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42Development of the semi-conductor analyzer for the control steam ethanol
Section 1. Analytical chemistry
Abdurakhmanov Ergash Abdurakhmanovich, professor of the Samarkand state university E-mail: ergash50@yandex.ru Ykhshilikova Lola Jurabayevna, master’s of the Samarkand state university Murodova Zulfiya Begmurodovna, doctorate of the Samarkand state university
Development of the semi-conductor analyzer for the control steam ethanol
Abstract: Are made and the analyzers on basis oxide cobalt are tested. Is shown, that the developed analyzer in a continuous mode have a low threshold of detecting, high selectivity in relation to ethanol.
Key words: pair’s ethanol, sensor control, semiconductor, oxide cobalt, gas the analyzer, range of definition, sensitivity, selectivity.
The area of application of semi-conductor sensor controls covers set of technological and ecological tasks, where the constant control in gas environments necessary [1]. Selective semi-conductor sensor controls is capable to decide practical problems of ecology: the control of structure of atmospheric air and technological gaseous of emissions; criminality: connected with detection explosive, poisoning and narcotic substances; food-processing industries and systems of certification of the goods: in quality «electronic noses» for recognition of smells; medicine: diagnostics of the various forms of infringements of an exchange of substances of diseases.
Now for application as primary elements of semi-conductor sensor controls the opportunities various metal oxide of a n-type electric conducting are widely investigated [2; 3]. One of the most perspective materials is oxide of zinc, dioxide of tin, oxide of iron, cobalt oxide etc. the Uniqueness of these materials at use as sensitive elements of semiconductor sensor controls is called by a number of their fundamental physical and chemical properties (electric conducting it appears of a surface, extremely sensitive to a condition, in a wide interval of temperatures, that is caused by presence free electrons in
a zone of conductivity, superficial oxygen vacancies, and also active chemisorptions of oxygen).
In the field of researches of processes of formation gas sensitive of elements on the basis of thin пленок of the mixed structure insufficiently investigated there is a lot of questions, for example, mechanism of physic-chemical processes proceeding at formation of thin-film layers zole-gele by a method; influence of technological modes of formation membrane on their structure, and, hence, and on their electro physical and gas sensitive of property; the reasons of occurrence of various structures thin пленок, problem of reproducibility of the characteristics of touch elements on their basis whence follows.
By the purpose of the given job was the development on a basis oxide of iron semi-conductor gas the analyzer for the control of the contents ethanol and research meteorological of parameters it of devices.
To reception semi-conductor nanocrystal thin is applied zole-gele the method which has rather simplified technology of reception nanostructure of composites on a basis oxide of metals [4]. Essential advantage of the given technique is the opportunity of achievement of high uniformity of synthesized
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Section 1. Analytical chemistry
materials. All initial substances are in a liquid phase, their mixing is realized at a molecular level, due to what a high degree of uniformity is reached. Thus, it is possible to ensure high quality of materials on cleanliness, to structure and uniformity of structure and to create highly a surface gas sensitive of a layer. To one more advantages of a method is the opportunity of enough simple management of parameters of created coverings as by direct change of a parity of components in a solution, and change ofparameters of technological process, for example, temperature soften, time soften. The technology also allows to make overlapping nanocrystal oxide with a matrix of an inorganic grid dioxide ofsilicon received from hydrolyzes tetra-oksi-silicon — Si (OC2H5)4, and, hence, to receive nanocrystal composites, structure and which properties do not vary in a range of working temperatures ofgauges, as against many nanodisperse of materials.
By development of methods of definition of harmful substances in air and creation gas analytical of devices the important difficult stage is the preparation gas and combined cycle of mixes connected to necessity of exact measurement of initial substances, charge of air, its clearing and liquid. Thus it is desirable to have the compact and simple equipment
allowing receiving reproduced and stable concentration of researched substance in air.
The static and dynamic ways of reception standard gas and steam gas of mixes are known. The most reliable and correct ways of preparation of samples steam gas of mixes ethanol are dynamic, based on an establishment of dynamic balance between sorption by a surface and additive by substance. By us at preparation steam gas of mixes steam ethanol was used diffusion measure with a polymeric membrane, where the contents of a determined component depends on structure and size of a membrane, temperature and speed of a flow of gas — thinner. In quality additive liquids we used waterless ethanol. The quantity of evaporation additive of liquids was defined gravimetric, weighing of capacity with additive by a liquid through everyone with 8 hours. Average concentration steam on an output from measure expected gravimetric under the formula:
С = ms/Q, (1)
where: mg — mass speed of evaporation found gravimetric, g/h; Q— charge of air through steam the chamber, l/h. The results of test dispenser during preparation GS ethanol in air are submitted in the table 1.
Table 1. - Dependence of concentration steam ethanol from temperature additive and speed of a flow gas of the carrier (n = 5, Р = 0.95)
Temperature measure, °C Speed of a flow gas of the carrier, l/h The contents ethanol in a mix (x ± Ax), mlyon1
30 25 80 ± 0.5
30 50 40 ± 0.5
30 100 20 ± 0.2
40 25 760 ± 0.7
40 50 380 ± 0.7
50 25 1360 ± 2.5
50 50 680 ± 1.0
60 25 2240 ± 3.5
60 50 1120 ± 2.5
70 25 2920 ± 4.0
70 50 1460 ± 3.5
As the concentration steam additive of a liquid is visible from the data given in the table depends on the charge gas of the carrier and temperature thermostat. The range additive of concentration can considerably be expanded by change to temperature and charge gas of the carrier. The received concentration meet the requirements, showed with gas to
analyzers, intended for definition паров этанола, for example, in industrial premises according to conditions of the safety precautions. Developed measure is convenient and is simple in operation.
As a result of the carried out research and performance is skilled — design jobs by us is created and is made semi-conductor portable gas analyzer intended
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Development of the semi-conductor analyzer for the control steam ethanol
for the control of the contents С2Н5ОН with the following characteristics: capacity consumed in a mode of measurement, 10 В*A; weight of the device no more than 5 kg.; overall dimensions no more 254 x 144 x 275 mm.; the time of an establishment of a target signal (indications), does not exceed 30 second; time heat, no more than 15 minutes. Gas to analyzers is intended for measurement of concentration steam ethanol and atheton in atmospheric both exhaled human air and departing gases of technological processes. The device consists from gas analyzer, filter of clearing of technological gases and power unit.
Gas to analyzers is executed as the portable device in the uniform block including the primary converter (a selective semi-conductor sensor control С2Н5ОН) and the secondary converter (the amplifier of a constant current), assembled in the metal case. The power supplies gas to analyzers are carried out as from a network of an alternating current by a voltage 220 V., and from the built in power unit with a voltage 12 V.
Conditions of operation gas to analyzers: mode of operations simple; average factor of operation — 0.25. Parameters of an environment: temperature from +10 up to +50 °С; atmospheric pressure 84.0-106.7 кРа (630-800) mm. mercury. An item; industrial vibrations with frequency 5-25 GG and amplitude, no more than 0.1 mm.; a deviation (rejection) of a voltage of a feed of an alternating current 220 V ± 10 %. Parameters of an analyzed mix on an input gas to analyzers maximal, and concentration of the certain component up to 5000.0 mln-1; temperature +10 + +50 °С; the charge of analyzed test 20 ± 2 l/h; pressure 84.0-106.7 кРа.
Check of a range of measurements gas to analyzers on ethanol spent at concentration of spirit 0-5000 mln-1 by submission on an input gas to analyzers standard verification of mixes of a determined component in air. The results of study of a range of measurements gas to analyzers “AG-C2H5OH and (СН3)2СО” on the channel of spirit are given in the table 2.
Table 2. - Results of check of a range of measurement of the channel ethanol of the analyzer “AG-C2 Н5 ОН” (n = 5; Р = 0.95)
№ Is entered С2 Н5 ОН, mln-1 Is found ethanol, mln 1
х ± Ах S Sr*10-2
1 50 51 ± 2 1.61 3.2
2 250 248 ± 5 4.02 1.6
3 500 495 ± 10 8.04 1.6
4 1000 990 ± 20 16.1 1.6
5 2500 2510 ± 25 20.1 0.8
6 5000 4985 ± 40 32.2 0.6
As the dependence of a signal developed gas to analyzers from concentration of a determined component on the channel С2 Н5 ОН follows from the given data, has rectilinear character. In the investigated interval of concentration the meaning Sr does not exceed 0.032.
Thus, the skilled sample gas to analyzers, intended for detecting steam ethanol is made.
Are appreciated basic metrological of the characteristic and operational parameters developed selective semi-conductor sensor control and created on its basis automatic gas to analyzers for definition steam ethanol.
References:
1. U-Sung Choi, Go Sakai, Kengo Shimanoe and Noboru Yamazoe. Sensing properties ofSnO2-Co3O4 composites to CO and H2. II Sensors and actuators, 98. - 2004. - P. 166-173.
2. Бубнов Ю. З. Полупроводниковые газовые микросенсоры.//Петербургский журнал электроники. -1996. - № 3 (12). - С. 87-91.
3. Bakin A. S., Bestaev M. V., Dimitrov D. Tz., Moshnikov V. A., Tairov Yu. M. Sn02 based gas sensitive sen-sor.//Thin Solid Films, 296. - 1997. - P. 168-171.
4. Семиченко Г. Д. Золь-гель процесс в керамической технологии. - Харьков, 1997.
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