JPH01132831A - Method for producing zirconia fiber - Google Patents

Abstract

PURPOSE:To provide the objective fiber in a highly reduced number of production processes and by low temperature calcination, by hydrolyzing a zirconium alkoxide solution containing a small amount of a stabilizing compound, spinning the obtained spinnable solution and subsequently calcining the produced fiber. CONSTITUTION:A zirconium alkoxide solution containing a small amount of a stabilizing compound capable of producing an oxide thereof stabilizing zirconia by calcination is first hydrolyzed to produce a spinnable solution. The solution is spun to provide a fiber precursor, which is normally calcined at 600-1200 deg.C for 1-5hr to provide the objective fiber. The above-mentioned oxide stabilizing the zirconia is preferably CaO and the stabilizing compound is therefore preferably a Ca compound. In this case, it is preferably that a zirconium alkoxide alcohol solution and a Ca compound solution containing water and a catalyst are separately prepared and both the solutions are mixed at the time of the hydrolysis.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for producing zirconia fibers.

[Prior Art] Since zirconia fibers have excellent mechanical strength at high temperatures, they are expected to be used as reinforcing materials for metal composite materials, for example.

The following methods are known for producing zirconia fibers. The polyzirconoxane produced by hydrolysis is dissolved in an organic solvent such as benzene, calcium acetylacetonate and a thickener are added to this to adjust the viscosity, and then the precursor is produced by spinning. 1700~2
Zirconia fibers are produced by firing at 000''C.

However, this manufacturing method is complicated because it requires many steps such as separating the polymer produced by hydrolysis, dissolving the polymer in an organic solvent, and adding a thickener. There was a problem.

Further, the firing temperature of the precursor is extremely high at 1,700 to 2,000° C., resulting in expensive manufacturing equipment and high energy consumption.

[Problems to be solved by the invention] The present invention solves the above problems that the conventional technology had,
The purpose of the present invention is to provide a method for producing zirconia fibers that can significantly reduce the number of production steps and sinter the precursor at a low temperature.

[Means for Solving the Problems] The present invention provides a stabilizing compound that is produced by firing an oxide that stabilizes zirconia, and a solution of a zirconium alkoxide containing the stabilizing compound in a small bottle that is hydrolyzed to form yarn. The present invention provides a method for producing zirconia fibers, which comprises: generating a solution having spinnability, producing precursor fibers by spinning the solution having spinnability, and firing the precursor fibers to produce zirconia fibers. .

In the present invention, the starting material used is usually a solution of zirconium alkoxide to which a stabilizing compound is added.

The zirconium alkoxide ultimately produces zirconia through firing and forms the main component of the fiber.

As the alkoxide, methoxide, ethoxide, propoxide, butoxide, bentoxide, etc. are used. Among them, propoxide is particularly desirable. The reason for this is that methoxide and ethoxide have a fast hydrolysis reaction rate, so the spinning time becomes too short, making management of the manufacturing process complicated, and butoxide and bentoxide leave organic matter behind on the zirconia fiber after firing. -1. Neither is preferable because it makes it easier.

Such zirconium alkoxides are usually used as alcohol solutions. The alcohol is not particularly limited, but methanol and ethanol are preferred because of their ease of availability. In that case, the amount of alcohol is preferably in the range of 2.7 to 27 moles of the zirconium alkoxide.

If the amount of alcohol is less than the above range, it is undesirable because it tends to cause cloudiness in the hydrolysis process, and if it is more than the above range, the hydrolytic single polycondensation reaction will be extremely slow, and it will take a long time to exhibit spinnability. This is not preferred because it requires a long time or does not exhibit spinnability.

On the other hand, the stabilizing compound generates an oxide upon firing, and the oxide is added to suppress the transformation of the tetragonal zirconia in the zirconia fiber into meso-oblique zirconia at high temperatures, which reduces the strength. .

The stabilizing compound is not particularly limited as long as it produces such an oxide upon firing and can be mixed well with the zirconium alkoxide solution. Specific examples include acetate, hydroxide, and chloride.

The stabilizing compound has an oxide of 1-1 in the zirconia fiber.
It is preferable that it is added to the solution in a proportion of 3 mol%. If the amount of oxide is less than h month mole %, the decrease in fiber strength at high temperatures will not be sufficiently suppressed, and if the amount of oxide is more than 13 mol %, the spinnability of the solution will deteriorate, which is not preferable.

As such an oxide, CaO is preferable, but M) HO,
Y2O3, Ce0a, Tl0z can also be used.

It is preferable that the amount of water U used in the hydrolysis ranges from 0.7 to 1.4 times the amount of zirconium alkoxide by mole. If the amount of water (1) is less than the above range, the solution will become cloudy, and if it is more than the above range, the solution will gel without exhibiting spinnability, which is not preferable.

In hydrolysis, it is desirable to separately prepare an alcoholic solution of zirconium alkoxide and a solution of a calcium compound containing water and a catalyst, and then mix the two. The reason for this is that calcium compounds, especially calcium acetate, are soluble in water but poorly soluble in alcohol, and because there is a preferable amount of water for hydrolysis of zirconium alkoxide as mentioned above, it is necessary to mix both solutions. This is to keep the amount of water within the required range.

In this case, hydrochloric acid is used as a catalyst, and the amount thereof is preferably 0.1 to 0.4 times the amount of zirconium alkoxide. If the amount of hydrochloric acid is less than the above range,
White turbidity tends to occur in the solution, and if the amount exceeds the above range, the solution will gel without substantially exhibiting spinnability, which is not preferable. In addition to hydrochloric acid, sulfuric acid, acetic acid, etc. can also be used as a catalyst.

Both solutions thus prepared are stirred and mixed to carry out a hydrolysis reaction. Although this reaction proceeds at room temperature, it is accelerated by heating to about 80° C., and the thread exhibits spinnability in about 1 to 6 hours.

This spinnable solution is cooled to room temperature and extruded from a nozzle for spinning to produce a precursor fiber.

This precursor fiber is then dried and fired.

This firing condition can be achieved at 500-1200''c for about 1-5 hours.

[Example] An ethanol solution of zirconium propoxide was prepared by dissolving zirconium propoxide in 13.5 molar amount of ethanol.

On the other hand, water, hydrochloric acid and ethanol (molar ratio to zirconium propoxide) were added to calcium acetate monohydrate.
5 times) to prepare a calcium solution.

Next, a calcium solution was added to the ethanol solution of zirconium propoxide to obtain a mixed solution of zirconia and calcia in various ratios after firing. The amounts of water and hydrochloric acid in this mixed solution were 1.07 times and 0.26 times by mole, respectively, per 1 mole of zirconium propoxide.

Next, this mixed solution was stirred, maintained at 80'C and left in the atmosphere, and after 3 to 6 hours, it showed spinnability and was spun to obtain a precursor fiber.

The precursor fibers were then left in the air to dry, then placed in an electric furnace and fired at various temperatures to produce zirconia fibers.

Next, regarding the manufactured zirconia fiber, X fJa
The ratio of tetragonal zirconia and monoclinic zirconia was determined by diffraction. The results are shown in FIG. In the figure, X is the mol% of calcia in the fiber, and X=O is a comparative example.

Some pieces were finely broken during firing, but in all of them, the tetragonal pieces had transformed into monoclinic zirconia, and the content of tetragonal zirconia was small.

The fibers thus produced according to the invention can be fired at low temperatures. Furthermore, since the tetragonal zirconia exists stably at high temperatures, there is extremely little decrease in mechanical strength.

[Effects of the Invention] According to the present invention, the conventional polymer separation step, the step of dissolving the polymer in an organic solvent, the step of adding a thickener, etc. are unnecessary, and the fifth manufacturing step is extremely simplified.

Further, since the firing temperature of the precursor fiber is approximately 1200"C or lower, which is significantly lower than the conventional 1700-2000"C, the manufacturing equipment is greatly simplified and energy consumption is also reduced.

Particularly, those containing 01 to 13 mol% of Ca based on zirconia exhibit an excellent effect in that the strength does not easily deteriorate because the tetragonal zirconia exists stably even at high temperatures.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the amount of square zirconia measured for zirconia fibers produced according to the present invention.

Claims (4)

[Claims] (1) A stabilizing compound produced by firing an oxide that stabilizes zirconia, a solution of zirconium alkoxide containing a small amount of the stabilizing compound is hydrolyzed to produce a solution with spinnability, and the thread is 1. A method for producing zirconia fibers, which comprises spinning a solution having properties to produce precursor fibers, and firing the precursor fibers to produce zirconia fibers. (2) The production method according to claim 1, wherein the stabilizing compound is contained in the solution at a rate of 1 to 13 mol% of its oxide in the zirconia fiber. (3) The oxide that stabilizes the zirconia is CaO,
The manufacturing method according to claim 2, wherein the material is MgO, Y_2O_3, CeO_2 or TiO_2. (4) The production method according to claim 2 or 3, wherein the stabilizing compound is calcium acetate.