WO2006136641A1 - Humidity sensor device based on iron oxide nanoparticles that are supported on sepiolite, production method thereof and applications of same - Google Patents

Humidity sensor device based on iron oxide nanoparticles that are supported on sepiolite, production method thereof and applications of same Download PDF

Info

Publication number
WO2006136641A1
WO2006136641A1 PCT/ES2006/070086 ES2006070086W WO2006136641A1 WO 2006136641 A1 WO2006136641 A1 WO 2006136641A1 ES 2006070086 W ES2006070086 W ES 2006070086W WO 2006136641 A1 WO2006136641 A1 WO 2006136641A1
Authority
WO
WIPO (PCT)
Prior art keywords
iron oxide
sensor device
tablet
humidity sensor
sepiolite
Prior art date
Application number
PCT/ES2006/070086
Other languages
Spanish (es)
French (fr)
Inventor
José Serafín MOYA CORRAL
Antonio Esteban Cubillo
Carlos PECHARROMAN GARCÍA
Laura Montanaro
Jean Marc TULLÍAN
Alfredo Negro
Original Assignee
Consejo Superior De Investigaciones Científicas
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Consejo Superior De Investigaciones Científicas filed Critical Consejo Superior De Investigaciones Científicas
Publication of WO2006136641A1 publication Critical patent/WO2006136641A1/en

Links

Classifications

    • 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
    • G01N27/121—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 for determining moisture content, e.g. humidity, of the fluid
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B38/00—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof
    • C04B38/08—Porous mortars, concrete, artificial stone or ceramic ware; Preparation thereof by adding porous substances
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/628—Coating the powders or the macroscopic reinforcing agents
    • C04B35/62844—Coating fibres
    • C04B35/62847—Coating fibres with oxide ceramics
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/622—Forming processes; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/626—Preparing or treating the powders individually or as batches ; preparing or treating macroscopic reinforcing agents for ceramic products, e.g. fibres; mechanical aspects section B
    • C04B35/628—Coating the powders or the macroscopic reinforcing agents
    • C04B35/62892—Coating the powders or the macroscopic reinforcing agents with a coating layer consisting of particles
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/71—Ceramic products containing macroscopic reinforcing agents
    • C04B35/78—Ceramic products containing macroscopic reinforcing agents containing non-metallic materials
    • C04B35/80—Fibres, filaments, whiskers, platelets, or the like
    • 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
    • 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
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/30—Constituents and secondary phases not being of a fibrous nature
    • C04B2235/32—Metal oxides, mixed metal oxides, or oxide-forming salts thereof, e.g. carbonates, nitrates, (oxy)hydroxides, chlorides
    • C04B2235/327—Iron group oxides, their mixed metal oxides, or oxide-forming salts thereof
    • C04B2235/3272—Iron oxides or oxide forming salts thereof, e.g. hematite, magnetite
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/52—Constituents or additives characterised by their shapes
    • C04B2235/5208—Fibers
    • C04B2235/5216—Inorganic
    • C04B2235/522—Oxidic
    • C04B2235/5232—Silica or silicates other than aluminosilicates, e.g. quartz
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/52—Constituents or additives characterised by their shapes
    • C04B2235/5208—Fibers
    • C04B2235/526—Fibers characterised by the length of the fibers
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
    • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
    • C04B2235/00—Aspects relating to ceramic starting mixtures or sintered ceramic products
    • C04B2235/02—Composition of constituents of the starting material or of secondary phases of the final product
    • C04B2235/50—Constituents or additives of the starting mixture chosen for their shape or used because of their shape or their physical appearance
    • C04B2235/52—Constituents or additives characterised by their shapes
    • C04B2235/5208—Fibers
    • C04B2235/5264—Fibers characterised by the diameter of the fibers

Definitions

  • the object of this invention is included in the general field of design and production of humidity sensors, and in particular in the improvement of the application properties of those sensors in terms of increasing the temperature and relative humidity ranges in which they are Usable, as well as the improvement of its characteristics of robustness, durability, ability and sensitivity.
  • a humidity sensor that can operate in a wide range of relative humidity (RH), frequently between 10 and 80%, as well as in a temperature range that extends to 300-400 0 C.
  • Main requirements for a humidity sensor are: (a) high sensitivity in a large range of HR; (b) quick response; (c) good reproducibility and lack of hysteresis phenomena; (d) resistant and of consistent structure so that it has adequate durability; (e) pollution resistant; (f) the response limit must be temperature dependent; and (g) simple structure and low cost.
  • Ceramic materials for this type of sensors, can be divided into: i) proton conductors, generally based on modified spinels or TiO 2 - V 2 O 5 ; ii) semiconductors, based on peroxides with perovskite type structure or on materials based on ZrO 2 ; and, iii) capacitors, such as those based on ⁇ -Al 2 O 3 .
  • iron oxides Fe 2 O 3 and Fe 3 O 4 play a special role, due to their low cost and the possibility they offer to modify their functional properties by means of a suitable doping, or by means of mixture of oxides with different oxidation state.
  • the mechanism of the moisture sensors of iron oxides was studied for the first time in the 70s and recently a large number of devices, sensors based on thin films deposited by a liquid phase or in silkscreen printing by metallic paint or even doped films with Fe 3 O 4 colloidal, they are proposed in the literature.
  • the new humidity sensors object of the present invention based on the use of superparamagnetic iron oxide nanoparticles or nanostructures supported or embedded in a sepiolite microfiber matrix allow working in a range of relative humidity (0% to 80% RH) ) without hysteresis cycle signal with rapid response and reproducible less than 10 seconds at ambient humidity, and with high resistance to environmental pollution.
  • a manufacturing process for the sensor device of the invention which comprises the following steps: a) Chemical deposition on a sepiolite microfiber substrate of an active powder of nanostructured or iron oxide nanoparticles (by example, of hematite, maghemite and magnetite). b) Obtaining a macroscopic structure by means of uniaxial or biaxial compression of the active powder in the form of a tablet, for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm.
  • Heat treatment of a compressed tablet obtained in b) is, in a range of temperatures between 20 0 C and 650 0 C, for 1 hour and 15 minutes, as a preliminary step to the screen printing of interdigitalized metal electrodes or deposited by sputtering on its surface (the metal contacts can be platinum, gold, silver or palladium), d) Second heating of the set of 15 minutes, in a temperature range between 20 0 C and 650 0 C, to improve the electrical conductivity, and subsequent drying.
  • Another particular embodiment of the invention is the process of the invention in which the weight of iron oxide (Fe 2 O 3 ) is 10%, the tablet is carried out by uniaxial pressing at 500 MPa.
  • the humidity sensing device of the invention can be used to control industrial processes such as the production of paper, fibers, electronic materials, precision instrument manufacturing, etc .; as well as for final use in products on the market: control systems in air conditioners, in dryers and dehumidifiers, in microwave ovens or in other appliances, for medicine (assisted breathing apparatus, sterilizers, incubators), for agriculture (programs of irrigation to save water and control systems for greenhouse cultivation) and for safety and environmental control systems.
  • the present invention is based on the fact that the inventors have observed that superparamagnetic iron oxide nanoparticles or nanostructures supported or embedded in a sepiolite microfiber matrix provides an improvement in the functional properties of the sensors constructed with them.
  • this new humidity sensor device allows to work in a wide range of relative humidity (0% to 80% RH) without a relevant hysteresis cycle signal caused by the difference in adsorption and desorption kinetics of the water molecules, depending on the weight of the iron oxide in the sensor assembly, achieving a rapid and reproducible response capacity to the surrounding humidity, less than 10 seconds.
  • this device is resistant to environmental pollution as a result of the iron oxide nanoparticles being embedded in the naturally occurring folisilicate that constitutes sepiolite.
  • the sensor device of the invention may comprise metal electrodes on the surface of the compressed tablet.
  • interdigitalized metal electrodes or deposited by sputtering can be screen printed;
  • the metal contacts can be selected from a noble metal, preferably platinum, gold, silver or palladium.
  • this sensor device can be subjected to a subsequent heat treatment to improve electrical conductivity.
  • an object of the present invention is a humidity sensor device, hereinafter sensor device of the invention, comprising an active powder of superparamagnetic nanostructures in the form of nanoparticles of iron oxide deposited and embedded in the naturally occurring folisilicate that constitutes sepiolite tablets in tablet form.
  • a particular object of the invention is the sensor device of the invention in which the iron oxide is between 5% and 30% by weight, preferably at 10% by weight.
  • Another particular object of the invention is the sensing device of the invention in which the weight of iron oxide is above 30% of the weight, preferably 47% of the weight.
  • Another particular object of the invention is the sensor device of the invention in which the iron oxide (Fe 2 O 3 and Fe 3 O 4 ) comes from a material belonging to the following group: hematite, maghemite and magnetite.
  • Another particular object of the invention is the sensor device of the invention in which the metal contacts are a noble metal, belonging to the following group: platinum, gold, silver or palladium.
  • a particular embodiment of the invention is the device of the invention with 10% and 47% weight of iron oxide and with interdigitalized gold electrodes screen-printed on its surface, respectively ( Figure 1).
  • Another object of the invention of the present invention is a manufacturing method of the sensing device of the invention, hereinafter the method of the invention, which comprises the following steps: e) Chemical deposition on a sepiolite microfiber substrate of a active powder of nanostructured or iron oxide nanoparticles (for example, hematite, maghemite and magnetite). So that the iron oxide superparamagnetic nanoparticles (of the order of 10 nm) are embedded in the matrix of sepiolite fibers (naturally occurring follicilicate) f) Obtaining a macroscopic structure by compressing the active powder in the form of a tablet , for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm.
  • a tablet for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm.
  • the compressed tablet obtained in b) is heat treated, in a range of temperatures between 20 0 C and 650 0 C, for 1 hour and 15 minutes, as a preliminary step to the screen printing of interdigitalized metal electrodes or deposited by sputtering on its surface (metal contacts can be platinum, gold, silver or palladium), and h) The metal contacts are subjected to a second 15-minute warm-up, in a temperature range between 20 0 C and 650 0 C, to improve the electrical conductivity, and let it dry overnight.
  • metal contacts can be platinum, gold, silver or palladium
  • Another particular object of the invention is the process of the invention in which iron oxide (Fe 2 O 3 and Fe 3 O 4 ) is obtained from a material belonging to the following group: hematite, maghemite and magnetite.
  • Another particular object of the invention is the process of the invention in which the metallic contact on the surface of the device tablet is deposited by a technique belonging to the following group: screen printing and sputerring.
  • Another particular object of the invention is the process of the invention in which the metal contacts are platinum, gold, silver or palladium.
  • the weight of iron oxide Fe 2 O 3
  • Another particular embodiment of the invention is the process of the invention in which the weight of iron oxide (Fe 2 O 3 ) is 10%, the tablet is carried out by uniaxial pressing at 500 MPa subsequently the tablet is heated to
  • an interdigitalized gold electrode is screen printed on its surface, followed by a second 15-minute warm-up at 520 0 C, and allowed to dry overnight.
  • the humidity sensing device of the invention can be used to control industrial processes such as the production of paper, fibers, electronic materials, precision instrument manufacturing, etc .; as well as for final use in products on the market: control systems in air conditioners, in dryers and dehumidifiers, in microwave ovens or in other appliances, for medicine (assisted breathing apparatus, sterilizers, incubators), for agriculture (programs of irrigation to save water and control systems for greenhouse cultivation) and for safety and environmental control systems.
  • Figure 1 Moisture sensing device of the invention constituted by a 12.55 mm diameter and 1.76 mm thick sepiolite tablet, with 47% iron oxide and with interdigitalized electrodes s of silk-screened gold on its surface.
  • the tablet was obtained by uniaxial pressing at 500 MPa of the active powder and was heated at 520 ° C for 15 minutes.
  • Figure 2 Variation of the resistivity of the sensor at 19 ° C as a function of the relative humidity of the atmosphere for a Fe 2 Os content of 10% (A) and 47% (B) by weight. The relative humidity remained constant for each measurement value for 30 minutes.
  • the two sets of curves refer to the different iron oxide contents (10% and 47% by weight of Fe 2 O 3 ) on the sepiolite substrate in the sensing device of the invention having been carried out measurements in different periods of time (1, 3, 5, 10, 15 and 30 minutes, The tablets were heated at 520 0 C for 1 hour before screen printing the gold electrodes, followed by a second 15 minute warm-up at 520 0 C, once printed and letting it dry all night.
  • Figure 3 Response of the sensor device at 19 ° C during cycles at different times under different levels of relative humidity (0% - 80% RH) for a Fe 2 ⁇ 3 content of 10% (A) and 47% (B ) by weight, according to the same parameters of Figure 2.
  • Figure 4 Variation of the sensor resistance at 40 0 C as a function of the relative humidity of the atmosphere for a Fe 2 ⁇ 3 content of 10% (A) and 47% (B) by weight for the same samples in Figure 2. The relative humidity remained constant for each value for 30 minutes.
  • the two sets of curves refer to the different iron oxide contents (10 and 47% by weight of Fe 2 O 3 ,, A and B, respectively) on the sepiolite substrate in the sensor device of the invention, measurements having been carried out in different periods of time (1, 2, 5, 10, 15 and 30 minutes).
  • Example 1 Manufacturing procedure of the device of the invention and efficacy tests as a humidity sensor.
  • the device according to the invention was manufactured by a method comprising the following steps: a) Chemical deposition on a sepiolite microfiber substrate of an active powder of nanostructured or iron oxide nanoparticles (for example, of hematite, maghemite and magnetite), in particular hematite was used. So that iron oxide superparamagnetic nanoparticles (of the order of 10 nm) are embedded in the sepiolite fiber matrix
  • a particular humidity sensor device of the invention was made up of a sepiolite tablet (12.55 mm in diameter and 1.76 mm thick), with a 47% weight of iron oxide (Fe 2 O 3 ) and with interdigitalized gold electrodes screen printed on its surface
  • the tablet was obtained by uniaxial pressing at 500 MPa of the active powder, heating the tablet at 520 ° C for 1 hour and 15 minutes before screen printing the gold electrodes, followed by a second heating of 15 minutes at 520 ° C, and allowed to dry overnight ( Figure 1).
  • the manufacturing process of the sepiolite tablet with 10% weight of iron oxide was carried out in the same way.
  • a device of the invention with a lower weight of iron oxide can operate in humidity ranges between 10% and 80% with a capacity of rapid response to humidity in the environment, less than 10 seconds (Figure 3A) while when higher iron oxide proportions are used, preferably 47% or greater, it can operate in humidity ranges between 0% and 10% with a capacity also for rapid response to the humidity of the environment, less than 10 seconds ( Figure 3B).

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Organic Chemistry (AREA)
  • Structural Engineering (AREA)
  • Materials Engineering (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Immunology (AREA)
  • Pathology (AREA)
  • General Health & Medical Sciences (AREA)
  • Biochemistry (AREA)
  • Analytical Chemistry (AREA)
  • Health & Medical Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Electrochemistry (AREA)
  • Inorganic Chemistry (AREA)
  • Nanotechnology (AREA)
  • Investigating Or Analyzing Materials By The Use Of Fluid Adsorption Or Reactions (AREA)

Abstract

The invention relates to a humidity sensor which is based on an active powder comprising iron oxide nanoparticles that are supported on microfibres of sepiolite. Depending on the content of said nanoparticles, the sensor can operate within a wide RH range (0 - 80%) with a rapid reproducible response (<10 s) and with no hysteresis phenomena. According to the invention, the iron oxide nanoparticles are embedded in the sepiolite microfibres and, as a result, the sensor is environmentally resistant.

Description

TÍTULOTITLE
DISPOSITIVO SENSOR DE HUMEDAD BASADO EN NANOPARTÍCULAS DE ÓXIDO DE HIERRO SOPORTADAS EN SEPIOLITA, SU PROCEDIMIENTO DE FABRICACIÓN Y SUS APLICACIONESMOISTURE SENSOR DEVICE BASED ON IRON OXIDE NANOPARTICLES SUPPORTED IN SEPIOLITA, ITS MANUFACTURING PROCEDURE AND ITS APPLICATIONS
SECTOR DE LA TÉCNICASECTOR OF THE TECHNIQUE
El objeto de esta invención se incluye en el campo general del diseño y producción de sensores de humedad, y en particular en la mejora de las propiedades de aplicación de esos sensores en cuanto al aumento de los rangos de temperatura y humedad relativa en los que son utilizables, así como la mejora de sus características de robustez, durabilidad, Habilidad y sensibilidad.The object of this invention is included in the general field of design and production of humidity sensors, and in particular in the improvement of the application properties of those sensors in terms of increasing the temperature and relative humidity ranges in which they are Usable, as well as the improvement of its characteristics of robustness, durability, ability and sensitivity.
ESTADO DE LA TÉCNICASTATE OF THE TECHNIQUE
La demanda de sensores de humedad se ha incrementado notablemente durante la última década, debido al interés de sus posibles aplicaciones industriales (producción de papel, fibras, materiales electrónicos, fabricación de instrumentos de precisión, etc.) así como para su uso final en productos del mercado. Más concretamente, para un rango de aplicaciones que comprende desde sistemas de control en aires acondicionados, en secadoras y deshumidificadores, en hornos microondas o en otros electrodomésticos, para medicina (aparatos para la respiración asistida, esterilizadores, incubadoras), para agricultura (programas de irrigación para ahorra agua y sistemas de control del cultivo en invernadero), para sistemas de control de la seguridad y el medioambiente.The demand for humidity sensors has increased markedly during the last decade, due to the interest of their possible industrial applications (production of paper, fibers, electronic materials, manufacture of precision instruments, etc.) as well as for their final use in products From the market. More specifically, for a range of applications ranging from control systems in air conditioners, in dryers and dehumidifiers, in microwave ovens or in other appliances, for medicine (assisted breathing apparatus, sterilizers, incubators), for agriculture (programs of irrigation to save water and control systems for greenhouse cultivation), for safety and environmental control systems.
En efecto, muchos procesos industriales son sensibles a la humedad así como también muchas aplicaciones domesticas. La calidad de los productos, el nivel de producción y los costes a menudo dependen del control del nivel de humedad. Salud, confort y productividad humana se ven significativamente afectadas por la humedad. Los aparatos eléctricos se dañan fácilmente debido a las cargas electrostáticas almacenadas en atmósferas demasiado secas.Indeed, many industrial processes are sensitive to moisture as well as many domestic applications. Product quality, production level and costs often depend on humidity level control. Health, comfort and human productivity are significantly affected by moisture. Electrical appliances are easily damaged due to electrostatic charges stored in too dry atmospheres.
Las aplicaciones anteriormente comentadas, requieren sensores que puedan operar en un gran rango de humedad relativa (HR), frecuentemente entre el 10 y el 80%, así como también en un intervalo de temperaturas que se extienda hasta los 300 - 4000C. Los principales requisitos para un sensor de humedad son: (a) alta sensibilidad en un gran rango de HR; (b) respuesta rápida; (c) buena reproducibilidad y carencia de fenómenos de histéresis; (d) resistente y de estructura consistente para que tenga una durabilidad adecuada; (e) resistente a la contaminación; (f) el límite de respuesta debe ser dependiente de la temperatura; y (g) de estructura simple y de bajo coste.The aforementioned applications require sensors that can operate in a wide range of relative humidity (RH), frequently between 10 and 80%, as well as in a temperature range that extends to 300-400 0 C. Main requirements for a humidity sensor are: (a) high sensitivity in a large range of HR; (b) quick response; (c) good reproducibility and lack of hysteresis phenomena; (d) resistant and of consistent structure so that it has adequate durability; (e) pollution resistant; (f) the response limit must be temperature dependent; and (g) simple structure and low cost.
Se han estudiado y diseñado muchos materiales para su utilización como sensores de humedad, incluso un número limitado de ellos ha logrado el nivel de transferencia tecnológica. Algunos sensores están basados en la variación de la conductividad iónica de electrolitos cerámicos (LiCl); otros en polímeros hidrofílicos sensibles a la adsorción de agua o con la propiedad de hincharse y otros se basan en materiales cerámicos que cambian su conductividad debido a la fisisorción de moléculas de agua.Many materials have been studied and designed for use as humidity sensors, even a limited number of them have achieved the level of technology transfer. Some sensors are based on the variation of the ionic conductivity of ceramic electrolytes (LiCl); others in hydrophilic polymers sensitive to water adsorption or with the property of swelling and others are based on ceramic materials that change their conductivity due to the fisisorción of water molecules.
Los materiales cerámicos, para este tipo de sensores, pueden dividirse en: i) conductores de protones, generalmente basados en espinelas modificadas o en TiO2- V2O5; ii) semiconductores, basados en óxidos con estructura tipo perovskita o en materiales basados en ZrO2; y, iii) condensadores, como por ejemplo los basados en α- Al2O3.Ceramic materials, for this type of sensors, can be divided into: i) proton conductors, generally based on modified spinels or TiO 2 - V 2 O 5 ; ii) semiconductors, based on peroxides with perovskite type structure or on materials based on ZrO 2 ; and, iii) capacitors, such as those based on α-Al 2 O 3 .
La conductividad superficial de estos materiales cerámicos aumenta con el incremento de HR. Entre los materiales conductores de protones, juegan un papel especial los óxidos de hierro Fe2O3 y Fe3O4, debido a su bajo costo y a la posibilidad que ofrecen de modificar sus propiedades funcionales por medio de un dopado adecuado, o mediante la mezcla de óxidos con distinto estado de oxidación. El mecanismo de los sensores de humedad de los óxidos de hierro fue estudiado por primera vez en los años 70 y recientemente una gran cantidad de dispositivos, sensores basados en películas delgadas depositadas mediante una fase líquida o en la serigrafía mediante pintura metálica o incluso películas dopadas con Fe3O4 coloidal, se encuentran propuestos en la literatura.The surface conductivity of these ceramic materials increases with the increase in RH. Among the conductive materials of protons, iron oxides Fe 2 O 3 and Fe 3 O 4 play a special role, due to their low cost and the possibility they offer to modify their functional properties by means of a suitable doping, or by means of mixture of oxides with different oxidation state. The mechanism of the moisture sensors of iron oxides was studied for the first time in the 70s and recently a large number of devices, sensors based on thin films deposited by a liquid phase or in silkscreen printing by metallic paint or even doped films with Fe 3 O 4 colloidal, they are proposed in the literature.
Otro papel fundamental en la determinación de las propiedades funcionales del sensor viene dado por la micro -nanoestructura (porosidad, tamaño de grano) y por la macroestructura (espesor, densidad) del material. Son también importantes la distribución del tamaño de poro. Es de interés resaltar que el uso de materiales nanocristalinos provoca importantes mejoras en la actuación del sensor. DESCRIPCIÓN DE LA INVENCIÓN Descripción BreveAnother fundamental role in determining the functional properties of the sensor is given by the microstructure (porosity, grain size) and by the macrostructure (thickness, density) of the material. Pore size distribution is also important. It is of interest to note that the use of nanocrystalline materials causes significant improvements in sensor performance. DESCRIPTION OF THE INVENTION Brief Description
Los nuevos sensores de humedad objeto de la presente invención basados en el uso de nanopartículas o nanoestructurados de óxido de hierro superparamagnético soportados o embebidos en una matriz de microfibras de de sepiolita permiten trabajar en un rango de humedades relativas (0 % a 80 % de HR) sin señal de ciclo de histéresis con rápida respuesta y reproducible menor de 10 segundos a la humedad ambiente, y con alta resistencia a la contaminación ambiental.The new humidity sensors object of the present invention based on the use of superparamagnetic iron oxide nanoparticles or nanostructures supported or embedded in a sepiolite microfiber matrix allow working in a range of relative humidity (0% to 80% RH) ) without hysteresis cycle signal with rapid response and reproducible less than 10 seconds at ambient humidity, and with high resistance to environmental pollution.
También es objeto de la invención un proceso de fabricación del dispositivo sensor de la invención, que comprende las siguientes etapas: a) Depósito por vía química sobre un sustrato de microfibras de sepiolita de un polvo activo de nanoestructurados o nanopartículas de óxido de hierro (por ejemplo, de hematita, maghemita y magnetita). b) Obtención de una estructura macroscópica mediante la compresión uniaxial o biaxial del polvo activo en forma de pastilla, por ejemplo, cilindricas o prismáticas, con un espesor comprendido entre 0.1 y 2 mm. c) Tratamiento térmico de a pastilla comprimida obtenida en b) es, en un rango de temperaturas comprendidas entre 200C y 6500C, durante 1 hora y 15 minutos, como paso previo a la serigrafía de electrodos metálicos interdigitalizados o depositados por sputtering sobre su superficie (los contactos metálicos pueden ser platino, oro, plata o paladio), d) Segundo calentamiento del conjunto de 15 minutos, en un rango de temperaturas comprendidas entre 200C y 6500C, para mejorar la conductividad eléctrica, y posterior secado. Otra realización particular de la invención lo constituye el procedimiento de la invención en el cual el peso de óxido de hierro (Fe2O3) es del 47%, la pastilla se lleva a cabo mediante prensado uniaxial a 500 MPa (1 MPa =106 Nw/m2).Also subject to the invention is a manufacturing process for the sensor device of the invention, which comprises the following steps: a) Chemical deposition on a sepiolite microfiber substrate of an active powder of nanostructured or iron oxide nanoparticles (by example, of hematite, maghemite and magnetite). b) Obtaining a macroscopic structure by means of uniaxial or biaxial compression of the active powder in the form of a tablet, for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm. c) Heat treatment of a compressed tablet obtained in b) is, in a range of temperatures between 20 0 C and 650 0 C, for 1 hour and 15 minutes, as a preliminary step to the screen printing of interdigitalized metal electrodes or deposited by sputtering on its surface (the metal contacts can be platinum, gold, silver or palladium), d) Second heating of the set of 15 minutes, in a temperature range between 20 0 C and 650 0 C, to improve the electrical conductivity, and subsequent drying. Another particular embodiment of the invention is the process of the invention in which the weight of iron oxide (Fe 2 O 3 ) is 47%, the tablet is carried out by uniaxial pressing at 500 MPa (1 MPa = 10 6 Nw / m 2 ).
Otra realización particular de la invención lo constituye el procedimiento de la invención en el cual el peso de óxido de hierro (Fe2O3) es del 10%, la pastilla se lleva a cabo mediante prensado uniaxial a 500 MPa .Another particular embodiment of the invention is the process of the invention in which the weight of iron oxide (Fe 2 O 3 ) is 10%, the tablet is carried out by uniaxial pressing at 500 MPa.
Finalmente, otro objeto de la invención es el uso del dispositivo sensor de humedad de la invención en procesos industriales o en la fabricación de aparatos que precisen o aporten control de la humedad o su medida. A título ilustrativo y sin que limite el alcance de la invención el dispositivo sensor de humedad de la invención puede utilizarse para controlar procesos industriales como la producción de papel, de fibras, materiales electrónicos, fabricación de instrumentos de precisión, etc.; así como para su uso final en productos del mercado: sistemas de control en aires acondicionados, en secadoras y deshumidificadores, en hornos microondas o en otros electrodomésticos, para medicina (aparatos para la respiración asistida, esterilizadores, incubadoras), para agricultura (programas de irrigación para ahorra agua y sistemas de control del cultivo en invernadero) y para sistemas de control de la seguridad y el medioambiente.Finally, another object of the invention is the use of the humidity sensing device of the invention in industrial processes or in the manufacture of devices that require or provide control of humidity or its measurement. By way of illustration and without limiting the scope of the invention, the humidity sensing device of the invention can be used to control industrial processes such as the production of paper, fibers, electronic materials, precision instrument manufacturing, etc .; as well as for final use in products on the market: control systems in air conditioners, in dryers and dehumidifiers, in microwave ovens or in other appliances, for medicine (assisted breathing apparatus, sterilizers, incubators), for agriculture (programs of irrigation to save water and control systems for greenhouse cultivation) and for safety and environmental control systems.
Descripción DetalladaDetailed description
La presente invención se basa en que los inventores han observado que nanopartículas o nanoestructurados de oxido de hierro superparamagnéticas soportadas o embebidas en una matriz de microfibras de sepiolita proporciona una mejora de las propiedades funcionales de los sensores construidos con ellas.The present invention is based on the fact that the inventors have observed that superparamagnetic iron oxide nanoparticles or nanostructures supported or embedded in a sepiolite microfiber matrix provides an improvement in the functional properties of the sensors constructed with them.
Una de las ventajas de este nuevo dispositivo sensor de humedad es que permite trabajar en un gran rango de humedades relativas (0% a 80% de HR) sin una señal relevante de ciclo de histéresis causada por la diferencia en la cinética de adsorción y desorción de las moléculas de agua, en función del peso del óxido de hierro en el conjunto del sensor, consiguiendo una capacidad de respuesta rápida y reproducible a la humedad del entorno, menor de 10 segundos. Por otro lado, este dispositivo es resistente a la contaminación medioambiental como consecuencia de que las nanopartículas de óxido de hierro se encuentran embebidas en el folisilicato de origen natural que constituye la sepiolita. Además, el dispositivo sensor de la invención puede comprender electrodos metálicos en la superficie de la pastilla comprimida. Así, se pueden serigrafiar electrodos metálicos interdigitalizados o depositados por sputtering; pudiendo los contactos metálicos ser seleccionados de un metal noble, preferentemente, platino, oro, plata o paladio. Finalmente, este dispositivo sensor se puede someter a un tratamiento térmico posterior para mejorar la conductividad eléctrica.One of the advantages of this new humidity sensor device is that it allows to work in a wide range of relative humidity (0% to 80% RH) without a relevant hysteresis cycle signal caused by the difference in adsorption and desorption kinetics of the water molecules, depending on the weight of the iron oxide in the sensor assembly, achieving a rapid and reproducible response capacity to the surrounding humidity, less than 10 seconds. On the other hand, this device is resistant to environmental pollution as a result of the iron oxide nanoparticles being embedded in the naturally occurring folisilicate that constitutes sepiolite. In addition, the sensor device of the invention may comprise metal electrodes on the surface of the compressed tablet. Thus, interdigitalized metal electrodes or deposited by sputtering can be screen printed; The metal contacts can be selected from a noble metal, preferably platinum, gold, silver or palladium. Finally, this sensor device can be subjected to a subsequent heat treatment to improve electrical conductivity.
Por lo tanto, un objeto de la presente invención lo constituye un dispositivo sensor de humedad, en adelante dispositivo sensor de la invención, que comprende un polvo activo de nanoestructurados superparamagnéticos en forma de nanopartículas de óxido de hierro depositadas y embebidas sobre el folisilicato de origen natural que constituye la sepiolita comprimidos en forma de pastilla.Therefore, an object of the present invention is a humidity sensor device, hereinafter sensor device of the invention, comprising an active powder of superparamagnetic nanostructures in the form of nanoparticles of iron oxide deposited and embedded in the naturally occurring folisilicate that constitutes sepiolite tablets in tablet form.
Un objeto particular de la invención lo constituye el dispositivo sensor de la invención en el que el óxido de hierro se encuentra entre el 5% y el 30% del peso, preferentemente en un 10% del peso.A particular object of the invention is the sensor device of the invention in which the iron oxide is between 5% and 30% by weight, preferably at 10% by weight.
Otro objeto particular de la invención lo constituye el dispositivo sensor de la invención en el que el peso de óxido de hierro se encuentra por encima del 30% del peso, preferentemente en un 47% del peso.Another particular object of the invention is the sensing device of the invention in which the weight of iron oxide is above 30% of the weight, preferably 47% of the weight.
Otro objeto particular de la invención lo constituye el dispositivo sensor de la invención en el que el oxido de hierro (Fe2O3 y Fe3O4) proviene de un material perteneciente al siguiente grupo: hematita, maghemita y magnetita.Another particular object of the invention is the sensor device of the invention in which the iron oxide (Fe 2 O 3 and Fe 3 O 4 ) comes from a material belonging to the following group: hematite, maghemite and magnetite.
Otro objeto particular de la invención lo constituye el dispositivo sensor de la invención en el que el los contactos metálicos son un metal noble, perteneciente al siguiente grupo: platino, oro, plata o paladio. Una realización particular de la invención es el dispositivo de la invención con un 10% y un 47% de peso de óxido de hierro y con electrodos interdigitalizados de oro serigrafiados en su superficie, respectivamente (Figura 1).Another particular object of the invention is the sensor device of the invention in which the metal contacts are a noble metal, belonging to the following group: platinum, gold, silver or palladium. A particular embodiment of the invention is the device of the invention with 10% and 47% weight of iron oxide and with interdigitalized gold electrodes screen-printed on its surface, respectively (Figure 1).
Otro objeto de la invención de la presente invención lo constituye un procedimiento de fabricación del dispositivo sensor de la invención, en adelante procedimiento de la invención, que comprende las siguientes etapas: e) Depósito por vía química sobre un sustrato de microfibras de sepiolita de un polvo activo de nanoestructurados o nanopartículas de óxido de hierro (por ejemplo, de hematita, maghemita y magnetita). De forma que las nanopartículas superparamagnéticas el óxido de hierro (del orden de 10 nm) se encuentran embebidas en la matriz de fibras de sepiolita (folisilicato de origen natural) f) Obtención de una estructura macroscópica mediante la compresión del polvo activo en forma de pastilla, por ejemplo, cilindricas o prismáticas, con un espesor comprendido entre 0.1 y 2 mm. g) La pastilla comprimida obtenida en b) es tratada térmicamente, en un rango de temperaturas comprendidas entre 200C y 6500C, durante 1 hora y 15 minutos, como paso previo a la serigrafía de electrodos metálicos interdigitalizados o depositados por sputtering sobre su superficie (los contactos metálicos pueden ser platino, oro, plata o paladio), y h) Los contactos metálicos se someten a un segundo calentamiento de 15 minutos, en un rango de temperaturas comprendidas entre 200C y 6500C, para mejorar la conductividad eléctrica, y se deja secar toda la noche.Another object of the invention of the present invention is a manufacturing method of the sensing device of the invention, hereinafter the method of the invention, which comprises the following steps: e) Chemical deposition on a sepiolite microfiber substrate of a active powder of nanostructured or iron oxide nanoparticles (for example, hematite, maghemite and magnetite). So that the iron oxide superparamagnetic nanoparticles (of the order of 10 nm) are embedded in the matrix of sepiolite fibers (naturally occurring follicilicate) f) Obtaining a macroscopic structure by compressing the active powder in the form of a tablet , for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm. g) The compressed tablet obtained in b) is heat treated, in a range of temperatures between 20 0 C and 650 0 C, for 1 hour and 15 minutes, as a preliminary step to the screen printing of interdigitalized metal electrodes or deposited by sputtering on its surface (metal contacts can be platinum, gold, silver or palladium), and h) The metal contacts are subjected to a second 15-minute warm-up, in a temperature range between 20 0 C and 650 0 C, to improve the electrical conductivity, and let it dry overnight.
Otro objeto particular de la invención lo constituye el procedimiento de la invención en el cual el oxido de hierro (Fe2O3 y Fe3O4) se obtiene de un material perteneciente al siguiente grupo: hematita, maghemita y magnetita.Another particular object of the invention is the process of the invention in which iron oxide (Fe 2 O 3 and Fe 3 O 4 ) is obtained from a material belonging to the following group: hematite, maghemite and magnetite.
Otro objeto particular de la invención lo constituye el procedimiento de la invención en el cual la comprensión del polvo activo se lleva a cabo de forma uniaxial o biaxial, preferentemente a 500 MPa (1 MPa =106 Nw/m2)Another particular object of the invention is the process of the invention in which the understanding of the active powder is carried out uniaxially or biaxially, preferably at 500 MPa (1 MPa = 10 6 Nw / m 2 )
Otro objeto particular de la invención lo constituye el procedimiento de la invención en el cual el contacto metálico sobre la superficie de la pastilla del dispositivo se deposita mediante una técnica perteneciente al siguiente grupo: serigrafía y sputerring. Otro objeto particular de la invención lo constituye el procedimiento de la invención en el cual los contactos metálicos son de platino, oro, plata o paladio.Another particular object of the invention is the process of the invention in which the metallic contact on the surface of the device tablet is deposited by a technique belonging to the following group: screen printing and sputerring. Another particular object of the invention is the process of the invention in which the metal contacts are platinum, gold, silver or palladium.
Otra realización particular de la invención lo constituye el procedimiento de la invención en el cual el peso de óxido de hierro (Fe2O3) es del 47%, la pastilla se lleva a cabo mediante prensado uniaxial a 500 MPa (1 MPa =106 Nw/m2) posteriormente la pastilla se calienta a 5200C durante 1 hora, se procede al serigrafiado de un electrodo interdigitalizado de oro en su superficie, seguido por un segundo calentamiento de 15 minutos a 5200C, y se deja secar toda la noche.Another particular embodiment of the invention is the process of the invention in which the weight of iron oxide (Fe 2 O 3 ) is 47%, the tablet is carried out by uniaxial pressing at 500 MPa (1 MPa = 10 6 Nw / m 2 ) subsequently the tablet is heated at 520 0 C for 1 hour, the interdigitalized gold electrode is screened on its surface, followed by a second 15-minute warm-up at 520 0 C, and allowed to dry all night.
Otra realización particular de la invención lo constituye el procedimiento de la invención en el cual el peso de óxido de hierro (Fe2O3) es del 10%, la pastilla se lleva a cabo mediante prensado uniaxial a 500 MPa posteriormente la pastilla se calienta aAnother particular embodiment of the invention is the process of the invention in which the weight of iron oxide (Fe 2 O 3 ) is 10%, the tablet is carried out by uniaxial pressing at 500 MPa subsequently the tablet is heated to
5200C durante 1 hora, se procede al serigrafiado de un electrodo interdigitalizado de oro en su superficie, seguido por un segundo calentamiento de 15 minutos a 5200C, y se deja secar toda la noche.520 0 C for 1 hour, an interdigitalized gold electrode is screen printed on its surface, followed by a second 15-minute warm-up at 520 0 C, and allowed to dry overnight.
Xxxx Finalmente, otro objeto de la invención es el uso del dispositivo sensor de humedad de la invención en procesos industriales o en la fabricación de aparatos que precisen o aporten control de la humedad o su medida. A título ilustrativo y sin que limite el alcance de la invención el dispositivo sensor de humedad de la invención puede utilizarse para controlar procesos industriales como la producción de papel, de fibras, materiales electrónicos, fabricación de instrumentos de precisión, etc.; así como para su uso final en productos del mercado: sistemas de control en aires acondicionados, en secadoras y deshumidificadores, en hornos microondas o en otros electrodomésticos, para medicina (aparatos para la respiración asistida, esterilizadores, incubadoras), para agricultura (programas de irrigación para ahorra agua y sistemas de control del cultivo en invernadero) y para sistemas de control de la seguridad y el medioambiente.Xxxx Finally, another object of the invention is the use of the humidity sensing device of the invention in industrial processes or in the manufacture of devices that require or provide control of humidity or its measurement. By way of illustration and without limiting the scope of the invention, the humidity sensing device of the invention can be used to control industrial processes such as the production of paper, fibers, electronic materials, precision instrument manufacturing, etc .; as well as for final use in products on the market: control systems in air conditioners, in dryers and dehumidifiers, in microwave ovens or in other appliances, for medicine (assisted breathing apparatus, sterilizers, incubators), for agriculture (programs of irrigation to save water and control systems for greenhouse cultivation) and for safety and environmental control systems.
DESCRIPCIÓN DE LAS FIGURASDESCRIPTION OF THE FIGURES
Figura 1 - Dispositivo sensor de humedad de la invención constituido por una pastilla de sepiolita de 12.55 mm de diámetro y 1.76 mm de espesor, con un 47% de óxido de hierro y con electrodos interdigitalizado s de oro serigrafíado en su superficie. La pastilla se ha obtenido mediante prensado uniaxial a 500 MPa del polvo activa y fue calentada a 520°C durante Ih 15 minutos.Figure 1 - Moisture sensing device of the invention constituted by a 12.55 mm diameter and 1.76 mm thick sepiolite tablet, with 47% iron oxide and with interdigitalized electrodes s of silk-screened gold on its surface. The tablet was obtained by uniaxial pressing at 500 MPa of the active powder and was heated at 520 ° C for 15 minutes.
Figura 2 - Variación de la resistividad del sensor a 19°C en función de la humedad relativa de la atmósfera para un contenido de Fe2Os del 10% (A) y 47% (B) en peso. La humedad relativa se mantuvo constante para cada valor de medida durante 30 minutos. Los dos conjuntos de curvas se refieren a los diferentes contenidos de óxido de hierro (10 % y 47 % en peso de Fe2O3) sobre el sustrato de sepiolita en el dispositivo sensor de la invención habiéndose llevado a cabo medidas en diferentes periodos de tiempo (1, 3, 5, 10, 15 y 30 minutos, Las pastillas fueron calentadas a 5200C durante 1 hora antes de serigrafiar los electrodos de oro, seguido por un segundo calentamiento de 15 minutos a 5200C, una vez impreso y dejándolo secar toda la noche.Figure 2 - Variation of the resistivity of the sensor at 19 ° C as a function of the relative humidity of the atmosphere for a Fe 2 Os content of 10% (A) and 47% (B) by weight. The relative humidity remained constant for each measurement value for 30 minutes. The two sets of curves refer to the different iron oxide contents (10% and 47% by weight of Fe 2 O 3 ) on the sepiolite substrate in the sensing device of the invention having been carried out measurements in different periods of time (1, 3, 5, 10, 15 and 30 minutes, The tablets were heated at 520 0 C for 1 hour before screen printing the gold electrodes, followed by a second 15 minute warm-up at 520 0 C, once printed and letting it dry all night.
Figura 3 - Respuesta del dispositivo sensor a 19°C durante los ciclos a diferentes tiempos bajo distintos niveles de humedad relativa (0% - 80% HR) para un contenido de Fe2θ3 del 10% (A) y 47% (B) en peso, según los mismos parámetros de la Figura 2. Figura 4 - Variación de la resistencia del sensor a 400C en función de la humedad relativa de la atmósfera para un contenido de Fe2θ3 del 10% (A) y 47% (B) en peso para las mismas muestras de la Figura 2. La humedad relativa se mantuvo constante para cada valor durante 30 minutos. Los dos conjuntos de curvas se refieren a los diferentes contenidos de óxido de hierro (10 y 47 % en peso de Fe2O3,, A y B, respectivamente) sobre el sustrato de sepiolita en el dispositivo sensor de la invención, habiéndose llevado a cabo medidas en diferentes periodos de tiempo (1, 2, 5, 10, 15 y 30 minutos).Figure 3 - Response of the sensor device at 19 ° C during cycles at different times under different levels of relative humidity (0% - 80% RH) for a Fe 2 θ 3 content of 10% (A) and 47% (B ) by weight, according to the same parameters of Figure 2. Figure 4 - Variation of the sensor resistance at 40 0 C as a function of the relative humidity of the atmosphere for a Fe 2 θ 3 content of 10% (A) and 47% (B) by weight for the same samples in Figure 2. The relative humidity remained constant for each value for 30 minutes. The two sets of curves refer to the different iron oxide contents (10 and 47% by weight of Fe 2 O 3 ,, A and B, respectively) on the sepiolite substrate in the sensor device of the invention, measurements having been carried out in different periods of time (1, 2, 5, 10, 15 and 30 minutes).
EJEMPLOS DE REALIZACIÓN DE LA INVENCIÓNEXAMPLES OF EMBODIMENT OF THE INVENTION
Ejemplo 1.- Procedimiento de fabricación del dispositivo de la invención y ensayos de eficacia como sensor de humedad.Example 1.- Manufacturing procedure of the device of the invention and efficacy tests as a humidity sensor.
El dispositivo s ensor de la invención se fabricó mediante un procedimiento que comprende las siguientes etapas: a) Depósito por vía química sobre un sustrato de microfibras de sepiolita de un polvo activo de nanoestructurados o nanopartículas de óxido de hierro (por ejemplo, de hematita, maghemita y magnetita), en particular se utilizó hematita . De forma que las nanopartículas superparamagnéticas el óxido de hierro (del orden de 10 nm) se encuentran embebidas en la matriz de fibras de sepiolitaThe device according to the invention was manufactured by a method comprising the following steps: a) Chemical deposition on a sepiolite microfiber substrate of an active powder of nanostructured or iron oxide nanoparticles (for example, of hematite, maghemite and magnetite), in particular hematite was used. So that iron oxide superparamagnetic nanoparticles (of the order of 10 nm) are embedded in the sepiolite fiber matrix
(folisilicato de origen natural) b) Obtención de una estructura macroscópica mediante la compresión del polvo activo en forma de pastilla, por ejemplo, cilindricas o prismáticas, con un espesor comprendido entre 0.1 y 2 mm. La comprensión se puede llevar a cabo de forma uniaxial o biaxial, c) Tratamiento térmico de la pastilla comprimida obtenida en b), en un rango de temperaturas comprendidas entre 200C y 6500C, porque cubre todo el rango posible de temperaturas en el que el proceso se puede hacer para obtener una pastilla que luego se pueda convertir en sensor de HR, durante 1 hora y 15 minutos, como paso previo a la serigrafía de electrodos metálicos interdigitalizados o depositados por sputtering sobre su superficie (los contactos metálicos pueden ser platino, oro, plata o paladio) d) Segundo calentamiento de 15 minutos de los contactos metálicos, en un rango de temperaturas comprendidas entre 20° C y 650° C, para mejorar la conductividad eléctrica, y completo secado posterior.(foliosilicate of natural origin) b) Obtaining a macroscopic structure by compressing the active powder in the form of a tablet, for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm. The understanding can be carried out uniaxially or biaxially, c) Heat treatment of the compressed tablet obtained in b), in a range of temperatures between 20 0 C and 650 0 C, because it covers the entire possible range of temperatures in that the process can be done to obtain a tablet that can then be converted into an HR sensor, for 1 hour and 15 minutes, as a previous step to the screen printing of interdigitalized metal electrodes or deposited by sputtering on its surface (metal contacts can be platinum, gold, silver or palladium) d) Second 15-minute heating of the metal contacts, in a temperature range between 20 ° C and 650 ° C, to improve the electrical conductivity, and complete subsequent drying.
A partir, de esta descripción general se elaboró un dispositivo sensor de humedad particular de la invención constituido por una pastilla de sepiolita (12.55 mm de diámetro y 1.76 mm de espesor), con un 47% de peso de óxido de hierro (Fe2O3) y con electrodos interdigitalizados de oro serigrafiados en su superficie La pastilla se obtuvo mediante prensado uniaxial a 500 MPa del polvo activo, calentando la pastilla a 520° C durante 1 hora y 15 minutos antes de serigrafiar los electrodos de oro, seguido por un segundo calentamiento de 15 minutos a 520° C, y se dejó secar toda la noche (Figura 1). El procedimiento de fabricación de la pastilla de sepiolita con el 10% de peso de óxido de hierro se llevó a cabo de la misma forma.From this general description, a particular humidity sensor device of the invention was made up of a sepiolite tablet (12.55 mm in diameter and 1.76 mm thick), with a 47% weight of iron oxide (Fe 2 O 3 ) and with interdigitalized gold electrodes screen printed on its surface The tablet was obtained by uniaxial pressing at 500 MPa of the active powder, heating the tablet at 520 ° C for 1 hour and 15 minutes before screen printing the gold electrodes, followed by a second heating of 15 minutes at 520 ° C, and allowed to dry overnight (Figure 1). The manufacturing process of the sepiolite tablet with 10% weight of iron oxide was carried out in the same way.
Como el dispositivo está basado en un material con una cierta resistencia en función del porcentaje de humedad relativa, debe aplicarse externamente un voltaje alterno en este caso se utilizó 3.6 V @ 1 kHz. Es una opción en la práctica se buscará el mínimo potencial que de señal medible y fiable.As the device is based on a material with a certain resistance depending on the percentage of relative humidity, an alternating voltage must be applied externally in this case 3.6 V @ 1 kHz was used. It is an option in practice will seek the minimum potential that measurable and reliable signal.
La validez de los dispositivos sensores de la invención fabricados con un 10% y 47% de peso de óxido de hierro fue comprobada en una cámara de humedad controlada, manteniendo constante la temperatura de medida, 19 y 40° C (ver Figura 2 y 4, respectivamente) . Este nuevo sensor de humedad permite trabajar en un gran rango de humedades relativas sin una señal relevante de histéresis, ver Figura 3, causada por la diferencia en la cinética de adsorción y desorción de las moléculas de aguaThe validity of the sensor devices of the invention manufactured with a 10% and 47% weight of iron oxide was checked in a controlled humidity chamber, keeping the measuring temperature constant, 19 and 40 ° C (see Figures 2 and 4 , respectively). This new humidity sensor allows working in a wide range of relative humidity without a relevant hysteresis signal, see Figure 3, caused by the difference in adsorption and desorption kinetics of water molecules
Así, un dispositivo de la invención con un menor peso de óxido de hierro, entre el 5% y el 30%, y más preferentemente el 10%, puede operar en rangos de humedad entre el 10% y el 80% con una capacidad de respuesta rápida a la humedad del entorno, menor de 10 segundos (Figura 3A); mientras que cuando se utilizan mayores proporciones óxido de hierro, preferentemente del 47 % o mayores, puede operar en rangos de humedad entre el 0% y el 10% con una capacidad también de respuesta rápida a la humedad del entorno, menor de 10 segundos (Figura 3B). Thus, a device of the invention with a lower weight of iron oxide, between 5% and 30%, and more preferably 10%, can operate in humidity ranges between 10% and 80% with a capacity of rapid response to humidity in the environment, less than 10 seconds (Figure 3A) while when higher iron oxide proportions are used, preferably 47% or greater, it can operate in humidity ranges between 0% and 10% with a capacity also for rapid response to the humidity of the environment, less than 10 seconds ( Figure 3B).

Claims

REIVINDICACIONES
1.- Dispositivo sensor de humedad caracterizado porque comprende un polvo activo de nanoestructurados superparamagneticos en forma de nanopartículas de óxido de hierro depositadas y embebidas sobre el folisilicato de origen natural que constituye la sepiolita comprimidos en forma de pastilla.1. Moisture sensing device characterized in that it comprises an active powder of superparamagnetic nanostructures in the form of iron oxide nanoparticles deposited and embedded in the naturally occurring folisilicate constituting the tablet-shaped sepiolite tablets.
2.- Dispositivo sensor de humedad según la reivindicación 1 caracterizado porque la concentración en peso de los nanoestructurados de óxido de hierro embebidas en la matriz de fibras de sepiolita se encuentra entre el 5% y el 30%.2. Moisture sensor device according to claim 1, characterized in that the weight concentration of the iron oxide nanostructures embedded in the sepiolite fiber matrix is between 5% and 30%.
3.- Dispositivo sensor de humedad según la reivindicación 2 caracterizado porque la concentración en peso de los nanoestructurados de óxido de hierro embebidas en la matriz de fibras de sepiolita es del 10%.3. Moisture sensing device according to claim 2, characterized in that the weight concentration of the iron oxide nanostructures embedded in the sepiolite fiber matrix is 10%.
4.- Dispositivo sensor de humedad basado en la reivindicación 1 caracterizado porque la concentración en peso de los nanoestructurados de óxido de hierro embebidas en la matriz de fibras de sepiolita se encuentran por encima del 30%. 4. Moisture sensor device based on claim 1 characterized in that the weight concentration of the iron oxide nanostructures embedded in the sepiolite fiber matrix is above 30%.
5.-- Dispositivo sensor de humedad según la reivindicación 4 caracterizado porque la concentración en peso de los nanoestructurados de óxido de hierro embebidas en la matriz de fibras de sepiolita es del 47%.5 .-- Humidity sensor device according to claim 4, characterized in that the weight concentration of the iron oxide nanostructures embedded in the sepiolite fiber matrix is 47%.
6.- Dispositivo sensor de humedad según las reivindicaciones 1 a la 5 caracterizado porque las nanopartículas de óxido de hierro provienen de un material perteneciente al siguiente grupo: hematita, maghemita y magnetita.6. Moisture sensing device according to claims 1 to 5, characterized in that the iron oxide nanoparticles come from a material belonging to the following group: hematite, maghemite and magnetite.
7.- Dispositivo sensor de humedad según las reivindicaciones 1 a la 6 caracterizado porque comprende un electrodo metálico interdigitalizado o depositado sobre la superficie de la pastilla.7. Moisture sensing device according to claims 1 to 6, characterized in that it comprises an interdigitalized metal electrode or deposited on the surface of the tablet.
8.- Procedimiento de fabricación del dispositivo sensor de humedad según las reivindicaciones 1 a la 7 caracterizado porque comprende las siguientes etapas: a) Depósito por vía química sobre un sustrato de microfibras de sepiolita de un polvo activo de nanoestructurados o nanopartículas de óxido de hierro, b) Obtención de una estructura macroscópica mediante la compresión uniaxial o biaxial del polvo activo en forma de pastilla, por ejemplo, cilindricas o prismáticas, con un espesor comprendido entre 0.1 y 2 mm, c) Tratamiento térmico de la pastilla comprimida obtenida en b), en un rango de temperaturas comprendidas entre 200C y 6500C, durante 1 hora y 15 minutos, como paso previo a la serigrafía de electrodos metálicos interdigitalizados o depositados por sputtering sobre su superficie (los contactos metálicos pueden ser platino, oro, plata o paladio) , d) Segundo calentamiento de 15 minutos de los contactos metálicos, en un rango de temperaturas comprendidas entre 200C y 6500C, para mejorar la conductividad eléctrica, y completo secado posterior.8. Method of manufacturing the humidity sensor device according to claims 1 to 7, characterized in that it comprises the following steps: a) Chemical deposition on a sepiolite microfiber substrate of an active powder of nanostructured or iron oxide nanoparticles , b) Obtaining a macroscopic structure by means of uniaxial or biaxial compression of the active powder in the form of a tablet, for example, cylindrical or prismatic, with a thickness between 0.1 and 2 mm, c) Heat treatment of the compressed tablet obtained in b ), in a range of temperatures between 20 0 C and 650 0 C, for 1 hour and 15 minutes, as a previous step to screen printing of interdigitalized metal electrodes or deposited by sputtering on its surface (the metal contacts can be platinum, gold, silver or palladium), d) Second 15-minute heating of the metal contacts, in a temperature range between 20 0 C and 650 0 C, to improve electrical conductivity, and complete subsequent drying.
9.- Procedimiento de fabricación del dispositivo sensor de humedad según la reivindicación 8 caracterizado porque las nanopartículas de óxido de hierro provienen de materiales pertenecientes al siguiente grupo: hematita, maghemita y magnetita. 9. Method of manufacturing the humidity sensor device according to claim 8, characterized in that the iron oxide nanoparticles come from materials belonging to the following group: hematite, maghemite and magnetite.
10.- Procedimiento de fabricación del dispositivo sensor de humedad según la reivindicación 8 caracterizado porque el contacto metálico sobre la superficie de la pastilla del dispositivo se deposita mediante una técnica perteneciente al siguiente grupo: serigrafía y sputtering.10. Method of manufacturing the humidity sensor device according to claim 8, characterized in that the metal contact on the surface of the device tablet is deposited by a technique belonging to the following group: screen printing and sputtering.
11.- Procedimiento de fabricación del dispositivo sensor de humedad según la según la reivindicación 10 porque el contacto metálico es de platino, oro, plata o paladio. 11. Method of manufacturing the humidity sensor device according to claim 10 because the metal contact is platinum, gold, silver or palladium.
12.- Procedimiento de fabricación del dispositivo sensor de humedad según la según la reivindicación 8 porque el peso de óxido de hierro (Fe2O3) es del 47%, la pastilla se lleva a cabo mediante prensado uniaxial a 500 MPa posteriormente la pastilla se calienta a 5200C durante 1 hora, se procede al serigrafiado de un electrodo interdigitalizado de oro en su superficie, seguido por un segundo calentamiento de 15 minutos a 5200C, y se deja secar completamente.12. Method of manufacturing the humidity sensor device according to claim 8 because the weight of iron oxide (Fe 2 O 3 ) is 47%, the tablet is carried out by uniaxial pressing at 500 MPa subsequently the tablet it is heated at 520 0 C for 1 hour, the interdigitalized gold electrode is screened on its surface, followed by a second 15 minute warm-up at 520 0 C, and allowed to dry completely.
13.- Procedimiento de fabricación del dispositivo sensor de humedad según la según la reivindicación 8 porque el peso de óxido de hierro (Fe2O3) es del 10%, la pastilla se lleva a cabo mediante prensado uniaxial o biaxial a 500 MPa, posteriormente la pastilla se calienta a 5200C durante 1, se procede al serigrafiado de un electrodo interdigitalizado de oro en su superficie, seguido por un segundo calentamiento de 15 minutos a 5200C, y se deja secar completamente.13.- Method of manufacturing the humidity sensor device according to claim 8 because the weight of iron oxide (Fe 2 O 3 ) is 10%, the tablet is carried out by uniaxial or biaxial pressing at 500 MPa, subsequently the tablet is heated to 520 0 C for 1, a gold interdigitalized electrode is screened on its surface, followed by a second 15 minute heating at 520 0 C, and allowed to dry completely.
14.- Uso del dispositivo sensor de humedad según las reivindicaciones 1 a la 8 en procesos industriales o en la fabricación de aparatos que precisen o aporten control de la humedad o su medida. 14. Use of the humidity sensor device according to claims 1 to 8 in industrial processes or in the manufacture of devices that require or provide control of humidity or its measurement.
PCT/ES2006/070086 2005-06-24 2006-06-22 Humidity sensor device based on iron oxide nanoparticles that are supported on sepiolite, production method thereof and applications of same WO2006136641A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ESP200501554 2005-06-24
ES200501554A ES2264646B1 (en) 2005-06-24 2005-06-24 MOISTURE SENSOR BASED ON IRON OXIDE NANOPARTICLES SUPPORTED IN SEPIOLITE.

Publications (1)

Publication Number Publication Date
WO2006136641A1 true WO2006136641A1 (en) 2006-12-28

Family

ID=37570138

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/ES2006/070086 WO2006136641A1 (en) 2005-06-24 2006-06-22 Humidity sensor device based on iron oxide nanoparticles that are supported on sepiolite, production method thereof and applications of same

Country Status (2)

Country Link
ES (1) ES2264646B1 (en)
WO (1) WO2006136641A1 (en)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108046829A (en) * 2017-12-20 2018-05-18 东北大学 A kind of nonmetallic mineral porous substrate and its preparation method and application
CN108320438A (en) * 2017-12-25 2018-07-24 程丹秋 A kind of intelligent repository warning device

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106501615B (en) * 2016-11-16 2019-03-01 河海大学 A kind of MEMS electrode formula low conductivity sensor and its measurement method

Non-Patent Citations (3)

* Cited by examiner, † Cited by third party
Title
CANTALINI C. ET AL.: "Silica effect on alpha-Fe2O3 humidity sensor", SENSORS AND ACTUATORS B-CHEMICAL, vol. 46, no. 3, 12 March 1998 (1998-03-12), pages 186 - 193, XP004147296 *
CHAUHAN P. ET AL.: "Humidity-sensing properties of nanocrystalline haematite thin films prepared by sol-gel processing", THIN SOLID FILMS, vol. 346, no. 1, 1 June 1999 (1999-06-01), pages 266 - 268, XP004177692 *
TONGPOOL R. ET AL.: "Sol-gel processed iron oxide-silica nanocomposite films as room-temperature humidity sensors", SENSORS AND ACTUATORS B - CHEMICAL, vol. 106, no. 2, 13 May 2005 (2005-05-13), pages 523 - 528, XP004867904 *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108046829A (en) * 2017-12-20 2018-05-18 东北大学 A kind of nonmetallic mineral porous substrate and its preparation method and application
CN108320438A (en) * 2017-12-25 2018-07-24 程丹秋 A kind of intelligent repository warning device

Also Published As

Publication number Publication date
ES2264646B1 (en) 2007-12-01
ES2264646A1 (en) 2007-01-01

Similar Documents

Publication Publication Date Title
Li et al. Porous ionic membrane based flexible humidity sensor and its multifunctional applications
Zhao et al. Proton-conductive gas sensor: a new way to realize highly selective ammonia detection for analysis of exhaled human breath
Farahani et al. Humidity sensors principle, mechanism, and fabrication technologies: a comprehensive review
Rubinger et al. Sulfonated polystyrene polymer humidity sensor: synthesis and characterization
Su et al. Humidity sensors based on TiO2 nanoparticles/polypyrrole composite thin films
Wang et al. An enrichment method to detect low concentration formaldehyde
Zhou et al. Surface modification of polysquaraines to sense humidity within a second for breath monitoring
Li et al. Highly sensitive and stable humidity nanosensors based on LiCl doped TiO2 electrospun nanofibers
Su et al. Fully transparent and flexible humidity sensors fabricated by layer-by-layer self-assembly of thin film of poly (2-acrylamido-2-methylpropane sulfonate) and its salt complex
Weiss et al. Surface-modified CAU-10 MOF materials as humidity sensors: impedance spectroscopic study on water uptake
Kan et al. Humidity sensor based on cobalt chloride/cellulose filter-paper for respiration monitoring
Solanki et al. Sequential elemental dealloying approach for the fabrication of porous metal oxides and chemiresistive sensors thereof for electronic listening
Wang et al. Humidity sensing properties of Pd2+-doped ZnO nanotetrapods
Su et al. In situ copolymerization of copolymer of methyl methacrylate and [3-(methacrylamino) propyl] trimethyl ammonium chloride on an alumina substrate for humidity sensing
Tripathy et al. Moisture sensitive inimitable Armalcolite/PDMS flexible sensor: A new entry
Yin et al. Moisture-induced reversible material transition behavior of nickel (II) bromide for low humidity detection
Tang et al. A Low‐Cost Polyaniline@ Textile‐Based Multifunctional Sensor for Simultaneously Detecting Tactile and Olfactory Stimuli
Yao et al. High‐performance flexible humidity sensors for breath detection and non‐touch switches
Adhyapak et al. Influence of Li doping on the humidity response of maghemite (γ-Fe2O3) nanopowders synthesized at room temperature
Cai et al. Sensitive and flexible humidity sensor based on sodium hyaluronate/MWCNTs composite film
WO2006136641A1 (en) Humidity sensor device based on iron oxide nanoparticles that are supported on sepiolite, production method thereof and applications of same
Sundaram Comparative study on micromorphology and humidity sensitive properties of thick film and disc humidity sensors based on semiconducting SnWO4–SnO2 composites
Su et al. Humidity sensing and electrical properties of a composite material of SiO2 and poly-[3-(methacrylamino) propyl] trimethyl ammonium chloride
TWI289202B (en) Humidity sensor and its fabricating method
Su et al. Effect of adding Au nanoparticles and KOH on the electrical and humidity-sensing properties of WO3 particles

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application
NENP Non-entry into the national phase

Ref country code: DE

WWW Wipo information: withdrawn in national office

Country of ref document: DE

122 Ep: pct application non-entry in european phase

Ref document number: 06764384

Country of ref document: EP

Kind code of ref document: A1