Centrifugal Planetary Mill Research Articles

Применение механоактивации для синтеза Y2Zr2O7 твердофазным способом

The effect of mechanical activation on the synthesis of yttrium zirconate Y2Zr2O7 by solid-phase method was studied. Mechanical activation of a stoichiometric mixture of zirconium and yttrium oxides was carried out in AGO–2 centrifugal planetary mill at a centrifugal factor of 40 g for 10 min. Using X-ray phase analysis and complex thermal analysis, the processes occurring during the calcination of the initial and mechanically activated mixture of oxides were investigated. The calculation of the sizes of Y2Zr2O7 crystallites, carried out according to the Scherrer formula, showed that after annealing the mechanically activated mixture of ZrO2 and Y2O3 in the temperature range of 1100–1200 °C for 3 h, nanocrystalline yttrium zirconate was formed.

Effect of chromium addition on the copper binder structure, properties and adhesion to diamond

The study covers the effect of chromium on the structure, mechanical properties, and adhesion of alloys used as a binder for metal-diamond composites. Cu–Cr powder mixtures were obtained by high-energy ball milling in a planetary centrifugal mill. This process was used to obtain two-phase Cu–Cr powders with uniformly distributed submicron Cr particles. Cu–Х%Cr compact samples (where Х = 10, 30 and 50 %) were obtained by hot pressing. It was found that Cu–30%Cr compact samples showed the best mechanical properties (9 times higher as compared to pure copper). These alloys feature a hardening mechanism based on the Hall–Petch law. The resulting alloys have a homogenous ultrafine structure, which results in high ultimate bending strength (2330 MPa). Chromium addition to the copper binder considerably increases its adhesion to diamond in metal-diamond composites due to chemical interaction between chromium included into the binder and diamond carbon with Cr3C2 carbide formation.

Влияние механической активации порошка вольфрама на структуру и свойства спеченного материала SN-CU-CO-W

Introduction. One of the methods for improving the properties of sintered materials is mechanical activation of powders. It ensures milling the powders, changing its energy state, intensifying the sintering of powder materials, and forming a fine-grained structure in it. When tungsten powders are mechanically activated in planetary centrifugal mills, nanoparticles can be formed, which have a high reactive power. The objective of the paper is to study the effect of mechanical activation of tungsten particles on the structure and properties of the sintered Sn-Cu-Co-W powder material. Research technique: Mechanical activation of W16,5 grade tungsten powder is carried out in a planetary centrifugal ball mill AGO-2U for 5…120 minutes with carrier speeds of 400…1,000 rpm. The mixture of tungsten, tin, copper, and cobalt powders are compacted by static pressing in molds and then sintered in vacuum at 820 °C. The morphology and size of powder particles, as well as the structure of the sintered samples, are studied by scanning electronic microscopy, X-ray microanalysis, and optical metallography. Porosity of the sintered samples is identified by the gravimetric method. Microhardness of the structural constituents and macrohardness of the sintered materials are measured, too. Results: in the modes under study, mechanical activation is accompanied by the formation of tungsten nanoparticles with the minimum size of 25 nm. Alongside this, the powder is exposed to cold working, which hinders further milling. Tungsten nanoparticles, characterized by high surface energy, have a significant effect on the dissolution-precipitation of cobalt during liquid-phase sintering of Sn-Cu-Co-W powder material. Addition of nanodispersed tungsten into the material slows down the growth of cobalt particles during sintering and contributes to the formation of a fine-grained structure. The sintered Sn-Cu-Co-W material, containing mechanically activated tungsten, features higher hardness of 105…107 HRB, which is explained by cold working of tungsten particles and dispersion hardening. The results can be applied for improving mechanical properties of Sn-Cu-Co-W alloys used as metallic binders in diamond abrasive tools.

Investigation of Molding Process and Consolidation of Preforms from Mechanically Synthesized Powders of Europium and Cerium Hafnates

Purpose of research. To study the process of molding and consolidation of preforms from mechanically synthesized powders of europium and cerium hafnates.Methods. Complex compounds of europium hafnateEu2HfO5 and cerium hafnate Ce2HfO5 have been synthesized from europium, hafnate and cerium oxides using mechanochemical synthesis in a planetary centrifugal mill. The rotational speed of the disk was 600 - 900 rpm and the rotational speed of the drums is 1000 - 1800 rpm, with the ratio of grinding bodies to the mass of the powder charge (35 - 45): 1, in an argon atmosphere. Synthesis lasts 5 - 120 minutes.Results. An X-ray phase analysis has been performed showing the formation of Eu2HfO5 and Ce2HfO5; as well as the study of the morphology of particles of the obtained powders, their technological properties, granulometric composition, formability and compaction, as well as the process of their consolidation.Conclusion. On the basis of the experimental studies aimed at studying the molding process and consolidation of preforms from mechanically synthesized powders of europium and cerium hafnates, it has been revealed the optimal mode of synthesis of cerium and europium hafnates. We have obtained a cerium hafnate powder with a particle size of 30-100 nm and a europium hafnate powder with a particle size of 40-70 nm by the method of mechanical activation. Using X-ray phase analysis, TEM and SEM methods, the mixed structure of lanthanide hafnates powders obtained by mechanosynthesis have been studied. The technological properties of mechanically synthesized powders of cerium and europium hafnate, as well as, their compaction and formability after pressing and sintering have been determined and studied. Samples from europium hafnate powder have a relative density higher than samples from cerium hafnate powder after consolidation at temperatures of 900-1200 ° C and isothermal holding time from 30 to 120 min. A study of the microhardness of lanthanide hafnate samples after sintering has shown that europium hafnate samples have greater hardness than cerium hafnate samples .

Применение мeханоактивации для получения церий-содержащих твердых растворов на основе циркона

Solid-phase synthesis of cerium-containing solid solutions based on ZrSiO4 was described. The synthesis was carried out using mechanical activation of a mixture consisting of zirconium oxide and hydrated amorphous silica with the addition of cerium oxide at a molar ratio of ZrО2:SiО2:CeО2 equal to 0.95:1.00:0.05. The mechanically activated in a centrifugal planetary mill mixture of reagents was calcined in the temperature range of 1200–1600 °C for 3 hours, which was accompanied by the essentially complete synthesis of zircon. The cerium content in the zircon structure was calculated from X-ray powder diffraction data.

Твердофазный синтез цирконата иттербия с применением механоактивации

Nanocrystalline ytterbium zirconate Yb4Zr3O12 was prepared by the solid-phase method using mechanical activation of stoichiometric mixture of zirconium and ytterbium oxides. Mechanical activation was carried out in an AGO-2 centrifugal-planetary mill at a centrifugal factor of 40 g for 10 min. The processes occurring during the calcination of the mechanically activated mixture of ytterbium and zirconium oxides in the range from 600 to 1300 °C were investigated using X-ray phase analysis, IR spectroscopy, and complex thermal analysis.

Exothermic synthesis of binary solid solutions based on hafnium and zirconium carbides

The paper presents the results of an experimental study into the possibility of producing ultra-high temperature ceramics constituting solid solutions of HfC and ZrC carbides by the single-stage electro-thermal explosion (ETE) method under pressure. Adiabatic flame temperature and phase composition of the equilibrium final product were calculated based on thermodynamic data. It was shown that when the ZrC content in the final product is less than 20 wt.%, adiabatic flame temperature reaches 3800– 3900 K, and the combustion product contains hafnium and zirconium carbides. The effect of mechanical activation modes in an AGO-2 planetary centrifugal mill used for a reaction mixture containing Hf, Zr and C powders on its properties, phase composition formation and the microstructure of carbide solid solutions was studied. It was shown that high-energy mixing in hexane leads to the destruction of the crystal structure of Hf and Zr particles and the formation of amorphous composite particles. The synthesized samples of ultra-high temperature ceramics were studied by X-ray phase and microstructure analyzes. It was shown that exothermic synthesis leads to the formation of single-phase solid solutions of HfC and ZrC carbides with the average particle size of 0.2–1.5 μm. The residual porosity of the binary carbides obtained is 10–12 %. It was found that, despite the high temperature of sample heating during ETE under pressure, the particle size of the resulting solid solutions is significantly (by an order of magnitude) smaller than the particle size of similar complex carbides (20–50 μm) obtained by other methods (SPS and hot pressing). This is associated with the rapidity of the exothermic interaction of the reagents (10–50 ms) during ETE.

Комбинированные технологии активации минерального сырья

Relevance. The efficiency of using the products of subsoil exploitation is a factor in strengthening the mineral resource base of the mining industry. The success of improving ore preparation technologies is associated with the activation of mineral raw materials in mills, including impact mills – disintegrators. A fundamentally new approach to ore processing technology includes a combination of grinding methods in mills and other activators. The issues of increasing the activity of substances on the basis of combination form an urgent scientific and industrial problem. The aim of the study of the phenomenon of combined activation is to search for the possibility of increasing the level of activation, to ensure the stability of the acquired activity and to establish patterns of relationships between the activation processes and the technological processes of using mineral raw materials. Objects: products of the development of deposits of solid mineral raw materials in various mining sectors of the national economy. Methods: Laboratory, semi-industrial and industrial experiment using improved equipment for the activation of mineral raw materials. Results. The concepts of “mechanical activation” in mills and “activation with large mechanical energy” in a disintegrator are detailed. An assessment is given to the directions of improving the mills. The results of mechanochemical activation of powders oxides in a planetary centrifugal mill “Aktivator-2s” are given. The practice of activating mineral raw materials with a combination of activators of various types is described. It has been established that the efficiency of combining mills depends on the initial size of the crushed material and equipment options are recommended depending on this. It is shown that the combination of drum and vibration mills reduced the energy consumption of the product. The results of the combination and the vibrating mill in the technological chain of the concrete complex are presented. The algorithm for the combined activation of mineral raw materials is illustrated by the example of the technology applied at the mine, which includes grinding, mixing binders, inert aggregates and grout, as well as transporting the concrete mixture to the place of use. As a quantitative indicator of activation, an equivalent of activity or a proportional ratio of the combined components is proposed. The efficiency of using solid mineral raw materials increases when it is prepared in activators.

Effect of tungsten nanoparticles on sintering of the Sn-Cu-Co-W powder material

The effect of tungsten nanoparticles on the kinetics of sintering of the Sn-Cu-Co-W powder material used as a binder in diamond tools was studied. The W16,5 grade tungsten powder was mechanically activated in the AGO-2U planetary centrifugal mill for 60 minutes at the carrier rotation frequencies of 800 RPM. The mixture of tungsten, tin, copper, and cobalt powders was compacted by static pressing in press dies and then sintered in vacuum at the temperature of 820°C. The morphology and sizes of powder particles, as well as the structure of the sintered samples, were studied by the methods of scanning electronic microscopy. It has been demonstrated that tungsten nanoparticles have a noticeable effect on the process of dissolution-reprecipitation of cobalt in liquid-phase sintering.

Effect of tungsten nanoparticles on interaction of Sn-Cu-Co metallic matrices with diamond

The effect of tungsten nanoparticles on interaction of sintered Sn-Cu-Co metallic matrices with diamond has been studied. Nanoparticles were obtained by grinding standard tungsten powder in a planetary-centrifugal mill. Commercially pure tin, copper, and cobalt powders were mixed with synthetic diamonds and the milled tungsten. Samples were shaped by static pressing in a mold and sintered in vacuum at 820°C. The sintered samples were subjected to static compression test, and hardness of the metallic matrices was measured. The structure of fractures and distribution of the elements over them were explored by the SEM and energy dispersive X-ray microanalysis methods. It has been determined that introducing tungsten nanoparticles into the composite material contributes to dispersion hardening of the metallic matrix and higher strength of its adhesion to diamond.

Solid-State Synthesis of Nanocrystalline Gadolinium Zirconate Using Mechanical Activation

Nanocrystalline gadolinium zirconate, Gd2Zr2O7, has been prepared by solid-state reaction, using mechanical activation of a stoichiometric mixture of Gd2O3 and ZrO2. The mechanical activation was performed in an AGO-2 centrifugal planetary mill for 10 min. The processes that occurred during heat treatment of the mechanically activated mixture of gadolinium and zirconium oxides were characterized by X-ray diffraction, IR spectroscopy, and a combination of thermoanalytical techniques. The average crystallite size of gadolinium zirconate prepared by calcining the mechanically activated oxide mixture at 1100 and 1200°C for 3 h was 29 and 68 nm, respectively, as determined using the Scherrer formula.

Influence of Ti and TiH2 Additives on the Structure and Properties of Copper Alloys for Diamond Cutting Tools

The influence of titanium and titanium hydride additives on the structure, mechanical properties, and wear resistance of copper alloys intended for use as a binder of the diamond cutting tool is investigated. Powder mixtures Cu–Ti and Cu–TiH2 are fabricated by mechanical alloying in a planetary centrifugal mill. Such treatment makes it possible to form single-phased powders of the copper-based solid solution in the Cu–Ti system and two-phased powders based on copper with uniformly distributed TiH2 particles in the Cu–TiH2 system. It is established that the maximal mechanical properties are characteristic of the samples of compositions Cu–2.5% Ti and Cu–10% TiH2 (higher than for pure copper by a factor of 2.0–3.5). Hardening in such alloys is implemented according to the solid-solution mechanism and due to the formation of the Cu3Ti3O phase. Grains of this phase have higher dispersity in alloys where TiH2 is used as the titanium-containing additive, due to which high values of the bending ultimate strength (920 MPa) and hardness (114 HB) are attained. It is established according to the results of comparative tribological investigations that samples of the Cu–10% TiH2 composition possess the best wear resistance. The reduced wear of these samples after the test according to the “rod–disc” scheme is an order of magnitude lower than for pure copper and lower by a factor of 5 than for Cu–2.5% Ti samples.

The Effect of Tungsten Nanoparticles on the Hardness of Sintered Sn-Cu-Co-W Alloys

The effect of tungsten nanoparticles and microparticles on the structure and hardness of sintered Sn–Cu–Co–W alloys has been studied. Tungsten powder of 19–24 μm sized particles was milled in a planetary-centrifugal mill, after which the size of particles was 25 nm to 20 μm. The milled and non-milled tungsten was then mixed with powders of tin, copper and cobalt. The specimens were compacted in moulds and sintered in vacuum at 820°C for 20 minutes. The structure of sintered materials was studied using X-ray diffraction analysis and scanning electron microscopy. Microhardness (HV0.01) of structural constituents and hardness of the materials were measured. It has been determined that it is alloys containing mechanically milled tungsten that have the highest hardness. The main factor influencing the rise of hardness is dispersion hardening with nanoparticles. A further factor is work hardening of tungsten microparticles during ball milling. The highest hardness of 109–111 HRB has been obtained in the Sn–Cu–Co–W alloy containing 23% wt. of milled tungsten, with the proportion of tin, copper and cobalt being 1/2.6/1.6.

Obtaining of tungsten nanopowders by high energy ball milling

The objective of the work is identifying the modes of ball milling of the W16,5 and PWT grade tungsten that ensure obtaining nanosized powders. Milling was performed with the AGO-2U planetary-centrifugal mill for 5, 15, 60, and 120 min at the carrier rotation frequencies of 400, 800, and 1000 rpm. After milling, the shape and size of tungsten powder particles was studied by scanning electron microscopy. The effect of work hardening and aggregation on milling of the powders has been demonstrated. As a result of ball milling, nanoparticles of tungsten sized from 25 nm have been obtained. It has been found that the minimum size of particles is achieved at the carrier rotation frequency of 800 rpm and milling duration of not less than 60 min.

Al30-PILLARED MONTMORILLONITE WITH ENHANCED TEXTURAL PROPERTIES DUE TO PRELIMINARY MECHANICAL TREATMENT

The effect of mechanical treatment of natural montmorillonite in a planetary-centrifugal mill on the efficiency of intercalating aluminum polyhydroxocomplexes [Al30O8(OH)56(H2O)26]18+ in the formation of pillared structures was studied. Measurements made using the photometry method showed that in the montmorillonite matrix, after intercalation of the Al30 polyhydroxocomplexes using mechanical treatment, an increase in the content of Al3+ cations by 13% was observed. According to the electrophoretic light scattering data, the particle size for the suspension of mechanically activated montmorillonite dispersed in water was about 100 nm. The raw, mechanically activated and pillared montmorillonites are characterized by the methods of low-angle X-ray diffraction, scanning electron microscopy, and low-temperature nitrogen adsorption-desorption. It was shown that preliminary mechanical activation of the initial substrate increases the basal distance d001 and significantly (approximately by 45–50%) increases the specific surface area and the total pore volume of Al30-pillared montmorillonite; in this case, both meso- and microporosity increase, and the pore size decreases by about 12%. The special importance of the size of montmorillonite particles during the intercalation and further formation of the pillared structure is shown. А decrease in the size of the montmorillonite particles during mechanical treatment increasing the area of the interphase boundary through which ion exchange takes place. It was shown that the small sizes of tactoids (about 100 nm) in an aqueous suspension play a key role in increasing the cation exchange capacity of mechanically activated montmorillonite. To a lesser extent, the efficiency of intercalation is influenced by the processes of defect formation and the related changes in the electrical properties of the silicate layers of montmorillonite. Based on the structural properties, the obtained pillared materials can be recommended for use as selective adsorbents, molecular sieves and catalysts.

Preparation of Nanosized α-Fe2O3 Using Mechanical Activation

The processes occurring during the mechanical activation of a-Fe2O3 (hematite) in the presence of oleic acid in a centrifugal-planetary mill have been investigated. Mechanical activation for 10 h afforded hematite powder with particles size of 10–40 nm, as shown by means of X-ray diffraction analysis, FTIR spectroscopy, high-resolution transmission electron microscopy, and specific surface area measurements. Longer milling has led to mechanochemical transformation of hematite into Fe3O4 (magnetite).

Fabrication of Metal Powders for Energy-Intensive Combustible Compositions Using Mechanochemical Treatment: 2. Structure and Reactivity of Mechanically Activated Al–Modifier–SiO2 Mixtures

The results of studying the particles of the aluminum–modifier–quartz composites after mechanochemical treatment (MCT) in a planetary centrifugal mill by various physicochemical methods are presented. Graphite (C), polyvinyl alcohol (PVA), and stearic acid (SA) are used as modifiers. To increase the dispersive ability of plastic metallic powders (metal–modifier), MCT was performed in the presence of quartz, the weight fraction of which in the composite varies from 5 to 20%. The largest grinding of aluminum particles is observed with an increase in the graphite content from 5 to 20% and SiO2 content from 5 to 10% in the composition of aluminum–modifier–quartz composites. The particle decreases, while that of crystallites increases with the MCT of the Al–SA–SiO2 system with an increased quartz content in the composite. The maximal imperfection of aluminum after MCT is characteristic of the Al–SA–5%SiO2 samples. An increase in the particle size and, correspondingly, a decrease in the specific surface with rather small crystallite sizes are observed after MCT for the Al–PVA–SiO2 composition. It is shown that the imperfection of the crystalline structure of aluminum particles increases with an increase in the quartz content in the system. The synthesized powder material is a composite formation of aluminum and quartz particles bound by polymer formed based on polyvinyl alcohol in this case. The MCT of the Al–modifier–SiO2 mixtures results in an increase in the powder activity both due to the accumulation and redistribution of defects in aluminum particles and due to the change of the surface structure due to the incorporation of modifying additives into the destructed oxide layer. The conceptual model of transformation of the surface layer and subgrain structure of aluminum particles during MCT is presented.

Preparation of nanocrystalline Gd2Zr2O7 from mechanically activated coprecipitated precursor

In this study, the effect of mechanical activation of coprecipitated hydroxide precursor on synthesis of gadolinium zirconate Gd2Zr2O7 has been studied. Mechanical activation of the precursor has been performed in an AGO-2 laboratory centrifugal-planetary mill at a centrifugal factor of 20 g with zirconia vials and balls. Particular attention has been given to carbonization of the as-prepared and mechanically activated precursors due to reaction with atmospheric carbon dioxide and their decarbonization in the course of calcination. The removal of the volatile components (H2O and CO2) from the as-prepared and mechanically activated precursors can be achieved by calcination at 1100–1200 °C for 3 h. Calcination of the as-prepared and mechanically activated precursors in the range of 700–1200 °C results in the formation of nanocrystalline fluorite-type Gd2Zr2O7. Gadolinium zirconate prepared from the mechanically activated precursor exhibits 4–9 times larger BET surface area relative to that of Gd2Zr2O7 synthesized at the same calcination conditions from the as-prepared precursor. In particular, this is beneficial for preparation of nanostructured dense ceramic materials with enhanced properties.

The Prospects of Using the Mechanical Activation Method in the Technological Processes of Oil and Gas Production

The need to improve the technological processes of raw fuel resources processing, to search for new technologies and to involve oil and gas waste production wastes as anthropogenic resources becomes urgent. The main directions of using the effects of the mechanical activation of substances in the technological processes of oil and gas production are analyzed. A brief description of the method of mechanical activation is provided. The prospect of using the method of mechanical activation to solve the problem of waste disposal is shown. The author analyzes the main directions of mechanical activation influence used for changing the composition and properties of hydrocarbons and considers the possibilities of mechanical activation of a substance as an efficient way for accelerating the mechano-chemical processes that occur in hydrocarbons due to intense mechanical loads. The article generalizes the research results concerning the effect of mechanical activation on changes in the physical-chemical properties of oil, fuel oil, bottoms and sludge. The results of using mechanical activation for the preparation of plug-back mixtures based on silica sand and quartziferous waste are summarized. The laboratory research was carried out at a centrifugal-planetary mill. It is established that under the conditions of mechanical activation of hydrocarbons their destruction occurs. The process of transformations is a chain nature. The areas of mechanical and chemical transformations, change of fraction content in residual fuel oil, bottom products, and natural gasoline have been investigated. It has been established that destruction of hydrocarbon fractions takes place. The author demonstrates that processing modes, time and mechanical loads affect the course of hydrocarbon destruction, and its results depend on the type of substance. The researcher proves that it is promising to use the method of mechanical activation to control the properties of mineral flour obtained on the basis of oil sludge. The results of the research indicate clearly that it is possible to get different volume of the light cuts yield by regulating the modes of hydrocarbons processing. The author shows the possibility of increasing the depth of oil refining, as well as the possibility of obtaining a cement mixture with the addition of up to 30% of mechanically activated quartziferous additive without deteriorating the characteristics of cement stone achieved. The method of mechanical activation is promising for the utilization of the wastes of oil and gas complex, as these wastes can be considered the anthropogenic raw materials.

Using mechanochemical treatment to obtain metal powders for energy-intensive combustible compositions. 2. Structure and reactivity of mechanically activated Al–modifier–SiО2 mixtures

The paper presents the results obtained when studying particles of aluminum-modifier-quartz composites by different physicochemical methods after mechanochemical treatment (MCT) in a planetary centrifugal mill. Graphite (C), polyvinyl alcohol (PVA) and stearic acid (SA) were used as modifiers. To increase the dispersibility of plastic metal powders in the composition (modifier metal), MCT was carried out in the presence of quartz with its mass fraction in the composite ranging from 5 to 20 %. The most significant grinding of aluminum particles was observed with an increase in the graphite content from 5 to 20 %, and SiO2 from 5 to 10 % in the composition of aluminum-modifier-quartz composites. The particle size decreases, while the crystallite size increases with an increase in the quartz content in the composite during the Al–SA–SiO2 system MCT. Al–SA–5%SiO2 showed the maximum defectiveness of aluminum after MCT. For the Al–PVA–SiO2 composition after MCT, an increase in the particle size and, accordingly, a decrease in the specific surface were observed at sufficiently low crystallite size values. It was shown that with an increase in the quartz content in the system, the defective crystal structure of aluminum particles increases as a result of MCT. In this case, the synthesized powder material is a composite formation of aluminum and quartz particles bound by a polymer obtained from polyvinyl alcohol. As a result of Al–modifier–SiO2 mixture MCT, powder activity increases due to the accumulation and redistribution of defects in aluminum particles, as well as changes in the surface structure occurring after modifying additives penetration into the oxide layer to be destroyed. A conceptual model for the transformation of the surface layer and subgrain structure of aluminum particles as a result of MCT is presented.