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Spectral Properties of GaS Nanoparticles Obtained by Laser Ablation
Arif Pashayev,
Aydin Ulubey,
Kerim Allahverdiev,
Sami Sozeri,
Majda Hadzic
Issue:
Volume 7, Issue 1, January 2018
Pages:
1-5
Received:
14 August 2017
Accepted:
29 August 2017
Published:
2 January 2018
Abstract: Bulk single crystals of GaS were grown by Bridgman-Stockbarger method in an evacuated (10-6 Torr) quartz ampoules of optical quality. Nanoparticles of quasi 2-D GaS crystals were obtained by laser ablation (LA) technique (KrF Excimer laser at 248 nm (COHERENT COMPex 201), and characterized by: XRF, GDOES, SEM, TEM and UV-VIS absorption spectroscopy. Nanoparticles obtained for the first time were ablated by using of excimer KrF laser operated at f = 50 Hz with pulse duration t = 4 ns and maximum energy 200 mJ. Obtained results are analyzed with respect to particle size. Absorption spectra of particles with diameter less than 18 nm turned out to be shifted in the blue range of spectra. Blue shift in the optical absorption spectra of GaS nanoparticles with decreasing the particle sizes was explained by presence of nanocrystals in the quantum size regime. These results are consistent with a perturbation of GaS band structure due to carrier confinement, resulting in a widening of the forbidden gap.
Abstract: Bulk single crystals of GaS were grown by Bridgman-Stockbarger method in an evacuated (10-6 Torr) quartz ampoules of optical quality. Nanoparticles of quasi 2-D GaS crystals were obtained by laser ablation (LA) technique (KrF Excimer laser at 248 nm (COHERENT COMPex 201), and characterized by: XRF, GDOES, SEM, TEM and UV-VIS absorption spectroscopy...
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Synthesis of Moderate Water-Uptake and Low Methanol Permeable Polymer Electrolyte Membrane from Functionalized Polyisoprene Impregnated Carbon Nanotubes
Issue:
Volume 7, Issue 1, January 2018
Pages:
6-12
Received:
16 October 2017
Accepted:
7 December 2017
Published:
2 January 2018
Abstract: The study of the synthesis of polymer electrolyte membrane exhibiting moderate water uptake and low methanol permeation for fuel cell application using functionalized polyisoprene impregnated with carbon nanotubes (CNTs) was carried out. The functionalization of the polymer with chlorosulphonic acid of different initial concentrations of 0.0013, 0.001, 0.0017, and 0.0023 mol/L at the minimum time of 1hr produced ion exchange capacities (IEC) of 1.22, 1.92, 2.74, and 4.92 mmol/g, respectively, and at the maximum sulphonation time of 18hrs the IEC were 7.74, 8.78, 11.10, and 16.93 mmol/g, respectively. Their corresponding degrees of sulphonation (DS) for 1hr were 3.53, 5.55, 7.91, and 14.21%, respectively, and while at 18hrs their corresponding DS were 22.35, 25.37, 32.04, and 48.88%, respectively, which implies that IEC and DS are directly proportional to the concentration of acid used and reaction time. Result also showed that synthesized membrane without carbon nanotubes absorbed so much of it weight in water; 31.34 and 73.97% of its weight in both 1 day and 6 days for membrane with 48.88% DS. Whereas the membrane that was impregnated with CNTs of the same DS exhibited a lesser absorption of 23.23 and 53.23% of its weight in both 1 day and 6 days, thereby reducing the high water uptake of the membrane that would have affected it negatively by 1.3 fold. Apart from the conductivity of the synthesized membrane witnessing an increase by 1 order with the membrane impregnated with CNTs from 10-3 S/cm to 10-2 S/cm, it was also found out that the methanol crossover was lower than that of commercial Nafion, where membrane impregnated with CNTs had methanol crossover improvement with a difference of 0.48 Mol/L over its counterpart without CNTs as a result of the presence of CNTs.
Abstract: The study of the synthesis of polymer electrolyte membrane exhibiting moderate water uptake and low methanol permeation for fuel cell application using functionalized polyisoprene impregnated with carbon nanotubes (CNTs) was carried out. The functionalization of the polymer with chlorosulphonic acid of different initial concentrations of 0.0013, 0....
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Effect of Lead Additions on Microstructure and Casting Properties of AZ91 Magnesium Alloy
Erkan Koc,
Mehmet Unal,
Yunus Turen,
Halil Ahmet Goren,
Ercan Candan
Issue:
Volume 7, Issue 1, January 2018
Pages:
13-17
Received:
7 November 2017
Accepted:
24 November 2017
Published:
2 January 2018
Abstract: In this study, the effect of Pb element addition varied between 0.2 - 0.4 wt.% on the microstructure and casting properties of AZ91 magnesium alloy were investigated. The microstructural results showed that as increasing Pb additions into the AZ91 alloy, the grains and the Mg17Al12 intermetallic phase becomes thinner. When examining the effect on casting properties; It was observed that the fluidity of AZ91 alloy increased as the increasing of Pb additions. In the hot tear tests two different mold systems were used. Hot tearing were observed in the longest section in the tests using "the mold same diameter, different lengths" and when the "the mold different diameter, same lengths" were used, hot tears were observed in all of the molds with diameters of 6, 8, 10 mm. Hot tearings were observed in 0.2 wt.% and 0.3 wt.% Pb additions, while hot tearing was not observed when this ratio increased to 0.4% for the 12 mm diameter test specimens. There was also not hot tearing were observed in any sample when the sample diameter was 16 mm.
Abstract: In this study, the effect of Pb element addition varied between 0.2 - 0.4 wt.% on the microstructure and casting properties of AZ91 magnesium alloy were investigated. The microstructural results showed that as increasing Pb additions into the AZ91 alloy, the grains and the Mg17Al12 intermetallic phase becomes thinner. When examining the effect on c...
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Improvement of Adhesive Strength of Poly(tetrafluoroethylene) Plates through Oxygen Plasma Treatment and Subsequent Photografting of Methacrylic Acid
Kazunori Yamada,
Marie Tachi,
Yuji Kimura
Issue:
Volume 7, Issue 1, January 2018
Pages:
18-27
Received:
12 September 2017
Accepted:
26 September 2017
Published:
5 January 2018
Abstract: Methacrylic acid (MAA) was grafted onto the surface of a poly(tetrafluoroethylene) (PTFE) plate by the combined use of the plasma treatment and photografting, and the adhesive strength between the MAA-grafted PTFE (PTFE-g-PMAA) plates with the same grafted amounts was investigated in relation to the location of grafting as well as the wettability and water absorptivity. The grafted amount at which the substrate breaking occurred at lower grafted amounts for the PTFE-g-PMAA plates prepared by the plasma treatment for shorter times before the photografting and by the photografting at higher monomer concentrations and/or at lower monomer concentrations after the plasma treatment. These grafting conditions are found to be factors affecting the location of photografting, the thickness and water absorptivity of the grafted layer, and wettability of the surface of the grafted layer. The substrate breaking was observed at the minimum grafted amount (about 2.2 µmol/cm2) for the PTFE-g-PMAA plates prepared at 2.0 M and 60°C after the plasma treatment for 10 s and at 2.0 M and 40°C after the plasma treatment for 120 s. The obtained results support that the combination of the oxygen plasma treatment with photografting of MAA is an effective procedure to enhance the adhesivity of the PTFE surface.
Abstract: Methacrylic acid (MAA) was grafted onto the surface of a poly(tetrafluoroethylene) (PTFE) plate by the combined use of the plasma treatment and photografting, and the adhesive strength between the MAA-grafted PTFE (PTFE-g-PMAA) plates with the same grafted amounts was investigated in relation to the location of grafting as well as the wettability a...
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Manufacturing of Ø 1,000 Grade Large Diameter Round Bloom and Development of Cost Effective Hot Forging Process Using the Round Bloom
Hisang Chang,
Jinmo Lee,
Namyong Kim,
Chaehun Lee,
Sanghyun Heo,
Sunryong Yoon,
Byeong Don Joo
Issue:
Volume 7, Issue 1, January 2018
Pages:
28-32
Received:
1 December 2017
Accepted:
12 December 2017
Published:
17 January 2018
Abstract: Taewoong is an open die forging company, specialized in the production of hot forged and ring rolled parts. Recently, Taewoong utilized continuous casting facilities that can manufacture Ø 1,000 grade large diameter round bloom to increase competitiveness of the company. This study focuses installed continuous casting facilities and ring rolling process using manufactured Ø 1,000 grade round bloom. Constitution of installed facilities was introduced and characteristics of the facilities, EAF (Electric Arc Furnace), LF (Ladle Furnace), VD (Vacuum Degassing), VOD (Vacuum Oxygen Decarburization) and CC (Continuous Casting) were described. Also, ring rolling experiments were performed using manufactured Ø 1,000 grade round bloom. Hot forging process design was performed to fabricate sound products. Work sequence design was performed using FE analysis software and optimal forging work sequence was derived. With the results, sound forged parts were formed and improvement of competitiveness was verified. Raw material recovery ratio was increased and the number of process and processing time were decreased. The results show utilized continuous cast facilities give opportunity to be a world competitive company by increasing competitiveness of the company.
Abstract: Taewoong is an open die forging company, specialized in the production of hot forged and ring rolled parts. Recently, Taewoong utilized continuous casting facilities that can manufacture Ø 1,000 grade large diameter round bloom to increase competitiveness of the company. This study focuses installed continuous casting facilities and ring rolling pr...
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