• Title/Summary/Keyword: Metal powders

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Effects of Metal Ions Mole Ratio, pH and Heat Treatment Condition on the Magnetic Properties and Formation of Co-precipitated M-type Barium Ferrite Powders (공침법으로 합성한 바륨 페라이트(BaM)의 형성과 자기적 성질에 미치는 금속이온 몰 비 및 pH와 열처리 조건의 영향)

  • Baek, In-Seung;Nam, In-Tak
    • Journal of the Korean Magnetics Society
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    • v.19 no.6
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    • pp.209-215
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    • 2009
  • M-type barium ferrite (BaFe12O19) powders were synthesized through the co-precipitation method. Starting material composition $Fe^{3+}:\;Ba^{2+}$ mole ratio was fixed as 8 and the relative amount of $Fe^{3+}$ and $Ba^{2+}$ was controlled. Structure and magnetic properties and powder morphology were investigated using XRD, SEM, VSM. Powder showing high coercivity and small magnetization was obtained at pH8 and $Fe_{3+}:\;Ba_{2+}$ of 12 : 1.5. Small magnetization value was originated from the existence of ${\alpha}-Fe_2O_3$. Single-phase Mtype barium ferrite were obtained regardless of the heat treatment condition and the amount of $Fe_{3+}\;and\;Ba_{2+}$ at pH$\approx$10. The largest value of magnetization (55.7 emu/g) under investigation were obtained when $Fe_{3+}:\;Ba_{2+}$ of 13.6 : 1.7 and furnace cooled powder in $O_2$. Particle size of powder was in the range of 50~200 nm.

Synthesis of indium hydroxide powders by a precipitation method (침전법을 이용한 Indium hydroxide 분말의 합성 연구)

  • Choi, Eun-Kyoung;Lee, Won-Jun;Han, Kyu-Sung;Kim, Ung-Soo;Kim, Jin-Ho;Hwang, Kwang-Teak;Kim, Jong-Young;Hwang, Hae-Jin;Shim, Kwang-Bo;Cho, Woo-Seok
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.27 no.3
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    • pp.122-129
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    • 2017
  • For the production of a high-density ITO target, $In_2O_3$ powders with a small particle size and low agglomeration should be synthesized. The purpose of this study is to control the size and shape of the Indium hydroxide precursor which affects the properties of the $In_2O_3$ powder. As a starting raw material, Indium metal was dissolved in a Nitric acid ($HNO_3$) solution. The effect of concentration, pH, and temperature on the properties of Indium hydroxide was investigated using ammonium hydroxide as a precipitant. Crystallite size of each sample was analyzed by X-ray diffraction and the shape and the size of the powder was analyzed by transmission electron microscopy. As a result, the particle size of Indium hydroxide was increased with increase in the concentration of $In(NO_3)_3$ and the particle size and shape of the Indium hydroxide remained unchanged with increase in the pH of the solution. The particle size increased with increase in the precipitation temperature during precipitation.

CO2 decomposition characteristics of Ba-ferrite powder (Ba-페라이트 분말을 이용한 이산화탄소 분해 특성)

  • Nam, Sung-Chan;Park, Sung-Youl;Jeon, Soon-Kwan;Yoon, Yeo-Il
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.12 no.11
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    • pp.5357-5364
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    • 2011
  • The objective of this study is development of carbon recycle technology which convert carbon dioxide captured from flue gas to carbon monoxide or carbon and reuse in industrial fields. Since carbon dioxide is very stable and difficult to decompose, metal oxide was used as activation agent for the decomposition of carbon dioxide at low temperature. Metal oxides which convert $CO_2$ to CO or carbon were prepared using Ba-ferrite by solid and hydrothermal synthesis. TPR/TPO and TGA were used in this study. The results of TPR by H2 and TPO by $CO_2$ showed that Ba-ferrite powders synthesized by hydrothermal method were better than those by solid method. TGA showed contrary results that reduction of Ba-ferrite powders synthesized using solid method by $H_2$ was 21.96 wt%, oxidation by $CO_2$ was 21.24 wt% and 96.72 wt% of $CO_2$ decomposition efficiency showing excellent oxidation-reduction characteristics at $500^{\circ}C$.

Magnetic Properties and Structure of Co-precipitated Barium Ferrite (BaM) Powders (공침법으로 합성한 바륨 페라이트(BaM) 분말의 결정구조와 자기적 성질)

  • Baek, In-Seung;Nam, In-Tak
    • Journal of the Korean Magnetics Society
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    • v.20 no.4
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    • pp.134-142
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    • 2010
  • Barium ferrite ($BaFe_{12}O_{19}$) powders were synthesized by the co-precipitation method. $Fe^{3+}:Ba^{2+}$ mole ratio was fixed 8 and relative amount of $Fe^{3+}$ and $Ba^{2+}$ was controlled. The effects of the pH (= 8, 9, 10), calcination temperature and time on the morphology, structure and magnetic properties of the barium ferrite particles are characterized using XRD, FESEM, and VSM respectively. Coercivity and magnetization value of powders were changed with calcination temperature and time, relative amount of $Fe^{3+}$ and $Ba^{2+}$ and pH. Single-phase barium ferrite was obtained when pH value was 9 in the investigated range of $Fe^{3+}:Ba^{2+}$ relative amount and secondary phases were appeared at $Fe^{3+}:Ba^{2+}$ relative amount of 14.4 : 1.8. The largest value of magnetization (65.7 emu/g) was obtained when $Fe^{3+}:Ba^{2+}$ mole ratio was 12.8 : 1.6 and calcination temperature was $900^{\circ}C$ with air calcination atmosphere. The largest value of coercivity (5280 Oe) was obtained with $O_2$ calcination atmosphere.

Mössbauer Studied of Multiferroic Bi2/3La1/3FeO3 Nanoparticles (Multiferroic Bi2/3La1/3FeO3 나노입자의 Mössbauer 연구)

  • Lee, Seung-Wha
    • Journal of the Korean Magnetics Society
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    • v.16 no.1
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    • pp.28-33
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    • 2006
  • La substituted perovskite $BiFeO_3$ have been prepared by a sol-gel method. Magnetic and structural properties of the powders were characterized with Mossbauer spectroscopy, XRD, SEM, and TG-DTA. The crystal structure is found to be a rhombohedrally distorted perovskite structure with the lattice constant $\alpha=3.985{\AA}\;and\;\alpha=89.5^{\circ}.\;Bi_{2/3}La_{1/3}FeO_3$ powders that were annealed at and above $600^{\circ}C$ have a single-phase perovskite structure. However, powders annealed at $900^{\circ}C$ have a typical perovskite structure with small amount of $Bi_2O_3$ phase. The Neel temperature of $Bi_{2/3}La_{1/3}FeO_3$ is found to be $680\pm3K$. The isomer shift value at room temperature is found to be 0.27 mm/s relative to the Fe metal, which is consistent with high-spin $Fe^{3+}$ charge states. Debye temperature far$Bi_{2/3}La_{1/3}FeO_3$ is found to be $305\pm5K$. The average hyperfine field $H_{hf}(T)$ of the $Bi_{2/3}La_{1/3}FeO_3$, shows a temperature dependence of $[H_{hf}(T)-H_{hf}(0)]/H_{hf}(0)=-0.42(T/T_N)^{3/2}-0.13(T/T_N)^{5/2}$ for $T/T_N<0.7$ indicative of spin-wave excitation.

Properties of SiC Electrocondutive Ceramic Composites according to Transition Metal (천이금속 영향에 따른 SiC계 도전성 세라믹 복합체의 특성)

  • Shin, Yong-Deok;Oh, Sang-Soo;Jeon, Jae-Duck;Park, Young;Yim, Seung-Hyuk;Lee, Dong-Yoon
    • Proceedings of the KIEE Conference
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    • 2004.07c
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    • pp.1588-1590
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    • 2004
  • The composites were fabricated, respectively, using 61vol.% SiC - 39vol.% $TiB_2$ and using 61vol.% SiC 39vol.% WC powders with the liquid forming additives of 12wt% $Al_2O_3+Y_2O_3$ by pressureless annealing at 1800$^{\circ}C$ for 4 hours. Reactions between SiC and transition metal $TiB_2$, WC were not observed in this microstructure. The result of phase analysis of composites by XRD revealed SiC(6H), $TiB_2$ and YAG($Al_5Y_3O_{12}$) crystal phase on the SiC-$TiB_2$, and SiC(2H), WC and YAG($Al_5Y_3O_{12}$) crystal phase on the SiC-WC composites. ${\beta}{\rightarrow}{\alpha}$-SiC phase transformation was ocurred on the SiC-$TiB_2$, but ${\alpha}{\rightarrow}{\beta}$-SiC reverse transformation was not occurred on the SiC-WC composites. The relative density, the flexural strength showed respectively value of 96.2%, 310.19Mpa in SiC-WC composites. The electrical resistivity of the SiC-$TiB_2$ and the SiC-WC composites is all positive temperature cofficient resistance(PTCR) in the temperature ranges from 25$^{\circ}C$ to 500$^{\circ}C$.

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Characterization and crystal growth of InP by VGF method using quartz ampoule

  • Park, E.S.;C.H. Jung;J.J. Myung;J.Y. Hong;Kim, M.K.
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.9 no.6
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    • pp.542-546
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    • 1999
  • InP single crystal, III-V binary compound semiconductor, was grown by VGF(vertical gradient freeze) method using quartz ampoule and its electrical optical properties were investigated. Phosphorous powders were put in the bottom of quartz ampoule and Indium metal charged in conical quartz crucible what was attached at the upper side position inside the quartz ampoule. It was vacuous under the pressure of $10^5$Torr and sealed up. Indium metal was melted at $1070^{\circ}C$ and InP composition was formed by diffusion of phosphorous sublimated at $450^{\circ}C$ into Indium melt. By cooling the InP composition melt ($2^{\circ}C$~$5^{\circ}C$/hr of cooling rate) in range of $1070^{\circ}C$~$900^{\circ}C$, InP crystal was grown. The grown InP single crystals were investigated by X-ray analysis and polarized optical microscopy. Electrical properties were measured by Van der Pauw method. At the cooling method. At the cooling rate of $2^{\circ}C$/hr, growth direction of ingot was [111] and the quality of ingot was better at the upper side of ingot than the lower side. It was found that the InP crystals were n-type semiconductor and the carrier concentration, electron mobility and relative resistivity were $10^{15}$~$10^{16}/\textrm{cm}^3$ , $2\times 10^3$~$3\times 10^4{\textrm}{cm}^2$/Vsec and$2\times 10^{-1}$~$2\times 10^{-3}$/ Wcm in the range of 150K~300K, respectively.

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Microstructures of Powders and Additively Manufactured Objects of an Alloy Tool Steel for Cold-Work Dies (냉간금형용 합금공구강 분말 및 적층조형체의 미세조직)

  • Kang, Jun-Yun;Yun, Jaecheol;Kim, Hoyoung;Kim, Byunghwan;Choe, Jungho;Yang, Sangsun;Yu, Ji-Hun;Kim, Yong-Jin
    • Journal of Powder Materials
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    • v.24 no.3
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    • pp.202-209
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    • 2017
  • A cold-work tool steel powder is used to fabricate 3-dimensional objects by selective laser melting using a high-pressure gas atomization process. The spherical powder particles form continuous carbide networks among the austenite matrix and its decomposition products. The carbides comprise Nb-rich MC and Mo-rich $M_2C$. In the SLM process, the process parameters such as the laser power (90 W), layer thickness ($25{\mu}m$), and hatch spacing ($80{\mu}m$) are kept fixed, while the scan speed is changed from 50 mm/s to 4000 mm/s. At a low scan speed of 50 mm/s, spherical cavities develop due to over melting, while they are substantially reduced on increasing the speed to 2000 mm/s. The carbide network spacing decreases with increasing speed. At an excessively high speed of 4000 mm/s, long and irregularly shaped cavities are developed due to incomplete melting. The influence of the scan pattern is examined, for which $1{\times}1 mm^2$ blocks constituting a processing layer are irradiated in a random sequence. This island-type pattern exhibits the same effect as that of a low scan speed. Post processing of an object using hot isostatic pressing leads to a great reduction in the porosity but causes coarsening of the microstructure.

Development of Copper Electro-Plating Technology on a Screen-Printed Conductive Pattern with Copper Paste

  • Eom, Yong-Sung;Son, Ji-Hye;Lee, Hak-Sun;Choi, Kwang-Seong;Bae, Hyun-Cheol;Choi, Jeong-Yeol;Oh, Tae-Sung;Moon, Jong-Tae
    • Journal of the Microelectronics and Packaging Society
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    • v.22 no.1
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    • pp.51-54
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    • 2015
  • An electro-plating technology on a cured isotropic conductive pattern with a hybrid Cu paste composed of resin matrix, copper, and solder powders has been developed. In a conventional technology, Ag paste was used to perform a conductive pattern on a PCB or silicon substrate. From previous research, the electrical conductive mechanism and principle of the hybrid Cu paste were concisely investigated. The isotropic conductive pattern on the PCB substrate was performed using screen-printing technology. The optimum electro-plating condition was experimentally determined by processing parameters such as the metal content of the hybrid Cu paste, applied current density, and time for the electroplating in the plating bath. The surfaces and cross-sections were observed using optical and SEM photographs. In conclusion, the optimized processing conditions for Cu electro-plating technology on the conductive pattern were a current density of $40mA/cm^2$ and a plating time of 20min on the hybrid Cu paste with a metal content of 44 vol.%. More details of the mechanical properties and processing conditions will be investigated in further research.

Preparation of Y2O2:Eu Red Phosphor by Sol-Gel and Calcination Process (솔-젤 및 소성공정에 의한 이트륨-유로퓸계 적색형광체 제조)

  • Yoon, Ho-Sung;Kim, Chul-Joo;Jang, Hee Dong
    • Korean Chemical Engineering Research
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    • v.46 no.3
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    • pp.506-511
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    • 2008
  • In this study sol-gel and combustion process was surveyed for the preparation of the red $Y_2O_3$: Eu phosphor, and the properties of phosphor was considered. Chelation and hydrolysis in amorphous citrate sol-gel process were completed in initial reaction stage, and water-forming condensation was superior to organic acid-forming condensation. The mole ratio of citric acid to metal ion had to be above to for the progress of sol-gel process. The dried gel powders are mostly amorphous, and crystallize completely at $700^{\circ}C$, and the crystallinity increases with increasing calcining temperature. The luminescence property of the phosphor was analyzed by measuring the emission spectra. The luminescence intensity increases when the calcination temperature and concentration of metal ions in solution increase.