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991.
Abdelhedi Mohamed Mnif Thameur Abbes Chedly 《Russian Journal of Nondestructive Testing》2018,54(5):345-355
This paper discusses the ability of ultrasonic wave velocity to evaluate some physical parameters within mortar. The behavior of ultrasonic pulse velocity within mortar subjected to incremetal stress was also studied. For experimentation, we carried out ultrasonic measurements on mortar samples before and during uniaxial compressive strength, perpendicularly to the stress direction. The water/cement ratios were varied in order to contribute certain specific characteristics. A set of expressions was obtained linking the initial velocities of longitudinal ultrasonic waves with compressive strength, density, porosity and load at elastic limit.The evolution of ultrasonic velocity through mortar samples under continuous incremental uniaxial stress were also investigated. The results illustrated the behavior of ultrasonic pulse velocity as a function of the applied stress. It was observed that velocity did not decrease under initial loading and until about 70% of the ultimate stress, where sudden decrease occurred, followed by the failure of the material. 相似文献
992.
Synthesis of cadmium sulfide‐reduced graphene oxide nanocomposites by pulsed laser ablation in liquid for the enhanced photocatalytic reactions in the visible light 下载免费PDF全文
Redhwan A. Moqbel Mohamed A. Gondal Talal F. Qahtan Mohamed A. Dastageer 《国际能源研究杂志》2018,42(4):1487-1495
The large‐scale applications of cadmium sulfide (CdS) nanoparticles (NPs) as a photo‐catalyst are limited by their poor stability (high aggregation tendency) and consequent reduction in the surface area and increased rate of recombination of photoinduced electron‐hole pairs, despite its inherent positive feature of being visible light active. It has been reported that the photocatalytic performance of CdS can be considerably improved if CdS is made as a composite material with reduced graphene oxide (rGO) in an optimum ratio. In this work, for the first time, we adopted the technique of pulsed laser ablation in liquids (PLAL) to synthesize highly pure CdS NPs and the required CdS/rGO nanocomposites using high purity (99.9%) microstructured CdS and graphene oxide as chemical precursors. PLAL is a simple and rapid 1‐step synthesis process (where the reaction time is reduced from several hours to a few minutes), which does not require high temperature, toxic chemicals, and the final treatment to remove the unwanted by‐products. The optical and morphological characterizations revealed that the anchoring of CdS on rGO transformed the CdS/rGO composite into an efficient photo‐catalyst by enhancing the following positive attributes required for a good photo‐catalyst: (1) The inherent tendency of aggregation of CdS is considerably reduced; CdS NPs with an average grain size of 20 nm are well placed on the rGO sheets; and hence, the surface area of the catalyst was significantly increased to provide more active sites. (2) The reduced rate of photoinduced electron‐hole recombination manifested in the photoluminescence spectrum indicated the effective charge separation. (3) The enhanced light absorption in the visible/infrared region ensured the effectiveness of this material in naturally abundant solar radiation. In the CdS/rGO composite, the rGO sheets play the role of a supporting matrix, cocatalyst, and electron acceptor for CdS. To evaluate the photo‐catalytic performance of CdS/rGO, we applied it as a visible light‐driven photo‐catalyst for degrading methylene blue dye and found that CdS/rGO nanocomposite was more efficient than pure CdS in the visible spectral region. Therefore, PLAL provides a simple and 1‐step route to synthesize high‐purity visible light–driven photo‐catalysts and solar cell material. 相似文献
993.
994.
Doddamani Saleemsab Kaleemulla Mohamed 《Journal of Failure Analysis and Prevention》2019,19(3):730-737
Journal of Failure Analysis and Prevention - This paper exhibits the investigative work conducted on fracture toughness of aluminum–graphite metal matrix composites. The materials chosen for... 相似文献
995.
Cissé Mohamed N'guessan Elise Tia V. Etienne Gérard Loiseau Didier Montet 《Journal of Food Safety》2020,40(3):e12785
Lactoperoxidase system (LPOS) was incorporated into chitosan solutions (0.5, 1, and 1.5%) to protect mangoes against two strains of fungi. Coating solutions effectiveness in vitro (in Petri dish) and in vivo (on mango) were studied on fungal (Phomopsis sp. RP257 and Pestalotiopsis sp.) growth isolated from mango cv Amelie. In vitro, chitosan concentration at least 1% containing or not LPOS effectively inhibited Pestalotiopsis sp. growth at 100%. Presence of LPOS or Lactoperoxydase system with iodine (LPOSI) in chitosan at 0.5% increased the percentage of inhibition from 26 to 93%. Edible films with LPOS inhibited Phomopsis sp. RP257 particularly when LPOS was incorporated in chitosan concentrations of 1 and 1.5%. Iodine did not influenced antifungal activity of LPOS against Pestalotiopsis sp. but decreased activity antifungal toward Phomopsis sp. RP257. The properties (water vapor permeability and mechanical properties) of chitosan films were not significantly changed by the incorporation of the enzyme system. in vivo condition, chitosan coating at 1 and 1.5% with or without enzyme system was sufficient to inhibit totally (100%) Pestalotiopsis sp. and was 60% efficient against Phomopsis sp. with chitosan only at 1 and 1.5%. However, when coating solution mainly at 1 and 1.5% was enhanced by LPOS with or without iodine, it inhibited totally (100%) Phomopsis sp. RP257. The presence of iodine slightly reduced antifungal activity against Phomopsis sp. RP257. 相似文献
996.
Mohamed Janshir Bin Gulam Mohamed Hafiz Abdul Mannan Rizwan Nasir Dzeti Farhah Mohshim Hilmi Mukhtar Aymn Abdulrahman Anas Ahmed 《应用聚合物科学杂志》2020,137(12):48476
Membrane technology has been considered a key factor for sustainable growth in high-efficiency gas separation. Current mixed matrix membranes (MMMs) technology is rising, but these membranes in the dense structure are having difficulties in operating at high pressures and scale up for commercialization. The purpose of this research is to synthesize composite MMMs (CMMMs) consisting of polyethersulfone (PES), carbon molecular sieve (CMS 1–5 wt %), and Novatex 2471 nonwoven fabric (support layer). The membranes' physical, chemical, and thermal properties were evaluated by different analytical equipment. The morphology of both PES and PES-CMS composite membranes had a porous and asymmetric structure, in which CMS was uniformly distributed in the polymer matrix. The thermal properties showed that the membranes were stable up to 350 °C with a single glass transition temperature. The functional groups in the membrane were confirmed by spectral analysis. The gas performance results showed that carbon dioxide permeance increased with increased CMS concentration and methane permeance decreased due to the hindering effect of CMS under similar operating conditions. The highest selectivity achieved was 12.774 using CMMM of 5 wt % of CMS at 10 bar, which on average was 137.80%, improved selectivity compared to pure PES membrane. The support layer was able to withstand high operating pressures and showed the ability to scale up. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48476. 相似文献
997.
998.
Because of the superior photocatalytic activities of nanocrystalline TiO2 and ZnO under UV irradiation, they were embedded into the glass system (SiO2, TiO2, ZnO, B2O3, Na2O, K2O, P2O5, Li2O and BaO) to provide easy separation from the aqueous system. Different contents of TiO2 and ZnO have been investigated. Conversion to glass-ceramic materials was carried out by heat treatment at 450 °C, which is the onset of the nucleation peak according to the differential thermal analysis (DTA) result, for different times. This heat treatment regime preserves the transparency of the prepared materials in the visible region and good absorption in the UV region. The high content of TiO2 or ZnO caused an improvement of microhardness of the prepared materials, though the presence of the two oxides with the same ratio decreased the microhardness values. Photocatalytic activity of the prepared glass-ceramic materials was investigated according to their efficiency for the degradation of humic acid (HA), the major precursor of disinfection by-products (DBPs), from water. All samples were proved to be photoactive with different extents. Four hours heat treatment at 450 °C appears to be the best conditions for the development of TiO2 and ZnO crystals leading to better photocatalytic activity. 相似文献
999.
1000.