Photoinduced free radical polymerization of thermoset lithium battery electrolytes

Series of solid poly(ethylene oxide)-methacrylate electrolytes have successfully been manufactured with an aim to serve in a multifunctional battery both as mechanical load carrier as well as lithium ion conductor. The electrolytes produced, in a solvent free process with no post cure swelling, hold a broad range of both mechanical as well as ion conducting properties. The monomer and Li-salt mixtures have been irradiated with UV light, initiating free radical polymerization to obtain solid smooth, homogenous specimens to be utilized as ion conducting electrolytes. The storage modulus at 20 °C is ranging from 1 MPa to almost 2 GPa. The conducting ability of the electrolyte ranges from 5.8 × 10^?10 up to 1.5 × 10^?6 S/cm. These large variations in both mechanical properties as well as ionic conductivity are discussed, but also the versatility within the production technique is emphasized.     

Poly(ether amine) and cross-linked poly(propylene oxide) diacrylate thin-film polymer electrolyte for 3D-microbatteries

This paper presents a novel thin-film electrolyte of a 2:1 blend of polyetheramine (glyceryl poly(oxypropylene)) and cross-linked oligomeric poly(propylene oxide) diacrylate with LiTFSI. The polyetheramine acts as a surfactant, and can thereby be applied as a conformal coating on complex surfaces—here demonstrated for porous LiFePO₄ cathodes—making it useful for 3D-microbatteries. The poly(propylene oxide) diacrylate blends with the surfactant and is easily UV cross-linked, thereby ensuring good mechanical stability. Electrolytes, ~ 2 μm thick, were casted onto LiFePO₄ cathodes and cycled against metallic lithium, displaying stable discharge capacities of ~ 8 mAh/g at room temperature and ~ 120 mAh/g at 60 °C. The electrolyte showed conductivities of 3.45 × 10^? 6 and 5.80 × 10^? 5 S cm^? 1 at room temperature and 60 °C, respectively.     

Evaluation of Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole as photostabilizer for poly(methyl methacrylate)

The photostabilization of poly(methyl methacrylate) (PMMA) films by Schiff bases of 2,5-dimercapto-1,3,4-thiadiazole compounds was investigated. The PMMA films containing concentration of complexes 0.5% by weight were produced by the casting method from chloroform solvent. The photostabilization activities of these compounds were determined by monitoring the hydroxyl index with irradiation time. The changes in viscosity average molecular weight of PMMA with irradiation time were also tracked (using benzene as a solvent). The quantum yield of the chain scission (Φ_cs) of these complexes in PMMA films was evaluated and found to range between 4.19 × 10^?5 and 8.75 × 10^?5. Results obtained showed that the rate of photostabilization of PMMA in the presence of the additive followed the trend:[1] > [2] > [3] > [4] > [5].According to the experimental results obtained, several mechanisms were suggested depending on the structure of the additive. Among them, UV absorption, peroxide decomposer, and radical scavenger for photostabilizer mechanisms were suggested.     

A new promising high temperature lithium battery solid electrolyte

Lithium lanthanoid silicates find importance as a solid electrolyte in high temperature lithium batteries in view of its high ionic conductivity at high temperatures. An first ever attempt is made to synthesis a new high temperature solid electrolyte viz., lithium samarium holmium silicate by sol–gel process and it has been characterized by thermal analysis (TGA–DTA), X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Lithium ion conductivity of 0.8087 × 10⁻⁷ Ω⁻¹ cm⁻¹ at 25 °C was obtained and it increases with increasing temperature. For the first time a highest conductivity of 0.1095 × 10⁻² Ω⁻¹ cm⁻¹ was obtained at 850 °C which is high compared to other high temperature lithium battery solid electrolytes.     

Development of novel low-temperature SOFCs with co-ionic conducting SDC-carbonate composite electrolytes

A series of ceria-based composite materials consisting of samaria doped ceria (SDC) and binary carbonates(Li₂CO₃–Na₂CO₃) were examined as functional electrolytes for low-temperature solid oxide fuel cells (SOFCs). DTA and SEM techniques were applied to characterize the phase- and micro-structural properties of the composite materials. Conductivity measurements were carried on the composite electrolytes with a.c. impedance in air. A transition of ionic conductivity with temperature was occurred among all samples with different carbonate content, which related to the interface phase. Single cells based on the composite electrolytes, NiO as anode and lithiated NiO as cathode, were fabricated by a simple dry-pressing process and tested at 400–600 °C. The maximum output power at 600 °C increased with the carbonate content in the composite electrolytes, and reached the maximum at 25 wt.%, then decreased. Similar trend has also shown at 500 °C, but the maximum was obtained at 20wt.%. The best performances of 1085 mW cm⁻² at 600 °C and 690 mW cm⁻² at 500 °C were achieved for the composite electrolytes containing 25 and 20 wt.% carbonates, respectively. During fuel cell operation, it found that the SDC-carbonate composites are co-ionic (O²⁻/H⁺) conductors. At lower carbonate contents, both oxide–ion and proton conductions were significant, when the content increased to 20–35 wt.%, proton conduction dominated. The detailed conduction mechanism in these composites needs further investigation.     

Reversibility of platinum voltammograms in aqueous electrolytes,ionic product and dissociative adsorption of water

Well-known reversibility of platinum voltammograms in supporting aqueous electrolytes formally contradicts the equilibrium defined by the ionic product of water: K_w = [H⁺] · [OH⁻] ≅ 1 × 10¹⁴, since at any pH value, concentration of one of these ions should be too low (⩽10⁷ M) to ensure reversibility in the whole potential region at usual scan rates. This contradiction could be overcome by allowing dissociative water adsorption on platinum. All available relevant data obtained by in situ physical methods appear to provide indirect experimental evidences for this hypothesis.     

Effects of different matrixes on the dosimetric response of α-terthiophene films from the kGy to MGy range

Films of polymethylmethacrylate (PMMA) and polystyrene (PS) containing α-terthiophene (3T) undergo a radiochromic effect when exposed to electrons and gamma rays. The films turn either red–green or red, due to the formation of oligomeric radical cations. In both matrixes, absorbance at 465 nm grows linearly with dose when α-terthiophene concentration reaches 12%. Explored range goes up to ∼2×10⁶ Gy, with dose rates spanning over three orders of magnitude. Concerning their application as dosimeters, a higher sensitivity characterises the 3T–PMMA moiety, suggesting its suitability from the kGy range up to 1 MGy. Above this value films become fragile. 3T–PS films are less sensitive, but more radiation resistant. Therefore they better suit the medium-to-high dose dosimetry range. Dose rate influences the response sensitivity in a complex way, however above 80 and up to 3.6×10⁴ Gy/min an approximate linearity exists between log(dose rate) and sensitivity, as in the analogous cellulose triacetate system.     

Proton transport properties of poly(aspartic acid) with different average molecular weights

We synthesized seven partially protonated poly(aspartic acids)/sodium polyaspartates (P-Asp) with different average molecular weights to study their proton transport properties. The number-average degree of polymerization (DP) for each P-Asp was 30 (P-Asp30), 115 (P-Asp115), 140 (P-Asp140), 160 (P-Asp160), 185 (P-Asp185), 205 (P-Asp205), and 250 (P-Asp250). The proton conductivity depended on the number-average DP. The maximum and minimum proton conductivities under a relative humidity of 70% and 298 K were 1.7 · 10^?3 S cm^?1 (P-Asp140) and 4.6 · 10^?4 S cm^?1 (P-Asp250), respectively. Differential thermogravimetric analysis (TG-DTA) was carried out for each P-Asp. The results were classified into two categories. One exhibited two endothermic peaks between t = (270 and 300) °C, the other exhibited only one peak. The P-Asp group with two endothermic peaks exhibited high proton conductivity. The high proton conductivity is related to the stability of the polymer. The number-average molecular weight also contributed to the stability of the polymer.     

Characteristics study of clear polymethylmethacrylate dosimeter,Radix W,in several kGy range

Basic characteristics of Radix W, a commercially available undyed polymethylmethacrylate (PMMA) dosimeter conventionally used by readout at 320 nm, were studied in the dose range of 0.5–8 kGy, for its wide application especially for the evaluation of the sterilization dose and the quality assurance of food irradiation. The characteristics of dose response, the effect of irradiation temperature, and its stability after irradiation were examined over candidate readout wavelengths of 270–320 nm. The dose response readout at shorter wavelength is higher than that at longer wavelength, and 280 nm is the suitable readout wavelength for measurement of dose range of 0.5–8 kGy. The post-irradiation stability of dose response for 6 kGy is less than 1% within 24 h after irradiation at an irradiation temperature of 20 °C. Dose response is higher with temperature at irradiation temperatures in the range of −40 to 20 °C.     

Preparation of a poly(methyl methacrylate)-reduced graphene oxide composite with enhanced properties by a solution blending method

Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by a simple solution blending method. The glass transition temperature of the produced PMMA/graphene composite was increased by 37 °C with 1.0 wt.% RGO content, which is approximately 40% of improvement compared to that of pure PMMA. The thermal expansion coefficient (TEC) decreased by 68% with as low as 0.1 wt.% RGO loading. The electrical conductivity of the nanocomposites reached up to 0.037 S/m even with only 2.0 wt.% RGO, which increased by more than twelve orders of magnitude. The resulting nanocomposites showed that a stable colloidal suspension of graphene dispersion in organic solvent before blending with PMMA is necessary to fabricate the nanocomposites with enhanced properties.     

Gamma-ray response of a clear,crosslinked PMMA dosimeter,Radix W

Radix W, a clear poly(methyl-methacrylate) (PMMA) dosimeter was developed with improved properties compared to the conventional clear PMMA dosimeter, Radix RN15. PMMA with a glass transition temperature (T_g) higher than 120 °C was selected making it possible to measure doses in a wide range of 1 to 150 kGy. Dose rates of 2.5–10 kGy/h were tested and did not affect significantly the dose response. The influence of irradiation temperature was reduced compared with Radix RN15.     

Experimental observations on the competing effect of tetrahydrofuran and an electrolyte and the strength of hydrate inhibition among metal halides in mixed CO2 hydrate equilibria

In the present work, experimental data on the equilibrium conditions of mixed CO₂ and THF hydrates in aqueous electrolyte solutions are reported. Seven different electrolytes (metal halides) were used in this work namely sodium chloride (NaCl), calcium chloride (CaCl₂), magnesium chloride (MgCl₂), potassium bromide (KBr), sodium fluoride (NaF), potassium chloride (KCl), and sodium bromide (NaBr). All equilibrium data were measured by using Cailletet apparatus. Throughout this work, the overall concentration of CO₂ and THF were kept constant at (0.04 and 0.05) mol fraction, respectively, while the concentration of electrolytes were varied. The experimental temperature ranged from (275 to 305) K and pressure up 7.10 MPa had been applied. From the experimental results, it is concluded that THF, which is soluble in water is able to suppress the salt inhibiting effect in the range studied. In all quaternary systems studied, a four-phase hydrate equilibrium line was observed where hydrate (H), liquid water (L_W), liquid organic (L_V), and vapour (V) exist simultaneously at specific pressure and temperature. The formation of this four-phase equilibrium line is mainly due to a liquid–liquid phase split of (water + THF) mixture when pressurized with CO₂ and the split is enhanced by the salting-out effect of the electrolytes in the quaternary system. The strength of hydrate inhibition effect among the electrolytes was compared. The results shows the hydrate inhibiting effect of the metal halides is increasing in the order NaF < KBr < NaCl < NaBr < CaCl₂ < MgCl₂. Among the cations studied, the strength of hydrate inhibition increases in the following order: K⁺ < Na⁺ < Ca²⁺ < Mg²⁺. Meanwhile, the strength of hydrate inhibition among the halogen anion studied decreases in the following order: Br^? > Cl^? > F^?. Based on the results, it is suggested that the probability of formation and the strength of ionic–hydrogen bond between an ion and water molecule and the effects of this bond on the ambient water network are the major factors that contribute to hydrate inhibition by electrolytes.     

New lithium ion conducting polymer electrolytes based on polysiloxane grafted with Si-tripodand centers

New kind of polymer host for lithium cations has been synthesized by catalyzed hydrosilylation reaction involving hydrogen atoms of a polysiloxane and double bonds of vinyl tris-2-methoxyethoxy silane. The obtained macromolecule can be regarded as siloxane backbone grafted with silicon tripodand elements with very short polyether chains. A family of Li ion conducting polymer electrolyte membranes have been prepared by dissolving LiPF₆ in thus obtained polymer matrix. Exceptionally high room temperature specific conductivities, exceeding 10⁻³ S/cm at 25 °C, have been measured for the studied polymer electrolytes. It is proposed that polyether chains tend to self-assembly in the presence of Li cations and this highly organized arrangement of Li coordination sites creates pathways of high lithium conductivity along the polysiloxane backbones. In addition to that, strong shielding of Li-cations suppresses the formation of ion pairs, thus increasing the charge carrier concentration. The electrolytes can be easily formed into dimensionally stable, flexible membranes.     

Graphene oxide doped polyaniline for supercapacitors

A novel high-performance electrode material based on fibrillar polyaniline (PANI) doped with graphene oxide sheets was synthesized via in situ polymerization of monomer in the presence of graphene oxide, with a high conductivity of 10 S cm^?1 at 22 °C for the obtained nanocomposite with a mass ratio of aniline/graphite oxide, 100:1. Its high specific capacitance of 531 F/g was obtained in the potential range from 0 to 0.45 V at 200 mA/g by charge–discharge analysis compared to 216 F/g of individual PANI. The doping and the ratio of graphene oxide have a pronounced effect on the electrochemical capacitance performance of the nanocomposites.     

Fibriform polyaniline/nano-TiO2 composite as an electrode material for aqueous redox supercapacitors

Fibriform polyaniline/nano-TiO₂ composite is prepared by one-step in situ oxidation polymerization of aniline in the presence of nano-TiO₂ particles, which contains 80% conducting polyaniline by mass, with a conductivity of 2.45 S/cm at 25 °C. Its maximum specific capacitance is 330 F g^?1 at a constant current density of 1.5 A g^?1, and can be subjected to charge/discharge over 10,000 cycles in the voltage range of 0.05–0.55 V.     

Spectrophotometric study of stability constants of cimetidine–Ni(II) complex at different temperatures

Cimetidine, a histamine H₂-receptor, has a structure which enables it to act as a chelating agent. The formation of nickel(II) complex with cimetidine has been studied spectrophotometrically at an absorption maximum of 622 nm at different temperatures. The data show that nickel(II) and cimetidine combine in the molar ratio of 1:2. The stability constants of the complex were calculated to be 1.40–2.4 × 10⁸ by continuous variation method and 1.24–2.4 × 10⁸ by mole ratio method at 25 and 40 °C, respectively. The immediately formed complex shows stability with respect to time and temperature.     

Electrochemical properties of liquid electrolyte added quasi-solid state TiO2 dye-sensitized solar cells

In this study a process has been introduced to replace traditional liquid or solid electrolyte coatings on dye-sensitized photoelectrode in solar cells. This process has more efficient diffusion of electrolyte, hence higher sensitivity. Better interfacial contact between polymer electrolyte and TiO₂ photoelectrode had improved electrochemical response and ionic conductivity of cell. Conductivity of this electrode was 9.33 × 10⁻³ S cm⁻¹ (at room temperature), which is much higher than the using traditional process for addition of electrolytes. It has 0.68 V open-circuit voltage and 3.19 mA cm⁻² short-circuit current density. Energy conversion efficiency of this cell was about 37% higher than the cell developed with traditional processes under constant light intensity (45 mW cm⁻²).     

Activity and stability of horseradish peroxidase in hydrophilic room temperature ionic liquid and its application in non-aqueous biosensing

The activity and stability of horseradish peroxidase (HRP) were investigated in a hydrophilic room temperature ionic liquid 1-butyl-3-methylimidazolium tetrafluroborate ([bmim][BF₄]) by electrochemical methods. Although no detectable activity exhibited in anhydrous [bmim][BF₄], HRP was active in the presence of a small amount of water (4.53%, v/v). And its activity can be improved by immobilization in agarose hydrogel. The immobilized HRP possesses excellent activity at 65 °C. It remained 80.2% of its initial activity after being immersed for 10.5 h in an aqueous mixture of [bmim][BF₄] with some hydrogen peroxide (H₂O₂) under room temperature, implying extremely high stability. Moreover, the immobilized HRP was found to be very sensitive and stable in H₂O-containing [bmim][BF₄] for the detection of H₂O₂, with a wide linear range of 6.10 × 10⁻⁷ to 1.32 × 10⁻⁴ mol l⁻¹ and low detection limit of 1.0 × 10⁻⁷ mol l⁻¹.     

Molecular mechanics investigation of some acrylic polymers using SPASIBA force field

The First generation SPASIBA force field is used to study normal vibrational modes of PMMA, and then extended to other thermoplastic polymers, namely PMA, PMAA and PAA, in order to determine its parameters transferability. To this end, FTIR and FTR spectra of pure PMMA samples, prepared by the emulsion polymerization of MMA and initiated by sodium, are recorded in 400–3500 cm⁻¹ and 200–3500 cm⁻¹, respectively. A detailed vibrational analysis was performed on the obtained spectra and the observed frequencies are assigned to their respective vibrational modes, supported by potential energy distribution (PED) analysis. Our numerical results reveal an RMS value of 7.8 cm⁻¹ corresponding to IR wavenumbers and 8.7 cm⁻¹ relatively to Raman wavenumbers. Our vibrational calculations on PMA, PMAA and PAA polymers reveal that the parameters transferability criterion, established by Shimanouchi, is verified for the SPASIBA force field.     

Quality variations of poultry litter biochar generated at different pyrolysis temperatures

Producing biochar and biofuels from poultry litter (PL) through slow pyrolysis is a farm-based, value-added approach to recycle the organic waste. Experiments were conducted to examine the effect of pyrolysis temperature on the quality PL biochar and to identify the optimal pyrolysis temperature for converting PL to agricultural-use biochar. As peak pyrolysis temperature increased incrementally from 300 to 600 °C, biochar yield, total N content, organic carbon (OC) content, and cation exchange capacity (CEC) decreased while pH, ash content, OC stability, and BET surface area increased. The generated biochars showed yields 45.7–60.1% of feed mass, OC 325–380 g kg⁻¹, pH 9.5–11.5, BET surface area 2.0–3.2 m² g⁻¹, and CEC 21.6–36.3 cmol_c kg⁻¹. The maximal transformation of feed OC into biochar recalcitrant OC occurred at 500 °C, yet 81.2% of the feed N was lost in volatiles at this temperature. To produce agricultural-use PL biochar, 300 °C should be selected in pyrolysis; for carbon sequestration and other environmental applications, 500 °C is recommended.