CP dynamics of heterogeneous organic material: characterization of molecular domains in coals

详细信息    查看全文

• 作者：Abelmann ; Kerstin ; Totsche ; Kai Uwe ; Knicker ; Heike ; Kö ; gel-Knabner ; Ingrid
• 关键词：¹³C NMR ; Cross polarization dynamics ; Rotating frame relaxation ; Organic material ; Coal
• 刊名：Solid State Nuclear Magnetic Resonance
• 出版年：2004
• 出版时间：June, 2004
• 年：2004
• 卷：25
• 期：4
• 页码：252-266
• 全文大小：495 K

文摘

Simplified equations are used in common approaches to describe cross polarization (CP) dynamics of solids. The CP behavior may be modulated by several nuclei interactions and physicochemical sample properties. At high magnetic fields and spinning speeds, these modulations can obscure the results. To elucidate their impact on the CP behavior of natural organic materials variable contact time (VCT) experiments were acquired with a high temporal resolution for two coal samples. The measurements were distinctly influenced by interfering fluctuations. Conventional approaches showed insufficient flexibility in terms of degrees of freedom to calculate the CP dynamics. The use of an original fundamental equation as model resulted in sufficient flexibility for such heterogeneous systems. The best results were obtained assuming a two component system. On these conditions a differentiation between amorphous and crystalline domains within the coal samples was enabled.