Biomass-derived bamboo charcoal has received significant research attention as electrode material for supercapacitors due to its abundant re-sources,low cost,excellent electrical conductivity,and tunable surface architecture.In this study,bamboo sawdust was employed as the precursor,potassium bicarbonate(KHCO3)was used as a porogen,and a hot-pressing technique was applied to densify the raw material,resul-ting in bamboo-derived carbon with a high specific surface area.The results indicated that the bamboo biochar treated by physicochemical syner-gistic activation had a well-developed porous structure(specific surface area of 1 205 m2/g,pore volume of 0.639 cm3/g).It exhibited a high specific capacitance of 372 F·g-1 at 0.5 A·g-1 and maintained 70.4％capacitance retention after 3 000 cycles at a high current density of 10 A·g-1,which showed good electrochemical stability.Therefore,the synergistic hot-pressing and KHCO3 activation is an effective strategy for enhancing the electrochemical performance of biochar.
The mechanical properties of polypropylene(PP)and polycaprolactam(PA6)were analyzed after they were immersed in three common automobile stain solutions,namely,No.95 gasoline,glass water and car wash liquid,respectively.The common machine learning methods such as grey correlation degree and technique for order preference by similarity to ideality were used to analyze and process the mechanical property data of the material after immersion,and the comprehensive evaluation was carried out,and the reliability of machine learning in the application of material property exploration was verified by material mechanism analysis and tensile fracture morphology analysis.The results showed that glass water and car washing liquid had little effect on the mechanical properties of polypropylene and great effect on the mechanical properties of polycaprolactam,95 gasoline had little effect on the mechanical properties of polycaprolactam and great effect on the mechanical properties of polypropylene.The comprehensive anti-aging value of polycaprolactam soaked in 95 gasoline was the highest in all six groups of tests,and the anti-aging performance was the best.The comprehensive anti-aging value of polypropylene soaked in No.95 gasoline is the lowest among all the six groups of tests,and the anti-aging performance is the worst.
Displacement-controlled cyclic compressive responses of polycrystalline superelastic NiTi shape memory alloys (SMAs) are investigated at a maximum strain epsilon(max) of 4.2 % and over frequencies ranging from 0.0007 Hz to 50 Hz in stagnant air. Our focus was on understanding the interactions among phase transition (PT), heat transfer and plastic flow of austenite phase during cyclic operation. We monitored temperature oscillations along with stress-strain relations and observed a critical frequency f(cri)(AY), below which the responses were primarily influenced by the frequency-dependent coupling between PT and heat transfer, and above which macroscopic plastic deformation of the austenite phase played an important role in the cycling process, interacting with PT and heat transfer. Such interactions at high frequencies (f>f(cri)(AY)) led to reductions in temperature magnitude, transition strain, latent heat, and hysteresis heat in subsequent cycles, eventually leading to stabilized responses without plastic deformation. Theoretical analysis considering the interactions among PT, heat transfer, and plastic deformation was conducted to interpret and quantify the experimental findings. We find that the initiation and saturation of macroscopic plastic deformation of SMAs due to heat accumulation acted as a negative feedback mechanism in the cyclic responses, preventing the materials from overheating and potential damage in applications.
To clarify the mechanical behavior and deformation mechanism of rare earth magnesium(Mg)alloy WE43 under extreme service loads,high-speed impact tests under various deformation temperatures and loading paths were conducted using a split Hopkinson pressure bar.The flow stress along extrusion direction(ED)and extrusion radial direction(ERD)decreases apparently with deformation temperature.Compared with conventional Mg alloys,it exhibits a slight anisotropy and an unusual C-shaped char-acteristic.Cellular dislocation,mechanical twin and fine grain that occur after high-speed impact deformation are insensitive to the loading direction,but strongly dependent on the deformation tem-perature,especially superimposed with adiabatic temperature rise.As a result,dynamic recrystallization(DRX)occurs even at an ambient temperature of 25 ℃.Double twinning and prismatic slip or pyramidal slip are the dominant deformation mechanisms at 25 ℃.These twins induce mechanical cutting refinement to form some fine-grained structures,accompanied by a small number of fine grains by twinning induced DRX.In contrast,the deformation at 250 ℃ is mainly controlled by prismatic slip and pyramidal slip,accompanied by various types of twinning in early deformation stage.Compared with 25 ℃,more fine-grained microstructures are formed at 150 and 250 ℃ through a synergy mechanism of twinning induced mechanical cutting and twinning induced DRX.
Currently,uranium molybdenum alloy(U-Mo)is a very popular fuel used in research reactors,space reactors,and small reactors for special purposes.During the irradiation process,the microstructure of the U-Mo fuel will undergo a series of changes,which may affect the fuel performance during reactor operation.These changes mainly include:the formation of the interaction layer between the U-Mo fuel core and the matrix,the release of fission products(mainly the release of fission gas),and the refinement of the grain size for U-Mo fuel with high burnup.This article summarizes the main characteristics of the above changes and the latest research progress for them.At the same time,it also proposed the development trends in the study of microstructural changes after fuel irradiation in today's world where advanced detection technology has made significant progress.
