Mechanical Activation Method Research Articles

Economic Evaluation of Thermal and Mechanical Activation Energies in Gypsum Production

Plaster is among the most needed raw materials in the world. In this study, thermal activation provided by calcination and mechanical activation methods provided by intensive milling in the plaster production process were evaluated in terms of activation energy. In this context, the energies of laboratory-scale thermal and mechanical activation processes were calculated and these activation methods were evaluated economically and the ideal activation methods were determined. Although the mechanical activation method creates additional investment and operating costs, it reduces the calcination temperature by 13 °C, thus provides lower energy costs. Addition of a mechanical activator mill before thermal activation in plaster production as a more economical and more environmentally friendly method was proposed.

A hydrometallurgical process flowsheet for recovering MoO3 from Molybdenite

In this study, a comprehensive hydrometallurgical processing of molybdenite (MoS2) concentrate was investigated. This investigation involved a novel approach combining mechanical activation, leaching, and polyelectrolyte extraction methods. The integrated method effectively addressed the challenge of low leaching rate of molybdenite, resulting in the successful production of high-purity molybdenum trioxide. Milled molybdenite samples were analyzed by different methods of X-ray diffraction, atomic force and electron microscopy, and BET. The increasing trend of the specific surface area during milling was determined by a model fitting which was useful for optimization of milling time. Several leaching reagents were studied to achieve high molybdenum dissolution. The most promising results were achieved through a two-hour process, yielding an impressive leaching efficiency of 80% and a resulting Mo concentration of 6700 mg/L. Molybdenum recovery was efficiently carried out through polyelectrolyte extraction, as confirmed by ICP and CHNS analyses, demonstrating selective precipitation of molybdenum from the solution. The subsequent calcination of the precipitated molybdenum(VI) compound resulted in the production of high-purity molybdenum trioxide. Furthermore, a conceptual hydrometallurgical treatment process for molybdenite concentrate was proposed, aiming to recover molybdenum, sulfuric acid, and copper. This proposed process presents a promising avenue for further exploration in pilot plant studies within the molybdenum industry.

ГЕОПОЛИМЕРЫ, ПОЛУЧЕННЫЕ МЕХАНОАКТИВАЦИЕЙ ИСХОДНЫХ КОМПОНЕНТОВ: ОБЗОР ТЕКУЩИХ ТЕНДЕНЦИЙ

The reaction potential of a substance can be significantly increased by thermal, mechanical, and chemical methods. A combined method is also possible, as in the case of developing geopolymers, the technology of which involves treating precursors with chemical reagents. On the other hand, with the increase in the number of publications devoted to the development of geopolymers, research to reduce the amount of CO2 emissions and the cost of geopolymers production becomes relevant. This review examines three generations of geopolymers: 1 – metakaolin based geopolymers, 2 – geopolymers based on rocks, and 3 – fly ash based geopolymers. A comparative analysis of ways to improve the physical and mechanical properties of fly ash based geopolymers by mechanical activation is presented. It has been established that mechanical activation of fly ash, in addition to improving the strength characteristics of geopolymers, makes it possible to synthesize a geopolymer without thermal curing. After this, the focus is on the method of mechanical activation of fly ash and clay minerals, especially kaolinite. The particular interest in metakaolin based geopolymers is due to the high potential for widespread application, since these geopolymer technologies have greater potential to reduce CO2 emissions and, therefore, production costs. Also, the development of protection against heavy metals or radioactive substances requires the implementation of technology exclusively using geopolymers based on metakaolin.

The use of clay from the Herpegezh deposit for the production of ready-made compositions for the preparation of drilling fluids

The preparation of drilling fluids from ready-made compositions allows you to reduce costs, including by obtaining the drilling mud of the required composition with an optimal consumption of reagents, simplifying technological equipment and reducing requirements for the qualification of maintenance personnel. One of the most common components of drilling fluids are clays, therefore, one of the important tasks is to study clays from various deposits in order to establish the possibility of their use in the production of compositions for the preparation of drilling fluids. The purpose of this study was to establish the chemical and technological characteristics of the clays of the Herpegezh deposit and to develop recommendations for the preparation of finished compositions. Particular attention was paid to the choice of the method of activation of raw materials, ensuring the maximum possible productivity, in particular, the traditional method of activation and mechanical activation in the disintegrator were compared. Also, as a result of the conducted experiments and processing of their results, the dependences of the technological characteristics of the drilling mud prepared from the Herpegezh clays on the mass fraction of the clay substance were established.

Reaction Process of Solid Waste Composite-Based Cementitious Materials for Immobilizing and Characterizing Heavy Metals in Lead and Zinc Tailings: Based on XRD, SEM-EDS and Compressive Strength Characterization.

This study investigates the synergistic effect and mechanism of gelling materials with blast furnace slag (BFS), steel slag (SS) and desulphurization gypsum (DG) as the main components on the hardening of heavy metal ions by lead and zinc tailings. It is found that lead and zinc tailing (LZT) is mainly composed of dolomite and quartz and contain small amounts of calcium, aluminum, iron, magnesium and other elements as well as heavy metals such as lead and zinc. By the mechanical activation method, it is found that the lead and zinc tailings powder has the largest specific surface area and the highest activity index when the ball milling time is 2 h. At a hardening timepoint of 28 d, the calcite crystals in the samples are intertwined with the amorphous C-S-H gel (C-S-H gels are mainly composed of 3CaO∙SiO2 and 2CaO∙SiO2), which enhances the structural strength of the samples. The chemical reaction analysis confirmed that the formation of calcite is a major driver for the hydration reaction of the steel slag-desulphurization gypsum (SSSDG) system. Overall, the slag, steel slag and desulphurization gypsum solid waste-based gelling materials have synergistic effects in hardening heavy metals by limiting the leaching of metal ions, adsorbing metal ions and hardening heavy metals, and facilitating the hydration process through the formation of compound salt precipitates.

Selective extraction of rare earth elements and cobalt from iron residue containing rare earth using mechanical activation and reductive leaching method

NdFeB waste is an important rare earth secondary resource, which is usually treated by hydrochloric acid preferential method in traditional industrial process. Herein, leaching residue containing about 0.5–1 % rare earth elements (REEs) and a small amount of cobalt is generated as a by-product in the process. The leaching residue is mainly composed of iron oxide and generally sold to steelmaking plants, resulting in the waste of REEs and cobalt resource. An efficient recycling process is proposed for selectively extracting REEs and cobalt from the iron residue containing rare earth by mechanical activation and reductive leaching method based on mineral liberation analysis (MLA) and thermodynamic analysis. By analyzing the composition of the raw materials, magnetite and limonite are in an encapsulated state with rare earth minerals. REEs and cobalt are mainly present in the rare earth aluminate phase. To achieve deep extraction of REEs and cobalt, the first step is to change the insoluble phase of iron residue by mechanical activation method. During this process, the crystal structures of Fe2O3 and Fe3O4 in the iron residue containing rare earth are disrupted and transformed into amorphous states. During the reductive leaching process, part of the iron is converted into divalent. The iron in the leaching solution can be removed by hematite method and achieved phase reconstruction. Thus, REEs and cobalt can be extracted selectively from leaching residue of NdFeB waste.

A comparative study by mechanical activation and conventional processes of BaTi0.95W0.05O3 ferroelectric ceramic

BaTi0.95W0.05O3 is synthesized by both mechanical activation process and conventional solid-state reaction technique for comparative study. The prepared sample is characterized by XRD and SEM. There is proper formation of perovskite structure in BTW from both of the methods confirmed by XRD. Scanning electron microscopy (SEM) depicts that the micro-grains obtained by the mechanical activation method had comparatively fine structure compared to that of the conventional solid-state process. The mechanically activated samples display enhanced electrical properties showing a high value of the dielectric constant and a low value of the dielectric loss. The remnant polarization (Pr) value and d33 values were also high in samples synthesized by the mechanical method.

A convenient and user-friendly hydrometallurgical process for preparing porous siliceous adsorbents using ascharite tailings: Mechanism of structural change and evaluation of adsorption properties

Ascharite tailings are discarded by the boron industry due to their low boron content and high magnesium content. Additionally, the large-scale storage of these tailings contributes to resource wastage and environmental pollution. The present study successfully prepared a siliceous adsorbent through the combined use of mechanical and acid activation methods. The tailings underwent acid treatment under mild conditions, leading to the dissolution of magnesium while maintaining the integrity of the silicate framework. This process resulted in the formation of a mesoporous structure primarily composed of slit-shaped pores. The specific surface area reached 234.7 m2 g−1, while the pore volume reached 0.31 cm3 g−1. The maximum adsorption capacity for methylene blue was 0.66 mg m−2 per unit of surface area. The pollutants displayed a flat orientation at equilibrium, with a maximum tilt angle of approximately 53°. The adsorption rate was limited due to the decrease in available adsorption sites. However, mechanical activation increased the density of active silanol sites from 2.76 to 4.34 mg m−2, significantly weakening the shielding effect on other potential sites. Thus, tailings resources can be effectively converted into valuable adsorbent materials using a convenient and controllable hydrometallurgical process.

Structural and electrical properties of PLZT x/65/35 ceramics prepared via mechanical activation method near the morphotropic phase boundary

This paper reports the effect of lanthanum addition on the structural and electrical properties of (Pb1-xLax)(Zr0.65Ti0.35)O3 (PLZT x/65/35, x = 8%,10%,12%,15%) ceramics near the morphotropic phase boundary. Studies were conducted on the PLZT x/65/35 ceramics synthesized via a combinatorial approach of high-energy ball milling (mechanical activation method) followed by Cold Isostatic Pressing (CIP). Due to the application of CIP, PLZT ceramics exhibited improved density and a closely packed microstructure. The SEM analysis showed that PLZT x/65/35 ceramics exhibited an increase in grain size with higher concentrations of La3+ ions. Room temperature X-ray diffraction results revealed the formation of perovskite PLZT phase. The investigation on temperature-dependent dielectric, ferroelectric properties of PLZT x/65/35 ceramics provided experimental confirmation of structures cited in XRD analysis. Among all the compositions, PLZT 8/65/35 samples showed a well saturated, uniform P–E hysteresis loop with a high remanent polarization (Pr). Poled PLZT 8/65/35 samples displayed electric field induced large strains with limited hysteresis. Piezoelectric charge coefficients (d33), electromechanical coupling factors (kp, k33, k31) were determined for poled PLZT x/65/35 ceramics and it was found that PLZT 8/65/35 ceramics reveal properties superior to other compositions. Furthermore, the unipolar strain, Pr, d33, kp, k33, k31 values of PLZT 8/65/35 composition exceeded the previously reported ones for the same composition prepared via sol-gel synthesis technique.

Construction of Bi12O17Cl2/ZnO-CN Z-scheme photocatalyst with ZIF-8 as precursor to remove antibiotics and Cr(VI) under visible light: Optimization, mechanism and degradation path

In this work, Bi12O17Cl2 and ZIF-8 were synthesized via a facile in-situ precipitation method, while ZnO-CN was obtained through the pyrolysis of ZIF-8. Then, a novel Bi12O17Cl2/ZnO-CN composite catalyst with Z-scheme heterojunction was prepared by mechanical mixing-low temperature activation method. When the ZnO-CN is pyrolyzed at 550 ℃ and accounts for 10 wt% in the Bi12O17Cl2/ZnO-CN composite, the composite exhibited a significantly higher degradation rate for levofloxacin hydrochloride (LVX) (94.50%) compared to Bi12O17Cl2 (67.30%) and ZnO-CN (36.80%), while also achieving a high removal rate of Cr(VI) under acidic conditions (92.00%). And the toxicity of LVX to wheat decreased significantly after photocatalytic degradation. Meanwhile, the Bi12O17Cl2/ZnO-CN has good universality, salt resistance and reuse stability. The experimental results of sample characterization show that the improved photocatalytic performance of Bi12O17Cl2/ZnO-CN composite can be attributed to the high-efficiency separation of electron-hole pairs (e--h+), enhanced light absorption in the visible region, increased specific surface area and active sites. Both the free radical capture experiment and electron paramagnetic resonance (EPR) test indicate that •O2- and h+ are the primary active species in the process of degrading LVX by Bi12O17Cl2/ZnO-CN. Combined with mechanism exploration experiment and iquid chromatography-mass spectrometry (LC-MS) analysis, a possible direct Z-scheme heterojunction electron transfer mechanism and photocatalytic degradation pathways for LVX was proposed. This work enhances the photocatalytic performance of Bi12O17Cl2 and provides an idea for antibiotic or Cr(VI) wastewater treatment.

Structural, electrical and electron emission property studies of high dielectric constant (Pb0.88La0.12)(Zr0.65Ti0.35)O3 ceramics for ferroelectric cathode applications

Ferroelectric materials with high dielectric constant produce high electron emission and the life span of ferroelectric cathodes might be potentially increased if their piezoelectric charge coefficient can be made negligible. For achieving these properties, two different methods were employed to synthesize (Pb0.88La0.12)(Zr0.65Ti0.35)O3 (PLZT12/65/35) ceramics viz., the conventional method (mortar and pestle) followed by uniaxial pressing and the high energy, mechanical activation method (abbreviated to MA, hereinafter). This was done using a high-energy ball mill to reduce particle size drastically. Cold isostatic pressing was used to compact the milled powder which resulted in a significant increase in the density. X-ray diffraction confirmed single phase with cubic perovskite structure. Particle size was measured from TEM images. Morphological studies were carried out by SEM analyses to observe the grain structure. Of these two syntheses methods, PLZT 12/65/35 ceramics prepared via high energy ball milling exhibited significantly higher dielectric constant, surpassing the previously reported values and also exhibited low remnant polarization value, negligible piezoelectric charge coefficient at room temperature. High temperature dielectric measurements at various frequencies confirm the relaxor behavior of PLZT 12/65/35 ceramics. Ferroelectric cathode configuration based on PLZT 12/65/35 ceramics with high relative permittivity allowed us to achieve exceptionally high current density and power obtained in Radio frequency range.

Fabrication and investigation of novel hafnium-zirconium carbonitride ultra-high temperature ceramics

By a combination of mechanical activation, combustion synthesis, and spark plasma sintering methods, bulk materials in the Hf-Zr-C-N system with various Hf/Zr atomic ratios were produced. The mechanical activation process in a low-energy mode (350 rpm) for 90 min resulted in the formation of layered Hf/Zr/C composite particles 10–30 μm in size, depending on the Hf/Zr ratio. The diffraction spectra of the as-synthesized powders were described by several isomorphic (Hf,Zr)(C,N)ss cubic phases with different nitrogen content. Spark plasma sintering contributed to the homogenization of the chemical composition and allowed production of the dense (∼98%) single-phase hafnium-zirconium carbonitrides with an FCC structure. The bulk ceramics exhibited superior hardness (∼17 GPa) and fracture toughness (∼5 MPa m1/2), relative to (Hf,Zr)C carbides prepared by similar methods.

Effect of Non-Functional Polyorganosiloxane Additives on the Hydrophysical Properties of Cement Systems

A research on the influence of non-functional organosilicon compounds (OSC) - polyorganosiloxanes on the hydrophysical properties of cement systems has been carried out. Two groups of polyorganosiloxanes with the most typical structure (linear, cyclolinear, and three-dimensional) have been studied: polyorganylsilsesquioxanes and polydiorganylsiloxanes. Within the group of polyorganylsilsesquioxanes the polyphenylsiloxane (PPS) and polyvinylsiloxane (PVS) differing in the type of radical and degree of structure completion were studied. Within the group of polydiorganylsiloxanes the polydimethylsiloxane liquid (PMS-6) and dimethylsiloxane rubber (SKTN) differing in molecular weight were studied.It has been established that non-functional organosilicon compounds (polydiorganylsiloxanes, polyorganylsilsesquioxanes) are able to hydrophobize the cement systems when introduced by the method of mechanical activation. At the same time, SKTN is a powerful agent for efflorescence formation, preventing the removal of calcium hydroxide Ca (OH)2 out of the cement stone.

Experimental Investigation of Microfluidic Device for Platelet Activation.

Wound healing is accelerated when Platelet Rich Plasma is activated and growth factors are released. In this study, it was aimed to stimulate platelets without using chemical stimulants. Two types of mechanical platelet activation methods have been proposed in this study. The first one is a microfluidic chip developed with the shear-induced platelet activation approach. The second one is a piezo-based ultrasound-assisted device which provides platelet activation by stimulating with an ultrasonic wave (0.55 and 1.1 MHz). Three different microfluidic chip designs were worked out to determine the optimal shear stress characteristics; 8-nodes (2789 µs, 288 shear pulses, and 98.3 dyne/cm2), 40-nodes (2765 µs, 1440 shear pulses, and 95.5 dyne/cm2) and pillar-shaped (1030 µs, 1656 shear pulses, and 48.1 dyne/cm2). The highest platelet activation rate (72.7%) was obtained from the chips with 8-nodes. In the ultrasound-assisted device, 32.4% activation rate was obtained from ultrasound waves with 0.55 MHz frequency and 10 Vp-p amplitude. These activation rates, determined by CD62P (P-Selectin) expression, are significantly higher than spontaneous activation of intact platelets (8.5%). In addition, the gradual increase in activation of stimulated platelets with incubation at room temperature showed that activation continued after stimulation. The results showed that these microfluidic devices can be used for platelet activation to enhance the effect of PRP treatment and might reduce adverse immune reactions that may happened due to the use of exogenous activator substances. Fast-response, low-cost, easy-to-use and controllable biomedical device have been developed for PRP applications.

Facile solid-phase synthesis of starch-fatty acid complexes via mechanical activation for stabilizing curcumin-loaded Pickering emulsions

Starch-fatty acid complexes used as emulsifiers have caught great attention because of their renewability and excellent emulsifying property, the development of a simple and efficient synthesis method for the fabrication of starch-fatty acid complexes is still greatly challenging. Herein, the rice starch-fatty acid complexes (NRS-FA) were successfully prepared by mechanical activation method using different long chain fatty acids (myristic acid, palmitic acid, and stearic acid) and native rice starch (NRS) as the raw materials. The results showed that the prepared NRS-FA with a V-shaped crystalline structure exhibited a higher digestion resistance than NRS. Moreover, when the chain length of fatty acids increased from 14 to 18 carbons, the contact angle of the complexes was much closer to 90°, and the average particle size was smaller, deriving the better emulsifying property of NRS-FA18 complexes, which were suitable to be used as an emulsifier to stabilize curcumin-loaded Pickering emulsions. The results of storage stability and in vitro digestion showed that the curcumin retention could reach 79.4 % after 28 days of storage and 80.8 % of curcumin was retained in the system after simulated gastric digestion, showing good encapsulation and delivery performance of prepared Pickering emulsions, which attributed to the enhancement of the coverage of particles at the oil–water interface.

Механоактивационный способ получения вяжущего для устройства цементогрунтовых свай

The physicochemical processes of grinding substances by mechanical activation method are considered. The analysis of the processes occurring in solid bodies during their mechanical processing is carried out. The main types of defects arising in the process of mechanical processing of layered silicates are described. For mechanical activation, the most common types of mills are presented, which include disintegrators and planetary mills. The principles of operation of disintegrators and planetary mills are considered in detail. Classification of mills intended for clinker grinding is given. The dependence of the specific energy consumption for clinker grinding and the strength of the samples on the type of mills is analyzed. The dependence of the specific surface of the crushed clinker and the strength of the samples on the speed of the rotor of the impact-reflective mill is investigated. Recommendations on the choice of the type of clinker grinding mills are given.

Dentinal tubule penetration of sodium hypochlorite in root canals with and without mechanical preparation and different irrigant activation methods.

This study evaluated the dentinal penetration depth of 2.5% sodium hypochlorite (NaOCl) in root canals with and without preparation and different irrigant activation protocols. Sixty-three bovine mandibular incisors were randomly allocated to 6 groups (n = 10): G1, preparation + conventional needle irrigation (CNI); G2, preparation + passive ultrasonic irrigation (PUI); G3, preparation + Odous Clean (OC); G4, no preparation + CNI; G5, no preparation + PUI; G6, no preparation + OC; and CG (negative control; n = 3). Samples were filled with crystal violet for 72 hours. Irrigant activation was performed. Samples were sectioned perpendicularly along the long axis, 3 mm and 7 mm from the apex. Images of the root thirds of each block were captured with a stereomicroscope and analyzed with an image analysis software. One-way analysis of variance, followed by the Tukey post hoc test, and the Student's t-test were used for data analysis, with a significance level of 5%. The NaOCl penetration depth was similar when preparation was performed, regardless of the method of irrigation activation (p > 0.05). In the groups without preparation, G6 showed greater NaOCl penetration depth (p < 0.05). The groups without preparation had a greater NaOCl penetration depth than those with preparation (p = 0.0019). The NaOCl penetration depth was similar in groups with root canal preparation. Without root canal preparation, OC allowed deeper NaOCl penetration. The groups without preparation had greater NaOCl penetration than those undergoing root canal preparation.

The effect of mechanical activation methods on the properties of local clays and waste bentonites

One of the most important indicators of mechanical activation of clay minerals is the effect of activation time on the strength of the mixture. One of the most important parameters in the preparation of drilling fluid based on clays is their ability to swell, and the effect on the swelling of clays during mechanical activation was studied. One of the most important parameters of clays used in the preparation of drilling fluids resistant to thermomechanical effects is their colloidal index. Therefore, the effect of mechanical activation time on the colloidal index of these clays was studied. The method of activation of bentonites and analysis of their rheological parameters was studied. In the process of mechanical activation of clays, their activation of chemical reagents created conditions for modifying the increased specific surface area of clay materials.

Relaxor multiferroic properties of nanostructured BaTiO3–Fe2O3–Bi2O3 lead free for energy storage applications

Relaxor multiferroic properties of nanostructured 0.30BaTiO3–0.52Bi2O3–0.18Fe2O3 mol% (BFBT) were prepared via the mechanical activation method. The mixed powders were ball milled at 10, 20, 30, 50 and 75 h to obtain nanostructured materials. Room temperature XRD patterns for these nanostructured materials at different ball-milling times were investigated. The ball milled of nanostructured BFBT at different ball-milling times is characterized and identified by FTIR. After 50 h, HRTEM revealed the nanostructure of BFBT with an average particle size of 27.86 nm. Dielectric characterization showed a broad and frequency-dependent diffusion in phase transition around 560 K that shifted to the higher temperature with increasing frequency. The dielectric diffusivity (Υ = 1.78) was calculated from the modified Curie–Weiss law. Dielectric permitivitty (ε′) data were fitted using the Vogel–Fulcher relation, confirming the relaxor nature. Furthermore, the slim P-E hysteresis loop demonstrates recoverable energy density (Wrec = 16.17 mJ/cm3) and energy storage efficiency (η = 89.3%) at 360 K. The Néel Temperature (TN = 394 K) was determined by the magnetic susceptibility measurements. The M-H date shows a weak ferromagnetic behavior of the 50 h mechanical milled sample. Therefore, the presented work provides guidelines for synthesizing nanostructured BFBT by mechanical milling for the development of high-potential lead-free energy storage applications.

Investigation of mechanical activation effect on high-volume natural pozzolanic cements

Abstract Mechanical activation is one of the most preferred methods to increase the reactivity of mineral, mining, and industrial wastes or materials with low pozzolanic content in cement production. The mechanical activation process of such materials takes a long time and requires high grinding energy. Although it seems like an advantage to using the materials in cement production by gaining reactivity thanks to mechanical activation, mechanical activation is a long duration and expensive process, causing an increase in cement production costs. In this study, a hybrid method is proposed for the mechanical activation of materials in a shorter duration and with lower energy consumption. A roller press and a hammer grinder were integrated before the laboratory type ball mill to realize the mechanical activation processes. To perform the mechanical activation processes in this way, two different hybrid grinding methods were tested and compared. Both methods activated volcanic tuff samples with low pozzolanic properties were investigated particle microstructures, energy consumption differences, mechanical activation durations and their effects on the cement performance, and mortar microstructures. The hybrid grinding method integrated with roller press and ball mill was determined to be the best mechanical activation method.