A nanostructured ternary coating of Ti/(Ru + Ti + Ce)O2 was prepared by the conventional electrodeposition on the titanium substrate as the cathode with different numbers of coating layers. The main objective of this work was to study nanostructured coatings of ceramic materials. For this purpose, the amount of precursor materials in the electrolyte was a variable parameter. Furthermore, the salt of TiCl4/RuCl3·xH2O/Ce(NO3)3·6H2O with different amounts, hydrogen peroxide, methanol, and distilled water were used as an aqueous–unaqueous bath. In addition, the coated samples were put to heat at 300, 450, 650, and 850 °C in an electric furnace for 1 h. The crystalline phase of the coating was characterized by X-ray diffraction (XRD). The chemical composition and microstructure of the coating were studied using energy-dispersive spectroscopy (EDS) and scanning electron microscopy analysis (SEM). Moreover, the electrochemical measurement of Ti/(Ru + Ti + Ce)O2 coatings was carried out. Results show that with the increase in the number of coating layers, the quality of morphology is improved. Then, the best quality of coatings is obtained at six layers on the titanium substrate with electrolyte including TiO2/RuO2/CeO2 with the molar ratio of 70:5:25 after heat treatment at 450 °C for 1 h. Besides, with the increase in CeO2 content from 5 wt% to 25 wt% and the number of coating layers, higher thickness of about (20.0 ± 0.1) µm and minimum over potential for chlorine evolution were obtained.
The stable and crystalline phase of pure nano- structured CeO2 was directly synthesized by flame-assisted spray pyrolysis and solid state diffusion route. Different characterization techniques, including X-ray diffraction （XRD）, scanning electron microscopy （SEM）, Fourier trans- form infrared spectroscopy （FTIR）, ultraviolet-visible （UV- Vis）, and thermo gravimetric analysis （TGA） were employed to examine the structural, morphological, optical, and thermal properties of the final product. Similarly, the comparative carbon dioxide （CO2）-sensing response of as-synthesized CeO2 nanoparticles by both routes was also reported. The CeO2 nanoparticles synthesized by solid state diffusion method exhibit good sensitivity （3.38 %） at room temperature, low operating temperature （398 K）, fast response time （32 s）, and recovery time （36 s） along with good stability.
Mn3+ and Bi3+ co-doped Y6WO12 samples with hexagonal structure were synthesized via an improved salt pyrogenation method at a temperature region of 700-1100 A degrees C for 3 h. In Y6WO12, Mn3+, substituting Y3+, occupies a seven-coordination site and its energy levels are treated in near O-h symmetry. The samples doped by Mn3+ alone emit the most intensive blue light at 420 nm under excitation at 247 nm due to charge transition (CT). The mechanism of sensitization of Bi3+ for Y6WO12:Mn3+ was also analyzed by taking account of metal-to-metal charge-transfer (MMCT) from Bi3+ to Mn3+. As a consequence, the phosphor Y6WO12:Mn3+/Bi3+ can emit blue light under radiation of 370 nm, and the emission intensity is enhanced about five times by the sensitizer Bi3+. The optimal doping concentration of Bi3+ is determined as 1 at% for the emission at 420 nm in Y6WO12:0.5 at% Mn3+ phosphors.
TG1; Powder of Ti-46at.%Al was synthesized through mechanical activation (MA) for different milling times, and the 16 h MAed powder was sintered by using a spark plasma sintering (SPS) process at different sintering temperatures. The XRD profiles showed that the MAed Ti-46at%Al powder for 12,16, and 20 h contained initial α-Ti and Al phases, and that the SPSed TiAl alloys contained the gamma TiAl and α2-Ti3Al phases. The TEM showed two different types of regions in the 16 h MAed Ti-46at.%Al powder. One type consisted of only Al with a grain size about 80 nm, and the other type a mixture of Al and Ti with a grain size of 30 nm. According to the optical micrographs of MA-SPSed samples, the alloys sintered at higher temperatures showed a coarser microstructure. In the case of the 1473 K sintering, typical duplex structures ((α2 + γ) lamella and γ phases) with interlamellar spacings of 50-400 nm and the grain size either less man 100 nm, or 1000 nm were observed.
In this paper, two ways of microstructural characterization, optical microscopy (OM) and polarized light microscopy (PLM), were both employed to describe the microstructure of semisolid slurry prepared by swirling enthalpy equilibration device (SEED). The results show that PLM is more reliable and accurate than OM to describe the special morphology feature of semisolid slurry made by SEED process. Meanwhile, the effects of pouring temperature and mass of molten liquid on the primary α-Al particle size and morphology were also investigated using PLM. The quantitative metallographic results measured from PLM demonstrate that the grain size and morphology and their distribution are significantly affected by both pouring temperature and the mass of molten liquid. The grain size poured with 2.7 kg liquid decreases from 659 to 186 μm, and grain morphology transforms from dendrite to globular structure with pouring temperature reducing from 690 to 630 °C. The decreasing pouring temperature also promotes the distribution of spherical structure on the cross section. Meanwhile, the mass of molten liquid decreasing from 2.7 to 2.3 kg can decrease the grain size by maximum of 44% at high pouring temperature.
The aim of this paper is to characterize the evolution of fine and spheroidal microstructure of Al–Zn–Mg–Cu alloy by strain-induced melting activation (SIMA) and recrystallization and partial remelting (RAP) routes. The phase transformation and microstructural evolution were investigated during the isothermal treatment in a wide semisolid temperature range from 550 to 610 °C. Effects of isothermal temperatures and processing routes on coarsening rate constant were also analyzed. The results show that during the semisolid isothermal treatment, recrystallization process occurred and intermetallic particles were gradually dissolved into the liquid matrix once the heating temperature was above the solidus. Further extension of soaking time led to the coarsening and spheroidization of the solid grains. The increase in the soaking temperatures raised the liquid fraction and accelerated the spheroidization process. Smaller spheroidal grains and better spheroidization effect were obtained in SIMA microstructure in comparison to RAP microstructure. The coarsening rate constants were, respectively, 319 and 454 μm3·s−1 in SIMA samples after soaked at 600 and 610 °C. The coarsening rate constants of 349 and 522 μm3·s−1 were achieved in RAP microstructure.
The microstructures and grain boundary morphologies of a novel Co–9Al–9W–2Ta–0.02B alloy doped with yttrium (Y) (0.01, 0.05, 0.10, and 0.20; at%) were investigated as functions of aging temperatures (900 and 1000 °C) and time (50 and 150 h). The aged alloys all exhibit a γ/γ′-Co3(Al, W) coherent microstructure in grain interiors, whereas an intermetallic κ-Co3(W) phase precipitates at grain boundaries. Y is found to fully segregate at grain boundaries and changes grain boundary precipitate morphologies. For 0.01Y alloy, bright κ-Co3(W) stripes precipitate along grain boundaries, where a needlelike κ-Co3(W) phase grows from grain boundaries or κ-Co3(W) stripes toward grain interior. As the nominal Y content increases, the stripe and needlelike κ-Co3(W) precipitates at grain boundaries are strongly restrained and disappear in 0.20Y alloy, leaving fine κ-Co3(W) particles scattered at grain boundaries. It is noted that more Y segregation may increase the number of low-angle grain boundaries (LABs, with misorientations of <15°), whereas it eliminates O impurities from grain boundaries. Finally, the effect of Y segregation on tensile behavior of Co–Al–W–Ta–B alloy was discussed from the viewpoints of grain boundary precipitate morphologies, grain boundary character distribution (GBCD), and impurity segregation.
To access, purchase, authenticate, or subscribe to the full-text of this article, please visit this link: http://dx.doi.org/10.1007/s12598-017-0920-y The forming process and mechanism of the reaction of Ti6Al4V investment casting made by Zr(C[H.sub.3]COO).sub.2-[Y.sub.2]O.sub.3 shell in vacuum casting was studied. Statistic was manipulated to study the distributions and types of the reaction layers. The morphology and composition of the reaction layers were tested using field emission scanning electron microscopy (FESEM) combined with energy-dispersive spectroscopy (EDS). Phase of the reaction layers was characterized by X-ray diffraction (XRD). Composition of the shell reaction zone was measured by X-ray fluorescence (XRF) method. The results suggest the reaction contains oxidation and element evaporation, and the melt reacts little with the shell but mainly with the remnant gas. The reaction layers contain three types due to different forming stages: the titanium oxidation film, the concretion film and the shell reaction zone. The interfacial temperature and pressure affect the reaction mechanism and degree, leading to three types of concretion films that differ in thickness, content and color.
Stir casting is an economical process for the fabrication of aluminum matrix composites.There are many parameters in this process,which affect the final microstructure and mechanical properties of the composites.In this study,micron-sized SiC particles were used as reinforcement to fabricate Al-3 wt% SiC composites at two casting temperatures（680 and 850 ℃） and stirring periods（2 and 6 min）.Factors of reaction at matrix/ceramic interface,porosity,ceramic incorporation,and agglomeration of the particles were evaluated by scanning electron microscope（SEM） and high-resolution transition electron microscope（HRTEM） studies.From microstructural characterizations,it is concluded that the shorter stirring period is required for ceramic incorporation to achieve metal/ceramic bonding at the interface.The higher stirring temperature（850 ℃） also leads to improved ceramic incorporation.In some cases,shrinkage porosity and intensive formation of Al4C3 at the metal/ceramic interface are also observed.Finally,the mechanical properties of the composites were evaluated,and their relation with the corresponding microstructure and processing parameters of the composites was discussed.
Platinum was electrodeposited onto a polyaniline-modified carbon fiber electrode by the cyclic voltammetric method in sulfuric acid, which may enable an increase in the level of platinum u tilization currently achieved in electrocatalyric systems. This electrode preparation consists of a two-step procedure: first electropolymerization of aniline onto carbon fiber and then electrodeposition of platinum. The catalytic activity of the platinum-polyaniline-modified carbon fiber electrode (Pt/PAni/C) was compared with that of a bare carbon fiber electrode (Pt/C) by the oxidation of methanol. The maximum oxidation current of methanol on Pt/PAni/C is 50.7 mA.cm-2, which is 6.7 times higher than 7.6 mA.cm-2 on the Pt/C.Scanning electron microscopy was used to investigate the dispersion of the platinum particles of about 0.4 μm.
The effects of annealing on the phase transformation behavior and superelasticity of cold-rolled Ti50Ni48Fe2 shape memory alloy were extensively investigated. Curves of temperature dependence of electrical resistivity reveal that both the cold-rolled and annealed specimens exhibit a B2→R→B19’two-stage martensitic transformation upon cooling and a B19’→B2 one-stage transformation upon heating, although the austenitic transformation temperature decreases with the increase of the annealing temperature. Tensile stress–strain curves show the critical stress for stress-induced martensite（rSIM）of Ti50Ni48Fe2 alloys decreases with the increase of annealing temperature due to the decrement of dislocation density caused by the recrystallization. As a result, the rSIM decreases. Upon a cold-rolling and annealing at 623 K for30 min, the Ti50Ni48Fe2 alloy exhibits excellent superelasticity with the maximum recoverable strain of 5.8 % at a loading strain of 7 %. In such a case, a complete superelasticity of 5 % can be obtained in the Ti50Ni48Fe2 alloy after deformation increasing to 15 cycles.
Effects of hot plastic deformation on microstructures and tensile properties of AZ91 alloy were investigated. Compared with as-T4 microstructures, the as-extruded samples of AZ91 alloy with fine grains exhibit better strength and ductility due to dynamic recrystallization. The succeeded rotation forging also provides finer grains while the strength in creases, but the elongation decreases. Simultaneously, wrought AZ91 alloy shows more balance properties than as-T4 condition ones. An interesting elongation of 228.5% is attained in the as-extruded AZ91 alloy in spite of the coarse grains with the size of 85 μm. The two-step method enhances the superplastic property of AZ91 alloy. The microstructure is still keep ing the same scale of grains after superplastic testing.
A highly accurate and reproducible micellar sensitized kinetic method was proposed for determination of V(VI). The method is based on its catalytic effect on the oxidation of Coomassie brilliant blue R 250 (CBB+) by bromate at pH 2.0. The reaction was monitored spectrophotometrically by measuring absorbance change with a fixed-time method of 5 min at 594 and 552 nm with and without surfactant. The variables influencing the calibration sensitivity were extensively investigated, and the optimal conditions were established. The linear calibration range was 10–1,600 μg·L−1 with a relative SD ranging from 0.35 % to 3.35 % (for five replicate measurements of 75, 500, 1,000, and 1,500 μg·L−1) and a detection limit of 3.8 μg·L−1. The selectivity was also investigated, and greatly enhanced by suitable masking agents. The method was successfully applied to the analysis of V(IV) in presence of excess V(V) up to 25 fold in environmental waters with the recoveries of 100.0 %–102.8 % for V(IV) and 95.7 %–99.7 % for total V. Its accuracy was validated by analysis of certified reference material via the present kinetic method and standard flame atomic absorption spectrometric method after extractive preconcentration with good agreement between certified and found values.
The crystal structure and magnetic properties of SmFe9-x Co (x) (x = 0, 1, 3, 5) alloys were studied by X-ray powder diffraction (XRD) and magnetic measurements. The Th2Zn17-type structure of the as-cast state is changed to TbCu7-type structure after quenching to a rotating molybdenum roll under certain velocity (12, 20, and 32 m center dot s(-1)). The (002) XRD peak appears and alpha-Fe phase disappears when the Co is added up to x = 5. Saturation magnetization of SmFe9 under different temperature shows 9 % change (112-102 A center dot m(2)center dot g(-1)) when the temperature is higher than 200 K. The saturation magnetization is 115 A center dot m(2)center dot g(-1) and coercivity is 0.304 T at 5 K for SmFe9 alloys. Increased saturation magnetization and decreased coercivity can be obtained for Co added up to x = 5 at 5 K.