Effect of mechanical activation on the regularities of self-propagating high-temperature synthesis in the titanium-nickel system

Итин, В. И.; Monasevich, T. V.; Братчиков, А. Д.

doi:10.1007/bf02672741

Cited by 19 publications

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“…Generally, an increase in the fraction of the product with the time of mechanical treatment reduces the efficiency of the preliminary stage because of a reduction in the calorific value of the system. This is responsible for the extremal nature of experimental dependences of the combustion temperature and, hence, the rate of the front on the time of mechanical activation [4,[10][11][12][13].…”

Section: Solution Of the Problem And Analysis Of The Resultsmentioning

confidence: 99%

Combustion of Mechanically Activated Heterogeneous Systems

Smolyakov¹

2005

Combust Explos Shock Waves

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A mathematical model for the combustion of preliminary activated heterogeneous systems is proposed which includes equations describing heat conduction, chemical kinetics, and the dynamics of the excess energy accumulated in condensed reagents at the stage of preliminary mechanical treatment. The excess energy decreases as a result of structure normalization and chemical transformation, whose activation energy, in turn, depends on the excess energy in the condensed reagents. The case of stationary combustion is analyzed in detail. The effect of mechanical activation on the velocity of the synthesis wave and its structure is analyzed by numerical modeling. The main conclusions are compared with available experimental data.Preliminary mechanical treatment of powder mixtures and separate reagents in an energy-intensive mill is an effective method for increasing chemical-reaction rates [1][2][3]. The intensive energetic action on the mixture increases the reactivity of the reagents by supplying them with additional energy accumulated in the form of structural imperfections, increases the reaction-surface area, and reduces the scale of heterogeneity of the system. The increase in the reaction surface and the decrease in the scale of heterogeneity due to mechanical treatment is manifested in continuous formation and grinding of microcomposites -layered structures of the starting components [4,5]. The activation of the reagents is manifested in a decrease in the energy barrier for chemical interactions. The increase in the interface, reduction in the scale of heterogeneity, and the activation of the reagents intensify chemical transformations. To distinguish the action of each of these factors and to operate them for the purpose of developing effective technologies is a difficult and important fundamental problem, whose solution holds promise for applications.It has been established that preliminary mechanical activation of a mixture or its separate components increases the number of systems that can react in a

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Section: Solution Of the Problem And Analysis Of The Resultsmentioning

confidence: 99%

Combustion of Mechanically Activated Heterogeneous Systems

Smolyakov¹

2005

Combust Explos Shock Waves

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“…Mechanical activation (MA) is widely used to improve the efficiency of solid state reactions [1,2], including SHS in low caloric green mixtures [3][4][5][6][7][8]. Despite earlier attempts [3,9,10], the processes lead ing to formation of mechanocomposites (agglomer ates) still remain obscure because of rich variety of accompanying physicochemical events.…”

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confidence: 99%

“…

In continuation of our previous studies [11,12], in this work I made an attempt to reveal a relationship between the inner layered structure of mechanocom posites and temperature characteristics of thermal explosion in activated reactive Ti-Ni mixtures.

MA of equiatomic mixtures of commercial Ti (PTM1 brand) and Ni (PNE1 brand) powders was carried out in an M 3 planetary mill under Ar (45 g, interrupted activation for 30 s periods + 5 min hold ing in air).

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confidence: 99%

Thermal explosion in Ti–Ni blends: Role of inner mechanocomposite structure

Шкода

2015

Int. J Self-Propag. High-Temp. Synth.

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246Mechanical activation (MA) is widely used to improve the efficiency of solid state reactions [1,2], including SHS in low caloric green mixtures [3][4][5][6][7][8]. Despite earlier attempts [3,9,10], the processes lead ing to formation of mechanocomposites (agglomer ates) still remain obscure because of rich variety of accompanying physicochemical events.In continuation of our previous studies [11,12], in this work I made an attempt to reveal a relationship between the inner layered structure of mechanocom posites and temperature characteristics of thermal explosion in activated reactive Ti-Ni mixtures.MA of equiatomic mixtures of commercial Ti (PTM1 brand) and Ni (PNE1 brand) powders was carried out in an M 3 planetary mill under Ar (45 g, interrupted activation for 30 s periods + 5 min hold ing in air). MA was performed until formation of mechanochemical products as detected by XRD. In all cases, powder weight was 80 g, ball diameter 5 mm, and mill/ball ratio 1 : 5.Thermal explosion in activated mixtures was initi ated in a 5 L constant volume reactor under Ar. Tem perature profiles were taken with a chromel-alumel thermocouple. Thus obtained thermograms were used to determine ignition temperature T ig and maximum temperature T max . Starting powders and combustion products were characterized by SEM (Philips SEM515), optical metallography (Axiovert 200M), and XRD (DRON Um). Figure 1 shows the averaged (over 5-7 experimen tal runs) values of ignition temperature T ig and maxi mum combustion temperature T max vs. duration (τ) of MA. A general trend is a gradual decrease followed by some fluctuations at τ = 4-6 min.At the very beginning of MA, powder particles lose their initial shape. They get comminuted and via freshly cleaved surfaces stick together thus forming laminated agglomerates, also termed as mechano composites (Fig. 2a). The processes of their fracturing BRIEF COMMUNICATIONS

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Combustion synthesis of bulk ceramics and metals

Liu,

Chen,

2025

Combustion Synthesis

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Effect of mechanical activation on the regularities of self-propagating high-temperature synthesis in the titanium-nickel system

Cited by 19 publications

References 1 publication

Combustion of Mechanically Activated Heterogeneous Systems

Combustion of Mechanically Activated Heterogeneous Systems

Thermal explosion in Ti–Ni blends: Role of inner mechanocomposite structure

Combustion synthesis of bulk ceramics and metals

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