scholarly journals Effects of Ambient Conditions on the Dielectric Properties of Thermally Sprayed Ceramic Coating

2018 ◽  
Author(s):  
M Niittymäki ◽  
B. Rotthier ◽  
K. Lahti ◽  
T. Suhonen ◽  
J Metsäjoki
Keyword(s):  
Dielectric Properties ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Thermal Spraying ◽  
Ceramic Coatings ◽  
Alumina Coating ◽  
Ambient Conditions ◽  
Coating Materials ◽  
Sprayed Coating ◽  
Thermally Sprayed

<p>Thermal spraying techniques are used to manufacture insulating coatings especially for demanding applications like fuel cells where normal insulating materials cannot be used. In electrical insulation applications, the mostly used coating materials are aluminum oxide (Al2O3), magnesium oxide (MgO) and magnesium aluminate (MgAl2O4). Dielectric properties of thermally sprayed ceramic coatings are strongly affected by ambient conditions, and in addition to this they are not well documented in the literature. In this paper the effects of environmental conditions on certain dielectric properties of a thermally sprayed coating are studied. DC resistivity as well as permittivity and losses at different frequencies at relative humidities of 20 % and 45 % at temperature of 20 °C, 40 °C and 60 °C will be reported in the paper for Al2O3 samples sprayed using HVOF (High Velocity Oxygen Fuel) technique. DC dielectric breakdown strength is also studied for the HVOF alumina coating at temperature of 20 °C and relative humidity of 20 %. Effects of ambient conditions and coating material composition are also analyzed.</p>

scholarly journals DC Dielectric Breakdown Behavior of Thermally Sprayed Ceramic Coatings

2017 ◽  
Author(s):  
Minna Niittymäki ◽  
Tomi Suhonen ◽  
Jarkko Metsäjoki ◽  
Kari Lahti
Keyword(s):  
Electric Field ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Strong Dependence ◽  
Degradation Process ◽  
Ceramic Coatings ◽  
Alumina Coating ◽  
Dc Resistivity ◽  
Ramp Rate ◽  
Thermally Sprayed

<p>Previous studies of dielectric properties of thermally sprayed insulating ceramic coatings are focused on linearly ramped dielectric breakdown strength as well as<br />DC resistivity, relative permittivity and dielectric loss characterizations. However, reports of the effects of ramp rate or of any kind of long term stressing on the breakdown strength cannot be found in literature. The aim of this paper was to study the DC breakdown behavior of one type of HVOF sprayed alumina coating under different stresses. It can be concluded that the ramp rate of DC breakdown measurement has no remarkably influence on the breakdown strength. The breakdown behavior was also studied using step-by-step tests with two constant step voltages and step durations. The DC resistivity of the alumina coating showed strong dependence on the applied electric field. The resistivity behaved ohmicly below the field strength of ~0.5 V/μm and above ~8…12 V/μm, however, the resistivity decreased approximately three decades in the nonohmic region (0.5 V/μm --&gt;). At electric field strengths above ~25 V/μm, the degradation started in the material leading to breakdown. However, when the step duration was longer (60 min), the degradation process started already slightly below the applied field of 25 V/μm.</p>

Influence of Chromium Ions on the Dielectric Properties of the PbO-Ga2O3-P2O5 Glass System

2007 ◽  
Vol 62 (5-6) ◽  
pp. 315-323 ◽  
Author(s):  
Gnanaprakasm Little Flower ◽  
Maddireddy Srinivasa Reddy ◽  
Musugu Venkata Ramana Reddy ◽  
Nalluri Veeraiah
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Dielectric Properties ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Oxidation States ◽  
Optical Absorption Spectra ◽  
Dielectric Breakdown Strength ◽  
Chromium Ions ◽  
Wide Range

PbO-Ga2O3-P2O5 glasses containing different amounts of Cr2O3, ranging from 0 to 1.0 mol%, were prepared. The dielectric properties (viz., constant ε’, loss tanδ , ac conductivity σac over a wide range of frequencies and temperatures, dielectric breakdown strength) have been studied as a function of the concentration of chromium ions. An anomaly has been observed in the dielectric properties of these glasses, when the concentration of Cr2O3 is about 0.4 mol%. This anomaly has been explained in the light of different oxidation states of chromium ions with the aid of data of differential thermal analysis and optical absorption spectra of these glasses.

Thermal Spraying in the U.S. Navy

1987 ◽  
Vol 3 (04) ◽  
pp. 256-263
Author(s):  
Stephen Vittori
Keyword(s):  
Thermal Spraying ◽  
Ceramic Coatings ◽  
Experimental Program ◽  
Quality Assurance Procedure ◽  
Thermally Sprayed Coatings ◽  
Thermally Sprayed ◽  
Sprayed Coatings ◽  
Control Corrosion ◽  
The U.S ◽  
Testing And Evaluation

Before the Navy introduced thermally sprayed coatings to control corrosion on shipboard valves, joints, fittings, etc., the only means of protecting these parts was frequent repainting—often after intervals as short as six months—a labor-intensive and costly operation. This paper describes the Navy's experimental program to assess the benefits of a changeover to flame-sprayed aluminum and ceramic coatings of selected components; the reduction in man-hours achieved; the quality assurance procedure adopted; and the testing and evaluation of results.

scholarly journals Thermally Sprayed Coatings: Novel Surface Engineering Strategy Towards Icephobic Solutions

Materials ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1434 ◽  
Author(s):  
Heli Koivuluoto ◽  
Enni Hartikainen ◽  
Henna Niemelä-Anttonen
Keyword(s):  
Surface Properties ◽  
Surface Engineering ◽  
Design Method ◽  
Composite Coatings ◽  
Thermal Spraying ◽  
Coating Materials ◽  
Sustainable Solutions ◽  
Thermally Sprayed Coatings ◽  
Thermally Sprayed ◽  
Sprayed Coatings

Surface engineering promotes possibilities to develop sustainable solutions to icing challenges. Durable icephobic solutions are under high interest because the functionality of many surfaces can be limited both over time and in icing conditions. To solve this, one potential approach is to use thermally sprayed polymer or composite coatings with multifunctional properties as a novel surface design method. In thermal spraying, coating materials and structures can be tailored in order to achieve different surface properties, e.g., wetting performance, roughness and protection against several weathering and wearing conditions. These, in turn, are beneficial for excellent icephobic performance and surface durability. The icephobicity of several different surfaces are tested in our icing wind tunnel (IWiT). Here, mixed-glaze ice is accreted from supercooled water droplets and the ice adhesion is measured using a centrifugal adhesion tester (CAT). The present study focuses on the icephobicity of thermally sprayed coatings. In addition, surface-related properties are evaluated in order to illustrate the correlation between the icephobic performance and the surface properties of differently tailored thermally sprayed coatings as well as compared those to other coatings and surfaces.

Role of microstructure in dielectric properties of thermally sprayed ceramic coatings

2016 ◽  
Author(s):  
Minna Niittymaki ◽  
Ilkka Rytoluoto ◽  
Kari Lahti ◽  
Jarkko Metsajoki ◽  
Tomi Suhonen
Keyword(s):  
Dielectric Properties ◽  
Ceramic Coatings ◽  
Thermally Sprayed

Effect of the Difference in Dielectric Constant of the Phases on Dielectric Property of the Composites

2015 ◽  
Vol 814 ◽  
pp. 137-143
Author(s):  
Hao Zhou ◽  
Qing Meng Zhang ◽  
Qun Tang ◽  
Hang Cui ◽  
Yao Hua Xu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
High Dielectric Constant ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Ferroelectric Properties ◽  
Relative Dielectric Constant ◽  
Practical Application ◽  
The Difference ◽  
High Dielectric

The composites have a great use in practical application. In common, the phases in composite have different relative dielectric constant and in order to reveal how the phases with different permittivity affect the composite’s dielectric properties, the experiments were carried out using inorganic and organic composite with different dielectric constant phases to make that clear. The barium niobate-based SiO2system glass–ceramic and fillers-epoxy resin composites were chosen, and the dielectric properties were tested to compare the difference of those composites. The results show that the existence of high dielectric constant phases in composites can improve the permittivity of composites and make the composites present ferroelectric properties, while the dielectric loss can also increased, and the difference in dielectric constant of the phases can decrease the dielectric breakdown strength.

scholarly journals Temperature Influence on PI/Si3N4 Nanocomposite Dielectric Properties: A Multiscale Approach

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1936
Author(s):  
Mohammed Houssat ◽  
Christina Villeneuve-Faure ◽  
Nadine Lahoud Lahoud Dignat ◽  
Marie-Laure Locatelli ◽  
Jean-Pascal Cambronne
Keyword(s):  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
Strong Correlation ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Multiscale Approach ◽  
Macro Scale ◽  
The Matrix ◽  
Underlying Mechanisms ◽  
Nanocomposite Dielectric

The interphase area appears to have a great impact on nanocomposite (NC) dielectric properties. However, the underlying mechanisms are still poorly understood, mainly because the interphase properties remain unknown. This is even more true if the temperature increases. In this study, a multiscale characterization of polyimide/silicon nitride (PI/Si3N4) NC dielectric properties is performed at various temperatures. Using a nanomechanical characterization approach, the interphase width was estimated to be 30 ± 2 nm and 42 ± 3 nm for untreated and silane-treated nanoparticles, respectively. At room temperature, the interphase dielectric permittivity is lower than that of the matrix. It increases with the temperature, and at 150 °C, the interphase and matrix permittivities reach the same value. At the macroscale, an improvement of the dielectric breakdown is observed at high temperature (by a factor of 2 at 300 °C) for NC compared to neat PI. The comparison between nano- and macro-scale measurements leads to the understanding of a strong correlation between interphase properties and NC ones. Indeed, the NC macroscopic dielectric permittivity is well reproduced from nanoscale permittivity results using mixing laws. Finally, a strong correlation between the interphase dielectric permittivity and NC breakdown strength is observed.

Dielectric Properties of BST/(Y2O3)x(ZrO2)1-x/BST Trilayer Films

2011 ◽  
Vol 1292 ◽  
Author(s):  
Santosh K. Sahoo ◽  
D. Misra
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Dielectric Breakdown ◽  
Breakdown Strength ◽  
Sol Gel ◽  
Middle Layer ◽  
Slight Variation ◽  
High Dielectric

ABSTRACTThin films of Ba1-xSrxTiO3 (BST) are being actively investigated for applications in dynamic random access memories (DRAM) because of their properties such as high dielectric constant, low leakage current, and high dielectric breakdown strength. Various approaches have been used to improve the dielectric properties of BST thin films such as doping, graded compositions, and multilayer structures. We have found that inserting a ZrO2 layer in between two BST layers results in a significant reduction in dielectric constant as well as dielectric loss. In this work the effect of Y2O3 doped ZrO2 on the dielectric properties of BST/ZrO2/BST trilayer structure is studied. The structure Ba0.8Sr0.2TiO3/(Y2O3)x(ZrO2)1-x/Ba0.8Sr0.2TiO3 is deposited by a sol-gel process on platinized Si substrate. The composition (x) of the middle layer is varied while keeping the total thickness of the trilayer film constant. The dielectric constant of the multilayer film decreases with the increase of Y2O3 amount in the film whereas there is a slight variation in dielectric loss. In Y2O3 doped multilayer thin films, the dielectric loss is lower in comparison to other films and also there is good frequency stability in the loss in the measured frequency range and hence very suitable for microwave device applications.

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