Project manager A.L. Gusev Foreign collaborators: prof. T.N. Veziroglu (University Miami, USA), prof. J. Hirschberg (University Miami, USA), prof. M.D. Hampton (University Orlando, USA), prof. H.H. Uchida (Tokai University, Japan), prof. A. Echarri (Espana), prof. A.J. Maeland (USA)
Summary of the Project
In this project, research and development efforts aimed at creating small and reliable hydrogen detectors
operating over a wide range of temperatures (T= 77 ■ 330 K) and pressures (P=1 ■ 5*105 Pa) are proposed. The intended research is based on the wide experience of the proposing investigators in development of sensors that are able to detect both hydrogen leaks and volume concentrations of hydrogen in various gas mixtures over a wider range of pressures and temperatures compared with those of the known analogs.
Hydrogen has been used heavily in space programs and in industry, world wide, for many years. Because of the enormous energy content of hydrogen, its ubiquitous nature, and the fact that hydrogen can be utilized in a non-polluting manner, hydrogen is finding ever increasing utilization. For example, the Tupolev 155 plane using liquid hydrogen and liquefied natural gas has undergone a complex of land and air tests and has established 14 world records. As a result of this increasing utilization of hydrogen, there is a great deal of interest in hydrogen detectors for reasons both of safety and efficiency.
It has been calculated that dimensions of damaged areas when accidents involve large cryogenic hydrogen tanks may be from several hundred meters to several kilometers. Thus, hydrogen sensors are critical for the safe utilization of hydrogen by allowing the detection of hydrogen leaks before reaching dangerous proportions.
Monitoring of gas environments in vacuum heat-shielding cavities of cryogenic tanks and pipelines is also critical. If undetected, hydrogen leaking into these cavities could reach explosive proportions. Furthermore, because of its very large ability to transport heat, hydrogen in the heat-shielding cavity will greatly decrease the insulation value of the cavity and potentially cause boil off of a large amount of the hydrogen in the tank or pipeline.
At present there are more than 50 methods of converting the concentration of measured gas components into electric and other types of signals. Some scientific institutions and world companies have made measurement transducers having very good metrological and dynamic characteristics. Based on these measurement transducers, high-precision and high-response devices and systems have been developed that are used for control over production processes in various industries, for scientific studies and the environment monitoring.
Project Proposal #1580 «Hydrogen Detectors»
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Many of the known hydrogen sensors are rather complicated electromechanical or optic-electronic systems. The high cost of such renders them inappropriate for many applications.
The majority of hydrogen transducers currently available are subject to effects produced by changes in temperature, pressure, environmental humidity, electromagnetic surges, and gas flows. The resulting errors are most often limited by controlling the above factors. However, such an approach results in great instrumentation costs, reduces reliability of gas analysis instrumentation, and is not always justified when developing high-precision gas analysis instrumentation.
To compensate for these errors, computer facilities as well as structural design methods for gas analysis instrumentation and systems have to be also used.
Methods of analysis based on physical and chemical phenomena accompanying the reaction of hydrogen and its isotopes with oxidizers are finding increasing application for selective identification of hydrogen.
The present work is dedicated to theoretical and experimental studies of hydrogen detectors functioning over a wide range of temperatures and pressures. Special emphasis will be placed on sensors to function at low temperatures both at reduced pressures and in vacuum.
The project objective is to create small and cheap continuously operating hydrogen detectors based on oxides of the transition metals and graphite materials containing catalytic additives of transition metals and alloys [1-3], as well as carbon nanomaterials [4-9].
Such sensors will allow detection of both accidental leaks of hydrogen and changes in hydrogen volume concentrations in various gas mixtures over a wider range of pressures and temperatures than the known analogs.
Moreover, some of the materials to be utilized in the detectors can absorb considerable amounts of hydrogen in emergency situations, lessening the consequences of any leak that does occur.
Characteristics of the detectors under development. The project implementation will result in development of hydrogen sensors having the following characteristics:
1. The range of operating temperatures is T = 77 ^ 330 K;
2. The range of operating pressures is P = (1 ■ 5 X105) Pa;
3. The accuracy of hydrogen concentration measurement over 0.2-3.1%, 3.1-20%, 20-95% ranges is ±0.1%, ±0.1%, ±0.1%, respectively.
Advantages over the known analogs. The novelty of intended research is proved by RF patents for sensor substances, the hydrogen detector, the technological process as well as for automatic fire prevention system of monitoring and efficient interfering in the technological process [10-16].
The project will result in creation of new sensor materials and development of manufacture technologies for the detectors that will operate over a wider temperature and pressure range.
Expected results.
International Scientific Journal for Alternative Energy and Ecology July 2000, Vol. 1 223
Copyright©2000 by STC "TATA"
1.Development of sensor materials based on oxides of transition metals containing catalytic additives, as well as of carbon nanomaterials.
2.Creation of the database including relations between thermal, electron [17], acoustic parameters of sensor materials and hydrogen concentration.
3.Design of sensors and systems for computer-aided control over important production processes.
4.Development of simple indicators for threshold hydrogen concentrations in the form of individual indicating tubes.
5.Creation of compositions and design of hydrogen absorbers.
Fundamental character of the research. It is well known that interaction of some metal oxides with hydrogen takes place with a rather low activation energy [1, 2].
Study of the process of hydrogen interaction with intermetallic compounds and carbon nanomaterials (fullerenes and their combinations, open nanotubes, empty nanofibres, graphite oxide) is of fundamental and applied importance for development of sensor materials. The preliminary results [1-10] point to future opportunities of new materials of this type for absorbing considerable amounts of hydrogen.
In the present Project VNIIEF scientists and their colleagues from :
The Institute of Chemical Physics Problems of RAS (Chernogolovka, Russia),.
The Physics Scientific Research Institute of SPSU (Saint-Petersburg, Russia) and
The L.V. Pisarzhevsky Physical Chemistry Institute (Kiev, Ukraine) ,
PROPOSE:
A) To carry out studies into the mechanisms of hydrogen interaction with manganese dioxide, MnO2, containing small amounts of palladium or its alloys with other metals, rhodium in particular.
B) To develop different methods for deposition of catalytic additives onto sensor materials. Effects produced by special preliminary processing of the manganese dioxide surface (y-radiation, surface activation by low-temperature plasma, vacuum burning, heating in oxygen, modifying by cobalt oxide C03O4, etc.) on its hydrogen-sorbing and other physicochemical properties will be studied.
C) To study sensor material surfaces electron-emission spectroscopy methods such as X-ray photoelectron spectroscopy, Auger-spectroscopy and electron energy losses spectroscopy.
D) To certify the samples under study using chemical and X-ray-phase analysis, IR and Raman spectroscopy.
E) To study the effects of the replacement of small quantities of manganese atoms by iron atoms in the preparation of manganese dioxide in the hopes that it will make it possible to control phase transformations in MnO2. Mossbauer spectroscopy will be used for this study.
F) To study the mechanism for deactivation of the sensing materials and determine the optimum conditions for the sensors.
G) To study the process of reversible hydrogen interaction with intermetalic compounds and carbon nanomaterials including those doped with various metals.
H) To determine the amount of reversible hydrogen sorption, the thermal reaction effects, the state
International Scientific Journal for Alternative Energy and Ecology Copyright©2000 by STC "TATA" July 2000, Vol. 1 224
diagrams, the optimum conditions for reversible interaction, and the effects produced by gases upon sorption and desorption processes.
I) To determine compositions those have the required operational characteristics.
J) To study methods of materials preparation including formation of the optimum porous structure, introduction of metal and organic binders as well as components having membrane properties to remove such reaction products as water.
As has been mentioned above, such processes will be studied over the following ranges of temperature, pressure, and hydrogen concentration, respectively: 77 ^330 K, 1 ■ 5 X105 Pa, and 0.2 and 100% hydrogen.
The results of these investigations are proposed to be used for increasing safety at nuclear power stations, in hydrogen main pipelines and cryogenic tanks [10,11], in dangerously explosive industrial applications, at large cryogenic complexes, and in road and air transport using hydrogen as a fuel. Furthermore, th
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