Application Of Insulation Materials Research Articles

Preparation and properties of core‐shell structured calcium copper titanate@polyaniline/silicone dielectric elastomer actuators

In this article, core‐shell structured calcium copper titanate@polyaniline (CCTO@PANI) was synthesized using a simple procedure involving in situ polymerization of aniline in aqueous hydrochloric acid solution. Then, polydimethyl siloxane (PDMS) filled with self‐prepared CCTO@PANI particles had high dielectric constant, low dielectric loss, and actuated strain which was greatly improved at low electric field. Meanwhile, the elastic modulus of CCTO@PANI/PDMS composites was increased slightly only with a good flexibility. Compared to pure silicone elastomer (8.94%), the CCTO/PDMS and CCTO@PANI/PDMS (The weight ratio of CCTO and aniline was 10) composites exhibited a greater actuated strain of 10.95% and 13.24% at a low electric field and filling content of 10 V/μm, respectively. This study provided a simple and effective method for the improvement of actuated strain at low electric field through addition of CCTO@PANI/PDMS composites due to the hyper‐electronic polarization and a strong polaron delocalization, facilitating the wide application of dielectric materials. POLYM. COMPOS., 40:E62–E68, 2019. © 2017 Society of Plastics Engineers

壁面漏热的冷却腔体内增加薄壁隔板引起的热效应数值研究

Adding thin compartmental plates near the internal walls of enclosures has been numerically modeled using the lattice Boltzmann method. This practice was found to be an effective way to further suppress the disadvantageous effects of heat leak, along with the application of insulation materials on the external surfaces. A modified extrapolation scheme for handling the thermal boundary of the thin plate was proposed and verified by comparison with the conventional coupled boundary scheme. The simulation of the natural convection during the cooling down processes and at steady states in the enclosure indicates that the existence of the plates leads to a higher cooling rate and a more favorable temperature uniformity. For a typical case, the one with plates takes 6% less time to reach the halfway point of the steady state and has 26% less temperature variance. Effects by the plates’ positions and sizes were parametrically investigated, in order to find an optimal geometrical configuration. In addition, the fluid’s intrinsic characteristics and the relative heat leak by using the Rayleigh number and Nusselt number, respectively, have been discussed in detail through hydrodynamic and convective heat transfer analyses.

Investigation of Surface Potential Decay Behavior of Insulator Polymers after High-Voltage Poling

In order to investigate the surface potential decay tendency of the insulator polymers such as Polypropylene (PP) and Polyvinyl Chloride (PVC), the high voltage corona triode was applied to inject the charge into the surface and volume of the samples. Due to that the surface potential decay tendency is of utmost important to the investigation of space charge storage mechanism in those polymers, the decay tendency of each sample was tested and observed. The results show that the polypropylene with cellular structure can stored larger amount of the surface charges than the polyvinyl chloride. The results could be put into industrial application of insulation materials in the related fields of electrical insulation engineering.

Graphene encapsulated rubber latex composites with high dielectric constant, low dielectric loss and low percolation threshold

A dielectric composite with high dielectric constant, low dielectric loss and low percolation threshold was prepared by using the combined strategy of encapsulating of graphene oxide nanosheets (GONS) on carboxylated nitrile rubber (XNBR) latex particles and the in situ thermal reduction in GONS at a moderate temperature. The encapsulation of GONS on XNBR latex particles was mainly realized via the hydrogen bonding interactions between GONS and XNBR during latex mixing. A segregated graphene network was obtained at a low content of thermally reduced graphene (TRG), resulting in a low percolation threshold (0.25vol.%). The dielectric constant at 100Hz obviously increased from 23 for pure XNBR to 2211 and 5542 for the composite with 0.5vol.% and 0.75vol.% of TRG, respectively. The dielectric loss of the composites retained at a low value (less than 1.5). Meanwhile, the elastic modulus only slightly increased with the presence of 0.1–0.5vol.% of TRG, keeping the good flexibility of the dielectric composites. This study provides a simple, low-cost and effective method to prepare high performance dielectric composites, facilitating the wide application of dielectric materials.

Dramatically improved dielectric properties of polymer composites by controlling the alignment of carbon nanotubes in matrix

Aligned multi-walled carbon nanotubes (MWCNTs)/polyvinyl alcohol composite films were prepared by using an easy and controllable electrospinning-in situ film-forming (EF) technique. A high dielectric constant (k), a low dielectric loss, a consistently high breakdown strength, and a high energy density were obtained by using this technique. The dramatically improved dielectric properties are ascribed to the good dispersion and alignment of MWCNTs in the matrix, facilitating the formation of a large number of separated nano-capacitors (high k and low direct current (DC) conductance). For comparison purposes, the same composite films were prepared by solution casting (SC). At the same MWCNT content, the SC method yielded a higher k, but a significantly higher dielectric loss and much lower breakdown strength and energy density because of the random dispersion of MWCNTs in the matrix and the formation of a MWCNT network, which result in a large increase in DC conductance. The formation mechanism of the different microstructures and the relationships between the microstructures and dielectric properties are clarified. Our results indicate that high-performance MWCNTs/polymer dielectric composites can be obtained by controlling the microstructure of the composites by using the EF technique, which widens the applications of dielectric materials.

A Review on Conduction Mechanisms in Dielectric Films

The conduction mechanisms in dielectric films are crucial to the successful applications of dielectric materials. There are two types of conduction mechanisms in dielectric films, that is, electrode-limited conduction mechanism and bulk-limited conduction mechanism. The electrode-limited conduction mechanism depends on the electrical properties at the electrode-dielectric interface. Based on this type of conduction mechanism, the physical properties of the barrier height at the electrode-dielectric interface and the effective mass of the conduction carriers in dielectric films can be extracted. The bulk-limited conduction mechanism depends on the electrical properties of the dielectric itself. According to the analyses of bulk-limited conduction mechanisms, several important physical parameters in the dielectric films can be obtained, including the trap level, the trap spacing, the trap density, the carrier drift mobility, the dielectric relaxation time, and the density of states in the conduction band. In this paper, the analytical methods of conduction mechanisms in dielectric films are discussed in detail.

Structure–property relationship of polyimides based on pyromellitic dianhydride and short‐chain aliphatic diamines for dielectric material applications

Most polyolefins that are used for dielectric materials exhibit a low dielectric constant and operating temperatures up to 70°C. Polyimides offer a means to a higher dielectric constant material by the introduction of a polar group in the polymer backbone and are thermally stable at temperatures exceeding 250°C. A common dianhydride, pyromellitic dianhydride (PMDA), is reacted with various short‐chain diamines to produce polymers with high imide density. Homopolymers and copolymers synthesized had dielectric constants ranging from 3.96 to 6.57. These materials exhibit a dielectric constant twice that of biaxially oriented polypropylene and therefore a twofold increase in capacitance as well as maintaining low dissipation factors that are acceptable for this application. The experimental dielectric constants of these materials are also compared to density functional theory calculations and exhibit a close relationship. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1276‐1280, 2013

Study of Oxides Formed in HfO<sub>2</sub>/Si Structure for High-<i>k</i> Dielectric Applications

Transmission electron microscopy (TEM) techniques were used for characterization of annealing (400, 600 and 800 °C) influence on the structural properties of the HfO2 film (45 nm thick) deposited on Si substrate. Such structures are considered as high-k dielectric materials for application in novel semiconductor devices. The studies showed that independently of the annealing temperature a very thin and flat amorphous layer is formed between HfO2 layer and Si substrate. This result was also found in the non-annealed sample. EDXS examination confirmed that the stoichiometry for the hafnium oxide layer in each sample corresponds to 1:2 for Hf:O (i.e. to HfO2). TEM images revealed differences in the microstructure of HfO2 layers in annealed samples, however the layers have similar thickness and interface roughness in all studied samples.

ICPADM 2012 10th International Conference on Properties and Applications of Dielectric Materials

ICPADM 2012 10th International Conference on Properties and Applications of Dielectric Materials

Water flow and heat transport including ice/water phase change in porous media: Numerical simulation and application

Abstract According to the basic law of water flow and heat transfer in porous media under freeze/thaw condition, based on the theories of continuum mechanics, thermodynamics and segregation potential, the governing equations for thermo-hydro (TH) coupling model are established. These equations include not only the effects of thermal conductivity, latent heat of phase change and the seepage velocity on temperature distribution, but also the effects of water flow in porous resulted by Soret effect and segregation potential on seepage velocity and water pressure distribution. Compared with the famous TH coupling laboratory test conducted by Mizoguchi, it was found that the presented TH coupled model predicts the freezing process in porous media well and satisfactorily reflects observed phenomena. Combining this basis and the construction of Galongla tunnel in Tibet of China, the effect of insulation materials is analyzed at first, and then research work is done to study the influence of position, thickness and types of insulation materials on heat preservation effect. The research results indicated that the application of insulation material with 6 cm thickness and 600 m long at the entrance, while 400 m long at the exit of Galongla tunnel can prevent the lining and surrounding rock from freezing–thawing damages effectively.

ICPADM 2009 report

The 9th ICPADM, the International Conference on the Properties and Applications of Dielectric Materials was held in Harbin, China, on July 19-23, 2009.

Epitaxial Growth of ZrO2 on GaN by MOMBE for High Dielectric Material Applications

ABSTRACTEpitaxial growth of ZrO2 has been achieved on MOCVD grown GaN template by oxides MBE using a reactive H2O2 oxygen source. Using the low temperature buffer followed by high temperature in-situ annealing and high-temperature growth, monoclinic, (100)-oriented ZrO2 thin film with decent structural quality and smooth surface morphology was achieved. The full width at half maximum of ZrO2 (100) rocking curve is 0.4 arc degree and the rms roughness for a 5μm by 5 μm AFM scan is 4.1Å. The use of epitaxially grown ZrO2 in the AlGaN/GaN HFET structure as a gate dielectric layer have resulted in the increase of the saturation-current density and pinch-off voltage as well as showed near symmetrical gate-drain I-V behavior.

The 6th International Conference on Properties and Applications of Dielectric Materials (ICPADM'2000); and the history of the ICPADM

In the interest of having written notes on some of the history of the DEIS activities, Prof. Kao, Founder of the International Conference on Properties and Application of Dielectric Materials, was asked to set down in writing some of his memories of how the ICPADIM came about. From the beginnings of the DEIS, the Society had sponsored conferences on electrical insulation in North America. Under the leadership of Eric Forster, who was the Meetings Chair for a number of years, the Society broadened its scope and began to sponsor meetings outside of North America. It is of historical interest to understand how the ICPADM came about. It was the first Pan-Asian conference sponsored by the DEIS and continues to hold the distinction of being our only Pan-Asian conference. Prof. Kao, one of the keynote speakers' at the ICPADM 2000, compares the most recent conference with the first in a Reporter's Notebook format. He has also drawn from his memory as to how the original conference came about.

Third International Conference on Properties and Applications of Dielectric Materials

Third International Conference on Properties and Applications of Dielectric Materials

An Overview of the 1985 International Conference on Properties and Applications of Dielectric Materials

An Overview of the 1985 International Conference on Properties and Applications of Dielectric Materials

Viscous dielectric materials for application in microwave microcircuits

Viscous dielectric materials made from mixtures of titania and Vaseline cover the relative-permittivity range from approximately 4 to 30. The main application is in experiments with microwave microcircuits. Measurements are reported using a resonance method with a cavity developed for this work. A previously quoted expression, giving mixture relative permittivity as a function of its component relative permittivities and their proportions, is shown to hold for this case.

Modern Dielectric Materials

Edited by J. B. Birks London: Heywood and Co. Ltd. Pp. 253. Price 42s. The aim of this book is to provide an introduction to the wide range of dielectric and insulating materials that are used in modern electrical technology. It is intended for engineers, physicists and chemists who are interested in the manufacture, development or practical applications of dielectric materials.