KR20020059420A - Temperature detector which is resistant to high temperatures and mechanically stable - Google Patents

Abstract

The present invention relates to a ceramic temperature sensor comprising a high temperature resistant matrix and a composite material having heat resistance up to at least 1400 ° C. consisting of one or more interlayer compounds having excellent PTC properties.

Description

Temperature detector, which is resistant to high temperatures and mechanically stable

For temperature measurement, many different temperature sensors are known. The function is explained by the use of various metal or ceramic materials, the electrical resistance of which materials vary with temperature. The change in resistance is evaluated as an effective signal of the electronic circuit adjusted for the change when the change in the temperature interval to be measured includes, for example, a linear constant characteristic curve. The electrical resistance may increase or decrease depending on the material as the temperature increases. The former is the positive temperature coefficient of electrical resistance (PTC), and the latter is the negative temperature coefficient of electrical resistance (NTC).

Metal temperature sensors mainly contain PTC properties. However, the temperature sensor is mechanically unstable and generally a magnetically supported temperature sensor cannot be used. Wire-type temperature sensors are generally mounted in ceramic sheaths, ie electrically insulated and / or metal sheaths. The sensor is a casing thermoelectric element. Also known is a temperature sensor which is provided on the surface of a suitable individual substrate by means of thick film technology and subsequent combustion, or encapsulated between two or multiple substrate layer structures. The temperature sensor is named as a thick film element.

PTC thermoelectric devices are also based on non-noble metals and can only be used within a limited temperature range up to 800 ° C. In principle, the above described embodiments require a carrier of inert material which provides mechanical protection for the temperature sensor element. Since the passive components of the thermoelectric element are also heated together, a constant inertia of signal change occurs, which negatively affects the speed of temperature measurement.

The transistor is a temperature dependent semiconductor resistor based on doped barium titanate (BaTiO ₃ ). The resistance characteristic is characterized by the fact that the resistance remains substantially constant up to the Curie temperature and then discontinuously increases by a predetermined amount. Typical resistors exhibit resistance characteristics that can be used within a very narrow limited temperature range and can be used up to 500 ° C.

Thermistors, NTC resistors are mainly composed of transition metal oxides, and stable acting oxides are mixed with the transition metal oxides so that the characteristic curve can be better reproduced. In addition, the thermistor and NTC resistance can be used only within a limited use range up to 1000 ° C because of its low thermal stability.

An object of the present invention is to provide a temperature sensor which is thermally heat resistant, mechanically stable and magnetically supported up to a very high temperature up to 1400 ° C. In addition, the present invention is that the temperature sensor should be able to measure the temperature within the use range of -40 ℃ to 1400 ℃.

The present invention relates to a high temperature resistant and mechanically stable ceramic temperature sensor.

1 shows a temperature measuring device under the use of a temperature sensor according to the invention.

2 is a graph showing the temperature dependence of the resistivity p, according to the first to fourth embodiments of the temperature sensor according to the invention, having a positive temperature coefficient;

3 is a graph showing the temperature dependence of the resistivity p, according to a fifth embodiment of the temperature sensor according to the invention, having a positive temperature coefficient;

The problem is solved according to the invention via a ceramic temperature sensor, wherein the temperature sensor comprises a composite material having a heat resistance up to at least 1400 ° C. consisting of a high temperature resistant matrix and at least one interlayer compound having excellent PTC properties. do.

The temperature sensor has a very high high temperature resistance, can bear a very high mechanical load and is thereby magnetically supported. With the magnetically supported structure as above, it is now possible to insert the thermosensitive material directly into the area to be measured. The omission of the passive material with passive volume, which is generally used, enables a rapid change of resistance in the sensor and thus a quick temperature measurement in a particularly preferred manner.

Another advantage of the temperature sensor according to the invention is that the sensor is stable in an oxidized and reduced atmosphere.

By incorporating a nearly linear increase in electrical resistance with increasing temperature in the range of -40 ° C to 1400 ° C, the temperature can be measured over the entire range.

Preference is given to temperature sensors according to the invention wherein the high temperature resistant matrix comprises trisilicontetranitride and / or the interlayer compound is a metal silicide.

In contrast, molybdenum, niobium, tungsten or titanium is mainly used as the metal.

In a preferred embodiment the temperature sensor is characterized in that it can be produced by a cold isostatic forming step before sintering.

Reference is made to DE 197 22 321 A1 for composite materials which may be used here.

When manufacturing a temperature sensor made of Si ₃ N ₄ / MSi ₂ composite material (M = metal), the first combined cold axial / isostatic molding is achieved.

Pre-conditioned Si ₃ N ₄ minutes with suitable sinter additives such as for example Al ₂ O ₃ , Y ₂ O ₃ and mixed with MSi ₂ , wherein M can be Mo, Nb, W, Ti- To prepare starting components at 90 parts by mass of different mass parts and in some cases organic compression and / or binding aids such as, for example, polyvinylbutyral, polyvinylalcohol, polyvinylacetate, polyethyleneglycol, For example in organic solvents such as ethanol, propanol or isopropanol.

Said preconditioned Si ₃ N ₄ minutes comprise 0 to 5 mass%, mainly 4.3 mass% Al ₂ O ₃ and, 5 to 9 mass%, mainly 5.7 mass% Y ₂ 0 ₃ .

The suspension is then dried in a rotary damper.

The mixture of MSi ₂ is now made so that a conductive ceramic is formed after sintering combustion.

The structure of the temperature sensor is made to be pre-compressed into a predetermined structure at 40 MPa.

Cold isostatic reshaping occurs at 200 MPa.

The second part of the temperature sensor production, which is made of Si ₃ N ₄ / MSi ₂ composite material, is made according to the molding process after debinding by sintering.

Zuntering I is made under constant N ₂ partial pressure, wherein the N ₂ partial pressure in the sintering gas between 1000 ° C. and the sintering temperature not higher than 1900 ° C. is not greater than 10 bar and the total sintering pressure is equal to argon and By mixing the same inert gas is increased to a value up to 100 bar.

As an alternative to shunting I, shunting II can be made under a constant N ₂ partial pressure, wherein the N ₂ partial pressure must be modified such that the partial pressure is within one range, with the temperature dependent on Limited and the total sintering pressure is increased to values up to 100 bar by mixing inert gases such as argon.

Upper limit: log p (N ₂ ) = 7.1566 ln (T)-52.719

Lower limit: log p (N ₂ ) = 9.8279 ln (T)-73.988.

The indication of T is in ° C. and the indication of p (N ₂ ) is bar. The sintering temperature is not higher than 1900 ° C. The resulting composite reaches a material density of at least 95%.

In another preferred embodiment of the present invention, the temperature sensor may be prepared by ceramizing at least one silicone organic polymer and at least one filler, the filler comprising at least one high melting point component having conductivity. And the filler component is from 20 to 50% by volume relative to the solvent-free polymer filler mixture, and the resistivity can be set by the filler component.

In this case a ceramic produced by ceramizing the filled, organic polymer is produced.

Composite materials which can be used here are known from DE 195 38 695 A1.

In another preferred embodiment of the invention, the temperature sensor is characterized in that the matrix comprises interlayer compounds and / or other reinforcing components of hard material particles, wherein the temperature sensor is decomposed generated during thermal decomposition of the polymer compound. By using a mixture of a metal filler and a silicon organic polymer that reacts with the product, it can be produced in a pyrolysis process and a reaction process.

Composite materials which can be used here are known from EP 0 412 428 A1.

The temperature sensor 1 composed of a composite material in FIG. 1 is limited by two connecting electrodes 2, which are connected with a resistance measuring device 4. The temperature sensor 1 proceeds through the temperature measuring zone 3.

The invention is explained in more detail below by way of examples.

Example 1

A composite component (A) consisting of 45 mass% Si ₃ N ₄ , 2.35 mass% Al ₂ O ₃ , 2.65 mass% Y ₂ 0 ₃ and 50 mass% MoSi ₂ is used and the average particle size of Si ₃ N ₄ used Is 0.7 μm and the average particle size of MoSi ₂ used is 1.8 μm. The composite component is precompressed to 30 MPa and cold isostatically compressed to 200 MPa in an axial compression tool after the addition of 0.5 mass% of polyvinylbutyral compression aid. After sintering in accordance with Zontering II, a temperature sensor having the temperature resistance characteristic shown in FIG. 2 is formed. The specific resistance at room temperature is approximately 2 · 10 ⁻³ dBm. The temperature coefficient in the temperature range of 20-1300 ° C. is approximately 5 · 10 ⁻³ K ⁻¹ .

Example 2

A composite component (B) consisting of 40.5 mass% Si ₃ N ₄ , 2.12 mass% Al ₂ O ₃ , 2.38 mass% Y ₂ O ₃ and 55 mass% MoSi ₂ is used, with the average particle size of Si ₃ N ₄ used Is 0.7 μm, and the average particle size of MoSi ₂ reaches 1,8 μm. The composite component is precompressed to 30 MPa and cold isostatically compressed to 200 MPa in an axial compression tool after the addition of 0.5 mass% of polyvinylbutyral compression aid. After sintering in accordance with Zontering II, a temperature sensor having the temperature resistance characteristic shown in FIG. 2 is formed. The specific resistance at room temperature is approximately 10 ⁻³ dBm.

Example 3

A composite component (C) consisting of 36 mass% Si ₃ N ₄ , 1.89 mass% Al ₂ O ₃ , 2.11 mass% Y ₂ O ₃ and 60 mass% MoSi ₂ was used, with the average particle size of Si ₃ N ₄ used Is 0.7 μm and the average particle size of MoSi ₂ used is 1,8 μm. The composite component is precompressed to 30 MPa and cold isostatically compressed to 200 MPa in an axial compression tool after the addition of 0.5 mass% of polyvinylbutyral compression aid. After sintering in accordance with Zontering II, a temperature sensor having the temperature resistance characteristic shown in FIG. 2 is formed. The specific resistance at room temperature is approximately 2 · 10 ⁻⁴ dBm.

Example 4

A composite component (D) consisting of 27 mass% Si ₃ N ₄ , 1.43 mass% Al ₂ O ₃ , 1.57 mass% Y ₂ O ₃ and 70 mass% MoSi ₂ was used, with the average particle size of Si ₃ N ₄ used Is 0.7 μm and the average particle size of MoSi ₂ used is 1,8 μm. The composite component is precompressed to 30 MPa and cold isostatically compressed to 200 MPa in an axial compression tool after the addition of 0.5 mass% of polyvinylbutyral compression aid. After sintering in accordance with Zontering II, a temperature sensor having the temperature resistance characteristic shown in FIG. 2 is formed. The specific resistance at room temperature is approximately 8 · 10 ^-5 dBm.

Example 5

7 volume% Al ₂ O ₃ , 10 volume% SiC, 20 volume% MoSi ₂ , residual precursor base material (precursor ceramic E) or 20 volume% SiC, according to EP 0 412 428 A1 or DE 195 38 695 A1 Two precursor composite ceramics are prepared from a filler combination of 20% by volume MoSi ₂ , residual precursor base material (precursor ceramic F). The resistance depending on the temperature of the ceramic compound is shown in FIG. 3. The specific resistance is 8 · 10 ^-3 Ωcm (precursor ceramic E) or 5.6 · 10 ^-3 Ωcm (precursor ceramic F) at 120 ° C and 3.0 · 10 ^-2 Ωcm (precursor ceramic at 1300 ° C). E) or 1.9 · 10 ⁻² cm 3 (precursor ceramic F). The temperature coefficient is 2.1 · 10 ⁻³ K ⁻¹ (precursor ceramic E) or 3.1 · 10 ⁻³ K ⁻¹ (precursor ceramic F) in the temperature range from room temperature to 1300 ° C.

Claims (7)

In the ceramic temperature sensor, Wherein said temperature sensor comprises a high temperature resistant matrix and a composite material having heat resistance up to at least 1400 ° C. consisting of one or more interlayer compounds having excellent PTC properties. The temperature sensor of claim 1, wherein the high temperature resistant matrix comprises trisilicontetranitride. The method according to claim 1 or 2. Wherein said interlayer compound is a metal silicide. The method of claim 3. The metal is molybdenum, niobium, tungsten or titanium. The temperature sensor according to any one of claims 1 to 4, wherein the temperature sensor can be manufactured through a cold isostatic forming step before sintering. 5. The at least one high melting point component of claim 1, wherein the temperature sensor can be prepared by ceramizing at least one silicon organic polymer and at least one filler. Wherein the filler component is from 20 to 50% by volume relative to the solvent-free polymer filler mixture, the resistivity of which can be set by the filler component. The process of claim 1, wherein the matrix comprises interlayer compounds of hard material particles and / or other reinforcing components, and the temperature sensor reacts with decomposition products produced upon pyrolysis of the polymer compound. A temperature sensor, which can be produced in a pyrolysis process and a reaction process by using a mixture consisting of a metal filler and a silicon organic polymer.