• 한국재료학회지
• /
• 제24권8호
• /
• pp.423-428
• /
• 2014

We synthesized Fe-doped $TiO_2/{\alpha}-Fe_2O_3$ core-shell nanowires(NWs) by means of a co-electrospinning method and demonstrated their magnetic properties. To investigate the structural, morphological, chemical, and magnetic properties of the samples, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy were used, as was a vibrating sample magnetometer. The morphology of the nanostructures obtained after calcination at $500^{\circ}C$ exhibited core/shell NWs consisting of $TiO_2$ in the core region and ${\alpha}-Fe_2O_3$ in the shell region. In addition, the XPS results confirmed the formation of Fe-doped $TiO_2$ by the doping effect of $Fe^{3+}$ ions into the $TiO_2$ lattice, which can affect the ferromagnetic properties in the core region. For comparison, pure ${\alpha}-Fe_2O_3$ NWs were also fabricated using an electrospinning method. With regard to the magnetic properties, the Fe-doped $TiO_2/{\alpha}-Fe_2O_3$ core-shell NWs exhibited improved saturation magnetization(Ms) of approximately ~2.96 emu/g, which is approximately 6.1 times larger than that of pure ${\alpha}-Fe_2O_3$ NWs. The performance enhancement can be explained by three main mechanisms: the doping effect of Fe ions into the $TiO_2$ lattice, the size effect of the $Fe_2O3_$ nanoparticles, and the structural effect of the core-shell nanostructures.

• 한국전기전자재료학회논문지
• /
• 제16권7호
• /
• pp.604-610
• /
• 2003

The effects of sintering additives such as B $i_2$ $O_3$ and $V_2$ $O_{5}$ on the microwave dielectric and sintering properties of (Z $n_1$$_{-xM}$ $g_{x}$)Ti $O_3$ system were investigated. Highly dense samples were obtained for (Z $n_{0.8}$M $g_{0.2}$)Ti $O_3$ at the sintering temperature range of 870~90$0^{\circ}C$ with B $i_2$ $O_3$ and $V_2$ $O_{5}$ additions of 〈1 wt.%, respectively. The microwave dielectric properties of (Z $n_{0.8}$M $g_{0.2}$)Ti $O_3$ with 0.45 wt.%B $i_2$ $O_3$ and 0.55 wt.% $V_2$ $O_{5}$ sintered at 90$0^{\circ}C$ were as follows : Q$\times$ $f_{o}$ = 50,800 GHz, $\varepsilon$$_{r}$ = 22, and $\tau$$_{f}$ = -53 ppm/$^{\circ}C$. In order to improve temperature coefficient of resonant frequency, Ti $O_2$ was added to the above system. The optimum amount of Ti $O_2$ was 15 moi.% when sintered at 87$0^{\circ}C$, at which we could obtain following results: Q$\times$ $f_{o}$ = 32,800 GHz, $\varepsilon$$_{r}$ = 26, and$\tau$$_{f}$ = 0 ppm/$^{\circ}C$.EX>.EX>.EX>.EX>.EX>.EX>.EX>.

• 한국재료학회지
• /
• 제34권4호
• /
• pp.202-207
• /
• 2024

In this study, we undertook detailed experiments to increase hydrogen production efficiency by optimizing the thickness of titanium dioxide (TiO₂) thin films. TiO₂ films were deposited on p-type silicon (Si) wafers using atomic layer deposition (ALD) technology. The main goal was to identify the optimal thickness of TiO₂ film that would maximize hydrogen production efficiency while maintaining stable operating conditions. The photoelectrochemical (PEC) properties of the TiO₂ films of different thicknesses were evaluated using open circuit potential (OCP) and linear sweep voltammetry (LSV) analysis. These techniques play a pivotal role in evaluating the electrochemical behavior and photoactivity of semiconductor materials in PEC systems. Our results showed photovoltage tended to improve with increasing thickness of TiO₂ deposition. However, this improvement was observed to plateau and eventually decline when the thickness exceeded 1.5 nm, showing a correlation between charge transfer efficiency and tunneling. On the other hand, LSV analysis showed bare Si had the greatest efficiency, and that the deposition of TiO₂ caused a positive change in the formation of photovoltage, but was not optimal. We show that oxide tunneling-capable TiO₂ film thicknesses of 1~2 nm have the potential to improve the efficiency of PEC hydrogen production systems. This study not only reveals the complex relationship between film thickness and PEC performance, but also enabled greater efficiency and set a benchmark for future research aimed at developing sustainable hydrogen production technologies.

• 한국전기전자재료학회논문지
• /
• 제35권2호
• /
• pp.165-171
• /
• 2022

The SiO₂/TiO₂ multilayer thin films used for narrow band pass filter were fabricated using E-beam evaporation method. The narrow band pass filter was used to enhance the resolution of spectroscopy and sensor applications with near infrared (NIR) light source. The narrow band pass filter with multilayer thin films were designed with Essential Macleod program. The multilayers of SiO₂/TiO₂ with 32 layers were deposited on the silicon encapsulation of IR with peak wavelength (λ_p) of 660 nm and NIR LEDs with λ_p of 830 nm, 880 nm, and 955 nm. After NIR light passed through the narrow band pass filter, the full width of half maximum of 33.4~48.6 nm became narrow to 20~24 nm owing to the absorption of photons with short or long wavelength of designed band of 20 nm. The SiO₂/TiO₂ band pass filter fabricated in this study can be used for sensor, optoelectronics, and NIR spectroscopy applications.

• 센서학회지
• /
• 제33권2호
• /
• pp.105-111
• /
• 2024

In this study, the H₂S gas sensing characteristics were evaluated using surface-modified SnO₂ microparticles by tip sonication. The surface-modified SnO₂ microparticles were synthesized using the following sequential process. First, bare SnO₂ microparticles were synthesized via a hydrothermal method. Then, the surfaces of bare SnO₂ microparticles were modified with Ti nanoparticles during tip sonication. The sensing characteristics of SnO₂ microparticles modified with Ti were systematically investigated in the range of 100-300℃, compared with the bare SnO₂ microparticles. In this study, we discuss in detail the improved H₂S sensing characteristics of SnO₂ microparticles via Ti nanoparticle modification.

• 한국수소및신에너지학회논문집
• /
• 제33권1호
• /
• pp.19-27
• /
• 2022

A series of QPAE/TiO₂-x (x = 1, 4, 7 and 10 wt%) organic/inorganic composite membranes were prepared as electrolyte membranes for alkaline anion exchange membrane fuel cells by controlling the content of inorganic filler with quaternized poly(arylene ether) (QPAE) random copolymer. Among the prepared QPAE/TiO₂-x organic/inorganic composite membranes, the highest ionic conductivity was 26.6 mS cm^-1 at 30℃ in QPAE/TiO₂-7 composite membrane, which was improvement over the ionic conductivity value of 6.4 mS cm^-1 (at 30℃) of the pristine QPAE membrane. Furthermore, the water uptake, swelling ratio, ionic exchange capacity, and thermal property of QPAE/TiO₂-x composite membranes were improved compared to the pristine QPAE membrane. The results of these studies suggest that the fabricated QPAE/TiO₂-x composite membranes have good prospects for alkaline anion exchange membrane fuel cell applications.

• 한국재료학회지
• /
• 제34권6호
• /
• pp.275-282
• /
• 2024

In this work, we investigated the photo-degradation performance of MnO₂-SiC fiber-TiO₂ (MnO₂-SiC-TiO₂) ternary nanocomposite according to visible light excitation utilizing methylene blue (MB) and methyl orange (MO) as standard dyes. The photocatalytic physicochemical characteristics of this ternary nanocomposite were described by X-ray diffraction (XRD), scanning electron microscopy (SEM), tunneling electron microscopy (TEM), ultraviolet-visible (UV-vis), diffuse reflectance spectroscopy (DRS), electrochemical impedance spectroscopy (EIS), photocurrent and cyclic voltammogram (CV) test. Photolysis studies of the synthesized MnO₂-SiC-TiO₂ composite were conducted using standard dyes of MB and MO under UV light irradiation. The experiments revealed that the MnO₂-SiC-TiO₂ exhibits the greatest photocatalytic dye degradation performance of around 20 % with MB, and of around 10 % with MO, respectively, within 120 min. Furthermore, MnO₂-SiC-TiO₂ showed good stability against photocatalytic degradation. The photocatalytic efficiency of the nanocomposite was indicated by the adequate photocatalytic reaction process. These research results show the practical application potential of SiC fibers and the performance of a photocatalyst composite that combines these fibers with metal oxides.

• 자원리싸이클링
• /
• 제29권5호
• /
• pp.48-54
• /
• 2020

소다배소 처리한 탈질폐촉매의 수침출 잔사로부터 TiO₂ 회수를 위하여 황산침출과 가수분해 반응을 실시하였다. Ti 성분의 황산침출은 70 ℃, 3 시간, 교반속도 500 rpm, 슬러리 농도 100 g/L로 고정하여 실시하였고, 황산농도는 4~8 M로 변화시키며 진행하였다. 침출액으로부터 Ti 성분의 침전회수는 가수분해반응을 이용하였으며, 실험조건은 100 ℃, 반응시간 2 시간으로 고정하였고, Ti 성분의 침전율은 침출액과 증류수의 혼합비와 침전반응 Seed 혼입유무에 따라 비교하였다. Ti의 침출율은 6 M에서 최대 95.2 %까지 도달 후 점차 감소하는 경향을 나타내었고, Si의 침출율은 황산농도 증가에 반비례하여 급격히 감소하여 91.7 %에서 8 M 조건에서는 3.0 %까지 억제되었다. 침출액을 이용한 가수분해는 부성분인 Si의 함량이 가장 낮은 8 M 침출액을 이용하여 진행하였다. 침출액의 혼합비에 의한 Ti의 침전회수율은 반응시간에 비례하였고 혼합비에 반비례하였다. 또한, 침전반응의 가속화를 위해 TiO₂(#325~#400 mesh, 0.2 g) seed를 첨가하였을 경우에 모든 혼합조건에서 침전회수율이 상승하였으며, 혼합비(침출액:증류수) 1:9~3:7 구간에서 98.8~99.8 %의 침전율이 달성되었다. 회수된 TiO₂의 순도는 침출액 혼합비 1:9~3:7 구간에서 혼합비가 낮을수록 증가하여 최대 99.46 %까지 상승함을 확인하였다.

• 한국세라믹학회지
• /
• 제44권3호
• /
• pp.137-141
• /
• 2007

$La_{2}O_{3}-TiO_{2}-SiO_{2}$ glass, a type that could not obtained so far by the conventional melting method, was prepared successfully using a sol gel process. Glass derived with the sol-gel process has compositions of $5La_{2}O_{3}-5TiO_{2}-90SiO_{2},\;5La_{2}O_{3}-10TiO_{2}-85SiO_{2}$, and $5La_{2}O_{3}-20TiO_{2}75SiO_{2}$. The UV-visible absorption edge of all glass compositions was below 400 nm. The measured density is in the range of 2.55-2.89, and was nearly identical to the calculated density and the refractive index of the glasses derived from the sol-gel ranges from 1.545 to 1.645. The molar additive coefficient of $TiO_{2}$ measured in this ternary system is lower than the calculated value, while the value of $La_{2}O_{3}$ is higher.

• 한국환경과학회지
• /
• 제32권5호
• /
• pp.385-394
• /
• 2023

There is a need for a method that can effectively remove wastewater containing small-sized particles such as TiO₂. In this study, we attempted to remove TiO₂ wastewater using electrocoagulation-electroflotation two-step separation. The TiO₂ wastewater was effectively removed via batch electrocoagulation-electroflotation separation. However, in the batch process, the simultaneous operation of electrocoagulation and electoflotation was challenging due to the high residual turbidity. In the continuous operation, electrocoagulation and electoflotation reactors were kept separate. The turbidity removal in continuous operation was similar to that in the batch process, nevertheless, the residual Al concentration was high, leading to the conclusion that counterterm ensures against residual Al were necessary.