Selecting an optimum electrolyte for zinc chloride electrolysis

In order to be able to select the optimum composition of an electrolyte in the ZnCl₂–NaCl–KCl system, the conductivity, surface tension and density were measured for a series of melts in the composition range 28–50 mol % ZnCl₂, 0–62 mol% KCl and 0–62 mol % NaCl. It was found that the results could be correlated with the phase diagram and that the difference between the temperature of measurement and the liquidus or glass transition point was an important parameter in defining the properties. The optimum composition was found to be 40 mol % ZnCl₂, 30 mol % KCl and 30 mol % NaCl.     

Sb6O13 and Bi2O3 as Oxidants for Si in Pyrotechnic Time Delay Compositions

Lead and its compounds in detonator time delays are being phased out owing to environmental and health concerns. It was found that changing from the conventional rolled lead elements to rigid aluminium tubes caused a significant decrease in the burn rate. It also impaired ignitability, especially of slow burning compositions such as Si BaSO₄. Consequently, potential alternatives for the latter and also the fast burning Si Pb₃O₄ system were sought. Bi₂O₃, prepared by thermal decomposition of bismuth subcarbonate, gave fast burning compositions with silicon as fuel (155 mm s⁻¹ with 20% Si). This system was ignitable by the spit of a shock tube. The Si Sb₆O₁₃ system required an initiating composition and yielded slow burning compositions. The lowest sustainable and reproducible burn rate in lead tubes, in the absence of additives, was 4.8 mm s⁻¹. In lead tubes, it was possible to reduce the burn rate further by adding fumed silica: A composition obtained by adding 10% fumed silica (add‐on basis) to a 10% Si–90% Sb₆O₁₃ composition still burned reliably at a burn rate of 2.3 mm s⁻¹.     

Electrolyte additive trimethyl phosphite for improving electrochemical performance and thermal stability of LiCoO2 cathode

The purpose of this paper is to investigate compositions on the interface between LiCoO₂ and electrolyte when trimethyl phosphite TMP(i) is used as an additive in 1 M LiPF₆/EC + DEC electrolyte system and the thermal stability of the electrolyte as well as Li_0.5CoO₂ mixed with the electrolyte. The electrochemical performance of LiCoO₂ electrode in the two electrolyte systems was also studied. It is found that the electrochemical performance, including capacity, cycle performance and 3.6 V plateau efficiency, has been improved in the electrolyte with TMP(i) additive. FTIR analysis indicates that Li_xPO_y is an important surface film composition on the cathode in TMP(i) containing system. A thicker and more passivating surface layer is formed when using TMP(i) additive as an additive. The thermal stability of the cathode is substantially improved in the electrolyte containing TMP(i) additive in the system, especially the exothermic peak around 190 °C, which is associated with the reaction between active surface of cathode and solvents, is obviously restrained.     

Selective Catalytic Synthesis of 2-Ethyl Phenol over Cu1− xCox Fe2O4–Kinetics, Catalysis and XPS Aspects

A systematic study of catalytic ethylation of phenol is carried out with ethanol as a function of feed composition, time on stream (TOS), temperature, and catalyst composition over Cu_{1 ?x} Co _x Fe₂O₄ (x=0.0–1.0) ferrospinel system. Phenol ethylation gives 2-ethyl phenol as a major product under the reaction conditions employed, while its selectivity decreases as temperature and Co-content increases. Compositions containing both Cu and Co (0<x<1) are found to be more efficient for better catalytic performance than the end compositions (x=0 and 1); x=0.5 shows the highest catalytic performance. TOS studies clearly exhibit the stable activity for x≤0.75 for at least 50h. X-ray photoemission spectra (XPS) and X-ray induced Auger electron spectroscopy analysis revealed the partial reduction of metal ions during reaction. Valence band studies clearly show an increase in overlap of metal-ion 3d bands from fresh to spent catalysts by a large decrease in energy gap between them. Cu-rich compositions display a large amount of Cu species on the surface and highlight its importance in the ethylation. High catalytic activity displayed by 0<x<1 emphasizing the importance of both Cu and Co for better catalytic performance.     

Electrochemical tuning of titania nanotube morphology in inhibitor electrolytes

The electrochemical behavior of fluorine containing electrolytes and its influence in controlling the lateral dimensions of TiO₂ nanotubes is thoroughly investigated. Potentiostatic anodization is carried out in three different electrolytes, viz., aqueous hydrofluoric acid (HF), HF containing dimethyl sulphoxide (DMSO) and HF containing ethylene glycol (EG). The experiments were carried out over a broad voltage range from 2 to 200 V in 0.1-48 wt% HF concentrations and different electrolytic compositions for anodization times ranging from 5 s to 70 h. The chemistry that dictates how the nature of electrolytes influences the morphology of nanotubes is discussed. Electrochemical impedance spectra were recorded for varying compositions of all the electrolytes. It was observed that composition of the electrolyte and its fluorine inhibiting nature has significant impact on nanotube formation as well as in controlling the aspect ratio. The inhibiting nature of EG is helpful in holding fluorine at the titanium anode, thereby allowing controlled etching at appropriate voltages. Thus our study demonstrates that HF containing EG is a promising electrolytic system providing wide tunability in lateral dimensions and aspect ratio of TiO₂ nanotubes by systematically varying the anodization voltage and electrolyte composition.     

Synthesis and properties of lithium disilicate glass-ceramics in the system SiO2–Al2O3–K2O–Li2O

The purpose of this study was the synthesis of lithium disilicate glass-ceramics in the system SiO₂–Al₂O₃–K₂O–Li₂O. A total of 8 compositions from three series were prepared. The starting glass compositions 1 and 2 were selected in the leucite–lithium disilicate system with leucite/lithium disilicate weight ratio of 50/50 and 25/75, respectively. Then, production of lithium disilicate glass-ceramics was attempted via solid-state reaction between Li₂SiO₃ (which was the main crystalline phase in compositions 1 and 2) and SiO₂. In the second series of compositions, silica was added to fine glass powders of the compositions 1 and 2 (in weight ratio of 20/100 and 30/100) resulting in the modified compositions 1–20, 1–30, 2–20, and 2–30. In the third series of compositions, excess of silica, in the amount of 30 wt.% and 20 wt.% with respect to the parent compositions 1 and 2, was introduced directly into the glass batch. Specimens, sintered at 800 °C, 850 °C and 900 °C, were tested for density (Archimedes’ method), Vickers hardness (H_V), flexural strength (3-point bending tests), and chemical durability. Field emission scanning electron microscopy and X-ray diffraction were employed for crystalline phase analysis of the glass-ceramics. Lithium disilicate precipitated as dominant crystalline phase in the crystallized modified compositions containing colloidal silica as well as in the glass-ceramics 3 and 4 after sintering at 850 °C and 900 °C. Self-glazed effect was observed in the glass-ceramics with compositions 3 and 4, whose 3-point bending strength and microhardness values were 165.3 (25.6) MPa and 201.4 (14.0) MPa, 5.27 (0.48) GPa and 5.34 (0.40) GPa, respectively.     

Density,viscosity and surface tension of high-silicate CaO–SiO2 and CaO–SiO2–Fe2O3 slags derived by aerodynamic levitation. The behavior of Fe3+ in high-silicate melts

Thermophysical data for liquid slag are required for the optimization and control of metallurgical processes. The density, surface tension and viscosity were measured by employing aerodynamic levitation under contactless conditions. The high-silicate slag (44 and 63 mass-% of SiO₂) of the CaO–SiO₂ and CaO–SiO₂–Fe₂O₃ systems (with 5 and 10 mass-% Fe₂O₃) was investigated under (80% Ar + 20% O₂) gas atmosphere. The temperature ranges were between 800 °C and 2000 °C for the density and 1500 °C–2000 °C for surface tension and viscosity measurements. The influence of the CaO/SiO₂ ratio on the investigated properties and the behavior of Fe³⁺ ions in high-silicate melts were examined. The density of the CaO–SiO₂ melt was lower than that of the CaO–SiO₂–Fe₂O₃ systems. The surface tension of all compositions tested decreased with temperature and showed compositional dependence. The viscosity measured was higher in the Fe₂O₃-containing slag. The Raman spectroscopy analyses confirmed the increase in the degree of polymerization with the addition of Fe₂O₃ for the silicate-rich slag. The formation of a complex anion of a ferric ion and contribution to the silicate network were assumed. The trends observed were related to the structural properties and different interionic bonding. Urbain's viscosity model and FactSage? 7.3 were applied for the assessment of the experimental data.     

Some properties of materials in the MgCr2O4-MgAl2O4 system

Conclusions We studied the relationships between the average sizes of the crystallites, the specific surface and the nature of the porosity and the composition and temperature of synthesizing powdered materials in the system MgCr₂O₄-MgAl₂O₄ and also the linear shrinkage during sintering of specimen prepared from the materials. It is shown that the relationships are nonlinear and their extremes correspond to the compositions close to MgCrAlO₄.Translated from Ogneupory, No. 3, pp. 13–15, March, 1988.     

Apatite formation on melt-derived bioactive glass powder based on SiO2-CaO-Na2O-P2O5 system

The higher melting temperature and longer soaking time during conventional glass melting route promoted the search for alternative in developing new bioactive glass (BG) composition with improved in fabrication temperature and melting time. The current project involved fabrication of new BG compositions based on SiO₂-CaO-Na₂O-P₂O₅ system via melt derived route. It was confirmed that all bioactive glass composition can be melted at temperature lower than 1400 °C. Formation of Si-O-Si (tetrahedral) functional group highlighted that silicate based glass was established as detected by Fourier transform infrared spectroscope (FTIR). BG bioactivity was performed by incubating the BG powder in Tris-buffer solution (pH 8) for 7, 14 and 21 days. In vitro test confirmed the apatite formation on the bioactive glass surface upon soaking in Tris-buffer solution with characteristic of carbonate group (C-O) and P-O band noticed from FTIR and present of crystalline peak observed in X-ray diffraction (XRD). Morphology of apatite formation on BG surface was observed using scanning electron microscope (SEM).     

Phase behaviour of ternary system styrene-maleic anhydride (SMA) and two styrene-acrylonitrile (SAN) copolymers having different compositions

The phase behaviour of the binary copolymer systems SMA-SAN and SAN-SAN can be described well using the copolymer repulsion model. However, the phase behaviour of the ternary system consisting of SMA-SAN(1)-SAN(2) with SAN(1) and SAN(2) having different chemical compositions is not known. In order to reveal this, the composition of the blends, the composition of the SMA (ranging from 22 to 34 wt% MA) at constant SAN compositions (26, 34 and 28, 32 wt% AN), the molar mass of the SMA (M_w=3.5 and 110 kg/mol) as well as the temperature (25 and 230°C) were varied. The number of phases was studied using differential scanning calorimetry (DSC) and a critical evaluation of the predicted and observed glass transition temperatures based on the Fox equation. The binodals and spinodals were calculated using the Flory-Huggins approach. From a comparison of predicted and observed miscibility, it is concluded that this ternary system can be described using the aforementioned model.     

The effect of the addition of alumina on the viscosity,surface tension,and foaming efficiency of 2.5(CaO/SiO2)-xAl2O3-yFeO-MgO melts

Viscosity and surface tension strongly influence the efficiency of slag foam in metallurgical processes. An excellent foaming slag preserves heat and lowers the cost of smelting in an electric furnace. In this study, we investigated the viscosity, surface tension, and foaming efficiency of a 2.5CaO/SiO₂-xAl₂O₃-yFeO-MgO slag. We also investigated the different valence oxygen ions by X-ray photoelectron spectroscopy (XPS). The results showed that with a gradual increase in the content of Al₂O₃, the viscosity initially increased and then decreased, and the changes in surface tension followed a similar pattern. The change in viscosity was caused by the increase in the degree of polymerization of the slag, which was determined by the competitive relationship between polymerization and the reduction in the stability of the overall network structure. Adding a small amount of Al₂O₃ to the slag slightly increased the number of Al–O–Al structures, whereas adding a large amount of the Al₂O₃ led to the formation of low-strength Al–O–Si structures, which reduced the stability of the network structure, thus reducing the viscosity. Because the surface tension is related to the concentration of non-bridging oxygens (NBOs), when the NBO content increased, the instability of the surface structure caused an increase in energy, thus increasing the surface tension. In addition, the CaO–SiO₂–5MgO-xAl₂O₃-yFeO five-element oxide in this study had the lowest surface tension at the same NBO concentration, which positively contributed to slag foaming. Finally, When the Al₂O₃ content in the system increased from 5.1 to 15.7 wt%, the foaming efficiency increased from 24.2 to 69.2 (minute‧centimeters), an increase of 286%.     

Some properties of highly refractory ceramics in the system MgO-MgAl2O4

Conclusions A region for compositions in the system MgO-MgAl₂O₄was detected which has great interest for practical use.Compositions containing up to 15% Al₂O₃ permit a big improvement to be obtained in the spalling resistance of periclase ceramics with a simultaneous reduction in the sintering temperature.Spinel and compositions close to it are distinguished from periclase by a lower volatilization capacity. This makes it possible to use the corresponding ceramic materials at temperatures that are much higher than with the ceramics containing a predominant content of periclase, despite the fact that in terms of deformation the spinel is much inferior to the periclase. The limiting service temperature of periclase ceramics (especially in vacuum) is limited not by the thermomechanical and refractory properties but by the high volatilization of the magnesia.It should be mentioned that there is a reduction in the sintering temperature and that bodies close in composition to spinel have high strengths.Bodies of intermediate composition containing from 20 to 50% Al₂O₃ apparently are of no practical interest as highly refractory ceramics.     

Effect of methanol addition on water–CO2–diethanolamine system: Influence on CO2 solubility and on liquid phase speciation

The aim of this study is the characterisation of VLE and chemical equilibria for the system CO₂/diethanolamine (DEA)/H₂O/methanol. The effect of MeOH composition has been studied using four compositions (from 0 to 30 wt% of methanol with a fixed composition (30 wt%) of DEA), the measurement being made at T = 298.15 K and at various CO₂ loadings (from 0.2 to 0.8). An original experimental device was used. This device combines a FT-IR spectroscopy analysis of the liquid phase with a VLE measurement cell.The data base obtained, including the new solubility data and the liquid phase composition, allows the modelling of the system CO₂/DEA/H₂O/methanol using an electrolyte equation of state [Fürst, W., Renon, H., 1993, Representation of excess properties of electrolyte solutions using a new equation of state, AIChE J, 39(2): 335–343] representing the equilibrium properties of the system and the liquid phase speciation.     

Thermal stability of Pd or Pt loaded Ce0.68Zr0.32O2 and Ce0.50Zr0.50O2 catalyst materials under oxidising conditions

The sintering behaviour of Pd or Pt loaded ceria–zirconia solid solutions of nominal composition Ce_0.50Zr_0.50O₂ and Ce_0.68Zr_0.32O₂ was studied under oxidising conditions. Calcination treatments were carried out under controlled oxidising atmosphere for periods of up to 96 h. Powder X-ray diffraction and BET nitrogen adsorption–desorption derived surface area data are reported for the bare materials and for those loaded with low (<1% w/w) amounts of the noble metals, palladium and platinum. Phase demixing was observed as sintering progressed for both of the compositions studied with some differences in behaviour observed between the noble metal free and noble metal loaded catalysts. The results are discussed from a thermodynamic viewpoint, which allows to distinguish the behaviour of the two compositions during the demixing process.     

Liquidus Temperature of SrO-Al2O3-SiO2 Glass-Forming Compositions

Despite the important role of strontium aluminosilicate glasses in various technologies, there is no available phase diagram for this ternary system in the ACerS-NIST Phase Equilibria Diagrams Database. Establishing the liquidus surface (liquidus temperature T_liq and primary devitrification phase) is crucial for glass composition design, because the liquidus temperature is intimately connected with the glass-forming ability of the melt. In this work, we have determined the liquidus surface by X-ray diffraction phase analyses of isothermally reacted samples from powder mixtures of 24 compositions. In the composition range of interest for industrial glasses, T_liq tends to decrease with increasing strontium-to-alumina ratio. We find that cristobalite, mullite, and slawsonite are the dominant devitrification phases for the compositions with high SiO₂, SiO₂+Al₂O₃, and SrO contents, respectively. By comparison with the phase diagrams for CaO-Al₂O₃-SiO₂ and MgO-Al₂O₃-SiO₂ systems, we have found that for the highest [RO]/[Al₂O₃] ratios, T_liq exhibits a minimum value for R = Ca. Based on the phase diagram established here, the composition of glass materials, for example, for liquid crystal display substrates, belonging to the SrO-Al₂O₃-SiO₂ family may be designed with a more exact control of the glass-forming ability by avoiding the regions of high liquidus temperature.     

Characterization of gases and solid residues from closed system pyrolysis of peat and coals at two heating rates

Closed system gold-tube pyrolysis experiments were performed on a peat and two coals (TY: R_o = 0.51%; SX: R_o = 0.94%) at temperatures ranging from 337 to 600 °C and a pressure of 50 MPa with heating rates of 2 and/or 20 °C/h. Solid reaction residues were analyzed microscopically. Yields and chemical and isotopic compositions of the generated gases were also determined. All three samples had similar thermal evolution pathways. With increasing heating temperature, vitrinite reflectances (VR_r) of the residues increased linearly from 0.72% to 4.50%. This increase was lesser for the sample with a higher hydrocarbon generation potential and at faster heating rates. Gas compositions are dominated by CO₂ and CH₄ throughout the experimental process. Total gas and CH₄ yields gradually increase with pyrolysis temperature for all samples. The carbon isotopic compositions of CH₄ generated from the peat are lighter than those from the coals. The δ¹³C_CH4 values exhibit a generic evolution pattern which the initial CH₄ is isotopically heavy, then becomes lighter at moderate temperatures, and finally becomes heavier again. Methane produced from the samples at low heating rate has higher transformation ratio than that at high heating rate under the same temperature, so tends to be isotopically heavy after pyrolysis temperature of more than 408 °C.     

Pseudocapacitive behavior of Ti/RhOx + Co3O4 electrodes in acidic medium: application to supercapacitor development

Mixtures of RhO_x+Co₃O₄ have been electrochemically studied by cyclic voltammetry in acid solution as a function of composition. The electrodes were prepared by thermal decomposition at 400 °C of mixtures of nitrate precursors. Their electrochemical behavior shows substantial dependence on the electrode’s composition. The Co site controls the electrochemical behavior of the system in the 5-10 mol.% Rh composition range. A significant increase in the electrodes’ active area is observed for compositions corresponding to more than 10 mol.% RhO_x in admixture with Co₃O₄. Above 10 mol.% Rh, the voltammetric curves become more similar to that for RhO_x and then RhO_x becomes able to stabilize the Co₃O₄ in the mixture. Electrodes of this kind have been found to perform as good materials in electrochemical capacitor applications, exhibiting specific capacitances of 500-800 F g⁻¹ over to 20-60 mol.% RhO_x composition range. The large specific capacitance exhibited by this system arises from a combination of the double-layer capacitance and the pseudocapacitance associated with Rh surface redox-type reactions.     

Energetics of Silica‐Poor Glasses in the Systems MgO–SiO2 and Mg0.5Ca0.5O–SiO2

A series of alkaline‐earth silicate glasses, with compositions ranging from the metasilicate to the ortho‐ and suborthosilicate, have been synthesized by aerodynamic levitation and CO₂ laser melting. They have been studied by high‐temperature oxide melt solution calorimetry with 2PbO·B₂O₃ as solvent. The enthalpies of formation from the oxides at room temperature () have been calculated from the solution enthalpies. Glasses in the Ca_0.5Mg_0.5O–SiO₂ system show greater energetic stability than those in the MgO–SiO₂ system, with a more pronounced negative enthalpy of mixing near the orthosilicate composition. This stabilization may explain why it is possible to prepare glasses poorer in silica (suborthosilicate) in the Ca_0.5Mg_0.5O–SiO₂ system but not in the MgO–SiO₂ system. The thermodynamic observations support earlier structural studies in these systems.     

In situ copolymerization behaviour of zinc dimethacrylate and 2-(N-ethylperfluoro-octanesulphonamido)ethyl acrylate in hydrogenated nitrile–butadiene rubber during peroxide crosslinking

The in situ copolymerization behaviour of zinc dimethacrylate (ZMA) and 2-(N-ethylperfluoro-octanesulphonamido)ethyl acrylate (RfSA) in hydrogenated nitrile–butadiene rubber (HNBR) initiated with di-tert-butyl peroxy di-isopropylbenzene (PO) was studied by transmission electron microscopy, dynamic mechanical analysis, surface tension and surface composition. About 80% of the monomers were copolymerized within the half-lifetime of PO at 140 °C. The compositions of the copolymers were almost the same as the co-monomer compositions at high conversions. The crosslinking of the HNBR proceeded within the press time of 300 min. At the initial stage of the copolymerization, ZMA seemed to form cluster domains in the HNBR matrix, followed by a decrease in the domain size to become too small to exhibit a tanδ peak of the clusters on phase separation between the matrix and the copolymer. The surface compositions were different from the average compositions. The RfSA unit in the copolymer was segregated at the surface of the vulcanizates with an increase in the press time. During phase separation and migration of the copolymer towards the surface, Zn and N were oxidized and ionized. Finally, the in situ copolymerizations formed a continuous network structure of which the domain size was 30–60 nm. © 1999 Society of Chemical Industry     

Effect of Nb content on the phase composition,densification, microstructure,and mechanical properties of high-entropy boride ceramics

Dense high-entropy (Hf,Zr,Ti,Ta,Nb)B₂ ceramics with Nb contents ranging from 0 to 20 at% were produced by a two-step spark plasma sintering process. X-ray diffraction indicated that a single-phase with hexagonal structure was detected in the composition without Nb. In contrast, two phases with the same hexagonal structure, but slightly different lattice parameters were present in compositions containing Nb. The addition of Nb resulted in the presence of a Nb-rich second phase and the amount of the second phase increased as the Nb content increased. The relative densities were all >99.5 %, but decreased from ～100 % to ～99.5 % as the Nb content increased from 0 to 20 at%. The average grain size decreased from 13.9 ± 5.5 μm for the composition without Nb additions to 5.2 ± 2.0 μm for the composition containing 20 at% Nb. The reduction of grain size with increasing Nb content was due to the suppression of grain growth by the Nb-rich second phase. The addition of Nb increased Young’s modulus and Vickers hardness, but decreased shear modulus. While some Nb dissolved into the main phase, a Nb-rich second phase was formed in all Nb-containing compositions.