Effect Of Mechanochemical Activation Research Articles

Enhancing aqueous carbonation via co-milled serpentine and wollastonite: Effects of mechanochemical activation

Carbon dioxide (CO2) storage through aqueous mineral carbonation is recognized as a promising technology for geochemical carbon removal. Previous studies predominantly focused on individual alkaline earth silicates, such as wollastonite or serpentine, overlooking their interactive effects on carbonation processes. To address this knowledge gap, we conducted aqueous carbonation tests using individually ball-milled serpentine (m-serpentine), wollastonite (m-wollastonite), mixtures of ball-milled serpentine and wollastonite (m-serpentine + m-wollastonite), and the co-milled serpentine and wollastonite (m-(serpentine + wollastonite)). The carbonation of (m-serpentine + m-wollastonite) involved the formation of a combination of calcite (CaCO3) and magnesite (MgCO3), suggesting that no significantly interactive effect between the serpentine and wollastonite. In contrast, carbonating m-(serpentine + wollastonite) results in the precipitation of Mg-bearing calcite ((Mg, Ca)CO3). Upon quantification, the carbonation degrees of m-(serpentine + wollastonite) is relatively higher than that of (m-serpentine + m-wollastonite). During the carbonation of m-(serpentine + wollastonite), the combination of serpentine and wollastonite facilitates mutual dissolution, leading to the release of more cations. However, these released ions do not diffuse into the bulk carbonating solution; instead, carbonation occurs exclusively at the mineral-water interface. Consequently, the co-milling process, merging Ca-rich wollastonite into Mg-rich serpentine, induces the formation of (Mg, Ca)SiO3. These novel insights into aqueous carbonation using a combination of Mg-containing and Ca-containing minerals underscore the significant role of mineral-mineral reactions in CO2 mineralization.

Effect of mechanochemical activation on hydration properties of lead-zinc sulfide tailings for concrete construction

Proper management of mine tailings containing high amount of sulfide is a crucial issue in order to reduce their environmental hazards including generation of acid mine drainage and release of heavy metals. This study was conducted targeting to understand the effects of using lead-zinc sulfide tailings (LZSTs) as cement substitution on the hydration properties of concrete samples. Mechanochemical activation of the LZSTs containing 19.9% sulfide content in mixtures of 20%, 40%, 60%, 80% and 100% was performed to cement-replacement in concrete production. Analyzes were performed on the produced concrete samples. X-ray diffraction, compressive strength, toxicity characteristic leaching procedure (TCLP), mercury intrusion porosimetry, X-ray spectroscopy, scanning electron microscopy, energy-dispersive fourier-transform infrared spectroscopy, thermogravimetric analysis and differential thermal analysis were performed on the constructed concrete samples. The results of XRD analysis confirmed that introduction of activated tailings in the concrete construction led to form hatrurite (Ca3SiO5) phase. According to the TCLP, with increseasing curing days, leached amount of studied toxic metals decreased and was lower than the allowable limit. The results of the mercury intrusion porosimetry (MIP) indicated that as the curing time prolonged, the critical pore size was reduced from 150 to 50 nm in the constructed sample containing 20% activated tailings. Therefore, by activating the tailings, the specific surface area was enlarged and more cohesion took place in the concrete samples. The compressive strength results indicated that the compressive strength after 90 curing days in the constructed sample containing 20% activated tailings was 40.85 MPa, while it was 38.15 MPa in the control sample. In general, the results indicated that the mechanochemical activated of LZSTs with calcium carbonate can be a suitable alternative for cement (up to 40%) in the production of concrete samples.

The Effect of Mechanochemical Activation on Carbothermic Reduction of Pyrolusite Ore

The Effect of Mechanochemical Activation on Carbothermic Reduction of Pyrolusite Ore

Mechanochemical activation for improving the direct mineral carbonation efficiency and capacity of a timber biomass ash

Biomass ashes generated from the combustion process of timber materials have the capacity to be used as sustainable feedstock materials for CO2 utilisation through mineral carbonation. However, the CO2 uptake capacity and efficiency of biomass bottom ash are normally quite limited under ambient conditions due to the low reactivity of the materials. This study investigates the use of timber biomass bottom ash for direct mineral carbonation, and the effects of mechanochemical activation as a pre-conditioning treatment. The effects of different mechanochemical activation conditions (i.e., milling time, the ball to sample mass charge ratio, and the water addition content) were systematically assessed. The mechanochemically activated biomass bottom ash samples before and after carbonation were characterised using X-ray diffraction, Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, and thermogravimetric analysis (coupled with mass spectroscopy). The results show that mechanochemical pre-conditioning can effectively improve both the mineral carbonation efficiency (kinetics) and capacity, most likely by increasing the reactivity of calcium (magnesium) silicate for mineral carbonation even at ambient temperature and pressure. The maximal CO2 uptake capacity has doubled at the optimised mechanochemical treatment conditions. Comparison of performances reported in literature using biomass ash with similar chemical compositions was carried out, where mechanochemical activation pre-treatment exhibited superior performances. The outcomes of this study also suggest that mechanochemical activation might also be effective for improving the mineral carbonation capacity of other alkali industrial waste containing calcium (magnesium) silicates.

Effects of mechanochemical activation on the structural, magnetic and optical properties of yttrium iron garnet-graphene nanoparticles

Yttrium iron garnet nanoparticles were exposed to mechanochemical activation by high-energy ball milling for 0, 2, 4, 8 and 12 h, with and without graphene nanoparticles. The samples were subsequently characterized by Mössbauer spectroscopy, X-ray powder diffraction (XRPD), magnetic measurements and optical diffuse reflectance spectroscopy. Examination of the quadrupole doublet's abundance as function of ball milling time indicated that graphene slowed down the precipitation of the yttrium iron perovskite (yttrium orthoferrite) phase. The increased linewidth of the doublet showed that the carbon from graphene preferentially entered the lattice of the yttrium orthoferrite. The saturation magnetization decreased with decreasing particle size for prolonged milling due to the occurrence of the antiferromagnetic hematite phase. The enhanced absorption in the infrared region could be associated with the incorporation of carbon from graphene in the lattice of the yttrium orthoferrite. The results are interesting for sensing and microwave applications.

MECHANOCHEMICAL AND CERAMIC SYNTHESIS OF COBALT FERRITE

In this work we studied the effect of mechanochemical activation on the formation of the cobalt ferrite phase from iron and cobalt oxalates. X-ray phase, X-ray diffraction and synchronous thermal analysis, scanning electron microscopy, low-temperature nitrogen adsorption-desorption method were used to study the composition and properties of the resulting product. It has been established that cobalt ferrite is formed at a temperature of 1100 °C during solid-phase interaction of the initial components, and the use of mechanochemical activation of the initial components in a roller-ring vibration mill makes it possible to reduce the synthesis temperature to 400 °C. It is shown that CoFe2O4 obtained using the method of mechanochemical synthesis has a more developed specific surface area and porous structure in comparison with cobalt ferrite obtained by the ceramic method.

Effect of Mechanochemical Activation on the Powder Dispersity of an Aluminum–Magnesium Spinel and Obtaining Dense Nanoceramics

Effect of Mechanochemical Activation on the Powder Dispersity of an Aluminum–Magnesium Spinel and Obtaining Dense Nanoceramics

The effect of mechano-chemical activation and surface treatment of limestone filler on the properties of construction composites

Abstract The effect of the combined actions of milling and hydrophobization procedures applied in construction composites synthesis was investigated. The mortars were prepared with cement (CEM I 42.5) and calcite aggregate complying the standard 1:3 mix ratio. The limestone filler (10 wt%) was added to the mixture upon its mechano-chemical activation in an ultra-centrifugal mill. The activation variables (milling time, rotor velocity, sieve mesh size) were altered to achieve the optimal quality of the powder. The treatment was optimized via chemometric tools. The r2 values (0.955–0.998) of second order polynomial models accurately predicted the output and the Standard score analysis chose the optimal activation parameters: 4.25 min; 48.58 m/s and 80 μm sieve. The selected filler and all three aggregate fractions were coated with stearic acid via dry procedure. The mortar mixes, prepared with uncoated (M1) and coated (M2) aggregate and filler, were cured for a period of 28 days during which compressive strength and water absorption were monitored. The dimensional changes in mortars were estimated via TMA dilatometer measurements. Thermo-analytical methods (DTA/TGA) were applied in the thermal behavior analysis. Mineralogical and morphological changes in the structure of hardened composite were detected by XRD and SEM, respectively. Limestone aggregate led to lower final compressive strengths in mortar, but it produced an infinitesimally small shrinkage at 1000 °C. The hydrophobization via stearic acid initiated the decrease in water absorption and formation of needle-like micro-network that filled structural voids reducing open porosity. The assessment of the effects of limestone utilization as a filler and as an aggregate on the mortar performances confirmed that this novel water-repellent composite is applicable in structural design.

Effect of mechanochemical activation and microgrinding on the intensity of combustion of solid fuel

The effect of mechanochemical activation and microgrinding on the intensity of combustion of solid fuel particles was studied. As applied to the rapid process of the combustion of solid fuel particles, mechanochemical activation was simulated within the framework of nonequilibrium thermodynamics with the expansion of the classical dependence of the local entropy of state of the reacting system on relaxation phenomena. The dependences of the intensity of burning (mass loss time) of deformed organic solid fuel particles on the relaxation processes of the momentum transfer of their excited states and on the mutual orientation of shear stresses and the first difference in normal stresses (a steric factor), which compensate for temperature power consumption, were established. The rate of combustion is determined by the size of burning particles, their density, and a ratio between the elastic and dissipative scattering of mechanical energy in the particles, which increases the diffusion mobility of burning components with a decrease in the time of their burning. The ranges of variation in the parameters of the burning system in which the particle size or mechanoactivation exerts a considerable effect on the combustion time of fuel particles were recognized. Experiments on the torch combustion of coal-dust fuel as the cumulative combustion of its particles confirmed the effect of mechanoactivation.

High calcination of ferroelectric BaTiO3 doped Fe nanoceramics prepared by a solid-state sintering method

This study examined the effects of the combination of starting materials on the properties of solid-state reacted BaTiO3 using two different types of BaCO3 and TiO2. In addition, the effect of mechanochemical activation by high energy milling and the Ba/Ti molar ratio on the reaction temperature, particle size and tetragonality were investigated. The TiO2 phase and size plays a major role in increasing the reaction temperature and particle size. With the optimum selection of starting materials and processing conditions, BaTiO3 with a particle size <200nm (Scherrer’s formula) and a tetragonality c/a of approximately 1.007 was obtained. Broadband dielectric spectroscopy is applied to investigate the electrical properties of disordered perovskite-like ceramics in a wide temperature range. From the X-ray diffraction analysis it was found that the newly obtained BaTi0.5Fe0.5O3 ceramics consist of two chemically different phases. The electric modulus M∗ formalism used in the analysis enabled us to distinguish and separate the relaxation processes, dominated by marked conductivity in the ε∗(ω) representation. Interfacial effects on the dielectric properties of the samples have been understood by Cole–Cole plots in complex impedance and modulus formalism. Modulus formalism has identified the effects of both grain and grain boundary microstructure on the dielectric properties, particularly in solid state routed samples.

Mechanochemical activation of starting oxide mixtures for solid-state synthesis of BiFeO3

We have studied the effect of mechanochemical activation on the reactivity of Bi2O3 + Fe2O3 oxide mixtures, assessed the temperature effect on the kinetics of BiFeO3 formation in the oxide mixtures before and after mechanochemical activation, and optimized the conditions of bismuth ferrite synthesis by solid-state reaction. A material with a BiFeO3 content of at least 98.3 wt % has been obtained, and its magnetic properties have been investigated.

Kinetics of refractory phosphate binder accumulation

The effect of mechanochemical activation on component interaction is studied. Corundum is ground to an identical fineness: together with H3PO4 solution, and also dry grinding followed by suspension. The chemical reaction rate (formation of aluminum hydrophosphate) with different hydrodispersion synthesis methods is due to a rapid increase in the number of active centers at the surface of a corundum grain during grinding and combination with acid.

Synthesis, structure and magnetic properties of distorted Y xLa 1− xFeO 3: Effects of mechanochemical activation and composition

The influence of mechanochemical treatment on the synthesis and properties of Y x La 1− x FeO 3 (0 ≤ x ≤ 1) orthoferrites is studied. Solid mixtures of the corresponding metal oxides were treated in a high-energy ball-mill. X-ray diffraction revealed that during the milling the disappearance of the reactants and a fast conversion to orthoferrite phase take place. Magnetic measurements showed a weak ferromagnetic behavior of the obtained materials, observing higher magnetization for larger x. The activated powders heated at 600 and 800 °C showed a progressive crystalline ordering together with a significant drop of magnetization. Thermal treatments at 1000 °C produced the formation of the phase Y 3Fe 5O 12 for the samples richer in yttrium, increasing the magnetization. Rietveld refinements of the diffraction patterns and dynamical scanning calorimetry were used respectively to determine the lattice parameters and Néel temperatures for the formed orthoferrites. The effect of the composition on the structure and magnetic behavior is discussed.

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).

Surfactant effects in the mechanical activation of ultrafine alumina powders made by pneumocirculation grinding

Studies have been made on the effects of mechanochemical activation with the addition of surfactants on the characteristics of the pneumocirculation grinding product from alumina powder and the properties of the corundum ceramic based on it. Processing the powder in an aqueous solution of polyvinyl alcohol and methyl cellulose with concentration up to 1% has a marked effect on the detailed crystal structure of the particles and improves the technological properties of the powder. Activation produces defects at the particle surfaces, which tend to intensify the consolidation of the powder up to high sintering temperatures.

Kinetics of specific surface area change using the Boltzmann model

During sintering of the 2MgO-2Al2O3-5SiO2 system, cordierite, an attractive ceramic material because of its properties, is obtained. Effects of mechanochemical activation of stoichiometric mixtures, performed to investigate possibilities of lowering cordierite formation temperature during sintering, were monitored by thermogravimetric and differential thermal analyses. Specific surface areas of the mechanically activated powder mixtures were determined by the BET method. Kinetics of the specific surface area increase was analyzed using the Boltzmann model. It was confirmed that with activation time increase, temperatures of phase transformations were shifted to lower values and, according to FTIR analysis no significant changes occurred during material aging. According to the obtained results, it may be concluded that since mechanochemical activation has an influence on the treated powder mixture, lowering of the cordierite formation temperature during the sintering process is expected.

Composition change of uranium perchlorates with organic ligands upon mechanochemical activation of exchange processes

Results of studies on the effect of mechanochemical activation of ligand exchange processes in uranyl perchlorate-dimethylsulfoxide are presented. Spectroscopic data show that mechanical activation of the exchange process in this system results in the replacement of H2O in the first coordination sphere of uranyl UO22+ by DMSO to form nanocrystals with a defined ligand sphere. Possible factors governing the noted features are considered.

Investigation of mechanochemically modified kaolinite surfaces by thermoanalytical and spectroscopic methods

The effect of mechanochemical activation (dry grinding), formamide intercalation, and thermal deintercalation on high- and low-defect kaolinite surfaces was studied by thermogravimetry and diffuse reflectance Fourier transform infrared spectroscopy. These investigations were completed with specific surface area and pore size distribution measurements. The surface acidity of the ground and the ground-and-intercalated kaolinites was probed with ammonia adsorption. The surface area and the pore volume as well as the amount of adsorbed ammonia increased with the rate of mechanochemical activation. At the same time the thermally deintercalated minerals showed increased surface area but decreased pore volume with the time of grinding. Adsorbed ammonia was detected as ammonium ion in the 1400–1500 cm −1 spectral range.

Recent Developments in SiAlON Research in New Zealand

An important aspect of previous sialon research in NZ has been the development of new synthesis methods, including refinements in carbothermal reduction and nitridation (CRN) methods and the use of mechanochemical activation of sialon precursors (either Al and Si nitrides and oxides or CRN mixtures). Mechanochemical activation of CRN mixtures of clay and carbon heated in N2 formed β-sialon (z = 2) at 1300oC (100oC lower than in unground mixtures) but 21R polytypoid and corundum were also formed. More recently, our attention has focussed on the technique of silicothermal reduction and nitridation (SRN) to synthesise other sialons, including the AlN polytypoids and Na and Li α-sialons. The interest in the polytypoids springs from their expected physical properties (thermal conductivity and good electrical insulation similar to AlN), their covalent bonding and relatively light weight arising from their high Al and N contents and their elongated crystal morphology which may improve the crack resistance of polytypoid composites with α-sialon. This paper describes the development of SRN single-step synthesis of high-purity dense 15R sialon from clay, Si and AlN, and the effect of additives on the synthesis and sintering of the product. A method is also described for SRN synthesis of Na and Li α-sialons from clay, Si and AlN using fluoride additives. Fluorides have the advantage of small size, high electronegativity, leading to their known facilitation of AlN synthesis. Furthermore, they do not readily enter the sialon structure but may toughen it by formation of glassy phases. Fluorides allow use of clay in this SRN synthesis by introducing M+ without additional oxygen, but have the disadvantage of generating SiF4 as a byproduct. The reaction using LiF proceeds readily at the very low temperature of 1200oC via an O-sialon intermediate by a mechanism which probably involves Si migration assisted by the formation of SiF4.The effect of mechanochemical activation (high energy grinding) on the SRN formation and sintering of Na and Li α-sialons, O and β-sialon has also been studied.Grinding the SRN O-sialon precursor promotes O-sialon formation in powders but not in pellets due to pre-reaction sintering, which is facilitated by the smaller particle size. Grinding Na and Li α-sialon SRN precursors forms a mixture of sialons rather than the target monophase product, while sintering of all the sialons is assisted by grinding their SRN precursors.

Effect of mechanical activation on structural-chemical properties of phosphorites

Effect of mechanochemical activation of mono-and mid-fraction of phosphorites from the Burenkhan deposit was studied by IR and ESR spectroscopies in vibration and planetary mills.