JPH02265643A - Manufacture of ultrafine particles and its device - Google Patents

Abstract

PURPOSE:To manufacture continuously by introducing inactive gas atmosphere in a reaction chamber, rising the temperature of a crucible up to a given temperature and feeding a raw material little by little. CONSTITUTION:The desired quantity of a desired raw material such as an organic compound is fed into a raw material storage section 10, and a base 5 is disposed and a reaction chamber 1 is sealed airtightly. The inside of the reaction chamber 1 is exhausted in the highly vacuumized state, and inactive gas such as He or Ar is introduced from an inactive gas source 3 into the reaction chamber 1. The inactive gas is adjusted to the given pressure to form the inactive gas atmosphere. Then, a raw material is fed from the raw material storage section 10 disposed separately from the crucible 4 in the reaction chamber 1 into the crucible 4 little by little after the crucible 4 reaches the given temperature. Then, the raw material is evaporated and gasified in a short time. The evaporated volume can be increased by said process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method and apparatus for producing ultrafine particles, and more particularly to a method and apparatus for producing ultrafine particles from raw materials containing substances that are susceptible to thermal decomposition.

[Prior Art] A method for producing ultrafine particles according to the prior art will be described with reference to FIG. 2.

A reaction chamber 1 formed of a vacuum container is connected to an exhaust system 2 and an inert gas source 3. Inside the reaction chamber 1 is a crucible 4 in which raw materials are loaded, and a crucible 4 to which generated am particles are attached. A substrate 5 is placed above the crucible 4 for the purpose. Board 5
is cooled by a cooling system (not shown) such as a liquid nitrogen system.

In producing ultrafine particles, first, raw materials of a predetermined composition such as organic compounds are charged into a crucible 4, and the reaction chamber 1 is hermetically sealed.

After evacuating the reaction chamber 1 to a high vacuum of, for example, 10-6 Torr using the exhaust system 2, helium (He), argon (A
An inert gas such as r) is introduced from an inert gas source 3 through a valve to maintain a predetermined inert gas pressure.

Thereafter, the substrate 5 is cooled, and the crucible 4 in which raw materials have been charged in advance is gradually heated to the evaporation temperature. The heated raw material liquefies and vaporizes from one surface. Note that some raw materials do not liquefy but sublimate directly from the solid phase.

The raw material gas molecules heated and evaporated in the crucible 4 collide with inert gas molecules in the atmosphere, are cooled, and gradually coagulate to form ultrafine particles. The generated ultrafine particles are attached to a cooled substrate 5 placed above the crucible 4 and collected.

If the raw material is an organic compound that is easily decomposed thermally, the raw material will decompose while being heated in the crucible, and the components that are easier to evaporate will evaporate first, so they will remain in the crucible. The composition of the liquid phase raw material gradually changes, and accordingly, the composition of the raw material gas molecules that evaporate also gradually changes.

[The problem that the invention attempts to solve! ] As mentioned above, the raw materials are charged into crucible 4,
According to the method of gradually raising the temperature of the raw material to the evaporation temperature (or sublimation temperature) and vaporizing the raw material, the raw material is is thermally decomposed.6 Normally, the desired amount or an additional amount is charged into the crucible, so it takes a considerable amount of time for all the raw materials to vaporize.

Therefore, when converting thermally unstable organic compounds, which are susceptible to thermal decomposition, into ultrafine particles, the raw material molecules will continue to be exposed to high temperatures and some will decompose, resulting in the resulting ultrafine particles. The decomposed composition is mixed in.

As the composition of the raw material in the crucible gradually changes, the composition of the ultrafine particles immediately after the start of evaporation differs from that immediately before the end of evaporation.

When trying to create large amounts of ultrafine particles, a large amount of raw material is charged into a large crucible, but when a large amount is charged at a time, the possibility that the raw material is thermally decomposed and its composition changes increases. .

In order to keep compositional changes as low as possible, when turning thermally unstable organic compounds into ultrafine particles, it is desirable to shorten the time the raw material is exposed to heat and keep the temperature low. The amount of raw material that can be charged into the crucible each time is small, and the same operation must be repeated many times to obtain the desired amount of ultrafine particles.

The purpose of the present invention is to maintain the composition of ultrafine particles constant,
An object of the present invention is to provide a method and apparatus for producing ultrafine particles that can continuously produce ultrafine particles in large quantities.

[Means for solving the problem] After introducing an inert gas atmosphere into the reaction chamber and raising the temperature of the crucible to a predetermined temperature, raw materials are supplied little by little.

In order to supply the raw materials to the crucible little by little, a raw material storage section and a crucible are respectively arranged within the reaction chamber.

A small amount of raw material is taken from the raw material storage section and transported onto the crucible.
Supply into the crucible.

[Function] If you put a small amount of raw material into the crucible while keeping it at a high temperature,
The raw material evaporates in a very short time. When evaporating in a short time, the composition of the ultrafine particles produced in an inert gas atmosphere is kept constant and almost the same as the raw material composition. This is thought to be because thermal decomposition is suppressed because the time of exposure to high temperatures is short.

Therefore, by continuously or intermittently charging a small amount of raw material into the crucible, a desired amount of ultrafine particles having substantially the same composition as the raw material composition can be continuously obtained.

[Example] FIGS. 1(A) and 1(B) show an ultrafine particle production apparatus according to an embodiment of the present invention, FIG. 1(A) is a sectional view, and FIG. 1(B) is a cross-sectional view.
) is a plan view.

The reaction chamber 1 is connected via a valve to an exhaust system 2 and via another pulp to an inert gas source 3.

The reaction chamber 1 is constructed by placing a Pel jar made of stainless steel or glass on a base made of stainless steel, for example. The exhaust system 2 is composed of, for example, a combination of a rotary pump and a diffusion pump.

The inert gas source 3 supplies an inert gas such as a group I gas such as He or Ar, or an inert gas such as H 2 or N 2 gas that can be considered inert to a predetermined raw material.

A crucible 4 and a raw material storage section 10 are arranged in the reaction chamber 1, and a transport tool 11 for transporting the raw material from the raw material storage section 10 to the crucible 4 is also arranged. A coolable substrate 5 is arranged above the crucible 4. The substrate 5 can be cooled to near liquid nitrogen temperature by a liquid nitrogen system (not shown).

The crucible 4 is, for example, W or M which also serves as a heater.

It consists of a container made of high melting point metal such as, a container made of quartz or alumina placed on a heater, a container made of quartz alumina or the like with a heater embedded in it, etc. The raw material storage section 10 stores the raw materials and can take them out as needed, and is made up of, for example, a stainless steel shelf, a container with an outlet at the bottom that can be opened and closed, etc. In this embodiment, there is an outlet 21 that can be opened and closed at the bottom. , and one in which one amount of raw material is supplied each time the actuator 22 is operated is used.

In the conveyor 11, the elongated member 24 is connected to the motor 13, which is a drive source, via a drive means 26 such as a gear.
is connected to a power source 17 via a controller 15 to perform reciprocating motion. The stopper 28 stops the movement of the elongated member 24 and causes the raw material placed thereon to fall into the crucible 4.

Further, a handle 14 for manual operation is provided in parallel with the motor 13.

The procedure for producing ultrafine particles will be explained below.

A desired amount of a desired raw material such as an organic compound is charged into the raw material storage section 10, a substrate 5 is placed thereon, and the reaction chamber 1 is hermetically sealed at a high vacuum (eg, 10'T).

rr or less), and an inert gas such as He or Ar is introduced into the reaction chamber 1 from the inert gas source 3. The inert gas is adjusted to a predetermined pressure (for example, 0.1 to 10 Torr) to create an inert gas atmosphere. The inert gas atmosphere may be allowed to flow.

No raw material is initially put into the crucible 4.

The crucible 4 is heated and set to an appropriate temperature as the evaporation temperature (or sublimation temperature) of the target raw material.

As the heating method, heating methods such as resistance heating, optical heating using a halogen lamp or laser beam, and induction heating can be used.

After the crucible 4 reaches a predetermined temperature, raw materials are intermittently or continuously introduced into the crucible 4 little by little from a raw material storage section 10 installed separately from the crucible 4 in the reaction chamber 1.

As means for supplying raw materials intermittently or continuously, (1) A means for reciprocating a rolling member, etc. that plays the role of transporting raw materials between the raw material storage section and the crucible using gouries, gears, etc. is illustrated. However, there are other methods (2) installing a belt conveyor from the raw material storage section above the crucible, dropping the raw materials from the raw material storage section onto the belt conveyor little by little and conveying them onto the crucible; (4) A means of forming a conveyance path to a crucible, providing an opening at the bottom of the raw material storage section, introducing the raw material into the conveyance path little by little by vibration, etc., and transporting the raw material to the crucible along the conveyance path, etc. A combination of these may also be used.

By intermittently or continuously introducing the raw material into the crucible 4 little by little from the raw material storage section 10, the raw material evaporates and vaporizes within a short time. Since it evaporates in a short time, there is little change in the composition of the raw material.Therefore, the composition of the obtained ultrafine particles is uniform and the same as that of the raw material.

Further, by evaporating at such a high temperature, the amount of evaporation per hour can be increased.

Raw materials are transported from the raw material storage section to the crucible little by little, so
An extremely large amount of raw material can be charged into the raw material storage section at one time, and a large amount of ultrafine particles can be continuously produced without breaking the vacuum.

[Example] 1. About 8 g of compound A was stored in the raw material storage section 10 of Mu A, the substrate 5 was placed, and the reaction chamber 1 was hermetically sealed. After evacuation, He gas was introduced into the reaction chamber 1 and adjusted to a pressure of I TOrr. Crucible 4 is preheated to 270 ml by resistance heating.
heated to ℃. By reciprocating the bed member 24 between the raw material storage section 10 and the crucible 4 using a driving means 26 consisting of a motor 13 and gears, compound A is intermittently introduced into the crucible in small amounts (approximately 10 mg each). I invested in it.

The introduced compound A instantly dissolves and vaporizes, grows as ultrafine particles in an inert atmosphere, and is cooled with liquid nitrogen to form a substrate 5.
Recovered above.

The purity of the ultrafine particles thus obtained was analyzed by thin layer chromatography, high performance liquid chromatography, etc. Third
Figure (A) shows the chromatogram of the ultra-RIQ element of Compound A, and a clear single peak is observed. In addition to the main peak,
Arrows indicate positions where faint signals are observed. The purity was 99.5%, which met the standard value of the purity test described in the Japanese Pharmacopoeia.

For comparison, ultrafine particles of compound A were created using the conventional method,
Analyzed by chromatography. FIG. 3(B) shows the chromatogram obtained, in addition to the main peak some small peaks are observed.

The highest purity was 90.5%. This value does not meet the purity verification test criteria.

2.8 B-4 Store about 2.5 g of compound B in the raw material storage section 10, place the substrate 5, and evacuate the inside of the reaction chamber 1, which is airtightly sealed, to remove He gas. It was introduced and named ITOrr. Crucible 4 was heated to 450°C. Similar to the above example, Compound B was intermittently introduced into the crucible 4 from the raw material storage section 10 little by little (approximately 5 mg) using the bed member 24 .

The introduced compound B evaporated instantaneously, grew into ultrafine particles in an inert atmosphere, and was collected on the cooled substrate 5.

The purity of the ultrafine particles recovered by high-performance liquid fluorography was measured to be 95.8%.

The purity of the conventional method was 51.7% or less.

According to the above example, it can be seen that a significant improvement in purity was obtained compared to the conventional method.

[Effects of the Invention] As described above, according to the present invention, raw materials can be evaporated and vaporized in an extremely short time.

Since the time that the raw material is exposed to high temperatures is significantly reduced, the possibility of thermal decomposition is extremely reduced.

Since the time during which the raw material is exposed to high temperatures is extremely short, even if temperatures considerably higher than those used in conventional methods are used, the extent to which the raw materials are thermally decomposed can be suppressed to below that of the conventional method.

Further, by evaporating at such a high temperature, the amount of evaporation per hour can be increased.

Raw materials are transported from the raw material storage section to the crucible little by little, so
An extremely large amount of raw material can be charged at once, and a large amount of ultrafine particles can be continuously produced without breaking the vacuum.

[Brief explanation of drawings]

1(A) and 1(B) show an embodiment of the present invention, FIG. 1(A) is a cross-sectional view, FIG. 1(B) is a plan view, and FIG. 2 is an ultrafine particle generation device according to the prior art. FIG. FIGS. 3(A) and 3(B) are chromatograms of ultrafine particles of Compound A prepared according to an example of the present invention and a conventional method. Reaction chamber Exhaust system Inert gas source Crucible Substrate Raw material storage section Flooring member Motor handle Controller Power supply outlet Actuator Spoon member Driving means Stopper (A) Cross-sectional view (B) Plan view Embodiment of the present invention Fig. 1

Claims (2)

[Claims] (1) A step of preparing a crucible heated to a predetermined temperature in an inert gas atmosphere, and supplying a raw material containing a substance that is susceptible to thermal decomposition little by little to the crucible, evaporating it, and having a composition almost the same as the raw material. A method for producing ultrafine particles, comprising: growing ultrafine particles in an inert gas atmosphere. (2) An airtight reaction chamber that can be evacuated, a gas source for supplying an inert gas to the airtight reaction chamber, a crucible disposed within the airtight reaction chamber, a means for heating the crucible, and a means disposed within the airtight reaction chamber. An apparatus for producing ultrafine particles, comprising: a raw material storage section, and a conveying means for transporting the raw material little by little from the raw material storage section to a crucible.