KR100764936B1 - A micro catalytic combustor using porous silicon reinforcement structure and its manufacturing method - Google Patents

Abstract

A micro catalytic combustor is provided to be capable of being formed in an ultra-fine shape by using a silicon reinforcement structure, and to ensure good strength and a simple production process by using a porous silicon structure identical to a reinforcement structure. A micro catalytic combustor acts as a heat source for a fuel cell. The micro catalytic combustor includes: an inlet(220) into which pre-mixed gases are injected; an outlet(230) from which a reaction resultant is discharged; and a combustion room(120) which is formed between the inlet and outlet and has an inner wall surface for supporting a catalyst, wherein the inner wall surface is formed of a porous silicon layer. The micro catalytic combustor is separated into a reinforcement structure(100) on which the combustion room is formed, and a cover structure(200) which covers the combustion room.

Description

Micro Catalytic Combustor using Porous Silicon Reinforcement Structure and Its Manufacturing Method

1 is a schematic diagram illustrating a fine fuel cell process.

2 is a perspective view of a microcatalyst combustor of the present invention.

3 is a front view of the microcatalyst combustor of the present invention.

4 is a side cutaway view of a microcatalytic combustor of the present invention.

5 is a schematic view showing a support manufacturing process.

6 is a schematic diagram of formation of a porous structure using an electrochemical etching method.

7 is a schematic view showing a cover body manufacturing process;

** Description of the symbols for the main parts of the drawings **

100: support 120: combustion chamber

130: porous layer 200: cover body

210: Pyrex glass 220: entrance

230: exit 300: sensor

330: meandering department

The present invention is a microcatalytic combustor that acts as a heat source for operation of a micro reactor or a micro reformer, and can be formed in an ultrafine form by applying a silicon support, and has excellent strength by adopting the same silicon porous structure as the support. It is an object of the present invention to provide a microcatalytic combustor employing a porous silicon support having a simple process.

Recently, as the market size of portable electronic devices is rapidly expanding, the demand for batteries employed in portable electronic devices is diversified. Among them, fuel cells are highly efficient and noiseless, and various types of fuels are available, and they are actively studied in terms of pollution. In particular, as the power consumption of portable electronic devices increases and becomes smaller, research into fuel cells has become focused.

PEMFC (40), which is a polymer electrolyte fuel cell among fuel cells, has been developed in a variety of sizes from several tens of watt units used in laptops to 100kW used in fuel cell vehicles, and has been widely used for military and robotic applications. The fuel of the PEMFC 40 mainly uses compressed hydrogen or metal hydride. In particular, a fuel reformer is required when using methanol or gasoline as fuel. 1 schematically illustrates a micro fuel cell process. It is a fuel cell system that uses hydrocarbon fuel to make hydrogen and produce electricity using it.

Methanol is mixed with water and vaporized to pass through the fuel transfer unit 10 and flow into the fuel reformer 20. When the fuel passes through the fuel reformer 20, various unnecessary gases such as carbon dioxide and carbon monoxide are simultaneously generated together with the hydrogen. The fuel is passed through the membrane 30 to filter only hydrogen, which is the actual fuel of the PEMFC 40. The jammed hydrogen enters the PEMFC 40 fuel cell and is used to generate electricity, producing water as a reactant.

On the other hand, the fuel transfer unit 10 and the fuel reformer 20 needs to be maintained at a suitable high temperature for smooth operation and high efficiency. It is common to employ a heater 50 for this purpose. As the fuel cell used in the portable electronic device is miniaturized, the heater needs to be miniaturized. Miniaturization and high temperature maintenance conditions of the heater 50 inevitably require a high energy density, the micro-catalytic combustor is emerging in the form of a heat source that meets these conditions.

Unlike ordinary combustors that operate by generating flames, catalytic combustors are combustion combustors that generate and sustain combustion using catalysts. There is an advantage. In addition, there is no problem such as anti-inflammatory, there is an advantage that the continuous combustion is possible in the micro-scale fine structure. In addition, it can be said that it is suitable as a fuel cell heater 50 of a portable device because the preheating device is not necessary when employing a catalyst that occurs at room temperature.

Conventional microcatalytic combustor manufactures a trench-shaped micro size combustion chamber on a silicon substrate, and a support of Al ₂ O ₃ is formed on the bottom of the combustion chamber by anodizing to support a platinum catalyst and then heat-resistant glass. I was using the method of splicing. However, Al ₂ O ₃ is a material that is widely used in the combustor of the macro size and exhibits excellent characteristics, but there are many problems in terms of manufacturing and combustor strength in the micro size.

First, in view of the manufacturing problem, there is a problem in that the manufacturing process is complicated because the combustion chamber is first generated in the silicon substrate and the Al ₂ O ₃ support is placed thereon. The complexity of the manufacturing process implies the difficulty in increasing the manufacturing cost and maintaining the yield, and it is necessary to reduce the manufacturing process in terms of mass production, manufacturing cost, and yield of fuel cells. In addition, heterogeneous support bonds are undesirable in view of the strength of the catalytic combustor. In particular, in the case of an operating device which continuously and regularly experiences a high temperature environment caused by combustion and a low temperature environment in which a fuel cell does not operate, such as a catalytic combustor, heterogeneous coupling between components may not be desirable in terms of strength.

Therefore, the present invention has been made to solve the problems of the prior art as described above, the object of the present invention is to adopt a porous structure of the same type as the support, the manufacturing process is simplified to reduce the manufacturing cost, the yield is maintained It is an object of the present invention to provide a micro-catalyst combustor employing a porous silicon support excellent in terms of ease and strength and a method of manufacturing the same.

A microcatalytic combustor employing the porous silicon support of the present invention for achieving the above object includes: an inlet into which a premixed gas is injected, the microcatalyst combustor serving as a heat source for a fuel cell; An outlet through which reactants are discharged; It provides a micro-catalytic combustor comprising a combustion chamber formed between the inlet and the outlet, the inner wall surface carrying the catalyst is formed of a porous silicon layer.

Preferably, the micro-catalyst combustor is separated into a support body on which the combustion chamber is formed and a cover body covering the combustion chamber.

Preferably, the inlet and the outlet are formed in the cover body, and the support and the cover body are joined.

Preferably, the porous silicon layer is formed by electrochemical etching.

Preferably, the plurality of ribs formed of silicon are arranged on the inner wall of the combustion chamber so as to be stabilized in the direction in which the reaction gas flows.

Preferably, the cover body is pyrex glass, and is firmly bonded to the support by anodic bonding.

Preferably, a plurality of temperature sensors are integrally formed at a portion corresponding to the combustion chamber of the cover body.

Preferably, the catalyst is characterized in that the platinum.

Also preferably, the temperature sensor may be formed in a meander type curved shape.

In another aspect of the present invention, the present invention provides a method for producing a microcatalytic combustor that serves as a heat source for a fuel cell, comprising the steps of: preparing a flat silicon substrate as a support; Forming a trench-shaped combustion chamber by etching on the upper surface of the silicon substrate; Providing an electrode on a bottom surface of the silicon substrate; Forming a porous silicon layer in a combustion chamber by an electrochemical etching method using the electrode of the silicon substrate as an anode; Supporting platinum on the porous silicon layer; Providing a flat cover body; Forming a plurality of temperature sensors on one surface of the cover body to correspond to the combustion chamber of the support body; And firmly bonding the cover body to cover the combustion chamber of the support.

Preferably, the step of forming the temperature sensor is preferably formed by a process by sputtering or evaporation using platinum.

Hereinafter, a microcatalyst combustor to which the porous silicon support according to the present invention having the configuration as described above is applied will be described in detail with reference to the accompanying drawings.

2 to 7 is a view showing a micro-catalyst combustor and a manufacturing method using the porous silicon support of the present invention, Figure 2 is a perspective view of the catalytic combustor, Figures 3 and 4 are a front view and a side cutaway, 5 and 7 are schematic diagrams illustrating a step of manufacturing the support and the cover body. 6 is a schematic diagram showing a method of forming a porous structure.

Hereinafter, the catalytic combustor structure of the present invention will be described in detail with reference to the accompanying drawings of FIGS. 2 to 4.

Referring to FIG. 2, the catalytic combustor of the present invention has a flat plate shape, and includes a concave combustion chamber 120 formed in a trench manner in an upper portion thereof, and a porous bottom portion is formed in the combustion chamber 120 to support the platinum catalyst. A silicon support 100; A cover body 200 coupled to the upper portion of the support 100 to cover the combustion chamber 120, and having an inlet 220 and an outlet 230 at positions corresponding to both ends of the combustion chamber 120, respectively; A plurality of upper surfaces of the cover body 200 opposite to the combustion chamber 120 are formed along the combustion chamber 120, meandered at a position corresponding to the combustion chamber 120, and measuring a changing temperature of the combustion chamber 120. It is composed of a sensor 300. In FIG. 2, the meandering unit 330 of the sensor 300 is not shown in detail in order to facilitate recognition, and its shape may be confirmed in FIG. 3.

The structure of the support body 100 and the cover body 200 is demonstrated with reference to FIG. 2 and FIG. FIG. 4 is a cutaway view taken along the line AA ′ of FIG. 2, and shows the support body 100 and the cover body 200 that are bonded for recognition. The support 100 is formed by etching the combustion chamber 120 in a trench manner on a plate-shaped silicon substrate. Specific manufacturing process will be described later. The thickness of the support 100 is preferably about 700 μm, of which the combustion chamber 120 is preferably 300 μm. Combustion chamber 120 is composed of a combustion unit 121 is formed in a straight line and a tapered portion 122 formed in correspondence with the inlet 220 and the outlet 230 of the fuel at both ends of the combustion unit 121, The end of the tapered portion 122 is smoothly processed in an arc shape. Although the shape of a combustion chamber is described in detail in this application, it is not limited to said shape, It can change freely within the limit that does not impair the technical summary of this invention.

The porous layer 130 is formed at the bottom of the combustion chamber. The porous layer 130 is formed by the silicon support according to the electrochemical etching process (electrochemical etching) as shown in FIG. 6, in which a number of perpendicular vertical holes are arranged, and the platinum catalyst supported on the porous layer 130 is formed. The area of contact with the fuel flowing in the combustion chamber 120, in particular hydrogen and the air mixture, is maximized. On the other hand, the bottom of the combustion chamber 120 may be formed by etching the entire flat to form a porous layer 130, as shown in Figure 2 a plurality of ribs extending from the bottom of the combustion chamber 120 from the bottom of the cover body 200 ( It is also desirable to stabilize the flow of the combusted flow by aligning 123 and placing them at appropriate intervals along the combustion chamber 120.

The cover 200 is processed to the same size as the support 100 to cover the upper portion of the combustion chamber 120. Holes for the inlet 220 and the outlet 230 are respectively penetrated at both ends of the combustion chamber 120, that is, at positions corresponding to the tapered portion 122. The inlet 220 is where the mixture of hydrogen and air, which is the fuel of the catalytic combustor of the present invention, is introduced, and the outlet 230 is where the reactant catalytically burned out by the platinum catalyst exits. The cover body 200 is generally made of pyrex glass, and the support body 110 and the cover body 200 are firmly bonded by anodic bonding.

The temperature sensor 300 for measuring the temperature of the combustion chamber 120 is formed on an upper side of the cover body 200, that is, the opposite side of the combustion chamber. The sensor 300 is preferably formed in plurality in a required position along the longitudinal direction of the combustion chamber 120. The material of the sensor 300 is preferably made of platinum. This is reasonable considering that the material of the catalyst is platinum. The temperature measurement method is a method of measuring the resistance of each sensor 300 to read the correct temperature from the relationship between the resistance and the temperature.

The sensor 300 is positioned directly above the first connecting portion 310 and the second connecting portion 320 and the combustion chamber 120 through which the external connection terminal contacts the combustion chamber 120 to adjust the temperature of a specific portion of the combustion chamber 120. Meander type (meander type) meander measuring portion (330) and the meandering portion 330 and the connecting portion 340 between the connecting portion (310,320). Like the combustion chamber 120, the sensor 300 is manufactured to have a fine size, and is manufactured using a process such as exposure and etching commonly known as a semiconductor process. The combination of the cover body 200 and the sensor 300 is firmly connected by platinum sputtering. Although the planar shape of the first connection part 310 and the second contact part 320 is not defined, it is preferable to form a tapered shape in order to facilitate and secure connection with external connection terminals. Maintaining the meander-type sensor shape on the combustion chamber 120 is intended to more accurately measure the average temperature of a specific portion of the combustion chamber 120, and it is natural to be insulated between the meandering paths.

Next, a manufacturing process of the support 100 will be described with reference to FIG. 5. FIG. 5 is a diagram illustrating the catalytic combustor shown in FIG. 2 cut along the line BB ′. Since the size of the catalytic combustor to which the porous silicon support of the present invention is applied is extremely small, and the size of the combustion chamber 120, the porous layer 130, the sensor 300, and the like is also extremely fine, the manufacturing process thereof is well known exposure, Semiconductor processes such as development and etching are used.

First, a p-type silicon substrate is prepared in the form of a flat plate. The size of the substrate is determined and provided according to the structure to which the catalytic combustor is attached, and prior to this, the substrate is subjected to conventional processes such as cleaning and polishing the surface. Thereafter, thermal oxidation forms a SiO ₂ layer on the surface. The thermal oxidation method is a method of forming an insulating film having excellent properties as a method of hardly generating defects in the oxide layer and the SiO ₂ / Si interface. This technique is classified into dry oxidation method and wet oxidation method according to the type of gas used in the oxidation reaction, and both are selected and applied according to the needs. The oxide layer serves as a mask for etching the combustion chamber 120. Next, PR (photo resist) coating is performed as shown in FIG. After coating in the form of a uniform film over the entire substrate, baking at a constant temperature (baking) to vaporize the PR solvent to make it hard. Next, through the exposure and development is prepared to remove the oxide film as shown in Fig. 5 (b). The exposure is prepared in advance in the combustion chamber 120 in the form of a mask, and then aligned (aligned), and then UV light is transferred to transfer, the development is using an aqueous base solution such as KOH aqueous solution. If the PR is a negative PR such as the SU series, acetone or certain solvents may be used, and the process is not particularly limited.

Next, the SiO ₂ oxide film is removed using PR using a BOE mask. Since PR is designed to have a combustion chamber shape, the removed oxide film also has a combustion chamber shape and has a shape as shown in FIG. In the figure, it can be confirmed that all oxide films not protected by the PR are removed. Next, an electrode for electrochemical etching of porous silicon is formed on the bottom surface of the silicon substrate. Although a conventional deposition method may be applied, it is preferable to use a simple and fast vacuum evaporation process rather than a sputtering process with a relatively slow deposition rate. Although the vacuum deposition method has a disadvantage in that the surface quality is bad, it can be seen as a suitable method when it may be removed after being used as an electrode as in the present invention. The electrode is formed as a multilayer of the Cr layer 160 and the Au layer 170 as shown in FIG.

Next, the silicon substrate is etched using the SiO ₂ oxide film as a mask to form the combustion chamber 120. In the etching method, all of various conventional methods may be employed, but in the present invention, Deep RIE (reactive ion etching) is used to maintain the combustion chamber 120 at a right angle. The Deep RIE method is a method in which ions collide with a silicon plane at a high speed to remove them. Some chemical reactions are added to increase the etching speed. As a result of etching, the combustion chamber 120 of the right angle wall is formed to a depth of 300 μm as shown in FIG. As described above, a plurality of ribs 123 may be regularly arranged in the combustion chamber, and it is natural that a PR mask should be appropriately designed accordingly.

Next, a method of forming a porous silicon layer and a platinum catalyst layer using electrochemical etching will be described with reference to FIGS. 5 and 6. FIG. 6 shows an enlarged view of the bottom surface of the combustion chamber 120 where etching occurs. The silicon substrate formed as shown in Fig. 5E is contained in a container as shown in Fig. 6 and subjected to electrochemical etching. As shown in Fig. 6 (a), the silicon substrate in the process is used as an anode and the platinum plate as a cathode is contained in a container made of Teflon. The vessel contains HF (hydrofluoric acid) solution and is stirred with a stirrer for faster process speeds. An appropriate magnitude of DC current is supplied between the cathode and anode. Alternatively, as shown in FIG. 6 (b), chromium (Cr) and platinum (Au) are sequentially attached to the rear surface of the silicon substrate in the process to form an anode, and the solution is mixed with dimethylformamide (DMF), HF, and water. Soak. In this manner, micropores are generated in the silicon substrate to form a porous structure. The porous structure need not be limited to a particular shape and is sufficient if the contact area is optimized to the maximum within the limit that the structure of the combustion chamber 120 can be maintained.

By etching, numerous porous silicon layers in the form of vertical holes are formed, and the silicon layers serve as a support for supporting platinum. The porous layer 130 is formed on the bottom and sidewalls of the combustion chamber 120 as shown in FIG. 5 (f), and then platinum is supported in the porous layer according to the impregnation method, as shown in FIG. 5 (g). 100) is completed.

Next, the manufacturing process of the cover body 200 is demonstrated with reference to FIG. FIG. 7 is a view illustrating the catalytic combustor shown in FIG. 2 cut along the line BB ′ similarly to FIG. 5. The cover body 200 is manufactured using pyrex glass. Pyrex glass acts as a base plate for supporting the temperature sensor 300. The Pyrex glass 210 cut to the size of the support 100 has through holes for the inlet 220 and the outlet 230 at positions corresponding to the tapered portion 122 of the combustion chamber 120 of the support 100, respectively. It is provided. Next, PR is coated as shown in FIG. Exposure is performed using a separate mask designed to form the sensor 300 of FIG. 3 in the PR coating layer, and development is performed using an appropriate solution. As a result, a cover body as shown in FIG. 7B can be obtained. Next, platinum is deposited on the developed PR coating layer and the cover body 200 using a sputtering technique. Sputtering deposition is a process in which a particle is removed from a target of a material to be deposited, that is, a platinum piece, using DC or RF magnetron and then transferred onto a specific substrate. This obtains the cover body 200 of Fig. 7 (c) in which a thin film made of platinum is formed on the developed PR coating layer.

Next, the PR coating and the unnecessary platinum film layer are removed through a lift-up process. Unlike the normal etching, the lift-up process removes the film deposited on the PR in the process of dissolving the PR in a solvent so that only the film deposited on the base plate remains. As a result of this, the cover body 200 shown in Fig. 7D is completed.

The support body 100 and the cover body 200 are firmly bonded by the anodic bonding method. After the bonding surface of the support body 100 and the cover body 200 is homogeneously polished as necessary, the two plates are forced to contact each other and a high voltage is applied in a high temperature environment of about 450 degrees. As a result, a chemical reaction occurs at the bonding surface, thereby forming a firm bonding. FIG. 7 (e) shows a cross-sectional view of the microcatalyst combustor of the present invention applying the porous silicon support of the final form completed using the above bonding method.

The combustion process of the microcatalyst combustor to which the porous silicon support of the present invention configured as described above is applied is as follows.

Hydrogen compressed as fuel and air as oxidant are mixed and introduced into the inlet 220 of the catalytic combustor 50. The introduced premixed gas passes through the combustion chamber 120 formed in a straight line and causes catalytic combustion by the platinum catalyst supported on the porous silicon layer 130. In the case of the present invention, stable catalyst combustion is possible by employing a platinum catalyst which exhibits very high reactivity, good corrosion resistance and stable properties even at high temperatures. Catalytic combustion occurs strongly at the beginning of the combustion chamber 120, the reaction degree is weak toward the outlet 230, but the reaction rate is constant when the catalytic combustion is stable. The reaction product exits through outlet 230 as water and nitrogen.

The temperature of the combustion chamber 120, measured by the temperature sensor 300, depends on the flow rate of the premixed gas injected at the inlet, but it has been found that a few hundred degrees can be reached within a short time. It is possible to control the operation of the catalytic combustor at an appropriate temperature by adjusting the flow rate of the premixed gas. In general, the premixed gas flow rate of the inlet 220 is fed back by feeding back the temperature value measured by the sensor 300 for each part. It is desirable to adjust

The present invention is not limited to the above-described embodiments, and the scope of application of the present invention is not limited to those of ordinary skill in the art to which the present invention pertains without departing from the gist of the present invention as claimed in the claims. Of course, various modifications can be made.

The microcatalyst combustor to which the porous silicon support of the present invention is applied as described above can be easily manufactured in a micro size by introducing a semiconductor process, using a silicon substrate as a support for supporting a platinum catalyst, and mass production is possible.

In addition, the manufacturing process is reduced by using the same type of porous silicon layer that is used by plating Al ₂ O ₃ as a support for a catalyst on a silicon substrate, thereby reducing the manufacturing cost and managing to increase the yield. There is a significant advantage in this respect.

In addition, there is an advantageous aspect in terms of thermal fatigue strength of the combustor by using silicon as the substrate of the catalyst support.

In addition, the support for the catalyst support is formed by a porous has the advantage that the contact area for the catalytic action is maximized.

Moreover, the combustor of this invention makes catalyst reactivity good, and it is stable in high temperature environment, and is excellent in corrosion resistance.

In addition, since the temperature sensor is manufactured to be embedded in the microcatalytic combustor, there is no need to attach a temperature sensor separately, and the measurement accuracy of the temperature is greatly improved.

In addition, since the temperature sensor is configured in a meandering type on the top of the cover body covering the combustion chamber, the measurement accuracy of the average temperature is improved, whereby accurate catalytic combustion can be controlled.

Claims (12)

In a microcatalytic combustor serving as a heat source for a fuel cell, An inlet through which the premixed gas is injected; An outlet through which reactants are discharged; And a combustion chamber formed between the inlet and the outlet, and the inner wall surface supporting the catalyst is formed of a porous silicon layer. The method of claim 1, wherein the microcatalytic combustor And a support body in which the combustion chamber is formed and a cover body covering the combustion chamber. The method of claim 2, wherein the inlet and outlet It is formed in the cover body, the support body and the cover body is a micro-catalyst combustor, characterized in that configured to be bonded. The method of claim 1, wherein the porous silicon layer is A microcatalytic combustor, characterized in that it is formed by electrochemical etching. The method of claim 1, And a plurality of ribs formed of silicon are arranged on the inner wall of the combustion chamber so as to be stabilized in the direction in which the reaction gas flows. The method of claim 2, wherein the cover body A microcatalyst combustor, which is pyrex glass and is firmly bonded to the support by anodic bonding. The method according to any one of claims 2, 3 or 6, And a plurality of temperature sensors are integrally formed in a portion corresponding to the combustion chamber of the cover body. 7. Microcatalytic combustor according to any one of the preceding claims, wherein the catalyst is platinum. 8. The microcatalyst combustor of claim 7, wherein the catalyst is platinum. The method of claim 7, wherein the temperature sensor A microcatalytic combustor, characterized in that it is formed in a meander type curved shape. In the manufacturing method of a microcatalyst combustor which acts as a heat source for a fuel cell, Preparing a flat silicon substrate as a support; Forming a trench-shaped combustion chamber by etching on the upper surface of the silicon substrate; Providing an electrode on a bottom surface of the silicon substrate; Forming a porous silicon layer in a combustion chamber by an electrochemical etching method using the electrode of the silicon substrate as an anode; Supporting platinum on the porous silicon layer; Providing a flat cover body; Forming a plurality of temperature sensors on one surface of the cover body to correspond to the combustion chamber of the support body; Firmly bonding the cover body to cover the combustion chamber of the support; Method for producing a micro-catalyst combustor comprising a. The method of claim 11, wherein forming the temperature sensor A method of producing a microcatalytic combustor, characterized in that it is formed by a process by sputtering or evaporation using platinum.

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