Hydrothermal reactions of γ-dicalcium silicate

Speakman, K.; Taylor, H. F. W.; Bennett, Jennifer M.; Gard, J. A.

doi:10.1039/j19670001052

Cited by 31 publications

(20 citation statements)

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“…The results are almost the same as those reported byBell et al" The results (XRD, "Si NMR, TG-DTA, and IR) show that the synthesized specimen is phase pure and its ion constitution is expected to be Ca,(Si,O,)(OH),, as suggested byTaylor et a[. ',(2) Thermal Decomposition (A) SEM, XRD, and TG: The specimens were heated at 300", 400", SOW, 550°, 600", 800", IOOO", and 1200°C in an electric furnace for 1 h.…”

supporting

confidence: 87%

Thermal Decomposition of Tricalcium Silicate Hydrate

Okada

Ishida²,

Mitsuda

1994

Journal of the American Ceramic Society

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C,SH,, can be prepared in stirred suspensions using lime and silicic acid with CdSi = 3.0 for 14 days at 270°C under saturated steam pressure. The C,SH,,5 which forms consists of long, fibrous or prismatic aggregates having a specific surface area of 14.0 m'/g. The specimen gives an average CdSi ratio of 2.98 (29 crystals) and lattice parameters of a = 1.00291(8) nm and c = 0.74842(11) nm by ATEM and XRD examinations, respectively. NMR examination confirms the existence of dimer silicate anions in C,SH,,s, suggesting the possible composition Ca,(Si,O,)(OH),. Upon being heated, C,SH,,5 dehydrates at 520-550°C with a sharp endothermy and decomposes to CaO plus a calciochondrodite-like phase, which on further heating dissociates, with a gradual weight loss, to a;-C,S with CaO at 800°C. The intermediate calciochondrodite-like phase has low crystallinity, but zgSi MAS NMR and infrared spectra identical for highly crystalline calciochondrodite. CPMAS measurements indicate the possibility that the calciochondrodite-like phase contains both protonated and unprotonated monosilicate anions. The amount of CaO which forms through the two-step process agrees with the calculated values from the stoichiometry of decomposition: [Ca,(Si,O,)(OH),] + [Ca,(SiO,),(OH),] + CaO + 2H,O + a;-(Ca,(SiO,) + 2Ca0 + H,O.

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supporting

confidence: 87%

Thermal Decomposition of Tricalcium Silicate Hydrate

Okada

Ishida²,

Mitsuda

1994

Journal of the American Ceramic Society

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“…Most astonishing, the structure of kilchoanite was not known in detail at this time but was only solved five years later by Taylor (1971). The structural predictions for Ca 8 Si 5 O 18 by Bennett et al (1966) and Speakman et al (1967) are based on similarities of the X-ray powder patterns and periodicities of selected-area electron diffraction patterns resembling both γ-Ca 2 SiO 4 and kilchoanite. With the solved structure of kilchoanite, Taylor (1971) produced also a sketch of the Ca 8 Si 5 O 18 structure.…”

mentioning

confidence: 96%

“…In addition, Speakman et al (1967) concluded that Ca 8 Si 5 O 18 is not an equilibrium product at any condition, and that Ca 8 Si 5 O 18 has an interstratified structure composed of alternate layers of kilchoanite and γ-Ca 2 SiO 4 (calcio-olivine). Most astonishing, the structure of kilchoanite was not known in detail at this time but was only solved five years later by Taylor (1971).…”

mentioning

confidence: 97%

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Pavlovskyite Ca8(SiO4)2(Si3O10): A new mineral of altered silicate-carbonate xenoliths from the two Russian type localities, Birkhin massif, Baikal Lake area and Upper Chegem caldera, North Caucasus

Galuskin¹,

Gfeller²,

Savelyeva³

et al. 2012

American Mineralogist

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The new mineral pavlovskyite Ca 8 (SiO 4 ) 2 (Si 3 O 10 ) forms rims together with dellaite Ca 6 (Si 2 O 7 )(SiO 4 ) (OH) 2 around galuskinite Ca 7 (SiO 4 ) 3 CO 3 veins cutting calcio-olivine skarns in the Birkhin gabbro massif. In addition, skeletal pavlovskyite occurs in cuspidine zones of altered carbonate xenoliths in the ignimbrites of the Upper Chegem caldera (North Caucasus). The synthetic analog of pavlovskyite has been synthesized before and is known from cement-like materials. Isotypic to pavlovskyite is the synthetic germanate analog Ca 8 (GeO 4 ) 2 (Ge 3 O 10 ). The crystal structure of pavlovskyite, space group Pbcn, a = 5.0851(1), b = 11.4165(3), c = 28.6408(8) Å, V = 1662.71(7) Å 3 , Z = 4, has been refined from X-ray single-crystal data to R1 = 3.87%. The new colorless mineral has a Mohs hardness of 6-6.5, biaxial (-), α = 1.656(2), β = 1.658(2), γ = 1.660(2) (589 nm), 2V (meas) = 80(5)°, 2V (calc) = 89.9°, medium dispersion: r > v, optical orientation: X = b, Y = c, Z = a.For comparison with pavlovskyite, the crystal structure of kilchoanite Ca 6 (SiO 4 )(Si 3 O 10 ) from the Birkhin massif [space group I2cm, a = 11.4525(2), b = 5.0867(1), c = 21.996(3) Å, V = 1281.40(4) Å 3 , Z = 4] has been refined from single-crystal X-ray data to R1 = 2.00%.Pavlovskyite represents a 1:1 member of a polysomatic series with calcio-olivine γ-Ca 2 SiO 4 and kilchoanite Ca 6 (SiO 4 )(Si 3 O 10 ) as end-member modules. The structure is characterized by strongly folded trisilicate units (Si 3 O 10 ) interwoven with a framework of CaO 6 and CaO 8 polyhedra. Olivine-like slices with orthosilicate groups are interstratified with the characteristic trisilicate module of Ca 4 (Si 3 O 10 ) composition. Although the optical properties of pavlovskyite and kilchoanite are similar, both minerals can be distinguished by chemical analyses (different Ca/Si ratio), X-ray diffraction, and Raman spectroscopy. The new mineral is named after V.E. Pavlovsky , an outstanding geologist in the area of Eastern Siberia, in particular of the Baikal region.

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“…In addition, there are some reports by Taylor and others on the topotactic reaction of γ-C 2 S (Speakman et al (1967);Taylor 1971;Buckle et al 1958). These reports show that hydrothermal reaction of γ-C 2 S at 180°C for 72 hours (3 days) to 10 days, leads to formation of calcio-chondrodite (Ca 5 (SiO 4 ) 2 (OH) 2 , Ca-O average interatomic distance: 0.2370nm), Ca 8 (SiO 4 ) 2 (Si 3 O 10 ), and kilchoanite (Ca 6 (SiO 4 ) (Si 3 O 10 ), average Ca-O interatomic distance: 0.2401nm) via topotactic reaction.…”

Section: Mechanisms Of Vaterite Formation Due To Carbonation Of γ-C 2 Smentioning

confidence: 99%

Carbonation of γ-Ca<sub>2</sub>SiO<sub>4</sub> and the Mechanism of Vaterite Formation

Saito

Sakai

Morioka

et al. 2010

ACT

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The carbonation of γ-Ca 2 SiO 4 (γ-C 2 S) and mechanism of vaterite formation have been investigated by evaluating the crystal structures of both γ-C 2 S and vaterite. The samples used were autoclaved calcium silicate hydrate hardening bodies prepared from Ordinary Portland Cement (OPC), γ-C 2 S and α-quartz and then subjected to accelerated carbonation. The ratio of OPC to γ-C 2 S was varied. Ca 2+ in both γ-C 2 S and vaterite was found to be coordinated to six O 2-. In addition, both γ-C 2 S and vaterite have similar atomic arrangements of O 2-and Ca 2+ and Ca-O bond distances. Therefore, it is proposed that vaterite mainly forms from γ-C 2 S via a topotactic reaction during accelerated carbonation.

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Hydrothermal reactions of γ-dicalcium silicate

Cited by 31 publications

References 0 publications

Thermal Decomposition of Tricalcium Silicate Hydrate

Thermal Decomposition of Tricalcium Silicate Hydrate

Pavlovskyite Ca8(SiO4)2(Si3O10): A new mineral of altered silicate-carbonate xenoliths from the two Russian type localities, Birkhin massif, Baikal Lake area and Upper Chegem caldera, North Caucasus

Carbonation of γ-Ca<sub>2</sub>SiO<sub>4</sub> and the Mechanism of Vaterite Formation

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