Insight into the structure-capacity relationship in biomass derived carbon for high-performance sodium-ion batteries

Carbonaceous materials are the most promising candidates as the anode for sodium-ion batteries (SIBs), however, they still suffer from low electric conductivity and sluggish sodium ion (Na+) reaction kinetics. Appropriate composition modulation using heteroatoms doping and structure optimization is highly desired. A basic empirical understanding of the structure-capacity relationship is also urgent in tackling the above problems. Herein, multi-functional nitrogen (N) doped carbon micro-rods with enlarged interlayer spacing are synthesized and investigated as the anode in SIBs, showing an ultra-stable capacity of 161.5 mAh g^(−1) at 2 A g^(−1) for over 5000 cycles. Experimental investigations and first-principle calculations indicate that the enlarged interlayer spacing can facilitate Na+ intercalation and N doping can guarantee the high electric conductivity and favorable electrochemical active sites. Additionally, pyridinic N is theoretically proved to be more effective to enhance Na+ adsorption than pyrrolic N due to the lower adsorption energy and stronger binding energy with Na+. Full SIBs show a high capacity and cyclability, making the biomass-derived carbon micro-rods to be a promising anode for practical SIBs applications.

Effects of the original state of sodium-based additives on microstructure,surface characteristics and filtration performance of SiC membranes

Sodium-contained compounds are promising sintering additives for the low-temperature preparation of reaction bonded SiC membranes.Although sodium-based sintering additives in various original states were attempted,their effects on microstructure and surface properties have rarely been studied.In this work,three types of sodium-based additives,including solid-state NaA zeolite residue(NaA)and liquidstate dodecylbenzene sulfonate(SDBS)and water glass(WG),were separately adopted to prepare SiC membranes,and the microstructure,surface characteristics and filtration performance of these SiC membranes were comparatively studied.Results showed that the SiC membranes prepared with liquid-state SDBS and WG(S-SDBS and S-WG)showed lower open porosity yet higher bending strength compared to those prepared with solid-state NaA(S-NaA).The observed differences in bending strength were further interpreted by analyzing the reaction process of each sintering additive and the composition of the bonding phase in the reaction bonded SiC membranes.Meanwhile,the microstructural differentiation was correlated to the original state of the additives.In addition,their surface characteristics and filtration performance for oil-in-water emulsion were examined and correlated to the membrane microstructure.The S-NaA samples showed higher hydrophilicity,lower surface roughness(1.80μm)and higher rejection ratio(99.99%)in O/W emulsion separation than those of S-WG and S-SDBS.This can be attributed to the smaller mean pore size and higher open porosity,resulting from the originally solid-state NaA additives.Therefore,this work revealed the comprehensive effects of original state of sintering additives on the prepared SiC membranes,which could be helpful for the application-oriented fabrication by choosing additives in suitable state.

A reverse particle grading strategy for design and fabrication of porous SiC ceramic supports with improved strength

Porous ceramics usually require high mechanical strength and maximized porosity simultaneously,while for conventional particle grading strategies,it is highly challenging to meet both demands.To this end,a reverse particle grading strategy was developed based on the linear packing model by unusually introducing coarse particles(d_(50)=16μm)into a fine particle(d50=5μm)matrix.Following the extrusion and sintering process,tubular porous SiC ceramic supports with improved mechanical strength were successfully fabricated.The effects of coarse particles on the rheological properties of the ceramic paste and the macroscopic properties and microstructure of the SiC supports were systematically investigated.With an increase in the content of coarse SiC particles to 30 wt%,the pressure generated during extrusion decreased from 5.5±0.2 to 1.3±0.1 MPa.Notably,the bending strength of the tubular supports increased from 36.6±5.6 to 49.1±4.5 MPa when 20 wt%coarse powder was incorporated.The notably improved mechanical strength was attributed to the distribution of coarse particles that prolonged the route of crack deflection.Additionally,the optimized tubular supports had an average pore size of 1.2±0.1μm,an open porosity of 45.1%±1.6%,and a water permeability of 7163±150 L/(m^(2)·h·bar)as well as good alkali and acid corrosion resistance.Significantly,the strategy was proven to be feasible for the scale-up fabrication of 19-channel SiC tubular porous ceramic supports.

Epsilon-negative BaTiO_(3)/Cu composites with high thermal conductivity and yet low electrical conductivity

Epsilon-negative materials with high thermal conductivity and low electrical conductivity are of great importance for high power microwave devices.In this work,BaTiO_(3)/Cu composites,as a class of epsilonnegative materials,are rationally designed to achieve a high thermal conductivity yet maintaining the electrical insulative character.Negative permittivity behavior induced by dielectric resonance and plasma oscillation is observed in these BaTiO_(3)/Cu composites,which can be explained by the Lorentz and Drude model respectively.An outstanding absorption ability is achieved near the zero-cross point of the permittivity.Benefiting from the positive temperature coefficient of resistance and the weak temperature dependence of thermal conductivity in BaTiO_(3)/Cu composites,sample containing 22.3 vol% of Cu content exhibits a thermal conductivity of up to 17.7 W/(m·k)and an electrical conductivity down to 0.0022(Ω cm)^(-1) at 150℃.Therefore,BaTiO_(3)/Cu composite is a promising candidate for applications in electromagnetic attenuation and thermal management.

Generation and Characterization of a Transgenic Zebrafish Expressing the Reverse Tetracycline Transactivator

Conditional expression of a target gene during zebrafish development is a powerful approach to elucidate gene functions. The tetracycline-controlled systems have been successfully used in the modulation of gene expression in mammalian cells, but few lines of zebrafish carrying these systems are currently available. In this study, we had generated a stable transgenic zebrafish line that ubiquitously expressed the second-generation of reverse Tet transactivator （rtTA-M2）. Southern blotting analysis and high-throughput genome sequencing verifed that a single copy of rtTA-M2 gene had stably integrated into the zebrafish genome. After induction with doxycycline （Dox）, a strong green fluorescent protein （GFP） was seen in rtTA-transgenic eggs injected with pTRE--EGFP plasmids. The fluorescent signal gradually decreased after the withdrawal of Dox and disappeared. However, leaky expression of GFP was undetectable before Dox- induction. Additionally, transgenic embryos expressing rtTA-M2 exhibited no obvious defects in morphological phenotypes, hatching behavior and expression patterns of developmental marker genes, suggesting that rtTA-M2 had little effect on the development of transgenic zebrafish. Moreover, expressed Dickkopf-1 （DKK1） in pTRE-DKKl-injected embryos led to alterations in the expression of marker genes associated with Wnt signaling. Thus, this rtTA-transgenic zebrafish can be utilized to dissect functions of genes in a temporal manner.