Mechanical Activation Process Research Articles

Fabrication of a novel hydrophobic zinc borate/polydopamine/talc nanocomposite with sandwich-like structure for enhanced tribological properties

Two-dimensional layered materials (2DLMs) as lubricant additives have received increasing attention due to their low interlaminar shear stress, outstanding chemical stability and lubrication effects, but the extreme pressure properties, dispersion and dispersion stability in base oils are poor. Herein, a hydrophobic zinc borate/polydopamine/talc (OA-ZB/PDA/TA) nanocomposite with sandwich-like structure is prepared by hydrothermal-assisted intercalation combined with mechanical activation process using natural talc 2DLMs as substrate and oleic acid (OA) as a surface hydrophobic modifier and peeling aid. No obvious sedimentation of OA-ZB/PDA/TA occurs in the rapeseed oil after 15 d, while pure TA is significantly deposited after 12 h, showing superior dispersion and dispersion stability. The OA-ZB/PDA/TA used as a lubricant additive in rapeseed oil exhibits excellent tribological performances under the loads from 147 to 784 N, particularly, wear scar diameter and coefficient of friction reduce by 51.4 and 33.7 % under 392 N, respectively, and the maximum nonseizure load (PB) increases by 27.0 % relative to pure TA. The TA-ZB-TA "sandwich-like" structure gives full play to the synergistic lubrication between ZB NPs and TA, resulting in the sliding and rolling effects under low load, friction film and rolling effect under medium load, and friction film under high load. Our work provides a new avenue for the enhanced extreme pressure properties and dispersion stability of 2DLMs in base oil.

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.

Physicochemical Properties Research of Mechanoactivated Flour from Wheat Germ Cake

In today’s accelerating world, the concept of waste-free production, based on the maximum utilization of all resources, becomes relevant. To increase the use efficiency of materials obtained as a result of grain processing, a man developed an integrated approach implying a disintegrator. The research aim is to study the mechanical activation process impact of flour from wheat germ cake (FWGC) on its physico-chemical properties. The authors revealed the rational mode of the grinding process: the rotation speed of the rotors is 10,500 rpm, the impact velocity is 175 m/s, the process duration is 180 sec, providing a weighted average particle size of the final mechanical powder of 52 microns with maximum bulk density parameters of 760 kg/m3 and water absorption capacity of 70 %. During mechanical activation, the chemical composition of FWGC changes: the mass fraction of proteins increases by 1.8 %, simple sugars – by 17 %, ash content – by 11 %, starch content decreases by 8 % compared to the FWGC obtained without mechanical activation. To determine the physico-chemical composition of the aqueous extract of the FWGC, a man run the microfiltration parameters selection: the aqueous extract flow rate of the FWGC over the membrane surface is not less than 1.0–1.2 m/s; the working pressure of the process is within 0.25 MPa; the extract temperature does not exceed (25 ± 5)°C. According to the microfiltration separation process research results of the aqueous FWGC extract, the mechanical activation increases the low-molecular-weight proteins proportion in flour, indicating a growth in its bioavailability and digestibility.

Making ultra-high strengthening and toughening efficiency in hybrid reinforcing of aluminum laminated composites via dispersion engineering

To overcome the strength-ductility trade-off dilemma, herein we propose a hybrid in-situ/ex-situ reinforced aluminum matrix composite to achieve a uniform dispersion of reinforcements and strong reinforcement-matrix interfacial bonding. To exploit the pros of inter/intra granular dispersion of reinforcements, nano- Al3BC particles have been in-situ synthesized into ultrafine-grained (UFG) Al grain interior reinforced by carbon nanotubes (CNTs) via an elemental powder mixture, mechanical activation and subsequent annealing process. The in-situ nano-scaled Al3BC were uniformly distributed inside the elongated ultrafine Al grains, enabling stronger dislocation pinning and retention, providing stronger effective stress which consequently helps to enhance strength and strain hardening. The as-fabricated (Al3BC, CNT)/UFG Al exhibits simultaneous enhancement in strength (394 MPa) and total elongation (19.7 %) compared with its counterpart without the nano-Al3BC, suggesting the promising strengthening effects of in-situ/ex-situ reinforcing benefitting from the uniform dispersion and the strong semi-coherent interface with the matrix.

Intensification of opening a thrust alloy based on platinum and rhodium

A high chemical resistance inherent in the alloys based on platinum group metals is one of the reasons for a number of difficulties that arise when dissolving such materials. Nowadays, the dissolution in aqua regia is one of the most effective methods for dissolving corrosion-resistant alloys. The main disadvantage of this method is a release of toxic gaseous substances such as nitrosyl chloride and nitrogen oxides. To decrease the volume of gases thus released without reducing the redox potential of the system, we proposed a method of dissolving a Pt – Rh alloy in HCl-HNO3 with a controlled dosed supply of HNO3 at a given value of the oxidation-reduction potential (ORP) of the system. The potential of the system has been chosen proceeding from the potential for HNO3 – HCl – Pt and HNO3 – HCl-Rh systems and amounted to 0.85 and 0.9 V. The impact of the dispersion and the inherent flaw of PtRh alloys on the dissolution indices of the alloy was also considered. It is shown that the dissolution of a Pt – Rh alloy with a rhodium content of 15 % in HCl – HNO3 at a constant value of ORP = 0.9 V compared to the use of the classic mixture (HCl:HNO3 = 1:3 vol.) provides a decrease in nitric acid consumption by 40%, reduction of the process time, increase in the recovery factor for both platinum and rhodium, and a two-fold reduction of the volume of released nitrogen oxides (theoretical calculation). It is also revealed that the process of mechanical activation of the alloy reduces the dissolution time and leads to almost quantitative dissolution of the sample.

Технологические основы переработки скарновых медно-золотосодержащих руд Кыргызской Республики

Introduction. The paper studies the matters of processing of skarn copper-gold ores from a deposit in the Kyrgyz Republic. Materials and methods. As a study task, the authors performed an analysis of the material composition, including micro- and macroscopic types of analyses are presented. Results. Textural-structural analysis and mineralogical characteristics of the main ore minerals is detailed. The characteristic features of the material composition of the studied types of ores are highlighted and described. The reagent suite for processing of skarn ores has been established by means of additional feed of weakly selective depressants (Na2SiO3) and effective flotation reagents to the process, the introduction of which can significantly improve the concentrate quality. The study direction is also supplemented by the consideration and introduction of the process of mechanical activation into the process flow diagram as a reserve in increasing the grade of metals in the concentrate through the mechanical liberation of minerals by ultrafine grinding. The forms of metal loss with concentrating tailings, which are represented by wollastonite, garnet (andradite) and pyroxenes, clay-micaceous minerals, feldspars, and talc are determined. Discussion. The main losses of sulphide copper are associated with the presence of intergrowths of copper minerals with barren minerals in the samples. When evaluating copper minerals in tailings, copper is present in sulphide minerals – 79.2% and 20.8% rel. belongs to the oxide minerals. Conclusion. The paper summarizes the results of the study with the developed closed flotation flowsheet for the processing of copper-gold skarn ores, which makes it possible to obtain the flotation concentrate with grade of Cu – 25.01%, Au – 55.02g/t, Ag – 401g/t, with recovery into concentrate of Cu – 84.65%, Au – 87.94%, Ag – 89.44%. Concentrate output 2.33%. The implementation of the proposed flowsheet will ensure the achievement of planned production performance in the processing of skarn ores. Resume. At the end of the study work, the authors issued recommendations on adjusting the reagent suite with the inclusion of the weakly selective depressant – liquid glass (Na2SiO3), introducing the process of attritioning the feed of the cleaning operation (ultrafine regrinding) and considering the regularity of the phase composition of the copper minerals of skarn ore from the copper grade, providing the initial grade of copper at 0.9-1.0% in the processed ore by blending the ore feed ore to the concentrator. Suggestions for practical application and direction for future research. The materials of the paper can be useful for mining and processing enterprises when processing skarn copper-gold ores.

Influence of chalcopyrite removal and mechanical exfoliation on the performance of molybdenite catalysts supported on activated bauxite for alcohol synthesis by Fischer-Tropsch process

The top-down approach was used to develop catalysts for higher alcohol synthesis by starting with low-grade molybdenite concentrate and mesoporous activated bauxite as the active metal and support, respectively. The results of the study showed that the process of chemical leaching significantly reduced copper in the form of chalcopyrite in the concentrate by over 95%. This reduction in copper content of purified catalysts led to an increase in the selectivity for C3+ alcohols compared to catalysts based on impure molybdenite. Additionally, the process of exfoliation not only reduced the particle size of the active component but also increased the selectivity for C3+ alcohols and the conversion of CO. The chemical–mechanical activation process developed in this study resulted in an improvement in catalyst activity of more than 50%.

Mechanical activation of coal gasification fine slag and mechanical and thermal properties of coal gasification fine slag–poly(vinyl chloride) composites

To facilitate the high-value utilization of activate coal gasification fine slag (CGFS), a wet mechanical activation process was used. As a result of this treatment, CGFS samples with different particle size distributions were obtained. The effects of mechanical activation on various physical and chemical properties of CGFS were investigated, including its particle size distribution, mineral composition, specific surface area, pore size, crystallinity, particle morphology, chemical bonding, and binding energy. Poly(vinyl chloride) (PVC)/CGFS composites were prepared via a melt blending process, and their mechanical and thermal properties were evaluated. It was found that with increasing levels of mechanical activation, the CGFS particle size distribution became more concentrated and the particle spacing became more uniform. With the increasing mechanical activation, the crystallinity was found to decrease and the content of amorphous mineral matter (such as SiO2 and Al2O3) increased. The observed increase in specific surface area and decrease in average pore diameter due to the mechanical activation was seen to lead to an increase in the number of active sites. The produced PVC/CGFS composite materials were found to exhibit good mechanical properties and dynamic thermal stability. The thermal stability of the PVC composites was also found to improve relative to the composites produced without the use of mechanical activation.

МЕТОДЫ ОЦЕНКИ МЕХАНОАКТИВИРОВАННОГО МИНЕРАЛЬНОГО СЫРЬЯ ДЛЯ КОМПОЗИЦИОННЫХ ВЯЖУЩИХ

In the conditions of constantly increasing construction volumes, there is a necessity to transfer to environmentally efficient technologies for the production of building materials in order to reduce industrial pressure on the ecosphere and ensure rational subsoil use. One of the solutions is to reduce cement consumption by using composite binders with a reduced proportion of the clinker component. Improving the quality of composite binders is possible due to the preliminary activation of the surface of raw components. One of the most effective methods of activating raw materials is mechanical activation. A reasonable choice of its method and mode is possible only on the basis of the results of comprehensive studies in the system "the object of mechanical activation – the instrument of mechanical activation – the indicator of mechanical activation – the product of improvement by methods of mechanical activation". A comprehensive determination of the activity of mechanoactivated mineral raw materials as an indicator of the effectiveness of mechanoactivation includes the use of various research methods and evaluation of: the area of the interface boundary, granulometric composition, morphostructural features, sorption capacity, donor-acceptor surface centers, the energy state of the system and other parameters. The paper proposes a decomposition of the methodology for evaluating mineral raw materials from the position of mechanical activation in the production of composite binders. The use of this methodology will make it possible to rank mineral raw materials of natural and technogenic origin, optimize the process of mechanical activation from the point of view of choosing a rational method and develop generalized recommendations for the selection of technological modes of milling, taking into account the genesis of raw materials for obtaining active mineral components of composite binders of various composition, type of hardening and functional purpose. The development and implementation of the principles of rational selection of mineral raw materials components, based on the example of their application in composite binders, will ensure the specified functional properties and implement a predictive assessment of the performance characteristics of building composites as a whole.

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.

Highly efficient synthesis of nano LiMn0.90Fe0.10PO4/C composite via mechanochemical activation assisted calcination

Among various lithium-ion batteries cathode materials, olivine-type phosphate LiMnPO4 has the advantages of high working voltage, superior theoretical energy density and high stability, however, its electronic and ionic insulation limit its application. In this work, LiMn0.90Fe0.10PO4/C (LMFP@C) nano composites are prepared via a mechanochemical activation assisted carbothermal reduction method, and the consequence of carbon coating amount on the electrochemical performance of the materials is discussed in detail. The results of physical and chemical properties analysis show that the mechanical liquid activation process can effectively reduce the particle size of the precursor to nanometer scale and make the raw material mixed evenly. The high crystallinity, particle nanometrization and uniform carbon coating enable LMFP@C composites with excellent electrochemical performance even when a small amount of carbon coating is introduced. Under an optimizing coated carbon amount of 2.5 wt%, the material showed ∼4.0 V and ∼3.6 V voltage platforms at 0.1, 0.2, 0.5, 1, and 2C, and released discharge specific capacities of ∼155 mAh·g−1 and ∼140 mAh·g−1 at 0.1 and 1C, respectively. It also shows optimal cycling stability with a capacity retention rate ∼100% after 100 cycles at 2C.

Improvement of methods for obtaining phosphorus fertilizers by mechanical activation

The article deals with the process of mechanical activation and determination of the influence of activating additives on the degree of solubility of low-grade phosphoresces of the Central Kyzylkum. As well as mechanical activation of samples of various types of low-grade phosphoresces with the addition of acid salts NH4H2PO4, (NH4)2HPO4, at a ratio of 5:5 in a mortar mill RM 200, with a mode of increasing the activation time to 60 minutes, by heating the resulting mixture to 200°C in various component ratios. Development of a waste-free and environmentally friendly technology for the production of NPK fertilizers.

STUDYING THE PROCESS OF SULFIDING AN OXIDIZED COPPER ORE BY THE METHOD OF MECHANOCHEMICAL ACTIVATION

In recent years, a new direction has appeared in metallurgical processes according to which the processing of concentrates is carried out by a combination of mechanical and metal-thermal methods of recovery. This contributes to the intensification of further redox processes and the production of fundamentally new modified products. In the case of enrichment of oxidized copper minerals, a more acceptable type of surface activation are mechanical activation processes with a combination of added reagents. It is established that sulfiding of oxidized copper minerals with elemental sulfur, silicon and sodium sulfides proceeds actively. As a result of the research, the optimal modes of sulfiding oxidized copper ores are determined. As a result of comprehensive research, a technology has been developed for processing oxidized copper minerals in a mill by sulfiding and subsequent flotation.

Investigation of mechanical activation of steelmaking slag and obtaining fine filler

The article presents the results of the mechanical activation of steel-smelting slag affecting the properties of the gypsum composition. As a result of the study, parameters were identified that characterize the reactivity of the slag during mechanical activation. It was established that the increase in the number of Bronsted active adsorption centers on the surface of the formed powders is responsible for their reactivity. However, the maximum increase in surface activity leads to a large percentage of residue on the sieve. Also, polynomial models were obtained that adequately describe the entire process of mechanical activation of waste from metallurgical production.

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.

Application of Renewable Natural Materials for Gas and Water Shutoff Processes in Oil Wells

We propose a complex sealing compound for increasing the efficiency of shutoff operations based on natural materials processing for materials such as sand, peat, rice, and husks. We studied the influence of mechanical activation processes on the mechanical and rheological properties of the developed sealants. Through mechanochemical activation, sand dissolution in a low-concentrated alkali solution was possible, and gelling the resulting sodium silicate while reinforcing it with undissolved sand particles to obtain a sealant composition. We used this approach to produce a hybrid sealing compound based on activated rice husks with up to 20% biogenic silicon dioxide combined with mechanically activated peat: the maximum shear strain of the hybrid sealant was 27.7 ± 1.7 Pa. We produced hydrogels based on sodium silicate, polyacrylamide, and chromium acetate, reinforced with mechanically activated rice husks. We studied the sealants’ rheological and filtration properties and observed the respective viscoplastic and viscoelastic properties. An increase in the dispersion concentration from 0 to 0.5% increased the maximum strain value of undestroyed hydrogel’s structure in the range 50–91 Pa and the maximum shear strain from 104 to 128 Pa. The high residual resistance factor values of the ideal fracture model make the natural and plant-renewable raw materials very promising for repair and sealing work.

ДОСЛІДЖЕННЯ ЕФЕКТИВНОСТІ ПРОЦЕСУ ВІБРОАКТИВАЦІЇ ГІДРАТНОГО ВАПНА

The efficiency of the process of mechanical activation of hydrated lime in the vibratory activator of the bunker type is considered in the work. This makes it possible to use highly active hydrated lime as a modifying reinforcing additive to cements. Also, the introduction of additives has a positive impact on the economic and environmental effects in the production of mortars and concrete structures. Theoretical and experimental studies of the vibrational regimes of the mixture and their influence on the rate and degree of dispersion of hydrated lime have been performed. Parameters of existence of effective modes of vibroactivation are established.

Studies for hydrometallurgical processing of titanium-magnesium production sludge with niobium extraction in solution

The material composition of sludge deposits from titanium-magnesium production was studied by chemical, X-ray, and microprobe analysis methods. Studies of the phase composition of the collector sludge showed that niobium is mainly bound with aluminum and titanium in oxide compounds. The particles of these compounds are very small and surrounded by the clay and carbonate component of the sludge collector. The chemical and mechanical activation processes of the sludge from the titanium-magnesium production sludge collector were executed based on the data obtained on the material composition. Alkaline leaching of sludge from sludge collector after preliminary activation was executed. The optimum conditions for the niobium extraction from the sludge of the sludge dump from the titanium-magnesium production were determined: sodium hydroxide concentration of 200 g/dm3, glycerol 5 g/dm3, S:L = 1:10, temperature 95 °C, leaching process duration - 4 hours. The addition of glycerol during alkaline leaching of sludge inhibits the transition of hexaniobate into insoluble sodium metaniobate enabling to increase the niobium extraction by 1.3 times with transfer into the solution of up to 80% of the extracted metal.

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.

Synthesis and physicochemical properties of β-silicon carbide prepared with reproduced carbon black and semiconductor packing waste by integrated mechanical and thermal activation (IMTA) process

Approximately 130,000 tons of tires are wasted annually and up to 3000 tons of waste assembly compounds containing 60–70 % silicon oxide from the semiconductor packing industry are produced in Taiwan. These huge amounts of waste materials have caused considerable environmental problems. Therefore, the current research focused to prepare the β-silicon carbide (β-SiC) synthesis using an integrated mechanical and thermal activation (IMTA) process with carbon black and waste assembly compounds from the waste tire industry and semiconductor packing industry, respectively. Four synthesis parameters including the C/Si molar ratio, ball-milling time, pyrolysis temperature, and pyrolysis time were investigated. The X-ray diffraction spectra confirmed that the granular- and whisker-like SiC were successfully synthesized. The research findings confirmed the formation of granular-like SiC at pyrolysis temperature of 1300 °C for 1 h. Either increased pyrolysis temperature or pyrolysis time, whisker-like SiC was formed with 280–375 nm in diameter and 7.5–20 µm. The C/Si molar ratio was the most critical parameter for improving the SiC quality. Based on the systematic analysis using Taguchi method, the optimum parameter for the SiC yield was determined with a C/Si molar ratio of 6:1 after 4 h of ball milling and a heating temperature of 1450 °C for 1.5 h. By comparing of physicochemical properties, the use of carbon and silicon recycled materials was verified to successfully synthesize β-SiC in this study.