Polyacrylonitrile-based FeCo/C nanocomposites: Preparation and magnetic properties

Metal–carbon nanocomposites that represent FeCo alloy nanoparticles uniformly distributed over the carbon matrix, were prepared by the IR pyrolysis of precursors comprising polyacrylonitrile (PAN), iron acetylacetonate, and cobalt acetate (the metal ratio in the precursors was Fe: Co = 1: 1, 3: 1). The composition of FeCo alloy nanoparticles satisfies the tailored ratio Fe: Co. The FeCo phase is formed at synthesis temperatures in the range 500–600°С; at T ≤ 500°С only FCC-Co-base solid solutions are observed. The nanocomposites prepared at T ≥ 600°С simultaneously contain FeCo intermetallic nanoparticles and an insignificant amount of a FCC-Co phase or a cobalt-base solid solution phase. The saturation magnetization of FeCo/C metal–carbon nanocomposites is determined by the mean nanoparticle size and the alloy composition, and ranges from 36 to 64 (A m²)/kg (when Fe: Co = 1: 1) and from 35 to 52 (A m²)/kg (when Fe: Co = 3: 1) at synthesis temperatures in the range 600–800°С.     

NiCo/C nanocomposites: Synthesis and magnetic properties

NiCo/C metal–carbon nanocomposites were prepared using NiCl₂–CoCl₂–polyacrylonitrile (PAN) precursors using IR-laser heating. The characterization of these NiCo/C nanocomposites by X-ray powder diffraction, transmission electron microscopy, and vibration magnetometry showed that the structure and properties of NiCo/C nanocomposites depended on the nickel concentration in the precursor and the synthesis temperature. The magnetization of NiCo/C nanocomposites increased from 0.46 to 17 A m²/kg as the synthesis temperature changed from 500 to 800°С.     

Synthesis and physical properties of layered silicates/polyurethane nanocomposites

Samples of polyurethane nanocomposites were synthesized using diphenylmethane diisocyanate, poly(ε‐caprolactone) diol, di(ethylene glycol), and a clay functionalized by hydroxyl groups. The inorganic content in the hybrids was 2 wt %, 4 wt %, and 8 wt %. The X‐ray analysis showed that exfoliation occurred for clay content equal to 2% (w/w), whereas for higher contents, the inorganic phase rearranges in an intercalated structure. FTIR analysis suggested that the degree of hydrogen bonding in the hard segments was greatly reduced because of the amount of silicate layers and their dispersion. The dynamic‐mechanical analysis showed that the presence of clay lamellae extends very much the temperature range before the hard domain transition, causing the loss of mechanical consistency of the samples. It is less than 100 °C for the pure polymer, and increases up to 200 °C for the nanocomposites. The permeability of water vapor decreases linearly with inorganic content up to 4% of inorganic phase, and levels off at higher concentrations. The permeability behavior, at low activities, is largely dominated by the diffusion phenomenon. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 2454–2467, 2005     

一种阿霉素/NO供体光敏纳米复合物的合成与性质研究

以硫化铜纳米晶(CuS-NCs)为核心,聚N-异丙基丙烯酰胺接枝壳聚糖(PNIPAM-g-CS)微粒为壳合成一种新型光敏纳米复合材料.在温度的调节下,N-异丙基丙烯酰胺(NIPAM)包覆CuS纳米晶,并接枝壳聚糖(CS),合成CuS杂PNIPAM-g-CS纳米复合材料.CuS在近红外光(980 nm)照射下具有光热效应,导致纳米复合物中PNIPAM-g-CS微粒受热体积收缩.负载阿霉素,这种纳米复合物就可作为光热诱导释放阿霉素的多功能纳米载体.再负载NO光敏供体(RBS),就可制备出阿霉素/RBS双负载的CuS杂PNIPAM-g-CS纳米载体.在可见光(365 nm)照射下,RBS光解释放NO.近红外光和可见光分别触发纳米载体释放阿霉素和NO,加上CuS纳米晶的光热效应,这种纳米载体可实现光触发双药物释放协同光热化疗杀伤肿瘤细胞.     

Synthesis and properties of silanized waterborne polyurethane/graphene nanocomposites

A series of silanized waterborne polyurethane (WPU)/graphene oxide (GO) chemical hybrids were synthesized from polycaprolactone diol, isophorone diisocyanate, dimethylol butanoic acid, and (3-aminopropyl) triethoxysilane with GO as multifunctional crosslink as well as reinforcing filler. With the addition of GO, dispersion size greatly decreased due to the increased water phase viscosity, while it increased after chain extension reaction due to the migration of GO into the PU particles. The GO covalently bonded to WPU via the sol–gel type reaction augmented contact angle, glass transition temperature (Tg), hardness, and Young’s modulus of the cast film up to 1 %. However, the effects were less pronounced at high content (1.5 %) due to the agglomeration of GO particles.     

Synthesis,morphology, and viscoelastic properties of cyanate ester/polyhedral oligomeric silsesquioxane nanocomposites

Cyanate ester (PT‐15, Lonza Corp) composites containing the inorganic–organic hybrid polyhedral oligomeric silsesquioxane (POSS) octaaminophenyl(T₈)POSS [ 1 ; (C₆H₄NH₂)₈(SiO_1.5)₈] were synthesized. These PT‐15/POSS‐ 1 composites (99/1, 97/3, and 95/5 w/w) were characterized by X‐ray diffraction (XRD), transmission election microscopy (TEM), dynamic mechanical thermal analysis, solvent extraction, and Fourier transform infrared. The glass‐transition temperatures (T_g's) of the composite with 1 wt % 1 increased sharply versus the neat PT‐15, but 3 and 5 wt % 1 in these cyanate ester composites depressed T_g. All the PT‐15/POSS composites exhibited higher storage modulus (E′) values (temperature > T_g) than the parent resin, but these values decreased from 1 to 5 wt % POSS. The loss factor peak intensities decreased and their widths broadened upon the incorporation of POSS. XRD, TEM, and IR data were all consistent with the molecular dispersion of 1 due to the chemical bonding of the octaamino POSS‐ 1 macromer into the continuous cyanate ester network phase. The amino groups of 1 reacted with cyanate ester functions at lower temperatures than those at which cyanate ester curing by cyclotrimerization occurred. In contrast to 1 , 3‐cyanopropylheptacyclopentyl(T₈)POSS [ 2 ; (C₅H₉)₇(SiO_1.5)₈CH₂CH₂CH₂CN] had low solubility in PT‐15 and did not react with the resin below or at the cure temperature. Thus, phase‐separated aggregates of 2 were found in samples containing 1–10 wt % 2 . Nevertheless, the T_g and E′ values (temperature > 285 °C) of these composites increased regularly with an increase in 2 . © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3887–3898, 2005     

Elastomer/LDH nanocomposites: Synthesis and studies on nanoparticle dispersion, mechanical properties and interfacial adhesion

Layered double hydroxides (LDHs) based elastomer nanocomposites have been synthesized and characterized in terms of nanoparticle dispersion, mechanical properties and interfacial adhesion. Since LDH has basic hydroxyl groups on its surface, its potential as reinforcing filler in elastomers and in additionally a crosslinking agent in carboxylated elastomers has been investigated in details. For this purpose, two different elastomers having widely different polarities and functional groups (e.g., ethylene propylene diene terpolymer, i.e. EPDM and carboxylated nitrile rubber, i.e. XNBR) have been used as the matrix. The pristine LDH based on Mg and Al was modified with decane sulfonate by the regeneration method. The morphological analysis of the nanocomposites (done by X-ray diffraction analysis and electron microscopy) shows that in both matrices LDH particles are dispersed in three different forms, i.e. as primary particles, as exfoliated layers and as soft clusters formed by both of them. However, their relative proportion differs drastically in the two matrices. We have shown in this study that the LDH can significantly improve the mechanical properties in both the system. In XNBR/LDH nanocomposites containing no conventional metal oxide curative, this improvement is very prominent due to secondary interaction between LDH and XNBR matrix indicating that LDH can crosslink carboxalated elastomers. It is also observed that LDH particle promotes strain-induced crystallization in XNBR/LDH. The fracture surface analysis shows that in XNBR/LDH nanocomposite very stable polymer-filler interface is formed and tensile failure takes place through the matrix rather than through the interface. In case of EPDM/LDH nanocomposites the opposite is observed and the polymer matrix hardly wets the surface of the LDH particle.     

Synthesis and electromagnetic properties of polyaniline-coated silica/maghemite nanoparticles

Polyaniline coated silica/maghemite nanoparticles (PANI/SiO₂/γ-Fe₂O₃ composites) were synthesized by the combination of a sol-gel process and an in-situ polymerization method, in which ferrous and ferric salts as well as tetraethyl orthosilica (TEOS) acted as the precursor for γ-Fe₂O₃ and silica, respectively. As a result, the SiO₂/γ-Fe₂O₃ particle showed a core-shell structure, with γ-Fe₂O₃ as the magnetic core and silica as the shell of the particle. The shell thickness can be controlled by changing the TEOS concentration. The PANI/SiO₂/γ-Fe₂O₃ composites revealed a multilayer core-shell structure, where PANI is the outer shell of the composite. The doping level and the conductivity of PANI/SiO₂/γ-Fe₂O₃ composites decreased with increasing the TEOS content due to the presence of the less coated PANI on the SiO₂/γ-Fe₂O₃ core at higher TEOS content. For a SQUID analysis at room temperature, all γ-Fe₂O₃ containing composites showed a typical superparamagnetic behavior. The saturation magnetization of SiO₂/γ-Fe₂O₃ nanoparticles decreased with increasing the TEOS content due to the increase in silica shell thickness, while the saturation magnetization of PANI/SiO₂/γ-Fe₂O₃ composites also decreased with increasing the TEOS content, which is attributed to the lower conductivity of PANI in the composites at higher TEOS content.     

镍/碳纳米纤维复合物的制备及其吸波性能

以乙二胺为碳源,自制的镍纤维为催化剂,利用原位复合的方法制备得到一系列不同比例的镍/碳纤维复合物,并研究了其吸波性能.由于镍纤维和碳纤维均具有一定的电磁波耗散能力,因此得到的产物无需任何处理,可以直接作为吸波材料使用.结果表明,通过改变镍纤维的加入量,可以改变产物的镍碳比,进而实现对复合材料吸波性能的调控.在合适比例条件下制备得到的纤维复合物具有较好的吸波性能,当纤维复合物含量为25%时,其反射率的最小值可达-14.3dB.该材料在轻质吸波材料领域具有很好的应用价值.     

Layered silicate/epoxy nanocomposites: synthesis,characterization and properties

Novel epoxy‐clay nanocomposites have been prepared by epoxy and organoclays. Polyoxypropylene triamine (Jeffamine T‐403), primary polyethertriamine (Jeffamine T‐5000) and three types of polyoxypropylene diamine (Jeffamine D‐230, D‐400, D‐2000) with different molecular weight were used to treat Na‐montmorillonite (MMT) to form organoclays. The preparation involves the ion exchange of Na⁺ in MMT with the organic ammonium group in Jeffamine compounds. X‐ray diffraction (XRD) confirms the intercalation of these organic moieties to form Jeffamine‐MMT intercalates. Jeffamine D‐230 was used as a swelling agent for the organoclay and curing agent. It was established that the d₀₀₁ spacing of MMT in epoxy‐clay nanocomposites depends on the silicate modification. Although XRD data did not show any apparent order of the clay layers in the T5000‐MMT/epoxy nanocomposite, transmission electron microscopy (TEM) revealed the presence of multiplets with an average size of 5 nm and the average spacing between multiplets falls in the range of 100 Å. The multiplets clustered into mineral rich domains with an average size of 140 nm. Scanning electron microscopy (SEM) reveals the absence of mineral aggregate. Nanocomposites exhibit significant increase in thermal stability in comparison to the original epoxy. The effect of the organoclay on the hardness and toughness properties of crosslinked polymer matrix was studied. The hardness of all the resulting materials was enhanced with the inclusion of organoclay. A three‐fold increase in the energy required for breaking the test specimen was found for T5000‐MMT/epoxy containing 7 wt% of organoclay as compared to that of pure epoxy. Copyright © 2004 John Wiley & Sons, Ltd.     

Synthesis,characterization and X‐ray shielding properties of polypyrrole/lead nanocomposites

Novel radiation shielding nanocomposites based on a conducting polymer were fabricated and investigated to determine their abilities in attenuation of X‐rays. Polypyrrole/Pb nanocomposites were prepared through chemical reduction of lead salt by a facile solution‐phase method using t‐BuOLi‐activated LiH and in situ chemical polymerization of pyrrole in the presence of dodecyl benzene sulfonic acid as dopant and surfactant and iron chloride as the oxidant. The morphology, composition, and electrical conductivity of resulting products were characterized by scanning electron microscopy, transmission electron microscopy, X‐ray diffraction analysis, energy‐dispersive X‐ray spectroscopy, fourier transform infrared spectroscopy, and standard four‐wire technique, respectively. In order to evaluate capability of nanocomposites in radiation shielding, X‐ray photon interaction parameters such as linear attenuation coefficient, attenuation percentage, and half‐value thickness were determined for the samples with different Pb loadings and thicknesses, at photon energies of 13.95, 17.74, 20.08, 26.34, and 59.50 keV. The investigation was carried out to explore the potential of polypyrrole/Pb nanocomposites as thin and light‐weight radiation shielding materials. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis and physicochemical properties of calcium hydroxylapatite/multi-walled carbon nanotubes nanocomposites

Calcium hydroxylapatite/carbon nanotubes (HA/CNT) composites with various CNT contents have been synthesized by coprecipitation from aqueous solutions in the CaCl₂-(NH₄)₂HPO₄-NH₃-CNT-H₂O system (25°C) under conditions modeling the interaction between HA (Ca₁₀(PO₄)₆(OH)₂), which is an inorganic component of osseous tissue, and multi-walled CNTs. The empirical formula of the composites is Ca₁₀(PO₄)₆(OH)₂ · nCNT · 6H₂O, where n = 0.2?C5.0. The synthesis products have been identified by the solubility (Tananaev??s residual concentration) method, pH measurements, chemical analysis, X-ray diffraction, IR spectroscopy, electron spectroscopy for chemical analysis, and scanning and transmission electron microscopy. The effect of the CNT concentration in aqueous solution on the composition of the HA/CNT composites and on the crystallographic and morphological characteristics of HA nanocrystals in HA/CNT has been investigated.     

Synthesis and properties of near IR induced self-healable polyurethane/graphene nanocomposites

A series of self-healable polyurethane (SHPU)/modified graphene (MG) nanocomposites were synthesized from poly(tetramethylene glycol) (PTMG) and 4,4′-methylene diphenyl diisocyanate (MDI) with minute amounts (0–1 wt%) of MG which was chemically modified graphene oxide (GO) with phenyl isocyanate and reduced in the presence of phenylhydrazine.     

Length-controllable catalyzing-synthesis and length-corresponding properties of FeCo/Pt nanorods

Newly designed magnetic-alloy/noble-metal FeCo/Pt nanorods have been first reported and fabricated through a length-controllable catalyzing-synthesis process in which the growth of FeCo nanorods was induced on Pt nanotips. The length of FeCo/Pt nanorods depends on the number of platinum nanotips. The proposed synthesis mechanism was corroborated by scanning electron microscopy, transition electron microscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. With the decrease of Fe content in Fe(x)Co(96-x)/Pt(4) nanoalloys from 77 to 15, the morphology changes from nanorods with different lengths to nanoparticles. The analysis of the magnetic hysteresis loops indicated that the magnetic saturation and coercivity were strongly dependent on the length of the nanorods in which maximum saturation magnetization and minimum coercivity were obtained for Fe(77)Co(19)/Pt(4) nanorods with the length of ～2.5 μm. In particular, FeCo/Pt exhibited length-dependent reactivity towards 1,1,2,2-tetrachloroethane, and Fe(77)Co(19)/Pt(4) nanorods with the length of ～2.5 μm yielded the greatest dechlorination rate. Moreover, Pt can enhance the dechlorination of 1,1,2,2-tetrachloroethane.     

Polylactide/montmorillonite nanocomposites: Structure, dielectric, viscoelastic and thermal properties

Polylactide-based systems composed of an organoclay (Cloisite^® 30B) and/or a compatibilizer (Exxelor VA1803) prepared by melt blending were investigated. Two types of not compatibilized nanocomposites containing 3 wt% or 10 wt% of the organoclay were studied to reveal the effect of the filler concentration on the nanostructure and physical properties of such systems. The 3 wt%-nanocomposite was also additionally compatibilized in order to improve the nanoclay dispersion. Neat polylactide and polylactide with the compatibilizer processed in similar conditions were used as reference samples. The X-ray investigations showed the presence of exfoliated nanostructure in 3 wt%-nanocomposite. Compatibilization of such system noticeably enhanced the degree of exfoliation of the organoclay. Viscoelastic spectra (DMTA) showed an increase of the storage and loss moduli with the increase of the organoclay content and dispersion. Dielectric properties of the nanocomposites show a weak influence of the nanoclay on segmental (α_S) and local (β)-relaxations in PLA, except for the highest nanoclay content. Above T_g a strong increase of dc conductivity related to ionic species in the clay is observed. It gives rise also to the Maxwell-Wagner-Sillars interfacial polarization and both real and imaginary parts of ε strongly increase. In the temperature dependence of low frequency dielectric constant and mechanical moduli (at 1 Hz) an additional maximum around 80-90 °C is observed due to cold crystallization of PLA.     

Synthesis,structure, and magnetic properties of the fullerene-based ferromagnets Eu3C70 and Eu9C70

Intercalation of C(70) with europium affords two kinds of magnetic compounds, a canted antiferromagnet Eu(x)C(70) (x approximately 3) and a ferromagnet Eu(x)C(70) (x approximately 9) with transition temperatures (T(C)) of 5 and 38 K, respectively. The Curie constants in the paramagnetic phase and the saturation moment in the ferromagnetic phase are both understood by the full moment of Eu(2+) for both systems. The structure of Eu(3)(-)(delta)C(70) (delta approximately 0.27) is pseudo-monoclinic, derived by a simple deformation of the parent face-centered cubic (fcc) structure. Eu(9)(-)(delta)C(70) (delta approximately 0.2) forms an fcc structure, in which cuboctahedral clustering of Eu(2+) ions is observed in the enhanced size octahedral holes. The observed T(C) of the Eu(9)(-)(delta)C(70) ferromagnet is comparable to or larger than those of simple binary Eu-based ferromagnets, such as Eu chalcogenides or carbides, despite the low atomic ratio of Eu in the chemical formulas. This can be understood by the short Eu(2+)-Eu(2+) distances and high coordination numbers permitted by the multiple occupation by Eu(2+) ions of the expanded octahedral interstitial sites in higher fullerene-based solids.     

Microstructure,electrical, and electromagnetic interference shielding properties of carbon nanotube/acrylonitrile–butadiene–styrene nanocomposites

Processing, electrical, and electromagnetic interference (EMI) shielding behaviors of carbon nanotube (CNT)/acrylonitrile–butadiene–styrene (ABS) nanocomposites were studied as function of CNT concentration. The nanocomposites were prepared by melt mixing followed by compression molding. The selective and good level of dispersion of CNT in the styrene–acrylonitrile section of the ABS polymer was found to create conductive networks in the ABS matrix at a nanofiller loading of 0.75 wt %. At this nanofiller loading, the nanocomposite electrical conductivity was 10^?5 S/m. This conductivity makes the nanocomposite suitable for electrostatic discharge protection applications. The EMI shielding effectiveness of the nanocomposites increased with the increase in nanofiller concentration. In the 100–1500 MHz frequency range, 1.1 mm thick plates made of ABS nanocomposite filled with 5 wt % CNT exhibit an EMI shielding effectiveness of 24 dB. At this shielding level, the nanocomposite is suitable for a broad range of applications. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

Ternary Ag/Polyaniline/Au nanocomposites: Preparation,characterization and electrochemical properties

Ternary Ag/Polyaniline/Au nanocomposites were synthesized successfully by immobilizing of Au nanoparticles (NPs) on the surface of Ag/Polyaniline (PANI) nanocomposites. Ag/PANI nanocomposites were prepared via in situ chemical polymerization of aniline in the presence of 4-aminothiophenol (4-ATP) capped silver colloidal NPs. Then, uniform gold (Au) NPs were assembled on the surface of resulted Ag/PANI nanocomposites through electrostatic interaction to get Ag/Polyaniline/Au nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), ultraviolet visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Moreover, Ag/PANI/Au nanocomposites were immobilized on the surface of a glassy carbon electrode and showed enhanced electrocatalytic activity for the reduction of H₂O₂ compared with Ag/PANI.     

Synthesis and properties of organic-silica nanocomposites with perhydropolysilazane

The synthesis and properties of the organic polymer-silica nanocomposites by blending perhydropolysilazane with organic polymer having hydroxyl groups have been described. Poly(methyl methacrylate) (PMMA)-silica nanocomposites with a PMMA/silica lamellar structure and spherical silica domains in a PMMA matrix were obtained with random copolymers and block copolymers. The effect of the architecture of the random and block copolymers on the morphology of composites has been summarized. The thermal stability, electrical properties, such as field break down, leakage current, etc., and surface hardness of the composites have been discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5174–5181, 2006