Dissertation > Excellent graduate degree dissertation topics show

Abstract

This paper introduces a tubular NASICON solid electrolyte CO2 gas sensor. The sensor is NASICON material uniformly coated on the hollow Al2O3 tube and sintered at a high temperature for a certain thickness of the base layer is formed at both ends of the surface of the base layer, respectively, to make the sensitive electrode and the contact electrode and the side of the sensitive electrode by melt quenching method of preparation of the auxiliary electrode, the auxiliary electrode material is BaCO3-Li2CO3 (1mol: 1mol). In order to provide heat to the component, the heating coils of about 30Ω through the tube as a heater. Experiment to ZrOCl2 · 8H2O, NaNO3, Si (OC2H5) 4, (NH4) 2HPO4, C2H5OH and NH3 · H2O as the main raw material, HNO3 as back solvents, using the sol-gel method NASICON material. Using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (IR), Raman spectroscopy (Raman), the electron diffraction spectroscopy (XPS), resistivity measurements and other methods, the material is a more comprehensive characterization. As can be seen from the XRD pattern of the material in the case of the different sintering temperatures, the 900 ° C sintered samples have a monoclinic crystal structure, and tend to complete. The IR spectra indicate that the material has a simple infrared absorption, unlike other multi-polyphosphate as complex, indicating that the material has a relatively pure phase structure. From XPS analysis, of each element in a valence state exists, calculated material MF Na3.2Zr2.3Si1.8PO12 with the the MF Na3Zr2Si2PO12 we want to achieve very close. Resistivity analysis shows that when the temperature of 250 ° C or less, the Na ion migration rate is slow, the resistivity of the material is very high, when the temperature is raised to about 300 ℃, the Na ion migration rate is significantly accelerated, having a higher ionic conductivity efficiency, the resistivity of the material is decreased rapidly. We introduced a variety of configurations of the NASICON solid electrolyte CO2 sensor, particularly improved piece structure. Within the heating tube CO2 gas sensor chip structure and indirectly heated sintered gas sensing element structure based on the design and tubular elements of the production process and the process is described in the form of pictures. In the experiment, the EMF values ??to the components of the output as a parameter to examine its performance. First test of the basic characteristics of the tubular member, including the sensitive characteristics of the relationship and elements of the output the EMF value with changes in the heating current (i.e., temperature) of CO2 gas, in response to the recovery characteristic, water resistance, immunity, and 30 days stability. Studies have shown that the components EMF absolute value increased with increasing heating current, specific performance showed a good linear relationship with the heating current I2 lt; WP = 63 gt; Department. (200-2000) in the CO2 gas volume concentration × 10-6 within the EMF values ??of the log value of the concentration showed a good linear relationship, which matches with the Nernst equation. Simultaneously with the increase of the heating current, the higher the sensitivity of the element, when current is 180mA, the sensitivity of the element to 55mV/decade. We choose 180mA working current as a tubular element to examine the other characteristics. Element having a response recovery characteristics vary with the level of CO2 concentration, the higher the concentration, the response and recovery the faster, wherein the air to 1000 × 10-6CO2 response and recovery time (65%), respectively, 9.6 seconds and 55 seconds. Influence of humidity on the tubular element, the performance of the substantially constant EMF value of the drift, but the sensitivity of the element in the case of both wet and dry. We selected the anti-interference characteristics of the five gases investigated tubular element, the bare element within a range of 200 × 10-6 to 4000 × 10-6, the volume concentration of the five gases have different degrees of interference which CH4 , H2S and C2H5OH interference is strong. The track measurements found that the EMF value is changing, especially in the beginning stages of larger changes within 30 days of the characteristics of the components. CO2 concentration of 1000 × 10-6 EMF biggest change in value of 8.8mV, less than 10%, and 500 × 10-6 and smaller changes in the EMF difference in the concentration of 1000 × 10-6 3.8mV tube different heating-element and chip components, so that the distribution of the thermal field. The tubular elements of the thermal field distribution more uniform thermal field distribution of the chip components undulating, tubular elements in the sensitivity, water resistance and stability, but also shows certain advantages. NASICON the thickness of the base layer, the sintering temperature and sintering time of the base layer on the performance of the tubular element are affected. The different thickness of the element, sensitivity, there are some differences, which may be the temperature impact. 1000 ° C sintered element, its sensitivity and good water resistance, high sintering temperature will reduce the sensitivity of the device. Found in the experiment, six hours the sintered element, its characteristic is preferably sintered at more than 10 hours, the element is inferior the sensitivity characteristics of the CO2 gas. Finally, in order to improve the water resistance of the element, we have tried a method of modification of the electrode surface using gaseous silica. Humidity environment, the contact surface of the electrode will be Na3PO4 precipitated using gaseous silica gel modified elements, not only the sensitivity improved, and there were significant improvements in water resistance.

Related Dissertations

CLC: > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Automation components,parts > Transmitter ( converter),the sensor
© 2012 www.DissertationTopic.Net Mobile

Research on the Tube-type Solid-electrolyte CO2 Gas Sensor

Abstract

Related Dissertations

Research on the Tube-type Solid-electrolyte CO₂ Gas Sensor