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1.
《稀有金属(英文版)》2016,(5)
Ti/SnO_2–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/SnO_2–Sb electrode. Ti/SnO_2–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/SnO_2–Sb electrodes are improved to different levels by doping different RE ions. Improved Ti/SnO_2–Sb electrodes by the introduction of different RE have higher oxygen evolution potential, better electro-catalysis ability, better coverage,and longer electrode life. 相似文献
2.
Shui-Jin Yang Yu-Lin Xu Wen-Peng Gong Yong-Kui Huang Guo-Hong Wang Yun Yang Chuan-Qi Feng 《稀有金属(英文版)》2016,35(10):797-803
H3PW12O40/TiO2–SiO2 was synthesized by impregnation method which significantly improved the catalytic activity under simulated natural light. The properties of the samples were characterized by Fourier transform infrared spectra (FTIR), X-ray powder diffraction pattern (XRD), Scanning electron micrographs (SEM), and Zeta potential. Degradation of methyl violet was used as a probe reaction to explore the influencing factors on the photodegradation reaction. The results show that the optimal conditions are as follows: initial concentration of methyl violet of 10 mg·L?1, pH of 3.0, catalyst dosage of 2.9 g·L?1, and light irradiation time of 2.5 h. Under these conditions, the degradation rate of methyl violet is 95.4 %. The reaction on photodegradation for methyl violet can be expressed as the first-order kinetic model, and the possible mechanism for the photocatalysis under simulated natural light is suggested. After used continuously for five times, the catalyst keeps the inherent photocatalytic activity for degradation of dyes. The photodegradation of methyl orange, methyl red, naphthol green B, and methylene blue was also tested, and the degradation rate of dyes can reach 81 %–100 %. 相似文献
3.
W. Nowicki Z. Piskuła P. Kirszensztejn 《Protection of Metals and Physical Chemistry of Surfaces》2016,52(5):786-792
A series of SiO2–SnO2 samples of the Sn/Si molar fractions of 0.05, 0.1, 0.25, 0.5 and 1.0 were synthesised by the sol-gel method in anhydrous conditions. The SiO2–SnO2 samples were characterised by XRD, low-temperature nitrogen adsorption, SEM, 29Si MAS NMR and TPD, using pyridine and acetonitrile as probes. It has been proved that incorporation of small or even insignificant amount of tin in the structure of SiO2 gel lattice considerably increased the number and power of acidic centres accessible to the probe molecules in the samples synthesised by the sol-gel method in anhydrous conditions. The increase in the number and power of acidic centres can substantially improve the catalytic properties of the SiO2–SnO2 system. 相似文献
4.
Yan-Xiu Wang Ting-An Zhang Guo-Zhi Lv Xiao-Feng Zhu Wei-Guang Zhang Li-Qun Xie 《稀有金属(英文版)》2016,35(6):495-501
Titanium has a great effect on the digestion of bauxite in the Bayer process because it reacts readily at high temperatures in alkaline sodium aluminate solution. Under this consideration, the hydrothermal conversion of Ti-containing minerals in the system of Na2O–Al2O3–SiO2–CaO–TiO2–H2O with increased temperatures was studied based on the thermodynamic analysis and systematic experiments. The results show that anatase converts to Al4Ti2SiO12 at low temperatures (60–120 °C), which is similar to anatase in crystal structure. As the temperature continues to rise, Al4Ti2SiO12 decomposes gradually and converts to Ca3TiSi2(Al2Si0.5Ti0.5)O14 at 200 °C. When the temperature reaches 260 °C, CaTiO3 forms as the most stable titanate species for its hexagonal closest packing with O2? and Ca2+. The findings enhance the understanding of titanate scaling in the Bayer process and clarify the mechanism of how additive lime improves the digestion of diaspore. 相似文献
5.
Raj Kumar Das Animes Kumar Golder 《Surface Engineering and Applied Electrochemistry》2017,53(6):570-579
This work focuses on the role of common supporting electrolytes (SEs) in the electro-chemical inertness of Ti-based materials employed for the anodic (direct) oxidation coupled with H2O2 electro-generation at the graphite cathode for the concurrent decomposition of organic contaminants. SEs are added to boost up the ionic conductivity of solution but a question always remains on the effect of SEs on the stability of anode materials. The use of ClO 4 ? is encouraged in the electro-Fenton process as it does not form complexes with Fe2+/Fe3+; however, it is found that ClO 4 ? corroded the TiO2 coated Ti (TiO2–Ti) anode very fast (>60 min) and, Ti4+ ions formed a yellow color complex (λmax = 380 nm) with H2O2. The influence of Cl–, NO 3 ? and SO 4 2? was insignificant on the stability of TiO2–Ti. The cell current efficiency of H2O2 formation dropped sharply with in the case of TiO2–Ti anode. The TiO2–Ti corrosion also reduced the mass transfer co-efficient of DO transport from bulk to the cathode surface because of Ti4+ adsorption on graphite. 相似文献
6.
The electrical characteristics of Ta/Ta2O5 films and Ta/Ti−O/Ta2O5 films deposited by RF reactive sputtering on Ta/Ti/Al2O3 substrates were investigated. Ta was used for the bottom and upper electrodes in order to simplify the fabrication process.
Dielectric materials were annealed at 700°C for 60 sec under vacuum. XRD analysis showed that Ta was crystalline and Ta2O5 was amorphous in an as-deposited state, but amorphous Ta2O5 was transformed to a crystalline state by rapid thermal heat treatment. We compared lnJ-E2, C−V, and C−F of both as-deposited and annealed dielectric thin films deposited on the Ta bottom electrode. From these results,
we concluded that introducing a Ti−O buffer layer could reduce the leakage current. The conduction mechanisms of Ti−O/Ta2O5 could be interpreted appropriately by hopping conduction and space-charge-limited current. 相似文献
7.
F. L. Yu Y. Bai P. D. Han Q. L. Shi S. Ni J. H. Wu 《Journal of Materials Engineering and Performance》2016,25(12):5220-5224
In the present work, the α/β Si3N4 ceramics were fabricated by spark plasma sintering (SPS) at 1400-1500 °C for 6 min with 3wt.%MgO + 5wt.%Al2O3 and 3wt.%MgO + 5wt.%Y2O3 as sintering additives. The results showed that the phase composition, microstructure and mechanical properties of α/β Si3N4 ceramics were highly dependent on the type of sintering additive. The incomplete phase transformation from α to β occurred in the presence of an oxynitride (Mg-Al(Y)-Si-O-N) liquid phase. Compared with MgO-Al2O3, MgO-Y2O3 can significantly improve the β conversion rate of as-sintered α/β Si3N4 ceramics. And the as-sintered ceramics using MgO + Al2O3 as sintering additives had higher mechanical properties. 相似文献
8.
The pH value and viscosity of Y2O3–SiO2 (Y–Si) slurry made by Y2O3 powders and silica sol for the face coat of Ti–6Al–4V investment casting were measured. The thermal behavior of the shell made by the Y–Si face coat system was investigated by differential scanning calorimeter (DSC), thermal gravimetric (TG) analysis combined with mass spectrometry (MS), and the phase transformations were determined by X-ray diffraction (XRD). Hot strength, residual strength, linear expansion coefficient, and wearing resistance performance of the shell were also tested. The microstructure and elements distribution of the interaction layer were studied by scanning electron microscope (SEM) and energy-dispersive spectrometer (EDS), respectively. The microhardness tester was applied for the microhardness. The results showed that the slurry was stable for at least 60 h. A very small amount of YZrO3 was formed below 1050 °C and Y2SiO5 was formed around 1450 °C. The shell made by Y–Si system had good mechanical property which could reduce cracks during the procedure of dewaxing and inclusions during pouring. Some Al volatilized from the melt, permeated the surface of the face coat shell, and formed the black reaction layer, which blocked the permeation of O so that O penetration was limited to 5 μm. The depth of Si penetration was about 60 μm. The hard layer was also around 60 μm. 相似文献
9.
N. V. Stolyarchuk I. V. Mel’nik Yu. L. Zub M. Barczak A. Dabrowski B. Alonso 《Protection of Metals and Physical Chemistry of Surfaces》2009,45(2):169-176
Xerogels with a bifunctional surface layer of the ≡Si(CH2)3NH2/≡Si(CH2)3SH composition are synthesized by hydrolytic co-polycondensation of bis(triethoxy)silane (C2H5O)3Si(CH2)2Si(OC2H5)3 and two trifunctional silanes, namely, 3-aminopropyltriethoxysilane and 3-mercaptopropyltrimethoxysilane. Using IR, 1H MAS NMR, and 13C CP/MAS NMR spectroscopic techniques, it is shown that in addition to complexing groups, the surface layer also contains water, silanol groups that are involved in the hydrogen bond formation and also residual ethoxysilyl groups. According to 29SiCP/MAS NMR spectroscopic data, the degree of polycondensation of synthesized xerogels exceeds 80%. It is found that the use of 1,2-bis(triethoxysilyl)ethane as the structuring agent in place of tetraethoxysilane allows one to synthesize bifunctional xerogels with the highly developed biporous structure (S sp = 607–680 m2/g, V c = 1.38–1.47 cm3/g, d = 2.9–3.1 and 18.3 nm). Changing the ratio structuring-silane/functionalizing-silane-mixture from 2: 1 to 4: 1 in the reaction system has virtually no effect on the porous structure parameters of final xerogels. 相似文献
10.
Electrochemical and interfacial properties of (PEO)10LiCF3SO3−Al2O3 composite polymer electrolytes (CPEs) prepared by either ball milling or stirring are reported. Ball milling was introduced
into a slurry preparative technique utilizing PEO, lithium salt and Al2O3 powder ranging from 5 to 15 wt.%. The ionic conductivity was increased by ball milling over a range of temperatures. In particular,
a significant increase at low temperature below the melting point of crystalline PEO was observed. Interfacial stability between
lithium electrode and CPE was significantly improved by the addition of alumina as well as by ball milling. The electrochemical
stability window produced by (PEO)10LiCF3SO3−Al2O3 ball milling was higher than that of stirring, which was about 4.4 V. Charge/discharge performance of Li/CPE/S cells with
(PEO)10LiCF3SO3−Al2O3-12 hr ball milling was superior to that of a pristine polymer electrolyte due to the low interface resistance and high ionic
conductivity. 相似文献
11.
M. Ghaderi M. Rezagholizadeh A. Heidary S. M. Monirvaghefi 《Protection of Metals and Physical Chemistry of Surfaces》2016,52(5):854-858
In this study, the Ni–B–Al2O3 composite was successfully coated on the surface of Ck45 steel by elecroless method. X-Ray diffraction analysis (XRD) and scanning electron microscopy (SEM) were utilized in order to investigate and identify the coating properties. Wear behavior of the coating was studied by the pinon- disk test. Corrosion behavior of the Ni–B and Ni–B–Al2O3 coatings was investigated by using Tafel polarization diagrams in the 3.5% NaCl solution at room temperature. The obtained data demonstrate that the addition of Al2O3 nanoparticles to the coating has resulted in improving the tribological behavior of the coating due to the presence of the composite nanoparticles. Also, the results of electrochemical testing show that corrosion resistance of the electroless Ni–B coating with Al2O3 nanoparticles has dramatically increased. 相似文献
12.
The influence of the holding time upon annealing on the temperature of the viscous–brittle transition (temperature of embrittlement) Tf in a cobalt-based amorphous alloy of the composition Co69Fe3.7Cr3.8Si12.5B11 with a very low saturation magnetostriction λs (<10–7) has been studied. It has been established that the dependence of the embrittlement temperature Tf on the of time of holding ta can be described by an Arrhenius equation and that the embrittlement at the annealing temperatures above and below 300°C is described by different kinetic parameters. In the alloy under study, irrespective of the holding time, embrittlement occurs in a very narrow range of annealing temperatures, which does not exceed 5 K. Based on the experimental data on the evolution of the hysteresis magnetic properties upon the isochronous annealings and upon the isothermal holding, the regime of heat treatment that ensures a very high (about 50000) magnitude of the permeability µ5 (H = 5 mOe, f = 1 kHz) without the transition of the alloy into a brittle state has been determined. 相似文献
13.
In this study, the surface morphology of Ni–P–SiO2 composite coating was investigated by field emission scanning electron microscopy (FESEM). The amount of SiO2 in the coating was examined by energy dispersive analysis of X-ray (EDX) and the Corrosion behavior of coating was evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques, showing the corrosion resistance of Ni–P–SiO2 diminished after heat treatment. The results showed that in the coating with 12.5 g/L SiO2, the coating hardness enhanced from 453VH to 980 VH before and after heat treatment. Furthermore, the wear behavior of the coating was analyzed before and after heat treatment. 相似文献
14.
E. Sadeghimeresht H. Hooshyar N. Markocsan S. Joshi P. Nylén 《Oxidation of Metals》2016,86(3-4):299-314
Isothermal oxidation behavior of an HVAF-sprayed NiCoCrAlY coating on AISI 304L was studied in an Ar–10 %H2–20 %H2O environment at 600 °C. Techniques such as BIB/SEM, EDS, and XRD were used to comprehensively characterize the coating and the coating/substrate interface to investigate the oxidation mechanisms. Results were also compared with those obtained from an uncoated AISI 304L substrate. The alumina-forming NiCoCrAlY coating was found to exhibit superior oxidation behavior due to the formation of a slow-growing and protective Al2O3 scale, while the chromia-forming bare 304L substrate lost its protective capability due to the formation of a duplex [Fe3O4 on (Fe,Cr)3O4 spinel oxide] corrosion product layer. 相似文献
15.
Noveed Ejaz Liaqat Ali Furqan Ahmed Khalid Mahmood Ghauri A. Nusair Khan 《Journal of Thermal Spray Technology》2017,26(5):913-928
A novel thermal barrier coating system was formulated to resist hot corrosion environments. In this coating system, 5% CaZrO3 was added to conventional yttria-stabilized zirconia (YSZ). The above composite coating system was compared with the standard YSZ system in the presence of a mixture of 50% Na2SO4 and 50% V2O5 at 950 °C. The results demonstrated that the lifetime of the CaZrO3-added composite system in this highly hostile environment was longer compared with the standard YSZ system. This is due to the fact that the preferential reaction of NaVO3 shifted from yttria to calcia, forming CaV2O4 instead of YVO4. The preferential reactions are discussed in terms of free energy changes and acid–base theory of molten salts with ceramic oxides. Furthermore, calculations of lattice distortion also proved that the CaZrO3-added composite system demonstrated less distortion, thus increasing the overall lifetime of the coating system. 相似文献
16.
Li Guolu Xu Zhonglin Dong Tianshun Wang Haidou Liu Jinhai Kang Jiajie 《Journal of Thermal Spray Technology》2016,25(7):1365-1372
NiCr–Cr3C2 coating was fabricated using supersonic plasma spraying technology. Subsequently, rolling/sliding contact fatigue (R/SCF) testing was carried out, using acoustic emission (AE) technology to monitor the failure process. The results showed that R/SCF consists of three failure modes, namely abrasion, spalling, and delamination. Abrasion is the main failure mode, but delamination is the most severe. The AE monitoring results indicated that the R/SCF failure process is composed of normal contact, crack initiation, crack propagation, and material removal stages. The frequency of each stage was analyzed by fast Fourier transform, revealing a peak frequency for each stage mainly distributed from 200 to 250 kHz. 相似文献
17.
Alka Gupta Ambreen Nisar Shobit Omar Kantesh Balani 《JOM Journal of the Minerals, Metals and Materials Society》2018,70(10):1937-1945
The grain growth kinetics of 8YSZ ceramics processed using spark plasma sintering (SPS) has been investigated in the temperature ranging from 1100°C to 1500°C. The activation energy during SPS densification was obtained as 332 kJ/mol with grain boundary diffusion as a dominant mechanism. Further, the effect of CeO2 on the densification kinetics of 8YSZ ceramic processed via SPS and conventional sintering (CS) has been delineated. The lower grain boundary mobility of CS-processed composites (an order of magnitude lower than SPS) is attributed to the solute drag and lattice distortion mechanism. However, no significant change in the grain boundary mobility was observed with CeO2 addition (~?14.7–43.9?×?10?18 m3/N/s for CS and 107.2–116.7?×?10?18 m3/N/s for SPS) revealing that the defect concentration is nearly constant in 8YSZ. The study highlights the effect of sintering techniques (SPS and CS) and reinforcement (CeO2) on engineering the desired microstructure of 8YSZ ceramic. 相似文献
18.
Yu. V. Pogorenko P. N. Pshenichnyi A. A. Omel’chuk V. V. Trachevskii 《Surface Engineering and Applied Electrochemistry》2017,53(6):533-541
In the system (1–x)PbF2–x YF3–x KF, solid solutions of aliovalent substitution with fluorite structure at 0.47 < x < 0.69 are formed, in which the fluorine ions are found to be in three structurally nonequivalent positions that differ in the local environment and mobility. There are immobile, locally mobile, and highly mobile anions. The conductivity of the synthesized polycrystalline samples is ensured by highly mobile interstitial fluoride ions, whose concentration and hence electrical conductivity increase on heating. The contribution of the surface conductivity of crystallites is not detected. The electronic component is two orders of magnitude lower than the ionic one. 相似文献
19.
I. B. Bobylev E. I. Kuznetsova N. A. Zyuzeva T. P. Krinitsina S. V. Sudareva E. P. Romanov 《The Physics of Metals and Metallography》2010,110(4):378-384
The fine structure and electrophysical properties of nonstoichiometric YBa2Cu3O7 − δ ceramics and the effect of low-temperature annealing (t ⩾ 200°C) in various atmospheres on these parameters have been studied. It has been shown that, during annealing in a vacuum,
the decomposition is quite sluggish; structures typical of initial stages of decomposition are observed. The decomposition
in an inert-gas atmosphere occurs more actively, and structures typical of stages of deep decomposition are realized. It has
been found that, during low-temperature annealing, the structure and properties are affected by two factors; these are the
decomposition into phases differing in the oxygen content, and water absorption, leading to the transformation with the formation
of a pseudo-cubic lattice. The annealing atmosphere substantially affects the kinetics of both processes. 相似文献
20.
In this study, the influence of adding SiO2 and Al2O3 to Ni–P coated on magnesium substrate and the related corrosion resistance behavior were evaluated. The surface morphology of Ni–P–SiO2–Al2O3 composite coating was investigated by field emission scanning electron microscopy (FESEM). The amount of Al2O3 and SiO2 in the coating was measured by energy dispersive analysis of X-ray (EDX) and the corrosion behavior of coating was monitored by electrochemical impedance spectroscopy (EIS) and polarization techniques, showing the corrosion resistance of Ni–P–SiO2–Al2O3 increases compare to Ni–P–SiO2 and Ni–P–Al2O3. Furthermore, the microhardness of the coating was examined and the final hardness of Ni–P–SiO2–Al2O3 reached 461 VH. 相似文献