There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

The major increase in discharge duration and plasma energy in a next step DT fusion reactor will give rise to important plasma-material effects that will critically influence its operation, safety and performance. Erosion will increase to a scale of several centimetres from being barely measurable at a micron scale in today's tokamaks. Tritium co-deposited with carbon will strongly affect the operation of machines with carbon plasma facing components. Controlling plasma-wall interactions is critical to achieving high performance in present day tokamaks, and this is likely to continue to be the case in the approach to practical fusion reactors. Recognition of the important consequences of these phenomena stimulated an internationally co-ordinated effort in the field of plasma-surface interactions supporting the Engineering Design Activities of the International Thermonuclear Experimental Reactor project (ITER), and significant progress has been made in better understanding these issues. The paper reviews the underlying physical processes and the existing experimental database of plasma-material interactions both in tokamaks and laboratory simulation facilities for conditions of direct relevance to next step fusion reactors. Two main topical groups of interaction are considered: (i) erosion/redeposition from plasma sputtering and disruptions, including dust and flake generation and (ii) tritium retention and removal. The use of modelling tools to interpret the experimental results and make projections for conditions expected in future devices is explained. Outstanding technical issues and specific recommendations on potential R&D avenues for their resolution are presented.

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Plasma{material interactions in current tokamaks and their implications for next step fusion reactors

This review article aims to provide an updated and comprehensive description of the development of the Electric Current Activated/assisted Sintering technique (ECAS) for the obtainment of dense materials including nanostructured ones. The use of ECAS for pure sintering purposes, when starting from already synthesized powders promoters, and to obtain the desired material by simultaneously performing synthesis and consolidation in one-step is reviewed. Specifically, more than a thousand papers published on this subject during the past decades are taken into account. The experimental procedures, formation mechanisms, characteristics, and functionality of a wide spectrum of dense materials fabricated by ECAS are presented. The influence of the most important operating parameters (i.e. current intensity, temperature, processing time, etc.) on product characteristics and process dynamics is reviewed for a large family of materials including ceramics, intermetallics, metal–ceramic and ceramic–ceramic composites. In this review, systems where synthesis and densification stages occur simultaneously, i.e. a fully dense product is formed immediately after reaction completion, as well as those ones for which a satisfactory densification degree is reached only by maintaining the application of the electric current once the full reaction conversion is obtained, are identified. In addition, emphasis is given to the obtainment of nanostructured dense materials due to their rapid progress and wide applications. Specifically, the effect of mechanical activation by ball milling of starting powders on ECAS process dynamics and product characteristics (i.e. density and microstructure) is analysed. The emerging theme from the large majority of the reviewed investigations is the comparison of ECAS over conventional methods including pressureless sintering, hot pressing, and others. Theoretical analysis pertaining to such technique is also proposed following the last results obtained on this topic.

Consolidation/synthesis of materials by electric current activated/assisted sintering

http://liu.diva-portal.org/smash/get/diva2:303552/FULLTEXT01

The Mn+1AXn phases: Materials science and thin-film processing

The MAX phases are a group of layered ternary compounds with the general formula Mn+1AXn (M: early transition metal; A: group A element; X: C and/or N; n = 1–3), which combine some properties of metals, such as good electrical and thermal conductivity, machinability, low hardness, thermal shock resistance and damage tolerance, with those of ceramics, such as high elastic moduli, high temperature strength, and oxidation and corrosion resistance. The publication of papers on the MAX phases has shown an almost exponential increase in the past decade. The existence of further MAX phases has been reported or proposed. In addition to surveying this activity, the synthesis of MAX phases in the forms of bulk, films and powders is reviewed, together with their physical, mechanical and corrosion/oxidation properties. Recent research and development has revealed potential for the practical application of the MAX phases (particularly using the pressureless sintering and physical vapour deposition coating rout...

Progress in research and development on MAX phases: a family of layered ternary compounds

A recently developed nondestructive method, called Magnetic Adaptive Testin g was applied for investigation of flake graphite cast iron samples having various metallic matrices and graphite structures. MAT is typical by its low required magnetization of samples, because it is based on measurement of families of minor magnetic hyst eresis loops. The flat samples were magnetized by an attached yoke and sensitive descriptors of their magnetic/structural state were obtained from evaluation of the measured d ata. Ultrasonic velocity measurements were performed and results of the non -destructive magnetic tests were compared with these data. A very good correlation was found between the magnetic descriptors and u ltrasonic velocity. Cast iron is one of the most frequently used industrial construction materials. Low cost of production, good ma- chinability, and excellent possibilities of shaping the details by casting attract an intense interest of industry. The cast irons are generally many-component alloys of iron with large content of carbon. The cast iron structure is classified by its metallic matrix composition (ferrite, pearlite, carbides, etc.) and by morphology of its graphite inclusion. The mechanical properties are fundamentally dependent both on the matrix composition and on the graphite shape (flaky, spheroidal, vermicular, etc.), size and density (1). One of the types of cast iron - the flake graphite cast iron - is frequently used for mechanical components in bearings, brake shoes, etc. be- cause of its high wear resistance and damping capacity. The flake graphite cast iron is an ideal material for automobile brake disks since it has excellent damping properties and thermal conductivity just because of the flaky graphite. A nondestructive inspection of construction materials made of cast iron is highly desirable. Various non-destructive evaluation techniques have been examined so far, as eg alter- nating current potential drop (2), laser acoustic wave (3), ultrasonic back-scattering (4), or eddy currents (5). Graphite and other structures composing the cast iron matrices may be evaluated using electromagnetic properties such as conduc- tivity and permeability (6). Magnetic measurements are also frequently used for characterization of changes in structure of ferromagnetic materials, because magnetization processes are closely related to microstructure of the materials. This fact also makes magnetic measurements an obvious candidate for non-destructive testing, for detection and characterization of any defects in materials and manufactured products made of such materials (7). One of the most frequently used magnetic measurements is the detection of B-H curve. Structural non- magnetic properties of ferromagnetic materials have been non-destructively tested using traditional magnetic hysteresis measurement methods for a long time with fair success. A number of techniques have been suggested, developed and currently used in industry, see eg (8). They are mostly based on detection of structural variations via the classical macro- scopic parameters of hysteresis loops. An alternative, more sensitive and more experimental- ly friendly approach to this topic was considered recently, based on magnetic minor loops measurement. The survey of this technique can be found in (9). The method, called Magnetic Adaptive Testing (MAT) was presented, which introduced general magnetic descriptors to diverse varia- tions in non-magnetic properties of ferromagnetic materi- als, optimally adapted to the just investigated property and material. MAT was successfully applied for characteriza- tion of material degradation in different specimens and it seems to be an effective tool eg for replacement of the destructive hardness and/or ductile-brittle transition tem- perature measurements. In this work the direct correlation between MAT pa- rameters and ultrasonic velocity in flake graphite cast iron is studied using samples with different graphite structures and matrices. Although ultrasonic velocity is not consid- ered as the most important parameter of cast irons, it is a frequently measured quantity. The micro-structure of flake graphite cast iron is the most important parameter from point of view of cast iron properties. The correlation between graphite morphology and magnetic parameters has already been studied recently (10) based on the meas- urements performed on three as cast samples with differ- ent chemical compositions. It was also shown that ultra- sonic velocity depends on the area fraction and length of graphite (6) on the same samples. The purpose of the present work is to study the direct correlation between ultrasonic velocity and MAT parame- ters on three series of flake graphite cast iron samples, where apart from as cast samples two kinds of heat treat- ments (annealing to obtain a ferrite based matrix and nor-

/pdf/correlation-between-ultrasonic-velocity-and-magnetic-2u7jq7mic7.pdf

Correlation between ultrasonic velocity and magnetic adaptive testing in flake graphite cast iron

. In this paper, we numerically study Turing patterns by the Finsler geometry (FG) modeling technique on thermally ﬂuctuating triangular lattices, which are often used for modeling cell membranes or lipid membranes, focusing on the origin of diffusion anisotropy. The FG modeling prescription allows us to assume direction-dependent diffusion described by Laplacian. To implement such diffusion anisotropy in the FG modeling, we need an internal degree of freedom (IDF), which depends on direction and position and is controlled by some external forces or stimuli. For such a direction-dependent IDF, we use velocity directions corresponding to thermal ﬂuctuations of the lattice vertices. We ﬁnd that anisotropic Turing patterns emerge in the direction along which vertices ﬂuctuate. In the simulations, direction-dependent diffusion coefﬁcients are unnecessary for input, and instead, the IDF aligns the direction of vertex ﬂuctuation along a direction implemented by external stimuli. Our results and techniques provide insight into the origin of diffusion anisotropy connected to Turing patterns.

Origin of anisotropic diffusion in Turing Patterns

Although electrochemical transients can provide very sensitive indication about the onset of localized corrosion, including initiation of stress corrosion cracking (SCC), information on location of the initiation site is not available. In the present study, we proposed an estimation method of location and magnitude of SCC initiation events, where electrochemical transients associated with local anodic events are measured by multiple reference electrodes and location of the initiation sites are estimated based on relative magnitude of the electrochemical transients simultaneously measured at multiple locations.

Tetsuya Uchimoto

Papers

Correlation between ultrasonic velocity and magnetic adaptive testing in flake graphite cast iron

Origin of anisotropic diffusion in Turing Patterns

Estimation Method of SCC Initiation Site Based on Electrochemical Transients