Production and evaluation of ceramic and metal matrix composite by powder metallurgy | Author : Sylvester O. Omole; Abel A. Barnabas; John F. Akinfolarin | Abstract | Full Text | Abstract :The quest to looking for new materials with improved performance in service is on the increase these days. This is one of the reasons why materials development is essential to reduce the cost of material procurement as well as having better results/performance. It is also what necessitated this research work. Sample of a natural clay deposit was milled in a ball mill to obtain -150 microns and its composition was determined using atomic absorption spectroscopy. -212 microns of iron filing was mixed with the clay in different proportions and compacted to produce 9 samples as follows: sample A 10 % clay with 90 % iron filing, B, 20 % clay 80 % iron filing, C, 30 % clay 70 % iron filing, D, 40 % clay 60 % iron filing, E, 50 % clay 50 % iron filing, F, 60 % clay 40 % iron filing, G, 70 % clay 30 % iron filing, H, 80 % clay 20 % iron filing and sample I, 90 % clay 10 % iron filing. The Compressed samples were sintered in a muffle furnace at a temperature of 1000O C and was held for 2 hours. Each sample was analysed for hardness, porosity, compressive strength and abrasive strength. The optimum results for the above test were obtained when the clay content was not more than 60 %. |
| A model for shear behavior of anchors in external shear walled frames | Author : Iffet Feyza Çirak; Hasan Kaplan; Salih Yilmaz; Özlem Çaliskan Degirmenci; Nihat Çetinkaya | Abstract | Full Text | Abstract :Retrofit of the existing seismically deficient buildings is a common need especially in earthquake prone regions. Chemical anchors are widely used to connect existing and newly added structural elements, such as shear walls. Therefore, modelling the behaviour of anchors which transfer axial and shear forces to the added members is important for design and analyses. There is no anchor model present in the current literature accounting shear behaviour. Therefore, a new model is established using results of a comprehensive experimental study conducted at Pamukkale University Earthquake and Construction Technology Research Laboratory. In this study, mentioned shear model is tested using two- story, one-bay RC frame specimens strengthened with external shear walls. In analyses of the models, SAP 2000 software is used and nonlinear shear behaviour of anchors is represented by NLLink elements. It is concluded that, suggested anchor shear model may be used for modelling external shear wall anchor behaviour. |
| Pristine and coated LiNi1/3Mn1/3Co1/3O2 as positive electrode materials for li-ion batteries | Author : Ahmed. M. Hashem; Rasha. S. El-Tawil; Mohamed Abutabl; Ali. E. Eid | Abstract | Full Text | Abstract :Layered LiNi1/3Mn1/3Co1/3O2 (NMC) positive materials were synthesized by efficient, low cost and easy manageable methods such as oxalate co-precipitation and sol-gel processes. Preliminary electrochemical results show that sol-gel sample provide better results than co-precipitated samples. With the aim to improve the properties of the co-precipitated samples these were coated with carbon and alumina bearing in mind the co-precipitated method is suitable for large scale production. The subsequently performed local structure investigations revealed well crystallized layered cathode materials with a-NaFeO2-type structure (R-3m space group). Sample tests using both the scanning electron microscope (SEM) and the transmission electron microscope (TEM) showed submicron particles with a slight tendency to agglomerate and furthermore the existence of a thin film that encapsulates the oxide particles. 7Li magic angle spinning nuclear magnetic resonance (7LiMAS NMR) measurements were carried out for pristine and coated samples to compare the cation arrangement in the transition metal layers. Finally, electrochemical tests revealed a remarkable improvement in capacity retention of the coated oxides compared to the parent compounds. |
| Characterization and organic vapor sensing properties of Langmuir-Blodgett film using perylendiimide material | Author : Yaser Acikbas; Matem Erdogan; Rifat Capan; Funda Yukruk | Abstract | Full Text | Abstract :LB thin film characterization and vapor sensing applications of 1,7-dibromo- N,N’-(bicyclohexyl)-3,4:9,10- perylendiimide (FY3) materials are reported in this study. The thin film deposition conditions of FY3 materials, which are prepared by LB film technique, are characterized by UV-vis spectroscopy and Quartz Crystal Microbalance (QCM) techniques. The typical frequency shift per layer is obtained as 50.15 Hz / layer and the deposited mass onto a quartz crystal is calculated as 399.36 ng / layer (1.50 ng mm-2). Vapor sensing properties of these LB films against three different volatile organic compounds (chloroform, benzene and toluene) are studied using the QCM technique. The sensitivities to vapors are determined between 3.62 x 10-4 and 1.60 x 10-4 Hz ppm-1. FY3 LB film is more sensitive to chloroform than other vapors. Responses of the FY3 LB film to these vapors are fast, large and reversible. Detection limits are calculated between 0.83 x 104 and 1.88 x 104 ppm. It can be concluded that this FY3 material is promising as a vapor sensing device at room temperature. |
| Effects of permeable cylinders on wake region | Author : Bengi Gözmen; Hüseyin Akilli | Abstract | Full Text | Abstract :This paper investigates the effects of permeable cylinder on vortex shedding downstream of the permeable cylinder in deep water flow by PIV technique. In order to reveal the effect of porosity ß on the vortex shedding, the permeable cylinder having four different porosities (ß = 0.4, 0.5, 0.6 and 0.7) with a diameter of 45 mm have been used. During the experiments, the free-stream velocity is U8= 156 mm/s, which corresponds to the Reynolds number of Re=5000 based on the solid cylinder diameter. The experiments show that the permeable cylinder is effective on the suppression of vortex shedding in the wake region for all porosities and in terms of the inner cylinder-outer permeable cylinder arrangement, it is understood that the inner-outer cylinder arrangement having the diameter ratio of D/d=1.5 is not effective on the attenuation of vortex shedding downstream of the inner cylinder-outer cylinder arrangement as expected. The inner and outer permeable cylinders behave like an impermeable cylinder having the diameter of D=45 mm for the porosities of ß = 0.4, 0.5 and 0.6. The suppression of the large scale vortices is weak. On the other hand, for the porosity ß = 0.7, the peak value of Reynolds shear stress drops to 0.0368 which is less than that of the bare cylinder. The reduction is approximately 10%. |
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