Kwang Seok Oh

Combinatorial approach for ferroelectric material libraries prepared by liquid source misted chemical deposition method

Combinatorial approach for discovering novel functional materials in the huge diversity of chemical composition and processing conditions has become more important for breakthrough in thin film electronic and energy-conversion devices. The efficiency of combinatorial method depends on the preparation of a reliable high-density composition thin-film library. The physico-chemical properties of each sample on the library should be similar to those of the corresponding samples prepared by one-by-one conventional methods. We successfully developed the combinatorial liquid source misted chemical deposition (LSMCD) method and demonstrated its validity in screening the chemical composition of Bi3.75LaxCe0.25-xTi3O12 (BLCT) for high remanent polarization (Pr). LSMCD is a cheap promising combinatorial screening tool. It can control the composition up to ppm level and produce homogeneous multicomponent library. LSMCD method allows us to prepare BLCT thin-film library at the variation of 0.4 mol% of La. Maximum 2Pr is 35 μC/cm−2 at x = 0.21. The intensity of (117) XRD peak is quantitatively related to 2Pr. Newly developed scanning piezoelectric deformation measurement for nano-sized samples using scanning probe microscope (SPM) is also found out to be reliable for determining the relative ranking of Pr value rapidly.

Highly reliable 64-channel sequential and parallel tubular reactor system for high-throughput screening of heterogeneous catalysts

Highly reliable 64-channel sequential and parallel tubular reactor for high-throughput screening of heterogeneous catalysts is constructed with stainless steel. In order to have a uniform flow rate at each channel, 64 capillaries are placed between the outlet of multiport valve and the inlet of each reactor. Flow rate can be controlled within ±1.5%. Flow distribution can be easily adjusted for sequential and parallel mode of operation. The reactor diameter is too big to have a uniform temperature distribution. Hence, the reactor body is separated into three radial zones and controlled independently with nine thermocouples. Temperature accuracy is ±0.5°C at 300°C and ±1°C at 500°C in sequential mode, while it is ±2.5°C in the range of 250–500°C in parallel mode. The temperature, flow rate, reaction sequence, and product analysis are controlled by LABVIEW™ software and monitored simultaneously with displaying a live graph. The accuracy in the conversion is ±2% at the level of 73% conversion when all reactor...

Chemiluminescence analyzer of NOx as a high-throughput screening tool in selective catalytic reduction of NO

Abstract A chemiluminescence-based analyzer of NOx gas species has been applied for high-throughput screening of a library of catalytic materials. The applicability of the commercial NOx analyzer as a rapid screening tool was evaluated using selective catalytic reduction of NO gas. A library of 60 binary alloys composed of Pt and Co, Zr, La, Ce, Fe or W on Al2O3 substrate was tested for the efficiency of NOx removal using a home-built 64-channel parallel and sequential tubular reactor. The NOx concentrations measured by the NOx analyzer agreed well with the results obtained using micro gas chromatography for a reference catalyst consisting of 1 wt% Pt on γ-Al2O3. Most alloys showed high efficiency at 275 °C, which is typical of Pt-based catalysts for selective catalytic reduction of NO. The screening with NOx analyzer allowed to select Pt-Ce(X) (X=1–3) and Pt–Fe(2) as the optimal catalysts for NOx removal: 73% NOx conversion was achieved with the Pt–Fe(2) alloy, which was much better than the results for the reference catalyst and the other library alloys. This study demonstrates a sequential high-throughput method of practical evaluation of catalysts for the selective reduction of NO.

Ferroelectric properties of Bi4−xCexTi3O12 (0<x<4) thin film array fabricated from Bi2O3∕CeO2∕TiO2 multilayers using multitarget sputtering

We fabricated a ferroelectric Bi4−xCexTi3O12 thin film library by solid-state mixing of Bi2O3∕CeO2∕TiO2 multilayers using a multitarget rf magnetron sputtering equipped with an automated shutter. Polarization-electrical field and the structure are mapped as a function of Ce content (x) from 0 to 4. The remnant polarization decreases as Ce content increases, and at x⩾0.8, Bi4−xCexTi3O12 samples exhibit a paraelectric property due to the formation of impurity phases such as Bi2Ti2O7 and CeO2. Among the thin film samples of the library, Bi3.85Ce0.15Ti3O12 exhibited the largest remnant polarization of 13.0μC∕cm2.

Discovery of New Heterogeneous Catalysts for the Selective Oxidation of Propane to Acrolein

Combinatorial synthesis and screening technique have been applied to investigate the catalytic activity and selectivity of ternary and quaternary mixed-metal oxide catalysts for the selective oxidation of propane. The catalyst libraries were prepared via a modified sol-gel method using a synthesis robot and library design software, and examined for the catalytic activities in a simple high-throughput reactor system connected to a mass spectrometer for product analysis. Ternary Mo-Cr-Te, V-Cr-Sb, and Mo-V-Cr catalysts have been selected for potential candidate by composition spread approach. In a next generation composition spread library, the composition space of these three ternary compositions was sampled. Screening of this 198-member library provided substantial evidence that each ternary system has its own optimum composition where acrolein formation is highest. In addition, the composition space of the quaternary reference system Mo-V-Te-Nb mixed-oxides has also been prepared and sampled.

High-throughput Screening of Transition Metal-doped TiO2 in Photodecomposition of Phenol Under Visible Light

A catalyst library consisting of 20 catalysts with different metal and weight fraction-doped TiO2 was prepared at one time for discovering the novel metal-doped TiO2 photocatalyst, which is active under visible light irradiation. Combinatorial microbeam XRD and UV-vis spectrometer were used for analysis of crystal structure and photoactivity of 20 catalysts in the library, respectively. Photodecomposition of phenol was chosen as a probe reaction. The library preparation, XRD characterization and reaction test for 20 catalysts were completed within 48 hours. Among the catalysts in the library, 1.5 wt% Co/TiO2 showed the best activity for phenol degradation.