Fabrication by Electrophoretic Deposition of Nano-Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> 3D Structure on Carbon Fibers as Supercapacitor Materials

Core–shell nanostructured magnetic Fe₃O₄@SiO₂ with particle size ranging from 3 nm to 40 nm has been synthesized via a facile precipitation method. Tetraethyl orthosilicate was employed as surfactant to prepare core–shell structures from Fe₃O₄ nanoparticles synthesized from pomegranate peel extract using a green method. X-ray diffraction analysis, Fourier-transform infrared and ultraviolet–visible (UV–Vis) spectroscopies, transmission electron microscopy, and scanning electron microscopy with energy-dispersive spectroscopy were employed to characterize the samples. The prepared Fe₃O₄ nanoparticles were approximately 12 nm in size, and the thickness of the SiO₂ shell was?~?4 nm. Evaluation of the magnetic properties indicated lower saturation magnetization for Fe₃O₄@SiO₂ powder (~?11.26 emu/g) compared with Fe₃O₄ powder (~?13.30 emu/g), supporting successful wrapping of the Fe₃O₄ nanoparticles by SiO₂. As-prepared powders were deposited on carbon fibers (CFs) using electrophoretic deposition and their electrochemical behavior investigated. The rectangular-shaped cyclic voltagrams of Fe₃O₄@CF and Fe₃O₄@C@CF samples indicated electrochemical double-layer capacitor (EDLC) behavior. The higher specific capacitance of 477 F/g for Fe₃O₄@C@CF (at scan rate of 0.05 V/s in the potential range of ??1.13 to 0.45 V) compared with 205 F/g for Fe₃O₄@CF (at the same scan rate in the potential range of?~???1.04 to 0.24 V) makes the former a superior candidate for use in energy storage applications.     

Effect of SnO2 intermediate layer on performance of Ti/SnO2/MnO2 electrode during electrolytic-manganese process

SnO₂ intermediate layers were coated on the titanium (Ti) substrate by thermal decomposition. Scanning electron microscope (SEM) and X-ray diffraction (XRD) results show that uniform SnO₂ intermediate layers with rutile crystal structure were successfully achieved. According to the results of linear sweep voltammetry (LSV), oxygen evolution potential (OEP) of the Ti/SnO₂/MnO₂ electrodes decreases with increasing SnO₂ content, indicating that the electro-catalytic oxidation activity of the electrode increases. Accelerated service life tests results demonstrate that SnO₂ intermediate layer can improve the service life of the Ti/SnO₂/MnO₂ electrode. As the content of SnO₂ intermediate layer increases, the cell voltage and the energy consumption decrease apparently.     

Comparison of hydrogen-storage properties of Mg-14Ni-3Fe2O3-3Ti and Mg-14Ni-2Fe2O3-2Ti-2Fe

Magnesium with oxides or transition elements prepared by mechanical grinding under H2 (reactive mechanical grinding) showed relatively high hydriding and dehydriding rates when the content of additives was about 20 wt%. Ni, Fe₂O₃, and Fe were chosen as the oxides or transition elements to be added. Ti was also selected since it was considered to increase the hydriding and dehydriding rates by forming Ti hydride. Samples Mg-14Ni-3Fe₂O₃-3Ti (Sample A) and Mg-14Ni-2Fe₂O₃-2Ti-2Fe (Sample B) were prepared by reactive mechanical grinding, and their hydrogen storage properties were compared. The activated Sample A had a little smaller hydriding rate than the activated Sample B, but a higher dehydriding rate than the activated Sample B. Sample A exhibits quite a larger dehydriding rate and quantity of hydrogen desorbed for 60 min than any other Mg-xNi-yFe₂O₃-zM (M=transition metals) samples. An addition of a relatively larger amount of Ti is considered to lead to quite a high hydriding rate and a high dehydriding rate of Sample A.     

Fe2O3在钛合金干滑动磨损及摩擦层形成中的作用

通过在Ti6Al4V合金滑动界面人工添加Fe_2O_3纳米颗粒及其与TiO_2、MoS_2的混合物,试图促进含Fe_2O_3摩擦层在室温下的快速形成;研究了Fe_2O_3、TiO_2、MoS_2在钛合金滑动过程中的作用,并探讨Fe_2O_3相对含量对钛合金磨损行为及磨损机制的影响。结果表明:干滑动下的Ti6Al4V合金耐磨性较差,磨面添加的TiO_2进一步加速磨损,MoS_2一定程度上降低了磨损但并不显著,而Fe_2O_3完全抑制磨损但增大了摩擦系数。高载下,富TiO_2、MoS_2颗粒并不能形成摩擦层,反而聚集在磨面犁沟或者凹坑处,而富Fe_2O_3则容易形成致密的摩擦层覆盖于磨损表面,这证实了钛合金高温耐磨性的改善是由于Fe_2O_3的出现。混合MoS_2+80%(质量分数)Fe_2O_3形成的摩擦层,兼具MoS_2的润滑性和Fe_2O_3的承载能力,给Ti6Al4V合金带来最佳的摩擦磨损性能。     

直流电弧等离子体法制备In(Sn)-O及Sn(In)(Sb)-O系纳米颗粒

采用一种新的直流电弧等离子体法,通过对熔融的金属进行爆破(或气化),制备出了单相SnO₂、In₂O₃纳米颗粒以及In₂O₃:Sn (ITO)、SnO₂:Sb (ATO)和SnO₂:In:Sb (IATO)多元复合纳米颗粒。XRD结果表明,所制备的SnO₂和In₂O₃基多元复合纳米颗粒均为单相结构,没有其它杂相;TEM结果表明,直流电弧等离子体所制备的单相纳米颗粒分散性好,尺寸约20-50nm。该法合成的纳米ITO和ATO颗粒所制备的ITO靶材和SnO₂电极密度高、电阻率低,表明所制备的ITO和ATO纳米颗粒可以应用于平板显示和导电电极领域。     

Band gap and superior refractive index tailoring properties in nanocomposite thin film achieved through sol-gel co-deposition method

Transparent nanocomposite ZrO₂-SnO₂ thin films with molar ratio 0.1/0.9 (ZS19), 0.3/0.7 (ZS37), 0.5/0.5 (ZS55), 0.7/0.3 (ZS73) and 0.9/0.1 (ZS91) of ZrO₂/SnO₂ were prepared by sol-gel dip-coating technique. X-ray diffraction (XRD) spectra showed a mixture of three phases: tetragonal ZrO₂ and SnO₂ and orthorhombic ZrSnO₄. X-ray photoelectron spectroscopy (XPS) gives Zr 3d, Sn 3d and O1s spectra on ZS55 thin film which revealed the presence of oxygen vacancies in the nanocomposite ZrO₂-SnO₂ thin film. Scanning electron microscopy (SEM) observations showed that microstructure of ZS55 consists of uniformly dispersed isolated SnO₂ particles in ZrO₂ matrix. An average transmittance greater than 85% (in UV-visible region) is observed in the films ZS55, ZS73 and ZS91, but superior optical properties was observed in ZS55 thin film. The composite system under certain compositional mixings (ZS55) displayed a refractive index supremacy over pure zirconia films which can be directly employed in extending the range of tunability of the refractive index. Besides, these films also demonstrated tailoring of band gap values. Photoluminescence (PL) spectra revealed an intense emission peak at 424 nm in ZS55 sample which indicates the presence of oxygen vacancies in ZrSnO₄. All these characterizations distinctly indicate a strong interrelation between the microstructural ordering and superior optical properties of the present ZrO₂-SnO₂ co-deposited composites.     

Effects of Plasma-spraying Powers on Microstructure and Microhardness of In-Situ Nanostructured FeAl2O4 Composite Coatings

In-situ nanostructured FeAl₂O₄ composite coatings were prepared using plasma spraying of Al/Fe₂O₃ composite powders applying different spraying powers. The effects of plasma-spraying powers on microstructure and property of FeAl₂O₄ composite coatings were investigated. The results indicated the composite coatings had the microstructure with thin lamellar splats rich in FeAl₂O₄ as matrix, and dispersed granules rich in Fe and thin lamellar splats rich in Al₂O₃ as second phases. The reaction degree of Al/Fe₂O₃ composite powders increased while applying spraying power of 25-30 kW and then decreased while applying spraying power of 30-40 kW, which first resulted in the increase and then in the decrease of the Al₂O₃ content. The coating prepared by applying spraying power of 30 kW had the maximum microhardness, which was attributed to the maximum Al₂O₃ content present in the coating and the most uniform microstructure of the coating.     

High Temperature Oxidation of Hot-Dip Aluminized T92 Steels

The T92 steel plate was hot-dip aluminized, and oxidized in order to characterize the high-temperature oxidation behavior of hot-dip aluminized T92 steel. The coating consisted of Al-rich topcoat with scattered Al₃Fe grains, Al₃Fe-rich upper alloy layer with scattered (Al, Al₅Fe₂, AlFe)-grains, and Al₅Fe₂–rich lower alloy layer with scattered (Al₅Fe₂, AlFe)-grains. Oxidation at 800 °C for 20 h formed (α-Al₂O₃ scale)/(AlFe layer)/(AlFe₃ layer)/(α-Fe(Al) layer), while oxidation at 900 °C for 20 h formed (α-Al₂O₃ scale plus some Fe₂O₃)/(AlFe layer)/(AlFe₃ layer)/(α-Fe(Al) layer) from the surface. During oxidation, outward migration of all substrate elements, inward diffusion of oxygen, and back and forth diffusion of Al occurred according to concentration gradients. Also, diffusion transformed and broadened AlFe and AlFe₃ layers dissolved with some oxygen and substrate alloying elements. Hot-dip aluminizing improved the high-temperature oxidation resistance of T92 steel through preferential oxidation of Al at the surface.     

Controllable Low-Temperature Hydrothermal Synthesis and Gas-Sensing Investigation of Crystalline SnO<Subscript>2</Subscript> Nanoparticles

SnO₂ nanoparticles have been successfully synthesized by a facile hydrothermal method from SnCl₂·2H₂O, hexamethylenetetramine, and trisodium citrate in water at 120 °C for 12 h. The effects of surfactant and precipitant on SnO₂ synthesis were investigated. SnO₂ nanoparticles can be synthesized in the temperature range of 120-180 °C with long reaction time in the presence of trisodium citrate. When NaOH was used as precipitant instead of hexamethylenetetramine, it is difficult to obtain SnO₂ nanoparticles at 120 °C in the presence of trisodium citrate. SnO₂ nanoparticles with an average size of about 5 nm show good crystallinity and excellent sensitivity to ethanol and acetaldehyde in about 55% relative humidity.     

The formation and evolution of oxide particles in oxide-dispersion-strengthened ferritic steels during processing

The fabrication of oxide-dispersion-strengthened (ODS) steels is a multi-stage process involving powder ball milling, degassing and consolidation by hot isostatic pressing. Y is introduced by mechanical alloying (MA) with either Y₂O₃ or Fe₂Y so a high density of Y–Ti–O-based oxide nanoparticles is formed. The evolution of ～2 nm oxide nanoparticles and larger >5 nm grain boundary oxides has been studied at each step of the processing. The nanoparticle dispersions produced in material MA with Fe₂Y were comparable to those produced by alloying with Y₂O₃. Hence the majority of oxygen which forms the nanoparticles must be incorporated from the atmosphere during MA, rather than being introduced via the alloying additions. During mechanical alloying, a high density of subnanometer particles are formed (2.5 ± 0.5 × 10²⁴ m^?3). The oxygen content of the nanoparticles decreases slightly on annealing, and then the composition of the nanoparticles remains constant throughout subsequent processing stages. The nanoparticle size increases during processing up to ～2 nm radius, while the number density decreases to 4 ± 0.5 × 10²³ m^?3. Grain boundary oxides (>5 nm) have a Ti–Cr–O-rich shell, and contain no Y before consolidation, but have similar core composition to the matrix nanoparticles after consolidation. The formation of the larger grain boundary oxides is shown to take place during the degassing and consolidation stages, and this occurs at the expense of the nanoparticles in the matrix. This work provides a mechanistic understanding of the importance of controlling the oxygen content in the powder during MA, and the resulting impact on the formation of the ODS microstructure.     

Preparation and characterization of nanostructured Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-13wt.%TiO<Subscript>2</Subscript> ceramic coatings by plasma spraying

Nanostructured and conventional Al₂O₃-13wt.%TiO₂ ceramic coatings were prepared by plasma spraying with nanostructured agglomerated and conventional powders, respectively. The microstructure and microhardness of the coatings were investigated using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and microhardness measurement. Meanwhile, the friction and wear behaviors were analyzed and compared using a ball-on-disk tribometer. The results show that the conventional coating has lamellar stacking characteristic and has some pores. However, the nanostructured coating shows a bimodal microstructure, which is composed of both fully melted regions and partially melted regions. According to the microstructural difference, the partially melted regions can be divided into liquid-phase sintered regions (a three-dimensional net or skeleton-like structure: Al₂O₃-rich submicron particles embedded in the TiO₂-rich matrix) and solid-phase sintered regions (remained nanoparticles). The microstructural characteristics of the liquid-phase sintered region are formed due to the selective melting of TiO₂ nanoparticles during plasma spraying. On the other hand, the TiO₂ and Al₂O₃ nanoparticles of the solid-phase sintered regions are all unmelted during plasma spraying. Due to the existence of nanostructured microstructures, the nanostructured coating has a higher microhardness, a lower friction coefficient, and a better wear resistance than the conventional coating.     

Highly selective acetone sensor based on ternary Au/Fe2O3-ZnO synthesized via co-precipitation and microwave irradiation

Ternary Au/Fe₂O₃-ZnO gas-sensing materials were synthesized by combining co-precipitation and microwave irradiation process. The as-prepared Au/Fe₂O₃-ZnO was characterized with X-ray diffractometer and scanning electron microscope, and its gas-sensing performance was measured using a gas-sensor analysis system. The results show that the as-prepared products consist of hexagonal wurtzite ZnO, face-centered cubic gold nanoparticles and orthorhombic Fe₂O₃ crystallines. The Au/Fe₂O₃-ZnO based sensor has a very high selectivity to ethanol and acetone, and also has high sensitivity (154) at a low working temperature (270 °C) and an extremely fast response (1 s) against acetone. It is found that the selectivity can be adjusted by Fe₂O₃ content added in the ternary materials. It possesses a worth looking forward prospect to practical applications in acetone detecting and administrating field.     

A novel two-step modifying process for preparation of chitosan-coated Fe3O4/SiO2 microspheres

Functionalized Fe₃O₄ nanoparticles decorated with silica and chitosan have been prepared via two steps in this paper. The first step involved magnetite nanoparticles (Fe₃O₄) homogeneously incorporated into silica spheres using the modified Stöber process. Second, the silica-coated Fe₃O₄ nanoparticles were covered with the outer shell of cationic polyelectrolyte chitosan by a layer-by-layer assembly process. X-ray diffraction results indicated that the surface-modified Fe₃O₄ nanoparticles did not lead to phase change compared with the pure Fe₃O₄. Transmission electron microscopy studies revealed nanoparticles remained monodisperse, and silica shells have trapped more than one magnetic core. Average particle sizes of chitosan-coated Fe₃O₄/SiO₂ microspheres are about 80–100 nm. In addition, super-paramagnetic properties of hybrid microspheres have also been detected by a vibrating-sample magnetometer. It may make the hybrid microspheres of important use in mild separation, enzyme immobilization, etc.     

Study on synthesis and anticorrosion properties of polymer nanocomposites based on super paramagnetic Fe2O3·NiO nanoparticle and polyaniline

In this study, Fe₂O₃·NiO/PANi nanocomposites were prepared and their anticorrosion properties were investigated. The Fe₂O₃·NiO nanoparticles were synthesized by precipitation–oxidation methods. Fe₂O₃·NiO–PANi nanocomposites were prepared by in situ polymerization of aniline monomer in the presence of Fe₂O₃·NiO nanoparticle. The structure of the polymer nanocomposite was characterized by SEM and X-ray method. The electrical conductivity, magnetic properties and anticorrosion properties of the materials were examined by the conventional four probe method, vibrating magnetometer and by impedance measurement method. The results show that the Fe₂O₃·NiO nanoparticles have the uniform size with the size ranging from 50 to 60 nm. By the formation of polymer nanocomposite, the Fe₂O₃·NiO phase is well dispersed in the PANi polymer matrix. But the Fe₂O₃·NiO nanoparticles are not exfoliated from its agglomerate structure. The polymer nanocomposite showed both magnetic and conductive properties. With increasing Fe₂O₃·NiO content, both the saturated magnetization and the coercive force increase and reach the value of 0.31 emu/g and 162.56 Oe by the Fe₂O₃·NiO content of 5%, respectively. In contrast, the electrical conductivity of the polymer nanocomposite decreases with increasing Fe₂O₃·NiO content from 0.353 S/cm of neat PANi to 0.075 S/cm by the Fe₂O₃·NiO content of 5%. From the anticorrosion investigation, it was revealed that the protective performance of polyurethane paint containing Fe₂O₃·NiO/PANi nanocomposite was significantly improved with increasing Fe₂O₃·NiO/PANi content.     

High-Temperature Corrosion of Aluminized and Chromized Fe–25.8 %Cr–19.5 %Ni Alloys in N2/H2S/H2O-Mixed Gases

Alloys of Fe–25.8 %Cr–19.5 %Ni (SUS310 stainless steel) were either chromized or aluminized via pack cementation, and corroded at 800 °C for 100 h in 1 atm of (0.9448 atm of N₂ + 0.031 atm of H₂O + 0.0242 atm of H₂S)-mixed gases. The chromized layer consisted primarily of Cr_1.36Fe_0.52 and some Cr₂₃C₆. Its corrosion resulted in the formation of Cr₂S₃ and some FeS and Fe₅Ni₄S₈. The aluminized coating consisted primarily of FeAl. Its corrosion resulted in the formation of α-Al₂O₃, Al₂S₃, and Cr₂S₃. Aluminizing was more effective than chromizing in increasing the corrosion resistance of the substrate, due mainly to the formation of α-Al₂O₃.     

Ultrasonic-assisted in situ synthesis and characterization of superparamagnetic Fe3O4 nanoparticles

Superparamagnetic Fe₃O₄ nanoparticles were synthesized via a modified coprecipitation method, and were characterized with X-ray diffraction (XRD), vibrating sample magnetometer (VSM), Zeta potential and FT-IR, respectively. The influences of different kinds of surfactants (sodium dodecyl benzene sulfonate, polyethyleneglycol, oleic acid and dextran), temperatures and pH values on the grain size and properties were also investigated. In this method, Fe³⁺ was used as the only Fe source and partially reduced to Fe²⁺ by the reducing agent with precise content. The following reaction between Fe³⁺, Fe²⁺ and hydroxide radical brought pure Fe₃O₄ nanoparticles. The tiny fresh nanoparticles were coated in situ with surfactant under the action of sonication. Comparing with uncoated sample, the mean grain size and saturation magnetization of coated Fe₃O₄ nanoparticles decrease from 18.4 nm to 5.9-9.0 nm, and from 63.89 emu g⁻¹ to 52-58 emu g⁻¹ respectively. When oleic was used as the surfactant, the mean grain size of Fe₃O₄ nanoparticles firstly decreases with the increase of reaction temperature, but when the temperature is exceed to 80 °C, the continuous increase of temperature resulted in larger nanoparticles. the grain size decreases gradually with the increasing of pH values, and it remains unchanged when the PH value is up to 11. The saturation magnetization of as-prepared Fe₃O₄ nanoparticles always decreases with the fall of grain size.     

Toughening and strengthening mechanism of plasma sprayed nanostructured Al2O3–13 wt.%TiO2 coatings

The starting materials of Al₂O₃, TiO₂, ZrO₂ and CeO₂ nanoparticles were agglomerated into sprayable feedstock powders and plasma sprayed to form nanostructured coatings. There were net structures and fused structures in plasma sprayed nanostructured Al₂O₃–13 wt.%TiO₂ coatings. The net structures were derived from partially melted feedstock powders and the fused structures were derived from fully melted feedstock powders. The nanostructured Al₂O₃–13 wt.%TiO₂ coatings possessed higher hardness, bonding strength and crack growth resistance than conventional Metco 130 coatings which were mainly composed of lamellar fused structures. The higher toughness and strength of nanostructured Al₂O₃–13 wt.%TiO₂ coatings were mainly related to the obtained net structures.     

Deposition of Al2O3-TiO2 Nanostructured Powders by Atmospheric Plasma Spraying

Al₂O₃-13%TiO₂ coatings were deposited on stainless steel substrates from conventional and nanostructured powders using atmospheric plasma spraying (APS). A complete characterization of the feedstock confirmed its nanostructured nature. Coating microstructures and phase compositions were characterized using SEM, TEM, and XRD techniques. The microstructure comprised two clearly differentiated regions. One region, completely fused, consisted mainly of nanometer-sized grains of γ-Al₂O₃ with dissolved Ti⁺⁴. The other region, partly fused, retained the microstructure of the starting powder and was principally made up of submicrometer-sized grains of α-Al₂O₃, as confirmed by TEM. Coating microhardness as well as tribological behavior were determined. Vickers microhardness values of conventional coatings were in average slightly lower than the values for nanostructured coating. The wear resistance of conventional coatings was shown to be lower than that of nanostructured coatings as a consequence of Ti segregation. A correlation between the final properties, the coating microstructure, and the feedstock characteristics is given.     

Electro-catalytic degradation properties of Ti/SnO<Subscript>2</Subscript>–Sb electrodes doped with different rare earths

Ti/SnO₂–Sb electrode has a good effect on the removal of organic pollutants. But its short service life limits its large-scale application in industry. Electro-catalytic degradation performances and service life of the electrode can be significantly improved by doping rare earth (RE) ions into the oxide coating of Ti/SnO₂–Sb electrode. Ti/SnO₂–Sb electrodes doped with different RE elements (Ce, Dy, La, and Eu) were prepared by the thermal decomposition method at 550 °C. Electro-catalytic degradation performances of electrodes doped with different RE elements were evaluated by linear sweep voltammetry (LSV) and Tafel curves. During the electrolysis, the conversion of p-nitrophenol was performed with these electrodes as anodes under galvanostatic control. The structures and morphologies of the surface coating of the electrodes were characterized by scanning electron microscope (SEM). The results demonstrate that the electro-catalytic degradation performances of Ti/SnO₂–Sb electrodes are improved to different levels by doping different RE ions. Improved Ti/SnO₂–Sb electrodes by the introduction of different RE have higher oxygen evolution potential, better electro-catalysis ability, better coverage, and longer electrode life.     

Synthesis and characterization of SnO2/polyaniline nanocomposites by sol–gel technique and microemulsion polymerization

Nanostructured SnO₂ was prepared based on the sol–gel method. Aniline monomer was polymerized by microemulsion polymerization in the presence of nanocrystalline SnO₂ to form inorganic–organic nanocomposite materials, in which SnO₂ nanoparticles were embedded within porous polyaniline (PANI). Structural and morphological characterization of SnO₂ and SnO₂/PANI was carried out using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The XRD pattern suggested that PANI did not modify the crystal structure of SnO₂. FT-IR spectrum proved that aniline was successfully composited with the nanostructured SnO₂. TEM analysis showed that the SnO₂ nanoparticles with a diameter of ca. 15 nm were embedded well in the porous PANI. Conductivity analysis indicated that the SnO₂/PANI nanocomposites had a higher conductivity than that of the pure SnO₂ nanopowders.