JPH11130523A - Calcium silicate complex sintered compact and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a calcium silicate complex sintered compact having an extremely small number of pores and extremely small pores, consequently having excellent mechanical properties such as strength and plane roughness in precision processing and to provide a method for producing the sintered compact. SOLUTION: This sintered compact is one obtained by pressure/electrical conductive sintering, comprises a crystal texture obtained by combining calcium silicate with aluminum silicate as a main component, has a density of >=98% the theoretical density and a maximum pore diameter of <=20% the average crystal particle diameter. The sintered compact is produced by baking a raw material mixture of at least one of wollastonite and a calcium silicate to be transferred to wollastonite by baking and at least one lithium aluminosilicate by a pressure/electrical conducting sintering. In a calcium silicate complex sintered compact having temperature effects in a wide use requiring thermal shock resistance, heat insulating properties, low thermal expansion, etc., since the sintered compact is baked without grain growth and hardly has pores or even if has any pores, the pores are extremely small and the sintered compact has excellent strength and plane roughness in processing.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to various low- and high-temperature parts / jigs / equipments requiring thermal shock resistance, various precision mold materials / precision inspection equipment parts / high-temperature instrument parts requiring low thermal expansion properties, and heat insulating properties. Calcium silicate composite sintered body suitable for heat insulating materials for semiconductors that require high precision, various precision parts that require high precision workability, etc. The present invention relates to a calcium silicate composite sintered body having excellent surface roughness during processing and a method for producing the same.

[0002]

2. Description of the Related Art Conventional ceramics, alumina, zirconia, silicon nitride, silicon carbide, etc. have excellent individual characteristics, but have advantages and disadvantages as a whole, and a kind of material requires thermal shock resistance. Required low-high temperature parts, jigs and equipment, various precision mold materials requiring low thermal expansion, precision inspection equipment parts, high-temperature instrument parts, heat-insulating materials for semiconductors requiring heat insulation, precision processing At present, it cannot be used for various applications such as various precision parts.

[0003] For example, alumina is used for various applications including IC package substrates. However, since it is inferior in thermal shock resistance, high temperature tools such as jigs for heat treatment of piezoelectric elements, magnetic materials, etc. Like bobbin for superconducting coil
It cannot be used for low-temperature jigs and tools that are used in a cryogenic liquid helium environment at -269 ° C.

[0004] Zirconia, silicon nitride, silicon carbide and the like are similar in that they have problems in any of the properties, and furthermore, these materials are difficult to process, so that the processing cost is high and the material cost is very high. Therefore, it cannot be used unless it has a very high added value.

[0005] Other ceramics include low thermal expansion ceramics represented by cordierite, spodumene, aluminum titanate and the like, and ceramics having excellent workability called machinable ceramics.

However, the biggest drawback of low thermal expansion ceramics is that they are not densified due to their difficulty in sintering and are porous, so that they are used only for very limited applications. Further, since machinable ceramics are rich in heat insulating properties and are often dense ceramics having a porosity of 0%, they are used as heat insulating materials and various jigs and tools in the semiconductor field where gas emission from raw materials is unfavorable. However, it is difficult to use as a general-purpose material in terms of low heat resistance, high material cost, and the like, and most of them are only prototype prototypes.

As described above, all of the conventional ceramics have advantages and disadvantages and cannot be used for a wide range of applications.

As a solution to the problems of such existing ceramics, the present applicant has previously made the calcium silicate and lithium aluminosilicate complex to improve the heat insulation and workability of calcium silicate. Has developed a calcium silicate composite sintered body having both low thermal expansion and heat insulating properties of lithium aluminosilicate (Japanese Patent Application Laid-Open Nos. 4-305046 and 6-55).
No. 394). Since the calcium silicate composite sintered body generates a remarkable liquid phase during sintering, the relative density can be easily obtained by normal pressure sintering without using hot pressing means such as hot pressing.
It is a sintered body that densifies to about 92 to 97%.

[0009]

Generally, the higher the temperature at the time of sintering and the longer the sintering time, the thicker the glass phase formed in the sintered body by the liquid phase and the more apparent the grain growth. It becomes to become. That is, since the liquid phase sintering promotes the grain growth during sintering, the crystal grain size increases and the strength is hardly increased. Further, in the sintered body containing lithium aluminosilicate as described above, the details are not clear, but because the Li component in the lithium aluminosilicate is volatilized when a liquid phase is formed, relatively large pores of about 10 μm are formed. It is formed inside, causing a decrease in density, a decrease in mechanical properties such as strength, and an increase in roughness of a machined surface upon grinding and polishing.

[0010] Accordingly, the present invention provides a calcium silicate composite sintered body comprising calcium silicate and lithium aluminosilicate, having extremely small and extremely small pores and having significantly improved mechanical properties and processed surface roughness. It is an object to provide a body and a method for producing the same.

[0011]

Under these circumstances, the present inventors have conducted intensive studies to carry out firing while avoiding the above-mentioned grain growth and pore formation as much as possible. However, in the case of heat generated from the inside of the powder, that is, a kind of self-heating, rapid temperature rise and short-time sintering are possible, and grain growth and pore formation are significantly suppressed. A dense, high-strength, and high-surface-roughness calcium silicate composite sintered body can be obtained. It has been found that pressure and current heating sintering methods such as discharge plasma sintering and plasma activated sintering are the most effective as the heating method, and completed the present invention.

That is, the present invention relates to a sintered body obtained by a pressure / current heating sintering method, wherein the sintered body is mainly composed of a composite structure of calcium silicate and lithium aluminosilicate, and has a density of 98% of the theoretical density. As described above, the present invention provides a calcium silicate composite sintered body characterized in that the maximum pore size is 20% or less of the average crystal grain size.

[0013] The present invention also relates to a pressure / current heating sintering method using a raw material blend containing at least one kind of wollastonite or calcium silicate which is transformed into wollastonite by firing and at least one kind of lithium aluminosilicate. And a method for producing the calcium silicate composite sintered body, characterized by firing.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The calcium silicate composite sintered body of the present invention is a composite sintered body containing calcium silicate and lithium aluminosilicate as main constituent phases. With only one of calcium silicate and lithium aluminosilicate, densification is not achieved, and strength,
The surface roughness is inferior.

The density of the calcium silicate composite sintered body of the present invention must be 98% or more of the theoretical density. If the density is less than this, the strength decreases as the voids increase, and the roughness of the processed surface becomes poor. The calcium silicate composite sintered body of the present invention may contain up to about 2% by weight of impurities contained in the raw material and inevitable impurities in the production process. Therefore, the above theoretical density
Strictly, 98% or more should be considered in consideration of the impurities of 2% by weight or less, but here, it is a numerical value converted by considering that it is composed only of calcium silicate and lithium aluminosilicate.

The size of the pores present in the calcium silicate composite sintered body of the present invention must be at most 20% or less of the average crystal grain size of the sintered body. If the maximum pore diameter is larger than this, strength, surface roughness, etc. decrease, which is not preferable. The maximum pore diameter is preferably 10 times the average crystal grain size.
%, More preferably 5% or less, whereby the above-mentioned properties are further improved.

The ratio of calcium silicate and lithium aluminosilicate in the calcium silicate composite sintered body of the present invention is such that the ratio of lithium aluminosilicate to the total amount of both is 1 to 99% by weight, particularly 5 to 95% by weight.
It is preferred that Both calcium silicate and lithium aluminosilicate are known to be difficult to sinter with simple materials, and lithium aluminosilicate is 1% by weight.
If it is less than 99% by weight or more than 99% by weight, it will be close to any one of them, so the generation of liquid phase will decrease during the sintering process, and the sintered body will not be densified to 98% of the theoretical density, And the processed surface becomes rough.

The ratio of calcium silicate to lithium aluminosilicate is more strictly determined in relation to the balance between the average particle sizes of the two powders used. That is, if one average particle size is relatively smaller, the preferred ratio of the powder to the total amount of both is reduced due to improvement in sinterability, and if the average particle size is larger, the preferred ratio of the powder is increased. Will be.

As the calcium silicate constituting the calcium silicate composite sintered body of the present invention, CaO is C, S
iO ₂ is abbreviated as S and includes CS, C ₂ S, C ₃ S, C ₃ S _{2 and the} like. Among them, CS wollastonite is preferable, and wollastonite has two types of α and β. However, β-wollastonite is most preferred. C ₂ S, C ₃ S, etc. may be contained, but if the amount is large, densification is impaired, so it is preferably up to 2% by weight.

As the lithium aluminosilicate constituting the calcium silicate composite sintered body of the present invention, Li ₂ O
Is L, Al ₂ O ₃ is A, SiO ₂ is S, and LAS ₂ eucryptite, LAS ₄ spodumene, and spodumene solid solution are exemplified. Of these, spojumen are preferred in terms of cost and the like as compared with eucryptite. Furthermore, although there are two types of spojumen, α and β, β-spodumene is most preferred.

In addition to the above, the calcium silicate composite sintered body of the present invention has a content of up to about 2% by weight.
Fe, Mg, M due to sintering aids or unavoidable impurity components
An oxide such as n, P, Al, Na, or K may be contained.

The content of each element in the calcium silicate composite sintered body of the present invention is expressed in terms of% by weight in terms of oxide.
0.1 ≦ Li ₂ O ≦ 10.0, 50.0 ≦ SiO ₂ ≦ 65.0, 0.1 ≦ CaO ≦ 48.
It is preferable that 0, 0.5 ≦ Al ₂ O ₃ ≦ 35.0.

When the content of each component is less than the lower limit of the range, Li ₂ O: strength, densification, thermal shock resistance, low thermal expansion SiO ₂ : strength, densification, thermal shock resistance, heat insulation gender, if the low thermal expansion CaO: strength, densification, when the heat-insulating Al ₂ O _3: strength, densification, heat shock resistance, characteristics of low thermal expansion is inferior, respectively.

When the content of each component exceeds the upper limit of the range, Li ₂ O: strength, densified SiO ₂ : strength, densified CaO: strength, densification, thermal shock resistance , Low thermal expansion Al ₂ O ₃ : The properties of strength, densification, thermal shock resistance, heat insulation, and thermal expansion coefficient are each inferior.

Further, the average crystal grain size of the calcium silicate composite sintered body of the present invention is 10 μm or less, further 2 μm or less,
In particular, it is preferably 1 μm or less. Average grain size is 10
If it exceeds μm, the strength of the sintered body will not be improved, and its ground / polished surface will be rough. Generally, the strength and the surface roughness depend on the crystal grain size constituting the sintered body. If the grain size is small, both the strength and the surface roughness are improved.

Further, the crystal grain size of the calcium silicate composite sintered body of the present invention is preferably at most 50 μm, more preferably at most 10 μm, particularly preferably at most 5 μm. When there is a crystal that is significantly coarser than the average crystal grain size, the crystal grain acts as a defect, causing a significant decrease in strength, and inevitably results in a significant loss of surface roughness. .

[0027] The calcium silicate composite sintered body of the present invention comprises at least one of wollastonite or calcium silicate which is transformed into wollastonite by firing;
It can be produced by sintering a raw material mixture containing at least one kind of lithium aluminosilicate by a pressurized / electrically heated sintering method.

Examples of the calcium silicate as a starting material include wollastonite and CSH (a precursor of calcium silicate crystalline hydrate, and a molar ratio of Ca and Si of Ca).
/ Si is a general term for amorphous hydrates that can have various ratios), tobermorite, zonotolite, gyrolite, orkenite, and the like. Any of these can be used alone or in combination of two or more. Among them, CSH, zonotolite and wollastonite are preferable, CSH having a Ca / Si molar ratio of about 0.5 to 1.5 is preferable, and wollastonite is preferably natural β-wollastonite.

As the other starting materials, lithium aluminosilicate, L: A: S = 1: 1: 2, 1: 1: 3, 1: 1: 4,
1: 1: 6, 1: 1: 8, 1: 1: 10, 1: 1: 12, 1: 1: 15, etc., either of which is used alone or in combination of two or more. be able to. Of these, LAS ₂ eucryptite,
The LAS ₄ spodumene and the LAS ₈ petalite are preferred, and from the viewpoint of cost and the like, naturally-occurring α-spodumene, β-spodumene obtained by calcining the α-spodumene, and natural petalite are preferred. Petalite becomes a β-spodumene solid solution at high temperatures.

These starting materials preferably have an average particle size of 10 μm or less, particularly 1 μm or less, in order to obtain a sintered body having a small crystal grain size as described above. This is because the size of the crystal grain size in the sintered body depends on the grain size of the starting material used.

As a method for easily obtaining ultrafine particles of 1 μm or less of these starting materials, the following methods are exemplified.

That is, ultra-fine particles of wollastonite are obtained by hydrothermally treating a slurry in which the Ca / Si molar ratio of the Si raw material and the Ca raw material is adjusted to 0.5 to 1.5 to synthesize calcium silicate hydrate. By firing at 1200 ° C and pulverizing if necessary,
Β-spodumene can be manufactured by sintering the spodumene at 1000 to 1300 ° C. and subjecting it to a phase transition to pulverize the obtained β-spodumene.

By calcination as described above, the former provides fine particles of β-wollastonite or an aggregate thereof, and the latter obtains a polycrystalline structure having fine β-spodumene crystal grain boundaries, In each case, ultrafine particles can be easily obtained by a ball mill or the like without using a special ultrafine pulverizer such as an attritor.

The composition of the raw material blend may be such that after firing, the lithium aluminosilicate is blended at a ratio of 1 to 99% by weight based on the total amount of calcium silicate and lithium aluminosilicate in the crystal phase of the sintered body. When a raw material having an impurity component content of 2% by weight or less is used, the lithium aluminosilicate raw material may be blended at a ratio of 1 to 99% by weight based on the total amount of the calcium silicate raw material and the lithium aluminosilicate raw material. it can.

In these raw materials, up to about 2% by weight, as a sintering aid or an unavoidable impurity component, Fe,
Mg, Mn, P, Al, Na, oxides such as K or a mixture thereof can be used without any problem, if it is a calcium silicate powder and lithium aluminosilicate powder usually used at an industrial level, It can be used without any special restrictions.

The calcium silicate composite sintered body of the present invention can be obtained by sintering the above-mentioned raw material mixture by a pressure / current heating sintering method. Examples of the pressurized / electrically heated sintering method include a discharge plasma sintering method and a plasma activated sintering method. According to these methods, unlike conventional sintering using an external heat method, grain growth and pore formation are performed. The sintering can be performed at a low temperature and in a short time while suppressing.

Next, a process in which the pressurized / electrically heated sintering method effectively acts on the sintering of the calcium silicate composite sintered body will be described with reference to the discharge plasma sintering method as an example. In the spark plasma sintering method, the sintering is performed by applying a DC pulse voltage / current to the raw material powder in the die by arbitrarily changing the on / off ratio of the DC voltage / current using a special pulse power supply device. Is the way. When the DC voltage is on, the powder rapidly expands in volume, and conversely when it is off, the volume contracts, so that the impurities adhering to the surface of the raw material powder are eliminated by repeated on / off, and the surface is cleaned. , Resulting in an extremely activated state.

Next, due to the Joule heat generated by energization and the self-heating effect due to the spark discharge generated between the powders, the calcium silicate and lithium aluminosilicate particle contacts locally reach the eutectic point. The liquid phase thus generated is further diffused in volume, surface and grain boundaries on the surface of the activated calcium silicate composite sintered powder at a very high speed and in a short time by the electric field effect accompanying the on / off pulse current. .

In the calcium silicate composite sintered body obtained by the above process, no grain growth is observed.
In addition, the pores which have been generated in the past are scarcely recognized due to the combination of low-temperature sintering and pressurization / electric heating. For this reason, it is considered that the obtained calcium silicate composite sintered body is a sintered body having high strength and extremely excellent surface roughness, which can be precisely machined.

In the above description, the discharge plasma sintering method has been described as an example. In addition to the above-described discharge plasma sintering method which is a low-voltage high-current control (current control), a high-voltage low-current control (voltage control) is also used. The plasma-activated sintering method is the same in that the powder is directly applied with a voltage and sintering is performed using plasma generated in the gap between the powder particles, thereby achieving the object of the present invention.

The firing temperature depends on the average particle size of the starting materials used, but is usually in the range of 900 to 1200 ° C., particularly 950 to 1150 ° C.
C. is preferred. If the temperature is below the lower limit of this temperature range, the sintered body does not become dense, and both the strength and the surface roughness decrease. On the other hand, if the upper limit is exceeded, densification is achieved, but the liquid phase becomes dominant and grain growth becomes remarkable, resulting in reduced strength and surface roughness. In addition, as a result of foaming in the sintered body, densification is impaired.

[0042]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

In each of the examples, when one of β-wollastonite and β-spodumene is small, it is difficult to completely identify the crystal phase of the sintered body. The crystal phase of the sintered body obtained with the ratio of β-wollastonite and β-spodumene used at 50:50 was confirmed. The crystal phases were β-wollastonite and β-spodumene. Nothing was found. Therefore, taking into account the weight loss (ignition loss) of each starting material at a high temperature, the ratio of the crystal phase of the sintered body is almost the same as that of the starting material, but the ratio of the crystal phase in the following examples is The numerical value of the ratio indicates a value as a pure content excluding this impurity.

Examples 1 to 4 (1) Raw Materials Used As a lithium aluminosilicate raw material, natural α-spodumene (Li ₂ O: 7.6% by weight, Al ₂ O ₃ : 26.5% by weight,
SiO ₂ : 64.5% by weight, other: 1.2% by weight, ignition loss 0.2% by weight)
- wollastonite (CaO: 46.2 wt%, SiO _2: 51.1 wt%, Other: 1.6 wt%, ignition loss 1.1 wt%) was used.

(2) Production of Raw Material Fine Particles (a) The natural α-spodumene used has an average particle diameter of 200
The temperature was raised to 1100 ° C. at a rate of 5 ° C./min, baked at this temperature for 1 hour, and then gradually cooled to obtain β-spodumene. The β-spodumene contained many fine cracks, and a kind of grain boundary appeared at a size of about 0.5 μm. When this powder was wet-pulverized by a ball mill for 72 hours, ultrafine particles having an average particle diameter of 0.45 μm were easily obtained. Milling conditions are mill volume: 400 liters,
Mill rotation speed: 100 rpm, media: 400 kg of alumina balls having a diameter of 5 mm, 100 kg of the above-mentioned β-spodumene coarse particles, and 100 kg of water were added to make a slurry concentration of 50%. (b) On the other hand, the natural β-wollastonite used had an average particle size of 2.5 μm, which was pulverized for 72 hours to obtain an average particle size of 0.5 μm.
2 μm ultrafine particles were obtained. Grinding conditions are as follows:
It is the same as in the case of spojumen except that 15% by weight of the dispersant is added to 00% by weight.

(3) Firing / Processing From the respective slurries, β-wollastonite raw material and β-spodumene raw material are collected at various ratios, and 3% by weight of polyvinyl alcohol as a binder is added to the slurry and mixed. And granulated with a spray dryer. After filling the granules in a die in which a lower puncher was set, the upper puncher was set to sandwich the granules, and further, punches were inserted vertically and pre-pressurized to about 100 kgf with a hydraulic jack. The material of the punch, die and puncher is graphite (made by Toyo Tanso), the size of the die is φ90mm × φ50.4mm × 100mm, and the size of the puncher is φ5
It is 0 mm x 50 mm. Further, in order to ensure the releasability of the sintered body, a 0.2 mm-thick carbon sheet was provided on each of the inner wall and the upper and lower puncher surfaces of the die in contact with the raw material powder. After the above pretreatment, the punch and the die were set in a spark plasma sintering machine (Sumitomo Coal Mining Co., Ltd., SPS-7.40) and sintering was performed. This device has a main body with a vertical uniaxial pressurizing mechanism, a special energizing mechanism with a built-in water cooling unit, a water-cooled vacuum chamber, a vacuum / atmosphere / gas atmosphere control mechanism, a vacuum exhaust device, a special DC pulse sintering power supply, and cooling. It consists of a water control unit, a position measuring mechanism, a displacement measuring device, a temperature measuring device and an operation control panel for controlling these. Using the above equipment, apply a predetermined pressure in a vacuum atmosphere,
The temperature was raised at a predetermined rate of 1 minute per minute, kept at a predetermined temperature for a predetermined time, cooled, and opened to the atmosphere at 500 ° C. Various conditions are as shown in Table 1. Both sides of the obtained sintered body are ground with a # 400 diamond grinding wheel (Okamoto Machine Tool Co., Ltd., precision surface grinder PSG-
52DX), and then polished for 30 minutes with 3 μm diamond abrasive grains (Shibayama Kikai Co., Ltd., Lapmaster 15).

(4) Various Measurement Methods Surface Roughness: The above polished surface was measured according to JIS B0601.
_max, was evaluated by the R _a (manufactured by Tokyo Seimitsu Co., Ltd., Surfcom 300B,
The radius of curvature of the stylus is 5 μm and the measuring distance is 3 mm). Density: Calculated by Archimedes' method. Flexural strength: Processing a sintered body to 3 × 4 × 40mm, JIS R 1601
Was measured by Crystal grain size and pore size: measured by scanning electron microscope (SEM) observation of the structure of the sintered body.

(5) Results As shown in Table 2, no grain growth was observed in any of the obtained sintered bodies, the average grain size was equivalent to the starting material grain size, and the pores were small. It was extremely small or not observed at all in comparison with the average crystal grain size, and had high density, high strength, and good surface roughness, which were not found in the past.

Example 5 Diatomaceous earth and slaked lime for industrial use were mixed at a Ca / Si molar ratio of 1 to prepare a slurry having a water / solids ratio (W / S) of 10.0, and a slurry of 200 ° C.
For 1 hour to obtain zonotlite. After drying this zonotorite at 120 ° C., it was fired at 1000 ° C. to be transformed to obtain β-wollastonite. The obtained β-wollastonite was ultrafine particles having an average particle size of 0.6 μm. In addition,
At this time, the weight loss was 4.6%, and this was 100% β-wollastonite containing no reaction product. This β-wollastonite and β-spodumene before pulverization obtained by phase transition in the same manner as in Examples 1 to 4 were blended under the conditions shown in Table 1, and pulverized with a ball mill in the same manner as in Examples 1 to 4. Ultra fine particles having an average particle size of 0.25 μm were obtained. This was subjected to discharge plasma firing at the temperature shown in Table 1 in the same manner as in Examples 1 to 4, to obtain a sintered body, and after grinding and polishing, various characteristic values were measured. As a result, as shown in Table 2, no grain growth was observed in the obtained sintered body, the average grain size was equivalent to the starting material grain size, no pores were observed, and a high density , High strength and good surface roughness.

Example 6 As a lithium aluminosilicate, a natural mineral, petalite having an average particle diameter of 8 μm (Li ₂ O: 4.2% by weight, Al ₂ O ₃ :
16.6 wt.%, SiO _2: 76.8% by weight, other: 1.4% by weight,
Loss on ignition 1% by weight) as calcium silicate
In the same manner as in Example 5, 0.6 μm β-wollastonite before pulverization obtained by transferring zonotolite was used. These raw materials were blended under the conditions shown in Table 1 and pulverized by a ball mill in the same manner as in Example 1 to obtain an average particle size of 0.36 μm. This was subjected to discharge plasma firing at the temperature shown in Table 1 in the same manner as in Examples 1 to 4, to obtain a sintered body, and after grinding and polishing, various characteristic values were measured. As a result, as shown in Table 2, no grain growth was observed in the obtained sintered body, the average grain size was equivalent to the starting material grain size, no pores were observed, and a high density , High strength and good surface roughness.

Examples 7 to 8 Diatomaceous earth and slaked lime for industrial use were mixed at a Ca / Si molar ratio of 1 to prepare a slurry having a water / solids ratio (W / S) of 10.0.
For 1 hour to synthesize CSH. After drying this CSH at 120 ° C., it was baked at 1000 ° C. for 1 hour. When the crystal phase was identified by X-ray diffraction, it contained no impurities
It was β-wollastonite that was 100% transformed. Its average particle size was 0.25 μm. The weight loss at this time is 13%. The β-spodumene before the pulverization that had undergone the phase transition as in Examples 1 to 4 and the β-wollastonite obtained from the above CSH were blended, and pulverized with a ball mill in the same manner as in Examples 1 to 4, and the average particle size was determined A 0.15 μm raw material was obtained. This was subjected to discharge plasma firing at the temperature shown in Table 1 in the same manner as in Examples 1 to 4, to obtain a sintered body, and after grinding and polishing, various characteristic values were measured. As a result, as shown in Table 2, no grain growth was observed in the obtained sintered body, the average grain size was equivalent to the starting material grain size, no pores were observed, and a high density , High strength and good surface roughness.

Example 9 Zonotolite used in Example 5 was mixed with β-spodumene before pulverization, which had undergone phase transition in the same manner as in Examples 1 to 4, in terms of solid content in consideration of loss on ignition, as shown in Table 1. Example 1
4 to obtain a raw material having an average particle diameter of 0.6 μm. This was subjected to discharge plasma firing at the temperature shown in Table 1 in the same manner as in Examples 1 to 4, to obtain a sintered body, and after grinding and polishing, various characteristic values were measured. As a result, as shown in Table 2, no grain growth was observed in the obtained sintered body, the average grain size was equivalent to the starting material grain size, no pores were observed, and a high density , High strength and good surface roughness.

Example 10 The α-spodumene before the phase transition used in Examples 1 to 4 was pulverized under the same conditions as in Examples 1 to 4 to 0.9 μm.
This α-spodumene was blended with the CSH used in Example 7 in terms of solid content in consideration of loss on ignition, as shown in Table 1, and pulverized in the same manner as in Examples 1-4 to obtain a raw material having an average particle size of 0.5 μm. I got This was subjected to discharge plasma firing at the temperature shown in Table 1 in the same manner as in Examples 1 to 4, to obtain a sintered body, and after grinding and polishing, various characteristic values were measured. As a result, as shown in Table 2, no grain growth was observed in the obtained sintered body, the average grain size was equivalent to the starting material grain size, no pores were observed, and a high density , High strength and good surface roughness.

Examples 11 to 14 Same as in Examples 1 to 4, but before the pulverization of β-spodumene,
The same natural mineral as in Examples 1 to 4 except that the average particle size is 25 μm
Β-wollastonite was mixed and pulverized with a ball mill to obtain an average particle size of 2 μm (Example 11) and 4.5 μm (Example 1).
2), 7.3 μm (Example 13) and 10 μm (Example 14) raw materials were obtained. This was subjected to discharge plasma firing at the temperature shown in Table 1 in the same manner as in Examples 1 to 4, to obtain a sintered body, and after grinding and polishing, various characteristic values were measured. As a result, Table 2
As shown in the figure, the obtained sintered body is inferior to Examples 1 to 10 due to the large particle size of the starting material, but is far superior to Comparative Example, and no grain growth is observed. The average particle size was equivalent to the starting material particle size, and no porosity was observed (Example 11), or even if observed, it was extremely small compared to the average crystal particle size (Examples 12 to 14). . These sintered bodies had unprecedented high density, high strength, and good surface roughness.

Example 15 The same procedure as in Example 2 was carried out except that a plasma activated sintering method (PASV (30 tonf) manufactured by Sodick Mechatech Co., Ltd.) was used instead of the discharge plasma sintering method as the pressurized / electrically heated sintering method. A sintered body was obtained in exactly the same manner. As a result, as shown in Table 2, no grain growth was observed in the obtained sintered body, the average grain size was equivalent to the starting material grain size, no pores were observed, and a high density , High strength and good surface roughness.

Comparative Examples 1 and 2 100% by weight of calcium silicate (Comparative Example 1)
Alternatively, a fired product was obtained in the same manner as in Example 1 or 2, except that the sintering conditions for spark plasma sintering were as shown in Table 1 except that the content was 0% by weight (Comparative Example 2). As a result, as shown in Table 2, they did not densify, and all of the density, the pore diameter, the strength, and the surface roughness were significantly inferior to Examples 1 and 2.

Comparative Examples 3 and 4 Example 9 (Comparative Example 3) or Example 10 except that atmospheric pressure sintering was performed under the conditions shown in Table 1 without using discharge plasma sintering.
A sintered body was obtained in the same manner as in (Comparative Example 4). As a result, as shown in Table 2, although these materials had a high density, the crystal grain size was larger than that of the examples, and the maximum pore size also exceeded 20% of the average crystal grain size. The surface roughness was inferior to the examples.

Comparative Examples 5 to 7 Regardless of the discharge plasma sintering,
A sintered body was obtained in the same manner as in Example 2 except that normal-pressure sintering was performed under firing conditions. As a result, as shown in Table 2, these have grown so that the average crystal grain size is much larger than the raw material grain size, and the maximum pore size is much larger than 20% of the average crystal grain size. there were. The density of these sintered bodies,
Both the strength and the surface roughness were inferior to the examples.

Comparative Example 8 Regarding the starting material particle diameters shown in Table 1,
A sintered body was obtained in the same manner as in Example 3, except that normal-pressure sintering was performed under firing conditions. As a result, as shown in Table 2, these have grown so that the average crystal grain size is much larger than the raw material grain size, and the maximum pore size is much larger than 20% of the average crystal grain size. there were. The density, strength and surface roughness of this sintered body were inferior to those of the examples.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

The calcium silicate composite sintered body of the present invention grows in a calcium silicate composite sintered body having excellent effects in a wide range of applications requiring thermal shock resistance, heat insulation, low thermal expansion, and the like. Calcined without any pores or very small if any,
The strength and surface roughness during processing are dramatically improved.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Toshiyuki Hashida 1-4-1-204, Mijinmine, Taihaku-ku, Sendai, Miyagi Prefecture (72) Inventor Masahiro Saito 8-7-20 Nagamachi, Taihaku-ku, Sendai City, Miyagi Prefecture Miyagi Kogyo Inside the Technical Center (72) Inventor Yoichi Watanabe 8-7-20 Nagamachi, Taihaku-ku, Sendai City, Miyagi Prefecture Inside the Miyagi Prefectural Industrial Technology Center (72) Inventor Chiharu Wada 2-4-2 Daisaku Sakura City, Chiba Prefecture Chichibu Onoda Co., Ltd. Inside the Central Research Laboratory of the Company (72) Inventor Makoto Katagiri 2-4-2 Daisaku, Sakura City, Chiba Prefecture Kochi Chichibu Inside the Central Research Laboratory of Noda Co., Ltd. (72) Inventor Makoto Sakemaki 2-4-2 Daisaku Sakura City, Chiba Prefecture Small Chichibu Noda Central Research Laboratory (72) Inventor Norihiko Misaki 6276 Onoda, Chiba, Onoda City, Yamaguchi Prefecture Chinobu Onoda Central Research Laboratory

Claims (6)

[Claims] 1. A sintered body obtained by a pressure / current heating sintering method, wherein the sintered body is mainly composed of a crystal structure of calcium silicate and lithium aluminosilicate, and has a maximum density of 98% or more of the theoretical density. Pore size is 20% of average crystal grain size
A calcium silicate composite sintered body, characterized in that: 2. The calcium silicate composite sintered body according to claim 1, wherein the lithium aluminosilicate is contained in an amount of 1 to 99% by weight based on the total amount of the calcium silicate and the lithium aluminosilicate. 3. The calcium silicate composite sintered body according to claim 1, wherein the calcium silicate is wollastonite and the lithium aluminosilicate is at least one selected from eucryptite, spodumene, and spodumene solid solution. 4. The content of each element is expressed in terms of weight% in terms of oxide.
In, 0.1 ≦ Li ₂ O ≦ 10.0, 50.0 ≦ SiO ₂ ≦ 65.0, 0.1 ≦ CaO ≦ 4
The calcium silicate composite sintered body according to claim 1, wherein 8.0, 0.5 ≦ Al ₂ O ₃ ≦ 35.0. 5. At least one of wollastonite or calcium silicate which is transformed into wollastonite by firing, and at least one of lithium aluminosilicate
The method for producing a calcium silicate composite sintered body according to any one of claims 1 to 4, wherein the raw material mixture containing the seed is fired by a pressurized / electrically heated sintering method. 6. The method according to claim 5, wherein the composition of the raw material mixture is 1 to 99% by weight as a ratio of lithium aluminosilicate to the total amount of calcium silicate and lithium aluminosilicate.