The effect of alloying additives on the magnetic permeability and permittivity of ferrite spinel

2021 ◽  
Vol 87 (1) ◽  
pp. 30-34
Author(s):  
V. G. Kostishin ◽  
R. M. Vergazov ◽  
S. B. Menshova ◽  
I. M. Isaev ◽  
A. V. Timofeev
Keyword(s):  
Magnetic Permeability ◽  
Sintering Temperature ◽  
Radiation Energy ◽  
High Heat ◽  
Titanium Oxides ◽  
Bismuth Oxides ◽  
Basic Substance ◽  
Alloying Additives ◽  
Absorbing Material ◽  
Ferrite Spinel

Coatings made of the materials that effectively absorb radiation, e.g., ferrite materials, are used to reduce the level of electromagnetic radiation in rooms containing household or industrial equipment. It is known that significant dissipation of the radiation energy is provided by the thickness of the shielding coating which should be comparable to the length of the electromagnetic wave in the material which, in turn, significantly decreases at high values of the magnetic permeability and permittivity of the radio-absorbing material. Ferrite radio-absorbing coatings are characterized by the high heat resistance, low flammability and small (10 – 20 mm) thickness. However, at frequencies less than 40 MHz, plates with a thickness of more than 30 mm are to be used to provide the effective absorption, and the weight and cost of the coatings increase significantly. The results of studying the effect of the sintering temperature and micro-additives of titanium, calcium and bismuth oxides on the dielectric constant of Ni- and Mn-Zn radio-absorbing ferrites are presented. Reactively pure starting oxide components with a basic substance content of more than 99.6 % wt. were used to synthesize samples using traditional oxide technology. It is shown that alloying with bismuth and titanium oxides is rather effective for obtaining radio-absorbing ferrites with a combination of high values of the magnetic permeability and dielectric permittivity. The obtained results can be used in production of ferrite radio- absorbing materials operating in the megahertz range.

Performance and Economic Analysis of Double Pass Solar Air Collector

2011 ◽  
Author(s):  
Akhilesh Gupta ◽  
Ravi Kumar ◽  
Bharat Ramani
Keyword(s):  
Porous Material ◽  
Economic Analysis ◽  
Thermal Performance ◽  
Convective Heat Transfer Coefficient ◽  
Radiation Energy ◽  
High Heat ◽  
Absorber Plate ◽  
Double Pass ◽  
Plate Temperature ◽  
Solar Air Collector

Solar collector is a type of heat exchanger which transfers solar radiation energy into the heat energy. Conventional solar air collectors have poor thermal efficiency primarily due to high heat losses and low convective heat transfer coefficient between the absorber plate and flowing air stream, leading to higher absorber plate temperature and greater thermal losses. Attempts have been made to improve the thermal performance of conventional solar air collectors by employing various design and flow arrangements. Double pass counter flow solar air collector with porous material in the second air passage is one of the important and effective design improvement that has been proposed to improve the thermal performance. This paper presents the performance and economic analysis of double pass solar air collector with and without porous material. Effects of various parameters on the thermal performance and pressure drop characteristics have been studied experimentally. The study concludes that double pass arrangement with porous material is economical and having short payback period. Also, the thermal performance of double pass solar air collector with porous material is significantly higher compared to double pass solar air collector without porous material and single pass arrangement.

Microstructure and Complex Magnetic Permeability of Ni0.3Zn0.7Fe2O4 Ferrite

2008 ◽  
Vol 591-593 ◽  
pp. 125-129 ◽  
Author(s):  
Vera Lúcia Othéro de Brito ◽  
Francisco Cristóvão Lourenço de Melo ◽  
Antônio Carlos da Cunha Migliano
Keyword(s):  
Magnetic Permeability ◽  
Sintering Temperature ◽  
Electronic Components ◽  
Ceramic Method ◽  
Magnetic Ceramics ◽  
Environmental Variations ◽  
Complex Magnetic Permeability ◽  
The One ◽  
Lower Frequencies

Ni-Zn ferrites are magnetic ceramics that are widely used in electric and electronic components. Among Ni1-xZnxFe2O4 ferrites, Ni0.3Zn0.7Fe2O4 is known to be the one of highest magnetic permeability in lower frequencies. This work is divided into two parts: the first part deals with the influence of sintering temperature and forming conditions on the microstructure of Ni0.3Zn0.7Fe2O4 ferrite. The second part deals with the influence of sintering temperature and environmental variations of temperature on the complex magnetic permeability of such ferrite. The ferrite studied in this work was fabricated by means of the conventional ceramic method. Complex magnetic permeability between 100 kHz – 100 MHz is discussed in relation to sintering temperature. The influence of environmental variations in temperature (-40 oC to +50 oC) on the complex magnetic permeability of the ferrite sintered at 1300 oC is discussed.

Equivalent Model of Modified Bismuth Oxides Described by Fractional Derivatives

2007 ◽  
Vol 336-338 ◽  
pp. 676-679 ◽  
Author(s):  
Tomasz Janiczek ◽  
Dorota Nowak ◽  
Witold Mielcarek ◽  
Krystyna Prociów
Keyword(s):  
Electrical Properties ◽  
Metal Oxide ◽  
Fractional Derivatives ◽  
Sintering Temperature ◽  
Electrical Response ◽  
Spectroscopic Technique ◽  
Electrical Circuit ◽  
Equivalent Model ◽  
Ionic Conductors ◽  
Bismuth Oxides

Metal oxide modified Bi2O3 finds the application in metal oxide varistors and as ionic conductors. Electrical properties of MeO-modified Bi2O3 change with MeO modifier and sintering temperature. In this paper we report how to predict Bi2O3 electrical properties using simulation model. Measurements of the electrical response of the modified Bi2O3 oxides were carried out using the impedance spectroscopic technique. As a result an equivalent model of electrical behaviour of modified Bi2O3, described by fractional derivates was proposed. To test the model, the series of simulation were run on computer, and after subjecting the results to verification the equivalent parameters of electrical circuit were determined. Model was elaborated with the view of facilitating the research on metal oxide ionic conductors and varistors.

scholarly journals Effects of Curved Wavefronts on Conductor-Backed Reflection-Only Free-Space Material Characterization Techniques

2015 ◽  
Vol 2015 ◽  
pp. 1-9
Author(s):  
Raenita A. Fenner ◽  
Edward J. Rothwell
Keyword(s):  
Plane Wave ◽  
Magnetic Permeability ◽  
Free Space ◽  
Material Characterization ◽  
Plane Waves ◽  
Characterization Methods ◽  
Radar Absorbing Material ◽  
Absorbing Material ◽  
Space Material ◽  
The Impact

A true plane wave is often not physically realizable in a laboratory environment. Therefore, wavefront curvature introduces a form of systematic error into Free-space material characterization methods. Free-space material characterization is important to the determination of the electric permittivity and magnetic permeability of conductor-backed and in situ materials. This paper performs an error analysis of the impact on wavefront curvature on a Free-space method called the two-thickness method. This paper compares the extracted electric and magnetic permeability computed with a plane wave versus a line source for a low-loss dielectric and magnetic radar absorbing material. These steps are conducted for TE and TM plane waves and electric and magnetic line sources.

Electron Microscopy of Silicon Nitride-Based Ceramics

1991 ◽  
Vol 49 ◽  
pp. 926-927
Author(s):  
Gareth Thomas
Keyword(s):  
Electron Microscopy ◽  
High Temperature ◽  
Silicon Nitride ◽  
World Wide ◽  
Sintering Temperature ◽  
Liquid Phase Sintering ◽  
High Temperature Strength ◽  
Sintering Additives ◽  
Glass Forming ◽  
Dense Product

Silicon nitride and silicon nitride based-ceramics are now well known for their potential as hightemperature structural materials, e.g. in engines. However, as is the case for many ceramics, in order to produce a dense product, sintering additives are utilized which allow liquid-phase sintering to occur; but upon cooling from the sintering temperature residual intergranular phases are formed which can be deleterious to high-temperature strength and oxidation resistance, especially if these phases are nonviscous glasses. Many oxide sintering additives have been utilized in processing attempts world-wide to produce dense creep resistant components using Si3N4 but the problem of controlling intergranular phases requires an understanding of the glass forming and subsequent glass-crystalline transformations that can occur at the grain boundaries.

Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

1996 ◽  
Vol 54 ◽  
pp. 478-479
Author(s):  
Matthew T. Johnson ◽  
Ian M. Anderson ◽  
Jim Bentley ◽  
C. Barry Carter
Keyword(s):  
Monte Carlo ◽  
Quantitative Analysis ◽  
Monte Carlo Simulations ◽  
Cross Section ◽  
Spatial Resolution ◽  
Low Voltage ◽  
Magnesium Ferrite ◽  
X Ray ◽  
Interaction Volume ◽  
Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

Study of the Kinetics of Thermal Destruction of Crossed Polyethylene

2019 ◽  
Vol 5 (12) ◽  
pp. 37-46
Author(s):  
K. Chalov ◽  
Yu. Lugovoy ◽  
Yu. Kosivtsov ◽  
E. Sulman
Keyword(s):  
Total Yield ◽  
Calorific Value ◽  
High Heat ◽  
Process Temperature ◽  
Optimum Process ◽  
Quantitative Composition ◽  
Pyrolysis Gas ◽  
Gaseous Products ◽  
Liquid Products ◽  
Kinetics Of

This paper presents a study of the process of thermal degradation of crosslinked polyethylene. The kinetics of polymer decomposition was studied by thermogravimetry. Crosslinked polyethylene showed high heat resistance to temperatures of 400 °C. The temperature range of 430–500 °C was determined for the loss of the bulk of the sample. According to thermogravimetric data, the decomposition process proceeds in a single stage and includes a large number of fracture, cyclization, dehydrogenation, and other reactions. The process of pyrolysis of a crosslinked polymer in a stationary-bed metal reactor was investigated. The influence of the process temperature on the yield of solid, liquid, and gaseous pyrolysis products was investigated. The optimum process temperature was 500 °C. At this temperature, the yield of liquid and gaseous products was 85.0 and 12.5% (mass.), Respectively. Samples of crosslinked polyester decomposed almost completely. The amount of carbon–containing residue was 3.5% by weight of the feedstock. With increasing temperature, the yield of liquid products decreased slightly and the yield of gaseous products increased, but their total yield did not increase. For gaseous products, a qualitative and quantitative composition was determined. The main components of the pyrolysis gas were hydrocarbons C1–C4. The calorific value of pyrolysis gas obtained at a temperature of 500 °C was 17 MJ/m3. Thus, the pyrolysis process can be used to process crosslinked polyethylene wastes to produce liquid hydrocarbons and combustible gases.

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