First high-resolution ¹¹B nuclear magnetic resonance (NMR) spectra of coal fly ash by satellite-transition magic angle spinning (STMAS) NMR

A study was conducted to demonstrate the first high-resolution ₁₁B nuclear magnetic resonance (NMR) spectra for coal fly ash (CFA) by satellite-transition magic angle spinning (STMAS) NMR. Two kinds of CFA, such as N-CFA and W-CFA were provided by a Japanese coal-fired plant to be used for performing the solid-state NMR investigations. Major chemical compositions of the two kinds CFAs were similar with different concentrations of calcium. ₁₁B NMR and STMAS spectra were acquired using a 16.4 T narrow bore magnet equipped with a home-built STMAS probe that was able to generate rf field strengths of up to 200 kHz for ₁₁B. The STMAS probe equipped with a MAS controller achieved stable rotor spinning and long-term keeping of an accurate magic angle. A double quantum filter (DQF) was also employed to eliminate the undesired signals arising from central transition (CT)-CT transfer and any outer satellite-transition-CT transfer.