Study On Controllable Treatment And Hydrophobic Modification Of Coatingsof SiC@SiO₂Nanocable

In this paper, the controllable treatment and hydrophobic modification of SiO2coatings of SiC@SiO2nanocables were studied. Firstly, the controllable treatment ofcoatings of SiC@SiO2nanocables were carried out by calcine method and solutionapproach, respectively. In terms of calcine method, calcine temperature and calcinetime, which played a significant role in the controllable treatment of SiO2coatings ofSiC@SiO2nanocables, were considered. The SiO2layers were almost removed for8hat1300℃. Unfortunately, the SiO2coatings could not be controlled in the process ofcalcination. However, We reported a controllable treatment process of SiC@SiO2nanocables in the solution, which is simple, highly efficient, low cost andenvironment-friendly. It illustrated that not only SiC nanowires withthickness-controlled SiO2coating layers but also highly purified SiC nanowires couldbe achieved. Furthermore, the reasonable reaction mechanism was proposed toelucidate the removing process of SiO2shell. And the two-phase reaction kineticequation was deduced. In addition, the accuracy of the equation was further verifiedby means of the experimental result. It is very important that the equation not onlycould provide the guidelines for achieving the thickness-controlled SiO2shell but alsolaid the foundation for the broader application of the SiC nanowires withthickness-controlled SiO2coatings and highly purified single-crystalline SiCnanowires in different fields. In addition, SiC nanowires coated with amorphous SiO2shell of different thickness and purified SiC nanowires show apparent emission peaks,which indicate that the SiC nanowires coated with an optimized SiO2thickness (3.03nm) have more excellent photoluminescence property than the bare SiC nanowiresand thicker SiO2-coated SiC nanowires.Furthermore, the hydrophobic modification of the residuals of preparingSiC@SiO2nanocables was carried out using KH570, Si69and FAS as modifiers respectively. In the process of modification, the volume fraction of modifier,modification time and modification temperature, which played a significant roles inthe effect of hydrophobic modification of product surfaces, were investigated,respectively. After modification, the mechanism of the surfaces of residuals exhibitinghydrophobicity was discussed in detail. With the index of contact angle, the optimumtechnological parameters of hydrophobic modification were selected by conditionalexperiments. The results indicated that the maximum contact angle (107°) of theresiduals was achieved under the optimum technological parameters (the volumefraction of modifier (KH570):2%, modification temperature:1h, modification time:60℃). The maximum contact angle (112°) of the residuals was achieved under theoptimum technological parameters (the volume fraction of modifier (Si69):1%,modification temperature:3h, modification time:55℃). And the maximum contactangle (134°) of the residuals was achieved under the optimum technologicalparameters (the volume fraction of modifier (FAS):1%, modification temperature:12hand modification time:20℃).Finally, the hydrophobic modification of SiC@SiO2nanocables was carried outusing FAS as modifiers. In the process of modification, modification time andmodification temperature, which played a significant roles in the effect ofmodification of product surfaces, were investigated in detail. With the index ofcontact angle, the optimum technological parameters of hydrophobic modificationwere selected by conditional experiments. The maximum contact angle (153°) of theSiC@SiO2nanocables was obtained under the optimum technological parameters (thevolume fraction of modifier:1%, modification time:24h and modificationtemperature:25℃). Moreover, it was found that SiC@SiO2nanocables surfaces weretransformed from super-hydrophilicity to super-hydrophobicity. And the resultsrevealed that the super-hydrophobic surfaces had long-term stabilities. Notably, therewas almost no change in the morphology, microstructure and crystalline ofSiO2-coated SiC nanowires before and after super-hydrophobic treatment. In addition,the mechanism of the SiO2-coated SiC nanowire surfaces showing thesuper-hydrophobic behavior was interpreted and analysed specifically. Consequently,we believed that the technique would make it possible to achieve large-scaleproduction of the super-hydrophobic SiO2-coated SiC nanowires in new industrialapplications.