how to synthesize conductive phase and prepare conductive pastes has received much attention in current researches. In most pastes, the precious metal silver is traditionally used as a high performance conductive phase because of its high electrical conductivity and stability. However, due to the high cost and scarcity of silver, there is a need to develop suitable replacements for pure silver. In addition, the performances of conductive paste with new conductive phase should be comparable with those Ag conductive pastes.To date, one of the strategies is to replace the Ag with less-expensive metals, such as Cu [5] and Ni [6]. Conductive pastes contain less-expensive metals exhibit good electrical conductivities while lack of stability. Carbon materials is another choice to replace Ag. However, carbon based conductive pastes [7,8] are disadvantage in electrical conductivity even though they show good stability. Except for these two methods, using composites made of Ag and carbon materials as conductive phase seems to be a better route, which have been proved by some research work [9][10][11][12].Compared with conventional carbon materials, graphene, a sp 2 -bonded two-dimensional (2D) carbon material, is more attractive as a component of composite due to its high electronic conductivity [13], high specific surface area [14] and high mechanical strength [15]. Herein, we report a facile preparation of Ag/chemically reduced graphene (Ag/G) nanocomposite by an in situ one-pot solvothermal route and demonstrate its use in conductive paste. Via in-situ solvothermal process, spherical Ag particles with a size less than 100 nm are wrapped by graphene. It was found that conductive paste contain this nanocomposite exhibits low sheet resistance and good stability after cured, which made us believe that the Ag/G nanocomposite is competent for preparation of conductive paste.
AbstractIn this work, we succeeded in the synthesis of Ag/chemically reduced graphene (Ag/G) nanocomposite by a facile in situ one-pot solvothermal route. X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectra and Fourier transform infrared spectroscopy results revealed the formation of Ag and the reduction of graphite oxide to graphene during the one-pot process. Scanning electron microscopy observation indicated that spherical Ag particles with a size less than 100 nm are wrapped by graphene. The Ag/G nanocomposite was used in a low temperature conductive paste. Thermal analysis was conducted to determine the proper curing process of the Ag/G conductive paste. The Ag/G conductive paste that contains 0.6 wt% graphene exhibits low sheet resistance (22 mΩ/sq/25 µm) and good stability after cured at 150 °C for 30 min, which made us believe that the Ag/G nanocomposite is a promising candidate for conductive paste.
The properties of chloride penetration of hybrid fiber reinforced self-compacting concrete (SCC) were investigated in this study. The results show that the chloride penetration resistance of concrete can be improved by single incorporation either carbon or cellulose fibers. The concrete chloride diffusion coefficient D RCM of 12-cm length carbon SCC with fiber content of 1.7, 2.72, and 3.4 kg/m 3 decreases by 10.3, 25.5, and 18.2% compared to reference concrete without any fibers, respectively. Moreover, the concrete chloride diffusion coefficient D RCM of cellulose SCC with fiber content of 1.2, 1.6, and 2.0 kg/m 3 decreases by 18.8, 22.4, and 26.7% compared to reference concrete, respectively. Based on the results of orthogonal experimental design, the chloride diffusion coefficients D RCM of hybrid fiber reinforced SCC are listed in order of importance, as follows: length of carbon fiber > content of carbon fiber > content of cellulose fiber; furthermore, the hybrid of 2.72-kg/m 3 carbon fiber with length of 12 mm and 2.0-kg/m 3 cellulose fiber exhibits the most significant effect on chloride diffusion coefficients D RCM of SCC.
This paper presents a computational impact angle control guidance law based on the energy cost weighted by arbitrary functions in order to shape the acceleration command as desired. The optimal guidance problem is established in the impact angle frame and is solved by the Gauss orthogonal collocation method. The proposed guidance law is formulated from the generalized optimal control framework, thus a new guidance law that allows achieving a specific guidance goal can be easily obtained in the way of devising a proper weighting function (smooth, piecewise, nonsmooth, or even discontinuous). This property provides more degrees of freedom in the guidance law design to accomplish a specified guidance objective. A hardware experiment is conducted to evaluate the real-time computational capacity of the proposed computational guidance law. Illustrative examples with several types of weighting functions, including smooth, piecewise, nonsmooth, and discontinuous functions, are provided to demonstrate the advantages and capacity of the proposed guidance law.
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