Investigating the pseudo – Capacitive properties of interlayer engineered VOPO4 by organic molecule intercalation

The varying oxidation states of vanadium has given vanadium phosphate-based compounds a very rich chemistry, that has resulted in increasing interest in them for varying applications such as energy storage systems, including supercapacitors. Among them is vanadyl phosphates that exist in several polymorphs and have seen lots of research on their applications in alkali metal rechargeable batteries. Layered VOPO₄ is of much interest due to its ability to undergo intercalation reaction. In this work, an organic molecule (triethylene glycol) was successfully intercalated into the layers of VOPO₄ in a two-step solvothermal reaction. This approach resulted in exfoliation of VOPO₄ layers leading to enlarged interlayer spacing, as well as enhancing the conductivity by reducing the band gap of the material. The intercalated material (TrEG-VOP) demonstrated an enhanced supercapacitor properties with capacitance 473 Fg^-1 and capacitance retention of 80% against capacitance 400 Fg^-1 and capacitance retention of 55% for the pristine (VOP)     

酚醛树脂基高比表面积活性炭的制备及其电容特性的初步研究

以酚醛树脂为原料，碱性化合物为活化剂制取酚醛树脂基高比表面积活性炭，初步考察了活化剂与酚醛树脂的质量比、活化温度、固化温度等工艺参数对活性炭的碘吸附性能和在有机电解液中的比电容的影响。实验结果表明，在活化剂与酚醛树脂的质量比为2，活化温度为1000℃，固化温度为110℃的工艺条件下，制得的高比表面积活性炭在1MLiPF6(DMC:EMC:EC=1:1:1)有机电解液中的比电容可达32．89F／g，而碘吸附值则在固化温度为120℃时达到最大值1400mg／g。     

Evidence of Nitrate Formation from the Thermal Decay of Alkali Metal Dinitramides

The thermal decomposition products of five alkali metal dinitra-mides were examined by mass spectral and X-ray diffraction analysis. All five salt residues (Li, Na, K, Rb and Cs) showed no evidence of the parent dinitramide by mass spectrometry and showed only metal nitrate adducts to be present. X-ray diffraction patterns of the decay residues matched JCPDS reference patterns and confirmed that the dinitramide salts thermally decomposed to their respective alkali metal nitrate.     

Hydrogen adsorption on M-ZSM-12 zeolite clusters (M = K,Na and Li): a density functional theory study

The molecular adsorption of hydrogen has been studied theoretically via DFT on additional framework with alkali metal atoms (K, Na and Li) in ZSM-12 zeolite. A 14T channel zeolite cluster model was used. Lewis acidity of alkali metals decreases with increasing atomic radius of alkali metal and H₂ adsorption. Adsorption enthalpy values were computed to be ?7.4 and ?5.1 kJ/mol on Li- and Na-ZSM-12 clusters, respectively. Hydrogen adsorption enthalpy values for Li- and Na-cases are meaningfully larger than the liquefaction enthalpy of hydrogen molecule. This designates that Li- and Na-ZSM-12 zeolites are potential cryoadsorbent materials for hydrogen storage.     

Effect of ultraviolet irradiation on the selective transport of alkali metal ions through 2,3-epithiopropyl methacrylate–methacrylic acid copolymer membrane

Cationic exchange membranes were prepared with 2,3-epithiopropyl methacrylate (ETMA)–methacrylic acid (MAc) copolymer. Transport of alkali metal ions against their concentration gradient through the membranes was investigated by using the system which contains HCl (left side) and alkali metal solution including two kinds of alkali hydroxides (right side). The effect of ultraviolet (UV) irradiation on the selective transport of alkali metal ions through the ETMA–MAc copolymer membranes was investigated. The membranes were irradiated with a 6-W low pressure mercury lamp at a distance of 10 cm at room temperature in air. The transport selectivity could be increased by using UV-irradiated membranes and the selectivity increased with increasing irradiation time up to 2–3 h, although the transport rate of alkali metal ions decreased with increasing time of UV irradiation. The maximum selectivity of K⁺/Na⁺, Na⁺/Li⁺, and K⁺/Li⁺ were 1.7, 2.0, and 4.2, respectively. In order to explain this phenomena, the effect of UV irradiation on the properties of the membranes was studied. It was concluded that the increase of the selectivity is attributed to the formation of the dense membrane by photocrosslinking of the membrane by UV irradiation.     

Zn/NaHZSM-5沸石在C5～C8链烷烃芳构化反应中的催化性能

采用氨气程序升温脱附（NH₃-TPD）、紫外-可见光谱和小型固定床反应器，重点研究了碱金属钠离子和过渡金属锌离子改性对纳米H-ZSM-5沸石表面酸性及其催化C₅～C₈链烷烃芳构化反应性能的影响。结果表明，用碱金属钠离子改性能够有效地消除沸石表面的强酸中心，适当降低催化剂表面酸量，从而减少甲烷、乙烷和丙烷等低值副产物的生成，优化芳构化反应产物分布。适宜的Zn²⁺负载量为3%（质量分数），过高的Zn²⁺负载量会使产物中干气生成量增大，不利于芳烃收率的提高。C₅～C₈链烷烃芳构化的适宜反应温度为530℃。     

碱金属催化添加剂对PX液相氧化过程的影响

验证了K+,Na+类添加剂在对二甲苯(PX)液相氧化体系中的助催化活性。对添加不同浓度碱金属离子的助催化作用进行了多组动力学实验,考察了添加K+,Na+对体系主反应和燃烧副反应和TA固体产品中4-CBA含量的影响,获得了对PX氧化过程的影响规律。实验发现,碱金属离子的添加有不同程度的活化效果;添加w(K+)=(30~100)×10-6可有效地加速主反应,但过大时(>500×10-6)作用就变得不明显,甚至会产生抑制;与K+相比,Na+对主反应的助催化活性要低得多。     

Optic properties of niobium-phosphate glasses containing lithium,sodium, and potassium oxides

The dependence of the optic properties of niobium-phosphate glasses containing alkali metal oxides on their composition and structural features is investigated. Along with the increase of the niobium oxide content, a shift of the optic absorption boundary to the long-wavelength range and a substantial increase of the refraction index (from 1.50 to 1.73) are observed. The increase of the alkali metal mass results in the decrease of the refraction index and a shift to the short-wavelength range. The correlation between the length of polyphosphate groups and the type of alkali oxide is registered: the chain length increases from lithium to potassium.     

Computational simulation of mass transfer in extraction of alkali metals by means of nanoporous membrane extractors

Theoretical study on extraction of alkali metals using a membrane contactor is carried out in this work. A novel model is built to simulate the flow and the concentration in a membrane extractor based on the finite element analysis. CFD model is applied by solving the 2D Navier–Stokes equations as well as mass conservation equations for steady state conditions in membrane extractors. The model predicts of the velocity field, the pressure and the concentration of alkali metal in the membrane module under laminar flow regime. The results of simulation were used for determination of concentration distribution and effect of extractant concentration on extraction efficiency and mass flux of cesium in the membrane extractor. Moreover, the simulation results for the extraction of cesium using the membrane extractor were compared with the experimental data in order to validate the proposed mass transfer model and showed great agreement.     

On-Line Chemical Analysis of Individual Alkali-Containing Aerosol Particles by Surface Ionization Combined with Time-of-Flight Mass Spectrometry

An aerosol mass spectrometer for measurements of the alkali metal content in individual submicron aerosol particles is presented. The instrument combines surface ionization of individual particles on a hot platinum surface with orthogonal acceleration time-of-flight mass spectrometry. The instrument simultaneously provides the content of different alkali metal elements in single particles with high sensitivity. The instrument is characterized in laboratory experiments, and determination of the alkali metal content is demonstrated for particle diameters of 50–500 nm. The technique is demonstrated in ambient air measurements at an urban background site, and sea spray particles and particles originating from biomass burning are identified based on their content of sodium and potassium. Possible further improvements and applications of the technique are discussed.     

水溶性聚酯合成及其溶解特性研究

研究了SIPM用量和聚合反应条件对酯交换反应速度、产物分子质量的影响,考察了合成产物的结构和碱溶解特性。结果表明:SIPM用量增加,酯交换反应速度下降,当SIPM质量分数由8%增加到12%时,反应速度明显下降,产物分子质量随聚合反应体系余压减小和SIPM用量降低而增大,得到的水溶性聚酯有很好的碱可溶性,减量率随NaOH浓度增加,碱解时间延长,温度提高而增大。     

碱金属化合物对V2O5/AC催化剂低温脱硝的影响

研究了碱金属化合物(K₂SO₄)对活性炭(AC)担载五氧化二钒(V₂O₅)组成的V₂O₅/AC催化剂的低温脱硝活性的影响。发现在V₂O₅/AC催化剂表面负载碱金属化合物(K₂SO₄)后其脱硝活性大大降低。用等体积浸渍法制备了V₂O₅/AC催化剂和K_x-V₂/AC(x=0.5,1,2)催化剂。采用5种模型对动力学实验数据进行关联。结果显示,无论V₂O₅/AC催化剂是否负载K₂SO₄,Eley-Rideal模型均比其他模型可更好地描述SCR脱硝反应,碱金属化合物(K₂SO₄)的存在提高了反应活化能,但并不改变反应机理。     

Electrical AC behaviour of MPCVD diamond Schottky diodes

The present work reports some experimental results on the electrical AC behaviour of metal–undoped diamond Schottky diodes fabricated with a free-standing MPCVD diamond film (5 μm thick). The metals are gold for the ohmic contact and aluminium for the rectifier. The capacitance and loss tangent vs. frequency shows that capacitance presents a relaxation maximum at frequencies near 10 kHz at room temperature. Although the simple model (small equivalent circuit) can justify the values for the relaxation, it cannot justify the departure from the Debye model, also verified in the Cole–Cole plot. Taking into account the existence of traps in the depletion region, a best fit to the experimental results was obtained. The difference between the Fermi level and the band edge of 0.2–0.3 eV is in agreement with the activation energy found from the loss tangent analysis. The capacitance with applied voltage (Mott–Schottky plots) gives a defect density of 10¹⁶ cm⁻³ with contact potentials near 0.5 V and the profile of defect density obtained shows a major density (approx. 10¹⁷ cm⁻³) in a layer with a thickness less than 50 nm from the junction, decreasing by one order of magnitude with increasing distance. Finally a structural model is proposed to explain the AC behaviour found.     

A study of the role of alkali metal salts as char gasification catalysts by Knudsen cell mass spectrometry

Knudsen cell mass spectrometry has been used to determine the gaseous species in thermodynamic equilibrium with admixtures of carbon and alkali metal salts. Both halides and carbonates were used as additives. In addition to measurements of equilibrium vapor pressures, the effect of added steam or carbon dioxide on the composition of the Knudsen cell effusate was examined. With the carbonates, the equilibrium pressure of the alkali metal over the solid phase is at least twice that of the decomposition pressure of the pure salt, but orders of magnitude below that appropriate to the carbothermic reduction of the carbonate. By way of contrast, the alkali halide-carbon admixtures exhibit no free metal vapor up to 1000 K, a temperature in the range employed for gasification. Apparently, the carbonates react with the carbon to form a stable phase with alkali metal activity substantially below unity. Inferences on the composition of such a phase and its role in promoting the carbon gasification rate are discussed.     

Characterization of γ-alumina doped with Li and K by infrared studies of CO adsorption and27Al-NMR

The influence of alkali metals on the Lewis acid sites of gamma-alumina has been studied with NMR and IR of adsorbed CO. The physical properties of the alumina are slightly changed by the addition of low alkali metal concentrations. Li and K are adsorbed selectively on tetrahedral Lewis Al³⁺ sites of the alumina surface. These effects on the tetrahedral cations are more marked with increasing molar concentration and ionic radius of the alkali metal added to alumina. Results demonstrate that the influence of the alkali metals is not only due to steric factors but also to possible electronic modifications.This work was supported by a grant from CONICET, Argentina.     

表面积对煤基电容炭电化学性能的影响

以河北无烟煤为原料,KOH为活化剂,采用化学活化法制备具有高比表面积的煤基电容炭,考察煤基电容炭的比表面积对无机/有机体系下双电层电容器电化学性能的影响。结果表明:随着碱煤比的增加,所制电容炭的比表面积、总孔容和中孔率增加。当碱煤比达到3.5时,所制电容炭的比表面积、总孔容和中孔率分别为3 389 m2/g、2.041 cm3/g、49.9%。可以看出,对于无机/有机体系,在相同的比表面积变化规律下,电容器电化学性能的变化规律略有不同。当碱煤比小于2时,所制电容炭的比表面积小于2 400 m2/g,此时对于无机/有机体系,电容器的比电容变化规律相同,比电容都随比表面积的增大增幅明显。当碱煤比大于2时,所制电容炭的比表面积大于2 400 m2/g,此时随着比表面积的继续增大,对无机体系,电极材料的比电容几乎维持不变,比电容最高可达331 F/g;对有机体系,电极材料的比电容增幅减缓,比电容最高可达192 F/g。当碱煤比为2时,电容炭的比表面积为2 382 m2/g,此时无论对于无机体系还是有机体系,电容器在保持相对较高比电容的同时具有相对较高的电容保持率。由此可知,一定程度上,提高电极材料的比表面积有利于提升超级电容器的电化学性能。制备具有适宜比表面积的电容炭,在得到较高电容性能电容器的同时更能有效控制成本。同时,以煤为原料制备电容炭,可提升煤的附加值,具有很好的市场前景。     

方肋微通道内流动沸腾的气泡动态与传热特性分析

为揭示方肋微通道热沉内流动沸腾的传热传质机理,本文基于耦合VOF方法与“饱和界面”相变模型对微通道内单个气泡绕流加热方肋的传热传质过程进行了数值研究。通过分析该过程中气泡增长速率与方肋壁面传热系数的变化,重点讨论了初始气泡体积和入口雷诺数Re对相变传热效率和流动结构的影响。结果表明：在气泡流经加热方肋过程中,气泡与方肋表面之间形成一层薄液膜,该薄液膜的相变蒸发极大强化方肋表面的换热效果,换热系数较相同条件下的单相流动提升6倍以上。此外液膜厚度随Re增大而变厚,液膜热阻相应增大,液膜蒸发对换热的促进作用随Re增大而降低。最后考察了气泡体积对方肋壁面换热的影响,结果表明：初始体积大的气泡具有更薄的液膜厚度及更大的蒸发面积,表现出更高的相变传热效率;而小气泡对壁面温度影响较小。     

尼龙6/PEO聚电解质抗静电复合材料的结构与性能研究

通过碱金属离子与聚氧化乙烯（PEO）的络合配位制备了不同比例的PEO聚电解质,将PEO聚电解质与尼龙6熔融共混挤出,制备抗静电尼龙6复合材料;测试了复合材料的力学性能和电性能;分析了影响机理,并借助傅立叶转换红外光谱和扫描电镜表征了复合材料的结构.结果表明,碱金属离子与PEO结构单元的物质的量比为1/6时,复合材料体积电阻率下降幅度达到了5个数量级,同时冲击强度明显提高,拉伸强度有所下降.红外谱图显示,尼龙6基体与聚电解质发生了相互作用.     

Fabrication of manganese oxide electrodes by radio frequency sputtering for electrochemical capacitors

Manganese oxide thin films were sputtered on graphite foils by radio frequency (RF) sputtering. At the 1,000th cycle of potential cycling, maximum mass specific capacitance of 341 F g^?1 was obtained in 0.5 M LiCl and with optimum sputtering conditions (5 sccm of oxygen, 20 mTorr, and 70 W) as well as annealing temperature (150 °C). These show its high electrochemical stability and good mass specific capacitance at a higher sweep rate of 100 mV s^?1. In addition, the higher the volume flow rates of oxygen, the larger the amount of trivalent manganese oxide and the higher the surface roughness, the higher the mass specific capacitance at lower volume flow rates of oxygen, but the amounts of trivalent manganese oxide were almost the same and the mass specific capacitance decreased due to decreasing surface roughness at higher volume flow rates of oxygen. Furthermore, the geometric specific capacitance increases with increasing sputtering pressure and power.     

Countercation intercalation and kinetics of charge transport during redox reactions of nickel hexacyanoferrate

The dynamics of charge propagation in nickel hexacyanoferrate, a model metal-substituted analogue of Prussian Blue-type cyanide-bridged systems, was considered in electrolytes containing potassium and other alkali metal cations. The apparent (effective) diffusion coefficients for charge transport were determined using a large-amplitude potential-step chronocoulometry and small-amplitude potential-step chronocoulometric potentiostatic intermittent titration. The dependence of diffusion coefficient on the potential applied is consistent with the intercalation like model of the counter-cation sorption/desorption during redox processes of nickel hexacyanoferrate. Some differences in diffusion coefficients may originate from distinct charge densities (membrane properties) of the oxidized and reduced metal hexacyanoferrate structures. The existence of strong attractive interactions between an alkali metal cation and the cyanometallate matrix is also expected. The overall dynamics of charge propagation seems to be controlled by transport of electrolyte cations within the film rather than by electron self-exchange (hopping) between the mixed-valence hexacyanoferrate(III,II) ionic sites.