Passive Control Reinforced Concrete Frame Mechanism with High Strength Reinforcements and Its Potential Benefits Against Earthquakes

Introduction In most reinforced concrete (RC) structures, a large stiffness is needed in order to limit structural deforma- tion for service load conditions. In seismic resistant structures, however, the energy dissipation demands are imposed and inelasti…     

Surfactant-decorated graphite nanoplatelets(GNPs) reinforced aluminum nanocomposites: sintering effects on hardness and wear

The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was addressed by sonication and non-covalent surface functionalization of graphite nanoplatelets(GNPs) using two types of surfactant: anionic(sodium dodecyl benzene sulfate(SDBS)) and non-ionic polymeric(ethyl cellulose(EC)). After colloidal mixing with Al powder, consolidation was performed at two sintering temperatures(550 and 620°C). The structure, density, mechanical and wear properties of the nanocomposite samples were investigated and compared with a pure Al and a pure GNPs/Al nanocomposite sample. Noticeably, EC-based 0.5 wt% GNPs/Al samples showed the highest increment of 31% increase in hardness with reduced wear rate of 98.25% at 620°C, while a 22% increase in hardness with reduced wear rate of 96.98% at 550°C was observed, as compared to pure Al. Microstructural analysis and the overall results validate the use of EC-based GNPs/Al nanocomposites as they performed better than pure Al and pure GNPs/Al nanocomposite at both sintering temperatures.     

Phase analysis of AlFe2B2 by synchrotron X-ray diffraction, magnetic and Mössbauer studies

The structural and magnetic properties of essentially phase pure AlFe_2B_2 prepared by arc melting were compared with a sample containing impurities. Analysis was carried out by means of synchrotron X-ray diffraction, magnetic measurements and M?ssbauer spectroscopy. The analysis of synchrotron X-ray diffraction data confirmed the orthorhombic structure of space group Cmmm for AlFe_2B_2 with Al_(13)Fe_4 as main impurity phase. The magnetic measurements revealed an unsaturated ferromagnetic state in AlFe_2B_2 with a transition temperature(T_c) of 286 K. Isothermal magnetization measurment at 5 K gave a saturation magnetization of 0.7 μB per Fe atom while Arrott plots establish the second order nature of ferromagnetic transition. The thermal evolution of M?ssbauer spectra confirmed the ferromagnetic nature of this material revealing an hyperfine field of 73 kOe and an isomer shift of 0.46 mm/s at 100 K. The M?ssbauer spectra of a phase pure sample was compared with the one containing impurity phases. It is suggested that the low temperature paramagnetic contribution in M?ssbauer spectra of phase pure material may have its origin in some intrinsic phenomena arising from defects or inhomogeneities in crystal structure.     

Infield superconducting properties of nano-sized Ag added Cu_(0.5)Tl_(0.5)Ba_2Ca_2Cu_3O_(10-δ)

Infield superconducting properties of {(Ag)_x/CUTl-1223};(x = 0, 0.5,1.0.2.0 and 4.0 wt %) nanoparticlessuperconductor composites were investigated under different applied magnetic field up to H = 8 T. The increase in critical temperature {T_c(0)} and decrease in normal state resistivity(p_o) were observed with increasing contents of Ag nanoparticles in CuTl-1223 superconducting matrix. The value of T_c~(onset)(K) remained almost unaffected by applying external magnetic field, but a decreasing trend in T_c(0) was observed by increasing the value of external applied magnetic field. The transition region below T_c~(onset)(K) showed Arrhenius behavior due to thermally activated flow of magnetic vortices. Enhancement in flux flow activation energy(U_o) and suppression in transition width(ΔT) of CuTl-1223 phase with addition of Ag nanoparticles showed the improvement in flux pinning strength of superconductor.     

Neighborhood topological effect on grain topology-size relationship in three-dimensional polycrystalline microstructures

A new grain topology-size relationship in three-dimensional(3D)polycrystalline microstructures has recently been established by considering the effects of non-random first nearest neighbor grains.In this contribution,a generalized form for this relationship is presented by considering the interactions of kth(k=1,2,3…)nearest neighbor grains,and large scale Monte Carlo-Potts model simulation is used to investigate the general neighborhood topological effect on the topology-size relationship.The results show that,unlike their first nearest neighbors(k=1),the topological correlations of 3D grains with their kth layers(k 2)of nearest-neighbors may have trivial effect on the topology-size relationship.     

Synthesis and superconductivity of (Ag)x/CuTl-1223 composites

Series of(Ag)x/(Cu0.5Tl0.5Ba2Ca2Cu3O10-δ) {(Ag)x/Cu Tl-1223} nano-superconductor composites were synthesized with different concentrations(i.e. x ? 0 4.0 wt%) of silver(Ag) nanoparticles. Low anisotropic Cu Tl-1223 superconducting matrix was prepared by solid-state reaction and Ag nanoparticles were prepared by a sol–gel method separately. The required(Ag)x/Cu Tl-1223 composition was obtained by the inclusion of Ag nanoparticles in Cu Tl-1223 superconducting matrix. Structural, morphological, compositional and superconducting transport properties of these composites were investigated in detail by x-ray diffraction(XRD), scanning electron microscopy(SEM), energy dispersive x-rays(EDX)spectroscopy and four-point probe electrical resistivity(ρ) measurements. The inclusion of Ag nanoparticles enhanced the superconducting properties without affecting the tetragonal structure of the host Cu Tl-1223 matrix. The improvement in superconducting properties of(Ag)x/Cu Tl-1223 composites is most likely due to enhanced inter-grains coupling and increased superconducting volume fraction after the addition of metallic Ag nanoparticles at the inter-crystallite sites in the samples. The presence of Ag nanoparticles at the grain-boundaries may increase the number of flux pinning centers, which were present in the form of weak-links in the pure Cu Tl-1223 superconducting matrix.     

Competing crystallite size and zinc concentration in silica coated cobalt ferrite nanoparticles

Silica coated(30 wt%) cobalt zinc ferrite(Co1 xZnxFe2O4, x?0, 0.2, 0.3, 0.4, 0.5 and 1) nanoparticles were synthesized by using sol–gel method. Silica acts as a spacer among the nanoparticles to avoid the agglomeration. X-ray diffraction(XRD) reveals the cubic spinel ferrite structure of nanoparticles with crystallite size in the range 37–45 nm. Fourier transform infrared(FTIR) spectroscopy confirmed the formation of spinel ferrite and SiO2. Scanning electron microscopy(SEM) images show that the nanoparticles are nearly spherical and non-agglomerated due to presence of non-magnetic SiO2 surface coating. All these measurements signify that the structural and magnetic properties of Co1 xZnxFe2O4 ferrite nanoparticles strongly depend on Zn concentration and nanoparticle average crystallite size in different Zn concentration regimes.& 2014 Chinese Materials Research Society. Production and hosting by Elsevier B.V. All rights reserved.     

Surfactant-decorated graphite nanoplatelets (GNPs) reinforced aluminum nanocomposites: sintering effects on hardness and wear

The exceptional properties of graphene make it ideal as a reinforcement to enhance the properties of aluminum matrices and this critically depends on uniform dispersion. In this study, the dispersion issue was addressed by sonication and non-covalent surface functionalization of graphite nanoplatelets (GNPs) using two types of surfactant: anionic (sodium dodecyl benzene sulfate (SDBS)) and non-ionic polymeric (ethyl cellulose (EC)). After colloidal mixing with Al powder, consolidation was performed at two sintering temperatures (550 and 620℃). The structure, density, mechanical and wear properties of the nanocomposite samples were investigated and compared with a pure Al and a pure GNPs/Al nanocomposite sample. Noticeably, EC-based 0.5wt% GNPs/Al samples showed the highest increment of 31% increase in hardness with reduced wear rate of 98.25% at 620℃, while a 22% increase in hardness with reduced wear rate of 96.98% at 550℃ was observed, as compared to pure Al. Microstructural analysis and the overall results validate the use of EC-based GNPs/Al nanocomposites as they performed better than pure Al and pure GNPs/Al nanocomposite at both sintering temperatures.