Alexander Ivashutenko

Influence of Oxygen Concentration on Plasma Dynamic Synthesis Product in Fe-O System

In spite of being known for centuries, iron oxides are still important. Such modifications as magnetite Fe3O4 and epsilon phase ε-Fe2O3 are of great scientific and practical interest due to their promising electromagnetic properties. Nonetheless, only few methods allow synthesizing both of these phases, but they have some well-known disadvantages, which limit the possibility of using them widely. This work shows a unique method of synthesizing these materials in one short-duration plasma dynamic process using a coaxial magnetoplasma accelerator with iron electrode system. The plasma chemical reaction occurs between the iron-containing plasma and gaseous precursor (oxygen). The influence of oxygen pressure on the products of plasma dynamic synthesis was also studied in the framework of this investigation. It was found that the higher oxygen concentration leads to the formation of product with predominant content of epsilon iron oxide ε-Fe2O3, as well as lower oxygen concentration results in obtaining the product with the dominance of magnetite phase.

Microstructure and Properties of the Composite on the Basis of Copper and Diamond

The paper presents the experimental material on obtaining and researching of three-dimensional composite heat-conducting copper-diamond materials in the system of spark plasma sintering. Earlier [1-5], it was established that in order to achieve the effect of the increased heat conductivity of a composite it is necessary to create the conditions hindering the movement of heat flux on the interface boundary. In this work we have attempted to obtain the material with heat conductivity higher than that of pure copper due to addition of diamond powder and synthesis of the composite in the system of spark plasma sintering. For comparison, we have considered copper and diamond compositions in the ratios of 50/50 and 40/60 correspondingly. The results of the heat conductivity analysis have not exceeded the indices of pure copper; however, according to SEM data, it has been found that at SPS-sintering local domains with enhanced adhesion form on the surfaces of diamonds.

Studying the Moulding Ways for the Metal Powdered Aluminum Reinforced with Carbon Fiber in the Spark Plasma Sintering Process

Aluminum and its alloys are used in many industrial areas, science and technology. Such materials are especially widespread in the aviation and automotive industries. Nonetheless, the usage of aluminum is somewhat limited for constructive purposes, due to its relatively low strength characteristics. Recently, the usage of aluminum reinforced with various materials, in particular with carbon fiber, has become an urgent issue. The choice of carbon fiber as reinforcing material is explained by its unsurpassed strength characteristics (more than that of the best steel grades), as well as by high level of thermophysical properties. Summarizing the properties of aluminum and carbon fiber in one material, it is necessary to expect the obtaining a unique material with a unique set of physical-mechanical and thermal characteristics. This paper shows the possibility to obtain dense bulk aluminum-carbon samples by means of spark plasma sintering from the point of the microstructure. The paper presents 3 different moulding ways of composites consisted of the powdered material reinforced with carbon fiber. It is shown that the densest structure with a uniform distribution of all elements in the sample is formed by using an additional easily removable liquid phase (isopropyl alcohol).

Effect of Oxygen Concentration in a Gaseous Mixture with Argon on the Phase Composition of Plasmodynamic Synthesis Products in an Iron–Oxygen System

The effect of a gaseous oxygen concentration in a mixture with argon on plasmodynamic synthesis products in an iron–oxygen system is described. X-ray diffractometry and scanning and transmission electron microscopy data showed that the products contain three different modifications of iron oxide: magnetite Fe3O4, hematite α-Fe2O3, and ε-Fe2O3 epsilon phase. A change in oxygen concentration leads to a significant change in the phase composition of the products and an increase in a yield of the ε phase.

Time-Keeping Factor at a Constant Temperature in the Process of Spark Plasma Sintering

The dependence of the effect of time delay at a constant maximum temperature on the physicomechanical parameters of the sintered sample has been considered. Based on the results of the work, it can be concluded that it is necessary to reduce the duration of all sections of the sintering process in order to exclude the recrystallization factor, which worsens the parameters of the ceramics.

Obtaining Intermetallic Compound Copper-Tin: Plasma Dynamic Synthesis and Spark Plasma Sintering

The intermetallic compound tin-copper (Cu-Sn) is widely used in the creation of high-quality bearings, electric conductive lubricants, 3D printers. However, when connecting two metals, the bond between atoms in the lattice becomes covalent or ionic. This leads to the fact that the material becomes more brittle. Additionally, the production of intermetallic compounds is cost-based in terms of both material resources and money. In this paper, the ceramics has been sintered based on the intermetallic copper-tin powders, obtained by plasma dynamic method. The raw powdered materials based on Cu-Sn were obtained using a coaxial magnetoplasma accelerator with copper electrodes by adding the crushed tin into the accelerator. Using X-ray diffractometry (XRD) and transmission electron microscopy (TEM) analyses, the presence of such phases as copper Cu and tin-copper Cu41Sn11 in the obtained material has been confirmed. Further, such-synthesized powdered products were used to obtain bulk samples using the spark plasma sintering technology at various sintering parameters. Images from scanning electron microscope showed a uniform sintering of the product at the sintering temperature of 440 °C under a pressure of 60 MPa. It was found that the sintered intermetallic ceramics has the Vickers hardness equal to 120 Hv. The obtained sample has the lower friction coefficient and the smaller wear area in comparison with the sample, made of pure copper.

Sintering of ceramics based on YBa2CuxOy Synthesized by plasma dynamic method

Yttrium-barium cuprates are of a great interest due their possible application in the manufacture of superconductors and devices on their basis. This paper shows the possibility to synthesize ultrafine powder of yttrium-barium cuprates using the system based on a coaxial magnetoplasma accelerator. Several methods, including X-ray diffractometry, scanning electron microscopy, transmission electron microscopy and energy dispersive X-ray spectroscopy, are used to investigate the synthesized products. It is found that during working cycle with a duration less than 1 ms, all necessary conditions are created to synthesize the powder with the stoichiometries YBa2Cu3O696 and YBa2Cu4O8. These materials can be used for sintering the multilayer ceramics using the system of spark plasma sintering.

The plasma dynamic synthesis of aluminum nitride in system with gaseous and solid precursors

Aluminum nitride is widely-used material for semiconductor devices and ceramics production. Despite the large number of known ways to obtain AlN powder, the problem of synthesizing high-purity and nanosized product is still urgent. This paper shows results on plasma dynamic synthesis of aluminum nitride using system based coaxial magneto plasma accelerator. The influence of using gaseous or solid precursors on such characteristics of the final product as phase content and particle size distribution was investigated. According to X- Ray diffractometry AlN phase content is increased in the case of use of solid nitrogen- containing precursor (melamine) in comparison with the use of gaseous nitrogen. The particle sizes distribution histograms are built in accordance with the data of bright-field TEM-images and shown in this paper. The most of particles are less than 100 nm in both experiment but there are some differences, depended on the precursor type, that are also described.