Impact of Al nanoparticles upon the microstructure and wear properties of Ni-Cr-Al nanocomposite coatings

Ni–7Cr and Ni–7Cr–2Al (wt.%) nanocomposite coatings were fabricated by co-electrodeposition of Ni with Cr (40 nm) or and Al (75 nm) nanoparticles from a nickel sulfate bath, their microstructure, friction and wear performance were comparably evaluated in order to elucidate the effect of Al nanoparticles on the properties of nanocomposite coatings. The results indicated that the co-deposition of minor Al nanoparticles significantly increases the microhardness and wear resistance because Al nanoparticles with surface amorphous oxides layers exert the dispersion-strengthening effect like Al₂O₃ nanoparticles.     

Preparation and properties of inhalable nanocomposite particles: effects of the size, weight ratio of the primary nanoparticles in nanocomposite particles and temperature at a spray-dryer inlet upon properties of nanocomposite particles

Nanoparticles are expected to be applicable to inhalation as carrier but there exist disadvantages because of their size. Their deposition dose to the lung will be small. To overcome this problem and utilize nanoparticles for inhalation, we have prepared nanocomposite particles as drug carriers targeting lungs. The nanocomposite particles are prepared as drug-loaded nanoparticles–additive complex to reach deep in the lungs and to be decomposed into nanoparticles when they deposit into lung. In this study, we examined the effect of preparation condition – inlet temperature, size of primary nanoparticles and weight ratio of primary nanoparticles – on the property of nanocomposite particles.

When the size of primary nanoparticles was 400 nm and inlet temperature was 90 °C, only the nanocomposite particles containing between 45 and 55% of primary nanoparticles could be decomposed into nanoparticles in water. On the other hand, when the inlet temperature was 80 °C, nanocomposite particles were decomposed into nanoparticles independent of the weight ratio of primary nanoparticles. Also, the aerodynamic diameter of the nanocomposite particles was between 1.5 and 2.5 μm, independent of the weight ratio of primary nanoparticles.

When the size of primary nanoparticles was 200 nm and inlet temperature was 70 °C, nanocomposite particles were decomposed into nanoparticles independent of the weight ratio of primary nanoparticles. Also, the aerodynamic diameters of them were almost 2.0 μm independent of the weight ratio of primary nanoparticles. When the nanocomposite particles containing nanoparticles with the size of 200 nm are prepared at 80 °C, no decomposition into nanoparticles was observed in water.

Fine particle values, FPF, of the nanocomposite particles were not affected by the weight ratio of primary nanoparticles when they were prepared at optimum inlet temperature.     

Processing and thermal properties evaluation of silylated apophyllite–filled epoxy nanocomposite

The primary objective of the research was to evaluate the rheology and thermal properties of silylated apophyllite–filled epoxy nanocomposite. Several n‐octyldimethylsiloxy‐apophyllite with different grafting degrees were synthesized by controlling the ratio of the apophyllite and n‐octyldimethylchlorosilane. The thermal studies of silylated apophyllite have shown that the onset decomposition temperature of silylated apophyllite far exceeds the onset temperature of conventional organoclays (~260 °C). Chemorheological measurements of 1.8 wt% silylated apophyllite–filled tetra functional epoxy (MY720) and difunctional epoxy (DER661) resin mixture showed that the addition of the silylated apophyllite does not dramatically affect the cure profile of the epoxy resin with the availability of 40 min of processing window after the addition of apophyllite. Wide angle X‐ray diffraction and transmission electron microscopy results of the shear mixed and cured nanocomposite suggest that the apophyllite was well dispersed in the epoxy matrix. The thermal studies of epoxy nanocomposite showed an increase in the char yield on the addition of silylated apophyllite to the epoxy resin. In addition, an improvement in the onset decomposition temperature of the cyanopropyldimethylsiloxy‐apophyllite epoxy nanocomposite was observed compared with that of pure epoxy resin. Copyright © 2011 John Wiley & Sons, Ltd.     

Proton irradiation effects on the structural and tribological properties of polytetrafluoroethylene

Polytetrafluoroethylene (PTFE) was irradiated with protons in a ground-based simulation facility to study the effects of proton irradiation on the structural and tribological properties of PTFE. The structural changes were characterized by X-ray photoelectron spectroscopy (XPS) and attenuated total-reflection FTIR (ATR-FTIR), while the tribological properties were evaluated by friction and wear tests. It was found that proton irradiation induced the degradation of PTFE molecular chains, resulting in the increase of C concentration and the decrease in F concentration on the sample surfaces, and the surface chemical structure and morphology of the samples changed, which affected the friction coefficient and decreased the wear rate of the specimens as the friction and wear tests revealed.     

Structure and properties of biodegradable wheat gluten/attapulgite nanocomposite sheets

Wheat gluten (WG) and Attapulgite (ATP) was mixed in acidic solution and freeze-dried, thermally compression-molded to form nanocomposite sheet. The influences of reduction and sonication on structure of wheat gluten were examined by Raman spectrum. The variation of disulfide bonding in wheat gluten show that the sonication is more effective than reduction on the breakage of disulfide bonds, whereas the content of disulfide bonds in the WG sheet molded by sonicated WG powder is the highest in the molded sheets. FT-IR analysis displays that the bands in the range of 1700-1600 cm⁻¹ shift to higher frequency after mixing WG and ATP powders and molding the nanocomposite. The tensile and bending properties of the WG sheet increase with addition of ATP powder, and the properties of the sheet molded by sonicated WG powder decrease for the reduction of the disulfide bonding, but the properties of the sheet can be improved by addition of ATP. The WG/ATP nanocomposite images observed by SEM and TEM show that rod-like ATP particles are evenly dispersed in WG matrix, but the crystal structure of ATP is impervious. The viscoelasticity of the WG sheet declines with addition of ATP particle, and that the α-relaxation of the WG sheet molded by sonicated WG powder shift to high temperature and become broad. Both mass and bending strength of 7 wt% WG/ATP nanocomposite sheet show a decline over a soil exposure time of 20 days.     

Preparation and properties of inhalable nanocomposite particles: effects of the temperature at a spray-dryer inlet upon the properties of particles

To overcome the disadvantages both of microparticles and nanoparticles for inhalation, we have prepared nanocomposite particles as drug carriers targeting lungs. The nanocomposite particles having sizes about 2.5 μm composed of sugar and drug-loaded PLGA nanoparticles can reach deep in the lungs, and they are decomposed into drug-loaded PLGA nanoparticles in the alveoli. Sugar was used as a binder of PLGA nanoparticles to be nanocomposite particles and is soluble in alveolar lining fluid. The primary nanoparticles containing bioactive materials were prepared by using a probe sonicator. And then they were spray dried with carrier materials, such as trehalose and lactose. The effects of inlet temperature of spray dryer were studied between 60 and 120 °C and the kind of sugars upon properties of nanocomposite particles. When the inlet temperatures were 80 and 90 °C, nanocomposite particles with average diameters of about 2.5 μm are obtained and they are decomposed into primary nanoparticles in water, in both sugars are used as a binder. But, those prepared above 100 °C are not decomposed into nanoparticles in water, while the average diameter was almost 2.5 μm. On the other hand, nanocomposite particles prepared at lower inlet temperatures have larger sizes but better redispersion efficiency in water. By the measurements of aerodynamic diameters of the nanocomposite particles prepared with trehalose at 70, 80, and 90 °C, it was shown that the particles prepared at 80 °C have the highest fine particle fraction (FPF) value and the particles are suitable for pulmonary delivery of bioactive materials deep in the lungs. Meanwhile the case with lactose, the particles prepared at 90 °C have near the best FPF value but they have many particles larger than 11 μm.     

Development of a polystyrene sulfonate/silver nanocomposite with self-healing properties for biomaterial applications

A silver polystyrene sulfonate polyelectrolyte was synthesized, showing a spontaneous reduction of silver ions to silver nanoparticles over a period of approximately 1 month. A follow-up of the nanoparticle formation via scanning electron microscopy (SEM) reveals migration of the nanoparticles towards the cracks of the polymer over time, leading to a self-healing process of the nanocomposite. Antibacterial tests show excellent antibacterial activity of our compound, which allows us to use this compound e.g. for external medical applications.     

A study on phase morphology and surface properties of polyurethane/organoclay nanocomposite

In this study, polyurethane/organically modified layered silicate (organoclay) nanocomposites were prepared through in situ polymerization in the presence of organoclay. Phase morphology of the polyurethane/organoclay nanocomposite was investigated by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The results suggest that the inter-domain repeat distance decreased with the introduction of organoclay. The organoclay has a more significant effect on the inter-domain repeat distance at a low hard segment content. Also with the increase of the hard segment, the inter-domain repeat distance and domain size increased markedly. The size of hard domain of the polyurethane was found to be in the range of 12-32 nm in this case, and it keeps nearly unchanged with the clay content. It is suggested by AFM phase imaging technique that the hard domain can self-organize further to form spherical aggregates. The introduction of clay into the polyurethane matrix resulted in the decrease in the size of the spherical aggregates from ∼800 nm to ∼500 nm, indicating clay has an important effect on the aggregation behavior of hard domains. The effect of clay on the surface energy was examined by means of AFM and goniometry techniques. The results obtained by two methods are consistent, i.e., with the increase of clay content, the surface energy decreased due to the effect of organic modifier.     

Study on solvent permeation resistance properties of nylon6/clay nanocomposite

Nylon6/clay nanocomposite is prepared by mixing organized montmorillonite with nylon6 in HAAKE mixer. Solvent permeation resistance of the nanocomposite is measured to estimate the resistance to solvent permeation. The nanocomposite shows resistance to solvent permeation superior to that of pure nylon6. In addition, the clay content was found to significantly influence the solvent permeation resistance of nylon6, and the maximum improvement in barrier properties of nylon6/clay composite was found as the clay content reached an “optimum” value. By using proper composites and processing conditions, the permeation rate of toluene and ethanol in nylon6/clay nanocomposite is about 3 and 4 times slower than that in pure nylon6 at 50 °C. Our investigation indicated that the crystalline property of nylon6 has a strong impact on the sorption and diffusion of small molecules in the polymer. The improvement in solvent barrier properties of nylon6/clay nanocomposite is attributable to incorporation of an impermeable phase such as the layered silicate, improvement in crystallinity and decrease of crystalline dimension, which are evidenced by XRD, AFM, DSC and polarized optical microscopy (POM) studies.     

A new hybrid nanocomposite prepared by emulsion copolymerization of ABS in the presence of clay

The preparation and characterizations of new hybrid organic–inorganic nanocomposites consisting of acrylonitrile–butadiene–styrene terpolymer and a Na⁺‐exchanged montmorillonite (MMT) are described by direct intercalation through one‐step emulsion polymerization. Those products were purified by successive hot acetone and toluene extraction, respectively, for more than 2 days. The IR spectra for the purified samples revealed the characteristic absorbances as a result of those of styrene, butadiene, acrylonitrile, and MMT. X‐ray diffraction spectra of the composites showed the enlarged 001 d‐spacing as much as 1.75 nm, but no signals were found for the partial insertion of copolymer chains. Moreover, it was evident that this direct intercalation was not accompanied by delamination of the clay interlayer. The thermogravimetric analytic measurement for the purified product confirmed that the onset temperature of decomposition was transferred to the higher temperature region as much as 40–50 °C. Morphological observations by transmission electron microscopy, scanning electron microscopy, and optical micrography demonstrated homogeneous dispersion of MMT particles in the copolymer matrix. The possible physical picture of this direct intercalation was discussed in terms of swelling characteristics of compacted bentonite and the monomer containing micelle sizes. © 2001 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 39: 719–727, 2001     

Structure and properties of an hybrid system based on bisphenol A polycarbonate modified by A polyamide 6/organoclay nanocomposite

Blends of poly(carbonate of bisphenol A) (PC) with minute amounts of a nanocomposite based in polyamide 6 (PA6) with a layered organoclay (nPA6) were obtained upon melt mixing by varying the contents of both nPA6 and organoclay. The ternary nanocomposites (NC) were composed of a PC-rich matrix with some mixed PA6 present, and by a neat nPA6 dispersed phase. Upon dissolution of the matrix of the NC’s, the dispersed phase showed a highly fibrillar morphology that resembled that of thermoplastic/liquid crystalline polymer (LCP) blends. The cryogenically fractured surfaces observed by SEM showed a very fine particle size that was attributed to the presence of PA6 in the matrix and indicated a low interfacial tension. The Young’s modulus behaviour is proposed to be a consequence of the slight orientation of the PC-rich matrix and the highly fibrillated and oriented nPA6 dispersed phase. The important reinforcement effect of the dispersed phase is attributed to the additive effects of its large degree of orientation, and the reinforcing effect of the organoclay.     

Synthesis and tribological properties of new fluoro-containing oligomers

Oligomers based on (polyfluoroalkyl)methyl oxiranes and thiiranes was first synthesized by the cationic polymerization in the presence of boron trifluoride etherate. Molecular weights of the products were defined by cryoscopic method. It was found that synthesized oligomers can be used as additives to industrial lubricants and sulfur oligomers are of the greatest positive tribological effect.     

Recyclability of a layered silicate-thermoplastic olefin elastomer nanocomposite

A multiple-pass study was undertaken with a layered silicate-thermoplastic olefin elastomer (TPO) nanocomposite to study the impact of processing history on the properties of the material. A set of 10 passes were completed through a co-rotating intermeshing twin-screw extruder with samples collected to monitor changes in the composite. The microstructure of the nanocomposite was characterized using TEM, XRD, FT-IR, steady and complex shear rheology, and mechanical testing. With progressive passes through the extruder, the TPO nanocomposite experienced both delamination of the organoclay as well as thermo-oxidative degradation. The onset and extent of degradation were found to be unaffected by the presence of the organoclay species in the polymer, though, inclusion of a maleated compatibilizer led to increased chain scission. The generated carbonyl groups along the polymer chain as a result of oxidation were speculated to have a significant effect on the developing percolating network of clay within the material and on the final rheological properties of the composite. Despite the occurrence of degradation in the nanocomposite during recycling, its rheological and mechanical properties remained significantly higher than those of the unfilled resin.     

Spin-crossover nanoparticles and nanocomposite materials

This contribution reports on the state of the art of the elaboration and the application of nanoparticles (NPs) and nanohybrid/nanocomposite materials based on spin-crossover (SCO) complexes. The first part of this review concerns the syntheses and the characterizations of the physical properties of SCO NPs. All of the methods including homogeneous and heterogeneous media syntheses developed for the elaboration of such NPs and the associated methods used for their morphological characterization are presented. A particular attention is paid on the effects of the size reduction and the influence of the environment on the SCO properties and to specific and recent remarkable advanced physical measurements realized on a batch of NPs or on an isolated object. The second part presents the elaboration of various nanocomposite or nanohybrid materials for which SCO NPs have been associated with magnetic entities, noble metals, different fluorescent dyes, and different active polymers with the objectives to go toward specific applications based on synergistic effects between the two components.     

Synthesis,characterization and antibacterial properties of a novel nanocomposite based on polyaniline/polyvinyl alcohol/Ag

In this study, a novel nanocomposite based on polyaniline/polyvinyl alcohol/Ag (PANI/PVA/Ag) has been successfully synthesized. The chemical reduction method was used to produce Ag nanoparticle colloidal solution from Ag⁺ ions. The polymerization of aniline occurred in situ for the preparation of polyaniline (PANI) in the presence of ammonium persulfate. With exposure to Ag nanoparticles on the PANI/PVA composite, a new nanocomposite was obtained. The morphology and particle size of the novel nanocomposite was studied by scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) analyses. According to XRD analysis, the size of nanoparticles was found to be in the range of 10–17 nm. SEM images showed the favored shape of nanoparticles as triangle which is a benign shape for antibacterial analysis. The antibacterial activity of the obtained nanocomposite was also evaluated against Gram positive bacteria Staphylococcus aureus (Staph. aureus) and Gram negative Escherichia coli (E. coli) using the paper disk diffusion method. The antibacterial study showed that the PANI/PVA composite did not have a very good antibacterial activity but PANI/PVA/Ag nanocomposites were found to be effective against two bacteria.     

Synthesis,characterization and microwave absorption properties of polyaniline/Sm-doped strontium ferrite nanocomposite

Sm-doped strontium ferrite nanopowders (SrSm_0.3Fe_11.7O₁₉) and their composites of polyaniline (PANI)/SrSm_0.3Fe_11.7O₁₉ with 10 wt% and 20 wt% ferrite were prepared by a sol–gel method and an in-situ polymerization process, respectively. The structure, magnetic properties and microwave absorption properties of the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscope (TEM), vibrating sample magnetometer (VSM) and vector network analyzer, respectively. The particle size of SrSm_0.3Fe_11.7O₁₉ was about 35 nm by using XRD. The ferrite successfully packed by PANI. PANI/SrSm_0.3Fe_11.7O₁₉ possessed the best absorption property with the optimum matching thickness of 3 mm in the frequency of 2–18 GHz. The value of the maximum reflection loss (RL) were −26.0 dB at 14.2 GHz with the 6.5 GHz bandwidth and −24.0 dB at 13.8 GHz with the 7.9 GHz bandwidth for the samples with 10 wt% and 20 wt% ferrite, respectively.     

Preparation and properties of inhalable nanocomposite particles for treatment of lung cancer

Nanoparticles have widely been studied in drug delivery research for targeting and controlled release. The aim of this article is application of nanoparticles as an inhalable agent for treatment of lung cancer. To deposit effectively deep the particles in the lungs, the PLGA nanoparticles loaded with the anticancer drug 6-{[2-(dimethylamino)ethyl]amino}-3-hydroxyl-7H-indeno[2,1-c]quinolin-7-one dihydrochloride (TAS-103) were prepared in the form of nanocomposite particles. The nanocomposite particles consist of the complex of drug-loaded nanoparticles and excipients. In this study, the anticancer effects of the nanocomposite particles against the lung cancer cell line A549. Also, the concentration of TAS-103 in blood and lungs were determined after administration of the nanocomposite particles by inhalation to rats.TAS-103-loaded PLGA nanoparticles were prepared with 5% and 10% of loading ratio by spray drying method with trehalose as an excipient. The 5% drug-loaded nanocomposite particles were more suitable for inhalable agent because of the sustained release of TAS-103 and higher FPF value. Cytotoxicity of nanocomposite particles against A549 cells was higher than that of free drug.When the nanocomposite particles were administered in rats by inhalation, drug concentration in lung was much higher than that in plasma. Furthermore, drug concentration in lungs administered by inhalation of nanocomposite particles was much higher than that after intravenous administration of free drug.From these results, the nanocomposite particle systems could be promising for treatment of lung cancer.     

Effect of montmorillonite on structure and properties of nanocomposite with PA6/PS/elastomer matrix

Polyamide nanocomposites with fair balance of mechanical properties were recently obtained by addition of finely dispersed clay-compatibilized rubber or rigid PS phase. This work deals with combination of both components, which recently led also to enhanced mechanical behaviour in an analogous reactively compatibilized ternary system.Application of clay to PA6/PS/EPR matrix leads to a decrease in particle size analogously to corresponding binary blends, but the effect of clay on toughness is predominantly contradictory, i.e., a decrease with increasing clay content was found. Also the toughening effect of formed core-shell (elastomer/clay) particles is lower in comparison with binary PA6/EPR. At the same time, in contrast to the PA/PS system, the presence of core-shell particles formed by PS/C15 preblending leads to fair mechanical behaviour including enhanced toughness. This documents a complex affecting of the system behaviour by clay and the expected synergistic cooperation of numerous clay-induced changes in both component parameters and structure. The obtained results indicate that a proper combination of rigid and elastomeric inclusions can lead to nanocomposites with balanced and enhanced mechanical behaviour.     

Transparent h-BN/polyacrylamide nanocomposite hydrogels with enhanced mechanical properties

In this study, a facile way has been proposed to prepare transparent, tough and flexible polyacrylamide (PAM) hydrogels which is composed of a dually crosslinked single network by chemical crosslinking of N,N'-methylenebisacrylamide (BIS) and physical crosslinking of hydrophilic hexagonal boron nitride (hBN) nanosheets. The resulting h-BN/PAM nanocomposite hydrogels are highly transparent, and exhibit significantly enhanced mechanical properties compared to the dark (GO)/PAM nanocomposite hydrogels or chemical crosslinking PAM hydrogels. Thus it opens up new opportunities for developing nextgeneration transparent, tough and flexible hydrogels that hold great promise in such important applications as light responsive soft robot and liquid microlenses.     

Novel polyester/SiO2 nanocomposite membranes: Synthesis,properties and morphological studies

In this paper, a new type of soluble polyester/silica (PE/SiO₂) hybrid was prepared by the ultrasonic irradiation process. The coupling agent γ-glycidyloxypropyltrimethoxysilane (GOTMS) was chosen to enhance the compatibility between the polyester (PE) and silica (SiO₂). Furthermore, the effects of the coupling agent on the morphologies and properties of the PE/SiO₂ hybrids were investigated using UV-vis and FT-IR spectroscopies and FE-SEM. The densities and solubilities of the PE/SiO₂ hybrids were also measured. The results show that the size of the silica particle was markedly reduced by the introduction of the coupling agent, which made the PE/SiO₂ hybrid films become transparent. Furthermore, thermal stability, residual solvent in the membrane film and structural ruination of membranes were analyzed by thermal gravimetric analysis (TGA). The effects of SiO₂ nanoparticles on the glass transition temperature (T_g) of the prepared nanocomposites were studied by differential scanning calorimetry (DSC). Moreover, their mechanical properties were also characterized. It can be observed that the Young's moduli (E) of the hybrid films increase linearly with the silica content. The results obtained from gas permeation experiments with a constant pressure setup showed that adding SiO₂ nanoparticles to the polymeric membrane structure increased the permeability of the membranes.