Very high critical current densities (Jc=8×105 A/cm2 at 4.2 K and 6 T) have been achieved in commercial Nb3Sn tape and more recently in multifilamentary Nb3Sn superconductors. The relative contributions of two types of pinning centers, grain boundaries and second phase particles, to flux pinning have been determined by correlating Jc with microstructure. It was found that grain boundaries were the only defect present in sufficient density to account for flux pinning in the multifilamentary Nb3Sn material. The dependence of Jc on grain size was measured, and the relationship between pinning force and grain size is discussed in terms of current theories for flux pinning in type-II superconductors.

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A study of the oxygen absorption characteristics and the nature of the products obtained from oils oxidizing under controlled conditions has permitted the evaluation of a number of factors involved in lubricating oil deterioration.Investigation of selected fractions of a distillate stock has shown considerable variations in reactivity toward oxygen.The rate of oxygen absorption approximately doubles for each 100 C. temperature increase over the interval 140°to 180°C ., provided it is not limited by physical factors. The presence or absence of water vapor in the oxidizing atmosphere has little effect on the oxidation of one type of oil.The oxidation of certain oils can be reduced greatly by adding natural or synthetic inhibitors.

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