JPH1174069A - Heating roller device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the rate of operation of a heating roller device by improving an abrasion resistance of the surface of the heating roller. SOLUTION: This device is equipped with a center shaft, a rotary heating roller 5 supported by the center shaft, and a heating means installed inside the heating roller 5. In this case, a hard carbon film 10, made of a hydrogenated amorphous carbon, is formed on the surface 5b of the heating roller 5. Preferably, the hard carbon film 10 is formed through an intermediate later 11, by which adhesiveness to the surface 5b of the heating roller 5 is increased. The intermediate layer 11 can be formed with an alloy film of a metal and silicon or germanium.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heating roller device used for drawing a yarn or a film in a heated state.

[0002]

2. Description of the Related Art A heating roller device is used to stretch a yarn or a film in a heated state.
No. 44, for example. This heating roller device includes a central shaft, a heating roller supported by the central shaft and rotating, and a heating unit provided inside the heating roller. The heat roller is formed of chromium molybdenum steel in a cylindrical shape, and its outer surface is covered with a hard chromium film formed by hard chrome plating.

Since the surface of the heat roller of such a heating roller device is stretched while heating the yarn or film, abrasion occurs due to sliding contact with the yarn or film which is slid by applying tension. I do. Therefore, in the conventional heat roller, as described above, a hard chromium film having a Vickers hardness of about 1000 is formed on the outer surface.

[0004]

However, since the heat roller is rotated at a high speed, even if a hard chromium film is formed, abrasion of the surface of the heat roller cannot be avoided.

When the surface of the heat roller is worn due to the use of the heating roller device, the cross-sectional shape becomes a groove shape, and when a yarn in which a plurality of filaments are twisted is drawn, the filament breaks. I do. Further, when the corners of the grooves formed by the wear become sharp, the yarn breaks. Also, when the film is stretched, the surface of the film may be damaged,
The problem of disconnection occurs.

Therefore, when the heat roller wears,
The operation of the heating roller device is stopped, and the worn heat roller is replaced with a new heat roller. Therefore, it takes time and effort to replace the heat roller,
There has been a problem that the operation rate of the heating roller device is reduced, and the drawing operation of a yarn or a film is delayed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem in the conventional heating roller device, and has greatly improved the wear resistance of the outer surface of the heating roller, thereby improving the heating roller device. An object of the present invention is to greatly extend the time that can be used without replacing the heat roller, and to significantly increase the operation rate.

[0008]

According to the present invention, in order to achieve the above object, a hard carbon film made of hydrogenated amorphous carbon is formed on the outer surface of a heat roller in the above-described heat roller device. It is more preferable to form the hard carbon film via an intermediate layer that enhances the adhesion to the outer surface of the heat roller. The intermediate layer may be formed of an alloy film of a metal and silicon or germanium belonging to Group IVb of the periodic table.

In the heating roller device according to the present invention,
Since the hard carbon film made of hydrogenated amorphous carbon formed on the outer surface of the heat roller has a black color and has properties very similar to diamond, DLC (diamond like carb)
on) Also called a membrane. This hard carbon film has a high mechanical hardness of Vickers hardness 4000 and a coefficient of friction of about 0.1, which is 1/5 to 1/10 that of a hard chromium film formed on the outer surface of a conventional heat roller. It has a low friction coefficient. In addition, the surface roughness of this hard carbon film is 1 nm or less, and it is excellent in surface smoothness.

[0010] Therefore, the heat roller in the heating roller device of the present invention having the hard carbon film formed on the outer surface is extremely excellent in abrasion resistance, and is at least 10 times as large as the heat roller provided with the conventional hard chromium film. A longer life can be achieved. Further, by forming the hard carbon film on the outer surface of the heat roller via the above-described various intermediate layers, the adhesion of the hard carbon film to the heat roller is further increased, and the wear resistance is further improved. .

[0011]

Embodiments of the present invention will be described below with reference to the drawings. First, the configuration of a heating roller device embodying the present invention will be described with reference to FIG. As shown in FIG. 1, this heating roller device supports a cylindrical heat roller 5 on a peripheral portion of a hollow central shaft 1 via a pair of flanges 2 and 3.

Each of the pair of flanges 2 and 3 has a disk shape, and has a symmetrical shape in which cylindrical portions 2a and 3a having an inner diameter larger than the central axis 1 are integrally provided, and the respective cylindrical portions 2a and 3a.
Bearings 6 and 7 are provided between the heat roller 5 and the central shaft 1 so that the heat roller 5 can rotate around the central shaft 1.

The heat roller 5 and the flanges 2 and 3 are fixed by fixing means such as screws (not shown). And
By rotating one of the flanges 2 and 3 by a rotation mechanism using a motor (not shown) as a rotation drive source,
The heat roller 5 rotates around the central axis 1. A gear or pulley for this purpose is mounted on one of the flanges 2 and 3, but is not shown.

Further, a pair of flange portions 1
a and 1b are formed, and a coil 9 is mounted therebetween through an iron core 8 made of a magnetic material. The terminal of the coil 9 is not shown in FIG.
Through the hollow portion 1c, and a low-frequency AC voltage is applied. When an alternating voltage is applied to the coil 9, an alternating magnetic flux is generated, and the alternating magnetic flux generates
A short-circuit current in the circumferential direction is induced in the inner peripheral wall of the heat roller 5 to cause the heat roller 5 to generate heat by induction heat generated by Joule heat.

The cylindrical heat roller 5 is provided with a hollow jacket chamber 5a, and a gas-liquid two-phase heat medium (for example, naphthalene) is sealed in the jacket chamber 5a. The heat medium sealed in the jacket chamber 5a evaporates and evaporates due to the heat generated by the heat roller 5, and when the evaporated substance touches the inner wall of the jacket chamber 5a on the surface of the heat roller 5 where the temperature is low, the heat medium is agglomerated. And generate latent heat. Due to the generation of the latent heat, the inner wall of the jacket chamber 5a on the surface portion having a low temperature is heated.

When the condensed heat medium touches the inner wall of the jacket chamber 5a at the surface of the heat roller 5 where the temperature is high, the heat evaporates by the heat. The surface temperature of the heat roller 5 is made uniform by repeating the absorption of heat by evaporation and evaporation of the heat medium and the generation of latent heat by aggregation. Therefore, in this heating roller device, the heating means having a temperature control function is constituted by the iron core 8, the coil 9, and the heat medium in the jacket chamber 5a.

Next, examples of the structure of the coating formed on the outer surface of the heat roller 5 in this heating roller device will be described with reference to FIGS.
It will be explained by. FIG. 2 is an enlarged cross-sectional view showing a part near the outer surface 5b of the first embodiment of the heat roller 5 in the heat roller device shown in FIG.

The heat roller 5 is made of chromium molybdenum steel, and has a hard carbon film 10 made of hydrogenated amorphous carbon on its outer surface 5b. The thickness of the hard carbon film 10 may be changed depending on the application, but is generally uniform in a range of 1 μm to 5 μm.

The hard carbon film 10 has an amorphous structure containing hydrogen, has a black color, and has properties very similar to diamond. That is, this hard carbon film 10
Has a high mechanical hardness of 4000 in Vickers hardness and an extremely low friction coefficient of 0.1. In addition, the surface roughness is 1 nm or less, and is extremely excellent in surface smoothness. Therefore, the heat roller 5 having the hard carbon film 10 formed on the outer surface is excellent in abrasion resistance and achieves ten times or more longer life than the conventional heat roll provided with the hard chrome film on the outer surface. can do.

Next, a second embodiment of the heating roller in the heating roller device according to the present invention will be described with reference to FIG. 3, which is a sectional view similar to FIG. In the heat roller 5 of the second embodiment, a hard carbon film 10 is formed on an outer surface 5b of the heat roller 5 via an intermediate layer 11 for improving the adhesion to the outer surface 5b. The intermediate layer 11 provided below the hard carbon film 10 is an alloy film of a metal and an element of Group IVb of the periodic table, or a two-layer film (laminated film) of a metal and an element of Group IVb of the periodic table. Formed.

As a specific material for the intermediate layer 11, titanium, chromium, aluminum, tantalum, molybdenum, tungsten, or the like can be used as a metal.
Silicon or germanium can be used as an element of Group IVb of the periodic table.

The thickness of the intermediate layer 11 is about 0.5 μm when it is made of an alloy film, and about 0.5 μm for each layer when it is made of a laminated film, and about 1.0 μm in total. Thus, the heat roll 5 of the second embodiment is
Since the hard carbon film 10 is formed on the surface with the intermediate layer 11 interposed therebetween, the intermediate layer 11 enhances the adhesion between the hard carbon film 10 and the base material (chromium molybdenum steel) of the heat roller 5.

The intermediate layer 11 is made of a metal and periodic table IVb.
When formed of a two-layer film with an element of group IV, the metal film therebelow serves to increase the adhesion to the outer surface of the heat roller 5, and the element of group IVb of the periodic table is a hard carbon film. 10
It has the role of increasing cohesion by covalently bonding with. Therefore, according to the embodiment in which the intermediate layer 11 is provided, the adhesion of the hard carbon film 10 to the heat roller 5 increases,
The wear resistance of the heat roller 5 is further increased, and the operation rate of the heat roller device can be further increased.

Next, a third embodiment of the heat roller in the heat roller device according to the present invention will be described with reference to FIG. 4 which is a sectional view similar to FIG. The heat roller 5 according to the third embodiment includes a hard carbon film 10 on an outer surface of the heat roller 5 via an intermediate layer 11 including a lower first intermediate layer 11a and an upper second intermediate layer 11b. Is formed.

The first intermediate layer 11a is made of titanium (T
i) or a chromium (Cr) film, and the second intermediate layer 11b is formed of silicon carbide (SiC) or tungsten carbide (WC).

The titanium or chromium coating of the first intermediate layer 11a has a function of improving the adhesion to the chromium molybdenum steel as the base material of the heat roller 5. Also, the second intermediate layer 11
b) Silicon carbide and tungsten carbide
Excellent alkali resistance. For this reason, when the oil agent, thread waste, fiber adhering agent, or the like that has become sludge or carbonized on the surface of the hard carbon film 10 formed on the heat roller 5 is removed by etching using an alkali solution, the hard carbon film 10 Even if the alkaline solution enters, the second
Is not etched. Therefore, the peeling phenomenon of the hard carbon film 10 does not occur.

As the above alkaline solution, a sodium hydroxide (NaOH) solution is used. That is, the sodium hydroxide solution is added to a strong alkali pH (p
H) is adjusted to be 11 to 13 and used as an agent for removing deposits on the surface of the heat roller 5. The treatment for removing the oil agent fixed on the surface of the heat roller 5 using the sodium hydroxide solution or the sludge or carbonized deposit of the lint or the fiber auxiliary includes the above-mentioned sodium hydroxide solution in a cotton waste. Instead, the attached matter fixed to the surface of the heat roller 5 is removed while being rubbed. Alternatively, the heat roller 5 is immersed in the above-mentioned sodium hydroxide solution to remove the surface deposits by etching.

At this time, even if an alkali solution enters through a pinhole which is rarely generated in the hard carbon film 10, the second intermediate layer 11b provided under the hard carbon film 10 does not It is not etched because it is resistant. Therefore, the hard carbon film 10 does not deteriorate such as peeling. The first intermediate layer 11a made of a titanium or chromium coating has a thickness of 0.5
μm, and the second intermediate layer 11 b made of silicon carbide or tungsten carbide is also 0.5 μm thick.
The thickness is about μm.

Next, a fourth embodiment of the heat roller in the heating roller device according to the present invention will be described with reference to FIG. 5, which is a sectional view similar to FIG. The heat roller 5 of the fourth embodiment has a hard layer 12 formed on the outer surface thereof, and includes a lower first intermediate layer 11a and an upper second intermediate layer 11b on the hard layer 12. The hard carbon film 10 is formed via the intermediate layer 11.

The hard layer 12 is composed of a hard chromium film, a carburized layer, or a quenched layer. The thickness of the hard chromium film used as the hard layer 12 is about 10 μm to 30 μm, and the thickness of the carburized layer is about 0.1 mm to 1.0 mm. The quenching layer may be provided only on the outer surface of the heating roll 5, but the entire heating roll 5 is formed as a quenching layer,
Its hardness may be increased.

When the hard layer 12 is formed of a hard chromium film, hard chrome plating by electrolytic plating is performed on the surface of the heat roller 5 to form a hard chromium film having the above-described thickness. When a carburized layer is formed near the outer surface of the heat roller 5 to form the hard layer 12, a carburizing gas containing carbon such as methane (CH ₄ ) or ethylene (C ₂ H ₄ ) and nitrogen (N ₂ )
Carburizing treatment is performed under the following conditions in a mixed gas atmosphere with a carrier gas.

(Carburizing conditions) Temperature 1100 ° C. Time 30 minutes Carburizing depth 0.5 mm In this example, chromium molybdenum steel, which is the base material of the heat roller 5 forming the carburized layer as the hard layer 12, is made of Japanese Industrial Standard (JIS). ) Type symbols, SCM 420 is used.

When a quenched layer is formed as the hard layer 12, SCM 435 or SCM 440 is used as a chromium molybdenum steel as a base material of the heat roller 5 with a symbol of the type of Japanese Industrial Standard. The quenching conditions differ depending on whether a quenched layer is formed only on the outer surface of the heat roller 5 or a quenched layer is formed on the entire surface. After the quenching process, a tempering process is also performed.

As an example, if the temperature is 830 to 88,
After heating to 0 ° C., quenching processing is performed by oil cooling, and then, after heating to a temperature of 530 to 630 ° C., rapid cooling is performed to perform tempering processing. At this time, if necessary, the outer surface of the heat roller 5 is polished.

The first intermediate layer 11a is formed of a titanium or chromium film having a thickness of about 0.5 μm as in the case of the third embodiment, and the second intermediate layer 11b is also formed of a film having a thickness of about 0.5 μm. Is formed of silicon carbide (SiC) or tungsten carbide (WC) of about 0.5 μm.

In the fourth embodiment, the first intermediate layer 11
The third embodiment differs from the third embodiment only in that a hard layer 12 is provided below a. That is, the coating of the outer surface of the heat roller 5 in the fourth embodiment has a structure of a hard layer-intermediate layer-hard carbon film. As a result of the abrasion test, with this configuration, the durability of the hard carbon film 10 is about twice as high as that without the hard layer 12, and the life of the heat roller is also about twice as long. It turns out. But the reason is not clear.

In the heating roller device shown in FIG. 1, as heating means having a temperature control function, Joule heat generated by the iron core 8 and the coil 9 and evaporation of the heating medium sealed in the jacket chamber 5a of the heating roller 5 are provided. Although the embodiment using the heating and the condensation has been described, a means using a heater wire, a means for introducing a temperature-controlled liquid into the heat roller 5 and the like can also be used as a heating means having a temperature control function. .

Further, although the description has been given of the example in which the shape of the heat roller is cylindrical, the outer shape and inner shape can be changed so as to match the intended use. Further, in the heating roller device shown in FIG. 1, the heat roller 5 is rotatably supported with respect to the central shaft 1;
And the heat roller 5 may be integrally rotated by rotating the central shaft 1 by a motor.

The hard carbon film formed on the surface of the heat roller has a thickness of about 1 μm to 5 μm in the description of each of the above embodiments. However, in the case of a heat roller requiring high wear resistance, the hard carbon film is thickened. In the case of a heat roller that does not require very high wear resistance, a thin hard carbon film may be formed. That is, the thickness of the hard carbon film formed on the surface of the heat roller may be adjusted depending on the application.

Here, a method of forming a hard carbon film and an intermediate layer on the outer surface of the heat roller of the heating roller device according to the present invention will be described with reference to FIGS. First, various methods for forming a hard carbon film will be described with reference to FIGS.

First, the method for forming a hard carbon film using the film forming apparatus shown in FIG.
The heat roller 5 made of chromium molybdenum steel is disposed in the vacuum chamber 20 having the heat roller 5. The heat roller 5 is connected to the vacuum chamber 2
The members that are supported in the area 0 are not shown. An anode 30 and a filament 32 are also provided in the vacuum layer 20.

[0042] Then, evacuated by an evacuation means such as a vacuum pump (not shown) of the vacuum layer 20 from the exhaust port 22, so that the degree of vacuum below 3 × 10- ⁵ torr. Thereafter, benzene (C ₆ H ₆ ) as a gas containing carbon is introduced into the vacuum chamber 20 from the gas inlet 21 to control the pressure in the vacuum chamber 20 to 1 to 5 × 10 ⁻³ torr. .

Thereafter, the anode 30 is connected to the anode power source 3
1, a DC voltage is applied, and an AC voltage is applied to the filament 32 from a filament power supply 33. At this time, the DC voltage applied from the anode power supply 31 to the anode 32 is a positive DC voltage of plus 10V. The voltage applied from the filament power supply 33 to the filament 32 is
10 A so that a current of 30 A flows through the filament 32.
V AC voltage.

Further, a DC negative voltage of −3 kV is applied to the heat roller 5 from a DC power supply 34. Then, plasma is generated in a region around the heat roller 5 disposed in the vacuum chamber 20, and a hard carbon film is formed on the surface of the heat roller 5. The formed film thickness of this hard carbon film is 1 μm to 5 μm.
And At this time, when the heat roller 5 is rotated, a hard carbon film having a more uniform film thickness can be formed.

Next, a method of forming a hard carbon film different from the above example will be described with reference to FIG. In the example shown in FIG. 7, a vacuum chamber 20 having a gas introduction port 21 and an exhaust port 22 is provided.
Inside, a heat roller 5 made of chromium molybdenum steel is arranged. The evacuated by the exhaust means of the vacuum pump or the like (not shown) of the vacuum chamber 20 from the exhaust port 22, so that the degree of vacuum below 3 × 10- ⁵ torr.

Thereafter, methane (CH ₄ ) is introduced into the vacuum chamber 20 as a gas containing carbon from the gas inlet 21,
Adjust so that the degree of vacuum is 0.1 torr. The heat roller 5 is connected to a high-frequency power source 37 having an oscillation frequency of 13.56 MHz through a matching circuit
A high frequency power of W is applied. As a result, plasma is generated around the heat roller 5 and 1 μm
A hard carbon film having a thickness of m to 5 μm is formed. At this time, by rotating the heat roller 5, a hard carbon film having a more uniform film thickness can be formed.

A method of forming a hard carbon film, which is different from the above examples, will be described with reference to FIG. The example shown in FIG. 8 is different from the example shown in FIG. 7 only in that a negative DC voltage of −600 V is applied from the DC power supply 39 instead of applying the high frequency power to the heat roller 5. . Also in this case, the plasma is generated in the peripheral region of the heat roller 5 so that the surface of the heat roller 5 has a thickness of 1 μm to 5 μm.
A hard carbon film having a thickness of

In each of the above-described examples of the method of forming the hard carbon film on the surface of the heat roller, methane or benzene is used as the carbon-containing gas for forming the hard carbon film. Any gas containing carbon can be used. For example, ethylene (C ₂ H ₄ )
Is also applicable. Further, these carbon-containing gases include argon (Ar), helium (He) or hydrogen (H
_Even when a mixed gas containing ₂ ) is used, a hard carbon film can be formed on the surface of the heat roller as in each of the above-described examples.

Next, a method of forming an intermediate layer formed below the hard carbon film will be described with reference to FIG.
As shown in FIG. 9, a target 40 made of an intermediate layer material held by a sputter cover 42 and a heat roller 5 forming an intermediate layer are arranged in the vacuum chamber 20 so as to face each other.

Thereafter, the inside of the vacuum chamber 20 is evacuated from the exhaust port 22. Then, an argon (Ar) gas is introduced from the gas inlet 21 as a sputtering gas. Thereafter, a negative DC voltage is applied to the target 40 from the target power supply 41, and a DC negative voltage of −50 V is applied to the heat roller 5 from the DC power supply 39.

Then, plasma is generated inside the vacuum chamber 20, and ions in the plasma sputter the surface of the target 40 made of an intermediate layer material. As a result, the intermediate layer material that has been knocked out from the surface of the target 40 adheres to the surface of the heat roller 5 to form an intermediate layer.

Even when two intermediate layers, ie, a first intermediate layer and a second intermediate layer, are formed on the outer surface of the heat roller 5, the methods of forming the respective intermediate layers are almost the same and differ. What is necessary is just to change the material of the target 40 for forming each intermediate layer.

For example, when forming the first intermediate layer, the target 40 is made of titanium or chromium, and when forming the second intermediate layer, the target 40 is made of silicon carbide or tungsten carbide. Note that when silicon carbide or tungsten carbide is used as the second intermediate layer, the atomic percentage of silicon and carbon or tungsten and carbon is 50% (1:
1).

Thereafter, a hard carbon film is formed on the upper surface of the one or two intermediate layers. The method of forming a hard carbon film on the upper surface of the intermediate layer may be the method described above with reference to FIGS. The method for forming the film of the intermediate layer is not limited to such a sputtering method, and other physical vapor deposition (PVD) methods such as a vacuum evaporation method and an ion plating method can also be used.

In each of the above embodiments, the base of the heat roller 5 is made of chromium molybdenum steel. However, depending on the application, stainless steel, KS steel, non-metal such as other metals, and ceramics may be used. It is also possible to use metal as the base material of the heat roller. When the heat roller is formed of an insulator such as ceramic, a metal material such as titanium or chromium of the intermediate layer is formed by a PVD method that does not require voltage application, and then a voltage is applied to the intermediate layer. A hard carbon film can be formed by the plasma CVD method as described above.

[0056]

As described above, the heating roller device according to the present invention has a very excellent wear resistance because the hard carbon film is formed on the outer surface of the heating roller. As compared with the roller, it is possible to achieve a ten-fold or longer life. Therefore, the time that can be used without replacing the heat roller of the heating roller device can be greatly extended, and the operation rate can be significantly increased.

By forming the hard carbon film on the outer surface of the heat roller via the various intermediate layers described in the embodiment, the adhesion of the hard carbon film to the heat roller is further increased, and the wear resistance is further improved. Is improved.

[Brief description of the drawings]

FIG. 1 is a sectional view along the axial direction showing a configuration of a heating roller device embodying the present invention.

FIG. 2 is a cross-sectional view of the first embodiment in which a part near an outer surface of a heat roller of the heat roller device shown in FIG. 1 is enlarged.

FIG. 3 is a cross-sectional view of the second embodiment.

FIG. 4 is a cross-sectional view of the third embodiment.

FIG. 5 is a sectional view of the fourth embodiment.

FIG. 6 is a schematic cross-sectional view of an apparatus for explaining an example of a method for forming a hard carbon film on an outer surface of a heat roller of a heating roller apparatus according to the present invention.

FIG. 7 is a schematic cross-sectional view of an apparatus for explaining another example of a method for forming a hard carbon film on the outer surface of a heat roller.

FIG. 8 is a schematic sectional view of an apparatus for explaining still another example of a method for forming a hard carbon film on the outer surface of a heat roller.

FIG. 9 is a schematic cross-sectional view of an apparatus for explaining an example of a method for forming an intermediate layer on the outer surface of a heat roller of the heating roller apparatus according to the present invention.

[Explanation of symbols]

 1: Central axis 2, 3: Flange 5: Heat roller 5a: Jacket chamber 5b: Outer surface of heat roller 6, 7: Bearing 8: Iron core 9: Coil 10: Hard carbon film 11: Intermediate layer 11a: First intermediate Layer 11b: Second intermediate layer 12: Hard layer 20: Vacuum layer 21: Gas introduction hole 22: Exhaust hole 30: Anode 31: Anode power supply 32: Filament 33: Filament power supply 34, 39: DC power supply 35: Matching circuit 37 : High frequency power supply 40: Target 41: Target power supply 42: Sputter cover

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F16C 13/00 F16C 13/00 C H05B 3/00 335 H05B 3/00 335 // C23C 16/26 C23C 16/26 (72) Inventor Takashi Toida 840 Takeno, Shimotomi, Tokorozawa-shi, Saitama, Japan Citizen Watch Co., Ltd.

Claims (3)

[Claims] 1. A heating roller device comprising: a central shaft; a heat roller supported and rotated by the central shaft; and a heating means provided inside the heat roller. A heating roller device comprising a hard carbon film made of hydrogenated amorphous carbon. 2. The heating roller device according to claim 1, wherein the hard carbon film is formed on an outer surface of the heat roller via an intermediate layer that enhances adhesion to the outer surface. Heating roller device. 3. The heating roller device according to claim 2, wherein the intermediate layer of the heat roller is made of an alloy film of metal and silicon or germanium.