Mössbauer and magneto-chemical study of solids formed by surface chemical reaction of OH–silica groups with iron diacetylacetonato chloride (C5H7O2)2FeCl

Смирнов, В. М.; Zemtsova, E. G.; Ivanov, E. B.; Osmolowsky, M. G.; Семенов, В. Г.; Murin, I. V.

doi:10.1016/s0169-4332(02)00537-8

Cited by 10 publications

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“…Smirnov et al [45] revealed an orienting surface effect on parallel spin ordering in an Fe 3+ ]. Experimentally, FR was only observed in high-purity samples after three to five impacts of a shot-filled hammer (after the first impact, FR was only detected in very plastic NH 4 I), which ensured shock compression of the powders and formation of grain boundaries.…”

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Ultrafast mechanochemical synthesis of mixed oxides

Zyryanov

2005

Inorg Mater

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Based on experimental data on the structure of disordered milling products in MO-M'O 3 systems, a theory is proposed for ultrafast mechanochemical synthesis in oxide systems, considered as a threshold process. The key points of the theory are (1) the development of a transient dynamic state ( D )* in contact regions via mass transfer by the roll mechanism in primary loading events and the formation of rotation regions ( D )* 2 in secondary events; (2) the formation of ordered reaction products supersaturated with vacancies as a result of the relaxation of the ( D )* and ( D )* 2 states under unloading and quenching conditions; (3) the formation, as a result of secondary events, of a nanocomposite through mechanochemical equilibrium due to diffusion between the ordered and disordered states of different compositions; and (4) rapid charge separation and recombination, leading to reduction of oxides during milling concurrently with the disintegration of particles and mechanochemical interactions. The principal factors influencing the dynamics of mechanochemical synthesis (established by linearizing the dependence of the chemical response of the system on mechanical load) are the molecular weight of the simple oxides involved, the enthalpy of the reaction, and the difference in Mohs' hardness between the reactants. The typical structures of mechanochemical synthesis products (solid solutions) are stable to disordering and compositional changes. The theory is supported by the trimodal mechanochemical synthesis rate distribution for mixed oxides and the mechanically induced electron-hole ferromagnetism. Ways of controlling the dynamics of mechanochemical synthesis and the structure of the products are discussed.

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confidence: 99%

Ultrafast mechanochemical synthesis of mixed oxides

Zyryanov

2005

Inorg Mater

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“…The common method of generation of Cl groups on the inorganic matrix surface (for instance, silica) is reaction (1) with ССl 4 , vapor at 200-400°С in dry argon stream [3].=Al-OH + CCl 4 > =Al-Cl + HCl + COCl 2 .In the case of γ-Al 2 O 3 at 200-500°C, the chlorinetion of the surface according to reaction (2) was accompanied by condensation of the dispersed carbon particles on the matrix surface. Depending on the treatment duration and the process temperature, the samples containing 0.3 to 3 wt % of carbon were prepared.…”

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“…The presence of carbon was confirmed by energy-dispersive X-Ray microanalysis; the elemental analysis data and the surface mapping revealed that carbon was quite evenly distributed at the pellet chip surface. The highest carbon condensation level was observed at 500°С.Heterogeneous reactions were performed using the previously described gas phase installation [3], in the dry argon stream (residual moisture content 0.5-1 mg H 2 O/m 3 ). The surface of γ-Al 2 O 3 (70 m 2 /g, pores diameter 5.7 nm), was hydrated by boiling in distilled water.…”

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“…Heterogeneous reactions were performed using the previously described gas phase installation [3], in the dry argon stream (residual moisture content 0.5-1 mg H 2 O/m 3 ). The surface of γ-Al 2 O 3 (70 m 2 /g, pores diameter 5.7 nm), was hydrated by boiling in distilled water.…”

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confidence: 99%

“…The common method of generation of Cl groups on the inorganic matrix surface (for instance, silica) is reaction (1) with ССl 4 , vapor at 200-400°С in dry argon stream [3].…”

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Formation of dispersed carbon in the course of chlorination with CCl4 vapor of γ-Al2O3 surface

2013

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The =Al-Сl surface groups of γ-Al 2 O 3 are known as more reactive towards the nucleophilic agents (water, alcohols) than the =Al-ОН groups [1,2]. The common method of generation of Cl groups on the inorganic matrix surface (for instance, silica) is reaction (1) with ССl 4 , vapor at 200-400°С in dry argon stream [3].=Al-OH + CCl 4 > =Al-Cl + HCl + COCl 2 .In the case of γ-Al 2 O 3 at 200-500°C, the chlorinetion of the surface according to reaction (2) was accompanied by condensation of the dispersed carbon particles on the matrix surface. Depending on the treatment duration and the process temperature, the samples containing 0.3 to 3 wt % of carbon were prepared. The presence of carbon was confirmed by energy-dispersive X-Ray microanalysis; the elemental analysis data and the surface mapping revealed that carbon was quite evenly distributed at the pellet chip surface. The highest carbon condensation level was observed at 500°С.Heterogeneous reactions were performed using the previously described gas phase installation [3], in the dry argon stream (residual moisture content 0.5-1 mg H 2 O/m 3 ). The surface of γ-Al 2 O 3 (70 m 2 /g, pores diameter 5.7 nm), was hydrated by boiling in distilled water. The content of OH groups was determined by differential thermal analysis using the DTA-500 device. The energy-dispersive X-Ray microanalysis was performed with Supra 40 VP X-ray emission microscope equipped with the INCA X-art attachment; Co was used as reference. ACKNOWLEDGMENTSThis work was financially supported by the Russian Foundation for Basic Research (project no. 11-03-00099-a). REFERENCES 1. Smirnov, V.M., Russ. J. Gen. Chem., 2002, vol. 72, no. 4, p. 590

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