop and 
deliver a brassboard hydrogen gas sensor and to develop and 
demonstrate in a laboratory setting the capability to detect 
gaseous oxygen. The effort proposed includes modification of the 
current hydrogen detector to meet NASA requirements, development of 
readout/interface circuitry, demonstration/ delivery of the 
hydrogen sensor with PC interface in brassboard form, performance 
of R&D to modify the design to detect oxygen, and demonstration of 
the oxygen detector in a laboratory test. Phase II would take the 
combined hydrogen/oxygen sensor to the prototype level. The net 
result will be a hydrogen/oxygen sensor meeting NASA requirements 
for detection of leaks in the 1-1000 ppm range during fueling 
operations. 

The diamond chemical sensor can work for either gases or liquids 
and operates as a direct electronic device known as a diode. The 
device can be modified to detect minute changes in the type and 
amount of any of several chemical agents that are in proximity to 
the diamond sensor. This causes large changes in the electrical 
current which flows through the detector diode. As a result, the 
usefulness of this sensor technology is not limited to hydrogen and 
oxygen but may be useful in many commercial applications such as 
identification of trace amounts of toxins in biological fluids, in-
process control of critical chemical concentrations, continuous and 
direct measurement of internal combustion engine noxious emissions, 
and direct measurements of low concentrations of gaseous hydrogen 
and hydrocarbons for mine safety. The ruggedness of diamond 
materials allows use of this detector in environments where no 
other device would survive. In addition, various aspects of this 
technology make it a strong candidate for the development of 
personal warning detectors which could be applied to a broad range 
of requirements in the government and private sectors.  

Key Words

Physitron, Inc.
3304 Westmill Drive
Huntsville, AL 35805-6132