Effect of CuO as a dopant in TiO2 on ammonia and hydrogen sulphide sensing at room temperature

The heterogeneous nanocomposites of CuO doped TiO₂ nanoparticles were synthesized using sol gel method by varying the concentration of CuO as 0.1, 0.5 and 1 mol% for the sensing of ammonia and hydrogen sulphide. The substitutional doping of CuO in TiO₂ matrix was confirmed by the X-ray diffraction. Average crystallite size of the doped nanocomposites was found to reduce with increase in concentration of CuO. The 0.1 mol% CuO doped TiO₂ nanocomposites showed highest sensitivity to ammonia (97%) with response time of 2 s, while 1 mol% was selective to H₂S gas (77%) with response time of 45 s for 50 ppm of each gas at room temperature.     

Shared orchestration within and beyond the classroom

With the introduction of personal computer devices such as smartphones and tablets into school classrooms, teachers have the added task of orchestrating complex dynamic systems of students interacting with networked technologies. One approach to managing the interactions is to add an orchestration system that enables a teacher view and control each student device. An alternative is to share responsibility for orchestration between the teacher, the students, and the technology. In this form of orchestration, the teacher and all the students have similar computer toolkits designed to guide the students through a productive learning activity. An advantage is that the teacher can hand over control to the students to continue the learning activity outside the classroom, assisted by the Activity Guide software.     

Microstructure and microwave-frequency electromagnetic properties of Ni0.4Zn0.6Fe2O4/Ba0.6Sr0.4TiO3 composites

(x)Ni_0.4Zn_0.6Fe₂O₄+(1−x)Ba_0.6Sr_0.4TiO₃ composite ceramics with x=0.6, 0.7, 0.8, 0.9 and 1 were synthesized by solid state reaction method. The high dense composites have only two phases, i.e., Ni_0.4Zn_0.6Fe₂O₄ and Ba_0.6Sr_0.4TiO₃. The permittivity ε′ of the composites decreases slightly with the frequency increasing from 3 MHz to 1 GHz. The permittivity ε′′ of the composites also shows a little increase with frequency in the 3 MHz–1 GHz range. The permeability displays a relaxation resonance within the 3 MHz–1 GHz frequency range. The permeability μ′ increases while the cut-off frequency decreases with the Ni_0.4Zn_0.6Fe₂O₄ concentration, obeying the Snoek's law μ_if_r=constant. The permittivity ε′ of the composites decreases with Ni_0.4Zn_0.6Fe₂O₄ concentration. The composites have a relatively higher ε′ than the pure Ni_0.4Zn_0.6Fe₂O₄ at 1–10 GHz. In the frequency range of 1–10 GHz, the magnetic permeability μ′ reaches its maximum and μ′′ shows a minimum for the composite with x=0.6 in all ceramics. The permeability μ′ of the composites decreases with dc magnetic field at 1–10 GHz. The permeability shows a domain wall resonance, and the resonance frequency shifts to high frequency with the dc magnetic field. The permittivity was also influenced by the dc magnetic field due to a magnetodielectric effect.     

A prescription for the removal of Compton-scattered gamma rays from gamma-ray spectra

A method for the interpolation between and extrapolation from measured detector response functions is described. This technique enables the removal of the Compton-scattered background (i.e. “stripping” or “unfolding”) of γ-ray spectra quickly, easily and accurately. Examples are presented, for both source and in-beam spectra, taken with Ge detectors. Some potential pitfalls in the accurate unfolding of spectra are discussed, and approximate remedies suggested.     

One-step solvothermal synthesis of Ag-Fe3O4 composite as a magnetically recyclable catalyst for reduction of Rhodamine B

In this study, we reported the synthesis and characterization of the Ag-Fe₃O₄ composite based on the one-step ethylenediamine (EDA)-assisted solvothermal process without adding any surfactants. The as-prepared composite displayed the hybrid structures, where the uniform Fe₃O₄ spheres were attached on the surface of the irregular Ag particles. The formation mechanism of the composite was investigated by the designed time-dependent experiments. The catalytic performance of the composite was tested for reduction of Rhodamine B (RhB) in the presence of NaBH₄, which indicated that the composite had an excellent catalytic activity, convenient magnetic separability, and long-term stability for RhB reduction.     

Effect of average grain size and sintered relative density on the imaginary part – µ″ of the complex magnetic permeability of (Cu0.12Ni0.23Zn0.65)Fe2O4 system

The influence of the sintered microstructure on the electromagnetic properties of Cu-doped NiZn ferrites were investigated. Two of the main variables of the thermal cycle have been modified: the maximum sintering temperature and the dwell time at that temperature, or sintering time. The evolution of the imaginary part – µ″ of the complex magnetic permeability was studied as a function of relative density, grain size and amplitude of the grain size distribution of the sintered pieces. The results show that µ″ depends on the sintered microstructure and that there is a limiting value of the average grain size (~20–25 µm) from which the electromagnetic properties of these kinds of materials worsened significantly.     

Incorporation of halloysite nanotubes into PVDF matrix: Nucleation of electroactive phase accompany with significant reinforcement and dimensional stability improvement

Poly(vinylidene fluoride)/halloysite nanotubes (PVDF/HNTs) nanocomposites were prepared via melt compounding. Electroactive β- and γ-phases of PVDF were nucleated by the HNTs due to electrical interaction between negatively charged surface of the HNTs and CH₂ groups of the PVDF. The ends and surface defects of the HNTs were also responsible for the formation of γ-phase, since long trans conformations with gauche defects were induced at the two regions via the formation of hydrogen bonding. In addition to nucleation of the electroactive phase, the HNTs were found to reinforce the PVDF matrix and improve its dimensional stability, as evidenced by the substantially increased tensile strength and Young’s modulus, and the remarkably decreased coefficient of thermal expansion (CTE). The improved tensile property and reduced CTE were attributed to the uniformly dispersed HNTs and good interfacial interaction between HNTs and PVDF matrix via hydrogen bonding.     

Synthesis of pure nanocrystalline ZrO2 via a simple sonochemical-assisted route

Pure nanocrystalline zirconia was synthesized via a sonochemical-assisted method based on the reaction between zirconyl nitrate and propylenediamine. Here, propylenediamine for the first time was used as precipitating agent to fabricate nanocrystalline zirconia via a sonochemical-assisted method. The effect of solvent and concentration of propylenediamine on the morphology and crystallite size was investigated. It was shown that morphology and crystallite size of the as-synthesized products could be greatly affected by these parameters. The as-prepared products were characterized by SEM and TEM images, XRD patterns, FT-IR and EDS spectroscopy.