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1.
《应用陶瓷进展》2013,112(4):186-195
Abstract

Multiwalled carbon nanotube (CNT) films have been successfully fabricated by electrophoretic deposition (EPD) on stainless steel substrates. Electrophoretic deposition was performed using optimised aqueous suspensions under constant voltage conditions. Triton X-100 was used as a surfactant to disperse CNT bundles, and iodine was added as a particle charger. CNT/SiO2 composite coatings were prepared by electrophoretic co-deposition. Experimental results show that the CNTs were efficiently mixed with SiO2 nanoparticles to form a network structure. Layered CNT/SiO2 porous composites were obtained by sequential EPD experiments alternating the deposition of CNT and SiO2 nanoparticles. The structure of all films deposited was studied in detail by scanning electron microscopy. Possible applications of CNT and CNT/SiO2 films are as porous coatings in the biomedical field, thermal management devices, biomedical sensors and other functional applications where the properties of CNTs are required.  相似文献   

2.
Nanocomposites containing carbon nanotubes (CNTs) as nanofillers and poly[ethylene‐co‐(acrylic acid)] (PEAA) or a polymer miscible mixture of PEAA and poly(2‐ethyl‐2‐oxazoline) (PEOx) as a matrix were prepared by the solution‐evaporation method with minimal damage to nanotubes. CNTs were prepared by chemical vapor deposition (CVD) with ethanol as the source of carbon. Raman spectroscopy confirmed the presence of single walled carbon nanotubes (SWNTs). High resolution transmission electron microscopy (HRTEM) showed the formation of multi walled carbon nanotubes (MWNTs). Thermal and mechanical properties of the nanocomposites were studied by analyzing samples containing different amounts of CNTs. The degree of crystallinity (Xc) of the PEAA‐based nanocomposite containing a smaller amount of CNTs was larger (Xc = 17.0%) than both the one of pure PEAA (Xc = 14.6 %) and PEAA‐based nanocomposite containing higher amounts of CNTs (Xc = 15.0%). The Young's modulus, ultimate stress, deformation at break, and toughness obtained from unidirectional tensile tests of the CNTs (1 wt%)‐PEAA nanocomposite were higher than both the one of pure PEAA and CNTs (5 wt%)‐PEAA nanocomposite. When a polymer mixture of PEAA/PEOx (containing 80 wt% of PEAA) was used as a matrix, a better mechanical response was also detected for nanocomposite containing 1 wt% CNTs. The nanocomposites containing small amounts of CNTs prepared here have potential to be used as coatings of metal or glass surfaces expecting a better mechanical performance than the one of pure matrix. POLYM. COMPOS., © 2011 Society of Plastics Engineers.  相似文献   

3.
The production of bioactive coatings consisting of 45S5 Bioglass® and mutli-walled carbon nanotubes (CNTs) by electrophoretic deposition (EPD) was investigated. In addition to pure Bioglass® coatings, the co-deposition and sequential deposition of Bioglass® particles (size <5 μm) and CNTs on stainless steel substrates were carried out in order to fabricate bioactive, nanostructured composite layers. The optimal experimental conditions were determined using well-dispersed suspensions by means of a trial-and-error approach by varying the relevant EPD parameters: applied voltage and deposition time. SEM images demonstrated the successful fabrication of Bioglass®/CNT composites by revealing their morphology and topography. The co-deposition of Bioglass® particles and CNTs resulted in homogenous and dense coatings exhibiting the presence of well-dispersed CNTs placed in-between micron-sized Bioglass® particles. This network of high-strength CNTs embedded in the glass layer could act as reinforcing element leading to higher mechanical stability of the coatings. The coatings obtained by sequential deposition offered a two-dimensional nanostructured fibrous mesh of CNTs covering the Bioglass® layer thus providing a controlled (ordered) nano-topographical surface. This surface nanostructure has the potential to promote the attachment and growth of osteoblast cells and to benefit the formation of bone-like nanosized hydroxyapaptite crystals in contact with body fluids.  相似文献   

4.
The purpose of this paper is to present an up-to-date comprehensive overview of current research progress in the development of carbon nanotube (CNT)–ceramic nanocomposites by electrophoretic deposition (EPD). Micron-sized and nanoscale ceramic particles have been combined with CNTs, both multiwalled and single-walled, using EPD for a variety of functional, structural and biomedical applications. Systems reviewed include SiO2/CNT, TiO2/CNT, MnO2/CNT, Fe3O4/CNT, hydroxyapatite (HA)/CNT and bioactive glass/CNT. EPD has been shown to be a very convenient method to manipulate and arrange CNTs from well dispersed suspensions onto conductive substrates. CNT–ceramic composite layers of thickness in the range <1–50 μm have been produced. Sequential EPD of layered nanocomposites as well as electrophoretic co-deposition from diphasic suspensions have been investigated. A critical step for the success of EPD is the prior functionalization of CNTs, usually by their treatment in acid solutions, in order to create functional groups on CNT surfaces so that they can be dispersed uniformly in solvents, for example water or organic media. The preparation and characterisation of stable CNT and CNT/ceramic particle suspensions as well as relevant EPD mechanisms are discussed. Key processing stages, including functionalization of CNTs, tailoring zeta potential of CNTs and ceramic particles in suspension as well as specific EPD parameters, such as deposition voltage and time, are discussed in terms of their influence on the quality of the developed CNT/ceramic nanocomposites. The analysis of the literature confirms that EPD is the technique of choice for the development of complex CNT–ceramic nanocomposite layers and coatings of high structural homogeneity and reproducible properties. Potential and realised applications of the resulting CNT–ceramic composite coatings are highlighted, including fuel cell and supercapacitor electrodes, field emission devices, bioelectrodes, photocatalytic films, sensors as well as a wide range of functional, structural and bioactive coatings.  相似文献   

5.
ABSTRACT

Poly (vinyl alcohol)/graphene oxide (PVA/GO) gamma irradiated nanocomposite films and hydrogels were prepared. In composite films, GO was initially irradiated by gamma ray in order to improve interactions between GO and PVA. The film containing 1?wt-% GO was very strong where tensile modulus and tensile yield strength were 45 and 115% higher than those of pure PVA. In the second set of experiments PVA/GO hydrogels were made by irradiating PVA/GO suspensions by gamma ray at various doses. It was an interesting finding that GO increased the gel portion of hydrogels through contribution of H-bonds between PVA and GO. The hydrogels prepared at 20?kGy had remarkable water swelling ratio that reached as high as 20 at water temperature of 80°C. The hydrogel metal ion adsorption capability was tested on Cu2+ ions. It was shown that the GO contributed significantly to the adsorption capacity of PVA hydrogels.  相似文献   

6.
Ceramic foam filters play an essential role in the quest for cleanliness of cast steel parts as they facilitate turbulence reduction during mold filling as well as removal of nonmetallic inclusions. A coating on these filters is able to increase their strength and filtration efficiency by improving the adhesion of inclusions to the filter strands. In this study, Al2O3‐C filters were coated with an alumina slip via slip and flame spraying. The phase composition and the microstructure of the coatings were investigated before and after immersion into molten steel contained in a metal casting simulator. After contact with molten steel, Al2O3‐C reference filter shows intense decarburization which often influence the quality of cast steel parts due to formation of gas bubbles. Slip‐sprayed alumina coatings on such a filter promote the deposition of inclusions due to formation of a vitreous alumina layer but will also cause gas bubble formation as they exhibit a high porosity. Flame‐spray coatings have low porosity and hence, prevent formation of gas bubbles. Furthermore, they showed the highest reactivity toward the steel melt and hence, are recommended for filtration of cast products with a high demand on cleanliness.  相似文献   

7.
The effects of graphene oxide (GO) on the yield stress‐pH of α‐Al2O3 (alumina) suspensions were investigated. For micron‐sized platelet alumina suspensions, micron‐sized GO additive increased the maximum yield stress by as much as six‐folds. This was attributed to GO‐mediated bridging interactions between the platelet particles. This type of bridging interactions was much less effective with submicron‐sized, spherical, and irregular shape alumina. Adsorption of the anionic GO reflected by the shift of pH of zero zeta potential to a lower pH is particularly high for platelet alumina. The 1.0 dwb % GO concentration added is sufficient to reinforce each platelet particle–particle bond, assisted by a directed GO–platelet interaction configuration. This is, however, not true with submicron‐sized particles as the particle concentration increases sharply with the inverse of the particle diameter to power of 3. Moreover, a GO sheet can adsorb several submicron‐sized particles and this does not produce the right interaction configuration. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3633–3641, 2013  相似文献   

8.
Gas hydrate/clathrate hydrate formation is an innovative method to trap CO2 into hydrate cages under appropriate thermodynamic and/or kinetic conditions. Due to their excellent surface properties, nanoparticles can be utilized as hydrate kinetic promoters. Here, the kinetics of the CO2 + tetra‐n‐butyl ammonium bromide (TBAB) semi‐clathrate hydrates system in the presence of two distinct nanofluid suspensions containing graphene oxide (GO) nanosheets and Al2O3 nanoparticles is evaluated. The results reveal that the kinetics of hydrate formation is inhibited by increasing the weight fraction of TBAB in aqueous solution. GO and Al2O3 are the most effective kinetic promoters for hydrates of (CO2 + TBAB). Furthermore, the aqueous solutions of TBAB + GO or Al2O3 noticeably increase the storage capacity compared to TBAB aqueous solution systems.  相似文献   

9.
Carbon nanotubes (CNTs) were dispersed in ethanol by bead milling to form a CNT suspension. The size and shape of the CNTs were not changed after bead milling. The Brownian motion of the CNTs was observed by an optical microscope. It was shown by analysis off the trajectory of individual CNTs that the diffusion coefficient of their translational Brownian motion was 4.5 × 10−13 m2 s−1. The ratio of the particle mobilities due to drift flow and diffusion flow was 2.4, which is almost the same as for a high-molecular-weight protein. Shear thinning occurred in the CNT suspension, which means that the CNTs were oriented in the suspension under a high shear rate at low viscosity. The intrinsic viscosity for shear rates of 0 and ∞ agreed with those calculated using Simha’s equation and Leal and Hinch’s equation, respectively. Based on the experimental results, the CNTs were found to be well dispersed as isolated and nanosized rod-like particles in the suspension. CNT-dispersed Si3N4 ceramics were fabricated using the CNT suspensions. As a result, the bead milling improved the bend strength of the CNT Si3N4 ceramics compared with the wet ball milling because granules of CNTs were eliminated by the bead milling.  相似文献   

10.
The suspensions of titania nanoparticles in different alcohols (methanol, ethanol and butanol) were prepared using triethanolamine (TEA) as a dispersant. The optimum concentration of TEA was 16.67, 8 and 0.33 mL/L in methanol, ethanol and butanol, respectively. Two component suspensions of titania (20 g/L) and carbon nanotubes (CNTs) (0.1, 0.2, 0.5 and 1 g/L) were prepared in different alcohols without and with optimum concentration of TEA. The finer and positively charged titania nanoparticles were heterocoagulated on the surface of coarser and negatively charged CNTs and generated the titania–CNT composite particles with the net positive charge. In the presence of TEA, titania nanoparticles completely covered CNTs surface due to their higher positive surface charge. At same CNT concentration, the deposition rate was faster for suspensions with TEA additive due to the faster mobility of the composite particles. The photocatalysis efficiency of coatings for methylene blue degradation increased as CNTs were incorporated in their microstructure.  相似文献   

11.
《Ceramics International》2017,43(5):4663-4669
Three component suspensions of hydroxyapatite (HA), chitosan and CNTs were prepared in ethanol base solution (15 vol% water and 0.05 vol% acetic acid). The adsorption of HA nanoparticles on CNTs was investigated by FTIR and SEM analysis. It was found that HA nanoparticles are adsorbed on CNTs via chemical bonding between -NH2 groups of chitosan (adsorbed on their surface) and -COOH groups of CNTs. Current density as well as kinetics of EPD was studied at 60 V. It was found that current density increases or remains nearly constant during EPD due to the rise in water electrolysis as deposit grows on the substrate. Deposition weight against EPD time showed a linear trend due to the absence of any voltage drop over the deposit during EPD. The incorporation of chitosan and CNTs in the microstructure of coatings was confirmed by TG/DTA and SEM analysis. CNTs exhibited high efficiency in reinforcing the microstructure of coatings and preventing from their cracking. CNTs incorporation in the coatings improved their mechanical properties (adhesion strength, hardness and elastic modulus) and corrosion resistance.  相似文献   

12.
A route based on aqueous colloidal processing followed by liquid-phase assisted spark-plasma-sintering (SPS) is described for fabricating eco-friendly nanocomposites of SiC with nano-carbonaceous phases (nanotubes, nanoplatelets, or nanoparticles). To this end, the conditions optimizing the aqueous colloidal co-dispersion of SiC nanoparticles, Y3Al5O12 nanoparticles (acting as sintering additives), and carbon nanotubes (CNTs), graphene oxide (GO) nanoplatelets, or carbon black (CB) nanoparticles were first identified. Next, homogeneous powder mixtures were prepared by freeze-drying, and densified by liquid-phase assisted SPS, thus obtaining nanocomposites of SiC with CNTs, reduced GO (rGO) nanoplatelets, or pyrolized?+?graphitized CB (p?+?gCB) nanoparticles. It is also shown that these nanocomposites are dense and have a high hardness of ~20?GPa regardless of the nano-carbonaceous phase chosen, but are markedly tougher with CNTs and rGO (i.e., with high aspect ratio nano-carbonaceous phases). Finally, arguments are provided for the appropriate choice of nano-carbonaceous phases for engineering ceramic nanocomposites.  相似文献   

13.
Vulcanizing reagent (VR) suspensions with different sulfur additions were mixed with CNTs suspensions and SBR latex, and then powder CNTs/SBR (PSBR) composites were prepared by spray‐drying process. Investigations showed that VR additions have significant influences on the properties of CNTs/PSBR composites. With the increment of VR additions, glass transition temperature (Tg) of the composites increased gradually, and reached the maximum when the sulfur addition was 4.0 phr, and then it would decrease if the sulfur addition continued to rise. The elongation at break of the vulcanizates decreased linearly. The tensile strength and hardness reached the maximum when the sulfur addition was 4.0 phr, and almost kept constant when the addition continued to rise. Yet the tear strength reached the maximum when the addition was of 2.5 phr, and then decreased slightly when the addition exceeded 4.0 phr, which was corresponding to the structure designability of the composites affected by the sulfur aggregates in the matrix. Under different temperatures, when the vulcanizing temperature was 150°C, the vulcanizing speed was proper, vulcanizing time was prolonged, and the vulcanizing security was intensified. Compared with the vulcanization of carbon black/PSBR composites, more sulfur additions are needed in the vulcanization of CNTs/PSBR composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007  相似文献   

14.
Pyrolyzed polyaniline–SiO2 substrates with the rough surface containing some holes were prepared by the pyrolysis of polyaniline–SiO2 composites at temperature of 900 °C. Carbon nanotubes/nanofibers (CNTs/CNFs) were grown on the rough surface and inside the holes using a CVD method with a xylene–ferrocene mixture as a carbon and catalyst precursor source. The structural and morphological properties of CNTs were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the SiO2 content of the substrates was responsible to the diameter and electron field emission properties of CNTs.  相似文献   

15.
为改善聚偏氟乙烯(PVDF)膜的抗污性能,以聚乙二醇2000接枝的GO/TiO2(PEG/GO/TiO2)纳米复合材料为添加剂,通过非溶剂诱导沉淀相分离法制备了一系列PEG/GO/TiO2/PVDF复合超滤膜。采用FTIR、SEM和接触角测试仪对其结构和形貌进行了表征,采用超滤法评价其纯水通量和抗污性能。结果表明,当PEG/GO/TiO2纳米复合材料质量分数为0.60%时,制备的PEG/GO/TiO2/PVDF复合超滤膜(记为0.60%PEG/GO/TiO2/PVDF)表现出最佳的亲水性和抗污性能,其接触角比PVDF膜下降8.2°,总孔隙率增加13.40%,PEG/GO/TiO2纳米复合材料在PVDF膜中分散较均匀。在0.08 MPa的工作压力下,0.60%PEG/GO/TiO2/PVDF的纯水通量高达282.44 L/(m2·h),对腐植酸溶液的过滤通量为131.96 L/(m2...  相似文献   

16.
Carbon nanotubes (CNTs) were synthesized by catalytic decomposition of acetylene over Fe, Ni and Fe–Ni catalysts supported on alumina. The growth of CNTs was carried out at various reaction conditions. The growth density and diameter of CNTs could be controlled by varying the catalyst composition and the growth parameters. The growth density of CNTs increased with increasing the activation time of catalysts in H2 atmosphere and/or decreasing acetylene concentration. At 600°C, higher density of CNTs was observed at 60 min for higher Fe containing catalyst, whereas at 90 min for higher Ni containing catalyst. The growth density of CNTs highly increased with increasing reaction time from 30 to 60 min. For all the catalysts, the diameter of CNTs decreased with increasing growth time further mainly due to hydrogen etching. Bimetallic catalysts produced narrower diameter CNTs than single metal catalysts. The growth of CNTs followed the tip growth mode and the CNTs were multi-walled CNTs.  相似文献   

17.
To improve the stability and activity of Pt catalysts for ethanol electro‐oxidation, Pt nanoparticles were selectively deposited on carbon‐nanotubes (CNTs)‐supported‐SnO2 to prepare Pt/SnO2/CNTs and Pt/CNTs was prepared by impregnation method for reference study. X‐ray diffraction (XRD) was used to confirm the crystalline structures of Pt/SnO2/CNTs and Pt/CNTs. The stabilities of Pt/SnO2/CNTs and Pt/CNTs were compared by analyzing the Pt size increase amplitude using transmission electron microscopy (TEM) images recorded before and after cyclic voltammetry (CV) sweeping. The results showed that the Pt size increase amplitude is evidently smaller for Pt/SnO2/CNTs, indicating the higher stability of Pt/SnO2/CNTs. Although both catalysts exhibit degradation of electrochemical active surface area (EAS) after CV sweeping, the EAS degradation for the former is lower, further confirming the higher stability of Pt/SnO2/CNTs. CV and potentiostatic current–time curves were recorded for ethanol electro‐oxidation on both catalysts before and after CV sweeping and the results showed that the mass specific activity of Pt/CNTs increases more than that of Pt/SnO2/CNTs, indicating that Pt/CNTs experiences more severe evolution and is less stable. The calculated area specific activity of Pt/SnO2/CNTs is larger than that of Pt/CNTs, indicating SnO2 can co‐catalyze Pt due to plenty of interfaces between SnO2 and Pt.  相似文献   

18.
BACKGROUND: This study compared the removal of aqueous Cr(VI) by multi‐walled carbon nanotubes (CNTs) modified by sulfuric acid, titanium dioxide (TiO2) and composite of CNTs and TiO2. RESULTS: More than 360 h contact time was needed to completely adsorb 3 mg L?1 of Cr(VI) by CNTs, indicating that the rate of adsorption by CNTs alone was slow. The reaction time approaching equilibrium depended on the Cr(VI) concentration. XPS analysis of CNTs after adsorbing Cr(VI) showed that the Cr(VI) on the surface of CNTs was partially reduced to Cr(III). A 3 mg L?1 solution of Cr(VI) was fully photocatalyzed by commercial TiO2 (Degussa P25) in less than 0.5 h under UV irradiation. Unlike P25, reduction by another commercial TiO2 (Hombikat UV100) took 4 h and more than 2 h were necessary for reduction by the composite. Thus the efficiency of Cr(VI) photo‐reduction by the composite was lower than by TiO2, but higher than that by CNTs. XPS analysis of TiO2 and composite showed the existence of both Cr(VI) and Cr(III) on their surfaces. CONCLUSION: In contrast to TiO2, the reduction rate of aqueous Cr(VI) using CNTs as adsorbent was slow. P25 had a markedly higher photocatalytic efficiency than the composite or UV100 alone. Using P25 to reduce aqueous Cr(VI) has a higher potential for practical application. The diameters of TiO2 and CNTs and the ratio of TiO2/CNTs are key problems in the preparation of TiO2/CNTs composite. Copyright © 2011 Society of Chemical Industry  相似文献   

19.
The sorption behavior of Sc(III) on different materials including activated carbon (AC), carbon nanotubes (CNTs), graphene oxide (GO), and the chelating resin Chelex 100 was investigated. In general, the sorption of scandium increases with increasing pH. For pH in the range from 2.5 to 5.5, the sorption of Sc(III) onto CNTs, GO, and Chelex 100 is quantitative, whereas a significantly lower amount of scandium ions was retained on AC. The specific amount of Sc(III) adsorbed at pH 2 attained 2.1, 2.9, 36.5, and 37.9 mg g?1 for AC-COOH, Chelex 100, GO, and CNTs-COOH, respectively. At pH 4, a similar value was obtained for oxidized AC (2.2 mg g?1), whereas the specific amount adsorbed significantly increased for Chelex (23.4 mg g?1). The highest values were obtained for GO (39.7 mg g?1) and oxidized CNTs (42.5 mg g?1). Better kinetic retention was observed at pH 2 for CNTs and GO, whereas at pH 4 the kinetic behavior of Chelex 100, GO, and CNTs toward Sc(III) was comparable.  相似文献   

20.
《Ceramics International》2019,45(11):13747-13760
TiO2-rGO nanocomposite coatings were obtained by electrophoretic deposition (EPD) technique of TiO2 nanoparticles and graphene oxide (GO) on stainless steel substrate. First, GO particles were synthesized using a modified Hummers' method. GO was reduced electrochemically to form a coating in the presence of nano-sized TiO2 particles. The influences of different parameters such as GO concentration, coupling co-electro-deposition parameters (electrophoretic duration and voltage) on thickness, surface morphology and, corrosion behavior of the as-synthesized TiO2-rGO nanocomposite coatings were systematically surveyed. The morphology and microstructure were investigated by field emission scanning electron microscopy (FE-SEM), Raman spectra and X-ray diffraction (XRD) techniques. Atomic force microscopy (AFM) was harnessed to evaluate the topography of the as-prepared GO powder. The bonding characteristics of as-synthesized and as-reduced GO were examined after deposition, by Energy Dispersive Analysis of X-Ray (EDX) and Fourier-transform infrared spectroscopy (FT-IR). Corrosion behavior of coatings and that of the pure TiO2 layer were evaluated by electrochemical impedance spectroscopy (EIS) and polarization techniques (by applying potentiodynamic polarization spectroscopy (PDS)). Detailed SEM studies showed that increasing EPD voltage brings about a coating with increased porosity and microcracks with higher thickness. In addition to that, the presence of rGO reduced corrosion current density (icorr) and shifted corrosion potential (Ecorr) toward more noble values in 3.5% NaCl at room temperature. Also, Analyses revealed that the optimum electrophoretically synthesized coating was obtained at GO concentration of 1 g/L, 30 V and 30 min at room temperature. The corrosion current density of the corresponding coating was remediated up to 0.2 μA cm−2, which means an anti-corrosion ability of about 30 times compared to TiO2-coated and bare 316L stainless steel. The results of impedance spectroscopic studies demonstrated that this coating renders as a barrier layer and resistance increased from 2.95 KΩ cm2 for TiO2-coated layer to 10.49 KΩ cm2 for the optimized layer.  相似文献   

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