Conductivity and fluidity spectra of two room temperature ionic liquids, BMIm-BF4 and HMIm-BF4, taken at different temperatures, are presented and compared with each other. BMIm-BF4 and HMIm-BF4 are short for 1-butyl-3-methyl-imidazolium tetrafluoroborate and 1-hexyl-3-methyl-imidazolium tetrafluoroborate, respectively. In their temperature and frequency dependences, flow of charge and shear flow are found to display close similarities. The distinguishing features of the ion dynamics in fragile ionic liquids as compared to ionic solids are seen to arise from the absence of a network that provides pre-formed vacant sites for the ions to move in. In ionic liquids, the dispersive behaviour of the frequency-dependent conductivity is thus characterized by a temperature-independent end frequency. This key feature, along with Arrhenius activated elementary displacements, is shown to yield the well-known non-Arrhenius temperature dependence of the DC conductivity. In Arrhenius-type plots, DC conductivity and fluidity can be superimposed over the entire temperature range above the glass transition. As a consequence, ionic conduction and shear flow can be traced back to elementary displacements with identical activation energy. On the inverse temperature axis, a small positive shift, Δ=(1/T⊗−1/T), is required for the superposition. Remarkably, fluidities taken at temperature T correspond to conductivities taken at the slightly lower temperature T⊗ not only at DC, but in the entire frequency range studied. Indeed, according to the data as well as to our modelling, the entire conductivity and fluidity spectra superimpose when considered at T⊗ and T, respectively, with identical values of their end angular frequency. The still unknown time correlation function for shear flow is hence expected to have significant features in common with the current density autocorrelation function.
Due to the ligand property of the DCA anion, both CuCl and NiCl2 are soluble in 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) ionic liquid. Cyclic voltammograms of Ni(II), Cu(I), and Ni(II)+Cu(I), respectively, in EMI-DCA were recorded on the glassy carbon electrode at 30°C. It is interesting to note that the thermodynamic deposition potentials of Ni and Cu are very close to each other. This is especially favorable for the electrodeposition of Ni-Cu alloys without any additive. The Ni-Cu alloys were electrodeposited using bulk controlled-potential electrolysis experiments. Energy-dispersive spectroscopy (EDS) data indicates that the composition of the Ni-Cu alloys not only depends on the deposition potential, but also on the Cu(I) and Ni(II) concentrations in the melt.
A continuous and adhesive Al layer was successfully electrodeposited on a Mg alloy in aluminum chloride/1-ethyl-3-methylimidazolium ionic liquid at room temperature. Surface morphology, crystal structure, and chemical composition of the deposit were examined with a scanning electron microscope, an X-ray diffractometer, and an X-ray energy dispersive spectroscope, respectively. The corrosion resistance of the Al-coated Mg alloy was also evaluated.
This work demonstrates that reticulate Sn film with nano-sized porosity can be obtained simply by direct electrodeposition of Sn nanowires without using any additive and template in a water and air stable ionic liquid, namely 1-ethyl-3-methylimidazolium dicyanamide (EMI-DCA) at 313 K.
Alkylation reaction of benzene with 1-dodecene was carried out catalyzed by Brønsted acidic ionic liquids. Catalytic ability of different Brønsted acidic ionic liquids was compared. Results showed that sulfonic Brønsted acidic ionic liquids could catalyze the alkylation reaction. Reaction conditions were optimized to get the best conversion.
Nuclear energy is reconsidered against global warming but the concerns (nuclear proliferation, radioactive waste, safety etc.) make it difficult to apply widely in the world. To comprehensively solve these difficulties, we have proposed Th-233U fuel cycle named THORIMS-NES (Thorium molten-salt nuclear energy synergetics). We calculated the mass balance of fissile materials and the production of minor actinide (MA) governing major part of radioactive waste for evaluating the smooth shift to Th-233U fuel cycle. Th-233U fuel cycle can generate 3 TWe at around 2050 and 10 TWe at around the end of this century by applying Pu obtained from spent nuclear fuel of conventional nuclear system and 233U produced by Accelerator Molten-Salt Breeders (AMSB).
A phosphate conversion process has been developed to reduce the high-level radioactive waste (HLW) generated in metal-electrorefining. In this study, the results of thermodynamic phosphate conversion reaction calculations are examined experimentally. Rare Earth Element (REE) chlorides were discovered to be easily converted into phosphates. Furthermore, regarding the use of an additive in the phosphate conversion reaction, the high temperature behavior of lithium phosphate was evaluated in elucidating its thermodynamic properties.
The transient mass transfer rate of Li+ ion caused by the electrochemical deposition and dissolution of Li metal in propylene carbonate (PC) and ionic liquid (IL) containing a lithium salt is numerically analyzed. The previous mesurements of transport properties such as diffusion coefficient of a lithium salt and electrolyte viscosity are used in the present calculation. The concentration profile of Li+ ion developed along electrode surface has been in-situ measured by holographic interferometry. The measurement values are reasonably compared with the calculations except for the apparent incubation period observed in the initial stage of electrochemical deposition and dissolution.
Electrolysis was conducted in a molten salt containing LiCl and KCl at 500°C for bcc Mg-11.9 wt.% Li-8.5 wt.% Al-0.57 wt.% Zn alloy fabrication. As-rolled Mg-11.9 wt.% Li-8.5 wt.% Al-0.57 wt.% Zn and Mg-2.6 wt.% Al-0.72 wt.% Zn foils were assembled into separate Mg/2 mol kg−1 MgCl2/Cu cells. Mg-11.9 wt.% Li-8.5 wt.% Al-0.57 wt.% Zn foil as anode exhibited higher discharge voltage and capacity than Mg-2.6 wt.% Al-0.72 wt.% Zn foil did in the cell.
In order to investigate the phonon dynamics of molten NaI, inelastic X-ray scattering measurements were preformed near the melting point at the beamline BL35XU of the SPring-8. A fast sound mode exceeding the ultrasonic velocity of sound by about 45% was observed as in other molten alkali halides, which is in fairly good agreement with a scaling formula using the effective mass of the salt constituents.
Red-emitting phosphors based on gadolinium oxysulfate were synthesized in a single phase form by our original flux method using alkaline metal sulfate such as Na2SO4 and the 0.6Li2SO4--0.4Na2SO4 eutectic mixture, and photoluminescence properties were characterized. Addition of the flux is significantly effective to enhance the emission intensity, and the luminescent peak intensity of Gd2O2SO4: 10%Eu3+ increased double and triples by using Na2SO4 and 0.6Li2SO4--0.4Na2SO4, respectively. The application of the 0.6Li2SO4--0.4Na2SO4 eutectic mixture works more effectively because the melting point (600°C) is significantly lower than that of Na2SO4 (887°C).
Formal redox potentials of the U4+/U3+ and U3+/U couples in molten LiCl-RbCl eutectic were determined by cyclic voltammetry. These redox potentials were more negative than those in the LiCl-KCl eutectic but positive comparing to those in the NaCl-CsCl eutectic. This relation would be correlated with the averaged alkali cation radius.
We report high-mobility rubrene single-crystal field-effect transistors with ionic-liquid electrolytes used for gate dielectric layers. As the result of fast ionic diffusion to form electric double layers, their capacitances remain more than 1.0 µF/cm2 even at 0.1 MHz. With high carrier mobility of 9.5 cm2/Vs in the rubrene crystal, pronounced current amplification is achieved at the gate voltage of only 0.2 V, which is two orders of magnitude smaller than that necessary for organic thin-film transistors with dielectric gate insulators. The results demonstrate that the ionic-liquid/organic semiconductor interfaces are suited to realize low-power and fast-switching field-effect transistors without sacrificing carrier mobility in forming the solid/liquid interfaces.
We examined a eutectic Li2WO4-Na2WO4-K2WO4 melt and several its derivative melts at 873 K to develop a stable bath which enables electrodeposition of high quality tungsten. Galvanostatic electrolysis at 25 mA cm−2 in the eutectic Li2WO4-Na2WO4-K2WO4 melt gave a powdery deposit consisting of both tungsten and tungsten oxide. A dendritic deposit of tungsten was obtained from a Li2WO4-Na2WO4-K2WO4-LiCl-NaCl-KCl melt, which has a lower viscosity, in the same electrolysis condition. The dendrite formation was completely suppressed by vibrating the electrode during the electrodeposition. However, the surface was covered with large and angular crystal grains. By addition of KF to the melt, the size of the crystal grains became much smaller and smooth surface was obtained. The XRD analysis and cross-sectional SIM observation revealed that the addition of KF suppressed the preferential growth of α-W crystal and gave the mixture of α-W and β-W resulting in smaller crystal grain size.
Physical and electrochemical properties of 1-ethyl-3-methylimidazolium ionic liquids of mixed anions, (FH)2.3F−, BF4−, and N(SO2CF3)2−, have been investigated. Molar volume shows almost linear behavior, whereas molar conductivity is decreased by mixing for the systems involving (FH)2.3F− due to the enhancement of ion association in spite of the decrease in viscosity. The currents at the anode and cathode limits in the cyclic voltammogram of EMIm(FH)2.3F decreases with decrease in the molar ratio of (FH)nF−, suggesting the involvement of (FH)nF− for both electrode reactions. Electrochemical stability of the BF4-TFSA mixture is unchanged by mixing.
Photoelectrochemical behavior of a single crystal n-TiO2 electrode was investigated in a hydrophobic room temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA). The photoanodic current was observed on the TiO2 electrode in BMPTFSA under irradiation of UV light. The flat-band potential was estimated from the onset potential of the photocurrent. The flat-band potential in neat BMPTFSA was different from that in BMPTFSA containing ferrocene.
EQCM (Electrochemical Quartz Crystal Microbalance) measurement during Sn(II)/Sn electrode reaction in a room-temperature ionic liquid was conducted using an impedance method EQCM, which can measure the resonance resistance and frequency simultaneously. The mass increased during Sn deposition and decreased during Sn dissolution. The viscosity and density of the electrolyte near the electrode, ηLρL, can be estimated by monitoring the resonance resistance. The change of the ηLρL value during Sn(II)/Sn electrode reaction could be accounted for by the concentration profile of Sn(II) near the electrode.
The anodic behaviors of Pd, Pt and Au have been investigated in LiCl-KCl eutectic melt at 683 K. Chemical reduction of the dissolved noble metal ions by H2 and CH4 has been also carried out. It was shown that Pd and Au could be dissolved anodically with a large dissolution rate, and that the dissolution rate of Pt was limited because of its passivation behavior. Fine particles of these noble metals were obtained by H2 or CH4 reduction though they combined together.
Sputter deposition of silver (Ag) onto an ionic liquid (IL) produced Ag nanoparticles whose size was varied greatly dependent on the sputtering conditions. Change in discharge current from 10 to 40 mA increased Ag particle size from 5.7 to 11 nm, though prolongation of sputtering time simply caused a higher concentration of Ag nanoparticles in IL without change in their size. Sputter deposition of Ag onto IL solutions containing HAuCl4 resulted in the appearance of a single surface plasmon resonance peak in the absorption spectra of the resulting solution, and their peak position was red-shifted with an increase in the concentration of HAuCl4. The obtained results clearly indicated that Ag metal species sputter-deposited in IL can reduce HAuCl4 to give AuAg alloy nanoparticles and that their chemical composition varies depending on the initial concentration of HAuCl4.
Reaction entropies of some metal complex redox couples in an amide-type room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) have been estimated by measuring the thermoelectromotive force at a non-isothermal cell. It is suggested that the reaction entropy is dependent on the difference in the charge densities of the oxidant and reductant of a redox couple, probably related to the coulombic interaction between the redox species and the ions composing the ionic liquid.
The electrochemical and spectroscopic properties of divalent and trivalent europium species have been investigated in a hydrophobic room-temperature ionic liquid, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA). The diffusion coefficients of Eu(II) and Eu(III) estimated by chronoamperometry were (3.9±0.4)×10−8 and (4.2±0.7)×10−8 cm2 s−1, respectively. The diffusion of Eu(II) is affected by the coordination between Eu(II) and TFSA−. The TFSA− ligand seems to act as a weaker ligand than CH3OH according to the splitting of the 5d levels observed from the absorption spectrum for Eu(II). The emission spectra of Eu(II) and Eu(III) were also obtained in BMPTFSA.
The electrodeposition of silver was investigated with 1-butyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl] amide containing Ag-TFSI at 150°C. The influence of current density on the morphology of the silver deposit was studied by cyclic voltammetry and scanning electron microscopy. The size of the silver crystallite became smaller and dendrite-like growth was suppressed with increasing current density.
Anodic oxidation of methanol was investigated at a Pt electrode in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)amide (BMPTFSA) room temperature ionic liquid. It was found that methanol can be oxidized electrochemically in the ionic liquid without water. The oxidation products were identified as dimethoxymethane and proton by gas chromatography and electrochemical measurements. The further oxidation of dimethoxymethane was also suggested by cyclic voltammetry.
The distribution coefficients of Am and Ce were measured in the eutectic LiCl-KCl/liquid Ga system at 773K. By using ZrCl4 as the oxide ion scavenger in order to avoid the formation of such oxychlorides as MO(n−2)+, the effect of oxide ion concentration was well controlled on the distribution coefficients of Am and Ce. The separation factor between Am and Ce was then obtained to be about 100. By comparing the present value with the other experimental and the predicted ones, it was confirmed that the Ga system was more selective than the Bi and Cd system.
The influence of ethylene carbonate (EC) addition in the lithium salt solution of the ionic liquids based on 1-ethyl-3-methyl imidazolium (EMI) and hexyltrimethyl ammonium (HTMA) cations on the electrochemical properties of the gel polymer electrolyte containing the solutions and a polymer matrix with poly(ethylene oxide) side chain has been investigated. The addition of EC improves the conductivity of the gel electrolyte regardless the kind of ionic liquid component. In contrast, the contribution of EC on the interface behavior toward lithium negative electrode is different by the kind of the ionic liquid. The EC addition in the gel electrolyte containing HTMA-based ionic liquid modifies the rate for reversible deposition-dissolution of lithium, while the effect of EC addition in the gel electrolyte containing EMI-based ionic liquid is distinct for the reaction of negative electrode.
In this paper, electrolysis tests were carried out for analyzing the gas purities evolving from the cup-shaped Fe-Ni-Al2O3 anodes, which were made by slip casting. The oxygen purity of the collecting anodic gas detected by Orsat apparatus was in an interval of 98–100%. SEM and XRD results showed that Fe-Ni-Al2O3 anode surface formed a layer that consisted of FeAl2O4, NiO, and Al2O3 mainly, as well as small amounts of metal phase Ni3Al.
The electrodeposition of Sb-Bi-Te alloy in AlCl3-NaCl-KCl molten salt containing SbCl3, BiCl3, and TeCl4 at 423 K was carried out under constant potential control and potential pulse control in the melt. The electrodeposition results show that the SbCl3 concentration is effective to control the composition of Bi-Sb-Te ternary alloy. The electrodeposited Bi0.5Sb1.5Te3 by pulse electrolysis with frequency=100 Hz and D. R. (Duty Ratio)=75%, had good crystallinity and the preferential orientation of the electrodeposit was the (110) plane in this electrodeposition experiments. The electrodeposit had homogeneous disk-like granules. The power factor of the electrodeposit was calculated as 3×10−5 Wm−1 K−2 from the Seebeck coefficient and the electrical conductivity.
LaNi5 alloy powders were prepared by electro-deoxidation of the oxide precursors in a eutectic CaCl2-NaCl melt at 850°C. The reduction pathway from the mixture of La3Ni2O7 and NiO to LaNi5 was studied by examination of partially reduced samples using XRD, SEM and EDX analysis, which were obtained by interrupting the reduction process after different reduction times. The first stage of the reaction involved the rapid formation of Ni and of LaOCl, then LaOCl and La2O3 were electrochemically reduced and alloyed with Ni particles nearby along with their surface. The morphology of LaNi5 particles reduced for the different durations of reduction can be changeable.
Electronic absorption spectra of tetravalent uranium in LiCl and CsCl were measured. Redox potentials of U4+/U3+ and U3+/U0 couples were estimated by cyclic voltammetry. By adding SrCl2 into the melts, changes in absorption spectra and cyclic voltammograms were seen. The effect of the coexisted Sr2+ on the coordination circumstance of uranium ions was discussed.
Laser-induced fluorescence was applied for the detection of lanthanide ions such as Tb3+ and Sm3+ in a pyrochemical processing. The fluorescence signals of Tb3+ and Sm3+ in LiCl-KCl molten salts were successfully observed at room temperature. Moreover, the fluorescence method was identified to be sensitive enough to detect a trace of Eu2+, originated from a reduction of Eu3+ contained in a LiCl-KCl eutectic reagent at a given high temperature molten salt condition. The non-destructive and direct fluorescence measurement can be an alternative method in on-line and in situ determination of the species and concentrations of lanthanides in a molten salt along with absorption measurement.
R&D of the nitride fuel cycle technology is underway at Japan Atomic Energy Agency (JAEA). Behavior of americium (Am) in the pyrochemical process, which includes anodic dissolution of AmN and recovery of Am into a liquid cadmium (Cd) cathode by electrolysis in LiCl-KCl eutectic melts, and nitride formation of Am recovered in liquid Cd, is presented.
Cu-Sn speculum alloy metallization of a non-conductive epoxy substrate was demonstrated through successive electrochemical processes: (i) electroless Cu deposition on the substrate and (ii) electrochemical alloying of the resulting Cu layer with Sn through a reduction-diffusion method using an ionic liquid bath at 150°C. The resulting Cu-Sn alloy layer, composed of Cu6Sn5 and/or Cu3Sn phases, was compact, smooth, and adhesive. Dependence of the intermetallic phases on alloying potential and time was examined to discuss the alloy formation mechanism, demonstrating that Cu-Sn alloy layers composed of desired phases could easily be prepared by controlling these parameters.
Au(100) single crystal surfaces were investigated using in-situ electrochemical atomic force microscopy (EC-AFM) in 1-butyl-3-methyl-imidazolium tetrafluoroborate (BMImBF4) and 1-butyl-3-methyl-imidazolium bis (trifluoromethanesulfonyl) imide (BMImTFSI). The protrusions with four-fold symmetry and interatomic distances of 0.3 nm were observed in the potential range from −0.42 to +0.68 V (vs. Fc/Fc+ electrode) in BMImBF4 and from −0.35 to +1.06 V in BMImTFSI. These observations corresponded to a bare and unreconstructed Au(100)-(1×1) structure. The top layer of the multi-layered island on Au(100) collapsed at a constant decay rate in both BMImBF4 and BMImTFSI and is consistent with previously reported for EMImBF4, EMImTFSI, and a sulfuric acid aqueous solution.
Electrochemical reduction of silicon tetrachloride has been investigated in an equimolar N-ethyl-N-methylpyrrolidinium chloride-zinc chloride melt at 423 K for low-cost production of silicon thin films. A dark-brown substance was formed preferentially on the Ni substrate near the electrode-gas-melt three-phase interface by potentiostatic electrolysis at 0 V vs Zn(II)/Zn. Both energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy suggested that some SiCl4 was electrochemically reduced to amorphous Si in the present system. Cross-sectional observation of electrodeposited films by scanning electron microscopy suggested that the deposition rate in the present system is about 100-fold higher than that in the room-temperature system investigated in our previous study. Contrivances of the electrode configuration and the SiCl4-supplying method enabled electrodepositing the Si-containing film on almost the whole Ni substrate.
A new molten salt system, N-ethyl-N-methylpyrrolidinium chloride (EMPyrCl)-ZnCl2, was investigated for the electrodeposition of molybdenum at intermediate temperature. A phase diagram was constructed for the EMPyrCl-ZnCl2 system, which shows the lowest melting point of 45°C at an equimolar composition. A thermal gravimetry indicated that thermal decomposition starts from 230°C for the equimolar melt. The viscosity and conductivity of the equimolar melt were 75 cP and 22 mS cm−1, respectively, at 150°C. The cathode limit of the equimolar melt was confirmed to be the deposition of metallic zinc by XRD analysis. A smooth metallic molybdenum film was electrodeposited on a nickel substrate by potentiostatic electrolysis at 0.01 V vs. Zn(II)/Zn in an equimolar melt containing MoCl5 (0.9 mol%) and KF (3.0 mol%) at 150°C.
Vinyl group-substituted room-temperature ionic liquids (RTILs) were used for aiming at fabrication of high-safety batteries. The imidazolium-based ionic liquids used in this study had a vinylmetylene group and another alkyl group on an imidazolium cation. The charge-discharge profiles of batteries composed of a LiCoO2 cathode were compared between the different RTILs to know the factors of RTIL influencing the battery performances. The charge/discharge efficiency of a graphite anode was also investigated for total evaluation of the battery performances.
Platinum (Pt) nanoparticles were synthesized with room-temperature ionic liquid (RTIL)-sputtering method under dry N2 or Ar atmosphere. The resulting Pt nanoparticles were well-dispersed in trimethyl-n-propylammonium bis((trifluoromethyl)sulfonyl)amide RTIL without any additive like dispersant. Electrocatalytic activity of the Pt nanoparticles embedded on a glassy carbon electrode (GCE) toward oxygen reduction reaction was examined. It was then found that the catalytic activity increases with increment of heat temperature for embedding the Pt nanoparticles onto GCE if the nanoparticles are synthesized under Ar atmosphere.
The electrochemical behavior of a graphitized electrode was investigated in a room-temperature ionic liquid based on bis(fluorosulfonyl)imide (FSI−) with the addition of propylene carbonate (PC) or vinylene carbonate (VC). The reversible, significant lithium-ion (Li+) insertion/extraction was observed in the additive-free FSI-based ionic liquid, while the additive systems showed weak, reversible responses (VC) and degraded responses (PC). AC impedance measurements suggested that the presence of FSI− extremely reduces the electrode/electrolyte interface impedance, which allows Li+ to intercalate into a graphitized electrode reversibly. By contrast, the addition of VC inhibits the reversible Li+ intercalation in spite of FSI− existence.
This work presents an electrochemical preparation routine of Mg-Li-Y alloys by codeposition of Mg, Li, and Y on a molybdenum electrode in LiCl-KCl-MgCl2-YCl3 melts at 943 K. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of yttrium on pre-deposited magnesium leads to the formation of a liquid Mg-Y solution. Chronopotentiometric measurements indicated that the codeposition of Mg, Li, and Y occurs at current density more negative −0.47 A cm−2. Mg-Li-Y alloys with different lithium contents were obtained via galvanostatic electrolysis.
Low-temperature chlorination of zirconium dioxide using molybdenum pentachloride has been investigated below 773 K. The chlorination ratio was measured by chemical analysis, and the products were identified by powder X-ray diffraction. The results indicated that substitution of chlorine using molybdenum pentachloride significantly reduces the reaction temperature. Almost all the zirconium dioxide was converted to chloride in 30 minutes at 668 K when the molar ratio of molybdenum pentachloride to zirconium dioxide exceeded two. The chlorination reaction between zirconium dioxide and molybdenum pentachloride was shown to be a three-dimensional diffusion reaction satisfying the Jander equation, and the activation energy was 67 kJ/mole. Chlorination at a practical reaction rate using molybdenum pentachloride was realized at much lower reaction temperature than that using chlorine gas and carbon.
To make functional glasses, ion-exchange treatment of the glass surface was carried out in TlNO3-NaNO3 molten salt at 673 K and 723 K for various time periods, and then the Tl ions embedded in the glass were reduced to metallic Tl nanoparticles by hydrogen gas. The color of the glass containing metallic Tl nanoparticles changed to brown or black. The Tl nanoparticles were detected by a qualitative TEM analysis. The optical absorption spectra of these treated glasses showed a peak at about 370 nm. With increases in the temperature of the molten salt, the band intensity of the absorption is enhanced. The absorption increase may correspond to larger particle sizes and densities with the increase in temperature. The Tl nanoparticles with 10–150 nm diameter were observed at neighboring parts of the glass surface by TEM and FE-SEM.
The effects of HF content on the ionic conductivity and the viscosity of low temperature molten fluorides, (CH3)4NF·mHF, (CH3)3N·mHF, KF·mHF, and NH4F·mHF melts, were investigated. The ionic conductivity of the (CH3)3N·mHF and (CH3)4NF·mHF melts increased, whereas their viscosity decreased with increasing the m value. The ionic conductivity and the viscosity of the (CH3)3N·mHF melts were lower and higher, respectively, than those of the (CH3)4NF·mHF melts at a given m value and a given temperature. The activation energy for ionic migration decreased with increasing the m value in both systems. Similar effects of the m value on the conductivity and viscosity were obtained for the KF·mHF and NH4F·mHF melts. The KF·mHF melts exhibited lower conductivity and higher viscosity than the NH4F·mHF melts at a given m value and a given temperature. It was concluded that these effects of the HF content can be explained in terms of the concentration change of molecular HF and the resulting change in electrostatic cation-anion interactions.
Raman spectra and the polarization behaviors of molten alkali carbonates coexisting inorganic powder were measured. The deformation and the change of polarization properties by the coexisting with the solid phase are discussed. The symmetry of the band shape of the Raman spectra for CO32− stretching band (ν1) was deformed asymmetrically by coexisting with α-Al2O3 powder. The deconvolution of spectra of mixtures exhibited two band components. The observed bands are evidence of the existence of two different types of CO32− ions in these systems. Raman depolarization ratio for molten carbonate systems increases from the base line with the decrease of the apparent average thickness. The degree of the anomalous behavior of the molten carbonate by the solid phase have been observed in the order of α-Al2O3>γ-LiAlO2>ZrO2 which is related to the surface acidity defined by the value of point of zero charge (pzc). Consequently, the carbonate ion is deformed asymmetrically by coexisting with inorganic oxide powder.
The effects of secondary cationic species on the ordering structure in room temperature ionic liquids (RTILs) are discussed. Binary RTILs refer to mixture of trimetyl-n-octylammonium bis(trifluoromethanesulfonyl)imide (N1118[TFSA]) and alkali or alkali-earth metal bis(trifluoromethanesulfonyl)imide (M[TFSA]y; M=Li, Na, K, Rb, Cs, Mg, Ca, Sr, Ba) in an appropriate molar ratio (x=0.1, 0.2, 0.3, 0.5), denoted as Mx[N1118]1−x[TFSA]1−x+xy. From SAXS and WAXS measurements of Mx[N1118]1−x[TFSA]1−x+xy, the intensity of first peak derived from the ordering structure increases with addition of M[TFSA]y. It is suggested that the metal cation has an intensive interaction with TFSA anion and cationic structural ordering are enhanced. We discussed the relationship between ionic size and the formation mechanism of the local ordering structure in binary ionic liquids containing alkali metal and alkali earth metal based on aliphatic quaternary ammonium (AQA) cations is clarified.
Pyrolysis of biomass in molten salt media have been conducted in a stainless steel reactor. Five kinds of mixed molten salts were used as thermal pyrolysis media and six kinds of biomass as feedstock. The experiments were carried out under atmospheric pressure and 400–600°C. The pyrolysis oils were examined using some spectroscopic and chromatographic analysis techniques. The effects of the type of molten salts and feeding conditions, reaction conditions, including temperature and space velocity, on yield of liquid product were investigated. This paper reports the feasibility for producing bio-fuels and bio-chemicals through the pyrolysis of biomass in molten salt media.
Local structure of molten lanthanum trichloride—alkali chloride ternary systems was analyzed in terms of Raman spectroscopy and pulsed neutron diffraction in order to accelerate the realization of pyrochemical reprocessing of nuclear spent fuels. In particular, not only vibrational modes of ionic species existing in molten LaCl3-ACl-NaCl (A=Li, K, Rb, and Cs) systems but also short range structure in molten LaCl3-CsCl-NaCl system on behalf of the systems described before were reported in some detail, the salt combinations of which could be of prototype in the reprocessing of UO2 and/or PuO2.
The short-range structural parameters for NaNO2 and KNO2 pure melts were determined by the time-of-flight neutron diffraction. The precise analyses of structural parameters obtained such as coordination number, interatomic distance, and temperature factor allowed us to conclude that (1) there exist stable NO2− anions in the melts, (2) NO2− anions behave like NO3− anions due to the existence of lone pairs of electrons, (3) the short-range structure of KNO2 pure melt is similar to that of NaNO2 pure melt but the cation site relative to anion is a little different from each other in terms of the cation size effect.
The quantitative structure-property relationship (QSPR) method was used to correlate and predict the infinite-dilution activity coefficients γi∞ of organic solutes in three ionic liquids (ILs). The correlated and predicted results from QSPR models agreed well with the experimental γi∞ values.