Oriented polycrystalline α-HgI2 thick films grown by physical vapor deposition

This work investigates the growth of polycrystalline α-HgI₂ thick films from physical vapor deposition. By varying the growth conditions, the as-deposited thick films are characterized by scanning electron microscopy, X-ray diffraction, current–voltage and photoconductivity measurements. The growth mechanism and its effects to the properties of these polycrystalline α-HgI₂ thick films are then discussed. Finally, the best deposition conditions for polycrystalline α-HgI₂ thick films compactly formed by separated columnar monocrystallines with uniform orientation along c-direction and with good crystallinity are reported.     

Structure and morphology of [icosahedral Al62Cu25.5Fe12.5]100−x[decagonal Al70Co15Ni15]x alloys, for x=10(03 and 510)

Alloys made from mixtures of Al₆₂Cu_25.5Fe_12.5 icosahedral quasicrystal (IQC) and Al₇₀Co₁₅Ni₁₅ decagonal quasicrystal (DQC) were studied by X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The transition from IQC to DQC was thus discussed by studying the evolution of their constituent phases in each alloy. Three approximant phases were found as common phases in most of the pseudo-binary alloys: λ-Al₁₃Fe₄, β-AlFe and τ3-Al₃Ni₂. It is found that, with the increment of the DQC content in the alloy, the λ phase changes from Al₁₃Fe₄ to Al₁₃Co₄ and the τ3 phase changes from Al₃Cu₂ to Al₃Ni₂. The formation of these phases were found also to follow the evolution of their corresponding e/a-constant lines in the Al–(Cu,Ni)–(Fe,Co) pseudo-ternary phase diagram. Under this framework, the roles played by the related approximants in the transition process are briefly discussed.     

Sol–gel preparation and photoluminescence properties of Ce-activated Y3Al5O12 nano-sized powders

Trivalent cerium-doped yttrium aluminum garnet (YAG:Ce³⁺) nanoparticles were successfully prepared by a facile sol–gel technique. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and photoluminescence (PL) spectroscopy were used to characterize the as-prepared phosphors. Well-crystallized fine nanoparticles were obtained at 1000 °C. Single-crystal nanoparticles with irregular shapes were obtained, with crystallite sizes ranging between 20 and 60 nm. PL intensity of the particles increased monotonically with decreasing Ce doping concentration and showed the maximum value at 0.1 at%.     

Synthesis and optical properties of high-purity CoO nanowires prepared by an environmentally friendly molten salt route

CoO nanowires with diameters of 50^_80 nm, and lengths of up to more than 5 μm have been successfully synthesized by a simple environmentally friendly molten salt route, in which the precursor CoCO₃ nanoparticles are decomposed to form high-purity CoO nanowires in NaCl flux. The structure features and morphology of the as-prepared CoO nanowires were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution TEM (HRTEM), and selected area electron diffraction (SAED). The chemical composition and oxidation state of the prepared nanowires were systemically studied by X-ray photoelectron spectra (XPS) and laser Raman spectroscopy. The results indicated that the as-prepared CoO nanowires were composed of pure cubic CoO phase. The growth mechanism of the synthesized nanowires was also discussed in detail based on the experimental results.     

Controlled synthesis of PAN/Ag2S composites nanofibers via electrospinning-assisted hydro(solvo)thermal method

The Ag₂S nanoparticles embedded in polyacrylonitrile (PAN) fibers matrix were successfully prepared by the combining electrospinning with the hydro(solvo)thermal process, without the presence of any templates or organic surfactants. What's more, the size and content of Ag₂S nanoparticles was tunable through proper controlling of the reaction conditions. Consequently, the Ag₂S nanoparticles with 10-100 nm diameter could be obtained via this two-step synthetic route. The as-synthesized composites nanofibers were investigated by X-ray diffraction(XRD), field-emission scanning electronic microscopy (FE-SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), Fourier transform infrared spectroscopy (FT-IR), and photoluminescence( PL), respectively. What's more, a possible formation mechanism of Ag₂S nanoparticles grown on PAN nanofibers was also proposed.     

Self-assembly of highly crystalline spherical BiVO4 in aqueous solutions

Spherical bismuth vanadate particles are self-assembled from aqueous Bi(NO₃)₃ and NH₄VO₃ solutions by adjusting pH and tuning the amount of surfactant sodium dodecyl sulfate (SDS) via facile hydrothermal method. The BiVO₄ samples were characterized by X-ray diffraction (XRD) and the peaks suited well with the pure phase monoclinic scheelite BiVO₄. Field emission scanning electron microscopy (SEM) showed the average size of the spherical particles was 5 μm and the assembling stages in the hydrothermal synthesis process were recorded. Transmission electron microscopy (TEM) and selected area electron diffraction (SAED) revealed the nanoparticles were single crystal. FT-IR spectroscopy test results demonstrated there was no SDS left in the samples. The mechanism of the self-assembling has also been proposed.     

A simple synthesis of large-scale SiC–SiO2 nanocables by using thermal decomposition of methanol: Structure, FTIR, Raman and PL characterization

Large-scale SiC nanocables were synthesized on a Ni(NO₃)₂-catalyzed Si substrate by using a simple and cheap method based on thermal decomposition of methanol. Based on X-ray diffraction and high-magnification transmission electron microscopy, the as-grown nanocables consisted of crystalline SiC cores and amorphous SiO₂ shells. The diameters of SiC cores were 5.7–10 nm and the thicknesses of SiO₂ shells were 9–20 nm. Dividing of nanocables was observed and its origin was investigated. An asymmetric feature of SiC TO band with a shoulder at the high-frequency side was attributed to the contribution of SiC TO mode. The nanocables displayed strong violet–blue emission. A possible growth mechanism was proposed.     

Tetragonal tungsten oxide nanobelts synthesized by chemical vapor deposition

Tungsten trioxide (WO₃) nanobelts in tetragonal structure were grown on Si substrates by a hot-wall chemical vapor deposition (CVD) method without using catalysts. The products were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, and photoluminescence (PL) spectrum. The width of the nanobelts is in the range of 50–100 nm with width-to-thickness ratios of 5–10 and lengths of up to tens of micrometers. These nanobelts grew along the [0 0 1] direction and can be identified as the tetragonal WO₃ structures. Raman and PL measurements indicate the high quality of the nanobelts. The vapor–solid growth mechanism could be applicable in our experiment.     

Synthesis and characterization of Bi3.15Nd0.85Ti3O12 nanotube arrays

Nd-substituted bismuth titanate (Bi_3.15Nd_0.85Ti₃O₁₂, BNT) nanotube arrays are fabricated by means of a sol–gel method utilizing porous anodic aluminum oxide (AAO) template. The morphologies and structures have been determined by scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The diameter and length of these nanotubes are about 200 nm and 60 μm, respectively, and their wall thickness is about 30 nm. The average grain size is around 40 nm. XRD data show that the BNT nanotubes possess bismuth-layered perovskite structure. High-resolution electron microscopy (HRTEM) image demonstrates that the BNT nanotubes are polycrystalline. Polarization–electric field (P–E) response curves of BNT nanotube arrays were measured, and a size induced polarization reduction phenomenon is observed.     

Crystallization and spectroscopic properties of Eu-doped CaF2 nanocrystals in transparent oxyfluoride glass-ceramics

Transparent oxyfluoride glass-ceramic in the system SiO₂–Al₂O₃–CaF₂–EuF₂ containing Eu-doped CaF₂ nanocrystals were produced by using the controlled crystallization of melt-quenched glass. X-ray diffraction and transmission electron microscopy data have revealed the formation of the CaF₂ nanocrystals of about 65 nm size. Photoluminescence spectra have shown an increase of the splitting of the luminescences associated to the Eu³⁺ ion along with annealing time which is consistent with the Eu³⁺ environment evolving from a glassy to a crystalline state.     

Peculiarities of the growth of KDP single crystals with incorporated aluminium oxyhydroxide nanoparticles

Grown for the first time are KH₂PO₄ (KDP) crystals with incorporated aluminium oxyhydroxide Al₂O₃·nH₂O nanoparticles (n=3.5–3.6). The influence of the nanoparticles on the structure perfection and the growth kinetics of the crystal faces are studied. The presence of the nanoparticles in the crystal matrix is confirmed by the results of chemical analysis, X-ray diffraction (XRD) analysis and transmission electron microscopy (TEM). The most essential inhibiting effect of the nanoparticles is observed for the {100} faces. The mechanism of influence of the nanoparticles on the {100} faces growth is explained on the base of the Cabrera–Vermilyea (C–V) model using Langmuir adsorption isotherm.     

Synthesis and characterization of single-crystalline PrCO3OH dodecahedral microrods and its thermal conversion to Pr6O11

Single-crystalline PrCO₃OH dodecahedral microrods with an orthorhombic structure have been successfully synthesized by the hydrothermal method used urea as the precipitator. Pr₆O₁₁ dodecahedral microrods have been obtained by thermal conversion of PrCO₃OH dodecahedral microrods at 600 °C in air for 6 h. The as-synthesized products were characterized by X-ray powder diffraction, field-emission scanning electron microscope, transmission electron microscopy, high-resolution transmission electron microscopy, selected-area electron diffraction, X-ray photoelectron spectra, fourier transform infrared spectroscopy and thermogravimetry–differential thermal analysis. The effect of the reaction parameters on the morphology of the product has been investigated. The dodecahedral microrods with larger size and better crystallinity can be obtained under the higher reaction temperature. The possible formation mechanism of PrCO₃OH microrods was discussed.     

Nanocomposites based on thermoplastic elastomers with functional basis of nano titanium dioxide

Nanocomposites based on a thermoplastic elastomer (TPE) (low-density polyethylene (LDPE) and 1,2-polybutadiene in a ratio of 60/40) with functional titanium dioxide nanoparticles of different nature, TiO₂/TPE, have been prepared and investigated by a complex of methods (X-ray diffraction analysis using X-ray and synchrotron radiation beams, scanning electron microscopy, transmission electron microscopy, and X-ray energy-dispersive spectroscopy). The morphology of the composites is found to be somewhat different, depending on the TiO₂ characteristics. It is revealed that nanocomposites with cellular or porous structures containing nano-TiO₂ aggregates with a large specific surface and large sizes of crystallites and nanoparticles exhibit the best deformation?strength and fatigue properties and stability to the effect of active media under conditions of ozone and vapor?air aging.     

Morphology transition of one-dimensional ZnO grown by metal organic vapour phase epitaxy on (0 0 0 1)-ZnO substrate

Metal organic vapour phase epitaxy (MOVPE) has been used to successfully grow one-dimensional (1D) ZnO deposits on (0 0 0 1)-ZnO substrate. Dimethylzinc–triethylamine and nitrous oxide were used as zinc and oxygen sources, respectively, with nitrogen as the carrier gas. Vertically aligned 1D ZnO structures were observed along the c-axis by using lower VI/II mole ratio R_VI/II<2025 and/or high growth temperatures (Tg>800 °C). The diameter, length, density and the mechanism of formation could be controlled with the growth time. Scanning electron microscopy (SEM) shows different structures, i.e., sharp-top, flat-top and open-top with slim bottom and large-top one-dimensional ZnO. A good structural quality was revealed by X-ray diffraction rocking curve with a full-width at half-maximum (FWHM) varying from 40 to 92 arcsec with increasing growth time.     

Synthesis of cubic ZrWMoO8 by a melt quenching method

We report a novel approach for fabrication of cubic ZrWMoO₈ applying a melt quenching method. The stoichiometric mixture of ZrO₂, WO₃ and MoO₃ in a 1:1:1 M ratio was melted and quenched at room temperature by pouring the melts between two metal plates. The quenched sample was characterized by X-ray diffraction (XRD), differential thermal analysis (DTA) and scanning electron microscopy (SEM) analysis. As quenched material is polyphase contains above 70% ZrWMoO₈. The obtained composite is thermal stable up to 930 °C. The ZrWMoO₈ was indexed as cubic with a lattice parameter a = 9.1263 (3) Å calculated by the “PowderCell” program. By SEM observation it was established that the microstructure of bulk composite material is built up of one-direction orientated agglomerates with cuboid crystal morphology.     

High-yield synthesis of single-crystal short Eu2O3 nanorods through a facile sol–gel template approach

High-yield Eu₂O₃ short nanorods have been prepared by a facile sol-gel method with polystyrene/polyelectrolyte (PS/PE) microreactor as template in an aqueous solution of europium nitrate in the presence of ammonia and urea. The properties of Eu₂O₃ nanorods were characterized by powder X-ray diffraction, thermogravimetric analysis, transmission electron microscopy (TEM), high-resolution transmission electron microscopy, field emission scanning electron microscopy (FESEM), and photoluminescence spectroscopy. The particle sizes measured from TEM and FESEM are about 200 nm×500 nm (W×L). A possible mechanism for the formation of such high-yield oxide nanorods is discussed.     

Micelle-assisted hydrothermal synthesis of the uniform Co3O4 nanorods and its chemoluminescence properties of CO oxidation

Uniform Co₃O₄ nanorods were prepared by a micelle-assisted hydrothermal method. The samples were characterized by scanning electron microscopy (SEM), energy disperse spectra (EDS), transmission electron microscopy (TEM), selected area electron diffraction (ED), X-ray diffraction (XRD), and N₂ adsorption. The chemoluminescence and catalytic oxidation properties of CO and CH₄ over Co₃O₄ nanorods were investigated. The results showed that the micelles played a key role in the formation of uniform nanorods, that the nanorods with a high crystallinity were obtained after being treated hydrothermally, and that the nanorods showed a higher chemoluminescence (CL) intensity of CO oxidation and a higher activity for CH₄ combustion than the bulk one. The adopted ‘one-pot’ synthesis is a facile method, since no further annealing at high temperatures is needed.     

Effects of ammonium citrate additive on crystal morphology of aluminum phosphate ammonium taranakite

In this communication, we demonstrated the growth of aluminum phosphate ammonium taranakite (NH₄-AlPO₄) crystals from regular hexagonal form into the disk-like form could be controlled by ammonium citrate (AMC) as the effective crystal growth modifier at 90 °C. Prepared crystals were characterized by field emission scanning electron microscopy (SEM) and X-ray diffraction (XRD). The effects of AMC's concentration on the crystal form and morphology of NH₄-AlPO₄ were studied. The results showed that the AMC's concentration is an important parameter to control the size and morphology of NH₄-AlPO₄ crystal. The formation mechanism of the special morphology of NH₄-AlPO₄ crystals was also analyzed.     

The effect of composition and temperature on the amount and type of nanoferrite particles inserted in Fe2O3–ZnO–MgO–SiO2 glass–ceramics

Glass–ceramics with the composition 2Fe₂O₃.1ZnO.1MgO.96SiO₂ [4ZnMgFe] and 2Fe₂O₃.2ZnO.3MgO.93SiO₂ [7ZnMgFe] (mol%) were prepared using the sol–gel method. X-ray diffraction (XRD), scanning electron microscopy (SEM), electron diffraction (ED) and Mössbauer spectroscopy (MS) were used to investigate the glass–ceramics structure. The samples contain ferrite nanoparticles embedded in a glass matrix. However, zinc ferrite nanoparticles seems to be the preferential crystalline phase formed. The amount of ferrite particles depends on treatment temperature and sample composition. The Mössbauer spectroscopy measurements show that ferrite nanoparticles can exhibit a ferrimagnetic behaviour combined with superparamagnetism.     

Energetics of CdSxSe1−x quantum dots in borosilicate glasses

The thermodynamics of CdSe quantum dots embedded in a glass matrix is of great interest because of the numerous applications as optical materials. In this study, the energetics and stability of CdSe quantum dots in a borosilicate glass matrix is investigated as a function of size using high-temperature oxide melt solution calorimetry. CdS_0.1Se_0.9 nanoparticles (1-40 nm) embedded in glass were analyzed by photoluminescence spectroscopy, electron microprobe, X-ray fluorescence, high-energy synchrotron X-ray diffraction, and (scanning) transmission electron microscopy using both electron energy loss and energy dispersive X-ray spectroscopy. As CdSe particles coarsen, their heat of formation becomes more exothermic. The interfacial energy of CdSe QDs embedded in a borosilicate glass, determined from the slope of enthalpy of drop solution versus calculated surface area, is 0.56 ± 0.01 J/m².