Ferrite Components Research Articles

Relation between the phase composition and technological characteristics of Mn-Zn ferrite powders

1. It has been established that the spinel phase content of mass-produced Type 2000NM and 2000NMI manganese-zinc ferrite powders ranges from 60 to 90%. 2. It is shown that the phase composition of these powders may be used as a measure of the extent of their oxidation. In view of the rapidity and ease with which phase analysis can be performed in the URS-501 x-ray diffraction apparatus, phase composition control could become a standard industrial technique, and would undoubtedly help to obtain reproducible properties in manganese-zinc ferrite components. 3. It was found that the greatest amount of hematite is produced when the calcining of powders is performed in the temperature range 600–800°C. 4. An interrelationship was discovered between the hematite content of powders on the one hand and the technological characteristics of the latter and the susceptibility of parts to cracking during sintering on the other.

A debate on the bainite reaction

The authors debate three topics central to the controversies which have enveloped the bainite reaction ever since it was first recognized as a distinctive mode of austenite decomposition. These include: “what is bainite?”, “the growth mechanism of the ferritic component of bainite”, and “the sources of bainitic carbide precipitation.” RFH concludes that bainite is the product of a shear transformation. Individual bainite plates are suggested to grow substantially more rapidly than volume diffusion-control allows, but a constraint such as the build-up of volume strain energy limits the extent of their growth. This mechanism of growth ensures extensive supersaturation of bainitic ferrite with respect to carbon. Whether or not carbides precipitate in association with bainite plates and whether the carbide is cementite ore, however, is a complex question in competitive reaction kinetics. New experimental evidence is presented to demonstrate thate carbide precipitated in lower bainite dissolves upon heating above the kinetic-B stemperature in an alloy steel containing 1.5 pct Si. This result is taken to support the existence of the metastable eutectoid reactionγ ⇌ α + e atca 350°C. HIA and KRK define bainite as the product of a nonlamellar eutectoid reaction. On this view, carbide precipitation thus plays an essential, rather than an ancillary role. Development of the Widmanstatten morphology by the ferritic component of bainite is shown to be inessential to the classification of a eutectoid structure as bainite. When this morphology is present, however, it is concluded to grow by the ledge mechanism, without the participation of shear, at rates of the order of or less than those allowed by volume diffusion-control. New experimental evidence is presented to show that the lengthening and thickening kinetics of individual plates within sheaves of upper bainite are consistent with this description. The results of a new calculation indicate that the initial carbon content of bainite plates lies between theα/α + Fe3C) and the extrapolatedα/(α+ γ) phase boundaries, in agreement with expectation from the ledge mechanism of growth.

Current Status of Time-Domain Metrology in Material and Distributed Network Research

The current status of time-domain metrology (TDM) in material and distributed network research is described. After a brief summary of earlier work, the operation and features of two prototype material measurement units are discussed. These semiautomated systems utilize a 5-V step recovery diode pulse generator and computer-controlled scanning procedures incorporating time-window stabilization and variable-dwell-time averaging. The larger, 10-ns time-window unit measures the complex permittivity and permeability over a frequency range of 0.1-10 GHz in about 10 min. The causes and magnitude of system errors are discussed along with continuing work to improve system performance. In distributed network research, the capabilities of TDM for calibration are being determined. From measured signal-to-noise ratios, it was calculated that random noise contributes less than 1 percent error for insertion loss measurements up to 50 dB over the frequency range 0.4-8 GHz. Other topics discussed include: identification and evaluation of error sources, pulse generator development, measurement configurations and procedures, and testing of waveguide and ferrite components.

Isolation Rating of Ferrite Components at High Pulse Powers (Correspondence)

Any method used to measure the isolation provided by a ferrite component at high pulse powers must also consider the effect of possible distortion to the pulse shape owing to the nonlinear phenomena in ferrites. When such pulse shape distortion occurs, measurement methods based on average crystal current measurement or temperature rise in a calorimeter yield erroneous results. It is necessary that the method of measurement of isolation must be one which finds the difference between the maximum heights of the input and output pulses to the component irrespective of the pulse shape at the two ports.

Measurements of Waveguide Component and Joint Mixing Products in 6-GHz Frequency Diversity Systems

A measuring procedure and circuit are described for power-level determination of odd order "mixing products" generated in waveguide components of 6-GHz FM diversity communication systems. Measured results at several carrier frequencies and diversity separations are presented for typical components used (joints, flexible sections, and ferrite components).

Magnetism in Microwave Devices

The functions of ferrite components in advanced microwave systems are briefly outlined, and the principal requirements described. The successful development of these sophisticated devices is the cumulative result of contributions from many areas of basic research and technology. As an example of the dependence of device performance on diverse efforts, the status and evolution of ferromagnetic digital phasers are reviewed. In this instance, materials research, ceramic technology, methods of numerical analysis, and the understanding of basic damping mechanisms have all contributed to the realization of practical devices. The application of ferrite devices to microwave integrated circuits is also outlined and some recent experimental results given. Other new trends in the field of microwave ferrite devices are briefly mentioned, as are areas most in need of further research.

The nature of hardening and embrittlement of steel 0Kh20N9S2BGTYu

1. Stell 0Kh20N9S2BGTYu has two temperature ranges of embrittlement \t-450–650\dgC and 700–850\dgC. In the high-temperature range \gs phase is formed. In the low-temperature range there is precipitation hardening of the ferritic component. At 500–550°C holding for 5 min results in substantial hardening and a reduction of plasticity, and therefore the temperature of the molten alkali used in pickling should not exceed 420°C. 2. The electron microscopic examination of the samples tempered in the embrittling low-temperature range showed precipitates of intermetallic phase with an ordered cubic structure coinciding crystallographically with the lattice of the matrix (\ga solid solution) but with a lattice parameter (5.7 \0A) double that of the matrix.

Experience with the preparation of ferrite powders by the method of simultaneous precipitation

1. The simultaneous precipitation of carbonates as a method of preparation of ferrite powders with a rectangular hysteresis loop was tested. 2. It is shown that powders synthesized by this method are of uniform chemical composition. 3. The influence of process parameters on the particle size of the powders was studied. 4. The feasibility of producing ferrite components with the required electromagnetic properties has been demonstrated.

Effect of multiple deformations on the resistance of low-carbon steel to cyclic stresses

1. Multiple deformation (5–6 cycles) at a stress equal to that of the plateau of flow with intermediate aging sharphy increases the resistance of St. 3 steel to cyclic stresses. The fatigue limit increases 40% and the working life 50–100 times. 2. The increase in the resistance to cyclic stresses is due to the formation of uniformly distributed networks of blocked dislocations in the ferritic component of low-carbon steel, which occurs during multiple elongation and subsequent aging.

Effect of manganese on the structure and properties of nonmagnetic stainless steels

1. Manganese increases the yield strength of austenitic steels. 2. In biphase austenitic-ferritic steels containing 4% Ni the influence of manganese depends on the amount of chromium in the steel: a) in steels with 18% Cr the amount of the austenitic phase increases with increasing amounts of manganese up to 14% but one cannot eliminate the ferritic components completely by alloying with manganese; b) in steels containing 15% Cr, 14% Mn is needed for the formation of the austenitic structure. 3. To obtain the austenitic structure in stainless steels with 18% Cr and 4% Ni one must add nitrogen as well as manganese. 4. The solubility of nitrogen in austenite increases with increasing concentrations of manganese.

Design and Development of X-Band Ferrite Components

ABSTRACTThis paper describes a four-port X-band junction waveguide circulator and an X-band field displacement isolator. The circulator employs a right angled H-type junction of two X-band waveguides. A full height cylindrical post of R-4 ferrite surrounded by a full height teflon cylinder is symmetrically placed at the junction. Hitherto, no 4-port waveguide circulator using this ferrite-dielectric condiguration has been reported in the literature. This circulator has a bandwidth of more than 500 mc/s. Maximum isolation approaches 40 db. and minimum insertion loss is negligible (less than 0·2 db.). Effects of dielectric loading on the circulator performance are also presented.This paper also describes an X-band field displacement type isolator which has a bandwidth of 1·5 kMc/s. for less than 1 db. insertion loss and greater than 20 db. isolation.

Gyromagnetic resonance graphical design data

A set of graphical solutions of Kittel's equation of gyromagnetic resonance is plotted. The graphs present the d.c. magnetic fields in normalized form as functions of sample shape for commonly used shapes. The curves help in the visualization of the magnetic condition of resonant elements and in the mechanization of the application of Kittel's equation to the design of ferrite microwave components.

Some ferrite components for isolation and controlled coupling

Microwave power division employing the field-controllable microwave permeability of ferrites has been used as the basis of current-controlled variable attenuators and switches. Three such devices are described:(a) A 4-port device in waveguide, with ferrite phase shift controlling power division between two ports of exit. Its operating range is 2.7-3.3 Gc/s.(b) A 3-port device, in waveguide or stripline, with a similar basis of control. However, its most suitable application is with a fixed field, as a circulator.(c) A cross-polarization waveguide device using a ferrite to control the rotation of polarization, thereby forming a reflective switch. It is simple and has a good bandwidth, but frequency control is difficult.The construction, mode of operation, and performance are given in each case.

Sigma-phase in steel 1Kh20N14S2

1. Dispersion hardening of steel 1Kh20N14S2 at 650°C occurs in two stages. The first stage lasting up to 500 hrs is characterized by the precipitation of secondary carbides Me23C6 and their coalescence, principally along austenite grains. The second stage is connected withσ-phase formation. 2. Upon holding in excess of 500 hrs, the coalesence of carbide Me23C6 prompts a formation ofα-phase (alloyed ferrite depleted in chrome) adjacent to the carbide particles. 3. The diffusional mobility of the atoms in the components of metastable ferrite secures a growth ofσ-phase nuclei. Particles of sigma grow also on account of dissolution of carbides. 4. In areas with a distorted crystal lattice,σ forms also along slip lines and twin boundaries. Precipitates ofσ-phase have an acicular form; ordinarily, they are globular.

Temperature Effects in Microwave Ferrite Devices

With proper choice of shape, it is possible to minimize the frequency shift of ferromagnetic resonance in microwave ferrite components operating over a wide range of ambient temperatures. Calculations have been made for minimum resonance frequency shift change in saturation moment. Curves relating the resonance frequency shift as a function of saturation magnetization are plotted for several ferrite geometries. Design curves are presented for reducing dependence of resonance frequency on temperature.

The influence of chemistry onB/Hloop shape, coercivity and flux-reversal time in ferrites

The factors which influence the shape of the B/H loop, the coercivity, the permeability and the flux-reversal time in ferrimagnetic spinels are considered on two levels; a macroscopic and an atomic level. To minimize consideration of shape-dependent properties, the ferrite components are assumed to be toroids. With the assumption that domain walls are present in the material, coercivity, permeability, flux reversal and the influence of grain-boundary magnetic poles on B/H loop shape are determined in terms of measurable physical parameters of the material. From these relationships it is possible for the design engineer to determine the optimum parameters for a given application. The spinel-like magnetic oxides may, to the first approximation, be considered as ionic lattices. In order to obtain some insight into the control of the macroscopically measurable physical parameters by chemical composition and preparation procedures, as a second approximation the directional character of the ionic orbitals is emphasized to describe the influence of covalent effects on magnetic moment, magnetic exchange, and crystalline anisotropy. These effects are applied theoretically to the cations of particular interest in ferrites. Finally, some properties of several ferrites are displayed graphically to illustrate the importance of processing and chemistry on the magnetic character of ferrospinels.

Some current and future applications for ferrite components in radio and television receivers

Some current and future applications for ferrite components in radio and television receivers

Improved Microwave Noise Measurements Using Ferrites

The ferrite isolator and the ferrite circulator have been applied separately to improve the accuracy of measuring small microwave noise powers or small power differences. Either the isolator or the circulator effectively isolated the input circuit of a microwave receiver from the impedance of the source. As a result, the measurement errors introduced by mismatched source impedances were reduced by as much as 98 per cent. The added input circuit losses of the ferrite components reduced the receiver sensitivity by only about 10 per cent. Since the accuracy of measuring small noise power differences was limited principally by impedance errors, the addition of ferrite isolation to the receiver input circuit increased the sensitivity of measurement to near the theoretical limit. The ferrite isolator was used as a passive transmission element in these experiments. The ferrite circulator, however, was used as an electrically-operated, microwave switch. This switch was used to replace the mechanical chopper in a Dicke-type radiometer. In addition to impedance isolation, the ferrite switch makes possible rapid comparison measurements of the microwave noise powers from any two sources, or of the noise powers from the same source in two different polarizations.

Some Applications and Characteristics of Ferrite at Wavelengths of 0.87 Cm and 1.9 Cms

This paper describes the use of ferrites in waveguide to produce Faraday rotations at 0.87 cm and 1.9 cms wavelengths. The Dicke radiometric receiver is briefly reviewed and its improvement by the use of ferrite waveguide components is described. Experimental equipment for securing data on the behavior of ferrites is discussed. Details are given for the construction of a unidirectional waveguide transmission line for 0.87 cm wavelength.

Steam Piping for High Pressures and High Temperatures

Consideration of the following matters is made important by recent progress to high operating steam pressures and temperatures: the changing and more favourable distribution of stress in a pipe, the accompanying creep, and their application to the rational and economical design of steam piping; the determination of permissible working stress; differences in American and British procedures and consequent differences in stress magnitudes; the influence of operating fluctuations of pressure and temperature and the choice of a design temperature at rated pressure to provide for them; tentative considerations of behaviour of ferritic and austenitic steels; the action of creep at operating pressure and temperature in reducing and removing the initial thermal expansion loading of a pipe-line, and in imposing it fully when cold. In these connexions some consideration should be paid to bolted, or otherwise removable, joints at terminal or other special positions; the problem of making a joint between ferritic and austenitic steel piping and components; the factors of materials and corrosion; promised adequacy of existing ferritic steels for present requirements, and application of the principles operative at very high temperatures to piping for less advanced conditions, and economy arising therefrom.