• 한국세라믹학회지
• /
• 제37권1호
• /
• pp.77-81
• /
• 2000

Silica glass films to utilize optical waveguides was fabricated by Aerosol Flame Deposition(AFD) method. As the amount of B2O3 increased in the sol solution of (92-x)SiO2-xB2O3-8P2O5, the thermophoretic deposition rate onto Si substrate was markedly lowered due to vaporizing out of B2O3 and P2O5 during the vaporization and reaction of the aerosol in the flame. GeO2 was added to 62SiO2-30B2O3-8P2O5 in order to control easily the refractive index of glass films. As the amount of GeO2 increased from 2 to 12 wt%, its refractive index increased from 1.4633 up to 1.4716.

• 한국재료학회지
• /
• 제14권2호
• /
• pp.115-120
• /
• 2004

Perovskite barium-strontium titanate, $(Ba, Sr)TiO_3$ was prepared and effects of $Sb_2$O$_3$ additives on its PTCR properties were investigated. $The (Ba,Sr)TiO_3$ with 0.05～0.25 mol% $Sb_2$$O_3$ showed semiconducting PTCR behavior and anomalous grain growth was also observed when it was sintered above $1330^{\circ}C$. It was considered that charge compensation by doping 8b203 as well as abnormal grain growth by sintering lead to resistivity reduction from insulating to semiconducting transition.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.1
• /
• pp.37-40
• /
• 2003

Amorphous $Al_2O_3$ nanotubes have been fabricated by utilizing the ZnO nanowires as template with wet etching method. ZnO nanowires synthesized by thermal evaporation are conformally coated with $Al_2O_3$ by atomic-layer deposition(ALD) method. The $Al_2O_3$-coated ZnO nanowires are of core-shell structure; ZnO core nanowires and $Al_2O_3$ shells. When the $ZnO/Al_2O_3$ core-shell structure is dipped in $H_3PO_4$ solution at $25^{\circ}C$ for a 6 min, the core ZnO materials are completely etched, and only $Al_2O_3$ nanotubes are remained. This nanotube fabrication is technically easier than others, and simply approachable. Transmission electron microscopy shows that the $Al_2O_3$ nanotubes have various thicknesses that can be controlled.

• 한국안광학회지
• /
• 제5권1호
• /
• pp.49-53
• /
• 2000

Sodium borate silicate 유리는 $10Na_2O-39B_2O_3-50SiO_2-CoO$ mol%와 $20Na_2O-14B_2O_3-65SiO_2-CoO$ mol%의 조성비로 혼합한 후 전기로에서 $1210^{\circ}C$ 온도로 2시간 동안 용융하여 공기 중에서 급냉 시켜 제작하였다. 급냉한 유리의 유전적 거동을 조사하기 위하여 온도와 주파수 함수로 유전상수와 비저항을 측정하였다. 유전율 스펙트럼에서 유리전이온도는 $Na_2O$ 20 mol%시료가 낮아졌으며 $Na_2O$ 함량이 증가함에 따라 유전상수는 크게 나타났다. 유리의 비저항 주파수 의존성은 non-Debye형 완화를 보였다.

• 한국결정성장학회지
• /
• 제31권6호
• /
• pp.270-275
• /
• 2021

ZnO는 출발물질인 황산아연과 알칼리 침전제인 NaOH와 Na₂CO₃에 의해 생성된 아연 중간생성물의 변이 거동과 결정화 조건에 따라 제조하였다. ZnO 결정화를 위해 아연 중간생성물인 Zn₄(OH)₆SO₄·H₂O, Zn₅(OH)₆(CO₃)₂·H₂O를 각각 400℃, 800℃에서 1시간 하소하였고, 하소 온도는 열중량 분석을 기반으로 하였다. 아연 중간생성물인 Zn₄(OH)₆SO₄·H₂O은 400℃에서 Zn₄(OH)₆SO₄·H₂O, ZnO 결정상이 혼재됨을 확인하였고, 800℃에서 완전히 열분해되어 순수한 ZnO만 형성되었다. Na₂CO₃와 반응하여 생성된 아연 중간생성물인 Zn₅(OH)₆(CO₃)₂·H₂O는 400℃ 이상에서 완전한 ZnO의 결정상을 확인하였다. Na₂CO₃와 반응을 통해 상대적으로 낮은 하소 온도에서 나노 입자의 ZnO를 합성할 수 있었다.

• 디지털산업정보학회논문지
• /
• 제12권3호
• /
• pp.25-31
• /
• 2016

Mechanical properties of Y2O3-containing tetragonal ZrO2 polycrystals(Y-TZP) were investigated. Several additives were used to modify the hardness and fracture toughness of Y-TZP. The effects of these individual additives were discussed and their interactions were also analysed. Each additive, such as CoO, Fe2O3, MnO2 was found to deteriorate the mechanical properties of Y-TZP when it was used singly. But the fracture toughness of Y-TZP was significantly improved when these additives and Al2O3 were added in combination at a certain ratio. The addition of CoO, Fe2O3 and MnO2 into Y-TZP resulted in the more complex behavior of fracture toughness and hardness. The specimen with 1.5 wt%-Fe2O3, 3.0 wt% -Al2O3 and 1.5 wt%-CoO showed the monoclinic to tetragonal phase ratio of 18% and the highest toughness of $10.8MPa{\cdot}m1/2$ with Vickers hardness of 1201 kgf/mm2. However, the toughness decreased as the ratio increased and macrocracks developed beyond the ratio of 25%. Sample No. 16 is improved high Physical and Mechanical Properties.

• 한국세라믹학회지
• /
• 제37권4호
• /
• pp.295-301
• /
• 2000

The effect of V2O5 addition on the low temperature sintering of Pb(Mn1/3Sb2/3)O3-PZT ceramics, which is known as a prominent material for piezoelectric transformer application was studied, and the densification behavior and piezoelectric characteristics of the samples as a function of heating rate were also examined. V2O5 led the system to liquid phase sintering by forming liquid phase during sintering, which accelerated densification through the particle rearrangement in the early stage of sintering. The liquid phase mostly existed at grain boundaries retarded the evaporation of PbO, while the densification temperature and the weight loss of V2O5-free samples were higher than those of samples with V2O5. Faster heating improved the densification of the samples regardless of V2O5 addition. The low temperature sintering at 100$0^{\circ}C$ was achieved in PMS-PZT ceramics with high density and reasonable dielectric and piezoelectric characteristics. This result revealed optimistic way to the development of multi-layered piezoelectric transformers.

• 한국전기전자재료학회논문지
• /
• 제30권12호
• /
• pp.788-793
• /
• 2017

Electrical behaviors of plasma-sprayed $Al_2O_3-TiO_2$ coatings have been investigated in terms of their $TiO_2$ content. On increasing the $TiO_2$ content from 6 to 30 wt%, the DC electrical conductivity increased by several orders of magnitude. From impedance spectroscopy analysis, the total conductivity of the grains and grain boundaries and their respective activation energies were determined without the electrode effects that could impede ionic transfer. An electron transference number was also estimated, ranging between 6.5% and 7.3% for 13 wt% $TiO_2$ and between 0.4% and 0.7% for 30 wt% $TiO_2$ in the coating. Because of the high electronic contribution to the total conductivity, the $Al_2O_3-TiO_2$ coating could be a new candidate material to obtain superior electrical conductivity as well as corrosion and wear resistances.

• Journal of Korean Society for Atmospheric Environment
• /
• 제22권E1호
• /
• pp.19-26
• /
• 2006

The decomposition of gaseous $CH_3CHO$ was investigated by metal loaded $TiO_2$ (pure $TiO_2,\;Pt/TiO_2,\;Pd/TiO_2,\;Mn/TiO_2\;and\;Ag/TiO_2$) with $UV/TiO_2$ process and $UV/TiO_2/O_3$ process at room temperature and atmospheric pressure. Metal loaded $TiO_2$ was prepared by photodeposition. Decomposition of $CH_3CHO$ was carried out in a flow-type photochemical reaction system using three 10W black light lamps ($300{\sim}400nm$) as a light source. The experimental results showed that the degradation rate of $CH_3CHO$ was increased with Pt and Ag on $TiO_2$ compared to pure $TiO_2$, but decreased with depositing Pd and Mn on pure $TiO_2$. The considerable increase in the degradation efficiency of the $CH_3CHO$ was found by a combination of photocatalysis and ozonation as compared to only by ozonation or photocatalysis. Loading of Pt on $TiO_2$ promoted conversion of gaseous ozone. The degradation rate of gaseous $CH_3CHO$ decreased with an increase of water vapor in the feed stream for the both $UV/TiO_2\;and\;UV/TiO_2/O_3$ processes. The pure $TiO_2$ was more affected by the water vapor than Pt loaded $TiO_2$.

• 한국세라믹학회지
• /
• 제27권6호
• /
• pp.799-807
• /
• 1990

In this study, effects of oxide additives on mechanical properties and microstructure of A1N and A1N polytype ceramics were investigated. Fine A1N powder was synthesized by nitriding alumiuim hydroxide prepared from Al-isopropoxide, at 1350$^{\circ}C$ for 10h in N2 atmosphere. By adding 3w/o Y2O3, 0.56w/o CaO, and 10w/o SiO2 to AlN powder, AlN and AlN polytype ceramics were prepared by hot-pressing under the pressure of 30 MPa at 1800$^{\circ}C$ for 1h. AlN ceramics with no additives formed considerable amount of AlON phase, while AlN ceramics doped with Y2O3 or CaO decreased AlON phase and formed Y-Al or Ca-Al oxide compound. AlN＋10w/o SiO2(＋3w/o Y2O3) composition produced AlON and AlN polytype compound having 21R as a major phase. Room temperature flexural strength of AlN ceramics with no additive was 246MPa, and room temperature flexural strength and critical temperature difference by thermal shock(ΔTc) of AlN ceramics dooped with Y2O3 or CaO were 532MPa/340$^{\circ}C$ and 423MPa/300$^{\circ}C$, respectively. Y2O3 and CaO used as sintering agent played roles of densification and oxygen removal of AlN ceramics, and affected grain growth/grain morphologies of AlN ceramics.