The adsorption of Sn on Pt(1 1 1) and its influence on CO adsorption as studied by XPS and FTIR

The coverage of Sn on Pt(1 1 1) which is obtained by electrochemical deposition from 5×10⁻⁵ M Sn²⁺ in 0.5 M H₂SO₄ has been determined by XPS for different deposition times. Complete suppression of hydrogen adsorption corresponds to a coverage of ?_max=0.35 (Sn to surface Pt atoms).Co-adsorption of CO with Sn on Pt(1 1 1) has been studied by FTIR spectroscopy. The IR spectra of the stretching vibration of CO can be interpreted in terms of the vibrational signature of the Pt(1 1 1)/CO system and no vibrational bands associated with CO on Sn are detected. At high Sn coverages, the 1840 cm⁻¹ band associated with bridge-bonded CO and the 2070 cm⁻¹ band assigned to on-top CO are present, however, no hollow site adsorption which is characterized by the 1780 cm⁻¹ band is revealed within the resolution of the experiment. This vibrational signature corresponds to a less compressed adlayer compared to the (2×2)-3CO saturation structure on Pt(1 1 1). At lower Sn coverages, signatures from both the compressed and the less compressed CO adlayer structures are seen in the spectra. From earlier structural and electrochemical studies it is known that Sn is adsorbed in 2D islands and influences CO molecules in its neighbourhood electronically. This leads to a disappearance of the IR band from CO adsorbed in the hollow site at high Sn coverages and to higher population of the weakly adsorbed state of CO for all Sn-modified surfaces, i.e. a relative increase of the amount of CO oxidised at low potentials. In addition to this electronic effect, Sn also exerts a co-catalytic effect at low Sn coverages on that part of CO which is adsorbed at a larger distance from Sn due to a bi-functional mechanism. The IR spectra shows for the Sn-modified Pt(1 1 1) surface that the transition from the compressed CO adlayer which is characterized by the hollow site adsorption of CO to the less compressed one which exhibits a characteristic band associated with bridge-bonded CO occurs already at 250 mV instead of 400 mV.     

Copolymerization of aniline and 4,4′-diaminodiphenyl sulphone and characterization of formed nano size copolymer

Aniline was copolymerized chemically in presence of five different concentrations of 4,4′-diaminodiphenyl sulphone using potassium persulphate. The copolymer exhibited good solubility in DMF and DMSO. Copolymers were characterized by UV-VIS, FTIR, XRD and SEM studies. The formation of polymer through N-H group was understood from the single N-H stretching vibrational frequency at 3378 cm⁻¹ and bands at 1630 and 1494 cm⁻¹ for quinonoid and benzenoid structures, respectively. The stretching vibration of sulphone SO at 1115 cm⁻¹ clearly indicated the presence of DDS in the copolymer. The X-ray diffraction studies revealed the formation of nano sized crystalline copolymer. When more DDS was incorporated in the copolymer the crystalline nature changed from less to more. The grain size of the copolymer calculated from Scherrer's formula was 83 nm. The nano size copolymer formation was also confirmed through surface morphology (100 nm) studies. The electrical property of the copolymer was studied by four-probe conductivity meter. The synthesized polymers have conductivity of 7.21 × 10⁻³ to 2.07 × 10⁻³ S cm⁻¹. The voltammetric and spectroelectrochemical results were also presented.     

Solubility and diffusivity of CO2 in carboxylated polyesters

The solubility of CO₂ in saturated polyester resins at different temperatures (306 and 343 K) and pressures (0.1-30 MPa) has been measured using a magnetic suspension balance. The solubility data were used for estimating the binary diffusion coefficients. The results show a good solubility of CO₂ in polymers, up to 0.64 g CO₂/g polymer. The diffusion coefficients of supercritical CO₂ in polymers have generally high values and are in the range from 0.156 × 10⁻⁸ to 10.38 × 10⁻⁸ cm²/s. DSC and XRD analyses of the semi-crystalline polymer samples indicate that amorphous degree of polymers after exposure to CO₂ is increased. The observed structural effects are dependent on pressure, temperature and time of exposure to CO₂.     

Experimental determination of methane hydrate dissociation curve up to 55 MPa by using a small amount of surfactant as hydrate promoter

Methane hydrate equilibrium has been studied upon continuous heating of the water-hydrate-gas system within the temperature range of 275-300 K. This temperature range corresponds to equilibrium pressures of 3.15-55 MPa. The hydrate formation/dissociation experiments were carried out in a high-pressure reactor under isochoric conditions and with no agitation. A small amount of surfactant (0.02 wt% sodium dodecyl sulfate, SDS) was added to water to promote hydrate formation. It was demonstrated that SDS did not have any influence on the gas hydrate equilibrium, but increased drastically both the hydrate formation rate and the amount of water converted into hydrate, when compared with the experiments without surfactant. To understand and clarify the influence of SDS on hydrate formation, macroscopic observations of hydrate growth were carried out using gas propane as hydrate former in a fully transparent reactor. We observed that 10^-3 wt% SDS (230 times less than the Critical Micellar Concentration of SDS) were sufficient to prevent hydrate particles from agglomerating and forming a rigid hydrate film at the liquid-gas interface. In the presence of SDS, hydrates grew mainly on the reactor walls as a porous structure, which sucked the solution due to capillary forces. Hydrates grew with a high rate until about 97 wt% of the water present in the reactor was transformed into hydrate.Our data on methane hydrate equilibrium both confirm already published literature data and complement them within the pressure range of 20-55 MPa.     

Determination of eugenol diffusion through LLDPE using FTIR-ATR flow cell and HPLC techniques

A time-resolved Fourier Transform Infrared-Attenuated Total Reflectance Spectroscopy (FTIR-ATR) technique was set up and used to study the diffusion of eugenol through Linear Low Density Polyethylene (LLDPE) at 16, 23 and 40 °C. The 1514 cm⁻¹ peak for eugenol (aromatic -CC- stretching) was monitored over time and used to determine the diffusion coefficient (D). The Fickian model was found to fit well to the experimental data and the D value of eugenol through LLDPE was found to be between 1.05 ± 0.01 and 13.23 ± 0.18 × 10⁻¹⁰ cm²/s. The FTIR-ATR results were compared with one and two side diffusion process using a permeation cell and quantified by High Performance Liquid Chromatography (HPLC) technique. Eugenol sorbed in LLDPE samples at different times, was extracted in methanol and the concentration determined by HPLC. The diffusion coefficient by both two-sided and one-sided HPLC technique was found to be approximately three times higher than the FTIR-ATR values although they were in the same order of magnitude of 10⁻¹⁰ cm²/s. The difference between the FTIR-ATR and HPLC results was mainly attributed to difference between the two measuring techniques.     

Separator grafted with siloxane by electron beam irradiation for lithium secondary batteries

Polyethylene (PE) separator grafted with 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane (siloxane) was newly prepared by electron beam irradiation. The degree of grafting and morphology of the grafted separators were characterized by FT-IR and scanning electron microscopy (SEM). The polymer electrolytes based on the grafted separators were prepared by immersing the separators in the electrolyte containing 1 M LiPF₆ in EC/DMC (1:1 by volume). The ionic conductivity of the grafted separators was changed with the degree of grafting and showed the highest value of 7 × 10⁻⁴ S cm⁻¹ at the degree of grafting of 6%. The electrochemical stability limit of the grafted separator with the degree of grafting of 6% was increased to 5.2 V. The Li ion cell using the grafted separator also showed an improved performance, suggesting that the grafted separator is a good candidate for the separator of lithium batteries at high voltage operation.     

Structure of syndiotactic propylene-ethylene copolymers: Effect of the presence of ethylene units on the structural transitions during plastic deformation and annealing of syndiotactic polypropylene

Syndiotactic propylene-ethylene copolymers have been synthesized with a single-center C_s-symmetric syndiospecific metallocene catalyst. A study of the effect of the presence of ethylene comonomeric units on the polymorphic behavior of syndiotactic polypropylene (sPP) and on the structural transitions occurring during stretching is reported. For copolymer samples with low ethylene contents, in the range 2-7 mol%, crystals of the helical form I, present in the melt-crystallized samples, transform into the trans-planar form III by stretching at high deformation. Form III transforms in part into the helical form II by releasing the tension, as it occurs for sPP. Samples with ethylene contents in the range 8-10 mol% are crystallized from the melt as a mixture of crystals of helical form I and form II. Both helical forms transform by stretching at low values of deformation (lower than 300%) into the trans-planar mesomorphic form, which transforms into the trans-planar form III by further stretching at higher deformations (higher than 500%). For these samples form III transforms back into the mesomorphic form, rather than into the helical forms, by releasing the tension. Unoriented samples of copolymers with ethylene content in the range 13-18 mol% are mainly crystallized in the helical form II, which transforms into the trans-planar mesomorphic form by stretching. Upon releasing the tension the mesomorphic form remains stable and no polymorphic transition is observed. The presence of ethylene comonomeric units stabilizes the trans-planar forms in fibers of the copolymer samples. This has been confirmed by the result that for high ethylene contents the trans-planar form III and the mesomorphic form do not transform in helical forms by annealing of fibers stretched at high deformations.     

Lanthanum-titanium-aluminum oxide: A novel thermal barrier coating material for applications at 1300 °C

Considerable efforts are being invested to explore new thermal barrier coating (TBC) materials with higher temperature capability to meet the demand of advanced turbine engines. In this work, LaTi₂Al₉O₁₉ (LTA) is proposed and investigated as a novel TBC material for application at 1300 °C. LTA showed excellent phase stability up to 1600 °C. The thermal conductivities for LTA coating are in a range of 1.0-1.3 W m⁻¹ K⁻¹ (300-1500 °C) and the values of thermal expansion coefficients increase from 8.0 to 11.2 × 10⁻⁶ K⁻¹ (200-1400 °C), which are comparable to those of yttria stabilized zirconia (YSZ). The microhardness of LTA and YSZ coatings were in the similar level of ∼7 GPa, however, the fracture toughness value was relatively lower than that of YSZ. The lower fracture toughness was compensated by the double-ceramic LTA/YSZ layer design, and the LTA/YSZ TBC exhibited desirable thermal cycling life of nearly 700 h at 1300 °C.     

Viscoelastic electrospun jets: Initial stresses and elongational rheometry

A novel method of characterization of viscoelastic longitudinal stresses in electrospun jets of semi-dilute and concentrated polymer solutions and melts is introduced. The measured longitudinal stresses at the beginning of the thin jet region in the jets of a 6 wt% aqueous solution of polyethylene oxide (M_w = 400 kDa) were of the order of 100 kPa, which is two orders of magnitude larger than in any other free viscoelastic jets issued from nozzles and orifices. This is attributed to elongation-driven stretching of polymeric liquids in the transition zone, between the preceding modified Taylor cone zone and the beginning of the thin jet region, where the stretching rates are of the order of 100-1000 s⁻¹. The Rouse relaxation times found were in the range of 3-8 ms, and the moduli of elasticity were of the order of 100 Pa. A novel explanation of the reasons for the formation of the straight sections in the electrospun jets is proposed. The straight sections are stabilized by the high initial longitudinal stresses in the jet generated due to strong electrically driven stretching in the transition zone. The further electrically driven stretching in the jet (after the transition zone) is relatively weak, and viscoelastic Rouse relaxation prevails. The relaxation distance of the longitudinal stresses along the jet increases with the applied voltage (which generates higher initial stresses in the transition zone) and thus the length of straight section of the jet should increase as the applied voltage increases.The results also point at an opportunity to develop an elongational rheometer for concentrated polymeric systems with stretching rates of the order of 100-1000 s⁻¹. The proposed rheometer employs excitation of electrically driven jets by single lateral pulses, and observation of the pulse propagation and widening along the jet. This reveals the level of the longitudinal stresses along the jet and allows evaluation of the viscoelastic Rouse relaxation time, modulus of elasticity and the elongational viscosity in the jet.     

Sulfonation and characterization of poly(styrene-isobutylene-styrene) triblock copolymers at high ion-exchange capacities

In this study, a triblock copolymer, poly(styrene-isobutylene-styrene), was sulfonated to eight different levels ranging from 0.36 to 2.04 mequiv./g (13 to 82 mol% of styrene; styrene is 19 mol% of the unsulfonated block copolymer). These sulfonated polymers were characterized with elemental analysis and infrared spectroscopy to confirm sulfonation and determine accurate sulfonation levels. Infrared analysis revealed four additional stretching vibrations as a result of sulfonation. Also, a linear relationship between absorbance at 1006 cm⁻¹ (stretching of the aromatic ring in styrene caused by the para-substituted sulfonic acid) and sulfonation level (measured by elemental analysis) was found. The density and water solubility of all the sulfonated polymers were measured and increased with increasing sulfonation level, as high as 1.31 g/cm³ and 351 wt%, respectively. In addition, a sulfonated triblock copolymer at 79 mol% sulfonation was neutralized with a cesium cation and revealed an increase in density, but a reduction in water solubility. This study demonstrates the resulting unique properties of sulfonated styrene-based block copolymers at higher ion-exchange capacities than previously reported.     

Electrochemical behavior of lithium intercalated in a molybdenum disulfide-crown ether nanocomposite

A new nanocomposite, obtained from the intercalation of the cyclic ether 12-Crown-4 into MoS₂, Li_0.32MoS₂(12-Crown-4)_0.19, is described. The laminar product has an interlaminar distance of 14.4 Å. The electrical conductivity of the nanocomposite varies from 2.5 × 10⁻² to 4.3 × 10⁻² S cm⁻¹ in the range 25-77 °C, being about four times higher than the analogous poly(ethylene oxide) (PEO) derivative at room temperature. The electrochemical step-wise galvanostatic intercalation or de-intercalation of lithium, leading to Li_xMoS₂(12-Crown-4)_0.19 with x in the range 0.07-1.0, indicates a Li/Li⁺ pair average potential of 2.8 V. The electrochemical lithium diffusion coefficients in the crown ether intercalates, determined by galvanostatic pulse relaxation between 15 and 37 °C at different lithium intercalation degrees, are higher than those of the PEO derivatives under similar conditions, being however the diffusion mechanism rather more complex. The variation of both, the lithium diffusion activation enthalpy and the quasi-equilibrium potentials, with the lithium content shows there are two different limit behaviors, at low and high lithium intercalation degree, respectively. These features are discussed by considering the high stability of the Li-crown ether complex and the different chemical environments found by lithium along the intercalation process.     

Studies based on the electrochemical response of 2-(2-nitrophenyl)-1H-benzimidazole at chemically modified electrodes with over-oxidized poly-1-naphthylamine

The development of a simple and efficient method to 2-(2-nitrophenyl)-1H-benzimidazole (NB) electrochemical determination using a polymer film coated chemically modified electrode is described. A glassy carbon (GC) electrode was modified employing an electro-polymerized film of 1-naphtylamine (1-NAP) followed by an over-oxidation treatment in 0.2 M sodium hydroxide solution (poly-1-NAPox electrode).The electrochemical behaviour of NB at the poly-1-NAPox electrode was investigated in a mixture of 10% ethanol + 90% buffer solution (pH 2) by cyclic voltammetry (CV) and square-wave voltammetry (SWV). The experimental results suggested that the poly-1-NAPox electrode had a good effect on NB electrochemical response because it avoided the electrode surface fouling as a consequence of the adsorption of NB reduction products, which was found when a bare GC electrode was employed as the working electrode. The NB cathodic current was dependent on the polymeric film over-oxidation degree (α).NB could be determined in the range from 2 × 10⁻⁶ to 5 × 10⁻⁵ M. The NB detection and quantification limits were 5 × 10⁻⁷ and 1.7 × 10⁻⁶ M, respectively. The percent relative standard deviation of the peak current to 10-replicated measurement using 1.2 × 10⁻⁵ M NB solution was 1.4%. The method showed to be rapid, simple and with a good sensitivity.     

Needle penetrometry with variable force loading for measuring viscosity of pelletized coal upon heating

A needle penetrometry was performed loading steady force in a range from 1×10⁻³ to 2 N to pelletized coal upon heating via a cylindrical needle. From the observed effects of shear rate on apparent viscosity of softening coal pellet, defined as the shear-rate to shear-stress ratio, it was found that the pellet behaved as a Newtonian fluid for shear rates lower than a critical one while as a pseudo-plastic fluid for higher shear rates. The penetrometry was also carried out varying the force with time. The variable force loading enabled to maintain the shear rate well below the critical one, and thereby to measure the apparent viscosity of coal pellets as Newtonian fluids over a temperature range from 600 to 800 K. Upon heating at 10 K min⁻¹, the apparent viscosity of Goonyella coal pellet decreased from about 10¹⁰ Pa s at 640 K down to a minimum of about 10⁴ Pa s at 755 K, and increased up to 10⁹ Pa s at 800 K. In a course of heating as above, the viscosity of Blind Canyon coal pellet decreased above 600 K, underwent a minimum of about 10⁶ Pa s at 715 K, and increased up to 10¹⁰ Pa s at 770 K. Decreasing the heating rate from 10 to 3 K min⁻¹ caused the minimum viscosities of the pellets to increase by 1-2 orders of magnitude.     

Sharpening of CVD diamond coated tools by 0.5−10 keV Ar ion beam

CVD diamond coated tungsten carbide tools have been used for cutting and drilling of soft materials such as aluminum and copper alloys. However, it is very difficult to obtain a tool having a sharp tip of the order of sub-μm by mechanical abrasive polishing methods. Therefore, we applied ion beam processing for sharpening the cutting edge of diamond coated tungsten carbide tools. Result shows that it is possible to obtain a 20-80 nm order tip width of a CVD diamond coated knife processed by a 0.5-10 keV Ar⁺ ion beam, and the sharpening speed of a tip of the knife depends on the ion beam energy. Namely, a tip width of a knife processes by a 1.0 keV Ar⁺ ion beam at an ion dose of 2.7 × 10²⁰ ions/cm² becomes 20 nm, and a tip width of a knife processed by a 10 keV Ar⁺ ion beam at an ion dose of 5.4 × 10¹⁹ ions/cm² becomes 40 nm. However, a facet with an apex angle in the range of 60-100° was formed on the cutting edge of a knife with an initial apex angle of 55°, and we found that the facet angle can be controlled by choosing ion beam energy of 0.5-10 keV. Moreover, results show that the processed knife machined by a 0.5 keV Ar⁺ ion beam has very smooth rake and flank faces, and also has a small line edge roughness of the cutting edge compared to those of the sharpened knife by a 1.0-10 keV Ar⁺ ion beam.     

Plastic deformation of polyethylene crystals as a function of crystal thickness and compression rate

Plastic deformation of polyethylene (PE) samples with crystals of various thickness was studied during uniaxial compression with initial compressive strain rates of 5.5×10⁻⁵, 1.1×10⁻³ and 5.5×10⁻³ s⁻¹. Samples with a broad range of crystals thickness, from usual 20 up to 170 nm, were obtained by crystallization under high pressure. The samples underwent recoverable compression below the compression ratio of 1.05-1.07. Following yield, plastic flow sets in above a compression ratio of 1.12. At a compression rate of 5.5×10⁻⁵ s⁻¹ the yield stress increases with the increase of crystal thickness up to 40 nm. For crystals thicker than 40 nm the yield stress levels off and remains constant. This experimental dependence was compared with the model developed on the basis of classical crystal plasticity and the monolithic nucleation of screw dislocations from polymer crystals. In that model contrary to the experimental evidence, the yield stress does not saturate with increase of crystal thickness. The activation volumes determined from strain rate jump experiments and from stress relaxation for crystals thicker than 40 nm are nearly constant at a level of 8.1 nm³. This activation length agrees very well with 40 nm for crystal thickness above which the yield stress levels off. It is proposed, as shown in a companion communication, that for PE crystals thicker than 40 nm two other modes of dislocation emission in the form of half loops of edge and screw dislocations begin to govern the strain rate, which no longer depend on lamella thickness.     

Water resistant sulfonated polyimides based on 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA) for proton exchange membranes

A series of sulfonated polyimides (SPIs) were synthesized in m-cresol from 4,4′-binaphthyl-1,1′,8,8′-tetracarboxylic dianhydride (BNTDA), 4,4′-diaminodiphenylether-2,2-disulfonicacid (ODADS), and 4,4′-diamino-diphenyl ether (ODA) in the presence of triethylamine and benzoic acid. The resulted polyimides showed much better water resistance than the corresponding sulfonated polyimides from 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTDA) and ODADS, which is contributed to the higher electron density in the carbonyl carbon atoms of BNTDA. Copolyimides S-75 and S-50 maintained their mechanical properties and proton conductivities after aging in water at 100 °C for 800 h. The proton conductivity of these SPIs was 0.0250-0.3565 S/cm at 20 °C and 100% relative humidity (RH), and increased to 0.1149-0.9470 S/cm at 80 °C and 100% RH. The methanol permeability values of these SPIs were in the range of 0.99-2.36 × 10⁻⁷ cm²/s, which are much lower than that of Nafion 117 (2 × 10⁻⁶ cm²/s).     

Effect of fermentation conditions on yeast growth and volatile composition of wine produced from mango (Mangifera indica L.) fruit juice

In this study mango juice fermentation at laboratory scale with controlled inoculation using selected yeast strain was performed (Saccharomyces cerevisiae 101). Effect of fermentation conditions (temperature, pH, SO₂ and aeration) on wine fermentation was evaluated based on yeast growth, duration, fermentation rate and volatile composition. The composition of the major volatile compounds with low boiling points was determined by gas chromatography under the different operating conditions of fermentation temperature (15-35 °C), pH (3.5-6.0), SO₂ (100-300 ppm) and aeration (initial dissolved O₂ and shaking at 30 rpm). Temperature had important effect on yeast growth and on the levels of volatile compounds. It was observed that the final concentrations of ethyl acetate and some of the higher alcohols decreased when fermentation temperature increased to 25 °C (35 mg/l at 15 °C and 27 mg/l at 25 °C). SO₂ stimulated the yeast growth up to certain level and in excess it inhibited the yeast metabolism. Ethanol concentration slightly increased with the addition of 100 ppm SO₂ (8.2 g/l) and decreased with increase in concentration of SO₂ (6.2 g/l in 300 ppm SO₂). Aeration by shaking increased the viable cell count (from 52 × 10⁶ in the absence of oxygen to 98 × 10⁶ in shaking at 30 rpm) but decreased the ethanol productivity (from 7.2 in initial dissolved O₂ to 6.5 g/l shaking at 30 rpm). With the results obtained it was concluded that the temperature (25 °C), pH (5), SO₂ (100 ppm) and must with initial oxygen were optimum for better quality of wine from mango fruits. The results of the present study considering the traditionally recognized preference for low alcoholic fermentation temperatures in wine making.     

Study of the influence of processing parameters on the production of carboxymethylchitin

Carboxymethylchitin was prepared at different reaction temperatures and from alkali chitin with different concentrations of alkali. Properties of the product were studied. Alkali chitin were prepared using freshly prepared sodium hydroxide of 45, 50, 55, 60 and 65% (w/w) concentration and carboxymethylated using monochloroacetic acid at controlled (35-40 °C) and uncontrolled (30-80 °C) temperature conditions. Molecular weight, viscosity, degree of deacetylation, etc. of the resultant product, i.e. carboxymethylchitin were determined. It was found that the reaction temperature has a profound influence on the property of the product than alkali concentration. A hygroscopic and completely water-soluble product was formed. Optimum conditions for the production of carboxymethylchitin were found to be 60% NaOH concentration and at 35-40 °C reaction temperature. At these conditions, it was obtained with a molecular weight of 4.11×10⁶ Da, viscosity 1926 cP and degree of deacetylation 45.02%.     

Synthesis and application as polymer electrolyte of hyperbranched copolyethers derived from cationic ring-opening polymerization of 3-{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}methyl- and 3-hydroxymethyl-3′-methyloxetane

A kind of novel hyperbranched copolyethers intending for the solid polymer electrolyte was synthesized via the cationic ring-opening polymerization of 3-{2-[2-(2-methoxyethoxy)ethoxy]-ethoxy}methyl-3′-methyloxetane (MEMO) and 3-hydroxymethyl-3′-methyloxetane (HMO) in the presence of BF₃·Et₂O as an initiator. Herein HMO was employed to create the hyperbranched structure, whereas MEMO was responsible for the ionic transportation of the resulting copolymers. The terminal structure featured by a cyclic fragment was definitely detected by MALDI-TOF measurement. The degree of branching of the copolymers was calculated by means of ¹³C NMR spectra. The DSC analysis implied that they hold the excellent segment motion performance and perfectly amorphous state beneficial for the ionic transportation. The ionic conductivity measurements showed that the sample HMO 30 reaches a maximum ionic conductivity of 8.0 × 10⁻⁵ S/cm at 30 °C and 7.4 × 10⁻⁴ S/cm at 80 °C, respectively, after doping with lithium salt LiTFSI. Moreover, the TGA assay exhibited that these hyperbranched copolymers possess the higher thermostability as compared with their liquid counterparts.     

Sorption of gold and silver on carbon adsorbents from thiocyanate solutions

Sorption recovery of thiocyanate gold and silver complexes on different carbon adsorbents has been studied using model solutions with concentrations 0.08-0.82 mmol/l and 0.16-1.06 mmol/l for gold and silver, respectively. The potassium thiocyanate concentration in these solutions was 0.25 mol/l and the pH of the contacting solution was ∼2. The degree of recovery exceeded 90% for gold and 80% for silver. The separate step-by-step desorption of thiocyanate gold and silver complexes was carried out by varying the initial concentration of thiocarbamide (desorption agent). The degree of recovery of noble metals can be increased up to 95% using basic thiocarbamide solutions (in 0.1-0.2 M NaOH) at the higher temperature of the process (up to 150 °C).