Self-doped N-propansulfonic acid polyaniline-polyethylene terephthalate film used as active sensor element for humidity or gas detection

In this work, we report the fabrication of sensors’ element for humidity or gases, prepared by in situ polymerization of aniline N-propansulfonic acid using ammonium persulfate in acidic medium. The polymer is being used in the form of powder or deposited in multiple layers onto the PET film. Various techniques including Fourier Transform infrared (FTIR), ultraviolet-–visible spectroscopy (UV–vis), X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to characterize the as-prepared sensing materials. The film has been tested for humidity influence, where the significant variations in electrical characteristics were observed, suggesting its usefulness for humidity sensors. Also, for different organic and inorganic gases, a relatively low operating temperature and important sensitivity were observed that indicate its applicability as an active element for general gases sensors. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47743.     

应用GT-Styrene~苯乙烯回收技术对裂解汽油的改质分析

通过采用GT-Styrene苯乙烯回收技术对传统的裂解汽油处理工艺进行改进,汽油的产品性能可以得到有效的改善,并回收有价值的苯乙烯产品和得到高质量的混合二甲苯产品。     

Impact strength elastomer composites based on polystyrene components separated from waste electrical and electronic equipment

The reuse of plastic components of waste electrical and electronic equipment (WEEE) is an important concern both for environmental issues and to preserve the material resources, with minimum energy consumption. Considering that polystyrene fraction was reported as approximate 80% of the total amount of WEEE plastic, this article aims to evaluate the recycling of this fraction, without separation by components, by melt compounding with styrene-butadiene block-copolymer (SBS) and hydrogenated and maleinized SBS, the blend of the two elastomers acting both as an impact modifier and compatibilizer. The composites are characterized by mechanical analysis, impact tests, dynamic mechanical analysis, differential scanning calorimetry, thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray analysis, and X-ray diffraction. The recycling conditions of the polystyrene fraction as composites without eliminating the WEEE additives for improved UV and flame resistance, with physical mechanical properties comparable to those of high-impact polystyrene resulted from the study. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48329.     

Novel Topology in Semiconducting Tetrathiafulvalene Lanthanide Metal-Organic Frameworks

Tetrathiafulvalene tetrabenzoate (TTFTB) and several lanthanide ions self-assemble into metal-organic frameworks (MOFs) that exhibit a novel topology, a (3,3,3,6,6)-coordinated net, which features an unusual ligand coordination mode and stacking motif. The Yb and Lu MOFs are electrically conductive, with pellet conductivity values of 9(7) × 10⁻⁷ and 3(2) × 10⁻⁷ S/cm, respectively. The crystallographically-determined bond lengths indicate partial oxidation of the ligand, with close S ⋅ ⋅ ⋅ S contacts between ligands providing likely charge transport pathways in the material. Magnetometry reveals temperature-independent paramagnetism, consistent with the presence of ligand-based radicals, as well as weak antiferromagnetic coupling between Yb³⁺ centers. These results illustrate the diversity of MOF structures and properties that are accessible with the TTFTB ligand owing to its electroactive nature, propensity for intermolecular interactions, and conformational flexibility.     

Optical gain in 1.3-μm electrically driven dilute nitride VCSOAs

We report the observation of room-temperature optical gain at 1.3 μm in electrically driven dilute nitride vertical cavity semiconductor optical amplifiers. The gain is calculated with respect to injected power for samples with and without a confinement aperture. At lower injected powers, a gain of almost 10 dB is observed in both samples. At injection powers over 5 nW, the gain is observed to decrease. For nearly all investigated power levels, the sample with confinement aperture gives slightly higher gain.     

The Effect of the Ionizing Radiation on Hydroxyapatite–Polydimethylsiloxane Layers

The bio hydroxyapatite (HAp) was used from a long time in different medical and environmental applications. The HAp layers with a uniform surface were used for various medical applications such as orthopedic and dental metal implants. In this work, we reported on the influence of X‐ray radiation on the structural and morphological properties of composite layers based on HAp and polydimethylsiloxane (PDMS) deposited on titanium substrates. The HAp:PDMS layers were investigated by different complementary methods such as scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and glow discharge optical emission spectrometry (GDOES). FTIR spectral analysis showed that the molecular structure of the coatings was not changed after their irradiation even though, the depth profile analysis performed by GDOES indicated a depletion of Ca and P elements from the HAp:PDMS irradiated samples. By SEM, we showed that the morphological features of the coatings were also changed, as the irradiated layers are delaminated. The biological assays confirmed that the antibacterial activity of HAp:PDMS composite layers increased after irradiation. The results obtained in this study highlighted that the biological properties of HAp:PDMS layers could be influenced by irradiation. POLYM. ENG. SCI., 59:2406–2412, 2019. © 2019 Society of Plastics Engineers     

Preparation and magnetoelectric properties of NiFe2O4–PZT composites obtained in-situ by gel-combustion method

Magnetoelectric composites of xNiFe₂O₄–(1 ? x)Pb(Zr,Ti)O₃ with x = 2, 5, 10, 20, 30% were prepared by citrate–nitrate combustion using PZT-based template powders. In order to ensure a better connectivity of dissimilar phases, we have used chemical methods for preparation in situ composites, followed by adequate sintering procedure. The structural, microstructural and functional properties of di-phase magnetoelectric composites of NiFe₂O₄–PZT are reported. The XRD analysis is demonstrating the synthesis of pure ferrite phase directly on the ferroelectric templates. An excellent mixing was obtained in the composite powders, as proved by a detailed SEM analysis.The magnetic and dielectric behaviors of the ceramic composites vary with the ratio of the two phases. The dielectric behavior is greatly influenced by the magnetic phase. The magnetoelectric (ME) coefficient was measured as a function of applied DC magnetic field. The maximum ME coefficient (dE/dH) varies from 0.0011 mV/(cm Oe) to 0.5 mV/(cm Oe) with increasing of NF addition.     

Excitation energy-dependent nature of Raman scattering spectrum in GaInNAs/GaAs quantum well structures

The excitation energy-dependent nature of Raman scattering spectrum, vibration, electronic or both, has been studied using different excitation sources on as-grown and annealed n- and p-type modulation-doped Ga_1 − xIn_xN_yAs_1 − y/GaAs quantum well structures. The samples were grown by molecular beam technique with different N concentrations (y = 0%, 0.9%, 1.2%, 1.7%) at the same In concentration of 32%. Micro-Raman measurements have been carried out using 532 and 758 nm lines of diode lasers, and the 1064 nm line of the Nd-YAG laser has been used for Fourier transform-Raman scattering measurements. Raman scattering measurements with different excitation sources have revealed that the excitation energy is the decisive mechanism on the nature of the Raman scattering spectrum. When the excitation energy is close to the electronic band gap energy of any constituent semiconductor materials in the sample, electronic transition dominates the spectrum, leading to a very broad peak. In the condition that the excitation energy is much higher than the band gap energy, only vibrational modes contribute to the Raman scattering spectrum of the samples. Line shapes of the Raman scattering spectrum with the 785 and 1064 nm lines of lasers have been observed to be very broad peaks, whose absolute peak energy values are in good agreement with the ones obtained from photoluminescence measurements. On the other hand, Raman scattering spectrum with the 532 nm line has exhibited only vibrational modes. As a complementary tool of Raman scattering measurements with the excitation source of 532 nm, which shows weak vibrational transitions, attenuated total reflectance infrared spectroscopy has been also carried out. The results exhibited that the nature of the Raman scattering spectrum is strongly excitation energy-dependent, and with suitable excitation energy, electronic and/or vibrational transitions can be investigated.     

Isotactic polypropylene–vapor grown carbon nanofibers composites: Electrical properties

Nanocomposites have been obtained by dispersing various amounts of vapor grown carbon nanofibers within isotactic polypropylene. Thermal investigations done by differential scanning calorimetry and dynamic mechanical analysis revealed the effect of the vapor grown carbon nanofibers on the melting, crystallization, α, and β relaxations. Direct current electrical features of these nanocomposites have been investigated and related to the thermal features of these nanocomposites. The effect of the loading with carbon nanofibers on the electrical properties of these nanocomposites is discussed within the percolation theory. The percolation threshold was estimated at about 5.5% wt carbon nanofibers. The temperature dependence of the direct current conductivity is analyzed in detail and it is concluded that the electronic hopping is the dominant transport mechanism. A transition from one‐dimensional hopping towards a three‐dimensional hopping was noticed as the concentration of carbon nanofibers was increased from 10% wt to 20% wt carbon nanofiber. The possibility of a differential negative resistivity is suggested. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45297.     

Centrifugally spun carbon fibers prepared from aqueous poly(vinylpyrrolidone) solutions as binder-free anodes in lithium-ion batteries

Aqueous solutions of poly(vinylpyrrolidone) (PVP) of various concentrations (20, 25, and 28 wt%) were successfully spun into fibers by centrifugal spinning. The pristine PVP fibers were annealed and carbonized to produce flexible carbon fibers for use as binder-free anodes in lithium-ion batteries. These flexible carbon fibers were prepared by developing a novel three-step heat treatment to reduce the residual stresses in the pristine PVP precursor fibers, and to prevent fiber degradation during carbonization. The thermogravimetric analysis data showed that the annealed fibers yielded a residual mass percentage of 36.0% while the pristine PVP fibers suffered a higher mass loss and only retained 26.5% of original mass above 450 °C (under nitrogen). The electrochemical performance of the carbon-fiber anodes was evaluated by conducting galvanostatic charge/discharge, rate performance, and cycle voltammetry experiments. The 20, 25, and 28 wt% derived binder-free anodes delivered specific charge capacities of 205, 189, and 275 mAh g⁻¹, respectively, after the first cycle at a current density of 100 mA g⁻¹. The results obtained in this work indicate that a feasible pathway towards a large-scale production of carbon-fiber anodes from a 100% aqueous solution can be achieved via centrifugal spinning and subsequent heat treatment.