JP3065421B2 - Cordierite composite material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cordierite composite material, and more particularly to a cordierite composite material having high strength at high temperatures and excellent creep properties.

[0002]

BACKGROUND ART cordierite has a low coefficient of thermal expansion over a wide temperature range, are known is as a material having excellent thermal shock resistance and heat resistance. However, in recent applications around automobile engines, more excellent creep characteristics and impact resistance at high temperatures are required.

As a typical example, monolithic cordierite used for purifying exhaust gas has been variously improved in strength and thermal shock resistance. For example, to improve strength and thermal shock resistance, cordierite has a length of 2
A method of combining single-crystal silicon carbide whiskers of about 0 μm (see JP-A-62-256776) or a method of combining long fibers of silicon carbide (Ceram. Eng.
Sci. Press. 10, 1231 ( 1989)).

[0004]

The former method Disclosed invention is to provide a small degree of improving the strength and thermal shock resistance, moreover dispersion with susceptibility have a worse defects during molding, because silicon carbide is fine whiskers, in an oxidizing atmosphere Damaged by firing
Easy-like there was a problem. On the other hand, although the latter method improves the toughness and strength is expected, this has directionality, since their preparation is also a special production of complex shape product has a drawback that undergo significant limitations .

[0005]

The object of the present invention is to overcome the drawbacks of the conventional methods and to obtain a cordierite composite material having high strength at high temperatures and excellent creep characteristics. As a result of various studies and studies, it has been found that the object can be achieved by adding a specific amount of silicon carbide having a specific shape to a cordierite matrix .

[0006] Thus, the present invention comprises a cordierite matrix and the plate Josumi of silicon, pairs total amount of both
The content of the plate-like silicon carbide is that provides cordierite composite material, characterized in that from 5 to 40 wt%.

In the present invention, the cordierite matrix may be cordierite alone, but is mainly composed of cordierite and a low-melting inorganic sintering agent such as soda feldspar . Co-over cordierite will be described later plate
The Jo silicon carbide 60 in including co over cordierite electrolyte composite
Preferably it is 95% by weight.

When the content of cordierite is less than 60% by weight , the low thermal expansion characteristic of cordierite is lost, and when it exceeds 95% by weight, high strength due to the combination of silicon carbide is obtained. It is not preferable because the effect of the formation may be weakened. And in cordierite composites
By employing 70-85% by weight cordierite content while retaining a low thermal expansion, high toughness, particularly preferred since high strength can be obtained.

Next, it is appropriate to employ 0 to 50% by weight of components other than cordierite, such as sintering aids, in the cordierite matrix in accordance with the above description. If the amount used exceeds the above range, low thermal expansion properties will be lost, which is not preferable. Of these ranges, the use of 20 to 30% by weight in accordance with the above indication is particularly preferable because excellent low thermal expansion can be maintained.

In the present invention, the content of the plate-like silicon carbide is
It requires 5 to 40 wt% der Rukoto to focus <br/> amount of the cordierite matrix and the plate-like silicon carbide. Improvement in strength and creep characteristics in the case where the content of the plate-like <br/> silicon carbide is less than 5 wt% becomes non charging component, 40 wt% in the reverse
When it exceeds the low thermal expansion property is lost, nor any unsuitable because sintering is inhibited.

[0011] When employing the 15-30 wt% as the content strength, particularly preferable since excellent creep characteristics, and the charge amount low thermal expansion. The plate-like silicon carbide used in the present invention is in the form of particles , having a diameter of 3 to 100 μm, and a diameter / thickness ratio of 5 to 3.
Those which are 0 disk-shaped particles are preferred.

[0012] With such a plate-shaped silicon carbide, it is not necessary to use a mixture of and difficulty and non-oxidizing atmosphere such as typified by whiskers may remembering charging component strength and high creep properties.

[0013] plate when the diameter of Josumi of silicon is less than 3μm oxidation loss occurs during tempering formed, is not preferable Re Izu since strength is lowered when exceeding 100μm reversed.

Among them , plate-like silicon carbide having a diameter of 5 to 50 μm
The use of element is particularly preferable because the strength and toughness can be improved and there is no influence of oxidation.

If the diameter / thickness ratio is less than 5 ,
Strength, improvement of toughness becomes non charging component, homogeneous mixture, is not preferable Re Izu since molding becomes difficult when more than 30 to reverse.

[0016] In particular, the ratio of the diameter / thickness of 10 to 20 Der
By adopting that plate of silicon carbide, mixing, without problems in molding, and strength, particularly preferable because the toughness is improved charge amount.

Plate Josumi Ka珪element used in [0017] the present invention
Is, for example, Ru can be synthesized by Acheson process. That is, a graphite powder is packed in a rod shape between a pair of fixed electrodes, and a raw material containing silica stone (silica) and coke (carbon) is set around the rod.

The temperature is increased by Joule heat generated in the core of the graphite powder when electricity is supplied to the graphite powder to promote reduction carbonization of silica to obtain silicon carbide. Controlling the diameter and thickness of the plate Josumi of silicon obtained by way of the energization of the time.

[0019] In addition, cordierite Matrix
, For example those mixed predetermined amounts using silica 0.5 to 20 [mu] m, alumina, cordierite raw materials magnesia, further optionally, albite, anorthite or low melting aids such as potassium feldspar 1300-140 using
0 resulting et al by grinding those allowed sintered about 1 to 5 hours at ℃
Ru is formed from the particles. And, as for the property, the porosity is from 50% to the dense one having substantially 0%.
It may be used in any until such a degree of porosity.

The thus obtained plate Josumi of silicon and particles forming the cordierite matrix are mixed and sintered. Mixing using a mixer such as, for example, pressurized kneader, but are mixed, the plate Josumi of silicon retains the original shape without being destroyed.

Forming a cordierite matrix
It is appropriate to adopt a particle diameter of about 3 to 100 μm. If the particle size is less than 3μm becomes difficult to uniform mixing of the silicon carbide, undesirable mixing, also Re Izu since there is a possibility that molding becomes difficult when conversely more than 100 microns m. Of these ranges, it is particularly preferable to adopt a thickness of 5 to 20 μm because a uniform composite can be easily obtained by mixing and molding.

The particles forming the mixed cordierite matrix and the plate-like silicon carbide have a temperature of 1200 to 14
Firing at 00 ° C. for 1 to 5 hours. If the sintering temperature and sintering time are less than the above range, the cordierite matrix
Binding of particles and plate-like silicon carbide formed becomes low strength not charge fraction and binding of particles and plate-shaped silicon carbide firing temperature and firing time reversed to form the cordierite matrix when exceeding the above range It has the effect of the process goes too composite disappears
Also unfavorable Re not.

Of these ranges, the firing temperature is 130
0 to 1,400 ° C., when adopting the calcination time 1-5 hours particles and plate-shaped silicon carbide to form the cordierite matrix moderately bound, particularly preferable because the effect of the composite is not easy to appear. The firing is carried out at ordinary air, but it may also be carried out optionally in a non-oxidizing atmosphere.

[0024] In addition, the cordierite matrix
Particles which form is made of other components, such as cordierite and sintering aid, which is baked formed prior to mixing with the plate Josumi of silicon
May be previously, but it may also form baked <br/> after adding the other components such as cordierite and sintering aid when mixed with plate-shaped silicon carbide.

[0025]

EXAMPLES Example 1 37% by weight of alumina having an average particle size of 1 μm and an average particle size of 5 μm
Magnesia 15 having 48% by weight of silica and an average particle size of 5 μm
% By weight and electrofused in an electric furnace to synthesize cordierite. This is pulverized with a pulverizer, and has an average particle size of 1
To obtain a code cordierite particles of 00μm. A portion of the synthetic cordierite is further pulverized to a cord having an average particle size of 20 μm.
Dierite particles .

[0026] Then Cody said average particle size 100μm
The average particle size 20μm Cody with Eraito particles 35 wt%
Water was added to mix well methylcellulose 7.5% by weight Eraito particles 5 wt% and the average particle albite 5 wt% of the diameter of 100μm and a binder, by further crushing after drying, the cordierite matrix Form
Particles were prepared .

This cordierite matrix is formed
Commercial plate Josumi of silicon particles formed (Canada, C-Axi
s Technology Co., Ltd., average particle size of 17μm, straight
Diameter / thickness ratio 10) was changed to plate-like silicon carbide and cordierite.
10 % by weight based on the total amount of particles forming the porous matrix
Combined mixed, mixed charge amount using a rotary mixer and dispersed.

Next, 26% by weight of water was added, and the mixture was kneaded with a pressure kneader, and an extrudate having a diameter of 20 mm and a length of 100 mm was obtained with a plunger type extruder. This was dried at 50 ° C. for 10 hours and fired at 1300 ° C. for 5 hours in the air to obtain a cordierite-based composite material.

The flexural strength test and a thermal shock test between room temperature and 1100 ° C. The obtained sample (△ T) and the Tsu line. At room temperature
Bending strength is 390 kg / cm ² , bending at 1100 ° C
The strength was 208 kg / cm ² and the ΔT was 600 ° C.

[0030] Example In 2 Example 1, except that a mixture of plate-like silicon carbide 40% by weight relative to the total amount of particles forming a plate-shaped silicon carbide and cordierite <br/> matrix Example 1 in the same manner as, extrusion, cordierite chamber of composite material obtained by firing
The flexural strength at temperature is 305 kg / cm ² ,
The flexural strength was 264 kg / cm ² and ΔT was 650 ° C.
Was.

Example 3 The synthetic cordierite obtained in Example 1 was further pulverized into cordierite particles having an average particle diameter of 3 μm. And 75% by weight of cordierite particles having an average particle size of 3 μm.
When a 5 wt% PVA aqueous solution of 10 wt% as a binder, in particular a mean diameter 5 [mu] m, the plate-shaped silicon carbide 2 0 weight ratio 10 of diameter / thickness of the plate-shaped silicon carbide used in Example 1 % and were mixed, charged minute mixed using a ball mill, and dispersed.

Next, after a 200 × 100 × 10 mm mold was filled by vibration, a rubber press was performed at ² t / cm ² to obtain a molded product. Bending at room temperature of the cordierite composite material obtained by calcining the molded body at 1400 ° C. for 5 hours in air.
Bending strength is 1100kg / cm ² , bending strength at 1100 ° C
The degree was 1100 kg / cm ² and ΔT was 650 ° C.

Example 4 75% by weight of cordierite particles having an average particle size of 3 μm
% To 60% by weight , average diameter 5μm, diameter / thickness
It is of the plate-shaped silicon carbide ratio 10 to 20 wt% 35 wt%
Molded as another embodiment 3 was changed to the bending strength at room temperature of the fired cordierite composite material 840
kg / cm ² , the bending strength at 1100 ° C. is 900 kg / cm ² .
cm ² and ΔT were 700 ° C.

[0034]

According to the present invention, the presence of plate-like silicon carbide can improve the strength and creep characteristics of the cordierite-based composite material . In addition, since silicon carbide is in the form of a plate, when extruded or pressed in one direction, the surface tends to be aligned in one direction in order to reduce resistance in the compression direction, and as a result, it is significantly destructed as compared with a random composite. Has the effect of increasing the resistance to In particular, the effect is remarkable in the case of a thin wall such as a filter.

Claims (2)

(57) [Claims] [Claim 1] containing a cordierite matrix and the plate Josumi <br/> of silicon, against the total amount of both the plate-shaped silicon carbide
A cordierite-based composite material having a content of 5 to 40% by weight. 2. A plate Josumi of silicon has a diameter in. 3 to 100 [mu] m
2. A disk having a diameter / thickness ratio of 5 to 30.
Cordierite composite material according to.