JP2007063045A - Method for producing alumina whisker and method for producing zinc oxide whisker - Google Patents

Abstract

The present invention provides a method for easily producing whiskers with low energy consumption and no risk of pollution.
An alumina whisker is manufactured by heat-treating an alloy containing Al, at least one of Zn and Cd, and at least one of Sn, Bi, In, Cu and Ni in an oxidizing atmosphere. To do. An alloy containing Zn, Cu, and any one of Bi, Sn and Cd is heat-treated in an oxidizing atmosphere to produce zinc oxide whiskers.
[Selection figure] None

Description

  The present invention relates to a method for producing an alumina whisker and a method for producing a zinc oxide whisker, and particularly relates to a method for producing whisker easily with low energy consumption and no risk of pollution.

In recent years, it is lightweight, high-strength, high-modulus, excellent in heat resistance and oxidation resistance, and can be processed into various forms because it is a thin, flexible and long fiber that maintains this property even in air at 1000 ° C. Resin, metal, ceramics The development of fibers made from various ceramics including silicon carbide, which is excellent as a reinforcing fiber for composite materials, is progressing.
As such fibers, methods for producing various whiskers and various ceramic nanotubes have been proposed. (For example, see Patent Documents 1 to 7).

  On the other hand, Patent Document 8 proposes a method for producing alumina whiskers. In this method, alumina and carbon are heated to a temperature of 1400 to 1650 ° C. to perform a gas phase reaction, and the resulting reaction gas is precipitated and recovered at a temperature of 1100 to 1300 ° C.

  Moreover, the manufacturing method of a zinc oxide whisker is proposed by patent document 9. FIG. This method is a method for producing a tetrapot-shaped zinc oxide whisker by oxidizing zinc vapor in an oxidizing atmosphere region by mixing a gas mixture obtained by diluting zinc vapor discharged from the crucible with a hydrocarbon-based fuel.

In the case of the method described in Patent Document 8, when manufacturing an alumina whisker, it is necessary to perform a considerably high temperature region, and there is a problem that energy consumption is large.
Moreover, in patent document 9, there exists a problem that an apparatus becomes large and energy consumption efficiency is bad.

JP 2004-244252 A JP 2004-231455 A JP 2004-175586 A Japanese Patent Laid-Open No. 2004-175587 JP 2004-002182 A Japanese Patent Laid-Open No. 2002-356776 JP 2004-180251 A Patent No. 942660 JP-A-5-97597

  An object of the present invention is to solve the above-described problems of the prior art, and to provide a method that can easily produce whiskers with low energy consumption and no risk of pollution.

The present invention can solve the above problems by adopting the following means.
<1> An aluminum whisker is manufactured by heat-treating an alloy containing Al, at least one of Zn and Cd, and at least one of Sn, Bi, In, Cu and Ni in an oxidizing atmosphere. This is a method for producing an alumina whisker.
<2> An alloy composed of Al, Zn and Cd at 20 to 70 mass%, Sn, Bi, In, Cu and Ni at 0.5 to 2 mass% and the balance Al. The method for producing alumina whiskers according to <1>, wherein the alumina whiskers are produced by heat treatment in an oxidizing atmosphere.
<3> An aluminum whisker is obtained by heat-treating an alloy containing Al, at least one of Zn and Cd, Sn, and any one of Bi, In, Cu and Ni in an oxidizing atmosphere. The method for producing an alumina whisker according to <1>, wherein the method is produced.
<4> At least one of Zn and Cd is 20 to 70% by mass, Sn is 0.5 to 2% by mass, and any one of Bi, In, Cu and Ni is 0.5 to 2% by mass, and the balance. The method for producing alumina whiskers according to <3>, wherein an alloy made of Al is heat-treated in an oxidizing atmosphere to produce alumina whiskers.
<5> A zinc oxide whisker characterized in that a zinc oxide whisker is manufactured by heat-treating an alloy containing Zn, Cu, and any one of Bi, Sn, and Cd in an oxidizing atmosphere. It is a manufacturing method.
<6> A zinc oxide whisker is manufactured by heat-treating an alloy composed of 20 to 40% by mass of Zn, 0.5 to 3% by mass of Bi and Sn, and the remainder Cu in an oxidizing atmosphere. <5> The method for producing a zinc oxide whisker according to <5>.

  According to the present invention, alumina whiskers and zinc whiskers can be easily manufactured with low energy consumption and no risk of pollution.

The method for producing the alumina whisker of the present invention includes:
(1) an alloy containing Al, at least one of Zn and Cd, and at least one of Sn, Bi, In, Cu and Ni;
(2) Preferably, an alloy containing Al, at least one of Zn and Cd, Sn, and any one of Bi, In, Cu and Ni;
Are heated in an oxidizing atmosphere to produce alumina whiskers.

The alloy (1) is an alloy obtained by melting and solidifying at least one of Zn and Cd having a vapor pressure higher than that of Al and at least one of Sn, Bi, In, Cu and Ni with respect to Al. Is preferably produced.

Among Zn and Cd, Zn is particularly preferable because it has a high vapor pressure and easily evaporates.
In the alloy (1), at least one of Sn, Bi, In, Cu and Ni is preferably contained in an amount of 0.5 to 2% by mass, more preferably 0.5 to 1 in the alloy. 0.5% by mass, more preferably 0.8-1.2% by mass.
Among at least one of Sn, Bi, In, Cu, and Ni, Sn has an effect of accelerating the dezincing phenomenon by breaking the oxide film formed on the surface of Al, and is effective in forming whiskers. Therefore, the most preferred alloys in the alloy (1) are Al—Zn—Sn alloys and Al—Zn—Sn—In alloys.

The alloy (2) is obtained by melting and solidifying at least one of Zn and Cd having a high vapor pressure with respect to Al, Sn, and any one of Bi, In, Cu and Ni. Make it.

Among Zn and Cd, Zn is particularly preferable because it has a high vapor pressure and easily evaporates.
In the alloy (2), Sn is preferably contained in the alloy in an amount of 0.5 to 2.0% by mass, more preferably 0.5 to 1.5% by mass, still more preferably 0.8. 8 to 1.2% by mass.

Any one of Bi, In, Cu and Ni is preferably contained in the alloy in an amount of 0.5 to 2% by mass, more preferably 0.5 to 1.5% by mass, still more preferably 0.8. Therefore, the most preferable alloys as the alloy (1) and the alloy (2) are Al—Zn—Sn alloy, Al—Zn—Sn—Cd alloy, Al—Zn—. Sn-Bi alloy, Al-Zn-Sn-Ni alloy, Al-Zn-Sn-Cu alloy, Al-Zn-Sn-In alloy.

The method for producing zinc oxide whiskers according to the present invention comprises heating an alloy (3) containing Zn, Cu, and any one of Bi, Sn, and Cd in an oxidizing atmosphere to produce zinc oxide whiskers. To manufacture.
The alloy (3) is preferably produced by melting and solidifying at least one of Zn and Cd, which have a higher vapor pressure than Cu, with respect to Cu.
In the alloy (3), an alloy composed of 20 to 40% by mass of Zn, 0.5 to 3% by mass of Bi and Sn, respectively, and the balance Cu is preferable, and Zn is contained in an amount of 15 to 35% by mass in the alloy. Preferably, it is 20-30 mass%, More preferably, it is 25-30 mass%.

Therefore, in the alloy (3), the most preferable alloy is a Cu—Zn—Bi—Sn alloy.

  Each of the above alloys is heat-treated in an oxidizing atmosphere. The reason why the above-described alloy is maintained in the oxidizing atmosphere is to form alumina and zinc oxide. However, when the thickness of the alumina and zinc oxide coating is thick and the hardness is high, the vapor pressure is reduced during the heat treatment. High Zn and Cd break the alumina and zinc oxide coatings and make it difficult to discharge them from the alloy. From this viewpoint, the oxidizing atmosphere is preferably a weak oxidizing atmosphere.

  In the present invention, a vacuum heating device can be used as a device for heat-treating the alloy in a weakly oxidizing atmosphere. In the case of using a vacuum heating device, it is possible to select a depressurization condition in the vacuum heating device and adjust the oxygen partial pressure to form a weakly oxidizing atmosphere.

  The pressure reduction conditions in the vacuum heating device vary depending on the alloy used, but in the case of an Al alloy, 0.01 to 0.2 Pa is preferable, 0.05 to 0.15 Pa is more preferable, and 0.1 to 0.15 Pa is still more preferable. . In the case of a Cu-based alloy, 20 Pa to 1 Pa, 10 Pa to 1 Pa, and 5 Pa to 1 Pa are more preferable.

  In the vacuum heating apparatus, the heat treatment conditions vary depending on the alloy. In the case of the alloy (1), 380 to 520 ° C is preferable, 350 to 450 ° C is more preferable, 400 to 450 ° C is further preferable, and (2) In the case of an alloy, 380 to 520 ° C is preferable, 350 to 450 ° C is more preferable, 400 to 450 ° C is more preferable, and in the case of the alloy (3), 700 to 850 ° C is preferable, and 750 to 850 ° C is more preferable. 780-820 degreeC is still more preferable.

  After the alloy is heat treated in an oxidizing atmosphere, the molten alloy is cooled. In cooling, it is preferable to cool sufficiently in the atmosphere during the heat treatment so that Al and Zn are not oxidized excessively.

  When the whiskers obtained by the present invention are each heat-treated in an oxidizing atmosphere, Zn and Cd having a high vapor pressure break the alumina and zinc oxide coating and are discharged from the alloy. It seems that there is a case where a whisker shape is applied due to a stress to lift the coating, and that the whisker shape may be formed by a passage of Zn and Cd vapor.

The alumina whisker obtained by the present invention has a small cross-sectional diameter, and the density, tensile strength, Young's modulus is comparable to BeO, B ₄ C, SiC, Si ₂ N _4, etc., and these whiskers are made into resin, metal, ceramics. By making it compatible, an excellent composite material can be produced. In particular, alumina whiskers are applied as FRP (Fiber Reinforced Metal) or FRM (Fiber Reinforced Metal) by being mixed in plastic or metal. For example, a WRP (Whisker Reinforced Plastic) fishing rod with higher electrical insulation and higher strength, which is replaced with carbon fiber reinforced plastic, is commercially available. In addition, a composite in which alumina whisker is mixed with zirconia has a higher elastic modulus and strength than zirconia alone, and has a feature that a certain level of strength can be maintained even at a high temperature at which zirconia undergoes plastic deformation.

  EXAMPLES Next, although an Example demonstrates this invention, this invention is not limited at all by these Examples. In the examples, “%” means “mass%”.

<Experimental sample for alumina whisker>
The composition of the experimental sample is as follows.
・ Al-70% Zn-0.5% Sn
・ Al-70% Zn-0.5% Sn-1.0% Cd
・ Al-70% Zn-0.5% Sn-1.0% Ni
・ Al-70% Zn-0.5% Sn-1.0% In
・ Al-70% Zn-0.5% Sn-1.0% Cu
・ Al-70% Zn-0.5% Sn-1.0% Bi

First, the total amount of the sample was set to 300 g, and the amounts of the constituent elements were measured, and then cast into ingots. Further, since Cu and Ni have a high melting temperature, Cu was used in a granular form, and Ni was used as a mother alloy that was previously alloyed with Al. The composition of this mother alloy is Al-20.25% Ni.
Then, these ingots were cut into 10 mm × 10 mm × 10 mm with a fine cutter, and the surface was polished to # 100 and # 1000 with abrasive paper, and the surface was polished to 9 μm diamond abrasive grains, respectively. It was made possible to observe whether the difference in whisker generation appears due to the difference in size.
<Experimental sample for zinc oxide whisker>
・ Cu-30% Zn-3% Bi-3% Sn
An experimental sample for zinc oxide whisker was prepared in the same manner as the experimental sample for alumina whisker.

<Experimental equipment>
A schematic diagram of the experimental apparatus is shown in FIG. The experimental sample 10 is a stainless steel wire, which is devised so that all six surfaces are dezinced and sealed in a quartz tube 12. Since the quartz tube 12 enters the electric furnace 14 and becomes high temperature, it is cooled with water in order not to damage the O-ring which is a contact portion with the main body. The quartz tube 12 is connected to a vacuum device (rotary pump) 18 and is kept at a vacuum of about 10 ⁻¹ Pa. Considering the error of the experiment time, the electric furnace was heated by the temperature control device 16 at a position sufficiently separated from the quartz tube, and when the processing temperature was reached, the heating part was moved to the place of the experimental sample 10. In cooling, the electric furnace 14 was separated and the cooling was performed slowly. At this time, in order to prevent Al from being oxidized, the rotary pump was not immediately stopped and the vacuum was maintained until it was sufficiently cooled.

<Experiment method>
The dezincing treatment temperature is set to 380 ° C., 400 ° C. and 420 ° C. for the experimental sample for alumina whisker, and the treatment times are all 4 hours, and the experimental sample for zinc oxide whisker is set to 800 ° C. and the treatment time is 4 hours. It was.
The experimental sample was weighed with an electronic balance in advance, the size of the sample was measured with a caliper, the surface area was calculated, and dezincing treatment was performed using the experimental apparatus shown in FIG. When placing the sample in the quartz tube, two stainless steel wires were handed over a concave table, and the sample was carefully placed thereon, so that all surfaces were dezinced.
After the treatment, the weight of the sample is measured, and then the amount of dezincing is calculated. Tables 1 and 2 show the samples prepared. And in order to observe the surface state, the secondary electron image was observed using EPMA.

<Experimental result>
Observation of secondary electron image by EPMA (A) Heat treatment temperature 380 ° C
(1) Al-70% Zn-0.5% Sn
Although a large change in shape is not seen, when observed with a secondary electron image as shown in FIG. 2, the surface is considerably uneven, and dumpling-like projections can be observed. In addition, when the magnification is increased, the projections appear to be fine spots and look like small whiskers.
(2) Al-70% Zn-0.5% Sn-1.0% Cd
As shown in FIG. 3, it is the same as (1), and a large shape change is not seen with the naked eye, but when observed with a secondary electron image, dumpling-like protrusions can be seen.
(3) Al-70% Zn-0.5% Sn-1.0% Bi
As shown in FIG. 4, it is the same as (2), and no significant change in shape is seen with the naked eye. When observed with a secondary electron image, dumpling-like protrusions can be seen.

Table 1 shows the dezincing amounts of the above (1) to (3). From Table 1, it is considered that zinc removed from the alloy contributes to the formation of the dumpling-like protrusions or whiskers.
<Experimental result>
Observation of secondary electron image by EPMA (B) Heat treatment temperature 400 ° C
(4) Al-70% Zn-0.5% Sn-1.0% Ni
It can be observed that whiskers are clearly formed on the entire surface with the naked eye.
As shown in FIG. 5, a large amount of distorted whiskers grows in the secondary electron image. Inside the whisker looks like a hollow.
(5) Al-70% Zn-0.5% Sn-1.0% Cu
With the naked eye, a large amount of whisker like white powder is formed on the entire surface. As seen in the secondary electron image as shown in FIG. 6, the fiber-shaped whiskers are mixed with the cactus-shaped whiskers. The whisker observed in this study is quite thin and short. The whisker appears to be clogged.
(6) Al-70% Zn-0.5% Sn-1.0% In
The whisker can be confirmed with the naked eye, but it has grown only partially. As shown in FIG. 7, when observed with a secondary electron image, it can be confirmed that a large amount of whisker-like hollow whiskers are formed. Moreover, in this sample, it can also be confirmed that whiskers are bundled to some extent. Furthermore, when it is enlarged, it can be seen that several new small whiskers are formed from the side of the whisker.

  Further, Table 2 shows the dezincification amounts of the above (4) to (6). From Table 2, it is considered that zinc removed from the alloy contributes to the formation of the dumpling-like protrusions or whiskers.

<Experimental result>
Observation of secondary electron image by EPMA (C) Heat treatment temperature 420 ° C
(7) Al-70% Zn-0.5% Sn-1.0% Bi
You can see that whiskers are clearly made even with the naked eye. As shown in FIG. 8, it can be confirmed that a large amount of thin hollow whiskers are formed in the secondary electron image.
(8) Al-70% Zn-0.5% Sn-1.0% Ni
Although the sample is largely distorted, whiskers cannot be confirmed with the naked eye. As seen in the secondary electron image as shown in FIG. 9, dumpling-like protrusions can be observed. Each one is fairly large and regular.
(9) Al-70% Zn-0.5% Sn-1.0% Cu
There is almost no change with the naked eye. As seen in the secondary electron image as shown in FIG. 10, dumpling-like protrusions can be confirmed.

From the above, it can be seen that whisker formation differs depending on the heat treatment temperature even if the alloy composition is the same.
Observation of secondary electron image by EPMA (D) Heat treatment temperature 800 ° C
(10) Cu-30% Zn-3% Bi-3% Sn
You can see that whiskers are clearly made even with the naked eye. As shown in FIG. 11, it can be confirmed that a large amount of thin hollow whiskers are formed in the secondary electron image.

It is a schematic block diagram of the apparatus for forming the whisker of this invention. It is a secondary electron image (magnification 500 times) by EPMA of Al-70% Zn-0.5% Sn (653K). It is a secondary electron image (magnification 3000 times) by EPMA of Al-70% Zn-0.5% Sn-1.0% Cd (653K). It is a secondary electron image (500-times multiplication factor) by EPMA of Al-70% Zn-0.5% Sn-1.0% Bi (653K). It is a secondary electron image (magnification 3000 times) by EPMA of Al-70% Zn-0.5% Sn-1.0% Ni (673K). It is a secondary electron image (magnification 3000 times) by EPMA of Al-70% Zn-0.5% Sn-1.0% Cu (673K). It is the secondary electron image (magnification 500 times) by EPMA of Al-70% Zn-0.5% Sn-1.0% In (673K). It is a secondary electron image (magnification 3000 times) by EPMA of Al-70% Zn-0.5% Sn-1.0% Bi (693K). It is a secondary electron image (magnification 500 times) by EPMA of Al-70% Zn-0.5% Sn-1.0% Ni (693K). It is a secondary electron image (500-times multiplication factor) by EPMA of Al-70% Zn-0.5% Sn-1.0% Cu (693K). It is a secondary electron image (magnification 3000 times) by EPMA of Cu-30% Zn-3% Bi-3% Sn (1073K).

Explanation of symbols

10 Experimental Sample 12 Quartz Tube 14 Electric Furnace 16 Temperature Controller 18 Vacuum Device (Rotary Pump)

Claims (6)

  An alloy whisker is manufactured by heat-treating an alloy containing Al, at least one of Zn and Cd, and at least one of Sn, Bi, In, Cu and Ni in an oxidizing atmosphere. A method for producing alumina whiskers.   An alloy comprising 20 to 70% by mass of Zn and Cd, 0.5 to 2% by mass of at least one of Sn, Bi, In, Cu and Ni, and the balance Al is heated in an oxidizing atmosphere. The method for producing an alumina whisker according to claim 1, wherein the whisker is produced by treatment.   An alumina whisker is manufactured by heat-treating an alloy containing Al, at least one of Zn, and Cd, Sn, and any one of Bi, In, Cu, and Ni in an oxidizing atmosphere. The method for producing an alumina whisker according to claim 1.   At least one of Zn and Cd is 20 to 70% by mass, Sn is 0.5 to 2% by mass, any one of Bi, In, Cu and Ni is 0.5 to 2% by mass, and the balance is Al. The method for producing an alumina whisker according to claim 3, wherein the alloy is heated in an oxidizing atmosphere to produce an alumina whisker.   A method for producing zinc oxide whiskers, characterized in that zinc oxide whiskers are produced by heat-treating an alloy containing Zn, Cu, and any one of Bi, Sn, and Cd in an oxidizing atmosphere.   A zinc oxide whisker is manufactured by heat-treating an alloy composed of 20 to 40% by mass of Zn, 0.5 to 3% by mass of Bi and Sn and the balance Cu, respectively, in an oxidizing atmosphere. Item 6. A method for producing a zinc oxide whisker according to Item 5.