CN111863526A - Temperature control switch - Google Patents
Temperature control switch Download PDFInfo
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- CN111863526A CN111863526A CN201910366137.1A CN201910366137A CN111863526A CN 111863526 A CN111863526 A CN 111863526A CN 201910366137 A CN201910366137 A CN 201910366137A CN 111863526 A CN111863526 A CN 111863526A
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- temperature
- vanadium
- single crystal
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- vanadium dioxide
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01H—ELECTRIC SWITCHES; RELAYS; SELECTORS; EMERGENCY PROTECTIVE DEVICES
- H01H37/00—Thermally-actuated switches
- H01H37/02—Details
- H01H37/32—Thermally-sensitive members
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- C—CHEMISTRY; METALLURGY
- C30—CRYSTAL GROWTH
- C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
- C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
- C30B29/10—Inorganic compounds or compositions
- C30B29/16—Oxides
Abstract
The invention provides a temperature control switch, which comprises a vanadium dioxide-based single crystal prepared by the following steps as a temperature sensing part: heating a raw material containing a vanadium source to a temperature between 950 ℃ and 1150 ℃ in a flowing inert gas atmosphere, and kept for 24 hours to 72 hours, and then cooled to room temperature at a speed of not more than 20 ℃/minute to obtain a vanadium dioxide-based single crystal, wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, the molar ratio of oxygen to vanadium is 2: 1 or more, wherein when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature control switch is in an on or off state, when the temperature of the temperature sensing part is higher than the phase transition temperature, the vanadium dioxide-based single crystal is in a metal state, so that the temperature control switch is in an off or on state.
Description
Technical Field
The invention relates to the field of temperature control, in particular to a temperature control switch.
Background
The electronic device can generate heat in different degrees in the working process, and if the electronic device generates heat, the electronic device can be damaged irreversibly, even a fire is caused, and thus great loss is caused. At present, the technical means of overheat protection for electronic devices mainly include: the thermal fuse technology, the low melting point solder technology by spring pull, the thermal fuse technology, the isolation technology, the potting technology, etc., but all have respective disadvantages. For example, thermal fuses have problems such as reliability, failure of devices due to solder aging, slow response speed of thermal fuses, large space occupied by isolation technology, and failure of sealing materials due to arcing inside piezoresistors when they fail.
The vanadium dioxide is a special vanadium-oxygen compound, which can generate insulator-metal phase transition near 340K, is tetragonal rutile phase vanadium dioxide in a metal state above 340K, is monoclinic phase vanadium dioxide in an insulator state below 340K, and has resistance change of 10 before and after phase transition5And has an extremely fast temperature response, and thus is of particular interest.
The growth of vanadium dioxide thin films on titanium dioxide or sapphire substrates is a main means for preparing large-size vanadium dioxide materials, but the growth process is limited by harsh conditions such as oxygen partial pressure, growth temperature and the like, and the large-scale production is difficult, and meanwhile, the vanadium dioxide epitaxial films grown on the substrates are generally polycrystalline films, so that the width of a thermal hysteresis loop of insulator-metal phase transition is widened. In addition, internal stress is easily generated in the thin film, resulting in variation in response to temperature. At present, the preparation of large-size high-quality vanadium dioxide-based single crystals is difficult to realize.
Disclosure of Invention
In one aspect, the present invention provides a temperature-controlled switch including a vanadium dioxide-based single crystal as a temperature sensing section, which is produced by:
heating a raw material containing a vanadium source to a temperature of between 950 ℃ and 1150 ℃ in a flowing inert gas atmosphere for 24 hours to 72 hours, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal,
Wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, the molar ratio of oxygen to vanadium is 2: 1 or more,
wherein when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature-controlled switch is in an on state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature-controlled switch is in an off state; or when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature controlled switch is in an off state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature controlled switch is in an on state.
Preferably, the source of vanadium is selected from the group consisting of: oxides of vanadium, oxygen-containing vanadium salts, vanadium oxyacid salts, and combinations thereof.
Preferably, the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate, vanadium ammonium sulfate, and combinations thereof.
Preferably, the source comprising vanadium is placed in a semi-open vessel.
Preferably, the semi-open container is a single-opening pipe which is positioned in a horizontal inert gas flow and is obliquely placed, the single-opening pipe is arranged in a way that a pipe orifice is higher than the bottom of the pipe, and the included angle between the length direction and the horizontal plane is 5-35 degrees. More preferably, the length direction of the single-opening tube forms an angle of 20 to 30 ° with the horizontal plane.
Preferably, the flowing inert gas atmosphere comprises convection of an inert gas.
Preferably, the inert gas is selected from the group consisting of: nitrogen, argon, and combinations thereof.
Preferably, the feedstock further comprises a source of a doping element.
Preferably, the vanadium dioxide-based single crystal is a rod-shaped single crystal having a length of 1 mm or more and a diameter of 100 μm or more.
Preferably, the temperature controlled switch comprises an electromagnetic relay.
Drawings
In order to more fully illustrate the invention, reference will now be made to the accompanying drawings, which are to be used in either an embodiment or a prior art description, and it is to be noted that the following description of the drawings is only a partial illustration of the invention, and that other drawings may be derived from the drawings provided by those skilled in the art without the benefit of the inventive faculty.
FIG. 1 is VO provided by an embodiment of the present invention2Temperature change resistance data of the single crystal;
fig. 2 is a schematic diagram of an intelligent overheat protection switch according to an embodiment of the present invention. .
Fig. 3 is a block diagram of an intelligent overheat protection switching device according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of the arrangement of the apparatus in one embodiment of the invention.
Detailed description of the preferred embodiments
The invention provides a temperature control switch, which comprises a vanadium dioxide-based single crystal prepared by the following steps as a temperature sensing part:
heating a vanadium source to a temperature between 950 ℃ and 1150 ℃ in a flowing inert gas atmosphere for 24 hours to 72 hours, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal,
wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, the molar ratio of oxygen to vanadium is 2: 1 or more,
wherein when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature-controlled switch is in an on state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature-controlled switch is in an off state; or when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature controlled switch is in an off state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature controlled switch is in an on state.
The temperature control switch of the invention uses the large-size vanadium dioxide-based single crystal prepared by a specific method. The method comprises heating a raw material containing a vanadium source to a temperature of 950 ℃ to 1150 ℃ for 24 hours to 72 hours in a flowing inert gas atmosphere, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal,
wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, and the molar ratio of oxygen to vanadium is 2: 1 or more.
By this method, a large-sized vanadium dioxide-based single crystal in a non-thin film form can be produced.
In the present invention, the vanadium dioxide-based single crystal includes a pure vanadium dioxide single crystal, and also includes a vanadium dioxide single crystal in which atoms of a doping element are doped. The vanadium dioxide-based single crystal has an insulator-metal phase transition and a narrow phase transition temperature difference.
The vanadium dioxide-based single crystal is produced by heating a raw material containing a vanadium source at a high temperature for a long time in a flowing inert gas atmosphere. The vanadium dioxide-based single crystal is not in the form of a thin film and can have a maximum dimension of the order of millimeters.
In order to produce a high-purity vanadium dioxide-based single crystal, the vanadium source of the present invention is an oxygen-containing compound which does not contain other metal elements than vanadium, and among themVanadium is +4 or +5 valent, and the molar ratio of oxygen to vanadium is more than 2: 1. Without being bound to any theory, the principle of such a vanadium source to form a vanadium dioxide-based single crystal is as follows: during heating, the vanadium source in the raw material decomposes vanadium and oxygen, producing vanadium-oxygen compounds. The stable phase of the vanadium-oxygen compound under the high-temperature oxygen-deficient condition is VO2. Thus, VO can be produced by vanadium source decomposition2Phase of simultaneous VO2The phase can generate solid-gas conversion at high temperature, and in the growth container, the continuous inert convection current can drive VO2The evaporation-deposition growth process of gaseous substances can obtain large-size high-quality VO2And (3) single crystal. The atmosphere of the preparation method of the vanadium dioxide-based single crystal is oxygen-deficient, so that if a low-valence vanadium source is selected, the vanadium dioxide-based single crystal cannot be further oxidized under the oxygen-deficient condition to form VO2Species of the species. In addition, if the molar ratio of oxygen to vanadium is less than 2: 1 per mole, VO formation is also not favored2And (3) single crystal. Alternatively, the molar ratio of oxygen to vanadium per mole may be 2: 1, 3: 1, 4: 1, etc. The redundant oxygen in the vanadium source and non-metallic elements (such as N, S, C, H and the like) except oxygen can not react on VO under the condition of flowing inert gas atmosphere 2The crystals of (2) have an adverse effect.
From the viewpoint of easy decomposition of the vanadium source, the vanadium source is preferably selected from the group consisting of: oxides of vanadium, oxygen-containing vanadium salts, vanadium oxyacid salts, and combinations thereof. Preferably, the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate, vanadium ammonium sulfate, and combinations thereof. Still more preferably, the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, and combinations thereof.
The vanadium source is typically in powder form, but may be in other forms. The invention has no special requirement on the granularity of the vanadium source.
The raw material containing a vanadium source may contain only a vanadium source, or may contain a source of a doping element other than a vanadium source. When the source of the doping element is contained, the doping element is doped in the vanadium dioxide single crystal, the whole crystal structure of the vanadium dioxide single crystal is not influenced, and the obvious adjustment effect on the phase transition temperature of the insulator-metal is generated.
The source of doping elements may be selected from the group consisting of: a molybdenum source, a tungsten source, a titanium source, an aluminum source, a niobium source, a chromium source, and combinations thereof. These doping element sources can also generally be in powder form and homogeneously mixed with the vanadium source in powder form. The mass ratio of the source of doping element to the source of vanadium may be in the range 0.01: 10 to 1: 10, for example 0.5: 10. The doping element source is generally an oxygen-containing compound containing no other metal element than the doping element or a salt that is easily decomposed into an oxygen-containing compound. For example, molybdenum trioxide or ammonium molybdate may be used as the molybdenum source.
After the raw materials are placed, the vanadium source is heated to a temperature between 950 ℃ and 1150 ℃ in a flowing inert gas atmosphere for 24 hours to 72 hours, and then cooled to room temperature at a speed of not more than 20 ℃/minute to obtain a vanadium dioxide-based single crystal.
The inert gas is a gas that does not react with the starting materials and products. The inert gas is flowing. Which serves to carry away gases generated or volatilized from the starting materials during the reaction. The inert gas used in common use may be one or more of nitrogen, argon, helium, and the like. Preferably, the inert gas is selected from the group consisting of: nitrogen, argon, and combinations thereof. In the method for producing a vanadium dioxide-based single crystal, the flowing inert gas atmosphere preferably includes convection of an inert gas. Under the environment including convection, the growth of vanadium dioxide crystals is more facilitated. The present invention does not particularly specify the flow rate of the inert gas.
Heating the sample to a temperature of 950-1150 ℃ under a flowing inert gas atmosphere for 24-72 hours, and then cooling to room temperature at a speed of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal.
The influence of the temperature rise process on the product of the invention is not obvious. Typically, the temperature may be increased at a ramp rate of, for example, 10 deg.C/minute.
The holding temperature and time are critical to the preparation method of the vanadium dioxide-based single crystal. The temperature is required to be between 950 ℃ and 1150 ℃, preferably between 1000 ℃ and 1150 DEG CIn the meantime. If the temperature is too low, large-sized high-quality single crystals cannot be formed, or even VO cannot be formed2A phase. If the temperature is too high, VO2VO at higher temperature and with tendency to generate oxygen vacancies in the material2If the phase is decomposed, a vanadium dioxide-based single crystal cannot be obtained. The incubation time is required to be 24 to 72 hours, preferably 48 to 60 hours. If the time is too short, the single crystal size is small and even only a granular powder is obtained. If the time is too long, the vanadium dioxide-based single crystal is difficult to grow continuously.
And after the heat preservation is finished, cooling to room temperature at the speed of not higher than 20 ℃/min. If the temperature reduction speed is too fast, residual stress is introduced into the vanadium dioxide-based single crystal, so that the quality of the single crystal is reduced. Preferably, the cooling rate is more than 5 ℃/minute so as not to take too long.
In the above manner, a large-sized vanadium dioxide-based single crystal can be formed in a specific temperature range by the synergistic effect of the thermal decomposition of the raw material containing a vanadium source and an optional doping element source and the inert gas flow on the transport of oxygen and vanadium atoms.
Preferably, the source comprising the vanadium source is placed in a semi-open vessel. Placing the raw materials in a semi-open container is beneficial to preventing inert gas flow from blowing away raw material powder and is also beneficial to providing a better microenvironment for single crystal growth. A semi-open container refers to a container having only one opening. A typical example of a semi-open container is a single-opening tube. The gas flows into the container through the opening and flows out through the opening again, and a stable convection atmosphere is formed in the container. The raw material powder is not carried out of the semi-open container by the gas flow and the deposition growth is carried out under the convection gas flow in the container.
When the raw materials are melted at the heating temperature of the process, the melted raw materials are prevented from flowing and spreading in the vessel. For example, when the vessel is a single-port tube and is positioned in a horizontal inert gas flow, if it is positioned horizontally or diagonally downward (the nozzle is below the bottom of the tube), the molten feedstock will tend to spread out and even flow out of the nozzle. A single-opening tube, also referred to herein as a sample tube, is a tube similar to a test tube, having a tube body of uniform thickness and a tube mouth and a tube bottom at both ends, respectively. At this time, the single-opening tube should be placed obliquely so that the opening is higher than the bottom of the tube, thereby collecting the molten raw material at the bottom of the tube. Meanwhile, in order to realize the gas phase convection growth in the reaction system, the inclination angle is not too large, otherwise, inert gas flow is difficult to enter a single-opening tube, only vanadium dioxide-based particles generated by the decomposition of a vanadium source can be obtained, and the growth of large-size single crystals cannot be carried out. Preferably, the angle between the length direction and the horizontal plane is 5 to 35 °. More preferably, the angle between the length direction and the horizontal plane is between 20 ° and 30 °. Preferably, the single-ported tube is positioned with its vertical plane parallel to the direction of the external inert gas flow, with its ports facing substantially in the upstream direction of the external inert gas flow.
The semi-open vessel may be otherwise provided so long as it is satisfied that the raw materials in the semi-open vessel may be in a flowing inert gas atmosphere including convection. When the raw material is melted in the temperature range of the present invention, the inclination angle of the semi-open vessel is set to avoid the melted raw material from spreading or flowing out of the vessel.
Since the vanadium dioxide-based single crystal preparation method is carried out in a flowing inert gas atmosphere and the raw materials are generally in powder form, loading the raw materials in the tube can provide a better semi-enclosed space, better forming convective circulation of gaseous vanadium oxygen species within the space. In addition, the use of a single open tube to hold the material also utilizes the feeding of the material into the heating device and the removal of the product from the heating device. When a single-opening tube is used, the raw material may be put into the tube, and then the tube may be placed in a heating device such as an annealing furnace in which an inert gas flow is horizontally passed, with the tube opening directed obliquely upward.
The sample tube can be a round or square tube. The material of the sample tube can be selected from one or more of quartz glass, corundum and graphite. The inner diameter of the device can be 0.5-2 cm, and the length of the device can be 5-20 cm. Preferably, the material of the sample tube is selected from one or more of quartz glass and corundum, the inner diameter is 0.8-1.2 cm, and the length is 8-12 cm. More preferably, the inner diameter is 0.9-1.1 cm, and the length is 9-11 cm.
In the method for producing a vanadium dioxide-based single crystal, the mass of the vanadium source compound may be 50 to 1000mg, preferably 200 to 600mg, and more preferably 300 to 400mg, from the viewpoint of the size of the single crystal product to be obtained.
When a semi-open container is used to provide the inclined surface, the semi-open container may be placed in an annealing furnace and an inert gas is passed through the annealing furnace. In other words, the whole of the semi-open container is in an external flowing inert gas atmosphere. The opening of the semi-open vessel is preferably directed substantially upstream of the flow of inert gas to the exterior so that the inert gas readily flows into the semi-open vessel and forms a convective atmosphere within the vessel that facilitates the growth of the single crystal of vanadium dioxide. The direction of the external inert gas flow may be inclined or horizontal as long as it can flow into the semi-open container. The direction of the external inert gas flow is preferably horizontal in view of the arrangement of the cavity of a typical heater such as an oven.
The large-size vanadium dioxide-based single crystal can be prepared by the preparation method of the vanadium dioxide-based single crystal. The large-sized vanadium dioxide-based single crystal may be a rod-shaped single crystal having a length of 1 mm or more. The maximum length can be as much as 6 mm or more. The rod-shaped single crystal may have a diameter of several hundred micrometers. Such size and shape facilitates its further fabrication into the desired device.
In particular, the insulator-metal phase transition temperature difference of the vanadium dioxide-based single crystal can reach below 0.05K. The insulator-metal phase transition temperature difference described herein refers to the temperature difference experienced to complete the transition from the fully insulator phase to the fully metal phase (tetragonal rutile phase). At this time, the resistivity of the insulating phase should be 10 of that of the metal phase5More than twice.
The insulator-metal phase transition temperature of the vanadium dioxide-based single crystal can also be changed by carrying out certain doping. The insulator-metal phase transition temperature of pure vanadium dioxide single crystals is about 340K, and can deviate from this temperature after doping, for example to about 320K. However, after doping, the insulator-metal transition temperature difference may be broadened to some extent, for example to about 1K.
The vanadium dioxide-based single crystal has large size and high quality, and is suitable for temperature-controlled switches. The preparation method is simple and cheap, and the flow is simple and easy to operate, so that the method has great application value. The temperature controlled switch may be used for an overheat protection switch. When overheated, the overheat protection switch may be used to turn off the power supply of the heat generation source to cool the overheated component, or may be used to turn on the power supply of the cooling source to cool the overheated component.
In the temperature-controlled switch of the invention, the circuit is designed such that when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature-controlled switch is in an on state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature-controlled switch is in an off state; or when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature controlled switch is in an off state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature controlled switch is in an on state. Temperature control switch of temperature control switch
The present invention is not limited to a specific circuit, and may be any circuit as long as it can perform a switching operation according to the temperature at which the temperature sensor is located. That is, the circuit is designed by the characteristic that the vanadium dioxide-based single crystal is in an insulating state below the phase change point and in a conducting state above the phase change point, so that the operation of the temperature-controlled switch responds to the temperature. The temperature controlled switch of the present invention may be turned on below a specific temperature and turned off above the specific temperature, or may be turned off below the specific temperature and turned on above the specific temperature.
For example, an electrically controlled switch including a normally closed type electromagnetic relay may be used. The normally closed electromagnetic relay is in a closed state when not energized, and is opened when energized. The vanadium dioxide-based single crystal temperature sensor is connected in series in a power supply circuit of the electromagnetic relay. When the temperature is lower than the insulator-metal phase transition temperature, the vanadium dioxide-based single crystal is in an insulator state, the power supply circuit does not supply power to the electromagnetic relay, and the temperature control switch is in a switch-on state. Once the temperature exceeds the insulator-metal phase transition temperature, the vanadium dioxide-based single crystal is in a conducting state, the power supply circuit supplies power to the electromagnetic relay, the normally-closed electromagnetic relay is disconnected, and the temperature control switch is in a disconnected state.
Also, for example, an electrically controlled switch including a normally open type electromagnetic relay may be used. The normally open type electromagnetic relay is in an open state when not energized, and is closed when energized. The vanadium dioxide-based single crystal temperature sensor is connected in series in a power supply circuit of the electromagnetic relay. When the temperature is lower than the insulator-metal phase transition temperature, the vanadium dioxide-based single crystal is in an insulator state, the power supply circuit does not supply power to the electromagnetic relay, and the temperature control switch is in a disconnected state. Once the temperature exceeds the insulator-metal phase transition temperature, the vanadium dioxide-based single crystal is in a conducting state, the power supply circuit supplies power to the electromagnetic relay, the normally-closed electromagnetic relay is closed, and the temperature control switch is in a conducting state.
For another example, when the temperature is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulating state. If the vanadium dioxide-based single crystal is connected in series in the circuit, the circuit is in an open circuit state. The open state may be operated in reverse, creating a closed state between the two outward ports of the thermostatic switch. The inversion operation may be performed by means of an inverter, for example. When the temperature is raised above the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal conductor state. At this time, an open state is formed between the two outward ports of the temperature controlled switch by the reverse phase operation. Thereby, overheat protection can be achieved.
For example, the phase transition of the vanadium dioxide-based single crystal may be converted into an overheat protection switching operation by other methods. For example, a switching transistor may be used, and an input voltage terminal of the switching transistor may be connected to an output terminal of a circuit including the vanadium dioxide-based single crystal, and the circuit may be designed such that the output terminal outputs a low level when the vanadium dioxide-based single crystal is in an insulating state, and outputs a high level when the vanadium dioxide-based single crystal is in a metallic state, thereby controlling the switching transistor through a phase change of the vanadium dioxide-based single crystal. Those skilled in the art can also design other switches based on the phase change of vanadium dioxide based single crystals.
The invention is illustrated by the following more detailed description.
A method for producing a vanadium dioxide-based single crystal according to an embodiment of the present invention includes the steps of:
a) adding vanadium source powder into the sample tube;
the sample tube is a round or square sample tube with a single opening, the material of the sample tube is selected from one or more of quartz glass, corundum and graphite, the inner diameter is 0.5-2 cm, and the length is 5-20 cm; the preferred conditions are: the sample tube is made of one or more of quartz glass and corundum, the inner diameter is 0.8-1.2 cm, and the length is 8-12 cm; more preferred conditions are: the inner diameter is 0.9-1.1 cm, and the length is 9-11 cm.
The vanadium source compound is selected from one or more of vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate and vanadium sulfate, preferably one or more of vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate and vanadium sulfate, and more preferably one or more of vanadium pentoxide, ammonium metavanadate and vanadyl oxalate.
The mass of the vanadium source compound is 50-1000 mg, preferably 200-600 mg, and more preferably 300-400 mg.
b) Placing the sample tube in a sample chamber of a tubular annealing furnace with a gas washing device, introducing inert gas to remove oxygen, and then maintaining the inert gas flow at a constant flow rate;
The sample tube is placed in the sample chamber in an inclined mode, the opening faces upwards and faces to the upstream of the airflow, and the tangential angle is 5-35 degrees, and preferably 20-30 degrees.
The sample chamber of the tubular annealing furnace with the gas washing device is selected from one or more of sample chambers with round shapes, square shapes and the like and two open ends.
The tubular annealing furnace sample chamber with the gas washing device is provided with a lining, and the lining is made of one or more materials selected from quartz glass, corundum and graphite; preferably one or more of quartz glass and corundum;
the gas washing process can be realized by vacuumizing and filling inert gas or continuously introducing the inert gas for flushing.
The inert gas is one or more selected from nitrogen, argon and helium; preferably one or more of nitrogen and argon inert gases.
The flow rate is 20 sccm-500 sccm, and the specific preferred value is selected according to the size of the sample chamber.
c) And setting a muffle furnace temperature control program, keeping the temperature of the muffle furnace at a high temperature for a certain time, cooling the muffle furnace, and finally collecting a single crystal sample from the sample tube.
The sample chamber of the tubular annealing furnace with the gas washing device is placed horizontally.
The high temperature is 950 ℃ to 1150 ℃, preferably 1000 ℃ to 1150 ℃.
The certain time is 24 to 72 hours, and preferably 48 to 60 hours.
The cooling rate is not higher than 20 ℃/min.
On the basis, a temperature control switch is prepared.
The vanadium dioxide-based single crystal temperature sensing part is connected in series in a power supply circuit of a normally closed or normally open electromagnetic relay switch to form a temperature control switch.
The connection mode is selected from one or more of metal welding, conductive silver adhesive, conductive gold adhesive and conductive polymer adhesive.
While the preferred embodiments of the present invention will now be described in conjunction with the following examples, it is to be understood that these descriptions are merely illustrative of the features and advantages of the present invention, and are not intended to limit the scope of the appended claims. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1:
adding 300mg of vanadium pentoxide powder into a circular single-opening quartz sample tube with the inner diameter of 1 cm and the length of 10 cm, obliquely placing the circular single-opening quartz sample tube into a horizontal tubular annealing furnace sample chamber with a quartz glass lining and a gas washing device, obliquely placing the sample chamber at an inclination angle of 25 degrees, washing off oxygen and water in the sample chamber by a mode of vacuumizing for three times and filling high-purity nitrogen, keeping the gas flow at 300sccm, and setting a muffle furnace program as follows: the temperature is rapidly raised to 1000 ℃ at the temperature rise rate of 10 ℃/min and is preserved for 60 hours, then the temperature is reduced at the temperature reduction rate of 10 ℃/min, the obtained vanadium dioxide single crystal is shown in figure 1, and figure 1 is an optical photo of the vanadium dioxide single crystal prepared in the embodiment. Fig. 4 shows a schematic view of the arrangement of sample tubes in a muffle furnace.
The insulator-metal phase transition behavior of the vanadium dioxide single crystal can be measured on an integrated physical property measurement system, and is shown in fig. 1. As can be seen from fig. 1: the phase transition point of the vanadium dioxide single crystal prepared by the embodiment is about 338K, the width of the thermal hysteresis loop is 1K, the vanadium dioxide single crystal can be completely changed from an insulator phase to a metal phase or completely from the metal phase to the insulator phase within 0.05K after the phase transition occurs, and the error of multiple-cycle test is not more than 0.05K.
As mentioned above, the vanadium dioxide based single crystal and the normally closed electromagnetic relay are used to form the temperature controlled switch. The vanadium dioxide-based single crystal is placed on a battery pack back plate (a heat-emitting end), and the temperature controlled switch is connected in series to an external circuit of the battery pack. When the battery pack operates to cause the temperature to exceed about 68 ℃, the switch opens and the circuit automatically opens. The temperature then drops below about 68 c, the switch is closed, the circuit is restored, and the battery continues to operate.
Example 2:
adding 500mg of ammonium metavanadate powder into a circular single-opening corundum sample tube with the inner diameter of 1.2 cm and the length of 12 cm, obliquely placing the sample tube in a tubular annealing furnace sample chamber which is lined with quartz glass and is provided with a gas washing device, obliquely placing the sample tube at an inclination angle of 15 degrees, washing off oxygen and water in the sample chamber by a mode of vacuumizing for three times and filling high-purity argon, keeping the gas flow at 200sccm, and setting a muffle furnace program as follows: rapidly heating to 1100 ℃ at the heating rate of 10 ℃/min, preserving the heat for 60 hours, and then cooling at the cooling rate of 15 ℃/min to obtain the vanadium dioxide single crystal.
The insulator-metal phase transition behavior of the vanadium dioxide single crystal was measured on a comprehensive physical property measurement system, and the same identification results as in example 1 were obtained.
As mentioned above, the vanadium dioxide based single crystal and the normally open type electromagnetic relay are used to form the temperature controlled switch. The vanadium dioxide-based single crystal is placed on a display screen back plate (a heating end), and the temperature control switch is connected in series to a power supply circuit of an electric refrigerating sheet assembly for refrigerating the display screen back plate. When the display screen back plate works to cause the temperature to exceed about 68 ℃, the switch is switched on, and the electric cooling fin assembly starts to work in a cooling mode. When the temperature drops below about 68 ℃, the switch is switched off, and the electric refrigerating sheet component stops refrigerating. As shown in fig. 3.
Example 3:
adding powder which is uniformly mixed by 300mg of vanadium pentoxide and 15mg of molybdenum trioxide into a circular single-opening quartz sample tube with the inner diameter of 1.2 cm and the length of 12 cm, obliquely placing the sample tube with a corundum lining and a gas washing device in a tubular annealing furnace sample chamber, wherein the lining is a corundum, the inclination angle is 25 degrees, washing off oxygen and water in the sample chamber by a three-time vacuumizing-high-purity nitrogen filling mode, keeping the gas flow at 300sccm, and setting the muffle furnace program as follows: rapidly heating to 980 ℃ at the heating rate of 8 ℃/min, preserving the heat for 60 hours, and then cooling at the cooling rate of 8 ℃/min to obtain the vanadium dioxide single crystal.
The insulator-metal phase transition behavior of the vanadium dioxide single crystal was measured on a comprehensive physical property measurement system, and the same identification results as in example 1 were obtained.
As mentioned above, the vanadium dioxide based single crystal and the normally open type electromagnetic relay are used to form the temperature controlled switch. The vanadium dioxide-based single crystal is placed on a back plate (a heating end) of the LED lamp bank, and the temperature control switch is connected in series with a power supply circuit of an electric refrigerating sheet assembly for refrigerating the back plate of the LED lamp bank. When the temperature of the back plate of the LED lamp bank exceeds about 68 ℃ due to work, the switch is switched on, and the electric cooling fin assembly starts cooling work. When the temperature drops below about 68 ℃, the switch is switched off, and the electric refrigerating sheet component stops refrigerating.
It will be apparent to those skilled in the art that various changes and modifications may be made in the embodiments of the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (10)
1. A temperature-controlled switch comprising a vanadium dioxide-based single crystal as a temperature sensing section, which is produced by:
heating a raw material containing a vanadium source to a temperature of between 950 ℃ and 1150 ℃ in a flowing inert gas atmosphere for 24 hours to 72 hours, and then cooling to room temperature at a rate of not more than 20 ℃/min to obtain a vanadium dioxide-based single crystal,
Wherein the vanadium source is an oxygen-containing compound containing no other metal element than vanadium, and wherein vanadium has a valence of +4 or +5, the molar ratio of oxygen to vanadium is 2: 1 or more,
wherein when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature-controlled switch is in an on state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature-controlled switch is in an off state; or when the temperature of the temperature sensing part is lower than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in an insulator state, so that the temperature controlled switch is in an off state, and when the temperature of the temperature sensing part is higher than the insulator-metal phase transition temperature of the vanadium dioxide-based single crystal, the vanadium dioxide-based single crystal is in a metal state, so that the temperature controlled switch is in an on state.
2. The temperature controlled switch according to claim 1,
The source of vanadium is selected from the group consisting of: oxides of vanadium, oxygen-containing vanadium salts, vanadium oxyacid salts, and combinations thereof.
3. The temperature controlled switch according to claim 1,
the source of vanadium is selected from the group consisting of: vanadium pentoxide, ammonium metavanadate, vanadyl oxalate, vanadyl sulfate hydrate, vanadium ammonium sulfate, and combinations thereof.
4. The temperature controlled switch according to claim 1,
the feedstock comprising a source of vanadium is placed in a semi-open vessel.
5. The temperature controlled switch according to claim 1,
the semi-open container is a single-opening pipe which is positioned in a horizontal inert gas flow and is obliquely placed, the pipe orifice of the single-opening pipe is higher than the pipe bottom, and the included angle between the length direction and the horizontal plane is 5-35 degrees.
6. The temperature controlled switch according to claim 1,
the flowing inert gas atmosphere comprises convection of an inert gas.
7. The temperature controlled switch according to claim 1,
the inert gas is selected from the group consisting of: nitrogen, argon, and combinations thereof.
8. The temperature controlled switch according to claim 1,
the feedstock also includes a source of a doping element.
9. The temperature controlled switch according to claim 1,
the vanadium dioxide-based single crystal is a rod-like single crystal having a length of 1 mm or more and a diameter of 100 μm or more.
10. The temperature controlled switch according to claim 1,
the temperature control switch comprises an electromagnetic relay.
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| CN201910366137.1A CN111863526A (en) | 2019-04-30 | 2019-04-30 | Temperature control switch |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2023024860A1 (en) * | 2021-08-24 | 2023-03-02 | 上海奥威科技开发有限公司 | Over-heating early warning and active safety control system apparatus, and control method |
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