WO2009131306A1 - A tungsten trioxide (wo3)-based gas sensor for sensing gaseous volatile organic compounds, and a production method therefor - Google Patents

A tungsten trioxide (wo3)-based gas sensor for sensing gaseous volatile organic compounds, and a production method therefor Download PDF

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WO2009131306A1
WO2009131306A1 PCT/KR2009/001032 KR2009001032W WO2009131306A1 WO 2009131306 A1 WO2009131306 A1 WO 2009131306A1 KR 2009001032 W KR2009001032 W KR 2009001032W WO 2009131306 A1 WO2009131306 A1 WO 2009131306A1
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sensor
gas
sno
gas sensor
sensitivity
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PCT/KR2009/001032
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Korean (ko)
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WO2009131306A9 (en
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이창섭
전재목
최경진
이형락
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한국이엔에쓰 주식회사
계명대학교 산학협력단
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D53/00—Separation of gases or vapours; Recovering vapours of volatile solvents from gases; Chemical or biological purification of waste gases, e.g. engine exhaust gases, smoke, fumes, flue gases, aerosols
    • B01D53/34—Chemical or biological purification of waste gases
    • B01D53/74—General processes for purification of waste gases; Apparatus or devices specially adapted therefor
    • B01D53/86—Catalytic processes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/12—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body in dependence upon absorption of a fluid; of a solid body in dependence upon reaction with a fluid, for detecting components in the fluid
    • G01N27/125—Composition of the body, e.g. the composition of its sensitive layer
    • G01N27/127—Composition of the body, e.g. the composition of its sensitive layer comprising nanoparticles
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
    • G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
    • G01N27/14—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature
    • G01N27/16—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of an electrically-heated body in dependence upon change of temperature caused by burning or catalytic oxidation of surrounding material to be tested, e.g. of gas
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
    • G01N27/26—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating electrochemical variables; by using electrolysis or electrophoresis
    • G01N27/403—Cells and electrode assemblies
    • G01N27/406—Cells and probes with solid electrolytes
    • G01N27/407—Cells and probes with solid electrolytes for investigating or analysing gases
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N33/00—Investigating or analysing materials by specific methods not covered by groups G01N1/00 - G01N31/00
    • G01N33/0004—Gaseous mixtures, e.g. polluted air
    • G01N33/0009—General constructional details of gas analysers, e.g. portable test equipment
    • G01N33/0027—General constructional details of gas analysers, e.g. portable test equipment concerning the detector
    • G01N33/0036—General constructional details of gas analysers, e.g. portable test equipment concerning the detector specially adapted to detect a particular component
    • G01N33/0047—Organic compounds

Definitions

  • the present invention relates to a gas sensor and a method for manufacturing the same, and more particularly, to a WO 3 gas sensor capable of detecting a volatile organic compound gas and a method for manufacturing the same.
  • VOCs Volatile Organic Compounds
  • acetaldehyde is a carbonyl compound which is widely spread in the air together with formaldehyde.
  • Aldehydes from the combustion and atmospheric oxidation of materials are involved in photochemical reactions to produce ozone, thereby increasing global warming, destroying the stratospheric ozone layer. have.
  • This acetaldehyde is well known as a sick house syndrome recently, so it is highly likely to appear in both indoor and outdoor air. Exposure to this aldehyde causes serious toxicity, which can cause direct body reactions such as irritating the respiratory tract of the neck, nose and bronchus, causing anesthesia to the central nervous system, causing paralysis, respiratory failure and lethargy. have. Therefore, the necessity of measuring the presence of gas also occurs in terms of environmental and human hazard detection.
  • the present invention has been made to meet the above-described demands, and provides a sensor and a method of manufacturing the same, by adding a suitable weight ratio of SnO 2 to WO 3 to form a sensor material, thereby improving detection sensitivity of volatile organic compound gas.
  • an object of the present invention is to provide a sensor and a method of manufacturing the same, which add a metal catalyst to the sensor material to improve the sensitivity and selectivity to the gas.
  • a substrate in order to solve the above problems, a substrate, an electrode formed on the upper surface of the substrate, the sensor material covering the electrode, made by adding SnO 2 to WO 3 It provides a WO 3- based gas sensor comprising a sensing film formed of a, and a heater formed on the lower surface of the substrate.
  • the SnO 2 has a range of 3 to 10% by weight based on the total weight of the sensor material, and thus the sensitivity is increased by adding metal oxide (SnO 2 ) to increase stability and inhibit particle growth of the parent material. You can let
  • the sensing material further includes a metal catalyst of any one of Pd, In, Ru, and Pt, thereby improving gas detection and selectivity at low concentration.
  • the metal catalyst has a range of 1% by weight or less based on the total weight of the sensor material.
  • forming an electrode on the upper surface of the substrate, covering the electrode, forming a sensing film by adding SnO 2 to WO 3 , and forming a heater on the lower surface of the substrate It provides a method for producing a WO 3- based gas sensor having a.
  • the SnO 2 relative to the total weight is characterized in that added in the range of 3 to 10% by weight.
  • any one of the metal catalyst of Pd, In, Ru, Pt is further added, the metal catalyst relative to the total weight is preferably added in the range of 1% by weight or less.
  • the present invention can have the following effects by using the WO 3 metal oxide as a sensor material as a semiconductor gas sensor.
  • the WO 3 based thick film gas sensor adds metal oxides (SnO 2 ) to increase stability and to suppress particle growth of the parent material, thereby having good sensitivity characteristics for trace VOCs gas.
  • a metal catalyst of any one of Pd, In, Ru, and Pt may be further added to the sensing material to improve gas detection and selectivity at low concentrations. In particular, it exhibits very good selectivity for acetaldehyde gas.
  • the gas sensor according to the present invention can be widely used for environmental pollutant gas measurement and can contribute to environmental improvement or human harmful gas prevention.
  • FIG. 1 is a flow chart showing a process for producing a WO 3 nano powder of a gas sensor according to the present invention
  • FIG. 2 is a view showing a SnO 2 / WO 3 sensor 100 according to an embodiment of the present invention, (a), (b), (c), (d) is a cross-section, front, back of the sensor, respectively , Shows the front after screen printing,
  • 3 is a SEM image showing a cross-sectional view after the thick film is applied to the alumina substrate relatively uniformly
  • FIG. 6 is a graph showing an XRD pattern when a metal oxide and a metal catalyst are added to WO 3 according to firing temperature
  • FIG. 7 is a SEM image of the surface state of WO 3 according to the firing temperature of (a) 300 °C, (b) 500 °C, (c) 700 °C, (d) 900 °C, respectively,
  • FIG. 10 is a graph showing the sensitivity characteristics of acetaldehyde gas of 100ppm by operating temperature of WO 3 according to the firing temperature
  • FIG. 11 is a graph showing sensitivity characteristics of 100 ppm acetaldehyde gas at each operating temperature according to addition of a metal oxide (SnO 2 ) and a metal catalyst.
  • FIG. 12 is a graph illustrating the sensitivity characteristics of acetaldehyde gas after adding SnO 2 at various weight ratios.
  • 13 is a graph showing sensitivity characteristics of acetaldehyde gas according to the type of metal catalyst
  • 15 is a graph measuring the sensitivity to acetaldehyde gas at a low concentration of less than 10ppm using 1% by weight Ru / 5% by weight SnO 2 / WO 3 sensor material,
  • FIG. 16 is a graph illustrating selectivity of various VOCs gases using 1 wt% Ru / 5 wt% SnO 2 / WO 3 sensor material;
  • 17 is a graph showing reaction recovery characteristics of acetaldehyde gas and other VOCs gases.
  • the sensor material is a metal oxide semiconductor, and WO 3 is used as a base material, and a sensor material for gas sensing is manufactured by varying the mixing ratio of other metal oxides (SnO 2 ) and various metal catalysts.
  • WO 3 synthesized by the sol-gel method was used as a detection material of acetaldehyde.
  • 1 is a schematic diagram for preparing a WO 3 nanopowder.
  • WCl 6 0.01mol in 0.1L ethyl alcohol (aldrich) solution was mixed and stirred for 36 hours at 70 °C completely dissolved to prepare a homogeneous W (OC 2 H 5 ) 6 sol (sol).
  • An aqueous solution of NH 4 OH was titrated to this W (OC 2 H 5 ) 6 sol at a pH of 5 or less to precipitate W (OH) 6 gel powder. Washing was performed using NH 3 NO 3 aqueous solution, distilled water and ethanol to remove residual Cl ⁇ ions.
  • a metal catalyst was added by impregnation, and the method is shown in FIG. 1.
  • Pd, Pt, Ru and In which are transition metals, were weighed to a weight ratio of 1 to 5 wt%, and then placed in a beaker, 1 ml of hydrochloric acid was added to completely dissolve the metal catalyst, and then a uniform solution was prepared.
  • WO 3 powder or SnO 2 / WO 3 powder was added to impregnate the metal catalyst, and then slowly heated while stirring with a magnetic stirrer to prepare WO 3 powder or SnO 2 / WO 3 powder supported with the metal catalyst.
  • the obtained material was dried at 100 ° C. for 12 hours, calcined at 500 ° C. for 2 hours, and then ground to obtain a sensor material.
  • FIG. 2 is a view showing a SnO 2 / WO 3 sensor 100 according to an embodiment of the present invention, (a), (b), (c), (d) is a cross-section, front, back of the sensor, respectively , Front side after screen printing.
  • the sensor 100 is made by using the sensor material according to the present invention, and an alumina (Al 2 O 3 ) substrate may be used as the substrate 10, and a pair of upper surfaces of the substrate 10 facing each other.
  • a comb-tooth-like (IDT (interdigit) type) platinum (Pt) electrode 20 is formed, and a heater 40 made of nickel-chromium (Ni-Cr) is formed on the lower surface.
  • Reference numeral 50 is an insulator.
  • the substrate 10 may be a substrate such as SiO 2 in addition to the alumina, and the sensor material used for the sensor 100 covers the comb portion of the pair of comb-shaped electrodes 20 and includes a sensing layer. 30 can be formed.
  • a cleaning process using acetone and heat treatment at 300 ° C. were performed.
  • the sensor material paste may be formed on the substrate by screen printing to form a thick film having a thickness of 20 ⁇ m. Thereafter, the formed thick film device was dried at room temperature for 24 hours, heated to 5 ° C./10 min in a convection dryer, and dried at 110 ° C. for 12 hours, followed by heat treatment at 500 ° C. for 1 hour.
  • various methods of forming the sensing film may include various sensing film deposition methods such as forming a sensing film through plasma deposition.
  • 3 is a SEM image showing a cross-sectional view after the thick film is applied to the alumina substrate relatively uniformly.
  • the gas sensor was fixed at a distance of 50 mm from the ground in a chamber of 10 L (250 mm ⁇ 200 mm ⁇ 200 mm) capacity, and the sensitivity was measured while changing the operating temperature of the sensor to 200 to 400 ° C. In order to remove the electrons inside the device, a stabilization treatment was performed for 12 hours at the same temperature as the measurement temperature.
  • the sensing gas was injected into the vessel through a vacuum pump, the fan was operated, When reached, the resistance change was measured with a multimeter.
  • the sensitivity of the sensor was defined as the ratio (Ra / Rg) of the electrical resistance value Rg after injection of the sensing gas to the electrical resistance value Ra in the air.
  • the gas sensor uses a change in electrical resistance caused by VOCs adsorption gas, and the measurement of acetaldehyde gas, but is not limited thereto, and is mainly targeted to volatile organic compounds such as formaldehyde.
  • the following equation was calculated as the sensitivity (R) of the sensor and the rate of change (%) of the resistance value (R a ) in the air before injection of the measurement gas and the resistance value (R g ) after injection of the sensing gas, and 10 minutes after injection. The highest value of was calculated as the sensitivity of the sensor.
  • the present invention is to produce a gas sensing sensor material by varying the mixing ratio of the main material WO 3 powder and metal oxide and metal catalyst, each sensor material measured by measuring the sensitivity using the above sensitivity calculation formula (Equation 1) XRD, SEM / EDS, and BET analyzers are used to measure the crystallization state, phase identification, surface state, elemental analysis, and specific surface area of.
  • Equation 1 XRD, SEM / EDS, and BET analyzers are used to measure the crystallization state, phase identification, surface state, elemental analysis, and specific surface area of.
  • FIG. 8 SEM images of the material and EDS results are shown. Referring to (a), (b), (c), and (d) of FIG. 8, the surface state of each sensor material can be confirmed through SEM images, and peaks of component elements of each sensor material appear from EDS results. You can see that.
  • 9 is a graph showing the results of measuring pore distribution according to the amount of SnO 2 added.
  • Table 1 shows the results of measuring the specific surface area of each sensor material according to the amount of SnO 2 added.
  • the sensor material added with 5wt.% SnO 2 which showed relatively uniform pore distribution, was the largest at 14.83m 2 / g at the specific surface area. This is believed to contribute to the improvement of sensitivity by inhibiting the growth of particles as SnO 2 is added to WO 3 , leading to an increase in specific surface area.
  • FIG. 10 is a graph showing the sensitivity characteristics of acetaldehyde gas of 100ppm by operating temperature of WO 3 according to the firing temperature. Referring to FIG. 10, it can be seen that WO 3 fired at 500 ° C. has the best sensitivity at 350 ° C. FIG.
  • FIG. 11 is a graph showing sensitivity characteristics of 100 ppm acetaldehyde gas at each operating temperature according to addition of a metal oxide (SnO 2 ) and a metal catalyst.
  • FIG. 12 is a graph illustrating the sensitivity characteristics of acetaldehyde gas after adding SnO 2 at various weight ratios to improve stability, which is one of essential requirements of a gas sensor.
  • a metal catalyst was added to the sensor material.
  • the metal catalyst is mixed with the metal oxide, the electrons are smoothly transferred, so that the increased amount of the adsorbed species is involved in the adsorption and desorption phenomenon, thereby increasing the change in the electrical conductivity.
  • the contact area of the catalyst with the gas is increased to affect the sensitivity, the selectivity, and the operating temperature.
  • FIG. 13 is a graph showing sensitivity characteristics of acetaldehyde gas according to the type of metal catalyst.
  • FIG. 14 is a graph showing the sensitivity characteristic of acetaldehyde gas according to the thickness of the thick film coated on the substrate. Referring to FIG. 14, it can be seen that the sensitivity decreases as the thickness of the thick film increases, and the best sensitivity is shown at 20 ⁇ m.
  • Figure 15 is a graph measuring the sensitivity to acetaldehyde gas at a low concentration of less than 10ppm using 1% by weight Ru / 5% by weight SnO 2 / WO 3 sensor material.
  • FIG. 16 is a graph illustrating the selectivity for various VOCs gases using 1 wt% Ru / 5 wt% SnO 2 / WO 3 sensor material.
  • the sensitivity of the 1 wt% Ru / 5 wt% SnO 2 / WO 3 sensor was measured for 100 ppm of various gases at an operating temperature of 300 ° C., and thus the sensitivity of acetaldehyde gas was much higher than that of other gases. You can see good. Thus, it can be seen that this sensor has a very good selectivity to acetaldehyde gas. It is thought that 1 wt% Ru / 5 wt% SnO 2 / WO 3 decomposes acetaldehyde gas better than other VOCs gases and activates the reaction to improve selectivity.
  • 17 is a graph showing reaction recovery characteristics of acetaldehyde gas and other VOCs gases.
  • the recovery characteristics are the result of forced exhaust for rapid progress of the experiment.
  • the reaction recovery characteristics of acetaldehyde gas are better than those of other VOCs gases.
  • the WO 3 gas sensor according to the present invention is a sensor material in which WO 3 is used as a base material and metal oxide (SnO 2 ) and various catalytic metals are added, and has excellent characteristics in acetaldehyde gas detection. You can check it.
  • the operating temperature is 300 °C
  • the thick film thickness is 20 ⁇ m
  • the binder is ethylene glycol (ethylene glycol)
  • the composition has a form of 1% by weight Ru + 5% by weight SnO 2 + WO 3 In this case, it can be seen that the most optimal sensitivity and selectivity and recovery response characteristics are shown.
  • the present invention can be utilized as a semiconductor gas sensor using the WO 3 metal oxide as a sensor material.
  • it since it has good sensitivity characteristics for trace VOCs gas, it can be widely used for environmental pollutant gas measurement, which can contribute to the development of environmental related industries, disaster related industries such as prevention of harmful gases, or medical related industries.

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Abstract

The present invention relates to a tungsten trioxide (WO3)-based gas sensor which can sense gaseous volatile organic compounds, and to a production method therefor. To this end, the present invention provides a gaseous VOC sensor which is a tungsten trioxide-based gas sensor comprising a substrate, an electrode formed on the upper surface of the substrate, a sensing layer formed from a sensor material and produced by covering the said electrode and adding tin dioxide (SnO2) to tungsten trioxide(WO3), and a heater formed on the under surface of the said substrate, and it provides a production method therefor.

Description

　휘발성 유기화합물 가스 감지용 ＷＯ₃계 가스 센서 및 그 제조방법₃₃-based gas sensor for detecting volatile organic compounds and its manufacturing method
본 발명은 가스 센서 및 그 제조방법에 관한 것으로, 보다 상세하게는 휘발성 유기화합물 가스를 감지할 수 있는 WO3계 가스 센서 및 그 제조방법에 관한 것이다.The present invention relates to a gas sensor and a method for manufacturing the same, and more particularly, to a WO 3 gas sensor capable of detecting a volatile organic compound gas and a method for manufacturing the same.
최근 지속적인 산업발달, 인구증가, 교통량의 증가로 광화학 스모그, 온실효과, 산성비, 오존층 감소 등 환경오염이 심각한 문제로 떠오르고 있다. 특히 인간의 건강이나 동식물의 생육에 위해를 줄 만큼의 충분한 양이 대기나 지표 중에 장기간 머무르고 있으며, 이러한 오염물질 중에서 최근 오존 등 광화학 옥시던트로 인한 대기오염과 공단지역에서의 건강피해가 가시화됨에 따라 휘발성 유기화합물이 대기오염물질로서 관심이 증대되고 있다. 여기서, 휘발성 유기화합물(VOCs: Volatile Organic Compounds)은 증기압이 높아 대기 중으로 쉽게 증발하는 물질로서 대기 중에 질소산화물 공존시 광화학반응을 일으킨다. 이는 오존, PAN 등 광화학 물질을 생성시켜 광화학 스모그를 유발하는데, 이런 휘발성 유기화합물이 인체에 노출되면 백혈병, 중추신경장애 및 생식기능의 장애 등 치명적 영향을 미치게 된다. 가령, 휘발성 유기화합물 중에서 아세트알데하이드는 포름알데하이드와 함께 대기 중에 많이 퍼져있는 카르보닐 화합물이다. 물질의 연소와 대기 산화로부터 나오는 알데히드는 광화학반응에 관여하여 오존을 생성하여 지구온난화를 가중시키며, 성층권의 오존층을 파괴하고 있으며, 상온에서 주로 기상으로 존재하는 물질로서 대기 중에 장기적으로 축적 및 체류하고 있다. Recently, due to continuous industrial development, population growth, and traffic increase, environmental pollution such as photochemical smog, greenhouse effect, acid rain, and ozone layer reduction have emerged as serious problems. In particular, a sufficient amount to harm human health or the growth of animals and plants has been in the air or the surface for a long time. There is increasing interest in organic compounds as air pollutants. Here, Volatile Organic Compounds (VOCs) are substances that easily evaporate into the atmosphere due to high vapor pressure and cause photochemical reactions when nitrogen oxides coexist in the atmosphere. This causes photochemical smog by generating photochemicals such as ozone and PAN, and when exposed to the human body, these volatile organic compounds have fatal effects such as leukemia, central nervous system disorders and reproductive dysfunction. For example, among the volatile organic compounds, acetaldehyde is a carbonyl compound which is widely spread in the air together with formaldehyde. Aldehydes from the combustion and atmospheric oxidation of materials are involved in photochemical reactions to produce ozone, thereby increasing global warming, destroying the stratospheric ozone layer. have.
이 아세트알데하이드는 최근 새집증후군으로 잘 알져진 만큼 실내외 공기 중 어디에서나 출현 가능성이 높다. 이 알데하이드에 노출될 경우 심각한 독성을 일으키는데 이는 목, 코, 기관지 등의 호흡기관을 자극하고, 중추신경계에 마취작용을 일으키며, 마비, 호흡기 장애, 혼수상태를 유발하는 등의 직접적인 신체반응을 야기하고 있다. 따라서 환경측면이나 인체유해성 감지측면에서도 가스의 존재유무를 측정할 필요성이 발생한다.This acetaldehyde is well known as a sick house syndrome recently, so it is highly likely to appear in both indoor and outdoor air. Exposure to this aldehyde causes serious toxicity, which can cause direct body reactions such as irritating the respiratory tract of the neck, nose and bronchus, causing anesthesia to the central nervous system, causing paralysis, respiratory failure and lethargy. have. Therefore, the necessity of measuring the presence of gas also occurs in terms of environmental and human hazard detection.
본 발명은 전술한 요구에 부응하고자 안출된 것으로, WO3에 적절한 무게비의 SnO2을 첨가하여 센서물질을 형성함으로써, 휘발성 유기화합물 가스의 감지 감도를 향상시킬 수 있는 센서 및 그 제조방법을 제공하는 것을 목적으로 한다.SUMMARY OF THE INVENTION The present invention has been made to meet the above-described demands, and provides a sensor and a method of manufacturing the same, by adding a suitable weight ratio of SnO 2 to WO 3 to form a sensor material, thereby improving detection sensitivity of volatile organic compound gas. For the purpose of
게다가 금속촉매를 센서물질에 첨가하여 상기 가스에 대한 감도와 선택성을 향상시키는 센서 및 그 제조방법을 제공하는 것을 목적으로 한다.In addition, an object of the present invention is to provide a sensor and a method of manufacturing the same, which add a metal catalyst to the sensor material to improve the sensitivity and selectivity to the gas.
상기 과제를 해결하기 위해, 본 발명의 일측면에 따르면, VOCs 가스 센서에 있어서, 기판과, 상기 기판의 상면에 형성된 전극과, 상기 전극을 커버하며, WO3에 SnO2을 첨가하여 만들어진 센서물질로 형성된 감지막과, 상기 기판의 하면에 형성된 히터를 포함하는 WO3계 가스 센서를 제공한다.In order to solve the above problems, according to an aspect of the present invention, in the VOCs gas sensor, a substrate, an electrode formed on the upper surface of the substrate, the sensor material covering the electrode, made by adding SnO 2 to WO 3 It provides a WO 3- based gas sensor comprising a sensing film formed of a, and a heater formed on the lower surface of the substrate.
바람직하게는 상기 센서물질의 전체중량 대비, 상기 SnO2는 3 내지 10 중량% 범위를 가지며, 이처럼 금속 산화물(SnO2)을 첨가하여 안정성 증가 및 모물질의 입자성장을 억제함으로 인해 감도 특성을 증가시키게 할 수 있다.Preferably, the SnO 2 has a range of 3 to 10% by weight based on the total weight of the sensor material, and thus the sensitivity is increased by adding metal oxide (SnO 2 ) to increase stability and inhibit particle growth of the parent material. You can let
또한, 상기 감지물질에 Pd, In, Ru, Pt 중 어느 하나의 금속 촉매가 더 포함되며, 이를 통해 저 농도의 가스검출 및 선택성을 개선할 수 있게 한다.In addition, the sensing material further includes a metal catalyst of any one of Pd, In, Ru, and Pt, thereby improving gas detection and selectivity at low concentration.
바람직하게는 상기 센서물질의 전체중량 대비, 상기 금속 촉매는 1 중량% 이하의 범위를 가진다.Preferably, the metal catalyst has a range of 1% by weight or less based on the total weight of the sensor material.
본 발명의 다른 측면에 따르면, 기판의 상면에 전극을 형성하는 단계와, 상기 전극을 커버하며, WO3에 SnO2를 첨가하여 감지막을 형성하는 단계와, 상기 기판의 하면에 히터를 형성하는 단계를 구비하는 WO3계 가스 센서의 제조방법을 제공한다.According to another aspect of the invention, forming an electrode on the upper surface of the substrate, covering the electrode, forming a sensing film by adding SnO 2 to WO 3 , and forming a heater on the lower surface of the substrate It provides a method for producing a WO 3- based gas sensor having a.
또한, 상기 감지막 형성 단계에서, 전체 중량대비 상기 SnO2는 3 내지 10 중량% 범위에서 첨가되는 것을 특징으로 한다.In addition, in the sensing film forming step, the SnO 2 relative to the total weight is characterized in that added in the range of 3 to 10% by weight.
또한, 상기 감지막 형성 단계에서, Pd, In, Ru, Pt 중 어느 하나의 금속 촉매가 더 첨가되는데, 전체중량 대비 상기 금속 촉매는 1 중량% 이하의 범위에서 첨가되는 것이 바람직하다.In addition, in the sensing film forming step, any one of the metal catalyst of Pd, In, Ru, Pt is further added, the metal catalyst relative to the total weight is preferably added in the range of 1% by weight or less.
본 발명은 반도체식 가스 센서로서, WO3계 금속산화물을 센서물질로 이용하여 다음과 같은 효과를 가질 수 있다.The present invention can have the following effects by using the WO 3 metal oxide as a sensor material as a semiconductor gas sensor.
첫째, WO3계 후막 가스 센서는 금속 산화물(SnO2)을 첨가하여 안정성 증가 및 모물질의 입자성장을 억제함으로 인해 미량의 VOCs 가스에 대해 좋은 감도 특성을 가지게 한다.First, the WO 3 based thick film gas sensor adds metal oxides (SnO 2 ) to increase stability and to suppress particle growth of the parent material, thereby having good sensitivity characteristics for trace VOCs gas.
둘째, 상기 감지물질에 Pd, In, Ru, Pt 중 어느 하나의 금속 촉매가 더 첨가되어 저 농도의 가스검출 및 선택성을 개선할 수 있게 한다. 특히, 아세트알데하이드 가스에 대해 매우 좋은 선택성을 나타낸다.Second, a metal catalyst of any one of Pd, In, Ru, and Pt may be further added to the sensing material to improve gas detection and selectivity at low concentrations. In particular, it exhibits very good selectivity for acetaldehyde gas.
따라서, 본 발명에 따른 가스 센서는 환경오염 가스 측정에 널리 활용될 수 있어 환경 개선이나 인체유해성 가스 예방에 기여할 수 있다.Therefore, the gas sensor according to the present invention can be widely used for environmental pollutant gas measurement and can contribute to environmental improvement or human harmful gas prevention.
도 1은 본 발명에 따른 가스 센서의 WO3 나노분말을 제조하기 위한 과정을 나타낸 흐름도,1 is a flow chart showing a process for producing a WO 3 nano powder of a gas sensor according to the present invention,
도 2는 본 발명의 일실시예에 따른 SnO2/WO3센서(100)를 나타낸 도면으로, 각각 (a), (b), (c), (d)는 상기 센서의 단면, 전면, 배면, 스크린 프린팅 후의 전면을 나타낸 것이며,2 is a view showing a SnO 2 / WO 3 sensor 100 according to an embodiment of the present invention, (a), (b), (c), (d) is a cross-section, front, back of the sensor, respectively , Shows the front after screen printing,
도 3은 상기 알루미나 기판에 비교적 균일하게 후막이 도포된 후의 단면도를 나타낸 SEM 영상,3 is a SEM image showing a cross-sectional view after the thick film is applied to the alumina substrate relatively uniformly,
도 4는 가스 측정 장치의 구성도이고,4 is a configuration diagram of a gas measuring apparatus,
도 5는 소성온도에 따른 WO3의 XRD 패턴을 나타낸 그래프이고,5 is a graph showing the XRD pattern of WO 3 according to the firing temperature,
도 6은 소성온도에 따른 WO3에 금속산화물과 금속촉매를 첨가하였을 경우의 XRD 패턴을 나타낸 그래프이고,6 is a graph showing an XRD pattern when a metal oxide and a metal catalyst are added to WO 3 according to firing temperature;
도 7은 각각 (a)300℃, (b)500℃, (c)700℃, (d)900℃의 소성온도에 따른 WO3의 표면상태를 관찰한 SEM 영상이고,7 is a SEM image of the surface state of WO 3 according to the firing temperature of (a) 300 ℃, (b) 500 ℃, (c) 700 ℃, (d) 900 ℃, respectively,
도 8은 각각 (a)WO3, (b)WO3+SnO2, (c)WO3+Ru, (d)WO3+SnO2+Ru에서는 WO3에 금속산화물과 금속촉매를 첨가한 각 센서물질의 SEM 영상과 EDS 결과를 나타낸 도면이고,8 shows (a) WO 3 , (b) WO 3 + SnO 2 , (c) WO 3 + Ru, and (d) WO 3 + SnO 2 + Ru, respectively, in which metal oxides and metal catalysts are added to WO 3 . SEM image and EDS results of the sensor material,
도 9는 SnO2 첨가량에 따른 기공 분포(pore distribution)를 측정한 결과를 나타낸 그래프이고,9 is a graph showing the results of measuring pore distribution according to SnO 2 addition amount,
도 10은 소성온도에 따른 WO3의 작동온도별 100ppm의 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이고,10 is a graph showing the sensitivity characteristics of acetaldehyde gas of 100ppm by operating temperature of WO 3 according to the firing temperature,
도 11은 금속산화물(SnO2)과 금속촉매의 첨가에 따른 각각의 작동온도에서의 100ppm의 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이고,FIG. 11 is a graph showing sensitivity characteristics of 100 ppm acetaldehyde gas at each operating temperature according to addition of a metal oxide (SnO 2 ) and a metal catalyst.
도 12는 SnO2를 다양한 무게비로 첨가한 후 아세트알데하이드 가스의 감도특성을 나타낸 그래프이고,12 is a graph illustrating the sensitivity characteristics of acetaldehyde gas after adding SnO 2 at various weight ratios.
도 13은 금속촉매의 종류에 따른 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이고,13 is a graph showing sensitivity characteristics of acetaldehyde gas according to the type of metal catalyst,
도 14는 기판 위에 도포된 후막의 두께에 따른 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이고,14 is a graph showing the sensitivity characteristic of acetaldehyde gas according to the thickness of the thick film applied on the substrate,
도 15는 1중량% Ru / 5중량% SnO2/WO3센서물질을 이용하여 10ppm 이하의 저 농도에서 아세트알데하이드 가스에 대한 감도를 측정한 그래프이고,15 is a graph measuring the sensitivity to acetaldehyde gas at a low concentration of less than 10ppm using 1% by weight Ru / 5% by weight SnO 2 / WO 3 sensor material,
도 16은 1중량% Ru/ 5중량% SnO2/WO3센서물질을 이용하여 다양한 VOCs 가스에 대한 선택성을 조사한 그래프이고,FIG. 16 is a graph illustrating selectivity of various VOCs gases using 1 wt% Ru / 5 wt% SnO 2 / WO 3 sensor material; FIG.
도 17은 아세트알데하이드 가스와 다른 VOCs 가스들의 반응회복특성을 나타낸 그래프이다.17 is a graph showing reaction recovery characteristics of acetaldehyde gas and other VOCs gases.
이하에서 첨부된 도면을 참조하여 본 발명의 바람직한 실시예를 설명한다.Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.
< 센서물질의 제조 ><Preparation of Sensor Material>
본 발명에 따른 가스 센서에서, 센서 물질은 금속 산화물 반도체로서, WO3을 기본물질로 하고 다른 금속산화물(SnO2)과 다양한 금속촉매의 혼합비를 달리하여 가스감지용 센서 물질을 제조한다.In the gas sensor according to the present invention, the sensor material is a metal oxide semiconductor, and WO 3 is used as a base material, and a sensor material for gas sensing is manufactured by varying the mixing ratio of other metal oxides (SnO 2 ) and various metal catalysts.
본 발명에서는 아세트알데하이드(Acetaldehyde)의 감지물질로서 졸-겔(sol-gel)법으로 합성한 WO3를 사용하였다. 도 1은 WO3 나노분말을 제조하기 위한 개략도이다. 에틸알코올(ethyl alcohol)(aldrich) 0.1L 용액에 WCl6 0.01mol을 혼합한 후 70℃에서 36시간 동안 교반하여 완전히 용해시켜 균질한 W(OC2H5)6 졸(sol)을 제조하였다. 이 W(OC2H5)6 sol에 NH4OH의 수용액을 pH 5 이하에서 적정하여 W(OH)6 겔(gel) 분말을 석출하였다. 세척은 잔류 Cl-이온를 제거하기 위해 NH3NO3 수용액과 증류수 및 에탄올을 이용하였다. 그리고 잔류 Cl-이온의 존재 유무는 AgNO3 용액을 사용하여 은거울반응의 유무를 통해 확인하였다. 세척된 침전물은 100℃에서 12시간 동안 건조하고 소성과정을 거쳐 WO3 나노 분말을 제조하였다. 또한, 센서 물질의 전기적 특성의 안정화를 위하여 SnO2를 다양한 조성비율로 증류수에 혼합한 후 자기교반기로 교반하면서 주 물질인 WO3에 첨가하였다.In the present invention, WO 3 synthesized by the sol-gel method was used as a detection material of acetaldehyde. 1 is a schematic diagram for preparing a WO 3 nanopowder. WCl 6 0.01mol in 0.1L ethyl alcohol (aldrich) solution was mixed and stirred for 36 hours at 70 ℃ completely dissolved to prepare a homogeneous W (OC 2 H 5 ) 6 sol (sol). An aqueous solution of NH 4 OH was titrated to this W (OC 2 H 5 ) 6 sol at a pH of 5 or less to precipitate W (OH) 6 gel powder. Washing was performed using NH 3 NO 3 aqueous solution, distilled water and ethanol to remove residual Cl − ions. The presence of residual Cl - ions was confirmed by the presence or absence of silver mirror reaction using AgNO 3 solution. The washed precipitate was dried at 100 ° C. for 12 hours and calcined to produce WO 3 nanopowder. In addition, in order to stabilize the electrical properties of the sensor material, SnO 2 was mixed with distilled water at various composition ratios and then added to WO 3 , the main material, while stirring with a magnetic stirrer.
가스센서의 기본적인 조건인 감도와 선택성을 향상시키기 위하여 금속촉매를 함침법으로 첨가하였으며, 그 방법을 도 1에 나타내었다. 함침법의 경우 전이금속인 Pd와 Pt, Ru, In을 1~5wt% 무게비가 되도록 칭량한 후 비이커에 넣고 염산 1ml를 첨가하여 금속촉매를 완전히 녹인 후 증류수를 첨가하여 균일 용액을 제조하였다. WO3분말이나 SnO2/WO3분말을 첨가하여 금속촉매를 함침시킨 후 자기교반기로 교반하면서 서서히 가열하여 금속촉매가 담지된 WO3분말이나 SnO2/WO3분말을 제조하였다. 얻은 물질을 100℃에서 12시간 건조하고 500℃에서 2시간 소성시킨 후 분말을 분쇄하여 센서물질을 얻었다.In order to improve sensitivity and selectivity, which are basic conditions of the gas sensor, a metal catalyst was added by impregnation, and the method is shown in FIG. 1. In the case of impregnation, Pd, Pt, Ru and In, which are transition metals, were weighed to a weight ratio of 1 to 5 wt%, and then placed in a beaker, 1 ml of hydrochloric acid was added to completely dissolve the metal catalyst, and then a uniform solution was prepared. WO 3 powder or SnO 2 / WO 3 powder was added to impregnate the metal catalyst, and then slowly heated while stirring with a magnetic stirrer to prepare WO 3 powder or SnO 2 / WO 3 powder supported with the metal catalyst. The obtained material was dried at 100 ° C. for 12 hours, calcined at 500 ° C. for 2 hours, and then ground to obtain a sensor material.
<후막 센서의 제작 및 구조>Fabrication and Structure of Thick Film Sensor
도 2는 본 발명의 일실시예에 따른 SnO2/WO3센서(100)를 나타낸 도면으로, 각각 (a), (b), (c), (d)는 상기 센서의 단면, 전면, 배면, 스크린 프린팅 후의 전면을 나타낸다.2 is a view showing a SnO 2 / WO 3 sensor 100 according to an embodiment of the present invention, (a), (b), (c), (d) is a cross-section, front, back of the sensor, respectively , Front side after screen printing.
상기 센서(100)는, 본 발명에 의한 센서 물질을 이용하여 만들어지는데, 기판(10)으로 알루미나(Al2O3) 기판이 사용될 수 있고, 상기 기판(10)의 상면에는 서로 대향하는 한 쌍의 빗살형{IDT(interdigit)형}의 백금(Pt) 전극(20)을 형성하고, 하면에는 니켈-크롬(Ni-Cr)으로 만들어진 히터(40)가 형성된다. 미부호 50는 절연체이다.The sensor 100 is made by using the sensor material according to the present invention, and an alumina (Al 2 O 3 ) substrate may be used as the substrate 10, and a pair of upper surfaces of the substrate 10 facing each other. A comb-tooth-like (IDT (interdigit) type) platinum (Pt) electrode 20 is formed, and a heater 40 made of nickel-chromium (Ni-Cr) is formed on the lower surface. Reference numeral 50 is an insulator.
또한, 기판(10)은 상기 알루미나 이외에 SiO2 등의 기판이 사용될 수 있으며, 상기 센서(100)에 사용되는 센서 물질은, 상기 한 쌍의 빗살형 전극(20)의 빗살부분을 덮으며 감지막(30)으로 형성할 수 있다. 상기 센서 물질을 후막으로 도포하기 전 기판 위의 오염물질을 제거하기 위해 아세톤을 이용한 세척과정과 300℃에서 열처리 과정을 거쳤다. 위의 과정을 거친 후, 센서 물질 페이스트(paste)를 기판 위에 스크린 인쇄법(screen printing)으로 20㎛의 두께로 후막을 형성할 수 있다. 이후 형성된 후막 소자는 상온에서 24시간 건조하고 대류 건조기에서 5℃/10min로 승온하여 110℃에서 12시간 건조 후 500℃에서 1시간 동안 열처리한다. 이때, 감지막을 형성하는 방법은 전술한 스크린 인쇄법 이외에 플라즈마 증착을 통한 감지막 형성 등 다양한 감지막 증착 방법이 사용될 수 있다.In addition, the substrate 10 may be a substrate such as SiO 2 in addition to the alumina, and the sensor material used for the sensor 100 covers the comb portion of the pair of comb-shaped electrodes 20 and includes a sensing layer. 30 can be formed. In order to remove the contaminants on the substrate before applying the sensor material to the thick film, a cleaning process using acetone and heat treatment at 300 ° C. were performed. After the above process, the sensor material paste may be formed on the substrate by screen printing to form a thick film having a thickness of 20 μm. Thereafter, the formed thick film device was dried at room temperature for 24 hours, heated to 5 ° C./10 min in a convection dryer, and dried at 110 ° C. for 12 hours, followed by heat treatment at 500 ° C. for 1 hour. In this case, in addition to the screen printing method described above, various methods of forming the sensing film may include various sensing film deposition methods such as forming a sensing film through plasma deposition.
도 3은 상기 알루미나 기판에 비교적 균일하게 후막이 도포된 후의 단면도를 나타낸 SEM 영상이다.3 is a SEM image showing a cross-sectional view after the thick film is applied to the alumina substrate relatively uniformly.
위와 같이 만들어진 SnO2/WO3 센서(100)의 특성을 파악하기 위해 도 4와 같은 가스 측정 장치를 구성하였다.In order to determine the characteristics of the SnO 2 / WO 3 sensor 100 made as described above was configured a gas measuring device as shown in FIG.
상기 가스센서를 10L(250mm×200mm×200mm) 용량의 용기(chamber)에서 지면으로부터 50mm의 간격을 두고 고정시키고 센서의 작동온도를 200~400℃로 변화시켜가며 감도를 측정하였다. 소자 내부에 있는 전자를 없애기 위해 측정온도와 동일한 온도에서 12시간 동안 안정화 처리를 하였으며, 이 용기 내에 진공 펌프(vacuum pump)를 통해 감지 가스를 주입하고, 팬(fan)을 동작시킨 후 평형농도에 도달될 때 멀티미터(multimeter)로 저항 변화를 측정하였다. 센서의 감도는 공기 중에서의 전기저항값(Ra)에 대한 감지가스 주입 후 전기저항값(Rg)의 비(Ra/Rg)로 정의하였다. 여기서, 본 가스센서는 VOCs 흡착가스에 의한 전기적 저항 변화를 이용하였으며, 아세트알데하이드(acetaldehyde) 가스에 대한 측정을 예로 들었으나, 이에 한정되는 것은 아니며, 포름알데하이드 등 휘발성 유기화합물에 주 대상이다.The gas sensor was fixed at a distance of 50 mm from the ground in a chamber of 10 L (250 mm × 200 mm × 200 mm) capacity, and the sensitivity was measured while changing the operating temperature of the sensor to 200 to 400 ° C. In order to remove the electrons inside the device, a stabilization treatment was performed for 12 hours at the same temperature as the measurement temperature.The sensing gas was injected into the vessel through a vacuum pump, the fan was operated, When reached, the resistance change was measured with a multimeter. The sensitivity of the sensor was defined as the ratio (Ra / Rg) of the electrical resistance value Rg after injection of the sensing gas to the electrical resistance value Ra in the air. Here, the gas sensor uses a change in electrical resistance caused by VOCs adsorption gas, and the measurement of acetaldehyde gas, but is not limited thereto, and is mainly targeted to volatile organic compounds such as formaldehyde.
아래의 식은 상기 센서의 감도(Sensitivity, S)로 측정가스가 주입 전인 공기 중의 저항값(Ra)과 감지 가스 주입 후의 저항값(Rg)의 변화율(%)로 계산하였고,주입 후 10분간의 감도 중 가장 높은 값을 센서의 감도로 계산하였다.The following equation was calculated as the sensitivity (R) of the sensor and the rate of change (%) of the resistance value (R a ) in the air before injection of the measurement gas and the resistance value (R g ) after injection of the sensing gas, and 10 minutes after injection. The highest value of was calculated as the sensitivity of the sensor.
[수학식][Equation]
Figure PCTKR2009001032-appb-I000001
Figure PCTKR2009001032-appb-I000001
<센서 물질의 특성 분석><Sensor Characterization of Sensor Materials>
본 발명은 주 물질인 WO3 분말 및 금속산화물과 금속촉매의 혼합비를 달리하여 가스감지용 센서 물질을 제조하는데, 전술한 감도 계산식(수학식1)을 이용하여 감도를 측정하고 제조된 각 센서물질의 결정화 상태, 상 확인, 표면상태, 원소분석, 비표면적을 측정하기 위해 XRD, SEM/EDS, BET 분석기를 이용하는데, 이하에서 센서 물질의 특성을 분석한다.The present invention is to produce a gas sensing sensor material by varying the mixing ratio of the main material WO 3 powder and metal oxide and metal catalyst, each sensor material measured by measuring the sensitivity using the above sensitivity calculation formula (Equation 1) XRD, SEM / EDS, and BET analyzers are used to measure the crystallization state, phase identification, surface state, elemental analysis, and specific surface area of.
우선 소성온도에 따른 WO3의 XRD 패턴과 WO3에 금속산화물과 금속촉매를 첨가하였을 경우의 XRD 패턴을 각각 도 5와 도 6에서 나타내었다.First it shows the XRD pattern when XRD pattern of WO 3 in accordance with the firing temperature and the WO 3 was added to the metal oxide and the metal catalyst in FIGS. 5 and 6, respectively.
도 5를 참조하면, 소성온도가 증가할수록 WO3의 결정성을 나타내는 피크의 강도(intensity)가 증가하는 것으로 보아 소성온도가 증가할수록 결정성이 증가하는 것을 확인할 수 있다. 이 결과를 표준자료인 JCPDS의 WO3의 여러 값들과 일치성을 비교한 결과, WO3가 가지고 있는 3개의 구조 중 사방정계(Orthorhombic) 구조와 일치함을 알 수 있다.Referring to FIG. 5, it can be seen that as the firing temperature increases, the intensity of the peak representing the crystallinity of WO 3 increases, so that the crystallinity increases as the firing temperature increases. As a result of comparing the results with the various values of WO 3 of the JCPDS standard data, it can be seen that the three structures of WO 3 are consistent with the Orthorhombic structure.
도 6을 참조하면, 금속촉매와 금속산화물을 첨가함에 따라 특정 2θ 값에서 새로운 피크가 형성되는 것을 확인할 수 있다.Referring to FIG. 6, it can be seen that as the metal catalyst and the metal oxide are added, a new peak is formed at a specific 2θ value.
소성온도에 따른 WO3의 표면상태를 SEM으로 관찰한 것을 도 7의 (a)300℃, (b)500℃, (c)700℃, (d)900℃에 나타내었다. 도 7을 참조하면, 소성온도가 증가할수록 WO3 입자가 성장하는 것을 SEM 영상을 통해 확인할 수 있다.SEM observation of the surface state of WO 3 according to the firing temperature is shown in (a) 300 ° C., (b) 500 ° C., (c) 700 ° C., and (d) 900 ° C. of FIG. 7. Referring to FIG. 7, it can be confirmed through SEM images that the WO 3 particles grow as the firing temperature increases.
도 8의 (a)WO3, (b)WO3+SnO2, (c)WO3+Ru, (d)WO3+SnO2+Ru에서는 WO3에 금속산화물과 금속촉매를 첨가한 각 센서물질의 SEM 영상과 EDS 결과를 나타내었다. 도 8의 (a), (b), (c), (d)를 참조하면, SEM 영상을 통해 각 센서물질의 표면상태를 확인할 수 있고, EDS 결과로부터 각 센서물질별 성분 원소의 피크가 나타나는 것을 확인할 수 있다.(A) WO 3 , (b) WO 3 + SnO 2 , (c) WO 3 + Ru, (d) WO 3 + SnO 2 + Ru, each sensor added with a metal oxide and a metal catalyst to WO 3 is shown in FIG. 8. SEM images of the material and EDS results are shown. Referring to (a), (b), (c), and (d) of FIG. 8, the surface state of each sensor material can be confirmed through SEM images, and peaks of component elements of each sensor material appear from EDS results. You can see that.
도 9는 SnO2 첨가량에 따른 기공 분포(pore distribution)를 측정한 결과를 나타낸 그래프이다.9 is a graph showing the results of measuring pore distribution according to the amount of SnO 2 added.
도 9을 참조하면, SnO2 를 5wt.% 첨가하였을 경우, 다른 센서물질들보다 비교적 균일한 기공 분포(pore distribution)을 보이는 것을 확인할 수 있다.Referring to FIG. 9, when 5 wt.% Of SnO 2 is added, it can be seen that the pore distribution is relatively uniform than that of other sensor materials.
표 1에는 SnO2 첨가량에 따른 각 센서물질별 비표면적을 측정한 결과를 나타내었다. 앞선 연구에서 비교적 균일한 기공 분포를 나타내었던 5wt.% SnO2를 첨가한 센서물질이 비표면적에서도 14.83m2/g으로 가장 큰 것으로 나타났다. 이는 WO3에 SnO2가 첨가됨에 따라 입자의 성장을 억제하여 비표면적의 증가를 초래함으로 인해 감도향상에 기여한 것이라고 사료된다.Table 1 shows the results of measuring the specific surface area of each sensor material according to the amount of SnO 2 added. In the previous studies, the sensor material added with 5wt.% SnO 2 , which showed relatively uniform pore distribution, was the largest at 14.83m 2 / g at the specific surface area. This is believed to contribute to the improvement of sensitivity by inhibiting the growth of particles as SnO 2 is added to WO 3 , leading to an increase in specific surface area.
Figure PCTKR2009001032-appb-I000002
Figure PCTKR2009001032-appb-I000002
< 센서물질에 대한 온도효과 ><Temperature Effect on Sensor Material>
도 10은 소성온도에 따른 WO3의 작동온도별 100ppm의 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이다. 도 10을 참조하면, 500℃로 소성한 WO3가 350℃에서 가장 좋은 감도를 가지는 것을 확인할 수 있다.10 is a graph showing the sensitivity characteristics of acetaldehyde gas of 100ppm by operating temperature of WO 3 according to the firing temperature. Referring to FIG. 10, it can be seen that WO 3 fired at 500 ° C. has the best sensitivity at 350 ° C. FIG.
도 11은 금속산화물(SnO2)과 금속촉매의 첨가에 따른 각각의 작동온도에서의 100ppm의 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이다.FIG. 11 is a graph showing sensitivity characteristics of 100 ppm acetaldehyde gas at each operating temperature according to addition of a metal oxide (SnO 2 ) and a metal catalyst.
도 11을 참조하면, WO3 단일물질일 경우에는 350℃에서 가장 좋은 감도를 나타냈으나, WO3에 SnO2와 Ru를 첨가하였을 경우에는 300℃에서 가장 좋은 감도를 가지는 것을 확인할 수 있다. 이것은 금속산화물의 양과 촉매금속의 종류에 따라 활성화 에너지가 적당한 온도에서 빠르게 변화하기 때문이다. 따라서 이후의 실험에서는 작동온도를 300℃로 고정하고 실험을 하였다. 300℃ 이상의 고온에서는 감도가 다시 낮아지는 특성을 보이는데 Mcaleer 등의 보고에 의하면 온도가 상승하면 소자표면의 활성이 증가하여 감도가 증가하다가 임계온도 이상이 되면 환원성 가스에 의한 산소 흡착종의 탈착과 공기로부터의 산소 흡착종의 재흡착이 대단히 신속하게 일어나서 가스가 소자의 표면에서 모두 반응하여 차단함으로써 소자내로 가스가 침투하지 못하게 되어 감도가 저하된다고 보고하였다.Referring to FIG. 11, in the case of the single material WO 3 , the best sensitivity was shown at 350 ° C., but when SnO 2 and Ru were added to WO 3 , the best sensitivity was found at 300 ° C. FIG. This is because the activation energy changes rapidly at an appropriate temperature depending on the amount of metal oxide and the type of catalytic metal. Therefore, in the subsequent experiments, the experiment was performed with the operating temperature fixed at 300 ° C. Sensitivity decreases again at high temperatures above 300 ℃. According to the report of Mcaleer et al., When the temperature rises, the activity of the surface of the device increases and the sensitivity increases. The resorption of oxygen-adsorbed species from the sapphire occurred very quickly and the gas reacted and blocked at the surface of the device, preventing the gas from penetrating into the device and reducing the sensitivity.
< SnO2의 첨가량에 따른 WO3의 가스 감지 특성 ><Gas Sensing Characteristics of WO 3 with Addition of SnO 2 >
도 12는 가스센서의 필수 요건 중의 하나인 안정성 향상을 위해 SnO2를 다양한 무게비로 첨가한 후 아세트알데하이드 가스의 감도특성을 나타낸 그래프이다.12 is a graph illustrating the sensitivity characteristics of acetaldehyde gas after adding SnO 2 at various weight ratios to improve stability, which is one of essential requirements of a gas sensor.
도 12를 참조하면, SnO2를 첨가하였을 경우 농도증가에 따라 감도가 증가하는 것을 확인할 수 있으며, 5wt.% SnO2를 첨가하였을 경우 감도가 가장 우수한 것을 확인할 수 있다. 이는 도 9에서 가장 좋은 기공분포와 비표면적을 나타내었던 센서물질과 일치하는 것으로 보아 비교적 균일한 기공분포와 비표면적 증가에 따른 물성이 가스감도에 영향을 미치는 것으로 생각된다.Referring to FIG. 12, when SnO 2 is added, the sensitivity increases with increasing concentration, and when 5wt.% SnO 2 is added, the sensitivity is the best. This is consistent with the sensor material exhibiting the best pore distribution and specific surface area in FIG. 9, which is thought to have a relatively uniform pore distribution and physical properties due to an increase in specific surface area.
<다양한 금속촉매의 첨가에 따른 가스감응 특성><Gas Sensitization Characteristics by Addition of Various Metal Catalysts>
아세트알데하이드 가스에 대한 감도와 선택성을 높이기 위하여 금속촉매를 센서물질에 첨가하였다. 금속산화물에 금속촉매를 혼합하였을 때 전자의 수수가 원활하게 됨으로써 증가된 양의 흡착종들은 흡탈착현상에 관여하게 되어 전기전도도의 변화를 증가시킨다. 이러한 촉매작용의 효과를 높이기 위해서는 가스에 대한 촉매의 접촉면적을 크게 함으로써 감도와 선택성 및 동작온도에 영향을 주는 것으로 판단된다.In order to increase the sensitivity and selectivity to acetaldehyde gas, a metal catalyst was added to the sensor material. When the metal catalyst is mixed with the metal oxide, the electrons are smoothly transferred, so that the increased amount of the adsorbed species is involved in the adsorption and desorption phenomenon, thereby increasing the change in the electrical conductivity. In order to increase the effect of such a catalysis, the contact area of the catalyst with the gas is increased to affect the sensitivity, the selectivity, and the operating temperature.
도 13은 금속촉매의 종류에 따른 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이다. FIG. 13 is a graph showing sensitivity characteristics of acetaldehyde gas according to the type of metal catalyst. FIG.
도 13을 참조하면, 5중량%를 갖는 SnO2/WO3를 기본센서물질로 하여 다양한 금속촉매를 첨가하였는데, 도 13에 나타낸 바와 같이, 1중량% Ru를 첨가한 센서물질이 다른 금속촉매들보다 감도가 더 좋은 것을 알 수 있다. 이는 1wt중량 Ru + 5중량% SnO2/WO3의 센서물질이 아세트알데하이드 가스를 다른 센서물질에 비해 빠른 속도로 산화시키면서, 좋은 선택성을 보인다는 것을 나타낸다. 그리고 금속촉매를 1중량%를 첨가한 이유는 Ru의 함량이 0~1중량% 함량에서는 아세트알데하이드 가스에 대해 감도가 증가하지만, 1중량% 이상의 함량에서는 감도가 거의 증가하지 않는 것으로 나타났다. 이는 1중량% 이상 첨가되면 Ru 입자들이 서로 뭉쳐져 표면에 고르게 확산이 되지 못하고 그로 인해 비표면적의 감소를 가져올 뿐만 아니라 감도저하에도 영향을 미치는 것으로 생각된다.Referring to FIG. 13, various metal catalysts were added using SnO 2 / WO 3 having 5% by weight as a basic sensor material. As shown in FIG. 13, the metal materials of the sensor material added with 1% by weight of Ru were different. You can see that the sensitivity is better than. This indicates that the sensor material of 1 wt weight Ru + 5 weight% SnO 2 / WO 3 shows good selectivity while oxidizing acetaldehyde gas at a faster rate than other sensor materials. The reason why 1 wt% of the metal catalyst was added was that the sensitivity of the acetaldehyde gas was increased in the Ru content of 0-1 wt%, but the sensitivity was hardly increased in the content of 1 wt% or more. It is thought that when more than 1% by weight of Ru particles are agglomerated with each other, the particles are not evenly diffused on the surface, thereby reducing the specific surface area and affecting the sensitivity.
<후막두께에 따른 가스 감응특성><Gas Response Characteristics According to Thick Film Thickness>
도 14는 기판 위에 도포된 후막의 두께에 따른 아세트알데하이드 가스에 대한 감도특성을 나타낸 그래프이다. 도 14를 참조하면, 후막의 두께가 증가할수록 감도는 감소하는 것을 확인할 수 있으며, 20μm일 경우 가장 좋은 감도를 나타낸다.14 is a graph showing the sensitivity characteristic of acetaldehyde gas according to the thickness of the thick film coated on the substrate. Referring to FIG. 14, it can be seen that the sensitivity decreases as the thickness of the thick film increases, and the best sensitivity is shown at 20 μm.
<저농도에서의 가스감도 특성><Gas Sensitivity Characteristics at Low Concentration>
도 15는 1중량% Ru / 5중량% SnO2/WO3센서물질을 이용하여 10ppm 이하의 저 농도에서 아세트알데하이드 가스에 대한 감도를 측정한 그래프이다.Figure 15 is a graph measuring the sensitivity to acetaldehyde gas at a low concentration of less than 10ppm using 1% by weight Ru / 5% by weight SnO 2 / WO 3 sensor material.
도 15를 참조하면, 저 농도에서도 거의 직선성으로 좋은 감도의 증가를 보이는 것을 확인할 수 있다. 삽입된 그림에서는 아세트알데하이드 가스의 넓은 농도 범위(1~1000ppm)에서도 비교적 고른 직선성의 감도의 증가를 보이는 것을 확인할 수 있다.Referring to FIG. 15, it can be seen that even at low concentrations, a good increase in sensitivity is almost linear. In the inserted picture, it can be seen that the sensitivity of linearity is relatively increased even in a wide concentration range of acetaldehyde gas (1 to 1000 ppm).
<센서물질에 따른 TMA 가스의 선택성 및 반응회복특성 ><Selectivity and Reaction Recovery Characteristics of TMA Gas According to Sensor Material>
도 16은 1중량% Ru/ 5중량% SnO2/WO3센서물질을 이용하여 다양한 VOCs 가스에 대한 선택성을 조사한 그래프이다.FIG. 16 is a graph illustrating the selectivity for various VOCs gases using 1 wt% Ru / 5 wt% SnO 2 / WO 3 sensor material.
도 16을 참조하면, 1중량% Ru/ 5중량% SnO2/WO3센서를 작동온도 300℃에서 100ppm의 다양한 가스에 대해 감도를 측정한 결과 다른 가스들의 감도보다 아세트알데하이드 가스에 대한 감도가 월등히 좋은 것을 확인할 수 있다. 따라서, 이 센서는 아세트알데하이드 가스에 대한 선택성이 매우 우수하다는 것을 알 수 있다. 이는 1중량% Ru/ 5중량% SnO2/WO3일 경우가 다른 VOCs 가스보다 아세트알데하이드 가스를 잘 분해시키고 반응을 활성화시켜 선택성을 향상시키는 것으로 생각된다.Referring to FIG. 16, the sensitivity of the 1 wt% Ru / 5 wt% SnO 2 / WO 3 sensor was measured for 100 ppm of various gases at an operating temperature of 300 ° C., and thus the sensitivity of acetaldehyde gas was much higher than that of other gases. You can see good. Thus, it can be seen that this sensor has a very good selectivity to acetaldehyde gas. It is thought that 1 wt% Ru / 5 wt% SnO 2 / WO 3 decomposes acetaldehyde gas better than other VOCs gases and activates the reaction to improve selectivity.
도 17은 아세트알데하이드 가스와 다른 VOCs 가스들의 반응회복특성을 나타낸 그래프이다.17 is a graph showing reaction recovery characteristics of acetaldehyde gas and other VOCs gases.
여기서, 회복특성은 실험의 빠른 진행을 위해 강제배기를 시킨 결과인데, 도 17을 참조하면, 다른 VOCs 가스들보다 아세트알데하이드 가스의 반응회복특성이 가장 좋은 것을 확인할 수 있다.Here, the recovery characteristics are the result of forced exhaust for rapid progress of the experiment. Referring to FIG. 17, it can be seen that the reaction recovery characteristics of acetaldehyde gas are better than those of other VOCs gases.
이상에서 살펴본 바와 같이, 본 발명에 따른 WO3 계 가스 센서는 WO3를 기본물질로 하고 금속산화물(SnO2)과 다양한 촉매금속을 첨가한 센서물질로서, 아세트알데하이드 가스 검출에 우수한 특성을 가짐을 확인할 수 있다. 특히, 아세트알데하이드 가스의 감지를 위해서는, 작동온도는 300℃이고, 후막 두께는 20μm이고, 바인더는 에틸렌 글리콜(ethylene glycol), 구성은 1중량% Ru + 5중량% SnO2 + WO3 형태를 가질 경우, 가장 최적의 감도 및 선택성 그리고 회복반응특성을 보임을 확인할 수 있다.As described above, the WO 3 gas sensor according to the present invention is a sensor material in which WO 3 is used as a base material and metal oxide (SnO 2 ) and various catalytic metals are added, and has excellent characteristics in acetaldehyde gas detection. You can check it. In particular, for the detection of acetaldehyde gas, the operating temperature is 300 ℃, the thick film thickness is 20μm, the binder is ethylene glycol (ethylene glycol), the composition has a form of 1% by weight Ru + 5% by weight SnO 2 + WO 3 In this case, it can be seen that the most optimal sensitivity and selectivity and recovery response characteristics are shown.
본 발명은 WO3계 금속산화물을 센서물질로 이용하여 반도체식 가스센서로 활용할 수 있다. 특히, 미량의 VOCs 가스에 대해 좋은 감도 특성을 가지므로 환경오염 가스 측정에 널리 활용될 수 있어 환경 개선 관련 산업, 인체유해성 가스 예방 등의 재난 관련 산업, 또는 의료 관련 산업의 발전에 기여할 수 있다.The present invention can be utilized as a semiconductor gas sensor using the WO 3 metal oxide as a sensor material. In particular, since it has good sensitivity characteristics for trace VOCs gas, it can be widely used for environmental pollutant gas measurement, which can contribute to the development of environmental related industries, disaster related industries such as prevention of harmful gases, or medical related industries.

Claims (8)

  1. VOCs 가스 센서에 있어서,In the VOCs gas sensor,
    기판과;A substrate;
    상기 기판의 상면에 형성된 전극과;An electrode formed on an upper surface of the substrate;
    상기 전극을 커버하며, WO3에 SnO2을 첨가하여 만들어진 센서물질로 형성된 감지막과;A sensing film covering the electrode and formed of a sensor material made by adding SnO 2 to WO 3 ;
    상기 기판의 하면에 형성된 히터;A heater formed on the bottom surface of the substrate;
    를 포함하는 것을 특징으로 하는 WO3계 가스 센서.WO 3- based gas sensor comprising a.
  2. 제1항에 있어서,The method of claim 1,
    상기 센서물질의 전체중량 대비, 상기 SnO2는 3 내지 10 중량% 범위를 갖는 것을 특징으로 하는 WO3계 가스 센서.WO 3 based gas sensor, characterized in that the SnO 2 relative to the total weight of the sensor material has a range of 3 to 10% by weight.
  3. 제1항에 있어서,The method of claim 1,
    상기 감지물질에 Pd, In, Ru, Pt 중 어느 하나의 금속 촉매가 더 포함되는 것을 특징으로 하는 WO3계 가스 센서.WO 3 -based gas sensor, characterized in that the sensing material further comprises a metal catalyst of any one of Pd, In, Ru, Pt.
  4. 제3항에 있어서,The method of claim 3,
    상기 센서물질의 전체중량 대비, 상기 금속 촉매는 1 중량% 이하의 범위를 갖는 것을 특징으로 하는 WO3계 가스 센서.WO 3 based gas sensor, characterized in that the metal catalyst has a range of less than 1% by weight based on the total weight of the sensor material.
  5. 기판의 상면에 전극을 형성하는 단계와;Forming an electrode on the upper surface of the substrate;
    상기 전극을 커버하며, WO3에 SnO2를 첨가하여 감지막을 형성하는 단계와;Covering the electrode and forming a sensing film by adding SnO 2 to WO 3 ;
    상기 기판의 하면에 히터를 형성하는 단계;Forming a heater on a bottom surface of the substrate;
    를 포함하는 것을 특징으로 하는 WO3 가스 센서의 제조방법.WO 3 gas sensor manufacturing method comprising a.
  6. 제5항에 있어서,The method of claim 5,
    상기 감지막 형성 단계에서, 전체 중량대비 상기 SnO2는 3 내지 10 중량% 범위에서 첨가되는 것을 특징으로 하는 WO3계 가스 센서의 제조방법.In the sensing film forming step, the SnO 2 to the total weight of the manufacturing method of the WO 3- based gas sensor, characterized in that added in the range of 3 to 10% by weight.
  7. 제5항에 있어서,The method of claim 5,
    상기 감지막 형성 단계에서, Pd, In, Ru, Pt 중 어느 하나의 금속 촉매가 더 첨가되는 것을 특징으로 하는 WO3계 가스 센서의 제조방법.In the sense film-forming step, Pd, In, Ru, WO 3 based method of manufacturing a gas sensor characterized in that one of the metal catalyst is further added of Pt.
  8. 제7항에 있어서,The method of claim 7, wherein
    상기 감지막 형성 단계에서, 전체중량 대비 상기 금속 촉매는 1 중량% 이하의 범위에서 첨가되는 것을 특징으로 하는 WO3계 가스 센서의 제조방법.In the sensing film forming step, the metal catalyst to the total weight of the manufacturing method of the WO 3- based gas sensor, characterized in that added in the range of 1% by weight or less.
PCT/KR2009/001032 2008-04-22 2009-03-03 A tungsten trioxide (wo3)-based gas sensor for sensing gaseous volatile organic compounds, and a production method therefor WO2009131306A1 (en)

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