The mitigation of pitch-derived carbon with different structures on the volume expansion of silicon in Si/C composite anode

The microstructures of carbon precursors significantly affect the electrochemical performance of Si/C composite anodes.However,the interaction between Si and carbon materials with different structures is still unclear.Pitch-based materials undergoing different thermal treatments are superior sources for synthesizing carbons with different structures.Herein,different types of mesophase pitch(domain,flow-domain and mosaic structure) obtained from controllable thermal condensation are utilized to prepare Si/C composite materials and the corresponding models are established through finite element simulation to explore the correlation between the lithium storage properties of Si/C composites and the structures of carbon materials.The results indicate that the flow-domain texture pitch P2 has a better ability to buffer the volume expansion of silicon particles for its highly ordered arrangement of carbon crystallites inside could disperse the swelling stress uniformly alongside the particle surface.The sample Si@P2 exhibits the highest capacity of 1328 mA h/g after 200 cycles at a current density of 0.1 A/g as well as the best rate performance and stability.While sample Si@P3 in which the mosaic texture pitch P3 composed of random orientation of crystallites undergoes the fastest capacity decay.These findings suggest that highly ordered carbon materials are more suitable for the synthesis of Si/C composite anodes and provide insights for understanding the interaction between carbon and silicon during the charging/discharging process.

Study of the Liquid Phase Volume Expansion for CO_2/Organic Solvent Systems

The supercritical antisolvent （SAS） process has been developed in recent years for the tormation of nanoand micro-particles. It is necessary to study the liquid phase volume expansion （LPVE） and find the relationships between the operating conditions and the LPVE in order to develop a practical method for determining the operation conditions and selecting an organic solvent for SAS process. The PR equation of state with vdW-1 mixing rule is used to calculate the LPVE for CO2/toluene, CO2/acetone and CO2/ethyl acetate systems, and the results show that the LPVE for each CO2/organic solvent system decreases as the temperature increases. The relationship between the LPVE and the solubility of CO2 in the liquid phase for CO2/organic solvent systems is investigated, and the results show that the LPVE is determined directly by the solubility of CO2 in the liquid phase, xCO2, and can be related to xCO2 independently. No matter what system of CO2/organic solvent is and how different the temperature is, the LPVEs have little difference as long as the solubility of CO2 in the liquid phase, xCO2, keeps constant. The lower temperature is always favorable to the SAS process. The higher the solubility of CO2 in an organic solvent under certain operation condition, the more suitable it is to the SAS process.

Role of renal proximal tubule transport in thiazolidinedioneinduced volume expansion

Thiazolidinediones （TZDs）, pharmacological activa-tors of peroxisome-proliferator-activated receptors γ （PPARγ）, significantly improve insulin resistance and lower plasma glucose concentrations. However, the use of TZDs is associated with plasma volume expansion, the mechanism of which has been a matter of contro-versy. Originally, PPARγ-mediated enhanced transcrip-tion of the epithelial Na channel （ENaC） γ subunit was thought to play a central role in TZD-induced volume expansion. However, later studies suggested that the activation of ENaC alone could not explain TZD-induced volume expansion. We have recently shown that TZDs rapidly stimulate sodium-coupled bicarbonate absorp-tion from renal proximal tubule （PT） in vitro and in vivo. TZD-induced transport stimulation was dependent on PPARγ/Src/EGFR/ERK, and observed in rat, rabbit and human. However, this stimulation was not observed in mouse PTs where Src/EGFR is constitutively activated. Analysis in mouse embryonic fbroblast cells confrmed the existence of PPARγ/Src-dependent non-genomic signaling, which requires the ligand binding ability but not the transcriptional activity of PPARγ. The TZD-in-duced enhancement of association between PPARγ and Src supports an obligatory role for Src in this signal-ing. These results support the view that TZD-induced volume expansion is multifactorial. In addition to the PPARγ-dependent enhanced expression of the sodium transport system（s） in distal nephrons, the PPARγ-dependent non-genomic stimulation of renal proximal transport may be also involved in TZD-induced volume expansion.

Structural Designs for Accommodating Volume Expansion in Sodium Ion Batteries

T At the forefront of energy storage field, developing sodium ion batteries （SIBs） has drew a wide concern due to relatively low cost and abundant resource, comparing with lithium ion batteries （LIBs）. Serious volume expansion constraints the electrochemical performance of the conver- sion/alloying materials, despite of their high reversible capacities or theoretical capacities. Here, from the perspective of structural designs, we systemat- ically study four types of routes to accommodate volume expansion. Delicate and peculiar nanostructures based on nanocrystallization engineering are widely focused on, covering nanosheet assembly and nanoarray construction. Robust materials such as carbon-based materials can be utilized as the buffer matrix, mitigating the mechanical stress during the charge/discharge process. Besides, recent studies have demonstrated void space reservation in nanostructures was also beneficial for adapting to volume changes. Moreover, for conversion materials, numerous works have confirmed the advanta- geous influence of interlayer spacing regulation. We also explained the superiority and challenges for further giving scope to structural designs. Sketching out the future studies in SIBs, in situ characterizations are supposed to be highlighted, as well as in-depth researches on the stress evolution caused by volume expansion.

Revealing Quasi-1D Volume Expansion in Na-/K-Ion Battery Anodes:A Case Study of Sb_(2)O_(3)Microbelts

Tailoring a rational structure to control the huge volume variation is practical in regulating alkali-ion battery performance on the basis of the anisotropic properties of crystallized anode materials.Here,a double-serrated orthorhombic antimony oxide(Sb_(2)O_(3))microbelt was prepared by a thermally induced recrystallization/sublimation process.In situ transmission electron microscopy(TEM),in situ X-ray powder diffraction(XRD),and ex situ scanning electron microscopy(SEM)measurements demonstrate that Sb_(2)O_(3)microbelts exhibit a quasi-one-dimensional expansion perpendicular to the belt(along the[100]direction)during sodiation.The unconstrained microbelt surface space can appropriately accommodate the oriented volume variation.Thus,Sb_(2)O_(3)microbelts exhibit enhanced cycling and rate performance in half-cell sodium-ion batteries samples.Via support of reduced graphene oxide(RGO),Sb_(2)O_(3)@RGOcomposites deliver good rate capability(312.3 mAh g−1 at 3 A g−1)for sodium-ion full-cell batteries and good cycling performance(473.9 mAh g−1 at 100 mA g−1 after 100 cycles)for half-cell potassium-ion batteries.In situ Raman measurements reveal that the conversion/alloying-type Sb_(2)O_(3)anode undergoes a fully reversible alloying reaction and partially reversible conversion mechanism,which explains its irreversible capacity during the first cycle.The delicate structural design and clarification of the alkali-ion storage mechanisms facilitate the development of Sb_(2)O_(3)anodes for energy storage applications.

Dynamics of vascular volume and hemodilution of lactated Ringer’s solution in patients during induction of general and epidural anesthesia

Objective： To investigate the dynamics of vascular volume and the plasma dilution of lactated Ringer＇s solution in patients during the induction of general and epidural anesthesia. Methods： The hemodilution of i.v. infusion of 1000 ml of lactated Ringer＇s solution over 60 min was studied in patients undergoing general （n=31） and epidural （n= 22） anesthesia. Heart rate, arterial blood pressure and hemoglobin （Hb） concentration were measured every 5 rain during the study. Surgery was not started until the study period had been completed. Results： General anesthesia caused the greater decrease of mean arterial blood pressure （MAP） （mean 15% versus 9%; P〈0.01） and thereby followed by a more pronounced plasma dilution, blood volume expansion （VE） and blood volume expansion efficiency （VEE）. A strong linear correlation between hemodilution and the reduction in MAP （r=-0.50;P〈0.01） was found. At the end of infusion, patients undergoing general anesthesia retained 47% （SD 19%） of the infused fluid in the circulation, while epidural anesthesia retained 29% （SD 13%） （P〈0.001）. Correspondingly, a fewer urine output （mean 89 ml versus 156 ml; P〈0.05） and extravascular expansion （454 ml versus 551 ml; P〈0.05） were found during general anesthesia. Conclusion： We concluded that the induction of general anesthesia caused more hemodilution, volume expansion and volume expansion efficiency than epidural anesthesia, which was triggered only by the lower MAP.

Self-heating Probe Instrument and Method for Measuring High Temperature Melting Volume Change Rate of Material

The castings defects are affected by the melting volume change rate of material. The change rate has an important effect on running safety of the high temperature thermal storage chamber, too. But the characteristics of existing measuring installations are complex structure, troublesome operation and low precision. In order to measure the melting volume change rate of material accurately and conveniently, a self-designed measuring instrument, self-heating probe instrument, and measuring method are described. Temperature in heating cavity is controlled by PID temperature controller; melting volume change rate υ and molten density are calculated based on the melt volume which is measured by the instrument. Positive and negative υ represent expansion and shrinkage of the sample volume after melting, respectively. Taking eutectic LiF＋CaF2 for example, its melting volume change rate and melting density at 1 123 K are -20.6% and 2 651 kg/m–3 measured by this instrument, which is only 0.71% smaller than literature value. Density and melting volume change rate of industry pure aluminum at 973 K and analysis pure NaCl at 1 123 K are detected by the instrument too. The measure results are agreed with report values. Measuring error sources are analyzed and several improving measures are proposed. In theory, the measuring errors of the change rate and molten density which are measured by the self-designed instrument is nearly 1/20-1/50 of that measured by the refitted mandril thermal expansion instrument. The self-designed instrument and method have the advantages of simple structure, being easy to operate, extensive applicability for material, relatively high accuracy, and most importantly, temperature and sample vapor pressure have little effect on the measurement accuracy. The presented instrument and method solve the problems of complicated structure and procedures, and large measuring errors for the samples with high vapor pressure by existing installations.

Gas expansion caused by formation uplifting and its effects on tight gas accumulation:A case study of Sulige gas field in Ordos Basin,NW China

Gas expansion caused by significant exhumation in the Sulige gas field in the Ordos Basin since Late Cretaceous and its effects on hydrocarbon accumulation have been investigated systematically based on comprehensive analysis of geochemical,fluid inclusion and production data.The results indicate that gas volume expansion since the Late Cretaceous was the driving force for adjustment and secondary charging of tight sandstone gas reservoirs in the Sulige gas field of the Ordos Basin.The gas retained in the source rocks expanded in volume,resulting in gas re-expulsion,migration and secondary charging into reservoirs,while the gas volume expansion in the tight reservoirs caused the increase of gas saturation,gas-bearing area and gas column height,which worked together to increase the gas content of the reservoir and bring about large-scale gas accumulation events.The Sulige gas field had experienced a two-stage accumulation process,burial before the end of Early Cretaceous and uplifting since the Late Cretaceous.In the burial stage,natural gas was driven by hydrocarbon generation overpressure to migrate and accumulate,while in the uplifting stage,the gas volume expansion drove internal adjustment inside gas reservoirs and secondary charging to form new reservoirs.On the whole,the gas reservoir adjustment and secondary charging during uplifting stage is more significant in the eastern gas field than that in the west,which is favorable for forming gas-rich area.

Ni-P-SBR composite-electroless-plating enables Si anode with high conductivity and elasticity for high performance Li-ion batteries application

Silica-based anode is widely employed for high energy density Li-ion batteries owing to their high theoretical specific capacity(4200 m A h g-1).However,it is always accompanied by a huge volume expansion(300%)and shrinks during the lithiation/delithiation process,further leading to low cycle stability.Efforts to mitigate the adverse effects caused by volume expansion such as robust binder matrix,Coreshell structure,etc.,inevitably affect the electronic conductivity within the electrode.Herein,a high conductivity and elasticity Si anode(Ni-P-SBR(styrene-butadiene rubber)@Si)was designed and fabricated via the Ni-P-SBR composite-electroless-plating process.In this design,the Si particles are surrounded by SBR polymer and Ni particles,where the SBR can adapt to the volume change and Ni particles can provide the electrode with high electronic conductivity.Therefore,the Ni-P-SBR@Si delivers a high initial capacity of 3470 m A h g-1and presents capacity retention of 49.4%within 200 cycles at 600 m A g-1.Additionally,a high capacity of 1153 m A h g-1can be achieved at 2000 m A g-1and can be cycled stably under bending conditions.This strategy provides feasible ideas to solve the key issues that limit the practical application of Si anodes.

Amorphous Sb/C composite with isotropic expansion property as an ultra-stable and high-rate anode for lithium-ion batteries

Antimony(Sb)is an intriguing anode material for Li-ion batteries(LIBs)owing to its high theoretical capacity of 660 m Ah·g^(-1)and appropriate working potential of~0.8 V(vs.Li^(+)/Li).However,just like all alloying materials,the Sb anode suffers from huge volume expansion(230%)during repeated insertion/extraction of Li+ions,resulting in structural deterioration and rapid capacity decay.In this work,a novel amorphous Sb/C composite with atomically dispersed Sb particles in carbon matrix is prepared via a straightforward high-energy ball milling approach.The intimate intermixing of amorphous Sb with C provides homogeneous element distribution and isotropic volume expansion during cycling,resulting in persistent structural stability.Meanwhile,the disordered structure of amorphous material shortens the diffusion distance of lithium ions/electrons,promoting fast reaction kinetics and rate capability.Benefiting from the aforementioned effects,the amorphous Sb/C exhibits a high reversible capacity of537.4 m Ah·g^(-1)at 0.1 A·g^(-1)and retains 201.0 m Ah·g^(-1)at an ultrahigh current rate of 10.0 A·g^(-1).Even after 1500deep cycles at 2.0 A·g^(-1),the amorphous Sb/C electrode still maintains 86.3%of its initial capacity,which outperforms all existing Sb-based anodes reported so far.Postmortem analysis further reveals a greatly reduced volume variation of merely 34.6%for the amorphous Sb/C electrode,much lower than that of 223.1%for crystalline Sb materials.This study presents a new approach to stabilizing Sb-based alloy anodes and contributes to the construction of high-performance amorphous anode materials for LIBs,enabling advanced energy storage.

Multifunctional roles of carbon-based hosts for Li-metal anodes:A review

With its high theoretical capacity,lithium(Li)metal is recognized as the most potential anode for realizing a high-performance energy storage system.A series of questions(severe safety hazard,low Coulombic efficiency,short lifetime,etc.)induced by uncontrollable dendrites growth,unstable solid electrolyte interface layer,and large volume change,make practical application of Li-metal anodes still a threshold.Due to their highly appealing properties,carbon-based materials as hosts to composite with Li metal have been passionately investigated for improving the performance of Li-metal batteries.This review displays an overview of the critical role of carbon-based hosts for improving the comprehensive performance of Li-metal anodes.Based on correlated mainstream models,the main failure mechanism of Li-metal anodes is introduced.The advantages and strategies of carbon-based hosts to address the corresponding challenges are generalized.The unique function,existing limitation,and recent research progress of key carbon-based host materials for Li-metal anodes are reviewed.Finally,a conclusion and an outlook for future research of carbon-based hosts are presented.This review is dedicated to summarizing the advances of carbon-based materials hosts in recent years and providing a reference for the further development of carbonbased hosts for advanced Li-metal anodes.

Enhanced electrochemical performance of Si/C electrode through surface modification using SrF_(2) particle

The silicon-based material exhibits a high theoretical specific capacity and is one of the best anode for the next generation of advanced lithium-ion batteries(LIBs).However,it is difficult for the silicon-based anode to form a stable solid-state interphase(SEI)during Li alloy/de-alloy process due to the large volume change(up to 300%)between silicon and Li4.4Si,which seriously limits the cycle life of the LIBs.Herein,we use strontium fluoride(SrF_(2))particle to coat the silicon-carbon(Si/C)electrode(SrF_(2)@Si/C)to help forming a stable and high mechanical strength SEI by spontaneously embedding the SrF_(2) particle into SEI.Meanwhile the formed SEI can inhibit the volume expansion of the silicon-carbon anode during the cycle.The electrochemical test results show that the cycle performance and the ionic conductivity of the SrF_(2)@Si/C anode has been significantly improved.The X-ray photoelectron spectroscopy(XPS)analysis reveals that there are fewer electrolyte decomposition products formed on the surface of the SrF_(2)@Si/C anode.This study provides a facile approach to overcome the problems of Si/C electrode during the electrochemical cycling,which will be beneficial to the industrial application of silicon-based anode materials.

Size effect of Si particles on the electrochemical performances of Si/C composite anodes

A series of Si/C composites were fabricated based on pitch and Si powders with particle sizes of 30, 100, 500, and 3000 nm. The size effects of the Si particles in the Si/C composites were investigated for lithium-ion battery anodes. The nanoscale Si and Si/C composites exhibited good capacity retentions. Scanning electron microscopy showed that exterior and interior cracks emerging owing to volume expansion as well as parasitic reactions with the electrolyte could well explain the performance failure.

Low-temperature oxidation behavior of MoSi_2 powders

The oxidation behavior of molybdenum disilicide （MoSi2） powders at 400, 500, and 600℃ for 12 h in air were investigated by using X-ray diffraction （XRD） and transmission electron microscopic （TEM） techniques. Significant changes were observed in volume, mass, and color. Especially at 500℃, the volume expansion was found to be as high as 7-8 times, the color changed from black to yellow-white, and the mass gain was about 169.34% after 8 h, with SiO2 and MoO3 as main reaction products. The gains in volume and mass were less at 400 and 600℃ compared with those at 500℃, probably due to the less reaction rate at 400℃ and the formation of silica glass scale at 600℃, which would protect the matrix and restrain the diffusion of oxygen and molybdenum. Thus, the accelerated oxidation behavior of MoSi2 powder appeared at 500℃ and the volume expansion was the sign of accelerated oxidation.

Yolk-Shell P3-Type K_(0.5)[Mn_(0.85)Ni_(0.1)Co_(0.05)]O_(2):A Low-Cost Cathode for Potassium-Ion Batteries

Low-cost preparation methods for cathodes with high capacity and long cycle life are crucial for commercializing potassium-ion batteries(PIBs).Presently,the charging/discharging strain that develops in the active cathode material of PIBs causes cracks in the particles,leading to a sharp capacity fade.Here,to abate the strain release and the need for an industrially relevant process,a simple low-cost co-precipitation method for synthesizing yolk-shell P3-type K_(0.5)[Mn_(0.85)Ni_(0.1)Co_(0.05)]O_(2) (YS-KMNC)was reported.As cathode material for PIBs,the YS-KMNC delivers a high reversible capacity(96 mAh g^(-1) at 20 mA g^(-1))and excellent cycle stability(80.5%retention over 400 cycles at a high current density of 200 mA g^(-1)).More importantly,a full battery assembled with the YS-KMNC cathode and a commercial graphite anode exhibits a high operating voltage(0.5-3.4 V)and an excellent cycling performance(84.2%retention for 100 cycles at 100 mA g^(-1)).Considering the low-cost,simple production process and high performance of YS-KMNC cathode,this work could pave the way for the commercial development of PIBs.

Development and Field Application of Phosphogypsum-Based Soil Subgrade Stabilizers

A phosphogypsum-based subgrade stabilizer(PBSS)was formulated using industrial by-product phosphogypsum(PG),mixed with slag and calcium-silicon-rich active material(GSR).The active powder(AP)was used to modify PBSS,and PBSS-AP was obtained.PBSS and PBSS-AP were each mixed with 10%silty soil,and cement and lime(CAL:5%lime+2%cement)were used as the traditional material for comparative experiments.Samples were cured under standard conditions,and tested for unconfined compressive strength(UCS),water stability,volume expansion,and leachate,to explore the stabilization effect of the three solidified materials on silty soil.The results showed that the comprehensive performance of sility soil mixed with 12%PBSS-AP was the best.The CaO,SiO_(2)and Al_(2)O_(3)provided by PG,Slag and GSR will react with water to form a stable C-S-H gel,which is conducive to stabilizing the soil.Field application results showed that the compaction exceeded 95%,the deflection was 144.9 mm,and UCS was 2.5 MPa after 28 days.These findings indicated that PBSS-AP is an effective stabilizer for subgrade soils.

In-situ construction of conducting alloy interphase towards modulating Li-ion storage kinetics

Interface engineering strategy shows great promise in promoting the reaction kinetic and cycling performance in the field of electrochemical energy storage application.In this work,an in-situ interface growth strategy is proposed to introduce a robust and conducting MoGe_(2) alloy interphase between the electrochemical active Ge nanoparticle and flexible MoS_(2) nanosheets to modulate their Li-ion storage kinetics.The structural evolution processes of the Ge@MoGe_(2)@MoS_(2) composite are unraveled,during which the initially-generated Ge metals serve as a crucial reduction mediator in the formation of MoGe_(2) species bridging the Ge and MoS_(2).The as-generated MoGe_(2) interface,chemically bonding with both Ge and MoS_(2),possesses multi-fold merits,including the maintaining stable framework of electrochemically inactive Mo matrix to buffer the strain-stress effect and the"welding spot"effects to facilitate the efficient Li^(+)/e^(-)conduction.As well,the introduction of MoGe_(2) interface leads to a unique sequential lithiation/de^(-)lithiation process,namely in the order of the electrochemically active MoS_(2)-MoGe_(2)-Ge during lithiation and vice versa,during which the electrode strain could be more effectively released.Benefited from the robust and rigid MoGe_(2) interface,the delicately designed Ge@MoGe_(2)@MoS_(2) composite exhibits an improved charge/discharge performances(866.7 mAh g^(-1) at 5.0 A g^(-1) and 838.5 mAh g^(-1) after 400 cycles)while showing a high tap density of 1.23 g cm^(-3).The as-proposed in-situ interface growth strategy paves a new avenue for designing novel high-performance electrochemical energy storage materials.

Sulphur-template method for facile manufacturing porous silicon electrodes with enhanced electrochemical performance

Sulphur(S)-template method based on conventional slurry-casting method has been developed to pro-duce porous silicon(Si)electrodes.The facile fabrication technology is suitable for current production line and expected to be widely applied to various electrode materials under large volume change during operation.Specifically,S particles as template agent are mixed with active material Si,carbon conductor and binder forming uniform slurry.After casting and drying,the electrodes are immersed in carbon disul-fide solution to remove S particles rapidly,generating pores in-situ at the original position of S particles.Electrochemical analysis shows that the pores inside electrodes are able to shorten lithium ion diffusion paths,reduce normal expansion rate and decrease formation of cracks in the Si electrode(2 mg_(Si)/cm^(2)),demonstrating a reversible capacity of 951 mAh/g at 0.5 A/g after 100 cycles(with a capacity retention of 99.5%)and a capacity of-826 mAh/g at 2 A/g.

Experimental evidence of pressure effects on spinel dissolution and peridotite serpentinization kinetics under shallow hydrothermal conditions

Serpentinization reactions are paramount to understand hydro-geothermal activity near plate boundaries and mafic–ultramafic massifs,as well as fluid and element transfer between the Earth’s mantle and crust.However,fluid-rock element exchange and serpentinization kinetics under shallow hydrothermal conditions is still largely unconstrained.Here we present two constant temperature(230℃)time-series of natural peridotite(77.5%olivine;13.7%enstatite;6.8%diopside;2%spinel)serpentinization experiments:at 13.4 MPa;and 20.7 MPa.Al-enriched lizardite was the main secondary mineral in all runs after olivine(olv)and orthopyroxene(opx)serpentinization(without any detectable brucite,talc or magnetite),while primary spinel and diopside partially dissolved during the experiments.Initial serpentinization stages comprises intrinsically coupled reactions between olivine and enstatite,as Al and Si are progressively transferred from orthopyroxene-derived to olivine-derived serpentine,while the opposite is true for Mg and Fe,with homogenization of serpentines compositions after 40 days.The Ni/Cr ratios of serpentines,however,remain diagnostic of the respective primary mineral.Estimated average serpentine content indicates fast serpentinization rates of 0.55 wt.%·day^(-1)(0.26 mmol·day^(-1))and 0.26 wt.%·day^(-1)(0.13 mmol·day^(-1))at 13.4 and 20.7 MPa,respectively.Approximately 2x faster serpentinization kinetics at lower pressure is likely linked to enhanced spinel dissolution leading to one order of magnitude higher available Al,which accelerates olivine serpentinization while delays orthopyroxene dissolution.Additionally,time-dependent increase in solid products masses suggests rock volume expands linearly 0.37%±0.01%per serpentine wt.%independently of pressure.Mass balance constrains suggests olv:opx react at~5:2 and~3:2 M ratios,resulting in Si-deficient and Si-saturated serpentines at the end of the low-pressure series(13.4 MPa)and high-pressure series(20.7 MPa),respectively.Elevated starting peridotite olv:opx ratio(7.94:1)therefore indicates orthopyroxene serpentinization is~3.3x and~5.4x faster than olivine at 13.4 MPa and 20.7 MPa,respectively.This contradicts previous assumptions that olivine should dissolve faster than orthopyroxene at experimental conditions.Finally,serpentinization-derived fluids develop pH>10 and become enriched in H_(2),CH_(4),Ca^(2+)and Si within 6 weeks.Aqueous silica concentrations are highest after 5 days(265.75 and 194.79µmol/kg)and progressively decrease,reaching 13.84 and 91.54µmol/kg at 13.4 and 20.7 MPa after 40 days,respectively.These concentrations are very similar to the low-silica(M6)and high-silica(Beehive)endmembers of the Lost City Hydrothermal Field(LCHF).Beyond fluid characteristics,serpentinization products and conditions analogous to the LCHF suggest similar mechanisms between our experiments and natural processes.Our results demonstrate constant temperature serpentinization of a common protolith leads to distinct serpentine and fluid compositions at different pressures.Although additional data is necessary,recent studies and our experiments suggest peridotite serpentinization rates at 230℃rapidly decrease with increasing pressures at least up to 35 MPa.Whether pressure directly influences olivine and orthopyroxene serpentinization kinetics or indirectly controls reaction rates due to spinel dissolution under hydrothermal conditions deserves further investigation.

温度调控制备锡或二氧化锡@中空多孔碳纳米纤维电极用于个性化定制锂离子电池

锂离子电池广泛应用于电动汽车、混合动力汽车、便携式电子设备等储能系统,但由于电荷在活性材料中传输缓慢以及活性材料易粉碎等缺点,开发同时具有高容量以及快充性能的电极材料仍然是一个极大的挑战.针对这一问题,本文通过温度调控将SnO_(2)量子点或Sn纳米团簇均匀负载在中空多孔碳纳米纤维(HPCNFs)的内部,用于制备个性化定制锂离子电池.一方面,高度互联的碳纳米纤维形成三维网络,加快了电子传输,提高了电子导电性.另一方面,中空多孔结构缩短了锂离子传输路径,促进了锂离子的快速扩散,同时,抑制了Sn和SnO_(2)的体积膨胀.由于具有较高的锂离子吸附性能以及快的离子扩散速率,低碳化温度下(450℃)合成的SnO_(2)@HPCNFs复合电极在0.1 A g^(-1)的小电流密度下具有较高的放电比容量(899.3 mA h g~(-1)).此外,由于在大的电流密度下,Sn的大孔结构能够储存更多的锂离子,以及具有较高的电子电导率,因此,高碳化温度下(850℃)制备的Sn@HPCNFs复合电极展现出优异的快充性能,同时,在5 A g^(-1)(~10 C)的高电流密度下具有238.8 mA h g^(-1)的放电容量.本文通过调控碳化温度来研究SnO_(2)和Sn电极之间的电化学行为,为构建高性能储能器件提供了新的思路.