Specific features of the formation of a porous structure in products of leaching of two-phase sodium borosilicate glasses in acid-salt solutions

Abstract

This paper reports on the results of an investigation into the influence of the addition of a KCl salt to an HCl acid solution on the leaching kinetics of two-phase sodium borosilicate glasses and on the structural parameters of the leaching products (porous glasses). The contributions from different molecular species of silica to its total amount in leaching solutions are evaluated using the kinetic spectrophotometric technique for determining silicon in the form of β -silicomolybdic heteropoly acid. It is revealed that the addition of the salt to the leaching acid solution leads to a fast polymerization process with the formation of weakly structurized silica gel.

Effect of leaching concentration and time on the morphology of pores in porous glasses

“…Here, the formation of the porous glass structure is associated with the polymerization of secondary silica. This process underlies the complex mechanisms of the coagulation and gelation of silica and can occur upon the collision of silica particles with a sufficiently low surface charge [16]. As shown in Fig.…”

“…In addition, the leaching conditions (i.e., acidic concentration, time of leaching and addition of basic solution) have also been investigated [5,6,9,[12][13][14][15][16]. It has been established that the hydrochloric acid (HCl) concentration and the leaching treatment time leads to the transformation of the micro-and mesoporous structure of porous glasses.…”

Influence of the composition of alkali borosilicate glass and leaching solution on the structure of nanoporous glasses

“…The analysis of the data obtained has revealed that the addition of KCl to the leaching solution in contact with alkali borosilicate glasses containing the additives K 2 O (NK-3) or K 2 O and PbO (NKS-1), as in the case of the glass without additives, results in a rapid polymerization with the formation of weakly structured silica. This can be clearly seen from a comparison of the data on the silica distribution over molecular forms [3] with the structural parameters of the porous glasses SHORT COMMUNICATIONS (Table 2). A considerable increase in the specific surface area of the nanoporous glasses is accompanied by the disappearance of the polymer forms of silica in the solution.…”

“…Glass samples in the form of polished disks 34.5 mm in diameter and 2 mm in thickness were suspended (immersed) by a platinum wire in acid solutions and leached without stirring in the course of boiling. The initial ratio of the glass surface area to the solution volume was 0.04 cm -1 , which provided a constant pH value of the solution during the experiment.In the solutions formed after through acid leaching of the samples, the kinetics of complex reactions with 1 This paper was presented at the Topical Meeting of the European Ceramic Society "Structural Chemistry of Partially Ordered Systems, Nanoparticles, and Nanocomposites," St. Petersburg, Russia, June 27-29, 2006. the participation of silica passed from the unstable phase of the glass into the solution was investigated according to the procedure described in [3,4]. The contribution from different molecular forms of silica to the total amount of this component in the solution was determined from the results of the kinetic spectrophotometric analysis for the presence of silicon in the form of β -silicomolybdic heteropoly acid (the error in the determination of the silicon content was ± 0.1 [5]).…”

“…The main factors that affect the distribution of secondary silica are the composition of the initial alkali borosilicate glass and leaching conditions, such as the temperature, composition, concentration, and pH of the acid solution. In our previous papers [2,3], it was shown that the presence of potassium chloride in the acid leaching solution leads to a rapid polymerization with the formation of weakly structured silica, which affects the packing of secondary silica.…”