Dissertation > Excellent graduate degree dissertation topics show

Raman Spectrometry Measurement of Hydrothermal Gases under Simulated Deep-sea Environment

Author: HuangYangYu
Tutor: MaJun
School: Ocean University of China
Course: Optical Engineering
Keywords: Raman spectra CO2 CH4 C2H6 C3H8 Simulated deep-sea environment
CLC: P733.3
Type: Master's thesis
Year: 2009
Downloads: 166
Quote: 2
Read: Download Dissertation

Abstract

The measurement and study of underwater hydrothermal materials has been an important topic of marine geological research for the recent decades. The technology of Laser Raman Spectrometry can measure underwater target in situ, in real time and continuously. Deep-sea in-situ laser Raman system, one of the guide- line subjects in China’s“Eleventh Five-Year Plan”for scientific research, has been established as a key project. The work of this thesis is carried out under this key project. We constructed a Laser Raman Spectrometry system in our laboratory, and utilized a high-temperature, high-pressure experimental platform to carry out the following studies: Raman spectra measurement of the aqueous solution of the main gas compositions in deep-sea hydrothermal areas; study of Raman peaks of CO2, CH4, C2H6 and C3H8 in aqueous solutions; recording these Raman peaks and their changes under different temperature and pressure; processing of complex Raman spectra with low signal-to-noise ratio with various methods including Gaussian fitting, polynomial fitting and linear regression. These studies provide data and reference for using laser Raman technology to extrapolate material composition and environmental information in deep-sea environment.In this thesis, we built a Nd: YAG laser with an emission wavelength of 532nm, a single-grating spectrometer and a laser Raman spectroscopy system with CCD. We used a high-temperature high-pressure platform to simulation the environment of a deep-sea hydrothermal vent (with maximum pressure of 40MPa and maximum temperature of 350℃). Under different pressure and temperature, we measured and analyzed the Raman spectra of the key compositions of deep-sea hydrothermal area, i.e. the aqueous solutions of CO2, CH4, C2H6, C3H8 and some of their admixture. The results show that at room temperature and 40MPa, the CO2 solution exhibits Fermi double peaks at 1384.9cm-1and 1278.3cm-1; the CH4 solution shows the Raman peakν1 at 2912.1cm-1; the C2H6 shows three Raman peaks that correspond toν3 (C-C stretch) at 997.4cm-1,ν1 (CH3 sym stretch) at 2893.7cm-1, and 2ν11 (CH3 d-stretch) at 2950.4cm-1, respectively; C3H8 has the most complicated structure and therefore the most Raman peaks. We obtained four peaks for that are located at 908.6cm-1 (C-C stretch), 2835.5, 2882.8 and 2960.8cm-1 (C-H stretch). All the peaks are shifted by 3~8cm-1 compared to the corresponding Raman peaks in gaseous phase. At room temperature no Raman peak of the aqueous solutions exhibit significant shift with changing pressure (≤40MPa), due to the presence of water molecules. At 40MPa and with increasing temperature (≤350℃), the Fermi peaks of CO2 solution shift toward higher wave number by 3.4cm-1 and 7.0cm-1, respectively; theν1 peak of CH4 solution is shifted to lower wave number by 3.1cm-1, Raman peaks of C2H6 solution and C3H8 solution are all shifted to lower wave number with varying magnitude; in the aqueous solution of CO2 and CH4 mixture, the CO2 Fermi double peaks are shifted higher by 4.3cm-1 and 3.8cm-1 respectively during the increase of temperature, while the CH4ν1 peak is shifted lower by 4.5cm-1. After a linear regression of these data, a correlation coefficient of R > 0.83 is obtained, which shows that from room temperature to 350℃, temperature changes affects the Raman frequency shift, the amount of which is linearly correlated with temperature.

Related Dissertations

CLC: > Astronomy,Earth Sciences > Oceanography > Marine basic science > Marine physics > Ocean Optics
© 2012 www.DissertationTopic.Net Mobile