• Proceedings of the Korean Vacuum Society Conference
• /
• 2014.02a
• /
• pp.475-475
• /
• 2014

Dye sensitized solar cells (DSSCs) are regarded as potential inexpensive alternatives to conventional solid-state devices. The flexible version, employing conductive-plastic-film substrates, is appealing for commercialization of DSSCs because it not only reduces the weight and cost of the device but also extends their applications. However, the need for high temperature does not permit the use of plastic-film substrate. So, development of low-temperature methods is therefore realization of flexible DSSCs. In this work, the electrophoretic deposition combined with hydrothermal treatment was employed to prepare nanocrystalline $TiO_2$ thin film at low temperature. We confirmed the prepared $TiO_2$ thin films with different voltages and deposition times in the electrophoretic deposition process. Properties of the $TiO_2$ films were investigated by various analysis method such as X-ray diffraction, field emission scanning electron microscopy (FESEM) and UV-visible spectrophotometer.

• Journal of the Korean Ceramic Society
• /
• v.27 no.5
• /
• pp.661-667
• /
• 1990

Spinel powders were synthesized at the comparatively low-temperature range(800~90$0^{\circ}C$) by the emulsion-hot kerosene drying method and the effects of kerosene-evaporative conditions on powder characteristics were investigated. In emulsion drying, more unagglomerated and sinterable powders could be synthesized through rapid evaporation of emulsion at the higher kerosene temperature. The completion of formation reaction of spinel observed at the low-temperature range confirmed the high reactivity of powders. The relative theoretical density and the fracture toughness of spinel pellets sintered at 1$650^{\circ}C$ for 4hrs. were 98% and 2.1MN/m3/2, respectively.

• Journal of Powder Materials
• /
• v.26 no.6
• /
• pp.481-486
• /
• 2019

Iron oxides currently attract considerable attention due to their potential applications in the fields of lithiumion batteries, bio-medical sensors, and hyperthermia therapy materials. Magnetite (Fe₃O₄) is a particularly interesting research target due to its low cost, good biocompatibility, outstanding stability in physiological conditions. Hydrothermal synthesis is one of several liquid-phase synthesis methods with water or an aqueous solution under high pressure and high temperature. This paper reports the growth of magnetic Fe₃O₄ particles from iron powder (spherical, <10 ㎛) through an alkaline hydrothermal process under the following conditions: (1) Different KOH molar concentrations and (2) different synthesis time for each KOH molar concentrations. The optimal condition for the synthesis of Fe₃O₄ using Fe powders is hydrothermal oxidation with 6.25 M KOH for 48 h, resulting in 89.2 emu/g of saturation magnetization at room temperature. The structure and morphologies of the synthesized particles are characterized by X-ray diffraction (XRD, 2θ = 20°-80°) with Cu-kα radiation and field emission scanning electron microscopy (FE-SEM), respectively. The magnetic properties of magnetite samples are investigated using a vibrating sample magnetometer (VSM). The role of KOH in the formation of magnetite octahedron is observed.

• Tribology and Lubricants
• /
• v.33 no.6
• /
• pp.296-302
• /
• 2017

Ball milling of elemental powders in advance and using an induction heating system for intermetallic coatings are known to enhance the reactivity of combustion synthesis. In this work, the effects of simultaneously applying these two incentive methods on the properties of intermetallic coatings are studied. Ni-Al powder compacts ball-milled with three different ball-to-powder weight ratio mixtures are synthesized and coated on mild steel by combustion synthesis in an induction heating system. Consequently, similar to an electrical heating system, the positive effects of ball milling on the combustion synthesis are confirmed in the induction heating system. The enhancement in synthetic reactivity achieved by applying the two incentive methods at the same time is greater than that by applying each incentive method separately. In particular, the enhancement is remarkable at low reaction temperature. However, there are limitations to improving the reactivity by simultaneously applying the two incentive methods to the combustion synthesis, unlike the reaction temperature. The microstructure and hardness of the coating layer are both influenced by the ball-charging ratio employed in the ball-milling process.

• Tribology and Lubricants
• /
• v.25 no.1
• /
• pp.7-12
• /
• 2009

Coating brittle intermetallic compounds on metal can enlarge the range of their use. It is found that intermetallic compound coating layers made by only combustion synthesis in an electric furnace have porous multi-phase structures containing several intermediate phases, even though the coating layers show good wear resistance. In this study, dense $Ni_{3}Al$ single phase layer corresponding to the initial composition of the mixed powder is coated on two different ferrous materials by the diffusing treatment after combustion synthesis. After- ward, sliding wear behaviors of the coating layer are evaluated in comparison with that of the coating layer with porous multi-phase structure made by only combustion synthesis. As a result, the wear properties of the coating layer composed of dense $Ni_{3}Al$ single phase are considerably improved at the range of low sliding speed com- pared with that of the coating layer with porous multi-phase structure, particularly in the running-in wear region. This is attributed to the fact that wear of the coating layer is progressed by shearing as a sequence of adhesion, not by occurring of pitting on the worn surface due to having dense structure without pores.

• Journal of Powder Materials
• /
• v.29 no.6
• /
• pp.485-491
• /
• 2022

Lithium lanthanum titanium oxide (LLTO) is a promising ceramic electrolyte because of its high ionic conductivity at room temperature, low electrical conductivity, and outstanding physical properties. Several routes for the synthesis of bulk LLTO are known, in particular, solid-state synthesis and sol-gel method. However, the extremely low ionic conductivity of LLTO at grain boundaries is one of the major problems for practical applications. To diminish the grain boundary effect, the structure of LLTO is tuned to nanoscale morphology with structures of different dimensionalities (0D spheres, and 1D tubes and wires); this strategy has great potential to enhance the ion conduction by intensifying Li diffusion and minimizing the grain boundary resistance. Therefore, in this work, 0D spherical LLTO is synthesized using ultrasonic spray pyrolysis (USP). The USP method primarily yields spherical particles from the droplets generated by ultrasonic waves passed through several heating zones. LLTO is synthesized using USP, and the effects of each precursor and their mechanisms as well as synthesis parameters are analyzed and discussed to optimize the synthesis. The phase structure of the obtained materials is analyzed using X-ray diffraction, and their morphology and particle size are analyzed using field-emission scanning electron microscopy.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.22 no.4
• /
• pp.342-349
• /
• 2009

This study investigated the growth characteristics of carbon nanotubes (CNTs) by changing a period of annealing time and a $C_{2}H_{2}/H_2$ flow ratio at temperature as low as $450^{\circ}C$ with inductively coupled plasma chemical vapor deposition. The 1-nm-thick Fe-Ni-Co alloy thin film served as a catalyst layer for the growth of CNTs, which was thermally evaporated on the 15-nm-thick Al underlayer deposited on the 50-nm-thick Ti diffusion barrier. The annealing at low temperature of $450^{\circ}C$ brought about almost no granulation of the catalyst layer, and the CNT growth was not affected by a period of annealing time. A study of changing the flow rate of $C_{2}H_{2}$ and $H_2$ showed that as the ratio of the $C_{2}H_{2}$ flow rate to the $H_2$ flow rate was lowered, the CNTs were grown to be longer With further decreasing the flow ratio, the length of CNTs reached the maximum and then became shorter. Under the optimized gas flow rates, we successfully synthesized CNTs with a uniform length over a 4-inch Si wafer at $450^{\circ}C$.

• Journal of the Korean Ceramic Society
• /
• v.44 no.12
• /
• pp.696-702
• /
• 2007

The family of (Sr,Mg)-doped $LaGaO_3$ compounds, which exhibit high ionic conductivity at $600-800^{\circ}C$ over a wide range of oxygen partial pressure, appears to be promising as the electrolyte for intermediate temperature solid oxide fuel cells. Conventional synthesis routes of (Sr,Mg)-doped $LaGaO_3$ compounds based on solid state reaction have some problems such as the formation of impurity phases, long sintering time and Ga loss during high temperature sintering. Phase stability problem especially, the formation of additional phases at the grain boundary is detrimental to the electrical properties of the electrolyte. From this point of view, we focused to synthesize single phase (Sr,Mg)-doped $LaGaO_3$ electrolyte at the stage of powder synthesis and to apply relatively low heat-treatment temperature using novel synthesis route based on combustion method. The synthesized powder and sintered bulk electrolytes were characterized by XRD, TG-DTA, FT-IR and SEM. AC impedance spectroscopy was used to characterize the electrical transport properties of the electrolyte with the consideration of the contribution of the bulk lattice and grain boundary to the total conductivity. Finally, relationship between synthesis condition and electrical properties of the (Sr, Mg)-doped $LaGaO_3$ electrolytes was discussed with the consideration of phase analysis results.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2012.08a
• /
• pp.79-79
• /
• 2012

A high temperature and a low temperature plasma process technologies were developed and demonstrated for synthesis, hybrid formation, surface treatment and CVD engineering of nano powder. RF thermal plasma is used for synthesis of spherical nano particles in a diameter ranged from 10 nm to 100 nm. A variety of nano particules such as Si, Ni, has been synthesized. The diameter of the nano-particles can be controlled by RF plasma power, pressure, gas flow rate and raw material feed rate. A modified RF thermal plasma also produces nano hybrid materials with graphene. Hemispherical nano-materials such as Ag, Ni, Si, SiO2, Al2O3, size ranged from 30 to 100 nm, has been grown on graphene nanoplatelet surface. The coverage ranged from 0.1 to 0.7 has been achieved uniformly over the graphene surface. Low temperature AC plasma is developed for surface modification of nano-powder. In order to have a three dimensional and lengthy plasma treatment, a spiral type of reactor has been developed. A similar plasma reactor has been modfied for nano plasma CVD process. The reactor can be heated with halogen lamp.

• Proceedings of the KAIS Fall Conference
• /
• 2010.11a
• /
• pp.313-317
• /
• 2010

Li, Zr doped mesoporous silica was synthesized in one pot and investigated for low temperature $CO_2$ adsorption. Herein CTAB and TEOS are used as structural directing agent and silica source respectively. The characteristics of the material was obtained from FT IR, XRD, SEM, TG and BET results. ICP AES results revealed the presence of lithium and zirconium. The material possesses high surface area ($962.22m^2g^{-1}$) with mono dispersed particles of about 2 nm. The maximum $CO_2$ adsorption capacity is 5 wt % (50 mg/g) of $CO_2$/g of sorbent at $25^{\circ}C$, which is regenerable at $200^{\circ}C$. This regeneration temperature of the adsorbent is lower than the reported lithium zirconium silicate powder. Until now, there is no report for the synthesis of Li, Zr doped mesoporous silica. The performance studies illustrate that Li, Zr doped mesoporous silica is tunable, regenerable, recyclable and selective sorbent and hence found to be a promising candidate for $CO_2$ adsorption.