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Carbon Nanotubes Synthesis Structure Properties And Applications

This paper reviews the potential of polymer and ceramic matrix composites for aerospace/space vehicle applications. Special, unique and multifunctional properties arising due to the dispersion of nanoparticles in ceramic and metal matrix are briefly discussed followed by a classification of resulting aerospace applications. The paper presents polymer matrix composites comprising majority of aerospace applications in structures, coating, tribology, structural health monitoring, electromagnetic shielding and shape memory applications. The capabilities of the ceramic matrix nanocomposites to providing the electromagnetic shielding for aircrafts and better tribological properties to suit space environments are discussed. Structural health monitoring capability of ceramic matrix nanocomposite is also discussed. The properties of resulting nanocomposite material with its disadvantages like cost and processing difficulties are discussed. The paper concludes after the discussion of the possible future perspectives and challenges in implementation and further development of polymer and ceramic nanocomposite materials.

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Polymer and ceramic nanocomposites for aerospace applications

Polymer/Inorganic nanocomposite coatings with superior corrosion protection performance: A review

The coupling of waves between the piezoelectric generators, detectors, and propagating media is challenging due to mismatch in the acoustic properties. The mismatch leads to the reverberation of waves within the transducer, heating, low signal-to-noise ratio, and signal distortion. Acoustic impedance matching increases the coupling largely. This article presents standard methods to match the acoustic impedance of the piezoelectric sensors, actuators, and transducers with the surrounding wave propagation media. Acoustic matching methods utilizing active and passive materials have been discussed. Special materials such as nanocomposites, metamaterials, and metasurfaces as emerging materials have been presented. Emphasis is placed throughout the article to differentiate the difference between electric and acoustic impedance matching and the relation between the two. Comparison of various techniques is made with the discussion on capabilities, advantages, and disadvantages. Acoustic impedance matching for specific and uncommon applications has also been covered.

A Review of Acoustic Impedance Matching Techniques for Piezoelectric Sensors and Transducers.

Any electric transmission lines involving the transfer of power or electric signal requires the matching of electric parameters with the driver, source, cable, or the receiver electronics. Proceeding with the design of electric impedance matching circuit for piezoelectric sensors, actuators, and transducers require careful consideration of the frequencies of operation, transmitter or receiver impedance, power supply or driver impedance and the impedance of the receiver electronics. This paper reviews the techniques available for matching the electric impedance of piezoelectric sensors, actuators, and transducers with their accessories like amplifiers, cables, power supply, receiver electronics and power storage. The techniques related to the design of power supply, preamplifier, cable, matching circuits for electric impedance matching with sensors, actuators, and transducers have been presented. The paper begins with the common tools, models, and material properties used for the design of electric impedance matching. Common analytical and numerical methods used to develop electric impedance matching networks have been reviewed. The role and importance of electrical impedance matching on the overall performance of the transducer system have been emphasized throughout. The paper reviews the common methods and new methods reported for electrical impedance matching for specific applications. The paper concludes with special applications and future perspectives considering the recent advancements in materials and electronics.

A Review of Electric Impedance Matching Techniques for Piezoelectric Sensors, Actuators and Transducers

The I²-phase of polyvinylidene fluoride (PVDF) is well known for its piezoelectric properties. PVDF films have been developed using solvent cast method. The films thus produced are in I±-phase. The I±-phase is transformed to piezoelectric I²-phase when the film is hot-stretched with various different stretching factors at various different temperatures. The films are then characterized in terms of their mechanical properties and surface morphological changes during the transformation from I±- to I²-phases by using X-ray diffraction, differential scanning calorimeter, Raman spectra, Infrared spectra, tensile testing, and scanning electron microscopy. The films showed increased crystallinity with stretching at temperature up to 80Â°C. The optimum conditions to achieve I²-phase have been discussed in detail. The fabricated PVDF sensors have been tested for free vibration and impact on plate structure, and its response is compared with conventional piezoelectric wafer type sensor. The resonant and antiresonant peaks in the frequency response of PVDF sensor match well with that of lead zirconate titanate wafer sensors. Effective piezoelectric properties and the variations in the frequency response spectra due to free vibration and impact loading conditions are reported. POLYM. ENG. SCI., 2012. Â© 2012 Society of Plastics Engineers.

Sensitivity of polyvinylidene fluoride films to mechanical vibration modes and impact after optimizing stretching conditions

Thin films of poly(vinylidene fluoride-trifluoroethylene) P(VDF-TrFE)were prepared using solvent cast method and characterized for structural, mechanical and surface morphological properties to investigate the presence of iÂÂ¢-phase through X-ray diffraction, scanning electronmicroscopy, differential scanning calorimeter, Raman and Infrared spectra, and tensile testing. The conditions to achieve iÂÂ¢-phase of P(VDF-TrFE) have been discussed in detail. Following the material characterization, the fabricated iÂÂ¢- phase P(VDF-TrFE) sensors have been tested for dynamic strain sensing application. Time response from the iÂÂ¢-phase P(VDF-TrFE) sensor due to the free vibration and impact on beam structure is obtained and is compared with iÂÂ¢-phase PVDF sensor and conventional piezoelectric wafer type sensor. The variations in the frequency response spectra due to free vibration and impact loading conditions are also reported, which reveal the fact that the sensitivity of the iÂÂ¢-phase P(VDF-TrFE) sensor to variousmodes of vibration is same as the iÂÂ¢-phase PVDF sensor. The resonant and antiresonant peaks in the frequency response of iÂÂ¢-phase P(VDF-TrFE) films match well with that of iÂÂ¢-phase PVDF sensor and Lead zirconate titanate (PZT) wafer sensors. Thus the fabricated iÂÂ¢-phase P(VDF-TrFE) sensors can be effectively used as the dynamic strain sensor.

Development of poly(vinylidene fluoride-trifluoroethylene) films and its quasi-static and dynamic strain response

For the transition into a sustainable mode of energy usage, it is important to develop photovoltaic materials that exhibit better solar-to-electricity conversion efficiencies, a direct optimal band gap, and are made of non-toxic, earth abundant elements compared to the state-of-the-art silicon photovoltaics. Here, we explore the non-redox-active pnictide chemical space, including binary A3B2, ternary AA'2B2, and quaternary AA'A''B2 compounds (A, A', A'' = Ca, Sr, or Zn; B = N or P), as candidate beyond-Si photovoltaics using density functional theory calculations. Specifically, we evaluate the ground state configurations, band gaps, and 0 K thermodynamic stability for all 20 pnictide compositions considered, besides computing the formation energy of cation vacancies, anion vacancies, and cation anti-sites in a subset of candidate compounds. Importantly, we identify SrZn2N2, SrZn2P2, and CaZn2P2 to be promising candidates, exhibiting optimal (1.1-1.5 eV) hybrid-functional-calculated band gaps, stability at 0 K, and high resistance to point defects (formation energies >1 eV), while other possible candidates include ZnCa2N2 and ZnSr2N2, which may be susceptible to N-vacancy formation. We hope that our study will contribute to the practical development of pnictide semiconductors as beyond-silicon light absorbers.

Jayanth S. Kumar

Papers

Polymer and ceramic nanocomposites for aerospace applications

Sensitivity of polyvinylidene fluoride films to mechanical vibration modes and impact after optimizing stretching conditions

Development of poly(vinylidene fluoride-trifluoroethylene) films and its quasi-static and dynamic strain response

Study of pnictides for photovoltaic applications.