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With the continuous advance of modern electronics, the demand for nonvolatile memory cells rapidly grows. In order to develop post-silicon electronic devices, it is necessary to find innovative solutions to the eco-sustainability problem of materials for nonvolatile memory cells. In this work, we realized a resistive memory device based on graphene oxide (GO) and GO/cellulose nanocrystals (CNC) thin films. Aqueous solutions of GO and GO with CNC have been prepared and drop cast between two metal electrodes. Such thin-film based devices showed a transition between low and high conductivity states upon the forward and backward sweeping of an external electric field. This reversible current density transition behavior demonstrates a typical memory characteristic. The obtained results open an easy route for electronic information storage based on the integration of nanocrystalline cellulose onto graphene based devices. [ABSTRACT FROM AUTHOR]

The aim of this work was to study the effect of the innovative combination of microcrystalline cellulose (MCC) and silver nanoparticles (Ag) on the poly (lactide acid) (PLA) composite properties, to modulate the PLA mechanical response and induce an antibacterial effect. The preparation and characterization of PLA-based composites with MCC and Ag nanoparticles by twin-screw extrusion followed by injection molding is reported. A film procedure was also performed to obtain PLA and PLA composite films with a thickness ranged between 20 and 60 μm. The analysis of disintegrability in composting conditions by means of visual, morphological, thermal, and chemical investigations was done to gain insights into the post-use degradation processes. Tensile test demonstrated the MCC reinforcing effect, while a bactericidal activity of silver-based composites against a Gram-negative bacteria ( Escherichia coli) and a Gram-positive bacteria ( Staphylococcus aureus) was detected at any time points and temperatures analyzed. Moreover, the disintegrability in composting showed that MCC is able to promote the degradation process. The combination of MCC and Ag nanoparticles in PLA polymer matrix offers promising perspectives to realize multifunctional ternary composites with good mechanical response and antibacterial effect, maintaining the optical transparency and the disintegrability, hence suitable for packaging applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 [ABSTRACT FROM AUTHOR]

In this work vinylester-matrix composites reinforced with woven jute fabrics were investigated. The effect of a simple fiber treatment with silicone on the mechanical and viscoelastic response in comparison to traditional treatments was analyzed. Unless the composite with acetylated fibers, all composites exhibited higher values of rubbery storage modulus than the matrix. All treated fiber composites have similar damping capacities. Furthermore, silicone had a plasticizing effect on the vinylester matrix. The composites with washed fibers and with fibers treated with silicone exhibited slightly higher stiffness and strength values than other treated fiber composites. In addition to its experimental simplicity, the treatment with silicone also allowed us to obtain the composites with best combination of stiffness, strength, and toughness. [ABSTRACT FROM AUTHOR]

Flax fiber-vinyl ester composites are milled and mixed with virgin matrices to produce recycled composites. The effect of this powder incorporation on the mechanical properties of a thermosetting matrix (vinyl ester) and a thermoplastic matrix (polypropylene) is studied. In the case of thermosetting matrix, flexural and tensile strength decrease with the addition of powder. For filler contents higher than 50 vol%, the strength reaches a constant value. Flexural and Young's moduli remain constant for different powder contents. In the case of thermoplastic matrix, strength and modulus decrease when powder is replaced by fibers. Both, fibers and powder act as reinforcement as moduli increase. Impact properties are improved with the addition of powder and fibers in comparison with the pure matrix. [ABSTRACT FROM AUTHOR]

In order to evaluate the effect of processing conditions, composites of MaterBi-Y matrix with 15 wt% sisal fibers are obtained with different temperature profiles and speeds of rotation of the screw, using a twin-screw extruder. Three different temperature profiles are selected. The speeds of rotation are 25, 60, and 80 rpm. The samples are obtained by compression at 180°C and 700 MPa for 10 min. The mechanical properties of composites increase when the rotation speed changes from 25 to 60 rpm and then decreases. Fiber breakage increases with rotational speed, but aspect ratio increases too. Increased modulus with fiber aspect ratio is easily understood because longer fibers carry more tensile loads as a result of increase in transfer length. The decrease in the mechanical properties at a high rotational speed can be due to the degradation of the matrix. The impact properties increase when temperature increases. The decrease in impact properties at temperatures above 185°C can be due to the thermal decomposition of the material. [ABSTRACT FROM AUTHOR]

Examines the potential of the use of natural fibers as reinforcements in polymers. Assessment of the processing behavior and final properties of natural fibers with polymeric matrices; Evaluation of the benefits of using physical and chemical treatments for the improvement of fiber-matrix interaction and composite mechanical properties; Use of the natural fibers for automotive applications.

In the former parts of this work ( J. Mat. Sci. 33 (1998) pp. 3137 and 3145) the kinetic characterisation and the mathematical modelling of the behaviour of an ablative material subjected to high heat fluxes were analysed. In this work the structure and morphology of the char produced from the degradation of the same ablative material, occurring as a consequence of plasma torch exposure, are evaluated in order to improve the ablative behaviour of an active protection. Usually the char produced from the degradation of polymeric ablators is weak and brittle, and therefore is susceptible of rapid removal by the mechanical stresses due to the high vehicle speed, this phenomena provokes a reduction of the thermal insulation. Reinforcing fibres and other inorganic fillers must be therefore included in the ablative formulation in order to improve the char stability. One of the roles of the char, which is very important, is to limit oxygen diffusion from the boundary layer to the bulk to prevent the exothermic degradation reactions of the polymeric matrix. Therefore, the mechanical characteristics and the physic-chemical properties of the char are of fundamental importance to ensure good quality of an ablative material. In this paper Scanning Electron Microscopy (SEM) elemental microanalysis (EDAX) and wide angle X-ray diffraction (WAXD) are used to provide respectively the morphological characteristics of the char and further insight on the crystalline structure resulting after quenching at room temperature. [ABSTRACT FROM AUTHOR]

Thermogravimetric studies and combined thermal analysis techniques have been used to characterize an ablative composite for thermal protection systems. The aim of the work was to utilize these techniques to obtain the main parameters used in the computer simulation of the space re-entry. In particular, a phenomenological model of the degradation kinetics of a silicon-based ablative composite has been developed using thermogravimetric analysis coupled with mass spectroscopic analysis. Simultaneous thermal analysis has also been used to calculate the ablation heat. The results are used as input for a computer model, developed in Part II, to enable calculation of the temperature profiles inside a thermal protection shield during the re-entry into the earth's atmosphere. Such a program can also be used in materials selection. © 1998 Kluwer Academic Publishers [ABSTRACT FROM AUTHOR]