Search

In this present study AZ91D magnesium alloy and AZ91D–5SiC–1Gr (wt%) hybrid metal matrix composite were produced through the stir casting process. Microstructural studies were carried out through X-ray diffraction (XRD), scanning electron microscope (SEM) and SEM with energy-dispersive X-ray analysis (EDAX). XRD study indicated the spinel crystal structure with double substitution of cubic and hexagonal closed pack materials. Ageing heat treatment comprising natural ageing (T4) and artificial ageing (T6) for 24 h was carried out on the materials. Both T4 and T6 heat-treated samples exhibited higher hardness than as-cast samples. Maximum hardness 88.8 ± 2.3 BHN and 129.9 ± 3.27 BHN were obtained for T6 heat-treated alloy and hybrid composite, respectively. Tensile properties of samples were evaluated by their stress–strain curves. Maximum values of ultimate tensile strength, yield strength (0.2%) and ductility obtained for T6 heat-treated hybrid composite were 193 MPa, 87.1 MPa and 11%, respectively. Corrosion behaviour of the samples was evaluated by the electrochemical polarization curves obtained through Tafel extrapolation method. Both the alloy and hybrid composite exhibited improved corrosion resistance as a result of natural ageing (T4) and artificial ageing (T6) heat treatment processes. Lowest corrosion rates 0.071 mm/year and 0.074 mm/year were obtained for AZ91D alloy and AZ91D–5SiC–1Gr (wt%) hybrid composite, respectively.

Amine-functionalized silica sorbents have been widely investigated for post-combustion CO2 capture at low temperature. In previous studies, amine-functionalized silica sorbents were prepared using a synthetic hierarchically porous silica, which is not commercially available in large quantities, because porous silica support structures strongly influence CO2 capture performance. Here, we propose a feasible and facile fabrication method for amine-functionalized silica sorbents using 3-aminopropyltrimethoxy silane (APTS) and fumed silica (FS), where APTS serves as both an active material and a binder. The APTS-functionalized FS sorbents have large amounts of active amino groups and porous structures and demonstrate good multicycle stability with excellent CO2 capture performance. In addition, cetyltrimethylammonium bromide was found to improve the diffusion pathway of CO2, leading to enhanced CO2 capture capacity because of the suppression of excessive condensation during preparation. Therefore, the APTS-functionalized FS sorbents could be cost- and energy-efficiently prepared using a novel one-pot synthesis method; the resulting sorbents exhibit excellent CO2 capture performance.

Amperometric sensor of polydiphenylamine (PDPA)/phosphotungstic acid (PTA)/zinc oxide (ZnO) on glassy carbon (GC) nanohybrid composite electrode (GC/PDPA/PTA/ZnO) fabricated via facile electrochemical deposition method. The structural geometry and surface morphology were recorded by X-ray diffraction spectrometer (XRD) and scanning electron microscopy (SEM). Electro-catalytic properties and performances of nanohybrid composite were recorded by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) methods. PTA-assisted PDPA/ZnO-ME shows linear steady-state response towards glucose with superior sensitivity of 20.30 μA μM−1 cm−2, lowest detection limit 0.1 μM, and rapid response less than 2 s. The improved electro-catalytic performance towards glucose by GC/PDPA/PTA/ZnO is due to the combined existence of diphenoquinone diamine (DPDI2+) and phosphotungstic acid anion which provides a higher electro-catalytic active spots leads to more electron transport pathway for the oxidation of glucose. Interference analyses confirm the prepared nanohybrid sensor is best apt for glucose detection claims its practical biomedical application.

Until now, SnO2 nanowires have been directly grown on alumina substrates with Au or Au-coated Pt electrodes by a thermal evaporation method using Sn or SnO2 powders under vacuum. However, in this study, SnO2 nanowires were successfully synthesized on the Pt phase of an alumina substrate by a thermal evaporation method using dibutyltin oxide [DBTO, (C4H9)2SnO] even at atmospheric pressure, resulting in nanowire networks between the Pt phases. Ar with 1% O2 was used as carrier gas with a flow rate of 100 mL/min at 900 °C (heating rate of 25 °C/min). The SnO2 nanowires consisted of straight and branched nanowires, and exhibited a SnO2 phase with a tetragonal structure. Both the DBTO and evaporation temperature play an important role on the synthesis of SnO2 nanowires at atmospheric pressure. The SnO2 nanowire sensor fabricated by an evaporation method showed a sensor response of ~ 500 for 0.05 ppm of NO2, being ~ 10 times greater than that of a SnO2 nanoparticle sensor. Furthermore, the SnO2 nanowire sensor showed excellent repeatability and selectivity for NO2 in the presence of SO2, Cl2, and H2S.

This work reports the synthesis, characterization, and antimicrobial activity of polyaniline/polyvinyl alcohol (PANI/PVA) and polydiphenylamine/polyvinyl alcohol (PDPA/PVA) co-polymer nanocomposite films. Initially, chemical oxidative polymerization was employed to synthesis PANI and PDPA by oxidizing aniline (AN) and diphenylamine (DPA) in the presence of ammonium peroxydisulfate (APS) as an oxidant. A trace amount of prepared PANI and PDPA were used to prepare nanocomposite films by solution casting technique, using PVA as a stabilizer. Surface morphological studies reveal the impregnated amorphous structure of PANI and PDPA size in the range of ~ 50–150 nm. Fourier transform infrared (FTIR) examines to confirm the presence of PANI, PDPA, and PVA in nanocomposite film. Disk diffusion approach was adopted to study the antimicrobial activity of PANI/PVA and PDPA/PVA nanocomposite films.

We report on the synthesis of an electrically conductive chitosan nanofibrous scaffold (NFS) by a “simple template free self-assembly method” from biopolymer chitosan in the presence of inorganic acids as dopants and ammonium persulphate (APS) as an initiator. The morphology of the chitosan nanofibers scaffold (CS-NFS) was examined by field emission scanning electron microscopy (FE-SEM). Physiochemical characterizations of the CSNFS were analyzed by Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis. It is found that the morphology and structure of the CS-NFS strongly depend on the kinds of dopant used. Cyclic voltammogram measurement reveals that CS nanofibers have high electrocatalytic activity compared to chitosan powder. The CS nanofibers are expected to be useful in electrical, optical, and electrochemical devices. Open image in new window

To simultaneously remove hydrogen sulfide and ammonia from hot coal gases, the ammonia decomposition abilities of various metal oxide catalysts were tested in the absence/presence of hydrogen sulfide, at 650 °C. Cobalt oxide, molybdenum oxide, and nickel oxide have high ammonia decomposition abilities (>95%) in the absence of hydrogen sulfide, but such abilities rapidly decreased during the reaction in the presence of hydrogen sulfide. To improve the simultaneous removal abilities of metal oxides, Zn-based catal sorbents were prepared via impregnation with various metals, such as cobalt, nickel, and molybdenum, on zinc oxide. The CZ-30 (promoted with 30 wt% cobalt oxide on zinc oxide) and NZ-30 (promoted with 30 wt% nickel oxide on zinc oxide) catal sorbents showed excellent sulfur removal capacities, which, calculated until the breakthrough point, were 0.35 and 0.39 g S/g catal sorbent, respectively, while MZ-30 promoted with molybdenum showed a low sulfur removal capacity of 0.08 g S/g catal sorbent. The ammonia decomposition ability of CZ-30, however, increased more than 18 times compared with Co3O4, whose ammonia decomposition ability was more than 95% until 465 min, even though the ammonia decomposition ability of NZ-30 sharply decreased after 30 min. The CZ catal sorbent is a good candidate for the simultaneous removal of ammonia and hydrogen sulfide.

A modified electrode was fabricated by grafting poly(2,5-dimethoxyaniline) (PDMA) onto multiwalled carbon nanotubes (MWNTs) and used for the electrocatalytic oxidation of ascorbic acid (AA). Cyclic voltammetry was used to fabricate the modified electrode and demonstrate the electroactivity of MWNT-g-PDMA-ME towards AA. Field emission scanning electron microscopy (FESEM) of MWNT-g-PDMA-ME revealed the combined presence of MWNT and PDMA. The MWNT-g-PDMA-ME exhibited excellent performance for AA at 320 mV with a high sensitivity (12.78 μA/mM) and linear concentration range of 1 to 5 mM (correlation coefficient of 0.9991). Differential pulse voltammetry (DPVs) showed that MWNT-g-PDMA-ME experiences negligible interference from other electro-active components.

Conducting hybrid submicrostructures composed of chitosan (CS and silica-based conducting poly[N-(3-trimethoxysilylpropyl)aniline] (PTMSPA were prepared by graft copolymerization. The spherical and fibrous morphologies of the CS-PTMSPA hybrid submicrostructures could be observed by optical and field emission electron microscopy. Under room temperature conditions, the CS-PTMSPA graft copolymers possessed the uniformly distributed spherical submicroparticles with diameters in the range of ca. 400–1,000 nm. On the other hand, under ice cold conditions (5 °C), CS-PTMSPA showed the development of randomly oriented fiber bundles. The diameter of a single fiber was in the range of ca. 100–500 nm. These CS-PTMSPA fibers were obtained by a temperature-driven template-free self-assembly pathway. Spectroscopic and thermal evaluations confirmed that CS-PTMSPA graft copolymer had been prepared by an oxidative polymerization method. The electrochemical performance of the CS-PTMSPA submicrostructures were compared with CS and PTMSPA by cyclic voltammetry with the Fe(CN)63−/4− system as a redox marker. The CS-PTMSPA submicrostructures showed high electrical conductivity (difference between the anodic and cathodic peaks = 0.24 and 0.29 V for CS-PTMSPA sphere and fiber, respectively compared to those of CS (0.14 V and PTMSPA (0.20 V), which was ascribed to the relatively high surface-to-volume ratios of these submicrostructures. Open image in new window

A layer-by-layer (LbL) film assembly was constructed that comprises alternative layers of poly(diphenylamine) (PDPA) and phosphotungstic acid (PTA). First, a layer of oxidized PDPA (referred to as PDPA(+)) was deposited by electropolymerization. Then, a layer of negatively charged PTA was deposited on the PDPA(+) layer . This processes was repeated several times to obtain multilayer LbL film (PDPA/PTA)n, where n is the number of double layers. The LbLs were characterized by UV-Vis spectroscopy, FT-IR spectroscopy and X- ray diffraction spectroscopy. The process of formation of the LbL assembly was monitored by electrochemical methods. Electrochemical studies revealed that this LbL film possesses a remarkable electrocatalytic activity towards oxidation of ascorbic acid in neutral aqueous medium. The enhanced electrocatalytic activity of (PDPA/PTA)n LbL film is attributed to the existence of tungsten atoms in the interlayers of PDPA.