• 공업화학
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• 제16권3호
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• pp.305-311
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• 2005

열플라즈마 공정은 고온, 고활성, 초급냉 등의 탁월한 특징을 갖고 있으며, 다양한 분야에 적용되고 있다. 본 총설에서는 열플라즈마 공정의 특징과 초미립 분말의 제조를 위한 시스템의 구성을 기술한다. 여기에는 금속, 세라믹, 복합 초미립 분말이 포함되며, 공정의 개발을 위하여 요구되는 핵심기술에 대하여 논의한다. 저자 등은 열플라즈마를 이용하여 다양한 형태의 고품질 초미립 분말을 제조하는 공정의 가능성을 제시하고자 하였다.

• 한국세라믹학회지
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• 제33권4호
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• pp.411-417
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• 1996

Ultrafine NiO/YSZ (Yttria Stabilized Zirconia) powders were made by using a glycine nitrate process which is used as anode material for solid oxide fuel cells. The specific surface areas of synthesized NiO/YSZ powders were examined with controlling pH of a precursor solution and the content of glycine. The binding of glycine with metal nitrates occurring in the precursor solution was analyzed by using FTIR. The characteristics of synthesized powders were examined with X-ray diffraction(XRD) Brunauer Emmett Teller with N2 absorption. scanning electron microscopy (SEM). and transmission electron microscopy (TEM). Ultrafine NiO/YSZ powders of 15-18 m2/g were obtained through GNP when the content of glycine was controlled to 1 or 2 times the stoichiometric ratio in the precursor solutions. Strongly acid precursor solution increased the specific surface area of the synthesized powders. This is suggested to be the increased binding of metal nitrates and glycine under a strong acid solution of pH=0.5 that lets glycine consist of mainly the amine group of {{{{ { NH}`_{3 } ^{+ } }}. After sintering and reducing treatment of NiO/YSZ powders synthesized by GNP the Ni/YSZ pellet showed ideal microstructure where very fine Ni particles of 3-5 ${\mu}{\textrm}{m}$ were distributed uniformly and fine pore around Ni metal particles was formed. leading to anincrease of the triple phase boundary among gas Ni and YSZ.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.473-476
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• 2005

Today's manufacturing industry is facing challenges from advanced difficult-to-machine materials (WC-Co alloys, ceramics, and composites), stringent design requirements (high precision, complex shapes, and high surface quality), and machining costs. Advanced materials play an increasingly important role in modem manufacturing industries, especially, in aircraft, automobile, tool, die and mold making industries. The greatly-improved thermal, chemical, and mechanical properties of the material (such as improved strength, heat resistance, wear resistance, and corrosion resistance), while having yielded enormous economic benefits to manufacturing industries through improved product performance and product design, are making traditional machining processes unable to machine them or unable to machine them economically. In this paper, mechanical characteristic evaluation test of fine powder type WC-Co alloy was accomplished to obtain clear data for miniaturized special die parts machining with high reliability and high quality.

• 한국분말재료학회지
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• 제17권6호
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• pp.443-448
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• 2010

The $\beta$ phase Ti-Nb-Sn-HA bio materials were successfully fabricated by high energy mechanical milling and pulse current activated sintering (PCAS). Ti-6Al-4V ELI alloy has been widely used as biomaterial. But the Al has been inducing Alzheimer disease and V is classified as toxic element. In this study, ultra fine sized Ti-Nb-Sn-HA powder was produced by high energy mechanical milling machine. The $\beta$ phase Ti-Nb-Sn-HA powders were obtained after 12hr milling from $\alpha$ phase. And ultra fine grain sized Ti-Nb-Sn-HA composites could be fabricated using PCAS without grain growth. After sintering, the microstructures and phase-transformation of Ti-Nb-Sn-HA biomaterials were analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). The relative density was obtained by Archimedes principle and the hardness was measured by Vickers hardness tester. The $\beta$-Ti phase was obtained after 12h milling. As result of hardness and relative density, 12h milled Ti-Nb-Sn-HA composite has the highest values.

• 한국산업융합학회 논문집
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• 제20권2호
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• pp.149-155
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• 2017

Mechanical properties of carbon coated $SiC_f/SiC$ composites have been investigated, in conjunction with a detailed analysis of microstructure. Especially, the fracture behavior of $SiC_f/SiC$ composites by the induction of carbon coating layers has been examined. The matrix region of $SiC_f/SiC$ composites with ultra-fine SiC powders were consolidated by a liquid phase sintering (LPS) process, using a sintering additive of $Al_2O_3-Y_2O_3$ powder compound. In this composite, plain and satin- woven Tyranno SA fabrics were also utilized as a reinforcing material. A carbon interfacial layer was coated around satin-woven SiC fabrics. The characterization of LPS-$SiC_f/SiC$ composites was investigated by means of SEM and three point bending test.

• International Journal of Aerospace System Engineering
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• 제7권1호
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• pp.16-20
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• 2020

The recent trend is increasing towards the usage of polymer matrix composites since they have a wide variety of applications. They have applications in the field of aircraft and space industry, sporting goods, medical devices, marine and automotive applications and also in commercial usage. The most commonly used fibre-reinforced polymer matrix composite is Glass fibre reinforced epoxy (GFRE) composite which is used in aviation, sports and automotive industries. However, the strength of GFRE composites is not adequate for structural applications. Therefore, the current research focuses on increasing the strength of GFRE composites by reinforcing with micro Graphite (Gr) particulates. The Gr used is an ultra-fine powder with particle size 250 ㎛. Gr is known to have good wear resistance, thermal conductivity and can operate at high temperatures. Gr particulates are mixed with the epoxy matrix in various weight ratios. Hand-lay technique is used for fabricating the composites. Mechanical properties such as tensile strength, elongation, compressive strength and flexural strength are obtained experimentally to study the effect of change in Gr content (0-5 wt. %). The tests were done as per ASTM standards.

• 대한금속재료학회지
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• 제46권4호
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• pp.223-226
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• 2008

The comparison of sintering behavior and mechanical properties of ultra-fine WC-10wt.%Co and WC-10wt.%Fe hard materials produced by high-frequency induction heated sintering (HFIHS) was accomplished using ultra fine powder of WC and binders(Co, Fe). The advantage of this process allows very quick densification to near theoretical density and prohibition of grain growth in nano-structured materials. Highly dense WC-10Co and WC-10Fe with a relative density of up to 99% could be obtained with simultaneous application of 60 MPa pressure and induced current within 1 minute without significant change in grain size. The hardness and fracture toughness of the dense WC-10Co and WC-10Fe composites produced by HFIHS were investigated.

• 한국방재학회 논문집
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• 제8권2호
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• pp.23-30
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• 2008

UHPCC는 고성능, 고강도와 우수한 역학적 특성을 지니고 있다. UHPCC는 동일한 하중 하에서 타 재료에 비해 단면을 축소할 수 있는 장점이 있으나, 보통콘크리트에 비해 외국에서 수입하는 실리카흄이 많이 사용되는 배합이 되어 제작비용을 증가시키는 원인이 된다. 최밀 충전구성에 의한 UHPCC의 우수한 역학적 특성은 분체에 해당되는 아주 가는 입경의 골재를 치환함으로서 변화시킬 수 있다. 본 연구는 실리카흄과 실리카플로우를 석회석 미분말로 치환된 UHPCC의 특성을 파악하고자 한다. 본 실험 시편은 치환종류에 따라 크게 세 가지로 분류한다. 압축강도와 플로우를 비교 검토하였으며, SEM, XRD와 NMR 방법등을 사용하여 미세조직과 수화반응 현상을 분석하였다. 결론적으로 석회석 미분말로의 치환은 UHPCC 구조부재의 시공 단가를 감소시키며, 굳지 않은 UHPCC의 특성을 향상시키는 유용한 치환이 된다고 볼 수 있다.

• 대한금속재료학회지
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• 제50권1호
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• pp.86-91
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• 2012

Ti-6Al-4V extra low interstitial (ELI) alloy has been widely used as an orthopedic implant material because of its excellent biocompatibility, corrosion resistance and mechanical properties. However, V-free titanium alloys such as Ti-6%Al-7%Nb and Ti-5%Al-2.5%Fe have recently been developed because of the toxicity of V. Hydroxyapatite (HA) is used as a coating material on Ti or Ti biomaterials due to its good biocompatibility. However, HA coated on Ti alloy causes a problem for tissue by peeling off during usage. Therefore, such peeling off during long time usage can be suppressed by adding HA in Ti or Ti alloy composites. The aim of this study was to manufacture an ultra fine grained (UFG) Ti-Nb-HA bulk alloy, which is usually difficult to fabricate using melting and casting technology, by rapid sintering process using high energy mechanical milled (HEMM) powder.