Wyniki wyszukiwania - Biblioteka Nauki

1

Study on Improvement of Surface Properties of SKD61 Powder on S45C Using Laser Cladding

100%

Kim C.-W. , Yoo H.-S.

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tom Vol. 67, iss. 4

1465--1468

EN

In this study, we investigated the effect of cladding on structural carbon steel (S45C) using 5%Cr-1.5%Mo-Fe powder (SKD61), which is expected to show economically efficient production of die-casting parts. The process conditions were performed under argon atmosphere using a diode laser source with specialized wavelength of 900-1070 nm, and the output conditions were 3, 4, and 5 kW, respectively. After the cladding was completed, the surface coating layer’s shape and the microstructure were analyzed. The hardness test was carried out with Micro Vickers hardness tester under 500 gram-force along the normal line at the interval of 0.2 mm from the surface to core direction on the cross-sectional area. In addition, polarization curve test of the surface coating layer was performed to investigate the corrosion resistance characteristics.

2

Study Of Rust Preventive Characteristics Of Rust Preventive Oil From Polarization Curve Measurement

75%

Iwashima D. , Ejiri K. , Nagase N. , Hatekeyama M. , Sunada S.

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2015

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tom Vol. 60, iss. 2A

915--917

EN

Fe-Cu-C sintered steels are widely used as powder materials, because of its small volumetric shrinkage. However, Cu, which acts as cathode enhance formation of rust Fe2O3·xH2O during fabrication. To prevent formation of Fe2O3·xH2O rust preventive oils are widely used. High viscosity of those rust preventive oils decrease workability. While, low viscosity degrade rust preventive performance. Therefore, it is necessary to develop new rust preventive oils with contradictory properties of low viscosity and superior rust prevention. In this study, we developed technique to quantitatively evaluate rust prevention ability by measuring polarization curve through thin corrosive solution on Fe-Cu-C sintered steels coated with rust preventive oils. The electrochemical measurements were carried out in corrosive solution of 0.35 mass % NaCl. Using a double capillary was added dropwise to the specimen. From the experimental, it is possible to evaluate the corrosion rate quantitatively in the surface of specimen, which was coated with rust preventive oil through thin corrosive solution. From the measurement results, Corrosion rate is reduced by coating the rust preventive oil. Especially, corrosion rate of the specimen coated with oil that showed best performance indicated 10000 times better than that of without oil ones. Zn addition negative correlation between corrosion rate and period of potential oscillation.

PL

Spiekane stale Fe-Cu-C są szeroko stosowane jako materiały proszkowe, ze względu na mały skurcz objętościowy. Jednak miedź, która zachowuje się jak katoda, wpływa na zwiększone powstawanie rdzy Fe2O3·xH2O w procesie wytwarzania stali. Aby zapobiec tworzeniu się Fe2O3·xH2O stosuje się oleje ochronne. Jednak wysoka lepkość olejów zmniejsza ich urabialność, natomiast niska lepkość zmniejsza ich właściwości ochronne. Z tych względów konieczne jest opracowanie nowego typu olejów przeciwrdzewnych charakteryzujących się zarówno niską lepkością jak i dobrymi właściwościami ochronnymi. W niniejszej pracy opracowano metodę ilościowej oceny właściwości ochronnych olejów za pomocą pomiaru krzywej polaryzacji poprzez cienką warstwę roztworu korozyjnego na spiekanych stalach Fe-Cu-C pokrytych olejami ochronnymi. Pomiary elektrochemiczne zostały przeprowadzone w roztworze korozyjnym NaCl (0,35 %wag.). Roztwór został naniesiony na próbkę za pomocą kapilary. Na podstawie wyników eksperymentalnych można ilościowo oszacować szybkość korozji zachodzącej na powierzchni próbki. Badania wykazały, że olej ochronny zmniejsza szybkość korozji. Olej dla którego otrzymano najlepsze wyniki wykazał poprawę właściwości ochronnych 10000 krotnie w porównaniu z próbkami bez oleju. Dodatkowo stwierdzono korelację pomiędzy szybkością korozji a okresem oscylacji potencjału.

3

Technical and Economical Evaluation of Proton Exchange Merobrane (PEM) Fuel Cell for Commercial Applications

63%

Katyara S. , Iżykowski J. , Staszewski Ł. , Shaikh F.

Present Problems of Power System Control

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2017

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tom Nr 8

41--49

EN

The green energy sources are the utmost needs of today’s world where the reserves of fossil fuel are depleting day by day. The Distributed Generation (DG) has become integral part of power system at commercial level. The most efficient among all DGs and Renewable Energy Sources (RES) is the Fuel Cell (FC) power generation. The fuel cell invariably converts chemical energy directly into electricity. The Fuel cells have normally 60 to 70% efficiency at working conditions. The polarization curve of fuel cell plays important role in improving its efficiency. This research presents the mathematical and Simulink modeling 6 kW, 45 Vdc of Proton Exchange Membrane (PEM) fuel cell. The input thermodynamic parameters of fuel cell are varied and their effects on the output electrical variable are observed. The DC/DC boost converter is used to step up the voltage of fuel cell to 100 Vdc at commercial usable level. A new mathematical equation is presented to improve the efficiency of fuel. The mathematical results are then varied through Simulink results.

4

Theoretical approach to the physics of fuel cells

51%

Wijewardena Gamalath K. A. I. L. , Peiris B. M. P.

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tom Vol. 2

15-27

EN

Ion transport rate of PAFC, AFC, PEMFC, DMFC and SOFC fuel cells under the influence of an electric field and concentration gradient were evaluated for static electrolytes. AFC are the best fuel cells for high er current applications while direct methanol fuel cells DMFC are the best for lower current applications AT lower temperatures. An equation for voltage output of a general fuel cell was obtained in terms of temperature and partial pressure of reactants. Performance of a 2D fuel cell was analyzed by simulating polarization and power curves for a fuel cell operating at 60 ?C with a limiting current density of 1.5 A cm- 2. The maximum power for this fuel cell was 8.454 W delivering 82% of maximum loading current density. When the temperature was increased by one third of its original value, the maximum power increased by 6.75% and at 60 ?C for a 10 times increment of partial pressure of reactants, the maximum power increased by 2.43%.The simulated power curves of the fuel cells were best described by cubic fits.