RU2452686C1 - Apparatus for purifying and modifying nanodiamonds - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: apparatus for purifying and modifying nanodiamonds has a vessel 1 for the starting material, a heater 2 which is controlled by an automatic control system 9, a gas mixture generating system and filtration system 3. The vessel 1 is fitted with gas and mechanical mixing apparatus. The gas mixing apparatus has gas mixture inlet pipes 7 in the vessel 1 below the top layer of the starting material, and gas flow breakers 8, which provide successive paired switching on of diametrically lying pipes 7. The mechanical mixing apparatus is in form of an electromechanical mixer 6 with blades, which is mounted at the bottom of the vessel 1. The gas mixture generating system has an oxygen concentrator 4, an ozoniser 5 and a system for controlling content of each of the components in the gas mixture. The filtration system 3 is in form of porous filters fitted with a system for reverse pulsed compressed air blowing.

EFFECT: invention enables simultaneous purification of nanodiamonds from graphite, amorphous carbon and gaseous impurities and modification of the nanodiamond surface with oxygen and ozone.

5 cl, 3 dwg, 2 ex

Description

The invention relates to the field of production of nanodiamond powders, nanotubes, onion carbon and other carbon nanomaterials and products based on them.

A device is known for removing non-diamond carbon impurities from a charge of artificial nanodiamonds (RF patent No.2015050), which contains a vessel for placing a charge, a heater, an ozone-air mixture generator and an additional vessel for placing a charge connected to the first vessel and having a passage greater than the first vessel gas section. The device is also equipped with an additional vessel heater. A mixture containing artificial diamonds is placed in a heated vessel through which an ozone-air mixture is passed. In the vessel, non-diamond forms of carbon are oxidized. A certain amount of the charge is carried away by the current of the ozone-air mixture and gaseous oxidation products and is transferred to an additional vessel, which is also filled with the charge and acts as a filter shutter, in which small fractions of diamond products are blown out from the first vessel and the charge is partially oxidized for its subsequent use in the first vessel.

The disadvantage of this device for removing impurities of non-diamond forms of carbon from a mixture of artificial diamonds is the heterogeneity of the obtained product in composition and particle size, since the design of the device a priori implies the presence of a density gradient of reactants and products both in diameter and in the length of the reaction volume. The use of this device leads to non-uniform and incomplete oxidation of non-diamond forms of carbon in the composition of the charge material, to obtain a product with a partially modified surface, burning of diamond fractions of small sizes, entrainment of small fractions with gas oxidation products. The specified device is intended only for cleaning a charge of artificial diamonds having microscopic dimensions and are not intended to produce other carbon-containing nanomaterials.

The specified device is selected by the applicant as a prototype.

The technical task of the invention is to provide a device for producing a nanodiamond with a modified surface, as well as optimizing the process of cleaning carbon nanomaterials from graphite, amorphous carbon and gas inclusions while simultaneously modifying the surface of carbon nanosized objects with oxygen and ozone.

To achieve the task in a device for cleaning and modifying nanodiamonds containing a vessel for placing the starting material, a heater, a gas mixture generation system and a filtration system, according to the invention, the vessel is equipped with gas and mechanical stirring devices, the gas mixing device including gas mixture inlet tubes placed in the vessel below the upper level of the source material layer, and gas flow breakers providing alternating pairwise switching diametrically Assumption tube and mechanical stirring device is embodied as an electromechanical agitator with blades mounted at the bottom of the vessel.

Moreover, the gas mixture generation system is equipped with an oxygen concentrator, as well as a content control system for the gas mixture of each of the components. Also, the device further comprises an inert gas input system, the heater of the claimed device is equipped with an automatic monitoring and control system, and the filtration system is a porous filter equipped with a reverse pulse purge system with compressed gas.

The presence of mechanical and gas mixing devices in the vessel enhances the uniformity of the final product in particle size due to the destruction of carbon nanomaterial aggregates and increases the efficiency of oxidation of impurities. Simultaneous mixing with a mechanical device made in the form of an electromechanical mixer with blades mounted in the bottom of the vessel and gas mixing means, including gas mixture inlet tubes located in the vessel below the upper level of the source material layer, and gas flow breakers, which provide alternating pairwise switching diametrically located tubes, allows to intensify the mixing process.

The presence of an oxygen concentrator in the device allows the cleaning and modification of nanodiamonds with oxygen or any of the gas mixtures.

The presence of a control system for the content in the gas mixture of each of the components allows you to control the composition of the mixture, and also makes it possible to apply both a mixture of gases at any ratio of components, and each component individually, depending on the type of carbon-containing material being processed.

The presence of an inert gas injection system makes it possible to suppress the spontaneous reaction of nanoparticle burning and regulation of oxidative processes.

The presence of an automatic control and management system helps to regulate the heating process in a wide temperature range and makes it possible to use this device for various types of carbon-containing nanomaterials.

Porous filters make it possible to capture material nanoparticles carried away by the gas flow, and the presence of reverse pulsed purge allows the filter to be cleaned, while returning the nanoparticles to the vessel, thus minimizing the loss of the final product.

Patent studies have not identified devices characterized by the claimed combination of features, therefore, we can assume that these devices meet the criterion of "novelty."

The use of a combination of distinctive features is also not known, which indicates compliance with the criterion of "inventive step".

In addition, the present invention can be used on an industrial scale and will find application, in particular, in the manufacture of carbon nanomaterials, i.e. characterized by the criterion of “industrial applicability”.

The essence of the proposed technical solution is illustrated by drawings, where

figure 1 is a diagram of the inventive device,

figure 2 is a fractionation table with centrifugation modes and corresponding fractions of different types of nanodiamonds; fractions 1-7.8 * - sediment, fractions 8, 9 - supernatant, centrifugation time of each fraction 5 min, except for the fraction 1-3 min, D - average particle size in the fraction;

figure 3 is a diagram - the yield of fractions by sequential centrifugation of the initially polydisperse inventive nanodiamond material indicated in the NdO diagram, and acid-chromium nanodiamonds modified by heating in air at 415 ° C (indicated in the Ch diagram St-415C) and at 425 ° C (designated Ch St-425C) for 1 hour.

A device for cleaning and modifying nanodiamonds contains a vessel 1 for placing the starting material, a heater 2, a gas mixture generation system and a filtration system 3. The gas mixture generation system is equipped with an oxygen concentrator 4, an ozonizer 5 and an air dryer, as well as a control system for the content in the gas mixture of each from the components.

The vessel is equipped with devices for mechanical and gas mixing of the source material, while the mechanical mixing device is made in the form of an electromechanical mixer 6 with blades installed in the bottom of the vessel, the gas mixing device includes L-shaped tubes 7 for entering the gas mixture, placed in the vessel below the upper level of the layer source material, and gas flow breakers 8, providing alternating pairwise inclusion of diametrically located tubes.

The filtration system is a porous filter 3, equipped with a reverse pulse purge system with compressed gas.

The device also includes an inert gas injection system, a device for the destruction of residual ozone and a gas analyzer for monitoring the ozone content in the air of the working zone. Also, the device is equipped with a monitoring and control system 9 of all processes.

To ensure the required temperature regime, on the side and bottom surfaces, the vessel 1 is equipped with heaters 2. Both groups of heaters are independently controlled by a system of automatic control and control of 9 temperature in the reaction volume.

The device operates as follows.

To carry out cleaning, the starting material is placed in vessel 1. From the gas mixture generation system, a working gas is fed into the vessel through the input system, the content of each of which through the valve system can vary from 0 to 100% depending on the type of material being processed. The supply of working gas to the vessel is carried out by alternately pairwise activation of diametrically arranged L-shaped tubes 7. Such a supply of working gas provides gas mixing of the starting material during the cleaning process. In this case, at the same time, the mixer 6 can be included to ensure mechanical mixing. During the cleaning process, the starting material is heated in the temperature range from +20 to + 550 ° C, depending on the type of material being processed, while the heaters are controlled by an automatic temperature control and temperature control system in the reaction volume.

Gaseous oxidation products are removed from the reaction volume by a working gas current through special porous filters 3, the pore size and shape of which exclude the removal of nanoparticles. To clean the pores of the filters, their reverse pulse purging by compressed gas is provided.

An inert gas (carbon dioxide) injection system is used to quench the spontaneous combustion reaction of nanoparticles and regulate oxidative processes.

An express analysis of the readiness of nanomaterials is carried out by visual inspection: the color of the initial product changes from black to gray, light gray, which indicates the completion of the oxidation of amorphous carbon and graphite.

Instrumental analysis: determination of the content of diamond and non-diamond phases of carbon is carried out by various methods.

Variable technological parameters: the volume of the carbon product loaded into the reactor, the temperature-time regimes of heating the carbon product, the composition of the working gas, the pressure of the working gas in the system, the volume and rate of removal of gaseous oxidation products - choose based on the composition of the cleaned (oxidizable) material and the desired type final target nanoproduct.

Example 1

A sample of nanodiamond material was obtained by processing carbon material in the inventive device. Next, fractionation was carried out by centrifugation of the obtained polydispersed nanodiamond and the fractionation results were compared with acid refined nanodiamonds modified in air flow at 415 ° C and 425 ° C for 1 hour. The inventive nanodiamond material is easily fractionated by centrifugation (figure 2), the fraction of small fractions after ozone cleaning / modification in the inventive device is the highest when fractioning under equal conditions compared to samples after oxidation in air (figure 2, 3). This is due to the fact that with ozone cleaning and modification using the inventive device, the isthmuses between the primary particles are noticeably thinner, which helps their disaggregation under conditions of active dispersion, leading to a significant increase in the proportion of small fractions and primary particles.

Particle sizes were measured by photocorrelation spectroscopy using Beckman-Coulter N5 (USA) and Malvern ZetaSizer Nano ZS (Great Britain) instruments.

Example 2

A sample of nanodiamond material was obtained by processing the mixture in the inventive device. The nanodiamond and the acid-chromium nanodiamond fraction, subjected to further purification by ion-exchange resins, fractionation and heating in air at 300 ° C, were mixed in methyl methacrylate (a monomer for the polymer of wide use - polymethyl methacrylate) and subjected to ultrasonic treatment for 2 minutes. Samples of the compared material settled in suspension for minutes, while samples obtained using the inventive device showed high sedimentation stability for at least a week (up to the present observation time). Thus, due to the special surface chemistry of the material obtained using the inventive device, the production of a number of polymer composites can be greatly simplified due to the "natural" sedimentation stability of nanodiamonds in suspensions of monomers or suspensions of polymers in various solvents.

Claims (5)

1. A device for cleaning and modifying nanodiamonds, containing a vessel for accommodating the source material, a heater, a gas mixture generation system and a filtration system, characterized in that the vessel is equipped with gas and mechanical mixing devices, the gas mixing device comprising a gas mixture inlet tube vessel below the upper level of the source material layer, and gas flow breakers, providing alternating pairwise inclusion of diametrically located tubes, and the device is mechanically The mechanical mixing is made in the form of an electromechanical mixer with blades mounted in the bottom of the vessel. 2. The device according to claim 1, characterized in that the gas mixture generation system is equipped with an oxygen concentrator, as well as a content control system for the gas mixture of each of the components. 3. The device according to claim 1, characterized in that it is additionally equipped with an inert gas injection system. 4. The device according to claim 1, characterized in that the heater is equipped with an automatic control and management system. 5. The device according to claim 1, characterized in that the filtration system is a porous filter equipped with a reverse pulse purge system with compressed gas.

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