Ultrafast regulation of nano-scale matrix defects using electrical property discrepancies to delay material embrittlement

Nano-scale phases can enhance or reduce the mechanical properties of materials,so it is very important to control the size of the phases.Copper-rich nanoclusters as matrix defects will significantly reduce the performance of materials for key nuclear power components,while traditional heat treatment method has a technical bottleneck for the dissolution of nanoclusters.A new method of using the inherent electrical property discrepancies between the matrix material and the nanoclusters to effectively dissolve the nanoclusters through pulsed electric current to realize the recovery of material aging degradation performance is proposed.The performance evolution of simulated steel in the aging-external field repair cycle was studied,and it was found the dislocations as the preferred nucleation sites of nanoclusters were regulated in virtue of the non-thermal effect of current,resulting in a decrease in dislocation density and entanglement release.In the subsequent thermal aging process,the embrittlement rate of the aged and tempered material trained by the electric pulse was slower than that of the untreated sample.When moving dislocations are pinned by nanoclusters under high stress,nano-scale dislocations can be induced into the clusters.The dislocations near the nanoclusters and the newly formed nano-scale dislocations in the nanoclusters act as fast diffusion channels,which can further accelerate the dissolution of the nanoclusters.

Artificial periosteum in bone defect repair--A review

Periosteum is a thin membrane that encases the surfaces of most bones.It is composed of an outer fibrous layer contains longitudinally oriented cells and collagen fibers and an inner cambial layer that consists of multipotent mesenchymal stem cells（MSCs）and osteogenic progenitor cells.Periosteum has a function of regulating cell and collagen arrangement,which is important to the integrity,modelling and remodelling of bone,particularly during bone defect repair.Apart from autograft and allograft,artificial periosteum,or tissue-engineered periosteum mimicking native periosteum in structure or function,made up of small intestinal submucosa,acellular dermis,induced membrane,cell sheets,and polymeric scaffolds,and so on,has been developed to be used in bone defect repair.In this review,we classify the artificial periosteum into three approaches based on the material source,that is,native tissues,scaffoldfree cell sheets and scaffold-cell composites.Mechanisms,methods and efficacy of each approach are provided.Existing obstacles and enabling technologies for future directions are also discussed.