Nanodielectric Material Research Articles

CuO and MWCNTs Nanoparticles Filled PVA–PVP Nanocomposites: Morphological, Optical, Thermal, Dielectric, and Electrical Characteristics

Copper dioxide (CuO) nanoparticles and Multiwall carbon nanotubes (MWCNTs) filled poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) blend matrix (50/50 wt%) based polymer nanocomposites (PNCs) (i.e., PVA/PVP:(15-x)CuO(x)MWCNTs for x = 0,1,5,7.5, 10,14, and 15wt%) have been prepared employing the solution-cast method. The morphologies of these PNCs are semicrystalline, according to an X-ray diffraction investigation. The FTIR, SEM, and AFM measurements of PNCs were used to investigate the development of the miscible mix, polymer-polymer and polymer–nanoparticle interactions, and the influence of CuO and MWCNTs nanofillers on the morphology aspects on the main chain of PVA/PVP blend. The nanofiller dispersion signposting for x = 14 wt% nanoloading in the PVA–PVP blend matrix significantly enhances the crystalline phase, diminishing the optical energy gap to 2.31 eV. The DC conductivity values augment with the upsurge in nanofiller level for maximum x = 14 wt%. The dielectric and electrical characteristics of these PNCs are investigated for an applied frequency range from 1 kHz to 1 MHz. The enhancement in the nanofiller level upto x = 14 wt% in the PVA/PVP matrix leads to the development of percolating network through the PNCs. These factors boost the dielectric permittivity values substantially, owing to the decrease in the nano-confinement phenomenon. The rise in applied frequency reduces dielectric permittivity and impedance values and enhances ac electrical conductivity. These PNCs having good dielectric and electrical characteristics can be used as frequency tunable nanodielectric material in electronic devices.

Progress of application of functional atomic force microscopy in study of nanodielectric material properties

The rapid development of the electrical and electronic industry requires components with miniaturization, flexibility, and intelligence. Dielectric materials, as important materials for the preparation of electronic components, are required to have excellent dielectric properties such as high breakdown electric field, high energy storage density and low dielectric loss. Owing to the lack of ultra-high resolution characterization tools, the research on the improvement of dielectric material properties stopped at a macroscopic level in the past. Atomic force microscopy, a measurement instrument which possesses a nanoscale high resolution, shows unique advantages in the study of nanodielectrics, and the advent of functional atomic force microscopy has made important contributions to characterization of the electrical, optical, and mechanical properties of nano-dielectric micro-regions. In this paper, we review the progress of atomic force microscopy, electrostatic force microscopy, Kelvin probe force microscopy, piezoelectric response force microscopy and atomic microscopy-infrared spectroscopy in the study of nanodielectric applications. Firstly, their structures and principles are introduced; secondly, their recent research progress of studying the microscopic morphology, interfacial structure, domain behavior and charge distribution in the nanometer region of dielectric materials is presented, and finally, the problems in the existing research and possible future research directions are discussed.

Polymer - silicate nanocomposities: Package material for nanodevices as an EMI shielding

Strontium silicate nanoparticles were filled in the organic matrix of poly ethylene glycol, polyvinyl alcohol and polyvinyl pyrrolidone polymers. Different weight percentages were selected for the preparation of thin films on the glass substrate using spin coating technique. Prepared polymer nanocomposite films were characterized for their structural analysis and compositional details using powder X-ray diffraction. Amorphous polymer films with intense diffraction peaks at around 43.8° and 73° exhibited the crystalline phase when doped with strontium silicate in polymer blend matrix. Structural information shows the stable existence of crystalline nanoparticles in the polymer matrix. Dielectric and electrical properties of these samples were studied in the frequency range from 100 Hz to 5500 Hz. Dielectric constant decreased with increase in frequency and changed to different values based on the loading of different weight percentage of nanoparticles. With increase in frequency, the dipolar ordering of polymer-polymer decreased and strengthens the polymer-nanoparticles interaction. Polyvinyl alcohol with 3- wt% of poly ethylene glycol showed the low dielectric constant and dielectric loss as less than 0.03 confirms their improved dielectric properties. Hence, this composition can be used as a better insulating polymeric nanodielectric material which finds application in packaging of nanoscale electronic devises to have better electromagnetic shielding.

Enhanced energy storage performance in a PVDF/PMMA/TiO2 blending nanodielectric material

The growing demand for miniaturization of electrical and electronic system poses a great challenge on energy storage capacitors, which requires associated dielectric materials exhibiting high energy density. In ferroelectric polymer dielectrics, it is one of the key issues to achieve both high dielectric permittivity and high breakdown strength. In this paper, we propose a method on improving the dielectric permittivity and breakdown strength concurrently taking the advantage of nanocomposite and blending. Our results show that PVDF/PMMA/TiO2 blending nanodielectric material presents improved relative dielectric permittivity of 12 and breakdown strength of 387 kV/mm compared with pristine PVDF, leading to an enhanced energy density about 5.8 J/cm3 and an efficiency of 77%. Further electric properties measurements and structure characterizations indicate that the moderate enhancement of permittivity can be ascribed to the doping of TiO2 nanoparticles, and the improved breakdown strength is caused by blending of PMMA with good insulating properties. Our results might provide a promising approach to develop high-performance energy-storage dielectric materials concerning the synergistic effect of blending and nanocomposite.

Characterization of the temperature dependence of the electrical and mechanical properties of a high breakdown strength nanodielectric composite

Advancements in the field of very compact, high dielectric strength, nanodielectric material capacitors have continued to be made. The capacitors are constructed from a proprietary nanodielectric, MU100, which is a polymer-ceramic composite composed of barium titanate and a binding agent. The MU100 material exhibits several novel qualities-including high dielectric strength along with facile machining and assembly characteristics. Electrical property characterization data of MU100 has been collected at standard ambient temperature conditions. Assessing MU100's properties over a wide temperature range is necessary to verify its suitability for field application and for continued improvement of capacitor design. The dielectric constant and thermal expansion were measured for the MU100 material from -40°C to 120°C. The results demonstrate the nanodielectric has a strong stability both electrically and mechanically across the entire temperature test range. The maximum dielectric constant change of MU100 relevant to standard temperature was +/-9.8% occurring at 130°C. The maximum linear coefficient of thermal expansion found was 1.5 PPM/°C. These values suggest that the MU100 material is suitable for high voltage applications where harsh environmental conditions are expected. It combines the thermal stability of ceramic substrates with the ability to easily machine and assemble the material.

Advanced nanodielectric material development and scaling for use in compact ultra-high voltage capacitor prototypes

The dielectric material employed in this effort is a proprietary nanocomposite material, MU100. The material was initially developed to shrink high frequency high voltage dielectric loaded antennas; however, due to its unique material characteristics, the nanocomposite has shown promise in development of high voltage capacitors. Previous work has shown small-scale samples of the high permittivity nanocomposite material to have an average dielectric strength of 220 kV/cm with peak breakdown fields in excess of 328 kV/cm. When scaling up to realize application specific voltages, failure modes become more pronounced due to volume effects of the nanocomposite and field enhancement factors at the electrode dielectric interfaces. This work describes how the material was increased in volume from small samples up to compact capacitor prototypes capable of repeatable performance at 250 kV to in excess of 500 kV with lifetimes greater than 104 shots.

Development of carboxyl-functionalized multi-walled nanotube/polydimethylsiloxane novel polymeric nanodielectric material

In this paper, we develop a new type of polydimethylsiloxane (PDMS)-based nanocomposite by incorporating carboxyl-functionalized multi-walled nanotube (MWCNT) to the polymer matrix as fillers. The dispersion of MWCNT during the material processing plays a significant role in deciding the final properties of the nanocomposites. A rapid evaporation and stirring method was used to minimize re-aggregation of the fillers during MWCNT/PDMS composites fabrication processing by solution blending. Furthermore, dispersions of MWCNT in solvents were investigated to correlate the degree of dispersion state with Hansen solubility parameters. The result indicated that carboxyl group can impart negative charges and create the long-term electrostatic stability of MWCNT in the solvents. The resultant MWCNT/PDMS composites exhibited high permittivity, low dielectric loss, and low percolation threshold.

Morphological, structural, dielectric and electrical properties of PEO–ZnO nanodielectric films

The morphological, structural, dielectric and electrical properties of aqueous solution-cast prepared poly(ethylene oxide)–zinc oxide (PEO–ZnO) nanocomposite films have been investigated as a function of ZnO nanoparticle concentrations up to 5 wt%. Scanning electron microscopy (SEM) images of these films show that the morphology of pristine PEO aggregated spherulites changes into fluffy, voluminous and highly porous with dispersion of ZnO nanoparticles into the PEO matrix. X-ray diffraction (XRD) study confirms that the crystalline phase of PEO greatly reduces at 1 wt% ZnO, and it again increases gradually with further increase of ZnO concentration. The dielectric relaxation spectroscopy (DRS) over the frequency range 20 Hz–1 MHz reveals that the real part of complex dielectric permittivity at audio frequencies decreases non-linearly whereas it remains almost constant at radio frequencies for these polymeric nanocomposites. Dispersion of nanosize ZnO particles into the PEO matrix reduces the values of dielectric permittivity which also exhibits a correlation with the dispersivity of ZnO nanoparticles. The relaxation peaks observed in the dielectric loss tangent and electric modulus spectra reveal that the electrostatic interactions of nanoscale ZnO particles with the ethylene oxide functional dipolar group of PEO monomer units decrease the local chain segmental dynamics of the polymer. Real part of ac conductivity spectra of these films have been analyzed by power law fit over the audio and radio frequency regions, respectively, and the obtained dc conductivity values for these regions differ by more than two orders of magnitude. The temperature dependent relaxation time and dc conductivity values of the nanodielectric material obey the Arrhenius relation of activation energies and confirm a correlation between dc conductivity and PEO chain segmental motion which is exactly identical to the characteristics of solid polymer electrolytes. Results imply that these nanocomposite materials can serve as low permittivity flexible nanodielectric for radio frequency microelectronic devices and also as electrical insulator for audio frequency operating conventional devices in addition to their suitability in preparation of solid polymer electrolytes.

Microstructure reconstruction and structural equation modeling for computational design of nanodielectrics

AbstractNanodielectric materials, consisting of nanoparticle-filled polymers, have the potential to become the dielectrics of the future. Although computational design approaches have been proposed for optimizing microstructure, they need to be tailored to suit the special features of nanodielectrics such as low volume fraction, local aggregation, and irregularly shaped large clusters. Furthermore, key independent structural features need to be identified as design variables. To represent the microstructure in a physically meaningful way, we implement a descriptor-based characterization and reconstruction algorithm and propose a new decomposition and reassembly strategy to improve the reconstruction accuracy for microstructures with low volume fraction and uneven distribution of aggregates. In addition, a touching cell splitting algorithm is employed to handle irregularly shaped clusters. To identify key nanodielectric material design variables, we propose a Structural Equation Modeling approach to identify significant microstructure descriptors with the least dependency. The method addresses descriptor redundancy in the existing approach and provides insight into the underlying latent factors for categorizing microstructure. Four descriptors, i.e., volume fraction, cluster size, nearest neighbor distance, and cluster roundness, are identified as important based on the microstructure correlation functions (CF) derived from images. The sufficiency of these four key descriptors is validated through confirmation of the reconstructed images and simulated material properties of the epoxy-nanosilica system. Among the four key descriptors, volume fraction and cluster size are dominant in determining the dielectric constant and dielectric loss.

Dielectric properties of sol–gel synthesized polysulfone–ZnO nanocomposites

The research on development of nanodielectric material is the requirement of capacitor industry. The polymeric material could not have a high dielectric constant due to limitation of structure and physical properties. However, combination of suitable nanofiller can increase the dielectric constant several times. We have reported the dielectric properties of polysulfone + ZnO nanodielectric system. The dielectric properties are observed to be governed by dipolar polarization fully and interfacial polarization partially. The relaxation time of dipoles is quite high: It means that nanodipoles have sufficient relaxation time to orient in the direction of field. Interface provides additional trapping level for storage of charge carriers energetically. The permittivity of new material increases many times of base material even at lower concentration of fillers.

Ambient-Processable High Capacitance Hafnia-Organic Self-Assembled Nanodielectrics

Ambient and solution-processable, low-leakage, high capacitance gate dielectrics are of great interest for advances in low-cost, flexible, thin-film transistor circuitry. Here we report a new hafnium oxide-organic self-assembled nanodielectric (Hf-SAND) material consisting of regular, alternating π-electron layers of 4-[[4-[bis(2-hydroxyethyl)amino]phenyl]diazenyl]-1-[4-(diethoxyphosphoryl) benzyl]pyridinium bromide) (PAE) and HfO2 nanolayers. These Hf-SAND multilayers are grown from solution in ambient with processing temperatures ≤150 °C and are characterized by AFM, XPS, X-ray reflectivity (2.3 nm repeat spacing), X-ray fluorescence, cross-sectional TEM, and capacitance measurements. The latter yield the largest capacitance to date (1.1 μF/cm(2)) for a solid-state solution-processed hybrid inorganic-organic gate dielectric, with effective oxide thickness values as low as 3.1 nm and have gate leakage <10(-7) A/cm(2) at ±2 MV/cm using photolithographically patterned contacts (0.04 mm(2)). The sizable Hf-SAND capacitances are attributed to relatively large PAE coverages on the HfO2 layers, confirmed by X-ray reflectivity and X-ray fluorescence. Random network semiconductor-enriched single-walled carbon nanotube transistors were used to test Hf-SAND utility in electronics and afforded record on-state transconductances (5.5 mS) at large on:off current ratios (I(ON):I(OFF)) of ~10(5) with steep 150 mV/dec subthreshold swings and intrinsic field-effect mobilities up to 137 cm(2)/(V s). Large-area devices (>0.2 mm(2)) on Hf-SAND (6.5 nm thick) achieve mA on currents at ultralow gate voltages (<1 V) with low gate leakage (<2 nA), highlighting the defect-free and conformal nature of this nanodielectric. High-temperature annealing in ambient (400 °C) has limited impact on Hf-SAND leakage densities (<10(-6) A/cm(2) at ±2 V) and enhances Hf-SAND multilayer capacitance densities to nearly 1 μF/cm(2), demonstrating excellent compatibility with device postprocessing methodologies. These results represent a significant advance in hybrid organic-inorganic dielectric materials and suggest synthetic routes to even higher capacitance materials useful for unconventional electronics.