An IR spectroscopic study of amorphous silicas

Isahakyan, Anna; Beglaryan, H. A.; Pirumyan, P. A.; Papakhchyan, L. R.; Zulumyan, N. H.

doi:10.1134/s0036024410121015

Cited by 14 publications

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“…On the other hand, strengthening of unsatur ated Si-O bonds in siloxane bridges formed under low temperature conditions occurs within the same temperature range of (950-1050°C) [15,16]. For this reason, in our view, when the rock is heated within this temperature range, simultaneous dehydration and talc crystal lattice destruction are accompanied by strengthening of unsaturated Si-O bonds and the for mation of enstatite.…”

Section: Resultsmentioning

confidence: 74%

The influence of mechanical treatment on the silicate network of talc

Zulumyan

Papakhchyan

Isahakyan

et al. 2012

Russ. J. Phys. Chem.

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INTRODUCTIONIt is known that, the most usual paragenetic talc forms finally produced in the process most often called steatitization are hydrothermally changed ultrabasic minerals and silica dolomites that underwent low stage thermal metamorphism [1]. It was found for many occurrences that steatitization, which follows serpentization, is a result of silicization and carboniza tion of serpentines or the transfer of СО 2 into them [1, p. 151; 2, p. 8]. It is therefore quite natural that, when these processes occur, silicate networks of serpentines, largely unchanged, become the anionic component of talc crystalline structure. Therefore, the peculiarities revealed in serpentines [3] should to a certain degree be inherent in talc.Serpentine peculiarities are first of all Si-O bonds with unusual strengths present in "hexagonal" rings of SiO 4 tetrahedra in silicate networks [3]. If siloxane bridges are formed at comparatively low temperatures (below 500°C), the bonds which form in them are inferior in strength to Si-O bonds of metasilicate chains passed into the silicate layer from primary ultrabasic minerals. Just the presence of such Si-O bonds which differ in electronic saturation in silicate networks of minerals causes their destruction under mechanical treatments (mechanoactivation) and also upon heating, when, starting from 400°C, the dehy dration of serpentines is accompanied by the destruc tion of their crystal lattices [3][4][5][6][7][8]. The degree and character of the destruction of silicate networks which result in different ratios between isolated ortho , oligo , and polysilicate components formed depends on both the ratio between primary ortho and metasil icate anions, which participated in the formation of serpentine silicate networks, and their distribution in silicate layers [9]. Note also the direct role played by hydroxyls, because the breakage of weak Si-O bonds is closely related to the detachment and formation of hydroxyl water [3].The talc silicate network is mainly borrowed from serpentine (Mg 6 [Si 4 O 10 ](OH) 8 ). It is therefore quite natural that the above reasoning concerning the spe cial features of serpentine silicate networks with cer tain restrictions imposed by the structure of talc (Mg 3 [Si 4 O 10 ](OH) 2 ) relates to talc silicate networks. It follows that it is quite reasonable to study the influence of mechanical treatment on talc silicate networks using the physicochemical approach applied to ser pentinites [3]. The results can be compared with the data on serpentinites.In view of this, the purpose of this work was to per form a physicochemical study of thermally treated and mechanically activated talc and quantitatively deter mine magnesium, silicon, etc. compounds extracted from thermally treated and mechanically activated samples using a new approach to acid treatment of ser pentinized minerals [10,11]. EXPERIMENTALWe performed chemical analysis of two different talc samples, Russian (I) and Taiwan (II). Their chem ical composition is given in Table 1.For mechanical activat...

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Section: Resultsmentioning

confidence: 74%

The influence of mechanical treatment on the silicate network of talc

Zulumyan

Papakhchyan

Isahakyan

et al. 2012

Russ. J. Phys. Chem.

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“…IR spectra of sample of fly ash (without thermal treatment) and fly ash samples annealed at 1000, 1100, 1200, and 1300 • C (FA, FA_1000, FA_1100, FA_1200, and FA_1300) are shown in Figure 1. The most intensive band at 1070 cm -1 has two spectral shoulders observed on the side The spectra of all FA samples are very similar and exhibit spectral bands characteristic for the vibration of the Si-O bond in SiO 4 tetrahedra and the Al-O bond (both in AlO 4 tetrahedra and AlO 6 octahedra) [1,23,[25][26][27][28][29][30][31][32][33][34][35].…”

Section: Ir Spectroscopymentioning

confidence: 93%

Infrared and Raman Spectroscopy of Mullite Ceramics Synthesized from Fly Ash and Kaolin

Ritz

2023

Minerals

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Infrared spectroscopy and Raman spectroscopy were used to characterize mullite ceramics prepared from fly ash and kaolin by annealing at 1000 °C, 1100 °C, 1200 °C, and 1300 °C. IR spectroscopy confirmed the presence of SiO4 tetrahedra and AlO6 octahedra in samples. The presence of mullite has been confirmed at all temperatures. The presence of quartz has been confirmed up to a temperature of 1100 °C, and the presence of an amorphous form of SiO2 has been confirmed at temperatures of 1200 °C and 1300 °C. The transformation of quartz into the amorphous form of SiO2 at temperatures above 1100 °C is assumed. Transformation was performed on the percentage intensity decrease of the bending vibration of Si-O-Si (at about 450 cm−1) and Al-O-Si (at about 550 cm−1). Raman spectroscopy confirmed the presence of mullite at different stages of structural ordering (a well-ordered structure at a temperature of 1100 °C and a disordered structure at a temperature of 1300 °C).

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“…However, a new approach to the acid treatment of thermally treated serpentines (Mg(Fe)) 6 [Si 4 O 10 ](OH) 8 made it possible to obtain amorphous silica that strongly differs in its specifi c structural features from the known conventional forms of SiO 2 and can signifi cantly simplify the process of obtaining β-wollastonite [18,19].…”

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Synthesis of β-wollastonite on the basis of silica formed from silicate layers of serpentine

et al. 2015

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Two-stage method for synthesis of β-wollastonite via reaction of calcium hydroxide and silica formed from silicate layers of serpentine and calcination of the resulting compounds was examined. It was found that the specifi c structural features of the silica used for this purpose make it possible to avoid a many hours' autoclave treatment and obtain such amorphous calcium hydro-and hydroxo-silicates that are converted under annealing, beginning at 800-810°C, to β-wollastonite by mixing a suspension of Ca(OH) 2 , SiO 2 , and H 2 O heated to its boiling point under atmospheric pressure. The optimal synthesis parameters, molar ratio of the starting substances and agitation duration, are determined.

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An IR spectroscopic study of amorphous silicas

Cited by 14 publications

References 1 publication

The influence of mechanical treatment on the silicate network of talc

The influence of mechanical treatment on the silicate network of talc

Infrared and Raman Spectroscopy of Mullite Ceramics Synthesized from Fly Ash and Kaolin

Synthesis of β-wollastonite on the basis of silica formed from silicate layers of serpentine

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