Production of carbon nanotubes by self-propagating high-temperature synthesis

Carbon nanotubes are prepared by the method of self-propagating high-temperature synthesis for the first time. The initial components for this synthesis are carboniferous materials (soda, limestone, and Teflon) and reducers (magnesium, lithium, and sodium) with addition of a nickel or iron catalyst. The morphology of the nanotubes (straight multiwall nanotubes apparently free of a catalyst, bent nanotubes completely filled with a catalyst, and carbon nanofibers) is similar to that of nanotubes grown by chemical methods. The nanotubes account for 2–4 wt % of the product synthesized.     

Luminescence of manganese-doped zinc sulfide obtained by self-propagating high-temperature synthesis

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 56, No. 4, pp. 628–631, April, 1992.     

Laser induced self-propagating high-temperature synthesis of TiNi alloy

TiNi alloy, especially porous TiNi, a good biocompatible material, can be made by laser induced selfpropagating high-temperature synthesis (SHS). A 40-W CO2 laser was used to ignite the powders of Ti and Ni, and TiNi intermetallic compound was synthesized by SHS in a reaction kettle of stainless steel.High-speed photography, X-ray diffraction, and scanning electron microscopy were used to investigate and analyze the reaction process, phase composing, and microstructure of the product, respectively. The influence factors on the reaction process and the product were discussed. The results indicate that laser induced SHS is an efficient, energy-saving method; The phase ingredient of the product consists of TiNi,Ti2Ni, and Ni3Ti. With the increase of the preparing pressure of the sample, the reacting rate decreases;With the increase of the laser power and the preheating temperature, the reacting rate increases. Under the condition of 30℃/min, the synthesis reaction had been carried out consistently and completely.     

Size-dependent ignition temperature of metallic compounds fabricated by self-propagating high-temperature synthesis

Considering the diffusion reaction at solid interfaces, the ignition temperature of compounds fabricated by self-propagating high-temperature synthesis (SHS) is modelled with the help of size-dependent activation energy. As reactant size decreases, ignition temperature also decreases. This is because of increased contact areas between the reactants and the lowered diffusion barrier, both of which must be calculated specifically for reactants in nanoscale. The model predictions and experimental results are consistent for some metallic compounds.     

Structure studies on porous titanium nickelide made by high-temperature self-propagating synthesis

Structure studies are reported on martensite transformations in porous TiNi alloy made by high-temperatures self-propagating synthesis. The transformations occur over a large temperature range and are incomplete. The structure data are used in reconstructing the heat release during the transition, where it is shown that it is determined by the superposition of martensite transformations occurring locally at various temperatures. Tomsk State Architectural and Building Academy. Kuznetsov Siberian Technical Physics Institute, Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 20–24, January, 1997.     

Structure of porous permeable materials in a titanium-aluminum-carbon-alloy-component system obtained by self-propagating high-temperature synthesis

A study is made of the structure of porous permeable materials obtained by the method of self-propagating high-temperature synthesis on the basis of the titanium-aluminum-carbon system and the same system with the introduction of alloy components: metals and nonmetals. It is shown that the structure of the skeleton of the unalloyed material includes a matrix on the basis of intermetallides and a solid solution with disperse titanium carbides distributed in its volume. It is established that depending on the mechanism by which the alloy components influence the structure of the skeleton of the material, they can be subdivided into those that do and do not give rise to carbides. Introducing elements of one of the groups into the reaction mixture, one can have a directed influence on the parameters of both the matrix and carbide components of the obtained material.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 9–13, January, 1992.     

Luminescence of zinc selenide obtained by the method of self-propagating high-temperature synthesis

We investigate the photo- and roentgenoluminescence of ZnSe polycrystals obtained by the method of a self-propagating high-temperature synthesis (SHS). We establish an identity between the spectra of stationary luminescence of the polycrystals investigated and ZnSe single crystals. We show that the long-wave radiation of SHS crystals is due in the main to the presence of uncontrolled oxygen impurities in the crystals as well as to intrinsic defects that form donor-acceptor centers of self-activated luminescence. Investigations of roentgenoluminescence in the mode of its pulse excitation make it possible to isolate short-lived (550, 495, and 452 nm) and long-lived (580 and 630 nm) components of the radiation spectrum. The transformation of the corresponding spectra on a change in the temperature of the crystals is shown. The results demonstrate the possibility of using zinc selenide polycrystals produced by the SHS method in applied luminescence. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 333–337, May–June, 1997.     

An analysis of phases in Ti-based composites obtained by self-propagating high-temperature synthesis

Composites suitable for triboengineering applications have been obtained by self-propagating high-temperature synthesis. X-ray structure investigations have been made of the phases arising from process combustion of a powder mixture of titanium and carbon in the presence of copper and metals of the iron group. Institute of the Physics of Strength and Materials, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh, Zavedenii, Fizika, No. 2, pp. 21–24, February, 1993.     

Structural study of Fe-Al nanomaterial produced by mechanical activation and self-propagating high-temperature synthesis

Mossbauer spectroscopy and X-ray diffraction are used for structural study of nanopowders resulting from a 60% Fe + 40% Al mixture after mechanical activation, as well as their nanocomposite derivatives arising in the process of self-propagating high-temperature synthesis. The different nature of the iron-aluminum interaction in these nanotechnological processes is demonstrated.     

Multiple self-propagating high-temperature synthesis and solid-phase reactions in thin films

A variety of self-propagating high-temperature synthesis in thin films has been found and investigated. This modification, called multiple self-propagating high-temperature synthesis, occurs in the solid phase and is a reversible phase transition. Multiple self-propagating high-temperature synthesis is similar in many respects to a metal—insulator phase transition. It is shown that for eutectic systems it is equivalent to a repeated transition through the eutectic temperature of bulk samples. It is inferred that multiple self-propagating high-temperature synthesis in bilayer films is governed by phase separation mechanisms that take place during eutectic solidification and eutectoid decomposition. Zh. éksp. Teor. Fiz. 115, 1756–1764 (May 1999)     

Factors controlling thermoluminescence from self-propagating high-temperature synthesis in powder bodies

Computer simulations are used to study the physicochemical processes that determine the light emission from the lateral surface of the sample during self-propagating high-temperature synthesis (SHS) in the Ni-Al powder system. It is shown that endothermic phase transitions in the components of the powder mixture control the character of change of the chemiluminescence intensity. The behavior of the emission from of the subareas of the lateral surface carries information about the parameters of state of the medium and physical mechanisms underlying SHS.     

Formation of self-propagating high-temperature synthesis products in Ti-Ni and Ti-Co systems

The structure and phase composition of specimens from mixtures of titanium powders with nickel and cobalt, hardened during combustion, are investigated in this paper. It is shown that under selected conditions dissolution of the components in the liquid phase is the guiding stage of combustion wave propagation.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 75–78, December, 1981.