Investigation of Co–B–S system as anode material for secondary alkaline battery

A series of novel Co–S–B systems were prepared by simple chemical reduction method as the anode material for secondary alkaline batteries. The prepared samples were investigated by inductivity coupled plasma optical emission spectrum (ICP), Brunauer–Emmetr–Teller (BET) method, scanning electron microscope (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), X-ray energy dispersive spectroscopy (EDS) and charge–discharge method. It was found that the BET surface area of Co–S–B system increases and its particle size decreases with increasing the sulfur content. Sulfur incorporation suppresses initial capacity fading of Co–B compound due to irreversible dissolution of boron, and Co–S–B electrodes show enhanced electrochemical capacity and excellent cycle performance. The discharge capacity of Co_75.4B₁₇S_7.6 reaches 513.6 mAh/g at a moderate current density of 100 mA/g and 470 mAh/g after 60 cycles, which is about 1.5 times that of conventional AB₅-type alloy. A proper mechanism was proposed to explain the electrochemical reaction process of Co–S–B electrode.     

Evaluation of Methods for Measuring Polyphenols in Conifer Foliage

There is a resurgence of interest in the quantification of polyphenols in plant tissues because of their presumed ecological importance in plant–litter–soil and plant–animal interactions. The influence of sample preparation, extracting solvent, foliage quality, and assay method was investigated for the quantification of total phenols and condensed tannins in conifer foliage. Our results suggest that it is not possible to recommend a single optimal protocol for quantification of total phenol and condensed tannin fractions from plant materials. In general, the use of aqueous acetone (50–70% v/v) with freeze-dried materials gave the highest recovery. The Folin-Ciocalteau method for total phenols and the butanol–HCl hydrolysis method for condensed tannins appear superior to other common assays tested. There were large differences (1.4–2.2 times) in the reactivity of purified condensed tannins among species, indicating the importance of an appropriate standard for polyphenol quantification. A solid-state ¹³C NMR method with an improved "interrupted decoupling" pulse sequence yielded the highest concentrations for condensed tannins. Assuming that ¹³C NMR provides an accurate measure of total condensed tannin, the other extraction/assay methods used in this study recovered 50–86% of the condensed tannin fraction. The recovery rate is correlated with the nitrogen content of the foliage, which suggests that the formation of protein–tannin complexes may limit the extractability of condensed tannins. While ¹³C NMR condensed tannin values may give the best value for total condensed tannin concentrations, the water-soluble fraction may have the greatest physiological and/or ecological significance.     

Thermal conductivity of insulating refractories measured by the standard method and by the cylinder method

Conclusions The coefficients of thermal conductivity of insulating refractories measured by the method prescribed in GOST 12170-66, using the recommended thermometers with a scale division of 0.1°C and thermal insulation made from firebrick with an apparent density of 1.0 g/cm³, are appreciably higher than data obtained by the cylinder method. At average temperatures of 200–500°C (400–1000°C on the hot face) the discrepancy comes within the range 50–200%; when T_mean=600–700°C (1200–1300°C on the hot face) the discrepancies diminish to 0–30%.The maximum apparatus error in determining the thermal conductivity according to GOST 12170-66 with the use of Beckmann thermometers and low thermal-conducting linings is 10–30% for – 0.2–1.0 kcal/(m·h·deg), which greatly exceeds that indicated in the standard, ±10%. The maximum proportion in the error comes from the measurement of the drop in water temperature as it passes through the calorimeter. Consequently, the use of the standard recommended thermometers with scale divisions of 0.1°C is unacceptable for measurements on materials with a low thermal conductivity, since it may lead to errors of about 100%.Detailed comparison of the results of measuring this factor on standard equipment using the Beckmann thermometers, and on the improved instrument designed by the Ukrainian Institute (the cylinder method), showed that the mean square deviation of the experimental values for thermal conductivity for identical specimens with respect to the interpolation curves in the case of standard determinations is 2–3 times greater than the corresponding deviation for the cylinder method.In most experiments the interpolation curves =f(T) for the standard method is different by ±15–25% from the curves obtained with the cylinder method. This displacement apparently is due to certain constant errors connected with the unaccounted-for sources of error in the standard methods.The proposed method of determining the coefficient of thermal conductivity is of interest for scientific-research work. The use of the cylinder method is industry is associated with difficulties in preparing the specimens — Editors.Translated from Ogneupory, No. 8, pp. 45–52, August, 1971.     

Separation of Gas Mixtures by the Absorption–Pervaporation Method

Absorption–pervaporation separation of gas mixtures is studied and compared with membrane gas separation. The absorption–pervaporation method ensures a much higher separation coefficient of the HCl–H₂mixture. An equation is derived for calculating the fluxes of the mixture components through the absorbent–membrane system.     

Production of roof refractories using magnesite chromite clinker

Conclusions A method for producing roof products using magnesite-chromite clinker from caustic magnesite and Kimpersai chromite was developed and tested on an industrial scale. The dry method of producing the clinker from 20–25% chromite and 75–80% magnesite powder is the best.Roof refractories made with the use of magnesite-chromite clinker satisfy the requirements of GOST for all factors except spalling resistance.Translated from Ogneupory, No. 7, pp. 9–14, July, 1967.     

Effects of the preparation methods on the performance of the Cu–Cr–Fe/γ-Al2O3 catalysts for the synthesis of 2-methylpiperazine

Co-precipitation, impregnation and ultrasonic sol–gel (USG) methods have been used to prepare Cu–Cr–Fe/γ-Al₂O₃ catalysts, which were further used to synthesize 2-methylpiperazine. The catalysts were characterized by XRD, XPS, TG/DSC, BET, TPR, AAS and TEM. It is found that preparation method can greatly impact the catalytic performance of the catalysts, the Cu–Cr–Fe/γ-Al₂O₃ catalyst prepared by the ultrasonic sol–gel method proved to be the most active and stable for this reaction. The dispersion and stabilization of Cu⁰ in the reduced catalysts are attributed to the existence of CuCr₂O₄ and Fe₂O₃. A surprising copper migration was detected by XPS analysis for the Cu–Cr–Fe/γ-Al₂O₃-USG catalyst after the calcination process, which may be crucial to the high activity and stability of this catalyst.     

Characterization of sintered TiC–SiC composites

TiC–SiC composites were fabricated using TiC and SiC powders as starting materials at the range of 1650–2000 °C in Ar atmosphere by two-step method. In the first step, the ingots with intragranular SiC or TiC particle were prepared by arc-melting technique, subsequently, crushed and ground into TiC and SiC composite powders. In the second step, TiC–SiC composites were sintered using these as-prepared composite powders by SPS method. It was concluded that these TiC–SiC composites prepared by two-step method showed more excellent properties than that prepared by arc-melting technique. The hardness of the fabricated TiC–SiC composites was 25–27 GPa at the load of 0.98–9.8 N, which was obviously greater than that of arc-melting composites. The thermal conductivity of the TiC–SiC composites was 18–48 W K⁻¹ m⁻¹ at the range of 298–1273 K and slightly decreased with increasing temperature. The electrical conductivity of the composites was (2–5) × 10⁵ S m⁻¹ at the range of 298–1273 K and slightly decreased with increasing temperature.     

Determination of JP-8 components in soils using solid-phase microextraction–gas chromatography–mass spectrometry

Jet Propellant-8 (JP-8) is a military fuel associated with a large percentage of chemical exposures documented by the US Department of Defense. A fast and sensitive solid-phase microextraction–gas chromatographic–mass spectrometric (SPME–GC–MS) method has been developed for the determination of 34 ‘marker compounds’ found in JP-8. Linear ranges (R² > 0.99) were determined for each marker component and precision was measured (<16% RSD) for these components over four concentrations within each calibration range. The method was applied for the analysis of JP-8 components from soil. The use of SPME over other sample extraction techniques eliminates solvents, minimizes sample handling, and increases sensitivity.     

Preparation of alkaline PVA-based polymer electrolytes for Ni–MH and Zn–air batteries

Alkaline PVA polymer electrolyte with high ionic conductivity of about 0.047 S cm^–1 at room temperature was obtained by a solution casting method. The PVA polymer electrolytes, blended with KOH and H₂O, were studied by DSC, TGA, cyclic voltammetric and a.c. impedance methods. The PVA polymer electrolytes show good mechanical strength and high ionic conductivity. The electrochemical stability window at the metal–electrolyte interface is ±1.2 V for stainless steel. Ni–MH and Zn–air batteries with PVA polymer electrolytes were assembled and tested. Experimental results show good electrochemical performances of the PVA-based Ni–MH and Zn–air batteries.     

Effect of preparation and reaction condition on the catalytic performance of Mo–V–Te–Nb catalysts for selective oxidation of propane to acrylic acid by high-throughput methodology

Combinatorial screening technique has been applied to investigate the catalytic activity and selectivity of quaternary Mo–V–Te–Nb mixed oxide catalysts treated with various chemicals during preparation for selective oxidation of propane to acrylic acid. The catalyst libraries were prepared by the slurry method and catalytic activities were examined in 32-channel high-throughput screening reactor system coupled with a mass spectrometer and/or gas chromatograph.The obtained results provided substantial evidence that the sample preparation condition would have strong effect on the catalytic performance for propane selective oxidation. Among screened samples, Mo–V–Te–Nb treated with HIO₃ solution presented a better performance. The reaction results of promising catalysts selected from the libraries were applied to further scale-up of the system and confirmed catalytic performance. Quantification of the result of Mo–V–Te–Nb treated with HIO₃ solution was realized by combination of GC and MS and relationship between the MS data and the GC results can be established.     

An express method for determining inorganic impurities in polycaproamide

Conclusions 1. A procedure has been developed for determining inorganic impurities in a polyamide crumb which permits the time of analysis to be shortened from 6–7 to 30–40 min.2. The method can be used for the qualitative determination of impurities in the polymer in the inspection of the production of Capron fibre and for the semiquantitative determination of titanium in the matted polymer.Daugavpils Factory. Translated from Khimicheskie Volokna, No. 3, pp. 67–68, May–June, 1969.     

Strontium carbonate supported cobalt catalyst for dry reforming of methane under pressure

Catalytic performance of Co–SrO catalyst for dry reforming of methane was investigated at 1 MPa, 1023 K. The catalyst prepared by oxalate co-precipitation method or citric acid method showed a steady activity for dry reforming of methane under pressure. The importance and stability of cobalt metal with strontium carbonate were suggested for the Co–SrO catalyst, and thus it should be denoted as Co–SrCO₃. In addition, cobalt supported on strontium carbonate prepared by impregnation method (Co/SrCO₃) showed the comparable activity with high tolerance to oxidative atmosphere under reaction conditions.     

Propane Selective Oxidation Over Monophasic Mo–V–Te–O Catalysts Prepared by Hydrothermal Synthesis

Two distinct phases, orthorhombic and hexagonal, of Mo–V–Te–O mixed oxide catalysts were prepared separately by the hydrothermal synthetic method and solid-state reaction, and these catalysts were tested for propane selective oxidation to acrylic acid. The hydrothermally synthesized orthorhombic phase of the Mo–V–Te–O catalyst showed high activity and selectivity for the oxidation of propane into acrylic acid. This catalyst also showed extremely high catalytic performance in the propene oxidation, producing acrylic acid in a high yield. The hexagonal Mo–V–Te–O catalyst was formed via the solid-state reaction between the orthorhombic Mo–V–Te–O and -TeVO₄. This phase showed poor activity to both propane and propene oxidations, although the hexagonal phase was constructed with the octahedra of Mo and V similar to the orthorhombic phase. Reaction kinetics study over the catalyst with orthorhombic structure revealed that propane oxidation was of first order with respect to propane and nearly zero order with respect to oxygen, suggesting that the rate-determining step of the reaction is C–H bond breaking of propane to form propene. Structural effects on the catalytic oxidation performance were discussed.     

Transition metal-based cathodes for hydrogen evolution in alkaline solution: Electrocatalysis on nickel-based ternary electrolytic codeposits

Nickel-molybdenum-iron, nickel-molybdenum-copper, nickel-molybdenum-zinc, nickel-molybdenum-cobalt, nickel-molybdenum-tungsten and nickel-molybdenum-chromium ternary codeposits, obtained through electrodeposition on mild steel strips have been characterized with the objective of qualitatively comparing and assessing their electrocatalytic activities as hydrogen electrodes in alkaline solution. It has been concluded that their electrocatalytic effects for the hydrogen evolution reaction (h.e.r.) rank in the following order: Ni–Mo–Fe>Ni–Mo–Cu>Ni–Mo–Zn>Ni–Mo–Co Ni–Mo–W>Ni–Mo–Cr>Ni-plated steel. Further investigations on these electrocatalysts have revealed that the cathodic overpotential contribution to the electrolysis voltage can be brought down by 0.3 V when compared with conventional steel cathodes. The best and most stable hydrogen evolving cathode of these, namely Ni–Mo–Fe, exhibited an overpotential of about 0.187 V for over 1500 h of continuous electrolysis in 6 M KOH at 300 mA cm^–2 and 353 K. The salient features of the codeposits, such as physical characteristics, chemical composition, current-potential behaviour and the varying effects of the catalytic activation method were analysed with a view to correlating the micro-structural characteristics of the coatings with the hydrogen adsorption process. The stability under open circuit conditions, the tolerance to electrochemical corrosion and the long term stability of Ni–Mo–Fe codeposit cathodes were very encouraging. An attempt to identify the pathway for the h.e.r. on these codeposit cathodes was made, in view of the electrochemical parameters obtained experimentally.     

Sol–gel coatings on metals for corrosion protection

Sol–gel protective coatings have shown excellent chemical stability, oxidation control and enhanced corrosion resistance for metal substrates. Further, the sol–gel method is an environmentally friendly technique of surface protection and had showed the potential for the replacement of toxic pretreatments and coatings which have traditionally been used for increasing corrosion resistance of metals. This review covers the recent developments and applications of sol–gel protective coatings on different metal substrates, such as steel, aluminum, copper, magnesium and their alloys. The challenges for industrial productions and future research on sol–gel corrosion protective coatings are also briefly discussed.     

Electrically induced liquid infiltration for the synthesis of carbon/carbon–silicon carbide composite

The electrically induced liquid infiltration (EILI) method for the synthesis of carbon/carbon–silicon carbide (C/C–SiC) materials was developed. The method involves Joule preheating of a porous carbon/carbon preform surrounded by silicon media, followed by silicon infiltration into the pore structure, and its reaction with carbon to form pore-free C/C–SiC composite. This technique is characterized by high heating rates (10²–10³ K/s) and short processing times (5–20 s), which distinguish it from conventional approaches. The influence of maximum treatment temperature, as well as preheating rate on the depth of infiltration, reaction kinetics, and the material microstructure was investigated. C/C–SiC composite with a compressive strength which was twice that of the initial C/C material was synthesized.     

Gunite repair of refractory linings of machines for pellet firing

Conclusions It is found that the main wear-prone elements in machines for firing pellets are the coolers; changing these requires stopping the machine every 70–90 days on average, interrupting the normal course of the technological process. Repairs revealed the efficiency of the guniting method for repair of linings of firing machines, in comparison with poured concrete. The lifetimes of gunite concrete linings were 2–3 times greater: 220–240 days.Translated from Ogneupory, No. 4, pp. 49–52, April, 1980.     

Solution of cellulose xanthate at elevated alkali contents

Conclusions A method has been developed for dissolving cellulose xanthate at a higher NaOH content in the first period of solution. The optimum NaOH content for this purpose is 9–9.6%.All-Union Synthetic Fibre Research Institute (VNIIV). Translated from Khimicheskie Volokna, No.2, pp. 60–61, March–April, 1969.     

Separate determination of the components of the precipitation bath in viscose fibre manufacturing

Conclusions A method based on high-frequency titration of bath samples with barium acetate and with sodium hydroxide is recommended for the determination of the contents of the components of the precipitation bath.The time for an analysis is 30–40 min, and the reproducibility is good.Translated from Khimicheskie Volokna, No. 6, pp. 57–58, November–December, 1983.     

Bubble-point pressures of the binary system carbon dioxide+linalool

A synthetic method was used to investigate high-pressure vapor–liquid equilibria of the binary system carbon dioxide+linalool. The bubble points of this system were measured at carbon dioxide mole fractions from 0.2 up to 0.993 and within temperature and pressure ranges of 283–371 K and 1.4–14.7 MPa, respectively. Critical points of this binary system were also determined experimentally for a carbon dioxide mole fraction range from 0.93 up to 0.993. The results were correlated by the Stryjek–Vera modified version of the Peng–Robinson equation of state using one-fluid van der Waals mixing rules with both one and two interaction parameters.