Two-Step Preparation of Hierarchical Porous Carbon Materials Derived from Tannin for Use as an Electrode Material for Supercapacitors

The development and utilization of biomass and agroforestry processing byproducts for high-value applications have been an important topic in the field of renewable materials research.Based on this,a two-step microwave hydrothermal pre-carbonization and KOH activation method was proposed to synthesize tannin-based activated carbons with a high specific surface area,hierarchical pore structure,and good electrochemical performance.The microstructure,texture properties,and physicochemical characteristics were investigated.The results show that the prepared tannin-based activated carbons presented a hierarchical pore structure(micro-and mesopores)with a specific surface area as high as 997.46 m^(3) g^(−1).The electrochemical analysis shows that the tannin-based activated carbons have good wettability and charge transfer rates.Under the three-electrode system with 6 M KOH as the electrolyte,the active material TAC_(600-4) had a maximum specific capacitance of 171 F g^(−1)at 0.5 A g^(−1).As the current density increases to 10 A g^(−1),the specific capacitance can still be maintained at 149 F g^(−1),indicating a good rate capability.Therefore,the specific surface area and pore size of tannin-based activated carbons can be effectively adjusted by the alkali/carbon ratio,making it a promising supercapacitor electrode material and providing a new method for the high-value development of tannins in the field of electrochemical energy storage.

Study on Microwave Pretreatment Technology to Improve the Effect of Shellac Impregnation of Fast-Growing Chinese Fir

To improve the mechanical properties of fast-growing Chinese fir(Cunnighamia lanceolate),expand its range of application,increase its value,and avoid the environmental pollution caused by impregnation with synthetic resin,Chinese fir was impregnated with a shellac solution.Since the shellac solution was difficult to penetrate into fast-growing Chinese fir,so microwave pretreatment was used to irradiate the wood to improve the permeability.This study investigated the effects of four factors,including the content of moisture in the wood before it was microwaved,the chamber pressure of microwave,the time of microwaving and the vacuum impregnation on the mechanical properties of Chinese fir wood.When the moisture content of wood before microwave was approximately 50%–60%,after microwaving and impregnation,the ultimate strength in static bending(modulus of rupture[MOR])and strength in compression perpendicular to the grain(SCPG)of the wood increased significantly.A microwave time of 100 seconds was more effective at improving the MOR and SCPG of the wood.If the wood was microwaved for too short or long period of time,the microwave pretreatment was not effective.When the samples were immersed in shellac for a longer period,the MOR and SCPG of Chinese fir gradually increased,but when the wood was impregnated for more than 12 hours,the increases were not significant.After the shellac penetrated the Chinese fir wood,it spread on the inner wall surface of tracheid to form a shellac film and easily formed plug-like deposits in microcapillaries.The use of Fourier-transform infrared spectroscopy,scanning electron microscopy and scanning electron microscopy-energy dispersion x-ray indicated that the microwave pretreatment can destroy the pit membranes on tracheids and facilitate the ability of shellac to penetrate the channel.

后纵隔外周型原始神经外胚层肿瘤:一例病例报道(英文)

Peripheral primitive neuroectodermal tumor(pPNET) is an extremely rare disease entity of malignant tumors belonging to the Ewing sarcoma family that usually occurs in children and adolescents. We describe a 41-year-old female who presented with right upper abdominal pain. Surgical resection and biopsy revealed small round-cell tumor. Combined with immunohistochemical analysis, pPNET was diagnosed. No evidence of recurrence was noted at 18 months postoperatively. Even thought pPNET is a highly malignant tumor, Wide tumor-free resection and multi-agent chemotherapy can also obtain good clinical outcomes.

Automatic detection and assessment of crack development in ultra-high performance concrete in the spatial and Fourier domains

Automatic detection and assessment of surface cracks are beneficial for understanding the mechanical performance of ultra-high performance concrete(UHPC).This study detects crack evolution using a novel dynamic mode decomposition(DMD)method.In this method,the sparse matrix‘determined’from images is used to reconstruct the foreground that contains cracks,and the global threshold method is adopted to extract the crack patterns.The application of the DMD method to the three-point bending test demonstrates the efficiency in inspecting cracks with high accuracy.Accordingly,the geometric features,including the area and its projection in two major directions,are evaluated over time.The relationship between the geometric properties of cracks and load-displacement curves of UHPC is discussed.Due to the irregular shape of cracks in the spatial domain,the cracks are then transformed into the Fourier domain to assess their development.Results indicate that crack patterns in the Fourier domain exhibit a distinct concentration around a central position.Moreover,the power spectral density of cracks exhibits an increasing trend over time.The investigation into crack evolution in both the spatial and Fourier domains contributes significantly to elucidating the mechanical behavior of UHPC.

Tribological properties of low-temperature time-dependent pretreated graphite for mechanical seal pairs in high-speed turbopump

The friction coefficient and wear rate of pretreated graphite with liquid nitrogen were obtained by using a ball-on-disk tester,and the wear of GCr15–graphite seal pairs with the low-temperature time-dependent pretreatment was discussed by comparing the wear morphology.The results show that liquid nitrogen pretreatment can affect the hardness and interlayer spacing of graphite.The range of the friction coefficients of pretreated graphite changes from 0.17 to 0.22.With the increase of liquid nitrogen pretreatment time,the wear mechanism of graphite would change from dominated three-body wear to adhesion wear.The experimental results of the mechanical seal with liquid nitrogen pretreatment show that the wear rate of stator is less than 0.00165 mm^(3)·N^(−1)·m^(−1),and the graphite shows a good low-temperature compatibility.

Friction and wear behavior of different seal materials under water-lubricated conditions

The shaft mechanical face seal in a high-speed turbopump of a liquid rocket engine often operates under extremely harsh conditions.For example,a low-temperature and low-viscosity fluid(such as liquid oxygen or liquid hydrogen)is used as a lubricant.The performance of the seal rings,especially the friction and wear behavior,directly determines whether the seal functions normal.In this study,the friction and wear behavior of several ring materials are tested using a pin-on-disk tribo-tester,and the wear morphology of the ring is investigated.The friction coefficients(COFs)and mass-wear rates under dry-friction and water-lubricated conditions,which are used to simulate low-viscosity conditions,are obtained.The results show that at a pressure-velocity(PV)value of 2.4 MPa-(m/s),the COF between the copper graphite(stator)and copper-chrome alloy disk(rotor)is low(with a value of 0.18)under the dry-friction conditions,and the 5-min wear mass of the copper graphite is approximately 2 mg.Under the water-lubricated conditions,compared with other materials(such as copper-chrome alloy,S07 steel,alumina ceramic coating,and nickel-based calcium fluoride),the S07 steel with a diamond-like carbon film is preferred for use in a high-speed turbopump under extreme conditions.The results of this study can provide theoretical and experimental guidance in the design of mechanical face seals in liquid rocket engines.