Use of fractals to describe microstructures of porous thick-film platinum electrodes

1992 ◽  
Vol 50 (1) ◽  
pp. 314-315
Author(s):  
Steven D. Toteda
Keyword(s):  
Fractal Dimension ◽  
Power Plants ◽  
Electrical Response ◽  
Cubic Phase ◽  
Platinum Electrodes ◽  
Fine Grained ◽  
Impedance Response ◽  
Platinum Particles ◽  
Energy Surfaces ◽  
Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

Poisoning of Highly Porous Platinum Electrodes by Amino Acids and Tissue Fluid Constituents

2015 ◽  
Vol 2 (11) ◽  
pp. 1785-1793 ◽  
Author(s):  
Christian Köhler ◽  
Lena Bleck ◽  
Maxi Frei ◽  
Roland Zengerle ◽  
Sven Kerzenmacher
Keyword(s):  
Amino Acids ◽  
Tissue Fluid ◽  
Platinum Electrodes ◽  
Highly Porous

scholarly journals Effects of Separated Fractions of Fbc Bottom Ash on Selected Properties of Cement Mortars

2020 ◽  
Vol 30 (4) ◽  
pp. 1-20
Author(s):  
Zbigniew Kledyński ◽  
Łukasz Krysiak
Keyword(s):  
Power Plants ◽  
Activity Index ◽  
Bottom Ash ◽  
High Water ◽  
Coarse Grained ◽  
Partial Replacement ◽  
Fine Grained ◽  
Cement Mortars ◽  
Inert Additive ◽  
High Silica

Abstract This paper discusses the effects of partial replacement of cement with fluidized bed bottom ash on the properties of mortars. The analyzed ash samples originating from four Polish power plants were separated by grain size selection into fine and coarse-grained fractions. This process leads to a creation of derivative samples of differing physical properties and, partially, phase compositions, as tested in XRD and TG analyses. Despite its high water demand, the obtained fine-grained fraction has the potential for application in cementbased composites as a reactive, pozzolanic additive. An acceptable activity index may be reached when the sulfate content is limited, implying benefits of combining the ash with low gypsum cements. The coarse-grained fraction is significantly less reactive, while a high silica and aluminate content is related to improved mechanical properties of the composite. It can, therefore, potentially be used as a quasi-inert additive or a substitute for sand.

Assessment of Homogeneity of Extruded Alumina-SiC Composite Rods Used in Microwave Heating Applications by Impedance Spectroscopy

2013 ◽  
Vol 1538 ◽  
pp. 323-328
Author(s):  
Justin R. Brandt ◽  
Rosario A. Gerhardt
Keyword(s):  
Electrical Conductivity ◽  
Electrical Response ◽  
Percolation Model ◽  
Homogeneous Distribution ◽  
Impedance Response ◽  
Silicon Carbide Whiskers ◽  
Percolation Behavior ◽  
Sic Whiskers ◽  
The Individual

ABSTRACTComposite rods consisting of Alumina (Al2O3) and Silicon Carbide whiskers (SiCw) are used to fabricate microwave cooking racks because they effectively act as a microwave intensification system that allows cooking at much faster rates than conventional microwave ovens. The percolation behavior, electrical conductivity and dielectric properties of these materials have been reported previously. However, it has been observed that the electrical response of the extruded bars is a function of the rod length and that long rods show substantially different behavior than thinner disks cut from them. A percolation model has been proposed that describes the effect of the alignment of the semiconducting SiC whiskers and the quality of the interfaces present in the composite rods: SiC-SiC and SiC-Al2O3-SiC for example. This study was undertaken with the goal of testing out whether the response of the individual sections could be used to generate the response of the full length rods and to assess the importance of the homogeneous distribution of the SiC fillers on the resultant impedance response.

Preparation of fine-grained MgO and Gd2O3 stabilized ZrO2 thin films by electron beam physical vapor deposition co-evaporation

1997 ◽  
Vol 12 (12) ◽  
pp. 3260-3265 ◽  
Author(s):  
F. Tcheliebou ◽  
M. Boulouz ◽  
A. Boyer
Keyword(s):  
Thin Films ◽  
Electron Beam ◽  
Average Particle Size ◽  
Electron Gun ◽  
Cubic Phase ◽  
Crystallographic Structure ◽  
Average Particle ◽  
Scanning Electron Micrographs ◽  
Dopant Content ◽  
Fine Grained

Thin films of ZrO2 doped with MgO and Gd2O3, 1–1.5 μm in thickness are formed onto nickel substrates by reactive thermal evaporation using a dual-hearth electron gun. X-ray diffraction patterns of the deposits show changes in the crystallographic structure and average particle size as a function of the dopant content. A mixture of monoclinic and tetragonal phases gradually disappears to become a single cubic phase with increasing dopant molar fraction. The average crystallite size deduced from diffraction line broadening decreases as the dopant content increases. This observation is strongly confirmed by scanning electron micrographs which reveal a smooth surface topography. Fine-grained materials obtained here are interpreted in terms of high nucleation rate and kinetically limited grain growth. It appears that composition, crystallographic structure, and microstructure relations are of paramount importance in ZrO2-based films prepared by electron-beam evaporation.

scholarly journals Highly Porous Platinum Electrodes for Dry Ear-EEG Measurements

2020 ◽  
Author(s):  
Max Eickenscheidt ◽  
Patrick Schäfer ◽  
Yara Baslan ◽  
Claudia Schwarz ◽  
Thomas Stieglitz
Keyword(s):  
Growth Form ◽  
Silver Chloride ◽  
Auditory Attention ◽  
Platinum Electrodes ◽  
Effective Surface Area ◽  
Effective Surface ◽  
Transmission Properties ◽  
Silver Silver ◽  
Silver Silver Chloride ◽  
Highly Porous

The interest in dry EEG electrodes has increased in recent years and especially as everyday suitability earplugs for measuring drowsiness or focus of auditory attention. However, the challenge is still the need for a good electrode material, which is reliable and can be easily processed for highly personalized applications. Laser processing as used here is a fast and very precise method to produce personalized electrode configurations that meet the high requirements of in-ear EEG electrodes, for example. The arrangement of the electrodes on the very flexible and compressible mats allows an exact alignment of the electrodes to the ear mold and contributes to a high wearing comfort, as no edges or metal protrusions are present. For better transmission properties, an adapted coating process for surface enlargement of platinum electrodes is used, which allows easy control of the thickness and growth form of the porous layer. The porous platinum-copper alloy is chemically very stable, shows no exposed copper residues and enlarges the effective surface area by 40. In a proof-of-principle experiment, these porous platinum electrodes could be used to measure the Berger effect in a dry state using just one ear of a test person. Their signal-to-noise ration and frequency transfer function is comparable to gel-based silver/silver chloride electrodes.

scholarly journals Effects of Intercropping on Soil Fractal Dimension and Physicochemical Properties in the Karst Areas

2021 ◽  
Author(s):  
Qin qin Xu ◽  
Kang ning Xiong ◽  
Yong kuan Chi
Keyword(s):  
Fractal Dimension ◽  
Physicochemical Properties ◽  
Soil Water ◽  
Soil Structure ◽  
Salvia Miltiorrhiza ◽  
Chemical Properties ◽  
Spatial Optimization ◽  
Organic Carbon Content ◽  
System Productivity ◽  
Fine Grained

Suitable soil structure and nutrient security are important for plant growth and development, characteristics of soil fractal dimension and distribution of physical and chemical properties and their interactions play an important role in studying the stability of soil structure and water and fertilizer cycles. As a sustainable management model, intercropping has positive benefits for erosion control, spatial optimization of resources, as well as improving system productivity. The effects of four intercropping methods on soil fractal dimension and physicochemical properties were investigated by intercropping Salvia miltiorrhiza with forage and S. miltiorrhiza with forest under typical karst rock desertification habitats in Guizhou. The results showed that soil nutrient content of intercropping was significantly higher than that of monoculture, the organic carbon content of soil grown under forest is higher than other treatments, and there was a non-significant change in soil water content of intercropping compared with monoculture. The soil fine-grained matter of intercropping was significantly higher than that of monoculture, while the soil fractal dimension showed a tendency to become larger with the increase of fine-grained matter. The intercropping planting, due to its component types and spatial and temporal configurations, leads to differences in soil water and fertilizer interactions, which can be combined with other ecological restoration measures to optimize the composite model and jointly promote the restoration and development of ecologically fragile areas.

scholarly journals INFLUENCE OF THE OPTIMAL GRAIN COMPOSITION OF AGGREGATE ON THE MAIN PHYSICAL AND MECHANICAL PROPERTIES OF FINE-GRAINED CONCRETE

2020 ◽  
pp. 151-157
Author(s):  
M.A. Dzhusupova ◽  
A. Talantbek kyzy
Keyword(s):  
Power Plants ◽  
Fractional Composition ◽  
Thermal Power ◽  
Physical And Mechanical Properties ◽  
Grain Composition ◽  
Fine Grained ◽  
Ash And Slag Waste ◽  
Slag Waste ◽  
Rational Composition ◽  
Artificial Origin

The article is devoted to the study of the possibility of reducing the consumption of cement in concrete by optimizing the fractional composition of small aggregates of natural and artificial origin and the use of ash and slag waste of thermal power plants. Using the computer program of the grain composition correction module allows you to quickly determine the rational composition of sand and ensure tight packaging of its grains in concrete. In addition, optimal quantities of hyperplasticizers were selected to produce concrete with the required physical and technical characteristics.

Fractal Features of Cracked Backfill Particle Size Distribution

2012 ◽  
Vol 588-589 ◽  
pp. 1894-1898
Author(s):  
Yong Jian Zhu ◽  
Dai Qiang Deng ◽  
Ping Wang
Keyword(s):  
Particle Size ◽  
Fractal Dimension ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Negative Correlation ◽  
Fractal Structure ◽  
Fine Grained ◽  
Calculation Data ◽  
Relationship Of

Based on the taking sample by geological drilling, combined with the fractal principle, analysis on the cracked backfill particle size of its fractal features and strength correlation. Even each backfill sand specimen particle size is difference, but calculation data shows that the particle size of each sand specimen has preferable fractal feature, the sand specimen particle size distribution has remarkable fractal structure by the linear fitted results of the sand specimens. The fractal relationship of strength and particle size distribution shows that with the increased of fractal dimension, the strength of backfill is decreased, that is to say there is negative correlation, the main cause is that the higher parameter D of the fractal dimension, the higher fine-grained content and more non-uniform of the particle size distribution, especially for the thinner full tailings, if properly increasing the content of slightly crude particles, the strength of backfill will be certainly improved to some extent.

scholarly journals In Situ Measurements in Fractured Till Using Sidewall Sensors

1999 ◽  
Vol 30 (4-5) ◽  
pp. 257-266 ◽  
Author(s):  
Larry Murdoch ◽  
Bill Harrar ◽  
Bertel Nilsson ◽  
William Slack ◽  
Robert Siegrist
Keyword(s):  
Hydraulic Head ◽  
Core Sample ◽  
Contaminated Site ◽  
Platinum Electrodes ◽  
Glacial Sediments ◽  
Fine Grained ◽  
In Situ Sensors ◽  
The Usa ◽  
A Site

Subsurface parameters, such as hydraulic head, often vary markedly with depth in fine-grained glacial sediments, but sensors placed in vertical boreholes are poorly suited to resolve these variations. One problem is that conventional methods only allow one, or perhaps a few, sensors to be placed in each borehole. To address such limitations we have developed a method for accessing the sidewall of a borehole. The method uses a device that pushes sensors or sediment samplers laterally into the sidewall to distances slightly less than the diameter of the borehole. The device can obtain a core sample 15 cm long and 4 cm in diameter, and then insert a permeable sleeve for extracting water samples. The same device has been used to insert several types of electrodes capable of measuring water content (using TDR waveguides), Eh (using platinum electrodes), or electrical resistivity (using a miniature Wenner-type array). At a site near Flakkebjerg, Denmark, we installed 22 water samplers and 19 resistivity electrodes in a single borehole to measure hydraulic head gradients in detail and to monitor the vertical migration of ionic tracers. This approach can be used to install horizontally oriented TDR waveguides at virtually any depth, thereby extending the TDR technique to the study of deep vadose zones. At a contaminated site in the USA, TDR wave guides were installed to a depth of 12 m in glacial till. Other applications include measurement of Eh at a site where in situ chemical oxidization was used, and the in situ sensors provided results that are similar to data obtained from soil cores.

Sign in / Sign up

Export Citation Format

Share Document