New shape-memory materials (SMMs) for applications in active control and morphing structures have been attracting special attention due to its unique properties. These SMM can be metallic alloys (SMAs), piezoelectric, and polymers such as polyurethanes (SMPUs). The latter detain higher recovery rates but better processability, however, the reaction time is longer when compared with the SMA. The addition of carbon nanotubes (CNTs) to SMPU seems to improve its overall properties with a great deal of potential in what concerns improved shape memory. There are two main techniques to attain SMPU/CNts nanocomposites: in situ polymerization and mechanical melt mixing. The study here presented establishes a comparison between these two techniques. To assess the suitability of the latter a rather extensive characterization was carried out. The homogeneity of the CNTs dispersion into the polymer matrix was established through SEM and the thermal characterization has shown a rise in the glass transition temperature consistent with CNT loading. Furthermore, shape memory seems to improve with the nanoparticle reinforcement. Within the two processing techniques it could be referred that melt processing seems to be simpler to use with better laboratory repeatability, thus detaining a greater potential should nanocomposite tailoring at a larger scale be envisaged.

No abstract

No abstract

No abstract

No abstract

In this paper, we present a digital certificate-based solution for smart meters. Our propose meets the identification requirements found in several scenarios related to Legal Metrology. Also, it extends previous models of smart meters authentication. This proposal results in a new class of digital certificate called "Metrologic Objects Digital Certificate." The ICP-Brasil Management Committee recently approved the use of these certificates. Fuel dispensers are the first implementation case. The objective is to reduce tampering on these instruments, so increasing their reliability.

SUMMARYThe intriguing behaviour of carbon nanotube suspensions shows that thermal conduction cannot be described by conventional approaches. These results led the researchers on the percolation and the interfacial layer resistance (also known as Kapitza resistance) as the main mechanisms governing the effective thermal conductivity enhancement for these nanoparticles suspensions. A numerical simulation on the behaviour of these suspensions, when subjected to a Brownian force field, was conducted to characterize the main factors affecting the dynamic interactions and percolation structures formation. To this end, three different numerical models based on continuum mechanics were developed. The obtained results suggest that the size, shape and aspect ratio of the nanoparticles are main factors controlling the dynamic network formation. On the other hand, the influence of the Brownian motion and the structural flexibility of the nanotubes seem to have a rather negligible effect on the results. The numerical model developed and proposed here may assist in understanding and correlating the experimental thermal conductivity data of nanofluids, contributing to demystify some of the intriguing behaviours reported.

In this work we study hydroxylated carbon nanotube (CNT) assembly on polyamide (PA) and polypropylene (PP) polymers activated by UV radiation from a theoretical and experimental perspective. Molecular computer simulation was done to understand the stable conformations and bulk properties (molecular dynamics) of the polymers before and after exposure to UV radiation at the molecular level. Our experiments suggest that PA presents more -OH active groups, producing a more hydrophilic surface, whereas PP exhibits less potential UV activation. These results suggest that it is possible a facile covalent functionalization method to tune organic polymer surface properties through SWCNT anchoring for nanotechnological applications requiring defined surface roughness and chemical functionality on inexpensive polymers.