Jeongho Song

Properties of a Dye Sensitized Solar Cell using Electrodes with Au Nano Powder Blocking Layers

Jeongho Song, Yunyoung Noh, Minkyoung Choi, Kwangbae Kim, and Ohsung Song* Department of Materials Science and Engineering, University of Seoul, Seoul 02504, Republic of Korea Abstract: We prepared working electrodes with blocking layers containing 0.0∼0.5 wt% Au nano powder to improve the energy conversion efficiencies (ECEs) of a dye sensitized solar cell (DSSC). TEM, FE-SEM, and AFM were used to characterize microstructure. XRD and micro-Raman were used to determine the phase and localized surface plasmon resonance (LSPR) effect of the blocking layer with Au nano powder. A solar simulator and a potentiostat were used to confirm the photovoltaic properties of the DSSC with the Au nano powder. From the results of the microstructure analysis, we confirmed that the Au nano powder had particle sizes of less than 70 nm, dispersed uniformly on the blocking layer. Based on the phase and composition analysis, we identified the presence of Au, and the Raman intensity increased as the amount of Au was increased. The photovoltaic results showed that the ECE reached 5.52% with the Au addition, compared to an ECE of 5.00% without the Au addition. This enhancement was due to the increased LSPR of the blocking layer with the Au addition. Our results suggest that we might improve the efficiency of a DSSC by the proper addition of Au nano powder on the blocking layer. †(Received November 24, 2015; Accepted February 22, 2016)

Diffusion of the High Melting Temperature Element from the Molten Oxides for Copper Alloys

To alloy high melting point elements such as boron, ruthenium, and iridium with copper, heat treatment was performed using metal oxides of , , and at the temperature of in vacuum for 30 minutes. The microstructure analysis of the alloyed sample was confirmed using an optical microscope and FE-SEM. Hardness and trace element analyses were performed using Vickers hardness and WD-XRF, respectively. Diffusion profile analysis was performed using D-SIMS. From the microstructure analysis results, crystal grains were found to have formed with sizes of 2.97 mm. For the copper alloys formed using metal oxides of , , and the sizes of the crystal grains were 1.24, 1.77, and 2.23 mm, respectively, while these sizes were smaller than pure copper. From the Vickers hardness results, the hardness of the Ir-copper alloy was found to have increased by a maximum of 2.2 times compared to pure copper. From the trace element analysis, the copper alloy was fabricated with the expected composition. From the diffusion profile analysis results, it can be seen that 0.059 wt%, 0.030 wt%, and 0.114 wt% of B, Ru, and Ir, respectively, were alloyed in the copper, and it led to change the hardness. Therefore, we verified that alloying of high melting point elements is possible at the low temperature of .

Fabrication of Metal Discs Using Molten Tin and Brass Droplets

This paper proposes a simple process to fabricate tin and brass metal discs with a large surface area from molten droplets for the wet-refining process of nonferrous metals by assuming they have precious metal elements. To optimize the droplet condition in a graphite crucible, the appropriate nozzle size was determined using a simulation program (STAR-CCM+) by varying the diameters (0.5, 1.0, and 2.0 mm). The simulation results showed that both tin and brass do not fall out with a 0.5 mm diameter nozzle but they do fall out in continuous ribbon mode with a 2.0 mm nozzle. Only the 1.0mm nozzle was expected to fabricate droplets. Finally, solidified metal discs were fabricated successfully with the 1.0 mm nozzle within 10 minutes by impacting the droplets with a cooling water flowing over a Ti plate placed at the 40° falling direction. The weight, average thickness, and surface area of the tin discs were 0.15 g, 107.8 μm, and 3.71 cm, respectively. The brass discs were 1.16 g, 129.15 μm, and 23.98 cm, respectively. The surface area of the tin and brass disc were 8.2 and 17.6 times the size of the tin and brass droplets, respectively. This process for precious metal extraction is expected to save cost and time.

Properties of the Master Alloys for White Gold Products with Silicon Contents

Abstract We prepared 8 samples of non-silver and silver-added master alloys containing silicon to confirm the existence ofnickel-silicides. We then prepared products made of 14K and 18K white gold by using the prepared master alloys containing0.25, 0.35, and 0.50 wt% silicon to check for nickel release. We then employed the EN 1811 testing standard to investigatethe nickel release of the white gold products, and we also confirmed the color of the white gold products with an UV-VIS-NIR-color meter. We observed NiSi x residue in all master alloys containing more than 0.50 wt% Si with EDS-nitric acid etching.For the white gold products, we could not confirm the existence of NiSi x through XRD after aqua-regia etching. In the EN1811 test, only the white gold products with 0.25 wt% silicon master alloys successfully passed the nickel release regulations.Moreover, we confirmed that our white gold products showed excellent Lab indices as compared to those of commercial whitegold ones, and the silver-added master alloys offered a larger L index. Our results indicate that employing 0.25 wt% siliconmaster alloys might be suitable for white gold products without nickel-silicide defects and nickel release problems. Key wordsmaster alloy, white gold, silicon content, nickel release, energy dispersive spectroscopy.