APPARATUS FOR THE PRODUCTION OF NANOPARTICLES AND METHOD FOR PRODUCING NANOPARTICLES

Abstract

A method for producing nanoparticles is provided. The method comprises the steps of providing a main tube that is closed at a bottom of the main tube and that comprises a sample position at the bottom, providing a main opening in the main tube, positioning a precursor material at the sample position, evaporating the precursor material by heating the precursor material by a heating device that is in thermal contact with the main tube, and providing a stream of a primary gas into the main tube through an inlet channel which is arranged within the main tube, wherein a cross section of the main tube at the sample position is smaller than at other positions of the main tube.

Claims

1. A method for producing nanoparticles, comprising: providing a main tube that is closed at a bottom of the main tube and that comprises a sample position at the bottom, providing a main opening in the main tube, positioning a precursor material at the sample position, evaporating the precursor material by heating the precursor material by a heating device that is in thermal contact with the main tube, and providing a stream of a primary gas into the main tube through an inlet channel which is arranged within the main tube, wherein a cross section of the main tube at the sample position is smaller than at other positions of the main tube.

2. The method according to claim 1, wherein a main direction of extension of the stream of primary gas encloses an angle of at least 0? and at most 45? with the direction of the gravitational force.

3. The method according to claim 1, wherein a primary dilution and/or a secondary dilution are provided to the nanoparticles.

4. The method according to claim 3, wherein an outlet tube is connected to the main opening of the main tube, the outlet tube comprises a first opening and a second opening, and for the primary dilution, a dilution gas is provided to the first opening of the outlet tube.

5. The method according to claim 3, wherein an outlet tube is connected to the main opening of the main tube, the outlet tube comprises a first opening and a second opening, and for the secondary dilution, a dilution gas is provided at the second opening of the outlet tube.

6. The method according to claim 1, wherein an outlet tube is connected to the main opening of the main tube, and the outlet tube comprises a first opening and a second, wherein the connection of the outlet tube to the main tube is arranged between the first opening and the second opening of the outlet tube.

7. The method according to claim 1, wherein an outlet channel extends parallel to the inlet channel within the main tube and the outlet channel is connected with the main opening, and the outlet channel has the same length as the inlet channel along a main axis of extension of the main tube.

8. The method according to claim 1, wherein the inlet channel is formed by an inlet tube that is arranged within the main tube and extends further outside of the main tube, and the inlet tube extends through an outlet tube.

9. The method according to claim 1, wherein an outlet tube is arranged within the main tube, and the outlet tube extends through the inlet channel.

10. The method according to claim 9, wherein the outlet tube extends further outside of the main tube.

11. The method according to claim 1, wherein the main tube is at least partially mounted within a holder and the sample position is arranged at a variable distance with respect to the holder.

12. The method according to claim 1, wherein the precursor material comprises a metal.

13. The method according to claim 1, wherein the primary gas is provided to the inlet channel by a mass flow controller.

14. A method for producing nanoparticles, the method comprising the steps of: providing a main tube that is closed at a bottom of the main tube and that comprises a sample position at the bottom, providing a main opening in the main tube, positioning a precursor material at the sample position, evaporating the precursor material by heating the precursor material by a heating device that is in thermal contact with the main tube, and providing a stream of a primary gas into the main tube through an inlet channel which is arranged within the main tube, wherein a cross section of the main tube at the sample position is smaller than at other positions of the main tube, and a main direction of extension of the stream of primary gas encloses an angle of at least 0? and at most 45? with the direction of the gravitational force.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The following description of figures may further illustrate and explain exemplary embodiments. Components that are functionally identical or have an identical effect are denoted by identical references. Identical or effectively identical components might be described only with respect to the figures where they occur first. Their description is not necessarily repeated in successive figures.

[0051] In FIG. 1 a cross section through an exemplary embodiment of the apparatus for the production of nanoparticles is shown.

[0052] FIGS. 2, 3 and 4 show exemplary embodiments of the arrangement for the production of nanoparticles.

[0053] With FIG. 5 an exemplary embodiment of the method for producing nanoparticles is described.

[0054] With FIG. 6 another exemplary embodiment of the method for producing nanoparticles is described.

DETAILED DESCRIPTION OF THE INVENTION

[0055] In FIG. 1 a cross section through an embodiment of an apparatus 20 for the production of nanoparticles is shown. The apparatus 20 comprises a main tube 21 that is connected with a holder 37 of the apparatus 20. The main tube 21 has the shape of a cylinder and it is closed at a bottom 22. At the bottom 22 the main tube 21 has a rounded shape. The main tube 21 is made of quartz glass. A part of the main tube 21 is arranged within the holder 37. The holder 37 is a rigid structure. The holder 37 is configured to connect different parts of the apparatus 20 with each other.

[0056] The apparatus 20 further comprises an inlet tube 27. The inlet tube 27 is arranged within the main tube 21 and comprises a first opening 24 to the outside of the apparatus 20 and a second opening 25 to the main tube 21. Within the part of the inlet tube 27 that is arranged within the main tube 21 an inlet channel 23 is formed. The inlet channel 23 comprises a first opening 24 to the outside of the apparatus 20 and a second opening 25 to the main tube 21. The inlet tube 27 further extends outside of the main tube 21. The inlet tube 27 is in places arranged within the holder 37. A part of the inlet tube 27 is arranged outside of the holder 37. The inlet tube 27 has the shape of a cylinder. The first opening 24 and the second opening 25 are the only openings of the inlet tube 27. Within the main tube 21 the inlet tube 27 does not extend completely towards the bottom 22. This means, the part of the inlet tube 27 that is arranged within the main tube 21 is shorter than the main tube 21.

[0057] The main tube 21 further comprises a main opening 26. The main opening 26 is arranged at the top of the main tube 21. This means, the main opening 26 is arranged at the side of the main tube 21 that faces away from the bottom 22. The inlet tube 27 is arranged at the center of the main tube 21. This means, that the inlet tube 27 is arranged at the center of the circular cross section of the main tube 21. As the diameter of the inlet tube 27 is smaller than the diameter of the main tube 21, a volume within the main tube 21 remains around the inlet tube 27. This volume forms an outlet channel 28. This means, the outlet channel 28 extends parallel to the inlet channel 23. The outlet channel 28 is connected with the main opening 26. Via the main opening 26 the outlet channel 28 and thus the main tube 21 is connected with an outlet tube 31 of the apparatus 20. The outlet tube 31 is in places arranged within the holder 37.

[0058] The main axis of extension of the main tube 21 and the main axis of extension of the outlet tube 31 enclose an angle of 90?. The outlet tube 31 has the shape of a cylinder. The outlet tube 31 comprises a first opening 24 and a second opening 25 to the outside of the apparatus 20, respectively. Furthermore, the outlet tube 31 comprises the connection to the main opening 26. The outlet tube 31 and the main tube 21 are connected with each other via an inner volume of the holder 37. At the center of the apparatus 20 the inlet tube 27 and the outlet tube 31 cross each other. The cross section of the outlet tube 31 is larger than the cross section of the inlet channel 23 and it is also larger than the cross section of the inlet tube 27. This means, the inlet tube 27 has a smaller diameter than the outlet tube 31. Therefore, the inlet tube 27 extends through the outlet tube 31. However, the inlet tube 27 and the outlet tube 31 are not connected with each other so that a gas within inlet tube 27 cannot directly pass from the inlet tube 27 to the outlet tube 31 without passing through the main tube 21. As the diameter of the outlet tube 31 is larger than the diameter of the inlet tube 27, a gas flowing from the first opening 24 of the outlet tube 31 to the second opening 25 of the outlet tube 31 can pass around the inlet tube 27 crossing the outlet tube 31. The connection of the outlet tube 31 to the main tube 21 is arranged between the first opening 24 and the second opening 25 of the outlet tube 31.

[0059] The main tube 21 further comprises a sample position 30 at the bottom 22. The sample position 30 is arranged at the lowest point of the main tube 21. The cross section of the main tube 21 at the sample position 30 is smaller than at other positions of the main tube 21.

[0060] Due to the arrangement of the inlet tube 27, the main tube 21 and the main opening 26, the second opening 25 of the inlet channel 23 arranged within the inlet tube 27 is arranged closer to the sample position 30 than the main opening 26.

[0061] A heating device 29 is arranged around the main tube 21 in the region of the sample position 30. The heating device 29 is a heating wire that is wound around the main tube 21 in the region of the sample position 30. This means, the heating device 29 is in thermal contact with the main tube 21. Around the heating device 29 an isolation device 38 is arranged. The isolation device 38 is configured to isolate the heating device 29 against the colder surrounding of the apparatus 20 during heating.

[0062] In FIG. 1 the flow of a gas provided to the apparatus 20 is shown by arrows. A primary gas can be provided at the first opening 24 of the inlet tube 27. The primary gas can flow down towards the sample position 30. Within the main tube 21 the primary gas flows towards the main opening 26. From the main opening 26 the primary gas flows into the outlet tube 31. In the outlet tube 31 the primary gas mixes with a dilution gas that is provided to the outlet tube 31 at its first opening 24. The primary gas and the dilution gas flow through the outlet tube 31 to its second opening 25.

[0063] FIG. 2 shows an exemplary embodiment of an arrangement 32 for the production of nanoparticles. The arrangement 32 comprises the apparatus 20. The arrangement 32 further comprises a particle filter 34 that is connected to the surroundings of the arrangement 32. The particle filter 34 is configured in such a way that air from the surroundings of the arrangement 32 is provided to the particle filter 34. The particle filter 34 is configured to filter nanoparticles out of the air provided to the particle filter 34. The particle filter 34 is connected with a blowing device 39. The blowing device 39 is configured to provide the air provided to the blowing device 39 to mass flow controllers 33 that are connected to the blowing device 39. Two mass flow controllers 33 are connected to the blowing device 39. The mass flow controllers 33 are configured to provide a controllable amount of air per time. One of the mass flow controllers 33 is connected to the first opening 24 of the inlet tube 27. The other mass flow controller 33 is connected to the first opening 24 of the outlet tube 31. In this way, controlled amounts of gas can be provided to both the inlet tube 27 and the outlet tube 31.

[0064] The second opening 25 of the outlet tube 31 is connected with another particle filter 34 and an outlet 40 of the arrangement 32. At the outlet 40 an aerosol provided at the second opening 25 of the outlet tube 31 can be provided. A part of the aerosol provided at the second opening 25 of the outlet tube 31 is led to the particle filter 34. The particle filter 34 is connected to a mass flow controller 33. The mass flow controller 33 provides the received gas to the surroundings of the arrangement 32. By employing the particle filter 34 that is connected to the second opening 25 of the outlet tube 31 the amount of aerosol provided per time at the outlet 40 can be controlled and adjusted.

[0065] FIG. 3 shows a further exemplary embodiment of the arrangement 32. In addition to the embodiment shown in FIG. 2 the arrangement 32 comprises a differential mobility analyzer 35. Furthermore, a charging element 41 is arranged between the second opening 25 of the outlet tube 31 and the differential mobility analyzer 35. The charging element 41 is configured to positively or negatively charge nanoparticles comprised by an aerosol provided at the second opening 25 of the outlet tube 31. In the differential mobility analyzer 35 the charged nanoparticles are analyzed with respect to their charge to drag ratio. The differential mobility analyzer 35 is connected to the outlet 40 and is configured to provide an aerosol with monodisperse nanoparticles to the outlet 40.

[0066] The arrangement 32 further comprises another particle filter 34 which is configured to be provided with air from the surroundings of the arrangement 32. The particle filter 34 is connected with another blowing device 39. The blowing device 39 is connected to another mass flow controller 33. The mass flow controller 33 is connected to the differential mobility analyzer 35. In this way, the flow of gas within the differential mobility analyzer 35 can be controlled. The differential mobility analyzer 35 is connected to another particle filter 34 which is connected to another mass flow controller 33. Via the mass flow controller 33 gas that is not required anymore by the differential mobility analyzer 35 is provided to the surroundings of the arrangement 32.

[0067] FIG. 4 shows another exemplary embodiment of the arrangement 32. In comparison to the embodiment shown in FIG. 2 the arrangement 32 further comprises a furnace 36. The furnace 36 is connected to the second opening 25 of the outlet tube 31. In the furnace 36 nanoparticles in the aerosol provided at the second opening 25 of the outlet tube 31 can be heated so that they form nanoparticles with a homogenous shape, for example the shape of spheres. The furnace 36 is connected to the outlet 40.

[0068] With FIG. 5 an exemplary embodiment of the method for producing nanoparticles is described. The method comprises the following steps that are not necessarily carried out in this order but can be carried out in this order. In a first step S1 the main tube 21 is provided. In a second step S2 the main opening 26 is provided in the main tube 21. In a third step S3 a precursor material is positioned at the sample position 30 within the main tube 21. In a fourth step S4 the precursor material is evaporated by heating the precursor material by the heating device 29 that is in thermal contact with the main tube 21. Preferably, the precursor material comprises silver. In a fifth step S5 a stream of a primary gas is provided into the main tube 21 through the inlet channel 23 that is arranged within the main tube 21. The main direction of extension of the stream of primary gas can enclose an angle of at least 0? and at most 45? with the direction of the gravitational force. As the evaporated precursor material condenses in the primary gas an aerosol comprising nanoparticles is formed. Via the stream of the primary gas provided by the mass flow controller 33, the aerosol is led through the main opening 26 towards the outlet tube 31. In a sixth step S6 a stream of a dilution gas is provided. A primary dilution and/or a secondary dilution are provided to the nanoparticles. This means, the dilution gas is provided at the first opening 24 of the outlet tube 31 for a primary dilution and/or the dilution gas is provided at the second opening 25 of the outlet tube 31 for a secondary dilution. The aerosol and the dilution gas mix such that an aerosol with a desired dilution is provided. Since the cross section of the main tube 21 at the sample position 30 is smaller than at other positions of the main tube 21, the nanoparticles can be formed in a reliable way.

[0069] With FIG. 6 another exemplary embodiment of the method for producing nanoparticles is described. In FIG. 6 an apparatus 20 as described with FIG. 1 is shown. In contrast to FIG. 1 however, the direction of the gas flow is reversed. This means, the outlet tube 31 is arranged within the main tube 21, the outlet tube 31 extends through the inlet channel 23, and the outlet tube 31 extends further outside of the main tube 21. The stream of primary gas is provided to the inlet channel 23 which extends from the right side in FIG. 6 towards the main tube 21. Within the main tube 21, the inlet channel 23 extends around the outlet tube 31. This means, within the main tube 21, a cross section of the inlet channel 23 has the shape of a ring. The aerosol comprising nanoparticles can leave the main tube 21 through the outlet tube 31 which has a first opening 24 at the top in FIG. 6. Reversing the direction of the gas flow as shown in FIG. 6 has the advantage that nanoparticles can be produced in a more reliable way.