JPH0524809A - Production of niobium nitride - Google Patents

Abstract

PURPOSE:To obtain almost pure delta type niobium nitride at a lower temperature than the conventional temperature by using a compact device and simultaneously obtain the delta and epsilon type niobium nitride producible also as a simple substance powder, coated substances, fiber, etc. CONSTITUTION:In the case of simple substance powder, a hydrolyzable niobium compound is mixed with an aqueous solution of an inorganic acid and hydrolyzed. The resultant aqueous solution containing niobium hydroxide is concentrated and dried to dehydrate and condense the niobium hydroxide. The prepared niobium oxide polymer is then burned at 750-1700 deg.C temperature in a nitrogen- based reducing atmosphere and nitrided. When fiber is formed, spinning is performed after concentrating. When coating is carried out, the aqueous solution before the concentrating and drying is applied onto a substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing niobium nitride, particularly .delta. Or .epsilon.

[0002]

2. Description of the Related Art Niobium nitride contains α, β, γ, δ, δ ',
There are various crystal forms of ε and ε, which are used as high-temperature structural materials, cemented carbide tool materials, hardeners, etc., and δ type is also drawing attention as a superconducting material.

As a method for producing such niobium nitride, conventionally, (1) a target of niobium was used as N ₂ + Ar.
A method of sputtering on a substrate in a gas (for example, JP-A-64-7246 and JP-A-60-29463), (2)
A CVD method in which NbCl ₅ / N ₂ / H ₂ gas or NbCl ₅ / NH ₃ gas is chemically reacted on a substrate (substrate) (for example, JP-A-62-20203). (3) Metallic niobium is 700
There has been proposed a method of reacting in nitrogen gas at a temperature of not less than 10 ° C. and a pressure of 10 to 100 Kgf / cm ² (for example, JP-A-1-167206).

However, the method (1) requires a large-scale apparatus, requires a high vacuum, and is a kind of vapor-phase chemical plating method, so that a single powder cannot be obtained (only a substrate is coated). There is a problem such as. Method (2) is also (1)
Similar to the above method, since it is a kind of vapor phase chemical plating method, there is a problem that a single powder cannot be obtained (only a coating material on a substrate such as glass fiber). Further, the method (3) has a problem that high pressure is required and a high temperature of 1300 ° C. or higher is required to obtain almost 100% δ-type niobium nitride.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems in the prior art, use a compact apparatus, and obtain substantially pure δ-type niobium nitride at a lower temperature than before, and It is an object of the present invention to provide a method for producing δ and ε type niobium nitride, which can be produced not only as a simple substance powder or a coating but also as a fiber or a wire.

[0006]

The above object is to hydrolyze the niobium compound by mixing a hydrolyzable niobium compound and an inorganic acid aqueous solution according to the present invention, and concentrate the resulting niobium hydroxide-containing aqueous solution. A niobium hydroxide is dried and dehydrated and condensed, and then the obtained niobium oxide polymer is fired at a temperature of 750 to 1700 ° C. in a nitrogen-based reducing atmosphere to be nitrided. This can be achieved by the manufacturing method.

The method of the present invention will be described in more detail. First, the hydrolysis step is carried out by mixing a hydrolyzable niobium compound and an aqueous solution of an inorganic acid. In this step, the niobium compound is hydrolyzed to a hydroxide [eg N
b (OH) ₅ ].

As the niobium compound used here,
General formula Nb (OR)_Five(However, R is C₁~ C_FourThe alkyl
Group), that is, Nb (OCH₃)_Five, Nb
(OC₂H _Five)_Five, Nb (O-n-C₃H₇)_Five, Nb (O-
iso-C₃H₇)_Five, Nb (O-n-C_FourH₉)_Five, Nb
(O-iso-C_FourH₉)_Five, Nb (O-sec-C
_FourH₉)_FiveNbO (C_FiveH₇O₂)₃Nbx_Five(However, x is C
l or Br), ie NbCl_Five, NbBr_FiveNb (HC
₂O_Four)_FiveEtc.

As the inorganic acid, HNO ₃ , HCl, H ₂
SO ₄ or the like is used. These inorganic acids are purely dissolved and used as an aqueous solution. The mixing ratio of the niobium compound and the inorganic acid is appropriately in the range of 1: 0.5 to 2 in terms of molar ratio. The inorganic acid concentration in the aqueous solution of inorganic acid is 10 to 10.
A range of 70% by weight is suitable. When the niobium compound is a solid, the aqueous solution of the inorganic acid and / or the niobium compound has a high solubility in water and, at the same time, a hydrolysis reaction is allowed to proceed slowly. Organic solvents that do not cause phase separation can be mixed. The organic solvent used here is methanol,
Examples thereof include lower alcohols such as ethanol, n-propanol, iso-propanol, t-butanol, etc., and acetone.

The mixing order of the niobium compound and the inorganic acid aqueous solution is not particularly limited, but it is preferable to add the inorganic acid aqueous solution to the niobium compound. Further, in order to allow the reaction to proceed smoothly, it is preferable to gradually mix them by an appropriate amount or by adding them in small amounts.

The temperature at the time of mixing is preferably room temperature or lower so that the reaction proceeds slowly. The next dehydration condensation step is basically performed by concentrating (solvent removal) the niobium hydroxide-containing aqueous solution obtained in the previous step and further drying. In this step, niobium hydroxide is dehydrated and condensed to form an amorphous niobium oxide polymer. However, when niobium nitride is made into fibers or coated, it is desirable to carry out preliminary processing in this dehydration condensation step. On the other hand, when niobium nitride is obtained as a powder, this basic step may be substantially carried out as it is, but it is preferable to use one of the following methods. (1) The niobium hydroxide-containing aqueous solution obtained in the previous step is spray-dried to concentrate and dry at the same time. (2) The niobium hydroxide aqueous solution is heated and concentrated, and then freeze-dried.

In the case of the method (2), it is appropriate that the heating temperature at the time of concentration is about 40 to 70 ° C. As the concentration method, other methods such as natural standing, decompression, and heating decompression can be adopted. As the drying method, natural drying or heat drying can be adopted, but the heating temperature in this case is 40 to 200.
A temperature of about ℃ is appropriate. In any case, since the concentration and the drying are based on the removal of the solvent, they can be simultaneously carried out by any method such as heating and natural standing.

In the case of fiberizing, first, the niobium hydroxide-containing aqueous solution is concentrated by heating, depressurizing, heating depressurizing, leaving, etc., preferably by heating. This operation is usually performed with stirring. When heating, a heating temperature of 40 to 70 ° C. is suitable. With the concentration of the aqueous solution, a partial dehydration condensation proceeds,
It becomes viscous. When the aqueous solution reaches a viscosity suitable for fiberization (for example, 10 poise or more) or spinnability, the viscous solution is spun by a known spinning means (nozzle extrusion, pulling with a rod). Then, the spun fiber is dried and dehydration condensation is completed. As the drying method, the heat drying method and the natural drying method described above are suitable.

In the case of coating, a niobium hydroxide-containing aqueous solution is applied onto a substrate such as a substrate or a wire by a method such as dipping, casting, spraying, etc., and concentrated or dried by heating or leaving it to stand. Are simultaneously performed to complete the dehydration condensation. In this case, a heating temperature of about 110 ° C is suitable.

In the final nitriding step, the amorphous niobium oxide polymer obtained in the previous step is processed for 750 in a nitrogen-based reducing atmosphere.
It is carried out by firing at a temperature of ˜1700 ° C., preferably 800˜1400 ° C. Through this step, the amorphous niobium oxide polymer is converted to crystalline (δ or ε type) niobium nitride. That is, δ-type niobium nitride (which becomes a superconductor at 1050 ° C) is produced at a temperature of 750 to 1050 ° C, and ε-type niobium nitride is produced at a temperature of 1100 ° C or higher. 7
Niobium nitride does not form below 50 ° C. Further, since an electric furnace capable of processing at a temperature of 1700 ° C. or higher in a nitrogen-based reducing atmosphere is not known, firing at 1700 ° C. or higher is not practical.

In the temperature range of 1050-1100 ° C., niobium nitride in which δ type and ε type are mixed is formed. Examples of the nitrogen-based reducing atmosphere used in this step include NH ₃ gas, N ₂ + H ₂ mixed gas and the like, preferably NH ₃ gas. The temperature rising rate is 5 to 10 ° C / min, and the holding time is 1
-10 hours is appropriate. When NH ₃ gas is used, it is not necessary to adjust the gas pressure during firing.

[0017]

EXAMPLES The present invention will be described in more detail below with reference to examples.

[0018]

Example 1 Niobium pentaethoxide Nb (OC ₂ H ₅ )
_5. 7.04 g was dissolved in 15.31 g of ethanol to prepare a uniform transparent solution (solution A). On the other hand, 2.32 g of HNO ₃ aqueous solution (60%) was dissolved in 15.31 g of ethanol to prepare an acidic solution (solution B). While stirring solution A in a beaker constantly, solution B was added dropwise thereto for about 30 minutes to obtain a uniform transparent mixed solution. Next, this beaker was left to stand on an oil bath maintained at 60 ° C., and the solution inside was concentrated while being constantly stirred. The solution gradually decreased in volume and, at the same time, increased in viscosity and became spinnable from a certain viscosity. 6m in this viscous solution
A gel rod was obtained by immersing an mφ glass rod and quickly pulling it up by hand.

The gel-like fiber obtained was naturally dried at room temperature for 2 days or more, then put in an alumina boat and allowed to stand in a quartz tube furnace. First, a 1 l / min N ₂ gas stream was passed for 30 minutes to replace the nitrogen in the furnace, and then 2
The dry ammonia gas was switched to 00 cc / min, the temperature was raised to 1050 ° C. at a heating rate of 5 ° C./min, and the temperature was maintained for 1 hour. Then, the N ₂ gas flow was switched again to cool to room temperature in the furnace. It was

It was confirmed by the X-ray diffraction that the fiber obtained by the above operation had metallic luster and was δ-NbN. Further, this fiber exhibited superconducting properties with an electric resistance of zero at 10.97K.

[0021]

Example 2 A uniform transparent mixed solution obtained in the same manner as in Example 1 is placed in a 100 ml tall beaker and set on a winding device driven by a motor (for example, Tensilon, trade name).

An alumina substrate molded to a size of 30 × 10 × 1 mm was hung from the head of the apparatus with a nylon thread and positioned so that it was directly above the liquid level of the solution in a tall beaker preset below. Head speed 1
It was gently immersed in the liquid by descending at a rate of mm / sec. After immersing the entire substrate in the liquid, the substrate was gently lifted from the liquid at a head speed of 0.5 mm / sec and dried in the air for 5 minutes, and then heat-treated in NH ₃ gas as described in Example 1 below. Was applied.

It was confirmed by X-ray diffraction that the coating film on the alumina substrate obtained as described above had metallic luster and was δ-NbN.

[0024]

Example 3 The homogeneous mixed solution obtained in the same manner as in Example 1 was pulverized by spray drying at a temperature of 130 ° C. This powder was subjected to the heat treatment in NH ₃ gas described in Example 1 below. The powder after heat treatment had a metallic luster and was confirmed to be δ-NbN by X-ray diffraction.

[0025]

Example 4 Niobium pentaisopropoxide Nb (OC
₃ H ₇ ) ₅ 19.42 g of isopropanol 30.04 g
To prepare a uniform transparent solution (solution A). on the other hand,
5.06 g of concentrated hydrochloric acid aqueous solution was added to isopropanol 30.04.
g to prepare an acidic solution (solution B).

While stirring the solution A in a beaker constantly,
Solution B was added dropwise to this for about 30 minutes to obtain a uniform transparent mixed solution. The obtained transparent mixed solution was mixed with 70
A transparent quartz substrate having a size of × 20 × 1 mm and having its surface cleaned by ultrasonic cleaning was molded as a film by the same operation as in Example 2, then dried at room temperature in the atmosphere for 5 minutes, and thereafter, as in Example 1. 13 in dry ammonia gas
It heat-processed at 00 degreeC for 1 hour.

The coating film on the quartz substrate obtained as described above has a grayish white color, and is ε-N by X-ray diffraction.
It was confirmed to be bN.

[0028]

Example 5 13.51 g of NbCl ₅ niobium chloride was dissolved in 14.52 g of acetone to prepare a uniform transparent solution (solution A). On the other hand, a sulfuric acid solution diluted with distilled water (50
%) 4.904 g was dissolved in 14.52 g of acetone to prepare an acidic solution (solution B).

While stirring the liquid A in a beaker constantly,
Solution B was added dropwise to this for about 40 minutes to obtain a uniform transparent mixed solution. The obtained transparent mixed solution was concentrated at 60 ° C. using a rotary distillation apparatus (rotary evaporator) to obtain an agar-like wet gel. This wet gel was freeze-dried by a freeze-drying device to obtain a white to pale yellow spherical powder, and the same heat treatment as in Example 4 was performed.

The powder obtained as described above was white to off-white and confirmed to be ε-NbN by X-ray diffraction.

[0031]

Example 6 Niobium oxyacetylacetonate N
bO (C ₅ H ₇ O ₂ ) ₃ 20.31 g was added to t-butanol 7
It was dissolved in 4.08 g to prepare a uniform transparent solution (solution A). On the other hand, 5.25 g of nitric acid aqueous solution (60%) was dissolved in 74.08 g of t-butanol to prepare an acidic solution (solution B).

While stirring the liquid A in the beaker constantly,
Solution B was added dropwise to this for about 60 minutes to obtain a uniform transparent mixed solution. The obtained transparent mixed solution was concentrated in the same manner as in Example 1 to give a viscous solution. Put this viscous solution into a glass syringe (needle inner diameter 0.5 mmφ),
A gel-like fiber was obtained by extruding it into the atmosphere at a constant pressure.

The obtained gel-like fiber was treated in the same manner as in Example 1 except that dry ammonia gas was replaced with N ₂ : H ₂ = 1: _2.
Using the mixed gas of No. 3, heat treatment was performed at 800 ° C. for 1 hour. It was confirmed by X-ray diffraction that the fiber obtained as described above had metallic luster and was δ-NbN.

[0034]

With the above-described structure, the method of the present invention can produce substantially pure δ-type niobium nitride at a low temperature of about 800 ° C. by using a compact apparatus, and also can produce δ- and ε-type niobium nitride as a single powder. There is an advantage that it can be manufactured not only as a coating or a coating, but also as a fiber or a wire.

There is also an advantage that NH ₃ gas, which does not require adjustment of gas pressure, can be used as a nitrogen-based reducing atmosphere during firing.

Claims (10)

[Claims] 1. A hydrolyzable niobium compound is mixed with an inorganic acid aqueous solution to hydrolyze the niobium compound, and the resulting niobium hydroxide-containing aqueous solution is concentrated and dried to dehydrate and condense the niobium hydroxide. Then, the method for producing niobium nitride is characterized in that the obtained niobium oxide polymer is fired at a temperature of 750 to 1700 ° C. in a nitrogen-based reducing atmosphere to be nitrided. 2. The niobium compound is Nb (OR) ₅ (wherein R represents a C ₁ -C ₄ alkyl group), NbO (C _{5
H 7 O 2) 3, NbX} 5 ( where X represents Cl or Br.)
And the method of claim 1 selected from the group consisting of Nb (HC ₂ O ₄ ) ₅ . 3. The inorganic acids are HNO ₃ , HCl and H ₂ SO _4.
The method of claim 1 selected from the group consisting of: 4. The method according to claim 1, wherein in the hydrolysis step, the niobium compound and / or the inorganic acid aqueous solution is further mixed with water and mixed with an organic solvent that does not cause phase separation of the niobium compound. 5. The molar ratio of the niobium compound and the inorganic acid is 1 :.
The method according to claim 1, which is in the range of 0.5 to 2. 6. The nitrogen-based reducing atmosphere is NH ₃ gas or N ₂
The method according to claim 1, which is a + H ₂ mixed gas. 7. The dehydration condensation step, wherein concentration and drying are simultaneously performed by spray drying, whereby the finally obtained niobium nitride is pulverized.
The method described. 8. In the dehydration condensation step, the concentration is carried out by heating, the drying is carried out by freeze-drying,
The method according to claim 1, wherein the finally obtained niobium nitride is powdered. 9. In the dehydration condensation step, the niobium hydroxide-containing aqueous solution is concentrated, spun, and then dried,
The method according to claim 1, wherein the finally obtained niobium nitride is made into fibers. 10. In the dehydration condensation step, an aqueous solution containing niobium hydroxide is applied onto a substrate and concentrated and dried,
The method according to claim 1, wherein the finally obtained niobium nitride is coated on the substrate.