Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. To employ CNTs as effective reinforcement in polymer nanocomposites, proper dispersion and appropriate interfacial adhesion between the CNTs and polymer matrix have to be guaranteed. This paper reviews the current understanding of CNTs and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT dispersion and functionalization on the properties of CNT/polymer nanocomposites. The fabrication techniques and potential applications of CNT/polymer nanocomposites are also highlighted.

Dispersion and functionalization of carbon nanotubes for polymer-based nanocomposites: a review

Carbon nanotube–polymer composites: Chemistry, processing, mechanical and electrical properties

Green synthesis of metal nanoparticles using plants

Thermal conductivity of carbon nanotubes and their polymer nanocomposites: A review

Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

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Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations.

Dielectric and ferroelectric behavior of SBN50 synthesized by solid-state route using different precursors

Multiwall carbon nanotubes (MWNT) were melt-mixed with 50/50 co-continuous blends of polyamide 6 (PA6) and acrylonitrile-butadiene-styrene (ABS). Blending sequence and moulding processes were found to have a strong impact on the conductivity of the blends with MWNT. Aggregated nature of the tubes, migration during processing and skin-core morphology generated during mould cooling step were found to be crucial parameters affecting the electrical conductivity of the blends. We report here the role of a reactive modifier: sodium salt of 6-amino hexanoic acid (Na-AHA) aiding in uniform dispersion of the MWNT in the 50/50 PA6/ABS blends and restricting the tubes utilizing specific interactions during melt-mixing in the PA6 phase in the blends. We further varied the MWNT to Na-AHA ratio from 1:1 to 1:15 to optimize the concentration of MWNT required in achieving lower electrical percolation threshold in co-continuous PA6/ABS blends. The associated percolation threshold was observed at approximately 0.5 wt% MWNT with high dielectric constant.

Specific interactions induced dispersion and confinement of multi-walled carbon nanotubes in co-continuous polymer blends.

(Ni1−xZnx)Nb2O6, 0≤x≤10, ceramics with >97% density were prepared by a conventional solid-state reaction, followed by sintering at 1200°–1300°C (depending on the value of x) The XRD patterns of the sintered samples (0≤x≤10) revealed single-phase formation with a columbite (Pbcn) structure The unit cell volume slightly increased with increasing Zn content (x) All the compositions showed high electrical resistivity (ρdc=16±03 × 1011Ω·cm) The microwave (4–5 GHz) dielectric properties of (Ni1−xZnx)Nb2O6 ceramics exhibited a significant dependence on the Zn content and to some extent on the morphology of the grains As x was increased from 0 to 1, the average grain size monotonically increased from 76 to 212 μm and the microwave dielectric constant (ɛ′r) increased from 236 to 261, while the quality factors (Qu×f) increased from 18 900 to 103 730 GHz and the temperature coefficient of resonant frequency (τf) increased from −62 to −73 ppm/°C In the present work, we report the highest observed values of Qu×f=103 730 GHz, and ɛ′r=261 for the ZnNb2O6-sintered ceramics

High Q Microwave Dielectric Ceramics in (Ni1−x Znx)Nb2O6 System

State of dispersion of purified multiwall carbon nanotubes (p-MWNT) in the presence of neutralized MWNT (n-MWNT) in aqueous solution was assessed through UV–Visible spectroscopy, dynamic light scattering measurements, and solution experiments. Raman spectroscopic analysis revealed that debundling of p-MWNT in the presence of n-MWNT in aqueous solution was persistent even in the solid mixture, which was supported by transmission electron microscopic analysis. The proposed mechanism behind the improved dispersion of p-MWNT in the presence of n-MWNT in aqueous solution has been based on the electrostatic charge repulsion between negatively charged n-MWNT. The state of dispersion of p-MWNT in the presence of n-MWNT in 45/55 polypropylene/acrylonitrile butadiene styrene (PP/ABS) blends was assessed through Raman spectroscopic analysis, bulk electrical conductivity measurements, solution experiment, and crystallization studies. Raman spectroscopic analysis indicated that the state of dispersion of MWNT was improved with increasing n-MWNT content of the mixture. This strategy led to a remarkable increase in the bulk electrical conductivity of 45/55 PP/ABS blends at 3 wt% MWNT content and was strongly dependent on the concentration of n-MWNT in the mixture. Differential scanning calorimetric measurements along with solution experiments revealed the subsequent migration of MWNT from the PP phase to the ABS phase in the blends during melt-mixing in the presence of higher fraction of n-MWNT. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers

Ajit R. Kulkarni

Papers

Dielectric and ferroelectric behavior of SBN50 synthesized by solid-state route using different precursors

Specific interactions induced dispersion and confinement of multi-walled carbon nanotubes in co-continuous polymer blends.

High Q Microwave Dielectric Ceramics in (Ni1−x Znx)Nb2O6 System

Dispersion of multiwall carbon nanotubes in blends of polypropylene and acrylonitrile butadiene styrene

Mixed alkali effect in the ac conductivity of glasses