Polyacrylonitrile‐carbon Nanotube‐polyacrylonitrile: A Versatile Robust Platform for Flexible Multifunctional Electronic Devices in Medical Applications

Flexible multifunctional electronic devices are of high interest for a wide range of applications including thermal therapy and respiratory devices in medical treatment, safety equipment, and structural health monitoring systems. This paper reports a scalable and efficient strategy of manufacturing a polyacrylonitrile‐carbon nanotube‐polyacrylonitrile (PAN‐CNT‐PAN) robust flexible platform for multifunctional electronic devices including flexible heaters, temperature sensors, and flexible thermal flow sensors. The key advantages of this platform include low cost, porosity, mechanical robustness, and electrical stability under mechanical bending, enabling the development of fast‐response flexible heaters with a response time of ≈1.5 s and relaxation time of ≈1.7 s. The temperature‐sensing functionality is also investigated with a range of temperature coefficient of resistances from ?650 to ?900 ppm K^?1. A flexible hot‐film sensing concept is successfully demonstrated using PAN‐CNT‐PAN with a high sensitivity of 340 mV (m s^?1)^?1. The sensitivity enhancement of 50% W^?1 is also observed with increasing supply power. The low cost, porosity, versatile, and robust properties of the proposed platform will enable the development of multifunctional electronic devices for numerous applications such as flexible thermal management, temperature stabilization in industrial processing, temperature sensing, and flexible/wearable devices for human healthcare applications.     

FPGA Implementation of a Power Amplifier Linearizer for an ETSI-SDR OFDM Transmitter

Most satellite digital radio （SDR） systems use orthogonal frequency-division multiplexing （OFDM） transmission, which means that variable envelope signals are distorted by the RF power amplifier （PA）. It is customary to back off the input power to the PA to avoid the PA nonlinear region of operation. In this way, linearity can be achieved at the cost of power efficiency. Another attractive option is to use a linearizer, which compensates for the nonlinear effects of the PA. In this paper, an OFDM transmitter conforming to European Telecommunications Standard Institute SDR Technical Specifications 2007-2008 was designed and implemented on a low-cost field-programmable gate array （FPGA） platform. A weakly nonlinear PA, operating in the L-band SDR frequency, was used for signal transmission. An adaptive linearizer was designed and implemented on the same FPGA device using digital predistortion to correct the undesired effects of the PA on the transmitted signal. Test results show that spectral distortion can be suppressed between 6-9 dB using the designed linearizer when the PA is driven close to its saturation region.     

A 2D quadrangular pyramid photoelectric autocollimator with extended angle measurement range

A photoelectric autocollimator with high accuracy and extended measurement range based on the quadrangular pyramid is proposed, and the corresponding algorithms are also deduced. A new image processing algorithm has been proposed to improve the accuracy, and the corresponding errors are also estimated, the error does not exceed half a pixel when the distance between the marks more than two radii. The experimental results have verified that the measurement range of the proposed two-dimensional (2D) quadrangular pyramid photoelectric autocollimator can be increased times than that of the flat mirror photoelectric autocollimator from 10′ to 15′. The accuracy is better than 1″ when the deflection is less than 15′.     

CdS Quantum Dots Encapsulated in Chiral Nematic Mesoporous Silica: New Iridescent and Luminescent Materials

Simultaneous integration of light emission and iridescence into a semiconducting photonic material is attractive for the design of new optical devices. Here, a straightforward, one‐pot approach for liquid crystal self‐assembly of semiconductor quantum dots into cellulose nanocrystal‐templated silica is developed. Through a careful balance of the intermolecular interactions between a lyotropic tetraalkoxysilane/cellulose nanocrystal dispersion and water‐soluble polyacrylic acid/mercaptopropionic acid‐stabilized CdS quantum dots, CdS/silica/nanocellulose composites that retain both chiral nematic order of the cellulose nanocrystals and emission of the quantum dots are successfully co‐assembled. Subsequent removal of the cellulose template and organic stabilizers in the composites by controlled calcination generates new freestanding iridescent, luminescent chiral nematic mesoporous silica‐encapsulated CdS films. The pores of these materials are accessible to analytes and, consequently, the CdS quantum dots undergo strong luminescence quenching when exposed to TNT solutions or vapor.     

Synthesis, characterization and electrochemical properties of 4.8 V LiNi0.5Mn1.5O4 cathode material in lithium-ion batteries

In this work the synthesis of a nickel doped cubic manganese spinel has been studied for application as cathode material in secondary lithium batteries. Six different experimental approaches have been tested in order to carry out a screening of the various possible synthetic routes. The used synthetic strategies were wet chemistry (WC), solid state (SS), combustion synthesis (CS), cellulose-based sol-gel synthesis (SG-C), ascorbic acid-based sol-gel synthesis (SG-AA) and resorcinol/formaldehyde-based sol-gel synthesis (SG-RF). The goal of our study is to obtain insights about how the synthesis conditions can be modified in order to achieve a material with improved electrochemical performances in such devices, especially in high current operating regimes. The synthesized materials have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), atomic absorption, inductively coupled plasma (ICP-MS) atomic emission spectroscopy, surface area measurements and tested as high voltage cathodes in Li-ion electrochemical devices.     

Oxidation of ZC63 Mg alloys reinforced with SiC particles between 390 °C and 500 °C in air

The ZC63 magnesium alloys reinforced with 10 wt.% of SiC particles with an average particle size of 50 μm were cast. The fabricated SiC_p/ZC63 composite consisted of an α-Mg matrix, unreacted α-SiC particles, and an intergranularly formed CuMgZn compound. It was oxidized at 390 °C to 500 °C up to 5 h in air. The oxide scales were thin and compact below 430 °C, but became porous and loose above 450 °C. They consisted primarily of MgO and a small amount of Mg₃N₂. SiC particles were stable over the temperature range explored.