• 한국세라믹학회지
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• 제25권6호
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• pp.639-644
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• 1988

The physical and dielectric properties of complex perovskite compound Sr(Mg1/3Nb1/3)O3-Ba(Mg1/3Nb2/3)O3-Ba(Mg1/3Ta2/3)O3(BMT) system were investigated as a function of composition. As the mole ratio of BMN was increased, lattice parameter ratio c/a was slightly increased, and density was increased in SMN-BMN system. However, in BMN-BMT system, lattice parameter ratio c/a and density were decreased with increasing the mole ratio of BMN. Dielectric constant, dielectric loss at $25^{\circ}C$ and 100kHz, and temperature coefficient of resonant frequency, the dependence of temperature in capacitance were increased with increasing the mole ratio of BMN in SMN-BMN-BMT system. These result can be explained according to the degree of order=disorder and dielectric constant.

• 한국자기학회지
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• 제8권3호
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• pp.125-130
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• 1998

13Cr-1.5Nb-Fe합금분말이 수분사법으로 제조되엇다. 제조된 합금뷴말을 압축기를 이용하여 ring현상으로 성형한후, 진공중에서 소결하였다. as-prepared 분말의 현상, 입도분포, 성분분석 및 포화자화물 조사하였으며, 소결된 시편의 투자율, 교류자기이력손실이 조사되었다. as-prepared 13Cr-1.5Nb-Fe합금분말의 포화자화는 160emu/g이었으며, 산소함유량은 약 600ppm이었다. 입도분포는 약 70$\mu$m에서 50%vol.을 나타낸다. 교류투자율은 소결온도 및 성형온도가 증가할수록 증가한다. 주파수 20KHz에서 교류자기이력손실은 12ton/cm2성령압력 및 120$0^{\circ}C$ 소결온도 조건에서 107W/cc로 가장우수하다.

• 한국전기전자재료학회논문지
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• 제13권11호
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• pp.926-931
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• 2000

The microwave dielectric properties and the microstructures as a mole fraction of (1-x)ZnNb$_2$O$_{6}$-xPb$_{5}$Nb$_4$O$_{15}$ ceramics with CuV$_2$O$_{6}$, Sb$_2$O$_3$ and glass(ZNPN ceramics) was investigated. 0.98ZN-0.02PN ceramics containing 1.5 wt% CuV$_2$O$_{6}$ 1.0 wt% Sb$_2$O$_3$ and 1.0 wt% glass had a dielectric constant($\varepsilon$$_{r}$) of 23, Qxf$_{o}$ value of 15000 and TCF(Temperature Coefficient of resonance Frequency) of -25 ppm/$^{\circ}C$ and it is possible to be co-fired with Ag electrode at 90$0^{\circ}C$. As sintered temperature increases over 90$0^{\circ}C$ the grain size of ZNPN ceramics was increasing for growth and it has poor co-fired properties with Ag electrode.e.ctrode.e.e.

• 한국분말재료학회지
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• 제22권6호
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• pp.426-431
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• 2015

Microstructural examination of the Nb-Si-B alloys at Nb-rich compositions is performed. The Nb-rich corner of the Nb-Si-B system is favorable in that the constituent phases are Nb (ductile and tough phase with high melting temperature) and $T_2$ phase (very hard intermetallic compound with favorable oxidation resistance) which are good combination for high temperature structural materials. The samples containing compositions near Nb-rich corner of the Nb-Si-B ternary system are prepared by spark plasma sintering (SPS) process using $T_2$ and Nb powders. $T_2$ bulk phase is made in arc furnace by melting the Nb slug and the Si-B powder compact. The $T_2$ bulk phase was subsequently ball-milled to powders. SPS is performed at $1300^{\circ}C$ and $1400^{\circ}C$, depending on the composition, under 30 MPa for 600s, to produce disc-shaped specimen with 15 mm in diameter and 3 mm high. Hardness tests (Rockwell A-scale and micro Vickers) are carried out to estimate the mechanical property.

• 대한금속재료학회지
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• 제46권8호
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• pp.482-488
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• 2008

For a better understanding of the correlation between a corrosion and a microstructure, it is necessary to study a phase transformation with an annealing condition for Zr-Nb alloy. Zr-5wt.%Nb alloy with different phase characteristics was prepared with various annealing conditions. A microstructural study and corrosion test were performed to investigate the effect of a phase such as the phase type, fraction, and size on corrosion. The corrosion behavior of the Zr-5Nb alloy was very sensitive to the annealing condition, which affected the formation of the ${\beta}$-phases (${\beta}$-Nb or ${\beta}$. The corrosion rate of the Zr-5Nb alloy annealed at $500^{\circ}C$ with the formation of the ${\beta}$-Nb phase was lower than that of the Zr-5Nb alloy annealed from 600 to $800^{\circ}C$ with the formation of the ${\beta}$-Zr phase. The highest corrosion rate was observed for the ${\beta}$-quenched Zr-5Nb alloy. After a consideration of the corrosion rate and micro structure of the Zr-5Nb alloy, the corrosion resistance of that alloy was improved due to the formation of a small sized ${\beta}$-Nb phase which could be controlled by the annealing condition.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2000년도 추계학술대회 및 발표대회 강연 및 발표논문 초록집
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• pp.17-17
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• 2000

• 한국결정성장학회지
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• 제16권1호
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• pp.32-37
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• 2006

희토류계 niobates인 $LaNbO_4$(Ln : Y, La, Gd)는 자체 발광형으로 $NbO^{3-}_4$ 이온의 전하 이동에 의한 넓은 띠의 청색 발광 스펙트럼을 410nm에서 나타낸다. 본 연구에서는 새로운 FED용 청색 및 적색 형광체를 개발하기 위하여 $LaNbO_4$ :X (X = Bi, Eu) 형광체를 합성하였으며, $1250^{\circ}C$에서 2시간 소성한 후 $1400^{\circ}C$에서 1시간 소성하였을 때 최대 발광피크를 얻을 수 있었다. 254nm의 여기하에서 $LaNbO_4$ : Bi는 $420\~450nm$ 영역에서 강한 청색 발광 스펙트럼을 나타내며 첨가된 $Bi^{3+}$ 이온 농도가 $1mol\%$일 때 최대 발광세기를 얻었다 $LaNbO_4$ : Eu의 경우는 첨가된 $Eu^{3+}$ 이온 농도가 $10mol\%$일 때 약 610nm에서 최대 적색 발광 스펙트럼을 나타내고 있다. $Eu^{3+}$ 이온 농도가 $10mol\%$ 이하에서는 $415\~460nm$, $530\~560nm$ 및 $570\~620nm$ 영역에서 피크가 관측되고 있다. 이들 형광체의 음극선 발광특성은 빛 발광 특성과 유사한 경향을 보였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 추계학술대회 논문집 전기물성,응용부문
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• pp.101-103
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• 2003

The $ZnNb_2O_6$ ceramics with 5wt% CuO and $B_2O_3$(1,3,5wt%) were prepared by the conventional mixed oxide method. The ceramics were sintered at the temperature of $950^{\circ}C{\sim}1025^{\circ}C$ for 3hr. in air. The structural properties were investigated with sintering temperature and $B_2O_3$ addition by XRD and SEM. Also, the microwave dielectric properties were investigated with sintering temperature and $B_2O_3$ addition. Increasing the sintering temperature, the peak of second phase ($Cu_3Nb_2O_6$) was increased. But no significant difference was observed as the $B_2O_3$ addition, In the $ZnNb_2O_6$ ceramics with 5wt% CuO and 5wt% $B_2O_3$ sintered at $975^{\circ}C$ for 3hr, the dielectric constant, quality factor, temperature coefficient of the resonant frequency were 19.30, 14,662GHz, $+4.18ppm/^{\circ}C$, respectively.

• 열처리공학회지
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• 제19권1호
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• pp.3-9
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• 2006

The phase changes, nitride precipitation and hardness variations of 14%Cr-6.7Ni-0.65Mo-0.26Nb-0.05V-0.03C super martensitic stainless steel were investigated after nitrogen permeation heat treatment at a temperature range between $1050^{\circ}C$ and $1150^{\circ}C$. The nitrogen-permeated surface layer was transformed into austenite. The rectangular type NbN, NbCrN precipitates and fine round type precipitate were coexisted in the surface austenite layer, while the interior region that was free from nitrogen permeation kept the martensitic phase. The hardness of surface austenite showed 280 Hv, while the interior region of martensite phase represented 340 Hv. When tempering the nitrogen-permeated steel at $450^{\circ}C$, a maximum hardness of 433 Hv was appeared, probably this is attributed to the secondary hardening effect of the precipitates. The nitrogen concentration decreased gradually with increasing depth below the surface after showing a maximum of 0.3% at the outmost surface. The strong affinity between nitrogen and Cr enabled the substitutional element Cr to move from interiors to the surface when nitrogen diffuse form surface to the interior. Corrosion resistance of nitrogen permeated steel was superior to that of solution-anneaed steel in the solution of 1N $H_2SO_4$.

• 한국재료학회지
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• 제8권11호
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• pp.1043-1047
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• 1998

CuO 및 C얘의 첨가가 $BiNbO_4$ 세라믹스의 고주파 유전특성에 미치는 영향을 조사하였다. CdO 첨가량이 증가함에 따라 소결밀도 및 품질계수는 감소하였고 소결온도가 증가하면 유전상수 및 품질계수는 증가하였다. $BiNbO_4$에 CuO 및 CdO를 각각 0.03wt% 첨가한 시편을 $960^{\circ}C$에서 소결시 유전율 41.2, 품질계수($Q{\times}f_0$) 6,500(at 5.6GHz), 공진주파수 온도계수 $3ppm^{\circ}C$의 우수한 고주파 유전특성을 얻을 수 있었다.