tailieunhanh - Carbon Alloys part 10

Tham khảo tài liệu 'carbon alloys part 10', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 299 Chapter 19 Basics of Nuclear Magnetic Resonance and its Application to Carbon Alloys Takashi Nishizawa Chemical and Environmental Tech. Lab. Kobe Steel Ltd. Kobe Hyogo 65J-227 Japan Abstract In this chapter applications of Nuclear Magnetic Resonance NMR spectroscopy to carbon carbon alloys are presented. The principles of NMR and explanations of such technical terms as FID relaxation time and spin locking are set out. A brief account is given of the preparations necessary for pitch samples and methods of determination of aromaticity from H-NMR spectra. A detailed description is given of 13C-NMR spectrometry which is the most suitable method to characterize pitches. Preparation of both solid-state and fused-state samples as well as solution liquid state samples assignments of spectral peaks in terms of functional groups in constituent molecules of pitches and an interpretation on a spectrum of a mesophase pitch in the liquid crystalline phase are all discussed. Finally chemical shifts of 7Li-NMR from systems of carbons and graphites containing lithium are listed and probable assignments made. Keywords H-NMR C-NMR Li-NMR Pitch Carbonaceous mesophase Graphite intercalation compound. 1 Introduction The nuclear magnetic resonance NMR technique cannot be used for carbon graphite materials as such but is a powerful tool to analyze pitches which are the parent materials of carbons as well as lithium contained within carbons and graphites. This chapter describes 1 the basics of H- and C-NMR spectroscopy . spin 1 2 2 the characterization of pitches and 3 the characterization of the several chemical states of lithium in Li-carbon and Li-graphite compounds by Li-NMR. This work has relevance to the lithium battery. 2 Apparatus An NMR spectrometer consists of a magnet a probe an oscillator a spectrometer and a computer. Figure 1 is an illustration of the magnet and probe for liquid solution 300 Chapter 19 Transmission coil Receiver coil Fig. 1. Illustration of a magnet .