RU2444743C2 - Vibration magnetometer - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: device is a vibration magnetometer which is designed to measure magnetisation of analysed substances directly during their chemical transformation. The magnetometer has a magnetic field source, a mechanical vibration generator, a signal detection system and a unit for holding the analysed sample. The unit for holding the analysed sample is in form of a flow-type microreactor. The magnetometer also has a device for heating and cooling the microreactor lying opposite the reactor in a gap between poles of the magnetic field source, and the microreactor has a chamber where the analysed sample is placed. Gas can pass through said chamber. There is a gap through which gas passes between the inner walls of the microreactor and the outer wall of the chamber where the sample is put.

EFFECT: possibility of continuous measurement of magnetisation with controlled composition of a gas medium and temperature range from 70 K to 1200 K.

3 cl, 2 dwg

Description

FIELD OF THE INVENTION

The invention relates to the field of measuring instruments for scientific research. The device proposed for patenting is a vibrating magnetometer designed to measure the magnetization of the studied substances directly in the process of their chemical transformations, which allows continuous measurement of the magnetization at a controlled composition of the gas medium and in the temperature range from 70 K to 1200 K.

Standard instruments offered by various instrument-making companies (for example, a magnetometer from Lake Shor Cryotronics Inc) do not allow the study of substances during their chemical transformations in a controlled gas environment over a wide temperature range. The analogue is an Weiss extraction magnetometer, which, however, does not allow measurements in situ. In magnetometers of this type, the test sample undergoes preliminary processing in the absence of a magnetic field and only then is placed in a magnetic field, where magnetization is measured in the temperature range from room temperature to the temperature of liquid nitrogen. Such a device does not allow measurements directly in the reaction process at elevated temperatures. E. Boellaard, A.M. van der Kraan, J.W. Geus // Appl, Catal. v. 147, (1996), p. 207.

Formulation of the problem

The main difficulty in the design of devices for this purpose is the combination of a flowing chemical reactor (with controlled parameters for temperature and gas flow) with the measuring system of the magnetometer. The reactor with the test sample, as well as the heating element and the cooling system should be located in the gap of the magnet. This condition requires the maximum possible miniaturization of all reactor components, since an increase in the gap between the poles of the magnet leads to a quadratic decrease in the magnetic field strength. The test sample should be fixedly fixed between gas-permeable and heat-resistant membranes in the working zone of the reactor. The generator of mechanical vibrations must have sufficient power in order to give reciprocating sinusoidal oscillations with a controlled frequency from 10 to 100 Hz and an adjustable amplitude from 0.5 to 3 mm to the reactor with the test sample. The reactor heating system should be stationary, and the electrical noise from the current flowing through the heater should be minimized (an order of magnitude smaller than the minimum recorded signal from the magnetometer).

This problem was solved in the present invention.

In a vibrating magnetometer containing a magnetic field source, a mechanical oscillation generator, a signal detection system, a test sample fixation unit, according to the invention, a test sample fixation unit is made in the form of a flow microreactor, the magnetometer contains a device for heating and cooling the microreactor, located near the reactor in the gap between the poles a magnetic field source, and the microreactor contains a chamber for placement of the test sample, configured to pass gas through it While a gap for the passage therethrough of gas between the inner walls of the microreactor and the outer wall of the chamber to accommodate the sample.

Preferably, the sample containment chamber comprises gas permeable membranes used to immobilize the sample in the microreactor chamber.

Preferably, the sample holding chamber comprises a thermocouple.

The invention is illustrated by the following drawings. Figure 1 shows a schematic diagram of a magnetometer. Figure 2 shows a quartz-ceramic microreactor.

The proposed vibration magnetometer consists of the following elements:

1 - an electromagnet with a maximum field strength of 2 T with a gap between the poles of 10 mm;

2 - magnet control unit, consisting of DC power supplies and a digital-to-analog converter (ADC) for communication with a control computer;

3 - Hall sensor with a power source and an analog-to-digital converter for communication with a control computer;

4 - a generator of mechanical vibrations (GMK), consisting of a servo drive connected through an ADC to a computer and a mechanical transducer of rotational motion to reciprocating;

5 - a reactor made of quartz and ceramic parts (separately described below);

6 - device for fastening the reactor to the MMC;

7 - heater with a water-cooled radiator. The heating element is placed in a brass block, into which cold water flows through the internal channels to cool the outside of the heater. This design allows you to cut off the heat flux from the heater to the Helmholtz coils;

8 is a cryostat associated with a refrigerant supply device. The cryostat is a tube made of insulating material with an integrated copper-constantan thermocouple. Refrigerant in the form of a stream of cold nitrogen is supplied to the lower part of the tube from a Dewar vessel, in which a heater is located, controlled by a temperature programmer and a cryostat thermocouple;

9 - the manipulator is a device that allows you to bring to the reactor from below either a heater or a cryostat;

10 - control system for heating and cooling, which includes a temperature programmer that allows you to heat or cool the test sample at a given speed to a given temperature;

11 - two-channel amplifier with a phase detector and ADC, designed to process and amplify the signal from the Helmholtz coils and transmit the signal in digital form to a computer;

12 - the gas preparation system includes flow-pressure regulators and a valve system that allows replacing one gas with another.

The microreactor consists of the following elements:

13 - Ceramic body;

14 - gas radiator-distributor is designed for uniform distribution of the incoming gas stream on the lower gas-permeable membrane and is a sleeve with 4 lateral through channels for the entrance of the gas stream;

15 - gas-permeable membranes of porous heat-resistant and chemically inert material;

16 - test substance weighing from 1 to 50 mg;

17 - Pt-PtRh thermocouple;

18 - quartz tube;

19 - annular space in which the gas is preheated;

20 - gas flow in the annulus;

21 - exit of the gas stream through a quartz tube.

The device operates as follows:

1) the investigated solid substance weighing from 5 · 10 ^-3 to 0.1 g is placed in the reactor 5 and fixed motionless between two gas-permeable membranes 15;

2) the reactor 5 is installed in the holder GMK 6;

3) using the gas preparation device 12 set the required gas flow through the reactor;

4) turn on the GMK 4 and set the value of the magnetic field necessary for the experiment using block 2; when examining the magnetic characteristics, the field sweep is set at a given speed;

5) in the study of isothermal processes, an inert gas is passed through the reactor, and using the temperature programmer 10, the required experimental temperature and the heating rate to a given temperature are set. After the temperature reaches a predetermined value, the inert gas current is replaced by a reaction gas or a mixture of reaction gases, after which a change in the magnetization with a given frequency is recorded. If necessary, stop the process by replacing the reaction gas with an inert gas and measure the magnetic characteristics (saturation magnetization, residual magnetization, coercive force) at the process temperature or any other temperature;

6) when studying the reaction in the programmed heating mode, a reaction gas stream is fed to the reactor 5 with the test substance and then the programmed heating is switched on, during which the change in magnetization is continuously recorded.

Claims (3)

1. A vibrating magnetometer containing a magnetic field source, a mechanical oscillation generator, a signal detection system, a test sample fixation unit, characterized in that the test sample fixation unit is made in the form of a flow microreactor, the magnetometer contains a device for heating and cooling the microreactor, located near the reactor in the gap between the poles of the magnetic field source, and the microreactor contains a chamber for accommodating the test sample, made with the possibility of passage of gas through it, while between the inner walls of the microreactor and the outer wall of the chamber for placing the sample there is a gap for the passage of gas through it. 2. The device described in claim 1, characterized in that the chamber for accommodating the sample contains gas-permeable membranes, which serve to immobilize the sample in the chamber of the microreactor. 3. The device described in claim 1, characterized in that the chamber for accommodating the sample contains a thermocouple.

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