Changes In Structure Of Material Research Articles

Use of pulse method for study of structural changes of materials

A dynamic pulse method for study thennophysical quantities of materials has been worked out. This method enables to estimate specific heat, thermal diffuslvlty and thermal conductivity within a single measurement. There were developed two types of measuring techniques for bulk materials and for thin metallic foils. The method is suitable for study of structural changes of materials.

Temperature dependence of magnetic anisotropy of textured polycrystalline materials

A method for the determination of the temperature dependence of several magnetic anisotropy constants (for example K 1( T), K 2( T) etc.) for a cubic ferromagnetic is proposed. The measurements were carried out on textured polycrystalline samples. The effective constants of the magnetic anisotropy for low-carbon cold rolled steels were determined by the torque curves for rotation about the perpendicular axis of the rolling plane for several temperatures. The K 1( T) relative temperature dependence for Fe is obtained. The temperature, above which material structural changes appear is found experimentally.

Technological implications in studies of nickel electrode performance and degradation

Several processes that are significant in sintered nickel electrode performance and degradation are addressed. The buildup of residual capacity is discussed in terms of the formation of a boundary layer between the current collector and the undischarged active material. The resistance characteristics that accompany the formation of the layer are presented, and the effects of changes in active material resistance and structure are correlated with electrode performance. Processes that can control nickel electrode recharge efficiency are also discussed, and data are presented indicating the kind of performance problems or changes that can be caused by changes in the interfacial morphology and physical structure of the active material deposit. Data are also presented indicating how variations in the composition of the active material can result during electrochemical deposition of active material into nickel electrodes.

Effects of diesel particle loading on screen diffusion batteries

Screen diffusion batteries are used to determine size distributions of submicron aerosols. Aerosols accumulate on the screen surface, causing a build-up of a dendrite structure that leads to the restriction of flow and an increase in aerosol collection efficiencies above those of clean screens. This report describes a study of the effect of diesel exhaust aerosol loading on the performance of diffusion batteries. The pressure drop across diffusion batteries, penetration of a test aerosol, and the microscopic structural changes of material on the screens were measured at successively increased loads. Our results showed that the continuous degrading of performance in terms of size distribution obtained by screen diffusion batteries was correlated to the microscopic structural changes of the material deposited on screens and the pressure drop increase. Of three types of screens tested, these effects increased with increasing mesh number (i.e. SS635 > SS400 > SS200). Thus, SS200 and SS400 mesh screens appeared to be more suitable as diffusion battery cell material for characterizing high concentration aerosols.

Prediction of transient mechanical response of type 316 stainless steel claddiing using an equation-of-state approach

Correlations of short-term mechanical properties of breeder reactor core component materials play an important role in design and safety analysis. A description of the short-term high strain-rate flow properties for 20% CW 316 SS was developed using a mechanical equation-of-state approach developed by Hart. The stress strain-rate relationship was developed from tensile yield strength data over the temperature range 427–871°C. The description, developed for constant structure or hardness, was then combined with simplified work hardening and recovery models to predict response of unirradiated 20% CW 316 SS over loading paths important to breeder reactor cladding. The advantage of the method is that it provides a description of mechanical response under a wide range of loading conditions, yet the formulation is simple in form with a single structure parameter used to describe material structure changes. The method is also shown to be applicable to neutron irradiated 316 SS. This implies that while neutron irradiation can change the hardness and ductility of 316 SS, the basic flow law is unchanged by irradiation.

Conducting filaments and switching phenomena in chalcogenide semiconductors

The sizes of the conducting filaments formed after switching operations in chalcogenide semiconductors have been measured as functions of input power in the on-state and specimen thickness using a scanning electron microscope. The experimental results show that the threshold switching involves double injection from both metallic contacts in the sandwich structure, and the combination of the electrothermal and the electronic processes. The conducting filament responsible for the switching consists of two permanent portions, one started from the anode and the other from the cathode, which have undergone a permanent change in material composition and structure after even one switching operation; and one temporary portion between the ends of the two permanent portions, which has not undergone any change in material composition or structure after many switching operations. The size of each portion depends strongly on the current level in the on-state, at which the filament is formed.

The early stages of stress removal in hydrostatically extruded copper

Two processes occur simultaneously in the early stages of annealing after hydrostatic extrusion of copper and its alloys with germanium, tin, and antimony: reduction of lattice defectiveness and redistribution of the dissolved component in association with changes in the structure of the material.

Recent Chemorheological Studies on Rubber Vulcanizates

Abstract The structural changes of materials caused by chemical reactions are reflected in the viscoelastic behavior of these substances. Such viscoelastic behavior induced by chemical reaction was termed “chemorheology” by Tobolsky. This phenomenon is not readily observed in linear polymers since molecular flow, because of diffusion or chemical reaction, is generally much more rapid than relaxation. It has become possible, however, to establish chemorheology of linear polymers, by taking physical flow into consideration. As there is no mechanism for flow in crosslinked polymers, the rheological behavior at sufficiently high temperatures is almost always determined by chemical reactions. A significant problem in the degradation of crosslinked polymers is the determination of whether the scission of the crosslinked polymer occurs along the main chains or at crosslink sites. Both extreme cases have been studied theoretically and experimentally by A. V. Tobolsky and coworkers, while the case in which both types of scission occur simultaneously was suggested by Horikx. However, because of the difficulty of analysis for the case of simultaneous occurrence of both types of scission, there is as yet nothing in the literature. This paper deals with the theoretical and experimental results of the chemorheological treatment of crosslinked polymers concerning their scission mechanisms.

Recent chemorheological studies on rubber vulcanizates

Abstract The structural changes of materials caused by chemical reactions are reflected in the viscoelastic behavior of these substances. Such viscoelastic behavior induced by chemical reaction was termed “chemorheology” by Tobolsky. This phenomenon is not readily observed in linear polymers since molecular flow, because of diffusion or chemical reaction, is generally much more rapid than relaxation. It has become possible, however, to establish chemorheology of linear polymers, by taking physical flow into consideration. As there is no mechanism for flow in crosslinked polymers, the rheological behavior at sufficiently high temperatures is almost always determined by chemical reactions. A significant problem in the degradation of crosslinked polymers is the determination of whether the scission of the crosslinked polymer occurs along the main chains or at crosslink sites. Both extreme cases have been studied theoretically and experimentally by A. V. Tobolsky and coworkers, while the case in which both ty...

Structural changes in materials exposed to liquid sodium

Structural changes in materials exposed to liquid sodium

比容積分析について

In this paper, we explain the method for analysing the structural changes of material by means of measuring the specific volume or gravity. As materials are to be affected in their specific volume or the gravity by the change of phase caused by heat treatment, aging and so on, and if the specific volume or the gravity reflects very sensibly the phase changes, we may be able to analyse the material conveniently by means of the precision chemical balnace only, without using special apparatus.So, we describe the measuring method, and by examining the data of the measurement, we know that the specific volume or the gravity well corresponds to the internal change.The results are consistent with the change of length ascertained by means of the dilatometer (it is natural that the change of specific volume of materials is affected by the third degree as compared with the length), and agree with the changes of the lattice constant observed by the X-ray analysis (it means that the lattice constant decreases with microscopic volume and the increases with expansion, and the change of the specific volume macrocopically corresponds to the microscopic change).We think the above justifies the analysis, and introduce some examples applied to the industrial method of the material analysis. That is: (1) Applying it on the analysis of the internal change in steel, iron and brass caused by heat treatment, there is a change peculiar to material in specific volume, so we can exactly know the internal change in composition. (2) And using the analysis of the aging in aluminium and its alloys, we can obtain the data as an aid for analysing the aging mechanism.

Domain Pattern in Silicon-Iron under Stress

This paper discusses investigations into the detailed changes in domain structure of ferromagnetic material under externally applied stress. The changes in the domain pattern of grain-oriented silicon steel with large grain size were observed and photographed while the specimen was stressed in tension.Experiments in which the grain under observation had the {110} plane in the surface of the specimen and the $〈110〉$ direction parallel to the specimen axis, along which tension was applied, are discussed in detail. At a load of approximately 0.2 kg/${\mathrm{mm}}^{2}$ the original domain pattern vanishes. After a transition stage in which, over a certain range of loads, no pattern is visible at all, a new stress-induced domain pattern appears. The behavior of these patterns in horizontal and vertical magnetic fields was studied, and an interpretation of both the transition stage and the stress-induced pattern is given. In these experiments the applied stresses are all within the elastic range of the material. In the plastic range, the knowledge of the stress-induced pattern permits the detection of residual lattice strains in suitably oriented materials.