用离子迁移技术实现大气压下电负性气体电子吸附截面的测量研究

电子吸附过程对于电负性气体的物理特性和化学特性都起着重要的作用。为此,采用脉冲电子源,配合经过优化设计的迁移管,简便有效地实现了大气压下电负性气体电子吸附截面数据的测量。首先对迁移管电场进行了优化设计,接着研究了脉冲电压峰值、迁移管长度和迁移电场强度对到达法拉第板电子数n_(e0)的影响规律;然后探讨了高电负性气样配置的方法,最后测量了几种SF_6分解产物的电子吸附截面数据,测量的气体包括SO_2、CF_4、SOF_2、SO_2F_2和SF_6。研究结果表明:所提出的方法能有效地测量电负性气体的电子吸附截面;迁移管中电场的均匀程度主要受迁移环厚度与迁移环间绝缘层厚度之比的影响,该比值越小,电场就越均匀;脉冲峰值电压对到达法拉第板电子数n_(e0)影响不大;在短迁移管情况下,迁移电场强度对ne0有较大影响,在长迁移管情况下则影响不大;电场均匀程度和气样质量浓度是影响测量准确度的主要因素。

从头算分子动力学研究硫脲嘧啶及其互变异构体在低能电子作用下的解离过程

运用玻恩-奥本海默分子动力学模型结合密度泛函理论研究了气相下硫脲嘧啶与低能电子吸附解离动力学过程,发现硫脲嘧啶及其互变异构体在吸附解离过程中一个重要的脱氢现象,即特定位置的化学键N—H键,C—H键断裂,使其在N位点和C位点失去氢原子,形成解离过程中最主要的负离子碎片——闭壳层脱氢负离子(TU-H)-为了更深刻地认识脱氢现象,分别对断裂的化学键进行势能曲线扫描,对键解离能、电子亲和能、负离子(TU-H)-出现势进行计算对比发现,在所有断裂的化学键中N—H键最容易发生断裂,而负离子(TU-H)-的形成主要源于N—H键的断裂.

二氧化硅吸附铝离子的X射线光电子能谱(XPS)表征

用X射线光电子能谱技术研究了不同pH条件下二氧化硅对铝离子的吸附作用。在pH分别为3.74、4.25和4.88条件下,吸附在二氧化硅表面的铝离子的Al2p电子结合能依次为74.30、74.90、75.10eV。根据Al3+在水溶液中的一级水解常数pK1=4.99,认为在pH=3.74条件下,吸附在二氧化硅表面的铝离子的形态为Al3+,而在其余两种pH条件下表面铝离子的形态为Al(OH)2+。

二维硼碳基纳米结构上的吸附及其性质

综述金属原子与非金属原子和分子在石墨烯、BC3平面等二维硼碳基纳米结构上的吸附所表现出的各种物理性质及可能的应用.纯净的石墨烯为零带隙的半金属、无磁且自旋轨道耦合效应非常弱,BC3平面为间接带隙半导体,但金属原子与非金属原子和分子的吸附可能使石墨烯体系在Dirac点处打开带隙、具有强自旋轨道耦合效应,可能使石墨烯体系与二维BC3体系具有磁有序、超导电性及应用在氢存储上.另外石墨烯表现出非常好的分子探测性能.

平板型电极微腔放电的特性

为研究微腔结构的放电特性,基于平行板电极、以微间隙介质板构建微腔,由直流电压激励驱动,分别得到了空气和氮气环境下微腔放电的击穿电压、伏安特性曲线及其与介质板间距、气体压强的关系。结果表明:不管是在空气还是N2中,微腔结构的放电特性均与传统板对板电极不同,击穿电压均随着微腔结构高度(两块介质板横截面之间的距离)的变小(从90μm变至20μm)而增大。利用粒子网格/蒙特卡罗(PIC/MCC)方法,对大气压N2中微电极所形成的放电结构的击穿特性进行了模拟研究。结果表明:与实验结果相似,击穿电压受微腔高度影响很大,该现象是由于微腔介质吸附电子所致。微腔越窄,吸附越强烈,对电子繁流过程的影响越大,击穿电压也越高。

七氟异丁腈负离子结构与反应活性的理论研究

新型环保绝缘气体七氟异丁腈(C4)在高压输电应用中备受关注.本文采用多种高精度量子化学理论方法研究了C4吸附电子后形成C4−负离子的结构、光谱、寿命以及与CO_(2)的反应机理和动力学.结果表明,电子进入C≡N的π^(*)反键轨道,通过弯曲C—C=N形成C4−负离子,绝热电子亲合能的最佳预测值为0.30 eV.在0~2 eV范围内C4−具有显著的光电子吸收峰,亚稳态C4−负离子经约9 kJ/mol能垒断裂C—F键生成稳定的长寿命[F...(CF_(3))_(2)CCN]−中间体.C4−+CO_(2)反应存在进攻F或CN上的C和N 3种复合-解离机理,在电气应用条件下,以CO_(2)进攻氰基CN途径为主,诱发负电荷从CN向CO_(2)转移.

In situ investigation of atmospheric corrosion behavior of PCB-ENIG under adsorbed thin electrolyte layer

The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.

Preparation, characterization, and catalytic performance of high efficient CeO_2-MnO_x-Al_2O_3 catalysts for NO elimination

A series of CeO2‐MnOx‐Al2O3 mixed oxide catalysts （Ce：Mn：Al mole ratio=6：4：x, x=0.25, 0.5, 1, 2） were prepared by a simple one‐step inverse co‐precipitation method to investigate the influence of the incorporation of Al3＋ into CeO2‐MnOx mixed oxides. CeO2‐MnOx, CeO2‐Al2O3, and MnOx‐Al2O3 mixed oxides, and CeO2 were prepared by the same method for comparison. The samples were characterized by XRD, Raman, N2 physisorption, H2‐TPR, XPS, and in situ DRIFTS. The catalytic re‐duction of NO by CO was chosen as a model reaction to evaluate the catalytic performance. The incorporation of a small amount of Al3＋into CeO2‐MnOx mixed oxides resulted in a decrease of crys‐tallite size, with the increase of the BET specific surface area and pore volume, as well as the in‐crease of Ce3＋and Mn4＋. The former benefits good contact between catalyst and reactants, and the latter promotes the adsorption of CO and the desorption, conversion and dissociation of adsorbed NO. All these enhanced the catalytic performance for the NO＋CO model reaction. A reaction mecha‐nism was proposed to explain the excellent catalytic performance of CeO2‐MnOx‐Al2O3 catalysts for NO reduction by CO.

Electron Attachment Studies for CHCl3 Using Ion Mobility Spectrometry

The dissociative electron attachment process for CHCl3 at different electric field have been studied with nitrogen as drift and carrier gas using corona discharge ionization source ion mobility spectrometry （CD-IMS）. The corresponding electron attachment rate constants varied from 1.26×10-8 cm3/（molecules s） to 8.24×10-9 cm3/（molecules s） as the electric field changed from 200 V/cm to 500 V/cm. At a fixed electric field in the drift region, the attachment rate constants are also detected at different sample concentration. The ionmolecule reaction rate constants for the further reaction between Cl^- and CHCl3 are also detected, which indicates that the technique maybe becomes a new method to research the rate constants between ions and neural molecules. And the reaction rate constants between Cl- and CHCl3 are the first time detected using CD-IMS.

Treatment of Organic Wastewater Containing Cr^(3+) by a Novel Complex Process of Electrodeposition and Biofilm

A novel complex process of electrodeposition and biofilm is utilized to treat organic wastewater containing Cr 3+, and its purifying mechanism is also described in this article. In details, organic materials in wastewater are consumed as nutritious source by biofilm composed of microorganism and EPS (extracellular polysaccharide substance). While one part of heavy metal ions, such as Cr 3+, is removed by electrodeposition, the other part is adsorbed on biofilm. In contrast, experimental data of single electrodeposition or biofilm process are listed. Further, the kinetic curves of microbes cultivated or microbes acclimated by Cr 3+ to degrade glucose are provided,too. In conclusion, the experimental results indicate that initial wastewater consists of C 6H 12O 6 (500 mg·L -1), Cr 3+ (10 mg·L -1), after treated with the complex process, concentrations of C 6H 12O 6 and Cr 3+ are on the scale of 15-20 mg·L -1, and less than 1 mg·L -1, respectively. Purified water can meet the standards of industrial reused water.

Treatment of Organic Wastewater Containing Cr3+ by a Novel Complex Process of Electrodeposition and Biofilm

A novel complex process of electrodeposition and biofilm is utilized to treat organic wastewater containing Cr 3+, and its purifying mechanism is also described in this article. In details, organic materials in wastewater are consumed as nutritious source by biofilm composed of microorganism and EPS (extracellular polysaccharide substance). While one part of heavy metal ions, such as Cr 3+, is removed by electrodeposition, the other part is adsorbed on biofilm. In contrast, experimental data of single electrodeposition or biofilm process are listed. Further, the kinetic curves of microbes cultivated or microbes acclimated by Cr 3+ to degrade glucose are provided,too. In conclusion, the experimental results indicate that initial wastewater consists of C 6H 12O 6 (500 mg·L -1), Cr 3+ (10 mg·L -1), after treated with the complex process, concentrations of C 6H 12O 6 and Cr 3+ are on the scale of 15-20 mg·L -1, and less than 1 mg·L -1, respectively. Purified water can meet the standards of industrial reused water.

tetracene分子在Ru(100)表面的吸附结构及其电子态研究

利用紫外光电子能谱(UPS)、角分辨紫外光电子能谱(ARUPS)和扫描隧道显微镜(STM)等方法研究了tetracene分子在Ru(100)表面上吸附的电子态,吸附位置和吸附取向.UPS实验显示,与tetracene分子有关的光电子谱峰在费米能级以下2.1,3.5,4.8,6.0,7.1和9.2eV处;ARUPS结果表明,tetracene分子的分子平面基本平行于衬底表面;从STM图像中可以看到tetracene分子的长轴沿[0001]和[1■10]两个晶向.基于密度泛函理论的从头算计算证实了上述结论.当分子长轴沿[0001]晶向时,分子中心位置在衬底表面的“短桥位”上,当分子长轴沿[1210]晶向时,分子中心位置在衬底表面的“四原子中心空位”上.

Ag(110)表面吸附酞菁铜分子的紫外光电子谱研究

用紫外光电子能谱(UPS)研究了酞菁铜分子在Ag(110)单晶表面上的吸附,随着酞菁铜分子覆盖度增加,衬底Ag的3d电子信号逐渐减弱,在此能带区域出现两个新的谱峰,这两个与吸附有机分子轨道有关的谱峰的束缚能分别为4.45和6.36eV.随着覆盖度的增加,在结合能为1.51和9.20eV处又出现了两个谱峰,它们同样来自吸附有机分子的轨道.随着覆盖度的继续增加,上述四个谱峰的强度逐渐增加,其能量位置均发生了明显的偏移.根据角分辨光电子能谱的实验结果,酞菁铜分子的分子平面基本与衬底表面平行.密度泛函理论计算证实了分子的平行吸附,酞菁铜分子吸附的最佳位置应该在"中心空位"上.

Effect of Electrolytes on Surface Charge Characteristics of Red Soils

The zero point of charge (ZPC) and the remaining charge σp at ZPC are two important parameters characterizing surface charge of red soils.Fourteen red soil samples of different soil type and parent material were treated with dithionite-citrate-dicarbonate (DCB) and Na2CO3 respectively.ZPC and σp of the samples in three indifferent electrolytes (NaCl,Na2SO4,and NaH2PO4) were determined.Kaolinite was used as reference.The results showed that ZPC of red soils was affected by the composition of parent materials and clay minerals and in significantly positive correlation with the content of total iron oxide (Fet),free iron oxide (Fed),amorphous iron oxide (Feo),aluminum oxide (Alo) and clay,but it was negatively correlated with the content of total silica (Sit).The σp of red soils was also markedly influenced by mineral components.Organic components were also contributing factor to the value of σp.The surface charges of red soils were evidently affected by the constitution of the electrolytes.Specific adsorption of anions in the electrolytes tended to make the ZPC of red soils shift to a higher pH value and to increase positive surface charges of the soils,thus leading to change of the σp value and decrease of the remaining net negative charges,even to the soils becoming net positive charge carriers.The effect of phosphate anion was greater than that of sulfate ion.

Zn Adsorption by Variable Charge Soils in Relation to pH

Zn adsorption by pure oxides or in the presence of a high concentration of inner electrolyte has been extensively studied. But, in studies on Zn adsorption in the complicated soil system, especially in variable charge soils, profound knowledge about the adsorption mechanism still lacks. In this paper, taking Zn ion adsorption by two typical variable charge soils as the object of the study, author discusses the relation between Zn adsorption and pH and possible adsorption mechanisms. The results showed that in the low pH range where the amount of Zn adsorbed did not exceed 50% of Zn added, the specific adsorption was the dominant mechanism. The species of Zn specifically adsorbed was free Zn2+ ion. In the middle and high pH ranges, the mechanisms of specific and electrostatic adsorptions, co-existed, accounting for about 70% and 30% , respectively. Noteworthily, in the high pH range, the hydroxyl Zn ion (ZnOH +) from Zn2+ hydrolysis probably was a preferable species for specific adsorption.

Adsorption of Potassium and Calcium Ions by Variable Charge Soils

Interactions of potassium and calcium ions with four typical variable charge soils in South China were examined by measuring pK-0.5pCa value with a potassium ion-selective electrode and a calcium ion-selective electrode,and pK value with a potassium ion-selective electrode.The results showed that adsorption of potassium and calcium ions increased with soil suspension pH,and the tendency of the pK-0.5pCa value changing with pH differed with respect to pH range and potassium to calcium ratio.Adsorption of equal amount of calcium and potassium ions led to release of an identical number of protons,suggesting similar adsorption characteristics of these two ions when adsorbed by variable charge soils.Compared with red soil,latosol and lateritic red soil had higher adsorption selectivities for calcium ion.The red soil had a greater affinity for potassium ion than that for calcium ion at low concentration,which seems to result from its possession of 2:1 type minerals,such as vermiculite and mica with a high affinity for potassium ion.The results indicated that adsorption of potassium and calcium ions by the variable charge soils was chiefly caused by the electrostatic attraction between the cations and the soil surfaces.Moreover,it was found that sulfate could affect the adsorption by changing soil surface properties and by forming ion-pair.

Adsorption Kinetics of Pb^(2+) and Cu^(2+) on Variable Charge Soils and Minerals: Ⅲ. Adsorption Kinetics of Pb^(2+) Within 30 Minutes

The adsorption kinetics of Pb^2+ on different soils and minerals with variable charges was studied by the two ion-selective electrode technique at different pH and concentrations.The results showed that more than 95% of adsorption on all the samples occurred during the first 5 minutes.All adsorption time-dependent data could fit the surface second-order equation very well.The values of Xm were goethite>kaolinite,and latosol>red soil at the same initial reaction concentration.The values of k were kaolinite>>goethite,and latosol>red soil at the same reaction pH and initial concentration.The higher the suspension pH,the faster the adsorption occurred.The meaning of Xm got by the two ion-selective electrode technique(one kind of batch technique) was different from that by the miscible displacement technique in that the former was only the equilibrium adsorption amount at a definite concentration and pH,but the latter was almost equal to the adsorption capacity at a definite pH with much less influence of concentration.One Pb^2+ was supposed to occupy two adsorption sites as the adsorption mechanism is concerned.

Synthesis and evaluation of carbon nanotubes composite adsorbent for CO2 capture： a comparative study of CO2 adsorption capacity of single-walled and multi-walled carbon nanotubes

As a preliminary investigation towards obtaining carbon nanotube composite adsorbent for CO2 capture, in this study CO2 adsorption performance of three commercial carbon nanotubes （CNTs） one single-walled carbon nanotubes （SWCNTs）, and two （2） different multi-walled carbon nanotubes （referred to as A-MWCNTs and B-MWCNTs） were evaluated and compared. The purpose of this study was to compare the different types of CNTs and select the best to serve as the solid anchor in the development of a hydrophobic composite adsorbent material for CO2 capture. The N2 physi- sorption of the CNTs was conducted to determine their surface area, pore volume and pore size. In addition, morphology and purity of the CNTs were checked with Transmission Electron Microscopy and Raman Spectroscopy, respectively. The CO2 adsorption capacity of the CNTs was evaluated using Thermo-gravimetric analysis （TGA） at 1.1 bar, at operating temperature ranged from 25 to 55 ~C and at different CO2 feed flow rates, in order to evaluate the effects of these variables on the CO2 adsorption capacity. The results of CO2 adsorption with the TGA show that CO2 adsorption capacity for both SWCNTs and MWCNTs was the highest at 25 ~C. Changing the CO2 flowrates had no significant effect on the adsorption capacity of MWCNTs, but decreasing the CO2 flow rate resulted in the enhancement of the CO2 adsorption capacity of SWCNTs. Overall, it was found that the SWCNTs displayed the highest CO2 adsorption capacity （29.97 gCO2/kg ad- sorbent） when compared to the MWCNTs （12.09 gCO2/kg adsorbent）, indicating a 150% increase in adsorption capacity over MWCNTs.

Removal of Cu2＋ from Aqueous Solutions Using Na-A Zeolite from Oil Shale Ash

Na-A zeolite was synthesized using oil shale ash （OSA）, which is a solid by-product of oil shale proc- essing. The samples were characterized by various techniques, such as scanning electron microscopy, X-ray diffrac- tion and Brunaner Emmet Teller method. The batch isothermal equilibrium adsorption experiments were performed to evaluate the ability of Na-A zeolite for removal of Cu （II） from aqueous solutions. The effects of operating pa- rameters, such as concentration of copper solutions, adsorbent dosages, pH value of solutions and temperature, on the adsorption efficiency were investigated. The equilibrium adsorption data were fitted with Langmuir and Freundlich models. The maximum adsorption capacity of Na-A zeolite obtained from the Langmuir adsorption iso- therm is 156.7 mg.g-t of Cu （lI）. The increase of pH level in the adsorption process suggests that the uptake of heavy metals on the zeolite follows an ion exchange mechanism. The batch kinetic data fit the pseudo-second order equation well. The thermodynamic parameters, such as changes in Gibbs free energy （AG）, enthalpy （AH） and en- tropy （AS）, are used to predict the nature of the adsorption process. The negative AG values at different tempera- tures confirm that the adsorption processes are spontaneous.

Adsorption of Potassium and Sodium Ions by Variable Charge Soils

Adsorption of potassium and sodium ions by four typical variable charge soils of South China was studied. The results indicated that the variable charge soils saturated with H and Al showed a much higher preference for potassium ions relative to sodium ions, and this tendency could not be changed by such factors as the pH, the concentration of the cations, the dielectric constant of solvent, the accompanying anions and the iron oxide content etc., suggesting that this difference in affinity is caused by the difference in the nature of the two cations. It was observed that a negative adsorption of sodium ions by latosol and lateritic red soil in a mixed system containing equal amount of potassium and sodium ions at low pH, which is caused by a competitive adsorption of potassium and sodium ions and repulsion of positive charge on the surfaces of soil particles for cations. The adsorption of potassium and sodium ions increased with the decreases in the dielectric constant of solvent and the iron oxide content. Sulfate affected the adsorption of potassium and sodium ions through changing the surface properties of the soils.