• Title/Summary/Keyword: Powder Sintering

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Insulating Behavior of Sintered AlN Ceramics Prepared by High-Energy Bead Milling of AlN Powder (AlN 분말의 고에너지 밀링에 따른 소결체의 절연 특성)

  • Ryu, Sung-Soo;Lee, Sung-Min
    • Journal of Powder Materials
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    • v.24 no.6
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    • pp.444-449
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    • 2017
  • Aluminum nitride (AlN) powder specimens are treated by high-energy bead milling and then sintered at various temperatures. Depending on the solvent and milling time, the oxygen content in the AlN powder varies significantly. When isopropyl alcohol is used, the oxygen content increases with the milling time. In contrast, hexane is very effective at suppressing the oxygen content increase in the AlN powder, although severe particle sedimentation after the milling process is observed in the AlN slurry. With an increase in the milling time, the primary particle size remains nearly constant, but the particle agglomeration is reduced. After spark plasma sintering at $1400^{\circ}C$, the second crystalline phase changes to compounds containing more $Al_2O_3$ when the AlN raw material with an increased milling time is used. When the sintering temperature is decreased from $1750^{\circ}C$ to $1400^{\circ}C$, the DC resistivity increases by approximately two orders of magnitude, which implies that controlling the sintering temperature is a very effective way to improve the DC resistivity of AlN ceramics.

Synthesis of Nano-Sized Cu Powder by PVA Solution Method and Thermal Characteristics of Sintered Cu Powder Compacts (PVA 용액법을 통한 나노 Cu 분말합성 및 소결체의 열적 특성)

  • Oh, Bok-Hyun;Ma, Chung-Il;Lee, Sang-Jin
    • Korean Journal of Materials Research
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    • v.30 no.2
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    • pp.93-98
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    • 2020
  • Effective control of the heat generated from electronics and semiconductor devices requires a high thermal conductivity and a low thermal expansion coefficient appropriate for devices or modules. A method of reducing the thermal expansion coefficient of Cu has been suggested wherein a ceramic filler having a low thermal expansion coefficient is applied to Cu, which has high thermal conductivity. In this study, using pressureless sintering rather than costly pressure sintering, a polymer solution synthesis method was used to make nano-sized Cu powder for application to Cu matrix with an AlN filler. Due to the low sinterability, the sintered Cu prepared from commercial Cu powder included large pores inside the sintered bodies. A sintered Cu body with Zn, as a liquid phase sintering agent, was prepared by the polymer solution synthesis method for exclusion of pores, which affect thermal conductivity and thermal expansion. The pressureless sintered Cu bodies including Zn showed higher thermal conductivity (180 W/m·K) and lower thermal expansion coefficient (15.8×10-6/℃) than did the monolithic synthesized Cu sintered body.

Die Compaction and Sintering Behavior of Fe Micro-nano-powder Feedstock for Micro-PIM (마이크로 PIM용 Fe 마이크로-나노 혼합분말 피드스톡의 다이성형 및 소결거동)

  • You, Woo-Kyung;Choi, Joon-Phil;Lee, Jai-Sung
    • Korean Journal of Metals and Materials
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    • v.49 no.1
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    • pp.32-39
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    • 2011
  • The present investigation was performed on the die compaction and sintering behavior of Fe micro-nano mixed powder with a mixed binder for powder injection molding. Warm die compaction of the feedstock for simulation of the static injection molding process was conducted using a cylindrical mold of 10 mm diameter at $100^{\circ}C$ under 4MPa. The die compaction of the micro-nanopowder feedstock underwent a uniform molding behavior showing a homogeneous distribution of nanopowders among the micropowders without porosity and distortion. After debinding, the powder compact maintained a uniform structure without crack and distortion, leading to a high green density of 64.2% corresponding to the initial powder loading of 65%. The sintering experiment showed that the micro-nanopowder compact underwent a near full and isotropic densification process during sintering. It was observed that the nanopowders effectively suppressed the growth of micropowder grains during densification process. Conclusively, the use of nanopowder for PIM feedstock might provide a new concept for processing a full density PIM parts with fine microstructure.

The Preparation of Seeded Alumina from Alkoxide: (II) Sintering (알콕사이드로부터 Seed가 첨가된 알루미나의 제조: (II) 소결특성)

  • 김창은;임광일;이해욱
    • Journal of the Korean Ceramic Society
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    • v.29 no.6
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    • pp.480-488
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    • 1992
  • The sintering behaviors of seeded alumina from alkoxide were studied. Room temp. desiccated powder exhibited better sintering behavior due to its packing ability and powder activity. $\alpha$-Al2O3 2wt% seeded compacts sintered with 97.5%TD, 1~3${\mu}{\textrm}{m}$ diameters at 140$0^{\circ}C$, 2hrs. Fe-nitrate doped compacts resulted in enhanced initial sintering behavior due to ionic effects of Fe3+ but failed to refined microstructure.

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Formation of Pores during Sintering of Lead Borosilicate Glass Frits (Lead Borosilicate Glass Frit의 소결시 기공의 형성 기구)

  • 황건호;김용석
    • Journal of Powder Materials
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    • v.9 no.1
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    • pp.38-42
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    • 2002
  • Effects of chemical compositions on the sintering behavior of the lead borosilicate glass developed for barrier ribs of plasma display panels were investigated in this study. Formation of pores during sintering of the glass was noted and their formation mechanism was investigated using XPS, TG/DTA, and XRD. The results indicated that pores are formed by the oxygen released from Pb-oxides during sintering.

Observations on the Influence of Hydrogen on the Sintering of an Al-2Mg Alloy

  • Schaffer, G.B.;Yao, J.Y.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09b
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    • pp.816-817
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    • 2006
  • Hydrogen, in even small quantities, is extremely deleterious to the sintering of aluminium. Understanding the cause of this effect is complicated by the multiple interactions that occur in multi-component systems. In this work, we examine the sintering rsponse of Al-2Mg (a simplified system) in pure nitrogen and nitrogen-hydrogen using dilatometry, differential scanning calorimetery, thermogravimetry and metallography.

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A Study on Vacuum Sintering of M2 HSS Powder (M2 분말의 진공소결에 관한연구)

  • Choe, Yeong-Taek
    • 한국기계연구소 소보
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    • s.20
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    • pp.89-104
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    • 1990
  • This study was carried out to obtain the most optimum conition in vacuum sintering of M2 HSS powder, by analysis of sintering characteristics and fracture strength in several conditions. The conclusion deduced from this study are as follows; -Boron was more effective element than graphite; at this time, the optimum amount of addition was 0.05 wt% -The optimum condition of sintering temperature and time were 1190- $1200^{\circ}C$ and 1-1.25hr, respectively -Fracture strength of vacuum sintered and heat-treated specimen in the most optimum condition was 2-2.5KN/ $mm^2$

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Effect of High Energy Ball Milling on Sintering Behavior and Thermal Conductivity of Direct Nitrided AlN Powder (직접질화법 AlN 분말의 소결거동 및 열전도도에 미치는 고에너지 볼밀링 효과)

  • Park, Hae-Ryong;Kim, Hyung-Tae;Lee, Sung-Min;Kim, Young-Do;Ryu, Sung-Soo
    • Journal of the Korean Ceramic Society
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    • v.48 no.5
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    • pp.418-425
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    • 2011
  • In this study, a high energy ball milling process was introduced in order to improve the densification of direct nitrided AlN powder. The sintering behavior and thermal conductivity of the AlN milled powder was investigated. The mixture of AlN powder and 5 wt% $Y_2O_3$ as a sintering additive was pulverized and dispersed by a bead mill with very small $ZrO_2$ bead media. The milled powders were sintered at $1700^{\circ}C-1800^{\circ}C$ for 4 h under $N_2$ atmosphere. The results showed that the sintered density was enhanced with increasing milling time due to the particle refinement as well as the increase in oxygen contents. Appropriate milling time was effective for the improvement of thermal conductivity, but the extensive millied powder formed more fractions of secondary phase during sintering, resulted in the decrease in thermal conductivity. The AlN powder milled for 10min after sintering at $1800^{\circ}C$ revealed the highest thermal conductivity, of 164W/$m{\cdot}K$ in tne densified AlN sintered at $1800^{\circ}C$.

Improvments in Cost Reduction for Vacuum Sintering and Vacuum and Overpressure Sintering for Tungsten Carbides

  • Ermel, Dieter
    • Journal of Powder Materials
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    • v.5 no.4
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    • pp.293-298
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    • 1998
  • In all larger hardmetal workshops furnaces for dewaxing, vacuum sintering or vacuum and overpressure sintering are today's standard. The furnace technology is well established. Equipment specifications such as operating overpressure, determine sintering cost, product quality, safety and reliability of the furnace and ultimately influence the competitiveness of the hard metal procucer in the global market. Essential furnace requirements are an efficient utilization of the furnace, an environmental friendly dewaxing system, high temperature uniformity, metallurgical treatment with process gases, as well as reduced cooling time by means of rapid cooling. Examples of reduced sintering costs are described achieved using a new design of vacuum sintering furnace with an improved rapid cooling device, cooling times are reduced by up to 45%. Additionally, a cost comparison of two different designs of vacuum overpressure sintering furnaces are included.

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Various Master Sintering Curve Concepts and its Applications

  • Park, Seong-Jin;Blaine, Deborah C.;German, Randall M.
    • Proceedings of the Korean Powder Metallurgy Institute Conference
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    • 2006.09a
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    • pp.66-67
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    • 2006
  • The master sintering curve (MSC) is derived from densification data over a range of heating rates and temperatures. To improve the accuracy, several modifications were proposed: multi-phase MSC for solid state sintering with phase changes, MSC for liquid phase sintering, and MSC with consideration of grain growth. The developed MSC models were applied to several material systems such as molybdenum, stainless steels, and tungsten heavy alloys (WHA), in order to evaluate the effect of compaction pressure, phase change, grain growth, and composition on densification, to classify regions having different sintering mechanism, and to help engineer design, optimize, and monitor sintering cycles.

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