WO2016006338A1

WO2016006338A1 - Composite and cooling device

Info

Publication number: WO2016006338A1
Application number: PCT/JP2015/064947
Authority: WO
Inventors: 廣瀬　左京
Original assignee: 株式会社村田製作所
Priority date: 2014-07-11
Filing date: 2015-05-25
Publication date: 2016-01-14

Abstract

The present invention provides a composite of a mixture containing: a ceramic material having vanadium dioxide and/or vanadium dioxide doped with another element as the principal component thereof; and vanadium pentoxide and/or a glass material containing vanadium having a valence of five. It is possible to use this composite in a cooling device which is usable without a power supply, exhibits excellent cooling efficiency, and has high heat-cycle resistance.

Description

Composites and cooling devices

The present invention relates to a composite and a cooling device.

With the recent improvement in performance of electronic equipment, the number of electronic components such as CPU (Central Processing Unit), power amplifier, FET (Field Effect Transistor), IC (Integrated Circuit), voltage regulator, etc., which become heat sources, has increased and introduced. The increase in energy generated overlaps with the problem of heat generation. In particular, mobile devices such as smartphones and tablet terminals have a problem that the heat deteriorates the capacity of the battery and seriously affects the reliability of the electronic devices to be configured. Therefore, it is required to control the temperature inside the device to a higher degree.

Control of the heat generated from the heat source as described above is performed by a cooling fan, a heat pipe, a heat sink, a thermal sheet, a Peltier element, or the like, which is an existing heat management solution. A cooling device in which a fan or a Peltier element is combined is described (see Patent Document 1).

However, the cooling device combining the heat sink and the fan or the Peltier element as described above has a relatively complicated structure and increases the size of the device, particularly for thin devices such as smartphones and tablet terminals. Hateful. Furthermore, since power is consumed, it is disadvantageous from the viewpoint of low power consumption (battery life).

Therefore, for thin devices such as smartphones and tablet terminals, the temperature is currently controlled only by means of heat dissipation through the housing, and the heat source and the housing are thermally coupled by a thermal sheet or the like to release heat.

JP 2010-223497 A

放熱 Heat dissipation through the enclosure as described above is limited because the surface area of the enclosure is limited. Therefore, the temperature of each heat source is measured, and when the temperature exceeds a predetermined temperature, the performance of the CPU or the like is limited (suppressing heat generation itself). That is, the temperature rise of the housing may hinder the performance of the CPU or the like. Naturally, in heat dissipation through such a case, in other words, heat dissipation by heat transfer to the entire device, heat is also transferred to the battery, which can lead to a decrease in battery capacity over time.

Therefore, the present inventor has considered a cooling device that can be used without a power source by arranging a ceramic material that absorbs heat accompanying a crystal structure phase transition, a magnetic phase transition, or the like in the vicinity of a heat source of an electronic device. did. Such a ceramic material is formed by sintering and used as a cooling device. However, cracks occur in the sintered body due to a heat cycle (thermal shock) due to heating and cooling of a cold object (for example, a heating element). I found out that there was a problem. Therefore, the present inventors tried to suppress the occurrence of cracks by combining with glass such as lead glass, borosilicate glass or bismuth glass, but in this case, the cooling characteristics of the cooling device deteriorated. It has been found that another problem arises that a sufficient cooling effect cannot be obtained. Further, as a method for preventing the occurrence of other cracks, it is conceivable to make a composite of a ceramic material and a resin. However, such a composite needs to be mixed with about 50% by volume of resin to maintain its shape and handleability, and the resin does not contribute to cooling and also has a low thermal conductivity, so the cooling device There arises a problem that the heat absorption efficiency as a whole is lowered. In particular, in small devices such as smartphones and tablet PCs where installation space is limited, this problem becomes significant because high heat absorption efficiency is required.

Therefore, an object of the present invention is to provide a composite that can be used as a cooling device that can be used without a power source, has excellent cooling efficiency, and has high resistance to heat cycles.

As a result of intensive studies to solve the above problems, the present inventor has found that a ceramic material containing vanadium oxide that absorbs heat in association with a crystal structure phase transition or a magnetic phase transition, and vanadium pentoxide (V ₂ O ₅ ) or 5 It discovered that the said subject could be solved by complex ^| conjugating with the glass material containing valent vanadium ( ^{V5 +} ), and it came to this invention.

According to a first aspect of the present invention, a ceramic material mainly composed of vanadium oxide;
A composite of a glass material comprising pentavalent vanadium and / or a mixture comprising vanadium pentoxide is provided.

According to a second aspect of the present invention, there is provided a cooling device comprising the above composite.

According to a third aspect of the present invention, there is provided an electronic component comprising the cooling device.

According to a fourth aspect of the present invention, there is provided an electronic apparatus comprising the cooling device or the electronic component.

According to the present invention, a ceramic material mainly composed of vanadium oxide that absorbs heat accompanying a crystal structure phase transition or a magnetic phase transition is fired with a glass material containing pentavalent vanadium and / or vanadium pentoxide. Thus, it is possible to provide a composite having excellent cooling efficiency and high resistance to heat cycle.

FIG. 1 shows the results of differential scanning calorimetry of V _0.995 W _0.005 O ₂ produced in the experimental example. FIG. 2 shows the endothermic test results of the cooling device of Example 2. FIG. 3 shows the endothermic test results of the cooling device of Comparative Example 3.

In this specification, the composite means a lump obtained by heat-treating a powder mixture of a ceramic material, vanadium pentoxide, a glass material or the like. Such a composite is not particularly limited as long as powders (or particles) are bonded to each other as a result of heat treatment, and the size, shape, formation mechanism, and the like are not particularly limited.

The ceramic material used in the present invention is a ceramic material that absorbs heat by latent heat.

The heat absorption by this ceramic material is done by absorbing the latent heat. Such a ceramic material can obtain a high cooling effect by temporally smoothing the heat by temporarily absorbing excess heat by latent heat.

As the ceramic material, a ceramic material mainly composed of vanadium oxide that absorbs heat by latent heat is used. The vanadium oxide only needs to contain vanadium and oxygen, and includes, for example, complex oxides and oxides doped with other elements.

The other element is not particularly limited as long as it can be contained in VO ₂ as a doping element, and examples thereof include W, Ta, Mo, and Nb.

Here, the main component means a component contained in the ceramic material by 50% by mass or more, particularly 60% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and further preferably 98% by mass. The above means a component contained in, for example, 98.0 to 99.8% by mass.

The ceramic material preferably has a latent heat amount of 5 J / g or more, more preferably 20 J / g or more. By having such a large amount of latent heat, a large cooling effect can be exhibited with a smaller volume, which is advantageous in terms of downsizing. Here, “latent heat” is the total amount of thermal energy required when the phase of a substance changes, and in this specification, solid-solid phase transitions such as electrical, magnetic, and structural phase transitions are used. This refers to the amount of heat generated and absorbed.

Specific ceramic material is not particularly limited, for example, JP-ceramic material described in JP 2010-163510, _{_{_{specifically, VO 2, LiVS 2, LiVO}}} 2, V 2 O 3, V 4 O 7 , V ₆ O ₁₁ , A _y VO ₂ (wherein A is Li or Na, 0.1 ≦ y ≦ 2.0, preferably 0.5 ≦ y ≦ 1.0), V _1-x M _x O ₂ (wherein M is W, Ta, Mo, Nb, Ru or Re, and 0 ≦ x ≦ 0.2, preferably 0 ≦ x ≦ 0.05).

In a preferred embodiment, the vanadium oxide contained in the composite of the present invention is an oxide containing V (vanadium) and M (wherein M is at least one selected from W, Ta, Mo and Nb). Thus, the oxide containing M in an amount of not less than 0 mol and not more than about 5 mol, preferably not more than 1 mol, when the total of V and M is 100 mol. Note that M is not an essential component, and the content molar part of M may be 0.

In another preferred embodiment, the vanadium oxide contained in the composite of the present invention is an oxide containing A (where A is Li or Na) and V (vanadium), wherein V is 100 mole parts. In this case, the content mole part of A is about 50 mole parts or more and about 100 mole parts or less.

In another preferred embodiment, the vanadium oxide contained in the composite of the present invention has a composition formula:
V _1-x M _x O ₂
(Wherein, M is W, Ta, Mo or Nb, 0 ≦ x ≦ 0.05)
Or the composition formula:
A _y VO ₂
(Wherein, A is Li or Na, 0.5 ≦ y ≦ 1.0)
It is an oxide represented by.

In a more preferred embodiment, the vanadium oxide contained in the composite of the present invention has a composition formula:
V _1-x W _x O ₂
(Where 0 ≦ x ≦ 0.01)
It is an oxide represented by.

In another preferred embodiment, the vanadium oxide contained in the composite of the present invention is vanadium oxide doped with Ti or vanadium oxide doped with other atoms selected from the group consisting of W, Ta, Mo and Nb. Because
When the other atom is W, the content mole part of the other atom is greater than 0 mole part and less than or equal to 5 mole part with respect to a total of 100 mole parts of vanadium, Ti, and other atoms,
When the other atom is Ta, Mo or Nb, the content mole part of the other atom is greater than 0 mole part and 15 mole parts or less with respect to 100 mole parts in total of vanadium, Ti and other atoms,
The content mole part of titanium is not less than 2 mole parts and not more than 30 mole parts with respect to 100 mole parts in total of vanadium, Ti and other atoms. By using such vanadium oxide, the moisture resistance of the ceramic material is improved.

In a preferred embodiment, the Ti-doped vanadium oxide may contain 5 to 10 mole parts of titanium with respect to 100 mole parts of Ti and other atoms in total.

In another preferred embodiment, the vanadium oxide contained in the complex of the present invention is
Formula: V _1-xy Ti _x M _y O ₂
[Wherein M is W, Ta, Mo or Nb;
x is 0.02 or more and 0.3 or less,
y is 0 or more,
When M is W, y is 0.05 or less,
When M is Ta, Mo or Nb, y is 0.15 or less. ]
It is vanadium oxide represented by these. By using such vanadium oxide, the moisture resistance of the ceramic material is improved.

Preferably, in the above formula, x may be 0.05 or more and 0.1 or less.

The temperature showing the latent heat of vanadium oxide, that is, the temperature at which this vanadium oxide undergoes phase transition can be adjusted by adding (doping) another element and adjusting the amount of the element added.

For example, vanadium oxide has the composition formula:
V _1-x W _x O ₂
When x is 0.005, the phase transition occurs at about 50 ° C., and when x is 0.01, the phase transition occurs at about 40 ° C.

The temperature at which the vanadium oxide undergoes phase transition is appropriately selected depending on the object to be cooled, the purpose of cooling, and the like. For example, when the object to be cooled is a CPU, the phase is increased at 20 to 100 ° C., preferably 40 to 60 ° It is preferable to transfer.

The ceramic material is preferably in the form of particles (powder). The average particle size of the core portion of the ceramic material (D50: the particle size distribution on a volume basis, the particle size at which the cumulative value is 50% in the cumulative curve with the total volume being 100%) is not particularly limited, For example, the thickness is 0.1 to several hundred μm, specifically 0.1 to 900 μm, typically about 0.2 to 50 μm, and preferably 0.5 to 50 μm. The average particle diameter can be measured using a laser diffraction / scattering soot particle diameter / particle size distribution measuring apparatus or an electronic scanning microscope. The average particle diameter is preferably 0.2 μm or more from the viewpoint of ease of handling, and is preferably 50 μm or less from the viewpoint that it can be more densely molded.

The ceramic material in the composite of the present invention has a volume fraction of 50% or more, preferably 60% or more, more preferably 70% or more. By setting the volume fraction of the ceramic material to 50% or more, the endothermic amount of the composite can be increased. Here, the volume fraction represents the volume ratio of the ceramic material showing the latent heat contained in% when the volume of the composite is 100%.

The glass material used in the present invention contains pentavalent vanadium (V ⁵⁺ ).

The glass material containing pentavalent vanadium preferably contains pentavalent vanadium in terms of V ₂ O ₅ , preferably 15% by mass or more, more preferably 20% by mass or more. By containing 15 mass% or more of pentavalent vanadium in terms of V ₂ O ₅ , it is possible to further suppress diffusion of impurities contained in the glass that affect the endothermic property of the ceramic material into the ceramic material. .

The glass material containing pentavalent vanadium (V ⁵⁺ ) is not particularly limited as long as it contains V ⁵⁺ (V ₂ O ₅ ), and a glass generally referred to as vanadium glass, such as Hitachi Chemical Bunny Tect (commodity) Name). The glass material containing pentavalent vanadium may contain at least one selected from the group consisting of alkaline earth, phosphorus, silicon, silver, tungsten, boron and tellurium in addition to pentavalent vanadium. . In addition, glass such as lead-based glass, borosilicate glass, or bismuth-based glass to which V ₂ O ₅ is added can also be used.

The softening point of the glass material is preferably in a temperature range in which the ceramic material (preferably VO ₂ ) does not substantially cause chemical alteration (for example, oxidation), and specifically, 500 ° C. or less is preferable. 400 ° C. or lower is more preferable, and 300 ° C. or lower is further preferable. By controlling the softening point of the glass material in such a temperature range, it is possible to suppress changes in the properties of the ceramic material (particularly the endothermic temperature and endothermic amount) when firing the mixture of the ceramic material and the glass material. Can do. The lower limit of the softening point of the glass material only needs to be higher than the temperature of the environment in which the composite (cooling device) of the present invention is installed, for example, 150 ° C. or higher, preferably 200 ° C. or higher, more preferably 250 ° C. or higher. If it is. The softening point of the glass material can be measured by a thermomechanical analyzer (TMA), thermogravimetry / differential thermal analysis (TG-DTA).

The vanadium pentoxide is preferably in the form of particles (powder). The average particle size (D50) is preferably about the same as that of the ceramic material, and is not particularly limited. For example, it is 0.1 to several hundred μm, specifically 0.1 to 900 μm, and typically about 0. .2 to 50 μm, preferably 0.5 to 50 μm. The average particle diameter can be measured using a laser diffraction / scattering soot particle diameter / particle size distribution measuring apparatus or an electronic scanning microscope. The average particle diameter is preferably 0.2 μm or more from the viewpoint of ease of handling, and is preferably 50 μm or less from the viewpoint that it can be more densely molded.

In the mixture of the ceramic material and vanadium pentoxide and / or glass material, the total content of vanadium pentoxide and glass material is preferably 20 to 50% by volume, more preferably 20 to 40% by volume, Preferably, it is 20 to 30% by volume. By setting the content of vanadium pentoxide and the glass material to 50% by volume or less, the ratio of the ceramic material in the composite increases, so that the endothermic amount of the composite can be increased. Moreover, by setting the ratio of vanadium pentoxide and the glass material to 20% by volume or more, the bonding between the particles of the ceramic material can be further strengthened, and the strength and heat cycle resistance of the composite can be increased.

In the mixture of the ceramic material and vanadium pentoxide and / or glass material, the content of V ⁵⁺ is preferably 1% by weight or more, for example, 5% by weight or more or 10% by weight in terms of V ₂ O _5. That can be the case.

The composite of the present invention can be obtained by heat-treating a mixture of a ceramic material, a glass material containing pentavalent vanadium and / or vanadium pentoxide. Accordingly, the present invention provides a method for producing the composite of the present invention, comprising heat treating a mixture of a ceramic material and a glass material.

In the production method of the present invention, preferably, before the heat treatment, a mixture of a glass material and / or vanadium pentoxide may be mixed and temporarily formed into a desired shape. The method of temporary molding is not particularly limited, and examples thereof include a method of molding by compression and a method of molding after mixing with a binder resin.

The temperature of the heat treatment is preferably not less than the softening point of the glass material and not more than a temperature at which vanadium oxide in the ceramic material does not substantially change, for example, not more than a temperature at which the valence of vanadium oxide does not substantially change. For example, the heating temperature can range from 300 ° C to 600 ° C.

Preferably, the heat treatment is performed in an atmosphere in which the vanadium oxide in the ceramic material is not substantially denatured, for example, an atmosphere in which the valence of vanadium in the vanadium oxide is not substantially changed (in other words, is not substantially oxidized / reduced). Done under. The heat treatment atmosphere can be appropriately selected depending on the temperature of the heat treatment. For example, in the range of 300 ° C. to 600 ° C., in order to prevent oxidation of vanadium oxide, in a reducing atmosphere, for example, in a mixed atmosphere of nitrogen and hydrogen. possible. Further, when the temperature is low, for example, when it is lower than 300 ° C., vanadium oxide is hardly oxidized and may be heated in the atmosphere.

The heating time is not particularly limited, but may be 10 minutes to 10 hours.

According to the method of the present invention, it is possible to obtain a composite that is very densified and has a large volume fraction of ceramic material. Without being bound by any theory, such a dense complex is thought to be obtained for the following reasons. When the mixture of ceramic material and glass material is heat treated, the glass material softens. The softened glass attracts the surrounding ceramic material particles to reduce its surface free energy, resulting in a smaller distance between the ceramic material particles and fewer voids. In the composite thus obtained, the proportion of the ceramic material (that is, vanadium oxide) in the composite is increased, and the endothermic amount is improved.

The present invention provides a cooling device including the above composite.

The shape of the cooling device of the present invention is not particularly limited, and can be any shape.

In one aspect, the cooling device of the present invention may be block-shaped. By making it into a block shape, the whole volume becomes large and more heat can be absorbed. In another aspect, the cooling device of the present invention may be in the form of a sheet. By making it into a sheet shape, the surface area increases, so it becomes easy to release absorbed heat to the outside.

The cooling device of the present invention is installed in another member, for example, a protective cover for protecting the cooling device, a heat conductive part such as a metal for enhancing heat conductivity, an insulating sheet for ensuring insulation, and an electronic device. Members (for example, pressure-sensitive adhesive sheets, pins, nails, etc.) may be included.

The present invention also provides an electronic component and an electronic apparatus having the cooling device of the present invention.

The electronic component is not particularly limited, but for example, an integrated circuit (IC) such as a central processing unit (CPU), a power management IC (PMIC), a power amplifier (PA), a transceiver IC, and a voltage regulator (VR). Light emitting diodes (LEDs), incandescent bulbs, semiconductor lasers and other light emitting elements, field effect transistors (FETs) and other components that can be heat sources, and other components such as substrates, heat sinks, housings, etc. Examples of parts that are commonly used.

The electronic device is not particularly limited, and examples thereof include a mobile phone, a smartphone, a personal computer (PC), and a tablet terminal.

Example 1
-Production of ceramic material Vanadium trioxide (V ₂ O ₃ ), vanadium pentoxide (V ₂ O ₅ ), and tungsten oxide (WO ₃ ) were used as ceramic raw materials, and these were V: W: O = 0.0.99. : 0.005: 2 (molar ratio) and weighed and dry-mixed. Thereafter, nitrogen / hydrogen / 1000 ° C. under a water atmosphere, heat treated 4 hours to synthesize _{V 0.995} W _0.005 O ₂ as a ceramic material (0.5 at% W-doped VO _2). Thereafter, pure water, partially stabilized zirconium balls (PSZ), a dispersant (SN Dispersant 5468) and a synthetic powder were weighed in a polypot, pulverized for 24 hours, and then dried to produce a ceramic material powder. Here, PSZ was used for pulverization with water, but it may be mixed by a dry method.

Differential scanning calorimetry (DSC) was performed on the V _0.995 W _0.005 O ₂ powder obtained above. The measurement was performed by sweeping the temperature from 0 ° C. to 100 ° C. and from 100 ° C. to 0 ° C., and the heat input / output (endotherm, exotherm) of the sample was evaluated. The results are shown in FIG. As shown in FIG. 1, it was confirmed that the ceramic material obtained above absorbs heat from about 50 ° C. when the temperature rises and dissipates heat in a lower temperature region than when it rises when the temperature falls. .

-Preparation of cooling device 30% by volume of V ₂ O ₅ powder is added to the ceramic material powder obtained above, mixed in an agate mortar, and then pellets having a diameter of 20 mm and a thickness of 3 mm using a mold and a press. Was made. The produced pellet was heat-treated in a nitrogen atmosphere at 500 to 750 ° C. to obtain a cooling device (composite) of Example 1.

Example 2
Example 1 except that vanadium-based glass (manufactured by Hitachi Chemical, VP-1175, softening temperature: about 400 ° C.) (30% by volume) was used instead of V ₂ O ₅ powder (30% by volume). Thus, a cooling device (composite) of Example 2 was obtained.

Comparative Example 1
Except not using the V ₂ O ₅ powder, in the same manner as in Example 1 to obtain a cooling device in Comparative Example 1 comprising only the powder of the ceramic material (complex).

Comparative Example 2
Example 1 except that bismuth-based low-melting glass (manufactured by Sekiya Rika, 2280-06, softening temperature: about 400 ° C.) (30% by volume) was used instead of V ₂ O ₅ powder (30% by volume). In the same manner, a cooling device (composite) of Comparative Example 2 was obtained.

Comparative Example 3
An acrylic resin (30% by volume) was added to the ceramic material powder obtained in the same manner as in Example 1, and this was solidified into pellets having a diameter of 20 mm and a thickness of 3 mm. Resin composite) was obtained.

Test example 1
-Endothermic test A PTC (Positive Temperature Coefficient) heater having an ultimate temperature of about 75 ° C. was used as a heating element, heat conduction grease was applied to the heater surface, and an ultrafine K thermocouple was attached. From there, the cooling devices prepared in Examples 1 and 2 and Comparative Examples 1 to 3 were pressed and fixed. While monitoring the temperature with a thermocouple, a rated DC current was passed through the PTC heater for 10 minutes, and then the cycle of stopping the current for 10 minutes was repeated twice. As a control, the same test was performed without installing a cooling device.

For each sample, the time to reach the maximum temperature (72 ° C.) was measured, and the delay time to reach the maximum temperature was calculated compared to the case where no cooling device was installed. The results are shown in Table 1 below. Moreover, the measurement result at the time of using the cooling device of Example 2 and the comparative example 3 as a representative is shown in FIG. 2 and FIG. 3, respectively.

As shown in Table 1, it was confirmed that the cooling devices of Examples 1 and 2 can delay the time to the highest temperature by 180 seconds and 200 seconds, respectively.

On the other hand, although the acrylic resin composite of Comparative Example 3 contained the same amount of V _0.995 W _0.005 O ₂ (W-doped VO ₂ ), the delay time was as short as 50 seconds. In addition, as shown in FIGS. 2 and 3, the temperature of the cooling device of Example 2 is 40 ° C. even after about 600 seconds after the energization is stopped. In the cooling device of Comparative Example 3, after the energization is stopped, The temperature became 40 ° C. or less in about 400 seconds. From this result, it can be seen that a larger amount of heat was stored in the cooling device of Example 2. The reason why such a difference arises even though both contain the same amount of W-doped VO ₂ is that the acrylic resin composite absorbs heat throughout the device because the thermal conductivity of the resin is low. This is considered to be because the heat absorption is not possible due to heat absorption only at a part in contact with the heater.

Further, Comparative Example 2 using a bismuth glass having a softening temperature similar to that of vanadium-based glass has a delay time of 105 seconds although the thermal conductivity is similar, and uses vanadium-based glass. It was about half of the case.

The present invention is not bound by any theory, but the reason is considered as follows. The glass contains impurities such as boron, phosphoric acid, sodium, and molybdenum, regardless of whether they are vanadium glass or bismuth glass. These impurities affect the latent heat characteristics of vanadium oxide (in this embodiment, V _0.995 W _0.005 O ₂ ), and when diffused into the vanadium oxide phase, the latent heat characteristics of vanadium oxide are deteriorated. When bismuth glass was used, such diffusion occurred, but when vanadium glass was used, it is considered that such diffusion did not occur.

・ Energy dispersive X-ray spectrometry (EDX)
In order to confirm the presence or absence of the diffusion of the impurities, the cross sections of the cooling devices obtained in Example 2 and Comparative Example 2 were observed by the EDX method.
As a result, in the cooling device of Example 2, the impurity element was detected in the glass phase, but the impurity element was hardly detected in the V _0.995 W _0.005 O ₂ particles, and the diffusion was substantial. It was confirmed that this did not occur. On the other hand, in the cooling device of Comparative Example 2, an impurity element was detected in the V _0.995 W _0.005 O ₂ particles, and it was confirmed that diffusion occurred. Although the present invention is not restricted by any theory, the reason why diffusion can be suppressed when vanadium glass is used is considered as follows. The vanadium-based glass contains V ₂ O ₅ (pentavalent vanadium), but V ₂ O ₅ has a property that it has structurally more gaps than VO ₂ and easily incorporates different elements. Therefore, it is considered that the impurities are preferentially diffused into the V ₂ O ₅ phase, not VO ₂ (in this example, V _0.995 W _0.005 O ₂ ).

Heat cycle test The cooling devices produced in Examples 1 and 2 and Comparative Examples 1 to 3 were subjected to a heat cycle test of −25 ° C. → 150 ° C. → −25 ° C. 100 times, and the element surface was observed with an optical microscope. . The case where a crack did not occur was evaluated as “◯”, and the case where a crack occurred was evaluated as “×”. The results are also shown in Table 1.

As shown in Table 1, Comparative Example 1, which is a sintered body of V _0.995 W _0.005 O ₂ alone, was cracked but was a composite with V ₂ O ₅ or vanadium-based glass. In Examples 1 and 2, it was confirmed that no cracks occurred in the heat cycle test. Although this invention is not restrained by any theory, it thinks as follows. In the sintered body of V _0.995 W _0.005 O ₂ alone, internal stress is generated at the grain boundary portion by sintering. It is considered that stress is further concentrated on the grain boundary portion due to the structural change of vanadium oxide during endothermic heat generation, and the grain boundary breaks to cause a crack. On the other hand, by using glass, particles can be bonded at a low temperature, and a lump can be formed without causing stress. Further, the bonding force between the particles can be increased. Therefore, it is considered that no breakage occurs even if stress is generated due to the structural change of vanadium oxide during endothermic generation.

From the above results, it was confirmed that the cooling devices of Examples 1 and 2 which are composites with vanadium pentoxide or vanadium-based glass have high heat cycle resistance and excellent endothermic properties.

The cooling device of the present invention can be used, for example, as a cooling device for a small communication terminal in which a thermal countermeasure problem has become remarkable.

Claims

A ceramic material mainly composed of vanadium oxide;
A composite of a glass material containing pentavalent vanadium and / or a mixture containing vanadium pentoxide.
When vanadium oxide is an oxide containing vanadium and M (where M is at least one selected from W, Ta, Mo and Nb), the total amount of vanadium and M is 100 mol parts 2. The composite according to claim 1, wherein the molar part of M is 0 to about 5 parts by mole.
The vanadium oxide is an oxide containing A (where A is Li or Na) and vanadium, and the content of A when the vanadium is 100 mol parts is about 50 mol parts or more and about 100 mol The composite according to claim 1, wherein the composite is less than or equal to parts.
Vanadium oxide has the formula:
V 1-x M x O 2
(In the formula, M is W, Ta, Mo or Nb, and x is 0 or more and 0.05 or less)
Or the formula:
A y VO 2
(In the formula, A is Li or Na, and y is 0.5 or more and 1.0 or less)
The composite according to claim 1, comprising one or more oxides represented by:
The vanadium oxide is Ti-doped vanadium oxide or further vanadium oxide doped with other atoms selected from the group consisting of W, Ta, Mo and Nb,
When the other atom is W, the content mole part of the other atom is greater than 0 mole part and less than or equal to 5 mole part with respect to a total of 100 mole parts of vanadium, Ti, and other atoms,
When the other atom is Ta, Mo or Nb, the content mole part of the other atom is greater than 0 mole part and 15 mole parts or less with respect to 100 mole parts in total of vanadium, Ti and other atoms,
2. The composite according to claim 1, wherein a content mole part of titanium is not less than 2 mole parts and not more than 30 mole parts with respect to a total of 100 mole parts of vanadium, Ti and other atoms.
The composite according to claim 5, wherein a content mole part of titanium is 5 mole parts or more and 10 mole parts or less with respect to a total of 100 mole parts of vanadium, Ti and other atoms.
Vanadium oxide has the formula:
V 1-x-y Ti x M y O 2
[Wherein M is W, Ta, Mo or Nb;
x is 0.02 or more and 0.3 or less,
y is 0 or more,
When M is W, y is 0.05 or less,
When M is Ta, Mo or Nb, y is 0.15 or less. ]
The composite according to claim 1, wherein the composite is vanadium oxide represented by the formula:
The composite according to claim 7, wherein x is 0.05 or more and 0.1 or less.
9. The composite according to claim 1, wherein the ceramic material has an average particle size of 0.1 to 50 μm.
A ceramic material mainly composed of vanadium oxide;
The composite according to any one of claims 1 to 9, wherein the composite is a composite comprising a glass material containing pentavalent vanadium.
The glass material containing pentavalent vanadium is a glass material containing at least one selected from the group consisting of alkaline earth, phosphorus, silicon, silver, tungsten, boron and tellurium in addition to pentavalent vanadium. The composite according to any one of claims 1 to 10, characterized in that
A ceramic material mainly composed of vanadium oxide;
10. The composite according to claim 1, which is a composite of a mixture containing vanadium pentoxide.
A ceramic material mainly composed of vanadium oxide;
The glass material containing pentavalent vanadium and / or the mixture containing vanadium pentoxide has a total content of the glass material containing vanadium pentoxide and pentavalent vanadium of 20 to 50% by volume. The complex according to any one of claims 1 to 12.
A cooling device comprising the composite according to any one of claims 1 to 13.
An electronic component comprising the cooling device according to claim 14.
An electronic apparatus comprising the cooling device according to claim 14 or the electronic component according to claim 15.