• Title/Summary/Keyword: low sintering temperature

Search Result 759, Processing Time 0.027 seconds

Preparation of PMN-PT-BT/Ag/MgO Nanocomposite and Dielectric Properties (PMN-PT-BT/Ag/MgO 나노복합체의 제조 및 유전 특성)

  • Jeong, Soon-Yong;Lim, Kyoung-Ran;Nahm, Sahn
    • Journal of the Korean Ceramic Society
    • /
    • v.39 no.11
    • /
    • pp.1074-1082
    • /
    • 2002
  • Nanocomposite PMN-PT-BT/Ag/MgO was prepared by sintering at $950{\circ}C$ with addition of $AgNO_3$ and MgO sol to the PMN-PT-BT powder sinterable at $1200{\circ}C$. The low-temperature-sinterable PMN-PT-BT/Ag powder prepared by the modified mixed oxide method was calcined at $600{\circ}C$ for 1h and surface modified with the MgO sol of 0-10 wt% and then subjected to consolidation at $850-950{\circ}C$ for 4h under a flowing oxygen. The nanocomposite PMN-PT-BT/Ag/MgO(0.5wt%) sintered at $950{\circ}C$ showed the microstructure with grains of $1-3{\mu}m$, the second phase of MgO of $0.1-0.3{\mu}m$ by SEM and Ag of << $1{\mu}m$ qualitatively by SIMS. It showed the sintered relative density of 99%, the room temperature dielectric constant of 17200, the dielectric loss of 2.1% and the specific resistivity of $5.46{\times}10^{12}{\Omega}{\cdot}cm$. But the PMN-PT-BT/Ag/MgO(0 wt%) nanocomposite sintered at $950{\circ}C$ showed a little better properties : the sintered relative density of 99.5%, the room temperature dielectric constant of 19500, the dielectric loss of 2.1% and the specific resistivity of $7.30{\times}10^{12}{\Omega}{\cdot}cm$.

A Study on the Development of High Permeability and Low Coercivity Ni-Zn Ferrite (고투자율, 저보자력을 갖는 Ni-Zn Ferrite의 개발에 관한 연구)

  • 고재귀
    • Journal of the Korean Magnetics Society
    • /
    • v.7 no.1
    • /
    • pp.13-18
    • /
    • 1997
  • The effects of the various raw material composition and sintered temperature on the physical properties of Ni-Zn ferrite have been investigated. They turned out to be spinel structure by X-ray diffraction and the size of grain from microscope was from 6 ${\mu}{\textrm}{m}$ to 16 ${\mu}{\textrm}{m}$. As the sintering temperature was increased from 1030 $^{\circ}C$ to 1070 $^{\circ}C$, the initial permeability and magnetic induction has increased and the both of Q factor and coercive force has decreased. The coercive force and curie temperature were almost the same at each specimen. Their values were about 0.20 Oe and 220 $^{\circ}C$. The frequency of specimen will used in the range from 400 kHz to 20 MHz. The basic composition of $Ni_{0.14}Zn_{0.64}Cu_{0.22}Fe_2O_4$ (specimen B) sintered at 1050 $^{\circ}C$ shows the best results at magnetic induction($B_r & B_m$).

  • PDF

Reaction Synthesis of Ti3AlC2 at High Temperature (고온 반응에 의한 Ti3AlC2합성)

  • 황성식;박상환;한재호;한경섭;김태우
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.1
    • /
    • pp.87-92
    • /
    • 2003
  • $Ti_3AlC_2$was synthesized from TiCx and Al powder as a starting materials at the temperature range between$800^{circ}C;and;1500^{\circ}C$. The vacuum sintering and hot pressing methods were imployed to synthesize$Ti_3AlC_2$. The high purity$Ti_3AlC_2$was synthesized using TiCx and Al powder as starting materials without formation of Ti-Al intermetallic compound and Al-C compound.$Ti_2$AlC and$Ti_3AlC_2$were preferentially synthesized at$800^{\circ}C$and above$1200^{\circ}C$, respectively.$Ti_2$AlC formed at low temperature was transformed to$Ti_3AlC_2$by further reaction with TiC. In this study, the synthesis mechanism for$Ti_3AlC_2$was proposed. The synthesized$Ti_3AlC_2$showed the nano laminating structure consisting of$Ti_3AlC_2$crystal with the thickness of 45~120 nm.

Effect of Fe and BO3 Substitution in Li1+xFexTi2-x(PO4)3-y(BO3)y Glass Electrolytes (Li1+xFexTi2-x(PO4)3-y(BO3)y 계 유리 전해질에서 Fe 및 BO3 치환 효과)

  • Choi, Byung-Hyun;Jun, Hyung Tak;Yi, Eun Jeong;Hwang, Haejin
    • Journal of the Korean Electrochemical Society
    • /
    • v.24 no.3
    • /
    • pp.52-64
    • /
    • 2021
  • The effect of Fe and BO3 doping on structure, thermal, and electrical properties of Li1+xFexTi2-x(PO4)3-y(BO3)y (x = 0.2, 0.5)-based glass and glass ceramics was investigated. In addition, their crystallization behavior during sintering and ionic conductivity were also investigated in terms of sintering temperature. FT-IR and XPS results indicated that Fe2+ and Fe3+ ions in Li1+xFexTi2-x(PO4)3-y(BO3)y glass worked as a network modifier (FeO6 octahedra) and also as a network former (FeO4 tetrahedra). In the case of the glass with low substitution of BO3, boron formed (PB)O4 network structure, while boron preferred BO3 triangles or B3O3 boroxol rings with increasing the BO3 content owing to boic oxide anomaly, which can result in an increased non-bridging oxygen. The glass transition temperature (GTT) and crystallization temperature (CT) was lowered as the BO3 substitution was increased, while Fe2+ lowered the GTT and raised the CT. The ionic conductivity of Li1+xFexTi2-x(PO4)3-y(BO3)y glass ceramics were 8.85×10-4 and 1.38×10-4S/cm for x = 0.2 and 0.5, respectively. The oxidation state of doped Fe and boric oxide anomaly were due to the enhanced lithium ion conductivity of glass ceramics.

Microwave Dielectric Properties of (1-x)CaTiO3-xYAIO3 and its Low Temperature Densification by CaB2O4 Addition ((1-x)CaTiO3-xYAIO3계의 마이크로파 유전특성과 CaB2O4첨가제의 영향)

  • 강보경;김경용;김범수;김주선;김병호
    • Journal of the Korean Ceramic Society
    • /
    • v.40 no.1
    • /
    • pp.81-86
    • /
    • 2003
  • Microwave dielectric properties have been investigated in the$(1-x)CaTiO_3-xYAlO_3$ (x=0.1~1.0) solid solution system. The mixtures of $CaTiO_3$ and $YalO_3$using solid state method were sintered at various temperatures. Their dielectric constants and related temperature coefficients were strongly depend on the composition of the solid solution. The optimum properties were recorded as for ${\varepsilon}_r=47,$ $Q{\times}f_0$=35000 and ${\tau}_f=+11ppm/^{\circ}C$ without sintering agent. Even at $1200^{\circ}C$ full densification has been achieved with addition of $CaB_2O_4$ in the $0.75CaTiO_3-0.25YalO_3$ composition. The sample of $0.3 wt%-CaB_2O_4$ added $ 0.75CaTiO_3-0.25YalO_3$ sintered at $1300^{\circ}C$ for 3 h showed optimum microwave dielectric properties of ${\varepsilon}_r=47$, $Q{\time}f_0=37000$ and ${\tau}_f=+17ppm/^{\circ}C$, which demonstrates the promising candidates for microwave dielectric materials covering 5~7 GHz range.

Preparation of shotcrete coarse aggregate with low grade clay and coal ash (저급 점토와 석탄회를 이용한 숏크리트용 골재의 제조)

  • Kim, Kyung-Nam;Jung, Hee-Su;Park, Hyun
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.20 no.3
    • /
    • pp.147-152
    • /
    • 2010
  • In this study, the artificial coarse aggregate was manufactured by using coal ash and low grade clay. The characteristics of a coal ash-clay system were investigated using XRD, XRF, TG-DTA, SEM and Dilatometer with various coal ash contents. The chemical compositions are the fly ash, bottom ash and clay, $Al_2O_3$ are 28.5 wt%, 32.4 wt% and 18.1 wt%, and $SiO_2$ are 33.0 wt%, 53.7 wt% and 68.4 wt% in weight ratio, respectively. The shrinkage of specimens started at around $850^{\circ}C$ and changed little up to $1100^{\circ}C$, but increased markedly at above $1100^{\circ}C$. The shrinkage rate is strongly related to the decarbonization amount of coal ash. At the sintering temperature $1150^{\circ}C$, it was found that quartz, mullite, anorthite and albite phase exist in all specimens. It was found that bottom-clay system specimen sintered at $1150^{\circ}C$ had a good compressive strength of 87.5 kg/$cm^2$, and the compressive strength of bottom-clay specimen was higher than that of fly-clay system specimen. The reusability of coal ash as a raw material in the process of shotcrete resources such as artifical coarse aggregate is highly expected.

Preparation and Characteristics of $Y_2O_3-CeO_2-ZrO_2$ Structural Ceramics : II. Mechanical Properties and Thermal Stability of Sintered Body ($Y_2O_3-CeO_2-ZrO_2$ 구조세라믹스의 제조 및 특성 : II. 소결체의 기계적 성질 및 열적 안정성)

  • 오혁상;이윤복;김영우;오기동;박홍채
    • Journal of the Korean Ceramic Society
    • /
    • v.34 no.1
    • /
    • pp.102-108
    • /
    • 1997
  • ZrO2 powders stabilized with Y2O3 and CeO2 of various compositions were prepared by the coprecipitation of water-soluble ZrOCl2.8H2O, YCl3.6H2O and Ce(NO3)3.6H2O, and their compacts were pressurelessly sintered at 1400 and 150$0^{\circ}C$ for 2hrs in air. 2mol% Y2O3-ZrO3 showed the most superior strength (1003MPa) and microhardness (12.6GPa), while 10 mol%CeO2-ZrO2 had the hightest toughness (13.3 MPa.m1/2) after sintering at 140$0^{\circ}C$. The addition of Y2O3 into Y2O3-ZrO3 decreased mean grain size and increased strength and hardness but decrease toughness. On the other hand, the addition of CeO2 into Y2O3-ZrO2 enhanced the stability of tetragonal phase during low-temperature aging for a long time under hydrothermal atmosphere.

  • PDF

Research Trend of Soft Magnetic Composite Materials with High Energy Efficiency (고에너지효율 연자성 복합 분말 소재의 연구개발 동향)

  • Kim, Hwi-Jun
    • Journal of the Korean Magnetics Society
    • /
    • v.21 no.2
    • /
    • pp.77-82
    • /
    • 2011
  • The use of soft magnetic materials have been increasing in the various industrial fields according to the increasing demand for high performance, automatic, miniaturing equipments in the recent our life. In this study, we investigated the effect of factors on the core loss and magnetic properties of electrical steel and soft magnetic composites. Furthermore, we reviewed the major efforts to reduce the core loss and improve the soft magnetic properties in the two main soft magnetic materials. Domain purification which results from reduced density of defects in cleaner electrical steels is combined with large grains to reduce hysteresis loss. The reduced thickness and the high electrical conductivity reduce the eddy current component of loss. Furthermore, the coating applied to the surface of electrical steel and texture control lead to improve high permeability and low core loss. There is an increasing interest in soft magnetic composite materials because of the demand for miniaturization of cores for power electronic applications. The SMC materials have a broad range of potential applications due to the possibility of true 3-D electromagnetic design and higher frequency operation. Grain size, sintering temperature, and the degree of porosity need to be carefully controlled in order to optimize structure-sensitive properties such as maximum permeability and low coercive force. The insulating coating on the powder particles in SMCs eliminates particle-to-particle eddy current paths hence minimizing eddy current losses, but it reduces the permeability and to a small extent the saturation magnetization. The combination of new chemical composition with optimum powder manufacturing processes will be able to result in improving the magnetic properties in soft magnetic composite materials, too.

Ag Impregnated HAp Coatings on Alumina Substrate by IBAD and Its Biological Test (IBAD를 이용하여 알루미나 위에 HAp를 Coating하는 연구와 이의 항균력 시험)

  • Park, Eui-Seo;Kim, Taik-Nam;Yim, Hyuk-Jun;Kim, Yun-Jong;Hwang, Deuk-Soo;Kim, Jung-Woo;Kim, Sun-Ok
    • The Journal of Engineering Research
    • /
    • v.3 no.1
    • /
    • pp.181-187
    • /
    • 1998
  • Hydroxyapatite was used as implant materials, because it has a good biocompatibility and is similar to human bone. However it is not expected to have a high strength as implant materials because of a low fracture strength after sintering of HAp. Alumina ($\alpha$-alumina) shows a stable chemical properties and high strength in physiological environments. Thus it was tried to use a HAp coatings on Alumina substrate as implant materials. In this study, HAp was coated on Alumina substrate by lon Beam Assisted Deposition(IBAD). Then Ag was impregnated on HAp coating layer, which showed antimicrobial effects. To carry out the ion exchange of $Ag^+$ with $Ca^{2+}$ in HAp on the surface, HAp coated alumina substrate was immersed in 20ppm, 100ppm $AgNO_3$ solution at room temperature for 48 hours. Antimicrobial test was studied by using bacteria, which normally caused periprosthetic infections. The follwing bacteria was used in antimicrobial test. Escherichia coli, Pseudomonas aeruginosa (gram negative) and staphylococcus epidermidis (gram positive). Ag impregnated HAp shows very good antimicrobial effects against these bacteria. The surface structure of sample, which was treated in $AgNO_3$ solution was studied by SEM, XRD. Ag release curve was studied in Simulated Body Fluid (SBF) solution.

  • PDF

Fabrication of Gd1.5Ba2Cu3O7-y Bulk Superconductors from the Powder Synthesized by a Solid-State Reaction Method (고상반응법으로 합성한 분말로부터 Gd1.5Ba2Cu3O7-y 벌크 초전도체의 제조)

  • Kim, Yong Ju;Park, Seung Yeon;You, Byung Youn;Park, Soon-Dong;Kim, Chan-Joong
    • Korean Journal of Materials Research
    • /
    • v.23 no.6
    • /
    • pp.309-315
    • /
    • 2013
  • $GdBa_2Cu_3O_{7-y}$(Gd123) powders were synthesized by the solid-state reaction method using $Gd_2O_3$ (99.9% purity), $BaCO_3$ (99.75%) and CuO (99.9%) powders. The synthesized Gd123 powder and the Gd123 powder with $Gd_2O_3$ addition ($Gd_{1.5}Ba_2Cu_3O_{7-y}$(Gd1.5)) were used as raw powders for the fabrication of Gd123 bulk superconductors. The Gd123 and Gd1.5 bulk superconductors were fabricated by sintering or a top-seeded melt growth (TSMG) process. The superconducting transition temperature ($T_{c,onset}$) of the sintered Gd123 was 93 K and the transition width was as large as 20 K. The $T_{c,onset}$ of the TSMG processed Gd123 was 82 K and the transition width was also as large as 12 K. The critical current density ($J_c$) at 77 K and 0 T of the sintered Gd123 and TSMG processed Gd123 were as low as a few hundreds A/$cm^2$. The addition of 0.25 mole $Gd_2O_3$ and 1 wt.% $CeO_2$ to Gd123 enhanced the $T_c$, $J_c$ and magnetic flux density (H) of the TSMG processed Gd123 sample owing to the formation of the superconducting phase with high flux pinning capability. The $T_c$ of the TSMG processed Gd1.5 was 92 K and the transition width was 1 K. The $J_cs$ at 77 K (0 T and 2 T) were $3.2{\times}10^4\;A/cm^2$ and $2.5{\times}10^4\;A/cm^2$, respectively. The H at 77 K of the TSMG-processed Gd1.5 was 1.96 kG, which is 54% of the applied magnetic field (3.45 kG).