RU2798232C1 - METHOD FOR OBTAINING SILVER HALIDE LIGHT GUIDES BASED ON AgClAgCl 0.25Br0.75 - AgI NANOCERAMICS - Google Patents

Abstract

FIELD: materials for infrared (IR) fibre optics.

SUBSTANCE: invention is related to silver halide light guides. The method for producing silver halide fibres based on nanoceramics of the AgCl_0.25Br_0.75 - AgI system includes computer simulation using the finite element method to determine the extrusion parameters - temperature, plunger pressure on the silver halide billet and the speed of movement of the billet through the spinneret when obtaining fibres, while nanoceramic workpiece with a diameter of 8.0 mm, a height of 16.0 mm based on two solid solutions of a hexagonal phase of the wurtzite, P6₃mc structure, and a cubic phase of the NaCl, Fm3m structure, composition AgCl_0.25Br_0.75, additionally containing silver iodide at a certain ratio of ingredients, is heated to 170°C, exposed for 60 minutes to warm up the workpiece and at a plunger pressure of 1200 MPa and its vibration on the workpiece with a frequency of 50 Hz, an amplitude of 50 mcm, which ensures its movement at a speed of 0.6 mm/min to form a silver halide light guide with a diameter of 450 mcm, length of 5 m with a defective surface in form of transverse grooves with a depth of 5 mcm, a width of 10 mcm and a step of 80 mcm.

EFFECT: invention enables production of radiation-resistant silver halide fibres with a defective structure, transparent in the mid and far IR ranges from 3.0 to 27.0 mcm, which makes it possible to detect the spectra of chemical compounds when determining chemicals with high sensitivity up to 0.0005 mol/l in a wider spectral range.

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Description

The invention relates to materials for infrared (IR) fiber optics, namely to a new type of radiation-resistant silver halide fibers with a defective surface, obtained by extrusion from nanoceramics based on the AgCl _0.25 Br _0.75 - AgI system. IR light guides are designed for making a curved loop in sensor fiber probes for mid-IR spectroscopy with high sensitivity up to 0.0005 mol/l when analyzing the concentration of chemicals. In addition, they can be used in laser technology and medicine, pharmaceuticals, optoelectronics and photonics.

Known sensory fiber probe for MIR spectroscopy, including a curved loop made of IR fibers based on silver halide single crystals AgBr _1-x Cl _x . The probe is designed for remote measurement of the chemical composition of liquids with a sensitivity of 0.002 mol/l in the spectral range from 2.5 to 18.0 µm [Kuppler L., Heise HM, Butvina LN, Novel developments in mid-IR fiber optic spectroscopy for analytical application, 2001, Journal of Molecular Structure, Vol. 563-564, P. 173-181]. The main disadvantage of IR optical fibers based on silver halide AgCl - AgBr system is photosensitivity. In addition, the authors do not indicate the chemical composition of the fibers. There is a task of remote online monitoring of chemicals at concentrations less than 0.001 mol/l, so the developed technique does not fully solve the existing problem.

Also known is a fiber probe with a curved IR light guide in the form of a loop based on silver halide system AgCl - AgBr, designed for the spectral range from 3 to 17 μm. A technique has been developed for determining the composition of a liquid in chemical reactors by immersing a loop in solutions. The sensitivity of the method is 0.001 mol/L. Thus, the disadvantages are the same, that is, IR fibers are photosensitive and the existing problem has not been solved [Artyushenko V., Bocharnikov A., Colquhoun G., Leach C., Lobachev V., Sakharova T., Savitsky D., Mid-IR fiber optics spectroscopy in the 3300-600 cm ^-1 range, 2008, Vol. 48, No. 2, P. 168-171].

The closest technical solution is the "Method for obtaining terahertz fibers of the AgBr - AgI system" [RF Patent for invention No. 2780732 dated 09/29/2022, priority 03/05/2022]. The method is reproducible and technological due to computer simulation used at the initial stage to determine the parameters of the extrusion process: temperature, plunger pressure on a single-crystal billet and the speed of movement of the billet through the spinneret in order to obtain a nanocrystalline structure of fibers based on solid solutions of silver bromide-iodide composition in wt . %:

silver bromide 70.0 - 96.0; silver iodide 30.0 - 4.0.

The light guides are resistant to photo- and radiation radiation and are transparent in the spectral range from 3.0 to 27.0 µm, which greatly expands the scope of their application.

But the fibers obtained by extrusion from single crystals of the AgBr - AgI system have a defect-free, smooth side surface, as well as fibers based on single crystals of the AgCl - AgBr system. Therefore, it is impossible to increase the sensitivity of the method for determining online monitoring of liquid chemicals to the required concentration - 0.0005 mol/l and even less than 0.001 mol/l using silver halide light guides with a smooth, defect-free surface.

There is a technical problem in the development of radiation-resistant silver halide infrared fibers with a defective side surface for the mid-IR range. Light guides are needed to make a sensitive curved loop in sensor fiber probes that are connected to an IR Fourier spectrometer for remote online monitoring of the composition of liquid chemicals with a sensitivity of up to 0.0005 mol/L. In addition, radiation-resistant, non-toxic, non-hygroscopic, and plastic silver halide IR light guides with a defective side surface, which ensures high spectral sensitivity, are in demand for laser medicine, pharmaceuticals, optoelectronics, and photonics.

The solution to the problem is achieved due to the fact that a method has been developed for obtaining silver halide fibers based on nanoceramics of the AgCl _0.25 Br _0.75 - AgI system, including computer simulation using the finite element method to determine the extrusion parameters - temperature, plunger pressure on the silver halide workpiece and movement speed preform through a spinneret when obtaining light guides, characterized in that a nanoceramic preform with a diameter of 8.0 mm, a height of 16.0 mm based on two solid solutions of a hexagonal phase of the wurtzite structural type, P6 ₃ mc, and a cubic phase of the structural type NaCl, Fm3m, composition AgCl _0.25 Br _0.75 additionally containing silver iodide in the following ratio of ingredients in mol. %:

AgCl _0.25 Br _0.75 75.0 - 80.0 silver iodide 25.0 - 20.0,

heated to 170°C, kept for 60 minutes to warm up the workpiece and at a plunger pressure of 1200 MPa and its vibration on the workpiece with a frequency of 50 Hz, an amplitude of 50 μm, which ensures its movement at a speed of 0.6 mm/min to form a silver halide light guide 450 µm in diameter, 5 m long, with a defective surface in the form of transverse grooves 5 µm deep, 10 µm wide and 80 µm in pitch.

The essence of the invention lies in the fact that a new type of silver halide IR fibers with a defective side surface based on nanoceramics of the AgCl _0.25 Br _0.75 - AgI system has been developed (Fig. 1. Micrograph of the side surface of an IR fiber based on two solid solutions of a hexagonal phase and a cubic phase composition 25 mol % AgI in AgCl _0.25 Br _0.75 ). The presence of transverse grooves on the side surface of the fiber with a depth of 5 µm, a width of 10 µm and a pitch of 80 µm leads to a 2-fold increase in sensitivity to 0.0005 mol/l in the analysis of chemicals, compared with a sensitivity of 0.001 mol/l and more for IR fibers based on single crystals of the systems AgCl - AgBr and AgBr - AgI (Fig. 2. Scheme of the method for measuring the concentration of chemicals).

The use of computer simulation at the initial stage in order to determine extrusion modes, rather than selecting them using the trial and error method, significantly reduces and reduces the cost of the process. In addition, the size of a nanoceramic preform with a diameter of 8.0 mm and a height of 16.0 mm is determined by modeling to obtain a silver halide light guide with a diameter of 450 μm and a length of 5 m with a defective side surface.

The workpiece consists of a solid solution of a hexagonal phase of the wurtzite structural type, P6 ₃ mc, and a solid solution of the composition AgCl _0.25 Br _0.75 , in the cubic lattice of which additionally contains silver iodide in the following ratio of components in mol. %:

AgCl _0.25 Br _0.75 75.0 - 80.0; silver iodide 25.0 - 20.0.

The composition of nanoceramics and, consequently, IR optical fibers of the AgCl _0.25 Br _0.75 - AgI system includes silver iodide, which is heavier in molecular weight compared to AgCl and AgBr, which imparts high nanodefectivity, densifies the crystal lattice, increases hardness and provides radiation resistance of the fiber to ultraviolet and beta radiation, and also expands the spectral transmission range from 20 to 27 microns, compared with AgCl - AgBr system fibers (analogues).

Example 1

A silver halide nanoceramic was fabricated based on a solid solution of a hexagonal phase of the wurtzite, P6 structural type.₃mc, and a cubic phase of the structural type NaCl, Fm3m, based on a solid solution of the composition AgCl_0.25Br_0.75, in the crystal lattice of which additionally contains silver iodide in the following ratio of ingredients in mol. %:

AgCl _0.25 Br _0.75 75.0; silver iodide 25.0.

Computer simulation using the finite element method determined the extrusion modes of a nanocrystalline preform with a diameter of 8.0 mm and a height of 16.0 mm. A billet for extrusion of a given size was made from nanoceramics. then it was placed in a container, on one end of which there is a die with a diameter of 450 microns, on the other - a plunger that creates pressure and vibration. The workpiece is heated to a temperature of 170°C. held for 60 minutes to warm up and at a plunger pressure of 1200 MPa and its vibration on the workpiece, frequency 50 Hz, amplitude 50 μm, it moves through the spinneret at a speed of 0.6 mm/min and a silver halide light guide with a diameter of 450 μm and a length of 5 m with a defective side surface in the form of transverse grooves with a depth of 5 microns, a width of 10 microns, a step of 80 microns (Figure 1).

The transmission spectra of the light guide were taken on an IR Fourier spectrometer IR Prestige-21, Shimadzu (1.28 - 41.7 μm) with a text fiber (Fig. 3). The light guides transmit without absorption windows from 3.0 to 27.0 μm.

The light guides are resistant to ultraviolet and visible irradiation at wavelengths of 260-500 nm for 530 minutes.

The resistance of optical fibers to beta irradiation with a gradual increase in dose from 50 to 1000 kGy was studied on a linear electron accelerator UELR-10-10S.

Example 2

Made nanoceramics based on two solid solutions of hexagonal and cubic phases, as in example 1. The cubic phase contains a solid solution of AgCl_0.25Br_0.75, in the crystal lattice of which contains silver iodide in the following ratio of ingredients in mol. %:

AgCl _0.25 Br _0.75 80.0; silver iodide 20.0.

Computer simulation for this composition of nanoceramics determined the extrusion modes of a workpiece with a size of 8 x 16 mm - a temperature of 170°C, a pressure on the workpiece of 1200 MPa and with a vibration of 50 Hz, with an amplitude of 50 μm. A silver halide light guide with a defective side surface 450 µm in diameter, 5 m long and with the same properties as in example 1 was fabricated by extrusion.

Example 3

From nanoceramics based on a solid solution of a hexagonal phase and a cubic phase of composition in mol. %:

AgCl _0.25 Br _0.75 77.0; silver iodide 23.0

prepared a workpiece for extrusion of an IR light guide with a defective side surface. Computer simulation, experiment and study of functional properties were carried out as in example 1.

When the compositions of the silver halide nanoceramics are different, given in the examples, as well as when the simulated extrusion modes are changed, it is not possible to obtain fibers with a defective side surface and the required functional properties.

Technical result

A method has been developed for obtaining a new type of radiation-resistant silver halide optical fibers based on the optimal compositions of nanoceramics of the AgCl _0.25 Br _0.75 - AgI system. Due to the optimal chemical composition of nanoceramics and simulated extrusion modes, fibers with a defective side surface are obtained. Light guides of this structure are transparent in the mid and far IR ranges from 3.0 to 27.0 μm, which makes it possible to detect the spectra of chemical compounds when determining chemicals with high sensitivity up to 0.0005 mol/l in a wider spectral range.

The use at the initial stage of computer simulation by the finite element method to determine the parameters of extrusion makes it possible to significantly reduce and reduce the cost of the process, as well as to stably obtain IR fibers with a defective side surface from optical nanoceramics.

The use of such fibers in the sensor fiber probes in the form of a curved loop with a diameter of 10 mm (Fig. 2) makes it possible to increase the sensitivity of the spectroscopic method by 2 times in comparison with fibers from single crystals of the AgCl - AgBr, AgBr - AgI systems (analogs and prototype). The use of non-toxic silver halide fibers with a combination of the above properties is also possible in diagnostic medicine, pharmaceuticals, laser technology, optoelectronics, and photonics.

Claims (3)

A method for producing silver halide fibers based on nanoceramics of the AgCl _0.25 Br _0.75 - AgI system, including computer simulation using the finite element method to determine the extrusion parameters - temperature, plunger pressure on the silver halide billet and the speed of movement of the billet through the spinneret when obtaining fibers, characterized in that that a nanoceramic preform with a diameter of 8.0 mm, a height of 16.0 mm based on two solid solutions of a hexagonal phase of the wurtzite structural type, P6 ₃ mc, and a cubic phase of the structural type NaCl, Fm3m, composition AgCl _0.25 Br _0.75 , additionally containing silver iodide in the following ratio of ingredients in mol. %: AgCl _0.25 Br _0.75 75.0-80.0 silver iodide 25.0-20.0, heated to 170 °C, kept for 60 minutes to warm up the workpiece and at a plunger pressure of 1200 MPa and its vibration on the workpiece with a frequency of 50 Hz, an amplitude of 50 μm, which ensures its movement at a speed of 0.6 mm/min to form a silver halide light guide 450 µm in diameter, 5 m long, with a defective surface in the form of transverse grooves 5 µm deep, 10 µm wide and 80 µm in pitch.

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