Characterization of MMoO4 (M = Ba, Sr and Ca) with different morphologies prepared using a cyclic microwave radiation

Scheelite molybdates (MMoO₄, M = Ba, Sr and Ca) were successfully prepared by the reactions of M(NO₃)₂·2H₂O and Na₂MoO₄·2H₂O in propylene glycol and NaOH using a microwave radiation. The phases were detected using XRD and SAED. TEM analysis revealed the presence of micro-sized bi-pyramids with a square base, nano-sized particles in clusters, and dispersed nano-sized particles for BaMoO₄, SrMoO₄ and CaMoO₄, respectively. Diffraction patterns of the bi-pyramids were simulated, and are in accord with the experimental results. Raman and FTIR spectra provide the evidence of scheelite structure with Mo-O stretching vibration in MoO₄²⁻ tetrahedrons at 742-901 cm^− 1.     

Characterization of CoWO4 nano-particles produced using the spray pyrolysis

CoWO₄ nano-particles were produced by spraying the solution containing CoCl₂·6H₂O and Na₂WO₄·2H₂O on glass slides at 250–450 °C. XRD, SAED, TEM, HRTEM and AFM revealed the presence of CoWO₄ nano-particles with their crystallographic planes aligning in systematic array. Raman spectra provide evidence of the wolframite structure, corresponding to the product phase. Their photoluminescence (PL) emissions show the narrow central peaks of the same spectral region at 411–419 nm.     

Characterization of Cu3SbS4 microflowers produced by a cyclic microwave radiation

Copper antimony sulfide (Cu₃SbS₄) crystals were produced from mixtures of different molar ratios of CuCl, SbCl₃ and thiourea in 40 and 60 ml ethylene glycol (EG) by a 300 W cyclic microwave radiation (CMR) for different lengths of time. In the present research, tetragonal Cu₃SbS₄ microflowers, characterized by X-ray and electron diffraction including electron microscopy and Raman analyses, were successfully produced in the 40 ml solution containing 2:2:4 molar ratio Cu:Sb:S for 40 cycles. Their UV-visible absorption was studied to determine the energy gap (E_g). A formation mechanism was also proposed to relate with the experimental results.     

Formation of titanium nitride on γ-TiAl alloys by direct metal–gas reaction

Two alloys, Ti-47Al-2Nb-2Cr (MJ12) and Ti-47Al-2Nb-2Mn + 0.8TiB₂ (MJ47), were nitrided in purified ammonia for 3.6 × 10³–3.6 × 10⁴ s (1–10 h) at a temperature range of 800–1,000 °C. The nitridation process can successfully improve alloy hardness which increased with an increase of the nitridation temperature and time. Hardness values of MJ12 and MJ47 with 1,000 °C nitridation for 3.6 × 10⁴ s were the highest at 700.5 ± 9.0 and 694.7 ± 21.8 kg mm⁻², respectively. The wear rate and friction coefficient were significantly reduced by the nitridation process. Wear resistance of both alloys increased by two orders of magnitude after nitridation compared to the corresponding alloys without nitridation. In addition, the alloys were analyzed using XRD, SEM, EDX and an optical microscope.     

Refluxing Synthesis and Characterization of UV-Light-Driven Ag-Doped PbMoO4 for Photodegradation of Rhodamine B

Journal of Electronic Materials - Silver-doped lead molybdate (Ag-doped PbMoO4) nanoparticles have been successfully synthesized by a reflux method using ethylene glycol as solvent. x-Ray powder...     

Fabrication of WO3 nanofibers by high voltage electrospinning

Mixtures of 0.1, 0.3, and 0.5 mmol ammonium metatungstate hydrate (AMH), and poly (vinyl alcohol) (PVA) were electrospun by a + 20 kV direct voltage to synthesize fibers. Those of 0.5 mmol AMH were further calcined to have PVA removed and crystalline degree improved. At 500 °C and 2 h calcination, WO₃ nanofibers, including two main stretching modes, 3.24 eV direct energy gap, and 378 nm wavelength violet emission were detected. A possible formation mechanism of WO₃ nanofibers was proposed according to the experimental results.     

Fabrication of ZnWO4 nanofibers by a high direct voltage electrospinning process

Mixtures of zinc acetate dihydrate, ammonium metatungstate hydrate, and 5 wt%, 6 wt%, and 7 wt% of poly (vinyl alcohol) (PVA) were electrospun by a +15 kV direct voltage to produce fibers. In the present research, the electrospun fibers of 6 wt% PVA were further calcined at 400-600 °C for 3 h. The sanmartinite monoclinic structured ZnWO₄ was detected by X-ray diffractometer (XRD) and selected area electron diffraction (SAED), weight loss by thermogravimetric analyser (TGA), morphology and particle size by scanning and transmission electron microscopes (SEM, TEM) and atomic force microscope (AFM), including their vibration modes by Fourier transform infrared spectrometer (FTIR) and Raman spectrometer. The 4.42 eV direct energy gap (E_g) and 460 nm emission wavelength, caused by the electronic transition of (WO₆)²⁻ octahedrons, were determined by UV-visible absorption and photoluminescence (PL) spectrometers. A possible formation mechanism of ZnWO₄ nanofibers was also proposed according to the experimental results.     

Cyclic microwave-assisted synthesis of flower-like and hexapod silver bismuth sulfide

Nanostructured AgBiS₂ with the shapes of flowers and hexapods was successfully produced from AgNO₃, BiCl₃ and sulfur sources (thioacetamide and thiourea) in ethylene glycol, by a cyclic microwave process. The phase was detected using X-ray diffraction (XRD) and selected area electron diffraction (SAED). Their SAED patterns were also in accordance with those of the simulations. Scanning and transmission electron microscopies (SEM and TEM) revealed the gradual transformation of nanostructured flowers into nanostructured hexapods, due to the microwave power increases. Their photoluminescence (PL) emissions were detected at the same wavelength of 435 nm, although they were produced under different conditions.     

Preparation of ear-like, hexapod and dendritic PbS using cyclic microwave-assisted synthesis

Different morphologies of PbS were prepared using microwave-assisted synthesis of 1:4, 1:1 and 4:1 molar ratios of Pb(CH₃COO)₂ to NH₂CSNH₂ in propylene glycol. Cubic PbS was detected using X-ray diffraction (XRD) and selected area electron diffraction (SAED). Raman spectrometry revealed the presence of vibrations at 134, 274 and 430 cm^− 1. The product morphologies for different molar ratios of Pb(CH₃COO)₂ to NH₂CSNH₂ were also characterized using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The obtained morphologies changed with molar ratios used for the starting agents. The simulated diffraction pattern was also in accordance with the interpretation of the experimental results.     

Characterization of cadmium sulfide nanorods prepared by the solvothermal process

Cadmium sulfide nanorods were successfully prepared from cadmium nitrate tetrahydrate and thiourea in ethylenediamine by 200 °C solvothermal reactions using hydroxyethyl cellulose (HEC) as a capping material. X-ray diffraction (XRD), selected area electron diffraction (SAED), and Raman spectroscopy showed that the products were hexagonal wurtzite CdS with the 1st and 2nd harmonic modes at 303.5 and 593.0 cm^− 1, respectively. The intensity ratios of the 2nd to 1st harmonic modes were increased with their aspect ratios, due to the great strength of exciton-phonon coupling. By using scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution TEM (HRTEM) and fast Fourier transformation (FFT), the products were in the shape of nanoparticles in the HEC-free solution, and became nanorods with higher aspect ratios in the HEC-added solutions — especially with longer reaction time. These nanorods were single crystals with growth in the [001] direction.