Poly(Vinylidene Fluoride-co-Hexafluoropropylene) Films Filled in Iron Nanoparticles for Infrared Shielding Applications.

In order to use the infrared (IR) radiation shielding materials, they should take a form of thin film coatings deposited on glass/polymer substrates or be used as fillers of glass/polymer. The first approach usually suffers from several technological problems. Therefore, the second strategy gains more and more attention. Taking into account this trend, this work presents the usage of iron nanoparticles (Fe NPs) embedded into the poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) films as the shielding material in near-infrared (NIR) and mid-infrared (MIR) region. The performed investigations show that the transmittance of copolymer films decreases with increasing content of the Fe NPs inside them. It is found that the average fade of IR transmittance for 1, 2.5, 5, 10, and 50 mg of Fe NPs is about 13%, 24%, 31%, 77%, and 98%, respectively. Moreover, it is observed that the PVDF-HFP films filled in the Fe NPs almost does not reflect the NIR and MIR radiation. Hence, the IR shielding properties of the PVDF-HFP films can be effectively tuned by the addition of proper amount of the Fe NPs. This, in turn, shows that the PVDF-HFP films filled in the Fe NPs constitute a great option for IR antireflective and shielding applications.

Biomechanics of the Upper Limbs: A Review in the Sports Combat Ambit Highlighting Wearable Sensors.

Over time, inertial sensors have become an essential ally in the biomechanical field for current researchers. Their miniaturization coupled with their ever-improvement make them ideal for certain applications such as wireless monitoring or measurement of biomechanical variables. Therefore, in this article, a compendium of their use is presented to obtain biomechanical variables such as velocity, acceleration, and power, with a focus on combat sports such as included box, karate, and Taekwondo, among others. A thorough search has been made through a couple of databases, including MDPI, Elsevier, IEEE Publisher, and Taylor & Francis, to highlight some. Research data not older than 20 years have been collected, tabulated, and classified for interpretation. Finally, this work provides a broad view of the use of wearable devices and demonstrates the importance of using inertial sensors to obtain and complement biomechanical measurements on the upper extremities of the human body.

Charge transport in MBE-grown 2H-MoTe2 bilayers with enhanced stability provided by an AlOx capping layer.

Thin layers of transition metal dichalcogenides have been intensively studied over the last few years due to their novel physical phenomena and potential applications. One of the biggest problems in laboratory handling and moving on to application-ready devices lies in the high sensitivity of their physicochemical properties to ambient conditions. We demonstrate that novel, in situ capping with an ultra-thin, aluminum film efficiently protects thin MoTe2 layers stabilizing their electronic transport properties after exposure to ambient conditions. The experiments have been performed on bilayers of 2H-MoTe2 grown by molecular beam epitaxy on large area GaAs(111)B substrates. The crystal structure, surface morphology and thickness of the deposited MoTe2 layers have been precisely controlled in situ with a reflection high energy electron diffraction system. As evidenced by high resolution transmission electron microscopy, MoTe2 films exhibit perfect arrangement in the 2H phase and the epitaxial relation to the GaAs(111)B substrates. After the growth, the samples were in situ capped with a thin (3 nm) film of aluminum, which oxidizes after exposure to ambient conditions. This oxide serves as a protective layer to the underlying MoTe2. Resistivity measurements of the MoTe2 layers with and without the cap, exposed to low vacuum, nitrogen and air, revealed a huge difference in their stability. The significant rise of resistance is observed for the unprotected sample while the resistance of the protected one is constant. Wide range temperature resistivity studies showed that charge transport in MoTe2 is realized by hopping with an anomalous hopping exponent of x ≃ 0.66, reported also previously for ultra-thin, metallic layers.

Graphene Oxide with Controlled Content of Oxygen Groups as a Filler for Polymer Composites Used for Infrared Radiation Shielding.

Infrared (IR) shielding materials are commonly used for different applications, such as smart windows or optical filters. Infrared radiation is responsible for about 50% of the energy coming from the sun. During a hot summer or cold winter a lot of energy is needed to keep the optimal temperature inside buildings and means of transport. To reduce the heat transmission and save energy IR shielding materials can be used as coatings made of polymer composites. Graphene oxide (GO) and its reduced forms have interesting IR absorption properties and might be used as a filler in a polymer matrix for IR shielding applications. Graphene oxide can be reduced by different methods. Depending on the reduction method reduced graphene oxide (rGO) with a different content of oxygen can be obtained exhibiting different properties. In this work we propose new polymer nanocomposites with poly(vinyl alcohol) as the matrix and 0.1 wt.% addition of graphene materials with different oxygen content to be used for IR shielding applications. The results show that the properties of the graphene filler strongly influence the infrared shielding properties of the obtained nanocomposites. The best IR shielding properties were obtained for the composites where rGO with the lowest oxygen content was used.

Hydrostatic-pressure-induced changes of magnetic anisotropy in (Ga, Mn)As thin films.

The impact of hydrostatic pressure on magnetic anisotropy energies in (Ga, Mn)As thin films with in-plane and out-of-plane magnetic easy axes predefined by epitaxial strain was investigated. In both types of sample we observed a clear increase in both in-plane and out-of-plane anisotropy parameters with pressure. The out-of-plane anisotropy constant is well reproduced by the mean-field p-d Zener model; however, the changes in uniaxial anisotropy are much larger than expected in the Mn-Mn dimer scenario.

Structural and magnetic properties of iron nanowires and iron nanoparticles fabricated through a reduction reaction.

The main goal of this work is to study the structural and magnetic properties of iron nanowires and iron nanoparticles, which have been fabricated in almost the same processes. The only difference in the synthesis is an application of an external magnetic field in order to form the iron nanowires. Both nanomaterials have been examined by means of transmission electron microscopy, energy dispersive X-ray spectrometry, X-ray diffractometry and Mössbauer spectrometry to determine their structures. Structural investigations confirm that obtained iron nanowires as well as nanoparticles reveal core-shell structures and they are composed of crystalline iron cores that are covered by amorphous or highly defected phases of iron and iron oxides. Magnetic properties have been measured using a vibrating sample magnetometer. The obtained values of coercivity, remanent magnetization, saturation magnetization as well as Curie temperature differ for both studied nanostructures. Higher values of magnetizations are observed for iron nanowires. At the same time, coercivity and Curie temperature are higher for iron nanoparticles.