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1.
The polymerization of aniline (ANI) in aqueous medium in the presence of (NH4)2S2O8 and montmorillonite (MMT) resulted in the formation of a nanocomposite (PANI–MMT). The inclusion of PANI in the composite was confirmed by FTIR studies. The extent of PANI loading in the composite increased with ANI concentration at a fixed oxidant/MMT amount and with the oxidant amount at a fixed ANI and MMT weight, but decreased with an MMT amount at a fixed ANI and oxidant level. TGA revealed a higher stability for the PANI–MMT composite relative to PANI and confirmed a PANI loading of ca. 51% in the composite. The conductivity increased in all the cases. XRD analysis revealed no expansion of the d001 spacing at 9.8 Å, implying no intercalation of PANI within the MMT layers. Scanning electron micrography studies revealed interesting morphological features for the composites. Transmission electron micrography analysis revealed distinctive features and confirmed the formation of PANI–MMT composite particles of diameters in the 300‐ to 400‐nm range. These composites could be obtained as stable colloids in the presence of poly (N‐vinyl pyrrolidone) under selective conditions. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 2948–2956, 2000  相似文献   

2.
《Ceramics International》2019,45(11):13809-13817
In this study, Al-Si/Al2O3 core-shell structured particles were fabricated via pressurized steam corrosion for 1 h followed by heating for 3 h at 1100 °C. After steam corrosion, a layer composed of disordered crystals covered the surfaces of the Al-Si alloy particles. After heating, Al-Si/Al2O3 core-shell structured particles with complete shells were prepared. The thickness of the shell was approximately 2 μm, and it enclosed the Al-Si alloy core. The shell exhibited excellent thermal stability because, even at 1100 °C, the mass gain ratio of the encapsulated particle was less than 0.5%. Scalloped patterns of alumina were formed by the oxidation of Al, which was inlaid through and upon the alumina shell. The shell formation mechanism suggested that the α-Al2O3 shell resulted from the combination of the decomposition of surface Al(OH)3 crystals and the oxidation of Al from the core.  相似文献   

3.
Polyaniline (PANI) was synthesized by chemical oxidative polymerization of aniline (ANI) in the presence of sulfonated crosslinked polystyrene (SCPS) particles in neutral water. The polymerization of ANI occurred preferentially on the surfaces of the SCPS particles, resulting in core/shell structured SCPS/PANI particles. The conductivities of the SCPS/PANI particles increased with increasing degree of sulfonation of the SCPS and with increasing ANI/SCPS weight ratios in the reactants. Conductive epoxy‐based composites were prepared by curing the blend of SCPS/PANI particles and epoxy resin with an aromatic amine curing reagent, indicating the core/shell structured particles were stable, to some extent, to alkaline environments, which will be of significant importance for the practical application of PANI in many cases. Copyright © 2006 Society of Chemical Industry  相似文献   

4.
This article describes the effect of the addition of different phases of alumina particles on the properties of electrodeposited Ni–Al2O3 composite coatings. The corrosion- and wear-resistant properties of Ni–Al2O3 composite coatings electrodeposited from a nickel sulfamate bath containing (i) alpha-alumina particles (Ni–Al2O3-1), (ii) gamma-alumina particles (Ni–Al2O3-2), and (iii) mixture of alpha, gamma, and delta alumina particles (Ni–Al2O3-3) have been studied. The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) studies showed superior corrosion resistance of Ni–Al2O3-2 composite coatings compared with other two coatings. The SEM images and EDAX spectra also corroborated well with the observed corrosion results. The pin-on-disk wear studies showed improved wear resistance of Ni–Al2O3-1 composite coating containing alpha alumina compared with other two coatings. The transfer of material from the pin onto the disk was evident from the optical microscopy images of the wear tracks and Raman spectra of the wear track. This study shows that the addition of pure gamma-alumina particles enhances the corrosion resistance, and that pure alpha-alumina particles enhance the wear resistance of Ni composite coatings to a greater extent.  相似文献   

5.
The interfacial reaction between alumina refractory and CaO–CaF2–SiO2–Al2O3–MgO–MnO slag was observed at 1873 K to estimate the stability of the spinel phase using computational thermodynamics under refining conditions of Mn‐containing steels. The concentration of MnO formed by the slag–steel reaction in the CaO–CaF2–SiO2–Al2O3–MgO melts generally increased by decreasing the CaO/SiO2 ratio of the initial melts. No intermediate compounds were formed at the refractory–slag interface when the initial CaO/SiO2 ratio was 0.5, whereas CaAl12O19 (CA6) and Mg(Mn)Al2O4 (spinel), identified from TEM analysis using EDS mapping and SAED patterns, were observed at the refractory–slag interface when the CaO/SiO2 ratio was 1.0 or greater. The (at.%Mg)/(at.%Mn) ratio in the spinel solution increased by increasing the CaO/SiO2 ratio, which originated from the fact that MgO activity continuously increased as the CaO/SiO2 ratio increased. From thermodynamic analysis considering the equilibrium constant (KSP) and activity quotient (QSP) of the spinel formation reaction at the slag–refractory interface and the bulk slag phase, the precipitation–dissolution behavior of the spinel phase was predicted, which exhibited good consistency with the experimental results. Hence, the dissolutive corrosion mechanism of alumina refractory into the CaO–CaF2–SiO2–Al2O3–MgO–MnO slag was proposed.  相似文献   

6.
The synthesis of polyaniline (PANI) with H4Nb6O17 (HNbO) to form PANI/HNbO lamellar nanocomposite by in situ polymerization using aniline (ANI) intercalation compound ANI/HNbO as the intermediate has been investigated. The properties of the samples were characterized by means of XRD, SEM, TEM, FT‐IR, UV–vis spectroscopy, and TG‐DTA. The in situ polymerization of ANI packed in a regular orientation in a mono‐ and bilayers (i.e., pseudo‐bilayers) structure within the HNbO interlayers led to PANI/HNbO nanocomposite powder using (NH4)2S2O8 as the catalyst with PANI monolayer packing orientation within the HNbO interlayers. PANI/HNbO nanocomposite showed improved thermal stability compared with original PANI by TG analysis. The PANI/HNbO nanocomposite was studied by cyclic voltammetry (CV), which indicated the good redox activity and electrochemical‐cycling stability in acidic solution. The interaction between PANI and nanosheets greatly affected the electrochemical behavior of PANI/HNbO nanocomposite. Two couples of redox peaks corresponded to two oxidation process of PANI in acid conditions. The PANI/HNbO nanocomposite exhibited much higher photocatalytic activities for the degradation of methylene blue (MB) in aqueous solution under visible light irradiation than HNbO itself. POLYM. COMPOS., 34:834–841, 2013. © 2013 Society of Plastics Engineers  相似文献   

7.
The chemical reactions involved in the corrosion of polycrystalline alumina (Al2O3) and calcium hexaluminate–hibonite (CaAl12O19) ceramics by two dicalcium silicate slags with additions of fluorspar (CaF2) were studied using a hot-stage microscopy (HSM) up to 1600 °C. The corrosion mechanism was investigated on post-mortem corroded samples and the phases formed at different stages of the dissolution process were characterised by reflected optical light microscopy (RLOM) and scanning electron microscopy (SEM) with energy dispersive X-ray spectrometry (EDS) microanalysis system.The attack of the fused slags on dense alumina substrates takes place through an interdiffusion mechanism producing successive layers of calcium aluminates. In porous hibonite samples chemical interactions were observed although only a layer of calcium dialuminate was formed. A sintering process in presence of liquid phase was also detected behind the reaction interphase.Thermodynamic calculations, based on the Al2O3–CaO–SiO2, Al2O3–CaO–SiO2–MgO, and Al2O3–CaO–SiO2–CaF2 phase equilibrium were used to further knowledge of the corrosion mechanism.  相似文献   

8.
This study investigates the effect of the incorporation of alumina particles on the thermomechanical properties of polybutylene succinate (PBS)/Al2O3 composites. The alumina surface was modified with the carboxylic groups of maleic acid through simple acid-base and in situ polymerization reactions. Scanning electron microscope (SEM) results revealed the introduction of maleic acid treated alumina significantly affect the morphology of the PBS/Al2O3 composites as compared to the neat PBS. The thermal conductivity of the composite (0.411?W?m?1 K?1) was more than twice that of neat PBS. The composite containing polymerization-modified alumina showed a 50% increase in storage modulus compared with that of neat PBS. In addition, universal testing machine (UTM) and differential scanning calorimetry (DSC) measurements indicated an increase in the tensile strength and degree of crystallinity after the incorporation of modified alumina in the PBS/Al2O3 composite.  相似文献   

9.
Ultrasonic irradiation is employed to assist the chemical oxidative polymerization of aniline in the presence of Fe3O4 nanoparticles in order to prepare a polyaniline (PANI)/Fe3O4 magnetic nanocomposite. In the chemical oxidative polymerization of aniline in the initially neutral medium, the optimum molar ratio of the oxidant ammonium persulfate to the monomer aniline is 2 : 1. The prepared PANI is in the emeraldine form and is doped by sulfate anions. Fe3O4 particles are encapsulated by PANI and dispersed well in PANI. Fe3O4 increases the doping level and decreases the crystallinity of PANI. The PANI/Fe3O4 nanocomposite possesses conductivity and magnetic properties. Increasing the Fe3O4 content increases the magnetization of the PANI/Fe3O4 composite but decreases its conductivity. © 2006 Wiley Periodicals Inc. J Appl Polym Sci 102: 2107–2111, 2006  相似文献   

10.
Polyaniline (PANI)‐α‐Fe2O3 nanocomposites (NCs) have been synthesized by chemical oxidative in situ polymerization of aniline in presence of α‐Fe2O3 nanoparticles at 5°C using (NH4)2S2O8 as an oxidant in an aqueous solution of sodium dodecylbenzene sulphonic acid (SDBS), as surfactant and dopant under N2 atmosphere. The room temperature conductivity of NCs decreases and coercive force (Hc) increases with an increase addition of α‐Fe2O3 in PANI matrix. The result of FTIR and TGA shows that the interaction between α‐Fe2O3 particles and PANI matrix could improve the thermal stability of NCs. NCs demonstrate the superparamagnetic behavior. The performance of PANI and PANI‐α‐Fe2O3 NCs as protective coating, against corrosion of 316LN stainless steel in 3.5% NaCl was assessed by potentiodynamic polarization technique. The study shows a good corrosion inhibition effect of both the coatings. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

11.
Polyelectrolyte complex (PEC) membranes prepared from poly(styrene sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDADMAC) were modified by crossflow polymerization of aniline (ANI). The PEC membranes were used as separators in a two-compartment setup where ANI monomer and ammonium persulfate (APS) oxidant diffused through the membranes to form polyaniline (PANI). APS and ANI having different distributions throughout the membranes, the reaction led to the asymmetric polymerization of PANI on one face of each PEC membrane thus producing Janus membranes. Due to the excess PANI content, the membrane displayed distinct asymmetric electrical conductivities on each face. Interestingly, very different ANI polymerizations were obtained when nonstoichiometric PEC membranes having different molar ratio of cationic and anionic polyelectrolytes (P+:P? represents PDADMAC:PSS) were used and transport of APS was fastest through the 2:1 PEC when compared to the 1:2 PEC. In all experiments, the polymerization was most intense on the ANI side of the membranes. Also, the influence of NaCl both during PEC fabrication and during polymerization was studied and found to have some effect on the solute permeability. Results showed that a higher content of PANI was formed on PEC membranes having excess P+ and with no NaCl added during PEC fabrication. Although X-ray diffraction confirmed the presence of PANI on both sides of each membrane, scanning electron microscopy images demonstrated that both sides of each membrane had different PANI content deposited. Electrical conductivity measurements using a four-point probe setup also showed that the PEC–PANI exhibits asymmetric electrical property on different sides. © 2021 Society of Industrial Chemistry.  相似文献   

12.
The corrosion resistance and mechanical properties directly affects the operation and service life of Al2O3-Cr2O3 refractories used in waste incinerators. In this study, ZrO2 particles were introduced via vacuum impregnation to adjust microstructure and properties of Al2O3-Cr2O3 refractories. The results showed that the impregnated ZrO2 particles and increasing impregnation times resulted in the decreased median pore size and increased compactness, and mechanical strengths of refractories were elevated from the inhibited cracks propagation by ZrO2 particles. The decreased amounts of large pores and increased amounts of small pores from the filled ZrO2 particles inhibited penetration of low melting point phases, and the formed CaZrO3 phase from the reactions between corrosion reagent and ZrO2 particles increased the viscosity of penetrated corrosion reagent, resulting in the decreased penetration index from 8.57% to 2.58%. Meanwhile, the filled ZrO2 particles around alumina particles prevented reactions between molten corrosion reagent and alumina, leading to the decreased corrosion index from 3.78% to .74%. The decreased pore size and formation of CaZrO3 phase were primary factors that enhanced the penetration resistance. And formation of wrapped layers from ZrO2 particles around alumina particles presented prominent effects on the strengthened corrosion resistance of Al2O3-Cr2O3 refractories.  相似文献   

13.
In flowing nitrogen, non‐oxides such as Al4O4C, Al2OC, Zr2Al3C4, and MgAlON bonded Al2O3‐based composites were successfully prepared by a gaseous phase mass transfer pathway using aluminum, zirconia, alumina, and magnesia as raw materials at 1873 K, after an Al–AlN core‐shell structure was formed at 853 K. Resin bonded Al–Al2O3–MgO–ZrO2 composites after sintering were characterized and analyzed by X‐ray diffraction (XRD), scanning electron microscope (SEM) and, energy dispersive spectrometer (EDS), and the influence of the MgO content on the sintered composites was studied. The results show that after sintering, the phase composition of the Al–Al2O3–ZrO2 composite is Al2O3, Al4O4C, Al2OC, and Zr2Al3C4, while the phase composition of the Al–Al2O3–ZrO2 composite with the addition of MgO 6 wt% and MgO 12 wt% is Al2O3, MgAlON, Al4O4C, Al2OC, and Zr2Al3C4 as well as Al2O3, MgAlON, Al2OC, and Zr2Al3C4, respectively. The addition of MgO changed the phase composition and distribution for the resin bonded Al–Al2O3–MgO–ZrO2 system composites after sintering. When the added MgO content is equal to or more than 12 wt%, the Al4O4C in the resin bonded Al–Al2O3–MgO–ZrO2 system composites is unable to exist in a stable phase.  相似文献   

14.
《Ceramics International》2017,43(18):16502-16511
Al2O3- and MgO-based refractories are widely used in the steel industry as lining materials for many metallurgical reactors. Due to their direct contact with slag and steel, they suffer corrosion and degradation, especially in the slag-line position, which limits their service performance. The purpose of this article is to obtain a better understanding of the corrosion behavior of the two refractories with different compositions of virtual steelmaking slags (wt%CaO/wt%SiO2 = 3.0–7.0, Al2O3: 18–35 wt%) using laboratory experiments and FactSage thermodynamic modeling. Pure Al2O3 and MgO-Al2O3 crucibles were adopted to simulate the two refractories, respectively, during the experiment. The results show that the degree of corrosion of both crucibles increases with an increase in slag basicity and a decrease in Al2O3 content in the slag. The Al2O3 crucible is more susceptible to corrosion than the MgO-Al2O3 crucible, which is attributed to the effect of the slag penetrating through the Al2O3 crucible matrix and substituting part of its matrix. For the MgO-Al2O3 crucible, there was no obvious slag substitution, but a transition layer was found in the contact region between the crucible and the slag. The Al2O3 in the crucible matrix reacts with slag to produce calcium alumina (CaAl12O19, CaAl4O7) and other complex oxides, while the MgO particles at the MgO-Al2O3 crucible-slag interface were only surrounded by liquid slag without an obvious chemical reaction between them. The mechanism of corrosion was studied by experiments combined with thermodynamic calculations and with the establishment of a new corrosion model. This study is expected to provide a guide for the design of related refractories and slags in industrial applications.  相似文献   

15.
《Ceramics International》2020,46(4):4215-4221
Alumina is widely used as a coating on a metal implant due to its favorable mechanical and biological properties. In this research, in order to improve mechanical and biological properties of alumina, a composition of nanoparticles of alumina (instead of microparticles) and titanium diboride micro powder is introduced. The atmospheric plasma spray (APS) technique was applied to deposit Al2O3–TiB2 on the pure titanium substrate. The properties of Al2O3–TiB2 nanocomposite coatings with various weight percent of TiB2 (20, 30 and 40 wt%) were experimentally studied. The characteristics of nanocomposite films of TiB2 (20, 30 and 40 wt%) were analyzed using Field Emission Scanning Electron Microscopy (FE-SEM), energy dispersive electron spectroscopy (EDX) and X-Ray Diffraction (XRD) tests. The XRD spectra exhibited that in addition to alumina and titanium diboride, the films contained titania. Thickness and morphology of the films were calculated from FE-SEM images and the thickness of the optimized coating (Al2O3-30 wt% TiB2) was about 30–45 μm. Also, the roughness, corrosion resistance, hardness and cytotoxicity (MTT) tests were studied. The highest of hardness and roughness of the samples were obtained from Al2O3-30 wt% TiB2. According to the obtained results from the polarization test, Al2O3-30 wt% TiB2 coating had the highest corrosion resistance (222558.9962 Ω cm2). Therefore, the toxicity of Al2O3-30 wt% TiB2 was investigated as the optimized coating and the results confirmed its non-toxicity and biocompatibility.  相似文献   

16.
《Ceramics International》2020,46(15):23686-23694
High-quality alumina (Al2O3) coating has an extensive demand in the fields of optoelectronics, solar cells, and corrosion/impurity resistant coatings and cutting tools. The quality of alumina coating depends on its hardness and transparency. To obtain hard and highly transparent alumina coating, which is also a widely used ceramic material, a novel, aerosol deposition approach is presented in which the starting powder, used to fabricate Al2O3 ceramic coatings, is composed of angular and spherical Al2O3 particles. Films fabricated using angular:spherical Al2O3 particle mixtures with ratios of 10:0, 7:3, 5:5, 3:7, and 0:10, showed significant variation in surface roughness and microstructure. The dramatic morphology modulation of the 3:7 angular:spherical Al2O3 mixture film, resulting from the superposition hammering effect caused by the aerosol mixture, improved transmittance (84.7%) and hardness (13.6 GPa). Previous studies used high-energy approaches to optimize Al2O3 film properties. This dual-particle approach, however, produces Al2O3 film with excellent transmittance and hardness while achieving a fast coating speed (32 mm2 × μm/min) without additional thermal treatment. Our proposed approach provides a novel and energy efficient method to produce transparent Al2O3 films with superior durability.  相似文献   

17.
15R–SiAlON bonded Al2O3 refractories were successfully synthesized using ferrosilicon nitride and alumina by liquid phase sintering. The phase composition and morphology were analyzed by means of X‐ray diffraction, scanning electron microscopy, and transmission electron microscopy. The results show that 15R–SiAlON reinforcement can be in situ obtained in the specimens with 5 wt% ferrosilicon nitride at 1500°C to 1700°C in flowing N2 of 0.1 MPa. The morphology of 15R–SiAlON is strongly dependent on the morphology of intermediate AlON phases formed at different temperatures. Fe–Si alloys from ferrosilicon nitride form liquid phase and accelerate the formation of 15R‐SiAlON, in which process the wettability of Fe–Si alloys is improved by the increase in Si content, carbon coating on particle, solution process and reactions. The 15R–SiAlON reinforced Al2O3 refractory materials possess high cold crushing strength of 138‐171 MPa.  相似文献   

18.
Peroxidase-catalyzed template-guided polymerization of aniline in the presence of γ- alumina nanosheet (NS) particles have been carried out in aqueous media and γ-Al2O3/PANI nanocomposite was obtained. The polymerization of aniline occurred in aqueous solution in the presence of SPS (sulfonated polystyrene) as a template and SDS (sodium dodecyl sulfate) as a surfactant. Both obtained nanocomposites were comparable by SEM images. It was demonstrated that the γ-Al2O3 NS/PANI-SPS nanocomposite has higher conductivity and the γ-Al2O3 NS/PANI-SDS nanocomposite has higher void areas. The higher conductivity of γ-Al2O3 NS/PANI-SPS nanocomposite is attributed to the higher coated areas of γ-Al2O3 NS during polymerization in comparison with γ-Al2O3 NS/PANI-SDS which are not coated efficiently as the former. The FT-IR studies showed that the γ-Al2O3 NS/PANI nanocomposite was formed by interaction of the polyaniline (PANI) and γ-Al2O3 NS. FTIR also showed that the amount of PANI in γ-Al2O3 NS/PANI-SPS is more than in γ-Al2O3 NS/PANI-SDS. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers  相似文献   

19.
Novel phase‐change microcapsules with paraffin as core and melamine‐formaldehyde (MF) resin as shell were synthesized through in situ polymerization, in which nano alumina (nano‐Al2O3) particles were dispersed in the shell by mixing nano‐Al2O3 with MF prepolymer solution using the direct addition method (i.e., adding nano‐Al2O3 into the MF prepolymer solution directly) and the predispersed addition method (i.e., predispersing the nano‐Al2O3 homogenously in water under the assistance of dispersant and wetting agents before mixing with the MF prepolymer). Scanning electron microscope experiments demonstrated that the predispersed addition method yielded the microcapsules having the better dispersion and less self‐agglomeration of alumina, compared to the direct addition method. Fourier transform infrared spectroscopy, energy dispersive X‐ray spectroscopy, and electron backscatter diffraction imaging confirmed that the nano‐Al2O3 particles were successfully incorporated in the shell by the predispersed addition method. The phase change behavior of microcapsules incorporated with different contents (up to 12.7% relative to the microcapsule) of nano‐Al2O3 particles in the shell was investigated by differential scanning calorimeter. The results revealed that the encapsulation efficiency for this kind of novel microcapsules was >77% and the incorporation of nano‐Al2O3 in the shell affected the phase change temperature. Thermal gravimetric analysis indicated that the addition of nano‐Al2O3 improved the thermal stability of microcapsules remarkably. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

20.
Polyaniline (PANI)/Nylon‐6 composite films were prepared by oxidative polymerization of aniline (ANI) inside host Nylon‐6 film. Such a composite has the desired electro‐active and mechanical properties to serve as a self‐standing functional unit. Comparative studies on sorption of ANI by Nylon‐6 matrix from various ANI containing media were conducted revealing superior ANI uptake from neutral ANI solution in water. ANI content was measured to be as high as 12%. Spectroscopic measurements showed that hydrogen bonding seemed to play important role in ANI sorption by Nylon‐6 matrix. Polymerization was monitored using atomic force microscopy and conductivity measurements. The morphology studies showed the appearance of PANI nanodomains on Nylon‐6 surface in the early stages of the polymerization. Eventually the domains coalesced during polymerization forming a continuous PANI layer. The conductivity measurements confirmed the change of the morphology from isolated islands to continuous conducting surface by drastic increase in conductivity. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009  相似文献   

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