Subjects: Other Disciplines >> Synthetic discipline submitted time 2023-03-28 Cooperative journals: 《中国科学院院刊》
Abstract： To realize sci-tech self-reliance and self-strengthening at higher levels in China, it is imperative for disruptive technologies to embark on a new journey and open new horizons. The layout and development of disruptive technologies is a complicated and systematic project with strategic significance, in which the identification of disruptive technologies holds the key and serves as the premise. To this end, based on the underlying logic that disruptive technologies are destined to transit from marginalized forces to mainstream power in the future through the process of 10→3→1 constringency, on the understanding that the generation of disruptive technologies is driven by science and technology, the study puts forward the identifying approach of “identifying-selecting-evaluating”, and develops a methodological framework for identifying disruptive technologies based on science with a view to providing reference for the early identification of disruptive technologies.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The effect of defects in metal Ti such as vacancies, self-interstitial atoms and impurity He atoms on mechanical properties of metal Ti sample was studied using molecular dynamics simulation. First, the stressstrain curves of perfect Ti sample at different strain rates were calculated. The results show that the stretching process can roughly be divided into three stages, elastic deformation, plastic deformation and fracturing. For comparison the stress-strain curves of metal Ti samples with vacancies, self-interstitial atoms and impurity He atoms were researched, respectively, in which the strain rate was set as 2�109 s- 1. Finally the corresponding Young's moduli were calculated. It is found that after carefully investigating that the mechanical properties of metal Ti are degraded by each of these effects in it and the degradation degree increases with increasing defect concentration. However, the stretching process of samples is not essentially affected by these effects (the stress-strain curves of Ti samples with defects have still 3 stages). In this process, self-interstitial atoms in samples always exist for they to be bonded by metal Ti atoms, but impurity He atoms in samples are released due to their extraordinarily low solution in metal Ti.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-19 Cooperative journals: 《金属学报》
Abstract： The formation of amorphous phase has been investigated in U-Co system over a wide range of compositions, namely, UxCo100-x (x=50~87.5) by mean of melt-spinning. Phase identification for the arc-melted ingots and rapidly quenched alloys, and the thermal stability of the amorphous phases thus formed have been examined by XRD and DSC, respectively. The component phases in the ingot alloys were structurally the same as those presented in U-Co phase diagram, but were associated with a certain compositional metastability. Rapid quenching experiment revealed that the ease of formation of amorphous phase occurred within the composition range of 58.5≤x≤78, and amorphous phase was most readily formed in the vicinity of U66.7Co33.3 composition. The dynamical crystallization temperatures of the amorphous phases were determined to be 534~550 K at a DSC heating rate of 20 K/min, and the highest reduced crystallization temperature (relative to the liquidus temperature) as calculated to be 0.535, and moreover, the exothermal enthalpies of crystallization were determined to be in a range of 4.8~8.5 kJ/mol. Upon room temperature electrochemical polarization in a 50×10- 6 Cl- electrolyte, these amorphous alloys exhibited corrosion potentials as high as about -50 mV, being much more positive than that of depleted uranium. In these amorphous alloys, it has also been found that the rust resistance performance appears to be parallel to the ease of amorphous phase formation.
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