Compaction behavior of bimodal iron nanopowder agglomerate

Song, Jun-ll,Lee, Geon-Yong,Choi, Joon-Phil,Lee, Jai-Sung Elsevier 2018 Powder technology Vol.338 No.-

<P><B>Abstract</B></P> <P>The compaction behavior of structure-modified Fe nanopowders having agglomerates of spherical shape and a bimodal particle size distribution was investigated in terms of the particle packing and microstructure during compaction process. To fabricate the structure-modified Fe nanopowders, the spray-dried Fe<SUB>2</SUB>O<SUB>3</SUB> nanopowder was hydrogen reduced at 400, 450 and 550 °C to control the degree of particle growth in agglomerates. The compaction behavior of fabricated Fe nanopowders was investigated by two different ways. In die compaction experiments, it was found that the bimodal nanopowder reduced at 550 °C showed higher green density compared to nanopowders reduced at 400 and 450 °C over the entire range of compacting pressure. Furthermore, the compact of the bimodal nanopowder achieved a remarkable green density over 80% of theoretical density (TD) at 1000 MPa pressure without any defects due to the effective packing by filling the interstices between the large nanoparticles with small nanoparticles. The obtained density-pressure data was fitted by the Panelli and Ambrozio Filho equation to compare the densification capacity between the fabricated Fe nanopowders. To investigate the agglomerate deformation occurrence at the low pressure range, a continuous compaction experiment was conducted; the observations were explained in terms of microstructural development on the basis of the apparent yield pressure obtained from continuous densification curves.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Compaction behavior of bimodal Fe nanopowder agglomerate was investigated. </LI> <LI> Agglomerate strength of bimodal nanopowder was low to be broken during tapping. </LI> <LI> Bimodal nanopowder showed higher green density than monomodal nanopowder. </LI> <LI> The effective packing of bimodal nanoparticles improved compactability. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Preparation and Properties of Barium Titanate Nanopowder/Epoxy Composites

Chandradass, J.,Bae, Dong-sik TaylorFrancis 2008 Materials and manufacturing processes Vol.23 No.2

<P> This article is focused on the preparation of barium titanate nanopowder/epoxy composites and studying the effect of barium titanate nanopowder on improving mechanical and thermal characteristics of the epoxy polymer. Composites are prepared by dispersing barium titanate nanopowder in epoxy resin and, subsequently, cross-linking by using diamino diphenyl methane (DDM) curing agents. Synthesis of barium titanate nanopowder/epoxy composites is carried out for different concentrations (1, 3, and 5 by weight) of barium titanate nanopowder at high temperature. High-temperature curing (HTC) involves mixing the resin-nanopowder solution followed by DDM hardener and curing at 120°C. Tensile, flexure, and impact results showed a maximum value of 72.7 MPa, 2.98 GPa, and 2 J/cm, respectively. DSC analysis revealed that curing occurs at low temperature in the presence of barium titanate nanopowder. Thermogravimetry analysis (TGA) showed the increased thermal stability in the nanoparticle filled epoxy composites as compared with the pure epoxy counterparts. Dynamic mechanical analysis (DMA) revealed, maximum storage modulus of 6400 MPa and glass transition temperature of 154°C for 3 wt% barium titanate nanopowder.</P>

비가압 성형한 Fe 나노분말응집체의 소결거동

유우경,정성수,이재성,You, Woo-Kyung,Jung, Sung-Soo,Lee, Jai-Sung 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.4

Sintering behavior of iron nanopowder agglomerate compact prepared by slurry compaction method was investigated. The Fe nanopowder agglomerates were prepared by hydrogen reduction of spray dried agglomerates of ball-milled $Fe_2O_3$ nanopowder at various reduction temperatures of $450^{\circ}C$, $500^{\circ}C$ and $550^{\circ}C$, respectively. It was found that the Fe nanopowder agglomerates produced at higher reduction temperature have a higher green density compact which consists of more densified nanopowder agglomerates with coarsed nanopowders. The sintering behavior of the Fe nanopowder agglomerates strongly depended on the powder packing density in the compact and microstructure of the agglomerated nanopowder. It was discussed in terms of two sintering factors affecting the entire densification process of the compact.

비스무스 나노분말 표지 전극의 카드뮴/납 검출특성에 관한 연구

이경자,김현진,이희민,이상훈,이민구,이창규,Lee, Gyeoung-Ja,Kim, Hyoun-Jin,Lee, Hi-Min,Lee, Sang-Hoon,Lee, Min-Ku,Lee, Chang-Kyu 한국분말야금학회 2008 한국분말재료학회지 (KPMI) Vol.15 No.5

Trace analysis of Cd and Pb at surface modified thick film graphite electrode with Bi nanopowder has been carried out using square-wave anodic stripping voltammetry (SWASV) technique. Bi nanopowder synthesized by gas condensation (GC) method showed the size of $50{\sim}100$ nm with BET surface area, $A_{BET}=6.8m^{2}g^{-l}$. For a strong adhesion of the Bi nanopowder onto the screen printed carbon paste electrode, nafion solution was added into Bi-containing suspension. From the SWASV, it was found that the Bi nanopowder electrode exhibited a well-defined responses relating to the oxidations of Cd and Pb. The current peak intensity increased with increasing concentration of Cd and Pb. From the linear relationship between Cd/Pb concentrations and peak current, the sensitivity of the Bi nanopowder electrode was quantitatively estimated. The detection limit of the electrode was estimated to be $0.15{\mu}g/l$ and $0.07{\mu}g/l$ for Cd and Pb, respectively, on the basis of the signal-to-noise characteristics (S/N=3) of the response for the $1.0{\mu}g/l$ solution under a 10 min accumulation.

Fabrication of a diamond impregnated tool using iron nanopowder binder

송준일,이건영,이선영,이재성 한양대학교 세라믹연구소 2018 Journal of Ceramic Processing Research Vol.19 No.3

To replace the high cost material of cobalt matrix, the feasibility of diamond impregnated tools using structure-modified Fenanopowder was investigated in terms of its compaction and related sintering properties. The structure was controlled thatthe spherical agglomerate shape for the easily rearrangement at low pressure range and the bimodal typed porous agglomeratestructure are principally responsible for the green density improvement. The structure modified Fe nanopowder showedhigher compactability than the structure non-treated Fe nanopowder during the compaction process and homogeneouslydispersed diamond in the segment. After sintering, the structure modified Fe nanopowder showed sound segment shape andreached 93.7%T.D. without substantial grain growth. The characteristics of compaction and the sintered segments wereevaluated in terms of the microstructure. Moreover, a prototype product was made and core-drilling test was carried out usingthe structure modified Fe nanopowder. The results are discussed in comparison with the standard of commercial products.

전기폭발법에 의한 CU/CUO 나노분말의 제조 및 분말특성

맹덕영,이창규,이남희,박중학,김흥회,이은구,Maeng, D.Y.,Rhee, C.K.,Lee, N.H.,Park, J.H.,Kim, W.W.,Lee, E.G. 한국재료학회 2002 한국재료학회지 Vol.12 No.12

Both Cu and Cu-oxide nanopowders have great potential as conductive paste, solid lubricant, effective catalysts and super conducting materials because of their unique properties compared with those of commercial micro-sized ones. In this study, Cu and Cu-oxide nanopowders were prepared by Pulsed Wire Evaporation (PWE) method which has been very useful for producing nanometer-sized metal, alloy and ceramic powders. In this process, the metal wire is explosively converted into ultrafine particles under high electric pulse current (between $10^4$ and $10^{ 6}$ $A/mm^2$) within a micro second time. To prevent full oxidations of Cu powder, the surface of powder has been slightly passivated with thin CuO layer. X-ray diffraction analysis has shown that pure Cu nanopowders were obtained at $N_2$ atmosphere. As the oxygen partial pressure increased in $N_2$ atmosphere, the gradual phase transformation occurred from Cu to $Cu_2$O and finally CuO nanopowders. The spherical Cu nanopowders had a uniform size distribution of about 100nm in diameter. The Cu-oxide nanopowders were less than 70nm with sphere-like shape and their mean particle size was 54nm. Smaller size of Cu-oxide nanopowders compared with that of the Cu nanopowders results from the secondary explosion of Cu nanopowders at oxygen atmosphere. Thin passivated oxygen layer on the Cu surface has been proved by XPS and HRPD.

Consolidation of Iron Nanopowder by Nanopowder-Agglomerate Sintering at Elevated Temperature

Lee, Jai-Sung,Yun, Joon-Chul,Choi, Joon-Phil,Lee, Geon-Yong The Korean Powder Metallurgy Institute 2013 한국분말재료학회지 (KPMI) Vol.20 No.1

The key concept of nanopowder agglomerate sintering (NAS) is to enhance material transport by controlling the powder interface volume of nanopowder agglomerates. Using this concept, we developed a new approach to full density processing for the fabrication of pure iron nanomaterial using Fe nanopowder agglomerates from oxide powders. Full density processing of pure iron nanopowders was introduced in which the powder interface volume is manipulated in order to control the densification process and its corresponding microstructures. The full density sintering behavior of Fe nanopowders optimally size-controlled by wet-milling treatment was discussed in terms of densification process and microstructures.

초음파 밀링한 WO3-CuO 나노혼합분말의 수소환원 거동

정성수 ( Sung Soo Jung ),윤의식 ( Eui Sik Yoon ),이재성 ( Jai Sung Lee ) 대한금속·재료학회 2009 대한금속·재료학회지 Vol.47 No.9

The hydrogen reduction behavior of ultrasonic ball-milled WO3-CuO nanopowder, which is highly related with micro-pore structure, was investigated by thermogravimetry(TG) and hygrometry system. EDS and TEM results represented that the ultrasonic ball-milled WO3-CuO nanopowder consisted of the agglomerates which was confirmed as a homogeneous mixture of WO3 and CuO particles. It was found that the reduction reaction of CuO was retarded by initial micro-pores which are smaller than 40 nm in the ultrasonic ball-milled WO3-CuO nanopowder. The earlier agglomeration of Cu particles at comparably low temperature decreased the volume of micro-pores in the WO3-CuO nanopowder which caused the retardation of WO3 reduction reaction. These results clearly explain that the micro-pore structure significantly affected the reduction reaction of WO3 and CuO in the WO3-CuO nanopowder.

화염법에 의한 천이금속 첨가 이산화티타늄 나노분말의 제조

박훈,지현석,이승용,안재평,이덕열,박종구,Park Hoon,Jie Hyunseock,Lee Seung-Yong,Ahn Jae-Pyoung,Lee Dok-Yol,Park Jong-Ku 한국분말야금학회 2005 한국분말재료학회지 (KPMI) Vol.12 No.6

Nanopowders of titanium dioxide $(TiO_2)$ incorporating the transition metal element(s) were synthesized by flame synthesis method. Single element among Fe(III), Cr(III), and Zn(II) was doped into the interior of $TiO_2$ crystal; bimetal doping of Fe and Zn was also made. The characteristics of transition-metal-doped $TiO_2$ nanopowders in the particle feature, crystallography and electronic structures were determined with various analytical tools. The chemical bond of Fe-O-Zn was confirmed to exist in the bimetal-doped $TiO_2$ nanopowders incorporating Fe-Zn. The transition element incorporated in the $TiO_2$ was attributed to affect both Ti 3d orbital and O 2p orbital by NEXAFS measurement. The bimetal-doped $TiO_2$ nanopowder showed light absorption over more wide wavelength range than the single-doped $TiO_2$ nanopowders.

플라즈마 이온질화에 의한 Fe 나노분말소결체의 표면경화 가능성 연구

윤준철,이재성,Yun, Joon-Chul,Lee, Jai-Sung 한국분말야금학회 2012 한국분말재료학회지 (KPMI) Vol.19 No.1

This study has been performed on the full density sintering of Fe nanopowder and the surface hardening by plasma ion nitriding. The Fe sintered part was fabricated by pressureless sintering of the Fe nanopowder at $700^{\circ}C$ in which the nanopowder agglomerates were controlled to have 0.5-5 ${\mu}m$ sized agglomerates with 150 nm Fe nanopowders. The green compact with 46% theoretical density(T.D.) showed a homogeneous microstructure with fine pores below 1 ${\mu}m$. After sintering, the powder compact underwent full densification process with above 98%T.D. and uniform nanoscale microstructure. This enhanced sintering is thought to be basically due to the homogeneous microstructure in the green compact in which the large pores are removed by wet-milling. Plasma ion nitriding of the sintered part resulted in the formation of ${\gamma}$'-$Fe_4N$ equilibrium phase with about 12 ${\mu}m$ thickness, leading to the surface hardening of the sintered Fe part. The surface hardness was remarkably increased from 176 $H_v$ for the matrix to 365 $H_v$.