JPS635327B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a boron structural material, and particularly aims to improve the film quality and mechanical properties of boron constituting the boron structural material, and to reduce the cost of the boron structural material. Boron has a hardness second only to diamond, and
Its wear resistance is also very high, making it a useful material for cutting tools, sliding machine parts, bearings, etc. It also has the excellent characteristic of having the highest specific elastic modulus (elastic modulus/density) among currently known materials. This property means that the propagation speed of sound waves is the highest among existing materials, making it particularly useful as an acoustic material. It is difficult to obtain boron-applied products in the form of dense lumps by methods such as casting or rolling.
For this reason, when manufacturing various boron-applied products, in most cases boron is deposited onto a substrate made of a material other than boron by vapor deposition, sputtering, chemical vapor deposition (CVD), etc. Used as a film-formed composite. Such conventional methods do not cause any major problems when applied to products that utilize the hardness of boron and its excellent wear resistance. However, this poses a very serious problem in acoustic materials such as speaker diaphragms, cartridge cantilevers, video disk cantilevers, etc. that utilize the magnitude of specific elastic modulus. In other words, the density and elastic modulus of the composite are greatly influenced by the properties of the substrate.
This is because the original properties of boron are greatly reduced. Conventionally, it has been possible to attach boron to Ta, Nb, Mo, W, etc. wires using the CVD method, and then dissolve and remove these core wires to obtain simple boron. When large-sized objects such as video disc cantilevers are made using these core wires and substrates, there are disadvantages in that the cost is high and it takes too much time to dissolve and remove the core wires and substrates. On the other hand, Fe, which is inexpensive and easy to dissolve and remove, is used for the core material and substrate, and boron is attached using the CVD method.
After that, attempts were made to obtain a boron structural material by dissolving and removing the core material and substrate, but the Fe
It has been difficult to produce mechanically strong boron with a good yield because Fe and boron have a eutectic point and the coefficient of thermal expansion of Fe is significantly different from that of boron. The present invention provides Ta, Mo, Nb, or W on Fe.
By using a substrate coated with Cr and then coated with Cr, the aim is to obtain a boron structural material with good mechanical properties at a high yield. The present invention will be specifically explained below. Coating Ta, Mo, Nb, or W on Fe,
Furthermore, a method of forming boron on a substrate coated with Cr by chemical vapor deposition (CVD) is as follows:
For example, a substrate placed in a reactor may be heated by infrared rays,
Heating is performed by high frequency heating, energization, etc., and boron is precipitated by a reductive decomposition reaction as shown in the following formula. 2BX ₃ +3H ₂ →2B+6HX (X is a halogen element such as C, Br, I, etc.)
In addition to BX ₃ , boron hydride or the like may be used as the raw material gas for the CVD method. Further, in this boron precipitation reaction, various crystal forms can be obtained depending on the heating temperature, gas pressure, amount of raw material gas flowing into the reactor, etc. Also on the Fe substrate
The method of coating Ta, Nb, or W is mainly performed by sputtering because these are high melting point substances. As for Cr, vacuum deposition or plating is also possible. 5-20 μm of Ta, Mo, Nb, or W on Fe
The reason why Cr is sputtered to a thickness of 0.05 to 1.5 μm is that the above chemical reaction
℃ or higher, so if you try to attach boron at 1200℃ using only Fe as the core material, Fe
This is because a chemical reaction occurs between Fe and boron, which turns into a liquid state and deforms the core material. This is because even if the CVD temperature is 1200°C or lower, the reaction between Fe and boron is intense and the yield of boron structural materials is poor. Here, the coating thickness of Ta, Mo, Nb, and W is 5~
The reason for limiting the thickness to 20 μm is as follows. That is, if these coatings are 5.0 μm or less, boron diffusion passes through these coating layers and reacts with Fe, reducing its effect. Moreover, if it is 20 μm or more, peeling from the Fe substrate tends to occur, which is not preferable. Furthermore, the reason why Cr is sputtered onto Ta, Mo, Nb, or W is that it is possible to remove the strain that occurs during the process of dissolving and removing the substrate. here
The reason why the Cr coating thickness was limited to 0.05 to 1.5 μm was because
If it is less than 0.05 μm, it will not be effective in removing strain.
This is because if the thickness is 1.5 μm or more, peeling from the substrate is likely to occur. Next, the method of coating Fe with Ta, Mo, Nb, or W and then dissolving and removing the Cr-coated substrate is mainly performed using FeCl ₃ , HCl, HF, Br.
- Perform with an acid such as methanol. In this way,
The base material is removed to create a structural material made of boron alone. Examples of the present invention will be described below. Example A Fe wire with a diameter of 2.0 mm and a length of 100 cm was prepared. After degreasing and cleaning, Ta was coated to a thickness of about 5 microns by sputtering. Next, 0.05 micron of Cr was coated on this by sputtering. Next, this coated Fe wire is heated to 1000℃ by energizing it.
1 part by volume of boron trichloride (BCl ₃ ) and 3 parts by volume of hydrogen (H ₂ ) were flowed at a rate of 2 per minute for 3 minutes. (At this time, boron adhered to a thickness of approximately 50 microns.) The sample thus prepared was cut into 4 cm lengths, and immersed in a solution of 50 gr of bromine dissolved in 200 ml of commercially available methanol. , and coated
Ta and Cr were dissolved. (At this time, boron was not dissolved.) Further, the time required for dissolution was 26 hours. Next, the bending strength of this pipe was measured. The measurement was made with a beam length of 3.5cm and a beam supported at both ends.
It was calculated from the load when the pipe broke by adding a load W. As a result, 18 out of 20 cut samples were good, with an average strength of 1.68 kg. Furthermore, the yield due to etching was 90%. These results are shown in Sample No. (1) in Table 1. Below, boron structural materials were created in the same manner under various conditions. The results are shown in Table 1. However, sample numbers 14 to 19 are comparative examples. In addition, the CVD time was controlled so that the inner and outer diameters of all samples were kept constant at 2.0 mm and 2.1 mm, respectively (wall thickness was constant at 50 μm).

[Table] As can be seen from the examples [sample numbers 1 to 13] and proportionality [sample numbers 14 to 19] in Table 1 above, on Fe,
Sputter Ta, Mo, Nb, or W, then
By using a substrate with Cr attached, Fe
Even if a substrate is used, a high-strength boron structural material can be produced with good yield and at low cost, and its industrial value is great.

Claims (1)

[Claims] 1 Iron (Fe) is coated with tantalum (Ta), molybdenum (Mo), niobium (Nb), or tungsten (W), and then chromium (Cr) is coated on top of this.
By chemical vapor deposition method (CVD method) on the substrate coated with
A method for producing a boron structural material, which comprises depositing boron and then dissolving and removing the substrate. 2 Ta, Mo, Nb, or W coating thickness is 5.0
The method for manufacturing a boron structural material according to claim 1, characterized in that the thickness is 20 μm. 3. The method for manufacturing a boron structural material according to claim 1, wherein the thickness of the Cr coating is 0.05 to 1.5 μm.