In order to evaluate the performance of the physical foaming warm-mix recycled asphalt mixture (WRAM), the hot mix plant recycling technology was adopted to develop AC-20 hot-mix recycled asphalt ...mixture (HRAM) and the WRAM of different reclaimed asphalt pavement (RAP) contents. The high temperature stability, water stability and low temperature crack resistance performance of the reclaimed asphalt pavement were evaluated. The results indicate that the physical foaming WRAM feature better high temperature stability, water stability and low temperature crack resistance compared to those of HRAM. With the increase in RAP contents, the high temperature stability of the physical foaming WRAM and HRAM rises notably but the water stability and low temperature crack resistance performance continues to drop.
In order to improve the strength of cement concrete pavement and reduce pavement cracking, the application effect of the hydration reaction enhancer Mixconverter in cement concrete pavement was ...studied by testing the compressive strength, bending strength, crack resistance and chloride ion permeability of concrete indoors. The test results show that the addition of Mixconverter to concrete can significantly improve the compressive and flexural strength of concrete, effectively prevent the expansion of plastic shrinkage and cracking of concrete, and significantly reduce the chloride ion diffusion coefficient. Finally, the test road pavement further proves the improvement effect of Mixconverter on concrete strength and cracking.
This paper mainly used the Superpave and the Marshall design methods to design the mix ratio of the hot mix plant recycled asphalt mixture. The road performance of AC-20, SUP-20 with 30% RAP content ...and AC-20 with 50% RAP content was studied to evaluate the water stability and high temperature stability and low temperature crack resistance of the recycled asphalt mixture. Research shows that the road performance of AC-20 mixed with 50% RAP content meets the technical requirements of the same type of asphalt mixture. It is recommended to use the Marshall design method for hot mix plant recycled asphalt mixture design.
China’s highway construction has moved from “construction-oriented” to the development stage of “equal attention to construction and maintenance”. The infrastructure represented by urban expressways, ...under heavy and complex traffic loads, is prone to a variety of diseases that take place in the middle and lower layers of pavement such as “frost boils” and “voids”, which cannot be repaired ideally with the help of conventional detection and treatment techniques. In order to solve the above problems, this paper adopts nondestructive testing plans such as ground penetrating radar and falling weight deflectometer to conduct multidimensional rapid detection of the road surface to obtain the image information and mechanical data of the road structure. Based on the improved calculation method, the pavement disease area, depth and type can be effectively judged. Combined with the observation of water level, the polymer grouting reinforcement plan is designed to eliminate the problems in the middle and lower layers of the road surface. It can effectively reduce the incidence of diseases in the upper layer of the sidewalk, and significantly improve the efficiency and service level of the sidewalk.
Although the high energy density and environmental benignancy of LiNi0.8Co0.15Al0.05O2 (NCA) holds promise for use as cathode material in Li‐ion batteries, present low rate capabilities, and fast ...capacity fade limit its broad commercial applications. Here, it is reported that surface modification of NCA cathode (R‐3m) with 5 nm‐thick nanopillar layers and Fm‐3m structures significantly improves electrode structure, morphology, and electrochemical performance. The formation of nanopillar layers increases cycling and working voltage stability of NCA by shielding the host material from hydrofluoric acid and improves structural stability with the electrolyte. The modified NCA cathode exhibits an enhanced 89% capacity retention at a rate of 1 C over that of pristine NCA (75.2%) after 150 cycles and effectively suppresses working voltage fade (a drop of 0.025 V after 300 cycles) during repeated charge–discharge cycles. In addition, the diffusion barrier of Li ions in NCA crystals at 0.80 V is noticeably smaller than that of Li ions in pristine NCA (0.87 eV). These findings demonstrate that this unique surface structure design considerably enhances cycle and rate performance of NCA, which has potential applications in other Ni‐rich layered cathode materials.
A surface design to induce the transformation of Ni3+ to Ni2+ and form a newly observed NiO phase in LiNi0.8Co0.15Al0.05O2 cathode is proposed. This surface layer formed NiO phase with Fm‐3m structure is stable and has a lower Li‐ion diffusion barrier, which produces excellent structural stability and cycle stability. It considerably improves cycle stability, rate performance, and effectively supresses voltage decay.
The nanosized LiMnPO4·Li3V2(PO4)3/carbon/graphene (LMP·LVP/C/G) composite is synthesized via a sol-gel method combined with freeze-drying. It is revealed that the composite is consisted of monoclinic ...Li3V2(PO4)3 and orthorhombic olivine-type LiMnPO4, which are homogeneously distributed in this mixture. While the LMP·LVP nanoparticles are intimately wrapped by a thin carbon layer. Particularly, the graphene nanosheets are closely coating on the LMP·LVP/C particles and constructing a highly conductively network, which exert significantly influence on the particle morphology with nanosize and rate capability with excellent performance for LMP·LVP/C/G composite. Due to the smaller polarization and higher Li+ diffusion induced by this hierarchical structure, the LMP·LVP/C/G composite delivers 116.3 mAh g−1 at ultrahigh rate of 10C, and ultrolong cycling life with capacity retention of 85.2% after 500 cycles. The synergistical effect between LMP·LVP and dual carbon wrapping with well-designed hierarchical structure provides an effective strategy to improve Li+ intercalation performance for cathode materials.
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•LMP·LVP/C/G composite is synthesized by a facile and scalable method.•Mutual doped LMP·LVP nanoparticles are coated by carbon and embedded in rGO nanosheets.•LMP·LVP/C/G composite delivers small polarization and high conductivity.•LMP·LVP/C/G composite presents ultrahigh rate capability and long cycling stability.
The nanosized LiMnPO4·Li3V2(PO4)3/carbon/graphene (LMP·LVP/C/G) composite is synthesized via a sol-gel method combined with freeze-drying. It is revealed that the composite is consisted of monoclinic ...Li3V2(PO4)3 and orthorhombic olivine-type LiMnPO4, which are homogeneously distributed in this mixture. While the LMP·LVP nanoparticles are intimately wrapped by a thin carbon layer. Particularly, the graphene nanosheets are closely coating on the LMP·LVP/C particles and constructing a highly conductively network, which exert significantly influence on the particle morphology with nanosize and rate capability with excellent performance for LMP·LVP/C/G composite. Due to the smaller polarization and higher Li+ diffusion induced by this hierarchical structure, the LMP·LVP/C/G composite delivers 116.3 mAh g−1 at ultrahigh rate of 10C, and ultrolong cycling life with capacity retention of 85.2% after 500 cycles. The synergistical effect between LMP·LVP and dual carbon wrapping with well-designed hierarchical structure provides an effective strategy to improve Li+ intercalation performance for cathode materials.
Although the high energy density and environmental benignancy of LiNi
Co
Al
O
(NCA) holds promise for use as cathode material in Li-ion batteries, present low rate capabilities, and fast capacity ...fade limit its broad commercial applications. Here, it is reported that surface modification of NCA cathode (R-3m) with 5 nm-thick nanopillar layers and Fm-3m structures significantly improves electrode structure, morphology, and electrochemical performance. The formation of nanopillar layers increases cycling and working voltage stability of NCA by shielding the host material from hydrofluoric acid and improves structural stability with the electrolyte. The modified NCA cathode exhibits an enhanced 89% capacity retention at a rate of 1 C over that of pristine NCA (75.2%) after 150 cycles and effectively suppresses working voltage fade (a drop of 0.025 V after 300 cycles) during repeated charge-discharge cycles. In addition, the diffusion barrier of Li ions in NCA crystals at 0.80 V is noticeably smaller than that of Li ions in pristine NCA (0.87 eV). These findings demonstrate that this unique surface structure design considerably enhances cycle and rate performance of NCA, which has potential applications in other Ni-rich layered cathode materials.
Although the high energy density and environmental benignancy of LiNi0.8Co0.15A0.05O2 (NCA) holds promise for use as cathode material in Li-ion batteries, present low rate capabilities, and fast ...capacity fade limit its broad commercial applications. Here, it is reported that surface modification of NCA cathode (R-3m) with 5 nm-thick nanopillar layers and Fm-3m structures significantly improves electrode structure, morphology, and electrochemical performance. The formation of nanopillar layers increases cycling and working voltage stability of NCA by shielding the host material from hydrofluoric acid and improves structural stability with the electrolyte. The modified NCA cathode exhibits an enhanced 89% capacity retention at a rate of 1 C over that of pristine NCA (75.2%) after 150 cycles and effectively suppresses working voltage fade (a drop of 0.025 V after 300 cycles) during repeated charge-discharge cycles. In addition, the diffusion barrier of Li ions in NCA crystals at 0.80 V is noticeably smaller than that of Li ions in pristine NCA (0.87 eV). These findings demonstrate that this unique surface structure design considerably enhances cycle and rate performance of NCA, which has potential applications in other Ni-rich layered cathode materials.
The porous spherical LiFePO4·LiMnPO4·Li3V2(PO4)3@C@rGO (Sample-G) composites are prepared via a spray drying process. The results show that the composites consist of orthorhombic olivine-type ...LiFe0.5Mn0.5PO4 and monoclinic Li3V2(PO4)3, which are evenly distributed. In particular, nanoparticles are embedded in graphene nanosheets, which are interconnected and stacked to form a porous sphere structure with an interior three-dimensional conductive network, resulting in the huge improvement on electrochemical performance and structural stability. Due to the increased Li+ diffusion coefficient, the composite possesses 98.6 and 82.9 mAh g−1 with capacities retention of 81.6% and 71.8% at 10 and 20C after 1000 cycles, respectively. The mutual cross-doping effect between LFP·LMP·LVP and a porous sphere structure with a 3D conductive network inside provides a practical method for improving the cycling and rate performance.
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