International conference on materials and mechanisms of superconductivity

International conference on materials and mechanisms of superconductivity

the industry-previews-research ,, the industry-previews-research volved in the development of cryogrinding technology for 20 years, through, to date,...

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the industry-previews-research ,, the industry-previews-research

volved in the development of cryogrinding technology for 20 years, through, to date, the company has marketed this technology by selling its equipment and supply of liquid nitrogen to British industry. Now the company has also recognized the market for a contract grinding service in the UK and is building its own facility at its Applied Research and Development Centre at Crewe, Cheshire

(UK).

Customers are asked to transport their materials to the UK facility, where the materials are processed and returned to the customer. Materials being processed by Air Products Ltd at present include polyesters, polyamides, EVA compounds, polyurethanes, and other thermoplastic polymers. Other materials which are being processed in this country using cryogrinding technology include colour

concentrates/pigments, powder coatings, rubbers, metals and a range of plastics. Almost any product that requires fine grinding without experiencing heat build-up or degradation, may be suited to the cryogrinding process offered by Air Products Ltd. Customer trials can be run at the Air Products facility at Crewe. (Air Products Limited, Hersham Place, Molesey Road, Walton-onThames, Surrey KT1 2 4RZ, UK)

International Conference on Materials and M e c h a n i s m s of Su perco ndu ct ivity Ames, IA, USA, 29-31 May 1985 The International Conference on Materials and Mechanisms of Superconductivity was held from May 29 to 31, 1985, at Iowa State University, Ames, IA 50011, USA. This conference, which was originally called the "Superconductivity in d- and f-Band Metals Conference', was expanded in scope and renamed to reflect the growth and changes in the field, It was a two and a half day conference involving 231 scientists from 14 countries. There were 33 plenary oral papers and 96 poster papers. Discussions centred primarily on the development of a fundamental understanding of the mechanisms which cause superconductivity and the discovery of new superconducting materials with unusual physical properties. The first day of the conference was dominated by discussions of heavy fermion superconductors. These materials have effective masses of the order of 100-1000 times the free electron mass. Specific heat-/values and the jump in specific heat at the transition temperature are of the order of joules per mole (Kelvin) 2, so they are qualitatively different from the ordinary s- and p-band superconductors of the transition metal superconductors. These phenomena usually occur just as the ltstates delocalize and this class of materials is thought to be a good place to look for p-wave or d-wave pairing. It is clear that the Fermi surface in this class of materials can be highly anisotropic. There are many clues, such as neutron scattering and ultrasonic attenuation, which point to the likelihood of p-wave pairing but conclusive proof has not yel appeared. Many of these materials seem to require a high density of states at the Fermi level, substantial electron phonon interactions, and incipient magnetic instability to explain their behaviour.

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Cryogenics 1985 Vol 25 October

On the second day, there were extensive discussions of layers and interfaces, tunnelling localization, amorphous and disordered materials, and the coexistence of superconductivity and magnetism. There has been a significant deepening of our understanding of these phenomena and real progress in the quantitative and predictive capacity of the theory. The report of superconductivity in simple hexagonal silicon (AAAA stacking) was particularly important because the theory of the pairing interaction is well established for this material. On the third day, discussion included a theory session on new mechanisms, a study of low carrier density superconductors. It is clear that a variety of physical processes can lead to pairing and the long range coherent effects of superconductivity other than the usual s-wave electron-phonon mechanism. Discussions centred on the basic ideas involved in phenomena such as dielectric effects, electron-hole coupling spin fluctuations and bipolaronic response, as well as on the character of the experiments needed to definitely show which of these effects contributes to the superconductivity. A true highlight of the conference came with the announcement of some high temperature Tc organic superconductors among the (BEDT-TTF)2 trihalides. A material with Tc = 8 K was reported by Murata of the Electrotechnical Laboratory of Ibaraki, Japan and a material with T c = 5 K was reported by Williams of the Argonne National Laboratory of USA. There is substantial opportunity to fine-tune the physical properties of these organic materials and this field is still wide open for further advances.

D.K Finnemore Ames Laboratory, Iowa State University, Ames, IA 5001 I, USA