RU2692352C1 - Plant for measuring shs process characteristics of inorganic compounds in autowave mode - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: invention relates to metallurgy, particularly, to plants (devices) for reactors for self-propagating high-temperature synthesis. It can be used for synthesis of materials from reaction mixtures consisting of solid-phase reagents or with introduction of gas-phase reagents into the working area of the reactor, as well as for performance of scientific research works in laboratory conditions. Proposed device comprises a reactor housing, a transparent front cover, a rear cover with a sealed electrical connector, pressure rings with a thread, electronic or mechanical pressure sensor, gas supply and discharge pipe from working space, fiery spiral holder with clamps, initiating device, gate with holes for light guides, upper and lower light guides, support of light guides, two photodiodes (upper and lower), a crucible with a hole for a thermocouple, a thermocouple, a table of steel, attachment of a table to the back cover, a connector for connection of a thermocouple, an electric connector for connection of a controlled electronic valve, a power supply unit. All electronic components of the reactor are connected to each other in a single system by means of a microcontroller board.EFFECT: creation of a compact unit for SHS designed for operation in laboratory conditions, due to the most effective use of the internal space of the reaction chamber when placing the main elements and structures, as well as by simplifying the reactor design with the possibility of using electronic measuring systems located in the reactor working space.1 cl, 1 dwg

Description

The invention relates to the field of metallurgy, in particular to installations (devices) reactors for carrying out self-propagating high-temperature synthesis, then a SHS reactor.

A sufficiently large number of devices for SVS are known: SU 874165, B01J 19/08, 10.23.1981, "Device for the synthesis of chalcogenides"; RU 1834845 A3, СВВ 31/30, 15.08.1993, "A method for producing refractory compounds based on titanium carbide and a device for its implementation"; RU 2038296 C1, C01B 31 / 30,27.06.1995, "A method of producing titanium carbide and a device for its implementation"; RU 2061580 06/10/1996 C1 - "Installation for producing blanks by self-propagating high-temperature synthesis"; RU 2091312 C1, C01G 1/00, 09/27/1997, "A method of obtaining refractory inorganic compounds and a device for its implementation"; RU 2541065 C2, 08.04.2013, “A method for producing titanium sulphides”; RU 147203 10.27.2014 U1 - “A device for producing phosphors”; RU 2665852 09/04/2018 C1 - "A method of manufacturing powder refractory products of the SVS and a device for its implementation"; RU 2665669 03.09.2018 C1 - "Line for the production of powder refractory products of SVS".

All of the above devices are narrowly specific field of application and do not have the versatility required for laboratory applications. In addition, these devices are designed to produce sufficiently large amounts of the SHS product, which determines their dimensions and weight, and, in combination with the characteristics of the synthesis of certain materials, have additional complications of the design of the reaction chambers, such as cooling equipment. These parameters are also important in laboratory conditions. For example, to study the fundamental characteristics of SHS, such as temperature and burning rate, are often limited to small sample sizes.

A device (SHS reactor) for the synthesis, described in the text of the patent RU 2240860 0.03.03.2003, "Method for the synthesis of powder materials, mainly refractory, and a device for its implementation," which has a certain universality, is known. However, this device is focused on industrial applications, it is not intended for installation of additional measuring equipment and cannot be used in laboratory conditions.

RU 2245222 01/27/2005 C1 - "A device for conducting SVS in space." This device is designed for special applications, namely, the conduct of the CBC in space.

The SVS-Az-4.5 device is known (Amosov A.P., Borovinskaya I.P., Merzhanov A.G. Powder technology of self-propagating high-temperature synthesis of materials: Textbook. Under the editorship of VN Antsiferov. - M .: Mashinostroenie-1, 2007, p. 311.), characterized by its limited scope - “azide technology”.

The closest analogue is the installation “SVS-Az-4.5”, given in the text of the textbook Amosov A.P., Borovinskaya I.P., Merzhanov A.G. Powder technology of self-propagating high-temperature synthesis of materials: Proc. benefit / Under the scientific editorship of V.N. Antsiferova. - M .: Mashinostroenie-1, 2007, p. 311.

Laboratory reactor SVS-Az-4,5 is designed to study the laws of the process of SHS when interacting with nitrogen, measuring linear velocities and temperatures of combustion. The reactor has observation windows. The reactor device also provides for the possibility of connecting thermocouples and initiating devices. The reactor is equipped with a massive fungal gate. The design of the reaction chamber is a metal cylinder with a bottom. The working position of the device is vertical, upwards. The object table is rigidly attached to the shutter.

The disadvantage of the closest analogue is the limited scope - "azide technology". The design of the reactor involves the presence of a massive fungal gate. This installation is quite difficult to maintain, because it does not have a collapsible design, and its operation is assumed only in a vertical position.

The task of the invention is to create a device that can be used in the laboratory to study the features of SHS processes, namely, to obtain data on the fundamental physico-chemical, thermal and gas-dynamic characteristics of the process.

The technical result of the invention is:

- reduction of resource-intensive ™ and increase in the efficiency of the reactor by reducing the physical dimensions;

- facilitating the operation and maintenance of the reactor in the laboratory, due to the most efficient use of the internal space of the reaction chamber when placing the main elements and structures, as well as by simplifying the design of the reactor;

- the possibility of using electronic measuring systems located in the working space of the reactor.

The technical result is achieved in that the installation for measuring the characteristics of the SHS process of inorganic compounds in autowave mode includes a cylindrical tube-shaped body, threaded pressing rings and caps covering the tube to form a chamber for accommodating an exothermic powder reaction mixture (pressing), and an initiator, placed in the working space of the installation according to the invention, the design of the device allows the use of electronic gas valves, if necessary, connect ie via a special connector. The case is fixed horizontally, on a support with the possibility of installing a rotating bed, to facilitate the operation and maintenance of the reactor, in the case of using additional equipment (chambers, pyrometers, etc.)

For a laboratory reactor, the necessary requirements are: the ability to install equipment for measuring temperature and burning rate.

In addition, measurements of the burning rate can be carried out with the help of external equipment (chambers, pyrometers) or with the help of equipment permanently located inside the reactor.

It is known that for such purposes it is possible to apply photodiodes installed along the vertical axis of symmetry of the sample at a known distance from each other. Obviously, the set of output voltages obtained by measuring the luminosity of the combustion wave in the sample allows us to establish the speed of movement of the combustion wave in the corresponding sample plane.

Since thermocouple measurements have proven to be the most reliable and versatile method for measuring temperatures in SHS studies, it is proposed to use a thermocouple installed inside a powder sample prepared using a special mold or thermocouple pressed into the sample to measure the combustion temperature. The location of the thermocouple in the hole in the bottom of the crucible allows you to simplify the installation and replacement of the thermocouple.

The drawing shows the scheme of the proposed reactor in longitudinal section (general view), where:

1 electronic pressure sensor;

2 pipe for the supply and removal of gas from the chamber;

3 holder for igniting helix with clips;

4 firing spiral, or other initiating device;

5 valve to protect the electronic components installed inside the reaction chamber, with openings for optical fibers;

6 upper and lower optical fibers, made in the form of tubes;

7 support photodiodes and light guides;

8 upper and lower photodiodes designed to measure the burning rate;

9 crucible with a thermocouple bore made of a refractory dielectric material;

10 thermocouples;

11 steel stage;

12 mounting the table to the back cover;

13 electrical connector for thermocouple;

14 internal electrical connector for connecting electronic components to the control board;

15 sealed electrical connector;

16 external connector for connecting electronic components to the control board;

17 control board;

18 personal computer;

19 power supply;

20 front cover of the reaction chamber of a transparent material; 21, 23 screw caps;

22 reaction chamber, which is a hollow steel cylinder;

24 back cover of the reaction chamber;

25 rubber sealing rings;

26 support for swivel mount;

27 solenoid valve.

The operation of the SVS reactor. In the initial state, the reaction chamber of the reactor remains open: the pressing ring 21 and the cover 20 are removed, the cover 24 is pressed by the ring 23, the supply of electric current to the initiating device 4 and the gas supply are not carried out. A control board 17 is connected to the personal computer 18.

Control Board 17 is designed for:

- control of power supply 19;

- control of current supply to the initiating device 4;

- control of the operation of the electronic valve connected to the connector 27 and communicating with the working space of the housing 22 through the nozzle 2;

- for processing the output signals of the photodiodes 8 and thermocouple 10 and transfer the processed data to the personal computer 18.

To carry out the synthesis of SHS in the crucible 9 placed inside the reaction chamber 22 on the stage 11, which is rigidly fixed on the back cover 24, load the reaction exothermic mixture of initial reagents, in the form of pressing or powder.

Pressing the reaction mixture is carried out using a special mold having a lower punch with a needle with a diameter of 1-3 mm located in its center. Or, with the help of another special mold that allows you to place a thermocouple 10 inside the compact.

In the case of loading the reaction mixture in the form of a powder, it is filled up so that the thermocouple 10 located in the crucible is completely covered by the reaction mixture.

Installed in the connector 3, the initiating device 4, in the form of a spiral made of tungsten, molybdenum or nichrome wire with a diameter of up to 1.0 mm, is brought into contact with the loaded reaction mixture to effect local initiation of the reaction.

Depending on the temperature range that can be achieved during the synthesis, the crucible 9 can be made of graphite, refractory material, refractory metal or steel.

Then, a cover 20 is installed in the reaction chamber 22, pressed by a threaded ring 21 and hermetically closes the working space by means of sealing rubber rings 25.

Then, inside the reactor vessel, through the nozzle 2, if necessary, create a vacuum, gas flow or excessive gas pressure (inert or reactive - nitrogen).

The design of the device involves the use of an electromagnetic gas valve 27 connected to the nozzle 2. This valve is controlled by the control board 17, the power supply unit 19 and the personal computer 18.

To create a special atmosphere inside the reactor, software is used to switch the operation of the electronic valve 27, with the readings of sensor 1, using the control board 17. Then, the CBC process is initiated.

The SVS process is initiated using the power supply 19 manually or using a control computer program installed on the connected personal computer 18, by applying an electric current pulse at a voltage of up to 50 V and a current of up to 80 A to the initiating device 4, in the form of a spiral. In the case of using a personal computer 18, it is advisable to use software tools that allow you to automatically stop the flow of current to the initiating device 4, when a certain temperature is reached, achieved through the exothermic effect of the synthesis reaction.

The process can be observed through the transparent front cover 20 and fix it with additional equipment, as well as the indications of thermocouple 10 and photodiodes 8, protected from high temperatures and reaction products using optical fibers 6, and a protective screen 5.

After the process is completed, pressure is equalized in the reactor vessel with atmospheric pressure, pressure ring 21 and cover 20 are removed, the resulting reaction products are discharged from crucible 9.

Determination of the speed of propagation of the combustion wave is carried out by comparing the time of appearance of the largest pulse in the output voltage spectra of photodiodes 8 installed at a known distance from each other or using external equipment (video cameras or high-speed pyrometers), the reaction temperature is also determined by thermocouple readings 10.

The change in pressure in the working space of the reactor, caused by the appearance of gaseous reaction products or the absorption of gaseous reactant, is measured using an electronic pressure sensor 1.

Registration of the output voltages of the sensors and transfer to the personal computer 18 is carried out using the control card 17.

Example 1 (device prototype). Pressing the reaction mixture, containing two pressed thermocouples at a certain distance, is placed on an object table, rigidly attached to the gate of the reactor. After that, the thermocouple is connected to the wires connected to the sealed connector in the gate. The sample is brought into contact with the initiating device by means of adjusting nuts holding the stage. Then, the shutter with the stage is placed inside the reactor, which is in a vertical position, through an opening in the upper part. The shutter is fixed with a clamping ring. After that, vacuuming is performed, and, then., The working space of the reactor is filled with a reacting gas — nitrogen. The initiation of the SVS process is carried out by applying a pulse of electric current to the initiating device, in the form of a spiral.

The determination of the speed of propagation of the combustion wave is carried out by comparing the start time of the reaction from the readings of thermocouples installed at a known distance from each other, the reaction temperature is also determined from the readings of the thermocouples.

Example 2 (the proposed device). To carry out the synthesis of SHS in the crucible, placed inside the reaction chamber, load the reaction exothermic mixture of initial reagents, in the form of a cylindrical extrusion with a hole located along the vertical axis of symmetry. The sample is placed in such a way that the thermocouple is in the sample hole. The initiating device, in the form of a spiral made of tungsten wire with a diameter, is brought into contact with the sample to effect a local initiation of the reaction.

Then, a cap is installed in the reactor vessel and pressed against the threaded ring. After that, in the working area of the reactor create an overpressure of inert gas (argon).

For this purpose, the required pressure is set on a personal computer using a control computer program. The entered data is transmitted to the connected control board, to which the pressure sensor and the solenoid valve are connected. The gas supply automatically stops when the set pressure is reached. Then, the SVS process is initiated using a control computer program installed on a connected personal computer, by applying an electric pulse of a given magnitude to the initiating device in the form of a spiral. The supply of current to the initiating device automatically stops when a certain temperature is reached that is monitored by a thermocouple reading.

The determination of the speed of propagation of the combustion wave is carried out automatically using a computer program, the reaction temperature is also determined from the readings of thermocouples, which are automatically recorded on a personal computer in the form of a time-temperature graph.

Claims (1)

The installation for the SVS, including the reaction chamber, which is a hollow steel cylinder containing two holes in the wall and mounted on a support that can be mounted on a rotary frame, an electronic pressure sensor, a nozzle installed in the corresponding hole in the housing for supplying and venting gas from working space, the holder of the igniting spiral with clips; ignition coil, gate for protection of electronic components installed inside the reaction chamber, with openings for optical fibers, upper and lower optical fibers, fastening of optical fibers, crucible with a hole for a thermocouple, a thermocouple, a steel stage, mounting the table to the back cover, a connector for connecting a thermocouple, internal connector for connecting electronic components to the control board; external connector for connecting electronic components to the control board; a power supply unit designed to power the control board card and electronic valve, as well as for supplying electric current to the initiating device, a connector for connecting a controlled electronic valve, two photodiodes installed behind a protective screen and additionally equipped with focusing optical fibers made in the form of tubes, as well as one thermocouple, which are interconnected in unified system through the microcontroller board.

Images