Showing 4 results for Absorption
D. Mostofinejad and M. Hoseinian,
Volume 25, Issue 2 (1-2007)
Abstract
It is well known that the characteristics of concrete components greatly affect the durability of high strength/high performance (HS/HP) concrete against frost action. Undoubtedly, precise recognition of this relationship leads
to appropriate selection of the type and proportions of concrete components in any particular project. In the current study, the aim is to investigate the possibility of developing some mathematical-experimental models to explain the frost resistance of high-performance concrete, regarding the role of some of its main components. To do so, the effects of four key elements, i.e. water, silica fume, coarse aggregate, and number of freeze-thawing cycles, were studied on the frost resistance of HS/HP concrete were studied. 24 concrete mix designs including 3 ratios of water to cementitious materials, i. e. 0.4, 0.3, and 0.25 4 ratios of silica fume to cementitious materials, i.e. 0, 5, 10, and 15 percent and 2 types of coarse aggregates, i. e. Limestone and Quartzite were utilized for HS/HP concrete. Overall, about 432 concrete cubes were cast, cured and tested under freeeze-thaw cycles. Finally, some models were proposed for describing the frost resistance of high strength concrete.
S.m.h. Mirbagheri, M. Daneshmand, Y. Tabatabaie,
Volume 33, Issue 3 (3-2015)
Abstract
In this paper, the behavior of energy absorption of crush-boxes, made of Aluminum foam advanced material, was investigated based on foam cellular structure homogeneity. Therefore, thin-walled tubes of Cu-Zn30wt.%.brass alloy with 27 mm diameter and 1 mm thickness were filled with A356-10vol.%SiC-Xwt.%. of TiH2 foam liquid. Foam samples with 1, 1.5, 2wt.%. of TiH2 were prepared by Form Grip into the brass tubes in order to produce crush-box .Then the crush-boxes as energy absorber elements were compressed by un-axial loading and then behaviors of progressive buckling foams were measured. Results showed by decreasing A356-10vol.% SiC foam density from 0.93 to 0.88 and then 0.43 g/cm3, the energy absorption would be changed from 12955 to 13465 and then to 11192 J, respectively. The sample with 1.5wt.% of TiH2 and density of 0.88 g/cm3 had the maximum energy absorption. Also, the results of foams cellular structure images showed that foams of homogenous cellular structure had a sizeable effect on the progressive buckling behavior. We developed a new parameter as "sorting coefficient", which can release the foams cellular structure non-homogeneity, and change the crush-boxes energy absorption during the progressive plastic buckling.
A. Baradaran, M. Tavoosi,
Volume 37, Issue 3 (12-2018)
Abstract
In the present study, the structural, optical and thermal behaviors of GeO2-PbO-CaO-SrO glasses were investigated to achieve the highest optical properties and thermal stability. Accordingly, different 50GeO2-(50-x)PbO-xCaO and 50GeO2-(50-x)PbO-xSrO (x=0, 10, 20) germanate glasses were prepared by the conventional melt and quench technique between two steel sheets. The produced samples were characterized using X-ray diffraction (XRD), differential thermal analysis (DTA), Fourier transform infrared (FTIR) and UV-Vis spectroscopy. Based on the obtained results, the addition of CaO to glass composition reduced the glass phase forming ability as well as optical and thermal behaviors of the prepared glasses. In contrast, the presence of SrO had no destructive effect on the optical properties of the prepared glasses; the highest values of glass transition (580 oC) and crystallization temperature (831 oC) were achieved in the sample containing 20 mole% of SrO.
S. H. Hashemi Rizi , A. Nourmohammadi Abadchi,
Volume 40, Issue 4 (3-2022)
Abstract
Development of materials with the ideal black body absorption spectrum are of great interest. Such materials could improve the efficiency of solar cells, and passive cooling and heat transfer systems as well as the protective and decorative coatings. Fabricating black anodizing coatings is promising for this purpose because they exhibit low light reflection from the surface. Such coatings can be produced through successive anodizing and black coating of aluminum alloys. In this study, the effect of anodizing repetition on the absorption coefficient of the black anodizing coatings on 2024 aluminum alloy was investigated, as model. All the parameters were fixed in the black coloring stage to evaluate the influence of the anodizing steps. After a one-step anodizing, the black coatings showed an absorption coefficient of 0.956 in the visible region and 0.911 in the of 220 to 2200 nm wavelength range, while their absorption coefficient increased after a three-step anodizing up to 0.982 in the visible region and up to 0.966 in the 220 to 2200 nm wavelength range. This indicates that anodizing repetition helps the optical absorption of black anodizing coatings to approach the optical absorption of an ideal black body.
