Battery-type electrodes of three-dimensional (3D) hierarchical cobalt hydroxide carbonate arrays on Ni foam were fabricated using a hydrothermal method for use in supercapacitors. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize their structures and morphologies. The cobalt hydroxide carbonate synthesized with 10 h reaction time showed the highest specific capacitance (1381 F g−1 at a current density of 2 A g−1) and excellent cycling stability (92% capacitance retention after 5000 cycles). Moreover, its capacitance increased by 33% at 2 A g−1 and by 10% at 20 A g−1 after 5000 charge–discharge cycles. This cobalt hydroxide carbonate composite is a promising candidate for electrochemical energy-related applications
Abstract:The major environmental impact of concrete comes from the CO 2 emissions, produced during the cement manufacturing process. The main goal of this research project is to evaluate the efficiency of limestone powder as a partial cement replacement, in order to reduce energy consumption and CO 2 emissions. This study utilizes limestone powders, with different particle sizes, to replace a portion of Portland cement using various ratios. Due to the dilution effect when partially replacing cement, there is a reduction in the concrete's physical properties. To assess the dilution effect, a modification to Féret's equation is used to calculate an efficiency factor for the limestone powder when compared to cement. To measure the environmental impact, a life cycle assessment is conducted on concrete made with limestone powder combined with cement. This allows for an evaluation of the various cement/limestone powder ratios that will maximize the environmental benefit, with minimal reduction in concrete strength. Additional microstructural analysis using petrographic examination was completed to provide a visual understanding of the distribution of the limestone particles within the cement paste. The results indicate that the efficiency of limestone powder in partially replacing cement can be achieved by particle packing and particle distribution in the concrete and the benefits of emission reductions exceed the loss in compressive strength when higher levels of limestone powder is used to replace cement.
Geosynthetics is a crucial mechanism in which the earth structures can be mechanically stabilized through strength enforcing tensile reinforcement. Moreover, geosynthetic reinforcement stabilizes steep slopes through incorporating the polymeric materials, becoming one of the most cost-effective methods in not only accommodating budgetary restrictions but also alleviating space constraints. In order to explicate on the applicability and widen the understanding of geosynthetic reinforcement technology, a synthesis study was conducted on geosynthetic reinforced steep slope. This study is very important because in not only highlighting the advantages and limitations of using geosynthetic reinforcement but also in investigating the current construction and design methods with a view to determining which best practices can be employed. Furthermore, this study also identified and assessed the optimal condition of the soil, performance measures, construction specifications, design criteria, and geometry of the slope. To further concretize the understanding of these parameters or factors, two case studies were reviewed and a summary of the best practices, existing methods, and recommendations were drawn in order to inform the employment of geosynthetics in reinforcing steep slopes.
To successfully process concrete, it is necessary to predict and control its flow behavior. However, the workability of concrete is not completely measured or specified by current standard tests. Furthermore, it is only with a clear picture of cement hydration and setting that full prediction and control of concrete performance can be generalized. In order to investigate the rheological properties of blended cement pastes, a rotational viscometer (RV) was used to determine the flow characteristics of ordinary and blended pastes to provide assurance that it can be pumped and handled. Additionally, a dynamic shear rheometer (DSR) was used to characterize both the viscous and elastic components of pastes. Ordinary Portland cement paste and blended pastes (slag, fly ash, and silica fume) were investigated in this study. e stress and strain of the blended specimens were measured by the DSR, which characterizes both viscous and elastic behaviors by measuring the complex shear modulus (the ratio of total shear stress to total shear strain) and phase angle (an indicator of the relative amounts of recoverable and nonrecoverable deformation) of materials. Cement pastes generally exhibit different rheological behaviors with respect to age, mineral admixture type, and cement replacement level.
This study, to evaluate the technology of the fire resistance design of Reinforced Concrete columns based on fire resistance performance design, was suppose to use as basic data for performance design through a measure of temperature and deformation using heat transfer analysis and Heat-load test of the Reinforced Concrete columns as parameter is the axial load ratio. In accordance with axial load without eccentricity, the load ratio of 0.30, 0.35, 0.40 and 0.47 were imposed on columns. As a result of this study, 0.40 or more of axial load ratio can be ensured that the fire resistance performance was considered satisfactory. 하였다. 우선, 구성재료의 열적 특성을 고려한 부재의 열전달 해 † Corresponding Author, E-Mail: yeo@kict.re.kr †
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