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首页> 外文期刊>RSC Advances >Solid-state reduction of silica nanoparticles via oxygen abstraction from SiO4 units by polyolefins under mechanical stressing
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Solid-state reduction of silica nanoparticles via oxygen abstraction from SiO4 units by polyolefins under mechanical stressing

机译：在机械应力下通过聚烯烃从SiO4单元中夺取氧来固态还原二氧化硅纳米颗粒

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Metal oxides with an oxidation number lower than the highest often exhibit attractive functional properties. However, conventional chemical or thermal reduction of the stable oxides is often laborious and cannot be stopped at an appropriate level of reduction. Therefore, we here try to explore non-conventional reduction processes in a solid-state without external heating. Unique features of reduction processes of SiO _(2) toward suboxides, SiO _( x ) (1 ≤ x < 2), were made possible by milling fumed silica nanoparticles with polyolefins (POL), i.e. , polypropylene (PP) or polyethylene (PE) and a fluorine-containing one, polyvinylidene difluoride (PVDF). We mainly examined the electronic and coordination states of Si by Si2p XPS spectra and ~(29) Si MAS NMR, respectively. They significantly differ from a similar commercial product obtained via a thermal route. Judging from the chemical shift of ~(29) Si MAS NMR as a criterion of the degree of reduction of SiO _(2) , the function of POL as a reductant is in the order PP ≈ PE > PVDF. Since the present solid-state reaction is free from the formation of unstable gaseous SiO as an intermediate, the products are free from the Si component in a Q ~(0) state close to that of metallic Si. From these results we conclude that the present silicon suboxides obtained by co-milling silica with POL are closer to those defined as a random bonding model of SiO, than a random mixture model, the former being unachievable by a thermal process. The main mechanism of the present solid-state reduction is the oxygen abstraction from the SiO _(4) units by the polarized POL, with its simultaneous oxidative decomposition up to the state of carbon. The reaction process is simple and scalable so that it may offer a new affordable fabrication method of silicon suboxides.
机译：氧化数低于最高的金属氧化物通常表现出有吸引力的功能特性。然而，稳定氧化物的常规化学还原或热还原通常很费力，并且不能在适当的还原水平下停止。因此，我们在这里尝试探索固态的非常规还原过程，而无需外部加热。通过将气相二氧化硅纳米颗粒与聚烯烃（POL）（即聚丙烯（PP）或聚乙烯（ PE）和一种含氟的聚偏二氟乙烯（PVDF）。我们主要通过Si2p XPS光谱和〜（29）Si MAS NMR检验了Si的电子和配位态。它们与通过热途径获得的类似商品明显不同。从〜（29）Si MAS NMR的化学位移作为SiO _（2）还原度的判据，POL作为还原剂的功能顺序为PP≈PE> PVDF。由于当前的固态反应没有形成不稳定的气态SiO作为中间产物，因此产物中的Q-（0）状态的Si组分接近于金属Si的Si组分。根据这些结果，我们得出结论：与无规混合模型相比，通过将二氧化硅与POL共研磨二氧化硅获得的低氧化硅更接近于SiO的无规键合模型，而前者是无法通过热处理获得的。目前的固态还原的主要机理是通过极化POL从SiO_（4）单元中提取氧，同时氧化分解到碳的状态。该反应过程是简单且可扩展的，因此它可以提供一种新的，负担得起的低价氧化硅制造方法。

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