Influence of bath composition and pH on the electrocodeposition of alumina nanoparticles and copper

The electrocodeposition of alumina particles (primary particle size 13 nm) in a copper matrix was investigated. Three copper plating baths covering a wide pH range were used: an acidic copper sulphate, a neutral pyrophosphate, and an alkaline sorbitol based bath. The highest amount of incorporated particles (ca. 11 wt.% alumina) was found for the pyrophosphate bath. From zeta potential measurements in diluted solutions we concluded that the particles are charged negatively in this electrolyte. A tentative electrostatic model is proposed to explain qualitatively the relation between the surface charge of the particles and the amount of incorporated particles. Furthermore, the microstructure, microhardness and electric conductivity of the layers were characterized.     

PMMA‐grafted‐silica/PVC nanocomposites: Mechanical performance and barrier properties

Poly(vinyl chloride) (PVC)/SiO₂ nanocomposites were prepared via melt mixture using a twin‐screw mixing method. To improve the dispersion degree of the nanoparticles and endow the compatibility between polymeric matrix and nanosilica, SiO₂ surface was grafted with polymethyl methacrylate (PMMA). The interfacial adhesion was enhanced with filling the resulting PMMA‐grafted‐SiO₂ hybrid nanoparticles characterized by scanning electron microscopy. Both storage modulus and glass transition temperature of prepared nanocomposites measured by dynamic mechanical thermal analysis were increased compared with untreated nanosilica‐treated PVC composite. A much more efficient transfer of stresses was permitted from the polymer matrix to the hybrid silica nanoparticles. The filling of the hybrid nanoparticles caused the improved mechanical properties (tensile strength, notched impact strength, and rigidity) when the filler content was not more than 3 wt %. Permeability rates of O₂ and H₂O through films of PMMA‐grafted‐SiO₂/PVC were also measured. Lower rates were observed when compared with that of neat PVC. This was attributed to the more tortuous path which must be covered by the gas molecules, since SiO₂ nanoparticles are considered impenetrable by gas molecules. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Synthesis,characterization, and ionic conductivity of nanocomposites: Polyelectrolyte systems

The synthesis, diffraction patterns, thermal stability, and ionic conductivity properties of methacrylate‐type polymers are analyzed here to assess their feasibility as polymer electrolytes. From the parent polymer, poly (N,N‐dimethylaminoethylmethacrylate), herein labeled PDMAEMA, a protonated derivative was used to prepare polymer/Montmorillonite nanocomposites with various clay contents (1, 3, and 5 wt %). AC spectroscopy provided the ionic conductivity data for the polymers and clay–polymer nanocomposites. Evidences of nanocomposite formation are shown using transmission electron microscopy and wide‐angle X‐ray diffraction. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of moisture and filler content on the structural,thermal and dielectric properties of polyamide‐6/boehmite alumina nanocomposites

Polyamide‐6 (PA‐6)/boehmite alumina (BA) nanocomposites were prepared via direct melt compounding. Structural, thermal and dielectric properties of ‘as‐received’ (including moisture) and ‘dried’ (thermally treated) specimens were examined. The BA nanofiller was homogeneously dispersed in the PA‐6 matrix. XRD and FTIR revealed that crystallization of PA‐6 in the γ phase was favoured over α phase with increasing BA content. The crystallinity index (CI) and the percentage of α and γ phases were also evaluated. Dried specimens exhibited a lower CI than as‐received specimens while the CI decreased with the addition of filler. Broadband dielectric spectroscopy revealed the presence of γ, β and α relaxations, the Maxwell–Wagner–Sillars effect and the contribution of conductivity relaxation in the as‐received samples. The drying procedure unmasked a double feature of both β and α modes. The results of the complementary techniques were analysed and the effects of moisture and/or the incorporation of BA nanofiller on the microstructure of the PA‐6 matrix are disclosed. © 2019 Society of Chemical Industry     

有机粘土／SBR纳米复合材料的结构与性能研究

采用十六烷基三甲基溴化铵（CTAB）和十八烷基三甲基溴化铵（STAB）分别对无机粘土进行有机改性,然后制备有机粘上／SBR纳米复合材料,研究不同季铵盐类改性剂对无机粘土的改性效果。结果表明：CTAB改性有机粘土与STAB改性有机粘土的片层间距分别从无机粘土的1．26nm增加到3．77nm和4．39nm;CTAB改性有机粘土的片层结构较稳定,而且在橡胶基体中的分散效果较好;所制备的有机粘土／SBR纳米复合材料的片层结构较多,力学性能较好。     

Synthesis and characterization of polyimide–silica nanocomposites using novel fluorine‐modified silica nanoparticles

Polyimide–silica nanocomposites were synthesized with 4,4′‐oxydianiline, 4,4′‐(4,4′‐isopropylidenediphenoxy)bis(phthalic anhydride), and fluorine‐modified silica nanoparticles. Fluorinated precursors such as 4″,4?‐(hexafluoroisopropylidene)bis(4‐phenoxyaniline) (6FBPA) and 4,4′‐(hexafluoroisopropylindene)diphenol (BISAF) were employed to modify the surface of the silica nanoparticles. The microstructures and thermal, mechanical, and dielectric properties of the polyimide–silica nanocomposites were investigated. An improvement in the thermal stability and storage modulus of the polyimide nanocomposites due to the addition of the modified silica nanoparticles was observed. The microstructures of the polyimide–silica nanocomposites containing 6FBPA‐modified silica exhibited more uniformity than those of the nanocomposites containing BISAF‐modified silica. The dielectric constants of the polyimide were considerably reduced by the incorporation of pristine silica or 6FBPA‐modified silica but not BISAF‐modified silica. The addition of a modifier with higher fluorine contents did not ensure a lower dielectric constant. The uniformity of the silica distribution, manipulated by the reactivity of the modifier, played an important role in the reduction of the dielectric constant. Using 6FBPA‐modified silica nanoparticles demonstrated an effective way of synthesizing low‐dielectric‐constant polyimide–silica nanocomposites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 882–890, 2007     

Modeling electrical conductivity of polymer nanocomposites with aggregated filler

A mean-field model is developed for the electrical conductivity of microcomposites and nanocomposites with polymer matrices. The model accounts for aggregation of filler into clusters (involving both conducting and nonconducting particles) and rearrangement of these clusters with the growth of volume fraction of filler (which leads to a reduction in tunneling resistivity and an increase in the number of bridging contacts between conducting particles). The governing equations involve five material constants with transparent physical meaning: the depolarization factor of clusters, volume fraction of polymer in clusters of filler, effective conductivity of an individual filler particle, and two coefficients characterizing an increase in the effective electrical conductivity of filler driven by the growth of bridging contacts between neighboring particles in clusters. Good agreement is demonstrated between results of simulation and experimental data on the electrical conductivity of epoxy resin reinforced with carbon black and graphite particles, poly(vinyl chloride) reinforced with copper and nickel particles, polypropylene loaded with spherical and spheroidal tin particles, poly(butylene terephthalate) reinforced with graphene nanosheets, and polypropylene loaded with multiwalled carbon nanotubes.     

Preparation and characterizations of tantalum pentoxide (Ta2O5) nanoparticles and UV‐curable Ta2O5‐acrylic nanocomposites

Tantalum pentoxide (Ta₂O₅) nanoparticles with the sizes in the range of 20–50 nm were prepared via a chemical route in which the oleic acid (OLEA) was adopted as the surfactant for the synthesis process. X‐ray diffraction (XRD) revealed the as‐synthesized Ta₂O₅ transforms from amorphous to hexagonal and orthorhombic structures at the temperatures of 700°C and 750°C, respectively, illustrating the suppression of recrystallization temperature of Ta₂O₅ due to the particle size reduction. UV‐curable nanocomposites containing the Ta₂O₅ nanoparticles and acrylic matrix were also prepared. Thermogravimetry analysis (TGA) found an about 10–20°C improvement on the 5% weight‐loss thermal decomposition temperatures (T_ds). Dielectric measurement showed that the dielectric constant of nanocomposite increases with the increase in the filler loading without severe deterioration of dielectric loss. The increment of dielectric constants was ascribed to the addition of high‐dielectric inorganic fillers as well as the presence of interfacial polarization at the organic/inorganic interfaces. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Electrical properties and thermal degradation of poly(vinyl chloride)/polyvinylidene fluoride/ZnO polymer nanocomposites

In this work, polymer nanocomposites consisting of a poly(vinyl chloride) (PVC) and polyvinylidene fluoride (PVDF) polymer network with ZnO nanoparticles as a dopant were prepared by solution casting. An XRD study of the PVC/PVDF/ZnO polymer nanocomposites shows predominantly sharp and high intensity peaks. However, the intensity and sharpness of the XRD peaks decreases with further increment in loading of ZnO (wt%), which reveals a proper intercalation of ZnO nanoparticles within the PVC/PVDF polymer system. Fourier transform infrared spectroscopy has been used to verify the chemical compositional change as a function of ZnO nanoparticle loading. TGA analysis clearly describes the thermal degradation of the pure polymer and polymer nanocomposites. The complex dielectric function, AC electrical conductivity and impedance spectra of these nanocomposites were investigated over the frequency range from 10 Hz to 35 MHz. These spectra were studied with respect to the Wagner ? Maxwell ? Sillars phenomenon in the low frequency region. Nyquist plots of the PVC/PVDF/ZnO nanocomposites were established from impedance measurements. The temperature‐dependent DC ionic conductivity obtained from the Nyquist plots follows Arrhenius behaviour. © 2016 Society of Chemical Industry     

Transport performance in novel elastomer nanocomposites: Mechanism,design and control

Functional elastomer nanocomposites have found numerous applications in diverse hi-tech areas. Transport phenomena, such as electrical conductivity, thermal conductivity and gas/liquid barrier properties, have been the major focus of functional elastomer nanocomposite research. Despite essential progress in these areas, a summary and discussion of state-of-the-art strategies for regulating the transport performances of nanocomposites based on the transportation mechanisms of electrons, phonons and mass are lacking. In the present review, a brief introduction of transport mechanisms in elastomer nanocomposites precedes a systematic summary of the important progress in elastomer nanocomposites with electrical/thermal conductivities and lowered mass permeabilities, with emphasis on the latest structural control strategies for tuning transport properties. Key applications of functional elastomer nanocomposites related to transport phenomena are also introduced. Overall, this review summarizes the state of the art in the design and performance enhancement of elastomer nanocomposites based on the relationships between their structures and transport properties, governed by the components/composition, interface/dispersion and fabrication.     

Improvement in dielectric and mechanical performance of CaCu<Subscript>3.1</Subscript>Ti<Subscript>4</Subscript>O<Subscript>12.1</Subscript> by addition of Al<Subscript>2</Subscript>O<Subscript>3</Subscript> nanoparticles

The properties of CaCu_3.1Ti₄O_12.1 [CC3.1TO] ceramics with the addition of Al₂O₃ nanoparticles, prepared via a solid-state reaction technique, were investigated. The nanoparticle additive was found to inhibit grain growth with the average grain size decreasing from approximately 7.5 μm for CC3.1TO to approximately 2.0 μm for the unmodified samples, while the Knoop hardness value was found to improve with a maximum value of 9.8 GPa for the 1 vol.% Al₂O₃ sample. A very high dielectric constant > 60,000 with a low loss tangent (approximately 0.09) was observed for the 0.5 vol.% Al₂O₃ sample at 1 kHz and at room temperature. These data suggest that nanocomposites have a great potential for dielectric applications.     

Optimal design on the mechanical and thermal properties of porous alumina ceramics based on fractal dimension analysis

In order to investigate the relationship between pore structure and thermal conductivity as well as mechanical strength, porous alumina ceramics (PAC) with various pore structures were fabricated, using starch as the pore‐forming agent. Fractal theory was employed to characterize the pore size distribution more accurately than ever used parameters. The results show that the increase in starch content in PAC leads to an enhanced porosity, a higher mean pore size, and reduced fracture dimension, thermal conductivity and strength. The fractal analysis indicated that the fractal dimension decreases gradually and reaches its minimum value with increasing the starch content up to 25 wt%, but the further incorporation results in an opposite trend. It is suggested from micro‐pore fractographic analysis that the optimization of both thermal insulation performance and mechanical strength are positively correlated with the increase in the mean pore size and proportion of 2‐14 μm pores but negatively corrected with the porosity. These results provide a new perspective and a deeper understanding for fabrication of PAC with both excellent thermal insulation and mechanical performance.     

Effect of clay on properties of polyimide‐clay nanocomposites

Effect of clay on mechanical, thermal, moisture absorption, and dielectric properties of polyimide‐clay nanocomposites was investigated. Nanocomposites of polyimide (ODA‐BSAA) hybridized with two modified clay (PK‐802 and PK‐805) were synthesized for comparison. The silicate layers in the polymer matrix were intercalated/exfoliated as confirmed by wide‐angle X‐ray diffraction and transmission electron microscopy. Thermal stability, moisture absorption, and storage modulus for these nanocomposites are improved as hybridized clay increases. Reduced dielectric constants due to the hybridization of layered silicates are observed at frequencies of 1 kHz–1 MHz and temperatures of 35–150°C. The tetrahedrally substituted smectite (PK‐805) resulted in higher mechanical strength and dielectric constants than those of octahedrally substituted smectite (PK‐802), which could be attributed to their stronger ionic bonding between clay layer and polymer matrix. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 318–324, 2007     

Laser shock processing of polycrystalline alumina ceramics

Laser shock processing (LSP) has been applied to polycrystalline α‐Al₂O₃ ceramics. X‐ray characterizations have revealed that LSP results in significant compressive residual stresses which can extend to a depth of more than 1.2 mm from the surface. The presence of compressive residual stresses improves the resistance of α‐Al₂O₃ ceramics to indentation cracking. Microstructural characterization suggests that the majority of α‐Al₂O₃ grains on the surface remains intact after LSP. However, damaged regions are occasionally present, which shows intergranular fractures and a limited plastic deformation in the vicinity of grain boundaries.     

Effects of the processing temperature on the nanostructure and mechanical properties of PCTG‐based nanocomposites

The influence of the processing temperature on both the dispersion level and the mechanical properties of the amorphous copolyester (PCTG)/organoclay (Cloisite® 20A) nanocomposite (NC) is studied in this article. At high processing temperatures, no change in the chemical nature of the matrix was observed, but its molecular weight decreased. Widely dispersed structures were observed by wide angle X‐ray diffraction (WAXD) and transmission electron microscopy whatever the processing temperature might be. Dispersion was greatest for the samples processed at 200°C due to the highest viscosity of these samples and decreased at higher processing temperatures (T_p). These different dispersion levels led to a large modulus increase (71%) after processing at 200°C and to lower ones (about 50%) after processing at 230 and 260°C. The ductility of the NCs decreased at lower processing temperatures. The decrease was attributed to the greater stiffness of the matrix, and was not significant enough to modify the ductile nature of the NCs, which showed clear yield points even at the lowest processing temperature (200°C). © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Effect of diblock copolymer surfactant on the microstructure and EM properties of CNT nanocomposites

Carbon nanotubes (CNTs) were chosen due to their excellent electrical properties. As delivered, CNTs are highly agglomerated, and to exploit their high aspect ratio is then necessary to disagglomerate them as much as possible. A diblock copolymer surfactant was used to aid CNT disagglomeration. Disagglomeration in solvent was assessed by TEM, whereas composite microstructure was observed by scanning electron microscopy. X‐band waveguide measurements were carried out to assess complex permittivity and absorbing performance. On a same weight percent of filler basis, samples produced with the aid of surfactant show higher real permittivity than samples produced without. An equivalent circuit analogy is suggested to explain the results and relates composite microstructure with macroscopic permittivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Characterization,conductivity studies,dielectric properties,and gas sensing performance of in situ polymerized polyindole/copper alumina nanocomposites

Conducting polymer composites of polyindole (PIN) and copper–alumina (Cu–Al₂O₃) nanocomposites were synthesized by in situ polymerization of indole with different contents of Cu–Al₂O₃ nanoparticles. The polymer nanocomposites were characterized by Fourier transform infrared (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), transmission electron microscope (TEM), differential scanning calorimetry, thermogravimetric analysis, and ammonia gas sensing performance was also analyzed. FTIR and XRD studies revealed the attachment of Cu–Al₂O₃ in the molecular chain of PIN. The presence of bright trapezoid channels and variation in morphology for different loading of nanoparticles were confirmed by SEM and TEM. The attachment of Cu–Al₂O₃ nanoparticles in the PIN matrix was confirmed through EDX spectroscopy. The glass transition temperature and thermal stability of the composites were greatly enhanced with the loading of Cu–Al₂O₃. Enhancement in alternating current conductivity, dielectric constant and the current–voltage characteristics of the prepared composite revealed the semiconducting nature of the system with an increase in the loading of nanoparticles. Also, nanocomposite exhibited an excellent sensitivity and fast response to ammonia gas. The evaluated result of the present study suggested that Cu–Al₂O₃ reinforced PIN hybrid is a good candidate for the fabrication of electrochemical devices.     

Effect of amine-terminated butadiene-acrylonitrile/clay combinations on the structure and properties of epoxy nanocomposites

The effect of the clay content and the method of its combination with amine-terminated butadiene-acrylonitrile (ATBN) on the structure and behavior of epoxy was studied. In the case of the simultaneous addition of both components, the increasing clay content had a very small effect on the size of the reaction-induced phase separation-formed particles at 5% rubber content due to predominant elimination of two major clay effects, i.e., the nucleation due to phase separation and the kinetics. As a result, both the time window between the onset of phase separation and vitrification and the viscosity at the cloud point did not change significantly. The minor change in the particle size/clay content dependences with different curing temperatures indicates that the balance between the two clay effects shifted. The corresponding study of the mechanical behavior indicated that the best balanced mechanical properties were obtained at certain clay/ATBN ratios, and thus, there was synergy between the components. Similar mechanical parameters were obtained for the application of both components in the form of ATBN/montmorillonite intercalate. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012