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1.
ZrB2@A1(OH)3‐Y(OH)3 core‐shell composite particles are synthesized by co‐precipitation method for strengthening the antioxidation of ZrB2 at high temperature. To reach better A1(OH)3‐Y(OH)3 composite shell and higher coating ratio on the ZrB2 particles surfaces, ZrB2 particles must be adequately dispersed in the ZrB2 suspension during the coating process. The dispersibility of ZrB2 particles under different conditions is investigated by the sedimentation method. Through test and analysis, the optimum conditions of the dispersibility of ZrB2 particles in the ZrB2 suspension are sedimentating for 15 minutes, ultrasonic dispersion for 10 minutes, the lower ZrB2 concentration, pH=9, the dispersant content for the 2% volume of ZrB2 suspension, and using the polyelectrolyte dispersant, respectively.  相似文献   

2.
SNMS depth profiles of layers of 0.4–0.8 m sized Si3N4, BN and partly SiC-coated B4C powder particles and of 10 m sized SiC fibres are obtained without great expenditure on time and specimen preparation. Close contact with Au foil provides for electrical conductivity. Averaged depth profiles of a great number of particles or fibres are obtained. AES serves as a comparative method; the carrier-gas heat extraction (inert gas fusion) technique is used for the semiquantification of OH signals in SNMS. Esterification of surface OH with ethanol during suspension is not detectable. Hydrolyzation or oxidation reactions having penetrated through the bulk of BN particles cause qualitatively different depth profiles than found on Si3N4 particles carrying a nm thin natural (hydr-)oxidic layer. The effects of preparative surface reactions like additive coating (SiC on B4C particles), etching and oxidation (of SiC fibres) can be monitored. Quantification attempts yield standard deviations between 10 and 50%.Presented on the 15. Kollquium über Werkstoffanalytik, Vienna, May 27–29, 1991  相似文献   

3.
This article presents a facile method to prepare silver/polystyrene composite microspheres. In this approach, monodispersed polystyrene (PS) particles were synthesized with carboxyl acid groups on the surfaces of the PS particles via dispersion polymerization at first. With the addition of [Ag(NH3)2]+ to the PS dispersion, [Ag(NH3)2]+ was absorbed to the surfaces of the PS particles, and then by heating the system, [Ag(NH3)2]+ complex ions were reduced to silver to form the Ag/PS composite microspheres. In the synthesis of PS dispersion, PVP was used as dispersant to stabilize the PS particles, it also acted as reducing agent in the reduction of [Ag(NH3)2]+ complex ions to silver, so no additional reducing agent was needed. The resulting composite microspheres were characterized by TEM, SEM, XPS, and XRD. The catalytic properties and surface‐enhance Raman scattering (SERS) was studied as well. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4547–4554, 2009  相似文献   

4.
To protect carbon/carbon (C/C) composites from oxidation at high temperature, a nano SiC?CMoSi2 (SiC n ?CMoSi2) coating on SiC pre-coated C/C composites was prepared by hydrothermal electrophoretic deposition. The phase composition, surface and cross-section microstructures of the prepared SiC n ?CMoSi2 coating deposited with different MoSi2/SiC n mass ratio were characterized by X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The influence of MoSi2 content in the hydrothermal electrophoretic deposition suspension on the phase composition, microstructure and high-temperature oxidation resistance of the multi-layer coatings were investigated. Results showed that the content of MoSi2 phase in the prepared coating increases with the increase of MoSi2 content in the suspension. The density and oxidation resistance of the SiCn-MoSi2 coating improve with the increase of MoSi2 mass content from 20 to 60 wt% in the deposition suspension. However, micro-cracks and micro-holes in the coating are found when deposited with 80 wt% MoSi2, and a decrease in oxidation resistance was also detected. The multi-layer coatings deposited with suspension of 60 wt% MoSi2 exhibited the best anti-oxidation ability, which can effectively protect C/C composites from oxidation in air at 1,873 K for 90 h with weight loss of 2.08%.  相似文献   

5.
A novel hydrothermal coating process has been developed to deposit amorphous Ni(OH)2·H2O over octahedral α-Fe2O3 particles by treating aqueous dispersion of the preformed cores in Ni(NO3)2/CH3COONa solution. NiO(core)/Fe2O3(shell) composite particles were prepared by air sintering of the Ni(OH)2·H2O(shell)/Fe2O3(core) particles at 200–500°C for 1–6 h. The changes of morphology, structure and weight of the hydrothermal and sintering products were studied by means of TEM, XRD, XPS, TG and IR analyzers. The nucleation and growth model was suggested for the non-isothermal decomposition of Ni(OH)2·H2O coatings and the kinetic equation was derived from the non-linear regression of the TG data. The activation in the thermal-decomposition process is 73.8 kJ mol−1 and the pre-exponential factor is 1.95×104 s−1.  相似文献   

6.
Two grades of isotactic polypropylene (homopolymer and block copolymer) were filled with magnesium and aluminium hydroxides, and studied focusing the mechanical and fracture characteristics of the composites. As expected, dispersion of such fillers in PP resulted in improved stiffness and reduced tensile yield strength. By one hand, the composites fracture resistance was characterised at low strain rate applying the J‐integral concept; the resistance to crack growth initiation (JIC) was found decreasing as the Mg(OH)2 concentration was raised in the copolymer PP matrix. By the other hand, the linear‐elastic fracture mechanics (LEFM) parameters were determined by means of instrumented impact tests at 1 m/s on the homopolymer PP filled with uncoated Al(OH)3 particles. The higher the Al(OH)3 mean particle size, the lower the composite fracture energy (GIC). In the opposite, with commercial surface‐coated filler grades it was not possible to achieve LEFM conditions to characterise the fracture toughness of filled PP at 1 m/s, because the Mg(OH)2 surface coating, which is applied in practice to improve the melt processing, acts increasing the composite plasticity and reducing the tensile yield strength.  相似文献   

7.
纸张涂料用纳米CaCO3表面改性的研究   总被引:4,自引:0,他引:4  
利用铝锆偶联剂对纳米CaCO3进行表面改性。采用红外光谱(IR)、X射线衍射分析(XRD)、热分析(TG-DTG)对改性前后的纳米CaCO3进行了表征。通过透射电镜(TEM)、粒度分析、吸油值、比表面积及静滴接触角等实验对纳米CaCO3的表面改性效果进行评价。红外光谱分析表明,偶联剂以化学键合的方式在纳米CaCO3的表面形成化学吸附。TEM及粒度分析结果显示,未改性纳米CaCO3存在严重的团聚现象,而改性后纳米CaCO3的分散性有很大改善。经表面改性,水滴在纳米CaCO3粉体压片表面静滴接触角变大,改性纳米CaCO3同时具有亲水性和亲油性,能够较好地分散在水和有机相中。将改性前后的纳米CaCO3分别加入到纸张涂料体系中,制得纳米CaCO3复合纸张涂料。涂料流变实验表明,经铝锆偶联剂表面改性的纳米CaCO3制得的复合纸张涂料具有较高的动态弹性模量和粘性模量。  相似文献   

8.
Polystyrene template microspheres of narrow size distribution were prepared by dispersion polymerization of styrene in a mixture of ethanol and 2-methoxy ethanol. These template particles dispersed in aqueous solution have been used for the entrapment of ferrocene by a swelling process of methylene chloride emulsion droplets containing ferrocene within these particles, followed by evaporation of methylene chloride. The effects of CH2Cl2 volume and the [CH2Cl2]/[FeC10H10] (w/w) ratio on the size and size distribution of the swollen template particles were elucidated. Air-stable Fe3C nanoparticles embedded in amorphous carbon matrix (Fe3C/C) have been prepared by thermal decomposition of the ferrocene-swollen template polystyrene particles at 500 °C for 2 h in a sealed cell. Decomposition of these swollen template particles for 2 h at higher temperatures led to the formation of carbon nanotubes (CNTs) in addition to the Fe3C/C composite nanoparticles. The yield of the CNTs increased as the annealing temperature was raised. An opposite behavior was observed for the diameter of the formed CNTs. The size and size distribution, crystallinity, and magnetic properties of the different Fe3C/C composite nanoparticles have also been controlled by the annealing temperature.  相似文献   

9.
The mechanism responsible for the inclusion of Al2O3 and SiC nanoparticles, the mixture of Nb2N and Ta2N (1: 1), MoS2, Cr2O3, and SiO2 with diverse electric conductivity, hydrophilicity, and resistance to solution components in chromium deposits from the sulfate–oxalate suspension solutions based on Cr(III) was studied. The main factors that determine the formation of chromium composite electrochemical coatings, their composition, and surface morphology were determined. The film on the surface of the growing deposit of the intermediates of the reduction of chromium ions plays the key role in the formation of composite coatings from Cr(III) and Cr(VI) sulfate–oxalate suspension solutions. The film can play the role of a structural mechanical barrier that hinders the incorporation of particles in the deposit, or it can fix the particles on the electrode surface by creating hydroxo bridges with chemisorbed hydroxide compounds on the particle surface.  相似文献   

10.
Composite Li10SnP2S12 (LSPS)/polyethylene oxide (PEO) films, containing 25 to 50 % polymer, were electrophoretically deposited from acetone-based suspension and tested as possible candidates for polysulfide barriers in Li/S batteries. It was found by XRD and XPS tests that saturation of composite films by LiI salt, followed by prolonged annealing at 90 °C, diminishes the crystallinity of neat LSPS and results in the formation of a novel composite Li10+xIxSnP2S12 (LISPS)/P(EO)3/LiI solid electrolyte (x < 1). The high room-temperature ion conductivity of amorphous sulfide Li10+xIxSnP2S12 (0.1–0.3 mS cm?1) is restricted by slow ion transport via the polymer electrolyte (PE) imbedded in ceramics and grain boundaries between the PE and sulfide. Increase in polymer content and temperature improves total ion transport in the LISPS/PEO system. Conformal EPD coating of sulfur and lithium sulfide cathodes by the developed composite electrolyte increased the reversible capacity and Faradaic efficiency of the Li/S and Li/Li2S cells and enabled their operation at 60 °C.  相似文献   

11.
Spray coating method is a cost-effective technique suitable for the preparation of uniform and large-area thin films. This article presents findings on the preparation of dense electrolyte thin films by spray coating method. Dense, crack-free Gd-doped CeO2 (GDC) thin films with a thickness of approximately 2 µm were successfully prepared on porous NiO-GDC substrates. The influence of the dispersion of GDC nanopowders in susupension on the microstructure of the thin films was investigated. Results show that agglomeration of GDC nanopowders in suspension resulted in a porous microstructure and a densely packed microstructure was obtained for the film prepared from a well-dispersed suspension.  相似文献   

12.
This paper focuses on the preparation of a superhydrophobic coating on glass/porcelain insulators which possess anti-icing property below freezing temperature. Inspired by lotus-effect, the fabrication of a superhydrophobic coating has two steps: the first step is to construct a hierarchical SiO2 coating on the substrate surface, and the second step is the chemical modification of the SiO2 coating with 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (PDTS). The precursor for the hierarchical SiO2 coating is a suspension of SiO2 sol particles and dispersible SiO2 powder particles. According to the TEM testing, SiO2 sol particles prepared by sol–gel method has an average particle size about 2–5 nm, while the size of the dispersible SiO2 particles is ca. 20 nm. The precursor was sprayed on glass/porcelain insulators, and then dried at ambient condition, finally heat-treated at 773 K for 2 h. The morphology of the superhydrophobic coating was characterized by TEM and AFM, and experimental results indicated that the coating featured [hierarchical structure consisting of both large bumps with micron-sized height (0.8 μm) and tiny papillae with the size about 30 nm] micron-sized roughness (0.8 μm) combined with nano-sized roughness (about 2 nm). Moreover, the scratch test showed that the coating tightly adhered to the surface of the glass/porcelain insulators. The superhydrophobic property of the coating was examined by a contact angle measurement, and the results demonstrated that the static water contact angle is high up to 163.6°, and the sliding angle is 1.4°. The superhydrophobic property of the coating was also confirmed by the outdoor tests in winter, and it was found that the superhydrophobic coating had the function in anti-icing, based on which the anti-icing mechanism underlying was discussed in terms of the interaction between impacting droplets and superhydrophobic surface.  相似文献   

13.
Ultrathin ZnO, ZrO2, and Al2O3 surface coatings are deposited via atomic layer deposition (ALD) with high conformality and atomic scale thickness control to enhance the electrochemical performance of LiMn2O4 for applications in lithium ion batteries. Two types of ALD-modified LiMn2O4 electrodes are fabricated: one is ALD-coated LiMn2O4 composite electrode and the other is electrode composed of ALD-coated LiMn2O4 particles and uncoated carbon/polyvinylidenefluoride network. Cycling performance and cyclic voltammetric patterns reveal that ZnO ALD coating is the most effective protective film for improving the electrochemical performance of LiMn2O4 at either 25 or 55 °C, followed by ZrO2 and Al2O3. After 100 electrochemical cycles in 1 C at 55 °C, the electrode consisting of LiMn2O4 particles coated with six ZnO ALD layers (as thin as ~1 nm) delivers the highest final capacity, more than twice that of the bare electrode. It is also found that amphoteric oxide coating on LiMn2O4 particles can enhance the cycleability of LiMn2O4 more effectively than coating on the composite electrode. Furthermore, for ALD coating either on the composite electrode or on LiMn2O4 particles, the effect of oxide ALD modification for improving capacity retention and increasing specific capacity of LiMn2O4 is more phenomenal at elevated temperature than at room temperature.  相似文献   

14.
Nano-sized TiO2–60 wt% SrO composite powders were synthesized from titanium isopropoxide and Sr(OH)2·8H2O by use of a sol–gel method. Ag spot-coated TiO2–60 wt% SrO composite powders containing 3, 5, or 7 wt% Ag were synthesized by hydrothermal-assisted attachment, by use of Ag hydrosol in a high-pressure bomb at 250 °C and 450 psi. Nano-sized Ag particles approximately 5–25 nm in diameter adhered to the TiO2–60 wt% SrO2 composite powders. The photocatalytic activity of Ag spot-coated TiO2–SrO powders in the degradation of phenol showed that all were highly active when irradiated with UV light. TiO2–60 wt% SrO composite powder spot-coated with 5 wt% Ag was more photocatalytically active under visible light than TiO2–SrO composite powder.  相似文献   

15.
Polystyrene coated silica(SiO2@PS) core-shell composite particles with averaged diameter of about 290 nm were prepared by in situ emulsion polymerization of styrene on the surface ofγ-methacryloxypropyltrimethoxysilane grafted SiO2 nanoparticles of 20-50 nm in diameter.Rheological behavior and dispersion stability of SiO2@PS suspension in 10 wt%PS solution were compared with suspensions of untreated SiO2 and silane modified SiO2 nanoparticles.Suspensions of the untreated and the silane modified SiO2 exhibited obvious shear thinning.The SiO-2@PS suspension exhibits shear viscosity considerably smaller than suspensions of untreated and silane modified SiO2 at low shear rates.Transmission electron microscopy showed that the composite particles can uniformly and stably disperse in PS solution compared to other suspensions,implying that the PS shell can effectively enhance the particle compatibility with PS macromolecules in solution.  相似文献   

16.
Using Fe3O4 nano-particles as seeds, a new type of Fe3O4/Au composite particles with core/shell structure and diameter of about 170 nm was prepared by reduction of Au3+ with hydroxylamine in an aqueous solution. Particle size analyzer and transmission electron microscope were used to analyze the size distribution and microstructure of the particles in different conditions. The result showed that the magnetically responsive property and suspension stability of Fe3O4 seeds as well as reduction conditions of Au3+to Au0are the main factors which are crucial for obtaining a colloid of the Fe3O4/Au composite particles with uniform particle dispersion, excellent stability, homogeneity in particle sizes, and effective response to an external magnet in aqueous suspension solutions. UV-Vis analysis revealed that there is a characteristic peak of Fe3O4/Au fluid. For particles with d(0.5)=168 nm, the λmax is 625 nm.  相似文献   

17.
《Solid State Sciences》2001,3(3):291-299
Preparation of core-shell structured TiO2–BaCO3 particles as precursor of BaTiO3 genesis, proceeds using a two step procedure, by first coating the TiO2 core by Ba(OH)2 shell followed by conversion of the shell region with CO2 gas by the formation of BaCO3. Straightforward experimental results reveal environmental scanning electron microscopy (ESEM) and scanning transmission electron microscopy (STEM) as suitable methods for analytical characterization of the core and shell regions from individual TiO2–BaCO3 grains. Evidence of coating the whole ensemble of TiO2 particles is possible using Photo Electro Motive Force (Photo EMF, PEMF) measurements. This method is able to indicate very sensitively changes of surface properties of TiO2 after coating with Ba(OH)2 and BaCO3, respectively. PEMF measurements were used for the first time with concern to this topic.  相似文献   

18.
In this study, to improve the specific capacitance of graphene-based supercapacitor, novel quadri composite of G/PPy/MnOx/Cu(OH)2 was synthesized by using a facile and inexpensive route. First, a two-step method consisting of thermal decomposition and in situ oxidative polymerization was employed to fabricate graphene/polypyrrole/manganese oxide composites. Second, Cu(OH)2 nanowires were deposited on Cu foil. Afterwards, for the electrochemical measurements, composite powders were deposited on Cu(OH)2/Cu foil substrate as working electrodes. The synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. The XRD analysis revealed the formation of PPy/graphene, Mn3O4/graphene, and graphene/polypyrrole/MnOx. In addition, the presence of polypyrrole and manganese oxides was confirmed using FT-IR and Raman spectroscopies. Graphene/polypyrrole/MnOx/Cu(OH)2 electrode showed the best electrochemical performance and exhibited the largest specific capacitance of approximately 370 F/g at the scan rate of 10 mV/s in 6 M KOH electrolyte. In addition, other electrochemical measurements (charge–discharge, EIS and cyclical performance) of the G/Cu(OH)2, G/PPy/Cu(OH)2, G/Mn3O4/Cu(OH)2, and G/PPy/MnOx/Cu(OH)2 electrodes suggested that the G/PPy/MnOx/Cu(OH)2 composite electrode is promising materials for supercapacitor application.  相似文献   

19.
This work reports the preparation, characterization, and electrocatalytic characteristics of a new metallic nanocatalyst. The catalyst, Pt black–graphene oxide (Pt-GO), was prepared by deposition of Pt black on the surface of graphene oxide nanosheet and characterized by transmission electron microscopy (TEM), energy-dispersive spectroscopy (EDS), and voltammetry. The Pt-graphene (Pt-GR) composite modified glassy carbon electrode (Pt-GR/GCE) was prepared with cyclic voltammetric scanning of Pt-GO/GCE in the potential range from ?1.5 to 0.2 in 0.1 M phosphate buffer solution at 50 mV·s?1 for 5 cycles. The electrocatalytic properties of the Pt-GR/GCE for methanol (CH3OH) oxidation have been investigated by cyclic voltammetry (CV); high electrocatalytic activity of the Pt-GR/GCE can be observed. This may be attributed to the high dispersion of Pt catalyst and the particular properties of GR support. The long-term stability of Pt-GR composite was investigated in 0.05 M CH3OH in 0.1 M H2SO4 solution. It can be observed that the peak current decreases gradually with the successive scans. The loss may result from the consumption of methanol during the CV scan. It also may be due to the poisoning organic compounds. The results imply that the Pt-GR composite has good potential applications in fuel cells.  相似文献   

20.
Photodeposition has been widely used as a mild and efficient synthetic method to deposit co‐catalysts. It is also worth studying how to synthesize non‐noble metal photocatalysts with uniform dispersion. Different synthetic conditions in photodeposition have a certain influence on particle size distribution and photocatalytic activity. Therefore, we designed experiments to prepare the inexpensive composite photocatalyst Ni(OH)2/g‐C3N4 by photodeposition. The Ni(OH)2 co‐catalysts disperse uniformly with particle sizes of about 10 nm. The photocatalytic hydrogen production rate of Ni(OH)2/g‐C3N4 reached about 19 mmol g?1 h?1, with the Ni(OH)2 deposition amount about 1.57 %. During 16 h stability testing, the rate of hydrogen production did not decrease significantly. The composite catalyst also revealed a good hydrogen production performance under sunlight. The Ni(OH)2 co‐catalyst enhanced the separation ability of photogenerated carriers, which was proved by surface photovoltage and fluorescence analysis.  相似文献   

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