Monitoring the morphology evolution of LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)during high-temperature solid state synthesis via in situ SEM

The particle morphology determined by the sintering process is the director factor affecting the electrochemical performance of Ni-rich NMC cathode materials.To prepare the ideal NMC particles,it is of great significance to understand the morphological changes during sintering process.In this work,the morphology evolution of LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)(NMC811)synthesis at temperature ranging from 300–1080℃were observed by in situ SEM.The uniform mixture of spherical Ni_(0.8)Mn_(0.1)Co_(0.1)(OH)_(2)precursor and lithium sources(LiOH)was employed by high temperature solid-state process inside the SEM,which enables us to observe morphology changes in real time.The results show that synthetic reaction of LiNi_(0.8)Mn_(0.1)Co_(0.1)O_(2)usually includes three processes:the raw materials’dehydration,oxidation,and combination,accompanied by a significant reduction in particle size,which is important reference to control the synthesis temperature.As heating temperature rise,the morphology of mixture also changed from flake to brick-shaped.However,Ni nanoparticle formation is apparent at higher temperature~1000℃,suggesting a structural transformation from a layered to a rock-salt-like structure.Combining the in-situ observed changes in size and morphology,and with the premise of ensuring the morphology change from flakes to bricks,reducing the sintering temperature as much as possible to prevent excessive reduction in particle size and layered to a rock-salt structure transformation is recommended for prepare ideal NMC particles.

Microstructure Evolution and Mechanical Behavior of Laser Melting Deposited TA15 Alloy at 500℃ under In-Situ Tension in SEM

TA15 alloy fabricated by laser melting deposition was investigated at 500℃ under tensile deformation. The damage behavior of microstructure was analyzed by the real time observation of the microstructure evolution, microcracks initiation and propagation using in-situ tensile equipment fitted in the SEM chamber. Finally, the mechanism of fracture was discussed. The result showed anisotropic mechanical properties in X-and Z-direction. The existence of columnar β grains and its orientation to the tensile direction were the major factors inducing the anisotropic mechanical properties. As compared to Z-direction specimen, high tensile strength was observed in X-direction specimen due to the resistance in slips propagation provided by the prior-β grain boundaries( β GBs). Accumulation of the cracks at prior β GB caused the shear fracture. In case of Z-direction specimen, parallel orientation of prior β GB and GB α with the tensile direction resulted in a homogeneous deformation. The high reduction of cross section showed the enhanced ductile characteristics at high temperature.

Junctional and somatic hypermutation-induced CX4C motif is critical for the recognition of a highly conserved epitope on HCV E2 by a human broadly neutralizing antibody

Induction of broadly neutralizing monoclonal antibodies(bNAbs)that bind to the viral envelope glycoproteins is a major goal of hepatitis C virus(HCV)vaccine research.The study of bNAbs arising in natural infection is essential in this endeavor.We generated a human antibody,8D6,recognizing the E2 protein of HCV isolated from a chronic hepatitis C patient.This antibody shows broadly neutralizing activity,which covers a pan-genotypic panel of cell culture-derived HCV virions(HCVcc).Functional and epitope analyses demonstrated that 8D6 can block the interaction between E2 and CD81 by targeting a highly conserved epitope on E2.We describe how the 8D6 lineage evolved via somatic hypermutation to achieve broad neutralization.We found that the V(D)J recombination-generated junctional and somatic hypermutation-induced disulfide bridge(C-C)motif in the CDRH3 is critical for the broad neutralization and binding activity of 8D6.This motif is conserved among a series of broadly neutralizing HCV antibodies,indicating a common binding model.Next,the 8D6 inferred germline(iGL)was reconstructed and tested for its binding affinity and neutralization activity.Interestingly,8D6 iGL-mediated relatively strong inhibition of the 1b genotype PR79L9 strain,suggesting that PR79L9 may serve as a potential natural viral strain that provides E2 sequences that induce bNAbs.Overall,our detailed epitope mapping and genetic studies of the HCV E2-specific mAb 8D6 have allowed for further refinement of antigenic sites on E2 and reveal a new mechanism to generate a functional CDRH3,while its iGL can serve as a probe to identify potential HCV vaccine strains.