Low-cost, green synthesis of highly porous carbons derived from lotus root shell as superior performance electrode materials in supercapacitor

Facile production of high quality activated carbons from biomass materials has greatly triggered much attention presently. In this paper, a series of interconnected porous carbon materials from lotus root shells biomass are prepared via simple pyrolysis and followed by a KOH activation process. The prepared carbons exhibit high specific surface areas of up to 2961 m^2/g and large pore volume～1.47 cm3/g. In addition, the resultant porous carbons served as electrode materials in supercapacitor exhibit high specific capacitance and outstanding recycling stability and high energy density. In particular, their specific capacitance retention was almost 100% after 10500 cycles at a current density of 2 A/g. Remarkabely, the impact of the tailored specific surface areas of various carbon samples on their capacitive performances is systematically investigated.Generally, it was believed that the highly-developed porosity features（including surface areas and pore volume and pore size-distributions）, together with the good conductivity of activated carbon species, play a key role in effectively improving the storage energy performances of the porous carbon electrode materials in supercapacitor.

Phase Evolution Study and Optimization of the Heat Treatment Process for High Current Capacity Bi-2223 Tapes

Powder in tube process（PIT） was adopted for the fabrication of single filament Bi-2223 tapes, and a heat treatment process including the first heat treatment（HT1）, intermediate rolling（IR）, and second heat treatment（HT2） was performed. The phase evolution mechanism and microstructure changes during these heat treatment processes were systematically discussed. The influences of HT1 parameters on the phase evolution process of Bi-2223 tapes were discussed. With the optimized HT1 process, a proper Bi-2223 content of about 90% was achieved. HT2 process was also optimized by adding a post annealing process. An obvious increase of current capacity was obtained due to the enhancement of intergrain connections. Single filament Bi-2223 tapes with the critical current of Ic-90 A were fabricated with the optimized sintering process.

Phase selection and solidification path transition of Ti-48Al-xNb alloys with different cooling rates

Ti-48Al-xNb alloys were solidified by containerless electromagnetic levitation with quenching system of the conical copper mold.The influence of cooling rates on phase selection of T1-48Al-xNb alloys was investigated.In near-equilibrium solidification condition,the dendrite βphase is observed as the leading phase.No other metastable phase(e.g.,α phase) is observed.In contrast,in rapid solidification condition,the metastable α phase is observed in as-quenched Ti-48Al-2Nb alloy.Furthermore,the metastable α phase is replaced by the primary β phase with Nb addition increasing.For Ti-48Al-(x=4,6,8)Nb alloys,increasing cooling rate results in a solidification path transition.The peritectic reaction(L+β→α) is therefore significantly suppressed.The relationships between primary dendrite arm spacing(λ_(1)) and cooling rate(τ) can be described.

Solidification characteristics of high Nb-containing γ-TiAl-based alloys with different aluminum contents

The effect of A1 content on the microstructure and solidification characteristics of Ti-A1-Nb-V-Cr alloys in as-cast and isothermally treated states was investigated using X-ray diffraction （XRD）, scanning electron microscopy （SEM） equipped with energy dispersive spectroscope （EDS）, and transmission electron microscopy （TEM）. The typical solidification characteristics are due to the joint influence of both the crystal temperature range and the solidification path. The wide crystallization temperature range contributes to obtaining coarse dendrites in the as-cast Ti47A17Nb2.5V1.0Cr （at%） alloy solidifying through the peritectic reaction. The β-solidifying Ti46A17Nb2.5V1.0Cr （at%） alloy with the narrow crystallization temperature range is attributed to the formation of a homogeneous finegrained microstructure. However, the crystallization temperature range of Ti48A17Nb2.5V1.0Cr （at%） alloy is equivalent to that of Ti46A17Nb2.5V1.0Cr alloy, but it is solidified by peritectic reaction, leading to the formation of finer dendrites.

Transition of solidification path in nonequilibrium solidification of Ti–48Al–8Nb alloy

The solidification behavior of Ti-48Al-8Nb alloy under nonequilibrium solidification conditions was studied by electromagnetic levitation technique.The solidification conditions are different undercooling（△T）under the same cooling condition and different cooling methods at the same undercooling condition,respectively.In different undercooling conditions,when the undercooling is above a critical value（△T＊≈211K）,a remarkable morphological transition from typical hypoperitectic solidification to a sole solidification of the（3 phase resulting in the suppression of the peritectic reaction occurs.For melts with different cooling conditions at the same undercooling（△T≈85 K）,the melt was rapidly cooled by quenching them in cooling media.With cooling rate increasing,a transition from β phase to peritectic α phase solidification mode is revealed for Ti-48Al-8Nb alloy.

Solidification microstructure characteristics of Ti–44Al–4Nb–2Cr–0.1B alloy under various cooling rates during mushy zone

Beta-solidifying TiAl alloy has great potential in the field of aero-industry as a cast alloy.In the present work,the influence of cooling rate during mushy zone on solidification behavior of Ti-44Al-4Nb-2Cr-0.1B alloy was investigated.A vacuum induction heating device combining with temperature control system was used.The Ti-44Al-4Nb-2Cr-0.1B alloy solidified from superheated was melted to β phase with the cooling rates of 10,50,100,200,400 and 700 K·min^（-1）,respectively.Results show that with the increase in cooling rate from 10 to 700 K·min^（-1）,the colony size of α_2/γ lamella decreases from 1513 to48 urn and the solidification segregation significantly decreases.Also the content of residual B2 phase within α_2/γlamellar colony decreases with the increase in cooling rate.In addition,the alloy in local interdendritic regions would solidify in a hypo-peritectic way,which can be attributed to the solute redistribution and enrichment of Al element in solidification.

Solidification researches using transparent model materials——A review

A review is given in the paper for solidification researches with transparent model materials.The effective experimental method was first proposed by Jackson and Hunt in 1965.The transparent model materials for solidification researches are a kind of non-faceted crystals known as "plastic crystals" or "globular molecules",which have very low entropy of melting as that of metals.According to Jackson's theory proposed in 1958,entropy of phase transformation will determine whether the phase interface morphology is smooth or rough in atomic scale,which will lead to faceted or nonfacted phase interface in microscopic and macroscopic scales.Succinonitrile(SCN) and its alloys with water,ethanol,acetone,and NH4Cl-H2O solution are most commonly used as transparent model materials for solidification researches of dendritic growth,anisotropy of solid-liquid interfacial energy,crystal nucleation,crystal grain formation,directional solidification,eutectic and peritectic solidification,solidification defects formation such as bubble,hot tearing,etc.Among these researches,the most impressive work was the critical test of dendritic growth theories with high purity succinonitrile by Glicksman et al.,which gave positive answer to the Ivantsov's analysis and negative answer to the ad hoc condition of the maximum velocity hypothesis.The future researches with transparent model materials could be suggested in three aspects:1) accurate measurement of material properties and alloy phase diagrams in more plastic crystals,especially to find more transparent eutectic and peritectic alloys;2) accurate measurement of the grain boundary groove shape to obtain precise data of the anisotropy parameters of the interfacial free energy in transparent model materials;3) to get clear pictures of solidification processes with morphology details in a relatively large area,with continuous movement of liquid and particles,in order to give experimental support to numerical simulations aimming at accurate description of microstructure formation during solidification of multicomponent alloys under complex conditions of real casting and welding processes.

Two-dimensional hybrid nanomaterials derived from MXenes(Ti3C2Tx)as advanced energy storage and conversion applications

The development of two-dimensional hybrid nanomaterial derived from MXenes as high performance electrode material is the key component for the advanced ene rgy storage and conversion systems.In the past decades,MXene derived nanomaterials have attracted greatly interest in scientific activity and potential applications because of their unique synergistic properties such as high thermal stability,excellent electrical conductivity,large surface area,easy to handle and outstanding electro and photo chemical properties.This review is focused on the synthesis of hybrid nanomaterials from MXene(Ti3C2Tx)for renewable energy conversion and storage application including hydrogen evolution reaction,supercapacitor,lithium-ion batteries and photocatalysis.Finally,we also summarized the prospect and opportunities of novel two-dimensional hybrid nanomaterials derived MXene(Ti3C2Tx)fo r futuristic sustainable energy technology.