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LiFe_ (1-x) M_xPO_4 film composite optical waveguide chemical sensor research

Author: PaTiMan·NiZhaMuDing
Tutor: ABuLiZi·YiMiTi
School: Xinjiang University
Course: Chemistry
Keywords: Nanomaterials LiFePO4 Waveguide sensing element Formaldehyde Xylene
CLC: TP212.2
Type: Master's thesis
Year: 2010
Downloads: 69
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Abstract


1990s developed nanomaterials, because of its special size distribution, with a surface effect, small size effect and macroscopic quantum tunneling effect, showing a series of unique mechanical, electrical, optical, magnetic and catalytic properties. The rise of nanotechnology research for the sensor opens up a new world. Since the optical waveguide chemical sensors with mechanical strength, resistance to electromagnetic interference, small size, high sensitivity, fast response, can operate at room temperature, ease of integration, etc., in the detection of environmental pollutants, industrial production, chemical, biological testing areas, especially In the field of detection of harmful gases to occupy an increasingly important position. In this thesis, the unique properties of nanomaterials and the superiority of the optical waveguide chemical sensors linked to lithium iron phosphate (LiFePO4) and dopant as sensitive reagents, p-xylene, formaldehyde and other volatile organic gases were studied . This thesis consists of the following parts: The first chapter is an introduction part, about the characteristics and applications of nano-materials, nano-materials and the relationship between the sensor, the sensor technology overview, gas sensors and their classification, and focuses on optical waveguide chemical sensors. Finally the source and subject of this thesis work content. The second chapter is part of an optical waveguide theory, introduces the light propagation and reflection, planar waveguide structure, lightwave transmission, optical waveguide sensing principle (evanescent wave sensing principle), planar waveguide optical coupling , glass optical waveguide (K ion exchanged glass waveguides and waveguide tin-doped glass) preparation technology and other theories. The third chapter is LiFePO4 film / tin-doped glass composite waveguide component gas research, hydrothermal synthesis of LiFePO4 powder and use it as sensitive reagent prepared LiFePO4 / tin-doped composite glass waveguide components. LiFePO4 of heat treatment temperature on the refractive index, thickness and light transmittance of the optical properties, the optical waveguide sensor screened prepare the optimum conditions (solvent, optimum heat treatment temperature-sensitive film thickness, etc.). The LiFePO4 / tin-doped glass composite waveguide element is fixed on the glass waveguide detection system, the sensing element detects toluene, xylene, chlorobenzene and other gases of the gas. Sensitive membrane through changes in optical properties of evanescent wave height sensing mechanism explained. The results show that the element 5 × 10-5 can be detected and having a xylene gas selectivity, lower concentrations of the organic volatile gas (1 × 10-4), the sensing element is only paraxylene gases have a response. The fourth chapter is LiFe0.99Ag0.01PO4 Film / tin-doped glass waveguide gas sensing element study. Synthesized by hydrothermal method of Ag-doped LiFePO4 powder and use it as as sensitive reagents. Filter out the best solvent to prepare thin films conditions, and change the amount of Ag-doped films were developed a LiFe0.995Ag0.005PO4 / tin-doped glass optical waveguide, LiFe0.99Ag0.01PO4 film / tin-doped glass waveguide and LiFe0 .98 Ag0.02PO4 Film / tin-doped glass waveguide formaldehyde gas sensing element, which LiFe0.99Ag0.01PO4 film / tin-doped glass waveguide sensor sensitivity and selectivity of formaldehyde gas preferably reversible and has a good response, The linear response range of 10-3 to 10-10. The high sensitivity of the sensing element (able to detect concentrations of less than 10-10 formaldehyde gas), fast response (response time less than 2s), good repeatability, when the gas concentration is less than 10-5, in addition to formaldehyde gas, the right other organic volatile gases is not responding. To see the pure solvent (PVA VC) of volatile organic gas if there is a response, developed under the same conditions PVA-VC composite film / tin-doped glass optical waveguide element, and the detection of volatile organic gas. The results show that when the gas concentration is 10-4, the optical waveguide element does not respond to formaldehyde gas, thereby determining the solvent (PVA Vc) of LiFe0.99Ag0.01PO4 Film / tin-doped optical waveguide by formaldehyde gas sensitive element Sensitivity of detection is not affected. Finally, we compare three different silver doping sensitivity of the sensing element, and use the film and the role of formaldehyde gas before and after the change in light transmittance, film scanning electron micrograph explain. Chapter V LiFe0.99Y0.01PO4 Film / tin-doped glass waveguide gas sensing element research, synthesized by hydrothermal method of Y-doped LiFePO4 powder and use it as sensitive reagents, rotary - spin coating method in the tin-doped glass waveguide surface preparation LiFe1-xYxPO4 film. Developed a LiFe0.99Y0.01PO4 Film / tin-doped glass waveguide and LiFe0.98Y0.02PO4 Film / tin-doped glass waveguide components, and studied the gas sensing properties, and film heat treatment time and heat treatment temperature on the gas resistance of. The results show that heat treatment at 150 ℃ (for 30 min) LiFe0.99Y0.01PO4 Film / tin-doped glass optical waveguide sensing element for different volatile organic gases have a good selectivity response. Transmittance and fluorescence characteristics through changes in interpretation of the sensing element xylene gas sensing mechanism. When the gas concentration is 10-7, the gas sensing element is responsive only to xylene. Finally, the factors that affect the emission of the sensing element to explain the different selective response in volatile organic gases. Chapter VI is the conclusion part of the main contents of the summary of the research work.

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CLC: > Industrial Technology > Automation technology,computer technology > Automation technology and equipment > Automation components,parts > Transmitter ( converter),the sensor > Chemical sensors
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