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Abstract  

Mechanochemical treatment (MChT) in various media (water, air, ethanol) of the V2O5/ammonium dimolybdate composition at the ratio V:Mo = 0.7:0.3 has been carried out. Physicochemical transformations in this system have been studied by means of X-ray powder diffraction (XRD) and thermal analysis as well as FTIR spectroscopy. Ammonium dimolybdate undergoes hydration with formation of 4-aqueous ammonium paramolybdate during the MChT in water. Changes of phase and chemical composition at activation are determined first of all by nature of medium in which milling was carried out. Maximal interaction of components occurs during modification of the studied system in water.

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Abstract  

The aim of this work was to compare the influence of organocations with different length of alkylammonium chain on the structural stability of clays towards mechanochemical treatment. An industrial product JP A030 (Envigeo, Inc., Slovakia) based on Jelšový Potok bentonite (Slovakia) and three organoclays prepared from this material via ion exchange with tetramethylammonium, octyltrimethylammonium and octadecyltrimethylammonium cations (TMA-JP A030, OTMA-JP A030 and ODTMA-JP A030, respectively) were ground for 1–20 min in a high-energy planetary mill. The products were investigated by X-ray diffraction analysis, thermal analysis, scanning electron microscopy and energy dispersive X-ray analysis. The long-chain organic cations apparently enhance the structural stability of bentonite during high-energy grinding.

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Abstract  

Calcination of sepiolite and of two sepiolite/CsCl mixtures, unground and air-ground was investigated by thermo-XRD-analysis. At 200 °C sepiolite, neat, mixed or air-ground with CsCl lost interparticle and zeolitic water. The framework of sepiolite persisted during the dehydration but became defected, mainly in the air-ground mixture, less in the unground mixture and little in the neat clay. At 500 °C, with the loss of bound water, the neat clay was folded and transformed into sepiolite anhydride. In sepiolite/CsCl mixtures the dehydrated variety persisted but the degree of crystal-imperfection increased in the air-ground mixture more than in the unground mixture. At 700 °C the neat clay remained crystallized, but the CsCl mixtures became amorphous. Some crystalline dehydrated sepiolite or sepiolite anhydride persisted in the unground and air-ground CsCl mixtures, respectively. At 850 °C, the neat clay crystallized into protoenstatite with some enstatite and clinoenstatite. The amorphous fraction of sepiolite in the unground sepiolite/CsCl mixtures crystallized into pollucite and forsterite and the crystalline fraction was transformed into enstatite, protoenstatite, and clinoenstatite. In the air-ground mixture, the amorphous phase was transformed into pollucite with some forsterite and the crystalline fraction into enstatite.

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Journal of Thermal Analysis and Calorimetry
Authors: E. Skwarek, S. Khalameida, W. Janusz, V. Sydorchuk, N. Konovalova, V. Zazhigalov, J. Skubiszewska-Zięba, and R. Leboda

of [ 10 , 11 ] indicated that milled oxides, including V 2 O 5 and MoO 3 , have improved catalytic properties. The perspectives of application of materials, activated via mechanochemical treatment, in electrochemical processes were noted in work

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With a complex of physico-chemical methods for analysis it is proved that in the course of mechanochemical treatment of a Syrian phosphorite and ammonium sulphate mixture new phases have been formed. The thermal analysis proves an increase in the reaction properties of the ammonium sulphate and the Syrian phosphorite which is a prerequisite for the increase in the content of P2O5 assimilated , in the activated phosphorite mixtures and the possibility to use them in the production of NP complex fertilizers.

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Abstract  

The applicability of mechanochemistry to produce uranium–lanthanoid mixed oxides is presented. Phase homogeneous uranium–cerium solid solutions of the type CexU1−xO2 (x = 0.3 ÷ 0.95) and polyphase systems containing LayU1−yO2+x (y = 0.12) were prepared by mechanochemical activation in air of sol–gel produced precursors. The possibility for synthesis of urania–lanthania solid solution by mechanochemical interaction of La2O3 with sol–gel produced U (IV,VI) oxide is established. The crystal structures of the obtained oxides before and after the mechanochemical treatment are analysed by the use of X-ray diffraction method. The size of the crystallites (8–16 nm), lattice parameters, crystallite strains and densities of the oxides are calculated by BRASS program for Rietveld calculation.

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Abstract  

The structure changes and the degree of reduction of U3O8 after mechanoactivation in agate and stainless steel vessels in different media are studied. Clearly expressed reduction of U(IV, VI) oxide, accompanied by oxygen release as a result of mechanochemical activation is observed. The highest degree of reduction is reached when mechanoactivation is performed in suspension with nonpolar organic solvents. The presence of acetaldehyde as a reducing agent did not cause valuable increase of the reduction process. Quantitative evaluation of the mechanochemically induced changes in the crystal structure of U3O8 is done. Decrease of the crystallite sizes of both the U3O8 and the reduced form, provoked by the mechanochemical treatment is observed for all the samples. No other uranium-contained compounds, formed during the mechanoactivation in the different media and mixtures were found.

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Abstract  

The thermal behaviour of mechanochemically treated kaolinite has been investigated under dynamic and controlled rate thermal analysis (CRTA) conditions. Ten hours of grinding of kaolinite results in the loss of the d(001) spacing and the replacement of some 60% of the kaolinite hydroxyls with water. Kaolinite normally dehydroxylates in a single mass loss stage between 400 and 600°C. CRTA technology enables the dehydroxylation of the ground mineral to be observed in four overlapping stages at 385, 404, 420 and 433°C under quasi-isobaric condition in a self-generated atmosphere. It is proposed that mechanochemical treatment of the kaolinite causes the localization of the protons when the long range ordering is lost.

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Abstract  

After mechanochemical treatment of multicomponent mixtures complex fertilizers containing nitrogen, phosphorous, potassium and sulphur (NPKS) with higher water capacity were obtained. As raw materials some solid wastes and ammonia and potassium sulfates were used. Due to the different ratio used, new solid phases in the mixtures are formed. New solid phases are confirmed by the stages and rate of mass changes and also by the thermal effects at different temperature ranges. New phases are also confirmed by using X-ray diffraction method. On the base of data obtained mechanism of chemical transformations is proposed. It was found that the kinetics of mechanical activated mixtures decomposition is significantly influenced by the time of treatment and proceeds in few stages. The results have shown that the soluble nutrients forms ratio and sorption capacity could be controlled by the initial components ratios and treatment conditions.

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Abstract  

Method for synthesis of UO2+x and uranium–thorium mixed oxides by using sol–gel method and mechanochemical activation is proposed. The synthesis of UO2+x and solid solutions with equal amount of metals or enriched to one of them is performed by external gelation process, thermal decomposition of the sol–gel products in air and subsequent mechanochemical activation in air in stainless steel vessels. The crystal structures of the obtained oxides before and after the mechanochemical treatment are analysed by the use of X-ray diffraction method. Quantitative phase analysis and calculations of the size of the crystallites, lattice parameters, and densities of the oxides are performed by BRASS program for Rietveld calculation. The proposed method leads to decrease of the lattice parameters and thus to higher density of the obtained oxides with crystallites size in the range of 12–16 nm.

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