Papers by Keyword: Mechanochemistry

Abstract: The process of mechanically activating chemical bonds usually involves applying external force. Since mechanical chemistry can be performed without solvents or with minimal amounts of solvent (catalytic quantities), it has become an imperative synthetic tool in multiple fields (e.g., physics, chemistry, and materials science) and is an attractive greener method for preparing diverse molecules. Catalysis, organic synthesis, solid-state medicinal preparation, metal complex synthesis, and many other chemistry fields have benefited from sustainable methods. The purpose of this paper is to shed light on the benefits of using mechanochemical methods to produce a pharmaceutical crystal that is composed of dendrimer nanocrystals. Consequently, we describe and examine the importance of mechanical procedures in forming dendrimers and pharmaceutical crystals in this review.

Abstract: Application of modern ways of ceramic materials’ consolidation and association of synthesis methods of organic and inorganic chemistry, sol-gel method and mechanochemistry, allowing to control processes of synthesis of the defined phases at molecular level, gives the chance to create highly effective composite materials. It is known that properties of composites on the basis of refractory compounds become dimensionally dependent at reduction of the particles’ size to several interatomic distances in one, two or three dimensions . Obtaining of durable nanostructural ceramics on the basis of ZrO₂ with substantial increase of mechanical properties can be realized by creation of material with fine homogeneous structure, on the basis of powders of nonoxygen compounds when strength properties and crack resistance increase at creation of –intra and –inter nanostructures. In work results of creation of the consolidated nanomaterials and composite ceramics with usage of the peculiarities set forth above for synthesis of precursors of powders and the defined phases that self-reinforce ceramic matrixes have been presented.

Abstract: The problems of ore mill tailings disposals and eco-economic efficiency of their use are considered. The paper provides the fundamentals of geo-mechanical control of the rock mass by low-strength solidifying mixtures of recyclable tailings. The essence and results of mechanochemical experiments on non-ferrous, ferrous metals and coal tailings are considered. A model to determine the economic and environmental efficiency of this technology is developed.

Abstract: Highly-crystallized fine LiMn₂O₄ powders have been synthesized by a combination of the mechanochemical (MC) and solvothermal (ST) treatments of LiOH and MnO₂ in Acetone. The MC product is amorphous, but, shows the formation of Mn-O-Li bond. The ST post treatment promotes the nucleation of LiMn₂O₄ by the chemical reduction of Mn⁴⁺ to Mn³⁺. The estimated chemical compositions are LiMn (III)_0.11Mn (IV)_1.89O_4.45 (MC) and LiMn (III)_0.76Mn (IV)_1.12O_3.88 (MC/ST). The MC/ST powder crystallized at 800°C indicates the cell capacity of 119mA.h.g^-1. The dilution of Acetone with Tetrahydrofuran is effective to reduce the particle size. The MC/ST product using the diluent shows the fine particle size of 150nm and the excellent cell capacity of 134mA.h.g^-1.

Abstract: Mechanochemical (MC) processes are often modified to a large extent with use of process control agents (PCAs). An appropriate PCA is, however, chosen semi-empirically for any MC process such as ball-milling. In this study, milling period and medium, PCA kinds and amount, and powder kinds, are altered as major parameters to systematically and mechanistically investigate the effect of PCAs on powder milling and the related phenomena. The model systems selected are TiO₂ and ZnO powders with various PCAs including alkanes, alcohols, water, and a few ionic liquids. According to X-ray line broadening analyses the viscosity and the structure of PCA molecules strongly affect the MC process. In addition, the MC process for harder TiO₂ is quite different from ZnO, and oxygen-derived polarity of PCA molecules would cause major difference on the milling behavior. Various parameters controlling the MC process will be discussed.

Abstract: This paper considers the mechanochemical synthesis of advanced electroceramic material with a perovskite structure as well as this method as an effective way for modifying the properties of BaTiO₃ by substitution of foreign ions. Dielectric properties mainly para-ferroelectric phase transitions in Ba_1-xSr_xTiO₃ solid solutions (0.0 x 0.6) are presented.

Abstract: A new method of sorbent activation by its mechanical grinding directly in the purified gas medium promises a technological breakthrough in the field of manufacturing and using of high purity gases. Simple design solutions and using reactive alloys as a sorbent allow making the gas purification process controllable and reducing the cost of this process by many times as well as reducing the concentration of the impurity in the end product.

Abstract: The efficiency of using in the charge of SHS-mixtures wollastonite “active” additives of micron size activated and modified by different organic compounds as a result of mechanochemical treatment(MCT) is considered. The structure, composition and morphology of modified particles of wollastonite depending on the conditions of MCT in mills-activators of dynamic action are studied. During SHS of composition metal-oxide materials, wollastonite particles play the role of the centre of the mixture combustion site, provide the local increase of temperature, change thermodynamic characteristics of the sample synthesis process as a whole and contribute to formation of nanostructurized SHS-ceramics with high strength and dielectric characteristics.

Abstract: To improve the dispersion of phthalocyanine blue powder, decrease its consumption and increase the use value of talc, TPBCP (Talc / Phthalocyanine Blue Composite Powder) was prepared by liquid phase mechanochemical method. By means of paint performance test, scanning electron microscopy (SEM) and fourier transform infrared spectroscopy (FT-IR), the properties and microstructure of composite powder were characterized. The hiding power and oil absorption value of talc/phthalocyanine blue composite powder were 12.88 g/m2 and 32.50 g/100g respectively, and the International Commission on Illumination (CIE) colorimetric data L, a, and b were 44.95, 1.65 and -17.18 respectively. It was equivalent for the hiding power of composite powder to 77.6% of that of pure phthalocyanine blue with a equivalent CIE. The formation of TPBCP was marked by phthalocyanine blue particles uniformly coated on talc surface. The results showed that TPBCP had similar performances with phthalocyanine blue and could instead of phthalocyanine blue to be applied in several fields.

Abstract: Mg-Al layered double hydroxide was synthesized by the method of mechanochemistry /crystallization at the dry milling time of 6 h, wet milling time of 2 h, milling speed of 250 r/min, and ball to powder weight ratio of 50 to 1 using brucite, Al(OH)₃ and Na₂CO₃ as the raw materials. Characterizations of the materials were achieved by XRD, TEM, FT-IR and TG-DSC. The results showed that well crystallized Mg-Al LDH with average partical size of 40 nm were synthesized under this condition. Mg-Al LDH was formed with CO₃^2- freely intercalated between the hydroxide host layers. The material generally decomposed via two distinct stages. The first stage at 229.5 °C was attributed to the loss of interlayer water, and the second stage at 407.8°C was due to the loss of hydroxyl groups from the brucite-like layer, as well as of the carbonate irons.