JPS6037561B2 - Manufacturing method of conductive composite ceramics - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a novel ceramic having electrical conductivity, properties, and low thermal expansion.

So far, as conductive ceramics, porous ceramics obtained by adding metal fluoride to metal dipolite or a mixture of this and disilicide and coagulating it, silicon carbide, lanthanum chromite, zirconia, etc. have been known. It is being However, these conductive ceramics exhibit non-linear conductivity with respect to temperature, which limits the usable temperature range.Also, due to their high coefficient of thermal expansion, they have poor thermal shock resistance and are susceptible to sudden changes in temperature. They have the drawbacks of being easily damaged due to porosity and having poor mechanical strength due to their porosity.

The inventors of the present invention have conducted various studies to improve the drawbacks of conventional conductive ceramics and develop conductive ceramics with a small coefficient of thermal expansion and a compact structure. The present inventors discovered that the object could be achieved by skillfully combining these substances with other substances.

That is, the present invention has a positive thermal expansion coefficient selected from (A) spodumene-based or eucryptite-based ceramics, (O-aluminum titanate-based ceramics, 1-cordierite-based ceramics, 0-mullite-based ceramics, and 2) zircon-based ceramics. A conductive material phase in the ceramic phase is prepared by preparing a low thermal expansion ceramic having a conductive material phase in the ceramic phase, adding at least 2% of conductive material powder to the powder, mixing well, molding this, and then firing it. has an at least partially continuous and dispersed microstructure, and has a thermal expansion coefficient of 6×10-6/de
The present invention provides a method for producing conductive composite ceramics having a conductive composite ceramic having a thickness of less than g.

The low thermal expansion ceramic used as a raw material in the method of the present invention has a positive coefficient of thermal expansion and is selected from the above.

Among these, the spodumene-based or eucryptite-based ceramics contain Sj0230 to 80% by weight, N203
or 10 to 50% by weight of Fe203 or both and 0.8 to 25% by weight of Li203, optionally with an external amount of 15% by weight to control the sinterability of the ceramics.
Na, K, Mg, Ca, Sr, Ba, C in amounts not exceeding
Zn, Cr, Mn, Co, Fe, Ni, Sn or Ti
and at least one oxide of clay, glass or feldspar in an amount not exceeding 1% by weight. Also{
o-Aluminum titanate ceramics are Yama 203
40-75% by weight of Fe203 and 25-6% by weight of Ti02, and optionally an additional amount of Fe203 not exceeding 3% by weight to promote its formation and 1% by weight to control sinterability.
Li, Na, K, Mg, Ca, in an amount not exceeding 0% by weight;
Sr, Ba, Cu, Zn, Cr, Mn, Co, Ni, Z
It contains oxides of n or Si, clay, glass, feldspar, etc. Furthermore, in one cordierite ceramic, the total amount of Mg○, mountain 203 and Si02 is 80% by weight or more, and regarding the composition of Mg○, N203 and Si02, the coordinates of these three components are (2, 33 65), (2
, 53 45), (20, 15, 65), (lo, 55
, 35), (30, 1fu55) and (30, 3535)
viscous, glass or feldspar in an amount not exceeding 1% by weight, or Sn, Ti, Zr in an amount not exceeding 25% by weight, as the case may be. Contains oxides, etc. Next, 〇 Mullite ceramics from Mt. 20340? wt% of Si02 and Ti02
At least one selected from 25 to 55% by weight and an amount not exceeding 25% by weight of Cr, Mn, Fe, Ca and N
It contains at least one kind selected from the oxides of i, clay, glass, feldspar, etc. Finally ■ Zircon ceramics include zircon (Zr02/Si02
) 70% by weight or more, Si02 30% by weight or less, Zr02
Consisting of 10% by weight or less, in some cases, 1 box% by weight
a silicate of at least one trivalent metal selected from Fe, Cr in an amount not exceeding 15% by weight selected from Co, Ni, Mn and an alkali metal. It contains at least one divalent metal silicate and also clay, glass, feldspar, etc. in an amount not exceeding 1% by weight. On the other hand, as the conductive substance in the method of the present invention, metals, carbon, cermets, metal nitrides, borides, carbides, or silicides, metal oxides, or mixtures thereof are used.

Examples of metals include silver, titanium, nichrome, etc. Examples of cermets include titanium-vitrochrome, etc. Examples of metal nitrides include titanium nitride, aluminum nitride, etc. Examples of metal borides Examples of the metal silicide include titanium boride and zirconium boride; examples of the metal carbide include silicon carbide and zirconium carbide; and examples of the metal silicide include molybdenum silicide. Examples of metal oxides include Re03, R
Single oxides like u02, Ti03, CaMn03
, LaMn03, CaC^]3, SrC03
, LaCr03, LaC. 〇3・Fe304・N
iFe204・La2NI. 4. La2C mountain.

In addition to metal oxygen salts and composite oxides such as 4,
Ti○, V○, Mn○, Coo, Ni○, Zn0, Cd
○, Ti203, V203, Fe203, Cr203,
La203, Ti○2, Sn○2, V205, Moo3
, W03, Re03 or CaTi0
3, SrTi03, side Ti03, LaTi03, L
aAI03, CaMn03, LaMn03,
CaC[]3, Shor03, LaC(]3, LaCo
03, Fe304, NiFe2○4, La2Nj○
4, La2CM04, Life5○8, MgW
A metal oxygen salt or composite oxide such as 04 is used as a base,
Examples include those that are given electrical conductivity by making the ratio of metal and oxygen non-stoichiometric.

According to the method of the present invention, a conductive composite ceramic having a desired low thermal expansion property is produced by mixing a predetermined low thermal expansion ceramic powder and a conductive substance in a predetermined ratio, and adding, for example, clay, feldspar, etc., as necessary. It can be manufactured by adding a binder such as carboxymethylcellulose or polyvinyl alcohol, molding it into an appropriate shape, and firing it.

This firing temperature varies depending on the type and composition of the materials used, but is usually selected in the range of 900 to 1600 oo.
At this time, in order to uniformly mix the conductive substance into the ceramic powder, a salt that changes into a conductive monster upon firing may be added to the ceramic powder in the form of a solution and mixed.

The above raw material powder for forming ceramics is composed of, for example, Si0240-7% by weight, AI20315-40% by weight, Li203-17% by weight, and Ti02, Z2 or P as a nucleating agent.
2Q2 to 10% by weight added, and in addition to these, Na, K, Mg, in an amount not exceeding 10% by weight,
Ca, Sr, Ba, Cu, Zn, Cr, Mn, Co, F
Using a material to which at least one of the oxides of e, Ni or Sn is added, conductive material powder is added to it, and 130
A low thermal expansion conductive composite glass-ceramic can be obtained in the same manner by heating the glass to 0 to 170,000 °C to melt the glass, molding it, and heat-treating this molded body at 700 to 900 °C.

In the method of the present invention, the proportion of the conductive substance powder and the ceramic powder used is such that the former accounts for at least 23% by volume, and the coefficient of thermal expansion (Q) of the desired conductive composite ceramic is determined.
) must be selected so that it is 16×10-6/deg or less, but this cannot be easily determined as the arithmetic average of both components.

The reason for this is that in addition to the above two components, a third phase is formed and this is related to the overall thermal expansion coefficient, and if one component is present in large amounts, its crystal grains form a continuous phase. However, since the other component becomes a discontinuous phase, it is conceivable that the larger component makes a larger contribution to the overall coefficient of thermal expansion. Therefore, the usage ratio of each component in the present invention can be calculated using the following formula. That is, the thermal expansion coefficient of the desired conductive composite ceramic is Q
, the coefficient of thermal expansion of the conductive material is Q. , the thermal expansion coefficient of ceramics is Q2, and the mixed amount of conductive material is x volume %, then in the range of 0<xmi50, Q=Q, 10 (magazine).

)2.Sheep......Q: in the range of m50<x<100.

2-(Masuko) 2. Sheep... ··side However, △Q is Q. It is the absolute value of the difference between and Q2.

Table 1 specifically shows the usage ratio of each component in the method of the present invention determined in this way. (x is the volume % of the conductive substance) Table 1 Conductive substance X: niobium oxide, vanadium oxide, tin oxide, zirconium boride, carbon, titanium boride, silicon carbide,
such as aluminum nitride.

X2: titanium carbide, nichrome, titanium metal, molybdenum silicide, thoria, titania, titanium silicate, lanthanum chromite metal palladium, zirconia, magnetite, etc.

X3: Stainless steel, silver, etc.

Ceramics Y: Eucryptite ceramics, aluminum titanate ceramics, glass ceramics equivalent to these, etc.

Y2: Spodumene ceramics, aluminum titanate ceramics, cordierite ceramics,
Glass ceramics etc. that correspond to these.

Y3: Mullite ceramics, zircon ceramics, glass ceramics equivalent to these, etc.

Conventional conductive ceramics exhibit non-linear conductivity with respect to temperature and exhibit large negative conductivity temperature characteristics in the temperature range up to several hundred degrees, whereas in the method of the present invention, the conductivity is dispersed. By selecting the type of conductive material, it is possible to obtain composite ceramics with linear conductivity and either positive or negative temperature characteristics, making it possible to use a wide range of temperatures, and to easily and safely control the temperature. It can be used as a heating element.

Furthermore, the composite ceramics obtained by the method of the present invention can be fired into a dense structure if necessary, so it has the characteristics of good thermal shock resistance, mechanical strength, high temperature chemical resistance, and thermal conductivity. There is.

As mentioned above, since the composite ceramic obtained by the method of the present invention has conductivity,
- Electrodes for chemical industry, such as electrodes for electrolytic oxidation synthesis of organic substances, devices for removing static electricity, such as sliding guides for threads, tapes, etc.
It is useful as a rotating sliding part, ■ thermistor, and its low thermal expansion makes it particularly suitable for applications that repeatedly encounter rapid heating and cooling, such as cooking heaters and electrodes that are subject to sudden changes in temperature.Furthermore, When used as a heating element, it emits far-infrared heat, making it suitable for dehydration and drying, evaporation of organic solvents, baking hardening of resins, and drying processing of resins, fibers, metals, and pharmaceuticals. be.

In this case, since the resistor and its holder can be integrated into a ceramic heater, there is an advantage that the structure can be simpler than that of a heater using nichrome, molybdenum silicate, or the like. Next, the present invention will be explained in more detail with reference to Examples.

Example 1 Silica stone powder 55. Parts by weight of alumina powder 24. parts by weight, iron oxide powder 4.5 parts by weight, lithium carbonate powder 14.
5 parts by weight and potassium carbonate powder2. Si
0260.6% by weight, AI20326.4% by weight Fe2
035.0% by weight, Li206.5% by weight, K201.
A ceramic powder consisting of 5% by weight was prepared.

Separately Nj03. weight percent and Fe20397. A conductive material was prepared by calcining a powder mixture consisting of % by weight at 1300 qo in a nitrogen stream and pulverizing it.

Next, the ceramic powder and the conductive material powder were mixed in various ratios, 1% by weight of clay was added to the total amount, green-mixed in a ball mill, and then reduced and fired for a little less than 1 hour at 1100 ○. The relationship between the amount of conductive material mixed and the specific resistance of the composite ceramic thus obtained is shown in FIG. 1, and the relationship with the coefficient of thermal expansion is shown as a graph in FIG. 2, respectively.

Further, the relationship between temperature and specific resistance for a conductive material mixed with 5% breaking amount is shown as a graph in FIG.

Example 2 Using the same ceramic powder as in Example 1, various conductive substance powders and 1% by weight of clay based on the total amount were added, and the composite ceramics were made by firing for 1 hour at 900 to 1150 qo in air or a reducing atmosphere. I got it.

The results are shown in Table 2. Table 2 Example 3 Ti0240. Weight % of Fe20312. weight%,
Mix well the powder containing 20348.0% by weight,
This was calcined at 1300°C and pulverized to obtain ceramic powder.

Various conductive material powders and 2% by weight of feldspar based on the total amount were added thereto, mixed well and molded, and then fired at 950 to 1600° C. in air or a reducing atmosphere to produce ceramics. The results are shown in Table 3. Table 3 Example 4 To obtain cordierite porcelain, clay, carbonate, magnesium, a small amount of iron oxide, alkali metal, oxide (RO
), alkali metal oxide (RO), etc. are thoroughly mixed,
It was pre-fired for 1 hour at a temperature of 5,000 yen, and then finely pulverized to obtain ceramic powder.

This chemical composition is Mg020.8% by weight, Mg20321
．． 2% by weight, Si0258.0% by weight, Fe2030.
0% by weight, ROO. 12% by weight, R'200.3% by weight of the box. Various conductive monster powders are added to this, mixed well, and after molding, in air or reducing atmosphere,
Ceramics were manufactured by firing at 950 to 1400 oo.

The results are No. 4 in Table 4. 1 and 2 are as follows. Example 5 To obtain mullite porcelain, 13 well-mixed raw materials were
After being temporarily held at 0000 for 1 hour, it was finely pulverized to obtain ceramic powder.

The chemical composition is: Mountain 20368% by weight, Si0227% by weight, Fe2035. % by weight. Various conductive material powders were added thereto, mixed well, molded, and fired at 950-1400 pm in air or reducing atmosphere to produce ceramics. The results are No. 4 in Table 4.
3 and 4 are as follows. Example 6 To obtain zircon porcelain, ``14 well-mixed raw materials were
After calcining at 20 oo for 2 hours, it was finely pulverized to obtain ceramic powder.

This chemical composition is Si022% by weight, Z2・Si029
8% by weight, and 2035% by weight of Fe. Various conductive material powders were added thereto, mixed well, molded, and fired at 950 to 1450 qo in air or a reducing atmosphere to produce ceramics. The results are No. 4 in Table 4.
4 and 5. Table 4 Example 7 Sj0272% by weight, Mountain 20317% by weight, Li204
In addition to 27% by weight of Ti0 and 1.5% by weight of Mg0, various conductive substance powders were further added to the powder, mixed well, and glass-melted at 160,000 yen.
This was molded.

This molded body was heat-treated at 800 to 900 qo to produce glass ceramics. The properties of this glass ceramic are shown in Table 5. Table 5

[Brief explanation of drawings]

Figure 1 is a graph showing the relationship between the amount of conductive material mixed and the specific resistance of the composite ceramic of the present invention, Figure 2 is a graph showing the relationship between the amount of conductive material mixed and the thermal expansion coefficient, and Figure 3 is the temperature It is a graph which shows the relationship between and specific resistance. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1. A positive material selected from (a) spodumene-based or eucryptite-based ceramics, (b) aluminum titanate-based ceramics, (c) cordierite-based ceramics, (d) mullite-based ceramics, and (e) zircon-based ceramics. The process is characterized by preparing a low thermal expansion ceramic having a low coefficient of thermal expansion, adding at least 25% by volume of a conductive material powder to the powder, mixing well, shaping the mixture, and then firing it. It has a structure in which the physical substance phase is at least partially continuous and dispersed, and the coefficient of thermal expansion is 6 × 10^-^6/deg.
The following method for producing conductive composite ceramics.