We report here extracting SiO₂ as spirosiloxane [(CH₃)₂C(O)CH₂CH(O)CH₃]₂Si from rice hull ash (RHA) to carefully control the SiO₂: C mole ratios, allowing direct carbothermal reduction to SiC, Si₃N₄, or Si₂N₂O without the need to add extra carbon and as a mechanism to preserve the original nanocomposite structure. We can adjust SiO₂: C ratios from 2 : 15 to 13 : 35 simply by reacting RHA with hexylene glycol (HG) with catalytic base to distillatively extract SiO₂ to produce silica depleted RHA (SDRHA) with SiO₂ contents of 40–65 wt% and corresponding carbon contents of 60–35 wt% with specific surface areas (SSAs) of >400 m² g⁻¹. On heating SDRHA_40–65 at 1400–1500 °C in an Ar, N₂, or N₂–H₂ atmosphere, XRD patterns reveal formation of SiC, Si₃N₄, or Si₂N₂O as the major phase with some residual hard carbon. SEM studies reveal mixtures of particles and whiskers in the products, which show BET specific surface areas >40 m² g⁻¹ after oxidative removal of excess carbon. Dilute acid and boiling water prewashing of RHA with milling eliminates typical product impurities compared to those found using conventional carbothermal reduction of agricultural wastes, which qualifies the resulting composites as components for electrochemical energy storage devices among other applications, to be reported elsewhere.

中文翻译：

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调整稻壳灰 (RHA) 中的 SiO2:C 摩尔比以控制碳热还原为纳米结构的 SiC、Si3N4 或 Si2N2O 复合材料

我们在此报告从稻壳灰 (RHA) 中提取 SiO ₂作为螺硅氧烷 [(CH ₃ ) ₂ C(O)CH ₂ CH(O)CH ₃ ] ₂ Si 以仔细控制 SiO ₂ : C 摩尔比，允许直接碳热还原为 SiC、Si ₃ N ₄或 Si ₂ N ₂ O，无需添加额外的碳，并作为保留原始纳米复合结构的机制。我们可以将 SiO ₂ : C 比从 2 : 15 调整到 13 : 35，只需将 RHA 与己二醇 (HG) 与催化碱反应以蒸馏提取 SiO ₂以生产具有40–65 wt% SiO ₂含量和 60–35 wt% 相应碳含量且比表面积 (SSAs) > 400 m ² g ^{-1 的}贫二氧化硅 RHA (SDRHA) 。在Ar、N ₂或 N ₂ –H ₂气氛中在 1400–1500 °C 下加热 SDRHA _40–65时，XRD 图案显示形成了 SiC、Si ₃ N ₄或 Si ₂ N ₂ O 作为主要相，一些残留的硬碳。SEM 研究揭示了产品中颗粒和晶须的混合物，这表明 BET 比表面积 >40 m ² g ^-1氧化去除多余的碳后。与使用传统碳热还原农业废物发现的那些相比，通过研磨对 RHA 进行稀酸和沸水预洗消除了典型的产品杂质，这使得所得复合材料有资格作为电化学储能装置的组件以及其他应用，将在别处报告。