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

Tribological properties of partly polished diamond coatings

Plastic deformation may occur in a mechanical structure during its manufacturing and service process, and may cause serious problem in the structural integrity. Therefore, a reliable pre-service or in service quantitative non-destructive evaluation (NDE) of plastic deformation is very important especially for a structure after suffering giant load such as a large earthquake. However, there is still no satisfactory method being established for the quantitative NDE of plastic deformation in key structures such as those of a nuclear power plant. For this purpose, three electromagnetic NDE methods, i.e., Magnetic Barkhausen Noise (MBN), Magnetic Incremental Permeability (MIP) and Magnetic Flux Leakage (MFL) method are studied via experiments in this paper to investigate their feasibility for evaluation of plastic deformation in carbon steel SS400. A special testing system integrated these three electromagnetic NDE methods is established to measure the magnetic property of testpieces with different plastic deformation, which was introduced by a tensile testing machine. It is found that the measurement signals of all these three methods have clear correlation with the plastic strains and show coincident tendency, which reveals the validity of these methods for the quantitative evaluation of plastic deformation. Among these methods, the MFL signals are of higher stability and repeatability but of relative low spatial resolution. The MBN method can give better resolution but of bigger standard deviation and is also not valid to evaluate a plastic strain of large scale. On the other hand, the MIP signals are more sensitive to the liftoff of sensor and to the remanent magnetization status, i.e. of more noise. Therefore, to measure the feature parameters of these three methods at the same time with an integrated testing system and to evaluate the plastic strain through signal fusion may give a better detectability and evaluation precision. [doi:10.2320/matertrans.M2014173]

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Quantitative Nondestructive Evaluation of Plastic Deformation in Carbon Steel Based on Electromagnetic Methods

To accurately measure crack lengths, we developed a real-time surface imaging method (SAW PA) combining an ultrasonic phased array (PA) with a surface acoustic wave (SAW). SAW PA using a Rayleigh wave with a high sensitivity to surface defects was implemented for contact testing using a wedge with the third critical angle that allows the Rayleigh wave to be generated. Here, to realize high sensitivity imaging, SAW PA was optimized in terms of the wedge and the imaging area. The improved SAW PA was experimentally demonstrated using a fatigue crack specimen made of an aluminum alloy. For further verification in more realistic specimens, SAW PA was applied to stainless-steel specimens with a fatigue crack and stress corrosion cracks (SCCs). The fatigue crack was visualized with a high signal-to-noise ratio (SNR) and its length was measured with a high accuracy of better than 1 mm. The SCCs generated in the heat-affected zones (HAZs) of a weld were successfully visualized with a satisfactory SNR, although responses at coarse grains appeared throughout the imaging area. The SCC lengths were accurately measured. The imaging results also precisely showed complicated distributions of SCCs, which were in excellent agreement with the optically observed distributions.

/pdf/ultrasonic-phased-array-with-surface-acoustic-wave-for-oa4aaqphvx.pdf

Ultrasonic phased array with surface acoustic wave for imaging cracks

Machinable ceramic substrate for CVD diamond coating

Accurate and simple magnetic material law is necessary to correctly model the complete electromagnetic systems. In this article, a new formulation based on the scalar quasi-static hysteresis Jiles-Atherton model extended to dynamic behavior using fractional derivative dynamic contribution is proposed. The fractional contribution is solved using convolution which highly reduces the numerical issues. The order of the fractional derivation provides a new degree of freedom and allows to obtain correct simulation results on a very large frequency bandwidth. By using such a formulation, highly space and time consuming space discretization techniques (finite differences, finite elements) are avoided while keeping the global accurate simulation results.

Dynamic Magnetic Scalar Hysteresis Lump Model Based on Jiles–Atherton Quasi-Static Hysteresis Model Extended With Dynamic Fractional Derivative Contribution

Tetsuya Uchimoto

Papers

Tribological properties of partly polished diamond coatings

Quantitative Nondestructive Evaluation of Plastic Deformation in Carbon Steel Based on Electromagnetic Methods

Ultrasonic phased array with surface acoustic wave for imaging cracks

Machinable ceramic substrate for CVD diamond coating

Dynamic Magnetic Scalar Hysteresis Lump Model Based on Jiles–Atherton Quasi-Static Hysteresis Model Extended With Dynamic Fractional Derivative Contribution