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The uprising demands for electrical power and electrification requires advanced dielectric functionalities including high capacitance density, high energy density, high current handling capability, high voltage, high temperature, high thermal conductivity, light weight, and environmental reliability. Nanodielectric engineering emerges and attracts extensive efforts from many countries as a result. Unlike prior reviews focusing on lab scale nanocomposite study, this review focuses on recent innovations in polymerbased nanodielectric design on a large scale and their film scale-up efforts for advanced capacitors. The unconventional polymer-nanofiller engineering and their process in the last two decades are discussed. The nanofunctionalized polymers on a molecular level for high dielectric constants and high dielectric strength are briefly described. The challenge associated with film scale-up and retention of nanodielectric properties are then pointed out to be crucial toward a transfer of dielectric and capacitor technology. Several important attempts at scaling up dielectric films and capacitors recently supported by the US government and industry are reviewed. An alternative strategic approach to achieving high performance polymer films is introduced by leveraging 2D surface coating on commercially mature large-scale polymer films. Future pathways for high quality scalable dielectric films exhibiting desirable dielectric properties and feasibility for capacitor manufacturing are suggested.to develop a more compact pulse-forming network for a pulsed high power microwave (HPM), a laser source, aircraft ignition systems, and high-power electrical systems. [1] The US NAVY strove to develop an all-electric warship for advancing its future combat capability (lethality and survivability). This warship required high-power weapons such as electromagnetic railguns for obtaining pin-point accuracy at a very long range electromagnetic launch systems for rapid aircraft and missile deployment and higher-power radar and sonar systems for "seeing" farther through both air and water. The US Army funded the development of the high-energy-density biaxially oriented polypropylene (BOPP) capacitor and the high-temperature polyetherimide dielectric for ground vehicles to realize better serviceability, higher power, and lower mass of the equipment that ground troops carry. [2,3] Although the energy density has been improved up to 3 J cm −3 via metallization control, the performance, and lifetime of BOPP capacitors degrade rapidly with increasing temperature (the ripple current handing capability decreases as the temperature increases from 85 to 105 °C).Improvements in the fault resistance and the reliability of dielectric materials will enable capacitors to withstand higher electrical current and heat without being excessively derated under extreme stress conditions. A large gap remains between the technology availability and the desired properties, such as combined high temperature and energy density and a low dissipation factor. Fa...

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Abstract-The objective of the present study was to investigate changes in the structural, textural, and surface properties of tubular halloysite under heating, which are significant in the applications of halloysite as functional materials but have received scant attention in comparison with kaolinite. Samples of a purified halloysite were heated at various temperatures up to 1400ºC, and then characterized by X-ray diffraction, electron microscopy, Fourier-transform infrared spectroscopy, thermal analysis, and nitrogen adsorption. The thermal decomposition of halloysite involved three major steps. During dehydroxylation at 500À900ºC, the silica and alumina originally in the tetrahedral and octahedral sheets, respectively, were increasingly separated, resulting in a loss of long-range order. Nanosized (5À40 nm) g-Al 2 O 3 was formed in the second step at 1000À1100ºC. The third step was the formation of a mullite-like phase from 1200 to 1400ºC and cristobalite at 1400ºC. The rough tubular morphology and the mesoporosity of halloysite remained largely intact as long as the heating temperature was <900ºC. Calcination at 1000ºC led to distortion of the tubular nanoparticles. Calcination at higher temperatures caused further distortion and then destruction of the tubular structure. The formation of hydroxyl groups on the outer surfaces of the tubes during the disconnection and disordering of the original tetrahedral and octahedral sheets was revealed for the first time. These hydroxyl groups were active for grafting modification by an organosilane (g-aminopropyltriethoxysilane), pointing to some very promising potential uses of halloysite for ceramic materials or as fillers for novel clay-polymer nanocomposites.

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When cubic PbCrO 3 perovskite (Phase I) is squeezed up to ∼1.6 GPa at room temperature, a previously undetected phase (Phase II) has been observed with a 9.8% volume collapse. Because the structure of Phase II can also be indexed into a cubic perovskite as Phase I, the transition between Phases I and II is a cubic to cubic isostructural transition. Such a transition appears independent of the raw materials and synthesizing methods used for the cubic PbCrO 3 perovskite sample. In contrast to the high-pressure isostructural electronic transition that appears in Ce and SmS, this transition seems not related with any change of electronic state, but it could be possibly related on the abnormally large volume and compressibility of the PbCrO 3 Phase I. The physical mechanism behind this transition and the structural and electronic/magnetic properties of the condensed phases are the interesting issues for future studies.high pressure | X-ray diffraction | DAC | electron state P hase transitions are one of the most fundamental research topics in physics, chemistry, bioscience, and geosciences. Ordinarily, an isostructural phase transition is accomplished with a volume collapse without any symmetrical change. For example, a 6.6% volume change at ∼105 GPa appears during the transition of the B8 structure of MnO due to the Mott transition (1), a 2% volume change at 5.5 GPa occurs in the transition of hexagonal to the same structure ThAl 2 (2), and a 4.0-6.5% volume change appears in the transition of the orthorhombic perovskites of PrFeO 3 , EuFeO 3 , and LuFeO 3 to also orthorhombic structure around 50 GPa (where the transition is considered a high-spin to low-spin transition of the Fe ions) (3). In these transitions, although their axial ratios of both a∕c and b∕c change with their volume at various pressures, the atomic symmetric does not change. In fact, the isostructural phase transitions induced by high pressures are rare and special transitions usually considered to be originating from the electronic structural change in the matter; such a transition appears in cubic Ce (γ-α) and SmS (B1) (4, 5) at room temperature at 0.7 GPa and 0.65 GPa with volume reductions of 15.0% and 13.6%, respectively. Recent evidence suggests that a transition in Ce occurs when the localized f -electron in this system becomes delocalized. Therefore, this transition has been contemporarily referred to as a kind of electronic transition. The volume collapse is therefore considered as a Kondo volume collapse (6). A similar transition appears in Cs, that is, from a face-centered cubic (fcc) phase II to fcc Phase III. It has also been considered as an electronic fcc isostructural transition from 6s to 5d, with a ∼9% volume reduction at around 4.2 GPa (7-9), although recent work has shown that the detailed structure of Phase III is no longer fcc but exactly belongs to a complex large monoclinic (C222 1 ) lattice with 84 atoms (10).Transition-metal oxides with ABO 3 perovskite structure show special properties, such as ferro-electricity, ferro-ma...