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41.
The inhibition effect of three organic additives on the precipitation and polymorphism of CaCO3 deposited on gold surfaces was investigated using electrochemical and microscopic techniques. Additives, two polyacrylic acid (PAA) polymers with different molecular weights (Mw 2100, Mw 30,000), and 1,2,4,5‐benzenetetracarboxylic acid (BTCA), were either added to the solution before or during deposition. In the presence of 100 ppm of one of the three additives in solution, almost no scale was observed on the surface for at least 24 hours. In the presence of lower concentrations of PAA Mw 2100, only distorted calcite crystals were obtained while with PAA Mw 30,000 the polymorph was spherical vaterite. A mixture of calcite and vaterite was observed with the BTCA additive. Addition of the polymers inhibits further nucleation and growth even if added after partial deposition of CaCO3 while BTCA has no effect once nucleation has started. The results indicate that the inhibit ion effect of the PAA polymers is due to adsorption on the electrode surface while the effect of BTCA is related to chelation of calcium ions in solution. 相似文献
42.
Hydrothermal Synthesis and Low-Temperature Sintering of Zinc Gallate Spinel Fine Particles 总被引:1,自引:0,他引:1
Nanosized powders of single-phase zinc gallate (ZnGa2 O4 ) spinel were hydrothermally synthesized from solutions in the presence of NaOH over the pH range of 1.9 to 7.0 and from solutions above pH 7.0, i.e., the very basic medium (pH of 13.85), by removing the residual ZnO phase by washing with aqueous H2 SO4 from the precipitate mixtures of zinc gallate spinel particles and ZnO. A very wide compositional range (Zn/2Ga = 0.705–1.157) of zinc gallate spinel solid solutions could be hydrothermally synthesized in the form of nanosized particles from acid and very basic mediums (pH of 2.4–13.85) in the presence of NaOH. These hydrothermally synthesized spinel powders showed good sinterability and almost full densification at 1100°C for 1 h. Dense sintered bodies consisting of single-phase zinc gallate spinel were fabricated at 1100°C using zinc gallate spinel powders having almost stoichiometric composition formed from the solution at pH 9.95 in the presence of aqueous ammonia. 相似文献
43.
Properties and Performance of Cation-Doped Ceria Electrolyte Materials in Solid Oxide Fuel Cell Applications 总被引:1,自引:0,他引:1
Christopher Milliken Sivaraman Guruswamy Ashok Khandkar 《Journal of the American Ceramic Society》2002,85(10):2479-2486
Cation-doped CeO2 electrolyte has been evaluated in single-cell and short-stack tests in solid oxide fuel cell environments and applications. These results, along with conductivity measurements, indicate that an ionic transference number of ∼0.75 can be expected at 800°C. Single cells have shown a power density >350 mW/cm2 . Multicell stacks have demonstrated a peak performance of >100 mW/cm2 at 700°C using metallic separators. 相似文献
44.
A series of long-chain quaternary ammonium halogen esters (UKK-chemicals), quaternary dimethyl tallow epoxypropyl ammonium
halogens (EPK1), quaternary ditallow methyl epoxypropyl ammonium halogens (EPK2), and EPK2 oligomers (EPK2P) were synthesized.
At acidic, neutral, or slightly basic conditions, EPK1-, EPK2-, EPK2P-, and UKK-chemicals operate as cationic chemicals. They
can be used, for example, as stock sizings, surface sizings, or fixatives. Stock sizing, surface sizing, and fixative experiments
indicate that EPK1-, EPK2-, EPK2P-, and UKK-chemicals function at least as well as or better than the corresponding synthetic
chemicals used in papermaking. 相似文献
45.
V. A. Roginsky T. K. Barsukova A. A. Remorova W. Bors 《Journal of the American Oil Chemists' Society》1996,73(6):777-786
The relative reactivities as well as the stoichiometric coefficients for a number of flavonoids, catechols, and—for comparison—standard
phenolic antioxidants were determined by analyzing the kinetics of oxygen consumption in organic and micellar systems, with
peroxidation initiated by lipid- and water-soluble azo initiators. The results demonstrated that the flavonoids did not behave
as classic phenolic antioxidants such as α-tocopherol, but showed only moderate chain-breaking activities. The results were
in line with other structure-activity relationship studies on the importance of the B-ring catechol structure, the 2,3-double
bond, and the 3,5-hydroxy groups. The data are discussed in view of possible explanations of the deviations flavonoids reveal
in their behavior compared with regular phenolic antioxidants. 相似文献
46.
47.
铝合金铁相团球化熔剂的研制 总被引:3,自引:1,他引:2
研制了一种铝合金铁相团球化熔剂,在含铁量较高(1.0%-4.0%Fe)的铝合金中加入该熔剂后,可使针片状的铁相变为团球状或颗粒状组织。从而大幅度提高原合金的机械性能,δb和δ分别提高20%-90%和40%-100%。生产实验表明:该熔剂团球化效果好(具有长效性),极便于在生产中推广应用。 相似文献
48.
GaN buffer and main layers were grown by the conventional hydride vapor phase epitaxy technique using GaCl3 consecutively. The deposited buffer layers were investigated by atomic force microscopy and X-ray analysis. To examine the behavior of the buffer layers at main layer growth temperature, heat treatment was conducted at 900°C. Based on the results of the buffer layer study, GaN thick films were grown at 1050°C. Optimum deposition conditions of buffer layer from the buffer and main layer studies generally coincided. On the φ scanning pattern, the GaN films grown on (0001) Al2 O3 were single-crystalline. Band-edge emission dominated photoluminescence was observed at room temperature. 相似文献
49.
50.
Ag-BaO thin films doped with lanthanum were prepared by vacuum deposition. Compared with the normal Ag-BaO thin film, there is almost no change with the shape and the peak site of the fluorescence spectrum; however, fluores-cence emission strength of the whole observation band(325 -600 nm)increases about 40%, and the increase of short wavelength range is more remarkable than that of long wavelength range, which we named “blue-stronger“ phenomenon. Analytic results show that, with the forming of intermetallic compounds between silver and lanthanum, the 4f-state energy levels lie just below the Fermi level within 5 eV. It is the energy exchange between the 4f energy levels and the conduction band that causes the increase effect of fluorescence emission, and it is the optical absorption cross section of 4f electron, which increases with the increase of energy of incidence photon, that gives rise to the “blue-stronger“ phenomenon. 相似文献