• 공업화학
• /
• 제16권3호
• /
• pp.305-311
• /
• 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.

• E2M - 전기 전자와 첨단 소재
• /
• 제9권1호
• /
• pp.38-43
• /
• 1996

A coprecipitation method was used for preparing Ca and Pt doped $SnO_2$ fine powder. Components of the powder were investigated by XPS and SIMS. Crystallite size and specific surface area were investigated by TEM, XRD, and BET analysis. $SnO_2$(Ca)/Pt based thick film devices were prepared by a screen printing technique for methane gas detection. Then sensing characteristics of the devices were investigated. As Ca and Pt added, the crystal growth of $SnO_2$ was suppressed during calcining and sintering, and the sensitivity of $SnO_2$(Ca)/Pt thick film to methane gas was enhanced. For the Pt doped $SnO_2$ fine particle, the thick film device shows sensitivity of about 83% to 2000 ppm methane gas at an operating temperature of >$400^{\circ}C$.

• 콘크리트학회논문집
• /
• 제13권6호
• /
• pp.561-567
• /
• 2001

석산에서 부순잔골재를 생산시에는 다량의 슬러지 미립분이 배출되고 있다. 그러나, 실무현장에서는 슬러지의 일부를 매립용등에 제한적으로 사용할 뿐, 대부분은 방치되거나 무분별하게 버려지고 있어 막대한 경제적 손실과 환경오염 문제를 유발시키고 있다. 따라서 본 연구에서는 석산폐기물인 슬러지를 공장제품용 시멘트 모르타르 제조에 골재대체용 충전재로 활용하기 위하여, 골재 종류 및 모르타르 배합비 등에 미립분 혼입률을 변화시켜 시멘트 모르타르의 강도 및 흡수 특성을 검토하였다. 연구결과, 시멘트 모르타르 제품을 제조할 때 슬러지를 골재에 10% 정도 대체하여 혼입하게 되면 기존의 시멘트 모르타르 제품보다 향상된 품질의 제품이 생산될 수 있는 것이 확인되었다.

• Tribology and Lubricants
• /
• 제24권2호
• /
• pp.96-103
• /
• 2008

PTFE is generally utilized as the form of composites with adding various fillers. The purpose of this paper lies on clarifying the friction and wear properties of the PTFE coating layer on steel. Especially, the effects of PTFE powder size for coating and surface roughness of the counter material on the properties are investigated. Sliding friction and wear tests are conducted at several sliding speeds by employing two types of PTFE coating layer using different powder sizes. One type of coating layer is composed of uniform fine powder, whereas the other type is made up of mixture powder of different sizes. As results, it is found that PTFE coating layer are effective to improve the wear resistance and to reduce the friction coefficient. It is clear that PTFE coating layers are abrasively removed by asperities of the counter material during sliding contact. However, PTFE coating layer with uniform fine powder shows somewhat better wear resistance than that with mixture powder of different sizes in low sliding speed region. It can be seen that the wear of the coating layer are drastically reduced because wear fragment from counter material are transferred to the coating layer. On the other hand, friction coefficient is shown not to be directly related with PTFE powder size in coating layer.

• 한국결정성장학회:학술대회논문집
• /
• 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
• /
• pp.87-89
• /
• 1997

The BaTiO$_3$ fine powder was prepared by hydrthermal method using titanium tetrahydoxide (Ti(OH)$_4$) and barium dihydroxide (Ba(OH)$_2$.8$H_2O$) as raw materials. The fine powder was obtained at temperatures as low as 160 to 185$^{\circ}C$. The properties of the BaTiO$_3$ powder were studied as a function of various parameters (reaction temperature, reaction time, Ba/Ti=ratio, etc). The average particle size of the BaTiO$_3$ increased with increasing reaction temperature. After hydrothermal treatment at 17$0^{\circ}C$ for 8 h, the average particle size of the BaTiO$_3$ powder was about 30 nm and the particle size distribution was narrow.

• 한국세라믹학회지
• /
• 제32권1호
• /
• pp.37-44
• /
• 1995

TiO2 fine powders were synthesized using oxygenolysis and hydrolysis reaction of TiCl4 vapor in gas phase. The TiO2 powder synthesized showed morphological differences depending on reaction system as follows: TiCl4-O2 reaction system produced the monosized particles having polyhedral shape with well-defined crystal planes and the particles did not agglomerate into secondary particles. TiCl4-H2O reaction system, whereas, produced the spherical secondary particles which consisted of fine primary particles. Other powder characteristics such as particle size, impurity content and rutile content are also reported in this study.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1994년도 하계학술대회 논문집 C
• /
• pp.1342-1344
• /
• 1994

Silver-Nickel alloy has been used as a electrical contact material for low voltage, low current. Since the solubility between Ag and Ni is very low, it is difficult to produce Ag-Ni alloy by using conventional melting method and disperse Ni powder homogeneously in Ag matrix. In this study we have been produced fine Ag-Ni alloy powder by using coprecipitation method. Firstly, we have produced silver-nickel nitrate solution by dissolving the Ag and Ni ingot in nitric acid solution and then, coprecipitate (Ag, Ni)carbonate dropping Ag-Ni nitrate solution to sodium carbonate solution. (Ag, Ni) carbonate is heat-treated in $H_2$ atmosphere, $400^{\circ}C$ and it has been analysed by TGA, SEM, XRD, ICP. It is represented Silver-Nickel alloy powder in the particle range of $0.1{\sim}0.5{\mu}m$.

• 한국세라믹학회지
• /
• 제28권8호
• /
• pp.647-653
• /
• 1991

In order to synthesize fine AlN powder by the direct nitridation of Aluminum metal power added LiF and BaF2 as additives was heated at 150$0^{\circ}C$ for 3 hrs. in nitrogen gas with flow rate of 20 mι/sec. Additives are promoted the nitridation by prevented the aggromerate of powders when 3% LiF and 2% BaF2 were added to Al metal powder. Rate of nitridation was about 100% and average size of AlN powders were very fine such as 0.3 ${\mu}{\textrm}{m}$. Specific surface area of synthesized AlN powder was 3.95$m^2$/g and also O2 and N2 contents were 2.595% and 33.25%, respectively.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.661-662
• /
• 2006

Development of recycling method at cemented carbide scraps was researched. Some properties of recycled cemented carbides were investigated. Recycled WC fine powder suffered the surface oxidation. Therefore it was necessary to be done by reduction treatment at 1073K-3.6ks under hydrogen atmosphere. When sintering condition at 1673K-3.6ks was treated under vacuum condition, it gained the deflective strength of about 90%, and gained hardness and sintering density about same value compared with commercial alloys. As a result, it was able to recycle only by 7 processes.

• 한국분말야금학회:학술대회논문집
• /
• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
• /
• pp.24-25
• /
• 2006

High-Speed Centrifugal Compaction Process is one of slip-using compacting method originally developed for processing of oxide ceramics. In this study, we apply the HCP to ultra-fine (0.1 micron) WC powder. Organic liquid of heptane was chosen as dispersing media to avoid possible oxidation of WC. The mixing apparatus was a key to obtain dense compacts. Only the slips mixed by high energy planetary ball mill were packed up to 55% by the HCP, and sintered to almost full density at 1673 K without any sintering aids. This sintered compact marked Vickers hardness of Hv 2750 at maximum.