Adsorption and Desorption Characteristics of Alkali Ions in Hydrated C_3S-nano SiO_2 Pastes

C3S pastes containing 0%,5%,10%,and 15%nano-SiO2 mixed with de-ionized water and alkali solutions were prepared.When C3S was completely hydrated,the pastes were ground into powders with a particle size less than 80μm.Adsorption and desorption characteristics of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water immersed in alkali solutions and those in C3S-nano SiO2 pastes mixed with alkali solutions,were investigated.Meawhile,the adsorption mechanisms of alkali ions were discussed.Results showed that the contents of alkali ions adsorbed by C3S-nano SiO2 pastes mixed with de-ionized water increased with increasing substitution levels of nano-SiO2 and/or the initial alkali concentrations.In C3S-nano SiO2 pastes mixed with de-ionized water,each paste was characterized by having a fixed alkali-adsorption capacity that was essentially independent of alkali concentration.No obvious difference between the adsorption capacity of a given paste for K~＋and Na~＋was observed.Adsorption of alkali ions in the pastes is considered to be caused by surface force which is related to the BET specific surface area of the paste,and charge compensation of C-S-H gel,mainly by electrostatic interactions.In C3S-nano SiO2 pastes mixed with alkali solutions,alkali ions may enter the structure of C-S-H gel to replace a part of Ca^2＋in the interlayer.This assumption is supported by the structural characterization of C-S-H gel using ^（29）Si MAS NMR.

Coordination and Supramolecular Assemblies from Alkali+-Cucurbit[5]uril-[CdCl_(4)]^(2-)Systems

Thispaper has investigated the coordination and supramolecular assemblies of alkali metal ions,cucurbit[5]uril(Q[5]),and[CdCl_(4)]^(2-)to confirm whether[CdCl_(4)]^(2-)can produce the“honeycomb effect”,induce coordination of alkali metal ions to Q[5],and form linear coordination polymers.In this work,the effect of alkali metal ions on the construction of Q[5]-Cd^(2+)ion system under acidic conditions was investigated.Five complexes were successfully obtained by solvent evaporation method.Among the five crystal structures obtained,it can be observed that the presence of[CdCl_(4)]^(2-)did not result in the complexation of alkali metal ions by the Q[5]molecule.Instead,a bowl-like Cd^(2+)@Q[5]complex was formed.Indeed,[CdCl_(4)]^(2-)did not produce the honeycomb effect but led to the formation of Q[5]-based honeycomb frameworks with hexagonal cellsoccupied by[CdCl_(4)]^(2-).The experimental results show that cadmium ion showed stronger ability to coordinate to Q[5]in HCl solution.

Selective exchange of alkali metal ions on EAB zeolite

EAB zeolite was successfully prepared and applied to selective adsorption of Li^(+),Na^(+)and K^(+)ions.The physical and chemical properties of the adsorbent were characterized by X-ray diffraction(XRD),X-ray fluorescence(XRF),scanning electron microscope(SEM)and thermogravimetry(TG)methods.The ion exchange behaviours for Li^(+),Na^(+)and K^(+)ions in monomcomponent and multicomponent solutions were studied.In independent ion exchange,the ion exchange capacities ratiosα(/Na/Li)andα(K/Li)were 3.8 and 6.2,respectively.In competitive ion exchange,the selectivitiesβ(Na/Li)andβ(K/Li)increased with the initial concentrations and reached 409 and 992 when the initial concentrations was 100 mmol/L.The thermodynamic study results showed that Gibbs free energy change(ΔGΘ)of ion exchange reaction between Li-EAB and K^(+)was-34.96 kJ/mol,indicating that ion exchange of K^(+)ions was more energetically favourable than Li^(+)ions.The calculation results showed that the energy barriers of ion exchange increased in the order K^(+)Na^(+)<Li^(+).The study shows that EAB zeolite is potential to be used in the separation of alkali ions.

Gallium-based anodes for alkali metal ion batteries

Alkali metal ion batteries(AMIBs)are playing an irreplaceable part in the energy revolution,due to their intrinsic advantages of large capacity/power density and abundance of alkali metal ions in the earth’s crust.Despite their great promise,the inborn deficiencies of commercial graphite and other anodes being researched so far call for the quest of better alternatives that exhibit all-round performance with the balance of energy/power density and cycling stability.Gallium-based materials,with impressive capacity utilization and self-healing ability,provide an anticipated solution to this conundrum.In this review,an overview on the recent progress of gallium-based anodes and their storage mechanism is presented.The current strategies used as engineering solutions to meet the scientific challenges ahead are discussed,in addition to the insightful outlook for possible future study.

Effect of alkali metal ions on the formation mechanism of HCN during pyridine pyrolysis

The catalytic effects of alkali metal ions(Na^(+)and K^(+))on NO_(x)precursor formation during coal pyrolysis were investigated using the N-containing compound pyridine as a model compound.Density functional theory calculations at the B3LYP/6-31G(d,p)level of theory were conducted to elucidate the mechanism of pyridine pyrolysis and the pathways for HCN formation.The calculation results indicate that Na^(+)and K^(+)have distinct influences on different pyrolysis reactions;these alkali metal ions facilitate the initial hydrogen transfer from C_(1)to N and C_(2),whereas they hinder the other hydrogen migration reactions.Both Na^(+)and K^(+)significantly reduce the activation energies for C–C bond breakage and triple-bond formation,whereas they increase the activation energies for the isomerization reactions.The different effects essentially result from the distinct charge distributions induced by the two ions.Due to the distinct influences on the different reactions,the rate-determining steps are modulated,affecting the competitiveness of the different possible pathways of HCN formation.The formation of HCN from pyridine is promoted in the presence of Na^(+)and K^(+)because all the overall activation energies are decreased for different pathways.The calculation results agree well with previous experimental studies.Thus,the findings offer a new and promising approach to reveal the formation mechanism of NO_(x)and facilitate the control of NO_(x)for coal utilization.

Two-dimensional organic cathode materials for alkali-metal-ion batteries

With the increasing demand for large-scale battery systems in electric vehicles（EVs） and smart renewable energy grids, organic materials including small molecules and polymers utilized as electrodes in rechargeable batteries have received increasing attraction. In recent years, two-dimensional（2D） organic materials possessing planar layered architecture exhibit optional chemical modification, high specific surface area as well as unique electrical/magnetic properties, which have been emerging as the promising functional materials for wide applications in optoelectronics, catalysis, sensing, etc. Integrating with high-density redox-active sites and hierarchical porous structure, significant achievements in 2D organic materials as cathode materials for alkali-metal-ion batteries have been witnessed. In this review, the recent progress in synthetic approaches, structure analyses, electrochemical characterizations of 2D organic materials as well as their application in alkali-metal-ion batteries containing lithium ion battery（LIB）, lithium sulfur battery（LSB）, lithium air battery（LAB） and sodium ion battery（SIB） are summarized systematically,and their current challenges including cycling stability and electron conductivity for cathode materials in battery fields are also discussed.

Effects of neutral salt and alkali on ion distributions in the roots,shoots,and leaves of two alfalfa cultivars with differing degrees of salt tolerance

The effects of neutral salt and alkali on the ion distribution were investigated in two alfalfa （Medicago sativa L.） cultivars, including Zhongmu 1, a high salt-tolerant cultivar, and Algonquin, a low salt-tolerant cultivar. The alkali stress expressed more serious growth inhibition than the neutral salt stress at the same Na＋ concentration. Compared with Algonquin, Zhongmu 1 did not exhibit a higher alkali tolerance under the Na2CO3-NaHCO3 treatment with the low Na＋ concentration （50 mmol L-l）. The alkali increased the accumulation of Na＋, Ca2＋, and Mg2＋ in the root and changed the Ca2＋ and Mg2＋ balance in the entire alfalfa plant. The salt and alkali stresses decreased the K＋ and Fe3＋ contents of the roots and leaves, the root Mn2＋ content, and the shoot Zn2＋ content, but they increased the Fe3＋ accumulation of the shoots, the shoot and leaf Cu2＋ contents, and the leaf Zn2＋ content in both alfalfa cultivars. Based on the results obtained under the conditions of this experiment, we found that the salt and alkali stresses reduced the plant growth in both alfalfa cultivars, while the alkali caused a stronger stress than the neutral salt in alfalfa. Thus, we conclude that under hydroponic conditions, the deleterious effects of the alkali on plants are due to the distribution change of some trophic ion balance in the roots, shoots, and leaves of the plants by causing of Na＋, CO3^2-, and/or HCO3- stresses.

Pitting corrosion resistance of a novel duplex alloy steel in alkali-activated slag extract in the presence of chloride ions

In this study, two types of reinforcing steels(conventional low-carbon steel and a novel duplex alloy steel with Cr and Mo) were exposed to chloride-contaminated extract solutions(ordinary Portland cement(OPC) extract and alkali-activated slag(AAS) extract) to investigate their pitting corrosion resistance. The results confirm that the pitting corrosion resistance of the alloy steel is much higher than that of the low-carbon steel in both extract solutions with various Na Cl concentrations. Moreover, for each type of steel, the AAS extract contributes to a higher pitting corrosion resistance compared with the OPC extract in the presence of chloride ions, likely because of the formation of flocculent precipitates on the steel surface.

Effect of Alkali Metal Ions(Li＋, Na＋ and K＋) on the Luminescent Properties of ZnTiO3：Eu3＋ Phosphors

A series of red emitting ZnTiO3 phosphors co-doped with Eu3＋） and alkali metal ions（Li＋, Na＋ and K＋） was prepared by sol-gel method. The crystal structure of the phosphors was investigated by using X-ray diffraction（XRD） and transmission electron microscopy（TEM） after annealing at 700 ℃. The results show that the crystal structure belongs to the hexagonal phase of ZnTiO3 with space group R-3：R. The influence of site occupancy of different alkali metal ions on the emission of ZnTiO3：Eu3＋） phosphors was investigated in detail. The emission intensity was significantly enhanced by introducing alkali metal ions. In contrast to Eu3＋） singly doped ZnTiO3, the red emission intensities of ZnTiO3：Eu3＋） with 4 mol% alkali metal ions（Li＋, Na＋, K＋） were enhanced by about 2.1, 1.7 and 1.4 times, respectively. In addition, the Commission Internationale Ed I＇eclairage（CIE） chromaticity coordinates of ZnTiO3：Eu3＋）, Li＋（0.672, 0.328） are quite similar to the National Television Standard Committee（NTSC） standard values for the red（0.670, 0.380）.

First-principles study on β-GeS monolayer as high performance electrode material for alkali metal ion batteries

Based on the density functional theory calculations,we have investigated the feasibility of two-dimensionalβ-GeS monolayer as high-performance anodes for alkali metal ion batteries.The results show that the electrical conductivity of β-GeS monolayer can be enhanced after adsorbing the alkali metal atoms owing to the semiconductor-to-metal transition.The low diffusion barriers of alkali metal atoms on the β-GeS surface indicate a rapid charge/discharge rate without metal clustering.Moreover,the low average open-circuit voltage(0.211 V)and a high theoretical capacity(1024 mAh·g^(-1))for Na suggest that theβ-GeS monolayer is a promising anode material for Na-ion batteries with high performance.

Revealing the structure design of alloyed based electrodes for alkali metal ion batteries with in situ TEM

Alloyed based anode materials with high theoretical specific capacity and low reaction potential are considered to be highly potential high-energy density anode materials for alkali metal ion batteries(AMIBs).Thus,the design of alloyed based materials with high electrochemical performance has attracted great attention.Among the numerous characterization methods for guiding electrode materials design,in situ transmission electron microscopy(TEM)gradually plays an irreplaceable role due to its high temporal and spatial resolution in directly observing the change of morphology,crystal structure and element evolutions.Herein,we reviewed the two current research hotspots and mainly focused on the structure design of alloyed based electrode material under the guidance of in situ TEM.Specifically,various nanostructure designs of alloyed based electrode materials with guidance of in situ TEM were employed to solve the key scientific issues of the violent volume change during alloying/dealloying processes for enhanced electrochemical performances.Mainly through introducing buffer space in the electrode material to reduce volume change to improve structural stability,including porous structure(0 D),nanotube structure(1 D),simple hollow structure,yolk-shell structure and some hybrid hollow structures(3 D).Furthermore,the direct guidance of in situ TEM is expected for creating new opportunities to nextgeneration electrode material design for AMIBs.

Effect of Doped Alkali Metal Ions on the SO_(2) Capture Performance of MnO_(2) Desulfurization Materials at Low Temperature

Sulfur dioxide(SO_(2))emissions from diesel exhaust pose a serious threat to the environment and human health.Thus,desulfurization technology and the performance of desulfurization materials must be improved.In this study,MnO_(2) was modified with various alkali metal ions using the impregnation method to enhance its SO_(2) capture performance.The composites were characterized intensively by scanning electron microscopy,energydispersive X-ray spectroscopy,X-ray diffraction spectroscopy,and Brunauer-Emmett-Teller theory.The SO_(2) capture performance of these composites were measured via thermogravimetry,and the effect of doping with alkali metal ions on the SO_(2) capture performance of MnO_(2) was investigated.Results showed that the SO_(2) capture performance of MnO_(2) could be enhanced by doping with alkali metal ions,and the MnO_(2) composite doped with LiOH(2.0 mol/L)had the best SO_(2) capture capacity(124 mgSO_(2)/gMaterial),which was 18%higher than that of pure MnO_(2).Moreover,the type and concentration of alkali metal ions had varying effects on the SO_(2) capture performance of MnO_(2).In our experiment,the SO_(2) capture performance of the MnO_(2) doped with NaOH,LiCl,Na2CO3,K2CO3,and Li2CO3 composites were worse than that of pure MnO_(2).Therefore,the influences of the type and concentration of alkali metal ions to be doped into desulfurization materials must be considered comprehensively.

Understanding charge transfer of Li^+ and Na^+ ions scattered from metal surfaces with high work function

For Li^＋ and Na^＋ ions scattered from high work function metal surfaces, efficient neutralization is observed, and it cannot be explained by the conventional free electron model. In order to explain these experimental data, we investigate the velocity-dependent neutral fraction with the modified Brako–Newns（BN） model. The calculated results are in agreement with the experimental data. We find that the parallel velocity effect plays an important role in neutralizing the Li^＋ and Na^＋ ions for large angle scattering. The nonmonotonic velocity behavior of neutral fraction is strongly related to the distance-dependent coupling strength between the atomic level and metal states.

燃煤锅炉烟气湿法脱硫废水中重金属及钙镁离子沉淀规律研究

燃煤锅炉烟气湿法脱硫废水中的重金属及钙镁等离子危害较大,开展其沉淀去除规律的研究有利于废水中有用元素的资源化回收和废水的回用。采用碱液沉淀法对脱硫废水进行分级处理,对沉淀产物采用SEM-EDS等手段进行表征。结果表明,采用氢氧化钙作为沉淀剂可以实现去除重金属、回收镁资源及去除氟化物和降低废水硬度等多种目标。在去除重金属离子的过程中,当脱硫废水pH值为9.0~9.5时,废水中的重金属离子可得到有效去除且达到污水排放标准,镁离子几乎没有损失,钙增加率也较低,仅为4.6%以下;将废水pH值调整为9.5~9.7可有效回收废水中的镁元素,镁的回收率在62%以上,回收效果较好。在碱性条件下,向废水中投加Na_(2)CO_(3)可有效降低废水中的钙离子和残留的镁离子,实现废水降硬的目标。不同pH值下沉淀物的SEM-EDS能谱显示,对脱硫废水进行梯级pH处理可以达到分级去除重金属污染物和回收镁元素的目标。通过对脱硫废水中重金属及钙镁结垢离子的沉淀规律研究,实现了废水的分质分盐有用成分的资源化回用,避免了产生杂盐危废造成二次污染的可能,达到了脱硫废水的零排放的目标。

钨矿碱分解工艺制备仲钨酸铵全流程仿真计算

以钨矿碱分解工艺制备仲钨酸铵全流程为对象,基于质量守恒、化学平衡、元素分配约束和指标约束等原理,构建钨矿配矿、磨矿、碱分解、脱磷、离子交换、除钼和蒸发结晶的热力学模型,进而根据各工序物料的迁移传递关系,应用MetCal软件平台,开发钨矿碱分解工艺制备仲钨酸铵全流程仿真计算系统,并采用典型工况下的实际值对模型计算的可靠性进行实例验证。研究结果表明:碱分解浓料中WO_(3)和P质量分数计算值与实际值的相对误差分别为-5.755%和-12.195%,钨渣中WO3、P、Fe、Mn和Ca质量分数的相对误差分别为-2.026%、-5.439%、-14.819%、-14.971%和11.826%;脱磷后液中WO3和P质量分数的相对误差分别为5.513%和-7.692%,脱磷渣中WO_(3)、P和Ca质量分数的相对误差分别为-5.834%、3.337%和7.113%;除钼后液中WO3和Mo质量分数的相对误差分别为-1.627%和-9.375%,除钼渣中WO_(3)、Mo、S和Cu质量分数的相对误差分别为2.547%、-8.827%、8.686%和9.692%。

KOH/NaOH两种碱性体系下合成纳米片层分子筛

以小分子阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)为结构导向剂,在KOH和NaOH 2种碱性体系下水热合成纳米片层分子筛,并分析K^(+)、Na^(+)和Silicalite-1晶种溶胶对合成样品的物相和形貌的影响。结果表明:以KOH为碱源,在添加Silicalite-1晶种溶胶的条件下,水热晶化96 h即可合成高结晶度、纳米薄片沿b轴方向有序堆积多层和随机堆积单层的混合形貌ZSM-5分子筛;以NaOH为碱源,在不添加Silicalite-1晶种溶胶的条件下,水热晶化48 h即可合成高结晶度、由纳米薄片和纳米棒紧密堆积而成的纺锤状聚集体形貌MOR分子筛。研究结果可为进一步优化合成MOR和ZSM-5分子筛纳米片提供思路。

Ion-induced kinetic electron emission from ~6LiF,~7LiF and MgF_2 thin films

Secondary electron yields for Ar^＋ impact on 6LiF, 7LiF and MgF2 thin films grown on aluminum substrates are measured each as a function of target temperature and projectile energy. Remarkably different behaviours of the electron yields for LiF and MgF2 films are observed in a temperature range from 25 ℃ to 300 ℃. The electron yield of LiF is found to sharply increase with target temperature and to be saturated at about 175 ℃. But the target temperature has no effect on the electron yield of MgF2. It is also found that for the ion energies greater than 4 keV, the electron yield of 6LiF is consistently high as compared with that of 7LiF that may be due to the enhanced contribution of recoiling 6Li atoms to the secondary electron generation. A comparison between the electron yields of MgF2 and LiF reveales that above a certain ion energy the electron yield of MgF2 is considerably low as compared with that of LiF. We suggest that the short inelastic mean free path of electrons in MgF2 can be one of the reasons for its low electron yield.

盐碱胁迫下2,4-表油菜素内酯和褪黑素对百合幼苗光合生理的影响

以‘西伯利亚’百合种球为试材,采用室内盆栽试验的方法,研究了中度(150 mmol·L^(-1))盐碱胁迫下叶施2,4-表油菜素内酯(EBR)、褪黑素(MT)及其复合处理对百合幼苗生长、光合和叶绿素荧光参数、离子转运及抗氧化系统的影响,以期为二者缓解百合盐碱胁迫提供参考依据。结果表明:盐碱胁迫下百合株高、叶表面积以及生物量显著下降,施用EBR和/或MT可以缓解百合受到的生长抑制。150 mmol·L^(-1)盐碱胁迫下,与喷施清水对照(CK)处理相比,EBR+MT处理的SPAD值增加37.2%,百合地上部和地下部N含量分别增加83.6%和40.7%,叶绿素荧光参数中PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)和光化学淬灭系数(qP)分别增加14.6%、42.9%和50.0%,而非光化学淬灭系数(NPQ)下降9.2%,净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)分别增加56.3%、29.7%和42.7%,胞间二氧化碳(Ci)下降19.3%。150 mmol·L^(-1)盐碱胁迫下,百合地上部和地下部Na^(+)含量增加,而K^(+)含量下降,EBR+MT处理后百合地上部和地下部K^(+)/Na^(+)值分别增加110.9%和98.8%;同时,施用EBR和/或MT处理能够促进百合Cu/Zn-SOD、POD以及CAT基因的表达,激活抗氧化酶SOD、POD以及CAT活性。综上所述,施用EBR和/或MT处理均能够不同程度的提高百合SPAD值,减缓盐碱胁迫对PSⅡ光系统的抑制,维持植物体内Na^(+)和K^(+)的平衡,激活SOD、POD和CAT等抗氧化酶基因表达并提高酶活性,促进百合株高和生物量的增加,其中以复合喷施EBR+MT处理下百合幼苗的抗盐碱性效果更好。

盐碱环境下氯化物侵蚀对混凝土桥梁耐久性的影响

为解决西北地区盐碱环境中钢筋混凝土桥梁的腐蚀及耐久性问题,通过现场调研西北地区盐碱环境中桥梁病害问题、土壤和桥梁中氯离子的分布情况,运用修正Fick第二定律和有限元模拟拟建桥梁各部位的氯离子扩散规律,并预测了桥梁的耐久性寿命,探讨了提高混凝土强度和保护层厚度等措施对桥梁耐久性寿命的提升效果。结果表明,盐碱环境中表层土壤氯离子含量最高,服役桥梁存在多种病害,下部结构最易受到氯离子侵蚀。服役桥梁下部结构承台、桥墩和桩基的耐久性寿命分别为55.3、63.1和91.5 a,通过合理提升混凝土强度、提高保护层厚度等可以使桥梁的耐久性达到要求。

超高镍正极材料空气稳定性研究及其电化学性能

超高镍氧化物被认为是锂离子动力电池的首选正极材料,但是其在空气中的存储稳定性较差,严重影响了实际应用。本文研究了LiNi_(0.95)Co_(0.025)Mn_(0.025)O_(2)(NCM)材料暴露在空气中的稳定性及其对电化学储锂性能的影响,进一步探索了超高镍正极材料颗粒表面残留碱性物质(残碱)随时间变化的形成机制。材料表征结果表明,超高镍材料在短时间内暴露于空气时,其表面形成孤岛状的残碱,且这些残碱颗粒的尺寸随着暴露时间的延长而增大。电化学交流阻抗谱(EIS)和微分容量曲线(dQ/dV)测试结果表明,残碱的形成显著增加了NCM正极材料的电化学阻抗,加剧了超高镍正极材料储锂循环中的不可逆相变和结构退化,从而影响了放电容量和循环寿命。在2.7~4.3 V(vs.Li^(+)/Li)的工作电压和0.5 C电流密度下,未暴露空气的初始NCM正极材料的首圈放电比容量为208.1 mAh/g,循环200圈后容量保持率为70.7%,而在空气中暴露12 h和14天后的NCM材料的首圈放电比容量分别为202.9 mAh/g和171.8 mAh/g,循环200圈后的容量保持率仅有60.1%和53.1%。