• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 춘계학술강연 및 발표대회강연 및 발표논문 초록집
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• pp.54-54
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• 2006

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.744-744
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• 2006

• 터널과지하공간
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• 제22권2호
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• pp.157-161
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• 2012

본 논문에서는 산업용 폭약을 이용한 충격고화기술을 ZnO-98%과 $Ga_2O_3$-2% 혼합분말에 적용하여 직경 30mm, 두께 6mm인 $ZnOGa_2O_3$고화체를 형성 시켰다. 고화체의 경도 및 상대밀도는 각각 220~250 Hv, 97%이었으며, 표면에 대한 주사현미경 관찰결과 균열 및 결함은 발생되지 않았으며, 분말입자들은 강한 충격파에 의해 변형되어 서로 결합되었음을 확인하였다. 또한 X-ray 분석결과로부터 입자 간의 격자결합 및 결정자의 변형을 확인 할 수 있었으며, 이러한 격자결합과 결정자의 변형은 높은 전기저항의 원인이 된다는 것을 보여주었다.

• 소성∙가공
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• 제12권6호
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• pp.521-528
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• 2003

Powder injection molding (PIM) uses the shaping advantage of injection molding but is applicable to metals and ceramics. This process combines a small quantity of polymer with an inorganic powder to form a feedstock that can be molded. After shaping, the polymeric binder is extracted and the powder is sintered, often to near-theoretical densities. According1y, PIM delivers structural materials in a shaping technology previously restricted to polymers. The process overcomes the shape limitations of traditional powder compaction, the costs of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of conventional casting. Since 1980s when major attention was given to PIM process, it has been widening the application area from small parts with complex shape and tailored properties to structural parts requiring strength and ductility as in automotive, military and medical industries.

• 한국세라믹학회지
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• 제50권3호
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• pp.218-225
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• 2013

The densification behavior and strength of sintered reaction bonded silicon nitrides (SRBSN) that contain $Lu_2O_3-SiO_2$ additives were improved by the addition of fine Si powder. Dense specimens (relative density: 99.5%) were obtained by gas-pressure sintering (GPS) at $1850^{\circ}C$ through the addition of fine Si. In contrast, the densification of conventional specimens did not complete at $1950^{\circ}C$. The fine Si decreased the onset temperature of shrinkage and increased the shrinkage rate because the additive helped the compaction of green bodies and induced the formation of fine $Si_3N_4$ particles after nitridation and sintering at and above $1600^{\circ}C$. The amount of residual $SiO_2$ within the specimens was not strongly affected by adding fine Si powder because most of the $SiO_2$ layer that had formed on the fine Si particles decomposed during nitridation. The maximum strength and fracture toughness of the specimens were 991 MPa and $8.0MPa{\cdot}m^{1/2}$, respectively.

• 한국세라믹학회지
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• 제44권4호
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• pp.235-239
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• 2007

For the pressure compaction process of the ceramic powder, the density distribution is very important for the uniform shrinkages at the sintered body. In this paper, we fabricated alumina green body using compaction process and simulated about same condition. Then comparison of simulation and experimental result confirmed that accuracy of simulation. On the average density of top and lower part was each $2.41g/cm^3,\;2.27g/cm^3$ and deviation at final step was calculated with 0.06 in simulation. Also, experiments show that total density of top and lower part was each $2.59g/cm^3,\;2.36g/cm^3$, and deviation was 0.09. Conclusion, that was not a difference to the simulation and experimental result. The application using the finite element simulation method is possible optimization of the compressing process, predict generated part of cracks and there is a possibility of getting result of more fast, more accurate then existing experience method.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.305-308
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• 2001

Powder injection molding (PIM) uses the shaping advantage of injection molding but is applicable to metals and ceramics. This process combines a small quantity of polymer with an inorganic powder to form a feedstock that can be molded. After shaping, the polymeric binder is extracted and the powder is sintered often to near-theoretical densities. Accordingly, PIM delivers structural materials in a shaping technology previously restricted to polymers. The process overcomes the shape limitations of traditional powder compaction, the costs of machining, the productivity limits of isostatic pressing and slip casting, and the defect and tolerance limitations of casting. The 17-4 PH stainless steel powders with average diameter of $10{\mu}m$ were injection-molded into flat tensile specimens. Sintering of the compacts was carried out at the various temperatures ranging from 900 to $1350^{\circ}C$. Sintering behavior of the compacts and tensile properties of sintered specimens were investigated.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 1997년도 추계학술강연 및 발표대회 강연 및 발표논문 초록집
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• pp.7-7
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• 1997

During sintering of very porous green bodies, as obtained by compaction of hard powders - such as tungsten carbide or ceramics - or by injection moulding, important shrinkage occurs. Due to heterogeneous green density field, gravity effects, friction on the support, thermal gradients, etc., this shrinkage is often non-uniform, which' may induce significant shape changes. As the ratio of compact dimension to powder size is very high, the mechanics of continuum is relevant to model such phenomena. Thus numerical techniques, such as the finite element method can be used to simulate the sintering process and predict the final shape of the sintered part. Such type of simulation has much been developed in the last decade firstly for hot isostatic pressing and next for die compaction. Finite element modelling has been recently applied to free sintering. The simulation of sintering should be based on constitutive equations describing the thermo-mechanical behaviour of the material under any state of stress and any temperature which may arise within the sintering body. These equations can be drawn either from experimental data or from micromechanical models. The experiments usually consist in free sintering and sinter-forging tests. Indeed applying more complex loading conditions at high temperature under controlled atmosphere is delicate. Micromechanical models describe the constitutive behaviour of aggregates of spheres from the deformation of two-sphere contact either by viscous flow or grain boundary diffusion. Such models are not able to describe complex microstructure and mechanisms as observed in real materials but they can give some basic information on the formulation of constitutive equations. Practically both experimental and theoretical approaches can be coupled to identify the constitutive equations. Such procedure has been performed for modelling the sintering of compacts obtained by die pressing of a mixture of tungsten carbide and cobalt powders. The constitutive behaviour of this material during sintering has been described by a linear viscous constitutive model, whose functions have been fitted from results of free sintering and sinter-forging experiments. This model has next been introduced in ABAQUS finite element code to simulate the sintering of heterogeneous green compacts of various geometries at constant temperature. Examples of simulations are shown and compared with experiments.

• 한국세라믹학회지
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• 제25권4호
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• pp.357-363
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• 1988

Ccompaction and sintering behavior of highly pure PSZ powders were investigated by laying the stress on the granulation processes. The particle size of coprecipitated PSZ powder was so fine that the agglomeration was severely formed during drying and calcing step and by this agglomeration differential sinering was occurred. The methanol dispersion of precipitates was the good method of avoiding severe agglomeration formed during drying process because of small surface tension than water. But perfect deagglomeraton was not possible due to high surface area of powders. So homogenization by granulation was needed, and among the method spray granulation was the most desirable to obtain homogeneous compacts and subsequent flaw-free ceramics.

• 한국결정성장학회지
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• 제8권4호
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• pp.605-611
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• 1998

단분산 입자계의 진동성향시 공정조건에 따라 형성되는 침점체의 미세구조와 물성을 분석할 수 있는 전산실험 모델이 개발되었다. 여기서 중요한 진동성형 변수들인 진폭(amplitude), 침적시간(frequency), 진동횟수(cycle)가 형성되는 침적체의 회절구조 및 충전밀도에 미치는 영향이 조사되었다. 형성되는 침적체의 비결정상으로부터 결정상으로의 상변이 조건이 결정되었다. 모델의 결과는 실제 실험결과를 만족시키는 진동횟수와 충전밀도의 경험식과도 부합하였다. 현 모델은 진동성형시 침적체의 조밀화 현상과 결정화 현상을 조사하는데 매우 효과적이다.