KR100435292B1 - Process for producing high toughness silicon oxynitride ceramics improving fracture toughness - Google Patents

Process for producing high toughness silicon oxynitride ceramics improving fracture toughness Download PDF

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KR100435292B1
KR100435292B1 KR1019960071439A KR19960071439A KR100435292B1 KR 100435292 B1 KR100435292 B1 KR 100435292B1 KR 1019960071439 A KR1019960071439 A KR 1019960071439A KR 19960071439 A KR19960071439 A KR 19960071439A KR 100435292 B1 KR100435292 B1 KR 100435292B1
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silicon oxynitride
powder
si3n4
alpha
sintering
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KR19980052450A (en
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한상무
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주식회사 포스코
재단법인 포항산업과학연구원
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    • C04B35/58—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on non-oxide ceramics based on borides, nitrides, i.e. nitrides, oxynitrides, carbonitrides or oxycarbonitrides or silicides
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Abstract

PURPOSE: A process is provided to produce alpha-sialon silicon oxynitride ceramics by using beta-Si3N4 instead of general alpha-Si3N4, which improves mechanical properties and fracture toughness of the silicon oxynitride ceramics. CONSTITUTION: The process for producing the alpha-sialon silicon oxynitride ceramics comprises the steps of: mixing and molding 55-74wt% of beta-Si3N4 powder containing 9-11vol% of alpha-Si3N4 particles, 5-9wt% of Y2O3 powder, and 20-36wt% of AIN powder; sintering the mixture at 1600-1800deg.C for 1-24 hours in an electric furnace under the nitrogen atmosphere. The process is a method for making duplex structure by causing abnormal grain growth through a phase transformation process in the sintering.

Description

고인성 산질화규소 요업체의 제조방법Manufacturing method of high toughness silicon oxynitride

본 발명은 산질화규소 요업체를 제조함에 있어서 제조시 사용되는 원료를 특성적으로 활용하여 소결중 발생하는 상변태를 이용, 이상입자 성장을 유도함으로써 높은 파괴인성 특성을 가지는 소결체를 제조하는 방법에 관한 것이다.The present invention relates to a method for producing a sintered body having high fracture toughness characteristics by inducing abnormal particle growth by utilizing phase transformations generated during sintering by using raw materials used in the manufacturing process in the production of silicon oxynitride. .

질화규소(Si3N4)를 기본으로 하는 요업체는 저비중, 화학적 안정성, 고경도 및 내열성 등 구조용 재료에 요구되는 제반 특성을 가지고 있으나 요업체 특유의 취성으로 인하여 그 이용이 제한되고 있다. 따라서 그 파괴인성을 증가시키고자 하는 노력이 이루어져 왔다. 파괴인성을 높이는 방법은 복합재료화, 신물질 적용등 여러가지가 있으나 이들 방법은 경제성 및 실용성면에서 많은 문제를 가지고 있다.Subcontractors based on silicon nitride (Si 3 N 4 ) have all the characteristics required for structural materials such as low specific gravity, chemical stability, high hardness and heat resistance, but their use is limited due to their brittleness. Thus, efforts have been made to increase the fracture toughness. There are many ways to increase fracture toughness, such as composite materialization and application of new materials, but these methods have many problems in terms of economy and practicality.

질화규소계 요업체는 일반적으로 α-Si3H4의 출발원료에 마그네시아(MgO), 알루미나(Al2O3)등을 조제로서 첨가, 소결함으로써 얻어지는 β-Si3N4를 일컫는다. 하지만 알루미나와 질화알루미늄, 또는 실리카(SiO2)와 질화알루미늄을 특정한 비율로 첨가하면 β-Si3N4의 결정구조를 유지하면서 Si와 N이 Al과 O로 치환된 고용체가얻어지며, 이를 β-사이알론(sialon)이라 한다. 또한 기본적으로 α-Si3N4의 결정구조를 유지하면서 Si와 N이 Al과 O로 치환된 고용체도 있는데 이를 α-사이알론이라 한다.Silicon nitride based companies generally refer to β-Si 3 N 4 obtained by adding and sintering magnesia (MgO), alumina (Al 2 O 3 ), and the like as starting materials of α-Si 3 H 4 . However, addition of alumina and aluminum nitride, or silica (SiO 2 ) and aluminum nitride in a specific ratio yields a solid solution in which Si and N are substituted with Al and O while maintaining the crystal structure of β-Si 3 N 4 . It is called sialon. There is also a solid solution in which Si and N are substituted with Al and O while maintaining the crystal structure of α-Si 3 N 4 , which is called α-sialon.

β-Si3N4또는 β-사이알론의 인성 증진법 가운데 최근 개발된 방법은 약100 기압의 질소분위기압 하에서 소결하여 평균입도보다 수 내지 수십배 큰 이상성장입자를 소수발생시켜 이중입도를 가지게 함으로써 균열전파경로를 휘어지게 하거나 가교를 구성시킴으로써 파괴를 방지하는 것이다. 이와 같은 미세구조 제어에 의한 파괴인성 증가는 β-Si3N4에 대하여 적용된 방법(예 :미국특허 5,449,649호 및 미국특허 5,472,919호)이 이미 제안되어 있다. 그러나 α-사이알론에 대해서는 이와같은 이중입도구조를 발달시키는 방법에 대해서는 알려진 바가 없다. 또한 상기 인용된 특허에서 사용되는 가압소결법은 제조비 상승의 문제점을 가지고 있다.The recently developed method of toughness enhancement of β-Si 3 N 4 or β-sialon is sintered under nitrogen atmosphere of about 100 atmospheres and cracks by generating a small number of abnormally grown particles that are several to several ten times larger than the average particle size. By breaking the propagation path or constructing a crosslinking, the destruction is prevented. The increase in fracture toughness by such microstructure control has already been proposed for methods applied to β-Si 3 N 4 (eg, US Pat. No. 5,449,649 and US Pat. No. 5,472,919). However, it is unknown how to develop such a dual particle size structure for α-sialon. In addition, the pressure sintering method used in the above-cited patents has a problem of an increase in manufacturing cost.

본 발명은 상술한 종래의 문제점을 해결하기 위해 출발원료상을 제어함으로써 산질화규소 요업체에서 소결중의 상변태를 통하여 이중입도구조를 발달시키는 방법을 제공하는 것을 목적으로 한다.It is an object of the present invention to provide a method for developing a dual particle size structure through phase transformation during sintering in a silicon oxynitride company by controlling the starting material phase to solve the above-mentioned conventional problems.

상기의 목적을 달성하기 위한 본 발명은 α-사이알론을 제조함에 있어, 그 출발원료인 질화규소의 결정상을 통상 사용하는 α-Si3N4가 아닌 β-Si3N4를 사용하여 α-사이알론을 제조하여 상변태과정을 거치게 함으로써 일부의 입자들만이 이상성장을 일으켜 이중입자구조가 발생하도록 하는 방법을 제공한다.The present invention for achieving the above object, in the production of α-sialon, α-Si using β-Si 3 N 4 instead of α-Si 3 N 4 which normally uses the crystal phase of silicon nitride as the starting material By preparing alon and undergoing phase transformation process, only some of the particles cause abnormal growth, thereby providing a method of generating a double particle structure.

이하에서, 본 발명의 방법을 더욱 상세히 설명한다.In the following, the method of the present invention is described in more detail.

본 발명은 요업체의 파괴인성을 증가시키기 위하여 원료출발질화규소의 상(Phase)을 보통 사용되는 α-Si3N4에서 β-Si3N4로 바꾸어 소결중 상변태과정을 통해 이상입자성장(abnomal grain growth)를 일으켜 이중입자구조(duplex structure)를 만드는 방법이다. α-Si3N4만을 사용하여서는 치밀한 소결체를 얻을 수 없으므로 Y2O3및 AlN을 첨가하여 치밀화를 돕는 저융점 액상을 소결중 생성시키는 동시에 최종적으로 α-사이알론 조성의 결정상입자만으로 이루어진 산질화규소 요업체를 제조하는 것이다. 소결중 상변태되어 석출되는 α-사이알론은 비슷한 결정구조를 가지는 α-Si3N4위에서 선호적으로 성장하게 된다. 이때의 α-Si3N4입자는 출발원료인 β-Si3N4분말안에 소량 포함되어 있는 미량상이다. 즉 α-사이알론의 최종 미세구조는 β-Si3N4원료분말중에 포함되어 있는 미량의 α-Si3N4입자에 의해 발달되는 이상성장입자들이 포함되는 이중입자구조가 되는것이다.The present invention is to change the phase of silicon nitride raw material starting from α-Si 3 N 4 to β-Si 3 N 4 in order to increase the fracture toughness of the urine company, the abnormal grain growth through the phase transformation process during sintering (abnomal It is a method of making a duplex structure by causing grain growth. Dense sintered body cannot be obtained by using only α-Si 3 N 4 , so silicon oxynitride consisting of only crystalline particles of α-sialon composition is produced during sintering of low melting liquid phase during sintering by adding Y 2 O 3 and AlN. To manufacture a urine manufacturer. Phase-transitioned α-sialon precipitated during sintering preferentially grows on α-Si 3 N 4 with similar crystal structure. The α-Si 3 N 4 particles at this time are trace amounts contained in a small amount in the β-Si 3 N 4 powder as a starting material. In other words, the final microstructure of α-sialon is a double particle structure containing abnormal growth particles developed by trace amounts of α-Si 3 N 4 particles contained in the β-Si 3 N 4 raw powder.

이 때의 조성 범위는 Si3N4-Y2O3-AℓN 삼성분계에서 (100-x)Si3N4+ x(0.1Y2O3+ 0.9AℓN)의 조성식을 만족하는 것이 바람직하고 여기서 x는 몰%로 표시되며 x=30부터 x=50까지의 값만이 허용된다. 이 조성조건은 소결체내에 유리상없이 α-사이알론만이 존재하는 조성으로서, 최대, 중앙 및 최소 질화규소 중량%로 나타낼 때 표 1과 같이 표시된다.The composition range at this time satisfies the composition formula of (100-x) Si 3 N 4 + x (0.1Y 2 O 3 + 0.9 AlN) in a Si 3 N 4 -Y 2 O 3 -ANN system. x is expressed in mole percent and only values from x = 30 to x = 50 are allowed. This composition condition is a composition in which only α-sialon is present in the sintered body without a glass phase, and is expressed as shown in Table 1 when expressed in terms of the maximum, middle, and minimum silicon nitride weight percent.

이 조성범위를 벗어날 경우에는 소결체내에 α-사이알론 외에 유리상이 나타나며 이 유리상은 소결체의 기계적 강도를 크게 저하시키는 원인이 된다.If it is out of this composition range, a glass phase other than α-sialon appears in the sintered compact, and this glass phase causes a large decrease in the mechanical strength of the sintered compact.

소결온도는 1600℃부터 1800℃사이로서, 이보다 낮은 온도에서는 치밀화가 이루어지지 않으며 높은 온도에서는 질화규소의 분해가 심해져 다공성의 취약한 소결체가 된다.The sintering temperature is between 1600 ° C and 1800 ° C. Densification is not performed at lower temperatures, and silicon nitride is severely decomposed at high temperatures, making the porous brittle sintered body.

소결시간은 1시간부터 24시간 사이로서 소결온도가 높을수록 소결시간은 짧아지며, 낮은 온도에서는 24시간 이상 소결해야 치밀한 소결체를 얻을 수 있다.The sintering time is between 1 hour and 24 hours. The higher the sintering temperature, the shorter the sintering time. At low temperature, the sintering time should be sintered more than 24 hours to obtain a compact sintered body.

표 1Table 1

다음에, 본 발명의 실시예를 설명한다.Next, an embodiment of the present invention will be described.

<실시예><Example>

상업적으로 시판되는 β-Si3N4원료분말(이 분말안에 포함되어 있는 α-Si3N4입자는 약 10용적%)과 Y2O3및 AℓN 분말을 통상적인 요업공정에 따라 혼합, 성형하고 흑연발열체 전기로를 이용하여 질소분위기 중에서 1600∼1800℃에서 1∼24시간 소결하였다. 이 때, 비교용 시편제조에는 통상적으로 이용되는 α-Si3N4분말을 사용하였다.A commercially available β-Si 3 N 4 raw powder (approximately 10 vol% of α-Si 3 N 4 particles contained in this powder) and Y 2 O 3 and AℓN powders are mixed and formed according to a conventional ceramic process. The graphite heating element was sintered at 1600 to 1800 ° C. for 1 to 24 hours in a nitrogen atmosphere. At this time, the α-Si 3 N 4 powder commonly used in the preparation of the comparative specimens.

성형체는 흑연도가니 안에 넣고 주위를 질화규소 분말로 채운후 뚜껑을 달아 열분해 및 분위기 제어시의 충격에서 보호하였다.The molded body was placed in a graphite crucible and filled with silicon nitride powder, and then capped to protect it from thermal decomposition and impact during atmosphere control.

얻어진 소결체를 경면연마하여 파괴인성 및 강도를 측정하였다. 표2는 소결시간에 따른 파괴인성 값으로서 β-Si3N4 원료분말을 사용하였을 때 더 높은 파괴인성을 나타낸다.The obtained sintered compact was mirror-polished to measure fracture toughness and strength. Table 2 shows higher fracture toughness when β-Si 3 N4 raw powder is used as fracture toughness value according to sintering time.

표 2TABLE 2

상술한 본 발명의 방법은 산질화규소 요업체의 기계적 성질 및 파괴인성 향상을 보다 경제적 및 실용적으로 이루어낼 수 있는 효과를 제공한다.The method of the present invention as described above provides the effect that can improve the mechanical properties and fracture toughness of silicon oxynitride manufacturers more economically and practically.

Claims (1)

α-Si3N4입자가 9∼11용적% 함유되어 있는 β-Si3N4분말 55∼74중량%, Y2O3분말 5∼9중량%, AlN 분말 20∼36중량%를 통상적인 요업공정에 따라 혼합 성형하는 단계와, 상기 혼합성형된 혼합물을 전기로를 이용하여 질소분위기 중에서 1600-1800 ℃에서 1∼24시간 소결하는 단계로 이루어진 것을 특징으로 하는 고인성 산질화규소요업체의 제조방법.α-Si 3 N 4 particles are in the 9 to 11% by volume of the β-Si 3 N 4 powder, which contains 55-74% by weight, Y 2 O 3 powder, 5-9% by weight, AlN powder, 20-36% by weight of conventional Mixing molding according to the ceramic process, and sintering the mixed molded mixture in a nitrogen atmosphere for 1 to 24 hours in a nitrogen atmosphere using an electric furnace, characterized in that the manufacturing method of high toughness silicon oxynitride manufacturers .
KR1019960071439A 1996-12-24 1996-12-24 Process for producing high toughness silicon oxynitride ceramics improving fracture toughness KR100435292B1 (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11046617B2 (en) 2017-09-20 2021-06-29 Lg Chem, Ltd. Tape casting slurry composition for preparing silicon nitride sintered body

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JPS62223009A (en) * 1986-03-20 1987-10-01 Ube Ind Ltd Production of alpha-sialon powder
EP0250592A1 (en) * 1985-12-20 1988-01-07 Research Development Corporation Of Japan Ceramics containing alpha-sialon
US4873210A (en) * 1987-12-02 1989-10-10 Gte Products Corporation Sialon containing high content of alpha prime phase
JPH04144969A (en) * 1990-10-06 1992-05-19 Natl Inst For Res In Inorg Mater Production of alpha-sialon-based sintered compact
US5120687A (en) * 1987-12-02 1992-06-09 The Morgan Crucible Company Plc Sialon containing high content of alpha prime phase

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EP0250592A1 (en) * 1985-12-20 1988-01-07 Research Development Corporation Of Japan Ceramics containing alpha-sialon
JPS62223009A (en) * 1986-03-20 1987-10-01 Ube Ind Ltd Production of alpha-sialon powder
US4873210A (en) * 1987-12-02 1989-10-10 Gte Products Corporation Sialon containing high content of alpha prime phase
US5120687A (en) * 1987-12-02 1992-06-09 The Morgan Crucible Company Plc Sialon containing high content of alpha prime phase
JPH04144969A (en) * 1990-10-06 1992-05-19 Natl Inst For Res In Inorg Mater Production of alpha-sialon-based sintered compact

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11046617B2 (en) 2017-09-20 2021-06-29 Lg Chem, Ltd. Tape casting slurry composition for preparing silicon nitride sintered body

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