RU2757067C1 - Method for determining combustion temperature of multi-layered reaction nanofilms with self-propagating high-temperature synthesis effect - Google Patents

Abstract

FIELD: measuring.

SUBSTANCE: invention relates to the field of nanotechnology of materials and can be applied in researching the properties of multi-layered reaction materials with a self-propagating high-temperature synthesis (SHS) effect, in particular, for determining the combustion temperature of such materials. Proposed is a method for determining the combustion temperature of multi-layered reaction nanofilms based on an application of electrical methods. The combustion temperature is determined by the change in the electrical resistance of a strip of the multi-layered reaction nanofilm prior to and after the process of self-propagating high-temperature synthesis, and the combustion temperature tshs is calculated by the formula tshs = to+(Rt-Rx)/Rx∙α, wherein to is the temperature prior to the SHS, Rx is the resistance of the strip of the multi-layered reaction nanofilm prior to the SHS, Rt is the resistance of the strip of the multi-layered reaction nanofilm after the end of the SHS, α is the temperature resistance coefficient of the multi-layered reaction nanofilm.

EFFECT: increased informational value and rapidity of determining the combustion temperature of multi-layered reaction nanofilms.

1 cl, 1 tbl, 1 dwg

Description

The invention relates to the field of nanotechnology of materials and can find application in studying the properties of reactive multilayer materials with the effect of self-propagating high-temperature synthesis (SHS), in particular for determining the combustion temperature of such materials. Reactive multilayer nanofilms with a large number of alternating layers are commonly referred to as reaction foils.

Reactive multilayer nanofilms are a class of energetic materials, usually consisting of two reagents. These reagents can be stimulated by an external source and quickly release stored chemical energy with a sudden release of light and heat. Self-propagating high-temperature synthesis occurs, as a result of which, within a fraction of a second, the temperature of a multilayer nanofilm, for example, Ni / Al, rises to (1500-1600) ° C.

A known method for determining the combustion temperature, as well as the ignition temperature of a multilayer reaction foil using thermocouples fixed on the surface of the foil strip on both sides [1]. The disadvantage of this method is that the thermocouples introduce too strong distortions in the SHS process. Thermocouples, in comparison with the thickness of the reaction multilayer nanofilms (several tens of microns), have significant dimensions and do not have time to warm up in fractions of a second to the SHS temperature.

A known method for determining the combustion temperature at which the temperature is measured using optical methods, in particular using a photodiode, previously calibrated using a pyrometer [2] - a prototype. Disadvantages of optical methods - these methods are inaccurate due to the lack of data on the emissivity of reactive multilayer nanofilms during the SHS reaction. Also, these methods are difficult in their practical application, since they require the use of expensive optical devices (for power supply and recording of measurement data).

The objective of the invention. Development of a simple economical method for determining the combustion temperature of a reaction nanofilm with the SHS effect.

This task is achieved in the following way. A method for determining the combustion temperature is proposed, based on measuring the resistance of a reaction nanofil strip before the start of ignition and after the end of combustion. Let us use the well-known formula to determine the resistance of the reaction nanofil strip when it is heated Rt = Rx (1 + α (tcvc-to). Here to is the initial temperature during measurements; tcvc is the combustion temperature of the reaction nanofil strip, which must be determined; α is the temperature coefficient resistance (TCR) of the reaction nanofil strip; Rx is the resistance of the reaction nanofil strip before the start of SHS; Rt is the resistance of the reaction nanofil strip at the end of the SHS.

During the SHS process, the electrical resistance of the reaction nanofil strip will increase by Rx⋅α (tcvc-to). Hence, the temperature of the SHS process will be tcvc = to + (Rt-Rx) / Rx⋅α. To determine the process temperature, it is necessary to know the TCR value of the reaction nanofil strip.

Compared to the analogue, this method is simple, it allows in a short time to determine the combustion temperature of the reaction nanofilm. The figure shows the implementation of the method for determining the combustion temperature of the reaction nanofilm Ni / Al. Here l is the length of the strip of the reaction nanofilm; Rн - load resistance for limiting the current passing through the reaction nanofilm from the power source. A voltage Uo = 0.3 V was applied to the input of the circuit. The values of the voltage across the SHS strip (foil) and the current passing through it before and after the initiation of the SHS process were measured. The initiation of the SHS process was carried out using an open flame (from the torch of a lighter) - a brightly luminous wave of gasless combustion propagated along the length of the strip of the reaction nanofilm, as a result of which the SHS process itself took place. The streak flashed, its resistance changed. This change in resistance was recorded with a voltmeter. A memorable oscilloscope was used as a voltmeter.

The measurement results are shown in Table 1.

Here l is the length of the nanofil strip, d is the thickness of the nanofil strip, R _x is the resistance of the nanofil strip before the SHS reaction, R _t is the resistance of the nanofil strip after the SHS reaction, t _SHC is calculated by the formula tcvc = to + (Rt-Rx) / Rx⋅ α is the combustion temperature of the reaction nanofilm. The TCR of the foil determined in a known manner was 3.125⋅10 ^-3 1 / ° C. The average temperature (see Table 1) was 1394 ° C.

To confirm the correctness of the proposed method for determining the combustion temperature of the reaction nanofilm, the results obtained were compared with the known literature data. In [3] for Ni / Al foil the value for combustion temperature is given equal to (1422 ± 50) ° С. In [4] for Ni / Al foil the value for combustion temperature is given equal to (1350-1500) ° С. Hence, it follows that our data on the combustion temperature of the Ni / Al foil are close to the values obtained by other researchers.

Sources of information

1.D.N. Kuzmenko et al. Influence of heating rate on ignition temperature of multilayer Ti / Al foil. Automatic welding, 11/2014, p. 24-37.

2. A.S. Rogachev, A.G. Merzhanov et al. Gasless combustion of multilayer bimetallic Ti / Al nanofilms. Combustion and Explosion Physics 2004, vol. 40, no. 2, p. 45-51.

3. Structure evolution and reaction mechanism in the Ni / Al reactive multilayer nanofoils / A.S. Rogachev [et al.] II Acta Materiala, 2014, 66, 89-96.

4. URL: www. Indium.com.

Claims (1)

A method for determining the combustion temperature of reaction multilayer nanofilms based on the use of electrical methods, characterized in that the combustion temperature is determined from the change in the electrical resistance of the strip of the reaction multilayer nanofilm before and after the process of self-propagating high-temperature synthesis and the combustion temperature tcvc is calculated by the formula tcvc = to + (Rt-Rx ) / Rx⋅α, where to is the temperature before the onset of SHS, Rx is the resistance of the strip of the reaction multilayer nanofilm before the onset of the SHS, Rt is the resistance of the strip of the reaction multilayer nanofilm after the end of the SHS, α is the temperature coefficient of resistance of the reaction multilayer nanofilm.

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