Search results for "Self-propagating high-temperature synthesis"
showing 10 items of 17 documents
Savaime sklindančios aukštatemperatūrinės sintezės būdu gautų aliuminio oksinitrido miltelių ir jų keramikų optinės savybės
2021
The reported study was funded by RFBR according to the Research Project No. 19-08-00655. V.P. acknowledges the State Research Program ‘Aug-stas enerģijas fizika un paātrinātāju tehnoloģijas’ (Projekta Nr. VPP-IZM-CERN-2020/1-0002). The Institute of Solid State Physics, University of Latvia as the Center of Excellence has received funding from the H2020-WIDESPREAD-01-2016-2017-Teaming Phase2 under Grant Agreement No. 739508, Project CAMART2.
A multilayer model for self-propagating high-temperature synthesis of inter-metallic compounds
2007
International audience; Self-propagating high-temperature synthesis of intermetallic compounds is of wide interest. We consider reactions in a binary system in which the rise and fall of the temperature during the reaction is such that one of the reacting metals melts but not the other. For such a system, using the phase diagram of the binary system, we present a general theory that describes the reaction taking place in a single solid particle of one component surrounded by the melt of the second component. The theory gives us a set of kinetic equations that describe the propagation of the phase interfaces in the solid particle and the change in composition of the melt that surrounds it. I…
Mechanically Activated SHS Reaction in the Fe-Al System: In Situ Time Resolved Diffraction Using Synchrotron Radiation
1998
The Mechanical Activation Self propagating High temperature Synthesis (M.A.S.H.S.) processing is a new way to produce nanocrystalline iron aluminide intermetallic compounds. This process is maily the combination of two steps ; in the one hand, a mechanical activation where the Fe - Al powder mixture was milled during a short time at given energy and frequency of shocks and in the other hand, a Self propagating High temperature Synthesis (S.H.S.) reaction, for which the exothermicity of the Fe + Al reaction is used. This fast propagated MASHS reaction has been in -situ investigated using the Time Resolved X - Ray Diffraction (TRXRD) using a X - ray synchrotron beam and an infrared thermograp…
Enhancement of self-sustaining reaction by mechanical activation: case of an FeSi system
1999
Mechanical high energy ball milling of an Fe2Si elemental powders mixture was used to activate a self sustaining combustion reaction or so-called self-propagating high-temperature synthesis (SHS) to form iron disilicide, a reaction for which the thermodynamic criterion is not favorable. A complete characterization of the milled powders before reaction was performed with energy dispersive X-ray spectrometry, specific surface measurements and X-ray diffraction profile analysis. Thermal and structural information describing the combustion front initiated by heating up a sample to 400°C in a Fe‐Si system is communicated. In order to isolate the phases involved in the gasless reaction, a time-re…
In situ synchrotron characterization of mechanically activated self-propagating high-temperature synthesis applied in Mo–Si system
1999
Abstract An original experiment was designed to monitor structural and thermal evolutions during the MASHS (Mechanically Activated Self-propagating High-temperature Synthesis) process in the Mo–Si system. Time-Resolved X-Ray Diffraction (TRXRD) coupled with an infrared imaging technique was performed to study, in situ, the formation of the α-MoSi2 phase in the combustion front. Despite a temporal resolution of 50 ms between two consecutive diffractograms, no intermediate phase was observed during the passage of the combustion front. The only reaction responsible for the self-sustentation is Mo+2Si→MoSi2 in the primary zone inside the combustion wave. The mechanical activation was found to i…
Simultaneous IR and time-resolved X-ray diffraction measurements for studying self-sustained reactions.
1998
Self-propagating high-temperature synthesis provides an attractive practical method for producing advanced materials such as ceramics, composites and intermetallics. This kind of reaction has been investigated in situ using time-resolved X-ray diffraction, with an X-ray synchrotron beam (D43 beamline, LURE, Orsay) coupled to simultaneous IR thermography to study structural transformations and thermal evolution. With short acquisition times (30 ms per pattern) it has been possible to observe several steps before obtaining compounds. Two different compound formations have been described: (i) the different steps of reaction, aluminium melting, subsequent temperature increase and fast reaction …
Determination of transport and kinetic properties in self-propagating high-temperature synthesis
2007
International audience; Exothermic reactions in solid powders are analyzed using the usual macroscopic modeling based on the heat transfer equation coupled to an Arrhenius type of dynamics. This problem have important applications in the synthesis of intermetallics and ceramic materials which occur when a high temperature reaction wave propagates throughout the system. Understanding the mechanism of such processes are thus crucial in mastering real laboratory experiments. We first analyze the model, both theoretically and numerically, for a set of representative parameters. We then use traditional data analyses procedures to estimate from the temperature profiles the same set of representat…
Combustion synthesis of MoSi2 and MoSi2–Mo5Si3 composites: Multilayer modeling and control of the microstructure
2010
International audience; In this work, we present a multilayer modeling for the formation of molybdenum silicides in the exothermic reaction between Mo and Si under the influence of a temperature pulse. The heating rate can either be a well-controlled ramp or be generated spontaneously by the propagation of a combustion synthesis front. The model addresses the specific situation above the melting point of silicon and describes the solid–liquid reaction taking place in a single representative particle of molybdenum surrounded by the melt of silicon. We obtain a set of kinetic equations for the propagation of the interfaces between the different layers (Mo/Mo5Si3 and Mo5Si3/MoSi2) in the solid…
Enhancement of self-sustaining reaction Cu3Si phase formation starting from mechanically activated powders
2000
Mechanical high-energy ball milling of an 3Cu Si elemental powders mixture was used to activate a self-sustaining combustion reaction or so-called self-sustaining high-temperature synthesis (SHS) to form the copper silicide phase, a reaction for which the thermodynamic criterion proposed by Munir for self-propagation reaction is not favorable. A complete characterization of the end-products was performed with X-ray diffraction analysis and scanning electron microscopy. Thermal and structural information describing the combustion front initiated by heating up a sample to 180°C in a Cu:Si system is communicated. This paper clearly shows that the mechanically activated self-sustaining high-tem…
In-situ time resolved X-ray diffraction study of the formation of the nanocrystalline NbAl3 phase by mechanically activated self-propagating high-tem…
1999
The mechanically activated self-propagating high-temperature synthesis (MASHS) technique was used to produce a NbAl3 intermetallic compound. This process results from the combination of two steps: a mechanical activation of the Nb 3Al powder mixture which is followed by a self-propagating high-temperature synthesis (SHS) reaction, induced by the exothermal character of the reaction Nb3Al. An original experiment was designed to study in-situ the formation of the NbAl3 phase in the combustion front: time-resolved X-ray diffraction coupled with an infrared imaging technique and a thermocouple measurement were performed to monitor the structural and thermal evolution during the SHS reaction. Ow…