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장인준,성영은,유성종 한국공업화학회 2018 한국공업화학회 연구논문 초록집 Vol.2018 No.0
In this study, we present a novel, facile and totally green approach toward the synthesis of atom or nanoparticle electrochemical catalyst by PVD with water soluble powder, glucose. PVD is employed for the facile preparation of various metal atom or NP, including noble metals, alloys, and transition-metal (oxides). In this strategy, glucose act as not only carrier for the transport of metal atom or nanoparticle from the bulk materials to the support surfaces but also stabilizer through their OH moieties of the glucose surfaces, which prevent the agglomeration of atoms and NPs during the synthesis process. This strategy can be extended to prepare atoms or NPs on a range of supports, such as carbon nanotubes, graphene oxide, and TiO2, thereby demonstrating its generality Furthermore, the prepared catalysts exhibited an improved activity for various electrochemical reactions, mainly attributed to their high surface area.
장인준,성영은,유성종 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
Highly active Ni<sub>x</sub>P<sub>y</sub> catalysts for HER are prepared using modified thermal decomposition method. In this process, nickel oxide (NiO) powder reduced to Ni<sub>x</sub>P<sub>y</sub> by phosphine gas (PH<sub>3</sub>) produced from sodium hypophosphite (NaH<sub>2</sub>PO<sub>2</sub>). Unlike conventional method, NiO is phosphidized from bi-located P source (NaH<sub>2</sub>PO<sub>2</sub>). Synthesized Ni<sub>x</sub>P<sub>y</sub> catalysts had multi-phase crystalline structure (Ni<sub>2</sub>P, Ni<sub>5</sub>P<sub>4</sub> and NiP<sub>2</sub>) and the Ni<sub>x</sub>P<sub>y</sub> with higher P content exhibited the smaller crystallite size. (Ni<sub>2P<50</sub>, <sub>Ni5</sub>P<sub>4</sub>~10, NiP<sub>2</sub>~2 nm). Consequently, Ni<sub>5</sub>P<sub>4</sub> and NiP<sub>2</sub> nanoparticles with higher HER activity are supported on micro-scaled Ni<sub>2</sub>P with better conductivity. The Ni<sub>x</sub>P<sub>y</sub> catalysts showed exceptionally higher HER activity in acidic media than single-phased Ni<sub>2</sub>P or Ni<sub>5</sub>P<sub>4</sub>. Therefore, modified phosphidation method and hierarchical structure of Ni<sub>x</sub>P<sub>y</sub> catalyst provide new instruction for designing excellent HER catalysts.
장인준,박일욱,이우식 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.4
To predict ultrasonic guided waves generated by a piezoelectric transducer (PZT) in a structure accurately, the dynamic coupling betweenthe base structure and the surface-bonded PZT must be modeled accurately and analyzed in an efficient way. For so-called smartbeams, which consist of a metallic base beam and a surface-bonded PZT layer, we propose a spectral element model that has the capabilityto accurately predict high frequency dynamic responses and guided waves. For the spectral element model, Timoshenko beam theoryis applied to both the base beam and PZT layer, and Mindlin-Herrmann rod theory is adopted to account for the effects of lateral contractionin the thickness direction of the base beam. The high accuracy of the spectral element model is validated by comparing the results ofthe spectral element model with conventional finite element method (FEM) results and results from the commercial finite element analysispackage ANSYS. The effects of PZT-induced axial-bending coupling and structural damping on the dynamics and guided waves arethen investigated using numeral simulation.