• Korean Journal of Materials Research
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• v.23 no.2
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• pp.143-148
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• 2013

Well-distributed $SnO_2$-Sn-$Ag_3Sn$ nanoparticles embedded in carbon nanofibers were fabricated using a co-electrospinning method, which is set up with two coaxial capillaries. Their formation mechanisms were successfully demonstrated. The structural, morphological, and chemical compositional properties were investigated by field-emission scanning electron spectroscopy (FESEM), bright-field transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). In particular, to obtain well-distributed $SnO_2$ and Sn and $Ag_3Sn$ nanoparticles in carbon nanofibers, the relative molar ratios of the Ag precursor to the Sn precursor including 7 wt% polyacrylonitrile (PAN) were controlled at 0.1, 0.2, and 0.3. The FESEM, bright-field TEM, XRD, and XPS results show that the nanoparticles consisting of $SnO_2$-Sn-$Ag_3Sn$ phases were in the range of ~4 nm-6 nm for sample A, ~5 nm-15 nm for sample B, ~9 nm-22 nm for sample C. In particular, for sample A, the nanoparticles were uniformly grown in the carbon nanofibers. Furthermore, when the amount of the Ag precursor and the Sn precursor was increased, the inorganic nanofibers consisting of the $SnO_2$-Sn-$Ag_3Sn$ nanoparticles were formed due to the decreased amount of the carbon nanofibers. Thus, well-distributed nanoparticles embedded in the carbon nanofibers were successfully synthesized at the optimum molar ratio (0.1) of the Ag precursor to the Sn precursor after calcination of $800^{\circ}C$.

• Journal of Integrative Natural Science
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• v.12 no.3
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• pp.69-73
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• 2019

Taguchi has used the signal-to-noise ratio (SN) to achieve the appropriate set of operating conditions where variability around target is low in the Taguchi parameter design. Taguchi has dealt with having constraints on both the mean and variability of a characteristic (the dual response problem) by combining information on both mean and variability into an SN. Many Statisticians criticize the Taguchi techniques of analysis, particularly those based on the SN. In this paper we propose a substantially simpler optimization procedure for parameter design to solve the dual response problems without resorting to SN.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.1
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• pp.22-31
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• 2008

The operating window method is a novel approach in quality improvement. But it has not received deserved attention in academic research. If a critical factor for competing failure modes can be identified, the probability of failure can be reduced by widening the operating window of this factor. Traditional SN ratio for the operating window advocated by Taguchi has a critical shortcoming, which has been derived under the assumption that failure rates are determined by the operating window factor only. A new metric for robustness is given for the operating window method, which has relaxed the restrictive assumption of Taguchi's SN ratio. And procedures for determining optimal conditions based on the new metric is presented. The effectiveness of the proposed approach over the traditional practice is tested with the aid of a wave soldering process.

• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.464-467
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• 1996

The microstructural evolution during mechanical alloying of Nb and Sn powders, of average composition Nb3Sn, has been investigated by X-ray diffraction(XRD) and scanning electron microscopy(SEM). Observations by SEM showed a progressive change of milling time. From the XRD studies, the structural development with milling time depends on the ball size for a given powder/ball ratio. Using a larger ball of 9.5mm diameter, the elemental powders initially alloy mechanically to form an A15 structure phase, and then amorphised with continued milling. However, in case of milling with a smaller ball of 3.968mm diameter, an amorphous phase is first formed. These results can be understood by considering the dependence of the milling energy on the ball size. The homogeneous stoichiometric $Nb_3Sn$ phase could be easily obtained by heat treatment of a supersaturated solid solution produced by MA. Heat treatment of an amorphous phase formed by MA resulted in the mixture of the $Nb_3Sn$ and $Nb_6Sn_5$ phases.

• Current Photovoltaic Research
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• v.2 no.4
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• pp.177-181
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• 2014

$Cu_2ZnSn(S_xSe_{1-x})_4$ (CZTSSe) absorber thin films were prepared on Mo coated soda lime glass substrates by sulfo-selenization of sputtered stacked Zn-Sn-Cu precursor thin films. The Zn-Sn-Cu precursor thin films were sulfo-selenized inside a graphite box containing S and Se powder using rapid thermal processing furnace at $540^{\circ}C$ in Ar atmosphere with pre-treatment at $300^{\circ}C$. The effect of different S/Se ratio on the structural, compositional, morphological and electrical properties of the CZTSSe thin films were studied using XRD (X-ray diffraction), XRF (X-ray fluorescence analysis), FE-SEM (field-emission scanning electron microscopy), respectively. The XRD, FE-SEM, XRF results indicated that the properties of sulfo-selenized CZTSSe thin films were strongly related to the S/Se composition ratio. In particular, the CZTS thin film solar cells with S/(S+Se)=0.25 shows best conversion efficiency of 4.6% ($V_{oc}$ : 348 mV, $J_{sc}$ : $26.71mA/cm^2$, FF : 50%, and active area : $0.31cm^2$). Further detailed analysis and discussion for effect of S/Se composition ratio on the properties CZTSSe thin films will be discussed.

• Korean Journal of Materials Research
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• v.30 no.10
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• pp.566-572
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• 2020

In the recent years, thin film solar cells (TFSCs) have emerged as a viable replacement for crystalline silicon solar cells and offer a variety of choices, particularly in terms of synthesis processes and substrates (rigid or flexible, metal or insulator). Among the thin-film absorber materials, SnS has great potential for the manufacturing of low-cost TFSCs due to its suitable optical and electrical properties, non-toxic nature, and earth abundancy. However, the efficiency of SnS-based solar cells is found to be in the range of 1 ~ 4 % and remains far below those of CdTe-, CIGS-, and CZTSSe-based TFSCs. Aside from the improvement in the physical properties of absorber layer, enormous efforts have been focused on the development of suitable buffer layer for SnS-based solar cells. Herein, we investigate the device performance of SnS-based TFSCs by introducing double buffer layers, in which CdS is applied as first buffer layer and ZnMgO films is employed as second buffer layer. The effect of the composition ratio (Mg/(Mg+Zn)) of RF sputtered ZnMgO films on the device performance is studied. The structural and optical properties of ZnMgO films with various Mg/(Mg+Zn) ratios are also analyzed systemically. The fabricated SnS-based TFSCs with device structure of SLG/Mo/SnS/CdS/ZnMgO/AZO/Al exhibit a highest cell efficiency of 1.84 % along with open-circuit voltage of 0.302 V, short-circuit current density of 13.55 mA cm^-2, and fill factor of 0.45 with an optimum Mg/(Mg + Zn) ratio of 0.02.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.5
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• pp.225-232
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• 2013

The influence of aging treatment, addition elements and rolling reduction ratio on the microstructure, mechanical, electrical and bendability properties of Cu-Ni-Si-P-x (x = Fe, Sn, Zn) alloys for connector material application was investigated. SEM/EDS analysis exhibited that Ni2-Si precipitates with a size of 20~100 nm were distributed in grains. Fe, Sn, Zn elemnets in Cu-Ni-Si-P alloy imporved the mechanical strength but it was not favor in increasing of electrical conductivity. As higher final rolling reduction ratio, the strength and electrical conductivity is increased after aging treatment, but it indicated excellent bendability. Especially, Cu-2Ni-0.4Si-0.5Sn-0.1Fe-0.03P alloy show the tensile strength value of 700MPa and the electrical conductivity was observed to reach a maximum of 40%IACS. It is optimal for lead frame and connector.

• KSTLE International Journal
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• v.4 no.2
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• pp.47-51
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• 2003

Sliding wear tests have been carried out in room temperature air and water in order to compare the wear resistance of Zr-xNb-xSn alloys of various alloying elements (Nb and Sn). The main focus was to quantitatively compare the wear properties of the recently developed Zr-xNb-xSn alloys with the commercial ones using the evaluation parameters of the wear resistance with the consideration of the worn area. As a result, the recently developed alloys had a similar wear resistance compared with the commercial ones. The dominant factor governing the wear resistance was the protruded volume of the wear debris that was formed on the worn area in the air condition, but the accommodation of the plastic deformation on the contact area in water. In addition, the worn area size appeared to be very different depending on the tested alloys. To evaluate the wear resistance of each test specimen, the ratio of the wear volume or the protruded volume to the worn area ($D_e$ or $D_p$) is investigated and proposed as the evaluation parameters of the wear resistance.

• Applied Chemistry for Engineering
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• v.5 no.3
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• pp.517-523
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• 1994

The effects of cure kinetics and mechanism of DGEBA(diglycidyl ether of bisphenol A)/MDA(4,4'-methylene dianiline) with SN(succinonitrile) and HQ(hydroquinone) as an additive and accelerator were investigated. Cure kinetics was evaluated by Kissinger equation and fractional-life method through DSC analysis. The activation energy has hydroxyl group as an accelerator, the activation energy and the starting cure-temperature were lower than those of DGEBA/MDA/SN system. Cure mechanism of those systems was investigated through FT-IR according to the various SN contents. The ratio was SN : HQ = 4 : 1. It has been known that the cure reactions of an epoxy-diamine system are composed of primary amine-epoxy reaction, secondary amino-epoxy reaction and epoxy-hydroxyl group reaction. But in DGEBA/MDA/SN system, primary amino-CN group reaction and CN group-hydroxyl group reaction were added to the above mentioned reactions. These reactions attributed to the long main chain and the low crossliking density. And in DGEBA/MDA/SN/HQ system, hydroxyl group of HQ formed a transition state with epoxide group and amime group and also opened the ring of the epoxide group rapidly, then amino-epoxy reaction took place easily.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.6
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• pp.245-250
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• 2019

We investigated the post-annealing effect of Sn-incorporated β-Ga₂O₃ (β-Ga₂O₃ : Sn) nanowires (NWs) grown on sapphire (0001) substrates using radio-frequency powder sputtering. The β-Ga₂O₃ : Sn NWs were converted to a porous structure during the vacuum annealing process at 800℃. Host non-stoichiometric Ga₂O_3-x, is transformed into stoichiometric Ga₂O₃, where Sn atoms separate and form Sn nano-clusters that gradually evaporate in a vacuum atmosphere. As a result, the amount of Sn atoms was reduced from 1.31 to 0.27 at%. Pores formed on the sides of β-Ga₂O₃ : Sn NWs were observed. This increases the ratio of the surface to the volume of β-Ga₂O₃ : Sn NWs.