Evaluation of sound velocity in binary molten electrolytes

A comparison of sound velocity evaluated from Nomoto's relation, ideal mixing relation Jacobson's free length theory and Schaaffs' collision factor theory has been made in six binary molten electrolytes (NaClKCl, NaClRbCl, NaClCsCl, KClLiCl, KClRbCl, KClKBr) at 800°C. The agreement between theoretical and experimental values is quite satisfactory. Discrepancies in the sound velocity values are maximum in the case of the NaClCsCl system where maximum interactions are observed. Non-ideality in the mixtures has been discussed in terms of sound velocity.     

Cathodic processes at electrolysis of chloride and chloride-fluoride melts of zirconium

Electrochemical reduction of zirconium from the NaClKClZrCl₄ molten mixture proceeds reversibly in two consequent steps:

With addition of sodium fluoride into the NaClKClZrCl₄ melt and also in the NaClKClK₂ZrF₆ molten mixture, reduction of zirconium occurs reversibly four-electrons step reaction:

     

Chronopotentiometric study of aluminium deposition from MClAlCl3 melts (MNa,K and Cs)

The kinetics of aluminium deposition from NaClAlCl₃, KClAlCl₃ and CsClAlCl₃ melts (C_AlCl3 = 3 × 10^?5 ?1 × 10^?3 mol cm^?3) was studied using the chronopotentiometric technique. It was found that in the system NaClAlCl₃ the reduction of Al(III) species is controlled by diffusion only, while in the system KClAlCl₃ and CsClAlCl₃, a chemical reaction precedes the reduction step. In the two latter systems the Al(III) in the complex anion AlCl^?₄ can be reduced also directly, if current density is sufficiently high.     

Kinetics of aluminium deposition from aluminium chloride—alkali chloride melts

The kinetics of aluminium deposition from NaClAlCl₃ and NaClKClAlCl₃ melts (c_AlCl3 < 0.4 mol%) was studied by linear sweep voltammetry and potential step amperometry. The reduction of AlCl₃ on tungsten and aluminium electrodes was found to be diffusion controlled. The diffusion coefficients of AlCl₃ were: 3.5 × 10^?5 cm² s^?1 at 820°C in NaClAlCl₃, 2.7 × 10^?5cm²s^?1 at 825°C, and 2.1 × 10^?5cm²s^?1 at 705°C in KClNaClAlCl₃. The rate constant for AlCl₃ reduction at these conditions was found to be in the order of 0.2 cm s^?1, in good agreement with extrapolated literature data.     

Thermodynamic studies on liquid AgClKClLiCl solutions

The thermodynamic properties of ternary AgClKClLiCl solutions were determined at various values of

and a different AgCl concentrations, using the formation cell: Ag(s)|AgClKClLiCl(l)|Cl₂(g), graphite. Dilute AgCl solutions were investigated in detail in order to extrapolate in γ_Agcl to X_AgCl å 0. Experimental values of Δ$\text{G}$^E_AgCl were interpreted by the Pelton, Flengas method and compared with Krupkowski's formalism, based only on data from the constituent binaries.     

Electrochemical study of titanium in chloride-fluoride melts

The study of electrochemical reduction of titanium in molten NaClKClK₂TiF₆ by means of linear sweep voltammetry and the quasi-steady-state method has revealed that the reduction of Ti(IV) to Ti proceeds reversibly in two consequent steps

The temperature dependence of the equilibrium constant for the metal—salt interaction is established. The effect of the fluorine ion concentration on the interaction mechanism of Ti metal with chloride—fluoride melts containing tetravalent ions of titanium is considered.     

Photoelectrochemical properties of thin low cost polycrystalline CdS photoanodes

In the present paper photoelectrochemical processes and physical properties of the photovoltaic CdS|KClK₃ Fe(CN)₆K₄ Fe(CN)₆|Pt electrolytic cell have been studied. CdS polycrystalline photoanodes were prepared by pyrolytic spraying. The electrode resistance was measured and the film structure and composition were analyzed by SEM. Optical measurements were performed in order to determine the absorbance and the energy gap of the sprayed CdS films. Current-voltage characteristics as a function of the redox couple concentration and light intensity were measured under incandescent illumination and sunlight. Fill factors varied in the range from 0.2 to 0.4 and the efficiency of the yet non-optimized cells reached 0.4%. The problem of stability of the photoanode and its passivation were also discussed.     

Etude des reactions anodiques des ions oxydes dissous dans l'eutectique LiCl-KCl sur electrodes de graphite par des methodes electrochimiques impulsionnelles

The oxide anodic reaction on a graphite electrode in fused LiClKCl eutectic has been investigated by use of chronopotentiometry, chronoamperometry and cyclic voltammetry. The analysis of the anode response shows the existence of two steps; the first is due to adsorbed oxide ions, whereas a second part of the signal corresponds to the diffusion of electroactive species towards the electrode. The amount of oxide ions γ_eq adsorbed on the graphite anode and the diffusion coefficent D of the electroactive species are calculated: γ_eq ? 8.10^?8 moles cm^?2 for a concentration of oxide ions in the liquid phase C_O^2? = 4,96.10^?5 moles cm^?3; D_O^2? = 2.10^?5 cm² s^?1 at 442°C.A rapid determination of the oxide ions content in the fused LiClKCl eutectic is proposed for a range of relatively high concentration values (C_O^2? > 20 ppm).     

Potential of the Pb,PbSO4/H2SO4 electrode at temperatures up to 240°C

Standard lead—lead sulphate electrode potential was determined over the temperature range 20–240°C from emf measurements of the Pb, PbSO₄H₂SO₄ (0.05M)K₂SO₄KClHCl(0.1M)/AgCl, Ag and Pb, PbSO₄H₂SO₄(m)K₂SO₄H₂SO₄(0.05M)PbSO₄, Pb cells where m = 0.005, 0.01, 0.1 and 0.5 M. To this effect lead—lead sulphate electrode potential was calculated using the temperature relationship of the standard silver—silver chloride electrode potential and activity coefficients of hydrochloric acid determined by Greeley et al. at temperatures up to 260°C. Diffusion potentials occurring at the phase boundaries in the cells under investigation were calculated using the Henderson's equation. Values of the standard lead—lead sulphate electrode potential were determined by extrapolation of the E°′ function to the zero ionic strength which was calculated using the second sulphuric acid dissociation constant determined by Lietzke et al. at temperatures up to 300°C. The standard electrode potential was described in the temperature range 20–240°C by the following relationship: E°_{Pb, PbSO4/SO^2?4}(V) = 0.040-0.00126T. A change in entropy ΔS° of the electrode reaction Pb + SO^2?₄ = PbSO₄ + 2e^? is constant in this temperature range and is ?243 JK^?1 mol^?1 (?1018 cal K^?1 mol^?1).     

Cathodic processes at electrolysis of chloride—fluoride and oxyfluoride melts of niobium

Electrochemical reduction of niobium from the KClKFK₂NbF⁷ molten mixture proceeds reversibly in two consequent steps:

Niobium pentoxide is dissolved in chloride—fluoride melt containing potassium fluo-niobate with formation of monoxyfluoride NbOF^?3₆, dioxyfluoride NbO₂F^?3₄ and niobate NbO^?₃ complexes in which the power of substitution of fluoride to oxygen is growing with the increase of the Nb₂O₅:K₂NbF₇ (1) ratio in the melt.The mechanism of the cathodic process is considerably changed depending upon the value of the ratio (1).     

Effect of NaCl or NaOH on the formation of CSH

Formation field and composition of CSH in the presence of NaCl and/or NaOH were investigated to clarify their effects on the durability of concrete. The CSH and other hydrates were prepared from the mixtures of various solutions. The silica gel, CSH and calcium hydroxide are precipitated in turn with increasing initial Ca/Si mole ratio of mixture. On the formation of hydrate, the liquid composition moves to and then situates on each solubility product curve regardless of ionic species or concentration. The CSH formed in this experiment has lower Ca/Si mole ratio than that of normal CSH formed in water and contains sodium ion. However, this CSH easily returns to normal CSH after dispersing in water. These characteristic of CSH are confirmed thermodynamically.     

Invariance of lamellar thickness with crystallization temperature of polyesteramide 6NT6 crystals

Polyesteramide of the type [COøCONH(CH₂)₆NHCOøCOO (CH₂)₆O]_n, conventionally referred to as PEA 6NT6, was crystallized from dilute solutions in benzyl alcohol at different temperatures. Single crystals were obtained in ellipsoidal and flat form, as revealed by electron microscopy. X-ray small- and wide-angle diffraction experiments were carried out on oriented mats of the lamellae. Invariance of long spacing with crystallization temperature in the range 72°–118°C was found. Annealing experiments revealed a quantized increase of the long spacing. The thermal behaviour of the single crystals was studied by differential scanning calorimetry and by i.r. spectroscopy. A chain-folding model based on tight folds and adjacent re-entry is proposed for this polymer.     

Semi-integral electroanalysis of the oxidation of glassy carbon in molten LiClKCl Eutectic melt containing CO32− ion under CO2 pressure (1 atm) at 470°C

The oxidation of carbon, in presence of an oxide ion donor (C0₃^2? in LiClKCl eutectic melt at 470°C, leads to the formation of dioxide carbon, thus reducing the active electrode area. A semi-integral analysis of voltammograms and chronoamperograms permits to precise this phenomenon and to take into account of it for determining the area variation during electrolysis, and consequently to establish a neopolarogram corresponding to a constant glassy carbon electrode area. The oxidation of carbon into CO₂ is an irreversible system, the value of the transfer coefficient is α = 0.27. The diffusion coefficient of carbonate ions has a value between 6.2–7.4 × 10^?6 cm²s^t?1.     

Investigation of orientation phenomena in drawn films of poly[(±)-β-aminobutyric acid]

Orientation data of drawn films of poly[(±)-β-aminobutyric acid] (structural unit [NHCHCH₃CH₂CO]_n), are derived from the infra-red dichroism of the NH stretching vibration and wide angle X-ray diffraction measurements. In combination with accessibility data from deuteration experiments, these parameters are used to examine the applicability of two-phase polymer models for uniaxial orientation to the investigated polymer.     

Activity tests of various catalysts for hydrocracking of coal by means of high pressure differential thermal analysis

The activities of fourteen kinds of catalysts for the hydrocracking of Taiheiyo coal were examined by a high pressure differential thermal analytical method. Exothermic peaks appeared at low temperatures (420–430°C) when MoO₃TiO₂, NiY zeolite and CoY zeolite were used as catalysts, indicating that these catalysts are highly active compared with other catalysts including MoO₃CoOAl₂O₃. The qualitative analysis of gas and liquid products revealed that MoO₃TiO₂ and CoY are good catalysts for the liquefaction reaction. The hydrogenation ability of the catalyst is concluded to be more important than its acidic property.     

Reaction of dinaphthyl and diphenyl ethers at liquefaction conditions

The reactions of 2,2′-dinaphthyl ether and diphenyl ether were studied at 375–425°C using 6.9 MPa (cold) hydrogen or nitrogen, 9,10-dihydrophenanthrene (DHP) and decalin as solvents, and a molybdenum sulfide catalyst. We chose to examine these compounds as models for the cleavage of diaryl ether bridges during coal liquefaction. The molybdenum sulfide was added to the reaction as MoS₃, which should transform to the active MoS₂ catalyst. Cleavage of the C_arO in 2,2′-dinaphthyl ether, at reaction temperatures of 375 and 400°C, proceeded in the sequence H₂ < DHPN₂ < DHPH₂ < DHPMoS₃N₂ < DHPMoS₃H₂ < MoS₃H₂ < Dec.MoS₃H₂. At 425°C, the MoS₃H₂ and Dec.MoS₃H₂ systems exchange places in this order. Diphenyl ether is less reactive than dinaphthyl ether toward hydrogenolysis reactions under these conditions. The conversion rate of diphenyl ether increases in the order H₂ < DHPH₂ < DHPMoS₃N₂ < DHPMoS₃H₂ < Dec.MoS₃H₂ < MoS₃H₂. Although the rates of conversion of the two ethers are different, the relative effects of using a reactive gaseous atmosphere, donor solvent, catalyst - or some combination of these factors - are the same for both compounds. In liquefaction experiments, hydrogen donor solvent or hydrogen shuttling solvent seems necessary to reduce retrogressive reactions. However, a solvent interacting strongly with catalyst and scavenging hydrogen atoms can reduce the activity of catalysts in hydrocracking reactions.     

Characteristics of HACaP complexes prepared from lignite humic acids

Calcium humate phosphorates, HACaP were prepared by direct interaction of humic acids (HA) from lignite, calcium ions and phosphate at pH 5 and 7. The complexes have been isolated by dialysis and their electrophoregrams and thermograms have been obtained. The phosphorus availability in the HACaP complexes was estimated by six selected extractant solutions of very different pH. The electrophoregram of the HACaP complex prepared at pH 7 shows simultaneous movement of phosphorus and HA and the differential thermogravimetric (DTG) curves indicated a slight decrease of the temperature of nucleus decomposition with respect to calcium humate. The study of phosphorus availability indicated that in the complexes, it is in available form.     

Characterization of vitrinite concentrates. 1. Fourier Transform infrared studies

A set of 21 vitrinite concentrates have been characterized by FTIR. Hydroxyl groups have been quantitatively determined by combining acetylation with FTIR procedures. Methods for the determination of extinction coefficients for various bands are discussed. Values are calculated by equating total hydrogen from elemental analysis to the fraction of hydrogen present as hydroxyl, aromatic CH and aliphatic CH groups. The variation in values of the extinction coefficients for aromatic and aliphatic CH bands are determined as a function of assumed values for the extinction coefficient of the OH bands. Large variations in the latter do not greatly affect calculated values of aliphatic and aromatic CH groups. The distribution of hydrogen between OH, aromatic CH and aliphatic CH groups is determined.     

The role of sulphates in cement clinkering reactions: phase formation in the system CaOAℓ2O3Fe2O3SiO2CaSO4K2SO4

The CaO-rich portions of the systems CaOA?₂O₃SiO₂K₂SO₄, CaOA?₂O₃K₂SO₄, CaOA?₂O₃SiO₂K₂SO₄CaSO₄ and CaOA?₂O₃Fe₂O₃CaSO₄K₂SO₄ have been studied experimentally. Schemes are presented showing phase assemblages compatible at subsolidus temperatures. Melting commences at about 825°C in assemblages containing K₂SO₄. Silicate, aluminate and ferrite phases are comparatively insoluble in molten alkali-rich sulphates. At clinkering temperatures, two immiscible liquids form; one is rich in K₂O and sulphate, the other is a silicate liquid. Some features of vapour-liquid-solid equilibria relevant to the S cycle in cement kilns are discussed.     

Hydrothermal reaction between C6S6H and kaolinite for the formation of tobermorite at 180°C

11 Å tobermorites were made from CSH (Ca/Si = 1.14) and kaolinite with Ca/(Si+Al) = 0.8 and Al/(Si+Al)= 0.15 at 180°C. The CSH was prepared from colloidal silica and lime at 130°C and 180°C for 2 h. Reaction gives in succession CSH, poorly crystalline Al-substituted tobermorite, and highly crystalline Al-substituted tobermorite. The addition of kaolinite markedly accelerates the formation of tobermorite within 4 h, more effectively with CSH prepared at 130°C than with that prepared at 180°C. X-ray fluorescence diffractometry shows that the Al coordination number is a mixture of 4 and 6 in the initial products and shifts to 4 with an increase in processing time. This agrees with the results for the degree of reaction of the kaolinite.