JPH09208206A - Impact resistant vitreous carbon material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a vitreous carbon material having a uniform structure in the cross section in the thickness direction and having excellent shock resistance by forming such a structure that the difference of the average lattice distance of graphite hexagonal mesh layers between in the surface layer part and in the center part of the cross section to a specified range. SOLUTION: This impact resistant vitreous carbon is produced to satisfy such requirement that the difference of the average lattice distance d002 , in the graphite hexagonal mash layers is within 0.01nm between in the surface layer part and in the center part in the cross section or that the difference of the grain size Lc (002) is within 1.5nm in the surface layer part and in the center part of the cross section. The obtd. material shows a uniform structure for both of the inner and outer layers in the cross section and has little inner stress or residual stress, so that stress fracture due to an external impact can effectively be reduced. Further, by controlling the average lattice distance of the graphite hexagonal mesh layers in the cross section to 0.345-0.365nm and controlling the grain size in the center part to 1.3-4.0nm, the shock resistance is further improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a glassy carbon excellent in impact resistance having a uniform structure in a cross section in the thickness direction and hardly causing material damage to severe machining or thermal shock. Regarding materials

Glassy carbon is a hard carbon material having a macroscopically non-porous structure obtained by carbonizing a thermosetting resin, and has high strength, low chemical reactivity, gas impermeability, self-lubricating property, robustness, etc. Because of its excellent properties, it has been widely put into practical use as various members in the fields of semiconductors and electrolytic chemistry by utilizing its unique physical properties. However, since the glassy carbon material is essentially composed of an amorphous carbonaceous structure, it does not have sufficient durability against corrosion such as oxidation, and has a brittleness peculiar to glassy material, which causes mechanical and thermal damage. There is a material defect that is easily damaged by impact.

[0003]

2. Description of the Related Art Among them, for improvement of durability against corrosion such as oxidation, specific gravity is 1.50 or more, total ash content is 700 pp
m or less, total sulfur content 500 ppm or less, crystal plane spacing 0.37
A highly corrosion-resistant glassy carbon material having a material property of 5 nm or less and a crystallite size of 1.3 nm or more has been proposed by the present applicant (JP-A-5-208867). However, there has been no example in which the resistance to mechanical and thermal shocks has been examined from the structural properties of glassy carbon.

[0004]

The damage of the glassy carbon material due to mechanical or thermal shock is mainly caused by a phenomenon in which the stress is biased inside the structure when the structure of the material is not uniform and the structure is not uniform. Occur. Especially when the thickness of the glassy carbon material is thicker than 5 mm, there is a difference in the internal and external structures of the material, which causes damage or damage during machining or when used under conditions involving thermal shock. Damage phenomena such as chipping are likely to occur.

The present inventor has studied the cause of damage to the glassy carbon material due to impact from the viewpoint of the material structure, and as a result, found that the cross-sectional structure of the glassy carbon material is nonuniform, particularly the surface layer part and the center part of the cross section. The impact of the difference in the crystallinity of graphite is significant, and controlling this difference in crystallinity within a specific range significantly improves impact resistance, and even thick glass-like carbon materials can be used during machining or use. We have clarified the fact that the damage phenomenon due to the thermal shock of the can be effectively suppressed.

The present invention has been completed based on the above findings, and the object of the present invention is to cause material damage to severe mechanical and thermal shocks even with a thick wall size. An object of the present invention is to provide a glass material having a low impact resistance and vitreous properties.

[0007]

The impact-resistant glassy carbon material according to the first aspect of the present invention for solving the above-mentioned problems is such that the average lattice spacing d _{00 2} of the graphite hexagonal mesh plane layer is the same as that of the surface layer portion. A structural feature is that the center portion of the cross section has a tissue structure with a range difference of 0.01 nm or less.

In this case, the average lattice spacing d _{00 2} of the graphite hexagonal mesh plane layer in the center of the cross section is 0.345 to 0.365.
It is preferably in the range of nm.

The impact-resistant vitreous carbon material according to the second aspect of the present invention has a texture structure in which the crystallite size Lc (002) is within a range of 1.5 nm in the surface layer portion and the center of the cross section. This is a feature of the configuration.

In this case, the crystallite size Lc (002) at the center of the cross section is preferably in the range of 1.3 to 4.0 nm.

In the present invention, the average lattice spacing d ₀₀₂ and the crystallite size Lc (002) of the graphite hexagonal mesh plane layer are “Lattice constant of artificial graphite and crystallite of crystallite” prepared by the 117th Committee of the Japan Society for the Promotion of Science. X-ray diffractometry according to "Measurement method of size" is used to draw a straight base line by taking into account the rise of the low-angle base line using a plate-shaped test piece.
It is a value calculated from the broad C (002) diffraction line obtained by measurement in the vicinity of g.

In the present invention, the surface layer of the glassy carbon material means the surface of the material, and the center of the cross section means the tomographic plane at the position where one side is polished from the surface to half the thickness of the cross section. .

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The impact resistant glassy carbon material of the present invention is not particularly limited in its production history, but the average lattice spacing d _{00 2 of} the graphite hexagonal mesh plane layer in the surface layer portion and the cross-sectional center portion is The difference is within 0.01 nm, or the crystallite size Lc (002) is 1.5 at the surface layer and the center of the cross section.
It is an essential physical property requirement that the difference is within nm. The glass-like carbon material that meets these physical property requirements has a uniform structure structure in the inner and outer layers in the thickness direction, and since internal stress and residual stress are extremely small, stress fracture due to external impact is effectively reduced. To do.

However, the difference in the average lattice spacing d _{00 2} between the graphite hexagonal mesh plane layer in the surface layer portion and the center portion of the cross section is 0.0.
It exceeds 1 nm, and the difference in crystallite size Lc (002) is 1.5.
When the thickness exceeds nm, the difference between the inner and outer structures becomes large, and the resistance to mechanical or thermal shock decreases, and the material damage or chipping increases.

In addition to the above physical properties, the average lattice plane spacing d ₀₀₂ of the graphite hexagonal mesh plane layer at the center of the cross section is 0.34.
When it is in the range of 5 to 0.365 nm and the crystallite size Lc (002) in the center of the cross section is in the range of 1.3 to 4.0 nm, it further contributes to the improvement of impact resistance.

The non-uniformity of the internal and external structures in the glassy carbon material becomes more remarkable as the thickness of the material increases, and the impact resistance tends to decrease particularly when the thickness is 5 mm or more. Therefore, sufficient mechanical and thermal shock resistance must be imparted to the thick glassy carbon material. 5mm
The glassy carbon material satisfying the physical property requirements of the present invention in the above thick size is, for example, a phenol resin having a molecular weight of 100 or more and a gelation time of 5 to 60 minutes and furan or a derivative compound thereof mixed with a viscosity of 1 to 100 poises. In the process of forming a resin composition having a resin content of 50% by weight or more, molding and curing the resin composition, and then firing and carbonizing the resin composition in a non-oxidizing atmosphere, the curing temperature rising rate of the resin composition, the final curing temperature, It can be produced by strictly controlling the rate of temperature rise during firing and carbonization, the final firing temperature, and the like.

The specific manufacturing process is as follows. First, a phenolic resin initial condensation product having a molecular weight of 100 or more and a gelation time of 5 to 60 minutes obtained by subjecting purified phenol and formalin to a condensation reaction as raw materials is mixed with furan or a derivative compound thereof to obtain a carbonization yield of 65. ~ 75
% Two-component resin composition is formed. As the furan derivative compound to be used at this time, furfuryl alcohol, furfural, methyl furan carboxylic acid ester or the like having compatibility with the phenol resin may be used alone or in combination of two or more. The mixing ratio of the furan-based component to the phenol resin is appropriately set according to the resin properties, and the properties are adjusted to have a viscosity of 1 to 100 poise and a resin content of 50% or more.

Then, the resin composition is cast-molded or multiple-coating-molded so that the finally obtained glassy carbon material has a wall thickness of 5 mm or more, molded into a desired shape, and heat-cured. If there is an internal / external difference in the structure of the cured molded product at this stage, the glassy carbon material finally obtained will also have an internal / external difference in the degree of development of carbon crystals, so the curing conditions are strictly controlled. There is a need to. Generally, the thermosetting resin is an exothermic reaction, and as the thickness increases, the internal heat storage increases. Therefore, the inside of the resin having a higher heat storage degree than the surface layer is more likely to cure. In order to avoid such non-uniformity of curing, the rate of temperature rise during heat curing is adjusted to 10 ° C./hr or less, preferably 5 ° C./hr or less, more preferably 2 ° C./hr or less. Then, the heating temperature is raised to a temperature at which the curing reaction ends, and the heating temperature is maintained for a sufficient time to completely cure. The curing temperature varies depending on the composition of the resin, the type of the curing agent, the composition, etc., but is usually maintained in the temperature range of 140 to 200 ° C. When the final curing temperature is low, it is necessary to hold for a long time, and it is preferable to maintain the temperature for 3 hours or more even at a high curing temperature.

The cured resin molded body is packed in a heating furnace kept in a non-oxidizing atmosphere, and is carbonized by firing in a temperature range of 800 ° C. or higher to be converted into glassy carbon. Since the cured resin has a low thermal conductivity, when it becomes thick, the decomposition and carbonization reaction of the internal structure is delayed with respect to the vicinity of the surface layer portion during the process of firing and carbonization. Therefore, as a result of the progress of carbonization in a state where the inside is under tension due to the preceding carbonization in the vicinity of the surface layer portion, a difference occurs in the crystal structure between the surface layer portion and the inside. In order to mitigate such a phenomenon, the heating rate of the firing carbonization is set to 4 ° C./hr or less, and the temperature is slowly raised so that the inner and outer layers are carbonized at a uniform rate. At the same time, in the process of raising the temperature, it is effective to reduce the internal / external structural difference by maintaining the temperature at each stage of the temperature range where the carbonization is severe, the temperature where the gas is generated, and the temperature where the carbonization ends and the structure changes. Is. Specifically, 300 to 400 ° C., 400 to 50
Hold at each temperature stage of 0 ° C. and 500 to 600 ° C. for 5 hours or more. Further, in order to achieve the soaking treatment, a method of packing a resin molded body in a graphite crucible in a state of being sandwiched between graphite plates and firing and carbonizing is also effective.

[0020]

EXAMPLES Examples of the present invention will be specifically described below in comparison with comparative examples, but the embodiments of the present invention are not limited to these examples.

Examples 1 to 5 and Comparative Examples 1 to 3 (1) Production of glassy carbon material Phenol and formalin purified by vacuum distillation were subjected to a condensation reaction in the presence of ammonia to give a molecular weight of 132 and a gelation time of 14 minutes. A phenol resin precondensate was prepared. To 100 parts by weight of this phenol resin, 30 parts by weight of furfuryl alcohol was added and mixed to obtain a viscosity of 40 poise,
A resin composition having a resin content of 55% was obtained. This resin composition was poured into a polyethylene vat, placed in a vacuum desiccator to perform defoaming treatment under a reduced pressure of 10 Torr, then transferred to an electric oven, and cured by the heating rate and final curing conditions shown in Table 1. It was applied and molded into a plate-shaped molded body.

Then, the thickness of each plate-shaped molded body is 10
A graphite plate of mm (Tokai Carbon Co., Ltd., G347) was sandwiched and put into a graphite crucible. The graphite crucible was packed in an electric furnace, and the surroundings were filled with graphite powder and encased in a graphite carbonization treatment.
As shown in Table 1, the conditions for calcination and carbonization are a heating rate of 1 to 1
Varying within the range of 0 ° C / hr, 350 ° C during firing, 45
Each temperature step of 0 ° C. and 550 ° C. was maintained for 5 hours, and finally the temperature was raised to a predetermined temperature. The glassy carbon plate obtained had a size of 80 mm in length and width and 6 mm in thickness.

The average lattice spacing d ₀₀₂ and the crystallite Lc (002) of the graphite hexagonal mesh plane layer in the surface layer portion and the center portion of the cross section of the glassy carbon plate obtained under each condition (Table 1) were measured, and It is shown in Table 2 together with the internal and external differences.

[0024]

[Table 1]

[0025]

[Table 2]

(2) Impact resistance of glassy carbon material From a glassy carbon plate having the physical properties shown in Table 1, 200 bolts (10 mm under neck) were cut out by M3 (JIS B0205) using a diamond tool. Table 3 shows the yields of processed products which are free from material damage and chipping phenomenon due to this machining. In addition, this M3 bolt is 5
Place in a muffle furnace kept at 00 ° C for 1 hour, then 2
The thermal shock test was performed under the condition of being rapidly immersed in water at 0 ° C. When this test was performed on 100 test pieces, the ratio of cracks in the material was measured, and the results are also shown in Table 3.

[0027]

[Table 3]

From the results shown in Table 3, the glassy carbon sheets according to the Examples have higher resistance to mechanical impact and thermal impact than the Comparative Examples which deviate from the physical property requirements of the present invention. It can be seen that the thermal shock resistance of is excellent.

[0029]

As described above, according to the present invention, the average lattice spacing d of the graphite hexagonal mesh plane layer in the surface layer portion and the central portion of the cross section is d.
By suppressing ₀₀₂ or the crystallite size Lc (002) within a specific range difference, it is possible to provide a glassy carbon material having high resistance to mechanical and thermal shocks. In particular, as it exhibits sufficient impact resistance even for thick glassy carbon materials with a thickness of over 5 mm, it can be used as various glassy carbon members that are subject to yields during machining and usage conditions with severe thermal history. Extremely useful.

Claims (4)

[Claims] 1. The average lattice spacing d _{00 2 of the} graphite hexagonal mesh plane layer.
However, the impact resistant glassy carbon material is characterized by having a texture structure within a range of 0.01 nm in the surface layer portion and the center portion of the cross section. Wherein the cross-sectional center portion average lattice spacing d _{00 2} graphite hexagonal plane layer of the impact resistant vitreous carbon material according to claim 1, wherein in the range of 0.345～0.365Nm. 3. An impact-resistant vitreous carbon material characterized by having a texture structure in which a crystallite size Lc (002) is within a range of 1.5 nm in a surface layer portion and a center portion of a cross section. 4. The crystallite size Lc at the center of the cross section
The impact-resistant glassy carbon material according to claim 3, wherein (002) is in the range of 1.3 to 4.0 nm.