• Title/Summary/Keyword: powder melting

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Parameters Effect on Fabrication of Nuclear Fuel by Plasma Deposition (플라즈마 침적에 의한 핵열료 제조에 미치는 변수들의 영향)

  • Jeong, In-Ha;Bae, Gi-Gwang
    • Korean Journal of Materials Research
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    • v.8 no.9
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    • pp.783-790
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    • 1998
  • New process development of nuclear fuel fabrication for nuclear power plant was attempted by induction plasma technology with yttria-stabilized-zirconia ($\textrm{ZrO}_{2}$-$\textrm{Y}_{2}\textrm{O}_{3}$)powder, similar to $\textrm{UO}_{2}$, in the respect of melting point and physicochemical characteristics. Extent of powder melting was affected greatly by plasma plate power and particle size. Being optimized such as, sheath gas composition, probe position, particle size and spraying distance, dense deposit of 97.91% T.D. with deposition rate 20mm/min was attained at the condition of 120/20$\ell$/min of Ar/$\textrm{H}_{2}$ flow rate, 80kw of plate power, 8cm of probe position, 200Torr of chamber pressure and 18cm of spraying distance. The pellet of 96.5% of theoretical density was formed with homogeneity and nice exterior view at the best condition of deposition experiments, and the possibility of new nuclear pellet fabrication process was confirmed. The main and interrelated effects on deposit density were assessed by ANOVA(Ana1ysis of Variance).

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Preliminary Study on Improvement of Surface Characteristics of Stellite21 Deposited Layer by Powder Feeding Type of Direct Energy Deposition Process Using Plasma Electron Beam (플라즈마 전자빔을 이용한 분말공급형 직접식 에너지 적층 공정으로 제작된 Stellite21 적층층의 표면 특성 개선에 관한 기초 연구)

  • Kim, Dong-In;Lee, Ho-Jin;Ahn, Dong-Gyu;Kim, Jin-Seok;Kang, Eun Goo
    • Journal of the Korean Society for Precision Engineering
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    • v.33 no.11
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    • pp.951-959
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    • 2016
  • The aim of this paper is to investigate the improvement of surface characteristics of Stellite21 deposited layer by powder feeding type of direct energy deposition (DED) process using a plasma electron beam. Re-melting experiments of the deposited specimen is performed using a three-dimensional finishing system with a plasma electron beam. The acceleration voltage and the travel speed of the electron beam are chosen as process parameters. The effects of the process parameters on the surface roughness and the hardness of the re-melted region are examined. The formation of the re-melted region is observed using an optical microscope. Results of these experiments revealed that the re-melting process using a plasma electron beam can greatly improve the surface qualities of the Stellite21 deposited layer by the DED process.

Effect of post heat treatment on fatigue properties of EBM 3D-printed Ti-6Al-4V alloy (분말 3D 프린팅된 Ti-6Al-4V 합금의 피로특성에 미치는 후열처리의 영향)

  • Choi, Young-Sin;Jang, Ji-Hoon;Kim, Gun-Hee;Lee, Chang-Woo;Kim, Hwi-Jun;Lee, Dong-Geun
    • Journal of Powder Materials
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    • v.25 no.4
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    • pp.340-345
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    • 2018
  • Additive manufacturing by electron beam melting is an affordable process for fabricating near net shaped parts of titanium and its alloys. 3D additive-manufactured parts have various kinds of voids, lack of fusion, etc., and they may affect crack initiation and propagation. Post process is necessary to eliminate or minimize these defects. Hot isostatic pressing (HIP) is the main method, which is expensive. The objective of this paper is to achieve an optimum and simple post heat treatment process without the HIP process. Various post heat treatments are conducted for the 3D-printed Ti-6Al-4V specimen below and above the beta transus temperature ($996^{\circ}C$). The as-fabricated EBM Ti-6Al-4V alloy has an ${\alpha}^{\prime}$-martensite structure and transforms into the ${\alpha}+{\beta}$ duplex phase during the post heat treatment. The fatigue strength of the as-fabricated specimen is 400 MPa. The post heat treatment at $1000^{\circ}C/30min/AC$ increases the fatigue strength to 420 MPa. By post heat treatment, the interior pore size and the pore volume fraction are reduced and this can increase the fatigue limit.

Fabrication of Mg Alloy Foam via Melting Foaming Method Using $CaCO_3$ as Blowing Agent ($CaCO_3$를 이용한 발포 마그네슘 합금의 제조)

  • Yang, Dong-Hui;Seo, Chang-Hwan;Wang, Xiao-Song;Hur, Bo-Young
    • Journal of Korea Foundry Society
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    • v.26 no.6
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    • pp.272-276
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    • 2006
  • For the first time AZ91 (MgAl9Zn1) and AM60 (MgAl6) Mg alloy foams with homogeneous pore structures were prepared successfully via melting foaming method by using $CaCO_3$ powder as blowing agent. The possible foaming mechanisms and pore structures of these Mg alloy foams were discussed and investigated. The results show that Mg alloy melt can affect $CaCO_3$ decomposition behavior and AZ91 Mg alloy is relative easy to be foamed into metal foam with high porosity and big pore size.

Investigating the Leaching Rate of TiTe3O8 Towards a Potential Ceramic Solid Waste Form

  • Noh, Hye Ran;Lee, Dong Woo;Suh, Kyungwon;Lee, Jeongmook;Kim, Tae-Hyeong;Bae, Sang-Eun;Kim, Jong-Yun;Lim, Sang Ho
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.18 no.4
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    • pp.509-516
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    • 2020
  • An important property of glass and ceramic solid waste forms is processability. Tellurite materials with low melting temperatures and high halite solubilities have potential as solid waste forms. Crystalline TiTe3O8 was synthesized through a solid-state reaction between stoichiometric amounts of TiO2 and TeO2 powder. The resultant TiTe3O8 crystal had a three-dimensional (3D) structure consisting of TiO6 octahedra and asymmetric TeO4 seesaw moiety groups. The melting temperature of the TiTe3O8 powder was 820℃, and the constituent TeO2 began to evaporate selectively from TiTe3O8 above around 840℃. The leaching rate, as determined using the modified American Society of Testing and Materials static leach test method, of Ti in the TiTe3O8 crystal was less than the order of 10-4 g·m-2·d-1 at 90℃ for durations of 14 d over a pH range of 2-12. The chemical durability of the TiTe3O8 crystal, even under highly acidic and alkaline conditions, was comparable to that of other well-known Ti-based solid waste forms.

Influence of Si-rich Phase Morphologies on Mechanical Properties of AlSi10Mg Alloys processed by Selective Laser Melting and Post-Heat Treatment (선택적 레이저 조형된 AlSi10Mg합금의 후열처리에 따른 Si-rich상 형상변화가 기계적 특성에 미치는 영향)

  • Nam, Jung-woo;Eom, Yeong Seong;Kim, Kyung Tae;Son, Injoon
    • Journal of Powder Materials
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    • v.28 no.2
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    • pp.134-142
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    • 2021
  • In this study, AlSi10Mg powders with average diameters of 44 ㎛ are additively manufactured into bulk samples using a selective laser melting (SLM) process. Post-heat treatment to reduce residual stress in the as-synthesized sample is performed at different temperatures. From the results of a tensile test, as the heat-treatment temperature increases from 270 to 320℃, strength decreases while elongation significantly increases up to 13% at 320℃. The microstructures and tensile properties of the two heat-treated samples at 290 and 320℃, respectively, are characterized and compared to those of the as-synthesized samples. Interestingly, the Si-rich phases that network in the as-synthesized state are discontinuously separated, and the size of the particle-shaped Si phases becomes large and spherical as the heat-treatment temperature increases. Due to these morphological changes of Si-rich phases, the reduction in tensile strengths and increase in elongations, respectively, can be obtained by the post-heat treatment process. These results provide fundamental information for the practical applications of AlSi10Mg parts fabricated by SLM.

Synthesis of NiTi Alloy Powder by the Reaction of NiO-TiH2 Mixing Powders (NiO-TiH2 혼합분말의 반응을 이용한 NiTi 합금분말 제조)

  • Jeon, Ki Cheol;Lee, Han-Eol;Yim, Da-Mi;Oh, Sung-Tag
    • Journal of Powder Materials
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    • v.22 no.4
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    • pp.266-270
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    • 2015
  • The synthesis of NiTi alloy powders by hydrogen reduction and dehydrogenation process of NiO and $TiH_2$ powder mixtures is investigated. Mixtures of NiO and $TiH_2$ powders are prepared by simple mixing for 1 h or ball milling for 24 h. Simple-mixed mixture shows that fine NiO particles are homogeneously coated on the surface of $TiH_2$ powders, whereas ball milled one exhibits the morphology with mixing of fine NiO and $TiH_2$ particles. Thermogravimetric analysis in hydrogen atmosphere reveals that the NiO and $TiH_2$ phase are changed to metallic Ni and Ti in the temperature range of 260 to $290^{\circ}C$ and 553 to $639^{\circ}C$, respectively. In the simple-mixed powders by heat-up to $700^{\circ}C$, agglomerates with solid particles and solidified liquid phase are observed, and the size of agglomerates is increased at $1000^{\circ}C$. From the XRD analysis, the presence of liquid phase is explained by the formation and melting of $NiTi_2$ inter-metallic compound due to an exothermic reaction between Ni and Ti. The simple-mixed powders, heated to $1000^{\circ}C$, lead to the formation of NiTi phase but additional Ni-, Ti-rich and Ti-oxide phases. In contrast, the microstructure of ball-milled powders is characterized by the neck-grown particles, forming $Ni_3Ti$, Ti-oxide and unreacted Ni phase.

The Characteristics Analysis of Track of Laser Metal Deposition Using AISI M2 Powder (AISI M2 파우더를 이용한 레이저 메탈 디포지션의 트랙 특성 분석)

  • Kim, WonHyuck;Song, MyungHwan;Park, InDuck;Kang, DaeMin
    • Transactions of the Korean Society of Automotive Engineers
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    • v.24 no.4
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    • pp.463-470
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    • 2016
  • In this paper, the characteristics analysis of LMD track, such as including track structure, track wear resistance and track thickness, were analyzed to enhance the deposition efficiency using a diode-pumped disk laser. SKD61 hot work steel plate and Fe based AISI M2 alloy were used as a the substrate and powder for the LMD process, respectively. The laser power, track pitch and powder feed rate among LMD parameters were adopted to estimate the deposition efficiency. As the laser power is increased, heat input and melting pool on the substrate is grown also increases, so resulting in the increased LMD track thickness was increased. Through EPMA mapping analysis of the cross-section in the LMD track, it was observed that all the elements are evenly distributed inside. Therefore, the entire hardness in the LMD track is expected to be almost uniform regardless of location. The characteristics of the LMD specimen were excellent compared to the STD11 specimen in terms of the wear track width and the wear rate as well as the coefficient of friction. Especially the wear rate of LMD specimen has been significantly reduced by 60 % or more. From Based on the experimental results, the prediction formula of LMD thickness was calculated by using laser power, track pitch and powder feed rate.

Electrical Properties of Thick-Film Resistor Prepared by Using RuO2-Glass Composite Powder (RuO2-유리 복합분말을 이용하여 제조된 후막 저항의 전기적 특성 연구)

  • Kim, Min-Sik;Ryu, Sung-Soo
    • Journal of Surface Science and Engineering
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    • v.50 no.5
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    • pp.301-307
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    • 2017
  • The purpose of this study is to investigate the electrical properties of thick-film resistor (TFR) prepared from $CaO-ZnO-B_2O_3-Al_2O_3-SiO_2$ (CZBAS) glass containing $RuO_2$ particles. $RuO_2$-glass composite powder was made by mixing and melting oxide powders of constituents. For comparison, $RuO_2$ powder was simply mixed with glass powder. $RuO_2$-40wt% glass composite and mixture were dispersed in an organic binder to obtain printable resistor paste and then thick-film was formed by screen printing, followed by sintering at the range between $750^{\circ}C$ and $900^{\circ}C$ for 10 min with a heating rate of $50^{\circ}C/min$ in an ambient atmosphere. $RuO_2$-glass composite sample showed much higher resistance compared to the simple mixed sample. This could be attributed to the difference in conducting mechanism. After sintering at $850^{\circ}C$, temperature coefficient of resistance of composite sample was lower than that of simple-mixed sample. TFR with dense and homogeneous microstructure could be obtained by using $RuO_2$-glass composite powder.

Solid Dispersion as a Strategy to Improve Drug Bioavailability (고체분산체를 이용한 약물의 생체이용율 향상을 위한 전략)

  • Park, Jun-Hyung;Chun, Myung-Kwan;Cho, Hoon;Choi, Hoo-Kyun
    • KSBB Journal
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    • v.26 no.4
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    • pp.283-292
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    • 2011
  • Solid dispersion is one of well-established pharmaceutical techniques to improve the dissolution and consequent bioavailability of poorly water soluble drugs. It is defined as a dispersion of drug in an inert carrier matrix. Solid dispersions can be classified into three generations according to the carrier used in the system. First and second generations consist of crystalline and amorphous substances, respectively. Third generation carriers are surfactant, mixture of polymer and surfactants, and mixture of polymers. Solid dispersions can be generallyprepared by melting method and solvent method. While melting method requires high temperature to melt carrier and dissolve drug, solvent method utilizes solvent to dissolve the components. The improvement in dissolution through solid dispersions is attributed to reduction in drug particle size, improvement in wettability, and/or formation of amorphous state. The primary characteristics of solid dispersions, the presenceof drug in amorphous state, could be determined by differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), and fourier-transformed infrared spectroscopy (FTIR). In spite of the significant improvement in dissolution by solid dispersion technique, some drawbacks have limited the commercial application of solid dispersions. Thus, further studies should be conducted in a direction to improve the congeniality to commercialization.