Evaluation of Composition,Microstructure Characterization and Interfacial Properties of Zn—SnO<Subscript>2</Subscript> Metal Matrix Composite Coating

In this paper the microstructure and tribological behavior of Zn—SnO₂ (Zn—Sn) alloys produced through chloride and sulphates co-deposition is presented for comparison. 7.0 wt % SnO₂ was added to Zn bath and deposited at 0.3 V. The interfacial effect and microchemistry of the fabricated composite was studied by optical microscope, X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with energy disperse spectrum (EDS). The tribological behavior of the metal composites with SnO₂ particles as reinforcement was studied using reciprocating sliding tester. The scanning electron microscopy (SEM) and atomic force microscope (AFM) of the composite surfaces indicates that there is good interfacial interaction between the alloy formulated matrixes made from the two baths and the substrate. Reasonable uniform distribution of Sn metal phase particulates is shown for both coating alloy. Increases in hardness and wear resistance are attributed to the uniform and coherent precipitation in the metal interface especially for Zn—7Sn—S—0.3V. In general, 7 wt % Sn additions to the bath showed more hastening to improved surface properties and better mechanical characteristics.     

Synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanosized powders prepared using a simple co-precipitation process

The synthesis and crystallization behavior of 3 mol% yttria stabilized tetragonal zirconia polycrystals (3Y-TZP) nanopowders prepared using a simple co-precipitation process at 348 K and pH = 7 were investigated using differential scanning calorimetry/thermogravimetry (DSC/TG), an X-ray diffractometer (XRD), the Raman spectra, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and an energy dispersive spectrometer (EDS). The activation energy of tetragonal ZrO₂ crystallization from 3Y-TZP freeze-dried precursor powders using a non-isothermal method, namely, 169.2 ± 21.9 kJ mol⁻¹, was obtained. The growth morphology parameter n was approximated as 2.0, which indicated that it had a plate-like morphology. The XRD, Raman spectra, and SAED patterns showed that the phase of the tetragonal ZrO₂ was maintained at 1273 K. The crystallite size of 3Y-TZP freeze-dried precursor powders calcined at 1273 K for 5 min was 21.3 nm.     

Preparation and microstructure characterization of a nano-sized Ti<Superscript>4+</Superscript>-doped AgSnO<Subscript>2</Subscript> electrical contact material

A Ti⁴⁺-doped nano-structured AgSnO₂ material was prepared using sol-gel method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The results show that Ti⁴⁺ cations are successfully doped into the crystal lattice of SnO₂, and thus significantly improve the electrical conductivity of the sample. Furthermore, the coating of Ag on Ti⁴⁺-doped SnO₂ nano-sized particles enhances the surface wettability and enables the resulting AgSnO₂ material to have better mechanical properties.     

Fabrication and magnetic properties of NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanorods

NiFe₂O₄ nanorods have been successfully synthesized via thermal treatment of the rod-like precursor fabricated by Ni-doped α-FeOOH, which was enwrapped by the complex of citric acid and Ni²⁺. The morphology evolution during the calcination of the precursor nanorods was investigated with transmission electron microscopy (TEM), and the phase and the magnetic properties of samples were analyzed through X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The results indicated that the diameter of the NiFe₂O₄ nanorods obtained ranged between 30 and 50 nm, and the length ranged between 2 and 3 μm. As the calcination temperature was up to 600°C, the coercivity, saturation magnetization, and remanent magnetization of the samples were 36.1 kA·m⁻¹, 27.2 A·m²·kg⁻¹, and 5.3 A·m²·kg⁻¹, respectively. The NiFe₂O₄ nanorods prepared have higher shape anisotropy and superior magnetic properties than those with irregular shapes.     

Gas sensing properties of nano-crystalline SnO<Subscript>2</Subscript>-CuO compounds

We fabricated a micro gas sensor for hydrogen sulfide (H₂S) gas using MEMS technology and the sol-gel process, and synthesized SnO₂-CuO as a sensing material by the sol-gel method. Synthesized particles of SnO₂-CuO were characterized with an average particle size of about 40 nm as measured by FE-SEM imagery and XRD peaks. The sensing material was coated on the micro platform and annealed at 400 °C. The maximum gas sensitivity (R_s= R_g/R_a) was 0.005 at 300 °C for 1.0 ppm — H₂S. The gas sensitivity showed linear behavior with increasing H₂S concentration.     

Luminescence properties of red-emitting Ca<Subscript>2</Subscript>Al<Subscript>2</Subscript>SiO<Subscript>7</Subscript>:Eu<Superscript>3+</Superscript> nanoparticles prepared by sol-gel method

A series of red-emitting Ca2-xAl2SiO7:xEu3+(x = 1 mol.%-10 mol.%) phosphors were synthesized by the sol-gel method.The effects of annealing temperature and doping concentration on the crystal structure and luminescence properties of Ca2Al2SiO7:Eu3+ phosphors were investigated.X-ray diffraction(XRD) profiles showed that all peaks could be attributed to the tetragonal Ca2Al2SiO7 phase when the sample was annealed at 1000℃.Scanning electron microscopy(SEM) micrographs indicate that the phosphors have an irregularly rounded morphology with particles of about 200 nm.Excitation spectra showed that the strong broad band at around 258 nm and weak sharp lines in 350-490 nm were attributed to the charge transfer band of Eu3+-O2-and f-f transitions within the 4f6 configuration of Eu3+ ions,respectively.Emission spectra implied that the red luminescence could be attributed to the transitions from the 5D0 excited level to the 7FJ(J = 0,1,2,3,4) levels of Eu3+ ions with the main electric dipole transition 5D0→7F2(618 and 620 nm),and Eu3+ ions prefer to occupy a lower symmetry site in the crystal lattice.Moreover,the photoluminescence(PL) intensity was strongly dependent on both the sintering temperature and doping concentration,and the highest PL intensity was observed at an Eu3+ concentration x = 7 mol.% after annealing at 1100℃.The obtained Ca2Al2SiO7:Eu3+ phosphor may have potential application for the red lamp phosphor.     

Microstructure and growth morphology of Frank-Kasper phase in rapidly solidified Mg<Subscript>32</Subscript>Al<Subscript>17</Subscript>Zn<Subscript>32</Subscript> ternary alloys

In the present investigation, the microstructures and growth morphology of Mg₃₂(Al,Zn)₄₉ Frank-Kasper phase in rapidly solidified Mg₃₂Al₁₇Zn₃₂ ternary alloys were studied in detail. The samples were characterised by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM) and energy dispersive spectrum (EDS). The results show that the microstructures mainly consist of Mg₃₂(Al,Zn)₄₉ Frank-Kasper phase and interdendritic Mg-rich Φ-phase. Under rapid solidification condition, Mg₃₂(Al,Zn)₄₉ Frank-Kasper phase reveals a perfect faceted dendritic characteristic in the shape of a three-fold symmetric microstructure with doublet tips in the axes direction. Observations for fracture surfaces show that the growth morphology of Mg₃₂(Al,Zn)₄₉ grains was truncated cubic, and its growth mechanism was also discussed.     

~ ~ 3＋ Sol-gel synthesis and photoluminescence characterization of La2Ti2O7.EU3＋nanocrystals

Eu³⁺ doped La₂Ti₂O₇ nanocrystals with pure monoclinic phase and size of about 100 nm were prepared by a citric acid (CA) assisted sol-gel method. Techniques of thermo-gravimetric (TG) and differential scanning calorimetry (DSC), X-ray diffraction (XRD), as well as transmission electron microscopy (TEM) were employed to characterize the as-synthesized nanoparticles. Furthermore, photoluminescence (PL) performances of the Eu³⁺ doped La₂Ti₂O₇ nanocrystals were evaluated with focus on the effects of calcination temperature and Eu³⁺ doping concentration on the photoluminescence properties.     

Performance and capacity fading reason of LiMn<Subscript>2</Subscript>O<Subscript>4</Subscript>/graphite batteries after storing at high temperature

Spinel LiMn₂O₄ was synthesized by a solid-state method. A 204468-size battery was fabricated and stored at 55°C. The structure and morphology of the LiMn₂O₄ cathode were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) technique. Energy dispersive spectroscopy (EDS) was used to analyze the surface component of the carbon anode. The discharge capacities of LiMn₂O₄ stored for 0, 24, 48, and 96 h are 106, 98, 96, and 92 mAh·g⁻¹, respectively. The cyclic performance is improved after storage. The capacity retentions of LiMn₂O₄ stored for 0, 24, 48, and 96 h are 83.8%, 85.8%, 86.9%, and 88.6% after 180 cycles. The intensity of all the LiMn₂O₄ diffraction peaks is weakened. Mn is detected from the carbon electrode when the battery is stored for 96 h. Cyclic voltammograms and electrochemical impedance spectroscopy (EIS) were used to examine the surface state of the electrode after storage. The results show that the resistance and polarization of LiMn₂O₄/electrolyte is increased after storage, which is responsible for the fading of capacity.     

Luminescence of complex ion WO12 in Dy doped nanocrystal Gd6WO12 phosphor

Nanocrystal Gd₆WO₁₂ phosphor doped with Dy³⁺ was prepared by a co-precipitation method. X-ray diffraction (XRD), scanning electron microscopy (SEM) and selected area electron diffraction (SAED) were used to characterize the structure and morphology of the resultant phosphor. It was found that the phosphor exists in tetragonal phase and the phosphor particles show sphere-like shape with an average size of 31 nm. In aid of excitation and emission spectra, the energy levels of the complex ion WO₁₂¹⁸⁻ were confirmed, and that the possible luminescent mechanisms for various wavelengths excitation were analyzed. The cross relaxation and energy transfer between complex ion and Dy³⁺ were discussed. The dependence of luminescent intensity and color coordinates on the excitation wavelength was also investigated.     

Effect of calcination temperature and atmosphere on crystal structure of BaTiO<Subscript>3</Subscript> nanofibers

Barium titanate (BaTiO₃, BT) nanofibers with a diameter range of 160 nm to 300 nm were prepared by drying electrospun BT/polyvinylpyrrolidone (BT/PVP) composite fibers for 1 h at 80 °C in vacuum with a subsequent calcination in air for 1 h at a temperature range of 650 °C to 750 °C. The morphology and crystal structure of calcined BT nanofibers were characterized with the aid of XRD, FT-IR, SEM, and TEM. The XRD and FR-IR measurements confirm that BT nanofibers with a diameter of about 160 nm and a tetragonal perovskite structure were present in the electrospun fibers after calcination for 1 h at 750 °C. The FR-IR analysis of the BT fibers reveals that the intensity level of the O-H stretching vibration bands (at 3430 cm⁻¹ and 1425 cm⁻¹) become weaker as the calcination temperature is increased and that a broad band at 570 cm⁻¹, which represents the Ti-O vibration, appears sharper and narrower after calcination at 750 °C due to the formation of metal oxide bonds. In contrast, BT fibers prepared by a refluxing process in a nitrogen atmosphere show a dramatic change in crystal structure: the tetragonal structure changes to a cubic perovskite structure, probably due to the suppression of carbonate contamination. Thus, the calcination temperature and atmosphere appear to have a significant influence on the crystal structure of BT.     

Novel AgCl/Ag<Subscript>2</Subscript>CO<Subscript>3</Subscript> heterostructured photocatalysts with enhanced photocatalytic performance

A series of novel AgCl/Ag₂CO₃ heterostructured photocatalysts with different AgCl contents (5 wt%, 10 wt%, 20 wt%, and 30 wt%) were prepared by facile coprecipitation method at room temperature. The resulting products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), respectively. The photocatalytic activity of the samples was evaluated by photocatalytic degradation of methyl orange (MO) under UV light irradiation. With the optimal AgCl content of 20 wt%, the AgCl/Ag₂CO₃ composite exhibits the greatest enhancement in photocatalytic degradation efficiency. Its first-order reaction rate constant (0.67 h^?1) is 5.2 times faster than that of Ag₂CO₃ (0.13 h^?1), and 16.8 times faster than that of AgCl (0.04 h^?1). The formation of AgCl/Ag₂CO₃ heterostructure could effectively suppress the recombination of the photo-generated electron and hole, resulting in an increase in photocatalytic activity.     

Hydrothermal synthesis of YBO3:Tb microflowers and their luminescence properties

Three-dimensional flowerlike YBO₃:Tb³⁺ phosphors have been successfully prepared by an efficient surfactant-free hydrothermal process directly without further sintering treatment. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy-dispersive X-ray (EDS) spectrometry, selected area electron diffraction (SAED), photoluminescence (PL) spectra were used to characterize the samples. The as-obtained samples present flowerlike agglomerates composed of nanoflakes with thickness of 20 nm and high crystallinity in spite of the moderate reaction temperature of 180 °C. The reaction mechanism has been considered as a dissolution/precipitation mechanism; the self-assembly evolution process has been proposed on homocentric layer-by-layer growth style. The different luminescent intensity with different molar ratio of Y-Tb [Y:Tb = 8:2; 7:3; 6:4; 5:5; 4:6], YBO₃:Tb³⁺ phosphors exhibit different light (white, red, green) under ultraviolet excitation, which might find potential applications in the fields such as light display systems and optoelectronic devices.     

Synthesis and measurement of structural and magnetic properties of K-doped LaCoO<Subscript>3</Subscript> perovskite materials

Polycrystalline La_1−x K _x CoO₃ (0 ≤ x ≤ 0.2) rare earth cobaltates have been synthesized by a solution combustion method using glycine as a fuel. The synthesized ceramic materials were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and magnetic measurements and studied for physical properties, such as photocatalytic activity. FTIR measurements in conjunction with XRD showed that phases beyond 10% K doping are accompanied by small amounts of impurities. Chemical titrations show the presence of Co⁴⁺ and account for the Co³⁺-Co⁴⁺ mixed-valency of the system. The parent LaCoO₃ shows spin-glass transition at low temperatures, whereas doped samples show transition from spin-glass behavior to paramagnetic ordering on progressive doping of K. “Mixed-conductor” nature of these ceramics positions them as viable candidates for solid oxide fuel cell (SOFC) applications.     

Gas phase synthesis of SnOx nanoparticles and characterization

Tin oxide nanoparticles with an average size ranging from 4 to 80 nm were synthesized by oxidation of tin vapor in a low vacuum (10–40 mbar) reactor containing an Ar/O₂ gas mixture. The effect of oxygen and argon partial pressure on the phase formation, size characteristics and morphology of the particles was studied by transmission electron microscopy (TEM) and X-ray diffraction (XRD) method. Electron spectroscopy chemical analysis (ESCA) was used to study the state of the particle surfaces. It was shown that with increasing the oxygen partial pressure, coarser SnO_x particles were synthesized. The ESCA shift for the tin 3d_5/2 line was 2 eV and the separation between this line and the oxygen 1s line was 44 eV. The oxygen 1s line was narrow and symmetric without the OH tail, indicating clean surface. The O/Sn ratios were estimated by using the areas of the tin and oxygen lines, and it was found that the oxidized tin vapor consisted of both SnO and SnO₂. At the oxygen concentration of 50 vol% and the total pressure of 10 mbar, the surface composition was estimated to be SnO_1.2. The particles were transformed to tetragonal SnO₂ after heat treatment at 350 °C for 24 h in air.     

Preparation and characterization of Eu^3＋-doped CaCO3 phosphor by microwave synthesis

A Eu³⁺-doped CaCO₃ phosphor with red emission was prepared by microwave synthesis. The scanning electron microscopy (SEM) image and laser particle size analysis show that the CaCO₃:Eu³⁺ particles are needle-like in the length range of 5.0–10.0 μm. The results of X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy (FT-IR), and Raman spectroscopy indicate that pure aragonite CaCO₃:Eu³⁺ is prepared using microwave irradiation and the Eu³⁺ ion as a luminescence center inhabits the site of Ca²⁺. The photoluminescence excitation (PLE) spectrum shows that the strong broad band at around 270 nm and weak sharp lines in 300–550 nm are assigned to the charge transfer band of Eu³⁺-O²⁻ and intra-configurational 4f-4f transitions of Eu³⁺, respectively. The photoluminescence (PL) spectrum implies that the red luminescence can be attributed to the transitions from the ⁵D₀ excited level to the ⁷F _J (J = 0, 1, 2, 3, 4) levels of Eu³⁺ ions with the mainly electric dipole transition ⁵D₀ → ⁷F₂ (614 and 620 nm), and the Eu³⁺ ions prefer to occupy the low symmetric site in the crystal lattice.     

Preparation and characterization of nanostructured Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript> and Sn<Subscript>0.5</Subscript>-Bi<Subscript>2</Subscript>Se<Subscript>3</Subscript>

Nanostructured Bi₂Se₃ and Sn_0.5-Bi₂Se₃ were successfully synthesized by hydrothermal coreduction from SnCl₂·H₂O and the oxides of Bi and Se. The products were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field emission scanning electron microscope (FESEM). Bi₂Se₃ powders obtained at 180°C and 150°C consist of hexagonal flakes of 50–150 nm in side length and nanorods of 30–100 nm in diameter and more than 1 μm in length. The product obtained at 120°C is composed of thin irregular nanosheets with a size of 100–200 nm and several nanometers in thickness. The major phase of Sn_0.5-Bi₂Se₃ synthesized at 180°C is similar to that of Bi₂Se₃. Sn_0.5-Bi₂Se₃ powders are primarily nanorod structures, but small amount of powders demonstrate irregular morphologies.     

Sol-gel preparation and characterization of Li1.3Al0.3Ti1.7（PO4）3 sintered with flux of LiBO2

Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ were prepared by sol-gel method. The structural identification, surface morphology, ionic conductivity, and activation energy of the pellets were studied by X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. The results show that all the Li_1.3Al_0.3Ti_1.7(PO₄)₃ pellets sintered with different mole fractions of LiBO₂ have similar X-ray diffraction patterns. The sintered pellet becomes denser and the boundary and corner of the particles become illegible with the increase of LiBO₂. Among the Li_1.3Al_0.3Ti_1.7(PO₃)₄ pellets sintered with different mole fractions of LiBO₂, the one sintered with 1 mol% LiBO₂ shows the highest ionic conductivity of 3.95×10⁻⁴ S.cm⁻¹ and the lowest activation energy of 0.2469 eV.     

Deposition and properties of highly <Emphasis Type="Italic">c</Emphasis>-oriented of InN films on sapphire substrates with ECR-plasma-enhanced MOCVD

InN films with highly c-axis preferred orientation were deposited on sapphire substrate by low-temperature electron cyclotron resonance plasma-enhanced metal organic chemical vapor deposition (ECR-PEMOCVD). Trimethyl indium (TMIn) and N2 were applied as precursors of In and N, respectively. The quality of as-grown InN films were systematically investigated as a function of TMIn fluxes by means of reflection high-energy electron diffraction (RHEED), X-ray diffraction analysis (XRD), and atomic force microscopy (AFM). The results show that the dense and uniform InN films with highly c-axis preferred orientation are successfully achieved on sapphire substrates under optimized TMIn flux of 0. 8 ml·min-1. The InN films reported here will provide various opportunities for the development of high efficiency and high-performance semiconductor devices based on InN material.     

Synthesis of LiFePO<Subscript>4</Subscript>/C as cathode material by a novel optimized hydrothermal method

Olivine LiFePO 4 , as a cathode material for lithium ion batteries, was prepared by a novel optimized hydrothermal method; afterwards, the product mixed with glucose was two-step (350℃ and 700℃) calcinated under high-purity N 2 atmosphere to obtain the LiFePO 4 /C composite. The study on the hydrothermal preparation method, which focused on the influences of molar ratios, initial pH value, reaction temperature, and duration, was made to promote the resultant performances and to investigate the relations between the performances and the reaction conditions. The resultant samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical tests, which include charge-discharge, electrochemical impedance spectroscopy, and cyclic voltammetry. The result shows that the optimal hydrothermal condition is to set the Li:Fe:P molar ratio at 3:1:1 and the reaction temperature at 180℃ for 5 h duration with an initial pH value of 7. The optimized sample, with an average particle size of 100 to 300 nm and a discharge capacity of 118.2 mAh·g-1 at 0.1C, exhibits a stable and narrow-gapped charge-discharge platform and small capacity losses after cycles.