Influence Of Mechanical Activation Research Articles

Influence of Mechanical Activation on Soil Properties and Plant Development

Influence of Mechanical Activation on Soil Properties and Plant Development

Influence of mechanical activation on the behavior of green high-strength mortar including ceramic waste

Abstract Solid waste management is a significant environmental issue for countries because of the need for huge landfills. The ceramic tile waste powder (CWP) is one of the wastes. Conversely, cement production, the main ingredient in concrete, emits large quantities of greenhouse gases, a significant environmental concern. Therefore, substituting some of the cement in concrete with CWP is an issue that deserves investigation to reduce the environmental impact of both materials. Accordingly, this study aims to investigate the influence of the grinding time and proportion of CWP as a substitute for cement on the properties of high-strength mortar (HSM). Three grinding times (10, 15, and 20 minutes) and three replacement percentages (10%, 20%, and 30% by weight) for CWP were adopted for each time. Ten mixtures (including the reference mixture) were executed. The fresh (flow rate), mechanical (compressive strength) durability (ultrasonic pulse velocity, dynamic elastic modulus, water absorption, density, percentage of voids and electrical resistivity) and microstructural properties were examined. The life cycle assessment (LCA) was also addressed. The results showed that the mechanical activation had a pronounced effect on the durability properties (especially water absorption and percentage of voids) more than on the compressive strength. Generally, a sustainable HSM (with more than 70 MPa of compressive strength) can be produced in which 30% of the cement was replaced with CWP with almost comparable performance to the CWP-free mortar. Furthermore, LCA results showed that mortars containing 30% CWP ground for 15 mins (GT15CWP30) had the lowest GWP per MPa.

The influence of mechanical activation on the structure and phase formation of an electro-thermal explosion in the Ti–Zr–C system

The TixZr1-xC solid solutions were synthesized by electro-thermal explosion under pressure in the (Ti + Zr + C) blends mechanically activated in hexane (MA-ETE). The effect of mechanical activation (MA) duration on reaction blend characteristics, ETE parameters, phase composition, and microstructure formation in solid solutions was investigated. At MA, the Ti + Zr blend deforms metal crystal lattices for 20 min, complete amorphization occurs for 40 min, and the carbide grains form a cubic structure for 90 min. The single-phase Zr0.50Ti0.50C solid solution with a grain size of 3–5 μm and a submicron composite with a grain size of 0.1–0.2 μm containing the Ti0.86Zr0.14C and Zr0.74Ti0.26C solid solutions were synthesized in a one-stage process for the first time without any additional thermotreatment. The influence of mechanical activation on diffusional mass transfer of reactants, structure, and phase formation is discussed.

Influence of Mechanical Activation on the Formation of Yttrium Aluminum Garnet (YAG) at Lower Temperature

Yttrium aluminum garnet (YAG) is an important material which require high temperature of 1600°C in its solid-state reaction. To lower this temperature, mechanical activation process has applied to the system which make the crystal arrangement broken thus make it more reactive. This process results in homogeneous and fine particle distribution of Al2O3 and Y2O3 compared to manually mixed powders. Moreover, milling process also reduce the particle size of the Al2O3 and Y2O3 from 4694 nm and 349 nm down to 274 nm. This also lessen the crystallite size of Al2O3 and Y2O3 from 1010 and 164 Å to 310 and 50 Å respectively. Then, after calcination at 1100°C, the milled powders form YAG phase in the opposite of manually mixed powders which form YAM phase. YAG formed have nearly round shape with finer grain compared to manually mixed powders which still has large grain of Al2O3 and Y2O3. This formation temperature is much lower than the require conventional solid-state reaction.

Influence of mechanical activation on crystal structure and physical properties of YbFeO3

Influence of mechanical activation on crystal structure and physical properties of YbFeO3

SHS in the Ni–Al–Mn System: Influence of Mechanical Activation

SHS in the Ni–Al–Mn System: Influence of Mechanical Activation

Effect of mechanical activation on the hypochlorite leaching of Sarcheshmeh molybdenite concentrate

ABSTRACT Hydrometallurgical extraction of molybdenum from sulfidic molybdenite concentrates is an important issue from technical, economic, and environmental viewpoints. The influence of mechanical activation on the hypochlorite leaching of a molybdenite concentrate (Kerman, Iran) were studied in a stirred reactor at batch mode. The effects of several critical parameters, including pH, temperature, reaction time, NaClO concentration, and liquid to solid (L/S) ratio on the rate and extent of molybdenum extraction from the concentrate were investigated. Maximum molybdenum extractions, 98% and 95%, obtained for the mechanically activated and nonactivated concentrates, respectively after 60 min at 50°C, stirring speed of 500 rpm, L/S of 333 mL/g, pH of 9, and using 40% NaClO solution. Specific surface area and particles size measurements in conjunction with FE-SEM images showed that improvement in the extraction after mechanical activation could be due to increasing the surface area and changing the crystal structure of the concentrate. Mechanical activation had a significant effect on molybdenum extraction after 2 min, (13% difference in extraction); however, after 60 min, molybdenum extractions from mechanically activated and nonactivated samples were 97% and 92%, respectively. It was found that mechanical activation has a significant effect on the leaching of molybdenite in short reaction times.

Titanium-Enriched Slag Prepared by Atmospheric Hydrochloric Acid Leaching of Mechanically Activated Vanadium Titanomagnetite Concentrates.

The titanium-enriched slag was obtained via atmospheric hydrochloric acid leaching of mechanically activated vanadium titanomagnetite concentrates (VTMCs). Under the influence of mechanical activation, specific physicochemical changes were observed via X-ray diffractometry, scanning electron microscopy, and granulometric laser diffraction analysis. Experimental findings revealed that the mechanical activation of VTMCs resulted in a decrease in the median volume particle diameter (d50) and an increase in the specific surface area (SA) with an increased milling time. The results of the leaching experiment revealed that the mechanical activation treatment favors the extraction of iron (Fe) and titanium dioxide (TiO2) from the VTMCs. The Fe and TiO2 extractions from the mechanically activated sample after 10 h compared with the unactivated sample were increased by 12.82% and 4.73%, respectively. The presence of the ilmenite phase in the titanium-enriched slag was confirmed by X-ray diffractometry and EDS patterns, and the content of the TiO2 in the enriched slag can get as high as 43.75%.

Effect of Mechanical Activation and Gamma-Irradiation on Structural-Phase State of Ti-Al-C Powder Reagents

The influence of mechanical activation and gamma-irradiation on the structural-phase state of Ti-Al-C powder reagents was studied. The following compositions were used for research: 1) 78% Ti + 14% Al + 8% C; 2) 80% Ti + 12% Al + 8% C; 3) 81% Ti + 10% Al + 9% C. Mechanical activation of these compositions leads to an increase in the diffuse background, a decrease in the intensity of diffraction reflections of mixture components and a broadening of peaks, as well as micro-deformations. Depending on the ratio of components, the structural parameters can either increase in comparison with the initial ones, or decrease. The effect of gamma radiation with a dose rate of 1 Gy/s and accumulated dose of 3·104 Gy on the mechanocomposites of the Ti-Al-C system causes unsystematic change in crystal lattices of elements, which can be explained by radiation-stimulated diffusion. Gamma-irradiation also reduces micro-deformations that occur after mechanical activation, while crystallites of the components remain nanoscale.

Influence of Mechanical Activation and Mechanical Alloying on the Structure, Phase State of the Fe-Ni-Co-Al-Nb Powder Composition and on High-Entropy Coatings Based on it

The article presents the assessment study of mechanical activation and mechanical alloying effect on the structure, phase state of the powder composition and of the coating based on it. The duration of mechanical activation was varied as follows: 1 h, 2 h, 4 h, 8 h, 16 h, 32 h. It is shown that in order to from a high-entropy FeNiCoAlNb alloy on the workpiece surface the duration of mechanical activation must be at least 4 hours. We described the mechanism of mechanical alloying and ways of accelerating this process.

Thermal properties of calcium-aluminate based materials

Good cementing properties, fast setting and strong thermal performance make calcium-aluminate a valuable raw material for use in the production of different types of new refractory materials, e.g., heat conductive/storage materials. The main aim of the study was to determine thermal properties of novel Nb-slag based materials with different fillers, and to clarify optimal composition and technology. Process of preparation of studied materials was following: mixing of components, casting to moulds and hardening of materials. To estimate potential application areas, we studied the following thermal properties of CA-based materials: thermal behaviour, coefficient of thermal expansion (CTE) and conductivity. For this small cylindrical specimens were cut out from produced materials, and plates sized 300 × 300 mm were used for conductivity studies. Different compositions of CA-based materials, the hardening process, and the influence of mechanical activation on the strength were analyzed. Best thermal properties similar to the analogous reference material were obtained by quartz sand and granite sand as filler materials. The thermal conductivity of the novel CA-based material is 1.5 times higher and the bending strength is about 3 times higher compared to commercial thermoplates.

The influence of high-energy ball milling and nanoadditives on the kinetics of heterogeneous reaction in Ni-Al system

Kinetic studies were performed utilizing high-speed temperature scanner in the Ni-Al system including those with and without mechanical activation (MA) of different duration in a planetary ball mill, with and without using carbon nanoadditives (NA). The temperature profiles were taken and treated at different heating rates from 100 up to 2600 °C/min considering the influence of activation duration and the role of nanoadditive on the characteristic points of thermograms. Kissinger method allowed to evaluate activation energy (Ea) for non-activated, activated (1, 2, 3, 5 min), nanoadditive (1 wt.%) containing and nanoadditive (1 wt.%) containing mechanoactivated (1, 3, 5 min) mixtures. The beneficial influence of NA on the interaction between Ni and Al in the non-activated and moderately mechanoactivated mixtures was demonstrated. The influence of MA and NA on the microstructure features and phase formation sequence at various heating rates were revealed. For all the mixtures under study, T* characteristic temperatures (the temperature, where the maximum exothermic effect was observed) were found to increase with increasing heating rates. It was unravelled that mechanical treatment leads to significant changes in the reaction kinetics and phase formation laws. Particularly, in an activated mixture, the formation of Ni3Al is followed by NiAl intermetallic, in contrast to non-activated mixture, where the reaction proceeds only with the NiAl formation. The both MA in 1 min and addition of 1 wt.% NA decreased the activation energy of the Ni-Al reaction, exhibiting commensurate impact on the effective activation energy value of the Ni-Al system. However, > 3 min MA in the presence of 1 wt.% NA have prohibitive effect on the reaction in the Ni-Al system.

The Influence of Mechanical Activation on Hydrogen Absorption by Intermetallic Compound LaNi2.5Co2.4Mn0.1

The influence of mechanical activation in a high energy planetary ball mill on hydrogen sorption and structural properties of intermetallic compound LaNi2.5Co2.4Mn0.1 in relation to its application as a filler in composite metal-polymer membranes for hydrogen separation from gas mixtures was studied. It has been determined that the basic results of performed processing are the decrease in the coherent scattering domain size and the increase in lattice microstrain while the unit cell parameters remain unchanged. In the temperature range of 298–333 K, the hydrogen absorption and desorption isotherms were measured, and the values of the related enthalpy and entropy, which do not depend on mechanical activation time, were determined. The results of this work allow us to consider the obtained data as reference values to describe the hydrogen sorption behavior of a metal-hydride component in composite membranes with satisfactory accuracy.

Influence of Mechanical Activation on the Properties of Oil Refining Supports and Catalysts

Scientific publications and patents on mechanochemical synthesis of inorganic supports and catalysts of oil refining processes (cracking, reforming, hydrotreating, and hydrocracking) were analyzed. It was shown that the introduction of mechanical activation into the process of synthesis of inorganic supports and catalysts typically enhances their catalytic activity and selectivity. Features of the mechanochemical synthesis of complex nickel-molybdenum oxides, which are precursors of nickel-molybdenum sulfide hydrotreating catalysts, were considered. It was demonstrated that, under mechanical activation conditions, it is possible to prepare β-NiMoO4, a highly active and thermostable nickel-molybdenum oxide containing Mo in tetrahedral coordination. The technology of producing highly dispersed carbide-containing catalysts with the use of the mechanical activation method, developed at the Institute of Hydrocarbon Processing, Siberian Branch, Russian Academy of Sciences, was described. The texture and morphology of the resultant highly dispersed bulk carbide-containing catalysts were considered. The size of the active particles was estimated at 2–5 nm. Сatalytic tests revealed high catalytic activity of the highly dispersed carbide-containing catalysts in the model reaction of dibenzothiophene hydrodesulfurization.

Effects of mechanical activation on the formation and sintering kinetics of barium strontium titanate ceramics

The influence of mechanical activation on the formation, sintering kinetics and morphology was investigated in sintered barium strontium titanate (BST) ceramics with different Ba-to-Sr ratios. Initial powders were mechanically activated for 20 and 120 min, leading to mechano-chemical reaction and formation of BaxSr1-xTiO3 phases. Agglomeration was found to represent an important factor in the process of formation of BaxSr1-xTiO3 phases around 800?C and during sintering. It reduces the effectiveness of mechanical activation on formation of BaxSr1-xTiO3 phases beyond the short period (20 min), while in the process of sintering, prolonged mechanical activation (120 min) leads to a significant reduction in sintering temperature and the corresponding value of activation energy. In addition, all three systems show a phase transformation around 1100?C, attributed to the hexagonal-to-cubic phase transition. Morphology of the final sintered ceramics can be correlated primarily with the state of the pre-sintered powder, where mechanically activated powders with smaller particle size produced more compact and less porous final product.

ВЛИЯНИЕ МЕХАНОАКТИВАЦИИ ЗОЛЫ УНОСА И РЕЖИМОВ ТВЕРДЕНИЯ НА ПРОЧНОСТЬ ГЕОПОЛИМЕРОВ НА ЕЕ ОСНОВЕ

The problems of increasing the reactivity of fly ash of the Apatity thermal power plant in the reactions of geopolymerization occurring under the influence of mechanical activation were considered. The effect of the normal and hydrothermal curing of fly ash activated with sodium hydroxide solution on the strength of the resulting geopolymers was studied.

Influence of mechanical activation and heat treatment on surface development and oxide layer thickness of Ti6Al4V ELI alloy

Purpose: The paper presents the results of mechanical activation of the surface on oxide layer thickness after heat treatment of TU6Al14V ELI alloy. Design/methodology/approach: Specimens were made from 5 mm diameter rod cut into semicircular slices. The samples were mechanically activated throughout mechanical treatment of the surface: one sandblasted with glass beads during 5 minutes and other ground with sandpaper grit 40, 180, 220 and 800 during 7.5 and 15 minutes. Findings: Then microstructure of specimens etched with Kroll solution was observed using an optical microscope and roughness parameters of the surface were measured. Research limitations/implications: Afterwards heat treatment (550°C, 5 hours) was conducted, then roughness parameters and thickness of the oxide layer were measured by means of a scanning microscope. Practical implications: The conducted research showed up that mechanical activation of the surface which cause an increase of surface development results in greater thickness of the oxide layer which is formed during heat treatment. Nevertheless, mechanical activation that results in a decrease of surface development, such as polishing, results in a decrease of oxide layer thickness. Originality/value: The results of the research can be used to obtain the desired thickness of the oxide layer in the production of the elements that require increased wear and corrosion resistance.

Influence of Mechanical Activation on the Phase Formation in the Synthesis of Cordierite from Talc and Andalusite

Cordierite is known as a leading candidate material for many applications. In this study, mechanical activation assisted synthesis of cordierite using andalusite as a starting material was attempted and phase formation of powder obtained from the heat treatment of talc-andalusite-silica system was investigated. The stoichiometric composition of cordierite (2MgO·2Al2O3·5SiO2) was prepared and ground in planetary ball mill at the rotational speed of 300 and 500 rpm for 0, 30, 60 and 90 min. The powder mixtures were heat treated in air at the temperature ranging from 1150 to 1350°C for 2 hours. Thermal reaction, phase present and microstructure of the starting materials and synthesized products were analyzed by differential thermal analysis (DTA), X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. It was found that cordierite phase increased with the grinding time and speed and synthesis temperature. The kinetics of phase formation in this system were also discussed.

Influences of mechanical activation and heating rate on reaction processes in combustion synthesis of NiAl-Al2O3 composites

This paper investigates the combustion synthesis of NiAl-Al2O3 composites by the heating of Ni, NiO and Al powder mixture from 20 °C to 1300 °C. The influence of mechanical activation (without and with 1 h) and heating rate (20 °C/min and 40 °C/min) on thermal events in combustion synthesis process are investigated. Thermal events are assessed by Differential Thermal Analysis (DTA), X-Ray Diffractometry (XRD) and Scanning Electron Microscopy (SEM). By heating the sample without mechanical activation, exothermic reaction of NiO reduction by Al and Ni-Al intermetallic phases (Al3Ni, Al3Ni2, AlNi and AlNi3) production happened in the presence of molten Al at 870 °C as one DTA peak. Mechanical activation causes occurrence of these reactions more separately at lower temperatures (590 °C and 630 °C). By decrement in the heating rate, these reactions happened in a more dispersed way at lower temperatures (590 °C and 630 °C). The reaction temperature for nickel aluminides formation in the presence of eutectic melt of AlNi3-Al is constant regardless of heating rate in mechanically activated powder. A seven-stage mechanism for reactions in a mechanically activated sample at a heating rate of 40 °C/min is proposed. Initially, by heating of the powder, an exothermic reaction between nickel oxide and aluminum and also nickel and aluminum occurs at 590 °C in solid state. NiO is consumed totally and Al2O3 is produced from the nickel oxide reduction by aluminum. Nickel aluminide phases are formed from reactions between aluminum and primary nickel and also from aluminum and nickel formed by aluminothermic reduction of nickel oxide. With continuation of heating process, Al-Al3Ni eutectic transition happens at 630 °C and results in the liquid phase formation. Presence of the molten phase accelerates the exothermic nickel aluminides formation reactions. Aluminum is consumed totally in this stage and more intermetallic phases are developed. By increasing the temperature, diffusion is enhanced. The remaining Al3Ni melts at 856 °C. This small amount of molten phase slightly enhances exothermic reactions between nickel aluminides and leads the system towards the equilibrium phase. After this event, reactions progresses gradually. The nickel core shrinks by the diffusion progressively and the whole nickel aluminides system undergoes a gradual evolution towards the NiAl equilibrium phase.

Influence of mechanical activation of a cordierite -based filler on sedimentation stability of lost foam refractory coatings

For the development of the Lost Foam refractory coatings with controlled rheologic properties, the influence of the mechanical activation process on the cordierite-based filler?s properties change was examined. First of all, the test referred to the change of filler particles? size and shape, as well as to dispersion ability and stability of the coating suspension. Cordierite was obtained by synthesis in a solid state, out of the mass consisting of kaoline, alumina, quartz, sepiolite. For characterization purposes, the following methods were used: X-ray diffraction, differential thermal analysis, SEM and optical microscopy. Mechanical activation of filler was performed in a vibrating mill. The upper boundary of the grain size was 100% -30 x 10-6 m, the times were (min): 15; 30; 60. The new composition of Lost foam refractory coatings has been developed with a change of the coating production process, as well. These newly synthesized coatings proved to be effective in terms of a positive influence on a surface quality, structural and mechanical properties of aluminium castings. Test results may be useful to have the Lost Foam refractory coatings specified together with other process parameters used for the production of castings according to this casting method.