KR100267797B1 - Fabrication of the non-brittle high-temperature ceramics using charcoal - Google Patents
Fabrication of the non-brittle high-temperature ceramics using charcoal Download PDFInfo
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- KR100267797B1 KR100267797B1 KR1019980033839A KR19980033839A KR100267797B1 KR 100267797 B1 KR100267797 B1 KR 100267797B1 KR 1019980033839 A KR1019980033839 A KR 1019980033839A KR 19980033839 A KR19980033839 A KR 19980033839A KR 100267797 B1 KR100267797 B1 KR 100267797B1
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Abstract
본 발명은 보다 간편한 염가의 공정으로 높은 파괴에너지를 갖는 고인성·고온 세라믹스를 제조하는 방법에 관한 것이다.The present invention relates to a method for producing high toughness and high temperature ceramics having high breakdown energy in a simpler and cheaper process.
탄소 망목구조를 형성하고 있으며 가공이 용이한 다공성의 숯을 사용하여 전구체를 성형하고 진공중에서 Si 분말과 반응결합 시켜 근사기본형의 고인성·고온 Si 섬유/SiC 복합체를 제조하였다. 반응결합을 할 때 숯에 대한 Si 분말의 무게비를 달리하여 층상형과 섬유상형 구조를 가지는 2 종류의 복합체를 제조하였다.Precursors were formed using porous charcoal, which forms a carbon network structure, and was easily reacted with Si powder in vacuum to prepare high toughness and high temperature Si fiber / SiC composites of approximate basic type. Two kinds of composites having a layered and fibrous structure were prepared by varying the weight ratio of Si powder to charcoal when reacting.
제조된 Si 섬유/SiC 복합체는 치밀화된 SiC에 의해 높은 강도값을 유지하며 침투된 Si 섬유와 치밀화되지 않은 큰 기공을 계면으로 하는 층상구조로 인하여 보다 높은 파괴에너지를 나타내었다. 반응생성물은 상온과 1300℃에서 강도값의 차이가 거의 없으며 방향에 따른 강도값의 변화도 거의 없었다. 또한 파괴에너지는 1300℃의 고온에서 Si 섬유의 소성변형에 의해 상온보다 더 높은 값을 나타내었다.The prepared Si-fiber / SiC composites exhibited higher fracture energy due to the layered structure that maintains a high strength value by densified SiC and infiltrates Si fibers with large pores that are not densified. The reaction product had almost no difference in strength value at room temperature and 1300 ° C, and there was little change in strength value along the direction. In addition, the fracture energy was higher than the room temperature due to the plastic deformation of the Si fiber at a high temperature of 1300 ℃.
숯에 반응결합을 적용함으로써 공정을 단순화시켜서 제조비용을 절감할 수 있었으며 섬유강화 복합체와 반응결합의 장점을 나타내는 근사기본형 Si 섬유/SiC 복합체를 제조할 수 있었다.By applying reaction bonds to charcoal, the manufacturing cost was reduced by simplifying the process, and an approximate basic Si-fiber / SiC composite that showed the advantages of fiber-reinforced composites and reaction bonds could be prepared.
Description
세라믹스는 일반적으로 예기치 못한 상황에서 잘 깨지는 취성파괴와 고가의 제조비용 때문에 고온 구조용 재료로 광범위하게 사용되지 못하고 있다. 이를 극복하기 위해서는 염가의 방법으로 높은 파괴에너지를 갖는 고인성 세라믹스를 제조하는 것이 우선되어야 한다.Ceramics are generally not widely used in high temperature structural materials due to brittle fractures and expensive manufacturing costs that break well under unexpected circumstances. In order to overcome this problem, it is necessary to manufacture high toughness ceramics having high breakdown energy by inexpensive method.
종래의 경우에 있어서, 고인성 세라믹스는 주로 입자(particulate)나 휘스커(whisker)를 보강한 단체 세라믹스, 200 ㎛두께의 세라믹스 판 위에 약한 계면층을 코팅하여 적층한 후 소결한 층상형 복합체, 압출법으로 제조된 지름 약 150∼200 ㎛의 세라믹스 봉에 약한 계면층을 코팅하여 가압소결한 섬유상 단체, 유기금속 전구체로부터 제조된 고강도 세라믹스 섬유를 이용한 섬유 강화 복합체 등의 방법으로 제조되었다.In the conventional case, the high toughness ceramics are mainly single-piece ceramics reinforced with particles or whiskers, layered composites sintered after coating and laminating a weak interfacial layer on a 200 μm-thick ceramics plate, and an extrusion method. A weak interface layer was coated on a ceramic rod having a diameter of about 150 to 200 μm to prepare a fiber-reinforced composite using a high-strength ceramic fiber made from an organometallic precursor.
입자나 휘스커를 보강한 단체 세라믹스는 세라믹스의 단점인 취성파괴를 극복하지 못하여 1000℃ 이상에서 파괴인성이 10 ㎫√m 이상을 넘지 못하였다. 층상형 복합체와 섬유상 단체는 각각 15 ㎫√m과 10 ㎫√m 정도의 파괴인성 값을 보여주었으나 고온에서 산화에 의한 물성저하와 고가의 제조비용 때문에 산업적인 실용화를 이루지 못하였다. 세라믹스 섬유강화 복합체는 높은 파괴인성(30 ㎫√m)을 획득할 수 있는 가장 양산적인 방법이나 고가의 세라믹 섬유 사용, 복잡한 제조 공정, 기계적 물성의 비등방성과 함께 1200℃ 이상의 온도에서 세라믹 섬유의 물성이 급격히 저하하여 고온 환경에서 사용하는데 문제점이 있었다.Single ceramics reinforced with particles or whiskers could not overcome brittle fracture, which is a disadvantage of ceramics, and the fracture toughness did not exceed 10 MPa√m above 1000 ℃. The layered composites and the fibrous bodies showed fracture toughness values of 15 MPa√m and 10 MPa√m, respectively, but they were not industrialized due to the deterioration of properties at high temperatures and the high cost of manufacturing. Ceramic fiber-reinforced composites are the most mass-produced method to achieve high fracture toughness (30 MPa√m), but the use of expensive ceramic fibers, complex manufacturing processes, anisotropy of mechanical properties, and physical properties of ceramic fibers at temperatures above 1200 ° C There was a problem in using it in a high temperature environment sharply lowered.
본 발명은 상기한 문제를 해결하기 위하여 안출된 것으로, 그 목적은 보다 간편한 염가의 공정으로 높은 파괴에너지를 갖는 고인성·고온 세라믹스를 제조하는 방법을 제공하고자 하는 것이다.The present invention has been made to solve the above problems, and its object is to provide a method for producing high toughness and high temperature ceramics having high breakdown energy in a simple and inexpensive process.
개발되어지는 새로운 제조 방법은 저가의 원료 사용으로 간단한 단일 공정을 통하여 근사기본형으로 높은 파괴에너지와 고온 안정성을 나타내는 세라믹스를 제조할 수 있으며 대형 제품에 적용이 용이해야 한다.The new manufacturing method to be developed is to produce ceramics showing high breakdown energy and high temperature stability as an approximate basic type through a simple single process using low cost raw materials and should be easy to apply to large products.
즉, 본 발명의 목적은 저가의 숯을 진공중에서 단일공정으로 규소(Si)와 반응결합시킨 보다 간편한 방법으로 고인성과 고온안정성을 나타내는 근사기본형의 Si 섬유/SiC 복합체를 제조하는 방법을 제공하는데 있다.That is, an object of the present invention is to provide a method for producing an approximate basic type Si fiber / SiC composite exhibiting high toughness and high temperature stability by a simpler method in which inexpensive charcoal is reacted with silicon (Si) in a single process in a vacuum. .
제1도는 본 발명에서 전구체로 사용한 숯의 미세구조 사진.1 is a microstructure photograph of char used as a precursor in the present invention.
제2도는 큰 기공 주위의 작은 기공의 미세구조 사진.2 is a microstructure picture of small pores around large pores.
제3도는 본 발명에 따른 반응생성물의 미세구조 사진.3 is a microstructure photograph of the reaction product according to the present invention.
제4도는 본 발명에 따른 반응생성물과 전구체로 사용한 숯의 X-선 회절분석(XRD) 결과 선도.4 is a diagram of X-ray diffraction analysis (XRD) results of char used as a reaction product and precursor according to the present invention.
제5도는 본 발명에 따른 반응생성물과 전구체로 사용한 숯의 3점 곡강도 측정 결과 선도.5 is a three-point bending strength measurement results of the char used as a reaction product and precursor according to the present invention.
상기한 목적을 실현하기 위해서, 본 발명은 탄소 망목구조를 형성하고 있으며 가공이 용이한 다공성의 숯을 전구체로 사용하여 용융 Si를 침투시킨 후 반응결합을 통하여 고인성·고온 Si 섬유/SiC 복합체를 제조하였다.In order to realize the above object, the present invention forms a carbon network structure and uses porous charcoal, which is easy to process, as a precursor to infiltrate molten Si, and then use a high toughness and high temperature Si fiber / SiC composite through a reaction bond. Prepared.
본 발명을 상세히 설명하면 다음과 같다. 먼저 탄소 망목구조로 이루어진 숯을 가공하여 반응결합을 위한 전구체를 성형하였다. 성형된 전구체를 진공 분위기를 유지하며 열처리 할 수 있는 전기로에 장입하고 주위를 숯에 대하여 무게비로 0.5∼2.5의 규소(Si) 분말로 채운 후 전기로 내부를 진공상태로 만들었다. 일정한 승온속도로 가열하여 용융 Si를 숯의 기공에 침투시킨 후 반응결합을 통하여 Si 섬유가 강화된 Si 섬유/SiC 복합체를 제조하였다.The present invention is described in detail as follows. First, the char for carbon network structure was processed to form a precursor for reaction bonding. The molded precursor was charged into an electric furnace that can be heat treated while maintaining a vacuum atmosphere, and the surroundings were filled with silicon (Si) powder of 0.5 to 2.5 by weight to charcoal, and the inside of the electric furnace was vacuumed. The molten Si was infiltrated into the pores of the char by heating at a constant temperature increase rate, and then Si fiber / SiC composites with reinforced Si fibers were prepared through reaction bonding.
[실시예]EXAMPLE
고인성·고온 Si 섬유/SiC 복합체의 제조를 위하여, 상용 참나무 숯을 4 mm× 5 mm ×40 mm 크기로 가공하여 전구체를 성형하고 주위를 숯에 대하여 0.5∼2.5의 무게비로 Si 분말의 양을 달리하여 채운 후 진공에서 5℃/min의 가열속도로 1750℃까지 열처리하였다.For the production of high toughness and high temperature Si fiber / SiC composites, commercial oak char is processed into 4 mm × 5 mm × 40 mm in size to form precursors and the amount of Si powder is added at a weight ratio of 0.5 to 2.5 relative to the char. After filling with different, heat treatment to 1750 ℃ at a heating rate of 5 ℃ / min in vacuum.
도 1은 전구체로 사용한 참나무 숯의 반응결합 전의 미세구조 사진이다. 반응결합 전의 숯은 층상구조를 이루고 있는 약 150 ㎛의 큰 기공, 큰 기공 사이에 존재하는 약 20 ㎛의 중간 기공, 큰 기공 주위에 있는 약 3 ㎛의 작은 기공의 3 종류기공으로 이루어져 있다.1 is a microstructure photograph before the reaction bonding of oak char used as a precursor. Charcoal before reaction bonding is composed of three types of pores of about 150 μm in a layered structure, about 20 μm of intermediate pores existing between the large pores, and about 3 μm of small pores around the large pores.
도 2는 큰 기공 주위에 있는 작은 기공 부분을 확대한 것으로 작은 기공들은 벌집과 같은 구조를 이루고 있음을 알 수 있다.2 is an enlarged portion of the small pore around the large pores can be seen that the small pores form a honeycomb-like structure.
도 3은 숯을 Si 분말과 진공중에서 반응결합 시킨 후의 미세구조 사진으로 3종류의 기공들이 용융 Si에 의해 완전히 치밀화되었음을 알 수 있다.3 is a microstructure photograph after the reaction of the charcoal and Si powder in vacuum, it can be seen that three kinds of pores are completely densified by molten Si.
도 4는 숯과 반응생성물의 X-선 회절분석(XRD) 결과이다. 숯은 비정질 상태의 탄소 peak를 나타내었으며, 반응생성물은 잔류탄소가 없이 β-SiC와 Si의 peak 만을 나타내었다. 그리고 반응생성물은 공기중 1300℃에서 2 시간 유지한 후에도 SiO2peak은 나타내지 않았다. 이것으로부터 반응결합을 통하여 숯이 모두 Si/SiC 복합체로 되었으며 반응생성물이 높은 산화저항성을 나타냄을 알 수 있었다.4 is an X-ray diffraction analysis (XRD) of the char and the reaction product. Charcoal showed an amorphous carbon peak, and the reaction product showed only β-SiC and Si peaks without residual carbon. The reaction product did not show SiO 2 peak even after maintaining at 1300 ° C. for 2 hours in air. From this, all the chars became Si / SiC composites through the reaction bonds, and the reaction products showed high oxidation resistance.
도 5는 숯과 반응생성물의 3점 곡강도를 측정한 결과이다. 상온에서 숯 자체도 큰 기공들의 층상구조와 작은 기공들의 벌집구조에 의해 비취성 파괴거동을 보이고 있다. 반응생성물 또한 침투된 Si 섬유와 치밀화되지 않은 큰 기공에 의한 층상구조로 인하여 상온과 1300℃에서 비취성 파괴거동을 보였다. 3점 곡강도 값은 숯이 약 35 ㎫이었으며 반응생성물은 상온과 1300℃에서 각각 170 ㎫과 180 ㎫으로 거의 차이가 없으며 방향에 따른 차이도 거의 없었다.5 is a result of measuring the three-point bending strength of the char and reaction products. At room temperature, the charcoal itself exhibits odorous fracture behavior due to the layered structure of large pores and the honeycomb structure of small pores. The reaction product also exhibited an odorless fracture behavior at room temperature and 1300 ° C due to the layered structure of the infiltrated Si fibers and large densified pores. The three-point bending strength was about 35 MPa for char, and the reaction products were 170 MPa and 180 MPa at room temperature and 1300 ℃, respectively.
파괴에너지는 3점 곡강도 측정에서 얻은 하중-변위 곡선의 아래 면적을 시편의 단면적의 2 배로 나누어 준 값으로 계산하였다. 숯 자체의 파괴에너지는 약 230J/㎡ 으로 세라믹스 단체보다 높은 값을 나타내었으며 반응생성물의 파괴에너지는 1300℃에서 약 820 J/㎡으로 상온에서의 560 J/㎡보다 더 높은 값을 나타내었다. 반응결합 후 밀도는 0.6에서 2.63으로 증가하였다. 표 1에 숯과 반응생성물의 밀도 및 기계적 물성값을 정리하였다.Fracture energy was calculated by dividing the area under the load-displacement curve obtained from the three-point bending strength measurements by twice the cross-sectional area of the specimen. The destruction energy of charcoal itself was about 230J / ㎡, which was higher than that of ceramics alone, and the destruction energy of the reaction product was about 820 J / ㎡ at 1300 ℃, higher than 560 J / ㎡ at room temperature. The density after the reaction bond increased from 0.6 to 2.63. Table 1 summarizes the density and mechanical properties of the char and reaction products.
상기와 같이 본 발명에 따른 제조방법으로 숯을 진공중에서 Si 분말과 반응결합시켜 제조한 근사기본형 Si 섬유/SiC 복합체는 높은 파괴에너지와 고온 안정성을 나타내었다.As described above, the approximate basic type Si fiber / SiC composite prepared by reacting char with Si powder in vacuum by the production method according to the present invention showed high fracture energy and high temperature stability.
상기한 바와 같이 본 발명은 기존의 단체 세라믹스, 층상형 복합체, 섬유상단체, 섬유 강화 복합체를 제조하는 방법들과는 달리, 공정을 단순화시켜서 제조비용을 절감할 수 있으며 숯에 반응결합을 적용함으로써 섬유강화와 반응결합의 장점을 동시에 나타내는 근사기본형 Si 섬유/SiC 복합체를 제조할 수 있다.As described above, the present invention, unlike the conventional methods for producing single ceramics, layered composites, fibrous single-strand, fiber-reinforced composites, can simplify the process to reduce the manufacturing cost and by applying the reaction bonds to the charcoal to strengthen the fiber and Approximate basic Si fiber / SiC composites can be produced that show the benefits of reactive bonding simultaneously.
제조된 Si 섬유/SiC 복합체는 치밀화된 SiC에 의해 높은 강도값을 유지하며 침투된 Si 섬유와 채워지지 않은 큰 기공에 의한 적층구조로 인하여 보다 높은 파괴에너지를 나타내게 한다. 반응생성물은 상온과 1300℃에서 강도값의 차이가 거의 없으며 방향에 따른 강도값의 변화도 거의 없다. 또한 파괴에너지는 1300℃의 고온에서 Si 섬유의 소성변형에 의해 상온보다 더 높은 값을 나타낸다.The prepared Si-fiber / SiC composite maintains a high strength value by densified SiC and exhibits higher fracture energy due to the laminated structure by the infiltrated Si fibers and the unfilled large pores. The reaction product has almost no difference in strength value at room temperature and 1300 ° C, and hardly changes in strength value according to the direction. In addition, the fracture energy is higher than room temperature due to the plastic deformation of the Si fiber at a high temperature of 1300 ℃.
본 발명은 고온에서 강도값과 파괴에너지를 유지할 수 있는 근사기본형 Si/SiC 복합체의 염가 대량 생산에 적용될 수 있으리라 기대된다.It is expected that the present invention can be applied to cheap mass production of an approximate basic Si / SiC composite that can maintain strength and fracture energy at high temperatures.
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