P. Peretyagin

Spark Plasma Sintered Si3N4/TiN Nanocomposites Obtained by a Colloidal Processing Route

Ceramic Si3N4/TiN 22 vol% nanocomposites have been obtained by Spark Plasma Sintering SPS. Our colloidal processing route allows obtaining dispersed nanoparticles of TiN smaller than 50 nm avoiding the presence of agglomerates. The nanostructured starting powders were obtained by using a colloidal method where commercial Si3N4 submicrometer particles were coated with anatase TiO2 nanocrystals. A later nitridation process led to the formation of TiN nanoparticles on the surface of Si3N4. A second set of powders was prepared by doping the above defined powders with yttrium and aluminium precursors using also a colloidal method as sources of alumina and yttria. After thermal nitridation and SPS treatment, it has been found that the addition of oxides dopants improves the mechanical performance KIC, σf but increases the electrical resistivity and significantly reduces the hardness. This is due to the formation of a continuous insulating glassy phase that totally envelops the conductive TiN nanoparticles, avoiding the percolative contact between them. The combination of colloidal processing route and SPS allows the designing of tailor-made free glassy phase Si3N4/TiN nanocomposites with controlled microstructure. The microstructural features and the thermoelectrical and mechanical properties of both kinds of dense SPSed compacts are discussed in this work.

Laser-beam modulation to improve efficiency of selecting laser melting for metal powders

Nowadays additive manufacturing becomes more and more popular. It depends on the results of last achievements in developing of the new constructions for modern machine tools. One of the most developed AM technology is SLM or SLS. About twenty years ago the technology of rapid prototyping started to grow up from building prototypes and developed to real functional item production. Especially this becomes more important in producing medical implants in the full accordance with individual digital 3D-model from metallic powder as Ti6Al4V or CoCr. The additive technology gives the possibility to reduce additional steps in implants production process as work preparation process, forwarding a work piece from one shop to another one, post treatment etc. This approach is very topical to production of tooth, knee and coxal implants. This idea is realized in the commercial SLM machines as EOS M280, SLM Solutions 125HL (Germany), Phenix systems PXS/PXM Dental (France) (fig. 1).

Antiresonance in (Ni,Zn) ferrite-carbon nanofibres nanocomposites

(NiZn)Fe2O4 carbon nanofiber (CNF) nanocomposites with concentrations up to 5% in volume of CNFs were prepared by traditional ceramic processing and a subsequent spark plasma sintering at 860 °C with a holding time of 1 min. Low-frequency conductivity and magnetic properties were studied, revealing the appearance of a ferromagnetic antiresonance when a certain value of conductivity is reached due to the introduction of a conductive second-phase CNF in the ferromagnetic matrix (ferrite), thereby opening a route to induce magnetically tunable transparency in these composites.

New Approach to Study and Research of Causes of Operational Characteristics Disturbance for Ceramic Tool Materials

The system approach to study the causes of operational characteristics disturbance for ceramic tool materials based on complex research and its systematization. In the present study the defects by volume and by surface are researched. The main directions of operational characteristics improvement for tool materials are showed.

Functionalization of carbon nanofibres obtained by floating catalyst method

The excellent physicochemical and electrical properties of carbon nanofibres (CNF) combined with the possibility of being produced at industrial scale at reasonable costs have promoted the interest in their use in very diverse areas. However, there are still some drawbacks that must be solved in order to optimize their set of properties such as the presence of impurities or the imperfections in the crystalline structure. In this work, different modification treatments of CNFs produced by the floating catalyst method have been studied. Three types of modification processes have been explored that can be grouped as mechanical, thermal, and chemical functionalization processes. Mechanical processing has allowed solving the agglomeration problem related to CNFs produced by floating catalyst method and the resulting modified product ensures the secure handling of carbon nanofibres. Thermal and chemical treatments lead to purer and more crystalline products by removing catalyst impurities and amorphous carbon. Functionalization processes explored in this work open the possibility of customized posttreatment of carbon nanofibres according to the desired requirements.

Specifics of Wear of Ceramic Cutting Tool Inserts Featuring Al2O3-TiC Dies when Face Milling Hardened Cast Iron

This work studies wear kinetics of index able inserts (II) made of mixed ceramics based on Russian-manufactured in case of fine milling of special hardened cast iron with globular graphite. In a wide range of cutting parameters typical for fine milling, an impact of tool insert wearing parameters on qualitative and quantitative characteristics of the cutting process have been studied. Morphological traits and nature of wear of work surfaces has been studied using optical and scanning electron microscopy. Criteria of II states, as well as specifics of contact work surface transformation, correlating with force parameters of the face milling process, have been determined.

Modeling process of spark plasma sintering of powder materials by finite element method

This paper investigates and analyses use of numerical modeling by finite element method (FEM) at studying of consolidation processes of materials from powder by spark plasma sintering (SPS). Tasks of SPS process optimization is discussed in detail. Examples of numeric analysis of SPS of current conducting and non-conducting materials are given. Numeric modeling of sample sintering with hybrid method when SPS process is combined with hot pressing (HP) process is studied. Also paper presents development prospects of principles of SPS process numeric modeling.

Main Technological Parameters Influence of Selective Electron Beam Melting on Properties of Thin-Walled Titanium Alloy Samples

Selective electron beam melting has been considered as the most advanced method of additive manufacturing of workpieces made of titanium and titanium-based alloys for the aircraft industry. The impact of basic technological parameters on the thickness of thin walls obtained with the use of selective electron beam melting has considered. Metallographic examination of the experimental samples has been performed.