소결첨가재에 의한 텅스텐의 기계적 특성평가

이상필,이진경 한국산업융합학회 2022 한국산업융합학회 논문집 Vol.25 No.4

Tungsten is a high melting point metal unlike other steel materials, and it is difficult to manufacture because of its high melting temperature. In this study, pressure sintering process method was applied to manufacture the tungsten materials at low temperature. Therefore, it is necessary to densify the sintered material by using a sintering additive. Studies have been conducted on how the amount of titanium for sintering tungsten affects the mechanical properties of tungsten in this study. In order to secure the densification mechanism of tungsten powder during the sintering process, the characteristics of the sintered tungsten material according to the change of titanium content were evaluated. It was investigated the relationship between sintering parameters and mechanical properties for densification of microstructures. The sintered tungsten materials according to sintering additive content showed high sintered density (about 16.31g/cm3) and flexural strength (about 584 MPa) when the content of sintering additive was 3 wt%. However, as the content of the sintering additive increases, mechanical property of flexural strength is decreased, and the porosity is increased due to the heterogeneous sintering around titanium.

Enhanced Nd-Rich Phase and Oxygen Control in Reduction-Diffusion Powders via Tailored Washing Process for Additive-Free Sintering of Fine Nd-Fe-B Particles

Vitalii Galkin,Rambabu Kuchi,Soon-Jae Kwon,Tae-hoon Kim,Jung-goo Lee,Jong-Ryul Jeong,Dongsoo Kim 한국자기학회 2024 Journal of Magnetics Vol.29 No.1

This paper reports the successful additive-free sintering of fine Nd-Fe-B powder prepared by reduction-diffusion (RD) and wet ball milling (WBM) washing. Fine Nd-Fe-B powder by RD poses difficulties in sintering without rare earth (RE) hydride additives due to oxidation or loss of the Nd-rich phase during the washing step. Here, the effect of different washing methods such as conventional water washing, acetic acid washing, and WBM washing on the Nd-rich phase and oxygen content of RD powders was examined. The WBM washing involves low energy milling in organic media, which simplifies the removal of impurities from the RD powder. Among all the samples, the magnet made by sintering with WBM powder showed the coercivity of 8.7 kOe and (BH)max of 33.7 MGOe, which are comparable to magnets made of acidic washed RD powder with the essential addition of NdHx of 10 wt% reported in other studies. This is considered that in the powder after WBM washing, oxygen content was decreased compared to water washing and Nd-rich phase remained compared to acidic washing, which resulted in successful densification during sintering and the formation of Ndrich areas in sintered body. This finding makes an important step towards the production of Nd-Fe-B based magnets from sintering with RD powder without additive.

탄화붕소 소결 거동 연구를 위한 율속제어소결의 적용

이혁재,Lee, Hyukjae 한국결정성장학회 2015 한국결정성장학회지 Vol.25 No.1

율속제어소결은 소결 공정 중 실시간으로 측정되는 시편의 팽창/수축거동을 이용해 일정한 수축거동을 하도록 로의 파워를 조정하는 소결방법으로, 온도를 조절하기 위해 로의 파워를 제어하는 일반적인 소결에 비해 시편의 소결 과정을 세밀히 제어할 수 있으며, 특히 소결공정의 최적화를 이룰 수 있는 장점이 있다. 본 연구에서는 탄화붕소의 소결에 율속 제어소결을 적용해 각 공정변수의 조절에 따른 소결온도 및 입자성장의 변화를 조사하여 그 상관관계를 규명하고 이를 기존의 이론에 맞추어 해석함으로써 율속제어소결을 어떻게 소결공정 최적화에 이용할 수 있는지 그 가능성을 알아보았으며 이를 통해 향후 미지 소재의 소결공정에 율속제어공정을 어떻게 적용할 수 있는지 고찰해 보았다. Under rate-controlled sintering, furnace power is controlled to maintain a specific specimen contraction rate. This thermal processing method guarantees continuous process with a minimum thermal energy applied over time and makes it possible to control the density of the sintered body precisely. In this study, the rate-controlled sintering is applied to the sintering of $B_4C$ in order to investigate how rate-controlled sintering variables can affect the sintering behavior and/or grain growth behavior of $B_4C$ and how the results can be interpreted using sintering theories to draw an optimal sintering condition of the rate-controlled sintering. Further, the applicability of the rate-controlled sintering into the study for sintering of unknown materials is also considered.

LPS - SiC 세라믹스의 굽힘강도 특성에 미치는 미시조직 영향

윤한기(HAN-KI YOON),정헌채(HUN-CHAE JUNG) 한국해양공학회 2006 韓國海洋工學會誌 Vol.20 No.5

In this study, monolithic liquid phase sintered SiC (LPS-SiC) was made by the hot pressing method with nano-SiC powder, whose particle size is 30 ㎚ and less on the average. Alumina (Al₂O₃), yttria (Y₂O₃), and silica (SiO₂) were used for sintering additives. To investigate the effects of SiO₂, the Al₂O₃/Y₂O₃ composition was fixed and the ratio of SiO₂ was changed, with seven different ratios tested. And to investigate the effects of the sintering temperature, the sintering temperature was changed, with 1760℃, 1780℃, and 1800℃ being used with a SiO₂ ratio of 3 wt%. The materials were sintered for 1 hour at 1760℃, 1780℃ and 1800℃ under a pressure of 20 ㎫. The effects on sintering from the sintering system used, as well as from the composition of the sintering additives, were investigated by density measurements. Mechanical properties, such as flexural strength, were investigated to ensure the optimum conditions for a matrix of SiCf/SiC composites. Sintered densityand the flexural strength of fabricated LPS-SiC increased with an increase in sintering temperature. Particularly, the relative density of a sintered body at 1800℃ with a non-content of SiO₂, a specimen of AYS0-1800, was 95%. Also, flexural strength was about 750㎫.

상압소결(常壓燒結)한 $SiC-ZrB_2$ 전도성(電導性) 복합체(複合體)의 미세구조(微細構造)와 특성(特性)에 미치는 In Situ YAG의 영향(影響)

신용덕,주진영,Shin, Yong-Deok,Ju, Jin-Young 대한전기학회 2006 전기학회논문지C Vol.55 No.11

The present study investigated the influence of the content of $Al_2O_3+Y_2O_3$ sintering additives on the microstructure, mechanical and electrical properties of the pressureless-sintered $SiC-ZrB_2$ electroconductive ceramic composites. Phase analysis of composites by XRD revealed mostly of ${\alpha}-SiC(4H),\;ZrB_2,\;{\beta}-SiC(15R)$ and In Situ $YAG(Al_5Y_3O_{12})$. The relative density and the flexural strength showed the highest value of 86.8[%] and 203[Mpa] for $SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature respectively. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed 3.7 and $3.6[MPa{\cdot}m^{1/2}]\;for\;SiC-ZrB_2$ composites with an addition of 8 and 12[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature respectively. Abnormal grain growth takes place during phase transformation from ${\beta}-SiC\;into\;{\alpha}-SiC$ was correlated with In Situ YAG phase by reaction between $Al_2O_3\;and\;Y_2O_3$ additives during sintering. The electrical resistivity showed the lowest value of $6.5{\times}10^{-3}[({\Omega}{\cdot}cm]$ for the $SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid at room temperature. The electrical resistivity of the $SiC-ZrB_2$ composites was all positive temperature coefficient(PTCR) in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. The resistance temperature coefficient showed the highest value of $3.53{\times}10^{-3}/[^{\circ}C]\;for\;SiC-ZrB_2$ composite with an addition of 8[wt%] $Al_2O_3+Y_2O_3$ as a sintering aid in the temperature ranges from $25[^{\circ}C]\;to\;700[^{\circ}C]$. In this paper, it is convinced that ${\beta}-SiC$ based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

常壓燒結한 SiC-ZrB₂ 電導性 複合體의 微細構造와 特性에 미치는 In Situ YAG의 影響

辛龍德(Yong Deok Shin),朱陳榮(Jin Young Ju) 대한전기학회 2006 전기학회논문지C Vol.55 No.11

The present study investigated the influence of the content of Al₂O₃+Y₂O₃ sintering additives on the microstructure, mechanical and electrical properties of the pressureless-sintered SiC-ZrB₂ electroconductive ceramic composites. Phase analysis of composites by XRD revealed mostly of α-SiC(4H), ZrB₂, β-SiC(15R) and In Situ YAG(Al?Y₃O₁₂). The relative density and the flexural strength showed the highest value of 86.8[%] and 203[㎫] for SiC-ZrB₂ composite with an addition of 8 and 12[wt%] Al₂O₃+Y₂O₃ as a sintering aid at room temperature respectively. Owing to crack deflection and crack bridging of fracture toughness mechanism, the fracture toughness showed 3.7 and 3.6[㎫ㆍm<SUP>1/2</SUP>] for SiC-ZrB₂ composites with an addition of 8 and 12[wt%] Al₂O₃+Y₂O₃ as a sintering aid at room temperature respectively. Abnormal grain growth takes place during phase transformation from β-SiC into α-SiC was correlated with In Situ YAG phase by reaction between Al₂O₃ and Y₂O₃ additives during sintering. The electrical resistivity showed the lowest value of 6.5×10?³ [Ωㆍ㎝] for the SiC-ZrB₂ composite with an addition of 8[wt%] Al₂O₃+Y₂O₃ as a sintering aid at room temperature. The electrical resistivity of the SiC-ZrB₂ composites was all positive temperature coefficient(PTCR) in the temperature ranges from 25[℃] to 700[℃]. The resistance temperature coefficient showed the highest value of 3.53×10?³/[℃] for SiC-ZrB₂ composite with an addition of 8[wt%] Al₂O₃+Y₂O₃ as a sintering aid in the temperature ranges from 25[℃] to 700[℃]. In this paper, it is convinced that β-SiC based electroconductive ceramic composites for heaters or ignitors can be manufactured by pressureless sintering.

Temperature and heating rate effects on tubular alumina filter

Tanikan Thongchai,Siriporn Larpkiattaworn 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8

The effect of temperature and heating rate on density, pore size, porosity, bending strength and water flux of sintered Al2O3 body was studied in this research. Carboxymethyl Cellulose (CMC) 3% by Al2O3 weight was used as additive. The Al2O3 particle sizes were varied at Al2O35 μm and the mixture of Al2O30.7 μm (50 wt%) and Al2O35 μm (50 wt%). The mixture was then extruded, dried and sintered at 1300°C-1600°C, vary heating rate at 180, 300 and 600°C/Hour. The sintered samples were measured density, porosity, pore size and bending strength. It was found that, particle size is the most important factor affecting density, porosity, pore size and bending strength. The sintering temperature and heating rate affected the density porosity and bending strength of sintered body. The sample prepared from the mixture of Al2O30.7 μm (50 wt%) and Al2O35 μm (50 wt%) sintered at 1300°C resulted in lowest density and bending strength. The porosity of sintered Al2O3 increased with increasing of particle size and decreasing sintered temperature. Increasing heating rate would slightly decrease density and slightly increase pore size and porosity. Therefore, heating rate and sintering temperature are factor affecting on porosity and pore size but particle size is an important factor for both pore sizes and bending strength. The sintered samples were measured bending strength and water flux. The sample prepared from the mixture of 0.7 μm (50 wt%) and 5 μm (50 wt%) with 3% CMC at 1400°C showed bending strength and water flux of 40.50 MPa and 3.7 m3/(m2.h), respectively.

Sintering behavior of garnet-type Li₇La₃Zr₂O₁₂-Li₃BO₃ composite solid electrolytes for all-solid-state lithium batteries

Shin, R.H.,Son, S.I.,Han, Y.S.,Kim, Y.D.,Kim, H.T.,Ryu, S.S.,Pan, W. North-Holland Pub. Co 2017 Solid state ionics Vol.301 No.-

<P>In this study, Li3BO3 glass ceramic was utilized as a sintering additive for producing garnet-type Li7La3Zr2O12 solid electrolytes by low temperature sintering. The shrinkage and wetting behaviors of the Li7La3Zr2O12-Li3BO3 composite powder during heating were analyzed by dilatometry. The sintering shrinkage of the Li7La3Zr2O12-Li3BO3 composite powder occurred in two stages and was related to the densification of the composite. It was also closely related to the wetting behavior of the Li3BO3 glass. The sintering of Li7La3Zr2O12-Li3BO3 from around 700 degrees C is driven by the viscous sintering of Li3BO3 glass, while sintering above 850 degrees C is due to particle rearrangement in Li7La3Zr2O12 as well as the solid-state sintering of Li7La3Zr2O12 after the melting of Li3BO3. The density of the Li7La3Zr2O12-8 w Li3BO3 composite sintered for 8 hat 1100 degrees C was 86.4% of the theoretical density, whereas the ionic conductivity was 1.94 x 10(-5) S cm(-1). (C) 2017 Elsevier B.V. All rights reserved.</P>

Effects of Additives of CaO and Rare-Earth Oxides on the Sintering Behavior of AlN Ceramics

Chih-Hung Chu,Yun-Hwei Shen,Chih-Peng Lin,Shaw-Bing Wen 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

The effect of additives of CaO plus three different rare-earth oxides (Y, Sm and Gd, separately) on the sintering behavior of AlN ceramics has been evaluated at 1700℃ by using a MoSi2 heater and ambient atmosphere. The results of density measurements show that the atomic weight of the rare-earth element may substantially affect the apparent density of the sintered AlN specimen due to the kinetics of atomic diffusion during sintering. The optimum results of this study show that these additives are effective in obtaining an apparent density of 3.26 g/cm3 (approaching a 100 % theoretical density of AlN). The Vicker's hardness of the sintered AlN can reach a high value of 1310 kg/mm2 and an apparent density of 3.34 g/cm3. A longer soaking time of between 3 and 5 h is necessary to practically eliminate the minor oxide phases. The effect of additives of CaO plus three different rare-earth oxides (Y, Sm and Gd, separately) on the sintering behavior of AlN ceramics has been evaluated at 1700℃ by using a MoSi2 heater and ambient atmosphere. The results of density measurements show that the atomic weight of the rare-earth element may substantially affect the apparent density of the sintered AlN specimen due to the kinetics of atomic diffusion during sintering. The optimum results of this study show that these additives are effective in obtaining an apparent density of 3.26 g/cm3 (approaching a 100 % theoretical density of AlN). The Vicker's hardness of the sintered AlN can reach a high value of 1310 kg/mm2 and an apparent density of 3.34 g/cm3. A longer soaking time of between 3 and 5 h is necessary to practically eliminate the minor oxide phases.

Effect of MgO-CaO-Al2O3-SiO2 glass additive on densification of Al2O3 ceramics

Dagyeong Lee,Hyun Seon Hong,Hyeondeok Jeong,Sung-Soo Ryu 한양대학교 세라믹연구소 2022 Journal of Ceramic Processing Research Vol.23 No.2

We investigated the effect of the MgO-CaO-Al2O3-SiO2 (MCAS) additive on the densification of Al2O3 ceramics. MCAS wassynthesized using a polymeric-complex method. We analyzed the densification behavior, using dilatometric analysis up to1600 oC, and the results showed that sinterability increased with increasing MCAS content. Al2O3 samples were prepared byisothermal sintering at 1400, 1500, and 1600 oC. The microstructure, phase formation, and hardness of the samples wereanalyzed and discussed in relation to both the MCAS content and sintering temperature. The density of the MCAS-dopedsamples sintered at 1500 and 1600 oC was over 98%, and the maximum relative density was 99.7%. The highest hardness (18GPa) was achieved for the sample prepared with 3 wt.% MCAS and sintered at 1500 oC for 1 h because further dopingresulted in excessive grain growth. These results elucidate the conditions required for pressure-free sintering.