JP2009129636A - Functionally gradient material, method for the same, and bulb - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a functionally gradient material strengthening connection between respective layers by uniformly and sufficiently melting/sintering silicon oxide in each layer from an insulating layer to a conductive layer. <P>SOLUTION: The insulating layer 11 containing silicon oxide of an insulating substance as a main constituent, a conductive layer 12 with silicon oxide of an insulating substance and molybdenum or tungsten of a conductive substance mixed therein, and an intermediate layer 13 gradually changing a coefficient of thermal expansion by mixing silicon oxide of an insulating substance and molybdenum or tungsten of a conductive substance therein are integrally connected by using a discharge plasma sintering device. The density of the insulating layer 11 is set ≥95% of theoretical density. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a functionally gradient material, a method for producing the functionally gradient material, and a tube using the functionally gradient material as a sealing means.

Mo tubes are used as sealing metal foils for tubes with airtight containers made of quartz glass, such as conventional halogen bulbs and high-pressure discharge lamps. Attempts have been made to use functionally graded materials formed by using a spark plasma sintering (SPS) method instead of the sealing metal foil for reasons such as lamp short life due to Mo foil oxidation. Functional gradient material is capable of melting and sintering the SiO ₂ contained in common to the conductive layer from the insulating layer (sealing layer), are know to be strongly binding strength between the layers. (For example, patent document 1).
JP 2007-112642 A

The technique of Patent Document 1 described above cannot uniformly melt SiO ₂ contained in each layer from the insulating layer to the conductive layer of the functionally graded material, and cannot obtain a bonding strength between layers for practical use. For this reason, when used as a lamp sealing part, both are heated by a burner or a laser so that the quartz bulb as the lamp housing and the insulating layer of the functionally gradient material are kept airtight. It is necessary to perform sealing by melting SiO ₂ .

  However, even if the functional sealing material can be manufactured as a single product due to a cause caused by the manufacturing method of the functional sealing material, when sealing with a quartz glass bulb that is a lamp housing, In many cases, the insulating layer and the valve cannot be hermetically sealed.

An object of the present invention is to provide a functionally graded material capable of strengthening the bonding between layers by uniformly melting and sintering SiO ₂ in each layer from the insulating layer to the conductive layer, and this functionality. The object is to provide a tube using a gradient material and a method for producing the functional gradient material.

  In order to solve the above-described problems, the functionally graded material of the present invention is a mixture of an insulating layer mainly composed of silicon oxide as an insulating substance and silicon oxide as an insulating substance and molybdenum or tungsten as a conductive substance. A conductive layer, and an intermediate layer in which the insulating material silicon oxide and the conductive material molybdenum or tungsten are mixed and the coefficient of thermal expansion is changed in stages, and the density of the insulating layer is 95 of the theoretical density. % Or more.

  Also, an insulating layer mainly composed of silicon oxide as an insulating material, a conductive layer in which silicon oxide as an insulating material and molybdenum or tungsten as a conductive material are mixed, silicon oxide as an insulating material and molybdenum as a conductive material Or an intermediate layer in which tungsten is mixed and the coefficient of thermal expansion is changed stepwise between the insulating material and the conductive material, and the density of the intermediate layer in contact with the insulating layer is 95 of the theoretical density. % Or more.

According to the present invention, the density of the bonded insulating layer is 95% or more of the theoretical density, or the density of the intermediate layer in contact with the insulating layer is 95% or more of the theoretical density. It is possible to improve the bonding between the layers by uniformly melting and baking the SiO ₂ of each layer.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a configuration diagram for explaining an embodiment relating to the functionally gradient material of the present invention.

FIG. 1 shows the overall structure of a functionally graded material (FGM). In the functionally graded material, Mo ₂ having an average particle size of 3 μm is mixed with SiO ₂ having an average particle size of 5 μm, and a discharge plasma sintering method (SPS method) is used. ) Created. In FIG. 1, 11 is an insulating insulating layer formed of 100% SiO ₂ (silicon oxide) which is an insulating material. A conductive conductive layer 12 is a mixture of SiO ₂ and a conductive substance of Mo (molybdenum) or W (tungsten).

Further, 13 is an intermediate layer in which SiO ₂ and Mo or W are mixed and the coefficient of thermal expansion is changed stepwise. This intermediate layer 13 is composed of four layers 131 to 134, for example. The intermediate layers 131 to 134 change the volume mixing ratio of SiO ₂ / Mo stepwise, and consequently change the coefficient of thermal expansion stepwise. The intermediate layer 13 is less conductive than the conductive layer 12 and is non-conductive as a whole. The number of layers of the intermediate layer 13 can be changed according to the purpose.

A sample having the configuration described in FIG. 1 was prepared, a part of each layer of the sample was cut out, and the density of the layer was determined from the ratio of the volume and weight. Also, each layer having a specific gravity of sigma (layer) is to be defined by the formula (1), than the density of the resulting layer by using Equation (1), can also be determined the volume mixing ratio of SiO ₂ and Mo.

σ (layer) = 100 / {a / σ (Mo) + b / σ (SiO ₂ )} (1)
(However, a + b = 100)
In formula (1), σ (Mo) is used the density of Mo, sigma a (SiO ₂₎ is a density of SiO _2, respectively 2.22 g / cm ³ and 10.22 g / cm ^3. Further, a represents the volume of Mo, and b represents the volume of SiO ₂ . In addition, it is preferable to select a portion where Mo is uniformly distributed with respect to SiO ₂ for cutting out the layer.

  With reference to FIG. 2, the outline in the case where the FGM of FIG. 1 is used as a sealing material for a quartz glass bulb as a lamp housing will be described.

  The length of the insulating layer 11 was about 10 mm. A bulb 21 having a thickness of 1 mm is used, and a range of 7 mm in width is heated from the top by a burner 22, and the sealing width at this time is about 7 mm. In the sealing test, it was confirmed by an infrared thermometer that the bulb 21 and the insulating layer 11 are sufficiently melted, so that the surface temperature of the insulating layer 11 is not less than 1670 ° C., the softening point. The sealing operation was performed at 1800 ° C. or higher.

  Here, with reference to FIG. 3, FIG. 4, one Embodiment of the manufacturing method of the functional gradient material of this invention at the time of using a discharge plasma sintering apparatus is described. 3 is a schematic configuration diagram, and FIG. 4 is a configuration diagram of the main part of FIG.

  In the water-cooled vacuum chamber 31, a cylindrical sintered die 32 made of graphite is disposed, and the functionally gradient material FGM is filled therein. On the upper and lower sides of the sintering die 32, an upper punch 34 and a lower punch 35 for pressing the functionally gradient material FGM, which is a workpiece filled inside, from above and below are provided. The upper punch table 33 and the lower punch table 36 are arranged so as to contact the upper punch 34 and the lower punch 35, respectively. Upper and lower end portions of the upper punch electrode 37 and the lower punch electrode 38 are led out of the water-cooled vacuum chamber 31. A large current is supplied from the sintering pulse power supply 39 between the upper punch electrode 37 and the lower punch electrode 38. This pulse current is supplied to the functionally gradient material FGM through the upper punch 34 and the lower punch 35, and is energized.

  Further, an upward pressure P is applied to the lower punch electrode 38 by the pressing mechanism 41 for sintering. The lower punch electrode 38 is provided so as to be movable upward, and moves upward by the pressure P. The cylinder portions of the upper punch electrode 37 and the lower punch electrode 38 are inserted from the upper and lower ends of the hollow portion of the sintering die 32, respectively, and the pressure P is transmitted to the upper punch electrode 37 and the lower punch electrode 38. The filled functional gradient material FGM is compressed from above and below. The control device 40 controls the pulse power source 39 for sintering and the pressurizing mechanism 41 for sintering, and controls the supply pulse current and the pressurizing pressure for the functionally gradient material FGM.

  FIG. 4 is an enlarged cross-sectional view showing a main part of the manufacturing apparatus of the shaft-integrated functional gradient material FGM in which the electrode shaft 42 is integrally sintered.

  An upper punch 34 and a lower punch 35 are inserted above and below the hollow portion of the sintering die 32. The upper punch 34 moves in the vertical direction in the hollow portion of the sintering die 32, while the lower punch 35 is fixed in the vertical direction in the hollow portion. The upper punch 34 is formed with a pore 341 opened at the lower end thereof, and an end portion 42b of the electrode shaft 42 inserted into the FGM is inserted therein. When the FGM SPS sintering is started, the pore 341 is inserted into the upper portion so that the end portion 42 b comes into contact with the upper portion of the pore 341. The lower punch 35 is in contact with the conductive layer 12 of the FGM.

The functional gradient material FGM described above is filled in a powder state in the hollow portion of the sintering die 32 before the start of SPS sintering. That is, first, the sintered die 32 is turned upside down, the upper punch 34 is inserted therein, and the upper punch 34 is placed on the lower side, so that the end of the electrode shaft 42 is introduced into the pore 341 and the electrode shaft 42 is moved. Stand upright in the center. Next, 100% SiO ₂ powder constituting the insulating layer 11 is filled. Next, a powder obtained by mixing SiO ₂ and Mo constituting the intermediate layer 13 in a volume ratio of 90% to 10%, for example, is filled in the hollow portion of the sintering die 32 and laminated on the insulating layer 11. Further, a powder in which SiO ₂ and Mo constituting the conductive layer 12 are mixed at a volume ratio of 75% to 25%, for example, is laminated. Thereafter, the upper end of the hollow portion of the sintering die 32 is closed by the lower punch 35. At this time, the length of the electrode shaft 42 is set such that the end 42a of the electrode reaches the conductive layer after firing and does not penetrate the FGM.

  Further, the firing die 32 closed by the upper punch 34 and the lower punch 35 is attached so that the upper punch 34 is on the upper side. Between the firing die 32, the upper punch 34 and the lower punch 35 and the FGM, a stress buffer graphite sheet is inserted in order to relieve the stress generated by the difference in the thermal expansion coefficient between the firing die and punch material and the FGM. It is common.

  In this state, under the control of the control device 40 of the SPS apparatus, the pulse power source 39 for sintering and the pressurizing mechanism 41 for sintering start operation, and SPS sintering of the functionally gradient material FGM is started. That is, the functional gradient material FGM in the hollow portion of the sintering die 32 is supplied with a large pulse current from the sintering pulse power supply 39 via the upper punch electrode 37 and the lower punch electrode 38. This pulse current is supplied to the powdery functional gradient material FGM filled and laminated in the hollow portion of the sintering die 32 through the upper punch 34 and the lower punch 35 and energized.

Further, an upward pressure P is applied to the lower punch electrode 38 by the pressing mechanism 41 for sintering. The lower punch electrode 38 is provided so as to be movable in the upward direction. The lower punch electrode 38 is moved upward by the pressure P and pushes up the functional gradient material FGM through the lower punch 35. Since the upper punch 34 and the upper punch electrode 37 are fixed in the vertical direction, the functionally gradient material FGM is compressed by the pressure P from below. By flowing a large current pulse current through the functional gradient material FGM, SiO ₂ contained in each layer of the functional gradient material FGM is uniformly heated and melted and sintered by spark discharge and Joule heat generated in the green compact particle gap. As a result, the insulating layer 11, the intermediate layer 13, and the conductive layer 12 constituting the functional gradient material FGM can be firmly bonded.

In the SPS method, since the sample temperature is increased by energizing the sample and firing is performed, when SiO ₂ particles are used as the insulator, the temperature of the SiO ₂ particles can be raised to the melting temperature or higher. For this reason, SiO ₂ is also present at the joint between the insulating layer 11 made of SiO ₂ and the non-conductive intermediate layer 13 made of a mixture of SiO ₂ and Mo or W, or at the joint between the intermediate layer 13 and the conductive layer 12. ₂ melts and bonds to each other, so that the two layers can be strongly bonded, and a functionally graded material having high strength can be obtained.

  Furthermore, according to the method of manufacturing the functionally gradient material of the present invention, the functionally gradient material can be sintered even when the electrode shaft 42 is inserted in the axial direction of the functionally gradient material FGM. This makes it very easy to produce functionally graded materials.

In the production of the functional gradient material described above, the optimal function is achieved by changing the density of the insulating layer 11, changing the density of the insulating layer 11 and the intermediate layer 13, or changing the volume mixing ratio of SiO ₂ and Mo of the intermediate layer 13. 1 to 3 experiments were performed on the gradient materials. The experimental results will be described below.

  In these experiments, an FGM of only a plurality of functionally graded material layers was prepared by sintering without inserting the electrode shaft 42. In this case, it is not necessary to use the upper punch 34 having the pores 341 as shown in FIG. 4 as the SPS manufacturing apparatus of FIG.

(Experiment 1)
In this example, a functionally gradient material for the insulating layer 11 made of only SiO ₂ was prepared. In this embodiment, samples with different densities of the insulating layer 11 are prepared.

In the sample, the amount of the SiO ₂ powder is adjusted so that the thickness of the insulating layer 11 is about 10 mm. Moreover, the sample changes the sintering temperature and changes the density of the insulating layer 11. FIG. 5 shows the relationship between the density of the manufactured insulating layer 11 and the presence or absence of airtightness. As shown in FIG. 5, it can be seen that the density of the insulating layer 11 must be 95% or more in order to obtain hermeticity.

(Experiment 2)
In this example, a functionally graded material composed of two layers of an insulating layer 11 and an intermediate layer 13 made of only SiO ₂ was prepared. The intermediate layer 13 is composed of SiO ₂ and Mo, and the volume mixing ratio of SiO ₂ / Mo is 98/2.

  In preparing the sample, the total amount of the powder is adjusted so that the thickness of the insulating layer 11 is about 10 mm and the thickness of the intermediate layer 13 is about 3 mm. Further, the sample has the density of the insulating layer 11 changed by changing the sintering temperature. When the sintering temperature rises due to the characteristics of the SPS method and the density of the insulating layer 11 increases, the density of the intermediate layer 13 adjacent thereto also increases.

  From the test results, it can be seen that in order to increase the density of the insulating layer to 95% or higher, the density of the intermediate layer 13 needs to be 95% or higher as shown in FIG.

(Experiment 3)
In this example, a functionally graded material composed of two layers of an insulating layer 11 and an intermediate layer 13 made of only SiO ₂ was prepared. In the sample, the volume mixing ratio of SiO ₂ / Mo of the intermediate layer 13 is (1) 85/15, (2) 87/13, (2) 90/10, (3) 93/7, (4) 93 / Samples with 7, (5) 95/5 and (6) 98/2 were prepared. In the preparation of the sample, the total amount of the powder is adjusted so that the thickness of the insulating layer 11 is about 10 mm and the thickness of the intermediate layer is about 3 mm.

  The density of the insulating layer 11 of the sample was 98% or more. In the prototype sample, a case where a crack is generated between the insulating layer 11 and the intermediate layer 13 is indicated as “present”, and a case where no crack is generated is indicated as “absent”. As shown in FIG. 7, it can be seen that as a condition for preventing cracks between the insulating layer 11 and the intermediate layer 13, the volume mixing ratio of Mo should be 10% or less.

  In this way, the reason why the quartz bulb and the functional sealing material cannot be sealed with airtightness was examined, and the conditions necessary for sealing with airtightness were examined. From the results of Experiments 1 to 3, the following was found.

1. As a condition for hermetically sealing the quartz bulb of the lamp housing, it is necessary to maintain the hermeticity after sealing unless the density of the insulating layer made of the functionally gradient material SiO ₂ is 95% or more of the theoretical density. I can't.

  2. In order for the density of the insulating layer to be 95% or more, the density of the intermediate layer in contact with the insulating layer must be 95% or more of the theoretical density.

3. When the volume density of Mo with respect to SiO ₂ in the intermediate layer in contact with the insulating layer is greater than 10%, cracks are generated.

  FIG. 8 is a diagram for explaining an embodiment of the tube of the present invention, and is a cross-sectional view of a main part of a tube-type halogen bulb using the functionally gradient material of the present invention described above for sealing. In the figure, the tubular halogen light bulb BP includes an airtight container 81, a tube actuating member 82 (filament), and a functional gradient material for sealing FGM.

  The airtight container 81 has an opening 81a to be sealed. And the opening 81a is sealed by the functional gradient material FGM for sealing. Since the airtight container 81 of this form is a case of a lighting tube, it is made of a light-transmitting and fire-resistant material such as quartz glass or light-transmitting alumina ceramics, but is made of quartz glass and is straight. It has a cylindrical shape, and both ends thereof form a pair of openings 81a.

  The tube operation member 82 is housed in the airtight container 81 in an airtight manner and performs a required operation as the tube BP, and is allowed to have various configurations. That is, the bulb BP is a member that is supplied with power from the outside and performs a desired electrical operation in the hermetic container 81. For example, in the case of a halogen bulb, an incandescent filament and an accompanying member. In the case of a high-pressure discharge lamp, it is a discharge electrode and an accompanying member.

  The illustrated tube operating member 82 is mainly composed of an incandescent filament, and a filament leg portion 82a (only one end is shown) extends from both ends thereof, and the filament leg portion 82a is disposed at both ends of the airtight container 81. The electrode shaft 42 (only one is shown) is connected to the inside of the airtight container 81 by welding or the like. The filament is composed of a double coil filament, and a plurality of ring anchors 82b are attached to prevent drooping during lighting.

As shown in FIG. 1, the functionally graded sealing material FGM is composed of an insulating layer 11, a conductive layer 12, and an intermediate layer 13, and is welded to the inner wall of the hermetic container 81 at the insulating layer 11 portion. Since the insulating layer 11 is made of 100% SiO ₂ , the thermal expansion coefficient is the same as that of the hermetic container 81, and there is no possibility of causing cracks due to the difference in thermal expansion coefficient during use of the halogen bulb.

  Since the tube BP shown in FIG. 8 is a halogen bulb, an organic halide such as iodine or bromine and argon (Ar), for example, are sealed at an appropriate pressure as an appropriate amount of halogen inside the hermetic container 81. Yes. Further, an infrared light reflection / visible light transmission type dichroic reflection film can be formed on the outer surface of the airtight container 81 as desired.

  In this embodiment, it is possible to obtain a tube-type halogen light bulb that can realize sealing in which the airtightness between the quartz bulb and the functional sealing material is further maintained.

The block diagram for demonstrating one Embodiment regarding the functional gradient material of this invention. The block diagram for demonstrating the outline | summary at the time of making the functional gradient material of FIG. 1 into a valve | bulb as a sealing material. The schematic block diagram for demonstrating one Embodiment of the manufacturing method of the functional gradient material of this invention. Sectional drawing for magnifying and explaining the principal part of FIG. Explanatory drawing for demonstrating the experimental result of the functional gradient material of this invention. Explanatory drawing for demonstrating the experimental result of the functional gradient material of this invention. Explanatory drawing for demonstrating the experimental result of the functional gradient material of this invention. The principal part sectional drawing for demonstrating one Embodiment regarding the tube using the functional gradient material of this invention.

Explanation of symbols

FGM Functional gradient material 11 Insulating layer 12 Conductive layer 13 Intermediate layer 21 Valve 42 Electrode shaft 31 Water-cooled vacuum chamber 32 Sintering die 34 Upper punch 35 Lower punch 81 Airtight container 82 Tube operating member

Claims (6)

An insulating layer mainly composed of silicon oxide as an insulating material;
A conductive layer in which the insulating material silicon oxide and the conductive material molybdenum or tungsten are mixed;
An intermediate layer in which the insulating material silicon oxide and the conductive material molybdenum or tungsten are mixed and the coefficient of thermal expansion is changed in stages,
The functional gradient material, wherein the density of the insulating layer is 95% or more of the theoretical density. An insulating layer mainly composed of silicon oxide as an insulating material;
A conductive layer in which the insulating material silicon oxide and the conductive material molybdenum or tungsten are mixed;
An intermediate layer in which silicon oxide as an insulating material and molybdenum or tungsten as a conductive material are mixed, and the coefficient of thermal expansion is changed stepwise between the insulating material and the conductive material,
The functional gradient material according to claim 1, wherein a density of the intermediate layer in contact with the insulating layer is 95% or more of a theoretical density.   The functional gradient material according to claim 2, wherein a volume mixing ratio of molybdenum or tungsten of the conductive substance to silicon oxide of the insulating substance of the intermediate layer in contact with the insulating layer is 10% or less. .   The functional gradient material according to any one of claims 1 to 3, wherein the density of the quartz glass bulb and the sealing portion is 95% or more.   The method for producing a functionally gradient material according to any one of claims 1 to 3, wherein the functional gradient material is fired by a discharge plasma sintering method.   A tube characterized by using the functional sealing material according to claim 1.

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