Interpretation of X-ray Powder Diffraction Patterns . By H. Lipson and H. Steeple. Pp. viii + 335 + 3 plates. (Mac-millan: London; St Martins Press: New York, May 1970.) £4.

X-Ray Diffraction

Fundamentals, processes and applications of high-permittivity polymer–matrix composites

Dielectric polymer nanocomposites are rapidly emerging as novel materials for a number of advanced engineering applications. In this Review, we present a comprehensive review of the use of ferroelectric polymers, especially PVDF and PVDF-based copolymers/blends as potential components in dielectric nanocomposite materials for high energy density capacitor applications. Various parameters like dielectric constant, dielectric loss, breakdown strength, energy density, and flexibility of the polymer nanocomposites have been thoroughly investigated. Fillers with different shapes have been found to cause significant variation in the physical and electrical properties. Generally, one-dimensional and two-dimensional nanofillers with large aspect ratios provide enhanced flexibility versus zero-dimensional fillers. Surface modification of nanomaterials as well as polymers adds flavor to the dielectric properties of the resulting nanocomposites. Nowadays, three-phase nanocomposites with either combination of fillers...

Recent Progress on Ferroelectric Polymer-Based Nanocomposites for High Energy Density Capacitors: Synthesis, Dielectric Properties, and Future Aspects.

Carbon nanotubes (CNTs) demonstrate remarkable electrical, thermal, and mechanical properties, which allow a number of exciting potential applications. In this article, we review the most recent progress in research on the development of CNT-polymer composites, with particular attention to their mechanical and electrical (conductive) properties. Various functionalization and fabrication approaches and their role in the preparation of CNT-polymer composites with improved mechanical and electrical properties are discussed. We tabulate the most recent values of Young's modulus and electrical conductivities for various CNT-polymer composites and compare the effectiveness of different processing techniques. Finally, we give a future outlook for the development of CNT-polymer composites as potential alternative materials for various applications, including flexible electrodes in displays, electronic paper, antistatic coatings, bullet-proof vests, protective clothing, and high-performance composites for aircraft and automotive industries.

Recent Advances in Research on Carbon Nanotube–Polymer Composites

Assessing the strengths and weaknesses of various types of pre-treatments of carbon nanotubes on the properties of polymer/carbon nanotubes composites: A critical review

Acid treatment and triethylene-tetramine (TETA) modification of multi-walled carbon nanotubes (MWCNTs) purposing to attain better dispersibility and stronger interfacial bonding between MWCNTs and epoxy matrix have been carried out in this paper. The epoxy and MWCNTs/epoxy composites were produced by cast molding method. Stress–strain curves show that TETA-MWCNTs/epoxy hold the greatest toughness of all samples with 0.5 wt.% nanoparticles. The Young’s modulus of TETA-MWCNTs/epoxy has a significant increase about 38% compared to the neat epoxy, while the Young’s modulus of unmodified MWCNTs/epoxy or acid-modified MWCNTs/epoxy has a bit of decrease. Tensile and impact strength tests reflect that TETA-MWCNTs reinforced epoxy composites have an obvious improvement of tensile strength about 30% and an enhancement of impact strength over 34% compared to the pure epoxy composites with only 0.5 wt.% loading of TETA-MWCNTs. Scanning electron microscopy images of fractured surface of MWCNTs/epoxy indicate homogeneous dispersibility of TETA-MWCNTs and strong interfacial adhesion between the TETA-MWCNTs and the epoxy in the MWCNTs/epoxy composite.

Effect of acid and TETA modification on mechanical properties of MWCNTs/epoxy composites

We report here a high dielectric percolative polymer nanocomposite, fabricated by a combination of triethylene-tetramine (TETA) modified multiwalled carbon nanotube (named as TETA-MWNT) within epoxy resin matrix. In this composite system, with various TETA-MWNT volume fractions, the dielectric constant (K) is well fitted by the scaling law of the percolation theory with the percolation threshold f
 c is 0.042 and the critical exponent p is 0.786. At 1,000 Hz of room temperature, the value of the dielectric constant is as high as 421 with the TETA-MWNT content of 4.14vol%, which is almost 60 times higher than that of epoxy resin. In contrast, a simple blend of pristine MWNT in epoxy composite shows evident lower dielectric constant and much higher loss with the same volume fraction.

Dielectric properties of epoxy composites with modified multiwalled carbon nanotubes

High dielectric constant copper phthalocyanine oligomer (o-CuPc) was chemically grafted to poly(p-chloromethyl styrene) (PCMS) to improve its dispersibility in PVDF. From SEM results, the size of o-CuPc-g-PCMS particles in the blend of poly(vinylidene fluoride) (PVDF) and o-CuPc-g-PCMS (o-CuPc-g-PCMS/PVDF) was about 70nm, less than 1/7 the size of o-CuPc in o-CuPc/PVDF. In addition, o-CuPc-g-PCMS in o-CuPc-g-PCMS/PVDF showed much improved dispersibility. Both of the improvements obviously enhanced the electric properties of the composite. The dielectric constant of o-CuPc-g-PCMS/PVDF was more than 325 (100Hz), which was about 7 times higher than that of o-CuPc/PVDF. The dielectric constant at high frequencies (∼1MHz) was also high (∼130).

PVDF based all-organic composite with high dielectric constant

To develop a high-dielectric constant composite of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and multi-walled carbon-nanotubes (MWCNTs) with desirable homogeneity, MWCNTs were treated with a nitro-sulfuric acid by ultrasonication. The chemically modified MWCNTs (a-MWCNTs) were characterized by Fourier transform infrared spectroscopy and a back-titration procedure. Improvement of the dispersibility of a-MWCNTs in polymer matrix, in comparison with unmodified MWCNTs in P(VDF-TrFE), was confirmed by field emission scanning electron microscopy. Electric behavior of the composites with different volume fraction of dispersed carbon nanotubes can be described by percolation theory, as well as the Maxwell–Wagner–Sillars mechanism. The percolation threshold (f
 c
 ) of composites with a-MWCNTs (f
 c
  = 0.0308) is larger than that of composites with MWCNTs (f
 c
  = 0.0216) due to better dispersion of a-MWCNTs in matrix and the reduction of aspect ratio of a-MWCNTs occurred in the modification procedure. The composite with 2.98 vol% (close to the percolation threshold) of a-MWCNTs has a dielectric constant of 592 at 100 Hz and room temperature.

High-dielectric constant percolative composite of P(VDF-TrFE) and modified multi-walled carbon-nanotubes

Abstract To develop a high dielectric constant composite of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] and multi-walled carbon-nanotubes (MWCNTs) with desirable homogeneity, MWCNTs were treated with a nitro-sulfuric acid by ultrasonication. Improvement of the dispersibility of chemically modified MWCNTs (a-MWCNTs) in polymer matrix, in comparison with that of unmodified MWCNTs in P(VDF-TrFE), was confirmed by field emission scanning electron microscopy (FESEM)-observed morphologies. Electric behavior of the composites with different volume fraction of dispersed carbon nanotubes phase can be described mainly by percolation theory. The percolation threshold (fc) of composites with a-MWCNTs (fc=0.0308) is larger than that of composites with MWCNTs (fc=0.0216) due to better dispersion of a-MWCNTs in polymer matrix and the reduction of aspect ratio of a-MWCNTs occurred in the modification procedure. The composite with 2.98 vol% (a volume fraction close to the percolation threshold) of a-MWCNTs has a dielectric constant of 592 at 100Hz and room temperature. The composite remains very flexible with an elastic modulus close to that of the parent copolymer.

Significantly enhanced dielectric response in composite of P(VDF-TrFE) and modified multi-walled carbon-nanotubes

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