Effect Of Mechanochemical Treatment Research Articles

Synthesis and modification of Ce-Zr oxide compositions as photocatalysts

In the paper, Ce-Zr oxide compositions were prepared using the coprecipitation and mechanochemical mixing methods of the initial precipitated oxides CeO2 and ZrO2. The effects of mechanochemical treatment (MChT), hydrothermal treatment (HTT) and microwave treatment (MWT) on the structure and physicochemical properties of the obtained samples were investigated. The obtained materials were characterized using the N2 adsorption/desorption, XRD, thermogravimetry (TG, DTA) and UV–vis/DRS, XPS methods. The photocatalytic properties of the prepared materials were tested as the rhodamine B degradation under visible light. Moreover, their mechanocatalytic activity was investigated. As a result of mechanochemical, hydrothermal and microwave treatment, almost all the obtained materials were characterized by a larger specific surface area. The use of both hydrothermal and microwave treatments of the wet gel resulted in the formation of the solid solution CeO0,2ZrO0,8O2. The obtained samples exhibited an increased photo- and mechanocatalytic activity under visible light.

Effect of mechanochemical treatment on phase composition and properties of Mn-containing cordierite materials

Mn-containing cordierites 2MnO·2Al2O3·5SiO2 were prepared by mechanochemical method from kaolinic clay, alumina and MnO2 after calcination at 1100°C. Phase composition of prepared samples, their texture properties and catalytic activity in ammonia oxidation reaction were found to depend on the activation time. The mechanochemical treatment of raw materials for 90-180s gave well-crystallized cordierite ceramic characterized by the surface enrichment with Mn cations and high catalytic activity in ammonia oxidation reaction. The increase activation time to 270-360s led to the possible interaction of MnO2 with Al-containing components during the mechanochemical treatment to form Mn-Al-spinel which is less selective.

CAVITATIONAL TREATMENT OF OIL DIESEL FRACTION

The results of investigation on the effect of mechanochemical treatment of the diesel fraction on its physicochemical characteristics are presented. Mechanochemical treatment of the diesel fraction was achieved by creating a cavitation effect in the hydrodynamic regime. The studies were carried out in the range of pressure gradients up to 50 MPa, the number of treatment cycles varied from 1 to 5, the temperature of raw material at the apparatus inlet was 0 0С. It is shown that the effect of cavitation is manifested not only in the processing of high-boiling hydrocarbons, but also in a middle distillate directions. So, as a result of the cavitation effect, the density of the diesel fraction and its pour point decrease, and the fractional composition changes. It is suggested that these changes are associated with hydrocarbon degradation. The collapse of gas bubbles leads to a local increase in the temperature of the medium to 800 0C, which, in turn, leads to the destruction of hydrocarbons. Increasing the pressure gradient of the hydrodynamic flow enhances the noted effect. Increasing the number of treatment cycles reduces the effect achieved. A possible reason is the destruction of hydrocarbons formed in the first stage of processing and the formation of polycyclic and aromatic structures. The results presented in the article extend ideas about cavitation regularities in the hydrocarbon environment

The effect of mechano-chemical treatment on structural properties of the drawn TiNi-based alloy wire

The rapid development of biomedical materials with the advanced functional characteristics is a challenging task because of the growing demands for better material properties in-clinically employed. Modern medical devices that can be implanted into humans have evolved steadily by replacing TiNi-based alloys for titanium and stainless steel. In this study, the effect of the mechano-chemical treatment on structural properties of the matrix and surface layer of the drawn TiNi-based alloy wire was assessed. A range of samples have been prepared using different drawing and etching procedures. It is clear from the results obtained that the fabricated samples show a composite structure comprising the complex matrix and textured oxycarbonitride spitted surface layer. The suggested method of surface treatment is a concept to increase the surface roughness for the enhanced bio-performance and better in vivo integration.

Effect of mechanochemical treatment on structure and electrical properties of montmorillonite

This study investigates the effect of grinding on the structure of montmorillonite (MMT). Both XRD and IR analyses indicate a gradual breakdown of the mineral layers and a decrease of the crystallinity with grinding. The prolonged grinding is accompanied with an amelioration of oxidant capacity of MMT which could be attributed to the conversion of structural Fe2+ to Fe3+ cations caused by adsorbed atmospheric oxygen and/or to the exposition of more Fe3+ cation to the surface of the mineral. The evolution of acidity of MMT during grinding has been carried out by determining the point of zero charge (pHpzc) of MMT and the pH of the aqueous suspension of MMT. It was shown that pHpzc increases with grinding from 6.2 to 8.1 respectively for untreated MMT and that ground for 30 min. On the other side the pH of MMT suspension increases from 4.75 to 8.18 respectively for untreated MMT and that ground for 75 min. These two results indicate that acidity of MMT has been lost during grinding. TGA analysis shows that the thermal decomposition of the ground MMT for 90 min takes place in a single step. This behavior has been explained by the formation of less tightly bound hydroxyl groups. Electrical and dielectric properties have been studied using impedance spectroscopy. It has been established that grinding is accompanied by an increase of dc conductivity and dielectric constant in the range of MHz. Moreover, it has been observed a shift of bound water relaxation frequency to lower frequency. These changes could be attributed to the enhancement of mobility of interlayer cations and to the perturbation of the state of interlayer water which could be connected to the defects in the octahedral sheet rather than being entirely localized at the interlayer space of MMT.

Effect of Mechanochemical Treatment on Acidic and Catalytic Properties of MgO-SiO2 Composition in the Conversion of Ethanol To 1,3-Butadiene

It was shown that mechanochemical treatment of the MgO-SiO2 composition leads to an increase of its activity and selectivity in the heterogeneous catalytic conversion of ethanol into 1,3-butadiene. This results from the formation of active reaction sites for aldol–crotonic condensation on the surface of the —Mg—O—Si≡ structural fragments, which are Lewis acidic sites.

Effects of mechanochemical treatment on the properties of kaolin and phosphate–kaolin materials

We have investigated the impact of the addition to the kaolin, by mechanochemical treatment, of bonding agents such as the potassium phosphate compounds (potassium dihydrogen phosphate KH2PO4, potassium monohydrogen phosphate K2HPO4 and potassium phosphate K3PO4) on the structural, thermal and mechanical properties of the kaolin products.The fresh and sintered samples were characterized by using several techniques: X-ray diffraction (XRD), infrared spectroscopy (IR), thermal techniques (DTA/TGA and dilatometry) and the Brazilian test. The addition of the bonding agent by mechanochemical treatment minimized defects after a sintering process. This resulted in reducing the sintering temperatures.

ChemInform Abstract: Effect of Mechanochemical Treatment on the Kinetic Properties of V,Mo,Ti‐Containing Oxide Systems

AbstractReview: 23 refs.

Effect of Mechanochemical Treatment on the Kinetic Properties of V,Mo,Ti-Containing Oxide Systems

A study was carried out on the use of various mechanochemistry procedures, namely, the mechanical activation of starting components for the traditional synthesis of catalysts, the activation of catalysts prepared by traditional methods, and the direct mechanochemical synthesis of catalysts from starting components, for the preparation of highly efficient catalytic compositions for various processes. Results are given for the mechanochemical treatment of V-P-O, V-Ti-O, Cu-Ce-O, and Ba-Ti-O compositions as well as MoO2. The prepared samples were studied by XRD, AFM, SEM, TEM, and XPS methods and improvement of the catalytic properties was found to be related primarily to formation of nanodimensional particles of active components or nanodimensional crystalline regions of the active phase as a result of mechanochemical treatment. This method was found to be successful both in the modification of known catalytic compositions and in the preparation of new catalytic compositions.

Effect of Mechanochemical Treatment on Physicochemical and Antitumor Properties of Betulin Diacetate Mixtures with Arabinogalactan

It was shown using gel-permeation chromatography that arabinogalactan in a SPEX 8000 ball mill changed its molecular-weight distribution (MWD) after mechanochemical treatment. The presence of betulin diacetate assisted the reduction of the MWD after dissolution of the mechanically activated mixture in water and evaporation of the solvent. Complexes of betulin diacetate with arabinogalactan were also obtained as thin films that were readily soluble in water. Mechanical composites of arabinogalactan with betulin diacetate were capable of inducing cell elimination processes mediated by disruption of ionic homeostasis in Ehrlich ascites carcinoma cells.

Effect of mechanochemical treatment on the solubility of coals of various ranks

The effect of the mechanochemical treatment of coals of various ranks on their dissolution in an acid melange was studied. It was found that the mechanochemical treatment weakly affects the reaction time of coal with the melange because it takes only 1–5 min; however, it determines the melange volume at which the dissolution of coals takes place. Preliminary mechanochemical treatment affects the specific surface area of coals after their treatment with the melange and the increase in the weight of coals.

Mechanochemical preparation of vanadium- and molybdenum-containing catalysts II: The effect of mechanochemical activation of vanadium pentoxide + ammonium dimolybdate compositions on chemical and phase transformations

We studied the effect of mechanochemical treatment (MCT) of V2O5 + (NH4)2Mo2O7 compositions (V: Mo = 0.7: 0.3) in ethanol, water, and air on the physicochemical properties of the compositions. X-ray powder diffraction, differential thermal analysis (DTA), and IR spectroscopy showed that mechanochemical treatment in water or ethanol does not change the phase state of vanadium pentoxide. (NH4)2Mo2O7 partially decomposes during MCT to yield nonstoichiometric molybdenum oxides. MCT in water leads to the complete decomposition of (NH4)2Mo2O7, and the nonstoichiometric molybdenum oxides that have been formed in 60–120 min are segregated into a molybdenum phase during further treatment for 240–360 min. During such a treatment, V2O5 first forms V2O5 · nH2O intercalation compounds, which then react with ammonia during long-term treatment to form ammonium hexavanadate (AHV).

Mechano-chemical effects on surface properties and molybdate exchange on hydrotalcite

AbstractThe effects of mechano-chemical treatment on the surface characteristics and sorption properties of hydrotalcite were studied. Non-milled (crushed) and milled samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), particle size analysis and specific area. A milling time of 2 h decreased the particle size of the hydrotalcite samples from 21 to 8.0 nm, the specific area from 97 to 5.7 m2g–1and the total pore volume from 0.41 to 0.01 cm3. After the crushed and milled samples had been separately calcined at 500ºC, they were agitated with 10–2M Na2MoO4aqueous solutions for 48 h. The molybdate ion content in the regenerated non-milled hydrotalcite samples (HTc-MoO4) was found to be 6.0 meq g–1while in the milled hydrotalcite (HTm-MoO4) samples this content was 2.5 meq g–1. The lower molybdate content was thought to be a result of compaction and, hence, reduced reactivity of the milled HT samples.

Solid state mechano‐chemical grafting copolymerization of hydroxyethyl cellulose with acrylic acid

AbstractThe effects of mechanochemical treatment on hydroxyethyl cellulose (HEC) and its grafting reaction with acrylic acid (AA) under solvent‐free conditions were studied through a vibratory ball‐milling machine, which was developed in our laboratory. Fourier transform infrared (FTIR) spectroscopy and 13C‐NMR analysis were used to investigate the structural development of HEC during vibromilling and the grafting mechanism. Further development of the structure and properties of the graft copolymer was characterized by viscosity measurement, wide‐angle X‐ray diffraction (WAXD), and thermal gravity (TG) analysis. The FTIR results showed a new peak at 1720 cm−1, corresponding to the CO absorbance peak of AA, which indicated that AA was successfully grafted onto HEC during the high‐energy vibromilling of the HEC/AA mixture at ambient temperature in the absence of a solvent and a catalyst. The WAXD showed the destruction of crystals of HEC during the milling, and the TG analysis demonstrated the improvement of the thermal stability of the copolymer. The effects of the processing conditions on the grafting rate and grafting efficiency were studied by chemical titration to determine the optimum grafting conditions. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Effect of mechanochemical treatment on petroleum coke–CO 2 gasification

The effect of mechanochemical treatment during the grinding of petroleum coke on its gasification by CO 2 was studied. An additive derived by drying the black liquor in papermaking industry is adopted in grinding process. Results show that the gasification reactivity of petroleum coke is effectively improved by grinding, and the activation by wet grinding is more noticeable than that by dry grinding. Besides, by wet grinding petroleum coke and additive together, the active metal species in additive are not easily volatilized in gasification, and retain a high catalytic reactivity to the coke–CO 2 reaction throughout most of the conversion range. Changes in crystal structure of the petroleum coke induced by mechanochemical treatment is related to its gasification reactivity. In general, the crystalline–amorphous phase transition is the tendency of long time mechanical grinding, while a crystal structure re-formation stage is observed after wet grinding of petroleum coke with and without additive for some time. Similar phenomenon has also been found in the reported data, but not given attention. Some discussion is made in the paper, and more work should be undertaken to disclose the mechanism.

Mechanochemical effect on low temperature synthesis of AlN by direct nitridation method

Effect of mechanochemical treatment on low temperature synthesis of AlN from Al metal in N 2 atmosphere was investigated. The Al powder, of 20-μm particle size, was dry milled using a planetary ball mill. Since Al powder is soft and malleable, the particle size tended to increase due to adhesion of the original particles during grinding. On the other hand, effective grinding was achieved by adding LiOH.H 2O, which is thought to cover the surfaces of Al powder and suppress the adhesion. Samples containing 0.5 mass% Li in Li/(Li+Al) were ground for various times up to 6 h, then nitrided for 1 h at various temperatures. AlN formation in these samples began at 570–640 °C, much lower than without LiOH.H 2O, indicating the accelerating effect of the added LiOH·H 2O. The conversion temperature was lowest in the sample ground for 1 h. This sample (mechano-sample) also showed a higher AlN conversion rate than the other samples, being almost completely converted at 580 °C. The mechanochemical treatment is found to be very effective for synthesizing AlN powder at very low temperatures (below the melting point of Al metal). It is thought to facilitate the formation of lithium aluminate on the surface of the Al metal particles, enhancing the diffusion of nitrogen.

Modification of low- and high-defect kaolinite surfaces: implications for kaolinite mineral processing

A comparison is made of the mechanochemical activation of three low- and one high-defect kaolinite using a combination of X-ray diffraction, thermal analysis, and DRIFT spectroscopy. The effect of mechanochemical alteration of the kaolinites is greater for the low-defect kaolinites. The effectiveness of the mechanochemical treatment is represented by the slope of the d(001) peakwidth–grinding time line. High-defect kaolinite is not significantly altered by the grinding treatment. The effect of mechanochemical treatment on peakwidth was independent of the presence of quartz; the quartz acts as an additional grinding medium. The effectiveness of the mechanochemical treatment depends on the crystallinity of the kaolinite. Two processes are identified in the mechanochemical activation of the kaolinite: first the delamination of kaolinite appears to take place in the first hour of grinding and second a recombination process results in the reaggregation of the ground crystals. During this process proton hopping occurs and reaction to form water takes place. This water is then adsorbed and coordinated to surface-active sites created during mechanochemical treatment.

Mechanochemistry and Processing Characteristics of Aqueous Emulsions of High-Viscosity Petroleum Products

The effect of mechanochemical treatment on the emulsification of high-viscosity petroleum products is reported. Thermally stable water-in-oil emulsions, whose viscosity is five times lower than the viscosity of the original petroleum product, are prepared for the first time by mechanochemical treatment in the presence of a surfactant. The critical fluxing temperature, thermal properties, and viscosity of asphalt emulsions prepared by mechanochemical treatment is identical to those of residual oil. A mechanism is suggested to explain the formation of inverted aqueous emulsions of petroleum products rich in tars and asphaltenes.

Effects of Mechanochemical Treatment on Yttrium Oxyapatite Formation

Structural changes of Y2O3-SiO2 solid system during a fine milling in air were investigated. The milling of a mixture in a molar ratio Y2O3/SiO2 = 7/9 affect the structure of the solids. After heating the samples at T > 1000°C new phases were obtained by a thermal reaction between Y2O3 and SiO2, as a result of the mechanochemical activation. The extent of the mechanochemical reaction was higher when using hydrous yttria instead of Y2O3. It was found that the yttrium oxyapatite is unstable and attempts to prepare this silicate by a solid-state reaction always results in the formation of a mixture containing Y2SiO5, Y2Si2O7, and yttrium oxyapatite.

Effect of mechanochemical treatment on the synthesis of calcium dialuminate

Calcium dialuminate (CaAl4O7) powders were synthesised from mechanochemically treated mixtures of aluminium hydroxide + calcium hydroxide and aluminium hydroxide + calcium carbonate. On grinding, both mixtures produce X-ray amorphous precursor phases which show 27Al MAS NMR resonances characteristic of Al in octahedral and tetrahedral sites, and a site identified by a resonance at 37–39 ppm (possibly pentahedral Al). Although grinding does not completely destroy the carbonate XRD reflections in the carbonate mixture, both precursors show a high degree of homogeneity and behave similarly on heating, forming monophase CaAl4O7 at <1050 °C. By contrast, the same unground compositions form mixtures of α-alumina and various calcium aluminates (but not CaAl4O7) on heating as high as 1250 °C. Calcium dialuminate synthesised from the carbonate-containing mechanochemical precursor had a smaller particle size which may be advantageous for subsequent fabrication and sintering.