Structural characterization of carboxyl cellulose nanofibers extracted from underutilized sources

Two different chemical methods, TEMPO-oxidation and nitro-oxidation, were used to extract carboxyl cellulose nanofibers(CNFs) from non-wood biomass sources(i.e., jute, soft and hard spinifex grasses). The combined TEMPO-oxidation and homogenization approach was very efficient to produce CNFs from the cellulose component of biomass; however, the nitrooxidation method was also found to be effective to extract CNFs directly from raw biomass even without mechanical treatment.The effect of these two methods on the resulting cross-section dimensions of CNFs was investigated by solution small-angle Xray scattering(SAXS), transmission electron microscopy(TEM) and atomic force microscopy(AFM). The UV-Vis spectroscopic data from 0.1 wt% TEMPO-oxidized nanofiber(TOCNF) and nitro-oxidized nanofiber(NOCNF) suspensions showed that TOCNF had the highest transparency( 95%) because of better dispersion, resulted from the highest carboxylate content(1.2 mmol/g). The consistent scattering and microscopic results indicated that TOCNFs from jute and spinifex grasses possessed rectangular cross-sections, while NOCNFs exhibited near square cross-sections. This study revealed that different oxidation methods can result in different degrees of biomass exfoliation and different CNF morphology.     

巨厚砾岩下孤岛综放工作面顶板结构的动态稳定性分析

介绍了综放采场顶板结构形式及其运动的控制因素，利用结构稳定理论和强度理论，分析了义马巨厚砾岩下孤岛综放工作面顶板结构的稳定性，建立了初次来压和周期来压期间顶板结构的动态稳定性判据．通过调整顶煤放出率，实现控制顶板的稳定性，从而实现安全开采．