气液耦合振动对热声发动机性能的影响

进行了气液耦合振动驻波型热声发动机定量模拟.重点比较分析了单纯气体振动系统和引入[EMIM][BF_4]室温离子液体作为液体活塞的气液耦合振动系统的运行参数,并考察了液体活塞的质量对热声发动机谐振频率、压力振幅以及板叠热端温度等的影响.     

A piperidinium-based ester-functionalized ionic liquid as electrolytes in Li/LiFePO<Subscript>4</Subscript> batteries

A new functionalized ionic liquid (IL) based on cyclic quaternary ammonium cations with ester group and bis(trifluoromethanesulfonyl)imide ([TFSI]^?) anion, namely, N-methyl-N-methoxycarbonylpiperidinium bis(trifluoromethanesulfonyl)imide ([MMOCPip][TFSI]), was synthesized and characterized. Physical and electrochemical properties, including Li-ion transference number, ionic conductivity, and electrochemical stability, were investigated. The electrochemical window of [MMOCPip][TFSI] was 6 V, which was wide enough to be used as a common electrolyte material. The Li-ion transference number of this IL electrolyte containing 0.1 M LiTFSI was 0.56. The half-cell tests indicated that the [MMOCPip][TFSI] obviously improved the cyclability of a Li/LiFePO₄ cell. For the Li/LiFePO₄ half-cells, after 20 cycles at room temperature at 0.1 C, the discharge capacity was 109.7 mAh g^?1 with 98.7% capacity retention in the [MMOCPip][TFSI]/0.1 M LiTFSI electrolyte. The good electrochemical performance demonstrated that the [MMOCPip][TFSI] could be used as electrolyte for lithium-ion batteries.     

A piperidinium-based ionic liquid electrolyte to enhance the electrochemical properties of LiFePO<Subscript>4</Subscript> battery

A piperidinium-based ionic liquid, N-methylpiperidinium-N-acetate bis(trifluoromethylsulfonyl)imide ([MMEPip][TFSI]), was synthesized and used as an additive to the electrolyte of LiFePO₄ battery. The electrochemical performance of the electrolytes based on different contents of [MMEPip][TFSI] has been investigated. It was found that the [MMEPip][TFSI] significantly improved the high-rate performance and cyclability of the LiFePO₄ cells. In the optimized electrolyte with 3 wt% [MMEPip][TFSI], 70 % capacity can be retained with an increase in rate to 3.5 C, which was 8 % higher than that of electrolyte without [MMEPip][TFSI]. For the Li/LiFePO₄ half-cells, after 100 cycles at 0.1 C, the discharge capacity retention was 78 % in the electrolyte without ionic liquid. However, in the electrolyte with 3 wt% [MMEPip][TFSI], it displayed a high capacity retention of 91 %. The good electrochemical performances indicated that the [MMEPip][TFSI] additive would positively enhance the electrochemical performance of LiFePO₄ battery.     

Solvation of AgTFSI in 1‐ethyl‐3‐methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid investigated by vibrational spectroscopy and DFT calculations

In this paper we investigate the solvation of silver bis(trifluoromethylsulfonyl)imide salt (AgTFSI) in 1‐ethyl‐3‐methylimidazolium TFSI [EMI][TFSI] ionic liquid by combining Raman and infrared (IR) spectroscopies with density functional theory (DFT) calculations. The IR and Raman spectra were measured in the 200–4000 cm⁻¹ spectral region for AgTFSI/[EMI][TFSI] solutions with different concentrations ([AgTFSI] <0.2 mole fraction). The analysis of the spectra shows that the spectral features observed by dissolution of AgTFSI in [EMI][TFSI] solution originate from interactions between the Ag⁺ cation and the first neighboring TFSI anions to form relatively stable Ag complexes. The ‘gas phase’ interaction energy of a type [Ag(TFSI)₃]²⁻ complex was evaluated by DFT calculations and compared with other interionic interaction energy contributions. The predicted spectral signatures because of the [Ag(TFSI)₃]²⁻ complex were assessed in order to interpret the main IR and Raman spectral features observed. The formation of such complexes leads to the appearance of new interaction‐induced bands situated at 753 cm⁻¹ in Raman and at 1015 and 1371 cm⁻¹ in IR, respectively. These specific spectral signatures are associated with the ‘breathing’ mode and the S–N–S and S–O stretching modes of the TFSI anions engaged in the complex. Finally, all these findings are discussed in terms of interaction mechanisms enabling the electrodeposition characteristics of silver from AgTFSI/[EMI][TFSI] IL‐based electrolytic solutions. Copyright © 2015 John Wiley & Sons, Ltd.     

离子液体中聚氧化乙烯(PEO)相变过程中的氢键效应

我们把Flory-Huggins模型推广应用到聚合物/离子液体体系,研究聚氧化乙烯(PEO)在离子液体[EMIM][BF_4]中相变过程中的氢键效应,理论模型考虑了三种类型氢键(Ⅰ型:PEO-[EMIM]~+氢键,Ⅱ型:PEO-[BF_4]~-氢键和Ⅲ型:[EMIM]~+-[BF_4]~-氢键)的形成,分析了三种类型的氢键分数随温度、 PEO体积分数的变化.研究发现,三种类型的氢键分数随温度的升高而减少.在较小PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数轻微地减小;在较大PEO体积分数条件下,增加PEO体积分数,Ⅰ型、Ⅱ型氢键分数急剧减少.Ⅲ型氢键分数随着PEO体积分数的增加而急剧降低.由于三种氢键效应,第二维里系数A_2随温度的增加而减小.通过计算分析不同分子量的PEO在[EMIM][BF_4]中的相图发现,在PEO体积分数较低的条件下,Ⅰ型、Ⅱ型和Ⅲ型氢键是PEO相变的主要驱动力;在PEO体积分数较高的条件下,Ⅰ型和Ⅱ型氢键在PEO相变过程中起到主导作用.     

In situ solidification of ionic liquid [EMIM][EtOSO3] from melt under high pressure

In situ solidification of 1-ethyl-3-methylimidazolium ethyl sulfate [EMIM][EtOSO₃] from melt under high pressure has been investigated by using Raman spectroscopy. The results indicate that [EMIM][EtOSO₃] might experience a phase transition at about 2.4 GPa upon compression, which could be identified as solidification to a superpressurized glass by pressure broadening of the sharp ruby R₁ fluorescence line. Upon cooling, it solidifies as a glassy state rather than crystallizes at low temperature down to 93 K. These facts are suggestive of a phase transition of liquid to a superpressurized glass induced by compression in [EMIM][EtOSO₃], which is similar to the glassy state at low temperature.     

Research for improvement on the extract efficiency of lignans in traditional Chinese medicines by hybrid ionic liquids: As a case of Suhuang antitussive capsule

Recently, efficient extraction of natural products from traditional Chinese medicines (TCMs) by green solvents is deemed an essential area of green technology and attracts extensive attentions. In this work, a green protocol for simultaneous ultrasonic-extraction of the native compounds with different polarities of TCMs by using a hybrid ionic liquids (HILs)-water system was reported for the first time. As a case study, three superior ILs (1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF4]), 1-ethyl-3-methylimidazolium acetate ([EMIM][OAc]), and 1-allyl-3-methylimidazolium chloride ([AMIM]Cl)) were chosen as the compositions of the HILs system, and the TCMs Suhuang antitussive capsule (SH) containing different-polarity lignans was selected. Primarily, an ultra-performance liquid chromatography coupled to triple quadrupole tandem mass spectrometry (UPLC-QqQ-MS/MS) method in the multiple reaction monitoring (MRM) mode was established for qualitative and quantitative analysis of 18 lignans. After majorization by uniform design experiment, the HILs prepared with [AMIM]Cl, [EMIM][BF4], and [EMIM][OAc] at a volume ratio of 1:5:5 could simultaneously extract multi-polarity lignans compared to single IL. Subsequently, the conditions of ultrasonic extraction employing with HILs and traditional organic solvent were optimized by the response surface methodology, respectively. The results indicated that the extract efficiency of the HILs system for target compounds was significantly improved compared with the traditional organic solvent-extraction, i.e. the content of total lignans in ethanol system was up to 47 mg/g, while that in the HILs system was up to 69 mg/g, with an increasing of 47%. Additionally, ¹H-NMR and ¹³C-NMR spectra were used to characterize the hydrogen-bond interactions in the HILs-lignan mixtures. Extraction with the HILs in TCMs is a new application schema of ILs, which not only avoids the use of volatile toxic organic solvents, but also shows the potential to be comprehensively applied for the extraction of bioactive compounds from TCMs.     

Raman study of lithium coordination in EMI‐TFSI additive systems as lithium‐ion battery ionic liquid electrolytes

Raman spectroscopy was performed on various mixtures of the ionic liquid salt, 1‐ethyl‐3‐methylimidazolium‐bis(trifluoromethylsulfonyl)imide (EMI‐TFSI). When EMI‐TFSI is used in combination with a lithium salt, it could be a potential electrolyte for lithium‐ion or lithium metal batteries. The Raman spectra of EMI‐TFSI, EMI‐TFSI 0.5 M Li‐TFSI, EMI‐TFSI 0.5 M Li‐TFSI 2 M vinylene carbonate (VC) and EMI‐TFSI 0.5 Li‐TFSI 2 M ethylene carbonate (EC) were collected and compared. A comparison of the peak positions of the δ_s CF₃ mode at 742 cm⁻¹ demonstrates that when carbonate additives are present, the lithium ion is no longer interacting with the TFSI anion. Instead, it is coordinated with the carbon–oxygen double bond of the carbonates. Copyright © 2006 John Wiley & Sons, Ltd.     

Thermal,vibrational, and dielectric studies on PVP/LiBF4+ionic liquid [EMIM][BF4]-based polymer electrolyte films

Free-standing polymer electrolyte membranes based on poly(vinyl) pyrrolidone (PVP)/salt(LiBF₄) having different amounts of ionic liquid (IL) [EMIM][BF₄] were prepared and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and alternating current (AC) impedance spectroscopic techniques. The DSC results show a shift in T_m of PVP with salt/or IL content. TGA and DTGA (first derivative of TGA) results give evidence of the presence of uncomplexed PVP, PVP/salt, and PVP/IL complexes. Signatures of these entities are also present in the dielectric spectra. Complexation of PVP with salt and IL has been confirmed by FT-IR analysis. Electrical conductivity as a function of temperature has been studied for PVP/LiBF₄/IL [EMIM][BF₄]. Role of IL in changing phase transition, conductivity, and dielectric relaxation frequency has been discussed.     

Quasi-solid state polymer electrolytes for dye-sensitized solar cells: Effect of the electrolyte components variation on the triiodide ion diffusion properties and charge-transfer resistance at platinum electrode

Quasi-solid state polymer electrolytes have been prepared from poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) as gelator for 1-ethyl-3-methylimidazolium based ionic liquids (with anions like trifluoromethanesulfonate [EMIM][TfO], bis(trifluoromethanesulfonyl)imide [EMIM][Tf₂N]) and polyacrylonitrile (PAN) for gelation of 1-ethyl-3-methylimidazolium dicyanamide [EMIM][DCA] as well as I⁻/I₃⁻ as the redox couple. All electrolytes exhibit high ionic conductivity in the range of 10^− 3 S/cm. The effect of gelation, redox couple concentration, I⁻/I₃⁻ ratio, choice of cations and additives on the triiodide diffusion and charge-transfer resistance of the platinum/electrolyte interface (R_ct) were studied. The apparent diffusion coefficient of triiodide ion (D(I₃⁻)) at various iodide/triiodide ratios in liquid and gelified electrolytes has been calculated from measurements of the diffusion limited current (I_lim) in electrochemical cell resembling the set-up of a dye-sensitized solar cell. The charge-transfer resistance of the platinum/electrolyte interface as well as the capacitance of the electrical double layer (C_dl) have been calculated from impedance measurements. Electrolytes with reduced content of polymer (2.5 wt.%) were doped with Al₂O₃ particles of different sizes (50 nm, 300 nm, 1 μm). The dispersion of the particles proceeds by speedy stirring of the hot electrolyte and the addition of PAN provides a homogeneous suspension. The addition of Al₂O₃ particles causes a slight increase of the triiodide diffusion constants. Furthermore the suggested enhancement of the charge transfer rate shows a dependence on the size of the particles.     

液体工质对气液热声发动机性能影响的实验研究

采用气液耦合振动是降低热声发动机谐振频率和提升其压力振幅的一种有效途径。为了研究液体工质对于气液热声发动机性能的影响,本文针对水、室温离子液体[EMIM][BF₄]、20%氯化钾溶液、40%和50%甲酸钾溶液五种液体工质进行了实验研究和分析。实验数据显示,在相同加热功率下,采用50%甲酸钾溶液时系统谐振频率最低,而水工质对应的谐振频率最高;40%甲酸钾溶液的压力振幅最大,而采用离子液体[EMIM][BF4]时系统压力振幅最小。研究结果表明:采用密度较大的液体工质可获得较低的谐振频率,而密度大、黏度小的液体工质则有利于获得更大的压力振幅。     

Sonoluminescence quenching and cavitation bubble temperature measurements in an ionic liquid

A comparison between the temperatures within imploding acoustic cavitation bubbles and the extent of sonoluminescence (SL) quenching by C₁–C₅ aliphatic alcohols in 1-ethyl-3-methylimidazolium ethylsulfate ([EMIM][EtSO₄], a well known imidazolium based room temperature ionic liquid (RTIL)), has been made at an ultrasound frequency of 213 kHz. The temperatures obtained ranged from 3500 ± 200 K, in neat [EMIM][EtSO₄], to about 3200 ± 200 K in RTIL-alcohol containing solutions. It was also found that the SL intensity decreased with increasing concentration (up to 1 M) of the alcohols to a greater extent compared with the relative changes to the bubble temperatures. Both the extent of the reduction in the bubble temperatures and the SL quenching were much smaller than those obtained in comparable aqueous solutions containing aliphatic alcohols. Possible reasons for the differences in the observed trends between water/alcohol and [EMIM][EtSO₄]/alcohol systems under sonication at 213 kHz are discussed.     

双金属离子对配合物的X光电子能谱

通过X光电子能谱法对双金属离子对配合物[Mo(dtc)4][Ln(dtc)4](Ln=La-Er，除Pm外）进行了研究，结果表明：在该离子对配合物的，存在＋3价的镧系离子和＋5价的钼离子，配体dtc是以双齿螯合的方式分别与中心离子配位的。     

Low‐cost high‐quality crystalline germanium based flexible devices

High performance flexible electronics promise innovative future technology for various interactive applications for the pursuit of low‐cost, light‐weight, and multi‐functional devices. Thus, here we show a complementary metal oxide semiconductor (CMOS) compatible fabrication of flexible metal–oxide–semiconductor capacitors (MOSCAPs) with high‐κ/metal gate stack, using a physical vapor deposition (PVD) cost‐effective technique to obtain a high‐quality Ge channel. We report outstanding bending radius ～1.25 mm and semi‐transparency of 30%. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Key technologies for dual high-k and dual metal gate integration

The key technologies for the dual high-k and dual metal gate, such as the electrical optimization of metal insert poly-Si stack structure, the separating of high-k and metal gate of n/pMOS in different regions of the wafer, and the synchronous etching of n/pMOS gate stack, are successfully developed. First, reasonable flat-band voltage and equivalent oxide thickness of pMOS MIPS structure are obtained by further optimizing the HfSiAlON dielectric through incorporating more Al-O dipole at interface between HfSiAlON and bottom SiO_x. Then, the separating of high-k and metal gate for n/pMOS is achieved by SC1(NH_4OH:H_2O_2:H_2O = 1 : 1 : 5) and DHF-based solution for the selective removing of n MOS TaN and Hf Si ON and by BCl_3-based plasma and DHF-based solution for the selective removing of pMOS TaN/Mo and HfSiAlON.After that, the synchronous etching of n/pMOS gate stack is developed by utilizing optimized BCl_3/SF_6/O_2/Ar plasma to obtain a vertical profile for TaN and TaN/Mo and by utilizing BCl_3/Ar plasma combined with DHF-based solution to achieve high selectivity to Si substrate. Finally, good electrical characteristics of CMOS devices, obtained by utilizing these new developed technologies, further confirm that they are practicable technologies for DHDMG integration.     

Magnesium ion-conductive poly(ethylene carbonate) electrolytes

Magnesium (Mg) electrolytes are presently under investigation for their promising performance capabilities in the next generation of batteries. The present work studies Mg-ion transport in polymers using different types of Mg salts. Polymer electrolytes comprising poly(ethylene carbonate) (PEC) with Mg salts (MgX₂; X?=?TFSI, ClO₄) were prepared by solution casting. The structural, thermal, and electrochemical properties of flexible self-standing membranes were studied as potential Mg electrolytes. The impedance results at 90 °C found the highest conductivities of 6.0?×?10^?6 S cm^?1 for PEC-Mg(TFSI)₂, and 5.2?×?10^?5 S cm^?1 for PEC-Mg(ClO₄)₂, at 40 mol%. FT-IR measurements revealed changes in the peak fraction from the region of carbonyl group, which explain the interaction with Mg ions. The glass transition temperature of the TFSI system decreased with increasing salt concentration due to the plasticizing effect of TFSI anions. Thermal gravimetric analysis revealed that the highest values of the 5% weight-loss temperature at 40 mol% are 174 °C for PEC-Mg(TFSI)₂ and 160 °C for PEC-Mg(ClO₄)₂. The electrochemical stability of PEC-Mg(TFSI)₂ at 40 mol% was up to 2.2 V. To confirm the redox reaction of Mg ions in PEC, CV measurement was carried out using symmetrical cells with quasi Mg electrodes. Cathodic and anodic current peaks were clearly observed, and the presence of these peaks indicates Mg-ion conduction in PEC.     

A two-dimensional analytical modeling for channel potential and threshold voltage of short channel triple material symmetrical gate Stack(TMGS) DG-MOSFET

In the present work, a two-dimensional(2D) analytical framework of triple material symmetrical gate stack(TMGS)DG-MOSFET is presented in order to subdue the short channel effects. A lightly doped channel along with triple material gate having different work functions and symmetrical gate stack structure, showcases substantial betterment in quashing short channel effects to a good extent. The device functioning amends in terms of improved exemption to threshold voltage roll-off, thereby suppressing the short channel effects. The encroachments of respective device arguments on the threshold voltage of the proposed structure are examined in detail. The significant outcomes are compared with the numerical simulation data obtained by using 2D ATLAS~(TM) device simulator to affirm and formalize the proposed device structure.     

Modified π-states in ion-irradiated carbon

CVD polycrystalline diamond film, pulse laser-deposited (PLD) carbon film and highly oriented pirolitical graphite (HOPG) as reference, were modified by means of Ar⁺ ion bombardment and characterized by means of Raman scattering, transmission electron microscopy, electron-diffraction (TEM), reflected electron energy loss specroscopy (REELS) and X-ray photoelectron spectroscopy (XPS) techniques. It was found that the diamond was transferred to a carbon with halo-like morphology and disordered stack of graphene segments. Instead of the well-known electron energy loss peak of graphite at 6.5 eV, a new REELS peak appeared at 4-5 eV energies. The observed effect was explained by the modification of π-system in carbon films as a consequence of the formation of non-planar, nanometer-sized graphitic planes.     

Room-temperature flexible thin film transistor with high mobility

We report a room-temperature and high-mobility InGaZnO thin-film transistor on flexible substrate. To gain both high gate capacitance and low leakage current, we adopt stacked dielectric of Y₂O₃/TiO₂/Y₂O₃. This flexible IGZO TFT shows a low threshold voltage of 0.45 V, a small sub-threshold swing of 0.16 V/decade and very high field-effect mobility of 40 cm²/V. Such good performance is mainly contributed by improved gate stack structure and thickness modulation of IGZO channel that reduce the interface trap density without apparent mobility degradation.