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- 검색키워드
- 저자 : A. M. El‑Taher (검색결과 3 건)
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A. M. El‑Taher,A. F. Razzk 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.10
Preventing the formation of large platelets of Ag3Snintermetallic compounds (IMCs) during solidification of solder jointshas become a significant challenge in the design of Sn–Ag–Cu lead-free solder alloys. Large platelets of Ag3Snare generallyconsidered as undesirable as their presence can create solidification defects and causes mechanical property anisotropy. In the present work, the synergetic effects of adding 0.1 wt% of Fe, Co, Te and 2 wt% Bi to Sn–3.0Ag–0.7Cu (SAC 307)solder are studied in terms of the growth of large platelets Ag3SnIMCs and the resulting alloy’ creep resistance as well astheir thermal behavior. Although minor Fe, Co, Te and Bi alloying elements addition causes large increase in the degree ofundercooling from 3.4 to 22.3 °C with maintaining the pasty range and melting temperature at the same levels, the modifiedSAC307–FeTeCoBi alloy exhibits considerable increase in creep resistance (~ 10 times) and large fracture life-time thanSAC (307) solder at same stress levels and testing temperatures. This is attributed to the transition of Ag3SnIMCs from largeplatelets into fine needle-like morphology and formation of new (Cu,Co)6Sn5, FeSn2,SnTe IMCs and Bi particles, whichcould provide more obstacles for dislocation movement at the interphase boundaries.
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Influence of thiourea synthesis with silica fume on the corrosion rate of reinforcement concrete
Tawfik Taher A.,El-Yamani Magdy A.,Serag Faried A.,Mohammed Shimaa M.,AbdEl-Hafez Gh.M. 한국자원공학회 2020 Geosystem engineering Vol.23 No.3
The examination of corrosion rate for steel reinforcement existent in concrete was carried out in the presence of silica fume and thiourea. The ordinary Portland cement (OPC) replacement was conducted with silica fume material at 5 and 10% by cement weight for concrete production, in addition to that using various percentage of thiourea (1, 2, 3 4 and 5%) added to concrete. Monitoring and estimating the corrosion rate for reinforcing steel existent in concrete with and without silica fume and thiourea was held with the usage of corrosion test cell. Besides, compressive and splitting tensile strength submerged in fresh and salty water of hardened concrete with and without silica fume and thiourea that were considered in the study. The immersion for all the samples of steel reinforcement with salty water (tap water with 1.5% of calcium sulphate and 3% of sodium chloride) for about 90 days of exposure were studied. The best results for the lowest corrosion rate were obtained when a mixture of silica fume with thiourea is used with concentrations of 10 and 3%, respectively compared with the ordinary concrete.
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Enhancement and optimization of gamma radiation shielding by doped nano HgO into nanoscale bentonite
Elhassan A. Allam,Rehab M. El-Sharkawy,Atef El-Taher,E.R. Shaaban,RedaElsaman,E. El Sayed Massoud,Mohamed E. Mahmoud 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.6
In this study, nano-scaled shielding materials were assembled and fabricated by doping different weightpercentages of Nano-mercuric oxide (N-HgO) into Nano-Bentonite (N-Bent) based on using (100-x% NBent þ x% N-HgO, x ¼ 10, 20, 30, and 40 wt %). The fabricated N-HgO/N-Bent nanocomposites werecharacterized by FT-IR, XRD, and SEM and evaluated to evaluate their shielding properties toward gammaradiation by using four different g-ray energies form three point sources; 356 keV from 133Ba, 662 keVfrom 137Cs as well as 1173, and 1332 keV from 60Co. The g-rays mass attenuation coefficients were plottedas a function of the doped N-HgO concentrations into N-HgO/N-Bent nanocomposites. The computedvalues of mass attenuation coefficients (mm), effective atomic number (Zeff) and electron density (Nel) bythe as-prepared samples were found to increase, while the half value layer (HVL) and mean free path(MFP) were identified to decrease upon increasing the N-HgO contents. It was concluded also that theincrease in N-HgO concentration led to a direct increase in the mass attenuation coefficient from 0.10 to0.17 cm2/g at 356 keV and from 0.08 to 0.09 cm2/g at 662 keV. However, a slight increase was observed inthe identified mass attenuation coefficients at (1172 and 1332 keV).
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