• Title/Summary/Keyword: 세라믹 소재

Search Result 615, Processing Time 0.027 seconds

FeO, $TiH_2$, Carbon 원료분말을 이용한 Fe-TiC 나노 복합분말 제조 및 소결

  • An, Gi-Bong;Kim, Ji-Sun
    • Proceedings of the Materials Research Society of Korea Conference
    • /
    • 2011.10a
    • /
    • pp.26-26
    • /
    • 2011
  • Fe계 TiC 합금은 미량의 합금원소를 첨가시켜 경화능, 내식성, 내마모성 성질을 개선한 특수 공구용 재료로서 현재 절삭, 내마모성, 광산, 금형재료 등의 분야에 널리 사용되고 있다. 금속과 세라믹의 복합재료인 초경합금은 비열처리용 공구강으로 WC, TiC 등의 4, 5, 6족 금속탄화물에 Co, Ni, Fe등의 철족이 결합금속으로 소결한 복합재료로 WC-Co계 초경합금이 주종을 이루고 있으나, 전략 소재로서 고가인 Co 원료를 대체하기 위한 재료로서 초경재료의 고경도와 공구강의 경제성 및 가공성의 장점을 이용한 Fe-TiC계 초경합금의 연구가 다양하게 진행되고 있다. 본 연구에서는 Fe기지에 서브마이크론 크기의 미세한 TiC 입자가 균일하게 분산된 Fe-TiC 복합분말을 경제적으로 제조하기 위해 순수한 Fe, Ti 원료분말에 비해 단가가 낮고 미세 분쇄가 용이한 FeO, $TiH_2$ 분말을 고에너지 밀링 후 반응 열처리 시키는 유사 기계화학적 공정을 시도하였다. 조성비 Fe-30wt%TiC 복합분말을 제조하기위해 마이크론(micron) 크기의 FeO, $TiH_2$, C 분말을 사용하였고, 1단계로 FeO와 C을 고에너지 밀링으로 혼합 후 반응시켜 환원시키는 공정과 2단계로 이렇게 환원된 분말과 TiH2를 고에너지 밀링으로 다시 혼합, 분쇄한 후 반응열처리 하는 두 단계 공정을 사용하였다. FeO의 환원 단계에서는 $700{\sim}1,000^{\circ}C$ 온도 범위에서 1시간 유지하였고, 고에너지 밀링 시 밀링시간, 회전속도를 변수로 두고 실험하였다. 환원된 분말은 수평관상로를 이용해 아르곤분위기에서 $1,000{\sim}1300^{\circ}C$까지 1시간 유지하여 반응열처리시켜 Fe-TiC 복합분말을 제조하였다. 준비된 복합분말을 XRD와 FE-SEM, EDS, 입도분석기 (LPSA) 등을 이용해 분말의 형태와 특성, 상, 조성, 입도, 분산도 등을 조사하였다. 제조된 Fe-TiC 나노복합분말을 방전플라즈마소결(SPS) 과 상압소결 실험을 진행하였다. Fe-TiC 복합분말 제조공정의 첫 번째 단계인 FeO의 환원반응은 $800^{\circ}C$이상의 온도에서 Fe로 환원이 진행됨을 확인하였다. 두 번째 단계인 반응열처리공정에서는 $1,000^{\circ}C$ 이상에서 TiC가 형성됨을 XRD 상분석을 통해 확인할 수 있었고, $1,100^{\circ}C$ 이상의 온도에서 반응열처리를 했을 때 XRD 분석결과와 산소 조성 분석 결과로부터 반응의 완결성과 순도에서 최적 온도 조건임을 확인하였다. 온도를 $1,300^{\circ}C$로 증가시킬 경우 반응의 완결성에 큰 변화가 없는 반면 분말입자간의 목형성이 일어나 가소결 되는 것을 FE-SEM을 통해 관찰하였다. 또한 최적조건으로 제조된 Fe-TiC 복합분말의 입도분석과 FE-SEM/EDS 관찰/분석을 시행한 결과 평균 입도 0.6 ${\mu}m$의 미세한 Fe-TiC 복합분말 내에 Fe분말 주변과 내부에 나노크기의 TiC입자가 균일하게 분산되어 존재하는 것을 확인하였다.

  • PDF

A Fundamental Study for Design of Electric Energy Harvesting Device using PZT on the Road (도로용 압전발전체 시험모듈 설계를 위한 기초 실험 연구)

  • Lee, Jae-Jun;Ryu, Seung-Ki;Moon, Hak-Yong;Kwon, Soo-Ahn
    • International Journal of Highway Engineering
    • /
    • v.13 no.4
    • /
    • pp.159-166
    • /
    • 2011
  • Green house gas emissions are increasing as development of the industrial economy of the international community. Many countries in the world are endeavoring to reduce green house gas emissions under severe climate change. In order to protect grobal warming, government is trying to reduce green gas emissions under "Low Carbon Green Growth Policy" and investing climiate-firendly industries such as renewable energy harvesting. Renewable energy has been rapidly developing as a result of investment for development technology of using natural energy such as solar, wind, tidal, etc. There are lots of waste energy in the road space. However, nobody is not interested in waste energy from the road space. This paper present a fundamentally experimental study of energy harvesting technique to use waste energy in the road. The waste energy in the road is covered a pressure and impact of vehicles on the road, the radiant heat from asphalt pavement, road noise and vibration etc. In this study, an energy harvesting device using piezoelectric element is proposed and various tests are conducted to investigate a characteristic of this device as function of impact loading based on piezoelectric effect behavior. This paper shows the energy harvesting results of the device using domestic piezoelectirc element as a function of impact load size and pavement types.

The Magnetic Properties of Nanocrystalline Fe73.5Cu1Nb3Si15.5B7 Alloy Powder Cores (Fe73.5Cu1Nb3Si15.5B7나노 결정립 합금 분말 코아의 자기적 특성)

  • Noh, T.H.;Choi, H.Y.;Ahn, S.J.
    • Journal of the Korean Magnetics Society
    • /
    • v.14 no.1
    • /
    • pp.7-12
    • /
    • 2004
  • The annealing-temperature dependence of magnetic properties in compressed powder cores being composed of ball-milled F $e_{73.5}$C $u_1$N $b_3$S $i_{15.5}$ $B_{7}$ alloy powders (size 250∼850${\mu}{\textrm}{m}$) and 5 wt% of ceramic insulators has been investigated. When annealed at 5$50^{\circ}C$ for 1 h and so transformed to $\alpha$-Fe phase nanocrystalline structure with the grain size of 11 nm (electrical resistivity : 110 $\mu$$.$cm), the highest effective permeability of 125 and quality factor of 53 were obtained, and the permeability persisted up to about 500 KHz. Further the core loss measured at the frequency of 50 KHz and the induction amplitude of 0.1 T was very low (230 mW/㎤). However the dc bias characteristics was not satisfactory as compared to that of conventional powder core materials(MPP, Sendust etc.). The inferior dc bias property of F $e_{73.5}$C $u_1$N $b_3$S $i_{15.5}$ $B_{7}$ alloy powder cores was attributed to the fact that the size of powder was too large for obtaining the same permeability with that of conventional materials.

Development of Intelligent Multiple Camera System for High-Speed Impact Experiment (고속충돌 시험용 지능형 다중 카메라 시스템 개발)

  • Chung, Dong Teak;Park, Chi Young;Jin, Doo Han;Kim, Tae Yeon;Lee, Joo Yeon;Rhee, Ihnseok
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.37 no.9
    • /
    • pp.1093-1098
    • /
    • 2013
  • A single-crystal sapphire is used as a transparent bulletproof window material; however, few studies have investigated the dynamic behavior and fracture properties under high-speed impact. High-speed and high-resolution sequential images are required to study the interaction of the bullet with the brittle ceramic materials. In this study, a device is developed to capture the sequence of high-speed impact/penetration phenomena. This system consists of a speed measurement device, a microprocessor-based camera controller, and multiple CCD cameras. By using a linear array sensor, the speed-measuring device can measure a small (diameter: up to 1 2 mm) and fast (speed: up to Mach 3) bullet. Once a bullet is launched, it passes through the speed measurement device where its time and speed is recorded, and then, the camera controller computes the exact time of arrival to the target during flight. Then, it sends the trigger signal to the cameras and flashes with a specific delay to capture the impact images sequentially. It is almost impossible to capture high-speed images without the estimation of the time of arrival. We were able to capture high-speed images using the new system with precise accuracy.

Current Status and Future Research Directions of Separator Membranes for Lithium-Ion Rechargeable Batteries (리튬이차전지용 분리막 이해 및 최신 연구 동향)

  • Kim, Jung-Hwan;Lee, Sang-Young
    • Membrane Journal
    • /
    • v.26 no.5
    • /
    • pp.337-350
    • /
    • 2016
  • Lithium-ion rechargeable batteries (LIBs) have garnered increasing attention with the rapid advancements in portable electronics, electric vehicles, and grid-scale energy storage systems which are expected to drastically change our future lives. This review describes a separator membrane, one of the key components in LIBs, in terms of porous structure and physicochemical properties, and its recent development trends are followed. The separator membrane is a kind of porous membrane that is positioned between a cathode and an anode. Its major functions involve electrical isolation between the electrodes while serving as an ionic transport channel that is filled with liquid electrolyte. The separator membranes are not directly involved in redox reactions of LIBs, however, their aforementioned roles significantly affect performance and safety of LIBs. A variety of research approaches have been recently conducted in separator membranes in order to further reinforce battery safeties and also widen chemical functionalities. This review starts with introduction to commercial polyolefin separators that are currently most widely used in LIBs. Based on this understanding, modified polyolefin separators, nonwoven separators, ceramic composite separators, and chemically active separators will be described, with special attention to their relationship with future research directions of advanced LIBs.

Optimization of anode and electrolyte microstructure for Solid Oxide Fuel Cells (고체산화물 연료전지 연료극 및 전해질 미세구조 최적화)

  • Noh, Jong Hyeok;Myung, Jae-ha
    • Korean Chemical Engineering Research
    • /
    • v.57 no.4
    • /
    • pp.525-530
    • /
    • 2019
  • The performance and stability of solid oxide fuel cells (SOFCs) depend on the microstructure of the electrode and electrolyte. In anode, porosity and pore distribution affect the active site and fuel gas transfer. In an electrolyte, density and thickness determine the ohmic resistance. To optimizing these conditions, using costly method cannot be a suitable research plan for aiming at commercialization. To solve these drawbacks, we made high performance unit cells with low cost and highly efficient ceramic processes. We selected the NiO-YSZ cermet that is a commercial anode material and used facile methods like die pressing and dip coating process. The porosity of anode was controlled by the amount of carbon black (CB) pore former from 10 wt% to 20 wt% and final sintering temperature from $1350^{\circ}C$ to $1450^{\circ}C$. To achieve a dense thin film electrolyte, the thickness and microstructure of electrolyte were controlled by changing the YSZ loading (vol%) of the slurry from 1 vol% to 5 vol. From results, we achieved the 40% porosity that is well known as an optimum value in Ni-YSZ anode, by adding 15wt% of CB and sintering at $1350^{\circ}C$. YSZ electrolyte thickness was controllable from $2{\mu}m$ to $28{\mu}m$ and dense microstructure is formed at 3vol% of YSZ loading via dip coating process. Finally, a unit cell composed of Ni-YSZ anode with 40% porosity, YSZ electrolyte with a $22{\mu}m$ thickness and LSM-YSZ cathode had a maximum power density of $1.426Wcm^{-2}$ at $800^{\circ}C$.

A study on temperature dependent acoustic receiving characteristics of underwater acoustic sensors (수중음향센서 수온 변화에 따른 음향 수신 특성 변화 연구)

  • Je, Yub;Cho, Yohan;Kim, Kyungseop;Kim, Yong-Woon;Park, Saeyong;Lee, Jeong-Min
    • The Journal of the Acoustical Society of Korea
    • /
    • v.38 no.2
    • /
    • pp.214-221
    • /
    • 2019
  • In this paper, a temperature dependent acoustic receiving characteristics of underwater acoustic sensor is studied by theoretical and experimental investigations. Two different types (low mid frequency sensor and high frequency sensor) of underwater acoustic sensors are designed with different configuration of baffle and conditioning plate. The temperature dependent characteristics of the acoustic sensors are investigated within the temperature range from $-2^{\circ}C$ to $35^{\circ}C$. The material properties of the piezoelectric ceramics, molding and baffle, which are the primary materials of the acoustic sensors, are measured with temperature change. The temperature dependent RVS (Receiving Voltage Sensitivity) characteristics of the acoustic sensors are simulated by using the measured material properties. The RVS changes of the acoustic sensors are measured by changing temperature in the watertank where the acoustic sensors are installed. The measured and the simulated data show that the temperature dependent characteristics of the acoustic sensors are mainly dependent for the sound speed changes of the molding material.

Structure and Elastic Properties of (Nb1-xTax)C, (Nb1-xHfx)C, Ultra-High Temperature Solid Solution Ceramics using the First Principles Calculation (제1원리계산을 이용한 (Nb1-xTax)C, (Nb1-xHfx)C 초고온 세라믹 고용체의 구조 및 탄성특성)

  • Kim, Myungjae;Kim, Jiwoo;Kim, Jiwoong;Kim, Kyung-Nam
    • Korean Journal of Materials Research
    • /
    • v.31 no.12
    • /
    • pp.682-689
    • /
    • 2021
  • NbC, HfC, TaC, and their solid solution ceramics have been identified as the best materials for ultrahigh-temperature ceramics. However, their structural stability and elastic properties are mostly unclear. Thus, we investigated structure and elastic properties of (Nb1-xTax)C and (Nb1-xHfx)C solid solutions via ab initio calculations. Our calculated results show that the stability of (Nb1-xTax)C and (Nb1-xHfx)C increases with the increase of Hf and Ta content, and (Nb1-xHfx)C is more stable than (Nb1-xTax)C at the same content of Hf and Ta. The lattice constants decrease with increasing of Hf and Ta content. (Nb1-xTax)C and (Nb1-xHfx)C carbides are mechanically stable and brittle. Bulk modulus of (Nb1-xTax)C increases with increasing Ta content. In contrast, bulk modulus of (Nb1-xHfx)C decreases with increasing Hf content. Hardness of solid solutions shows the highest values at the (Nb0.25Ta0.75)C and (Nb0.75Hf0.25)C. In particular, (Nb0.75Hf0.25)C shows the highest hardness for the current system. The results indicate that the overall mechanical properties of (Nb1-xHfx)C solid solutions are superior to those of (Nb1-xTax)C solid solutions. Therefore, controlling the Hf and Ta element and content of the (Nb1-xTax)C and (Nb1-xHfx)C Solid solution is crucial for optimizing the material properties.

Effect of sintering temperature on microstructure and dielectric properties in (Dy, Mg)-doped BaTiO3 (Dy 및 Mg가 첨가된 BaTiO3에서 소결 온도가 미세구조와 유전특성에 미치는 영향)

  • Woo, Jong-Won;Kim, Sung-Hyun;Choi, Moon-Hee;Jeon, Sang-Chae
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.32 no.5
    • /
    • pp.175-182
    • /
    • 2022
  • Rare-earth elements were doped with Mg to enhance the temperature stability of dielectric properties of BaTiO3 for its application to MLCC (Multi-Layer Ceramic Capacitor). The additives strongly affect both grain growth and densification behaviors during sintering, and hence dielectric properties. The additive effects therefore should be examined in each system with different additives. This study investigated the crystal structure, grain growth and densification behaviors and related variations in dielectric constant with respect to sintering temperature. Dielectric constant appears to be varied with grain size in a temperature range between 1200 and 1300℃, suggesting the importance of grain size control. The temperature dependence of grain size variation was well explained by an established theory correlating the grain growth behavior with grain boundary structure. This accordance provides a basis for sintering technique to control grain growth thus to improve dielectric constant in rare-earth doped BaTiO3.

The effect of Dy2O3 addition on crystal structure, grain growth, and dielectric properties in BaTiO3 (BaTiO3에서 Dy2O3 첨가가 결정구조, 입자성장 및 유전특성에 미치는 영향)

  • Ahn, Won-Gi;Choi, Moonhee;Kim, Minkee;Moon, Kyoung-Seok
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.32 no.4
    • /
    • pp.136-142
    • /
    • 2022
  • The crystal structure, grain growth behavior, and dielectric properties of BaTiO3 have been studied with the addition of Dy2O3. The powders were synthesized at ratios of (100-x)BaTiO3-xDy2O3 (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250℃ for 2 hours in air. As the amount of added Dy2O3 was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba12Dy4.67Ti8O35 appeared when Dy2O3 was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy2O3 increased. It can be explained that the grain growth behavior of the Dy2O3 added-BaTiO3 occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.