Anahit G. Aleksanyan

National Academy of Sciences of Armenia | NAS RA · A. B. Nalbandyan Institute of Chemical Physics

The aim of this investigation was to synthesis Ti-5Al-2.5Fe alloy by “hydridecycle” (HC) method. The crystal structure of obtained alloy was studied by powder X-raydiffraction. It was found that the alloy was a near α-alloy, containing main α-phase (hexagonalclose-packed structure, space group 194: P63/mmc) and small amount of β-phase (body-centere...

Finding new energy effective methods for the production of refractory multi-principal element alloys (MPEAs) is a challenge for rapidly developing MPEA materials science. Formation of equimolar TiZrHfVNb MPEA and evaluation of alloy potential for use as hydrogen storage material were investigated. In this study, we demonstrated, for the first time...

In the present work a new approach is proposed for Ti2AlNx MAX phase synthesis using highly efficient methods: self-propagating high-temperature synthesis (SHS) and Hydride Cycle (HC). Two ways of synthesis were developed, which differ in the use of different precursors and methods for the forming of Ti2AlNx MAX phase. The synthesis in Way 1 was ca...

MAX phases are new type of easily machinable cermets, demanded in modern materials science as construction materials. One of the most widely studied and promising representatives of the titanium-based MAX phases are hexagonal Ti2AlC and Ti3AlC2. Current methods of their synthesis are unsuitable for their mass production. The creation and developmen...

The wide use of titanium alloys is limited by high costs of both their producing technology and processing. The expansion of area of their application depends on development of more efficient, resource-saving, economical methods providing reduction in the cost of titanium alloys and titanium made products. The hydride cycle (HC) method for synthesi...

The results of our study of the formation of aluminides in the Ti-Al-Zr system by the hydride cycle (HC) method were presented. The characteristics of aluminides (phase composition, density, and absorption properties) were found to depend on the ratios of titanium and zirconium hydrides and aluminum powders, pressure during compaction of the reacti...

Design of alloys and structural materials with appropriate properties is vital to all major branches of science and industry, and the development of nontraditional technologies including nanotechnology is an important factor in changing traditional metallurgy and material sciences. A new method of synthesis of binary and multicomponent alloys has b...

The results of our study of formation of aluminides by the hydride cycle (HC) method in Ti–Al and Ti–Al–Nb systems and of their hydrides under the conditions of self-propagating high-temperature synthesis are presented. The HC method was developed at the High-Temperature Synthesis Laboratory of the Nalbandyan Institute of Chemical Physics, Armenian...

Metal hydrides are promising as compact and safe hydrogen storage materials. Among them, the hydrides of ternary and more complex alloys are provided with properties required in modem hydride material science. In this work, the mechanism of formation of ternary alloys in Ti-V-Mn system in the "hydride cycle" mode was investigated. TiV1.2Mn0.8, TiV0...

Current technology requires that newly created materials have not only a set of functional properties but also be solid, lightweight, plastic, and easily machined. Intermetallic compounds based on the Nb–Al system occupy a prominent place among the advanced materials due to their unique properties. High-temperature intermetallides based on Nb and A...

The hydride cycle process was successfully applied to synthesize single-phase α2-Ti3Al, γ-TiAl, and TiAl3 aluminides. The formation of aluminides was found to proceed by solid-state reaction mechanism, without melting. The process takes advantage of its relatively low temperatures (600–1000°C), short duration (2–3 h) of a single-step synthetic proc...

Combined self-propagating high-temperature synthesis and hydride cycling methods form a novel and recently developed technique allowing preparing specific multiple-phase materials. Ternary Laves phase related to bcc solid solution and binary bcc V-Ti alloys and their hydrides were prepared using this route. In this report, the microstructure and hy...

According to H-1 NMR study in fcc hydrides of disordered Ti-V alloys hydrogen atoms are distributed over both octahedral and tetrahedral sites. The occupancy of octahedral sites increases with the vanadium concentration. In hydrides of ternary Ti-V-Cr alloys hydrogen atoms occupy tetrahedral sites only.

In this work the results of investigation of mechanism of alloy formation in Ti–Nb system by “Hydride cycle” (HC) method are presented. The temperature regime of dehydrogenation-sintering is defined; the dependences of phase composition of the synthesized alloys on the dispersity and ratio of source reagents (TiH2 and NbHx powders) are studied. X-r...

Explored was the SHS reaction of Ti-Hf, Zr-Hf, and Ti-Zr-Hf alloys with hydrogen. The reaction of compacted alloys with hydrogen and deuterium could be carried out without preliminary crushing. Hydrogenation of the alloys yielded hydrogen-rich hydrides with H/Me = 2.0−2.28. Crystal structure of the synthesized hydrides was found to depend on compos...

In the present work, the possibility of formation of titanium and vanadium based alloys of BCC structure using hydride cycle was investigated. The mechanism of formation of alloys in Ti–V system from the powders of hydrides TiH2 and VH0.9 (or of V) by compaction followed by dehydrogenation was studied. Then, the interaction of the synthesized alloy...

In the present work, an essentially new approach to production of quasicrystals in Ti-Zr-Ni system is described. It consists in co-compaction and dehydrogenation-sintering of mixture of powders of Ni with two and more hydrides of transition metals of IV group (Ti, Zr). The interaction of some of received quasicrystals with hydrogen in combustion mo...

Briefly overviewed are the SHS-based processes developed at our lab for synthesis of metal hydrides and their alloys. More than 200 binary and complex hydrides have been synthesized by SHS reactions of metals in hydrogen. Radiation-induced synthesis of transition metal hydrides, termed Thermal-Radiation Synthesis (TRS), was suggested and used to pr...

We report the presence of large proportions of -phase in Ti-Hf-Zr alloys, prepared using the hydride cycle technique. We show that the -phase extends across the concentration triangle of Ti-Zr-Hf and report the partitioning of the three metals across the two sites in this structure from neutron and X-ray data. We examine the symmetry of the order p...

The possibility of producing intermetallic compounds by dehydrogenation/annealing of “zirconium hydride-Group VIII metal” powder compacts has been demonstrated. Compared to the known methods for preparation of IMCs (induction/arc melting, powder metallurgy, and combustion synthesis), our method affords the synthesis of of IMCs at temperatures below...

A novel technique is suggested for synthesis of refractory metal alloys by dehydrogenation of compacted mixtures of transition metal hydrides. This technique is applicable to preparation of not only binary but also multi-component alloys, intermetallics, and alloys of III, IV, V, and VIII Group metals with various additives. In this work, the resul...

Investigated was the crystal structure of the Ti-Zr, Ti-Hf, and Ti-Zr-Hf alloys prepared by the novel method of “hydride cycling” suggested by us recently. The XRD data showed formation of the ω-phase in alloys with hydrides ratios TiH2/ZrH2 (TiH2/HfH2) ≈ 2, 1, 0.44: Ti0.67Zr0.33 (Ti2Zr), Ti0.67Hf0.34 (Ti2Hf), etc. The ω-phase is unusual for binary...

The compacting ability of SHS-hydrides of titanium, zirconium, hafnium, etc. was studied in dependence of the process conditions. The dependences of physical and mechanical properties of obtained compact hydrides from the dispersion and chemical composition of hydride powders, pressure of pressing, temperature of dehydrogenation, etc. were determin...

In the present work, an essentially new approach to production of alloys of the refractory metals is presented. It consists in co-compacting and dehydrogenation-sintering of mixture of powders of two and more hydrides of transition metals of III, IV and V groups, or of mixture of powder of any of these hydrides with a transition metal of III–VIII g...

In Ti-Zr, Ti-Hf and Ti-Zr-Hf systems, the alloys were received by developed in the IChPh of Armenian NAS principally new, “hydride cyclization”, method, and the alloys crystal structures were studied. The X-ray analyses proved that at hydride ratios in charge: TiH2/ZrH2; TiH2/HfH2 ͌ 2; 1; 0.44; Ti0.67Zr0.33 (Ti2Zr), Ti0.67Hf0.34 (Ti2Hf), etc., the...

The chemical and phase-structural transformations were researched upon obtaining intermetallic compounds of metals of IV and VIII groups using hydrides of titanium and zirconium. The possibility of alloys and IMC obtaining was demonstrated. The ability of obtained compact alloys and IMC to hydrogenation in combustion regime (SHS) forming the IMC hy...

Studies of the combustion processes in the Ti–H, Zr–H, and Ti–Zr–H systems made it possible to develop a principally new method for producing refractory metal alloys through the compaction of a titanium hydride–zirconium hydride powder mixture followed by dehydrogenation. The procedure is briefly described. Experimental data on the formation of tit...

Powders of TiH2 and ZrH2 were obtained using the self-spreading high-temperaturesynthesis. The mixed and ground TiH2 and ZrH2 powder were press-compacted to 50 mmdiameter and 3 mm thick discs, then discs were vacuum sintered in the temperature range from10000 to 1300°C. The structure of thus produced specimens is characteristic of the martensiticβ...

The thermal-radiation processes in the system Sc–H2 have been investigated. The high-current 4 MeV electron accelerator LAE-5 has been used with a focused electron beam. As a result of experiments at different doses and dose rates (0.025–1.5 Mrad/s) in vacuum and in a hydrogen atmosphere, the main peculiarities of the thermal-radiation processes in...

A special hermetic chamber was elaborated and constructed to treat materials by the electron beam in vacuum and in hydrogen atmosphere (PH=1–2 atm; 1 atm=101 325 Pa). The investigation was carried out on the high current electron accelerator LAE-5 using a focused electron beam. The system of temperature measurement during irradiation was developed....

The interaction of ZrN0.17 (HCP structure) and ZrC0.4 (FCC structure) with hydrogen under the action of an accelerated electron beam was investigated. The experiments were carried out on the linear accelerator LAE-5 in the range of irradiation dose power 0.1–1 MRad/s up to a dose of 100 MRad. Upon irradiation of nitrogen solid solutions in zirconiu...

The experimental data are presented regarding combined influence of hydrogen and nitrogen on the synthesis of hydridonitrides on the base of Ti, Zr, Nb and V. The method of self-propagating high temperature synthesis (SHS) technique was used. The monophase hydridonitrides with HCP and FCC structure and high hydrogen content were formed: TiN0,3H1,1;...

INTRODUCTION Last years the linear electron accelerators (LAE) are widely applied to investigation of radiation effects in metals and alloys. The systematic study of radiation-chemical processes in a solid body have shown that ionization and excitation of electron and nuclear sublattices render considerable influence on physical-chemical properties...

In this work, the results of investigation of influence of radiation damages appeared at irradiation by accelerated electron beam on the interaction with hydrogen of bimetallic solid solutions of nitrogen on the basis of titanium are presented. The possibilities of radiation-stipulated hydrogenation in this system were investigated and the peculiar...

The action of high flow ionizing radiation on inorganic solid materials results in excitation of electron and nuclear sublattices of irradiated substance [1].

This paper treats the combustion processes observed in the Nb–N–H system, and its application to the synthesis of niobium hydridonitrides. In particular the Self-Propagating high-temperature synthesis (SHS) process in Nb–H and Nb–N systems was studied. The combustion products were hydrides and nitrides, respectively. The determination of the main f...

The experimental data concerning nanoscale hydrides of transition metals, obtained by synthesis in combustion wave are presented. The systems Ti–H, Zr–H, Ti–N–H, Zr–N–H, Ti–Zr–N–H were studied. In all samples, the dimensions of grains were as low as 50nm. The peculiarities of self-propagating high-temperature synthesis processing and structure caus...

Radiation-assisted thermal synthesis of titanium hydride is achieved in a Ti-H 2 system. It is shown that a temperature rise in an irradiated sample initiates the exothermic reaction of hydride formation, proceeding as "thermal explosion". It has been found that titanium samples pre-irradiated in vacuum (radiation dose 30-40 Mrad) are capable of re...

The SHS method is highly effective for synthesis of hydridonitrides of transition metals. It has been found that in the combustion processes under certain conditions the monophase hydridonitrides with HCP structure and high hydrogen content are formed: TiN 0.3H1.1, ZrN0..3H1.53, Ti0.88Zr0.12N0.28H1.39.

The presented investigations constitute the cycle of studies of interaction of the metals of group III and IV with two reacting gases, nitrogen and hydrogen in the SHS mode.

Nanocrystalline hydrides are a new class of materials perspective for wide problems of hydrogen material science.

The structure and thermal features of hydride-nitrides prepared by self-propagating high-temperature synthesis are studied. Conditions are established for forming single-phase hydride-nitrides with a hexagonal structure in the systems Ti−N−H, Zr−N−H, and Ti−Zr−N−H. It is shown that presence of nitrogen in the lattice promotes the solubility of hydr...

For the first time we have discovered the homogenization reaction during combustion investigations in hydrogen atmosphere of multicomponent systems based on IV and V group metals. As a result the monophase multicomponent hydrogen-containing compositions have been obtained.

The combustion processes in Y-H, Y-N and Y-N-H systems are studied by the self-propagating high-temperature synthesis (SHS) method. The main regularities of the combustion processes and of the formation of end products are determined. Di- and trihydrides, nitride and hydro-nitride of yttrium are created. The combustion of yttrium in a gas mixture i...

Combustion ofTi andZr powders in nitrogen(10–70 atm) with subsequent burn-up of the produced α-alloys in hydrogen and alsoTi-Zr powder combustion in anN 2+H2 mixture have been studied. The optimal conditions for producing monophase nitrogen-containing alloys and monophase hydronitrides with high hydrogen concentration have been found. The effect of...

Combustion processes of the metal powder mixtures (Ti and Zr) in nitrogen (10-70 atm) with the following burning of the obtained α-alloys in hydrogen and combustion of Ti-Zr powders in the N2-N2 mixture are studied. The optimal conditions are revealed for obtaining one-phase nitrogen-containing alloys and one-phase hydridonitrides with high hydroge...

The process of combustion of hafnium in the mixture of hydrogen and nitrogen by SHS (self-propagating high-temperature synthesis) was studied. It was determined that concurrent sequential and parallel reactions occur during Hf-N-H system combustion. The combustion reaction can develop in three different ways, depending on the parameters of the proc...

The objective of the present investigation was to study the thermal decomposition upon dynamic heating of the hydrides and hydronitrides of titanium, zirconium, and hafnium prepared by the SHS method, to determine their temperature range of stability, and to clarify the nature of decomposition and formation of the hydronitrides under equilibrium co...