Nanofibrillated cellulose from eucalyptus pulp, produced by high-pressure homogenization, was used as cement partial replacement for cement paste at a content ranging from 0% to 0.5% by weight of cement. The effect of the content of nanofibrillated cellulose on porosity, thermal properties, compressive strength and degree of cement hydration was investigated. Results have shown an improvement in the compressive strength by more than 50% with 0.3 wt% of added nanofibrillated cellulose. The porosity was reduced by nanofibrillated cellulose addition, and the greatest result was achieved with mixture incorporating 0.3 wt% nanofibrillated cellulose. The coefficient of thermal expansion and the thermal conductivity measurements, relative to nanofibrillated cellulose-reinforced cement pastes, have pointed out the reinforcement effectiveness of nanofibrillated cellulose. The degree of cement hydration has increased with nanofibrillated cellulose content. This trend was confirmed by X-ray diffraction and Fourier Transform Infrared spectroscopy. These analyses have revealed that the presence of nanofibrillated cellulose promoted the hydration of cement, by producing more portlandite and calcium silicate gel, which is likely the main reason accounting for the strong enhancement in the compressive strength.
This study was conducted on the reduction reaction of the azo dye Reactive Black 5 by means of the Mn85Al15 particles prepared by melt-spinning and ball-milling processes. The morphology, the surface elementary composition and the phase structure of the powders were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The degradation efficiency of the ball milled powder was measured by using an ultraviolet-visible absorption spectrophotometer and the collected powder was analyzed by means of Fourier transform infrared spectroscopy technique to characterize the functional groups in the extract. The degradation of Reactive Black 5 and the analysis of the aromatic by-products were investigated by high performance liquid chromatography coupled with tandem mass spectrometry. The ball-milled powder shows higher degradation efficiency and the Reactive Black 5 solution was completely decolorized after 30 min. The degradation kinetics and the formation by-products depend on the pH and temperature of the solution. The analyses of the extracted product confirmed the cleavage of the (–N[double bond, length as m-dash]N–) bonds. Our findings are expected to pave the way for a new opportunity with regard to the functional applications of nanostructured metallic particle
The microstructure, mechanical properties, and strengthening mechanisms of an Al-Mg-Si alloy (AA6060) subjected to severe plastic deformation using equal channel angular pressing (ECAP) were investigated. Samples were passed through a die with an inner angle of F = 90° and outer arc of curvature of ¿ = 37° at room temperature up to 12 passes via route Bc. Electron backscatter diffraction (EBSD) was used to evaluate the microstructure and misorientation boundaries. The microstructure showed a large fraction of low-angle boundaries associated with subgrain formation in the first ECAP pass, while after eight and 12 passes, a heterogeneous ultrafine grain structure with an average grain size around 0.57 and 0.47 µm, respectively, was obtained. In order to characterize the mechanical properties, microhardness and tensile tests were carried out. Results of mechanical property tests show that microhardness, yield stress, and ultimate tensile strength increase as ECAP pass number increases up to a maximum value of 120 HV, 344 MPa, and 355 MPa, respectively, after five passes. The Hall–Petch effect, dislocation, solid solution, and precipitation strengthening were evaluated to determine the dependence of the yield stress on the ECAP pass number. The results show that the strength effect arises from the subgrain microstructure rather than from the high-angle grain boundaries developed.Peer ReviewedPostprint (published version
Research in the field of magnetic shape memory alloys (MSMAs) has increased in recent years due to their great interest in their potential applications in smart devices because the reversible deformations undergone. These applications range from actuators, sensors to a magnetic refrigerator and a micro-energy transducer. The well-known example of these alloys is the Heusler type, which has excellent properties, such as; the metamagnetic properties, the magnetocaloric effect (MCE) and the giant magnetoresistance effect (MR). The characterization of the different structures of this type of material is vital for the understanding of their macroscopic and microscopic behavior. The structures of these Heusler alloys are: a high temperature L21 and B2 austenite and L10, 10M and 14M martensite a low temperature. This paper provides a comprehensive review on the recent progress in the development of magnetostructural transformation and magnetocaloric effect, as well as the shape-memory effect induced by the magnetic field in Ni-Mn-X (X= In, Sn, Sb) and Ni-Co-Mn-Y (Y= In, Sn, Sb) Heusler-type MSMAs. The possible challenges and remaining issues are briefly discussed.
An ultrafine grained Al-Mg-Si alloy was prepared by severe plastic deformation using the Equal Channel Angular Pressing (ECAP) method. Samples were ECAPed through a die with an inner angle of Φ=90º and outer arc of curvature of ψ= 37° from 1 to 12 ECAP passes at room temperature following route Bc. To analyze the evolution of the microstructure at increasing ECAP passes x-ray diffraction and Electron Backscatter Diffraction analyses were carried out. The results revealed two distinct processing regimes, namely: i) from 1 to 5 passes, the microstructure evolved from elongated grains and sub-grains to a rather equiaxed array of ultrafine grains and ii) from 5 to 12 passes where no change in the morphology and average grain size was noticed. In the overall behavior, the boundary misorientation angle and the fraction of high-angle boundaries increase rapidly up to 5 passes and at a lower rate from 5 to 12 passes. The crystallite size decreased down to about 45 nm with the increase in deformation. The influence of deformation on precipitate evolution in the Al-Mg-Si alloy was also studied by differential scanning calorimetry. A significant decrease in the peak temperature associated to the 50% of recrystallization was observed at increasing ECAP passes.
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