New nanostructured manganites of LaMeIICuZnMnO6 (MeII — Mg, Ca, Sr, Ba)

The copper-zinc manganites of LaMeIICuZnMnO6 (MeII — Mg, Ca, Sr, Ba) have been synthesized with the high-temperature interaction of alkaline earth metals carbonates with oxides of lanthanum (III), copper (II), zinc (II) and manganese (III). The synthesized polycrystalline copper-zinc manganites have been grinded on the Retsch vibration mill MM301 (Germany). As a result their nanostructured particles have been obtained. Their sizes have been determined using an electron microscope Mira3 LMU, Tescan. Methods of radiography determined that all synthesized nanostructured copper-zinc manganites crystallize in the cubic syngony with the following parameters of a lattice: LaMgCuZnMnO6 — а = 13.530.02 Å, Vo = 2476.810.06 Å3, Z = 4, Voelect.cell = 619.200.02 Å3, roent = 4.52; pick = 4.500.01 g/cm3; LaCaCuZnMnO6 — а = 13.690.02 Å, Vo = 2565.730.06 Å3, Z = 4, Voelect.cell. = 641.430.02 Å3, roent = 4.43; pick = 4.410.01 g/cm3; LaSrCuZnMnO6 — а = 13.910.02 Å, Vo = 2691.420.06 Å3, Z = 4, Voelect.cell = 672.850.02 Å3, roent = 4.99; pick. = 4.960.01 g/cm3; LaBaCuZnMnO6 — а = 14.550.02 Å, Vo = 3080.270.06 Å3, Z = 4, Voelect.cell = 770.070.02 Å3, roent = 4.95; pick = 4.940.01 g/cm3. The X-ray investigations demonstrated that the values of lattice parameters of the studied copper-zinc manganites have been increased from Mg to Ba. As a result of the investigations, these compounds can be included in Pm3m spatial group.

Experiment and analysis on chaotic characteristics vibration mill with variable rotational speed

In an attempt to improve the current low efficiency and high consumption situation of vibration mills, this paper analyses the chaotic motion characteristics of the system and the movement of vibration mill. The complex stiffness-dispersion coupling of the system is also studied, so as to investigate the effect of the system’s chaotic motion characteristics on the efficiency improvement and energy consumption reduction. Based on the ADAMS software, this paper establishes a simplified vibration mill mechanical model, analyzes the singularity and stability of the system, and determines the critical speed at which the vibration motor becomes chaotic according to the bifurcation diagram. Then the chaotic state of the grinding machine with sinusoidal variation in its motor speed is studied based on the Poincaré principle, singular attractor and maximum Lyapunov exponent. Lastly, a 200[Formula: see text]h vibration test on diamond powder with an average particle size of 10 [Formula: see text]m was carried out. Test results under the two operating conditions of variable and constant speeds are compared and analyzed. Our results show that with variable speed the vibration mill achieved higher grinding efficiency but smaller particle grain size. The research elaborated in this paper provides a valuable reference for the engineering application of the chaotic characteristics of vibration mill.

DEVELOPMENT OF A MATHEMATICAL MODEL FOR THE RESEARCH OF THE DYNAMICS OF VIBRATION MILL WITH TWO DRIVES FOR BULK MATERIALS FINE GRINDING

Reducing by grinding the size of various materials as raw materials for its further use is an urgent applied task. The requirements for the final product obtained by fine grinding are its homogeneity in shape and size of individual parts. It is necessary to reduce the time of the grinding operation, reduce energy consumption to obtain a unit of product of the required quality. One way to solve the problem is to use high-tech universal equipment, namely mills for fine grinding of materials. One way to solve the given problem is to use high-tech universal equipment, namely mills for fine grinding of materials. Their optimal design, construction, manufacture and operation are ensured by studying their dynamics at the stage of their development. In particular, such a study of the dynamics can be carried out on the basis of previously created mathematical models of these mills. The use of computer technology and appropriate mathematical CAD systems will speed up and optimize the process of studying the dynamics of the corresponding mill of fine grinding of materials. The purpose of the research is to build a mathematical nonlinear parameterized model of vibrating mill with two drives for bulk materials fine grinding for further study on its basis the dynamics of the mill with the development of optimal designs for mills with similar structure and the principle of operation and selection of optimal modes of operation. The mathematical model is presented as a system of expressions describing the of the mill points motion, which will include in the form of symbolic symbols all its parameters (kinematic, geometric, dynamic, force). This model is constructed using the Lagrange equation of the second kind and asymptotic methods of nonlinear mechanics. The mathematical model for studying of the dynamics of vibration mill with two drives for bulk materials fine grinding is nonlinear and universal. The non linearity of the model makes it possible to adequately determine of the above parameters influence on the amplitude of oscillations of the mill working chamber as the main factor in the intensity in the technological process of the fine grinding bulk materials fine grinding. The possibility of a wide range of changes in the parameters of the mill in the obtained models makes it universal based on the possibility of application for the study of dynamic processes in vibrating mills of different types with two or one drive which are different by shape, size, location of the suspension and more. This model can also be used to develop optimal designs for vibrating mills for different industries, which will be used to grind different types of materials in different volumes and productivity.

Influence research of an α–form alumina type on the properties of samples from vibrocasting mullite corundum granular masses

The technology of refractories vibrocasting was developed by JSC "URIR named after A. S. Berezhnoy" in particular highly refractory mullite corundum crucibles for melting of heat-resistant alloys in induction furnaces. At manufacturing of highly refractory vibrocasting mullite corundum refractories a-form alumina, as a dispersion binder, which milling to a particles size of less than 10 μm (the content of particles less than 4 μm in such alumina is more than 50 %) is used. For improvement the casting characteristics of vibrocasting masses dispersants are used. At research milling kinetics alumina of all brands was milling in a vibration mill for a specified time. For this research a certain amount of the investigated alumina of each brand was loaded into a vibration mill, and after a specified grinding time (30, 45, 60, 75 and 90 min), a sample of alumina after milling was taken in a specified amount. In this work, the kinetics of changes the dispersion of alumina (S, N and NR brands) during their milling was studied. The dispersion of alumina which were needed (the content of particles less than < 10 μm in such alumina is not less than 90 %, the content of particles less than < 4 μm — not less than 50 %) was achieved in almost the same milling time was found (~ 45 min). With a further increase of milling time to 60, 75 and 90 minutes, the dispersion of alumina N and NR brands increases in comparison with alumina S brand and after 90 minutes of milling, the content of particles < 4 μm in alumina, respectively, is ~ 60, ~ 75 and ~ 80 %. After fired at a temperature of 1580 °C the properties of vibrocasting mullite corundum samples, which contain alumina S, N and NR brands, are characterized by a high level of apparent density (above 3 g/cm3), open porosity (less than 16 %) and cold crushing strength (above 140 N/mm2). The high properties make it possible to use a-form alumina N and NR brands along a-form alumina S brand in the technology of vibrocasting mullite corundum refractories, including the highly refractory mullite corundum crucibles.

COMPOSITE BINDERS BASED ON CONCRETE SCRAP

The object of research is composite binders obtained from concrete scrap of destroyed buildings and structures for the production of various construction products and structures. Fractions of concrete scrap of 0,0–0,16 mm and 0,16–0,315 mm are used, since x-rayphase analysis of various fractions of concrete scrap shows that these fractions have the highest content of non-hydrated particles of alite and belite. The influence of the specific surface area on the normal density of cement dough and the setting time of binders is established. Comparative physical and mechanical indicators of hardening of binders with different specific surfaces indicate that the most stable results with a uniform increase in strength is the composition of a binder with a specific surface of 964 m2 / kg, with an increase in strength from 2 to 7 days – 27 % and from 7 to 28 days – 21 %. This binder is characterized by optimal strength at the age of 28 days – 25,5 MPa. With a specific surface of 964 m2/kg, the best conditions are created for the formation of the primary frame and its further fouling with various calcium crystalline hydrates, which ensure optimal density and strength. This composite binder has a specific surface area of 964 m2/kg and is more energyefficient. Composite binders obtained in a vibration mill from concrete scrap fractions (0,0–0,16 and 0,16–0,315 mm) meet the requirements of normative documentation on setting time and physico-mechanical parameters, which allows to recommend them for use as binders in the production of construction products and structures for various purposes.

Mechanochemical amorphization of chitin: impact of apparatus material on performance and contamination

Herein, we present a study of the impact of the jar and ball medium on the performance in the mechanochemical amorphization of chitin. We measured the crystallinity index of chitin after milling it in a vibration mill in an apparatus made of copper, aluminum, brass, tungsten carbide, zirconia, stainless steel, polytetrafluoroethylene (PTFE), or poly(methyl methacrylate) (PMMA). These materials offer a range of Vickers hardness values and the impact of these parameters is discussed. The role of the size and mass of the balls is also studied in the case of stainless steel. This study also highlights one of the major challenges during milling, which is contamination of the studied samples.