| In this paper,a series of interesting phenomena have been discovered when repeating others’ experiments of fabricating the micro-nano hierarchical structure on the sodalime float glass surface by the hydrothermal method.Such as,the gel layer formed after the glass was hydrothermally treated at 180℃ for 24 h has the ability to absorb CO2 from air,and the dried gels have a multilayer structure.The thickness of the gel layer formed on the glass two sides is different.The thicker gel layer always appears on the glass surface air-side.Based on existing theories,it is difficult to give a reasonable explanation for the above hydrothermal corrosion behaviors of the sodalime float glass.In addition,the formation process of gels and the hydrothermal reaction process of glass are not clear at present,and the relevant research references are scarce.In the experiments,the glass was hydrothermally treated for different time.By comparing the physical and chemical characteristics before and after hydrothermal treatment of the reactants and the resultants,the formation process of the gel coatings on the glass surface and the hydrothermal reaction process of the glass are revealed.The results show that:(1)the gel layer formed when the glass hydrothermally treated at 180℃ for 24 h is composed of magnesium silicate hydrate(M-S-H)gels with nanoflake morphology and calcium silicate hydrate(C-S-H)gels with nanowire morphology.The ability of the gel layer to absorb CO2 from air is attributed to the intrinsic characteristics of C-S-H gels.The absorbed CO2 exists in the form of CO32" in the C-S-H gels,and the CO32-is further combined with Ca2+in the gels to form CaCO3 compound.(2)The difference between the gel layer thickness on the glass two sides,and the glass tin-side possessing a relatively high corrosion resistance,all of them can be attributed to the tin effect of float glass.During the forming process of float glass,the total amount of Sn2+diffused into the glass tin-side is higher than that of air-side because the glass tin-side is directly contact with the molten tin.These Sn2+ions coordinate tetradentately with the surrounded O2-,which improves the chemical stability of the glass tin-side through the"network supplement" effect.(3)The hydrothermal reaction of sodalime float glass has undergone ion exchange,etching,release and dissolution of ions,combination of ions,gelation and gel separation process.The ion exchange reaction between H+ionized by water molecules and Na+ in the glass network structure provides the required OH-for the etching reaction of glass.OH-attacks the glass network structure,and Ca2+,Mg2+and silicate ions are released.The released Mg2+ is dissolved in the etching solution at first,then Mg2+is combined with hydrosilicate ions and their compounds followed by precipitation on the glass surface to form M-S-H gel layer.Subsequently released Mg2+ions are mainly distributed in the M-S-H gel layer and the upper part of the etched layer.The released Ca2+can not dissolved on the etching solution after reaching the specific concentration,and it is mainly distributed in the etched layer.When the ratio of Ca2+to the alkaline earth metal ions in the gel layer of glass surface is relatively high,the C-S-H gels have a tendency to separate from the M-S-H gels.The M-S-H gels show a nanoflake micromorphology after drying,and the C-S-H gels show a nanowire micromorphology after drying.The hydrothermal corrosion behavior and reaction process of sodalime float glass in 0.06 mol/L sodium citrate solution are also studied in this paper.The results show that:(1)The etching solution contained sodium citrate is moderately alkaline after 6 h hydrothermal treatment with the glass,and its pH value is higher than that of the pure water etching solution.(2)The moderately alkaline etching solution promotes the hydration degree of the released siliceous ions and inhibits the dissolution of hydrosilicates.The majority of hydrosilicates are involved in the formation of gels.(3)At the initial stage of hydrothermal reaction,the citrate ions in the etching solution can coordinate with Mg2+and Ca2+ exposed on the glass surface.This characteristic may make the vector direction of OH-attacking on the glass surface change with the progress of hydrothermal reaction,and finally result in the nanoporous morphology of the etched layer.(4)The citrate ions in the etching solution are involved in the formation of the M-S-H gel layer on the glass surface after the sodalime float glass was hydrothermally treated at 180℃ for 24 h in sodium citrate solution.There is no nanowire layer with C-S-H gel as the main component after the sample was dried.This is attributed to the high pH value of the etching solution,which reduces the migration rate and dissolution rate of hydrosilicates,and thus restricts the formation of C-S-H gel layer.On the other hand,another reason may be that the coordination between citrate ions and alkaline earth metal ions on the glass surface reduces the OH-etching rate.In this paper,it is found that a kind of abrasion-resistant micro-protrusion can be constructed on the glass surface by hydrothermal corrosion with pure water,while a kind of nanoporous structure can be constructed on the glass surface by hydrothermal corrosion with sodium citrate solution.Based on the micro "armor" structure constructed by hydrothermal corrosion with pure water,an abrasion-resistant micro-nano hierarchical structure has been successfully fabricated on the glass surface by a two-step hydrothermal corrosion method through process exploration.This method can be used as a supplement to embossing-CVD method to fabricate abrasion-resistant micro-nano hierarchical structure on the surface of special-shaped glass.In this paper,sandblasted sodalime float glass is used as raw material,and an abrasion-resistant hierarchical structure with micro-submicro-nano scales has been fabricated on the sandblasted glass surface by a two-step hydrothermal corrosion method.After 1,000 cycles of rigorous abrasion,the surface of the obtained sample can still maintain a certain hierarchical structure,and the water contact angle of the hydrophobilized sample can reach more than 130° after 1,000 cycles abrasion. |
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